Patent ID: 8272483

Claim:
A vehicle wet-type multi-plate brake device in which a mating plate attached to a frame support connected to an axle housing is configured to engage with or disengage from a friction plate attached to a brake hub connected to an axle shaft by a plurality of hydraulic pistons, the hydraulic pistons being provided in a circumferential direction around a brake center and each hydraulic piston being provided with an oil chamber to which operation oil acting on each hydraulic piston is supplied, wherein an annular piston sleeve is slidably provided between an inner-peripheral surface of a piston housing and an outer-peripheral surface of the hydraulic piston, an inner peripheral surfaces of the annular piston sleeves defining a plurality of hydraulic piston holes accommodating the hydraulic pistons, wherein the piston sleeve has a sliding resistance so as to move together with each hydraulic piston upon supplying a hydraulic pressure to the oil chamber, wherein a return plate urged by a returning force is disposed so as to be capable of coming into contact with a front end of the piston sleeve and of moving by a predetermined distance, wherein upon supplying the hydraulic pressure to the oil chamber, the hydraulic piston and the piston sleeve move together by the predetermined distance against the returning force of the return plate, and then only the hydraulic piston slides until coming into contact with a brake plate, including the friction plate and the mating plate, so that a positional relationship between the piston sleeve and the hydraulic piston is controlled to maintain a constant piston stroke of the hydraulic piston, and wherein the return plate is annular in shape and defines a plurality of piston through-holes, penetrating the return plate, formed at an equal distance from a center of the return plate, wherein the hydraulic pistons are inserted in the plurality of piston through-holes, and wherein the return plate has a plurality of piston sleeve contact portions, formed in a periphery of the plurality of piston through-holes, that come into contact with the front end of the piston sleeves.