Power plants – Pressure fluid source and motor – Pulsator
Patent
1997-07-10
1998-12-29
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Pulsator
92 5R, 92 65, B60T 1722
Patent
active
058529365
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a pressure medium actuated control device, comprising a cylinder with a cylinder chamber, at least first and second piston elements displaceable relative to each other in the cylinder chamber, a first piston rod which is joined to the first piston element and which protrudes out of the cylinder chamber, and a pressure medium reservoir opening into a portion of the cylinder chamber located between the piston elements, the second piston element having an end portion sealing against the cylindrical wall of the cylinder chamber with an end edge which, in a rest position of the piston element, permits communication between the reservoir and the cylinder chamber and which, after initial movement of the second piston element, breaks said communication to enclose a pressure medium volume between the piston elements.
Control cylinders of the above described type are used for various applications where there is a need for automatic compensation for changes in the stroke of the control cylinder piston rod. One example of such an application is the control cylinder in a friction clutch between a vehicle engine and a transmission, where the length of travel of the clutch pressure plate must compensate for the wear on the friction disc and the pressure plate so that the clutch will not begin to slip after a certain amount of wear. This means that the piston joined to the piston rod must be allowed to back into the cylinder as the disc is worn to thereby allow the pressure plate to advance a distance corresponding to the wear. This occurs automatically by virtue of the fact that pressure medium in the space between the pistons is able to drain into the reservoir as the wear takes place.
In certain applications there is a need to receive continuous information concerning the position of a first piston element relative to the cylinder. This can be achieved with various different known types of position sensors placed at suitable locations outside the cylinder to sense the position of some part of the piston rod projecting outside the cylinder or of some link or lever attached thereto.
SUMMARY OF THE INVENTION
The purpose of the present invention is in general to achieve a control cylinder with a compensation function of the type described by way of introduction, in which a position sensor is integrated so as to eliminate the need for a separate position sensor placed outside the cylinder or at an unsuitable location outside the cylinder. A particular purpose is to achieve a control device of this type which is particularly suited for use in operation of a vehicle clutch.
This is achieved according to the invention by virtue of the fact that the first piston element is joined to a second piston rod, which is directed oppositely to the first piston rod and sealingly projects into a through-bore in the second piston element, and that a position sensor is arranged to sense the position of the first piston element relative to the cylinder, said sensor comprising a first sensor element in the form of an elongated body which extends past the distal end of the second piston rod and parallel therewith and cooperates with a second sensor element, one of said sensor elements being fixed relative to the cylinder while the other of said sensor elements is fixed relative to the second piston rod.
The design according to the invention provides a control cylinder with a position sensor function, in which the position sensor is entirely integrated in the cylinder and is therefore not affected by the external conditions at the mounting location of the control cylinder. The sensor is also completely protected against external damage.
The control cylinder according to the invention is particularly suited for use as a "flange-mounted" clutch cylinder in vehicles, i.e. in an installation where the cylinder has a front flange which is screwed directly to the clutch housing and where the piston rod is not accessible from outside.
In one embodiment, the position sensor can be a linea
REFERENCES:
patent: 3654549 (1972-04-01), Maurer et al.
patent: 4585207 (1986-04-01), Shelton
patent: 4656457 (1987-04-01), Brausfeld et al.
patent: 4745999 (1988-05-01), Brugger et al.
AB Volvo
Lopez F. Daniel
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