Method for creating low pressure in a brake activation device of a motor vehicle brake system
A method for creating low pressure in a brake activation device of a motor vehicle brake system, comprising a pneumatic brake force booster the interior of which is divided into at least one low-pressure chamber and one working chamber, a brake master cylinder and a pneumatic motor pump unit for creating the low pressure in the low-pressure chamber, which motor pump unit comprises a low-pressure pump and a motor driving the low-pressure pump, a low-pressure level in the low-pressure chamber or a pressure difference between the low-pressure chamber and the working chamber being detected by a sensor and the motor pump unit being activated by an electronic control unit if the pressure falls below a first predefined, lower low-pressure level Pe in the low-pressure chamber and being deactivated if a second predetermined, upper low-pressure level Pa is reached.
1. A method for creating low pressure in a brake activation device of a motor vehicle brake system comprising (i) a pneumatic brake force booster having an interior that is divided into at least one low-pressure chamber and one working chamber, (ii) a brake master cylinder, and (iii) a pneumatic motor pump unit including a low-pressure pump and a motor that is configured to drive the low-pressure pump to create a low pressure in the low-pressure chamber, the method comprising the steps of:
detecting either a low-pressure level (P) in the low-pressure chamber or a pressure difference between the low-pressure chamber and the working chamber;
activating the motor pump unit if the pressure falls below a first predefined, lower low- pressure level (Pe) in the low-pressure chamber;
deactivating the motor pump unit if the pressure reaches a second predetermined, upper low-pressure level (Pa); and
controlling the first predefined, lower low-pressure level (Pe) and the second predefined, upper low-pressure level (Pa) in the low-pressure chamber as a function of a speed (v) of the vehicle.
2. The method as claimed in claim 1 , wherein the detecting step is accomplished by a sensor.
3. The method as claimed in claim 1 , wherein the activating step and the deactivating step are accomplished by an electronic control unit.
4. The method as claimed in claim 1 further comprising the step of reducing the first predefined, lower low-pressure level (Pe) in a low speed range of the vehicle.
5. The method as claimed in claim 1 further comprising the step of increasing the second predefined, upper low-pressure level (Pa) when the speed (v) of the vehicle reaches a predefined speed (v n ).
6. The method as claimed in claim 5 , wherein a deactivation function of the motor pump unit above the predefined speed (v n ) of the vehicle is combined with a time control system.
7. The method as claimed in claim 1 , wherein the motor pump unit is controlled by an electronic pump control unit which is connected to an electronic longitudinal dynamics control unit of the vehicle by a bus system.
8. The method as claimed in claim 1 , wherein the motor pump unit is controlled by an electronic longitudinal dynamics control unit of the vehicle.
9. The method as claimed in claim 1 , wherein the motor pump unit is controlled by an electronic anti-lock braking system (ABS) or an electronic stability program (ESP) control unit which is connected to an electronic longitudinal dynamics control unit of the vehicle by a bus system.
10. A system for creating low pressure in a brake activation device of a motor vehicle brake system, comprising:
a pneumatic brake force booster having an interior that is divided into at least one low- pressure chamber and one working chamber;
a brake master cylinder;
a pneumatic motor pump unit that is configured to create a low pressure in the low- pressure chamber, wherein the pneumatic motor pump unit includes a low-pressure pump and a motor that is configured to drive the low-pressure pump;
a sensor that is configured to detect a low-pressure level (P) in the low-pressure chamber or a pressure difference between the low-pressure chamber and the working chamber; and
an electronic control unit that is configured to (i) activate the motor pump unit if the pressure falls below a first predefined, lower low-pressure level (Pe) in the low-pressure chamber, and (ii) deactivate the motor pump unit if the pressure reaches a second predetermined, upper low-pressure level (Pa),
wherein the first predefined, lower low-pressure level (Pe) and the second predefined, upper low-pressure level (Pa) in the low-pressure chamber are controlled as a function of a speed (v) of the vehicle.