Abstract: The object of the present invention is to exhibit the function of a throttle valve mechanism without making the whole of a master cylinder large-sized and to simplify the structure and to reduce the number of pieces of parts. In order to attain this object, the present invention has throttle valve mechanisms with a floating valve body which sits and throttles the flow of the hydraulic fluid to the reservoir from the pressure generating chambers when the pistons operate and which opens when the pistons do not operate, and the throttle valve mechanisms are arranged in the fluid passage for the supplementation of the hydraulic fluid, and the throttle valve mechanisms have a floating valve body with a throttle passage and a valve seat with and from which the floating valve body is brought into contact and is separated, and the valve seat is provided at the tip of the connecting portions to the cylinder body of the reservoir.

Abstract: There is provided a master cylinder in which a large quantity of working fluid can be supplied rapidly, the air bleeding takes less time in the manufacturing process, and satisfactory performance can be provided when traction control is operated. For the master cylinder MC, a first supply passage 19 for supplying a working fluid from a working fluid reservoir to a pressure chamber 9 through a working fluid supply port 20a, supply passages 22, 23 and 24, and a working fluid supply port 5b formed in a piston 5, a second supply passage 50 is formed in parallel with the first supply passage directly between the working fluid supply port 20a and the pressure chamber 9, and a check valve 51 is disposed in the second supply passage 50.

Abstract: An object of the present invention is to provide a master cylinder in which the buckling of spring is prevented and the packing is not damaged. To achieve this object, in a master cylinder in which a return spring is disposed between the end wall of a cylinder and a piston, and a packing fitted to the piston slides on the inner peripheral wall of the cylinder, the return spring 30 comprises a cylindrical large-diameter coil portion A with a diameter almost in contact with the inner peripheral wall of the cylinder 12 and a small-diameter coil portion B with a diameter enough smaller than the diameter of the inner peripheral wall of the cylinder 12, and the installation length of the small-diameter coil portion B is set so as to be nearly equal to a length of the range in which the packing 24 slides.

Abstract: In a master cylinder, a communicating passage is formed in a piston guide which is disposed in a cylinder housing so that the communication passage is in communication with the through hole in said piston guide for supplying oil, and an annular spacer is interposed between the annular seal disposed at the side of the piston guide and the piston guide, an annular spacer which has a plurality of projections protruding outward from the external surface at intervals, so that the annular spacer is positioned in the cylinder housing with the projections of the annular spacer abutting the internal surface of the cylinder housing, and an oil passage is formed between the external surface of the annular spacer excluding the projections and the internal surface of the cylinder housing.

Abstract: In a master cylinder, a sleeve for guiding the piston and a cap for forming a cylinder housing are connected with each other and integrally formed, and a primary piston and a secondary piston are coupled with via a retainer and thus integrally formed. Consequently, when the master cylinder is disassembled, the sleeve and the piston can be pulled out simultaneously, thereby allowing the simultaneous withdrawal of the secondary and primary pistons.

Abstract: A valve for an automotive brake master cylinder piston is disposed at the end of forward stroke of the brake master cylinder piston in a passage defined along the axis of the master cylinder piston and communicating mutually an oil reservoir and an oil outlet, and is adapted to close and open the passage when abutting upon the departing from a side wall surface of the end of forward stoke of the master cylinder piston in accordance with a forward stroke motion and a return stroke motion of the master cylinder piston.