JPH0412667Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a molding shaft for a variable capacitor, and more particularly to a molding shaft that prevents microcracks from occurring on the separation surface of a molding die.

[Problems to be solved by conventional techniques and ideas]

The rotor shaft 1 of the conventional variable capacitor is
As shown in FIG. 4A, a driven part 1b having a screw hole 1a protrudes from the lower end, a stepped part 1d is provided at the upper part of the collar part 1c, and a screw is screwed into the upper end of the shaft part 1e. The stepped portions 1f are formed in sequence, and the stepped portions 1f are formed in sequence.
A stopper ring 2 is fitted to d, a washer 3 and a plurality of rotor plates 4, 4... and washers 5, 5... are sequentially fitted to the shaft portion 1e, and finally a nut 6 is tightened to the threaded portion 1f. . In addition, as shown in FIG. 4B, a part of the flange 1c is provided to protrude to form a stopper 1g.
There is also a configuration in which the stopper ring is eliminated.
Regardless of the shape, forming the material by cutting it from a round bar material results in a poor material yield and increases the number of man-hours, so as shown in Figure 5, the molding die 7
Shafts are often manufactured using injection molding. However, the molding die 7 is formed by joining together a mold 7a for molding the lower part of the rotor shaft 1 and molds 7b and 7c for molding the upper part, and performing injection molding. For this reason, due to misalignment of the molds 7a, 7b, 7c and temperature differences between the molds, stress is concentrated on the part 8 located at the separation surface of the mold (hereinafter referred to as "parting surface") when the mold is opened. is added. especially,
In the case of a shaft having a protrusion such as a threaded part or a reverse tapered shape, the protrusion gets caught in the molds 7b and 7c due to contraction immediately after the material is injected, and there is no shrinkage movement of the protrusion, so that the parting surface 8 Stress is concentrated,
As shown in FIG. 6, minute cracks called micro-cracks 9 occur, and the torsional strength of the rotor shaft 1 decreases due to these micro-cracks 9. In the worst case, the shaft portion 1e In some cases, the base of the tube was broken. Therefore, technical problems arise that must be solved in order to overcome these deficiencies.

[Means for solving the problem] This invention was proposed in order to solve the problem in view of the above problem, and it is a stepped part of the shaft that is injection molded in the rotor shaft of a variable capacitor. It is an object of the present invention to provide a molding shaft for a variable capacitor, which is characterized in that a notch is formed in the axial direction on the parting surface.

[Effect]

This idea disperses the concentration of stress on the parting surface caused by slight misalignment of the mold and material shrinkage during injection molding by drilling notches in the axial direction at appropriate locations on the parting surface of the molding shaft. It is possible to prevent the occurrence of microcracks. Even if a micro-crack occurs, the notch allows it to shift in the axial direction, thereby increasing the fracture resistance compared to the conventional one.

〔Example〕

An embodiment of this invention will be described below in detail with reference to the attached drawings. Incidentally, the same reference numerals will be used for the components used in the description of the conventional type. Figures 1A to 1C show a rotor shaft 1 of a variable capacitor, with a screw hole 1 at the lower end.
A driven portion 1b having a diameter of 1.a is provided, and a stepped portion 1d is provided in a stepped manner on the upper portion of the collar portion 1c. This collar portion 1c has a stopper portion 1g formed by partially protruding in the horizontal direction, and notches 10, 10 are formed in the axial direction on both sides of the stepped portion 1d, respectively. Furthermore, the stepped portion 1
A shaft portion 1e is provided at the upper part of the shaft portion 1e, a threaded portion 1f is screwed onto the upper end of the shaft portion 1e, and a tip shaft portion 1h is provided protrudingly from the head of the threaded portion 1f. Note that both side surfaces of the shaft portion 1e are flush with the notch portion 10, and the flat portion 1
i and 1i are provided.

In this way, when the rotor shaft 1 having the above shape is injection molded using the molding die 7 shown in FIG. This concentration can be dispersed in the axial direction by the notches 10, 10, and the occurrence of microcracks can be prevented. Even if micro-cracks should occur, the micro-cracks 9, 9 are displaced in the axial direction as shown in FIG. 2, so that no large cracks occur and the strength of the shaft portion 1e is maintained. Further, as a modification, the strength of the root of the shaft portion 1e may be increased by making the shape of the notch 10 chamfered as shown in FIG. 3A, or rounded as shown in FIG. 3B. may be increased to prevent the occurrence of microcracks.

[Effect of idea]

This invention, as detailed in the above example,
By providing a notch in the parting surface of the rotor shaft to be injection molded, stress concentrated on the parting surface due to shrinkage of the material and the timing of mold opening and mold release can be dispersed to the notch. Therefore, the occurrence of micro-cracks can be suppressed, and even if they occur, the micro-cracks will not occur on the same plane or on the same line, such as being displaced in the axial direction of the rotor shaft due to the notch, and the rotor This improves the fracture resistance of the shaft.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention. Figure 1A is a plan view of the rotor shaft, Figure 1B is a cutaway front view of the same part, Figure 1C is a side view of the same, Figure 2 is an enlarged slope view of the main part, and Figures 3A and B are notches. FIG. 3 is a front cross-sectional view of a main part showing a modification example of FIG. 4 to 6 show conventional types. 4A and 4B are assembled longitudinal sectional views of the rotor shaft, FIG. 5 is a longitudinal sectional view of the molding die, and FIG. 6 is an oblique view of the rotor shaft. Explanation of symbols, 1...Rotor shaft, 1d...Stepped portion, 7...Forming mold, 8...Parting surface,
10... Notch.

Claims (1)

[Scope of utility model registration request] In the rotor shaft of a variable capacitor, a notch is bored in the axial direction in a stepped part of the injection-molded shaft and located on the separation surface of the molding die. Molded shaft of capacitor.