| 摘要 |
A hollow cylinder is slidably received in a bore formed through an engine block with its closed end in contact with a lobed cam mounted on a camshaft, and a piston connected to a push rod is received in an end portion of the bore. A plunger disposed in the bore partly intrudes into the cylinder so as to define a first oil pressure chamber in the cylinder and a second oil pressure chamber between the plunger and the piston. When oil pressure applied to the first chamber is decreased as the engine speed lowers, the plunger moves toward the first chamber to allow the second chamber to communicate with an oil-reserving chamber through a hole. The amount of valve lift in a medium oil pressure range depends on the degree of closing of this hole by the plunger which is moved together with the cylinder by the rotating cam.
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