RU2382346C1 - Method of determination of stiffness and nonelastic resistance of automobile tyre and test bench for automobile tyres tests - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: invention refers to vehicle engineering, to tests of automobile tyres in particular. Method of determination of stiffness and nonelastic resistance of automobile tyre is performed as per characteristics of its standard elasticity upon wheel loading by vertical force and curve of free damped oscillations upon over-wheel mass relief. During loading and relief torsion torque is continuously applied to hub of wheel with tested automobile tyre. Test bench for automobile tyres testing contains gimbal-mounted frame, supporting rolling platform, devices for loading of tested tyre by vertical force and torsion torque, strain-gauge hub for measurement of vertical force, sensor of vertical movements and recording equipment. Stepless tyre loading by vertical force as well as load removal is performed by change of moment of inertia test bench frame with respect to its axis of fastening by means of lengthwise movement of load trolley of loading fixture, and wheel loading by torsion torque is performed by electric motor by means of chain drive and back-geared.

EFFECT: determination of stiffness and nonelastic resistance of automobile tyre when loading conditions correspond to actual conditions of its operation and reduction of labour intensity during automobile tyres tests performance.

6 cl, 2 dwg

Description

The invention relates to the field of transport engineering, in particular to the testing of car tires.

A known method of determining the inelastic resistance of car tires according to the curves of free damping vertical oscillations of the wheel mass, which are recorded when it is dumped.

The method can be implemented on a lever-type stand, which is a pivotally mounted frame, the moment of inertia of which is relative to the axis of attachment, and therefore, the vertical load on the tire under test varies with the number of ballast weights. The device for dropping is a lever with which the wheel mass is lifted until the start of the separation of the car tire from the supporting surface and is reset, which causes its free damped vibrations. In turn, free damped oscillations are recorded using a vibrograph and processed. Processing the curve of free decaying vibrations of the wheel mass is reduced to determining the attenuation coefficient. One of the first lever-type stands was developed at MVTU im. Bauman [1].

Currently, for testing tires by the method of dropping, more advanced test benches are used that have pneumatic-hydraulic devices in their construction for lifting and dropping the wheel mass, and vibration is recorded by analog-to-digital converters of electronic computers and electric rechord or laser vertical displacement sensors [2].

However, the disadvantages of existing stands of this type are the stepwise change in the vertical load on the test tire and the high complexity of removing and installing ballast weights.

A known method of determining the coefficients of stiffness and inelastic resistance of car tires according to the characteristics of their normal elasticity, which are recorded during stepless loading of a rotating wheel by normal force [3].

The method can be implemented using the stand [4], the loading device of which is an electromechanical drive, consisting of a gear motor, a pair of bevel gears and a pair of nut-screw. To load a car tire with vertical force, the translational movement of a vertically located screw is converted into rotation of the frame of the stand relative to the axis of the hinge assembly. The vertical load on the test tire is measured using a strain gauge hub [5], and a linear strain gauge of the strain gauge type is also used to measure the vertical movement of the frame, which determines the radial deformation of the tire. To simulate the rolling of the wheel with the tire under test on a flat supporting surface, a platform with small diameter rollers is used, one of which is supplied with torque from the motor shaft.

Despite the versatility of the stand, its disadvantages include the fact that it does not allow you to adjust the vertical load on the test tire steplessly when determining its inelastic resistance, if necessary, by the method of dropping. In addition, the conditions of loading the tire with a torque do not fully correspond to the actual conditions of its operation, especially in the driving mode.

The technical result consists in determining the stiffness and inelastic resistance of a car tire under the conditions of loading the actual conditions of its operation, as well as in reducing the complexity of testing tires.

The technical result is achieved by the fact that in the processes of loading and dropping to the wheel hub with the tested car tire, torque is constantly supplied; stepless loading of the tire by vertical force, as well as unloading, is carried out by changing the moment of inertia of the frame of the stand relative to the axis of its fastening by longitudinal movement of the load carriage of the loading device, and the wheel is loaded with torque using an electric motor through a reduction gear and a chain gear; the loading screw is parallel to the longitudinal axis of the frame of the stand and, depending on the direction of rotation, can move the cargo trolley with cargo plates, equipped with rollers with flanges, along the guides along the frame of the stand; the torque is fed directly by the chain to the sprocket mounted on the flange of the tensometric wheel hub with the tire under test; the strain gauge hub consists of a hub with two flanges, one of which is located on its end and is intended for fastening the drive sprocket of the chain drive, and the other flange is removable, located in the central part of the hub and is used for fastening wheels of various types and sizes; in the central part of the axis with strain gauges, which undergoes the greatest deformation when vertical force is applied to the tire, it has flat surfaces for gluing strain gauges, the electric wires of which are laid in a longitudinal open groove, and also pass through a through hole connecting the opposite flat surfaces of the central part of the axis.

The invention is illustrated by drawings. Figure 1 shows a diagram of a test bench for car tires, and figure 2 - the design of the strain gauge hub for measuring the vertical load on the test tire.

The test bench for automobile tires (Fig. 1) is a pivotally mounted frame 4 mounted on a support 12, to which a tensometric hub 15 is mounted, designed to measure the vertical load on the wheel with the tested car tire 3. The torque to the tensometric hub is supplied from the electric motor- gear 13 through a chain gear. The tension of the chain 14 is adjusted by moving the electric motor-reducer along the frame 4. The test tire is supported by platform 1 with small diameter rollers 2, which allow simulating the rolling of a car tire on a flat surface without sliding. Depending on the size of the tire being tested, the position of the support pad may vary in height.

A stepless change in the moment of inertia of the frame relative to the axis of its attachment and vertical load on the wheel is carried out by longitudinal movement of the load trolley 8, on the studs 7 of which load ballast plates are installed and fixed 6. Changing the number of load plates extends the range of stepless loading of car tires by vertical force. Moving the trolley with cargo plates along the frame of the stand is performed using an electric motor 11, a gearbox 12 and a power pair, which is a lead screw 9 and a nut. To reduce the noise and load on the thread of the screw-nut power pair when moving along the stand frame, the freight trolley has rollers with flanges that do not allow the trolley to move in the transverse direction relative to the frame.

Strain gauge hub (figure 2) consists of a sleeve 10, to the end flange of which is attached an asterisk 6 of a chain gear for loading the test car tire with torque. In addition, for fastening the wheel mover to the hub, there is a flange 4 with holes for bolts or studs for mounting the wheel disk. Installation and fixing of the flange are carried out using a spline connection and a snap ring. The strain gauge hub can rotate on angular contact bearings 3 and 8 mounted on the axis 1. The preload of these bearings is adjusted with special nuts 2 and 7.

Axis 1, on which the strain gauge hub is mounted, in the middle part most susceptible to deformation when the test tire is loaded with vertical load, has flat surfaces A and D for reliable gluing of strain gauges. The signal from the strain gauges 5 and 9, glued to the axis, is fed through the strain gauge to the analog-to-digital converter of the electronic computer. Electric wires (not shown in the drawing) connecting the strain gauge sensors and the strain gauge are laid in a milled longitudinal open groove of the B axis, and also pass through the hole B connecting the opposite flat surfaces A and D under the load cells.

To measure the vertical displacements of the test bench frame and the deformation of the test tire, reochordal or laser type vertical displacement sensors (not shown in the drawings) are used, the signal from which also goes to one of the channels of the analog-to-digital converter of an electronic computer.

Dropping the wheel mass to excite its free damped oscillations is performed in the following order. First of all, the electric motor of the device for loading the test tire with vertical force is launched, as a result of which the cargo trolley moves along the frame of the stand and the moment of inertia of the frame changes relative to the axis of its attachment, and therefore, the vertical load on the wheel changes. The required value of the vertical load on the wheel is controlled using a strain gauge hub on the computer screen. After turning off the electric motor, the wheel mass is lifted until the beginning of the separation of the test tire from the surface of the rollers of the support platform with the help of a pneumatic-hydraulic lift-ejector with a stop in the stand frame. In this case, the start of separation is controlled by the free rotation of the support rollers. Next, the electric motor of the device for loading the test tire with a torque is launched and the rod of the pneumohydraulic lift-ejector is dropped. Using an electronic computer, the signal from the vertical displacement sensor is recorded in the form of the time dependence of the input voltage on the channel of the analog-to-digital converter.

Registration of the normal elasticity characteristics of a car tire, during the processing of which the coefficient of normal stiffness is determined, is also carried out using a computer and an analog-to-digital converter, one of the channels of which receives voltage from the tensometric hub and the other from the vertical displacement sensor. In this case, first of all, the electric motor of the device for loading the tire with vertical force is also started and by moving the cargo trolley along the frame of the stand, the test tire is completely unloaded, which is controlled on the computer screen and by the free rotation of the rollers of the support platform. Next, the electric motor of the device for loading the tire with a torque is started, and the rotational direction of the rotor of the electric motor of the device for loading the tire with vertical force changes in the direction of increasing load. When the specified value of the vertical load on the tire is reached, which is controlled by the strain gauge hub on the monitor screen, the direction of rotation of the rotor of the electric motor is reversed and the tire is completely unloaded.

Information sources

1. Kolesnikov K.S. Determination of internal losses in a car tire // Automotive and tractor industry. - 1952. - No. 9.

2. The dissertation for the degree of candidate of technical sciences. Improving the smoothness of vehicles by internal suspension of the wheels. V.V. Mazur. - M.: MSTU "MAMI", 2004.

3. Rykov S.P. Methods for modeling and evaluating the absorbing and smoothing ability of pneumatic tires: a Training manual. Ed. 2nd, rev. and add. - Bratsk: BrSU, 2005 .-- 128 p.

4. Patent No. 2199102 (RF). A method of constructing the radial elasticity characteristics of a tire on a rotating wheel and a device for its implementation / Bratsk State Technical University. S.P. Rykov and V.N. Tarasyuk. - Application. 12/25/2000.

5. Copyright certificate No. 1515077 (USSR). Device for measuring forces on the wheel of a vehicle / Bratsk Industrial Institute. S.P. Rykov and V.G. Melentiev. - Application. 01/04/1988.

Claims (6)

1. A method for determining the stiffness and inelastic resistance of a car tire according to the characteristics of its normal elasticity when loading the wheel with vertical force and free damped vibration curves when dropping the wheel mass, characterized in that the torque is constantly supplied to the wheel hub with the tested car tire during loading and dropping . 2. A test bench for automobile tires, which contains a pivotally mounted frame, a support roller platform, devices for loading the test tire with vertical force and torque, containing in its design an electric motor, a reduction gear, a screw-nut pair and load plates , a tensometric hub for measuring vertical load, which has the ability to rotate on bearings mounted on an axis with tensometric sensors, a vertical displacement sensor and a register The apparatus is characterized in that stepless loading of the tire by vertical force, as well as unloading, is carried out by changing the moment of inertia of the frame of the stand relative to the axis of its fastening by longitudinal movement of the load carriage of the loading device, and the wheel is loaded with torque using an electric motor through a reduction gear and chain transmission. 3. A test bench for automobile tires according to claim 2, characterized in that in the device for loading the test tire with vertical force, the screw is parallel to the longitudinal axis of the frame of the stand and, depending on the direction of rotation, can move a cargo trolley with cargo plates equipped with rollers with flanges, along the guides along the frame of the stand. 4. The test bench for automobile tires according to claim 2, characterized in that in the device for loading the test tire with vertical force, the torque is applied by the chain directly to the sprocket mounted on the flange of the tensometric wheel hub with the test tire. 5. A test bench for automobile tires according to claim 2, characterized in that the strain gauge hub consists of a sleeve with two flanges, one of which is located at its end and is designed to mount a drive sprocket for a chain drive, and the other flange is removable, located in the central part bushings and is used for mounting wheels of various types and sizes. 6. A test bench for automobile tires according to claim 2, characterized in that the axis with strain gauges in the central part, which is most subjected to deformation when vertical forces are applied to the tire, has flat surfaces for gluing strain gauges, the electric wires of which are laid in a longitudinal open groove , and also pass through a through hole connecting the opposite flat surfaces of the central part of the axis.

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