JP4033029B2

JP4033029B2 - Processing method of thrust dynamic pressure bearing device

Info

Publication number: JP4033029B2
Application number: JP2003110115A
Authority: JP
Inventors: 力浜田; 英生峯
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2003-04-15
Filing date: 2003-04-15
Publication date: 2008-01-16
Anticipated expiration: 2023-04-15
Also published as: JP2004316748A

Description

【０００１】
【発明の属する技術分野】
本発明は、ハードディスク装置等に用いられる流体軸受装置の製造において、プレス装置を用いてシャフトとフランジの締結とスラスト動圧溝加工を同時に行うスラスト動圧軸受装置の加工方法に関するものである。
【０００２】
【従来の技術】
近年ノートパソコンに搭載されるハードディスク装置では、小型化と耐衝撃性の向上が強く要望されており、結果として流体軸受装置の中のシャフトとスラスト軸受の締結強度と締結精度の向上が不可欠となってきている。これを解決するための手段として、プレス装置を用いてシャフトとフランジの締結とスラスト動圧溝加工を同時に行う加工法を提案しているが、これを従来例として、図７を用いて以下説明する。図７において、フランジ２１、シャフト２２とこのシャフト２２に設けられフランジ２１の内周が挿入される締結部２３とからなる。２４は下金型で、シャフト２２の外周を保持する穴２５と、フランジ２１にスラスト動圧溝を加工する動圧溝に対応した溝２６を有する。２７はフランジ２１の外周拘束部であり、プレス加工時のフランジ２１の外方向への変形を規制することでフランジ２１とシャフト２２の締結を促進する。なお外周拘束部２７を下金型２４とは別部材で構成する場合もある。２８は上金型であり、下金型２４と同様にスラスト動圧溝を加工する動圧溝に対応した溝２６を有し、かつ矢印Ｘ方向へ動かすことによりフランジ２１とシャフト２２の締結及びフランジ２１の両面へのスラスト溝加工が可能となる。
【０００３】
なお、フランジ２１の下面は下金型２４に対しＨだけ隙間を介してセットしている理由は、プレス加工時のシャフト２２の圧縮変形に伴うシャフト２２外周内に位置すべきフランジ２１上面の溝の加工の不十分さを補うためである。
【０００４】
以上のように構成された従来例の動作を以下説明する。フランジ２１外径が約５ｍｍ、シャフト２１の外径が３ｍｍの場合、上金型２８の加工荷重を約５トンに設定することで、フランジ２１とシャフト２２の締結及びフランジ２１へのスラスト動圧溝加工が可能であった。なお本加工後のフランジ加工精度が不十分の場合は、第２のプレス工程によりフランジ２１の動圧溝加工面の厚さと平面度を矯正することもある。
【０００５】
【特許文献１】
特開平５−１０２７６９号公報
【０００６】
【発明が解決しようとする課題】
しかしながらこのような加工法では、上金型２８の下降に伴う加工荷重の一部がフランジ２１を介してシャフト２２へ伝わる構造のために、加工条件特に加工荷重によってはシャフト２２の最も弱い底面部に割れや変形を発生するという品質上の課題があった。
【０００７】
【課題を解決するための手段】
本発明は上記プレス加工方法によるスラスト動圧軸受装置の加工方法に於いて、フランジとシャフトの寸法や形状を工夫することにより、シャフトに割れや変形が発生せず、かつ締結とスラスト動圧溝加工を同時に加工できるようにしたものである。
【０００８】
上記課題を解決するために請求項１記載の発明は、スラスト動圧溝が形成されるフランジと、前記フランジの穴の内周に挿入される締結部を端面に有し、前記締結部と隣接して前記端面に形成される段部により前記フランジを、接触して挿入方向に支持するシャフトとに対し、前記フランジに動圧溝を加工するための溝を有する上型、および前記溝を有するとともに前記シャフトを挿入位置決めする穴および前記フランジの外周を拘束する外径拘束部を有し、前記フランジの前記段部と接触する下面との間に隙間を設ける構成とした下型とにより、前記フランジのスラスト動圧溝加工と前記シャフトへの締結がプレス加工により同時に行われるスラスト動圧軸受装置の加工に於いて、前記上型を前記下型方向に下降させ、前記フランジの穴の周囲に設けた微小突起を接触状態で押圧することにより、前記微小突起の、前記穴に挿入された前記締結部側への変形を開始せしめるとともに、前記下型と、前記フランジを介して前記上型とにより挟み込まれた前記シャフトの変形を開始せしめ、押圧を継続することにより前記隙間がゼロとなってからの前記フランジ両面の溝加工を開始せしめるとともに、前記フランジの外周を前記外径拘束部に接触させた状態で、前記フランジのスラスト動圧溝加工と前記シャフトへの締結を完了するスラスト動圧軸受装置の加工方法で、これにより、プレス加工の際にシャフトが大きく変形しない大きさとした微小突起に上型の荷重全てが加わって変形が始まるが、この微小突起の上型との当接部より外側がフランジの外周側への変形を防ぐ働きをするため、シャフトの塑性変形発生前の、過重が小さい段階で微小突起の変形が締結部側へ発生してシャフトとの締結力が発生し、また、フランジとシャフト段部を接触状態とし、かつ下型とフランジ下面との間に隙間を有している為、押圧加工時に下型とフランジ下面との間の隙間がゼロになって以降、シャフトに加重を作用させずにフランジとシャフトを締結できることとなり、押圧加工時に、フランジとシャフト段部との接触による位置規正効果によりシャフトの軸方向位置ズレを防止しつつ、フランジの圧縮変形に伴うシャフトの割れや必要以上の変形を防止することができる。
【０００９】
上記課題を解決するために請求項２記載の発明は、請求項１記載の構成において微小突起の外周とフランジ内周間で決定される面積を、前記シャフト底面のハブ圧入部外周とディスク止めネジ穴間で決定される面積に対し同等以下となるよう設定することにより加工を行うもので、これにより、シャフトの割れや変形が発生する前に微小突起部の締結が可能となる。
【００１０】
上記問題点を解決するために請求項３記載の発明は、請求項１又は２記載の構成において微小突起の高さを、締結強度が締結部の形状で決まる最大の締結強度の５０％以上となるよう実験的に決定することにより加工を行うものであり、さらに請求項４記載の発明は、請求項１又は２記載の構成において微小突起の高さを０．０１ｍｍ以上に設定して加工を行うものであり、これらにより締結部でフランジが変形する体積すなわち微小突起の体積が、フランジと締結部形状とで決まる隙間体積に対し十分な充填量となるので、締結強度も確保できることとなる。
【００１１】
【発明の実施の形態】
図１〜図６に本発明の実施の形態を示す。図１は本発明における第１の発明の説明図で、フランジ１、シャフト２とこのシャフト２に設けられフランジ１の内周が挿入される締結部３とからなり、フランジ１の内周と締結部３の挿入隙間はＹで示してある。４は下金型で、シャフト２の外径を保持する穴５と、フランジ１にスラスト動圧溝を加工するための溝６を有する。７はフランジ１の外周拘束部であり、プレス加工時のフランジ１の外方向への変形を規制することでフランジ１とシャフト２の締結を促進する。なお本実施例では外周拘束部７を下金型４と一体的に設けてあるが、別部材で構成しても良い。８は上金型であり、下金型４と同様にスラスト動圧溝を加工するための溝６を有し、かつ矢印Ｘ方向へ動かすことによりフランジ１とシャフト２の締結及びフランジ１の両面へのスラスト溝加工が可能となる。
【００１２】
なお、フランジ１の下面を下金型４に対しＨだけ隙間を介してセットしている理由は、プレス加工時のシャフト２の圧縮変形に伴うシャフト２外周内に位置すべきフランジ１上面の溝の加工の不十分さを補うためである。またＹはフランジ１の内周と締結部３との隙間を示している。
【００１３】
以上のように構成された第１の実施形態に於ける動作について図２を用いて以下説明する。
【００１４】
本実施形態に於いて、フランジ１の外径が約５ｍｍ、シャフト２の外径が３ｍｍの場合、スラスト動圧溝加工が完了するときの上金型８の加工荷重は約３トン、締結が完了する荷重は約５トンであるので、シャフト２の変形や割れを防止するためには、シャフト２が受ける荷重を如何に低減するかがポイントとなる。そこで、図２にプレス加工に於けるシャフト２が受ける荷重の時間変化を示す。上金型８がＸ方向へ下降しフランジ１と接触を始めるとシャフト２が変形を始め、隙間Ｈが０になるまで比例してシャフト荷重は増え、Ａで示す時間に至る。次ぎに上金型８が更に下降するとフランジ１が外径方向へ変形を始め、フランジ１の外周が外周拘束部７に当接するまでシャフト荷重は増大し、点Ｂで示す時間に至る。更に上金型８を下降させた時始めてフランジ１が締結部３側へ変形を始めるが、この時外周拘束部７で強制的にフランジ１を内周方向へ変形させているので、シャフト荷重は急激に上昇し、Ｃ点で示す時間に至る。更に上金型８が下降すると始めてフランジ１が締結部３と接触を始め、点Ｄで示す時間にフランジ１とシャフト２の締結が完了する。シャフト２の変形や割れを防止するためには当然Ｄ点の最大シャフト荷重を低減することが重要であり、本発明は隙間Ｙを小さくすることで、ＢとＣ間のシャフト荷重増大を防止するものである。
【００１５】
図３は上金型８の加工荷重を４トンに下げたときの、隙間Ｙと締結強度の関係を実験的に求めたグラフである。締結強度は締結部３の形状及びフランジ１とシャフト２の材質で決定される最大強度であり、実験例では約５０Ｋｇである。また隙間Ｙを徐々に大きくすると締結強度は急激に低下し、Ｙが０．０５ｍｍでは加工荷重４トンでほとんど締結出来なくなる。以上の実験データから、隙間Ｙを０．０３ｍｍ以下とすることで、加工荷重を４トンに低下させても飽和締結強度の約６割が確保でき、その結果、シャフトの割れ、変形の低減と同時に、締結強度を確保できることになる。なお上記実施形態では、隙間Ｙを正の数値で示しているが、隙間Ｙを負の数値、すなわち圧入にしても効果があることは言うまでもない。
【００１６】
次ぎに本発明の第２の発明の実施形態について、図４を用いて以下説明する。図４は図１とほぼ同じ構成であるが、差異として直径Ｅ、高さＦの微小突起９をフランジ１に設けた点である。
【００１７】
上記構成の第２の実施形態に於ける動作について、以下図５を用いて説明する。図５にプレス加工に於けるシャフト２が受ける荷重の時間変化を示す。上金型８がＸ方向へ下降しフランジ１と接触を始めるとシャフト２が変形を始め、隙間Ｈが０になるまで比例してシャフト荷重は増え、Ａ点で示す時間に至る。同時にフランジ１も微小突起９の外形寸法Ｅで示す範囲に上金型８の荷重全てが加わるので変形が始まるが、フランジ１のＥ寸法で示す当接部より外側自体が拘束部７と同様外周側への変形を防ぐ働きをするため、フランジ１のＥ寸法で示す範囲の変形が即締結部３側へ発生し、Ａ点に於いて既に締結力が発生する。更に上金型８を下降させていくと、フランジ１の外周が外径拘束部７に当接しＢ点に到達する。しかしながらこの時点でスラスト動圧溝加工が不十分のため、上金型８を下降させ、Ｄ点で十分なスラスト動圧溝加工が完了することとなる。
【００１８】
次ぎにシャフト２の割れや変形を確実に防止するための条件について以下説明する。シャフト２の下部形状は図４に示すように、図示しないハブを取付るためのシャフト２外径より小さなハブ取付直径部を設けたり、図示しないディスクを取り付けるためのディスク取付ネジを設けることが一般的である。結果、この部位がプレス加工に対する強度が最も少さくなり、シャフト２の割れや変形もこの部位に発生する。そこでシャフト２の変形や割れを防止し、かつ締結荷重を小さくするための条件は、微小突起９をシャフト２底面のハブ圧入外周とディスク止めネジ穴間で決定される面積に対し同等以下となるよう構成しておく。これによりシャフト２の変形が発生する前に微小突起９が変形を始め、この変形はフランジ１の変形と相まって締結に寄与できることとになる。
【００１９】
次ぎに本発明の第３の実施形態について以下説明する。第２の実施形態においてはシャフト２の割れや変形が発生しない必要条件を示したが、第３の実施形態は第２の実施形態の必要条件の中で、十分な締結強度を確保するためになされたものである。よって第３の実施形態における構成は、第２の実施形態の説明で用いた図４と全く同じ構成であり、同じ形状、動作となる。
【００２０】
第３の実施形態のポイントは、第２の実施形態で微小突起９の外径寸法Ｅが制約される中で、締結部３近傍の変形体積をＦ寸法で示される部分の体積で確保しようとするものであり、実際は図６に示す実験の結果で決定できる。図６は、上金型８の加工荷重をスラスト動圧溝が加工できる３トンに固定し、この時の微小突起９の寸法を、Ｅは第２の実施形態における条件を満足できる２．６ｍｍ以下、Ｆは０．０１から０．０４ｍｍまで変化させる時の、締結強度を５個の平均値で求めた実験結果である。この図６の実験結果から、締結力確保のためには微小突起９の外径寸法Ｅの影響は小さく、高さ寸法Ｆの影響が大きいと言える。かつこの微小突起９のＦ寸法の効果は極めて大きいので、Ｆを０．０１ｍｍ以上とすれば上金型８による加工荷重が３トンでも、飽和締結強度の約５０％を確保できることになる。なお当然の事ながら本実験は第２の実施形態における条件をも満足しているので、シャフト３の割れや変形の発生は皆無であった。
【００２１】
【発明の効果】
以上の説明から明らかなように、本発明の第１の発明のスラスト動圧軸受装置の加工方法により、プレス加工の際にシャフトが大きく変形しない大きさとした微小突起に上型の荷重全てが加わって変形が始まるが、この微小突起の上型との当接部より外側がフランジの外周側への変形を防ぐ働きをするため、シャフトの塑性変形発生前の、過重が小さい段階で微小突起の変形が締結部側へ発生してシャフトとの締結力が発生し、また、フランジとシャフト段部を接触状態とし、かつ下型とフランジ下面との間に隙間を有している為、押圧加工時に下型とフランジ下面との間の隙間がゼロになって以降、シャフトに加重を作用させずにフランジとシャフトを締結できることとなり、押圧加工時に、フランジとシャフト段部との接触による位置規正効果によりシャフトの軸方向位置ズレを防止しつつ、フランジの圧縮変形に伴うシャフトの割れや必要以上の変形を防止することができ、品質の高いスラスト軸受装置を低コストで提供できることになる。
【００２２】
また第２の発明では、第１の発明において、微小突起の外周とフランジ内周間で決定される面積を、シャフト底面のハブ圧入部外周とディスク止めネジ穴間で決定される面積に対し同等以下となるよう設定して加工を行うものであるため、シャフトの割れや変形が発生する前に微小突起部の締結が可能となり、これにより、品質の高いスラスト軸受装置を低コストで提供できることになる。
【００２３】
更に第３、第４の発明では、シャフトに微小突起を設け、この高さを十分な締結力が得られる高さとすることで、品質の高いスラスト軸受装置を低コストで提供できることになる。
【図面の簡単な説明】
【図１】第１の実施形態における軸受形状とその加工方法を説明する断面図
【図２】第１の実施形態におけるシャフト荷重の説明図
【図３】第１の実施形態における隙間Ｙと締結強度の説明図
【図４】第２の実施形態における軸受形状とその加工方法を説明する断面図
【図５】第２の実施形態におけるシャフト荷重の説明図
【図６】第３の実施形態における微小突起高さ寸法Ｆと締結強度の関係を示す説明図
【図７】従来例の軸受形状とその加工方法を説明する断面図
【符号の説明】
１フランジ
２シャフト
３締結部
４下金型
５穴
６溝
７外径拘束部
８上金型
９微小突起[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a processing method of a thrust dynamic pressure bearing device in which a shaft and a flange are fastened and thrust dynamic pressure groove processing is simultaneously performed using a press device in the manufacture of a fluid dynamic bearing device used for a hard disk device or the like.
[0002]
[Prior art]
In recent years, there has been a strong demand for downsizing and improvement in impact resistance of hard disk drives mounted on notebook computers. As a result, it is essential to improve the fastening strength and fastening accuracy of the shaft and thrust bearing in the hydrodynamic bearing device. It is coming. As a means for solving this, a processing method for simultaneously performing fastening of a shaft and a flange and thrust dynamic pressure groove processing using a press device has been proposed. This will be described below using FIG. 7 as a conventional example. To do. In FIG. 7, it consists of a flange 21, a shaft 22, and a fastening portion 23 provided on the shaft 22 into which the inner periphery of the flange 21 is inserted. A lower mold 24 has a hole 25 for holding the outer periphery of the shaft 22 and a groove 26 corresponding to the dynamic pressure groove for processing the thrust dynamic pressure groove in the flange 21. Reference numeral 27 denotes an outer peripheral restraining portion of the flange 21, which promotes the fastening of the flange 21 and the shaft 22 by restricting the outward deformation of the flange 21 during press working. In some cases, the outer peripheral restraining portion 27 may be formed of a member different from the lower mold 24. An upper die 28 has a groove 26 corresponding to a dynamic pressure groove for machining a thrust dynamic pressure groove, like the lower die 24, and is moved in the direction of the arrow X to fasten the flange 21 and the shaft 22. Thrust groove machining on both surfaces of the flange 21 is possible.
[0003]
The reason why the lower surface of the flange 21 is set with respect to the lower mold 24 through a gap is that the groove on the upper surface of the flange 21 to be positioned in the outer periphery of the shaft 22 due to the compression deformation of the shaft 22 during press working. This is to compensate for the insufficient processing.
[0004]
The operation of the conventional example configured as described above will be described below. When the outer diameter of the flange 21 is about 5 mm and the outer diameter of the shaft 21 is 3 mm, the working load of the upper mold 28 is set to about 5 tons, whereby the flange 21 and the shaft 22 are fastened and the thrust dynamic pressure on the flange 21 is set. Groove processing was possible. If the flange processing accuracy after the main processing is insufficient, the thickness and flatness of the dynamic pressure groove processing surface of the flange 21 may be corrected by the second pressing step.
[0005]
[Patent Document 1]
JP-A-5-102769 [0006]
[Problems to be solved by the invention]
However, in such a processing method, because the part of the processing load accompanying the lowering of the upper mold 28 is transmitted to the shaft 22 via the flange 21, the bottom surface of the shaft 22 is the weakest depending on the processing conditions, particularly the processing load. There was a quality problem in that cracks and deformation occurred.
[0007]
[Means for Solving the Problems]
The present invention provides a thrust hydrodynamic bearing device machining method according to the above-described press machining method. By devising the dimensions and shape of the flange and shaft, the shaft does not crack or deform, and the fastening and thrust dynamic pressure grooves It is designed to process at the same time.
[0008]
The invention of claim 1, wherein in order to solve the above problems, possess a flange thrust dynamic pressure groove is formed, a fastening portion to be inserted into the inner periphery of the hole of the flange on the end face, adjacent to the fastening portion And an upper die having a groove for processing a dynamic pressure groove in the flange with respect to a shaft that contacts the flange by a step portion formed on the end surface and supports the flange in the insertion direction , and the groove. the have a outside diameter restraining portion that restrains the outer periphery of the hole and the flange to the insertion position shaft, by a lower die having a configuration in which the gap between the lower surface in contact with the stepped portion of the flange with the fastening to the flange of the thrust dynamic pressure groove processing and the shaft is at the machining of the thrust dynamic pressure bearing device which is performed simultaneously by pressing, the upper die is lowered into the lower mold direction, the hole of the flange By pressing the microprotrusion provided in the enclosure in a contact state, the microprotrusion is started to be deformed toward the fastening portion inserted into the hole, and the upper mold is inserted through the lower mold and the flange. The shaft sandwiched by the mold is started to be deformed, and by continuing the pressing, the groove on both sides of the flange is started after the gap becomes zero, and the outer periphery of the flange is connected to the outer diameter restraining portion. This is a thrust hydrodynamic bearing device machining method that completes the thrust dynamic pressure groove machining of the flange and the fastening to the shaft in a state where it is in contact with the shaft , so that the shaft is not greatly deformed during press working. Deformation starts when all the load of the upper mold is applied to the microprojection, but the outer side of the contact portion with the upper mold of this microprojection works to prevent deformation to the outer peripheral side of the flange. Therefore, before the plastic deformation of the shaft occurs, the deformation of the minute projections occurs on the fastening part side at a stage where the overload is small, and the fastening force with the shaft is generated. Since there is a gap between the mold and the lower surface of the flange, the flange and the shaft can be fastened without applying a load to the shaft after the gap between the lower mold and the lower surface of the flange becomes zero during pressing. Thus, during pressing, the shaft can be prevented from being displaced due to compression deformation of the flange or more than necessary while preventing the axial displacement of the shaft due to the position regulating effect caused by the contact between the flange and the shaft step. .
[0009]
The invention of claim 2, wherein in order to solve the above problems, an area that is determined between claim 1 periphery and the flange peripheral configuration smell Te fine small protrusions according, the hub press fit portion outer periphery of the shaft bottom surface those against the area to be determined between the disk set screw hole for machining by setting so as to be equal to or less, which enables fastening of the minute projections before cracking or deformation of the sheet Yafuto occurs .
[0010]
The invention of claim 3, wherein in order to solve the above problem, the height of the microprojections in the configuration of claim 1 or 2, wherein the fastening strength over 50% of the maximum joint strength determined by the shape of the fastening portion and so as are those for machining by determining experimentally, further fourth aspect of the present invention, a process to set the height of the microprojections than 0.01mm in the structure according to claim 1 or 2, wherein As a result, the volume at which the flange is deformed at the fastening portion, that is, the volume of the minute projections is sufficient for the gap volume determined by the flange and the shape of the fastening portion, so that the fastening strength can be secured.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
1 to 6 show an embodiment of the present invention. FIG. 1 is an explanatory view of a first invention in the present invention, which comprises a flange 1, a shaft 2, and a fastening portion 3 provided on the shaft 2 and into which the inner periphery of the flange 1 is inserted. The insertion gap of the part 3 is indicated by Y. A lower mold 4 has a hole 5 for holding the outer diameter of the shaft 2 and a groove 6 for processing a thrust dynamic pressure groove in the flange 1. Reference numeral 7 denotes an outer peripheral restraint portion of the flange 1 that promotes fastening of the flange 1 and the shaft 2 by restricting deformation of the flange 1 in the outward direction during press working. In this embodiment, the outer peripheral restraining portion 7 is provided integrally with the lower mold 4, but it may be constituted by another member. Reference numeral 8 denotes an upper die, which has a groove 6 for machining a thrust dynamic pressure groove like the lower die 4, and is moved in the arrow X direction to fasten the flange 1 and the shaft 2 and both surfaces of the flange 1. Thrust groove machining is possible.
[0012]
The reason why the lower surface of the flange 1 is set with respect to the lower die 4 with a gap of H is that the groove on the upper surface of the flange 1 to be positioned in the outer periphery of the shaft 2 due to the compression deformation of the shaft 2 during press working. This is to compensate for the insufficient processing. Y indicates a gap between the inner periphery of the flange 1 and the fastening portion 3.
[0013]
The operation of the first embodiment configured as described above will be described below with reference to FIG.
[0014]
In this embodiment, when the outer diameter of the flange 1 is about 5 mm and the outer diameter of the shaft 2 is 3 mm, the processing load of the upper die 8 when the thrust dynamic pressure groove processing is completed is about 3 tons, and the fastening is since complete load is approximately 5 tons in order to prevent deformation and cracking of the shaft 2, or how reduce the load shea Yafuto 2 receives becomes point. Therefore, FIG. 2 shows the time change of the load that the shaft 2 receives in the press working. When the upper mold 8 descends in the X direction and starts to contact the flange 1, the shaft 2 begins to deform, and the shaft load increases proportionally until the gap H becomes 0, reaching the time indicated by A. Next, when the upper die 8 is further lowered, the flange 1 starts to deform in the outer diameter direction, and the shaft load increases until the outer periphery of the flange 1 comes into contact with the outer peripheral restraining portion 7, and the time indicated by point B is reached. Further, the flange 1 starts to be deformed toward the fastening portion 3 side only when the upper die 8 is lowered. At this time, the flange 1 is forcibly deformed in the inner peripheral direction by the outer peripheral restraining portion 7, so that the shaft load is It rises rapidly and reaches the time indicated by point C. Furthermore, the flange 1 begins to contact the fastening portion 3 only when the upper mold 8 is lowered, and the fastening of the flange 1 and the shaft 2 is completed at the time indicated by the point D. Naturally, it is important to reduce the maximum shaft load at the point D in order to prevent deformation and cracking of the shaft 2, and the present invention prevents the shaft load from increasing between B and C by reducing the gap Y. Is.
[0015]
FIG. 3 is a graph in which the relationship between the gap Y and the fastening strength is experimentally obtained when the processing load of the upper die 8 is lowered to 4 tons. The fastening strength is the maximum strength determined by the shape of the fastening portion 3 and the material of the flange 1 and the shaft 2 and is about 50 kg in the experimental example. Further, when the gap Y is gradually increased, the fastening strength is drastically reduced, and when Y is 0.05 mm, it is almost impossible to fasten with a processing load of 4 tons. From the above experimental data, by setting the gap Y to be 0.03 mm or less, it is possible to secure about 60% of the saturation fastening strength even if the processing load is reduced to 4 tons, and as a result, the shaft cracking and deformation can be reduced. At the same time, the fastening strength can be secured. In the above-described embodiment, the gap Y is indicated by a positive numerical value, but it goes without saying that there is an effect even if the gap Y is a negative numerical value, that is, press-fitting.
[0016]
Next, an embodiment of the second invention of the present invention will be described below with reference to FIG. Figure 4 is substantially the same configuration as FIG. 1, in that provided in diameter E as the difference, the small projections 9 of height F to the flange 1.
[0017]
The operation of the second embodiment having the above configuration will be described below with reference to FIG. FIG. 5 shows the time change of the load that the shaft 2 receives in the press working. When the upper die 8 descends in the X direction and starts to contact the flange 1, the shaft 2 starts to deform, and the shaft load increases proportionally until the gap H becomes zero, reaching the time indicated by point A. At the same time, the flange 1 is also deformed because all the load of the upper mold 8 is applied within the range indicated by the external dimension E of the microprotrusion 9, but the outer side of the contact part indicated by the E dimension of the flange 1 is the same as the restraint part 7. In order to prevent the deformation to the side, the deformation in the range indicated by the dimension E of the flange 1 occurs immediately to the fastening portion 3 side, and the fastening force is already generated at the point A. When the upper mold 8 is further lowered, the outer periphery of the flange 1 comes into contact with the outer diameter restricting portion 7 and reaches the point B. However, since the thrust dynamic pressure groove machining is insufficient at this time, the upper die 8 is lowered , and sufficient thrust dynamic pressure groove machining is completed at the point D.
[0018]
Next, conditions for reliably preventing cracking and deformation of the shaft 2 will be described below. Lower shape of the shaft 2, as shown in FIG. 4, may be provided a small hub mounting diameter portion than the shaft 2 the outer diameter of the order Ru attached a hub, not shown, be provided with a disk mounting screws for mounting the disk (not shown) generally Is. As a result, this portion has the least strength against pressing, and the shaft 2 is also cracked and deformed. Therefore, the conditions for preventing deformation and cracking of the shaft 2 and reducing the fastening load are equal to or smaller than the area determined by the microprojection 9 between the hub press-fit outer periphery of the shaft 2 and the disk set screw hole. It is configured as follows. Thereby, before the deformation of the shaft 2 occurs, the minute projections 9 start to deform, and this deformation can be combined with the deformation of the flange 1 to contribute to fastening.
[0019]
Next, a third embodiment of the present invention will be described below. In the second embodiment, the necessary condition that the shaft 2 is not cracked or deformed is shown, but the third embodiment is a necessary condition of the second embodiment in order to ensure sufficient fastening strength. It was made. Therefore, the configuration in the third embodiment is exactly the same as that in FIG. 4 used in the description of the second embodiment, and has the same shape and operation.
[0020]
The point of the third embodiment is to secure the deformation volume in the vicinity of the fastening portion 3 with the volume of the portion indicated by the F dimension while the outer diameter dimension E of the microprojection 9 is restricted in the second embodiment. Actually, it can be determined by the result of the experiment shown in FIG. FIG. 6 shows that the processing load of the upper die 8 is fixed to 3 tons where the thrust dynamic pressure groove can be processed, and the dimension of the microprotrusion 9 at this time is 2.6 mm, where E can satisfy the conditions in the second embodiment. Hereinafter, F is an experimental result obtained by calculating the fastening strength with an average value of five pieces when changing from 0.01 to 0.04 mm. From the experimental results in FIG. 6, it can be said that the outer diameter dimension E of the microprojections 9 is small and the height dimension F is large in order to secure the fastening force. In addition, since the effect of the F dimension of the minute projections 9 is extremely large, if F is set to 0.01 mm or more, even if the processing load by the upper mold 8 is 3 tons, about 50% of the saturation fastening strength can be secured. As a matter of course, since this experiment also satisfied the conditions in the second embodiment, there was no occurrence of cracking or deformation of the shaft 3.
[0021]
【The invention's effect】
As is apparent from the above description, the thrust dynamic pressure bearing device processing method according to the first aspect of the present invention applies all of the upper mold load to the microprojections whose size is such that the shaft is not greatly deformed during pressing. However, since the outer side of the contact portion with the upper mold of this microprotrusion works to prevent the outer periphery of the flange from being deformed, the microprotrusion of the microprotrusion is reduced at a stage where the overload is small before the plastic deformation of the shaft occurs. Deformation occurs on the side of the fastening part, resulting in a fastening force with the shaft, and because the flange and the shaft step part are in contact with each other and there is a gap between the lower mold and the lower surface of the flange. Sometimes, after the gap between the lower mold and the lower surface of the flange becomes zero, the flange and the shaft can be fastened without applying a load to the shaft. While preventing axial misalignment of the shaft due to the effect, it is possible to prevent cracking or excessive deformation of the shaft caused by the compressive deformation of the flange, so that a high thrust bearing device quality can be provided at low cost.
[0022]
In the second invention, in the first invention, with respect to the area of the area to be determined between the outer periphery and the flange inner periphery of microprojections, it is determined between the hub press fit outer periphery of the shaft bottom and the disk set screw hole Since it is set to be equal to or less than the machining, it is possible to fasten the minute projections before the shaft breaks or deforms, thereby providing a high-quality thrust bearing device at a low cost. become.
[0023]
Furthermore, in the third and fourth inventions, a high-quality thrust bearing device can be provided at a low cost by providing minute projections on the shaft and making this height high enough to obtain a fastening force.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a bearing shape and a processing method thereof in the first embodiment. FIG. 2 is an explanatory view of a shaft load in the first embodiment. FIG. 3 is a fastening with a gap Y in the first embodiment. Explanatory drawing of strength [FIG. 4] Cross-sectional view explaining the bearing shape and processing method in the second embodiment [FIG. 5] Explanatory drawing of shaft load in the second embodiment [FIG. 6] In the third embodiment Explanatory diagram showing the relationship between the microprojection height F and the fastening strength. FIG. 7 is a cross-sectional view illustrating a conventional bearing shape and processing method.
1 Flange 2 Shaft 3 Fastening part 4 Lower mold 5 Hole 6 Groove 7 Outer diameter restraint part 8 Upper mold 9 Micro protrusion

Claims

A flange thrust dynamic pressure groove is formed, a fastening portion to be inserted into the inner periphery of the hole of the flange possess the end face, said flange by the step portion formed on the end surface adjacent to the fastening portion, to a shaft supported in the insertion direction contact with, restrain the upper die, and the hole and the outer periphery of the flange insert positioning said shaft and having said groove having a groove for machining dynamic pressure grooves on the flange to have a external diameter restraining portion by the lower mold having a configuration in which the gap between the lower surface in contact with the stepped portion of the flange, the engagement of the thrust dynamic pressure groove processing and the shaft of the flange pressing in the processing of the thrust dynamic pressure bearing device are simultaneously performed by the processing, the upper die is lowered into the lower mold direction, to press the microprotrusions provided around the hole of the flange in contact The microprotrusions are started to deform toward the fastening portion inserted into the hole, and the shaft sandwiched between the lower mold and the upper mold via the flange is started to deform. Then, by continuing the pressing, the groove machining on both sides of the flange after the gap becomes zero is started, and the thrust dynamic pressure of the flange is in a state where the outer periphery of the flange is in contact with the outer diameter restraining portion. A machining method for a thrust hydrodynamic bearing device, characterized by completing the groove machining and fastening to the shaft .

The processing is performed by setting the area determined between the outer periphery of the minute protrusion and the inner periphery of the flange to be equal to or less than the area determined between the outer periphery of the hub press-fit portion on the bottom surface of the shaft and the disk set screw hole. A processing method for a thrust hydrodynamic bearing device according to claim 1.

The thrust hydrodynamic bearing device according to claim 1 or 2, wherein the processing is performed by experimentally determining the height of the microprotrusions so that the fastening strength is 50% or more of the maximum fastening strength determined by the shape of the fastening portion. Processing method.

The method for processing a thrust hydrodynamic bearing device according to claim 1 or 2, wherein the processing is performed with the height of the fine protrusions being 0.01 mm or more.