Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1995-09-14
1998-07-14
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031133, B60T 844
Patent
active
057793263
DESCRIPTION:
BRIEF SUMMARY
This application is the U.S. national-phase application of PCT International Application No. PCT/EP93/03246.
BACKGROUND OF THE INVENTION
The present invention pertains to an actuating unit, comprising a pneumatic brake booster, preferably a vacuum brake booster, as well as a main brake cylinder arranged downstream of the pneumatic brake booster, for a locking-protected motor vehicle brake system with a central electronic control unit, to the inputs of which output signals of sensors detecting the rotation behavior of the wheels to be braked are sent, wherein two pressure spaces, limited by at least two pistons, as well as a modulator space are provided in the main brake cylinder. The modulator space forms part of the first pressure space in the normal braking mode and can be connected to the wheel brakes in the brake pressure control mode separately from the first pressure space. The modulator space is limited by a modulator piston which is in force-transmitting connection with the movable wall of the brake booster and forms an outer part of the first primary piston which limits the first pressure space and is made of at least two parts. The other inner part of the modulator piston cooperates with an input member transmitting the actuating force of the brake booster to actuate a control valve which is arranged in a control housing and controls a pneumatic pressure difference acting on the movable wall.
Such an actuating unit is known, e.g., from DE-OS 41 01 480. In the brake pressure control mode, the necessary pressure modulation is performed by ventilating the vacuum chamber of the pneumatic brake booster which is otherwise connected to the vacuum source. An external pneumatic valve arrangement, which makes possible a connection between the vacuum chamber and the vacuum source or the atmosphere as a function of control signals of the central electronic control unit, is provided for this purpose.
The considerable reduction in the vacuum level, which occurs in the pressure control mode because of the interruption in the energy or vacuum storage taking place in the vacuum chamber, can be considered to be particularly disadvantageous in the prior art actuating unit. Relatively large surfaces, to which the pneumatic pressure difference can be admitted and which can be embodied only with a brake booster of tandem design, are therefore necessary within the brake booster housing. Especially the considerable size and the high manufacturing costs are felt to be disadvantageous in the case of a tandem brake booster. In addition, it is necessary to move large masses (e.g. the control housing), especially during operation.
Another disadvantage is that a high degree of opening of the atmospheric sealing seat is provided at the valve piston of the control valve in the control which leads to an unsatisfactory release behavior of the brakes and is considered to be another disadvantage.
The dimensioning of the vacuum chambers of the prior art actuating unit, which must be fairly small in order to achieve a rapid pressure build-up and rapid reduction in pressure in the brake pressure control mode, also is considered a disadvantage. However, the consequence of this is the absence of a vacuum reserve. The use of the above-mentioned pneumatic valve arrangement also causes additional costs, which adversely affect the price of the system.
DE-PS 29 25 550 discloses an actuating unit which is comprised of a vacuum brake booster and a main brake cylinder arranged downstream of the vacuum brake booster. The movable wall of the brake booster is arranged displaceably on and separately from the control housing via the intermediary of a spring.
The movable wall moves forward during the actuation of the brake booster, while the control housing remains in the starting position until it is carried by the movable wall due to its engagement with a radial collar provided on the control housing. This leads to poor meterability of the brake force in the initial area of actuation. The carrying of the control housing leads to an abrupt change
REFERENCES:
patent: 3321916 (1967-05-01), Cripe
patent: 4767165 (1988-08-01), Burgdorf
patent: 5096267 (1992-03-01), Volz
patent: 5172964 (1992-12-01), Levrai et al.
patent: 5181769 (1993-01-01), Schiel et al.
patent: 5332302 (1994-07-01), Maas
Feigel Hans-Jorg
Neumann Ulrich
Schiel Lothar
Graham Matthew C.
ITT Automotive Europe GmbH
Lewis J. Gordon
Twomey Thomas N.
LandOfFree
Actuating unit for a locking-protected motor vehicle brake syste does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Actuating unit for a locking-protected motor vehicle brake syste, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Actuating unit for a locking-protected motor vehicle brake syste will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1875386