JP6624680B2 - Sliding device - Google Patents

Description

  The present invention relates to a sliding device including a shaft member and a sliding member that supports the shaft member. More specifically, the present invention relates to a shaft member made of a synthetic resin and a slide made of a synthetic resin and flake graphite on a back metal layer. And a sliding member having a moving layer.

Conventionally, a sliding device having a structure in which two members whose sliding surfaces that are in sliding contact with each other are both a resin composition has been used. One of the two members is a shaft member that performs a rotating operation or a reciprocating operation, and the other is a sliding member having a sliding layer that supports the shaft member.
As a shaft member, a material in which hard particles such as carbon fibers, glass fibers, metal particles, and ceramic particles are contained in a synthetic resin in order to increase strength has been conventionally known (see Patent Documents 1 and 2). .

  On the other hand, as a sliding member, a sliding member having a resin composition obtained by adding scaly graphite as a solid lubricant to a synthetic resin has been conventionally used (Patent Document 3). Natural graphite is generally classified into scaly graphite, scaly graphite and soil graphite according to its properties. The degree of graphitization is highest for scaly graphite at 100%, then at 99.9% for scaly graphite, and as low as 28% for soil graphite. Conventionally, as a graphite as a solid lubricant for a sliding member, flaky graphite having a high degree of graphitization or flaky particles obtained by mechanically pulverizing natural graphite such as flaky graphite has been used.

  This scaly graphite is a crystal in which carbon atoms form a regular network structure and a large number of AB planes (hexagonal mesh planes, basal planes) are laminated, and have a thickness in the C-axis direction perpendicular to the AB planes. It is. Since the bonding force due to the van der Waals force between the stacked AB surfaces is much smaller than the bonding force in the in-plane direction of the AB surfaces, shear is likely to occur between the AB surfaces. Therefore, this graphite has a thin plate shape as a whole because the thickness of the lamination is smaller than that of the AB plane. It is considered that the flaky graphite particles function as a solid lubricant by shearing between AB surfaces when subjected to an external force.

JP 2001-132775 A JP-A-5-179277 JP 2005-89514 A

  A sliding device having a structure in which a shaft member and a sliding member, both of which slide surfaces slide with each other, is a resin composition, is frequently started and stopped in an environment where oil is supplied between the sliding surfaces. (Hereinafter referred to as “intermittent operation”) is often performed, and when the operation state changes to the stop state, the oil film formed between the sliding surfaces is interrupted, and the shaft is temporarily stopped. An extreme pressure load is applied to the sliding surface of the sliding member from the member, especially from the hard particles protruding on the surface. A sliding member using a resin composition containing flake graphite particles in a synthetic resin as in Patent Document 3 is used for a sliding portion that supports a shaft member made of a resin composition containing hard particles. It was found that the resin on the sliding surface of the sliding member was cracked and dropped from the sliding surface, resulting in a decrease in sliding performance.

  Therefore, an object of the present invention is to provide a sliding device having a structure in which a sliding member is a combination of a shaft member and a sliding member, both of which are made of a resin composition. Another object of the present invention is to provide a sliding device which is less likely to cause cracking and falling off of the resin on the sliding surface of the sliding member and has excellent wear resistance.

According to one aspect of the present invention, there is provided a sliding device including a shaft member made of a synthetic resin in which 5 to 50% by volume of hard particles are dispersed, and a sliding member that supports (supports) the shaft member. Is done. The sliding member includes a back metal layer and a sliding layer provided on the back metal layer, and the sliding layer is made of a synthetic resin and flaky graphite particles dispersed in the synthetic resin, and the flaky graphite. The total volume of the particles accounts for 5 to 50% by volume of the volume of the sliding layer. The flake graphite particles have a flat plate shape, and the cross-sectional structure thereof is such that a plurality of AB planes of the graphite crystal are laminated in a thickness direction of the flat plate shape (that is, a C-axis direction perpendicular to the AB plane of the graphite crystal). are doing. The average particle size of the flaky graphite particles is 3 to 25 μm. The flaky graphite particles include void-containing flaky graphite particles having voids inside the tissue. Here, the void-containing flaky graphite particles, among the flaky graphite particles,
The length in the major axis direction is 3 μm or more,
In the cross-sectional structure is a void extending in the major axis direction of the flake graphite particles, the void length in a direction parallel to the major axis direction of the flake graphite particles, the length of the major axis direction of the flake graphite particles It has a void of 50% or more. The volume ratio of the void-containing flake graphite particles to the total volume of the flake graphite particles in the sliding layer is 10% or more.

  In the sliding device of the present invention, flake graphite particles dispersed in the sliding layer of the sliding member mainly act as a lubricating component. As described above, the flaky graphite particles dispersed in the sliding layer are crystals having a large number of AB planes (hexagonal planes) laminated and having a thickness in the C-axis direction perpendicular to the AB plane. When the surface consisting of the AB surface of the graphite crystal is exposed on the sliding surface, the AB surface comes into contact with the mating shaft in the sliding direction with the mating shaft. Therefore, when a load is applied from the mating shaft substantially parallel to the sliding surface, shearing easily occurs between the AB surfaces, and as a result, the frictional force between the sliding surface and the mating shaft surface decreases, and the sliding force decreases. Layer wear is reduced.

  Further, the sliding member of the sliding device of the present invention may be used in an intermittent operation mode in a situation where an extreme pressure is temporarily applied to the sliding layer when the sliding layer is changed from the operating state to the stopped state. The void-containing flaky graphite particles having voids inside the tissue dispersed in the sliding layer can prevent the resin on the sliding surface from falling off for the following reasons.

The maximum length (gap) in the direction perpendicular to the long axis direction of the voids in the structure (internal structure) of the void-containing flaky graphite particles is 0 in the cross-sectional structure perpendicular to the sliding surface of the sliding layer. It is about 0.01 μm to 1 μm. The void-containing flaky graphite particles contained in the sliding layer undergo elastic deformation so that a gap inside the particles becomes small when an external force is applied. That is, the gap is elastically deformed so that the length of the gap in a direction substantially perpendicular to the long axis direction of the gap becomes small.
In the sliding member of the sliding device of the present invention, when an extreme pressure load is temporarily applied to the sliding surface when the device changes from the operation state to the stop state, the flake-like voids included in the sliding layer are formed. The graphite particles undergo elastic deformation so as to reduce the voids, thereby alleviating the extreme pressure load applied to the sliding layer. Since the void-containing flake graphite particles having such a buffering action are dispersed in the sliding layer, the extreme pressure load applied to the synthetic resin of the sliding layer is reduced, and as a result, the resin on the sliding surface falls off. Is prevented.

  The flaky graphite particles having a length of less than 3 μm in the major axis direction have a low effect of relieving the extreme pressure load applied to the sliding surface of the sliding layer, even if there are voids inside the tissue. When the length in the major axis direction is 3 μm or more, an effect of relaxing an extreme pressure load applied to the sliding surface of the sliding layer is obtained. By dispersing the flaky graphite particles, even when an extreme pressure is applied to the sliding surface of the sliding layer, the synthetic resin on the sliding surface can be prevented from cracking or falling off.

  In the sliding member of a conventional sliding device having a sliding layer in which flaky graphite particles having no voids in the tissue are dispersed in a synthetic resin, the sliding device in which the sliding member is used is stopped from an operating state. The extreme pressure applied to the sliding surface temporarily causes the synthetic resin on the sliding surface to crack and fall off, and the falling part of this synthetic resin becomes the starting point, causing the sliding layer to wear. Is more likely to occur.

  The average particle size of the flaky graphite particles (all flaky graphite particles including void-containing flaky graphite particles) is preferably 3 to 25 μm. When the average particle size of the flaky graphite particles is less than 3 μm, an aggregated portion of the flaky graphite particles is easily formed in the sliding layer, and the strength of the sliding layer may be reduced. If the average particle size of the flake graphite particles exceeds 25 μm, the load applied to the sliding layer during sliding may cause shearing of the flaky graphite particles in the sliding layer, which may lower the strength of the sliding layer.

  According to one embodiment of the present invention, the volume ratio of the void-containing flaky graphite particles to the total volume of the flaky graphite particles in the sliding layer is preferably 20% or more. When the volume ratio of the void-containing flake graphite particles to the total volume of the flake graphite particles in the sliding layer is 20% or more, the wear resistance is further improved as compared with the case where the volume ratio is less than 20% by volume. This is because the volume ratio of the void-containing flake graphite particles dispersed in the sliding layer is increased, and the extreme pressure load from the shaft member on the sliding layer is further reduced. It is considered that the resin hardly falls off from the resin and the wear resistance is improved. Further, the volume ratio of the void-containing flake graphite particles is preferably 25% by volume or more.

  According to one embodiment of the present invention, the average aspect ratio (A1) represented by the average of the ratio of the major axis to the minor axis of the flaky graphite particles (all flake graphite particles including void-containing flaky graphite particles) is: , 5 to 15. When the average aspect ratio of the flaky graphite particles is 5 or more, the wear resistance is further improved as compared with the case where the average aspect ratio is less than 5. This is because the surface area of the flaky graphite particles increases, the contact area of the flaky graphite particles with the synthetic resin increases, and the adhesive property with the synthetic resin increases. It is thought that it becomes difficult. Further, the average aspect ratio of the flaky graphite particles is preferably 6 or more. Further, when the average aspect ratio of the flaky graphite particles is 15 or less, shear is unlikely to occur in the flaky graphite particles in the sliding layer due to an extreme pressure applied to the sliding layer when the operating state is stopped. However, when the average aspect ratio of the flaky graphite particles exceeds 15, the flaky graphite particles in the sliding layer may be sheared and the strength of the sliding layer may be reduced.

According to one embodiment of the present invention, the flake graphite particles (all flake graphite particles including void-containing flake graphite particles) preferably have an anisotropic dispersion index S1 of 3 or more. This anisotropic dispersion index S1 is defined as the average of the values of the ratio X1 / Y1 for each flaky graphite particle. Here, X1 is the length in the direction parallel to the sliding surface of the flake graphite particles in the cross-sectional structure perpendicular to the sliding surface of the sliding layer, and Y1 is the length of the sliding surface of the sliding layer. On the other hand, it is the length in the direction perpendicular to the sliding surface of the flaky graphite particles in the vertical section structure.
The value of the anisotropic dispersion index S1 increases as the proportion of the major axis direction of the flake graphite (the direction in which the surface composed of the AB plane spreads) is oriented substantially parallel to the sliding surface increases.

  The flaky graphite particles have an anisotropic dispersion index S1 of 3 or more, and if the proportion of those whose major axis direction is substantially parallel to the sliding surface is large, the flaky graphite particles exposed on the sliding surface of the sliding layer. Of these, the proportion of those in which the AB surface is oriented substantially parallel to the sliding surface increases, so that the frictional force between the sliding surface of the sliding layer and the shaft member surface decreases, and the wear amount of the sliding layer decreases. The flake graphite particles more preferably have an anisotropic dispersion index of 4 or more.

  Further, when an extreme pressure load from the shaft member is applied to the sliding surface of the sliding member when the device using the sliding member is changed from the operation state to the stop state as described above, the anisotropic dispersion index S1 is 3 or more. In that case, the void-containing flaky graphite particles also have a large proportion of those whose longitudinal direction and the direction of extension of the voids of the internal structure of the particles are oriented substantially parallel to the sliding surface. The effect of alleviating the extreme pressure load applied to the sliding layer by the voids is further enhanced.

  According to one embodiment of the present invention, the synthetic resin used for the sliding layer of the sliding member is PAI (polyamide imide), PI (polyimide), PBI (polybenzimidazole), PA (polyamide), phenol, epoxy , POM (polyacetal), PEEK (polyether ether ketone), PE (polyethylene), PPS (polyphenylene sulfide) and PEI (polyetherimide).

According to one embodiment of the present invention, the sliding layer of the sliding member has 1 to 20 volumes of one or more solid lubricants selected from spheroidal graphite, MoS ₂ , WS ₂ , h-BN and PTFE. %. By containing a solid lubricant, the sliding characteristics of the sliding layer can be enhanced.

According to one embodiment of the present invention, the sliding layer of the sliding member is selected from CaF ₂ , CaCo ₃ , talc, mica, mullite, iron oxide, calcium phosphate, and Mo ₂ C (molybdenum carbide). The seed or two or more fillers may further comprise 1 to 10% by volume. By containing the filler, it becomes possible to enhance the wear resistance of the sliding layer.

  According to one embodiment of the present invention, the sliding member may further include a porous metal layer between the back metal layer and the sliding layer. By providing the porous metal layer on the surface of the back metal layer, the bonding strength between the sliding layer and the back metal layer can be increased. That is, the bonding force between the back metal layer and the sliding layer can be enhanced by the anchor effect due to the impregnation of the composition constituting the sliding layer into the pores of the porous metal layer.

  The porous metal layer can be formed by sintering a metal powder such as Cu, Cu alloy, Fe, and Fe alloy on the surface of a metal plate or a strip. The porosity of the porous metal layer may be about 20 to 60%. The thickness of the porous metal layer may be about 0.05 to 0.5 mm. In this case, the thickness of the sliding layer coated on the surface of the porous metal layer may be about 0.05 to 0.4 mm. However, the dimensions described here are examples, and the present invention is not limited to this value, and can be changed to different dimensions.

  According to one embodiment of the present invention, the synthetic resin used for the shaft member is PAI (polyamide imide), PI (polyimide), PBI (polybenzimidazole), PA (polyamide), PF (phenol), EP (epoxy) ), POM (polyacetal), PEEK (polyetheretherketone), PE (polyethylene), PPS (polyphenylenesulfide), and PEI (polyetherimide).

According to one embodiment of the present invention, the hard particles used for the shaft member are selected from CF (carbon fiber), GF (glass fiber), BN, Al ₂ O ₃ , SiC, SiO ₂ , AlN and TiO ₂ . It can consist of one or two or more selected. Since the shaft member contains these hard particles, the strength (rigidity) of the shaft member is increased. The average particle size of the hard particles can be 1 to 50 μm.

The shaft member further contains 1 to 10% by volume of one or more fillers selected from CaF ₂ , CaCo ₃ , talc, mica, mullite, iron oxide, calcium phosphate, and Mo ₂ C (molybdenum carbide). Can be included. The shaft _member, MoS _2, WS 2, h-BN and one or more solid lubricants selected from PTFE can further comprise 5% by volume or less.

The figure which shows the sliding device by one example of this invention. The figure which shows the cross section of the sliding member of the sliding device by one example of this invention. The figure which shows the cross section of the shaft member of the sliding device by one example of this invention. The figure which shows the cross section of a flaky graphite particle containing voids. The figure explaining the aspect ratio (A1) and the anisotropic dispersion index (S1) of flaky graphite particles. The figure which shows the cross section of the sliding member by other examples of this invention. The figure which shows the cross section of one specific example of the sliding device of this invention.

FIG. 1 schematically shows an example of a sliding device 1 according to the present invention. The sliding device 1 includes a shaft member 2 and a sliding member 3 that supports the shaft member 2. The sliding member 3 has a back metal layer 4 and a sliding layer 5.
As a specific form of the sliding device 1 of the present invention, a sliding device in which a cylindrical shaft member 2 is supported by a cylindrical sliding member 3 can be used (see FIG. 7). In this case, the sliding layer 5 is formed on the inner surface of the cylindrical sliding member 3. However, the sliding device according to the present invention is not limited to this form, and may have a form in which the shaft member 2 and the sliding member 3 are flat plates, or any other form.

FIG. 2 schematically shows a cross section of an example of the sliding member 3 of the sliding device according to the present invention. The sliding member 3 has a sliding layer 5 provided on a back metal layer 4. The sliding layer 5 comprises a synthetic resin 6 and 5 to 50% by volume of flake graphite particles 7. In the cross-sectional structure of the flaky graphite particles 7, a plurality of AB planes of the graphite crystal are laminated in the thickness direction of the flat plate shape (the C-axis direction of the graphite crystal). The average particle size of the flaky graphite particles 7 is 3 to 25 μm.
Observing the cross-sectional structure in the direction perpendicular to the sliding surface of the sliding layer 5, the flaky graphite particles 7 have an elongated shape having a long axis and a short axis. The major axis of the flake graphite particles 7 extends in a direction parallel to the AB plane of the graphite crystal.

The flaky graphite particles 7 are composed of void-containing flaky graphite particles 71 and other non-void-containing flaky graphite particles 72. The non-porous flaky graphite particles 72 include not only flaky graphite particles having no gap in the internal structure, but also flaky flakes that have voids but do not satisfy the requirements for the void-containing flaky graphite particles described above. Graphite particles are also included.
The volume ratio of the void-containing flake graphite particles 71 to the total volume of the flake graphite particles 7 in the sliding layer 5 is 10% or more, preferably 20% or more, and more preferably 25% or more. .
Note that a porous metal layer 8 may be provided between the sliding layer 5 and the back metal layer 4. FIG. 6 schematically shows a cross section of an example of the sliding member provided with the porous metal layer 8.

FIG. 4 shows a schematic view of the void-containing flake graphite particles 71. The void-containing flake graphite particles 71 dispersed in the sliding layer 5 have voids 9 in the internal structure, and the voids 9 extend in a direction substantially parallel to the long axis direction of the void-containing flake graphite particles 71.
In the void 9, the length L1 of the void in the direction parallel to the long axis direction of the void-containing flake graphite particles 71 is 50% or more of the long axis L of the flake graphite particles 71. The maximum length of the void 9 in the direction perpendicular to the long axis direction of the void-containing flake graphite particles 71 is about 0.01 to 1 μm.
Although FIG. 4 shows the flaky graphite particles 71 having one void 9 in the internal structure, the internal structure may have a plurality of voids. (The length L1 of the gap in this case is a value obtained by subtracting the length overlapping in the direction parallel to the long axis direction from the total length of each gap.)

  Next, a method of measuring the volume ratio of the void-containing flake graphite particles 71 to the total volume of the flake graphite particles 7 contained in the sliding layer 5 will be described. An electronic image is taken of a cross section of a plurality of portions in a direction perpendicular to the sliding surface of the sliding layer 5 at a magnification of 1000 (another magnification is also possible) using an electron microscope. Using a general image analysis method (for example, analysis software: Image-Pro Plus (Version 4.5); manufactured by Planetron Co., Ltd.), the flake graphite particles 7 in the photographed image are replaced with the void-containing flake graphite particles 71. And other non-void-containing flake graphite particles 72. The total area of all the flaky graphite particles 7 and the total area of all the void-containing flaky graphite particles 71 in the captured image are measured, and the area ratio of the void-containing flaky graphite particles 71 to the flaky graphite particles 7 is calculated. This area ratio corresponds to the volume ratio.

  The average aspect ratio A1 represented by the average of the ratio between the major axis L and the minor axis S of the flaky graphite particles 7 dispersed in the sliding layer 5 is preferably 5 to 15. More preferably, the average aspect ratio A1 is 6 or more.

  The flake graphite particles 7 dispersed in the sliding layer 5 preferably have an anisotropic dispersion index S1 of 3 or more. The anisotropic dispersion index S1 is X1 which is the length in the direction parallel to the sliding surface of the flake graphite particles 7 in the cross-sectional structure perpendicular to the sliding surface of the sliding layer 5, and X1 of the sliding layer 5. When the length in the direction perpendicular to the sliding surface of the flake graphite particles 7 in the cross-sectional structure in the direction perpendicular to the sliding surface is Y1 (see FIG. 5), the ratio X1 / X1 of each flake graphite particle is obtained. It is expressed as the value of Y1 averaged over all flake graphite particles. More preferably, the anisotropic dispersion index S1 is 4 or more.

The sliding member of the sliding device described above will be described in detail below along the manufacturing process.
(1) Preparation of Raw Material Graphite Particles As the raw material of the flaky graphite particles, flaky graphite particles having a flat plate shape are used, and any of natural flaky graphite particles and artificial flaky graphite particles may be used. The flaky graphite particles have an average particle size of 3 to 30 μm in a direction parallel to the AB plane (hexagonal mesh plane) measured by a laser diffraction type particle size measuring device, and have an average thickness of 0.2 μm. It is preferable to use one having a thickness of about 3.5 μm. In addition, the flaky graphite particles as a raw material have no void in the internal structure.

(2) Preparation of Synthetic Resin Particles It is preferable to use synthetic resin particles as raw materials having an average particle size of 50 to 150% of the average particle size of the flaky graphite particles. As the synthetic resin, a resin composed of one or more selected from PAI, PI, PBI, PA, phenol, epoxy, POM, PEEK, PE, PPS and PEI can be used.

(3) Mixing The ratio between the prepared flaky graphite particles and the synthetic resin particles is adjusted so that the volume ratio of the flaky graphite particles is 5 to 50% by volume. The flaky graphite particles and the synthetic resin particles are diluted with an organic solvent and mixed using a roll mill to prepare a composition having a viscosity of 40,000 to 110,000 mPa · s.

  Conventionally, the viscosity of a diluent of a resin composition containing graphite particles and other filler particles has been usually about 15,000 mPa · s at the maximum. However, here, the viscosity of the diluted composition is set to 40,000 to 110,000 mPa · s, which is larger than usual. When the viscosity of the composition exceeds 110,000 mPa · s, the concentration of the solvent is too low, and it is difficult to uniformly disperse the resin particles and the flaky graphite particles, and further, at the time of mixing with a roll mill, the flake graphite particles are broken. May occur.

  The gap between the rolls of the roll mill is set to an interval corresponding to about 400% of the average particle size of the flaky graphite particles, and the resin particles, the flaky graphite particles and the other filler particles are uniformly dispersed in the organic solvent.

  The above-mentioned relationship that the average particle size of the synthetic resin particles is 50 to 150% of the average particle size of the flaky graphite particles is that an excessive load is applied to the flake graphite particles when passing through the gap between the rolls, and shear occurs. This is suitable for preventing such a situation. When the sliding layer further contains a solid lubricant or filler, the solid lubricant or filler particles preferably have an average particle size of 50% or less of the average particle size of the flaky graphite particles.

  The mixing method of the synthetic resin particles and the flake graphite particles is not limited to the mixing method using the roll mill described in the above embodiment, or using another mixer, or adjusting under other mixing conditions. Is also possible.

(4) Back metal As the back metal layer, a metal plate of Fe alloy, Cu, Cu alloy, or the like can be used. A porous metal layer may be formed on the surface of the back metal layer, that is, on the side that is the interface with the sliding layer. The porous metal layer can have the same composition as the back metal layer, or can use a different composition or material.

(5) Coating Step The composition after mixing is applied to one surface of the back metal layer or the porous metal layer on the back metal layer, and the back metal coated with the composition is used to make the thickness of the composition uniform. Is passed between rolls having a predetermined constant gap.
The viscosity of the composition after mixing is closely related to the long-axis anisotropic dispersion (orientation) of the flaky graphite particles in the sliding layer of the sliding member. For the dispersion, it was found that setting the conditions in this coating step was important.

When the viscosity of the composition is high in the mixing step (that is, the proportion of the organic solvent is small), when the back metal layer coated with the composition passes between the rolls, the flaky graphite particles in the composition are converted to the flat surface thereof. This is because the (AB surface of the graphite crystal) is less likely to flow so as to be oriented in a direction parallel to the sliding surface.
On the other hand, if the viscosity of the composition is 110,000 mPa · s or less, the flaky graphite particles are likely to flow together with the organic solvent in the coating step. It is oriented in the moving layer, that is, dispersed anisotropically. Specifically, when the viscosity of the composition is 110000 mPa · s or less, the flake graphite particles dispersed in the sliding layer have an anisotropic dispersion index S1 of 2.5 or more. Further, when the viscosity of the composition is 100000 mPa · s or less, the anisotropic dispersion index becomes 3 or more, and when the viscosity is 80000 mPa · s or less, the anisotropic dispersion index becomes 4 or more.

(6) Pre-drying step The back metal layer (or the back metal layer and the porous metal layer) coated with the composition is pre-dried so that the organic solvent remains in the composition in an amount of 5 to 15% by volume. In the conventional manufacturing method, the pre-drying step is not performed before the rolling step, but the pre-drying step reduces the volume ratio of the organic solvent in the composition to about 5 to 15% in the rolling step described later. Is closely related to the formation of void-containing flaky graphite particles.
In the production of a conventional sliding member, a preliminary drying step was not provided before the rolling step.

(7) Rolling Step The back metal layer (or the back metal layer and the porous metal layer) coated with the composition is passed between rolls having a predetermined constant gap after pre-drying to make the thickness uniform. . In the composition after the preliminary drying step, only 5 to 15% by volume of the organic solvent remains, so that the frequency of contact between the flaky graphite particles and the synthetic resin particles in the composition is high. Therefore, when the composition passes through the gap between the rolls in the rolling step, by applying a load from the rolls in a state where the flaky graphite particles and the synthetic resin particles are in contact, the surface of the flaky graphite particles is localized. It is considered that a high load is applied to the inside and voids are formed inside.

The viscosity of the conventional composition is made to be about 15000 mPa · s at the maximum, and the proportion of the organic solvent in the composition is large (about 40 to 50% by volume). Since the preliminary drying for reducing was not performed, the ratio of the organic solvent in the composition was too large in the rolling step, and the load of forming voids inside the flake graphite particles was not applied. .
If the residual ratio of the organic solvent in the composition in the preliminary drying step is less than 5%, the composition is less likely to flow in the rolling step, and the thickness of the sliding member (sliding layer) is made uniform and the sliding is performed. Not only is it difficult to smooth the moving surface, but also an excessive load is applied to the flaky graphite particles during the rolling process, and the flaky graphite particles are likely to be sheared into a plurality of small particles.

(8) Drying and Firing Step After the rolling step, heating for drying the organic solvent remaining in the composition and firing the synthetic resin is performed to obtain a sliding member.

  In addition, unlike the manufacturing method of the above embodiment, by performing a rolling process on a conventional sliding member having a sliding layer in which only flake graphite particles having no voids in the synthetic resin are dispersed, An attempt was made to form voids inside the flake graphite particles in the moving layer, but as a result, no formation of voids was found in the internal structure of the flake graphite particles. This is because the flaky graphite particles of the sliding layer of the sliding member are held (constrained) by the synthetic resin whose strength has already been increased by firing, so that the flaky graphite particles are synthesized by the load in the rolling process. It is considered that the flake graphite particles are not subjected to a load such that voids are formed inside the tissue only by flowing together with the resin.

(9) Measurement The average particle size of the flaky graphite particles is measured by photographing an electronic image of a cross section perpendicular to the sliding surface of the sliding member with an electron microscope at a magnification of 1000 times. Specifically, the average particle size of the flaky graphite particles is determined by a general image analysis method (for example, analysis software: Image-Pro Plus (Version 4.5); manufactured by Planetetron Corporation). The area is measured by using it and converted to the average diameter when it is assumed to be a circle. However, the photographing magnification of the electronic image is not limited to 1000 times, and can be changed to another magnification.

  The fact that the flaky graphite particles have a cross-sectional structure in which a plurality of AB planes of graphite crystals are laminated in the thickness direction (C-axis direction) of the flat plate shape is perpendicular to the sliding surface of the sliding member. In the cross section in the direction, an electron image of a plurality (for example, 20) of flaky graphite particles is photographed at a magnification of 2000 using an electron microscope, and the cross-sectional structure of the flaky graphite particles in the photographed image has a flat plate-like thickness. It can be confirmed by observing that a plurality of layered portions are formed in the vertical direction.

  By the above method, it can also be confirmed that the volume ratio of the void-containing flaky graphite particles to the total volume of the flaky graphite particles contained in the sliding layer is 10% or more.

  The aspect ratio A1 of the flaky graphite particles is obtained by taking an image obtained by photographing an electronic image of the cross section in the direction perpendicular to the sliding surface of the sliding member at a magnification of 200 using an electron microscope using the above-described image analysis method. It is determined as the ratio (L / S) of the length L of the major axis to the length S of the minor axis of the flake graphite particles (see FIG. 5). In addition, the length L of the major axis of the flake graphite particles indicates the length at the position where the length of the flake graphite particles in the electronic image is the maximum, and the length S of the minor axis of the flake graphite particles Indicates the length at the position where the length in the direction orthogonal to the direction of the length L of the long axis is maximum.

  The anisotropic dispersion index S1 of the flaky graphite particles is obtained by converting the electronic image obtained by the above-described method into a direction parallel to the sliding surface of each of the flaky graphite particles in the sliding layer using the above-described image analysis method. The length X1 and the length Y1 in the direction perpendicular to the sliding surface are measured, and the average value of the ratio (X1 / Y1) of the lengths is calculated and obtained (see FIG. 5).

  FIG. 3 schematically shows a cross section of an example of the shaft member 2 of the sliding device 1 according to the present invention. In the shaft member 2, hard particles 11 are dispersed in a synthetic resin 10. As a manufacturing process of the shaft member, after mixing the synthetic resin and the hard particles, the mixture is pelletized, and can be molded into a predetermined shape such as a columnar shape or a flat shape by injection molding.

  The synthetic resin 10 of the shaft member 2 is made of PAI (polyamide imide), PI (polyimide), PBI (polybenzimidazole), PA (polyamide), PF (phenol), EP (epoxy), POM (polyacetal), PEEK (poly (Ether ether ketone), PE (polyethylene), PPS (polyphenylene sulfide), and PEI (polyetherimide).

The shaft member 2 is composed of a synthetic resin 10 and hard particles 11 dispersed in the synthetic resin 10, and the hard particles 11 can occupy 5 to 50% by volume of the sliding layer 5.
The hard particles 11 of the shaft member 2 are made of one or more selected from CF (carbon fiber), GF (glass fiber), BN, Al ₂ O ₃ , SiC, SiO ₂ , AlN and TiO _2. be able to. The average particle size of the hard particles 11 can be about 1 to 50 μm.

The shaft member 2 contains 1 to 10% by volume of one or more fillers selected from CaF ₂ , CaCo ₃ , talc, mica, mullite, iron oxide, calcium phosphate, and Mo ₂ C (molybdenum carbide). It can further include. Further, the shaft member 2 may further include 5 vol% or less of one or more solid lubricants selected from MoS ₂ , WS ₂ , h-BN and PTFE.

  Examples 1 to 11 and Comparative Examples 12 to 16 of the sliding device according to the present invention were produced as shown below. The compositions of the sliding layers of the shaft members and the sliding members of Examples 1 to 11 and Comparative Examples 12 to 16 are as shown in Table 1.

The shaft members of Examples 1 to 11 and Comparative Examples 12 to 16 were prepared by mixing resins (EP, PF) and hard particles (CF (carbon fiber), SiO ₂ particles) shown in Table 1 and pelletizing them. It was molded into a cylindrical shape using an injection molding machine.

  The flaky graphite particles used as raw materials in Examples 1 to 11 and Comparative Examples 12 to 16 have a structure in which a large number of AB surfaces (hexagonal mesh planes) that spread in a plane are stacked and have a thickness in the C-axis direction. Since the thickness of the laminate is smaller than the extent of the AB plane, the shape of the particles is a thin plate. The scaly graphite particles had no voids in the internal structure.

The synthetic resin (PAI, PI) particles which are the raw materials of Examples 1 to 11 and Comparative Examples 12 to 16 had an average particle diameter of 125% with respect to the average particle diameter of the flake graphite particles which were the raw materials. Using. The solid lubricant (spherical graphite, PTFE) used as a raw material in Examples 5 to 7 had an average particle diameter of 100% of the average particle diameter of the flaky graphite particles as a raw material, and was used as a filler (CaCoO). ₃ ) The particles having an average particle size of 25% of the average particle size of the flaky graphite particles were used.

  The composition shown in Table 1 using the above raw materials was diluted with an organic solvent to prepare a composition having the viscosity shown in the column of "Viscosity (mPa · s)" in Table 1, and then the composition was prepared using a roll mill. Was mixed. In Examples 1 to 11 and Comparative Examples 12 to 16, the gap between the rolls of the roll mill was set to a ratio of 400% to the average diameter of the flaky graphite particles used as a raw material.

  Next, the composition of the sliding member after mixing was applied to one surface of a back metal layer made of an Fe alloy, and then the composition was coated with a roll to a predetermined thickness. The back metal layers of Examples 1 to 9 and Comparative Examples 12 to 16 used Fe alloys, and Examples 10 and 11 used Fe alloys having a porous sintered portion of Cu alloy on the surface.

  Next, for Examples 1 to 11 and Comparative Examples 13 to 16, a rolling step was performed after performing a preliminary drying step so that 10% of the solvent in the composition remained, and for Comparative Example 12, a preliminary drying step was performed. The rolling step was performed without performing the step (the remaining amount of the organic solvent was 50%), and thereafter, the organic solvent of the composition was dried and the synthetic resin was fired to produce a sliding member. The sliding layers of the fabricated sliding members of Examples 1 to 11 and Comparative Examples 12 to 16 had a thickness of 0.3 mm, and the back metal layer had a thickness of 1.7 mm.

The average particle size of the graphite particles was measured for each sliding member produced by the measurement method described above, and the results are shown in the “average particle size” column of Table 1. In addition, by the measurement method described above, the volume ratio of the void-containing flaky graphite particles to the total volume of the flaky graphite particles in the sliding layer was measured, and the results are shown in the “volume ratio” column of Table 1. (The volume ratio in parentheses in Comparative Example 16 will be described later.)
Further, the average aspect ratio (A1) and anisotropic dispersion index (S1) of the flake graphite particles described above were measured, and the results were shown in Table 1 in the “Aspect Ratio (A1)” column, “Dispersion Index (S1)”. ) "Column.

Further, for each of the examples and comparative examples, the sliding member was formed into a cylindrical shape with the sliding layer being on the inside, and the shaft member was formed into a cylindrical shape (see FIG. 7). A sliding test was performed under the conditions. The amount of wear of the sliding layer of each of the examples and comparative examples after the sliding test is shown in the “wear amount” column of Table 1.
In each of the examples and comparative examples, the sliding surface after the sliding test was checked for the presence or absence of resin dropout using a shape measuring device (roughness measuring device). "Resistant" is shown in Table 1 if there is a dropout (recess) of resin with a depth of 10 μm or more on the sliding surface, and "No" if not. The results are shown in FIG.

  As can be seen from the results shown in Table 1, in Examples 1 to 11, the synthetic resin did not fall off on the sliding surface of the sliding layer of the sliding member after the sliding test, but in Comparative Examples 12 to 16, After the sliding test, the synthetic resin fell off on the sliding surface of the sliding layer. The sliding members of Examples 1 to 11 were prevented from dropping out of the synthetic resin on the sliding surface of the sliding layer, as described above, because the gaps of the flaky graphite particles containing voids in the sliding layer caused the shaft to become loose. It is considered that the extreme pressure load applied from the member to the synthetic resin on the sliding surface of the sliding layer was reduced. Further, in Examples 1 to 11, the wear amount of the sliding layer after the sliding test was smaller than in Comparative Examples 12 to 16. The reason for this is that, as described above, in Examples 1 to 11, the extreme pressure load applied to the sliding surface was reduced, and the falling off of the synthetic resin was prevented because the synthetic resin was prevented from falling off. Probably because it did not.

Furthermore, Examples 4 to 9 in which the aspect ratio (A1) of the flaky graphite particles was 5 or more resulted in a smaller wear amount than Examples 1 to 3 in which the aspect ratio (A1) was less than 5. . This is because, as described above, by increasing the surface area of the flaky graphite particles, the contact area of the flaky graphite particles with the synthetic resin is increased, and the adhesion with the synthetic resin is increased. It is considered that it is difficult to fall off the sliding surface, and thus the wear resistance is improved. However, from the results of Examples 10 and 11, it can be understood that the amount of abrasion is smaller when the average aspect ratio (A1) of the flaky graphite particles is 15 or less.
In addition, in Examples 4 to 7, the abrasion loss was smaller than in Examples 8 to 11 in which the anisotropic dispersion index (S1) was less than 4. However, as described above, this was a scaly shape. It is considered that the large percentage of the graphite particles whose major axis direction is oriented substantially parallel to the sliding surface makes it easier to relieve the extreme pressure load applied to the sliding surface.

  In Comparative Example 12, a composition containing graphite particles was diluted with an organic solvent so that the viscosity became 15000 mPa · s, and a preliminary drying step was performed to reduce the residual amount of the organic solvent in the composition before the rolling step. Because there was no, the proportion of the organic solvent in the composition is large, the load in which voids are formed inside the flaky graphite particles in the composition when the back metal layer coated with the composition in the rolling step passes between the rolls It is probable that no voids were formed in the internal tissue because they were not added. Therefore, the sliding member of Comparative Example 12 does not include the flake graphite particles containing voids in the sliding layer. In the sliding test, the sliding member of Comparative Example 12 was applied to the synthetic resin on the sliding surface of the sliding layer without relaxing the extreme pressure load from the shaft member. Is considered to have dropped and wear of the sliding surface was promoted.

  In Comparative Example 13, the volume ratio of the void-containing flaky graphite particles to the total volume of the flaky graphite particles contained in the sliding layer was too low at 5.3%, and the function of alleviating the extreme pressure load was insufficient. It is considered that the resin on the surface of the sliding layer fell off, and the amount of wear of the sliding layer increased.

  In Comparative Example 14, since the flaky graphite particles contained in the sliding layer were as small as 3% by volume, the effect of lowering the frictional force between the sliding layer and the partner shaft was insufficient, and the wear amount of the sliding layer was large. It is thought that it became.

  In Comparative Example 15, since the flaky graphite particles contained in the sliding layer were as large as 60% by volume, it is considered that the strength of the sliding layer was low and the wear amount of the sliding layer was large.

Comparative Example 16 is a comparative material for confirming the influence of the length (L) of the void-containing flake graphite particles in the major axis direction on the action of relaxing the extreme pressure load. Specifically, in Comparative Example 16, the flaky graphite particles of the raw material were smaller in average particle size than those of the Examples, and the average particle size of the flaky graphite particles dispersed in the sliding layer was 1.5 μm. It was made to become. The parenthesized value 10.5 of Comparative Example 16 shown in "Volume Ratio" in Table 1 is not the volume ratio of the void-containing flaky graphite particles, but of the flaky graphite particles dispersed in the sliding layer.
The length L of the flaky graphite particles in the major axis direction is 1.5 μm or more,
and,
The internal structure has a void, and the void has a length (L1) in the direction parallel to the major axis direction of the flake graphite particles that is 50% or more of the length (L) of the major axis direction of the flake graphite particles. The volume ratio of certain flaky graphite particles is shown.
In the sliding member of Comparative Example 16, the synthetic resin on the sliding surface of the sliding layer after the sliding test fell off, and the amount of wear increased. From the results of Example and Comparative Example 16, it was found that the flaky graphite particles having a length of less than 3 μm in the major axis direction had an extreme pressure applied to the sliding surface of the sliding layer even if there was a void inside the tissue. It is understood that the effect of alleviating the natural load is low.

1: Sliding device 2: Shaft member 3: Sliding member 4: Back metal layer 5: Sliding layer 6: Synthetic resin of sliding member 7: Flake graphite particles 71: Void-containing flake graphite particles 72: Non-void content Scale-like graphite particles 8: porous metal layer 9: voids 10: synthetic resin of shaft member 11: hard particles

Claims (12)

A sliding device comprising a shaft member and a sliding member supporting the shaft member,
The shaft member is made of a synthetic resin and hard particles dispersed in the synthetic resin, and the volume of the hard particles is 5 to 50% by volume of the volume of the shaft member.
The sliding member includes a back metal layer, and a sliding layer provided on the back metal layer,
The sliding layer is made of a synthetic resin and flake graphite particles dispersed in the synthetic resin,
The total volume of the flaky graphite particles accounts for 5 to 50% by volume of the volume of the sliding layer,
The flaky graphite particles have a flat plate shape, and the cross-sectional structure of the flaky graphite particles has a plurality of AB planes of graphite crystals stacked in the thickness direction of the flat plate shape,
The average particle size of the flaky graphite particles is 3 to 25 μm,
The flaky graphite particles are void-containing flaky graphite particles, that is, the length in the major axis direction is 3 μm or more,
In the cross-sectional structure is a void extending in the major axis direction of the flake graphite particles, the length of the void in the direction parallel to the major axis direction of the flake graphite particles, the major axis of the flake graphite particles Including void-containing flaky graphite particles having voids that are 50% or more of the length in the direction,
A sliding device, wherein a volume ratio of the void-containing flake graphite particles to the total volume of the flake graphite particles in the sliding layer is 10% or more.   The sliding device according to claim 1, wherein a volume ratio of the void-containing flake graphite particles to the total volume of the flake graphite particles in the sliding layer is 20% or more.   The sliding device according to claim 1, wherein an average aspect ratio represented by an average of a ratio between a major axis and a minor axis of the flake graphite particles is 5 to 15. 4. The flaky graphite particles have an anisotropic dispersion index of 3 or more, and the anisotropic dispersion index is represented by an average of the ratio X1 / Y1 for each flaky graphite particle, where X1 is the sliding layer. In a cross-sectional structure perpendicular to the sliding surface, the length in the direction parallel to the sliding surface of the flake graphite particles,
Y1 is a length in a direction perpendicular to the sliding surface of the flake graphite particles in a cross-sectional structure perpendicular to the sliding surface of the sliding layer. The sliding device according to any one of the above.   The synthetic resin of the sliding layer is composed of one or more selected from PAI, PI, PBI, PA, phenol, epoxy, POM, PEEK, PE, PPS, and PEI. The sliding device according to any one of the above.   6. The sliding layer according to claim 1, wherein the sliding layer further includes 1 to 20% by volume of one or more solid lubricants selected from spheroidal graphite, MoS2, WS2, h-BN, and PTFE. A sliding device according to any one of the preceding claims.   The said sliding layer further contains 1-10 volume% of 1 or 2 or more types of filler (s) selected from CaF2, CaCo3, talc, mica, mullite, iron oxide, calcium phosphate, and Mo2C. A sliding device according to any one of the preceding claims.   The sliding device according to any one of claims 1 to 7, further comprising a porous metal layer between the back metal layer and the sliding layer.   9. The synthetic resin of the shaft member is one or more selected from PAI, PI, PBI, PA, phenol, epoxy, POM, PEEK, PE, PPS and PEI. The sliding device according to any one of the above.   The method according to any one of claims 1 to 9, wherein the hard particles are made of one or more selected from carbon fibers, glass fibers, BN, Al2O3, SiC, SiO2, AlN, and TiO2. The described sliding device.   11. The shaft member according to claim 1, wherein the shaft member further includes 1 to 10% by volume of one or more selected from CaF2, CaCo3, talc, mica, mullite, iron oxide, calcium phosphate, and Mo2C. A sliding device according to any one of the preceding claims.   The sliding according to any one of claims 1 to 11, wherein the shaft member further includes 5 vol% or less of one or more selected from MoS2, WS2, h-BN, and PTFE. apparatus.