JP2002039918A - Method for measuring dynamic characteristics of wheel for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for precisely measuring a dynamic load applied to a vehicle wheel by innovating a conventional problem that the dynamic characteristic of the vehicle wheel cannot have been obtained precisely, because its calculation data from stroke of shock absorber not always gives an accurate result. SOLUTION: A washer-shaped strain sensor 10, generating output expressing receiving load, is arranged between the body frame of a vehicle and a tire. The washer-shaped strain sensor 10 is used during the running of the vehicle, to measure the dynamic load acting on the tire. The horizontal force of the tire, the coefficient thereof, the slip angle of the tire and the steering characteristics thereof are calculated from the measured dynamic load, to calculate the cornering characteristics of the tire of an actual vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring dynamic characteristics of a vehicle wheel.

[0002]

2. Description of the Related Art Conventionally, a damper stroke sensor for measuring a stroke amount of a shock absorber is attached to a shock absorber of a vehicle, and a dynamic load of a wheel is calculated from the measured stroke amount of the shock absorber. 2. Description of the Related Art There is known a method for measuring dynamic characteristics of a vehicle wheel in which the dynamic characteristics of wheels are obtained from a dynamic load.

[0003]

However, there is a problem that the dynamic load of the wheel calculated from the stroke amount of the shock absorber is not always accurate, so that it is difficult to accurately determine the dynamic characteristics of the wheel. On the other hand, a washer-type strain sensor that generates an output indicating the received load is prepared, the washer-type strain sensor is arranged between the vehicle body and the wheels, and the movement of the wheels is performed using the washer-type strain sensor during running of the vehicle. 2. Description of the Related Art A suspension system for a vehicle is known in which a load is measured, and the same load as the measured dynamic load is applied to wheels in a direction opposite to the direction of the dynamic load to absorb vehicle vibration (Japanese Patent Application Laid-Open No. HEI 9-163572). 6-227225).

[0004] Certainly, this suspension measures the dynamic load of the wheels. However, this dynamic load measurement is for absorbing vehicle vibration, not for measuring the dynamic characteristics of wheels. Accordingly, an object of the present invention is to provide a method for measuring the dynamic characteristics of a vehicle wheel, which can accurately measure the dynamic characteristics of the vehicle wheel.

[0005]

According to a first aspect of the present invention, there is provided a washer-type strain sensor for generating an output representing a received load, wherein the washer-type strain sensor is connected to a vehicle body and a wheel. And measuring the dynamic load acting on the wheel using a washer-type strain sensor while the vehicle is running, and determining the dynamic characteristics of the wheel from the measured dynamic load. I have. That is, in the first aspect, the dynamic characteristics of the wheel are obtained from the dynamic load of the wheel measured using the washer-type strain sensor.

According to a second aspect, in the first aspect, a cornering characteristic of the wheel is obtained from the measured dynamic load. According to a third aspect, in the second aspect, the lateral force coefficient of the wheel is obtained from the measured dynamic load. That is, in the third aspect, the lateral force coefficient representing the cornering characteristic of the wheel is obtained.

According to a fourth aspect, in the second aspect, the slip angle of the wheel is determined, and the relationship between the slip angle and the lateral force coefficient is determined. Here, the relationship between the slip angle and the lateral force coefficient indicates the cornering characteristics of the wheel. According to a fifth aspect, in the fourth aspect, the relationship between the slip angle and the lateral force coefficient and the measured dynamic load is determined. Here, the relationship between the slip angle and the lateral force coefficient and the measured dynamic load represents the cornering characteristics of the wheel.

According to a sixth aspect, in the second aspect, the vehicle has a front wheel and a rear wheel, and a slip angle of the front wheel and a slip angle of the rear wheel are obtained, respectively, Seeking steer characteristics. That is, in the sixth aspect, a steering characteristic representing the cornering characteristic of the wheel is required. According to a seventh aspect, in any one of the fourth to sixth aspects, the distance between the center of gravity and the axle, which is the distance between the center of gravity of the vehicle and the axle, is determined from the measured dynamic load. The slip angle is obtained from the distance between the center of gravity and the axle. That is, in the seventh aspect, the distance between the center-of-gravity axles is accurately obtained, and thus the slip angle is accurately obtained.

According to an eighth aspect of the present invention, in the first aspect, the washer-type strain sensor is disposed so that the shock absorber of the vehicle extends through the internal space of the washer-type strain sensor. That is, in the eighth aspect, the space required for disposing the washer-type strain sensor is reduced. According to a ninth aspect, in the eighth aspect, the washer-type strain sensor is arranged between one end of a coil spring concentrically arranged with the shock absorber and a vehicle body or a wheel. That is, in the ninth aspect, the dynamic load acting on the coil spring is input to the washer-type strain sensor and measured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The case where the present invention is applied to a four-wheeled vehicle will be described below. However, the present invention can also be applied to motorcycles, tricycles, and the like. Referring to FIG. 1, reference numeral 1 denotes a shock absorber constituting a suspension device or a shock absorber of an automobile. The shock absorber 1 comprises a telescopic upper part 2 and a lower part 3.
Is provided. The upper part 2 is connected at its upper end to a cross member (not shown) of the vehicle body frame,
The lower part 3 is connected at its lower end to a lower arm (not shown), which is an axle (not shown).
Are connected to the wheels or tires.

An upper sheet 4 and a lower sheet 5 each having a flange shape are fixed to the upper part 2 and the lower part 3, respectively. Between the upper sheet 4 and the lower sheet 5, a sensor assembly 6 and a coil spring 7 in a compressed state are movably inserted with respect to the shock absorber 1 coaxially with the shock absorber 1. The sensor assembly 6 includes an annular first attachment 8 located on the upper seat 4 side, an annular second attachment 9 located on the upper end side of the coil spring 7, and the first and second attachments 8, 9. Annular washer-type strain sensor 10 inserted between
And As can be seen from FIG. 1, it can be seen that the shock absorber 1 is arranged so as to extend through the internal space of the attachments 8, 9 and the washer-type strain sensor 10.

Referring to FIGS. 1 and 2, an annular flat convex surface 8a is formed on the outer peripheral portion of the bottom surface of the first attachment 8, that is, the surface facing the washer-type strain sensor 10, and the remaining central portion is formed. An annular flat concave surface 8b is formed. Similarly, on the top surface of the washer-type strain sensor 10, that is, the surface facing the first attachment 8, an annular flat convex surface 10a is formed on the outer peripheral portion, and the annular flat concave surface 1a is formed on the remaining central portion.
0b is formed. As a result, the first attachment 8
And the washer-type strain sensor 10
a and 10a are in contact with each other. In this way, even if the washer-type strain sensor 10 itself is distorted, the first attachment 8 is connected to the washer-type strain sensor 1.
0, so that measurement errors can be reduced.

On the other hand, the bottom of the washer-type strain sensor 10
That is, an annular flat convex surface 10c is formed at the center of the surface facing the second attachment 9, and an annular flat concave surface 10d is formed at the remaining outer peripheral portion. As a result, the washer-type strain sensor 10 comes into contact with the flat top surface of the second attachment 9 at the annular flat convex surface 10c. When a load acts on the tire, the shock absorber 1 and the coil spring 7 expand and contract according to the load. This load is applied to the washer-type strain sensor 1 via the second attachment 9.
Input to 0. Therefore, the sensor assembly 6 or the washer-type strain sensor 10 is located at a position that receives a load acting on the tire. In this case, the annular flat convex surface 10c of the washer-type strain sensor 10 forms a load input surface. The output of the washer-type strain sensor 10 is output via a cable 10e.

By the way, considering that the coil spring 7 is conventionally inserted between the upper seat 4 and the lower seat 5, in this embodiment, the sensor assembly 6 is inserted between the upper seat 4 and the coil spring 7. Will be. Instead, the coil spring 7 and the lower seat 5
The sensor assembly 6 can be inserted between them. Further, a damper stroke sensor may be attached between the upper seat 4 and the lower seat 5 to measure the amount of expansion and contraction of the shock absorber 1 or the coil spring 7.

FIG. 3 schematically shows an actual vehicle tire dynamic characteristic measuring system 11 according to this embodiment. Referring to FIG. 3, a real vehicle tire dynamic characteristic measuring system 11 includes a data logger 12 for storing input data, a washer-type strain sensor 10, a vehicle speed sensor 13, and a steering angle sensor 1.
4, a lateral G sensor 15, a front and rear G sensor 16, and a yaw angular velocity sensor 17. Each washer-type strain sensor 10
Consists of a so-called load cell, and generates an output voltage representing the load received by the washer-type strain sensor 10. These washer-type strain sensors 10 in the form of the above-described sensor assembly 6 are incorporated in the shock absorbers 1 on the front left, front right, rear left, and rear right of the automobile. The vehicle speed sensor 13 generates an output voltage indicating the vehicle speed of the vehicle, and is mounted inside a brake caliper (not shown) of the vehicle. The steering angle sensor 14 generates an output voltage indicating the steering angle of the vehicle, and is attached to a steering stroke rod (not shown) of the vehicle. The lateral G sensor 15 generates an output voltage representing the lateral acceleration (lateral G) of the vehicle, and the longitudinal G sensor 16 generates the longitudinal acceleration (longitudinal G) of the vehicle.
Generates an output voltage representing Also, the yaw angular velocity sensor 1
7 generates an output voltage representing the yaw angular velocity of the vehicle. The lateral G sensor 15, the front and rear G sensor 16, and the yaw angular velocity sensor 17 are mounted on the center axis of the vehicle and as close as possible to the center of gravity of the vehicle. The output voltages of these sensors are input to the data logger 12 via the corresponding amplifiers 18 and stored at time intervals of, for example, about several tens of ms. The actual vehicle tire dynamic characteristic measuring system 11 is mounted on an automobile, and the data logger 12 is particularly arranged at a portion of the automobile where heat is not generated.

Next, the method for measuring the dynamic characteristics of the actual vehicle tire in this embodiment will be described with reference to the routine for measuring the dynamic characteristics of the actual vehicle tire shown in FIG. Referring to FIG. 4, first, in step 30, the washer-type strain sensor 10 is calibrated before the washer-type strain sensor 10 is attached to a vehicle. That is, the washer-type strain sensor 10
Of the washer-type strain sensor 10 at this time is recorded. This is performed for a plurality of types of loads, for example, ten types of loads, and the relationship between the loads and the output voltage of the washer-type strain sensor 10 is obtained, for example, in the form of a linear regression equation.

In the following step 31, the washer-type strain sensor 10 is offset after the washer-type strain sensor 10 is mounted on a vehicle. That is, each tire is placed on a load meter, and the above-described linear regression equation is offset so that the load obtained from the output of the washer-type strain sensor 10 at this time matches the output of each load meter. Next step 3
In 2, the data is measured. That is, the car actually runs on a predetermined course, for example, a circuit,
At this time, the dynamic load, vehicle speed, steering angle, lateral G, longitudinal G, and yaw angular velocity are measured. Here, these measurement data are mileage from a predetermined starting position of the circuit,
That is, it is stored in association with the traveling position of the automobile on the circuit. These measurement data are compiled each time the car makes a circuit.

In the subsequent step 33, the actual vehicle dynamic characteristics, for example, the actual vehicle tire cornering characteristics are measured using the measurement data thus obtained. The measurement of the actual vehicle tire cornering characteristics can be performed by, for example, an external computer. In this case, the measurement data is taken out from the data logger 12 and transferred to the external computer.

FIG. 5 shows a routine for measuring the tire cornering characteristics of an actual vehicle executed by an external computer.
Referring to FIG. 5, first, in step 40, measurement data to be used for measuring the actual vehicle tire cornering characteristics is selected from the stored measurement data. In the present embodiment, the measurement data for one circuit lap in the lap with the minimum lap time is selected, and the actual vehicle tire cornering characteristics are measured. In this way, all the selected lateral Gs can be regarded as the limit (maximum) lateral G determined by the shape of the course and the like.

In the following step 41, the lateral force is calculated. This lateral force is a force generated in a direction perpendicular to the traveling direction of the tire on the contact surface of the tire when it is assumed that the vehicle is running at the limit lateral G, and is an index representing the actual vehicle tire cornering characteristics. one of. The lateral force is calculated by the following equation. Lateral force = lateral G / static load In the following step 42, a lateral force coefficient (friction coefficient) between the tire and the road surface is calculated by the following equation.

[0021] In Steps 41 and 42, when the lateral force and the lateral force coefficient for one tire are to be obtained, the static load and the dynamic load acting on the corresponding tire are used as the static load and the dynamic load. When the lateral force and the lateral force coefficient for the left and right front tires are to be obtained, the front static load as the static load and the dynamic load, that is, the sum of the static loads acting on the left and right front tires, and the front dynamic load, When the sum of the dynamic loads acting on the front tire is used and the lateral force and lateral force coefficient for the left and right rear tires are to be obtained, the rear static load as the static load and dynamic load, that is, the sum of the static loads acting on the left and right rear tires , And rear dynamic load, that is, the sum of the dynamic loads acting on the left and right rear tires. Furthermore, when the lateral force and the lateral force coefficient for all tires are to be obtained, the total static load as the static load and the dynamic load, that is, the sum of the static loads acting on all the tires, and the total dynamic load, that is, An acting dynamic load is used. As described above, since the lateral G in this case can be regarded as the critical lateral G, the lateral force coefficient calculated in step 42 can be regarded as the critical lateral force coefficient.

In the next step 43, the distance Lf between the front center of gravity and the axle, which is the distance between the center of gravity of the vehicle and the front axle, and the distance Lr between the rear center of gravity, which is the distance between the center of gravity of the vehicle and the rear axle, are as follows. Each is calculated by the formula. Lf = (rear dynamic load / total dynamic load) · wheel base Lr = (front dynamic load / total dynamic load) · wheel base Since the position of the center of gravity of the vehicle varies depending on the running state of the vehicle, it was measured in this manner. If the distance between the center-of-gravity axles is determined using the dynamic load, the center-of-gravity axle distance can be calculated more accurately.

In the following step 44, a front slip angle βf and a rear slip angle βr when the vehicle is assumed to make a steady circular turn are calculated by the following equations. βf = −γ · Lf / V + θ / N βr = γ · Lr / V Here, γ represents the yaw angular velocity, V represents the vehicle speed, θ represents the steering angle, and N represents the steering gear ratio.

In the following step 45, the relationship between the limit lateral force coefficient calculated in step 42, the front slip angle or the rear slip angle calculated in step 44, and the dynamic load is obtained, and output in the form of a graph, for example. Is done. This relationship is one of the indices indicating the actual vehicle tire cornering characteristics. FIG. 6 is an example of a graph showing the relationship between the limiting lateral force coefficient, the front slip angle, and the dynamic load. The way of obtaining this relationship will be briefly described. First, a dynamic load within a predetermined dynamic load range is extracted from the dynamic loads of the left front tire or the right front tire selected in step 40, and this dynamic load is extracted. The limit lateral force coefficient and the front slip angle obtained from the measurement data when the load is obtained are extracted. Next, the extracted critical lateral force coefficient and the front slip angle are plotted so that the dynamic range of the extracted dynamic load is known.

That is, in the example shown in FIG.
f (2.45 ± 0.10 kN), 300 ± 10 kgf
(2.94 ± 0.10 kN), 350 ± 10 kgf
(3.43 ± 0.10 kN), 400 ± 10 kgf
(3.92 ± 0.10 kN), 450 ± 10 kgf
(4.41 ± 0.10 kN), 500 ± 10 kgf
A dynamic load range of (4.90 ± 0.10 kN) is set in advance, and the dynamic loads within these dynamic load ranges and the limit lateral force coefficient and the front slip angle when these dynamic loads are obtained are determined. Is extracted. Next, the critical lateral force coefficient and the front slip angle are plotted using predetermined symbols (□, +, Δ, Δ, ×, ○) for each dynamic load range.

The limiting lateral force coefficient represents a lateral force standardized (dimensionless) by a dynamic load. Therefore, the relationship among the limiting lateral force coefficient, the front slip angle, and the dynamic load (dynamic load range) is as follows. This is one of the indices indicating the actual vehicle tire cornering characteristics including the dependence. By obtaining such a relationship, the dynamic load (dynamic load range) and the slip angle when the standardized lateral force is generated can be easily grasped.

Referring again to FIG. 5, the following step 46
Then, the relationship between the limit lateral force coefficient calculated in step 42 and the front slip angle or the rear slip angle calculated in step 44 is obtained, and output in the form of a graph, for example. This relationship is also one of the indexes indicating the actual vehicle tire cornering characteristics. FIG. 7 is an example of a graph showing the relationship between the limit lateral force coefficient and the front slip angle. The curve in this graph is obtained by approximating each plot in the graph of FIG. In the example shown in FIG. 7, curves representing the relationship between the limit lateral force coefficient and the front slip angle are shown for the two types of tires A and B.

By expressing the tire cornering characteristics with a single curve, the tire cornering characteristics of tires having different specifications can be easily compared. For example, considering that the actual vehicle tire cornering characteristics are more excellent when the slope of the curve near the front slip angle is near zero is larger, the tire B in the example shown in FIG. It can be seen that it has characteristics.

The relationship between the critical lateral force coefficient and the front slip angle or the rear slip angle is obtained for various circuits, and these can be compared. FIG.
FIG. 8 shows an example. In the example shown in FIG. 8, the relationship between the limit lateral force coefficient and the front slip angle is compared for each of the circuits Suzuka, Fuji, and Tokachi. As a result, it is possible to rank the circuits with respect to the limiting lateral force coefficient.

Referring again to FIG. 5, the following step 47
Then, the steering characteristic Δβ is calculated by the following equation. Δβ = (| βf | − | βr |) (βf · βr) / | βf
· Βr | where Δβ> 0 means understeer and Δβ <
If it is 0, it is oversteer.

In the following step 48, the steering characteristic Δβ is output, for example, in the form of a graph. An example of this graph is shown in FIG.
Is shown in In FIG. 9, the vertical axis represents the steering characteristic Δβ, and the horizontal axis represents the traveling distance of the vehicle from the start position. In the example shown in FIG. 9, the steer characteristics Δβ for the two types of tires A and B are shown.
It is shown. When the steering characteristics are represented by a graph as described above, the steering characteristics of tires having different specifications can be easily compared. For example, the steering characteristic Δβ
Considering that the steering stability is better when is a positive value and the absolute value is smaller, the tire B has a better steering stability than the tire A in the example shown in FIG. Understand.

In FIGS. 6 to 9, Corona XIV manufactured by Toyota Motor Corporation is used as the automobile, and a washer-type load cell LCW-CS (for 2 tons) manufactured by Kyowa Dengyo Co., Ltd. is used as the washer-type strain sensor 10. I have. The size of the tires used was 210 / 650R18 for both front and rear, the rim size of each tire was 8.2J × 18, and the air pressure of each tire was 160
kPa.

As described above, in the present embodiment, the relationship between the lateral force, the limit lateral force coefficient and the front slip angle or the rear slip angle and the dynamic load, the relationship between the limit lateral force coefficient and the front slip angle or the rear slip angle, or The actual vehicle tire cornering characteristics are evaluated based on the steering characteristics. However, the actual vehicle tire cornering characteristics may be evaluated using other parameters or relationships.

In the embodiments described above,
A washer-type strain sensor 10 is provided for all tires of an automobile. However, it is also possible to provide a washer-type strain sensor for only the front tire or only the rear tire, for example. In the above-described embodiment, the tire dynamic characteristics of the actual vehicle are measured using the measurement data for one circuit of the circuit. However, it is also possible to measure the actual vehicle tire dynamics using a part of the measurement data of the circuit.

[0035]

As described above, the dynamic characteristics of the vehicle wheel can be accurately measured.

[Brief description of the drawings]

FIG. 1 shows a sensor assembly incorporated in a vehicle suspension.

FIG. 2 is a side view and a top view of a washer-type strain sensor.

FIG. 3 is a schematic diagram of an actual vehicle tire dynamic characteristic measurement system.

FIG. 4 is a flowchart showing an actual vehicle tire dynamic characteristic measurement routine.

FIG. 5 is a flowchart showing an actual vehicle tire cornering characteristic measurement routine.

FIG. 6 is a graph showing an example of a relationship among a limit lateral force coefficient, a front slip angle, and a dynamic load.

FIG. 7 is a graph showing an example of a relationship between a limit lateral force coefficient and a front slip angle.

FIG. 8 is a graph comparing and showing an example of a relationship between a limit lateral force coefficient and a front slip angle.

FIG. 9 is a graph showing an example of a steering characteristic.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Shock absorber 6 ... Sensor assembly 7 ... Coil spring 10 ... Washer type strain sensor

Continued on the front page F term (reference) 3D001 AA00 DA01 DA03 DA17 EA08 EA22 EA32 EA36 EA41

Claims (9)

[Claims] 1. A washer-type strain sensor for generating an output representing a received load is provided, the washer-type strain sensor is disposed between a vehicle body and wheels, and the washer-type strain sensor is provided during running of the vehicle. Measure the dynamic load acting on the wheel using, to determine the dynamic characteristics of the wheel from the measured dynamic load,
A method for measuring dynamic characteristics of a vehicle wheel including the steps. 2. The method for measuring dynamic characteristics of a vehicle wheel according to claim 1, wherein cornering characteristics of the wheels are obtained from the measured dynamic loads. 3. The method for measuring dynamic characteristics of a vehicle wheel according to claim 2, wherein a lateral force coefficient of the wheel is obtained from the measured dynamic load. 4. The method for measuring dynamic characteristics of a vehicle wheel according to claim 2, wherein a slip angle of the wheel is obtained, and a relationship between the slip angle and the lateral force coefficient is obtained. 5. The dynamic characteristic measuring method for a vehicle wheel according to claim 4, wherein a relation between the slip angle and the lateral force coefficient and the measured dynamic load is obtained. 6. The vehicle wheel according to claim 2, wherein the vehicle has a front wheel and a rear wheel, a slip angle of the front wheel and a slip angle of the rear wheel are obtained, and a steering characteristic is obtained from the slip angles. Dynamic characteristics measurement method. 7. The center-of-gravity axle distance, which is the distance between the vehicle center of gravity and the axle, is determined from the measured dynamic load, and the slip angle is determined from the determined center-of-gravity axle distance.
7. The method for measuring dynamic characteristics of a vehicle wheel according to any one of claims 1 to 6. 8. The method for measuring dynamic characteristics of a vehicle wheel according to claim 1, wherein the washer-type strain sensor is disposed so that a shock absorber of the vehicle extends through an internal space of the washer-type strain sensor. 9. The washer-type strain sensor is arranged between one end of a coil spring concentrically arranged with the shock absorber and a vehicle body or a wheel.
4. The method for measuring dynamic characteristics of a vehicle wheel according to claim 1.