Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1996-11-11
1999-10-05
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
188355, 188356, 303 10, 303 11, 303 12, 3031191, 303DIG3, 60412, B60T 1352, B60T 1344, B60T 1702
Patent
active
059611898
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to brake systems for automotive vehicles with a pneumatic brake power booster including two chambers, one of the chambers being adapted to be acted upon by a low pressure and the other one by a higher pressure, and at least one of the chambers being adapted to be connected to a pneumatic pump.
BACKGROUND OF THE INVENTION
German patent No. 27 16 471 discloses a brake system of this type wherein a compressed air pump can be connected to a high pressure chamber of a brake power booster by way of an electrically operable solenoid valve. The pressure in the high pressure chamber is adjusted by way of a pulsed electric actuation of the solenoid valve. A low pressure chamber is directly connected to a vacuum pump.
A disadvantage of this known brake system is the use of a solenoid valve which is complicated and costly and requires an electric or electronic controlling or regulating unit for the actuation. The compressed air pump as well as the vacuum pump are pumps with uninterrupted operation which permanently develop the maximum possible excess pressure or vacuum. The result is a high energy consumption because the full pump rate must be provided in each operating condition of the brake system.
Therefore, an object of the present invention is to overcome the above-mentioned shortcomings, i.e., to suggest an inexpensive, energy-saving and simple generic brake system.
SUMMARY OF THE INVENTION
It is particularly appropriate to activate and deactivate the pump in response to the pressure prevailing in the chamber associated with the pump. In this case, the pump is operated demand-responsively, i.e., when the pressure level in the chamber is below a necessary minimum or in excess of a maximum value. It is thereby ensured that the required pressure level is always available. Further, this arrangement permits an energy saving operation of the pump because the pump is actually activated only in the case of need.
A particularly simple activation and deactivation of the pump is possible when it is driven by an electric motor. The operating means may be electric pressure switches, especially switches responding to vacuum which initiate or interrupt the current supply of the electric motor as a function of the pressure prevailing in the associated chamber. Further, it is advantageous that electric motors are low-cost standard component parts which can be easily connected and operated independently of other aggregates. Expediently, the pressure switches have a hysteresis which prevents a continuous activation and deactivation of the electric motor proximate the pressure level required for switching operations.
Another possibility of activating or deactivating the pump as a function of the pressure prevailing in the associated chamber includes mounting a sensor to sense the power input of the electric motor in the current supply of the motor and controlling the pump in response to the output signal of the sensor. For example, a current sensor may be provided having a variable signal which corresponds to a varying power input of the pump when a constant voltage is applied to the electric motor. The pump can be deactivated at a determined value of the power input and can be re-activated after a defined interval, for example. Thus, there is no need for electric pressure switches.
When the pump is configured as an excess pressure pump, its suction side can be connected to a low pressure chamber by way of a valve assembly operable by the pressure prevailing in this chamber. The pressure side of the pump supplies air directly into the high pressure chamber. It is thereby rendered possible that the pump aspirates air from the low pressure chamber as long as permitted by the pressure prevailing in this chamber. Subsequently, the valve assembly can switch over to a second switch position in which a circulation supply may be provided, for example. However, it is easier to achieve that the suction side of the pump is connected to the atmosphere in the second switch position of
REFERENCES:
patent: 3756666 (1973-09-01), Leiber
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patent: 4497618 (1985-02-01), Anderson et al.
patent: 4738112 (1988-04-01), Nomura et al.
patent: 4932727 (1990-06-01), Wagner et al.
patent: 5658131 (1997-08-01), Aoki et al.
Official English Language Translation of the International Examination Report for Application No. PCT/EP95/01828.
PCT Search Report--Application No. PCT/EP95/01828.
German Search Report--Application No. P4416833.0.
Bohm Peter
Drott Peter
Feigel Hans-Jorg
Kahrs Manfred
Lutteke Harald
Butler Douglas C.
Continental Teves AG & Co. oHG
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