Decompression apparatus for engines.

摘要

For automatic depression during starting, a decompression device (9) is rotatably supported in the cam gear (6) on the camshaft (1) of an engine. The device has a shaft (10) mounted in the cam gear, a U-shaped portion (11), and a decompression cam (12) formed on the shaft and having a semicircular cross section. Inlet valve cam (4) has a recess (4a) at a part of its periphery and the decompression cam (12) is positioned in that recess (4a). A centrifugally rotated weight (13) is mounted on the cam gears and is operatively engaged with the U shaped portion (11) of the decompression device (9). The weight (13) and the decompression device (9) are so arranged that when the rotational speed of the camshaft at starting is below a speed which causes the reverse rotation of the engine, the periphery of the decompression cam (12) projects beyond the periphery of valve cam (4) to open the corresponding valve for reducing the compression pressure in the engine, and that when the rotational speed exceeds the speed which causes the reverse rotation of the engine, the periphery of the decompression cam (12) retracts to or below the periphery of the valve cam (4) to close the valve during at least a part of the compression stroke of the engine.