JPS58225263A - Screw gear made of resin - Google Patents

Abstract

PURPOSE:To prevent the production of burrs in manufacturing a screw gear by way of injection molding, by embedding the tip parts of gear teeth located at one end face of the gear, and cutting off the tip portions of the gear teeth located at the other end face and retracting the same inwards from the end face of the gear. CONSTITUTION:The tip portions of gear teeth 2 located on the side of one end face 4' of a screw gear 1 made of resin are embedded at 10 from the end face 4' over a prescribed width l1, while the tip parts 12 of the gear teeth 12 located on the side of the other end face 4 of the gear 2 are not cut at the end face 4 but cut off to end at the flat tooth bottom 14 on the side of the end face 4. Further, the tip parts 12 of the gear teeth 2 cut off to terminate at the flat tooth bottom 14 are retracted from the end face 4 over a prescribed width l2 so that a retracted part 15 contiguous with the flat tooth bottom 14 is formed between the end face 4 and the tip parts 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin screw gear having a plurality of threaded teeth formed on its outer periphery, which is used in a speedometer drive gear of a vehicle transmission or the like.

Conventionally, as this type of resin screw gear, for example, the first,
There is something like the one shown in Figure 2.

That is, the resin threaded gear l is produced by injection molding of heat-resistant and wear-resistant resin such as nylon 66, and has a plurality of threaded teeth 2 formed on the outer periphery and a shaft hole in which the shaft is fitted. It has 3.

However, in such a conventional resin threaded gear, since the plurality of threaded teeth 2 are formed with a certain helix angle, the threaded teeth 2 at the gear end face 4° 4'
By cutting the tip 5 at the end surface 4.4', the tip 5
The tip of the screw tooth ends at an acute angle and becomes thinner, and the tip of the screw tooth becomes thinner in the gap between the mold that molded the screw tooth body during injection molding and the mold that closes the end surface of this mold. There was a problem in that burrs were likely to occur in the part 5, and that the injection mold for the tip of the threaded teeth, which was weak in strength, was chipped and the threaded teeth 2 were damaged during use of the resin screw gear l.

The present invention has been made by focusing on such conventional problems, and in a resin screw gear, the tip of the screw tooth located at one end of the gear end face is buried over a certain width, and the end face of the gear is buried. The tip of the screw tooth located at the other end is removed so that it terminates at the flat part of the tooth bottom, and the tooth profile is formed such that the tip of the screw tooth is retreated inward over a certain width from the end surface of the gear. Trap Yoshi aims to solve the above problems.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 8 is an explanatory diagram showing an embodiment of the present invention, and FIG. 4 is an end view thereof.

First, to explain the structure, 1 is a resin screw gear made by injection molding of heat-resistant and abrasion-resistant resin such as nylon 66, and has screw teeth 2 with a plurality of threads, for example, 6 threads, on the outer circumference.
is formed with a predetermined thread angle, and is provided with a shaft hole 3 on the inside into which a shaft is fitted.

The screw tooth tips of the screw teeth 2 which are located on the side of one end surface 4' of the resin screw gear 2 are buried by forming a buried portion 10 over a certain width λ1 from the end surface 4'. , On the other hand, the screw tooth tip 12 located at the end surface 4@ has a shape in which the screw tooth tip 12 is not cut by the end surface 4 but terminates at the bottom flat portion 14 on the end surface 4 side. In addition, the threaded tooth tip 12 that has been removed so as to terminate at the bottom flat portion 14 is retracted over a certain width from the end surface 4, and the end surface 4 and the threaded tooth tip 12 are removed. A retracted portion 15 that continues to the tooth bottom flat portion 14 is formed in between.

Here, as for the buried width of the buried portion 10 and the retreat width of the retreated portion 15, for example, taking the resin screw gear of the actual size shown in Fig. 8.4 as an example, the buried width is also = 0.5 to 1. .5 words, setback width 1. = 0.5 mackerel or more is desirable.

Next, the effect will be explained.
11 First, when injection molding the resin screw gear l of the present invention, the tips of the screw teeth on the end surface portion 4' side are formed over a certain width from the end surface portion 4' due to the formation of the embedded portion 10. Because it is embedded, no burr occurs at the end of the threaded tooth tip on the end face 4' side at the end of the threaded tooth tip with respect to the buried part IO, and the threaded tooth tip 12 on the end face 4 side is flat on the tooth bottom. 14, and a constant width from the end face 4! , are retracted by the formation of the recessed portion 15, so there is no possibility of deburring due to the gap between the metal parts located at the end face portion 4. Therefore, deburring after injection molding of the resin screw gear 1 is possible. This eliminates the need for cleaning work.

On the other hand, when the resin screw gear 1 of the present invention is used as a speedometer drive gear of a vehicle transmission, even if another screw gear meshes with the screw teeth 2 of the resin screw gear 1, the end face 4' side The tip of the screw tooth 2 is reinforced by forming the embedded part 1O, and the screw tooth tip 12 on the end face 4 side is removed so as to terminate at the tooth bottom flat part 14, so that it is not connected to other gears. This meshing also reliably prevents the threaded tooth tips 12 from chipping and the threaded teeth 2 from being damaged, thereby ensuring the reliability and durability of the resin threaded gear.

As explained above, according to the present invention, in a resin screw gear in which a plurality of threaded teeth are formed on the outer periphery, the tip of the screw tooth located at one end of the gear end surface is buried over a certain width. Then, the tip of the screw tooth located at the other end of the gear end face is removed so that it terminates at the flat part of the tooth bottom, and the tip of the screw tooth is retreated inward over a certain width from the tip of the screw tooth. The threaded tooth shape reliably prevents the occurrence of burrs at the tip of the threaded teeth when resin screw gears are injection molded. This eliminates the need for inspection and greatly improves the productivity of resin screw gears.

In addition, the tip of one screw tooth is buried by forming a buried part, and the tip of the other screw tooth is removed so as to end at the flat part of the tooth bottom, and at a position set back by a certain width from the end surface. Because the ends are terminated, the meshing strength of the tips of each screw tooth is increased, preventing the tips of the screw teeth from chipping and damaging the screw teeth during use, and increasing the reliability and durability of resin screw gears. You can also get the effect of being able to improve your

[Brief explanation of the drawing]

Fig. 1 is an explanatory view showing a conventional example, Fig. 2 is an end view of Fig. 1, Fig. 8 is an explanatory view showing an embodiment of the present invention, and Fig. 4 is an end view of Fig. 8. be. l... Resin screw gear 2... Screw teeth 3... Shaft hole 4.4'... End face lO... Buried part
12...Screw tooth tip 14...Flat bottom part
15...Backwards patent applicant Fuji Iron Works Co., Ltd. Agent Patent attorney Susumu Takeuchi Figure 3 Figure 4

Claims (1)

[Claims] (1) In a resin screw gear with multiple threaded teeth formed on the outer periphery, the tip of the screw tooth located at one end of the gear end face is buried across a fixed width trap, and the tip located at the other end of the gear end face is buried. The flat end of the screw tooth tip is removed so that it terminates at the flat part of the tooth bottom, and a constant l! A resin screw gear characterized in that the tips of the screw teeth are retracted inward over the entire length. (Oil) One of the embedded width t-0,5/i of the tip of the screw tooth
The resin screw gear according to item 1, wherein L to 1.5 mm and the recess width of the other end of the screw teeth is 0.5 mm or more.