JP2010196566A - Oil path for cooling cylinder head of multi-cylinder engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil path for cooling a cylinder head of a multi-cylinder engine, having oil return piping connected to a cylinder block for passage of return oil from the cylinder head cooling oil path and arranged toward an engine lower part from the cylinder block, shortening a longitudinal length of the engine and improving ease of installation and maintenance of the oil return piping by optimizing the position of the oil return piping. <P>SOLUTION: The oil return piping is provided to pass between a crankshaft and a transmission shaft, and as viewed in an engine side, is arranged within a range overlapping with a rotation locus of a crank web projecting in a radial direction of the crankshaft and is arranged at a position shifted from the crank web with respect to an axial direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an oil passage for cooling a cylinder head of an air-cooled multi-cylinder engine, and more particularly to an oil return pipe.

  In an engine in which the oil supplied to the cylinder head is returned from the cylinder block to the oil pan below the engine via the oil return pipe, there is an example in which the oil return pipe is faced to the oil pan through between the crankshaft and the transmission ( For example, see Patent Document 1.) In this example, in order to prevent interference between the crank web and the oil return pipe, the oil return pipe is arranged between the outermost track of the crank web and the transmission shaft. Result The front and rear length of the engine was large.

Japanese Patent No. 3470355 (FIG. 4)

  The present invention intends to optimize the position of the oil return pipe to shorten the longitudinal length of the engine and to improve the assembly and maintenance of the oil return pipe.

The present invention solves the above problems, and the invention according to claim 1
In a cylinder head cooling oil passage of a multi-cylinder engine that is connected to the cylinder block and passes an oil return pipe through which return oil from the cylinder head cooling oil passage passes from the cylinder block toward the lower side of the engine,
The oil return pipe is provided between the crankshaft and the transmission shaft, and the pipe is arranged in a range overlapping with a rotation trajectory of a crank web protruding in the crankshaft radial direction in a side view of the engine. The present invention relates to an oil passage for cooling a cylinder head of a multi-cylinder engine, which is disposed at a position shifted from the crank web.

A second aspect of the present invention is the cylinder head cooling oil passage of the multi-cylinder engine according to the first aspect,
An oil pump is disposed between the crankshaft and the transmission, and the oil return pipe is passed between the oil pump and the crankshaft in a side view.

According to a third aspect of the present invention, in the oil passage for cooling the cylinder head of the multi-cylinder engine according to the first or second aspect,
The lower end of the oil return pipe is set to a height that does not protrude below the lower surface of the crankcase to which the oil pan is connected.

According to a fourth aspect of the present invention, in the cylinder head cooling oil passage of the multi-cylinder engine according to the first to third aspects of the present invention,
A drive member storage chamber (such as a cam chain chamber) for storing a valve train drive transmission member is provided at the center in the left-right direction of the engine, and an oil return pipe is disposed between the side wall of the drive member storage chamber and the crank web. It is characterized by that.

According to a fifth aspect of the present invention, in the oil passage for cooling the cylinder head of the multi-cylinder engine according to the first or second aspect,
The upper end of the oil return pipe is inserted through the seal member into the lower part of the drain oil passage at the upper part of the crankcase that continues to the lower side of the oil gallery in the cylinder block, and the middle part of the oil return pipe is fixed to the oil pump. It is characterized by this.

In the invention of claim 1,
The oil return pipe is arranged close to the crankshaft so as to overlap the crank web rotation trajectory when viewed from the side of the engine, and is shifted in the axial direction so that the crank can be controlled while suppressing interference with the crank web. The oil return pipe can be arranged using the empty space without increasing the distance between the crankshaft and the transmission shaft without increasing the distance between the crankshaft and the transmission shaft.

In the invention of claim 2,
Since the oil pump is disposed between the crankshaft and the transmission, and the oil return pipe is disposed in the gap between the oil pump and the crankshaft, it is possible to suppress an increase in the longitudinal length of the engine.

In the invention of claim 3,
Since the oil return pipe does not protrude from the lower surface of the crankcase with the oil pan removed, it is possible to protect the pipe during maintenance, and there is no need to catch the pipe during maintenance compared to when the pipe protrudes. Improves.

In the invention of claim 4,
Since an empty space between the drive member housing chamber and the crank web is used, the oil return pipe can be arranged efficiently.

In the invention of claim 5,
The middle part of the oil return pipe is fixed to the oil pump below the crankcase, and the upper end has a plug-in structure, so it can be easily removed and fixed during pipe assembly and maintenance. improves.

1 is a side view of a motorcycle equipped with a four-cylinder engine according to an embodiment of the present invention. It is the figure which looked at the longitudinal cross-section of the said engine from the right side. It is the figure which looked at the longitudinal cross-section of the engine principal part containing the cam chain chamber of the said engine from the right side. It is the figure which looked at the air cooling type oil cooler of FIG. 2 from the front. It is a front view of a cylinder block center part. It is VI-VI sectional drawing of FIG. It is a top view of a cylinder block. It is a bottom view of a cylinder head. It is a top view of a cylinder head. It is XX sectional drawing of FIG. Top view of oil jacket lid XII-XII sectional view of FIG. It is XIII-XIII sectional drawing of FIG. It is a rear view of a cylinder block. It is a bottom view of a cylinder block. It is a side view of the peripheral part of an oil return piping. It is a top view of a lower crankcase.

  FIG. 1 is a side view of a motorcycle 2 equipped with a four-cylinder engine 1 according to an embodiment of the present invention. Arrow F points forward. The body frame of the motorcycle 2 includes a head pipe 3, a main frame 4 extending obliquely rearward from the head pipe 3, a center frame 5 extending downward from the rear end of the main frame 4, the head pipe 3 and the main frame 4. An auxiliary frame 6 that connects the frames 4, a down frame 7 that extends downward from the auxiliary frame 6, a seat stay 8 that extends backward from the main frame 4, and a midline that connects the center of the center frame 5 and the center of the seat stay 8. And a frame 9. A front fork 11 that supports the front wheel 10 is supported by the head pipe 3 so as to be steerable. A steering handle 12 is connected to the front fork 11. A rear fork 14 that supports the rear wheel 13 is supported on the rear portion of the center frame 5 so as to swing up and down, and a cushion unit 15 is provided between the connection portion between the seat stay 8 and the mid frame 9 and the rear fork 14. Is provided. The engine 1 is supported by the down frame 7, the main frame 4, and the center frame 5, and the power of the engine 1 is transmitted to the rear wheel 13 via the rear wheel drive chain 16. A fuel tank 17 is provided on the main frame 4 so as to be positioned above the engine 1, and a tandem seat 18 for a driver and a passenger is mounted on the seat stay 8. An exhaust pipe 19 extends from the engine 1, bends downward, extends rearward, and is connected to a rear muffler 20. An air-cooled oil cooler 21 is provided in the down frame 7 in front of the engine 1.

  FIG. 2 is a view of the longitudinal section of the engine 1 as viewed from the right. The engine 1 is an air-cooled four-cylinder DOHC wet sump engine, and a cooling system oil circuit is shown in the figure. The cylinder 24 in this figure shows a II-II cross section in FIG. The arrow F points to the front corresponding to the front of the vehicle when the engine is mounted on the vehicle. In this engine, an internal combustion engine 25 and a transmission 26 are integrated. The outer shell of the engine 1 includes a crankcase 27 composed of an upper crankcase 27A and a lower crankcase 27B, a cylinder block 28, a cylinder head 29, a cylinder head cover 30, and an oil pan 31. A crankshaft 32, a transmission main shaft 33, and a countershaft 34 are rotatably supported by bearings on a mating surface of the crankcase 27 that is divided into two vertically.

  The cylinder block 28 has four cylinders, and a piston 35 is slidably accommodated in each cylinder 24 and connected to the crankshaft 32 via a connecting rod 36. A combustion chamber 37 is provided below the cylinder head 29 facing the upper surface of each piston 35. Spark plugs 38 are inserted from above the cylinder head 29 toward the combustion chambers 37, respectively, and their tips face the combustion chambers 37. The cylinder head 29 is provided with an intake port 39 and an exhaust port 40 connected to each combustion chamber 37, and an inner end thereof opens to the combustion chamber 37. At the inner end openings of the intake port 39 and the exhaust port 40, an intake valve 41 and an exhaust valve 42 for opening and closing the respective openings are provided. A valve operating mechanism 45 including an intake cam shaft 43 and an exhaust cam shaft 44 is provided on the mating surface of the cylinder head 29 and the cylinder head cover 30.

  An oil pan 31 having a shallow bottom portion and a deep bottom portion is connected to the lower portion of the lower crankcase 27B. An oil suction pipe 47 having a strainer 46 is provided at the deep bottom portion of the oil pan 31, and an oil pump 48 is connected to the upper portion thereof. The oil pump 48 includes a cooling system oil pump and a lubrication system oil pump, and is connected to the same oil pump shaft.

  The engine 1 is provided with a cooling system oil circuit and a lubrication system oil circuit independently. Each oil circuit is supplied with oil separately from the cooling system oil pump and the lubrication system oil pump. FIG. 2 shows the cooling system oil pump 48 and the cooling system oil circuit, and the illustration of the lubricating system oil pump and the lubricating system oil circuit is omitted. Since the present invention is limited to those related to the cooling system, in the following description, the cooling system oil pump 48 and the cooling system oil circuit will be simply referred to as the oil pump 48 and the oil circuit.

  The details of the oil passage will be described later. First, the overall configuration of the oil passage will be described. In the oil circuit of FIG. 2, a discharge pipe A1 connected to the oil pump 48 extends forward in the oil pan and bends upward to reach an oil cooler connecting portion 49 at the lower front of the lower crankcase 27B. An oil cooler forward pipe A2 is connected to the oil cooler connecting portion 49, and is connected to the air-cooled oil cooler 21 at the upper front of the engine. The oil cooled here is sent to the oil introduction part 50 at the lower front of the cylinder block 28 via the oil cooler return pipe A3. The oil introduction part 50 is connected to the supply side oil gallery A4.

  The valve drive member includes a cam chain and a timing belt, but the cam chain 51 (see FIG. 3) is used in the engine 1 of the present embodiment. Therefore, in the following description, the valve drive member housing chamber is used. Is called a cam chain chamber 52. When this engine is mounted on a vehicle, it is a parallel four-cylinder engine in which four cylinders 24 are arranged in the left-right direction (see FIG. 7). Since the cam chain chamber 52 is provided in the center, Two are grouped together. In the supply side oil gallery A4, the oil passage is divided into right and left, and is connected to a cylinder block rising oil passage A5 that faces the left and right blocks. The upper part of the cylinder block rising oil passage A5 is connected to the cylinder block upper surface distribution groove A6 for the left and right blocks. On the lower surface of the cylinder head 29 covering the upper part of the distribution groove A6, the lower end of the cylinder head supply oil passage A7 provided independently for each cylinder is opened so as to communicate with the distribution groove A6. The upper end of the cylinder head supply oil passage A7 communicates with the spark plug oil jacket A8, and the periphery of the spark plug 38 is cooled by the supplied oil.

  The spark plug oil jacket A8 is connected to the cylinder head oil discharge oil passage A9 provided for each cylinder on the rear side of the cylinder 24. The lower end of the oil discharge oil passage A9 in the cylinder head opens into a cylinder block upper surface collection groove A10 for the left and right blocks. The cylinder block upper surface collection groove A10 is connected to a discharge side oil gallery A12 provided at the lower portion of the cylinder block 28 by a cylinder block lowering oil passage A11 for each of the left and right blocks. Since the discharge side oil gallery A12 extends over the left and right blocks, the cylinder block descending oil passage A11 for each of the left and right blocks is combined into one, and is connected to the crankcase discharge oil passage A13 via the discharge connecting portion 53. It is a series. An oil return pipe A14 is connected to the lower end of the crankcase discharge oil passage A13 and opens above the oil pan 31.

  FIG. 3 is a view of a longitudinal section of the engine 1 including the cam chain chamber 52 as viewed from the right side. The cam chain chamber 52 is provided at a substantially central portion in the left-right direction of the engine 1. The cam chain chamber 52 in this figure shows a III-III cross section in FIG. In FIG. 3, an intake cam shaft 43 and an exhaust cam shaft 44 are rotatably supported on mating surfaces of a cylinder head 29 and a cylinder head cover 30, and a cam shaft driven sprocket 56 is provided on each shaft. The crankshaft 32 supported by the mating surfaces of the upper and lower crankcases 27A and 27B is provided with a camshaft drive sprocket 57 having a half diameter of the camshaft driven sprocket 56. The cam chain 51 is wound around these sprockets, and the intake cam shaft 43 and the exhaust cam shaft 44 rotate according to the rotation of the crankshaft 32.

  The crankshaft 32 rotates in the direction of arrow W. A cam chain guide is provided around the cam chain 51. The upper part between the two driven sprockets is a fixed upper cam chain guide 58, and the cam chain 51 on the front side of the cam chain chamber 52 is fixed on the rear side of the cam chain chamber 52. The cam chain 51 on the feeding side is provided with a oscillating cam chain guide 60. The swing cam chain guide 60 swings around the lower end bolt 61. A cam chain tensioner 63 is provided on the cam chain tensioner mounting portion 62 on the rear wall of the cylinder block 28, and the swinging cam chain guide 60 is pushed by the projecting shaft 63a to prevent the cam chain 51 from slackening.

  FIG. 4 is a front view of the air-cooled oil cooler 21 of FIG. In the drawing, left and right are indicated by arrows L and R corresponding to the left and right sides of the vehicle when the engine 1 is mounted on the vehicle. The same applies to the other drawings described below. The upper end of the oil cooler outgoing pipe A2 is connected to the right side of the oil cooler 21, and the flange 66 of the outgoing pipe at the lower end is connected to the oil cooler connecting part 49 at the front of the lower crankcase (FIG. 2). . The upper end of the oil cooler return pipe A3 is connected to the left side of the oil cooler 21, and the flange 67 of the return pipe at the lower end is connected to the oil introduction part 50 at the front of the cylinder block 28 (FIG. 2).

  FIG. 5 is a front view of the central portion of the cylinder block 28. In the drawing, the upper side of the engine corresponding to the upper side of the vehicle is indicated by an arrow Up together with left and right L and R when the engine 1 is mounted on the vehicle. The same applies to the other drawings described below. In the figure, an oil introduction portion 50 is provided at the lower front portion of the cylinder block 28. Here, the flange portion 67 (FIG. 4) of the return pipe at the lower end of the oil cooler return pipe A3 is connected. The oil introduction part 50 communicates with the supply side oil gallery A4. Cylinder block rising oil passages A5 stand up from both ends of the supply side oil gallery A4. This cylinder block 28 is provided with a cam chain chamber 52 at the center in the left-right direction, and the cylinders are separated into two left and right, so that oil is supplied to the supply side oil gallery A4 in order to send oil to the left and right blocks. It is distributed to the left and right through. The upper end of the cylinder block rising oil passage A5 is connected to the cylinder block upper surface distribution groove A6.

  6 is a cross-sectional view taken along the line VI-VI in FIG. 5 and is a vertical cross-sectional view of the cylinder block 28 including the cylinder block rising oil passage A5. The lower part of the cylinder block rising oil passage A5 communicates with the supply side oil gallery A4, and the upper part of the cylinder block rising oil path A5 communicates with the cylinder block upper surface distribution groove A6. The figure also shows the cylinder block upper surface recovery groove A10 and the discharge side oil gallery A12.

  FIG. 7 is a top view of the cylinder block 28. Since the cam chain chamber 52 is opened at the center in the left-right direction of the cylinder block 28, the cylinder 24 is divided into two on the left and right. In the engine 1, the upper crankcase 27A and the cylinder block 28 are integrally coupled by a stud bolt. A plurality of stud bolt insertion holes 68 can be seen in the figure. On the upper surface of the cylinder block 28, distribution grooves A6 are provided on both sides of the cam chain chamber 52, respectively. Recovery grooves A10 are also provided on both sides of the cam chain chamber 52, respectively. All of these grooves are provided outside the stud bolt insertion hole 68 so as to be curved. The upper ends of the cylinder block ascending oil passages A5 are opened at positions where the left and right distribution grooves A6 of the cam chain chamber 52 are marked m1 and m2 near the respective cam chain chambers 52. The upper ends of the in-cylinder block descending oil passages A11 are opened at the positions of the left and right recovery grooves A10 of the cam chain chamber 52 where the reference numerals n1 and n2 are attached.

  FIG. 8 is a bottom view of the cylinder head 29. A cam chain chamber 52 is opened at the center in the left-right direction. In each combustion chamber 37 corresponding to each cylinder 24 in FIG. 7, an ignition plug insertion hole 69, an inner end 39a of each of the two intake ports 39, and an inner end 40a of the exhaust port 40 are opened. These openings are provided with a spark plug 38, an intake valve 41, and an exhaust valve 42 shown in FIG. The front and rear flat portions of the combustion chamber 37 serve as a lid that covers the upper surfaces of the cylinder block upper surface distribution groove A6 and the cylinder block upper surface recovery groove A10 in FIG.

  In the front and back plane portions of the combustion chamber 37, lower ends of a cylinder head supply oil passage A7 and a cylinder head oil discharge oil passage A9 shown in FIG. In FIG. 7, the lower end of the cylinder head supply oil passage A7 opens at a position of the cylinder block upper surface distribution groove A6 with the reference numerals f1, f2, f3, and f4. In FIG. 7, the lower end of the cylinder head oil discharge oil passage A9 opens at a position marked with reference numerals g1, g2, g3, and g4 of the cylinder block upper surface recovery groove A10. Oil is supplied from the cylinder block upper surface distribution groove A6 to the cylinder head supply oil passage A7. Further, the oil is discharged from the cylinder head oil discharge oil passage A9 to the cylinder block upper surface collection groove A10.

  FIG. 9 is a top view of the cylinder head 29. A cam chain chamber 52 is opened at the center. Two spark plug insertion holes 69 are provided on the left and right sides of the cylinder head. Two intake valve mounting holes 70 are provided on the rear side of each spark plug insertion hole 69. Two exhaust valve mounting holes 71 are provided on the front side of each spark plug insertion hole 69. A bearing portion 84 of the intake cam shaft 43 is provided between each pair of intake valve mounting holes 70, and a bearing portion 85 of the exhaust cam shaft 44 is provided between each pair of exhaust valve mounting holes 71.

  A spark plug oil jacket A8 is provided around each spark plug insertion hole 69. The spark plug oil jacket A8 is connected to the cylinder head supply oil passage A7 and the cylinder head oil discharge oil passage A9. The upper part of the spark plug oil jacket A8 is covered with an oil jacket lid member 72 shown in FIGS.

  FIG. 10 is a cross-sectional view taken along the line XX in FIG. 9 and is a vertical cross-sectional view of the cylinder head 29 including the spark plug insertion hole 69. An oil jacket A8 is provided around the spark plug insertion hole 69. The oil jacket A8 is an annular groove (see FIG. 9), and the periphery of the spark plug 38 (FIG. 2) is cooled by the supplied oil. The upper end of the cylinder head supply oil passage A7 reaches the front side of the spark plug oil jacket A8. The rear side of the spark plug oil jacket A8 is connected to the cylinder head oil discharge oil passage A9, and the cooled oil around the spark plug 38 is discharged to the cylinder head oil discharge oil passage A9. The upper portion of the spark plug oil jacket A8 is covered with an oil jacket lid member 72.

  11 to 13 are three views of the oil jacket lid member 72, FIG. 11 is a top view, FIG. 12 is a sectional view taken along line XII-XII in FIG. 11, and FIG. 13 is a sectional view taken along line XIII-XIII in FIG. In this engine 1, the valve mechanism 45 is covered with the cylinder head cover 30 (FIGS. 2 and 3), but the upper part of the spark plug 38 is not covered with the cylinder head cover 30. Touch the air flow. A lid member cooling fin 73 is provided on the upper surface of the oil jacket lid member 72 and serves to cool the periphery of the spark plug 38. Further, as described above, since the spark plug 38 is exposed to the outside air, water may enter the periphery of the spark plug 38. Therefore, a drain hole 74 is provided in the oil jacket lid member 72. The oil jacket lid member 72 is provided with a pair of mounting screw hole insertion holes 72a.

  In the upper surface of the cylinder block 28 on the right side of the cam chain chamber 52 in FIG. 7, the cylinder is attached to the cylinder block upper surface distribution groove A6 from the portion adjacent to the upper end opening position m2 of the cylinder block rising oil passage A5 by the symbol s. A bypass groove B1 is formed so as to reach a portion denoted by reference numeral g3 in the block upper surface recovery groove A10. The upper end opening position m2 of the cylinder block rising oil passage A5 and the start point s of the bypass groove B1 communicate with each other by a bypass groove B2 formed on the lower surface of the cylinder head in FIG. When the upper surface of the cylinder block 28 is covered by the lower surface of the cylinder head 29, the bypass oil passage that short-circuits the cylinder block upper surface distribution groove A6 and the cylinder block upper surface recovery groove A10 without passing through the oil jacket A8 by the bypass grooves B1 and B2 B is formed. This is because the cooled oil that has risen from the rising oil passage A5 in the cylinder block and the high-temperature oil that has passed through the oil jacket A8 are merged in the cylinder block upper surface collection groove A10, so that the front side and the rear side of the cylinder block 28 are combined. In order to eliminate the uneven cooling in the cylinder block 28. A lubricating oil distribution groove 75 that distributes lubricating oil that lubricates each part of the valve operating mechanism 45 is formed in a groove form on the opposite side of the bypass oil passage with the cam chain chamber 52 interposed therebetween, that is, on the upper surface of the left cylinder block 28. Is formed.

  FIG. 14 is a rear view of the cylinder block 28. The left and right cylinder block upper surface collection grooves A10 shown in FIG. 7 are also shown in FIG. A cylinder block descending oil passage A11 extends downward from the middle of each of the left and right collection grooves A10. The pair of descending oil passages A11 in the cylinder block reaches the discharge side oil gallery A12 at the lower part of the cylinder block and merges there. In the middle of the discharge-side oil gallery A12, a discharge connection portion 53 is provided slightly to the left of the center, and the discharge-side oil gallery A12 communicates with the crankcase discharge oil passage A13 through this. In the drawing, a tensioner mounting portion 62 is provided at the center of the rear surface of the cylinder block 28.

  FIG. 15 is a bottom view of the cylinder block 28. A discharge connecting portion 53 for connecting the oil passage to the crankcase discharge oil passage A13 is opened slightly on the left side of the middle of the discharge side oil gallery A12 on the rear surface side of the cylinder block 28. In this figure, the supply side oil gallery A4 and the oil introduction part 50 are also shown.

  FIG. 16 is a side view of the peripheral portion of the oil return pipe A14. The discharge connection portion 53 communicates with the upper end of the crankcase discharge oil passage A13 provided at the upper portion of the upper crankcase 27A. The crankcase discharge oil passage A13 is a short oil passage. The upper end of the oil return pipe A14 is inserted into the lower end of the crankcase discharge oil path A13 via a seal member 82, and the middle part of the oil return pipe A14 is attached to and detached from the oil pump 48 via a support member 80. It is fixed as possible. The lower portion of the oil return pipe A14 extends to the vicinity of the lower end surface of the lower crankcase 27B, but does not protrude below the lower end surface of the lower crankcase 27B. The lower end of the oil return pipe A14 is opened toward the oil pan 31. FIG. 16 shows a locus 79a of the maximum outer circumference of the crank web 78 (FIG. 2). The oil return pipe A14 overlaps the locus 79 of the crank web 78 in a side view.

  FIG. 17 is a top view of the lower crankcase 27B. A bottom plate 27Ba is provided on the left and right end portions of the lower crankcase 27B and the lower surface of the front edge portion. The lower surface of the central portion is a lower opening 27Bb for connection to an oil pan. In the figure, the crankshaft 32 supported by the bearing 83 is shown in cross section. The oil return pipe A14 is passed through a narrow space between the side wall of the cam chain chamber 52, the crank web 78, and the oil pump 48, and is supported by the oil pump 48 via a support member 80.

  In the oil passage described above, the cylinder head cooling oil sent from the oil pan 31 via the oil pump 48 is the discharge pipe A1, the oil cooler forward pipe A2, the oil cooler return pipe A3, the supply side oil gallery A4, the cylinder. Ascending oil passage A5, Cylinder block upper surface distribution groove A6, Cylinder head supply oil passage A7, Spark plug oil jacket A8, Cylinder head oil discharge oil passage A9, Cylinder block upper surface recovery groove A10, Cylinder block lowering oil passage The cylinder head 29 is cooled by returning to the oil pan 31 via A11, the discharge side oil gallery A12, the crankcase discharge oil passage A13, and the oil return pipe A14. In this circulation path, a part of the oil flows through the bypass grooves B1 and B2 without passing through the spark plug oil jacket A8, thereby eliminating the uneven cooling of the cylinder block 28.

  In FIG. 16, an oil return pipe A14 is provided between the crankshaft 32 and the transmission main shaft 33, and the pipe A14 is disposed in a range overlapping the rotation locus 79 of the crank web 78 in a side view of the engine. In FIG. 17, it is arranged at a position where it does not interfere with the crank web 78 in the axial direction. As a result, the oil return pipe A14 can be disposed close to the crank web 78 while suppressing interference with the crank web 78, and the engine 1 can be made large without increasing the distance between the crankshaft 32 and the transmission main shaft 33. It is possible to arrange using empty space without converting.

  In FIG. 16, an oil pump 48 is disposed between the crankshaft 32 and the transmission main shaft 33, and the oil return pipe A14 is passed between the oil pump 48 and the crankshaft 32 in a side view. Since the oil return pipe A14 is disposed in the gap between the oil pump 48 and the crankshaft 32, the longitudinal length of the engine 1 is suppressed from becoming longer.

  In FIG. 16, the lower end of the oil return pipe A14 is set to a height that does not protrude below the lower surface of the lower crankcase 27B to which the oil pan 31 is connected. Since the oil return pipe A14 does not protrude from the lower surface of the crankcase 27 from which the oil pan 31 has been removed, it is possible to protect the pipe during maintenance, and there will be no catching on the pipe during maintenance compared to when the pipe protrudes. , Workability is improved.

  As seen in the top view of the lower crankcase 27B of FIG. 17, this engine includes a cam chain chamber 52 in the center. The oil return pipe A14 is disposed between the side wall of the cam chain chamber 52, the crank web 78, and the oil pump 48. Since an empty space among the cam chain chamber 52, the crank web 78, and the oil pump 48 is used, the oil return pipe can be arranged efficiently.

  As shown in FIG. 16, the upper end of the oil return pipe A14 is inserted into the lower part of the crankcase exhaust oil passage A13 via a seal member 82, and the intermediate part of the oil return pipe A14 is supported by the oil pump 48. Removably fixed via a member 80. For this reason, removal and fixing at the time of pipe assembly and maintenance can be easily performed, and assembling and maintenance are improved.

  A12: Oil gallery on the discharge side, A13: Oil passage in the crankcase, A14: Oil return pipe, 27 ... Crankcase, 27A ... Upper crankcase, 27B ... Lower crankcase, 28 ... Cylinder block, 29 ... Cylinder head, 31 ... oil pan, 32 ... crankshaft, 33 ... main shaft, 34 ... countershaft, 48 ... oil pump, 52 ... cam chain chamber, 78 ... crank web, 79 ... locus of crank web,

Claims (5)

In a cylinder head cooling oil passage of a multi-cylinder engine that is connected to the cylinder block and passes an oil return pipe through which return oil from the cylinder head cooling oil passage passes from the cylinder block toward the lower side of the engine,
The oil return pipe is provided between the crankshaft and the transmission shaft, and the pipe is arranged in a range overlapping with a rotation trajectory of a crank web protruding in the crankshaft radial direction in a side view of the engine. An oil passage for cooling a cylinder head of a multi-cylinder engine, which is disposed at a position shifted from the crank web.   The multi-cylinder engine according to claim 1, wherein an oil pump is disposed between the crankshaft and the transmission, and the oil return pipe is passed between the oil pump and the crankshaft in a side view. Cylinder head cooling oil passage.   3. The cylinder head cooling of a multi-cylinder engine according to claim 1, wherein the lower end of the oil return pipe is set to a height that does not protrude below the lower surface of the crankcase to which the oil pan is connected. Oil passage.   A drive member storage chamber (such as a cam chain chamber) for storing a valve train drive transmission member is provided at the center in the left-right direction of the engine, and an oil return pipe is disposed between the side wall of the drive member storage chamber and the crank web. The oil passage for cooling a cylinder head of a multi-cylinder engine according to any one of claims 1 to 3.   The upper end of the oil return pipe is inserted into the lower part of the oil discharge passage at the upper part of the crankcase that is connected to the lower side of the discharge side oil gallery in the cylinder block via a seal member, and the middle part of the oil return pipe is fixed to the oil pump. An oil passage for cooling a cylinder head of a multi-cylinder engine according to claim 1 or 2.

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