Method of Determining an Initial Pressure in a Motor Vehicle Brake System

• US 20080231108A1
• Filed: 08/28/2006
• Published: 09/25/2008
• Est. Priority Date: 09/01/2005
• Status: Active Grant

• Current Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Original Assignee: Continental Teves AG & Company HG (Continental AG)
• Inventors: Kohl, Andreas, Attallah, Faouzi, Sikorski, Frank, Kroh, Lukas, Muller, Jochen, Magel, Guntjor, Mahlo, Rudiger
• Granted Patent: US 8,205,948 B2
• Time in Patent Office: Days
• US Class Current: 303/3
• CPC Class Codes: B60T 8/3655 Continuously controlled electromagnetic valves
• CPC Class Codes: B60T 8/4059 involving the rate of delivery
• CPC Class Codes: B60T 8/4275 Pump-back systems

Abstract

A method of determining an initial pressure which prevails between a master brake cylinder and an inlet valve of a wheel brake cylinder of a motor vehicle brake system. It determines the initial pressure taking into consideration the variation of a follow-up voltage of a clock-operated motor of a pump, which is used for the return delivery of brake fluid from a low-pressure accumulator into the master brake cylinder. Several characteristic quantities of the voltage variation are measured and in each case taken into account to determine an initial pressure value, and the quality and/or reliability of the measured characteristic quantities is evaluated. The characteristic quantities and/or the initial pressure values determined therefrom are filtered and/or conditioned in the event of lack in quality and/or reliability of the measured characteristic quanitites. The initial pressure values determined from the various characteristic quantities are averaged, with only pressure values of similar size being taken into consideration and the initial pressure values are temporally averaged in order to dampen fluctuations.

Claims

1-9. -9. (canceled)

10. A method of determining an initial pressure which prevails between a master brake cylinder and an inlet valve of a wheel brake cylinder of a motor vehicle brake system, which determines the initial pressure taking into consideration the variation of a follow-up voltage of a clock-operated motor of a pump for return delivery of brake fluid from a low-pressure accumulator into the master brake cylinder;

the method comprising the following steps;

measuring several characteristic quantities of the voltage variation

determining an initial pressure value from the characteristic quantities,

evaluating the reliability of the measured characteristic quantities,

filtering and/or conditioning the characteristic quantities or the initial pressure values in the event of lack in reliability of the measured characteristic quantities,

averaging the initial pressure values determined from the various characteristic quantities, in which case only pressure values of similar size are taken into consideration,

temporally averaging the initial pressure values in order to dampen fluctuations; and

generating output information representing an averaged initial pressure value.

11. The method as claimed in claim 10,

wherein the characteristic quantities of the follow-up voltage variation during an on-off-on cycle of a supply voltage at the motor comprise two or more of the following quantities:

the last voltage value when the supply voltage U^OnL is still enabled, the first voltage value when the supply voltage U^OnF is enabled again, the first voltage value after the supply voltage U^Off is disabled, the difference between the last voltage value with the supply voltage still enabled and the first voltage value after the supply voltage U^Fall is disabled, the lowest achieved voltage value with the supply voltage U^Min disabled, the sum of the voltage values with the supply voltage U^Sum disabled, the rise of the voltage drop when the supply voltage U^Slope is disabled, the difference between the lowest achieved voltage value with the supply voltage disabled and the first voltage value with the supply voltage U^Rise being enabled again, the time t^Fall until the voltage drops to zero.

12. The method as claimed in claim 10,

wherein for each characteristic quantity of the voltage variation, a linear relation between characteristic quantity and initial pressure is assumed, the two parameters of which are obtained from measurements for calibration.

13. The method as claimed in claim 10,

wherein the filling levels of two low-pressure accumulators are taken into account to evaluate the reliability of the measured characteristic quantities.

14. The method as claimed in claim 10,

further comprising the step of not determining initial pressure values from the latest measured characteristic quantities and maintaining the previous averaged initial pressure value if the measured characteristic quantities are assessed not to be reliable.

15. The method as claimed in claim 10,

wherein an initial pressure value is determined from the characteristic quantities in spite of lacking reliability of the measured characteristic quantities.

16. An electrohydraulic brake system with a master cylinder and at least one wheel brake with an inlet valve, with a low-pressure accumulator and a pump operated by a clock-operated motor, the pump pumping pressure fluid from the low-pressure accumulator toward the master cylinder, the system performing a method for determining an initial pressure taking into consideration the variation of a follow-up voltage of the clock-operated motor of a pump for return delivery of brake fluid from a low-pressure accumulator into the master brake cylinder by

measuring several characteristic quantities of the voltage variation

determining an initial pressure value from the characteristic quantities,

evaluating the reliability of the measured characteristic quantities,

filtering and/or conditioning the characteristic quantities or the initial pressure values in the event of lack in reliability of the measured characteristic quantities,

averaging the initial pressure values determined from the various characteristic quantities, in which case only pressure values of similar size are taken into consideration,

temporally averaging the initial pressure values in order to dampen fluctuations;

and

generating output information representing an averaged initial pressure value.

17. The brake system as claimed in claim 16,

wherein the averaged initial pressure is used as a controlled variable for regulating braking interventions.

18. The brake system as claimed in claim 16,

wherein the averaged initial pressure is used as a comparison value for testing the operability of a pressure sensor.