DE102010021577A1 - Brake systems testing method for motor cars, involves adding braking pressure value to displacement and force-measurement value that is determined when hand set is configured, so that way force pressure curve is generated - Google Patents

Abstract

The method involves performing a brake test process with two simultaneous and interrelated functional connection working devices. A displacement and force-measurement value is determined when a hand set (1) is configured. The braking pressure transferred to the hand set is determined at an on board diagnosis (OBD) terminal (E) of a vehicle adapted diagnostic interface (2) adapted through a control device (C). The braking pressure value is added to the displacement and force-measurement value, so that a way force pressure curve is generated. The simultaneous and interrelated functional connection working devices are switched electronic stability program (ESP) actuators or switched anti-lock braking system (ABS) actuators. An independent claim is also included for a device for testing brake systems of motor cars, comprising a decorated measurement device.

Description

The invention relates to a method and a device for testing brake systems of motor vehicles with a measuring device for detecting the force applied to a Pedalwerk actuating forces, which is designed as a handset having a force and a displacement sensor and performs operations of the brake pedal, the method at least each comprises a setting stroke, measuring stroke and leak test, wherein in the setting stroke, the brake system is first conditioned, then recorded in the measuring stroke, the recording of a path-force curve and subsequently the tightness of the brake system is assessed in the leak test.

Braking systems of motor vehicles have a fundamental safety relevance and must therefore be regularly checked both in the manufacturing process at the car manufacturer as well as later vehicle inspections. Numerous methods and arrangements are already available for testing. So plate test benches can be used in which the vehicle is driven at a defined speed on different plates and there braked to a standstill. About the reaction between the wheels and the plates, a statement about the braking force of the individual wheels can be made. Also known are roller test stands, in which the individual axles of the vehicle are positioned on rollers, which are subsequently driven and braked again. Here, too, a statement regarding the braking force is possible on the reaction between the wheel and roller. Although such for example DE 36 06 118 A1 principle proven, remains a subjective factor, because by the manual operation of the brake pedal an exact statement about applied pedal forces and pedal travel covered is only partially possible. Because even for experienced test persons, it is difficult to qualitatively evaluate the force applied by the foot to the brake pedal and the path thus effected. Therefore, a measurement of the applied pedal force and caused by this force path is sought in order to take into account the relationship between pedal force and pedal travel and braking force.

In DE 100 09 168 A1 A device is described with magnetically sensitive components for detecting a driver's applied pedaling force in a vehicle. The device comprises a carrier plate and a tongue element. The tongue element is formed integrally with the support plate and is bolted to the pedal mounted.

As soon as a foot force is applied to the pedal, the relative position between the tongue element and the carrier plate changes. Consequently, the magnetic field existing in this area also changes. This change is analogous to the force exerted on the pedal, so that a statement regarding the Pedalbetätigungskraft is possible. However, the covered pedal travel is disregarded.

By contrast, the pedal travel is at the DE 44 24 094 C1 taken into account known device. Here, a test device is used for the review of an anti-lock brake system in a motor vehicle having a sensor for detecting the pedal movements in response of the control system. The sensor is connected to an evaluation device.

In DE 2 250 728 a so-called pedal force meter is described which comprises a housing, a foot plate acted upon by the pedal actuation force and a device for outputting a signal dependent on the pedal actuation force. The housing has a designed as an adapter base plate with which the entire device can be releasably secured to the brake pedal. The base plate, together with a peripheral frame, forms a contour which is closed off the top of the footboard. In the free interior measuring elements are arranged, with which the force of the tread plate is determined. Alternatively, the signals generated by the measuring elements can also be fed wirelessly to an evaluation device via an associated cable or by conversion into electromagnetic waves or ultrasound.

The brake test can be further improved if one off DE 403 06 723.5 known measuring device for detecting the force applied to a pedal unit actuating forces is used. This configured as a handset device includes a force and a displacement sensor and performs operations of the brake pedal. The process is subdivided into the steps of setting strokes, measuring stroke and leak test and can be parameterized in many ways. During the stroke, the brake system is conditioned as a test requirement. In the subsequent measuring stroke, a path-force characteristic is recorded, from which a pedal travel at a test force is determined. From the curve thus determined, information on any air present in the hydraulic system, on faulty assemblies or on incorrect build-up of components can be seen. Finally, a leak test is carried out, which allows an evaluation of the tightness of the brake system. These tests are usually carried out without negative pressure support of the internal combustion engine.

If typical characteristic values of a brake system are also evaluated when the internal combustion engine is running (brake booster with negative pressure) are to be detected in addition to the above-described displacement and force measurement of the pedal actuation and the brake pressure and displayed in curves. On the basis of these results, evaluations are carried out according to response pressure, response force, saturation of the brake booster, hysteresis values and brake pressures at defined paths and forces. These evaluations enable a good and complex evaluation of the structural design and current state of a brake system. The disadvantage, however, that these tests previously require a complicated analog measurement setup for which, inter alia, a pressure sensor for the brake pressure mounted on the vehicle and a cable for a potentiometer for position detection and a force sensor with actuator must be mounted in the passenger compartment.

The object of the invention is to provide a technical solution that allows a temporally and qualitatively optimized verification of the braking system of vehicles. In this case, in particular, a largely automated procedure is sought using technical components that are already available in the vehicle, but have not yet been used for tasks of the brake test.

This object is achieved by the Bremsenprüfprozess is performed with two simultaneously and interactively working devices, wherein configured as a handset measuring device determines the distance and force measurement and wherein an additional, on OBD (on board diagnose) connection of the vehicle adapted diagnostic interface via a control unit query cyclically determines the brake pressure, which is transmitted to the handset, which adds this pressure value of the already determined path-force curve, so that a path-force-pressure curve is generated. Advantageous embodiments of these method steps and an apparatus for carrying out the method are the subject of dependent claims, whose technical features are described in more detail in one embodiment.

The method according to the invention is suitable for various types of testing of brake systems, with the use in the development process for system design or for the analysis of the brake system of test vehicles being mentioned as a preferred application. It is a temporally and qualitatively optimized review possible, which is achieved in particular by the largely automated process. In this case, technical components are used in an advantageous manner, which are already available in the vehicle, but have not yet been used for tasks of the brake test. This concerns the brake pressure signal available on the vehicle CAN because modern brake control devices with an ESP function have at least one integrated pressure sensor whose parameters can be read out via diagnostic functions.

The diagnostic interface adapted to the OBD connection can be configured in various ways, the basic structure consisting, for example, of DE 10 2005 025 068 B4 is known. The connection between the diagnostic interface and the handset is preferably designed as a fast CAN connection. Consequently, the pressure values of the brake system supplied by the vehicle control unit are promptly integrated into the path-force curve of the brake tester. Thus, the test of the brake system in the measuring stroke can be extended by the determination of the pressure value, so that an additional criterion is taken into account. The entire testing process requires only a short time of about 20 seconds. This means that the necessary data from practical testing is available to the system developer faster and with greater accuracy than previously available.

Hereinafter, an embodiment of the invention will be described with reference to the drawings. Show it:

1 the basic device-technical structure for carrying out the method

2 an example generated path-force-pressure curve of a measurement with brake booster vacuum and Hystereseaufzeichnung

Out 1 the structure of a device for carrying out the method according to the invention in a stylized representation can be seen. Here are the numbers 1 to 5 Assemblies of the test equipment and the letters A to E assemblies of the vehicle.

The brake pedal A is in operative connection with a brake booster and master cylinder B, an electronic brake control unit (ECU) C and a brake pressure sensor D. The brake control unit C controls the braking forces of the vehicle wheels and the brake pressure sensor D is assigned a diagnostic interface (eg OBD II) E.

In this case, the brake pedal A is a measuring device 1 assigned to the detection of applied to the pedal mechanism actuating forces acting as a handset 1 is configured and has a force and displacement sensor. At the diagnostic interface E becomes a diagnostic interface 2 adapted for the brake pressure diagnostic query. The handset 1 and the diagnostic interface 2 are preferably via a fast CAN connection 3a connected with each other. Furthermore, between the handset 1 and a host system 5 a radio connection 4 intended to exchange the measured data. Alternatively it is possible that instead of the connections 3a and 4 over a radio connection 3b a direct data exchange between the diagnostic interface 2 and the host system 5 he follows. Regardless of the specific variant realizes the host system 5 Parameterization, process control, data storage, results analysis, visualization and statistical evaluations.

When using such a device structure for carrying out the method, the brake system is first conditioned in the set stroke, then carried out in the measuring stroke, the recording of a path-force characteristic and finally the tightness of the brake system is evaluated in the leak test. Such a procedure is generally known, so that it is possible to dispense with more detailed explanations here. However, it is essential in the present case that the Bremsenprüfprozess is performed with two simultaneously and interactively working devices, which as a handset 1 configured measuring device determines the distance and force measured value and wherein the adapted at the OBD port E of the vehicle diagnostic interface 2 cyclically determines the brake pressure via a control unit query. This determined brake pressure is applied to the handset 1 transmit, which adds this pressure value of the already determined path-force curve, so that a path-force-pressure curve is generated. Likewise, it is possible that the combination of parameters is not immediate in the handset 1 is done, but in the host system 5 ,

The described method can be configured differently. This allows the brake testing process to be carried out with any desired ABS / ESP actuators. Likewise, the brake testing process can be performed with or without hysteresis. Furthermore, the determined points of the path-force-pressure curve of a measurement can be stored in a database and / or archived or exported to text files or further processed with a spreadsheet system.

2 shows the path-force-pressure curve of a measurement with brake booster vacuum and a hysteresis record. Here, a variant with constant operating speed of the brake pedal A is shown, wherein the brake pedal A from the handset 1 was applied to a test force and after a waiting time at the same speed in the starting position was driven back. In the picture according to 2 By way of example, a number of evaluation points P1, P2, P3 (path-pressure curve) and P4, P5, P6 (path-force curve) are shown, which can be included in the evaluation of the brake system. In this case, the force "F" in Newton is recorded on the left vertical leg, the pressure "p" in bar on the right vertical leg and the path "s" in millimeters on the horizontal base. Based on the thus generated path-force-pressure curve, an evaluation of the structural design and the current state of the brake system investigated here is possible.

LIST OF REFERENCE NUMBERS

1

Measuring device / handset for pedal forces

2

Diagnostic interface for brake pressure request

3a

(CAN) connection between 1 and 2

3b

(Radio) connection between 2 and 5

4

Radio connection between 1 and 5

5

host system

A

brake pedal

B

Brake booster and master cylinder

C

electronic brake control unit

D

Brake pressure sensor

e

Diagnostic interface

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3606118 A1 [0002]
• DE 10009168 A1 [0003]
• DE 4424094 C1 [0005]
• DE 2250728 [0006]
• DE 40306723 [0007]
• DE 102005025068 B4 [0012]

Claims (10)

Method for testing brake systems of motor vehicles with a measuring device for detecting the applied to a pedal assembly actuating forces, which is designed as a handset having a force and a displacement sensor and executes actuations of the brake pedal, the method at least one set stroke, measuring stroke and leak test wherein, in the setting stroke, the brake system is first conditioned, then the measuring stroke takes place a path-force characteristic curve and subsequently the tightness of the brake system is evaluated in the leak test, characterized in that the brake testing process is carried out with two devices working simultaneously and in operative connection with each other being used as a handset ( 1 ) configured measuring device the Weg- and force measured value and wherein an additional, on the OBD (on board diagnose) connection (E) of the vehicle adapted diagnostic interface ( 2 ) via a control unit query cyclically determines the brake pressure to the handset ( 1 ) is transmitted, which adds this pressure value of the already determined path-force curve, so that a path-force-pressure curve is generated. A method according to claim 1, characterized in that the Bremsenprüfprozess is performed at arbitrarily switched ABS actuators. A method according to claim 1, characterized in that the Bremsenprüfprozess is performed at any switched ESP actuators. A method according to claim 1, characterized in that the Bremsenprüfprozess is performed with hysteresis. A method according to claim 1, characterized in that the Bremsenprüfprozess is performed without hysteresis. A method according to claim 1, characterized in that the determined points of the path-force-pressure curve of a measurement marked with special evaluation points and stored in a database and / or archived. A method according to claim 6, characterized in that the stored and / or archived measured values are exported to text files. A method according to claim 6, characterized in that the stored and / or archived measured values are further processed with a spreadsheet system. Device for carrying out the method according to at least one of claims 1 to 8, characterized in that the device is a handset ( 1 ) equipped measuring device with a force and a displacement sensor for detecting the force applied to a pedal mechanism actuating forces and adapted to the OBD (on board diagnose) connection (E) of the vehicle diagnostic interface ( 2 ) for cyclically detecting the brake pressure, wherein the handset ( 1 ) and the diagnostic interface ( 2 ) with each other and with a host system ( 5 ) are in operative connection. Method according to Claim 9, characterized in that the connection between the diagnostic interface ( 2 ) and Handset ( 1 ) as a fast CAN connection ( 3a ) is configured.

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