Miller cycle engine

Abstract

Disclosed is a Miller cycle engine wherein the heat efficiency is improved by increasing the supply air pressure and the reliability of the mechanical strength and thermal load of the engine body is maintained by maintaining the in-cylinder maximum pressure. Specifically disclosed is a Miller cycle engine characterized by being provided with a supply air valve varying means (36) which controls the valve opening / closing time of the supply air valve (14), a stream turbine (28) which serves as a supply air pressure adding device for additionally increasing only the supply air pressure with respect to supercharging by a supercharger (20) or increasing the supply air pressure more than the exhaust air pressure, and a valve closing time control means (34) which advances the valve closing time of the supply air valve (14) further as the supply air pressure added by the steam turbine (28); is higher to thereby maintain approximately the same in-cylinder maximum pressure as the in-cylinder maximum pressure before the addition.

Description

technical field [0001] The invention relates to a Miller cycle engine in which the gas supply valve is closed earlier or later than the bottom dead center so that the compression ratio is smaller than the expansion ratio, and especially relates to a technique for improving the thermal efficiency of the Miller cycle by increasing the gas supply pressure. Background technique [0002] The Miller cycle engine closes the air supply valve earlier or later than the bottom dead center to maintain the compression ratio of the engine smaller than the expansion ratio, thereby avoiding the occurrence of knocking and helping to achieve high thermal efficiency. Furthermore, a large expansion ratio is realized, and the combustion gas is sufficiently expanded so that the combustion energy can be more effectively utilized as torque. [0003] Figure 7 The P-V diagram shown by the solid line is a P-V diagram of an internal combustion engine with a supercharger, and represents a Miller cycle ...

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Problems solved by technology

[0016] However, in the above-mentioned patent documents 1 and 2, there is no disclosure of the technology of improving the thermal efficiency of the Miller cycle engine by increasing the suction work formed by the exhaust stroke and the air supply stroke.

[0017] In addition, as referenced Figure 7 As already explained, if only increasing the supercharging pressure of the supercharger, not only the improvement of the thermal efficiency of the suction work cannot be obtained, but also the mechanical strength or heat of the engine body due to the increase of the maximum pressure (Pmax) in the cylinder will be affected. Problems with bad effects of load

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