JP2008281146A - Sliding member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding member capable of reducing time involved in reaching from a slide start to a state that a sliding surface is lubricated. <P>SOLUTION: A sliding member which is formed by sintering metal powders including copper and iron and which keeps a sintered alloy layer 30 including a plurality of air holes 31 on a sliding surface 25 with a shaft 22, is a strand-like body 25 which impregnates a lubricating oil 32 in a range of kinematic viscosity between 460 and 1,500 cSt in the air holes 31 and consists of a plurality of filaments 36, wherein self-lubricating grains 37 are woven between the filaments 36 and held on the sliding surface 25 so as to come into contact with the lubricating oil 32. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sliding member used for sliding parts of various machines.

  Sliding members are used for parts (sliding parts) in which various members slide relative to each other, such as bearings and gears in various machines (construction machines, civil engineering machines, transport machines, heavy machinery, machine tools, automobiles, etc.) It has been. The environment in which the sliding member is used varies depending on the application location and the use of the machine, and is required to have characteristics suitable for the environment.

  For example, a bearing used for a connecting portion of a boom, an arm, and a bucket constituting a working device of a hydraulic excavator is slid at a lower speed than a shaft that rotates at a relatively high speed such as a drive shaft of a rotary machine. In addition, it supports the shaft where high surface pressure is applied. Therefore, a sliding member (bush) used in such an environment is required to be suitable for use at low speed and high surface pressure.

  As a sliding member suitable for such an environment, a metal powder containing iron is porous so that it can be used without lubrication for a long period of time (for example, several years) even in a low speed / high surface pressure environment. There is one in which a sintered alloy is formed and the internal pores are impregnated with lubricating oil (see Patent Document 1, etc.).

Japanese Patent No. 2832800

  However, the sliding member of the above technique requires a certain amount of frictional heat so that the impregnated lubricating oil is appropriately supplied to the sliding surface with the counterpart material (shaft) at the start of sliding. It takes some time for the moving surface to start from sliding to the lubricated state. For this reason, for example, if sliding occurs before the sliding surface becomes lubricated, or if minute sliding (vibration) occurs, abnormal wear such as fretting wear or abnormal noise may occur due to poor lubrication. There was also.

  An object of the present invention is to provide a sliding member capable of shortening the time required for the sliding surface to reach a lubrication state from the start of sliding.

  (1) In order to achieve the above object, the present invention is formed by sintering a metal powder containing iron and copper, and a sintered alloy layer having a plurality of pores is formed on a sliding surface with a counterpart material. A sliding member comprising a lubricating oil impregnated in the pores with a kinematic viscosity in the range of 460 to 1500 cSt, a plurality of filaments, and a filamentous body composed of self-lubricating particles woven into the plurality of filaments. The filamentous body is held on the sliding surface while at least a part of the filamentous body is in contact with the lubricating oil.

  (2) The diameter of the filament in (1) is preferably smaller than the diameter of the holes.

  (3) Preferably, the filaments of the above (1) or (2) include those having a length smaller than the diameter of the holes.

  (4) In the lubricating oil according to any one of (1) to (3), preferably, the self-lubricating particles include one made of a fluororesin, molybdenum disulfide, or carbon. Shall.

  (5) In the sintered alloy layer according to any one of (1) to (4), preferably, the filament includes one made of any of an aramid fiber, a polyester fiber, a carbon fiber, and a glass fiber. It shall be.

  According to the present invention, the time required for the sliding surface to reach the lubrication state from the start of sliding is shortened, so that the sliding characteristics of the sliding member at the start of sliding can be improved.

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

  FIG. 1 is a side view of a hydraulic excavator as an example of a machine in which a sliding member according to an embodiment of the present invention is used.

  The hydraulic excavator shown in this figure 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 working device 5 provided on the driver room 3 side on the upper swing body 2 are provided. Yes.

  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 It has.

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

  FIG. 2 is a sectional view of a bearing provided with a sliding member according to an embodiment of the present invention.

  In FIG. 2, the bearing 12 includes a boss 15, a cylindrical sliding member (hereinafter referred to as “bush” as appropriate) 16 fitted inside the boss 15, and shields provided on both side surfaces of the bush 16. An oil member 17, a dust seal 18 that is press-fitted on both sides of the bush 16 in the boss 15 so that the oil shielding member 17 contacts the bush 16, and a bracket 19 that is disposed on both sides of the boss 15 via a gap. And 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, and the bracket 19 and the bush 16, respectively. , A shaft 22 slidably provided with the bush 16, and a rotation locking bolt 23.

  The shaft 22 is made of a steel material. First, after carburizing, nitriding, induction hardening, etc., the outer surface is subjected to chemical conversion treatment using zinc phosphate, manganese phosphate, etc., and various types including diffusion plating. It is preferable to modify the surface by a plating process or a sulfuration process. 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 non-rotatable. Further, the boss 15 and the bush 16 are fitted and fixed to each other by, for example, shrink fitting such as shrink fitting or cooling fitting. Therefore, the bearing 12 is configured such that the shaft 22 and the bracket 19 rotate relative to the boss 15 and the bush 16 so that the shaft 22 and the bush 16 slide relative to each other.

FIG. 3 is a partial sectional view of a sliding member according to an embodiment of the present invention, and FIG. 4 is an enlarged view schematically showing the vicinity of the sliding surface.
In FIG. 3, the bush 16 includes a sintered alloy layer 30 provided on a sliding surface 25 (an inner peripheral side of the bush 16) with a shaft 22 that is a sliding counterpart, and a radial direction of the sintered alloy layer 30. It has a back metal layer 40 provided on the outside.

  In FIG. 4, the sintered alloy layer 30 is made of an iron-based porous composite sintered alloy formed by sintering metal powder containing iron powder, copper powder, and other trace elements. It has a hole 31 and a thread-like body 35 (35a, 35b, 35c, 35d, 35e). The broken line L in the figure schematically shows the interface of the lubricating oil 32 at the start of sliding (for example, at the time of restarting operation after operation stop), and as the shaft 22 and the sintered alloy layer 30 slide. The space between the shaft 22 and the sintered alloy layer 30 is filled with the lubricating oil 32 as shown in the figure.

  The sintered alloy layer 30 is subjected to a high hardness treatment by any method among induction hardening, carburizing and quenching, nitriding or gas soft nitriding. The hardened layer 50 (see FIG. 5 described later) formed by this treatment 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 high hardness treatment include cementite, martensite, ferrite, pearlite, and the like. It is included.

  The sintered alloy layer 30 of the present embodiment contains 20% by weight of copper powder. In addition, although the sintered alloy layer 30 contains iron and copper as essential elements, the amount of copper contained may be in the range of 3 to 98% by weight, and preferably 10% by weight or more.

  The air holes 31 are impregnated with lubricating oil 32 and are exposed to the outside as concave portions 33 on the sliding surface 25. Some of the plurality of holes 31 communicate with each other. The lubricating oil 32 is exposed to the recess 33 by flowing through the communicating air holes 31 to form an oil reservoir on the sliding surface 25.

  It is preferable that the ratio (porosity) occupied by the holes 31 in the sintered alloy layer 30 is about 5 to 30%. This is because when the porosity is less than 5%, the amount of the lubricating oil impregnated becomes insufficient, and it may not function sufficiently as a non-greasy bearing, while the porosity is 30%. This is because the mechanical strength of the bush 16 itself is reduced if it exceeds.

  The lubricating oil 32 is a high-viscosity oil, and the kinematic viscosity is preferably in the range of 460 to 1500 cSt. This is because when the kinematic viscosity is less than 460 cSt, it is difficult to retain the lubricating oil when used in a relatively high surface pressure environment, such as when used for a bearing of a hydraulic excavator, When the kinematic viscosity exceeds 1500 cSt, the fluidity decreases and the occurrence of capillary action (described later) by the filament 35 on the sliding surface 25 is hindered, making it difficult to maintain the sliding surface 25 in a lubricated state. Because it becomes. Note that the lubricating oil 32 of the present embodiment has a kinematic viscosity of 460 cSt.

  As the lubricating oil 32, a general lubricating oil having a composition that is generally commercially available, such as mineral oil or synthetic oil, wax based on paraffin, and the like can be used. However, the composition itself is not particularly limited as long as the viscosity is within the above range.

FIG. 5 is an enlarged cross-sectional view of the cross section of the thread-like body 35 in the sliding member according to the embodiment of the present invention.
The thread-like body 35 secures the lubricating oil 32 by a capillary phenomenon and holds the sliding surface 25 in a lubricated state, and at least a part thereof is held on the sliding surface 25 while being in contact with the lubricating oil 32. In FIG. 5, the filament 35 is composed of a plurality of filaments 36 and self-lubricating particles 37 woven into the plurality of filaments 36.

  The filament 36 is a thin fiber, natural fiber (for example, cotton, hemp, hair, silk), chemical fiber (for example, rayon, acetate fiber, aramid fiber, polyester fiber, acrylic fiber), inorganic fiber (for example, glass fiber) Carbon fiber, ceramic fiber, whisker), metal fiber (for example, stainless steel fiber), carbon fiber, or the like can be used. The length of the filament 36 is preferably non-uniform. In this way, as will be described later, the thread-like body 35 is held in a posture placed on the sliding surface 25 (the thread-like body 35c in FIG. 4), or a part of the thread-like body 35 is in the hole 31 (recess 33). The thread-like body 35 can be arranged in various portions near the sliding surface 25, for example, by being held in an intrusive posture (thread-like body 35b in FIG. 4). Accordingly, since the sliding surface 25 is promoted to be held in a lubricated state, the bearing performance of the bush 16 can be extended.

  In addition, from the viewpoint of improving the lubricity of the bush 16, it is preferable to use a fiber (for example, a chemical fiber) having better self-lubricating property than the other filament 36 for the filament 36. Further, from the viewpoint of improving the strength of the thread-like body 35, the thread-like body 35 is preferably formed of filaments of aramid fibers (for example, para-type wholly aromatic polyamide fibers), polyester fibers, carbon fibers, and glass fibers. In addition, when comprising the filament 35 in this way, it is sufficient that at least one of the above-mentioned fibers is included.

  The self-lubricating particles 37 are particles of a solid lubricant having self-lubricating properties. The self-lubricating particles 37 improve the lubricity of the thread-like body 35 and the bush 16 and hold the lubricating oil 32 in the thread-like body 35. The diameter is preferably at least smaller than the diameter of the hole 31 (for example, 50 μm) and smaller than the diameter of the thread 35 so that the thread 35 enters the hole 31. As the self-lubricating particles 37, from the viewpoint of improving lubricity, it is preferable to use fluororesin (for example, polytetrafluoroethylene (PTFE)), molybdenum disulfide, carbon such as graphite, and the like. It is good to include what consists of these. When such self-lubricating particles 37 are used, the thread 35 or the self-lubricating particles 37 themselves are released onto the sliding surface 25 by the continuous use of the bush 16 or the like and can move freely (FIG. 4). The thread-like body 35 and the self-lubricating particles 37 also act as lubricants on the thread-like body 35e), so that the sliding characteristics of the bush 16 are improved.

  In order to arrange the thread-like body 35 on the sliding surface 25, it is preferable to use a suction force into the bush 16 generated when the lubricating oil 32 is impregnated in the air holes 31. Specifically, the following processing is performed.

  In order to perform this treatment, first, the lubricating oil 32 having a high viscosity state at normal temperature is heated to lower the viscosity (liquefaction). The thread-like body 35 formed in an appropriate diameter and length is mixed in the lubricating oil 32 thus reduced in viscosity, and the bush 16 is immersed in the lubricating oil 32 and left in a vacuum atmosphere. Thereby, the air in the air holes 31 of the bush 16 is sucked to the outside, and the lubricating oil 32 and the thread-like body 35 are sucked toward the inside of the bush 16. When the bush 16 that has sucked the lubricating oil 32 and the filament 35 is taken out into the air and allowed to cool to room temperature, the low-viscosity lubricating oil 32 returns to the high-viscosity lubricating oil in the air holes 31 of the bush 16 and is fluid. Lose. Thereby, the lubricating oil 32 and the thread-like body 35 can be retained in the air holes 31 of the bush 16.

  According to the above processing, the thread-like body 35 is arranged in the sliding surface 25 and the hole 31 in various postures according to conditions (for example, the diameter and length of the thread-like body 35 and the diameter of the hole 31). . For example, the filament 35a in FIG. 4 is held in the hole 31 so that the end is positioned on the lubricating oil interface L at the start of sliding. Further, the filament 35b is held in the hole 31 so that a part of the end protrudes from the lubricating oil interface L. The filament 35c is held so as to be placed on the sliding surface 25. The entire thread-like body 35 d is held so as to be accommodated in the lubricating oil 32 in the hole 31. In addition, although different from what is arrange | positioned by said process, the thread-like body 35e is discharge | released on the sliding surface 25 by sliding of the axis | shaft 22 and the bush 16, and can move freely.

  As described above, various cases can be considered for the arrangement of the thread-like body 35. According to the above procedure, the thread-like body 35 is disposed on at least the sliding surface 25. On the other hand, there is a layer of a small amount of lubricating oil 32 on the sliding surface 25, and this lubricating oil 32 is connected to the lubricating oil in the air holes 31. Therefore, the sliding surface 25 can be in a lubricated state from the start of sliding due to the lubricating oil contained in the thread 35 disposed on the sliding surface 25 and the capillary phenomenon of the thread 35. Thus, with respect to the arrangement of the thread-like body 35 on the sliding surface 25, a part of the thread-like body 35 such as the thread-like bodies 35b and 35c is formed from the viewpoint of making the sliding surface 25 in a lubricated state from the start of sliding. It is sufficient if it is in contact with the lubricating oil 32.

  However, in order to further promote the entry / exit action of the lubricating oil 32 from the inside of the hole 31 (concave portion 33), it is preferable to arrange the thread-like body 35 in various positions near the sliding surface 25 in various postures. . For that purpose, first, the diameter of the filament 35 is preferably made smaller than the average diameter (for example, 50 μm) of the air holes 31. If the lubricating oil 32 including the thread-like body 35 having such a diameter is sucked into the bush 16 as described above, the ratio of the thread-like body 35b disposed on the sliding surface 25 so that a part thereof enters the hole 31. Can be high. As a result, the thread-like body 35 becomes a flow path of the lubricating oil 32 that directly connects the sliding surface 25 and the inside of the hole 31, so that the lubricating oil 32 in the bush 16 can be easily led out onto the sliding surface 25, and Excess lubricating oil 32 on the sliding surface 25 can be easily reduced into the bush 16 after the movement is completed. Further, in order to further promote the action of the lubricating oil 32 in and out, the length of the thread-like body 35 is made non-uniform, and at least longer and shorter than the average diameter (for example, 50 μm) of the holes 31 are included. It is better to Thereby, the thread-like body 35 is arranged so as to be placed on the sliding surface 25 like the thread-like body 35c, or a part of the thread-like body 35 enters the hole 31 (recess 33) like the thread-like body 35b. Or like the filaments 35a and 35d so that the whole enters the hole 31. Therefore, the filaments 35 can be arranged in various postures in various portions of the sintered alloy layer 30 constituted by the non-uniformly shaped holes 31.

  In FIG. 3, the back metal layer 40 is made of an iron-based material. Similarly to the sliding surface 25 of the sintered alloy layer 30, the back metal layer 40 is also formed with a hardened layer by a surface modification treatment such as carburizing and nitriding, thereby further improving 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 is improved as compared with the case where the bush 16 is constituted only by the sintered alloy layer. As a result, the amount of elastic deformation of the bush 16 is reduced, so that fretting wear and abnormal noise can be suppressed.

Next, the operation and effect of the present embodiment will be described.
First, in order to facilitate understanding of the effects of the present embodiment, a comparative example of the present embodiment will be described.

  Unlike the above-described embodiment, the first comparative example (first comparative example) is one in which a sintered alloy layer is impregnated with only lubricating oil (see Patent Document 1, etc.). In this technique, a certain amount of frictional heat is required for the lubricating oil impregnated in the sintered alloy layer to be properly supplied to the sliding surface with the counterpart material (shaft). It takes some time to reach lubrication. For this reason, for example, if sliding occurs before the sliding surface becomes lubricated, or if minute sliding (vibration) occurs, abnormal wear such as fretting wear or abnormal noise may occur due to poor lubrication. There was also. In addition, in connection with this, there is a technique of impregnating the lubricant with particulate solid lubricant, but since the solid lubricant is present in the lubricant, the action of positively coming out on the sliding surface is In addition, it was difficult to expect the lubricating effect of the solid lubricant. Thus, with this type of technology, it has been difficult to reduce the time required for the sliding surface to reach the lubrication state from the start of sliding.

  As a next comparative example (second comparative example), there is a technique of impregnating a sintered alloy layer with PTFE or fluororesin particles as a single body or a composite material. However, even in this type of technology, PTFE or the like is in the form of particles as in the above-described solid lubricant and is present in the lubricating oil. Therefore, it has been difficult to shorten the time required from the start of sliding to the lubrication state.

  On the other hand, as a technique for improving the sliding characteristics of the sliding member, a technique for improving lubricity by enclosing solid lubricant fine particles (self-lubricating particles) in microcapsules and impregnating them with lubricating oil is also considered. It is done. However, in this case, it is difficult to recover the self-lubricating particles after the capsule is cracked, and the amount of what flows out to the outside inevitably increases, so the period during which the lubricity can be maintained is shortened.

  In contrast to these techniques, the sliding member according to the present embodiment is provided with the sintered alloy layer 30 in which the air holes 31 are impregnated with the lubricating oil 32, and at least a part of the sliding member, for example, the thread-like bodies 35 b and 35 c. 32 and a thread-like body 35 held in contact with the sliding surface 25. According to the sliding member of the present embodiment configured as described above, the lubricating oil 32 is formed on the sliding surface 25 by the lubricating oil contained in the filament 35 and the capillary phenomenon of the filament 35 regardless of the presence or absence of frictional heat. Retained. In addition, since the self-lubricating particles 37 woven into the thread 35 act as a lubricant, and the lubricating oil 32 derived by the capillary phenomenon is secured in the thread 35, the lubricating oil 32 is further retained. Promoted. As a result, the sliding surface 25 can be kept in a lubricated state from the start of sliding without waiting for the supply of the lubricating oil 32 due to frictional heat as in the first comparative example. Therefore, according to the present embodiment, the time required for the sliding surface 25 to reach the lubricating state from the start of sliding is shortened, so that the sliding characteristics of the sliding member at the start of sliding can be improved. .

  In the first comparative example, as a phenomenon that is particularly noticeable at the beginning when the sliding member is impregnated with the lubricating oil, the lubricating oil is supplied to the sliding surface more than necessary by frictional heat, and the surplus amount Sometimes leaked to the outside. On the other hand, in the present embodiment, the thread 35 and the self-lubricating particles 37 prevent the lubricating oil 32 from flowing out of the pores 31, so that the greasing interval is set as compared with the comparative example. Can be extended.

  Further, as described above, since the self-lubricating particles 37 are woven into the thread-like body 35 of the present embodiment, the self-lubricating particles 37 are also included in the lubricant even after the sliding surface reaches the lubrication state. The sliding characteristics during sliding are also improved. This effect can also be obtained when the filament 35 is missing from the pores 31 and moves freely on the sliding surface 25. Further, even if the self-lubricating particles 37 are once released from the filament 35, the filament 35 can trap the self-lubricating particles 37 again between the plurality of filaments 36. And the life can be extended. As described above, this embodiment not only shortens the time required from the start of sliding to the lubrication state, but also improves the sliding characteristics of the sliding member after the sliding surface reaches the lubrication state. And the outstanding effect of extending the lifetime of a sliding member can also be exhibited.

The side view of the hydraulic shovel which is an example of the machine in which the sliding member which is embodiment of this invention is used. Sectional drawing of the bearing provided with the sliding member which is embodiment of this invention. The fragmentary sectional view of the sliding member which is an embodiment of the invention. The enlarged view of the sliding surface vicinity of the sliding member which is embodiment of this invention. The expanded sectional view of the cross section of the filament 35 in the sliding member which is embodiment of this invention.

Explanation of symbols

22 shaft (partner material)
25 Sliding surface 30 Sintered alloy layer 31 Hole 32 Lubricating oil 35 Threaded body 36 Filament 37 Self-lubricating particles

Claims (5)

A sliding member formed by sintering a metal powder containing iron and copper, and having a sintered alloy layer having a plurality of pores on a sliding surface with a counterpart material,
A lubricating oil having a kinematic viscosity impregnated in the pores in the range of 460 to 1500 cSt;
A plurality of filaments, and a filament formed of self-lubricating particles woven into the plurality of filaments,
The sliding member, wherein at least a part of the filamentous body is held on the sliding surface while being in contact with the lubricating oil. The sliding member according to claim 1,
A sliding member characterized in that a diameter of the filament is smaller than a diameter of the hole. The sliding member according to claim 1 or 2,
The sliding member is characterized in that the filament has a length smaller than the diameter of the hole. In the sliding member in any one of Claim 1 to 3,
The self-lubricating particles include those made of any one of fluororesin, molybdenum disulfide, and carbon. In the sliding member in any one of Claim 1 to 4,
A sliding member characterized in that the filament includes any of aramid fiber, polyester fiber, carbon fiber, and glass fiber.

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