Abstract: A hydraulic motor 11 is switched to a high-speed mode when pressure oil is supplied to a pressure chamber 23 of a tilt piston 17 based on the transmission of a speed signal to a high-low speed switching valve 18, and the hydraulic motor 11 is switched to a low-speed mode when pressure oil is discharged from the pressure chamber 23 of the tilt piston 17. A first braking purpose speed changing mechanism 13 operates so as to discharge pressure oil from the pressure chamber 23 of the tilt piston 17 when the pressure of pressure oil between a counterbalance valve 15 and a direction changeover valve 103 becomes equal to a tank pressure. Therefore, it is possible to provide a variable hydraulic motor driving device which is capable of preventing braking operation from being excessively long and also capable of preventing a large shock from occurring at a time of stoppage due to a large braking force generated from an early stage of braking operation.

Abstract: A hydraulic motor 11 is switched to a high-speed mode when pressure oil is supplied to a pressure chamber 23 of a tilt piston 17 based on the transmission of a speed signal to a high-low speed switching valve 18, and the hydraulic motor 11 is switched to a low-speed mode when pressure oil is discharged from the pressure chamber 23 of the tilt piston 17. A first braking purpose speed changing mechanism 13 operates so as to discharge pressure oil from the pressure chamber 23 of the tilt piston 17 when the pressure of pressure oil between a counterbalance valve 15 and a direction changeover valve 103 becomes equal to a tank pressure. Therefore, it is possible to provide a variable hydraulic motor driving device which is capable of preventing braking operation from being excessively long and also capable of preventing a large shock from occurring at a time of stoppage due to a large braking force generated from an early stage of braking operation.

Abstract: A motorized gear reducer wherein a first external gear 41 is mounted on an input rotary shaft 11 coupled to a driving motor 3 and wherein a second external gear 43 is capable of engaging with the first external gear. The front end portion 63 of the first external gear side of the input rotary shaft is unable to make a relative rotation with respect to the input rotary shaft but made movable in the axial direction of the input rotary shaft. The front end portion thereof movably axially engages with the first external gear. The front end portion and the first external gear are allowed to select one of the conditions including making an integral rotation and freely making relative rotations in accordance with the axial movement of the front end portion.