Engine and method for manufacturing an engine

Abstract

To improve assembly workability of an engine.SOLUTION: In an engine (1), a split face (LD) of a crank case (11) is offset to one of right and left sides from a stud bolt (71) between cylinders. A main shaft (31) penetrates a first crank case (11R), which is one of the right and left crank cases with a narrower width, and attached to a second crank case (11L) at a position where the main shaft does not penetrate the second crank case (11L), the second crank case being the other one of the right and left crank cases with a larger width. When a predefined component near the main shaft (31) including the first crank case (11R) is not attached, the first crank case (11R) is movable to a position where it is inserted into the main shaft (31) and fixed to the second crank case (11L), with the main shaft (31) attached to the second crank case (11L).SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an engine and a method for manufacturing an engine.

Background Art

[0002] An engine in which a left - right split crankcase, a cylinder block, and a cylinder head are fastened with stud bolts is known. An engine configured with parallel two cylinders and having a configuration in which the split surface of the crankcase is offset to the side of the transmission located on the left side of the crankcase is disclosed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of a parallel two - cylinder engine, it is desirable to arrange the stud bolts between the cylinders at equal positions from the center of each cylinder bore. However, there is a possibility that the split surface of the crankcase may not be at an equal position from the center of each cylinder, and the stud bolts may not be arranged at the desired positions. In the engine described in Patent Document 1, since the split surface of the crankcase is offset to one side (left or right) of the crankcase, it becomes easier to arrange the stud bolts at equal positions from the center of each cylinder. However, since either the left or right crankcase becomes wide, the workability involving the movement of the wide crankcase deteriorates. For example, the workability may deteriorate when passing the crankshaft through the wide crankcase. The present invention has been made in view of the above circumstances, and an object thereof is to improve the assembly workability of the engine.

Means for Solving the Problems

[0005] In an engine comprising a split crankcase, a parallel twin-cylinder cylinder block, and a cylinder head fastened together with stud bolts, and a main shaft and counter shaft constituting at least a part of a transmission located within the crankcase, the split surface of the crankcase is offset to one side from the stud bolts between the cylinders, the main shaft is mounted to the second crankcase at a position where it passes through the narrower first crankcase on one side but not through the wider second crankcase on the other side, and when predetermined parts around the main shaft, including the first crankcase, are not mounted, the engine is provided such that the first crankcase can be moved to a position where it is inserted onto the main shaft and fixed to the second crankcase, with the main shaft mounted to the second crankcase.

[0006] Furthermore, in a method for manufacturing an engine in which a left and right split crankcase, a parallel twin cylinder block, and a cylinder head are fastened together with stud bolts, and a main shaft and counter shaft constituting at least a part of a transmission are provided within the crankcase, the split surface of the crankcase is offset to one side to the left or right from the stud bolts between the cylinders, the main shaft is a member that penetrates the narrower first crankcase on one side but does not penetrate the wider second crankcase on the other side, and is attached to the second crankcase in a position where the main shaft is attached to the second crankcase during engine assembly, and the first crankcase is inserted onto the main shaft and joined to the second crankcase. [Effects of the Invention]

[0007] According to the present invention, the ease of engine assembly can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side cross-sectional view of an engine according to an embodiment of the present invention. [Figure 2]This is a cross-sectional view of the engine, taken by cutting it through a plane passing through the cylinder section, crankshaft, main shaft, and countershaft. [Figure 3] This is a diagram showing the end face of a cylinder block. [Figure 4] This is a diagram showing the left crankcase from the split surface side. [Figure 5] This is a diagram showing the right-side crankcase from the split surface side. [Figure 6] This diagram shows the connecting passage along with the surrounding configuration with the left and right crankcases fastened and fixed together. [Figure 7] This diagram illustrates the assembly of the main shaft and the left and right crankcases. [Figure 8] This is a cross-sectional view showing the pump shaft together with the surrounding structure. [Figure 9] This diagram illustrates the assembly of the pump shaft and the left and right crankcases. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a side cross-sectional view of engine 1 according to an embodiment of the present invention. Engine 1 is a water-cooled engine mounted on a motorcycle, and can also be called an internal combustion engine or power unit. Engine 1 comprises a crankcase 11 that rotatably supports a crankshaft 10, and a cylinder section 12F that forms the front cylinder (also called the front bank) that extends forward and upward from the top of the crankcase 11. The cylinder section 12F comprises a cylinder block 12a, a cylinder head 12b connected to the upper surface of the cylinder block 12a, and a head cover 12c that covers the upper surface of the cylinder head 12b.

[0010] A cylinder bore 15 is formed in the cylinder block 12a, and a piston 16 is provided in the cylinder bore 15. The piston 16 is connected to the crankshaft 10 via a connecting rod 17. The cylinder head 12b is formed with an intake port 18a and an exhaust port 18b, and intake valves 19a and exhaust valves 19b for opening and closing the respective ports 18a, 18b are arranged. Between the cylinder head 12b and the head cover 12c, a valve operating mechanism 20 for driving the respective valves 19a, 19b is arranged.

[0011] In this description, the descriptions of directions such as front, rear, left, right, up, and down are the directions based on the engine 1 unless otherwise specified, and are consistent with the directions based on the motorcycle on which the engine 1 is mounted. The symbol FR shown in each figure indicates the front of the engine, the symbol UP indicates the upper part of the engine, and the symbol LH indicates the left side of the engine.

[0012] The crankcase 11 is formed as a hollow case in which a sealed crank chamber 11a for housing the main part of the crankshaft 10 (such as the crank web 10c) and a transmission chamber 11b for housing the transmission 21 are partitioned by a partition wall 11c. The crankcase 11 of the present embodiment is of a left-right split type, and an oil pan 22 is integrally formed at the lower part of the crankcase 11. The oil pan 22 functions as an oil storage chamber in which oil for lubricating each part of the engine 1 accumulates.

[0013] The crankshaft 10 is rotatably supported by the crankcase 11 along the left-right direction of the engine (corresponding to the vehicle width direction). The transmission chamber 11b is formed at the rear part of the crankcase 11 (behind the sealed crank chamber 11a). In the transmission chamber 11b, a main shaft 31 and a counter shaft 32 rotatably supported by the crankcase 11 are provided.

[0014] Also, in the sealed crank chamber 11a, a balancer 25 and a balancer shaft 26 for suppressing the primary vibration of the engine 1 by the piston 16 of the cylinder part 12F of the engine 1 are arranged. At the front lower part and the left side of the crankcase 11, a cartridge-type oil filter 27 and an oil cooler 28 are arranged.

[0015] Figure 2 is a cross-sectional view of the engine 1 cut along a plane passing through the cylinder block 12F, the crankshaft 10, the main shaft 31, and the countershaft 32. As shown in Figure 2, the cylinder bores 15 are arranged in the left-right direction. The sealed crank chamber 11a of the crankcase 11 communicates with the cylinder bores 15. As shown in Figures 1 and 2, a transmission 21 is formed by gear groups 31a, 32a, etc. provided on the main shaft 31 and the countershaft 32, which can transmit the rotation of the crankshaft 10 to the countershaft 32 at multiple types of gear ratios. The main shaft 31 and the countershaft 32 are arranged parallel to the crankshaft 10. The countershaft 32 functions as the output shaft of the engine 1 and drives the rear wheels, which are the drive wheels, via a power transmission mechanism (e.g., a chain transmission mechanism).

[0016] As shown in Figure 1, a feed pump 41 is arranged at the lower part of the crankcase 11, above the oil pan 22, which sucks the oil in the oil pan 22 through an oil strainer 23 and supplies it to the lubrication parts of the engine 1. The feed pump 41 includes an inner rotor 41b and an outer rotor 41c that constitute a feed pump rotor 41r. When the inner rotor 41b rotates integrally with the pump shaft 42, the oil in the oil pan 22 is sucked and discharged to the engine lubrication parts. The pump shaft 42 is arranged parallel to the crankshaft 10 and is rotatably supported by the crankcase 11. The feed pump 41 is an example of a lubricating oil pump, and the feed pump rotor 41r is an example of a pump rotor.

[0017] As shown in Figure 2, the right ends of the crankshaft 10 and the main shaft 31 protrude to the right, which is one of the left and right outer sides, from the crankcase 11. A primary drive gear 35 is attached to the right end of the crankshaft 10. A primary driven gear 36 that meshes with the primary drive gear 35 and a clutch mechanism 51 that can interrupt the power transmission between the primary driven gear 36 and the main shaft 31 are attached to the right end of the main shaft 31.

[0018] A clutch cover 2, which functions as a right-side crankcase cover covering the right-side opening of the crankcase 11, is fastened to the right end of the crankcase 11. The crankcase 11 and the clutch cover 2 form a clutch chamber 11d that houses the clutch mechanism 51 to the right side of the sealed crank chamber 11a and transmission chamber 11b. The clutch mechanism 51 is an example of an auxiliary device on the right side of the engine, and the clutch chamber 11d is an example of an auxiliary device room on the right side of the engine.

[0019] The left end of the crankshaft 10 protrudes to the left from the crankcase 11. A generator 61, which generates electricity by the rotation of the crankshaft 10, is attached to this left end. A generator cover 3, which functions as a left-side crankcase cover covering the left-side opening of the crankcase 11, is fastened and fixed to the left end of the crankcase 11. The crankcase 11 and the generator cover 3 form a generator chamber 11e, which houses the generator 61, to the left of the sealed crank chamber 11a and the transmission chamber 11b. The generator 61 is an example of an auxiliary unit on the left side of the engine, and the generator room 11e is an example of an auxiliary unit room on the left side of the engine.

[0020] In Figure 2, the symbols LC indicate positions equal to the center C of each cylinder bore of the parallel twin cylinders. The symbols LD indicate the positions of the dividing surfaces of the left and right crankcases 11, and hereafter, the dividing surfaces will be denoted by the symbols LD. As shown in Figure 2, the dividing surfaces LD of the left and right crankcases 11 are positioned at a location offset by a value S to one side (the right side in this embodiment) from the equal position LC from the center C of each cylinder bore. The dividing surface LD is a surface that extends along a vertical plane perpendicular to the axis of the crankshaft 10. The oil pan 22 is divided into left and right halves and integrally formed in the left crankcase 11L and the right crankcase 11R, respectively.

[0021] Figure 3 shows the end face of the cylinder block 12a. In this engine 1, the cylinder block 12a and cylinder head 12b of the cylinder section 12F are stacked on the crankcase 11, and these are fastened together as a single unit by multiple stud bolts 71 (six on the cylinder section 12F in this configuration). The stud bolts 71 are inserted through bolt holes 72 provided around the cylinder bore 15. The bolt holes 72 are formed at the four corners around each cylinder bore 15, and four stud bolts 71 fasten around each cylinder bore 15. Furthermore, a common bolt hole 72 is formed between the cylinder bores 15 at the overlapping portion of the perimeters of adjacent cylinder bores 15, and two stud bolts 71 are inserted through it.

[0022] As shown in Figure 3, the dividing surfaces LD of the left and right crankcases 11 are offset to one side relative to the position LC, so that the stud bolts 71 between cylinders can be placed on position LC. This makes it easier to evenly fasten the crankcase 11, cylinder block 12a, and cylinder head 12b. The stud bolt 71 between cylinders fits into the left crankcase 11L.

[0023] A cam chain chamber 73 is formed on the right side, which is one side in the direction of the cylinder arrangement. A cam chain, which functions as a transmission member that transmits the rotation of the crankshaft 10 to the valve train 20, is arranged in the cam chain chamber 73. In this embodiment, a cam chain chamber 73 is formed on the right side of the cylinder section 12F, and a semi-cam gear train valve train drive unit is provided to drive the cam chains arranged in each cam chain chamber 73 by reducing the rotation of the crankshaft 10. The valve train drive unit has a sprocket around which one end of the cam chain is wound, and a gear train that reduces the rotation of the crankshaft 10 and transmits it to the sprocket. The sprocket and gear train are arranged together on the right side of the crankcase 11 and housed in the clutch chamber 11d.

[0024] Figure 4 shows the left crankcase 11L from the split surface LD side. The left crankcase 11L has a left main shaft hole 76L through which the left end of the main shaft 31 is fixed via a bearing 75L (see Figure 2), a left counter shaft hole 78L through which the left end of the counter shaft 32 is fixed via a bearing 77L, and a left pump shaft hole 79L through which the pump shaft 42 is inserted. An oil filter 27 and an oil cooler 28 are also provided in the left crankcase 11L.

[0025] The side wall 11LW of the left crankcase 11L also serves as the left partition wall separating the inner space of the crankcase from the generator room 11e. In the region of this side wall 11LW that overlaps with the generator room 11e in the left-right direction, a left-side connecting passage 80L is formed that communicates in the left-right direction. The left-side connecting passage 80L has a through hole 80La that penetrates in the left-right direction, and an enclosure wall 80Lb that endlessly surrounds the periphery (front-to-back and top-to-bottom) of the through hole 80La and extends in the left-right direction to the position of the dividing surface LD.

[0026] Figure 5 shows the right crankcase 11R from the split surface LD side. The right crankcase 11R has a hole 76R for the right main shaft, through which the right side of the main shaft 31 is fixed via a bearing 75R (see Figure 2), a hole 78R for the right counter shaft, through which the right end of the counter shaft 32 is fixed via a bearing 77R, and a hole 79R for the right pump shaft, through which the pump shaft 42 is inserted.

[0027] The side wall 11RW of the right crankcase 11R also serves as the right partition wall separating the inner space of the crankcase 11 from the clutch chamber 11d. In the region of this side wall 11RW that overlaps with the clutch chamber 11d in the left-right direction, a right-side communication passage 80R is formed that communicates in the left-right direction. The right-side communication passage 80R has a through hole 80Ra that penetrates in the left-right direction, and an enclosure wall 80Rb that endlessly surrounds the periphery (front-to-back and top-to-bottom) of the through hole 80Ra and extends in the left-right direction to the position of the dividing surface LD.

[0028] When the left and right crankcases 11 are fastened and fixed together, the end faces of the left and right enclosure walls 80Lb and 80Rb come into contact with each other, and through holes 80La and 80Ra within each enclosure wall 80Lb and 80Rb form an independent communication passage 80 connecting the generator chamber 11e and the clutch chamber 11d, as shown in Figure 6. In other words, the left communication passage 80L and the right communication passage 80R form an independent communication passage 80 connecting the left and right auxiliary chambers, the generator chamber 11e and the clutch chamber 11d, within the crankcase 11. A sealing material is appropriately inserted between the left and right crankcases 11.

[0029] In this engine 1, the oil in the generator chamber 11e and the oil in the clutch chamber 11d are drawn in by the first suction oil pump 91, which will be described later. In Figure 7, the flow of oil in the clutch chamber 11d by the first suction oil pump 91 is shown by arrow Yc, and the flow of oil in the generator chamber 11e is shown by arrow Ya. As shown in Figure 7, a suction port 80k connected to the first suction oil pump 91 is provided downstream of the communication passage 80, which consists of a left communication passage 80L and a right communication passage 80R, and the oil in the generator chamber 11e and the oil in the clutch chamber 11d can be drawn in from this suction port 80k. As a result, the oil in the left and right auxiliary chambers can be drawn in by a single oil pump 91.

[0030] Next, we will explain the structure related to the assembly of the main shaft 31 and the left and right crankcases 11R and 11L. As shown in Figure 2, the main shaft 31 has a structure that penetrates the right crankcase 11R but not the left crankcase 11L. Furthermore, the main shaft 31 is fixed to the left crankcase 11L via left and right bearings 75L and 75R. During engine assembly, as shown in Figure 7, the wide left crankcase 11L is rotated 90 degrees and placed on a workbench or similar surface, and the main shaft 31 is fixed to the left crankcase 11L. Then, the narrow right crankcase 11R is moved downwards from above relative to the left crankcase 11L, thereby inserting the main shaft 31 into the right crankcase 11R and moving the right crankcase 11R to a position where it can be joined to the left crankcase 11L. This process improves the workability of assembling the engine 1, and in particular, since the narrow right crankcase 11R is relatively light, the crankcase movement work is easy.

[0031] When assembling the main shaft 31 and the left and right crankcases 11R and 11L, it is necessary to remove certain parts around the main shaft 31 (such as the clutch mechanism 51) so as not to interfere with the assembly process. Also, there are parts that cannot be installed after the crankcases 11L and 11R have been fixed together. For example, parts related to the transmission 21 (such as the counter shaft 32 and gear groups 31a and 32a) must be installed on each shaft 31 and 32 and the crankcases 11L and 11R in advance.

[0032] Figure 7 shows parts that are pre-installed on each shaft 31, 32 and crankcases 11L, 11R with solid lines, and parts that are removed with dashed lines (two-dot dashed lines). However, when assembling the main shaft 31 and the left and right crankcases 11L, 11R, it is necessary to appropriately select which parts to remove and which parts to install depending on the structure of engine 1.

[0033] Furthermore, the orientation of each component when assembling the main shaft 31 and the left and right crankcases 11R and 11L does not have to be limited to the orientation shown in Figure 7. Also, the assembly work may be performed manually by an employee or using an assembly device such as a robotic arm.

[0034] Figure 8 is a cross-sectional view showing the pump shaft 42 together with the surrounding structure. This engine 1 includes a feed pump 41 that supplies oil from the oil pan 22 to the lubrication points of the engine 1, a first suction oil pump 91 which is a scavenging pump that sucks oil from the generator chamber 11e, and a second suction oil pump 92 which is a scavenging pump that sucks oil from the sealed crank chamber 11a. These pumps 41, 91, and 92 supply oil to the lubrication points (piston 16, valve train 20, transmission 21, clutch mechanism 51, etc.), and oil discharged from the lubrication points is quickly recovered into the oil pan 22.

[0035] As shown in Figure 8, the feed pump 41, the first suction oil pump 91, and the second suction oil pump 92 are arranged on a common pump shaft 42. More specifically, the pump structure is described in detail, and the casings 41g, 91g, and 92g for the feed pump 41, the first suction oil pump 91, and the second suction oil pump 92 are integrally formed in the left crankcase 11L. Each casing 41g, 91g, and 92g is formed side by side in the left-right direction. The pump rotors 41r, 91r, and 92r of each pump 41 are arranged within each casing 41g, 91g, and 92g, and each pump rotor 41r, 91r, and 92r are attached to the pump shaft 42, which penetrates each casing 41g, 91g, and 92g in the left-right direction.

[0036] The rotation of the pump shaft 42 activates the pumps 41, 91, and 92. In this case, the feed pump 41 draws oil from the oil pan 22 through the oil strainer 23 and pumps it into the oil line formed in the left crankcase 11L. Reference numeral 93 in Figure 8 indicates a relief valve. The relief valve 93 adjusts the oil pressure in the oil line to an appropriate range. The oil that has lubricated the lubrication points is supplied to the oil pan 22 via the oil cooler 28 by the first suction oil pump 91 and the second suction oil pump 92.

[0037] As shown in Figure 8, the first suction oil pump 91, which sucks oil from the generator room 11e, is located on the far left, so that it can efficiently suck oil from the generator room 11e. Furthermore, since this engine 1 has an independent communication passage 80 connecting the generator chamber 11e and the clutch chamber 11d, the first suction oil pump 91 can also draw oil from the clutch chamber 11d. In other words, the first suction oil pump 91 serves as both an oil pump for drawing oil from the generator chamber 11e and an oil pump for drawing oil from the clutch chamber 11d. Therefore, the number of oil pumps can be reduced. The first suction oil pump 91 is an example of an oil pump for auxiliary equipment room suction, and the second suction oil pump 92 is an example of a pump for crankcase suction.

[0038] Next, we will explain the structure related to the assembly of the pump shaft 42 and the left and right crankcases 11R and 11L. As shown in Figure 8, the pump shaft 42 has a structure that penetrates the right crankcase 11R but not the left crankcase 11L. Furthermore, the pump shaft 42 is fixed to the left crankcase 11L. An oil pump driven gear 94 is attached to the right end of the pump shaft 42. Furthermore, an auxiliary drive oil pump 95 for driving the hydraulic control system auxiliary equipment is positioned between the oil pump driven gear 94 and the feed pump 41 on the pump shaft 42.

[0039] The oil pump driven gear 94 meshes with a gear that transmits rotation from the crankshaft 10. This gear train is located in the clutch chamber 11d. Hydraulic control system auxiliary equipment is not particularly limited, but examples include the hydraulic operating mechanism of the clutch mechanism 51 and the hydraulic operating mechanism of the transmission 21. The auxiliary drive oil pump 95 is a necessary pump when a hydraulic control system auxiliary is installed, and unnecessary when a hydraulic control system auxiliary is not installed. This auxiliary drive oil pump 95 consists of a casing 95g integrally formed with the right crankcase 11R and a pump rotor 95a attached to the pump shaft 42. When a hydraulic control system auxiliary is not installed, the pump rotor 95a is not installed, and the right crankcase 11R is shared.

[0040] During engine assembly, as shown in Figure 9, the left crankcase 11L is installed rotated 90 degrees, and the pump shaft 42 is fixed to the left crankcase 11L. Then, the narrower right crankcase 11R is moved downward from above relative to the left crankcase 11L, thereby inserting the pump shaft 42 into the right crankcase 11R and moving the right crankcase 11R to a position where it can be joined to the left crankcase 11L. This process improves the ease of assembly of the engine 1, and in particular, the crankcase movement work is easy because the narrower right crankcase 11R is relatively lighter.

[0041] When assembling the pump shaft 42 with the left and right crankcases 11R and 11L, it is necessary to remove certain parts around the pump shaft 42 (such as the oil pump driven gear 94 and the pump rotor 95a of the auxiliary drive oil pump 95) so as not to interfere with the assembly process. Also, there are parts that cannot be installed after the crankcases 11L and 11R have been fixed together. For example, the pump rotors 92g, 91g, and 41g on the left crankcase 11L side must be attached to the pump shaft 42 beforehand.

[0042] Furthermore, the split surface LD of the crankcase 11 is not limited to being offset to the right of the inter-cylinder stud bolts 71, but may also be offset to the left of the inter-cylinder stud bolts 71. In addition, at least a part of the engine's internal structure, including the main shaft 31, pump shaft 42, and each oil pump 41, 91, 92, 95, may be arranged or structured symmetrically.

[0043] As explained above, in the engine 1 of this implementation, as shown in Figure 2, the dividing surface LD of the crankcase 11 is offset to one side from the stud bolts 71 between the cylinders, and the main shaft 31 is attached to the left crankcase 11L in a position where it passes through the narrower right crankcase 11R on one side, but does not pass through the wider left crankcase 11L on the other side. Furthermore, when the predetermined parts around the main shaft 31, including the right crankcase 11R, are not attached, the right crankcase 11R can be moved to a position where it is inserted onto the main shaft 31 and fixed to the left crankcase 11L, with the main shaft 31 attached to the left crankcase 11L.

[0044] This configuration allows the stud bolts 71 between cylinders to be mounted in a position that allows for even fastening of the cylinder sections 12F of the engine 1 while avoiding the position of the dividing surface LD of the crankcase 11. As shown in Figure 7, during engine assembly, after mounting the main shaft 31 to the wider left crankcase 11L, the narrower right crankcase 11R can be moved to insert the main shaft 31 through the case 11R, thereby fixing the crankcases 11 together. Since the narrower right crankcase 11R is relatively lighter, the workability of assembling the engine 1 is improved.

[0045] The right crankcase 11R corresponds to the first crankcase in this disclosure, and the left crankcase 11L corresponds to the second crankcase in this disclosure. As shown in Figure 3, the cylinder block 12a has a cam chain chamber 73 on one side in the direction of cylinder alignment, and the dividing surface LD of the crankcase 11 is offset towards the cam chain chamber 73 side. This configuration improves the ease of assembly around the cam chain.

[0046] As shown in Figure 8, the stud bolts 71 between cylinders are fitted into the wide left crankcase 11L, and the casings 41g, 91g, and 92g for the oil pumps 41, 91, and 92 are formed in the left crankcase 11L, with the pump rotors 41r, 91r, and 92r positioned within the casings 41g, 91g, and 92r. With this configuration, the pump rotors 41r, 91r, and 92r can be made wider, and the oil pump capacity can be secured without increasing the outer diameter of the pump rotors 41r, 91r, and 92r.

[0047] Furthermore, an oil pan 22 is integrally formed at the bottom of the crankcase 11, and the oil pan 22 is divided into left and right halves, each formed in the respective crankcases 11L and 11R. This configuration suppresses the increase in the number of parts and improves the assembly workability of the engine 1.

[0048] Furthermore, the crank chamber within the crankcase 11 is a sealed crank chamber 11a from which oil is drawn in by a second suction oil pump 92. The second suction oil pump 92 and the feed pump 41, which functions as a lubrication oil pump supplying oil to lubrication points, are arranged side by side in the crankcase 11. This configuration allows for the integration of multiple oil pumps, simplifies the structure around the oil pumps, and improves the assembly efficiency of the engine 1.

[0049] Furthermore, the engine 1 has a generator room 11e and a clutch room 11d which constitute the left and right auxiliary equipment rooms, and a first suction oil pump 91 which functions as an auxiliary equipment room suction oil pump that draws oil from the generator room 11e and the clutch room 11d. The first suction oil pump 91 is arranged alongside the second suction oil pump 92 and the feed pump 41. With this configuration, multiple oil pumps can be consolidated, the structure around the oil pumps can be simplified, and the assembly workability of the engine 1 can be improved.

[0050] Furthermore, the engine 1 of this embodiment includes a first suction oil pump 91 that sucks oil from the generator room 11e, which constitutes one of the left or right auxiliary equipment rooms, and discharges it to the oil pan 22, and a connecting passage 80 (left connecting passage 80L and right connecting passage 80R) that connects the generator room 11e and the clutch room 11d, which constitute the left and right auxiliary equipment rooms, and moves the oil from the clutch room 11d to the generator room 11e by the suction force of the first suction oil pump 91. With this configuration, the oil supplied to the left and right auxiliary equipment rooms can be sucked up by a common oil pump, and the number of parts and weight of the engine 1 can be reduced.

[0051] Furthermore, the casing 91g and the connecting passage 80 of the first suction oil pump 91 are formed in the crankcase 11. This configuration reduces the number of parts in the engine 1 compared to when the casing 91g and the connecting passage 80 are manufactured as separate parts.

[0052] Furthermore, the engine 1 has a second suction oil pump 92 that functions as a crankcase suction oil pump for drawing oil from the crankcase within the crankcase, and the second suction oil pump 92 is located on the same shaft as the first suction oil pump 91. With this configuration, the pump shaft 42 that drives the two oil pumps 92 and 91 can be made common, and the number of parts in the engine 1 can be reduced.

[0053] Furthermore, it has a feed pump 41 that supplies oil from the oil pan 22 to the lubrication points, and the feed pump 41 is arranged on the same shaft as the first suction oil pump 91 and the second suction oil pump 92. With this configuration, the pump shaft 42 that drives the three oil pumps 41, 91, and 92 can be made common, and the number of parts of the engine 1 can be reduced.

[0054] Furthermore, the crankcase 11 is split into left and right sections, with the first suction oil pump 91, the second suction oil pump 92, and the feed pump 41 arranged on the same axis in the left crankcase 11L. This configuration allows the three oil pumps 91, 92, and 41 to be arranged together in the left crankcase 11L, improving the ease of assembly of the engine 1.

[0055] Furthermore, the oil pump driven gear 94 and other components that make up the gear train of the oil pump drive system are located in the right-side crankcase 11R. This configuration simplifies the structure around the oil pump and improves the ease of assembling engine 1.

[0056] Furthermore, the right crankcase 11R has an auxiliary drive oil pump 95 that functions as another oil pump supplying oil to the hydraulic control system auxiliary equipment, and the auxiliary drive oil pump 95 is located on the same axis as the other oil pumps 91, 92, and 41. With this configuration, the four oil pumps 95, 91, 92, and 41 can be consolidated, simplifying the structure around the oil pumps and improving the ease of assembly of the engine 1.

[0057] [Other embodiments] The above embodiments represent only one aspect of the present invention and can be modified and applied as needed without departing from the spirit of the invention.

[0058] For example, in the above embodiment, the dividing surface LD of the crankcase 11 is shown as being offset to the right of the inter-cylinder stud bolts 71, but it is not limited to this, and may be offset to the left of the inter-cylinder stud bolts 71. Also, the shape and arrangement of the main shaft 31 and each oil pump may be symmetrical. Furthermore, although the above embodiment described the application of the present invention to engine 1 and a method for manufacturing (assembly method) of engine 1 shown in Figure 1, the present invention may also be applied to an engine different from engine 1 and a method for manufacturing (assembly method) of that engine. Furthermore, the engines to which the present invention can be applied are not limited to engines mounted on motorcycles, but may also be applied to engines mounted on saddle-type vehicles other than motorcycles, vehicles other than saddle-type vehicles, and other mobile devices.

[0059] [Configurations supported by the above embodiment] The above embodiment supports the following configuration.

[0060] (Configuration 1) An engine comprising a left and right split crankcase, a parallel twin cylinder block, and a cylinder head fastened together with stud bolts, and having a main shaft and a counter shaft constituting at least a part of a transmission within the crankcase, wherein the split surface of the crankcase is offset to one side to the left or right of the stud bolts between the cylinders, the main shaft is attached to the second crankcase at a position where it passes through the narrower first crankcase on one side but does not pass through the wider second crankcase on the other side, and when predetermined parts around the main shaft including the first crankcase are not attached, the engine is movable to a position where the first crankcase is inserted onto the main shaft and fixed to the second crankcase with the main shaft attached. This configuration allows the stud bolts between cylinders to be mounted in a position that allows for even fastening of the engine's cylinder sections while avoiding the division surface of the crankcase. Furthermore, during engine assembly, after mounting the main shaft to the wider second crankcase, the narrower first crankcase can be moved and the main shaft inserted through it, thereby connecting the crankcases. The narrower first crankcase can be made relatively lighter, improving the ease of engine assembly.

[0061] (Configuration 2) The engine according to Configuration 1, wherein the cylinder block has a cam chain chamber on one side in the direction of cylinder arrangement, and the dividing surface of the crankcase is offset toward the cam chain chamber side. This configuration improves the ease of assembly around the cam chain.

[0062] (Configuration 3) The engine according to Configuration 1 or 2, wherein the stud bolts between the cylinders are fitted into the second crankcase, an oil pump casing is formed in the second crankcase, and a pump rotor is arranged inside the casing. This configuration allows for a wider pump rotor, ensuring sufficient oil pump capacity without increasing the outer diameter of the pump rotor.

[0063] (Configuration 4) An engine according to any one of Configurations 1 to 3, wherein an oil pan is integrally formed at the lower part of the crankcase, and the oil pan is divided into left and right halves and formed in the first crankcase and the second crankcase, respectively. This configuration helps to limit the number of parts and improves the ease of engine assembly.

[0064] (Configuration 5) The engine according to any one of Configurations 1 to 4, wherein the crank chamber in the crankcase is a sealed crank chamber from which oil is drawn in by a suction oil pump, and the suction oil pump and the lubrication oil pump that supplies oil to the lubrication points are arranged side by side in the crankcase 11. This configuration allows for the consolidation of multiple oil pumps, simplifying the structure around the oil pumps and improving the ease of engine assembly.

[0065] (Configuration 6) The engine according to Configuration 5, wherein the engine has left and right auxiliary compartments and an auxiliary compartment suction oil pump for sucking oil from the left and right auxiliary compartments, and the auxiliary compartment suction oil pump is arranged alongside the suction oil pump and the lubrication oil pump. This configuration allows for the consolidation of multiple oil pumps, simplifying the structure around the oil pumps and improving the ease of engine assembly.

[0066] (Configuration 7) A method for manufacturing an engine comprising a left and right split crankcase, a parallel twin cylinder block, and a cylinder head fastened together with stud bolts, and the crankcase containing a main shaft and a counter shaft that constitute at least a part of a transmission, wherein the split surface of the crankcase is offset to one side to the left or right from the stud bolts between the cylinders, the main shaft is a member that penetrates the narrower first crankcase on one side but does not penetrate the wider second crankcase on the other side, and during engine assembly, the main shaft is attached to the second crankcase, and the first crankcase is inserted onto the main shaft and joined to the second crankcase. This configuration improves the ease of engine assembly. [Explanation of Symbols]

[0067] 1…Engine (internal combustion engine) 10 Crank Axle 10c Crankweb 11 Crankcase 11 11a Sealed crank chamber 11b Transmission Room 11d Clutch compartment (auxiliary equipment compartment) 11e Generator Room (Auxiliary Equipment Room) 11L Left-side crankcase (second crankcase) 11R Right-side crankcase (first crankcase) 12F Cylinder section 12a Cylinder block 12b Cylinder head 12c headcover 21 transmission 22 Oil pan 31 Main axis 32 Counter axis 41 Feed pump (lubricating oil pump) 41g, 91g, 92g, 95g Oil pump casing 41r, 91r, 92r, 95a pump rotor 42 Pump shaft 51. Clutch mechanism (auxiliary equipment) 61. Generator (auxiliary equipment) 71 Stud bolts 73 Cam chain chamber 91. First suction oil pump (oil pump for auxiliary equipment room suction) 92. Second suction oil pump (crankcase suction oil pump) 95. Oil pump for auxiliary drive LD crankcase split surface

Claims

1. In an engine in which a left and right split crankcase (11), a parallel twin cylinder block (12a), and a cylinder head (12b) are fastened together with stud bolts (71), and a main shaft (31) and a counter shaft (32) that constitute at least a part of the transmission 21 are provided inside the crankcase (11), The dividing surface (LD) of the crankcase (11) is offset to one side from the stud bolt (71) between the cylinders. The main shaft (31) is attached to the second crankcase (11L) at a position where it passes through the narrower first crankcase (11R) on one side but does not pass through the wider second crankcase (11L) on the other side. When predetermined parts around the main shaft (31), including the first crankcase (11R), are not installed, the first crankcase (11R) is movable to a position where it is inserted onto the main shaft (31) and fixed to the second crankcase (11L) while the main shaft (31) is installed on the second crankcase (11L). engine.

2. The cylinder block (12a) has a cam chain chamber (73) on one side in the direction of cylinder arrangement, The dividing surface (LD) of the crankcase (11) is offset towards the cam chain chamber (73). The engine according to claim 1.

3. The stud bolt (71) between the cylinders is fitted into the second crankcase (11L), The casings (41g, 91g, 92g) for the oil pump (41, 91, 92) are formed in the second crankcase (11L). Pump rotors (41r, 91r, 92r) are arranged within the aforementioned casing (41g, 91g, 92g). The engine according to claim 1.

4. An oil pan (22) is integrally formed at the lower part of the crankcase (11), The oil pan (22) is divided into left and right halves and formed in the first crankcase (11R) and the second crankcase (11L), respectively. The engine according to claim 1.

5. The crank chamber (11a) within the crankcase (11) is a sealed crank chamber 11a from which oil is drawn in by a suction oil pump (91). The suction oil pump (91) and the lubrication oil pump (41) that supplies oil to the lubrication points are arranged side by side in the crankcase (11). The engine according to claim 1.

6. The engine has left and right auxiliary compartments (11d, 11e) and an auxiliary compartment suction oil pump (92) that sucks oil from the left and right auxiliary compartments (11d, 11e). The auxiliary oil pump (92) is positioned alongside the suction oil pump (91) and the lubrication oil pump (41). The engine according to claim 5.

7. In a method for manufacturing an engine in which a left and right split crankcase (11), a parallel twin cylinder block (12a), and a cylinder head (12b) are fastened together with stud bolts (71), and a main shaft (31) and a counter shaft (32) that constitute at least a part of the transmission 21 are provided inside the crankcase (11), The dividing surface (LD) of the crankcase (11) is offset to one side from the stud bolt (71) between the cylinders. The main shaft (31) is a member that penetrates the narrow first crankcase (11R) on one side, but does not penetrate the wider second crankcase (11L) on the other side, and is attached to the second crankcase (11L). During engine assembly, the main shaft (31) is attached to the second crankcase (11L), and the first crankcase (11R) is inserted onto the main shaft (31) and joined to the second crankcase (11L). Engine manufacturing method.

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