JP2006250333A - Hollow power transmission shaft - Google Patents

Hollow power transmission shaft Download PDF

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JP2006250333A
JP2006250333A JP2005071537A JP2005071537A JP2006250333A JP 2006250333 A JP2006250333 A JP 2006250333A JP 2005071537 A JP2005071537 A JP 2005071537A JP 2005071537 A JP2005071537 A JP 2005071537A JP 2006250333 A JP2006250333 A JP 2006250333A
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power transmission
transmission shaft
diameter portion
hollow
hardness
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Katsuhiro Sakurai
勝弘 櫻井
Akira Nakagawa
亮 中川
Kazuhiko Yoshida
和彦 吉田
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NTN Corp
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NTN Corp
NTN Toyo Bearing Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To prevent decrease in hardness of a polar surface layer, in a quenched hollow power transmission shaft. <P>SOLUTION: In the hollow power transmission shaft 1, almost all area L in an axial direction is subjected to high frequency quenching for forming a hardened layer S. Amount of decrease in hardness of the polar surface part Sf with respect to the maximum hardness is set to be ΔHv50 or less. A coolant is supplied to an outer circumferential surface 1g of hollow power transmission shaft material so that a cooling rate by the coolant is 130°C/sec. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、等速自在継手等の継手に連結される中空状動力伝達シャフトに関し、例えば、自動車の動力伝達系を構成するドライブシャフト（駆動軸）やプロペラシャフト（推進軸）に適用することができる。   The present invention relates to a hollow power transmission shaft connected to a joint such as a constant velocity universal joint, and can be applied to, for example, a drive shaft (drive shaft) and a propeller shaft (propulsion shaft) constituting a power transmission system of an automobile. it can.

例えば、自動車の動力伝達系において、減速装置（ディファレンシャル）から駆動輪に動力を伝達する動力伝達シャフトは、ドライブシャフト（駆動軸）と呼ばれることがある。特に、ＦＦ車に使用されるドライブシャフトでは、前輪操舵時に大きな作動角と等速性が要求され、また、懸架装置との関係で軸方向の変位を吸収する機能が要求されるので、その一端部をダブルオフセット型等速自在継手やトリポード型等速自在継手等の摺動型等速自在継手を介して減速装置側に連結し、その他端部をバーフィールド型等速自在継手（ゼッパジョイントと呼ばれることもある。）等の固定側等速自在継手を介して駆動輪側に連結する機構が多く採用されている。   For example, in a power transmission system of an automobile, a power transmission shaft that transmits power from a speed reducer (differential) to drive wheels may be called a drive shaft (drive shaft). In particular, a drive shaft used in an FF vehicle requires a large operating angle and constant velocity during front wheel steering, and also requires a function of absorbing axial displacement in relation to the suspension system. Is connected to the reducer side through a sliding type constant velocity universal joint such as a double offset type constant velocity universal joint or a tripod type constant velocity universal joint, and the other end is connected to a barfield type constant velocity universal joint (Zepper joint). In many cases, a mechanism that is connected to the drive wheel side via a fixed-side constant velocity universal joint is employed.

上記のようなドライブシャフトとしては、従来、また現在においても、中実シャフトが多く使用されているが、自動車の軽量化、ドライブシャフトの剛性増大による機能向上、曲げ一次固有振動数のチューニング最適化による車室内の静粛性向上等の観点から、近時では、ドライブシャフトを中空シャフト化する要求が増えてきている。
ドライブシャフト等に適用される中空状動力伝達シャフトとしては、例えば、下記の特許文献１、特許文献２に記載されているように、鋼製のパイプ素材に塑性加工を施して、大径部と小径部を有する中空状シャフト素材を成形し、この中空状シャフト素材に高周波焼入れを施したものが知られている。
特開２００３―１３１４３号公報 特開２００１―２０８０３７号公報 As a drive shaft as described above, a solid shaft is often used in the past and now, but the weight of the car is improved, the function is improved by increasing the rigidity of the drive shaft, and the tuning of the bending primary natural frequency is optimized. Recently, there has been an increasing demand for a drive shaft to be a hollow shaft from the viewpoint of improving the quietness of the interior of the vehicle.
As a hollow power transmission shaft applied to a drive shaft or the like, for example, as described in Patent Document 1 and Patent Document 2 below, a steel pipe material is subjected to plastic working, and a large diameter portion and A hollow shaft material having a small-diameter portion is formed, and the hollow shaft material is induction-hardened.
Japanese Patent Laid-Open No. 2003-13143 Japanese Patent Laid-Open No. 2001-208037

一般に、高周波焼入れは、高周波電流による電磁誘導を利用して鋼材の表面付近を加熱して焼入れを行なう熱処理方法であるが、高周波焼入れを中空状動力伝達シャフトの熱処理に適用した場合、焼入れ硬化層の極表面部の硬度がそれよりも深い領域の硬度よりも下がることがある。これは、高周波加熱後の冷却時に、冷却材で先に冷却された極表面部が素材内部の熱で自己テンパーされるためと考えられる。このよう硬化層の極表面部の硬度低下は、静的捩り強度等の静的強度に影響する他、硬化層表面の圧縮残留応力が低下して捩り疲労強度等の動的強度に影響する場合がある。 Generally, induction hardening is a heat treatment method in which the vicinity of the surface of steel is heated by using electromagnetic induction by high frequency current. When induction hardening is applied to the heat treatment of a hollow power transmission shaft, a hardened hardening layer is used. In some cases, the hardness of the extreme surface portion of this material may be lower than the hardness of the deeper region. This is thought to be due to the fact that the extreme surface portion previously cooled by the coolant is self-tempered by the heat inside the material during cooling after high-frequency heating. Such a decrease in the hardness of the extreme surface portion of the hardened layer affects not only the static strength such as static torsional strength, but also the dynamic residual strength such as torsional fatigue strength by reducing the compressive residual stress on the hardened layer surface. There is.

本発明の課題は、高周波焼入れによる硬化層の極表面部の硬度低下を抑制し、中空状動力伝達シャフトの静的強度と動的強度を高めることである。   The subject of this invention is suppressing the hardness fall of the pole surface part of the hardened layer by induction hardening, and raising the static strength and dynamic strength of a hollow power transmission shaft.

上記課題を解決するため、本発明は、軸方向中間部が大径部に形成されると共に、該大径部よりも軸方向両側部がそれぞれ小径部に形成された中空状動力伝達シャフトにおいて、高周波焼入により形成された硬化層を有し、該硬化層が、外周表面から所定深さに至る領域に、該硬化層の最大硬度に対する硬度低下量△Ｈｖが△Ｈｖ≦５０である極表面部を有する構成を提供する。   In order to solve the above-mentioned problems, the present invention provides a hollow power transmission shaft in which an axial intermediate portion is formed in a large diameter portion, and both axial sides are formed in small diameter portions from the large diameter portion. An extreme surface having a hardened layer formed by induction hardening, wherein the hardened layer is in a region extending from the outer peripheral surface to a predetermined depth, and a hardness reduction amount ΔHv with respect to the maximum hardness of the hardened layer is ΔHv ≦ 50 The structure which has a part is provided.

また、軸方向中間部が大径部に形成されると共に、大径部よりも軸方向両側部がそれぞれ小径部に形成された中空状動力伝達シャフトの製造方法であって、パイプ素材に塑性加工を施して、大径部と小径部を有する中空状シャフト素材を成形し、中空状シャフト素材を外周表面側から高周波誘導加熱した後、該外周表面に冷却材を供給し、冷却速度１３０℃／ｓｅｃ以上で冷却して高周波焼入れを行なう鋼製を提供する。   A method for manufacturing a hollow power transmission shaft in which an axial intermediate portion is formed in a large diameter portion and both axial side portions are formed in small diameter portions from the large diameter portion, respectively, and is plastically processed into a pipe material To form a hollow shaft material having a large diameter portion and a small diameter portion, and after subjecting the hollow shaft material to high frequency induction heating from the outer peripheral surface side, a coolant is supplied to the outer peripheral surface, and a cooling rate of 130 ° C. / A steel product that is induction-quenched by cooling at least sec.

上記構成により、高周波焼入れによる硬化層の極表面部が冷却時に自己テンパーされる現象が防止され、極表面部の硬度低下が抑制される。   By the said structure, the phenomenon in which the extreme surface part of the hardened layer by induction hardening is self-tempered at the time of cooling is prevented, and the hardness fall of an extreme surface part is suppressed.

上記の塑性加工としては、スウェージング加工やプレス加工等が採用される。前者のスウェージング加工には、ロータリースウェージングとリンクタイプスウェージングがあり、その何れも採用することができる。   As the plastic processing, swaging processing, press processing, or the like is employed. The former swaging process includes rotary swaging and link type swaging, both of which can be employed.

例えば、ロータリースウェージングは、機内の主軸に組込まれた一対又は複数対のダイスとバッカーとが回転運動を行なうと共に、外周ローラとバッカー上の突起により一定ストロークの上下運動を行なって、挿入されるパイプ素材に打撃を加えて絞り加工を行なう加工法である。   For example, in rotary swaging, a pair or a plurality of dies and a backer incorporated in a main shaft in the machine perform a rotational motion, and a vertical stroke of a fixed stroke is performed by a peripheral roller and a protrusion on the backer, and then inserted. This is a processing method in which a pipe material is blown to perform drawing.

また、プレス加工は、パイプ素材をダイスに軸方向に押し込んで絞り加工を行なう加工法である。   The press working is a working method in which a pipe material is pressed into a die in the axial direction to perform drawing.

上記の塑性加工は、パイプ素材の軸方向全域に対して行っても良いし、軸方向両側部に対してのみ部分的に行なっても良い。前者の場合、塑性加工後の中空状シャフト素材は、軸方向中間部の大径部と軸方向両側部の小径部において、塑性加工に伴う加工硬化と縮径による増肉が認められる。後者の場合、塑性加工後の中空状シャフト素材は、軸方向両側部の小径部において、塑性加工に伴う加工硬化と縮径による増肉が認められるが、軸方向中間部の大径部には、これらの現象は認められない。   The plastic working may be performed on the entire axial direction of the pipe material, or may be performed partially only on both sides in the axial direction. In the former case, the hollow shaft material after plastic working is recognized to have increased thickness due to work hardening and shrinkage due to plastic working in the large diameter portion at the axial intermediate portion and the small diameter portions at both axial side portions. In the latter case, the hollow shaft material after plastic processing is recognized to have increased thickness due to work hardening and shrinkage due to plastic processing at the small diameter parts on both sides in the axial direction. These phenomena are not recognized.

あるいは、上記の塑性加工として、パイプ素材の軸方向中間部を内周側から加圧して拡径させる加工法を採用することもできる。この場合、塑性加工後の中空状シャフト素材は、軸方向中間部の大径部において、塑性加工に伴う加工硬化と拡径による減肉が認められる。
上記の塑性加工の後、例えば、小径部の端部の連結部に、継手との連結に供される歯型（スプラインやセレーション等）を転造やプレス加工等の手段によって加工しても良い。この歯型は、小径部の両端部の連結部にそれぞれ形成しても良いし、小径部の一端部又は他端部の連結部にのみ形成しても良い。 Alternatively, as the plastic processing, a processing method in which an axially intermediate portion of the pipe material is pressurized from the inner peripheral side to expand the diameter can be employed. In this case, in the hollow shaft material after plastic processing, thinning due to work hardening and diameter expansion associated with plastic processing is recognized in the large diameter portion in the intermediate portion in the axial direction.
After the above-described plastic working, for example, a tooth mold (spline, serration, etc.) used for connection with the joint may be processed by means of rolling, pressing, or the like at the connecting portion at the end of the small diameter portion. . This tooth pattern may be formed at each of the connecting portions at both ends of the small diameter portion, or may be formed only at the connecting portion at one end or the other end of the small diameter portion.

パイプ素材の材質としては、例えば、ＳＴＫＭやＳＴＡＭ等の機械構造用炭素鋼、または、それらをベースに加工性や焼入れ性等の改善のために合金元素を添加した合金鋼を用いることができる。   As the material of the pipe material, for example, carbon steel for mechanical structure such as STKM or STAM, or alloy steel to which an alloy element is added for improving workability and hardenability based on them can be used.

また、高周波焼入れの方式としては、定置方式と移動方式とがあるが、本発明ではそのいずれの方式も採用することができる。   In addition, as the induction hardening method, there are a stationary method and a moving method, and any of these methods can be employed in the present invention.

本発明によれば、高周波焼入れによる硬化層の極表面部の硬度低下を抑制し、中空状動力伝達シャフトの静的強度と動的強度を高めることができる。   ADVANTAGE OF THE INVENTION According to this invention, the hardness fall of the extreme surface part of the hardened layer by induction hardening can be suppressed, and the static strength and dynamic strength of a hollow power transmission shaft can be improved.

以下、本発明の実施形態を図面に従って説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

図１は、中空状の動力伝達シャフト１と、動力伝達シャフト１の一端部に連結された摺動型等速自在継手２と、動力伝達シャフト１の他端部に連結された固定型等速自在継手３とを備えた自動車の動力伝達機構を示している。この実施形態の動力伝達機構において、摺動型等速自在継手２は減速装置（ディファレンシャル）に連結され、固定型等速自在継手３は駆動輪側に連結される。動力伝達シャフト１の一端部は摺動型等速自在継手２のトリポード部材２ａにスプライン連結され、摺動型等速自在継手２の外輪２ｂの端部外周と動力伝達シャフト１の外周にブーツ２ｃがそれぞれ固定されている。   FIG. 1 shows a hollow power transmission shaft 1, a sliding type constant velocity universal joint 2 connected to one end of the power transmission shaft 1, and a fixed type constant speed connected to the other end of the power transmission shaft 1. The power transmission mechanism of the motor vehicle provided with the universal joint 3 is shown. In the power transmission mechanism of this embodiment, the sliding type constant velocity universal joint 2 is connected to a reduction gear (differential), and the fixed type constant velocity universal joint 3 is connected to the drive wheel side. One end of the power transmission shaft 1 is splined to a tripod member 2a of the sliding type constant velocity universal joint 2, and a boot 2c is provided on the outer periphery of the outer ring 2b of the sliding type constant velocity universal joint 2 and the outer periphery of the power transmission shaft 1. Are fixed respectively.

また、動力伝達シャフト１の他端部は固定型等速自在継手３の内輪３ａにスプライン連結され、固定型等速自在継手３の外輪３ｂの端部外周と動力伝達シャフト１の外周にブーツ３ｃがそれぞれ固定されている。尚、同図には、摺動型等速自在継手２としてトリポード型等速自在継手が例示され、固定型等速自在継手３としてバーフィールド型等速自在継手が例示されているが、他の型式の等速自在継手が用いられる場合もある。   The other end of the power transmission shaft 1 is splined to the inner ring 3 a of the fixed type constant velocity universal joint 3, and a boot 3 c is provided on the outer circumference of the outer ring 3 b of the fixed type constant velocity universal joint 3 and the outer circumference of the power transmission shaft 1. Are fixed respectively. In the drawing, a tripod type constant velocity universal joint is illustrated as the sliding type constant velocity universal joint 2, and a barfield type constant velocity universal joint is illustrated as the fixed type constant velocity universal joint 3. Some types of constant velocity universal joints may be used.

図２は、動力伝達シャフト（ドライブシャフト）１を示している。この動力伝達シャフト１は、軸方向の全域に亘って中空状をなし、軸方向中間部に大径部１ａ、大径部１ａよりも軸方向両側部にそれぞれ小径部１ｂを有している。大径部１ａと小径部１ｂとは、軸端側に向かって漸次縮径したテーパ部１ｃを介して連続している。   FIG. 2 shows a power transmission shaft (drive shaft) 1. The power transmission shaft 1 is hollow over the entire region in the axial direction, and has a large-diameter portion 1a at an axial intermediate portion and small-diameter portions 1b at both axial sides of the large-diameter portion 1a. The large-diameter portion 1a and the small-diameter portion 1b are continuous via a tapered portion 1c that is gradually reduced in diameter toward the shaft end side.

小径部１ｂは、等速自在継手（２、３）との連結に供される端部側の連結部１ｄと、ブーツ（２ｃ、３ｃ）が固定される軸方向中間部側のブーツ固定部１ｅと、連結部１ｄとブーツ固定部１ｅとの間の最小径部１ｆとを有している。   The small-diameter portion 1b includes an end-side connection portion 1d used for connection with the constant velocity universal joints (2, 3), and an axial intermediate portion-side boot fixing portion 1e to which the boots (2c, 3c) are fixed. And a minimum diameter portion 1f between the connecting portion 1d and the boot fixing portion 1e.

連結部１ｄには、等速自在継手（２、３）にスプライン連結されるスプライン１ｄ１と、等速自在継手（２、３）に対する軸方向抜け止め用の止め輪を装着するための止め輪溝１ｄ２が形成されている。   A retaining ring groove for attaching a spline 1d1 splined to the constant velocity universal joints (2, 3) and a retaining ring for axially retaining the constant velocity universal joints (2, 3) to the coupling portion 1d. 1d2 is formed.

ブーツ固定部１ｅには、ブーツ（２ｃ、３ｃ）の小径端部の内周を嵌合するためのブーツ固定溝１ｅ１が形成されている。   The boot fixing portion 1e is formed with a boot fixing groove 1e1 for fitting the inner periphery of the small diameter end portion of the boot (2c, 3c).

この実施形態において、最小径部１ｆは、内径及び外径が軸方向にほぼ一定であり、軸方向にほぼ均一な形状を有している。   In this embodiment, the minimum diameter portion 1f has an inner diameter and an outer diameter that are substantially constant in the axial direction and has a substantially uniform shape in the axial direction.

また、同図にハッチングを付して示しているように、この動力伝達シャフト１は、止め輪溝１ｄ２の近傍から軸端に至る一部領域を除く、軸方向のほぼ全域Ｌに亘って、焼入れ処理による硬化層Ｓを有している。軸方向域Ｌにおいて、硬化層Ｓは、外周表面１ｇから所定深さｈ０の領域に形成され、硬化層Ｓから内周表面１ｉに至る領域は焼入れ処理により硬化していない未硬化層Ｓ０になっている。尚、外周表面１ｇから内周表面１ｉに至る全肉厚領域に硬化層Ｓが形成されるようにしても良い。図４に軸方向昼間部のＡ部拡大断面図を示す。   Further, as shown with hatching in the figure, the power transmission shaft 1 has a substantially entire region L in the axial direction except for a partial region from the vicinity of the retaining ring groove 1d2 to the shaft end. It has the hardened layer S by the quenching process. In the axial region L, the hardened layer S is formed in a region having a predetermined depth h0 from the outer peripheral surface 1g, and a region from the hardened layer S to the inner peripheral surface 1i becomes an uncured layer S0 that has not been hardened by the quenching process. ing. The hardened layer S may be formed in the entire thickness region from the outer peripheral surface 1g to the inner peripheral surface 1i. FIG. 4 is an enlarged cross-sectional view of the A part in the axial daytime part.

上記構成の動力伝達シャフト１は、例えば、つぎのような態様で製造することができる。まず、機械構造用炭素鋼管（ＳＴＫＭ）等のパイプ素材に軸方向全域に亘ってロータリースウェージング加工を施して、軸方向中間部に大径部１ａ、軸方向両側部に小径部１ｂを有する中空状シャフト素材１'を成形する。   The power transmission shaft 1 having the above configuration can be manufactured, for example, in the following manner. First, a rotary swaging process is applied to a pipe material such as a carbon steel pipe for machine structure (STKM) over the entire axial direction, and a hollow having a large-diameter portion 1a at an axial middle portion and small-diameter portions 1b at both axial sides. The shaft material 1 ′ is formed.

前記機械構造用炭素鋼管としては、Ｃが０．２０ｗｔ％以上で０．４５ｗｔ％以下、Ｓｉが０．０５ｗｔ％以上で０．３５ｗｔ％以下、Ｍｎが１．０ｗｔ％以上で２．０ｗｔ％以下、Ａｌが０．０５ｗｔ％以下、Ｓが０．０１ｗｔ％以下で含有し、残部がＦｅおよび不可避不純物を有する鋼材により形成されているものが望ましい。   As the carbon steel pipe for mechanical structure, C is 0.20 wt% or more and 0.45 wt% or less, Si is 0.05 wt% or more and 0.35 wt% or less, and Mn is 1.0 wt% or more and 2.0 wt% or less. It is desirable that Al is contained at 0.05 wt% or less, S is contained at 0.01 wt% or less, and the balance is formed of a steel material having Fe and inevitable impurities.

このようにして成形された中空状シャフト素材１'には、軸方向全域に亘って、ロータリースウェージング加工による加工硬化と縮径による増肉もしくは減肉が認められる。そして、この中空状シャフト素材１'の小径部１ｂの端部に転造加工やプレス加工等によってスプライン１ｄ１を成形して連結部１ｄを形成すると共に、連結部１ｄに転造加工や切削加工等によって止め輪溝１ｄ２を形成する。また、ブーツ固定部１ｅとなる部位に転造加工や切削加工等によってブーツ固定溝１ｅ１を形成する。   In the hollow shaft material 1 ′ thus formed, work hardening by rotary swaging and thickness increase or decrease due to diameter reduction are recognized over the entire axial direction. Then, the spline 1d1 is formed by rolling or pressing at the end of the small diameter portion 1b of the hollow shaft material 1 ′ to form the connecting portion 1d, and the connecting portion 1d is subjected to rolling or cutting. Thus, the retaining ring groove 1d2 is formed. Further, a boot fixing groove 1e1 is formed by rolling or cutting at a portion to be the boot fixing portion 1e.

その後、図３に示すように、中空状シャフト素材１'の外周表面１ｇの側に、例えば移動式の高周波誘導加熱コイル４を外装し、高周波誘導加熱コイル４に所定周波数の高周波電流を通じつつ、これを軸方向に移動させて、外周表面１ｇの側から軸方向域Ｌに対して高周波焼入れを行なう。この高周波焼入れは、定置式焼入れ方式であってもよい。その際、比較的厚肉の小径部１ｂに対しては、高周波誘導加熱コイル４に通じる高周波電流の周波数を相対的に低くし、比較的薄肉の大径部１ａに対しては、高周波誘導加熱コイル４に通じる高周波電流の周波数を相対的に高くして、焼入率を変更してもよい。そして、高周波誘導加熱コイル４により中空状シャフト素材１'を外周表面１ｇから高周波誘導加熱した後、外周表面１ｇに冷却材、例えば冷却水を散布し、冷却速度１３０℃／ｓｅｃ以上、好ましくは３００℃／ｓｅｃ以上で冷却して焼入れを行なう。冷却速度の調整は、冷却水の温度、水量（散布量）等の冷却条件を調整することによって行なうことができる。   After that, as shown in FIG. 3, for example, a mobile high-frequency induction heating coil 4 is sheathed on the outer peripheral surface 1 g side of the hollow shaft material 1 ′, and a high-frequency current having a predetermined frequency is passed through the high-frequency induction heating coil 4. This is moved in the axial direction, and induction hardening is performed on the axial region L from the outer peripheral surface 1g side. This induction hardening may be a stationary quenching method. At that time, the frequency of the high-frequency current leading to the high-frequency induction heating coil 4 is relatively lowered for the relatively thick small-diameter portion 1b, and the high-frequency induction heating is performed for the relatively thin-walled large-diameter portion 1a. The quenching rate may be changed by relatively increasing the frequency of the high-frequency current leading to the coil 4. Then, after high-frequency induction heating of the hollow shaft material 1 ′ from the outer peripheral surface 1g by the high-frequency induction heating coil 4, a coolant such as cooling water is sprayed on the outer peripheral surface 1g, and the cooling rate is 130 ° C./sec or more, preferably 300. Cooling is performed at a temperature of at least ° C./sec and quenching is performed. Adjustment of a cooling rate can be performed by adjusting cooling conditions, such as the temperature of cooling water, and the amount of water (dispersion amount).

上記の高周波焼入れにより、中空状シャフト素材１'の軸方向域Ｌにおいて、外周表面１ｇから所定深さｈ０の領域に硬化層Ｓが形成される。   By the induction hardening described above, the hardened layer S is formed in the region of the predetermined depth h0 from the outer peripheral surface 1g in the axial direction region L of the hollow shaft material 1 ′.

図５は、上記のようにして形成した硬化層Ｓの硬度分布を示している。横軸は外周表面１ｇから内径方向に図った深さ（ｍｍ）、縦軸は硬度（Ｈｖ：ビッカース硬度）である。図６は、図５の硬度分布において、外周表面１ｇの近傍部分を拡大したものである。同図において、硬化層Ｓの硬度分布は、外周表面１ｇから深さｔ１の位置にかけて上昇し、深さｔ１の位置から深さ（ｔ１＋ｔ２）の位置までほぼ最大硬度を保った状態で推移し、その後、徐々に硬度が低下する傾向を示している。ここで、ほぼ最大硬度を維持する領域の深さ方向寸法ｔ２がｔ２≧１ｍｍであるとき、この深さ領域ｔ２を「フラット部Ｓｇ」と定義する。硬化層Ｓの最大硬度は、フラット部Ｓｇの一部領域又は全部領域で現れる。尚、熱処理条件によっては、０≦ｔ２＜１ｍｍとなり、フラット部Ｓｇが現れない場合もある。   FIG. 5 shows the hardness distribution of the hardened layer S formed as described above. The horizontal axis represents the depth (mm) measured from the outer peripheral surface 1g in the inner diameter direction, and the vertical axis represents the hardness (Hv: Vickers hardness). FIG. 6 is an enlarged view of the vicinity of the outer peripheral surface 1g in the hardness distribution of FIG. In the figure, the hardness distribution of the hardened layer S rises from the outer peripheral surface 1g to the position of the depth t1, and changes in a state where the maximum hardness is maintained from the position of the depth t1 to the position of the depth (t1 + t2). Thereafter, the hardness gradually decreases. Here, when the depth direction dimension t2 of the region that maintains the substantially maximum hardness is t2 ≧ 1 mm, the depth region t2 is defined as “flat portion Sg”. The maximum hardness of the hardened layer S appears in a partial region or the entire region of the flat portion Sg. Depending on the heat treatment conditions, 0 ≦ t2 <1 mm and the flat portion Sg may not appear.

外周表面１ｇからフラット部Ｓｇに至る深さ領域ｔ１の硬度は、フラット部Ｓｇに現れる硬化層Ｓの最大硬度と同じかそれよりも低くなっている。この深さ領域ｔ１を「極表面部Ｓｆ」と定義する。この実施形態において、硬化層Ｓの最大硬度に対する極表面部Ｓｆの硬度低下量△Ｈｖは△Ｈｖ≦５０であり、極表面部Ｓｆの硬度低下量△Ｈｖが従来よりも小さい範囲に規制されている。極表面部Ｓｆの深さｔ１は、例えば０．５ｍｍ、又は０．５ｍｍの近傍の値をとる。   The hardness of the depth region t1 from the outer peripheral surface 1g to the flat portion Sg is equal to or lower than the maximum hardness of the hardened layer S appearing in the flat portion Sg. This depth region t1 is defined as “polar surface portion Sf”. In this embodiment, the hardness reduction amount ΔHv of the extreme surface portion Sf with respect to the maximum hardness of the hardened layer S is ΔHv ≦ 50, and the hardness reduction amount ΔHv of the extreme surface portion Sf is restricted to a range smaller than before. Yes. The depth t1 of the pole surface portion Sf takes, for example, a value in the vicinity of 0.5 mm or 0.5 mm.

上記のように、高周波加熱後の冷却時の冷却速度を１３０℃／ｓｅｃ以上に調整することにより、冷却時に極表面部Ｓｆが自己テンパーされる現象が防止され、極表面部Ｓｆの硬度低下が抑制される共に、圧縮残留応力の低下が抑制される。そして、硬化層Ｓの最大硬度に対する極表面部Ｓｆの硬度低下量△Ｈｖを△Ｈｖ≦５０に規制することにより、中空状動力伝達シャフト１の静的強度と動的強度を高めることができる。   As described above, by adjusting the cooling rate at the time of cooling after high-frequency heating to 130 ° C./sec or more, the phenomenon that the extreme surface portion Sf is self-tempered during cooling is prevented, and the hardness of the extreme surface portion Sf is reduced. In addition to being suppressed, a decrease in compressive residual stress is suppressed. The static strength and dynamic strength of the hollow power transmission shaft 1 can be increased by restricting the hardness reduction amount ΔHv of the pole surface portion Sf with respect to the maximum hardness of the hardened layer S to ΔHv ≦ 50.

自動車の動力伝達機構を示す一部切欠け断面図である。It is a partially cutaway sectional view showing a power transmission mechanism of an automobile. 実施形態に係る動力伝達シャフトを示す一部断面図である。It is a partial sectional view showing a power transmission shaft concerning an embodiment. 中空状シャフト素材を示す断面図である。It is sectional drawing which shows a hollow shaft raw material. 図２のＡ部拡大断面図である。It is the A section expanded sectional view of FIG. 外周表面から深さ方向の硬度を示すグラフである。It is a graph which shows the hardness of a depth direction from an outer peripheral surface. 図５のＢ部拡大図である。It is the B section enlarged view of FIG.

符号の説明Explanation of symbols

１ 動力伝達シャフト
１ａ 大径部
１ｂ 小径部
１ｆ 平滑部
１ｉ 内周表面
１ｇ 外周表面
Ｓ 硬化層
Ｓｆ 極表面部

DESCRIPTION OF SYMBOLS 1 Power transmission shaft 1a Large diameter part 1b Small diameter part 1f Smoothing part 1i Inner peripheral surface 1g Outer peripheral surface S Hardened layer Sf Extreme surface part

Claims (2)

軸方向中間部が大径部に形成されると共に、該大径部よりも軸方向両側部がそれぞれ小径部に形成された中空状動力伝達シャフトにおいて、
高周波焼入により形成された硬化層を有し、該硬化層が、外周表面から所定深さに至る領域に、該硬化層の最大硬度に対する硬度低下量△Ｈｖが△Ｈｖ≦５０である極表面部を有することを特徴とする中空状動力伝達シャフト。 In the hollow power transmission shaft in which the axially intermediate portion is formed in the large diameter portion, and the axially opposite side portions are formed in the small diameter portions respectively than the large diameter portion,
An extreme surface having a hardened layer formed by induction hardening, wherein the hardened layer is in a region extending from the outer peripheral surface to a predetermined depth, and a hardness reduction amount ΔHv with respect to the maximum hardness of the hardened layer is ΔHv ≦ 50 A hollow power transmission shaft having a portion. 軸方向中間部が大径部に形成されると共に、該大径部よりも軸方向両側部がそれぞれ小径部に形成された中空状動力伝達シャフトの製造方法であって、
パイプ素材に塑性加工を施して、前記大径部と小径部を有する中空状シャフト素材を成形し、
前記中空状シャフト素材を外周表面側から高周波誘導加熱した後、該外周表面に冷却材を供給し、冷却速度１３０℃／ｓｅｃ以上で冷却して高周波焼入れを行なうことを特徴とする中空状動力伝達シャフトの製造方法。 A method of manufacturing a hollow power transmission shaft in which an axially intermediate portion is formed in a large diameter portion, and both axial sides are formed in small diameter portions from the large diameter portion, respectively.
Plastic processing is performed on the pipe material to form a hollow shaft material having the large diameter portion and the small diameter portion,
A hollow power transmission characterized in that after the high-frequency induction heating of the hollow shaft material from the outer peripheral surface side, a coolant is supplied to the outer peripheral surface, and cooling is performed at a cooling rate of 130 ° C./sec or higher for induction hardening. Manufacturing method of shaft.
JP2005071537A 2005-03-14 2005-03-14 Hollow power transmission shaft Pending JP2006250333A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019530840A (en) * 2016-07-07 2019-10-24 ボナトランス グループ アー．エス． Railcar axle

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59114131A (en) * 1982-12-21 1984-07-02 Nhk Spring Co Ltd Driving shaft for vehicle
JPH03162528A (en) * 1989-11-02 1991-07-12 Gkn Automot Ag Heat treatment of drive shaft
JPH0565541A (en) * 1991-09-10 1993-03-19 Kawasaki Steel Corp Manufacture of high strength resistance welded steel tube for automotive use excellent in ductility and three-point bendability
JP2005048957A (en) * 2004-09-28 2005-02-24 Ntn Corp Method for manufacturing power transmitting shaft
JP2005061637A (en) * 2004-09-28 2005-03-10 Ntn Corp Power transmitting shaft

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59114131A (en) * 1982-12-21 1984-07-02 Nhk Spring Co Ltd Driving shaft for vehicle
JPH03162528A (en) * 1989-11-02 1991-07-12 Gkn Automot Ag Heat treatment of drive shaft
JPH0565541A (en) * 1991-09-10 1993-03-19 Kawasaki Steel Corp Manufacture of high strength resistance welded steel tube for automotive use excellent in ductility and three-point bendability
JP2005048957A (en) * 2004-09-28 2005-02-24 Ntn Corp Method for manufacturing power transmitting shaft
JP2005061637A (en) * 2004-09-28 2005-03-10 Ntn Corp Power transmitting shaft

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019530840A (en) * 2016-07-07 2019-10-24 ボナトランス グループ アー．エス． Railcar axle

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