GB2435911A

GB2435911A - A plain bearing

Info

Publication number: GB2435911A
Application number: GB0704109A
Authority: GB
Inventors: Isei Naka; Takuya Tanaka
Original assignee: Daido Metal Co Ltd
Current assignee: Daido Metal Co Ltd
Priority date: 2006-03-08
Filing date: 2007-03-02
Publication date: 2007-09-12
Anticipated expiration: 2027-03-02
Also published as: GB0704109D0; GB2435911B; JP2007239866A

Abstract

An object of the present invention is to improve not only the embeddability of plain bearings but the antiseizure properties of the same. In the present invention, a plain bearing comprises a coating layer 6 provided on the surface of a bearing alloy layer 2 that constitutes the base material. The coating layer 6 includes a composite region 5 where a resin region 3 and a soft metal region 4 are present together. The soft metal region 4 is a region made up mainly of a soft metal and may be softer than the resin region 3, and therefore has excellent embeddability. Since soft metal region 4 and resin region 3 are present together on the sliding surface of the coating layer 6, the embeddability can be improved, compared with plain bearings whose coating layer includes a resin region 3 alone; thus, the antiseizure properties can also be improved. The soft metal may be tin, lead, bismuth, indium, silver, copper or aluminium while the resin is preferably polyamideimide, polyimide, epoxy, phenol, polybenzoimidazole, polyphenylene sulphide, polyamide or polyether ether ketone. The resin may also contain a solid lubricant.

Description

Background of the Invention

The present invention relates to a plain bearing having a coating layer provided on the surface of its base material.

As plain bearings for automotive engines, for example, there are proposed plain bearings each of which is produced by joining a copper or aluminum bearing alloy to a back metal made of a steel plate and providing the surface of the bearing alloy with a resin coating layer made up mainly of a synthetic resin, so as to improve its initial conformability, antiseizure properties and wear resistance (see, for example, JP-A-7-247493 and JP-A-2002-242 933) During the use of a plain bearing, however, foreign matters such as iron powder can sometimes enter between the sliding surface of the plain bearing and its counter member, thereby causing seizure. In bearings having a conventional structure, though they have a resin coating layer provided on their sliding surface, the resin coating layer presents the problem of being poor in embeddability, and thus, they have the problem of their antiseizure properties' deteriorating.

The present invention has been made in the light of the above circumstances. Accordingly, an object of the present invention is to provide a plain bearing which has improved embeddability so as to attain improved antiseizure properties.

Summary of the Invention

To achieve the above object, the present invention provides a plain bearing having a base material and a coating layer, which has a sliding surface, provided on the surface of the base material, characterized in that the coating layer includes a composite region where a resin region(s) and a soft metal region(s) are present together on the side of the sliding surface.

The resin region produces initial conformability, antiseizure properties and wear resistance effects. The soft metal region is a region which is made up mainly of a soft metal and is softer than the resin region, and therefore, excelling in embeddability. And besides, the soft metal region is wider than the region a soft metal particle alone occupies, whereby it is more likely to have foreign matters embedded in it. The resin region hardly produces foreign-matter embedding effect even if it has soft metal particles dispersed on its surface. And in the composite region of the coating layer, since the soft metal region(s) and the resin region(s) are present together on the slide surface, its embeddability can be improved, compared with the coating layer where the resin region alone is present; as a result, its antiseizure properties can also be improved. And due to the presence of the resin region(s), the effect of the resin region(s) can also be achieved, unlike the coating layer where the soft metal region alone is present.

As a base material for the plain bearing, a known material such as copper bearing alloy, aluminum bearing alloy, steel or stainless steel can be used and a suitable one can be selected depending on the objective.

The materials that can form the soft metal region include Sn, Pb, Bi, In, Ag, Cu, Al and an alloy thereof. Preferably one or more selected from the above materials are used.

Preferably a solid lubricant is added to the resin region. Adding a solid lubricant makes it possible to improve the wear resistance and antiseizure properties of the plain bearing, because a solid lubricant has the function of improving lubrication characteristic. Solid lubricants which can be added to the resin region include MoS2, graphite (hereinafter referred to as Gr), PTFE (polytetrafluoroethylene), (CF) (carbon fluoric) and BN. Preferably one or more selected from the above lubricants are used.

As a resin for the resin region, a thermosetting resin, a thermoplastic resin or the mixture thereof can be used. The thermosetting resins which can be used for the resin region include, for example, PAl (polyamideimide), P1 (polyirnide), EP (epoxy) and PF (phenol) resins. The thermoplastic resins include, for example, PBI (polybenzoimidazole), EPS (polyphenylene sulfide), PA (polyamide) and PEEK (polyether ether ketone) resins.

The surface area the soft metal region occupies is preferably 10 to 90% of the entire surface of the composite region. If the surface area the soft metal region occupies is 10% or higher, the foreign-matter embedding effect, which is the effect peculiar to the soft metal region, is easy to achieve. If the surface area the soft metal region occupies is higher than 90%, there is a fear that the wear resistance of the plain bearing tends to deteriorate, whereas if it is 90% or lower, the required wear resistance can be reliably achieved. The surface area the soft metal region occupies is more preferably 20 to 80% of the entire surface of the composite region.

Preferably at least on the surface of the composite region, the bearing includes a soft metal layer made up of one or more selected from the group consisting of Sn, Pb, Bi, In, Ag, Cu, Al and an alloy thereof. The thickness of this soft metal layer can be such that it allows the soft metal layer to wear away during the initial running (preferably 5 pm or less) so that the resin and the soft metal are immediately exposed. Thus, such thickness prevents the effect of the resin region from being retarded. It is preferable from the manufacturing viewpoint that this soft metal layer is made up of the same pure metal(s) or alloy(s) as the one(s) used for the soft metal region of the composite region.

Brief Description of the Drawings

Fig. 1(a) is a schematic cross-sectional view showing one example of the present invention and Fig. 1(b) is a schematic plan view showing the same; and Figs. 2(a) to 2(f) are plan views each showing the coating layer, in the unfolded state, of a half bearing to which the present invention is applied.

In the drawings, numerical reference 1 denotes a back metal layer (base material), 2 a bearing alloy layer (base material), 3 a resin region, 4 a soft metal region, 5 a composite region, 6, 7, 9, 11, 13, 15 and 18 denote coating layers, respectively, and 8, 10, 12, 14, 16 and 20 composite regions, respectively.

Detailed Description of the Invention

In the following, the present invention will be described in detail based on several examples and comparative examples. First, specimens were prepared as follows. An aluminum alloy plate, which was to be a bearing alloy layer, was placed on a steel plate, which was to be a back metal layer, and the aluminum alloy plate and the steel plate were put between rollers and joined to give a bimetal. The total plate thickness of the resultant bimetal was 1.5 mm. The bimetal thus produced was used to prepare specimens. Although an aluminum alloy was used as the bearing alloy layer as described above, a copper alloy can also be used as a bearing alloy layer. In Table 1, Al in the column of bearing alloy layer denotes an aluminum alloy.

The specimens thus prepared were subjected to pretreatment of blasting and degreasing and a coating layer was provided on the surface of the bearing alloy layer of each specimen. The coating layer was provided as follows. For the specimens used in Examples, on the surface of the bearing alloy layer on the sliding surface, for example, a seal having a number of perforations was stuck and the resin fluid described below was applied through the seal by spray coating.

For the coating resin fluid, PAl as a therrnosetting resin and PBI as a thermoplastic resin were selected as base resins. And solid lubricants were mixed into the coating resin fluid. As the solid lubricants, Mo32, Gr and PTFE were selected. Table 1 shows the mixing ratio of the base resins and the solid lubricants used. The coating thickness was 5 to 25 tm. The specimens each having a coating layer thus provided were dried at 100 C, then the seal was removed, and the specimens were cured at 180 to 400 C. Thus, a number of independent resin regions were formed on the surface of the bearing alloy layer.

The seal described above was for forming, on the surface of the bearing alloy layer, regions where resin fluid was coated and regions where resin fluid was not coated; therefore, a number of separated seals may also be stuck on the surface of the bearing alloy layer.

Then, on the portion of the bearing alloy surface other than the resin regions, soft metals described below were plated. As the soft metals, an Sn alloy and a Pb alloy were selected. The thickness of the plating was 5 to 25 jim, which was the same as the thickness of the resin regions. Thus, soft metal regions were formed on the surface of the bearing alloy layer so that they filled in the spaces among resin regions. As a result, on the surface of the bearing alloy layer was formed a coating layer having a composite region, where a number of independent resin regions and soft metal regions arranged so that they filled in the space among the resin regions were present together, on its sliding surface. In this case, the entire coating layer was made up of the composite region. Table 1 shows the materials used as soft metals, the occupancy of the soft metal region in the composite region on the sliding surface, and the thickness of the coating layer (film thickness) Fig. 1 schematically shows one example of the bearings of the present invention thus produced. In Figs. 1(a) and 1(b), reference numeral 1 denotes a back metal layer, numeral 2 a bearing alloy layer (base material), numeral 3 a resin region, numeral 4 a soft metal region, numeral 5 a composite region where resin region 3 and soft metal region 4 are present together, and numeral 6 a coating layer having composite region 5. Although the shape of the plan view of each independent resin region 3 is circle in Fig. 1(b), the shape is not limited to a circle, but may be a quadrangle, triangle or ellipse. The shape having a long side in a direction at a prescribed angle to the sliding direction is preferable. The prescribed angle is particularly preferably 45 to 85 . It is also possible to replace resin region 3 with soft metal region 4 so that soft metal region 4 is present independently.

For Comparative Examples, resin fluid was applied to the entire surface of the bearing alloy layer of each specimen by spray coating, and cured at to 400 C. Thus, a resin coating layer was provided.

Seizure test and wear test were conducted for the specimens obtained in Examples and Comparative Examples. The seizure test was conducted under the test conditions shown in Table 2. In this case, foreign particles were added to the oil to be supplied.

The foreign particles corresponded to those of second type specified in JIS Z 8901 and the particle median diameter was in the range of 27 to 31 plm. The specific load was upped by 1 MPa for every 10 minutes, and when the temperature of the bearing back reached 180 C or higher, seizure was judged to occur. The results are shown in Table 1. The wear test was conducted under the conditions shown in Table 3 and the amount of wear was determined. The results are also shown in Table 1.

Table 1

______________ Bearing composition ____________ Test results Coating layer Film P.inount Seizure Bearing Resin region(s) (vol%) Soft metal region(s) thickness of wear load alloy layer Hase -esin Solid_lubricant Material Occupancy (MPa) _____________ _____________ PAl PBI M0S2 Or PTFE Sn Pb (%) (ln) (j.an) __________ 1 Al ________ 60 40 ______ ______ 0 ______ 10 5 1.6 12 2 Al _______ 60 40 ______ ______ 0 ______ 40 15 2.5 17 3 Al _______ 50 50 ______ ______ ______ 0 60 5 3.6 15 4 Al ________ 40 60 ______ 0 ______ 40 15 3.5 16 Al 40 20 40 ______ ______ 0 ______ 10 5 5.4 -12 6 Al 60 ______ 40 ______ ______ 0 ______ 20 15 6.8 16 7 Al 60 ______ 40 ______ ______ 0 ______ 40 15 6.9 19 Example 8 Al 60 ______ 40 ______ ______ 0 ______ 60 15 7.1 18 9 Al 60 ______ 40 ______ ______ 0 ______ 80 15 7.2 15 Al 60 ______ 40 ______ ______ ______ 0 40 25 6.6 19 ii Al 60 ______ 40 ______ ______ 0 ______ 90 15 10.8 12 12 Al 60 ______ 25 15 ______ ______ 0 80 15 10.1 15 13 Al 60 ______ 25 ______ 15 0 ______ 40 15 7.6 18 14 Al 40 ______ 60 ______ ______ 0 ______ 40 15 7.8 18 ____________ 15 Al 100 ______ ______ ______ ______ ______ 0 80 15 8.9 14 1 Al ________ 60 40 ---15 3.5 8 Comparative -________ _______ ______ ______ ______ ______ ______ ____________ 2 Al 40 _______ 60 ---15 8.3 9 Example -____________ _______ ______ ______ ______ ______ ______ ______ ___________ ___________ __________ _____________ 3 Al 60 _______ 40 ---15 7.5 9 -11 -

Table 2

Seizure test conditions Item _____ Test conditions Unit Outside diameter: 4,27.2 x mm Specimen size Inside diameter: 4,22.0 __________ lUp by MPa for every 10 Specific load MPa _______ __________ mins __________ _________ Velocity -2 rn/sec Lubricant SAE#30 -Oil temperature 60 00 Oil supply 20 cc/mm Shaft material S55C Quenching -Hardness -500-600 HvlO Roughness 1 pm or less Rmax Second type specified in -Foreign particles Z 8901 ___________ Foreign particle 27-31 pm -median diameter Amount of foreign 2 mg/cc particles_added ____________________________

Table 3

Abrasion test conditions Item Test conditions Unit Outside diameter: 4,27.2 x mm Specimen size Inside diameter: 4,22.0 __________ Specific load 5 MPa Velocity 0.01 rn/sec Lubricant SAE#30 -Oil temperature 60 C Hardness 500-600 HvlO Roughness -1 pm or less Rmax Shaft material S55C Quenching -Test duration 4 Hrs The test results shown in Table 1 indicate the following. First, in Comparative Examples 1 to 3 in which the respective coating layers did not have soft metal regions, the seizure load is 9 MPa or lower.

In contrast, in Examples 1 to 15 in which the respective coating layers had soft metal regions, the seizure load is 12 MPa or higher. This shows that the -12 -bearings of Examples 1 to 15 were superior to those of Comparative Examples 1 to 3 in antiseizure properties.

Where the coating layer is made up of a resin region alone, like the cases of Comparative Examples 1. to 3, when foreign matters enter between the bearing and its counter member, the foreign matters are difficult to embed in the coating layer. This possibly results in decrease in the seizure load. On the other hand, where the coating layer includes a soft metal region, like the cases of Examples 1 to 15, the foreign matters becomes easy to embed in the coating layer because of the soft metal region. This possibly results in increase in seizure load. In both cases, foreign matters are broken during sliding to 5 jim or smaller in size.

Examples 1 to 15 will be studied in more detail. En examples 2 to 4, 6 to 10 and 12 to 15 where the occupancy of the soft metal region is 20 to 80%, the seizure load is 14 MPa or higher, which is higher than that of Examples 1, 5 and 11. The ratio of the soft metal region to the coating layer possibly allows a very high foreign-matter embedding effect to be produced while keeping good wear resistance, thereby increasing the seizure load. The more the occupancy of the soft metal region increases, the more the abrasion wear tends to increase. Accordingly, the occupancy of the soft metal region is preferably 20 to 80%, taking into account the seizure load and abrasion wear, though -13 -a good foreign-matter embedding effect can be achieved even when the occupancy is 10 to 90%.

Preferably, the film thickness of the coating layer is 5 pm or more. And more preferably, the film thickness is 10 pm or more. Preferably, the maximum film thickness is around 40 tm. The maximum film thickness is more preferably 25 pm or less, taking into account the clearance or the like during wearing.

Accordingly, the film thickness of the coating layer is more preferably 10 to 25 pm, taking into account practical applications.

When the present invention is applied to a sliding bearing half, the coating layer can be formed as shown in Figs. 2(a) to 2(f). Figs. 2(a) to 2(f) are plan views showing the respective coating layers, in the unfolded state, each provided on the inside face of a sliding bearing half.

Of these coating layers, coating layer 7 of Fig. 2(a) is provided on almost the entire inside circumferential face of the bearing and is made up of: dotted resin regions 3 arranged regularly in the axial direction (in the direction shown by arrow A) and in the circumferential direction (in the direction shown by arrow B); and soft metal region 4 surrounding the dotted resin regions 3. In this case, composite region 8 where resin regions 3 and soft metal region 4 are present together constitutes almost the entire coating layer 7.

-14 -Coating layer 9 of Fig. 2(b) is also provided on almost the entire inside circumferential face of the bearing and is made up of: dotted resin regions 3 arranged diagonally to the axial direction and to the circumferential direction; and soft metal region 4 surrounding the dotted resin regions 3. In this case, too, composite region 10 where resin regions 3 and soft metal region 4 are present together constitutes almost the entire coating layer 9.

Coating layer 11 of Fig. 2(c) is also provided on almost the entire inside circumferential face of the bearing. And in the vicinity of mid section of the coating layer in the circumferential direction, on which most of load is imposed, is formed composite region 12 where resin regions 3 and soft metal region 4 are present together, arid the vicinity of both end portions of the coating layer in the circumferential direction is made up of soft metal region 4 alone.

In coating layer 13 of Fig. 2(d), like coating layer 11 of Fig. 2(c), in the vicinity of mid section of the coating layer in the circumferential direction, on which most of load is imposed, is formed composite region 14 where resin regions 3 and soft metal regions 4 are present together, and the vicinity of both end portions of the coating layer in the circumferential direction is made up of soft metal region 4 alone. In this case, resin regions 3 and soft -15 -metal regions 4 in composite region 14 each extend linearly in the axial direction and are arranged alternately in the circumferential direction.

In coating layer 15 of Fig. 2(e), like coating layer 13 of Fig. 2(d), on in the vicinity of the mid section of the coating layer in the circumferential direction, on which most of load is imposed, is formed composite region 16 where resin regions 3 and soft metal regions 4 are present together, and the vicinity of both end portions of the coating layer in the circumferential direction is made up of soft metal region 4 alone. In this case, resin regions 3 and soft metal regions 4 in composite region 16 each extend in the circumferential direction and are arranged alternately in the axial direction.

Coating layer 18 of Fig. 2(f) is also provided on almost the entire inside circumferential face of the bearing. And almost the entire coating layer 18 is made up of composite region 20 where resin regions 3 and soft metal regions 4 are present together. In this case, resin regions 3 and soft metal regions 4 each extend linearly at a prescribed angle (for example, 60 ) to the circumferential direction and are arranged alternately in the direction perpendicular to the above direction.

In Figs. 2(a) to 2(f), resin regions 3 and soft metal region(s) 4 may be arranged inversely.

The present invention is not limited to -16 -Examples described above, but may be modified or extended as follows.

As a method of forming the resin regions, not only spray coating, but pad printing, roll coating or screen printing can be employed. As a method of forming the soft metal region(s), not only plating, but rrietallizing, cold spraying or sputtering can be employed.

The coating layer may be formed in such a manner as to first form a soft metal region(s) and then form a resin region(s).

Claims

-17 -CLAIMS: 1. A plain bearing having a base material and a coating

layer, which has a sliding surface, provided on the surface of the base material, characterized in that the coating layer comprises a composite region where a resin region and a soft metal region are present together on the side of the sliding surface.

2. The plain bearing according to claim 1, characterized in that the resin region contains a solid lubricant.

3. The plain bearing according to claim 1 or 2, characterized in that the soft metal region comprises one or more metals selected from Sn, Pb, Bi, In, Ag, Cu, Al and an alloy thereof.

4. The plain bearing according to any one of claims 1 to 3, characterized in that the resin region comprises one or more resins selected from PAl, P1, EP, PF, PBI, PPS, PA and PEEK resins.

5. The plain bearing according to claim 2, characterized in that he solid lubricant is one or more solid lubricants selected from M0S2, graphite, PTFE, CF4 and BW.

6. The plain bearing according to any one of claims 1 to 5, characterized in that the surface area occupied by the soft metal region occupies is 10 to 90% of the total surface area of the composite region.

7. The plain bearing according to any one of claims 1 to 6, characterized in that the plain bearing -18 -has a soft metal layer comprising one or more soft metals selected from Sn, Pb, Bi, In, Ag, Cu, Al and an alloy thereof at least on the surface of the composite region.

8. A plain bearing substantially as hereinbefore described with reference to and, as show-n in Figure 1(a) and Figure 1(b).

9. A plain bearing comprising a coating layer substantially as hereinbefore described with reference to and as shown in any of Figures 2A to 2F.