Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2001-02-20
2003-03-11
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090160, C123S090170, C123S339240
Reexamination Certificate
active
06530351
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-44708 filed in Feb. 22, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an apparatus for controlling valve timing of an internal combustion engine, which varies valve overlap in response to running conditions of the internal combustion engine.
2. Description of Related Art
Such a technology has been publicly known which achieves preferable performance of an internal combustion engine by controlling valve timing of an intake valve and an exhaust valve in response to running conditions of the internal combustion engine incorporated in a vehicle, etc. In such a technology, in order to take into consideration the combustion stability during the idling of an internal combustion engine, the combustion stability has been secured by lowering the amount of the remaining gas in a combustion chamber by preventing the valve opening periods of the intake valve and the exhaust valve from overlapping. (Japanese Patent Laid-Open Publication No. HEI 05-71369).
By controlling a valve timings of the intake valve and the exhaust valve so that such valve overlap is not produced in such an idling state, fuel that is injected through a fuel injection valve is adhered to an intake port and the inner surface of the combustion chamber when the engine is still cold, and the mixture becomes leaner than a predetermined air-fuel ratio, thereby causing the combustion to become unstable, wherein the drivability may be lowered due to cold hesitation.
Also, where the fuel injection amount is increased when cold in order to prevent such cold hesitation, the fuel efficiency and emission may be worsened.
SUMMARY OF THE INVENTION
The present invention was developed in order to solve the aforementioned problem. It is therefore an object of the invention to prevent the cold hesitation by suppressing becoming lean of the air-fuel ratio without increasing the fuel at cold idling.
In order to achieve the aforementioned object, one aspect of the invention is providing an apparatus for controlling the valve timing of an internal combustion engine, which varies valve overlap in response to running conditions of the internal combustion engine, wherein the valve overlap when cold idling is made larger than that when hot idling.
In the apparatus for controlling valve timing, when cold running, the valve overlap is made larger than that when hot running even in the case of idling. Fuel carburetion is increased in the combustion chamber and intake port due to blow-back of exhaust from an exhaust port and combustion chamber. Therefore, even if fuel injected from a fuel injection valve is adhered to the intake port and the inner surface of the combustion chamber when cold running, it is instantaneously carbureted. Accordingly, the mixture is subject to a sufficient air-fuel ratio without increasing the fuel supplied to the combustion chamber, wherein combustion will be further stabilized rather than in the case where the valve overlap is not increased, and cold hesitation can be prevented to maintain the drivability in a comparatively favorable state. Further, since the fuel does not have to be increased, it is possible to prevent fuel efficiency and emission from worsening.
Also, taking fuel stability into consideration when cold idling, the valve overlap is made smaller when hot idling than when cold idling. For example, an attempt was made so that the valve overlap does not occur. Therefore, the amount of the remaining gas in the combustion chamber is reduced, wherein it is possible to sufficiently stabilize the fuel.
In addition, in the apparatus for controlling valve timing, the valve opening period of both or any one of the intake valve and exhaust valve is controlled so that the valve overlap when cold idling is generated when an internal combustion engine is in cold idling, and no valve overlap is generated when hot idling thereof.
For example, by differently using the valve overlap in such cold idling and hot idling, the amount of the remaining gas is decreased when hot idling in which the fuel carburetion is sufficient, whereby an attempt is made so that the fuel stability becomes sufficient. And, when cold idling in which fuel carburetion is not usually sufficient, fuel is sufficiently carbureted due to blow-back of the exhaust to stabilize the combustion, thereby bringing about the aforementioned effect.
Another aspect of the invention is providing an apparatus for controlling valve timing, having a variable valve overlap mechanism that adjusts valve overlap by varying both or any one of the valve closing timing of an intake valve and the valve opening timing of an exhaust valve in an internal combustion engine and achieves valve overlap when cold running when the variable valve overlap mechanism itself does not operate.
The variable valve overlap mechanism is devised to be set to a timing that achieves valve overlap for cold running where the variable valve overlap mechanism itself does not operate. Therefore, even in a case where the variable valve overlap mechanism cannot be driven due to an insufficient output of oil pressure, etc., when cold running just after the starting of an internal combustion engine, the variable overlap mechanism is set to a valve timing that achieves valve overlap for cold running, before the starting of the internal combustion engine after the stop of the internal combustion engine. Therefore, in a situation such that the variable valve overlap mechanism does not sufficiently function when cold idling just after starting of the internal combustion engine, it is possible to achieve valve timing for cold running. It is possible to provide necessary valve overlap, for example, a state where no valve overlap is provided, and a state that larger valve overlap is secured than the valve overlap for cold running, since the valve overlap mechanism can be driven after the warm-up of the internal combustion engine.
Therefore, the mixture will have a sufficient air-fuel ratio without increasing the amount of the fuel into the combustion chamber when cold idling, and combustion can be stabilized still further than in the case of not increasing the valve overlap, and the cold hesitation can be prevented, wherein drivability can be maintained in a comparatively favorable state, and no increase in fuel consumption is required. The fuel efficiency and emission can be prevented from worsening. Accordingly, for example, when hot idling in which fuel carburetion is sufficient, the amount of the remaining gas in the combustion chamber is reduced, thereby achieving sufficient stabilization of combustion.
In addition, the variable valve overlap mechanism may be provided with one or both of an intake cam and an exhaust cam, whose profiles differ from each other in the rotation axis direction, a rotation direction shifter that can vary the valve overlap by consecutively adjusting the valve lift by adjusting the position in the rotation axis direction with respect to the cams whose profiles are different from each other in the aforementioned rotation axis direction, and a valve overlap setter for non-operation state, which when the variable valve overlap mechanism does not operate, sets the position of the cams in the rotation axis direction to the position corresponding to the valve timing at which the aforementioned valve overlap for cold running can be achieved.
The variable valve overlap mechanism is provided with one or both of an intake cam and an exhaust cam whose profiles differ from each other in the rotation axis direction. And, the cam is adjusted by the rotation axis direction shifter with respect to the position thereof in the rotation axis direction, whereby the valve lift is consecutively adjusted to enable consecutive changes in the valve timing.
And, when the variable valve overlap mechanism does not operate, the valve overlap setter for the non-operation state sets the positi
Corrigan Jaime
Denion Thomas
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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