Mechanism of returning to neutral for axle driving apparatus

A mechanism of returning to neutral for an axle driving apparatus comprising:

• a housing containing a fluid sump;
• a hydrostatic transmission for driving axles, said hydrostatic transmission including a variable capacity hydraulic pump and a hydraulic motor, wherein suction and discharge ports of said hydraulic pump are connected with respective discharge and suction ports of said hydraulic motor through fluid passages;
• a capacity changing member provided for said hydraulic pump, said capacity changing member being shiftable between a neutral position making said hydraulic pump discharge substantially no fluid and an acting range making said hydraulic pump discharge fluid;
• a biasing member which biases said capacity changing member in said acting range so as to return to said neutral position;
• orifices connecting said fluid passages to said fluid sump;
• a shutting member facing said orifices so as to be operable to open and shut said orifices toward said fluid sump, wherein said shutting member is interlocked with said capacity changing member;
• pistons having said orifices therethrough, said pistons being slidably fit to said respective fluid passages and being pressed at outer surfaces thereof against said shutting member by hydraulic pressure in said fluid passages;
• grooves provided in said shutting member so as to communicate with said orifices of said pistons;
• and
• biasing members pushing said pistons so as to press the outer surfaces thereof against said shutting member, wherein the biasing forces of said biasing members for pushing said pistons are smaller than that of said biasing member for returning said capacity changing member to neutral.

A mechanism for returning to neutral for an axle driving apparatus comprising:

• a housing containing a fluid sump;
• a hydrostatic transmission for driving axles, said hydrostatic transmission including a variable capacity hydraulic pump and a hydraulic motor, wherein suction and discharge ports of said hydraulic pump are connected with respective discharge and suction ports of said hydraulic motor through fluid passages;
• a capacity changing member provided for said hydraulic pump, said capacity changing member being shiftable between a neutral position making said hydraulic pump discharge substantially no fluid and an acting range making said hydraulic pump discharge fluid;
• a biasing member which biases said capacity changing member in said acting range so as to return to said neutral position;
• orifices connecting said fluid passages to said fluid sump;
• and
• a shutting member facing said orifices so as to be operable to open and shut said orifices toward said fluid sump, wherein said shutting member is interlocked with said capacity changing member so that at least one of said orifices is open to said fluid sump during returning of said capacity changing member from said acting range to said neutral position, wherein when said capacity changing member is in said neutral position, said shutting member shuts one of said orifices.