Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-01-31
2001-05-15
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090160, C123S090170
Reexamination Certificate
active
06230675
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a valve lift control system for the intake valves of internal combustion engines.
BACKGROUND OF THE INVENTION
Various proposals have been made to change the timing of opening the intake valve in relation with the top dead center of the piston movement depending on the rotational speed of the engine so that the output property of the engine may be improved over a wide rotational speed range.
For instance, according to the proposal made in Japanese patent laid open (kokaki) publication No. 63-106310, a plurality of cams for producing different timings and total lifts are provided on a common camshaft for each cylinder, and are actuated by individual rocker arms rotatably supported on a common rocker shaft. The adjacent ones of these rocker arms can be selectively connected to each other so that the valve timing and the total lift of the corresponding valve may be changed in a stepwise fashion. According to the proposal made in Japanese patent laid open (kokai) publication No. 5-10161, the phase relationship between the rotational angles of the camshaft and the crankshaft can be varied in a continuous manner. Japanese patent (kokoku) publication No. 5-43847 discloses a combination of these two technologies.
However, when the phase relationship of the camshaft in relationship with the crankshaft is changed in the arrangement where a plurality of cams are provided for each cylinder to the end of varying the opening timing and the total lift of the intake valve, it is possible that the piston at the top dead center may interfere with the intake valve if the timing and the lift of the intake valve are not properly selected. Such an interference is highly destructive, and should be avoided by all means. As shown in
FIG. 12
, when the cam lift is relatively small, even if the cam phase is advanced or the opening timing of the intake valve is advanced, the intake valve would not interfere with the piston at the top dead center. However, as shown in
FIG. 13
, when the cam lift is relatively large, if the cam phase is advanced or the opening timing of the intake valve is advanced as indicated by the solid line, the intake valve may interfere with the piston at the top dead center.
BRIEF SUMMARY OF THE INVENTION
In view of such problems of the prior art, a primary object of the present invention is to provide a valve lift control system for the intake valves of internal combustion engines which permits the valve timing to be advanced and the valve lift to be increased at the same time without risking the interference between the intake valve and the piston.
A second object of the present invention is to provide a valve lift control system which can maximize the engine performance by allowing the optimum selection of the valve timing and the valve lift.
A third object of the present invention is to provide a valve lift control system which is simple and economical to build.
A fourth object of the present invention is to provide a valve lift control system which is durable in use.
According to the present invention, such objects can be accomplished by providing a valve lift control system for engine intake valves, comprising: a first valve control unit for selectively changing a lift of an intake valve of an engine; a second valve control unit for selectively changing a phase angle relationship of a timing of opening the engine intake valve in relation with a crankshaft angle; and a central control unit for selectively activating the first and second valve control units according to an operating condition of the engine; the second valve control unit being provided with means for limiting an advancing of the opening timing of the engine intake valve when the first valve control unit has selected a large valve lift.
It is thus possible to limit the advancing of the timing of opening the engine intake valve only when a large valve lift is selected and the advancing of the valve timing may cause an interference between the engine valve and the piston. The valve lift is otherwise optimized, and the maximum performance of the engine can be attained under all possible circumstances. It is also conceivable to limit the valve lift when the valve timing is most advanced for the same effect. However, the valve timing is more suited for quick and fine adjustment than the valve lift.
This arrangement can be accomplished either electronically or mechanically. It is, however, preferable to provide both electronic and mechanical arrangements for limiting the valve lift for a maximum reliability of the system. According to an electronic arrangement, the limiting means comprises a computer provided with a programmed interlock routine for limiting the advancing of the opening timing of the engine valve when the first valve control unit has selected a large valve lift. According to a mechanical arrangement, the limiting means comprises a mechanical arrangement which mechanically prohibits the advancing of the opening timing of the engine intake valve when the first valve control unit has selected a large valve lift.
Because the activation of the limiting means occurs only when the first valve control unit is activated and the system is in the high speed mode, if the first and second valve control units are provided with hydraulic actuators for selectively changing the valve lift and the valve timing, respectively, the limiting means preferably comprises a solenoid valve which selectively conducts a hydraulic pressure from the first valve control unit to the second valve control unit for activation of the limiting means. This arrangement simplifies the hydraulic circuit.
According to a preferred embodiment, the second valve control unit comprises a proportional actuator which is capable of producing a substantially continuous displacement of a moveable member according to a duty ratio of electric current supplied to a solenoid valve for controlling a hydraulic pressure supplied to the proportional actuator, and the limiting means comprises a stopper pin which engages the moveable part within a prescribed limit of motion under the hydraulic pressure conducted from the first valve control unit. This is reliable in operation and simple in structure.
For a compact design of the second valve control unit, the proportional actuator preferably comprises a rotary actuator which is incorporated between a camshaft and a sprocket wheel for the actuation of the camshaft. Likewise, for compact and reliable design of the first valve control unit, the first valve control unit may comprise at least two cams provided for each cylinder, at least two rocker arms individually engaging the cams, and a hydraulically actuated pin in a guide hole passed jointly across the rocker arms, one of the rocker arms associated with one of the cams having a generally small cam lift being adapted to directly actuate the engine intake valve while the other of the rocker arms is not, whereby the engine intake valve is actuated according a cam lift of a selected one of the cams depending on a position of the pin.
REFERENCES:
patent: 5031583 (1991-07-01), Konno
patent: 5669341 (1997-09-01), Ushirono et al.
patent: 5803029 (1998-09-01), Yoshihara et al.
patent: 5893345 (1999-04-01), Sugimoto et al.
patent: 6131541 (2000-10-01), Hasegawa et al.
patent: 6170448 (2001-01-01), Asakura
patent: 63-106310 (1988-05-01), None
patent: 5-10161 (1993-01-01), None
patent: 5-43847 (1993-07-01), None
Kobayashi Toshiki
Yoshiki Koichi
Blackman William D.
Carrier Joseph P.
Carrier Blackman & Associates P.C.
Honda Giken Kogyo Kabushiki Kaisha
Lo Weilun
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