JP2024078404A - Sliding member and plain bearing - Google Patents

Abstract

The present invention provides a technology for improving wear resistance.
[Solution] A sliding member comprising a base layer and a resin coating layer formed on the base layer, the resin coating layer comprising a polyamideimide resin as a binder, a solid lubricant, boehmite particles in an amount of more than 0 volume % and not more than 1.0 volume %, and unavoidable impurities.
[Selected figure] Figure 5

Description

The present invention relates to a sliding member and a sliding bearing having a resin coating layer.

Conventionally, in a sliding member having a backing metal layer and a sliding layer, it is known to form a resin coating layer made of a synthetic resin and a solid lubricant dispersed in the synthetic resin. For example, Patent Document 1 discloses a configuration in which the resin coating layer contains a solid lubricant and a hard material.

Patent No. 6122488

In the conventional sliding members disclosed in Patent Document 1 and the like, the hard material is, for example, SiC. The hard material added to conventional sliding members is, for example, SiC, which is an extremely hard material with a Mohs hardness of approximately 8.5 to 9.5. It was previously thought that the inclusion of such hard materials in the resin coating layer would suppress wear of the resin and improve wear resistance. However, because these hard materials are extremely hard, when the resin containing the hard material is transferred to the opposing material, the transferred hard material wears away the resin coating layer.

The present invention was made in consideration of the above problems, and aims to provide a technology that improves wear resistance.

To achieve the above object, the sliding member is a sliding member having a base layer and a resin coating layer formed on the base layer, and the resin coating layer is composed of polyamideimide resin as a binder, a solid lubricant, boehmite particles in an amount of more than 0 volume % and not more than 1.0 volume %, and unavoidable impurities.

Compared to conventionally used hard materials such as SiC, boehmite (AlOOH) has a smaller contact angle with engine oil. Therefore, the friction coefficient of a sliding member using boehmite particles is smaller than that of a sliding member using conventional hard materials, and the amount of transfer of a resin coating layer containing boehmite particles to a mating material is less than that of a conventional resin coating layer.

Although boehmite is a relatively hard material, conventionally used hard materials such as SiC are harder. Therefore, in a sliding member in which boehmite particles are used as a hard material, even if a mating material is transferred, the resin coating layer is less worn by the transferred hard material than a conventional resin coating layer. Therefore, a sliding member containing boehmite as a hard material can have improved wear resistance compared to a sliding member containing a material such as SiC as a hard material.

FIG. 2 is a perspective view of a sliding member according to an embodiment of the present invention. FIG. 1 is a diagram showing the contact angle of a hard object. FIG. 3A is a diagram showing the friction coefficient of a hard object, and FIG. 3B is a schematic diagram of a friction coefficient evaluation tester. FIG. 4A is a diagram showing the change in friction volume depending on the amount of boehmite added, FIG. 4B is a schematic diagram of a testing machine for measuring the friction volume, and FIG. 4C is a diagram for explaining a method for measuring the amount of wear. FIG. 5A is a graph showing the change in wear amount depending on the amount of boehmite and the amount of molybdenum disulfide added, and FIG. 5B is a schematic diagram of a test machine for measuring the wear amount. FIG. 6A is a diagram showing the change in seizure pressure depending on the amount of boehmite and the amount of molybdenum disulfide added, and FIG. 6B is a schematic diagram of a test machine for measuring the seizure pressure.

Here, the embodiments of the present invention will be described in the following order.
(1) Configuration of the slide member (2) Manufacturing method of the slide member:
(3) Test results:
(4) Other embodiments:

(1) Configuration of sliding member:
FIG. 1 is a perspective view of a sliding member 1 according to an embodiment of the present invention. The sliding member 1 includes a backing metal 10, a lining 11, and an overlay 12. The sliding member 1 is a metal member having a half-shaped shape obtained by dividing a hollow cylinder into two equal parts in the diametric direction, and has a semicircular cross section. A plain bearing A is formed by combining two sliding members 1 into a cylindrical shape. The plain bearing A bears a cylindrical mating member 2 (crankshaft of an engine) in a hollow portion formed inside. The outer diameter of the mating member 2 is formed slightly smaller than the inner diameter of the plain bearing A. A lubricating oil (engine oil), which is a liquid lubricant, is supplied to the gap formed between the outer peripheral surface of the mating member 2 and the inner peripheral surface of the plain bearing A. At that time, the outer peripheral surface of the mating member 2 slides on the inner peripheral surface of the plain bearing A.

The sliding member 1 has a structure in which a backing metal 10, a lining 11, and an overlay 12 are layered in that order from the farthest from the center of curvature. Therefore, the backing metal 10 constitutes the outermost layer of the sliding member 1, and the overlay 12 constitutes the innermost layer of the sliding member 1. The backing metal 10, the lining 11, and the overlay 12 each have a constant thickness in the circumferential direction and a constant thickness in the diameter direction. For example, the backing metal 10 has a thickness of 1.0 mm to 2.0 mm, and the lining 11 has a thickness of 0.2 mm to 0.4 mm. The backing metal 10 is formed, for example, from steel.

The lining 11 is a layer laminated on the inside of the backing metal 10 and constitutes the base layer. The lining 11 is formed of, for example, an Al alloy or a Cu alloy. The thickness of the overlay 12 is, for example, 6 μm. The thickness of the overlay 12 may be 2 to 20 μm. Hereinafter, the inner side refers to the side toward the center of curvature of the sliding member 1, and the outer side refers to the side opposite the center of curvature of the sliding member 1. The inner surface of the overlay 12 constitutes the sliding surface with the mating material 2.

The overlay 12 is a layer laminated on the inner surface of the lining 11 and constitutes the resin coating layer of the present invention. The overlay 12 is composed of polyamideimide resin as a binder, molybdenum disulfide particles as a solid lubricant, boehmite particles as a hard material, and inevitable impurities.

In this embodiment, the volume fraction of the total volume of the molybdenum disulfide particles in the overlay 12 is 10% to 70% by volume, and can be selected from, for example, 28% to 40% by volume, 28% to 34% by volume, 30% to 34% by volume, etc. The volume ratio of the polyamide-imide resin to the molybdenum disulfide particles is calculated based on the masses of the polyamide-imide resin and the molybdenum disulfide particles measured before mixing the two, and their specific gravities. The average crystal grain size of the molybdenum disulfide particles is 0.1 to 5.0 μm. Here, the crystal grain size is the radius of a circle equal to the area of the crystal grains observed in the cross section, and the average crystal grain size is the average of the radii of the circles. The average grain size can be measured, for example, by Microtrack Bell's MT3300II (same below).

The volume fraction of the total volume of the boehmite particles in the overlay 12 is greater than 0 volume % and less than or equal to 1.0 volume %, and can be, for example, 0.1 volume % to 0.7 volume %. The volume ratio of the polyamide-imide resin to the boehmite particles is calculated based on the masses of the polyamide-imide resin and the boehmite particles measured before mixing the two, and their specific gravities. The 50% particle size of the boehmite particles according to JIS R1629-1997 is 0.6 μm to 0.9 μm. In another embodiment, a resin coating layer containing an additive, for example, barium sulfate particles, may be formed.

The boehmite particles have a smaller contact angle with engine oil than conventionally used hard materials such as SiC. FIG. 2 is a diagram showing the contact angle of hard materials. Specifically, the contact angle of a plurality of hard materials with engine oil (0W-8) was measured at room temperature (25° C.) using a known contact angle meter. The hard materials are boehmite, SiC, CrN, and SiO _2. As shown in FIG. 2, the contact angle of boehmite is smaller than that of hard materials such as SiC. Therefore, when comparing a resin coating layer containing boehmite particles with a resin coating layer containing a hard material such as SiC, it is considered that the friction coefficient of the former during mixed lubrication is smaller than that of the latter.

Figure 3A shows the friction coefficient under mixed lubrication. The friction coefficient was measured using a ball-on-plate tester as shown in Figure 3B. Specifically, a sample Sa is attached to a stage St capable of reciprocating sliding in a linear direction, and a ball Ba is formed from the same material as the mating material and attached to an arm Am. A sensor Sn such as a strain gauge is attached to the arm Am. The sample Sa has the same layer structure as the backing metal 10, lining 11, and overlay 12 described above, but has a flat shape, and the hard material of each sample Sa is 1.17% by volume. The sample Sa is set on the stage St in an orientation that allows the ball Ba to come into contact with the overlay 12.

In this state, the overlay 12 was immersed in engine oil (0W-8) and the temperature was set to 90°C. Then, with the reciprocating sliding speed of the stage St set to 3 mm/s, a load N (1.96 N) was applied to the arm Am, and the force acting on the arm Am was measured by the sensor Sn, thereby measuring the friction coefficient of each overlay.

As shown in FIG. 3A, the resin coating layer containing boehmite particles has a smaller friction coefficient during mixed lubrication than resin coating layers containing other hard materials. Therefore, when a resin coating layer containing boehmite particles slides against a counter material, the amount of the resin coating layer containing boehmite particles that is transferred to the counter material is less than the amount of the resin coating layer containing hard materials such as SiC that is transferred to the counter material. As a result, in a resin coating layer containing boehmite particles, the amount of wear caused by the transferred hard materials on the resin coating layer is less than the amount of wear caused by the transferred hard materials on the resin coating layer on a resin coating layer containing hard materials such as SiC.

Furthermore, boehmite particles are a material with a Mohs hardness of 3.5 to 4, and can be said to be a relatively hard material. However, compared with hard materials such as SiC that have been used in the resin coating layer in the past, for example, SiC (Mohs hardness is 8.5 to 9.5), SiO ₂ (Mohs hardness is 4.5 to 6.5), CrN (Mohs hardness of Cr alone is 7 to 8.5), etc., boehmite particles are not harder than these. Therefore, in this sense, in a resin coating layer containing boehmite particles, the amount of wear of the resin coating layer caused by a hard material transferred to a counter material is smaller than the amount of wear of the resin coating layer caused by a hard material transferred to a counter material in a resin coating layer containing a hard material such as SiC. As a result of the above, a sliding member containing boehmite particles as a hard material can improve wear resistance compared to a sliding member containing a material such as SiC as a hard material.

(2) Manufacturing method of slide member:
The sliding member 1 can be manufactured, for example, by sequentially carrying out the steps of (a) forming a half-split substrate, (b) a coating pretreatment step, (c) a coating step, (d) a drying step, and (e) a firing step. Of course, the manufacturing method of the sliding member 1 is not limited to the steps described above.

(a) Half-split substrate forming step The half-split substrate forming step is a step of forming a substrate in which the back metal 10 and the lining 11 are bonded together into a half shape. For example, the substrate in which the back metal 10 and the lining 11 are bonded together may be formed by sintering the material of the lining 11 on a plate material corresponding to the back metal 10. Also, the substrate in which the back metal 10 and the lining 11 are bonded together may be formed by bonding the plate material corresponding to the back metal 10 and the lining 11 together by rolling. Furthermore, the substrate in which the back metal 10 and the lining 11 are bonded together may be processed into a half shape by performing mechanical processing such as pressing or cutting.

(b) Pre-coating treatment step The pre-coating treatment step is a surface treatment for improving the adhesion of the overlay 12 (resin coating layer) to the surface of the lining 11. For example, as the pre-coating treatment step, a roughening treatment such as sandblasting may be performed, or a chemical treatment such as etching or chemical conversion treatment may be performed. Note that the pre-coating treatment step is preferably performed after degreasing the oil content of the half-split substrate with a cleaning agent.

(c) Coating Step The coating step is a step of coating the overlay 12 onto the lining 11. In carrying out the coating step, a coating liquid is prepared by mixing molybdenum disulfide particles, boehmite particles (and additives in some embodiments) with a polyamide-imide resin. In addition, a solvent such as N-methyl-2-pyrrolidone or xylene may be used as necessary to increase the dispersibility of the molybdenum disulfide particles, boehmite particles, and additives, or to adjust the viscosity of the coating liquid.

At this time, mixing is performed so that the volume fraction of the total volume of the molybdenum disulfide particles in the overlay 12 is 10 volume % to 70 volume %, and the volume fraction of the total volume of the boehmite particles is greater than 0 volume % and 1.0 volume % or less. If additives are included, mixing is performed so that the expected volume fraction is achieved, including the additives.

The coating process is not particularly limited as long as it can form the overlay 12 on the lining 11. For example, air spray, airless spray, pad, screen printing, etc. can be used. Pressure may also be applied and the inner surface of the lining 11 may be rubbed with a cloth, a plate, etc. Furthermore, the coating process may be performed by a coating roll. For example, the coating liquid may be applied to a cylindrical coating roll having a diameter smaller than the inner diameter of the lining 11, and the coating roll may be rotated on the inner surface of the lining 11 to perform the coating process. By adjusting the roll gap between the coating roll and the inner surface of the lining 11 and the viscosity of the coating liquid, the coating liquid may be applied to the inner surface of the lining 11 so that the film thickness after the baking process (e) described later is the desired thickness. The coating process may be performed multiple times, resulting in the desired film thickness.

(d) Drying Step The drying step is a step of drying the polyamide-imide resin. For example, a drying step may be performed at 40 to 180° C. for 5 to 60 minutes.

(e) Baking Step The polyamide-imide resin is then baked (cured) at 200 to 300° C. for 30 to 60 minutes, for example, to manufacture the sliding member 1 .

(3) Test results:
The sliding member 1 according to the present embodiment manufactured as described above was used as an example, and an evaluation test of wear resistance and an evaluation test of seizure resistance were performed. First, a test was performed to evaluate the relationship between the concentration of boehmite particles and the wear amount of the resin coating layer. FIG. 4A shows the measurement results of the wear amount for a plurality of samples manufactured by changing the amount of boehmite particles added and setting the volume fraction of the molybdenum disulfide particles contained in the overlay 12 to 30 volume %. The horizontal axis of FIG. 4A shows the amount of boehmite particles added (volume %), and the vertical axis shows the volume (μm ³ ) of the resin coating layer worn by the wear test. In FIG. 4A, a test was performed on each of a plurality of samples of the same composition, and a curve obtained from the statistical results is shown by a solid line. In addition, on the graph, the measurement results for some samples are shown by white circles.

Figure 4B is a schematic diagram of an apparatus for performing the test shown in Figure 4A. In the test machine shown in Figure 4B, the test axis Ax formed by the mating material can rotate around its axis. The test axis Ax is immersed in oil O at room temperature (25°C). The oil O is, for example, a paraffin-based oil.

The sample Sa is held in contact with the upper end of the test axis Ax, and a force is applied from the sample Sa toward the test axis Ax by the weight Wt attached to the arm Am. In the test shown in FIG. 4A, the sample Sa is flat. The test axis Ax was rotated at 60 rpm with a force of 90 N acting between the multiple samples Sa with different volume fractions of boehmite particles and the test axis Ax as the mating material. This test was performed for one hour for each sample Sa, and the volume of the worn resin coating layer was measured using a measuring device (laser microscope). The volume of the worn resin coating layer was determined by setting cross sections at multiple locations (three locations Ps1 to Ps3 shown in FIG. 4C) in the worn portion Ps of the worn sample Sa in a direction perpendicular to the direction of the test axis Ax during sliding as shown in FIG. 4C, and integrating the average value of the cross-sectional area of each cross section over the width Pw.

In the test shown in FIG. 4A, the wear volume was measured for multiple volume fractions of boehmite particles, from 0 volume% to 1.5 volume%. When the volume fraction of boehmite particles changes within this range, the wear volume is largest when the volume fraction of boehmite particles is 0 volume%, and the wear volume gradually decreases as the volume fraction of boehmite particles increases. Furthermore, when the volume fraction of boehmite particles exceeds 1.0 volume%, it can be seen that the wear volume hardly changes even if the volume fraction of boehmite particles increases. Therefore, if the volume fraction of boehmite particles in the resin coating layer is greater than 0 volume% and less than or equal to 1.0 volume%, the wear resistance can be improved. Note that the volume fraction of boehmite particles needs to be greater than 0 volume%, but according to FIG. 4A, even if a small amount of boehmite particles, such as 0.1 volume% or 0.25 volume%, is added, the wear resistance can be reliably improved compared to when no boehmite particles are added.

Next, an evaluation test for samples with different volume fractions of molybdenum disulfide will be described. Figure 5A shows the results of measuring the amount of wear for each of sample Sa1, in which the volume fractions of molybdenum disulfide particles and boehmite particles contained in the overlay 12 are 30 volume% and 0.7 volume%, sample Sa2, in which they are 32 volume% and 0.4 volume%, sample Sa3, in which they are 34 volume% and 0.1 volume%, sample Sa0, in which they are 28 volume% and 1.0 volume%, and sample Sa01, in which they are 29 volume% and 0.85 volume%.

In Figure 5A, the horizontal axis indicates the amount of molybdenum disulfide added (volume %), the depth axis indicates the amount of boehmite particles added (volume %), and the vertical axis indicates the amount of wear (μm) of the resin coating layer worn away by the wear test. In Figure 5A, the amount of wear after the wear test for each of the five types of samples mentioned above is indicated by the height of the gray bar graph extending in the vertical direction. That is, the amount of wear for sample Sa1 is 4.0 μm, the amount of wear for sample Sa2 is 4.0 μm, the amount of wear for sample Sa3 is 5.0 μm, the amount of wear for sample Sa0 is 2.0 μm, and the amount of wear for sample Sa01 is 2.0 μm.

Figure 5B is a schematic diagram of a static load bearing test machine for carrying out the wear amount evaluation test shown in Figure 5A. In the test machine shown in Figure 5B, the test axis Ax formed by the mating material can rotate in the R direction around the axis. In addition, a disk is attached to the test axis Ax so that it is coaxial with the test axis Ax, and tension T can be applied in the arrow direction by a belt. The test axis Ax is supported via the sample Sa, and 80°C engine oil (0W-20) O is supplied between the sample Sa and the test axis Ax via an oil supply port.

Tests were conducted on samples Sa1 to Sa3, each of which had a different volume fraction of boehmite particles, by setting the tension T to 3000 N and repeating an operation pattern of rotating and stopping for 15 seconds each for 21,000 cycles. After the test, the amount of wear was measured for each sample Sa1 to Sa3. The amount of wear of the resin coating layer was the difference in thickness measured with a thickness gauge before and after the test.

The wear amount of samples Sa1 to Sa3, Sa0, and Sa01 is 2.0 μm to 5.0 μm. Here, a sample using the same type of hard material as the sliding member disclosed in Patent Document 1 is used as a comparative example. Specifically, a comparative example was created in which the overlay 12 contains 0.7 volume % SiC as a hard material and 40 volume % graphite as a solid lubricant, and the wear amount was evaluated under the same conditions as samples Sa1 to Sa3, Sa0, and Sa01. As a result, the wear amount was 7 μm. Therefore, samples Sa1 to Sa3, Sa0, and Sa01 according to this embodiment all have smaller wear amounts than a resin coating layer using a hard material harder than boehmite particles.

From the results of FIG. 4A, it can be seen that the wear amount decreases as the volume fraction of boehmite particles increases. It can also be seen that when the volume fraction of boehmite particles exceeds 1.0 volume %, the reduction in the wear amount becomes smaller. Focusing on sample Sa1 shown in FIG. 5A, sample Sa1 has the same volume fraction of boehmite particles and molybdenum disulfide as the sample tested in FIG. 4A. Therefore, in the example shown in FIG. 5A, if the volume fraction of molybdenum disulfide is fixed at 30% and the volume fraction of boehmite particles is increased, it is considered that the nature of the wear amount will change in the same way as in FIG. 4A. Therefore, in samples in which the volume fraction of boehmite particles is increased more than in sample Sa1, it is considered that the wear amount will decrease at least until the volume fraction exceeds 1.0 volume %. Therefore, when the volume fraction of molybdenum disulfide is 30 volume percent, by manufacturing a sliding member in which the volume fraction of boehmite particles is in the range of 0.7 volume percent to 1.0 volume percent, it is possible to obtain a sliding member with a smaller amount of wear and higher wear resistance than the comparative example.

On the other hand, from the results of FIG. 4A, it is considered that the wear amount increases as the volume fraction of boehmite particles decreases. Therefore, when the volume fraction of boehmite particles in sample Sa1 shown in FIG. 5A decreases, the wear amount increases as the volume fraction of boehmite particles decreases. Here, focusing on sample Sa3 shown in FIG. 5A, the wear amount of sample Sa3 is 5.0. Therefore, let us consider a hypothetical sample Sh in which the volume fraction of boehmite particles in sample Sa3 is not changed and the volume fraction of molybdenum disulfide is reduced to 30 volume%. If the volume fraction of boehmite particles is not changed and the volume fraction of molybdenum disulfide is reduced, the volume fraction of polyamide-imide resin increases instead. Comparing molybdenum disulfide and polyamide-imide resin, polyamide-imide resin is harder and contributes to improving wear resistance. Therefore, if the volume fraction of molybdenum disulfide is reduced and the volume fraction of polyamide-imide resin is increased instead, the wear amount may decrease, but it is considered that the wear amount will not increase. In Figure 5A, the upper limit of the possible wear amount for sample Sh is shown by a white bar graph. From the above, it can be said that if a sliding member is manufactured in which the volume fraction of boehmite particles is in the range of 0.1 volume % to 0.7 volume % when the volume fraction of molybdenum disulfide is 30 volume %, a sliding member with a smaller wear amount and higher wear resistance can be obtained compared to the wear amount of the comparative example.

From the above, when the volume fraction of molybdenum disulfide is 30 volume%, if a sliding member is manufactured in which the volume fraction of boehmite particles is in the range of 0.1 volume% to 1.0 volume%, it can be said that a sliding member with a smaller wear amount and higher wear resistance can be obtained compared to the wear amount of the comparative example. As described above, it is considered that the wear amount will not increase even if the volume fraction of molybdenum disulfide is reduced and the volume fraction of polyamide-imide resin is increased instead. Therefore, if the volume fraction of boehmite particles is in the range of 0.1 volume% to 1.0 volume%, it is considered that a sliding member with high wear resistance can be obtained even if the volume fraction of molybdenum disulfide is less than 30 volume%. For example, it is considered that a sliding member with high wear resistance can be obtained even if the volume fraction of molybdenum disulfide is 28 volume%, 29 volume%, etc.

Furthermore, focusing on sample Sa3 shown in FIG. 5A, consider the case where the volume fraction of molybdenum disulfide is fixed at 34% and the volume fraction of boehmite particles is increased. In this case, it is considered that the nature of the wear amount changes in the same way as in FIG. 4A. For this reason, in a sample in which the volume fraction of boehmite particles is increased from that of sample Sa3, it is considered that the wear amount decreases at least until the volume fraction exceeds 1.0 volume%. Therefore, when the volume fraction of molybdenum disulfide is 34 volume%, if a sliding member is manufactured in which the volume fraction of boehmite particles is in the range of 0.1 volume% to 1.0 volume%, a sliding member with a smaller wear amount and higher wear resistance than the comparative example can be obtained.

It is considered that the change in the amount of wear is also equivalent in sample Sa2. From the above, when the volume fraction of molybdenum disulfide is 30 vol% to 34 vol%, if a sliding member with a volume fraction of boehmite particles in the range of 0.1 vol% to 1.0 vol% is manufactured, a sliding member with a smaller amount of wear and higher wear resistance compared to the comparative example can be obtained. It is considered that the change in the amount of wear is also equivalent in samples Sa0 and Sa01. For example, let us consider a case where the volume fraction of molybdenum disulfide is not changed and the volume fraction of boehmite particles is reduced to 0.1 vol%, using sample Sa0, which has a volume fraction of molybdenum disulfide of 28 vol% and a volume fraction of boehmite particles of 1.0 vol%, as a reference. In this case, it is considered that the amount of wear of the sample increases as the volume fraction of boehmite particles decreases, but even if it is reduced to 0.1 vol%, it is considered that the amount of wear is smaller than 5.0 μm. As described above, focusing on sample Sa3, if the volume fraction of molybdenum disulfide is reduced without changing the volume fraction of boehmite particles, the volume fraction of polyamide-imide resin will increase instead, and the amount of wear may decrease, but it is thought that the amount of wear will not increase. Therefore, whether the volume fraction of molybdenum disulfide is 28 volume% or 29 volume% as in samples Sa0 and Sa01, by manufacturing a sliding member in which the volume fraction of boehmite particles is in the range of 0.1 volume% to 1.0 volume%, it is possible to obtain a sliding member with a smaller amount of wear and higher wear resistance than the comparative example.

Figure 6A shows the results of measuring the seizure surface pressure for sample Sa0, in which the volume fractions of molybdenum disulfide particles and boehmite particles contained in the overlay 12 are 28 volume % and 1.0 volume %, sample Sa1, in which the volume fractions are 30 volume % and 0.7 volume %, and sample Sa2, in which the volume fractions are 32 volume % and 0.4 volume %.

In Figure 6A, the horizontal axis indicates the amount of molybdenum disulfide added (volume %), the depth axis indicates the amount of boehmite particles added (volume %), and the vertical axis indicates the seizure surface pressure (MPa) measured in the test. In Figure 6A, the seizure surface pressure after the wear test for each of the three types of samples described above is indicated by the height of the vertically extending bar graph. That is, the seizure surface pressure for sample Sa0 is 56 MPa, the seizure surface pressure for sample Sa1 is 77 MPa, and the seizure surface pressure for sample Sa2 is 107 MPa.

Figure 6B is a schematic diagram of a static load bearing test machine for performing the evaluation test of the seizure surface pressure shown in Figure 6A. In the test machine shown in Figure 6B, the test axis Ax formed by the mating material can rotate around its axis. The test axis Ax is supported via the sample Sa, and 140°C engine oil (0W-20) O is supplied between the sample Sa and the test axis Ax via an oil supply port. A member that applies a load N is connected to the sample Sa, and a load cell Lc is connected to the member.

When a load N is applied to each of the multiple samples Sa0 to Sa2 with different volume fractions of boehmite particles, the load is increased in 3 kN steps from 0 kN, 3 kN, 6 kN, and so on. Each load is maintained for 3 minutes and then increased by 3 kN, and the test shaft Ax is rotated for 3 minutes with the load constant. The rotation speed is 6400 rpm. In this example, the seizure load was measured using the above test machine. Here, the seizure load is the load when a predetermined temperature (the temperature at which seizure is assumed to occur) is reached. The temperature can be measured by a temperature sensor attached to the bearing of the test shaft Ax.

The seizure surface pressure of samples Sa0 to Sa2 is 56 to 107 MPa. Again, samples using the same type of hard material as the sliding member disclosed in Patent Document 1 are used as comparative examples. Specifically, a comparative example was created in which the overlay 12 contained 0.7 volume % SiC as the hard material and 40 volume % graphite as the solid lubricant, and the seizure surface pressure was evaluated under the same conditions as samples Sa0 to Sa2. As a result, the seizure surface pressure was 55 MPa. Therefore, samples Sa0 to Sa2 according to this embodiment all have a higher seizure surface pressure than a resin coating layer using a hard material harder than boehmite particles.

In this embodiment, the hardness of the overlay 12 is considered to vary mainly depending on the volume fraction of the boehmite particles and the volume fraction of the polyamide-imide resin. That is, the higher the volume fraction of the boehmite particles, the less the amount of wear of the resin coating layer caused by hard materials. Also, when comparing molybdenum disulfide and polyamide-imide resin, polyamide-imide resin is harder. Therefore, when the volume fraction of the boehmite particles is the same, the higher the volume fraction of the polyamide-imide resin (the lower the volume fraction of molybdenum disulfide), the less the amount of wear of the resin coating layer.

If the resin coating layer is hard, the resin coating layer cannot conform to the mating material as a result of sliding, and it becomes less compatible with the mating material and more likely to generate heat. Therefore, in the overlay 12 of this embodiment, the larger the volume fraction of the boehmite particles, the smaller the baking surface pressure, and the larger the volume fraction of the polyamideimide resin, the smaller the baking surface pressure.

Focusing on sample Sa0 shown in FIG. 6A, the baking surface pressure increases when the volume fraction of boehmite particles is reduced from that of sample Sa0, and when the volume fraction of molybdenum disulfide is increased (when the volume fraction of polyamide-imide resin is reduced). The baking surface pressures of samples Sa1 and Sa2 are both greater than that of sample Sa0, so the change in baking surface pressure due to the volume fraction of boehmite particles and the volume fraction of molybdenum disulfide is supported by the baking surface pressure values of samples Sa1 and Sa2.

From the above, by manufacturing a sliding member in which the volume fraction of boehmite particles is less than 1.0 volume % and the volume fraction of molybdenum disulfide is more than 28 volume %, it is possible to obtain a sliding member with a higher seizure surface pressure and higher seizure resistance than the comparative example.

(4) Other embodiments:
In the above embodiment, the sliding member 1 constituting the sliding bearing A for bearing the crankshaft of the engine has been exemplified, but the sliding bearing A for other applications may be formed using the sliding member 1 of the present invention. For example, radial bearings such as gear bushings for transmissions, piston pin bushings, boss bushings, etc. may be formed using the sliding member 1 of the present invention.

The surface of the base layer is coated with a resin coating layer, and the base layer is a layer that constitutes a part of the sliding member. Therefore, the composition and shape of the base layer are not limited. The mating member is not limited to a cylindrical shaft as in the above embodiment, and may be a flat surface or a spherical surface. The resin coating layer is formed on the base layer. In other words, the base layer is coated so that the base layer does not come into contact with the mating member. Furthermore, although the thickness of the resin coating layer is 6 μm in the above embodiment, the thickness is not limited. In other words, the thickness may be various depending on the application of the sliding member, the material of the mating member, the relative speed between the sliding member and the mating member, etc.

The sliding member may be any member that is used in a state where at least one of the sliding member and the mating member rotates or moves back and forth with a liquid lubricant interposed between the resin coating layer and the mating member. Therefore, the sliding member is not limited to a radial bearing as in the above embodiment, but may be a thrust bearing, various washers, or a swash plate for a car air conditioner compressor.

The solid lubricant may be any material that is in a solid state in the environment in which the sliding member is used, and that reduces the coefficient of friction between the sliding member and the mating material when the solid lubricant is present compared to when the solid lubricant is not present. Therefore, it is not limited to the above-mentioned molybdenum disulfide, and may be any of various solid lubricants, such as graphite, boron nitride, tungsten disulfide, PTFE (polytetrafluoroethylene), graphite fluoride, MCA (melamine cyanurate), etc. One type of these solid lubricants may be used, or two or more types may be used.

The additive may or may not be included in the resin coating layer. The additive may have various uses. For example, when barium sulfate is used as an additive, the additive transfers to the mating material, coating the mating material and suppressing the occurrence of seizure.

In addition, various intermediate layers may be formed between the base layer and the resin coating layer. For example, a layer for improving adhesion between the base layer and the resin coating layer, or a layer for preventing diffusion of materials between the base layer and the resin coating layer may be formed.

1...sliding member, 2...mating material, 10...backing metal, 11...lining, 12...overlay, A...sliding bearing

Claims (3)

A sliding member comprising a base layer and a resin coating layer formed on the base layer,
The resin coating layer is
A polyamide-imide resin as a binder;
A solid lubricant;
% by volume or more and 1.0% by volume or less of boehmite particles;
Inevitable impurities,
A sliding member comprising: The solid lubricant is molybdenum disulfide.
The sliding member according to claim 1 . A plain bearing comprising a base layer and a resin coating layer formed on the base layer,
The resin coating layer is
A polyamide-imide resin as a binder;
A solid lubricant;
% by volume or more and 1.0% by volume or less of boehmite particles;
Inevitable impurities,
A plain bearing consisting of:

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