| 摘要 |
A valve assembly having a valve (10, 110, 210, 310, 410) that is caused to reciprocate between open and closed positions by engagement of a cam follower (16, 116, 216, 316,416) with a cam (14, 114, 214, 314, 414) that is carried by a rotatable camshaft (12, 112, 212, 312, 412). The valve is resiliently urged against the cam by a coil spring (18, 118, 218, 318, 418), but its return to its closed position is delayed by application of a non-mechanical force against the valve, in opposition to the force imposed by the coil spring, by hydraulic force imposed by hydraulic fluid in a housing (22, 122, 322, 422) that acts against an enlarged portion (10c, 110c, 310c, 410c) of the valve, or by an electromagnetic force imposed by an electromagnetic device (228) that acts on an enlarged portion (210c) of the valve (210). The non-mechanical, hydraulic imposing force in an embodiment of the invention involves the use of a magneto-rheological fluid within a sealed housing (322), and the viscosity of this magneto-rheological fluid substantially increases when a magnetic coil (330) in the sealed housing is energized.
|
