JP5750016B2 - Oil passage structure of air-oil cooled internal combustion engine - Google Patents

Description

  The present invention relates to an oil passage structure of an air-oil cooled internal combustion engine that can reduce the manufacturing cost and suppress the temperature rise of oil for cooling a cylinder head.

In the air-oil cooled internal combustion engine, an oil passage for cooling is provided in the cylinder head, the oil passage is provided so as to surround the spark plug hole, and a cooling structure that is passed between the two portions of the exhaust port, For example, it is shown in the following Patent Document 1.
According to the cooling structure shown in Patent Document 1, it is possible to effectively reduce the amount of oil in the cylinder head around the seat surface of the spark plug hole and between the two portions of the exhaust port, which are higher than the surroundings. It can cool and can make uniform the wall temperature of a combustion chamber.
Further, since the oil return passage is arranged adjacent to the combustion chamber and the cylinder bore, the head side cooling oil passage can be connected to the oil return passage with a simple structure.

  However, in the cooling structure disclosed in Patent Document 1, the temperature of the oil after passing through the bifurcated portion of the exhaust port is increased because the oil is cooled around the seat surface of the spark plug hole and between the exhaust ports. It passes through the inside of the head and flows into the oil return passage adjacent to the combustion chamber and the cylinder bore, and is more susceptible to heat conduction.

Since the performance of the oil will be affected if its temperature rises above a certain value, the cooling oil should be cooled to the oil passage so that it will not receive heat as much as possible after it has been cooled. It is preferable to flow.
However, when the oil return passage is disposed away from the combustion chamber to be cooled, the head-side oil cooling passage becomes longer, and the temperature of the oil after cooling the portion that is most desired to be cooled tends to increase. Further, when the oil return passage is arranged away from the combustion chamber or the cylinder bore, the structure of the head side cooling oil passage connected to the combustion chamber may be complicated, and the manufacturing cost may increase.

JP 2006-97611 A (FIGS. 3 to 6)

  In view of the above prior art, the present invention provides a manufacturing cost without complicating the structure of the head side cooling oil passage even when the oil return passage is arranged away from the combustion chamber in the air-oil cooled internal combustion engine. It is an object to provide a low-cost oil passage structure, and the oil return passage is made to flow as much as possible so that the temperature of the cooling oil is not raised as much as possible after cooling the portion to be cooled most in the cylinder head. It is an object of the present invention to provide an oil passage structure that can be used.

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a cylinder and a cylinder head to which a valve mechanism is attached and housed are fastened to a crankcase, and the valve valve is installed in the cylinder head. An air oil cooling system is provided with a head side cooling oil path that branches off from the lubricating oil path of the mechanism, and an oil return path that guides oil from the head side cooling oil path to the crankcase in the cylinder. In the oil passage structure of an internal combustion engine, after the oil has flowed around the ignition plug or exhaust port of the cylinder head, the head side cooling oil passage communicates with the mating surface of the cylinder head and the cylinder. A communication portion is provided, and the oil return passage is provided apart from the communication portion, and the cylinder side is provided with the communication portion from the communication portion. Yl to return passage is provided with a cylinder-side oil passage for flowing the oil to the outer portion of the cylinder, adjacent to the cylinder bore of the cylinder, a cam chain chamber in which the cam chain is accommodated for driving the valve operating mechanism The oil return passage is provided outside the cam chain chamber, and the cylinder side oil passage is configured to communicate with the oil return passage so as to go around the cam chain chamber . This is an oil passage structure for an air-oil cooled internal combustion engine.

  According to a second aspect of the present invention, in the oil passage structure of the air-oil cooled internal combustion engine according to the first aspect, the cylinder side oil passage is provided as a groove on the mating surface on the cylinder side. To do.

  According to a third aspect of the present invention, in the oil passage structure of the air-oil cooled internal combustion engine according to the second aspect, an oil receiving portion having a shape coinciding with the communicating portion is provided at an upstream end of the cylinder side oil passage. It is characterized by that.

  According to a fourth aspect of the present invention, in the oil passage structure of the air-oil cooled internal combustion engine according to the first aspect, the communication portion is formed so as to extend in parallel with an axis of the cylinder and reach the mating surface. It is characterized by that.

  According to a fifth aspect of the present invention, in the oil passage structure of the air-oil cooled internal combustion engine according to the fourth aspect, a stud bolt that fastens the cylinder head and the cylinder surrounds a combustion chamber of the cylinder head. The communication portion is disposed between the combustion chamber peripheral wall and the stud bolt.

According to the oil passage structure of the air-oil cooled internal combustion engine of the first aspect of the present invention, the cooling oil after flowing in the vicinity of the high temperature portion in the cylinder head, such as around the spark plug or the exhaust port, The oil is communicated from the communication part to the cylinder side, and the oil that has been communicated flows through the cylinder-side oil passage provided on the cylinder side to the oil return passage that is separated from the communication part. Therefore, it is possible to form a path leading to the oil return path, resulting in an oil path structure with a low manufacturing cost.
In general, since the temperature on the cylinder side where the combustion gas is expanded is lower than that on the cylinder head side where the combustion chamber is located, the temperature rise of the oil after cooling the portion to be cooled most is suppressed. Can do.
The cam chain chamber is a space in the cylinder, and the outside of the cam chain chamber has the lowest temperature in the cylinder because the space is interposed between the combustion chamber and the cylinder bore. By taking advantage of such temperature distribution characteristics and disposing the oil return passage outside the cam chain chamber, it becomes possible to efficiently cool the cooling oil whose temperature has increased.

  According to the invention of claim 2, in addition to the effect of the invention of claim 1, the cylinder side oil passage can be easily formed by casting or the like at the time of manufacturing the cylinder.

  According to the invention of claim 3, in addition to the effect of the invention of claim 2, the shape of the oil receiving portion of the cylinder side oil passage matches the shape of the communicating portion of the head side cooling oil passage. Becomes smooth

  According to the invention of claim 4, in addition to the effect of the invention of claim 1, the communication portion can be provided with a simple structure.

  According to the invention of claim 5, in addition to the effect of the invention of claim 4, the head side cooling oil passage can be provided compactly in the narrow metal portion region of the cylinder head.

1 is a left side view of a motorcycle equipped with an air-oil cooled internal combustion engine having an oil passage structure of an air-oil cooled internal combustion engine according to an embodiment of the present invention. FIG. 2 is a cross-sectional development view of the air-oil cooled internal combustion engine as viewed in the direction of arrows II-II in FIG. 1. FIG. 3 is a plan view showing only a cylinder head taken out from the direction of arrows III-III in FIG. FIG. 4 is a left side view showing only a cylinder head taken along line IV-IV in FIGS. 2 and 3. FIG. 10 is a plan view of an oil passage core for forming a head side cooling oil passage indicated by a broken line in FIG. 3 and indicated by a two-dot chain line in FIG. 9. FIG. 6 is a rear side view of the oil passage core as viewed in the direction of arrows VI-VI in FIG. 5. FIG. 7 is a left side view of the oil passage core as viewed in the direction of arrows VII-VII in FIG. 5. FIG. 6 is a top perspective view of the oil passage core as viewed in the direction of arrow VIII in FIG. 5. FIG. 3 is a plan view showing only a cylinder taken along line IX-IX in FIG. 2. It is explanatory drawing of the modification of the X section in FIG. FIG. 3 is a top perspective view showing only a cylinder, taken along the line IX-IX in FIG. 2. It is explanatory drawing of another modification at the time of applying the bypass channel in this embodiment to a multicylinder internal combustion engine.

An oil passage structure for an air-oil cooled internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS.
In the description of the present specification and the claims, the front-rear, left-right, top-bottom, and the like directions are such that the air-oil cooled internal combustion engine including the oil passage structure of the air-oil cooled internal combustion engine according to the present embodiment is mounted on a small vehicle. Follow the direction of the vehicle in the state. In this embodiment, the small vehicle is a motorcycle.
In the figure, an arrow FR indicates the front of the vehicle, LH indicates the left side of the vehicle, RH indicates the right side of the vehicle, and UP indicates the upper side of the vehicle.
Also, the small black arrow added in the drawing schematically shows the flow of the cooling oil according to the present invention in the present embodiment. In FIGS. 5 to 8, the oil passage core is shown as an oil passage. The flow of oil was shown schematically.

1 to 12 relate to an embodiment of the present invention. In FIG. 1, an air-oil cooled internal combustion engine (hereinafter simply referred to as “internal combustion engine”) 1 of the present embodiment is mounted on a motorcycle 2. It shows in the state.
The internal combustion engine 1 according to the present embodiment includes a transmission 4 (see FIG. 2) integrally in the rear portion of the crankcase 10 to constitute a so-called power unit, and the crankshaft 11 is connected to the motorcycle 2. This is an air-oil cooled single-cylinder four-stroke cycle internal combustion engine that is mounted on the motorcycle 2 so as to be oriented in the vehicle width direction, that is, the left-right direction.

As shown in FIG. 1, the body frame 20 of the motorcycle 2 equipped with the internal combustion engine 1 according to this embodiment has a pair of left and right main frames 22 extending slightly downward from the head pipe 21 to the rear. Further, it bends downward to form a steeply inclined portion 22a and reaches the lower end.
Further, a pair of left and right down frames 23 extend downward from the head pipe 21 at an obliquely steep angle and extend substantially parallel to the steeply inclined portion 22a of the main frame 22 in a side view.

  From the upper part of the steeply inclined portion 22a of the main frame 22, a seat rail 25 extends rearward via a gusset 24, and a back stay 26 that connects the center portion of the seat rail 25 and the lower portion of the steeply inclined portion 22a is a seat. The rail 25 is supported.

In the body frame 20 as described above, a front fork 27 is pivotally supported on the head pipe 21, and a front wheel 28 is pivotally supported at the lower end thereof.
A rear fork 29 supported at the front end at the lower portion of the steeply inclined portion 22a of the main frame 22 extends rearward, and a rear wheel 30 is pivotally supported at the rear end thereof, between the rear fork 29 and the gusset 24 of the body frame 20. In addition, a rear cushion 31 is interposed.
A fuel tank 32 is installed in front of the main frame 22, and a seat 33 is supported behind the fuel tank 32 and supported by the seat rail 25.

  The internal combustion engine 1 suspended from the main frame 22 and the down frame 23 is constructed by integrating the transmission 4 (see FIG. 2) as described above, and the cylinder axis C is slightly tilted forward on the crankcase 10. The cylinder 12, the cylinder head 13, and the cylinder head cover 14 are suspended in a standing posture.

From the cylinder head 13 of the internal combustion engine 1, an intake pipe 35 extends from the intake port 15 and extends to the air cleaner 37 via the throttle body 36.
In front of the cylinder head 13, an exhaust pipe 38 extends from the exhaust port 16, bends downward, extends rearward under the internal combustion engine 1, and reaches a muffler 39 on the right side of the rear wheel 30.

  As shown in FIG. 2, the crankcase 10 of the internal combustion engine 1 constitutes a transmission chamber 40 that supports the crankshaft 11 and accommodates the transmission 4 behind the crank chamber 17 in which the crankshaft 11 is disposed. doing.

On the front crank chamber 17 of the crankcase 10, a cylinder 12 having a single cylinder bore 12a and a cylinder head 13 are stacked on the cylinder 12 via a gasket 18 (see FIG. 9). As a result, the cylinder head 13 and the cylinder 12 are integrally fastened to the crankcase 10, and the cylinder head cover 14 covers the cylinder head 13.
The cylinder 12, the cylinder head 13, and the cylinder head cover 14, which are overlaid on the front side portion of the crankcase 10, extend upward from the crankcase 10 in a slightly forwardly inclined posture (see FIG. 1).

A piston 50 is slidably fitted in a cylinder bore 12a of the cylinder 12 (see FIG. 2), and the piston 50 and the crankshaft 11 are connected by a connecting rod 51 to constitute a crank mechanism.
A combustion chamber 52 covered with an upper wall 53 of the combustion chamber is formed at the lower portion of the cylinder head 13 so as to face the piston 50 in the cylinder bore 12a and define a combustion chamber peripheral wall 52a coinciding with the cylinder bore 52a.
In the combustion chamber upper wall 53, an intake port 15 (see FIGS. 1 and 4) that opens into the combustion chamber 52 and is opened and closed by an intake valve (not shown) extends rearward, and an exhaust port that is opened and closed by an exhaust valve (not shown). 16 (see FIGS. 1 and 4) extends forward, and a spark plug 55 facing the combustion chamber 52 is mounted.

The cylinder head 13 includes valve-operated parts such as a valve camshaft 61 that opens and closes an intake and exhaust valve (not shown), a driven cam chain sprocket 62, an intake rocker arm 65, an exhaust rocker arm 66, and a support member 67 thereof. A valve operating mechanism 60 is attached and accommodated.
Cam chain chambers 12b and 13b in which a cam chain 64 for driving the valve operating mechanism 60 is accommodated are provided on the left side (outer side) of the cylinder 12 and the cylinder head 13.

  A cam chain 64 is inserted between the driven cam chain sprocket 62 fitted to the valve camshaft 61 of the valve mechanism 60 and the drive cam chain sprocket 63 fitted to the crankshaft 11 through the cam chain chambers 12b and 13b. (See Fig. 2), the valve drive cam shaft 61 is rotated at half the number of revolutions of the crankshaft 11, and the intake rocker arm 65 and the exhaust rocker arm 66 are swung to suck and exhaust the valve at the required timing. Open and close with.

In addition to the drive chain sprocket 63, an AC generator 56 is attached to a portion of the crankshaft 11 protruding leftward from the left bearing wall 10L of the crankcase 10 and covered with a left case cover 57L.
On the other hand, a primary drive gear 58 is fitted to a portion of the crankshaft 11 that protrudes to the right from the right bearing wall 10R of the crankcase 10, and the right side thereof is covered with a right case cover 57R.

  In the transmission chamber 40 of the crankcase 10, the main shaft 41 and the countershaft 42 of the transmission 4 are oriented between the left and right bearing walls 10L and 10R parallel to each other in the left-right direction behind the crankshaft 11. The main gear group 41g pivotally supported by the main shaft 41 and the counter gear group 42g pivotally supported by the counter shaft 42 are always meshed to constitute the transmission 4. .

A multi-plate friction type transmission clutch 43 is provided on the right side portion of the crankshaft 10 of the main shaft 41 that protrudes to the right from the right bearing wall 10R.
A clutch outer 43a of the transmission clutch 43 is supported by a primary driven gear 44 rotatably supported on the main shaft 41 via a buffer member, and is connected to a clutch inner 43b integrally fitted to the main shaft 41. A plurality of clutch plates are interposed therebetween, and the compression member 43c is driven to connect and disconnect.

  The primary driven gear 44 meshes with the primary drive gear 58 fitted on the crankshaft 11, and the rotational power of the crankshaft 11 is transmitted to the primary drive gear 58 on the crankshaft 11 side and the primary driven gear on the transmission clutch 43 side. The transmission clutch 43 is transmitted to the transmission clutch 43 via the gear 44. The transmission clutch 43 is in a neutral state without transmitting the rotational power of the crankshaft 11 to the transmission 4 during the gear change of the transmission 4, so that the transmission 4 When the gear change is completed, the rotational power of the crankshaft 11 is transmitted to the main shaft 41 of the transmission 4.

The counter shaft 42 penetrates the left bearing wall 10L of the crankcase 10 to the left and protrudes to the outside to become the final output shaft 42 of the internal combustion engine 1, and an output sprocket 45 is spline fitted to the protruding portion. Yes.
A drive chain 46 wound around the output sprocket 45 is laid over a driven sprocket 47 on the rear wheel 30 side to form a chain transmission mechanism, and power is transmitted to the rear wheel 30 (see FIG. 1).

In the internal combustion engine 1 of the present embodiment as described above, the cooling of the cylinder 12 and the cylinder head 13 is basically performed by air cooling by the cooling fins 12c and 13c formed respectively.
However, the periphery of the combustion chamber upper wall 53 covering the combustion chamber 52 of the cylinder head 12 and the periphery of the portion where the ignition plug 55 is mounted and the periphery of the combustion chamber side opening 16a of the exhaust port 16 are in the deeper combustion chamber upper wall 53. It is difficult to directly provide the cooling fins 13c, and depending on the specifications such as the compression ratio of the internal combustion engine 1, the cooling fins may not be sufficiently cooled by heat radiation.

  Therefore, in the internal combustion engine 1 of the present embodiment, a head side cooling oil passage (hereinafter simply referred to as “cooling oil passage”) 7 is provided in the combustion chamber upper wall 53, and a part of the lubricating oil is used for cooling. The high-temperature portion of the cylinder head 13 is sufficiently cooled.

  The stud bolt 19 shown in FIG. 2 has a stud bolt hole 68 (see FIG. 3) drilled in each of the support member 67, the cylinder head 13, and the cylinder 12 of the valve mechanism 60 so as to surround the cylinder bore 12a and the combustion chamber 52. ) Is inserted from above to below and fastened to the crankcase, and the support member 67, the cylinder head 13 and the cylinder 12 are fastened together.

In this embodiment, the number of stud bolts 19 is four, but one stud bolt hole 68A (see FIG. 3) of the four stud bolt holes 68 is between the inner surface and the outer surface of the stud bolt 19. The bolt hole gap is used as an oil supply passage, and further communicates with an oil pump discharge port (not shown) in the crankcase 10 via an oil supply passage (not shown).
Therefore, a part of the oil from the oil pump is used as a lubricating oil passage for the valve mechanism 60 with the stud bolt hole 68A as a valve camshaft 61, a driven cam chain sprocket 62 housed in the upper part of the cylinder head 13, The air is supplied to the intake rocker arm 65, the exhaust rocker arm 66, etc. and their support members 67, etc.

On the other hand, the combustion chamber upper wall 53 of the combustion chamber 52 is formed below the cylinder head 53, and the cooling oil passage 7 provided in the combustion chamber upper wall 53 is a stud bolt hole which is a lubricating oil passage. It communicates so as to branch from 68A.
Therefore, the stud bolt hole 68A as the lubricating oil passage forms an oil supply passage to the cooling oil passage 7.

FIG. 3 shows the upper wall portion 13 d of the cylinder head 13 to which the valve mechanism 60 is attached, with the valve mechanism 60 removed. The combustion chamber upper wall 53 is positioned below the cooling chamber, and the cooling oil passage 7 is provided in the combustion chamber upper wall 53 as shown by a broken line in FIG. 3 (see FIG. 2).
Further, the spark plug mounting hole 55a for attaching the spark plug 55 is formed so as to open in the combustion chamber upper wall 53 as indicated by a broken line in FIG. 3, and the combustion chamber side opening 15a of the intake port 15 and the exhaust port 16 is formed. , 16a is opened in the combustion chamber upper wall 53 so as to be inscribed in the combustion chamber peripheral wall 52a (see FIG. 3).

  The cooling oil passage 7 includes an oil inflow passage 71 through which oil is diverted from a stud bolt hole 68A as a lubricating oil passage, a communication portion 72 that forms an oil outflow passage through which oil flows out to the cylinder 12, and an oil inflow passage. The cooling passage 73 is provided between the communication port 71 and the communication portion 72 and flows around the spark plug 55 and the exhaust port 16.

The cooling passage 73 is connected to the oil inflow passage 71, and constitutes the right side in the flow direction among the upper flow passage 73a toward the spark plug mounting hole 55a and the flow passage surrounding the spark plug mounting hole 55a and the exhaust port 16. The first passage 73b is composed of a second passage 73c that forms the left side in the flow direction. The first passage 73b and the second passage 73c are joined together and connected to the communication portion 72.
As shown in FIG. 4, the communicating portion 72 has its axis R extending downward in parallel with the cylinder axis C, reaching the mating surface 70 between the cylinder head 13 and the cylinder 12, and opening oil to the cylinder 12 side. Spill.

  In FIGS. 3 and 4, hatching surrounded by a broken line indicates a cooling oil passage 7 provided in the combustion chamber upper wall 53 of the cylinder head 13, and the shape of the cylinder head other than the oil inflow passage 71 is the cylinder head. The oil passage core 8 is the same as the sand core for forming the cooling oil passage 7 at the time of casting 13.

FIG. 5 is a plan view of the oil passage core 8 showing the oil passage core 8 in the same direction as the cooling oil passage 7 shown in FIG. 3. 6 is a rear side view of the oil passage core 8 taken along line VI-VI in FIG. 5, and FIG. 7 is a left side view of the oil passage core 8 taken along line VII-VII in FIG. These are the upper surface perspective views of the oil path core 8 by the VIII arrow view in FIG.
5 to 8, for reference, in addition to the respective reference numerals of the oil passage core 8, the corresponding reference numerals of the cooling oil passage 7 are added in the brackets, and the formed cooling oil passage 7 Add oil flow with small black arrows.

The oil passage core 8 includes a first boss 81 that forms an oil inflow passage 71, a second boss 82 that forms a communication portion 72 as an oil outflow passage, the periphery of the spark plug 55, and the periphery of the exhaust port 16 And a cooling passage portion 83 that forms a cooling passage 73 that communicates between the oil inflow passage 71 and the communication portion 72.
Under the first boss 81, a leg 81a that determines the posture at the time of setting is provided in the mold (see FIGS. 6 and 8), but a stud bolt hole 68A as an oil supply passage to which the oil inflow passage 71 is connected. The portion of the leg 81a after casting becomes a part of the stud bolt hole 68A (see FIG. 4).

In the middle portion of the cooling passage 83, the side is offset laterally with respect to the first straight line L1 connecting the first boss 81 and the second boss 82 with the center of gravity (CG) of the oil passage core (8) interposed therebetween. In this position (see FIG. 5), a side protrusion 84 that protrudes further from the cooling passage 83 is provided, and the side protrusion 84 is provided with a third boss 85 that protrudes downward. Yes.
That is, the center of gravity CG is at a position offset to one side (here, the right side in the flow direction) with respect to the straight line L1, and the third boss 85 is on the center of gravity CG side with respect to the straight line L1, and is further than the center of gravity. Arranged at the offset position. Therefore, since the first boss 81, the second boss 82, and the third boss 85 are disposed so as to surround the center of gravity CG of the oil passage core 8, the oil passage core 8 is used for the cylinder head 13 during casting. It is possible to stand on its own in a stable mold.
The third boss 85 serves as a leg portion that determines the posture at the time of setting in the mold, and forms a projecting portion 75 in the cooling passage 73 after the cylinder head 13 is cast.
Further, the protrusion 75 extends to the mating surface 70 when the cylinder head 13 is fastened to the cylinder 12.

Since the oil passage core 8 of this embodiment has the third boss 85 even if the surface area of the second boss 82 forming the communication portion 72 is reduced to reduce the lateral width, The first to third bosses 81, 82, and 85 can stand by themselves in the mold of the cylinder head 13 during casting.
Accordingly, the surface area of the communicating portion 72 of the formed cooling oil passage 7 can be reduced, and the oil flow after cooling in the cooling passage 73 can be discharged to the cylinder 12 side without decreasing the flow rate. Since the rate can be increased, cooling can be performed efficiently.

Further, since the third boss 85 is provided in the side protrusion 84 that protrudes further to the side of the cooling passage 83, the protrusion 75 of the cooling oil passage 7 that is formed also extends to the side of the cooling passage 73. Since it is located so as to protrude, the influence on the flow of oil flowing through the cooling passage 73 can be suppressed.
Therefore, the structure of the oil passage core 8 of the present embodiment is excellent in manufacturability, and the formed cooling oil passage 7 provides good cooling performance.

  The cooling passage 83 surrounds the periphery of the spark plug mounting hole 55a of the spark plug 55 and the exhaust port 16, and connects the spark plug mounting hole 55a of the spark plug 55 and the central portions 55c and 16c of the exhaust port 16 to each other. The second passage portion 83b located on the third boss 85 side, the second passage portion 83c located on the other side, the first passage portion 83b and the second passage portion 83c are It has an upper flow path portion 83a connected to one boss 81, and a second boss portion 82 is provided on the second straight line L2.

  Therefore, since the first passage portion 83b and the second passage portion 83c of the cooling passage portion 83 of the oil passage core 8 are substantially equal in length, the exhaust port 16 of the cooling passage 73 of the formed cooling oil passage 7 is formed. The first passage 73b and the second passage 73c on both sides surrounding the periphery of the spark plug 55 can be made to have substantially equal lengths, and the high temperature portions of the combustion chamber upper wall 53 and the combustion chamber peripheral wall 52a can be uniformly cooled. Can do.

  The first passage portion 83b is provided with a third boss for allowing the oil passage core 8 to be self-supporting at the time of casting on the side protrusion portion 84 that protrudes laterally around the exhaust port 16. As described above, the influence of the first passage 73b of the oil passage 7 on the oil flow is suppressed.

  As shown in FIG. 3, in the present embodiment, the cylinder is configured such that the stud bolt holes 68 of the plurality of stud bolts 19 that fasten the cylinder head 13 and the cylinder 12 surround the combustion chamber peripheral wall 52 a of the cylinder head 13. Since the oil passage core 8 is arranged in the head 13 and the second boss 82 and the third boss 85 are arranged between the combustion chamber peripheral wall 52a and the stud bolt hole 68, the cylinder The second boss 82 and the third boss 85 can be compactly arranged in the narrow metal portion region of the head 13.

  That is, the stud bolt 19 is disposed in the cylinder head 13 so as to surround the combustion chamber peripheral wall 52 a of the cylinder head 13, and the communication portion 72 of the cooling oil passage 7 is disposed between the combustion chamber peripheral wall 52 a and the stud bolt 19. Therefore, the cooling oil passage 7 can be compactly arranged in the narrow metal portion region of the cylinder head 13.

A cylinder 12 is fastened by a stud bolt 19 below the cylinder head 13 provided with the cooling oil passage 7 as described above.
As shown in FIG. 9, the cylinder 12 is provided with an oil return passage 9 that guides oil from the cooling oil passage 7 into the crankcase 10.

In FIG. 9, the position of the cooling oil passage 7 in the cylinder head 13 in the state of being fastened to the cylinder 12 is indicated by a two-dot chain line.
The oil inflow passage 71 of the cooling oil passage 7 is connected to a stud bolt hole 68A serving as an oil supply passage, and the communication portion 72 has a shape that coincides with the communication portion 72 at the joint surface 70 between the cylinder 12 and the cylinder head 13. And communicates with an oil receiving portion 90 recessed on the cylinder 12 side.

On the other hand, as shown in FIGS. 9 and 11, an oil return hole 9 drilled in the cylinder 12 opens in the mating surface 70. The oil return hole 9 is a space in the cam chain chamber 12b adjacent to the cylinder bore 12a. The cylinder 12 is provided on the left side of the cylinder 12 opposite to the cylinder bore 12a.
A groove 91 provided in the mating surface 70 on the cylinder 12 side is provided between the oil receiving portion 90 and the oil return hole 9 so as to go around the cam chain chamber 12b. In a state where the cylinder 12 and the cylinder head 13 are fastened, the oil receiving portion 90 and the groove 91 allow oil received from the communicating portion 72 of the cooling oil passage 7 to be returned to the oil separating portion 72 and the communicating portion 72. It becomes a cylinder side oil passage 92 that flows into the hole 9.

As described above, since the communicating portion 72 extends parallel to the cylinder axis C and reaches the mating surface 70, in addition to the manufacturing advantage that the structure of the communicating portion 72 is simplified, the cooling action at the cylinder head 13 is completed. The oil is immediately sent to the cylinder 12 side.
The oil flows through a cylinder-side oil passage 92 having a temperature lower than that of the cylinder head 13, and the cam chain having the lowest temperature among the cylinders 12 sandwiching the space of the cam chain chamber 12b from the combustion chamber 52 and the cylinder bore 12a. Since the oil is flowed to the oil return hole 9 provided away from the communication portion 72 outside the chamber 12b, the oil is suppressed from being subjected to unnecessary heating and can be relatively cooled. The rise in oil temperature can be suppressed.

Even if the oil return hole 9 is provided so as to be separated from the communication portion 72 of the cooling oil passage 7, the groove-shaped cylinder side oil passage 92 formed on the mating surface 70 can connect the oil return hole 9. Therefore, a flow path to the oil return path 9 can be obtained without complicating the mold production of the cylinder head 13 and the cylinder 12, and the manufacturing cost can be reduced.
In particular, since the recessed oil receiving portion 90 and the groove 91 can be formed by casting when the cylinder 12 is cast, the formation is easy and the cost can be reduced.
Further, the oil receiving part 90 is formed in the same shape as the communication part 72 and forms a flow path integral with the communication part 72, so that the flow of oil is smooth.

Note that a cylinder-side oil passage 92 ′ may be formed by enclosing a groove 91 ′ and a cam chain chamber 12 b on the rear side of the cylinder 12 as indicated by a two-dot chain line in FIG. 11.
In this case, the cylinder-side oil passage 92 'can be set longer than the above-described cylinder-side oil passage 92 that is configured to go around the cam chain chamber 12b on the front side of the Linder 12, and the relatively low temperature intake port 15 side (FIG. 3). Therefore, there are advantages in preventing oil from being heated or cooling.

Further, as shown in FIG. 10, the oil return hole 9 ′ may be a vertical hole having a wave length side instead of a circular cross-sectional hole. In that case, the oil return hole 9 ′ may be formed on the outer surface of the cam chain chamber 12 b or the cylinder 12. Heat transfer to the cooling fins 12c is increased, and oil cooling can be enhanced.
9 and 10, what is indicated by a two-dotted line on the mating surface 70 other than the cooling oil passage 7 is a gasket 18 of the mating surface 70.

As described above, the oil passage core 8 of the present embodiment, which is a sand core for forming the cooling oil passage 7, is provided with a cooling passage portion 83 so that the cylinder head 13 can stand by itself in the mold when the cylinder head 13 is cast. The third boss 85 is provided on the side protrusion 84 that protrudes more laterally.
Therefore, as shown in FIGS. 5, 6, and 8, the formed cooling oil passage 7 branches downward from the intermediate portion of the first passage 73 b of the cooling passage 73 by the third boss 85. The protrusion 75 is provided. The protrusions 75 extend to their mating surfaces 70 when the cylinder head 13 is fastened to the cylinder 12.

  Since the projecting portion 75 branches off from the first passage 73b of the cooling passage 73 and protrudes downward, it is suppressed from affecting the oil flow in the cooling oil passage, but oil stagnation is likely to occur. The oil temperature may increase.

  Therefore, in the present embodiment, as shown in FIGS. 9 and 11, when the cylinder head 13 and the cylinder 12 are fastened to the cylinder 12 side of the mating surface 70 of the cylinder head 13 and the cylinder 12, the protruding portion A bypass oil receiving portion 95 having a shape matching the lower end portion of 75 is recessed.

Further, a bypass groove 96 for connecting the bypass oil receiving portion 95 and the oil receiving portion 90 is formed on the mating surface 70 on the cylinder 12 side. The bypass oil receiving portion 95 and the bypass groove 96 are connected to the bypass oil receiving portion 95. A bypass passage 97 is formed with the upper end as the upstream end.
The flow passage cross-sectional area by the bypass groove 96 that forms the bypass passage 97 is set smaller than the flow passage cross-sectional area of the cooling oil passage 7.
The bypass groove 96 may be formed on the mating surface 70 on the cylinder head 13 side.

  Therefore, the oil in the protruding portion 75 of the cooling oil passage 7 flows into the bypass passage 97 from the end thereof, and forms an integral flow path with the communication portion 72 on the downstream side of the cooling oil passage 7. Since the oil is fed up to 90, the oil is prevented from staying in the projecting portion 75, and an increase in the temperature of the oil is suppressed.

Further, the bypass passage 97 is set to have a flow passage cross-sectional area smaller than the flow passage cross-sectional area of the cooling oil passage 7, so that it is avoided that the bypass flow hinders the flow of cooling oil in the cooling oil passage 7. Can do.
Further, since the bypass passage 97 is formed as a bypass oil receiving portion 95 whose upstream end portion coincides with the lower end portion of the protruding portion 75, the protruding portion 75 and the bypass oil receiving portion 95 form an integral flow path. Thus, the flow of the bypass oil in the bypass oil receiving portion 95 is smooth.

  Further, the bypass flow path 97 has a simple configuration on the mating surface 70 and can be formed by casting or the like, so that the manufacturing cost is reduced.

FIG. 12 shows a modified example in which the bypass passage 97 of the present embodiment is applied to an air-oil cooled multi-cylinder internal combustion engine (hereinafter simply referred to as “multi-cylinder internal combustion engine”) 1 ′.
As shown in FIG. 12, the multi-cylinder internal combustion engine 1 ′ has four cylinders in which the first cylinder C1 to the fourth cylinder C4 are arranged in series in order from the right side in the cylinder row direction. A combustion chamber is formed for each, and a spark plug mounting hole 55a for mounting the spark plug 55 is provided at the top of the combustion chamber upper wall 53 '.
A pair of intake port combustion chamber side openings 15a 'and a pair of exhaust port combustion chamber side openings 16a' are provided on the combustion chamber upper wall 53 'of each cylinder.

  The combustion chamber upper wall 53 'of the second cylinder C2 and the third cylinder C3 passes through the periphery of the spark plug mounting hole 55a from the rear side of the cylinder, that is, from between the intake port combustion chamber side opening 15a', and forward of the cylinder. The first cooling oil passages 77A and 77B are provided so as to pass through the side, that is, between the exhaust port combustion chamber side openings 16a '.

  The first cooling oil passages 77A and 77B of the second cylinder C2 and the third cylinder C3 are respectively connected to the oil supply passages 76A and 76B on the rear side of the cylinder, and the oil supply passages 76A and 76B merge on the upstream side. Not connected to the discharge port of the oil pump.

The combustion chamber upper wall 53 'of the first cylinder C1 and the fourth cylinder C4 passes through the periphery of the spark plug mounting hole 55a from the front side of the cylinder, that is, from between the exhaust port combustion chamber side opening 16a', and outside the cylinder. Third cooling oil passages 79A and 79B are respectively provided so as to be pulled out.

  The third cooling oil passages 79A and 79B of the first cylinder C1 and the fourth cylinder C4 are connected to the oil return passages 9A and 9B on the right and left cylinder sides, respectively, and the oil return passages 9A and 9B are on the downstream side thereof. And is connected to an oil return system in a crankcase (not shown).

Further, the downstream end 77Aa on the cylinder front side of the first cooling oil passage 77A of the second cylinder C2 and the upstream end portion 79Aa on the cylinder front side of the third cooling oil passage 79A of the first cylinder C1 are second cooled. They are connected by an oil passage 78A.
The downstream end 77Ba on the cylinder front side of the first cooling oil passage 77B of the third cylinder C3 and the upstream end portion 79Ba on the cylinder front side of the third cooling oil passage 79B of the fourth cylinder C4 are the second cooling oil passage. Connected by 78B.

Therefore, in the multi-cylinder internal combustion engine 1 ′ of FIG. 12, the first cooling oil passage 77A, the second cooling oil passage 78A, and the third cooling oil passage 79A of the first cylinder C1 are connected in series in the cylinder head. The head side cooling oil passage (hereinafter simply referred to as “cooling oil passage”) 7A is formed.
The first cooling oil passage 77B, the second cooling oil passage 78B, and the third cooling oil passage 79B of the fourth cylinder C4 form a series of cooling oil passages 7B in the cylinder head.

Although both the cooling oil passage 7A and the cooling oil passage 7B are formed by an oil passage core (not shown) made of a sand core, the oil passage core is not shown in FIG. 5 to 8 are provided with bosses at the upstream end, downstream end and intermediate portion of the passage formed in the same manner as described in FIG.
In particular, the boss at the intermediate portion branches from the cooling oil passage 7A to each intermediate portion of the cooling oil passage 7A and the cooling oil passage 7B in the same manner as in the case of the oil passage core 8 described above. Since the projecting portions 75A1 and 75A2 and the projecting portions 75B3 and 75B4 branched from the cooling oil passage 7B are formed, there is a risk of oil stagnation and oil temperature increase in each projecting portion.

Therefore, in the modification of the present embodiment, the lower end of the projecting portion 75A1 of the first cylinder C1 communicates with the downstream portion 7Aa of the cooling oil passage 7A, and the lower end of the projecting portion 75A1 of the first cylinder C1 A bypass passage 97A having a protruding portion communication passage 98A communicating with the lower end portion of the protruding portion 75A2 of the second cylinder C2 is provided.
Further, the lower end portion of the projecting portion 75B4 of the fourth cylinder C4 communicates with the downstream portion 7Ba of the cooling oil passage 7B, and the lower end portion of the projecting portion 75B4 of the fourth cylinder C4 and the projecting portion 75B3 of the third cylinder C3. A bypass passage 97B having a protruding portion communication passage 98B communicating with the lower end portion is provided.
The flow passage cross-sectional areas of the bypass passages 97A and 97B are set smaller than the flow passage cross-sectional areas of the cooling oil passages 7A and 7B, respectively, and the flow of bypass oil is the flow of oil in the cooling oil passages 7A and 7B. Is prevented.

Therefore, in the first cylinder C1 and the second cylinder C2, the oil in the projecting portion 75A2 flows to the projecting portion 75A1 via the projecting portion communication passage 98A and further flows to the downstream portion 7Aa of the cooling oil passage 7A by the bypass passage 97A. As a result, an increase in oil temperature due to oil stagnation in the protrusions 75A1 and 75A2 is suppressed.
Further, it is not necessary to provide a bypass passage communicating with the downstream portion 7Aa of the cooling oil passage 7A for each of the protrusion portions 75A1 and 75A2 by the protrusion portion communication passage 98A, thereby simplifying the structure and reducing the cost.
The same applies to the third cylinder C3 and the fourth cylinder C4.

The features of the oil passage structure of the above-described air-oil cooled internal combustion engine according to the present embodiment will be described below.
That is, the cylinder 12 and the cylinder head 13 in which the valve mechanism 60 is mounted and housed are fastened to the crankcase 10, and the stud bolt hole 68 </ b> A serving as a lubricating oil passage for the valve mechanism 60 is inserted into the cylinder head 13. In the oil passage structure of the air-oil-cooled internal combustion engine 1, the cooling oil passage 7 is provided, and the cylinder 12 is provided with the oil return passage 9 that guides the oil from the cooling oil passage 7 to the crankcase 10. The cooling oil passage 7 is provided with a communication portion 72 that is in communication with the mating surface 70 between the cylinder head 13 and the cylinder 12 after the oil flows around the ignition plug 55 and the exhaust port 16 of the cylinder head 13. The oil return passage 9 is provided apart from the communication portion 72, and a cylinder-side oil passage 92 through which oil flows from the communication portion 72 to the oil return passage 9 is provided on the cylinder 12 side. It is.

Therefore, the oil for cooling after flowing in the vicinity of the high temperature portion in the cylinder head 13 such as the vicinity of the spark plug 55 and the exhaust port 16 is communicated to and communicated from the communication portion 72 on the cylinder head 13 side to the cylinder 12 side. After the oil passes through the cylinder-side oil passage 92 provided on the cylinder 12 side and flows into the oil return passage 9 that is separated from the communication portion 72, the oil return passage 9 does not have to be complicated to manufacture the mold. It is possible to form a route that leads to an oil passage structure with a low manufacturing cost.
In general, since the temperature on the cylinder 12 side where the combustion gas is expanded is lower than that on the cylinder head 13 side where the combustion chamber 52 is located, the temperature of the oil after the portion to be cooled is cooled is increased. Can be suppressed.
The cam chain chamber 12b is a space in the cylinder 12, and the space outside the cam chain chamber 12b is the lowest in the cylinder 12 because the space is interposed between the combustion chamber 52 and the cylinder bore 12a. . By taking advantage of the temperature distribution characteristics and disposing the oil return passage 9 outside the cam chain chamber 12b, it becomes possible to efficiently cool the cooling oil whose temperature has increased .

  Further, since the cylinder side oil passage 92 is provided as a groove 91 in the mating surface 70 on the cylinder 12 side, the cylinder side oil passage 92 can be easily formed by casting or the like when manufacturing the cylinder.

  Further, since an oil receiving portion 90 having a shape matching the communication portion 72 is provided at the upstream end of the cylinder-side oil passage 92, the oil flow from the cylinder head 13 to the cylinder 12 becomes smooth during the oil communication. .

  Further, since the communication portion 72 is formed so as to extend parallel to the axis C of the cylinder 12 and reach the mating surface 70, the communication portion 72 can be provided with a simple structure.

  A stud bolt 19 for fastening the cylinder head 13 and the 12 cylinder is disposed so as to surround the combustion chamber 52 of the cylinder head 13, and the communication portion 72 is provided between the combustion chamber peripheral wall 52 a and the stud bolt 19. Thus, the cooling oil passage 7 can be provided compactly in the narrow metal portion region of the cylinder head 13.

  A cam chain chamber 12b for accommodating a cam chain 64 for driving the valve operating mechanism 60 is provided on the outer side of the cylinder 12 adjacent to the cylinder bore 12a of the cylinder 12, and the oil return passage 9 is connected to the cam chain chamber. The cylinder side oil passage 12 communicates with the oil return passage 9 so as to go around the cam chain chamber 12b.

As mentioned above, although the oil passage structure of the air-oil cooled internal combustion engine of one embodiment of the present invention has been described, the present invention naturally includes aspects different from the above-described embodiments within the scope of the claims. These can be changed as appropriate.
A small vehicle equipped with an air-oil cooled internal combustion engine is not limited to a motorcycle, and the degree of cylinder tilting forward from the vertical and the number of cylinders are not limited to those shown in the drawings. Even when an air-oil cooled internal combustion engine is used, it can be applied as an oil passage structure of an air-oil cooled internal combustion engine, and the same effect can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Air-oil cooling internal combustion engine (internal combustion engine), 7 ... Cooling oil passage (head side cooling oil passage), 9 ... Oil return passage, 10 ... Crank case, 12 ... Cylinder, 12a ... Cylinder bore, 12b ... Cam chain Chamber, 13 ... Cylinder head, 13b ... Cam chain chamber, 15 ... Intake port, 15a ... Combustion chamber side opening, 16 ... Exhaust port, 16a ... Combustion chamber side opening, 19 ... Stud bolt, 52 ... Combustion chamber, 52a ... Combustion Chamber peripheral wall, 53 ... Combustion chamber upper wall, 55 ... Spark plug, 55a ... Spark plug mounting hole, 60 ... Valve mechanism, 61 ... Valve camshaft, 62 ... Driven cam chain sprocket, 65 ... Intake rocker arm, 66 ... Exhaust Rocker arm, 67 ... Support member, 68 ... Stud bolt hole, 68A ... (Lubricating oil passage, oil supply passage) Stud bolt hole, 70 ... Mating surface, 72 ... Communication portion, 90 ... Oil receiving portion, 91 ... Groove, 92 ... Siri Oil side oil passage, C ... cylinder axis, R ... (communication part) axis

Claims (5)

The crankcase (10) is fastened with the cylinder (12) and the cylinder head (13) in which the valve mechanism (60) is mounted and accommodated,
In the cylinder head (13), a lubricating oil passage (68A) of the valve operating mechanism (60) is branched to provide a head side cooling oil passage (7).
The oil passage of the air-oil cooled internal combustion engine (1) in which the cylinder (12) is provided with an oil return passage (9) for guiding oil from the head side cooling oil passage (7) to the crankcase (10). In structure
After the oil flows around the spark plug (55) or the exhaust port (16) of the cylinder head (13) in the head side cooling oil passage (7), the cylinder head (13) and the cylinder ( 12) provided with a communication portion (72) communicating with the mating surface (70) with
The oil return passage (9) is provided apart from the communication portion (72);
On the cylinder (12) side, a cylinder side oil passage (92) for flowing oil is provided from the communication portion (72) to the oil return passage (9) ,
A cam chain chamber (12b) in which a cam chain (64) for driving the valve operating mechanism (60) is accommodated in an outer portion of the cylinder (12) adjacent to a cylinder bore (12a) of the cylinder (12). Is provided,
The oil return passage (9) is provided outside the cam chain chamber (12b),
The oil passage of the air-oil cooled internal combustion engine, wherein the cylinder side oil passage (92) is configured to communicate with the oil return passage (9) so as to go around the cam chain chamber (12b). Construction.   The oil passage structure of an air-oil cooled internal combustion engine according to claim 1, wherein the cylinder side oil passage (92) is provided as a groove (91) in the mating surface (70) on the cylinder side.   The air-oil cooled internal combustion engine according to claim 2, wherein an oil receiving portion (90) having a shape coinciding with the communication portion (72) is provided at an upstream end of the cylinder-side oil passage (92). Oil passage structure.   2. The air-oil cooled internal combustion engine according to claim 1, wherein the communication portion is formed so as to extend parallel to an axis of the cylinder and reach the mating surface. Oil passage structure. A stud bolt (19) for fastening the cylinder head (13) and the cylinder (12) is disposed so as to surround the combustion chamber (52) of the cylinder head (13), and
The oil passage structure of an air-oil-cooled internal combustion engine according to claim 4, wherein the communication portion (72) is disposed between a combustion chamber peripheral wall (52a) and the stud bolt (19).

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