Patent ID: 7946834

Claim:
A balance shaft module comprising: a first eccentric balance weight; a first balance shaft wherein the first eccentric balance weight is formed an end portion of the first balance shaft; a second eccentric balance weight; a second balance shaft positioned in parallel to the first balance shaft, wherein the second eccentric balance weight is formed an end portion of the second balance shaft; and a hydraulic pump having a first gear equipped on other end portion of the first balance shaft, and a second gear equipped on other end portion of the second balance shaft wherein the first gear and the second gear are externally meshed to be engaged each other to rotate synchronously; wherein a first centroid of the first eccentric balance weight is configured to be distanced by a predetermined length from a center line of the first balance shaft and a second centroid of the second eccentric balance weight is configured to be distanced by a predetermined length from a center line of the second balance shaft; wherein the first centroid of the first eccentric balance weight and the second centroid of the second eccentric balance weight are configured to have rotary phase offset of 180 degrees; and wherein the first eccentric balance weight and the second eccentric balance weight are configured to face each other symmetrically.