JP3770310B2 - Electric power steering device - Google Patents

Electric power steering device Download PDF

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Publication number
JP3770310B2
JP3770310B2 JP2000340752A JP2000340752A JP3770310B2 JP 3770310 B2 JP3770310 B2 JP 3770310B2 JP 2000340752 A JP2000340752 A JP 2000340752A JP 2000340752 A JP2000340752 A JP 2000340752A JP 3770310 B2 JP3770310 B2 JP 3770310B2
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Prior art keywords
worm
worm shaft
shaft
cam
electric power
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JP2002145082A (en
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賢二 山元
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JTEKT Corp
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JTEKT Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C25/00—Bearings for exclusively rotary movement adjustable for wear or play
    • F16C25/06—Ball or roller bearings
    • F16C25/08—Ball or roller bearings self-adjusting
    • F16C25/083—Ball or roller bearings self-adjusting with resilient means acting axially on a race ring to preload the bearing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
    • F16C19/02—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows
    • F16C19/04—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for radial load mainly
    • F16C19/06—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for radial load mainly with a single row or balls
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
    • F16C19/54—Systems consisting of a plurality of bearings with rolling friction
    • F16C19/56—Systems consisting of a plurality of bearings with rolling friction in which the rolling bodies of one bearing differ in diameter from those of another
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2361/00—Apparatus or articles in engineering in general
    • F16C2361/61—Toothed gear systems, e.g. support of pinion shafts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H57/00—General details of gearing
    • F16H57/02—Gearboxes; Mounting gearing therein
    • F16H57/021—Shaft support structures, e.g. partition walls, bearing eyes, casing walls or covers with bearings
    • F16H2057/0213—Support of worm gear shafts

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Gears, Cams (AREA)
  • Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Power Steering Mechanism (AREA)
  • Gear Transmission (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は操舵補助力の発生源として電動モータを用いてなる電動式動力舵取装置に関するものである。
【０００２】
【従来の技術】
自動車用の電動式舵取装置として、操舵輪に連なる第１操舵軸と、この第１操舵軸にトーションバーを介して連結されると共に舵取機構に連なる第２操舵軸とを備える装置がある。この装置では、第１および第２の操舵軸の回転方向への相対変位量をトルクセンサにより検出し、このトルクセンサの検出結果に基づいて電動モータの回転を減速機構を介して第２操舵軸に伝えることにより、操舵輪の回転に応じた舵取機構の動作を電動モータの回転により補助し、舵取りのための運転者の労力負担を軽減するようにしている。
【０００３】
上記の減速機構として、ウォームとウォームホイールを有するものが提供されている。ウォームが設けられているウォーム軸およびウォームホイールが設けられている第２操舵軸は、その軸長方向の両端が軸受により支持されて、径方向および軸長方向への移動が阻止されている。
ウォーム軸及びウォームホイールを組み付けるときに、加工精度の範囲内でウォームとウォームホイールとの間に適当なバックラッシが存在するように調整されているが、組立後において、ウォーム及びウォームホイールの歯の摩耗が増大すると、バックラッシが増大して過大となり、騒音の原因となる。
【０００４】
そこで、例えば特開２０００−４３７３９号公報のように、ウォーム軸をウォームホイールに向けて偏倚可能とし、付勢手段によってウォーム軸をその偏倚方向である径方向へ付勢することにより、バックラッシの増大を抑制することが提案されている。
【０００５】
【発明が解決しようとする課題】
しかしながら、付勢手段およびこの付勢手段の付勢力を調整する部材を、ウォーム軸の径方向に沿って配置しなければならない関係上、装置が大型になるという問題がある。
本発明は上記課題に鑑みてなされたものであり、小型で且つバックラッシの増大やこれに伴う騒音の発生を抑制することができる電動式動力舵取装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記目的を達成するため、
請求項１記載の発明は、ステアリングシャフトに負荷されるトルクに応じて駆動される操舵補助用の電動モータの回転をウォーム軸およびウォームホイールを介して舵取り機構に伝える電動式動力舵取装置において、上記ウォーム軸を軸方向に付勢する付勢部材と、付勢部材の付勢力の少なくとも一部を、ウォーム軸を径方向ウォームホイール側へ付勢する力に変換するカム機構とを備え、上記ウォーム軸は径方向ウォームホイール側へ偏倚できるようにカム機構を介してハウジングに保持されることを特徴とするものである。
【０００７】
本発明では、ウォーム軸及びウォームホイールの歯の摩耗により各部品間の寸法誤差が増大しても、これをウォーム軸をウォームホイール側へ偏倚させることにより、吸収することができる。したがって、バックラッシの増大を抑制することができる。しかも、付勢部材をウォーム軸の軸方向に沿ってレイアウトできるので、電動式動力舵取装置を小型にすることができる。
請求項２記載の発明は、請求項１において、上記付勢部材の付勢力を調整する調整部材をさらに備えることを特徴とするものである。本発明では、電動式動力舵取装置を組み立てのために、付勢部材を組み込む際に、調整部材により付勢部材の付勢力を調整することにより、各部品の寸法誤差の影響を受けることなく、バックラッシを調整することができる。調整して組み込んだ後は、自動的にバックラッシの増大を抑制する働きが担保されるので、特に調整部材を操作する必要がない。
【０００８】
請求項３記載の発明は、請求項１又は２において、上記カム機構は、相係合するカム面をそれぞれ有する第１および第２のカム部材を含み、第１のカム部材は、軸受を介してウォーム軸を回転自在に支持し且つ軸受と共にウォーム軸の径方向ウォームホイール側へ偏倚可能とされ、第２のカム部材は、ハウジングの支持孔にウォーム軸の軸方向のみの変位を許容される状態に支持されていることを特徴とするものである。本発明では、例えば摩耗の発生等の経時変化によりウォームホイールとウォーム軸との間のバックラッシが増大しようとすると、第１のカム部材がウォーム軸側へ変位することにより、第２のカム部材がウォーム軸を伴ってウォームホイール側へ変位し、上記のバックラッシの増大を未然に防止することができる。
【０００９】
【発明の実施の形態】
本発明の好ましい実施の形態を添付図面を参照しつつ説明する。
図１は本発明の一実施の形態の電動式動力舵取装置の概略構成を示す模式図である。図１を参照して、電動式動力舵取装置１は、操舵輪（ステアリングホイール）２に連結している操舵軸（ステアリングシャフト）３と、操舵軸３の先端部に設けられたピニオンギヤ４と、このピニオンギヤ４に噛み合うラックギヤ５とを有し、車両の左右方向に延びるラック軸６とを有している。
【００１０】
ラック軸６の両端部にはそれぞれタイロッド７が結合されており、各タイロッド７は対応するナックルアームを介して対応する車輪８に連結されている。操舵輪２が操作されて操舵軸３が回転されると、この回転がピニオンギヤ４およびラックギヤ５によって、車両の左右方向に沿ってのラック軸６の直線運動に変換される。これにより、車輪８の転舵が達成される。
操舵軸３は、操舵輪２に連なる筒状の第１の操舵軸９と、ピニオンギヤ４に連なる第２の操舵軸１０とに分割されており、これら第１および第２の操舵軸１０はトーションバー１１を介して同一の軸線上で互いに連結されている。
【００１１】
トーションバー１１を介する第１の操舵軸９と第２の操舵軸１０との相対回転変位量により操舵トルクを検出するトルクセンサ１２が設けられており、このトルクセンサ１２のトルク検出結果は制御部１３に与えられる。制御部１３では、トルク検出結果に基づいて、ドライバ１４を介して操舵補助用の電動モータ１５への印加電圧を制御する。電動モータ１５のモータ軸１６（図２参照）の回転が、ウォーム機構を含む減速機構１７を介して第２の操舵軸１０に伝達され、操舵が補助される。
【００１２】
図２を参照して、減速機構１７は、互いに噛み合うウォーム軸１８とウォームホイール１９とを備えている。ウォーム軸１８は電動モータ１５のモータ軸１６に連なり、軸長方向の中間に一体にウォーム歯２０を形成している。ウォームホイール１９は、第２の操舵軸１０に一体回転可能に係合されている。
ウォーム軸１８は、第２の操舵軸１０の軸芯と交差するように配置されている。ウォーム軸１８は軸長方向に相対向する第１及び第２の端部２１，２２を有する。第１の端部２１は、玉軸受を用いてなる第１の軸受２３を介してギヤハウジング２４の軸受孔２５に回転可能に支持されている。
【００１３】
第１の軸受２３の外輪２６の一方の端部はギヤハウジング２４の位置決め段部２７に当接して位置決めされる。一方、外輪２６の他方の端部（モータ軸側の端部）と位置決めねじ２８の端面との間には、例えばゴム板からなる弾性部材２９が介在している。４９は位置決めねじ２８を止定するロックナットである。弾性部材２９の比較的強い弾性反発力により、通常、外輪２６は位置決め段部２７に押し当てられている。第１の軸受２３の内輪３０の一方の端部はウォーム軸１８の位置決め段部３１に係合している。ウォーム軸１８の第１の端部２１は動力伝達継手３２を介して上記モータ軸１６の端部に連結されている。
【００１４】
ウォーム軸１８はウォームホイール１９に向けて偏倚が可能となしてあり、バックラッシ調整機構３３を設けて、ウォーム軸１８とウォームホイール１９の間のバックラッシの増大を抑制できるようにしてある。
具体的には、ウォーム軸１８の第２の端部２２を支持する第２の軸受３４をウォームホイール１９に向けて偏倚が可能としてある。ギヤハウジング２４においてウォーム軸１８を収容している空所３５は、ウォーム軸１８の第２の端部２２の延長方向に沿って延びる収容孔３６を介して外部に開放している。この収容孔３６に上記のバックラッシ調整機構３３の大部分が収容されている。
【００１５】
バックラッシ調整機構３３は、第１および第２のカム部材３７，３８を含むカム機構３９と、収容孔３６の入口に形成されるねじ部４０にねじ込まれる調整部材としての調整ねじ４１と、調整ねじ４１と第２のカム部材３８との間に介在し、第２のカム部材３８をウォーム軸１８の軸方向に弾性的に付勢する例えば圧縮コイルばねからなる付勢部材４２とを備えている。４３は調整ねじ４１を止定するためのロックナットである。
【００１６】
図２および拡大図である図３を参照して、第１および第２のカム部材３７，３８はそれぞれウォーム軸１８の軸長方向に対して所定の角度（例えば４５°）にて傾斜するカム面４４，４５が形成され、これらのカム面４４，４５は互いに摺動自在に係合している。カム面４４，４５には互いの相対回転を止め且つ互いの相対摺動を確保するための係合構造５０が設けられている。係合構造として、カム面４４，４５の何れか一方に形成された突条を、他方に形成された凹条に嵌め合わせる構造が考えられる。
【００１７】
第１のカム部材３７は、第２の軸受３４を介してウォーム軸１８の第２の端部２２を回転自在に支持し且つ第２の軸受３４と共にウォーム軸１８の径方向すなわちウォームホイール側へ偏倚可能とされている。これを実現するため、第１のカム部材３７とこれを収容する空所３５の内面との間には所定量の隙間が確保されている。図３を参照して、第１のカム部材３７は、第２の軸受３４の外輪５１の外周面および外輪５１の調整ねじ４１側の端面に当接して、外輪５１を保持している。第２の軸受３４の内輪５２の反調整ねじ４１側の端面はウォーム軸１８の第２の端部２２に形成された段部に当接し、位置決めされている。
【００１８】
一方、収容孔３６に収容される第２のカム部材３８はウォーム軸１８の軸線回りの回転を止められ、ウォーム軸１８の軸長方向への移動のみを許容されている。これを実現するために第２のカム部材３８の外周面と収容孔３６の内周面との間に係合構造４６が設けられている。係合構造４６としては、第２のカム部材３８の外周面および収容孔３６の内周面の何れか一方に形成されて、ウォーム軸１８の軸方向と平行に延びる凸条と、他方に形成されて上記凸条に係合する凹条とを含むものであっても良い。凸条と凹条が複数設けられて、くし状をなしていても良く、また例えばスプライン構造をなしていても良い。
【００１９】
係合構造４６、第２のカム部材３８及び係合構造５０によって、第１のカム部材３７は回転を止められているので、第１のカム部材３７は、ウォーム軸１８の軸方向に移動したときに、ウォーム軸１８の径方向ウォームホイール側及びその反対方向へ変位することになる。
付勢部材４２としての例えば圧縮コイルばねの対向端部は、調整ねじ４１および第２のカム部材３８の相対向する端面にそれぞれ形成される案内突起４７，４８に嵌められている。
【００２０】
バックラッシ調整機構３３を電動式動力舵取装置１に組み込むときに、ロックナット４３を弛緩した状態で調整ねじ４１を操作することにより付勢部材４２としての例えば圧縮コイルばねの撓み量を調整し、この付勢力の一部をウォーム軸１８をウォームホイール１９側へ偏倚させる付勢力に変換し、バックラッシを少なくするように調整する。ウォーム軸１８の第２の端部２２のウォームホイール１９に向けての偏倚量は、例えば３０ミクロン程度である。
【００２１】
弾性部材２９の弾性反発力は付勢部材４２の付勢力よりも格段に大きく設定してあるので、通常は、第１の軸受２３が位置決め段部２７に当接しており、このため、弾性部材２９がバックラッシ調整に寄与するようには働いていない。しかし、非常に大きな動力変動等が生じてウォーム軸１８が軸長方向に振動する場合等では、弾性部材２９がこの振動を抑制するように働く。
本実施の形態では、ウォーム軸１８及びウォームホイール１９の歯の摩耗等により各部品間の寸法誤差が増大しても、これをウォーム軸１８をウォームホイール１９側へ偏倚させることにより自動的に吸収できるので、バックラッシが過大に増大することがない。しかも、付勢部材４２を含むバックラッシ調整機構３３をウォーム軸１８の軸方向に沿ってレイアウトできるので、電動式動力舵取装置１を小型にすることができる。
【００２２】
特に、ウォーム軸１８が鉄製であってウォームホイール１９が合成樹脂製である場合にバックラッシの増減に伴う不具合を解消するのに顕著な効果を発揮できる。すなわち、合成樹脂製のウォームホイール１９は、歯打ち音自体が生じ難いという利点や、摩耗粉がギヤの噛み合い部に進入しても容易に回転できるという利点があるものの、鉄製のウォーム軸１８と組み合わされた場合に、摩耗や温度収縮によりバックラッシが増大する方向へと寸法減少することが予想される。しかしながら、上記のバックラッシ調整機構３３によりバックラッシの増大を抑制することができるわけである。
【００２３】
逆に、合成樹脂製のウォームホイール１９が温度膨張や膨潤により寸法増加し、バックラッシが極端に減少してウォームホイール１９の回転抵抗が増大し、トルク伝達効率が悪くなることも予想される。しかしながら、バックラッシ調整機構３３によりバックラッシの極端な減少を防止できるので、抵抗トルクが増大することを防止することができる。
また、バックラッシ調整機構３３の組み込み時に調整ねじ４１により付勢部材４２の付勢力を一旦、調整しておけば、その後は、自動的にバックラッシを調整する働きが担保されるので、特に調整ねじ４１を操作する必要がない。
【００２４】
なお、本発明は上記実施の形態に限定されるものではなく、例えば弾性部材２９を廃止しても良い。その他、本発明の特許請求の範囲内で種々の変更を施すことができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態の電動式動力舵取装置の概略構成を示す模式図である。
【図２】バックラッシ調整機構を含む電動式動力舵取装置の要部の断面図である。
【図３】図２の要部を拡大した図である。
【符号の説明】
１ 電動式動力舵取装置
３ 操舵軸（ステアリングシャフト）
１５ 電動モータ
１６ モータ軸
１７ 減速機構
１８ ウォーム軸
１９ ウォームホイール
２２ 第２の端部
３３ バックラッシ調整機構
３４ 第２の軸受
３６ 収容孔
３７ 第１のカム部材
３８ 第２のカム部材
３９ カム機構
４１ 調整ねじ
４２ 付勢部材
４４，４５ カム面
４６ 係合構造
５０ 係合構造[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus using an electric motor as a generation source of steering assist force.
[0002]
[Prior art]
As an electric steering apparatus for an automobile, there is an apparatus provided with a first steering shaft connected to a steering wheel, and a second steering shaft connected to the first steering shaft via a torsion bar and connected to a steering mechanism. . In this apparatus, the relative displacement amount in the rotation direction of the first and second steering shafts is detected by a torque sensor, and the rotation of the electric motor is controlled by the second steering shaft via the speed reduction mechanism based on the detection result of the torque sensor. Thus, the operation of the steering mechanism according to the rotation of the steering wheel is assisted by the rotation of the electric motor, so that the burden on the driver for steering is reduced.
[0003]
As the speed reduction mechanism, a mechanism having a worm and a worm wheel is provided. The worm shaft provided with the worm and the second steering shaft provided with the worm wheel are supported at both ends in the axial length direction by bearings to prevent movement in the radial direction and the axial length direction.
When the worm shaft and worm wheel are assembled, adjustment is made so that an appropriate backlash exists between the worm and the worm wheel within the range of machining accuracy. If this increases, the backlash increases and becomes excessive, which causes noise.
[0004]
Therefore, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-43739, the worm shaft can be biased toward the worm wheel, and the worm shaft is biased in the radial direction that is the biasing direction by the biasing means, thereby increasing backlash. It has been proposed to suppress this.
[0005]
[Problems to be solved by the invention]
However, there is a problem that the apparatus becomes large because the biasing means and the member for adjusting the biasing force of the biasing means must be arranged along the radial direction of the worm shaft.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric power steering apparatus that is small in size and can suppress an increase in backlash and generation of noise associated therewith.
[0006]
[Means for Solving the Problems]
To achieve the above objective,
The invention according to claim 1 is an electric power steering apparatus that transmits rotation of a steering assisting electric motor driven according to torque applied to a steering shaft to a steering mechanism via a worm shaft and a worm wheel. An urging member that urges the worm shaft in the axial direction; and a cam mechanism that converts at least a part of the urging force of the urging member into a force that urges the worm shaft toward the radial worm wheel, The worm shaft is held by the housing via a cam mechanism so as to be biased toward the radial worm wheel.
[0007]
In the present invention, even if a dimensional error between the parts increases due to wear of the teeth of the worm shaft and the worm wheel, this can be absorbed by biasing the worm shaft toward the worm wheel. Therefore, an increase in backlash can be suppressed. Moreover, since the urging member can be laid out along the axial direction of the worm shaft, the electric power steering apparatus can be reduced in size.
The invention described in claim 2 is characterized in that in claim 1, an adjusting member for adjusting the biasing force of the biasing member is further provided. In the present invention, when the urging member is incorporated for assembling the electric power steering apparatus, the urging force of the urging member is adjusted by the adjusting member without being affected by the dimensional error of each component. The backlash can be adjusted. After the adjustment and incorporation, the function of automatically suppressing the increase in backlash is ensured, so that it is not particularly necessary to operate the adjustment member.
[0008]
According to a third aspect of the present invention, in the first or second aspect, the cam mechanism includes first and second cam members each having a cam surface engaged with each other, and the first cam member is interposed via a bearing. the worm shaft is capable biased to rotatably support and radial worm wheel side of the worm shaft along with且one bearings Te, the second cam member is allowed displacement of only axial worm shaft into the supporting hole of the housing It is characterized by being supported in a state where In the present invention, for example, if the backlash between the worm wheel and the worm shaft is increased due to a change over time such as the occurrence of wear, the first cam member is displaced toward the worm shaft, so that the second cam member is Displacement toward the worm wheel side along with the worm shaft can prevent the increase in the backlash.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, an electric power steering apparatus 1 includes a steering shaft (steering shaft) 3 connected to a steering wheel (steering wheel) 2, and a pinion gear 4 provided at the tip of the steering shaft 3. The rack gear 5 meshes with the pinion gear 4 and the rack shaft 6 extends in the left-right direction of the vehicle.
[0010]
Tie rods 7 are coupled to both ends of the rack shaft 6, and each tie rod 7 is connected to a corresponding wheel 8 via a corresponding knuckle arm. When the steering wheel 2 is operated and the steering shaft 3 is rotated, this rotation is converted by the pinion gear 4 and the rack gear 5 into a linear motion of the rack shaft 6 along the left-right direction of the vehicle. Thereby, steering of the wheel 8 is achieved.
The steering shaft 3 is divided into a cylindrical first steering shaft 9 connected to the steering wheel 2 and a second steering shaft 10 connected to the pinion gear 4. These first and second steering shafts 10 are torsional. The bars 11 are connected to each other on the same axis.
[0011]
A torque sensor 12 is provided for detecting a steering torque based on a relative rotational displacement amount between the first steering shaft 9 and the second steering shaft 10 via the torsion bar 11, and the torque detection result of the torque sensor 12 is a control unit. 13 is given. The control unit 13 controls the voltage applied to the steering assisting electric motor 15 via the driver 14 based on the torque detection result. The rotation of the motor shaft 16 (see FIG. 2) of the electric motor 15 is transmitted to the second steering shaft 10 via a speed reduction mechanism 17 including a worm mechanism, and steering is assisted.
[0012]
Referring to FIG. 2, the speed reduction mechanism 17 includes a worm shaft 18 and a worm wheel 19 that mesh with each other. The worm shaft 18 is connected to the motor shaft 16 of the electric motor 15, and worm teeth 20 are integrally formed in the middle in the axial direction. The worm wheel 19 is engaged with the second steering shaft 10 so as to be integrally rotatable.
The worm shaft 18 is disposed so as to intersect the axis of the second steering shaft 10. The worm shaft 18 has first and second ends 21 and 22 that face each other in the axial direction. The first end 21 is rotatably supported in a bearing hole 25 of the gear housing 24 via a first bearing 23 using a ball bearing.
[0013]
One end of the outer ring 26 of the first bearing 23 is abutted against the positioning step 27 of the gear housing 24 and positioned. On the other hand, an elastic member 29 made of, for example, a rubber plate is interposed between the other end portion (end portion on the motor shaft side) of the outer ring 26 and the end surface of the positioning screw 28. Reference numeral 49 denotes a lock nut for fixing the positioning screw 28. The outer ring 26 is normally pressed against the positioning step portion 27 by the relatively strong elastic repulsive force of the elastic member 29. One end of the inner ring 30 of the first bearing 23 is engaged with the positioning step 31 of the worm shaft 18. The first end 21 of the worm shaft 18 is connected to the end of the motor shaft 16 via a power transmission joint 32.
[0014]
The worm shaft 18 can be biased toward the worm wheel 19, and a backlash adjusting mechanism 33 is provided so that an increase in backlash between the worm shaft 18 and the worm wheel 19 can be suppressed.
Specifically, the second bearing 34 that supports the second end 22 of the worm shaft 18 can be biased toward the worm wheel 19. A space 35 that accommodates the worm shaft 18 in the gear housing 24 is open to the outside through a housing hole 36 that extends along the extending direction of the second end 22 of the worm shaft 18. Most of the backlash adjusting mechanism 33 is accommodated in the accommodation hole 36.
[0015]
The backlash adjustment mechanism 33 includes a cam mechanism 39 including first and second cam members 37, 38, an adjustment screw 41 as an adjustment member screwed into a screw portion 40 formed at the inlet of the accommodation hole 36, and an adjustment screw 41, and a biasing member 42 made of, for example, a compression coil spring, which is interposed between the second cam member 38 and elastically biases the second cam member 38 in the axial direction of the worm shaft 18. . Reference numeral 43 denotes a lock nut for fixing the adjustment screw 41.
[0016]
Referring to FIG. 2 and FIG. 3 which is an enlarged view, the first and second cam members 37 and 38 are cams inclined at a predetermined angle (for example, 45 °) with respect to the axial length direction of the worm shaft 18. Surfaces 44 and 45 are formed, and these cam surfaces 44 and 45 are slidably engaged with each other. The cam surfaces 44 and 45 are provided with an engagement structure 50 for stopping mutual relative rotation and ensuring mutual sliding. As the engagement structure, a structure in which a protrusion formed on one of the cam surfaces 44 and 45 is fitted to a recess formed on the other is conceivable.
[0017]
The first cam member 37 rotatably supports the second end portion 22 of the worm shaft 18 via the second bearing 34 and moves together with the second bearing 34 in the radial direction of the worm shaft 18, that is, toward the worm wheel side. It can be biased. In order to realize this, a predetermined amount of gap is secured between the first cam member 37 and the inner surface of the space 35 that accommodates the first cam member 37. Referring to FIG. 3, the first cam member 37 is in contact with the outer peripheral surface of the outer ring 51 of the second bearing 34 and the end surface of the outer ring 51 on the adjustment screw 41 side, and holds the outer ring 51. The end face of the inner ring 52 of the second bearing 34 on the counter adjustment screw 41 side is in contact with the step formed on the second end 22 of the worm shaft 18 and positioned.
[0018]
On the other hand, the second cam member 38 accommodated in the accommodation hole 36 is prevented from rotating around the axis of the worm shaft 18 and is only allowed to move in the axial length direction of the worm shaft 18. In order to realize this, an engagement structure 46 is provided between the outer peripheral surface of the second cam member 38 and the inner peripheral surface of the accommodation hole 36. The engaging structure 46 is formed on one of the outer peripheral surface of the second cam member 38 and the inner peripheral surface of the accommodation hole 36, and is formed on the other side with a ridge extending parallel to the axial direction of the worm shaft 18. And a concave line that engages with the convex line. A plurality of ridges and ridges may be provided to form a comb shape, for example, a spline structure.
[0019]
Since the rotation of the first cam member 37 is stopped by the engagement structure 46, the second cam member 38 and the engagement structure 50, the first cam member 37 has moved in the axial direction of the worm shaft 18. Sometimes, the worm shaft 18 is displaced in the radial worm wheel side and in the opposite direction.
Opposing end portions of, for example, a compression coil spring as the urging member 42 are fitted into guide protrusions 47 and 48 formed on the opposing end surfaces of the adjusting screw 41 and the second cam member 38, respectively.
[0020]
When the backlash adjusting mechanism 33 is incorporated in the electric power steering apparatus 1, the amount of deflection of, for example, the compression coil spring as the biasing member 42 is adjusted by operating the adjusting screw 41 in a state where the lock nut 43 is loosened. A part of this urging force is converted into an urging force that biases the worm shaft 18 toward the worm wheel 19 and is adjusted to reduce backlash. The amount of deviation of the second end 22 of the worm shaft 18 toward the worm wheel 19 is, for example, about 30 microns.
[0021]
Since the elastic repulsive force of the elastic member 29 is set to be much larger than the urging force of the urging member 42, the first bearing 23 is normally in contact with the positioning step portion 27. Therefore, the elastic member 29 does not work to contribute to backlash adjustment. However, when a very large power fluctuation or the like occurs and the worm shaft 18 vibrates in the axial direction, the elastic member 29 works to suppress this vibration.
In the present embodiment, even if a dimensional error between parts increases due to wear of teeth of the worm shaft 18 and the worm wheel 19, this is automatically absorbed by biasing the worm shaft 18 toward the worm wheel 19. As a result, the backlash does not increase excessively. In addition, since the backlash adjusting mechanism 33 including the urging member 42 can be laid out along the axial direction of the worm shaft 18, the electric power steering apparatus 1 can be reduced in size.
[0022]
In particular, when the worm shaft 18 is made of iron and the worm wheel 19 is made of a synthetic resin, a remarkable effect can be exhibited in solving the problems associated with increase / decrease in backlash. That is, the worm wheel 19 made of synthetic resin has the advantage that the rattling noise itself is less likely to occur and the advantage that it can easily rotate even if wear powder enters the gear meshing portion. When combined, it is expected that the size will decrease in the direction of increasing backlash due to wear and temperature shrinkage. However, the backlash adjustment mechanism 33 can suppress an increase in backlash.
[0023]
Conversely, the size of the worm wheel 19 made of synthetic resin increases due to temperature expansion and swelling, the backlash is extremely reduced, the rotational resistance of the worm wheel 19 is increased, and the torque transmission efficiency is also expected to deteriorate. However, since the backlash adjustment mechanism 33 can prevent an extreme decrease in backlash, it is possible to prevent an increase in resistance torque.
Further, once the urging force of the urging member 42 is adjusted once by the adjusting screw 41 when the backlash adjusting mechanism 33 is assembled, the function of automatically adjusting the backlash is ensured thereafter. There is no need to operate.
[0024]
In addition, this invention is not limited to the said embodiment, For example, you may abolish the elastic member 29. FIG. In addition, various modifications can be made within the scope of the claims of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part of an electric power steering apparatus including a backlash adjustment mechanism.
FIG. 3 is an enlarged view of a main part of FIG. 2;
[Explanation of symbols]
1 Electric power steering device 3 Steering shaft (steering shaft)
15 Electric motor 16 Motor shaft 17 Deceleration mechanism 18 Worm shaft 19 Worm wheel 22 Second end 33 Backlash adjustment mechanism 34 Second bearing 36 Housing hole 37 First cam member 38 Second cam member 39 Cam mechanism 41 Adjustment Screw 42 Biasing members 44, 45 Cam surface 46 Engagement structure 50 Engagement structure

Claims (3)

ステアリングシャフトに負荷されるトルクに応じて駆動される操舵補助用の電動モータの回転をウォーム軸およびウォームホイールを介して舵取り機構に伝える電動式動力舵取装置において、
上記ウォーム軸を軸方向に付勢する付勢部材と、
付勢部材の付勢力の少なくとも一部を、ウォーム軸を径方向ウォームホイール側へ付勢する力に変換するカム機構とを備え、
上記ウォーム軸は径方向ウォームホイール側へ偏倚できるようにカム機構を介してハウジングに保持されることを特徴とする電動式動力舵取装置。In the electric power steering apparatus that transmits the rotation of the steering assisting electric motor driven according to the torque applied to the steering shaft to the steering mechanism via the worm shaft and the worm wheel,
A biasing member for biasing the worm shaft in the axial direction;
A cam mechanism that converts at least a part of the urging force of the urging member into a force that urges the worm shaft toward the radial worm wheel;
The electric power steering apparatus according to claim 1, wherein the worm shaft is held in a housing via a cam mechanism so as to be biased toward the radial worm wheel. 請求項１において、上記付勢部材の付勢力を調整する調整部材をさらに備えることを特徴とする電動式動力舵取装置。The electric power steering apparatus according to claim 1, further comprising an adjustment member that adjusts an urging force of the urging member. 請求項１又は２において、
上記カム機構は、相係合するカム面をそれぞれ有する第１および第２のカム部材を含み、
第１のカム部材は、軸受を介してウォーム軸を回転自在に支持し且つ軸受と共にウォーム軸の径方向ウォームホイール側へ偏倚可能とされ、
第２のカム部材は、ハウジングの支持孔にウォーム軸の軸方向のみの変位を許容される状態に支持されていることを特徴とする電動式動力舵取装置。In claim 1 or 2,
The cam mechanism includes first and second cam members each having a cam surface engaged with each other,
The first cam member, is capable biased radially worm wheel side of the worm shaft along with rotatably supporting且one bearings of the worm shaft via a bearing,
The electric power steering apparatus, wherein the second cam member is supported by the support hole of the housing in a state in which only displacement in the axial direction of the worm shaft is allowed.
JP2000340752A 2000-11-08 2000-11-08 Electric power steering device Expired - Fee Related JP3770310B2 (en)

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