Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-07-27
2001-07-17
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090340
Reexamination Certificate
active
06260526
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a valve movement control system of an internal combustion engine having a hydraulic operational characteristic variable mechanism for altering operational characteristic such as opening-closing time of an engine valve, including a hydraulic phase variable mechanism for altering opening-closing time of an engine valve such as a suction valve or an exhaust valve.
Hitherto, there has been known a valve movement control system of an internal combustion engine having a hydraulic phase variable mechanism which alters opening-closing time of a suction valve or an exhaust valve by altering relative phase of a camshaft to a crankshaft in accordance with operational state of the engine, in order to improve engine output and fuel consumption.
For example, in a valve timing control system of an internal combustion engine disclosed in Japanese Laid-Open Patent Publication Hei 11-173119, a valve timing adjusting mechanism provided on an end of a suction side camshaft has a rotor housing drivingly connected to a crankshaft and a vane rotor having a plurality of vanes drivingly connected to the suction side camshaft. On both sides of the each vane are formed a retard chamber and an advance chamber respectively, and charging and discharging of operating oil to the retard chamber and the advance chamber are controlled by a OCV (oil control valve) operated based on operational state of the engine, so that relative phase of the suction side camshaft to the crankshaft is altered to adjust opening-closing timing of the suction valve.
The operating oil supplied by an oil pump driven by the engine and controlled by the OCV is charged to or discharged from the retard chamber and the advance chamber, passing through a head oil passage provided in a cylinder head, an annular oil groove provided on an inner peripheral surface of a journal bearing formed by the cylinder head and a bearing cap for supporting the camshaft, and an oil passage provided in the camshaft.
Generally, a minute gap exists between the camshaft and the journal bearing. Therefore, in the prior art, when the engine is stopped to stop the oil pump and the operating oil is not supplied to the oil passage, the operating oil in the oil passage provided in the suction side camshaft and the operating oil in the retard chamber and the advance chamber flow out through the minute gap as time goes by, though by very small amount, so that the operating oil in the oil passage, the retard chamber and the advance chamber has a tendency to decrease.
When the engine is started from the state that operating oil in the oil passage, the retard chamber and the advance chamber is reduced, some waiting time is required after the engine is started to drive the oil pump, for filling the oil passage and the retard chamber or the advance chamber with the operating oil (whether any one chamber or both chambers must be filled with the operating oil depends on setting of the valve timing adjusting mechanism during the engine is stopped), and enabling the valve timing adjusting mechanism to operate. However, a time required for the engine to reach a loaded operation necessitating valve timing adjustment is relatively long in general and the oil passage and the retard chamber or the advance chamber can be filled with the operating oil during the time, therefore the above-mentioned required waiting time does not came into question.
However, on re-starting of the engine when the engine is started from a state that warming-up is completed, the time required for the engine to reach the loaded operation is relatively short in general, so that sometimes the oil passage and the retard chamber or the advance chamber are not filled with the operating oil before the engine reaches the loaded operation. In this case, the valve timing adjusting mechanism can not operate until the oil passage and the retard chamber or the advance chamber are filled with the operating oil. This late operation causes lowering of the engine output, and lowering of drive-ability in case of an engine mounted on a vehicle.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the foregoing, and an object of the invention is to provide a hydraulic operational characteristic variable mechanism with no operational lag or a shortened operational lag on re-starting of the engine. Another object of the invention is to provide a structure facilitating preparation of a operating oil reserve chamber.
The present invention provides a valve movement control system of an internal combustion engine, comprising a camshaft driven by a crankshaft having a cam journal supported for rotation by a support member; a hydraulic operational characteristic variable mechanism provided on the camshaft for altering operational characteristic of an engine valve driven by a cam of the camshaft; an operating oil passage extending from an oil pressure supply source driven by the internal combustion engine to the operational characteristic variable mechanism passing through a plurality of members including at least the camshaft and the support member; and an oil pressure control valve provided in the operating oil passage for controlling pressure of operating oil sent to the operating characteristic variable mechanism. The operating oil passage forms a control oil passage having a first oil passage and a second oil passage between an operation chamber of the operational variable mechanism and the oil pressure control valve, the first oil passage provided in the camshaft has an end communicating with the operation chamber and another end communicating with the second oil passage formed between the cam journal and the support member. In such a valve movement control system, an operating oil reserve chamber communicating with the control oil passage is provided above the cam journal.
According to this invention, since the operating oil reserve chamber is provided above the cam journal and there is a greater quantity of the operating oil above the minute gap between the cam journal and the support member in comparison with the prior art, even if the operating oil flows out through the minute gap during the engine is stopped, the oil pressure supply source is not driven and the operating oil is not supplied to the operation chamber of the operational characteristic variable mechanism and the control oil passage, a time required for the operating oil in the operation chamber and the first and second oil passages to decrease to the same extent as the prior art can be prolonged
As the result, a possibility that the operation chamber and the first and second oil passages are filled with the operating oil or relatively large quantity of the operating oil remains in the operation chamber and the first and second oil passages upon re-starting such as starting after idle stop can be raised, by setting a quantity of the operating oil reserved in the operating oil reserve chamber suitably. Therefore, there is no operation lag or operation lag time is shortened, so that the engine can be operated by the engine valve of a desired operational characteristic relatively soon and output lowering caused by non-operation of the operational characteristic variable mechanism can be prevented with a high possibility.
In such a valve movement control system of an internal combustion engine, the support member may comprise a lower member and a cam holder disposed above the lower member, and the operating oil reserve chamber may be provided in the cam holder and may communicate with the second oil passage within the cam holder.
According to this valve movement control system, the operating oil reserve chamber can be provided utilizing the cam holder disposed above the lower member to support the cam journal from the upside. Therefore, there is no necessity to dispose an additional member for forming the operating oil reserve chamber above the cam journal. Moreover, it is possible to provide an operating oil reserve chamber in a customary engine having a phase variable mechan
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Lo Weilun
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