Hydraulic play compensation element for a valve gear of an internal combustion engine

#The invention relates to a hydraulic clearance compensation element for a valve train of an internal combustion engine according to the precharacterising part of claim 1.

#Such a clearance compensation element is known from DE 38 00 945. In this clearance compensation element, the additional controllable check valve in the connection between the pressure chamber and the supply chamber, under certain engine operating conditions such as in particular during engine braking operation, serves to prevent lengthening of the clamping length of the clearance compensation element by closing this additional check valve. While an increase in the clamping length when the additional check valve is open takes place by opening the one-way valve provided in the connection between the pressure chamber and the supply chamber, a throttling channel, which bridges the one-way valve between the pressure chamber and the supply chamber, is used for a possible decrease in clamping length. In order to prevent an irreversible decrease in clamping length when the additional check valve is closed, as a result of the pressure liquid flowing out from the pressure chamber via the throttling channel, the throttling channel must be closed when the additional check valve is closed. In practical operation, the type of throttling channel which is used in the known clearance compensation element, said channel being a throttling port, as well as the way of closing said throttling channel when the additional check valve is closed, cause difficulties.

#It is thus the object of the invention to provide a design of the generic clearance compensation element where these difficulties do not occur.

#The drawing shows one advantageous embodiment of the invention.

#The following are shown in the drawing:

#FIG. 1 a longitudinal section of a clearance compensation element with a buffer space in the state with the smallest possible volume; and

#In a (merely suggested) engine housing 1 of an internal combustion engine (not shown in detail), a clearance compensation element 3 is slidably inserted in a housing borehole 2, in longitudinal direction of the borehole. The clearance compensation element 3 comprises as its first component a cylinder part 4, closed on one side, in which a piston part 6 is slidably held between a valve plunger or valve stem (not shown) and an optionally provided compression spring 5. The compression spring 5 is supported by the closed bottom part of the cylinder part 4 and by a facing wall of the piston part 6. As a result of this, the cylinder part 4 and the piston part 6 are pretensioned in opposite movement directions so that on the one hand the closed bottom part of the cylinder part 4 rests without play against a control cam (not shown), while on the other hand the piston part 6 rests without play against the plunger or stem of the charge exchanging valve.

#The piston part 6 and the cylinder part 4 enclose a pressure chamber 7 which is filled with lubricating oil from a supply chamber 8 formed in the piston part 6, with said lubricating oil being supplied from the housing borehole. In the drawing, this supply is shown by flow arrows. In this way, the supply chamber 8 is continuously being fed with lubricating oil from the lubricating oil circulation system of the internal combustion engine.

#In order to prevent any return flow of lubricating oil from the pressure chamber 7 to the supply chamber 8, a connection channel 9, provided between said two chambers, can be closed off by a spring-loaded one-way valve 10 arranged on the side of the pressure chamber. If any play develops in the valve train, the compression spring 5 located in the pressure chamber 7 slides the piston part 6 in the direction of the plunger coupling. As a result of the pressure decrease which then occurs in the pressure chamber 7, the one-way valve 10 is controlled by the pressure of the lubricating oil in the supply chamber 8, and lubricating oil is supplied to the pressure chamber 7.