JP5958145B2

JP5958145B2 - Electric power steering apparatus and manufacturing method thereof

Info

Publication number: JP5958145B2
Application number: JP2012162340A
Authority: JP
Inventors: 晴彦清田
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 2012-07-23
Filing date: 2012-07-23
Publication date: 2016-07-27
Anticipated expiration: 2032-07-23
Also published as: JP2014019376A

Description

この発明の対象となる電動式パワーステアリング装置は、自動車の操舵装置として利用するもので、電動モータを補助動力として利用する事により、運転者がステアリングホイールを操作する為に要する力の軽減を図るものである。本発明は、この様な電動式パワーステアリング装置を構成するウォームホイールの構造及びその製造方法を改良して、小型且つ軽量の構造を低コストで実現する事を意図したものである。 The electric power steering apparatus that is the object of the present invention is used as a steering apparatus for an automobile. By using an electric motor as auxiliary power, a driver can reduce the force required to operate the steering wheel. Is. The present invention is intended to improve the structure of the worm wheel constituting such an electric power steering apparatus and the manufacturing method thereof to realize a small and lightweight structure at a low cost.

操舵輪（フォークリフト等の特殊車両を除き、通常は前輪）に舵角を付与する際に、運転者がステアリングホイールを操作する為に要する力の軽減を図る為の装置として、パワーステアリング装置が広く使用されている。又、この様なパワーステアリング装置で、補助動力源として電動モータを使用する電動式パワーステアリング装置も、近年普及し始めている。電動式パワーステアリング装置は、油圧式のパワーステアリング装置に比べて、小型・軽量にでき、補助動力の大きさ（トルク）の制御が容易で、しかもエンジンの動力損失が少ない等の利点がある。 Power steering devices are widely used as devices for reducing the force required for the driver to operate the steering wheel when giving a steering angle to the steered wheels (usually the front wheels except for special vehicles such as forklifts). It is 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. Compared with a hydraulic power steering device, the electric power steering device is advantageous in that it can be made smaller and lighter, can easily control the magnitude (torque) of auxiliary power, and has less engine power loss.

電動式パワーステアリング装置の構造は、各種知られているが、何れの構造の場合でも、ステアリングホイールの操作によって回転させられ、回転に伴って操舵輪に舵角を付与する回転軸に、電動モータの補助動力を、減速機を介して付与する。この減速機として一般的には、ウォーム減速機が使用されている。ウォーム減速機を使用した電動式パワーステアリング装置の場合、前記電動モータにより回転駆動されるウォームと、前記回転軸と共に回転するウォームホイールとを噛合させて、前記電動モータの補助動力をこの回転軸に伝達自在とする。 Various structures of the electric power steering apparatus are known. In any structure, the electric motor is mounted on the rotating shaft that is rotated by the operation of the steering wheel and gives a steering angle to the steered wheels in accordance with the rotation. The auxiliary power is applied through a reduction gear. In general, a worm reducer is used as the reducer. In the case of an electric power steering device using a worm speed reducer, a worm that is rotationally driven by the electric motor and a worm wheel that rotates together with the rotating shaft are engaged with each other, and auxiliary power of the electric motor is applied to the rotating shaft. Communicate freely.

例えば特許文献１には、図１３〜１４に示す様な、電動式パワーステアリング装置が開示されている。ステアリングホイール１により所定方向に回転させられる、回転軸であるステアリングシャフト２の前端部は、ハウジング３の内側に回転自在に支持しており、この部分にウォームホイール４を固定している。このウォームホイール４と噛合するウォーム歯５をウォーム軸６の軸方向中間部に設け、電動モータ７により回転駆動されるウォーム８の両端部は、深溝型玉軸受等の１対の転がり軸受９ａ、９ｂにより、前記ハウジング３内に回転自在に支持されている。そして、この状態で、前記ウォームホイール４と前記ウォーム歯５とを噛合させて、前記電動モータ７の補助動力を、このウォーム４に伝達可能としている。 For example, Patent Literature 1 discloses an electric power steering device as shown in FIGS. A front end portion of a steering shaft 2 that is a rotating shaft that is rotated in a predetermined direction by the steering wheel 1 is rotatably supported inside the housing 3, and the worm wheel 4 is fixed to this portion. Worm teeth 5 meshing with the worm wheel 4 are provided in the axial direction intermediate portion of the worm shaft 6, and both ends of the worm 8 driven to rotate by the electric motor 7 are paired with a pair of rolling bearings 9 a such as a deep groove ball bearing, 9b is rotatably supported in the housing 3. In this state, the worm wheel 4 and the worm teeth 5 are engaged with each other so that the auxiliary power of the electric motor 7 can be transmitted to the worm 4.

電動式パワーステアリング装置のより具体的な構造に就いて、図１５に示す。ウォームホイール４ａは、この電動式パワーステアリング装置の出力部となる回転軸１０に、１対の転がり軸受１１ａ、１１ｂの間部分で締り嵌め等により外嵌固定し、この回転軸１０と共に回転する様にしている。この回転軸１０はハウジング３ａ内に、前記両転がり軸受１１ａ、１１ｂにより、回転のみ自在に支持した状態で、トーションバー１２により、ステアリングシャフト２ａの前端部と結合している。電動モータ７（図１３〜１４参照）は、トルクセンサ１３が検出する、前記ステアリングシャフト２ａに加えられるトルクの方向及び大きさに応じてウォーム８ａを回転駆動し、前記回転軸１０の補助トルクを付与する。この回転軸１０の回転は、１対の自在継手１４ａ、１４ｂ及び中間シャフト１５を介して、ステアリングギヤユニット３０の入力軸に伝達し、操舵輪に所望の舵角を付与する。 FIG. 15 shows a more specific structure of the electric power steering apparatus. The worm wheel 4a is externally fixed to the rotary shaft 10 serving as an output portion of the electric power steering device by an interference fit between a pair of rolling bearings 11a and 11b, and rotates together with the rotary shaft 10. I have to. The rotary shaft 10 is coupled to the front end portion of the steering shaft 2a by a torsion bar 12 in a state in which only the rotation is supported by the rolling bearings 11a and 11b in the housing 3a. The electric motor 7 (see FIGS. 13 to 14) rotates the worm 8 a according to the direction and magnitude of the torque applied to the steering shaft 2 a detected by the torque sensor 13, and generates auxiliary torque for the rotating shaft 10. Give. The rotation of the rotating shaft 10 is transmitted to the input shaft of the steering gear unit 30 via the pair of universal joints 14a and 14b and the intermediate shaft 15, and gives a desired steering angle to the steered wheels.

上述の様な電動式パワーステアリング装置を構成するウォームホイール４ａは、製造コストの低廉化と軽量化とを目的として、金属製のホイール部１６の周囲に合成樹脂製の歯部１７を結合固定した構造を採用している。この様に、金属製のホイール部と合成樹脂製の歯部とを組み合わせたウォームホイールに関して記載した刊行物として、特許文献２〜５が存在する。このうちの特許文献２、３には、金属製のリム部の周囲に歯部を、合成樹脂を射出成形により結合する事が記載されている。又、特許文献４、５には、金属製のホイール部の周囲に設けた合成樹脂部分に削り加工を施す事により、この合成樹脂部分に歯部を設ける事が記載されている。更に、特許文献６〜８には、電動式パワーステアリング装置用のウォームホイールではないが、金属製のホイール部の周囲に合成樹脂製の歯部を、高周波誘導加熱により溶着する事が記載されている。 In the worm wheel 4a constituting the electric power steering device as described above, a synthetic resin tooth portion 17 is coupled and fixed around the metal wheel portion 16 for the purpose of reducing the manufacturing cost and reducing the weight. The structure is adopted. As described above, Patent Documents 2 to 5 exist as publications relating to a worm wheel in which a metal wheel portion and a synthetic resin tooth portion are combined. Of these, Patent Documents 2 and 3 describe joining a tooth portion around a metal rim portion and synthetic resin by injection molding. Patent Documents 4 and 5 describe that a tooth portion is provided in the synthetic resin portion by cutting the synthetic resin portion provided around the metal wheel portion. Further, Patent Documents 6 to 8 describe that although not a worm wheel for an electric power steering device, a synthetic resin tooth portion is welded around a metal wheel portion by high frequency induction heating. Yes.

図１５に示した従来構造の場合、前記回転軸１０に前記ホイール部１６を外嵌固定する作業が面倒なだけでなく、嵌合強度を確保する為に、このホイール部１６の軸方向寸法（厚さ）を、このホイール部１６に必要とされる以上に大きくせざるを得ない。この為、前記回転軸１０を支持している前記両転がり軸受１１ａ、１１ｂ同士のピッチが必要以上に大きくなり、電動式パワーステアリング装置の小型・軽量化を図る面から不利になる。特許文献２、３に記載された構造の場合、ホイール部の内径寄り部分の厚さ寸法を、外周縁部の厚さ寸法よりも小さくしている。但し、前記特許文献２、３に記載された構造の場合には、前記ホイール部と合成樹脂製の歯部とを、この歯部の射出成形時に結合するものである為、製造装置が複雑になる等の不利益がある。又、特許文献４〜８に記載された技術は、上述した小型・軽量化の要求に応えられるものではない。 In the case of the conventional structure shown in FIG. 15, not only is the work of externally fitting and fixing the wheel portion 16 to the rotating shaft 10, but also the axial dimension ( The thickness) must be larger than required for the wheel portion 16. For this reason, the pitch between the rolling bearings 11a and 11b supporting the rotating shaft 10 becomes larger than necessary, which is disadvantageous in terms of reducing the size and weight of the electric power steering apparatus. In the case of the structure described in Patent Documents 2 and 3, the thickness dimension of the portion near the inner diameter of the wheel portion is made smaller than the thickness dimension of the outer peripheral edge portion. However, in the case of the structures described in Patent Documents 2 and 3, since the wheel part and the synthetic resin tooth part are joined at the time of injection molding of the tooth part, the manufacturing apparatus is complicated. There are disadvantages such as. In addition, the techniques described in Patent Documents 4 to 8 do not meet the above-described demand for reduction in size and weight.

特開２０１１−０９４７６３号公報JP 2011-094763 A 特開２００６−２７３１２１号公報JP 2006-273121 A 特開２００７−２１６７２１号公報JP 2007-216721 A 特開２００９−０７２８４１号公報JP 2009-072841 A 特開２０１０−０２３１３５号公報JP 2010-023135 A 特開昭５２−０２５８７３号公報JP 52-025873 A 特開２００３−１１８００６号公報JP 2003-118006 A 特開２００４−２８６１７９号公報JP 2004-286179 A

本発明は、上述の様な事情に鑑みて、小型且つ軽量の電動式パワーステアリング装置を低コストで実現できる構造及びその製造方法を実現すべく発明したものである。 In view of the above-described circumstances, the present invention has been invented to realize a structure capable of realizing a small and lightweight electric power steering apparatus at a low cost and a manufacturing method thereof.

本発明の電動式パワーステアリング装置及びその製造方法のうち、請求項１に記載した電動式パワーステアリング装置の発明は、ハウジングと、回転軸と、ウォームホイールと、ウォームと、電動モータとを備える。
このうちのハウジングは、固定の部分に支持されて回転しない。
又、前記回転軸は、このハウジングに対し回転自在に設けられて、ステアリングホイールの操作により回転させられ、回転に伴って操舵輪に舵角を付与する。
又、前記ウォームホイールは、前記ハウジングの内部でこの回転軸の一部に、この回転軸と同心に支持されて、この回転軸と共に回転する。
又、前記ウォームは、ウォーム軸の軸方向中間部にウォーム歯を設けて成り、このウォーム歯を前記ウォームホイールと噛合させた状態で、前記ハウジングに対し回転自在に支持されている。
更に、前記電動モータは、前記ウォームを回転駆動する。 Of the electric power steering apparatus and the manufacturing method thereof according to the present invention, the electric power steering apparatus according to claim 1 includes a housing, a rotating shaft, a worm wheel, a worm, and an electric motor.
Of these, the housing is supported by a fixed portion and does not rotate.
The rotating shaft is rotatably provided with respect to the housing, and is rotated by an operation of a steering wheel, and gives a steering angle to the steered wheels as it rotates.
The worm wheel is supported on a part of the rotating shaft inside the housing, concentrically with the rotating shaft, and rotates together with the rotating shaft.
The worm is formed by providing worm teeth at an axially intermediate portion of the worm shaft, and is supported rotatably with respect to the housing in a state where the worm teeth are engaged with the worm wheel.
Further, the electric motor rotationally drives the worm.

特に、本発明の電動式パワーステアリング装置に於いては、前記ウォームホイールを、円輪状のホイール部と、このホイール部の周囲にこのホイール部と同心に設けられて、このホイール部の外周面に溶着された合成樹脂製の歯部とから成るものとしている。又、このホイール部と前記回転軸とを金属材により一体に構成している。
又、前記回転軸を、中空円管状に構成しており、その内周面のうち、軸方向に関して前記ホイール部と整合する部分に、径方向外側に向けて凹んだ凹部を設けている。
更に、前記ホイール部の軸方向に関する厚さ寸法は、前記歯部若しくはこの歯部となるべき中間素材を溶着固定する為、外径側端部に全周に亙って設けられたリム部で大きく、このリム部よりも内径寄り部分で軸方向側面から凹入される状態で形成された肉盗み部に対応する部分で小さくなっている。
In particular, in the electric power steering apparatus according to the present invention, the worm wheel is provided on the outer peripheral surface of the wheel portion, and the wheel portion is provided concentrically with the wheel portion around the wheel portion. It consists of the synthetic resin tooth part welded. Further, the wheel portion and the rotating shaft are integrally formed of a metal material.
Moreover, the said rotating shaft is comprised by the hollow circular tube, The recessed part dented toward the radial direction outer side is provided in the part which aligns with the said wheel part about the axial direction among the internal peripheral surfaces.
Further, the thickness in the axial direction of the wheel unit, the intermediate material should be the teeth or the teeth for welded and fixed at the rim portion provided over the entire periphery on the outer diameter side end portion Larger than the rim portion, it is smaller at a portion corresponding to the meat stealing portion formed in a state of being recessed from the axial side surface at a portion closer to the inner diameter.

この様な本発明を実施する場合に、例えば請求項２に記載した発明の様に、前記肉盗み部を、前記リム部の軸方向片面にのみ設ける。
この様な請求項２に記載した発明を実施する場合に好ましくは、請求項３に記載した発明の様に、前記肉盗み部を、前記ホイール部の側面に全周に亙って設ける。そして、前記ハウジングに対して前記回転軸を回転自在に支持する転がり軸受の一部を、前記肉盗み部の内部に入り込ませる。
或いは、上述の様な請求項２に記載した発明を実施する場合に、例えば請求項４に記載した発明の様に、前記肉盗み部を、前記ホイール部の軸方向片面の開口部の幅が最も広く、奥部に向かうに従って漸次狭くなる形状（断面Ｖ字形）とする事もできる。
又は、本発明を実施する場合に、請求項５に記載した発明の様に、前記肉盗み部を、前記リム部の軸方向両面に設ける事もできる。 When implementing the present invention as described above, the meat stealing portion is provided only on one surface in the axial direction of the rim portion, for example, as in the invention described in claim 2.
In the case of carrying out the invention described in claim 2, preferably, the meat stealing portion is provided on the side surface of the wheel portion over the entire circumference as in the invention described in claim 3. And a part of rolling bearing which supports the said rotating shaft rotatably with respect to the said housing is made to enter the inside of the said meat stealing part.
Alternatively, when carrying out the invention described in claim 2 as described above, for example, as in the invention described in claim 4, the width of the opening portion of the wheel portion on one side in the axial direction of the meat stealing portion is set. It is also possible to have the shape that is the widest and gradually narrows toward the back (V-shaped cross section).
Or when implementing this invention, like the invention described in Claim 5, the said meat stealing part can also be provided in the axial direction both surfaces of the said rim | limb part.

又、請求項６に記載した、電動式パワーステアリング装置の製造方法に関する発明は、前記リム部に前記歯部若しくはこの歯部となるべき中間素材を外嵌し、この歯部若しくはこの歯部となるべき中間素材の周囲に高周波誘導コイルを配置すると共に、前記回転軸を径方向及び軸方向の位置決めを図って保持した状態で、前記高周波誘導コイルに通電して前記リム部を発熱させ、このリム部の外周面と前記歯部若しくはこの歯部となるべき中間素材の内周面とを溶着する。 According to a sixth aspect of the present invention, there is provided an electric power steering apparatus manufacturing method, wherein the rim portion is externally fitted with the tooth portion or an intermediate material to be the tooth portion, and the tooth portion or the tooth portion. A high-frequency induction coil is arranged around the intermediate material to be formed, and the rim portion is heated by energizing the high-frequency induction coil in a state where the rotary shaft is positioned in the radial direction and the axial direction. The outer peripheral surface of the rim portion is welded to the tooth portion or the inner peripheral surface of the intermediate material to be the tooth portion.

この様な本発明の電動式パワーステアリング装置の製造方法を実施する場合に、例えば請求項７に記載した発明の様に、前記回転軸の一部で前記ホイール部に隣接する部分に設けられた、この回転軸を前記ハウジング内に回転自在に支持する為の転がり軸受の内輪を外嵌固定する為の内輪嵌合部をチャックにより把持する。そして、前記回転軸の径方向に関する位置決めを図ると共に、このチャックの軸方向端面を前記内輪嵌合部の端部に存在する段差面に突き当てて、前記回転軸の軸方向に関する位置決めを図る。更に、この状態で、前記高周波誘導コイルの内周面と前記リム部の外周面とを、前記歯部若しくはこの歯部となるべき中間素材を介して径方向に対向させる。
When carrying out such a method for manufacturing an electric power steering apparatus according to the present invention, for example, as in the invention described in claim 7, the rotating shaft is provided in a part adjacent to the wheel part. , to grip the inner fitting portion for the rotary shaft fitted to the inner ring of the rolling bearing for rotatably supporting in the housing and fixed by a chuck. Then, positioning in the radial direction of the rotating shaft is attempted, and the axial end surface of the chuck is abutted against a step surface existing at the end of the inner ring fitting portion, thereby positioning in the axial direction of the rotating shaft. Further, in this state, the inner peripheral surface of the high-frequency induction coil and the outer peripheral surface of the rim portion are opposed to each other in the radial direction via the tooth portion or an intermediate material to be the tooth portion.

或いは、請求項８に記載した発明の様に、前記回転軸を中空円管状とする。そして、この回転軸の両端開口部に、互いに対向する先端部を円すい状の凸面としたセンタリング治具の先端部を挿入して、前記回転軸の径方向及び軸方向の位置決めを図る。更に、この状態で、前記高周波誘導コイルの内周面と前記リム部の外周面とを、前記歯部若しくはこの歯部となるべき中間素材を介して径方向に対向させる。 Or like the invention described in Claim 8, the said rotating shaft is made into a hollow circular tube. And the front-end | tip part of the centering jig which made the front-end | tip part which mutually opposes into a conical convex surface is inserted in the both-ends opening part of this rotating shaft, and the radial direction and axial direction positioning of the said rotating shaft are aimed at. Further, in this state, the inner peripheral surface of the high-frequency induction coil and the outer peripheral surface of the rim portion are opposed to each other in the radial direction via the tooth portion or an intermediate material to be the tooth portion.

更には、請求項９に記載した発明の様に、前記リム部の外周面と前記歯部若しくはこの歯部となるべき中間素材の内周面とを溶着する為にこのリム部を前記高周波誘導コイルへの通電に基づいて発熱させる際に、前記回転軸の一部に別の高周波誘導コイルにより高周波焼き入れ処理を施す事もできる。この高周波焼き入れ処理を施す部分としては、例えば、前記回転軸と別の回転軸とをトルク伝達可能に結合する自在継手のヨークの基部を外嵌固定する為に前記回転軸の端部に設けたセレーション部がある。 Furthermore, as in the invention described in claim 9, the rim portion is used for the high frequency induction in order to weld the outer peripheral surface of the rim portion and the tooth portion or the inner peripheral surface of the intermediate material to be the tooth portion. When heat is generated based on energization of the coil, high-frequency quenching can be performed on a part of the rotating shaft by another high-frequency induction coil. As the part to be subjected to the induction hardening process, for example, it is provided at the end of the rotary shaft in order to externally fix and fix the base of the universal joint that couples the rotary shaft and another rotary shaft so as to transmit torque. There is a serration section.

上述の様に構成する本発明の電動式パワーステアリング装置及びその製造方法は、小型且つ軽量の構造を低コストで実現できる。
即ち、回転軸とホイール部とを一体とし、しかもこのホイール部の軸方向に関する厚さ寸法を、径方向外端部で大きく、内径寄り部分で小さくしているので、歯部若しくはこの歯部となるべき中間素材の軸方向に関する幅寸法、並びに、前記回転軸とウォームホイールとの結合強度を確保しつつ、このウォームホイールの肉厚の低減による軽量化を図れる。又、前記ホイール部の内径寄り部分に設けた肉盗み部に、電動式パワーステアリングホイールを構成する他の部分を配置できる為、この分の小型化も図れる。更に、前記ホイール部と前記歯部若しくはこの歯部となるべき中間素材とを高周波誘導加熱により溶着する為、歯部若しくはこの歯部となるべき中間素材を、射出成形と同時にホイール部に結合固定する場合の様に、複雑な設備が不要になり、製造コストを抑える事もできる。 The electric power steering device and the manufacturing method thereof according to the present invention configured as described above can realize a small and lightweight structure at low cost.
That is, since the rotating shaft and the wheel portion are integrated, and the thickness dimension in the axial direction of the wheel portion is large at the radially outer end portion and small at the inner diameter side portion, the tooth portion or the tooth portion It is possible to reduce the weight of the worm wheel by reducing the thickness of the worm wheel while ensuring the width dimension of the intermediate material in the axial direction and the coupling strength between the rotating shaft and the worm wheel. Moreover, since the other part which comprises an electrically driven power steering wheel can be arrange | positioned in the meat stealing part provided in the inner diameter side part of the said wheel part, the size reduction of this part can also be achieved. Furthermore, in order to weld the wheel part and the tooth part or the intermediate material to be the tooth part by high frequency induction heating, the tooth part or the intermediate material to be the tooth part is bonded and fixed to the wheel part simultaneously with the injection molding. This eliminates the need for complicated equipment and reduces manufacturing costs.

本発明の実施の形態の第１例を示す、図１４のＡ−Ａ断面に相当する図。The figure equivalent to the AA cross section of FIG. 14 which shows the 1st example of embodiment of this invention. 回転軸及びウォームホイールを取り出し、更に歯部となる環状中間素材と組み合わせた状態を、図１と同方向から見た断面図。Sectional drawing which took out the rotating shaft and the worm wheel, and also looked at the state combined with the cyclic | annular intermediate material used as a tooth part from the same direction as FIG. 図２の下方から見た端面図。The end view seen from the lower part of FIG. ホイール部と環状中間素材とを、高周波誘導加熱により溶着する状態を示す断面図。Sectional drawing which shows the state which welds a wheel part and a cyclic | annular intermediate raw material by high frequency induction heating. 本発明の実施の形態の第２例を示す、図１と同様の図。The figure similar to FIG. 1 which shows the 2nd example of embodiment of this invention. 同第３例を示す、図１と同様の図。The figure similar to FIG. 1 which shows the 3rd example. 回転軸及びウォームホイールを取り出して図６と同方向から見た断面図。Sectional drawing which took out the rotating shaft and the worm wheel, and was seen from the same direction as FIG. ホイール部と環状中間素材とを、高周波誘導加熱により溶着する状態を示す断面図。Sectional drawing which shows the state which welds a wheel part and a cyclic | annular intermediate raw material by high frequency induction heating. 本発明の実施の形態の第３例を示す、図２と同様の図。The figure similar to FIG. 2 which shows the 3rd example of embodiment of this invention. 同第４例を示す、図４と同様の図。The figure similar to FIG. 4 which shows the 4th example. 同第５例を示す、図４と同様の図。The figure similar to FIG. 4 which shows the said 5th example. 同第６例を示す、図４と同様の図。The figure similar to FIG. 4 which shows the 6th example. 従来構造の１例を示す、部分切断側面図。The partially cut side view which shows an example of a conventional structure. 同じく図１３のＢ−Ｂ拡大断面図。Similarly BB expanded sectional drawing of FIG. より具体的構造を示す、図１４のＡ−Ａ断面に相当する図。The figure equivalent to the AA cross section of FIG. 14 which shows a more specific structure.

［実施の形態の第１例］
図１〜４は、請求項１、２、６に対応する、本発明の実施の形態の第１例を示している。尚、本例を含めて本発明の特徴は、電動式パワーステアリング装置を構成するウォーム減速機のウォームホイール４ｂ及びこのウォームホイール４ｂと共に回転する回転軸１０ａの構造及びその製造方法にある。その他の部分に関しては、前述の図１５に示した構造を含め、前述の特許文献１〜５に記載される等により従来から知られている構造及びその製造方法と同様であるから、説明を省略若しくは簡略にし、以下、本例の特徴部分を中心に説明する。 [First example of embodiment]
1 to 4 show a first example of an embodiment of the present invention corresponding to claims 1, 2, and 6. FIG. The feature of the present invention including this example is the structure of the worm wheel 4b of the worm speed reducer constituting the electric power steering device, the structure of the rotating shaft 10a rotating with the worm wheel 4b, and the manufacturing method thereof. The other parts are the same as the structure and the manufacturing method known from the prior art described in Patent Documents 1 to 5 including the structure shown in FIG. Or, for simplicity, the following description will focus on the features of this example.

前記ウォームホイール４ｂは、炭素鋼等の、高周波誘導加熱が可能な金属製で円輪状のホイール部１６ａと、合成樹脂製で円環状の歯部１７ａとから構成している。このうちのホイール部１６ａは前記回転軸１０ａの中間部外周面に、この回転軸１０ａと一体に形成している。この為に、金属製の素材に、熱間鍛造等の塑性加工を施す事により、前記回転軸１０ａと前記ホイール部１６ａとを一体に、且つ、互いに同心に形成している。又、この回転軸１０ａの内周面のうち、軸方向に関して前記ホイール部１６ａと整合する部分には、径方向外側に向けて凹んだ凹部３１を設けている。 The worm wheel 4b is composed of an annular wheel portion 16a made of metal such as carbon steel and capable of high-frequency induction heating, and an annular tooth portion 17a made of synthetic resin. Of these, the wheel portion 16a is formed integrally with the rotary shaft 10a on the outer peripheral surface of the intermediate portion of the rotary shaft 10a. For this purpose, the rotating shaft 10a and the wheel portion 16a are formed integrally and concentrically with each other by subjecting a metal material to plastic working such as hot forging. Further, in the inner peripheral surface of the rotating shaft 10a, a concave portion 31 that is recessed outward in the radial direction is provided in a portion that is aligned with the wheel portion 16a in the axial direction.

本例の場合、このホイール部１６ａの軸方向に関する厚さ寸法は、前記歯部１７ａを溶着固定する為、外径側端部に全周に亙って設けられたリム部１８で大きく、このリム部１８よりも内径寄り部分に設けた肉盗み部１９で小さくなっている。この肉盗み部１９は、前記リム部１８の軸方向両側面のうち、転がり軸受１１ｂに対向する片側面から凹入した状態で、全周に亙って形成されている。又、前記肉盗み部１９を、前記リム部１８の径方向内端部（内周縁）まで形成して、この肉盗み部１９の内径側端部を、前記回転軸１０ａの外周面に一致させている。又、前記リム部１８の外周面の中心軸と前記回転軸１０ａの回転中心とは、互いに一致している。 In the case of this example, the thickness dimension in the axial direction of the wheel portion 16a is large in the rim portion 18 provided over the entire circumference at the outer diameter side end portion in order to weld and fix the tooth portion 17a. It is smaller at the meat stealing portion 19 provided in the portion closer to the inner diameter than the rim portion 18. The meat stealing portion 19 is formed over the entire circumference in a state of being recessed from one side surface facing the rolling bearing 11b of both side surfaces in the axial direction of the rim portion 18. Further, the meat stealing portion 19 is formed up to the radially inner end (inner peripheral edge) of the rim portion 18, and the inner diameter side end of the meat stealing portion 19 is made to coincide with the outer peripheral surface of the rotary shaft 10a. ing. The central axis of the outer peripheral surface of the rim portion 18 and the rotational center of the rotary shaft 10a coincide with each other.

更に、前記歯部１７ａは前記リム部１８の外周面に、高周波誘導加熱により溶着し、結合固定している。この為に、予め押し出し成形及び切断により、或いは射出成形により、円環状に形成した環状中間素材２０を前記リム部１８に、締り嵌めにより外嵌する。次いで、これら環状中間素材２０及びリム部１８の周囲に円環状の高周波誘導コイル２１を、これら環状中間素材２０及びリム部１８と同心に配置した状態で、この高周波誘導コイル２１に通電する。 Further, the tooth portion 17a is welded and fixed to the outer peripheral surface of the rim portion 18 by high frequency induction heating. For this purpose, an annular intermediate material 20 formed in an annular shape by extrusion molding and cutting in advance or by injection molding is externally fitted to the rim portion 18 by an interference fit. Next, the high-frequency induction coil 21 is energized in a state where an annular high-frequency induction coil 21 is arranged around the annular intermediate material 20 and the rim portion 18 and concentric with the annular intermediate material 20 and the rim portion 18.

そして、前記リム部１８を含む前記ホイール部１６ａを発熱させて、前記環状中間部材２０の内周面部分を溶融させ、この環状中間部材２０の内周面と前記リム部１８の外周面とを溶着させる。この際、前記高周波誘導コイル２１と前記回転軸１０ａとの、径方向及び軸方向に関する位置決めを図り、この高周波誘導コイル２１により前記リム部１８を、均一に発熱させる。この結果、前記環状中間部材２０がこのリム部１８の周囲に結合固定される。尚、これら環状中間部材２０の内周面とリム部１８の外周面との結合強度を高くする為に、予めこのリム部１８の外周面に、セレーション状の凹凸、若しくはローレット目の如き、微小な凹凸を形成しておく。 Then, the wheel portion 16a including the rim portion 18 is heated to melt the inner peripheral surface portion of the annular intermediate member 20, and the inner peripheral surface of the annular intermediate member 20 and the outer peripheral surface of the rim portion 18 are joined together. Weld. At this time, the high-frequency induction coil 21 and the rotary shaft 10a are positioned in the radial direction and the axial direction, and the rim portion 18 is uniformly heated by the high-frequency induction coil 21. As a result, the annular intermediate member 20 is coupled and fixed around the rim portion 18. In order to increase the bonding strength between the inner peripheral surface of the annular intermediate member 20 and the outer peripheral surface of the rim portion 18, the outer peripheral surface of the rim portion 18 is preliminarily formed on the outer peripheral surface of the rim portion 18, such as serration-like irregularities or knurled eyes. The unevenness is formed.

前記環状中間部材２０を前記リム部１８の周囲に結合固定したならば、その後、前述の特許文献４、５に記載される等により従来から知られている方法により、前記環状中間素材２０の外周面に歯を形成し、この環状中間素材２０を前記歯部１７ａとする。更にその後、前記ウォームホイール４ｂを前記回転軸１０ａと共にハウジング３ａ内に組み込んで、図１に示す様な電動式パワーステアリング装置とする。 If the annular intermediate member 20 is coupled and fixed to the periphery of the rim portion 18, then the outer periphery of the annular intermediate material 20 is obtained by a conventionally known method such as described in Patent Documents 4 and 5 described above. Teeth are formed on the surface, and the annular intermediate material 20 is used as the tooth portion 17a. After that, the worm wheel 4b is incorporated in the housing 3a together with the rotating shaft 10a to obtain an electric power steering apparatus as shown in FIG.

上述の様な本例の電動式パワーステアリング装置及びその製造方法によれば、小型且つ軽量の構造を、低コストで実現できる。この理由は、以下の通りである。
先ず、前記回転軸１０ａと前記ウォームホイール４ｂのホイール部１６ａとを一体とし、しかもこのホイール部１６ａに肉盗み部１９を設けて、このホイール部１６ａの軸方向に関する厚さ寸法を、径方向外端部で大きく、内径寄り部分で小さくしている。前記回転軸１０ａと前記ホイール部１６ａとを一体とした事で、これら回転軸１０ａとホイール部１６ａとの嵌合強度確保の為、このホイール部１６ａの内径側端部の軸方向厚さを確保する必要がない。前記歯部１７ａの軸方向に関する幅寸法を確保する為には、前記ホイール部１６ａの外径側端部に設けた、前記リム部１８の幅寸法さえ確保すれば足りる。この為、前記回転軸１０ａと前記ウォームホイール４ｂとの結合強度を確保しつつ、前記ホイール部１６ａの内径側部分の軸方向厚さを小さく抑えて、前記ウォームホイール４ｂの軽量化を図れる。 According to the electric power steering apparatus of the present example and the manufacturing method thereof as described above, a small and lightweight structure can be realized at low cost. The reason for this is as follows.
First, the rotating shaft 10a and the wheel portion 16a of the worm wheel 4b are integrated, and the stealing portion 19 is provided in the wheel portion 16a, and the thickness dimension in the axial direction of the wheel portion 16a is set to the outside in the radial direction. It is large at the end and small at the inner diameter side. By integrating the rotating shaft 10a and the wheel portion 16a, the axial thickness of the inner diameter side end of the wheel portion 16a is secured in order to secure the fitting strength between the rotating shaft 10a and the wheel portion 16a. There is no need to do. In order to ensure the width dimension of the tooth portion 17a in the axial direction, it is only necessary to secure the width dimension of the rim portion 18 provided at the outer diameter side end portion of the wheel portion 16a. For this reason, while ensuring the coupling strength between the rotating shaft 10a and the worm wheel 4b, the axial thickness of the inner diameter side portion of the wheel portion 16a can be kept small, and the worm wheel 4b can be reduced in weight.

又、図示の例の場合には、前記肉盗み部１９内に、転がり軸受１１ｂの外輪を保持する為、ハウジング３ａ内に設けた保持部２２の端部を進入させている。この為に本例の場合には、前述した図１５に示した従来構造に比べて、１対の転がり軸受１１ａ、１１ｂ同士のピッチを短くでき、その分、電動式パワーステアリングホイールの小型・軽量化も図れる。 In the case of the illustrated example, in order to hold the outer ring of the rolling bearing 11b in the meat stealing portion 19, the end portion of the holding portion 22 provided in the housing 3a is advanced. Therefore, in the case of this example, the pitch between the pair of rolling bearings 11a and 11b can be shortened as compared with the conventional structure shown in FIG. 15, and the electric power steering wheel can be made smaller and lighter accordingly. Can also be achieved.

更に、前記ホイール部１６ａと前記歯部１７ａとを高周波誘導加熱により溶着する為、前述の特許文献２、３に記載された如く、歯部若しくはこの歯部となるべき中間素材を射出成形と同時にホイール部に結合固定する場合の様に、複雑な設備が不要になり、製造コストを抑える事もできる。即ち、前記歯部１７ａの元となる、前記環状中間部材２０は、一体押し出し成形した円筒状の前素材を所定長さに切断するか、仮に１個ずつ射出成形する場合でも、簡単な射出成形型により造れる。又、前記ホイール部１６ａと前記歯部１７ａと溶着する為の前記高周波誘導加熱コイル２１は、単純な円環状のもので足りる為、設備コストは低く抑えられる。この為、上述の様に製造コストを抑えられる。 Further, in order to weld the wheel portion 16a and the tooth portion 17a by high-frequency induction heating, as described in Patent Documents 2 and 3, the tooth portion or an intermediate material to be the tooth portion is simultaneously formed with injection molding. As in the case of coupling and fixing to the wheel portion, complicated equipment is not required, and the manufacturing cost can be reduced. In other words, the annular intermediate member 20 that is the basis of the tooth portion 17a is a simple injection molding even when a cylindrical front material that has been integrally extruded is cut into a predetermined length or injection molded one by one. Can be made by mold. Moreover, since the high frequency induction heating coil 21 for welding the wheel portion 16a and the tooth portion 17a suffices, the equipment cost can be kept low. For this reason, the manufacturing cost can be suppressed as described above.

［実施の形態の第２例］
図５は、請求項１〜３に対応する、本発明の実施の形態の第２例を示している。本例の場合には、ハウジング３ａに対して回転軸１０ａを回転自在に支持する転がり軸受１１ｂの一部を、肉盗み部１９の内部に入り込ませている。即ち、上述した実施の形態の第１例の場合、保持部２２の先端部のみを肉盗み部１９内に進入させ、転がり軸受１１ｂに関してはこの肉盗み部１９外に位置させていたのに対して、本例の場合には、保持部２２ａを前記肉盗み部１９内に、より深く進入させて、この保持部２２ａ内に保持された前記転がり軸受１１ｂの軸方向の一部を、前記肉盗み部１９内に配置している。
この様な本例の構造によれば、１対の転がり軸受１１ａ、１１ｂ同士のピッチをより短くできて、電動式パワーステアリングホイールをより小型・軽量化できる。
その他の部分に関しては、上述した実施の形態の第１例の場合と同様であるから、同等部分に関する図示並びに説明は省略する。 [Second Example of Embodiment]
FIG. 5 shows a second example of an embodiment of the present invention corresponding to claims 1 to 3. In the case of this example, a part of the rolling bearing 11b that rotatably supports the rotary shaft 10a with respect to the housing 3a is made to enter the meat stealing portion 19. That is, in the case of the first example of the above-described embodiment, only the distal end portion of the holding portion 22 is made to enter the meat stealing portion 19 and the rolling bearing 11b is positioned outside the meat stealing portion 19. In the case of this example, the holding portion 22a is moved deeper into the meat stealing portion 19, and a part of the rolling bearing 11b held in the holding portion 22a in the axial direction is transferred to the meat stealing portion 19. It is arranged in the stealing unit 19.
According to the structure of this example, the pitch between the pair of rolling bearings 11a and 11b can be shortened, and the electric power steering wheel can be made smaller and lighter.
The other parts are the same as in the case of the first example of the embodiment described above, and therefore illustrations and explanations regarding the equivalent parts are omitted.

［実施の形態の第３例］
図６〜８は、請求項１、５に対応する、本発明の実施の形態の第３例を示している。
本例の場合には、ホイール部１６ｂの軸方向両側面に肉盗み部１９ａ、１９ａを設けて、このホイール部１６ｂの径方向外径寄り部分の形状を、軸方向に関して対称にしている。
この様な形状を採用する事により本例の場合には、図８に示す様に、高周波誘導コイル２１により前記ホイール部１６ｂを加熱する際に、このホイール部１６ｂの外周縁部に存在するリム部１８ａを、軸方向全幅に亙り均一に発熱させる事ができる。この結果、このリム部１８ａの外周面と環状中間素材２０の内周面との結合部の品質を良好にし易い。
その他の部分に関しては、前述した実施の形態の第１例の場合と同様であるから、同等部分に関する説明は省略する。 [Third example of embodiment]
6 to 8 show a third example of the embodiment of the invention corresponding to claims 1 and 5.
In the case of this example, the meat stealing portions 19a and 19a are provided on both side surfaces in the axial direction of the wheel portion 16b, and the shape of the portion near the radially outer diameter of the wheel portion 16b is symmetric with respect to the axial direction.
In the case of this example by adopting such a shape, as shown in FIG. 8, when the wheel portion 16b is heated by the high-frequency induction coil 21, the rim present on the outer peripheral edge portion of the wheel portion 16b is used. The portion 18a can be heated uniformly over the entire axial width. As a result, it is easy to improve the quality of the joint portion between the outer peripheral surface of the rim portion 18a and the inner peripheral surface of the annular intermediate material 20.
The other parts are the same as in the case of the first example of the above-described embodiment, and thus the description of the equivalent parts is omitted.

［実施の形態の第４例］
図９は、請求項１、２、４に対応する、本発明の実施の形態の第４例を示している。本例の場合には、ホイール部１６ｃの軸方向片面の径方向中間部に、このホイール部１６ｃの軸方向片面の開口部の幅が最も広く、奥部に向かうに従って漸次狭くなる、断面Ｖ字形の肉盗み部１９ｂを形成している。
この様な形状を有する肉盗み部１９ｂは、鍛造加工により容易に形成できる為、前記ホイール部１６ｃを含む部材の生産性を向上できる。但し、本例の構造は、保持部２２（図１参照）を内部に進入させる事は難しいので、１対の転がり軸受１１ａ、１１ｂ（図１参照）同士のピッチを短くして小型・軽量化を図る面からは不利である。
その他の部分に関しては、前述した実施の形態の第１例の場合と同様であるから、同等部分に関する図示並びに説明は省略する。 [Fourth Example of Embodiment]
FIG. 9 shows a fourth example of an embodiment of the present invention corresponding to claims 1, 2, and 4. In the case of this example, the width of the opening on the one axial surface of the wheel portion 16c is the widest at the radial intermediate portion of the one axial surface of the wheel portion 16c, and gradually decreases toward the back. The meat stealing portion 19b is formed.
Since the meat stealing portion 19b having such a shape can be easily formed by forging, the productivity of the member including the wheel portion 16c can be improved. However, since it is difficult for the structure of this example to enter the holding portion 22 (see FIG. 1), the pitch between the pair of rolling bearings 11a and 11b (see FIG. 1) is shortened to reduce the size and weight. It is disadvantageous in terms of planning.
The other parts are the same as in the case of the first example of the embodiment described above, and therefore illustrations and explanations regarding the equivalent parts are omitted.

［実施の形態の第５例］
図１０は、請求項６、７に対応する、本発明の実施の形態の第５例を示している。本例の場合には、内径を拡縮自在としたチャック２３により、回転軸１０ａの一部でホイール部１６ａに隣接する部分に設けられた、内輪嵌合部２４を把持する。この内輪嵌合部２４は、転がり軸受１１ｂの内輪（図１参照）を外嵌固定する為の円筒面で、前記回転軸１０ａと、高精度で同心に加工されている。従って、前記チャック２３により前記内輪嵌合部２４を把持する事により、前記回転軸１０ａの径方向に関する位置決めを、高精度で図れる。同時に、前記チャック２３の軸方向端面を、前記内輪嵌合部２４の端部に存在する段差面２５に突き当てて、前記回転軸１０ａの軸方向に関する位置決めを図る。更に、この状態で、高周波誘導コイル２１の内周面とリム部１８の外周面とを、環状中間素材２０を介して径方向に対向させる。 [Fifth Example of Embodiment]
FIG. 10 shows a fifth example of an embodiment of the present invention corresponding to claims 6 and 7. In the case of this example, the inner ring fitting portion 24 provided in a portion of the rotating shaft 10a adjacent to the wheel portion 16a is gripped by the chuck 23 whose inner diameter is freely expandable. The inner ring fitting portion 24 is a cylindrical surface for externally fitting and fixing the inner ring (see FIG. 1) of the rolling bearing 11b, and is processed concentrically with the rotating shaft 10a with high accuracy. Therefore, by gripping the inner ring fitting portion 24 by the chuck 23, positioning in the radial direction of the rotary shaft 10a can be achieved with high accuracy. At the same time, the axial end surface of the chuck 23 is abutted against the stepped surface 25 existing at the end of the inner ring fitting portion 24 to position the rotary shaft 10a in the axial direction. Further, in this state, the inner peripheral surface of the high frequency induction coil 21 and the outer peripheral surface of the rim portion 18 are opposed to each other in the radial direction via the annular intermediate material 20.

この様な本例の製造方法によれば、前記高周波誘導コイル２１の内周面と前記リム部１８の外周面とを、径方向及び軸方向に関して、高精度に位置決めした状態で対向させられる。この為、前記高周波誘導コイル２１として、例えば軸方向に関する幅寸法が大きめのものを使用する必要がなくなり、設備の小型化と共に消費電力の低減を図れる等、製造コストの低廉化を図り易くできる。
その他の部分に関しては、前述した実施の形態の第１例の場合と同様であるから、同等部分に関する図示並びに説明は省略する。 According to such a manufacturing method of this example, the inner peripheral surface of the high-frequency induction coil 21 and the outer peripheral surface of the rim portion 18 are opposed to each other in a state of being positioned with high precision in the radial direction and the axial direction. For this reason, it is not necessary to use a high-frequency induction coil 21 having a large width in the axial direction, for example, and it is possible to easily reduce the manufacturing cost, such as downsizing the equipment and reducing power consumption.
The other parts are the same as in the case of the first example of the embodiment described above, and therefore illustrations and explanations regarding the equivalent parts are omitted.

［実施の形態の第６例］
図１１は、請求項６〜８に対応する、本発明の実施の形態の第６例を示している。本例の場合には、中空円管状の回転軸１０ａの両端開口部に、互いに対向する先端部を円すい状の凸面としたセンタリング治具２６ａ、２６ｂの先端部を挿入して、前記回転軸１０ａの径方向及び軸方向の位置決めを図っている。
この様な本例の製造方法によれば、前記回転軸１０ａの位置決めを、より高精度に行える。特に、この回転軸１０ａの倒れ方向の変位を、より十分に抑えられる。尚、図示の例では、前記センタリング治具２６ａ、２６ｂに加えてチャック２３も設けているが、このチャック２３は省略しても良い。
その他の部分に関しては、上述した実施の形態の第５例の場合と同様であるから、同等部分に関する説明は省略する。 [Sixth Example of Embodiment]
FIG. 11 shows a sixth example of an embodiment of the present invention corresponding to claims 6-8. In the case of this example, the end portions of the centering jigs 26a and 26b having conical convex surfaces at the opposite end portions are inserted into the opening portions at both ends of the hollow circular rotating shaft 10a, and the rotating shaft 10a is inserted. Are positioned in the radial direction and the axial direction.
According to such a manufacturing method of this example, the rotation shaft 10a can be positioned with higher accuracy. In particular, the displacement of the rotating shaft 10a in the falling direction can be more sufficiently suppressed. In the illustrated example, a chuck 23 is also provided in addition to the centering jigs 26a and 26b. However, the chuck 23 may be omitted.
The other parts are the same as in the case of the fifth example of the above-described embodiment, and thus the description of the equivalent parts is omitted.

［実施の形態の第７例］
図１２は、請求項６、７、９に対応する、本発明の実施の形態の第７例を示している。本例の場合には、高周波誘導コイル２１への通電に基づいて、ホイール部１６ａのリム部１８と環状中間素材２０とを溶着するのと同じ（同一のチャッキング）工程で、回転軸１０ａの端部に設けたセレーション部２７に、別の高周波誘導コイル２８により、高周波焼き入れ処理を施す。このセレーション部２７は、前記回転軸１０ａの端部と中間シャフト１５の端部とをトルク伝達可能に接続する為の自在継手１４ａ（図１３参照）のヨークを結合する為に設けている。 [Seventh example of embodiment]
FIG. 12 shows a seventh example of the embodiment of the invention corresponding to claims 6, 7, and 9. In the case of this example, on the basis of the energization to the high frequency induction coil 21, the rim portion 18 of the wheel portion 16a and the annular intermediate material 20 are welded in the same process (same chucking) as the rotating shaft 10a. The serration unit 27 provided at the end is subjected to a high-frequency hardening process by another high-frequency induction coil 28. The serration portion 27 is provided for coupling a yoke of a universal joint 14a (see FIG. 13) for connecting the end portion of the rotary shaft 10a and the end portion of the intermediate shaft 15 so as to transmit torque.

本例の場合には、それぞれが高周波誘導コイル２１、２８により行う工程を集約する事で、設備の簡略化と共に作業時間の短縮化を可能にして、製造コストの低廉化を可能にしている。
尚、前記回転軸１０ａの反対側端部には、ステアリングシャフト２ａ（図１４参照）の先端部と、回転方向に関する所定角度の相対変位を可能に、且つ、この所定角度相対変位した場合にトルク伝達可能にする為の、歯車状の凹凸部２９を設けている。この凹凸部２９に関しても、耐摩耗性向上の為に高周波焼き入れする必要があれば、更に第三の高周波誘導コイルにより、同時に焼き入れ処理する事もできる。但し、この場合には、この第三の高周波誘導コイルに関しては、径方向に関して退避可能な分割型として、前記回転軸１０ａの出し入れを可能にする必要がある。
その他の部分に関しては、前述した実施の形態の第５例の場合と同様であるから、同等部分に関する説明は省略する。
又、前述した実施の形態の各例の場合、肉盗み部をホイール部の側面に全周に亙って設けているが、このホイール部の側面の円周方向複数箇所に等間隔に設ける事もできる。但し、この場合には、回転軸を回転自在に支持する転がり軸受の外輪を保持する為の保持部を、前記肉盗み部の内部に進入させる事はできない。 In the case of this example, the steps performed by the high-frequency induction coils 21 and 28 are consolidated, thereby simplifying the facility and shortening the working time, thereby reducing the manufacturing cost.
It should be noted that the opposite end of the rotating shaft 10a can be displaced relative to the tip of the steering shaft 2a (see FIG. 14) at a predetermined angle with respect to the rotation direction, and torque is generated when the relative displacement is performed at the predetermined angle. A gear-shaped concavo-convex portion 29 is provided to enable transmission. If it is necessary for the uneven portion 29 to be induction hardened in order to improve wear resistance, the uneven portion 29 can be simultaneously hardened by a third high frequency induction coil. However, in this case, the third high-frequency induction coil needs to be able to be put in and out of the rotary shaft 10a as a split type that can be retracted in the radial direction.
The other parts are the same as in the case of the fifth example of the above-described embodiment, and thus the description of the equivalent parts is omitted.
Further, in each example of the above-described embodiment, the meat stealing portion is provided on the side surface of the wheel portion over the entire circumference, but it is provided at equal intervals in a plurality of circumferential directions on the side surface of the wheel portion. You can also. However, in this case, the holding portion for holding the outer ring of the rolling bearing that rotatably supports the rotating shaft cannot enter the inside of the meat stealing portion.

図１０〜１２に示した、ホイール部と環状中間素材の溶着方法は、このホイール部に肉盗み部が存在する構造に限らず、このホイール部の軸方向に関する厚さ寸法が内径側から外径側まで均一な構造に関しても適用できる。
又、前述した実施の形態の各例の場合、肉盗み部をホイール部の側面に全周に亙って設けているが、このホイール部の側面の円周方向複数箇所に等間隔に設ける事もできる。但し、この場合には、回転軸を回転自在に支持する転がり軸受の外輪を保持する為の保持部を、前記肉盗み部の内部に進入させる事はできない。 The method of welding the wheel portion and the annular intermediate material shown in FIGS. 10 to 12 is not limited to the structure in which the meat stealing portion exists in the wheel portion, and the thickness dimension in the axial direction of the wheel portion is the outer diameter from the inner diameter side. It can also be applied to a uniform structure up to the side.
Further, in each example of the above-described embodiment, the meat stealing portion is provided on the side surface of the wheel portion over the entire circumference, but it is provided at equal intervals in a plurality of circumferential directions on the side surface of the wheel portion. You can also. However, in this case, the holding portion for holding the outer ring of the rolling bearing that rotatably supports the rotating shaft cannot enter the inside of the meat stealing portion.

１ステアリングホイール
２、２ａステアリングシャフト
３、３ａハウジング
４、４ａ、４ｂウォームホイール
５ウォーム歯
６ウォーム軸
７電動モータ
８、８ａウォーム
９ａ、９ｂ転がり軸受
１０、１０ａ回転軸
１１ａ、１１ｂ転がり軸受
１２トーションバー
１３トルクセンサ
１４ａ、１４ｂ自在継手
１５中間シャフト
１６、１６ａ、１６ｂ、１６ｃホイール部
１７、１７ａ歯部
１８、１８ａリム部
１９、１９ａ、１９ｂ肉盗み部
２０環状中間素材
２１高周波誘導コイル
２２、２２ａ保持部
２３チャック
２４内輪嵌合部
２５段差面
２６ａ、２６ｂセンタリング治具
２７セレーション部
２８高周波誘導コイル
２９凹凸部
３０ステアリングギヤユニット
３１凹部
DESCRIPTION OF SYMBOLS 1 Steering wheel 2, 2a Steering shaft 3, 3a Housing 4, 4a, 4b Worm wheel 5 Worm tooth 6 Worm shaft 7 Electric motor 8, 8a Worm 9a, 9b Rolling bearing 10, 10a Rotating shaft 11a, 11b Rolling bearing 12 Torsion bar 13 Torque sensor 14a, 14b Universal joint 15 Intermediate shaft 16, 16a, 16b, 16c Wheel part 17, 17a Teeth part 18, 18a Rim part 19, 19a, 19b Meat stealing part 20 Annular intermediate material 21 High frequency induction coil 22, 22a Holding Part 23 chuck 24 inner ring fitting part 25 step surface 26a, 26b centering jig 27 serration part 28 high frequency induction coil 29 uneven part 30 steering gear unit
31 recesses

Claims

A housing that is supported by a fixed portion and does not rotate, a rotary shaft that is rotatably provided to the housing, is rotated by an operation of a steering wheel, and gives a steering angle to a steered wheel as it rotates, and the housing A worm wheel that is supported concentrically with the rotary shaft and rotates together with the rotary shaft, and a worm tooth at the axial intermediate portion of the worm shaft. In an electric power steering apparatus including a worm rotatably supported inside the housing in an engaged state with the worm wheel, and an electric motor that rotationally drives the worm.
The worm wheel is composed of an annular wheel portion and a synthetic resin tooth portion provided around the wheel portion and concentrically with the wheel portion and welded to the outer peripheral surface of the wheel portion. ,
The wheel portion and the rotating shaft are integrally formed of a metal material,
The rotating shaft is configured in a hollow circular tube, and a recess that is recessed toward the outside in the radial direction is provided in a portion of the inner peripheral surface that matches the wheel portion in the axial direction.
The thickness dimension in the axial direction of the wheel portion is larger at the rim portion provided on the outer diameter side end portion over the entire circumference in order to weld and fix the tooth portion, and at the portion closer to the inner diameter than this rim portion. An electric power steering device characterized in that it is reduced in a portion corresponding to a meat stealing portion formed in a state of being recessed from an axial side surface.

The electric power steering apparatus according to claim 1, wherein the meat stealing portion is provided only on one axial surface of the rim portion.

The meat stealing portion is provided on the entire side surface of the wheel portion, and a part of a rolling bearing that rotatably supports the rotating shaft with respect to the housing is located inside the meat stealing portion. The electric power steering apparatus according to claim 2, wherein the electric power steering apparatus is inserted.

3. The electric power steering apparatus according to claim 2, wherein the meat stealing portion has a shape in which the width of the opening on one side in the axial direction of the wheel portion is the largest and gradually becomes narrower toward the inner portion.

The electric power steering apparatus according to claim 1, wherein the meat stealing portion is provided on both axial surfaces of the rim portion.

It is a manufacturing method of the electric power steering device given in any 1 paragraph of Claims 1-5, Comprising: The above-mentioned tooth part or an intermediate material used as this tooth part is externally fitted to the above-mentioned rim part, and this tooth part A high-frequency induction coil is disposed around the rim portion, and in a state where the rotary shaft is positioned while being positioned in the radial direction and the axial direction, the high-frequency induction coil is energized to heat the rim portion. A method for manufacturing an electric power steering apparatus, wherein an outer peripheral surface and an inner peripheral surface of the tooth portion are welded.

An inner ring fitting portion provided on a part of the rotating shaft adjacent to the wheel portion for fixing an inner ring of a rolling bearing for rotatably supporting the rotating shaft in the housing. The chuck is held and positioned in the radial direction of the rotating shaft, and the axial end surface of the chuck is abutted against the step surface existing at the end of the inner ring fitting portion to relate to the axial direction of the rotating shaft. In a state where positioning is intended, the inner peripheral surface of the high-frequency induction coil and the outer peripheral surface of the rim portion are opposed to each other in the radial direction via the tooth portion or an intermediate material to be the tooth portion. A method of manufacturing the described electric power steering apparatus.

The rotating shaft is a hollow circular tube, and a tip end portion of a centering jig having a conical convex surface at the opposite end portions of the rotating shaft is inserted into both ends of the rotating shaft. The inner peripheral surface of the high-frequency induction coil and the outer peripheral surface of the rim portion are opposed to each other in a radial direction through the tooth portion or an intermediate material to be the tooth portion in a state where the direction is positioned. The manufacturing method of the electric power steering device described in any one of 6-7.

The rotation of the rim portion when the rim portion is heated based on energization of the high-frequency induction coil in order to weld the outer peripheral surface of the rim portion and the tooth portion or the inner peripheral surface of the intermediate material to be the tooth portion. The method for manufacturing an electric power steering apparatus according to any one of claims 6 to 8, wherein a part of the shaft is subjected to a high-frequency hardening process using another high-frequency induction coil.