Abstract: A four-stroke internal combustion engine including variable compression ratio comprises a crankcase including a crankshaft having a crankpin and being supported by the crankcase and rotatable with respect thereto about a crankshaft axis, a connecting rod including a big end and a small end, a crank member being rotatably mounted on the crankpin, and comprising at least a bearing portion which is eccentrically disposed with respect to the crankpin, a crank member drive system for rotating the crank member at a rotation frequency with respect to the crankcase which is half of that of the crankshaft, and a control system for operating the engine with repetitive cycles, wherein the compression ratio in the compression stroke is changed. The control system is configured to interrupt the repetitive cycles by rotating the crankshaft an additional single revolution between two successive combustion strokes for switching between a high and low compression ratio.

Abstract: A heat engine includes a system for varying the compression ratio of the engine. The compression ratio varying system comprises: at least one eccentric part rotatably mounted on a crank pin. The eccentric part has an eccentric outer face that co-operates with one end of a rod, as well as at least one ring gear. A device for controlling the angular position of the eccentric part, includes an actuating pinion mounted on an actuating shaft. The control device also comprises at least one stepped intermediate pinion having at least first and second steps each formed by a pinion, the pinion of the first step meshing with the actuating pinion and the pinion of the second step meshing with the gear of the eccentric part.

Abstract: A heat engine includes a system for varying compression ratio, which comprises a crankshaft including at least a crank pin and an arm, and an eccentric part rotatably mounted on the crank pin. The eccentric part includes an eccentric outer surface intended for engaging with one end of a connecting rod and one toothed ring gear. A control device controls the angular position of the eccentric part. The control device includes an actuating shaft provided with an actuating pinion, at least one intermediate shaft passing axially, from side to side, through a journal and the arm of said crankshaft via a corresponding bore. The intermediate shaft is provided with a first intermediate pinion meshing with said actuating pinion and a second intermediate pinion meshing with an eccentric part.

Abstract: A method of assembling a crankshaft and a crank member comprises supplying a crankshaft including a crankpin which extends between crank arms, supplying two halves of a crank member, which are fixed to each other about the crankpin such that in assembled condition the crank member is rotatable about the crankpin and comprises a bearing portion having an outer circumferential wall for bearing a big end of a connecting rod and an external crank member gear for driving the crank member about the crankpin, wherein the halves are fitted about the crankpin, hence creating two contact faces at opposite sides of the crankpin, after which both halves are fixed to each other in circumferential direction by means of applying at least a fixation at a fixing place located remote from the bearing portion and the toothed surface of the crank member gear.

Abstract: An engine comprises a crankcase and a crankshaft. The crankshaft has a central main portion, a crankpin and a crankshaft web. A crank member is rotatably and eccentrically mounted on the crankpin. An external crank member gear meshes with an external drive shaft gear. A driven portion of the drive shaft is located at a side of the crankshaft web which is opposite to its side where the crankpin is located and is drivably coupled via a first transmission to an intermediate member which is rotatably mounted to the crankshaft. The intermediate member is drivably coupled to a control shaft portion of a control shaft via a second transmission which control shaft portion is located at axial distance of the driven portion of the drive shaft and the control shaft is rotatable at a fixed rotational position with respect to the crankcase under operating conditions at fixed compression ratio.

Abstract: A heat engine includes a system for varying the compression ratio of the engine. The compression ratio varying system comprises: at least one eccentric part rotatably mounted on a crank pin. The eccentric part has an eccentric outer face that co-operates with one end of a rod, as well as at least one ring gear. A device for controlling the angular position of the eccentric part, includes an actuating pinion mounted on an actuating shaft. The control device also comprises at least one stepped intermediate pinion having at least first and second steps each formed by a pinion, the pinion of the first step meshing with the actuating pinion and the pinion of the second step meshing with the gear of the eccentric part.

Abstract: A four-stroke internal combustion engine with variable compression ratio, comprises a crankcase, a crankshaft, a connecting rod having a big end and a small end. A piston is rotatably connected to the small end. A crank member rotatably mounted on the crankpin has a bearing portion which is eccentrically disposed with respect to the crankpin, wherein the bearing portion has an outer circumferential wall including a location of maximum eccentricity (P) which bears the big end of the connecting rod such that the connecting rod is rotatably mounted on the bearing portion of the crank member via the big end. Under operating conditions at or close to top dead center of the piston the angle between the connecting rod plane and the piston plane changes from a pre-angle before top dead center to a post-angle after top dead center.

Abstract: A four-stroke internal combustion engine including variable compression ratio comprises a crankcase including a crankshaft having a crankpin and being supported by the crankcase and rotatable with respect thereto about a crankshaft axis, a connecting rod including a big end and a small end, a crank member being rotatably mounted on the crankpin, and comprising at least a bearing portion which is eccentrically disposed with respect to the crankpin, a crank member drive system for rotating the crank member at a rotation frequency with respect to the crankcase which is half of that of the crankshaft, and a control system for operating the engine with repetitive cycles, wherein the compression ratio in the compression stroke is changed. The control system is configured to interrupt the repetitive cycles by rotating the crankshaft an additional single revolution between two successive combustion strokes for switching between a high and low compression ratio.

Abstract: An engine comprises a crankcase and a crankshaft. The crankshaft has a central main portion, a crankpin and a crankshaft web. A crank member is rotatably and eccentrically mounted on the crankpin. An external crank member gear meshes with an external drive shaft gear. A driven portion of the drive shaft is located at a side of the crankshaft web which is opposite to its side where the crankpin is located and is drivably coupled via a first transmission to an intermediate member which is rotatably mounted to the crankshaft. The intermediate member is drivably coupled to a control shaft portion of a control shaft via a second transmission which control shaft portion is located at axial distance of the driven portion of the drive shaft and the control shaft is rotatable at a fixed rotational position with respect to the crankcase under operating conditions at fixed compression ratio.

Abstract: A four-stroke internal combustion engine with variable compression ratio, comprises a crankcase, a crankshaft, a connecting rod having a big end and a small end. A piston is rotatably connected to the small end. A crank member rotatably mounted on the crankpin has a bearing portion which is eccentrically disposed with respect to the crankpin, wherein the bearing portion has an outer circumferential wall including a location of maximum eccentricity (P) which bears the big end of the connecting rod such that the connecting rod is rotatably mounted on the bearing portion of the crank member via the big end. Under operating conditions at or close to top dead center of the piston the angle between the connecting rod plane and the piston plane changes from a pre-angle before top dead center to a post-angle after top dead center.

Abstract: A method of assembling a crankshaft and a crank member comprises supplying a crankshaft including a crankpin which extends between crank arms, supplying two halves of a crank member, which are fixed to each other about the crankpin such that in assembled condition the crank member is rotatable about the crankpin and comprises a bearing portion having an outer circumferential wall for bearing a big end of a connecting rod and an external crank member gear for driving the crank member about the crankpin, wherein the halves are fitted about the crankpin, hence creating two contact faces at opposite sides of the crankpin, after which both halves are fixed to each other in circumferential direction by means of applying at least a fixation at a fixing place located remote from the bearing portion and the toothed surface of the crank member gear.