JP2007270724A - Blow-by gas reducing device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cost by simplifying a structure, by effectively heating blow-by gas by exhaust gas of the high temperature, by constituting a part of a blow-by gas recirculating means out of an outside space of a double wall structure of an exhaust emission control catalyst or an exhaust pipe of the double wall structure arranged between an internal combustion engine and an exhaust muffler. <P>SOLUTION: The blow-by gas reducing devices 65, 64, 71 and 76 of the internal combustion engine 23 have the exhaust emission control catalyst 66 arranged between the internal combustion engine 23 and the exhaust muffler 72, and the blow-by gas recirculating means recirculating the blow-by gas generated by the internal combustion engine 23 to intake air systems 48, 52, 56 and 57. The exhaust emission control catalyst 66 is composed of the double wall structure. A part of the blow-by gas recirculating means 65, 64, 71 and 76 is composed of the outside space 71 of the double wall structure of the exhaust emission control catalyst 66. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a blow-by gas reduction device for an internal combustion engine in which a blow-by gas recirculation means for recirculating blow-by gas generated in the internal combustion engine to an intake system is constituted by an exhaust purification catalyst having a double wall structure or an outer sealed space of an exhaust pipe. It is about.

  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. When mixed in, the deterioration of the lubricating oil is promoted. As a preventive measure, a gas-liquid separation means is provided in a blow-by gas recirculation passage for recirculating the blow-by gas to the intake system, and this gas-liquid separation device is provided integrally with the exhaust pipe, and the blow-by gas is heated by the heat of the exhaust pipe. Thus, there has been a thing that prevents condensation of moisture and oil in blow-by gas (for example, Patent Document 1).

JP-A-4-246217

  However, in the thing of patent document 1, since the gas-liquid separator was attached to the exhaust pipe integrally, and the pipe was connected to the inlet and outlet of this gas-liquid separator, the blow-by gas flow path became complicated, The blow-by gas is difficult to flow smoothly, and a work for attaching a gas-liquid separator to the exhaust pipe is required, which may reduce productivity.

  The present invention eliminates such problems, and the invention according to claim 1 or 2 is directed to an exhaust purification catalyst or exhaust pipe having a double wall structure provided between an internal combustion engine and an exhaust muffler. By constructing a part of the blow-by gas recirculation means in the outer space of the double wall structure, the blow-by gas can be effectively heated with the high-temperature exhaust gas, and the structure is simplified and the cost is reduced. It aims to be able to plan.

  According to a third aspect of the present invention, an air cleaner is disposed on an upper part of an internal combustion engine mounted on a vehicle with a cylinder inclined forward, and an exhaust purification catalyst or an exhaust gas is provided between the front end of the internal combustion engine and the air cleaner. The purpose of this is to keep the blow-by gas at a high temperature by shortening the path for guiding the blow-by gas by arranging the pipe.

  Furthermore, the invention described in claim 4 aims to prevent the exhaust purification catalyst or the exhaust pipe covered with the vehicle body cover from being cooled by the blow-by gas by disposing the exhaust purification catalyst or the exhaust pipe in the vehicle body cover. It is said.

  The invention according to claim 1 is an internal combustion engine comprising an exhaust purification catalyst provided between the internal combustion engine and an exhaust muffler, and blowby gas recirculation means for recirculating blowby gas generated in the internal combustion engine to an intake system. In the blow-by gas reduction device, the exhaust purification catalyst has a double wall structure, and a part of the blow-by gas recirculation means is formed by an outer space of the double wall structure of the exhaust purification catalyst. An engine blow-by gas reduction device.

  According to a second aspect of the present invention, there is provided an internal combustion engine blow-by comprising an exhaust pipe provided between the internal combustion engine and an exhaust muffler, and blow-by gas recirculation means for recirculating blow-by gas generated in the internal combustion engine to an intake system. In the gas reduction device, the exhaust pipe has a double wall structure, and a part of the blow-by gas recirculation means is formed by an outer space of the double wall structure of the exhaust pipe. It is a gas reduction device.

  According to a third aspect of the present invention, in the blow-by gas reduction device for an internal combustion engine in which an air cleaner case is disposed above an internal combustion engine mounted on a vehicle with a cylinder inclined forward, the downstream portion of the blow-by gas recirculation means is the air cleaner. 3. The internal combustion engine according to claim 1, wherein the exhaust purification catalyst or the exhaust pipe is connected between a front end of the internal combustion engine and the air cleaner case. This is a blow-by gas reduction device.

  According to a fourth aspect of the present invention, the exhaust purification catalyst or the exhaust pipe is disposed in a space in a vehicle body cover that covers the internal combustion engine, and the blow-by of the internal combustion engine according to any one of the first to third aspects. It is a gas reduction device.

  According to the first aspect of the present invention, a part of the blow-by gas recirculation means for recirculating the blow-by gas generated in the internal combustion engine to the intake system is a double wall of the exhaust purification catalyst provided between the internal combustion engine and the exhaust muffler. By constituting the outer space of the structure, heat exchange between the high-temperature exhaust and the blow-by gas can be efficiently performed with a wide heat exchange area at a position close to the exhaust port of the internal combustion engine.

  Further, since the blow-by gas passage is configured in the outer space of the double wall structure of the exhaust purification catalyst, the shape of the blow-by gas passage is simplified, and the blow-by gas can flow smoothly into the intake system, and the exhaust purification The structure is simplified only by slightly increasing the outer diameter of the catalyst, and the entire blow-by gas reduction device can be reduced in size and cost.

  According to a second aspect of the present invention, a part of the blowby gas recirculation means for recirculating blowby gas generated in the internal combustion engine to the intake system is a double wall structure of an exhaust pipe provided between the internal combustion engine and the exhaust muffler. The heat exchange between the high-temperature exhaust and the blow-by gas can be efficiently performed with a wide heat exchange area at a position close to the exhaust port of the internal combustion engine, and the double wall structure of the exhaust pipe. Since the blow-by gas passage is configured in the outer space of the exhaust gas, the shape of the blow-by gas passage is simplified, the blow-by gas can flow smoothly into the intake system, and the outer diameter of the exhaust pipe is only slightly increased. The structure is simplified, and the entire blow-by gas reduction device can be reduced in size and cost.

  According to a third aspect of the present invention, an air cleaner case is disposed on an upper portion of an internal combustion engine mounted on a vehicle with a cylinder inclined forward, and the exhaust purification catalyst or the air cleaner between the front end portion of the internal combustion engine and the air cleaner case. By disposing the exhaust pipe, the exhaust purification catalyst or the exhaust pipe can be disposed in the middle of the blow-by gas recirculation pipe that is piped from the internal combustion engine to the air cleaner case. As a result, the blow-by gas recirculation pipe The piping is simplified, the length of the blow-by gas recirculation pipe is shortened by the length of the exhaust purification catalyst or the exhaust pipe, the heat radiation from the blow-by gas recirculation pipe is reduced, and the heat exchange efficiency of the blow-by gas is improved. improves.

  According to a fourth aspect of the present invention, when the exhaust purification catalyst and the exhaust pipe are arranged in a space in the vehicle body cover that covers the internal combustion engine in order to reduce the vehicle running resistance, a running wind is applied to the exhaust purification catalyst or the exhaust pipe. However, the exhaust purification catalyst or the exhaust pipe rises in temperature, but the low temperature blow-by gas recirculation means that exchanges heat with the exhaust purification catalyst or the exhaust pipe prevents the exhaust purification catalyst or the exhaust pipe from rising in temperature. The deterioration over time of the exhaust purification catalyst or the exhaust pipe is suppressed.

  Embodiments of the invention described in claims 1 to 4 shown in FIGS. 1 to 4 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 55 at one place on the left side of the top, and the right frame 41 by bolts 55 at two places on the right and left sides of the top part. 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 through a U-shaped communication pipe 54 in a side view. A filter element (not shown) is disposed in the purification chamber 52, the upstream end of the intake pipe 56 penetrating the air cleaner case 49 is opened in the purification chamber 52, and air is sucked into the duct chamber 51 from the intake port 53. After that, it flows into the purification chamber 52 through the communication pipe 54, and dust in the intake air is removed by a filter element (not shown) in the purification chamber 52 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, the exhaust system will be described.

  To the exhaust port (not shown) in the cylinder head 26, the inner pipe 62 of the upstream side exhaust pipe 61 having a double wall structure composed of the inner pipe 62 and the outer pipe 63 arranged concentrically on the outer periphery thereof is communicated. The upstream end of the upstream side exhaust pipe 61 is attached to the lower surface of the cylinder head 26, and the upstream side exhaust pipe 61 is bent upward around the left side of the cylinder head 26 and then bent rearwardly. The downstream end of the pipe 61 is connected to the upstream end of the exhaust purification catalyst 66, and the downstream end of the inner pipe 67 of the exhaust purification catalyst 66 is connected to the exhaust muffler 73 directed in the vehicle width direction via the downstream exhaust pipe 72. Connected to the left upstream end, the exhaust muffler 73 is directed downwardly with a tail pipe 74, and the exhaust muffler 73 protrudes rearward from the transmission case 28 as shown in FIG. The unit 28a is integrally attached via a bracket 75.

  As shown in FIG. 4, the exhaust purification catalyst 66 having a double wall structure includes an inner tube 67 having a large number of small holes, an outer tube 68 disposed concentrically on the outer side thereof, It comprises a catalyst carrying tube 69 concentrically arranged inside the inner tube 67, and a ring-shaped partition wall 70 is airtightly attached to the downstream portion between the inner tube 67 and the outer tube 68, and the 2 The inner pipe 62 of the upstream exhaust pipe 61 having the heavy wall structure is airtightly joined to the inner pipe 67 of the exhaust purification catalyst 66 having the double wall structure, and the outer pipe 63 of the upstream exhaust pipe 61 is connected to the exhaust pipe 61. The purification catalyst 66 is airtightly joined to the outer tube 68.

  In the four-stroke cycle internal combustion engine 23, a blow-by gas communication path (not shown) having a gas-liquid separation function communicating with the space in the head cover 27 from the crank chamber is formed, and the blow-by of the upstream exhaust pipe 61 and the space in the head cover 27 are formed. The gas flow path 64 is communicated with a blow-by gas upstream recirculation pipe 65, and the blow-by gas flow path 64 of the upstream exhaust pipe 61 and the blow-by gas flow path 71 of the exhaust purification catalyst 66 are communicated with each other, and the exhaust purification catalyst. The blow-by gas downstream flow pipe 76 of the exhaust purification catalyst 66 and the purification chamber 52 of the air cleaner 48 communicate with each other by a blow-by gas downstream-side return pipe 76 that passes through the outer pipe 68 of the air cleaner 66 and the air cleaner case 49 of the air cleaner 48. The 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 blow-by gas is purified by the air cleaner 48 via the blow-by gas upstream reflux pipe 65, the blow-by gas flow path 64 of the upstream exhaust pipe 61, the blow-by gas flow path 71 of the exhaust purification catalyst 66, and the blow-by gas downstream reflux pipe 76. It is discharged into the chamber 52.

  A radiator 77 and a louver 78 are disposed at the front of the power unit 22. Further, a heat shield plate 79 is attached to the rear stay 37 that supports the rear frame 39, so that the heat shield plate 79 prevents the heat from being released from the exhaust muffler 73. ing.

  Since the embodiment shown in FIGS. 1 to 4 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 starting the operation of the four-stroke cycle internal combustion engine 23, the upstream side exhaust pipe 61, the exhaust purification catalyst 66, the downstream side exhaust pipe 72, and the exhaust muffler 73 are heated to a high temperature by the high-temperature exhaust gas passing through them.

  The blow-by gas that leaks into the crank chamber of the four-stroke cycle internal combustion engine 23 and reaches the space in the head cover 27 via a blow-by gas communication passage (not shown) is blown by the upstream exhaust pipe 61 via the blow-by gas upstream reflux pipe 65. The blow-by gas that flows into the gas flow path 64 and flows into the blow-by gas flow path 64 passes through the blow-by gas flow path 71 of the exhaust purification catalyst 66, and passes through the blow-by gas downstream reflux pipe 76 to the purification chamber of the air cleaner 48. The fresh air introduced into the purification chamber 52 and sucked into the purification chamber 52 through the intake pipe 56 is sucked into the combustion chamber of the four-stroke cycle internal combustion engine 23 and combusted together with the fuel injected from the fuel injection valve 59.

  The blow-by gas passage 64 of the upstream exhaust pipe 61 and the blow-by gas passage 71 of the exhaust purification catalyst 66 are formed by connecting the inner pipe 62 of the upstream exhaust pipe 61 and the inner pipe 67 of the exhaust purification catalyst 66 having a wide heat exchange area. High temperature exhaust gas flows through the inner pipe 62 of the upstream exhaust pipe 61 and the inner pipe 67 of the exhaust purification catalyst 66. Therefore, the blow-by gas passage 64 and the exhaust purification catalyst 66 of the upstream exhaust pipe 61 are provided. As a result of heating, the blow-by gas flowing in the blow-by gas passage 71 of the filter element in the purification chamber 52 of the air cleaner 48 and the air cleaner case 49 of the air cleaner 48, the intake pipe 56, and the throttle body 57 are caused by condensation of moisture and oil. Adhesion to the inner surface is reduced, and the gas can smoothly flow into the combustion chamber of the four-stroke cycle internal combustion engine 23.

  Further, in the upstream side exhaust pipe 61 and the exhaust purification catalyst 66, the inner pipe 62 and the outer pipe 63 and the inner pipe 67 and the outer pipe 68 are respectively concentric and have a simple flow path shape and a flow path longitudinal direction. Since the blow-by gas channel 64 and the blow-by gas channel 71 having a uniform cross-sectional area are formed, the blow-by gas can flow into the purification chamber 52 of the air cleaner 48 without receiving a large resistance.

  Further, since the blow-by gas flow path 64 and the blow-by gas flow path 71 are configured by the upstream side exhaust pipe 61 and the exhaust purification catalyst 66 of the double wall structure, respectively, the structure is simple, low cost, light weight and compact blow-by. A gas reduction device is obtained.

  Furthermore, the cylinder head 26 of the four-stroke cycle internal combustion engine 23 is inclined forward of the three-wheeled vehicle 1, and extends from the cylinder head 26 of the four-stroke cycle internal combustion engine 23 to the air cleaner 48 disposed above the rear portion of the power unit 22. The blow-by gas passages formed are a blow-by gas upstream reflux pipe 65 that connects the head cover 27 and the outer pipe 63 of the upstream exhaust pipe 61, a blow-by gas flow path 64 of the upstream exhaust pipe 61, and an exhaust purification catalyst 66. The blow-by gas flow path 71, and the blow-by gas downstream recirculation pipe 76 connecting the outer pipe 68 of the exhaust purification catalyst 66 and the air cleaner case 49 of the air cleaner 48, most of this blow-by gas passage is heated internally. On the blow-by gas occupied by the blow-by gas flow path 64 of the upstream exhaust pipe 61 and the blow-by gas flow path 71 of the exhaust purification catalyst 66 and cooled by the outside air Since the flow-side reflux pipe 65 and the blow-by gas downstream-side reflux pipe 76 are short, the blow-by gas that passes through the blow-by gas passage and flows into the purification chamber 52 of the air cleaner 48 is maintained at a high temperature.

  In addition, the outer pipe 63 of the upstream side exhaust pipe 61 and the outer pipe 68 of the exhaust purification catalyst 66 are covered with the rear body cover 45 and are not subjected to traveling wind, and as a result, the temperature tends to be high without being cooled. The blow-by gas that passes through the blow-by gas passage 64 surrounded by the inner pipe 62 and the outer pipe 63 of the side exhaust pipe 61 and the blow-by gas passage 71 surrounded by the inner pipe 67 and the outer pipe 68 of the exhaust purification catalyst 66 Since the outer pipe 63 of the upstream exhaust pipe 61 and the outer pipe 68 of the exhaust purification catalyst 66 are cooled to a low temperature, the deterioration over time due to the heat of the outer pipe 63 of the upstream exhaust pipe 61 and the outer pipe 68 of the exhaust purification catalyst 66 Is suppressed.

  In the embodiment described above, the upstream exhaust pipe 61 and the exhaust purification catalyst 66 are provided with 64 and the blowby gas passage 71, respectively, but only one of them may form a blowby gas passage.

[BRIEF DESCRIPTION OF THE DRAWINGS] It is a side view of the three-wheeled vehicle carrying the internal combustion engine provided with one Embodiment of the blowby gas reduction apparatus based on this invention. It is a principal part top view of FIG. It is a principal part side view of FIG. FIG. 2 is a longitudinal side view of the exhaust purification catalyst of FIG. 1.

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 ... Inlet, 54 ... Communication pipe, 55 ... Bolt, 56 ... Intake pipe, 57 ... Throttle body, 58 ... Throttle cable, 59 ... Fuel injection Valve, 60 ... Fuel hose, 61 ... Upstream exhaust pipe, 62 ... Inner pipe, 63 ... Outer pipe, 64 ... Blowby gas flow path, 65 ... Blowby gas upstream reflux pipe, 66 ... Exhaust gas purification catalyst, 67 ... Inner pipe , 68 ... outer pipe, 69 ... catalyst support pipe, 70 ... partition wall, 71 ... blow-by gas flow path, 72 ... downstream exhaust pipe, 73 ... exhaust muff , 74 ... tail pipe, 75 ... bracket, 76 ... blow-by gas downstream return pipe, 77 ... radiator, 78 ... louver, 79 ... heat shield.

Claims (4)

In a blow-by gas reduction device for an internal combustion engine, comprising an exhaust purification catalyst provided between the internal combustion engine and an exhaust muffler, and blow-by gas recirculation means for recirculating blow-by gas generated in the internal combustion engine to an intake system,
The exhaust purification catalyst has a double wall structure,
A blow-by gas reduction device for an internal combustion engine, wherein a part of the blow-by gas recirculation means is constituted by an outer space of a double wall structure of the exhaust purification catalyst. In a blow-by gas reduction device for an internal combustion engine, comprising an exhaust pipe provided between the internal combustion engine and an exhaust muffler, and blow-by gas recirculation means for recirculating blow-by gas generated in the internal combustion engine to an intake system.
The exhaust pipe has a double wall structure,
A blow-by gas reduction device for an internal combustion engine, characterized in that a part of the blow-by gas recirculation means is constituted by an outer space of a double wall structure of the exhaust pipe. In the blow-by gas reduction device for an internal combustion engine in which an air cleaner case is disposed on the upper part of the internal combustion engine mounted on the vehicle with the cylinder inclined forward,
The downstream portion of the blow-by gas recirculation means is connected to the air cleaner case, and the exhaust purification catalyst or the exhaust pipe is disposed between a front end portion of the internal combustion engine and the air cleaner case. The blow-by gas reduction device for an internal combustion engine according to claim 1 or 2. 4. The blow-by gas reduction device for an internal combustion engine according to claim 1, wherein the exhaust purification catalyst or the exhaust pipe is disposed in a space in a vehicle body cover that covers the internal combustion engine.

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