Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1993-09-24
1995-10-03
Ballato, Josie A.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303 11, 30312205, B60T 840, B60T 848, B60T 894
Patent
active
054546320
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic brake system having: (1) anti-lock control and/or traction slip control, (2) an electric-motor-driven hydraulic pump for auxiliary pressure supply during a controlled braking operation and during a traction slip control operation by means of brake management, and (3) an electronic control unit for controlling the auxiliary pressure and for modulating or controlling the braking pressure in the wheel brakes of the controlled wheels in dependence on the rotational behavior of the wheels and/or on signals representing the proper operation of the brake system and of the electronic elements or pointing out malfunctions.
Hydraulic brake systems that are known and provided with electronic anti-lock control and traction slip control are equipped with a one-circuit or multi-circuit hydraulic pump for auxiliary pressure supply. Usually, electric-motor-driven pumps are used that are turned on by the associated electronic control unit upon the onset of control. The hydraulic energy consumption varies very much depending on the control operation and control phase. The nominal capacity of the motor-and-pump unit, of course, is arranged to handle the maximum demand that may appear in certain situations during an anti-lock control operation. As regards traction slip control by means of brake management, where the pump is to deliver the pressure for the application of the brake, less energy and less hydraulic pressure, in principle, are needed as compared with anti-lock control. For cost reasons, the same unit is used for anti-lock control and traction slip control, although a smaller, less potential motor-and-pump unit would be sufficient for traction slip control.
The noise developed upon the onset of control and caused by the turning-on or rather by the operation of the hydraulic pump, however, is felt as a disturbance, namely a reduction in driving comfort, during a traction slip control operation.
SUMMARY OF THE INVENTION
Therefore, it is an objective of the present invention to reduce decisively these troublesome noises in a simple manner incurring as little expenditure as possible. In achieving this aim, however, operational reliability is not to be reduced even in unfavorable situations.
It has been found that this object is achieved by arranging a brake system of the type referred to above, so that during a traction slip control operation, the speed of the hydraulic pump or rather of the pump motor is reduced by limiting the power consumption of the drive motor to a predetermined value where the speed and the noise development are small relative to the noise development with nominal capacity. In addition, the control unit will cancel the power limitation in situations critical to safety and reliability or in case of certain malfunctions of the control system. The speed limitation is expediently controlled by the electronic control unit or by additional circuitry.
In accordance with the present invention, there is, thus, a limitation of the current consumption and, hence, of the power consumption of the drive motor of the hydraulic pump in case of a traction slip control operation, thereby considerably reducing the mainly motor-speed-dependent noise development to a level which no longer will be felt to be troublesome or, at most, minimally so. In practice, a speed of 40% to 60% of the nominal speed is sufficient during traction slip control. In situations critical to safety and reliability, such as in case of insufficient supply voltage, extreme outside temperatures etc., the power limitation is cancelled. Consequently, noise reduction is achieved without any losses as regards the safety and reliability of the controlled brake system.
In accordance with an advantageous embodiment of the present invention, which is characterized by particularly low manufacturing expenditure, an ohmic resistor is inserted into the electric attachment of the pump motor in order to limit the power consumption, with the ohmic resistor being bridged by the conta
REFERENCES:
patent: 4728156 (1988-03-01), Burgdorf et al.
patent: 4892364 (1990-01-01), Burgdorf
patent: 5000520 (1991-03-01), Schmitt
Burgdorf Jochen
Kuhn Wieland
Alfred Teves GmbH
Ballato Josie A.
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