Actuation systems

Details Actuation systems Actuation systems

1996-06-24

1998-03-17

Lopez, F. Daniel

Power plants

Pressure fluid source and motor

With control means for structure storing work driving energy

60413, F16D 3102

Patent

active

057273898

DESCRIPTION:

BRIEF SUMMARY
This invention relates to fluid pressure operated actuation systems and in particular, though not exclusively, to such actuation systems for the operation of vehicle clutches used in semi-automatic transmissions of the form described in, for example, the Applicants earlier European patents Nos. 0038113, 0043660, 0059035 and 0101220 and other fluid pressure operated functions.
Actuation systems are already known in which a pump supplies pressurised fluid to interconnected closed centre and open centre circuits each of which includes at least one consumer and the closed centre circuits includes an accumulator which is charged by the pump.
Problems arise with such actuating systems in that the operation of the open centre circuit is often affected by the charging of the accumulator in the closed centre circuit.
It is an object of the present invention to provide an actuating system which at least mitigates the above problem.
Thus according to the present invention there is provided an actuation system comprising: charged by the pump; the accumulator or to the reservoir thus actuating the second consumers and also being operable in response to accumulator pressure levels below a predetermined charge level to restrict the flow of fluid to the or each first consumer to a level sufficient to ensure effective operation of the or each first consumer whilst generating a back pressure sufficient to ensure charging of the accumulator.
By restricting the flow to the first consumer(s) when charging of the accumulator is required in the above manner unaffected operation of the first consumer(s) is ensured.
Both the first and second consumers may be actuated via the valve means.
The valve means may include a first valve having a valve member (such as a spool) which is displaceable both to connect the second consumer(s) to the accumulator or reservoir and also to restrict the flow of fluid to the first consumer(s).
The valve member may be displaced by a solenoid which is activated by a control means which controls operation of the second consumer(s) and also by signals from an accumulator pressure level sensor. Alternatively the displacement of the valve member in response to the accumulator pressure level falling below the predetermined charge level could be achieved by the action of fluid pressure on the valve member.
Where a spool type valve member is used in the first valve means the spool may be provided with one or more grooves or other formation through which the restricted flow to the first consumer(s) takes place.
In an alternative construction the valve means may include a first valve having a valve member which is displaced both to connect the second consumer(s) to the accumulator or reservoir and also to control the rate of charging of the accumulator.
The actuation system may include a separate charging valve means to restrict the flow of fluid to the or each first consumer at accumulator pressure levels below a predetermined charge level.
The actuation system may also include a second valve means to limit the pressure level to which the accumulator can be charged. Conveniently this second valve means may comprise a charging valve and venting valve arrangement of the form 94 20983.0 the disclosure of which is hereby included in the present application.
Several embodiments of the present invention will now be described, by way of example with reference to the accompanying drawing in which:
FIG. 1 shows details of a clutch/steering actuation system in accordance with the present invention;
FIG. 2 shows details of a charging and venting valve arrangement which may be used in the system of FIG. 1;
FIG. 3 shows details of a second form of clutch/steering actuation system in accordance with the present invention;
FIG. 4 shows details of a further form of clutch/steering actuation system in accordance with the present invention which employs a charging and venting valve arrangement similar to that shown in FIG. 2, and
FIG. 5 shows an alternative form of part of the system shown in FIG. 4.
Referring to FIG. 1, the clu

REFERENCES:
patent: 2977761 (1961-04-01), Lewis
patent: 3785393 (1974-01-01), Tanguy
patent: 4332270 (1982-06-01), Budecker

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