Lubrication structure for internal combustion engine

Abstract

Lubrication structure for an internal combustion engine (10), comprising: an oil pump (20) installed in a crankcase (11) formed by connecting an upper crankcase part (17) with a mating surface (16A) of a lower crankcase part (16) from above; a main oil passage (36) which is present in the lower crankcase part (16) to supply oil discharged from the oil pump (20) to the respective areas of the internal combustion engine (10); an oil supply line (51) which is present in the lower crankcase part (16) and supplies oil from the main oil passage (36) to a mating surface oil line which is formed in the mating surface (16A) of the lower crankcase part (16); an auxiliary oil passage (57) in the upper crankcase part (17) for supplying oil to a piston nozzle (40, 41) which expels oil towards a piston (27) of the internal combustion engine (10); and an oil connecting line (56), which runs across the lower crankcase part (16) and the upper crankcase part (17), branches off from the oil supply line (51) to communicate with the auxiliary oil passage (57) and to supply oil in the oil supply line (51) to the auxiliary oil passage (57).

Description

Background for internal combustion engine; field of invention

[0001] The present invention relates to a lubrication structure for an internal combustion engine, which supplies oil to a piston nozzle for cooling a piston of an internal combustion engine. Description of the state of the art

[0002] The thermal stress on a piston increases with an increase in engine output power, making it increasingly important to incorporate a piston nozzle that cools the piston by spraying oil onto its rear surface. A piston moving back and forth within a cylinder block causes the connecting rod to follow a large curved path, thus limiting the position of the piston nozzle, which sprays oil onto the piston's rear surface, to a very narrow area.

[0003] Furthermore, arranging an oil line to supply oil to the piston nozzle is also difficult, and it is necessary to provide oil pressure to expel oil from the piston nozzle. JP 2013-79623 A shows a lubrication structure in which oil is supplied to a piston nozzle (injector), which sprays oil onto a piston, using oil lines (an oil channel and an oil distribution pipe) that are externally attached to a crankcase and a cylinder block.

[0004] From US patent 2005 / 0005895A1, a lubrication structure is known in which, after lubricating the timing chain in the chain chamber, oil is returned to the oil pan via bores located on both sides of the crankshaft. From JP S63-183409U, a lubrication structure for an internal combustion engine is known in which oil used to cool the piston is supplied to a piston nozzle via a main oil passage in the cylinder block.

[0005] If the oil line for supplying oil to the piston nozzle is complex, the number of machining operations required for the oil line increases. Furthermore, if the oil is supplied to the piston nozzle (the injector nozzle) via oil lines (the oil channel and the oil distribution pipe) that are externally mounted on the engine, as described in Patent Specification 1, the number of components, the number of assembly steps, and the weight and cost of the engine all increase. In addition, there is a risk of oil leakage in the externally mounted oil line. Disclosure of the invention

[0006] In light of the circumstances explained above, an objective of the invention is to provide a lubrication structure for an internal combustion engine which can reduce the number of components and the like by simplifying an oil line for supplying oil to a piston nozzle and at the same time increasing the piston cooling performance.

[0007] The above objective, as well as further objectives, can be achieved according to the invention by creating, in accordance with one aspect: a lubrication structure for an internal combustion engine, comprising an oil pump, a main oil passage, an oil supply line, an auxiliary oil passage, and an oil connecting line. The oil pump is installed in a crankcase formed by connecting an upper crankcase part to a mating surface of a lower crankcase part from above. The main oil passage is located in the lower crankcase part to supply oil discharged from the oil pump to the respective areas of the internal combustion engine. The oil supply line is located in the lower crankcase part and delivers oil from the main oil passage to a mating surface oil line formed in the mating surface of the lower crankcase part.The auxiliary oil passage is located in the upper crankcase section to supply oil to a piston nozzle, which then expels oil towards a piston in the internal combustion engine. The oil connection line extends through the lower and upper crankcase sections, branches off from the oil supply line to communicate with the auxiliary oil passage, and carries oil from the oil supply line to the auxiliary oil passage.

[0008] According to the invention, an oil connecting line branches off from an oil supply line and extends over a lower and an upper crankcase section, thus simplifying its design and avoiding a complex shape. The oil connecting line is not configured with separate components for a crankcase, thereby reducing the number of components and the like. Oil from a main oil passage is supplied to the piston nozzle via the oil supply line, the oil connecting line, and an auxiliary oil passage under controlled oil pressure. Consequently, the piston cooling capacity can be increased by the oil ejected from the piston nozzle.

[0009] The special features and other characteristic features of the invention are explained below with reference to the accompanying drawings, and further advantageous effects and functions of the invention also result from this. Brief description of the drawings Fig. Figure 1 is a right-hand view illustrating an engine in which an embodiment of a lubrication structure for an internal combustion engine according to the invention is applied; Fig. 2 is a view according to arrow II in Fig. 1 Fig. Figure 3 is a right-side view of the engine after removing a clutch cover and the like from the one shown in Fig. 1 engine shown; Fig. 4 is a top view showing the engine after a cylinder block of the in Fig. The second engine shown was removed; Fig. Figure 5 is a top view of a lower crankcase part after removal of an upper crankcase part according to Fig. 4; Fig. 6 is a sectional view along line VI-VI in the Fig. 4 and Fig. 5; Fig. 7 is a sectional view along line VII-VII in Fig. 4 and Fig. 5; Fig. 8 is a sectional view along line VIII-VIII in the Fig. 4 and Fig. 5; Fig. 9 is a system diagram showing the engine's lubrication system according to Fig. 1 illustrates; and Fig. Figure 10 is a perspective view illustrating a lower crankcase part of an engine in which a further embodiment of the lubrication structure for an internal combustion engine according to the invention is applied. Detailed description

[0010] The following describes an embodiment of the invention with reference to the drawing.

[0011] Fig. Figure 1 is a right-hand view of an engine in which an embodiment of a lubrication structure for an internal combustion engine according to the invention is used. Fig. 2 is a view according to arrow II in Fig. 1. An engine 10 as an internal combustion engine according to Fig. 1 and Fig. 2 is, for example, mounted on a motorcycle, and the engine block 12 is connected to a crankcase 11 in a forward-leaning manner.

[0012] The engine block 12 is formed by a cylinder block 13, a cylinder head 14, and a cylinder head cover 15, which are sequentially connected to each other from above. By burning a gas mixture that is fed to a combustion chamber (not shown) in the cylinder head 14, a piston 27 within the cylinder block 13 performs a reciprocating motion, and this reciprocating motion drives a crankshaft 23 ( Fig. 3) via a connecting rod (not shown) for rotation.

[0013] As in Fig. As shown in Figure 3, the crankcase 11 is formed by bringing a mating surface 17A of an upper crankcase part 17 into contact with a mating surface 16A of a lower crankcase part 16 from above, and the upper crankcase part 17 is connected to the lower crankcase part 16 in this state. An oil pan 18 for lubricating the engine is located in a lower area of ​​the lower crankcase part 16. An oil strainer 19 is located in the oil pan 18.

[0014] An oil filter 21 is installed in the front section of the lower crankcase part 16. An oil pump 20 is located in a right side wall of the lower crankcase part 16, in a position where the oil pump 20 is covered by a clutch cover 22. In the oil pump 20, a pump shaft 25 is driven by a torque from a countershaft 24, which in turn is driven by a torque from a crankshaft 23 via a clutch mechanism (not shown), causing a pump rotor 26 to rotate together with the pump shaft 25.

[0015] As in the Fig. 5 and Fig. As shown in Figure 6, a shaft insertion hole 30 is located in the lower crankcase part 16, through which the pump shaft 25 of the oil pump 20 is inserted. In addition, a second oil suction line 32 (hereinafter simply referred to as the suction line) is located in the lower crankcase part 16. Fig. 9), namely formed in a side area in the periphery of the shaft insertion hole 30, furthermore a first oil pressure line (hereinafter simply ‘pressure line’) 33, in the other side area such that the second suction line 32 and the first pressure line 33 communicate with the oil pump 20.

[0016] The second suction line 32 communicates with a first suction line 31 in the lower crankcase part 16, extending vertically along the engine 10. The first suction line 31 is designed to connect to the oil strainer 19 located in the oil pan 18 ( Fig. 3) As in the Fig. 5 and Fig. As shown in Figure 6, the first pressure line 33 communicates with a second pressure line 34, which is formed in the lower crankcase part 16 such that it extends horizontally along the engine 10. The second pressure line 34 can be connected to the oil filter 21.

[0017] As in Fig. As shown in Figure 7, an oil discharge line 35, which can be connected to the oil filter 21, is formed parallel to the second pressure line 34 in the lower crankcase part 16. As further shown in the Fig. 5 and Fig. As can be seen in Figure 7, a main oil passage 36 extends in the lower crankcase part 16, which communicates with the oil discharge line 35, the main oil passage running horizontally in the lateral width direction of the engine 10 and being shaped orthogonally to the oil discharge line 35.

[0018] As in the Fig. 3 and Fig. As can be seen in Figure 9, the pump rotor 26 of the oil pump 20 rotates, causing oil located in the oil pan 18 to flow sequentially into the first suction line 31 and the second suction line 32, passing through the oil strainer 19, and then being drawn into the oil pump 20 to be pressurized. The pressurized oil is then transferred according to the Fig. 6 and Fig. 9 is discharged into the first pressure line and flows through the second pressure line 34 to the oil filter 21 for filtration. As in the Fig. 7 and Fig. As shown in Figure 9, the filtered oil flows through the oil discharge line 35 into the main oil passage 36 and is supplied to the respective areas of the engine 10 from the main oil passage 36.

[0019] The respective sections of the engine 10 to which oil is to be supplied include, for example, a crankshaft bearing 37, a countershaft bearing 38, a drive shaft bearing 39, a front piston nozzle 40 and a rear piston nozzle 41 and the like.

[0020] The crankshaft bearing 37 after Fig. 5 is a point that rotatably supports the crankshaft 23. The engine 10 is designed according to Fig. 2 and Fig. 4 a four-cylinder in-line engine, such that the crankshaft bearing 37 contains a first crankshaft bearing section #1, a second crankshaft bearing section #2, a third crankshaft bearing section #3, a fourth crankshaft bearing section #4 and a fifth crankshaft bearing section #5, which are sequentially formed at predetermined intervals in the lateral width direction of the engine 10 from the left side of the engine 10 in the lower crankcase part 16.

[0021] As in the Fig. 5 and Fig. As can be seen in Figure 7, the respective crankshaft bearing sections 37 (the first crankshaft bearing section #1 to the fifth crankshaft bearing section #5) are connected to the main oil passage 36 via a crankshaft bearing oil line 42. These crankshaft bearing sections 37 (the first crankshaft bearing section #1 to the fifth crankshaft bearing section #5) are located in a crankshaft chamber 43 within the crankcase 11.

[0022] The respective crankshaft bearing sections 37 (the first crankshaft bearing section #1 to the fifth crankshaft bearing section #5) contain (not shown) bearing metals between the respective crankshaft bearing sections 37 and the crankshaft 23. Oil at suitable oil pressure is supplied to the respective crankshaft bearing sections 37 (the first crankshaft bearing section #1 to the fifth crankshaft bearing section #5) from the main oil passage 36 via the crankshaft bearing oil line 42, so that a continuous oil film is present between the bearing metals and the crankshaft 23.

[0023] As in Fig. As shown in Figure 9, oil supplied from the main oil passage 36 to the respective crankshaft bearing sections 37, and lubricating them, is supplied to an alternator 44 for its lubrication in the case of the first crankshaft bearing section #1. In the case of the second crankshaft bearing section #2 up to the fourth crankshaft bearing section #4, the oil, after lubricating these respective crankshaft bearing sections 37, is supplied to a large connecting rod end 45 to lubricate the sliding parts of the large connecting rod end 45 and the crankshaft 23. In the case of the fifth crankshaft bearing section #5, the oil, after lubricating the respective crankshaft bearing sections 37, is supplied to a valve mechanism 46 in the cylinder head 14 to lubricate it. After lubricating the third crankshaft bearing section #3, the oil is not supplied to any further parts.

[0024] In Fig. The 5 illustrated countershaft bearings 38 rotatably support the countershaft 24 ( Fig. 3) of the transmission mechanism, and drive shaft bearing 39 after Fig. The drive shaft 28 is rotatably supported by bearings 5. The countershaft bearings 38 and the drive shaft bearings 39 are located in the gearbox chamber 47 within the crankcase 11. The countershaft bearings 38 are formed on the side walls 48A and 48B, which define the gearbox chamber 47 in the lower crankcase part 16 and are opposite each other. The drive shaft bearings 39 are also formed on the side walls 48A and 48B, opposite each other, in the lower crankcase part 16, adjacent to the countershaft bearings 38.

[0025] In the lower crankcase part 16, a partition 49 separating the crankcase chamber 43 and the transmission chamber 47 is formed continuously up to the side walls 48A and 48B. A transmission oil line 50 is formed as a mating-surface oil line on the mating surface 16A of the lower crankcase part 16 at the side wall 48A, the partition 49 and the side wall 48B to communicate with the countershaft bearings 38 and the drive shaft bearings 39.

[0026] As in Fig. 5 and Fig. As shown in Figure 8, the transmission oil line 50 communicates with the main oil passage 36 via a rear oil supply line 51. This line is formed at a central point in the lateral width direction of the engine 10 in the lower crankcase part 16. Furthermore, the rear oil supply line 51 comprises a horizontal section 52 formed in the lower crankcase part 16 to communicate with the main oil passage 36 and extending horizontally parallel to the mating surface 16A of the lower crankcase part 16, and a vertical section 52 formed in the lower crankcase part 16 to connect with the horizontal section 52 and the transmission oil line 50, extending vertically with respect to the mating surface 16A of the lower crankcase part 16.

[0027] Accordingly, as in the Fig. 8 and Fig. As shown in Figure 9, the oil from the main oil passage 36 is sequentially routed through the horizontal conduit section 52 of the rear oil supply line 51 and the vertical conduit section 53 to an outlet 54, which is described below, according to Fig. The oil supplied to the transmission oil line 50 is directed to the countershaft bearing 38 and the drive shaft bearing 39 and lubricates sliding areas of the countershaft 24 and the countershaft bearing 38, as well as sliding areas of the drive shaft 28 and the drive shaft bearing 39.

[0028] The aforementioned opening 54 is located at a boundary point with the transmission line 50, for example in the vertical line section 53 of the rear oil supply line 51. The opening 54 reduces the oil pressure of the oil supplied to the transmission line 50 from the rear oil supply line 51 and prevents leakage of the oil flowing in the transmission oil line 50.

[0029] As in the Fig. 4, Fig. 6 and Fig. As shown in Figure 7, each cylinder within the engine 10 of this embodiment contains a front piston nozzle 40 and a rear piston nozzle 41. Oil is sprayed from the front piston nozzle 40 and the rear piston nozzle 41 against the rear face of the piston 27, thereby cooling the piston 27, which is subject to high thermal stress. The front piston nozzle 40 and the rear piston nozzle 41 are connected at a point below the cylinder block 13, which is connected to the upper crankcase part 17, within this upper pistoncase part 17 of this embodiment. The front piston nozzle 40 is located in a front position with respect to the piston 27, and the rear piston nozzle 41 is located in a rear position with respect to the piston 27.This causes the front piston nozzle 40 to spray oil on a front side against the rear surface of the piston 27, and the rear piston nozzle 41 to spray oil on a rear side against the rear surface of the piston 27.

[0030] As in Fig. 7 and Fig. As shown in Figure 9, oil from the main oil passage 36 is supplied to the front piston nozzle 40 via a front oil supply line 55, which is formed on a front face of the lower crankcase part 16. The front oil supply line 55 runs transversely to the lower crankcase part 16 and the upper crankcase part 17 at a central position in the lateral width direction of the engine 10.

[0031] As in the Fig. 8 and Fig. As shown in Figure 9, oil is supplied to the rear piston nozzle 41 from the main oil passage 36 via the rear oil supply line 51, an oil connecting line 56 branching off from the rear oil supply line 51, and an auxiliary oil passage 57, the latter communicating with the oil connecting line 56 and the rear piston nozzle 41. The oil connecting line 56 runs straight across the lower crankcase section 16 and the upper crankcase section 17, and it communicates with the vertical section 53 of the rear oil supply line 51 and the auxiliary oil passage 57. Furthermore, the oil connecting line 56 is located at the central point in the lateral direction of the engine 10. The oil connecting line 56 and the rear oil supply line 51 are located in the same vertical plane within the lower crankcase section 16.

[0032] The outlet 54 is designed as a constriction at a downstream point where the oil connecting line 56 branches off from the vertical section 53 of the rear oil supply line 51. Consequently, oil pressure is ensured for the oil flowing in the main oil passage 36 through the oil connecting line 56. In this state, oil coming from the oil connecting line 56 is introduced into the secondary oil passage 57.

[0033] As in the Fig. 4 and Fig. As shown in Figure 8, the auxiliary oil passage 57 extends along the entire longitudinal extent of the upper crankcase section 17, parallel to the lateral width of the engine 10, in the upper region of the upper crankcase section 17. Furthermore, the auxiliary oil passage 57 is located between the vertical section 53 of the rear oil supply line 51 and the main oil passage 36, as viewed in a side view of the engine 10. The oil connecting line 56 communicates with a central point in the auxiliary oil passage 57, located laterally across the engine 10. The respective rear piston nozzles 41, which are installed corresponding to the respective cylinders, communicate with the auxiliary oil passage 57. This ensures that the oil reaching the auxiliary oil passage 57 from the main oil passage 36 via the rear oil supply line 51 and the oil connecting line 56 is supplied to the rear piston nozzles 41.

[0034] As in Fig. As shown in Figure 5, the aforementioned oil connection line 56 is located near the third crankshaft bearing section #3 of the crankshaft bearing 37. The gearbox chamber 37 is located behind the third crankshaft bearing section #3, creating a large space. The side wall 48A is located behind the second crankshaft bearing section #2, and the side wall 48B is located behind the fourth crankshaft bearing section #4, thus ensuring the strength and rigidity of the second crankshaft bearing section #2 and the fourth crankshaft bearing section #4. In comparison, the third crankshaft bearing section #3 is located near the oil connection line 36, making it possible to form a thickened, curved reinforcement section 60 between the third crankshaft bearing section #3 and a circumferential region of the oil connection line 56.Accordingly, the strength and rigidity of the third crankshaft bearing section #3 are increased by the thickened reinforcement area 60.

[0035] As in the Fig. 4, Fig. 7 and Fig. As shown in Figure 8, a ventilation chamber 58 is located in an upper part of the upper crankcase section 17, which separates oil contained in blow-by gas, integrated with the upper crankcase section 17 adjacent to a rear side of the auxiliary oil passage 57. The oil separated in the ventilation chamber 58 is fed to the oil pan 18 ( Fig. 3) via an oil return line 59, which is located in the Fig. 4 and Fig. The vent chamber 58 is covered by a vent chamber cover 61 ( as shown in Figure 5). Fig. 2), which is attached from above to the upper crankcase part 17.

[0036] The above setup according to the present embodiment achieves the following effects (1) to (6): (1) As in the Fig. 5 and Fig. As shown in Figure 8, the oil connecting line 56 runs continuously through the lower crankcase part 16 and the upper crankcase part 17, branching off from the rear oil supply line 51, which supplies oil from the main oil passage 36 to the transmission oil line 50, which is formed in the mating surface 16A of the lower crankcase part 16. Consequently, the oil is supplied to the rear piston nozzles 41 from the oil connecting line 56 through the auxiliary oil passage 57. In this way, the oil connecting line 56 branches off from the existing rear oil supply line 51, runs through the lower crankcase part 16 and the upper crankcase part 17, and can be simplified by avoiding a complex shape. Furthermore, the oil connecting line 56 is not formed by a component separate from the crankcase 11, so that the number of components, the number of assembly steps, and the weight and cost of the engine 10 can be reduced.

[0037] The oil coming from the main oil passage 36 is supplied to the rear piston nozzle 41 via the rear oil supply line 51, the oil connecting line 56, and the auxiliary oil passage 57 in a state where oil pressure is ensured. Consequently, the cooling capacity for the piston 27 can be increased by the oil expelled from the rear piston nozzle 41 and the front piston nozzle 40. (2) The rear oil supply line 51 and the oil connecting line 56 are located in the same vertical plane within the inner crankcase part 16, and their lateral positions coincide within the lower crankcase part 16. Consequently, when machining the rear oil supply line 51 and the oil connecting line 56 in the lower crankcase part 16, the machine tool, for example a drill, can be moved and tilted only in the longitudinal direction with respect to the lower crankcase part 16, and the machine tool does not need to be moved laterally with respect to the lower crankcase part 16. As a result, machining the rear oil supply line 51 and the oil connecting line 56 is simplified.Furthermore, the rear oil supply line 51 and the oil connecting line 56 are provided in the same vertical plane within the lower crankcase part 16, so that the line length of the oil connecting line 56 is also reduced and the machining time for the oil connecting line 56 can be reduced. (3) The rear oil supply line 51 and the oil connecting line 56 are arranged in the crankcase 11 at the central position in the lateral width direction of the engine 10. Consequently, oil can be supplied to the transmission oil line 50 equally on the left and right sides from the rear oil supply line 51, and oil can also be supplied to the auxiliary oil passage 57 equally on the left and right sides from the oil connecting line 56. (4) In the vertical section 53 of the rear oil supply line 51, the opening 54 is located downstream (in particular, at the boundary with the transmission oil line 50 in the vertical section 53 of the rear oil supply line 51) with respect to the point where the oil connecting line 56 branches off. Consequently, no excessive oil pressure acts on the oil flowing to the transmission oil line 50, thus preventing oil leakage from the transmission oil line 50. Furthermore, the oil pressure for expelling oil from the rear piston nozzle 41 can be advantageously ensured for the oil supplied to the rear piston nozzle 41 from the main oil passage 36 via the rear oil supply line 51, the oil connecting line 56, and the auxiliary passage 57. Furthermore, by selecting the muzzle, 54 settings of the oil pressure of the oil supplied to the rear piston nozzle 41 can be easily made. (5) As in the Fig. 4 and Fig. As shown in Figure 8, the auxiliary oil passage 57 is located between the vertical section 53 of the rear oil supply line 51 and the main oil passage 36 in the side view of the engine 10. Consequently, the rear oil supply line 51 and the oil connecting line 56, which communicate with the main oil passage 36 and the auxiliary oil passage 57, as well as the main oil passage 36 and the auxiliary oil passage 57 themselves, are located within a fixed area in the longitudinal direction of the crankcase 11. This simplifies the configuration of the aforementioned oil passage (main oil passage 36, rear oil supply line 51, oil connecting line 56, and auxiliary oil passage 57). Accordingly, the machining of these oil passages (main oil passage 36, rear oil supply line 51, oil connecting line 56, and auxiliary oil passage 57) can also be simplified. (6) In the crankcase 11, the oil channels (the rear oil supply line 51, the oil connecting line 56, and the auxiliary oil passage 57), which supply oil from the main oil passage 36 to the rear piston nozzle 41, are all located within the crankcase 11, unlike components separate from the crankcase 11. Consequently, it is possible to design the ventilation chamber 58 as an integral part of the upper crankcase section 17 adjacent to the auxiliary oil passage 57. This allows for a compact design of the engine 10 while maintaining the capacity of the ventilation chamber 58.

[0038] While the embodiment of the invention has been described to this extent, this embodiment is merely an example without limiting effect on the claims. The embodiment can be carried out in various versions, with different omissions, substitutions and modifications, without deviating from the scope of protection of the invention, since substitutions and modifications are included within the scope of protection of the claims as outlined by the claims and their equivalents.

[0039] For example, according to Fig. 10 The third crankshaft bearing section #3 of the crankshaft bearing 37 and the partition 49 of the transmission chamber 47 are connected by a connecting section 52. The third crankshaft bearing section #3 and the transmission oil line 50 can communicate with each other via a connecting groove 63 formed in the mating surface 16A at the connection area 62 in the lower crankcase part 16. The connecting groove 63 is configured such that it is surrounded by a recessed area formed in the mating surface 16A when the lower crankcase part 16 and the mating surface 17A of the upper crankcase part 17 are formed. Furthermore, the connecting groove 63 communicates with the transmission oil line 50 at the central location in the lateral width direction of the engine 10.

[0040] The oil lubricating the third crankshaft bearing section #3 is supplied to the transmission oil line 50 via the aforementioned connecting groove 63. This limits the temperature increase in the third crankshaft bearing section #3 and ensures a sufficient quantity of oil from the transmission oil line 50 to the countershaft bearing 38 and the input shaft bearing 39. Furthermore, the connecting groove 63 communicates with the transmission oil line 50 at the central point laterally to the engine 10, and the oil from the connecting groove 63 can be supplied in such a way that it is distributed evenly on the left and right sides of the transmission oil line 50.Furthermore, the third crankshaft bearing section #3 and the partition wall 49 of the gearbox chamber 47 are connected by the connecting section 52, thereby reinforcing the third crankshaft bearing section #3 and increasing the strength and rigidity of the third crankshaft bearing section #3.

[0041] As in Fig. As shown by a dashed line 9, the oil, after being filtered by the oil filter 21, can be cooled by an oil cooler 64 and then fed to the main oil passage 36. Furthermore, the engine 10, as an internal combustion engine, is not limited to a motorcycle engine, but can also be an engine for a four-wheeled car, an outboard motor, a watercraft, or a multi-purpose engine.

Claims

[1] Lubrication structure for an internal combustion engine (10), comprising: an oil pump (20) installed in a crankcase (11) formed by connecting an upper crankcase part (17) with a mating surface (16A) of a lower crankcase part (16) from above; a main oil passage (36) which is present in the lower crankcase part (16) to supply oil discharged from the oil pump (20) to the respective areas of the internal combustion engine (10); an oil supply line (51) which is present in the lower crankcase part (16) and supplies oil from the main oil passage (36) to a mating surface oil line which is formed in the mating surface (16A) of the lower crankcase part (16); an auxiliary oil passage (57) in the upper crankcase part (17) for supplying oil to a piston nozzle (40, 41) which expels oil towards a piston (27) of the internal combustion engine (10); and an oil connecting line (56), which runs across the lower crankcase part (16) and the upper crankcase part (17), branches off from the oil supply line (51) to communicate with the auxiliary oil passage (57) and to supply oil in the oil supply line (51) to the auxiliary oil passage (57). [2] Lubrication structure for an internal combustion engine according to claim 1, wherein the oil supply line (51) and the oil connecting line (56) are located in the same vertical plane within the crankcase (11). [3] Lubrication structure for an internal combustion engine according to claim 2, wherein the oil supply line (51) and the oil connecting line (56) are arranged in a central position in a lateral width direction of the engine (10). [4] Lubrication structure for an internal combustion engine according to one of claims 1 to 3, in which a constriction section is placed in the oil supply line (51) at a point where the oil connecting line (56) branches off. [5] Lubrication structure for an internal combustion engine (10) according to one of claims 1 to 4, wherein the oil supply line (51) comprises a horizontal line section (2) that communicates with the main oil passage (36) and is located in the lower crankcase part (16), extending in a horizontal direction, and a vertical line section (53) that communicates with the horizontal line section (52) and the mating surface oil line, and is located in the lower crankcase part (16), extending in a vertical direction, and The auxiliary oil passage (57) is located between the main oil passage (36) and the vertical pipe section (53) in a side view of the internal combustion engine (10). [6] Lubrication structure for an internal combustion engine (10) according to one of claims 1 to 5, wherein a ventilation chamber (58) is provided in the upper crankcase part (17) adjacent to a rear area of ​​the auxiliary oil passage (57). [7] Lubrication structure for an internal combustion engine (10) according to one of claims 2 to 6, wherein the piston nozzle (40, 41), to which oil is supplied from the auxiliary oil passage (57), is a rear piston nozzle (41) which expels oil towards a rear side of the piston (27). [8] Lubrication structure for an internal combustion engine (10) according to one of claims 1 to 7, wherein the mating surface oil line is a transmission oil line (50) which directs oil to the respective bearing sections (38, 39) which support a countershaft and a drive shaft of a transmission mechanism.

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