Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2000-01-21
2001-05-08
Ryznic, John E. (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
C060S560000
Reexamination Certificate
active
06226993
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a fully hydraulic brake booster/master cylinder unit according to the precharacterizing clause of claim
1
. Such a brake booster/master cylinder unit is known, for example, from WO 97/18116.
DE 40 29 114 A1discloses a hydraulic brake booster/master cylinder unit with a first booster chamber and a second booster chamber. During operation, hydraulic pressure is fed from the first booster chamber via a pressure-reducing valve, a pressure-regulating valve or a directional or shut-off valve to the second booster chamber, in order to implement specific characteristic curves.
In contrast to the brake booster/master cylinder units still predominantly used today, in fully hydraulic brake booster/master cylinder units the boosting of the actuating force introduced is not achieved with the aid of a vacuum, but purely hydraulically. In a similar way to conventional vacuum brake boosters, the actuating force normally introduced by the vehicle driver via a brake pedal is boosted proportionally, in that hydraulic fluid under pressure is supplied to a booster chamber in a controlled manner by means of a valve, in order to assist the pressure build-up in the pressure chamber or pressure chambers of the master cylinder which are connected to the individual brake circuits of the vehicle brake system. When the brake is released, this booster chamber is then relieved of pressure again in a controlled manner by means of said valve.
It is desirable to design fully hydraulic brake booster/master cylinder units in such a way that the boosting force exerted in each case by the brake booster is variable, so that, for example, adaptation to different load states of the vehicle can take place. In specific driving situations, it may also be desirable to exert an additional braking force, for example when it has been recognized that the actuating force exerted by the driver is not sufficient in order, for example, to avoid a collision with an obstacle. The vehicle driver should, however, notice such actions on the system as little as possible, so as not to be needlessly irritated.
SUMMARY OF THE INVENTION
The object on which the invention is based, is to provide a brake booster/master cylinder unit, in which brake boosting can be adapted to the operating conditions and braking situations prevailing in each case, without this being brought to the vehicle driver's notice in a disturbing way.
Proceeding from the brake booster/master cylinder unit mentioned in the introduction, this object is achieved in that there is, in addition to the first booster chamber, a second booster chamber, to which hydraulic fluid under pressure can be supplied independently of the first booster chamber. In a way which is particularly advantageous in terms of design, the second booster chamber is produced by means of an auxiliary piston which is arranged sealingly and floatingly in the bore of the brake booster/master cylinder unit and of which one end wall forms a further boundary wall of the first booster chamber and the opposite other end wall forms a boundary wall of the second booster chamber.
Whilst the first booster chamber is supplied with hydraulic fluid under pressure in the usual way, in order, as is customary, to boost the actuating force introduced by the vehicle driver, the braking force may be boosted, as required, by the supply of hydraulic fluid under pressure into the second booster chamber, for example as a function of predetermined parameters, such as, for example, the load state, the stopping distance still available, etc., without the driver noticing this, since braking force feedback takes place only via the first booster chamber. Thus, for example, a vehicle brake system can be produced, in which a specific actuating force introduced by the driver always brings about the same vehicle deceleration, irrespective of the vehicle load. For this purpose, additional braking force assistance is provided, according to the load of the vehicle, by the introduction of hydraulic fluid under pressure into the second booster chamber, so that the driver, as a result of his actuating force, obtains vehicle deceleration which always corresponds to that which he would obtain by means of this actuating force if the vehicle were not loaded. By means of the second booster chamber, fully automatic braking operations can also be carried out, such as are necessary, for example, in connection with recently propounded headway control systems. A vehicle driver may nevertheless act in the usual way, by depressing the brake pedal, on such a braking operation taking place automatically, for example in order to boost it.
In a preferred embodiment of the brake booster/master cylinder unit according to the invention, a valve independent of a displacement of the input member of the brake booster/master cylinder unit controls the supply of pressurized hydraulic fluid to the second booster chamber. Advantageously, this valve is an electromagnetic valve designed, in particular, as a proportional valve.
According to a development of the invention, a release switch cooperating with said input member detects the end of actuation of the brake booster/master cylinder unit and the valve controlling the supply of pressurized hydraulic fluid to the second booster chamber thereupon assumes a position in which the pressure present in the second booster chamber is reduced.
In preferred embodiments of the brake booster/master cylinder unit according to the invention, a first pressure sensor detects the pressure in the first pressure chamber (primary pressure chamber) of the master cylinder and a second pressure sensor detects the pressure in the first booster chamber. By evaluation of the signals from these pressure sensors, it is possible, for example, to determine whether the braking force assistance provided by means of the first booster chamber is sufficient to achieve a desired deceleration.
All the embodiments of the brake booster/master cylinder unit according to the invention advantageously cooperate with an electronic control apparatus activating the valve which controls the supply of pressurized hydraulic fluid to the second booster chamber. Preferably, the control apparatus will control said valve, inter alia, as a function of signals from the release switch and/or from the pressure sensors. The control apparatus may, of course, also carry out the activation, for example in cooperation with a pedal travel sensor, of that valve which controls the supply of hydraulic pressure to the first booster chamber.
REFERENCES:
patent: 4096696 (1978-06-01), Van House
patent: 4244185 (1981-01-01), Belart
patent: 4244186 (1981-01-01), Mehren
patent: 4543791 (1985-10-01), Burgdorf et al.
patent: 4736588 (1988-04-01), Leiber
patent: 4843819 (1989-07-01), Leiber
patent: 4891945 (1990-01-01), Becker
patent: 5066077 (1991-11-01), Farr
patent: 5081841 (1992-01-01), Nishii
patent: 5120115 (1992-06-01), Schmitt et al.
patent: 2017185 (1971-11-01), None
patent: 2725941 A1 (1978-12-01), None
patent: 3832722 A1 (1990-03-01), None
patent: 4029114 A1 (1991-04-01), None
patent: 420175 (1990-09-01), None
patent: 09099833 (1995-04-01), None
patent: 97/18116 (1997-05-01), None
Lucas Industries Public Limited Company
MacMillan Sobanski & Todd LLC
Ryznic John E.
LandOfFree
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