Bearing element, camshaft bearing and piston engine

Abstract

The bearing element (1) for a camshaft bearing of a piston engine comprises an oil feeding hole (2) arranged in the upper half of the bearing element (1), an oil supply groove (3A, 3B) arranged on a bearing surface and extending from the oil feeding hole (2) towards the lower half of the bearing element (1), and an oil spreading groove (5) arranged in the lower half of the bearing element (1) and in fluid communication with the oil supply groove (3A, 3B), the width of the oil spreading groove (5) being at most 30 percent of the width of the oil supply groove (5).

Description

[0001] Bearing element, camshaft bearing and piston engine

[0002] Technical field of the invention

[0003] The present invention concerns a bearing element for a camshaft bearing of a piston engine, as defined in claim 1 . The invention also concerns a camshaft bearing for a piston engine and a piston engine.

[0004] Background of the invention

[0005] In large piston engines, such as ship and powerplant engines, the camshaft is typically supported by slide bearings. A typical camshaft bearing comprises a bearing shell having an inner circumferential surface forming a bearing surface. Lubrication oil is introduced onto the bearing surface to form an oil film between the bearing surface and camshaft. The lubrication oil is typically supplied from the engine block and introduced onto the bearing surface via an oil feeding hole that extends from the outer surface of the bearing shell to the inner surface.

[0006] Different kinds of camshaft bearings are known. In the simplest form of camshaft bearings, the bearing surface is a plain surface. Some camshaft bearings comprise a groove extending from the oil feeding hole partially over the bearing surface. Also bearings having a groove extending over the whole bearing surface in the circumferential direction are known, but they are usually not used in the highly loaded bearings next to the cams of the camshaft.

[0007] As the valve tappet rollers are spring-biased against the cams of the camshaft, the camshaft bearings are relatively highly loaded even when the rotation speed of the camshaft is low. The most loaded part of the bearing is the lower part. The lubrication of the camshaft bearings is least effective when the rotation speed of the camshaft is low. As a result, the camshaft bearings may suffer from insufficient lubrication during slow turning and start of the engine. In some applications, start-ups and slow turning may occur regularly, which can lead to significant wear of the camshaft bearings, if sufficient lubrication of the bearings is not ensured. Summary of the invention

[0008] An object of the invention is to provide an improved bearing element for a camshaft bearing of a piston engine. Other objects of the invention are to provide an improved camshaft bearing and an improved piston engine.

[0009] The bearing element according to the invention has an inner circumferential surface configured to form a bearing surface and an outer circumferential surface. The bearing element comprises, in a use position,

[0010] - at least one oil feeding hole arranged in the upper half of the bearing element and extending from the outer circumferential surface to the inner circumferential surface of the bearing element,

[0011] - at least one oil supply groove arranged on the bearing surface and extending from said at least one oil feeding hole towards the lower half of the bearing element, and

[0012] - an oil spreading groove arranged in the lower half of the bearing element and in fluid communication with said at least one oil supply groove, the longitudinal direction of the oil spreading groove differing from the axial direction of the bearing element and the width of the oil spreading groove being at most 30 percent of the width of the oil supply groove.

[0013] The camshaft bearing according to the invention comprises a bearing element defined above.

[0014] The piston engine according to the invention comprises a camshaft bearing defined above.

[0015] In the bearing element according to the invention, the lubrication oil is supplied onto the bearing surface through one or more oil feeding holes arranged in the upper part of the bearing. The most loaded part of the bearing is the lower part. When the rotation speed of the camshaft is high, the rotating motion of the camshaft effectively conveys lubrication oil to the lower part of the bearing element. However, during start-up of the engine and during slow turning of the camshaft, the lubrication of the lower part of the bearing is less effective. The oil supply groove ensures that a sufficient amount of lubrication oil is conveyed to the lower half of the bearing also during slow turning of the camshaft. The oil spreading groove in the lower half of the bearing element facilitates spreading of the lubrication oil below the camshaft. As the oil spreading groove is narrow compared to the oil supply groove, a sufficient oil film thickness can be maintained also during higher rotation speeds of the camshaft. The oil spreading groove further helps to convey dirt particles away from the bearing and may reduce problems caused by thermal expansion of the bearing element.

[0016] According to an embodiment of the invention, the bearing element comprises a first oil supply groove extending from one of said at least one oil feeding holes to a first circumferential direction, and a second oil supply groove extending from one of said at least one oil feeding holes to a second circumferential direction, each of said oil supply grooves being in fluid communication with the oil spreading groove. By providing the bearing element with two oil supply grooves, the same bearing element can be used in bearings for camshafts having different rotation directions. Also, the second oil supply groove can function as a discharge groove conveying excess lubrication oil away from the bearing.

[0017] According to an embodiment of the invention, the bearing element comprises at least one oil pocket that is formed by a recessed area arranged on the bearing surface between the oil spreading groove and one of said at least one oil supply groove and extending in the axial direction of the bearing element over at least 50 percent of the width of the bearing element. The oil pocket functions as an oil reserve for the lubrication oil supplied to the most loaded part of the bearing. The oil pocket also helps spreading the lubrication oil over the whole width of the bearing surface.

[0018] According to an embodiment of the invention, the bearing element comprises a first oil pocket arranged between the first oil supply groove and the oil spreading groove and a second oil pocket arranged between the second oil supply groove and the oil spreading groove. In case of a bearing element with two oil supply grooves, an oil pocket can be arranged at the lower end of each of the oil supply grooves.

[0019] According to an embodiment of the invention, each of said at least one oil pockets extends in the axial direction of the bearing element over at least 70 percent of the width of the bearing element. A greater width of the oil pocket improves spreading of the lubrication oil on the bearing surface. According to an embodiment of the invention, each of said at least one oil pockets extends in the circumferential direction of the bearing element over an angle of 10-30 degrees.

[0020] According to an embodiment of the invention, the width of the oil spreading groove is less than 20 percent, or less than 15 percent of the width of the oil supply groove. A narrower oil spreading groove is advantageous when the rotating speed of the camshaft is higher.

[0021] According to an embodiment of the invention, the width of each of said at least one oil supply grooves is 15-30 percent of the width of the bearing element. This ensures sufficient oil supply to the lower part of the bearing element.

[0022] According to an embodiment of the invention, the oil spreading groove extends over 60-120 degrees, or over 80-100 degrees, in the circumferential direction of the bearing element. The oil spreading groove thus extends over the most loaded area of the bearing element.

[0023] According to an embodiment of the invention, each of said at least one oil feeding holes is located in an area extending to an angular distance of 45 degrees from the topmost point of the bearing element. The oil feeding hole is thus located in the uppermost fourth of the bearing element.

[0024] According to an embodiment of the invention, the oil spreading groove runs in a direction differing from the circumferential direction of the bearing element. A longitudinal direction differing from the circumferential direction of the bearing element facilitates maintaining a sufficient lubrication oil film thickness over the whole width of the bearing element.

[0025] According to an embodiment of the invention, the depth of the oil spreading groove is less than 1.0 mm. A sufficiently shallow oil spreading groove helps ensuring that sufficient lubrication oil film thickness is maintained also when the rotation speed of the camshaft is higher.

[0026] Brief description of the drawings

[0027] Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which Fig. 1 shows a bearing element according to an embodiment of the invention, and

[0028] Fig. 2 shows a cross-sectional view of the bearing element of figure 1 .

[0029] Detailed description of embodiments of the invention

[0030] Figure 1 shows a bearing element 1 according to an embodiment of the invention. The bearing element 1 can be used in a camshaft bearing of a large piston engine. The expression “large piston engine” refers here to an engine having a cylinder diameter of at least 150 mm. The engine could be, for instance, a main or an auxiliary engine of a ship or a powerplant engine. The bearing element 1 is configured to form part of a slide bearing. The bearing is a camshaft bearing that is configured to support a camshaft of the engine against an engine block.

[0031] The bearing element 1 is a bushing and extends thus over a full circle. The bearing element 1 has an inner circumferential surface and an outer circumferential surface. The inner circumferential surface is configured to function as a bearing surface. The inner circumferential surface is thus configured to support the camshaft that can rotate relative to the bearing element 1 .

[0032] The bearing element 1 comprises an oil feeding hole 2 extending from the outer circumferential surface to the inner surface. Via the oil feeding hole 2, lubrication oil can be fed onto the inner surface of the bearing element 1 . Lubrication oil can be supplied via channels formed within the engine block to the bearing element 1 and supplied via the oil feeding hole 2 onto the bearing surface. An oil film is thus formed between the bearing surface and the camshaft rotating against the bearing element 1 such that direct contact between the surfaces of the bearing element 1 and the camshaft is prevented.

[0033] In the embodiment of the figures, the bearing element 1 comprises a single oil feeding hole 2. The oil feeding hole 2 is arranged in the upper half of the bearing element 1 . The expression “upper half’ refers here to a portion that is above an imaginary horizontal plane dividing the bearing element 1 into two halves of equal size when the bearing element 1 is in use. The lower half of the bearing element 1 is the portion below said imaginary plane. Also other expressions used in this application and referring to directions mean directions in a use position of the bearing element 1 . In the embodiment of the figures, the center axis of the oil feeding hole 2 is positioned at an angular distance of 10 degrees from the topmost point of the bearing element 1 . However, the center axis of the oil feeding hole 2 could also be aligned with the topmost point of the bearing element 1 . Preferably, the oil feeding hole 2 is located within an area extending to an angular distance of 45 degrees from the topmost point of the bearing element 1 .

[0034] The bearing element 1 further comprises an oil supply groove 3A, 3B arranged on the bearing surface and extending from the oil feeding hole 2 towards the lower half of the bearing element 1 .

[0035] In the embodiment of the figures, the bearing element 1 comprises a first oil supply groove 3A and a second oil supply groove 3B. The first oil supply groove 3A extends from the oil feeding hole 2 to a first circumferential direction, which is in figure 1 counterclockwise. The second oil supply groove 3B extends from the oil feeding hole 2 to a second circumferential direction, which is in figure 1 clockwise. The oil supply grooves 3A, 3B are configured to convey lubrication oil from the oil feeding hole 2 to the lower part of the bearing element 1 . The width of the oil supply groove 3A, 3B can be 15-30 percent of the width of the bearing element 1 . The depth of the oil supply groove 3A, 3B could be, for instance, in the range of 1 .0 to 4.0 mm in the middle of the oil supply groove 3A, 3B seen in the axial direction of the bearing element 1. In the embodiment of the figures, the first and second oil supply grooves 3A, 3B are otherwise identical, but the second oil supply groove 3B is longer, as the oil feeding hole 2 is not arranged in the topmost point of the bearing element 1. The first and second oil supply grooves 3A, 3B are aligned with a middle plane of the bearing element 1 .

[0036] The bearing element 1 further comprises an oil spreading groove 5 arranged in the lower half of the bearing element 1 and in fluid communication with the oil supply grooves 3A, 3B. The longitudinal direction of the oil spreading groove 5 differs from the axial direction of the bearing element 1. The oil spreading groove 5 is thus configured to convey lubrication oil in the circumferential direction of the bearing element 1. In the embodiment of the figures, the oil spreading groove 5 is not parallel to the circumferential direction of the bearing element 1 , but the oil spreading groove 5 runs in a direction that differs from the circumferential direction of the bearing element 1 . However, the oil spreading groove 5 could also be parallel to the circumferential direction of the bearing element 1. For instance, the oil spreading groove 5 could be aligned with the middle plane of the bearing element 1 .

[0037] The width of the oil spreading groove 5 is at most 30 percent of the width of the oil supply groove 3A, 3B. The oil spreading groove 5 can be even narrower, for example less than 20 percent or less than 15 percent of the width of the oil supply groove 3A, 3B. The oil spreading groove 5 can be less deep than the oil supply groove 3A, 3B. The depth of the oil spreading groove 5 can be configured to be less than 1 .0 mm. The oil spreading groove 5 can be configured to be even less deep, for example less than 0.5 mm deep.

[0038] In the embodiment of the figures, the bearing element 1 comprises a first oil pocket 4A and a second oil pocket 4B. Each oil pocket 4A, 4B is formed by a recessed area that is arranged on the bearing surface between the oil spreading groove 5 and one of the oil supply grooves 3A, 3B. The first oil pocket 4A is between the first oil supply groove 3A and the oil spreading groove 5 and the second oil pocket 4B is between the second oil supply groove 3B and the oil spreading groove 5. Each oil pocket 4A, 4B extends in the axial direction of the bearing element 1 over at least 50 percent of the width of the bearing element 1 , preferably over at least 70 percent of the width of the bearing element 1. In the circumferential direction of the bearing element 1 , each oil pocket 4A, 4B can be formed to extend over an angle of 10-30 degrees. One end of the oil spreading groove 5 is connected to the first oil pocket 4A and the other end of the oil spreading groove 5 is connected to the second oil pocket 4B. The first oil supply groove 3A extends from the oil feeding hole 2 to the first oil pocket 4A and the second oil supply groove 3B extends from the oil feeding hole 2 to the second oil pocket 4B.

[0039] In the embodiment of the figures, the oil spreading groove 5 is connected to the first oil pocket 4A at a position that is located from the middle plane of the bearing element 1 towards a first edge of the bearing element 1 , and to the second oil pocket 4B at a position that is located from the middle plane of the bearing element 1 towards a second edge of the bearing element 1 . The longitudinal direction of the oil spreading groove 5 thus deviates from the circumferential direction of the bearing element 1 .

[0040] Each of the first oil pocket 4A and the second oil pocket 4B can be positioned such that the center axis of the oil pocket 4A, 4B is located at an angular distance of 40-70 degrees from the lowermost point of the bearing element 1 . Preferably, the center axis of the oil pocket 4A, 4B is located at an angular distance of 45-65 degrees from the lowermost point of the bearing element 1 . In the embodiment of the figures, the first oil pocket 4A and the second oil pocket 4B are arranged symmetrically about a plane that is parallel to the axial direction of the bearing element 1 and vertical in the use position of the bearing element 1 .

[0041] The oil spreading groove 5 can extend over 60-120 degrees in the circumferential direction of the bearing element 1. Preferably, the oil spreading groove 5 extends over 80-100 degrees in the circumferential direction of the bearing element 1 . In the embodiment of the figures, the oil spreading groove 5 is arranged to extend to the same angular distance from the lowermost point of the bearing element 1 in each circumferential direction.

[0042] The oil supply groove 3A, 3B extending from the oil feeding hole 2 towards the lower half of the bearing element 1 in the rotation direction of the camshaft ensures that a sufficient amount of lubrication oil is supplied to the most loaded part of the bearing. The oil supply groove 3A, 3B reduces the thickness of the oil film, but as the oil supply groove 3A, 3B is located in a less loaded part of the bearing, the oil film thickness can be maintained at a sufficient level.

[0043] The oil pocket 4A, 4B receiving the lubrication oil from the oil supply groove 3A, 3B functions as an oil reserve, from which the lubrication oil is supplied to the most loaded part of the bearing. The oil pocket 4A, 4B also spreads the lubrication oil onto the whole width of the bearing surface. However, in certain applications also a bearing element 1 without the oil pockets 4A, 4B could be used.

[0044] The oil spreading groove 5 improves the functioning of the bearing 1 when the rotation speed of the camshaft is low. It supplies lubrication oil to the most loaded part of the bearing and helps avoiding oil starvation. When the rotation speed of the camshaft is higher, the oil spreading groove 5 decreases the oil film thickness. However, as the cross-sectional area of the oil spreading groove 5 is much smaller than that of the oil supply groove 3A, 3B, the effect is minimized. The bearing element 1 according to the invention thus provides reliable operation both at low and high rotation speeds of the camshaft. The bearing element 1 could comprise two or more oil feeding holes 2. In case of two oil feeding holes 2, the first oil supply groove 3A could be connected to a first oil feeding hole and the second oil supply groove 3B could be connected to a second oil feeding hole. Although the figures show an embodiment com- prising two oil supply grooves 3A, 3B, the bearing element 1 could be provided with a single oil supply groove. In that case, there could be a single oil pocket between the oil spreading groove and the lower end of the oil supply groove. The oil supply groove and the oil spreading groove should be positioned such that the oil supply groove is located in the rotation direction of the camshaft before the oil spreading groove.

Claims

Claims:1 . A bearing element (1 ) for a camshaft bearing of a piston engine, the bearing element (1 ) having an inner circumferential surface configured to form a bearing surface and an outer circumferential surface, the bearing element (1 ) comprising, in a use position,- at least one oil feeding hole (2) arranged in the upper half of the bearing element (1 ) and extending from the outer circumferential surface to the inner circumferential surface of the bearing element (1 ),- at least one oil supply groove (3A, 3B) arranged on the bearing surface and extending from said at least one oil feeding hole (2) towards the lower half of the bearing element (1 ), and- an oil spreading groove (5) arranged in the lower half of the bearing element (1 ) and in fluid communication with said at least one oil supply groove (3A, 3B), the longitudinal direction of the oil spreading groove (5) differing from the axial direction of the bearing element (1 ) and the width of the oil spreading groove (5) being at most 30 percent of the width of the oil supply groove (3A, 3B).

2. A bearing element (1 ) according to claim 1 , wherein the bearing element (1 ) comprises a first oil supply groove (3A) extending from one of said at least one oil feeding holes (2) to a first circumferential direction, and a second oil supply groove (3B) extending from one of said at least one oil feeding holes (2) to a second circumferential direction, each of said oil supply grooves (3A, 3B) being in fluid communication with the oil spreading groove (5).

3. A bearing element (1 ) according to claim 1 or 2, wherein the bearing element (1 ) comprises at least one oil pocket (4A, 4B) that is formed by a recessed area arranged on the bearing surface between the oil spreading groove (5) and one of said at least one oil supply grooves (3A, 3B) and extending in the axial direction of the bearing element (1 ) over at least 50 percent of the width of the bearing element (1 ).

4. A bearing element (1 ) according to claims 2 and 3, wherein the bearing element (1 ) comprises a first oil pocket (4A) arranged between the first oil supply groove (3A) and the oil spreading groove (5), and a second oilpocket (4B) arranged between the second oil supply groove (3B) and the oil spreading groove (5).

5. A bearing element (1 ) according to claim 3 or 4, wherein each of said at least one oil pockets (4A, 4B) extends in the axial direction of the bearing element (1 ) over at least 70 percent of the width of the bearing element (1 )-6. A bearing element (1 ) according to any of claims 3 to 5, wherein each of said at least one oil pockets (4A, 4B) extends in the circumferential direction of the bearing element (1 ) over an angle of 10-30 degrees.

7. A bearing element (1 ) according to any of the preceding claims, wherein the width of the oil spreading groove (5) is less than 20 percent of the width of the oil supply groove (3A, 3B).

8. A bearing element (1 ) according to claim 7, wherein the width of the oil spreading groove (5) is less than 15 percent of the width of the oil supply groove (3A, 3B).

9. A bearing element (1 ) according to any of the preceding claims, wherein the width of each of said at least one oil supply grooves (3A, 3B) is 15- 30 percent of the width of the bearing element (1 ).

10. A bearing element (1 ) according to any of the preceding claims, wherein the oil spreading groove (5) extends over 60-120 degrees in the circumferential direction of the bearing element (1 ).

11. A bearing element (1 ) according to claim 10, wherein the oil spreading groove (5) extends over 80-100 degrees in the circumferential direction of the bearing element (1 ).

12. A bearing element (1 ) according to any of the preceding claims, wherein each of said at least one oil feeding holes (2) is located in an area extending to an angular distance of 45 degrees from the topmost point of the bearing element (1 ).

13. A bearing element (1 ) according to any of the preceding claims, wherein the oil spreading groove (5) runs in a direction differing from the circumferential direction of the bearing element (1 ).

14. A bearing element (1 ) according to any of the preceding claims, wherein the depth of the oil spreading groove (5) is less than 1 .0 mm.

15. A camshaft bearing of a piston engine, wherein the bearing comprises a bearing element (1 ) according to any of the preceding claims.

16. A piston engine comprising a camshaft bearing according to claim 15.

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