| 摘要 |
An internal combustion engine comprising a spring-loaded engine valve (13) actuatable by means of a cam (2), a tappet (4) and a push rod (10), the cam (2) having a pre-lift ramp (5) for effecting exhaust braking of the engine. A single piston (6) is slidable in the tappet (4) between a bottom stop (8) and a top stop (7) therein and biased by a spring (9) against the top stop (7) and/or the push rod (10). The tappet (4) has an inlet (14) for hydraulic, control fluid to bias the piston (6) towards the top stop (7). There is also a valve (17) preventing escape of hydraulic fluid from the tappet (4) during exhaust braking. During normal operation of the engine when the pre-lift ramp (5) lifts the tappet (4) the valve (17) is held open and hydraulic control fluid flows from the tappet (4) so that the piston (6) contacts the bottom stop (8) and the engine valve (13) remains closed, whereas during exhaust braking of the engine when the pre-lift ramp (5) lifts the tappet (4) the valve (17) is closed and hydraulic control fluid cannot flow from the tappet (4) so that the pistons (6) remains against the stop (7) and the engine valve (13) opened to effect exhaust braking. <IMAGE>
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