Motors: expansible chamber type – Working member position feedback to motive fluid control – Plural input signal means for single motor valve
Patent
1998-07-02
1999-11-09
Nguyen, Hoang
Motors: expansible chamber type
Working member position feedback to motive fluid control
Plural input signal means for single motor valve
91376R, 605471, F15B 1316, F15B 910
Patent
active
059792922
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of operating a pneumatic brake force booster which includes a booster housing having its interior subdivided by a movable wall into a first chamber (vacuum chamber) and a second chamber (working chamber), and a control housing accommodating a control valve that controls a pneumatic pressure differential which acts upon the movable wall, the control valve comprising a first sealing seat that is operable by an actuating rod and, when opened, permits ventilating the working chamber, a second sealing seat which, when opened, permits a connection between the two chambers, and an elastic valve member which interacts with the two sealing seats, wherein the first sealing seat or another sealing seat interacting with the valve member is operable independently of the actuating rod to the effect of ventilating the working chamber by an electromagnet actuatable by an electronic control unit, and wherein the hydraulic pressure is determined which is introduced into a master brake cylinder connected downstream of the brake force booster.
International patent application WO 93/24353 discloses a method of this type. When the method known in the art is implemented, a memorized nominal braking pressure value is constantly associated with the instantaneous actuating speed of a brake pedal actuating the brake force booster and compared with a measured actual braking pressure value. The brake force booster is driven in response to the comparison result. A disadvantage of the prior art method is that the pressure values are preset by evaluation of the brake pedal movement so that a mere independent activation (which is carried out without operation of the brake force booster by the driver) cannot be realized. Thus, the system for implementing the known method is inappropriate for use in some applications, for example, as a hill holder, for precharging the hydraulic brake system, or for collision avoidance. A pneumatic brake force booster with electromagnetic auxiliary control is disclosed in German patent No. 44 05 092 wherein the first sealing seat is provided on a cylindrical sleeve which is connected to the armature of an electromagnet arranged in the control housing. To permit operation of the prior art brake force booster by the driver, there is provision of a valve piston which is in a force-transmitting connection with the actuating rod. The armature is axially supported on the valve piston and may thus be entrained by the valve piston upon operation by the driver. In the event of independent activation, or energization of the electromagnet, the first sealing seat will lift from the valve member, thereby permitting the atmosphere to flow into the working chamber.
German patent application No. 42 38 333 discloses a vacuum brake force booster having a control valve which is includes a third sealing seat that is operable by an electromagnet and replaces the second sealing seat in terms of effect in an independent activation. The control valve is operated by the electromagnet in opposition to the direction of operation by the driver so that the valve member is moved away from the first sealing seat on the valve piston by displacement of the third sealing seat.
Therefore, an object of the present invention is to disclose a method of operating pneumatic force boosters of the above mentioned generic type which permits a quick pressure increase to a desired value and obviates the need for operation of the brake force booster by the driver. Preferably, the desired pressure value is below the limit which is maximally achievable by the independent activation.
According to the present invention, this object is achieved because the electromagnet is actuated by way of an invariably predefined current variation, and after a fixed pressure value in the master brake cylinder is reached, the hydraulic pressure is controlled by variations of the electric current being fed to the electromagnet. To specify the idea of the present invention, current strength without influencing the control valve, incr
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patent: 4505351 (1985-03-01), Nishikawa et al.
patent: 4966420 (1990-10-01), Schiel et al.
patent: 5096267 (1992-03-01), Volz
patent: 5168790 (1992-12-01), Konishi
patent: 5390497 (1995-02-01), Cottam
Berthold Thomas
Fuhrer Jochen
Klesen Christof
Krebs Stefan
Neu Thorsten
ITT Manufacturing Enterprises Inc.
Nguyen Hoang
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