四冲程和二冲程活塞式汽油机有非常笨重和复杂的曲柄连杆机构,这些发动机中基本的摩擦机械损失是由该曲柄连杆机构的工作引起的。此外,在四冲程发动机中还必须配有配气机构,就使得发动机的结构更加复杂和笨重。虽然在曲轴箱扫气的二冲程发动机中配气机构比较简单,但由于燃烧室扫气使用了燃料空气的混合气,此时又形成了无效的燃料损失。由于上述原因,过去曾提出过转子-活塞式结构的发动机,其中最著名的是汪克尔发动机。众所周知,这种发动机机体为一个中空的长短幅圆外旋轮线形状的燃烧室,其内部装有带内啮合齿的三角形转子、偏心轴和一个总是与转子齿轮啮 Four-stroke and two-stroke piston-type gasoline engines have very bulky and complicated crank-and-rod mechanisms in which the basic frictional mechanical losses are caused by the operation of the crank-and-connecting rod mechanism. In addition, the four-stroke engine must also be equipped with valve train, making the engine’s structure more complex and cumbersome. Although the two-stroke crankcase scavenging engine with a relatively simple gas distribution mechanism, but because the combustion chamber scavenging fuel air mixture, then formed an invalid fuel loss. For the above reasons, the engine of the rotor-piston type has been proposed in the past, the most notable of which is the Wankel engine. It is well-known that this engine body is a hollow, long and short outer circular toroidal combustion chamber with a triangular rotor with internal teeth, an eccentric shaft,