Internal-combustion engines – Convertible cycle
Reexamination Certificate
1999-12-01
2001-07-10
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Convertible cycle
Reexamination Certificate
active
06257176
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal combustion engine having a variable engine cycle, and a controller thereof.
2. Description of the Related Art
A variable cycle internal combustion engine having a structure that allows a 2-cycle internal combustion engine to run also at four cycles or six cycles has been proposed in Japanese Patent Unexamined Publication No. Heisei 7-238840(1995).
The above-mentioned publication discloses the following features: 1) running at different engine cycles, and inlet and exhaust valves consisting of a solenoid valve; 2) both a camshaft for four cycles and a camshaft for six cycles so that a rocker arm is driven by either of the camshafts in accordance with a displacement of the center axis of a locker hinge; 3) running either at four cycles or at six cycles by selection of the camshaft revolving speed; and 4) running at two cycles by opening and closing inlet and exhaust ports and a scavenging air port for the two-cycle action instead of using the inlet and exhaust valves, meanwhile when running at four cycles, the inlet and exhaust ports are opened and closed by inlet and exhaust valves disposed at an upper part of the combustion chamber.
The above-described solenoid-driven inlet and exhaust valves of feature
1
) have technical problems. The mechanisms of features
2
) and
3
) have complicated structures for changing actions and thus result in decreased reliability and increased costs. As for the mechanism of feature
4
), since in the case of the four-cycle action the inlet and exhaust ports and the scavenging air port for the two-cycle action remain as they are, whether or not the four-cycle action proceeds normally is not known; the disclosure with respect to feature
4
) is insufficient.
The above-mentioned Japanese publication describes some means for realizing a variable cycle engine, but does not specifically disclose how to select the cycles or a control method.
SUMMARY OF THE INVENTION
Considering the above-described problems, it is an object of the present invention to provide a highly reliable variable cycle engine with a comparatively simple structure. It is another object of the present invention to provide a controller for adequate selection of the cycles in a variable cycle engine such as the one described above.
To meet the above first object, according to the first aspect of the invention, there is provided a variable cycle internal combustion engine, including: a first cam driving an inlet valve and an exhaust valve, the first cam having at least one first projection; a second cam driving the inlet valve and exhaust valve, the second cam having at least one second projection, the number of which is different from that of the first projection; and a cam change mechanism for changeover between the first and second cams, so that the engine is operable at different engine cycles.
With this structure, the first cam and the second cam having a different number of projections are selectively used by the cam change mechanism and, for example, two-cycle action is carried out when the first cam is selected while four-cycle action is carried out when the second cam is selected. Existing mass-produced parts may be used as a cam change mechanism for selection between a high-speed valve timing cam, which is appropriate for the high revolving speed range of the engine, and a low-speed valve timing cam, which is appropriate for the low revolving speed range. Therefore, a highly reliable variable cycle internal combustion engine can be realized using a relatively simple structure.
Further, according to the second aspect of the invention, there is provided a controller of a variable cycle internal combustion engine, the engine including: a first cam driving an inlet valve and an exhaust valve, the first cam having at least one first projection; a second cam driving the inlet valve and exhaust valve, the second cam having at least one second projection, the number of which is different from that of the first projection; and a cam change mechanism for changeover between the first and second cams, so that the engine is operable at different engine cycles, the controller including: an engine running state detection unit detecting engine load and engine revolving speed; and a control unit for selecting an engine cycle based on the detected engine load and engine revolving speed and controlling the cam change mechanism so as to operate at the selected engine cycle.
With this structure, the cam change mechanism is controlled to operate at the engine cycle that is selected according to the detected engine load and engine revolving speed. Thus, it is possible to improve the engine output (volumetric efficiency) at the medium and high revolving speed of the engine by running the engine at the engine cycle appropriate to the engine running state without causing problems, such as unstable combustion.
The entire disclosure of each and every foreign patent application from which the benefit of foreign priority has been claimed in the present application is incorporated herein by reference, as if fully set forth.
REFERENCES:
patent: 4612884 (1986-09-01), Ajiki et al.
patent: 5036801 (1991-08-01), Imajou
patent: 58-152139 (1983-09-01), None
patent: 64-63617 (1989-03-01), None
patent: 7-238840 (1995-09-01), None
Abe Kenji
Akiyama Eitetsu
Shimasaki Yuichi
Tsuzuki Shunichi
Ali Hyder
Arent Fox Kintner Plotkin & Kahn
Honda Giken Kogyo Kabushiki Kaisha
Wolfe Willis R.
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