Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
1999-04-21
2001-07-31
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090440
Reexamination Certificate
active
06267090
ABSTRACT:
TECHNICAL FIELD
The present invention relates to internal combustion engines, and, more particularly, to internal combustion engines including a rocker arm shaft and rocker arms.
BACKGROUND ART
Internal combustion engines, such as multi-cylinder diesel engines, typically include a crankshaft, a camshaft and a rocker arm shaft. The crankshaft is connected with a plurality of piston rods, which in turn are connected with a plurality of corresponding pistons. Reciprocating movement of the pistons within corresponding combustion cylinders causes rotation of the crankshaft.
The crankshaft is typically interconnected with the camshaft via a gear set and thereby rotatably drives the camshaft during operation. The camshaft includes a plurality of cams, with each cam being associated with an inlet valve, and an exhaust valve or a fuel injector valve. More particularly, the rocker arm shaft carries a plurality of rocker arms, with each rocker arm having a roller follower which engages a corresponding cam on the camshaft. Rotation of the camshaft causes oscillatory pivotal movement of the rocker arms about the rocker arm shaft.
A problem with a conventional internal combustion engine as described above is that the rocker arm shaft is rigidly and immovably carried by a housing. The rocker arms pivot through a relatively small pivoting angle about the stationary rocker arm shaft. The small angle through which the rocker arms pivot is not sufficient to allow the formation of a hydrodynamic oil film between the rocker arms and the rocker arm shaft. As a result, the friction between the rocker arms and the rocker arm shaft may be relatively high and the energy required to pivot the rocker arms is increased. This decreases the efficiency of the engine. Additionally, the increased friction may cause increased wear or spalling between the rocker arms and the rocker arm shaft.
It is known to oscillate a rocker arm shaft through a small rotational angle using a rack and pinion arrangement in order to change the eccentricity of the rocker arms relative to the rocker arm shaft. However, the rocker arm shaft does not continuously or fully rotate within the rocker ends. Such a slight pivotal movement is not sufficient to create a hydrodynamic oil film between the rocker arm shaft and the rocker arms, or to reduce friction or improve efficiency of the internal combustion engine. An example of an internal combustion engine including such a rocker arm shaft is disclosed in U.S. Pat. No. 5,111,781 (Kaku, et al).
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the invention, an internal combustion engine includes a housing; a camshaft rotatably carried by the housing and having a plurality of cams; a rocker arm shaft rotatably carried by the housing and rotatably driven by the engine; and a plurality of rocker arms rotatably carried by the rocker arm shaft, with each rocker arm being associated with a respective cam.
In another aspect of the invention, a method of operating an internal combustion engine includes the steps of: providing a rocker arm shaft and a plurality of rocker arms carried by and rotatable relative to the rocker arm shaft; and rotating the rocker arm shaft within the rocker arms.
REFERENCES:
patent: 3021826 (1962-02-01), Fezzy et al.
patent: 4132196 (1979-01-01), Wherry
patent: 4627391 (1986-12-01), Derringer
patent: 4690110 (1987-09-01), Nishimura et al.
patent: 4708101 (1987-11-01), Hara et al.
patent: 4800850 (1989-01-01), Yoshida et al.
patent: 4829948 (1989-05-01), Yoshida et al.
patent: 4848285 (1989-07-01), Konno
patent: 4986227 (1991-01-01), Dewey, III
patent: 5111781 (1992-05-01), Kaku et al.
patent: 5211143 (1993-05-01), Fontichiaro et al.
patent: 5253622 (1993-10-01), Bornstein et al.
patent: 5441020 (1995-08-01), Murata et al.
patent: 5445115 (1995-08-01), Murata et al.
patent: 5445117 (1995-08-01), Mendler
patent: 5732669 (1998-03-01), Fischer et al.
patent: 5960754 (1999-10-01), Sugimoto et al.
patent: 5970932 (1999-10-01), Richardson et al.
Caterpillar Inc.
Denion Thomas
Nguyen Tu M.
Taylor Todd T.
LandOfFree
Internal combustion engine with rotatable rocker arm shaft... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Internal combustion engine with rotatable rocker arm shaft..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Internal combustion engine with rotatable rocker arm shaft... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442570