Abstract: A cylinder block construction of an engine having a pair of balancer shafts provided at its opposite sides, in which the cylinder block is formed with a pair of bearing boss portions for supporting the balancer shafts, respectively. The cylinder block construction includes a pair of mounting portions for securing a pair of engine mounts to the cylinder block, respectively, which are, respectively, provided, in the vicinity of the bearing boss portions, at opposite side walls of the cylinder block so as to be integrally formed with the bearing boss portions.

Abstract: Rotary piston engine comprises a casing which includes a rotor housing and a pair of side housings secured to the opposite sides of the rotor housing. The housings are formed with water jackets which are mutually communicating to provide circulation of cooling liquid. The side housing is formed with reinforcement ribs so as to prevent deformation of the inner wall of the side housing.

Abstract: Casing for liquid-cooled rotary piston engines having a rotor housing made of aluminum based alloy and side housings made of cast iron. The rotor and side housings are formed with cooling liquid passages which are connected together at the junction between the rotor and side housings. At each junction of the passage in the rotor housing with corresponding one in the side housing, the diametrical dimension of the passage in the aluminum alloy rotor housing is smaller than that of the passage in the cast iron side housing so that a shoulder is formed at the junction of the passages by aluminum alloy surface projecting into the passage beyond the edge of the passage opening in the cast iron side housing. The arrangement is effective to prevent or suppress electrochemical corrosion of the casting material.

Abstract: Rotor housing for rotary piston engines having a base and a chromium-plated inner wall. The base is made of an iron-based material having a hardness of not less than 105 in Vickers' scale and the chromium-plated layer has a hardness not less than 850 in Vickers' scale. The rotor housing is used with a rotor having apex seals of iron-based material which includes 50 to 75% in volume of carbide at least in a sliding surface which is adapted to be brought into sliding engagement with the inner wall of the rotor housing, said apex seal having a hardness of 700 to 900 in Vickers' scale at the sliding surface.

Abstract: Rotary piston engine has an intake port formed in one of the side housings, said intake port being connected with an intake passage which has a curved portion merging to the intake port. The radius of curvature of the curved portion is varied in widthwise direction of the passage with smaller radius at the side opposite to the direction of rotor rotation whereby the difference in flow resistance thus produced effectively bends the direction of mixture flow towards the direction of rotor rotation to establish recommendable stratified fuel distribution.