To solve the problem of a running vehicle using an engine connecting type hydraulic pump as a drive source, in which the hydraulic pump is driven to exceed a limit revolution by action of energy upon going down a slope or other external energy, so that breakage in the hydraulic pump and malfunction of the hydraulic pump may occur, and thereby steering or braking system of the running vehicle may be out of control.

To avoid the above problem, a disc brake device is disposed between a flywheel 1 of an engine and the hydraulic pump 2. When the rotation of the hydraulic pump exceeds the limit rotational number, control force is mechanically applied to the engine and the hydraulic pump, and thereby to lower the revolution of the hydraulic pump to a safety area.