JPH0750002B2 - Sliding friction force measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an apparatus for measuring a sliding friction force generated between an automobile tire and a road surface,
In particular, the present invention relates to a sliding frictional force measuring device capable of performing a simple measurement and imparting a wheel alignment (tire attitude angle) to the measurement wheel under the same conditions as when the vehicle is attached to the measurement wheel.

[0002]

2. Description of the Related Art In recent years, high performance tires, particularly tires having a high anti-slip effect, have been demanded due to higher performance of automobiles and prohibition of use of spiked tires.
There is an increasing need to perform tire performance evaluation strictly and promptly.

By the way, as a sliding frictional force measuring device for a tire, a device having the principle schematically shown in FIG. 8 is conventionally known. In this device, the measurement wheel 1 is attached to the lower end of the support member 35, and the upper end of the support member 35 is rotatably supported by a fulcrum 36.
Reference numeral 5 is provided with a telescopic portion 35a so that it can follow the vertical displacement of the measurement wheel 1 due to the unevenness of the road surface G. The driving force or braking force is applied to the measurement wheel 1 by a driving braking device (not shown). A horizontal load detector 34 is provided near the center of the support member 35 in the length direction. When this device is used, the device is mounted so that the upper part of the device is exposed on the floor surface of the vehicle by penetrating the floor surface between the front and rear wheels of a vehicle (not shown) such as a truck. Then, while the trolley is traveling with the measurement wheel 1 grounded on the road surface G, a driving force or a braking force is applied to the drive braking device to generate a frictional force F between the measurement wheel 1 and the road surface G, so that the horizontal movement occurs. The magnitude of the sliding friction force F is indirectly obtained from the reaction force Fa detected by the load detector 34 and the ratio of the lengths of K and L. Specifically, a balance formula of the moment around the fulcrum 36, F =-(K / L) · Fa
Thus, the frictional force F can be obtained. Note that W is a ground reaction force that the measurement wheel 1 receives from the road surface G.

[0004]

However, in the above-mentioned sliding friction measuring device, since the sliding friction force F is obtained by using the ratio of the lengths of K and L, the measuring wheel 1 is measured according to the unevenness of the road surface. When the elastic part 35a is vertically displaced and the elastic part 35a expands and contracts to change the length of L, the magnitude of the reaction force Fa detected by the horizontal load detector 34 changes even if the sliding friction force F is constant. Therefore, in order to obtain F from Fa, it is necessary to constantly measure the length of L and make a correction according to the change, and there is a problem that a complicated correction calculation is required. Furthermore, since the device described above is not provided with means for adjusting the wheel alignment of the measuring wheel,
Even if the sliding frictional force of the tire is measured by this device, there is a problem that a large error occurs as compared with the value when the same tire is attached to an automobile. Then, in order to avoid these problems, there is a problem that there is no method other than the subjective judgment of the test driver when actually mounting the tires on the automobile and evaluating the sliding friction force.

[0005]

In order to solve the above problems, in the sliding frictional force measuring device of the present invention according to claim 1, a measuring wheel, and a supporting member for supporting the measuring wheel,
Driving braking means for applying a driving force or braking force to the measuring wheel, and a horizontal load detector for measuring a horizontal load applied to the support member when the driving force or braking force is applied to the measuring wheel by the driving braking means. In the measuring device for measuring the sliding frictional force of the measuring wheel, the horizontal load detectors are provided at two positions above and below the supporting member. Further, in the sliding frictional force measuring device of the present invention according to claim 2, in the sliding frictional force measuring device according to claim 1, means for adjusting a kingpin angle of a measuring wheel, means for adjusting a kingpin offset amount, Means for adjusting the caster angle, means for adjusting the camber angle,
And a means for adjusting the rudder angle are provided.

[0006]

In the sliding frictional force measuring device of the present invention having the above-mentioned structure, when the driving force or the braking force is gradually applied by the driving braking means while the measuring wheel is traveling while being in contact with the road surface, the measuring wheel and the road surface are A frictional force is generated on the contact surface of. Then, this frictional force increases in proportion to the magnitude of the driving force or the braking force, but when it exceeds a predetermined limit value, that is, the maximum frictional force value determined by the friction coefficient between the road surface and the measurement wheel, the measurement wheel slips. In this state, it comes into contact with the ground and a sliding friction force of a magnitude smaller than the maximum friction force is activated. Then, these frictional forces are detected by horizontal load detectors provided at two upper and lower positions as forces acting on the supporting member. In more detail, focusing on the forces acting on various parts of the device, and summing the components of the force in the horizontal direction, the resultant force is zero. Specifically, the forces acting on the load detectors at two locations. Since the total force between the force acting on the wheel and the force acting on the wheel becomes zero, conversely, the magnitude of the frictional force acting on the wheel can be known by obtaining the difference between the detected loads of the load detectors at two locations. In the invention according to claim 2, the adjustment means is provided to adjust the wheel alignment of the measurement wheel to enable measurement under the same measurement conditions as when the vehicle is mounted.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sliding friction force measuring device according to the present invention will be described below with reference to the accompanying drawings. 1 is a front view of the embodiment, FIG. 2 is a side view, FIG. 3 is a sectional view taken along line AA of FIG. 1, and FIG. 4 is a sectional view taken along line BB of FIG. As shown in the figure, in this device, a measurement wheel 1 is attached to an axle 2, and the axle 2 is rotatably supported by a bearing box 3. Then, the transmission shaft 4 extending from the axle 2.
A drive braking device 5 as drive braking means is provided at the tip of the. The bearing box 3 is pivotally attached to a support 7 via a pin 6, and a hydraulic cylinder 8 is provided between the support 7 and the bearing box 3, and when the hydraulic cylinder 8 is extended / contracted, the measurement wheel 1 and the axle are rotated. 2 is tilted integrally around the pin 6. And the support 7 is 2
It is attached to the support tool 10 through parallel screws 9 of a book, and when the screws 9 and 9 are rotated, the connecting position of both can be changed. The support tool 10 is fixed to the lower end of the piston rod 11 of the air cylinder 12, and adjusts the air pressure inside the air cylinder 12 to apply a grounding force to the measurement wheel 1.

Next, the upper end of the piston rod 11 will be described. The piston rod 11 projects above the air cylinder 12, and a pinion 15 is slidably fitted to the upper end of the piston rod 11 via a key 14. Moreover, the pinion 15 is constantly moved by the movement preventing tool 16 to the air cylinder 1
2 is held at a predetermined position on the upper end surface. Therefore, even if the piston rod 11 moves up and down, the pinion 15 always meshes with the rack 17 at a fixed position. Further, since the rack 17 is reciprocally driven by the piston rod 19 of the hydraulic cylinder 20,
The rack 17 is driven by operating the hydraulic cylinder 20.
The piston rod 11 can be rotated via the pinion 15 and the key 14. In this way
The direction of the measuring wheel 1, that is, the steering angle can be changed. A steering load detector 18 is interposed between the rack 17 and the piston rod 19 so that the steering force can be measured.

Next, the support structure of the air cylinder 12 will be described. The air cylinder 12 is supported by a carriage (not shown) by an upper support structure U and a lower support structure D. First, the upper support structure U will be described. The support ring 22 is tiltably attached to the upper outer surface of the air cylinder 12 by the pins 21 and 21a, and further, the attachment positions of the pins 21 and 21a on the side surfaces of the support ring 22. Pins 23 and 23a are fixed to the position orthogonal to. And
These pins 23, 23a are pivotally supported by fixtures 25, 25a, and the fixture 25 is fixed to a pedestal (not shown) on the trolley via a load detector 24. Therefore, the air cylinder 12 is supported so as to be tiltable in all directions, and the force acting on the air cylinder 12 can be measured by the horizontal load detector 24. In addition to the horizontal load, a vertical load (such as a ground reaction force of the measuring wheel 1) acts on the horizontal load detector 24. However, the horizontal load detector 24 is a so-called three-component force sensor, It is possible to independently detect the force (front-back / left-right direction) and the vertical force (up-down direction).

Next, the lower support structure D will be described. A ring 26 is slidably inserted into the lower portion of the air cylinder 12, and the ring 26 is provided with an inner support ring 28, an outer support ring 30, and a hydraulic cylinder. It is supported on the carriage via 31, 31a and the like. That is, the ring 26 has a support inner ring 2
8 is tiltably attached via the pins 27, 27a, and pins 29, 29a are fixed to the support inner ring 28 at positions orthogonal to the attachment positions of the pins 27, 27a. It is pivotally attached to the support outer ring 30. Cylinder rods of hydraulic cylinders 31 and 31a are fixed to the support outer ring 30 in directions orthogonal to each other.
The hydraulic cylinders 31 and 31a are horizontal load detectors 32,
It is attached to the carriage via 32a and sliders 33, 33a.

When the sliding frictional force of the tire is measured using this embodiment, each part of the device is adjusted prior to the measurement,
The wheel alignment of the measuring wheel 1 is set to be the same as when the vehicle is mounted. The setting method will be described with reference to FIGS. 5 is a front view showing a state where wheel alignment is set in the embodiment, FIG. 6 is a side view of the same, and FIG. 7 is a view showing a steering angle. First, the kingpin inclination angle (α) is adjusted by expanding and contracting the hydraulic cylinder 31. Next, the camber angle (β) is adjusted by expanding and contracting the hydraulic cylinder 8. Next, the kingpin offset amount (ε) is adjusted by rotating the screw 9 to change the connecting position of the support tool 7 and the support tool 10. Further, the caster angle (δ) is adjusted by expanding and contracting the hydraulic cylinder 31a. When adjusting the steering angle (θ), the hydraulic cylinder 20
The rack 17 is moved by expanding and contracting to rotate the pinion 15 and the piston rod 11.

Next, the operation of this embodiment will be described with reference to FIG. In the figure, L is the distance from the fulcrum position of the upper support structure U to the road surface G, K is the distance between the fulcrums of the upper support structure U and the lower support structure D, and F is the friction that the measurement wheel 1 receives from the road surface G. Force, Fta is the horizontal load detector 32
The horizontal load detected by a, Ftb is the component force in the front-rear direction of the horizontal load detected by the horizontal load detectors 24, 24a, and W is the ground reaction force that the measurement wheel 1 receives from the road surface G. It is assumed that the entire apparatus is mounted on a bogie (not shown) and is moving to the right in the figure. As shown in the figure, when the driving force or the braking force is gradually applied by the driving braking means while the measuring wheel 1 is traveling to the right in the state where it is grounded on the road surface G, friction is caused on the contact surface of the measuring wheel 1 with the road surface G. Force F is generated. The frictional force F increases in proportion to the magnitude of the driving force or the braking force. However, when the frictional force F exceeds a predetermined maximum value, that is, the maximum frictional force value determined by the friction coefficient between the road surface G and the measurement wheel 1, the measurement is performed. The wheel 1 comes into contact with the ground in a slipping state, and a sliding frictional force having a magnitude smaller than the maximum frictional force is activated. These frictional forces are detected by horizontal load detectors 24, 24a, and 32a provided at two upper and lower locations as forces acting on the air cylinder 12 via the support 7, the support 10, the piston rod 11, and the like.

The relational expression between the loads Fta and Ftb detected by the horizontal load detector and the frictional force F is as follows. (The positive and negative signs of the force are positive in the left direction in the figure.) From the balance condition of the moment with the upper support structure U as the center, L · F = −K · Fta (1) Lower part From the balance condition of moment around the support structure D, (L−K) · F = K · Ftb ··· (2) From the equation (1), Substituting this into equation (2), Therefore, F = − (Fta + Ftb) As described above, regardless of the change of L, Fta
F can be obtained from the resultant force of Ftb and Ftb. Specifically, Fta is the horizontal load detected by the horizontal load detector 32a, and Ftb is the horizontal load detectors 24, 2
It is a horizontal load detected by 4a, which act in opposite directions to each other. Therefore, F can be known by obtaining the difference in size between Fta and Ftb. In the above description, of the frictional force acting on the measurement wheel, the component in the traveling direction of the truck is obtained, but in the same manner, the magnitude of the lateral frictional force of the truck can be obtained. .

The present invention is not limited to the above-mentioned embodiment, but may have a structure similar to that of a strut suspension in which a coil spring is used instead of an air cylinder to provide a grounding force. Further, the hydraulic cylinder used for adjusting each angle of the wheel alignment may be replaced with a mechanism that expands and contracts with a ball screw or the like, and more simply, a structure may be used in which the screw is tightened and fixed at a predetermined angle.

[0015]

As described above, according to the present invention, since the upper and lower horizontal load detectors are provided, it is not necessary to correct the measurement value even if the measurement wheel is vertically displaced due to the unevenness of the road surface. It is possible to always measure the sliding friction force by the difference between the magnitudes of the detected loads of the two horizontal load detectors, and it is possible to simply and quickly measure the sliding friction force. Furthermore, since the same alignment angle as when mounting the vehicle can be added to the measurement wheel,
This has the effect of enabling accurate measurement of sliding frictional force under the same conditions as actual vehicle measurements.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of a sliding frictional force measuring device according to the present invention.

FIG. 2 is a side view of an embodiment of the sliding frictional force measuring device according to the present invention.

3 is a plan view of an upper support structure portion taken along a line AA in FIG. 1. FIG.

FIG. 4 is a plan view of a lower support structure portion taken along a line BB in FIG.

FIG. 5 is a front view showing a state where wheel alignment is set in the embodiment.

FIG. 6 is a side view showing a state where wheel alignment is set in the embodiment.

FIG. 7 is a plan view for explaining a steering angle.

FIG. 8 is a schematic view showing a conventional sliding friction measuring device.

[Explanation of symbols]

 1 ... Measuring wheel 5 ... Drive braking device (drive braking means) 7 ... Support tool (supporting member) 8 ... Hydraulic cylinder (camber angle adjusting means) 9 ... Screw (Kingpin offset amount adjusting means) 11 ... Piston rod (supporting member) 12 ... Air cylinder (supporting member) 15 ... Pinion (steering angle adjusting means) 17 ... Rack (steering angle) Adjusting means) 20 ... Hydraulic cylinder (steering angle adjusting means) 24, 32 ... Horizontal load detector 31 ... Hydraulic cylinder (king pin angle adjusting means) 31a ... Hydraulic cylinder (caster angle adjusting means) ) Α ・ ・ ・ ・ Kingpin inclination angle β ・ ・ ・ ・ Camber angle δ ・ ・ ・ ・ Caster angle ε ・ ・ ・ ・ Kingpin offset amount θ ・ ・ ・ ・ Rudder angle

Claims (2)

[Claims] 1. A measuring wheel, a support member for supporting the measuring wheel, a driving braking means for applying a driving force or a braking force to the measuring wheel, and a driving force or a braking force for the measuring wheel by the driving braking means. In a sliding frictional force measuring device for a measuring wheel, which comprises a horizontal load detector that measures a horizontal load applied to the support member when a load is applied, the horizontal load detectors are provided at two positions above and below the support member. A sliding friction force measuring device. 2. The sliding friction measuring device according to claim 1, further comprising means for adjusting a kingpin angle of a measuring wheel,
A sliding friction force measuring device comprising: a means for adjusting a kingpin offset amount; a means for adjusting a caster angle; a means for adjusting a camber angle; and a means for adjusting a rudder angle.