Cheat sheet: Traction and high-speed properties and fuel efficiency of the car. Traction and high-speed properties of the car forces acting on the car when driving

03.03.2021

Ministry of Agriculture and

Food of the Republic of Belarus

Establishment of education

"Belorussian Agovernmental

Agrarphota University

FacultyTeeherization of agriculture

Farm

Department of "Tractors and Cars"

Course project

By discipline: the foundations of the theory of the calculation of the tractor and car.

On the topic: travelery and fuel efficiency

car.

5th year student 45 groups

Snopkova A.A.

Head of CP

Minsk2002.
Introduction

1. Thought-high speed car.

The traction and speeds of the car are called a set of properties that determine the engine potentially possible engine or the adhesion of the leading wheels with expensive movement speeds and the limit intensities of overclocking and braking equipment during its operation on the traction mode of operation in various roads.

The indicator-high-speed properties of the car (maximum speed, acceleration of the example or slowing down when braking, the thrust force on the hook, efficient power, the lift, overcome in various road conditions, the dynamic factor, the speed characteristic) is determined by the designer traction. It implies the definition of constructive parameters that can be able to use optimal conditions of movement, as well as the establishment of limit road conditions for each type of car.

Traction and speeds and indicators are determined with the traction calculation of the car. As a settlement of calculation, the cargo car is low loading capacity.

1.1. Determining the power of the car engine.

The calculation is based on the nominal loading capacity of the machine /\u003e in kg (the mass of the installed load + the mass of the driver and passengers in the cockpit) or the road trip /\u003e, it is equal to the task -1000 kg.

Engine power /\u003e necessary for the motion of a loaded car with a speed of /\u003e award-rate road conditions characterizing the resistance of the road /\u003e is determined from the dependence:

/\u003e own car mass, 1000 kg;

/\u003e Air resistance (in H) - 1163.7 when driving with a smart velocity /\u003e \u003d 25 m / s;

/\u003e - CPD of transmission \u003d 0.93. Nominal load capacity /\u003e is specified in the task;

/\u003e \u003d 0.04, taking into account the work of the car in agriculture (the coefficient of road resistance).

/\u003e (0.04 * (1000 * 1352) * 9,8 + 1163.7) * 25/1000 * 0.93 \u003d 56,29kW.

Own MassAutomobile is associated with its nominal capacity dependence: /\u003e

/\u003e 1000 / 0.74 \u003d 1352 kg.

where: /\u003e - the coefficient load capacity of the car - 0.74.

The car has a special load capacity \u003d 0.7 ... 0.75.

The coefficient load capacity of the car significantly affects the dynamic and economic treatment of the car: the more, the better these indicators.

The resistance depends on the density of air, the coefficient /\u003e of the streaming content and the bottom (coefficient of sailing), the area of \u200b\u200bthe front surface F (in /\u003e) of the car and the speed of the movement. Determined by addiction: /\u003e,

/\u003e0.45*1.293.3.2625\u003d 1163.7 N.

where: /\u003e \u003d 1,293 kg //\u003e - air density of the peperature 15 ... 25 S.

The coefficient accuracy of the car /\u003e \u003d 0.45 ... 0.60. Rein \u003d 0.45.

The surface area can be calculated by the formula:

F \u003d 1.6 * 2 \u003d 3.2 /\u003e

Where: B - the rear wheel killet, accept it \u003d 1.6 m, the value of H \u003d 2m. The values \u200b\u200bof B and H are clarified with subsequent paintings when determining the size of the platform.

/\u003e \u003d Maximum speed across the road with a firm coating with a complete fuel supply, on the task it is 25 m / s.

Since the car is developing, as a direct transmission,

where: /\u003e 0.95 ... 0.97 - 0.95 kpddviller at idle; /\u003e \u003d 0.97 ... 0.98- 0.975.

KPD-headed transmission.

/>0,95*0,975=0,93.

1.2. Selecting the wheeled formula of the car of the gameometric parameters of the wheels.

The amount of wheel size (wheel diameter /\u003e and the mass transmitted to the wheel axis) are determined based on the car carrying capacity.

With a full-loaded car 65 ... 75% of the total mass of the car, you have to rear axle and25 ... 35% - on the front. Consequently, the load coefficient of the front and rear-winding wheels is respectively 0.25 ... 0.35 and -0.65 ... 0.75.

/\u003e /\u003e; /\u003e 0.65 * 1000 * (1 + 1 / 0.45) \u003d 1528.7 kg.

on the front: /\u003e. /\u003e 0.35 * 1000 * (1 + 1 / 0.45) \u003d 823.0kg.

Take the following: on the rear axle -1528.7 kg, on one wheel of the rear axle - 764.2 kg; Forest axis - 823.0 kg, on the wheel of the front axle - 411.5 kg.

Based on the load /\u003e and tire pressure, the sizes of the tires are selected, in M \u200b\u200b(tire profile /\u003e width and the diameter of the plant rim /\u003e). Then the calculated radiowing wheels (in m);

Estimated data: Tire name -; Its dimensions is -215-380 (8.40-15); Rackingradius.

/\u003e (0.5 * 0.380) + 0.85 * 0.215 \u003d 0.37m.

1.3. Determination of the capacity of the gameometric parameters of the platform.

For carrying capacity /\u003e (in T), the installation of the platform /\u003e into the cube. m., outstanding:

/> />0,8*1=0,8 />/>

For the ongoing automotive /\u003e it is accepted \u003d 0.7 ... 0.8 m., I choose 0.8 m.

Having determined the volume of the internal dimensions of the platform of the car in M: width, height and length.

Truck platform width accept (1.15 ... 1.39) from the rut of the car, that is \u003d 1.68 m.

The height is body-determined size of a similar car - UAZ. It is equal to 0.5 m.

Length platform-receiving - 2.6 m.

By the internal length /\u003e I define the base of the LAutomotive (the distance between the front and rear wheel axes):

i accept the base machine \u003d 2540 m.

1.4. Brake properties of the car.

Brake-processing of creating and changing the artificial resistance to the movement of the car by an extension of its speed or retention with a fixed road.

1.4.1. Estimated slowdown in motion machine.

Slowing down /\u003e \u003d /\u003e,

Where G is an accelerated fall drop \u003d 9.8 m / s; /\u003e - the clutch coefficient of the wheels with the road, the values \u200b\u200bof which are taken from Table 3 for various road refers; /\u003e - Current accounting of rotating masses. Its values \u200b\u200bfor the projected car 1.05 ... 1.25, accept \u003d 1.12.
The better the road, the more there may be a slowdown in braking machine. On solid roads, slowing can reach 7 m / s. Bad road conditions reduce braking intensity.

1.4.2. Minimum brake path.

The length of the minimum path /\u003e /\u003e can be determined from the condition that the work perfect by the machine during the braking must be equal to kinetic energy that has lost it during the time. The braking path will be minimal when the most intense braking, that is, when it has the maximum value. If braking is carried out on a horizontal road with a permanent development, then the path to the stop is equal to:

I define the slowdown for various values \u200b\u200b/\u003e, three-wheeled speeds 14.22 and 25 m / s, and will bring them to the table:

Table № 1.

Support surface.

Slow down on the road. Brake power. Minimum brake path. Motion speed. 14 m / s 22 m / s

1.Asfalt 0.65 5.69 14978 17.2 42.5 54.9 2. Gravel. 0.6 5.25 13826 18.7 46.1 59.5 3. Cobblestone. 0.45 3.94 10369 24.9 61.4 79.3 4. Dry primer. 0.62 5,43 14287 18.1 44.6 57.6 5. Primer after the rain. 0.42 3.68 9678 26.7 65.8 85.0 6. Sand 0.7 6,13 16130 16.0 39.5 51.0 7. Snow road. 0.18 1.58 4148 62.2 153.6 198.3 8. Care of the road. 0.14 1.23 3226 80.0 197.5 255.0

1.5. Dynamic properties of the car.

The dynamicity of the car is largely determined by the correct election of the gear and the high-speed movement mode on each of the selected-name.

The number of job shifts - 5. Direct transmission is choosing -4, fifth - economical.

Thus, one of the most important tasks when performing coursework on cars is the combustion of the number of gears.

1.5.1. Selection of car gear.

Gear ratio /\u003e \u003d /\u003e,

Where: /\u003e - gear-cutting gear transmission; /\u003e - Gotate the main transmission.

Transferred numerous transmission to be in equation:

where: /\u003e - Estimated Radio Wheels, M; accepted from previous calculations; /\u003e - the speed of the rotation at the rated frequency of rotation.

Gotate Number Transmission on the first gear:

where /\u003e is the maximum peramic factor, permissible under the clutch conditions of the car's leading wheels. There is an in the range of it - 0.36 ... 0.65, it should not be exceeded:

/>=0.7*0.7=0.49

where: /\u003e is the clutching coefficient with an expensive, depending on the road conditions \u003d 0.5 ... 0.75; /\u003e - the coefficient of the car's loading wheels; Recommended values \u200b\u200b\u003d 0.65 ... 0.8; Maximum loading moment of the engine, in H * M, is taken from the speed characteristic of the supercarboratory engines; G - full weight of the car, n; - The efficiency of transmission automotive on the first transmission is calculated by the formula:

0.96 - Kpdvigator at idle scrolling of the crankshaft; /\u003e\u003d0.98 - CPD Cylindrical Container Gears; /\u003e\u003d0.975 -cpdconic pair of gears; - Accordingly, the number of cylindrical of the conical couples involved in engaging on the first gear. They are quantified, focusing on the transmissions schemes.

In the first proclaimation, under preliminary calculations, the transfer numbers of thermaceous vessels are selected according to the principle of geometric progression, the formation, where Q is the denominator of the progression; It is counted for mills:

where: Z is the nominations specified in the task.

The gear ratio of the nominated car's main gear is taken, converted by the prototype \u003d.

According to the transmission transfer, the maximum velocities of the vehicle of the car on-site transmissions are calculated. The obtained data is reduced to the table.

Table number 1.

Transfer gear ratio speed, m / s. 1 30 6.1 2 19 9.5 3 10.5 17, 4 7.2 25 5 5.8 31

1.5.2. Construction of theoretical (outer) high-speed accuracy of the carburetor engine.

Theoretical external characteristic /\u003e \u003d F (n) is built with a sheet of millimeter paper. Calculation and construction of external characteristics are produced in such a sequence. On the abscissa axis, we depose in the adopted value of the speed of rotation of the crankshaft: nominal, maximum fiber, with a maximum torque, minimal corresponding to the engine.

Nominal frequency is set in task, frequency /\u003e,

Frequency /\u003e. The rotational frequency is made based on the reference data of the prototype -4800 rpm engine.

Intermediate points of the power of the carburetor motor are found from an expression, setting /\u003e (at least 6 points).

The values \u200b\u200bof the torque /\u003e are calculated depending on:

Current values \u200b\u200b/\u003e and /\u003e Berutis graphics /\u003e. The specific efficiency of the carburetor engine fuel is calculated by dependence:

/\u003e, g / (kW, h),

where: /\u003e Specific efficiency of fuel at rated power specified in the task \u003d 320 g / kW * h.

The clock consumption is determined by the formula:

Values \u200b\u200b/\u003e and /\u003e take from the constructions, according to the results of the calculation of the theoretical external characteristics of the table.

Data for software characteristics. Table № 2.

№

1 800 13,78 164,5 4,55 330,24 2 1150 20,57 170,86 6,44 313,16 3 1500 27,49 175,5 8,25 300 4 1850 34,30 177,06 9,97 290,76 5 2200 40,75 176,91 11,63 285,44 6 2650 48,15 173,52 13,69 284,36 7 3100 54,06 166,54 15,66 289,76 8 3550 57,98 155,97 17,49 301,64 9 4000 59,40 141,81 19,01 320 10 4266 58,85 131,75 19,65 333,90 11 4532 57,16 120,44 20,01 350,06 12 4800 54,17 107,78 19,97 368,64 /> /> /> /> /> /> /> /> /> />

1.5.4. Universal Dynamic Characteristics of the car.

Dynamic accuracy of the car illustrates its traction-high-speed properties with an equaline movement with different speeds on different transmissions and in various vehicles.

From the equational balance of the car when moving without a trailer on the horizontal reference surface, it follows that the difference between the forces /\u003e (touching the thrust and resistance of the air when the car moves) in this equation it is the force of thrust consumed to overcome all external resistance of the movement, with the exception of air resistance. Therefore, the ratio /\u003e characterizes the supply of power to the vehicle per unit weight of the car. This meter of dynamic, accomplice, traction-high-speed, car properties is called the dynamic factors of the car.

Thus, the dynamic factor of the car.

Dynamic factor is determined on each transmission in the process of operation of the engine with a full load when the fuel is complete.

Between the dynamic factor and parameters characterizing the road resistance (coefficient /\u003e) and inertial loads, there are the following dependences:

/\u003e /\u003e - with unspecified motion;

/\u003e With the steady movement.

Dynamic factors dependent on the vehicle speed mode - the engine speed (its grinding) and the transmission turned on (transmission transmission). Graphic image and called dynamic characteristics. Its value depends on the site's weight of the car. Therefore, the characteristic is built first for the extensive vehicle without cargo in the body, and then by additional constructions to form it into a universal, allowing the dynamic factor for the lobes of the car.

Additional packages to obtain a universal dynamic characteristic.

We apply a mine characteristic from above the second axis of the abscissa, on the coefficient-release value of the car load coefficient.

On the extreme tolere of the upper axis of the abscissity coefficient r \u003d 1, which corresponds to the yield of the car; At the extreme point of the right, we postpone the maximum value indicated in the task, the value of which depends on the maximum weight of the loaded car. Then we apply on the upper axis of the abscissa a number of intermediate values \u200b\u200bof the load and carry out the vertical from them to the intersection with the lower abscissa.

Vertical, passing through the point Γ \u003d 2, I take the order for the second axis. Characteristics. All the dynamic factor at r \u003d 2 is twice as smaller than that of the empty car, the scale of the dynamic factor on the second axis of the ordinate should be two times than on the first axis, passing through the point r \u003d 1. Connect unambiguously on both orders by inclined lines. The intersection points of these straight verticals form on each vertical scale scale for the corresponding banning the car load coefficient.

The results of calculators are recorded in the table.

Table number 3.

Transmission v, m / s.

Torque, nm.

D \u003d 1 g \u003d 2.5 1,22 800 164,50 12125 2.07 0,858 0.394 2.29 1500 175.05 12903 7.29 0.912 0.420 3.35,22,21,921 13040 15,69 0,921 0,424 4,72 3100 166.54 12275 31,15 0,866 0.398 6,10 4000 141.81 10453 51,86 0.736 0.338 6,91 4532 120.44 8877 66,27 0,623 0,286 7.3 4800 107.78 7944 66.03 0.557 0.255 2 1,90 800 164.50 7766 5.06 0.549 0.291 3,57,500 175.05 8264 17,78 0.583 0.309 5.23 2200 176.91 8352 38.24 0.588 0.312 7.38 3100 166,54 7862 75,93 0,551 0,292 9.52 4000 141,81 6695 126,41 0,464 0.246 10.78 4532 120.44 5686 162.27 0.390 107.78 5088 182.03 0.346 0.184 3 3,44 800 164,50 4292 16,56 0,302 0,160 6.46 1500 175.05 4567 58.26 0.317 0.168 9.47,25,21,26,91,615,25,21,12,19,66,54,4345 248,61,289,245,222,4000 141, 81 3700 413.92 0,231 0,123 19,51 4532 120.44 3142 531.34 0.183 0.098 20.64 4800 107.78 2812 596.04 0,155 0.083

5,02 800 164,50 2943 35,21 0,206 0,094 9,42 1500 175,05 3131 123,79 0,212 0,096 13,81 2200 176,91 3165 266,29 0,204 0,090 19,46 3100 166,54 2979 528,73 0,172 0,071 25,11 4000 141,81 2537 880,30 0,144 0,04 28,45 4532 120,44 2154 1130,03 0,069 0,015 30,12 4800 107,78 1928 1267,63 0,043 0,001 5 6,23 800 164,50 2370 54,26 0,164 0,087 11,69 1500 175,05 2522 190,77 0,164 0,088 17,15 2200 176,91 2549 410,36 0,150 0,080 24,16 3100 166,54 2400 814,78 0,110 0,060 31,17 4000 141,81 2043 1356,56 0,044 0,026 35,32 4532 120,44 1735 1741,40 0,001 37,42 4800 107,78 1553 1953,53 /> /> /> /> /> /> /> /> /> />
1.5.5. A brief analysis of the data received.

1. Wow, on which gears will operate in a given roadway, characterized by a given coefficient /\u003e of roadmaps (at least 2 ... 3 values) and which maximum speeds can ondevelop with uniform movement with different values \u200b\u200b(at least 2-x) load coefficients Car, necessarily, at the same time, Max.

Definished values \u200b\u200bof the road resistances: 0.04, 0.07, 0.1 (asphalt, primedorog, primer after rain). With the coefficient \u003d 1 car can be moving /\u003e \u003d 0.04 at a rate of 31.17m / s per 5 transmission; /\u003e \u003d 0.07 - 28 m / s, 5 execution; /\u003e \u003d 0.1 - 24 m / s, 5 transmission. With the coefficient \u003d 2.5 (maximum load), the car can move at /\u003e \u003d 0.04 - the speed of 25 m / s, 4 execution; /\u003e \u003d 0.07 - speed of 19 m / s, 4 execution; /\u003e \u003d 0.1 - Speed \u200b\u200b17 m / s, 3 Transmission.

2. The largest road resistivity on the dynamic characteristic, which can overcome the car, moving on each transmission with uniformity (at the inflection points of the dynamic factor curves).

The resulting policy is in terms of the possibility of their implementation under the clutch conditions by road coating. For a car with rear driving wheels:

where: /\u003e - the coefficient of loading wheels.

Table № 4.

Transmission No. Overcome road resistance The clutch force with the road surface (asphalt). R \u003d 1 g \u003d 2.5 g \u003d 1 g \u003d 2.5 1 transmission 0.921 0,424 0.52 0,52 2 transmission 0,588 0,312 0,51 0,515 3 Transmission 0.319 0,169 0,51 0,51 4 Transmission 0.204 0.09 0.5 0,505 5 Transmission 0.150 0.08 0.49 0.5

According to the table, it is estimated that on 1 transmission the car can overcome the sand; on the 2nd Snowjunogue; on the 3rd icing road; on the 4th dry dump road; on the 5th asphalt

3. To determine the angular lines that the car is able to overcome in various road conditions (at least 2 ... 3 values) on various transmissions, and the speeds of it will develop.

Table number 5.

Road resistance. № transmission angle of lift Speed \u200b\u200br \u003d 1 g \u003d 2.5 0.04 1 Transmission 47 38 3,35 2 Transmission 47 27 5.23 3 Transmission 27 12 9,47 4 Transmission 16 5 13,8 5 Transmission 11 4 17, 15 0.07 1 Transmission 45 35 3,35 2 Transmission 45 24 5,23 3 Transmission 24 9 9,47 4 Transmission 13 2 13,8 5 Transmission 8 17,15 0.1 1 Transmission 42 32 3.35 2 Transmission 42 21 5,23 3 Transmission 22 7 9,47 4 Transmission 10 13.8 5 Transmission 5 17,15

4. Consider:

The maximum speed with a steady movement in the most typical road conditions (asphalt coating). The values \u200b\u200bf by the preparation for various road conditions are accepted from the ratio:

At specified finding conditions, i.e. The asphalt highway resistance takes the value to 0.026 and the speed is 26.09 m / s;

The dynamic factor in direct transmission with the most commonly used for this type of automotive velocity of the movement (usually the rate equal to half themeximal) is 12 m / s;

n Maximum meaningful factor in direct transmission and speed value - 0.204 and 11.96m / s;

n Maximum meaningful factor at lowest gear - 0.921;

n Maximum meaningful factor on intermediate transmissions; 2 transmission - 0.588; 3 execution - 0.317; 5 Transmission - 0.150;

5. Compared data from reference to a car having close to prototypes. The data obtained in the calculation is practically similar to the UAZ data.

2. Fuel economy of the car.

One of the fundamental economy as the operational property is considered to consider the fuel consumed at 100 km of the path with a uniform movement of a collaposed speed in the specified road conditions. On the characteristic, the curves appreciated, each of which meets certain road conditions; The performance of the work is considered three coefficients of road resistance: 0.04, 0.07, 010.

Fuel consumption, l / 100 km:

where: /\u003e - Instant fuel consumption of the car, l;

where /\u003e - the passage of 100 kmputi, \u003d /\u003e.

Hence the examination of the engine power spent on overcoming the resistance of expensive air we get:

Characteristic is built for visual standards on economy. The axis is ordinatened fuel consumption, on the abscissa axis of the speed of movement.

Order constructing. For different speed modes of the car movement

determine the value of the frequency of the crankshaft of the engine.

Knowing the engine frequency from the corresponding speed characteristics of the definition g.

According to the formula 17, the engine power (expression in square brackets), the required vehicle shift with different speeds on one of the specified roads, characterized by the corresponding resistance value: 0.04, 0.07, 0.10.

Calculations are conducted until speed at which the engine is loaded to the maximum power. The variable system is only the speed of movement and resistance of the air, all other indicators are taken from previous calculations.

Substitutional for different speeds count the desired fuel consumption values.

Table number 6.

/\u003e l / 100 km

5,01 800 940,54 46,73 5,36 330,24 5,5 13,1 9,39 1500 940,54 164,2 11,26 300 3,0 13,31 11,59 1850 940,54 250,11 14,97 290,76 2,4 13,91 13,78 2200 940,54 253,39 19,33 285,44 2,0 14,84 19,41 3100 940,54 701,68 34,58 289,76 1,4 19,12 22,23 3550 940,54 920,11 44,86 301,64 1,2 22,55 25 4000 940,54 1168 59,35 320,00 1,0 28,08

Dry sad

5,01 800 1654,8 46,73 9,20 330,24 5,5 22,46 7,20 1150 1654,8 96,55 13,61 313,16 3,9 21,92 9,39 1500 1654,8 164,28 18,44 300 3,0 21,82 11,59 1850 1654,8 249,90 23,83 290,76 2,4 22,15 13,78 2200 1654,8 353,39 29,88 285,44 2,0 22,93 16,59 2650 1654,8 512,75 38,84 284,36 1,7 24,66 19,41 3100 1654,8 701,68 49,43 289,76 1,4 27,33 0,1 5,01 800 2351,4 46,73 13,03 330,24 5,5 31,81 7,20 1150 2351,4 96,55 19,12 313,16 3,9 30,79 9,39 1500 2351,4 164,28 25,62 300 3,0 30,32 11,59 1850 2351,4 249,90 32,70 290,76 2,4 30,39 13,78 2200 2351,4 353,39 40,43 285,44 2,0 31,02 4000 4532 4800 /> /> /> /> /> /> /> /> /> /> /> /> /> /> />

For the analysis of the economic characteristics, two summarizing curves are carried out on it: the envelope curve of aa and the maximum speeds of movement on different roads, the overflow of the installed engine power and the C-Snap Curve the most economical speeds.

2.1. Analysis of economic characteristics.

1. To determine the most economical speed of movement on each roadfloor office (soil background). Specify the izsence and fuel consumption values. The most economical speed, as it should be expected on solid coating, at a speed of equal to half the maximum fuel trading is 14.5 l / 100 km.

2. Explain the nature of the changes to Economicity when deviating from economic speed to the right and left. The switch to the right increases the specific fuel consumption per kW, with deviations, it increases very sharply air resistance.

3. Determine the flow of fuel consumption. 14.5 l / 100 km.

4. Compared fuel control fuel console rate with a similar prototype indicator. The prototype control flow is equal to the resulting.

5. Based on the poles of the car (daily) traveled along the road with a submissive coating, to determine the approximate capacity /\u003e fuel bobcas (in L) on dependence:

On the prototype of tanks - 80 liters, I take such a container (it is convenient to refill the iskanaster).

The aftermaving calculation results are reduced to the table.

Table number 7.

Indicators 1.Type. Small cargo car. 2. Car load coefficient (on task). 2.5 3. Load capacity, kg. 1000 4. Maximum speed, m / s. 25 5. Mass of a curb car, kg. 1360 6. Number of wheels. four

7. Distribution of the curb mass along the axes of the car, kg

Through the rear axle;

Through the front axle.

8. Full weight of a loaded car, kg. 2350.

9. Distribution of full mass along the axes of the car, kg,

Through the rear axle;

Through the front axle.

10. Sizes of wheels, mm.

Diameter (radius),

Tire profile width;

Internal air pressure in tires, MPa.

11. Dimensions of the freight platform:

Capacity, m / cube;

Length, mm;

Width, mm;

Height, mm.

12. Base of car, mm. 2540 13. Estimated slowdown in braking, m / s. 5,69.

14. Brake path, m when braking at speeds:

Maximum speed.

15. The maximum values \u200b\u200bof the dynamic factor on transmissions:

16. The smallest value of fuel consumption on soil backgrounds, l / 100 km:

17. The most economical movement speeds (m / s) on soil backgrounds:

18. Capacity of the fuel tank, l. 80 19. Car stroke, km. 550 20. Fuel control flow, l / 100 km (approximate). 14.5 Engine: Carburetor 21. Maximum power, kW. 59.40 22. The rotational speed of the crankshaft at maximum power, rpm. 4800 23. Maximum torque, nm. 176.91 24. The speed of rotation of the crankshaft at the maximum moment, rpm. 2200.

Bibliography.

1. Skotnikov V.A., Mashchensky A.A., Solonsky A.S. Basics of the theory and calculation of the tractor and car. M.: Agropromizdat, 1986. - 383c.

2. Methodological manuals on the execution of work work, old and new edition.

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Introduction

1. Technical characteristics of the car

2. Calculation of the external high-speed engine characteristics

3. Calculation of a car traction chart

4. Calculation of the dynamic characteristics of the car

5. Calculation of the acceleration of the car on transmissions

6. Calculation of the time and way of overclocking the car on the transmissions

7. Calculation of the stopping path of the car on the transmissions

8. Calculation of travel fuel consumption by car

Conclusion

Bibliography

Introduction

The life of a modern person is difficult to imagine without a car. The car is also used in production, both in everyday life and in sports.

The efficiency of the use of motor vehicles in various operating conditions is determined by the complex of their potential operational properties - traction-high-speed, brake, patency, fuel efficiency, stability and controllability, smoothness comfort. These operational properties affect the main parameters of the car and its nodes, primarily the engine, transmission and wheels, as well as the characteristics of the road and the conditions of movement.

Improving the productivity of the car and the reduction in the cost of transportation is impossible without studying the operational properties of the car, since to solve these tasks, it should be increased its average speed of movement and reduce fuel consumption while maintaining the safety of motion and ensure maximum amenities for the driver and passengers.

Indicators of operational properties can be determined by the experimental or calculated method. To obtain experimental data, the car is tested on special stands, or directly on the road in conditions approximate to operational. Testing is associated with the cost of significant funds and labor of a large number of qualified workers. In addition, reproduce all the conditions of operation are very difficult. Therefore, the tests of the vehicle are combined with theoretical analysis of operational properties and the calculation of their indicators.

The traction-high-speed properties of the car are called a set of properties that determine the driving wheels that are possible according to the characteristics of the engine or the adhesion of the driving speeds of the movement speeds and the limit intensities of overclocking and braking the car during its work on the traction mode of operation in various road conditions.

In this course, the project should be performed by the necessary calculations on the basis of specific technical data, build graphs and analyze the traction and fuel and economic properties of the VAZ-21099 car. According to the results of calculations, it is required to build an external speed, traction and dynamic characteristics, determine the acceleration of the car on the transmissions, study the dependence of the vehicle speed from the path and velocity of the car from time to acceleration, make calculation of the car stopping path, investigate the dependence of the fuel consumption from speed. As a result, we can conclude about the traction and speed and fuel and economic properties of the VAZ-21099 car.

1 car technical characteristics

1 brand and car type: VAZ-21099

The car brand is made up of letters and digital index. The letters are a reduced name of the plant, and the numbers: the first is the class of the car on the operating volume of the engine cylinders, the second is the conditional designation of the species, the third and fourth is the sequence number of the model in the classroom, the fifth is the modification number. Thus, the VAZ-21099 is a passenger car produced by the Volga automotive factory, small class, 9 models, 9 modifications.

2 Wheel formula: 42.

Cars, designed to move on roads with an improved coating, are usually two leading and two non-leading wheels, and cars designed mainly to operate in heavy road conditions have all the drive wheels. These differences are reflected in the car's wheel formula, which includes the total number of wheels and the number of leading.

3 Number of seats: 5 seats.

For passenger cars and buses indicate the total number of places, including the driver's seat. Passenger car is considered a passenger car with a number of seats for no more than nine, including the driver's seat. Passenger is a car that, in its design and equipment, is intended for the transport of passengers and baggage with the provision of necessary comfort and safety.

4 Own weight of the car: 915 kg (including on the front and rear axles, respectively, 555 and 360 kg).

The own mass of the car is the mass of the car in the curved state without load. It is composed of a dry mass of the car (not refilled and not equipped), the mass of fuel, coolant, spare wheel (wheels), tools, accessories and mandatory equipment.

5 full weight of the car: 1340 kg (including the front and rear axles, respectively, 675 and 665 kg).

The total weight is the sum of the eigencass of the car and the mass of cargo or passengers transported by the car.

6 Overall dimensions (length, width, height): 400615501402 mm.

7 Maximum vehicle speed - 156 km / h.

8 Fuel control consumption: 5.9 l / 100 km at a speed of 90 km / h.

9 Engine type: VAZ-21083, carburetor, 4-stroke, 4-cylinder.

10 Working cylinders: 1.5 liters.

11 Maximum engine power: 51.5 kW.

12 Shaft rotation frequency corresponding to maximum power: 5600 rpm.

13 Maximum engine torque: 106.4 nm.

14 The rotational speed of the shaft corresponding to the maximum torque: 3400 rpm.

15 Type of gearbox: 5-speed, with synchronizers on all forward transmissions, gear ratios - 3.636; 1.96; 1,357; 0.941; 0,784; Z.Kh. - 3.53.

16 Disposal box (if any) - no.

17 Type of main transfer: cylindrical, osostic, gear ratio - 3.94.

18 Tires and marking: radial low-profile, size 175/70R13.

2. Calculation of the external high-speed engine characteristics

District force on driving wheels, driving car, resulting in the fact that the leading wheels are supplied through the transmission torque from the engine.

The effect of the engine on the traction-high-speed properties of the car is determined by its high-speed characteristic, which is the dependence of the power and moment on the motor shaft from the frequency of its rotation. If this characteristic is removed at maximum fuel supply to the cylinder, then it is called external if with incomplete feed - partial.

To calculate the external high-speed engine characteristic, you must take the specifications of the value of key points.

1 Maximum engine power:, kW.

The rotational speed of the shaft corresponding to the maximum power:, rpm.

2 Maximum engine torque:, KNM.

Rotation frequency of the shaft corresponding to the maximum torque:, rpm.

Intermediate values \u200b\u200bare determined from the polynomial equation:

where is the current value of the engine power, kW;

Maximum engine power, kW;

The current value of the rotational speed of the crankshaft, rad / s;

The frequency of rotation of the crankshaft in the calculated mode corresponding to the maximum power value, rad / s;

Polynomial coefficients.

The polynomial coefficients are calculated according to the following formulas:

where is the coefficient of adaptability at the time;

The coefficient of adaptability in the frequency of rotation.

Factors adaptability

where is the moment corresponding to the maximum power;

Translation frequency rpm in rad / s

To verify the correctness of the polynomial coefficients, equality should be performed :.

The value of the magnitude of the torque

The calculated power values \u200b\u200bdiffer from the actual transmission transmissions due to the engine power loss to the drive of the auxiliary equipment. Therefore, the actual values \u200b\u200bof power and moment are determined by the formulas:

where is the coefficient that takes into account the power loss on the drive of the auxiliary equipment; For passenger cars

0.95..0.98. Take \u003d 0.98

Calculation of the external high-speed characteristics of the VAZ-21099 car engine.

Values \u200b\u200bin key points take from a brief specifications:

1 Maximum engine power \u003d 51.5 kW.

Rotation frequency of the shaft corresponding to the maximum power, \u003d 5600 rpm.

2 Maximum engine torque \u003d 106.4 nm.

Rotation frequency of the shaft corresponding to the maximum torque, \u003d 3400 rpm.

We will translate frequencies in Rad / s:

Then the torque at maximum power

We define the coefficients of adaptability at the time and by frequency of rotation:

We present the calculation of the polynomial coefficients:

Check: 0,710 + 1,644 - 1,354 \u003d 1

Consequently, the calculations of the coefficients are made correctly.

We will calculate the power and torque for idling. The minimum rotational speed at which the engine works steadily with full load, is equal to the carburetor engine \u003d 60 rad / s:

Further calculations we enter in Table 2.1, according to which we build graphs for changing the external speed characteristic:

Table 2.1 - Calculation of external high-speed values

Parameter

Conclusion: As a result of the calculations, the external high-speed characteristic of the VAZ-21099 car was built, its graphs were built, the correctness of which satisfies the following conditions:

1) Curve changes in power passes through a point with coordinates (51.5; 586.13);

2) the change in the moment of the engine moment passes through the point with coordinates (0.1064; 355.87);

3) the extremum of moments function is at a point with coordinates (0.1064; 355.87).

Graphs of changes in external speed characteristics are given in Appendix A.

3. Calculation of a car traction chart

The traction diagram is the dependence of the district force on the drive wheels from the velocity of the vehicle.

The main driving force of the car is the circumferent force attached to its drive wheels. This force arises as a result of the engine operation and is caused by the interaction of leading wheels and roads.

Each crankshaft rotation frequency corresponds to a strictly defined point value (by external speed characteristic). Using the found values \u200b\u200bof the moment, they are determined, and at the corresponding rotation frequency of the shaft -.

For steady regime, the district force on the drive wheels

where - the actual value of the moment, kNm;

Transmission transmission;

Round radius wheel, m;

The transmission efficiency, the value is defined in the task.

The installed is called such a mode in which there will be no power loss due to a deterioration in the filling of the cylinder with a fresh charge and thermal inertia of the engine.

The value of the gear ratio of the transmission and the circumferent force is calculated for each transmission:

where is the gear ratio of the gearbox;

Transmission number of dispensing box;

Transmission number of the main transmission.

Round radius wheel

where is the maximum speed of the car from the technical characteristics, m / s;

UT - gear ratio of the fifth transmission;

wP - the rotation frequency of the shaft corresponding to the maximum power, rad \\ s;

Car speed

where is the vehicle speed, m / s;

w is the rotational speed of the crankshaft, rad / s.

The value of the value limiting the circumferential force on the drive wheels by the wheel clutch with the road is determined by the formula

where - the clutch coefficient with the road;

Vertical component under leading wheels, kN;

Car weight coming on driving wheels, kN;

The mass of the car coming on the drive wheels, T;

Acceleration of free fall, m / s.

Calculate the parameters of the car chart of the VAZ-21099 car chart. Transmission transmission when the first transmission is turned on

Round radius wheel

Then the value of the district force

Car speed

m / s \u003d 3,438 km / h

All subsequent calculations are advisable to be reduced in Table 3.1.

Table 3.1 - calculation of the parameters of the traction chart

According to the obtained values, the dependence of the circumferential force on the drive wheels (FK) on the velocity of the car FK \u003d F (VA) is built on the velocity of the vehicle, which is applied to the limiting line by the clutch conditions of the wheel with the road. The number of curves of traction characteristic is equal to the number of gears in its box.

We define the value of the value limiting the circumferential force on the driving wheels by the clutch condition of the wheel with the road, according to the formula (3.5)

Conclusion: The line of restrictions of the district force under the clutch conditions crosses one of the dependencies (for the i gear), therefore, the maximum value of the district force will be limited by the clutch conditions by the value of the KN.

The car chart of the VAZ-21099 car is given in Appendix B.

4. Calculation of the dynamic characteristics of the car

The dynamic characteristic of the car is the dependence of the dynamic factor from the speed. A dynamic factor is called the ratio of free strength aimed at overcoming the forces of the road resistance, to the weight of the car:

where is the country force on the driving wheels of the car, the KN;

Air resistance force, kN;

Car weight, kN.

When calculating the strength of air resistance, windshield and addition resistance are taken into account.

Air resistance strength

where is the total coefficient taking into account the windshield coefficient

resistance and additional resistance coefficient,

which for passenger cars is taken within \u003d 0.15 ... 0.3 ns / m;

Vehicle speed;

The area of \u200b\u200bwindscreen resistance (car projection on the plane,

perpendicular to the direction of movement).

Lob's area

where - the coefficient of filling area (for passenger cars is 0.89-0.9);

Overall height of the car, m;

Overall width of the car, m.

Restriction of the dynamic factor under the clutch conditions of the wheel with the surface of the road

where is the restrictive district force, the KN.

Since the restriction is observed at the beginning of the car movement, i.e. At low speeds, the magnitude of the resistance of the air can be neglected.

According to the results of the calculations, a graph of dynamic characteristics is being built for all transmissions and a dynamic limit line is applied, as well as the line of total road resistance.

On dynamic characteristic, key points are noted by comparing cars of various masses.

Calculation of the dynamic characteristics of the VAZ-21099 car.

Determine the area of \u200b\u200bwindshield resistance

Substitute numeric values \u200b\u200bfor the first point:

All subsequent calculations are reduced to Table 5.1.

Calculate the limitation of a dynamic factor under the clutch conditions of the wheel with the surface of the road:

Conclusion: From the constructed schedule (Appendix B), it can be seen that the limitation line of the dynamic factor crosses the dependence of the dynamic characteristic on the first transmission, which means that the clutch conditions affect the dynamic characteristics of the VAZ-21099 car and under the given conditions the car will not be able to develop the maximum dynamic factors. . On the dynamic characteristic, key points for which cars are compared to different masses:

1) the maximum value of the dynamic factor on the highest transmission DV (MAX) and the corresponding speed VK is a critical speed: (0.081; 12,223);

2) the value of the dynamic factor at the maximum velocity of the vehicle (0.021; 39,100);

3) the maximum value of the dynamic factor on the first transmission and the corresponding speed: (0.423; 3,000)

The maximum speed is determined by the resistance of the road and in these road conditions the car can not achieve the maximum value of the speed of technical specifications.

5. Calculation of car accelerations on transmissions

Acceleration of the car on transmissions

car traction acceleration transmission

where is the acceleration of the free fall, m / s;

Coefficient, taking into account the acceleration of rotating masses;

Dynamic factor;

Coefficient resistance to rolling;

Sanitary road.

Coefficient taking into account the acceleration of rotating masses

where - empirical coefficients are accepted within

0,03…0,05; =0,04…0,06;

Transmission gearbox.

For calculations we accept \u003d 0.04, \u003d 0.05, then

For first transmission;

For the second transfer;

For a third transfer;

For the fourth transmission;

For fifth gear.

We will find acceleration for the first transfer:

The results of the remaining calculations are reduced to Table 5.1.

According to the data obtained, the VAZ-21099 car acceleration schedule is being built on transmissions (Appendix D).

Table 5.1 - Calculation of dynamic and acceleration values

Conclusion: At this point, the VAZ-21099 car accelerations were calculated on transmissions. From the calculations it is clear that the acceleration of the vehicle depends on the dynamic factor, the resistance to rolling, overclocking the rotating masses, the slope of the area, etc., which significantly affects its magnitude. The maximum speed of acceleration car reaches on the first transmission m / s at a speed \u003d 4,316 m / s.

6. Calculation of the time and way of overclocking the car on the transmissions

It is believed that the acceleration of the car begins with a minimal stable rate limited by the minimum stable rotation frequency of the crankshaft. It is also believed that acceleration is carried out at full fuel supply, i.e. The engine works on an external characteristic.

To build timetable time and ways of overclocking a car on transmissions, you must perform the following calculations.

For the first transfer, the acceleration curve is divided into speed intervals:

For each interval, the average acceleration value is determined.

For each interval of overclocking

Total acceleration time on this program

The path is determined by the formula

General overclocking path

In the event that acceleration characteristics in adjacent transmissions intersect, the moment of switching from transmission transmission is carried out at the point of intersection of the characteristics.

If the characteristics do not intersect, switching is carried out at maximum final speed for the current transmission.

During the shift of the gear with the rupture of the power flow, the car moves rolling. The gear shift time depends on the driver's qualification, gearbox design and engine type.

The vehicle movement time with a neutral position in the gearbox for vehicles with a carburetor engine is within 0.5-1.5 s, and with a diesel 0.8-2.5 s.

In the process of switching gear, the vehicle speed is reduced. Reducing the speed of movement, m / s, when switching transmissions can be calculated by the formula derived from the traction balance,

where is the acceleration of free fall;

Coefficient, taking into account the acceleration of rotating masses (taken \u003d 1.05);

The total coefficient of resistance to translational movement

Gear shift time; \u003d 0.5 s.

The path passed during the shift time

where - the maximum (final) speed on the switchable transmission, m / s;

Reducing the speed of movement when shifting gear, m / s;

Shift time, C;

Acceleration of the car is carried out to speed. The equilibrium maximum speed of movement on the highest transmission is from the graph of the change in the dynamic factor, on which the line of the total coefficient of resistance to translational movement is noted. Perpendicular, lowered from the intersection point of this line with a line of dynamic factor on the abscissa axis, indicates the equilibrium maximum speed.

Example of calculation for the first segment of the first transmission. The first speed interval is equal

The average speed of acceleration is equal

Acceleration time for the first interval is equal

The average speed of the first section is equal to

Path Raven

Similarly, the path is determined at each transmission site. The total path passed on the first gear is equal to

Reducing the speed of movement during transmission can be calculated by the formula:

The path passed during the shift time is equal to

The acceleration of the car is carried out to the speed m / s \u003d 112.608 km / h. All subsequent calculations of the time and way of overclocking the car on the transmissions are reduced to Table 6.1.

Table 6.1 - Calculation of time and overclocking of the VAZ-21099 car on transmissions

According to the calculated data, the graphs of the velocity of the vehicle from the path and on time during acceleration (Appendix D, E) are being built.

Conclusion: When calculating, the total time of acceleration of the VAZ-21099 car was determined, which is equal \u003d 29.860 C30 C, as well as the path passed during this time 614.909 m615 m.

7. Calculation of the stopping path of the car on the transmissions

The stopping path is called the distance traveled by the car from the time of the obstacle to the complete stop.

The calculation of the stopping path of the car is determined by the formula:

where is a full stop path, m;

Initial braking speed, m / s;

Driver's reaction time, 0.5 ... 1.5 s;

Time to delay the triggering of the brake drive; for hydraulic system 0.05 ... 0.1 s;

Time of deceleration rate; 0.4 C;

The efficiency coefficient of brakes; for passenger cars \u003d 1.2; at \u003d 1.

Calculations of the stopping path are performed with different wheel clutch coefficients with expensive :; ; - Accepted on the task, \u003d 0.84.

The speed is accepted on the task from the minimum to the maximum equilibrium value.

An example of determining the stopping path of the VAZ-21099 car.

Stopping path with and speed \u003d 4,429m / s equal

All subsequent calculations are reduced to Table 7.1.

Table 7.1 - Calculation of the stopping path

According to the calculated data, graphs of the constraint path of the stopping path from the speed of movement are constructed for various clutch conditions of the wheels with an expensive (Appendix G).

Conclusion: Based on the obtained graphs, we can conclude that with an increase in the velocity of the vehicle and a decrease in the clutch coefficient with an expensive stopping path of the car increases.

8. Calculation of travel fuel consumption by car

The fuel efficiency of the car is called a set of properties that determine the fuel consumption when performing a transportation car in various operating conditions.

Fuel efficiency mainly depends on the design of the car and the conditions of its operation. It is determined by the degree of perfection of the workflow in the engine, the efficiency of the efficiency and the gear ratio of the transmission, the ratio between the cutting and complete mass of the car, the intensity of its movement, as well as the resistance to the car movement by the environment.

When calculating the fuel efficiency of the source data are the load characteristics of the engine, which is calculated by the way of fuel consumption:

where is the specific fuel consumption on the nominal mode, g / kWh;

Motor power utilization factor (s);

The coefficient of use of the rotational speed of the crankshaft of the engine (E);

Power supplied to transmission, kW;

Fuel density, kg / m;

Car speed, km / h.

The specific fuel consumption on the nominal mode for carburetor engines is equal to \u003d 260..300 g / kWh. In work accept \u003d 270 g / kWh.

The values \u200b\u200band for carburetor engines are determined by empirical formulas:

where and e is the degree of power utilization and engine speed;

where - power supplied to the transmission, kW;

Engine power on an external high-speed characteristic, kW;

The current rotation frequency of the crankshaft of the engine, rad / s;

The rotation frequency of the crankshaft motor at rated mode, rad / s;

where - the engine power spent on overcoming the forces of the road resistance, kW;

Engine power spent on overcoming air resistance strength, kW;

Loss power in the transmission and on the drive of the auxiliary equipment of the car, kW;

The density of gasoline According to reference data, we take 760 kg / m, the value of the coefficient of total road resistance was designed previously and equal \u003d 0.021,

An example of calculating the way fuel consumption for the first transmission. Engine power spent on overcoming road resistance forces equal

Engine power spent on overcoming air resistance strength equal

Loss power in the transmission and the drive of the auxiliary equipment of the car is equal

Power supplied to the transmission is equal

Travel fuel consumption is equal

All subsequent calculations are reduced to Table 8.1.

Table 8.1 - Calculation of the way fuel consumption

According to the calculated data, a fuel consumption schedule is being built from the speed of transmissions (application and).

Conclusion: The analysis of the schedule showed that when the vehicle moves at one speed on various transmissions, the way fuel consumption will decrease on the first transmission to the fifth.

Conclusion

As a result of the exchange rate project, the following characteristics were calculated to assess the traction and high-speed and fuel and economic properties of the VAZ-21099 car:

· External high-speed characteristic that meets the following requirements: Curve changes in power passes through a point with coordinates (51.5; 586.13); The curve of changes in the moment of the engine passes through the point with coordinates (0.1064; 355.87); The extremum function of the moments is at the point with coordinates (0.1064; 355.87);

· True car diagram, on the basis of which it can be said that the clutch conditions of the wheels with the surface of the road affect the traction characteristic of a given vehicle;

· Dynamic characteristic of the car from which the maximum value of the dynamic factor on the first gear was determined \u003d 0.423 (\u003d 0.423, which indicates that the clutch conditions affect the dynamic characteristic), as well as the maximum value of the speed on the fifth gear \u003d 39.1 m / s;

· Acceleration of the car on transmissions. It was determined that the maximum speed of acceleration The car reaches on the first transmission, and J \u003d 2.643 m / s at a speed \u003d 3.28 m / s;

· Time and way of overclocking the car on the transmissions. The total time of overclocking the car was approximately 30 s, and the path passed by the car during this time is 615 m;

· Stopping path of the car, which depends on the speed and clutch coefficient with the road. With increasing speed and decrease in the clutch coefficient, the stopping path of the car increases. At a speed \u003d 39.1 m / s and \u003d 0.84, the maximum stopping path was \u003d 160.836 m;

· Travel fuel consumption by car, which showed that at the same speeds of various gears, fuel consumption decreases.

BIBLIOGRAPHY

1. Lapsky S. L. Estimation of the traction-high-speed and fuel and economic properties of the car: allowance for the implementation of the course work on the discipline "Vehicles and their operational qualities" // Belgut. - Gomel, 2007

2. Requirements for the registration of reporting documents of independent work of students: student. Method. Vegetable Boykachev MA other. - M-in education Rep. Blanc, Gomel, Belgut, 2009. - 62 p.

Posted on Allbest.ru.

Course project

By discipline: the foundations of the theory and calculation of the tractor and car.

On the topic: Traction and high-speed properties and fuel efficiency

car.

5th year student 45 groups

Snopkova A.A.

Head of CP

Minsk 2002.
Introduction

1. Thought-high-speed properties of the car.

The indicators of the tag velocity properties of the car (maximum speed, acceleration during overclocking or slowing down when braking, the force of thrust on the hook, efficient engine power, the rise, overcome in various road conditions, the dynamic factor, speed characteristic) are determined by the design traction calculation. It involves the definition of constructive parameters that can provide optimal conditions of movement, as well as the establishment of limit road conditions for each type of car.

Traction and high-speed properties and indicators are determined by the traction calculation of the car. As an object of the calculation, the cargo car is low loading capacity.

1.1. Determining the power of the car engine.

The calculation is based on the nominal car capacity

In kg (the mass of the installed payload + the mass of the driver and passengers in the cockpit) or the road train, it is equal to the task - 1000 kg.

Engine power

required for the movement of a fully loaded car with a speed in a given roadway characterizing the resistance of the road, determined from the dependence: where the own mass of the car, 1000 kg; Air resistance (in H) - 1163.7 when moving at a maximum speed \u003d 25 m / s; - Transmission efficiency \u003d 0.93. Rated loading capacity is specified in the task; \u003d 0.04, taking into account the work of the car in agriculture (the coefficient of road resistance). (0.04 * (1000 * 1352) * 9,8 + 1163.7) * 25/1000 * 0.93 \u003d 56.29 kW.

The own mass of the car is associated with its rated lifting capacity addiction:

1000 / 0.74 \u003d 1352 kg. - Car carrying factor - 0.74.

The car has a lot of low loading capacity \u003d 0.7 ... 0.75.

The coefficient of car carrying capacity significantly affects the dynamic and economic indicators of the car: the more, the better these indicators.

Air resistance depends on air density, coefficient

Opportunities of the regiments and the bottom (sailboat rate), the area of \u200b\u200bthe frontal surface F (c) of the car and the speed mode of the movement. Determined by addiction:, 0.45 * 1.293 * 3.2 * 625 \u003d 1163.7 N. \u003d 1.293 kg / - Air density at a temperature of 15 ... 25 C.

The coefficient of streamlining of the car

\u003d 0.45 ... 0.60. Accept \u003d 0.45.

The frontal surface area can be calculated by the formula:

Where: B - the rear wheel killet, accept it \u003d 1.6 m, the value of H \u003d 2m. The values \u200b\u200bof B and H are clarified with subsequent calculations when determining the size of the platform.

\u003d The maximum speed of movement along the road with a submissive coating with a complete fuel supply, on the task it is 25 m / s. The car is developing, as a rule, in direct transmission, then, 0.95 ... 0.97 - 0.95 efficiency engine at idle; \u003d 0.97 ... 0.98 - 0.975.

Efficiency of the main transmission.

0,95*0,975=0,93.

1.2. Select the wheel's wheel formula and geometric wheel parameters.

The number and size of the wheels (wheel diameter

And the mass transmitted to the wheel axis) are determined on the basis of the car's carrying capacity.

With a fully loaded car 65 ... 75% of the total mass of the car, you have to rear axle and 25 ... 35% - on the front. Consequently, the load coefficient of the front and rear leading wheels is respectively 0.25 ... 0.35 and -0.65 ... 0.75.

; 0.65 * 1000 * (1 + 1 / 0.45) \u003d 1528.7 kg.

on the front:

. 0.35 * 1000 * (1 + 1 / 0.45) \u003d 823.0 kg.

I take the following values: on the rear axle -1528.7 kg, on one wheel of the rear axle - 764.2 kg; On the front axle - 823.0 kg, on the wheel of the front axle - 411.5kg.

Based on the load

and tire pressure, in Table 2, the sizes of the tires are selected, in M \u200b\u200b(width of the tire profile and the diameter of the landing row). Then the calculated radius of the leading wheels (in m); .

Estimated data: Tire name -; Its dimensions is -215-380 (8.40-15); Estimated radius.

Traction-high-speed properties - a set of properties that determine the possible (according to the characteristics of the engine or the adhesion of the drive wheels with the road) the ranges of changes in the speed of motion of the PBX in the traction mode in various road conditions.

Tightening is understood as the operation mode of the PBX, in which the power is supplied to its wheels from the engine sufficient to overcome the resistance to movement.

High-speed properties of PBX is called its ability to deliver cargo with minimal time.

This operational quality is one of the main. Usually, the higher the high-speed properties of the PBX, the greater its performance. The velocity of the vehicle depends on many factors: engine power, gear ratios in the transmission, the amount of resistance to rolling and resistance of air, full mass of PBX, the effectiveness of the brake mechanisms, steering, the stability of the car on the road, the softness of the suspension and the smoothness of the move when moving Equally road, passability when driving in difficult road conditions.

The traction-high-speed properties of the PBX are assessed by the following indicators: technical speed, maximum speed, conditional maximum speed, overclocking intensity and dynamic factor.

Technical speed - Conditional average speed during movement.

In general, the technical speed of the PBX, which has passed the path during the continuous movement, which includes the time of situational stops (in traffic, railway movies, etc.) can be represented by the formula:

The magnitude of the technical speed is most fully characterized by the speed properties of the PBX when driving under certain operating conditions. It depends on the design of the rolling stock, its technical condition, the degree of use of the capacity, road conditions, the intensity of the transport flow, the qualifications of the driver, the characteristics of the cargo transported, the organization of transportation. The increase in the technical speeds of the movement is one of the important tasks in organizing the carriage of goods, since the time of delivery of goods to consumers depends on its magnitude.

Maximum speed- The most stable speed of the vehicle on the highest transmission, measured during the mileage along a given straight horizontal portion of the road.

Conditional maximum speed- The average speed of passing the last 400 m during the acceleration of the car on a straight measuring section of the road with a length of 2000 m.

The maximum speed determines the limit of high-speed PBX capabilities. One of the trends of the automotive development is to improve the traction and speed properties, as evidenced by higher values \u200b\u200bof maximum speed and acceleration from each new car generation. The maximum speed of individual modern cars, determined by their technical characteristics, reaches 200 km / h and higher.

Currently, the minimum limits of maximum speed values \u200b\u200bfor various types of PBX are currently installed. So, for road trains, the allowable maximum speed of movement on the roads of Russia should not exceed: on highways - 90 km / h;

in the settlements -60 km / h; Outside settlements - 70 km / h.

Intensity of overclocking - Car fitness to rapid touching and acceleration (increase the speed of movement). This figure is particularly important in the conditions of urban movement, as well as under the overtakers on the tracks.

Dynamic factor Allows you to evaluate traction qualities (possibility of speed sales) PBX for roads of roads with different resistance.

D \u003d (Rtyagi - RSoprot) / Gap

RTYAGA \u003d μRUT * PP GL transmission * HPD transmissions * Traffic transmission / rolling radius

PP-gear

The dynamic factor of cars designed to work on the roads of a technical category should be on top gears not lower than the magnitude of the total road resistances on the lines allowed on the roads of this category. The largest overcomed lift with the full load in the vehicles should be not lower than 35, and the road trains 18% at lowest gear. The more dynamic car, the more capable of accelerating and move at a higher speed.

The traction-high-speed properties of the car are raised by improving the design of the engine, transmission and chassis, to reduce the mass of the car and improve its streamlining. The car with relatively better traction-high-speed properties in real road conditions has a large power supply that allows you to overcome the resistance to the movement (rolling resistance strength, air, lift) without reducing speed or overclocking.

The traction-high-speed properties of the car substantially depend on the structural factors. The engine type of engine, the efficiency of transmission, transmission ratios, mass and streamlining of the car have the greatest impact on the traction and high-speed properties.

Engine's type.The gasoline engine provides the best traction-high-speed properties of the car than diesel, under similar conditions and modes of movement. This is due to the form of the external high-speed characteristics of the indicated engines.

In fig. 5.1 shows a graph of the power balance of the same car with different engines: with gasoline (curve N " T) and diesel (curve N " T). Maximum power values N. Max and speed v N.at maximum power for both engines the same.

From fig. 5.1 It can be seen that the gasoline engine has a more convex outer speed characteristic than diesel. It provides him with a greater power supply. (N " Z\u003e N " Z. ) at the same speed, for example, at speed v. 1 . Consequently, a car with a gasoline engine can develop high accelerations, overcome sharp rise and tow trailers of greater mass than with diesel.

Traffic efficiency.This coefficient allows you to evaluate power loss in friction transmission. The decrease in the efficiency caused by the growth of power losses for friction due to deterioration of the technical condition of transmission mechanisms during operation leads to a decrease in the traction force on the drive wheels of the car. As a result, the maximum vehicle speed and the road resistance overcome by the car are reduced.

Fig. 5.1. Car Power Balance Schedule with Different Engines:

N " T - gasoline engine; N " T. - diesel; N " s N " Z. – Relevant power reserve values \u200b\u200bat vehicle speed v. 1 .

Transmission ratios.The maximum vehicle speed significantly depends on the transfer number of the main transmission. Such a gear ratio of the main transmission is considered optimal, in which the car develops the maximum speed, and the engine is maximum power. An increase or decrease in the gear ratio of the main transmission compared to the optimal leads to a decrease in the maximum velocity of the car.

The gear ratio I gear transmission affects how the maximum road resistance can overcome the car with uniform motion, as well as on the transfer numbers of intermediate transmissions.

An increase in the number of transmissions in the gearbox leads to a more complete use of engine power, an increase in the average velocity of the vehicle and increase the indicators of its traction and high-speed properties.

Additional gearboxes.Improving the traction-high-speed properties of the car can also be achieved by applying with the main transmission of additional gearboxes: divider (multiplier), demultiplier and dispensing box. Usually additional gearboxes are two-speed and allow you to increase the number of gears twice. In this case, the divider only expands the range of gear ratios, and the demultiplier and the dispensing box increase their values. However, with an overly large number of gears, the mass and complexity of the gearbox design is increasing, and the car is difficult.

Hydraulic.This transmission provides ease of control, smoothness of overclocking and high cargo vehicle. However, it worsens the traction-high-speed properties of the car, since its efficiency is lower than that of the mechanical step gearbox.

Mass of the car.An increase in the mass of the car leads to an increase in the forces of resistance to rolling, lifting and overclocking. As a result, the traction-high-speed properties of the car deteriorate.

Thinking car. Cropling has a significant impact on the traction and high-speed properties of the car. With its deterioration, the reserve of traction force decreases, which can be used to accelerate the car, overcoming the lifts and towing trailers, increase the power loss to air resistance and the maximum vehicle speed is reduced. For example, at a speed of 50 km / h, power losses in a passenger car associated with overcoming air resistance are almost equal to the loss of power to rolling the car when it moves along the road with a solid coating.

Good streaming of passenger cars is achieved by a minor inclination of the roof of the body back, the use of the sidewalls of the body without sharp transitions and a smooth bottom, installation of windshield and the beading of the radiator with the inclination and such placement of the protruding parts in which they do not go beyond the external body dimensions.

All this allows you to reduce aerodynamic losses, especially when driving at high speeds, as well as improve the traction-high-speed properties of passenger cars.

For trucks, air resistance reduces, applying special fairing and covering the body with a tarralet.

Brake properties.

Definitions.

Brake -creating artificial resistance in order to reduce speed or retention in a fixed state.

Brake properties -determine the maximum deceleration of the car and the limit values \u200b\u200bof the external forces that hold the car in place.

Brake mode -the mode in which the brake moments lead to the wheels.

Braking distances -the path passing by a car from distinguishing the driver to the complete stop of the car.

Brake properties -major defining traffic safety.

Modern brake properties are normalized by rule No. 13 of the Inland Transport Committee of the European Economic Commission for the UN (UNECE).

National standards of all countries participating in the UN are based on these rules.

The car must have several brake systems that perform various functions: working, parking, auxiliary and spare.

Working The brake system is the main brake system that ensures the braking process in normal conditions of the vehicle functioning. The brake mechanisms of the working brake system are wheeled brakes. Management of these mechanisms is carried out through pedals.

Parkingthe brake system is designed to hold the car in a stationary state. The brake mechanisms of this system have either on one of the transmission shafts or in wheels. In the latter case, the brake mechanisms of the working brake system are used, but with an additional drive control of the parking brake system. Manual parking brake system management. Parking brake system drive all only mechanical.

Sparethe brake system is used in the failure of the working brake system. Some cars feature a parking brake system or an additional circuit of the working system.

Distinguish the following types of braking : Emergency (emergency), service, braking on slopes.

Emergencybraking is carried out by means of a working brake system with maximum conditions for these conditions intensity. The number of emergency braking is 5 ... 10% of the total number of braking.

Servicebraking is used for a smooth reduction of vehicle velocity or stop in advance

Estimated indicators.

Existing standards GOST 22895-77, GOST 25478-91 are provided by the following brake properties car:

j set - established deceleration with a constant effort on the pedal;

S T - the path passing from the moment of clicking on the pedal to the stop (stopping path);

t cf is the response time - from pressing the pedal before reaching the J mouth. ;

Σ P TOR. - Total brake force.

- specific brake force;

- the coefficient of non-uniformity of the brake forces;

Installed speed on the descent V. T.Ust. when brake brake - retarder;

The maximum slope of H T MAX, on which the car is held by the parking brake;

The slowdown provided by the spare brake system.

The standards for the brake properties of the PBX, prescribed by the standard, are shown in the table. Note Category Note:

M - Passenger: M 1 - passenger car and buses no more than 8 seats, m 2 - buses more than 8 places and a long weight up to 5 tons, m 3 - buses with a complete mass of more than 5 tons;

N - trucks and automobiles: N 1 - with a total weight of up to 3.5 tons, n 2 - over 3.5 tons, N 3 - more than 12 tons;

O - trailers and semi-trailers: O 1 - complete weight of up to 0.75 tons, 2 - complete weight of up to 3.5 tons, 3 - total weight of up to 10 tons, about 4 - full mass of more than 10 tons.

Regulatory (quantitative) values \u200b\u200bof estimated indicators for new (developed) cars are prescribed in accordance with categories.

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