To exhibit performance even in a heavy car by fixing capacity increasing-decreasing pumps capable of freely changing a width of two rotors to positions of being mutually rotated by 180 degrees, connecting respective moving arms to each other by a connecting arm, rotating a nut gear, and changing a width of the rotors.

A single capacity increasing-decreasing pump is put in a case, and another one capacity increasing-decreasing pump is put in the case in a position of being rotated by 180 degrees, and a casing part is fixed, and shafts are housed in respective bearings. Next, an upper outlet 37 and an inlet 43 are connected to each other by a pipe 15, and a lower inlet 38 and an outlet 44 are connected to each other by a pipe 16. Respective moving arms are connected to each other by a connecting arm 17, and a bar having a square thread is installed on the connecting arm, and is projected from a hole of the case. A nut gear is fitted in a square thread part, and a metal fitting to sandwich this and a motor having a gear to mesh with the nut gear are provided, and oil is put in intermediate cases of the pumps, and is sealed by a cover. It can be used even in large torque, and rotation can be reliably transmitted.