Four-cycle engine and engine generator

Abstract

An engine generator includes a four-cycle engine including a cylinder, one inlet port that supplies air-fuel mixture into the cylinder, one inlet valve that opens / closes the inlet port, a piston reciprocable inside the cylinder, a crank shaft that converts reciprocating movement of the piston into rotating movement, a connecting rod that connects the piston and the crank shaft to each other, and a recoil starter that rotates the crank shaft. The engine has a geometric compression ratio not smaller than about 8.5. The valve closure timing of the inlet valve is defined as a timing when the closing inlet valve has a valve lift of about 1 mm, and is within a range from after the bottom dead center to the top dead center.

Description

technical field [0001] The invention relates to a four-stroke engine and an engine generator, in particular to a four-stroke engine and an engine generator with a manual starting device. Background technique [0002] In general, it is known that in order to improve the thermal efficiency of an engine, it is effective to increase the compression ratio (expansion ratio) in the combustion chamber. However, if the compression ratio is increased, the pressure at the time of compression increases, and therefore, the cranking torque (cranking torque) at the time of starting the engine increases. In the case of an engine with a manual starter, if the starting torque increases when the engine is started, the operator needs more force, so the compression pressure decompression shown in Japanese Patent Laid-Open No. 60-156976 is sometimes applied. decompression device. [0003] However, when the exhaust valve is opened to release the intake air-fuel mixture to the exhaust pipe side d...

AI Technical Summary

Problems solved by technology

[0003] However, when the exhaust valve is opened to release the intake air mixture to the exhaust pipe side during the compression process at the time of engine startup, the unburned air mixture flows into the exhaust system, which may cause an explosion (afterfire) inside the muffler.

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