| 摘要 |
A plurality of axially extending ribs are formed in the inner periphery of a valve body at its front end for slidably supporting the outer peripheral surface of the output shaft at its rear end. With this arrangement, any dimensional error which may occur in the region of the ribs can be suppressed small during the manufacturing of the valve body if a diameter shrinkage occurs in the inner periphery thereof. Accordingly, when the rear end of the output shaft is slidably fitted into the ribs, the output shaft is less likely to be askew with respect to the axis of the valve body. Accordingly, a biased abrasion of an annular seal member which is disposed between an opening formed in the front portion of a shell and the outer periphery of the output shaft at its front end to maintain a hermetic seal therebetween can be suppressed.
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