ENGINE LUBRICATION STRUCTURE AND MOTORCYCLE

Abstract

Engine lubrication structure configured to supply oil from an oil pump to individual components of an engine (1) in which a balance shaft (33, 34) is arranged parallel to a crankshaft (30) in a crankcase (4), wherein: the engine (1) has a turbocharger (2) which is configured to compress intake air using exhaust gas from the engine (1), a main gallery (43) which supplies oil to a crankshaft bearing (30) via a first oil channel (44) and to a balance shaft bearing (33, 34) via a second oil channel (45), and a sub-gallery (48) which receives oil that has first been supplied to the balance shaft bearing (33, 34) via a third oil channel (49) extending from the balance shaft bearing (33, 34) to the sub-gallery (48), and which supply individual engine components that have received oil supplied to the balance shaft bearing (33, 34) are provided in the crankcase (4), and a fourth oil channel (24a), which supplies oil to the turbocharger (2), is connected to the subgallery (48).

Description

[0001] The present invention relates to a lubricating structure of an engine having a turbocharger, an engine lubricating structure for supplying oil to individual components of an engine, and a motorcycle having one of such engine lubricating structures.

[0002] Among motorcycles with a supercharger, there are some that have a turbocharger that uses engine exhaust gas as a power source for the turbocharger. In such motorcycles, an exhaust manifold is attached to the exhaust ports of a cylinder head, and the turbocharger is attached to the exhaust manifold.

[0003] Typically, turbochargers are conveniently lubricated by supplying a portion of the oil circulating in the engine to a drive section of the turbocharger (see, for example, JP S61-47436 U). JP S61-47436 U discloses a turbocharger lubrication structure in which oil pumped up from an oil pan is supplied to a main gallery via an oil cooler and an oil filter. Oil is supplied to the turbocharger from a passage branching off from an oil passage located upstream of the oil cooler.

[0004] In general, in engine lubrication structures, oil is pumped from an oil pan by an oil pump and supplied to individual engine components via an oil passage branching off a main gallery. Among such engine lubrication structures, there are some in which oil is supplied from a main gallery directly to shaft bearings where high oil pressure is required (see, for example, JP H04-107543 U). JP H04-107543 U discloses an engine with a dual-axis balancer structure in which balancer shafts are arranged in front of and behind a crankshaft. Oil passages to the bearings of the front and rear balancers and the bearings of various transmission shafts branch off a main gallery where the oil pressure is high.

[0005] In JP S61-47436 U, pumped-up oil is fed directly to a turbocharger without passing through the oil cooler or oil filter. This can cause problems such as oil reaching the main gallery via the oil cooler and oil filter without sufficient pressure, and only an insufficient amount of oil is supplied from the main gallery to the individual engine shafts.

[0006] The present invention has been made in view of the above problems, and an object of the invention is therefore to provide an engine lubricating structure that can appropriately supply oil to individual shafts in the engine while lubricating a turbocharger, and a motorcycle using the same.

[0007] In the engine lubrication structure disclosed in JP H04-107543 U, high-pressure oil is supplied to the bearing of each shaft because the oil passages to the bearings of the respective shafts branch off individually from the main gallery. However, high-pressure oil used to lubricate the bearing of each shaft is directly returned to the oil pan and thus is not used effectively. Furthermore, the oil passages, except for some of them, are not formed in a well-organized manner. The installation of new pipes causes an increase in weight and the number of machining steps, and the lengthening of the oil passages causes a certain reduction in oil pressure.

[0008] The invention has also been made in view of the above problems, and therefore, another object of the invention is to provide an engine lubricating structure that can shorten oil passages without causing an increase in weight or the number of machining steps, and enables effective use of high-pressure oil supplied from a main gallery, and a motorcycle using the same.

[0009] DE 694 04 782 T2 discloses an engine lubrication structure of an internal combustion engine that supplies oil to a drive shaft of a transmission arranged parallel to a crankshaft and a balance shaft in a crankcase. The balance shaft, the crankshaft, and the drive shaft are arranged on a joining surface between an upper housing and a lower housing of the vertically split crankcase, and the drive shaft is arranged on a rear side of the crankshaft when the internal combustion engine is arranged horizontally in the installed position. A main channel branches into several oil passages formed in the crankcase so that oil can be distributed to respective sections of the internal combustion engine, including a crankshaft bearing, a balance shaft bearing, and the drive shaft.

[0010] Another engine lubrication structure is known from US 2006 / 0 068 656 A1, in which the bearings of a balance shaft are supplied with lubricating oil from an oil pump via oil channels. An engine turbocharger connected externally to a separate oil channel is also supplied with lubricating oil from the oil pump.

[0011] Another engine lubrication structure of an internal combustion engine for a motorcycle is known from WO 2015 / 004 758 A1.

[0012] From JP 5 956 055 B2, a motorcycle internal combustion engine is known in which an oil filter and an oil cooler are arranged side by side in a right-left direction on an outer surface of an engine body. A first engine lubrication channel, extending in the right-left direction, is connected to a drain channel for the oil cooler. A second engine lubrication channel is connected to the first engine lubrication channel to extend forward and is arranged parallel to an inflow channel and an outlet channel for the oil filter. A third engine lubrication channel is connected to the second engine lubrication channel and extends upward from the second engine lubrication channel in front of the first engine lubrication channel.

[0013] A first aspect of the invention provides an engine lubricating structure having the features of claim 1.

[0014] With this configuration, high-pressure oil is supplied from the oil pump to the main gallery, and high-pressure oil is also supplied from the main gallery to the balance shaft bearing. Furthermore, oil from the balance shaft bearing is supplied to the other shafts and the turbocharger via the sub-gallery and oil passages. Thus, high-pressure oil can be used effectively. Since the oil passage leading to the turbocharger is connected to the sub-gallery, the turbocharger can be lubricated while oil is properly supplied to the bearings. Since the same oil passages are used to supply oil to the balance shaft bearing and the sub-gallery, there is no need to form independent oil passages for these purposes in the crankcase. Consequently, independent pipes are not required, the weight or number of machining steps does not increase, and the oil passages can be shortened.

[0015] In the engine lubrication structure according to the first aspect of the invention, the sub-gallery is preferably provided with a piston nozzle that discharges oil to a piston. With this configuration, since oil that has passed through the balance shaft bearing is at high pressure, the oil can be reused to cool the piston by supplying the oil from the sub-gallery to the piston nozzle.

[0016] In the engine lubrication structure according to the first aspect of the invention, the balancer shaft is preferably arranged below the sub-gallery, and the main gallery is arranged below the balancer shaft. With this configuration, the oil passage from the main gallery to the balancer shaft and the oil passage from the balancer shaft to the sub-gallery can be formed straight, thereby allowing these oil passages to be formed short to prevent oil pressure reduction.

[0017] In the engine lubricating structure according to the first aspect of the invention, an oil return passage that returns oil supplied to the turbocharger to the crankcase is preferably connected to the crankcase, the balance shaft is disposed forward of the crankshaft, and the oil return passage is connected to a wall of a balance chamber that houses the balance shaft. With this configuration in which the oil return passage is connected to the wall of the balance chamber, when oil used to lubricate the interior of the turbocharger is returned to the interior of the crankcase, the oil flows down the wall surface of the balance chamber. Consequently, the oil is not mixed, and thus oil scattering and generation of air bubbles can be prevented.

[0018] The first aspect of the invention also provides a motorcycle having an engine lubricating structure according to the first aspect of the invention.

[0019] The first aspect of the invention enables oil to be appropriately supplied to the individual shafts in the engine while lubricating the turbocharger.

[0020] A second aspect of the invention provides an engine lubricating structure having the features of claim 6.

[0021] With this configuration, high-pressure oil from the oil pump is supplied to the main gallery, and high-pressure oil from the main gallery is also supplied to the balancer shaft bearing. Consequently, the balancer shaft is supported for rotation by the bearing via an oil film, preventing the balancer shaft from locking. Since high-pressure oil is supplied to the sub-gallery via the balancer shaft bearing, the oil from the sub-gallery can be reused to lubricate various engine components. Furthermore, since the same oil passage is used to supply oil from the main gallery to the balancer shaft bearing and the sub-gallery, independent oil passages for these purposes are not required in the crankcase. Consequently, independent pipes are not required, the weight or number of machining steps does not increase, and the oil passages can be shortened.

[0022] In the engine lubrication structure according to the second aspect of the invention, the main gallery is preferably arranged below the balance shaft, and the sub-gallery is formed above the balance shaft in parallel with the main gallery. With this configuration, oil can be supplied from the main gallery, which is arranged below the balance shaft, to the sub-gallery, which is arranged above the balance shaft, via the balance shaft bearing. Since the main gallery and the sub-gallery are parallel to each other, the areas in which these galleries are formed in the crankcase can be made small, and the crankcase can be downsized accordingly.

[0023] In the engine lubrication structure according to the second aspect of the invention, the crankcase is preferably vertically divisible and includes an upper case and a lower case, the main gallery is formed in the lower case, the sub-gallery is formed in the upper case, and the balance shaft bearing is formed at a connecting plane of the upper case and the lower case. With this configuration, the oil is returned to the inside of the crankcase even if oil leakage occurs at the bearing arrangement position. Since no sealing member is required to prevent oil leakage, the number of components can be reduced.

[0024] In the engine lubrication structure according to the second aspect of the invention, the balance shaft is preferably arranged on a straight line connecting the main gallery and the sub-gallery in the crankcase. With this configuration, the oil passages can be shortened, and a reduction in oil pressure can be prevented.

[0025] In the engine lubrication structure according to the second aspect of the invention, the sub-gallery preferably supplies the oil that has passed through the balance shaft bearing to a piston nozzle, which serves to cool a piston. With this configuration, since the oil that has passed through the balance shaft bearing has a high pressure, the oil can be reused for cooling the piston by supplying it from the sub-gallery to the piston nozzle.

[0026] In the engine lubrication structure according to the second aspect of the invention, a lubrication path from the main gallery to the sub-gallery and a lubrication path from the main gallery to a crankshaft bearing are preferably different from each other. With this configuration, the influence of a decrease in oil pressure in the sub-gallery on the oil pressure at the crankshaft bearing can be reduced.

[0027] In the engine lubrication structure according to the second aspect of the invention, the above-mentioned oil gallery is preferably formed on one of the left side and the right side in the crankcase, and another oil gallery that supplies oil from the main gallery to a cylinder head is formed on the other side. With this configuration, the oil pressure in the main gallery can be evenly distributed between the left and right sides. Furthermore, since the sets of oil galleries are spaced apart from each other in the left-right direction, a decrease in oil pressure in the sub-gallery does not affect the oil pressure in the cylinder head.

[0028] In the engine lubrication structure according to the second aspect of the invention, the balance shaft is preferably a front balance shaft arranged in front of the crankshaft, and a lower balance shaft is arranged below the crankshaft, and the main gallery is formed in front of the lower balance shaft in the crankcase. With this configuration, the front-rear width of the crankcase can be made smaller than in the case where balance shafts are arranged in front of and behind the crankshaft in one crankcase. Furthermore, the lower balance shaft does not interfere with the arrangement of the main gallery.

[0029] The second aspect of the invention also provides a motorcycle having the engine lubrication structure according to the second aspect of the invention. With this configuration, high-pressure oil can be supplied to individual components of the motorcycle's engine and can be effectively utilized there.

[0030] According to the second aspect of the invention, since oil is supplied from the main gallery to the sub-gallery via the balancer shaft bearing, high-pressure oil coming from the sub-gallery can be reused to lubricate various components of the engine. Furthermore, since the same oil passage is used to supply oil from the main gallery to the balancer shaft bearing and the sub-gallery, independent pipes are not required, and the oil passages can be shortened. Fig. 1 is a right side view showing a general configuration of a motorcycle engine according to an embodiment of a first aspect of the present invention. Fig. 2 is a front view of the Fig. 1 shown engine and its surroundings. Fig. 3 is a front view of the engine including a turbocharger according to the embodiment of the first aspect of the invention. Fig. 4 is a perspective view of a part of the engine including the turbocharger according to the embodiment of the first aspect of the invention. Fig. 5 is a front view of a crankcase according to the embodiment of the first aspect of the invention. Fig. 6 is a right side view of the engine according to the embodiment of the first aspect of the invention, from which a clutch housing is removed. Fig. 7 is a sectional view along line AA in Fig. 5 of the crankcase. Fig. 8 is a sectional view along line BB in Fig. 5 of the crankcase. Fig. 9 is a perspective view of an engine according to an embodiment of a second aspect of the invention. Fig. 10 is a right side view of a crankcase according to the embodiment of the second aspect of the invention. Fig. 11 is a side view showing an arrangement of shafts used in the embodiment of the second aspect of the invention. Fig. 12 is a block diagram illustrating lubrication paths of the engine according to the embodiment of the second aspect of the invention. Fig. 13 is a front view of the crankcase according to the embodiment of the second aspect of the invention. Fig. 14A, Fig. 14B and Fig. 14C are sectional views of the crankcase according to the embodiment of the second aspect of the invention. Fig. 15A and Fig. 15B are another set of sectional views of the crankcase according to the embodiment of the second aspect of the invention. Fig. 16 is a perspective view of an upper case and a lower case of the crankcase according to the embodiment of the second aspect of the invention.

[0031] An embodiment of a first aspect of the present invention will be described in detail below with reference to the accompanying drawings. Although the first aspect of the invention, which relates to an engine with a turbocharger, is applied to a motorcycle, its scope is not limited to this case. The first aspect of the invention can also be applied to other types of motorcycles, buggy-type motorized tricycles, automobiles, etc. Regarding the directions relative to the vehicle, the forward, backward, left, and right directions are indicated by arrows FR, RE, L, and R, respectively. It should also be noted that in each drawing, some of the components and elements are omitted for simplicity.

[0032] First, a general configuration of a motorcycle according to the embodiment of the first aspect of the invention will be described with reference to Fig. 1 to 4 described. Fig. 1 is a right side view showing a general configuration of an engine 1 of the motorcycle according to the embodiment of the first aspect of the invention. Fig. 2 is a front view of the engine 1 and its surroundings. Fig. 3 is a front view of the engine 1 including a turbocharger 2 according to the embodiment of the first aspect of the invention. Fig. Figure 4 is a perspective view of a part of the engine 1 including the turbocharger 2 according to the embodiment of the first aspect of the invention. Fig. 1 and Fig. 2, the turbocharger 2 and other components and elements are omitted for simplicity.

[0033] As in Fig. 1 and Fig. 2, the motorcycle according to the embodiment of the first aspect of the invention is a motorcycle equipped with the turbocharger 2, that is, a turbocharger that uses exhaust gas of the engine 1 as a drive source (see FIG. Fig. 3). The engine 1 is a two-cylinder, four-stroke internal combustion engine. The engine 1 is configured such that components such as pistons (not shown) are housed in a cylinder assembly 12 formed of a cylinder block 10 and a cylinder head 11, and a cylinder head cover 13 is attached to the top of the cylinder assembly 12 (cylinder head 11). A crankcase 4, which houses a crankshaft (not shown), is attached to a lower, rear portion of the cylinder assembly 12.

[0034] The crankcase 4 is configured to be divisible in the vertical direction and includes an upper case 40 and a lower case 41. A space for containing various shafts is formed in the crankcase 4 by combining the upper case 40 and the lower case 41 together. An upper front portion of the upper case 40 has an opening, and the cylinder block 10 is attached to the upper case 40 so as to close the opening. The lower case 41 is formed with an opening in the bottom, and an oil pan 5 is attached to the lower case 41 so as to close the opening.

[0035] As in Fig. 3, an oil cooler 14 for cooling oil present in the engine 1 and an oil filter 15 for filtering dirty oil are mounted on a front portion of the lower case 41 at a right position and a left position, respectively.

[0036] The crankcase 4 is formed with respective openings on the left and right sides. A magnet cover 16 (in Fig. 1 not shown) which covers a magnet (not shown) is attached to the crankcase 4 so as to close its left opening, and a clutch cover 17 which covers a clutch (not shown) is attached to the crankcase 4 so as to close its right opening.

[0037] The engine 1 according to the embodiment of the first aspect of the invention is a water-cooled engine equipped with a water pump 18 for supplying cooling water. The right-side surface of the crankcase 4 is provided with the water pump 18 in front of the clutch cover 17. Although not shown in the drawings, a side stand for supporting a vehicle body (engine 1) is arranged on the lower left side of the crankcase 4.

[0038] As in Fig. 3 and Fig. As shown in Figure 4, the turbocharger 2 is arranged in front of the engine 1 so as to be close to (next to) the front surface of the crankcase 4. The turbocharger 2 includes a housing body 23 formed by integrally molding an exhaust manifold (hereinafter referred to as a bend portion 21) and a turbine housing (hereinafter referred to as a housing portion 22). The bend portion 21 is attached to exhaust ports of the engine 1, thereby securing the turbocharger 2 to the engine 1.

[0039] The housing portion 22 is shaped like a cylinder whose axis extends in the vehicle width direction (left-right direction) and accommodates a turbine (not shown) inside. The bent portion 21 is connected to an upper portion of the cylindrical housing portion 22. The bent portion 21 includes a connecting portion connected to the housing portion 22 and a pair of branch pipes 21a extending upward from the connecting portion. Tip portions of the branch pipes 21a are connected to two respective front exhaust ports of the cylinder head 11.

[0040] An exhaust pipe (not shown) is connected to a right end portion of the housing portion 22. A bearing housing 24, which houses a bearing (not shown) of a turboshaft (not shown), is arranged on the left side of the housing portion 22. A compressor housing 25, which houses a compressor (not shown), is arranged on the left side of the bearing housing 24.

[0041] One end of an intake pipe 24a for supplying oil from the crankcase 4 to the turbocharger 2 is connected to an upper portion of the bearing housing 24, and the other end of the intake pipe 24a is connected to the upper housing 40. In particular, the upper housing 40 is formed with a connection port 40a for the intake pipe 24a at a front right position. As shown in Fig. 8, the connecting terminal 40a is cylindrical and projects forward from a right end portion of a sub-gallery 48 (described below).

[0042] The intake pipe 24a extends from the connecting port 40a to the left along the sub-gallery 48 and is then bent downward to extend around (underneath) the housing portion 22. The intake pipe 24a extends under an operating shaft 28 of a relief valve 26 (described below) so that it does not pass through a movable portion of the operating shaft 28. Then, the intake pipe 24a extends upward along the housing portion 22 and is connected to an upper end portion of the bearing housing 24.

[0043] One end of a drain pipe 24b for returning oil used to lubricate the interior of the turbocharger 2 to the crankcase 4 is connected to a lower portion of the bearing housing 24, and the other end of the drain pipe 24b is connected to the lower housing 41. Specifically, the lower housing 41 is formed with a connection port 41a for the drain pipe 24b at a front center (in the left-right direction) position. The connection port 41a is formed on the front surface of the lower housing 41 below the turbocharger 2.

[0044] A turbine is mounted on one (right) end portion of the turboshaft extending in the vehicle width direction, between the housing portion 22 and the compressor housing 25, and the compressor is mounted on the other (left) end portion of the turboshaft. Thus, the turbine and compressor can rotate together on the turboshaft.

[0045] The relief valve 26 is arranged below the compressor housing 25. The relief valve 26 is provided for adjusting the inflow rate of exhaust gas into the turbine (housing section 22). The relief valve 26 has a main body unit 27 for adjusting the flow rate of exhaust gas inside the housing section 22 by detecting the pressure in the compressor housing 25. The main body unit 27 is arranged below the compressor housing 25, and the operating shaft 28, which extends to the housing section 22, is attached to the main body unit 27.

[0046] A valve cone (not shown) is attached to the housing-side tip of the operating shaft 28. The valve cone causes the valve to open or close when the operating shaft 28 is driven by the main body unit 27, thereby adjusting the flow rate of exhaust gas inside the housing section 22. For example, when the turbocharger pressure has increased rapidly, the main body unit 27 drives the operating shaft 28, causing the valve cone to open, thereby reducing the flow rate of exhaust gas into the housing section 22.

[0047] A compressor pipe (not shown) for introducing air into the turbocharger 2, which has passed through an air cleaner (not shown), is connected to a left end portion of the compressor housing 25. An intake pipe (not shown) for introducing air into the engine 1, which has been compressed in the compressor housing 25, is connected to an upper portion of the compressor housing 25.

[0048] In the motorcycle equipped with the thus configured turbocharger 2, while exhaust gas from the engine 1 is introduced into the housing portion 22 through the bent portion 21 according to a throttle operation of a rider, external air is introduced into the compressor housing 25 via the air cleaner and the compressor pipe.

[0049] In the housing section 22, the turbine is rotated at high speed by a flow of exhaust gas. The exhaust gas is expelled to the outside via the exhaust pipe. In the compressor housing 25, the compressor rotates according to the rotation of the turbine, thereby compressing air there. The compressed air is admitted to the engine 1 via the intake pipe.

[0050] By compressing air by the turbocharger 2 in the above manner, an air-fuel mixture exceeding a total displacement of the engine 1 can be supplied to the engine 1 to increase its output power.

[0051] A portion of the oil circulating through the engine 1 is supplied from the sub-gallery 48 to the turbocharger 2 (bearing housing 24) through the intake pipe 24a, thereby lubricating the turboshaft and bearing. After being used to lubricate the turbocharger 2, the oil is returned to the crankcase 4 (oil pan 5) via the drain pipe 24b. The sectional area of ​​the drain pipe 24b is larger than that of the intake pipe 24a. Thus, the resistance of the oil return flow channel is reduced, and thus the return of oil from the turbocharger 2 can be performed smoothly.

[0052] Incidentally, in conventional motorcycles equipped with a turbocharger—that is, a turbocharger that compresses intake air using exhaust gas from an engine—the turbocharger is arranged in front of an oil pan. In this case, if the drive shaft (turboshaft) of the turbocharger is located below an oil surface in the oil pan, oil used to lubricate the interior of the turbocharger is not easily returned to the oil pan. To solve this problem, a turbocharger oil return passage is provided with a separate (dedicated) oil pump (scavenge pump), which forcibly returns oil used to lubricate the turbocharger to the oil pan.

[0053] Since the turbocharger, in particular, is a component that heats up to very high temperatures (e.g., higher than 800°C), if oil remains inside the turbocharger after the engine is stopped, not only will heat accelerate oil deterioration, but the bearing may also seize. It is therefore desirable to expel oil from the turbocharger as soon as the engine is stopped.

[0054] In view of the foregoing, in the embodiment of the first aspect of the invention, the sub-gallery 48 for supplying oil to the shafts in the engine 1 is provided with the oil passage (connecting port 40a and intake pipe 24a) to the turbocharger 2. With this measure, not only can oil be supplied to the shafts at a sufficiently high pressure, but oil can also be supplied to the turbocharger 2. In addition, since the connecting port 41a of the drain pipe 24b is arranged below the turbocharger 2, oil can be smoothly discharged from the turbocharger 2 using its own weight.

[0055] In the following, with reference to Fig. 5 to 8, a description will be given of the arrangement of shafts and oil supply paths in the engine 1 according to the embodiment of the first aspect of the invention. Fig. 5 is a front view of the crankcase 4 according to the embodiment of the first aspect of the invention. Fig. 6 is a right side view of the engine 1 according to the embodiment of the first aspect of the invention, from which the clutch cover 17 is removed. Fig. 7 is a sectional view along line AA in Fig. 5 of the crankcase 4. Fig. 8 is a sectional view along line BB in Fig. 5 of the crankcase 4.

[0056] First, the arrangement of the waves is described. As in Fig. 5 and Fig. As shown in Fig. 6, in addition to a crankshaft 30, various shafts for transmitting drive power of the engine 1 are housed in the crankcase 4. The following describes the arrangements of the various shafts using the position of the crankshaft 30 as a reference. The crankshaft 30 is housed slightly forward of the center of the crankcase 4. Two pistons (not shown) are attached to the crankshaft 30 via respective connecting rods (not shown) and arranged in the axial direction.

[0057] A countershaft 31 is arranged at the upper rear side of the crankshaft 30. The right end of the countershaft 31 is provided with a clutch (not shown). A drive shaft 32 is arranged at the lower rear side of the countershaft 31. The drive shaft 32 is provided with various gear ratios. A plurality (two according to the embodiment) of balance shafts 33 for preventing rotation-induced vibration of the engine 1 are arranged around the crankshaft 30.

[0058] The balance shafts 33 include a first balance shaft 34, which is arranged in front of the crankshaft 30, and a second balance shaft 35, which is arranged (to the right) below the crankshaft 30. The first balance shaft 34 and the second balance shaft 35 extend parallel to the axis of the crankshaft 30 and are arranged such that the straight line connecting the first balance shaft 34 and the crankshaft 30 and the second balance shaft 35 and the crankshaft 30 form approximately a right angle.

[0059] As in Fig. As shown in Fig. 7, in the first embodiment of the first aspect of the invention, the first balance shaft 34, the crankshaft 30, and the drive shaft 32 are arranged on a connecting plane of the upper case 40 and the lower case 41. Specifically, three bearings are formed on the connecting plane of the upper case 40 and the lower case 41 so as to be arranged in the front-rear direction, and receive the first balance shaft 34, the crankshaft 30, and the drive shaft 32 in this order from the front. The second balance shaft 35 is supported by the lower case 41 and a balance case 6 that accommodates the second balance shaft 35. A bearing is formed on a connecting plane of the lower case 41 and the balance case 6, and the second balance shaft 35 is set in this bearing.

[0060] A multitude (only two are in Fig. 7) of through holes 42 / 60 through which fastening bolts 7 are inserted are formed through the lower case 41 and the balance case 6. The plurality of through holes 42 / 60 are formed at such positions as to insert the crankshaft 30 or the second balance shaft 35 therebetween in the front-back direction. The upper case 40 is formed with screw holes (not shown) at positions corresponding to the plurality of through holes 42 / 60 respectively. The upper case 40, the lower case 41, and the balance case 6 are fixed to each other (integrated together) by inserting the fastening bolts 7 into the through holes 42 / 60 from below and screwing them into the upper case 40.

[0061] The following is a description of the oil passages in the crankcase 4. As in Fig. As shown in Figure 7, a main gallery 43, which is an oil passage in the engine 1, is formed in the lower case 41 below the first balance shaft 34 in front of the second balance shaft 35. The main gallery 43 extends in the left-right direction.

[0062] Oil passages 44 and 45 for supplying oil from the main gallery 43 to the crankshaft 30 and the first balance shaft 34, respectively, and an oil passage 46 for supplying oil from the crankshaft 30 to the second balance shaft 35 are formed in the lower case 41. An oil passage 47 for supplying oil to the drive shaft 32 is connected to the oil passage 46. The oil passages 44 and 47 are formed to extend obliquely through the respective through holes 42. With this measure, the through holes 42 for the fastening bolts 7 can be used as parts of the oil passages.

[0063] On the other hand, in the upper housing 40, the sub-gallery 48 is formed above the first balance shaft 34 so as to extend in the left-right direction. An oil passage 49 for supplying oil from the first balance shaft 34 to the sub-gallery 48 is formed in the upper housing 40.

[0064] In the exemplary embodiment, oil stored in the oil pan 5 is pumped upward by an oil pump and supplied to the main gallery 43. The oil supplied to the main gallery 43 is supplied to the shafts and bearings while maintaining a sufficiently high pressure. A portion of the oil, ie, oil supplied to the first balance shaft 34, is then supplied to the sub-gallery 48 through the oil passage 49.

[0065] The oil supplied to the sub-gallery 48 is then fed to the turbocharger 2 (see Fig. 3) via the connecting port 40a of the intake pipe 24a and the intake pipe 24a. As described below, oil is also supplied to piston nozzles 50 (see Fig. 8). In this way, oil that was used to lubricate the first balance shaft 34 is reused to lubricate the turbocharger 2 and cool the pistons. As described above, oil can be supplied to the individual components provided in the engine 1.

[0066] In the embodiment, the shafts are arranged as described above, and the main gallery 43 and the sub-gallery 48 are formed in open areas located around the two balance shafts 33. Specifically, the first balance shaft 34 is arranged below the sub-gallery 48, and the main gallery 43 is formed below the first balance shaft 34. This structure allows the oil passages to the shafts (bearings) to be formed in the form of straight through holes. Thus, the oil passages can be formed by simple drilling, and the number of machining steps can be reduced.

[0067] In particular, since the oil passage 45 from the main gallery 43 to the first balance shaft 34 and the oil passage 49 from the first balance shaft 34 to the sub-gallery 48 can be straight, the oil passages 45 and 49 can be made short, thereby preventing a reduction in oil pressure.

[0068] Since the crankshaft 30 and the second balance shaft 35 are adjacent to each other in the lower case 41, the oil passage 46 for connecting the crankshaft 30 and the second balance shaft 35 can be easily formed by drilling. Thus, the crankcase 14 can be made lighter than a structure that separates (independent) oil passages formed using unused fixed portions of the crankcase 4.

[0069] As in Fig. As shown in Figure 8, a portion of the oil supplied to the subgallery 48 is contained deep therein and supplied to the piston nozzles 50. The pistons (not shown) are cooled by oil ejected to them from the piston nozzles 50. The supply of oil to the piston nozzles 50 reduces the oil pressure in the subgallery 48. However, since the lubrication path from the main gallery 43 (see Figure 8) is Fig. 7) to the sub-gallery 48 is different from that from the main gallery 43 to the bearing of the crankshaft 30, the influence of the oil pressure reduction due to the ejection by the piston nozzles 50 on the pressure of oil supplied to the bearing of the crankshaft 30 can be reduced.

[0070] Since the piston nozzles 50 have open ends, when the engine 1 is stopped and the driving of the oil pump is stopped, air inside the crankcase 4 is sucked through the piston nozzles 50 and fed into the turbocharger 2 (see. Fig. 3) via the sub-gallery 48 and the intake pipe 24a (see Fig. 3) As a result, when oil in the oil passages is replaced with air, the air can be easily admitted into the oil passages, allowing for smooth oil discharge. Thus, the oil passages are not clogged with oil.

[0071] In addition, since the sub-gallery 48 is arranged above the oil surface in the crankcase 4, the connecting port 40a (see Fig. 7) of the intake pipe 24a above the oil surface. This increases the degree of freedom in determining the location of the connecting port 41a of the discharge pipe 24b, which is located below the connecting port 40a of the intake pipe 24a.

[0072] Furthermore, the oil return passage (drain pipe 24b and connecting port 41a) is connected to a wall of a balance chamber that houses the first balance shaft 34. Thus, when oil used to lubricate the interior of the turbocharger 2 is returned to the interior of the crankcase 4, the oil flows down the wall surface of the balance chamber. As a result, the oil is not mixed, and thus oil scattering and the generation of air bubbles can be prevented.

[0073] As described above, according to the embodiment, high-pressure oil is supplied from the oil pump to the main gallery 43, and high-pressure oil is also supplied from the main gallery 43 to the bearings of the balance shafts 33. In addition, oil from the bearing of the first balance shaft 34 is supplied to the other shafts and the turbocharger 2 via the sub-gallery 48 and the oil passages. Thus, high-pressure oil can be effectively utilized. Since the oil passage leading to the turbocharger 2 is connected to the sub-gallery 48, the turbocharger 2 can be properly lubricated while oil is being supplied to the shafts. Since the same oil passages are used to supply oil to the bearing of the first balance shaft 34 and the sub-gallery 48, independent oil passages for these purposes do not need to be formed in the crankcase 4. Accordingly, independent pipes do not need to be provided, the weight or the number of machining steps is not increased, and the oil passages can be shortened.

[0074] The first aspect of the invention is not limited to the above embodiment and can be modified in various ways. The first aspect of the invention is not limited to the sizes, shapes, etc. shown in the accompanying drawings, and they can be appropriately modified within the scope so that the advantages of the first aspect of the invention can be obtained. Other modifications can also be appropriately made as long as the related object of the invention is achieved.

[0075] For example, although the above embodiment is directed to the two-cylinder engine 1, the invention is not limited to this case; the invention can also be applied to single-cylinder engines and engines having three or more cylinders.

[0076] Although the above embodiment is directed to the water-cooled engine 1, the invention is not limited to this case; the invention can also be applied to air-cooled engines and other types of engines.

[0077] Although in this embodiment, the sub-gallery 48 is arranged in front of the crankshaft 30, the invention is not limited to this case; the sub-gallery 48 may be arranged behind the crankshaft 30.

[0078] Although in this embodiment, oil from the sub-gallery 48 is supplied only to the turbocharger 2 and the piston nozzles 50, the invention is not limited to this case; oil may also be supplied from the sub-gallery 48 to the cylinder head 11, etc.

[0079] Although in this embodiment, when circulating in the engine 1, oil is supplied from the main gallery 43 to the sub-gallery 48 via the bearing of the first balance shaft 34, the invention is not limited to this case; oil may be directly supplied to the sub-gallery 48 from the main gallery 43.

[0080] While providing the above-described advantage that oil can be appropriately supplied to the individual shafts in the engine while lubricating the turbocharger, the first aspect of the invention is particularly useful when applied to lubricating structures of engines with a turbocharger and to motorcycles having such a lubricating structure.

[0081] An embodiment of a second aspect of the invention will be described in detail below with reference to the accompanying drawings. Although the second aspect of the invention is directed to an engine lubrication structure of a motorcycle, its scope of application is not limited to this case. The second aspect of the invention can also be applied to other types of vehicles, such as automobiles, etc. Regarding the directions relative to the vehicle, the forward, backward, left, and right directions are indicated by the arrows FR, RE, L, and R, respectively.

[0082] Fig. 9 is a perspective view of a motor 101 according to the embodiment of the second aspect of the invention. Fig. 10 is a right side view of a crankcase 121 according to the embodiment of the second aspect of the invention. Fig. 11 is a side view showing an arrangement of shafts used in the embodiment of the second aspect of the invention. In Fig. 10, for convenience, a countershaft 147 and a clutch 157 are drawn by double-dotted lines, and a front balance shaft 151 and a drive shaft 149 are drawn by broken lines.

[0083] As in Fig. As shown in Figure 9, the engine 101 is a parallel two-cylinder internal combustion engine configured such that a cylinder assembly 110 is disposed on the crankcase 121. The cylinder assembly 110 is configured such that a cylinder head 112 is disposed on a cylinder block 111 disposed on the crankcase 121, and a head cover 113 is attached to the top of the cylinder head 112. An oil pan 5 for storing oil is attached to the bottom of the crankcase 121. A generator cover 123 defining a generator space is attached to a left side portion of the crankcase 121. An oil filter 125 and an oil cooler 126 are attached to a front portion of the crankcase 121.

[0084] As in Fig. As shown in FIG. 10, the crankcase 121 is configured to be divisible in the vertical direction and includes an upper case 127 and a lower case 128. A right-side space 131 of the crankcase 121 is exposed to the outside by removing a clutch cover (not shown). The right-side space 131 of the crankcase 121 is a space separated from the inside of a crank chamber and an insert chamber by side walls of the upper case 127 and the lower case 128, and surrounded by a peripheral wall 132 protruding from side walls of the upper case 127 and the lower case 128. A part of the right-side space 131 of the crankcase 121 is viewed from the outside through an opening of a connecting surface 133 for connecting a clutch cover of the peripheral wall 132.

[0085] Three main shafts, i.e., a crankshaft 141, a countershaft 147, and a drive shaft 149, are arranged parallel to each other by side walls (bearing journal walls) of the crankcase 121 to form a triangle. The crankshaft 141 is housed inside the crank chamber and rotatably supported at a connecting plane 134 of the upper case 127 and the lower case 128. The countershaft 147 is housed inside the insert chamber, arranged behind the crankshaft 141, and rotatably supported by side walls of the upper case 127. The drive shaft 149 is housed inside the insert chamber, arranged behind the countershaft 147, and rotatably supported at the connecting plane 134 of the upper case 127 and the lower case 128.

[0086] A front balance shaft 151 is arranged in front of the crankshaft 141, and a lower balance shaft 154 is arranged below the crankshaft 141. The front balance shaft 151 is arranged in a front balance chamber 186 (see Fig. 15B) and is rotatably supported at the connecting plane 134 of the upper housing 127 and the lower housing 128. The lower balance shaft 154 is connected to a connecting plane 135 (see Fig. 14a) of the lower housing 128 and a balancer housing 129 attached to the lower housing 128. Switching between a single-axis balancer and a dual-axis balancer can be performed by attaching or removing the lower balancer shaft 154 by removing the balancer housing 129 from the lower housing 128.

[0087] A primary drive gear 142 of the crankshaft 141, a primary driven gear 148 of the countershaft 147, and a lower balancer driven gear 155 of the lower balancer shaft 154 are arranged in the right-side space 131 of the crankcase 121. The primary driven gear 148, a front balancer driven gear 152, and the lower balancer driven gear 155 mesh with the primary drive gear 142. Since the three types of gears are thus driven by the single gear, the crankshaft 141 does not need to be provided with other gears, and thus its overall length can be shortened.

[0088] As mentioned above, the right-side space 131 of the crankcase 121 is exposed to the outside through the opening of the connecting surface 133 for connecting to the clutch cover. Most of the primary drive gear 142 is exposed to the outside of the crankcase 121, and a clutch 157 is fully exposed to the outside. The front differential driven gear 152 is hidden inside the crankcase 121, and a large part of the lower differential driven gear 155 is exposed to the outside. Since the gears are thus exposed to the outside of the right-side space 131, they can be easily arranged with respect to each other (phase matching).

[0089] As in Fig. As shown in Figure 11, the crankshaft 141 is configured such that crank webs 143 are connected to each other by crankpins (not shown) and crank journals (not shown). Pistons 145 are respectively connected to the crankpins through connecting rods 144, thereby converting reciprocating motions of the pistons 145 into rotation of the crankshaft 141. Rotational power of the crankshaft 141 is transmitted to the countershaft 147 through the primary drive gear 142 and the primary driven gear 148. Rotational power of the countershaft 147 is transmitted to the input shaft 149 at a prescribed gear stage corresponding to a combination of shift gears (not shown).

[0090] Rotational energy of the crankshaft 141 is also transmitted to the front balance shaft 151 through the primary drive gear 142 and the front balance driven gear 152, and to the lower balance shaft 154 through the primary drive gear 142 and the lower balance driven gear 155. The front balance shaft 151 and the lower balance shaft 154 cancel periodic vibration of the crankshaft 141. Since the connecting rods 144, the lower balance shaft 154, the front balance shaft 151, and the countershaft 147 are arranged around the crankshaft 141, that is, respectively above, below, in front of, and behind the crankshaft 141, the space inside the crankcase 121 (see Fig. 10) be used effectively.

[0091] Since, in the thus configured crankcase 121, the lower balance shaft 154 is arranged below the crankshaft 141, the front-rear width of the crankcase 121 can be made smaller than in the case where balance shafts are arranged in front of and behind a crankshaft, and the degree of mass concentration can be reduced. Furthermore, since a main gallery 162 (see FIG. Fig. 10) is arranged in front of the lower balance shaft 154, the lower balance shaft 154 does not interfere with the arrangement of the main gallery 162. With this arrangement, which is different from a conventional arrangement in which a main gallery is arranged to the right below a crankshaft, the lubrication paths to the individual components of the engine 101 must be changed.

[0092] In particular, lubrication paths of the crankcase 121 are required that are specialized for the dual-axis balance structure in which the balance shafts 152 and 154 are arranged in front of and below the crankshaft 141. In the exemplary embodiment, a sub-gallery 176 is formed in addition to the main gallery 162 in the crankcase 121, and oil coming from the main gallery 162 is supplied to the sub-gallery 176 via a bearing 173 (see FIG. Fig. 14A) of the front balance shaft 151. Since oil that has passed through the front balance shaft 151 has a sufficiently high pressure, oil can be reused to lubricate various components of the engine 101 by causing it to pass through the subgallery 176.

[0093] Lubrication paths in the crankcase 121 of the engine 101 according to the embodiment of the second aspect of the invention will be described below with reference to a block diagram of Fig. 12 described.

[0094] As in Fig. 12, oil is collected in an oil pan 122 (see Fig. 9) located under the crankcase 121. Oil in the oil pan 122 is sucked through a strainer by an oil pump 161 driven by the countershaft 147, and then pumped to the oil filter 125 by the oil pump 161. Oil in the oil filter 125 is pumped to the oil cooler 126 and then to the main gallery 162 by the oil pump 161. Meanwhile, small foreign matter is removed from the oil by the oil filter 125, and the oil is cooled by the oil cooler 126.

[0095] As in Fig. As shown in Figure 13, the oil filter 125 and the oil cooler 126 are mounted on a front portion of the crankcase 121. The installation surface of the oil filter 125 is formed with an inlet 164 communicating with the oil pump 161 and an outlet 165 communicating with the oil cooler 126. The inlet 164 of the oil filter 125 is formed below the centerline, and the outlet 165 of the oil filter 125 is formed on the centerline. The installation surface of the oil cooler 126 is formed with an inlet 167 communicating with the oil filter 125 and an outlet 168 communicating with the main gallery 162. The inlet 167 of the oil cooler 126 is formed on the centerline, and the outlet 168 of the oil cooler 126 is formed above the centerline.

[0096] Oil present in the main gallery 162 is supplied to bearings 173a, 173b and 173c of the front balance shaft 151 through oil channels 172a, 172b and 172c, which are respectively formed in right, middle and left bearing journal walls 171a, 171b and 171c (see. Fig. 16) of the lower housing 128. Oil present in the right bearing 173a of the front balance shaft 151 is supplied to the sub-gallery 176 through an oil channel 175a formed in a right bearing journal wall 174a (see Fig. 14A) of the upper housing 127. Oil present in the sub-gallery 176 is supplied to piston nozzles 177 and used to cool the pistons 145 (see Fig. 11). Oil present in the subgallery 176 is also supplied to a bearing 178 of a turboshaft (not shown) of a turbocharger.

[0097] Oil present in the left bearing 173c of the front balance shaft 151 is supplied to the cylinder head 112 through an oil channel 175c, which is formed in a left bearing journal wall 174c (see Fig. 15A) of the upper housing 127. Oil present in the cylinder head 112 is supplied to and lubricates a cam-tappet contact portion via the interior of a camshaft (not shown), and is then supplied to the oil pan 122 via an oil return passage 185 and a timing chain space 193 formed in the upper housing 127 (see FIG. Fig. 13), etc. In this way, the lubrication path leading from the main gallery 162 to the sub-gallery 176 and the lubrication path leading from the main gallery 162 to the cylinder head 112 are formed separately from each other in the crankcase 121.

[0098] Oil present in the main gallery 162 is also supplied to bearings 202a, 202b and 202c of the crankshaft 141 through oil channels 201a, 201b and 201c, which are respectively formed in right, middle and left bearing journal walls 171a, 171b and 171c (see. Fig. 16) of the lower housing 128. Oil present in the right bearings 202a of the crankshaft 141 and oil present in the central bearing 202b of the crankshaft 141 are supplied to bearings 203a and 204b of the lower balancer shaft 154 through oil passages 203a and 203b of the journal walls 171a and 171b, respectively. Oil is supplied to the drive shaft 149 via an oil passage 205 branching off from the oil passage 203a. Oil present in the left bearing 202c of the crankshaft 141 is supplied to the countershaft 147 through an oil groove formed in the journal wall 171c.

[0099] As described above, the lubrication paths leading from the main gallery 162 to the bearings 173a to 173c of the front balancer shaft 151 and the lubrication paths leading from the main gallery 162 to the bearings 202a to 202c of the crankshaft 141 are formed separately from each other in the crankcase 121. Oil is supplied to the sub-gallery 176 and the cylinder head 112 along the lubrication paths including the bearings 173a and 173c of the front balancer shaft 151, respectively. Oil is supplied to the bearings 204a and 204b of the lower balancer shaft 154, the countershaft 147, and the drive shaft 149 along the lubrication paths including the bearings 202a to 202c of the crankshaft 141.

[0100] The engine lubrication structure according to the second aspect of the invention will be described in detail below. First, the lubrication path to the sub-gallery 176 will be described with reference to Fig. 13 and Fig. 14 described. Fig. 13 is a front view of the crankcase 121 according to the embodiment of the second aspect of the invention. Fig. 14A, Fig. 14B and Fig. 14C are sectional views along lines AA, BB and CC in Fig. 13 of the crankcase 121 according to the embodiment of the second aspect of the invention. For the sake of simplicity, fastening bolts and the countershaft 147 are shown in Fig. 14A is omitted, and the different waves are in Fig. 14B and Fig. 14C omitted.

[0101] As in Fig. 13 and Fig. As shown in Fig. 14A, the crankcase 121 is vertically separable and is formed of the upper case 127 and the lower case 128. The balance case 129 is mounted on the bottom of the lower case 128 below the crankshaft 141. Ordinary fastening bolts are inserted into the upper case 127, the lower case 128, and the balance case 129, whereby the upper case 127 and the lower case 128 are fastened together by the fastening bolts at the joint plane 134, and the lower case 128 and the balance case 129 are fastened together by the fastening bolts at the joint plane 135. The front balance shaft 151, the crankshaft 141, and the drive shaft 149 (see Fig. Fig. 11) are supported on the connecting plane 134 of the upper housing 127 and the lower housing 128.

[0102] The counterwave 147 (see Fig. 11) is supported by the side walls of the upper housing 127, and the lower balance shaft 154 is supported at the connecting plane 135 of the lower housing 128 and the balance case 129. That is, in the crankcase 121, the front balance shaft 151 is arranged in front of the crankshaft 141, and the lower balance shaft 154 is arranged below the crankshaft 141. The countershaft 147 and the drive shaft 149 are arranged behind the crankshaft 141. The main gallery 162 for distributing oil supplied from the oil pump 161 (see Fig. 12) to the individual components of the engine 101, is formed in front of the lower balance shaft 154 in the lower housing 128 of the crankcase 121.

[0103] The main gallery 162 is formed on the lower front side of the crankshaft 141 so as to bypass the lower balance shaft 154, which is arranged directly under the crankshaft 141. The main gallery 162 is formed under the front balance shaft 151 so as to extend straight in the left-right direction of the lower housing 128 (ie, perpendicular to the paper surface of Fig. 14A). The sub-gallery 176 for supplying oil to individual components of the engine 101 is formed on the upper front side of the crankshaft 141. The sub-gallery 176 is formed above the front balancer shaft 151 in parallel with the main gallery 162. With the above structure, the respective areas in which the main gallery 162 and the sub-gallery 176 are formed in the crankcase 121 can be made small, and the crankcase 121 can be downsized accordingly.

[0104] The oil passages 172a and 175a for supplying oil from the main gallery 162 to the sub-gallery 176 via the bearing 173a of the front balance shaft 151 are formed in a right portion of the crankcase 121. The oil passage 172a extends from the main gallery 162 to a mounting surface 181 for the bearing 173a of the front balance shaft 151 of the lower case 128. The oil passage 175a extends from a mounting surface 182 for the bearing 173a of the front balance shaft 151 of the upper case 127 to the sub-gallery 176. The mounting surfaces 181 and 182 for the bearing 173a of the front balance shaft 151 are provided with respective oil grooves 183 (see FIG. Fig. 16) which are oil channels connecting the oil channels 172a and 175a.

[0105] As mentioned above, the upper housing 127 and the lower housing 128 are firmly fastened to each other by the fastening bolts. Thus, the bearing 173a of the front balance shaft 151 is aligned with the mounting surface 181 of the lower housing 128 and the mounting surface 182 of the upper housing 127 without forming a gap. Since the front balance shaft 151 is accommodated in the front balance chamber 186 (see FIG. Fig. 14B), even if an oil leak occurs there, the oil can be returned to the oil pan 122 (see Fig. 9). Since the oil passage encompasses the arrangement position of the bearing 173a, no sealing member such as an O-ring is required to prevent oil leakage, unlike the case where an oil passage is formed for this purpose to bypass the arrangement position of the bearing 173a, resulting in a reduction in the number of components.

[0106] In the crankcase 121, the front balance shaft 151 is arranged approximately on the straight line connecting the main gallery 162 and the sub-gallery 176. That is, the main gallery 162, the front balance shaft 151, and the sub-gallery 176 are arranged approximately in an upward line in this order. Therefore, the oil passages 172a and 175a can be formed straight, and thus can be made short, thereby suppressing oil pressure reduction. Furthermore, since each of the oil passages 172a and 175a in the upper case 127 or the lower case 128 can be formed by a single machining operation, the number of machining steps can be reduced.

[0107] Since high-pressure oil from the oil pump 161 (see Fig. 12) of the main gallery 162, high-pressure oil from the main gallery 162 is supplied to the bearing 173a of the front balance shaft 151. Consequently, a sufficiently thick oil film is formed on the bearing 173a of the front balance shaft 151, which requires high oil pressure, thereby preventing the front balance shaft 151 from locking. When oil is supplied to the bearing 173a of the front balance shaft 151, the oil still has a sufficiently high pressure. To utilize this high oil pressure, oil that has passed through the right bearing 173a of the front balance shaft 151 is delivered to the sub-gallery 176 while maintaining its sufficiently high pressure.

[0108] As in Fig. As shown in Figure 14B, oil that has been conveyed to the subgallery 176 passes deep through the subgallery 176 and reaches the piston nozzles 177. The oil is conveyed from the piston nozzles 177 to the pistons 145 (see Figure 14B). Fig. 11), thereby cooling the pistons 145. The oil pressure in the sub-gallery 176 is reduced by supplying oil to the piston nozzles 177. However, since the lubrication path from the main gallery 162 to the sub-gallery 176 differs from that from the main gallery 162 to the bearing 202a of the crankshaft 141 (see Fig. 14A), the influence of the oil pressure reduction on the oil pressure at the bearing 202a of the crankshaft 141 due to the supply of oil to the piston nozzles 177 can be reduced.

[0109] As in Fig. 14C, oil conveyed to the subgallery 176 runs deep (downstream) past the piston nozzles 177 (see Fig. 14B) and is connected to the bearing 178 of the turbo shaft (see Fig. 12) of the turbocharger (not shown) is supplied from the turbocharger inlet 179. In this way, oil that has been used to lubricate the bearing 173a of the front balance shaft 151 is reused for cooling through the piston jets 177 and for lubricating the bearing 178 of the turboshaft. Furthermore, since the oil passages 172a and 175a are formed in the front walls of the lower case 128 and the upper case 127, respectively, the crankcase 121 does not need to have useless fixed portions for forming independent oil passages corresponding to the oil passages 172a and 175a, resulting in a weight reduction of the crankcase 121.

[0110] In the following, the lubrication path to the cylinder head 112 is described with reference to Fig. 13, Fig. 15A, Fig. 15B and Fig. 16 described. Fig. 15A and Fig. 15B are sectional views along lines DD and EE in Fig. 13 of the crankcase 121 according to the embodiment of the second aspect of the invention. Fig. Fig. 16 is a perspective view of the upper housing 127 and the lower housing 128 of the crankcase 121 according to the embodiment of the second aspect of the invention. For simplicity, the shafts in Fig. 15B omitted.

[0111] As in Fig. 13 and Fig. As shown in Fig. 15A, oil passages 172c and 175c for supplying oil from the main gallery 162 to the cylinder head 112 via the bearing 173c of the front balance shaft 151 are formed in a left portion of the crankcase 121. The oil passage 172c extends from the main gallery 162 to a mounting surface 181 for the bearing 173c of the front balance shaft 151 of the lower case 128. The oil passage 175c extends from a mounting surface 182 for the bearing 173c of the front balance shaft 151 of the upper case 127 to the cylinder head 112 (see Fig. Fig. 9). The mounting surfaces 181 and 182 for the bearing 173c of the front balance shaft 151 are provided with respective oil grooves 183 (see Fig. 16) which are oil passages connecting the oil passages 172c and 175c.

[0112] Since the front balance shaft 151 is accommodated in the front compensation chamber 186 (see Fig. 15B), even if an oil leak occurs there, the oil can be returned to the oil pan 122 (see Fig. 9). Since the oil passage encompasses the location of the front balance shaft 151 as in the case of the lubrication path to the sub-gallery 176, no sealing member such as an O-ring is required to prevent oil leakage, unlike when an oil passage for this purpose is formed by bypassing the location of the bearing 173c, resulting in a reduction in the number of components. Furthermore, since the oil passages 172c and 175c are formed in the left walls of the lower case 128 and the upper case 127, respectively, the crankcase 121 does not need to have useless fixed portions for forming independent oil passages corresponding to the oil passages 172c and 175c, resulting in a reduction in the weight of the crankcase 121.

[0113] Since high-pressure oil from the oil pump 161 (see Fig. 12) of the main gallery 162, high-pressure oil from the main gallery 162 is supplied to the bearing 173c of the front balance shaft 151. Consequently, a sufficiently thick oil film is formed on the bearing 173c of the front balance shaft 151, which requires high oil pressure, thereby preventing the front balance shaft 151 from locking. When oil is supplied to the bearing 173c of the front balance shaft 151, the oil still has a sufficiently high pressure. To utilize this high oil pressure, oil that has passed through the left bearing 173c of the front balance shaft 151 is delivered to the cylinder head 112 while maintaining its sufficiently high pressure.

[0114] Oil supplied to the cylinder head 112 is admitted into the interior of the camshaft from its left end and lubricates the cam, tappet, etc. when subjected to centrifugal force. In this way, oil used to lubricate the bearing 173c of the front balancer shaft 151 is reused to lubricate the cylinder head 112. The oil pressure in each of the oil passages 172c and 175c is reduced by the supply of oil to the cylinder head 112. However, since the lubrication path from the main gallery 162 to the cylinder head 112 differs from that from the main gallery 162 to the bearing 202c of the crankshaft 141 (see Fig. 15A), the influence of the oil pressure reduction on the oil pressure at the bearing 202c of the crankshaft 141 due to the supply of oil to the cylinder head 112 can be reduced.

[0115] The oil channels 172a and 175a for supplying oil from the main gallery 162 to the sub-gallery 176 are formed on the right side in the crankcase 121 (see Fig. 14A), and the oil passages 172c and 175c for supplying oil from the main gallery 162 to the cylinder head 112 are formed on the left side in the crankcase 121 (see Fig. 15A). Thus, the oil pressure in the main gallery 162 can be evenly distributed between the left and right sides. Furthermore, since the set of oil passages 172a and 175a and the set of oil passages 172c and 175c are spaced apart from each other in the left-right direction, the oil pressure reduction due to the supply of oil to the piston nozzles 177 does not affect the oil pressure in the cylinder head 112. Similarly, the oil pressure reduction due to the supply of oil to the cylinder head 112 does not affect the oil pressure in the sub-gallery 176.

[0116] As in Fig. 15B, the oil return passage 185 is for returning oil from the cylinder head 112 (see Fig. 9) into the interior of the crankcase 121 in a right-hand portion of the crankcase 121. That is, in the crankcase 121, oil is returned from the cylinder head 112 on the opposite side to the oil passages 172c and 175c in the left-right direction. In the crankcase 121, an outlet 187 of the oil return passage 185 is connected to the front balance chamber 186, which accommodates the front balance shaft 151. In the front balance chamber 186, the outlet 187 of the oil return passage 185 is arranged in front of the front balance shaft 151 on the right side in the crankcase 121.

[0117] With the outlet 187 arranged at this position, return oil from the oil return passage 185 can be drained at the position farthest from the front balance shaft 151. Return oil drained from the outlet 187 of the oil return passage 185 flows down an inner wall surface in the front balance chamber 186 of the crankcase 121, thus avoiding contact with any rotating components, such as a balance weight of the front balance shaft 151. Consequently, the likelihood of oil mist occurring in the front balance chamber 186 and thus mixing of oil mist into blow-by gas can be reduced. Furthermore, since return oil does not come into contact with any rotating components, return oil from the cylinder head 112 can be quickly returned to the oil pan 122.

[0118] The oil return passage 185 is formed of a vertical passage 191 extending downward from the connecting plane 136 of the crankcase 121 and the cylinder assembly 110, and an inclined passage 192 extending obliquely from the lower end of the vertical passage 191 to reach a front portion of the crankcase 121. The inclined passage 192 is inclined so as to extend vertically when the crankcase 121 (engine 101) is mounted in the vehicle. That is, the inclination of the inclined passage 192 is determined by considering a mounting angle of the crankcase 121. This allows return oil to be quickly returned to the oil pan 122. The term "vertical" used herein is not limited to the case where the inclined passage 192 extends completely vertically, and includes the case where it extends approximately vertically.

[0119] Since the oil return channel 185 is located in the front walls of the cylinder assembly 110 (see Fig. 9) and the upper case 127, the crankcase 121 does not need to have useless fixed portions for forming an independent oil passage corresponding to the oil return passage 185, resulting in a weight reduction of the crankcase 121. In this regard, the oil return passage 185 extends in front of the sub-gallery 176 in the crankcase 121. Since the oil return passage 185 is formed in an unused area, in which the sub-gallery 176 is formed, of the front wall of the crankcase 121, this results in a further weight reduction of the crankcase 121.

[0120] As in Fig. As shown in FIG. 16, the timing chain space 193 for accommodating a timing chain (not shown) is formed in a left portion of the crankcase 121. Since the timing chain space 193 is formed on the side opposite the oil return passage 185 in the left-right direction in the crankcase 121, the amount of oil flowing into the timing chain space 193 can be reduced. Consequently, return oil comes into contact with the timing chain less frequently, and thus the possibility of oil mist occurring in the timing chain space 193 can be reduced. In addition, since return oil is efficiently returned to the oil pan 122 through the oil return passage 185 and the timing chain space 193 from both sides in the left-right direction of the cylinder head 112, oil can be prevented from remaining in the cylinder head 112.

[0121] As described above, as in Fig. As shown in Fig. 16, the oil passages 172c and 175c are formed on the left side in the crankcase 121, and the oil return passage 185 is formed on the right side in the crankcase 121. Thus, the lubrication path is formed in which oil is supplied to the camshaft from the left side of the cylinder head 112 and returned to the crankcase 121 from the right side of the crankcase 121. In addition, since the oil return passage 185 is formed between the oil passages 172a and 175a and the oil passages 172c and 175c, the left-right width of the crankcase 121 can be shortened.

[0122] As described above, according to the embodiment, high-pressure oil is supplied from the oil pump 161 to the main gallery 162, and high-pressure oil is also supplied from the main gallery 162 to the bearings 173a to 173c of the front balancer shaft 151. Consequently, the front balancer shaft 151 is rotationally supported by the bearings 173a to 173c via oil films, which can prevent the front balancer shaft 151 from locking. Since high-pressure oil is supplied to the sub-gallery 176 via the bearing 173a of the front balancer shaft 151, the oil coming from the sub-gallery 176 can be reused to lubricate various components of the engine 101. In addition, since the same oil passages 172a and 175a are used to supply oil from the main gallery 162 to the bearing 173a of the front balance shaft 151 and the sub-gallery 176, independent oil passages for these purposes do not need to be formed in the crankcase 121.As a result, there is no need for independent pipes, the weight or number of machining steps is not increased, and the oil channels can be shortened.

[0123] The second aspect of the invention is not limited to the above embodiment and can be modified in various ways. The second aspect of the invention is not limited to the sizes, shapes, etc. shown in the accompanying drawings, and they can be appropriately modified within the scope so that the advantages of the second aspect of the invention can be obtained. Other modifications can also be appropriately made as long as the related object of the invention is achieved.

[0124] For example, although in the embodiment of the second aspect of the invention, oil from the sub-gallery 176 is supplied to the piston nozzles 177 and the bearing 178 of the turboshaft, the second aspect of the invention is not limited to this structure. It is sufficient for the sub-gallery 176 to supply oil received via the bearing 173a of the front balance shaft 151 to several components of the engine 101. For example, the sub-gallery 176 may supply oil to the cylinder head 112. In this case, the oil passages 172c and 175c need not be formed in the crankcase 121.

[0125] In the embodiment of the second aspect of the invention, the oil passages 172a and 175a for supplying oil from the main gallery 162 to the sub-gallery 176 are formed on the right side in the crankcase 121, and the oil passages 172c and 175c for supplying oil from the main gallery 162 to the cylinder head 112 are formed on the left side in the crankcase 121. However, the second aspect of the invention is not limited to this structure; a structure is possible in which the oil passages 172a and 175a for supplying oil from the main gallery 162 to the sub-gallery 176 are formed on the left side in the crankcase 121, and the oil passages 172c and 175c for supplying oil from the main gallery 162 to the cylinder head 112 are formed on the right side in the crankcase 121.Furthermore, the second aspect of the invention is not limited to this structure in which the oil passages 172a and 175a are formed in an end portion of the crankcase 121; for example, the oil passages 172a and 175a may be formed in a central portion in the left-right direction of the crankcase 121.

[0126] Although in the embodiment of the second aspect of the invention, the front balance shaft 151 and the lower balance shaft 154 are arranged in the crankcase 121, the second aspect of the invention is not limited to this structure. It is sufficient that at least one balance shaft is arranged in the crankcase 121; for example, a balance shaft may be arranged behind the crankshaft 141.

[0127] Although in the embodiment of the second aspect of the invention, the front balance shaft 151 is arranged at the connecting plane of the upper housing 127 and the lower housing 128, the second aspect of the invention is not limited to this structure. The front balance shaft 151 can be arranged in either the upper housing 127 or the lower housing 128.

[0128] Although in the embodiment of the second aspect of the invention, the crankcase 121 is formed from the upper case 127 and the lower case 128, the second aspect of the invention is not limited to this structure. The crankcase 121 may be divisible in the horizontal direction and formed from a left case and a right case.

[0129] Although in the embodiment of the second aspect of the invention, the sub-gallery 176 extends parallel to the main gallery 162, the second aspect of the invention is not limited to this structure. The main gallery 162 and the sub-gallery 176 do not always have to be parallel to each other. Although the main gallery 162 and the sub-gallery 176 are straight in this embodiment, the second aspect of the invention is not limited to this structure. The shapes of the main gallery 162 and the sub-gallery 176 can be appropriately changed according to the shape of the crankcase 121.

[0130] Although in the embodiment of the second aspect of the invention, oil is caused to pass through the bearing 173a of the front balancer shaft 151 by forming the oil grooves 183 formed in the bearing mounting surfaces 181 and 182 of the right journal walls 171a and 174a, the second aspect of the invention is not limited to this structure. It is sufficient to cause oil to pass through the bearing 173a of the front balancer shaft 151. For example, the bearing 173a or the front balancer shaft 151 may be formed with an oil groove.

[0131] Providing the above-described advantage that oil passages can be shortened without causing an increase in weight or the number of machining steps, and that high-pressure oil supplied from the main gallery can be effectively used, the second aspect of the invention is particularly useful when applied to the engine lubrication structures of motorcycles. Description of reference symbols 1 engine 2 turbochargers 24a Intake pipe (fourth oil channel) 24b Drain pipe (oil return channel) 30 Crankshaft 33 balance shafts 34 first balance shaft 35 second balance shaft 4 crankcase 40a connecting port (oil channel) 41a Connection port (oil return channel) 43 Main Gallery 44 Oil channel (first oil channel) 45 Oil channel (second oil channel) 48 Subgallery 49 Oil channel (third oil channel) 50 piston nozzles 101 Engine 121 Crankcase 127 upper housing 128 lower housing 134 Connection level of lower housing and upper housing 141 Crankshaft 145 pistons 151 front balance shaft (balance shaft) 154 lower balance shaft 161 Oil pump 162 Main Gallery 172a, 175a oil channel 172c, 175c oil channel (other oil channel) 173 Front balance shaft bearing 176 Subgallery 177 Piston nozzle 202 crankshaft bearing

Claims

[1] An engine lubrication structure configured to supply oil from an oil pump to individual components of an engine (1) in which a balance shaft (33, 34) is arranged parallel to a crankshaft (30) in a crankcase (4), wherein: the engine (1) has a turbocharger (2) which is configured to compress intake air using exhaust gas from the engine (1), a main gallery (43) which supplies oil to a bearing of the crankshaft (30) via a first oil channel (44) and to a bearing of the balance shaft (33, 34) via a second oil channel (45), and a sub-gallery (48) to which oil which has first been supplied to the bearing of the balance shaft (33, 34) is then supplied through a third oil channel (49) formed from the bearing of the balance shaft (33, 34) to the sub-gallery (48), and which supplies oil which has been supplied to the bearing of the balance shaft (33, 34) to individual components of the engine, are provided in the crankcase (4), and a fourth oil channel (24a), which supplies oil to the turbocharger (2), is connected to the sub-gallery (48). [2] The engine lubricating structure according to claim 1, wherein the sub-gallery (48) is provided with a piston nozzle (50) which jets oil to a piston. [3] An engine lubricating structure according to claim 1 or 2, wherein: the balance shaft (33,34) is arranged under the sub-gallery (48), and the main gallery (43) is arranged under the balance shaft (33,34). [4] An engine lubricating structure according to any one of claims 1 to 3, wherein: an oil return channel (24b) which returns oil supplied to the turbocharger (2) to the crankcase (4) is connected to the crankcase (4), the balance shaft (33,34) is arranged in front of the crankshaft (30), and the oil return channel (24b) is connected to a wall of a compensation chamber which accommodates the balance shaft (33,34). [5] A motorcycle having an engine lubricating structure according to any one of claims 1 to 4. [6] An engine lubrication structure configured to supply oil from an oil pump (161) to individual components of an engine (101) in which a balance shaft (151) is arranged parallel to a crankshaft (141) in a crankcase (121), the engine lubrication structure comprising: a main gallery (162) to which oil is supplied from the oil pump (161), a sub-gallery (176) which supplies individual components of the engine (101) with oil which has passed through a bearing (173a) of the balance shaft (151), and Oil channels (172a, 175a) which are designed such that oil coming from the main gallery (162) is first supplied to the bearing (173a) of the balance shaft (151) and the oil which has passed through the bearing (173a) of the balance shaft (151) is then supplied to the sub-gallery (176), and wherein the main gallery (162), the sub-gallery (176) and the oil channels (172a,175a) are provided in the crankcase (121). [7] An engine lubricating structure according to claim 6, wherein: the main gallery (162) is arranged under the balance shaft (151), and the sub-gallery (176) is provided above the balance shaft (151) parallel to the main gallery (162). [8] An engine lubricating structure according to claim 6 or 7, wherein: the crankcase (121) is divisible in the vertical direction and has an upper housing (127) and a lower housing (128), the main gallery (162) is provided in the lower housing (128), the sub-gallery (176) is provided in the upper housing (127), and the bearing (173a) of the balance shaft (151) is arranged on a connecting plane (134) of the upper housing (127) and the lower housing (128). [9] The engine lubricating structure according to any one of claims 6 to 8, wherein the balance shaft (151) is arranged on a straight line connecting the main gallery (162) and the sub-gallery (176) in the crankcase (121). [10] An engine lubricating structure according to any one of claims 6 to 9, wherein the sub-gallery (176) supplies the oil which has passed through the bearing (173a) of the balance shaft (151) to a piston nozzle (177) which serves to cool a piston (145). [11] The engine lubricating structure according to any one of claims 6 to 10, wherein a lubrication path from the main gallery (162) to the sub-gallery (176) and a lubrication path from the main gallery (162) to a bearing (202) of the crankshaft (141) are different from each other. [12] An engine lubricating structure according to any one of claims 6 to 11, wherein the oil passages (172a,175a) are provided on one of the left side and the right side in the crankcase (121), and another oil passage (172c,175c) arranged to supply oil from the main gallery (162) to a cylinder head (112) is provided on the other side. [13] An engine lubricating structure according to any one of claims 6 to 12, wherein: the balance shaft (151) is a front balance shaft arranged in front of the crankshaft (141), and a lower balance shaft (154) is arranged below the crankshaft (141), and the main gallery (162) is provided in front of the lower balance shaft (154) in the crankcase (121). [14] A motorcycle having an engine lubricating structure according to any one of claims 6 to 13.

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