JP2002331423A - Method of manufacturing gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a gear capable of exhibiting superior efficiency at mass production time, and capable of generating an excellent generating tooth regardless of a construction material of a blank gear. SOLUTION: The blank gear 3 is ground by a double lead gear cutting worm 2 by preparing the double lead gear cutting worm 2 having a surface roughened gear cutting tooth 2a, and the blank gear 3 having a blank-shaped blank tooth 31 capable of meshing with the gear cutting tooth 2a. In this case, a relative position of the double lead gear cutting worm 2 and the blank gear 3 is changed so as to change a position where a tooth space of the blank toothr 31 meshes with a tooth thickness thick part from a tooth thickness thin part of the gear cutting tooth 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a gear. This manufacturing method is particularly suitable for use in manufacturing a worm wheel.

[0002]

2. Description of the Related Art For example, a worm speed reducer having a worm and a worm wheel is used in an electric steering apparatus in order to extremely reduce the rotational speed of an electric motor and amplify the rotational torque.

[0003] In the worm wheel used in the worm speed reducer, a tooth is created by mechanically grinding a metal material with a hob cutter. At this time, since it is difficult to manufacture the hob cutter having a small diameter close to the diameter of the worm meshing with the worm wheel, it is necessary to grind the material with a hob cutter having a diameter considerably larger than the diameter of the worm. Accordingly, a worm wheel as a generating gear having generating teeth can be obtained. For this reason, even if the worm wheel is created with high accuracy, in a product such as a worm reducer, the tooth surface of the worm tooth to be meshed with the worm wheel is the axial length of the tooth surface of the created tooth in the worm wheel. The point contact state occurs in the vicinity of the center, and theoretically, both tooth surfaces do not come into contact over a wide range evenly.

On the other hand, when the worm and the worm wheel of the product are engaged with each other, if the backlash of these teeth is large, it may cause the teeth to hit or vibrate, so that the backlash is preferably as small as possible. Are known.

[0005] Therefore, the following method of manufacturing a worm wheel can be performed on an actual product. That is, first, as a raw material, a blank wheel having blank-shaped blank teeth that can be engaged with the worm teeth for temporary assembly is manufactured in advance using resin. The temporary assembling worm and the blank wheel are assembled in such a manner that the worm and the blank wheel are slightly interfered with each other, for example, by setting a slightly smaller center distance between the worm and the blank wheel. In this state, when the blank teeth of the blank wheel were ground by wear to some extent by running-in, and the teeth came into contact with the worm teeth for provisional assembly, the creation of the worm wheel having the created teeth was completed. And The worm wheel thus obtained is assembled as a final product by selecting a worm for this assembling, which has a reduced backlash.

[0006]

However, according to the above-mentioned conventional manufacturing method, although the resin blank wheel is softer than the metal blank wheel, the teeth formed on the worm teeth for provisional assembly are different from the teeth formed on the worm for temporary assembly. Grinding the blank wheel until it comes into contact with the surface requires a considerably long running-in operation, and there is a concern about efficiency in mass production. Such a defect is not limited to the case where the generating gear to be generated is a worm wheel.

In this regard, it is conceivable to employ the method of manufacturing a resin gear with a bone described in Japanese Patent Application Laid-Open No. 2000-84747. In this manufacturing method, first, a gear cutting worm having tooth cutting teeth whose surface is roughened by abrasive grains is prepared. Further, as a raw material, a blank wheel having blank-shaped blank teeth that can mesh with the teeth of the gear cutting worm is manufactured in advance. This blank wheel includes a core made of a metal material and a surface layer made of a resin formed around the core. The blank tooth is covered by its surface. Then, the blank wheel is ground with a gear cutting worm. In this way, a worm wheel having a generating tooth is created.

[0008] According to the manufacturing method described in the publication, the surface of the gear tooth of the gear worm is roughened, and the tooth layer of the gear worm is used to grind the surface layer to create the tooth of the worm wheel. , Shortens the grinding time of the blank wheel,
It is thought that the efficiency at the time of mass production is improved. Further, it is considered that the durability of the obtained worm wheel is also improved because the tooth of the worm wheel is constituted by the surface layer portion made of resin and the core portion made of a metal material is present inside the surface portion.

However, in the manufacturing method described in the publication, the blank gear is ground by gradually reducing the distance between the center of the gear such as a gear worm and the blank gear such as a blank wheel. , The initial positions of the gears and the blank gears must be determined independently, and the gears must be driven to rotate and the blank gears must also be driven synchronously with it, which still has a problem with efficiency in mass production. There is.

In other words, if this is not the case, a defect due to an error in the relative position in the rotational direction between the gear and the blank gear extends to all the generated teeth, so that only one tooth surface of the blank tooth is gear-cut. This is because the teeth are ground or the created teeth are not good. In particular,
In the manufacturing method described in the publication, since the blank teeth consist of a core portion and a surface layer portion, if not, the core portion may be ground by a gear-cutting gear, and the gear-cutting gear may be consumed quickly. Would. Further, in the manufacturing method described in the publication, since the blank teeth are covered with an elastic surface layer, it is possible to forcefully engage the gear and the blank gear, but their interference amount is small. If it is too large, the torque in the opposite direction of the device that drives the two will also be applied,
It is not even possible to start the creation by rotating both.

Further, when it is desired to obtain a metal-made gear in consideration of strength and durability, the manufacturing method using a worm or the like for provisional assembly surely has poor grindability. Further, in that case, as in the manufacturing method described in the above publication, even if a tooth cutting gear having a roughened tooth cutting surface is used, the center distance between the tooth cutting gear and the blank gear is gradually reduced. If the grinding proceeds while reducing the size of the gear, the grinding performance of the gear is not sufficient. Therefore, the above two manufacturing methods cannot cope with such a case.

The above problem is not only when the generating gear to be created is a worm wheel, but when the creating gear is a worm wheel, the axis of the worm wheel is curved while being inclined with respect to the teeth of the worm wheel. This tendency is particularly large because the axis of the worm is curved while being greatly inclined with respect to the teeth of the worm.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and is capable of exhibiting excellent efficiency at the time of mass production, and capable of generating excellent generated teeth regardless of the material of the blank gear. It is an object of the present invention to provide a manufacturing method of the present invention.

[0014]

According to a method of manufacturing a gear of the present invention, a raw material and a toothed gear having toothed teeth having a roughened surface are prepared, and the raw material is ground with the toothed gear. By doing so, in a gear manufacturing method for creating a creation gear having creation teeth,

[0015] The tooth cutting gear is a double lead gear cutting in which the tooth cutting teeth change in the axial direction from a portion having a small tooth thickness (a portion having a large tooth groove) to a portion having a large tooth thickness (a portion having a large tooth groove). A gear having a blank tooth having a blank tooth having a blank shape capable of meshing with the tooth cutting tooth, wherein a tooth groove of the blank tooth has a large tooth thickness from a thin portion of the tooth cutting tooth. The relative position between the double reed gear and the blank gear is changed so as to change the position of engagement with the portion.

In the manufacturing method of the present invention, first, a thin portion of the tooth cutting tooth of the double lead gear is simply inserted into the tooth groove of the blank tooth of the blank gear. As a result, the initial positions of the double lead gear and the blank gear are determined. Thereafter, the grinding can be started by rotating and driving the multiple-lead toothed gear and the blank gear is driven by the multiple-lead toothed gear. This allows
The blank tooth is ground while receiving substantially the same pressure by both tooth surfaces of the thin tooth portion of the incisor, and the creation of a new tooth proceeds. And, by changing the relative position between the double lead gear and the blank gear as the grinding progresses,
The blank tooth is ground while still under substantially equal pressure by both tooth surfaces of the thicker part of the incisor and the creation of the created tooth can be completed.

Thus, in this manufacturing method, the initial positions of the gear and the blank gear can be easily determined, and there is no need to synchronously rotate the gear and the blank gear. Even in this case, since the blank tooth is ground while receiving substantially the same pressure by both tooth surfaces of the tooth cutting tooth, the error in the relative position of the tooth cutting gear and the blank gear in the rotational direction is automatically determined. It is absorbed and does not cause defects in all the generated teeth. For this reason, the efficiency at the time of mass production is surely improved.

Further, in this manufacturing method, since a blank gear having blank teeth is used and the blank gear is ground by a gear having teeth which are roughened, the grinding time of the generating gear is reduced. And the efficiency in mass production is improved. Even if the gear and the blank gear are forcibly engaged, if the gear is rotated in this state,
Since the blank gear simply follows the gear, the creation can be started easily.

Furthermore, in this manufacturing method, even when it is desired to obtain a metal generating gear in consideration of strength and durability, the grinding of the blank gear proceeds while the blank teeth mesh with the gear cutting teeth of the gear cutting gear. , The gears show high grindability,
That case can be dealt with.

Therefore, according to the manufacturing method of the present invention,
Excellent efficiency can be exhibited during mass production, and good formed teeth can be created regardless of the material of the blank gear.

In order to adjust the surface roughness of the tooth incisor, a first means for applying a shot blast or the like to at least the tooth surface of the tooth incisor to roughen it, and a first means for coating a hard coating after the first means. 2
Means, the third means for fixing the abrasive grains, etc. can be adopted. According to the test results of the inventors, when manufacturing a worm wheel used for a worm reduction gear of an electric steering device, as a second means, shot blasting is performed with shot grains of 0.1 mm or less, and thereafter, It is preferable to apply a Ti-based coating such as TiN or a Cr-based coating such as hard chrome plating by a PVD method or the like. In this case, it is also preferable to electrodeposit abrasive grains of 0.2 mm or less as a third means.

It is preferable that the tooth incisors have a small surface roughness from a portion having a small tooth thickness to a portion having a large tooth thickness. In this case, it is possible to simultaneously improve the grindability and finish the tooth surface of each newly created tooth.

The effect of the present invention is great when the double lead gear is a worm. In this case, the generating gear is a worm wheel. In this case, the change of the relative position between the multiple-lead toothed gear and the blank gear can be performed by moving the multiple-lead toothed gear in the axial direction. It is preferable that the movement in the axial direction be equal to or less than the difference between the lead of the tooth cutting teeth at both ends of the multiple-lead toothed gear with respect to one rotation of the multiple-lead toothed gear. As a result, each generating tooth of the generating gear is ground at least once by the same portion of the tooth cutting tooth of the multiple-lead tooth cutting gear, and no excessive force acts on the generating tooth.
The tooth surface of the created tooth becomes good.

As the blank gear, a gear made of a metal material, a gear made of an easy-to-cut material that can be easily ground, and the like can be used. When a blank gear made of a metal material is employed, a material such as a metal material may be mechanically ground using a hob cutter. According to the blank gear, the durability of the generated gear is improved, although the machinability when implementing the present invention is inferior. On the other hand, when a blank gear made of an easy-to-cut material is used, the blank gear can be roughly formed of the easy-to-cut material. According to this blank gear, the durability of the generating gear is inferior, but the cutting gear and the quietness when implementing the present invention are excellent. As the easy-cutting material, for example, a resin can be adopted.

For this reason, it is preferable to employ a blank gear that can form at least a newly formed tooth by a surface layer portion made of an easily-cuttable material. In this case, since the surface layer can be easily ground, the grinding time of the generating gear is further reduced, and the efficiency in mass production is further improved. Also,
More preferably, the blank gear comprises a core made of a metal material and a surface layer made of resin as an easily-cuttable material formed around the core. If this is the case, while being excellent in the machinability and quietness when implementing the present invention,
The durability of the generating gear is improved. Further, if the blank teeth are covered with an elastic surface layer, it is possible to forcibly mesh the gears with the blank gears to some extent. Is simply driven by the gear, so creation can be easily started.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a worm wheel manufacturing method will be described below with reference to the drawings.

The worm wheel to be manufactured is used for a worm reduction gear of an electric steering device. First, as shown in FIG. 1, a double lead worm 1 meshable with a worm wheel 3 (see FIG. 4) to be manufactured.
Is obtained with a hob cutter or the like. This double lead worm 1
Is changed from a portion where the tooth 1a is thin in the axial direction (a portion where the tooth space is large) to a portion where the tooth 1a is thick (a portion where the tooth space is large).

In order to adjust the surface roughness of the teeth 1a of the double lead worm 1, the teeth 1a are formed with shot grains of 0.1 mm or less.
Is subjected to shot blasting to roughen the surface, and thereafter, the teeth 1a are coated with a Ti-based coating such as TiN or a Cr-based coating such as hard chrome plating by a PVD method.
Further, abrasive grains of 0.2 mm or less may be electrodeposited on the teeth 1a. At this time, the surface roughness is made finer from the portion having the smaller tooth thickness to the portion having the larger tooth thickness (the abrasive particle diameter is reduced if the abrasive particles are electrodeposited). Thus, the multi-lead toothed worm 2 shown in FIG. 2 is obtained. Also in this double-lead tooth cutting worm 2, the tooth cutting teeth 2a are changed in the axial direction from a portion having a small tooth thickness (a portion having a large tooth groove) to a portion having a large tooth thickness (a portion having a small tooth groove). Double lead gear cutting worm 2
A rough surface 2b made of a hard film or abrasive grains is formed on the surface of the tooth cutting tooth 2a.

On the other hand, as shown in FIG. 3, a blank gear 3 having blank-shaped blank teeth 31 that can mesh with the gear teeth 2a of the double-lead gear worm 2 is prepared as a material. The blank gear 3 includes a core 3a made of a metal material and a surface layer 3b made of a resin formed around the core 3a. The surface portion 3b has a thickness that can form a newly formed tooth.

At the time of grinding, first, a thin portion of the tooth cutting tooth 2a of the double lead cutting worm 2 is simply inserted into the tooth groove of the blank tooth 31 of the blank gear 3. Thus, the initial positions of the double-lead gear worm 2 and the blank gear 3 are determined. Thereafter, the double lead gear worm 2 is rotationally driven by a device (not shown), and the blank gear 3 is driven by the double lead gear worm 2. At this time, since the blank teeth 3 are covered with the elastic surface layer 3b, it is possible to forcibly mesh the double-lead toothed worm 2 and the blank gear 3 to some extent. If the gear worm 2 is rotationally driven, the blank gear 3 simply follows the double lead gear worm 2, so that the creation can be started easily. When the grinding is started in this manner, the blank teeth 31 are ground while receiving substantially the same pressure by the two tooth surfaces of the thin tooth portion of the gear incisor 2a, and the creation of a created tooth proceeds.

As the grinding progresses, as shown in FIG. 4, the multiple lead cutting worm 2 is advanced in the axial direction, and the relative position between the multiple lead cutting worm 2 and the blank gear 3 is changed. At this time, the axial movement of the multiple-lead toothed worm 2 is less than or equal to the difference between the lead of the gear teeth 2a at both ends of the multiple-lead toothed worm 2 with respect to one rotation of the multiple-lead toothed worm 2. . Thus, the blank tooth 3 is ground while still receiving substantially the same pressure by both tooth surfaces of the thick tooth portion of the tooth cutting tooth 2a, and the creation of the creation tooth 31 is completed. During this time, in this manufacturing method, since the surface roughness of the tooth incisor 2a is reduced from the portion having a small tooth thickness to the portion having a large tooth thickness, the grindability is improved and the tooth surface of each generating tooth 31 is finished. Can be simultaneously realized. In addition, worm wheel 3
Of the multiple-incision worm 2
The grinding is performed at least once by the same part of a, and no excessive force acts on the generating tooth 31, and the tooth surface of the generating tooth 31 is improved. Thus, the worm wheel 3 to be manufactured is obtained.

Thus, in this manufacturing method, the initial positions of the double-lead gear cutting worm 2 and the blank gear 3 are easily determined, and the double-lead gear cutting worm 2 and the blank gear 3 are synchronously driven to rotate. No need. Even in this case, since the blank teeth 3 are ground while receiving substantially the same pressure by both tooth surfaces of the gear cutting teeth 2a, the relative position of the double-lead gear cutting worm 2 and the blank gear 3 in the rotational direction is reduced. Are automatically absorbed, and no defects are generated in all the generated teeth 31.

In this manufacturing method, the blank teeth 31
The worm wheel 3 is formed by grinding the blank gear 3 using a double-lead cutting worm 2 having a tooth cutting tooth 2a having a roughened surface.
Grinding time is reduced.

Further, in this manufacturing method, since the blank gear 3 can form the generating teeth 31 by the surface layer portion 3b made of resin, the surface layer portion 3b can be easily ground. It is shorter and the efficiency in mass production is further improved. In addition, since the blank gear 3 is employed, the worm wheel 3 is improved in cutability and quietness, and the durability of the worm wheel 3 is improved.

Therefore, according to this production method, it is possible to produce the worm wheel 3 having excellent generating teeth 31 while exhibiting excellent efficiency in mass production.

The worm wheel 3 obtained is assembled as a worm reduction gear of an electric steering device by selecting a predetermined worm.

When the worm wheel is manufactured by the present manufacturing method, the material is not limited to the one composed of the core part 3a made of a metal material and the surface part 3b made of a resin.
It may be an integrated metal material or resin. For example, a helical gear may be manufactured by molding, for example, a sintered metal or resin that is not processed by a hob cutter, and a portion that meshes with a worm in a worm speed reducer or the like may be processed by the double-lead gear cutting worm 2. . In this case, the effect of reducing the manufacturing cost is increased.

The double lead worm 2 has a rough surface 2b formed on the teeth 1a of the double lead worm 1 which can be engaged with the worm wheel 3 to be manufactured. Also have a slightly larger outer diameter. Because of this, it does n’t really matter,
The resulting worm wheel 3 may have a slightly larger backlash with the multiple lead worm 1. If the backlash poses a problem, a double-lead cutting worm in which the rough surface 2b is formed on a double-lead worm whose diameter is reduced by the thickness of the rough surface 2b can be adopted.

[Brief description of the drawings]

FIG. 1 is a perspective view of a multiple lead worm according to an embodiment.

FIG. 2 is a perspective view of a multi-lead gear cutting worm according to the embodiment.

FIG. 3 is an enlarged partial cross-sectional view of a double-lead gear cutting worm and a blank gear in an initial stage of grinding according to the embodiment.

FIG. 4 is an enlarged partial cross-sectional view of a double-lead gear worm and a blank gear at the end of grinding according to the embodiment.

[Explanation of symbols]

2 ... gear cutting gear (multi-lead gear cutting worm) 2a ... gear cutting tooth 2b ... rough surface 3 ... material, generating gear (blank gear, worm wheel) 31 ... generating tooth, blank tooth 3a ... core 3b ... surface layer

Continuation of the front page (72) Inventor Yoshiharu Inakuma 1-1-1, Asahi-cho, Kariya-shi, Aichi Prefecture Inside Toyota Machine Works Co., Ltd.

Claims (5)

[Claims] A material and a toothed gear having toothed teeth with a roughened surface are prepared, and the material is ground with the toothed gear to create a toothed gear with toothed teeth. In the method for manufacturing a gear, the gear cutting gear is a double-lead gear cutting gear in which the gear cutting teeth change from a thinner portion to a thicker portion in the axial direction, and the material is the gear cutting gear. A blank gear having a blank tooth having a blank shape capable of meshing with a tooth, wherein a position where a tooth groove of the blank tooth meshes from a thin portion of the tooth cutting tooth to a thick portion of the tooth cutting tooth is changed. A method of manufacturing a gear, characterized by changing a relative position between the double-lead toothed gear and the blank gear. 2. The gear manufacturing method according to claim 1, wherein the tooth incisors have a small surface roughness from a portion having a small tooth thickness to a portion having a large tooth thickness. 3. The method according to claim 1, wherein the double lead gear is a worm. 4. The blank gear according to claim 1, wherein at least the newly formed teeth can be constituted by a surface layer portion made of an easy-to-cut material which is a material which can be easily ground.
4. The method for manufacturing a gear according to 2 or 3. 5. The gear according to claim 4, wherein the blank gear comprises a core made of a metal material and a surface layer made of a resin as an easily-cuttable material formed around the core. Manufacturing method.