JPS61178176A - Shot peening method for gear - Google Patents

Abstract

PURPOSE:To increase the surface compression residual stress of the radiused part of deddendum and improve the fatigue strength of a gear by pressing a jig into a space between teeth for tensioning the above described radiused part and applying shot peening through the penetration hole of the jig in a condition so tensioned. CONSTITUTION:Inside of a ring-shaped jig 1, a projection 4 coupled to a space between the teeth of a gear 5 and sized to press open a space between adjacent teeth is so provided as to correspond to every other tooth flanks, and a penetration hole 2 is made at the center of each projection 4. By pressing the projection 4 of the jig 1 into a space between the teeth of the gear 5, tensile stress is caused on the radiused part of the tooth flank. In this state, the deddendum is applied with shot peening through the penetration hole 2 and compression residual stress on the surface of the above described radiused part is increased, thereby enabling the improvement of the fatigue strength of the gear.

Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は歯車のストレスピーニング法に関シ、詳しくは
歯車に引張応力を生じさせた状態でショットピーニング
を施す方法に関する。DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a stress peening method for gears, and more particularly to a method for subjecting gears to shot peening in a state where tensile stress is generated.

（従来の技術） 自動車などに用いられる歯車は疲労強度の向上が求めら
れておシ、従来、ショットと呼ぶ璃鉄製小粒子を被加工
品表面に多数投射するショットピーニング処理を歯車に
施すことが行われている。これによυ疲労強度が向上す
るのは、ショットピーニングによってショットを受けた
最表面は塑性変形して圧縮残留応力が発生し、それが外
力による引張応力を緩和するためである。また、トーシ
ョンバー、コイルスプリング、板バネなどには、あらか
じめ引張応力を付与した状態でショットピーニング処理
を行う、いわゆるストレスピーニング法が行われている
。この方法を用いると、通常のショットピーニング処理
よりも高い圧縮残留応力が発生し、それによってよυ高
い疲労強度が得られる。(Conventional technology) Gears used in automobiles and the like are required to have improved fatigue strength. Conventionally, gears have been subjected to shot peening treatment in which a large number of small particles of hot iron called shot are projected onto the surface of the workpiece. It is being done. This improves the υ fatigue strength because the outermost surface that has been shot by shot peening is plastically deformed and compressive residual stress is generated, which relieves the tensile stress caused by external force. Furthermore, torsion bars, coil springs, leaf springs, and the like are subjected to shot peening treatment in a state in which tensile stress is applied in advance, which is the so-called stress peening method. Using this method, higher compressive residual stresses are generated than in conventional shot peening processes, thereby resulting in higher fatigue strength.

（発明が解決しようとする問題点） しかしながら、従来、ストレスピーニング法を歯車のよ
うな、形状の複雑なものに適用するのは困難であシ、歯
車の内径壁に静水圧的圧力を付加し、歯底に引張応力を
発生させてショットピーニング処理を行う方法が提案さ
れているにすぎない。この方法では歯車に付与される引
張応力は、第４図に示すような歯底部８に最も大きく付
与され、歯車の部位の中で最も高い疲労強度が要求され
る歯元アール部７に有効に付与されているとは言い難い
。(Problem to be solved by the invention) However, conventionally, it has been difficult to apply the stress peening method to items with complex shapes such as gears, and it has been difficult to apply the stress peening method to items with complex shapes such as gears. However, only a method has been proposed in which shot peening is performed by generating tensile stress on the tooth bottom. In this method, the tensile stress applied to the gear is greatest at the root portion 8 as shown in Fig. 4, and is effectively applied to the tooth root rounded portion 7, which requires the highest fatigue strength among the parts of the gear. It is hard to say that it has been granted.

本発明は歯車の歯元アール部の圧縮残留応力を増大させ
、歯車の疲労強度を向上させるショットピーニング法を
提供することを目的とするものである。An object of the present invention is to provide a shot peening method that increases the compressive residual stress in the root radius of a gear and improves the fatigue strength of the gear.

（問題点を解決するための手段） 本発明の歯車のショットピーニング法ハ、外部から歯底
に向って形成された貫通孔を有する治具を歯車の歯と歯
の間に押し込むことによって歯元アール部に引張応力を
生じさせておき、該貫通孔を通してショットピーニング
処理を該歯車に施すことを特徴とする。(Means for Solving the Problems) The shot peening method for gears of the present invention is achieved by pushing a jig having a through hole formed from the outside toward the tooth root between the teeth of the gear. The gear is characterized in that a tensile stress is generated in the rounded portion and shot peening is applied to the gear through the through hole.

上記治具の形状は、歯車の隣り合う二つの歯の歯先の間
にはマリ、かつ上記二つの歯の間を押し開くことができ
る凸部を有し、該凸部の中央に外部から歯底に向う貫通
孔を有する形状であれば、特に限定されない。The shape of the jig has a groove between the tips of two adjacent teeth of the gear and a convex part that can push open the space between the two teeth, and a convex part in the center of the convex part from the outside. There is no particular limitation as long as the shape has a through hole toward the bottom of the tooth.

（作用） 本発明の歯車のショットピーニング法は、治具を隣シ合
う由と歯の間に押し込むことにより歯元アール部に引張
応力を生じさせるととができ、該治具が外部から歯底に
向って形成された貫通孔を有するので、引張応力を生じ
させた状態で、該貫通孔を通してショットを投射するこ
とによるショットピーニング処理を歯車に施すことがで
き、そのため、最も高い疲労強度が要求される歯元アー
ル部に大きな圧縮残留応力を発生させることができ、歯
車の疲労強度を大幅に向上させることができる。(Function) In the gear shot peening method of the present invention, tensile stress is generated in the tooth root radius by pushing a jig between adjacent teeth, and the jig is applied to the teeth from the outside. Since the through-hole is formed toward the bottom, the gear can be subjected to shot peening treatment by projecting shot through the through-hole while creating tensile stress, thus achieving the highest fatigue strength. A large compressive residual stress can be generated in the required tooth root radius, and the fatigue strength of the gear can be significantly improved.

（実施例） 本発明を実施例により図面を参照して説明する。(Example) The present invention will be explained by way of examples with reference to the drawings.

本実施例は、本発明を平歯車に適用したものである。第
１図ａ）、　ｂ）及びＣ）に示すような、歯車の外周を
おおうリングの内側に、隣り合った二つの歯の歯先の間
にはまり、かつ上記二つの歯の間を押し開く大きさの凸
部４を歯みぞひとつおきに対応するように有し、貫通孔
２を該凸部４の中央に、該リングに貫通するように設け
、該凸部４の片側の厚さが歯みぞより薄くなるようにテ
ーパー３を設けた治具１を、テーパー３をつけた側が浸
炭・焼き入れ歯車５と接するように該歯車５に重ね、次
いで該テーパー３に沿って該歯車５に押しはめ込む。貫
通孔２は、ちょうど該歯車５の歯底と向い合い、この歯
底の両側の歯元アール部には引張応力が生じる。この状
１暢で、第２図ａ）に示すように貫通孔２を通してショ
ットピーニング処理を、平均粒径ａ８ｍｍの鋳鉄製ショ
ット６を用い、アークハイト０ｊ５Ａの条件で行う。そ
の結果、第２図ａ）に示すイ１、ハのようにひとつおき
の歯底及びその両側の歯元にショットピーニング処理が
施される。次に、該治具１を該歯車５からはずし、第２
図ｂ）に示すように、口のような未処理の歯底に貫通孔
２が配置されるように該治具１を一つずらし、上記と同
様にして該治具１を該歯車５に押しはめ、上記と同様に
してショットピーニング処理を行って、該歯車のストレ
スピーニング処理全完了する。In this embodiment, the present invention is applied to a spur gear. As shown in Figure 1 a), b) and C), a ring that fits inside the ring that covers the outer periphery of the gear, fits between the tips of two adjacent teeth, and pushes open the gap between the two teeth. A through hole 2 is provided in the center of the protrusion 4 so as to penetrate through the ring, and the thickness of one side of the protrusion 4 is A jig 1 provided with a taper 3 so as to be thinner than the tooth groove is stacked on the gear 5 so that the side with the taper 3 is in contact with the carburized/quenched gear 5, and then attached to the gear 5 along the taper 3. Push it in. The through hole 2 just faces the tooth bottom of the gear 5, and tensile stress is generated in the root radius portions on both sides of the tooth bottom. In this state, shot peening is performed through the through hole 2 as shown in FIG. 2a) using cast iron shot 6 having an average grain size of a8 mm and an arc height of 0j5A. As a result, the shot peening treatment is performed on every other tooth bottom and the tooth root on both sides as shown in A1 and C shown in FIG. 2A. Next, the jig 1 is removed from the gear 5, and the second jig 1 is removed from the gear 5.
As shown in Figure b), shift the jig 1 by one position so that the through hole 2 is located at the bottom of the untreated tooth, such as the mouth, and attach the jig 1 to the gear 5 in the same manner as above. Push the gear together and perform shot peening in the same manner as above to complete the stress peening process for the gear.

上記のようにしてストレスピーニング処理を施した平歯
車の歯元アール部の表面から深さ方向への残留応力分布
をエックス線回折により測定した。比較例として従来法
によるショットピーニング処理を施しだ平歯車の歯元ア
ール部の残留応力分布を実施例と同様にして測定した。The residual stress distribution in the depth direction from the surface of the root rounded portion of the spur gear subjected to the stress peening treatment as described above was measured by X-ray diffraction. As a comparative example, the residual stress distribution in the root radius of a spur gear that had been subjected to shot peening treatment using a conventional method was measured in the same manner as in the examples.

これらの結果を第３図に示す。実線は実施例を、点線は
比較例を表わす。第５図から明らかなように、実施例は
、比較例に比して、疲労強度の向上に有効である表面残
留応力が大幅に増大している。この表面圧縮残留応力の
増大によシ、平歯車の疲労強度は約２５チ向上した。These results are shown in FIG. The solid line represents the example, and the dotted line represents the comparative example. As is clear from FIG. 5, the surface residual stress, which is effective in improving fatigue strength, is significantly increased in the example as compared to the comparative example. Due to this increase in surface compressive residual stress, the fatigue strength of the spur gear was improved by about 25 inches.

（発明の効果） 本発明方法は、上記したように貫通孔を有する治具を歯
車にセットすることによシ、歯元アール部に引張応力を
発生させ、その状態で該貫通孔を通してショットピーニ
ング処理を施すことにより歯元アール部の表面圧縮残留
応力を増大させることができ、歯車の疲労強度を大幅に
向上させることができる。(Effects of the Invention) As described above, the method of the present invention generates tensile stress in the root radius by setting a jig having a through hole on a gear, and in this state, shot peening is carried out through the through hole. By performing the treatment, the surface compressive residual stress of the root rounded portion can be increased, and the fatigue strength of the gear can be significantly improved.

更に、本発明方法は、貫通孔を有する治具“を歯車の歯
と歯の間に押しはめ込むという非常に簡単な方法で歯元
アール部に引張応力を発生させることができ、また、シ
ョットピーニング処理を、該貫通孔を通して従来と同様
に行うことができるので、従来困難であった複雑な形状
である歯車の歯元アール部のストレスピーニング処理を
簡単に行うことができる。Furthermore, the method of the present invention can generate tensile stress in the tooth root radius by a very simple method of fitting a jig with through holes between the teeth of a gear. Since the process can be performed through the through hole in the same manner as before, it is possible to easily perform stress peening on the root rounded part of the gear, which has a complicated shape, which has been difficult in the past.

【図面の簡単な説明】[Brief explanation of drawings]

第１図ａ）は本発明の一実施例の治具を平歯車にはめた
ところを示す平面図、第１図ｂ）は第１図ａ）の治具の
要部拡大側面図、第１図Ｃ）は第１図ａ）の治具の要部
拡大平面図、 ＠２図ａ）は本発明の一実施例の１回目のストレスピー
ニング処理を示す図、第２図ｂ）は本発明の一実施例の
２回目のストレスピーニング処理を示す図、 第３図は本発明の一実施例及び比較例による平歯車の歯
元アール部の圧縮残留応力分布を示す図、 第４図は歯車の部分平面図を表わす。 図中、 １・・・治具　　　　　　２・・・貫通孔３・・・テー
パー　　　　４・・・凸部５・・・歯車　　　　　　６
・・・ショット７・・・歯元アール部　８・・・歯底部
ほか１名 第１図 （ＣＩ） 第２図 第３図 表面２１）もの′ｌＰ！駈（ｍｍ） 第４図Figure 1a) is a plan view showing a jig according to an embodiment of the present invention fitted into a spur gear, Figure 1b) is an enlarged side view of the main part of the jig in Figure 1a), Figure C) is an enlarged plan view of the main part of the jig in Figure 1 a), Figure 2 a) is a diagram showing the first stress peening treatment according to an embodiment of the present invention, and Figure 2 b) is a diagram showing the jig according to the present invention. Figure 3 is a diagram showing the second stress peening treatment of an example. Figure 3 is a diagram showing the compressive residual stress distribution of the root radius of spur gears according to an example of the present invention and a comparative example. represents a partial plan view of . In the figure, 1...Jig 2...Through hole 3...Taper 4...Protrusion 5...Gear 6
...Shot 7...Tooth base radius 8...Tooth bottom and 1 other person Figure 1 (CI) Figure 2 Figure 3 Surface 21) Things'lP! Cane (mm) Fig. 4

Claims (1)

【特許請求の範囲】[Claims] 外部から歯底に向って形成された貫通孔を有する治具を
歯車の歯と歯の間に押し込むことによって歯元アール部
に引張応力を生じさせておき、該貫通孔を通してショッ
トピーニング処理を該歯車に施すことを特徴とする歯車
のショットピーニング法。A jig with a through hole formed from the outside toward the tooth bottom is pushed between the teeth of the gear to generate tensile stress in the tooth root radius, and shot peening treatment is performed through the through hole. A shot peening method for gears that is characterized by applying it to gears.