JP5225910B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an engine main body having a crankcase that rotatably supports a crankshaft, and a cylinder block that has a cylinder bore that slidably fits a piston connected to the crankshaft and is coupled to the crankcase. A scavenging pump is formed at a lower portion of the crank chamber that communicates with the cylinder bore and an oil storage chamber that stores lubricating oil, and sucks up the oil in the crank chamber and returns it to the oil storage chamber side. The present invention relates to an internal combustion engine disposed in the crankcase.

  In order to improve the performance of the internal combustion engine by making the internal pressure of the crank chamber negative, the oil in the crank chamber is transferred to the oil storage chamber isolated from the crank chamber and the pressure pulsation in the crank chamber due to the reciprocating motion of the piston. An internal combustion engine that is returned via a reed valve that opens and closes in response is known, for example, in Japanese Patent Application Laid-Open No. H10-228707. However, in such an internal combustion engine, when the crank chamber becomes positive pressure due to excessive blow-by, there is a problem that the oil discharge efficiency to the oil storage chamber by the reed valve is reduced. The oil in the room is forcibly discharged to the oil storage chamber side by a scavenging pump to prevent a decrease in oil discharge efficiency.

JP 2007-64081 A JP 2005-282568 A

  However, as disclosed in Patent Document 2, even if the oil in the crank chamber is forcibly discharged to the oil storage chamber side using a scavenging pump, the crank chamber is negatively charged in an excessive blow-by state. In order to maintain the pressure, it is necessary to increase the size and speed of the scavenging pump, which causes problems such as an increase in the size of the internal combustion engine and an increase in friction.

  The present invention has been made in view of such circumstances, so that oil can be reliably discharged from the crank chamber to the oil storage chamber side by a scavenging pump and the pressure in the crank chamber can be maintained at an appropriate negative pressure. An object of the present invention is to provide an internal combustion engine.

To achieve the above object, the present invention has a crankcase for rotatably supporting a crankshaft and a cylinder bore for slidably fitting a piston connected to the crankshaft, and is coupled to the crankcase. A crank chamber communicating with the cylinder bore and an oil storage chamber for storing lubricating oil are formed in a lower portion of an engine body having a cylinder block to be separated from each other. In an internal combustion engine in which a scavenging pump that returns to the chamber side is disposed in the crankcase, a partition wall provided in the engine body across the crank chamber and the oil storage chamber opens at a positive pressure in the crank chamber A recirculation valve that discharges the blow-by gas in the crank chamber to the oil storage chamber side through a reed valve. Hole is provided, wherein the balancer shaft which is rotatably supported in the crankcase so as to rotate together with the crankshaft, together with the balancer disposed in the crank chamber is provided, the communication hole, the It is provided in the partition wall at a position overlapping with the balancer shaft when viewed from the axial direction of the balancer shaft, and the balancer shaft is provided with a hollow portion coaxially provided to the crank chamber and open to the communication hole side . It shall be the first feature.

According to the present invention, in addition to the configuration of the first feature, a cam chain for transmitting power from the crankshaft is caused to travel to a camshaft of a valve operating device disposed on a cylinder head side coupled to the cylinder block. A cam chain passage is provided in the cylinder block and the cylinder head through the oil storage chamber, and is connected to the crankshaft and disposed in the oil storage chamber. The second feature is that the reed valve is arranged at a position avoiding overlapping as seen in FIG.

In addition to the configuration of the first or second feature, the present invention provides a ball disposed between the crank chamber and the communication hole while allowing gas to flow between one end of the balancer shaft and the partition wall. that the bearing is interposed shall be the third feature.

  According to the first aspect of the present invention, the oil in the crank chamber is forcibly discharged to the oil storage chamber side by the scavenging pump regardless of the internal pressure of the crank chamber. Can be reliably reduced. When the pressure in the crank chamber becomes positive, blow-by gas can be immediately discharged from the crank chamber to the oil storage chamber by the reed valve above the maximum oil level in the oil storage chamber. Negative pressure can be maintained.

In addition, the communication hole connecting the crank chamber and the oil storage chamber so as to be opened and closed by the reed valve is disposed at a position overlapping the balancer shaft when viewed from the axial direction of the balancer shaft. Therefore, it is not necessary to widen the partition wall that separates the crank chamber and the oil storage chamber in order to secure a space for this purpose, which can contribute to the compactness of the crankcase.

Furthermore, the balancer shaft is coaxially provided with a hollow portion that communicates with the crank chamber and is open to the communication hole side, so that the blow-by gas in the crank chamber reaches the communication hole through the hollow portion, and the oil accompanying the blow-by gas Can be prevented from directly adhering to the reed valve, and the reed valve can be operated smoothly. Further, blow-by gas from which oil has been separated in the hollow portion by rotation of the balancer shaft can be discharged from the reed valve to the oil storage chamber side.

According to the second feature of the present invention, since the reed valve is arranged so as not to overlap the generator and the cam chain when viewed in the axial direction of the crankshaft, oil scattered from the generator and the cam chain is reed valve. Therefore, the smooth operation of the reed valve can be maintained.

According to the third aspect of the present invention, since the ball bearing that allows the gas flow is disposed between the crank chamber and the communication hole, the blow-by gas in the crank chamber has a gap between the inner ring, the outer ring, and the ball. through will reach a communicating hole, the oil entrained in the blow-by gas is prevented from directly adhering to the reed valve, Ru can facilitate the operation of the reed valve.

Left side view of motorcycle Partial cutaway left side view of the internal combustion engine with the left crankcase cover removed FIG. 3 is a longitudinal sectional view of the internal combustion engine viewed from the same direction as FIG. 2, and is a sectional view taken along line 3-3 in FIG. 4. 4-4 sectional view of FIG. The perspective view which looked at the internal combustion engine and the intake box from the rear diagonally upward Sectional drawing of the left case half body along the 6-6 line of FIG. 2 is an enlarged view of the main part of FIG. Sectional view taken along line 8-8 in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  A first embodiment of the present invention will be described with reference to FIGS. 1 to 8. First, in FIG. 1, a vehicle body frame F of a motorcycle has a front end that supports a front fork 11 that supports a front wheel WF so as to be steerable. A head pipe 12, a pair of left and right main frames 13 extending rearward and downward from the head pipe 12, hangers 14 hanging downward from the front part of the main frames 13, and the rear part of the main frame 13 ... A pivot frame 15 that extends downward from the main frame 13, a seat rail 17 that extends rearward with a front end supported by the upper end of a column 16 that is erected on the rear of the main frame 13, and the main frame 13. A rear stay 18 connecting the rear part and the rear part of the seat rail 17.

  An engine main body 19 of an internal combustion engine E disposed below the main frame 13 is supported at the rear portion of the main frame 13 in the body frame F, the lower portion of the hanger 14, and the lower portion of the pivot frame 15. Further, the front end of the swing arm 20 that pivotally supports the rear wheel WR driven by the power exhibited by the internal combustion engine E at the rear end is supported by the pivot frame 15 so as to be swingable up and down. A link 21 and a rear cushion unit 22 are provided between the section and the column 16 of the vehicle body frame F.

  A fuel tank 23 disposed above the engine body 19 is mounted on the main frame 13, and a riding seat 24 disposed behind the fuel tank 23 is supported by the seat rails 17. A radiator 25 is disposed in front of the engine body 19, and the radiator 25 is supported by the vehicle body frame F and the engine body 19.

  A part of the internal combustion engine E and a part of the vehicle body frame F are covered with a vehicle body cover 27, and the vehicle body cover 27 extends from the front of the head pipe 12 to the rear part of the main frame 13. 25 and an upper part of the internal combustion engine E, a front cowl 28, a pair of left and right side cowls 29 which are connected to the rear portions on both sides of the front cowl 28 and cover the lower part of the internal combustion engine E, and a rear cowl 30 which covers the seat rail 17 Prepare.

  2 and 3, the engine body 19 of the internal combustion engine E includes a crankcase 33 that rotatably supports a crankshaft 32 having an axis extending in the width direction of the vehicle body frame F, and a front upper end of the crankcase 33. The cylinder 34 is coupled to the upper end of the cylinder 34, the cylinder head 35 is coupled to the upper end of the cylinder 34, and the head cover 36 is coupled to the upper end of the cylinder head 35.

  Referring also to FIG. 4, the crankcase 33 includes a left case half 38 and a right case half 39 that are coupled to each other by a coupling surface 37 that extends along a plane orthogonal to the axis of the crankshaft 32.

  As clearly shown in FIG. 2, the crankcase 33 is provided with a mission case 40 extending rearward. A transmission (not shown) for shifting the rotational power from the crankshaft 32 is accommodated in the transmission case 40, and the output shaft 41 of the transmission protrudes from the left side wall of the transmission case 40. . As shown in FIG. 1, a driving sprocket 42 is fixed to the output shaft 41, and a driven sprocket 43 is fixed to the axle of the rear wheel WR. An endless chain 44 is connected to the driving sprocket 42 and the driven sprocket 43. Is wrapped around.

  The cylinder 34 has a cylinder bore 48 in which a piston 47 connected to the crankshaft 32 through a connecting rod 46 is slidably fitted. The axis of the cylinder bore 48, that is, the cylinder axis C is slightly Inclined backward. That is, the engine body 19 is mounted on the vehicle body frame F with the cylinder axis C slightly tilted backward.

  A combustion chamber 49 that faces the top of the piston 47 is formed between the cylinder 34 and the cylinder head 35, and an intake port 50 that can communicate with the combustion chamber 49 is formed on a front side wall 35 a of the cylinder head 35. An exhaust port 51 that can communicate with the combustion chamber 49 is provided on the rear side wall 35b of the cylinder head 35. The cylinder head 35 switches between communication and blocking between the combustion chamber 49 and the intake port 50. An intake valve 52 is disposed so as to be openable and closable, and an exhaust valve 53 that switches communication / blocking between the combustion chamber 49 and the exhaust port 51 is disposed so as to be openable and closable.

  The head cover 36 is coupled to the cylinder head 35 such that the upper surface 36a thereof is disposed slightly above the main frame 13 in a side view, and the cylinder cover C is tilted backward. Thus, the upper surface 36a of the head cover 36 is inclined downward and rearward. Further, a valve operating chamber 54 is formed between the cylinder head 35 and the head cover 36, and a valve operating apparatus having an intake side camshaft 55 corresponding to the intake valve 52 and an exhaust side camshaft 56 corresponding to the exhaust valve 53. 57 is accommodated in the valve operating chamber 54 so as to open and close the intake valve 52 and the exhaust valve 53.

  Referring also to FIG. 5, an exhaust side connection cylinder portion 58 constituting a part of the exhaust port 51 is integrally projected on the rear side wall 35 b of the cylinder head 35 so as to protrude rearward. The upstream end of the exhaust pipe 59 that communicates with the exhaust port 50 is connected to the exhaust-side connecting cylinder 58. The exhaust pipe 59 is bent from the rear side wall 35 b of the cylinder head 35 to the left side of the engine body 19 and extends forward of the engine body 19, and is bent downward from the front of the engine body 19 to below the crankcase 33. The downstream end of the exhaust pipe 59 is connected to an exhaust muffler 60 disposed below the mission case 40.

  An intake box 64 is disposed in front of the cylinder head 35. The intake box 64 has a box body 65 formed in a box shape by forming a rectangular opening 67 at the upper end, and a front portion of the box body 65. As shown in FIG. 2, an air filter 68 accommodated in the intake box 64 is sandwiched between the box body 65 and the lid member 66.

  Thus, the lid member 66 is integrally provided with an intake duct 69 extending forward, and the front end of the intake duct 69 is opened. Therefore, air introduced into the intake duct 69 from the front end of the intake duct 69 is guided into the intake box 64, but is purified by passing through the air filter 68 disposed at the inlet of the intake box 64. It will be.

  By the way, an intake side connecting cylinder portion 63 that constitutes a part of the intake port 50 is integrally projected on the front side wall 35a of the cylinder head 35 so as to protrude upward. On the rear wall, that is, the rear wall 65a of the box body 65, a step portion 65b (see FIG. 2) connected to the protruding end of the intake side connecting cylinder portion 63 is formed. That is, the rear wall 65a of the intake box 64 comes into contact with or is close to the front side wall 35a of the cylinder head 35 by connecting the stepped portion 65b to the intake side connecting cylinder portion 63.

  In addition, a flange portion 65c surrounding the opening portion 57 is integrally provided at the upper end of the intake box 64 so as to project outward, and the upper surface of the intake box 64, that is, the upper surface 65d of the flange portion 65c, is In a state in which the portion 65b is connected to the intake side connecting cylinder portion 63, it is inclined slightly upward and rearwardly lower than the upper surface of the main frame 13 in a side view, and as shown in FIG. 2 and FIG. The upper surface 65d of the box 64 is substantially continuous with the upper surface 36a of the head cover 36 along the upper surface of the main frame 13 in the body frame F.

  The intake box 64 accommodates a throttle body 71 that is an intake passage forming member that guides the air purified by the air filter 58 to the intake port 50 side. The throttle body 71 includes the intake box 64. Are connected to the protruding end of the intake side connecting cylinder 63 together with the step 65b.

  A throttle valve 72 that opens and closes the intake passage 70 is pivotally supported on the throttle body 71, and a fuel injection valve 73 that injects fuel into the intake passage 70 on the downstream side of the throttle valve 72 is provided to the throttle body 71. Mounted. Moreover, the fuel injection valve 73 is attached to the lower portion of the throttle body 71 so as to avoid a narrow space between the throttle body 71 and the cylinder head 35 and the head cover 36, and forms a part of the intake box 64. The intake duct 69 that is integrally provided to the front and extends forward is disposed in front of the fuel injection valve 73.

  By the way, the fuel tank 23 is disposed above the engine body 19 and the intake box 64. The lower surface 23a of the fuel tank 23 has the intake air in a side view as shown in FIGS. The upper surface 65d of the box 64 and the upper surface 36a of the head cover 36 are formed along the upper surface 36a, and a part of the lower surface 23a of the fuel tank 23 closes the opening 67 at the upper end of the intake box 64. The box 64 is in close contact with the flange portion 65c at the upper end via a gasket (not shown).

  In addition, a fuel pump 61 for supplying the fuel in the fuel tank 23 to the fuel injection valve 73 is attached to the lower surface 23a of the fuel tank 23 behind the head cover 36, and the intake box 64, the head cover 36 and the fuel pump 61 are arranged side by side while being adjacent to each other.

  Referring again to FIG. 4, a left crankcase cover 75 constituting a part of the engine body 19 is coupled to the left case half 38 of the crankcase 33. An outer rotor 77 is fixed to one end portion of the crankshaft 32 protruding in the direction, and the left crankcase is configured such that an inner stator 78 that constitutes a generator 76 together with the outer rotor 77 is surrounded by the outer rotor 77. It is fixed to the cover 75. That is, the generator 76 is connected to the crankshaft 32.

  Meanwhile, a crank chamber 79 communicating with the cylinder bore 48 is formed in the crankcase 33, and an oil storage chamber 80 for storing oil is defined between the crankcase 33 and the left crankcase cover 75. It is isolated and formed.

  Further, at the lower part of the crankcase 33, a scavenging pump 81 for returning the oil in the crank chamber 79 to the oil storage chamber 80 side, and the lubricating parts of the internal combustion engine E by sucking up the oil in the oil storage chamber 80 A feed pump 82 is provided, and the pumps 81 and 82 are provided with a coaxial pump shaft 83.

  The scavenging pump 81 is a trochoid in which an inner rotor 84 fixed to the pump shaft 83 and an outer rotor 85 meshing with the inner rotor 84 are accommodated in a pump chamber 86 formed in the lower part of the crankcase 33. As shown in FIG. 6, a suction path 87 is provided at the lower portion of the crankcase 33 to guide the oil in the lower portion of the crank chamber 79 to the pump chamber 86 side, and the oil from the pump chamber 86 is provided. A discharge path 88 is provided for guiding the oil to the oil storage chamber 80 side.

  The feed pump 82 is a trochoid pump in which an inner rotor 89 fixed to the pump shaft 83 and an outer rotor 90 meshing with the inner rotor 89 are accommodated in a pump chamber 91. The case 33 is formed by a left case half 38 and a cover member 92 fastened to the left case half 38.

  One end of a pump shaft 83 rotatably supported by the crankcase 33 protrudes from the cover member 92 toward the oil storage chamber 80, and a driven sprocket 93 fixed to the protruding end of the pump shaft 83, and an oil An endless chain 95 is wound around a drive sprocket 94 provided integrally with the crankshaft 32 in the storage chamber 80, and the pump shaft 83 is rotationally driven by the power transmitted from the crankshaft 32.

  Referring also to FIG. 7, an oil strainer 96 is disposed below the oil reservoir chamber 80, and the oil sucked up from the oil strainer 96 is placed in the left case half 38 of the crankcase 33. A suction path 97 leading to the pump chamber 91 of the feed pump 82 is provided.

  The left case half 38 between the driven sprocket 93 and the oil strainer 96 is provided with an arcuate wall portion 98 that covers a part of the driven sprocket 93 from the side, and the driven sprocket 93 and the crankshaft 32. In the left case half 38, an arcuate wall 99 that covers a part of the driven sprocket 93 from the side allows the chain 95 to travel between the drive sprocket 94 and the driven sprocket 93. Provided integrally. Further, a cover plate 100 that covers the driven sprocket 93 from the axially outer side is fastened to the left case half 38, and the wall portions 98 and 99 and the cover plate 100 cause the driven sprocket 93 to rotate. Oil bubbling is prevented from reaching the oil strainer 96 side directly.

  In FIG. 8, a wall portion 101 that rises upward is integrally provided at the lower portion of the left case half 38 between the wall portion 98 and the oil strainer 96. Notches for forming flow holes 102 and 103 are provided between the case half 37 and the left crankcase cover 75. The oil flowing from the driven sprocket 93 side to the oil strainer 96 side in the lower part of the oil storage chamber 80 flows through the flow holes 102 and 103, and it is suppressed as much as possible that the oil in which bubbles are generated flows into the oil strainer 96. Will be.

  The left case half 38 constituting a part of the crankcase 33 integrally has a partition wall 38a separating the crank chamber 79 and the oil storage chamber 80, and the partition wall 38a is connected to the right side of the crank chamber 79. A communication hole 110 that communicates between the crank chamber 79 and the oil storage chamber 80 is provided via a reed valve 105 that is opened during pressure, and the reed valve 105 is a maximum oil level of oil stored in the oil storage chamber 80. It is disposed in the partition wall 38a on the oil storage chamber 80 side so as to be positioned above L.

  The reed valve 105 has one end of a lead 106 and one end of a stopper plate 107 facing the lead 106 from the opposite side of the partition wall 38a attached to the partition wall 38a with a screw member 108. A through hole 109 is provided to prevent the operation of the lead 106 from being hindered by the presence of oil between the lead 106 and the stopper plate 107.

  By the way, the crankcase 33 has a balancer shaft 111 having an axis parallel to the crankshaft 32 and having a bottomed hollow portion 111a opened at one end thereof coaxially. A balancer 112 that is rotatably supported so as to rotate and is disposed in the crank chamber 79 is provided on the balancer shaft 111.

  Thus, in order to rotatably support one end portion of the balancer shaft 111, a support hole 113 is provided on the surface of the partition wall 38a facing the crank chamber 79, and the balancer that enters the support hole 113 is provided. A ball bearing 114 that allows gas flow is interposed between one end of the shaft 111 and the partition wall 38a. Moreover, the end of the communication hole 110 on the crank chamber 79 side opens to the inner end of the support hole 113, and the communication hole 110 opened and closed by the reed valve 105 is viewed from the axial direction of the balancer shaft 111. Therefore, the ball bearing 114 is disposed between the crank chamber 79 and the communication hole 110 at a position overlapping the balancer shaft 111.

  Incidentally, the rotational power from the crankshaft 32 is connected to the timing transmission means 115 on the intake side and exhaust side camshafts 55 and 56 of the valve operating device 57 accommodated in the valve operating chamber 54 between the cylinder head 35 and the head cover 36. The timing transmission means 115 is arranged in the oil storage chamber 80 and provided to the crankshaft 32, and the intake side and exhaust side camshaft 55. , 56 is formed by winding an endless cam chain 119 around driven sprockets 117, 118 fixed to one end of the cam chain 119. 33 left case half 38, cylinder block 34 and cylinder head 5 to be provided.

  In addition, the reed valve 105 is connected to the crankshaft 32 and avoids overlapping with the generator 76 and the cam chain 119 disposed in the oil storage chamber 80 when viewed in the axial direction of the crankshaft 32. Placed in.

  Next, the operation of the first embodiment will be described. The intake box 64 having the upper surface 65d inclined rearward and downward is substantially aligned with the upper surface 36a of the head cover 36 along the upper surface of the main frame 13 in the body frame F. The rear wall 65a of the intake box 64 is arranged in front of the cylinder head 35 so as to be close to or abutting the front side wall 35a of the cylinder head 35 in a continuous manner. In addition, a throttle body 71 that forms an intake passage 70 that guides air purified by the air filter 68 to the intake port 50 side is accommodated, and the fuel tank 23 disposed above the engine body 19 and the intake box 64 is accommodated. The lower surface 23a includes the upper surface 65d of the intake box 64 and the head cover 36 in a side view. Since is formed along the upper surface 36a, as compared to what the air cleaner is disposed above the engine body, it is possible to set a large capacity of the fuel tank 23.

  A fuel injection valve 73 for injecting fuel into the intake passage 70 on the downstream side of the throttle valve 72 is attached to the lower portion of the throttle body 71 along the lower end of the main frame 13 in the vehicle body frame F. Since an intake duct 69 that is connected to the intake box 64 and extends forward is disposed in front, the intake passage 70 of the throttle body 71 is straightened and shortened so that the throttle body 71 is directly connected to the intake port 50. Thus, the output of the internal combustion engine E can be improved, and the fuel injection valve 73, the throttle body 71, and the intake box 64 can be configured in a compact manner, and the overhang of the intake box 64 from the cylinder head 35 can be avoided.

  An opening 67 and a flange portion 65c surrounding the opening 67 are provided at the upper end of the intake box 64 whose upper end is opened, and a part of the lower surface 23a of the fuel tank 23 that closes the opening 67 is a flange portion 65c. And the fuel pump 61 attached to the lower surface 23a of the fuel tank 23 at the rear of the head cover 36 is arranged side by side in front of and behind the fuel tank 23. However, it can also serve as a lid member for the intake box 64, and a lid member dedicated to the intake box 64 is not required, so that the number of parts can be reduced, the shape of the intake box 64 can be simplified, and the fuel pump The shape of the fuel tank 23 can be optimized by arranging 61 at a lower position in the lower part of the fuel tank 23.

  By the way, a crank chamber 79 communicating with the cylinder bore 48 is formed below the crankcase 33 in the engine body 19, and an oil storage chamber 80 for storing lubricating oil between the crankcase 33 and the left crankcase cover 75 in the engine body 19. Is formed so as to be isolated from the crank chamber 79, and a scavenging pump 81 that sucks up the oil in the crank chamber 79 and returns it to the oil storage chamber 80 side is disposed in the crankcase 33. The oil in 79 is forcibly discharged to the oil storage chamber 80 side by the scavenging pump 81 regardless of the internal pressure of the crank chamber 79, and the frictional horsepower due to the oil agitation of the crankshaft 32 is reliably reduced. be able to.

  Further, the blow-by gas in the crank chamber 7979 is stored in the partition wall 38a provided in the engine main body 19 with the crank chamber 79 and the oil storage chamber 80 separated from each other via a reed valve 105 that opens when the crank chamber 79 is positively pressurized. Since the communication hole 110 for discharging to the chamber 80 side is provided, blow-by gas can be immediately discharged from the crank chamber 79 to the oil storage chamber 80 side when the pressure in the crank chamber 79 becomes positive. The inside can be maintained at an appropriate negative pressure.

  A balancer shaft 111 disposed in the crank chamber 79 is provided on the balancer shaft 111 that is rotatably supported by the crankcase 33 so as to rotate in conjunction with the crankshaft 32, and the communication hole 110 includes the communication hole 110. Since the partition wall 38a is provided at a position overlapping the balancer shaft 111 when viewed from the axial direction of the balancer shaft 111, the space between the crank chamber 79 and the oil storage chamber 80 is secured in order to secure a space for arranging the communication hole 110. There is no need to widen the partition wall 38a, which can contribute to the compactness of the crankcase 33.

  Further, a cam chain 119 that transmits power from the crankshaft 32 to the intake and exhaust camshafts 55 and 56 of the valve operating device 57, and a generator 76 that is connected to the crankshaft 32 and disposed in the oil storage chamber 80. In addition, since the reed valve 105 is disposed at a position avoiding overlapping when viewed in the axial direction of the crankshaft 32, oil scattered from the generator 76 and the cam chain 119 is less likely to hit the reed valve 105, and the reed valve 105 The smooth operation of the valve 105 can be maintained.

  Further, since the ball bearing 114 interposed between one end of the balancer shaft 111 and the partition wall 38a is disposed between the crank chamber 79 and the communication hole 110 while allowing the gas to flow, the blow-by gas in the crank chamber 79 is The ball bearing 114 reaches the communication hole 110 through the gap between the outer ring and the ball, and the oil accompanying the blow-by gas is prevented from directly adhering to the reed valve 105, and the reed valve 105 is operated. It can be smoothed.

  As another embodiment of the present invention, as shown by a chain line in FIG. 4, a crank chamber 79 and a hollow portion 111 a are provided on a balancer shaft 111 having a bottomed hollow portion 111 a coaxially opened at one end side, that is, the communication hole 110 side. You may make it provide the through-hole 121 which connects between. In this way, the blow-by gas in the crank chamber 79 reaches the communication hole 110 through the through-hole 121 and the hollow portion 111a, and oil accompanying the blow-by gas is prevented from directly attaching to the reed valve 105. Thus, the operation of the reed valve 105 can be smoothed. Further, blow-by gas from which oil has been separated in the hollow portion 111 a by the rotation of the balancer shaft 111 can be discharged from the reed valve 105 to the oil storage chamber 80 side.

  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.

19 .... Engine body 32 ... Crankshaft 33 ... Crankcase 34 ... Cylinder block 38a ... Bulkhead 47 ... Piston 48 ... Cylinder bores 55, 56 ... Camshaft 57 ... Valve operating device 76 ... Generator 79 ... Crank chamber 80 ... Oil storage chamber 81 ... Scavenging pump 105 ... Reed valve 110 ... Communication hole 111... Balancer shaft 111 a .. hollow portion 112. Balancer 114... Ball bearing 119... Cam chain 120.

Claims (3)

The crankcase (33) for rotatably supporting the crankshaft (32) and a cylinder bore (48) for slidably fitting a piston (47) connected to the crankshaft (32), A lower part of an engine body (19) having a cylinder block (34) coupled to a case (33) is provided with a crank chamber (79) communicating with the cylinder bore (48), and an oil reservoir chamber for storing lubricating oil ( 80) and is formed is isolated from each other, arranged said the crank chamber (79) the oil reservoir chamber sucks up oil (80) scavenging pump for returning the side (81) in the crankcase (33) In an internal combustion engine
A reed valve (105) is opened to a partition wall (38a) provided in the engine body (19) with a space between the crank chamber (79) and the oil reservoir chamber (80) when the crank chamber (79) is positive. ) Through which the blow-by gas in the crank chamber (79) is discharged to the oil storage chamber (80) side is provided ,
A balancer (112) disposed in the crank chamber (79) on a balancer shaft (111) rotatably supported by the crankcase (33) so as to rotate in conjunction with the crankshaft (32). And the communication hole (110) is provided in the partition wall (38a) at a position overlapping the balancer shaft (111) when viewed from the axial direction of the balancer shaft (11).
Wherein the balancer shaft (111), an internal combustion institutions, characterized in that the hollow section that is open to the communication hole (110) side with leads to the crank chamber (79) (111a) are provided coaxially. A cam chain for transmitting power from the crankshaft (32) to the camshafts (55, 56) of the valve gear (57) disposed on the cylinder head (35) side coupled to the cylinder block (34). A cam chain passage (120) for running (119) is provided in the crankcase (33), the cylinder block (34) and the cylinder head (35) through the oil storage chamber (80), and the crankshaft (32) connected to the generator (76) disposed in the oil storage chamber (80) and the cam chain (119) at a position avoiding overlapping with the crankshaft (32) when viewed in the axial direction. internal combustion engine according to claim 1, characterized in that said reed valve (105) is disposed. Between one end of the balancer shaft (111) and the partition wall (38a), a ball bearing (114) disposed between the crank chamber (79) and the communication hole (110) while allowing gas flow is interposed. internal combustion agencies according to claim 1 or 2, characterized in that it is so.

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