JP2006250095A - Fuel retention preventing structure in two-cycle internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a stable drive state in a two-cycle internal combustion engine in which mixture is taken into a crank chamber in a crankcase through an intake passage formed in the crankcase for pre-compression, so that the mixture is taken into a combustion chamber for combustion. <P>SOLUTION: The intake passage 39 is formed in the crankcase 20 for communication of the inside of the crank chamber 24 with the outside 3. A reed valve 40 is provided to be engaged in with the intake passage 39 to be installed on the crankcase 20. A fuel passage 51 is formed in the crankcase 20 in such a way that fuel 13 is naturally fed downward from an inner bottom part of the intake passage 39 toward the crank chamber 24. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, the air-fuel mixture is sucked into the crank chamber in the crankcase through the intake passage formed in the crankcase and pre-compressed, and then the air-fuel mixture is sucked into the combustion chamber and burned. The present invention relates to a fuel pool prevention structure in a cycle internal combustion engine.

  Conventionally, the above two-cycle internal combustion engine is disclosed in Patent Document 1 below. According to this publication, the internal combustion engine is slidably fitted into a crankcase, a crankshaft supported by the crankcase, a cylinder projecting from the crankcase, and the crankshaft. A piston and a connecting rod for interlockingly connecting the crankshaft and the piston to each other are provided, and a space surrounded by the protruding end of the cylinder and the piston is a combustion chamber.

  The internal combustion engine is generally provided with an intake passage that allows the crankcase to communicate with the inside and outside of the crankcase, and a reed valve that is fitted into the intake passage and attached to the crankcase is provided.

  When the internal combustion engine is driven, first, an air / fuel mixture from the outside of the internal combustion engine is sucked into the crank chamber through the reed valve and the intake passage, and is precompressed here. Next, this air-fuel mixture passes through the scavenging passage and is sucked into the combustion chamber where it is burned. And the thermal energy by this combustion is converted into driving force, and this driving force is output via the said crankshaft.

JP-A-2-109727

  By the way, it is assumed that the internal combustion engine is in an idling state and the flow rate of the air-fuel mixture passing through the intake passage is small. Then, a part of the fuel in the air-fuel mixture may be collected at the inner bottom portion of the intake passage.

  If the fuel accumulation described above occurs, the fuel lump that has accumulated in this way tends to be intermittently sucked into the crank chamber. Then, the concentration of the air-fuel mixture sucked into the combustion chamber becomes non-uniform. As a result, there arises a disadvantage that the driving state at the time of idling becomes unstable.

  The present invention has been made paying attention to the above situation, and an object of the present invention is to preliminarily presume the air-fuel mixture through the intake passage formed in the crankcase and suck the air-fuel mixture into this crankcase. In the two-cycle internal combustion engine in which the air-fuel mixture is sucked into the combustion chamber after being compressed and burned, a stable driving state is ensured in the internal combustion engine.

  Another object of the present invention is to facilitate the molding of the internal combustion engine described above.

In the first aspect of the invention, an intake passage 39 is formed in the crankcase 20 to allow communication between the inside and outside of the crank chamber 24, and the reed valve 40 is fitted in the intake passage 39 and attached to the crankcase 20. In internal combustion engines,
A fuel passage 51 is formed in the crankcase 20 for allowing the fuel 13 to flow naturally from the inner bottom of the intake passage 39 toward the crank chamber 24.

  In addition to the invention of claim 1, the invention of claim 2 divides the crankcase 20 by a flat surface passing through the intake passage 39, and the fuel passage 51 is defined by a groove 51a formed in the section 20a. Formed.

  In this section, the reference numerals appended to the above terms are not to be construed as limiting the technical scope of the present invention to the section “Example” described later or the contents of the drawings.

  The effects of the present invention are as follows.

According to a first aspect of the present invention, there is provided a two-cycle internal combustion engine including a reed valve that is formed in an intake passage that allows the crankcase to communicate with the inside and outside of the crankcase, and that is fitted into the intake passage and attached to the crankcase.
A fuel passage is formed in the crankcase for allowing the fuel to flow naturally from the inner bottom of the intake passage toward the crank chamber.

  Here, it is assumed that the internal combustion engine is in an idling state and the flow rate of the air-fuel mixture passing through the intake passage is small. Then, a part of the fuel in the air-fuel mixture may be collected at the inner bottom portion of the intake passage.

  However, the fuel that is going to accumulate in the inner bottom of the intake passage passes through the fuel passage and flows into the crank chamber one after another. For this reason, it is prevented that the lump of fuel accumulated in the inner bottom portion of the intake passage is intermittently sucked into the crank chamber. Therefore, the concentration of the air-fuel mixture sucked from the crank chamber into the combustion chamber is prevented from becoming uneven. As a result, a stable driving state is ensured in the internal combustion engine.

  According to a second aspect of the present invention, the crankcase is divided by a flat surface passing through the intake passage, and the fuel passage is formed by a groove formed in the cross section.

  Therefore, when a fuel passage is to be formed in the crankcase, first, a groove is formed in the cross section of the crankcase in a state where the crankcase is divided by the flat surface. Next, it is only necessary to join the two cross-sections together so that the crankcase is integrated, thereby forming the fuel passage.

  Here, in a crankcase having a generally complicated structure, the operation of drilling a fuel passage that penetrates from the inner bottom of the intake passage toward the crank chamber is complicated. Compared with this operation, the above-described operation for forming the groove into the sectional surface is relatively easy.

  Moreover, the formation of the groove in the divided cross section is not limited to a straight line, but can be easily curved so as to avoid the bolt holes formed in the crankcase.

  Therefore, the desired shape of the fuel passage can be easily formed, that is, the above-described internal combustion engine can be easily formed.

  The invention relates to a fuel pool prevention structure in a two-cycle internal combustion engine according to the present invention. The air-fuel mixture is sucked into a crank chamber in the crankcase through a suction passage formed in a rank case and precompressed. In a two-cycle internal combustion engine that is inhaled and combusted, the best mode for carrying out the present invention in order to achieve the object of ensuring a stable driving state in the internal combustion engine is as follows: It is as follows.

  That is, the two-cycle internal combustion engine includes an intake passage that allows the crankcase to communicate with the inside and outside of the crankcase, and includes a reed valve that is fitted into the intake passage and attached to the crankcase. A fuel passage is formed in the crankcase for allowing fuel to flow naturally from the inner bottom of the intake passage toward the crank chamber.

  In order to explain the present invention in more detail, an embodiment thereof will be described with reference to the accompanying drawings.

  2 and 3, reference numeral 1 is a vehicle exemplified as a racing cart, and an arrow Fr indicates the front in the traveling direction of the vehicle 1. Moreover, the right and left mentioned below shall mean the width direction of the vehicle 1 toward the said front.

  A vehicle body 2 of the vehicle 1 is suspended on a body frame 3 constituting the skeleton, a pair of left and right front wheels 4 that are slidably suspended on the front portion of the body frame 3, and a rear portion of the body frame 3. A pair of left and right rear wheels 5, a seat 6 supported in the middle of the vehicle body 2 in the longitudinal direction of the vehicle 1, and a front portion of the vehicle body frame 3, and interlocked with the front wheels 4. A handle 7 and a pair of left and right footrests 8 disposed on the outer side of the seat 6 and supported by the vehicle body frame 3 are provided.

  The vehicle 1 is disposed between the seat 6 and the right footrest 8 and is driven by the internal combustion engine 11 that drives the rear wheels 5, and the internal combustion engine 11 includes air 12 and fuel 13 on the atmosphere side. An intake device 14 that can supply an air-fuel mixture and an exhaust device 16 that guides exhaust 15 discharged from the internal combustion engine 11 to the outside of the internal combustion engine 11 are provided. The internal combustion engine 11 is a reed valve type two-cycle single cylinder engine.

  In all the drawings, the stationary member 19 of the internal combustion engine 11 includes a crankcase 20 supported by the vehicle body frame 3, a cylinder 21 protruding upward from the crankcase 20, and a left side surface of the crankcase 20. A case cover 22 is provided so as to be entirely openable and closable. The inside of the crankcase 20 is a crank chamber 24, and a sealed internal space 25 is formed between the crankcase 20 and the case cover 22. A case cover 22 is detachably fixed to the crankcase 20 by a fastener.

  A crankshaft 28 having an axis 27 extending in the width direction of the vehicle 1 is supported by the crankcase 20 so as to be rotatable around the axis 27. A piston 29 is slidably fitted into the cylinder 21, and the crankshaft 28 and the piston 29 are connected to each other by a connecting rod 30. The crankshaft 28 is included in the crank chamber 24 and a pair of left and right crank main shafts 33 and 34 supported by the bearing 32 on the crankcase 20, and is formed integrally with the crank main shafts 33 and 34. A pair of left and right crank arms 35, and a crank pin 36 that is installed on both crank arms 35 and connected to the large end of the connecting rod 30 are provided.

  A space surrounded by the protruding end of the cylinder 21 and the piston 29 is a combustion chamber 38. An intake passage 39 that communicates the inside and outside of the crank chamber 24 is formed in the front portion of the crankcase 20. The intake passage 39 extends in the longitudinal direction of the vehicle 1 and substantially in the horizontal direction. A reed valve 40 that is fitted into the intake passage 39 and attached to the front portion of the crankcase 20 is provided. A scavenging passage 41 for communicating the crank chamber 24 with the combustion chamber 38 is formed in the crankcase 20. Further, an exhaust passage 42 that allows the combustion chamber 38 to communicate with the outside of the cylinder 21 is formed in the cylinder 21.

  The intake device 14 includes a carburetor 44 connected to the front portion of the crankcase 20 and communicating with the intake passage 39, and an intake silencer 45 connected to the carburetor 44. On the other hand, the exhaust device 16 includes an exhaust pipe 46 connected to the rear portion of the cylinder 21 and communicating with the exhaust passage 42, an exhaust pipe muffler 47 and an exhaust silencer 48 sequentially connected to the exhaust pipe 46. Yes. A spark plug 50 is attached to the protruding end of the cylinder 21.

  The inner bottom portion of the intake passage 39 is a recess that opens upward. A fuel passage 51 is formed in the crankcase 20 to allow the fuel 13 to flow naturally from the inner bottom of the intake passage 39 toward the crank chamber 24. The fuel passage 51 extends linearly so as to incline downward from the inner bottom of the intake passage 39 toward the crank chamber 24.

  In the above case, the crankcase 20 is divided into left and right by a flat surface that passes through the intake passage 39 and extends perpendicular to the crankshaft 28. That is, the crankcase 20 has a split structure composed of left and right members. These two members are integrally coupled to each other by joining the divided sections 20a to each other by fastening. The fuel passage 51 is formed by a groove 51a formed in at least one of the divided sections 20a. Although not shown, the groove 51a has a U-shaped cross section.

  A driven shaft 53 is provided that extends in parallel with the crankshaft 28 and is disposed radially outward of the crankshaft 28. The driven shaft 53 is supported across the crankcase 20 and the case cover 22 of the stationary member 19 by a bearing 55 so that the driven shaft 53 can rotate around the axis 54.

  A flywheel magneto 57 accommodated in the internal space 25 and disposed on the axis 54 of the driven shaft 53 is provided. The flywheel magneto 57 includes a stator 59 supported by the case cover 22 and a rotor 61 fixed to the driven shaft 53 by a key 60 and rotating together with the driven shaft 53.

  An interlocking device 63 for interlockingly connecting the rotor 61 of the flywheel magneto 57 via the driven shaft 53 to one crank main shaft 33 which is one end of the crankshaft 28 is provided. This interlocking device 63 is accommodated in the internal space 25. The interlocking device 63 includes a drive gear 65 fixed to the crank main shaft 33 by a key 64 and a driven gear 66 that is integrally formed with the driven shaft 53 and meshes with the drive gear 65. The drive gear 65 and the driven gear 66 have the same module and the same number of teeth. As viewed from the line of sight along the axial direction of the crankshaft 28 (FIG. 4), at least a portion of each of the crankshaft 28 and the flywheel magneto 57 overlap each other.

  On the outer peripheral surface of the rotor 61, a protrusion 67 is formed in a part of the circumferential direction. Further, a pulsar coil 68 is provided opposite to the protrusion 67, and the pulsar coil 68 is fixed to the case cover 22.

  A well-known exhaust control valve 69 is provided that can change the height of the upper edge of the opening of the exhaust passage 42 on the combustion chamber 38 side. Further, an auxiliary machine 70 is provided which is accommodated in the internal space 25 and supported so as to straddle the crankcase 20 and the case cover 22 of the stationary side member 19. The auxiliary machine 70 is a governor device that controls the exhaust control valve 69 so that the timing when the exhaust 15 is discharged from the combustion chamber 38 through the exhaust passage 42 is variable. The auxiliary machine 70 is disposed outward in the radial direction of the crankshaft 28. The flywheel magneto 57 and the auxiliary machine 70 are offset from each other in the circumferential direction of the crankshaft 28.

  The auxiliary machine 70 includes a governor shaft 71 that extends in parallel with the crankshaft 28 and is disposed radially outward of the crankshaft 28. The governor shaft 71 is supported across the crankcase 20 and the case cover 22 of the stationary member 19 by a bearing 73 so that the governor shaft 71 can rotate about its axis 72.

  The auxiliary machine 70 is housed in the internal space 25, disposed on the axis 72 of the governor shaft 71, and fixed to the governor shaft 71. A spherical weight 75 to be inserted, a movable body 76 supported by the governor shaft 71 so as to be movable in the axial direction of the governor shaft 71, and the weight 75 through the movable body 76. And a spring 77 to be brought into pressure contact with the inner surface. The exhaust control valve 69 is linked to the movable body 76 by a linked body such as a rotating arm.

  Another interlocking device 79 for interlockingly connecting the governor shaft 71 to one crank main shaft 33 which is one end portion of the crankshaft 28 is provided. This interlocking device 79 is accommodated in the internal space 25. The interlock device 79 includes the drive gear 65 and a driven gear 80 that is fixed to the governor shaft 71 and meshes with the drive gear 65.

  A water pump 83 which is an example of another auxiliary machine 70 disposed on a shaft center 82 extending in parallel with the crankshaft 28 is provided outside the crankshaft 28 in the radial direction. The water pump 83 includes a pump shaft 84 disposed on the shaft center 82 and a pair of left and right supporting the pump shaft 84 on the crankcase 20 so that the pump shaft 84 can rotate around the shaft center 82. A bearing 85, a positioning tool 86 for positioning the bearing 85 at a predetermined position in the axial direction of the pump shaft 84, and a rotor fixed to the pump shaft 84 and fitted into a pump chamber 87 formed in the crankcase 20. 88.

  Still another interlocking device 91 for interlockingly connecting the water pump 83 to the rotor 61 of the flywheel magneto 57 is provided. The interlocking device 91 includes the driven gear 66 and a driven gear 92 that is fixed to the pump shaft 84 and meshes with the driven gear 66.

  The interlocking devices 63, 79, 91 are arranged at substantially the same position in the axial direction of the crankshaft 28. A crank arm 35 of the crankshaft 28 and a rotor 88 of the water pump 83 are disposed on one side of the interlocking devices 63, 79, 91. In this case, in the axial direction of the crankshaft 28, the crank arm 35 of the crankshaft 28 and the rotor 88 of the water pump 83 are disposed at substantially the same location. Further, the flywheel magneto 57 and the rotating body 74 of the auxiliary machine 70 are disposed on the other side of the interlocking devices 63, 79, 91.

  The other crank main shaft 34, which is the other end portion of the crankshaft 28, serves as an output portion of the internal combustion engine 11. On the axis 27 of the crankshaft 28, a drive side member 95 of the centrifugal clutch 94 is fixed to the other crank main shaft 34. A driven member 96 of the centrifugal clutch 94 is supported on the crank main shaft 34 of the crankshaft 28 on the axis 27 of the crankshaft 28. The driven member 96 is rotatable about the shaft 27 and relative to the crankshaft 28 and the drive member 95. A chain winding type interlocking device 97 for interlockingly connecting the rear wheel 5 to the driven member 96 is provided.

  An oil sump portion 100 for accumulating the lubricating oil 99 is formed at the inner bottom portion of the internal space 25. At least the lower part of the driven gear 92 of the further interlocking device 91 is disposed in the oil reservoir 100 and is bathed by the lubricating oil 99.

  In addition, reference numeral 102 denotes a starter motor, and the crankshaft 28 can be interlocked with the starter motor 102.

  When the internal combustion engine 11 is driven, the crankshaft 28 is first cranked by driving the starter motor 102. Then, the air 12 outside the internal combustion engine 11 is sucked into the crank chamber 24 through the intake device 14, the reed valve 40, and the intake passage 39. At this time, the fuel 13 is mixed into the air 12 by the carburetor 44 of the intake device 14 to generate an air-fuel mixture, and the air-fuel mixture is pre-compressed in the crank chamber 24.

  Next, the air-fuel mixture passes through the scavenging passage 41 and is sucked into the combustion chamber 38 where it is ignited by the spark plug 50 and burned. The timing of ignition by the spark plug 50 is determined based on an output signal output from the pulsar coil 68 when the projection 67 faces the pulsar coil 68. Combustion gas generated by the combustion is discharged to the outside of the internal combustion engine 11 as exhaust 15 through the exhaust passage 42 and the exhaust device 16.

  Based on the heat energy by the combustion, the crankshaft 28 is rotated A in one direction, and power is output. The driven shaft 53 and the flywheel magneto 57 are interlocked with the crankshaft 28 via the interlocking device 63 and rotated around the shaft center 54. Thereby, the flywheel magneto 57 generates electric power, and the electric power is used as a power source for discharging and controlling the spark plug 50. In this case, the crankshaft 28 and the rotor 61 of the flywheel magneto 57 are reversely rotated A and B.

  Further, the governor shaft 71, the rotating body 74, and the weight 75 of the auxiliary machine 70 are interlocked with the crankshaft 28 via the interlocking device 79 and rotated around the shaft center 72. If the crankshaft 28 is at a high speed, the centrifugal force of the weight 75 interlocking with the crankshaft 28 is increased, and the movable body 76 moves in one axial direction of the governor shaft 71 against the urging force of the spring 77. Moved. If the crankshaft 28 is at a low speed, the centrifugal force of the weight 75 interlocked therewith becomes small, and the movable body 76 is moved in the direction opposite to the one direction by the biasing force of the spring 77. The exhaust control valve 69 is controlled in conjunction with each movement of the movable body 76 described above, and the timing for the exhaust 15 is automatically adjusted.

  The water pump 83 is interlocked with the crankshaft 28 via the interlocking devices 63 and 91, and the pump shaft 84 and the rotor 88 of the water pump 83 are rotated D around the axis 82. As a result, cooling water is discharged from the pump chamber 87, and this cooling water is circulated and cooled in each part of the internal combustion engine 11, and then cooled by air and returned to the suction part of the water pump 83.

  The driven gear 92 of the interlocking device 91 scoops up the lubricating oil 99 of the oil reservoir 100. Then, the lubricating oil 99 is transferred to the driven gear 66, the driving gear 65, and the driven gear 80 that sequentially mesh with the driven gear 92, and lubricates the meshing portions of the gears 65, 66, 80, and 92. To do.

  When the crankshaft 28 reaches a predetermined number of times, the centrifugal clutch 94 is connected. Then, the driving force from the crankshaft 28 is transmitted to the rear wheel 5 through the centrifugal clutch 94 and the interlocking device 97, so that the vehicle 1 can travel.

  According to the above configuration, the fuel case 51 that allows the fuel 13 to flow naturally from the inner bottom of the intake passage 39 toward the crank chamber 24 is formed in the crankcase 20.

  Here, it is assumed that the internal combustion engine 11 is in an idling state and the flow rate of the air-fuel mixture passing through the intake passage 39 is small. Then, a part of the fuel 13 in the air-fuel mixture may be collected at the inner bottom portion of the intake passage 39.

  However, the fuel 13 that tends to accumulate in the inner bottom portion of the intake passage 39 passes through the fuel passage 51 and flows into the crank chamber 24 one after another. For this reason, it is prevented that the lump of the fuel 13 accumulated in the inner bottom portion of the intake passage 39 is intermittently sucked into the crank chamber 24. Therefore, the concentration of the air-fuel mixture sucked from the crank chamber 24 into the combustion chamber 38 is prevented from becoming uneven. As a result, a stable driving state is secured in the internal combustion engine 11.

  Further, as described above, the crankcase 20 is divided by a flat surface passing through the intake passage 39, and the fuel passage 51 is formed by the groove 51a formed in the section 20a.

  Therefore, when the fuel passage 51 is to be formed in the crankcase 20, first, the groove 51a is formed in the cross section 20a in a state where the crankcase 20 is divided by the flat surface. Next, the crankcase 20 may be integrated by joining the two cross sections 20a to each other, whereby the fuel passage 51 is formed.

  Here, in the crankcase 20 having a generally complicated structure, the operation of drilling the fuel passage 51 penetrating from the inner bottom portion of the intake passage 39 toward the crank chamber 24 is complicated. And compared with this operation | work, the shaping | molding operation | work of the groove | channel 51a to the above-mentioned dividing surface 20a is comparatively easy.

  In addition, the formation of the groove 51a in the dividing surface 20a is not limited to a straight line, but can be easily curved so as to avoid a bolt hole formed in the crankcase 20.

  Therefore, the desired shape of the fuel passage 51 can be easily formed, that is, the internal combustion engine 11 can be easily formed.

  In addition, although the above is based on the example of illustration, the said internal combustion engine 11 may be mounted in vehicles other than a vehicle, and may be used for an industrial machine etc.

FIG. 5 is a side sectional view taken along line 1-1 in FIG. 4. 1 is an overall plan view of a vehicle. FIG. 3 is a view taken along line 3-3 in FIG. 2. FIG. 4 is a partially enlarged cutaway view of FIG. 3. FIG. 5 is a cross-sectional view of the other side portion taken along line 5-5 in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Internal combustion engine 12 Air 13 Fuel 14 Intake device 20 Crankcase 20a Cross section 21 Cylinder 24 Crank chamber 28 Crankshaft 29 Piston 30 Connecting rod 38 Combustion chamber 39 Intake passage 40 Reed valve 41 Scavenging passage 51 Fuel passage 51a Groove

Claims (2)

In a two-cycle internal combustion engine having a reed valve that is formed in an intake passage that communicates the inside and outside of the crankcase with the crankcase, and that is fitted in the intake passage and attached to the crankcase.
2. A fuel pool prevention structure in a two-cycle internal combustion engine, wherein a fuel passage that allows natural flow of fuel from an inner bottom portion of the intake passage toward the crank chamber is formed in the crankcase.   2. The fuel pool prevention in a two-cycle internal combustion engine according to claim 1, wherein the crankcase is divided at a flat surface passing through the intake passage, and the fuel passage is formed by a groove formed in the cross section. Construction.

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