Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-04-10
2001-08-07
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090150, C123S090310, C123S090120
Reexamination Certificate
active
06269785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable valve timing mechanism for changing opening/closing timing of at least an inlet valve or an exhaust valve of an internal combustion engine (hereinafter referred to simply as an “engine”) according to engine operating conditions.
2. Description of Related Art
Hitherto, there has been known a vane type variable valve timing mechanism as disclosed in JP-A-8-121123 as a variable valve timing mechanism for driving a camshaft via a timing pulley and a chain sprocket which rotate in synchronism with a crank shaft of an engine to give a phase difference by relative rotation between the timing pulley and the chain sprocket and the camshaft.
The vane type variable valve timing mechanism relatively rotates the crank shaft and the camshaft by rotating vanes by a pressure difference between two hydraulic chambers provided on both sides in each vane in the circumferential direction.
The conventional variable valve timing mechanism supplies oil to respective hydraulic chambers via oil passages provided within the camshaft. However, it may be preferable to supply hydraulic pressure from an end opposite to the camshaft (front side) because of the design condition for the engine when, for example, it is difficult to provide the oil passage within the camshaft.
Another known helical type variable valve timing mechanism is disclosed in JP-A-7-507120 (PCT publication number in Japan). This helical type variable valve timing mechanism supplies hydraulic pressure from the end of the front side. However, the helical type variable valve timing mechanism has such problems that it requires a large number of parts.
Furthermore, in case of the vane type variable valve timing mechanism, a clearance between a vane rotor and a housing member is required because the vane rotor rotates relative to the housing member. It then becomes difficult to control the phase difference between the vane rotor and the housing member with high degree of accuracy when pressure oil within the hydraulic chamber leaks via this clearance. Therefore, it is important to reduce the leak of the oil for the vane type variable valve timing mechanism.
SUMMARY OF THE INVENTION
The present invention is made in light of the foregoing problems, and it is an object of the present invention to provide a variable valve timing mechanism which can reduce the leakage of the pressure oil from the hydraulic chambers and the oil passages in the variable valve timing mechanism supplying pressure oil from the front side.
According to a variable valve timing mechanism of the present invention, it includes a housing, a vane rotor having a plurality of oil pressure chambers in a circumferential direction of the vane rotor for rotating relative to the housing by controlling an oil pressure in the oil pressure chambers and being accommodated in the housing, and an oil distributor for distributing an oil to the oil pressure chambers from an end of the housing opposite to the other end of the housing supporting a driven shaft.
The oil supply to the oil pressure chambers is carried out via an oil passage installed in the oil distributor, and an oil passage in the driven shaft is obviated. Accordingly, the oil is supplied from the front side, that is, from the end of the housing opposite to the other end of the housing supporting the driven shaft.
According to another aspect of the present invention, an oil passage is formed in the housing. Accordingly, the oil supply to the oil pressure chambers is supplied from a location separated from a small clearance between the housing and the vane rotor. Therefore, an oil leakage via the clearance is reduced.
According to another aspect of the present invention, the variable valve timing mechanism of the present invention includes a cylindrical member disposed between the oil distributor and at least one of the housing and the vane rotor for preventing the oil from leaking from the oil pressure chambers via the clearance between the housing and the vane rotor. Therefore, an oil leakage from the oil pressure chambers is reduced.
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Dahbour Fadi H.
Denso Corporation
Nixon & Vanderhye P.C.
Walberg Teresa
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