Radius wheels of the car. Rolling radius and assessment of the interaction of the wheel of the mobile machine with the road what is the radius of the wheel

For the selection of tires and the definition of the wheel rolling radius, you need to know the load distribution over bridges.

In passenger cars, the load distribution from full mass over bridges depends mainly on the layout. When classical layout on the rear axle accounts for 52 ... 55% of the load from the total mass, for the front-wheel drive vehicles 48%.

RED rolling radius is selected depending on the load on one wheel. The highest load on the wheel is determined by the position of the center of mass of the car, which is installed by the preliminary sketch or prototype of the car.

G2 \u003d Ga * 48% \u003d 14000 * 48% \u003d 6720n

G1 \u003d ga * 52% \u003d 14000 * 52% \u003d 7280

Consequently, the load on each wheel of the front and rear axle of the car can be determined according to the formulas:

P1 \u003d 7280/2 \u003d 3360

P2 \u003d 6720/2 \u003d 3640

The distance from the front axle to the center of the masses by the formula:

L-base of the car, mm.

a \u003d (6720 * 2.46) / 14000 \u003d 1.18m.

Distance from center of mass to rear axle:

b \u003d 2.46-1.18 \u003d 1.27m

Tier Type (on the Table of Gostov) - 165-13 / 6.45-13. For these sizes, you can determine the radius of the wheel in a free state:

Where b-width of the tire profile (165 mm)

d - Tire rim diameter (13 inches)

1Dype \u003d 25.4mm

rc \u003d 13 * 25.4 / 2 + 165 \u003d 330 mm

The rolling radius of the RK wheel is determined taking into account deformation depending on the load:

rk \u003d 0.5 * d + (1-k) * b (9)

where k is the coefficient of radial deformation. For standard and wide-profile tires k take 0.3

rk \u003d 0.5 * 330 + (1-0.3) * 165 \u003d 280mm \u003d 0.28m

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P e t r o z a in about d with to and y

STATE UNIVERSITY

Forest larger faculty

Department "Traction Machines"

Forest machines

(Lecture Abstract. Part 2)

This abstract of lectures does not pretend to complete the outlined material, so it is necessary to use recommended literature to fully study individual issues (every question is considered in detail in the process of auditing classes).

In the outflow, the appointment and place of forest (mobile) machines in the logging and tracked machinery, the total and loading dynamics of the wheeled and tracked machines (traction balance of cars and tractors, travelers - high-speed characteristics and power balance, permeability, stability and total dynamics of forest vehicles are presented.) Types of transmissions, their device and the principle of operation (dignity and disadvantages), the requirements for them are considered; Elements of mechanical and hydraulic transmissions (clutches, gearboxes, dispensing boxes, cardan and main transmissions, Differential and its kinematics and static transfers, the mechanisms of rotation of tracked machines, the basis of the theory of rotation of tracked (splitting) machines, the definition of the main parameters of rotation and brake systems, Elements of the steering, installation of controlled wheels, etc., Schemes of hydromeflip and hydrotransformer, their characteristics).

In conclusion, brief information about the running systems of the wheeled vehicles, the pendants of the wheeled and tracked machines are given.

The abstract can be used when learning the following disciplines:

"Theory and design of the wheeled and tracked machines",

"Mobile Machine Transmissions",

"Transmissions and forest management mechanisms",

"Forestry vehicles",

"Forestry machines"

and it can be useful to students and graduate students engaged in the traction calculations of the wheeled and tracked machines during courses and thesis design, the study of traction - coupling qualities, the foundations of the theory of rotation, etc. Forest and general purpose machines.

Abstract Designed by Professor of the Department "Traction Machines"

M. I. Kulikov

Introduction

The leading place in the mechanization of timber industrial works is becoming increasingly more and more place. Forest machines - machines used in the forest industry for the transportation of the forest, which includes daving (trivide) and exporting forests (wheeled and tracked tractors, timber trucks, etc.). The base for most forest cars serve cars and general-purpose tractors (ZIL, MAZ, Urals, KAMAZ, KRAZ, T-130, MTZ-82, etc.). A number of requirements are presented to forest machines, the main of which are:

1. The design of the machine design of the operating conditions and ensuring high-performance work.

2. High-skate dynamic qualities, high permeability, good adhesion of the propeller with soil, high maneuverability, good adaptability for operation in various climatic conditions, etc.

3. The design of the design, which gives the opportunity to upgrade the initial basic model for a long time.

4. High reliability and wear resistance of parts, nodes and units, their unification.

5. High efficiency is the minimum cost of fuel, spare parts, maintenance, and so on.

In addition, additional requirements are presented to forestry vehicles: an increase in the flight load, an increase in the speed of movement and improved passability.

The fulfillment of these requirements is usually achieved by an increase in the power of the engine per ton of the mass of the road train and an increase in its overall load capacity. From year to year, the capacity of automotive engines and carrying capacity of road trains increase (ZIL-131-110 kW-12.0 T; MAZ-509-132 kW-17.0 t; KRAZ-255 - 176 kW-23.0 t; KRAZ-260-220 kW-29 , 0 t).

Improving transmission and running systems play a leading role in an increase in the average velocity of the vehicle and increase its passability. Forest trouts are made by special tractors - the trilateral, transporting wood in a semi-loaded position. In recent years, there has been intensive development of new designs of special machines.

For the first time, skiing tractors were created in the USSR - 1946. GOnt the main in the forest work, tracked cars are used, having better permeables than wheeled (most logging are produced in areas with a small carrier capacity of soils). However, the advantages of the wheel propulsion are high speeds of movement, smoothness, etc. Forced constructors to go along the way of developing new wheeled machines with increased patency (TLK-4, TLK-6, SHL and other).

Improving the performance and traction and coupling qualities of caterpillar tractors is achieved by increasing the carrying capacity and power of the engines.

Engine torque transmission leading

Wheels of the forest machine. Efficiency of transmission

In modern cars and tractors, both foreign and domestic tractors, internal combustion engines are used, in the development of which there has been a tendency to increase their high-speed. This leads to their compactness and low weight. However, on the other hand, this leads to the fact that the torque on the shaft of these engines is significantly less than the moment that must be supplied to the driving wheel of the machine, despite the relatively greater power of these engines. Consequently, to obtain on the drive wheels the required torque of torque, the system is needed to the system - "Engine - drive wheels", enter an optional device that provides not only the transmission of the engine moment, but also its increase. The role of this device on modern cars and tractors performs transmission. The transmission includes a number of mechanisms: clutch, gearbox, cardanny, main, final (boring) transmission, turning mechanisms, and additional gearboxes (dispensing boxes) that set a constant gear ratio. The moment of the engine is transmitted by the gearbox by couplings of the clutch. On modern machines, friction clutches of clutches received the main distribution. The ratio of the moment of friction of the coupling M M to the nominal moment of the engine is called the coefficient of the reserve of the clutch of the clutch β:

β \u003d m / m (1)

The magnitude of this coefficient varies in a wide range (1.5 - 3.8) for trucks and tractors and is selected from the conditions of the size of the friction operation during the buxation during the period of overclocking the tractor unit, as well as protection from breakdowns of engine parts and transmission with possible overloads.

When choosing a coefficient β, a possible change in the friction coefficient of the coupling discs is also taken into account, reduce the pressure of the springs due to wear of the friction surfaces, etc. From the clutch of the clutch torque through the gearbox and other transmission elements are transmitted by the drive wheels. In the absence of a bucking between the leading and driven discs, the clutch of the clutch (Δ hrap \u003d 0) the gear ratio of the transmission is generally determined by: I TR \u003d Ω E / Ω K \u003d N E / N K, (2)

where ω e and n e is the angular velocity and the speed of the engine crankshaft;

ω to and n k - respectively angular speed and speed of rotation of the drives.

Equality (2) can be represented as:

i TR \u003d I K ∙ I RK ∙ I GL ∙ II KP \u003d I K ∙ I RK ∙ I O, (2)

where I K is the gear ratio of the gearbox;

i RK - gear ratio of the dispensing box;

i ch - gear ratio of the main (central) transmission;

i. - gear ratio of the mechanism of rotation;

i KP - the gear ratio of the final (on-board) transmission;

i on-proper gear ratio carried out in the main, turning mechanism, and finite transmissions, as well as in other transmission gearboxes.

Torque on the driving wheels of the machine is determined:

M k \u003d m ∙ i tr ∙ η tr, (3)

η Tr - transmission efficiency, which is determined from the ratio:

η Tr \u003d n k / n e \u003d (n e - n tr) / n e \u003d 1- (n tr / n e), (4)

where n k is the power supplied to the driving wheels;

N Tr - power lost in transmission.

The efficiency of the transmission η tru takes into account the mechanical losses that take place in bearings, gear pairing gearbox, central and end transmission and loss when scattering oil. The efficiency of the transmission is usually determined experimentally. It depends on the type of transmission design, the quality of manufacture and its assembly, on the degree of loading, oil viscosity, etc. The efficiency of modern automotive and tractor transmissions at rated mode of operation is in the range of 0.8..0.93 and depends on the number of pairs of gears included sequentially η Kp \u003d 0.97..0.98; η c.p. \u003d 0.975..0.990.

In accordance with this, the value of η tr approximately can be counted:

η Tr \u003d η C.P. ∙ η. KP (4)

Excluding losses at idling:

η HOT \u003d 1-M HYD / ME, (5)

where M hol is the moment of resistance in the primary transmission shaft, occurring at idle transmission scrolling.

m. c, m. to - The number of pairs of the cylindrical and conical gears accordingly.

Rolling Radius Wheel

The car (tractor) is moving as a result of a different forces on it, which are divided into driving forces and resistance forces to movement. The main driving force is the thrust force attached to the drive wheels. The thrust force arises as a result of the engine operation and is caused by the interaction of leading wheels with the road. The traction force P K is defined as the ratio of the torque on the semi-axes to the radius of the leading wheels with the uniform movement of the car. Consequently, to determine the traction force you need to know the magnitude of the radius of the drive wheel. Since elastic pneumatic tires are installed on the wheels of the car, then the magnitude of the wheel radius during movement changes. In this regard, the following wheel radios distinguish:

1. Nonal - wheel radius in free state: R n \u003d d / 2 + h, (6)

where D is the diameter of the rim (landing diameter of the tire), m;

H - complete tire profile height, m.

2. Static R C is the distance from the road surface to the axis of the loaded stationary wheel.

r c \u003d (d / 2 + h) ∙ λ, (7)

where the λ-coefficient of the tire radial deformation.

3. Dynamic R D is distround from the surface of the road to the axis of a rolling grower of the feminine wheel. This radius increases with a decrease in the perceived load with the wheel G to and an increase in the internal pressure of the air in the tire P sh.

With an increase in the velocity of the vehicle under the action of centrifugal forces, the tire is stretched in the radial direction, as a result of which the radius R D increases. When rolling the wheel, the deformation of the rolling surface is changed in comparison with a fixed wheel. Therefore, the shoulder of the application of the equal tangent reactions of the road R D differs from R s. However, as experiments showed, for practical traction calculations, it is possible to take R C ~ R.

The kinematic radius (rolling) of the wheel R to is the radius of such a conditional non-deforming ring, which has the same angular and linear speed with this elastic wheel.

The wheel rolling under the action of torque, the elements of the tread entering in contact with the road, compressed, and the wheel with equal frequencies of rotation passes a smaller way than during free rolling; In the wheel, loaded by the braking torque, the tread elements included in contact with the road, stretched. Therefore, the braking wheel passes with equal speed numbers a slightly larger way than a freely rolling wheel. Thus, under the action of torque, the radius R to - decreases, and under the action of the braking torque increases. To determine the value of R to the "chalk fingerprint" method on the road with chalk or paint, a cross line is applied to which the wheel of the car rolls, and then leaves prints on the road.

Measuring the distance l. Between extreme fingerprints, the rolling radius is determined by the formula: R K \u003d l. / 2π ∙ n, (8)

where n is the wheel rotation frequency corresponding to the distance l. .

In the case of a complete wheel bounce distance l. \u003d 0 and radius R k \u003d 0. During slipping of non-rotating wheels ("UZ"), the speed of rotation n \u003d 0 and r to
.

Some things are swearing and difficult to remember, but you need to know. Especially motorists. Especially considering themselves specialists and having their own opinions on any occasion. The devil lies in the trifles, and just about one such little thing this article.

There is no radius tire

Many now do not even understand what I am a clone. "Well, radius, and what? I have the wheels 195-65R15, the radius 15, all the way it is written, what are you smarting?! " That's what I am smart. R15 has no relation to the radius. Neither R nor 15.

Now on the Internet you can find a lot of information, only such trifles, as the marking of automotive tires, do not relate to the most popular. We better concerned the engine power or the number of "buns" in the cabin, right? And the choice of wheels will leave the manager in the store. Well, or a friend will ask. He is exactly in the know! He has a third car!

In fact, to understand these boring figures does not interfere with even just for general development. Moreover, it will save it and will affect the behavior of the car, but about it later. So far, clean leafs, in order, then it was possible to understand each other well.

So, 195/65R15. Classic case. Tree squatting near your car. The first digit is the width of the tire of the tire, roughly speaking, the tread width. It is expressed in millimeters. That is 195 mm. - This is the width of your wheel. With the understanding of this figure, most problems have no problems.

After fraction 65 is the magnitude of the profile. It is expressed as a percentage of width. Not in millimeters! The profile is part of the tire, "sticking over the disk." Side. That is, the height of this sidewall will be 195x65% \u003d 125.75 mm. And not 65 mm. And not something else. Moreover, from this scheme unambiguously follows that the height of 65% with a width of 195 will be one, and if the tire with marking (conditional) 225 / 65R15 is already completely different! 225x65% \u003d 146.25 mm. Although the numbers 65 are the same!

R is the radial tire design, or rather, the method of laying metal cord inside it. Sometime of the tire design assumed a diagonal laying, but it was a long time ago. Now the "diagonal" tires will almost not meet, everything is completely radial, and the letter r nobody will not know anything new, only disputes about the notorious radius will cause ...

And finally, the number 15. This is a diameter. The diameter of the planting part of the tire, the inner diameter, the part that is in contact with the disk. It is expressed in inches. 1 inch \u003d 2.54 cm. That is, 15x2.54 \u003d 38.1 cm is also the outer diameter of the disk, if anyone did not guessed ...

What tires can be put, and what you can not?

And then the most interesting begins. We can play with these numbers if we want to put on the car other tires (discs). Ideally, the main thing is that the total diameter does not differ, or differ slightly. Example.

The wheel 195/65R15 has such a common diameter: 38.1 cm - inside, plus 125.75 mm x2 \u003d 251.5 mm (the profile is on top, and there is a bottom). We translate into centimeters for simplicity, it turns out 38.1 cm + 25.15 cm \u003d 63.25 cm. That's how! This is the diameter of the wheel in the amount.

Now, if you wish, put other wheels the car owner must understand the following: the car producers understand the same way as we. Considering the wheel diameter, the suspension is designed, the brake system and body. Therefore, for the same car model (for example, for the Volkswagen Polo sedan), three dimensions of the wheels are officially allowed. The simplest version is content with 175/70R14 (total diameter 60.06 cm), 185/60R15 (60.3 cm) and 195 / 55R15 (59.55 cm).

It turns out that the "wheel on 14" is greater, albeit slightly than the wheel of 15 in the case of 195/55. This is the question touched above, that for the winter wheels to deliver more ... you need to carefully calculate. Will a large diameter digit mean and larger wheel size as a whole? Not always.

The car (tractor) is moving as a result of a different forces on it, which are divided into driving forces and resistance forces to movement. The main driving force is the thrust force attached to the drive wheels. The thrust force arises as a result of the engine operation and is caused by the interaction of leading wheels with the road. The traction force P k is defined as the point of mind on the semi-axes to the radius of the leading wheels with the uniform movement of the car. Consequently, to determine the traction force you need to know the magnitude of the radius of the drive wheel. Since elastic pneumatic tires are installed on the wheels of the car, then the magnitude of the wheel radius during movement changes. In this regard, the following wheel radios distinguish:

1. Nonal - wheel radius in free state: R n \u003d d / 2 + h, (6)

where D is the diameter of the rim, m;

H - complete tire profile height, m.

2. Static R C is the distance from the road surface to the axis of the loaded stationary wheel.

r c \u003d (d / 2 + h) ∙ λ, (7)

where the λ-coefficient of the tire radial deformation.

4 Kinematic radius (rolling) wheels R to - the radius of such a conditional non-deforming ring, which has the same angular and linear speed with this elastic wheel.

Measuring the distance l. Between extreme fingerprints, the rolling radius is determined by the formula: R K \u003d l. / 2π ∙ n, (8)

where n is the wheel rotation frequency, respective distance l. .

In the case of a complete wheel bounce distance l. \u003d 0 and radius R k \u003d 0. During the slide of the unwilling wheels ("UZ"), the speed of rotation n \u003d 0 and R to.

In the general case, the car wheel consists of rigid rim, elastic sidewalls and contact printing. The tire's contact comfrequency is the elements of the tires in contact with the support surface during the time consideration. Its shape and dimensions depend on the type of tire, load on the tire, air pressure, the deformation properties of the supporting surface and its profile.

Depending on the ratio of the deformations of the wheel and the reference surface, the following types of movement are possible:

Elastic wheel on the non-deformable surface (movement of the wheel on the road with a solid coating);

Hardwheel on the deformable surface (movement of the wheel on loose snow);

The deformable wheel according to the deformable surface (the movement of the wheel on the deformable soil, loose snow with reduced air pressure).

Depending on the trajectory there are straight and curvilinear movements. Note that the resistance of the curvilinear movement exceeds the resistance to the straight line. This is especially true for three-axle cars with a balancing rear trolley. So, when moving a three-axis car along a trajectory with a minimum radius on a high clutch road, traces of tires remain, from the exhaust pipe goes black smoke, the fuel consumption increases dramatically. All this is a consequence of the increase in resistance to curvilinear movement several times compared with straightforward.

Below, we consider the radii of the elastic wheel for a private case, with the straight-line movement of the wheel on the non-deformable reference surface.

There are four radius of the automotive wheel:

1) free; 2) static; 3) dynamic; 4) Radius of rolling wheel.

Free Radius Wheel - characterizes the size of the wheel in unloaded under the rated pressure of the air in the tire. This radius is equal to half the outer diameter of the wheel.

r c \u003d 0.5 D n ,

where r C. - free radius of the wheel in m;

D N. - The outer diameter of the wheel in M, which is determined experimentally in the absence of a wheel contact with an expensive and nominal air pressure in the bus.

In practice, this radius is used by the designer to determine the overall dimensions of the car, the gaps between the wheels and the body of the car during its kinematics.

Static radius of the wheel - the distance from the supporting surface to the axis of rotation of the wheel in place. Determined experimentally or calculated by the formula

r ct \u003d 0.5 d + l z h,

where r T. - static radius of the wheel in m;

d. - landing diameter of wheel rim in m;

l Z.- The vertical deformation coefficient of the tire. Accepted for toroid tires L z \u003d 0.85 ... 0.87; For tires adjustable pressure l Z.=0,8…0,85;

H is the height of the tire profile in m.

Dynamic wheel radiusr D. - the distance from the support surface to the axis of rotation of the wheel while driving. When the wheel moves along a solid support surface at a low speed in the slave is received

r CT »R D .

Round rolling radius R k is the path passing by the center of the wheel, when it is turned to one radian. Determined by the formula

r K. = ,

where S. - the path passing by the wheel in one turn in m.;

2p - the number of radians in one turn.

When rolling the wheel on it can act torque M kr and brakes M. T moments. In this case, the torque reduces rolling radius, and the brake increases.

When the wheel moves through, when there is a path and there is no rotation of the wheel, rolling radius tends to infinity. If it occurs in place, then the rolling radius is zero. Consequently, the rolling radius of the wheel varies from zero to infinity.

The experimental dependence of the rolling radius from the attached moments is presented in Fig.3.1. On the chart, lay out five characteristic points: 1,2,3,4,5.

Point 1 - corresponds to the movement of the wheel by the SMA when the braking torque is applied. Round radius at this point tends to infinity. The point 5 - corresponds to the wheel bounce in place when the torque is applied. Rolling radius at this point approaches zero.

Plot 2-3-4 - is conditionally densely, and point 3 corresponds to the radius r Co. When rolling the wheel in the slave mode.

Fig.3.1. Dependence r k \u003d f (m).

Radius of the wheel in this linear section is determined by the formula

r K \u003d R Co ± L T. M,

where l. T - the coefficient of tangential tire elasticity;

M. - attached to the wheel moment in N.M.

The "+" sign is to take if a braking moment is applied to the wheel, and the "-" sign - if the torque.

In areas 1-2 and 4-5 there are no dependences to determine the rolling radius of the wheel.

For the convenience of presenting the material in the future, we introduce the concept of "Radius of the Wheel" R K. , having in mind the following: if the kinematics of the car (path, speed, acceleration) are determined, then under the radius of the wheel it is understood as the rolling radius of the wheel; If the speaker parameters are defined (force, moment), then under this radius is a dynamic radius of the wheel r D. . Taking into account the continued dynamic radius and rolling radius will be marked r K. ,