Bearing shell, main bearing for piston engine and piston engine
By designing the narrow part of the oil slot on the spindle shell of the piston engine, the problem of air erosion wear is solved, the effect of reducing pressure fluctuations and wear, and extending the service life of the spherical shaft.
Patent Information
- Application Number
- CN202280097215.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-06-22
- Publication Date
- 2025-01-28
AI Technical Summary
In piston engines, the main bearing is susceptible to cavitation wear, resulting in pressure fluctuations and aggravation of wear, and the prior art is difficult to effectively prevent this problem.
A improved bearing shell is designed, including the oil groove arranged in the direction of the bearing shell in the direction of the bearing shell. The second part of the oil groove is narrower than the first part, preventing the sudden cutting of lubricating oil, and avoiding the formation of negative pressure and shock waves.
Through this design, negative pressure and shock waves are prevented in the lower part of the bearing shell, reducing air erosion wear, and prolonging the service life of the spherical bearing.
Smart Images
Figure CN119384560A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a bearing shell for a main bearing of a piston engine as defined in claim 1. The invention also relates to a main bearing for a piston engine and to a piston engine. Background Art
[0002] The crankshaft of a piston engine is supported on the engine block by bearings (which may be referred to as main bearings). The piston is connected to the crankshaft by a connecting rod. The bearing that connects the connecting rod to the crankshaft may be referred to as a big end bearing, and the bearing that connects the piston to the connecting rod may be referred to as a small end bearing.
[0003] The main bearings, the big end bearings and the small end bearings require lubrication. In large piston engines, such as ship engines or power plant engines, the main bearings are usually lubricated via the engine block. The crankshaft is provided with a bore through which lubricating oil is supplied to the big end bearing. Furthermore, the connecting rod is provided with a bore through which lubricating oil can be supplied to the small end bearing.
[0004] A typical main bearing of a large piston engine is provided with an oil groove extending over a portion of the bearing circumference. When a bore of the crankshaft is in fluid communication with the oil groove, lubricating oil can flow into the bore.
[0005] During the use of the engine, the bearings wear via different wear mechanisms. One wear mechanism that particularly affects the main bearings is cavitation wear. Cavitation refers to the phenomenon whereby small vapor-filled cavities are formed in a liquid due to a pressure drop. When the pressure of the liquid increases, the cavities collapse and shock waves are generated, which lead to wear. Pressure fluctuations are induced in the main bearings via different mechanisms. One mechanism involves the sudden closing of the crankshaft bore. Summary of the invention
[0006] The object of the invention is to provide an improved bearing shell for a main bearing of a piston engine. The specific features of the bearing shell according to the invention are given in claim 1. Other objects of the invention are to provide an improved main bearing for a piston engine and a piston engine as defined in the other claims.
[0007] The bearing shell according to the present invention has an inner surface forming a bearing surface, and the inner surface of the bearing shell is provided with a first oil groove arranged in the circumferential direction of the bearing shell at a first end of the bearing shell, and the first oil groove includes a first portion having a constant width. The first oil groove includes a second portion, which forms a continuation of the first portion in the circumferential direction of the bearing shell, and the second portion is narrower than the first portion.
[0008] Due to the second portion of the first oil groove, the flow into the bore of the crankshaft journal is not suddenly cut off when the oil inlet of the journal leaves the area of the first portion of the first oil groove, but the flow into the bore can continue at a restricted flow rate when the oil inlet is in the area of the second portion. This prevents the formation of negative pressure in the lower part of the bearing shell and prevents shock waves behind the negative pressure.
[0009] According to an embodiment of the present invention, the cross-sectional area of the second portion is smaller than the cross-sectional area of the first portion.
[0010] According to an embodiment of the present invention, the width of the second portion of the first oil groove is smaller than the diameter of the oil inlet of the crankshaft journal on which the bearing is arranged.
[0011] According to an embodiment of the present invention, the width of the first portion of the first oil groove is 15%-30% of the width of the bearing shell.
[0012] According to an embodiment of the present invention, the width of the second portion of the first oil groove is 5%-50% of the width of the first portion. According to an embodiment of the present invention, the width of the second portion is 5%-20% of the width of the first portion. If the second portion is too narrow, it does not allow sufficient flow to prevent cavitation. On the other hand, a second portion that is too wide is not sufficient to restrict the flow into the bore of the crankshaft journal.
[0013] According to an embodiment of the present invention, the depth of the first portion of the first oil groove decreases toward the second portion.
[0014] According to an embodiment of the present invention, the depth of the second portion of the first oil groove decreases toward an end portion located away from the first portion.
[0015] According to an embodiment of the present invention, the first portion of the first oil groove extends at an angle of 10-30 degrees.
[0016] According to an embodiment of the present invention, the second portion of the first oil groove extends at an angle of 10-30 degrees.
[0017] According to an embodiment of the present invention, the cross section of the second portion of the first oil groove is V-shaped, rectangular, semicircular or elliptical.
[0018] According to an embodiment of the present invention, the bearing shell comprises a second oil groove provided at a second end of the bearing shell.
[0019] According to an embodiment of the present invention, the second oil groove comprises a first portion and a second portion forming a continuation of the first portion, the second portion being narrower than the first portion. The second oil groove may be identical to the first oil groove. This is not essential, but by arranging the bearing shell with identical oil grooves arranged at opposite ends of the bearing shell, the same bearing shell can be used in clockwise and counterclockwise rotating engines.
[0020] The main bearing according to the invention comprises a first lower bearing shell and a second upper bearing shell, wherein the first bearing shell is the bearing shell defined above.
[0021] According to an embodiment of the present invention, the second bearing shell has an inner surface forming a bearing surface, and the inner surface of the second bearing shell is provided with an oil groove extending over the entire bearing shell in a circumferential direction of the bearing shell.
[0022] A piston engine according to the invention comprises a main bearing as defined above. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Embodiments of the present invention are described in more detail below with reference to the accompanying drawings, in which
[0024] Figure 1 An example of a lower bearing shell of a prior art main bearing is shown,
[0025] Figure 2 An example of an upper bearing shell of a prior art main bearing is shown,
[0026] Figure 3 shows a perspective view of a bearing shell according to an embodiment of the invention,
[0027] Figure 4 Shows Figure 3 Plan view of the bearing shell,
[0028] FIG. 5A to FIG. 5C Cross-sectional views of a main bearing at different crank angles are shown according to an embodiment of the present invention. DETAILED DESCRIPTION
[0029] Figure 1 and Figure 2 Prior art bearing shells 1 and 2 of a main bearing of a piston engine are shown. Figure 1 The lower half of the bearing is shown, Figure 2 The upper half of the bearing is shown. The engine in which the bearing can be used is a large internal combustion engine, such as a main engine or auxiliary engine of a ship or an engine used for generating electricity at a power plant. The engine has a cylinder bore of at least 150 mm. Each cylinder of the engine is provided with a piston that moves in a reciprocating manner in the cylinder. The engine may have any reasonable number of cylinders.
[0030] The piston is connected to the crankshaft via a connecting rod. The connecting rod connects the piston to the crankshaft and converts the reciprocating motion of the piston into the rotational motion of the crankshaft.
[0031] The crankshaft is mounted in the engine block via main bearings. A main bearing is provided on each side of each connecting rod. The main bearings are sliding bearings.
[0032] Figure 2 The upper bearing shell 2 includes an oil groove 5. The oil groove 5 is provided on the inner surface of the bearing shell 2. The oil groove 5 of the upper bearing shell 2 extends over the entire bearing shell 2 in the circumferential direction of the bearing shell. An oil hole 6 is provided on the upper bearing shell 2. The oil hole 6 is arranged along the oil groove 5 and allows lubricating oil to be supplied to the oil groove 5 from the outside of the bearing.
[0033] Figure 1 The lower bearing shell 1 includes a first oil groove 3 and a second oil groove 4. The first oil groove 3 is provided at a first end of the bearing shell 1 in a circumferential direction, and the second oil groove 4 is provided at a second end. Each of the first oil groove 3 and the second oil groove 4 extends at an angle of about 20 degrees. The width of the first oil groove 3 and the second oil groove 4 corresponds to the width of the oil groove 5 of the upper bearing shell 1. The first oil groove 3 and the second oil groove 4 are configured to be connected to the oil groove 5 of the upper bearing shell 2 to form a continuous oil groove.
[0034] Figure 3 and Figure 4 A bearing shell 1 according to an embodiment of the invention is shown. The bearing shell 1 may be used as a lower bearing shell in a main bearing of a piston engine, such as the engine described above in connection with the discussion of the prior art.
[0035] The bearing shell 1 is semicircular. The bearing shell 1 has an inner surface forming a bearing surface. The bearing surface is provided with a first oil groove 3 and a second oil groove 4. The first oil groove 3 is provided at a first end of the bearing shell 1 along the circumferential direction of the bearing shell 1. The second oil groove 4 is provided at a second end of the bearing shell 1.
[0036] The first oil groove 3 comprises a first portion 3a and a second portion 3b. The first portion 3a starts from the first end of the bearing shell 1. Therefore, it can be a continuation of the oil groove from another bearing shell. The first portion 3a has a constant width. In the embodiment of the drawings, the width of the first portion 3a is about 20% of the width of the bearing shell 1 in the axial direction. The width of the first portion 3a can be, for example, in the range of 10%-30% of the width of the bearing shell 1.
[0037] The second portion 3b forms a continuation of the first portion 3a. The second portion 3b is narrower than the first portion 3a. In the embodiment of the accompanying drawings, the width of the second portion 3b is approximately 40% of the width of the first portion 3a. The width of the second portion 3b may, for example, be in the range of 5%-50% of the width of the first portion 3a. The width of the second portion 3b may be constant.
[0038] The depth of the second part 3b may be the same as the depth of the first part 3a, or the depth may be different. The second part 3b may be deeper than the first part 3a or not as deep as the first part 3a. Preferably, the cross-sectional area of the second part 3b is smaller than the cross-sectional area of the first part 3a. The depth of the first part 3a and the second part 3b does not need to be constant. The depth of the first part 3a may decrease toward the second part 3b. Similarly, the depth of the second part 3b may decrease toward the end located away from the first part 3a.
[0039] In the embodiment of the drawings, the first portion 3a extends at an angle of about 20 degrees in the circumferential direction of the bearing shell 1. Moreover, the second portion 3b extends at an angle of about 20 degrees. The first portion 3a may extend at an angle of, for example, 10-30 degrees. Similarly, the second portion 3b may extend at an angle of, for example, 10-30 degrees.
[0040] Different cross-sectional shapes of the second portion 3b are possible. The cross section of the second portion 3b may be, for example, V-shaped, rectangular, semicircular or elliptical. In the embodiment of the figures, the cross section is rectangular.
[0041] The bearing shell 1 is configured to be installed so that the rotation direction of the crankshaft is from the first end toward the second end of the bearing shell 1. Therefore, a certain point on the circumference of the crankshaft journal first enters the area of the first portion 3a of the first oil groove 3.
[0042] exist Figure 3 and Figure 4 In the embodiment of the present invention, the second oil groove 4 further includes a first portion 4a and a second portion 4b. The first portion 4a and the second portion 4b of the second oil groove 4 are constructed in a similar manner to the corresponding portions 3a, 3b of the first oil groove 3. Since the first oil groove 3 and the second oil groove 4 are identical to each other, the same bearing shell 1 can be used in clockwise and counterclockwise rotating engines.
[0043] The bearing shell 1 according to the invention can be used in a main bearing, wherein the upper bearing shell is a bearing shell according to the prior art. The upper bearing shell 2 can be, for example Figure 2 Therefore, the first oil groove 3 and the second oil groove 4 of the lower bearing shell 1 form a continuous oil groove together with the oil groove 5 of the upper bearing shell 2. In the rotation direction of the crankshaft, the second oil groove 4 of the lower bearing shell 1 forms the front end of the combined oil groove, and the first oil groove 3 forms the rear end.
[0044] The width of the first portion 3a, 4a of the first oil groove 3 and the second oil groove 4 of the lower bearing shell 1 corresponds to the width of the oil groove 5 of the upper bearing shell 2. In addition, the depth of the first portion 3a, 4a of the first oil groove 3 and the second oil groove 4 of the lower bearing shell 1 corresponds to the depth of the oil groove 5 of the upper bearing shell 2. The lower bearing shell 1 does not include any oil hole.
[0045] FIG. 5A to FIG. 5C 1 shows cross-sectional views of a main bearing according to an embodiment of the present invention at different crank angles. The bearing comprises a lower bearing shell 1 and an upper bearing shell 2. FIG. 5A to FIG. 5C In the embodiment, the upper bearing shell 2 is similar to Figure 2 The prior art bearing shell, and the lower bearing shell 1 is similar to Figure 3 and Figure 4 The upper bearing shell 2 is provided with an oil hole 6, through which lubricating oil is continuously supplied to the oil groove 5 of the upper bearing shell 2.
[0046] The bearing supports the journal 7 of the crankshaft. The direction of rotation of the crankshaft, indicated by arrow A in the figure, is clockwise in the figure. There is a gap between the journal 7 and the bearing surface, so the journal 7 can move in the radial direction within the bearing. Small radial movements are FIG. 5A to FIG. 5C The figures are significantly exaggerated to better illustrate the function of the bearing.
[0047] The journal 7 is provided with a radial bore 8, which extends through the journal 7. The ends of the bore 8 form a first oil inlet 8a and a second oil inlet 8b. The radial bore 8 of the journal 7 is in fluid communication with an axial bore 9, which is configured to supply lubricating oil to the big end bearing of at least one connecting rod. Via the connecting rod, the lubricating oil is further supplied to the small end bearing of the connecting rod. The term "axial" here does not mean that the bore 9 is parallel to the rotation axis of the crankshaft, but that the axial bore can guide the lubricating oil in the axial direction of the crankshaft.
[0048] exist Figure 5A In the case of the first oil inlet 8a of the bore hole 8 of the journal 7 is located at the region of the oil groove 5 of the upper bearing shell 2. Therefore, the lubricating oil can flow into the bore hole 8 via the first oil inlet 8a.
[0049] exist Figure 5B In the case of the crankshaft, the crankshaft has rotated so that the first oil inlet 8a is located at the area of the second part 3b of the first oil groove 3 of the lower bearing shell 1. In a bearing without the second part 3b, the fluid communication between the first oil groove 3 and the first oil inlet 8a would be closed. Due to the inertial force, the journal 7 has moved away from the second part 3b of the first oil groove 3 in the radial direction. If the oil supply from the first oil groove 3 to the bore 8 of the journal 7 is prevented, the radial movement of the journal will cause underpressure. Moreover, the inertial force of the connecting rod and the flowing oil causes a suction effect. However, since the second part 3b of the first oil groove 3 keeps part of the oil supply into the bore 8, the formation of a vapor-filled cavity in the lubricating oil is prevented.
[0050] exist Figure 5CIn the case of the crankshaft, the crankshaft has rotated so that the first oil inlet 8a is no longer at the region of the first oil groove 3 of the lower bearing shell 1. The journal 7 has moved radially into a direction in which the distance between the first oil inlet 8a and the bearing surface has decreased. This increases the pressure of the lubricating oil around the region of the first oil inlet 8a. Moreover, the centrifugal force acting on the oil increases the pressure. If a vapor-filled cavity had been formed at an earlier stage, the cavity would have collapsed due to the increased pressure, which would have led to pressure pulses and thus to wear of the bearing. However, due to the gradual closing of the first oil groove 3 of the lower bearing shell 1, strong pressure pulses are avoided.
[0051] The second portion 3 b of the first oil groove 3 is preferably dimensioned such that the width of the second portion 3 b is smaller than the diameter of the oil inlets 8 a , 8 b of the bore 8 of the journal 7 .
[0052] Even a relatively narrow second portion 3b of the first oil groove 3, for example a groove with a width of 5% to 20% of the width of the first portion 3a, is sufficient to prevent the formation of underpressure. If the second portion 3b is wider, for example 20%-50% of the width of the first portion 3a, the flow into the bore 8 of the journal 7 continues at a greater flow rate when the oil inlet 8a, 8b moves away from the area of the first portion 3a of the first oil groove 3. This reduces the influence of the backflow caused by centrifugal force. However, if the second portion 3b is too wide, cavitation may occur when the oil inlet 8a, 8b moves away from the area of the second portion 3b. Therefore, the width of the second portion 3b is preferably at most 50% of the width of the first portion 3a.
[0053] It will be appreciated by a person skilled in the art that the invention is not limited to the embodiments described above, but may be varied within the scope of the appended claims.
Claims
1. A bearing shell (1) for a main bearing of a piston engine, the bearing shell (1) having an inner surface forming a bearing surface, the inner surface of the bearing shell (1) being provided with a first oil groove (3) arranged along the circumferential direction of the bearing shell (1) at a first end of the bearing shell (1), the first oil groove (3) comprising a first portion (3a) having a constant width, characterized in that: The first oil groove (3) includes a second portion (3b) forming a continuation of the first portion (3a) along the circumferential direction of the bearing shell (1), and the second portion (3b) is narrower than the first portion (3a).
2. The bearing shell (1) according to claim 1, wherein: The cross-sectional area of the second portion (3b) is smaller than the cross-sectional area of the first portion (3a).
3. The bearing shell (1) according to claim 1 or 2, wherein: The width of the second portion (3b) of the first oil groove (3) is smaller than the diameter of the oil inlet (8a, 8b) of the crankshaft journal (7) provided on the bearing shell (1).
4. The bearing shell (1) according to any one of claims 1 to 3, wherein: The width of the first portion (3a) of the first oil groove (3) is 15%-30% of the width of the bearing shell (1).
5. The bearing shell (1) according to any one of the preceding claims, wherein: The width of the second portion (3b) of the first oil groove (3) is 5%-50% of the width of the first portion (3a).
6. The bearing shell (1) according to claim 5, wherein: The width of the second portion (3b) of the first oil groove (3) is 5%-20% of the width of the first portion (3a).
7. The bearing shell (1) according to any one of the preceding claims, wherein: The depth of the first portion (3a) of the first oil groove (3) decreases toward the second portion (3b).
8. The bearing shell (1) according to any one of the preceding claims, wherein: The depth of the second portion (3b) of the first oil groove (3) decreases toward an end portion located away from the first portion (3a).
9. The bearing shell (1) according to any one of the preceding claims, wherein: The first portion (3a) of the first oil groove (3) extends at an angle of 10 to 30 degrees.
10. The bearing shell (1) according to any one of the preceding claims, wherein: The second portion (3b) of the first oil groove (3) extends at an angle of 10 to 30 degrees.
11. The bearing shell (1) according to any one of the preceding claims, wherein: The cross section of the second portion (3b) of the first oil groove (3) is V-shaped, rectangular, semicircular or elliptical.
12. The bearing shell (1) according to any one of the preceding claims, wherein: The bearing shell (1) comprises a second oil groove (4) arranged at a second end of the bearing shell (1), and the second oil groove (4) comprises a first portion (4a) and a second portion (4b) forming a continuation of the first portion (4a), the second portion (4b) being narrower than the first portion (4a).
13. A main bearing for a piston engine, the bearing comprising a first lower bearing shell (1) and a second upper bearing shell (2), wherein the first bearing shell (1) is a bearing shell (1) according to any one of the preceding claims.
14. The main bearing according to claim 13, wherein: The inner surface of the second bearing shell (2) is provided with an oil groove (5) extending along the circumferential direction of the bearing shell (2) over the entire bearing shell (2).
15. A piston engine comprising a main bearing according to claim 13 or 14.