DE102007023320A1 - Analogized or analog-controlled hydraulic separating valves pressure/opening current characteristics calibrating method, involves effecting calibration of valves based on comparison of target braking torque with actual braking torque - Google Patents

Abstract

The method involves attaining a braking force with a downstream main cylinder (21) by analogized or analog-controlled hydraulic separating valves (1, 2) and inlet valves (3-6) for wheel brakes (FL, FR, RR, RL). Additional braking force is introduced into the wheel brakes by hydraulic pumps (16, 16`). Calibration of the separating valves is effected on the basis of a comparison of a required target braking torque with an effective actual braking torque, where the actual braking torque is determined by wheel speed sensors (23, 24) under the consideration of a motor torque of a driving motor.

Description

The The present invention relates to a method for calibrating the Pressure / current characteristic opening an analogized or analog controlled hydraulic isolation valve a regulated brake system for motor vehicles, in which a with Help of a pedal-operated Brake pressure generated brake pressure with downstream master cylinder via a Separating valve and over an inlet valve passes to a wheel brake and over Exhaust valve from the wheel brake in a low-pressure reservoir conductive is, and where an additional brake pressure einsteuerbar in the wheel brakes by means of a hydraulic pump is.

In the further development of braking systems with anti-lock regulations ABS or electronic stability programs ESP are increasingly analogized valves for controlling the hydraulic fluid used, the so-called AD valves. The current at which the AD valve opens, However, it depends strongly on the pressure difference across the valve. Around to be able to control the AD valves, It is necessary to use this current value, which is referred to here as the "opening point", to know.

The opening point is still of manufacturing tolerances and wear of the valve and other components of the brake system. Therefore, during the Operating the motor vehicle adjustment of the hydraulic system to the Regulator necessary. The opening points have to be stored in the controller.

Around To operate analog valves with a sufficient accuracy it is necessary the opening characteristics to know. To manufacture the AD valves so that each valve identifies identical characteristics (e.g., current-pressure characteristics), is not possible due to tolerances or represents an unreasonable expense. Even if this is possible, provides the change over the Lifetime is another problem. To calibrate each valve individually, is a very high expenditure of time in production and increases the costs considerably. But without the valves with a corresponding To be able to operate with accuracy the functional benefit decreases. Previous considerations were directed towards "current ramps" that provide a pressure dynamic should produce. These procedures were bad by the time Assignment of current and pressure values inaccurate.

From the DE 102 21 456 A1 a method for calibrating the pressure / opening flow characteristic of an analogized hydraulic valve is known. In the previously known method, brake pressure is produced in the brake system and a wheel brake in a diagnostic or calibration process with a test rod which is applied to the brake pressure transducer. By opening the exhaust valve, pressure medium is discharged from the wheel brake into the low-pressure accumulator and the pressure in the brake system is reduced. Subsequently, in the previously known method, the inlet valve is closed and the pressure medium is conveyed back by driving hydraulic pump. In this case, the dependent on the control of the pump pressure in the brake system or the pressure difference across the hydraulic valve to be calibrated is measured or estimated and switched to be calibrated hydraulic valve by ramp-shaped or stepwise change of the valve current. The valve-commutating current flowing at the beginning of the switching process, ie at the beginning of the opening or closing of the valve, is determined. The time allocation of current and pressure values is very inaccurate.

Of the The invention is therefore based on the object, a method for calibrating from analogized isolation valves, to develop that reliable, onboard, automatic and independent from the driver is working.

These The object is achieved by the method according to claim 1. there It is envisaged that the calibration of the isolation valve based on a comparison of the requested desired braking torque with the actual Actual braking torque has occurred.

there is provided that the actual braking torque by means of wheel speed sensors considering the engine torque of the drive motor is determined.

• • Schließen des zu kalibrierenden Trennventils und Zuführen eines vorab definierten Ventilstromes I_Soll;
• • Einstellen eines Soll-Bremsmoments durch einen aktiven Druckaufbau mit Hilfe der hydraulischen Pumpe und
• • Vergleichen des Soll-Bremsmoments mit dem Ist-Bremsmoment.

According to an advantageous development, the following method steps are carried out:

• Closing the isolating valve to be calibrated and supplying a predefined valve current I _setpoint ;
• • Setting of a set braking torque by an active pressure build-up with the help of the hydraulic pump and
• • Comparison of the desired braking torque with the actual braking torque.

at A particularly advantageous development is provided that a comparison of the desired braking torque with the actual braking torque of the motor vehicle is evaluated to see whether the separator valve to be calibrated is overflowed.

In a further advantageous development of the method according to the invention, the valve current I _{Soll is} stored as a point of a pressure-opening current characteristic.

In carrying out the method, the driving situation of the motor vehicle is taken into account. The driving situation of the motor vehicle is determined by means of a longitudinal acceleration signal and the engine torques of the drive motor.

The Procedure is during a constant trip performed. It is stopped when a switching operation of the transmission of the drive motor of the Motor vehicle performed or if a delay or acceleration command is determined

The Invention will be related to an embodiment in the context closer with the enclosed drawing explained. In the drawing show:

1 a circuit diagram of a braking device with analog controllable valves to which the present method is feasible and

2 a schematic flow diagram of the present method.

A circuit diagram of the vehicle brake system, to which the present method is feasible, is in 1 shown. The vehicle brake system has hydraulically actuated wheel brakes FL, FR, RR, RL on all four vehicle wheels. The term FL stands for the English term "front-left", which designates the front left wheel brake, and the same applies to the front right wheel brake and the wheel brakes on the rear axle.The hydraulically actuated wheel brakes FL, FR, RR, RL are using a pedal-operated pressure transducer 14 , which is designed as a vacuum brake booster and the master cylinder 21 downstream, acted upon by hydraulic pressure medium. For applying the hydraulic wheel brakes FL, FR, RR, RL with a pressure, the hydraulically actuated wheel brakes FL, FR, RR, RL with the interposition of intake valves 3 . 4 . 5 . 6 via a hydraulic line 17 . 18 with the master cylinder 21 connected. At a pressure reduction, the controlled pressure medium via exhaust valves 9 . 10 . 11 . 12 in two low-pressure accumulators 19 . 20 drained. To determine the hydraulic pressure applied is a pressure sensor 13 in the from the master cylinder 21 outgoing hydraulic pipe 17 intended.

Starting from the pedal-operated pressure transducer 14 with downstream master cylinder 21 downstream of each of the two hydraulic brake circuits are an isolation valve 1 . 2 and an electric switching valve 7 . 8th assigned. The isolation valves 1 . 2 are analogue controllable normally open SO valves and are used for all controls during an active pressure build-up by a hydraulic pump 16 . 16 ' needed. The isolation valves 1 . 2 be in these active pressure build-up phases by the hydraulic pumps 16 . 16 ' closed, so that the pressure build-up is not in the master cylinder 21 is controlled. The electrical switching valve 7 . 8th - also known as EUV - is a normally closed SG-valve, which is a connection between the master cylinder 21 and the suction side of the pump 22 produces or interrupts. In the driven state, the electrical switching valve 7 . 8th open and the pump 16 . 16 ' can brake fluid from the master cylinder 21 suck in and provide for example for a traction control.

For the present method, only the analogized isolation valves 1 and 2 relevant. The present method makes it possible to easily calibrate these AD valves. The present method is performed during operation on public roads.

The idea underlying the present method is that the separating valve to be calibrated 1 . 2 a closing current I _{Soll is} supplied and subsequently a pressure build-up by the hydraulic pump 16 . 16 ' is carried out. If the requested desired braking torque does not correspond to the actual braking torque, then it can be assumed that the closing current I _{Soll was} too low and the separating valve 1 . 2 was overflowed. For calibrating the isolation valve 1 . 2 Thus, the requested target braking torque is compared with the actual actual braking torque.

The calibration ensures that the isolation valves 1 . 2 open at reproducible braking torques. The braking torques can be transmitted by knowing the ratio of braking torque to hydraulic pressure in the wheel brakes FL, FR, RR, RL, so that in an intact system, the hydraulic pressure in the wheel brakes FL, FR, RR, RL is known.

The calibration of the system is described below with reference to the in 2 illustrated flowchart explained. Preferably, in the first process step 25 a pre-calibration of the Öffungsstrom characteristic made in the factory. Alternatively, a calibration on the chassis dynamometer of the motor vehicle manufacturer would be possible, as is the method step 26 represents. In an autonomous pressure build-up, the in the flowchart after 2 is abbreviated ECBA for Electronic Controlled Brake Actuation, the braking torque is available as a controlled variable (method step 27 ). In the process step 28 It is checked whether the difference between the requested target braking torque and the actual actual braking torque is an allowable value. The requested setpoint brake torque is transferred from the ECBA to a setpoint current I _{setpoint of} the isolation valve 1 . 2 implemented, the on reaching the expected braking torque in the over to flow.

Such a check whether the setpoint braking torque corresponds to the set actual braking torque is possible with any autonomous ECBA control. By taking into account a longitudinal acceleration signal, engine torque of the drive motor and other parameters, the driving situation of the motor vehicle can be taken into account. On the set actual braking torque can be by returning the driving convincing delay, the by the wheel speed sensors 23 . 24 be measured, taking into account the motor torque of the drive motor are closed. If the driving situation of the motor vehicle is suitable for the calibration routine, such as during an ECBA request from a constant drive of the motor vehicle in the plane, the recalibration of the isolation valves 1 . 2 possible.

Small requirements can be covered by one axle (method step 29 ). In these situations, the isolation valves 1 . 2 To be calibrated by axle. In this way, the total braking torque on both axes is sufficiently large, even if a faulty set isolation valve 1 . 2 should be overflowed. In principle, at least the summation requirement with the sum position of the braking torques is possible with every ECBA braking.

The axle calibration also leads in the process steps 30 and 31 for carrying out the described comparison between the requested desired braking torque and the actual actual braking torque.

The Procedure is aborted if a speed limit falls below is in which no meaningful evaluation of the braking torque is possible.

1

isolation valve Brake circuit front axle

2

isolation valve Brake circuit rear axle

3

intake valve FL

4

intake valve FR

5

intake valve RR

6

intake valve RL

7

electrical Changeover valve brake circuit front axle

8th

electrical Changeover valve brake circuit rear axle

9

outlet valve FL

10

outlet valve FR

11

outlet valve RR

12

outlet valve RL

13

pressure sensor

14

pedalbetätigbarer Brake pressure transducer

15

brake pedal

16 16 '

hydraulic pump

17

hydraulic Line brake circuit front axle

18

hydraulic Line brake circuit rear axle

19

Low-pressure accumulator Brake circuit front axle

20

Low-pressure accumulator Brake circuit rear axle

21

master cylinder

22

Pressure fluid reservoir

23

wheel speed sensors

24

wheel speed sensors

Claims (8)

Method for calibrating the pressure / opening flow characteristic of an analogized or analogically controlled hydraulic separating valve ( 1 . 2 ) of a regulated brake system for motor vehicles, in which a by means of a pedal-operated brake pressure transducer ( 14 ) generated brake pressure with downstream master cylinder ( 21 ) via a separating valve ( 1 . 2 ) and via an inlet valve ( 3 . 4 . 5 . 6 ) to a wheel brake (FL, FR, RR, RL) and via an exhaust valve ( 9 . 10 . 11 . 12 ) from the wheel brake (FL, FR, RR, RL) into a low pressure accumulator ( 19 . 20 ), and wherein an additional brake pressure in the wheel brakes (FL, FR, RR, RL) by means of a hydraulic pump ( 16 . 16 ' ) einsteuerbar, characterized in that the calibration of the separating valve ( 1 . 2 ) Based on a comparison of the requested desired braking torque with the actual actual braking torque is done. A method according to claim 1, characterized in that the actual braking torque by means of wheel speed sensors ( 23 . 24 ) is determined taking into account the engine torque of the drive motor. A method according to claim 1 or 2, characterized in that the following method steps are carried out: • closing the calibration valve to be calibrated ( 1 . 2 ) and supplying a predefined valve current I _target ; • Setting of a set braking torque by active pressure build-up by means of the hydraulic pump ( 16 . 16 ' ) and • comparing the desired braking torque with the actual braking torque. A method according to claim 3, characterized in that a comparison of the desired braking torque with the actual braking torque of the motor vehicle is evaluated to the effect whether the to be calibrated separating valve ( 1 . 2 ) is overflowed. A method according to claim 3 or 4, characterized in that the valve current I _{Soll is} stored as a point of a pressure-opening flow characteristic. Method according to one of the preceding claims, characterized characterized in that in the implementation of the method the driving situation of the motor vehicle becomes. Method according to Claim 6, characterized that the driving situation of the motor vehicle with the aid of a longitudinal acceleration signal and the engine torque of the drive motor is determined. Method according to claim 7, characterized in that that the procedure during a constant trip performed is and is canceled when a gear shift operation of the drive motor of the motor vehicle or if a deceleration or acceleration command is determined.