An internal combustion engine includes a crankcase in which a crankshaft is rotatably mounted in bearings including bearing covers, to which at least one connecting rod carrying a piston is linked. The piston is movable in a cylinder covered by a cylinder head forming a combustion chamber and gas exchange valves are arranged in the cylinder head, which are actuated by at least one camshaft, which is connected to a gear train gear wheel situated on the crankshaft via a differential gear. A mass differential gear including two balance shafts is present. The mass differential gear is situated in a gear frame and attached to the crankcase below the crankshaft and driven by a mass shaft drive gear situated on the crankshaft, which is arranged axially essentially next to the gear train gear wheel/idler gear. The gear train gear wheel/idler gear is arranged on the main bearing cover.

A balancer apparatus equipped with an oil pump includes a pump housing including a pump containing chamber provided therein, a pump forming member contained in the pump containing chamber and configured to discharge oil introduced from an intake portion from a discharge portion to an oil passage of the internal combustion engine when a rotational force is transmitted thereto, a control oil chamber provided between the pump containing chamber and the pump forming member in a radial direction with respect to a rotational axis of the pump forming member and configured to change a hydraulic pressure of the oil to be discharged from the pump forming member with the aid of the oil introduced therein after being discharged from the discharge portion, passing through an oil passage of the internal combustion engine, and being subjected to a pressure adjustment, and a balancer housing including a bearing retainer portion configured to transmit the rotational force from the internal combustion engine to the pump forming member. The bearing retainer portion supports a balancer shaft disposed along the rotational axis of the pump forming member. The balancer housing is attached to the pump housing in a direction of the rotational axis of the pump forming member. The balancer apparatus equipped with the oil pump further includes a plurality of oil passage opening portions formed together on one side surface of the balancer housing and each connected to an oil passage connected to a main oil gallery of the internal combustion engine. The plurality of oil passage opening portions includes a discharge oil passage opening portion of a discharge oil passage connecting the discharge portion and the main oil gallery of the internal combustion engine to each other, a feedback oil passage opening portion of a feedback oil passage connecting the main oil gallery of the internal combustion engine and the control oil chamber to each other, and a bearing oil passage opening portion of a bearing oil passage connecting the main oil gallery of the internal combustion engine and the bearing retainer portion to each other.

A balancer apparatus equipped with an oil pump includes a pump housing including a pump containing chamber provided therein, a pump forming member contained in the pump containing chamber and configured to discharge oil introduced from an intake portion from a discharge portion to an oil passage of the internal combustion engine when a rotational force is transmitted thereto, a control oil chamber provided between the pump containing chamber and the pump forming member in a radial direction with respect to a rotational axis of the pump forming member and configured to change a hydraulic pressure of the oil to be discharged from the pump forming member with the aid of the oil introduced therein after being discharged from the discharge portion, passing through an oil passage of the internal combustion engine, and being subjected to a pressure adjustment, and a balancer housing including a bearing retainer portion configured to transmit the rotational force from the internal combustion engine to the pump forming member. The bearing retainer portion supports a balancer shaft disposed along the rotational axis of the pump forming member. The balancer housing is attached to the pump housing in a direction of the rotational axis of the pump forming member. The balancer apparatus equipped with the oil pump further includes a plurality of oil passage opening portions formed together on one side surface of the balancer housing and each connected to an oil passage connected to a main oil gallery of the internal combustion engine. The plurality of oil passage opening portions includes a discharge oil passage opening portion of a discharge oil passage connecting the discharge portion and the main oil gallery of the internal combustion engine to each other, a feedback oil passage opening portion of a feedback oil passage connecting the main oil gallery of the internal combustion engine and the control oil chamber to each other, and a bearing oil passage opening portion of a bearing oil passage connecting the main oil gallery of the internal combustion engine and the bearing retainer portion to each other.

An internal combustion engine unit including an internal combustion engine body, a balancer device attached to a lower portion of the internal combustion engine body, and an oil pan attached to the lower portion of the internal combustion engine body so as to surround the balancer device. The balancer device is disposed facing an outlet of an oil outflow hole, and the oil outflow hole is formed in the internal combustion engine body so as to return a lubricating oil in the internal combustion engine body to the oil pan.

Balancer device has upper and lower housings 3 and 4 having therein an accommodation section 10, a pair of drive and driven side shafts 5 and 6 which are rotatably supported by four plain bearings 11 to 14 provided in the accommodation section and to which a rotation force is transmitted from a crankshaft, and arc band-shaped thrust receiving portions 32a and 33a which thrust flange portions of drive and driven gears 8 and 9 provided at the drive and driven side shafts respectively can contact from a thrust direction. First and second oil storing grooves 34 and 35, groove passages 36 and 37 and vertical groove passages 38a to 39b are formed at the thrust receiving portions on a gravity direction lower side with respect to a meshing portion of the both gears. With this configuration, it is possible to suppress occurrence of abrasion of the thrust receiving portion.

Balancer shaft 5 and 6 rotatably set through bearings 1114 and an oil pump 2 driven by power from the balancer shaft 5 and 6 are provided in a balancer housing. Oil discharged from an outlet portion 42 of the oil pump 2 is supplied to a main oil gallery 10 through an outlet passage 48. A bearing filter 55 that filters a part of the oil is provided in the outlet passage 48 that extends from the outlet portion 42. A communication passage 50 that branches off from the outlet passage 48 and communicates with the bearings 1114 supplies a part of the oil having been filtered by the bearing filter 55 to the bearings 1114. By filtering the oil that is going to be supplied to the bearing portion, decrease in durability of the bearing portion can be suppressed.

An internal combustion engine unit including an internal combustion engine body, a balancer device attached to a lower portion of the internal combustion engine body, and an oil pan attached to the lower portion of the internal combustion engine body so as to surround the balancer device. The balancer device is disposed facing an outlet of an oil outflow hole, and the oil outflow hole is formed in the internal combustion engine body so as to return a lubricating oil in the internal combustion engine body to the oil pan.

An internal combustion engine includes: an oil filter that is mounted to a mounting surface formed on a crankcase and clarifies an oil flowing in; an oil cooler that is disposed on a front side of the crankcase, cools the oil flowing in from the oil filter and returns the oil into a flow path in the crankcase; and a bracket formed on a front wall of the crankcase and having the mounting surface. An outflow port through which the oil flows out toward the oil cooler and an inflow port through which the oil flows in from the oil cooler are disposed in the bracket. Accordingly, in the internal combustion engine, routes of oil passages can be simplified as much as possible.

Balancer device has upper and lower housings 3 and 4 having therein an accommodation section 10, a pair of drive and driven side shafts 5 and 6 which are rotatably supported by four plain bearings 11 to 14 provided in the accommodation section and to which a rotation force is transmitted from a crankshaft, and arc band-shaped thrust receiving portions 32a and 33a which thrust flange portions of drive and driven gears 8 and 9 provided at the drive and driven side shafts respectively can contact from a thrust direction. First and second oil storing grooves 34 and 35, groove passages 36 and 37 and vertical groove passages 38a to 39b are formed at the thrust receiving portions on a gravity direction lower side with respect to a meshing portion of the both gears. With this configuration, it is possible to suppress occurrence of abrasion of the thrust receiving portion.

Balancer shaft 5 and 6 rotatably set through bearings 1114 and an oil pump 2 driven by power from the balancer shaft 5 and 6 are provided in a balancer housing. Oil discharged from an outlet portion 42 of the oil pump 2 is supplied to a main oil gallery 10 through an outlet passage 48. A bearing filter 55 that filters a part of the oil is provided in the outlet passage 48 that extends from the outlet portion 42. A communication passage 50 that branches off from the outlet passage 48 and communicates with the bearings 1114 supplies a part of the oil having been filtered by the bearing filter 55 to the bearings 1114. By filtering the oil that is going to be supplied to the bearing portion, decrease in durability of the bearing portion can be suppressed.