Patent ID: 8857400

Claim:
A balancer device for an internal combustion engine, comprising: a pair of balancer shafts, including, a drive balancer shall and a driven balancer shaft, each incorporated with a balancer weight and disposed in parallel to each other, the two balancer shafts being coupled such that the two balancer shafts rotates both at twice the rotational speed of the engine in opposite directions; a lower housing including a pair of bearing lower halves for each balancer shaft; an upper housing configured to be joined to the lower housing so as to form a balancer housing, the upper housing including bearing upper halves corresponding to the bearing lower halves of the lower housing for jointly forming radial bearings for the balancer shafts; a pump housing integrally formed at an axial end of one of the upper and lower housings as an integral extension thereof to internally define a part of a pump chamber of an oil pump; a pump cover joined to the pump housing from an outer axial end thereof to jointly define the pump chamber with the pump housing; and a pump rotor received in the pump chamber; wherein an axial end of the driven balancer shaft adjoining the pump housing is coupled with the pump rotor, and an axial end of the drive balancer shaft is provided with a member which is configured to be actuated by a crankshaft of the engine, the radial bearings for the balancer shafts being formed solely in the balancer housing and/or an integral extension thereof wherein a number of radial bearings supporting the drive balancer shaft is smaller than a number of radial bearings supporting the driven balancer shaft, and wherein a distance between the radial bearings formed by the upper housing and the lower housing for the drive balancer shaft is larger than a distance between the radial bearings formed by the upper housing and the lower housing for the driven balancer shaft.