JP2007225077A - Sliding bearing and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding bearing appropriate for a use environment wherein the sliding bearing is slid at a low speed and receives face pressure varying from low contact pressure to high contact pressure and its manufacturing method. <P>SOLUTION: The sliding bearing 16 is formed by sintering metal powders including copper and iron wherein a sintered alloy layer 30 with a plurality of pores 31 which communicates with each other has a surface regarded as a sliding surface 34 for sliding relative to a shaft 22. The sliding surface 34 is treated with a surface modification by carburizing, nitriding or sulphonitriding treatment method. A recessed part 35 with molybdenum disulfide dispersed and permeated is formed by colliding molybdenum disulfide after the surface modification treatment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plain bearing that supports a shaft and a method of manufacturing the same.

  In various machines represented by construction machines, civil engineering machines, conveyance machines, heavy machinery, machine tools, automobiles, etc., plain bearing devices may be used. There are various environments in which the sliding bearing device is used, and there is a demand for a device having characteristics corresponding to each usage environment. For example, the bearing device used in the boom, arm, and bucket connecting portion in the excavator of a hydraulic excavator can be used at a place where the shaft rotates at a relatively high speed, such as a drive shaft of a rotating machine. Compared to sliding at low speed, it is used in an environment where high surface pressure is applied.

  As one of the plain bearing devices corresponding to such usage environments, a porous bearing is formed of an iron-based sintered alloy, and this is impregnated with a lubricating oil, so that it can be used for a long time even in a low speed / high surface pressure environment. There is one that can be operated without grease (for example, several years or more) (see Patent Document 1).

Japanese Patent No. 2832800

  However, in this type of plain bearing device, the plain bearing requires time until the microscopic shape of the sliding surface becomes compatible with the surface shape of the shaft, or when the load on the bearing is relatively low ( For example, when a slight slide such as fretting occurs in a hydraulic excavator during an operation that does not involve excavation work, a malfunction may occur such as an abnormal noise due to this. Therefore, the bearing characteristics are further improved for use in an environment where the surface pressure applied to the sliding surface (sliding surface) varies from a low surface pressure to a high surface pressure while sliding at a relatively low speed. There is a need.

  An object of the present invention is to provide a plain bearing suitable for an operating environment that slides at a low speed and receives a surface pressure that varies from a low surface pressure to a high surface pressure, and a method for manufacturing the same.

  (1) In order to achieve the above object, the present invention sinters metal powder containing copper and iron and slides the surface of the sintered alloy layer formed with a plurality of continuous air holes relative to the shaft. The sliding surface is subjected to surface modification treatment by any of carburizing, nitriding, or nitrosulphurizing treatment, and after the surface modification treatment, the first solid lubrication is performed. It is assumed that the first solid lubricant has a recess formed by diffusing and penetrating the agent particles.

  (2) In the above (1), preferably, the sintered alloy layer is impregnated with a lubricant inside the continuous air hole.

  (3) In the above (2), preferably, the lubricant contains particles of a second solid lubricant.

  (4) In the above (3), preferably, the second solid lubricant is contained in the lubricant in an amount of 2 to 10 wt%.

  (5) In any of the above (2) to (4), preferably, the lubricant has a viscosity of 260 to 950 cSt.

  (6) In any one of the above (1) to (5), preferably, the porosity of the continuous air hole is 5 to 30%.

  According to the present invention, it is possible to improve the tribological characteristics of the bearing in a low-speed / low-surface pressure use environment, so that the bearing is slid at a low speed and receives a surface pressure varying from a low surface pressure to a high surface pressure. A plain bearing suitable for the environment can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a side view of a hydraulic excavator which is an example of a machine provided with the slide bearing of the present invention.
The hydraulic excavator shown in FIG. 1 is provided on a lower traveling body 1, an upper revolving body 2 that is turnably mounted on the lower traveling body 1, and one side (left side in FIG. 1) on the upper revolving body 2. The engine room 4 provided on the other side (right side in FIG. 1) on the upper swing body 2 and the front work machine 5 provided on the driver room 3 side on the upper swing body 2 I have.

  The front work machine 5 is provided on the upper swing body 2 so as to be able to move up and down, a boom hydraulic cylinder 7 for moving the boom 6 up and down, and rotatably provided at the tip of the boom 6. An arm 8, an arm hydraulic cylinder 9 for rotating the arm 8, a bucket 10 rotatably provided at the tip of the arm 8, and a bucket hydraulic cylinder 11 for rotating the bucket 10 And.

  The boom 6, the arm 8, the bucket 10, and the hydraulic cylinders 7, 9, and 11 are connected to each other by a sliding bearing device 12 so as to be rotatable. Although each slide bearing device used for the front work machine 5 has a different size and shape depending on the installation location, the basic configuration is substantially the same.

FIG. 2 is a cross-sectional view of a configuration example of a slide bearing device including the slide bearing of the present invention.
In FIG. 2, the sliding bearing device 12 includes a boss 15, a cylindrical bush (sliding bearing; also referred to as simply a bearing hereinafter) 16 fitted in the boss 15, and both sides of the bush 16. The oil shielding member 17 disposed, the dust seal 18 press-fitted on both sides of the bush 16 in the boss 15 so as to abut the oil shielding member 17 toward the bush 16, and disposed on both sides of the boss 15. A bracket 19, a shim 20 provided in the gap between the bracket 19 and the boss 15, an O-ring 21 mounted on the outer peripheral side of the gap between the bracket 19 and the boss 15, the bracket 19 and the bush 16 are provided. A shaft 22 inserted through the bush 16 and slidably provided with the bush 16 and a rotation locking bolt 23 are provided.

  The shaft 22 is made of a steel material. First, after carburizing, nitriding and induction hardening, the outer surface is formed (for example, zinc phosphate, manganese phosphate, etc.), various plating processes including diffusion plating, Alternatively, surface modification treatment is preferably performed by a sulfuration treatment method or the like. The rotation locking bolt 23 is provided so as to penetrate the shaft 22 and the bracket 19, and makes the shaft 22 and the bracket 19 unrotatable. Further, the boss 15 and the bush 16 are fitted and fixed to each other by a shrink fit such as shrink fit or cooling fit.

FIG. 3 is a partial cross-sectional view showing an enlarged and schematic view of the vicinity of the interface with the shaft of the bearing of the present invention in the plain bearing device shown in FIG.
In FIG. 3, the bush 16 has a sintered alloy layer 30 located on the interface side with the shaft 22 (inner circumferential side of the bush 16) and a backing metal layer 40 located on the radially outer side. These are joined together to form a two-layer structure.

  The sintered alloy layer 30 is made of a porous composite sintered alloy formed by sintering metal powder containing 10% by weight of copper powder, iron powder, and other trace elements. A sliding surface 34 that is a moving sliding surface, and a solid lubricant layer 33 that is formed on the inner peripheral side of the sintered alloy layer 30 (the interface side with the shaft 22) so as to include the sliding surface 34. A plurality of pores (communication vent holes) 31 communicated with each other are provided. The sintered alloy layer 30 contains copper and iron as essential elements, and the amount of copper contained in the sintered alloy layer 30 is not limited to only 10% by weight, but may be in the range of 3 to 98% by weight.

The solid lubricant layer 33 self-impregnates the sliding surface 34 while allowing molybdenum disulfide to diffuse and penetrate into the sintered alloy by causing the molybdenum disulfide particles (MoS ₂ ) to collide with the sliding surface 34 as a projection material (shot). As a result of imparting the lubrication characteristics, it is formed afterwards on the sliding surface 34 side, and has a recess 35 formed on the sliding surface 34 by the action of collision of molybdenum disulfide particles. In FIG. 3, the sliding surface 34 is simply expressed as a substantially flat surface, but it is assumed that innumerable concave portions 35 are formed on the sliding surface 34. Further, the sliding surface 34 is subjected to a surface modification treatment by a carburizing, nitriding, or sulfurating treatment method before the solid lubricant layer 33 is formed, and a hardened layer ( (Not shown) improves the mechanical strength of the bush 16. As a standard of the thickness of the hardened layer, about 1 to 8 mm, preferably about 2 mm is good. Examples of the iron alloy phase in the hardened layer after the surface modification treatment include cementite, martensite, ferrite, pearlite, and the like. It is included. The formation method and operation of the solid lubricant layer 33 will be separately described in detail in the section describing the bearing manufacturing method of the present embodiment.

  The pores 31 are impregnated with lubricating oil 32 and communicate with the recesses 35 on the sliding surface 34. For this reason, the lubricating oil 32 is exposed to the recess 35 by flowing through the pores 31 and forms an oil reservoir on the sliding surface 34. In the present embodiment, the lubricating oil 32 impregnated in the pores 31 has a viscosity of 460 cSt. In addition, it is preferable that the viscosity of this lubricating oil exists in the range of 260-950 cSt. This is because if the viscosity is less than 260 cSt, the fluidity of the lubricating oil is too high, so that it is difficult to keep the lubricating oil in the pores 31 and a “galling phenomenon” may occur during use. On the other hand, when the viscosity exceeds 950 cSt, the fluidity of the lubricating oil decreases, so that the lubricating oil that has oozed into the sliding surface 34 with the shaft 22 due to frictional heat returns to the pores 31 again. This is because there is a possibility that it will become difficult to maintain a stable sliding characteristic in the long term. In addition, as the lubricating oil, general lubricating oils having a commercially available composition such as mineral oil or synthetic oil, and waxes based on paraffin can be used. The composition itself is not particularly limited. However, grease is excluded because it contains fibers and cannot be impregnated into the pores 31.

In the present embodiment, the lubricant 32 has solid lubricant particles (eg, graphite, MoS ₂ , tungsten disulfide (WS ₂ ), manganese sulfide (MnS) having self-lubricating properties with a particle size of about 0.5 to 50 μm. ), Calcium fluoride (CaF ₂ ), etc.) may be contained in an amount of 2 to 10% by weight. When such solid lubricant particles are contained in the lubricating oil 32, further lubrication characteristics can be obtained by sliding the solid lubricant particles themselves.

  Furthermore, the porosity of the pores 31 is preferably about 5 to 30%. This is because when the porosity is less than 5%, the amount of impregnation of the lubricating oil becomes insufficient, and it may not function sufficiently as a non-greasy bearing. On the other hand, when the porosity exceeds 30%, the mechanical strength of the bush 16 itself is lowered.

  The back metal layer 40 is made of an iron-based material. The back metal layer 40 is also surface-modified by a carburizing, nitriding, or sulfurating treatment method, like the sliding surface 34 of the sintered alloy layer 30, and further improves the mechanical strength of the bush 16. . In addition, the standard of the thickness of this hardened layer is about 1-3 mm, Preferably about 2 mm is good. The back metal layer 40 subjected to the surface modification treatment as described above reinforces the strength of the bushing 16 and contributes to prevention of bearing breakage that is frequently observed in bearings made of only an iron-based sintered alloy. Further, by forming the bush 16 with a two-layer structure of the back metal layer 40 and the sintered alloy layer 30, the elastic modulus of the entire bearing becomes larger than when the bush 16 is constituted only by the sintered alloy layer. Thereby, the amount of elastic deformation of the bush 16 can be reduced, the fretting resistance characteristic of the bush 16 can be improved, and the occurrence of abnormal noise can be suppressed.

  Next, the manufacturing method of the bearing of the present embodiment configured as described above will be described.

  First, a backing metal made of an iron-based material is prepared. For example, an SCM material that is carburized steel is preferably used as the material of the back metal. Further, this backing metal becomes the backing metal layer 40 which is a layer on the outer peripheral side of the bush 16, and is formed so as to have an outer shape of the bush when wound in a cylindrical shape. Next, a metal powder mainly composed of copper powder and iron powder, which is uniformly mixed, is dispersed on the upper surface of such a back metal, and this is formed into a plate shape similar to the back metal. The copper in the powder used here is at least 3% by weight, preferably 10% by weight or more.

  The powder thus formed and the back metal are put into a reduction furnace or the like, and the above powder is sintered in an atmosphere of about 800 degrees to produce a porous composite sintered alloy on the back metal. This is the sintered alloy layer 30 that is the inner peripheral layer of the bush 16. Sintering in this procedure refers to primary sintering, and sintering is performed so that the pores remain positively so that the porosity of the sintered alloy after generation is in the range of 5 to 30%. Next, this porous composite sintered alloy is bonded to the back metal by diffusion bonding or the like to obtain a plate-shaped bearing material having a two-layer structure. Then, the bearing material formed into the two-layer structure is wound by a press or the like and bent, and is processed into a cylindrical shape which is an optimum shape as a bearing, thereby forming an approximate shape of the bush.

  Next, carburizing treatment is applied to the bush to modify the surface. This treatment is intended for both the sintered alloy layer 30 and the back metal layer 40, whereby the respective surface hardness is improved, and the sliding surface 34 of the sintered alloy layer 30 with the shaft 22 is wear resistant. Thus, the strength of the back metal layer 40 is reinforced. The surface modification treatment is not limited to the carburizing treatment method, but may be any treatment that improves the surface hardness, such as nitriding or nitronitriding treatment. Further, after this treatment, if necessary, the dimensional accuracy may be increased by machining or pressing.

  Following this surface modification treatment, the solid lubricant layer 33 is formed on the interface side of the sintered alloy layer 30 with the shaft 22 by causing the molybdenum disulfide particles to collide with the sliding surface 34. When the molybdenum disulfide particles collide with the sliding surface 34, a driving method using a shot peening technique is used. The implantation method means that fine particles (for example, molybdenum disulfide particles having a particle diameter of about 50 μm) are applied at a predetermined pressure (for example, 0.3 MPa or more) as compared with a projection material (shot) used in general shot peening. Along with the compressed air, it is driven at a high speed (for example, an injection speed of 80 m / second or more) (hereinafter referred to as fine particle shot peening). When fine particles are driven into the material to be treated by this method and collide with each other, fine concave portions are formed as compared with the concave portions formed on the surface of the material to be treated by general shot peening, and the heat generated at the time of the collision is used. Surface modification processing such as miniaturization of the surface of the material to be processed and work hardening is performed on the material to be processed.

  When molybdenum disulfide particles are caused to collide with the sliding surface 34 using such fine particle shot peening, fine concave portions 35 are formed on the sliding surface 34 as described above, and the sliding surface 34 is cured. At the same time, molybdenum disulfide diffuses and permeates from the sliding surface 34 due to the collision with the sliding surface 34, and a solid lubricant layer 33 having self-lubricating properties is formed on the interface side with the shaft 22.

In the above description, the case where the molybdenum disulfide particles are collided as projection fine particles has been described. However, for example, solid lubricants such as graphite, WS ₂ , MnS, and CaF ₂ , and metal particles such as Mo and W are also used. May be used. In addition to fine particles having self-lubricating properties such as these, solid lubricants are made by colliding fine particles made of materials such as steel, hard particles, and ceramics, which are used as general shot peening projection materials. Even if the surface modification treatment of the sliding surface 34 is performed without forming a layer, the minute concave portions can be formed on the sliding surface 34 as in the case of the solid lubricant, so the use of the bearing device is started. It is possible to improve the initial conformability of the bearing at the time.

Finally, the pores 31 in the sintered alloy layer 30 are impregnated with the high-viscosity lubricating oil 32 to obtain the final shape bush 16. This impregnation treatment is performed as follows. First, the lubricating oil is heated and liquefied to lower the viscosity. The bush is immersed in the liquefied lubricating oil and left to stand in a vacuum atmosphere. As a result, the air in the air holes 31 of the bush is sucked out of the air holes 31, while the liquefied lubricating oil 32 is sucked into the air holes 31 of the bush. When the bush 16 that has sucked the lubricating oil 32 is taken out into the air and allowed to cool to room temperature, the liquefied lubricating oil 32 returns to the original high-viscosity lubricating oil in the pores 31 of the bush 16 and loses fluidity. Thereby, the high-viscosity lubricating oil 32 can be retained in the pores 31 of the bush 16. In addition, since heating temperature changes according to a viscosity, the heating temperature of the high viscosity lubricating oil 32 is not specifically limited, What is necessary is just to heat until the lubricating oil 32 liquefies. Further, the immersion time and the degree of vacuum of the bush 16 in the liquefied lubricating oil 32 are not particularly limited. This is because the immersion time and the degree of vacuum also depend on the viscosity of the lubricating oil used. What is important here is that the bush 16 is immersed in the liquefied lubricating oil until the pores 31 of the bush 16 are saturated with the lubricating oil 32. For example, when a lubricating oil having a viscosity of 460 cSt is heated to 60 to 80 ° C. and the bush is immersed in this lubricating oil under a vacuum of 2 × 10 ⁻² mmHg, the pores of the bush will be lubricating in about 1 hour. Saturated with

  Since the lubricating oil 32 impregnated in the pores 31 in this manner has extremely low fluidity, it hardly flows out even if the bush 16 and the shaft 22 repeat relative sliding. As a result, the oil film continues to be supplied stably over an extremely long period (for example, several years). The presence of such a microscopic “oil sump” (oil film) prevents the so-called “galling phenomenon” occurring between the driving shaft 22 and the bushing 16 from being caused by micro metal contact between the two. To do.

Next, the wear resistance characteristics of the sliding bearing according to the present embodiment were evaluated using a Ring On Ring type testing machine. In this test, in a hydraulic oil environment, the mating material is rotated at 1200 rpm, a step load is applied to the test piece, and the load is increased step by step. Measure. The contact area between the mating member and the test piece is 50 mm ² . In the test, test pieces made of the following three materials (a) to (c) were used.
(A) High-viscosity oil impregnated porous composite sintered alloy with molybdenum-sulfide fine particle shot peening (impregnated oil with a viscosity of 460 cSt, Fe—Cu—C based sintered alloy. This is referred to as a “test piece according to the form of
(B) Porous composite sintered alloy with high viscosity oil impregnated type back metal (using impregnated oil having a viscosity of 460 cSt, Fe—Cu—C based sintered alloy; hereinafter, “test piece of base material of this embodiment”) Called)
(C) Induction quenching material of carbon steel (S45C) subjected to fine particle shot peening of molybdenum disulfide (hereinafter referred to as “S45C test piece”)
FIG. 4 shows the results of the above test. As shown in FIG. 4, the friction coefficient of the test piece (a) according to the present embodiment may rise around the load of 100 kgf (980 N) and change around 0.03, but after the start of the test. The value of about 0.01 was maintained until about 250 kgf (2451N), and then remained around 0.02 up to 1000 kgf (9806N), although there was some vertical fluctuation. Here, when the load applied to the test piece (a) is converted into the surface pressure using the contact area value (50 mm ² ), the friction coefficient is ^{2 to 3} kgf / mm ² (load load: 100 to 150 kgf). In the low surface pressure range, it is generally around 0.03, while in the high surface pressure region of 6 kgf / mm ² (load load: 300 kgf) or more, it is generally around 0.02, from the low surface pressure region to the high surface pressure region. In general, stable fluctuations were observed. As shown in the figure, in this test piece (a), the microscopic shape of the sliding surface of the test piece is formed by sliding into a shape suitable for the surface shape of the counterpart material, so-called “familiarity”. The characteristics up to (referred to as initial conformability characteristics) are significantly better than the results of the other two test pieces (2) and (3), and the friction coefficient at the initial stage of sliding is 0.04 at the highest. It only increased to the extent. Furthermore, although the load of 1000 kgf or more could not be applied due to the characteristics of the testing machine used in this test, the inventors have obtained the knowledge that the test piece (a) is durable even when a further load is applied. It was found that the test piece (a) according to the present embodiment also has excellent load bearing characteristics.

On the other hand, the friction coefficient of the base material test piece (b) of the present embodiment in which fine particle shot peening has not been applied and the S45C test piece (c) in which fine particle shot peening has been applied is the increase in the friction coefficient immediately after the start of the test. Although there is a difference in the way, it shows an almost similar transition once it rises to about 0.1 by the load load of 100 kgf (980 N), and then increases from about 250 kgf (2451 N) to about 0.05 for familiarity. After 400 kgf (3922 N), the load resistance performance of the material was exceeded and a rapid increase was observed. Here, when these results are also converted to surface pressure in the same manner as the test piece (a) of the present embodiment, the friction coefficient is approximately in the low surface pressure region of ^{2 to 3} kgf / mm ² (load load: 100 to 150 kgf). While changing around 0.1, the high surface pressure region of 6 kgf / mm ² (load load: 300 kgf) or more changes around 0.05, which is higher than the test piece (a) in any region. The value changed. Among them, the coefficient of friction in the low surface pressure region is generally 0.1, which is significantly higher than that of the test piece (a). As mentioned earlier, as shown in the figure, the initial conformability characteristics of the test pieces (b) and (c) are significantly inferior to those of the test piece (a). As described above, the base material test piece (b) and the S45C test piece (c) have large fluctuations in the friction coefficient due to the load change, and particularly higher friction than the test piece (a) in the low surface pressure region. The coefficient is shown, and the load-bearing characteristics also have less than half of the test piece (a) according to the present embodiment.

  From the above test results, the inventors have found that the solid lubricant layer made of molybdenum disulfide formed on the sliding surface and the high-viscosity oil-impregnated sintered alloy layer provided on the radially outer side are synergistic. It has been found that due to the effect, the plain bearing according to the present embodiment has remarkably good tribological characteristics.

  Next, the effect of this embodiment will be described.

The conventional sliding bearing, which is made of a high-viscosity oil-impregnated porous composite sintered alloy with a backing metal, without subjecting the sliding surface to fine particle shot peening with molybdenum disulfide, is slid from the beginning of use. It takes time for the microscopic shape of the surface to be formed into a shape suitable for the surface shape of the shaft that is the counterpart material (so-called familiarity), the initial familiarity is not good, and the load on the bearing is not good. When the surface pressure is relatively low (for example, in a hydraulic excavator, when the excavator is slightly operated while the bucket is empty, for example, when the operation is not accompanied by substantial excavation work), When a phenomenon (so-called fretting phenomenon) occurs in which the shaft and the bearing slide relative to each other by only a few millimeters, there may be a problem such as an abnormal sound due to the phenomenon. Therefore, the surface pressure applied to the sliding surface (sliding surface) while being slid at a relatively low speed is changed from a low surface pressure (for example, about ² to 3 kgf / mm ² ) to a high surface pressure (for example, 6 kgf / mm ² or more). However, it was necessary to further improve the characteristics of the bearing in order to use it in an environment that fluctuates.

  In contrast to such a technique, this embodiment uses a high-viscosity oil-impregnated porous composite sintered alloy with a backing as a base material, and molybdenum disulfide particles are finely shot peened on a sliding surface 34 with the shaft. By doing so, a solid lubricant layer 33 formed by diffusion and permeation of molybdenum disulfide and a fine concave portion 35 formed by the action of a collision are formed on the sliding surface 34, and the lubricating oil 32 is provided in the pores 31. The oil reservoir is formed on the sliding surface 34 having self-lubricating characteristics by being exposed to the concave portion 35.

  With this configuration, the bearing according to the present embodiment slides relative to the shaft 22 via the fine recess 35 on the sliding surface 34, thereby sliding the surface of the shaft 22 and the optimum surface shape. Since it is easily formed on the moving surface 34, excellent initial conformability characteristics can be obtained, and it can be used with low friction without sliding-in from the beginning of use. Further, since the sliding surface 34 becomes a solid lubricant layer 33, self-lubricating properties are imparted, so that even if a slight sliding such as fretting occurs in a low-speed / low-surface pressure environment, the self-lubricating property is provided. Since the bush 16 can be smoothly slid with respect to the shaft 22 depending on the characteristics, excellent anti-fretting characteristics that suppress the generation of abnormal noise can be obtained. Further, since the lubricating oil 32 is exposed from the pores 31 to the recesses 35, a good oil sump is formed on the sliding surface 34 having self-lubricating characteristics, so that while sliding at a relatively low speed, Even in an environment where the pressure applied to the bearing fluctuates from a low surface pressure to a high surface pressure, excellent tribological characteristics capable of maintaining low friction can be obtained. Note that this effect is not easily obtained by fine particle shot peening of molybdenum disulfide on a bearing formed of carbon steel or the like, as indicated by the test results shown in FIG. That is, it is obtained for the first time by performing fine particle shot peening on a bearing made of a porous composite sintered alloy with a high viscosity oil-impregnated back metal backing, and the lubrication provided by the porous composite sintered alloy with a high viscosity oil-impregnated back metal It is obtained for the first time by a remarkable synergistic effect between the effect and the surface modification effect of fine particle shot peening.

  Further, when the concave portion 35 is formed on the sliding surface 34 by fine particle shot peening as described above, compressive residual stress is applied to the sliding surface 34. Thereby, the fatigue strength in the environment of the repeated load of the sliding face 34 can further be improved. Further, the recess 35 not only holds the impregnated lubricating oil 32 but also has a holding effect of grease periodically supplied for maintenance or the like, so that the grease supply interval can be extended. One of the merits of the present embodiment is also possible. In the above description, the case where molybdenum disulfide particles, which are solid lubricants, are mainly used as the projection material for fine particle shot peening has been described. However, as mentioned in the explanation of the manufacturing method, If fine particles made of a material such as hard particles or ceramic are used, the surface treatment for forming the recesses 35 is performed on the sliding surface 34, so that a bearing having excellent initial conformability can be obtained.

  Furthermore, in this embodiment, as a method for forming a cylindrical bearing, a plate-shaped bearing material having a two-layer structure of a back metal layer and a sintered alloy layer is first manufactured, and then the bearing material is converted into a cylindrical shape. The method of winding in the shape is adopted. As a result, a cylindrical two-layer structure bearing can be manufactured simply by winding a plate-shaped bearing material having a two-layer structure that is easy to manufacture. Thus, they can be easily manufactured as compared with the method of joining them to obtain a two-layer structure bearing. Further, the compressive residual stress of the concave portion 35 imparted by the fine particle shot peening acts so that the two-layer structure bearing manufactured in this way maintains a cylindrical shape, so that the bearing is deformed by a load received during use. It is one of the merits of this embodiment to suppress the above and contribute to the deformation resistance of the bearing. In the description of the method for producing a sintered alloy layer, it was explained that copper powder and iron powder were sprayed and formed on the upper surface of the back metal, and then placed in a reduction furnace to produce a sintered alloy on the upper side of the back metal. However, the production method of the sintered alloy is not limited to this. For example, the plate-shaped backing metal and the plate-shaped sintered alloy are prepared separately with the same width and length dimensions, and then joined together to form a plate-shaped bearing having a two-layer structure. Material may be obtained. That is, if a manufacturing method that passes through a procedure of manufacturing a bearing by manufacturing a plate-shaped bearing material having a two-layer structure and then winding it into a cylindrical shape, the two-layer structure is used regardless of the manufacturing method of the sintered alloy layer. The effect that the bearing which has a structure can be manufactured easily is acquired.

It is a side view of the hydraulic excavator which is an example of the machine provided with the slide bearing of this Embodiment. It is sectional drawing of the example of 1 structure of the slide bearing apparatus provided with the slide bearing of this Embodiment. FIG. 3 is a partial cross-sectional view showing an enlarged and schematic view of the vicinity of the interface with the shaft of the slide bearing of the present invention in the slide bearing device shown in FIG. 2. It is a figure which shows the change of the friction coefficient accompanying the load change of the slide bearing of this Embodiment.

Explanation of symbols

12 Slide bearing device 16 Bush (Slide bearing)
22 Shaft 30 Sintered alloy layer 31 Pore 32 Lubricating oil 33 Solid lubricant layer 34 Sliding surface 35 Recessed portion 40 Back metal layer

Claims (6)

A sliding bearing that sinters metal powder containing copper and iron and has a sliding surface that slides relative to the shaft on the surface of a sintered alloy layer in which a plurality of continuous air holes are formed,
The sliding surface is subjected to a surface modification treatment by any of carburizing, nitriding, or nitrosulphurizing treatment, and further, by colliding particles of the first solid lubricant after the surface modification treatment. A plain bearing having a concave portion formed and diffused and penetrated by the first solid lubricant. The plain bearing according to claim 1,
A sliding bearing, wherein the sintered alloy layer is impregnated with a lubricant inside the continuous air hole. The plain bearing according to claim 2,
The sliding bearing, wherein the lubricant contains particles of a second solid lubricant. The plain bearing according to claim 3,
The slide bearing according to claim 2, wherein the second solid lubricant is contained in the lubricant in an amount of 2 to 10 wt%. In the slide bearing in any one of Claims 2 thru | or 4,
The sliding bearing according to claim 1, wherein the lubricant has a viscosity of 260 to 950 cSt. In the slide bearing in any one of Claims 1 thru | or 5,
The sliding bearing according to claim 1, wherein a porosity of the continuous air hole is 5 to 30%.

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