KR101649581B1 - A Method For Fabricating Worm-wheel - Google Patents

Abstract

The present invention relates to a method for manufacturing a worm-wheel, which includes carrying out insert molding of a worm-wheel shaft while a worm-wheel is manufactured in an integral type by injection molding to satisfy the circularity and concentricity of a tooth form with no need for modifying a displacement amount of a worm-wheel boss, allows manufacture of a gear structure of a gear-forming section by injection molding without hobbing work, and has an improved structure to discharge the resultant worm wheel product easily from the injection mold. The method for manufacturing a worm-wheel according to the present invention comprises the steps of: press fitting a worm-wheel shaft to a worm-wheel hub; preliminarily preparing injection by disposing the worm-wheel shaft press fitted to the worm-wheel hub to a core block of a boss injection mold; injection molding a boss by matching a fixed mold plate with a movable mold plate of the boss injection mold and injecting a resin into the inner space of the core block to carry out integral molding a worm-wheel boss at the outer side of the worm-wheel hub; discharging the boss by demolding the fixed mold plate and the movable mold plate of the boss injection mold and discharging a boss product having the worm-wheel hub formed integrally with the worm-wheel boss; secondarily preparing injection molding by disposing the boss product between the movable core and the fixed core of the product injection mold; injection molding a product by matching the movable core with the fixed core of the product injection mold and injecting a resin into the inner part of a worm-gear tooth form core to carry out integral molding of a gear-forming section at the outer side of the boss product; and discharging the product by demolding the movable core and fixed core of the product injection mold and discharging the worm-wheel product having the gear-forming section formed integrally at the outer side of the boss product.

Description

[0001] The present invention relates to a method for manufacturing a worm wheel,

The present invention relates to a worm wheel manufacturing method, and more particularly, it relates to a worm wheel manufacturing method that inserts and forms a worm wheel shaft in the process of manufacturing an integrated worm wheel by an injection molding method, thereby satisfying the roundness and concentricity of the tooth profile, The present invention relates to a worm wheel manufacturing method which can be manufactured as an injection mold without any work, and whose structure is improved so that the manufactured worm wheel product can be easily taken out from an injection mold.

Generally, a worm shaft and a worm wheel are used to transmit a driving force of a motor. When the worm shaft and the worm wheel are made of a metal material, noise or vibration occurs at a portion where they contact each other.

Accordingly, the worm shaft is made of a metal material such as steel, and the worm wheel is made of a synthetic resin material (plastic material) on a boss made of a metal such as steel and a gear part having a toothed shape.

In the conventional method for manufacturing a worm wheel, a press-in method and an injection method are mainly used. In the press-fitting method, the boss cut to a predetermined thickness is press-fitted into the center of a gear portion cut to have the same thickness and fused at a high frequency. Thereafter, the teeth are post-machined on the outer peripheral surface of the gear portion to complete the manufacture of the wormholes.

However, the conventional indentation method has a problem in that the manufacturing process is complicated and takes a long time to manufacture, and the post-processing is required to form the tooth profile, thereby deteriorating the productivity.

As a conventional prior art for solving the problems of the conventional press-fitting method, as disclosed in Korean Patent Laid-Open Publication No. 2009-0016130 (published on Mar. 23, 2009), a boss is placed in an injection mold, A method of manufacturing a worm wheel for a reduction gear unit of a steering apparatus using injection molding to produce a worm wheel by discharging it to a mold has been proposed.

However, the injection method of the above-described worm wheel manufacturing method requires not only a hobbing process of post-machining an additional tooth form using a hob to the gear portion formed by injection but also difficulty in precise dimension control due to the resin shrinkage problem.

In the conventional injection molding method, the roundness and the concentricity of the hub and the boss coincide with each other due to an assembly error in which the shaft is shaken during the process of pressing the worm wheel shaft into the worm wheel hub after molding the worm wheel boss and gear forming part, In this case, it is difficult to process the gear using the hob.

As a prior art for improving this, as disclosed in Korean Patent Laid-Open Publication No. 10-2013-0100411 entitled " Wormwheel of an electric power assisted steering apparatus and method for manufacturing the same "(published on Mar. 31, 2013), an electric power assisted steering In the speed reducer of the apparatus, the moldability of the worm wheel can be improved by injection molding the hub, the boss, and the gear forming portion integrally to manufacture a worm wheel.

In this case, since the gear of the gear forming portion is formed at an oblique angle, it is difficult to take out the gear forming portion due to interfering with the injection mold due to the gear during the process of drawing the gear forming portion from the injection mold, There is a possibility of occurrence.

Korean Patent Laid-Open Publication No. 2009-0016130 "Method for manufacturing a worm wheel for a reduction gear of a steering apparatus using injection molding" (Published on Mar. 23, 2009) Korean Patent Laid-Open Publication No. 10-2013-0100411 "Wormwheel of electric power assist steering device and method for manufacturing the same" (Publication date: Sep. 31, 2013)

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a worm wheel, which is capable of satisfying the roundness and concentricity of the teeth in the process of manufacturing the worm wheel as an injection mold, The present invention also provides a worm wheel manufacturing method in which the structure of the worm wheel can be easily taken out from the injection mold.

According to another aspect of the present invention, there is provided a method of manufacturing a boss injection molding machine, the method including a press-fitting step of press fitting a worm wheel shaft into a worm wheel hub, a first injection preparing step of placing a worm wheel shaft press- A boss injection step of injecting resin into the inner space of the core block after the stationary side mold plate and the movable side mold plate of the mold are combined to form a worm wheel boss integrally on the outer side of the worm wheel hub; A boss extracting step of taking out a boss product in which the worm wheel shaft, the worm wheel hub and the worm wheel boss are integrated after demoulding the movable side template, and a boss extracting step of separating the boss product from the movable side core and the fixed- Injection molding step for molding the product injection mold and the fixed core; And a worm wheel which is integrated with the gear forming part on the outer side of the boss product after demoulding the movable side core and the fixed side core of the product injection mold is taken out And a product take-out step.

The product take-out step further includes a rotation guide step of rotating the worm wheel-shaped core with respect to the worm wheel shaft when the worm wheel is taken out.

Wherein the rotation guide step includes a step of guiding the ball member inserted into the guide groove formed at an oblique angle into the inside of both guide bars vertically penetrating the both sides of the movable core and interlocking with the take- So that the worm gear tooth core is rotated in the direction of inclination corresponding to the gear teeth of the worm gear when the worm gear is taken out.

Since the worm wheel boss and the gear forming unit are integrally formed through the boss injection step and the product injection step in a state where the worm wheel shaft and the worm wheel hub are press-fitted, in the conventional injection method, each worm wheel component part is molded into the finished product Unlike the method of assembling the worm wheel shaft to the worm wheel hub later, since the worm wheel shaft is inserted and formed before molding, the reference axis is always constant, so that the conditions such as the roundness, concentricity and run-out of the teeth can be satisfied , It is possible to omit the hobbing process for machining the gear teeth of the gear forming portion, which is a useful advantage of improving the productivity and reducing the cost.

In addition, the present invention has an advantage in that the worm gear teeth are guided to rotate in the process of taking out the worm gear product, so that the formability of the gear-formed portion during the take-off can be eliminated by eliminating the interference phenomenon of the undercut portion.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flowchart showing a method of manufacturing a worm wheel according to the present invention; Fig.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a boss injection mold.
3 is a perspective view showing a product injection mold to which the worm wheel manufacturing method according to the present invention is applied.
FIG. 4 is an exploded perspective view of FIG. 3; FIG.
5 is an exploded perspective view of a movable core and a fixed core according to the present invention.
6 is a perspective view showing the guide means of the present invention.
FIGS. 7A and 7B are explanatory views showing a state in which the movable core of the present invention is operated in reverse and the worm wheel product is taken out. FIG.

Referring to FIG. 1, a method of manufacturing a worm wheel according to the present invention includes a press-fitting step (S1) of press-fitting a worm wheel shaft into a worm wheel hub, a first worm wheel shaft being disposed in a core block of a boss injection mold, Injection molding step (S2) of injecting resin into the inner space of the core block after the fixed side mold plate and the movable side mold plate of the boss injection mold are assembled, and a worm wheel boss is formed integrally on the outer side of the worm wheel hub (S4) for removing the boss product in which the worm wheel shaft, the worm wheel hub and the worm wheel boss are integrated after demoulding the fixed side mold plate and the movable side mold plate of the boss injection mold, and a step A second injection preparation step (S5) of placing the movable side core and the fixed side core of the product injection mold between a movable side core and a fixed side core of a product injection mold; A product injection step (S6) of injecting a resin into the inner part of the boss product to form a gear forming part integrally on the outer side of the boss product, and a step of, after the movable side core and the fixed side core of the product injection mold are demolded, And a product take-out step (S7) for taking out the worm-wheel-product integrated with the gear-forming section.

In the first injection preparing step S2, the worm wheel hub and the worm wheel shaft integrated by press-fitting are inserted into the core of the boss injection mold, Block.

The boss injection step S3 is a step in which the movable side template is moved forward to join the fixed side template to the fixed side template, then the liquid resin is injected into the inner space of the core block and then cured by cooling so that the worm wheel boss is integrally formed As shown in Fig.

2, the boss injection mold has a movable side mold 120 and a fixed side mold 110 for integrally molding the worm wheel hub 20 and the worm wheel boss 30, And a core block for injecting in the form of a worm wheel boss is provided between the movable die 110 and the movable die plate.

In the product injection step S6, after the movable side core of the product injection mold is advanced to the stationary side core side, the liquid resin is injected into the internal space (cavity) between the worm gear tooth core and the boss product, Thereby forming a gear-forming portion integrally on the outer side of the boss product and injecting the worm-wheel-shaped product.

The product take-out step (S7) has a step of advancing the take-out plate toward the fixed-side core and causing the take-out pin to push out the worm wheel product.

Further, the product take-out step (S7) preferably further comprises a rotation guide step (S7-1) of rotating the worm wheel-shaped core with respect to the worm wheel shaft when the worm wheel product is taken out.

The rotation guide step (S7-1) includes projecting on the outer circumferential surface of the worm wheel tooth core in a guide groove formed vertically through both sides of the movable core and inclined inside the both side guide bars, So that when the worm wheel is taken out, the rotating direction of the worm wheel-shaped core is rotated in an oblique direction corresponding to the gear of the worm gear.

3 to 7B, a worm wheel boss 30 integrated with a worm wheel hub 20 is seated by a boss injection mold 100 and a movable side core (hereinafter referred to as a " worm wheel " A fixed side core 210 having an inner side face opposing the movable side core 220 and having a resin injection port 215 on the outer side thereof and a fixed side core 210 disposed on the inner side of the movable side core 220, And a take-out means 300 for taking out a worm wheel product 50 having a worm gear formed by the product injection mold 200. The take-out means 300 has a worm gear-

The take-out means 300 includes a plurality of take-out pins 320 coupled to the movable core 220 so as to penetrate therethrough, a take-out plate 310 coupled to the ends of the take-out pins 320 so as to be fixed, And guide means (400) for guiding rotation of the worm gear tooth core (230) when taken out.

The product injection mold 200 is for integrally forming the gear forming portion 40 on the outer side of the boss product and includes a worm wheel boss 30 integrated with the worm wheel hub 10 in a state where the worm wheel shaft 10 is coupled to the worm wheel hub 20 And the gear forming portion 40 is integrally formed on the outside of the worm wheel boss 30 by injecting resin into the cavity provided outside.

The product injection mold 200 for this purpose is composed of upper and lower parts in the figure, but actually, the fixed-side core 210 and the movable-side core 220 may be arranged left and right.

The movable core 220 has a worm wheel boss 30 integrated with the worm wheel hub 20 on one side by the boss injection mold 100 and is fixed to the outer side of the worm wheel boss 30 and the movable core 220, And a cavity is formed between the inner circumferential surfaces of the inner circumferential surfaces.

The surfaces of the movable core 220 and the fixed core 210 facing each other have a shape corresponding to the shape of the worm wheel boss 30.

The movable core 220 includes a first movable core 222 which surrounds the outside of the worm tooth core 230 and a second movable core 222 which is coupled to the lower side of the first movable core 222 ).

The worm gear tooth core 230 has a gear tooth 232 on the inner circumferential surface thereof, which corresponds to the gear of the worm gear.

The product injection mold 200 includes a base plate 202, a support block 204 coupled to the base plate 202, a support block 204 stacked on the support block 204 and having a fixed side core 210 and a movable side core And a plurality of cover blocks 205 surrounding the cover blocks 220.

The product injection mold 200 has a worm wheel shaft 10 inserted into a hollow formed at the center of the movable core 220 and supporting the worm wheel shaft 10 at a lower portion of the worm wheel shaft 10, A supporting shaft 250 is provided.

A guide means 400 for guiding the rotation of the worm wheel tooth core 230 to implement the rotation guide step S7-1 is provided.

The guiding means 400 includes a pair of guide grooves 415 vertically penetrating the both sides of the movable core 220 and fixedly coupled to the take-out plate 310 at the lower portion thereof, A guide bar 410 having a sectional structure and a ball member 420 coupled to the outer circumferential surface of the worm wheel toothed core 230 so as to protrude from the outer circumference and to be housed in the guide groove 415.

That is, the guide groove 415 has a structure formed so as to have an inclination angle corresponding to the gear of the gear forming portion 40.

The ball member 420 has a structure in which it is slid in the guide groove 415 which is inclined in the rotating operation of the worm-tooth-shaped core 230.

The guide means 400 may further include a plurality of ball bearings 430 interposed between the outer circumferential surface of the worm gear tooth core 230 and the movable core 220.

The first and second movable cores 222 and 224 are formed with coupling holes 225 through which the guide bar 410 passes.

The boss injection step S3 of the present invention having such a configuration places the worm wheel hub 20 fitted to the worm wheel shaft 10 into the movable side mold plate 120 of the boss injection mold 100, The worm wheel boss 30 is formed integrally with the worm wheel hub 20 by injecting resin into the inner space of the core block 130 assembled through the resin injection port 115. [ .

The boss extracting step S4 then demolds the movable side mold 120 and the fixed side mold 110 of the boss injection mold 100 and causes the movable side mold 120 and the fixed side mold 110 to be opened The product of the worm wheel boss 30 integrally formed with the worm wheel hub 20 is taken out using the plate 140 and the spin pin 145. [

If the roundness and concentricity of the worm wheel boss 30 product formed integrally with the worm wheel hub 20 taken out in the boss take-out step S4 are unsatisfactory, the deformation amount of the worm wheel boss 30 can be appropriately modified.

In the product injection step S6, the worm wheel shaft 10 having the worm wheel hub 20 integrated with the worm wheel boss 30 integrated with the boss injection mold 100 is inserted into the hollow 221 of the movable core 220, The movable side core 220 is advanced toward the stationary side core 210 and then the movable side core 220 and the movable side core 220 are assembled through the resin injection port 215. [ The liquid resin is injected into the cavity of the worm gear tooth core 230 disposed between the worm gear teeth.

As the injected resin is hardened through the cooling process, the gear form corresponding to the gear teeth of the worm gear tooth core 230 is formed into the gear forming portion 40, and the formed gear forming portion 40 is formed by the worm wheel boss 30, So that the worm wheel product 50 is manufactured.

7A, when the movable core 220 is moved backward to demold the movable core 220 and the fixed core 210, Side core 220 are separated from each other.

At this time, the ball member 420 is positioned at the uppermost end of the guide groove 415.

More specifically, the take-out step for taking out the worm wheel product 50 to the outside includes advancing the take-out plate 310 to the fixed-side core 210 side, and a plurality of take-out pins 320 And the support shaft 250 are advanced, the worm wheel product 50 is lifted from the movable core 220 and separated.

7B, the inner peripheral surface of the worm gear tooth core 230 and the gear teeth formed on the outer peripheral edge of the gear forming portion 40 are engaged with each other when the worm wheel product 50 is taken out, The worm gear tooth core 230 is rotated by the friction force generated due to the structural characteristic of the worm gear tooth core 230 and the movement of the guide bar 410 interlocked with the take-out plate 310 during the forward movement of the take- The ball member 420 protruding from the outer periphery of the core 230 slides along the guide groove 415 at an inclined angle formed inside the guide bar 410 and moves downward.

The ball member 420 accommodated in the guide groove 415 is slid along the inclination angle of the guide groove 415 when the worm wheel product 50 is taken out, 40 do not interfere with the gear teeth 232 formed on the inner circumferential surface of the worm tooth-shaped core 230, and a natural take-out operation is performed.

The ball bearing 430 is interposed between the worm gear tooth core 230 and the first movable side core 222 to rotate the worm wheel tooth core 230 in order to reduce frictional force during rotation of the worm gear tooth core 230 And the like.

The worm wheel boss 30 and the gear forming portion 40 are moved in the respective boss injection step S3 and the product injection step (S3) in the state where the worm wheel shaft 10 and the worm wheel hub 20 are press- S6. Therefore, unlike the conventional method of assembling the worm wheel shaft to the worm wheel hub after molding each of the worm wheel component parts into the finished product, since the worm wheel shaft is inserted and formed before molding, the reference axis It is possible to satisfy the conditions such as roundness, concentricity and run-out of the tooth profile, and the hooping process for machining the gear teeth of the gear forming portion can be omitted, thereby improving the productivity and reducing the cost Lt; / RTI >

In addition, the present invention has an advantage in that the worm gear teeth are guided to rotate in the process of taking out the worm gear product, so that the formability of the gear-formed portion during the take-off can be eliminated by eliminating the interference phenomenon of the undercut portion.

10: worm wheel shaft 20: worm wheel hub
30: worm wheel boss 40: gear forming part
50: Worm wheel product 100: Boss injection mold
110: fixed side mold plate 115: resin injection portion
120: movable side mold plate 130: core block
140: Plate 145:
200: product injection mold 202: base plate
204: support block 205: cover block
210: fixed side core 215: resin injection port
220: movable core 221: hollow
222, 222: first and second movable core 230: worm gear tooth core
232: gear teeth 250: support shaft
300: take-out means 310: take-out plate
320: extraction pin 400: guide means
410: guide bar 415: guide groove
420: Ball member 430: Ball bearing

Claims (3)

A press-fitting step (S1) of press-fitting the worm wheel shaft (10) into the worm wheel hub (20)
A first injection preparing step S2 of placing the worm wheel shaft 10 pushed into the worm wheel hub 20 in the core block 130 of the boss injection mold 100,
The resin is injected into the inner space of the core block 130 after the fixed side mold plate 110 and the movable side mold plate 120 of the boss injection mold 100 are combined to form a worm wheel boss A boss injection step S3 for integrally molding the boss 30,
After removing the fixed side mold plate 110 and the movable side mold plate 120 of the boss injection mold 100, the worm wheel shaft 10, the worm wheel hub 20 and the worm wheel boss 30, A boss extracting step S4,
A second injection preparation step (S5) of arranging the boss product between the movable side core (220) and the fixed side core (210) of the product injection mold (200)
After the movable core 220 and the fixed core 210 of the product injection mold 200 are combined with each other, resin is injected into the worm gear tooth core 230 to form the gear forming portion 40 on the outer side of the boss product. A product injection step (S6)
A product taking-out step of taking out a worm-wheel product (50) integrated with the gear forming part (40) on the outside of the boss product after demoulding the movable side core (220) and the fixed side core (210) of the product injection mold (S7). ≪ / RTI >
The method according to claim 1,
The product take-out step S7 further includes a rotation guide step S7-1 for rotating the worm wheel-shaped core 230 with respect to the worm wheel shaft 10 when the worm wheel product 50 is taken out .
The method of claim 2,
The rotation guide step S7-1 includes a guide groove formed at an angle to the inside of both guide bars 410 penetrating vertically through both sides of the movable core 220 and interlocked with the take- A ball member 420 coupled to be protruded from the outer circumferential surface of the worm wheel tooth core 230 is slidably coupled to the worm wheel tooth core 415,
Wherein when the worm wheel (50) is taken out, the rotation direction of the worm wheel-shaped core (230) is rotated in an oblique direction corresponding to the gear of the worm wheel.

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