GB2047829A

GB2047829A - Testing a vehicle braking installation provided with an anti-lock device

Info

Publication number: GB2047829A
Application number: GB8003109A
Authority: GB
Original assignee: Wabco Fahrzeugbremsen GmbH
Current assignee: Wabco Fahrzeugbremsen GmbH
Priority date: 1979-02-01
Filing date: 1980-01-30
Publication date: 1980-12-03
Also published as: FR2447838B1; DE2903756A1; JPS55103445A; FR2447838A1; GB2047829B

Abstract

Testing apparatus is described for the static and dynamic testing of an anti-lock brake pressure control installation in a motor vehicle. The apparatus does not test the signal processing circuitry of the installation but the power supply, the wheel sensors and the brake pressure valves. The static tests involve testing the resistances of the coils, the electrical continuity of an indicator lamp used to warn the driver of the breakdown of an anti-lock installation, the functioning of by-pass means for disabling the anti-lock installation in the event of malfunction and also the presence of electrical power where it is required by the installation together with the voltage output from the generator or alternator of the vehicle with the engine running. The dynamic tests are carried out on a rolling road and include tests of the correct functioning of the wheel sensors and the brake pressure control valves including tests for erroneous cross-overs of connections. <IMAGE>

Description

SPECIFICATION Testing apparatus for the braking installation of a vehicle that is provided with an anti-lock device The invention relates to a testing apparatus for the braking installation of a vehicle that is provided with an anti-lock device.

Anti-lock devices are provided in the braking systems of vehicles to prevent the wheels locking when the vehicle is braked hard as in an emergency or is braked on slippery roads. As a result of the provision of an anti-lock device the braking distance of the vehicle is shortened compared with the distance without the device, and the steering capability of the vehicle is maintained whereas it would be lost if the wheels were to lock.

An anti-lock device consists basically of an electronic part, a vehicle cabling system or loom, several sensors attached to the wheels for producing indications of the speed of the wheels and solenoid valves for influencing the braking pressure.

In detail, the solenoid valves for each separately controlled brake consist of an inlet valve for permitting the pressure to be increased during a braking operation and an outlet valve for reducing the pressure. When the inlet and outlet valves are closed, the particular pressure in the brake cylinder(s) at the time is maintained.

Further, the anti-lock device includes a safety circuit for monitoring the electronic part. A defect detected by the safety circuit is indicated to the driver by an indicator lamp and the electronic part is switched off by suitable means so that normal braking without the anti-lock device is obtainable.

In the future it is likely to become necessary to test anti-lock device vehicle cabling systems and installations when they are newly built, after repair work and when carrying out normal brake testing.

A testing circuit for an anti-lock device is described in DE-PS 23 38859. However, with this circuit, which operates without using a roller test bed, it is not possible to test the operation of the system sufficiently, because, for example, the actuation of the solenoid valves can be detected only acoustically.

An object of the invention is, therefore, to provide a testing apparatus for an anti-lock brake installation which allows testing to be carried out as far as possible fully automatically, so that fewer demands are made on the skill ofthe tester.

According to the present invention there is provided testing apparatus for the braking installations of a vehicle that is provided with an anti-lock device, including first connectors by means of which the apparatus can be connected to a cabling system of a vehicle under test, second connectors by means of which the apparatus can be connected to a roller test bed on which a vehicle under test can run, an actuation circuit for actuating the roller test bed and/or for supplying the vehicle installation with test currents through the cabling system, and an enquiry circuit for detecting and evaluating measured values from the vehicle installation and/or the roller test bed.

Examples of the invention may have the advantage that more types of defect can be identified than in the case of previously known testing circuit.

However, apparatus according to the invention may be arranged not to test the function of the electronic part of the anti-lock device but only the associated vehicle wiring loom, the sensors, the solenoid valves and the brakes. Preferably the vehicle is provided with a multi-way socket into which a matching plug connected to the apparatus can be inserted for making the connections to the vehicle wiring loom and via it to the components to be tested on the vehicle.

A special advantage of a testing apparatus according to the invention lies in the fact that the measured values can be taken from the vehicle installation as well as from the braking force measuring systems of the roller test bed. Moreover, it is possible for the apparatus to actuate the drive motors of the roller test bed. The test itself is in the form of a test program which is automatically stepped onwards and also provides indication of defects detected.

The course of the test is not dependent upon settings of adjustable values made by the tester or his inputs to the testing apparatus.

Using a testing apparatus according to the invention it is also possible to find defects which would impair the control of the anti-lock device as a result of incorrect rates of brake pressure increase and decrease, as the enquiry circuit in the testing apparatus can be arranged to assess the brake pressure changes by monitoring the dynamic braking behaviour.

In orderthatthe invention may be fully understood and readily carried into effect it will now be described with reference to the accompanying drawing which shows a block diagram of one example of testing apparatus according to the invention.

The testing apparatus 1 contains a step-by-step switching device 5 with control logic 5', an actuation circuit 6 and an enquiry circuit 7. Connectors 3 and 4 are provided for connection to a roller test bed (not shown) and connectors 2 are provided for connection to a vehicle cabling system or loom (not shown), these connectors being joined to the actuation circuit 6 and the enquiry circuit 7. It will be appreciated that the connectors 2,3 and 4 are shown diagrammatically in the Figure, and at least some forms of the apparatus may include many more such connectors.

Connected to the step-by-step switching device 5 and to the control logic 5' are a changeover switch 11, for selecting an axle of a vehicle to be tested, a start button 12 for starting the test program running, a signal lamp 10 for indicating the actuation of the brakes, a signal lamp 9 for indicating defects and a numerical test step indicator 8.

Atypical test of a vehicle installation proceeds, in principle, as follows: The tester drives the vehicle with the axle associated with the installation to be tested onto the roller test bed, connects the testing apparatus to the roller The drawing originally filed was informal and the print here reproduced is taken from a later filed formal copy.

test bed and to the vehicle cabling system using the connectors 2, 3 and 4 and starts the test program of the testing apparatus by pressing the start button 12.

There follows first of all a sequence of static tests, which includes, for example, the following tests as steps: 1. the vehicle power supply 2. the coil resistances ofthe wheel sensors 3. the coil resistances of the solenoid inlet valves 4. the coil resistances of the solenoid outlet valves 5. the electrical continuity through the indicator lamp for showing a breakdown of the anti-lock device.

6. the voltage output from the generator or alter nator of the vehicle (engine running) 7. the functioning of the means for switching off the electronic part of the anti-lock device The static test can, if desired, be carried out without the vehicle being located on the roller test bed.

If, for example, the measured values of the power supply investigated by test 1 lie within predetermined limits, this is determined by the enquiry circuit 7 which gives a signal to the step-by-step switching device 5 which then switches on the next step (2) of the test.

In the subsequent tests (2 to 5), defined currents are passed by the actuation circuit 6 to the wheel sensors, the solenoid valves and the indicator lamp.

The resistances are checked by the enquiry circuit 7 by measuring the voltages dropped across them and comparing them with predetermined values. Each time a measured value lies within permissible variations the next test is switched to automatically.

If a defect occurs, for example because a measured value lies outside the range of permissible variations, this is indicated by the illumination of the signal lamp 9 and the automatic stepping onward procedure is interrupted. The identity of the defective component discovered by the particular test is indicated by the number of the test which is shown by the indicator 8.

When the sequence of static tests has been completed without defects, all defects discovered having been put right, a sequence of dynamic tests begins.

This sequence of tests is carried out separately for each axle of the vehicle. The changeover switch 11 should therefore be adjusted by the tester appropriately for the different axles.

The sequence of dynamic tests consists of, for example, the following tests as steps: 8. the functioning of the wheel sensors 9. the possible erroneous crossoverofthe connections of the sensors 10. the functioning of the solenoid valves 11. the possible erroneous crossover of the connections of the solenoid valves In this sequence of tests the roller motors are started individually by means of the connectors 3 and the braking force produced when the brake is operated is monitored by the enquiry circuit 7 by means of the connectors 4. The illumination of the lamp 10 indicates to the tester when the brake should be operated.

The wheel sensors produce voltages dependent on the speed of the wheels and therefore should correspond to that of the rollers, and the size of the voltage is monitored by the enquirycircuit7 and compared with an indication of the speed of the rollers. If, for example, in one step of a test, the lefthand roller is driven, then the next test step can take place only after a voltage corresponding to the roller speed has been measured at the connection to the left wheel sensor. If this voltage is discovered by the enquiry circuit 7 at another connection, then it is clear that an erroneous crossover of the connections to the sensors has occurred and a defect is therefore indicated.

The remaining test steps of the sequence of dynamic tests take place correspondingly.

With a testing apparatus according to the invention it is impossible for an incorrect measured value to be read from the measuring system of the roller test bed and to be fed into the testing apparatus as the correct value.

A testing apparatus according to the invention makes it possible to carry out quickly and automatically a sequence of tests on the braking installation of a vehicle that is equipped with an anti-lock device.

The cost of apparatus according to the invention is only slightly higher than that of apparatus for carrying out the same tests manually. As specially trained personnel are not necessary to operate the apparatus since its operation is automatic and the reference levels and permissible variations for the measured values are incorporated in the enquiry circuit, it follows that the staffing costs for running the apparatus can be kept low.

Claims

1. Testing apparatus for the braking installations of a vehicle that is provided with an anti-lock device, including first connectors by means of which the apparatus can be connected to a cabling system of a vehicle under test, second connectors by means of which the apparatus can be connected to a roller test bed on which a vehicle under test can run, an actuation circuit for actuating the roller test bed and/or for supplying the vehicle installation with test currents through the cabling system, and an enquiry circuit for detecting and evaluating measured values from the vehicle installation and/or the roller test bed.

2. An apparatus according to claim 1, including a step-by-step switching device for automatically stepping through the test of all the functions to be tested.

3. An apparatus according to claim 2, wherein the step-by-step switching device has a starting button and a test step indicator.

4. An apparatus according to any of claims 1 to 3, further including a changeover switch for selecting the particular axle of the vehicle to be tested.

5. An apparatus according to any of claims 1 to 4, further including a control logic for controlling a test current generating circuit and the enquiry circuit.

6. An apparatus according to any of claims 1 to 5, further including signal lamps for indicating defects and for indicating when a brake actuation is taking place.

7. A testing apparatus for the braking installation in a vehicle, which installation includes an anti-lock device, the apparatus being substantially as described herein with reference to the accompanying drawing.