Fluid-pressure and analogous brake systems – With pump – Pressure control
Reexamination Certificate
1999-07-13
2001-08-14
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
With pump
Pressure control
C303S113200
Reexamination Certificate
active
06273525
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and a device for determining a quantity describing the system pressure in a brake circuit. The phrase “system pressure in a brake circuit” is equivalent to the term “brake circuit pressure” which is why the latter is used hereinafter.
BACKGROUND INFORMATION
Methods and devices for determining a quantity describing the brake circuit pressure are known in various versions from the related art.
German Patent Application No. 43 40 921 describes a brake pressure control system where the brake circuit pressure is estimated for each brake circuit. The hydraulic system disclosed in German Patent Application No. 43 40 921 has two brake circuits. Each of the two brake circuits has two wheels, each connected to the brake circuit by an intake valve and a discharge valve. Each brake circuit also has a precharge pump, a return pump, a return valve and a reversing valve. With the two pumps, a brake pressure can be generated upstream from the intake valves if a brake pressure is to be built up at the wheels. The return valve and the reversing valve are to be driven accordingly. The desired brake pressure can be achieved in the respective brake wheel with the intake and discharge valves assigned to the respective wheel. Based on one brake circuit, valve control signals are determined at least for the intake valves from setpoint brake pressures for the wheel brake cylinders. The brake cylinder pressures enter into the determination of the setpoint brake pressures, with the prevailing brake circuit pressure and the control times of the intake valves being taken into account in the determination of the brake cylinder pressures. The brake circuit pressure is estimated with the help of a recursive method. Distinction is made between two situations in estimating the brake circuit pressure. In one situation, the required pressure buildup is available, i.e., both the precharge pump and the return pump are receiving current, and the return valve and the reversing valve are connected accordingly. It is assumed that in this situation the two pumps are supplying a constant volume flow. The new value for the estimated brake circuit pressure is obtained as a function of the old estimated value for the brake circuit pressure, the control times of the intake valves in the brake circuit, the wheel brake cylinder pressures and the admission pressure set by the driver. In the other situation, both pumps are turned off. The new value for the estimated brake circuit pressure is obtained here as a function of the old estimated value for the brake circuit pressure and the admission pressure set by the driver. The old estimated value for the brake circuit pressure is weighted with a constant factor so that the resulting reduction in pressure in the brake circuit is simulated.
The method according to the present invention and the device for determining the quantity representing the brake circuit pressure according to the present invention can be used in combination with systems for controlling brake slip or drive slip and in combination with systems for controlling a quantity describing the driving dynamics of a vehicle. Systems for regulating drive slip or brake slip are described in a general form, for example, in the book “Bremsanlagen fur Kraftfahrzeuge” (Brake System for Motor Vehicles) published by Robert Bosch GmbH of Stuttgart, VDI Verlag, Dusseldorf, 1
st
edition, 1994. Systems for controlling a quantity describing the driving dynamics of a vehicle are described, for example, in the article “FDR-Die Fahrdynamikregelung von Bosch” (Bosch Method of Regulating driving Dynamics) published in Automobiltechnische Zeitschrift (ATZ), (Automotive Engineering Journal) vol. 96, no. 11 (1994) pp. 674-689.
The object of the present invention is to improve the determination of a quantity describing the brake circuit pressure.
SUMMARY OF THE INVENTION
A brake system according to the present invention contains first means (e.g., a first arrangement) for each wheel brake cylinder having an intake valve and a discharge valve plus at least one storage chamber assigned to the respective brake circuit. Furthermore, the brake system contains second means for each brake circuit with which a pressure buildup can be achieved independently of the driver. These first and second means include at least one pump, a precharge valve and a discharge valve. It is possible to provide a motor for each pump or one motor for the two pumps together. In particular, it is also possible for a pump with two pump elements and one motor to be used in this connection, with one pump element being assigned to each brake circuit.
The advantage of the method according to the present invention and the device according to the present invention with regard to determination of a quantity representing the brake circuit pressure in a pressure buildup that is independent of the driver is that at least the pump delivery performance detected is taken into account in determining the quantity representing the brake circuit pressure. This pump delivery performance enters into a quantity describing the status of the brake circuit, with the quantity representing the brake circuit pressure being determined at least as a function of the quantity describing the status of the brake circuit during a pressure buildup that is independent of the driver.
The quantity describing the status of the brake circuit is advantageously determined at least as a function of the intake valves opened in the corresponding brake circuit or as a function of the value of the quantity representing the brake circuit pressure. In taking into account the intake valves opened in the corresponding brake circuit, a distinction is made first according to the number of intake valves opened and then according to the type of intake valves opened. A better simulation of the pressure actually prevailing in the brake circuit is achieved in determining the quantity representing the brake circuit pressure due to the differentiation according to type, i.e., differentiating whether the intake valve of a front wheel or the intake valve of a rear wheel is opened.
Likewise, a better simulation of the pressure actually prevailing in the brake circuit by the quantity representing the brake circuit pressure is achieved by taking into account the pump delivery performance during the pressure buildup that is independent of the driver. Various criteria are provided for determining the pump delivery performance during a pressure buildup that is independent of the driver. At least one criterion taken into account is whether the pump is in a startup phase. Another criterion taken into account here is at least one factor influencing the pump delivery rate resulting from the brake circuit pressure. Furthermore, another criterion taken into account is at least whether a pressure buildup that is independent of the driver is occurring in another brake circuit of the brake system while the pump is delivering. Then at least one factor for weighting the quantity describing the status of the brake circuit is determined as a function of at least one of these criteria. Thus the pump delivery performance during a pressure buildup that is independent of the driver enters into the quantity describing the status of the brake circuit.
In addition, it is advantageous, starting from the quantity describing the status of the brake circuit to determine a quantity which describes the change in brake circuit pressure over time. The instantaneous value for the quantity representing the brake circuit pressure is determined at least as a function of the quantity describing the change in brake circuit pressure over time or as a function of a previous value for the quantity representing the brake circuit pressure.
Moreover, in determining the quantity describing the change in brake circuit pressure over time, a quantity representing the volume delivered into the brake circuit through the precharge valve is taken into account. The quantity representing the volume delivered into the brake
Erban Andreas
Gerdes Manfred
Weiss Karl-Josef
Kenyon & Kenyon
Robert & Bosch GmbH
Schwartz Christopher P.
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