Abstract:
A desmodromic valve system which provides direct bidirectional displacement of a valve stem of an internal combustion engine without the aid of a rocker arm, utilizing a semirigid basket operating in conjunction with a plurality of cams for each valve. The basket is disposed about the camshaft of the engine and secured to the valve stem by an integral retainer on a bottom portion of the basket, and is constrained to motion along the valve stem axis. The basket has a pair of downwardly oriented cam followers in the upper portion thereof, spaced apart from the valve stem axis. A central cam and a parallel pair of side cams are fixedly mounted on the camshaft so as to rotate therewith, the cams substantially surrounded by the basket and cooperating therewith to provide reciprocating valve action with positive bidirectional drive. The central cam is aligned with the valve stem axis, and the side cams are spaced apart from the valve stem axis, parallel to the central cam and respectively aligned with the cam followers. During a first part of a valve cycle, the central cam pushes the valve stem down so as to positively open the associated valve, and the valve stem pulls said basket down with it via the retainer. During a second part of the valve cycle, the side cams push the basket up via their respective cam followers and thereby cause the basket to pull the valve stem so as to positively close the valve.
Abstract:
A desmodromic valve system which provides direct bidirectional displacement of a valve stem of an internal combustion engine without the aid of a rocker arm, utilizing a semirigid basket operating in conjunction with a plurality of cams for each valve. The basket is disposed about the camshaft of the engine and secured to the valve stem by an integral retainer on a bottom portion of the basket, and is constrained to motion along the valve stem axis. The basket has a pair of downwardly oriented cam followers in the upper portion thereof, spaced apart from the valve stem axis. A central cam and a parallel pair of side cams are fixedly mounted on the camshaft so as to rotate therewith, the cams substantially surrounded by the basket and cooperating therewith to provide reciprocating valve action with positive bidirectional drive. The central cam is aligned with the valve stem axis, and the side cams are spaced apart from the valve stem axis, parallel to the central cam and respectively aligned with the cam followers. During a first part of a valve cycle, the central cam pushes the valve stem down so as to positively open the associated valve, and the valve stem pulls said basket down with it via the retainer. During a second part of the valve cycle, the side cams push the basket up via their respective cam followers and thereby cause the basket to pull the valve stem so as to positively close the valve.
Abstract:
A desmodromic valve system which provides direct bidirectional displacement of a valve stem of an internal combustion engine without the aid of a rocker arm, utilizing a semirigid basket operating in conjunction with a plurality of cams for each valve. The basket is disposed about the camshaft of the engine and secured to the valve stem by an integral retainer on a bottom portion of the basket, and is constrained to motion along the valve stem axis. The basket has a pair of downwardly oriented cam followers in the upper portion thereof, spaced apart from the valve stem axis. A central cam and a parallel pair of side cams are fixedly mounted on the camshaft so as to rotate therewith, the cams substantially surrounded by the basket and cooperating therewith to provide reciprocating valve action with positive bidirectional drive. The central cam is aligned with the valve stem axis, and the side cams are spaced apart from the valve stem axis, parallel to the central cam and respectively aligned with the cam followers. During a first part of a valve cycle, the central cam pushes the valve stem down so as to positively open the associated valve, and the valve stem pulls said basket down with it via the retainer. During a second part of the valve cycle, the side cams push the basket up via their respective cam followers and thereby cause the basket to pull the valve stem so as to positively close the valve.
Abstract:
A unitary cam follower and valve preload spring for a desmodromic valve mechanism having opening and closing cams mounted in parallel on an overhead camshaft so as to facilitate positive bidirectional drive of a valve. The device comprises a generally tubular spring member of oblong transverse cross-section, a shaped extension spring, preferably a band or basket. The spring member is configured to be nonrotatably mounted on the camshaft with its longitudinal axis parallel to the camshaft axis and its major axis aligned with the valve stem axis, substantially surrounding the opening and closing cams circumferentially and engaging the valve stem and closing cam so as to pull the valve stem in response to an upward force applied to the upper portion of the spring member by the closing cam. The spring member is further configured to elongate along its major axis in response to tension applied thereto during assembly so as to preload the valve stem, and it has an effective spring rate which varies depending on conditions.
Abstract:
A desmodromic valve system which provides direct bidirectional displacement of a valve stem of an internal combustion engine without the aid of a rocker arm, utilizing a semirigid basket operating in conjunction with a plurality of cams for each valve. The basket is disposed about the camshaft of the engine and secured to the valve stem by an integral retainer on a bottom portion of the basket, and is constrained to motion along the valve stem axis. The basket has a pair of downwardly oriented cam followers in the upper portion thereof, spaced apart from the valve stem axis. A central cam and a parallel pair of side cams are fixedly mounted on the camshaft so as to rotate therewith, the cams substantially surrounded by the basket and cooperating therewith to provide reciprocating valve action with positive bidirectional drive. The central cam is aligned with the valve stem axis, and the side cams are spaced apart from the valve stem axis, parallel to the central cam and respectively aligned with the cam followers. During a first part of a valve cycle, the central cam pushes the valve stem down so as to positively open the associated valve, and the valve stem pulls said basket down with it via the retainer. During a second part of the valve cycle, the side cams push the basket up via their respective cam followers and thereby cause the basket to pull the valve stem so as to positively close the valve.