JP2007270723A - Blow-by gas ventilator of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the deterioration in lubricating oil, by maximally checking mixing of moisture in blow-by gas in the lubricating oil, by promoting atomization of the blow-by gas, by raising the atmospheric temperature in a crankcase, by heating and introducing a part of fresh air extracted from an intake system into the crankcase. <P>SOLUTION: This internal combustion engine 23 has a blow-by gas reducing device 64. This blow-by gas ventilator of the internal combustion engine is composed of fresh air introducing passages 62 and 63 having the large fresh air introducing space volume for introducing the fresh air into the crankcase from an intake system 48, and fresh air heating means 66 and 68 heating the fresh air introducing passage 62 introducing the fresh air by a high temperature source in the internal combustion engine 23. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a blow-by gas ventilation device for an internal combustion engine that heats fresh air in an intake system and introduces the fresh air into a crank chamber and recirculates blow-by gas in the crank chamber to the intake system.

  In the internal combustion engine, a part of the exhaust gas combusted in the combustion chamber from the gap between the cylinder wall and the piston peripheral wall slightly leaks into the crank chamber as blow-by gas, and the moisture in the leaked blow-by gas is the lubricating oil in the crank chamber. If mixed in, it will cause deterioration of the lubricating oil. As a preventive measure, by introducing a part of the fresh air from the intake system into the crank chamber, the leaked blow-by gas is forcibly discharged from the crank chamber, ventilating the crank chamber, and suppressing the dilution of the lubricating oil. There was a technique to do (for example, patent document 1).

Japanese Patent Laid-Open No. 2005-121008

  However, in the cold season, the ratio of moisture in the blow-by gas condensing into moisture increases, so that the effect of preventing moisture from being mixed into the lubricating oil in the crank chamber may not be sufficiently obtained.

  The present invention overcomes such difficulties, and the invention according to claims 1 to 4 is a method in which a part of fresh air extracted from the intake system is heated and introduced into the crank chamber. The purpose is to prevent the mixing of moisture in the blow-by gas into the lubricating oil as much as possible by increasing the ambient temperature in the crank chamber and promoting atomization of the blow-by gas, thereby suppressing deterioration of the lubricating oil.

  According to a first aspect of the present invention, there is provided an internal combustion engine having a blow-by gas reduction device for an internal combustion engine, wherein a fresh air introduction passage for introducing a part of fresh air from an intake system into the crank chamber and the internal combustion engine or an auxiliary machine. A blow-by gas ventilation apparatus for an internal combustion engine, comprising a fresh air heating means for heating the fresh air introduction passage.

  In the claims and specification of the present application, in the description of "fresh air heating means for heating the fresh air introduction passage by an internal combustion engine or an auxiliary machine", the internal combustion engine means an internal combustion engine body, Means an exhaust system such as an exhaust pipe and an exhaust purification catalyst, a radiator and other heat generating auxiliary equipment.

  The invention according to claim 2 is characterized in that the air cleaner case has a double wall structure, and at least a part of the fresh air introduction passage is constituted by an outer space between the double walls of the air cleaner case. Item 2. A blow-by gas ventilation device for an internal combustion engine according to Item 1.

  The invention according to claim 3 is characterized in that an exhaust system including an exhaust muffler, an exhaust purification catalyst, an exhaust pipe and the like is disposed adjacent to the double wall structure of the air cleaner case as a fresh air heating means. The blow-by gas ventilation device for an internal combustion engine according to claim 2.

  According to a fourth aspect of the present invention, the exhaust pipe has a double wall structure, the inner space of the exhaust pipe of the double wall structure is an exhaust passage, and at least a part of the fresh air flowing through the fresh air introduction passage is the 2. The blow-by gas ventilation device for an internal combustion engine according to claim 1, wherein the blow-by gas ventilation device is configured to flow in an outer space of an exhaust pipe having a double wall structure.

  In the invention described in claim 1, since at least a part of the fresh air extracted from the intake system is heated by the fresh air heating means and introduced into the crank chamber, the ambient temperature in the crank chamber increases, The atomization of the gas is promoted, the condensation of the water vapor in the blow-by gas is prevented, and the lubricating oil of the moisture in the blow-by gas is restricted. As a result, the deterioration of the lubricating oil is suppressed.

  In the invention described in claim 2, since at least a part of the fresh air introduction passage is obtained by the double structure of the air cleaner case, the structure is simplified and the cost can be reduced and the weight can be reduced. Since the introduction space volume is obtained, a large amount of hot fresh air is supplied into the crank chamber in response to pressure fluctuations in the crank chamber, the ambient temperature in the crank chamber rises, and the deterioration of the lubricating oil is effectively suppressed. .

  According to the third aspect of the present invention, the fresh air introduction passage in the outer space between the double walls located outside the air cleaner case is effectively heated by the high temperature exhaust system, and is constituted by the double walls. Due to the heat insulation structure, the intake air passing through the center portion of the air cleaner case is sucked into the internal combustion engine at a low temperature, and high charging efficiency can be maintained.

  In a fourth aspect of the invention, due to the high-temperature exhaust gas flowing through the inner space of the double-walled exhaust pipe, a part of the fresh air in the air cleaner case flowing through the outer space between the outer double walls is at a high temperature. In addition to being effectively heated, the fresh air introduction passage can be simply configured so that the cost can be reduced.

  Embodiments of the invention described in claims 1 to 3 shown in FIGS. 1 to 3 will be described below.

  The three-wheeled vehicle 1 shown in FIG. 1 includes one front wheel 2 and a pair of left and right rear wheels 3, and the front wheel 2 is pivotally supported substantially upright on the front portion of the front vehicle body 4. A pair of left and right rear wheels 3 are rotatably attached to a lower steering shaft and are provided on both sides of a rear vehicle body 6 attached to a lower rear portion of the front vehicle body 4 via a swing mechanism 5.

  A bar handle 7 for steering the front wheel 2 is attached to the upper end of the steering shaft (not shown), and the bar handle 7 is steered by a driver (not shown) seated on a seat 8 provided at the rear of the front vehicle body 4. Thus, the front wheel 2 can be turned to the left and right.

  The swing mechanism 5 is interposed between a joint case 10 attached to the lower rear portion of the front vehicle body 4 via a link 9 so as to be swingable up and down, and the joint case 10 and the rear portion of the front vehicle body 4. A cushion unit 11 and a joint shaft 13 fitted to the joint case 10 via a damper 12, and a power unit 22 of the rear vehicle body 6 is integrally attached to the rear end of the joint shaft 13 via a bracket 14. The rear vehicle body 6 can swing up and down with respect to the front vehicle body 4 in accordance with the unevenness of the road surface.

  Further, in the three-wheeled vehicle 1, a wind screen 16 is raised upward from the upper portion of the front cover 15 at the front of the front vehicle body 4, and a roof 17 is extended downward from the upper end of the wind screen 16. The rear end of 17 is supported by a pair of left and right posts 18 raised upward from the rear portion of the front vehicle body 4, and a carrier box 19 is disposed behind the pair of left and right posts 18.

  Furthermore, a fuel tank 20 is disposed below the seat 8, and a fuel pump 21 for supplying fuel to a 4-stroke cycle internal combustion engine 23 described later is provided in the fuel tank 20.

  As shown in FIGS. 2 and 3, the power unit 22 constituting most of the rear vehicle body 6 includes a four-stroke cycle internal combustion engine 23 and a belt-type continuously variable transmission 24. A cylinder head 26 and a head cover 27 are sequentially stacked and integrally coupled in front of the cylinder block 25, and a transmission case 28 that also serves as a crankcase is integrated behind the cylinder block 25 of the four-stroke cycle internal combustion engine 23. The bracket 14 is integrally connected to the joint shaft 13 with two bolts 33 and is integrally connected to the cylinder block 25 of the power unit 22 and the transmission case 28 with bolts 34.

  In the power unit 22, as shown in FIG. 3, the crankshaft 29 rotatably supported by the mating surface of the cylinder block 25 and the transmission case 28 and the transmission case 28 are rotatably supported. The transmission driven shaft 30 is provided with pulleys (not shown), and a belt 31 is stretched between these pulleys. As shown in FIG. 2, the transmission driven shaft 30 and the transmission case 28 are connected to each other. The output shaft 32 rotatably supported is connected via a gear (not shown), and left and right rear wheels 3 are attached to an axle 32a projecting outward from the output shaft 32. A four-stroke cycle internal combustion engine When the crankshaft 29 rotates in the operating state 23, the transmission driven shaft 30 is rotationally driven via the belt 31 of the belt-type continuously variable transmission 24, and the output shaft 32 and the rear wheel are further driven via gears (not shown). 3 is driven to rotate, The tricycle 1 can run.

  The power unit 22 is provided with a frame structure for supporting auxiliary equipment and a rear body cover 45, which will be described later.

  As shown in FIG. 3, this frame structure has a pair of left and right front stays 35 that stand upright substantially upward from the cylinder block 25, and left and right 1 branches from the front stays 35 obliquely forward and upward. A pair of front branch stays 36, a pair of left and right rear stays 37 integrally standing upright from the rear of the transmission case 28, and left and right front branch stays as shown in FIGS. 36, a front frame 38 integrally coupled to the upper end of 36, a rear frame 39 integrally coupled to the upper ends of the left and right rear stays 37, a front end coupled to the front frame 38 and a rear end of the rear frame 39. A front bracket 42 integrally joined to the front frame 38, and a rear frame 39, which is composed of a pair of left and right left frames 40 and 41 joined integrally to the upper end of the front stay 35. With the rear bracket 43 joined together, With 44, the rear body cover 45 is attached integrally to the the front and rear of the rear part body cover 45, a front opening 46 and the rear opening 47 is formed.

  Next, the intake system will be described.

  As shown in FIG. 2, an air cleaner case 49 of a substantially rectangular parallelepiped air cleaner 48 is attached to the left frame 40 by bolts 61 at one place on the left side of the top, and the right frame 41 by bolts 61 at two places on the right and left sides of the top. The air cleaner case 49 is partitioned by a partition wall 50 into a triangular duct chamber 51 and a trapezoidal purification chamber 52 in a plan view, and the upper part of the duct chamber 51 has a triangular shape. An air inlet 53 is formed, and the duct chamber 51 and the purification chamber 52 communicate with each other by a U-shaped communication pipe 54 in a side view, and the purification chamber 52 has a front wall, a left wall, and a rear wall. The inner wall 55 is joined to the bottom wall and the top wall of the air cleaner case 49 at a predetermined interval in parallel with each other, and the right end of the front wall of the inner wall 55 is joined to the partition wall 50, and the rear wall of the inner wall 55 The right end of the air cleaner case 49 is separated from the right wall of the air cleaner case 49 by a predetermined gap. The purifying chamber 52 is configured with a double wall structure with the inner wall 55, and a filter element (not shown) is disposed inside the inner wall 55 of the purifying chamber 52, and the intake air penetrating the air cleaner case 49 and the inner wall 55. The upstream end of the pipe 56 is opened into the purification chamber 52, and air is sucked into the duct chamber 51 from the intake port 53 and then flows into the purification chamber 52 through the communication pipe 54. The dust in the intake air is removed by the filter element that is not used, and then flows into the intake pipe 56.

  A throttle body 57 is interposed in the intake pipe 56. The intake pipe 56 is located above the power unit 22, and the downstream end of the intake pipe 56 is connected to an intake port (not shown) of the cylinder head 26, so that the throttle A slot valve (not shown) in the body 57 is connected to the rear end of the throttle cable 58 extended from the throttle grip 7a of the bar handle 7, and the throttle valve in the throttle body 57 is required by operating the throttle grip 7a. The degree of opening is adjusted.

  A fuel injection valve 59 is disposed downstream of the intake pipe 56 adjacent to the cylinder head 26, and a synthetic resin fuel is supplied to a fuel discharge port (not shown) of the fuel pump 21 provided in the fuel tank 20. The upstream end of the hose 60 is connected, and the downstream end of the fuel hose 60 is connected to the fuel injection valve 59.

  Further, in the purification chamber 52 of the air cleaner case 49, the space between the air cleaner case 49 and the inner wall 55 partitioned by the inner wall 55 opens into the purification chamber 52 between the right end of the inner wall 55 and the inner wall 55. A fresh air introduction passage 62 is formed, and the other end portion of the fresh air introduction pipe 63 that penetrates the air cleaner case 49 and opens at one end to the fresh air introduction passage 62 is the crank chamber wall of the four-stroke cycle internal combustion engine 23. A part of the fresh air from which dust has been removed in the purification chamber 52 passes through the fresh air introduction passage 62 and the fresh air introduction pipe 63. It is introduced into the crank chamber.

  A one-way valve (not shown) is provided at the downstream end of the fresh air introduction pipe 63, which is opened when the pressure in the crank chamber is reduced and closed when the pressure in the crank chamber is increased.

  Further, in the four-stroke cycle internal combustion engine 23, a blow-by gas communication passage (not shown) having a gas-liquid splitting function communicating with the space in the head cover 27 from the crank chamber is formed, and the space in the cylinder head 26 and the air cleaner 48 are formed. The purification chamber 52 is communicated with a blow-by gas recirculation pipe 64, and blow-by gas generated in the crank chamber reaches a space in the cylinder head 26 via a blow-by gas passage (not shown). The blowby gas is discharged into the purification chamber 52 of the air cleaner 48 via the blowby gas recirculation pipe 64.

  Further, the exhaust system will be described.

  The upstream end of the front exhaust pipe 65 is attached to the lower surface of the cylinder head 26 so that the upstream part of the front exhaust pipe 65 communicates with an exhaust port (not shown) in the cylinder head 26, and the front exhaust pipe 65 is connected to the cylinder head. 26, which is bent upward after bypassing the left side of 26, and is bent rearward, and the downstream end of the front exhaust pipe 65 is located at the upper left side of the power unit 22 and is directed to the front-rear direction of the vehicle body. The rear end of the exhaust purification catalyst 66 is connected to the left upstream end of an exhaust muffler 68 directed in the vehicle width direction via a rear exhaust pipe 67, and the exhaust muffler 68 is directed downward and obliquely downward. A tail pipe 69 is connected, and the exhaust muffler 68 is integrally attached to a protruding portion 28a protruding rearward from the transmission case 28 via a bracket 70, as shown in FIG.

  As shown in FIG. 2, the rear portion of the exhaust purification catalyst 66 is disposed in parallel to the left side wall of the air cleaner case 49 with a slight gap, and the exhaust muffler 68 is disposed on the rear side wall of the air cleaner case 49. The left side wall of the air cleaner case 49 is heated by the exhaust heat emitted from the exhaust purification catalyst 66 and the rear exhaust pipe 67, and the rear side wall of the air cleaner case 49 is The exhaust muffler 68 is heated by the exhaust heat dissipated.

  A radiator 71 and a louver 72 are arranged in front of the power unit 22 at the front thereof.

  Since the embodiment shown in FIGS. 1 to 3 is configured as described above, the following operations are performed and effects can be obtained.

  When the four-stroke cycle internal combustion engine 23 is started and the throttle grip 7a of the bar handle 7 is operated, the rotational speed of the crankshaft 29 increases, and the driving force is transmitted to the output shaft 32 via the belt-type continuously variable transmission 24. The rear wheel 3 integrated with the axle 32a protruding outward from the output shaft 32 is rotationally driven, and the three-wheeled vehicle 1 can travel.

  After a certain period of time has elapsed since the start of the operation of the four-stroke cycle internal combustion engine 23, the exhaust purification catalyst 66, the rear exhaust pipe 67 and the exhaust muffler 68 are heated to a high temperature with the high-temperature exhaust gas passing through the exhaust purification catalyst 66.

  Then, the left side wall and the rear side wall of the air cleaner case 49 of the air cleaner 48 adjacent to the exhaust purification catalyst 66, the rear exhaust pipe 67 and the exhaust muffler 68 are heated to a high temperature, and the new side wall and the rear side wall of the air cleaner case 49 are in contact with each other. The fresh air in the air introduction passage 62 is heated and introduced into a crank chamber (not shown) via a fresh air introduction pipe 63, the atmospheric temperature in the crank chamber rises, water droplets contained in the blow-by gas evaporate, The lubricating oil collected at the bottom of the chamber is greatly suppressed from deterioration due to moisture.

  The blow-by gas containing water vapor is discharged into the purification chamber 52 of the air cleaner 48 via a blow-by gas communication path (not shown), the space in the head cover 27, and the blow-by gas recirculation pipe 64, and from the intake port 53 to the duct chamber 51. The intake air is supplied to the combustion chamber in the four-stroke cycle internal combustion engine 23 from the intake pipe 56 through the intake port (not shown) of the four-stroke cycle internal combustion engine 23 together with the fresh air that is sucked and flows into the purification chamber 52 through the communication pipe 54. The blow-by gas is purified by burning with fuel.

  Further, the crank chamber of the four-stroke cycle internal combustion engine 23 and the air cleaner 48 are separated from each other, and the fresh air introduction passage 62 is long. As a result, the volume of fresh air introduced to the chamber 52 is increased, and a large amount of fresh air is introduced into the crank chamber in response to pressure fluctuations in the crank chamber. Is prevented from being mixed into the lubricating oil, and deterioration of the lubricating oil is suppressed.

  Furthermore, since the heat of the exhaust gas generated in the four-stroke cycle internal combustion engine 23 can be used effectively to heat the fresh air introduced into the combustion chamber, no special fuel or electric power is required, resulting in an increase in cost. Energy saving can be achieved.

  Furthermore, even if the air cleaner 48 is adjacent to the exhaust purification catalyst 66, the rear exhaust pipe 67 and the exhaust muffler 68, the air cleaner case 49 has a double wall structure and a new structure constituted by a double wall structure. Since fresh air passes through the air introduction passage 62 and the inner wall 55 is cooled, the fresh air in the purification chamber 52 is not likely to be heated to a high temperature, and high filling efficiency can be maintained.

  Moreover, since the exhaust purification catalyst 66, the rear exhaust pipe 67, and the exhaust muffler 68 are disposed adjacent to the air cleaner 48, the rear vehicle body 6 is formed compact.

  Next, an embodiment of the invention described in claim 1 and claim 4 shown in FIGS. 4 to 5 will be described.

  The other parts of the three-wheeled vehicle 1 except for the blow-by gas reduction device, the intake system and the exhaust system have the same structure as that of the embodiment shown in FIGS. 1 to 3 (partially omitted in the overlapping parts). Therefore, the same code | symbol is attached | subjected and description of the part is abbreviate | omitted.

  The upstream end of the upstream side exhaust pipe 73 is connected to an exhaust port (not shown) of the cylinder head 26, the upstream end of the upstream side exhaust purification catalyst 74 is connected to the downstream end of the upstream side exhaust pipe 73, and the upstream side exhaust purification catalyst 74. The downstream end of the intermediate exhaust pipe 75 is connected to the upstream end of the inner pipe (not shown) of the intermediate exhaust pipe 75 having a double-walled structure bent in a side view, and the downstream end of the inner pipe of the intermediate exhaust pipe 75 Is connected to the upstream end of the downstream side exhaust catalyst 76, and the downstream end of the downstream side exhaust catalyst 76 is connected to the exhaust muffler 68 via the downstream side exhaust pipe 77.

  A fresh air introduction passage (not shown) is formed by the inner pipe of the intermediate exhaust pipe 75 having a double wall structure and the outer pipe arranged concentrically therewith, and a portion of the fresh air introduction passage close to the downstream side exhaust catalyst 76; The purification chamber 52 of the air cleaner 48 is communicated with an upstream fresh air introduction pipe 78, a portion of the fresh air introduction passage of the intermediate exhaust pipe 75 close to the upstream exhaust purification catalyst 74, and a crank chamber of the four-stroke cycle internal combustion engine 23. (Not shown) is communicated with the downstream fresh air introduction pipe 79, and a part of the fresh air flowing into the purification chamber 52 of the air cleaner 48 passes through the upstream fresh air introduction pipe 78 to the intermediate exhaust pipe 75. A part of the fresh air in the fresh air introduction passage is heated by heat exchange with the high-temperature exhaust gas flowing in the inner pipe, and is then passed through the fresh air introduction pipe 79 on the downstream side. To be introduced. Further, the blow-by gas generated in the crank chamber is discharged into the purification chamber of the air cleaner 48 via the blow-by gas recirculation pipe 64 disposed close to the catalyst 74 and the exhaust pipe 75.

  In the embodiment shown in FIGS. 4 to 5, the internal pipe of the intermediate exhaust pipe 75 is connected to the high-temperature exhaust gas that has passed through the upstream side exhaust pipe 73 and the upstream side exhaust purification catalyst 74 from the combustion chamber of the four-stroke cycle internal combustion engine 23. As a result, a part of the fresh air is directly heat-exchanged through the air, so that the part of the fresh air is effectively heated to a high temperature. Water is further prevented from mixing into the oil, and the deterioration of the lubricating oil is remarkably suppressed. Furthermore, since the reflux pipe 64 is heated by the catalyst 74 and the exhaust pipe 75, condensation of blow-by gas in the reflux pipe can be prevented, and deterioration of the lubricating oil can be further suppressed.

  The fresh air introduced from the air cleaner 48 into the crank chamber of the four-stroke cycle internal combustion engine 23 is heated not by the intermediate exhaust pipe 75 but by the upstream side exhaust purification catalyst 74 or the downstream side exhaust catalyst 76, or both. Further, fresh air may be heated by the radiator 71, or fresh air may be heated by another heat source.

1 is a side view of a three-wheeled vehicle equipped with an embodiment of a blow-by gas ventilation device for an internal combustion engine according to the present invention. It is a principal part top view of FIG. It is a principal part side view of FIG. It is a top view of other embodiments of the present invention. FIG. 5 is a side view of FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Three-wheeled vehicle, 2 ... Front wheel, 3 ... Rear wheel, 4 ... Front vehicle body, 5 ... Swing mechanism, 6 ... Rear vehicle body, 7 ... Bar handle, 8 ... Seat, 9 ... Link, 10 ... Joint case, 11 ... Cushion unit, 12 ... Damper, 13 ... Joint shaft, 14 ... Bracket, 15 ... Front cover, 16 ... Wind screen, 17 ... Roof, 18 ... Post, 19 ... Carrier box,
20 ... Fuel tank, 21 ... Fuel pump, 22 ... Power unit, 23 ... 4-stroke cycle internal combustion engine, 24 ... Belt type continuously variable transmission, 25 ... Cylinder block, 26 ... Cylinder head, 27 ... Head cover, 28 ... Transmission case , 29 ... crankshaft,
30 ... Transmission driven shaft, 31 ... Belt, 32 ... Output shaft, 33 ... Bolt, 34 ... Bolt, 35 ... Front stay, 36 ... Front branch stay, 37 ... Rear stay, 38 ... Front frame, 39 ... Rear Frame, 40 ... Left frame, 41 ... Right frame, 42 ... Front bracket, 43 ... Rear bracket, 44 ... Bolt, 45 ... Rear body cover, 46 ... Front opening, 47 ... Rear opening, 48 ... Air cleaner, 49 ... Air cleaner case, 50 ... Bulkhead, 51 ... Duct chamber, 52 ... Purification chamber, 53 ... Intake port, 54 ... Communication pipe, 55 ... Inner wall, 56 ... Intake pipe, 57 ... Throttle body, 58 ... Throttle cable, 59 ... Fuel injection Valve, 60 ... Fuel hose, 61 ... Bolt, 62 ... Fresh air introduction passage, 63 ... Fresh air introduction pipe, 64 ... Blowby gas recirculation pipe, 65 ... Front exhaust pipe, 66 ... Exhaust gas purification catalyst, 67 ... Rear exhaust pipe , 68 ... Exhaust muffler, 69 ... Tail pipe, 70 ... Bracket, 71 ... Radiator, 72 ... Louver, 73 ... Upstream Exhaust pipe, 74 ... upstream exhaust purification catalyst, 75 ... intermediate exhaust pipe, 76 ... downstream exhaust catalyst, 77 ... downstream exhaust pipe, 78 ... upstream fresh air introduction pipe, 79 ... downstream fresh air introduction pipe

Claims (4)

In an internal combustion engine equipped with a blow-by gas reduction device for an internal combustion engine,
A fresh air introduction passage for introducing a part of fresh air from the intake system into the crankcase;
A blow-by gas ventilation device for an internal combustion engine, comprising a fresh air heating means for heating the fresh air introduction passage by the internal combustion engine or an auxiliary machine. 2. The blow-by of an internal combustion engine according to claim 1, wherein the air cleaner case has a double wall structure, and at least a part of the fresh air introduction passage is constituted by an outer space between the double walls of the air cleaner case. Gas ventilation device. 3. An internal combustion engine according to claim 2, wherein an exhaust system comprising an exhaust muffler, an exhaust purification catalyst, an exhaust pipe and the like is disposed adjacent to the double wall structure of the air cleaner case as a fresh air heating means. Blowby gas ventilator. The exhaust pipe has a double wall structure, an inner space of the double wall structure exhaust pipe is an exhaust passage, and at least a part of the fresh air flowing through the fresh air introduction passage is in the double wall structure exhaust pipe. The blow-by gas ventilation device for an internal combustion engine according to claim 1, wherein the blow-by gas ventilation device is configured to flow in an outer space.

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