EP3411588B1

EP3411588B1 - Bearing arrangement

Info

Publication number: EP3411588B1
Application number: EP16705557.3A
Authority: EP
Inventors: Franco CAVRESSI; Hannu Nurmi; Jaakko ISTOLAHTI; Janne LEPPÄKANGAS
Original assignee: Wartsila Finland Oy
Current assignee: Wartsila Finland Oy
Priority date: 2016-02-02
Filing date: 2016-02-02
Publication date: 2019-11-27
Anticipated expiration: 2036-02-02
Also published as: CN108779751A; KR20180104151A; EP3411588A1; WO2017134332A1; KR102097882B1; CN108779751B

Description

Technical field of the invention

The present invention relates to a bearing arrangement for a common rail fuel injection pump of a piston engine in accordance with the preamble of claim 1.

Background of the invention

A typical high-pressure pump of a common rail fuel injection system of a large piston engine, such as a ship or a power plant engine comprises one or more reciprocating plungers, which are configured to pressurize fuel in a fluid chamber. The plungers are moved by cams of a camshaft. The camshaft is supported by lubricated plain bearings. A bearing of the high-pressure pump comprises a housing and a bearing element that is arranged within the housing and comprises a sliding surface against which a journal of the camshaft rotates. In a prior art solution, lubricating oil is supplied onto the sliding surface through an oil port, which is arranged in an upper part of the bearing element. The oil port can be connected to another oil port via a groove, which is arranged on the sliding surface of the bearing element. Highest bearing load is experienced in a lower part of the bearing. Due to the location of the oil ports, renewing of the lubricating oil film in the most loaded area of the bearing is not effective, which increases the risk of seizure of the bearing.
DE 10 2007 055782 A1 shows a fuel injection pump suitable for use in a common rail injection system of a piston engine, the pump comprising a bearing arrangement configured to carry radial forces.

Summary of the invention

An object of the present invention is to provide an improved bearing arrangement for a common rail fuel injection pump of a piston engine. The characterizing features of the bearing arrangement according to the invention are given in the characterizing part of claim 1.
The bearing arrangement according to the invention is configured to carry radial forces and comprises a housing, a bearing element that is arranged within the housing and provided with a sliding surface for supporting a rotating journal or shaft, at least one oil feeding port opening onto the sliding surface of the bearing element, and an oil supply bore that is arranged in the housing. The bearing arrangement further comprises an oil groove that is arranged between the housing and the bearing element for establishing fluid communication between the oil supply bore and the oil feeding port.
By arranging the oil groove between the housing and the bearing element, lubricating oil can be supplied to the oil feeding ports of the bearing arrangement on the rear side of the bearing element without disturbing oil film formation on the sliding surface. The sliding surface can thus be made flat, which improves the thickness of the oil film.
According to the invention, the sliding surface of the bearing element comprises an oil pocket that is arranged around the oil feeding port. The oil pocket is a recess that is configured to hold a certain amount of oil. The oil pocket helps to distribute the oil onto the sliding surface.
According to an embodiment of the invention, the width of the oil pocket is 30-95 % of the width of the bearing element. A wide oil pocket distributes the oil film uniformly across the whole width of the sliding surface. Therefore, the width is preferably at least 60 % of the width of the sliding surface.
The oil groove can be arranged either in the housing or in the bearing element. According to an embodiment of the invention, the arrangement comprises at least two oil feeding ports. By providing the bearing arrangement with two or more oil feeding ports, the oil can be supplied to several locations on the sliding surface, which makes the oil film more uniform.
According to an embodiment of the invention, the oil groove extends from the oil supply bore to both directions along the perimeter of the bearing element for connecting each of the oil feeding ports to the oil supply bore. By having oil feeding ports on both sides of the oil supply bore and arranging the oil groove to extend to opposite directions from the oil supply bore, possible rotation of the bearing element in relation to the housing does not completely cut oil supply to the oil feeding ports.
According to an embodiment of the invention, the sliding surface of the bearing element is flat outside the oil pocket(s). A maximal area of the sliding surface can thus be utilized for forming an oil film.
According to an embodiment of the invention, the oil groove is configured to end to an oil feeding port. By ensuring that the oil groove does not contain dead ends, the risk of cavitation can be reduced.
According to an embodiment of the invention, at least one oil feeding port is arranged in a sector that extends 60 degrees to each direction from the lowermost point of the bearing element. This improves lubrication in the lower part of the bearing arrangement.
A high-pressure pump for a common rail fuel injection system in accordance with the invention comprises a bearing arrangement defined above.
According to an embodiment of the invention, at least one oil feeding port is arranged in the proximity of the area where the highest bearing load appears. Oil is thus supplied to the most loaded area of the bearing.

Brief description of the drawings

Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which

Fig. 1 shows schematically a high-pressure pump for a common rail fuel injection system,
Fig. 2 shows a cross-sectional side view of a bearing arrangement according to an embodiment of the invention, and
Fig. 3 shows another view of the bearing arrangement of figure 2.

Description of embodiments of the invention

In figure 1 is shown a simplified view of a high-pressure pump of a common rail fuel injection system of a piston engine. The engine where the high-pressure pump can be used is a large internal combustion engine, such as a main or an auxiliary engine of a ship or an engine that is used at a power plant for producing electricity. The engine comprises a plurality of cylinders and the high-pressure pump supplies pressurized fuel to several cylinders of the engine. The expression "high-pressure pump" refers here to a pump that is capable of raising the pressure of a liquid fuel, such as light fuel oil or marine diesel oil to a level that is suitable for direct fuel injection into the cylinders of the engine. The pressure after the high-pressure pump can be, for instance, in the range of 500 to 3000 bar.
In the example of figure 1, the high-pressure pump comprises two plungers 10 for pressurizing the fuel. However, the pump could also be provided with only one plunger 10 or it could comprise more than two plungers 10. Each of the plungers 10 is arranged to move in a reciprocating manner and to protrude into a fluid chamber 11, where the plunger 10 pressurizes the fuel. The fuel injection system where the high-pressure pump is used comprises one or more low-pressure pumps for supplying fuel to the high-pressure pump. For moving the plungers 10, the high-pressure pump comprises a camshaft 7. In the example of figure 1, the camshaft 7 comprises one cam 12 for each plunger 10. As the camshaft 7 rotates, the plungers 10 are moved by the cams 12 in a reciprocating manner. There is a phase difference between the two plungers 10 such that when one of the plungers 10 is at top dead center, the other plunger 10 is at bottom dead center. This ensures that the output of the high-pressure pump is as constant as possible. Cam followers 13 transform the rotational movement of the cams 12 into the reciprocating movement of the plungers 10. The camshaft 7 can be driven by the crankshaft of the engine where the high-pressure pump is used. Alternatively, the camshaft 7 could be driven for example by an electric motor or a hydraulic motor.
The camshaft 7 of the high-pressure pump is supported by bearings that are configured to carry radial loads. In the example of figure 1, the camshaft 7 is supported by three bearings. The minimum number of radial bearings is two, but depending on the number of the plungers 10, the high-pressure pump could also comprise more than three radial bearings. The bearings of the high-pressure pump are lubricated plain bearings. Each bearing comprises a housing 1 and a bearing element 2 that is arranged within the housing 1. The camshaft 7 is provided with journals 6, which are arranged to rotate within the bearing elements 2. Lubricating oil is supplied between each bearing element 2 and journal 6 for forming a fluid film and minimizing friction in the rotating contact. Due to the high-pressure the pump needs to produce, the load of the bearings is relatively high. The highest load occurs at the bottom of the bearings.
Figures 2 and 3 show a bearing arrangement according to an embodiment of the invention. The bearing arrangement can be used in the bearings of a high-pressure pump of a common rail fuel injection system. The bearing arrangement comprises a housing 1 and a bearing element 2, which is arranged within the housing 1. The bearing element 2 comprises a sliding surface 3, against which a journal 6 or a shaft 7 can rotate. The sliding surface 3 is thus the inner surface of an annular bearing element 2. The sliding surface 3 extends over the whole inner perimeter of the bearing element 2. For supplying lubricating oil between the bearing element 2 and a journal 6, the bearing arrangement comprises at least one oil feeding port 4, which opens onto the sliding surface 3 of the bearing element 2. In the embodiment of figures 2 and 3, the bearing arrangement comprises three oil feeding ports 4, but the number of oil feeding ports 4 can be, for instance, between 1 and 4. Each oil feeding port 4 of the bearing arrangement is surrounded by an oil pocket 9, which is arranged on the sliding surface 3 of the bearing element 2. An oil pocket 9 is a recess, which is configured to hold a certain amount of oil. The oil pockets 9 help to distribute the oil evenly onto the sliding surface 3. The width of an oil pocket 9 is 30-95 % of the width of the bearing element 2 in the axial direction of the bearing element 2. A wider oil pocket 9 distributes the oil more effectively over the whole width of the sliding surface 3. Therefore, the width of the oil pocket 9 is preferably at least 60 percent of the width of the bearing element 2. The length of the oil pocket 9 in the direction of the perimeter of the bearing element 2 is at most the same as the width of the oil pocket 9. In the embodiment of figures 2 and 3, the oil pockets 9 are rectangular. However, the oil pockets 9 could also be for example circular or elliptical. Outside the oil pockets 9, the sliding surface 3 of the bearing element 2 is flat. No recesses or grooves are thus formed outside the oil pockets 9. A flat sliding surface 3 improves the thickness of the oil film and maximizes the use of the sliding surface 3.
For supplying the lubricating oil to the oil feeding ports 4, the bearing arrangement comprises an oil supply bore 5, which is arranged in the housing 1 of the bearing arrangement. The oil supply bore 5 is arranged to supply the oil to the oil feeding ports 4 from an upper part of the bearing arrangement. The oil from the oil supply bore 5 is received by an oil groove 8, which is arranged between the housing 1 and the bearing element 2. In the embodiment of figures 1 and 2, the oil groove 8 is formed in the housing 1. The outer perimeter of the bearing element 2 is thus flat. However, the oil groove 8 could also be formed in the bearing element 2, or the oil groove 8 could be partly in the housing 1 and partly in the bearing element 2. The oil groove 8 is configured to establish fluid communication between the oil supply bore 5 and each of the oil feeding ports 4. From the end of the oil supply bore 5, the oil groove 8 extends to both directions along the perimeter of the bearing element 2. This ensures that even if the bearing element 2 rotates in relation to the housing 1, oil supply to the oil feeding ports 4 is not completely cut, but lubricating oil is supplied to at least one of the oil feeding ports 4.
The oil groove 8 is configured such that at both ends it ends to an oil feeding port 4. The oil groove 8 does thus not extend beyond those oil feeding ports 4 that are farthest from the oil supply bore 5 and it does not contain dead ends. This prevents cavitation.
In the embodiment of figures 2 and 3, two of the oil feeding ports 4 are located in a lower part of the bearing element 2. In a high-pressure pump of a common rail fuel injection system, this is the most loaded area of the bearings. By arranging at least one of the oil feeding ports 4 in the proximity of the area with the highest bearing load, it is ensured that this area is properly lubricated. Preferably at least one oil feeding port 4 is arranged in a sector that extends 60 degrees to each direction from the lowermost point of the bearing element 2. In the embodiment of figures 2 and 3, the oil supply bore 5 extends below the bearing element 2. This end of the oil supply bore 5 is closed by a plug 14. The plug 14 is arranged close to the bearing element 2 to minimize the volume between the oil groove 8 and the plug 14. By this way creating of an oil damper is avoided.
It will be appreciated by a person skilled in the art that the invention is not limited to the embodiments described above, but may vary within the scope of the appended claims.

Claims

A bearing arrangement for a common rail fuel injection pump of a piston engine, the bearing arrangement being configured to carry radial forces and comprising
- a housing (1),

- a bearing element (2) that is arranged within the housing (1) and provided with a sliding surface (3) for supporting a rotating journal (6) or shaft (7),

- at least one oil feeding port (4) opening onto the sliding surface (3) of the bearing element (2),

- an oil supply bore (5) that is arranged in the housing (1), and

- an oil groove (8) that is arranged between the housing (1) and the bearing element (2) for establishing fluid communication between the oil supply bore (5) and the oil feeding port (4),
characterized in that the sliding surface (3) of the bearing element (2) comprises an oil pocket (9) that is arranged around the oil feeding port (4).
A bearing arrangement according to claim 1, wherein the width of the oil pocket (9) is 30-95 % of the width of the bearing element (2).
A bearing arrangement according to claim 2, wherein the width of the oil pocket (9) is 60-95 % of the width of the bearing element (2).
A bearing arrangement according to any of the preceding claims, wherein the oil groove (8) is arranged in the housing (1).
A bearing arrangement according to any of the preceding claims, wherein the oil groove (8) is arranged in the bearing element (2).
A bearing arrangement according to any of the preceding claims, wherein the arrangement comprises at least two oil feeding ports (4).
A bearing arrangement according to claim 6, wherein the oil groove (8) extends from the oil supply bore (5) to both directions along the perimeter of the bearing element (2) for connecting each of the oil feeding ports (4) to the oil supply bore (5).
A bearing arrangement according to any of the preceding claims, wherein the sliding surface (3) of the bearing element (2) is flat outside the oil pocket(s) (9).
A bearing arrangement according to any of the preceding claims, wherein the oil groove (8) is configured to end to an oil feeding port (4).
A bearing arrangement according to any of the preceding claims, wherein at least one oil feeding port (4) is arranged in a sector that extends 60 degrees to each direction from the lowermost point of the bearing element (2).
A high-pressure pump for a common rail fuel injection system, characterized in that the pump comprises a bearing arrangement according to any of the preceding claims.
A high-pressure pump according to claim 11, wherein at least one oil feeding port (4) is arranged in the proximity of the area where the highest bearing load appears.