JP4523537B2 - Engine exhaust purification system for small vehicles - Google Patents

Description

In the present invention, an exhaust port is provided on a lower side surface of a cylinder head included in an engine constituting a part of a power unit, and an exhaust pipe having an upstream end connected to the exhaust port extends downward from the cylinder head and extends rearward. The present invention relates to an exhaust emission control device for an engine in a small vehicle in which a hose that is discharged and guides secondary air is connected to the exhaust port via a metal connecting pipe.

A metal connection pipe is provided in the exhaust pipe that guides exhaust gas discharged from the engine of the power unit that is swingably supported on the body frame of the scooter, and a rubber hose that guides secondary air is connected to the connection pipe. For example, Japanese Patent Application Laid-Open No. H10-228473 is known.
Japanese Patent No. 3127527

  By the way, the reason for using the hose to guide the secondary air from the air cleaner is to ensure the degree of freedom in arrangement, but the temperature at the upstream end of the connecting pipe needs to be lowered to a temperature at which the hose can be connected. is there. Therefore, if the connecting pipe is bent to adjust the length of the connecting pipe and sufficiently radiate heat from the connecting pipe, the temperature at the upstream end of the connecting pipe can be lowered to a temperature at which the hose can be connected. However, if the connecting pipe is bent and lengthened in this way, not only an extra space is required for arranging the elongated connecting pipe, but also when an air cleaner is arranged above the connecting pipe, There is a problem that the air cleaner inhales the air warmed by the air.

The present invention has been made in view of such circumstances, and avoids the occurrence of a problem in the arrangement of the long connecting pipe, and the air cleaner sucks in the warmed air even if the air cleaner is above the power unit. An object of the present invention is to provide an exhaust emission control device for an engine in a small vehicle that can be prevented.

In order to achieve the above object, according to a first aspect of the present invention, there is provided an exhaust pipe in which an exhaust port is provided on a lower side surface of a cylinder head provided in an engine constituting a part of a power unit and an upstream end is connected to the exhaust port However , after extending obliquely downward from the cylinder head toward one side in the vehicle width direction , the hose that extends rearward through the lower front portion of the power unit and leads the secondary air is connected via a metal connecting pipe. An exhaust purification device for an engine in a small vehicle connected to the exhaust port and having an air cleaner disposed above the power unit ,
The connection pipe is composed of an upstream portion disposed on the other side of the power unit in the vehicle width direction, and a downstream portion connected to the upstream portion, and a part of the downstream portion of the connection pipe. Includes a first portion extending from the other side in the vehicle width direction to one side and approaching the exhaust pipe, a second portion connected to the first portion and reversed near the exhaust pipe, and a vehicle width connected to the second portion. A U-shaped portion bent in a substantially U shape is formed by the third portion extending in the other direction , and the U-shaped portion is disposed between the lower side surface of the cylinder head and the exhaust pipe in a side view. It is characterized by that.

  According to a second aspect of the invention, in addition to the configuration of the first aspect of the invention, a part of the U-shaped portion is disposed between a lower side surface of the cylinder head and the exhaust pipe. .

According to a third aspect of the invention, in addition to the configuration of the first or second aspect of the invention, a radiator through which engine coolant flows is disposed on one side of the power unit in the vehicle width direction. To do.

  According to the first aspect of the present invention, it is possible to adjust the length of the connecting pipe by forming the U-shaped part in a part of the connecting pipe, and the U-shaped part is a cylinder head in a side view. Since the space between the lower side surface and the exhaust pipe of the cylinder head is disposed, the elongated connection pipe can be disposed by effectively utilizing the empty space between the lower side surface of the cylinder head and the exhaust pipe. Moreover, the U-shaped part is disposed below the cylinder head, and even if an air cleaner is disposed above the power unit, the cylinder head blocks the heat from the U-shaped part from affecting the air cleaner side. It is possible to prevent the air cleaner from sucking warmed air.

  According to the invention described in claim 2, the U-shaped portion of the connecting pipe is set sufficiently long to sufficiently lower the temperature at the upstream end of the connecting pipe, and a part of the U-shaped portion is removed from the exhaust pipe. By heating with this heat release, the heated secondary air can be supplied to the exhaust port to improve the exhaust gas purification performance.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.

  1 to 16 show an embodiment of the present invention. FIG. 1 is a side view of a scooter type vehicle, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. 4 is an enlarged view of the main part of FIG. 2, FIG. 5 is a side view corresponding to FIG. 4 with the radiator cover removed, FIG. 6 is a perspective view of the exhaust emission control device, and FIG. FIG. 8 is an enlarged cross-sectional view of the vicinity of the driven pulley of the continuously variable transmission, FIG. 9 is an enlarged left side view of the air cleaner, FIG. 10 is a view taken along arrow 10 in FIG. 9, and FIG. 11 is an enlarged sectional view taken along line 11-11, FIG. 12 is a sectional view taken along line 12-12 in FIG. 11, FIG. 13 is a sectional view taken along line 13-13 in FIG. 4, and FIG. FIG. 15 is a cross-sectional view showing the radiator upright to show the water circulation path, and FIG. 15 is a part of the fan cover as seen from the direction of arrows 15-15 in FIG. Away side view, FIG. 16 is a 16 arrow view of FIG. 15.

  In the following description, front and rear and left and right are based on the traveling direction of the scooter type vehicle.

  First, in FIG. 1, a body frame 21 of a scooter-type vehicle that is a motorcycle extends from a head pipe 25 that supports a front fork 24 that pivotally supports a front wheel WF so as to be steerable and supports a step floor 26. The rear frame 22 includes a rear frame 23 that extends rearward from the rear portion of the front frame 22 and supports the occupant seat 27. A power unit P that pivotally supports the rear wheel WR and drives the rear wheel WR is suspended on the vehicle body frame 21 via a suspension link 28 so as to be swingable up and down, and the power unit P is interposed between the rear frame 23 and the power unit P. A rear cushion 29 is provided for buffering the vertical swinging.

  2 and 3, the engine E of the power unit P includes a crankcase 31, a cylinder block 32 coupled to the front end of the crankcase 31 in a forward inclined posture, and a cylinder head 33 coupled to the front end of the cylinder block 32. Are provided as the engine body 30.

  A crankshaft 35 having an axis extending in the left-right direction is rotatably supported by a crankcase 31, and a piston 37 slidably fitted into a cylinder bore 36 included in the cylinder block 32 is connected via a connecting rod 38 and a crankpin 39. A spark plug 40 is connected to the crankshaft 35, a spark plug 40 is attached to the cylinder head 33, a valve mechanism 41 including a camshaft 65 provided with a decompression means 34 is provided, and a head cover 42 covering the valve mechanism 41 is provided. It is coupled to the front end of the cylinder head 33.

  The crankcase 31 is formed by joining left and right case halves 31L and 31R that are divided into left and right on a vertical plane including the axis of the cylinder bore 36, and the crankshaft 35 is composed of left and right case halves 31L. , 31R, and ball bearings 43, 44 are interposed between the case halves 31L, 31R and the crankshaft 35, respectively.

4 and 5 together, an air cleaner 45 is disposed above the power unit P, and the air cleaner 45 is connected to an intake port 46 (see FIG. 14) provided on the upper side surface of the cylinder head 33. The carburetor 47 and the intake pipe 48 are connected. An exhaust port 49 is provided on the lower side surface of the cylinder head 33, and an exhaust pipe 50 having an upstream end connected to the exhaust port 49 extends obliquely downward from the cylinder head 33 toward one side in the vehicle width direction. After that, the downstream end of the exhaust pipe 50 is connected to an exhaust muffler 51 that extends rearward through the lower front part of the power unit P and is disposed on the right side of the rear wheel WR.

  Referring also to FIG. 6, the exhaust gas discharged from the exhaust port 49 is purified by an exhaust purification device 54 that introduces secondary air into the exhaust gas, and the exhaust purification device 54 is directed forward. A suction pipe 55 that is open and supported by the rear frame 23; a secondary air cleaner 58 that is connected to the suction pipe 55 through a conduit 57; and according to the intake negative pressure. A secondary air control valve 59 connected to the secondary air cleaner 58 so as to control the air flow rate, and a secondary air control valve that allows only the flow from the secondary air control valve 59 side. 59, a reed valve 60 connected to 59, a rubber hose 61 whose upstream end is connected to the reed valve 60 so as to guide air from the reed valve 60, and a metal made of a metal whose upstream end is connected to the hose 61. And a connecting pipe 62, the secondary air control valve 59 the negative pressure taking-out pipe 63 for guiding the intake negative pressure is connected to the intake pipe 48.

7, the connecting pipe 62, an upstream-side portion disposed in the vehicle width direction the other side portion of the power unit P, is more configuration and a downstream portion communicating with the upstream portion, downstream of the connection pipe 62 A part of the side part includes a first part extending from the other side in the vehicle width direction to one side and approaching the exhaust pipe 50, a second part connected to the first part and inverted near the exhaust pipe 50, A U-shaped portion 62a that is bent in a substantially U shape is formed by a third portion that is connected to the second portion and extends to the other side in the vehicle width direction , and this U-shaped portion 62a is a cylinder head in a side view. 33 is disposed between the lower side surface of 33 and the exhaust pipe 50. Moreover the connection tube 62, the downstream end communicating with the third portion is connected to the cylinder head 33 so as to communicate the passage 69 provided in the sheet cylinder head 33 so as to communicate the exhaust port 49. In addition, the U-shaped portion 62a is positioned so that a part of the U-shaped portion 62a (that is, the second portion) is located between the lower side surface of the cylinder head 33 and the exhaust pipe 50, as clearly shown in FIG. Has been placed.

  In FIG. 3 again, a drive sprocket 64 is fixed to the crankshaft 35 outside the ball bearing 43 interposed between the left case half 31L and the crankshaft 35 in the crankcase 31, and the valve mechanism 41 is A driven sprocket 66 is fixed to the camshaft 65 provided, and an endless timing chain 67 is wound around the drive sprocket 64 and the driven sprocket 66. Thus, the left case half 31L, the cylinder block 32, and the cylinder head 33 are provided with a chain passage 68 for running the timing chain 67.

  In addition, a transmission case 71 that houses the transmission device T that constitutes the power unit P in cooperation with the engine E is connected to the left case half 31L so as to extend to the left side of the rear wheel WR.

  The transmission case 71 extends from the outer surface of the cylinder block 32 along the axis of the crankshaft 35 and extends rearward so as to be integrated with the left case half 31L of the crankcase 31. And an outer case 73 coupled to the inner case 72 from the left side, and a reduction gear case 74 coupled to the right rear portion of the inner case 72. A dry space is formed between the inner case 72 and the outer case 73. A transmission chamber 75 is formed, and a reduction gear chamber 76 isolated from the transmission chamber 75 is formed between the inner case 72 and the reduction gear case 74 so as to store oil therein, and the axle of the rear wheel WR. 77 is rotatably supported by the rear portion of the inner case 72 and the reduction gear case 74 in the transmission case 71.

  The transmission device T includes a V-belt type continuously variable transmission 78 housed in a transmission chamber 75, and a gear reduction provided between the continuously variable transmission 78 and the axle 77 and housed in the reduction gear chamber 76. It consists of a mechanism 79.

  Outside the drive sprocket 64, the crankshaft 35 penetrates the left case half 31L in a liquid-tight and rotatable manner and enters the transmission chamber 75, and the continuously variable transmission 78 includes a transmission chamber. A drive pulley 80 mounted on one end of the crankshaft 35 within 75 and a driven shaft 81 having an axis parallel to the crankshaft 35 and rotatably supported by the transmission case 71 are mounted via a centrifugal clutch 82. Driven pulley 83, and a drive pulley 80 and an endless V-belt 84 wound around the driven pulley 83.

  The driving pulley 80 is a fixed pulley half 85 fixed to one end of the crankshaft 35, and a movable pulley that is slidably mounted on the crankshaft 35 on the axially inward side of the fixed pulley half 85. The V belt 84 is wound around a V-shaped annular groove 87 formed between the pulley halves 85 and 86. A ramp plate 88 is fixed to the crankshaft 35 on the back side of the movable pulley half 86, and a plurality of weight rollers 89 are accommodated in a floating state between the movable pulley half 86 and the ramp plate 88. Thus, when the rotational speed of the crankshaft 35 increases, the weight rollers 89 receiving the centrifugal force move radially outward of the crankshaft 35 to bring the movable pulley half 86 close to the fixed pulley half 85. As a result, the contact radius of the V-belt 84 to both pulley halves 85 and 86 is increased.

  The driven shaft 81 penetrates the inner case 72 in a liquid-tight and rotatable manner. One end of the driven shaft 81 is rotatably supported by the outer case 73 via a ball bearing 90, and the other end of the driven shaft 81. The part is rotatably supported on the reduction gear case 74 via a ball bearing 91, and the intermediate part of the driven shaft 81 is rotatably supported on the inner case 72 via a ball bearing 92.

  In FIG. 8, a cylindrical bush 93 is attached to one end of the driven shaft 81. The bush 93 is made of a porous sintered alloy and impregnated with oil. In addition, the bush 93 is press-fitted into the inner ring 90 a of the ball bearing 90, and the outer ring 90 b of the ball bearing 90 is fitted and fixed to a bearing housing 73 a provided in the outer case 73.

  On the other hand, the driven pulley 83 is slidably fitted to the inner cylinder 96 that coaxially surrounds the driven shaft 81 so as to allow relative rotation, and to allow relative rotation around the axis and relative movement in the axial direction. A caulking outer cylinder 97, a fixed pulley half 98 fixed to the inner cylinder 96, a movable pulley half 99 fixed to the outer cylinder 97 opposite to the fixed pulley half 98, and the movable pulley half 99 And a torque cam mechanism 100 provided between the inner cylinder 96 and the outer cylinder 97 so that an axial component force is applied between the pulley halves 98 and 99 in accordance with the relative rotational phase difference between the fixed pulley halves 98. And a coil spring 101 that elastically urges the movable pulley half 99 toward the fixed pulley half 98 side, and a V-shaped annular groove formed between the fixed pulley half 98 and the movable pulley half 99. 102 to V bell 84 is wound. Between the inner cylinder 96 and the driven shaft 81, there is provided a centrifugal clutch 82 that enters a power transmission state as the engine speed exceeds the set speed.

  Thus, the distance between the fixed pulley half 98 and the movable pulley half 99 in the driven pulley 83 is such that the axial force generated by the torque cam mechanism 100, the axial elastic force generated by the coil spring 101, and the fixed pulley half. By determining the balance with the force from the V-belt 84 acting in the direction of spacing the body 98 and the movable pulley half 99, the movable pulley half 86 is brought close to the fixed pulley half 85 in the drive pulley 80. When the winding radius of the V belt 84 around the driving pulley 80 increases, the winding radius of the V belt 84 around the driven pulley 83 decreases.

  The gear reduction mechanism 79 housed in the reduction gear chamber 76 is rotatably supported by the inner case 72 and the reduction gear case 74 in parallel with the first gear 103 provided on the driven shaft 81, the driven shaft 81 and the axle 77. A second gear 104 provided on the intermediate shaft 107 and meshed with the first gear 103, a third gear 105 provided on the intermediate shaft 107, and a fourth gear 106 provided on the axle 77 meshed with the third gear 105. It consists of.

  A kick shaft 108 is rotatably supported on the outer case 73 of the transmission case 71, and a kick pedal (not shown) is provided on the outer end of the kick shaft 108. A kick type starter 109 is provided between the kick shaft 108 and the crankshaft 35 on the inner surface side of the outer case 73 so that the power of the kick shaft 108 can be transmitted to the crankshaft 35 according to the depression operation of the kick pedal. It is done.

  A plurality of radially arranged fins 110 are projected on the outer surface of the fixed pulley half 85 in the drive pulley 80, and the fixed pulley half 85 also functions as a blower fan. On the other hand, a connecting pipe part 111 is provided at the front part of the outer case 73, and a duct (not shown) connected to the connecting pipe part 111 extends upward from the connecting pipe part 111. Thus, the air in the transmission chamber 75 is discharged to the outside through the connection pipe portion 111 and the duct in accordance with the rotation of the fixed pulley half 85 that functions as a blower fan.

  By the way, a part of the first to fourth gears 103 to 106 constituting the gear reduction mechanism 79 is immersed in the lower part of the reduction gear chamber 76 which is formed in the transmission case 71 and accommodates the gear reduction mechanism 79 to achieve lubrication. Oil to be stored is stored, and in order to discharge the breather gas to the outside at the time of thermal expansion of the gas in the speed reducer chamber 76 as the oil temperature rises, the lead-out pipe portion 113 leading to the upper part in the speed reducer chamber 76 is transmitted. One end of the breather tube 114 is connected to the lead-out pipe portion 113 provided at the upper portion of the gear reduction case 74 in the case 71. That is, one end of the breather tube 114 is connected to the gear reduction case 74 through the upper part in the reduction gear chamber 76.

  The breather tube 114 extends to the front side of the vehicle body frame 21 while tilting slightly upward along the upper portion of the transmission case 71, and an intermediate portion of the breather tube 114 is disposed on the upper portion of the transmission case 71. A clamp member 115 is attached to hold. The other end of the breather tube 114 rises upward at a portion corresponding to the air cleaner 45 and opens upward.

  9 and 10, the cleaner case 116 of the air cleaner 45 includes a front case member 117 and a rear case member 118, which are coupled to each other along the width direction of the vehicle body frame 21, and the front and rear cases. An element support frame 121 that holds a cleaner element 120 that divides the inside of the cleaner case 116 into an unpurified chamber and a purified chamber, and includes a front member and a rear case member 117. 118.

  A suction chamber 122 is formed between the front and rear case members 117 and 118 and the cover member 119, and the front end of the suction chamber 122 opens forward as a suction port 122a. A duct 123 that connects the rear portion of the suction chamber 122 to the unpurified chamber is attached to the side wall of the rear case member 118 on the cover member 119 side, and the upstream end of the connecting pipe 124 connected to the vaporizer 47 is located in the purifier chamber. It is rushed.

  11 and 12, the cover member 119 in the cleaner case 116 is integrally provided with a breather outlet cover 119a so as to cover the other end of the breather tube 114 from the outside. The other end of the breather tube 114 is held by the breather outlet cover 119a.

  That is, the inner surface of the breather outlet cover 119a is integrally provided with a holding cylinder part 125 having a rectangular cross-sectional shape and closed at the upper end so as to extend vertically, and the other end of the breather tube 114 is disposed inside the holding cylinder part 125. Inserted into. Moreover, on the inner surface of the holding cylinder portion 125, four protrusions 126, 126... Projectingly come into contact with each other at four locations spaced at equal intervals in the circumferential direction of the outer surface of the breather tube 114. By inserting the other end portion into the holding cylinder portion 125, the other end portion of the breather tube 114 is elastically held. Further, a substantially U-shaped holding groove 127 for inserting and holding the breather tube 114 in front of a portion inserted into the holding cylinder portion 125 is provided in the support wall portion 128 provided continuously with the holding cylinder portion 125. The other end portion of the breather tube 114 held by the holding groove 127 is inserted and held in the holding cylinder portion 125 while being bent in a substantially L shape.

  Referring also to FIG. 13, a support cylinder portion 129 that projects endlessly around the crankshaft 35 is integrally provided on the right case half 31 </ b> R of the crankcase 31, and is formed outside the support cylinder portion 129. A right cover 131 that forms a transmission chamber 130 is coupled to the end of the right case half 31R, and the crankshaft 35 penetrates the right cover 131 in a liquid-tight and rotatable manner.

  A generator 134 including a stator 132 fixed to the right cover 131 and an outer rotor 133 fixed to the crankshaft 35 so as to surround the stator 132 is disposed outside the right cover 131. A fan 135 is fixed to the crankshaft 35 outside the generator 134. The fan 135 is configured such that a plurality of blades 135b, 135b,... Are integrally provided on an outer peripheral portion of a base portion 135a fastened to the outer rotor 133 of the generator 134 by a plurality of bolts 156.

  Referring also to FIG. 14, an oil pump 112 is attached to the right case half 31R in the transmission chamber 130, and the pump housing 136 of the oil pump 112 contacts the right case half 31R. An end plate 137 that is in contact with the pump cover 138 that is fastened to the right case half 31R with the end plate 137 interposed between the right case half 31R and the pump housing 136 includes The inner rotor 139 and the outer rotor 140 are accommodated. A pump shaft 141 connected to the inner rotor 139 so as not to rotate relative to the inner rotor 139 is rotatably supported by the pump cover 138 and the right cover 131.

  A driven gear 142 is mounted on the pump shaft 141 through a pin 143 so as not to rotate relative to the pump shaft 141, and a driving gear 144 that meshes with the driven gear 142 is fixed to the crankshaft 35 by press fitting or the like. A driving sprocket 145 is fixed to the pump shaft 141 by press fitting or the like. The driven sprocket 146 is mounted on the pump shaft 149 of the cooling water pump 148 by a pin 150 so as not to be relatively rotatable. A chain 147 is wound around.

  The pump housing 151 of the cooling water pump 148 is formed by fastening a pump cover 153 to a housing main portion 152 formed integrally with the right cover 131, and in a pump chamber 155 formed by the pump housing 151. The arranged impeller 154 is fixed to the pump shaft 141 that is supported in a liquid-tight and rotatable manner by the housing main portion 152.

  Meanwhile, a cooling water jacket 158 is formed in the cylinder block 32 and the cylinder head 33 of the engine body 30, and a discharge port 159 provided in the housing main portion 152 of the pump housing 151 is provided in the cylinder block 32. The cooling water jacket 158 is connected to the inlet 158 a via the connection pipe 160. Thus, one end of the connecting pipe 160 is fitted in a liquid-tight manner to the inlet 158 a of the cooling water jacket 158, and the right cover 131 integrally having the housing main part 152 is connected to the right case half of the crankcase 31. When fastening to 31R, the other end of the connecting pipe 160 is fitted into the discharge port 159 in a liquid-tight manner.

  As shown in FIG. 13, the fan 135 fixed to the crankshaft 35 is surrounded by a fan cover 161 fastened to the right case half 31 </ b> R of the crankcase 31, and is cooled by cooling air sucked by the fan 135. A radiator 162 disposed outside the fan 135 so as to be cooled is attached to the fan cover 161 with a plurality of bolts 163.

  The radiator 162 is formed by connecting an upper tank 164 and a lower tank 165 arranged in parallel in the horizontal direction by a radiator core 166, and has a circular louver 167 substantially corresponding to the outer end rotation locus of the fan 135. A radiator cover 168 that covers the radiator 162 from the outside is attached to the fan cover 161 with the louver 167 facing the radiator core 166.

  Further, at the lower part of the radiator cover 168, at least a part of the exhaust pipe 50 extending downward from the cylinder head 33 and extending rearwardly through the lower portion of the engine body 30 in the power unit P, in this embodiment the upper part of the exhaust pipe 50 is provided. An exhaust pipe cover 168a that covers the half from the outside is provided integrally.

  By the way, the air sucked through the louver 167 and the radiator core 166 by the rotation of the fan 135 forms a scroll flow in the fan cover 161. As shown in FIG. Is formed such that a wind exhaust port 170 arranged on a plane orthogonal to the scroll flow indicated by an arrow 169 opens obliquely forward and downward. By forming the air exhaust port 170 in this manner, the scroll flow in the fan cover 161 is rectified without being disturbed, thereby suppressing wind noise generated when air flows through the louver 167. it can.

  Further, an upward force along the outer periphery of the fan cover 161 acts on the air flow discharged from the air exhaust port 170, but an air cleaner 45 is disposed above the fan cover 161. The air cleaner 45 has a suction port 122a that opens forward. Therefore, there is a possibility that the air cleaner 45 may inhale the air that has passed through the radiator core 166 and has been warmed. However, in order to prevent air that has risen along the outer periphery of the fan cover 161 from the exhaust port 170 toward the air cleaner 45 side above the exhaust port 170 and as shown in FIG. For example, two shielding walls 171 and 172 spaced apart in the vertical direction are provided so as to face the above-described rising air flow. In FIG. 16, in order to clearly show the shielding walls 171 and 172, the shielding walls 171 and 172 are subjected to a shading process.

  With such shielding walls 171 and 172, the air cleaner 45 can be warmed and sucked in fresh air that has not been warmed without sucking air discharged from the fan cover 161.

  A thermostat 175 for controlling the flow rate of the cooling water discharged from the cooling water jacket 158 to the radiator 162 is disposed on the side of the cylinder block 32 in the engine body 30, and this thermostat 175 is provided with a cooling water pump. It is attached to the pump cover 153 of the pump housing 151 at 148 so as to communicate with the suction port 176 provided in the pump cover 153.

  In addition, the thermostat 175 is disposed in front of the radiator 162 so as to be substantially at the same position as the radiator core 166 of the radiator 162 along the width direction of the vehicle body frame 21, and the thermostat 175 is disposed on the radiator 162. At the same time, it is covered with a radiator cover 168 from the outside.

  As shown in FIG. 14, a connection pipe 177 leading to the outlet 158 b of the cooling water jacket 158 is provided on the right side surface of the cylinder head 33 in the vicinity of the intake port 46, and the connection pipe 177 has a cooling water hose 178. Are connected at their upstream ends. Further, the downstream end of the cooling water hose 178 is connected to a T-shaped joint 179, and the cooling water hose 180 whose upstream end is connected to the joint 179 is connected to the upper tank 164 in the radiator 162. Further, the joint 179 and the thermostat 175 are connected by a bypass cooling water hose 181 that guides the cooling water from the cooling water jacket 158 to the thermostat 175 side. Connected.

  Next, the operation of this embodiment will be described. One end portion of the driven shaft 81 that is a component of the transmission T that constitutes the power unit P together with the engine E is attached to the outer case 73 facing the transmission chamber 75 that is a dry space. It is made of a porous sintered alloy, impregnated with oil, and rotatably supported through a cylindrical bush 93 and a ball bearing 90 that are mounted on the driven shaft 81. The bush 93 is supported by the ball bearing 90. The inner ring 90a is press-fitted.

  Therefore, it is not necessary to perform troublesome processing on the bush 93 for lubrication, the lubricity of the one end support portion of the driven shaft 81 is improved, and long life and low cost without using special bearing materials or lubricating oil. A simple support structure can be realized. Moreover, since the bush 93 is interposed between the ball bearing 90 and the driven shaft 81, the wear of the driven shaft 81 due to friction can be reduced as compared with the case where the driven shaft 81 is directly fitted to the ball bearing 90. Since this can be easily replaced when the bushing 93 is worn, the cost is also reduced in this respect.

  The outer ring 90 b of the ball bearing 90 is fitted and fixed to the bearing housing 73 a of the outer case 73, and a bush 93 is interposed between the driven shaft 81 and the ball bearing 90 so that the outer surface of the ball bearing 90 is outside. The diameter can be made relatively large, and the surface pressure applied to the outer case 73 to which the ball bearing 90 is fitted and fixed can be reduced.

  By the way, the transmission device T that constitutes the power unit P together with the engine E includes a continuously variable transmission 78 that changes the output of the engine E, and a gear reduction mechanism that reduces the output of the continuously variable transmission 78 and transmits it to the rear wheels WR. 79, in a transmission case 71 connected to the engine body 30 and extending to the side of the rear wheel WR, a transmission chamber 75 for housing the continuously variable transmission 78, and a gear reduction mechanism. 79, and a reduction gear chamber 76 in which oil is stored is formed in the lower portion. The reduction gear chamber 76 is provided above the reduction gear case 74 in the transmission case 71 so as to communicate with the upper portion in the reduction gear chamber 76. A breather tube 114 having one end connected to the lead-out pipe portion 113 is extended forward along the upper portion of the transmission case 71, and the other end of the breather tube 114 is opened upward. That.

  Therefore, it is possible to surely prevent the muddy water repelled as the scooter type vehicle travels from entering the breather tube 114, and the breather tube 114 extends forward along the transmission case 71. The passage in the breather tube 114 can be lengthened to promote oil gravity separation, and oil can be prevented from adhering to and depositing on the other end opening of the breather tube 114.

  An air cleaner 45 is disposed above the power unit P, and the other end of the breather tube 114 is covered with a breather outlet cover 119a provided on the cleaner case 116 of the air cleaner 45 from the outside. Since it is held by the outlet cover 119a, a dedicated part for holding the other end of the breather tube 114 is not required, the number of parts can be reduced, and the other end of the breather tube 114 is covered from the outside. Thus, the appearance can be improved.

  Further, an exhaust port 49 is provided on the lower side surface of the cylinder head 33 provided in the engine E, and an exhaust pipe 50 having an upstream end connected to the exhaust port 49 extends downward from the cylinder head 33 and passes below the engine body 30 to the rear. The hose 61 for guiding the secondary air for purifying the exhaust gas is connected to the exhaust port 49 via the metal connecting pipe 62, but a part of the connecting pipe 62 is substantially omitted. A U-shaped portion 62a bent in a U-shape is formed, and the U-shaped portion 62a is disposed between the lower side surface of the cylinder head 33 and the exhaust pipe 50 in a side view.

  For this reason, it is possible to adjust the length of the connection pipe 62 by forming the U-shaped portion 62a, and the connection pipe 62 is made long by effectively utilizing the empty space between the lower side surface of the cylinder head 33 and the exhaust pipe 50. Can be arranged. Moreover, the U-shaped portion 62a is disposed below the cylinder head 33, and even if the air cleaner 45 is disposed above the power unit P as in this embodiment, heat dissipation from the U-shaped portion 62a is performed. The cylinder head 33 can block the air cleaner 45 from affecting the air cleaner 45, and the air cleaner 45 can be prevented from sucking warmed air.

  Further, since a part of the U-shaped portion 62a is disposed between the cylinder head 33 and the exhaust pipe 50, the U-shaped portion 62a in the connecting pipe 62 is set sufficiently long so that the temperature at the upstream end of the connecting pipe 62 is sufficiently high. In addition, by heating a part of the U-shaped portion 62a by heat radiation from the exhaust pipe 50, the heated secondary air can be supplied to the exhaust port 49 to improve the exhaust gas purification performance.

  Further, a radiator 162 and a thermostat 175 for controlling the flow rate of the cooling water discharged from the cooling water jacket 158 to the radiator 162 are disposed on the right side of the engine body 30 having the cooling water jacket 158. Since the radiator core 165 provided in the radiator 162 along the width direction of the vehicle body frame 21 and the thermostat 175 arranged at substantially the same position are covered from the outside by the common radiator cover 168, the radiator 162 and the thermostat 175 are covered. In covering from the outside, the number of parts and assembly man-hours can be reduced.

  An exhaust pipe 50 connected to the cylinder head 33 extends rearwardly through the lower part of the engine body 30, and the radiator cover 168 has an exhaust pipe cover portion that covers at least a part of the exhaust pipe 50 from the outside. Since 168a is integrally provided, in addition to the radiator 162 and the thermostat 175, at least a part of the exhaust pipe 50 below the engine main body 30 is covered from the outside by the radiator cover 168 to further reduce the number of parts. Can do.

  Further, a cooling water pump 148 is attached to the engine body 30, and a thermostat 175 is attached to a pump cover 153 in the pump housing 151 of the cooling water pump 148, so that it is substantially the same as the radiator core 166 along the width direction of the vehicle body frame 21. The cooling water pump 148 can be arranged by effectively using the space between the thermostat 175 and the engine main body 30 at the same position, and the layout around the engine E can be made compact.

  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. It is.

Side view of scooter type vehicle 1 is an enlarged view of the main part of FIG. 3-3 sectional view of FIG. 2 is an enlarged view of the main part of FIG. Side view corresponding to FIG. 4 with the radiator cover removed Perspective view of exhaust purification device 7 arrow view of FIG. Cross section showing the vicinity of the driven pulley of a continuously variable transmission Expanded left side view of air cleaner FIG. 10 arrow 10 view 11-11 enlarged sectional view of FIG. 12-12 sectional view of FIG. Sectional view along line 13-13 in FIG. Sectional view showing the engine body along line 14-14 in FIG. 5 with the radiator upright to show the water circulation path FIG. 13 is a partially cutaway side view of the fan cover as viewed from the direction of arrows 15-15 in FIG. 16 arrow view of FIG.

33 ... Cylinder head
45 ... Air cleaner 49 ... Exhaust port 50 ... Exhaust pipe 61 ... Hose 62 ... Connection pipe 62a ... U-shaped part
162 ··· Radiator E · · · Engine P · · · Power unit

Claims (3)

An exhaust port (49) is provided on the lower side surface of the cylinder head (33) included in the engine (E) constituting a part of the power unit (P), and an exhaust pipe (upstream end connected to the exhaust port (49)) ( 50), wherein after extending obliquely downward from the cylinder head (33) toward the one side in the vehicle width direction, extends rearwardly through the lower front of the power unit (P), it leads to a secondary air hose ( 61) connected to said exhaust port via a metal connecting tube (62) (49), met exhaust purification device of an engine in a small vehicle air cleaner (45) is arranged above the power unit (P) And
The connecting pipe (62) is composed of an upstream part disposed on the other side in the vehicle width direction of the power unit (P) and a downstream part connected to the upstream part,
A part of the downstream part of the connection pipe (62) includes a first part extending from the other side in the vehicle width direction to one side and approaching the exhaust pipe (50), and the exhaust pipe ( A U-shaped portion (62a) bent in a substantially U-shape is formed by the second portion that inverts near the second portion and the third portion that continues to the second portion and extends to the other side in the vehicle width direction ,
The engine exhaust gas purification apparatus for a small vehicle, wherein the U-shaped part (62a) is disposed between a lower side surface of the cylinder head (33) and the exhaust pipe (50) in a side view. The exhaust purification of an engine in a small vehicle according to claim 1, characterized in that the second part of the U-shaped part (62a) is arranged between the cylinder head (33) and the exhaust pipe (50). apparatus. The engine exhaust purification in a small vehicle according to claim 1 or 2, characterized in that a radiator (162) through which engine coolant flows is arranged on one side of the power unit (P) in the vehicle width direction. apparatus.

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