Vacuum booster

摘要

According to one embodiment, a vacuum booster includes a booster shell and a booster piston which divides an interior of the booster shell into a front vacuum chamber and a rear operation chamber. The vacuum booster further includes a valve cylinder in which a control valve controls a communication state of the operation chamber depending on a movement of an input rod. A bearing cylinder is provided on a rear wall of the booster shell. A bearing bush is mounted in the bearing cylinder to support the valve cylinder, and a seal lip is provided at a rear end of the bearing bush integrally therewith to contact elastically closely with the valve cylinder. A grease reservoir is provided in an inner surface of the bearing bush, and an extension grease reservoir is provided in an inner surface of the seal lip.

主权项

1. A vacuum booster, comprising:
a booster shell; a booster piston which is accommodated in the booster shell to divide an interior thereof into a front vacuum chamber and a rear operation chamber, the front vacuum chamber being connected to a vacuum source; a valve cylinder which is connected to the booster piston; an input rod which extends in an axial direction, and is contained inside the valve cylinder; a control valve which is contained inside the valve cylinder to control the operation chamber to communicate with the front vacuum chamber and with the atmosphere depending on a movement of the input rod in the axial direction; a bearing cylinder which is provided on a rear wall of the booster shell; a bearing bush which is mounted in the bearing cylinder to support slidably an outer circumferential surface of the valve cylinder, the bearing bush being made of an elastic material; a seal lip which is provided at a rear end of the bearing bush integrally therewith to contact elastically closely with the outer circumferential surface of the valve cylinder, the seal lip being thinner than the bearing bush; a grease reservoir which is provided in an inner circumferential surface of the bearing bush to retain a lubrication grease; and an extension grease reservoir which is provided in an inner circumferential surface of the seal lip and which extends to a distal end of the seal lip as the seal lip tapers toward the distal end, wherein the extension grease reservoir is provided in the inner circumferential surface of the seal lip continuously with the grease reservoir to hold the same grease, wherein a depth of a bottom portion of the extension grease reservoir is inclined and becomes shallower towards the distal end of the seal lip in the axial direction, and wherein the bottom portion of the grease reservoir and the bottom portion of the extension grease reservoir are continuous.