JP6196800B2 - Sliding member - Google Patents

Description

  The present invention relates to a sliding member.

  As a sliding member such as a bearing material, it is known to use a copper alloy using graphite as a solid lubricant. For example, Patent Document 1 describes a method of blending massive graphite coated with copper and dispersing massive graphite on the surface of a bearing when manufacturing a copper-based sintered alloy bearing. Patent Document 2 discloses that a bar-shaped solid lubricant mainly composed of graphite is embedded in a recess such as a hole formed on the surface of a metal substrate through sodium silicate, and both graphite and sodium silicate are contained. It describes that it functions as a solid lubricant.

JP-A-5-209207 Japanese Patent No. 3960672

  However, in the method of Patent Document 1, since a large amount of foreign matter is intentionally mixed in the sintered alloy, although it is difficult to cleave with the copper coating, a decrease in the overall strength is inevitable. Further, in the method of Patent Document 2, it is necessary not only to prepare a solid lubricant mainly composed of graphite having a shape matched to a recess such as a hole, but also to adhere graphite using sodium silicate as an adhesive. The drying process was required (Patent Document 2 [0017]). Furthermore, since the solid lubricant mainly composed of adhered graphite is distributed on the sliding surface in the order of mm, there are a large number of places where the solid lubricant is small in the order of mm and is in contact with the sliding member. The sliding member has a problem that a discontinuous solid lubricating region in the order of mm occurs.

  Therefore, the present invention provides a sliding member that does not cause a decrease in strength, does not require a treatment such as adhesion or drying, and does not generate a discontinuous surface when manufacturing a sliding member made of a copper alloy. It aims at arranging graphite on the moving member surface.

  The present invention comprises a plurality of circular recesses formed on a sliding surface and graphite held in the circular recesses, and a raised portion formed around the circular recess is formed at the center of the circular recess. The above-mentioned problem has been solved by using a sliding member having a reduced diameter opening plastically deformed to the side.

  As a method of forming a circular recess that generates a raised portion around the above, by forming a dimple with particles applied to the surface of the sliding member once manufactured, while deforming by external force to form a circular recess, It is preferable that a part of the meat of the circular recess is accumulated or deformed in the periphery to generate a raised portion.

  In addition, it does not need to be a perfect perfect circle, and may be elliptical as long as graphite can be held inside.

  As a method of holding the graphite in the circular recess, it is only necessary that a thin exfoliated piece of graphite fits in the circular recess. For example, by moving the graphite lump directly in contact with the sliding surface, If a part of the lump of graphite is peeled off and attached in the circular recess, the graphite can be held electrostatically by itself. Alternatively, the graphite can be held in the circular recess by removing the liquid after the graphite is dispersed in the liquid and poured into the circular recess.

  The bulging portion may be plastically deformed toward the center of the circular concave portion before or after holding the graphite. However, if it is held before plastic deformation, either direct pressure welding of graphite or introduction with a graphite dispersion liquid is possible, but if held after plastic deformation, the opening is reduced in diameter so that direct pressure welding is possible. Is difficult to introduce by graphite dispersion liquid.

  Regardless of the procedure, by holding graphite in a circular recess formed in an appropriate size and occupying an appropriate occupancy ratio, the surface of the graphite itself can be reduced without causing a reduction in the strength of the member itself. Can be arranged. Because graphite is surrounded by a reduced diameter opening without using other adhesive components, graphite can be kept attached for a long period of time, so no extra treatment is required and an adhesive is used. It can be arranged with higher uniformity than in the case.

  According to the present invention, it is possible to use from a copper alloy member for a long period of time without causing a decrease in strength, without requiring treatment such as adhesion and drying, and suppressing the occurrence of discontinuous surfaces. In addition, a useful copper alloy sliding member having graphite on the surface can be obtained.

  Even more preferably, under the conditions of this invention, the graphite surrounded and held by the reduced diameter of the opening acts as a solid lubricant, so that the sliding member is supplied with lubricating oil. It can also be used over a long period of time without so-called lubrication.

Sectional drawing of the 1st procedure example among the manufacturing methods of the sliding member concerning this invention Sectional drawing of the 2nd example of a procedure among the manufacturing methods of the sliding member concerning this invention Conceptual diagram when the reduced diameter opening is not formed Disc surface photograph after introduction of graphite in Examples Schematic of the ring-on-disk tester used in the examples The graph which shows the result of the friction test in an Example Disc surface photo after friction test in Examples

  The present invention will be specifically described below. The present invention is a copper alloy-based sliding member that can be used for a long period of time without the need to supply lubricating oil with graphite held in a circular recess formed on the surface. Here, copper alloy-based means that 50% by mass or more is an alloy made of copper, and may be a bronze-based copper alloy containing 1% by mass to 15% by mass of Sn. A component that becomes such a bronze-based copper alloy is preferable because of its high strength. In addition, an element contained in a general copper alloy such as Fe or P may be included.

  In the sliding member according to the present invention, after forming the outer shape of the sliding member, (A) a step of forming the circular recess on the sliding surface, (B) a step of holding graphite in the circular recess, (C ) The step of reducing the diameter of the circular recess is obtained by changing the order of (B) and (C). That is, it can be obtained by any one of the procedure shown in FIG. 1 and the procedure shown in FIG.

  The method for forming the outer shape of the sliding member with the copper alloy material is not particularly limited. For example, a powder blended at a predetermined component ratio may be melted and then cooled by a mold, or may be formed by sintering after the powder is hardened.

  Then, first, in any procedure, the step (A) for forming the circular recess is performed. 1 and 2 are the procedures from (a) to (b). The method for forming the circular concave portion is not particularly limited as long as it can be formed while generating a raised portion around the circular concave portion. For example, there is a method in which particles having a hardness higher than that of a copper alloy are collided to form the circular recess as fine dimples on the surface. The particles are preferably spherical, but circular recesses can be formed even if they are not perfect spheres. Note that the circular recess does not have to be a perfect circle, and may be an ellipse as long as the deformation is such that graphite can be held inside.

  The subsequent steps vary depending on the procedure. First, the step (B) for holding graphite in the circular recess will be described. This step is performed after (A) (b to c) in the procedure of FIG. 1, but after (C) (c to d) in the procedure of FIG. The method for holding the graphite in the circular recess is not particularly limited as long as the graphite exfoliation piece can be electrostatically introduced and held in the circular recess. However, it is desirable that the bonding is not based on an adhesive. For example, there is a method in which a lump of graphite is rubbed while being pressed against a sliding surface having a circular recess, and the lump of graphite is scraped off at the edge of the recess and the peeled piece is fixed in the recess. The graphite lump used here may not be pure graphite, and may have sulfur, clay, and other binding components for lumping graphite. Note that these coupling components do not significantly affect the electrostatic adhesion to the sliding surface. As another method, the solvent may be dried after applying the dispersion liquid in which the exfoliated pieces of graphite are dispersed in the liquid.

  However, among the above-mentioned holding methods, when performing a method in which the massive graphite is pressed and rubbed on the sliding surface, it is preferable to execute (B) before (C) below. This is because, after executing the following (C), the diameter of the opening is reduced, so that it is somewhat difficult to hold the graphite inside the circular recess even if the graphite is pressed. On the other hand, when a graphite dispersion is used, the order of (B) and (C) can be either, and either the procedure of FIG. 1 or the procedure of FIG.

Next, the step (C) for reducing the diameter of the circular recess will be described. This step is performed after (B) (c to d) in the procedure of FIG. 1, and after (A) (b to c) in the procedure of FIG.
The raised portion formed around the circular recess in the step (A) is plastically deformed toward the center of the circular recess to reduce the diameter. If the diameter is not reduced, the graphite is peeled off from the edge of the circular recess due to the sliding pressure, and the state as shown in FIG. 3 is likely to occur. If the diameter of the opening is reduced, the hole becomes smaller, but a large space is left inside, that is, sufficient graphite can be held. The formed graphite is difficult to peel off during sliding, and can maintain slidability for a long period of time.

  As a method of reducing the diameter of the opening, it is necessary to apply pressure enough to plastically deform the entire sliding surface. Specifically, the processing is performed by a burnishing tool, a press machine, a simple roller, and the circular recess. A hammer with a sufficiently large area can be used. When pressure is applied with a material having graphite on the surface, the reduced diameter opening can be formed while graphite is replenished in the circular recess.

  In this step (C), it is preferable that the sliding surface is smoothed as the raised portion is deformed. That is, it is preferable that after the deformation, the top of the raised portion is pressed down to the same height as the periphery of the circular recess.

  The area occupied by the circular recess on the sliding surface at the time of holding graphite is preferably 5% or more, more preferably 7% or more, and further preferably 10% or more. On the other hand, since the higher the ratio occupied by the circular recesses, the easier it is to hold graphite, there is no particular upper limit as long as the strength of the sliding member itself can be secured.

  The average size of the openings on the surface of each of the circular recesses is preferably 5 μm or more at the time of formation. If the opening is too small, it is difficult to introduce graphite into the circular recess, and it is difficult to hold the graphite depending on the shape.

  On the other hand, it is preferable that the diameter-reduced opening after the opening is formed and the surrounding raised portion is plastically deformed toward the center side is 75 μm or less. This is because if the diameter exceeds 75 μm, the reduced-diameter opening is too wide to hold the graphite exfoliation pieces.

  Specific examples of the copper alloy-based sliding member according to the present invention will be described below. First, as a test material, a sintered body of a copper alloy containing tin, iron, sulfur, and phosphorus was prepared on a hot-rolled steel sheet having a thickness of 5 mm so as to form a sintered body layer having a thickness of 2 mm. Its plasticity is equivalent to CDA (American Copper Development Association) standard C90280, which is a bronze alloy containing sulfide.

  The sintered body layer had a hardness of about 220 Hv and a structure in which fine sulfides were mainly included in the grain boundary portion. This plate material was processed into a disk shape of Φ50 mm × Φ26 mm × h6.2 mm to obtain a test piece. Then, the side surface of the sintered copper alloy layer of this disk was finished by turning to obtain a test surface.

  On this surface, a circular concave portion which is a microdimple was formed by fine particle peening. Glass beads having an average particle diameter of 50 μm were used as the projection material. The size of each circular recess is about 20 μm. On the surface, a black core of uni4.0B manufactured by Mitsubishi Pencil Co., Ltd. was applied as a graphite source and rubbed evenly to introduce graphite into the circular recess. Furthermore, roller burnishing was performed on this surface, and the raised portion around the circular recess was pushed in to form a reduced diameter opening. A photograph of this surface is shown in FIG.

<Surface roughness Ra measurement>
Before and after starting the following coefficient of friction test, the surface roughness (that is, the height direction) is measured by a contact-type roughness meter over a straight line in the radial direction on the surface of the disk specimen. The displacement in the axial direction of the surface depression caused by wear before and after the test was calculated. The area wear amount was defined as the area wear amount, and the volume wear amount was calculated by integrating the disk test piece for one round. When Ra before the friction coefficient test was measured, it was 0.24 μm.

<Friction coefficient test>
The friction coefficient of this sliding member was measured. For the measurement, a ring-on-disk tester having the structure shown in FIG. 5 was used. A disk fixed to a rotating plate 16 connected to a spherical air bearing (not shown) composed of a hemispherical surface and a porous carbon concave surface disposed at the lower portion by rotating a ring test piece 11 disposed at the upper portion of the apparatus by a motor. This is a method of contacting with the test piece 12. The friction torque during the experiment was detected as a bending strain of the cantilever using a leaf spring fixed around the disk test piece 12 and converted into a frictional force.

  The ring test piece 11 which is a counterpart material was a ring-shaped test piece (hardness 700-7520 Hv) having an outer diameter φ40 × inner diameter φ30 × thickness 14 mm using carbon steel S45C subjected to induction hardening on one end side. . After the heat treatment, the test surface was lapped to obtain a mirror surface (0.003 / 0.55 Ra / Rmax). As the disk test piece 12, the sintered body as described above was used, and graphite was already introduced on the surface.

  The ring test piece 11 was placed on the surface of the disk test piece 12 with the axis aligned, and the disk 13 was placed thereon. A ball joint 14 was provided at the center of the disk 13 and a load of 80 N was applied from above. This load was measured with a strain gauge 15 provided above the ball joint, and it was confirmed whether the load was maintained. The rotating plate 16 on which the disk test piece 12 is placed in a state where the disk test piece is immersed in lubricating oil (viscosity: 5 cSt @ 40 ° C.) at normal temperature is rotated to 0.05 m / s with respect to the ring, and friction is caused. The friction coefficient was measured until the distance was 360 m, and this was recorded at a cycle of 0.2 seconds. The result is shown in FIG. The coefficient of friction did not exceed 0.1 throughout, and the effect of decreasing the coefficient of friction over time was observed. This is considered that the graphite stored in the dimples is more evenly diffused with sliding, and the smoothness is further improved with use. Moreover, it is considered that the effect continues for a long time due to the effect of the reduced diameter opening.

  Moreover, the surface photograph after wash | cleaning with methanol after completion | finish and dropping a graphite and shavings is shown in FIG. No seizure of the surface was observed, and it was confirmed that it worked well as a sliding member. When Ra was measured at this time, it was 0.35 μm.

11 Ring test piece 12 Disc test piece 13 Disk 14 Ball joint 15 Strain gauge 16 Rotating plate

Claims (1)

The manufacturing method of the copper alloy type | system | group sliding member with which the sliding surface was filled with graphite which performs the following step A thru | or C in the order of A, B, C, or A, C, B.
A. A step of causing a plurality of particles to collide with the sliding surface to form a plurality of circular recesses having raised portions around the periphery.
B. Introducing graphite into the circular recess.
C. Plastically deforming the raised portion toward the center of the circular recess to reduce the diameter of the opening of the circular recess and smoothing the entire sliding surface.