JP6369993B2 - Intake structure in internal combustion engines - Google Patents

Description

According to the present invention, there is provided a cylinder head having an intake port that is formed between a cylinder block in which a piston is slidably fitted and a combustion chamber that faces the top of the piston, and the cylinder block. An intake system that is coupled and forms an intake passage that communicates with the intake port so as to form an intake path together with the intake port, corresponding to the intake port, can slide in the radial direction of the intake passage And a slide type throttle valve having a stepped portion facing the upstream side in the flow direction in the intake passage at the front end portion in the valve closing side slide direction and connected to the cylinder head, and the single intake air At least a part of the path on the downstream side of the throttle valve corresponds to the side that opens first when the throttle valve is opened from the closed position. It relates an internal combustion engine divided by the partition walls into a plurality of divided paths including a low load side divisional path arranged, in particular to an improved intake structure.

  The intake path composed of the intake port of the cylinder head and the intake passage leading to the intake port is divided into a plurality of partition walls, so that the partition wall is disposed just downstream of the throttle valve that changes the intake flow rate. An air intake structure which has been made is known from Patent Document 1.

Japanese Patent No. 4044195

  By the way, when the slide-type slot valve opens small in the low load state of the engine, the vortex is generated downstream of the throttle valve, and the intake flow is pushed against the wall surface of the low load side division path, thereby improving the flow velocity. Although it is possible to actively guide air to the low load side split path while exhibiting the above, in the one disclosed in Patent Document 1, the partition wall is disposed just downstream of the throttle valve. There is no vortex on the downstream side of the throttle valve in the valve state, and it is difficult to say that the combustion efficiency at low load is excellent.

  The present invention has been made in view of such circumstances, and can improve the combustion efficiency at low load by actively guiding air to the low load side split path when the sliding throttle valve is small opened. An object of the present invention is to provide an intake structure for an internal combustion engine.

  In order to achieve the above object, the present invention provides a cylinder block in which a piston is slidably fitted, and a combustion chamber facing the top of the piston is formed between the cylinder block and communicated with the combustion chamber. An intake system that is coupled to a cylinder head having an intake port to form an intake passage that communicates with the intake port so as to form an intake path together with the intake port, corresponding to the intake port, includes the intake passage. The cylinder head has a slide type throttle valve having a stepped portion facing the upstream side along the flow direction in the intake passage at the front end portion in the valve closing side sliding direction. And at least a part of the single intake path downstream of the throttle valve is opened from the closed position of the throttle valve. In an internal combustion engine that is divided by a partition wall into a plurality of divided paths including a low-load-side divided path that is arranged to correspond to the first opening side sometimes, the upstream end of the partition wall along the flow direction is the intake passage The first feature is that a predetermined distance equal to or greater than the diameter of the portion corresponding to the throttle valve is set at a position between the throttle valve and the throttle valve.

  According to the present invention, in addition to the configuration of the first feature, the intake system includes a carburetor having the throttle valve, and the intake passage of the carburetor gradually moves toward the downstream side along the flow direction. A second feature is that a diameter-enlarged portion formed so as to expand the diameter is formed on the downstream side along the flow direction from the throttle valve.

According to the present invention , in addition to the configuration of the first or second feature, a distance between the partition wall and a lower inner surface of the intake passage in the intake passage of the low load side divided passage is smaller than the diameter. The third feature.

  According to the present invention, in addition to any of the first to third features, the cylinder head is provided with the partition wall so as to divide at least a part of the intake port, and the intake path is bent. A fourth feature is that the distance between the upstream end of the bent portion along the flow direction and the throttle valve is set to be equal to or greater than the predetermined distance.

  According to the present invention, in addition to any one of the first to fourth features, the intake system includes an intake pipe connected to the cylinder head through the intake port, and the low load side split path Of these, a fifth feature is that a portion formed in the intake pipe is formed so as to be gradually reduced in diameter toward the cylinder head side.

  According to the present invention, in addition to any one of the first to fifth features, the intake system includes an intake pipe connected to the cylinder head through the intake port, and the throttle valve. A carburetor connected to the upstream end of the intake pipe, and the upstream end of the partition wall along the flow direction is set to a position flush with the connection surface of the intake pipe and the carburetor. The sixth feature.

  In addition to the configuration of the fourth feature of the present invention, the intake system includes an intake pipe that extends linearly and is connected to the cylinder head, and an upstream end of the bent portion along the flow direction is It is a seventh feature that it is arranged at a connection portion between the intake pipe and the cylinder head.

  According to the present invention, in addition to the configuration of the fourth feature, the intake system includes an intake pipe having a bent portion and connected to the cylinder head, and the throttle valve at an upstream end of the intake pipe. And an carburetor to be connected, and an upstream end of the bent portion along the flow direction is arranged at a connection portion between the carburetor and the intake pipe.

  Furthermore, in addition to any of the configurations of the first to eighth features, the present invention provides a ninth feature in which the low load side divided path is disposed closer to the cylinder block side in the intake path. And

According to the first feature of the present invention, the upstream end along the flow direction of the partition wall is located at a position that allows a predetermined distance equal to or larger than the diameter of the intake passage of the portion corresponding to the throttle valve to the throttle valve. Sufficient space is maintained to maintain the vortex generated downstream of the throttle valve due to the contracted flow generated by the throttle valve being throttled in the small valve open state, and the vortex causes the intake flow to flow on the wall surface of the low load side split path. By obtaining the effect of pressing, air can be actively guided to the low load side divided path while exhibiting the effect of improving the flow velocity, and the combustion efficiency at the time of low load can be increased.

Furthermore, according to the second feature of the present invention, the intake passage of the carburetor having a throttle valve gradually increases in diameter toward the downstream side downstream of the throttle valve along the flow direction. It is possible to facilitate guiding the intake air to the low load side divided passage side during the valve operation.

  According to the fourth feature of the present invention, the partition wall divides at least a part of the intake port, and the distance between the upstream end along the flow direction of the bent portion formed in the intake path and the throttle valve is equal to or greater than a predetermined distance. Therefore, the space necessary for maintaining the vortex until the intake reaches the bent part from the throttle valve is secured, and the air is positively guided to the low load side dividing path while exhibiting the effect of improving the flow velocity. Combustion efficiency at low load can be increased.

  According to the fifth feature of the present invention, since the low load side split path formed in the intake pipe gradually decreases in diameter toward the cylinder head, the flow rate of the intake air flowing through the low load side split path is set to the combustion chamber. And the generation of eddy currents in the combustion chamber can be promoted.

  According to the sixth aspect of the present invention, since the upstream end along the flow direction of the partition wall is in a position flush with the connection surface of the intake pipe and the carburetor, it is necessary to form the partition wall in the carburetor. Therefore, the cost can be reduced, and there is no deviation due to tolerance with the partition wall on the intake pipe side, and there is no possibility that the performance will be affected by the deviation.

  According to the seventh feature of the present invention, the connecting portion between the linearly extending intake pipe and the cylinder head becomes the upstream end along the flow direction of the bent portion, so that the distance from the throttle valve to the bent portion is sufficiently large. The bent portion does not affect the formation of the vortex on the downstream side of the throttle valve.

  According to the eighth feature of the present invention, since the upstream end along the flow direction of the bent portion formed in the intake pipe is located at the connection portion between the carburetor and the intake pipe, the distance from the throttle valve to the bent portion is sufficient. The bent portion does not affect the formation of the vortex on the downstream side of the throttle valve.

  Furthermore, according to the ninth feature of the present invention, since the low load side divided path is arranged closer to the cylinder block side in the intake path, combustion is performed through the low load side divided path in the low load region of the internal combustion engine. A tumble flow can be generated in the combustion chamber by the intake air flow introduced into the chamber.

It is a principal part vertical side view of the internal combustion engine of 1st Embodiment. It is a principal part enlarged view of FIG. It is a figure for demonstrating the state of the intake flow in the intake path at the time of low load driving | running | working of an internal combustion engine. It is a principal part vertical side view of the internal combustion engine of 2nd Embodiment. It is a principal part enlarged view of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, front and rear, left and right, and top and bottom refer to directions viewed from a passenger who rides a motorcycle on which an internal combustion engine is mounted.

  The first embodiment of the present invention will be described with reference to FIGS. 1 to 3. First, in FIG. 1, the internal combustion engine is mounted on, for example, a motorcycle. The crankcase 10 includes a crankcase 10 that rotatably supports a crankshaft 7 that has an axis lined in the vehicle width direction of the motorcycle, and a cylinder bore 9 that slidably engages a piston 8 that is connected to the crankshaft 7. A combustion chamber 14 is formed between the cylinder block 11 coupled to the front upper portion of the case 10 and rising upward with a slight forward inclination, and the cylinder block 11 facing the top of the piston 8. A cylinder head 12 coupled to the upper portion, and a valve operating chamber 15 is formed between the cylinder head 12 and the cylinder head 12. And a head cover 13 to be engaged.

  The cylinder head 12 is provided with an intake port 16 that opens to the side wall thereof, and an intake system 17 that communicates with the intake port 16 is connected to the rear side wall of the cylinder head 12. The cylinder head 12 is provided with an exhaust port 18 that opens to the front side wall thereof, and an exhaust system (not shown) that allows the upstream end to pass through the exhaust port 18 is connected to the front side wall of the cylinder head 12. The

  An intake valve 21 for switching communication and blocking between the intake port 16 and the combustion chamber 14 and an exhaust valve 22 for switching communication and blocking between the exhaust port 18 and the combustion chamber 14 can open and close the cylinder head 12. An intake side valve spring 23 that urges the intake valve 21 toward the valve closing side is provided between the cylinder head 12 and the intake valve 21, and the exhaust valve 22 is urged toward the valve closing side. An exhaust valve spring 24 is provided between the cylinder head 12 and the exhaust valve 22.

  The valve operating chamber 15 accommodates a valve operating mechanism 25 that drives the intake valve 21 and the exhaust valve 22 to open. The valve mechanism 25 includes a camshaft 26 having an axis parallel to the axis of the crankshaft 7 and disposed between the intake valve 21 and the exhaust valve 22, and between the camshaft 26 and the intake valve 21. And an exhaust-side rocker arm 28 interposed between the camshaft 26 and the exhaust valve 22.

  The camshaft 26 is rotatably supported by the cylinder head 12 so as to rotate with the power transmitted from the crankshaft 7, and swings in accordance with the rotation of the camshaft 26 and the intake valve. An intake-side rocker arm 27 that drives the opening 21 to the open side is swingably supported by an intake-side rocker shaft 29 supported by the cylinder head 12, and swings in accordance with the rotation of the camshaft 26 to exhaust the exhaust valve 22. An exhaust-side rocker arm 28 that drives the door to the opening side is swingably supported by an exhaust-side rocker shaft 30 supported by the cylinder head 12.

  Referring also to FIG. 2, the intake system 17 includes an intake pipe 31 connected to a rear side wall of the cylinder head 12 and extending rearward from the cylinder head 12, and a throttle valve 33. A carburetor 32 connected to the upstream end of the pipe 31 and an air cleaner (not shown) connected to the upstream end of the carburetor 32 are provided. The intake system 17 has an intake path 35 together with the intake port 16. The intake passage 34 communicating with the intake port 16 is formed individually corresponding to the intake port 16 as configured.

  The intake port 16 passing through one end portion of the combustion chamber 14 is formed to bend so as to swell toward the front upper side, and extends linearly so as to communicate with the other end of the intake port 16. The intake pipe 31 extends rearward from the rear side wall of the cylinder head 12.

  The carburetor 32 is liquid-tight under the carburetor body 36 so as to form a float chamber between the carburetor body 36 forming a part of the intake passage 34 and the carburetor body 36. A float chamber body 37 to be coupled, and the throttle valve 33 that is slidable in the radial direction of the intake passage 34 so as to change the cross-sectional area of the intake passage 34 immediately above the float chamber 38. Prepare.

  The upper part of the vaporizer body 36 is integrally provided with an upwardly extending valve cylinder part 36a, and the throttle valve 33 is slidably fitted to and supported by the valve cylinder part 36a. A throttle wire 39 linked to and coupled to a throttle operating portion such as an accelerator grip is connected to the upper portion of the throttle valve 33, and the throttle valve 33 is connected between the cap 40 attached to the upper portion of the valve cylinder portion 36a and the throttle valve 33. A return spring 41 is provided to urge the valve 33 in the valve closing direction (downward). Further, a stepped portion 33 a facing the upstream side along the flow direction 43 in the intake passage 34 is formed at the front end portion, ie, the lower end portion, of the valve closing side sliding direction 42 of the throttle valve 33. The step portion 33a is formed in the flow direction 43 of the cylindrical portion by cutting away the upstream side along the flow direction 43 of the cylindrical portion of the throttle valve 33 at the lower end. It is formed by the downstream side wall along.

  Further, the intake passage 34 of the carburetor 32 has a diameter-expanding portion 34 a formed so as to gradually increase in diameter toward the downstream side at a portion downstream of the throttle valve 33 along the flow direction 43. Formed.

  The vaporizer main body 36 integrally has a boss portion 36 b protruding into the float chamber 38, and a float 44 surrounding the boss portion 36 b is accommodated in the float chamber 38. The float 44 is supported by a float chamber body 37 via a pivot 45 so as to swing up and down, and the carburetor body 36 is provided with a fuel inflow hole 46 through which fuel can be supplied into the float chamber 38. In addition, a float valve 47 that opens and closes the fuel inflow hole 46 by vertically swinging the float 44 is disposed.

  The needle jet 48 formed in a cylindrical shape is screwed onto the boss portion 36b so that the upper end portion of the needle jet 48 faces the lower portion of the portion corresponding to the throttle valve 33. The main jet 49 is screwed to the lower end portion. An annular chamber 50 is formed between the vaporizer main body 36 and the needle jet 48, and a bleed air passage 51 for introducing air from the upstream side along the flow direction to the annular chamber 50 from the throttle valve 33. A metering jet 52 is provided at the upstream end of the bleed air passage 51 provided in the vaporizer main body 36. A needle valve 532 is provided at the lower end of the throttle valve 33 so as to protrude downward, and the needle valve 53 is inserted into the needle jet 48. Then, fuel measured by the main jet 49 is mixed with air and atomized in accordance with the opening / closing slide of the throttle valve 33 and is sucked into the intake passage 34 from the upper end of the needle jet 48.

  Further, the carburetor main body 36 is provided with a slow port 54 that opens to the intake passage 34 at a portion corresponding to the stepped portion 33a of the throttle valve 33, and a slow jet 55 that communicates with the slow port 54 includes the main jet. 49, and in a state where the throttle valve 33 is lowered to the lower limit during idling operation of the internal combustion engine, an amount of fuel necessary for idling operation is passed from the slow port 54 to the intake passage 34. Inhaled.

  By the way, at least a part of the intake path 35 on the downstream side of the throttle valve 33 is arranged corresponding to the side that is initially opened when the throttle valve 33 is opened from the closed position. In this embodiment, a part of the intake path 35 downstream from the throttle valve 33 is divided into the low load side divided path 35a and the divided path 35a. It is divided into a high load side divided path 35b.

  Moreover, a partition wall that divides the intake path 35 into the low load side divided path 35a and the high load side divided path 35b is provided in the cylinder head 12 so as to divide at least a part of the intake port 16. In this embodiment, a partition wall 58 that divides a part of the intake port 16 is provided integrally with the cylinder head 12, and the cylinder head is formed in the intake pipe 31 that is cast in a straight tube shape. A partition wall 59 connected to the 12 partition walls 58 is integrally formed.

  An upstream end of the partition walls 58 and 59 along the flow direction 43, that is, an upstream end 59 a of the partition wall 59 formed in the intake pipe 31 along the flow direction 43 is connected to the throttle valve in the intake passage 34. A predetermined distance LA1 equal to or larger than the diameter D1 of the portion corresponding to 33 is set at a position where it is located between the throttle valve 33 and the throttle valve 33.

  Moreover, the upstream end 59a of the partition wall 59 formed in the intake pipe 31 along the flow direction is set at a position flush with the connection surface 60 of the intake pipe 31 and the carburetor 32. In the intake pipe 31, the partition wall 59 is formed over the entire length thereof.

  By the way, the portion of the intake passage 35 corresponding to the intake port 16 forms a bent portion 61, and the distance between the upstream end 61a of the bent portion 61 along the flow direction and the throttle valve 33 is the predetermined value. In this embodiment, the upstream end 61a of the bent portion 61 is disposed at the intake pipe 31 and the connecting portion 64 of the cylinder head 12.

  The low load side divided path 35a is disposed closer to the cylinder block 11 side in the intake path 35, and the partition walls 58 and 59 are connected to the lower inner surface of the intake port 16 and the intake pipe 31. Are arranged so as to form the low load side divided path 35a.

  In addition, the portion formed in the intake pipe 31 of the low load side divided path 35a is formed so as to gradually reduce the diameter toward the cylinder head 12 side, and the partition wall in the intake pipe 31 is formed. The distance LD1 between 59 and the lower inner surface of the intake pipe 31 is set so as to gradually decrease toward the downstream side along the flow direction 42.

  Next, the operation of this first embodiment will be described. The intake system 17 that forms the intake passage 34 that communicates with the intake port 16 so as to form the intake passage 35 together with the intake port 16 provided in the cylinder head 12. A sliding throttle valve 33 having a stepped portion 33a facing the upstream side in the flow direction in the intake passage 34 is connected to the cylinder head 12 and has a sliding throttle valve 33 at the front end portion in the valve closing side sliding direction 42. A plurality of divided paths 35a including a low-load side divided path 35a that is arranged corresponding to a side that is first opened at the time of valve opening operation from the valve closing position of the throttle valve 33 at least partly downstream from the throttle valve 33. 35b is divided by partition walls 58, 59, and an upstream end 59a of the partition walls 58, 59 along the flow direction 43 is formed in the intake passage 34. Since a predetermined distance LA1 equal to or larger than the diameter D1 of the portion corresponding to the throttle valve 33 is set at a position between the throttle valve 33, air is supplied to the low load side divided path 35a while exhibiting the effect of improving the flow velocity. It can be actively guided to increase the combustion efficiency at low load.

  By setting the upstream end 59a of the partition walls 58, 59 along the flow direction 43 as described above according to the present invention, as shown in FIG. 3 (a), the stepped portion of the throttle valve 33 in the small valve open state. A space for maintaining the vortex 62 generated downstream of the throttle valve 33 due to the contracted flow generated by the throttle 33a is sufficiently secured on the downstream side of the throttle valve 33, and the vortex 62 sucks air into the wall surface of the low load side divided path 35a. By obtaining the effect of pressing the flow, air can be actively guided to the low load side divided path 35a while exhibiting the effect of improving the flow velocity, and the combustion efficiency at the time of low load can be increased.

  On the other hand, in the conventional structure in which the partition wall 63 is disposed up to a position close to the throttle valve 33, the flow state of the intake air flow downstream of the throttle valve 33 when the throttle valve 33 is in the small valve open state is As shown in FIG. 3B, a vortex affecting the low load side intake passage 35a cannot be formed on the downstream side of the throttle valve 33. In comparison, the function of guiding air to the low load side divided path 35a is insufficient.

  Further, a partition wall 58 is provided in the cylinder head 12 so as to divide at least a part of the intake port 16, the intake passage 35 is formed to have a bent portion 61, and the flow direction of the bent portion 61 is 43, the distance between the upstream end 61a and the throttle valve 33 is set to be equal to or greater than the predetermined distance LA1, so that a space necessary for maintaining the vortex is secured until the intake air reaches the bent portion 61 from the throttle valve 33. In addition, it is possible to increase the combustion efficiency at the time of low load of the internal combustion engine by actively guiding the air to the low load side divided path 35a while exhibiting the effect of improving the flow velocity.

  Further, the enlarged diameter portion 34 a formed so that the intake passage 34 of the carburetor 32 having the throttle valve 33 gradually increases in diameter toward the downstream side along the flow direction 43 has a larger flow direction than the throttle valve 33. Therefore, when the throttle valve 33 is opened slightly, it is possible to facilitate guiding the intake air to the low load side dividing passage 35a side.

  Further, the portion formed in the intake pipe 31 in the low load side divided path 35a is formed so as to gradually reduce the diameter toward the cylinder head 12, so that the suction flowing through the low load side divided path 35a As the air flow velocity approaches the combustion chamber 14, the generation of vortex flow in the combustion chamber 14 can be promoted.

  Further, since the upstream end 59a of the partition walls 58, 59 along the flow direction 43 is set to be flush with the connection surface 60 of the intake pipe 31 and the vaporizer 32, the partition wall 58, 59 is partitioned within the vaporizer 32. There is no need to form a wall, the cost can be reduced, and there is no deviation due to tolerance with the partition wall 59 on the intake pipe 31 side, and there is no possibility that the performance will be affected by the deviation. .

  Further, in the intake system 17, the intake pipe 31 extends linearly and is connected to the cylinder head 12, and the upstream end 61 a along the flow direction 43 of the bent portion 61 included in the intake passage 35 is connected to the intake pipe 31 and the cylinder. Since it is disposed at the connection portion 64 of the head 12, a sufficient distance from the throttle valve 33 to the bent portion 61 is ensured, and the bent portion 61 does not affect the formation of a vortex on the downstream side of the throttle valve 33.

  Further, since the low load side divided path 35a is arranged closer to the cylinder block 11 side in the intake path 35, the low load side divided path 35a is circulated in the low load region of the internal combustion engine to the combustion chamber 14. A tumble flow can be generated in the combustion chamber 14 by the introduced intake air flow.

  A second embodiment of the present invention will be described with reference to FIGS. 4 and 5. First, in FIG. 4, an engine body 66 of the internal combustion engine includes a crankcase 70 that rotatably supports a crankshaft 67, A cylinder block 69 having a cylinder bore 69 for slidably fitting a piston 68 connected to the crankshaft 67 and coupled to the front upper portion of the crankcase 70 and extending forward until it is substantially horizontal. A combustion chamber 74 facing the top of the piston 68 is formed between the cylinder block 71 and a cylinder head 72 coupled to the front of the cylinder block 71, and a valve operating between the cylinder head 72 And a head cover 73 that forms a chamber 75 and is coupled to an upper portion of the cylinder head 72.

  The cylinder head 72 is provided with an intake port 76 that opens to the upper side wall thereof, and an intake system 77 that communicates with the intake port 76 is connected to the upper side wall of the cylinder head 72. The cylinder head 72 is provided with an exhaust port 78 that opens to the lower side wall thereof, and an exhaust system 80 including an exhaust pipe 79 passing through the upstream end of the exhaust port 78 is connected to the lower side wall of the cylinder head 72. Is done.

  An intake valve 81 for switching communication and blocking between the intake port 76 and the combustion chamber 74 and an exhaust valve 82 for switching communication and blocking between the exhaust port 78 and the combustion chamber 74 can open and close the cylinder head 72. An intake side valve spring 83 that biases the intake valve 81 toward the valve closing side is provided between the cylinder head 72 and the intake valve 81, and the exhaust valve 82 is biased toward the valve closing side. An exhaust valve spring 84 is provided between the cylinder head 72 and the exhaust valve 82, and the valve operating chamber 15 accommodates a valve operating mechanism 85 that opens and drives the intake valve 81 and the exhaust valve 82. The

  Referring also to FIG. 5, the intake system 77 includes an intake pipe 91 connected to an upper wall of the cylinder head 72 and extending rearward from the cylinder head 72, and a throttle valve 93. A carburetor 92 connected to the upstream end of the pipe 91, and an air cleaner (not shown) connected to the upstream end of the carburetor 92, the intake system 77, along with the intake port 76, has an intake path 95. An intake passage 94 communicating with the intake port 76 is formed individually corresponding to the intake port 76 as configured.

  The intake pipe 91 communicating with the intake port 76 is formed by bending backward from the upper side wall of the cylinder head 72. The carburetor 92 includes a carburetor main body 96, a float chamber body 97, and the throttle valve 93, as in the first embodiment.

  The throttle valve 93 is slidably supported on the valve cylinder portion 96a of the upper portion of the carburetor body 96, and a throttle wire 99 is connected to the upper portion of the throttle valve 93, and a cap attached to the upper portion of the valve cylinder portion 96a. A return spring 101 is provided between 100 and the throttle valve 93. Further, a stepped portion 93 a facing the upstream side along the flow direction 103 in the intake passage 94 is formed at the front end portion, ie, the lower end portion, of the valve closing side sliding direction 102 of the throttle valve 93.

  Further, the intake passage 94 of the carburetor 92 has a diameter-expanded portion 94 a formed so as to gradually increase in diameter toward the downstream side in a portion downstream of the throttle valve 93 along the flow direction 43. Formed.

  The float 104 accommodated in the float chamber 38 between the vaporizer body 96 and the float chamber body 97 is supported by the float chamber body 97 via the pivot 105 so as to be swingable up and down. A float valve 107 that opens and closes a fuel inflow hole 106 is provided in the carburetor body 96.

  A needle jet 108 for inserting a needle valve 113 provided below the throttle valve 93 is screwed into the carburetor main body 96, and a main jet 109 is screwed into the lower end portion of the needle jet 108. A bleed air passage 111 for introducing air from the upstream side along the flow direction 103 from the throttle valve 93 is provided in the annular chamber 110 between the carburetor body 96 and the needle jet 108 in the carburetor body 96. A metering jet 112 is provided at the upstream end of the air passage 111.

  The carburetor body 96 is provided with a slow port 114 that opens to the intake passage 94 at a portion corresponding to the stepped portion of the throttle valve 93, and a slow jet 115 that communicates with the slow port 114 is connected to the main jet 109. Screwed in parallel.

  Further, a butterfly choke valve 125 disposed upstream of the throttle valve 93 along the flow direction 43 of the intake passage 94 is rotatably supported by the carburetor body 96.

  By the way, a part of the intake path 95 downstream of the throttle valve 93 is divided into the low load side divided path 95a and the high load side divided path 95b. A partition wall that is divided into a low load side divided path 95a and a high load side divided path 95b is provided in the cylinder head 72 so as to divide at least a part of the intake port 76. In this embodiment, A partition wall 118 that divides a part of the intake port 76 is provided integrally with the cylinder head 72, and a partition wall 119 that is continuous with the partition wall 118 of the cylinder head 72 is formed integrally with the intake pipe 91. The

  An upstream end of the partition walls 118 and 119 along the flow direction 43, that is, an upstream end 119 a of the partition wall 119 formed in the intake pipe 91 along the flow direction 43 is connected to the throttle valve in the intake passage 94. A predetermined distance LA2 equal to or larger than the diameter D2 of the portion corresponding to 93 is set at a position where it can be located between the throttle valve 93 and the throttle valve 93.

  Moreover, the upstream end 119a of the partition wall 119 formed in the intake pipe 91 along the flow direction 43 is set at a position flush with the connection surface 120 of the intake pipe 91 and the carburetor 92. In addition, the partition wall 119 is formed in the intake pipe 91 over its entire length.

  Incidentally, a portion of the intake path 95 from the intake pipe 91 to the intake port 76 forms a bent portion 121, and the bent portion 121 is connected between the upstream end 121 a along the flow direction 43 and the throttle valve 93. Is set to be equal to or greater than the predetermined distance LA2. Moreover, the upstream end 121a of the bent portion 121 along the flow direction 43, that is, the upstream end of the intake pipe 91 is set to the connection portion 124 of the intake pipe 91 and the carburetor 92, and the flow direction of the bent portion 121 The distance between the upstream end 121a along the line 43 and the throttle valve 93 is the same as the predetermined distance LA2.

  Further, the low load side divided path 95a is disposed closer to the cylinder block 11 side in the intake path 95, and the partition walls 118 and 119 are connected to the lower inner surface of the intake port 76 and the intake pipe 91, respectively. Are arranged so as to form the low load side divided path 95a.

  Further, the portion formed in the intake pipe 91 in the low load side divided path 95a is formed so as to gradually reduce the diameter toward the cylinder head 72 side, and the partition wall in the intake pipe 91 is formed. The distance LD2 between 119 and the lower inner surface of the intake pipe 91 is set so as to gradually decrease toward the downstream side along the flow direction 103.

  The same effect as that of the first embodiment described above can also be achieved by the second embodiment.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

8, 68 ... piston 11, 71 ... cylinder block 12, 72 ... cylinder head 14, 74 ... combustion chamber 16, 76 ... intake port 17, 77 ... intake system 31, 91 ... Intake pipes 32, 92 ... Vaporizers 33,93 ... Throttle valves 33a, 93a ... Step portions 34,94 ... Intake passages 34a, 94a ... Expanded diameter portions 35,95 ..Intake paths 35a, 95a ... Low load side divided paths 35b, 95b ... Division paths 42,102 ... Valve closed side slide directions 43, 104 ... Flow directions 60, 120 ... Connection surfaces 61, 121 ... bent portions 61a, 121a ... upstream ends 64, 124 ... connecting portions 58, 59, 118, 119 ... partition walls 59a, 119a ... partitions along the flow direction of the bent portions. Upstream end D1, along the wall flow direction 2 ... The diameter of the portion corresponding to the throttle valve of the intake passage LA1, LA2 ... predetermined distance

Claims (9)

Combustion chambers (14, 74) that allow the tops of the pistons (8, 68) to face the cylinder blocks (11, 71) into which the pistons (8, 68) are slidably fitted, and the cylinder blocks (11, 71). ) And a cylinder head (12, 72) having an intake port (16, 76) that can communicate with the combustion chamber (14, 74), and an intake path together with the intake port (16, 76). An intake system (17) that individually forms an intake passage (34, 94) that communicates with the intake port (16, 76) so as to constitute (35, 95) corresponding to the intake port (16, 76). , 77) enables the intake passage (34, 94) to slide in the radial direction and faces the upstream side along the flow direction (43, 103) in the intake passage (34, 94) ( 33a 93a) having a sliding throttle valve (33, 93) having a front end portion in the valve closing side sliding direction (42, 102) and connected to the cylinder head (12, 72), and a single intake path (35, 95), at least part of the downstream side of the throttle valve (33, 93) corresponds to the side that opens first when the throttle valve (33, 93) is opened from the closed position. In an internal combustion engine that is divided by a partition wall (58, 59; 118, 119) into a plurality of divided paths (35a, 95a; 35b, 95b) including low load side divided paths (35a, 95a) arranged
An upstream end (59a, 119a) along the flow direction (43, 103) of the partition wall (58, 59; 118, 119) is the throttle valve (33, 93) in the intake passage (34, 94). An intake structure in an internal combustion engine, wherein a predetermined distance (LA1, LA2) equal to or larger than the diameter (D1, D2) of the portion corresponding to is set at a position between the throttle valve (33, 93).   The intake system (17, 77) includes a carburetor (32, 92) having the throttle valve (33, 93), and the intake passage (34, 94) of the carburetor (32, 92) An enlarged diameter portion (34a, 94a) formed so as to gradually increase in diameter toward the downstream side along the flow direction (43, 103) is formed in the flow direction (43, 103) rather than the throttle valve (33, 93). 2. The intake structure for an internal combustion engine according to claim 1, wherein the intake structure is formed on the downstream side along the line. Before SL low-load dividing path (35a, 95a) the distance between the lower inner surface of the in the intake passage (34,94) in the partition wall (59,119) and the intake passage (34,94) of (LD1, LD2 ) Is smaller than the diameter (D1, D2), the intake structure in the internal combustion engine according to claim 1 or 2 .   The partition wall (58, 118) is provided in the cylinder head (12, 72) so as to divide at least a part of the intake port (16, 76), and the intake path (35, 95) is a bent portion. (61, 121), and the distance between the upstream end (61a, 121a) and the throttle valve (33, 93) along the flow direction (43, 103) of the bent portion (61, 121). Is set to be equal to or greater than the predetermined distance (LA1, LA2).   The intake system (17, 77) includes an intake pipe (31, 91) connected to the cylinder head (12, 72) through the intake port (16, 76), and the low load side divided path ( 35a, 95a), a portion formed in the intake pipe (31, 91) is formed so as to be gradually reduced in diameter toward the cylinder head (12, 72). The intake structure in the internal combustion engine according to any one of claims 1 to 4.   The intake system (17, 77) is connected to the cylinder head (12, 72) through the intake port (16, 76), and the throttle valve (33, 93). And a carburetor (32, 82) connected to the upstream end of the intake pipe (31, 91), and the flow direction (43, 103) of the partition wall (58, 59; 118, 119). ) Along the connection surface (60, 120) of the intake pipe (31, 91) and the carburetor (32, 82). An intake structure for an internal combustion engine according to any one of claims 1 to 5.   The intake system (17) includes an intake pipe (31) extending linearly and connected to the cylinder head (12), and an upstream end of the bent portion (61) along the flow direction (43, 103) The intake structure for an internal combustion engine according to claim 4, wherein (61a) is disposed in a connection portion (64) of the intake pipe (31) and the cylinder head (12).   The intake system (77) has a bent portion (121) and is connected to the cylinder head (72). The intake pipe (91) has the throttle valve (93) and the intake pipe (91). And an upstream end (121a) along the flow direction (103) of the bent portion (121) is connected to the carburetor (92) and the intake pipe (91). The intake structure for an internal combustion engine according to claim 4, wherein the intake structure is disposed at a connection portion (124).   The low load side divided path (35a, 95a) is arranged close to the cylinder block (11, 71) side of the intake path (35, 95). An intake structure for an internal combustion engine according to claim 1.

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