JP6627413B2 - Internal combustion engine lubrication structure and motorcycle - Google Patents

Description

  The present invention relates to a lubrication structure for an internal combustion engine that supplies oil to various parts of the internal combustion engine and a motorcycle.

  Generally, in a lubrication structure of an internal combustion engine, oil is pumped up from an oil pan by an oil pump, and is supplied to each part of the internal combustion engine through an oil passage branched at a main gallery. As a lubricating structure for an internal combustion engine of this type, there has been known a structure in which an oil passage toward a crankshaft and an oil passage toward various transmission shafts are separated (for example, see Patent Document 1). In the internal combustion engine described in Patent Literature 1, an oil passage from the main gallery to various speed change shafts is branched on the way, and oil is supplied to a bearing of a balancer shaft at an upper part of a crankcase through the branched oil passage.

JP 2015-090146 A

  In the lubrication structure for an internal combustion engine disclosed in Patent Document 1, an oil passage extends from a main gallery below a crankcase to a bearing of a balancer shaft above an crankcase. Since the crankshaft and the transmission shaft are arranged between the main gallery and the balancer shaft, the oil passage is complicated by forming the oil passage so as to avoid them. For this reason, the oil passage becomes longer, the pressure loss due to the flow passage resistance increases, and the oil pressure followability due to crank rotation fluctuation has deteriorated. Further, when an oil passage is formed by intersecting a plurality of pipes, the weight of the crankcase increases and burrs occur at the intersection.

  The present invention has been made in view of the above, and an object of the present invention is to provide a lubricating structure of an internal combustion engine and a motorcycle that can simplify an oil passage from a main gallery to a bearing of a balancer shaft.

A lubrication structure for an internal combustion engine according to the present invention is a lubrication structure for an internal combustion engine that supplies oil to a bearing of a balancer shaft arranged in a crankcase in parallel with a crankshaft. And a first oil passage for supplying the oil of the main gallery to the bearing of the crankshaft, and a second oil supply for supplying the oil passing through the bearing of the crankshaft to the bearing of the balancer shaft. An oil passage is formed, and a drive shaft of a transmission is disposed in the crank case in parallel with the crank shaft. The crank case branches from the middle of the second oil passage to supply oil to the drive shaft. A third oil passage for supplying is formed .

According to this configuration, oil is supplied from the main gallery to the bearing of the crankshaft through the first oil passage, and further supplied to the bearing of the balancer shaft through the second oil passage. Oil is sent to the balancer shaft bearing halfway through a first oil passage common to the crankshaft bearing. Therefore, the oil passage from the main gallery to the balancer shaft can be simplified. Since the oil passage can be shortened, the pressure loss due to the flow path resistance can be reduced, and the oil pressure followability due to crank rotation fluctuation can be improved. Further, since the first and second oil passages are formed in the crankcase, the weight of the crankcase can be reduced and a deburring operation occurs, as compared with a configuration in which a new pipeline is provided to form the oil passage. Not even. Further, the oil can be sent to the drive shaft halfway through the first and second oil passages common to the bearings of the crankshaft and the balancer shaft. Therefore, the oil passage can be simplified as compared with a configuration in which an oil passage that directly connects the bearing of the drive shaft to the main gallery is formed.

  In the lubrication structure for an internal combustion engine according to the present invention, the second oil passage is formed linearly. According to this configuration, machining of the second oil passage can be facilitated. Further, the second oil passage can be made shorter.

  In the lubrication structure for an internal combustion engine of the present invention, the balancer shaft is disposed below the crankshaft. According to this configuration, it is possible to extend the second oil passage in the vertical direction and supply oil from the crankshaft bearing to the balancer shaft bearing through the second oil passage.

  In the lubricating structure for an internal combustion engine according to the present invention, the crankcase includes an upper case and a lower case, and the first oil passage and the second oil passage are formed in the lower case. According to this configuration, since the first and second oil passages are formed in the same lower case, the oil passage can be further simplified.

  In the lubrication structure for an internal combustion engine of the present invention, the balancer shaft is a lower balancer shaft disposed below the crankshaft, and the main gallery is formed in the crankcase in front of the lower balancer shaft. According to this configuration, the front-rear width of the crankcase can be reduced as compared with the configuration in which the balancer shaft is disposed before and after the crankshaft in the crankcase. Further, the arrangement of the lower balancer shaft does not interfere with the main gallery.

  A motorcycle according to the present invention includes the above-described lubrication structure for an internal combustion engine. According to this configuration, the oil passage from the main gallery of the crankcase of the motorcycle to the bearing of the balancer shaft can be simplified.

  According to the lubrication structure for an internal combustion engine of the present invention, oil is sent to the balancer shaft bearing halfway through the first oil passage common to the crankshaft bearing. Therefore, the oil passage from the main gallery to the balancer shaft bearing can be simplified.

FIG. 2 is a perspective view of the internal combustion engine of the present embodiment. It is a right view of the crankcase of this Embodiment. It is a side view which shows the shaft arrangement concerning this Embodiment. FIG. 2 is a block diagram illustrating a lubrication path of the internal combustion engine of the present embodiment. It is a front view of the crankcase of this Embodiment. FIG. 6 is a cross-sectional view of FIG. 5 taken along line AA. It is a perspective view of the upper case and the lower case which concern on this Embodiment.

  Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings. In the following, an example in which the lubrication structure of an internal combustion engine is applied to a motorcycle will be described. However, the present invention is not limited to a motorcycle, and may be applied to other vehicles such as a four-wheeled vehicle. FIG. 1 is a perspective view of the internal combustion engine of the present embodiment. FIG. 2 is a right side view of the crankcase according to the present embodiment. FIG. 3 is a side view showing the arrangement of the shaft according to the present embodiment. In FIG. 2, for convenience of explanation, the countershaft and the clutch are indicated by two-dot chain lines, and the front balancer shaft and the drive shaft in the crankcase are indicated by broken lines.

  As shown in FIG. 1, the internal combustion engine 1 is a parallel two-cylinder engine, and is configured by disposing a cylinder 10 in a crankcase 21. The cylinder 10 is configured by attaching a cylinder head 12 and a head cover 13 to a cylinder block 11 arranged on a crankcase 21. An oil pan 22 for storing oil for lubrication and cooling is attached to a lower portion of the crankcase 21. A generator cover 23 forming a generator chamber is attached to the left side of the crankcase 21. An oil filter 25 and an oil cooler 26 are attached to a front portion of the crankcase 21.

  As shown in FIG. 2, the crankcase 21 has an upper and lower split structure including an upper case 27 and a lower case 28. By removing a clutch cover (not shown), the right space 31 of the crankcase 21 is opened to the outside. are doing. The right space 31 of the crankcase 21 is separated from a crank chamber, a transmission chamber, and the like inside the case by sidewalls of the upper case 27 and the lower case 28, and is surrounded by a peripheral wall 32 protruding from the sidewalls of the upper case 27 and the lower case 28. Space. The right space 31 of the crankcase 21 is partially visible from the outside with an opening formed by a mating surface 33 formed with the clutch cover formed on the peripheral wall 32.

  On the side wall (journal wall) of the crankcase 21, three main axes of a crankshaft 41, a countershaft 47, and a drive shaft 49 are triangularly arranged in parallel. The crankshaft 41 is housed in a crank chamber inside the case, and is rotatably supported by a mating surface 34 of the upper case 27 and the lower case 28. The counter shaft 47 is housed in a transmission chamber inside the case, and is rotatably supported by the side wall of the upper case 27 behind the crankshaft 41. The drive shaft 49 is accommodated in a transmission chamber inside the case, and is rotatably supported by the mating surface 34 of the upper case 27 and the lower case 28 behind the counter shaft 47.

  A front balancer shaft 51 is arranged in front of the crankshaft 41, and a lower balancer shaft 54 is arranged below the crankshaft 41. The front balancer shaft 51 is housed in a front balancer chamber (not shown), and is rotatably supported by a mating surface 34 of the upper case 27 and the lower case 28. The lower balancer shaft 54 is rotatably supported by a mating surface 35 (see FIG. 6) of the lower case 28 and the balancer housing 29 by attaching the balancer housing 29 to the lower case 28. By attaching and detaching the balancer housing 29 to and from the lower case 28, the lower balancer shaft 54 is detached, and the one-axis balancer and the two-axis balancer can be switched.

  In the right space 31 of the crankcase 21, a primary drive gear 42 of the crankshaft 41, a primary driven gear 48 of the countershaft 47, a front balancer driven gear 52 of the front balancer shaft 51, and a lower balancer driven gear 55 of the lower balancer shaft 54. Is contained. The primary drive gear 42 meshes with a primary driven gear 48, a front balancer driven gear 52, and a lower balancer driven gear 55. In this way, by driving three types of gears with a single gear, there is no need to separately cut the gears into the crankshaft 41, and the overall length of the crankshaft 41 is shortened.

  The right space 31 of the crankcase 21 is open to the outside with the mating surface 33 with the clutch cover as an opening as described above. The primary drive gear 42 is exposed to the outside from the crankcase 21 except for a part, and the clutch 57 and the primary driven gear 48 are entirely exposed to the outside. The front balancer driven gear 52 is hidden inside the crankcase 21, and the lower balancer driven gear 55 is exposed outside the crankcase 21 except for a part. By exposing the gears from the right space 31 to the outside in this manner, the alignment (phase adjustment) between the gears is facilitated.

  As shown in FIG. 3, the crankshaft 41 is configured by connecting a crank web 43 with a crank pin (not shown) and a crank journal (not shown). A piston 45 is connected to the crankpin via a connecting rod 44, and the reciprocating motion of the piston 45 is converted into a rotational motion of the crankshaft 41. The rotation of the crankshaft 41 is transmitted to the counter shaft 47 via the primary drive gear 42 and the primary driven gear 48. The rotation of the counter shaft 47 is transmitted to the drive shaft 49 at a predetermined speed ratio according to the combination of the transmission gears (not shown).

  The rotation of the crankshaft 41 is transmitted to the front balancer shaft 51 via the primary drive gear 42 and the front balancer driven gear 52, and transmitted to the lower balancer shaft 54 via the primary drive gear 42 and the lower balancer driven gear 55. You. The periodic vibration generated in the crankshaft 41 is canceled by the front balancer shaft 51 and the lower balancer shaft 54. A space in the crankcase 21 (see FIG. 2) is provided by disposing a connecting rod 44 upward, a lower balancer shaft 54 below, a front balancer shaft 51 forward, and a counter shaft 47 rearward with the crankshaft 41 as the center. Is being used effectively.

  Since the lower balancer shaft 54 is arranged below the crankshaft 41 in the crankcase 21 configured as described above, the front-rear width of the crankcase 21 is reduced as compared with the configuration in which the balancer shaft is arranged before and after the crankcase 21. The size can be reduced, and the mass can be further concentrated. Further, since the main gallery 62 (see FIG. 2) is formed in front of the lower balancer shaft 54, the arrangement of the lower balancer shaft 54 is prevented from interfering with the main gallery 62. In this case, the lubrication path for each part of the internal combustion engine 1 must be changed because it is different from the configuration in which the main gallery is disposed immediately below the crankshaft as in a normal crankcase.

  In particular, a lubrication path for the crankcase 21 specialized in a two-axis balancer structure in which the balancer shafts 52 and 54 can be arranged in front of and below the crankshaft 41 is required. In the present embodiment, an oil passage 103 extending from the bearing 102 of the crankshaft 41 to the bearing 104 of the lower balancer shaft 54 is formed downstream of the oil passage 101 extending from the main gallery 62 to the bearing 102 of the crankshaft 41 (see FIG. 4). See FIG. 6). Since the oil is sent to the bearing 104 of the lower balancer shaft 54 halfway through the same oil passage as the bearing 102 of the crankshaft 41, it is possible to simplify the oil passage.

  Hereinafter, the lubrication path of the internal combustion engine formed in the crankcase will be described with reference to FIG. FIG. 4 is a block diagram showing a lubrication path of the internal combustion engine of the present embodiment.

  As shown in FIG. 4, oil is stored in an oil pan 22 below the crankcase 21 (see FIG. 1). The oil in the oil pan 22 is sucked from the strainer by an oil pump 61 driven by a counter shaft 47. The oil sucked by the strainer is sent to the oil filter 25 by the oil pump 61. The oil in the oil filter 25 is sent to the oil cooler 26 by the oil pump 61 and then sent to the main gallery 62. At this time, in the oil filter 25, fine foreign substances in the oil are removed by the filter, and the oil is cooled in the oil cooler 26.

  The oil filter 25 and the oil cooler 26 are arranged on the front surface of the crankcase 21 (see FIG. 5). On the installation surface of the oil filter 25, an inlet 64 connected to the oil pump 61 and an outlet 65 connected to the oil cooler 26 are formed (see FIG. 5). The inlet 64 of the oil filter 25 is formed below the center, and the outlet 65 of the oil filter 25 is formed at the center. On the installation surface of the oil cooler 26, an inlet 67 connected to the oil filter 25 and an outlet 68 connected to the main gallery 62 are formed (see FIG. 5). The inlet 67 of the oil cooler 26 is formed at the center, and the outlet 68 of the oil cooler 26 is formed above the center.

  The oil in the main gallery 62 passes through oil passages 72a-72c in the right, middle, and left journal walls 71a-71c (see FIG. 7) of the lower case 28, and each bearing 73a- of the front balancer shaft 51, respectively. 73c. The oil in the right bearing 73a of the front balancer shaft 51 is supplied to the sub gallery 76 through an oil passage 75a in a right journal wall (not shown) of the upper case 27. The oil in the sub gallery 76 is supplied to the piston jet 77 and used for cooling the piston 45 (see FIG. 2). Further, the oil in the sub gallery 76 is supplied to a bearing 78 of a turbo shaft (not shown) of the supercharger.

  The oil in the bearing 73c of the left front balancer shaft 51 is supplied to the cylinder head 12 through an oil passage 75c in a left journal wall (not shown) of the upper case 27. The oil in the cylinder head 12 passes through the inside of a camshaft (not shown) to lubricate the contact portion between the cam and the tappet, and an oil return passage 85 formed in the upper case 27 and a cam chain chamber 93 (see FIG. 5). ) Is returned to the oil pan 22. As described above, the lubrication path from the main gallery 62 to the sub gallery 76 and the lubrication path from the main gallery 62 to the cylinder head 12 are formed separately.

  The oil in the main gallery 62 passes through the oil passages 101a-101c in the right, middle, and left journal walls 71a-71c (see FIG. 7) of the lower case 28, and passes through the bearings 102a of the crankshaft 41, respectively. -102c. The oil in the right and middle bearings 102a and 102b of the crankshaft 41 is supplied to the bearings 104a and 104b of the lower balancer shaft 54 through the oil passages 103a and 103b in the journal walls 71a and 71b. The oil passage 103a on the right side branches in the middle, and oil is supplied to the drive shaft 49 through the oil passage 105. The oil in the bearing 102c on the left side of the crankshaft 41 is supplied to the counter shaft 47 through an oil groove on the journal wall 71c.

  As described above, the lubrication path from the main gallery 62 to the bearings 73a to 73c of the front balancer shaft 51 and the lubrication path from the main gallery 62 to the bearings 102a to 102c of the crankshaft 41 are formed separately in the crankcase 21. Have been. The oil is supplied to the sub gallery 76 and the cylinder head 12 through the lubrication paths of the bearings 73a and 73c of the front balancer shaft 51. The oil is supplied to the bearings 104 a and 104 b of the lower balancer shaft 54, the counter shaft 47, and the drive shaft 49 through the lubrication paths of the bearings 102 a to 102 c of the crankshaft 41.

  Hereinafter, the lubrication structure of the internal combustion engine will be described in detail. The lubrication path of the lower balancer shaft will be described with reference to FIGS. FIG. 5 is a front view of the crankcase of the present embodiment. FIG. 6 is a cross-sectional view of FIG. 5 taken along line AA. FIG. 7 is a perspective view of the upper case and the lower case of the present embodiment. FIG. 6 omits a fastening bolt and a counter shaft for convenience of explanation.

  As shown in FIGS. 5 and 6, the crankcase 21 includes an upper case 27 and a lower case 28 which are split vertically, and a balancer housing 29 is attached to the lower case 28 below the crankshaft 41. A common tightening bolt (not shown) is inserted into the upper case 27, the lower case 28, and the balancer housing 29, and a mating surface 34 between the upper case 27 and the lower case 28 and a mating surface 35 between the lower case 28 and the balancer housing 29 are formed. It is tightened with tightening bolts. A front balancer shaft 51, a crankshaft 41, and a drive shaft 49 are supported on the mating surface 34 of the upper case 27 and the lower case 28.

  A counter shaft 47 (see FIG. 3) is supported on a side surface of the upper case 27, and a lower balancer shaft 54 is supported on a mating surface 35 of the lower case 28 and the balancer housing 29. That is, in the crankcase 21, the front balancer shaft 51 is arranged in front of the crankshaft 41, and the lower balancer shaft 54 is arranged below the crankshaft 41. A counter shaft 47 and a drive shaft 49 are disposed behind the crankshaft 41. A main gallery 62 for distributing oil to various parts of the internal combustion engine 1 in front of the lower balancer shaft 54 is formed in the lower case 28 of the crankcase 21.

  The main gallery 62 is formed diagonally below and forward of the crankshaft 41 so as to avoid the lower balancer shaft 54 located immediately below the crankshaft 41. The main gallery 62 is linearly formed below the front balancer shaft 51 in the left-right direction of the lower case 28 (the direction perpendicular to the plane of FIG. 6). The upper case 27 is formed with a sub-gallery 76 that supplies oil to various parts of the internal combustion engine 1 at an obliquely forward position above the crankshaft 41 (see FIG. 7). The sub gallery 76 is formed above the front balancer shaft 51 and parallel to the main gallery 62.

  As shown in FIGS. 6 and 7, the lower case 28 is formed with oil passages 101 a to 101 c for supplying the oil of the main gallery 62 to the bearings 102 a to 102 c of the crankshaft 41. The passages 101b and 101c are shown in FIG. 4). The oil passages 101a to 101c extend obliquely from the main gallery 62 to the bearing installation surface 106 of the crankshaft 41. At this time, the oil passages 101a to 101c penetrate through the bolt holes 95 of the fastening bolts. The bolt hole 95 has a larger diameter than the shaft portion of the fastening bolt, and a gap between the bolt hole 95 and the shaft portion of the fastening bolt is an oil passage. The oil passages 101a to 101c can be shortened by linearly extending the oil passages 101a to 101c without avoiding the bolt holes 95.

  Further, the lower case 28 is formed with oil passages 103a and 103b that supply the oil passing through the right and middle bearings 102a and 102b of the crankshaft 41 to the bearings 104a and 104b of the lower balancer shaft 54. The oil passages 103a and 103b extend directly below the bearing installation surface 106 of the crankshaft 41 to the bearing installation surface 111 of the lower balancer shaft 54. Since the oil passages 103a and 103b are formed linearly in the vertical direction, the processing of the oil passages 103a and 103b can be facilitated, and the oil passages 103a and 103b can be shortened.

  Further, since the oil passages 101a to 101c and the oil passages 103a and 103b are formed in the same lower case 28, the oil passage can be simplified. Oil grooves 107a to 107c (see FIG. 7) are formed on the bearing installation surface 106 of the crankshaft 41. The right and middle oil grooves 107a and 107b are oil passages connecting the oil passages 101a and 101b and the oil passages 103a and 103b. The left oil groove 107c extends on the upper surface of the journal wall 71c toward the countershaft 47 (see FIG. 3), and is used to supply oil that has passed through the bearing 102c of the crankshaft 41 to the countershaft 47. It is on the road.

  Further, the lower case 28 is formed with an oil passage 105 that branches off from the middle of the right oil passage 103 a and supplies the oil that has passed through the right bearing 102 a of the crankshaft 41 to the drive shaft 49. The oil passage 105 extends obliquely from the middle of the oil passage 103a to the mating surface 34 of the upper case 27 and the lower case 28. At this time, the oil passage 105 penetrates through the bolt hole 95 of the fastening bolt, and the gap between the bolt hole 95 and the shaft portion of the fastening bolt is an oil passage as described above. The oil passage 105 can be shortened by linearly extending the oil passage 105 without avoiding the bolt holes 95.

  Since the oil passage 105 extends obliquely, the oil passage 105 toward the drive shaft 49 can be shortened. An oil groove 108 (see FIG. 7) extending from the outlet of the oil passage 105 toward the drive shaft 49 is formed on the upper surface (the mating surface 34) of the journal wall 71a. Since the oil passages 101a, 103a, 105 and the oil groove 108 are formed in the journal wall 71a supporting the right end of the crankshaft 41, they are linearly arranged from the main gallery 62 toward the right end of the drive shaft 49 in a top view. Have been. Therefore, the oil passage from the main gallery 62 to the drive shaft 49 can be simplified.

  Further, the inclination angles of the oil passage 101a and the oil passage 105 with respect to the mating surface 34 of the upper case 27 and the lower case 28 are formed to be the same, and the diameters of the oil passage 101a and the oil passage 105 are formed to be the same. Accordingly, the oil passages 101a and 105 can be formed by processing the crankcase 21 from the same direction with a processing tool having the same diameter, and the processing cost can be reduced. The outlet of the oil passage 105 is an orifice installation portion 109 in which an orifice (not shown) can be installed. By installing the orifice in the orifice installation section 109, even if the oil passage 105 has the same diameter as the oil passage 101a, it is possible to suppress the oil flow from the oil passage 105 to the drive shaft 49.

  As described above, the oil is sent from the main gallery 62 to the bearings 102a to 102c of the crankshaft 41, and the oil of the bearings 102a and 102b is supplied to the bearings 104a and 104b of the lower balancer shaft 54 through the oil passages 103a and 103b. . The oil in the bearing 102a is supplied to the drive shaft 49 through an oil passage 105 branched in the middle of the oil passage 103a. Some of the oil passages 101a and 101b are also used by the crankshaft 41 and the lower balancer shaft 54, and some of the oil passages 103a are also used by the lower balancer shaft 54 and the drive shaft 49. Therefore, it is possible to simplify the lubrication path in the crankcase 21 and shorten the entire length of the oil passage.

  As described above, according to the present embodiment, the oil is supplied from the main gallery 62 to the bearings 102a to 102c of the crankshaft 41 through the oil passages 101a to 101c, and further passed through the oil passages 103a and 103b. Oil is supplied to bearings 104a and 104b of the shaft 54. The oil is sent to the bearings 104a and 104b of the lower balancer shaft 54 halfway through oil passages 101a and 101b common to the bearings 102a and 102b of the crankshaft 41. Therefore, the oil passage from the main gallery 62 to the lower balancer shaft 54 can be simplified. Since the oil passage can be shortened, the pressure loss due to the flow path resistance can be reduced, and the oil pressure followability due to crank rotation fluctuation can be improved. Further, since an oil passage is formed in the crankcase 21, the weight of the crankcase 21 can be reduced and a deburring operation does not occur as compared with a configuration in which an oil passage is formed by providing a new pipeline.

  Note that the present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range in which the effects of the present invention are exhibited. In addition, the present invention can be appropriately modified and implemented without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the oil passage 103 is formed in the right and middle journal walls 71a and 71b, but is not limited to this configuration. It is sufficient that the oil passage 103 is formed in the journal wall 71 on which the lower balancer shaft 54 is supported. For example, when the lower balancer shaft 54 is supported by the middle and left journal walls 71b and 71c, the oil passage 103 is formed in the journal walls 71b and 71c.

  In the above-described embodiment, the two front balancer shafts 51 and the lower balancer shaft 54 are arranged in the crankcase 21. However, the present invention is not limited to this configuration. It is sufficient that at least one balancer shaft is disposed in the crankcase 21.

  Further, in the above-described embodiment, the front balancer shaft 51 is disposed on the mating surface 34 of the upper case 27 and the lower case 28, but the present invention is not limited to this configuration. The front balancer shaft 51 may be arranged on either the upper case 27 or the lower case 28.

  Further, in the above-described embodiment, the crankcase 21 is configured to include the upper case 27 and the lower case 28 of the upper and lower split structure. However, the present invention is not limited to this configuration. The crankcase 21 may be configured to include a left case and a right case having a left / right split structure.

  Further, in the above-described embodiment, the oil passage 103 is formed in a straight line, but is not limited to this structure. The oil passage 103 only needs to be formed so that the oil that has passed through the bearing 102 of the crankshaft 41 can be supplied to the lower balancer shaft 54, and may be formed in, for example, an arc shape.

  In the above-described embodiment, the lower balancer shaft 54 is arranged on the mating surface 35 of the lower case 28 and the balancer housing 29. However, the present invention is not limited to this configuration. The lower balancer shaft 54 may be disposed on the lower case 28. In this case, the balancer housing 29 may not be provided.

  Further, in the above-described embodiment, the lower balancer shaft 54 is arranged below the crankshaft 41, but is not limited to this configuration. Instead of the lower balancer shaft 54, a rear balancer shaft may be arranged behind the crankshaft 41.

  In the above-described embodiment, the oil passages 101 and 103 are formed in the same lower case 28, but the present invention is not limited to this structure. For example, the oil passages 101 and 103 may be formed over the upper case 27 and the lower case 28.

  In the above-described embodiment, the oil is supplied to the drive shaft 49 through the oil passage 105 branched from the middle of the oil passage 103a. However, the present invention is not limited to this structure. The drive shaft 49 may be supplied with oil through another lubrication path.

  Further, in the above-described embodiment, the oil groove 107 is formed in the bearing installation surface 106 of the journal wall 71 so that the oil passes through the bearing 102 of the crankshaft 41. However, the present invention is not limited to this configuration. Any structure may be used as long as oil can pass through the bearing 102 of the crankshaft 41. For example, an oil groove may be formed in the bearing 102, or an oil groove may be formed in the crankshaft 41.

  As described above, the present invention has an effect that the oil passage from the main gallery to the bearing of the balancer shaft can be simplified, and is particularly useful for a lubrication structure of an internal combustion engine of a motorcycle.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 21 Crankcase 27 Upper case 28 Lower case 41 Crankshaft 49 Drive shaft 51 Front balancer shaft 54 Lower balancer shaft (balancer shaft)
62 Main gallery 73 Bearing of front balancer shaft 101 Oil passage (first oil passage)
102 Crankshaft bearing 103 Oil passage (second oil passage)
104 Bearing of lower balancer shaft 105 Oil passage (third oil passage)
109 Orifice installation part

Claims (6)

A lubrication structure for an internal combustion engine that supplies oil to bearings of a balancer shaft arranged in parallel with a crankshaft in a crankcase,
In the crankcase, a main gallery that distributes oil to various parts of the internal combustion engine, a first oil passage that supplies the oil of the main gallery to the bearing of the crankshaft, and an oil that has passed through the bearing of the crankshaft. A second oil passage for supplying to a bearing of the balancer shaft is formed ;
A drive shaft of a transmission is arranged in the crank case in parallel with the crank shaft,
A lubrication structure for an internal combustion engine , wherein a third oil passage that branches off from the middle of the second oil passage and supplies oil to the drive shaft is formed in the crankcase .   The lubricating structure for an internal combustion engine according to claim 1, wherein the second oil passage is formed in a straight line.   The lubricating structure for an internal combustion engine according to claim 1 or 2, wherein the balancer shaft is disposed below the crankshaft. The crankcase is composed of an upper case and a lower case,
The lubricating structure for an internal combustion engine according to any one of claims 1 to 3, wherein the first oil passage and the second oil passage are formed in the lower case. The balancer shaft is a lower balancer shaft arranged below the crankshaft,
The lubrication structure for an internal combustion engine according to any one of claims 1 to 4, wherein the main gallery is formed in the crankcase in front of the lower balancer shaft. A motorcycle comprising the internal combustion engine lubrication structure according to any one of claims 1 to 5 .

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