| 摘要 |
An automatic brake booster having the functioning of an automatic brake, or more specifically, an improvement of bellows contained in a shell thereof is disclosed. The bellows comprises a stepped tubular member having portions of different diameters, namely, a reduced diameter, a medium diameter and an increased diameter. By using a reinforcing ring having a rigidity in the step, an expansion to increase the diameter of the bellows when the atmosphere is introduced into the internal space of the bellows can be prevented. Different diameters of the portions of the bellows allows the likelihood to be minimized that an output loss of the brake booster may be caused by contact of bellows portions to each other as the bellows is axially shrunk. As compared with an accordion-like bellows, the stepped tubular bellows can utilize a simplified die assembly and manufacturing steps and thus can be manufactured inexpensively.
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