JP2007098632A - Method and apparatus for producing toothed wheel, toothed wheel, and motor with decelerating mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mold a toothed wheel having undercut-shaped teeth with an apparatus simple in structure without carrying out forcible extraction. <P>SOLUTION: In the internal space of a former 40, the fitting part 22 of an annular flat spring 20 is inserted into the engagement channel 13 of a tooth type cavity insert 10 to set the cavity insert 10 annually. The taper surface 30a of a taper ring 30 is contacted with the taper surface 10b of the cavity insert 10 and pressed to make the adjacent cavity inserts 10 be adhered to each other to be restricted, and mold clamping is carried out. When the restriction of the cavity inserts 10 by the taper ring 30 during mold opening is released, the cavity insert 10 is automatically moved outside in the diameter direction by the spring force of the annular flat spring 20, so that the undercut part of a molding is separated completely from the cavity insert. The molding having the undercut part is ejected in the rotary shaft direction to be demoldable. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gear used for a reduction mechanism of a motor and the like, and more particularly, a gear formed by curving a tip of a tooth and a bottom of a tooth groove toward a rotating shaft, a manufacturing method of the gear, and a manufacturing device of the gear The present invention also relates to a motor with a speed reduction mechanism including the gear.

  Conventionally, in a worm and a worm wheel used in a speed reduction mechanism or the like, in order to increase the contact area between the worm tooth and the worm wheel tooth so that a large load can be transmitted, the tip and teeth of the worm wheel tooth are used. A so-called hourglass worm wheel is used in which the bottom of the groove is curved toward the rotating shaft side of the worm wheel, and the tooth profile side surface is shaped like a drum. In particular, in the case of a resin gear, a drum-type worm wheel is preferably used because the tooth-shaped strength can be maintained by using a drum-shaped gear.

  Conventionally, such a drum-type worm wheel has a problem that the processing cost is increased because the tooth surface is processed into a curved shape by cutting. Moreover, when it is going to manufacture the gear which has a curved-shaped tooth | gear by shaping | molding using a metal mold | die, a curved part will be an undercut shape. Therefore, it is necessary to operate the divided tooth mold inserts using a complicated cam mechanism or the like, and there is a problem that the mold cost is increased. In addition, if the mold is forcibly removed after molding and is manufactured without incurring the mold cost, there is a problem that the teeth are deformed due to the forced removal.

Therefore, if the drum-shaped worm wheel is divided into two on a plane perpendicular to the rotation axis, and the half is divided at the center of the curved shape (the most concave point on the rotation axis side), this half division is It can be manufactured as a molded product without an undercut part. And the method of assembling this half-divided body and manufacturing a drum type worm wheel is used (for example, refer patent document 1). In addition, as a method for producing a resin molded product having an undercut part, the undercut part is deformed and released by releasing it under a specific temperature condition, and then solidified while returning to the undercut shape as it is cooled. (For example, refer to Patent Document 2).
JP 2002-310267 A (page 4-6, FIG. 1, FIG. 3, FIG. 7) JP 2003-326570 A (page 9-10, FIG. 2, FIG. 4)

However, when a drum-type worm wheel is manufactured as in Patent Document 1, it is necessary to perform an assembly process after molding, which increases the number of processes. In addition, when manufacturing a drum-type worm wheel as in Patent Document 2, even if it is slightly deformed, it can be restored to its original shape by the elasticity of the resin even if it is forcibly removed. When the limit is exceeded, it cannot be restored to its original state, and there is a problem that the teeth are deformed and an effective contact area cannot be secured.
Furthermore, the worm wheel used for the motor with a speed reduction mechanism sometimes has teeth damaged when an excessive rotational force (torque) is applied from the motor as a drive source.

  The present invention has been made in view of the above circumstances, and its purpose is to provide a gear having a deep undercut tooth, such as a drum-type worm wheel, without excessive force and without being complicated. An object of the present invention is to provide a gear manufacturing method and a gear manufacturing apparatus that can be formed without using a cam mechanism. Another object of the present invention is to provide a gear manufactured by the above manufacturing method and a motor with a speed reduction mechanism including the gear. Another object of the present invention is to provide a gear with which teeth are hardly damaged and a motor with a speed reduction mechanism including the gear.

  According to the present invention, there is provided a method of manufacturing a gear in which a toothed portion or a tooth groove is provided with a curved portion that is recessed toward the rotating shaft, and a cavity for molding the gear is formed inside a mold body. A cavity forming step to be formed, a filling step for filling the cavity with a molten resin, and a mold releasing step for releasing the molded product from the cavity are performed. In the cavity forming step, the mold is formed inside the mold body. In the formed space, a plurality of tooth mold inserts obtained by dividing the annular body in which the inverted shapes of the tooth tips and the tooth grooves are formed on the inner peripheral surface in a circumferential direction are arranged in a substantially annular shape, Engage each elastic member for urging radially outward, move the tooth mold inserts radially inward to closely contact each other, and seal the inner circumferential space of the contacted tooth mold inserts Clamp the cavity In the mold release step, the mold is opened after the molten resin is cured, and the molded product is released by moving the tooth mold insert radially outward by the urging force of the elastic member. The

As described above, in the present invention, an annular body in which the inverted shape of the tooth tip and the tooth gap is formed on the inner peripheral surface is divided into multiple teeth in the circumferential direction, and this tooth mold insert is arranged in a substantially annular shape. After being brought into close contact with each other, the cavity can be formed by clamping the inner peripheral space so as to be sealed. At the time of mold opening, the closely spaced tooth mold inserts are separated from each other in the circumferential direction again to be divided, and moved radially outward.
Moreover, in this invention, the elastic member which urges | biases this tooth type nest to radial direction outer side is engaged with each of the tooth type nest which was stuck. When the mold is opened, the tooth mold insert is moved radially outward by the biasing force of the elastic member.

  With such a configuration, when the mold is opened, a sufficient clearance is automatically secured between the tooth mold insert and the molded product by the elastic member, and the undercut portion of the molded product is completely removed from the tooth mold insert. Become. Therefore, in this state, the molded product can be ejected in the direction of the rotation axis and released. In this way, a gear having an undercut shape at the tooth tip or tooth gap can be formed without using a complicated cam mechanism and without forcibly removing the gear. Further, the gear can be formed in a short time. Therefore, the manufacturing time can be shortened compared to the conventional case, and the manufacturing cost can be kept low.

In the present invention, in the cavity forming step, an annular body in which an inverted shape of the tooth tip and the tooth groove and a reinforcing wall that connects adjacent teeth in the circumferential direction is formed on the inner circumferential surface is formed in the circumferential direction. It is preferable that a gear having the reinforcing wall formed at the end portion in the rotation axis direction of the gear is manufactured by using a plurality of tooth-type inserts that are divided into two.
Thus, if the reinforcement wall which connects the adjacent tooth | gear in the circumferential direction in the edge part of the rotating shaft direction of the tooth surface of a gearwheel is formed, damage to a tooth | gear is prevented by the reinforcement wall and durability improves.

Further, in the present invention, in the cavity forming step, a bent leaf spring portion disposed so as to open a spring foot in the circumferential direction, and a tip of the spring foot of the leaf spring portion are connected to the tooth mold nest. It is preferable to use an elastic member provided with an engaging portion that can be engaged. If comprised in this way, the tooth type nest engaged with the front end side of the spring leg can be urged | biased to the circumferential direction and radial direction outer side by the spring leg opening with the spring force of a leaf | plate spring part.
More specifically, in the cavity forming step, the leaf spring portions and plate-like locking portions formed so as to be insertable into the engagement grooves of the tooth mold insert are alternately connected in the circumferential direction. It is preferable to use an elastic member made of an annular leaf spring formed in a substantially annular shape. Since such an annular leaf spring is expanded in diameter by the spring force of the leaf spring portion, the tooth type nest can be moved radially outward. Further, by inserting a plate-like locking portion into the engagement groove of the tooth mold nest, the tooth mold nest can be easily engaged with the annular leaf spring.

  Further, in the present invention, in the cavity forming step, the tooth mold nest is restrained and moved radially inward by bringing a nest lock member into contact with a tapered surface provided on the outer peripheral surface of the tooth mold nest, In the mold release step, it is preferable that the tooth mold insert is released from the radial lock by releasing the restriction of the tooth mold insert by the insert lock member. If comprised in this way, a tooth | gear type nest | insert can be moved to radial inside only by pressing a taper surface with a nest | locking lock member, and it can restrain in the state closely_contact | adhered substantially annularly, and can form a cavity. Further, the restraint state of the tooth type insert can be released simply by moving the insert lock member in the direction away from the tapered surface.

  According to the present invention, the object is a gear manufacturing apparatus in which a toothed portion or a tooth groove is provided with a curved portion that is recessed toward the rotating shaft, and an internal space for forming a cavity for forming the gear is provided. A plurality of tooth mold nestings disposed in a substantially annular manner in an inner space of the mold body, an elastic member engageable with each of the tooth mold nestings, and the plurality of tooth mold nestings. And a constraining means that can be constrained in a substantially annular shape, and an inversion shape of the tooth tip and the tooth gap is formed on the inner peripheral surface of the tooth mold insert, and the mold body is The cavity can be formed by sealing the inner peripheral space of the close contacted tooth mold insert, and the elastic member urges the tooth insert insert radially outward when the mold is opened. To the release position where the molded product in the cavity can be released Be moved outwardly, it is solved by.

  If comprised in this way, as mentioned above, the tooth-type nest | insert with which the inverted shape of the tooth tip and the tooth gap was formed in the inner peripheral surface arrange | positions substantially cyclic | annular form, it mutually adheres and restrains, The inner peripheral space is sealed The mold can be clamped to form a cavity. Then, an elastic member is engaged with each of the close-fitting tooth mold inserts, and when the mold is opened, the tooth mold inserts can be moved radially outward by the biasing force of the elastic members. Therefore, when the mold is opened, a sufficient clearance is secured between the tooth mold insert and the molded product, and the undercut portion of the molded product is completely removed from the tooth mold insert. Therefore, in this state, the molded product can be released without forcibly removing it by protruding in the direction of the rotation axis.

  In the present invention, the inner peripheral surface of the tooth type insert is formed with a reversal shape of a reinforcing wall that connects adjacent teeth in the circumferential direction, and the cavity is formed at the end of the gear in the rotation axis direction. It is preferable that the gear provided with is formed so as to be moldable. When configured in this way, as described above, the reinforcing wall prevents the teeth from being damaged and improves the durability.

In the present invention, the elastic member is connected to the bent leaf spring portion disposed so that the spring foot is opened in the circumferential direction and the tip of the spring foot of the leaf spring portion, and is engaged with the tooth type nest. It is preferable to provide a locking portion that can be mated. If comprised in this way, as above-mentioned, the tooth type nest | insert nested on the front end side of the spring leg by the spring force of a leaf | plate spring part can be urged | biased to the circumferential direction and radial direction outer side.
More specifically, the elastic member is formed by alternately connecting the leaf spring portions and plate-like locking portions formed so as to be insertable into the engagement grooves of the tooth type insert in the circumferential direction. It is preferable to be constituted by an annular leaf spring formed in an annular shape. As described above, such an annular leaf spring is expanded in diameter by the spring force of the leaf spring portion, and the tooth type nest can be moved radially outward. Further, by inserting a plate-like locking portion into the engagement groove of the tooth mold nest, the tooth mold nest can be easily engaged with the annular leaf spring.

  Further, in the present invention, a taper surface is provided on the outer peripheral surface of the tooth type nest, and the restraining means includes a nest lock member having an abutting portion that abuts on the taper surface. It is preferable to be configured to be movable between a constrained state in which the mold nest is constrained in an annularly close state and a release state in which the tooth nest is movable to the release position. If comprised in this way, as above-mentioned, a tooth type nest | insert can be moved to radial inside only by pressing a taper surface with a nest | locking lock member, and can be restrained in the state closely_contact | adhered to the substantially cyclic | annular form. In addition, by moving the nesting lock member in the direction away from the tapered surface, the constrained state of the tooth type nesting can be released.

  Further, in the present invention, it is preferable to configure a motor with a speed reduction mechanism using the gear manufactured by each of the above manufacturing methods as a worm wheel. As a result, a worm wheel that has a large meshing area with the teeth of the worm, can transmit a large load, and is difficult to damage the teeth is formed without forcibly removing it and without using an expensive complicated cam mechanism. It becomes possible.

The present invention has the following effects.
(1) A gear-shaped cavity having an undercut portion is formed using a tooth-type insert obtained by dividing the annular body in the circumferential direction, and an elastic member that is urged radially outward is engaged with the tooth-type insert. The Thus, when the mold is opened, the tooth mold insert is automatically moved radially outward by the biasing force of the elastic member, and the undercut portion of the molded product can be completely removed from the tooth mold insert. Thereby, the gear which has an undercut shape in a tooth tip or a tooth gap can be formed without using a complicated cam mechanism and without forcibly removing it. Therefore, it is possible to shorten the manufacturing time and the manufacturing cost.
(2) By using an annular leaf spring, which is formed in a substantially annular shape by alternately connecting plate-like locking portions and leaf spring portions in the circumferential direction, the tooth type nest is easily engaged with the annular leaf spring. Can be made. In addition, the opening angle of the leaf spring portion can be reduced to reduce the diameter of the annular leaf spring, and the tooth type insert can be brought into close contact. Further, the annular leaf spring can be expanded by the spring force of the leaf spring portion, and the tooth mold nest can be automatically moved radially outward.
(3) By providing a reinforcing wall that connects adjacent teeth in the circumferential direction, tooth damage is prevented and durability is improved.
(4) A tapered surface is provided on the outer peripheral surface of the tooth mold nest, and the tooth nest is moved radially inward by contacting the nest lock member with the taper surface, and is constrained to be in a substantially annular contact state. be able to. Further, the restraint state of the tooth type insert can be released simply by moving the insert lock member in the direction away from the tapered surface.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be noted that members, arrangements, and the like described below do not limit the present invention, and it goes without saying that various modifications can be made in accordance with the spirit of the present invention.
1 to 17 are views showing an embodiment of the present invention, FIG. 1 is a side view of a motor with a speed reduction mechanism, FIG. 2 is a perspective view of a worm wheel of Example 1, FIG. 3 is a front view of the worm wheel, 4 is a cross-sectional view taken along the line AA in FIG. 5 is a cross-sectional view of a manufacturing apparatus for forming a worm wheel, FIG. 6 is a plan view of a tooth mold nest installation surface provided in the manufacturing apparatus, and FIG. 7 is a plan view of a tooth mold nest closely attached in an annular shape. FIG. 8, FIG. 8 is a sectional view taken along line BB and CC in FIG. 7, FIG. 9 is a plan view of the annular leaf spring, and FIG. 10 is an explanatory view showing an engagement method between the annular leaf spring and the tooth type insert. is there. 11 to 17 are explanatory views showing the manufacturing process of the worm wheel, FIG. 11 is an explanatory view showing a state in which the tooth mold insert and the annular leaf spring are set in the mold body, and FIG. 12 is a taper to the tooth mold insert. FIG. 13 is an explanatory view showing a state in which the ring is brought into contact with and moved radially inward, FIG. 13 is an explanatory view showing a state in which the tooth type insert is closely attached in an annular shape, and FIG. 14 is a plan view of the state of FIG. FIG. 15 is a plan view of a state in which the tooth type nest is closely attached in an annular shape by a taper ring as viewed from above, FIG. 16 is an explanatory view showing a state in which the restriction of the tooth type nest by the taper ring is released, and FIG. It is explanatory drawing which shows the state which moved to radial direction outer side and the molded product became mold release possible.
18 to 21 are views showing another embodiment of the present invention. FIG. 18 is a perspective view of the worm wheel of the second embodiment, FIG. 19 is a sectional view taken along the line DD in FIG. 18, and FIG. FIG. 21 is a cross-sectional view taken along lines EE and FF in FIG. 20.

(Example 1: Configuration of worm wheel and motor with reduction mechanism)
The motor M with a speed reduction mechanism of this example is an embodiment in which the gear of the present invention is applied to a worm wheel, and is suitably used for driving various devices that are electrically operated in a vehicle or the like. As shown, the motor M1 and the worm gear M2 connected to the output shaft of the motor M1 are provided. The worm gear M2 includes a worm W1 provided at the tip of the output shaft of the motor M1, and a worm wheel W2 that meshes with the worm W1 and has a rotation axis that is orthogonal to the rotation axis of the worm W1.

The worm W1 is connected to the output shaft of the motor M1, and the outer shape thereof is an elongated drum shape in which the substantially central portion of the cylindrical shape is reduced in diameter so as to have an arc shape in a side view as shown in FIG. ing. Teeth (not shown) are spirally formed on the outer peripheral surface around the rotation axis of the worm W1, and the tooth tip and the root of the teeth are formed along the drum-shaped surface.
As shown in FIG. 2, the worm wheel W <b> 2 has teeth 1 that engage with the teeth of the worm W <b> 1 on the outer peripheral surface. The tooth tip 1a and the tooth bottom 1b of the tooth 1 are respectively formed so as to have a substantially arcuate shape, with the center portion being concaved toward the rotation axis. That is, the worm wheel W2 is formed in a flat drum shape, and the tooth tip 1a and the tooth bottom 1b are formed along the drum surface. FIG. 3 is a front view of the worm wheel W2, and FIG. 4 is a cross-sectional view of the worm wheel W2 (AA cross-sectional view of FIG. 2).

The worm W1 and the worm wheel W2 have a circular arc shape at the center when the worm W1 is viewed from the side and a circular shape at the outer periphery when the worm wheel W2 is viewed from the direction of the rotation axis so that the respective rotation axes are orthogonal to each other. When they are meshed with each other, the degree of curvature is adjusted so as to increase the number of teeth in contact therewith.
Further, when the worm W1 and the worm wheel W2 are meshed so that their rotation axes are orthogonal to each other, the arc shapes of the tooth tip 1a and the tooth bottom 1b of the worm wheel W2 are centered on the rotation center of the worm W1. It is meshed so as to have an arc shape. The degree of arcuate curvature of the tooth tip 1a and the tooth bottom 1b of the worm wheel W2 and the degree of curvature around the rotation axis of the teeth formed on the outer peripheral surface of the worm W1 are determined by the contact area between adjacent tooth surfaces. The degree of curvature is adjusted so as to increase.

  With such a configuration, the worm gear M2 has a larger contact amount between the teeth of the worm W1 and the teeth of the worm wheel W2, compared to a conventional worm gear using a cylindrical gear having an outer peripheral surface. Accordingly, in the motor M with a speed reduction mechanism having such a worm gear M2, torque crossing when the rotational force (torque) of the motor M1 is transmitted from the output shaft of the worm wheel W2 to the outside is suppressed.

  In this example, the worm wheel W2 is made of resin and manufactured by injection molding or the like by the manufacturing apparatus S described later, but materials other than resin may be used. For example, the worm wheel W2 may be made of metal and cast.

(Example 1: Configuration of manufacturing apparatus)
Next, a manufacturing apparatus S for manufacturing the drum-shaped worm wheel W2 used in the motor M with the speed reduction mechanism described above will be described.
FIG. 5 shows a cross-sectional view of the manufacturing apparatus S. The manufacturing apparatus S of the present embodiment is a mold apparatus that forms a cavity K for manufacturing the worm wheel W2 by injection molding or the like, and has a plurality of tooth mold inserts 10 arranged in an annular shape and processed into an annular shape. An annular leaf spring 20, a ring-shaped taper ring 30 set on the outer periphery of the tooth mold insert 10, and a space 41 for arranging the tooth mold insert 10, the ring leaf spring 20, and the taper ring 30 inside are formed. And a molded body 40. FIG. 6 is a plan view of an installation surface 40a provided for placing the tooth mold insert 10 in the internal space of the manufacturing apparatus S. FIG.

The tooth type insert 10 is for forming a mold surface having a shape obtained by reversing the outer peripheral surface of the drum shape of the worm wheel W2, and has substantially the same thickness as the outer periphery of the worm wheel W2, as shown in FIG. The annular body is radially divided into multiple shapes. 8 (a) and 8 (b) are cross-sectional views (cross-sectional views taken along BB and CC in FIG. 7) of the tooth tip portion and the tooth gap portion of the tooth mold insert 10, respectively.
The tooth mold insert 10 is set on the installation surface 40a of the space portion 41 of the mold body 40 and is restrained in a state of being in close contact with the ring as shown in FIG. In this example, the lower opening of the inner circumferential space of this closely-attached annular body is closed by the installation surface 40a as shown in FIG. 5, and the upper opening is closed by the template 43, so that the drum-shaped gear shape is formed. A cavity K is formed.

As shown in FIGS. 7 and 8, the tooth-type insert 10 has a tooth forming surface 10 a that faces toward the inner peripheral side when it is closely attached in an annular shape. The tooth forming surface 10a is formed in a shape obtained by inverting the shape of the tooth 1 described above. That is, in the tooth forming surface 10a, the portion forming the tooth root 1b protrudes radially inward to form the tooth bottom forming portion 11, and the portion forming the tooth tip 1a is recessed radially outward to become the tooth tip forming portion 12. ing.
As described above, the tooth tip 1a and the tooth bottom 1b of the worm wheel W2 of this example have a shape in which the central portion is curved and is recessed in an arc shape. Accordingly, the tooth bottom forming portion 11 and the tooth tip forming portion 12 have shapes inverted from each other, that is, a shape protruding in an arc shape when viewed from the side.

The tooth mold nest 10 is configured such that the radially inner side (side connected to the tooth forming surface 10a) is in close contact with the adjacent tooth mold nest 10, but the circumference of the tooth mold nest 10 on the radially outer side. The width of the direction is substantially constant. That is, the circumferential surface is bent. Accordingly, the radially outer portion of the tooth mold insert 10 has a gap between the adjacent tooth mold inserts 10 even when the radially inner portion is in close contact with the adjacent tooth mold insert 10.
Further, the tooth type insert 10 has a tapered surface 10b in which the upper end side of the surface facing the radially outer side is inclined radially inward. In this example, by sliding a taper surface 30a of a taper ring 30 (to be described later) along the taper surface 10b, the tooth mold nest 10 can be moved radially inward and brought into close contact with the adjacent tooth mold nest 10. .

Further, the tooth type insert 10 is formed with an engagement groove 13 in a direction facing the circumferential direction when arranged in an annular shape. The engagement groove 13 is arranged so as to be positioned on a substantially annular line when the tooth mold insert 10 is brought into close contact with the ring. However, since this engagement groove 13 is formed in the radially outer portion of the tooth mold nest 10, the ends of the adjacent engagement grooves 13 are not in contact with each other, and the diameter of the adjacent tooth mold nest 10 is An intermittent annular groove is formed through a gap in the outer portion in the direction.
Further, the tooth type insert 10 is provided with a rod-shaped guide member 14 protruding from the lower end surface. The guide member 14 is inserted into a guide groove 42 having a long hole shape in plan view formed radially on the installation surface 40a shown in FIG. The guide member 14 can be slid in the radial direction by being guided in the radial direction along the guide groove 42.

As shown in FIG. 9, the annular leaf spring 20 is formed in a substantially annular shape by bending a plate material, and a leaf spring portion 21 in which the plate material is bent in a mountain shape and a tip of a spring leg of the leaf spring portion 21 in the circumferential direction. The plate-like locking portions 22 bent in the direction are alternately arranged in the circumferential direction. The leaf spring portion 21 is arranged so that the spring leg opening direction is the circumferential direction.
In such a configuration, as shown in FIG. 10A, when a spring force acts to increase the opening angle of the leaf spring portion 21, the locking portion 22 moves radially outward based on this spring force. Is done. Therefore, when the plate-like engaging portion 22 is inserted into the engaging groove 13 of the tooth mold insert 10 and mounted as shown in FIG. Moved to. That is, when the tooth mold insert 10 is mounted on the annular leaf spring 20 in this way, a biasing force that biases the tooth mold insert 10 radially outward is exerted by the diameter expansion force of the annular leaf spring 20.
Thus, since the annular leaf spring 20 of this example is expanded in diameter by the spring force of the leaf spring portion 21, the engaged tooth mold nest 10 can be moved radially outward. Further, the tooth-type insert 10 can be easily engaged with the annular leaf spring 20 by inserting the plate-like locking portion 22 into the engagement groove 13 of the tooth-type insert 10.

The tapered ring 30 is formed in a ring shape, and a tapered surface 30a (see FIGS. 12 and 16) is formed on the inner peripheral side. The tapered surface 30a has substantially the same shape as the surface formed by the continuous taper surface 10b when the tooth mold insert 10 is closely attached in an annular shape.
In this example, when the cavity is formed, the taper surface 30a of the taper ring 30 is brought into contact with the taper surface 10b of the tooth mold nest 10 disposed on the installation surface 40a. Then, when the taper ring 30 is pressed toward the tooth nest 10 in this state, the taper surface 10b is slid along the taper surface 30a as shown in FIG. Along with this, the tooth mold nest 10 is moved radially inward to the position shown in FIG.
The taper ring 30 corresponds to a nested lock member as a restraining means of the present invention.

By this movement, the planar position of the tooth mold nest 10 moves from a state of being spaced apart from each other in the circumferential direction as shown in FIG. 14 to a state of being in close contact with each other in the circumferential direction as shown in FIG. Along with this movement, the annular leaf spring 20 on which the tooth mold insert 10 is mounted in an annular shape is expanded in diameter as shown in FIG. 14 (from the center to the locking portion 22) as the tooth mold insert 10 moves inward in the radial direction. From the distance R1) to a reduced diameter state (the distance from the center to the locking portion 22 is R2 (<R1)) shown in FIG. In this reduced diameter state, the tooth type insert 10 is urged radially outward by the spring force of the annular leaf spring 20, but the tapered surface 10b is surrounded and restrained from the diagonally upward by the tapered surface 30a. The tooth type nest 10 is kept in close contact and is restrained.
The opening of the taper ring 30 is formed such that a template 43 having substantially the same plane shape as the opening can be inserted as shown in FIG. A sprue is provided in the approximate center of the template 43, and the inverted shape of the worm wheel W2 is formed on the surface of the template 43 tooth insert 10.
In this example, the taper ring 30 has a ring shape, but the taper ring 30 and the template 43 may be formed integrally.

(Example 1: Manufacturing method of worm wheel)
Next, a method for manufacturing the worm wheel W2 using the manufacturing apparatus S configured as described above will be described with reference to FIGS. In this example, a method of forming a resin worm wheel W2 by injection molding using the manufacturing apparatus S will be described.
First, the manufacturing apparatus S is clamped to form a cavity K (cavity forming step).
In this step, first, as shown in FIG. 11, by inserting the guide member 14 into the guide groove 42, the plurality of tooth mold inserts 10 are set on the installation surface 40a in a substantially annular shape, and the tooth mold insert 10 The engaging portion 22 of the annular leaf spring 20 is inserted into the intermittent annular groove formed by the engaging groove 13. Thereby, as shown in FIG. 14, it will be in the state which the adjacent tooth type nest | insert 10 does not contact | adhere.

  Subsequently, as shown in FIG. 12, the tapered surface 30 a of the taper ring 30 is brought into contact with the tapered surface 10 b of the tooth mold insert 10. In this state, the taper ring 30 is pressed toward the tooth mold insert 10 side, and the tooth mold insert 10 is moved radially inward. Then, when the tooth nest 10 is moved radially inward to the position shown in FIG. 13, it is brought into close contact with each other in the circumferential direction as shown in FIG. At this time, since the taper ring 30 encloses and constrains the taper surface 10b obliquely from above with the taper surface 30a, the tooth mold insert 10 is constrained while being kept in close contact. Then, the template 43 is inserted into the opening of the taper ring 30. Then, the mold plate 43 comes into contact with the upper surface of the tooth mold insert 10 to enter the mold clamping state shown in FIG. As described above, when the taper ring 30 and the mold plate 43 are integrally formed, the mold is clamped when the movement of the tooth mold insert 10 inward in the radial direction is completed, and the cavity K is formed.

  Next, molten resin is injected into the cavity K and filled (filling step). That is, molten resin is injected into the cavity K through an injection unit (not shown) connected to the sprue of the template 43 through the sprue. Then, the molten resin material injected into the cavity K is cooled and solidified using a cooling device (not shown). Thereby, the worm wheel W2 as a molded product is formed in the cavity K.

  Then, after the worm wheel W2 is molded as described above, the mold is opened to release the molded product (mold release step). That is, the taper ring 30 and the template 43 are removed as shown in FIG. As a result, the restriction of the tooth mold insert 10 by the taper ring 30 is released, and the tooth mold insert 10 can be moved radially outward. Then, the annular leaf spring 20 is expanded in diameter by the spring force of the leaf spring portion 21, and the tooth mold insert 10 is automatically moved radially outward. Thereby, the undercut portion of the worm wheel W2 of the molded product is completely removed from the tooth mold insert from the tooth mold insert 10, and the tooth tip 1a and the tooth bottom 1b of the worm wheel W2 and the tooth bottom of the tooth mold insert 10 are obtained. A sufficient clearance is ensured between the forming portion 11 and the tooth tip forming portion 12 as shown in FIG.

Thereby, in the mold release process of this example, the worm wheel W2 which has an undercut part protrudes in a rotating shaft direction, and will be in the state which can be released. Therefore, the worm wheel W2 of the molded product is taken out from the installation surface 40a side using the ejector pin 44 for ejecting the molded product, and the mold is released. Then, after the worm wheel W2 is taken out of the mold body 40, unnecessary portions formed by the sprue of the mold plate 43 are removed by a predetermined method, thereby completing the molding of the worm wheel W2.
Here, in the worm wheel W2 formed as described above, as shown in FIG. 2, the center portions of the tooth tip 1a and the tooth bottom 1b of the tooth 1 are recessed and curved toward the rotating shaft side, It is formed so as to form a substantially arc shape. Thus, by using the molding apparatus S of this example, it is impossible to use a gear having an undercut shape (tooth tip 1a and tooth bottom 1b) in the tooth tip or tooth groove without using a complicated cam mechanism. It can be molded without punching. Further, the gear can be formed in a short time. Therefore, the manufacturing time can be shortened compared to the conventional case, and the manufacturing cost can be kept low.

(Example 2: Configuration of worm wheel)
The worm wheel W3 of the present example has a configuration in which adjacent teeth and end portions of the teeth are connected in the circumferential direction so that damage to the teeth is prevented and durability is improved. Hereinafter, with reference to FIGS. 18 to 21, only the parts different from the first embodiment will be described, and the description of the same parts will be omitted.
As shown in FIG. 18, the worm wheel W3 of the present example is formed so as to have a substantially arc shape, with the center portions of the tooth tip 101a and the tooth bottom 101b being curved toward the rotation axis. That is, the tooth tip 101a and the tooth bottom 101b of the worm wheel W3 are formed along the hourglass surface. And the reinforcing wall 102 is provided so that the both ends of the axial direction of this tooth tip 101a may be connected to the circumferential direction, respectively. FIG. 19 is a cross-sectional view (DD cross-sectional view of FIG. 18) of the worm wheel W3 of this example.
The worm wheel W3 of this example can be used for a motor with a speed reduction mechanism. The configuration of this example is suitable because a large torque (torque) can be transmitted with a small torque cross and teeth are not easily damaged.

(Example 2: Configuration of manufacturing apparatus)
The manufacturing apparatus S1 (not shown) of the present example is different from the first embodiment only in that a tooth mold insert 110 is used instead of the tooth mold insert 10 of the manufacturing apparatus S of the above embodiment 1.
The tooth type nest 110 of this example is for forming a mold surface having a shape obtained by inverting the drum-shaped outer peripheral surface of the worm wheel W3 described above, and an annular body as shown in FIG. It is made into a shape. FIGS. 21A and 21B are cross-sectional views (cross-sectional views taken along line EE and FF in FIG. 20) of the tooth tip portion and the tooth gap portion of the tooth mold nest 110.

This tooth type nest 110 is set on the installation surface 40a of the space 41 of the mold body 40 in the same manner as the tooth type nest 10 of the above embodiment, and is constrained by the taper ring 30 so as to be in close contact with the ring. The tooth forming surface 110a of the tooth type nest 110 of this example is formed in a shape obtained by inverting the shape of the tooth 101. That is, in the tooth forming surface 110a, a portion forming the tooth base 101b protrudes radially inward to form the tooth bottom forming portion 111, and a portion forming the tooth tip 101a is recessed radially outward to become the tooth tip forming portion 112. ing. And the part which forms the reinforcement wall 102 becomes the reinforcement wall formation part 113 which consists of the inversion shape of the reinforcement wall 102 which connects the adjacent tooth | gear 101 to the circumferential direction.
In this example, by using this tooth type nest 110, it is impossible to make a gear having an undercut shape (tooth tip 101a and tooth bottom 101b) in the tooth tip or tooth groove without using a complicated cam mechanism. It can be molded without punching. Further, the gear can be formed in a short time. Therefore, the manufacturing time can be shortened compared to the conventional case, and the manufacturing cost can be kept low.

(Example 2: Worm wheel manufacturing method)
In the manufacturing method of this example, the cavity forming process of the first embodiment is performed using the tooth mold insert 110 of this example instead of the tooth mold insert 10 of the manufacturing apparatus S of the first embodiment. As a result, the central portions of the tooth tip 101a and the tooth bottom 101b are concaved and curved toward the rotation shaft, and the reinforcing wall 102 is provided so as to connect both axial ends of the tooth tip 101a in the circumferential direction. The wheel W3 can be manufactured.

  Moreover, in the said Example 1 and 2, although the ring-shaped annular leaf | plate spring 20 was used as an elastic member, an elastic member does not necessarily need to be cyclic | annular. For example, a substantially C-shaped leaf spring in which one portion of the annular leaf spring 20 of the above embodiment is cut, or a substantially arc-shaped leaf spring obtained by dividing the annular leaf spring 20 into a plurality in the circumferential direction may be used. In short, any elastic member that can be expanded and contracted is provided between adjacent tooth mold inserts 10 and both ends of the elastic members are engaged with the adjacent tooth insert inserts 10. Further, the taper ring 30 as the nesting lock member does not necessarily have an annular shape. In short, the tapered ring 30 has an abutting portion that abuts on the tapered surface 10b, and can be constrained in a state in which the tooth type nesting 10 is in close contact with the annular shape. Any shape is acceptable.

It is a side view of the motor with a speed reduction mechanism concerning the present invention. It is a perspective view of the worm wheel of Example 1. FIG. It is a front view of the worm wheel of Example 1. It is AA sectional drawing of FIG. It is sectional drawing of the manufacturing apparatus for shape | molding the worm wheel of Example 1. FIG. It is a top view of the tooth type nest installation surface provided in the manufacturing apparatus of Example 1. It is a top view of the tooth type nest | insert closely_contact | adhered to the cyclic | annular form of Example 1. FIG. It is BB sectional drawing and CC sectional drawing of FIG. 3 is a plan view of the annular leaf spring of Example 1. FIG. It is explanatory drawing which shows the engagement method of the annular leaf | plate spring of Example 1, and a tooth type nest | insert. It is explanatory drawing which shows the state which set the tooth type nest | insert and the annular leaf | plate spring to the type | mold body. It is explanatory drawing which shows the state which makes a taper ring contact | abut to a tooth type nest and moves. It is explanatory drawing which shows the state by which the tooth type nest | insert was closely_contact | adhered cyclically | annularly by the tapering. It is the top view which looked at the state of FIG. 11 from upper direction. It is the top view which looked at the state by which the tooth type nest | insert was closely_contact | adhered cyclically | annularly by the tapering. It is explanatory drawing which shows the state which cancels | releases restraint of the tooth type nest by tapering. It is explanatory drawing which shows the state which the tooth type nest moved to the radial direction outer side, and the molded product became mold release possible. It is a perspective view of the worm wheel of Example 2. FIG. It is DD sectional drawing of FIG. It is a top view of the tooth type nest | insert closely_contact | adhered to the cyclic | annular form of Example 2. FIG. It is EE sectional drawing and FF sectional drawing of FIG.

Explanation of symbols

1, 101 tooth, 1a, 101a tooth tip, 1b, 101b tooth bottom 10 tooth type insert, 10a tooth forming surface, 10b taper surface, 11 tooth bottom forming portion,
12 ... tooth tip forming part, 13 ... engagement groove, 14 ... guide member,
20 ... Annular leaf spring, 21 ... Leaf spring part, 22 ... Locking part,
30 ... Taper ring, 30a ... Tapered surface, 40 ... Mold body, 40a ... Installation surface,
41 ··· Space, 42 ··· Guide groove, 43 ··· Template, 44 ··· Ejector pin,
102 ... Reinforcing wall, 110 ... Tooth mold insert, 110a ... Tooth forming surface,
111 ... Tooth bottom forming part, 112 ... Tooth tip forming part, 113 ... Reinforcing wall forming part,
K ... cavity, M ... motor with speed reduction mechanism, M1 ... motor M2, worm gear, S, S1 ... manufacturing equipment, W1 ... worm W2, W3 ... worm wheel

Claims (13)

A method of manufacturing a gear provided with a curved portion that is recessed on the rotating shaft side in a tooth tip or a tooth groove,
A cavity forming step for forming a cavity for molding the gear inside the mold body, a filling step for filling the cavity with molten resin, and a mold releasing step for releasing the molded product from the cavity are performed. ,
In the cavity forming step, a plurality of tooth mold nestings in which an annular body in which an inverted shape of the tooth tip and the tooth groove is formed on an inner peripheral surface is divided into multiple spaces in the circumferential direction in the space formed in the mold body Are arranged in a substantially annular shape, and an elastic member for urging radially outward is engaged with each of the tooth mold inserts, and the tooth mold inserts are moved radially inward so that they are in close contact with each other. The cavity is formed by clamping so as to seal the inner circumferential space of the tooth mold insert,
In the mold releasing step, the mold is opened after the molten resin is cured, and the molded product is released by moving the tooth mold insert radially outward by the biasing force of the elastic member. Method.   In the cavity forming step, a plurality of annular bodies in which an inverted shape of the tooth tip and the tooth gap, and a reinforcing wall that connects adjacent teeth in the circumferential direction are formed on the inner circumferential surface are divided into multiple portions in the circumferential direction. The gear manufacturing method according to claim 1, wherein a gear having the reinforcing wall formed at an end portion in a rotation axis direction of the gear is manufactured by using a tooth type insert.   In the cavity forming step, a bent-shaped leaf spring portion disposed so that the spring leg is opened in the circumferential direction, and a latch connected to the tip of the spring leg of the leaf spring portion and engageable with the tooth type nest The gear manufacturing method according to claim 1, wherein an elastic member provided with a portion is used.   In the cavity forming step, the leaf spring portion and a plate-like locking portion formed so as to be insertable into the engagement groove of the tooth nest are alternately connected in the circumferential direction to form an annular shape. The gear manufacturing method according to claim 3, wherein an elastic member made of a leaf spring is used. In the cavity forming step, the tooth-type insert is restrained and moved radially inward by bringing a lock-in member into contact with a tapered surface provided on the outer peripheral surface of the tooth-type insert.
2. The gear manufacturing method according to claim 1, wherein, in the releasing step, the restriction of the tooth mold insert by the insert lock member is released to move the tooth mold insert radially outward. 3. A gear manufacturing apparatus in which a curved portion that is recessed toward the rotating shaft is provided in the tooth tip or tooth gap,
A mold body having an internal space for forming a cavity for molding the gear, a plurality of tooth mold inserts arranged in a substantially annular manner in the internal space of the mold body, and each of the tooth mold inserts An elastic member that can be engaged, and a restraining means that can restrain the plurality of tooth-type inserts in close contact with each other substantially annularly,
On the inner peripheral surface of the tooth mold insert, an inverted shape of the tooth tip and the tooth gap is formed,
The mold body is configured to be capable of forming the cavity by sealing an inner peripheral space of the tooth mold nest that is in close contact when the mold is clamped,
The elastic member moves the tooth mold insert radially outward to a release position where the molded product in the cavity can be released by urging the tooth mold insert radially outward when the mold is opened. A gear manufacturing apparatus.   A reversal shape of a reinforcing wall that connects adjacent teeth in the circumferential direction is formed on the inner peripheral surface of the tooth mold insert, and the cavity is a gear provided with the reinforcing wall at an end in the rotation axis direction of the gear. The gear manufacturing apparatus according to claim 6, wherein the gear manufacturing apparatus is moldable.   The elastic member includes a bent leaf spring portion disposed so that a spring leg is opened in a circumferential direction, and a locking portion that is coupled to a tip of the spring leg of the leaf spring portion and can be engaged with the tooth type nest. And a gear manufacturing apparatus according to claim 6.   The elastic member is an annular plate formed in a substantially annular shape by alternately connecting the plate spring portion and a plate-like locking portion formed so as to be insertable into the engagement groove of the tooth type insert in the circumferential direction. The gear manufacturing apparatus according to claim 8, comprising a spring. A tapered surface is provided on the outer peripheral surface of the tooth mold insert,
The restraining means comprises a nesting lock member having an abutting portion that abuts against the tapered surface, and the nesting lock member is constrained in a state of constraining the tooth mold nest in an annular contact state, and the tooth mold nest is released. The gear manufacturing apparatus according to claim 6, wherein the gear manufacturing apparatus is configured to be movable between a released state movable to a position.   A gear manufactured by the method for manufacturing a gear according to any one of claims 1 to 5.   The tooth tip or tooth groove is provided with a curved portion that is recessed toward the rotating shaft, and has a reinforcing wall that connects adjacent teeth in the circumferential direction, and the reinforcing wall is formed at the end of the tooth in the rotating shaft direction. A gear characterized by that.   A motor with a speed reduction mechanism, comprising a worm wheel comprising the gear according to claim 11.

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