JP2003056566A - Slide bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide bearing, causing no water pollution, reducing discharge amount of industrial waste and having superior sliding characteristics. SOLUTION: Comprising a overlay layer consisting a 30-70 vol.% solid lubricant, containing lead particles and resin binder residual selected from at least one type of a polyamideimide resin, a polyimide resin, an epoxy resin and a polybenzoimidazol resin, the sliding bearing is formed to be low in friction coefficient and superior in wear resistance and non-seizure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slide bearing in which a bearing metal layer is covered with an overlay layer.

[0002]

2. Description of the Related Art Conventionally, in a sliding bearing having a bearing metal layer such as a copper alloy or an aluminum alloy formed on a steel backing metal, which is mainly used for an engine for an internal combustion engine or the like, the compatibility of the bearing metal layer is To improve non-seizure characteristics, soft metal is applied to the bearing metal layer surface by wet plating to 5-20μ
In general, it was formed as an overlay layer by covering with a thickness of m (hereinafter referred to as Prior Art 1). The soft metal used is a lead-based material with excellent compatibility and non-seizure resistance, and tin is added as an element to improve corrosion resistance, copper is added as an element to improve fatigue strength, and indium is added as an element to further improve compatibility and anti-seizure. In general, tin is 6 to 15% by weight, copper is 1 to 5% by weight, and indium is 0 to 0% by weight.
About 15% by weight is added.

On the other hand, in recent years, high output and high rotation of an internal combustion engine or intermittent operation of the engine due to improvement of fuel consumption have been performed, and sliding bearings used in the engine have severe operating conditions. It has become to. In order to meet such usage conditions, for example, Japanese Patent Laid-Open No. 58-10
No. 8299 gazette, an overlay coating containing a solid lubricant such as graphite or molybdenum disulfide for the purpose of improving wear resistance and non-seizure property, using a thermosetting resin such as a phenol resin or an epoxy resin as a binder. To
There has been proposed a sliding bearing in which an aluminum alloy bearing formed by press-contacting an aluminum alloy on a steel backing is coated (hereinafter referred to as prior art 2).

Further, in Japanese Patent Laid-Open No. 4-83914,
For the purpose of improving fatigue resistance and non-seizure resistance, a sliding bearing has been proposed in which an overlay coating containing polyimide resin as a binder and a solid lubricant of molybdenum disulfide is coated on the surface of an aluminum bearing alloy. (Hereinafter, referred to as Prior Art 3).

Further, in Japanese Patent Laid-Open No. 10-37962, in order to improve wear resistance, the hard particles of a slide bearing coated with an overlay coating composed of a resin binder, hard particles and a solid lubricant are spherical. Has been proposed (hereinafter referred to as Prior Art 4).

[0006]

In the case of the prior art 1 in which the overlay layer is formed by the above-mentioned wet plating, the borofluoride bath is often used because of its excellent throwing power and plating efficiency. This fluorinated bath is PH3
It is a strong acid of up to 5 and also contains a large amount of metal ions such as lead, tin and indium. The washing water and waste liquid are subjected to pH adjustment after removing the plating sludge and discharged to a general river. However, even if the wash water and the waste liquid are treated in this way, the water quality of the river will be contaminated.
There is a problem that the removed plating sludge remains as industrial waste. In terms of such water pollution and generation of industrial waste, the plain bearings of the related arts 2 to 4 which are coated with the overlay film described above do not have the problem of water pollution and generate a small amount of industrial waste. Therefore, it is not effective enough for the severe use conditions such as high output and high rotation of the internal combustion engine or intermittent operation in recent years. The present invention has been made in view of the above circumstances, and an object thereof is to be able to significantly reduce the amount of industrial waste discharged without the problem of water pollution and to have excellent sliding characteristics. The present invention provides a plain bearing having

[0007]

In order to achieve the above object, in the invention according to claim 1, in a sliding bearing having a bearing metal layer coated with an overlay layer, the overlay layer contains lead particles. ~ 70% by volume solid lubricant, polyamide-imide resin, polyimide resin,
A resin binder balance selected from at least one or more of epoxy resin and polybenzimidazole resin;
It is characterized by being composed of.

The bearing metal layer includes bearing alloys such as copper alloys and aluminum alloys.

As the resin binder for the overlay layer,
A resin selected from at least one of a polyamide-imide resin, a polyimide resin, an epoxy resin, and a polybenzimidazole resin was used. Each of these resins has a strong adhesive force with the metal powder, and also has high heat resistance and strength. Examples of the polyamide-imide and polyimide-based resins include polyamino-bis-maleimide, diisocyanate-modified, BPDA-modified, and sulfone-modified resins of these. In particular, a polyamide-imide resin is preferable as a resin binder because it has high fatigue strength. This polyamide-imide resin is a polymer in which an amide bond and an imide bond are alternately bonded in the main chain, and a modified polyamide-imide resin is also available. It includes.

Since the lead particles contained in the solid lubricant are soft, they can be easily deformed by an external force and abnormal seizure wear can be prevented. When the temperature of the sliding surface of the sliding bearing rises due to the heat of rubbing, the lead particles are melted and the latent heat of fusion that robs the surrounding heat of the sliding bearing prevents the temperature of the sliding surface from rising. Further, it does not form a solid solution with or reacts with the steel of the mating shaft material, and does not weld to the mating shaft material. In this way, a great effect is exhibited with respect to the non-seizure property. Furthermore, since the above-mentioned resin binder having a relatively low thermal conductivity contains lead particles, the temperature rise of the lead particles becomes large as compared with the lead plating of the usual wet overlay, and the sliding surface of the outermost surface layer. By repeating melting and solidification, the sliding stability of the sliding surface is improved.

The solid lubricant containing lead particles is 30 to 70% by volume. If it is less than 30% by volume, the effect on anti-seizure property and friction performance is small, and if it exceeds 70% by volume, the strength of the coating itself is significantly reduced to increase the wear amount, and further the cavitation resistance is also significantly increased. Deteriorate (increased volume reduction). The average particle size of the lead particles is 0.5 to
10 μm. If it is less than 0.5 μm, the number of lead particles increases and the surface area of the entire lead increases. For this reason, it becomes difficult for the resin to rotate on the surface of the lead particles, that is, the wettability with the resin rapidly deteriorates, and the film strength decreases. On the other hand, if it exceeds 10 μm, it becomes easy to separate from the resin at the stage of coating material, and it becomes difficult to coat the bearing metal layer.

As described above, the resin binder greatly contributes to the improvement of the load resistance and wear resistance of the entire overlay layer, and the lead particles contribute largely to the improvement of the non-seizure property and the reduction of the friction coefficient. ing. Further, since lead has excellent ductility, the sliding outermost layer is covered with lead over a wide range, which further enhances the effect of improving anti-seizure property and reducing the friction coefficient.

Further, in the invention according to claim 2, the solid lubricant is at least one kind in the range of 20% by volume or less of indium, 10% by volume or less of silver, 20% by volume or less of tin and 10% by volume or less of copper. It is characterized in that it is composed of mixed metal particles or alloy particles containing and containing 40% by volume or less of metal in total and the balance being lead.

As the solid lubricant, indium, silver, tin and copper, which are added in addition to lead, are preferably added according to the sliding environment used.

Indium has almost the same effect as lead, but since it has a property of being easily compatible with oil, its wettability with lubricating oil is further improved, and wear resistance and non-seizure property are improved.
Further, since indium has a lower melting point than lead, when indium is added in an amount of more than 20% by volume, the melting point in a state where indium and lead are alloyed is lowered, and fatigue resistance and wear resistance are reduced. descend.

Silver is not included in the category of low-melting-point metals, but since it is excellent in non-sticking property, it improves non-seizure property and also improves fatigue strength. Silver is
Even when added in excess of 10% by volume, the effect remains the same.

Although tin has almost the same effect as lead in terms of sliding characteristics, it can further improve the corrosion resistance when the plain bearing is used in an environment where the overlay layer is easily corroded. Even if tin is added in an amount of more than 20% by volume, the effect remains the same.

This element itself is not a solid lubricant, but copper reacts with sulfur contained in the lubricating oil to form a sulfide, so that the lubricating performance is improved. Even if copper is added in an amount of more than 10% by volume, the effect does not change.

The above-mentioned metal element powder may be added as an individual powder, or an alloy powder prepared in advance may be added to the resin. When powders of metal elements are added individually, the segregation of each metal is unevenly present in the resin, so the variation in properties becomes large, and due to contact between metal powders during use of sliding bearings. Mutual diffusion occurs and the melting point changes significantly, so the sliding characteristics change. Therefore, it is desirable to add it as alloy powder.

Further, in the invention according to claim 3, the solid lubricant contains at least one kind of molybdenum disulfide, graphite, antimony trioxide and hexagonal boron nitride, and 80% by volume or less of lubricating particles and the balance. Is composed of lead particles.

As solid lubricants, molybdenum disulfide, graphite, antimony trioxide, and hexabonal boron nitride, which are added in addition to lead, assist the effects of improving anti-seizure property and reducing friction coefficient of lead-based solid lubricants. However, if it is added in an amount of more than 80% by volume, the effect of lead originally on improving the slidability is impaired. Further, it is desirable that the molybdenum disulfide, graphite, antimony trioxide, and hexagonal boron nitride have an average particle diameter that is similar to that of lead particles.

Further, in the invention according to claim 4, the solid lubricant contains at least one kind of molybdenum disulfide, graphite, antimony trioxide, and hexagonal boron nitride, and less than 80% by volume of lubricating particles and the balance. Is composed of the mixed metal particles or alloy particles.

As the solid lubricant, molybdenum disulfide, graphite, antimony trioxide and hexabonal boron nitride, which are added in addition to the mixed metal particles according to claim 2, are also contained in the non-lead solid lubricant as described above. Although it has a role of assisting the effect of improving the seizure property and reducing the friction coefficient, when it is added in an amount exceeding 80% by volume, the effect of improving the sliding property originally possessed by lead is hindered. Further, similarly to the above, it is desirable that the molybdenum disulfide, graphite, antimony trioxide, and hexagonal boron nitride have an average particle diameter of about the same as that of the lead particles.

Furthermore, in the invention according to claim 5, at least one of alumina, aluminum nitride, silica, chromium oxide, silicon nitride, silicon carbide and zirconia is contained, and the total amount thereof is 0.5 to 10% by volume. The above hard particles are included in place of part of the solid lubricant or part of the resin binder.

The hard particles contained in place of a part of the solid lubricant or a part of the resin binder improve the wear resistance of the overlay layer, but when added in excess of 10% by volume, The mating material may be damaged, the friction coefficient increases, and the non-seizure property decreases. If it is less than 0.5% by volume, the wear resistance cannot be improved.
It is preferably 1 to 5% by volume.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings and tables. FIG. 1 is a sectional view of a slide bearing 1 according to an embodiment. First, slide bearing 1
The configuration will be described with reference to FIG. A copper-based material was used for the bearing metal layer (bearing alloy) 3 of the sliding bearing 1 according to the present invention. The copper alloy powder is sprinkled on the steel backing metal 2 at a constant thickness, and sintering and rolling are repeated to make the thickness of the backing metal 1: 1.
A material having a thickness of 5 mm and a bearing metal layer 3 thickness of 0.3 mm was manufactured. The final component of the bearing metal layer 3 is 23 wt% lead-
It was 2 wt% tin-residual copper. A test piece was cut out from this continuous material, pretreated by degreasing and pickling the test piece, and the following coating material liquids were sprayed on the bearing surface to form an overlay layer 4.

As a resin (base resin) used for the overlay layer 4, a polyamide-imide (hereinafter, PAI) resin,
Polyimide (hereinafter PI) resin, epoxy (hereinafter E)
P) resin and polybenzimidazole (hereinafter, PBI)
Resin was used.

As a solid lubricant, based on lead (hereinafter, Pb), indium (hereinafter, In), silver (hereinafter, A)
g), tin (hereinafter Sn), and copper (hereinafter Cu) metal particles were used. Other solid lubricants include molybdenum disulfide (hereinafter MoS ₂ ), graphite (hereinafter
Gr), antimony trioxide (hereinafter, Sb ₂ O ₃ ) and hexabonal boron nitride (hereinafter, h-BN) were used.

Alumina (hereinafter referred to as Al ₂
O ₃ ), aluminum nitride (hereinafter, AlN), silica (hereinafter,
SiO ₂ ), chromium oxide (hereinafter CrO ₂ ), silicon nitride (hereinafter Si ₃ N ₄ ), silicon carbide (hereinafter SiC) and zirconia (hereinafter ZrO ₂ ) were used.

A resin solution was prepared by blending these so as to have the composition of the overlay layer 4 shown in Table 1. The resin solution was sprayed on the above-mentioned bearing metal layer 3 and dried at 120 ° C. It was baked at 250 ° C. As a result, the overlay layer 4 having a thickness of about 20 μm was formed. Thus, in the process of forming the overlay layer 4, unlike wet plating, there is no discharge of cleaning water and waste liquid containing a large amount of metal ions and no generation of plating sludge, so there is no problem of water pollution in the river, Industrial waste can also be significantly reduced. With respect to each of the examples and comparative examples of the thus obtained test piece, each test of friction coefficient, wear amount, seizure and cavitation was conducted.

[0031]

[Table 1]

With respect to the friction coefficient and the wear amount, the thrust type tester was used under the test conditions shown in Table 2, and the results shown in Table 1 were obtained. For the seizure load, a seizure test was conducted using a thrust type tester under the test conditions shown in Table 3, and the results shown in Table 1 were obtained. Regarding the friction coefficient and the wear amount, the lower the numerical value is, the more excellent it is. Regarding the seizure load, the higher the numerical value is, the more excellent it is. As the lubricating oil, a lubricating oil having a low sulfur concentration of 0.1% by weight (SAE
# 30) was used. For volume reduction, a cavitation test was conducted under the test conditions shown in Table 4 using a tester utilizing ultrasonic waves, the weight loss of the overlay layer was measured, and this was converted into volume to obtain the volume loss. Regarding the volume reduction, the lower the value, the better.

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

From the test results shown in Table 1 regarding the coefficient of friction, the amount of wear and the seizure load, the following was found. First, in Examples 1 and 2 and Comparative Examples 1 and 2 in which the overlay layer 4 is composed only of a base resin and Pb particles as a solid lubricant, in Comparative Examples 1 and 2, the amount of Pb particles as a solid lubricant is used. Is higher than the upper limit of 70% by volume and 80% by volume (the amount of base resin is lower than the lower limit of 30% by volume of 20% by volume), the coefficient of friction is low and the seizure load is high. However, the amount of wear is extremely large.
On the contrary, when the amount of the base resin is 80% by volume which is higher than the upper limit of 70% by volume (when the amount of the Pb particles as the solid lubricant is 20% by volume lower than the lower limit of 30% by volume), the wear amount However, the coefficient of friction is extremely high and the seizure load is low. On the other hand, as in Examples 1 and 2, when the amount of the base resin and the amount of Pb particles are 40% by volume and 60% by volume or 60% by volume and 40% by volume, respectively, the friction coefficient is low, The amount of wear is small and the seizure load is high. Thus, when the overlay layer 4 is composed only of the base resin and Pb particles, the amount of the base resin falls within the range of 70 to 30% by volume and the amount of Pb particles within the range of 30 to 70% by volume. The friction coefficient, wear resistance, and anti-seizure property can be improved when it is in the water.

The overlay layer 4 contains I other than Pb particles.
As a comparison of the case where metal particles such as n, Ag, Sn, and Cu are added as a solid lubricant, when Example 1 and Examples 3 to 6 are compared, the friction coefficient shows almost the same value and the wear amount. Indicates that the values of Examples 3 to 6 are lower than those of Example 1. The seizure load in Examples 3 to 6 is equal to or higher than that in Example 1. As described above, in the overlay layer 4, in addition to Pb particles, Examples 3 to
By adding the element shown in 6, that is, a solid lubricant such as In, Ag, Sn and Cu, wear resistance and non-seizure property can be improved. In particular, In and Ag have a remarkable effect on non-seizure property, and Cu has a remarkable effect on wear resistance.

Further, as a comparison of the case where the solid lubricant other than the metal particles described above is added to the overlay layer 4, when Example 1 and Examples 7 to 10 are compared, the friction coefficient and the wear amount are 10 to 10 show a value equal to or slightly lower than the value of Example 1, but the seizure load of Examples 7 to 10 shows a value higher than that of Example 1. As described above, in the overlay layer 4, in addition to Pb particles, Examples 7 to
Solid lubricant shown in 10, namely, MoS ₂ , Gr, Sb ₂ O
By adding ₃ and h-BN or the like, the non-seizure property can be improved. In particular, the effect is remarkable when MoS ₂ is added.

Further, as a comparison of the case where hard particles are added to the overlay layer 4 in addition to the solid lubricant, when Example 1 and Example 22 are compared, Example 22 has a lower wear amount than Example 1. When comparing Example 7 with Examples 11 to 17, the friction coefficient is the same as that of Example 7 in Examples 11 to 17, and the seizure load is slightly lower in Examples 11 to 17 than in Example 7. However, the amount of wear can be significantly reduced. As described above, in the overlay layer 4, Examples 11 to 11 are formed.
Hard particles shown in 17 and 22, namely Al ₂ O ₃ , Al
N, SiO ₂ , CrO ₂ , Si ₃ N ₄ , SiC and ZrO ₂
The wear resistance can be remarkably improved by adding such as.

The base resin of the overlay layer 4 is PA
As a comparison in the case of using a resin other than the I resin, when comparing Example 3 and Examples 18 to 20, the friction coefficient of Examples 18 to 20 is higher than that of Example 3. The wear amounts of Examples 18 to 20 are lower than those of Example 3. Further, the seizure load in Example 20 is equivalent to that in Example 3, but in Examples 18 and 19, the value is lower than that in Example 3. In the comparison among Examples 18 to 20, the friction coefficients are almost the same, but the wear amount shows a low value in the PBI resin, and the seizure load shows
The PI resin shows a low value. As described above, due to the difference in the type of the base resin, a slight difference can be seen in the sliding characteristics of the overlay layer.

In Example 21, the contents of the base resin (PAI) and MoS ₂ were the same as those of Example 17, but the content of Pb particles was a little small, and the hard particles were 5% by volume of ZrO ₂ , instead of 5% by volume. 3% by volume of Al ₂ O ₃ is added, and further 3% by volume of solid lubricant metal particles Sn is added. The test result of Example 21 shows the same values for the friction coefficient, the wear amount, and the seizure load as compared with the test result of Example 17, and instead of ZrO ₂ , A of the same capacity was used.
Even if l ₂ O ₃ and Sn are added, no big difference is found in the test results. In Example 22, the content of the base resin (PAI) is the same as that of Example 1, the content of Pb particles is small, and the hard particles Al ₂ O ₃ 3% by volume are added.

Regarding the volume reduction, Comparative Examples 1 and 4
The values are almost the same except that the values of 8 and 8 are extremely high. This is because in Comparative Example 1, the amount of the base resin was 20% by volume, which was lower than the lower limit of 30% by volume, and the amount of Pb particles was 80% by volume, which was higher than the upper limit of 70% by volume. Conceivable. Further, in Comparative Example 4, although the amount of the base resin was 40% by volume within the reference value, the remaining 60% by volume was not Pb particles but MoS ₂ , and P
It is considered that this is due to the fact that b particles are not contained at all. Further, in Comparative Example 8, the amount of Pb particles is 65% by volume within the reference value, but it is considered that this is because the amount of base resin is 20% by volume, which is lower than the lower limit of 30% by volume.

In Comparative Example 4, 60% by volume of MoS ₂ was added in place of 60% by volume of Pb of Example 1 to eliminate Pb particles, but the friction coefficient showed the same value. , The amount of wear and the seizure load were significantly reduced. It is considered that this is because Pb particles were not contained at all.

In Comparative Example 5, the content of Pb particles in Comparative Example 2 was changed from 20% by volume to 10% by volume, and 10% by volume of Gr was added. 2 is slightly higher than that of Comparative Example 5
Shows a value slightly lower than that of Comparative Example 2. Further, the wear amount of Comparative Example 5 is extremely higher than that of Comparative Example 2. This is because the amount of the base resin is 80% by volume which is higher than the upper limit value of 70% by volume, the amount of Pb particles is lower than that of Comparative Example 2 and 10% by volume which is lower than the lower limit value of 30% by volume. It is thought that.

Further, in Comparative Example 6, 15% by volume of Si ₃ N ₄ was added in place of 15% by volume of the solid lubricant (In, Sn and Cu) other than the Pb particles of Example 6, but abrasion was observed. Although the amount of Comparative Example 6 was the same as that of Example 6, the friction coefficient of Comparative Example 6 was extremely higher than that of Example 6, and the seizure load was that of Comparative Example 6 of Example 6. The value was lower than 6. This is more than the upper limit of 10% by volume.
It is considered that this is due to the addition of 5% by volume of Si ₃ N ₄ .

Comparative Example 7 was prepared by adding 10% by volume of Si ₃ N ₄ instead of 10% by volume of Gr of Comparative Example 5, but the friction coefficient of Comparative Example 7 was higher than that of Comparative Example 5. The abrasion amount of Comparative Example 7 was extremely lower than that of Comparative Example 5, and the seizure load of Comparative Example 7 was slightly lower than that of Comparative Example 5. Although the wear resistance is improved by Si ₃ N ₄ , the amount of the base resin is 80% by volume higher than the upper limit of 70% by volume, and the amount of Pb particles is 30% by the lower limit, as in Comparative Example 5. It is considered that this is due to 10% by volume, which is lower than 10% by volume.

Further, in Comparative Example 8, the content of Pb particles of Comparative Example 1 was changed from 80% by volume to 65% by volume, and 15% by volume of Gr was added. Comparative Example 8 shows a slightly higher value than Comparative Example 1, and the wear amount and the seizure load of Comparative Example 8 are lower than those of Comparative Example 1. It is considered that this is because the amount of the base resin is 20% by volume which is lower than the lower limit value of 30% by volume and 15% by volume of Si ₃ N _{4 which} is higher than the upper limit value of 10% by volume is added. .

[0048]

As is apparent from the above description, in the invention according to claim 1, a sliding bearing having a low coefficient of friction and excellent wear resistance and non-seizure property is provided for river water pollution and industrial disposal. It can be created without causing a large number of objects.

Further, in the invention according to claim 2, the wear resistance and anti-seizure property of the slide bearing can be further improved.

In the invention according to claim 3, the non-seizure property of the slide bearing can be further improved.

In the invention according to claim 4, the non-seizure property of the slide bearing can be further improved.

Further, in the invention according to claim 5, the wear resistance of the slide bearing can be further improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a slide bearing according to an embodiment.

[Explanation of symbols]

1 Sliding bearing 2 back money 3 Bearing metal layer 4 Overlay layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takuya Tanaka             Daidome, 2 Sanaru-cho, Kita-ku, Nagoya-shi, Aichi             Within Taru Industry Co., Ltd. (72) Inventor Takayuki Shibayama             Daidome, 2 Sanaru-cho, Kita-ku, Nagoya-shi, Aichi             Within Taru Industry Co., Ltd. F-term (reference) 3J011 JA01 QA05 SB04 SC01 SC03                       SC14 SD01 SD03 SD04 SE02                       SE04 SE06

Claims (5)

[Claims] 1. A plain bearing in which a bearing metal layer is covered with an overlay layer, wherein the overlay layer contains 30 to 70% by volume of a solid lubricant containing lead particles, a polyamideimide resin, a polyimide resin, an epoxy resin, and a polybenzoate. A plain bearing characterized by comprising a resin binder balance selected from at least one of imidazole resins. 2. The solid lubricant contains at least one of indium 20% by volume or less, silver 10% by volume or less, tin 20% by volume or less, and copper 10% by volume or less and a total of 40% by volume or less. The sliding bearing according to claim 1, wherein the sliding bearing is composed of mixed metal particles or alloy particles composed of metal and the balance being lead. 3. The solid lubricant is molybdenum disulfide,
2. The sliding bearing according to claim 1, wherein at least one of graphite, antimony trioxide, and hexagonal boron nitride is contained, and the balance is 80% by volume or less of lubricating particles and the balance is lead particles. 4. The solid lubricant is molybdenum disulfide,
3. Lubricant particles containing at least one of graphite, antimony trioxide, and hexaboron boron nitride, and 80% by volume or less of lubricating particles, and the balance being composed of the mixed metal particles or alloy particles. Plain bearing. 5. A hard particle containing at least one of alumina, aluminum nitride, silica, chromium oxide, silicon nitride, silicon carbide and zirconia, the total amount of which is 0.5 to 10% by volume of the solid lubricant. The sliding bearing according to any one of claims 1 to 4, wherein the sliding bearing is included in part or in place of a part of the resin binder.