Abstract: There is provided a balancer device of an engine, configured to reduce rotation vibrations of the engine. A crankshaft is provided with a primary drive gear. A countershaft is provided with a primary driven gear meshed with the primary drive gear. A plurality of balancer shafts are provided with balancer driven gears meshed with the primary drive gear.

Abstract: An asymmetry cylinder de-activation (CDA) engine provided with a first, a second, a third and a fourth cylinder of which CDA apparatuses are mounted thereto respectively may include a crankshaft connected with pistons of each cylinder through a first, a second, a third and a fourth cranking journal respectively, and a controller configured to control operations of the CDA apparatuses, in which phase differences between cranking journals according to firing order may include 90±10 degrees and 270±10 degrees.

Abstract: It is common for crankshafts of internal combustion engines to have main bearing journals provided between each of the conrod bearing journals. However, to reduce engine friction, the fewest main bearing journals that can be used while still meeting the design targets is preferred. A crankshaft for an in-line, four-cylinder engine, according to an embodiment of the disclosure, has three main bearing journals. Bridges, one each located between first and second conrod bearing journals and between third and fourth conrod bearing journals. The bridges have a cross-section with at least two concavities to improve the strength of the bridge compared to, for example, a cylindrical bridge, without greatly increasing the mass of material used in the bridge. Furthermore, a locus of a centroid of cross sections through the bridge are not coincident with an axis of rotation of the crankshaft, but instead is displaced toward the nearer conrod bearing journal.

Abstract: An engine includes a cylinder system, a driving system including a piston and a crankshaft, a power generating system and a cooling system. The power generating system is disposed on a side of the driving system and includes a generator and a counterweight. The generator includes a main body and a rotor pivotally disposed within the main body. The cooling system is disposed on an opposite side of the driving system and includes a first water pump in fluid communication with the cylinder system. An outline of the rotor is projected along the crankshaft to form a first projecting zone. Projections of the first water pump and the driving system along the crankshaft overlap the first projecting zone.

Abstract: A system and method for operating a hybrid vehicle having an engine and an eMachine coupled by a clutch using a hybrid controller is presented. The method determines an idle fuel rate of the engine, determines a hybrid efficiency index for the hybrid vehicle, determines an expected energy storage rate increase for an operating condition where the engine is decoupled from a vehicle transmission using said clutch, multiplies the expected energy storage rate increase by the hybrid efficiency index to determine an expected fuel rate reduction of the engine in the operating condition; and decouples the engine from the vehicle transmission using the clutch if the expected fuel rate reduction is greater than the idle fuel rate.

Abstract: An idle gear assembly comprises an outer ring having gear teeth formed on an external surface thereof and engaged with a crank gear and any one of the left and right balance gears. A bearing includes an inner member and an outer member in a radial direction of the bearing and a plurality of rolling bodies disposed between the inner member and the outer member. A ring has elasticity in a radial direction thereof. A hub has a flange, which is in contact with the bearing, and a penetration hole. The flange and the penetration hole are formed at one side of the hub in an axial direction. A nut is inserted through another side and mounted at a hollow portion of the ring. A bolt is inserted through the insertion hole of the bearing, the penetration hole, and the nut and fixes the bearing and the hub.

Abstract: A timing drive is disclosed for coupling the crankshaft to the first camshaft of an internal combustion engine. The timing drive includes a first mechanical transmission coupling the engine crankshaft to an intermediate shaft located in a cylinder block, and a second mechanical transmission coupling the intermediate shaft to the first camshaft. A second camshaft may be operably coupled to the first camshaft through a mechanical transmission coupling.

Abstract: In an engine (internal combustion engine), a crankcase is provided with a fastening area that surrounds the opening and contacts the oil pan, a balance shaft housing is disposed in the crankcase to surround the opening, and four housing side fastening sections are provided to the crankcase to fasten the crankcase and the balance shaft housing. The fastening section of the four housing side fastening sections in a first axial direction side of a balance shaft is disposed on the inside of the fastening area, and the fastening section of the four housing side fastening sections in a second axial direction side of the balance shaft is disposed on the outside of the fastening area.

Abstract: A generation control method for a vehicle may include a deceleration driving determination step of determining whether a driving state of the vehicle is a deceleration driving state, an acceleration driving determination step of determining whether the driving state of the vehicle is an acceleration driving state when the driving state of the vehicle is not the deceleration driving state, and a constant speed driving generation step of performing constant speed driving generation when the driving state of the vehicle is not the deceleration driving state or the acceleration driving state.

Abstract: A crankshaft comprising a cheek, a torsion-absorbing pendulum pivotally coupled to the cheek, and a rotational speed actuated brake to oppose motion of the pendulum relative to the cheek. The brake is configured to provide greater opposition to the motion at lower rotational speeds than at higher rotational speeds.

Abstract: A drive device (10) for a forming machine (11) includes a hypocycloid gear assembly (20) having an eccentric gear (23), a stationary annulus gear (24) and a planetary gear system (28). The planetary gear system (28) includes an orbiting gear (29) orbiting and rolling in an annulus gear (24). The orbiting gear (29) is connected to at least one first planetary gear (35). On the first planetary gear (35), a first planetary gear equalization mass (m2) is disposed diametrically opposite an output bearing. At least one first eccentric gear equalization mass (m3) is arranged on the eccentric gear (23). The first eccentric gear equalization mass (m3) is arranged diametrically opposite, relative to a planetary gear axis (PA) about which the planetary gear system (28) rotates. The resultant forces and torques acting on the annulus gear (24) can at least be reduced by the equalization masses.

Abstract: A gear transmission mechanism is provided between a crankshaft and the balancer shaft. The balancer shaft includes a pair of bearing portions supported for rotation on a crankcase and a gear wheel supporting portion formed in a tapering shape such that a diameter thereof decreases away from one bearing portion. A tubular boss portion is provided integrally on the driven gear wheel and has a tapering attachment hole in which the gear wheel supporting portion is fitted. A fitting recessed portion in which a pin which has an axial line along a radial direction of the balancer shaft and is fitted at a half portion on one end side thereof in a large diameter end portion of the gear wheel supporting portion is fitted at a half portion on the other end side thereof is provided on the boss portion on the large diameter end side of the attachment hole.

Abstract: A balancer device for an internal combustion engine includes upper and lower housings made of aluminum alloy. The upper housing includes a leg part fixed to the engine. The lower housing is coupled to the upper housing by tightening bolts. A pair of balancer shafts are rotatably supported by the upper and lower housings. A positioning pin is disposed at a distal end portion of the leg part for positioning the upper housing with respect to the engine by positional correspondence to a positioning hole of the engine when the tightening bolts are tightened. The leg part is inclined outwardly with respect to a body of the upper housing such that a distal end of the positioning pin is located outside of a proximal end of the leg part with respect to the body of the upper housing when the tightening bolts are loosened.

Abstract: An object is to provide a method and a system of controlling a load during misfire of an engine, whereby additional stress on a crank shaft is calculated from torsional vibration of the crank shaft to obtain an output limit rate, and an operation output of an engine is controlled on the basis of the output limit rate.

Abstract: An internal combustion engine includes a crankcase, a case cover for covering a side of the crankcase, a crankshaft and a balancer shaft. A balancer has a balancer driven gear and a balance weight provided on the balancer driven gear and is acted upon and driven by a driving force of the crankshaft to rotate. An oil pump is accommodated in the crankcase and has an oil pump driving shaft disposed in parallel to the crankshaft and the balancer shaft. The oil pump includes a pump driven gear. The balancer has a pump driving gear which has a diameter smaller than that of the balancer driven gear and rotates together with the balancer driven gear. The pump driving gear meshes with the pump driven gear. The oil pump driving shaft is disposed within a range of rotation of the balance weight as viewed in an axial direction thereof.

Abstract: An air-cooled internal combustion engine includes an engine block, a blower assembly including a blower housing and a fan, and a static cover. The static cover includes multiple air intake openings and is configured to prevent user access to a moving component of the engine. The blower housing is configured to at least partially direct air to the engine block. The fan is configured to move air into the blower assembly through the air intake openings when rotating in a first direction in a cooling mode and to move air out of the blower assembly through the air intake openings when rotating in an opposite second direction in a debris-removal mode.

Abstract: A breather apparatus for an internal combustion engine for a vehicle in which an air cleaner is disposed above a crankcase. A breather tube is provided for guiding blow-by gas exhausted from the crankcase. The breather tube is coupled with a breather chamber formed in the air cleaner to separate gas and liquid in the breather chamber in the air cleaner. An upstream side flow path, coupled to the breather tube, and a downstream side flow path, continuously extending in a substantially U-shape to the upstream side flow path, are formed in the breather chamber.

Abstract: Methods and systems are provided for an oil pump mounting structure that provides accessibility and removal of the oil pump without removing a balancer shaft. While periodically servicing or replacing the oil pump may be necessary throughout the lifetime of an engine, it is desirable to allow for easy removal of the oil pump without removing and reassembling other engine components. To provide alignment and a rigid connection between the oil pump and engine frame while allowing for removal of the oil pump without removing other components, dowel bolts with unthreaded, threaded, and dowel portions are used to mount the oil pump to the engine frame.

Abstract: A method for operating an internal combustion engine is disclosed, in which method test injections are carried out in order to adapt, during the operation of the internal combustion engine, the injection parameters used for the control of the injection processes. For this purpose, during the test injections, an electric machine which is coupled to the internal combustion engine generates negative torque impulses in a manner synchronized with the positive torque impulses generated by the test injections, which negative torque impulses counteract the torque impulses generated by the test injections. In this way, rotational speed oscillations generated by the test injections are eliminated. Also described is an internal combustion engine of said type.

Abstract: A balance system for implementation within an engine crankcase, as well as an engine employing such a system and a method of balancing forces as performed by such a system, are disclosed. In at least one embodiment, the balance system includes a crankshaft with at least one eccentric portion and a counterbalance assembly having at least one connecting arm and a counterbalance weight with first and second ends, where each of the at least one connecting arm includes a respective circular orifice that is positioned around and supported by a respective one of the at least one eccentric portion. The balance system further includes first and second hinged arms rotatably coupled proximate the first and second ends of the counterbalance weight, respectively, where the arms at least indirectly link the ends of the counterbalance weight to a portion of the engine crankcase and guide movement of the counterbalance weight.

Abstract: An engine including: a primary balancer driven by a crankshaft via a gear drive device and rotates in a direction reverse to a direction of the crankshaft; an electric motor driven by the primary balancer via a belt drive device to rotate in a direction reverse to the direction of the crankshaft; an auxiliary flywheel provided to a rotary shaft of the electric motor via a clutch. An engine control unit including a first device for increasing and decreasing effective moment of inertia around the crankshaft by engaging or disengaging the clutch in accordance with an operating condition of the engine, and a second device for controlling torque to be transmitted to the gear drive device via the belt drive device by power-driving or regeneratively driving the electric motor in accordance with a crank angular acceleration.

Abstract: A primary drive gear 10 is configured so as to have its position changed, by mounting the primary drive gear 10 in an axial direction within a length range of a crankshaft so as to displace a toothed portion 12 of said primary drive gear 10 in the axial direction of said crankshaft in response to a boss portion 13 integrally provided on said toothed portion 12 of said primary drive gear 10 so that said primary drive gear 10 is registered with a position in the axial direction of the primary driven gear meshing with said primary drive gear 10.

Abstract: A rolling bearing of a balancer shaft device is positioned on an imaginary circle concentric with an axis of a shaft portion of a balancer shaft as viewed in a radial cross-section, and includes a cylindrical portion which covers the shaft portion. An outer circumferential surface of the cylindrical portion defines an inner ring raceway surface of an inner ring member on which a rolling element of the rolling bearing rolls. A part of the shaft portion of the balancer shaft, at a position on which the rolling bearing is disposed, has a cutout formed at a portion which does not contribute to offsetting of rotational vibration of a crankshaft.

Abstract: A three cylinder engine includes a vibration alleviation unit for alleviating vibrations in a vehicle. The vibration alleviation unit is disposed at least one of upon the crankshaft and upon a part that operates in unison with the crankshaft. The three cylinder is supported by engine mounts that are positioned upon at least both ends of the engine in the direction of the crankshaft axis. Given that KV and KH represent spring constants of one of the engine mounts in the pitch and yaw directions of the crankshaft, MV and MH represent components of a primary couple that occurs in the three cylinder engine in the pitch and yaw directions, and MV0 represents the sum of MV and MH, then spring constants of the engine mounts are set such that KV >KH and the vibration alleviation unit is set so as to satisfy the condition 0 <MV/MV0 <0.5.

Abstract: A mass equalization gear mechanism of an internal combustion engine is provided, having a gear mechanism housing (8) with bearing points (16, 17, 18), at least one equalization shaft (6) with a drive section (9) and an imbalance section (12) and rolling bearings (10, 11, 15) by which the equalization shaft is mounted in the bearing points. In this context, the gear mechanism housing is hydraulically sealed, with the result that the imbalance section and at least one of the rolling bearings is hydraulically separated from the drive section and is provided with autonomous lubrication.

Abstract: An internal combustion engine includes a crankcase, a case cover for covering a side of the crankcase, a crankshaft and a balancer shaft. A balancer has a balancer driven gear and a balance weight provided on the balancer driven gear and is acted upon and driven by a driving force of the crankshaft to rotate. An oil pump is accommodated in the crankcase and has an oil pump driving shaft disposed in parallel to the crankshaft and the balancer shaft. The oil pump includes a pump driven gear. The balancer has a pump driving gear which has a diameter smaller than that of the balancer driven gear and rotates together with the balancer driven gear. The pump driving gear meshes with the pump driven gear. The oil pump driving shaft is disposed within a range of rotation of the balance weight as viewed in an axial direction thereof.

Abstract: A balancer device for an internal combustion engine includes upper and lower housings made of aluminum alloy. The upper housing includes a leg part fixed to the engine. The lower housing is coupled to the upper housing by tightening bolts. A pair of balancer shafts are rotatably supported by the upper and lower housings. A positioning pin is disposed at a distal end portion of the leg part for positioning the upper housing with respect to the engine by positional correspondence to a positioning hole of the engine when the tightening bolts are tightened. The leg part is inclined outwardly with respect to a body of the upper housing such that a distal end of the positioning pin is located outside of a proximal end of the leg part with respect to the body of the upper housing when the tightening bolts are loosened.

Abstract: An internal combustion engine has a multi-joint crank drive which includes a plurality of coupling members rotatably mounted on a crankshaft and a plurality of articulated connecting rods rotatably mounted on an eccentric shaft, wherein each of the coupling members is pivotably connected to a piston connecting rod of a piston of the internal combustion engine and to one of the articulated connecting rods. In order that the second-order mass forces can be better compensated without a considerable increase in the friction losses, the required packaging space, the weight of the multi-joint crank drive, or the bearing forces in the bearings of the crankshaft, the articulated connecting rods are provided with additional masses and have a center of mass that lies outside the longitudinal center planes of the articulated connecting rods.

Abstract: A system and a method for reducing a rotational imbalance of a drive train of a hybrid vehicle are provided. The drive train includes an internal-combustion engine, an electric machine, and a crankshaft. A reduction or nullification of the rotational imbalance takes place by actuating the electric machine. The actuation is implemented as an adaptive feed forward control, which provides an actuation signal for the electric machine. The actuation signal represents a desired torque to be generated by the electric machine, so that the electric machine outputs a torque that is at least approximately inverse with respect to the rotational imbalance to the crankshaft for the superimposition of the torque generated by the internal-combustion engine.

Abstract: A two-cycle engine having a structure in which the shaft center Ccy of the cylinder 3 is offset onto the exhaust port 32 side with respect to the rotational center Ccr of the crankshaft 4, and the offset amount S of the shaft center Ccy with respect to the rotational center Ccr is set greater than 1 mm and less than 6 mm. Furthermore, in this case, the center of gravity of the counterweight 42 of the crankshaft 4 is shifted onto the rear side in the rotational direction with respect to the line passing the rotational center Ccr of the crankshaft 4 and the center Ccp of the crank pin 41.

Abstract: The invention relates to a rolling bearing provided with at least one row of rolling elements disposed between an inner raceway and an outer raceway. At least one of the raceways is coated with a tungsten sulphide (WS2) coating. The invention also relates to an internal combustion engine (M) having at least one balance shaft rotated by a crankshaft of the internal combustion engine (M), the at least one balance shaft being freely supported in rotation in a frame (B) of the internal combustion engine (M) by at least one such rolling bearing.

Abstract: A balancing shaft may have at least one unbalance portion and at least one bearing point, wherein the at least one unbalance portion is associated with the at least one bearing point. The balancing shaft on the bearing point may define a transverse opening which separates a first part bearing surface from a second part bearing surface.

Abstract: The invention relates to a countershaft for a single or multiple cylinder motor having at least one unbalanced weight section (21, 22; 23, 24) and at least one bearing point (16, 17) that is allocated to the at least one unbalanced weight section (21, 22; 23, 24), wherein the bearing point (16, 17) has a radial circumferential surface (18) that extends only partially over a circumference of the bearing point (16, 17) so that a centrifugal force resulting from rotation of the countershaft (11) lies within a region of the bearing point (16, 17) that is formed by the circumferential surface (18) extending partially over the circumference of the bearing point (16, 17) and having a ring (25) that surrounds the partially extended circumferential surface (18) of the bearing point (16, 17) and is connected by a force and/or form and/or material fitting connection to the bearing point (16, 17), wherein the circumferential surface (18) of the bearing point (16, 17) has a receptacle region (33) for receiving the ring (2

Abstract: A method of balancing a crankshaft includes connecting a torsion-absorbing pendulum to a cheek of the crankshaft, which is coupled to a crankpin. As the pendulum connected to the cheek has insufficient mass to balance the crankshaft, a lightening bore is formed through a bisection plane of the cheek. In forming the lightening bore, enough material is removed from the cheek so that the mass of the pendulum becomes sufficient to balance the crankshaft.

Abstract: An engine including: a primary balancer driven by a crankshaft via a gear drive device and rotates in a direction reverse to a direction of the crankshaft; an electric motor driven by the primary balancer via a belt drive device to rotate in a direction reverse to the direction of the crankshaft; an auxiliary flywheel provided to a rotary shaft of the electric motor via a clutch. An engine control unit including a first device for increasing and decreasing effective moment of inertia around the crankshaft by engaging or disengaging the clutch in accordance with an operating condition of the engine, and a second device for controlling torque to be transmitted to the gear drive device via the belt drive device by power-driving or regeneratively driving the electric motor in accordance with a crank angular acceleration.

Abstract: A mass-balancing transmission of an internal combustion engine (1) is provided, having a transmission housing (8) and a balancing shaft (6) with a bearing point (10, 11) at which the balancing shaft is mounted radially in a bearing seat (12, 13) of the balancing housing, and having an unbalanced section (9) which is formed in one part with the bearing point of the originally shaped balancing shaft. The bearing point is set back radially compared to the unbalanced section with the result that the diameter relationship: d2>d1 applies for the external envelope circle d1 of the bearing point and the external envelope circle d2 of the unbalanced section. Considered in the axial direction of the balancing shaft, the external envelope circle d2 of the unbalance section and the external envelope circle d1 of the bearing point extend offset to one another with an eccentricity of e.

Abstract: A balancer housing (30) consists of an upper housing (32) and a lower housing (31), and receives a pair of rotatably supported balancer shafts (11, 21) therein. An oil strainer mounting portion (37) is formed as a cylindrical wall extending downward from a bottom wall of the lower housing, and an inlet passage (67) leading to an inlet end of an oil pump (60) extends along a length of the balancer shafts adjacent to the oil strainer mounting portion. A communication passage consisting of a pair of circular holes (66) arranged along an axial line of the inlet passage is passed through a wall separating an interior of the oil strainer mounting portion with the inlet passage. The two holes provides an adequate cross sectional area without increasing the height of the balancer housing.

Abstract: In a balancer device (10) including a pair of balancer shafts (11, 21), the radial bearings (41-44) for the balancer shafts are formed solely in the balancer housing (30) and/or an integral extension (52) thereof. Because a pump cover (56) provided separately from the balancer housing does not include a radial bearing for either balancer shaft, the pump cover is not required to be attached to the balancer housing when machining the radial bearing bores in the balancer housing so that the manufacturing process is simplified, and the coaxiality of the bearing halves for each balancer shaft can be ensured without difficulty as opposed to the case where the pump cover is provided with a bearing bore which is required to be aligned with the corresponding bearing bore of the balancer housing.

Abstract: A balancing system configured to be applied to an inline-four internal combustion engine is disclosed. The balancing system comprises counter rotating eccentric masses (22, 23, 24, 25) projecting from the opposite side of a support (21). The support (21) is placed centrally under the driving shaft, being fixed by screws to the wall of the engine.

Abstract: An internal combustion engine includes a balance shaft assembly having a housing mounted to the cylinder block wherein the housing supports a pair of balance shafts rotatably driven by the crankshaft. The pair of balance shafts rotate in opposite directions and each include a hollow tubular body with an internal eccentric mass. A first of the pair of balance shafts is drivingly connected to a drive sprocket at a first end and can include a first drive gear at a second end that is meshingly engaged with a first driven gear at an end of a second of the pair of balance shafts. A first oil pump is provided at the first end of the pair of balance shaft, and a second oil pump is provided at a second end of the pair of balance shafts. The gears of the oil pumps transfer torque between the pair of balance shafts.

Abstract: A torque ripple compensating device for an internal combustion engine is provided. The torque ripple compensating device comprises a first member, a second member, and a third member. The first member is in driving engagement with an output of the internal combustion engine. The second member is in driving engagement with the first member. The third member is in driving engagement with the second member. An angular deviation between the first member and the third member causes a cyclical acceleration of the third member. The cyclical acceleration of the third member applies a torque to the output of the internal combustion engine through the first member. The torque ripple compensating device is able to be passively or dynamically adapted for both an amplitude and a phase of a torque ripple while minimizing an interference with an operation of the internal combustion engine.

Abstract: An internal combustion engine with a cylinder and with a crank drive is described herein. The internal combustion engine includes a crankshaft in which the crankshaft mounted in the crankcase has an associated crankshaft throw for the cylinder. The internal combustion engine further includes a compensation weight serving as a counterbalance for mass compensation arranged on the crankshaft on the side opposite the crankshaft throw, where the compensation weight includes an outward-facing side and a distance from a peripheral surface of the outward-facing side to a longitudinal axis of the crankshaft is not constant along the length of the peripheral surface of the outward-facing side.

Abstract: A structure of an engine includes: a crankshaft module configured to convert reciprocal motion of a piston into rotational motion; and a first balance shaft module and a second balance shaft module configured to reduce vibration of the engine, in which the first balance shaft module is directly gear-meshed with the crankshaft module, and the second balance shaft module is gear-meshed with the crankshaft module through an intermediate gear.

Abstract: An apparatus for damping vibrations in an internal combustion engine. The apparatus includes a crankshaft with a lobe. The lobe has a flange with an opening that is coupled to the body of the lobe. A pendulum is pivotally coupled to the flange in a manner to allow the pendulum to follow an epicycloidal path of movement.

Abstract: An apparatus for damping vibrations in an internal combustion engine. The apparatus includes a pendulum-type torsional absorber that uses a hydraulic snubber mechanism to limit travel of the pendulum without causing noise or damage to the absorber, crankshaft or other engine components.

Abstract: A nutating balance device for mitigating vibrations of an internal combustion engine having a crankshaft includes a coupler coupled to the engine crankshaft. The device also includes a weight coupled to the coupler. The coupler is configured to move the weight in sync with the crankshaft. The nutating balance device can generate variable torque pulsations or moments corresponding to torque harmonic frequencies of the internal combustion engine.

Abstract: A crankshaft is provided. The crankshaft includes an unsupported axially-aligned shaft section interposing an outer main bearing journal and an inner main bearing journal, the unsupported axially-aligned shaft section having a central axis aligned with a rotational axis of the crankshaft, and a pendulum absorber coupled to the unsupported axially-aligned shaft section, the pendulum absorber including a blade extending from the unsupported axially-aligned shaft section and a pendulous counterweight coupled to the blade.

Abstract: An internal combustion engine including: an even number of inline cylinders, each accommodating a piston; a crankshaft rotatably mounted about an axis; first and second balance shafts rotatably mounted about balancing axes parallel to and separate from the engine axis; and first and second mechanisms for rotating the first and second balance shafts at rotating speeds that are dependent on a rotating speed of the crankshaft. The balancing axes of the first and second balance shafts coincide, and the second rotating mechanism adjusts a phase difference between angular positions of the first and second balance shafts around the balancing axis.

Abstract: A balancer device of an internal combustion engine, has a drive gear engaged with an input gear to which a rotation force is transmitted from a crankshaft; a balancer drive shaft to which the rotation force is transmitted from the drive gear and which has a balancer weight; a balancer drive gear rotating integrally with the balancer drive shaft; a balancer driven gear engaged with the balancer drive gear; and a balancer driven shaft rotating integrally with the balancer driven gear and having a balancer weight. At least one of the drive gear, the balancer drive gear and the balancer driven gear is provided, on both axial direction side surfaces thereof, with ring-shaped grooves whose diameters are different from each other. The ring-shaped grooves are formed up to a depth from the surface of the gear at which both the ring-shaped grooves overlap each other in the axial direction.

Abstract: A crankshaft for an engine having an odd number of cylinders is provided. In one example, the crankshaft includes a central pin coupling a first and a second asymmetric counterweight and a pair of pins coupling cheeks absent counterweights. The crankshaft can improve engine balance at least during some conditions.