JP2019157823A - Engine cooling structure - Google Patents

Abstract

To provide an engine cooling structure capable of improving the cool-ability around the engine ignition plug by accelerating evaporation of adhesion fuel on an intake port wall.SOLUTION: An engine cooling structure that includes an oil passage A for guiding the oil from an oil pump 48 to the vicinity of a combustion chamber 37 of the cylinder head 29 and for returning the return oil from the vicinity of the combustion chamber 37 into an oil pan, in which a fuel injection valve 54 is arranged on the upstream of a suction port 39 so that the injection fuel from the fuel injection valve 54 provided on the upstream of the suction port 39 directs a suction port outlet 39a, and a port bypass passage C for guiding the return oil from the vicinity of the combustion chamber 37 of the cylinder head 29 is formed in a suction port lower wall 39c of the cylinder head 29.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an engine cooling structure.

2. Description of the Related Art Conventionally, in an internal combustion engine, a configuration is known in which an appropriate oil lower portion is provided for dropping lubricating oil directly from above the cylinder head onto the oil flow surface in the cylinder head, and the lubricating oil is dropped particularly on the intake side ( For example, see Patent Document 1).
In this type of internal combustion engine, since the intake port wall is generally cold when cold, the temperature of the intake air is low and fuel vaporization is difficult to promote, and after warming up, the area around the spark plug is positive in order to suppress knocking. Need to cool down.

JP 2012-225176 A

However, in Patent Document 1, it is desired to further improve the effect on warm-up performance by merely cooling the oil by utilizing heat exchange with the oil on the upper surface of the intake port wall.
The present invention has been made in view of the above-described circumstances, and provides an engine cooling structure that can promote the vaporization of the fuel adhering to the intake port wall and improve the cooling performance around the spark plug of the engine. With the goal.

  The engine cooling structure according to the present invention guides oil from the oil pump (48) to the periphery of the combustion chamber (37) of the cylinder head (29), and returns oil from the periphery of the combustion chamber (37) to the oil pan. In the engine cooling structure provided with the oil passage (A) returning to the inside, the fuel injection from the fuel injection valve (54) provided upstream of the intake port (39) is directed to the intake port outlet (39a). The valve (54) is arranged upstream of the intake port (39), and the return oil from around the combustion chamber (37) of the cylinder head (29) is placed in the lower wall (39c) of the intake port of the cylinder head (29). A port bypass passage (C) that guides the air is formed.

  In the above invention, the port bypass passage (C) may be provided with an on-off valve (100), and the port bypass passage (C) may be closed after the engine is warmed up.

  In the above invention, the oil passages (A6, A7, A8, A9, A10, B) around the combustion chamber (37) of the cylinder head (29) are plug-side passages passing through the inside of the spark plug seat (70). (A8) and a bypass passage (B) that bypasses the periphery of the combustion chamber (37), and an on-off valve (101) may be provided in the bypass passage (B).

  In the above invention, the on-off valve (101) of the bypass passage (B) may be closed when the engine is cold.

  The engine cooling structure according to the present invention guides the oil from the oil pump (48) to the periphery of the combustion chamber (37) of the cylinder head (29) and also returns the return oil from the periphery of the combustion chamber (37). In the engine cooling structure provided with the oil passage (A) returning into the oil pan, the injected fuel from the fuel injection valve (54) provided upstream of the intake port (39) is directed to the intake port outlet (39a). The fuel injection valve (54) is disposed upstream of the intake port (39), and the intake port lower wall (39c) of the cylinder head (29) extends from the periphery of the combustion chamber (37) of the cylinder head (29). A port bypass passage (C) for guiding the return oil is formed, and when the engine is cold, the combustion chamber (37) around the cylinder head (29) is surrounded by the port bypass passage (C). Is returned to the intake port lower wall (39c), and after the engine is warmed up, the cylinder head (29) is combusted from the intake port lower wall (39c) through the port bypass passage (C). It changes so that oil may be poured into the spark plug seat (70) around a chamber (37).

  An engine cooling structure according to the present invention includes an oil passage that guides oil from an oil pump to the periphery of a combustion chamber of a cylinder head and returns oil returned from the periphery of the combustion chamber into an oil pan. The fuel injection valve is disposed upstream of the intake port so that the fuel injected from the fuel injection valve provided upstream of the intake port is directed toward the intake port outlet, and the cylinder head is disposed in the lower wall of the intake port of the cylinder head. A port bypass passage was formed to guide the return oil from around the combustion chamber. According to this configuration, the warmed high-temperature oil flowing in the port bypass passage facilitates the vaporization of the fuel adhering to the lower wall of the intake port and improves the engine warm-up performance.

  In the above invention, an opening / closing valve may be provided in the port bypass passage, and the port bypass passage may be closed after the engine is warmed up. According to this configuration, an increase in intake air temperature after warm-up can be suppressed, a decrease in intake air density can be suppressed, and engine performance can be improved.

  In the above invention, the oil passage around the combustion chamber of the cylinder head includes a plug-side passage that passes through the inside of the spark plug seat and a bypass passage that bypasses the periphery of the combustion chamber. May be provided. According to this configuration, the heating performance of the intake port can be adjusted by opening and closing the on-off valve of the bypass passage, and the warm-up performance and the engine cooling performance after warm-up can be further enhanced.

  In the above invention, the on-off valve of the bypass passage may be closed when the engine is cold. According to this configuration, the warming performance of the intake port can be improved and the warm-up performance can be further enhanced by positively utilizing the temperature rise of the spark plug seat.

  An engine cooling structure according to the present invention includes an oil passage that guides oil from an oil pump to the periphery of a combustion chamber of a cylinder head and returns oil returned from the periphery of the combustion chamber into an oil pan. The fuel injection valve is disposed upstream of the intake port so that the fuel injected from the fuel injection valve provided upstream of the intake port is directed toward the intake port outlet, and the cylinder head is disposed in the lower wall of the intake port of the cylinder head. A port bypass passage for guiding return oil from around the combustion chamber of the engine, and when the engine is cold, the return oil from the periphery of the combustion chamber of the cylinder head is guided into the lower wall of the intake port via the port bypass passage. After warm-up, the inside of the intake port lower wall through the port bypass passage and around the combustion chamber of the cylinder head And changes to flow oil to the fire plug seat. According to this configuration, it is possible to promote the vaporization of the fuel adhering to the lower wall of the intake port and improve the warm-up performance of the engine. Further, the spark plug seat can be cooled by utilizing the cooling effect of the intake port.

1 is a right side view of a motorcycle provided with an engine cooling structure according to a first embodiment of the present invention. It is the figure which looked at the longitudinal cross-section of the engine principal part from the left. It is the figure which looked at the longitudinal cross-section of the engine principal part of the position different from FIG. 2 from the left. It is a top view of a cylinder block. It is a bottom view of a cylinder head. It is the figure which looked at the longitudinal cross-section of the engine principal part which concerns on the 2nd Embodiment of this invention from the left. It is a top view of the cylinder block of 2nd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the description, descriptions of directions such as front and rear, right and left and up and down are the same as directions with respect to the vehicle body unless otherwise specified. Further, in each figure, the symbol FR indicates the front of the vehicle body, the symbol UP indicates the upper side of the vehicle body, and the symbol LH indicates the left side of the vehicle body.

<First Embodiment>
FIG. 1 is a right side view of a motorcycle 2 equipped with a four-cylinder engine 1 having an engine cooling structure according to a first embodiment of the present invention.
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, a down frame 7 extending downward from the auxiliary frame 6, a seat stay 8 extending rearward from the main frame 4, and a mid frame connecting the center of the center frame 5 and the center of the seat stay 8. 9 and.

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 be able to swing up and down, and a cushion unit 15 is provided between a connection portion between the seat stay 8 and the mid frame 9 and the rear fork 14. It has been.

  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 on the down frame 7 in front of the engine 1.

FIG. 2 is a view of the longitudinal section of the main part of the engine 1 as viewed from the left, and is viewed from a direction different from FIG. FIG. 3 is a view showing a longitudinal section of a main part of the engine 1 at a position different from that in FIG.
The engine 1 is an air-cooled four-cylinder DOHC wet sump engine. In this engine, an internal combustion engine 25 and a transmission 26 are integrated. The engine 1 includes a crankcase 27 including an upper crankcase 27A and a lower crankcase 27B. A cylinder block 28, a cylinder head 29, and a cylinder head cover 30 are connected to the crankcase 27. The crankcase 27 includes an oil pan 31. The crankshaft 32, the main shaft 33 of the transmission, and the countershaft 34 are rotatably supported by bearings on the mating surface of the crankcase 27 that is divided into two vertically.

A piston 35 is slidably accommodated in each cylinder 24 of the cylinder block 28, and the piston 35 is 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. As shown in FIG. 3, ignition plugs 38 are inserted from above the cylinder head 29 toward the respective combustion chambers 37, and their tips face the combustion chambers 37. The spark plug 38 is supported by a plug seat (ignition plug seat) 70. The cylinder head 29 is provided with an intake port 39 and an exhaust port 40 connected to each combustion chamber 37.
As shown in FIG. 2, inner end portions 39 a and 40 a serving as inlets and outlets of the intake port 39 and the exhaust port 40 to the combustion chamber 37 are open 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 that open and close 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.

In FIG. 3, an intake cam shaft 43 and an exhaust cam shaft 44 are rotatably supported on the mating surfaces of the cylinder head 29 and the cylinder head cover 30, and cam shaft driven sprockets (not shown) are respectively provided on the shafts 43 and 44. ) Is provided.
A crankshaft 32 is supported on the mating surfaces of the upper and lower crankcases 27A and 27B. The crankshaft 32 is provided with a camshaft drive sprocket (not shown). Cam chains (not shown) are 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 accommodation chamber for the valve train drive member is called a cam chain chamber 52 (see FIG. 4).

  As shown in FIG. 3, 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 provided with a cooling system oil pump and a lubrication system oil pump separately, and oil is supplied separately.
FIG. 3 shows a cooling system oil pump 48 and a cooling system oil circuit, and illustration of the lubricating system oil pump and the lubricating system oil circuit is omitted.
Hereinafter, the oil pump 48 and the cooling system oil circuit for the cooling system are simply referred to as the oil pump 48 and the oil circuit.

Next, the oil circuit will be described.
A discharge pipe A1 is connected to the oil pump 48, and the discharge pipe A1 reaches an oil cooler connecting portion 49. As shown in FIG. 1, the oil cooler connecting part 49 is connected to an oil cooler going-out pipe A2, and the oil cooler going-out pipe A2 is connected to the oil cooler 21 at the upper front of the engine. The oil cooled here passes through the oil cooler return pipe A3 and is sent to an oil gallery A4 provided at the lower front portion of the cylinder block 28 as shown in FIG. The oil gallery A4 extends to the left and right to send oil around the four cylinders 24.
The oil gallery A4 is connected to the oil passage A5 in the cylinder block, and the oil passage A5 in the cylinder block is continuous with the cylinder block upper surface groove A6.

As shown in FIG. 4, the cylinder block upper surface groove A6 is formed on the upper surface of the cylinder block 28 and extends in the left-right direction. As shown in FIG. 3, the cylinder block upper surface groove A6 is connected to the oil passage A7 in the cylinder head. The oil passage A7 in the cylinder head extends in an oblique direction, and the upper end thereof communicates with an oil jacket A8 formed around the spark plug 38.
When oil is supplied from the oil passage A7 in the cylinder head to the oil jacket A8, the periphery of the spark plug 38 is cooled by the oil.

  The oil jacket A8 is connected to an oil passage A9 in the cylinder head provided for each cylinder 24 on the rear side of the cylinder 24. The cylinder head internal oil passage A <b> 9 extends in an obliquely upward and downward direction, and a lower end thereof opens to a cylinder block upper surface groove A <b> 10 formed on the upper surface of the cylinder block 28. The cylinder block upper surface groove A10 includes an upstream groove portion A10-1, a downstream groove portion A10-2, and a midstream groove portion A10-3 between the upstream groove portion A10-1 and the downstream groove portion A10-2. The upstream groove portion A10-1, the downstream groove portion A10-2, and the midstream groove portion A10-3 are provided for each cylinder 24. The cylinder block upper surface groove A10 is provided separately for the left and right blocks. The cylinder block upper surface groove A10 extends in the left-right direction along the upper surface of the cylinder block 28, and is connected to the cylinder block oil passage A11. The cylinder block oil passage A11 extends downward from a midway portion in the longitudinal direction of the cylinder block upper surface groove A10.

The cylinder block oil passage A <b> 11 is connected to an oil gallery A <b> 12 that extends in the left-right direction and is provided below the cylinder block 28.
The oil gallery A12 is connected to the oil passage A13 in the crankcase, and the oil passage A13 in the crankcase is connected to the oil return pipe A14. The lower end of the oil return pipe A14 is open to the oil pan 31.

  The oil sent from the oil pan 31 via the oil pump 48 returns to the oil pan 31 through the above-described parts and circulates to cool the cylinder head 29. The oil from the oil pump 48 is guided to the periphery of the combustion chamber 37 of the cylinder head 29 by the oil passage through which the oil indicated by the reference signs A1, A2,. A cooling oil passage (oil passage) A to be returned is formed.

FIG. 4 is a top view of the cylinder block 28.
A cam chain chamber 52 is opened at the center in the left-right direction of the engine 1.
The cylinder 24 is divided into two on the left and right. In the engine 1, the upper crankcase 27A (see FIG. 2) and the cylinder block 28 are integrally coupled by a stud bolt (not shown). A stud bolt (not shown) is inserted through the stud bolt insertion hole 68.

A pair of front and rear cylinder block upper surface grooves A6 and A10 are provided on the upper surface of the cylinder block 28, respectively. The cylinder block upper surface grooves A6 and A10 are provided on both sides of the cam chain chamber 52, respectively. The cylinder block upper surface grooves A6 and A10 are both curvedly provided outside the stud bolt insertion holes 68.
In the front left and right cylinder block upper surface grooves A6, the upper ends of the cylinder block oil passages A5 are opened at positions m1 and m2 near the cam chain chamber 52, respectively.
In the cylinder block upper surface groove A10 on the rear side, the upper ends of the cylinder block oil passages A11 are opened at positions n1 and n2 in the middle of the grooves, respectively.
The cylinder block upper surface grooves A6 and A10 are covered and covered with a flat portion 37a (see FIG. 5) around the combustion chamber 37.

FIG. 5 is a bottom view of the cylinder head 29.
In each combustion chamber 37 corresponding to each cylinder 24, a spark plug insertion hole 69 is opened. A spark plug 38 (see FIG. 3) is inserted into the spark plug insertion hole 69, and the spark plug 38 is fixed to the plug seat 70. Each combustion chamber 37 has an inner end 39 a of two intake ports 39 and an inner end 40 a of an exhaust port 40.

A lower end A7a of the oil passage A7 in the cylinder head and a lower end A9a of the oil passage A9 in the cylinder head are opened in the flat portion 37a around the combustion chamber 37. As shown in FIG. 4, the lower end A7a of the cylinder head inner oil passage A7 opens at positions f1, f2, f3, and f4 of the cylinder block upper surface groove A6. As shown in FIG. 4, the lower end A9a of the cylinder head oil passage A9 opens at positions g1, g2, g3, and g4 of the cylinder block upper surface groove A10.
The oil is supplied from the cylinder block upper surface groove A6 to the cylinder head oil passage A7. The oil is discharged from the cylinder head oil passage A9 to the cylinder block upper surface groove A10.

An oil jacket A8 is provided on the plug seat 70 (see FIG. 3) above the spark plug insertion hole 69. The oil jacket A8 is an annular groove, and the periphery of the spark plug 38 is cooled by the oil flowing through the oil jacket A8.
As shown in FIG. 3, the upper end of the oil passage A7 in the cylinder head reaches the front side of the oil jacket A8. The rear side of the oil jacket A8 is connected to the oil passage A9 in the cylinder head, and the oil around the spark plug 38 that has finished cooling is discharged to the oil passage A9 in the cylinder head. The upper portion of the oil jacket A8 is covered with an oil jacket lid member 72. The oil jacket lid member 72 includes cooling fins 73 that come into contact with the air flow, and water drain holes 74 that enter the periphery of the spark plug 38. The oil jacket lid member 72 is screwed to the cylinder head.

  As shown in FIG. 2, a fuel injection device (fuel injection valve) 54 is disposed in the intake port 39. The fuel injection device 54 is disposed so that the injected fuel is directed toward the inner end (intake port outlet) 39 a of the intake port 39. In the present embodiment, the fuel injection device 54 is provided with a nozzle 54a at the tip so as to face the intake port lower wall 39c on the inner end 39a side. The fuel injection device 54 is supplied with fuel from the fuel tank 17 (see FIG. 1). The fuel injection device 54 injects fuel in the direction of the axis L of the fuel injection device 54 by opening and closing a nozzle 54 a at the tip by a valve (not shown).

In this embodiment, as shown in FIG. 3, a port bypass passage C is provided that branches from the midstream groove A10-3 of the cylinder block upper surface groove A10 and reaches the downstream groove A10-2 of the cylinder block upper surface groove A10.
The port bypass passage C is formed in the cylinder head 29 as shown in FIG. As shown in FIG. 2, the port bypass passage C includes an upstream passage C3, a downstream passage C5, and a connection passage C4 that connects the upstream passage C3 and the downstream passage C5.
The upstream side passage C3 connects the midstream groove portion A10-3 and the connection passage C4. The downstream side passage C5 connects the connection passage C4 and the downstream groove portion A10-2. The upstream side passage C <b> 3 and the downstream side passage C <b> 5 extend upward from the lower surface of the cylinder head 29.

  Specifically, as shown in FIG. 4, the cylinder block upper surface groove A10 includes a first branch groove C1 branched at one end C1a and a second branch groove C2 branched at one end C2a. As shown in FIG. 2, an upstream side passage C3 of the port bypass passage C extends upward at the other end C1b of the first branch groove C1. Further, the downstream side passage C5 of the port bypass passage C has a lower end C5a connected to the other end C2b of the second branch groove C2.

  The connecting passage C4 is formed along the intake port 39 inside the intake port lower wall 39c. The connecting passage C4 has a larger diameter than the upstream passage C3 and the downstream passage C5. The connecting passage C4 extends to the upstream side in the combustion injection direction from the intersection position La where the axis L intersects the intake port lower wall 39c, and is connected to the downstream passage C5 at the upstream end. The oil flowing through the connecting passage C4 exchanges heat with the intake port lower wall 39c to which the injected fuel easily adheres, and warms the intake port lower wall 39c. The connecting passage C4 extends to the upstream side across the intersection position La and is formed with a large diameter so that heat exchange is easy.

  As shown in FIG. 2, each of the upstream side passage C3, the connection passage C4, and the downstream side passage C5 extends linearly in the cylinder head 29. The connection passage C4 is formed by drilling the rear portion of the port lower wall 39c from the outside, and the rear portion of the hole is closed by a closing member 90 and sealed. The upstream side passage C <b> 3 and the downstream side passage C <b> 5 can be formed by drilling from the lower surface of the cylinder head 29.

As shown in FIG. 4, a wax-type thermo three-way valve (open / close valve) 100 is disposed in the vicinity of the downstream groove A10-2.
The thermo three-way valve 100 includes three connection ports (not shown), and a middle flow groove portion A10-3, a downstream groove portion A10-2, and a port bypass passage C are connected to each connection port. .

  The thermo three-way valve 100 opens and closes the flow path by expanding the wax according to the temperature of the oil flowing inside and moving a valve body (not shown). The thermo three-way valve 100 is configured such that the wax expands when the temperature is equal to or higher than a predetermined temperature. The predetermined temperature is based on a temperature at which the engine 1 can be determined as being warmed up.

When the temperature of the oil is low, the thermo three-way valve 100 closes the midstream groove A10-3 to restrict the flow of oil from the midstream groove A10-3 to the downstream groove A10-2, and Open to allow the oil flow from the port bypass passage C to the downstream groove A10-2.
Further, when the temperature of the oil is high, the thermo three-way valve 100 opens the midstream groove portion A10-3 to allow the oil to flow from the midstream groove portion A10-3 to the downstream groove portion A10-2, and the port bypass passage. C is closed to restrict the oil flow from the port bypass passage C to the downstream groove A10-2.
That is, the thermo three-way valve 100 allows the oil to flow from the cooling oil passage A to the port bypass passage C when the temperature of the oil is low. The thermo three-way valve 100 prevents the oil from flowing from the cooling oil passage A to the port bypass passage C when the temperature of the oil is high.

When the engine 1 is started, the oil pump 48 is activated, the oil is sucked up from the oil pan 31, and the oil circulates in the cooling oil passage A. The oil passes through the combustion chamber 37 and is heated.
When the engine is cold from when the engine 1 is started to when the engine 1 is warmed up, the temperature of the engine 1 is low.
The thermo three-way valve 100 opens the port bypass passage C when the temperature of the oil flowing inside is low. For this reason, the oil heated through the combustion chamber 37 flows into the port bypass passage C and passes through the connection passage C4 in the intake port lower wall 39c. Therefore, the heated oil warms the intake port lower wall 39c and the intake port 39, and the fuel adhering to the intake port lower wall 39c can be easily vaporized.
The intake port 39 is warmed up early, and fuel vaporization is promoted. In the engine 1, it is not necessary to supply fuel excessively, and unburned fuel can be suppressed, emission, and fuel consumption can be improved.

After the engine 1 is sufficiently warmed up, the temperature of the port lower wall 39c is also high. For this reason, the heat exchange of oil in the connection passage C4 is also reduced, and the temperature of the oil flowing through the thermo three-way valve 100 is increased. When the temperature of the oil increases, the thermo three-way valve 100 closes the port bypass passage C. Therefore, the oil heated around the combustion chamber 37 flows directly into the cylinder block oil passage A11 without being bypassed from the cylinder block upper surface groove A10 to the port bypass passage C.
After the warm-up, the temperature of the entire engine 1 is high, and the intake port 39 is also hotter than when it is cold. Even if oil does not pass through the port bypass passage C, the vaporization of the injected fuel is good.

As shown in FIG. 4, on the upper surface of the cylinder block 28 on the right side of the cam chain chamber 52, a position m1 of the cylinder block oil passage A5 in the cylinder block upper surface groove A6 and a cylinder block upper surface groove A10 are short-circuited. A combustion bypass passage (bypass passage) B is formed.
The combustion bypass passage B includes a bypass groove B1 connected to the cylinder block upper surface groove A10, and a bypass groove B2 (see FIG. 5) connected to the opening position m1 of the front cylinder block oil passage A5.
The bypass groove B <b> 1 is formed between the opening position m <b> 1 of the front cylinder block oil passage A <b> 5 and the rear cylinder block upper surface groove A <b> 10, and extends along the outer periphery of the cylinder 24. One end B1a of the bypass groove B1 is separated from the opening position m1 of the front cylinder block oil passage A5, and the other end B1b is connected to the cylinder block upper surface groove A10.
A bypass groove B2 (see FIG. 5) is formed on the lower surface of the cylinder head 29 so as to correspond between the opening position m1 of the oil passage A5 in the cylinder block and one end B1a of the bypass groove B1.
When the upper surface of the cylinder block 28 is covered by the lower surface of the cylinder head 29, the opening position m1 of the oil passage A5 in the cylinder block and the bypass groove B1 communicate with each other via the bypass groove B2, and the bypass groove B1 and the bypass groove B2 A combustion bypass passage B that does not pass through the oil jacket (passage on the plug side) A8 and short-circuits the cylinder block upper surface groove A6 and the cylinder block upper surface groove A10 is formed.

By the combustion bypass passage B, the oil rising from the cylinder block oil passage A5 cooled by the oil cooler 21 and the high-temperature oil passing through the oil jacket A8 can be merged in the cylinder block upper surface groove A10. By combining the hot oil and the bypassed oil, the temperature difference between the front side and the rear side of the cylinder block 28 can be reduced, and the cooling unevenness in the cylinder block 28 can be eliminated.
Lubricating oil distribution that distributes lubricating oil that lubricates each part of the valve operating mechanism 45 (see FIG. 2) on the opposite side of the combustion bypass passage B across the cam chain chamber 52, that is, on the upper surface of the left cylinder block 28. A groove 75 is formed in a groove form.

As shown in FIG. 4, a thermo valve 101 is disposed in the combustion bypass passage B. The thermo valve 101 is a wax type valve. The thermo valve 101 has a temperature sensing portion (not shown) disposed on the cylinder block upper surface groove A10 side of the combustion bypass passage B, and opens and closes according to the temperature of oil on the cylinder block upper surface groove A10 side. The thermo valve 101 is configured such that the wax expands when the temperature is equal to or higher than a predetermined temperature. The predetermined temperature of the thermo valve 101 is based on a temperature at which it can be determined that the engine 1 has been warmed up.
When the oil temperature is low, the thermo valve 101 closes the combustion bypass passage B and regulates the flow of oil in the combustion bypass passage B. When the oil temperature is high, the thermo valve 101 opens the combustion bypass passage B and burns. The oil flow in the bypass passage B is permitted.

When the temperature of the oil in the cylinder block upper surface groove A10 is low, the thermo valve 101 closes the combustion bypass passage B.
Therefore, when cold, the oil that has flowed into the front cylinder block upper surface groove A6 does not flow into the combustion bypass passage B but flows into the oil jacket A8 via the cylinder head internal oil passage A7. Therefore, compared with the case where the combustion bypass passage B is opened, the flow rate of the oil passing through the oil jacket A8 increases, and the flow rate of the heated oil flowing into the cylinder block upper surface groove A10 increases.
When the cooler is closed, the thermo valve 101 closes the combustion bypass passage B, so that the amount of oil that can flow into the port bypass passage C is increased, and the port lower wall 39c is more easily warmed.

When the temperature of the oil in the cylinder block upper surface groove A10 increases, the thermo valve 101 opens and the oil flows into the combustion bypass passage B.
Therefore, after warming up, the oil flowing into the front cylinder block upper surface groove A6 is divided into oil that passes through the oil jacket A8 and oil that passes through the combustion bypass passage B and bypasses the oil jacket A8. And in the cylinder block upper surface groove | channel A10 of a downstream, when they merge, it is possible to reduce the oil temperature of the discharge side oil paths A11-A14 which pass the cylinder block 28. FIG. Therefore, the temperature difference due to oil in the cylinder block 28 can be reduced, and uneven cooling in the cylinder block 28 can be suppressed.

  As described above, in the first embodiment to which the present invention is applied, the oil from the oil pump 48 is guided to the periphery of the combustion chamber 37 of the cylinder head 29 and the return oil from the periphery of the combustion chamber 37 is supplied to the oil pan. In the engine cooling structure provided with the oil passage A returning to the inside, the fuel injected from the fuel injection device 54 provided upstream of the intake port 39 is directed toward the inner end (intake port outlet) 39a of the intake port 39. The injection device 54 is disposed upstream of the intake port 39, and a port bypass passage C that guides return oil from around the combustion chamber 37 of the cylinder head 29 is formed in the port lower wall 39c of the cylinder head 29. Therefore, the warmed high-temperature oil flowing in the port bypass passage C can promote the vaporization of the fuel adhering to the port lower wall 39c and improve the warm-up performance of the engine 1.

  In the first embodiment, the port bypass passage C is provided with a thermo three-way valve 100 constituting an on-off valve, and the port bypass passage C is closed after the engine is warmed up. Therefore, an excessive increase in temperature of the intake port 39 after engine warm-up can be suppressed, a decrease in intake air density can be suppressed, and engine performance can be improved.

  In the first embodiment, the oil passages A6 to A10 around the combustion chamber 37 of the cylinder head 29 bypass the oil jacket A8 that forms a plug-side passage passing through the plug seat 70 and the combustion chamber 37. And a combustion bypass passage B that passes therethrough, and a thermo valve 101 is provided in the combustion bypass passage B. Therefore, the heating performance of the intake port 39 can be adjusted by opening and closing the thermo valve 101, and the warm-up performance and the engine cooling performance after warm-up can be further enhanced.

  In the first embodiment, the thermo valve 101 is closed when cold. Therefore, by actively utilizing the temperature rise of the plug seat 70, the heating performance of the intake port 39 can be improved, and the warm-up performance can be further enhanced.

<Second Embodiment>
FIG. 6 is an explanatory diagram of a main part of the engine 1 according to the second embodiment of the present invention.
In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
In the second embodiment, the oil cooler 21, the oil cooler forward pipe A2, and the oil cooler return pipe A3 of the first embodiment are omitted.
In the second embodiment, instead of the discharge pipe A1 and the oil return pipe A14, a discharge pipe A21, a connection pipe A24, a four-way valve (switching valve) 200, and the like are provided.

A four-way valve 200 is arranged in the cooling oil passage A of the second embodiment.
The four-way valve 200 includes four connection ports 200a, 200b, 200c, and 200d, a valve body 200e in which two flow paths are formed, and a drive source (not shown) that moves the valve body 200e. The four-way valve 200 moves the valve element 200e between a position indicated by a solid line and a position indicated by a broken line to switch the connection of the flow paths.

A discharge pipe A21 is connected to the first connection port 200a. The discharge pipe A21 extends from the oil pump 48.
The connection pipe A22 is connected to the second connection port 200b. The connecting pipe A22 is connected to the oil gallery A4.
A return exhaust pipe A23 is connected to the third connection port 200c. The return discharge pipe A <b> 23 opens above the oil pan 31 and returns the oil to the oil pan 31.
A connection pipe A24 is connected to the fourth connection port 200d. The connecting pipe A24 is connected to the crankcase oil passage A13.

The four-way valve 200 is controlled by an ECU (not shown).
The four-way valve 200, when cold, communicates the first connection port 200a and the second connection port 200b, communicates the discharge pipe A21 and the connection pipe A24, and communicates the third connection port 200c and the fourth connection port 200d. The return discharge pipe A23 and the connection pipe A24 are communicated.
After the warm-up, the four-way valve 200 allows the first connection port 200a and the fourth connection port 200d to communicate with each other, allows the discharge pipe A21 and the connection pipe A24 to communicate with each other, and the second connection port 200b and the third connection port 200c. And the connecting pipe A22 and the return exhaust pipe A23 are communicated.

Therefore, the four-way valve 200 sends oil from the oil pump 48 to the oil gallery A4 when it is cold, and sends it from the oil pump 48 to the oil passage A13 in the crankcase after warming up. That is, the four-way valve 200 changes the oil flow in the oil passages A4 to A13 to the forward direction similar to that of the first embodiment when cold, and changes to the reverse direction opposite to the forward direction after warming up. .
The ECU (not shown) controls the four-way valve 200 during cold from the start of the engine 1 until a predetermined time. The ECU (not shown) performs control after warm-up on the four-way valve after a predetermined time. The predetermined time is set in advance as a time for warming up according to the engine 1.
Instead of the configuration for determining whether the engine is cold and after warm-up based on a predetermined time, a configuration may be adopted in which a temperature sensor (not shown) is provided to determine when the engine 1 is cold and after warm-up.

FIG. 7 is an explanatory diagram of the upper surface of the cylinder block 28 according to the second embodiment.
The upper surface of the cylinder block 28 of the second embodiment is different from the first embodiment in the following points. In the cylinder block upper surface groove A10, the thermo three-way valve 100 and the midstream groove portion A10-3 are omitted.
In the second embodiment, all the oil that has flowed into the cylinder block upper surface groove A10c passes through the port bypass passage (port passage) C.

  In the second embodiment, when cold, oil flows in the same forward direction as in the first embodiment. At this time, the oil heated by cooling the plug seat 70 flows into the port bypass passage C and warms the port lower wall 39c. Therefore, similarly to the first embodiment, the port lower wall 39c and the intake port 39 are warmed up early to facilitate vaporization of the injected fuel.

After warming up, oil flows in the opposite direction. The oil sucked up from the oil pan 31 passes through the discharge pipe A21 and the connection pipe A24, is supplied from the crankcase oil passage A13 to the cylinder block upper surface groove A10, and is sent to the port bypass passage C.
In the intake port 39, the injected fuel injected by the fuel injection device 54 is vaporized, and the intake port 39, the port lower wall 39c, and the like are cooled by the latent heat of vaporization. For this reason, the oil passing through the connecting passage C4 is cooled by exchanging heat with the port lower wall 39c. The cooled oil is supplied to the oil jacket A8 via the oil passage A9 in the cylinder head and cools around the combustion chamber 37. The cooled oil returns to the oil pan 31 via the oil passage A7 in the cylinder head.
Therefore, in the second embodiment, instead of the oil cooler, the cooling effect of the intake port 39 is used to cool the plug seat 70 that becomes a high temperature during high-load operation of the engine 1 and to suppress knocking of the engine 1. can do.

  As described above, in the second embodiment to which the present invention is applied, the oil from the oil pump 48 is guided to the periphery of the combustion chamber 37 of the cylinder head 29 and the return oil from the periphery of the combustion chamber 37 is supplied to the oil pan. In the engine cooling structure provided with the oil passage A returning to the inside, the fuel injected from the fuel injection device 54 provided upstream of the intake port 39 is directed toward the inner end (intake port outlet) 39a of the intake port 39. The injection device 54 is disposed upstream of the intake port 39, and a port bypass passage C is formed in the port lower wall 39c of the cylinder head 29 to guide the return oil from the periphery of the combustion chamber 37 of the cylinder head 29. The return oil from around the combustion chamber 37 of the cylinder head 29 is introduced into the port lower wall 39c through the port bypass passage C. , After engine warm-up, via a port bypass passage C, and changed to flow oil from the port under wall 39c into the combustion chamber 37 around the plug seat 70 of the cylinder head 29. Therefore, the heated high-temperature oil flowing in the port bypass passage C can promote the vaporization of the fuel adhering to the port lower wall 39c and improve the warm-up performance of the engine. Further, the plug seat 70 can be cooled by utilizing the cooling effect of the intake port 39.

The above-described embodiment is merely an aspect of the present invention, and can be arbitrarily modified and applied without departing from the gist of the present invention.
In the above embodiment, a configuration has been described in which the on-off valves 100 and 101 are operated according to the temperature of oil using a wax-type valve, but the configuration of the valve is not limited, and a slide valve, a gate valve, or the like may be used. A solenoid valve may be used.
The wax-type on-off valve 100 is configured to open and close at a predetermined temperature based on the characteristics of the wax. The oil passage A may be opened and closed by controlling the solenoid valve.
In the above embodiment, the cylinder block upper surface groove A10 may be the cylinder block upper surface groove A10 in which the branch grooves C1 and C2 are omitted.

48 Oil pump 29 Cylinder head 37 Combustion chamber 39 Intake port 39a Intake port outlet 39c Inlet port lower wall 100 On-off valve 101 Bypass passage on-off valve A Oil passage A6, A7, A9, A10 Oil passage around combustion chamber A8 Plug side passage (Oil passage around the combustion chamber)
B Bypass passage (oil passage around combustion chamber)
C Port bypass passage 54 Fuel injection valve

Claims (5)

An oil passage (A) is provided for guiding oil from the oil pump (48) to the periphery of the combustion chamber (37) of the cylinder head (29) and returning the return oil from the periphery of the combustion chamber (37) into the oil pan. In the engine cooling structure
The fuel injection valve (54) is arranged upstream of the intake port (39) so that the fuel injected from the fuel injection valve (54) provided upstream of the intake port (39) is directed to the intake port outlet (39a). The engine is characterized in that a port bypass passage (C) for guiding return oil from around the combustion chamber (37) of the cylinder head (29) is formed in the lower wall (39c) of the intake port of the cylinder head (29). Cooling structure.   2. The engine cooling structure according to claim 1, wherein the port bypass passage (C) is provided with an on-off valve (100), and the port bypass passage (C) is closed after the engine is warmed up.   The oil passages (A6, A7, A8, A9, A10, B) around the combustion chamber (37) of the cylinder head (29) are connected to the plug-side passage (A8) passing through the inside of the spark plug seat (70) and combustion. The engine cooling according to claim 1 or 2, further comprising a bypass passage (B) that bypasses and surrounds the chamber (37), and an on-off valve (101) is provided in the bypass passage (B). Construction.   The engine cooling structure according to claim 3, wherein the on-off valve (101) of the bypass passage (B) is closed when the engine is cold. An oil passage (A) is provided for guiding oil from the oil pump (48) to the periphery of the combustion chamber (37) of the cylinder head (29) and returning the return oil from the periphery of the combustion chamber (37) into the oil pan. In the engine cooling structure
The fuel injection valve (54) is arranged upstream of the intake port (39) so that the fuel injected from the fuel injection valve (54) provided upstream of the intake port (39) is directed to the intake port outlet (39a). A port bypass passage (C) for guiding return oil from around the combustion chamber (37) of the cylinder head (29) is formed in the intake port lower wall (39c) of the cylinder head (29),
When the engine is cold, the return oil from around the combustion chamber (37) of the cylinder head (29) is guided into the intake port lower wall (39c) via the port bypass passage (C). It is changed so that oil flows from the inside of the lower wall (39c) of the intake port to the spark plug seat (70) around the combustion chamber (37) of the cylinder head (29) via the port bypass passage (C). Characteristic engine cooling structure.

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