Vacuum booster, brake system equipped with the vacuum booster, and method of manufacturing plate plunger for vacuum booster

A method of manufacturing a vacuum booster including an input shaft to which an input is applied, a control valve that is operated by the input shaft, a power piston that operates on atmospheric air introduced by the operation of the control valve, an output shaft that puts out an output in which the input has been boosted by a servo ratio by the operation of the power piston, a reaction disc to which a reaction force of the output of the output shaft is transmitted and which elastically deforms, and a plate plunger with which the reaction disc that has elastically deformed comes into contact to transmit the reaction force to the input shaft and which determines the servo ratio, the method comprising

• primarily processing a plate plunger base material so that an outer peripheral diameter of the reaction disc contact surface is equal to or greater than an outer peripheral diameter corresponding to the smallest servo ratio among a variety of different servo ratios, and
• secondarily processing the servo ratio determination surface,
• wherein the plate plunger has, on a corner portion between an outer peripheral surface and a surface that opposes the reaction disc, a servo ratio determination surface that is formed by an inclined surface and determines the servo ratio, and
• wherein the servo ratio determination surface comprises a reaction disc contact surface that determines the servo ratio and a reaction disc non-contact surface.

A method of manufacturing a brake system including a brake pedal, a brake booster that boosts a pedal force of the brake pedal by a predetermined servo ratio and outputs the boosted pedal force, a master cylinder that operates on the output of the brake booster and generates hydraulic pressure, and brake cylinders that generate brake force with the hydraulic pressure generated in the master cylinder to apply brakes to wheels, wherein the brake booster includes an input shaft to which an input is applied, a control valve that is operated by the input shaft, a power piston that operates on atmospheric air introduced by the operation of the control valve, an output shaft that puts out an output in which the input has been boosted by a servo ratio by the operation of the power piston, a reaction disc to which a reaction force of the output of the output shaft is transmitted and which elastically deforms, and a plate plunger with which the reaction disc that has elastically deformed comes into contact to transmit the reaction force to the input shaft and which determines the servo ratio, the method comprising

• primarily processing a plate plunger base material so that an outer peripheral diameter of the reaction disc contact surface is equal to or greater than an outer peripheral diameter corresponding to the smallest servo ratio among a variety of different servo ratios, and
• secondarily processing the servo ratio determination surface,
• wherein the plate plunger has, on a corner portion between an outer peripheral surface and a surface that opposes the reaction disc, a servo ratio determination surface that is formed by an inclined surface and determines the servo ratio, and
• the servo ratio determination surface comprises a reaction disc contact surface that determines the servo ratio and a reaction disc non-contact surface.