Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1995-02-16
1997-11-18
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9039, F01L 134, F01L 118
Patent
active
RE0356620
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a valve operating apparatus for selectively transmitting the rotation of high- and low-speed cams to intake and exhaust valves in an engine to select the timing to open and close the intake and exhaust valves and the lifts or distances by which they are lifted, so that the engine can have good output power characteristics in low- and high-speed ranges of operation thereof, and more particularly to a valve operating apparatus having rocker arms, a rocker shaft, and an engaging means for engaging and disengaging the rocker arms and the rocker shaft, between the high- and low-speed cams and the intake and exhaust valves.
BACKGROUND ART
Heretofore, the intake and exhaust valves of automotive OHC (overhead camshaft) engines are opened and closed by the rotation of the crankshaft that is transmitted through a valve operating apparatus.
Some valve operating apparatus are capable of not only opening and closing the intake and exhaust valves at a predetermining timing with a predetermined lift, but also selectively varying the timing and the lift. The valve operating apparatus with such a mechanism for selecting valve operating modes can control the valve overlap, etc., for optimum values depending on the operating conditions of the engine, so that the engine can produce the highest possible output power at all times.
More specifically, one known valve operating apparatus has a low-speed cam having a cam profile for a low-speed range of operation of the engine, and a high-speed cam having a cam profile for a high-speed range of operation of the engine, the low- and high-speed cams being mounted on a camshaft. The timing to open and close the valves of the engine is controlled by the low-speed cam in the low-speed range of operation, and by the high-speed cam in the high-speed range of operation.
FIGS. 38 through 40 of the accompanying drawings show a mechanism for selecting high- and low-speed cams.
As shown in FIG. 38, rocker arms 104, 105, 104' are interposed between cams 102, 103, 102' and valves 101 to be actuated by the cams.
The cams 102, 102' serve as low-speed cams, and the cam 103 as a high-speed cam. The rocker arms 104, 104' are low-speed rocker arms that are actuated by the cams 102, 102', respectively, and the rocker arm 105 is a high-speed rocker arm that is actuated by the cam 103.
The rocker arms 104, 105, 104' are angularly movably supported on a rocker shaft 106, and angularly movable about the rocker shaft 106 when they are pushed by the cams 102, 103, 102'.
The low-speed rocker arms 104, 104' and the high-speed rocker arm 105 can be engaged or disengaged by pistons 107, 108 and a stopper 109.
More specifically, as shown in FIGS. 39 and 40, the pistons 107, 108 and the stopper 109, which are arranged in series with each other and held in contact end to end, are disposed in cylinders 104a, 105a, 104'a that are defined coaxially in the rocker arms 104, 105, 104', respectively. The rocker shaft 106 and the rocker arm 104' have oil passages 106a, 104'b defined respectively therein. When oil is supplied through the oil passages 106a, 104'b into a space in an end of the cylinder 104'a, the pistons 107, 108 and the stopper 109 are axially moved forwardly, thereby connecting the low-speed locker arms 104, 104' and the high-speed rocker arm 105 to each other. When the oil is discharged, the pistons 107, 108 and the stopper 109 are retracted under the bias of a return spring 110, thereby disconnecting the low-speed rocker arms 104, 104' and the high-speed rocker arm 105 from each other.
The rocker arm 105 is normally urged upwardly by a return spring 111.
In the low-speed range of operation, as shown in FIG. 39, the oil is discharged from the space in the end of the cylinder 104'a, allowing the pistons 107, 108 and the stopper 109 to move to the right under the force of the return spring 110. The piston 107 is placed in the rocker arm 104', the piston 108 in the rocker arm 105, and the stopper 109 in the rocker arm 104. Therefore, the high-speed rocker a
REFERENCES:
patent: 4429853 (1984-02-01), Chaffiotte et al.
patent: 4726332 (1988-02-01), Nishimura et al.
patent: 4768475 (1988-09-01), Ikemura
patent: 4844023 (1989-07-01), Konno et al.
patent: 4901685 (1990-02-01), Fukuo et al.
patent: 5099806 (1992-03-01), Murata et al.
Miyamoto Hideki
Murata Shinichi
Nakamura Noboru
Yoshida Michiyasu
Lo Weilun
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
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