Cylindrical part

Abstract

A cylindrical member, which is a cylindrical part molded by injection molding, has a cylindrical shape having a substantially uniform thickness in a circumferential direction and whose both end-face edge portions are opened, in which a band-state groove portion for forming a thin portion along the outer circumference of a cylindrical center portion forming a cylindrical portion and a thick edge portion along the outer circumference of the both end-face edge portions are provided. Since the band-state groove portion and the thick edge portion are provided, the temperature of the cylindrical member does not become relatively high at the center portion, while the temperature of the end-face portions does not become relatively low at molding, and molding contraction rates are made uniform in general and the cylindrical member with good form accuracy can be obtained.

Description

technical field [0001] The present invention relates to an injection molded cylindrical part. Background technique [0002] In conventional molding techniques, when a cylindrical resin part is produced by injection molding, the diameter near the center tends to shrink and become smaller. The reason why the central portion becomes smaller in this way will be described using FIGS. 23 and 24 . [0003] FIG. 23 is a diagram showing the temperature distribution of the mold 101 and the cylindrical member 103 at the time of completion of resin filling in the form of isotherms during molding of a conventional resin cylindrical member. The direction of the arrow in the figure shows the direction in which the temperature on the isotherm line becomes lower. [0004] When the molten resin material is filled into the cavity of the metal mold 101, the heat of the resin is transferred into the metal mold, so that the temperature of the metal mold 101 rises. At this time, since there are...

AI Technical Summary

Problems solved by technology

However, in the state of FIG. 26 , since the zoom frame 105 is fitted into the larger portion of the diameter deformation near the end 104b of the cam frame 104, the radial gap S1 between the zoom frame 105 and the cam frame 104 increases, At the same time, a fitting gap S2 between the cam follower 106 and the cam groove 104c is also generated.

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