JP6482923B2 - Bearing device - Google Patents

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JP6482923B2
JP6482923B2 JP2015066435A JP2015066435A JP6482923B2 JP 6482923 B2 JP6482923 B2 JP 6482923B2 JP 2015066435 A JP2015066435 A JP 2015066435A JP 2015066435 A JP2015066435 A JP 2015066435A JP 6482923 B2 JP6482923 B2 JP 6482923B2
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sintered body
sintered
housing
bearing
iron
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洋介 須貝
洋介 須貝
容敬 伊藤
容敬 伊藤
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NTN Corp
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Description

本発明は、軸受装置に関するものである。 The present invention relates to a bearing device .

粉末冶金法は、金属粉末等からなる原料粉末を所定の形状および寸法に圧縮成形し、これを金属粉末が溶融しない温度で加熱することにより、粉末同士を強固に結合して金属製品を製造する技術である。粉末冶金法によれば、ニアネットシェイプに造形することができ、溶製材を機械加工する場合に比べて低コストに大量生産できるという利点が得られる。   In the powder metallurgy method, a raw material powder made of metal powder or the like is compression-molded into a predetermined shape and size, and heated at a temperature at which the metal powder does not melt, whereby the powder is firmly bonded to produce a metal product. Technology. According to the powder metallurgy method, it is possible to form a near net shape, and it is possible to obtain an advantage that mass production can be performed at a low cost as compared with the case of machining a melted material.

粉末冶金法で製作した焼結体は多数の気孔を有するため、溶製材に比べて強度が劣るという問題がある。そこで、焼結部材の緻密化による強度アップを図るため、焼結後の焼結体に対して塑性加工を加えて表面に露出した気孔を塞ぎ、さらにこの焼結体を、潤滑剤を用いて鍛造する焼結部材の製造方法が下記特許文献1に記載されている。   Since the sintered compact manufactured by the powder metallurgy method has a large number of pores, there is a problem that the strength is inferior to that of the melted material. Therefore, in order to increase the strength by densification of the sintered member, plastic processing is applied to the sintered body after sintering to close pores exposed on the surface, and this sintered body is further bonded with a lubricant. A method for manufacturing a sintered member to be forged is described in Patent Document 1 below.

特開2012−77348号公報JP 2012-77348 A

特許文献1では、焼結体の緻密化を目的として焼結後に鍛造等の塑性加工を行っているが、焼結体を塑性変形させることで、緻密化以外にも、複雑な形状の焼結体が低コストに量産可能になる、という効果も得ることができると考えられる。また、焼結体を加締めることが可能になれば、焼結部材と他部材を相互にを固定するための固定構造として、これまでにない安価な構造を提供できるようになる。その一方で、溶製材からなる機械部品を焼結品と置き換えるためには、相応の強度が要求されるため、単に焼結体を柔らかくするだけでは不十分である。このように強度と塑性変形の容易性とを両立する、という観点から焼結体の組成が検討されたことはなく、そのような焼結体を実現できれば、粉末冶金法の適用対象を拡大し、各種機械部品や精密部品の低コスト化を図ることが可能になると考えられる。   In Patent Document 1, plastic processing such as forging is performed after sintering for the purpose of densification of the sintered body, but in addition to densification, sintering of complex shapes is performed by plastic deformation of the sintered body. It is thought that the effect that the body can be mass-produced at low cost can also be obtained. Moreover, if it becomes possible to caulk the sintered body, an unprecedented inexpensive structure can be provided as a fixing structure for fixing the sintered member and the other member to each other. On the other hand, in order to replace a machine part made of melted material with a sintered product, a corresponding strength is required, and it is not sufficient to simply soften the sintered body. Thus, the composition of the sintered body has not been studied from the viewpoint of achieving both strength and ease of plastic deformation. If such a sintered body can be realized, the application object of the powder metallurgy method will be expanded. Therefore, it is considered possible to reduce the cost of various machine parts and precision parts.

ちなみに、特許文献1の焼結部材では、鉄粉に黒鉛粉末を加えて高温で焼結しているため、焼結部材中の鉄組織は硬いγ‐Fe(パーライト組織)が主体となる。従って、焼結部材を塑性変形させようとすれば、大型プレス機等による極端に大きな加圧力が必要となり、製品コストが高騰する。また、焼結体自身が硬質であるため、これを加締めることも困難である。   Incidentally, in the sintered member of Patent Document 1, since the graphite powder is added to the iron powder and sintered at a high temperature, the iron structure in the sintered member is mainly composed of hard γ-Fe (pearlite structure). Therefore, if the sintered member is to be plastically deformed, an extremely large pressing force by a large press machine or the like is required, and the product cost increases. Further, since the sintered body itself is hard, it is difficult to caulk it.

そこで、本発明は、必要強度を有しつつ塑性変形させることが容易な焼結部材を提供することを目的とする。   Therefore, an object of the present invention is to provide a sintered member that has the required strength and can be easily plastically deformed.

上記目的を達成するため、本発明の焼結部材は、塑性変形させるべき部分を備えた焼結部材であって、鉄粉を、黒鉛粉を加えることなく成形し、焼結することで形成した焼結体からなり、かつ前記焼結体における鉄組織の面積比で90%以上がフェライト相で形成されていることを特徴とするものである。塑性変形させるべき部分を塑性変形させたものを焼結部材としてもよい。   In order to achieve the above object, the sintered member of the present invention is a sintered member having a portion to be plastically deformed, and formed by forming and sintering iron powder without adding graphite powder. It is made of a sintered body, and 90% or more of the area ratio of the iron structure in the sintered body is formed of a ferrite phase. A sintered member may be obtained by plastically deforming a portion to be plastically deformed.

本発明の焼結体は、隣接した鉄粒子同士が相互に拡散した鉄系焼結体であるので高強度となる。その一方で鉄組織の面積比で90%以上がフェライト相で形成することで、焼結体を容易に塑性変形させることが可能となる。従って、単純形状に形成した焼結体を、その後の塑性加工で塑性変形させて複雑形状に仕上げ、あるいは焼結体を、加締め等により部分的に塑性変形させることで他部材と結合することが可能となる。そのため、溶製材からなる部材を焼結部材に置き換えることが容易となり、低コスト化を図ることができる。   Since the sintered body of the present invention is an iron-based sintered body in which adjacent iron particles diffuse to each other, the strength is high. On the other hand, when the area ratio of the iron structure is 90% or more formed of the ferrite phase, the sintered body can be easily plastically deformed. Therefore, the sintered body formed into a simple shape is plastically deformed by subsequent plastic processing to finish it into a complicated shape, or the sintered body is partially plastically deformed by caulking or the like to be joined to other members. Is possible. Therefore, it becomes easy to replace the member made of the melted material with the sintered member, and the cost can be reduced.

焼結体の伸び値を5%以上にすることで、焼結体を容易に塑性変形させることが可能となる。   By setting the elongation value of the sintered body to 5% or more, the sintered body can be easily plastically deformed.

焼結部材の表面に、通油性を低下させるための被膜を形成することにより、焼結部材を含油部材に接触させて配置した場合でも、含油部材に含まれる潤滑油が焼結部材に移動して焼結部材の表面から滲み出ることを防止することができる。被膜は酸化鉄で形成し、あるいはめっきで形成することができる。このように被膜を形成した場合の焼結部材の通油度は、50×10-4g/2min以下にするのが好ましい。 By forming a film for reducing oil permeability on the surface of the sintered member, even when the sintered member is placed in contact with the oil-containing member, the lubricating oil contained in the oil-containing member moves to the sintered member. Thus, bleeding from the surface of the sintered member can be prevented. The coating can be formed of iron oxide or can be formed by plating. The oil permeability of the sintered member when the coating is formed in this way is preferably 50 × 10 −4 g / 2 min or less.

焼結部材の密度は7.0g/cm3以上にするのが好ましい。 The density of the sintered member is preferably 7.0 g / cm 3 or more.

以上に述べた焼結体で形成されたハウジングと、ハウジングの内周に配置された焼結含油軸受とを備え、ハウジングを加締めることで焼結含油軸受をハウジングに固定すれば、軸受装置の低コスト化を図ることができる。   If the sintered oil-impregnated bearing provided with the housing formed of the sintered body described above and the inner periphery of the housing is fixed to the housing by caulking the housing, Cost reduction can be achieved.

以上のように、本発明によれば、必要強度を有しつつ容易に塑性変形可能な焼結部材を提供することができる。そのため、複雑な形状の部材も粉末冶金法で製作することが可能となる。また、焼結部材を加締めることで当該焼結部材と他部材を相互に固定することが可能となり、焼結部材の固定構造を多様化することができる。従って、各種機械部品あるいは精密部品等の焼結材料への置き換えを促進し、これらの部品および当該部品を用いた機構の低コスト化を図ることができる。   As described above, according to the present invention, it is possible to provide a sintered member that has the required strength and can be easily plastically deformed. Therefore, a member having a complicated shape can be manufactured by the powder metallurgy method. In addition, the sintered member and the other member can be fixed to each other by caulking the sintered member, and the fixing structure of the sintered member can be diversified. Therefore, it is possible to promote replacement of various mechanical parts or precision parts with sintered materials, and to reduce the cost of these parts and mechanisms using the parts.

本発明にかかる焼結体の金属組織を模式的に示す図である。It is a figure which shows typically the metal structure of the sintered compact concerning this invention. 引張試験で使用する試験片の平面図である。It is a top view of the test piece used by a tension test. (a)図は塑性変形前の焼結部材の断面図であり、(b)図は塑性変形後の焼結部材の断面図である。(A) is a sectional view of the sintered member before plastic deformation, and (b) is a sectional view of the sintered member after plastic deformation. 焼結体の鉄組織を模式的に示す図である。It is a figure which shows typically the iron structure of a sintered compact. (a)図は流体軸受装置の断面図であり、(b)図は(a)図中の領域Xの拡大断面図である。(A) A figure is sectional drawing of a hydrodynamic bearing apparatus, (b) A figure is an expanded sectional view of the area | region X in (a) figure. 表面に被膜を形成した焼結体の断面図である。It is sectional drawing of the sintered compact which formed the film on the surface. 通油度の測定装置の概略構造を示す図である。It is a figure which shows schematic structure of the measuring device of oil permeability.

本発明の焼結部材は、原料粉末を圧縮成形して圧紛体を成形する圧縮成形工程、および圧紛体を焼結させる焼結工程を順次経て製造される。   The sintered member of the present invention is manufactured through a compression molding process in which raw powder is compression molded to form a compact and a sintering process in which the compact is sintered.

原料粉末は、鉄粉に焼結助剤や離型用潤滑剤等の添加剤を必要に応じて配合し、均一に混合することで調製される。既存の鉄系焼結部材では、鉄組織をパーライト相(γ‐Fe)にするために原料粉末に炭素源として黒鉛粉を配合し、あるいは鉄組織同士の結合力を高めるために原料粉末に微量の銅粉を配合する場合が多いが、本発明では、これら黒鉛粉および銅粉は原料粉末に配合されておらず、添加剤を除く原料粉末の全てが鉄粉となっている。   The raw material powder is prepared by blending iron powder with additives such as a sintering aid and a release lubricant as required and mixing them uniformly. In existing iron-based sintered members, graphite powder is added as a carbon source to the raw material powder to make the iron structure a pearlite phase (γ-Fe), or a small amount is added to the raw material powder to increase the bonding force between the iron structures. However, in the present invention, these graphite powder and copper powder are not mixed in the raw material powder, and all of the raw material powder excluding the additive is iron powder.

鉄粉としては、いわゆる純鉄粉(α‐Fe粉)が使用される。純鉄粉の種類としては還元鉄粉とアトマイズ鉄粉とがある。アトマイズ鉄粉は内部に空孔を有しておらず、その表面は球状に近い不規則形状をなす。従って、アトマイズ鉄粉を使用すれば、鉄粉内部に多数の空孔を有する還元鉄粉と比較して、焼結体の空孔の総量を少なくすることができ、高密度の焼結体を製作することができる。この観点から、本発明では、鉄粉としてアトマイズ鉄粉(水アトマイズ鉄粉)を使用するのが好ましい。   As the iron powder, so-called pure iron powder (α-Fe powder) is used. As types of pure iron powder, there are reduced iron powder and atomized iron powder. Atomized iron powder does not have pores inside, and its surface has an irregular shape close to a sphere. Therefore, if atomized iron powder is used, the total amount of pores in the sintered body can be reduced compared to reduced iron powder having a large number of pores inside the iron powder, and a high-density sintered body can be obtained. Can be produced. From this viewpoint, in the present invention, it is preferable to use atomized iron powder (water atomized iron powder) as the iron powder.

また、鉄粉としては、市販品(粒径45μm〜200μm程度の粒度分布を有する)を篩分けして得た小径粒子、例えば100Meshアンダー、好ましくは145Meshアンダーの粒子が使用される。なお、100Meshの篩の目開きは150μmであり、145Meshの篩の目開きは106μmである。このように小粒径の鉄粉を使用することで、粗大気孔を少なくし、焼結体を高密度化および高強度化することができる。この時の鉄粉の見かけ密度は、2.9g/cm3以上、好ましくは3.0g・cm3以上とする。なお、見かけ密度の上限は、概ね3.5g/cm3以下である。 As the iron powder, small-diameter particles obtained by sieving a commercial product (having a particle size distribution of about 45 μm to 200 μm in particle size), for example, particles of 100 mesh under, preferably particles of 145 mesh are used. The mesh size of the 100 mesh screen is 150 μm, and the mesh size of the 145 mesh screen is 106 μm. By using iron powder having a small particle diameter in this way, coarse air holes can be reduced, and the sintered body can be densified and strengthened. The apparent density of the iron powder at this time is 2.9 g / cm 3 or more, preferably 3.0 g · cm 3 or more. Note that the upper limit of the apparent density is approximately 3.5 g / cm 3 or less.

次いで、圧縮成形工程にて原料粉末を金型内で圧縮成形し、圧紛体を得る。この時の成形圧力は、400MPa以上、800MPa程度が好ましい。成形圧力が下限値を下回ると、粗大気孔が多くなって強度低下を招き、上限値を上回ると、焼結体が高密度になりすぎて、サイジング工程で焼結体を塑性変形させることが難しくなるためである。   Next, the raw material powder is compression-molded in a mold in a compression molding step to obtain a compact. The molding pressure at this time is preferably about 400 MPa or more and about 800 MPa. If the molding pressure is lower than the lower limit, the number of coarse air holes increases and the strength is reduced. If the molding pressure is higher than the upper limit, the sintered body becomes too dense and it is difficult to plastically deform the sintered body in the sizing process. It is to become.

次いで、圧粉体を焼結工程で焼結させる。焼結炉内の雰囲気ガスとしては、鉄と炭素の反応を防止するため、炭素を含まないガス、例えば水素ガス、窒素ガス、アルゴンガス、又はこれらの混合ガスを使用し、あるいは真空下で焼結するのが好ましい。焼結温度(焼結炉内の雰囲気温度)としては、800℃〜1000℃の範囲内が好ましい。焼結温度が800℃を下回ると、粒子間の拡散が不十分となって焼結体の強度が不十分となり、1000℃を上回ると、粒子間の拡散が過剰に進んで焼結体が硬くなりすぎ、塑性変形させることが困難となるためである。   Next, the green compact is sintered in a sintering process. As an atmosphere gas in the sintering furnace, a gas not containing carbon, for example, hydrogen gas, nitrogen gas, argon gas, or a mixed gas thereof is used in order to prevent the reaction between iron and carbon, or sintering under vacuum. It is preferable to tie. The sintering temperature (atmospheric temperature in the sintering furnace) is preferably in the range of 800 ° C to 1000 ° C. When the sintering temperature is lower than 800 ° C., the diffusion between the particles is insufficient and the strength of the sintered body becomes insufficient. When the sintering temperature is higher than 1000 ° C., the diffusion between the particles proceeds excessively and the sintered body becomes hard. This is because it becomes difficult to cause plastic deformation.

以上の焼結工程を経ることで、本発明の焼結体が得られる。この焼結体1の密度は7.0g/cm3以上、7.9g/cm3以下である。図1に拡大して示すように、この焼結体1は、鉄組織2のみからなり、かつ隣接する鉄組織2間に多数の空孔3を有する。遊離黒鉛や銅組織は焼結体1中に存在しない。また、原料粉末が黒鉛粉を含んでおらず、かつ雰囲気ガスに炭素も存在しないため、焼結中に鉄と炭素が反応することがない。従って、焼結後の鉄組織2は基本的に全てフェライト相(α−Fe)となる。フェライト相は、Hv200以下の軟質な金属組織であるため、焼結体1全体がフェライト相で形成されることにより、変形性に富む鉄系焼結体1を得ることができる。 The sintered body of the present invention is obtained through the above sintering process. The density of the sintered body 1 is 7.0 g / cm 3 or more and 7.9 g / cm 3 or less. As shown in an enlarged view in FIG. 1, the sintered body 1 is composed of only an iron structure 2 and has a large number of holes 3 between adjacent iron structures 2. Free graphite and copper structure are not present in the sintered body 1. In addition, since the raw material powder does not contain graphite powder and carbon does not exist in the atmospheric gas, iron and carbon do not react during sintering. Therefore, the iron structure 2 after sintering basically becomes a ferrite phase (α-Fe). Since the ferrite phase is a soft metal structure of Hv 200 or less, the entire sintered body 1 is formed of the ferrite phase, so that the iron-based sintered body 1 having excellent deformability can be obtained.

その後、焼結体1の全体あるいは一部を、後述のように塑性加工によって異なる形状に変形させることで、最終製品としての焼結部材が得られる。塑性加工の前後何れかの段階で、必要に応じて焼結体1にサイジングを施す。その後、必要に応じて焼結部材に潤滑油を含浸させることができる。   Then, the sintered member 1 as a final product is obtained by deforming the whole or a part of the sintered body 1 into different shapes by plastic working as will be described later. Sizing is performed on the sintered body 1 as necessary at any stage before or after the plastic working. Thereafter, the sintered member can be impregnated with lubricating oil as necessary.

焼結体の塑性変形のし易さを評価する物性値として、JIS Z2550に記載されている伸び値がある。表1に、本発明の焼結体(実施例)と既存の鉄系焼結体(比較例)について伸び値を測定した結果を示す。

Figure 0006482923

As a physical property value for evaluating the ease of plastic deformation of a sintered body, there is an elongation value described in JIS Z2550. Table 1 shows the results of measuring the elongation values of the sintered body (Example) of the present invention and the existing iron-based sintered body (Comparative Example).
Figure 0006482923

ここでの「伸び値」は、JIS Z2241に規定の金属材料引張試験を行った時の試験片の「破断伸び」、つまり破断後の試験片の永久伸び量を試験片の原標点距離に対して百分率で表した値である。試験片は、図2に示すように、JIS Z2550の付図1.2に記載された形状および寸法に準拠して製作される。因みに試験片の各部の寸法は概ね、b:5.7mm、c:5.96mm、Lc(原評点間距離):32.0mm、Ld:87.8mm、Lt:96.5mm、W:8.7mm、R1:4.35mm、R2:25.0mmである。 The “elongation value” here is the “breaking elongation” of the test piece when the metal material tensile test specified in JIS Z2241 is performed, that is, the permanent elongation of the test piece after the break is the original test point distance of the test piece. It is a value expressed as a percentage. As shown in FIG. 2, the test piece is manufactured in accordance with the shape and dimensions described in JIS Z2550 Appended Figure 1.2. By the way, the dimensions of each part of the test piece are generally b: 5.7 mm, c: 5.96 mm, Lc (distance between original scores): 32.0 mm, Ld: 87.8 mm, Lt: 96.5 mm, W: 8. 7 mm, R 1 : 4.35 mm, and R 2 : 25.0 mm.

実施例1の試験片は、上記の原料粉末を使用し、かつ上記の各工程を経て製作されている。比較例1の試験片は、原料粉末として鉄粉と0.2〜1.0質量%の銅粉との混合粉末を使用し、比較例2の試験片は、原料粉末として鉄粉と0.2〜0.8質量%の黒鉛粉との混合粉末を使用している。比較例1および比較例2は、何れも焼結温度を1100℃〜1150℃で焼結され、かつ何れも焼結時の雰囲気ガスとして、ブタンガスやプロパンガス等の液化石油ガスと空気とを混合してNi触媒で熱分解させた吸熱型ガス(COおよびCO2含有ガス。いわゆるRXガス)が使用されている。その他の条件は、成形圧力を含め、実施例1、比較例2、および比較例2で共通する。   The test piece of Example 1 is manufactured using the above raw material powder and through each of the above steps. The test piece of Comparative Example 1 uses a mixed powder of iron powder and 0.2 to 1.0% by mass of copper powder as the raw material powder, and the test piece of Comparative Example 2 uses iron powder and 0. A mixed powder with 2 to 0.8% by mass of graphite powder is used. In Comparative Examples 1 and 2, both are sintered at a sintering temperature of 1100 ° C. to 1150 ° C., and both are mixed with liquefied petroleum gas such as butane gas or propane gas and air as an atmosphere gas at the time of sintering. An endothermic gas (CO and CO2 containing gas, so-called RX gas) thermally decomposed with a Ni catalyst is used. Other conditions are common to Example 1, Comparative Example 2, and Comparative Example 2, including the molding pressure.

表1から明らかなように、実施例1では金属組織がほぼ全てフェライト相(α―Fe)となるため、焼結体1の硬度が低く、その結果、伸び値の値も5%以上の高い値を有する。これに対して、比較例1ではCuがFeに拡散して組織が硬くなるため、焼結体の強度は実施例1よりも向上するものの、伸び値の値は実施例1よりも低くなる。また、比較例2では、黒鉛粉や雰囲気ガスに含まれる炭素がFeに拡散して鉄組織が硬いパーライト相(γ−Fe)となるため、比較例1と同様に、焼結体の強度は実施例1よりも向上するが、伸び値は実施例1よりも低くなる。なお、焼結体の伸び値が大きすぎると強度不足となり易いので、伸び値は6%以下であるのが好ましい。   As is clear from Table 1, in Example 1, since the metal structure is almost entirely the ferrite phase (α-Fe), the hardness of the sintered body 1 is low, and as a result, the elongation value is also high at 5% or more. Has a value. On the other hand, in Comparative Example 1, since Cu diffuses into Fe and the structure becomes hard, the strength of the sintered body is improved as compared with Example 1, but the elongation value is lower than that of Example 1. In Comparative Example 2, carbon contained in the graphite powder and atmospheric gas diffuses into Fe and the iron structure becomes a hard pearlite phase (γ-Fe). Therefore, as in Comparative Example 1, the strength of the sintered body is Although improved over Example 1, the elongation value is lower than Example 1. In addition, since an intensity | strength will become insufficient when the elongation value of a sintered compact is too large, it is preferable that an elongation value is 6% or less.

このように本発明の焼結体1は、鉄系焼結体であり、鉄粒子同士が拡散した状態にあるので高強度となる。その一方で、焼結体1の伸び値は5%以上であり、そのために塑性変形させ易いという特性を有する。従って、図3(a)に示すように、焼結体1を単純形状に製作した後、その塑性変形させるべき部分1a(例えばリング状焼結体1の外周面)を転造や鍛造等の塑性加工で塑性変形させることで、図3(b)に示すような最終形状を有する焼結部材1’を得ることが可能となる。焼結体1が軟らかいため、塑性変形させる際にも良好な成形性が得られ、また低い加圧力で成形できるので大型プレス機等を用いることなく低コストに量産することが可能となる。図3(b)に示すようなアンダーカットを有する最終製品形状を圧紛体の時点で成形しようとすると、金型形状を工夫する等の対策が必要となり、製造コストを押し上げる要因となるが、本発明ではそのような問題がない。従って、本発明により、必要強度を確保しつつ焼結体1の形状自由度を高めることができ、粉末冶金法の適用対象を拡大して、機械部品等の低コスト化を図ることが可能となる。なお、本発明の焼結体1は、鉄組織が主にフェライト相で形成されているため、耐腐食性に優れ、かつ良好な磁気特性から磁性材としての使用にも適合する、という特徴も有している。   Thus, the sintered body 1 of the present invention is an iron-based sintered body and has high strength because the iron particles are in a diffused state. On the other hand, the elongation value of the sintered body 1 is 5% or more, and therefore has the property of being easily plastically deformed. Therefore, as shown in FIG. 3A, after the sintered body 1 is manufactured in a simple shape, the portion 1a to be plastically deformed (for example, the outer peripheral surface of the ring-shaped sintered body 1) is rolled or forged. By plastically deforming by plastic working, it becomes possible to obtain a sintered member 1 ′ having a final shape as shown in FIG. Since the sintered body 1 is soft, good moldability can be obtained even when plastically deformed, and since it can be molded with a low pressure, it can be mass-produced at low cost without using a large press or the like. If the final product shape having an undercut as shown in FIG. 3 (b) is to be formed at the time of the compact, it is necessary to take measures such as devising the shape of the mold, which increases the manufacturing cost. The invention does not have such a problem. Therefore, according to the present invention, it is possible to increase the shape flexibility of the sintered body 1 while ensuring the necessary strength, and it is possible to expand the application object of the powder metallurgy method and reduce the cost of machine parts and the like. Become. The sintered body 1 of the present invention has a feature that since the iron structure is mainly formed of a ferrite phase, it has excellent corrosion resistance and is suitable for use as a magnetic material because of its good magnetic properties. Have.

ここでいう「塑性変形」は、塑性加工により目視で形状の変化が認識できる程度まで変形させて最終形状に仕上げることを意味する。このように塑性変形させることで、通常は焼結体1が単純形状(図3(a))から複雑形状(図3(b))に変化する。   “Plastic deformation” as used herein refers to finishing to a final shape by plastic deformation to such an extent that a change in shape can be visually recognized. By plastically deforming in this way, the sintered body 1 usually changes from a simple shape (FIG. 3A) to a complex shape (FIG. 3B).

以上の説明では、焼結体1の鉄組織の全てをフェライト相で形成する場合を説明したが、図4に示すように、焼結体1の鉄組織2をフェライト相α−Feとパーライト相γ−Feの二相組織にすることもできる。これにより、焼結体1の伸び値を確保しつつ、焼結体1で形成した焼結部材の強度アップを図ることができる。この場合、パーライト相の存在割合が過剰となると、焼結体1が硬くなりすぎるので、パーライト相はフェライト相の粒界に存在(点在)する程度に抑える。ここでいう「粒界」は、粉末粒子間に形成される粒界の他、粉末粒子中に形成される結晶粒界(図4中に破線で示す)の双方を意味する。焼結体1におけるフェライト相の割合は、その任意断面における面積比で、90%以上(パーライト相が10%以下)、好ましくは95%以上(パーライト相が5%以下)とする。ちなみに上記比較例3では、フェライト相とパーライト相の面積比は、30%〜70%:70%〜30%程度であり、本発明品よりもパーライト相の割合が相当多い。   In the above description, the case where the entire iron structure of the sintered body 1 is formed of the ferrite phase has been described. However, as shown in FIG. 4, the iron structure 2 of the sintered body 1 is converted into the ferrite phase α-Fe and the pearlite phase. A two-phase structure of γ-Fe can also be used. Thereby, the strength of the sintered member formed of the sintered body 1 can be increased while securing the elongation value of the sintered body 1. In this case, if the ratio of the pearlite phase is excessive, the sintered body 1 becomes too hard, so the pearlite phase is suppressed to the extent that it exists (is scattered) at the grain boundary of the ferrite phase. The “grain boundary” here means both a grain boundary formed between the powder particles and a crystal grain boundary formed in the powder particle (indicated by a broken line in FIG. 4). The ratio of the ferrite phase in the sintered body 1 is 90% or more (the pearlite phase is 10% or less), preferably 95% or more (the pearlite phase is 5% or less) as an area ratio in the arbitrary cross section. Incidentally, in the comparative example 3, the area ratio of the ferrite phase to the pearlite phase is about 30% to 70%: 70% to 30%, and the ratio of the pearlite phase is considerably larger than that of the product of the present invention.

図4に示す二相組織は、例えば炉内雰囲気としてRXガス等の炭素を含むガスを使用することで得ることができる。なお、この場合の焼結温度は、全ての鉄組織をフェライト相とする場合と同様に、800℃〜1000℃程度とするのが好ましい。   The two-phase structure shown in FIG. 4 can be obtained, for example, by using a gas containing carbon such as RX gas as the furnace atmosphere. Note that the sintering temperature in this case is preferably about 800 ° C. to 1000 ° C., as in the case where all the iron structures are made the ferrite phase.

以上に述べた焼結体1は、強度や硬さが既存の鉄系焼結体よりも劣るため、ギヤ、軸等の動力伝達系に使用される部材よりは、非動力伝達系に使用される部材への適用に向くものである。非動力伝達系に使用される部材の一例として、例えば図5(a)に示す流体軸受装置における、軸受11を収容するためのハウジング10を挙げることができる。   Since the sintered body 1 described above is inferior in strength and hardness to existing iron-based sintered bodies, it is used in non-power transmission systems rather than members used in power transmission systems such as gears and shafts. It is suitable for application to members. As an example of a member used in the non-power transmission system, for example, a housing 10 for housing the bearing 11 in the hydrodynamic bearing device shown in FIG.

図5(a)に示す流体軸受装置は、光ディスクや磁気ディスク等の情報記録媒体を回転駆動するスピンドルモータ、あるいはファンモータにおける回転支持に適合するものである。以下では、光ディスク14用のスピンドルモータに用いた軸受装置を例示し、その概略構成を説明する。   The hydrodynamic bearing device shown in FIG. 5A is suitable for rotation support in a spindle motor or a fan motor that rotationally drives an information recording medium such as an optical disk or a magnetic disk. Below, the bearing apparatus used for the spindle motor for optical disks 14 is illustrated, and the schematic structure is demonstrated.

この軸受措置は、ベース17に固定されたハウジング10と、ハウジング10の内周に収容された軸受11と、軸受11の内周に挿入された軸部材12とを主要な構成要素とする。軸部材12にはロータ13が取り付けられており、ロータ13に取り付けたマグネット16と、ハウジング15に取り付けたステータコイル15との間に生じる励磁力で軸部材12が回転駆動される。このように軸部材12を回転側とする他、軸部材12を固定側として軸受11を回転させることもできる。軸受11は、潤滑油を含浸させた焼結金属からなる焼結含油軸受である。軸受11を軟質金属等の溶製材で形成することができる。   This bearing measure mainly includes a housing 10 fixed to the base 17, a bearing 11 accommodated in the inner periphery of the housing 10, and a shaft member 12 inserted in the inner periphery of the bearing 11. A rotor 13 is attached to the shaft member 12, and the shaft member 12 is rotationally driven by an exciting force generated between a magnet 16 attached to the rotor 13 and a stator coil 15 attached to the housing 15. In this way, the shaft member 12 can be rotated, and the bearing 11 can be rotated with the shaft member 12 as the fixed side. The bearing 11 is a sintered oil-impregnated bearing made of a sintered metal impregnated with a lubricating oil. The bearing 11 can be formed of a melted material such as a soft metal.

軸受11の内周面に形成された二つのラジアル軸受面で、軸方向に離隔する二つのラジアル軸受部Br1,Br2が構成される。ラジアル軸受部Br1,Br2は、ラジアル軸受面と軸部材12の外周面との間のラジアル軸受隙間に形成した油膜で軸部材12をラジアル方向で回転自在に支持する。また、軸部材12の端部をハウジング10の底部11aに接触させることで、スラスト荷重を支持するスラスト軸受部Bsが構成されている。   Two radial bearing portions Br1 and Br2 separated in the axial direction are constituted by two radial bearing surfaces formed on the inner peripheral surface of the bearing 11. The radial bearing portions Br1 and Br2 support the shaft member 12 rotatably in the radial direction with an oil film formed in a radial bearing gap between the radial bearing surface and the outer peripheral surface of the shaft member 12. Further, the thrust bearing portion Bs that supports the thrust load is configured by bringing the end portion of the shaft member 12 into contact with the bottom portion 11 a of the housing 10.

ラジアル軸受部Br1,Br2は、軸受11のラジアル軸受面および軸部材12の外周面の双方を円筒面状にしたいわゆる真円軸受の他、軸受11のラジアル軸受面あるいは軸部材12の外周面のどちらか一方に複数の動圧発生溝をヘリングボーン型等の形状に配列してなる動圧軸受で構成することもできる。また、スラスト軸受部Bsを同様の動圧軸受で構成することもできる。このように各軸受部を動圧軸受で構成する場合、ハウジング10の内部を潤滑油で充満させ、油面を軸受11の大気開放側の端部に形成したテーパシール11a上に配置するのが好ましい。   The radial bearing portions Br1 and Br2 are not only so-called circular bearings in which both the radial bearing surface of the bearing 11 and the outer peripheral surface of the shaft member 12 are cylindrical, but also the radial bearing surface of the bearing 11 or the outer peripheral surface of the shaft member 12. It is also possible to configure a dynamic pressure bearing in which a plurality of dynamic pressure generating grooves are arranged in a herringbone type or the like on either side. Moreover, the thrust bearing part Bs can also be comprised with the same dynamic pressure bearing. Thus, when each bearing part is comprised with a dynamic pressure bearing, the inside of the housing 10 is filled with lubricating oil, and it arrange | positions on the taper seal 11a formed in the edge part by the side of the atmosphere open | release side of the bearing 11. preferable.

図5(a)に示すハウジング10は、円筒状の側部10aと底部10bからなる有底筒状をなし、側部10aの内周に軸受11が嵌合されると共に、底部10bに軸受11の一方の端面が軸方向に係合している。このハウジング10は、上述した焼結体1(図1等参照)で形成されている。すなわち、有底筒状に成形した圧紛体を焼結し、側部10aの内周面および外周面、底部10bの上面および下面にそれぞれサイジングを行うことで有底筒状に形成されている。なお、ハウジング10の側部10aと底部10bは別部材にすることもできる。この場合、底部10bの材料は任意に選択することができ、上述の焼結体1で形成する他、軟質金属等の溶製材で形成することもできる。   The housing 10 shown in FIG. 5A has a bottomed cylindrical shape including a cylindrical side portion 10a and a bottom portion 10b. The bearing 11 is fitted to the inner periphery of the side portion 10a, and the bearing 11 is fitted to the bottom portion 10b. One end face of this is engaged in the axial direction. The housing 10 is formed of the above-described sintered body 1 (see FIG. 1 and the like). That is, the powder compact formed into a bottomed cylindrical shape is sintered, and formed into a bottomed cylindrical shape by sizing the inner and outer peripheral surfaces of the side portion 10a and the upper and lower surfaces of the bottom portion 10b. Note that the side portion 10a and the bottom portion 10b of the housing 10 may be separate members. In this case, the material of the bottom portion 10b can be arbitrarily selected, and in addition to the sintered body 1, the bottom 10b can be formed of a melted material such as a soft metal.

このようにハウジング10(特に側部10a)を変形性に富む焼結体1で形成することにより、図5(b)に示すように、側部10aの上端を加締め等により部分的に塑性変形させることが可能となる。この場合もハウジングが単純形状(破線部)から複雑形状(加締め部20)に変化しており、ハウジング10の破線部分が塑性変形させるべき部分1aとなる。加締めによって形成された加締め部20を軸受11の他方の端面と係合させることで、ハウジング10に対する軸受11の位置決めを行い、ハウジング10に軸受11を固定することができる。ハウジング10が変形性に富む焼結体1で形成されているため、加締めは低荷重で行うことができ、そのためにハウジング10と軸受11を低コストに固定することが可能となる。   Thus, by forming the housing 10 (particularly the side portion 10a) with the deformable sintered body 1, as shown in FIG. 5B, the upper end of the side portion 10a is partially plasticized by caulking or the like. It can be deformed. Also in this case, the housing changes from a simple shape (dashed line portion) to a complicated shape (caulking portion 20), and the broken line portion of the housing 10 becomes a portion 1a to be plastically deformed. By engaging the caulking portion 20 formed by caulking with the other end surface of the bearing 11, the bearing 11 can be positioned with respect to the housing 10, and the bearing 11 can be fixed to the housing 10. Since the housing 10 is formed of the deformable sintered body 1, the caulking can be performed with a low load. Therefore, the housing 10 and the bearing 11 can be fixed at a low cost.

従来の流体軸受装置では、ハウジングを真鍮等の軟質金属、あるいは樹脂で形成している。軟質金属製のハウジングは、切削等の機械加工で形成されているために加工コストが高騰する問題があり、また剛性が低いために加締めの際にハウジング全体が変形するおそれがある。一方、樹脂製のハウジングは、ハウジング10に軸受11を接着固定する必要があり、接着剤を硬化させるためにベーキング等の処理を要するため、組立コストが高騰する問題がある。また、ハウジング10を加締めることも困難となる。これに対し、ハウジング10を上記の焼結体1で形成すれば、衝撃荷重が与えられた際にも破損し難い高強度のハウジング10とすることができ、かつこれを低コストに製造することができる。また、ハウジング10の加締めも容易であるため、軸受11をハウジング10に低コストに固定することができる。従って、部品コストおよび組立コストの両面から、流体軸受装置の低コスト化を図ることができる。   In the conventional hydrodynamic bearing device, the housing is formed of a soft metal such as brass or a resin. Since the housing made of soft metal is formed by machining such as cutting, there is a problem that the processing cost increases, and since the rigidity is low, the entire housing may be deformed during caulking. On the other hand, the resin housing requires the bearing 11 to be bonded and fixed to the housing 10, and a process such as baking is required to cure the adhesive, resulting in a problem that the assembly cost increases. Moreover, it becomes difficult to crimp the housing 10. On the other hand, if the housing 10 is formed of the above-described sintered body 1, it can be made a high-strength housing 10 that is not easily damaged even when an impact load is applied, and is manufactured at a low cost. Can do. Moreover, since the caulking of the housing 10 is easy, the bearing 11 can be fixed to the housing 10 at low cost. Therefore, the cost of the hydrodynamic bearing device can be reduced in terms of both component cost and assembly cost.

なお、以上の説明では、軸受11の固定のためにハウジング10を加締める場合を例示したが、ハウジング10と相互に固定する部材(他部材)は軸受11に限られない。例えば軸受11のテーパシール11aを軸受11と別体のシール部材(図示省略)で形成した流体軸受装置では、ハウジング10に設けた加締め部20でシール部材の端面を拘束することにより、シール部材(さらに軸受11)をハウジング10に固定することができる。このように本発明は、焼結部材(ハウジング10)と他部材を相互に固定する際の固定構造として広く適用することができる。加締め部20の形状は、他部材の軸方向移動を拘束できるものであれば任意であり、図5(b)に示す形状には限定されない。   In the above description, the case where the housing 10 is crimped to fix the bearing 11 is illustrated, but a member (other member) that is mutually fixed to the housing 10 is not limited to the bearing 11. For example, in a hydrodynamic bearing device in which the taper seal 11 a of the bearing 11 is formed by a seal member (not shown) separate from the bearing 11, the end surface of the seal member is constrained by a crimping portion 20 provided in the housing 10, thereby Further, the bearing 11 can be fixed to the housing 10. Thus, the present invention can be widely applied as a fixing structure when the sintered member (housing 10) and the other member are fixed to each other. The shape of the crimping part 20 is arbitrary as long as it can restrain the movement of the other member in the axial direction, and is not limited to the shape shown in FIG.

ところで、軸受11の素材としては、既に述べたように軟質金属や焼結金属が用いられる。特に後者の場合は、焼結金属中の空孔に潤滑油を含浸させ、焼結含油軸受11として使用するのが一般的である。このようにハウジング10の内周に焼結含油軸受11を嵌合させる場合、焼結含油軸受11の外周面に滲み出した潤滑油が多孔質の焼結体1からなるハウジング10に移動し、これがハウジング表面に滲みだして気化するおそれがある。気化した潤滑油は、例えば記録媒体14や記録媒体14に記録された情報をピックアップする対物レンズ等の周囲環境を汚染し、データの読み取りおよび書き込み精度を低下させる要因となる。   By the way, as described above, a soft metal or a sintered metal is used as the material of the bearing 11. Particularly in the latter case, it is general to use the sintered oil-impregnated bearing 11 by impregnating the pores in the sintered metal with lubricating oil. When the sintered oil-impregnated bearing 11 is thus fitted to the inner periphery of the housing 10, the lubricating oil that has oozed out to the outer peripheral surface of the sintered oil-impregnated bearing 11 moves to the housing 10 made of the porous sintered body 1, This may ooze out on the housing surface and vaporize. The vaporized lubricating oil pollutes the surrounding environment such as an objective lens that picks up information recorded on the recording medium 14 and the recording medium 14, for example, and causes a decrease in data reading and writing accuracy.

かかる事態を防止するため、図6に示すように、焼結体1からなるハウジング10の表面に、通油性を低下させるための被膜21を形成するのが好ましい。   In order to prevent such a situation, as shown in FIG. 6, it is preferable to form a film 21 for reducing oil permeability on the surface of the housing 10 made of the sintered body 1.

この被膜21の一例として、Fe34等からなる酸化鉄被膜を挙げることができる。この酸化鉄被膜21は、例えば焼結後のハウジング10をサイジングし、超音波洗浄を行ってから水蒸気処理を施すことで形成される。水蒸気処理は、スチーム処理炉内で、焼結体の表面を400℃〜600℃の高温水蒸気に30分〜2時間程度接触させて酸化させる処理である。このようにハウジング10の表面に酸化鉄被膜21を形成することで、表面の空孔3が封孔されるため、焼結体における通油度を低下させることができる。 An example of the coating 21 is an iron oxide coating made of Fe 3 O 4 or the like. The iron oxide coating 21 is formed, for example, by sizing the housing 10 after sintering and performing ultrasonic treatment after performing ultrasonic cleaning. The steam treatment is a treatment in which the surface of the sintered body is contacted with high-temperature steam at 400 ° C. to 600 ° C. for about 30 minutes to 2 hours to oxidize in a steam treatment furnace. By forming the iron oxide coating 21 on the surface of the housing 10 in this way, the holes 3 on the surface are sealed, so that the oil permeability in the sintered body can be reduced.

この他、被膜21は、めっき被膜で形成することもできる。めっきの一例として、無電解Niめっきを挙げることができる。   In addition, the coating 21 can be formed of a plating coating. An example of plating is electroless Ni plating.

このように表面を封孔する被膜21を形成することで、焼結体1の通油度を50×10-4g/2min以下にすることができる。これにより、ハウジング10の表面への潤滑油の滲み出しを防止することができ、滲みだした潤滑油の気化による上記の不具合を防止することができる。 By forming the coating film 21 that seals the surface in this way, the oil permeability of the sintered body 1 can be reduced to 50 × 10 −4 g / 2 min or less. Thereby, the seepage of the lubricating oil to the surface of the housing 10 can be prevented, and the above-described problems due to the vaporization of the lubricating oil that has started to leak can be prevented.

ここで、通油度とは、焼結体1が、その多孔質組織を介してどの程度油(潤滑油)を流通させることができるかを定量的に示すためのパラメータであり、図7に示すような試験装置100を用いて測定することができる。同図に示す試験装置100は、円筒状の試料W(ここでは焼結金属製の軸受部材)を軸方向両側から挟持固定した筒状の保持部101,102と、油を貯留するタンク103と、タンク103内に貯留された油を保持部101に供給するための配管104とを備える。試料Wの軸方向両端部と保持部101,102との間は、図示しないシール体(例えばゴムワッシャ)によりシールされている。以上の構成において、室温(26〜27℃)環境下でタンク103内に貯留された油(流体動圧軸受装置1の内部空間に充填される潤滑油と同種の潤滑油)に0.4MPaの加圧力を負荷し、潤滑油を、配管104の内部流路および保持部101の内部流路105を介して試料Wの軸方向貫通孔に2分間供給し続ける。試料Wの下方には吸油体(例えば、紙や布)106が配されており、上記態様で試料Wに潤滑油が供給されたときに試料Wの外径面に開口した表面開口から滲み出して滴下した油を吸油体106で採取する。そして、試験前後における吸油体106の重量差から通油度[単位:g/2min]が算出される。   Here, the oil permeability is a parameter for quantitatively indicating how much oil (lubricating oil) can be circulated through the porous structure of the sintered body 1. It can be measured using a test apparatus 100 as shown. A test apparatus 100 shown in FIG. 1 includes cylindrical holding portions 101 and 102 in which a cylindrical sample W (here, a bearing member made of sintered metal) is sandwiched and fixed from both sides in an axial direction, and a tank 103 that stores oil. And a pipe 104 for supplying the oil stored in the tank 103 to the holding unit 101. A gap between both ends of the sample W in the axial direction and the holding portions 101 and 102 is sealed by a sealing body (not shown) (for example, a rubber washer). In the above configuration, 0.4 MPa is applied to oil stored in the tank 103 in a room temperature (26 to 27 ° C.) environment (the same type of lubricating oil as that filled in the internal space of the fluid dynamic bearing device 1). The applied pressure is applied, and the lubricating oil is continuously supplied to the axial through hole of the sample W for 2 minutes through the internal flow path of the pipe 104 and the internal flow path 105 of the holding unit 101. An oil absorbing body (for example, paper or cloth) 106 is disposed below the sample W, and oozes out from the surface opening that opens to the outer diameter surface of the sample W when the lubricating oil is supplied to the sample W in the above-described manner. The oil dripped in this manner is collected by the oil absorber 106. Then, the oil permeability [unit: g / 2 min] is calculated from the weight difference between the oil absorbent bodies 106 before and after the test.

下記表2は、上記実施例1、比較例1、および比較例2のそれぞれに各種被膜21を形成し、通油度、ドライ密度、および含油率を測定した結果を示すものである(n=3)。被膜は酸化鉄被膜(スチーム)と無電解Ni被膜の二種類としており、また、焼結品(未サイジング)とサイジング品のそれぞれについて上記の各値を測定している。

Figure 0006482923
Table 2 below shows the results of measuring the oil permeability, dry density, and oil content by forming various coatings 21 on each of Example 1, Comparative Example 1, and Comparative Example 2 (n = 3). There are two types of coatings: an iron oxide coating (steam) and an electroless Ni coating, and the above values are measured for each of a sintered product (unsized) and a sized product.
Figure 0006482923

また、下記表3は被膜21を形成していない場合の通油度、ドライ密度、および含油率を測定した結果を示すものである。

Figure 0006482923
Table 3 below shows the results of measuring the oil permeability, dry density, and oil content when the coating 21 is not formed.
Figure 0006482923

表2および表3から明らかなように、実施例および比較例を問わず、焼結体の表面に被膜21を形成することで(表2)、被膜を形成していない場合(表3)に比べ、通油度を大幅に小さく(0〜3[×10-4g/2min])することができる。従って、ハウジング10の表面への油の滲み出しを確実に防止することができる。 As is clear from Table 2 and Table 3, regardless of the example and the comparative example, by forming the film 21 on the surface of the sintered body (Table 2), when the film is not formed (Table 3) In comparison, the oil permeability can be significantly reduced (0 to 3 [× 10 −4 g / 2 min]). Accordingly, it is possible to reliably prevent oil from seeping out from the surface of the housing 10.

また、表2から、実施例1では被膜21を形成した際の通油度が比較例1および比較例2よりも低くなることも理解できる。これは、実施例における鉄組織がフェライト相であるため、比較例に比べてサイジングの際に塑性変形し易く、これに伴って表面開孔が小さくなること、およびフェライト相にはスチーム処理による酸化鉄被膜(Fe34等)が生じやすく、酸化鉄被膜を厚くできること、による。 It can also be seen from Table 2 that in Example 1, the oil permeability when forming the coating 21 is lower than those in Comparative Example 1 and Comparative Example 2. This is because the iron structure in the example is a ferrite phase, so that it is more likely to be plastically deformed during sizing than in the comparative example, resulting in a smaller surface opening, and the ferrite phase is oxidized by steam treatment. This is because an iron coating (Fe 3 O 4 or the like) is likely to occur and the iron oxide coating can be thickened.

以上の実施形態では、焼結体1で形成した焼結部材として流体軸受装置のハウジング10を例示しているが、ハウジングに限らず、種々の部材を本発明の焼結体1で形成することができる。当該部材は、例示したような情報機器用のスピンドルモータに限らず、自動車、産業機器等に装備される種々の装置、機構に用いることができる。   In the above embodiment, the housing 10 of the hydrodynamic bearing device is illustrated as the sintered member formed of the sintered body 1, but not limited to the housing, various members are formed of the sintered body 1 of the present invention. Can do. The member is not limited to the spindle motor for information equipment as illustrated, but can be used for various devices and mechanisms equipped in automobiles, industrial equipment, and the like.

1 焼結体
1a 塑性変形させるべき部分
2 鉄組織
3 気孔
10 ハウジング(焼結部材)
20 加締め部
1 Sintered body 1a Part to be plastically deformed 2 Iron structure 3 Pore 10 Housing (sintered member)
20 Caulking section

Claims (7)

焼結体で形成されたハウジングと、当該ハウジングの内周に配置された焼結含油軸受とを備える軸受装置において、
前記焼結体が、鉄粉を、黒鉛粉を加えることなく成形し、焼結することで形成され、かつ前記焼結体における鉄組織の面積比で90%以上がフェライト相で形成され
前記ハウジングを加締めることで前記焼結含油軸受をハウジングに固定したことを特徴とする軸受装置
In a bearing device comprising a housing formed of a sintered body and a sintered oil-impregnated bearing disposed on the inner periphery of the housing,
The sintered body is formed by forming and sintering iron powder without adding graphite powder , and 90% or more of the area ratio of the iron structure in the sintered body is formed by the ferrite phase ,
A bearing device , wherein the sintered oil-impregnated bearing is fixed to the housing by caulking the housing .
前記焼結体の伸び値が5%以上である請求項1記載の軸受装置The bearing device according to claim 1, wherein an elongation value of the sintered body is 5% or more. 前記ハウジングの表面に、通油性を低下させるための被膜を形成した請求項1または2記載の軸受装置The bearing device according to claim 1, wherein a film for reducing oil permeability is formed on a surface of the housing . 前記被膜を酸化鉄で形成した請求項3記載の軸受装置The bearing device according to claim 3, wherein the coating is formed of iron oxide. 前記被膜を鍍金で形成した請求項3記載の軸受装置The bearing device according to claim 3, wherein the coating is formed by plating. 前記焼結体の通油度を50×10-4g/2min以下にした請求項3〜5何れか1項に記載の軸受装置The bearing device according to claim 3, wherein an oil permeability of the sintered body is 50 × 10 −4 g / 2 min or less. 前記焼結体の密度を7.0g/cm3以上とした請求項1〜6何れか1項に記載の軸受装置The bearing device according to claim 1, wherein a density of the sintered body is 7.0 g / cm 3 or more.
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