JP2008260471A

JP2008260471A - Electric power steering device

Info

Publication number: JP2008260471A
Application number: JP2007106016A
Authority: JP
Inventors: Haruhiko Kiyota; 晴彦清田
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 2007-04-13
Filing date: 2007-04-13
Publication date: 2008-10-30

Abstract

【課題】出力軸１０の先端部とウォーム８の基端部との間に設けたトルク継手部２０に組み込んだ弾性部材２５、２６の剛性が、このトルク継手部２０で伝達されるトルクの大きさに応じて変化する構造を実現する。
【解決手段】スプライン孔１１ａとスプライン軸部１２ａとの係合に基づくトルク継手部２０は、上記トルクの伝達方向に関する剛性が低い低剛性伝達部２９と、同じくこの剛性が中間である中剛性伝達部２８と、同じくこの剛性が高い高剛性伝達部２７とを、軸方向に関して互いに直列に配置して成る。このうちの低剛性伝達部２９の、トルクの伝達方向に関する隙間の大きさを、上記高剛性伝達部２７の同方向の隙間よりも小さく、上記中剛性伝達部の同方向の隙間の大きさをその中間とする。
【選択図】図２The rigidity of an elastic member (25, 26) incorporated in a torque joint portion (20) provided between the tip end portion of an output shaft (10) and the base end portion of a worm (8) is the magnitude of torque transmitted by the torque joint portion (20). A structure that changes according to the height is realized.
A torque coupling portion 20 based on engagement between a spline hole 11a and a spline shaft portion 12a has a low-rigidity transmission portion 29 having a low rigidity in the torque transmission direction, and a medium-rigidity transmission in which this rigidity is intermediate. The portion 28 and the high-rigidity transmission portion 27, which is also highly rigid, are arranged in series with each other in the axial direction. Of these, the size of the gap in the direction of torque transmission of the low-rigidity transmission portion 29 is smaller than the gap in the same direction of the high-rigidity transmission portion 27, and the size of the gap in the same direction of the medium-rigidity transmission portion. The middle.
[Selection] Figure 2

Description

この発明に係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減速機のウォーム軸の基端部と、上記電動モータの出力軸の先端部との接続部に設けるトルク継手部の特性を改良して、上記ステアリングホイールの操作感の向上を図るべく発明したものである。 The electric power steering apparatus according to the present invention is used as a steering apparatus for an automobile, and uses an electric motor as auxiliary power to reduce the force required for the driver to operate the steering wheel. is there. The present invention improves the characteristics of the torque joint provided at the connection between the base end of the worm shaft of the reduction gear constituting the electric power steering device and the tip of the output shaft of the electric motor. Invented to improve the operational feeling of the steering wheel.

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。 A power steering device is widely used as a device to reduce 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) Has been. 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. The electric power steering device can be made smaller and lighter than the hydraulic power steering device, has advantages such as easy control of the magnitude (torque) of auxiliary power and less power loss of the engine.

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、上記電動モータにより回転駆動されるウォームと、上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、上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 attached to the rotating shaft that is rotated by the operation of the steering wheel and gives a steering angle to the steered wheel as the wheel rotates. Auxiliary power is applied through a speed reducer. 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６〜７に示す様な電動式パワーステアリング装置が記載されている。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。又、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の両端部を、深溝型玉軸受等の１対の転がり軸受９ａ、９ｂにより、上記ハウジング３内に回転自在に支持している。 For example, Patent Document 1 describes 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. Also, worm teeth 5 meshing with the worm wheel 4 are provided in the axially intermediate portion of the worm shaft 6, and both ends of the worm 8 driven to rotate by the electric motor 7 are connected to a pair of rolling bearings such as a deep groove type ball bearing. 9a and 9b are rotatably supported in the housing 3.

上記ウォーム８を上記電動モータ７の出力軸１０により回転駆動する為に、上記ウォーム軸６の基端部にスプライン孔１１を、このウォーム軸６の基端面に開口する状態で形成している。又、上記出力軸１０の先端部にスプライン軸部１２を形成している。そして、このスプライン軸部１２と上記スプライン孔１１とをスプライン係合させる事で、上記出力軸１０と上記ウォーム軸６とを、回転力の伝達を自在に結合している。 In order to rotationally drive the worm 8 by the output shaft 10 of the electric motor 7, a spline hole 11 is formed in the proximal end portion of the worm shaft 6 so as to open to the proximal end surface of the worm shaft 6. A spline shaft 12 is formed at the tip of the output shaft 10. The spline shaft portion 12 and the spline hole 11 are spline-engaged so that the output shaft 10 and the worm shaft 6 are freely coupled to transmit rotational force.

更に、図７に示した従来構造の場合、上記ウォームホイール４と上記ウォーム歯５との噛合部のバックラッシュをなくす為に、上記ウォーム軸６の先端部（図７の右端部）を上記ウォームホイール４に向け弾性的に押圧する様にしている。即ち、上記ウォーム軸６の先端部で先端側の転がり軸受９ａよりも突出した部分に押圧駒１３を外嵌し、この押圧駒１３と上記ハウジング３との間にコイルばね１４等の弾性部材を設けている。そして、このコイルばね１４により、上記押圧駒１３を介して、上記ウォーム歯５を上記ウォームホイール４に向け押圧している。この様な構成により、これらウォーム歯５とウォームホイール４との間のバックラッシュを抑え、上記電動モータ７の起動時や回転方向の変換時に、上記ウォームホイール４と上記ウォーム歯５との噛合部での歯打ち音の発生を抑えている。 Further, in the case of the conventional structure shown in FIG. 7, in order to eliminate backlash at the meshing portion between the worm wheel 4 and the worm tooth 5, the tip of the worm shaft 6 (the right end in FIG. 7) is connected to the worm. The wheel 4 is elastically pressed toward the wheel 4. That is, the pressing piece 13 is externally fitted to a portion protruding from the leading end side rolling bearing 9 a at the tip of the worm shaft 6, and an elastic member such as a coil spring 14 is provided between the pressing piece 13 and the housing 3. Provided. The worm teeth 5 are pressed against the worm wheel 4 by the coil spring 14 via the pressing piece 13. With such a configuration, backlash between the worm teeth 5 and the worm wheel 4 is suppressed, and the meshing portion of the worm wheel 4 and the worm teeth 5 is activated when the electric motor 7 is started or when the rotation direction is changed. The occurrence of rattling noise is suppressed.

上述の様な電動式パワーステアリング装置では、上記ウォームホイール４と上記ウォーム歯５との噛合部での歯打ち音の発生を抑えられるが、上記スプライン軸部１２と上記スプライン孔１１とのスプライン係合部での歯打ち音の発生は抑えられない。特に、このスプライン係合部には、或る程度隙間を設ける必要がある。この理由は、上記スプライン孔１１と上記スプライン軸部１２とをスプライン係合させる作業を容易に行なえる様にする必要上、更には上記ウォームホイール４と上記ウォーム歯５との間のバックラッシュを抑えるべく、上記ウォーム軸６の先端部を上記ウォームホイール４に向け揺動変位させる必要上である。この様な必要上設けられる、上記スプライン係合部の隙間に基づいて、上記電動モータ７の起動時や回転方向の変換時に、このスプライン係合部で、雄スプライン歯の側面と雌スプライン歯の側面との衝突に基づく、騒音や振動が発生する。 In the electric power steering apparatus as described above, it is possible to suppress the occurrence of rattling noise at the meshing portion between the worm wheel 4 and the worm tooth 5, but the spline engagement between the spline shaft portion 12 and the spline hole 11. Generation of rattling noise at the joint cannot be suppressed. In particular, it is necessary to provide a certain gap in the spline engaging portion. This is because the spline hole 11 and the spline shaft 12 need to be easily engaged in spline engagement, and backlash between the worm wheel 4 and the worm teeth 5 is further reduced. In order to suppress this, it is necessary to swing and displace the tip of the worm shaft 6 toward the worm wheel 4. Based on the clearance between the spline engaging portions provided as described above, when the electric motor 7 is started up or when the rotation direction is changed, the spline engaging portions use the side surfaces of the male spline teeth and the female spline teeth. Noise and vibration are generated based on the collision with the side.

電動モータの出力軸とウォーム減速機のウォーム軸との間でトルクを伝達する為のトルク継手部で、歯打ち音と呼ばれる騒音や振動が発生する事を防止する為の構造として従来から、特許文献２〜５に記載された構造が知られている。図８は、このうちの特許文献２〜４に記載された、電動モータの出力軸とウォーム減速機のウォーム軸との間に設置するトルク継手部の構造を示している。この従来構造の場合には、互いの間でトルクを伝達すべき１対の回転軸１５ａ、１５ｂの互いに対向する端面に凹凸部１６ａ、１６ｂを形成し、これら両凹凸部１６ａ、１６ｂを、弾性部材１７を介して凹凸係合させる。金属材料製の上記両回転軸１５ａ、１５ｂに設けた、上記両凹凸部１６ａ、１６ｂの円周方向側面同士は、上記弾性部材１７を介して噛合するので、噛合部で歯打ち音の如き騒音や振動が発生する事はなくなる。尚、特許文献３には、上記弾性部材１７の形状を工夫する事により、この弾性部材１７の耐久性向上を図る為の構造が記載されている。又、特許文献４には、上記両凹凸部１６ａ、１６ｂ同士の間での上記弾性部材１７の締め代を、一部で残部よりも大きくする事で、この弾性部材１７の組み付け性を向上させる為の構造が記載されている。更に、特許文献５には、電動モータの出力軸とステアリングシャフトとを、１対の回転軸の端部同士を、１対の回転伝達部材及び中間介在部材を介して凹凸係合させる事で、上記出力軸から上記ステアリングシャフトに振動や衝撃が加わらない様にする構造が記載されている。 A torque joint for transmitting torque between the output shaft of the electric motor and the worm shaft of the worm speed reducer, and has been patented as a structure to prevent the generation of noise and vibration called rattling noise. The structures described in Documents 2 to 5 are known. FIG. 8 shows the structure of a torque joint portion installed between the output shaft of the electric motor and the worm shaft of the worm speed reducer described in Patent Documents 2 to 4. In the case of this conventional structure, the concave and convex portions 16a and 16b are formed on the opposing end surfaces of the pair of rotating shafts 15a and 15b to which torque should be transmitted between them, and both the concave and convex portions 16a and 16b are made elastic. Concave and convex engagement is achieved via the member 17. Since the circumferential side surfaces of the two concavo-convex portions 16a and 16b provided on the two rotating shafts 15a and 15b made of a metal material are engaged with each other via the elastic member 17, noise such as rattling noise is generated at the engaging portion. And vibration will not occur. Patent Document 3 describes a structure for improving the durability of the elastic member 17 by devising the shape of the elastic member 17. Patent Document 4 discloses that the tightening allowance of the elastic member 17 between the concave and convex portions 16a and 16b is partially larger than the remaining portion, thereby improving the assembling property of the elastic member 17. The structure for this is described. Furthermore, in Patent Document 5, the output shaft of the electric motor and the steering shaft are engaged with each other between the ends of a pair of rotating shafts via a pair of rotation transmission members and an intermediate interposed member. A structure is described in which vibration and impact are not applied from the output shaft to the steering shaft.

上述の様な特許文献２〜５に記載された従来構造の場合、上記両回転軸１５ａ、１５ｂ同士の間で伝達するトルクの大きさと、上記弾性部材１７の弾性変形量との関係が、ほぼ直線的になる。言い換えれば、この弾性部材１７の剛性（弾性）が、上記両回転軸１５ａ、１５ｂ同士の間で伝達するトルクの大きさに応じて変化する事はない。この為、上記弾性部材１７の剛性は、上記両回転軸１５ａ、１５ｂ同士の間で伝達するトルクの最大値に応じて規制する必要があり、上記剛性の値が相当に大きくならざるを得ない。この為、上記図８に示した様なトルク継手部の構造を、前述の図７に示した電動モータ７の出力軸１０の先端部とウォーム軸６の基端部とに組み込んだ場合に、トルク伝達に関する特性が、ステアリングホイールの操作感を良好にする面から好ましくないものになる。上記特許文献５に記載された発明の構造も、ほぼ同様の問題を生じる。この点に就いて、以下に説明する。 In the case of the conventional structures described in Patent Documents 2 to 5 as described above, the relationship between the magnitude of the torque transmitted between the rotary shafts 15a and 15b and the amount of elastic deformation of the elastic member 17 is almost equal. Become linear. In other words, the rigidity (elasticity) of the elastic member 17 does not change according to the magnitude of the torque transmitted between the rotating shafts 15a and 15b. For this reason, the rigidity of the elastic member 17 needs to be regulated according to the maximum value of the torque transmitted between the rotary shafts 15a and 15b, and the rigidity value must be considerably increased. . For this reason, when the structure of the torque coupling portion as shown in FIG. 8 is incorporated in the distal end portion of the output shaft 10 and the proximal end portion of the worm shaft 6 of the electric motor 7 shown in FIG. Characteristics relating to torque transmission are undesirable from the viewpoint of improving the operational feeling of the steering wheel. The structure of the invention described in Patent Document 5 also causes almost the same problem. This point will be described below.

上記出力軸１０から上記ウォーム軸６に伝達するトルクが小さい場合、即ち、ステアリングホイール１を操作する為の操舵力を補助する為、ステアリングシャフト２（図６参照）に付与する補助力が小さくて済む場合には、この出力軸１０からこのウォーム軸６に、トルクが緩徐に伝達される事が好ましい。言い換えれば、この様な場合には、上記出力軸１０の回転が上記ウォーム軸６に、弾性部材による十分な緩衝作用を受けた状態で伝達される事が好ましい。これに対して、上記図８に示した様なトルク継手部の構造の場合、上記弾性部材１７の剛性を大きくせざるを得ない為、上記出力軸１０の回転が上記ウォーム軸６に、かなり直接的に（上記弾性部材１７による緩衝をあまり受けずに）伝達される。この結果、上記ステアリングホイール１を操作する運転者に違和感を与える。勿論、上記弾性部材１７の剛性を低く（軟らかく）すれば、この様な違和感をなくせる。但し、大きなトルクを伝達する際の、上記弾性部材１７の弾性変形量が過大になり、トルク伝達の遅れに伴う操舵感の悪化や、この弾性部材１７の耐久性の低下に繋がる為、上記弾性部材１７の剛性を低くする事は難しい。 When the torque transmitted from the output shaft 10 to the worm shaft 6 is small, that is, to assist the steering force for operating the steering wheel 1, the assisting force applied to the steering shaft 2 (see FIG. 6) is small. In the case where it can be completed, it is preferable that torque is transmitted slowly from the output shaft 10 to the worm shaft 6. In other words, in such a case, it is preferable that the rotation of the output shaft 10 is transmitted to the worm shaft 6 in a state where it receives a sufficient buffering action by the elastic member. On the other hand, in the case of the structure of the torque joint portion as shown in FIG. 8, the rigidity of the elastic member 17 must be increased. It is transmitted directly (without much buffering by the elastic member 17). As a result, the driver who operates the steering wheel 1 feels uncomfortable. Of course, if the rigidity of the elastic member 17 is made low (soft), such a sense of incongruity can be eliminated. However, the amount of elastic deformation of the elastic member 17 when transmitting a large torque becomes excessive, leading to deterioration in steering feeling due to a delay in torque transmission and a decrease in durability of the elastic member 17. It is difficult to reduce the rigidity of the member 17.

特開２００４−３０６８９８号公報JP 2004-306898 A 特開２００２−１４５０８３号公報JP 2002-145083 A 特開２００５−２１２６２２号公報Japanese Patent Laying-Open No. 2005-212622 特開２００５−２１２６２３号公報JP 2005-212623 A 特開２００６−１８３６７６号公報JP 2006-183676 A

本発明は、上述の様な事情に鑑み、出力軸の先端部とウォームの基端部との間に設けたトルク継手部に組み込んだ弾性部材の剛性が、このトルク継手部で伝達されるトルクの大きさに応じて変化する構造を実現すべく発明したものである。 In view of the circumstances as described above, the present invention provides a torque transmitted by the torque joint portion in which the rigidity of the elastic member incorporated in the torque joint portion provided between the tip end portion of the output shaft and the base end portion of the worm is transmitted. The invention was invented to realize a structure that changes in accordance with the size.

本発明の電動式パワーステアリング装置は、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、トルク継手部とを備える。
このうちのハウジングは、固定の部分に支持されて回転する事がない。
又、上記回転軸は、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。尚、この様な回転軸としては、前述の図６に示したステアリングシャフト２の他、中間シャフト１８、ステアリングギヤユニット１９の入力軸（ピニオン軸）等が採用可能である。勿論、上記回転軸が何れであるかにより、上記ハウジングを支持する為の固定の部分は異なる。
又、上記ウォームホイールは、上記ハウジングの内部で上記回転軸の一部に、この回転軸と同心に支持されており、この回転軸と共に回転する。
又、上記ウォームは、ウォーム軸の軸方向中間部にウォーム歯を設けて成る。そして、このウォーム歯を上記ウォームホイールと噛合させた状態で、上記ウォーム軸の軸方向端部を、軸受により、上記ハウジングに対し回転自在に支持されている。
又、上記電動モータは、上記ウォームを回転駆動する為、その出力軸をこのウォームと同心に配置している。
又、上記トルク継手部は、上記出力軸の先端部と上記ウォームの基端部との間に設けられて、この出力軸からこのウォームへのトルクの伝達を自在としている。そして、上記トルク継手部は、駆動側凹凸部と、被駆動側凹凸部と、弾性部材とから成る。
このうちの駆動側凹凸部は、上記出力軸側にこの出力軸と同心に設けられて、この出力軸と共に回転する。
又、上記被駆動側凹凸部は、上記ウォーム側にこのウォームと同心に設けられて、上記駆動側凹凸部と上記トルクの伝達方向に関して凹凸係合し、このウォームと共に回転する。
又、上記弾性部材は、上記駆動側凹凸部と上記被駆動側凹凸部との間に、上記トルクの伝達方向に関して挟持されている。 The electric power steering apparatus of the present invention includes a housing, a rotating shaft, a worm wheel, a worm, an electric motor, and a torque joint portion.
Of these, the housing is supported by a fixed portion and does not rotate.
The rotating shaft is provided so as to be rotatable 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. As such a rotation shaft, in addition to the steering shaft 2 shown in FIG. 6, the intermediate shaft 18, the input shaft (pinion shaft) of the steering gear unit 19, and the like can be employed. Of course, the fixed portion for supporting the housing differs depending on which of the rotating shafts.
The worm wheel is supported on a part of the rotating shaft inside the housing and concentrically with the rotating shaft, and rotates together with the rotating shaft.
The worm is provided with worm teeth at an intermediate portion in the axial direction of the worm shaft. Then, with the worm teeth meshed with the worm wheel, the axial end of the worm shaft is rotatably supported by the housing by a bearing.
The electric motor has its output shaft arranged concentrically with the worm for rotationally driving the worm.
The torque joint portion is provided between the distal end portion of the output shaft and the proximal end portion of the worm so that torque can be transmitted from the output shaft to the worm. The torque joint portion includes a driving side uneven portion, a driven side uneven portion, and an elastic member.
Of these, the drive-side uneven portion is provided concentrically with the output shaft on the output shaft side, and rotates together with the output shaft.
The driven-side uneven portion is provided concentrically with the worm on the worm side, engages with the drive-side uneven portion in the torque transmission direction, and rotates together with the worm.
The elastic member is sandwiched between the driving-side uneven portion and the driven-side uneven portion with respect to the torque transmission direction.

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、上記駆動側凹凸部と上記被駆動側凹凸部との係合に基づく上記トルク継手部は、上記トルクの伝達方向に関する剛性が低い低剛性伝達部と、同じくこの剛性が高い高剛性伝達部とを、軸方向に関して互いに直列に配置して成る。又、このうちの低剛性伝達部の、上記トルクの伝達方向に関する隙間の大きさを、上記高剛性伝達部の同方向の隙間の大きさよりも小さくしている。 In particular, in the electric power steering apparatus according to the present invention, the torque joint portion based on the engagement between the driving-side uneven portion and the driven-side uneven portion has a low rigidity with low rigidity in the torque transmission direction. The transmission unit and the high-rigidity transmission unit having the same high rigidity are arranged in series with each other in the axial direction. In addition, the size of the gap in the torque transmission direction of the low-rigidity transmission portion is made smaller than the size of the gap in the same direction of the high-rigidity transmission portion.

上述の様な本発明の電動式パワーステアリング装置を実施する場合に好ましくは、請求項２に記載した様に、トルクの伝達方向に関する剛性が、低剛性伝達部と高剛性伝達部との中間である、中剛性伝達部を、軸方向に関してこれら低剛性伝達部及び高剛性伝達部と直列に配置する。そして、この中剛性伝達部の、上記トルクの伝達方向に関する隙間の大きさを、これら低剛性伝達部及び高剛性伝達部の同方向の隙間の中間の値とする。
尚、トルクの伝達方向に関する低剛性伝達部の隙間の大きさは、請求項３に記載した様に零にする事もできるし、或いは、請求項４に記載した様に、前記出力軸と上記ウォームとの間に存在する可能性のあるミスアライメントを補償できる（製造現場で許容できる最大のミスアライメントが発生した場合にも、円周方向の一部で隙間が消失せず、上記低剛性伝達部に存在する弾性部材が弾性的に圧縮されない）だけの小さな値とする事もできる。 When the electric power steering apparatus of the present invention as described above is implemented, preferably, the rigidity in the torque transmission direction is intermediate between the low rigidity transmission section and the high rigidity transmission section. A certain middle rigidity transmission section is arranged in series with the low rigidity transmission section and the high rigidity transmission section in the axial direction. And the magnitude | size of the clearance gap regarding the transmission direction of the said torque of this middle rigidity transmission part is made into the intermediate value of the clearance gap of the same direction of these low rigidity transmission parts and high rigidity transmission parts.
In addition, the size of the gap of the low-rigidity transmission portion with respect to the torque transmission direction can be zero as described in claim 3, or, as described in claim 4, the output shaft and the above-mentioned Can compensate for misalignment that may exist with the worm (even if the maximum misalignment allowed at the manufacturing site occurs, the gap does not disappear in a part of the circumferential direction, and the above-mentioned low-rigidity transmission It is also possible to make the value as small as possible (the elastic member present in the portion is not elastically compressed).

上述の様な構成を有する本発明の電動式パワーステアリング装置によれば、出力軸の先端部とウォームの基端部との間に設けたトルク継手部の剛性を、このトルク継手部で伝達されるトルクの大きさに応じて変化させられる。具体的には、このトルクが小さい場合に上記剛性を低く抑えつつ、このトルクが大きい場合にこの剛性を高くできる。
即ち、本発明の構造によれば、このトルクが小さい場合には、低剛性伝達部及び高剛性伝達部のうちの低剛性伝達部のみが、このトルクを伝達する。この状態では、残りの高剛性伝達部には、未だ、トルクの伝達方向に関する隙間が存在する為、この高剛性伝達部がトルク伝達に供される事はない。この状態では、上記トルク継手部の剛性を低くできて、十分な緩衝作用を受けられる。この結果、出力軸からウォームに、トルクが緩徐に伝達される為、この出力軸の回転がこのウォーム軸に、直接的に伝達される事がなくなり、ステアリングホイールを操作する運転者に違和感を与える事がなくなる。 According to the electric power steering apparatus of the present invention having the above-described configuration, the rigidity of the torque joint portion provided between the distal end portion of the output shaft and the base end portion of the worm is transmitted by this torque joint portion. It is changed according to the magnitude of torque. Specifically, the rigidity can be increased when the torque is large while the rigidity is kept low when the torque is small.
That is, according to the structure of the present invention, when this torque is small, only the low-rigidity transmission part of the low-rigidity transmission part and the high-rigidity transmission part transmits this torque. In this state, since the remaining high-rigidity transmission parts still have a gap in the torque transmission direction, the high-rigidity transmission parts are not used for torque transmission. In this state, the rigidity of the torque joint portion can be lowered and a sufficient buffering action can be received. As a result, since torque is slowly transmitted from the output shaft to the worm, the rotation of the output shaft is not directly transmitted to the worm shaft, which makes the driver operating the steering wheel feel uncomfortable. Things disappear.

これに対して、上記トルクが大きくなると、このトルクの伝達方向に関する、上記低剛性伝達部の弾性変形量が増大し、上記高剛性伝達部の隙間が消失する。そして、それ以上のトルクを伝達する場合には、上記低剛性伝達部だけでなく、上記高剛性伝達部も、このトルクの伝達に供される。この為、上記トルク伝達に関する、上記トルク継手部の剛性を高くできる。この結果、トルク伝達の遅れに伴う操舵感の悪化を防止できる。又、この状態では、上記低剛性伝達部で伝達されるトルクの大きさは一定となり、この低剛性伝達部の弾性変形量がそれ以上大きくなる事はない為、この低剛性伝達部を構成する弾性部材の耐久性が低下する事を防止できる。
要するに、本発明によれば、トルク継手部で伝達するトルクが小さい場合にこのトルク継手部の剛性を低く抑えつつ、このトルクが大きい場合にこのトルク継手部の剛性を高くできる。この為、このトルク継手部の耐久性を確保しつつ、ステアリングホイールを操作する運転者に違和感を与える事を防止できる。 On the other hand, when the torque increases, the amount of elastic deformation of the low-rigidity transmission portion in the torque transmission direction increases, and the gap of the high-rigidity transmission portion disappears. And when transmitting the torque beyond it, not only the said low-rigidity transmission part but the said high-rigidity transmission part is provided for transmission of this torque. For this reason, the rigidity of the torque joint portion relating to the torque transmission can be increased. As a result, it is possible to prevent a deterioration in steering feeling due to a delay in torque transmission. In this state, the magnitude of the torque transmitted by the low-rigidity transmission unit is constant, and the amount of elastic deformation of the low-rigidity transmission unit does not increase any more. It can prevent that durability of an elastic member falls.
In short, according to the present invention, the rigidity of the torque joint portion can be increased when the torque is large while the rigidity of the torque joint portion is kept low when the torque transmitted by the torque joint portion is small. For this reason, it is possible to prevent the driver operating the steering wheel from feeling uncomfortable while ensuring the durability of the torque joint portion.

更に、請求項２に記載した発明の様に、低剛性伝達部及び高剛性伝達部に加えて中剛性伝達部を設ければ、上記出力軸と上記ウォームとの間で伝達されるトルクの変動に応じて、上記トルク継手部の剛性を３段階に変化させられる。この為、上記低剛性伝達部と上記高剛性伝達部とだけを設けて、上記トルク継手部の剛性を２段階だけ変化させる場合に比べて、トルク継手部の耐久性確保と、ステアリングホイールの操作感向上とを、より高次元で両立させられる。
トルクの伝達方向に関する低剛性伝達部の隙間に関しては、請求項３に記載した様に零にすれば、ステアリングホイールの操作感向上の面からは有利である。即ち、上記隙間を零にすれば、上記出力軸の起動直後から、この出力軸から上記ウォームへのトルク伝達が開始されるので、上記ステアリングホイールの操作開始直後から、電動モータによるアシスト力を得られ、上記操作感の向上を図れる。
これに対して、請求項４に記載した様に、上記隙間として、ミスアライメントを補償できるだけの、小さな正の値を設定すれば、出力軸とウォームとの間にミスアライメントが存在しても、上記低剛性伝達部に存在する弾性部材が弾性的に圧縮されない。この結果、上記ミスアライメントに基づいてトルク継手部で発生する伝達効率の低下（ロストルクの増大）を抑えられる。
上記隙間に関して、何れの値（零又は正の値）を採用するかは、発生し得るミスアライメントの大きさ、電動モータの出力、低剛性部に設置する弾性部材の弾力等に応じて設計的に選択する。 Further, as in the invention described in claim 2, if a medium-rigidity transmission portion is provided in addition to the low-rigidity transmission portion and the high-rigidity transmission portion, the fluctuation of torque transmitted between the output shaft and the worm is changed. Accordingly, the rigidity of the torque joint can be changed in three stages. For this reason, as compared with the case where only the low-rigidity transmission portion and the high-rigidity transmission portion are provided and the rigidity of the torque joint portion is changed by two stages, the durability of the torque joint portion is ensured and the steering wheel is operated. Improvement of feeling can be achieved at a higher level.
With regard to the clearance of the low-rigidity transmission portion with respect to the torque transmission direction, if it is set to zero as described in claim 3, it is advantageous from the viewpoint of improving the operational feeling of the steering wheel. That is, if the clearance is set to zero, torque transmission from the output shaft to the worm is started immediately after the output shaft is started, so that the assist force by the electric motor is obtained immediately after the steering wheel operation is started. Therefore, the operational feeling can be improved.
On the other hand, as described in claim 4, if a small positive value that can compensate for misalignment is set as the gap, even if misalignment exists between the output shaft and the worm, The elastic member present in the low-rigidity transmission portion is not elastically compressed. As a result, a decrease in transmission efficiency (an increase in loss torque) that occurs at the torque joint portion based on the misalignment can be suppressed.
Which value (zero or positive value) to use for the gap is designed according to the size of misalignment that can occur, the output of the electric motor, the elasticity of the elastic member installed in the low-rigidity part, etc. Select

［実施の形態の第１例］
図１〜４は、請求項１、２、４に対応する、本発明の実施の形態の１例を示している。尚、本例の電動式パワーステアリング装置の特徴は、トルク継手部２０で伝達するトルクが小さい場合にこのトルク継手部２０の剛性を低く抑えつつ、このトルクが大きい場合にこのトルク継手部の剛性を高くすると共に、弾性部材の耐久性を確保すべく、この弾性部材が過度に押し潰される事を防止する為の構造にある。その他、電動式パワーステアリング装置全体の構造及び作用に就いては、前述した従来構造と同様であるから、この従来構造と同等部分に関する図示並びに説明は、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。尚、前述の図６〜７と図１とで、ハウジング３に対する電動モータ７の取付方向が異なっているが、この点は、設置する自動車に応じ適宜設計的に変更するものであって、本発明の特徴部分とは関係がない。 [First example of embodiment]
1-4 show an example of an embodiment of the present invention corresponding to claims 1, 2, and 4. The electric power steering apparatus according to the present embodiment is characterized in that when the torque transmitted by the torque joint portion 20 is small, the rigidity of the torque joint portion 20 is kept low while the rigidity of the torque joint portion is high. In order to secure the durability of the elastic member, the elastic member is prevented from being excessively crushed. In addition, since the structure and operation of the entire electric power steering apparatus are the same as those of the conventional structure described above, illustrations and descriptions regarding the same parts as those of the conventional structure are omitted or simplified. The explanation will focus on the part. 6 to 7 and FIG. 1 are different in the mounting direction of the electric motor 7 with respect to the housing 3, but this point is appropriately changed in design according to the vehicle to be installed. It has nothing to do with the features of the invention.

本例の構造の場合には、図１〜２に示す様に、ウォーム軸６の基端部に、特許請求の範囲に記載した被駆動側凹凸部であるスプライン孔１１ａを、このウォーム軸６の基端面（図１〜２の左端面）に開口する状態で、このウォーム軸６と同心に形成している。又、上記電動モータ７の出力軸１０の先端部に、特許請求の範囲に記載した駆動側凹凸部であるスプライン軸部１２ａを、この出力軸１０と同心に形成している。そして、このスプライン軸部１２ａと上記スプライン孔１１ａとを、特許請求の範囲に記載した凹凸係合であるスプライン係合させる事で、上記出力軸１０と上記ウォーム軸６とを、回転力の伝達を可能に結合している。但し、上記スプライン軸部１２ａの外周面に形成した雄スプライン歯のピッチ、並びに、上記スプライン孔１１ａの内周面に形成した雌スプライン歯のピッチは、通常のスプライン歯のピッチよりも粗くしている。図示の例では、これら各スプライン歯の中心角ピッチを、それぞれ６０度としている。又、上記両軸１２ａ、６の中心軸に直交する仮想平面に関する、上記各スプライン歯の断面形状は、略等脚台形としている。 In the case of the structure of this example, as shown in FIGS. 1 and 2, the spline hole 11 a that is the driven side uneven portion described in the claims is provided at the base end portion of the worm shaft 6. It is formed concentrically with the worm shaft 6 in a state of opening to the base end surface (the left end surface in FIGS. 1 and 2). Further, a spline shaft portion 12 a which is a drive side uneven portion described in the claims is formed concentrically with the output shaft 10 at the tip portion of the output shaft 10 of the electric motor 7. Then, the spline shaft portion 12a and the spline hole 11a are engaged with the spline which is the concave-convex engagement described in the claims, whereby the output shaft 10 and the worm shaft 6 are transmitted with rotational force. Is possible to combine. However, the pitch of the male spline teeth formed on the outer peripheral surface of the spline shaft portion 12a and the pitch of the female spline teeth formed on the inner peripheral surface of the spline hole 11a are made coarser than the pitch of the normal spline teeth. Yes. In the illustrated example, the center angle pitch of each spline tooth is 60 degrees. Moreover, the cross-sectional shape of each spline tooth regarding the virtual plane orthogonal to the central axis of both the shafts 12a, 6 is a substantially isosceles trapezoid.

上記スプライン孔１１ａと上記スプライン軸部１２ａとのうち、スプライン孔１１ａの（中心軸に直交する仮想平面に関する）内周面の断面形状、及び、断面積（この断面形状により周囲を囲まれる部分の面積）に関しては、トルク継手部２０の全長に亙り同じである（変化していない）。又、上記スプライン孔１１ａの内周面は、上記トルク継手部２０の全長に亙り、上記ウォーム軸６を構成する金属材が露出している。従って、上記スプライン孔１１ａの内周面に関しては、上記トルク継手部２０の全長に亙り、十分に大きな剛性を確保している。 Of the spline hole 11a and the spline shaft portion 12a, the cross-sectional shape of the inner peripheral surface (with respect to a virtual plane orthogonal to the central axis) of the spline hole 11a and the cross-sectional area (the portion surrounded by the cross-sectional shape) The area) is the same over the entire length of the torque coupling portion 20 (no change). Further, the inner peripheral surface of the spline hole 11a extends over the entire length of the torque joint portion 20, and the metal material constituting the worm shaft 6 is exposed. Therefore, with respect to the inner peripheral surface of the spline hole 11a, a sufficiently large rigidity is ensured over the entire length of the torque joint portion 20.

これに対して、上記スプライン軸部１２ａの外周面に関しては、基端部（図１〜２の左端部）から先端部（図１〜２の右端部）に向けて、断面積（中心軸に直交する仮想平面に関して、外周面の断面形状により周囲を囲まれる部分の面積）を３段階に変化させると共に、材質に関しても、基端部と、中間部乃至先端部とで異ならせている。即ち、上記スプライン軸部１２ａの軸方向に関して、基端部に高剛性スプライン軸部２１を、中間部に中剛性スプライン軸部２２を、先端部に低剛性スプライン軸部２３を、それぞれ設けている。これら各スプライン軸部２１〜２３の断面積に関しては、基端部に設けた高剛性スプライン軸部２１から先端部に設けた低剛性スプライン軸部２３に向かう程大きくしている（高剛性スプライン軸部２１の断面積＜中剛性スプライン軸部２２の断面積＜低剛性スプライン軸部２３の断面積）。 On the other hand, with respect to the outer peripheral surface of the spline shaft portion 12a, the cross-sectional area (from the central axis to the central axis) from the base end portion (left end portion in FIGS. With respect to the orthogonal virtual plane, the area of the portion surrounded by the cross-sectional shape of the outer peripheral surface is changed in three stages, and the material is also different between the base end portion and the intermediate portion or the tip end portion. That is, with respect to the axial direction of the spline shaft portion 12a, a high-rigidity spline shaft portion 21 is provided at the base end portion, an intermediate-rigid spline shaft portion 22 is provided at the intermediate portion, and a low-rigidity spline shaft portion 23 is provided at the distal end portion. . The cross-sectional areas of these spline shaft portions 21 to 23 are increased from the high rigidity spline shaft portion 21 provided at the base end portion toward the low rigidity spline shaft portion 23 provided at the distal end portion (high rigidity spline shaft). Cross-sectional area of portion 21 <cross-sectional area of medium-rigidity spline shaft portion 22 <cross-sectional area of low-rigidity spline shaft portion 23).

尚、上記各スプライン軸部２１〜２３は、断面積が異なるが、外周面の形状に関しては、相似形としている。従って、上記スプライン孔１１ａと上記スプライン軸部１２ａとを中立位置にした（雄スプライン、雌スプライン各歯の山部の位相を半ピッチ分ずらせた＝雄スプライン、雌スプライン各歯の山部の位相と谷部の位相とを一致させた）状態で、円周方向（トルクの伝達方向）に関して存在する隙間の大きさは、上記各スプライン軸部２１〜２３同士、互いに異なる。具体的には、図４に示す様に、高剛性スプライン軸部２１に関する円周方向隙間の厚さδ_H が最も大きく、中剛性スプライン軸部２２に関する円周方向隙間の厚さδ_M がそれに続き、低剛性スプライン軸部２３の円周方向隙間の厚さδ_S が最も小さく（δ_H ＞δ_M ＞δ_S ＞０）なっている。 The spline shafts 21 to 23 have different cross-sectional areas, but are similar in shape to the outer peripheral surface. Accordingly, the spline hole 11a and the spline shaft portion 12a are in a neutral position (the phase of the crests of the male spline and female spline teeth is shifted by a half pitch = the phase of the crests of the male spline and female spline teeth. In the state in which the phases of the troughs are matched), the sizes of the gaps existing in the circumferential direction (torque transmission direction) are different from each other. Specifically, as shown in FIG. 4, the thickness δ _H of the circumferential clearance with respect to the high-rigidity spline shaft portion 21 is the largest, and the thickness δ _M of the circumferential clearance with respect to the medium-rigidity spline shaft portion 22 is Subsequently, the thickness δ _S of the circumferential clearance of the low-rigidity spline shaft portion 23 is the smallest (δ _H > δ _M > δ _S > 0).

又、上記各スプライン軸部２１〜２３の外周面の材質に関しては、基端部に設けた高剛性スプライン軸部２１の外周面を金属製（一般的には、炭素鋼、ステンレス鋼等の鉄系合金製）としている。これに対して、中間部に設けた中剛性スプライン軸部２２、及び、先端部に設けた低剛性スプライン軸部２３の外周面は、弾性材製としている。これら中剛性、低剛性、両スプライン軸部２２、２３の外周面を覆う弾性材としては、ニトリルゴム、シリコンゴム、ウレタンゴム等のゴム、或いはポリウレタンの如きエラストマー、合成樹脂等を使用する。 As for the material of the outer peripheral surface of each of the spline shaft portions 21 to 23, the outer peripheral surface of the high-rigidity spline shaft portion 21 provided at the base end portion is made of metal (generally, iron such as carbon steel or stainless steel). Made of an alloy). On the other hand, the outer peripheral surfaces of the medium-rigidity spline shaft portion 22 provided at the intermediate portion and the low-rigidity spline shaft portion 23 provided at the tip portion are made of an elastic material. As the elastic material covering the outer peripheral surfaces of these medium rigidity, low rigidity, and both spline shaft portions 22 and 23, rubber such as nitrile rubber, silicon rubber, urethane rubber, elastomer such as polyurethane, synthetic resin, or the like is used.

上述の様な、上記各スプライン軸部２１〜２３を構成する為に本例の場合には、上記高剛性スプライン軸部２１に関しては、上記スプライン軸部１２ａと一体に形成する事で、この高剛性スプライン軸部２１の（中心部から外周面に至る）全体を、金属製としている。これに対して、上記中剛性、低剛性、両スプライン軸部２２、２３は、上記スプライン軸部１２ａのうちで上記高剛性スプライン軸部２１よりも先端側に突出した支持軸部２４に、上述の様な弾性材を外嵌支持する事で構成している。このうち、支持軸部２４の基半部には、上記中剛性スプライン軸部２２を構成する為の中剛性側弾性部材２５を、同じく先半部には、上記低剛性スプライン軸部２３を構成する低剛性側弾性部材２６を、それぞれ外嵌支持している。上記支持軸部２４の外周面、及び、これら両弾性部材２５、２６の内周面の断面形状は、これら支持軸部２４と弾性部材２５、２６との間でトルクの伝達が可能な様に、非円形（例えば四角形、より好ましくは、上記スプライン軸部１２ａの外周面と相似である六つ星形等）に形成している。上記両弾性部材２５、２６は、それぞれ上記支持軸部２４に締り嵌めで外嵌する事で、上記スプライン軸部１２ａに、トルクの伝達を可能に支持している。 In the case of the present example in order to configure each of the spline shaft portions 21 to 23 as described above, the high-rigidity spline shaft portion 21 is formed integrally with the spline shaft portion 12a. The entire rigid spline shaft portion 21 (from the central portion to the outer peripheral surface) is made of metal. On the other hand, the medium rigidity, low rigidity, both spline shaft portions 22 and 23 are connected to the support shaft portion 24 that protrudes more distally than the high rigidity spline shaft portion 21 in the spline shaft portion 12a. It is configured by supporting and fitting an elastic material such as Among them, the base half portion of the support shaft portion 24 is configured with the medium-rigidity elastic member 25 for configuring the medium-rigidity spline shaft portion 22, and the low-rigidity spline shaft portion 23 is configured with the front half portion. The low-rigidity elastic members 26 that are to be fitted are supported by external fitting. The cross-sectional shape of the outer peripheral surface of the support shaft portion 24 and the inner peripheral surfaces of both elastic members 25 and 26 is such that torque can be transmitted between the support shaft portion 24 and the elastic members 25 and 26. , Non-circular (for example, a quadrangle, more preferably a six star shape similar to the outer peripheral surface of the spline shaft portion 12a). The both elastic members 25 and 26 are supported by the spline shaft portion 12a so as to be able to transmit torque by being externally fitted to the support shaft portion 24 by an interference fit.

本例の場合、上記中剛性側弾性部材２５の径方向に関する厚さ寸法Ｔ₂₅を、上記低剛性側弾性部材２６の同方向の厚さ寸法Ｔ₂₆よりも小さく（Ｔ₂₅＜Ｔ₂₆）している。従って、これら両弾性部材２５、２６の材質（硬度）を同じとしても、上記中剛性スプライン軸部２２の剛性が、上記低剛性スプライン軸部２３の剛性よりも高くなる。但し、上記厚さ寸法Ｔ₂₅、Ｔ₂₆の相違のみでは、これら両スプライン軸部２２、２３の剛性の差を十分に出せない場合には、上記両弾性部材２５、２６の材質（硬度）を異ならせても良い。何れにしても、上記高剛性スプライン軸部２１と前記スプライン孔１１ａとのスプライン係合部が、円周方向隙間の厚さδ_H が最も大きい、高剛性伝達部２７を構成する。又、上記中剛性スプライン軸部２２と上記スプライン孔１１ａとのスプライン係合部が、円周方向隙間の厚さδ_M が中間である、中剛性伝達部２８を構成する。更に、上記低剛性スプライン軸部２３と上記スプライン孔１１ａとのスプライン係合部が、円周方向隙間の厚さδ_S が最も小さい低剛性伝達部２９を構成する。 In the case of this example, the thickness dimension T ₂₅ in the radial direction of the medium-rigid side elastic member 25 is made smaller than the thickness dimension T ₂₆ in the same direction of the low-rigid side elastic member 26 (T ₂₅ <T ₂₆ ). ing. Therefore, even if the material (hardness) of both the elastic members 25 and 26 is the same, the rigidity of the medium-rigidity spline shaft portion 22 is higher than the rigidity of the low-rigidity spline shaft portion 23. However, if the difference in rigidity between the spline shaft portions 22 and 23 cannot be sufficiently obtained only by the difference in the thickness dimensions T ₂₅ and T ₂₆ , the material (hardness) of the elastic members 25 and 26 is set to be the same. It may be different. Anyway, a spline engagement portion between the spline hole 11a and the high-rigidity spline shaft portion 21, the largest thickness [delta] _H of the circumferential clearance, constituting the high-rigidity transmitter 27. Further, a spline engagement portion of the rigid spline shaft portion 22 and the spline hole 11a in the above is the thickness [delta] _M of circumferential clearance is an intermediate to form a middle rigid transmission unit 28. Further, a spline engagement portion between the low-rigidity spline shaft portion 23 and the spline hole 11a constitute the smallest thickness [delta] _S in the circumferential clearance less rigid transmission unit 29.

上述の様な構成を有する本例の電動式パワーステアリング装置の作動時には、電動モータ７からステアリングシャフト２（図６参照）に補助動力を付与すべく、この電動モータ７の出力軸１０により、前記ウォーム軸６を回転駆動する。この際、上記補助動力の大きさに応じて、上記低剛性伝達部２９と、上記中剛性伝達部２８と、上記高剛性伝達部２７とのうちの１以上の伝達部を介して、上記ウォーム軸６を回転駆動する。又、上記補助動力が小さい状態から大きい状態に変化する場合には、その程度に応じて、上記各伝達部２９、２８、２７のうちの何れの部分を介して上記ウォーム軸６を回転駆動するかを異ならせる。 When the electric power steering apparatus of this example having the above-described configuration is operated, the output shaft 10 of the electric motor 7 is used to apply auxiliary power from the electric motor 7 to the steering shaft 2 (see FIG. 6). The worm shaft 6 is driven to rotate. At this time, depending on the magnitude of the auxiliary power, the worm is transmitted through one or more of the low-rigidity transmission portion 29, the medium-rigidity transmission portion 28, and the high-rigidity transmission portion 27. The shaft 6 is driven to rotate. Further, when the auxiliary power changes from a small state to a large state, the worm shaft 6 is rotationally driven through any one of the transmission portions 29, 28, 27 according to the degree. Make them different.

先ず、上記補助動力が最も小さい場合には、上記各伝達部２９、２８、２７のうちの低剛性伝達部２９のみで、上記出力軸１０から上記ウォーム軸６にトルクを伝達する。即ち、この場合には、上記最も小さい、厚さがδ_S である円周方向隙間が消失（上記スプライン孔１１ａの内周面に形成した雌スプライン歯の円周方向側面と、前記低剛性側弾性部材２６の外周面に形成した雄スプライン歯の円周方向側面とが当接）し、上記低剛性伝達部２９が上記トルクを伝達する。この状態では、上記スプライン孔１１ａの内周面と、前記中剛性側弾性部材２５の外周面及び前記高剛性スプライン軸部２１の外周面との間には、全周に亙り（トルクの伝達方向に関して後側は勿論、前側に関しても）隙間が介在したままとなる。上記低剛性側弾性部材２６の剛性は低い為、上記出力軸１０から上記ウォーム軸６に、図５のａ範囲に示す様に、トルクが緩徐に伝達される。即ち、ステアリングホイール１を操作する為の操舵力を補助する為、ステアリングシャフト２（図６参照）に付与する補助力が小さくて済む場合には、上記出力軸１０の回転が上記ウォーム軸６に、弾性部材による十分な緩衝作用を受けた状態で伝達される。従って、前記電動モータ７への通電開始時に、上記出力軸１０の起動トルクが上記ウォーム軸６に、直接的に（いきなり）伝達される事が防止される。この為、上記ステアリングホイール１を操作する運転者に違和感を与える事を防止できる。 First, when the auxiliary power is the smallest, torque is transmitted from the output shaft 10 to the worm shaft 6 only by the low rigidity transmission portion 29 of the transmission portions 29, 28, 27. That is, in this case, the smallest circumferential gap having a thickness of δ _S disappears (the circumferential side surface of the female spline teeth formed on the inner circumferential surface of the spline hole 11a and the low rigidity side). The circumferential surface of the male spline teeth formed on the outer peripheral surface of the elastic member 26 abuts), and the low-rigidity transmission portion 29 transmits the torque. In this state, between the inner peripheral surface of the spline hole 11a and the outer peripheral surface of the medium-rigid side elastic member 25 and the outer peripheral surface of the high-rigidity spline shaft portion 21, the entire circumference (torque transmission direction) With respect to the rear side as well as the front side, the gap remains interposed. Since the rigidity of the low-rigidity elastic member 26 is low, torque is slowly transmitted from the output shaft 10 to the worm shaft 6 as shown in the range a of FIG. That is, when the assisting force applied to the steering shaft 2 (see FIG. 6) is small to assist the steering force for operating the steering wheel 1, the rotation of the output shaft 10 is applied to the worm shaft 6. And transmitted in a state of being sufficiently buffered by the elastic member. Therefore, the start torque of the output shaft 10 is prevented from being transmitted directly (suddenly) to the worm shaft 6 at the start of energization of the electric motor 7. For this reason, it is possible to prevent the driver who operates the steering wheel 1 from feeling uncomfortable.

これに対して、上記補助動力が少し大きくなると、上記最も小さい、厚さがδ_S である円周方向隙間だけでなく、中程度の厚さδ_M の円周方向隙間もが消失し、上記低剛性伝達部２９に加えて、上記中剛性伝達部２８も上記トルクを伝達する。この状態でも、上記スプライン孔１１ａの内周面と、上記高剛性スプライン軸部２１の外周面との間には、全周に亙り隙間が介在したままとなる。この結果、図５のｂ範囲に示す様に、上記少し大きめの補助動力を、上記出力軸１０から上記ウォーム軸６に、確実に伝達して、上記ステアリングホイール１を回転させる為に必要となる操舵力を、適切に軽減できる。 In contrast, when the auxiliary power is slightly increased, not only the smallest circumferential gap with a thickness of δ _S but also a circumferential gap with a medium thickness of δ _M disappears. In addition to the low-rigidity transmission unit 29, the medium-rigidity transmission unit 28 also transmits the torque. Even in this state, a gap remains between the inner peripheral surface of the spline hole 11a and the outer peripheral surface of the high-rigidity spline shaft portion 21 over the entire periphery. As a result, as shown in the range b in FIG. 5, the slightly larger auxiliary power is required to reliably transmit the output shaft 10 to the worm shaft 6 and rotate the steering wheel 1. Steering force can be reduced appropriately.

又、上記補助動力が更に大きくなると、上記最も小さい、厚さがδ_S である円周方向隙間、上記中程度の厚さδ_M の円周方向隙間に加えて、前記最も大きい厚さがδ_H である円周方向隙間迄もが消失し、前記高剛性伝達部２７が、上記低剛性伝達部２９及び上記中剛性伝達部２８により伝達し切れないトルクを伝達する。従って上記ウォーム軸６は上記出力軸１０により、図５のｃ範囲に示す様に、十分に大きなトルクにより回転駆動される。 Further, when the auxiliary power is further increased, the largest thickness is δ in addition to the smallest circumferential gap having a thickness δ _S and the middle gap δ _{M having} a thickness δ _S. _Even the circumferential clearance that is _H disappears, and the high-rigidity transmission portion 27 transmits torque that cannot be transmitted by the low-rigidity transmission portion 29 and the medium-rigidity transmission portion 28. Therefore, the worm shaft 6 is rotationally driven by the output shaft 10 with a sufficiently large torque as shown in the range c of FIG.

上記補助動力が大きくなる過程で、上記高剛性伝達部２７を構成する、前記高剛性スプライン軸部２１の外周面に形成した雄スプライン歯と、上記スプライン孔１１ａの内周面に形成した雌スプライン歯とが衝突するが、この衝突は、低剛性伝達部２９を構成する低剛性側弾性部材２６及び上記中剛性伝達部２８を構成する中剛性側弾性部材２５の弾性に抗しつつ（これら両弾性部材２６、２５が上記両スプライン歯同士の動きを或る程度緩衝した後に）行なわれるので、緩徐に行なわれる。従って、上記補助動力の伝達方向が逆転する様な場合、或いは悪路走行等に伴って振動が加わる様な場合にも、上記高剛性スプライン軸部２１と上記スプライン孔１１ａとのスプライン係合部で、歯打ち音等の耳障りな騒音や振動が発生する事はない。又、大きな補助動力を伝達する場合にも、上記両弾性部材２６、２５を介して伝達する補助動力は限られた値である為、これら両弾性部材２６、２５が過度に弾性変形する事はなく、これら両弾性部材２６、２５の耐久性が損なわれる事はない。 In the process of increasing the auxiliary power, the male spline teeth formed on the outer peripheral surface of the high-rigidity spline shaft portion 21 constituting the high-rigidity transmission portion 27 and the female spline formed on the inner peripheral surface of the spline hole 11a. The teeth collide with the teeth, while resisting the elasticity of the low-rigidity elastic member 26 constituting the low-rigidity transmission portion 29 and the middle-rigidity elastic member 25 constituting the medium-rigidity transmission portion 28 (both of them). Since the elastic members 26 and 25 are performed after the movement of the two spline teeth is buffered to some extent, the operation is performed slowly. Accordingly, even when the transmission direction of the auxiliary power is reversed or when vibration is applied due to traveling on a rough road or the like, the spline engaging portion between the high-rigidity spline shaft portion 21 and the spline hole 11a. Thus, no annoying noise or vibration such as rattling noise is generated. Even when a large auxiliary power is transmitted, the auxiliary power transmitted through the elastic members 26 and 25 is a limited value. Therefore, the elastic members 26 and 25 may not be elastically deformed excessively. In addition, the durability of both the elastic members 26 and 25 is not impaired.

又、本例の構造は、上記ウォーム軸６の基端部をハウジング３に対し回転自在に支持する為の転がり軸受９ｂの内径側に設置できる等、小型且つ軽量に構成できる。又、上記ウォーム軸６の基端部と上記出力軸１０の先端部とを結合する作業は、上記両弾性部材２６、２５を上記スプライン孔１１ａ内に挿入する事で、容易に行なえる。更に、上記ウォーム軸６の基端部と上記出力軸１０とは、前記トルク継手部２０の内部に存在する隙間により、相対変位を可能に結合している。従って、上記ウォーム軸６と出力軸１０との位置関係が、トルク伝達に基づく弾性変形、摩耗、温度変化、吸水等により多少変化した場合でも、上記トルク継手部２０の内部に存在する隙間部分での変位に基づいて、この変化を吸収（補償）できる。この為、上記位置関係が多少変化しても、上記ウォーム軸６の基端部と上記出力軸１０との結合部で、コジリが発生する事はなく、コジリに基づく伝達効率の低下や耐久性の低下を招く事はない。尚、上記スプライン孔１１ａの内周面と前記スプライン軸部１２ａとの係合部にグリースを介在させれば、この係合部の作動をより滑らかにして、上記コジリの防止に加えて、前記歯打ち音等の異音や振動の発生をより確実に防止できる。
尚、図示の例とは逆に、出力軸の側にスプライン孔を、ウォーム軸の側にスプライン軸を、それぞれ設ける事もできる。 Further, the structure of this example can be configured to be small and light, such as being able to be installed on the inner diameter side of the rolling bearing 9b for rotatably supporting the base end portion of the worm shaft 6 with respect to the housing 3. Further, the operation of joining the base end portion of the worm shaft 6 and the distal end portion of the output shaft 10 can be easily performed by inserting the elastic members 26 and 25 into the spline hole 11a. Further, the base end portion of the worm shaft 6 and the output shaft 10 are coupled to each other so as to be capable of relative displacement by a gap existing inside the torque joint portion 20. Therefore, even when the positional relationship between the worm shaft 6 and the output shaft 10 is slightly changed due to elastic deformation based on torque transmission, wear, temperature change, water absorption, etc., the gap portion existing in the torque joint portion 20 is not affected. This change can be absorbed (compensated) based on the displacement of. For this reason, even if the positional relationship changes to some extent, the joint between the base end portion of the worm shaft 6 and the output shaft 10 does not cause squeezing, resulting in a decrease in transmission efficiency and durability due to scouring. It will not lead to a decline. In addition, if grease is interposed in the engagement portion between the inner peripheral surface of the spline hole 11a and the spline shaft portion 12a, the operation of the engagement portion is made smoother, in addition to the prevention of galling, Generation of abnormal noise such as rattling noise and vibration can be prevented more reliably.
Contrary to the illustrated example, a spline hole can be provided on the output shaft side, and a spline shaft can be provided on the worm shaft side.

本発明の実施の形態の１例を示す、図６の拡大Ａ−Ａ断面に相当する図。The figure equivalent to the expanded AA cross section of FIG. 6 which shows an example of embodiment of this invention. 図１のＢ部拡大断面図。The B section expanded sectional view of FIG. 図２のＣ−Ｃ断面図。CC sectional drawing of FIG. 図３のＤ部拡大図。The D section enlarged view of FIG. 電動モータの出力軸とウォーム軸との間の、捩れ角と伝達トルクの大きさとの関係を示す線図。The diagram which shows the relationship between the torsion angle and the magnitude | size of transmission torque between the output shaft of an electric motor, and a worm shaft. 従来構造の第１例を示す、電動式パワーステアリング装置の全体構成の部分切断側面図。The partial cutaway side view of the whole structure of the electric power steering device which shows the 1st example of conventional structure. 図６の拡大Ａ−Ａ断面図。The expanded AA sectional view of FIG. 従来構造の第２例を示す、継手部の分解斜視図。The disassembled perspective view of the joint part which shows the 2nd example of conventional structure.

Explanation of symbols

１ステアリングホイール
２ステアリングシャフト
３ハウジング
４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ウォーム
９ａ、９ｂ転がり軸受
１０出力軸
１１、１１ａスプライン孔
１２、１２ａスプライン軸部
１３押圧駒
１４コイルばね
１５ａ、１５ｂ回転軸
１６ａ、１６ｂ凹凸部
１７弾性部材
１８中間シャフト
１９ステアリングギヤユニット
２０トルク継手部
２１高剛性スプライン軸部
２２中剛性スプライン軸部
２３低剛性スプライン軸部
２４支持軸部
２５中剛性側弾性部材
２６低剛性側弾性部材
２７高剛性伝達部
２８中剛性伝達部
２９低剛性伝達部 DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Housing 4 Worm wheel 5 Worm tooth 6 Worm shaft 7 Electric motor 8 Worm 9a, 9b Rolling bearing 10 Output shaft 11, 11a Spline hole 12, 12a Spline shaft part 13 Pressing piece 14 Coil spring 15a, 15b Rotating shafts 16a, 16b Uneven portion 17 Elastic member 18 Intermediate shaft 19 Steering gear unit 20 Torque joint portion 21 High rigidity spline shaft portion 22 Medium rigidity spline shaft portion 23 Low rigidity spline shaft portion 24 Support shaft portion 25 Medium rigidity side elastic member 26 Low-rigidity elastic member 27 High-rigidity transmission part 28 Medium-rigidity transmission part 29 Low-rigidity transmission part

Claims

A housing that is supported by a fixed portion and does not rotate; a rotating shaft that is rotatably provided to the housing and is rotated by an operation of a steering wheel; A worm wheel that is supported concentrically with the rotary shaft inside the housing and rotates together with the rotary shaft, and a worm tooth is provided at an axially intermediate portion of the worm shaft. In a state where the worm teeth are engaged with the worm wheel, the worm shaft is rotatably supported with respect to the housing by a bearing at the axial end of the worm shaft, and the output shaft is driven to rotate the worm. An electric motor arranged concentrically with the worm, and provided between the tip end of these output shafts and the base end of the worm, from this output shaft to this worm A torque coupling portion that allows torque transmission freely, the torque coupling portion being provided concentrically with the output shaft on the output shaft side and rotating together with the output shaft, and on the worm side. Concentric engagement with the drive-side uneven portion provided in concentric relation with the worm in the torque transmission direction, and a driven-side uneven portion rotating with the worm, the driven-side uneven portion, and the drive-side uneven portion, In the electric power steering apparatus comprising an elastic member sandwiched with respect to the direction of transmission of the torque between, the torque coupling based on the engagement between the driven side uneven portion and the drive side uneven portion The low-rigidity transmission part with low rigidity in the torque transmission direction and the high-rigidity transmission part with high rigidity are arranged in series with respect to the axial direction. The size of the gap regarding the transfer direction of the torque, the electric power steering apparatus characterized in that is smaller than the size in the same direction of the gap of the high-rigidity transmission unit.

The middle rigidity transmission part, whose rigidity in the torque transmission direction is intermediate between the low rigidity transmission part and the high rigidity transmission part, is arranged in series with the low rigidity transmission part and the high rigidity transmission part in the axial direction. 2. The electric type according to claim 1, wherein the size of the clearance of the rigidity transmission portion in the torque transmission direction is set to an intermediate value between the size of the clearance in the same direction of the low rigidity transmission portion and the high rigidity transmission portion. Power steering device.

The electric power steering apparatus according to any one of claims 1 to 2, wherein a clearance of the low-rigidity transmission unit in the torque transmission direction is zero.

The size of the gap of the low-rigidity transmission part with respect to the torque transmission direction is set to a value that is small enough to compensate for misalignment that may exist between the output shaft and the worm. The electric power steering apparatus described in the item 1.