JP4574228B2 - Ball screw for electric actuator - Google Patents

Ball screw for electric actuator Download PDF

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JP4574228B2
JP4574228B2 JP2004145842A JP2004145842A JP4574228B2 JP 4574228 B2 JP4574228 B2 JP 4574228B2 JP 2004145842 A JP2004145842 A JP 2004145842A JP 2004145842 A JP2004145842 A JP 2004145842A JP 4574228 B2 JP4574228 B2 JP 4574228B2
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screw shaft
screw
electric actuator
ball screw
shaft
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JP2005325956A (en
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守久 吉岡
良則 池田
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NTN Corp
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NTN Corp
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この発明は、自動車の電動式ディスクブレーキ等に用いられ、ねじ軸に摺動面を必要とする電動アクチュエータ用ボールねじに関する。   The present invention relates to a ball screw for an electric actuator that is used in an electric disc brake or the like of an automobile and requires a sliding surface on a screw shaft.

近年、自動車に使用されてきた油圧式アクチュエータに代えて、電動モータでその機能を代替する電動アクチュエータの開発が多く行われている。その電動アクチュエータとしては、モータの回転運動を高速，高効率に直線運動に変換する駆動部品としてボールねじが多く使用されている。
このようなボールねじを用いた電動アクチュエータの一例として、図６に示すように、モータでボールねじ３０のねじ軸３１を回転させ、ナット３２と一体に進退する出力軸３４に設けられた連結ピン３５を介して、アーム３６等を作動させるようにしたものが提案されている（例えば特許文献１）。アーム３６は、トランスミッションや電動式ディスクブレーキに動作を伝動する。 In recent years, in place of hydraulic actuators that have been used in automobiles, many electric actuators have been developed that substitute their functions with electric motors. As such an electric actuator, a ball screw is often used as a drive component that converts the rotational motion of the motor into linear motion at high speed and high efficiency.
As an example of such an electric actuator using a ball screw, as shown in FIG. 6, a connecting pin provided on an output shaft 34 that rotates a screw shaft 31 of a ball screw 30 with a motor and advances and retracts integrally with a nut 32. There has been proposed one in which the arm 36 and the like are operated via 35 (for example, Patent Document 1). The arm 36 transmits the operation to the transmission and the electric disc brake.

このような構造の電動アクチュエータでは、外力によってボールねじ３０の部分に作用する曲げ方向の力でナット３２とねじ軸３１との間に僅かな相対変位が生じる。この相対変位に起因してボールねじ３０におけるボール３３の負荷バランスが崩れることから、ボールねじ３０に摩耗や破損が生じ、耐久性を損ねると言われる。そこで、この課題を解消する対策として、特許文献１に開示の電動アクチュエータでは、ねじ軸３１とナット３２との間に弾性係数の小さいブッシュ３７を設けて曲げ力を吸収し、ボールねじ３０の信頼性および耐久性を向上させるようにしている。すなわち、前記ブッシュ３７は、外力による曲げ方向の荷重を、ボールねじ３０が直接受けないようにする手段として用いられている。
特開２００３−１９４１７４号公報 In the electric actuator having such a structure, a slight relative displacement occurs between the nut 32 and the screw shaft 31 due to the force in the bending direction acting on the portion of the ball screw 30 by the external force. It is said that the load balance of the ball 33 in the ball screw 30 is lost due to this relative displacement, so that the ball screw 30 is worn or damaged, and the durability is impaired. Therefore, as a countermeasure for solving this problem, in the electric actuator disclosed in Patent Document 1, a bushing 37 having a small elastic coefficient is provided between the screw shaft 31 and the nut 32 to absorb the bending force, and the ball screw 30 is reliable. To improve performance and durability. That is, the bush 37 is used as a means for preventing the ball screw 30 from directly receiving a load in the bending direction due to an external force.
JP 2003-194174 A

しかし、上記構成の電動アクチュエータにおけるボールねじ３０では、ねじ軸３１とナット３２との間にブッシュ３７を設けているため、ブッシュ３７が曲げ方向荷重によってねじ軸３１のねじ溝３１ａに押し付けられながらスライドする。この場合、ブッシュ３７は、曲げ荷重により傾こうとするナット３２の力を受けて、ねじ軸３１の外周に押圧されながら接している。このため、図６の一部Ａを拡大して示す図７のように、ブッシュ３７がねじ山部３１ｂの凹凸を摺動するときに、ブッシュ３７の内径面にねじ軸３１のエッジによるかじりが発生する。特に、ブッシュ３７がねじ軸３１の範囲を越えて摺動するときに上記かじりが発生する。その結果、ブッシュ３７側の摩耗が進行してナット３２が傾き易くなり、ブッシュ３７による曲げ力の吸収効果が低下する。   However, in the ball screw 30 in the electric actuator having the above configuration, since the bush 37 is provided between the screw shaft 31 and the nut 32, the bush 37 is slid while being pressed against the screw groove 31a of the screw shaft 31 by the load in the bending direction. To do. In this case, the bush 37 is in contact with the outer periphery of the screw shaft 31 while receiving the force of the nut 32 that tends to tilt due to the bending load. For this reason, as shown in FIG. 7 showing an enlarged portion A of FIG. 6, when the bush 37 slides on the unevenness of the thread portion 31 b, the inner surface of the bush 37 is galled by the edge of the screw shaft 31. appear. In particular, the above-mentioned galling occurs when the bush 37 slides beyond the range of the screw shaft 31. As a result, the wear on the bush 37 side progresses and the nut 32 is easily tilted, and the effect of absorbing the bending force by the bush 37 is reduced.

また、上記構成の電動アクチュエータでは、図８のように、ボールねじ３０のナット３２に連結されたリンク部（外力Ｆr1を受ける力点）３８と、ブッシュ３７の設けられたボールねじ３０の部分（外力Ｆr1の支点）３９との距離Ｌ１が短いため、外力Ｆr1によりボールねじ３０が受ける曲げ荷重の影響は少なくて済む。しかし、周辺構造との干渉を避ける必要がある等の制約で、図９のように、リンク部（外力Ｆr2を受ける力点）３８を、ブッシュ３７の設けられたボールねじ３０の部分（外力Ｆr2の支点）３９から離した場合（距離Ｌ２）、外力が入力される位置と外力の支点とが大きく離れる。このため、ボールねじ３０が受ける曲げ荷重の影響が大きくなってしまう。 In the electric actuator having the above-described configuration, as shown in FIG. 8, the link portion (power point receiving the external force F r1 ) 38 connected to the nut 32 of the ball screw 30 and the portion of the ball screw 30 provided with the bush 37 ( the distance L1 between the fulcrum) 39 of the external force F r1 is short, the less the effect of the bending load the ball screw 30 is subjected by an external force F r1. However, due to restrictions such as the need to avoid interference with the surrounding structure, as shown in FIG. 9, the link portion (power point that receives the external force F r2 ) 38 is connected to the portion of the ball screw 30 provided with the bush 37 (external force F). When separated from ( r2 fulcrum) 39 (distance L2), the position where the external force is input and the fulcrum of the external force are greatly separated. For this reason, the influence of the bending load which the ball screw 30 receives will become large.

すなわち、図８の場合と、図９の場合の支点３９で受ける曲げ荷重には、
Ｆr1・Ｌ１＜Ｆr2・Ｌ２
の大小関係がある。
このことから、図９のように、リンク部３８とボールねじ３０の部分３９とが離れる構造の場合には、ブッシュ３７をリンク部３８の位置まで延長して、連結部品である出力軸３４をブッシュ３７で支える構造とすることが望ましい。 That is, the bending load received at the fulcrum 39 in the case of FIG. 8 and FIG.
F r1 · L1 <F r2 · L2
There is a large and small relationship.
Accordingly, as shown in FIG. 9, in the case where the link portion 38 and the portion 39 of the ball screw 30 are separated from each other, the bush 37 is extended to the position of the link portion 38, and the output shaft 34 as a connecting part is attached. A structure supported by the bush 37 is desirable.

そこで、上記構成のボールねじ３０の改良品として、本発明者等は、ナットを回転部材とし、ねじ軸を連結部品の設けられたスライド部材とすると共に、ねじ軸をブッシュで受ける構造とし、かつねじ軸として研削よりも量産性に優れた転造によりねじ溝を加工したものを用いたボールねじを試作した。また、この試作品では、摺動抵抗の低減や耐摩耗性の向上を図るために、ねじ軸の摺動面を、焼入れにより表面硬度を高めたものとした。   Therefore, as an improved product of the ball screw 30 having the above configuration, the present inventors have a structure in which the nut is a rotating member, the screw shaft is a slide member provided with a connecting part, and the screw shaft is received by a bush. A ball screw using a screw shaft with a thread groove machined by rolling, which is superior to grinding, was manufactured as a screw shaft. Moreover, in this prototype, in order to reduce sliding resistance and improve wear resistance, the sliding surface of the screw shaft was made harder by increasing the surface hardness.

しかし、この試作品の構造のものでは、次に挙げる問題が生じる。
・ねじ軸を高周波焼入する場合の焼入範囲が広くなり、熱処理時間が長くなる。
・ねじ軸における摺動面部分とねじ部との間で同軸精度が出ない。すなわち、上記構造の摺動面では、雄側および雌側ともに径・面粗さを管理し、摺動部の隙間を適正にすることで滑らかなスライドが可能となり、隙間の不適切による異常摩耗や騒音の発生を防止できる。そこで、この課題を達成するためには、上記試作品の場合にも、ねじ軸を熱処理した後に、研削等による仕上げ工程が必要になる。しかし、ねじ軸におけるねじ溝の転造加工が、素材丸棒を２対のロールダイスによって挟み込んで塑性変形させる加工方法であるのに対して、ねじ軸素材の両端に設けたセンタ孔を用いて研削を行う摺動面の仕上げ加工は、軸端のセンタ孔と素材外径とに関連が無い。このことから、特に素材丸棒がセンタレスで製作されたものである場合、外径を基準に転造されたねじ部に対して、センタ孔を用いて研削加工した摺動面の外径は、芯ずれが発生する。 However, the following problems arise in this prototype structure.
・ The hardened range when induction hardening the screw shaft is widened, and the heat treatment time is extended.
· Coaxial accuracy does not appear between the sliding surface part of the screw shaft and the screw part. In other words, on the sliding surface with the above structure, the diameter and surface roughness are controlled on both the male and female sides, and smooth sliding is possible by making the gap between the sliding parts appropriate, and abnormal wear due to inappropriate gaps. And noise generation can be prevented. Therefore, in order to achieve this problem, also in the case of the above-mentioned prototype, after the heat treatment of the screw shaft, a finishing process such as grinding is required. However, the rolling process of the thread groove on the screw shaft is a processing method in which the material round bar is sandwiched between two pairs of roll dies and plastically deformed, whereas the center holes provided at both ends of the screw shaft material are used. The finishing process of the sliding surface to be ground is not related to the center hole of the shaft end and the material outer diameter. From this, especially when the material round bar is manufactured centerless, the outer diameter of the sliding surface ground by using the center hole with respect to the thread portion rolled based on the outer diameter is Misalignment occurs.

この発明の目的は、外力により受ける曲げ力を吸収でき、摺動抵抗の低減，耐摩耗性の向上が可能で、製造が容易な電動アクチュエータ用ボールねじを提供することである。   An object of the present invention is to provide a ball screw for an electric actuator that can absorb bending force due to external force, can reduce sliding resistance, and can improve wear resistance, and is easy to manufacture.

この発明の電動アクチュエータ用ボールねじは、ナットを回転させ、ねじ軸をスライドさせる形態で使用される電動アクチュエータ用ボールねじにおいて、表面が焼入され電動アクチュエータにおける前記ねじ軸の外周にあって前記ねじ軸の先端が突出する部品に対して摺接させる環状部品を、前記ねじ軸の外周に圧入状態に取付けたことを特徴とする。 この構成によると、ねじ軸の先端側に外力を受けたときに、ねじ軸のねじ部に曲げ力が作用するが、ねじ軸の外周には、電動アクチュエータにおける前記ねじ軸の外周にあってねじ軸の先端を突出させる部品に対して摺接させる環状部品が取付けられているので、ねじ軸のねじ部に加わる曲げ荷重を吸収することができる。また、環状部品は焼入れにより表面硬度を高めたものとし、この環状部品をねじ軸の外周に圧入状態に取付けているので、例えば、ねじ軸が転造によるもので、転造前のねじ軸素材がセンタレスで製作された場合でも、センタ孔を後加工して摺動面の研削仕上げを行う必要がない。このため製造が容易となるばかりか、ねじ軸における摺動面（この発明では環状部品の外周面）とねじ溝との同軸度精度を向上させることができ、摺動抵抗の低減や耐摩耗性の向上が可能となる。また、ねじ軸の熱処理においては、摺動面の焼入れによる表面硬化を、別部品である環状部品で済ませておくことができるので、高周波焼入れによる移動焼入れ時間を短縮でき、この点でも製造が容易となる。 The ball screw for an electric actuator according to the present invention is a ball screw for an electric actuator that is used in a form in which a nut is rotated and a screw shaft is slid. The surface of the ball screw is hardened and is on the outer periphery of the screw shaft in the electric actuator. An annular component that is slidably contacted with a component protruding from the tip of the shaft is attached to the outer periphery of the screw shaft in a press-fit state. According to this configuration, when an external force is applied to the tip end side of the screw shaft, a bending force acts on the threaded portion of the screw shaft , but the outer periphery of the screw shaft is located on the outer periphery of the screw shaft in the electric actuator. Since the annular component that is slidably contacted with the component that projects the tip of the shaft is attached, the bending load applied to the screw portion of the screw shaft can be absorbed. Also, the annular parts are made hardened by quenching, and this annular part is press-fitted to the outer periphery of the screw shaft. For example, the screw shaft is made by rolling, and the screw shaft material before rolling Even if the center is manufactured without a center, it is not necessary to post-process the center hole to finish the sliding surface. This not only facilitates the manufacture, but also improves the accuracy of coaxiality between the sliding surface of the screw shaft (in this invention, the outer peripheral surface of the annular part) and the thread groove, reducing sliding resistance and wear resistance. Can be improved. In addition, in the heat treatment of the screw shaft, surface hardening by quenching of the sliding surface can be completed with an annular part which is a separate part, so the moving quenching time by induction quenching can be shortened, and manufacturing is also easy in this respect It becomes.

この発明において、前記環状部品を、軸方向に並べて複数設けても良い。ねじ軸の軸方向摺動範囲が広い場合には、ねじ軸の摺動面を１つの環状部品で構成しようとすると環状部品が長くなるので、ねじ軸への環状部品の圧入作業が容易でないが、この場合に環状部品を複数個に分割して圧入することで、その作業を容易に行うことができる。   In the present invention, a plurality of the annular parts may be provided side by side in the axial direction. If the axial direction sliding range of the screw shaft is wide, the annular part becomes longer if the sliding surface of the screw shaft is configured with one annular part. However, it is not easy to press-fit the annular part into the screw shaft. In this case, the work can be easily performed by dividing the annular part into a plurality of parts and press-fitting them.

この発明において、前記環状部品が、内輪付きのニードル軸受における内輪と同一規格のものであっても良い。この構成によると、規格品であるニードル軸受の内輪を環状部品として用いることができるので、環状部品として特別に製品を製作する必要がなく、環状部品を安価に調達できる。   In the present invention, the annular part may be of the same standard as the inner ring in the needle bearing with the inner ring. According to this configuration, since the inner ring of the standard needle bearing can be used as the annular part, it is not necessary to manufacture a special product as the annular part, and the annular part can be procured at low cost.

前記環状部品が、内輪付きのニードル軸受における内輪と同一規格のものである場合において、前記ねじ軸がねじ溝を転造加工したものであって、ねじ軸の前記環状部品が圧入される軸部の外径を、前記転造加工の前のねじ軸素材の外径としたものであっても良い。 このようなねじ軸素材の外径に寸法設定した場合、別途に研削加工等を行って径を合わせることなく、標準品のニードル軸受の内輪を前記環状部品として使用でき、低コスト化が図れる。   When the annular part is of the same standard as the inner ring in a needle bearing with an inner ring, the screw shaft is formed by rolling a thread groove, and the shaft part into which the annular part of the screw shaft is press-fitted The outer diameter of the screw shaft may be the outer diameter of the screw shaft material before the rolling process. In the case where the outer diameter of such a screw shaft material is set, the inner ring of a standard needle bearing can be used as the annular part without separately performing grinding or the like to adjust the diameter, and the cost can be reduced.

この発明の電動アクチュエータ用ボールねじは、ナットを回転させ、ねじ軸をスライドさせる形態で使用される電動アクチュエータ用ボールねじにおいて、表面が焼入され電動アクチュエータにおける前記ねじ軸の外周にあって前記ねじ軸の先端を突出させる部品に対して摺接させる環状部品を、前記ねじ軸の外周に圧入状態に取付けたため、外力により受ける曲げ力を吸収でき、摺動抵抗の低減や耐摩耗性の向上が可能で、製造も容易という効果が得られる。 The ball screw for an electric actuator according to the present invention is a ball screw for an electric actuator that is used in a form in which a nut is rotated and a screw shaft is slid. The surface of the ball screw is hardened and is on the outer periphery of the screw shaft in the electric actuator. An annular part that is slidably contacted with the part that protrudes the tip of the shaft is attached to the outer periphery of the screw shaft in a press-fit state, so that the bending force received by the external force can be absorbed, reducing sliding resistance and improving wear resistance. The effect that it is possible and manufacture is also easy is acquired.

この発明の第１の実施形態を図１ないし図３と共に説明する。図１は、この実施形態にかかるボールねじを用いた電動アクチュエータの断面図を示す。この電動アクチュエータは、駆動源であるモータ１と、モータ１の回転をスライド動作に変換するボールねじ２とを備え、ボールねじ２はハウジング８内に設置されている。ハウジング８は、断面概形がハット状の後部材９と、断面概形がＬ字状の中間部材１０と、円筒状の前部材１１とでなり、これらの部材をこの順序で連結して全体が略円筒状に組み立てられる。ハウジング８の後部材９と中間部材１０は、それらの一端のフランジ部９ａ，１０ａを互いに対向させて連結され、両フランジ部９ａ，１０ａの対向部内側に、ハウジング円筒空間部８ａから外径側に張り出すギヤ部空間８ｂが形成される。前記モータ１は、その出力軸１ａがハウジング８の軸方向と平行となるようにハウジング８の後部外周に設置され、モータ出力軸１ａが後部材９のフランジ部９ａを貫通して前記ギヤ部空間８ｂ内に突入させてある。   A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cross-sectional view of an electric actuator using a ball screw according to this embodiment. The electric actuator includes a motor 1 that is a drive source and a ball screw 2 that converts rotation of the motor 1 into a sliding motion. The ball screw 2 is installed in a housing 8. The housing 8 is composed of a rear member 9 having a hat-shaped cross section, an intermediate member 10 having an L-shaped cross section, and a cylindrical front member 11, and these members are connected in this order to form a whole. Is assembled into a substantially cylindrical shape. The rear member 9 and the intermediate member 10 of the housing 8 are connected so that the flange portions 9a and 10a at one end thereof are opposed to each other, and the outer diameter side from the housing cylindrical space portion 8a is formed inside the opposed portions of the flange portions 9a and 10a. A gear portion space 8b is formed to project over the surface. The motor 1 is installed on the outer periphery of the rear portion of the housing 8 so that the output shaft 1a thereof is parallel to the axial direction of the housing 8, and the motor output shaft 1a passes through the flange portion 9a of the rear member 9 and the gear portion space. It is made to enter into 8b.

ボールねじ２は、図２に示すように、ねじ軸３と、ナット４と、これらねじ軸３およびナット４のねじ溝６，７の間に介在させたボール５と、ねじ溝６，７間のボール５を拾い上げてねじ溝６，７間に戻す循環路（図示せず）とを備える。前記循環路は、ねじ溝６，７間で形成される螺旋状のボール転走路を、その両端を連結して周回経路とするものであり、ナット４に設けられた駒やリターンチューブ等の循環用部材（図示せず）により構成される。ねじ軸３は、ハウジング８内にこれと同心状に配置される。ナット４は、ハウジング８の内周に軸受１２，１３を介して回転自在に設けられる。   As shown in FIG. 2, the ball screw 2 includes a screw shaft 3, a nut 4, a ball 5 interposed between the screw shaft 3 and the screw grooves 6 and 7 of the nut 4, and the screw grooves 6 and 7. And a circulation path (not shown) for picking up the balls 5 and returning them between the thread grooves 6 and 7. The circulation path is a spiral ball rolling path formed between the thread grooves 6 and 7 and is connected to both ends to form a circulation path. Circulation of a piece, a return tube, etc. provided in the nut 4 It is comprised by the member (not shown). The screw shaft 3 is disposed concentrically with the housing 8. The nut 4 is rotatably provided on the inner periphery of the housing 8 via bearings 12 and 13.

ナット４の外周には、これと同心とされ前記ハウジング８のギヤ部空間８ｂ内に配置されるギヤ１５が一体に形成され、このギヤ１５がモータ出力軸１ａに設けられたギヤ１４に噛み合わされている。これら両ギヤ１４，１５は、モータ１の回転をナット４に伝達する回転伝達系を構成する。   A gear 15 that is concentric with the nut 4 and is disposed in the gear portion space 8b of the housing 8 is integrally formed on the outer periphery of the nut 4. The gear 15 is engaged with a gear 14 provided on the motor output shaft 1a. ing. Both the gears 14 and 15 constitute a rotation transmission system that transmits the rotation of the motor 1 to the nut 4.

ハウジング前部材１１の内周にはブッシュ１６が圧入嵌合して固定されている。このブッシュ１６の後端には外径側に張り出すフランジ部１６ａが形成され、このフランジ部１６ａがハウジング中間部材１０の前端とこれに対向するハウジング前部材１１の後端とで挟み付けられている。また、ブッシュ１６の前端は、ハウジング前部材１１の前端に形成された内向きのフランジ部１１ａで受け止められ、これによりブッシュ１６は軸方向に位置決めされている。   A bush 16 is press-fitted and fixed to the inner periphery of the housing front member 11. A flange portion 16a is formed at the rear end of the bushing 16 so as to project to the outer diameter side. The flange portion 16a is sandwiched between the front end of the housing intermediate member 10 and the rear end of the housing front member 11 facing the housing intermediate member 10. Yes. Further, the front end of the bush 16 is received by an inward flange portion 11 a formed at the front end of the housing front member 11, whereby the bush 16 is positioned in the axial direction.

ボールねじ２のねじ軸３は、その後半部がねじ溝６（図２）の形成されたねじ部３ａとされ、前半部の先端はハウジング８から前方に突出させてあり、突出する先端部に連結ピン（図示せず）の嵌合する連結孔１７が形成されている。また、ねじ軸３の前半部外周の前記ブッシュ１６の設置範囲に対応する部分には、ブッシュ１６に摺接させる環状部品１８が圧入状態に取付けられている。   The screw shaft 3 of the ball screw 2 has a screw portion 3a formed with a screw groove 6 (FIG. 2) at its rear half, and the front end of the front half protrudes forward from the housing 8. A connection hole 17 into which a connection pin (not shown) is fitted is formed. An annular part 18 that is slidably contacted with the bush 16 is attached in a press-fit state to a portion corresponding to the installation range of the bush 16 on the outer periphery of the front half of the screw shaft 3.

ねじ軸３は、そのねじ部３ａのねじ溝６（図２）を転造により加工したものである。すなわち、ねじ軸３のねじ溝６は、転造前のねじ軸素材の外径を基準にして、ロールダイスにより塑性加工される。また、図３に示すように、転造前のねじ軸素材における前記環状部品１８の取付部の呼び外径ｄ１は、環状部品１８の圧入が可能な寸法に形成される。さらに、環状部品１８の取付部から先端側の部分は前記外径ｄ１よりも若干小さい外径ｄ２に形成され、これにより環状部品１８の圧入を円滑に行えるようにされている。環状部品１８のねじ軸３への圧入は、転造により前記ねじ溝６を加工したねじ軸３に対して、熱処理、曲り矯正、ねじ部３ａのスケール落としを実施した後で行う。環状部品１８は、予め焼入れによって表面硬度を高めたものとされるが、ここでは専用の部品を用いず、内輪付きのニードル軸受における内輪と同一規格のもの、すなわちニードル軸受の内輪として製作された製品が、環状部品１８として転用される。このため、ねじ軸素材における環状部品１８の取付部の呼び外径ｄ１は、ここではニードル軸受の内輪内径が適用可能な整数値とされている。   The screw shaft 3 is formed by rolling the thread groove 6 (FIG. 2) of the threaded portion 3a. That is, the screw groove 6 of the screw shaft 3 is plastically processed by a roll die with reference to the outer diameter of the screw shaft material before rolling. As shown in FIG. 3, the nominal outer diameter d1 of the mounting portion of the annular part 18 in the threaded shaft material before rolling is formed to a dimension that allows the annular part 18 to be press-fitted. Furthermore, the portion on the tip side from the mounting portion of the annular part 18 is formed to have an outer diameter d2 slightly smaller than the outer diameter d1, so that the annular part 18 can be press-fitted smoothly. The annular part 18 is press-fitted into the screw shaft 3 after heat treatment, bending correction, and scale reduction of the screw portion 3a are performed on the screw shaft 3 in which the thread groove 6 is processed by rolling. The annular part 18 is supposed to have a surface hardness increased by quenching in advance, but here, a dedicated part is not used, but the inner part of the needle bearing with the inner ring is of the same standard, that is, manufactured as the inner ring of the needle bearing. The product is diverted as an annular part 18. For this reason, the nominal outer diameter d1 of the attachment portion of the annular part 18 in the screw shaft material is an integer value to which the inner ring inner diameter of the needle bearing can be applied.

この構成の電動アクチュエータは、ねじ軸３の先端の連結孔１７に嵌合される連結ピンやアーム（いずれも図示せず）を介して、例えば自動車のトランスミッションや電動式ディスクブレーキに連結され、モータ１の回転がボールねじ２を介してスライド動作に変換されてトランスミッションや電動ディスクブレーキに伝達される。すなわち、モータ１の回転出力がギヤ１４，１５を介してナット４に伝達され、ナット４の回転がボール５を介してねじ軸３のスライド動作に変換され、そのスライド動作が前記連結ピンやアームを介してトランスミッションや電動ディスクブレーキに伝達される。   The electric actuator having this configuration is connected to, for example, an automobile transmission or an electric disc brake via a connection pin or an arm (both not shown) fitted in the connection hole 17 at the tip of the screw shaft 3, and the motor The rotation of 1 is converted into a sliding motion via the ball screw 2 and transmitted to the transmission and the electric disc brake. That is, the rotation output of the motor 1 is transmitted to the nut 4 via the gears 14 and 15, and the rotation of the nut 4 is converted into the sliding motion of the screw shaft 3 via the ball 5, and the sliding motion is converted to the connecting pin or arm. Is transmitted to the transmission and the electric disc brake.

この電動アクチュエータにおいて、ねじ軸３の先端側に外力を受けると、ボールねじ２におけるねじ軸３の後半部のねじ部３ａに曲げ力が作用するが、ねじ軸３の前半部は環状部品１８を介してハウジング８の内周のブッシュ１６に摺動自在に支持されているので、ねじ軸３のねじ部３ａに加わる曲げ荷重を吸収することができる。   In this electric actuator, when an external force is applied to the tip end side of the screw shaft 3, a bending force acts on the screw portion 3 a of the second half portion of the screw shaft 3 in the ball screw 2, but the front half portion of the screw shaft 3 has an annular part 18. Therefore, the bending load applied to the screw portion 3a of the screw shaft 3 can be absorbed.

この電動アクチュエータにおけるボールねじ２は、ボールねじ使用機器である電動アクチュエータのブッシュ１６に摺接させる環状部品１８を、焼入れにより表面硬度を高めたものとし、この環状部品１８をねじ軸３の外周に圧入状態に取付けているので、次の利点が得られる。すなわち、ねじ軸３が転造によるもので、転造前のねじ軸素材がセンタレスで製作された場合でも、センタ孔を後加工して前記ブッシュ１６に対する摺動面の研削仕上げを行う必要がなく、製造が容易となる。また、ねじ軸３における摺動面、つまりこの実施形態では環状部品１８の外周面と、ねじ溝６との同軸度精度を向上させることができて、摺動抵抗の低減や耐摩耗性の向上が可能となる。さらに、ねじ軸３の熱処理においては、摺動面の焼入れによる表面硬化を、別部品である環状部品１８で済ませておくことができるので、高周波焼入れによる移動焼入れ時間を短縮でき、この点でも製造が容易となる。なお、この実施形態では、前記ブッシュ１６が、請求項１で言う「電動アクチュエータにおける前記ねじ軸の外周にあって前記ねじ軸の先端を突出させる部品」である。 The ball screw 2 in this electric actuator has an annular part 18 that is brought into sliding contact with the bush 16 of the electric actuator, which is a ball screw using device, with a surface hardness increased by quenching, and this annular part 18 is placed on the outer periphery of the screw shaft 3. Since it is installed in the press-fit state, the following advantages are obtained. That is, even if the screw shaft 3 is formed by rolling and the screw shaft material before rolling is manufactured centerless, there is no need to post-process the center hole and finish grinding of the sliding surface with respect to the bush 16. Manufacturing becomes easy. Further, the accuracy of coaxiality between the sliding surface of the screw shaft 3, that is, the outer peripheral surface of the annular component 18 and the screw groove 6 in this embodiment can be improved, and sliding resistance is reduced and wear resistance is improved. Is possible. Furthermore, in the heat treatment of the screw shaft 3, since the surface hardening by quenching of the sliding surface can be completed by the annular part 18 which is a separate part, the moving quenching time by induction hardening can be shortened, and this point is also produced. that is Do not easy. In this embodiment, the bush 16 is a “part on the outer periphery of the screw shaft in the electric actuator that projects the tip of the screw shaft” according to claim 1.

さらに、この実施形態のボールねじ２では、ねじ軸３における環状部品１８の取付部の外径ｄ１を、内輪付きニードル軸受における内輪の内径と同一規格の整数値としているので、環状部品１８として、ニードル軸受の内輪を転用でき、環状部品１８を安価に調達できる。   Furthermore, in the ball screw 2 of this embodiment, the outer diameter d1 of the mounting portion of the annular part 18 in the screw shaft 3 is an integer value of the same standard as the inner diameter of the inner ring in the needle bearing with the inner ring. The inner ring of the needle bearing can be diverted, and the annular part 18 can be procured at a low cost.

図４は、この発明の他の実施形態を示す。この実施形態の電動アクチュエータは、図１に示した第１の実施形態において、ねじ軸３の外周に圧入状態に取付ける環状部品１８を、軸方向に並べて複数個（ここでは２個）設けたものである。その他の構成は図１に示す第１の実施形態の場合と同じである。   FIG. 4 shows another embodiment of the present invention. In the electric actuator of this embodiment, in the first embodiment shown in FIG. 1, a plurality (two in this case) of annular parts 18 attached in a press-fit state on the outer periphery of the screw shaft 3 are arranged in the axial direction. It is. Other configurations are the same as those of the first embodiment shown in FIG.

ブッシュ１６に対するねじ軸３の軸方向摺動範囲が広い場合には、ねじ軸３の摺動面を１つの環状部品１８で構成しようとすると環状部品１８が長くなるので、ねじ軸３への環状部品１８の圧入作業が容易でないが、この場合に上記したように環状部品１８を複数個に分割して圧入することにより、その作業を容易に行うことができる。   When the axial sliding range of the screw shaft 3 with respect to the bush 16 is wide, if the sliding surface of the screw shaft 3 is configured by one annular component 18, the annular component 18 becomes long. Although the press-fitting work of the part 18 is not easy, in this case, the work can be easily performed by dividing the annular part 18 into a plurality of parts and press-fitting as described above.

この発明の第１の実施形態にかかるボールねじを用いた電動アクチュエータの断面図である。It is sectional drawing of the electric actuator using the ball screw concerning 1st Embodiment of this invention. 同電動アクチュエータにおけるボールねじの部分断面図である。It is a fragmentary sectional view of the ball screw in the electric actuator. 同ボールねじにおけるねじ軸の部分破断正面図である。It is a partially broken front view of the screw shaft in the ball screw. この発明の他の実施形態にかかるボールねじを用いた電動アクチュエータの断面図である。It is sectional drawing of the electric actuator using the ball screw concerning other embodiment of this invention. 同電動アクチェータにおけるねじ軸の部分破断正面図である。It is a partially broken front view of the screw shaft in the same electric actuator. 従来例のボールねじを用いた電動アクチュエータの部分断面図である。It is a fragmentary sectional view of the electric actuator using the ball screw of the prior art example. 図６におけるＡ部の拡大断面図である。It is an expanded sectional view of the A section in FIG. 従来例におけるボールねじへの曲げ力作用の説明図である。It is explanatory drawing of the bending-force effect | action to the ball screw in a prior art example. 従来例におけるボールねじへの曲げ力作用の他の説明図である。It is another explanatory view of the bending force action to the ball screw in the conventional example.

符号の説明Explanation of symbols

２…ボールねじ
３…ねじ軸
４…ナット
１６…ブッシュ
１８…環状部品 2 ... Ball screw 3 ... Screw shaft 4 ... Nut 16 ... Bush 18 ... Ring component

Claims (4)

ナットを回転させ、ねじ軸をスライドさせる形態で使用される電動アクチュエータ用ボールねじにおいて、表面が焼入され電動アクチュエータにおける前記ねじ軸の外周にあって前記ねじ軸の先端を突出させる部品に対して摺接させる環状部品を、前記ねじ軸の外周に圧入状態に取付けたことを特徴とする電動アクチュエータ用ボールねじ。 In a ball screw for an electric actuator that is used in a form in which a nut is rotated and a screw shaft is slid, the surface is hardened and the outer periphery of the screw shaft in the electric actuator is protruded from the tip of the screw shaft A ball screw for an electric actuator, wherein an annular part to be slidably contacted is attached to the outer periphery of the screw shaft in a press-fitted state. 請求項１において、前記環状部品を、軸方向に並べて複数設けた電動アクチュエータ用ボールねじ。   The ball screw for an electric actuator according to claim 1, wherein a plurality of the annular parts are arranged in the axial direction. 請求項１または請求項２において、前記環状部品が、内輪付きのニードル軸受における内輪と同一規格のものである電動アクチュエータ用ボールねじ。   The ball screw for an electric actuator according to claim 1 or 2, wherein the annular component is of the same standard as an inner ring in a needle bearing with an inner ring. 請求項３において、前記ねじ軸がねじ溝を転造加工したものであり、前記ねじ軸の前記環状部品が圧入される軸部の外径を、前記転造加工の前のねじ軸素材の外径とした電動アクチュエータ用ボールねじ。   4. The threaded shaft according to claim 3, wherein the threaded shaft is formed by rolling a thread groove, and an outer diameter of a shaft portion into which the annular part of the threaded shaft is press-fitted is set to an outer diameter of the threaded shaft material before the rolling process. Ball screw for electric actuator with a diameter.
JP2004145842A 2004-05-17 2004-05-17 Ball screw for electric actuator Expired - Fee Related JP4574228B2 (en)

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JP5547563B2 (en) * 2010-06-25 2014-07-16 Ｎｔｎ株式会社 Electric actuator
KR101724170B1 (en) * 2012-10-05 2017-04-06 주식회사 만도 An Electric Power Steering Apparatus
JP6091149B2 (en) * 2012-10-12 2017-03-08 Ntn株式会社 Electric linear actuator
EP3401571B1 (en) * 2017-05-11 2021-07-07 SFS Intec Holding AG Ball screw
CN107387699B (en) * 2017-07-25 2019-08-27 北京新立机械有限责任公司 A kind of lead screw of elevator spline structure

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000309279A (en) * 1999-04-27 2000-11-07 Koyo Seiko Co Ltd Rack and pinion type motor-driven power steering system
JP2002054708A (en) * 2000-08-08 2002-02-20 Makishinkoo:Kk Screw shaft whirl-stop structure of screw jack
JP2004138183A (en) * 2002-10-18 2004-05-13 Nsk Ltd Actuator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000309279A (en) * 1999-04-27 2000-11-07 Koyo Seiko Co Ltd Rack and pinion type motor-driven power steering system
JP2002054708A (en) * 2000-08-08 2002-02-20 Makishinkoo:Kk Screw shaft whirl-stop structure of screw jack
JP2004138183A (en) * 2002-10-18 2004-05-13 Nsk Ltd Actuator

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