JPH0121239Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a resin worm gear.

The worm gear 1 has a shaft 2 as shown in FIG.
It is fitted into the shaft 2 so that it can freely rotate, or is fitted and fixed so that it rotates integrally with the shaft 2, and is used to transmit rotational power to a worm wheel (not shown). In the case of a small worm gear 1, this type of worm gear 1 is manufactured by injection molding using a resin material such as nylon resin. However, the conventional worm gear 1 has the following drawbacks: poor accuracy and poor occlusion. That is, in the conventional worm gear 1, the boss portion 3 that fits onto the shaft 2 has a large wall thickness.
Since the gear part 4 is formed on the outer periphery of the boss part 3, the distance from the inner periphery of the boss part 3 to the outer end of the gear part 4 is very large. On the other hand, there were variations in accuracy, such as deflection of the tooth surface of the gear part 4, which caused misalignment. Furthermore, for the same reason, the diameter of the hole in the boss portion 3 is non-uniform, which also causes poor fitting with the shaft 2.

The present invention was provided with the aim of solving these conventional problems, and its features include an inner cylindrical portion for shaft fitting and a gap provided in the inner cylindrical portion. an outer cylindrical portion that is fitted concentrically to the outside; a worm gear portion formed on the outer periphery of the outer cylindrical portion; a circumferential connection portion that connects the inner and outer cylindrical portions at one end in the axial direction of the outer cylindrical portion; It has an inner diameter larger than the inner diameter of the outer cylinder part and an outer diameter larger than the outer diameter of the worm gear part, and is provided concentrically with the inner cylinder part outside the end opposite to the connecting part of the outer cylinder part. a reinforcing cylinder part, and a plurality of plate-shaped reinforcements provided at equal intervals in the circumferential direction in the gaps between the inner cylinder part, the outer cylinder part, and the reinforcing part, and extending over the entire axial length of the outer cylinder part and the reinforcing part. The ribs are integrally formed from a resin material.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. FIGS. 2 and 3 show a worm gear made of resin, and in the same figure, 5 is an inner cylindrical portion having a shaft fitting hole 6 on the inner periphery. An outer cylindrical portion 7 and a reinforcing cylindrical portion 8 are provided concentrically on this outer periphery with a predetermined gap therebetween. A spiral worm gear part 9 is integrally formed on the outer peripheral surface of the outer cylinder part 7, and the outer cylinder part 7 is integrally connected to the inner cylinder part 5 via a circumferential connecting part 10 at one end in the axial direction. is formed. The reinforcing cylindrical portion 8 is integrally provided on the side opposite to the connecting portion 10 of the outer cylindrical portion 7, and the reinforcing cylindrical portion 8 is formed to have a slightly larger diameter than the outer diameter of the gear portion 9. The inner diameter of the reinforcing cylinder part 8 is the same as that of the outer cylinder part 7.
It is larger than the inner diameter of the inner cylinder part 5 and the outer cylinder part 7.
Four reinforcing ribs 13 are provided at equal intervals in the circumferential direction in the gaps 11 and 12 between the reinforcing cylinder part 8 and the reinforcing cylinder part 8 . The reinforcing rib 13 has a flat plate shape and is formed over the entire axial length of the outer cylindrical portion 7 and the reinforcing cylindrical portion 8. Of course, it goes without saying that these parts are integrated.

According to the worm gear having the above configuration, the inner cylinder part 5 for shaft fitting and the outer cylinder part 7 having the gear part 9 on the outer periphery.
Since the gap 11 is provided between the gear part 9 and the gear part 9, the wall thickness of each part can be made thinner than in the past, and there is less cooling distortion during injection molding. Prevents fringing and improves occlusion. Furthermore, the accuracy of fitting the inner cylinder portion 5 to the shaft can be improved. In addition, since there is a connecting portion 10 and a reinforcing cylindrical portion 8, and a reinforcing rib 13 is provided between the inner and outer cylindrical portions 7, a predetermined strength can be ensured despite the thin wall thickness.

This worm gear is molded in the following manner using a mold as shown in FIGS. 4 and 5.
That is, a pin mold 15 for a shaft fitting hole is provided on the movable table 14 side.
and four gap-forming projection molds 16 are provided so as to surround this, and these are inserted into the outer mold 18 of the fixing base 17 and set as shown in FIG.
Next, a worm gear is molded by injecting plastic material or the like into the gaps between these molds 15, 16, and 18. After the material has cooled, when the moving table 14 is rotated around its axis in the drawing direction, the protrusion mold 16 is fitted between the reinforcing ribs 13, so the entire worm gear and the moving table 14 are interfering with each other. Therefore, the molded product, that is, the worm gear, can be smoothly and easily removed from the gear forming portion 19 of the outer mold 18 while being rotated. After that, push out pin 2
0 to the end face of the reinforcing rib 13 to separate the molded product from the molds 15 and 16.

Note that the end of the reinforcing cylinder part 8 on the gear part 9 side is the third
It may be tapered so that the gear portion 9 side becomes narrower as shown by the imaginary line in the figure.

The present invention has a gap 1 between the inner cylinder part 5 and the outer cylinder part 7.
1, the wall thickness of each part becomes thinner, and it is possible to prevent the occurrence of distortion that occurs when the resin material is cooled. Poor fitting to the shaft can be suppressed.

Further, a connecting portion 10 and a reinforcing tube portion 8 are provided at both ends of the outer tube portion 7, and the inner tube portion 5, the outer tube portion 7, and the reinforcing tube portion 8 are provided.
Since a reinforcing rib 13 is provided between the outer cylindrical part 7 and the reinforcing cylindrical part 8 over the entire length in the axial direction, a predetermined strength can be secured even though the respective wall thicknesses are thinner, and the outer cylindrical part 7 and the reinforcing cylindrical part 8 are By providing the connecting portion 10 and the reinforcing tube portion 8 at both ends of the tube portion 7, the worm gear portion 9
Even if some distortion occurs at both ends, the distortion does not affect the central part where the worm gear part 9 engages with the worm wheel.

In addition, the outer diameter of the reinforcing cylinder part 8 is the same as that of the worm gear part 9.
For example, after inserting a protrusion mold into the outer mold and molding the worm gear,
The worm gear can be rotated using a protrusion mold and removed from the outer mold in the axial direction, and a device with a simpler structure is required compared to a device that splits the mold.

Furthermore, since the inner diameter of the reinforcing cylinder part 8 is larger than the inner diameter of the outer cylinder part 7, the rotational torque when the protrusion mold is rotated is received by the reinforcing rib 13, which is a large part in the radial direction on the side of the reinforcing cylinder part 8. The torque acting on this portion is smaller than the rotational torque received by the reinforcing ribs 13 of the outer cylinder portion 7, and therefore the reinforcing ribs 13
The thickness of the worm gear part 9 can be reduced accordingly, and distortion of the worm gear part 9 caused by providing the reinforcing ribs 13 can be reduced.

Moreover, since the reinforcing rib 13 is provided in a flat plate shape in the axial direction, the worm gear can be easily removed from the projection mold by pushing out the worm gear in the axial direction after being removed from the outer mold.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a conventional example, Fig. 2 is a cutaway front view of the gear of the present invention, Fig. 3 is a side view of the same, Fig. 4 is a sectional view of a mold for molding the gear of the present invention, and Fig. 5. is a front view of the same part. 5...Inner cylinder part, 7...Outer cylinder part, 8...Reinforcement cylinder part, 9...Gear part, 10...Connection part, 13...
Reinforced ribs.

Claims (1)

[Scope of utility model registration request] An inner cylindrical part 5 for shaft fitting and a gap 1 in this inner cylindrical part 5.
1 and a worm gear part 9 formed on the outer periphery of the outer cylindrical part 7.
and the inner and outer cylinder parts 5, 7 at one end in the axial direction of the outer cylinder part 7.
a connecting portion 10 in the circumferential direction that connects the outer cylindrical portion 7 and a connecting portion 10 on the opposite side of the outer cylindrical portion 7 and having an inner diameter larger than the inner diameter of the outer cylindrical portion 7 and an outer diameter larger than the outer diameter of the worm gear portion 9. A reinforcing cylindrical part 8 is provided concentrically with the inner cylindrical part 5 on the outside of the end, and an outer cylindrical part is provided at equal intervals in the circumferential direction between the inner cylindrical part 5, the outer cylindrical part 7, and the reinforcing cylindrical part 8. A worm gear made of resin, in which a plurality of flat reinforcing ribs 13 provided over the entire length of the reinforcing cylinder part 7 and the reinforcing cylinder part 8 in the axial direction are integrally formed of a resin material.