The present invention provides an internal combustion engine comprising a crankshaft, the crankshaft comprising main bearing journals and cranks for connecting the crankshaft to piston rods of the engine, wherein the crankshaft is provided with counterweights, wherein at least a first counterweight is formed as a separate element and connected to the crankshaft. The present invention is characterized in that at least a second counterweight is formed integrally with the crankshaft.

The present disclosure shows a crankshaft having at least one counterweight that is preferably screwed to the crankshaft via at least two screws, with the counterweight having a contact surface at which it contacts a counter-contact surface of the crankshaft. In this respect, the position of the counterweight at the crankshaft is fixed via at least one positioning element independent of the screw connection.

A balance shaft is proposed that includes: i) an unbalance shaft having an unbalance section and an adjacent bearing pin having a cylindrical partial circumference which is oriented towards the shaft imbalance; ii) a bearing ring which surrounds the bearing pin and bears against the cylindrical partial circumference and delimits a free space with a bearing pin back radially opposite thereto; and, iii) a clamping element which is clamped in the free space and clamps the bearing ring radially against the cylindrical partial circumference. The clamping element is intended to secure the bearing ring against axial sliding on both sides on the bearing pin, and the clamping element is connected in an axially interlocking manner to the unbalance shaft on one side and to the bearing ring on the other side.

A balance shaft is proposed that includes: i) an unbalance shaft having an unbalance section and an adjacent bearing pin having a cylindrical partial circumference which is oriented towards the shaft imbalance; ii) a bearing ring which surrounds the bearing pin and bears against the cylindrical partial circumference and delimits a free space with a bearing pin back radially opposite thereto; and, iii) a clamping element which is clamped in the free space and clamps the bearing ring radially against the cylindrical partial circumference. The clamping element is intended to secure the bearing ring against axial sliding on both sides on the bearing pin, and the clamping element is connected in an axially interlocking manner to the unbalance shaft on one side and to the bearing ring on the other side.

A balance shaft is proposed that includes: i) an unbalance shaft having an unbalance section and an adjacent bearing pin having a cylindrical partial circumference which is oriented towards the shaft imbalance; ii) a bearing ring which surrounds the bearing pin and bears against the cylindrical partial circumference and delimits a free space with a bearing pin back radially opposite thereto; and, iii) a clamping element which is clamped in the free space and clamps the bearing ring radially against the cylindrical partial circumference. The clamping element is intended to secure the bearing ring against axial sliding on both sides on the bearing pin, and the clamping element is connected in an axially interlocking manner to the unbalance shaft on one side and to the bearing ring on the other side.

A balance shaft is proposed that includes: i) an unbalance shaft having an unbalance section and an adjacent bearing pin having a cylindrical partial circumference which is oriented towards the shaft imbalance; ii) a bearing ring which surrounds the bearing pin and bears against the cylindrical partial circumference and delimits a free space with a bearing pin back radially opposite thereto; and, iii) a clamping element which is clamped in the free space and clamps the bearing ring radially against the cylindrical partial circumference. The clamping element is intended to secure the bearing ring against axial sliding on both sides on the bearing pin, and the clamping element is connected in an axially interlocking manner to the unbalance shaft on one side and to the bearing ring on the other side.

Embodiments are directed toward an engine. In some embodiments, the engine includes a water pump and a balancer shaft. In some embodiments, the water pump has a plain bearing. In some embodiments, plain bearing is supplied with pressurized oil. In some embodiments, the balancer shaft drives the water pump as well as cam shafts.

The present invention provides a rotary engine comprising: a housing provided with three lobe accommodation parts; a rotor which is provided with two lobes continuously accommodated in the lobe accommodation parts, has an intake storage part communicating with an intake port provided on the front surface-side, and has an exhaust storage part communicating with an exhaust port provided on the rear surface-side; an intake-side housing cover provided with an intake hole communicating with the intake storage part; an exhaust-side housing cover provided with an exhaust hole communicating with the exhaust storage part; and a crankshaft, wherein the flow of an exhaust gas into a stroke chamber during an intake stroke is reduced by preventing the exhaust storage part, at a portion of a section in which the exhaust port is open, from communicating with the exhaust hole during the intake stroke.

The present invention provides a rotary engine comprising: a housing provided with three lobe accommodation parts; a rotor which is provided with two lobes continuously accommodated in the lobe accommodation parts, has an intake storage part communicating with an intake port provided on the front surface-side, and has an exhaust storage part communicating with an exhaust port provided on the rear surface-side; an intake-side housing cover provided with an intake hole communicating with the intake storage part; an exhaust-side housing cover provided with an exhaust hole communicating with the exhaust storage part; and a crankshaft, wherein the flow of an exhaust gas into a stroke chamber during an intake stroke is reduced by preventing the exhaust storage part, at a portion of a section in which the exhaust port is open, from communicating with the exhaust hole during the intake stroke.

A crankshaft (1) for a crankcase scavenged two stroke piston engine (2) is disclosed. The crankshaft (1) is configured to rotate around a rotation axis (ax) during operation. The crankshaft (1) comprises a crankpin (3) configured to move in a crank plane (cp) during operation, and a first and a second counterweight (5, 7) arranged on either side (S1, S2) of the crank plane (cp). The first counterweight (5) has a first outer radius (r1) measured from the rotation axis (ax) and the second counterweight (7) has a second outer radius (r2) measured from the rotation axis (ax). The first outer radius (r1) is smaller than the second outer radius (r2). The present disclosure further relates to a power unit (10), a crankcase scavenged two stroke piston engine (2), and a hand-held power tool (20).