JP2009192058A - Worm wheel and its manufacturing method - Google Patents

Worm wheel and its manufacturing method Download PDF

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JP2009192058A
JP2009192058A JP2008036229A JP2008036229A JP2009192058A JP 2009192058 A JP2009192058 A JP 2009192058A JP 2008036229 A JP2008036229 A JP 2008036229A JP 2008036229 A JP2008036229 A JP 2008036229A JP 2009192058 A JP2009192058 A JP 2009192058A
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worm wheel
tooth
tool
gear
molded
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Japanese (ja)
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Akisada Kanazawa
顕禎 金澤
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NSK Ltd
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NSK Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a worm wheel capable of improving the machining accuracy of gear teeth while securing the strength of a forming die. <P>SOLUTION: The worm wheel 1 has tooth faces formed by the die and machined by using a tool on which diamond abrasive grains are deposited. On tooth bottoms between the molded teeth 1a, undercut portions 1b are formed which are cut off into cylindrical shapes in the axial direction. It is not necessary to use the tool for machining the undercut portions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、好適には、電動パワーステアリング装置の減速機構に用いられるウォームホイールを仕上げ加工する際、ギヤの加工精度の向上が可能なウォームホイールおよびその製造方法に関するものである。   The present invention preferably relates to a worm wheel capable of improving the machining accuracy of a gear when finishing a worm wheel used in a reduction mechanism of an electric power steering apparatus, and a manufacturing method thereof.

電動モータを動力源とする電動パワーステアリング装置では、ステアリングホイールに印加された操舵トルクに対応して、電動モータから補助操舵トルクを発生して、動力伝達機構中の減速機構により減速して操舵機構の出力軸に伝達するようになっている。   In an electric power steering apparatus using an electric motor as a power source, an auxiliary steering torque is generated from the electric motor in response to the steering torque applied to the steering wheel, and the steering mechanism is decelerated by a reduction mechanism in the power transmission mechanism. Is transmitted to the output shaft.

この動力伝達機構としてウォーム減速機構を用いた電動モータを動力源とする電動パワーステアリング装置では、電動モータの駆動軸側のウォームに、ウォームホイールが噛合してあり、このウォームホイールは、操舵機構の出力軸（例えば、ピニオン軸、コラム軸）に嵌合してある。   In an electric power steering apparatus using an electric motor using a worm speed reduction mechanism as a power transmission mechanism as a power source, a worm wheel meshes with a worm on the drive shaft side of the electric motor. It is fitted to an output shaft (for example, pinion shaft, column shaft).

ところで、図３に示すようなヘリカルギヤ形状のウォームホイール１０の加工成形において、射出成形等によりインボリュート歯形のギヤ形状にブランクを加工する樹脂ギヤの場合、成形型の強度の必要から、図４に示すように、成形ギヤ１０の歯底空隙１０ａを形成するものとなる成形型の歯先の厚さ(先端幅)ｔを確保しなければならない。このため、成形型の歯先を成形ギヤの軸心方向に延長すると、成形型の歯先が細くなって強度が低下するので、成形型の歯先をあまり長くできない。そのため、成形されたギヤの歯底径ｒも小さくすることはできない。   By the way, in the processing of the helical gear-shaped worm wheel 10 as shown in FIG. 3, in the case of a resin gear for processing a blank into an involute tooth shape by injection molding or the like, the strength of the forming die is shown in FIG. Thus, the thickness (tip width) t of the tip of the molding die that forms the tooth gap 10a of the molding gear 10 must be ensured. For this reason, if the tooth tip of the molding die is extended in the axial direction of the molding gear, the tooth tip of the molding die becomes thin and the strength decreases, so that the tooth tip of the molding die cannot be made too long. Therefore, the root diameter r of the molded gear cannot be reduced.

したがって、このように成形された中間体としての成形ギヤをウォームホイールに仕上げ加工する際に、ダイヤモンド砥粒等を付着させた工具で直接加工することが提案されている（特許文献１）。この場合、工具の歯先が成形ギヤの歯底に当たる影響で加工精度が低下するので、加工精度を上げるために、ホブ加工等により成形ギヤの歯底部分を含めて事前に加工除去する必要がある。
特開平８−１７５４０３号 Accordingly, it has been proposed to directly process with a tool to which diamond abrasive grains or the like are attached when finishing the formed gear as the intermediate body thus formed into a worm wheel (Patent Document 1). In this case, the machining accuracy decreases due to the impact of the tooth tip of the tool on the bottom of the molded gear. Therefore, in order to increase the machining accuracy, it is necessary to perform machining removal including the bottom of the molded gear in advance by hobbing or the like. is there.
JP-A-8-175403

しかしながら、従来の上記ウォームホイールの加工においては、ホブ加工等の前加工を行う場合、コスト高になるのを避けられない。   However, in the conventional processing of the worm wheel, when pre-processing such as hobbing is performed, the cost is unavoidable.

また、前加工を行わない成形ギヤ１０への直接加工で、工具の歯先が被削ギヤ歯底部１０ａを加工する場合、成形ギヤ１０の歯底径ｒの精度を確保しなければ工具歯先の接触状態が一定にならず、加工によるギヤ歯精度を上げられないという問題点があった。   In addition, when the tool tooth tip processes the gear bottom portion 10a by direct machining on the forming gear 10 without pre-machining, the tool tooth tip must be secured unless the accuracy of the root diameter r of the forming gear 10 is ensured. The contact state is not constant, and there is a problem that the gear tooth accuracy by machining cannot be increased.

そこで、本発明は、上述した従来の不具合を解消して、成形型の強度を確保しつつ、成形したギヤ歯の加工精度の向上が可能なウォームホイールを提供することを課題としている。   Therefore, an object of the present invention is to provide a worm wheel capable of solving the above-described conventional problems and ensuring the strength of the mold and improving the machining accuracy of the molded gear teeth.

上記課題を達成するために、本発明では、型によって成形された被削樹脂ギヤの歯面に対して、ダイヤモンド砥粒等の超硬砥粒を付着させた工具で加工して成形するウォームホイールにおいて、前記成形された被削樹脂ギヤには、各歯間の歯底部が軸方向に円柱状にくり貫かれた形状のアンダーカット部が、前記工具で加工する必要のない部分として形成されていることを特徴としている。   In order to achieve the above object, according to the present invention, a worm wheel is formed by processing with a tool in which cemented carbide grains such as diamond abrasive grains are adhered to the tooth surface of a workable resin gear molded by a mold. In the molded resin resin gear, an undercut portion having a shape in which a tooth bottom portion between teeth is hollowed in a cylindrical shape in the axial direction is formed as a portion that does not need to be processed by the tool. It is characterized by being.

本発明のウォームホイールの製造方法は、各歯間の歯底部が軸方向に円柱状にくり貫かれた形状のアンダーカット部を有する被削樹脂ギヤを型によって成形し、該被削樹脂ギヤを前記アンダーカット部を除いて超硬砥粒を付着させた工具で仕上げ加工することを特徴とする。   The method for producing a worm wheel according to the present invention includes molding a work resin gear having an undercut portion having a shape in which a tooth bottom portion between teeth is hollowed in a cylindrical shape in an axial direction, and A finishing process is performed with a tool to which cemented carbide abrasive grains are adhered except for the undercut portion.

以上のように、型で成形された被削樹脂ギヤは、アンダーカット部を有しているので、ダイヤモンド砥粒等の超硬砥粒を付着させた工具で直接加工する際、工具による歯底加工を行う必要がなく、工具歯先の歯に対する接触状態を一定に維持することができるので、型強度を確保することができると共に、加工精度を向上させることができる。   As described above, since the cut resin gear formed by the mold has an undercut portion, when machining directly with a tool to which carbide abrasive grains such as diamond abrasive grains are attached, the bottom of the tool Since it is not necessary to perform machining and the contact state of the tool tip with respect to the teeth can be maintained constant, the mold strength can be ensured and the machining accuracy can be improved.

以下、本発明の実施形態について図面を参照して説明する。   Embodiments of the present invention will be described below with reference to the drawings.

図１は、本発明の実施形態を示すウォームホイールの概略的斜視図、図２は、図１のウォームホイールの部分断面Ａを示す拡大図である。   FIG. 1 is a schematic perspective view of a worm wheel showing an embodiment of the present invention, and FIG. 2 is an enlarged view showing a partial cross section A of the worm wheel of FIG.

図１に示すような形状のウォームホイール１において、その歯形状の部分断面Ａを図２に示している。図２において、図示しない成形型から取り出された被削樹脂ギヤである成形ギヤ１は、その２つの歯１ａ，１ａ間の谷である歯元部(歯底部)に、ウォームホイール１の軸方向に円柱状にくり貫いた形状のアンダーカット部１ｂを有している。   In the worm wheel 1 shaped as shown in FIG. 1, a tooth-shaped partial cross section A is shown in FIG. In FIG. 2, a molding gear 1 which is a workable resin gear taken out from a molding die (not shown) has an axial direction of the worm wheel 1 at a root portion (bottom portion) which is a valley between the two teeth 1 a and 1 a. Has an undercut portion 1b formed in a cylindrical shape.

このウォームホイール１を成形するための成形型においては、アンダーカット部１ｂを成形する部分が形成されており、その部分の先端幅Ｔは、従来より大きく取れる(Ｔ＞ｔ、背景技術参照)ので、強度を確保することができ、この部分を成形ギヤの軸心方向に若干延長することができるため、成形ギヤの歯底径Ｒを従来より若干小さく(Ｒ＜ｒ、背景技術参照)することができる。   In the mold for forming the worm wheel 1, a portion for forming the undercut portion 1b is formed, and the tip width T of the portion can be made larger than before (T> t, refer to the background art). Since the strength can be secured and this portion can be slightly extended in the axial direction of the molded gear, the root diameter R of the molded gear should be slightly smaller than before (R <r, see background art). Can do.

したがって、ホブ加工等による成形ギヤの歯底部分を含めた前加工を行わずに、ダイヤモンド砥粒等の超硬砥粒を付着させた工具で、成形ギヤを直接加工する際、工具歯先がアンダーカット部１ｂ内で非接触状態になり、歯底加工を行わなくて良いので、工具歯先のギヤ歯面に対する接触状態を、歯面以外の接触に影響されずに一定に維持することができ、加工精度を向上させることができる。   Therefore, when machining the formed gear directly with a tool to which carbide abrasive grains such as diamond abrasive grains are attached without performing pre-processing including the tooth bottom portion of the molded gear by hobbing or the like, the tool tooth tip is Since it becomes a non-contact state in the undercut part 1b and it is not necessary to perform the tooth bottom processing, the contact state of the tool tooth tip with the gear tooth surface can be kept constant without being affected by the contact other than the tooth surface. And processing accuracy can be improved.

なお、成形型のアンダーカット部１ｂを成形する部分の先端幅Ｔや先端部長さは、使用する樹脂の材質と、型強度及びギヤ歯強度の関係から適宜選定する必要がある。   It should be noted that the tip width T and the tip length of the part for molding the undercut portion 1b of the mold must be appropriately selected from the relationship between the material of the resin used, the mold strength, and the gear tooth strength.

また、本発明のウォームホイールは、特に、電動パワーステアリング装置の減速機構に組み込まれるウォームホイールとして用いるのが好適と言える。   Moreover, it can be said that the worm wheel of the present invention is particularly suitable for use as a worm wheel incorporated in a speed reduction mechanism of an electric power steering apparatus.

本発明の実施形態を示すウォームホイールの斜視図である。It is a perspective view of the worm wheel which shows embodiment of this invention. 図１のウォームホイールの部分断面Ａを示す拡大図である。It is an enlarged view which shows the partial cross section A of the worm wheel of FIG. 従来のウォームホイールを示す斜視図である。It is a perspective view which shows the conventional worm wheel. 図３のウォームホイールの部分断面Ｂを示す拡大図である。It is an enlarged view which shows the partial cross section B of the worm wheel of FIG.

符号の説明Explanation of symbols

１ ウォームホイール
１ａ ギヤ歯
１ｂ アンダーカット部 1 Worm wheel 1a Gear tooth 1b Undercut part

Claims (2)

型によって成形された被削樹脂ギヤの歯面に対して、超硬砥粒を付着させた工具で加工して成形するウォームホイールにおいて、
前記成形された被削樹脂ギヤには、各歯間の歯底部が軸方向に円柱状にくり貫かれた形状のアンダーカット部が、前記工具で加工する必要のない部分として形成されていることを特徴とするウォームホイール。 In the worm wheel that is molded by processing with a tool with cemented carbide grains attached to the tooth surface of the workable resin gear formed by the mold,
An undercut portion having a shape in which a bottom portion between each tooth is hollowed in a cylindrical shape in the axial direction is formed as a portion that does not need to be processed by the tool in the molded resin gear. A worm wheel characterized by 各歯間の歯底部が軸方向に円柱状にくり貫かれた形状のアンダーカット部を有する被削樹脂ギヤを型によって成形し、
該被削樹脂ギヤを前記アンダーカット部を除いて超硬砥粒を付着させた工具で仕上げ加工することを特徴とするウォームホイールの製造方法。 Molding a cutting resin gear having an undercut portion in a shape in which the tooth bottom portion between each tooth is hollowed out in a cylindrical shape in the axial direction,
A method for producing a worm wheel, wherein the machined resin gear is finished with a tool to which cemented carbide grains are adhered except for the undercut portion.
JP2008036229A 2008-02-18 2008-02-18 Worm wheel and its manufacturing method Withdrawn JP2009192058A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013515937A (en) * 2009-12-29 2013-05-09 ロールス−ロイス・コーポレーション Face coupling
CN104534058A (en) * 2014-12-23 2015-04-22 湖北省三胜工程机械有限公司 High wear-resisting performance driving wheel with seepage diamond particles

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013515937A (en) * 2009-12-29 2013-05-09 ロールス−ロイス・コーポレーション Face coupling
CN104534058A (en) * 2014-12-23 2015-04-22 湖北省三胜工程机械有限公司 High wear-resisting performance driving wheel with seepage diamond particles

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