JP2010023135A - Manufacturing method for worm wheel, and worm speed reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a manufacturing method for a worm wheel 5b not only capable of ensuring bending rigidity of a worm wheel tooth 9b but also reducing an abrasion amount at usage and capable of attaining enhancement of shape accuracy and dimension accuracy of a tooth part 8b. <P>SOLUTION: Firstly, by injection molding of synthetic resin, an intermediate material 15a provided with an original tooth part 16 in which original teeth 17, 17 adjacent to each other in a circumferential direction are connected to each other by connection parts 13a, 13a provided on one end part in a tooth trace direction of the respective original teeth 17, 17 is formed. Subsequently, the original tooth part 16 is machined by a machining worm 14 having the same shape-same dimension as the worm engaged at usage. Thereby, only the tooth surfaces of the respective original teeth 17, 17 are cut without shaving off the respective connection parts 13a, 13a, thereby, worm wheel teeth 9b, 9b can be formed from the respective original teeth 17, 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to, for example, a worm speed reducer incorporated in an electric power steering apparatus and a method for manufacturing a worm wheel constituting the worm speed reducer.

  As a device for reducing the force required for the driver to operate the steering wheel when giving a steering angle to the steering wheel of a vehicle (usually the front wheel, excluding special vehicles such as forklifts), a power steering device is used. Widely used. In addition, an electric power steering apparatus that uses an electric motor as an auxiliary power source in such a power steering apparatus has begun to spread in recent years. In addition, a reduction gear is incorporated in such an electric power steering apparatus, but as this reduction gear, a worm reduction gear having a large lead angle and reversibility with respect to the transmission direction of power is generally used. Has been.

  4 to 5 show a structure described in Patent Document 1 as an example of a conventional structure of a worm speed reducer incorporated in such an electric power steering apparatus. This worm speed reducer is provided inside a speed reducer housing 2 fixed to the electric motor 1, and a worm shaft 4 having a worm 3 formed in the middle in the axial direction and a worm meshed with the worm 3. A wheel 5. Of these, the worm shaft 4 is rotatably supported inside the housing 2 by a pair of ball bearings 6, 6 fitted on both ends in the axial direction. At the same time, one end portion (left end portion in FIG. 4) of the worm shaft 4 is connected to the output shaft 7 of the electric motor 1 so that the worm shaft 4 can be driven to rotate.

  The worm wheel 5 is rotatably provided inside the housing 2, and its own rotation center axis is disposed at a twisted position with respect to the worm shaft 4. Then, by engaging the worm wheel teeth 9, 9 constituting the tooth portion 8 formed on the outer peripheral edge portion of the worm wheel 5 with the worm 3, the worm wheel 5 is connected between the worm wheel 5 and the worm shaft 4. Rotation force can be transmitted freely. In the case of the example shown in the drawing, the worm wheel 5 is made of metal at the inner end portion and the intermediate portion in the radial direction, and at the outer end portion in the radial direction including the tooth portions 8 (shown with a diagonal lattice). Part) is made of synthetic resin 10. Thereby, the reduction of the hitting sound and sliding sound which generate | occur | produce in a meshing part at the time of a driving | operation and weight reduction are aimed at. Further, such a worm wheel 5 is externally fitted and fixed to an intermediate portion of the steering shaft 11. As a result, the rotational driving force generated by the electric motor 1 can be transmitted to the steering shaft 11 via the worm speed reducer including the worm shaft 4 and the worm wheel 5.

  The electric power steering apparatus including the worm reduction gear as described above operates as follows. In order to give the steering wheel a steering angle, when the driver operates the steering wheel and the steering shaft 11 rotates, a torque sensor (not shown) detects the rotation direction and torque of the steering shaft 11, and A signal representing the detected value is sent to a controller (not shown). Then, the controller energizes the electric motor 1 and rotates the steering shaft 11 in the same direction as the rotation direction based on the operation of the steering wheel via the worm reducer. As a result, the steering shaft 11 rotates in response to assist torque (auxiliary power) generated by the electric motor 1 based on energization in addition to torque generated based on the operation of the steering wheel. Therefore, the force required for the driver to operate the steering wheel can be reduced by this auxiliary power. On the other hand, for example, when the electric motor 1 to which the worm shaft 4 is connected fails, the worm speed reducer is reversely operated based on the operation of the steering wheel. This prevents the steering wheel from being disabled.

  By the way, in the case of the worm wheel 5 constituting the worm speed reducer as described above, as shown in FIG. 6, the tooth portion 8 is formed on the cylindrical synthetic resin 10 portion by the hob cutter 12 having a plurality of slits formed on the outer peripheral surface. (See FIGS. 4 and 5) is generally performed (see, for example, Patent Documents 1 and 2). As described above, when it is necessary to cause the worm speed reducer to perform the reverse operation, the hob cutter 12 has a larger diameter than the worm 3 in use (see FIGS. 4 and 5) in order to ensure strength. Things are being used.

  On the other hand, a large bending stress is applied to the worm wheel teeth 9 and 9 formed on the outer peripheral edge portion of the worm wheel 5 constituting the worm speed reducer as described above during torque transmission. For this reason, conventionally, as described in Patent Documents 3 and 4, for example, it has been considered to secure the bending rigidity (strength) of the worm wheel teeth. FIG. 7 shows a worm wheel 5a having a conventional structure described in Patent Document 3 among them. In the case of this worm wheel 5a, among the plurality of worm wheel teeth 9a, 9a constituting the tooth portion 8a, the worm wheel teeth 9a, 9a adjacent to each other in the circumferential direction are connected to each other. They are connected to each other by connecting portions 13 and 13 provided at one end in the direction (the back end in FIG. 7). This ensures the bending rigidity of the worm wheel teeth 9a, 9a.

  However, in order to form the tooth portion 8a having the connecting portions 13 and 13 as described above in the synthetic resin 10 portion, the portions to be the connecting portions 13 and 13 are left out of the synthetic resin 10 portion. It is necessary to form the worm wheel teeth 9a and 9a as they are (without shaving off). For this reason, as is apparent from FIG. 8, the processing using the hob cutter 12 having a diameter larger than that of the worm 3 in use (see FIGS. 4 and 5), which is a general processing method as described above. Actually, it becomes difficult (the connecting portion 13 is scraped off). Therefore, in practice, as described in Patent Document 3, the tooth portion 8a having the above-described configuration is processed by injection molding (molding) of synthetic resin.

  However, when the processing method by injection molding of synthetic resin is adopted, the shape (tooth profile) of the worm wheel teeth 9a and 9a that can be processed is shown in FIG. 7 except when a special mold is used. As described above, the tooth thickness T is constant in the direction of the tooth trace, and is limited to the same tooth shape as each tooth constituting the helical gear. For this reason, when the worm speed reducer is used, the contact area between the worm wheel teeth 9a, 9a and the worm is reduced (point contact), and the contact surface pressure between the worm wheel teeth 9a, 9a and the worm is high. Become. Therefore, the amount of wear of each of the worm wheel teeth 9a, 9a is increased, which causes a rattle sound (tooth noise, abnormal noise).

  Further, in the case of the worm wheel 5a made by synthetic resin injection molding, the shape accuracy and dimensions of the tooth portion are caused by deformations called sinks caused by the cooling and shrinkage of the synthetic resin during the synthetic resin injection molding. It becomes difficult to ensure accuracy. In particular, as the outer diameter of a worm wheel for high torque transmission increases, the amount of deformation due to sinking increases, making it difficult to ensure shape accuracy and dimensional accuracy that can satisfy the desired performance. As described above, when the shape accuracy and dimensional accuracy of each tooth portion are deteriorated, the meshing accuracy with the worm is deteriorated, so that the rotational torque fluctuation and the transmission error are increased. For this reason, there is a possibility of deteriorating the steering sensation of the steering wheel to which auxiliary power is applied via the worm reducer. Also, it may cause abnormal noise.

  In Patent Document 1, as shown in FIG. 9, a tooth portion 8 {connecting portions 13 and 13 (FIG. 7) is formed on a synthetic resin 10 portion by a processing worm 14 formed by electrodepositing abrasive grains on the surface. , 8)) is described. The machining worm 14 has a large number of worm surfaces (portions shown with fine diagonal lattices) that are the same shape and size as the worm 3 (see FIGS. 4 and 5) that meshes with the tooth portion 8 during use. It consists of electrodepositing abrasive grains. Then, as shown in FIGS. 9 (a) and 9 (b), the intermediate material 15 having an outer peripheral surface formed in a cylindrical shape and the processing worm 14 are respectively in a speed relationship corresponding to the reduction ratio of the worm reducer. In this state, the working worm 14 is pressed against the outer peripheral surface (synthetic resin 10 portion) of the intermediate material 15. Then, the outer peripheral surface of the intermediate material 15 is ground (or cut) by the working worm 14 to form the tooth portion 8 on the outer peripheral surface of the intermediate material 15 as shown in FIG. .

In the case of the machining method described in Patent Document 1, the machining worm 14 having helically continuous teeth is used, so that the machining worm 14 has a larger diameter than the worm 3 in use. Even if not, sufficient strength can be secured. For this reason, as this processing worm 14, a worm having substantially the same diameter as the worm 3 in use can be used. Further, the tooth surfaces of the worm wheel teeth 9, 9 formed on the synthetic resin 10 portion have a shape that substantially conforms to the tooth profile of the worm 3 in use (substantially matches the tooth profile of the worm 3 in use). Therefore, the contact area between the worm wheel teeth 9 and 9 and the worm 3 can be increased, and the contact surface pressure between the worm wheel teeth 9 and 9 and the worm 3 can be decreased. Therefore, the wear amount of each of these worm wheel teeth 9, 9 can be suppressed. Further, unlike the case where the above-described processing method by injection molding of synthetic resin is adopted, deformation due to sink does not occur, and thus the gear accuracy of the obtained worm wheel 5 can be sufficiently ensured.
However, in Patent Document 1, such a processing worm 14 as described above is used to process the tooth portion 8a including the connecting portions 13 and 13 as shown in FIG. Is not described at all.

JP 2006-142400 A JP 2003-334724 A JP 2006-290019 A JP-A-9-250604

  In view of the circumstances as described above, the present invention can not only ensure the bending rigidity of the worm wheel teeth but also reduce the amount of wear during use, and can improve the shape accuracy and dimensional accuracy of the tooth portion. Invented to realize the manufacturing method and the worm speed reducer.

Among the worm wheel manufacturing method and the worm speed reducer according to the present invention, the worm wheel manufacturing method according to claim 1 is such that at least a surface layer portion of the tooth portion is made of a synthetic resin, and a plurality of the tooth portions are formed. This invention relates to a method of manufacturing a worm wheel in which the worm wheel teeth adjacent in the circumferential direction are connected to each other at the end of the worm hole teeth.
In particular, in the case of the worm wheel manufacturing method of the present invention, first, the tooth thickness of the worm wheel is constant in the direction of the teeth and is arranged in a helical gear shape at the portion to be the tooth portion. A raw tooth portion (helical gear) that has a plurality of raw teeth and connects the adjacent teeth in the circumferential direction among the respective raw teeth at the end portions of the respective teeth in the direction of the teeth. , Helical gears) to form intermediate materials.
In order to form such an intermediate material, for example, the injection molding of synthetic resin, that is, the shape of the portion corresponding to the portion to be the bare tooth portion of the inner surface of the cavity (internal tooth type) It can be formed by injection molding using a metal mold shaped like a helical gear.

And if the intermediate material which has such a shape is formed, compared with the worm which meshes the bare tooth part of this intermediate material at the time of use, the tooth pitch in the axial direction is the same, and the tooth tip and The diameters of the roots are equal to or greater than each other {for example, the tooth tip and the tooth base are each slightly larger (about 1 to 10%, more preferably about 1 to 3% relative to the worm meshed during use)} Abrasive grains (for example, diamond abrasive grains) are processed on the surface by a processing worm formed by electrodeposition, adhesion or the like.
The worm meshed with the worm wheel at the time of use may be either a cylindrical worm or a drum worm. The machining worm is selected from a cylindrical worm and a drum worm according to the worm meshed with the worm wheel during use.

According to a second aspect of the present invention, there is provided a worm speed reducer in which a worm and a worm wheel are engaged with each other.
Particularly, in the worm speed reducer described in claim 2, the worm wheel is manufactured by the manufacturing method of the present invention described in claim 1.

In the worm wheel manufacturing method of the present invention as described above, it is possible not only to secure the bending rigidity of the worm wheel teeth, but also to reduce the amount of wear during use and to obtain a worm wheel with high gear accuracy.
That is, in the case of the present invention, by using a machining worm having the same shape and the same size as the worm in use, among the tooth portions of the intermediate material, the teeth adjacent in the circumferential direction are connected to each other. It is possible to grind (or cut) only the tooth surfaces of these individual teeth without scraping off the portion to be cut. For this reason, also about each worm wheel tooth | gear formed from these each elementary tooth, it will be in the state with which the worm wheel teeth | gear adjacent in the circumferential direction were connected. Therefore, the bending rigidity of each worm wheel tooth can be secured.
In the case of the present invention, the tooth surface of each worm wheel tooth can be machined into a shape along the tooth profile of the worm in use (substantially matches the tooth profile of the worm in use). For this reason, the contact area between the worm wheel teeth and the worm in use can be increased, and the contact surface pressure between the worm wheel teeth and the worm can be reduced. Therefore, the wear amount of each worm wheel tooth can be suppressed.
Furthermore, in the case of the present invention, the final processing of each of these worm wheel teeth is performed by the above-described processing worm. Even when deformations due to sink marks or the like occur in each of the above-described tooth teeth constituting the tooth portion, the deformed portion can be scraped off by processing with the processing worm. For this reason, the shape accuracy and dimensional accuracy of the worm wheel finally obtained can be sufficiently increased.
In the case of the worm speed reducer of the present invention incorporating the worm wheel manufactured by the above-described manufacturing method, the bending rigidity of each worm wheel tooth is improved, the amount of wear is reduced, and further, the tooth The durability can be improved based on the improvement of the shape accuracy and dimensional accuracy of the part. In addition, since the meshing accuracy between the worm wheel teeth and the worm in use can be improved, fluctuations in rotational torque and transmission errors can be reduced, and noise generation can be suppressed to ensure quietness during use. .

[First example of embodiment]
1 and 2 show a first example of an embodiment of the present invention corresponding to claims 1 and 2. The feature of this example is the manufacturing method of the worm wheel 5b and the structure of the worm speed reducer that includes the worm wheel 5b. Since the structure and operation of the other parts are the same as in the case of the conventional structure described above, overlapping illustrations and explanations are omitted or simplified, and the following description will focus on the characteristic parts of this example.

  In the case of this example, prior to manufacturing the worm wheel 5b, an intermediate material 15a as shown in FIGS. The intermediate material 15a forms a bare tooth portion 16 at a portion to be the tooth portion 8b of the worm wheel 5b. The bare tooth portion 16 has a substantially constant tooth thickness T in the direction of the tooth trace, and a plurality of bare teeth 17, 17 arranged in a helical gear shape and these bare teeth adjacent in the circumferential direction. 17 and 17 are composed of connecting portions 13a and 13a that connect each other. In the case of this example, all of these connecting portions 13a, 13a are adjacent to each other in the circumferential direction at one end portion {the end portion on the back side in FIG. It is provided in a portion between the teeth 17 and 17.

  Further, in the case of this example, the intermediate material 15a having such a configuration is formed, for example, in the shape of a portion corresponding to the portion to be the bare tooth portion 16 in the inner surface of the cavity, such as a helical gear. A synthetic resin is made by injection molding using a mold (not shown) having a shape (the tooth position is biased to one axial side). Specifically, in a state where a metal sleeve (not shown) constituting the radial inner end and intermediate portion of the worm wheel 5b is installed inside the mold having such an inner surface shape, Synthetic resin is injection molded. Thereafter, the mold is removed while being slightly displaced in the twisting direction on the side opposite to the side in which the connecting portions 13a and 13a are formed (the front side in FIG. 1A). The intermediate material 15a is obtained. The intermediate material 15a formed in this way corresponds to the worm wheel 5a shown in FIG.

  If such an intermediate material 15a is formed, the intermediate material 15a is not used as a worm wheel as it is, and the tooth portion 8b is formed on the bare tooth portion 16 formed on the outer diameter side of the intermediate material 15a. Form. For this reason, in the case of this example, the machining worm 14 is used as a tool for machining the tooth portion 8b. That is, compared to the worm 3 (see FIGS. 4 and 5) meshed at the time of use, the tooth pitch P in the axial direction is the same, and the diameter dimensions of the tooth tip and the tooth base are each equal to or larger than { The tooth tips and bottoms are slightly larger (about 1 to 10%, more preferably about 1 to 3% with respect to the worm to be meshed during use)} Electrodeposition of abrasive grains (for example, diamond abrasive grains) on the surface of the worm The raw tooth portion 16 is processed by the processing worm 14 formed as described above.

  Specifically, as shown in FIGS. 2 (a) and 2 (b), the intermediate material 15a having the teeth 16 formed on the outer peripheral surface and the working worm 14 are respectively connected to the worm speed reducer. The processing worm 14 is pressed against the outer peripheral surface (synthetic resin 10 portion) of the intermediate material 15a while being rotated at a speed relationship corresponding to the reduction ratio. As a result, the tooth surfaces of the raw teeth 17, 17 constituting the raw tooth portion 16 are ground (or cut) by the working worm 14. In this grinding (or cutting) operation, the center-to-center distance between the processing worm 14 and the intermediate material 15a has a predetermined size (for example, the center-axis distance between the completed worm wheel and the worm in use). Do until. Then, by performing such processing, the tooth portion 8b is formed on the outer peripheral surface of the intermediate material 15a as shown in FIG.

  The tooth portion 8b formed in this manner is composed of a plurality of worm wheel teeth 9b, 9b and a plurality of connecting portions 13a, 13a as shown in FIG. Of these, the worm wheel teeth 9b, 9b each have a tooth surface that follows the tooth profile of the machining worm 14, and the thickness t at the middle of the tooth trace direction is the thickness T at both ends of the tooth trace direction. It is smaller than (t <T). Further, each of the connecting portions 13a and 13a is connected to the worm wheel teeth 9b and 9b adjacent in the circumferential direction, and one end portion of the worm wheel teeth 9b and 9b in the tooth line direction {FIG. ) At the back end}.

According to the manufacturing method of this example as described above, the worm wheel 5b not only can ensure the bending rigidity of the worm wheel teeth 9b, 9b, but can reduce the amount of wear during use, and has high shape accuracy and dimensional accuracy. Can be obtained.
That is, in the case of this example, by using a machining worm 14 having substantially the same shape and the same size as the worm 3 at the time of use, the element teeth 16 of the intermediate material 15a are adjacent to each other in the circumferential direction. Only the tooth surfaces of these raw teeth 17 and 17 can be ground (or cut) without scraping off the connecting portions 13a and 13a that connect the teeth 17 and 17 to each other. For this reason, also with respect to the worm wheel teeth 9b, 9b formed from these raw teeth 17, 17, the worm wheel teeth 9b, 9b adjacent in the circumferential direction are connected to each other by the connecting portions 13a, 13a. It becomes a state. Therefore, the bending rigidity of each of these worm wheel teeth 9b, 9b can be ensured.

  Further, in the case of this example, the tooth surfaces of the worm wheel teeth 9b, 9b can be processed into a shape along the tooth profile of the worm 3 in use (matching the tooth profile of the worm 3 in use). For this reason, the contact area between the worm wheel teeth 9b, 9b and the worm 3 in use can be increased, and the contact surface pressure between the worm wheel teeth 9b, 9b and the worm 3 in use can be reduced. Therefore, the wear amount of each of these worm wheel teeth 9b, 9b can be suppressed, and the generation of rattle noise can be effectively prevented.

  Furthermore, in the case of this example, since the final processing of each of the worm wheel teeth 9b, 9b is performed by the processing worm 14, of the respective raw teeth 17, 17 formed by injection molding, The portion with reduced accuracy due to deformation due to sink marks or the like can be scraped off by the processing worm 14. For this reason, the shape accuracy and dimensional accuracy of the tooth portion 8b of the worm wheel 5b finally obtained can be sufficiently increased.

  As described above, according to the manufacturing method of this example, not only the bending rigidity of the worm wheel teeth 9b and 9b can be secured, but also the wear amount can be suppressed, and the shape of the worm wheel teeth 9b and 9b can be reduced. The worm wheel 5b with sufficiently improved accuracy and dimensional accuracy can be obtained. Therefore, it is possible to improve the durability of the worm gear reducer incorporating the worm wheel 5b. In addition, since the meshing accuracy between the worm wheel teeth 9b, 9b and the worm 3 in use can be improved, rotational torque fluctuations and transmission errors of the worm speed reducer can be reduced, and generation of abnormal noise can be suppressed. , Ensuring quietness during use. When such a worm speed reducer is incorporated in an electric power steering device, the steering wheel can have a good steering feeling.

  Further, in the case of this example, the diameter of the tooth tip and the root of the working worm 14 is equal to or greater than that of the worm 3 at the time of use, so the teeth of the worm wheel teeth 9b and 9b are the same. It is possible to prevent the tip (tooth bottom) and the tooth bottom (tooth tip) of the worm 3 from interfering with each other. For this reason, it can avoid that the meshing part of the worm hole 5b and the worm 3 locks. Further, since a gap can always be formed between the tooth tip (tooth bottom) of each of the worm wheel teeth 9b, 9b and the tooth bottom (tooth tip) of the worm 3, a lubricant is provided between these parts. It is possible to improve the lubrication state of the meshing portion. As a result, the durability of the worm reducer can be more sufficiently ensured.

[Second Example of Embodiment]
FIG. 3 shows a second example of an embodiment of the present invention corresponding to claims 1 and 2. In the case of this example, among the plurality of bare teeth 17a, 17a constituting the bare tooth portion 16a of the intermediate material 15b, the neighboring teeth 17a, 17a in the circumferential direction are connected to each other of the bare teeth 17a, 17a. Connecting portions 13a provided alternately at one end portion in the tooth trace direction {the back side end portion in FIG. 3 (a)} and the other end portion in the tooth trace direction {the front end portion in FIG. 3 (a)}, 13b is mutually connected. In order to manufacture the intermediate material 15b having such a configuration, also in this example, the shape of the portion corresponding to the portion that should be the raw tooth portion 16a is formed on the inner surface of the cavity, such as a helical gear (tooth The synthetic resin is made by injection molding using a mold (not shown) having a shape in which the position of is alternately biased on both sides in the axial direction.

After the intermediate material 15b is formed in this manner, the intermediate material 15b is used by using the processing worm 14 (see FIGS. 2 and 9) as in the case of the first example of the embodiment described above. The raw tooth portion 16a is processed. And the tooth | gear part 8c which consists of several worm wheel teeth 9c and 9c and several connection parts 13a and 13b as shown in FIG.3 (b) is formed from this raw-tooth part 16a. In the case of the tooth portion 8c of the worm wheel 5c of this example having such a configuration, the connecting portions 13a and 13b are respectively connected to one end side and the other end side of the worm wheel teeth 9c and 9c in the tooth line direction. Since they are alternately arranged, the bending rigidity of each of the worm wheel teeth 9c, 9c can be increased as compared with the case of the first example of the embodiment described above.
Other configurations and operations are the same as those in the first example of the embodiment described above.

  When the present invention is carried out, the machining with the machining worm can be performed by dry machining and while the machining site is air-cooled. By processing in this way, even when a part of the synthetic resin is melted by processing at a high speed rotation, the melted portion can be blown off in the form of a film by rapid cooling. Therefore, the machining worm can be prevented from being clogged and the machining efficiency can be improved. Moreover, when implementing this invention, glass fiber can also be included in the synthetic resin part which comprises a worm wheel. If glass fiber is included in this way, the strength and rigidity can be further improved, and the durability of each worm wheel tooth constituted by this synthetic resin can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cut perspective view showing a first example of an embodiment of the present invention, where (a) shows an intermediate material and (b) shows a worm wheel. FIG. 10 is also a view corresponding to FIG. 9. The figure similar to FIG. 1 which shows the 2nd example of embodiment of this invention. Sectional drawing of the part incorporating a worm reduction gear among electric power steering devices. FIG. The partial front view which shows the state before processing the tooth | gear part of a worm wheel with a hob cutter which is an example of the conventional method. The fragmentary cutaway perspective view which shows the worm wheel of an example of the conventional structure. The fragmentary sectional view for demonstrating that the tooth | gear part provided with the connection part cannot be processed with the hob cutter larger diameter than the worm | warm at the time of use. It is a figure which shows the processing process of the conventional worm wheel, (a) is the state before grinding (or cutting) a worm wheel with a processing worm, (b) is a roll cross-section of (a), (c ) Shows the state after grinding (or cutting) with a working worm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Housing 3 Worm 4 Worm shaft 5, 5a-5c Worm wheel 6 Ball bearing 7 Output shaft 8, 8a-8c Tooth part 9, 9a-9c Worm wheel tooth 10 Synthetic resin 11 Steering shaft 12 Hob cutter 13, 13a, 13b Connecting part 14 Processing worm 15, 15a, 15b Intermediate material 16, 16a Raw tooth part 17, 17a Raw tooth

Claims (2)

  At least the surface layer part of the tooth part is made of a synthetic resin, and among the plurality of worm wheel teeth constituting the tooth part, the worm wheel teeth adjacent in the circumferential direction are in the direction of the streak of each worm wheel tooth. A method of manufacturing a worm wheel that is connected to each other at the ends, wherein the worm wheel has a constant tooth thickness in the direction of the teeth and is arranged in a helical gear shape at a portion that is to be a tooth portion of the worm wheel. A plurality of bare teeth, and among these bare teeth, neighboring teeth in the circumferential direction form a bare tooth portion that is connected to each other at the end of the tooth trace direction of each bare tooth. After the intermediate material is used, the abrasive grains are fixed to the surface of the worm having the same tooth pitch in the axial direction and the diameters of the tip and bottom of the tooth being equal to or greater than those of the worm to be meshed during use. Processing war Accordingly, processing the Motoha portion of the intermediate material, manufacturing method of a worm wheel.   A worm speed reducer comprising a worm and a worm wheel meshed with each other, wherein the worm wheel is produced by the worm wheel manufacturing method according to claim 1.

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