Motors: expansible chamber type – With motive fluid valve – Valved piston
Patent
1991-09-25
1992-11-03
Look, Edward K.
Motors: expansible chamber type
With motive fluid valve
Valved piston
60587, 60589, 60592, 403326, F15B 1108
Patent
active
051598710
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a cylinder-piston unit having a central valve, as generically defined hereinafter. Such a unit is already known from U.S. Pat. No. 4,550,567, in which the central valve shaft is embodied as a screw, the cylinder head of which reaches behind the spring plate remote from the piston. Toward the piston, the valve shaft is screwed into a valve body carrying the closing element of the central valve, and the actuating spring engages this valve body. In turn, the valve body is longitudinally guided in a piston in a bore that has a flat valve seat on its bottom.
Stringent demands for the functional reliability of such cylinder-piston units having a central valve are made, particularly if the unit is to be used in vehicle brake systems. However, the known unit has the disadvantage that the screw connection between the valve shaft and the valve body is not secured against loosening. As a result, a change in the spacing between the closing element and the valve seat can occur, which disadvantageously causes a change in the closing travel of this valve. As a result, because of a change in the spacing between the spring plates, a change in the tethering arrangement of the restoring spring also ensues. Moreover, the screw connection allows errors in alignment between the valve shaft and the valve body, which disadvantageously change the closing behavior of the central valve.
ADVANTAGES OF THE INVENTION
The piston-cylinder unit according to the invention has the advantage over the prior art that because the sleeve fits over the snap ring, a form-fitting connection between the sleeve and the valve shaft is attained, which satisfies very high safety requirements. Even if the snap ring breaks, the connection cannot come undone, because the snap ring cannot escape from the groove of the valve shaft. The action of the actuating spring upon the valve shaft is therefore reliably maintained. Moreover, no change in the valve closing travel and in the tethering arrangement of the restoring spring can occur. In addition, the material connection between the valve closing element and the valve shaft makes for great safety against disconnection of these two components having special relevance to safety. Finally, it is advantageous that the individual parts comprising the spring plate, springs, valve shaft and closing element, sleeve and snap ring, form a component unit that can be pre-assembled independently of the piston and tested before it is introduced into the cylinder.
By the provisions recited herein, advantageous further features of and improvements to the piston-cylinder unit disclosed are possible.
The provision of dimensioning of the valve closing element in view of the size of the inside bore of the sleeve allows the closing element to be joined to the valve shaft in a single joining process, which happens before the mounting of the individual parts (spring plate, springs) that are to be lined up on the valve shaft. The quality of the connection can therefore be assured better than in the case of a valve shaft having pre-mounted components.
A further feature is advantageous in the sense that the embodiment of the valve seat, in the closing process of the central valve, effects centering of the closing element, the shaft of which, by the shaping of the collar, can compensate for alignment errors without thereby reducing the size of the contact surface area of the spring plate remote from the piston on the valve shaft.
DRAWING
An exemplary embodiment of the invention is shown in the drawing and described in further detail in the ensuing description. Shown are:
FIG. 1 illustrates a cross-sectional view of a cylinder-piston unit having a central valve, and
FIG. 2 illustrates an enlarged cross-sectional view of the central valve as a pre-assembled component unit, on a different scale from FIG. 1.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
The cylinder-piston unit 10 shown in the drawing is used in a traction control system with braking intervention in a motor vehicle.
REFERENCES:
patent: 4405251 (1983-09-01), Kolchinsky et al.
patent: 4922120 (1990-05-01), Becker et al.
Standard Handbook of Fastening and Joining, McGraw Hill Book Co., 1977, pp. 3-2 and 3-10 to 3-11.
Greigg Edwin E.
Greigg Ronald E.
Look Edward K.
Lopez F. Daniel
Robert & Bosch GmbH
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