JP6897347B2 - Engine cooling oil passage structure - Google Patents

Description

The present invention relates to a cooling oil passage structure of an engine, particularly an engine that cools a cylinder with cooling oil.

Patent Document 1 discloses an engine cooling oil passage structure in which a cylinder-side cooling oil passage is continuously formed around a cylinder bore in the cylinder.

Japanese Unexamined Patent Publication No. 2016-98723

In order to shorten the width of the cylinder and realize the miniaturization of the engine, in the plan view of the cylinder, the cylinder bore, the cylinder side cooling oil passage around the cylinder bore, the cam chain chamber, and the stud bolt insertion hole are provided. It is necessary to design as tightly as possible. Here, the stud bolt insertion hole is a hole through which a stud bolt for connecting the cylinder head and the head cover to the crankcase is inserted.

Further, in order to shorten the width dimension of the cylinder, the width of the cooling oil passage on the cylinder side located between the cylinder bore and the cam chain chamber is narrowed, or only a part of the cooling oil passage is narrowed. May be done. However, in general, it is necessary to secure a width of the cooling passage that does not break during casting. Further, when considering the flow of the refrigerant (water or oil), it is not appropriate to form a portion in the cooling passage where the refrigerant is difficult to flow locally. For these reasons, there is a limit to narrowing the width of the cylinder-side cooling oil passage to shorten the width dimension of the cylinder.

Further, as described in Patent Document 1, when the cylinder-side cooling oil passage is continuously formed around the cylinder bore in the cylinder, the rigidity of the cylinder is lowered, and in the unlikely event, the cylinder bore is deformed. There is a fear.

An object of the present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an engine cooling oil passage structure capable of realizing a compact and lightweight engine.

In the engine cooling oil passage structure according to the present invention, a cylinder and a cylinder head are sequentially coupled to a crank case, a cylinder bore is formed in the cylinder, and a cam chain chamber is formed on the side of the cylinder bore, and a cylinder is formed in the cylinder. In an engine cooling oil passage structure in which a side cooling oil passage is formed on the cylinder head and a cylinder head side cooling oil passage is formed, the cylinder side cooling oil passage is provided around the cylinder bore. The cylinder has an oil passage abolished section in which the cylinder-side cooling oil passage is not formed between the cylinder bore and the cam chain chamber, and the cylinder-side cooling oil passages on both sides of the oil passage abolished section. However, the cylinder is configured to communicate with the cylinder head side cooling oil passage, and the cylinder has a plurality of the oil passage abolished sections in which the cylinder side cooling oil passage is not formed. The oil passage abolition section between the cam chain chamber is provided for the longest time, and a plurality of stat bolt insertion holes for inserting stat bolts for connecting the cylinder head to the crank case together with the cylinder are provided in the cylinder. However, at least both ends of the longest oil passage abolished section, which is provided at least between the cylinder bore and the cam chain chamber so as to be separated from each other and the cylinder side cooling oil passage is not formed, are the stat bolt insertion holes. It is positioned closer to the cam chain chamber side than the center, and the longest length of the oil passage abolished section is set to half the length between the centers of the stat bolt insertion hole. ..

According to the present invention, the cylinder has an oil passage abolished section in which a cylinder-side cooling oil passage is not formed between the cylinder bore and the cam chain chamber, so that the cam chain chamber is brought closer to the center of the cylinder bore. be able to. As a result, the width dimension of the cylinder can be shortened, so that the engine can be made smaller and lighter. Further, since the cylinder-side cooling oil passages on both sides of the oil passage abolished section are configured to communicate with the cylinder head-side cooling oil passage, the engine oil in the cylinder-side cooling oil passage is used for cooling the cylinder head side. Can lead to oil passages. As a result, the cylinder head, which is a high temperature portion, can be effectively cooled.

The right side view which shows the engine to which one Embodiment of the cooling oil passage structure of the engine which concerns on this invention is applied. A perspective view of the cylinder and the cylinder head of FIG. 1 as viewed diagonally from the front left. FIG. 3 is a perspective view showing a plurality of cylinder head side cooling oil passages formed in the cylinder head of FIG. 2 visually from diagonally left front together with the cylinder. A perspective view showing a plurality of cylinder head side cooling oil passages formed in the cylinder head of FIG. 2 visually from diagonally right front together with the cylinder. The front view which shows the plurality of cylinder head side cooling oil passages formed in the cylinder head of FIG. 2 together with a cylinder. The right side view which shows the plurality of cylinder head side cooling oil passages formed in the cylinder head of FIG. 2 together with a cylinder. The left side view which shows the plurality of cylinder head side cooling oil passages formed in the cylinder head of FIG. 2 together with a cylinder. The rear view which shows the plurality of cylinder head side cooling oil passages formed in the cylinder head of FIG. 2 together with a cylinder. The plan view which shows the cylinder head and the cylinder of FIG. The plan view which shows the plurality of cylinder head side cooling oil passages formed in the cylinder head of FIG. 9 together with a cylinder and a cylinder head gasket. The bottom view which shows the cylinder head of FIG. The bottom view which shows the cylinder head and the cylinder head gasket of FIG. 2 is a plan view of a cylinder showing a plurality of cylinder-side cooling oil passages formed in the cylinders of FIGS. 2 and 10. The plan view which shows the cylinder of FIG. 13 together with a cylinder head gasket.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a right side view showing an engine to which one embodiment of the cooling oil passage structure of the engine according to the present invention is applied. In the present embodiment, the expressions of front / rear, left / right, and up / down are based on the driver who rides in the vehicle equipped with the engine.

The engine 10 shown in FIG. 1 is, for example, a single-cylinder engine mounted on a motorcycle, and is configured such that a cylinder assembly 12 is tilted forward and extended from the front of a crankcase 11. The cylinder assembly 12 is configured by sequentially joining the cylinder 13, the cylinder head 14, and the head cover 15 from the side of the crankcase 11.

Of these, the cylinder 13 and the cylinder head 14 use stat bolts (not shown) that are inserted into the stud bolt insertion holes 28, 29 (see FIGS. 3 and 9) formed in the cylinder 13 and the cylinder head 14, which will be described later. It is coupled to the front upper surface of the crankcase 11.

As shown in FIGS. 1 and 11, a combustion chamber 17 is formed in the cylinder head 14, and an intake port 18 and an exhaust port 19 are formed in communication with the combustion chamber 17.

An air-fuel mixture (fuel-air mixture) is supplied to the intake port 18 from the engine intake system. This engine intake system includes an air cleaner, a throttle body, and a fuel injector (not shown). Instead of these throttle bodies and fuel injectors, carburetors may be used. Further, an exhaust pipe (not shown) of the engine exhaust system is connected to the exhaust port 19. The engine exhaust system discharges the exhaust generated by the combustion of the air-fuel mixture in the combustion chamber 17 and the cylinder bore 20 (described later) by the ignition of the spark plug 16. The spark plug 16 is installed on the right side wall of the cylinder head 14.

As shown in FIGS. 2 and 3, the cylinder head 14 is provided with an exhaust pipe mounting surface 21 for connecting and mounting the exhaust pipe to the exhaust port 19. Mounting bolt holes 22 are formed on the exhaust pipe mounting surface 21 at positions above and below the exhaust port 19 with the exhaust port 19 interposed therebetween. The exhaust pipe is attached to the exhaust pipe mounting surface 21 by screwing a mounting bolt (not shown) to the mounting bolt hole 22, and is connected to the exhaust port 19.

The cylinder 13 is formed with a cylinder bore 20 (see FIGS. 3 and 4) that communicates with the combustion chamber 17 of the cylinder head 14. A piston (not shown) is slidably arranged in the cylinder bore 20. The piston reciprocates as the air-fuel mixture burns in the combustion chamber 17 of the cylinder head 14 and the cylinder bore 20 of the cylinder 13, and this reciprocating motion is rotatably supported by the crankcase 11 via a connecting rod (not shown). It is converted into the reciprocating motion of the crankshaft 30 (FIG. 1).

The supply of the air-fuel mixture to the combustion chamber 17 described above is controlled by an intake valve (not shown) that opens and closes the intake port 18 with respect to the combustion chamber 17. Further, the exhaust gas from the combustion chamber 17 is controlled by an exhaust valve (not shown) that opens and closes the exhaust port 19 with respect to the combustion chamber 17. These intake valves and exhaust valves are driven by a valve gear (not shown) installed between the cylinder head 14 and the head cover 15. In this valve gear, the intake valve is driven by an intake cam and an intake arm (not shown), and the exhaust valve is driven by an exhaust cam and an exhaust rocker arm (not shown).

In the engine 10 shown in FIG. 1, two intake valves and two exhaust valves are provided for each cylinder. Therefore, as shown in FIGS. 2, 9 and 11, the cylinder head 14 is formed with two intake valve insertion holes 23 through which the intake valve is inserted and two exhaust valve insertion holes 24 through which the exhaust valve is inserted. ing. Further, by providing two intake valves and two exhaust valves in one cylinder, as shown in FIGS. 10 and 11, the intake port 18 and the exhaust port 19 are formed in a bifurcated shape in the cylinder head 14, respectively. Will be done. Of these, the exhaust port 19 is inclined and curved to one side (for example, the right side) in the left-right direction toward the exhaust pipe mounting surface 21 in a plan view of the cylinder head 14 so that the connected exhaust pipe does not interfere with the frame 25. Is formed.

Here, the bifurcated portion of the exhaust port 19 is indicated by reference numeral 19A, the bifurcated branch portion of the exhaust port 19 is indicated by reference numeral 19B, and the curved surface outside the exhaust port 19 is indicated by reference numeral 19C.

As shown in FIGS. 2, 3 and 9, in the cylinder 13 and the cylinder head 14, a cam chain chamber 26 accommodating a cam chain (not shown) for transmitting power to the valve gear is provided in the cylinder 13 and a cam chain chamber. 27 are formed on the cylinder head 14, respectively. Of these, the cam chain chamber 26 of the cylinder 13 has substantially the same shape as the cam chain chamber 27 of the cylinder head 14 in a plan view of the cylinder 13 and the cylinder head 14, and communicates with the cam chain chamber 27. Further, the cam chain chamber 26 of the cylinder 13 is formed on the side (for example, the left side) of the cylinder bore 20 in the cylinder 13.

Further, as shown in FIGS. 3 and 13, four stud bolt insertion holes 28 are formed in the cylinder 13 around the cylinder bore 20 at substantially equal intervals so as to penetrate the cylinder 13 in the vertical direction. Further, in the cylinder head 14, as shown in FIG. 9, four stud bolt insertion holes 29 also penetrate in the vertical direction of the cylinder head 14 at positions corresponding to the four stud bolt insertion holes 28 of the cylinder 13. Is formed. Of these, at least two stud bolt insertion holes 28 of the cylinder 13 on the cam chain chamber 26 side (left side) are located between the cylinder bore 20 and the cam chain chamber 26 before and after the cylinder 13, as shown in FIG. It is formed so as to be separated in the direction.

By the way, in the engine 10 shown in FIG. 1, an oil pan 31 for storing engine oil is provided in the lower part of the crankcase 11. The engine oil stored in the oil pan 31 is boosted by the drive of the oil pump 33 installed in the clutch cover 32 and guided to the oil filter 34. Here, the clutch cover 32 is arranged on the right side of the crankcase 11 and includes a clutch cover outer 35. The oil filter 34 is also installed on the clutch cover 32. Further, the oil pump 33 is driven by the rotational force of the crankshaft 30.

The engine oil purified by the oil filter 34 is guided to the crankshaft 30, the piston, the countshaft (not shown), the drive shaft (not shown), and the like through oil passages (not shown) such as in the clutch cover 32 and the crankcase 11. Then, these crankshafts 30 and the like are lubricated. Further, the engine oil purified by the oil filter 34 is guided to the valve gear through an oil passage (not shown) in the cylinder 13 and the cylinder head 14, and lubricates the valve gear. Further, the engine oil purified by the oil filter 34 is guided from the oil outflow portion 36 of the clutch cover 32 to the oil cooler 37, cooled by the oil cooler 37, and then the oil inflow portion provided in the cylinder head 14. It flows into 38.

The engine oil that has flowed into the oil inflow section 38 is introduced into the cooling oil passage 40 (FIGS. 3 and 4) formed in communication with the cylinder 13 and the cylinder head 14 as cooling oil. As a result, the area around the exhaust port 19 of the cylinder head 14, which is the hottest in the engine 12, the area below the spark plug 16 and the area below the intake port 18, and the area around the combustion chamber 17 in the cylinder head 14 and the cylinder 13 are cooled. The cooling oil passage 40 is configured such that the cylinder head side cooling oil passage 40A formed in the cylinder head and the cylinder side cooling oil passage 40B formed in the cylinder 13 communicate with each other. The cylinder head side cooling oil passage 40 is formed mainly by the core at the time of casting the cylinder head 14, and the cylinder side cooling oil passage 40B is formed by the core or machining.

As shown in FIGS. 3 and 4, the cylinder head side cooling oil passage 40A includes a first cylinder head side cooling oil passage 41, a second cylinder head side cooling oil passage 42, and a third cylinder head side cooling oil. It includes a passage 43, a fourth cylinder head side cooling oil passage 44, a fifth cylinder head side cooling oil passage 45, and a sixth cylinder head side cooling oil passage 46. Further, as shown in FIGS. 3 and 13, the cylinder-side cooling oil passage 40B is discontinuously formed around the cylinder bore 20 on the mating surface 55 of the cylinder 13 with the cylinder head, and the first cylinder-side cooling is performed. It is configured to have an oil passage 51 for cooling, an oil passage 52 for cooling on the second cylinder side, an oil passage 53 for cooling on the third cylinder side, and an oil passage 54 for cooling on the fourth cylinder side.

Here, of the cylinder head side cooling oil passage 40A, the first cylinder head side cooling oil passage 41, the third cylinder head side cooling oil passage 43, and the sixth cylinder head side cooling oil passage 46 are shown in FIG. As shown in FIG. 8, it has a foot equivalent space formed by core supporting feet for supporting the core forming each of these oil passages.

That is, the first cylinder head side cooling oil passage 41 has two foot equivalent spaces 47-1, and the third cylinder head side cooling oil passage 43 has one foot equivalent space 47-3, and the sixth cylinder head side. The cooling oil passage 46 has two foot equivalent spaces 47-6, respectively. However, these foot equivalent spaces 47-1, 47-3 and 47-6 are closed by the cylinder head gasket 48 arranged between the cylinder 13 and the cylinder head 14, as shown in FIGS. 11 and 12. As a result, it is configured so as not to communicate with the cylinder-side cooling oil passage 40B.

As shown in FIGS. 3 to 6, the first cylinder head side cooling oil passage 41 has the above-mentioned oil inflow portion 38 as an inflow end, and passes from below the spark plug 16 to the right side and below the exhaust port 19. , The exhaust port 19 is formed at least half around. The outflow end 49 of the first cylinder head side cooling oil passage 41 communicates with the inflow end 50 of the second cylinder head side cooling oil passage 42. Therefore, the cooling oil that flows from the oil cooler 37 into the cooling oil passage 41 on the first cylinder head side and flows in the cooling oil passage 41 on the first cylinder head side is below the spark plug 16 in the cylinder head 14. In addition, the right side and the lower side of the exhaust port 19 are cooled. The first cylinder head side cooling oil passage 41 is configured as another cylinder head side cooling oil passage.

The second cylinder head side cooling oil passage 42 of the cylinder head 14 is located above the combustion chamber 17 between the intake port 18 and the exhaust port 19, as shown in FIGS. 4, 7, 9 and 10. It is formed in a triangular shape in a plan view. The second cylinder head side cooling oil passage 42 is opened on the upper surface of the cylinder head 14 as shown in FIG. 9, and the flow path is formed by closing the opening with a lid (not shown). Further, the outflow end 56 of the second cylinder head side cooling oil passage 42 communicates with the inflow end 57 of the third cylinder head side cooling oil passage 43. Therefore, the cylinder head is caused by the cooling oil that flows from the first cylinder head side cooling oil passage 41 into the second cylinder head side cooling oil passage 42 and flows in the second cylinder head side cooling oil passage 42. Above the combustion chamber 17 in 14, the bifurcated portion 18A of the intake port 18 and the bifurcated portion 19A of the exhaust port 19 are cooled, respectively.

The third cylinder head side cooling oil passage 43 is another cylinder head side cooling oil passage, and is exhausted through the left side and the lower side of the exhaust port 19 as shown in FIGS. 3, 5 and 7. It is formed around port 19 at least halfway around. The outflow end 58 of the third cylinder head side cooling oil passage 43 communicates with the first cylinder side cooling oil passage 51 of the cylinder 13. Therefore, the cooling oil that flows from the cooling oil passage 42 on the second cylinder head side into the cooling oil passage 43 on the third cylinder head side and flows in the cooling oil passage 43 on the third cylinder head side causes the cylinder head. The left side and the lower side of the exhaust port 19 at 14 are cooled.

As shown in FIGS. 3, 4, 5, and 10, the fourth cylinder head side cooling oil passage 44 has an outer curved surface 19C on the left side of the exhaust port 19 from the mating surface 59 with the cylinder in the cylinder head 14. It is formed so as to pass through the outer side of the cylinder and extend to the mating surface 60 with the head cover and the upper part of the bifurcated branch portion 19B of the exhaust port 19. Further, as shown in FIGS. 2 and 9, the fourth cylinder head side cooling oil passage 44 is a mounting bolt that opens into the exhaust valve insertion hole 24 and the exhaust pipe mounting surface 21 in a plan view of the cylinder head 14. It is formed so as to surround the peripheral wall 63 of the cylinder head 14 with the hole 22.

Further, the fourth cylinder head side cooling oil passage 44 has an ascending passage 44A and a descending passage 44B, and is formed in a long U-shape by these. That is, in the ascending passage 44A, the inflow end 61 on the mating surface 59 side of the cylinder head 94 communicates with the first cylinder side cooling oil passage 51 of the cylinder 13 and reaches the outer curved surface 19C on the left side of the exhaust port 19. It rises along and reaches above the bifurcated branch portion 19B of the exhaust port 19. Further, the down passage 44B communicates with the up passage 44A, descends from above the bifurcated branch portion 19B of the exhaust port 19 along the outer curved surface 19C on the left side of the exhaust port 19, is adjacent to the up passage 44A, and has an outflow end. 62 communicates with the second cylinder side cooling oil passage 52 of the cylinder 13.

Here, the ascending passage 44A and the descending passage 44B are provided on the outer side of the outer curved surface 19C of the exhaust port 19. In the curved exhaust port 19, the outer curved surface 19C has an inner surface as compared with the inner curved surface. This is because the surface area of the exhaust gas increases, and the temperature tends to rise due to the exhaust gas.

The fourth cylinder head side cooling oil passage 44 guides the cooling oil from the cylinder 13 side to the cylinder head 14 side by the up passage 44A, and then returns it to the cylinder 13 side again by the down passage 44B. This is because highly viscous oil was used as the cooling material instead of water. That is, unlike water, in highly viscous oil, air bubbles mixed in the oil in the cooling passage flow together with the oil, so that the air bubbles are satisfactorily discharged without locally staying in the cooling passage. .. The fourth cylinder head side cooling oil passage 44 can be configured by the up passage 44A and the down passage 44B because the characteristics of the oil as described above are utilized.

The cooling oil from the first cylinder side cooling oil passage 51 of the cylinder 13 flows into the fourth cylinder head side cooling oil passage 44 configured as described above, so that the left side of the exhaust port 19 in the cylinder head 14 is left. The outside of the outer curved surface 19C and the space between the mating surface 60 of the cylinder head 14 and the head cover and the upper part of the exhaust port 19 are cooled. As a result, the mounting bolt holes 22 and mounting bolts for mounting the exhaust pipe in the cylinder head 14, and the head cover gasket 64 arranged between the mating surface 60 with the head cover and the head cover 15 are cooled.

As shown in FIGS. 3 and 7, the fifth cylinder head side cooling oil passage 45 is a passage formed for positioning the cam chain chamber 26 of the cylinder 13 at the center of the cylinder bore 20, as will be described later. In the fifth cylinder head side cooling oil passage 45, the inflow end 65 communicates with the second cylinder side cooling oil passage 52 of the cylinder 13, and the outflow end 66 is the third cylinder side cooling oil passage of the cylinder 13. Communicate with 53. Utilizing the above-mentioned oil characteristics (good discharge of air bubbles), the cooling oil in the second cylinder side cooling oil passage 52 passes through the fifth cylinder head side cooling oil passage 45 to the third. Although it is guided to the cylinder-side cooling oil passage 53, the cylinder head 14 is cooled by the cooling oil flowing in the fifth cylinder-side cooling oil passage 45.

In the sixth cylinder head side cooling oil passage 46, as shown in FIGS. 3, 4, 8 and 10, the inflow end 67 communicates with the third cylinder side cooling oil passage 13 of the cylinder 13, and the cylinder head. The outflow end 68 passes below the intake port 18 of the 14 and communicates with the fourth cylinder side cooling oil passage 54 of the cylinder 13. The inflow end 67 and the outflow end 68 are an oil passage abolished section for improving the rigidity of the cylinder 13 between the third cylinder side cooling oil passage 53 and the fourth cylinder side cooling oil passage 54 shown in FIG. (Described later) are formed close to each other so as to be minimized in order to secure the cooling performance of the cylinder 13.

Therefore, the cooling oil from the third cylinder side cooling oil passage 53 flows in the sixth cylinder head side cooling oil passage 46 by utilizing the characteristics of the oil (good air bubble discharge property), and then the third cylinder side cooling oil passage 53 is used. 4 By flowing through the cylinder-side cooling oil passage 54, the intake port 18 in the cylinder head 14 is cooled, and the filling efficiency of the intake air (air-fuel mixture) flowing in the intake port 18 is improved.

As shown in FIGS. 3, 4 and 13, the cylinder-side cooling oil passage 40B formed in the cylinder 13 is formed discontinuously as described above, so that the mating surface 55 with the cylinder head in the cylinder 13 is formed. The first oil passage abolished section 71 is between the first cylinder side cooling oil passage 51 and the second cylinder side cooling oil passage 52, and the second cylinder side cooling oil passage 52 and the third cylinder side cooling are used. The second oil passage abolished section 72 is located between the oil passage 53, and the third oil passage abolished space 73 is located between the third cylinder side cooling oil passage 53 and the fourth cylinder side cooling oil passage 54. A fourth oil passage abolished section 74 exists between the cylinder-side cooling oil passage 54 and the first cylinder-side cooling oil passage 51, respectively. These first to fourth oil passage abolished sections 71, 72, 73 and 74 are sections in which the cylinder side cooling oil passage 40B is not formed on the mating surface 55 of the cylinder 13 with the cylinder head.

In these first to fourth oil passage abolished sections 71, 72, 73 and 74, the cylinder side cooling oil passage 40B is continuously formed around the cylinder bore 20 of the mating surface 55 with the cylinder head of the cylinder 13. Compared with the case, the rigidity of the cylinder 13 is improved, and the cooling performance around the combustion chamber 17 in the cylinder head 14 and the cylinder 13 is ensured.

As shown in FIGS. 13 and 14, the upstream end of the first cylinder side cooling oil passage 51 passes through the inflow port 75 of the cylinder head gasket 48 to the outflow end 58 of the third cylinder head side cooling oil passage 43. The downstream end communicates with the inflow end 61 of the cooling oil passage 44 on the fourth cylinder head side via the outflow port 76 of the cylinder head gasket 48. As a result, the first cylinder-side cooling oil passage 51 guides the cooling oil in the third cylinder head-side cooling oil passage 43 to the fourth cylinder head-side cooling oil passage 44, and at the same time, the cylinder bore 20 of the cylinder 13 Cool a part of the surroundings.

The upstream end of the second cylinder side cooling oil passage 52 communicates with the outflow end 62 of the fourth cylinder head side cooling oil passage 44 through the inflow port 77 of the cylinder head gasket 48, and the downstream end is the cylinder head gasket. It communicates with the inflow end 65 of the cooling oil passage 45 on the fifth cylinder head side via the outflow port 78 of 48. As a result, the second cylinder-side cooling oil passage 52 guides the cooling oil in the fourth cylinder head-side cooling oil passage 44 to the fifth cylinder head-side cooling oil passage 45, and at the same time, the cylinder bore 20 of the cylinder 13 Cool a part of the surroundings.

The upstream end of the third cylinder side cooling oil passage 53 communicates with the outflow end 66 of the fifth cylinder head side cooling oil passage 45 through the inflow port 79 of the cylinder head gasket 48, and the downstream end is the cylinder head gasket. It communicates with the inflow end 67 of the cooling oil passage 46 on the sixth cylinder head side via the outflow port 80 of 48. As a result, the third cylinder head side cooling oil passage 53 guides the cooling oil in the fifth cylinder head side cooling oil passage 45 to the sixth cylinder head side cooling oil passage 46, and the cylinder bore 20 of the cylinder 13 Cool a part around the.

The upstream end of the fourth cylinder side cooling oil passage 54 communicates with the outflow end 68 of the sixth cylinder head side cooling oil passage 46 through the inflow port 81 of the cylinder head gasket 48, and the downstream end is the oil return passage 82. Communicate with. The oil return passage 82 is formed so as to penetrate the cylinder 13 in the vertical direction, and guides the cooling oil to the oil pan 31 of the crankcase 11. As a result, the fourth cylinder side cooling oil passage 54 guides the cooling oil from the sixth cylinder head side cooling oil passage 46 to the oil return passage 82, and cools a part around the cylinder bore 20 of the cylinder 13. To do.

As shown in FIG. 13, among the above-mentioned first oil passage abolished section 71, second oil passage abolished section 72, third oil passage abolished section 73, and fourth oil passage abolished section 74, for cooling on the second cylinder side. The second oil passage abolished section 72 existing between the oil passage 52 and the third cylinder side cooling oil passage 53, that is, the second oil passage abolished section 72 existing between the cylinder bore 20 and the cam chain chamber 26 is the most. It has been set for a long time.

The length P1 between both ends of the second oil passage abolished space 72 is two stud bolt insertion holes 28 formed in the cylinder 13 between the cylinder bore 20 and the cam chain chamber 26 in the front-rear direction of the cylinder 13. It is set to about half of the center-to-center length P2. Further, both ends of the second oil passage abolished section 72 are positioned so as to be biased toward the cam chain chamber 26 side from the center of the stud bolt insertion hole 28 formed between the cylinder bore 20 and the cam chain chamber 26 as described above. ..

Further, since the second oil passage abolished section 72 is set to the maximum as described above, the cam chain chamber 26 is set closer to the center of the cylinder bore 20, for example, the cylinder side cooling oil passage 40B (second cylinder). It is provided so as to be in contact with the virtual line M on the outer periphery of the side cooling oil passage 52 and the third cylinder side cooling oil passage 53). Further, as shown in FIGS. 3 and 13, a part of the cam chain chamber 26 on the cylinder bore 20 side is lightened, and the cylinder side cooling oil passage 40B (second cylinder side cooling oil passage 52 and third). It is a bulging portion 83 that bulges toward the center of the cylinder bore 20 from the virtual line M on the outer circumference of the cylinder-side cooling oil passage 53).

As shown in FIGS. 10 and 13, the cooling oil cooled by the oil cooler 37 (FIG. 1) is cooled by the first cylinder head side cooling oil passage 41 and the second cylinder head side cooling as shown by arrow A. After sequentially flowing through the water passage 42 and the cooling oil passage 43 on the third cylinder head side, they flow through the cooling oil passage 51 on the first cylinder side as shown by the arrow B in FIG. 13, and then the arrow in FIG. As shown in C, it flows in the cooling oil passage 44 on the fourth cylinder head side. Cooling oil flowing through the first cylinder head side cooling oil passage 41, the second cylinder head side cooling oil passage 42, the third cylinder head side cooling oil passage 43, and the fourth cylinder head side cooling oil passage 44. Cools the area below the spark plug 16 and around the exhaust port 19.

The cooling oil flowing through the fourth cylinder head side cooling oil passage 44 is in the second cylinder side cooling oil passage 52 in FIG. 13, in the fifth cylinder head side cooling oil passage 45 in FIG. 10, and in FIG. 13. Flows sequentially in the third cylinder side cooling oil passage 53 as shown by arrow D. After that, the cooling oil in the cooling oil passage 53 on the third cylinder side flows in the cooling oil passage 46 on the sixth cylinder head side in FIG. 10 as shown by arrow E to cool the lower part of the intake port 18, and the figure shows the figure. It flows through the fourth cylinder side cooling oil passage 54 of No. 13 as shown by an arrow F, reaches the oil return passage 82, and is returned to the oil pan 11 of the crankcase 11. The cooling oil flows sequentially through the first cylinder side cooling oil passage 51, the second cylinder side cooling oil passage 52, the third cylinder side cooling oil passage 53, and the fourth cylinder side cooling oil passage 54, so that the cylinder The periphery of the combustion chamber 17 in the 13 and the cylinder head 14 is cooled.

Since it is configured as described above, according to the present embodiment, the following effects (1) to (13) are obtained.
(1) As shown in FIGS. 3, 5 and 10, the cylinder head 14 passes from the mating surface 59 with the cylinder to the left side of the exhaust port 19, and with the mating surface 60 with the head cover and the upper part of the exhaust port 19. The fourth cylinder head side cooling oil passage 44 is formed between the two. Therefore, even when the mating surface 60 of the cylinder head 14 with the head cover is brought close to the exhaust port 19 to reduce the size of the engine 10 in the vertical direction, the head cover gasket 64 arranged between the cylinder head 14 and the head cover 15 is exhausted. Damage (heat damage) caused by heat from the port 19 can be reduced, and sealing performance can be ensured. As a result, both the miniaturization of the engine 10 and the improvement of the sealing property of the engine 10 can be realized.

(2) As shown in FIGS. 2 and 9, the fourth cylinder head side cooling oil passage 44 is a mounting bolt that opens into the exhaust valve insertion hole 24 and the exhaust pipe mounting surface 21 in a plan view of the cylinder head 14. It is formed between the hole 22 and the hole 22. Therefore, it is possible to prevent creep from occurring in the mounting bolt hole 22 by cooling the mounting bolt hole 22, and by screwing the mounting bolt into the mounting bolt hole 22, the tightening torque is reduced. Can be suppressed. As a result, the sealing property between the exhaust pipe mounting surface 21 of the cylinder head 14 and the exhaust pipe can be improved.

(3) The fourth cylinder head side cooling oil passage 44 is formed so as to sandwich the peripheral wall 63 of the cylinder head 14 in a plan view of the cylinder head 14. Therefore, since the peripheral wall 63 above the exhaust port 19 that becomes hot can be cooled, heat damage to the head cover gasket 64 arranged between the cylinder head 14 and the head cover 15 can be reduced.

(4) As shown in FIGS. 5 and 10, the exhaust port 19 is formed so as to be curved to the right side so that the connected exhaust pipe does not interfere with the frame 25, and the connection with the exhaust pipe becomes smooth. It is configured as follows. Since the surface area of the outer curved surface 19C of the exhaust port 19 is larger than that of the inner curved surface, the temperature of the exhaust port 19 is likely to rise due to exhaust gas. In the present embodiment, the cooling oil passage 44 on the fourth cylinder head side is formed on the outer side of the outer curved surface 19C of the exhaust port 19, so that the cooling oil flows through the cooling oil passage 44 on the fourth cylinder head side. Therefore, the exhaust port 19 can be effectively cooled, and the temperature rise can be suppressed.

(5) As shown in FIGS. 3 and 5, the fourth cylinder head side cooling oil passage 44 formed in the cylinder head 14 is outside the outer curved surface 19C of the exhaust port 19 from the mating surface 59 with the cylinder. The ascending passage 44A leading to the upper part of the exhaust port 19 and the descending passage 44B provided adjacent to the ascending passage 44 from above the exhaust port 19 to the mating surface 59 with the cylinder through the ascending passage 44A. Therefore, it is formed in a U shape. Therefore, the outer curved surface 19C of the exhaust port 19 and the upper part of the exhaust port 19 can be intensively cooled by positively exchanging heat with the cooling oil. Further, the productivity of the cylinder head 14 can be improved by forming the fourth cylinder head side cooling oil passage 44 on the outer side of the outer curved surface 19C which is one side of the exhaust port 19.

(6) As shown in FIGS. 3, 4 and 10, the cylinder head 14 has a first cylinder passing downward from the right side of the exhaust port 19 in addition to the cooling oil passage 44 on the fourth cylinder head side. A head-side cooling oil passage 41 is formed, a second cylinder head-side cooling oil passage 42 is formed above the bifurcated portion 19A of the exhaust port 19, and a third cylinder head passes downward from the right side of the exhaust port 19. A side cooling oil passage 43 is formed. Since the exhaust port 19 is surrounded by the cooling oil passages 41, 42, 43 and 44 on the first to fourth cylinder head sides in this way, the exhaust port is provided by the cooling oil flowing in these cooling oil passages. The cooling performance of 19 can be improved. Moreover, since the exhaust pipe mounting surface 21 is opened and the lower mounting bolt holes 22 can be cooled together, a decrease in the tightening torque of the exhaust pipe can be further suppressed.

(7) In the cylinder head 14, as described above, the first cylinder head side cooling oil passage 41, the second cylinder head side cooling oil passage 42, and the third cylinder head side cooling oil passage 41 are provided around the exhaust port 19. 43 and the fourth cylinder head side cooling oil passage 44 are formed. Therefore, the heat exchange efficiency between the exhaust gas flowing in the exhaust port 19 and the engine oil (cooling oil) flowing in the cooling oil passages 41, 42, 43 and 44 on the first to fourth cylinder head sides is improved.

Therefore, when the temperature of the engine oil (cooling oil) is low and the viscosity is high when the engine 10 is started to cool down, the engine oil (cooling oil) is used in the cooling oil passages 41 on the first to fourth cylinder head sides. Since it becomes difficult to flow in 42, 43 and 44, it becomes easy to be heated by the exhaust in the exhaust port 19, and the temperature rises at an early stage. As a result, it is possible to improve the warm-up performance when the engine 10 is started to cool down.

(8) As shown in FIGS. 3 and 13, the cylinder 13 has a second oil passage abolished section 72 in which the cylinder side cooling oil passage 40B is not formed between the cylinder bore 20 and the cam chain chamber 26. Therefore, the cam chain chamber 26 can be brought close to the center of the cylinder bore 20. As a result, the left and right width dimensions of the cylinder 13 can be shortened, so that the engine 10 can be made smaller and lighter.

(9) The second cylinder side cooling oil passage 52 and the third cylinder side cooling oil passage 53 on both sides of the second oil passage abolished section 72 are configured to communicate with each other by the fifth cylinder head side cooling oil passage 45. Has been done. Therefore, the cooling oil in the cooling oil passage 52 on the second cylinder side can be guided to the cooling oil passage 45 on the fifth cylinder head side, whereby the cylinder head 14 having a high temperature can be effectively cooled.

(10) As shown in FIG. 13, the cylinder 13 has a second oil passage abolished section 72 in which the cylinder side cooling oil passage 40B is not formed between the cylinder bore 20 and the cam chain chamber 26. Therefore, the cam chain chamber 26 is centered on the cylinder bore 20 so that the cam chain chamber 26 is in contact with the virtual line M on the outer periphery of the second cylinder side cooling oil passage 52 and the third cylinder side cooling oil passage 53. Can be brought closer. Therefore, while ensuring the wall thickness around the cylinder bore 20 in the cylinder 13 to a required dimension, the cam chain chamber 26 is brought closer to the center of the cylinder bore 20, the lateral width dimension of the cylinder 13 is shortened, and the engine 10 is made smaller. Can be changed.

(11) In the cylinder 13, the length P1 of the second oil passage abolished section 72 is about half the length P2 between the centers of the two stud bolt insertion holes 28 located between the cylinder bore 20 and the cam chain chamber 26. It is set. Further, both ends of the second oil passage abolished section 72 are positioned closer to the cam chain chamber 26 than the center of the stud bolt insertion hole 28 located between the cylinder bore 20 and the cam chain chamber 26. As a result, the left and right width dimensions of the cylinder 13 are shortened while ensuring the wall thickness dimension L between the stud bolt insertion hole 28 and the cam chain chamber 26 and the cooling performance around the cylinder bore 20 in the cylinder 13. Therefore, the engine 10 can be miniaturized.

(12) In the cam chain chamber 26, a bulging portion 83 that bulges toward the center of the cylinder bore 20 from the virtual line M on the outer periphery of the second cylinder side cooling oil passage 52 and the third cylinder side cooling oil passage 53. Is formed. As a result, if the wall thickness dimension T between the cylinder bore 20 and the bulging portion 83 in the cylinder 13 is within the range of the wall thickness dimension around the cylinder bore 20 required for the cylinder 13, the weight of the cylinder 13 can be reduced. it can.

(13) On the mating surface 55 of the cylinder 13 with the cylinder head, a first cylinder side cooling oil passage 51, a second cylinder side cooling oil passage 52, and a third cylinder side cooling oil passage 53 are provided around the cylinder bore 20. And the fourth cylinder side cooling oil passage 54 is formed. Further, on the mating surface 55 with the cylinder head, a first oil passage abolished section 71 is provided between the first cylinder side cooling oil passage 51 and the second cylinder side cooling oil passage 52, and the second cylinder side cooling oil is provided. The second oil passage abolished section 72 is between the passage 52 and the third cylinder side cooling oil passage 53, and the third oil passage abolished section is between the third cylinder side cooling oil passage 53 and the fourth cylinder side cooling oil passage 54. 73 has a fourth oil passage abolished section 74 between the fourth cylinder side cooling oil passage 54 and the first cylinder side cooling oil passage 51. Therefore, it is possible to improve the rigidity of the cylinder 13 and prevent deformation around the cylinder 20 while ensuring the cooling performance around the combustion chamber 17 in the cylinder 13 and the cylinder head 14.

By preventing deformation around the cylinder bore 20 in the cylinder 13, it is possible to avoid a seal failure of the cylinder head gasket 48 between the cylinder 13 and the cylinder head 14, so that it is possible to prevent a failure of the engine 10 due to the blow-by of the internal pressure of the cylinder bore 20. .. Further, by preventing deformation of the cylinder 13 around the cylinder bore 20, it is possible to prevent poor tracking of the piston ring and an increase in engine oil consumption.

Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention, and the replacements and changes thereof can be made. , It is included in the scope and gist of the invention, and is also included in the scope of the invention described in the claims and the equivalent scope thereof. For example, in the present embodiment, the case where the engine 10 is a single-cylinder engine has been described, but the present invention may be applied to a multi-cylinder engine in which two intake valves and two exhaust valves are provided for each cylinder.

10 ... engine, 11 ... crank case, 13 ... cylinder, 14 ... cylinder head, 15 ... head cover, 17 ... combustion chamber, 19 ... exhaust port, 19A ... forked part of exhaust port, 19C ... outer curved surface of exhaust port, 20 ... Cylinder bore, 21 ... Exhaust pipe mounting surface, 22 ... Mounting bolt hole, 26 ... Cam chain chamber, 28 ... Stud bolt insertion hole, 40 ... Cooling oil passage, 40A ... Cylinder head side cooling oil passage, 40B ... Cylinder Side cooling oil passage, 41 ... 1st cylinder head side cooling oil passage (other cylinder head side cooling oil passage), 42 ... 2nd cylinder head side cooling oil passage, 43 ... 3rd cylinder head side cooling Oil passage (other cylinder head side cooling oil passage), 44 ... 4th cylinder head side cooling oil passage (cylinder head side cooling oil passage), 44A ... up passage, 44B ... down passage, 45 ... 5th cylinder Head side cooling oil passage, 48 ... Cylinder head gasket, 52 ... Second cylinder side cooling oil passage, 53 ... Third cylinder side cooling oil passage, 59 ... Cylinder mating surface, 60 ... Head cover mating surface , 63 ... Cylinder head peripheral wall, 64 ... Head cover gasket, 71 ... 1st oil passage abolished section, 72 ... 2nd oil passage abolished section, 73 ... 3rd oil passage abolished section, 74 ... 4th oil passage abolished section, 83 ... bulge, M ... virtual line, P1 ... length, P2 ... center-to-center length

Claims (3)

A cylinder and a cylinder head are sequentially coupled to a crank case, a cylinder bore is formed in the cylinder, and a cam chain chamber is formed on the side of the cylinder bore, a cylinder-side cooling oil passage is formed in the cylinder, and a cylinder head is formed in the cylinder head. In the cooling oil passage structure of the engine in which the side cooling oil passages are formed respectively,
The cylinder-side cooling oil passage is provided around the cylinder bore, and the cylinder has an oil passage abolished section in which the cylinder-side cooling oil passage is not formed between the cylinder bore and the cam chain chamber. It exists, and the cylinder-side cooling oil passages on both sides in this oil passage abolished section are configured to communicate with the cylinder head-side cooling oil passage.
The cylinder has a plurality of oil passage abolished sections in which the cylinder-side cooling oil passage is not formed, and the oil passage abolished section between the cylinder bore and the cam chain chamber is provided for the longest time. Be,
The cylinder is provided with a plurality of stat bolt insertion holes for inserting stat bolts for connecting the cylinder head to the crankcase together with the cylinder, at least separated from each other between the cylinder bore and the cam chain chamber. Be,
Both ends of the longest oil passage abolished section in which the cylinder-side cooling oil passage is not formed are positioned closer to the cam chain chamber side than the center of the stat bolt insertion hole, and further, the longest oil passage abolished section. The length of the oil passage structure for cooling the engine is set to half the length between the centers of the stat bolt insertion holes. The engine cooling oil passage structure according to claim 1, wherein the cam chain chamber is provided so as to be in contact with a virtual line on the outer periphery of the cylinder side cooling oil passage. The engine cooling according to claim 1 or 2, wherein a part of the cam chain chamber is formed so as to bulge toward the center side of the cylinder bore from the virtual line on the outer periphery of the cylinder side cooling oil passage. Oil passage structure.

Images