Offset valve lifter effecting valve rotation

Abstract

An arrangement for rotating a valve of a reciprocating internal combustion engine relative to the valve seat in addition to the normal reciprocating motion of the valve, whereby to more evenly distribute wear on the valve and on the valve seat, and, in the case of an exhaust valve, to more uniformly distribute heating of the valve and thus avoid or minimize thermal distortion of the exhaust valve. The rotation of the valve is obtained by use of the well known principle in accordance with which the central longitudinal axis of the valve lifter is offset from the central plane (as measured in the lengthwise dimension of the cam shaft) of the rotating cam which imparts reciprocatory movement to the valve lifter and thus to the valve. The offset relation just described imparts a rotary movement to the valve lifter which, in turn, imparts a rotary movement to the valve during the period of cam rotation when the valve is lifted off the valve seat. In applicant's construction, two aligned bores preferably of equal diameter are provided in the cylinder block or engine body, the two bores lying on a common axis X-X with each other and with the central plane of the cam which actuates the valve lifter. The first or upper bore in the cylinder block receives a guide bushing having a valve-stem-receiving bore which is concentric and coaxial with the internal diameter of its corresponding cylinder block bore and thus lies on the axis X-X. The second or lower bore in the cylinder block receives a second guide bushing having a valve-lifter-stem-receiving bore lying on an axis Y-Y which is eccentric relative to internal diameter of its corresponding cylinder block bore. Thus the valve lifter whose stem is received by the bore of the second guide bushing lies on an axis Y-Y which is eccentric relative to the axis X-X which passes through the central plane of the cam. This eccentric relation of the axis of the valve lifter relative to the central plane of the cam causes rotation of the cam to impart a rotary motion to the valve lifter, which, in turn, imparts a rotary movement to the valve during the period when the valve is off the valve seat. Applicant's construction has the advantage that the two aligned preferably equal diameter bores in the cylinder block or engine body can be made by relatively simple and inexpensive machining operations, with the eccentric relation of the valve lifter to the cam being provided by a guide bushing having an eccentric bore therein, thereby eliminating the need for drilling an eccentric bore in the cylinder block for receiving the stem of the valve lifter.