Power plants – Pressure fluid source and motor – Pulsator
Patent
1992-10-28
1994-08-16
Look, Edward K.
Power plants
Pressure fluid source and motor
Pulsator
60402, B60T 1320, F16D 3102
Patent
active
053375645
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a force augmenting device, such as a clutch-servo for engaging and disengaging vehicle clutches, which device constitutes, a working or slave device arranged for fluid connection with a master cylinder to be operated by the vehicle's driver, comprising a working cylinder unit which has a piston installed in a working cylinder, housing or the like, which piston is connected to the unit which is to be actuated by the force or pressure augmenting device, and a control valve unit for the working cylinder, with a valve body which is installed in a valve housing with a supply channel and a return channel for a servo pressure fluid where the master cylinder has a fluid connection with the working cylinder unit and the control valve unit in such a way that the fluid from the master cylinder simultaneously exerts a force on the piston and on the valve body, in order to try to move the piston and the valve body respectively when the driver operates the master cylinder, and the valve body is arranged so as to provide communication between the working cylinder's cylinder space and the return channel for the servo pressure fluid when the master cylinder is not in operation, there being no functionally determined mechanical connection between the working cylinder unit and the valve unit.
A device of the above-mentioned type is described in U.S. Pat. No. 3,182,443, but since it comprises very many components it will thus be liable to failure during use. Furthermore these components have to be produced with fine tolerances, which makes this an expensive arrangement. The valve device is installed inside the piston, which therefore also has to be dismantled if the valve unit fails.
A further device of the above-mentioned type is also known from DE 24 40 039, where the piston is mechanically connected to a valve body which follows the movement of the piston when the clutch pedal is moved. Due to the substantial movement of the valve body, this will be subject to relatively heavy wear and tear, and as the working cylinder and the valve unit constitute a mechanical unit, both have to be dismantled if only one of the devices should fail. Moreover, the valve sealing rings are subject to great differential pressure, which makes the valve body hard to move.
Moreover, from EP patent application No. 0 310 733 it is known that a master cylinder may be hydraulically connected to a working cylinder and a control valve, the pressure from the master cylinder controlling the control valve which in its turn regulates the servo pressure fluid's access to a second working cylinder. The control valve which is shown, however, is a seat valve. Valves of this kind are unsuitable for proportional control purposes, and it has been shown that seat valves used in this connection cause relatively severe hysteresis while in addition the force required to operate the master cylinder will be highly dependent on the pressure of the servo pressure fluid.
The object of the invention is to provide a clutch-servo of the type described which is not encumbered with the above-mentioned disadvantages.
SUMMARY OF THE INVENTION
This object is achieved by providing in the above-described force or pressure augmenting device a valve unit that comprises a slide valve where the valve body is axially movable in a bore and comprises a first and a second end section and respectively whose diameter is adapted to suit the diameter of related bore sections of the bore, and which are connected to each other via a stem section, whose diameter is smaller than the diameter of the end sections, so that the bore, the end sections and the stem section define a valve room, whereby the outer end of the first end section, calculated in the longitudinal direction, is arranged so as to be actuated by the fluid from the master cylinder and to abut against a shoulder of the valve housing, a return device attempts to move the valve body against the shoulder, and the return channel and the supply channel for servo fluid are situated bes
REFERENCES:
patent: 2328637 (1943-09-01), Freeman
patent: 2467273 (1949-04-01), Rockwell
patent: 2879645 (1959-03-01), Ingres
patent: 3182443 (1965-05-01), Hermanns
patent: 4254623 (1981-03-01), Dauvergne
patent: 4449369 (1984-05-01), Dauvergne
patent: 4469011 (1984-09-01), Loeffler
patent: 4494377 (1985-01-01), Sato
patent: 5061016 (1991-10-01), Hirobe
Bakke Asbjorn
Pedersen Tore
Kongsberg Automotive A/S
Look Edward K.
Ryznic John
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