Power plants – Pressure fluid source and motor – Pulsator
Patent
1998-05-05
1999-08-17
Ryznic, John E.
Power plants
Pressure fluid source and motor
Pulsator
60585, B60T 1700, B60T 1126
Patent
active
059376490
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a brake master cylinder for a hydraulic vehicle brake system according to the preamble of patent claim 1. The invention relates, in particular, to a brake master cylinder suitable for interacting with a brake pressure regulating system which comprises traction control and/or driving dynamics control. Such a brake master cylinder is known from DE 41 12 134 A1 which describes a wheelslip-controlled hydraulic brake system for automobiles.
Hydraulic vehicle brake systems are nowadays often equipped with a brake pressure regulating system which is intended, above all, to prevent the wheels of the vehicle from locking in the event of very sharp braking. A brake pressure regulating system of this type is usually referred to as an antilock system. Increasingly, however, the capabilities inherent in such a brake pressure system are also used for preventing or at least limiting the spin of driven vehicle wheels which may occur, in particular, during acceleration on slippery ground. This is referred to as traction control. Even further developed systems use the brake pressure regulating system in order to neutralize critical vehicle states, for example an imminent swerving of a vehicle on a bend approached too quickly. For this purpose, signals from various sensors are processed, which give information on instantaneous variables, such as, for example, driving speed, steering angle lock, transverse acceleration and other parameters describing the instantaneous driving state, whereupon, when a hazardous driving state is detected, the system attempts to eliminate this hazardous driving state, inter alia by controlled braking actions on individual wheels. Such systems are designated as driving dynamics controls. A fundamental difference between a brake pressure regulating system designed only for antilock braking and a brake pressure regulating system which is employed, furthermore, for traction control or driving dynamics control is that the latter must be capable of building up brake pressure when the brake master cylinder is both actuated and not actuated, since the vehicle driver himself does not actuate the brake when traction control or driving dynamics control is taking effect.
Conventional brake pressure regulating systems have a so-called return pump which is designed for high pressure and a small volumetric flow and is not selfpriming. The hydraulic fluid therefore has to be supplied to the return pump under a particular admission pressure. In brake pressure regulating systems designed only for antilock braking, the pressure generated by the driver in the brake master cylinder by actuating the brake pedal is, under certain circumstances, sufficient for this purpose. If, however, the brake pressure regulating system is also to be employed for traction control and/or driving dynamics control, there must be a so-called precharge pump which can provide the return pump with sufficient admission pressure even when the brake master cylinder is not actuated. The installation of a precharge pump in a brake pressure regulating system normally requires a plurality of electromagnetic valves.
The object on which the invention is based is to simplify brake pressure regulating systems with a traction control and/or driving dynamics control function.
Proceeding from a brake master cylinder of the type initially mentioned, this object is achieved, according to the invention, in that a throttle is arranged in the fluid connection, existing in the installed state of the brake master cylinder, between the delivery side of the precharge pump, the reservoir and the at least one pressure chamber, said throttle not impeding a hydraulic fluid stream out of the reservoir into the at least one pressure chamber and throttling a hydraulic fluid stream from the return connection to the reservoir. By virtue of the common fluid connection between the delivery side of the precharge pump, the reservoir and the at least one pressure chamber in the master cylinder housing, according to the invention the precharge pump act
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Barz Uwe
Mallmann Markus
Wagner Bernd
Lucas Industries Public Limited Company
Ryznic John E.
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