JP2008248975A - Sintered metal part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the sliding characteristics of a sintered metal sliding member impregnated with a lubricating oil, particularly those during the initial sliding. <P>SOLUTION: A bearing surface 4 in slidable contact with the outer peripheral surface of a shaft 2 to be supported is formed on the inner periphery of the sintered oil retaining bearing 1. A large number of surface opening holes 5 are present in the bearing surface 4, and a large number of dimples 6 are formed in the bearing surface. Such a second lubricant 7 that is not pulled into inner vacant holes 3 through the surface opening holes 5 in the dimples 6 is held on the dimples 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sintered metal part having a sliding surface, and more particularly to a sintered metal part impregnated with a lubricating oil.

  Conventionally, various machine parts, especially machine parts used in places that slide with other machine elements such as bearings and power transmission parts, are made of sintered metal and impregnated with lubricating oil etc. Sintered metal parts made to be used are preferably used.

  For example, a so-called sintered oil-impregnated bearing in which lubricating oil is impregnated into a sintered metal bearing is known as a sliding bearing constituting a motor spindle for information equipment (see, for example, Patent Document 1). .

In addition, as a sliding bearing having both liquid lubrication performance and solid lubrication performance, a sintered oil-impregnated bearing in which lubricating oil is impregnated inside and solid lubricant powder such as graphite or molybdenum disulfide is fixed on the surface layer portion. Is known (see, for example, Patent Document 2). Such a configuration aims to exhibit stable bearing performance even when the lubricating oil is insufficient in the bearing portion.
JP-A-10-281150 JP-A-8-20836

  By the way, the impregnation of the sintered oil into the sintered metal bearing is usually performed by immersing the sintered metal bearing in the lubricant under a reduced pressure environment (so-called vacuum impregnation). At this time, for example, if the impregnation operation is performed in a state where the lubricating oil is heated and the viscosity resistance is lowered, the lubricating oil easily enters the internal holes of the sintered metal bearing. However, in a product that has been impregnated by this method, there may be a case where there is no lubricating oil on the bearing surface during the initial sliding, and the lubricating action by the lubricating oil cannot be sufficiently obtained.

  That is, since the lubricating oil usually has a fiber expansion coefficient several hundred times that of a metal, after impregnating the heated lubricating oil, the product is cooled to the operating temperature (for example, room temperature), so that the shrinkage ratio is reduced. Large lubricants can be drawn into the sintered bearing, leaving no lubricant on the bearing surface. In this case, the shaft and the bearing are in sliding contact with each other, and a sufficient lubrication effect cannot be obtained. This causes an increase in friction, and there is a concern about generation of abnormal noise and vibrations, including wear of the bearing.

  Patent Document 2 proposes a sintered metal component blended with graphite or diverted molybdenum for the purpose of ensuring lubrication performance, but is still in direct contact sliding and is sufficient. It is hard to say that a good lubricating action is obtained.

  In view of the above circumstances, an object of the present invention is to improve the sliding characteristics of sintered metal parts impregnated with lubricating oil, particularly the sliding characteristics during initial sliding.

  In order to solve the above-mentioned problems, the present invention is a sintered metal part having a sliding surface, in which an internal hole is impregnated with a first lubricant, and is made to slide relative to a mating member. As the first lubricant impregnated in the internal holes oozes out on the sliding surface with the movement, a concave portion is formed on the sliding surface in the case of sliding through the mating member and the first lubricant. The sintered metal part is characterized in that the recessed portion is filled with a second lubricant which is not drawn into the internal hole through the opening existing on the surface of the recessed portion.

  As described above, according to the present invention, a lubricant (second lubricant) having a property different from that of the lubricant used by impregnating the inside of the sintered sliding member is arranged on a part of the sliding surface. Features. Specifically, a recess for holding the second lubricant is provided on the sliding surface, and a second lubricant having a property that is not drawn into the internal hole through the surface opening of the recess is selected. And used. According to such a configuration, a sliding lubrication state is ensured between the metal part and the counterpart member by the first lubricant (lubricant oil or the like) impregnated in the internal pores of the sintered metal part in a steady state. At the time of initial sliding, the sliding lubricant state is ensured between the metal component and the mating member by the second lubricant held in the recess. Therefore, even if the first lubricant does not remain on the sliding surface, the second lubricant held in the recess can be brought close to the normal sliding lubrication state. It is possible to suppress the occurrence of wear and abnormal noise in as much as possible.

  As the second lubricant retained in the recess, a lubricant having an arbitrary composition can be used as long as it is not drawn into the internal hole through the surface opening of the recess. For example, semi-solid (eg, gel) grease can be used. Of these, jelly-like lubricants exhibiting high deformation resistance and excellent shape retention are preferred.

  The second lubricant is preferably one that can stay in the recess against the pulling force into the internal holes caused by an arbitrary temperature change within the operating temperature range. As described above, the impregnated lubricant and sintered metal parts have a large difference in fiber expansion coefficient. Therefore, lubrication is not limited to cooling after impregnation, but is also affected by temperature changes within the assumed use (atmosphere) temperature range. This is because the agent may be drawn into the internal holes.

  The concave portion is not particularly limited as long as it has a shape capable of being filled and accommodated with the second lubricant. It may be intermittent or continuous. For example, a plurality of concave portions can be formed in a hole shape or a groove shape, and these hole portions or groove portions can be connected to each other. Considering the function as the sliding surface, it is preferable that a large number of dimples are formed on the sliding surface as the recesses. Of course, the second lubricant is arranged on the sliding surface. However, if the lubrication state and the sliding state by both the first and second lubricants are taken into consideration, the second lubricant is preferably slid. This is because it is preferable that they are evenly distributed on the moving surface.

  The sintered metal part having the concave portion and the second lubricant having the above-described configuration is suitable for, for example, a use in which a shaft inserted in the inner periphery is supported by a sliding surface provided on the inner periphery, that is, a sintered oil-impregnated bearing. Can be used.

  As described above, according to the present invention, it is possible to improve the sliding characteristics of the sintered metal part impregnated with the lubricating oil, particularly the sliding characteristics during the initial sliding.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  FIG. 1 shows a sintered oil-impregnated bearing 1 according to an embodiment of the present invention. The sintered oil-impregnated bearing 1 in the figure has a cylindrical shape and is formed of sintered metal. The sintered oil-impregnated bearing 1 has a large number of internal holes 3, and the internal holes 3 are impregnated with a lubricating oil as a first lubricant. On the inner periphery of the sintered oil-impregnated bearing 1, a bearing surface 4 that slides with the outer peripheral surface of the shaft 2 to be supported (one-dot chain line in the figure) is provided.

  FIG. 2A is an enlarged cross-sectional view of a region A in FIG. As shown in the figure, the bearing surface 4 has a large number of surface apertures 5, and with the relative rotation of the shaft 2, internal voids are formed through the surface apertures 5 of the bearing surface 4 facing the outer peripheral surface of the shaft 2. The lubricating oil retained in the hole 3 is oozed out. The bearing surface 4 is provided with a large number of dimples 6 in addition to the surface openings 5. The dimple 6 holds a second lubricant 7 that is not drawn into the internal hole 3 through the surface opening 5 of the dimple 6.

  The sintered oil-impregnated bearing 1 having the above configuration includes, for example, a step (a) of compacting a metal powder as a raw material, a step (b) of sintering a compacted body, and a step (c) of sizing the sintered body. And the step (d) of impregnating the lubricating oil and the step (e) of filling the dimple with the second lubricant. Here, the dimple 6 is formed in the sizing step (c). Hereinafter, each process will be described in detail.

(A) Powder compacting process First, the metal powder used as a raw material is filled in a molding die, and a compact compact having a shape close to that of a finished product is obtained by compression molding. As the raw material, for example, a material mainly composed of Fe or Fe-based alloy metal powder is used. Of course, other metal powders such as Cu or Cu-based alloy metal powder can also be used as the raw material. What mixed the seed | species metal powder can also be used as a raw material. Moreover, you may use as a raw material what added powdery solid lubricants, such as graphite and molybdenum disulfide, as needed.

(B) Sintering process The compacting body obtained by the said process (a) is sintered by heating to the sintering temperature of the metal powder used as a raw material, and a sintered compact is obtained. Depending on the type of metal powder used, the sintering operation can be performed in a non-carburizing atmosphere in order to avoid the carburizing action due to sintering.

(C) Sizing process The sintered compact obtained by the said process (b) is shaped into a predetermined shape by giving a pressing force using a suitable metal mold. In this embodiment, although not shown in the drawings, by using a sizing pin that shapes the inner peripheral surface of the sintered body and having a protrusion having a shape corresponding to the dimple 6 on the outer periphery of the sintered body, A bearing surface 4 having a surface opening 5 of an appropriate size on the periphery is formed, and a plurality of dimples 6 to hold the lubricant 7 are formed on the bearing surface 4.

(D) Impregnation step The sintered body finished in the shape of the finished product (the shape shown in FIG. 1) through the steps (a) to (c) is impregnated with lubricating oil. Specifically, the sintered body is evacuated in a suitable container, and the sintered body is immersed in a lubricating oil bath filled with the lubricating oil, so that the lubricating oil is introduced into the internal holes 3. Impregnate. At this time, since the impregnation of the lubricating oil into the internal holes 3 is performed reliably and in a short time, the impregnation operation can be performed in a state where the lubricating oil is heated.

  And after an impregnation operation | work, an oil removal operation | work is performed using a suitable oil removal apparatus. Thereby, the excess lubricating oil adhering to the surface is removed while the lubricating oil impregnated in the internal holes 3 is left as it is.

(E) Lubricant Filling Step into Dimples Lubricant 7 is filled into dimples 6 formed on the inner periphery of the oil-containing sintered body obtained through the step (d). As the lubricant 7 filling the dimple 6, a lubricant that is not drawn into the internal hole 3 through the surface opening 5 of the dimple 6 is selected and used. In this case, it is important to design the dimple 6 including the processing method and select the lubricant 7 in consideration of the relationship between the aperture diameter of the surface aperture 5 and the pulling action of the lubricant 7.

  In the sintered oil-impregnated bearing 1 having the above-described configuration, the lubricating oil retained in the internal hole 3 oozes out onto the bearing surface 4 through the surface opening 5 with the relative rotation of the shaft 2. As a result, a lubricating oil film is formed between the shaft 2 and the sintered oil-impregnated bearing 1, and the shaft 2 is rotatably supported via the lubricating oil film.

  Further, as shown in FIG. 2B, when the relative rotation of the shaft 2 is started, the lubricant 7 held on the dimple 6 on the bearing surface 4 is preferentially brought into contact with the shaft 2 so that the shaft rotates relatively. The sliding lubrication state is ensured between the two. Therefore, even when the lubricant does not ooze out at the start of rotation, direct contact sliding between the shaft 2 and the bearing surface 4 can be avoided as much as possible. Generation of abnormal noise can be suppressed as much as possible.

  Further, as described above, for the convenience of the impregnation work on the sintered oil-impregnated bearing 1, after the impregnation work, the lubricating oil impregnated in a high temperature state is cooled and drawn into the internal holes 3, and at the start of use, In particular, when used for the first time after production, there may be a case where no lubricating oil remains on the bearing surface 4. However, even in such a case, the sliding state with respect to the shaft 2 can always be maintained as smoothly as possible by the action of the lubricant 7 held in the dimple 6, so that wear and noise during the initial sliding can be maintained. The occurrence of vibration can be suppressed as much as possible. In addition, since it is not necessary to perform a familiar operation after manufacturing, the time and cost required for such work can be reduced. Moreover, if the lubricant 7 is held on the inner periphery of the sintered oil-impregnated bearing 1 as in this embodiment, there is no fear that the lubricant 7 will be scattered by the centrifugal force accompanying the rotation.

  Further, in this way, if taking in the lubricating oil accompanying cooling is taken into account, for example, any internal temperature 3 within the operating temperature range via the surface opening 5 of the dimple 6 can be changed. The second lubricant 7 should not be selected and used so as not to be drawn into. For example, since this kind of sintered oil-impregnated bearing 1 is assumed to be used in the range of −40 ° C. to 120 ° C., the maximum temperature drop (cooling) within this temperature range is assumed. Even if it exists, it is preferable to use the lubricant 7 which can remain in the dimple 6 against the pulling force to the internal hole 3 generated through the surface opening 5. Alternatively, even when the lubricating oil held in the internal holes 3 is heated and expanded due to the temperature rise and acts to push out the lubricant 7 through the surface openings 5 of the dimples 6, It is also important that it can be held without being extruded.

  The lubricant 7 that can be used is not particularly limited as long as the above conditions are satisfied. For example, various lubricants such as high-viscosity grease can be used, and among them, a gel-like lubricant, particularly a jelly-like lubricant can be used. The lubricant which forms is suitable. The jelly-like lubricant here has a high deformation resistance and a self-shape retaining property, and once maintained in the dimple 6 and withdrawing force from the surface opening 5. High resistance against (capillary force). Needless to say, the portion sliding in contact with the shaft 2 can function as a normal lubricant by forming a liquid phase by frictional heat. Such a jelly-like lubricant has, for example, a mineral oil or a synthetic oil as a base oil, and a powdered metal soap (thickener) is dispersed and stirred in the base oil, and then the heated one is cooled as it is without stirring. Can be obtained.

  An example of the jelly-like lubricant is shown together with its production method and characteristics.

  First, a thickener (here, lithium stearate) also shown in Table 1 is supplied into a base oil having the characteristics shown in Table 1 below, and stirred while degassing. In addition, after deaeration, nitrogen gas is introduce | transduced and it is set as nitrogen gas atmosphere.

  After confirming that it is in a sufficiently stirred state, it is heated with a heater. The heating temperature at this time (temperature in a sufficiently heated state) is set to 200 ° C to 205 ° C.

  The liquid object sufficiently heated as described above is filled into a sintered metal bearing (sintered oil-impregnated bearing) in an oil-impregnated state. In FIG. 1, the liquid object is filled into a plurality of recesses (dimples 6) provided on the bearing surface 4 of the sintered oil-impregnated bearing 1. And the jelly-form lubricant of the state hold | maintained at the recessed part is obtained by naturally cooling to normal temperature in this state.

  The jelly-like lubricant thus obtained does not easily change its own shape due to its own weight like a liquid. In addition, when the same jelly-like lubricant is prepared in a test tube, it does not fall even if the top and bottom of the test tube are replaced.

  In this embodiment, a plurality of dimples 6 are formed on the bearing surface 4 as recesses for holding the lubricant 7. However, it is desirable that the dimples 6 are dispersed evenly. If the dimples 6 are formed to be evenly distributed, the shaft 2 is supported in a specific region of the bearing surface 4 depending on how the sintered oil-impregnated bearing 1 is attached to other parts or used. In addition, both sliding lubrication with the lubricating oil and sliding lubrication with the lubricant 7 can be satisfied.

  Here, the dimple 6 should be at least larger than the surface opening 5. Further, the size of the dimple 6 should be limited to a size that can function as the bearing surface 4. This is to ensure a substantial bearing area.

  In this embodiment, since the dimple 6 is formed on the inner periphery of the sintered body with a sizing pin, the dimple 6 can be formed simultaneously with the sizing (dimension sizing) of the sintered body. There is no need to provide a separate process. Further, if a large number of dimples 6 are formed by pressing the sizing pins to the inner periphery, a predetermined number and a predetermined size of dimples 6 are formed regardless of the size of the sintered body (sintered oil-impregnated bearing). be able to.

  Of course, the method of forming the dimples 6 in the sizing step (c) described in the above embodiment is merely an example, and the dimples 6 can be formed by other methods. For example, depending on the size, a large number of dimples 6 are formed by using a means for applying an external force by particle collision, such as blasting (including sand blasting, shot peening, etc.) such as shot blasting. You can also In this case, the size, depth, etc. of the dimple 6 can be easily adjusted by the shot diameter, the injection speed, and the like. Further, in the present invention, a porous body made of sintered metal is used as a target for dimple processing, and therefore, the meat of the portion subjected to the processing is deformed in a form absorbed by the internal holes 3. Therefore, with this type of workpiece, the dimples 6 can be formed without worrying about the swell after processing, which is a preferable processing method.

  Moreover, although the case where the dimple 6 was provided as a recessed part for hold | maintaining the lubricant 7 was demonstrated in the said embodiment, of course, you may make shapes other than this. FIG. 3 and FIG. 4 show an example, and a sintered oil-impregnated bearing 11 according to the same figure has a bearing surface 14 for rotating and supporting the shaft 2 on the inner periphery, and a concave portion on the bearing surface 14 in the axial direction. A plurality of extending grooves 16 are provided. In the plurality of grooves 16, a lubricant (second lubricant) 17 that is not drawn into the internal holes 13 through the surface openings 15 of the grooves 16, for example, jelly-like lubrication similar to the above embodiment. The agent is filled.

  In the case of the sintered oil-impregnated bearing 11 having the above configuration, the lubricant 17 held in the groove 16 on the bearing surface 14 preferentially comes into contact with the shaft 2 at the start of relative rotation of the shaft 2. A sliding lubrication state is ensured. For this reason, even if the lubricant does not ooze out, direct contact sliding between the shaft 2 and the bearing surface 14 can be avoided as much as possible. It can be suppressed as much as possible. Further, as described above, due to the impregnation work of the sintered oil-impregnated bearing 11, even when the lubricating oil does not remain on the bearing surface 14 at the start of use, particularly when used for the first time after manufacture, The sliding state with the shaft 2 can be maintained as smoothly as possible by the action of the lubricant 17 held in the plurality of grooves 16. For this reason, it is possible to suppress the occurrence of wear, abnormal noise, and vibration during initial sliding as much as possible.

  Further, in a state where the shaft 2 reaches a predetermined rotational speed (steady state), the lubricating oil held in the internal hole 13 is transferred to the bearing surface 14 through the surface opening 15 with the relative rotation of the shaft 2. It oozes out. Thus, a lubricating oil film is formed between the shaft 2 and the sintered oil-impregnated bearing 11, and the shaft 2 is rotatably supported via the lubricating oil film.

  Moreover, if the groove | channel 16 extended in an axial direction is provided as a recessed part, in addition to forming the groove | channel 16 by a plastic working by the above-mentioned sizing process (c), forming the groove | channel 16 in the stage of a compacting process (a). Is also possible. Thus, if it forms in the stage before sintering, since the possibility that it will have a bad influence on the shaping | molding precision of other parts, such as the bearing surface 14, by the plastic processing of the groove | channel 16, it is preferable. Of course, as the recess, as long as the lubricants 7 and 17 can be held therein, various forms other than the dimple 6 and the groove 16, for example, a spiral continuous groove, are formed over the entire axial length of the bearing surface. It is also possible to adopt such a configuration.

  In any case, the dimples 6 and the grooves 16 as the concave portions do not require as high surface accuracy and dimensional accuracy as the bearing surface 4. Therefore, as described above, various recess forming means can be used without any particular problem.

  Moreover, in the above embodiment, the sintered oil impregnated bearings 1 and 11 having the bearing surfaces 4 and 14 are illustrated as the sintered metal sliding members having the sliding surfaces. The present invention can also be applied to such a sintered metal sliding member. For example, although not shown, in a torque limiter of a coil spring built-in type used in a drive unit of a paper feeder of a printer or a copying machine, this torque limiter is configured and slidably contacted with a coil spring built in the outer periphery. The inner ring is made of sintered metal, and the inside is impregnated with lubricating oil, and a concave portion such as a dimple is provided on the outer peripheral surface serving as a sliding surface, and an internal hole is formed in the concave portion through a surface opening of the concave portion. It is also possible to adopt a configuration in which a lubricant that is not drawn, for example, a jelly-like lubricant is filled.

It is a longitudinal cross-sectional view of the sintered oil-impregnated bearing which concerns on one Embodiment of this invention. FIG. 2 is an enlarged cross-sectional view of a region A in FIG. 1, (a) is a state before inserting the shaft, (b) is a cross-sectional view showing a state when the shaft is inserted and the shaft starts relative rotation. It is. It is a longitudinal cross-sectional view of the sintered oil-impregnated bearing which concerns on other embodiment. It is BB sectional drawing of the sintered oil-impregnated bearing shown in FIG.

Explanation of symbols

1, 11 Sintered oil-impregnated bearing 2 Shaft 3, 13 Internal hole 4, 14 Bearing surface 5, 15 Surface opening 6 Dimple 7, 17 Lubricant 16 Groove

Claims (4)

A sintered metal part having a sliding surface, in which the internal holes are impregnated with the first lubricant, and the internal holes are impregnated with relative sliding with the counterpart member. When the first lubricant oozes out on the sliding surface, it slides through the mating member and the first lubricant.
A concave portion is formed on the sliding surface, and the concave portion is filled with a second lubricant which is not drawn into the internal hole through an opening existing on the surface of the concave portion. Sintered metal parts.   2. The sintered metal part according to claim 1, wherein the second lubricant can remain in the concave portion against a pulling force into the internal hole caused by an arbitrary temperature change within a use temperature range.   The sintered metal part according to claim 1, wherein a large number of dimples as the recesses are formed on the sliding surface.   The sintered metal part according to any one of claims 1 to 3, wherein the sliding surface is provided on an inner periphery, and a shaft inserted in the inner periphery is supported by the sliding surface.

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