JPH02238341A - Chassis dynamometer - Google Patents

Abstract

PURPOSE:To assume a low friction road and to perform evaluation by providing a means for sending a load command signal corresponding to friction coefficient, detecting a grounding load by a grounding-load changing means, and feeding back the detected signal to a grounding load controller. CONSTITUTION:A grounding load signal which is sent out of a grounding load command part 10 is inputted into a grounding controller 11, and hydraulic cylinder 14 is driven. Then, a tire A is moved up and down. Thus, the grounding load of the tire A to a chassis dynamo-roller 1a is changed, and the equivalent state as a low friction road is reproduced. When a vehicle runs on an actual road, the movement of a load occurs. The movement must be reproduced. For this purpose, the number of rotations of the roller 1a is detected, and the speed signal is converted in an f/v converter 18. The speed signals is differentiated in a differentiator 19. The differentiated signal is inputted into the command part 10. After the operation, the load command signal is inputted into the controller 11. The grounding load of the tire to the roller 1a is controlled by the same operation as the reproduced operation on the low friction road, and the reproduction of the load movement on the vehicle can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a chassis dynamometer, and particularly to a chassis dynamometer that can perform vehicle running tests assuming various running routes.

[Prior Art] Chassis dynamometers that perform various driving performance tests on automobiles, such as pattern driving tests such as 1o mode tests, are well known. The drive wheels of the test vehicle are brought into contact with rollers whose load characteristics are arbitrarily controlled, and various tests are conducted on the test vehicle under conditions similar to actual driving.

According to such a conventional chassis dynamometer, it is possible to simulate high-speed driving or low-speed driving, as well as driving up and down slopes, and it is possible to perform a vehicle driving test under conditions similar to driving on an actual road.

As a technology related to such a dynamometer, the present applicant has previously proposed a monitor device for vehicle pattern running tests (Japanese Patent Application No. 63-9 2922).

[Problems to be Solved by the Invention] However, since the conventional chassis dynamometer and the above-mentioned vehicle pattern traveling test monitoring device proposed by the applicant use a chassis dynamometer roller installed indoors, The frictional resistance (μ) between the roller and the roller is always constant. Therefore, in order to evaluate vehicles assuming low-friction roads such as icy roads and snow-covered roads, a device for simulating low-friction roads is required, but conventional devices did not take this into account. .

Therefore, vehicle evaluation on low-friction roads had to be based on actual road driving tests, which posed a problem in terms of ensuring the safety of experimenters. Furthermore, actual road driving tests were affected by seasonal weather conditions, making it impossible to conduct the tests efficiently and making it impossible to reproduce the test conditions.

Purpose of the Invention The present invention has been made to solve the above-mentioned problems, and provides a chassis dynamometer that enables pattern running tests of vehicles assuming low-friction roads by changing the ground contact load on the rollers of the chassis dynamometer. The purpose is to provide a meter.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a ground contact load variable means for varying the ground contact load of a tire of a test vehicle that is grounded on a chassis dynamometer roller, and an operation of the ground contact load variable means. a ground load command section that sends a load command signal corresponding to a friction coefficient set between the chassis dynamo and the tire to a ground load controller that controls the ground load controller; and feedback means for inputting a detection signal to the ground load controller.

[Operation] With the above configuration, a ground load signal corresponding to a predetermined friction coefficient is sent from the ground load command section to the ground load controller.

The controller controls the operation of a ground contact load variable means, such as a hydraulic cylinder, and causes the tires of the test vehicle to contact the ground with an appropriate load on the rollers of the chassis dynamo.

As a result, the braking force F of the vehicle is F - μW (μ: friction coefficient, W is the ground load), so by reducing the ground load W, the braking force F can be reduced, as if the friction coefficient You can get the same effect as setting it low.

[Embodiment] An embodiment of the present invention will be described based on FIGS. 1 to 3.

In the figure, reference numeral 10 denotes a ground load command unit that sends out a load signal corresponding to a set friction coefficient in order to form a road surface with a predetermined friction coefficient.

The load corresponding to the friction coefficient to be set is generally F-μW
(F: braking force, μ: coefficient of friction, W: load) Therefore, by changing the load W, the apparent coefficient of friction can be lowered.

That is, in order to reproduce a low-friction road surface between the chassis dynamometer roller and the tires, lowering the braking force F for a certain slip ratio S will make the road surface equivalent to a low-friction road surface, as shown in Figure 2. Take advantage of what you can get.

Actually, as shown in Fig. 3, the braking force F-slip ratio S characteristic of each tire of the vehicle with respect to the chassis dynamometer roller is actually measured using the ground load as a parameter.
Select the ground load closest to the F-S characteristic to be installed.

The ground load signal selected in this way is input to the ground load controller 11.

12 is a servo valve unit which receives a signal from the ground load controller 11 and receives a hydraulic pressure RI. 13
The operation of the hydraulic cylinder 14 is controlled using the hydraulic pressure from the hydraulic cylinder 14.

A load is applied by the operation of the hydraulic cylinder 14,
be removed. Incidentally, the load is applied to the tires of the vehicle only from the hydraulic cylinder 14.

Reference numeral 15 denotes a load cell, and the load cell 15 detects the ground load, and feedback control is performed by manually inputting this detection signal to the ground load controller 11.

Further, 16 is a hub nut fixing device, which restricts the movement of the vehicle in the longitudinal direction.

A connecting jig 16a for connecting to a tire hub nut is formed at the tire side tip of the hub nut fixing device 16. A bearing is installed inside this connection jig 16a to connect the tire while allowing rotation of the tire.

17 is a detection unit that detects the rotation speed of the roller 1a,
It consists of a pulse generator section 17a and a pulse pickup section 17b.

18 is an f/v converter that converts the detection signal of the pulse pickup section 17b into a speed signal; 19 is an f/v converter for converting the detection signal of the pulse pickup section 17b into a speed signal;
This is a differential calculator that performs a differential operation on the output signal from the v converter 18, and the output signal from this calculator is input to the ground load command section 10.

As a result, it is possible to adjust the vehicle weight, and the load movement of the vehicle can be simulated using the adjusted vehicle weight value, thereby making it possible to control the ground contact load for each of the four wheels independently.

In this case, the calculation section 19, the ground contact load control section 11, etc. can be made common as necessary.

Next, the operation of an embodiment according to the present invention will be explained.

Reproducing a low-friction road In order to reproduce a low-friction road, as shown in Figure 2, by lowering the braking force F for a certain slip ratio S, a state equivalent to that of a low-friction road can be obtained. Make use of it.

That is, since the braking force F is F - μW (μ: coefficient of friction, W: ground contact load), the braking force F can be lowered by lowering the load W instead of lowering μ.

Actually, in advance, the braking force (F) of each tire of the test vehicle against the chassis dynamometer roller - slip ratio (S)
is actually measured using the ground load as a parameter.

After obtaining the F-S characteristic as shown in FIG. 3, for example, the ground load exhibiting the characteristic closest to the assumed F-S characteristic is selected.

The selection of the ground load corresponding to this friction coefficient is performed by the ground load command unit 10. The ground load signal sent from the ground load command unit 10 is input to the ground load controller 11, and the ground load controller 11 drives the hydraulic cylinder 14 via the servo valve unit 12.
The tire A fixed to the hub nut fixing device 16 is moved up and down. As a result, the ground contact load of the tires A on the chassis dynamometer roller 1a is changed, and a state equivalent to a low-friction road is reproduced.

Reproduction of vehicle load shift When a vehicle travels on an actual road, load shift (change in front and rear wheel load sharing) occurs due to acceleration and deceleration of the vehicle.

Therefore, in order to bring the braking force closer to actual road driving,
It is also necessary to reproduce the load movement of the vehicle.

This load movement of the vehicle is determined by the vehicle acceleration (dv/dt). Here, dt is a minute time, and dv indicates a change in vehicle speed in this minute time.

Therefore, the pulse generator 17a and pulse pickup 17b attached to the chassis dynamometer roller 1a
As a result, the rotational speed of the roller 1a is detected, the detected signal is converted into a speed signal by the f/v converter 18, and the speed signal is differentiated by the differential calculator 19.

The dv/dt signal obtained in this manner is input to the ground load command section 10, and after a predetermined calculation, the load command signal is input to the ground load controller 11.

The ground contact load controller 11 controls the ground contact load of the tire on the dynamo roller 1a by an operation similar to the operation for reproducing a low-friction road surface, and reproduces the load movement of the vehicle.

Furthermore, since the ground contact load can be varied independently for each of the four wheels, it is also possible to reproduce overlapping roads and uneven roads.

That is, the straddling road can be reproduced by changing the ground load of the left and right tires with respect to the chassis dynamometer roller 1a, and by setting different coefficients of friction between the left and right tires and the chassis dynamometer roller.

Furthermore, a patchy road can be reproduced by temporally varying the ground contact load and thereby temporally varying the friction coefficient.

Furthermore, since the ground contact load can be varied independently for each of the four wheels, it is possible to evaluate changes in vehicle behavior due to differences in the number of passengers.

Incidentally, FIG. 4 shows an example of a specific configuration of the ground load variable means of the above embodiment, and only the one installed on one side of the vehicle is shown in the figure.

The U-shaped support body 22 is fixed to the main body of the device, and a hydraulic cylinder 14 for applying a grounding load is attached to the tip of an upper arm portion 24. Hydraulic cylinder 1
The piston 14a of No. 4 is connected to the arm 16a of the hub nut fixing device 16. A load cell 15 is provided at this connection portion.

With such a configuration, the operation of the hydraulic cylinder 14 based on the control signal from the servo valve unit 12,
Adjust the ground load of each wheel. In other words, in order to reproduce a low-friction road, apply force in the direction of the white arrow in the figure, and when reproducing the load movement of the vehicle (for example,
During nose dive during braking, the ground contact load on the front wheels is increased and the ground contact load on the rear wheels is decreased, as shown by the black arrows in the figure.

[Effects of the Invention] As described above, this invention can change the coefficient of friction between the tire and the chassis dynamometer roller by changing the ground load of the tire, so it is suitable for low-friction roads such as roads on ice and snow. vehicle evaluation.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a configuration according to an embodiment of the present invention, Figs. 2 and 3 are diagrams showing braking force (F) vs. slip ratio (S) characteristics, and Fig. 4 is a diagram showing variable ground load. It is a perspective view showing a specific example of means. Chassis dynamometer roller ground load command unit ground load controller hydraulic cylinder load cell 7a ... pulse generator 7b ... pulse pickup 8 ... f/v converter 9 ... differential calculator

Claims (1)

[Claims] A chassis dynamometer used as a vehicle running test device includes a ground load variable means for varying the ground load of a tire of a test vehicle grounded by a roller of the chassis dynamometer, and a ground load controller for controlling the operation of the ground load variable means. and a ground contact load command unit that sends a load command signal corresponding to a friction coefficient set between the chassis dynamometer roller and the tire to the ground contact load controller;
A chassis dynamometer comprising feedback means for detecting the ground load changed by the ground load variable means and inputting a detection signal to the ground load controller.