| 摘要 |
The present invention relates (with reference to Figure 1), to a valve operating mechanism for operating a poppet valve (10). The mechanism comprises: a cam (13) mounted on a camshaft (14); a first rocker (15) which is pivotally mounted on a first rocker shaft (17) and which is driven by the cam (13) to pivot in an oscillatory manner; and a second rocker (16) which is pivotally mounted on a second rocker shaft (21) spaced apart from the first rocker shaft (17) and which engages the poppet valve (10). The first rocker (15) has a cam surface (30) and the second rocker (16) has a reaction surface (31). A follower member (27) is arranged between the cam surface (30) and the reaction surface (31) in simultaneous abutment with both. As the first rocker (15) pivots the follower member (27) moves relative to the cam surface (30) and relays camming action of the part of the cam surface (30) engaged by the follower member (27) to the reaction surface (31) and thereby causes the second rocker (16) to pivot and impart motion to the poppet valve (10). A control mechanism (28,29) can move the follower member (27) relative to the cam surface (30) in order to vary which part of the cam surface (30) is engaged by the follower member (27). The rocker shafts (17,21) are arranged with respect to one another and the control mechanism (28,29) is configured such that when the follower member (27) is moved by the control mechanism (28,29) to increase maximum lift of the poppet valve then distance between the follower member (27) and the first rocker shaft (17) is increased and distance between the follower member (27) and the second rocker shaft (21) is decreased. |
