Motors: expansible chamber type – Working member position feedback to motive fluid control – Electrical input and feedback signal means
Patent
1998-01-26
1999-12-28
Nguyen, Hoang
Motors: expansible chamber type
Working member position feedback to motive fluid control
Electrical input and feedback signal means
91367, 91367R, F15B 1316
Patent
active
060066482
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of operating a pneumatic brake power booster including a movable wall and a control valve controlling a pneumatic pressure differential which acts upon the movable wall, the control valve having at least two sealing seats and an elastic valve member which interacts with the sealing seats, and, on the one hand, being operable by the driver by way of an actuating rod and, on the other hand, by a solenoid which is in a force-transmitting connection with one of the sealing seats.
German patent application No. 43 24 688 discloses a brake power booster for implementing a method of this type. The brake power booster is operable electromechanically irrespective of the driver's wish, i.e. of a brake pedal actuation. The special characteristics of the prior art brake power booster include sensor elements which permit identification of the valve member of the control valve in order to achieve a controlled proportioning of the independent actuating force to be generated by the solenoid. Further, an information about the travel covered during the control process by the electromechanically operable sealing seat is required for the control. This necessitates further sensor elements including the associated electronics.
However, the use of the mentioned sensor means involves a considerable amount of costs.
The article "Electronically Controlled Brake Power Booster" published in the Automobile Technology Journal ATZ 97 (1995) January, No.1, pages 36-37, describes an electrically operable booster with a proportional control. The control valve of the booster is drivable by a proportional electromagnet. A disadvantage in the mentioned booster is the comparatively high weight of the proportional magnet and the related increased overall dimensions of the booster. Another disadvantage is the relatively exact control which is assessed as costly.
Therefore, an object of the present invention is to disclose a method of the previously mentioned type which, when implemented, obviates the need for any additional sensor means and can be achieved at low cost with already provided parts. Another objective is to extend the control range predetermined due to tolerances.
SUMMARY OF THE INVENTION
According to the present invention, this object is achieved because the hydraulic pressure introduced into the master brake cylinder is determined and, along with a preset pressure value signal, is sent to a pressure controller, the output quantity of which corresponds to a control current for the solenoid and is supplied to a limiter. The limiter defines the limits of the desired control range, and its output quantity is compared with the value of the current supplied to the solenoid. The comparison result is sent to a current controller which generates the voltage to be applied to the solenoid.
A second solution of the object to be achieved involves that the hydraulic pressure introduced into the master brake cylinder is determined and, after a comparison with a preset pressure value signal, is sent to a non-linear transmission member with an upward and downward limitation. Connected downstream of the transmission member is a booster having an output quantity which is compared with the value of the current supplied to the solenoid. The comparison result is sent to a current controller which generates the voltage that is to be applied to the solenoid. It is favorable that a pre-control value is added to the output quantity of the non-linear transmission member.
Further details, features and advantages of the present invention can be taken from the following description of four embodiments, making reference to the accompanying drawings wherein corresponding individual parts have been assigned like reference numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 is a greatly simplified view of a first design of a brake system for implementing the method of the present invention.
FIG. 2 is a view, corresponding to FIG. 1, of a second design of a brake system for
REFERENCES:
patent: 4953444 (1990-09-01), Cunningham et al.
patent: 5704694 (1998-01-01), Kozakai
Article published in "ATZ Automobiltechnische Zeitschrift 97", No. 1, Jan. 1995, Germany, pp. 36, 37.
ITT Manufacturing Enterprises Inc.
Nguyen Hoang
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