JP5345405B2 - Cylinder head cooling structure - Google Patents

Description

  The present invention relates to a cooling structure for a cylinder head of an air-cooled four-cycle internal combustion engine mounted on, for example, a motorcycle.

  Conventionally, in an air-cooled four-cycle internal combustion engine, a bottom wall that partitions a valve chamber and an intake / exhaust port in a cylinder head is provided, and the inside of the cylinder head including the bottom wall is cooled with oil, A technique for providing a cooling air passage and cooling a cylinder head with traveling air is known (see Patent Document 1).

JP 2000-329002 A

In the prior art, since the cooling air passage is formed around the spark plug, the temperature around the spark plug exposed to a high temperature can be lowered. When the temperature rises, there is a problem that the temperature of the oil recovered from the cylinder head increases due to the heat of the exhaust port.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to increase the cooling effect of the cylinder head while maintaining the function of returning the oil, thereby enhancing the cooling effect of the cylinder head and enhancing the cooling effect of the oil flowing through the bottom wall.

In order to achieve the above object, the invention described in claim 1 is provided with a combustion chamber (14) in a lower portion of the cylinder head (7) of the engine (4) with the cylinder head (7) facing upward, and an upper portion. Provided with a valve chamber (21) partitioned through the combustion chamber (14) and a bottom wall (20) , a cam chain chamber (51) is provided at a side of the cylinder head (7) , and the cam chain An ignition plug insertion recess (33) is provided on the side of the cylinder head (7) opposite to the chamber (51), and the ignition plug mounting portion communicates with the combustion chamber (14) in the insertion recess (33). (34) is provided and opened at the front part of the peripheral wall of the cylinder head (7) and opened at the rear part of the peripheral wall of the cylinder head (7) and the exhaust port (16) communicating with the combustion chamber (14). Intake port (1) communicating with the chamber (14) ) A cooling structure of a cylinder head provided with, between said exhaust port (16) and said bottom wall (20), said cooling air introducing portion for introducing a running wind above the exhaust port (16) (60) is provided, a communication path (70) is provided above the intake port (17) and is connected to the cooling air introduction part (60) and opens as an outlet for cooling air, and the insertion recess (33) is provided with the insertion recess (33). A communication portion (33) that communicates with the cooling air introduction portion (60) and the communication passage (70), and is arranged on the upper surface of the bottom wall (20) near the front portion of the peripheral wall of the cylinder head (7). An oil return passage (53) inclined so as to descend in the left-right direction toward the cam chain chamber (51) is formed, and left and right outer walls (67, 68) of the opening of the cooling air introduction part (60) are Forming outwardly and forming却風introduction portion (60) on the edge the Kamuchen chamber opening towards (51) and wherein the tilting diagonally downward.

The invention as set forth in claim 2, the flange fastening section for fastening the flange (9a) and (62, 63) provided in the exhaust pipe (9) around the opening of the exhaust port (16), the flange fastening section (62 63) and the oil return passageway (53) , the cooling air introduction part (60) is formed as an opening .

According to a third aspect of the present invention, the flange fastening portion (62) includes an upper flange fastening portion (62) for fastening the flange (9a) of the exhaust pipe (9) , and a lower flange fastening portion (63) . The cooling air introduction part (60) is provided from above the upper flange fastening part (62) to around the lower flange fastening part (63) .

According to a fourth aspect of the present invention, the exhaust pipe attachment portion (61) for fastening the flange (9a) of the exhaust pipe (9) is provided with the flange fastening portion (62, 63), and the exhaust pipe attachment portion ( 61) is provided in a substantially rhombus shape that is long in the vehicle width direction on the front side of the peripheral wall of the cylinder head (7) opposite to the cam chain chamber (51), and the flange fastening portions (62, 63) are substantially omitted. A flange fastening portion (62) opposite to the cam chain chamber (51) is provided at both ends in the vehicle width direction of the exhaust pipe mounting portion (61) provided in a rhombus, and the cam chain chamber ( 51) side flange fastening portion (63) is located on the lower side, and the cooling air introduction portion (60) extends from above the upper flange fastening portion (62) to the periphery of the lower flange fastening portion (63). It is characterized by being provided.

According to a fifth aspect of the present invention, the cooling air introduction portion (60) is a central portion between the upper flange fastening portion (62) and the lower flange fastening portion (63), and the exhaust port (16). It is divided into two parts by a rib (64) connected to the bottom wall (20) above the center position.

According to a sixth aspect of the present invention, a guide portion (54) for guiding oil to the cam chain chamber (51 ) is provided on the upper surface of the bottom wall (20) of the cylinder head (7) , and the guide portion (54) is characterized in that it is inclined so as to descend toward the cam chain chamber (51) .

The invention described in claim 7 is provided with a secondary air pipe mounting portion (41) for supplying fresh air to the exhaust port (16) , and the upper wall of the secondary air pipe mounting portion (41) is in the vehicle longitudinal direction. It is characterized in that it is inclined forward.

The invention described in claim 8 is a cylinder head cover (8 ) formed separately from the cylinder head (7) substantially parallel to the mounting surface (S) of the cylinder head (7) and the cylinder block (6). ) Is configured to be attachable.

The invention as set forth in claim 9, wherein the cylinder head (7) wherein the cylinder head cover (8), but rubber packing for sealing the joint (M) is the relative cylinder head cover (8) of said cylinder head (7) ( 37) .

According to the first aspect of the present invention, the oil return passage that guides the oil on the bottom wall to the cam chain chamber side is separated from the exhaust port by way of the cooling air introduction portion, thereby suppressing an increase in the temperature of the oil. It is Ru can. Awnings exhaust port to secure a wide cooling air introducing portion, it is possible to cool the bottom wall by the cooling air introduced from the cooling Kazeshirube unit. That is , while maintaining the function of returning the oil, the cooling port can be enlarged to increase the cooling effect of the cylinder head and to increase the cooling effect of the oil flowing through the bottom wall.
In addition, securing a wide cooling air introduction portion removes the fillet and has the effect of reducing the weight of the cylinder head.
Furthermore, since the oil in the oil return passage flows without staying toward the cam chain chamber, the oil return is improved as before, and the cooling effect by the oil can be enhanced.
And since it can make it easy to take in a driving | running wind in the wide range from the front side, there exists an effect which can improve the cooling performance of a cylinder head and a bottom wall.
In addition, compared with the case where the intake port side is blocked, the pressure on the intake port side is reduced, so that the traveling air taken from the cooling air introduction part can flow smoothly without stagnation inside, and the cylinder head and oil Has the effect of effectively cooling.
Furthermore, since the cooling air flows to the upper side of the intake port in the same manner as the cooling air introduction part, the cooling air flows smoothly and communicated with the side closer to the bottom wall, compared with the case where it is provided below the intake port. The oil can be effectively cooled.
In addition, compared to the case where the spark plug mounting portion side is closed, the pressure on the spark plug mounting portion side is reduced, so that the traveling wind taken from the cooling air introducing portion can flow smoothly without stagnation inside. There is an effect that the periphery of the spark plug mounting portion can be effectively cooled.
According to the invention described in claim 2, with the mounting portion of the exhaust pipe can be secured, the oil return passage can suppress an increase in the temperature of the oil to leave from the exhaust port, the only cooling air introducing portion by a flange The bottom wall is cooled in a wide range by the cooling air introduced from the cooling air introduction portion while ensuring a wide area, and the cylinder head and the oil can be effectively cooled.
In addition, securing a wide cooling air introduction portion removes the fillet and has the effect of reducing the weight of the cylinder head.
According to the third aspect of the present invention, it is possible to secure the flange mounting portion of the exhaust pipe and to suppress the rise in oil temperature because the oil return passage is away from the exhaust port, and to secure a wide cooling air introduction portion. Thus, there is an effect that the bottom wall is cooled in a wide range by the cooling air introduced from the cooling air introduction portion , and the cylinder head and the oil can be effectively cooled.
In addition, securing a wide cooling air introduction portion removes the fillet and has the effect of reducing the weight of the cylinder head.
According to the sixth aspect of the present invention, the oil flowing through the bottom wall and going to the cam chain chamber can be reliably guided by the guide portion, so that the oil return is good as before and the oil can be collected smoothly. .
According to the seventh aspect of the present invention, since it becomes easier to guide the traveling wind to the upper side of the upper wall of the secondary air pipe mounting portion, there is an effect that the cylinder head and the bottom wall can be cooled.
According to the eighth aspect of the present invention, the maintainability is improved as compared with the case where the cylinder head and the cylinder head cover are integrated, and a large mold is used on the cylinder head cover mounting portion side of the cylinder head. Therefore, productivity is improved.
According to the ninth aspect of the invention, the cylinder head can be effectively cooled by the cooling air, so that the rubber packing can be avoided from being exposed to a high temperature and the durability of the rubber packing can be improved.

1 is a partial side view of a motorcycle including a cylinder head according to an embodiment of the present invention. It is sectional drawing of the engine which follows the AA line of FIG. It is a right view of the cylinder head of embodiment of this invention. It is a top view of the cylinder head of an embodiment of this invention. It is sectional drawing which follows the DD line | wire of FIG. It is sectional drawing which follows the BB line of FIG. It is sectional drawing which follows the CC line of FIG. It is a front view of a cylinder head of an embodiment of this invention. It is a rear view of the cylinder head of this embodiment.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partial side view of a motorcycle equipped with an air-cooled four-cycle engine of this embodiment. In the following drawings, FR indicates the front of the vehicle body, RR indicates the rear of the vehicle body, L indicates the left side of the vehicle body, and R indicates the right side of the vehicle body.
The head pipe 1 is attached with a pair of left and right main frames 2 and 2 that extend rearward and then descend downward, and a pair of left and right down frames 3 and 3 that extend obliquely rearward and downward. The engine 4 is suspended at the lower ends of the main frames 2 and 2 and the down frames 3 and 3 via attachment members so as to connect the main frames 2 and 2 and the down frames 3 and 3. The engine 4 includes a crankcase 5, a cylinder block 6, a cylinder head 7, and a cylinder head cover 8 as an outer case, and the cylinder head 7 is mounted with the cylinder head 7 slightly inclined to the front side.

  An exhaust pipe 9 is connected to the front surface of the cylinder head 7 of the engine 4, and a silencer 10 is connected to the downstream side. An intake pipe 11 is connected to the rear surface of the cylinder head 7, a throttle valve 12 is interposed in the intake pipe 11, and an air cleaner 13 is attached to the upstream side of the throttle valve 12.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. 4 showing the cylinder head 7 of the engine 4 together with a part of the cylinder block 6 and the cylinder head cover 8. FIG. 3 is a right side view of the cylinder head.
As shown in FIG. 2, a combustion chamber 14 is recessed in a lower portion of the cylinder head 7 at a position corresponding to the cylinder inner wall of the cylinder block 6. The mixture of fuel and air compressed by the piston 15 moving up and down in the cylinder block 6 burns in the combustion chamber 14 and pushes down the piston 15. Extend curved toward the front of the cylinder head 7 to the combustion chamber 14, an exhaust port 16 you opening at the front of the peripheral wall of the cylinder head 7, extends curved toward the rear of the cylinder head 7, the cylinder intake port 17 you opening at the rear of the peripheral wall of the head 7 is connected, is opened and closed by the intake ports 17 each valve seat 18a of the exhaust port 16 the combustion chamber 14, an intake valve 18 for opening and closing the 19a and the exhaust valve 19 .

A valve chamber 21 that is partitioned from the combustion chamber 14 via a bottom wall 20 is provided at the top of the cylinder head 7. A shaft support portion 25 is provided on the bottom wall 20 to support the camshaft 22 and the rocker arm shaft 24 of the rocker arm 23.
Specifically, as shown in FIG. 3, a support hole 26 of the camshaft 22 is formed in the shaft support portion 25 in the left-right direction of the vehicle. Support holes 27 and 27 of a pair of rocker arm shafts 24 that are distributed in the vehicle front-rear direction with respect to the support hole 26 are formed in the vehicle left-right direction above the support hole 26. As shown in FIG. 2 , a relief hole 29 for the cam 28 of the camshaft 22 is formed in the shaft support portion 25.
An intake valve guide 30 and an exhaust valve guide 31 for guiding the intake valve 18 and the exhaust valve 19 are inserted and fixed to the bottom wall 20 toward the combustion chamber 14.

As shown in FIG. 3, air cooling fins 32 are formed on the peripheral wall of the cylinder head 7. A lower part of the right side portion of the cylinder head 7 is formed by cutting out a part of the air cooling fin 32 and hollowing out the inside to form an insertion recess 33 for a spark plug. A lower surface 35 of the insertion recess 33 is a rear surface of the combustion chamber 14 and is located on the side opposite to a cam chain chamber 51 described later , and a spark plug mounting portion 34 that is a screw hole is formed therein. (See FIG. 6) . The insertion recess 33 communicates with a cooling air introduction portion 60 that opens on the exhaust port 16 side, which will be described later, and a communication passage 70 that opens on the intake port 17 side.
Further, a secondary air pipe mounting portion 41 that is a mounting portion of a secondary air pipe 40 that supplies fresh air to the exhaust port 16 to purify the exhaust gas is provided on the right side of the cylinder head 7. The secondary air pipe mounting portion 41 communicates with the exhaust port 16 through the connection path 42 (see FIG. 5). The secondary air pipe mounting portion 41 is arranged with the major axis side inclined in the vehicle longitudinal direction and the front side inclined slightly downward. The secondary air pipe mounting portion 41 includes bolt fastening portions 43 and 43 at both ends, and the upper wall 44 and the lower wall 45 are bent into a square shape (formed so as to be bent at an obtuse angle).
As shown in FIG. 1, the secondary air pipe 40 attached to the secondary air pipe attaching portion 41 extends obliquely forward and is connected to the downstream side of the air cleaner 13.

Here, as shown in FIG. 2, a relatively narrow joint portion M substantially parallel to the mounting surface S of the cylinder head 7 and the cylinder block 6 is formed on the upper surface of the peripheral wall 36 of the cylinder head 7. . On the other hand, the cylinder head cover 8 formed separately from the cylinder head 7 covers the valve operating chamber 21 above the cylinder head 7. The cylinder head cover 8 is attached to the cylinder head 7 by bringing the peripheral end surface T of the cylinder head cover 8 into contact with the joint M of the cylinder head 7 with the rubber packing 37 interposed therebetween. Here, at the upper part of the rubber packing 37, a protrusion 39 is formed which is inserted into the groove 38 on the peripheral end surface T of the cylinder head cover 8 and narrower than the lower part.
The cylinder head cover 8 is fastened and fixed to the cylinder head 7 by inserting a bolt (not shown) on the upper surface and tightening the bolt into the head cover mounting screw hole 46 on the upper surface of the shaft support portion 25.

FIG. 4 is a plan view of the cylinder head. As shown in FIG. 4, four fastening holes 47 are provided on the upper surface of the shaft support portion 25 of the cylinder head 7 for inserting a bolt (not shown) and fixing the cylinder head 7 to the cylinder block 6. Here, an oil passage 48 for sending oil to the cylinder head cover 8 and supplying oil from the cylinder head cover 8 to the valve operating chamber 21 is formed in the right rear portion of the shaft support portion 25.
On the left side of the cylinder head 7, a cam chain chamber 51 is provided on the bottom wall 20 having an elongated rectangular opening 50 extending in the longitudinal direction of the vehicle body in plan view. The cam chain chamber 51 is a space portion in which a cam chain that drives the cam shaft 22 supported by the shaft support portion 25 of the valve operating chamber 21 via a cam sprocket (not shown) travels.
6 is a cross-sectional view taken along line BB in FIG. As shown in FIG. 6, the cam chain chamber 51 has an outer portion surrounded by the left side wall, the front wall, and the rear wall of the cylinder head 7, and the inner portion is an insertion recess 33 formed for the spark plug mounting portion 34. The rear wall 52 is formed, and the lower part is opened to the cylinder block 6 side.

As shown in FIG. 4, the oil staying on the bottom wall 20 is inclined from the right side wall of the cylinder head 7 toward the left side wall on the upper surface of the bottom wall 20 of the cylinder head 7, near the front wall of the cylinder head 7. An oil return passage 53 is formed (indicated by an arrow) that guides the air to the front end of the opening 50. The oil return passage 53 is an obliquely inclined guide so as to guide the path previously set in the left-right direction of the vehicle at a position before the opening 50 to the rear toward the front end of the opening 50 and guide it to the cam chain chamber 51. A portion 54 is provided. Here, the guide portion 54 is inclined so as to descend toward the cam chain chamber 51. 7 is a cross-sectional view taken along the line CC of FIG. FIG. 7 shows a state where the guide portion 54 is inclined so as to be lowered toward the front side and continues to the cam chain chamber 51.

FIG. 8 is a front view of the cylinder head. As shown in FIG. 8, the exhaust port 16 is a front portion of the peripheral wall of the cylinder head 7 and opens between a combustion chamber 14 and a valve operating chamber 21 (not shown). A cooling air introduction portion 60 is formed between the upper surface of the bottom wall 20 and the oil return passage 53 .
Specifically, the exhaust port 16 includes an exhaust pipe mounting portion 61 to which the flange portion 9a (see FIG. 1) of the exhaust pipe 9 is attached. The exhaust pipe mounting portion 61 is formed in a substantially rhombus shape, and flange fastening portions 62 and 63 that are screw holes are provided around the exhaust port 16 at both ends in the longitudinal direction. The flange fastening portions 62 and 63 and the bottom wall A cooling air introduction portion 60 is provided between the upper surface 20 and the oil return passage 53 .

The exhaust pipe mounting portion 61 formed in a substantially rhombic shape is disposed on the right side of the vehicle (leftward when viewed from the front of the cylinder head 7), and is located on the right side of the cylinder head 7 because the cam chain chamber 51 is disposed on the left side of the cylinder head 7. The flange fastening portion 62 is located on the upper side, and the left flange fastening portion 63 is located on the lower side. The cooling air introduction part 60 is provided from the upper side of the upper flange fastening part 62 to the periphery of the lower flange fastening part 63.
Here, the cooling air introduction part 60 is divided by a rib 64 connected to the bottom wall 20 at the center part of the upper flange fastening part 62 and the lower flange fastening part 63 and above the center position of the exhaust port 16. ing.
Therefore, the cooling air introduction portion 60 is formed as a rectangular right introduction portion 65 on the right side of the vehicle with the rib 64 as a boundary, the left side of the vehicle with the rib 64 as a boundary, and the lower edge along the periphery of the exhaust pipe mounting portion 61. The left introduction portion 66 is formed as a left introduction portion 66 whose upper edge is inclined obliquely downward, and the left introduction portion 66 includes an inclined wall 67 whose outer side expands toward the front side in the vehicle front-rear direction. The right introduction portion 65 also includes an inclined portion 68 whose outer side expands toward the front side in the vehicle front-rear direction.

FIG. 9 is a rear view of the cylinder head. As shown in FIG. 9, the intake port 17 is a rear portion of the cylinder head 7 and opens between a combustion chamber 14 and a valve operating chamber 21 (not shown). A communication path 70 communicating with the cooling air introduction part 60 formed on the upper side is formed.
Specifically, the intake port 17 includes an intake pipe attachment portion 71 to which the flange portion 11a (see FIG. 1) of the intake pipe 11 is attached. The intake pipe attachment portion 71 is formed in a substantially rhombus shape, and flange fastening portions 72 and 73 that are screw holes are provided around the intake port 17 at both ends in the longitudinal direction.

The intake pipe attachment portion 71 formed in a substantially rhombus shape is disposed on the right side of the vehicle because the cam chain chamber 51 is disposed on the left side portion of the cylinder head 7, and the flange fastening portion 72 on the left side of the vehicle is on the upper side. The right flange fastening portion 73 is located on the lower side. The communication passage 70 is a lower flange fastening portion provided with an upper left communication passage 75 opened above the upper flange fastening portion 72 and a rib 74 connecting the intake pipe mounting portion 71 and the bottom wall 20 as a boundary. The upper right communication path 76 that opens above 73 and the lower left communication path 77 that opens below the upper flange fastening portion 72 are configured. That is, the upper left communication passage 75 and the upper right communication passage 76 that are connected to the cooling air introduction portion 60 are formed between the oil return passage 53 on the upper surface of the bottom wall 20 and above the intake pipe attachment portion 71.

FIG. 5 is a cross-sectional view taken along the line DD of FIG. As shown also in FIG. 5, the cooling air introduction part 60 at the front part of the cylinder head 7 includes an inclined part 68 so that the right side introduction part 65 opens the outer wall obliquely to the right front side, and the left side introduction part 66 has an outer side. An inclined wall 67 is provided so that the wall opens obliquely to the left front side, and opens between the oil return passage 53 on the upper surface of the bottom wall 20 and the exhaust port 16. Here, the down frames 3 and 3 are arranged on the front side of the cooling air introduction portion 60, but the inclined wall 67 and the inclined portion 68 are opened outward so as to cover the space between the down frames 3 and 3. Is formed.
The cooling air introduction portion 60 communicates with the insertion recess 33 of the spark plug mounting portion 34 on the side of the cylinder head 7 and also communicates with the communication passage 70 of the intake port 17 at the rear of the cylinder head 7. The bottom wall 20 of the cylinder head 7 is positioned above the wind introduction portion 60, the insertion recess 33 of the spark plug attachment portion 34, and the communication path 70 . As a result , a cooling air flow path X (see also FIGS. 2 and 4) during traveling is provided below the bottom wall 20 that divides the combustion chamber 14 and the valve operating chamber 21 and at a substantially central portion in the left-right direction of the vehicle . It becomes possible to form.

According to the above embodiment, when the motorcycle starts traveling, the front portion of the peripheral wall of the cylinder head 7 , above the opening of the exhaust port 16 and between the oil return passage 53 and the exhaust port 16 on the upper surface of the bottom wall 20. Traveling wind is introduced from the cooling air introduction part 60 (right introduction part 65, left introduction part 66) formed therebetween, and this traveling wind is above the opening of the intake port 17 (upper left communication path 75, upper right communication path 76). And it passes through the communicating path 70 opened below (lower left communicating path 77) and is discharged rearward. At this time, in the insertion recess 33 of the spark plug mounting portion 34, the cooling air is taken in outside air so as to be drawn into the traveling wind that passes from the cooling air introduction portion 60 to the opening of the communication path 70, thereby cooling the spark plug mounting portion 34. While flowing backwards.
By the way, on the bottom wall 20 of the cylinder head 7, oil flows from the vehicle right side to the left side on the oil return passage 53 provided on the front side, and turns counterclockwise in the guide portion 54. It flows to the club.

Here, since the traveling wind flows smoothly under the bottom wall 20 as cooling air, and the oil return passage 53 of the bottom wall 20 is arranged at a distance from the exhaust port 16, the oil on the bottom wall 20 is The temperature rise of the oil flowing through the return passage 53 can be suppressed. Therefore, the cooling air introduction part 60 can be secured wide enough for the oil return passage 53 to be away from the exhaust port 16, and the bottom wall 20 can be cooled in a wide range by the cooling air introduced from the cooling air introduction part 60. The cooling effect of the cylinder head 7 can be enhanced, and the cooling effect of the oil flowing through the bottom wall 20 can be enhanced. Therefore, the cylinder head 7 and the oil can be effectively cooled.

The oil return passage 53 is formed obliquely so as to descend to the left side, and is further inclined at the terminal by the guide portion 54 and is guided to the cam chain chamber 51, so that the oil does not stay and moves toward the cam chain chamber 51. And flows smoothly. Accordingly, the oil return is improved as before, the oil can be smoothly collected while maintaining the oil return function, and the cooling effect by the oil is enhanced.
Further, securing the cooling air introduction part 60 widely removes the fillet, so that the weight of the cylinder head 7 can be reduced.

In particular, the left introduction portion 66 that is a cooling air introduction portion around the lower flange fastening portion 63 includes an inclined wall 67 that is inclined so as to expand outward toward the front side in the vehicle front-rear direction. The traveling wind can be easily taken in a wide range from the front side, and the cooling performance of the cylinder head 7 and the bottom wall 20 can be improved. Further, since the right introduction portion 65, which is the cooling air introduction portion above the upper flange fastening portion 62, is also provided with an inclined portion 68 whose outer wall opens obliquely to the front right, this portion is also effectively cooled. Wind can be taken in.
Here, since the cooling air introduction part 60 is formed above the upper flange fastening part 62 and the lower flange fastening part 63 of the exhaust port 16, the mounting part of the flange part 9 a of the exhaust pipe 9 is reliably secured. it can.

Then, around the intake port 17, by providing the communication path 70 communicating with the cooling air introducing portion 60 provided open to the exhaust port 16 side around the intake port 17, only the cooling air introducing portion 60 is formed an intake Compared with the case where the port 17 side is closed, the pressure on the intake port 17 side is reduced, so that the traveling air taken from the cooling air introduction portion 60 can flow smoothly without stagnation inside the cylinder head 7. And can cool the oil effectively.
Of course, since the communication passage 70 on the intake port 17 side is also provided with an upper left communication passage 75 and an upper right communication passage 76 through which the cooling air flows upward as in the cooling air introduction portion 60, the cooling air flows smoothly and the bottom. By connecting the side closer to the wall 20 to the exhaust port 16 side, the oil can be effectively cooled compared to the case where it is provided only below the intake port 17.

Furthermore, an insertion recess 33 communicating with the cooling air introduction portion 60 and the communication passage 70 is provided above the ignition plug attachment portion 34 provided on the surface of the combustion chamber 14 facing the cam chain chamber 51 , so that the ignition plug attachment portion is provided. Compared with the case where the 34 side is closed, the pressure on the spark plug mounting portion 34 side is reduced, so that the traveling wind taken from the cooling air introducing portion 60 flows smoothly without stagnation inside, and the spark plug mounting portion 34 The surroundings can be cooled effectively.

The upper wall 44 of the secondary air pipe mounting part 41 that supplies fresh air to the exhaust port 16 is inclined forward in the vehicle front-rear direction, so that the traveling wind is sent to the upper wall 44 of the secondary air pipe mounting part 41. Therefore, the cylinder head 7 and the bottom wall 20 can be cooled by traveling wind passing through the side.
Since the cylinder head cover 8 formed separately from the cylinder head 7 is configured to be attachable at the joint M of the cylinder head 7 substantially parallel to the mounting surface S of the cylinder head 7 and the cylinder block 6. Compared with the case where the cylinder head 7 and the cylinder head cover 8 are integrated, the maintainability is improved, and a large mold can be used on the side of the cylinder head 7 where the cylinder head cover 8 is attached. Therefore, productivity can be improved as compared with the conventional structure in which the upper portion of the cylinder head 7 is partially closed with a small lid and a small core must be used.

  A rubber packing 37 that seals the joint M of the cylinder head 7 to the cylinder head cover 8 is interposed between the cylinder head 7 and the cylinder head cover 8 with the protrusion 39 sandwiched between the peripheral end surface T of the cylinder head cover 8. Since both are attached, it is possible to prevent the rubber packing 37 from being exposed to a high temperature by the cylinder head 7 that is effectively cooled by the cooling air, and the durability of the rubber packing 37 can be improved.

  The present invention is not limited to the above-described embodiment, and is not limited to a motorcycle, for example, and can be applied to a saddle-ride type vehicle such as a three-wheel or a four-wheel.

4 Engine 6 Cylinder block 7 Cylinder head 8 Cylinder head cover 9 Exhaust pipe 9a Flange (flange)
14 Combustion chamber 16 Exhaust port 17 Intake port 20 Bottom wall 21 Valve chamber 33 Communication portion (insertion recess)
34 Spark plug mounting portion 37 Rubber packing 41 Secondary air piping mounting portion 51 Cam chain chamber 53 Oil return passage 54 Guide portion 60 Cooling air introduction portion
61 Exhaust pipe mounting part 62 Flange fastening part 63 Flange fastening part
64 ribs 66 left introduction part
67 Inclined wall (outer wall)
68 Inclined part (outer wall)
70 Communication path S Mounting surface M Joint

Claims (9)

A combustion chamber (14) is provided in the lower part of the cylinder head (7) of the engine (4) with the cylinder head (7) facing upward, and the upper part is defined via the combustion chamber (14) and the bottom wall (20). valve operating chamber (21) provided to be, the cam chain chamber on the side of the cylinder head (7) provided (51), a side of said opposite side of the cylinder head and the cam chain chamber (51) (7) An insertion recess (33) for the spark plug is provided in the part, an ignition plug mounting part (34) communicating with the combustion chamber (14) is provided in the insertion recess (33), and a front portion of the peripheral wall of the cylinder head (7) The cylinder head is provided with an exhaust port (16) that opens at the rear and communicates with the combustion chamber (14) and an intake port (17) that opens at the rear of the peripheral wall of the cylinder head (7) and communicates with the combustion chamber (14). a cooling structure, the exhaust Between the port (16) and the bottom wall (20), there is provided a cooling air introduction part (60) for taking running air above the exhaust port (16), and above the intake port (17). A communication passage (70) that opens to the cooling air introduction portion (60) and opens as a cooling air outlet is provided, and the insertion recess (33) is connected to the cooling air introduction portion (60) and the communication passage (70). And communicates with the cam chain chamber (51) in the lateral direction of the vehicle on the upper surface of the bottom wall (20) near the front of the peripheral wall of the cylinder head (7). An oil return passage (53) inclined to the outside is formed, and left and right outer walls (67, 68) of the opening of the cooling air introduction part (60) are formed to open outward and the cooling air introduction part ( 60) the upper edge of the opening of the cam chain chamber ( Cooling structure of a cylinder head, characterized in that tilting obliquely downward toward 1). A flange fastening portion (62, 63) for fastening the flange (9a) of the exhaust pipe (9 ) is provided around the opening of the exhaust port (16) , and the flange fastening portion (62 , 63) and the oil return passage ( 53) The cooling structure for a cylinder head according to claim 1, wherein the cooling air introduction part (60) is formed between the cooling air introduction part (60) and the cooling air introduction part ( 53) . The flange fastening portion (62) includes an upper flange fastening portion (62) for fastening the flange (9a) of the exhaust pipe (9 ) and a lower flange fastening portion (63), and the cooling air introduction portion. 3. The cooling structure for a cylinder head according to claim 2, wherein (60) is provided from above the upper flange fastening portion (62) to the periphery of the lower flange fastening portion (63) . The flange fastening portion (62, 63) is provided in the exhaust pipe attaching portion (61) for fastening the flange (9a) of the exhaust pipe (9), and the exhaust pipe attaching portion (61) is the cylinder head (7). The exhaust pipe mounting provided in a substantially rhombic shape that is long in the vehicle width direction and opposite to the cam chain chamber (51) at the front of the peripheral wall of the peripheral wall, and the flange fastening portions (62, 63) are provided in a substantially rhombic shape The flange fastening portion (62) on the opposite side to the cam chain chamber (51) is provided on the upper side, and the flange fastening portion (63 on the cam chain chamber (51) side). ) Is located on the lower side, and the cooling air introduction part (60) is provided from above the upper flange fastening part (62) to the periphery of the lower flange fastening part (63). cooling structure of a cylinder head according to claim 3 wherein The cooling air introduction part (60) is a central part between the upper flange fastening part (62) and the lower flange fastening part (63), and is located above the center position of the exhaust port (16) ( The cooling structure for a cylinder head according to claim 4 , wherein the cooling structure is divided into two parts by a rib (64) connected to 20) . Wherein the upper surface of the bottom wall (20) of the cylinder head (7), the guide portion for guiding the oil to the cam chain chamber (51) and (54) is provided, said guide portion (54) the cam chain chamber ( 51) The cooling structure for a cylinder head according to any one of claims 1 to 5 , which is inclined so as to be lowered toward the inside. A secondary air pipe mounting part (41) for supplying fresh air to the exhaust port (16) is provided, and the upper wall of the secondary air pipe mounting part (41) is inclined forward in the vehicle longitudinal direction. The cooling structure for a cylinder head according to any one of claims 1 to 6 . A cylinder head cover (8) formed separately from the cylinder head (7) is attachable substantially parallel to the mounting surface (S ) between the cylinder head (7) and the cylinder block (6) . A cooling structure for a cylinder head according to any one of claims 1 to 7 . The cylinder head (7) and the cylinder head cover (8) are attached via a rubber packing (37) that seals a joint (M) of the cylinder head (7) to the cylinder head cover (8) . 9. A cooling structure for a cylinder head according to claim 8, wherein:

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