JPWO2006123453A1 - Metal bearing - Google Patents

Abstract

A metal bearing comprising a sintered body having a bearing surface slidable with respect to a shaft member, the main component of which is a metal or an alloy, and pores on the surface and inside thereof. Is present in the dispersion solvent with at least one of a gas and a liquid having a boiling point lower than that of the dispersion solvent.

Description

  The present invention relates to a metal bearing comprising a sintered body having a bearing surface slidable with respect to a shaft member, the main component of which is a metal or an alloy, and pores on the surface and inside.

  Conventionally, an oil-impregnated bearing in which a lubricating oil is impregnated in a sintered body is known as a metal bearing formed of a metal sintered body as a main component (see, for example, Patent Document 1). According to such a metal bearing, the lubrication on the bearing surface is ensured by the so-called self-lubricating property in which the lubricating oil impregnated in the sintered body oozes out to the bearing surface due to heat generated by sliding contact with the rotating shaft. can do.

In addition, as other metal bearings, it is made of a graphite-dispersed Cu-based sintered alloy in which graphite particles are mixed with a copper-nickel alloy powder by means such as a ball mill and subjected to pressure forming and then sintered. A bearing has been proposed (see, for example, Patent Document 2). In such a metal bearing, excellent wear resistance can be exerted by free graphite having high lubricity and a copper-nickel alloy having excellent strength and corrosion resistance.
JP 2002-39183 A JP 2002-180162 A

  However, the conventional oil-impregnated bearing in which the sintered body is impregnated with lubricating oil has a low vapor pressure (low surface tension) in the low temperature region, or the volume of the lubricating oil in the low temperature region is thermally contracted. For example, the lubricating oil impregnated in the sintered body is difficult to ooze out to the bearing surface and the self-lubricating property is lost. As a result, problems such as seizure on the sliding contact surface between the bearing and the shaft member or clogging of pores due to contact with each other occur. Generally, when the operating temperature is −30 ° C. or lower, the self-lubricating property of the oil-impregnated bearing is extremely lowered.

On the other hand, in the high temperature region, the lubricating oil impregnated in the sintered body is likely to ooze out due to factors such as high vapor pressure (high surface tension) or large thermal expansion, and it is depleted when the usage time is long. May end up. As a result, as in the case of low temperatures, the lubricating action of the lubricating oil decreases, causing problems such as seizure on the sliding contact surface between the bearing and the shaft member or clogging of pores due to contact with each other. . Generally, when the operating temperature is 100 ° C. or higher, the continuous operation time of the impregnated bearing is restricted.
The volume ratio of pores provided on the surface and inside of the sintered body of metal or alloy used for the bearing is generally about 17 to 23 vol%, and the volume of the lubricating oil that can be impregnated in the pores is limited. is there.

  Further, when the oil-impregnated bearing and the shaft member pivotally supported by the bearing interfere with each other, the pores of the sintered body on the bearing surface may be crushed and the lubricating oil may be prevented from seeping out. For this reason, there is a problem that high machining accuracy is required for the inner diameter dimension of the bearing and the outer dimension of the shaft member, which increases the cost.

  Further, in the bearing made of the graphite-dispersed Cu-based sintered alloy, graphite powder is simply mixed with a copper-nickel alloy powder by a ball mill, so that the graphite is dispersed as a lump. . For this reason, graphite may not adhere uniformly to the bearing surface.

  When sintering what fixed the graphite particle on the surface of a metal particle, since melting | fusing point of a metal and graphite differs greatly, the fusion | melting in the contact surface of metal particles is inhibited by presence of graphite. For this reason, the problem that the mechanical strength of a sintered compact falls significantly also generate | occur | produces.

On the other hand, motor motors for automobiles have a wide operating environment temperature range, and the temperature varies depending on the position where the motor is disposed. Specifically, in the case of a motor for an automobile, the range of the operating environment temperature is about −40 to 120 ° C., and the bearing surface of the bearing with respect to the operating environment temperature of the motor by sliding with the shaft member, Further, the temperature is raised to about 30 to 50 ° C. For this reason, particularly in automobile motor bearings, those capable of ensuring lubricity on the bearing surface in a wide temperature range are required.
The motor motor bearings are maintenance-free and have been used for more than 10 years.

  In general, when the operating temperature range is wide, when the operating time is long, or when interference between the shaft member and the bearing is unavoidable, change to an oil-impregnated bearing (or a plain bearing) instead of a ball bearing (or It is also assumed that a rolling bearing is used, but the use of a ball bearing increases the cost. Further, since it is necessary to make a mounting space for the bearing large, a unit using the bearing, for example, a motor becomes large, and the mountability of the motor is impaired.

  The present invention has been devised in view of the above problems, and an object of the present invention is to provide a metal bearing having a long service life without being affected by the service temperature.

  In order to achieve the above object, the first characteristic configuration of the metal bearing according to the present invention includes a bearing surface that is slidable with respect to the shaft member, is mainly composed of metal or alloy, and has pores on the surface and inside. In a metal bearing comprising a solid body, a dispersion solvent is provided in the pores, and the ferromagnetic particles are present in the dispersion solvent with at least one of a gas and a liquid having a boiling point lower than the boiling point of the dispersion solvent. There is in point to do.

  That is, according to this configuration, when the temperature of the bearing surface of the metal bearing is increased by sliding contact with the shaft member, the temperature of the inside of the pores is also increased. In the pores that have reached a certain temperature or more, when the ferromagnetic particles are accompanied by a liquid in the dispersion solvent, the liquid is vaporized to form a balloon and surround the ferromagnetic particles. Since the balloon surrounding the ferromagnetic particles is present in the pores using the dispersion solvent as a medium, the thermal expansion is suppressed by the dispersion solvent surrounding the thermal expansion due to the temperature rise of the bearing surface, and the internal pressure rises. To do. After the internal pressure reaches atmospheric pressure, the balloon moves from the pores to the bearing surface with the ferromagnetic particles. The ferromagnetic particles that have moved to the bearing surface are stressed by the sliding contact between the bearing and the shaft member, and the coupling due to the magnetic aggregation between the ferromagnetic particles is released to form finer particles that are magnetically attracted to the bearing surface. To do. Thereby, the ferromagnetic fine particles can form a film-like structure (hereinafter referred to as “coating”) composed of a group of ferromagnetic fine particles on the bearing surface, and can be used as a bearing effect medium. .

  In this way, it is possible to form a coating mainly composed of a ferromagnetic material on the bearing surface, so that lubricity from the metal bearing side to other parts of the metal bearing or the shaft member side, as in conventional oil-impregnated bearings, etc. The supply of lubricating oil or the like for ensuring safety is no longer necessary. Furthermore, by interposing the ferromagnetic particles in the gap between the metal bearing and the shaft member by magnetic adsorption, seizure on the sliding contact surface between the metal bearing and the shaft member does not occur, and slidability can be maintained over a long period of time. It can be secured.

  Therefore, a metal bearing having a long service life can be provided without being affected by the service temperature due to the above configuration. And since it can prevent that a bearing and a shaft member interfere directly with a film, it becomes unnecessary to make processing precision high and can suppress cost.

  A second characteristic configuration of the metal bearing according to the present invention is that the ferromagnetic particles have a surface modifier on the surface.

  In other words, according to this configuration, the surface of the hydrophilic ferromagnetic particles is modified to be hydrophobic by the surface modifier, thereby improving the dispersibility of the ferromagnetic particles in the hydrophobic dispersion solvent. In addition, the gas that should surround the ferromagnetic particles can be prevented from being released from the ferromagnetic particles.

  A third characteristic configuration of the metal bearing according to the present invention is that the surface modifier has a thermal decomposition rate of 5% or less with respect to a temperature rise of the bearing surface due to sliding with the shaft member. .

  That is, according to this configuration, the surface modifier can be utilized as a lubricant after moving to the bearing surface.

  A fourth characteristic configuration of the metal bearing according to the present invention is that the ferromagnetic particles are magnetite particles.

  That is, according to this configuration, by using magnetite particles as the ferromagnetic particles, a preferred embodiment of a metal bearing having a long service life is provided without being affected by the service temperature.

  The 5th characteristic structure of the metal bearing which concerns on this invention exists in the point whose average particle diameter of the said magnetite particle | grain is 0.15 micrometer or less.

  That is, according to this configuration, the saturation magnetization of the single particles is reduced, and therefore, the magnetic aggregation of the magnetite particles can be easily released.

The 6th characteristic structure of the metal bearing which concerns on this invention exists in the point whose BET value of the said magnetite particle | grain is 10 m < ² > / g or more.

  That is, according to this structure, more gas and liquid can be accompanied with the surface of a magnetite particle.

  A seventh characteristic configuration of the metal bearing according to the present invention is that the dispersion solvent is at least one synthetic oil selected from polyalphaolefin, polyol diester, and polyalkylene glycol.

  That is, according to this configuration, by using the synthetic oil as a dispersion solvent, a preferred embodiment of a metal bearing having a long service life is provided without being affected by the service temperature.

  According to an eighth feature of the metal bearing of the present invention, the dispersion solvent is a polyalphaolefin, and the polyalphaolefin has a polymerization degree of at least one of those having a polymerization degree of 2 and 3. It has the main component.

  That is, according to this configuration, by using the polyalphaolefin as a dispersion solvent, a preferred embodiment of a metal bearing having a long service life can be provided without being affected by the service temperature.

  The ninth feature of the metal bearing according to the present invention is the metal bearing according to claim 2, wherein the surface modifier is at least one compound selected from a titanium coupling agent and a silane coupling agent.

  That is, according to this configuration, by using the coupling agent as the surface modifier, a preferred embodiment of a metal bearing having a long service life can be provided without being affected by the service temperature.

  A tenth characteristic configuration of the metal bearing according to the present invention is that the liquid is at least one liquid selected from alcohols having a boiling point in a temperature range of 60 ° C to 130 ° C and water.

  That is, according to this configuration, a preferred embodiment of a metal bearing having a long service life is provided by using the liquid without being affected by the service temperature.

  According to an eleventh characteristic configuration of the metal bearing according to the present invention, when the bearing surface is heated by sliding with the shaft member, the ferromagnetic particles move to the bearing surface, and the ferromagnetic particles move to the bearing surface. This is in the point of forming a film mainly composed of.

  That is, according to this configuration, the coating enables smooth sliding between the bearing and the shaft member. Further, seizure does not occur on the bearing surface, and slidability can be ensured over a long period of time. Furthermore, the sliding contact between the bearing and the shaft member can prevent a phenomenon such as galling on the sliding contact surface.

  A metal bearing according to the present invention includes a sintered body having a bearing surface slidable with respect to a shaft member, the main component being a metal or an alloy, and pores on the surface and inside thereof. And the ferromagnetic particles are present in the dispersion solvent with at least one of a gas and a liquid having a boiling point lower than that of the dispersion solvent. In other words, when the bearing surface is heated by sliding contact with the shaft member or the like, the temperature of the inside of the pores is also increased. In the pores that have reached a certain temperature or more, when the ferromagnetic particles are accompanied by a liquid in the dispersion solvent, the liquid is vaporized to form a balloon and surround the ferromagnetic particles. Since the balloon surrounding the ferromagnetic particles exists in the pores using the dispersion solvent as a medium, even if the thermal expansion of the bearing surface is caused by the temperature rise of the bearing surface, the balloon is surrounded by the dispersion solvent surrounding it and the internal pressure rises. After the internal pressure reaches atmospheric pressure, the balloon moves from the pores to the bearing surface with the ferromagnetic particles. Since the temperature in the pores reaches a constant temperature sooner as it is closer to the bearing surface, the internal pressure increases in order from the gas surrounding the ferromagnetic particles close to the bearing surface, and only those that have reached a certain pressure move to the bearing surface. A self-lubricating mechanism can be realized.

  The ferromagnetic particles that have moved to the bearing surface are stressed by the sliding contact between the bearing and the shaft member, and the coupling due to magnetic aggregation between the ferromagnetic particles is released, and the fine particles become magnetically attracted to the bearing surface. Thereby, the ferromagnetic fine particles can form a film on the bearing surface, and can be used as a bearing effect medium.

  Further, when the dispersion solvent moves to the bearing surface together with the ferromagnetic particles, when the dispersion solvent receives a load from the shaft member, a gap deviation between the bearing and the shaft member is formed, and the pressure distribution of the oil film is accordingly changed. Is formed. As a result, the dispersion solvent forms a fluid lubrication layer, which can exhibit a self-lubricating action. Furthermore, the dispersion solvent receives stress that moves in the rotation direction of the shaft member due to the pressure distribution of the oil film generated by the load of the shaft member and the rotation of the shaft member, and the ferromagnetic particles attached to the bearing and the shaft member are removed Move in the direction of rotation. Therefore, the dispersion solvent can be a lubricant that lubricates the gap between the bearing and the shaft member together with the ferromagnetic particles.

  In this way, a coating composed mainly of a ferromagnetic material can be formed on the bearing surface based on the magnetic attraction force on the sliding contact surface, so that self-lubricating due to thermal expansion of impregnated oil, as in conventional oil-impregnated bearings, etc. Therefore, it is not necessary to supply lubricating oil or the like for ensuring lubricity from the metal bearing side to other parts of the metal bearing or the shaft member side. Further, by interposing the ferromagnetic particles in the gap between the metal bearing and the shaft member by magnetic adsorption, the ferromagnetic particles slide on the sliding contact surface between the metal bearing and the shaft member, and seizure does not occur. It is possible to ensure slidability over a long period of time. And since it can prevent that a bearing and a shaft member interfere directly by the said film, it becomes unnecessary to make a processing precision high and can suppress cost.

  In general, when the ferromagnetic particles are fine particles and the magnetic cohesion force between the fine particles is larger than the gravity of the fine particles, it is difficult to release the aggregation of the ferromagnetic fine particles. However, in the case of the ferromagnetic fine particles existing in the gap between the bearing and the shaft member, a stress corresponding to the gap based on the unevenness of the sliding contact surface between the bearing and the shaft member and the dimensional accuracy of both is received. This stress acts on a group of particles aggregated repeatedly so as to cancel the aggregation of the ferromagnetic fine particles. That is, the stress acting on the ferromagnetic fine particles is transmitted to the bearing and the shaft member, but most of the stress is converted into a force for solving the aggregation of the particles, so that the ferromagnetic fine particles damage the bearing and the shaft member. Aggregation can be released without any problem.

  After forming a coating made of a group of ferromagnetic fine particles in the gap between the bearing and the shaft member, the particle group receives stress from the bearing and the shaft member, so that the particles constituting the particle group move and the particles The shape of the group can be freely changed. That is, the group of ferromagnetic fine particles can convert a large amount of external stress into its own shape deformation, and thus can exhibit a lubricating action as a solid. For this reason, the sliding friction coefficient as a metal bearing can be made smaller than the rolling friction coefficient of a ball when a rigid ball bearing is used. Further, since the group of ferromagnetic fine particles has a solid lubricating action, it is possible to prevent the generation of abnormal noise that occurs due to friction. Furthermore, even on the sliding contact surface between the bearing and the shaft member, the occurrence of a phenomenon such as galling can be prevented by the solid lubricating action of the ferromagnetic particles. The group of ferromagnetic particles present in the gap between the bearing and the shaft member gradually approaches a single particle while releasing the aggregation due to the sliding of the particles.

  Here, the group of ferromagnetic fine particles present in the gap between the bearing and the shaft member is always held in the gap between the bearing and the shaft member in a state where they can be deformed and moved by a magnetic attraction force. Is. For this reason, once ferromagnetic particles with larger magnetic cohesion between particles than the gravity of a single particle are magnetically adsorbed to the bearing surface or the outer peripheral surface of the shaft member, the ferromagnetic particles should not fall off due to gravity. Can do.

  Therefore, the metal bearing according to the present invention can form a coating containing a ferromagnetic material as a main component on the sliding contact surfaces of the bearing and the shaft member, and has a long service life without being affected by the service temperature. Can be provided. Since the ferromagnetic particles are used as a lubricant, it is possible to prevent the lubricating oil from being oozed out to the bearing surface depending on the operating temperature as in the conventional oil-impregnated bearing, or the lubricating oil being exhausted. The ferromagnetic particles are dispersed throughout the bearing surface as the gas is released over the entire bearing surface, and the aggregation of the group of ferromagnetic particles is gradually released. It can be uniformly adsorbed on the sliding contact surface with the member.

Such ferromagnetic particles are not particularly limited, but for example, those having the following characteristics are preferable.
1. Magnetic Properties It is preferable that the ferromagnetic particles have a magnetic property in which the ratio of the saturation magnetic flux density to the coercive force is large. Since such ferromagnetic particles have a large magnetic attraction force, it is difficult to fall off from the gap between the shaft member and the bearing.

2. Thermal stability Ferromagnetic particles preferably have a higher oxidation start temperature and magnetic Curie point. When the temperature of the bearing surface rises due to sliding with the shaft member, if the ferromagnetic particles are oxidized or exposed to a temperature exceeding the magnetic Curie point, the magnetic attractive force of the ferromagnetic particles weakens and the ferromagnetic particles May fall out of the gap. For this reason, it is particularly preferable that the ferromagnetic particles have an oxidation start temperature and a magnetic Curie point that are higher than the highest temperature at which the bearing surface is heated by sliding with the shaft member. Incidentally, the average temperature of the bearing surface of the metal bearing in the motor for automobiles rises to near 170 ° C. Therefore, when the metal bearing according to the present invention is applied to an automobile motor, it is preferable that both the oxidation start temperature and the magnetic Curie point are 170 ° C. or higher. Furthermore, according to the experiment by the present inventor, it has been found that the bearing surface of the automobile motor reaches 200 ° C. locally. For this reason, it is particularly preferable that both the oxidation start temperature and the magnetic Curie point are 200 ° C. or higher.

3. Solid lubricity The ferromagnetic particles are preferably spherical or granular. With such ferromagnetic particles, the magnetically agglomerated ferromagnetic particles themselves can easily relieve stress when they receive stress from the bearing and shaft member. That is, in spherical and granular particles, the particles are magnetically aggregated with each other in a state close to point contact. For this reason, the ferromagnetic particles on the bearing surface act so as to release the aggregation of the particles by receiving various stresses such as compression, shearing, and tension from the bearing and the shaft member, and from the group of ferromagnetic fine particles. The coating film can be easily formed in the gap between the bearing and the shaft member. In addition, since the spherical and granular particles have a small area in contact with the sliding contact surface between the bearing and the shaft member, the particles are slid in a magnetically adsorbed state when stress is applied to the particles. When the ferromagnetic particles are hard particles, the ferromagnetic particles present in the gap between the shaft member and the bearing may attack the shaft member and the bearing. For this reason, it is preferable to release the aggregation of the ferromagnetic particles to a state close to a single particle. As a result, the ferromagnetic particles magnetically adsorbed on the sliding contact surfaces of the shaft member and the bearing become slippery and can exhibit a solid lubricating action of relaxing stress received from the shaft member and the bearing.

4). Self-lubricating ferromagnetic particles preferably have a large specific surface area. Specifically, the BET value is preferably 10 m ² / g or more. In order to move the ferromagnetic particles to the bearing surface, a liquid having a boiling point lower than that of the gas or dispersion solvent is adsorbed or impregnated to the ferromagnetic particles. However, the larger the specific surface area of the ferromagnetic particles, the more the gas or liquid is allowed to move. It can accompany the surface of the ferromagnetic particles, and self-lubricating property can be obtained over a longer period. In addition, examples of the gas or liquid having a boiling point below the temperature range of the bearing surface that is heated by sliding with the shaft member and that is inexpensive include water and various alcohols. For this reason, when water or various alcohols are used, it is preferable that the ferromagnetic particles have a large specific surface area and high hydrophilicity.

5. Impregnation The size of the ferromagnetic particles is preferably 1 μm or less. In general, the openings of the pores of the sintered metal body used for the metal bearing have various shapes and sizes, and vary depending on the material and use of the sintered metal body. For example, the pore opening of the copper-based sintered body is narrower than that of the iron-based sintered body. In addition, when the metal bearing is applied to a motor that requires high quietness, the pore opening of the sintered metal body is narrowed. The opening part of the pores of such a metal sintered body has a size of about 1 to 50 μm. For this reason, the ferromagnetic particles dispersed in the dispersion solvent are required to have a size that can enter the pores from the pores of the metal bearing and can move from the pores to the bearing surface. .

6). Dispersion stability Ferromagnetic particles preferably have a narrow particle size distribution. Usually, the density of the ferromagnetic particles is larger than the density of the dispersion solvent. For example, even if the ferromagnetic particles have a density ratio close to 8 times that of the dispersion solvent, the ferromagnetic particles can be stably dispersed in the dispersion solvent by using the ferromagnetic particles having a narrow particle size distribution. .

7). Aggregation releasing property The ferromagnetic particles preferably have a small saturation magnetization of a single particle. Thereby, the magnetic aggregation at the time of kneading is easily released. In addition, it is easy to release magnetic aggregation by increasing the kneading time.

8). Production Method The ferromagnetic particles can be produced, for example, by a dry method or a wet method. The dry method is a method in which powder produced by a powder or gold method is physically broken to form particles, and the wet method is a method in which particles are generated in a liquid. In general, ferromagnetic particles prepared by a dry method have a wide particle size distribution. From the viewpoint of the above dispersion stability, if the filtering is performed according to the particle size distribution in order to narrow the particle size distribution of the ferromagnetic particles, it becomes 10% or less of the produced particles and becomes an expensive particle. Therefore, it is preferable to produce the ferromagnetic particles by a wet method.

9. Material Examples of granular ferromagnetic particles that can be produced by a wet method include magnetite, Ni—Zn ferrite, Mn—Zn ferrite, and iron. The attractive force of the ferromagnetic particles that are magnetically adsorbed in the gap between the shaft member and the bearing largely depends on the ratio of the saturation magnetic flux density to the coercive force of the ferromagnetic particles. Magnetite particles are preferred because the ratio of the saturation magnetic flux density to the coercive force is as large as 0.8 to 0.9 Am ² / kg / Oe, depending on the size of the particles. Magnetite particles obtained by a wet method have a polyhedral shape close to a sphere, and are preferable from the viewpoint of releasing magnetic aggregation. In the wet method, particles are deposited while oxygen gas is sprayed onto a dissolved solution such as iron sulfate. Therefore, smaller particles are deposited in a shorter time, and the size of the deposited particles is uniform. Moreover, although the oxidation start temperature depends on the size of the particles, for example, the oxidation start temperature of magnetite particles having an average particle size of 0.15 μm is around 250 ° C. The magnetic Curie point of the magnetite particles is 620 ° C. Thus, magnetite particles are preferable from the viewpoint of thermal stability.

10. Magnetite Particle Size When using magnetite particles, the average particle size is preferably 0.3 μm or less, more preferably 0.15 μm or less, and even more preferably 0.08 μm or less. That is, the smaller the average particle diameter of the magnetite particles, the smaller the saturation magnetization of the single particles, and thus the magnetic aggregation of the particles can be easily released. As a result, the ferromagnetic particles can be deagglomerated to a single particle or a state close to a single particle, so that the ferromagnetic particles present in the gap between the shaft member and the bearing attack the shaft member and the bearing. Can be prevented, and a solid lubricating action can be exhibited. Furthermore, for example, when measuring the particle size distribution of magnetite particles having an average particle size of 0.15 μm, it has been confirmed that the standard deviation of the particle size with respect to the average particle size is 0.2 and the particle size distribution is also narrow. .

11. Physical properties of magnetite particles An example of the physical properties of such magnetite particles is shown in Table 1. These magnetite particles can be preferably applied as ferromagnetic particles. The larger the BET value, the more gas or liquid can accompany the surface, and the BET value of the magnetite particles is preferably 10 m ² / g or more, preferably 21.5 m ² / g or more. More preferably. For example, when magnetite particles having a BET value of 21.5 m ² / g are used as the impregnation material, the adsorption amount of water can be increased to 2.8 wt% by leaving the magnetite particles in a supersaturated water vapor atmosphere. .

  The metal or alloy that forms the sintered body of the metal bearing according to the present invention can be the same as the conventional metal bearing, and is not particularly limited. That is, conventional sintered metal bearings are made of iron, iron-carbon, iron-copper, iron, etc. from the viewpoints of load resistance, impact resistance, crushing strength, caulking, durability, manufacturing cost, etc. -Copper-carbon system, iron-copper-tin system, etc. are applied according to a use. Since these metals and alloys are both ferromagnetic, they can be preferably applied to metal bearings using ferromagnetic particles.

  Although the dispersion solvent used for the metal bearing according to the present invention is not particularly limited, for example, those having the following characteristics are preferable.

1. Lubricity The dispersion solvent preferably disperses the ferromagnetic particles in the pores, and after moving to the bearing surface, preferably exhibits a liquid lubricating action on the sliding contact surface between the bearing surface and the shaft member. Thereby, it is possible to prevent the sliding contact surface between the bearing surface and the shaft member from being damaged.
Further, it is preferable that the dispersion solvent has a smaller viscosity change with temperature. Thereby, since lubricity can be ensured in a wide temperature range, the dispersed solvent can smoothly move in the gap between the bearing surface and the shaft member regardless of the temperature of the dispersed solvent. Therefore, it is possible to prevent the generation of abnormal noise, suppress sudden heat generation on the sliding contact surface, and make it difficult to cause hydrolysis and thermal decomposition of the dispersion solvent.
Furthermore, the dispersion solvent is preferably one having thermal stability. That is, the dispersion solvent is preferably one that does not chemically change even at high temperatures, such as thermal decomposition and hydrolysis. Thereby, lubricity can be maintained in the sliding contact surface between the bearing surface and the shaft member. Specifically, the dispersion solvent is preferably one that is difficult to be thermally decomposed and hydrolyzed at 150 ° C., more preferably one that is difficult to thermally decompose and hydrolyze at 190 ° C., and one that is difficult to thermally decompose and hydrolyze at 200 ° C. or higher. Further preferred. If it is such a dispersion solvent, it can be applied to automotive applications and the like used even in a high temperature atmosphere.

2. Dispersibility of ferromagnetic particles The dispersion solvent is preferably lipophilic (or hydrophobic) or nonpolar. In particular, in the case of dispersing hydrophilic ferromagnetic particles accompanied by polar alcohol or the like, the dispersion solvent improves the dispersibility as the lipophilicity increases, and contributes to the stable dispersion as the polarity is low. .

3. Hygroscopic Dispersion solvent preferably has low hygroscopicity, and more preferably has no hygroscopicity. Moisture dissolved in the dispersion solvent becomes a water vapor balloon near the bearing surface due to the temperature rise of the bearing surface, and moves with the dispersion solvent to the bearing surface. Thereby, the dispersion solvent is wasted, and the self-oiling property of the ferromagnetic particles is hindered. Further, moisture promotes the hydrolysis reaction of the dispersion solvent on the bearing surface. For this reason, the one where the ratio of the water | moisture content which exists in a dispersion | distribution solvent is low is preferable.

  Examples of the dispersion solvent include (1) polyoxyethylene glycerin fatty acid ester obtained by addition polymerization of ethylene oxide to mono fatty acid glycerin, and (2) polyoxyethylene fatty acid obtained by addition polymerization of ethylene oxide using sorbitan fatty acid ester using an alkali catalyst. Ester, (3) Ether oxide type nonionic surfactant such as polyoxyethylene sorbitol fatty acid ester which is added with ethylene oxide to sorbitol and then esterified with fatty acid, (4) Polyester glycol and fatty acid are esterified Alternatively, polyethylene glycol fatty acid mono (di) ester obtained by addition polymerization of ethylene oxide to higher fatty acid, and (5) polyglycerin fatty acid ester obtained by esterifying fatty acid with polyglycerol obtained by condensing glycerin using an alkali catalyst. And Le type nonionic surfactant, polyalphaolefins, polyalkylene glycols can be employed including synthetic oils such as polyol diester. Since these are highly lipophilic and nonpolar solvents, they can stably disperse ferromagnetic particles with alcohol or the like as a liquid.

  Among these, synthetic oils such as polyalphaolefin, polyol diester, and polyalkylene glycol are more preferable because they are excellent in properties such as lubricity in addition to the dispersibility of the ferromagnetic particles. For example, polyalphaolefin is preferable because it can easily increase the viscosity index and has a small change in kinematic viscosity over a wide temperature range. Polyalphaolefin has a low pour point, can suppress an increase in kinematic viscosity at low temperatures, and does not have a hygroscopic property, so that hydrolysis reaction hardly occurs.

Polyalphaolefins, alpha-olefin CH ₃ excellent pour point and viscosity index (CH _{2) 7} CH = _C a CH ₂ polymerized by ethylene _{10 H 21 - (CHC 8 H} 17 CH 2) n-H of the formula It is a synthetic oil having The polyalphaolefin has properties such as viscosity, boiling point, and thermal decomposability that change depending on the degree of polymerization. For example, the polyalphaolefin has a molecular weight of about 500 and a degree of polymerization of at least one of those having a degree of polymerization of 2 and 3. It is particularly preferable to have a certain component as a main component because it exhibits the following characteristics.

  The thermal decomposition temperature of this polyalphaolefin is around 230 ° C., and the temperature at which thermal decomposition starts is around 200 ° C. For this reason, even after oozing into the gap between the bearing and the shaft member as a dispersion solvent, thermal decomposition is difficult. The boiling point exceeds 200 ° C. even at 0.1 atm and hardly evaporates at atmospheric pressure. For this reason, even after oozing into the gap between the shaft and the bearing, it can exist as a liquid. Since the viscosity index is as large as 138, the lubricity can be maintained in a wide temperature range. Since the kinematic viscosity at 40 ° C. is as low as 31 cSt, for example, even when the ferromagnetic particles are impregnated into the pores at a low pressure, the dispersibility is not impaired. The pour point is −57 ° C., an increase in kinematic viscosity at −30 ° C. can be suppressed, and it can be used as a lubricating oil even at an extremely low temperature of −30 ° C.

  In the metal bearing according to the present invention, the ferromagnetic particles preferably have a surface modifier on the surface. That is, by modifying the surface of the hydrophilic ferromagnetic particles to be hydrophobic with the surface modifier, the dispersibility of the ferromagnetic particles in the hydrophobic dispersion solvent can be improved and the ferromagnetic particles can be improved. The gas that should surround the particles can be prevented from being released from the ferromagnetic particles.

  Further, the surface modifier preferably has heat decomposition resistance, and specifically, the surface modification agent preferably has a thermal decomposition rate of 5% or less with respect to the temperature rise of the bearing surface due to sliding with the shaft member. As a result, the surface modifier is adsorbed on the surface of the ferromagnetic particles even after moving to the bearing surface. That is, if the surface modifier is not thermally decomposed after moving to the bearing surface, the property as the surface modifier can be maintained, so that the surface modifier is adsorbed on the surface of the ferromagnetic particles on the bearing surface, It can be combined with a dispersion solvent. Therefore, when such a surface modifier is applied, the surface modifier 6 is also ferromagnetic on the sliding contact surface 3 between the bearing 1 and the shaft member 2 as schematically shown in FIG. Chemisorbed on the surface of the particles 4 and the dispersion solvent 5. As described above, since the dispersion solvent 4 is adsorbed on the surface of the ferromagnetic particles 4 via the surface modifier 6, the ferromagnetic particles 4 are not only solid-lubricated but also are liquids by the adsorbed dispersion solvent 4. This also has a lubricating action.

  As the surface modifier, a conventionally known surface modifier such as a surfactant or a coupling agent or a magnetic ionic liquid can be applied. As the surfactant, for example, a fatty acid ester, a derivative of a fatty acid ester, a nonionic anionic surfactant of a phosphate ester, or the like can be used. Since these have a hydrophilic group and a hydrophobic group, the hydrophilic group forms a hydrogen bond with the surface of the ferromagnetic particle, and the hydrophobic group interacts with the molecular chain of the dispersion solvent. Thus, the dispersibility of the ferromagnetic particles is improved, and when the gas adsorbed on the ferromagnetic particles thermally expands, it works together with the dispersion solvent to suppress the thermal expansion. As such a phosphate ester, for example, an ester composed of a phosphate monoester and a phosphate diester produced by reacting polyoxyethylene isotridecyl alcohol obtained by adding ethylene oxide to isotridecyl alcohol with anhydrous phosphoric acid. A mixture of can be applied. Further, from the viewpoint of thermal decomposition resistance, for example, if it is a carboxylic acid ester having an isopropoxy group as a hydrophilic group and a following formula (1) as a hydrophobic group, the thermal decomposition rate at 180 ° C. is 2%, The thermal decomposition rate at 200 ° C. is 4%. In addition, if the phosphoric acid ester has the same hydrophilic group and the following formula (2) as a hydrophobic group, the thermal decomposition rate at 180 ° C. is 2%, and the thermal decomposition rate at 200 ° C. is 5%. Such a surfactant can be preferably applied since it has excellent thermal decomposition resistance.

  Such higher fatty acid esters have a thermal decomposability of 2 to 5 wt% or less even at a temperature of 200 ° C. or higher. On the other hand, the maximum temperature of the bearing surface of various motors for automobiles is between 120 ° C. and 150 ° C. Even if the temperature rises to such a temperature, there is almost no change in the composition of the surfactant. Also, the lubricating action of the liquid is not lost on the bearing surface. In addition, these surfactants form an adsorption film on the surface of iron-based, iron-copper-based, iron-copper-tin-based metals and alloys, and thus have a function as an oil-based agent, and the bearing surface is a shaft. Adhesive wear due to direct contact with the member does not occur.

  Even when a coupling agent is used as the surface modifier, the same effect as that obtained when a surfactant is used can be obtained. For example, a titanium coupling agent can be preferably applied. Since the titanium coupling agent has a hydrolyzable hydrophilic functional group and a hydrophobic functional group, the hydrophilic group hydrolyzes with the hydroxyl group adsorbed on the ferromagnetic particle, and the ferromagnetic particle Hydrophobic groups are formed. Thereby, the ferromagnetic particles can be stably dispersed in the hydrophobic dispersion solvent.

  Although it does not specifically limit as a titanium coupling agent, For example, what is shown to following formula (3)-(5) is applicable preferably. In the following formulas (3) to (5), for example, the carbon number of the alkyl chain is not particularly limited.

  In addition, when using the titanium coupling agent shown to the said Formula (3), since SP value is 8.1, it is preferable to use fatty acid ester with SP value of 8-9 as a dispersion solvent. Further, the titanium coupling agent shown in the above formula (4) has an SP value of 9.2, and the titanium coupling agent shown in the above formula (5) has an SP value of 9.6. When the titanium coupling agent is used, it is preferable to use a fatty acid ester having an SP value of 9 to 10 as the dispersion solvent.

  A silane coupling agent can also be used as the coupling agent. The silane coupling agent is not particularly limited, but preferably has a long-chain alkyl having high affinity with the dispersion solvent, and includes decyltrimethoxysilane, hexyltrimethoxysilane represented by the following formulas (6) to (8), Examples thereof include phenyltriethoxysilane. These silane coupling agents have high boiling points of 132 ° C / 10 mmHg, 202 ° C / 10 mmHg, and 236 ° C / 10 mmHg, respectively, and do not evaporate on the bearing surface. Of course, the carbon number of the alkyl chain and the carbon number of the alkoxy group of these silane coupling agents can be arbitrarily changed.

  When the silane coupling agent is used, the silane coupling agent is made into an aqueous solution or an alcohol solution, added to the ferromagnetic particles with moisture absorption or alcohol, and stirred for about 60 minutes. Thereafter, the silane coupling agent is adsorbed on the surface of the ferromagnetic particles by being left at a temperature lower than the boiling points of water and alcohol, and the ferromagnetic particles are dispersed in the dispersion solvent. In addition, since phenyl triethoxysilane has high hydrophobicity, it is dissolved in an acetic acid water-alcohol solvent, for example.

  Furthermore, a fatty acid can also be used as a coupling agent. That is, it is possible to stably disperse the ferromagnetic particles in the dispersion solvent by reacting the fatty acid with the hydroxyl group adsorbed on the ferromagnetic particles and using a fatty acid having an HLB value close to that of the fatty acid as the dispersion solvent. it can.

As the magnetic ionic liquid is not particularly _{limited, [Fe X M Y N Z} Cl 4] n- ( where, M, N are each a transition metal atom, x + y + z = 1 , n is x, y, the z It is possible to use those having at least one kind of anion selected from the anions represented by: Specifically, it has [FeCl ₄ ] ⁻ where x = 1, y = z = 0, and n = 1 as anions, and 1-ethyl-3-methylimidazolium, 1-butyl- 3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-decyl-3-methylimidazolium iron (III) chloride 1-ethyl-3-methylimidazolium, iron (III) chloride 1 Examples include -butyl-3-methylimidazolium, 1-octyl-3-methylimidazolium iron (III) chloride, and 1-decyl-3-methylimidazolium iron (III) chloride. Since such a magnetic ionic liquid can be magnetically adsorbed and coated on the ferromagnetic particles, the ferromagnetic particles can be dispersed in the dispersion solvent. The 1-position alkyl group is not particularly limited, but a higher carbon number is preferable because the degree of hydrophobicity is increased, and the 1-position alkyl group preferably has 6 to 20 carbon atoms.

  Further, since the thermal decomposition temperature of the magnetic ionic liquid is 280 ° C., the magnetic ionic liquid is magnetically adsorbed to the ferromagnetic particles without deteriorating the properties even after moving to the bearing surface. Further, since the magnetic ionic liquid has almost no vapor pressure, it does not evaporate even after moving to the bearing surface. For this reason, on the sliding contact surface between the bearing surface and the shaft member, the lubricating action of the ferromagnetic particles can be increased by the lubricating action of the liquid by the magnetic ionic liquid.

  As described above, when the surface modifier is not chemically altered even in the environment of the gap between the bearing surface and the shaft member, the ferromagnetic fine particle group is discharged into the gap between the bearing surface and the shaft member. Again, the surface modifier surrounds the periphery of the group of ferromagnetic fine particles and combines with the dispersion solvent to disperse the group of ferromagnetic fine particles. As a result, even if the lubrication state in the gap becomes boundary lubrication, the presence of the surface modifier and the dispersion solvent prevents the metals from directly contacting each other, and the cohesive wear of the bearing surface caused by this does not occur. Even if the bearing surface receives excessive stress from the shaft member, the presence of the dispersion solvent surrounding the ferromagnetic fine particles causes a lubrication phenomenon in which the ferromagnetic fine particles slide better, resulting in a strong gap in the gap between the bearing and the shaft member. The lubricating action of the magnetic particles can be increased.

  The liquid accompanied by the ferromagnetic particles present in the dispersion solvent has a boiling point lower than that of the main component of the dispersion solvent, and can be vaporized in the dispersion solvent. The gas and liquid accompanied by the ferromagnetic particles are not particularly limited, but are preferably selected according to the operating environment temperature of the bearing and the temperature rise of the bearing surface by sliding with respect to the shaft member. Preferably has a boiling point lower than the highest temperature reached on the bearing surface. In other words, vaporization is possible even when the temperature of the bearing surface is lower than the boiling point of the liquid, but if a liquid whose boiling point is lower than the highest temperature of the bearing surface is selected, the bearing surface is caused by sliding with the shaft member. The liquid can be surely vaporized by raising the temperature. In addition, when using the liquid whose boiling point is higher than the temperature of a bearing surface, the same effect can be acquired by providing the apparatus for heating a bearing surface separately.

  When the range of the operating environment temperature and the temperature of the bearing surface is wide, a plurality of types of gases or liquid mixtures having different boiling points can be selected. A plurality of types of gases or liquids are mixed in accordance with their vapor pressures so that they can correspond to each other in the temperature range, and further, the gases or liquids are accompanied by the ferromagnetic particles at a rate corresponding to the temperature frequency of the bearing surface. Therefore, even if the temperature of the bearing surface changes due to sliding contact, the ferromagnetic particles can be efficiently moved to the bearing surface according to the temperature range and temperature frequency of the bearing surface. Further, both the gas and the liquid may be accompanied by the ferromagnetic particles.

  For example, the maximum average temperature on the bearing surface of a motor motor bearing is 150 ° C. Therefore, when a liquid is caused to accompany the ferromagnetic particles, the ferromagnetic particles are surely discharged to the bearing surface of the sintered body if the boiling point is in a temperature range reaching 130 ° C. Then, the temperature range from room temperature to 130 ° C. is divided into 5 to 6 regions every 20 ° C., and a liquid having a boiling point in each temperature region is accompanied with the ferromagnetic particles. Thus, if the motor operates within a temperature range of −30 ° C. to 120 ° C., the ferromagnetic particles can be discharged to the bearing surface of the sintered body. If the temperature range from room temperature to 130 ° C. is further subdivided, the liquid accompanying the ferromagnetic particles can efficiently move the ferromagnetic particles to the bearing surface.

  Further, when the operating temperature of the bearing is an extremely low temperature of −30 ° C. or lower, it is difficult to discharge ferromagnetic particles to the bearing surface even with a liquid having a boiling point close to room temperature. Therefore, when a product incorporating a bearing is started under such extremely low temperature conditions, there should be no ferromagnetic particles or dispersed solvent on the bearing surface until the temperature exceeds a certain temperature due to sliding with the shaft member. become. For this reason, it is preferable to leave the bearing at a temperature equal to or higher than room temperature for a certain period of time before use and to allow the ferromagnetic particles to exude to the bearing surface in advance. For example, if the bearing is incorporated in a product after allowing some of the ferromagnetic particles to ooze out on the bearing surface in advance for 30 minutes at 60 ° C., good lubricity can be obtained from the start. Further, the same effect can be obtained by bringing gas into the ferromagnetic particles. That is, for example, when accompanied by a liquid that becomes a gas at a temperature lower than the use start temperature, the balloon surrounds the ferromagnetic particles at the start, and the pressure of the balloon increases immediately after the start, so the ferromagnetic particles are moved to the bearing surface. Can be made.

  Multiple types of gases and liquids to be adsorbed on ferromagnetic particles can be used with a single ferromagnetic particle accompanied by a plurality of gases and liquids, or a single ferromagnetic particle with a different type of gas or liquid. It can be arbitrarily selected depending on the compatibility of the gas and liquid to be mixed.

  As a means for bringing a gas or a liquid into the ferromagnetic particles, it is preferable to make the ferromagnetic particles exist in an impregnated or adsorbed state. Thereby, even if the liquid is vaporized and the gas is thermally expanded, it can move to the bearing surface with the ferromagnetic particles without being separated from the ferromagnetic particles.

  For example, since magnetite has a hydroxyl group on its surface, it adsorbs many organic solvents such as water, alcohols, ethers, and ketones. In the temperature range from room temperature to 130 ° C., when adsorbed on magnetite and considering the temperature difference of the difference in boiling point, for example, acetaldehyde (boiling point: 20.2 ° C.), diethyl ether (boiling point: 34.5 ° C.), Dichloromethane (boiling point: 40.2 ° C), ethyl formate (boiling point: 54.5 ° C), methanol (64.7 ° C), ethyl acetate (76.8 ° C), ethanol (78.5 ° C), cyclohexane (81.4 ° C), 1-propanol (boiling point: 97.4 ° C) ), Water (boiling point: 100 ° C), 1-butanol (boiling point: 117.6 ° C), 2-methoxyethanol (boiling point: 124.5 ° C), isobutyl acetate (boiling point: 126.3 ° C), isopentyl alcohol (boiling point: 130.8 ° C), etc. Can be mentioned. By combining these liquids in consideration of the temperature difference in boiling point, the ferromagnetic particles can be discharged to the bearing surface in a wide temperature range.

  An example of a method for manufacturing a metal bearing according to the present invention will be described by taking magnetite, which is a ferromagnetic particle, as an example. First, magnetite particles are prepared. This magnetite is a fine particle of submicron or less, and is magnetically aggregated when used as a particle. Then, magnetite is impregnated or adsorbed with at least one of gas and liquid.

  When a coupling agent is used as the surface modifier, for example, when adding magnetite to the dispersion solvent, the coupling agent is mixed at a ratio of 2 wt%, preferably 3 wt% or more with respect to the magnetite. Stir. As a result, the adsorbed hydroxyl group on the surface of the magnetite particles hydrogen bonds with the hydrophilic group of the coupling agent, and the hydrophobic group of the coupling agent interacts with the long chain of the dispersion solvent, so that the magnetite is stably dispersed in the dispersion solvent. Can be made. The same method can be used when a surfactant is used as the surface modifier.

  When using a magnetic ionic liquid as the surface modifier, first, the magnetic ionic liquid is diluted with a liquid that accompanies the ferromagnetic particles. Specifically, for example, alcohol is dissolved in the magnetic ionic liquid at a rate of 10 wt%. At this time, for example, alcohol having a boiling point of 60 ° C. to 130 ° C. may be used according to the temperature of the bearing surface. Also, a plurality of types of alcohols can be used. For example, a mixed solution of 6 wt% methanol and 4 wt% 1-butanol can be used. Next, a magnetic ionic liquid solution is added to the magnetically agglomerated magnetite and stirred well to magnetically adsorb the magnetic ionic liquid on the magnetite.

  The magnetite thus obtained is dispersed in a dispersion solvent. In order to reduce the degree of aggregation of magnetically agglomerated magnetite, it is necessary to generate a shearing force, a compressive force, and a tensile force at the agglomerated portion of the magnetite when mixing the magnetite with a dispersion solvent. For this reason, it is preferable to raise the mixing ratio of a magnetite and a dispersion solvent rather than the original mixing ratio of a magnetite and a dispersion solvent. That is, by mixing and kneading a high concentration of magnetite and a dispersion solvent using a surface modifier such as a surfactant, the dispersion solvent is adsorbed on the magnetite. As a result, the magnetite and the dispersion solvent having a high viscosity are adsorbed. And a mixture is formed. When such high-concentration magnetite and the dispersion solvent are filled in a stirring device such as a pressure kneader and kneaded, the dispersion solvent is further adsorbed on the magnetite together with kneading, and the viscosity increases. After the dispersion solvent adsorption on the magnetite converges and the increase in viscosity converges, when the kneader is further rotated, various stresses such as shear force, compressive force and tensile force act on the magnetite agglomerated part efficiently. Therefore, the agglomeration of magnetite is released, and a magnetite having a low agglomeration degree with a magnetite particle size of 200 nm or less can be obtained. In this way, the mixed solution in which the magnetite having a low degree of aggregation is dispersed is diluted with a dispersion solvent as necessary, and is impregnated into the pores of the sintered body of metal or alloy at a low pressure. By such a method, magnetite can be confined in the pores with at least one of gas and liquid.

Even if the degree of agglomeration of the magnetite is reduced by kneading with a pressure kneader, stress will not be directly applied to the agglomerated part of the particles when the degree of agglomeration is reduced. However, magnetite is still magnetically agglomerated. When such magnetite is discharged to the bearing surface, it receives a stress corresponding to the surface condition between the bearing surface and the shaft member. For example, when the convex part of the shaft member and the convex part of the bearing face each other and the load is transmitted from the shaft member side to the bearing side, the agglomerated magnetite is attracted to the slight gap formed on the convex part of both by magnetic adsorption. It is sandwiched and receives stress from the shaft member side. As a result, the agglomerated particles become a group of particles having a lower degree of aggregation. At this time, many stresses act as a force for solving the magnetic aggregation. The conventional solid lubricating action, for example, solid lubricating action in graphite particles is due to its own slip fracture, but the solid lubricating action in the present invention solves the agglomerated particles by direct stress acting on the contact part of the agglomerated particles. Therefore, it is a solid lubricating action by the aggregation of the particles being released by the sliding of the particle group. As described above, the aggregated particle group discharged to the bearing and the shaft member receives various stresses, gradually lowers the degree of aggregation of the particle, and forms a coating film composed of the magnetite fine particle group.
Even in such a case, there is a possibility that the magnetite attacks the shaft member and the bearing if the degree of magnetic coagulation of the magnetite discharged to the bearing surface is large. For this reason, it is preferable to lengthen the kneading time and release the aggregation of the magnetite to a single particle or close to a single particle.

Examples will be described below.
(Impregnation material 1)
As the ferromagnetic particles, magnetite particles having an average particle size of 0.08 μm, a standard deviation of the particle size distribution of 0.05 μm, and a BET value of 34 m ² / g were used.
As a dispersion solvent, a polyalphaolefin having a viscosity index of 138, a kinematic viscosity at 40 ° C. of 31 cSt, a kinematic viscosity at 100 ° C. of 5.8 cSt, a pour point of −57 ° C. and a molecular weight of about 500 was used.
A Ti-based coupling agent represented by the above formula (3) was used as the surface modifier.

  The magnetite particles were allowed to stand for 30 minutes in an atmosphere of supersaturated water vapor at 121 ° C. and 2 atm to absorb moisture. A Ti-based coupling agent was added to the magnetite particles at 3.5 wt%, and the mixture was kneaded for 24 hours while adding polyalphaolefin to a very small amount up to 10 wt%. Thereafter, polyalphaolefin was added with mixing until the total weight was 65 wt%, to prepare an impregnated material.

(Impregnation material 2)
The same ferromagnetic particles, dispersion solvent, and surface modifier as those used in Example 1 were used.
And the solution which mixed methanol (boiling point 64.5 degreeC), 1-butanol (boiling point 117.4 degreeC), and water so that it might become 1: 2.5: 2 by weight ratio was prepared. The solution was cooled to 10 ° C., and magnetite particles were immersed in this solution and left for 30 minutes. Ti-based coupling agent was added at 3.5 wt% to magnetite particles adsorbed with alcohol in a temperature environment of 10 ° C., and kneaded for 24 hours while adding polyalphaolefin to a very small amount up to 10 wt%. Thereafter, polyalphaolefin was added at 10 ° C. with mixing until 65 wt% with respect to the total weight to prepare an impregnated material.

  In order to visualize and observe the behavior of the impregnated materials 1 and 2 produced, instead of impregnating these impregnated materials into the internal pores of the sintered metal body with low pressure, the impregnated materials 1 and 2 are placed in the respective beakers. Was placed in an oil bath, and the behavior of the impregnated material was observed by changing the temperature of the oil bath. The results are shown in Tables 2 and 3. Table 2 shows the results of experiments with the oil bath temperature rise and fall rates set to 1 ° C / min. Table 3 shows the results with the oil bath temperature change rate set to 0.1 ° C / min. It is the result. The results in Tables 2 and 3 show the behavior at the moment when the described temperature is reached.

  In the impregnating material 1, bubbles were generated from the time when the temperature was raised to 100 ° C. This is because the water vapor pressure has increased to near atmospheric pressure. In Table 2, bubbles were continuously generated in the temperature lowering process from 170 ° C to 130 ° C. Thereafter, the generation frequency of bubbles decreased, and the generation of bubbles stopped at 100 ° C. In Table 3, water vapor was completely consumed in the process of reaching the temperature of 140 ° C. during the temperature lowering process. These results are considered to be because the water vapor adsorbed on the magnetite particles was consumed continuously and completely consumed in the temperature lowering process. It is considered that the reason why the bubbles are generated depends on the total time of exposure to a temperature higher than the boiling point of water.

  In the impregnating material 2, bubbles were generated from the time when the temperature was raised to around 70 ° C. This is because the vapor pressure of methanol has increased to around atmospheric pressure. In Table 2, bubbles were continuously generated in the temperature lowering process up to 100 ° C. Thereafter, the generation frequency of bubbles decreased, and the generation of bubbles stopped at 70 ° C. In Table 3, bubbles were continuously generated until the temperature decreased to 150 ° C. In any case, it was found that the bubble generation time was extended as compared with the case where the impregnated material 1 was used. This is considered to be due to mixing methanol and 1-butanol, and sharing the generation frequency of bubbles at 70 to 170 ° C. between methanol, water and 1-butanol.

Next, impregnated materials 1 and 2 were low-pressure impregnated into a metal sintered body to form bearing parts, each of which was attached to a motor, and a continuous operation test was performed by changing the operation temperature and operation time of the motor. The operating conditions of the motor were set to be 72 minutes at 20 ° C, 144 minutes at 40 ° C, 360 minutes at 55 ° C, 504 minutes at 75 ° C, 288 minutes at 90 ° C, and 72 minutes at 120 ° C. One cycle was repeatedly operated continuously.
As a result, no abnormal noise or odor was observed from the sliding surface even when 50 cycles were repeated in any case. In Example 1, an abnormal noise was generated at the stage of entering 55 cycles, and then an abnormal odor was also generated. In Example 2, an abnormal noise was generated at the stage of entering 75 cycles, and then an abnormal odor was also generated.

  As a comparative example, when a motor using a conventional bearing was operated under the same conditions, an abnormal noise was generated at the stage of entering 5 cycles, followed by an abnormal odor.

  As described above, the operating temperature of the conventional metal bearing is -30 ° C to slightly over 100 ° C, whereas the metal bearing according to the present invention is used as a bearing component in the temperature range of -40 ° C to 120 ° C. Can do. Furthermore, it has been found that in a temperature cycle environment in which the temperature continuously changes in a temperature range of 20 ° C. to 120 ° C., the operating life is 10 times or more that of a conventional bearing.

  Therefore, the metal bearing according to the present invention can be applied to various bearing parts such as a vehicle electromagnetic valve and a motor bearing part.

The schematic diagram which shows the state of the ferromagnetic particle in the sliding contact surface of the metal bearing and shaft member which concern on this invention

Explanation of symbols

1 Bearing 2 Shaft member 4 Ferromagnetic particles 5 Dispersing solvent

Claims (11)

In a metal bearing comprising a sintered body having a bearing surface slidable with respect to a shaft member, the main component being a metal or an alloy, and pores on the surface and inside,
A metal bearing comprising a dispersion solvent in the pores, wherein the ferromagnetic particles are present in the dispersion solvent with at least one of a gas and a liquid having a boiling point lower than that of the dispersion solvent.   The metal bearing according to claim 1, wherein the ferromagnetic particles have a surface modifier on the surface.   The metal bearing according to claim 2, wherein the surface modifier has a thermal decomposition rate of 5% or less with respect to a temperature rise of the bearing surface due to sliding with the shaft member.   The metal bearing according to claim 1, wherein the ferromagnetic particles are magnetite particles.   The metal bearing according to claim 4, wherein the magnetite particles have an average particle size of 0.15 μm or less. The metal bearing according to claim 4 or 5, wherein the magnetite particles have a BET value of 10 m ² / g or more.   The metal bearing according to claim 1, wherein the dispersion solvent is at least one synthetic oil selected from polyalphaolefin, polyol diester, and polyalkylene glycol.   2. The metal bearing according to claim 1, wherein the dispersion solvent is a polyalphaolefin, and the polyalphaolefin has, as a main component, one having a polymerization degree of 2 or 3 as a main component.   The metal bearing according to claim 2, wherein the surface modifier is at least one compound selected from a titanium coupling agent and a silane coupling agent.   The metal bearing according to claim 1, wherein the liquid is at least one liquid selected from alcohols having a boiling point in a temperature range of 60 ° C. to 130 ° C. and water.   When the temperature of the bearing surface is raised by sliding with the shaft member, the ferromagnetic particles move to the bearing surface, and a coating containing ferromagnetic particles as a main component is formed on the bearing surface. The metal bearing according to any one of 10.

Images