Multilayer sliding material

Abstract

There is provided a multi-layer sliding material, comprising a back metal layer, a bearing alloy layer bonded onto the back metal layer, and a coating layer bonded onto the bearing alloy layer, said coating layer being made of an alloy consisting of 20 to 80 mass % Pb, at least one optional element not more than 10 mass % in total selected from the group consisting of In, Sb, Sn and Ag, and the balance Cu and incidental impurities. The material may further comprise a conforming layer made of an alloy containing not less than 80 mass % Pb.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a multi-layer sliding material comprising a bearing alloy layer and a Cu-based alloy layer bonded onto the bearing alloy layer which Cu-based alloy layer acts to enhance the fatigue resistance and the wear resistance of the multi-layer sliding material.

[0002] In prior arts, a bearing used in an engine is constituted to have a back metal layer made of a steel which back metal layer has a semi-cylindrical or cylindrical shape, and a bearing alloy layer made of a Cu-based bearing alloy or an Al-based bearing alloy which bearing alloy layer is bonded onto the back metal layer. The Cu-based or Al-based bearing alloy is superior regarding the load carrying capacity, however, it is inferior regarding other characteristics required in the bearing such as anti-seizure property, em-beddability, conformability and etc. To improve this problem, the conventional bearing is made to have a conforming layer provided on the bearing alloy layer so that the bearing characteristics may be improved.

[0003] Hitherto, a conforming layer provided on a Pb—Cu bearing alloy layer is made to contain not more than 6 mass % Cu, which is dispersed in the Pb-based matrix of the conforming layer to thereby strengthen the matrix. The advantage brought about by this Cu is disclosed in JP-A-61-266544. However, even in the case of the alloy used as the surface layer of a sliding material disclosed in this publication, the fatigue resistance and wear resistance of this alloy are insufficient when the alloy is used as the conforming layer.

SUMMARY OF THE INVENTION

[0004] The invention is achieved in taking the above-explained circumstances of the prior art into consideration, and the object of the invention is to provide a multi-layer sliding material having superior fatigue resistance and superior wear resistance.

[0005] According to the first aspect of the invention, there is provided a multi-layer sliding material, comprising a back metal layer, a bearing alloy layer bonded onto the back metal layer, and a coating layer bonded onto the bearing alloy layer, said coating layer being made of an alloy consisting of 20 to 80 mass % Pb, and the balance Cu and incidental impurities.

[0006] In the multi-layer sliding material of the invention, the hardness of the coating layer becomes high because the content of the balance Cu contained in the coating layer is in the range of 20 to 80 mass %, so that the fatigue resistance and wear resistance of the sliding material are enhanced. In a case where the content of Cu is less than 20 mass %, the hardness-raising effect of Cu becomes small with the result that the enhancement of each of the fatigue resistance and the wear resistance becomes insufficient. In another case where the content of Cu exceeds 80 mass %, the hardness of the coating layer becomes excessively high with the results that the initial conformability thereof is lowered, that the anti-seizure property thereof is also lowered, and that the fatigue resistance thereof decreases due to the decrease in the toughness of the coating layer.

[0007] Each of Pb and Cu, which are substantially evenly dispersed in the coating layer as an amorphous state prior to the use of the sliding material, comes to be precipitated as crystal grains due to heat occurring during the use thereof. Thus, the Pb crystal grains present on the surface act to enhance the anti-seizure property of the sliding material with the Cu crystal grains acting to enhance both of the wear resistance and fatigue resistance. Namely, the coating layer comes to have an enhanced fatigue resistance and an enhanced wear resistance while maintaining a good lubrication on the surface of the coating layer.

[0008] The bearing alloy layer may be made of a Cu-based alloy containing 5 to 30 mass % Pb or an Al-based alloy containing not more than 20 mass % Sn, which Cu-based alloy may further contain 2 to 15 mass % Sn and/or 0.01 mass % P and which Al-based alloy may further contain 2 to 7 mass % Si.

[0009] Sn contained in the Al-based bearing alloy layer is a soft metal similarly to Pb. It is preferred that the content of the soft metal (, that is, Pb or Sn) contained in the bearing alloy layer is less than that of the soft metal (Pb) contained in the coating layer. By selecting the contents of the soft metals in this manner, the hardness decreases in the order of the bearing alloy layer and the coating layer, so that such functions of each of them as the bearing alloy layer bears a load and as the coating layer brings about other bearing characteristics can be effectively exerted.

[0010] In the coating layer, at least one not more than 10 mass % in total selected from the group consisting of In, Sb, Sn and Ag may be added, which at least one acts to enhance the mechanical strength of the coating layer and the corrosion resistance thereof. In a case where the total amount of the at least one of the additive elements exceeds 10 mass %, the wear resistance of the coating layer is deteriorated.

[0011] Further, a conforming layer containing not less than 80 mass % Pb may be provided on the coating layer as occasion arises. Namely, since the coating layer contains a relatively much amount of Cu, the hardness thereof becomes high, so that the initial conformability thereof becomes insufficient in certain cases. In this case, by providing the soft conforming layer containing a much amount of Pb, the initial conformability of the sliding material can be improved while enhancing the anti-seizure property thereof.

[0012] Further, the conforming layer may be made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu.

[0013] In this case of providing the conforming layer, it is preferred that the hardness of each of the bearing alloy layer, the coating layer and the conforming layer decreases in this order. Namely, it is preferred that the Cu-based alloy and the Al-based alloy each used as the bearing alloy layer have hardness ranges of 75 to 200 Hv and 30 to 150 Hv, respectively, that the coating layer has a hardness range of 20 to 180 Hv, and that the conforming layer has a hardness range of 5 to 20 Hv. Further, it is preferred that the coating layer has a thickness of 10 to 20 pm and that the conforming layer has a thickness of 2 to 10 μm. in addition, a metal layer of Ni etc. may be provided, as a bonding layer, between the bearing alloy layer and the coating layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a partial, sectional view of a multi-layer sliding material according one embodiment of the invention; and

[0015] FIG. 2 is a partial, sectional view of a multi-layer sliding material according to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] FIG. 1 shows the cross section of a multi-layer sliding material according to the first embodiment of the invention, which sliding material comprises a steel back metal layer 1, a bearing alloy layer 2 bonded onto the steel back metal layer 1, and a coating layer bonded onto the bearing alloy layer by an electroplat-ing technique. The coating layer 3 is made of an alloy consisting of 20 to 80 mass % Pb (lead), and the balance Cu (copper) and incidental impurities. In this coating layer 3, there may be added at least one not more than 10 mass % in total selected from the group consisting of In (indium), Sb (antimony), Sn (tin) and Ag (silver).

[0017] The bearing alloy layer 2 may be made of a Cu-based alloy or a Al-based alloy. As the Cu-based alloy, it is preferred to use a Cu-based alloy containing 5 to 30 mass % Pb and the balance Cu and incidental impurities. As the Al-based alloy, it is preferred to use an Al-based alloy containing not more than 20 mass % Sn and the balance Al (aluminum) and incidental impurities. In this case, it is preferred that the content of Pb or Sn (which is a soft metal) contained in the bearing alloy layer 2 (, that is, the Cu-based alloy or the Al-based alloy layer) is less than the content of Pb contained in the coating layer 3. The Cu-based alloy layer may be bonded onto the steel back metal layer 1 by sintering, and the Al-based alloy layer may be bonded onto the steel back metal layer by pressure-bonding after the Al-based alloy has been formed into a sheet by a continuous casting process.

[0018] FIG. 2 shows a partial cross section of a multi-layer sliding material according to another embodiment of the invention. The difference between ones shown in FIGS. 1 and 2 resides in a conforming layer 4 bonded onto the coating layer 3. The conforming layer 4 is made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu.

[0019] In order to confirm the characteristics of the multi-layer sliding material according to each of the embodiments, there were produced, by use of the multi-layer sliding materials of the embodiments, sliding bearing samples Nos. 1 to 14 shown in Table 1, and there were produced comparative sliding bearing samples Nos. 1 to 4 by use of comparative multi-layer sliding materials which samples are also shown in Table 1. In Table 1, the numerical value before each of the atomic symbols indicates the content (mass %) of the element.

	TABLE 1
				maximum	maximum	amount
				specific load	specific load	of
	bearing alloy layer	coating layer	conforming layer	without seizure	without fatigue	wear
No.	composition	Hv	composition	Hv	composition	Hv	(MPa)	(MPa)	(mm)
inventive products
1	90Cu—5Pb—5Sn	120	20Cu—80Pb	20			125	110	5
2	90Cu—5Pb—5Sn	120	30Cu—70Pb	50			120	115	4
3	90Cu—5Pb—5Sn	120	40Cu—60Pb	65			120	115	4
4	90Cu—5Pb—5Sn	120	50Cu—50Pb	90			120	120	3.5
5	90Cu—5Pb—5Sn	120	60Cu—40Pb	120			117.5	120	3
6	90Cu—5Pb—5Sn—0.5P	190	70Cu—30Pb	150			115	125	2.5
7	90Cu—5Pb—5Sn—0.5P	190	80Cu—20Pb	180			115	125	2
8	90Cu—5Pb—5Sn	120	50Cu—50Pb	90	88Pb—10Sn—2Cu	10	125	120	5
9	80Cu—17Pb—3Sn	90	30Cu—70Pb	50			125	115	4
10	80Cu—17Pb—3Sn	90	30Cu—70Pb	50	88Pb—10Sn—2Cu	10	130	115	5.5
11	90Al—4Sn—6Si	100	30Cu—70Pb	50			127.5	115	4
12	90Al—4Sn—6Si	100	30Cu—70Pb	50	88Pb—10Sn—2Cu	10	130	112.5	5.5
13	90Cu—5Pb—5Sn	120	45Cu—50Pb—5In	90			125	117.5	4
14	90Cu—5Pb—5Sn	120	45Cu—50Pb—5Ag	90			120	125	3
comparative products
1	90Cu—5Pb—5Sn	120			88Pb—10Sn—2Cu	10	120	80	13
2	90Al—4Sn—6Si	100			88Pb—10Sn—2Cu	10	120	65	12
3	90Cu—5Pb—5Sn	120	10Cu—90Pb	14			125	80	8
4	90Cu—5Pb—5Sn	120	90Cu—10Pb	240			80	90	2

[0020] In each of the products Nos. 1 to 10, 13 and 14 relating to the invention, the Cu-based alloy layer was bonded onto the steel back metal layer, and the coating layer was bonded onto the bearing alloy layer. Further, in each of the products Nos. 8 and 10, the conforming layer was bonded onto the coating layer. In each of the products Nos. 11 and 12 relating to the invention, the bearing alloy layer was made of the Al-based alloy, in each of which products Nos. 11 and 12 the bonding layer of Ni was provided between the bearing alloy layer and the coating layer. Further, in No.12, the conforming layer was bonded onto the coating layer.

[0021] In the comparative product No.1, the Cu-based alloy layer was bonded onto the steel back metal layer, onto which Cu-based alloy layer the conforming layer was bonded. In each of the comparative products Nos. 3 and 4, the Cu-based alloy layer was bonded onto the steel back metal layer, onto which Cu-based alloy layer the coating layer was bonded. In the comparative product No. 2, the Al-based alloy layer was bonded onto the steel back metal layer, onto which Al-based alloy layer the bonding layer was bonded, onto which bonding layer the conforming layer was bonded.

[0022] In each of the products Nos. 1 to 14 relating to the invention, the thickness of the coating layer was 15 μm. In each of the products Nos. 8, 10 and 12 relating to the invention, the thickness of the conforming layer was 5 μm. In each of the comparative products Nos. 1 to 4, the thickness of each of the coating layer and the conforming layer was 15 μm.

[0023] Regarding each of the products Nos. 1 to 14 relating to the invention and the comparative products Nos. 1 to 4 were performed a seizure test, a fatigue test and a wear test, the results thereof being shown in Table 1. The conditions of each of the seizure test, the fatigue test and the wear test are shown in Table 2.

TABLE 2
method of test	seizure test	fatigue test	wear test
seize of bearing	diameter	diameter	outer diameter 27.2
	53 mm ×	53 mm ×	mm × inner diameter
	width 13 mm	width 17 mm	22 oil groove 8 mm
rotation rate	3600 rpm	3250 rpm	speed: 2 m/s
lubricant	VG68	VG68	SAE#30
feed rate of	12.5 ml/min	oil pressure	oil bath
lubricant		0.49 Mpa
temperarure of	100° C.	100° C.	25° C.
fed lubricant
shaft material	S55C	S55C	S55C
other			specific load:	9 MPa
			time:	4 h

[0024] As apparent from the test results, each of the products Nos. 1 to 14 relating to the invention is superior in each of the fatigue resistance and the wear resistance in comparison with the comparative products Nos. 1 and 2 in each of which the conforming layer was bonded onto the conventional bearing alloy layer. In each of the products Nos. 1 to 7 relating to the invention and the comparative products Nos. 3 and 4, the anti-seizure property is deteriorated as the hardness of the coating layer increases, and the fatigue resistance increases as the hardness of the coating layer increases, however, the excessive increase in the hardness (as shown in the comparative product No. 4) causes the decrease in toughness with the result that the fatigue resistance is deteriorated.

[0025] In the product No. 13 relating to the invention in which In is added in the coating layer, the effect of In which is a soft metal is brought about regarding the anti-seizure property. In the product No. 14 relating to the invention in which Ag is added in the coating layer, the fatigue resistance is enhanced without deteriorating the anti-seizure property because Ag acts to strengthen the coating layer and because Ag itself is relatively good in anti-seizure property.

[0026] The present invention is not limited to the embodiments shown in the drawings, that is, the present invention is not limited to ones used to produce the bearings of engines, and the present invention can be modified variously within the scope of the claims.

Claims

1. A multi-layer sliding material, comprising a back metal layer, a bearing alloy layer bonded onto the back metal layer, and a coating layer bonded onto the bearing alloy layer, said coating layer being made of an alloy consisting of 20 to 80 mass % Pb, and the balance Cu and incidental impurities.

2. A multi-layer sliding material according to claim 1, said bearing alloy layer being made of a Cu-based alloy containing 5 to 30 mass % Pb.

3. A multi-layer sliding material according to claim 1, said bearing alloy layer being made of an Al-based alloy containing not more than 20 mass % Sn.

4. A multi-layer sliding material according to claim 1, further comprising a conforming layer containing not less than 80 mass % Pb which conforming layer is bonded onto the coating layer.

5. A multi-layer sliding material according to claim 2, further comprising a conforming layer containing not less than 80 mass % Pb which conforming layer is bonded onto the coating layer.

6. A multi-layer sliding material according to claim 3, further comprising a conforming layer containing not less than 80 mass % Pb which conforming layer is bonded onto the coating layer.

7. A multi-layer sliding material, comprising a back metal layer, a bearing alloy layer bonded onto the back metal layer, and a coating layer bonded onto the bearing alloy layer, said coating layer being made of an alloy consisting of 20 to 80 mass % Pb, at least one element not more than 10 mass % in total selected from the group consisting of In, Sb, Sn and Ag, and the balance Cu and incidental impurities.

8. A multi-layer sliding material according to claim 7, said bearing alloy layer being made of a Cu-based alloy containing 5 to 30 mass % Pb.

9. A multi-layer sliding material according to claim 7, said bearing alloy layer being made of an Al-based alloy containing not more than 20 mass % Sn.

10. A multi-layer sliding material according to claim 7, further comprising a conforming layer containing not less than 80 mass % Pb which conforming layer is bonded onto the coating layer.

11. A multi-layer sliding material according to claim 8, further comprising a conforming layer containing not less than 80 mass % Pb which conforming layer is bonded onto the coating layer.

12. A multi-layer sliding material according to claim 9, further comprising a conforming layer containing not less than 80 mass % Pb which conforming layer is bonded onto the coating layer.

13. A multi-layer sliding material according to claim 1, further comprising a conforming layer made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu which conforming layer is bonded onto he coating layer.

14. A multi-layer sliding material according to claim 2, further comprising a conforming layer made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu which conforming layer is bonded onto he coating layer.

15. A multi-layer sliding material according to claim 3, further comprising a conforming layer made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu which conforming layer is bonded onto he coating layer.

16. A multi-layer sliding material according to claim 7, further comprising a conforming layer made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu which conforming layer is bonded onto he coating layer.

17. A multi-layer sliding material according to claim 8, further comprising a conforming layer made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu which conforming layer is bonded onto he coating layer.

18. A multi-layer sliding material according to claim 9, further comprising a conforming layer made of an alloy consisting of not less than 80 mass % Pb, and at least one optional element not more than 20 mass % in total selected from the group consisting of Sn and Cu which conforming layer is bonded onto he coating layer.