JP3259982B2 - Exhaust gas purification device for motorcycle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle provided with a unit swing type power unit, and more particularly to an apparatus for purifying unburned components contained in exhaust gas from an engine of the motorcycle.

[0002]

2. Description of the Related Art Recently, exhaust gas regulations have been tightened even for motorcycles having a small exhaust gas amount per vehicle. For this reason, some motorcycles introduce secondary air into the exhaust system of the engine, as shown in, for example, Japanese Utility Model Publication No. Sho 60-33292, to reduce the amount of H contained in the exhaust gas.
Exhaust gas purification measures for burning unburned components such as C and CO are employed.

This conventional secondary air introduction device is employed in a general motorcycle in which an engine is fixed to a frame, and a supply pipe for supplying secondary air to an exhaust system of the engine, an engine, and the like. The position is fixed with respect to the frame.

On the other hand, in a scooter-type motorcycle, a space between a front fork and a seat is occupied as a space for accommodating a driver's foot, and an engine and its accessories are installed between the front fork and a seat. Is very difficult, the engine is driven by the rear wheels and the V
It is integrated with the belt transmission.

The power unit in which the engine and the V-belt transmission are integrated has a transmission case which accommodates the V-belt transmission and extends rearward on one side of the engine. A rear wheel is supported at the rear end of the transmission case, and an exhaust silencer connected to the exhaust pipe of the engine is disposed on the opposite side of the rear end of the transmission case. This power unit has a front part on the engine side that is swingably supported by the frame. When the rear wheels receive an impact from the road surface, the entire power unit, including the engine, turns off the rear wheels and exhaust noise. It swings up and down with the container.

[0006]

However, in the prior art, there has been no known motorcycle of this kind having a unit swing type power unit in which an engine of the power unit is provided with a secondary air introduction device as described above. . At present, there is a tendency for emission regulations to be tightened more and more due to social demands, and it is necessary to use a secondary air introduction device even for scooter-type motorcycles, which have relatively low emissions. It is becoming.

The present invention has been made in view of the above circumstances, and it is possible to provide a layout in which the engine is swung up and down while suppressing the thermal influence from the secondary air introduction pipe. The control unit for the secondary air introduction pipe can be arranged using the dead space around the engine, and even if moisture in the exhaust gas is condensed in the exhaust system, this moisture can be prevented from flowing into the control unit. It is an object of the present invention to provide a motorcycle exhaust purification device capable of smoothly supplying secondary air.

[0008]

To achieve the above object, according to an aspect of the present invention includes an engine, extends rearwardly from one side of the crankcase of the engine, a transmission case that the rear wheel is supported on a rear end portion The power unit includes a power unit, and a front part of the power unit is pivotally supported on the vehicle body so as to be swingable, and at the rear of a crankcase of the power unit,
The located on the opposite side across the rear wheel and the transmission case
It assumes a motorcycle with an exhaust silencer that swings together with the power unit .

[0009] Then, the engine is, the crankcase
A cylinder extending forward from the base, and an exhaust passage opened downward in front of the crankcase, and an exhaust silencer provided at a lower end of the exhaust passage through a lower position than the cylinder at an open end of the exhaust passage. A secondary air inlet pipe for introducing secondary air for burning unburned components contained in the exhaust gas to the exhaust system of the engine from the exhaust passage to the exhaust pipe while connecting the exhaust pipe connected to the exhaust pipe connect, the secondary air induction pipe, the exhaust along the exhaust pipe
In addition to guiding the air silencer ahead,
Reed valve that opens and closes in response to exhaust pulsation and during deceleration operation
A normally open type cutoff that blocks the introduction of secondary air to the exhaust system
Established a control unit including bets valve, the control unit
Is installed higher than the exhaust passage of the engine
With the exhaust muffler and the crankcase
By tilting the mating front end upward,
Formed at the boundary between the front end of the air silencer and the crankcase
It is characterized by being housed in a space that expands upward .

[0010]

According to this structure, since the secondary air introduction pipe into which the high-temperature exhaust gas flows is provided along the exhaust pipe, the two hot pipes are collectively arranged through a low position below the cylinder. Heat effect on the surrounding parts of the engine.

[0011] The control unit may include a front end of the exhaust silencer.
Crankcase by tilting the part upward
In the space obtained at the border with
Therefore, there is no need to secure a dedicated space for disposing the control unit around the power unit having a complicated structure, and the control unit can be arranged without difficulty.

In addition, since the control unit including the reed valve and the cut valve is provided at a position higher than the exhaust passage of the engine, even if the moisture contained in the exhaust gas is condensed in the exhaust system, this control unit is not used. It is difficult for water to directly flow into the control unit.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment shown in the drawings.

FIG. 10 shows a scooter-type motorcycle, in which reference numeral 1 denotes a frame constituting the vehicle body,
2 is a front fork and 3 is a front wheel. Frame 1
Has a pair of left and right main pipes 4a, 4b.
The main pipes 4a and 4b include a horizontal portion 5 extending substantially horizontally in the front-rear direction behind the front wheel 3, an upright portion 6 rising from the rear end of the horizontal portion 5, and a support portion extending rearward from the upper end of the upright portion 6. 7 are provided. The rear half of the support portion 7 forms an inclined portion 7a that is inclined obliquely rearward and upward. The rear ends of the inclined portions 7a of the main pipes 4a, 4b are integrally connected by a substantially U-shaped connecting portion 8, and the upper surface of the rear end of the inclined portion 7a is an auxiliary projecting above the connecting portion 8. Pipe 9 is welded. The main pipe 4
A step board 10 on which the driver's foot rests is provided in the horizontal portion 5 of a, 4b.

As shown in FIGS. 1 and 2, a support portion 7 of the main pipes 4a and 4b supports a fuel tank 11 and a storage box 12 for storing a helmet or the like, which are arranged side by side. The fuel tank 11 has a box shape having a tapered front portion, and is located on the front half of the support portion 7.

The storage box 12 has a substantially circular opening 12 a on the upper surface, and is located on the rear half of the support 7. The peripheral wall 12b of the storage box 12 is curved in an arc shape so as to follow the opening shape of the opening 12a. For this reason, as shown in FIG. 2, spaces 13 a and 13 b having a shape that expands toward the side are provided on both left and right sides between the storage box 12 and the fuel tank 11.
Are formed.

A seat 14 is arranged above the fuel tank 11 and the storage box 12. The seat 14 covers the fuel tank 11 and the storage box 12 from above. When the seat 14 is turned upward with the front end as a pivot point, the opening 12a of the fuel tank 11 and the storage box 12 is exposed. It has become.

A unit swing type power unit 16 is disposed below the support 7 of the main pipes 4a and 4b. As shown in FIG. 7, the power unit 16 includes a four-cycle engine 17 and a transmission case 19 extending rearward from a left side of a crankcase 18 of the engine 17. And this power unit 16
, I.e., the upper part of the crankcase 18 is pivotally supported via a pivot shaft 21 to an engine bracket 20 welded to the support portion 7 of the main pipes 4a and 4b.

A rear wheel 23 is supported between a rear portion of the transmission case 19 and an auxiliary arm 22 extending rearward from a right side portion of the crankcase 18. These transmission cases 19
And the rear of the auxiliary arm 22 are connected to the main pipe 4a,
4b is suspended via a pair of shock absorbers 24a, 24b provided between the shock absorbers 24a and 24b.

Therefore, when the rear wheel 23 gets over the unevenness, the power unit 1 including the engine 17
The whole 6 swings up and down about the pivot shaft 21, and the transmission case 19 also functions as a rear arm.

The left side surface of the transmission case 19 is covered by a case cover 25. A transmission chamber 26 is formed between the transmission case 19 and the case cover 25. In the transmission chamber 26, an automatic V-belt transmission 28 for interlocking the crankshaft 27 of the engine 17 and the rear wheel 23 is provided. Is housed.

As shown in FIG. 7, the engine 17 includes a cylinder block 30 extending forward from the front end of the crankcase 18. The cylinder block 30
As is the axis X ₁ of the cylinder 30a is inclined forward until the horizontal angle close, is in the cylinder 30a piston 3
1 is housed. The piston 31 is connected to the connecting rod 32
And a plurality of cooling fins 33 formed on the outer peripheral surface of the cylinder block 30.

A cylinder head 34 is connected to the front end face of the cylinder block 30. As shown in FIG.
An intake passage 36 and an exhaust passage 37 connected to the combustion chamber 35 are formed inside the cylinder head 34. The intake passage 36 and the exhaust passage 37 are provided with an intake port 36a and an exhaust port 37b that open to the combustion chamber 35. The intake port 36a and the exhaust port 37b are connected to an intake valve 38 and an exhaust valve 39, respectively.
It can be opened and closed individually.

Inside the cylinder head 34, the valve operating chamber 4
1 is formed. A camshaft 42 for driving the opening and closing of the intake valve 38 and the exhaust valve 39 is accommodated in the valve operating chamber 41, and the camshaft 42 is linked to the crankshaft 27 via a timing chain 43.

The intake passage 36 is extended above the cylinder head 34 as shown in FIG.
The upstream end of 6 is opened rearward. An intake pipe 45 is connected to an upstream open end of the intake passage 36.
As shown in FIGS. 1 and 2, the intake pipe 45 extends rearward above the cylinder block 30, and a carburetor 46 is connected to an upstream end of the intake pipe 45. The vaporizer 46 is connected to an air cleaner 48 via a joint 47. The air cleaner 48 is provided in the transmission case 1.
9 and is attached to the upper surface of the air cleaner 48.
A series of intake systems from to the intake pipe 45 are swingable integrally with the power unit 16.

The exhaust passage 37 is provided in the cylinder head 3
4 is open on the lower surface. An exhaust pipe 50 is connected to an open end of the exhaust passage 37. As shown in FIG. 1, the exhaust pipe 50 is guided rearward from below the cylinder block 30 through a lower side of the crankcase 18. A box-shaped exhaust silencer 51 is connected to the rear end of the exhaust pipe 50. The exhaust silencer 51 is connected to the crankcase 18.
Located immediately after the right side of the crankcase 18
And the auxiliary arm 22 is bolted. Therefore, a series of exhaust systems from the exhaust passage 37 to the exhaust silencer 51 are also swung together with the power unit 16.

Then, after the right side of the crankcase 18,
The surface is curved in an arc shape centered on the crankshaft 27, and the front surface of the exhaust silencer 51 facing the rear surface rises rearward so as to be located rearward as going upward.
It is inclined to. From this, the crankcase 18
A dead space 52 is formed at the boundary between the exhaust muffler 51 and the exhaust muffler 51 so as to expand upward.

As shown in FIGS. 7 and 8, the engine 1
7 is surrounded by an air shroud 5.
5 is covered. At the right end of the air shroud 55, a fan cover 56 is provided continuously. An axial fan 57 is disposed inside the fan cover 56, and the fan 57 is located on the right side of the cylinder block 30. A rotation shaft 58 of the fan 57 is supported by a boss 60 of a support stay 59 extending from the crankcase 18 via a bearing 61, and a driven pulley 62 is mounted on the rotation shaft 58.

The fan cover 56 also integrally covers a flywheel magnet 63 fixed to the right end of the crankshaft 27. The flywheel magneto 63 includes a drive pulley 64 that rotates integrally with the flywheel magneto 63, and a V belt 65 is wound between the drive pulley 64 and the driven pulley 62. For this reason, the fan 57 is
When the fan 57 is driven to rotate, the outside air is sucked through the suction port 66 on the right side of the fan cover 56, and the outside air becomes cooling air. The air is forcibly blown around the cylinder block 30.

The left end of the air shroud 55
As shown in FIG. 8, a downwardly opening discharge port 67 is provided, and the cooling air blown around the cylinder block 30 is discharged to the outside through the discharge port 67.

The cylinder head 34 of the engine 17 of this embodiment is of a water-cooled type. Most of the cylinder head 34 is exposed to the outside without being covered with the air shroud 55. A cooling water passage 70 is provided inside the cylinder head 34 around the combustion chamber 35. The cooling water passage 70 is connected to a radiator 71 via a pipe (not shown). The radiator 71 is installed outside the suction port 66 of the fan cover 56. For this reason, the radiator 71
The radiator 71 is located in a suction path of the engine cooling air, and the cooling air is always guided to the radiator 71 during operation of the engine.

The cylinder head 34 has a radiator 71
A cooling water pump 72 is provided to guide the cooling water subjected to the heat exchange to the cooling water passage 70, and the cooling water pump 72 is driven by the cam shaft 42.

From the periphery of the engine 17, the fuel tank 1
1 and around the storage box 12, the cover 7
3 covered. The upper end of the cover 73 is the sheet 1
4 and a tail lamp 74 is incorporated in the rear surface of the cover 73. A rear fender 75 is provided continuously below the tail lamp 74.
The rear fender 75 covers a range from the rear to the rear of the rear wheel 23. The upper portion of the rear fender 75 enters between the inclined portions 7a of the main pipes 4a and 4b and extends forward along the inclined portions 7a. The extended portions cover the storage box 12 from below. I have.

Incidentally, the power unit 16 includes:
A secondary air introduction device 80 for burning unburned components such as HC and CO contained in the exhaust gas of the engine 17 is provided. As shown in FIGS. 1 to 3, the secondary air introduction device 80 includes a secondary air introduction pipe 81 having a smaller diameter than the exhaust pipe 50. The secondary air introduction pipe 81 is configured by connecting a first pipe 81a made of a metal pipe and a second pipe 81b made of a flexible pipe such as a rubber hose. A connection fitting 82 is provided at the tip of the first pipe 81a.
Is provided. The connection fitting 82 is screwed into a mounting hole 83 of the cylinder head 34 as shown in FIG. The mounting hole 83 is open to the exhaust passage 37, and the opening end of the mounting hole 83 to the exhaust passage 37 is connected to the exhaust port 37a.
Is provided at a position immediately opposite to the exhaust gas flow direction. As shown in FIG. 1, the first pipe 81a connected to the cylinder head 34 is bent downward toward the rear after being led out below the cylinder head 34, and along the side surface of the exhaust pipe 50 as it is. Guided backwards. The first pipe 81a is located at a position higher than the lower surface of the exhaust pipe 50, and is inserted under the radiator 71 in the front-rear direction.

The rear part of the first pipe 81a is provided with a radiator 7
Behind 1 is bent upward. As shown in FIGS. 1 to 3, the second pipe 81 b connected to the first pipe 81 a is guided to the upper part of the muffler 51 through the right side of the crankcase 18, and from there to the right main pipe 4 b. The fuel tank 1 through the inside
It is guided to the gap between the storage box 1 and the storage box 12, and crosses this gap from right to left. The distal end of the second pipe 81b is guided to a left space 13a formed between the fuel tank 11 and the storage box 12.

In this space 13a, an air filter 85 dedicated to secondary air is arranged. Air filter 85
As shown in FIG. 3 and FIG. 4, a cylindrical filter case 86 vertically elongated in the vertical direction is provided. The filter case 86 has a triangular shape that expands toward the side as viewed in plan, and is efficiently accommodated in the space 13a.

At the lower part of the peripheral surface of the filter case 86, an inlet 87 for secondary air is formed. At the center of the upper surface of the filter case 86 higher than the inlet 87, a secondary air is provided. An air outlet 88 is formed. An element 89 is housed inside the filter case 86. The element 89 has a hollow cylindrical shape with a closed bottom surface, and has an inflow passage 89a for filtered secondary air therein. The element 89 is pressed upward by a spring 90 interposed between the element 89 and the bottom plate 86 a of the filter case 86, and the upper end of the inflow passage 89 a of the element 89 is fitted and held in the outlet 88 by this pressing. Have been. The outlet 88 extends upward, and the second pipe 81b is connected to an open end of the outlet 88.

The air filter 85 is located on the left main pipe 4a as shown in FIGS. In this case, brackets 90a, 90b extending upward to support the fuel tank 11 and the seat 14 are welded to the left and right main pipes 4a, 4b, and the filter case 86 is attached to the inner surface of the left bracket 90a. The tongue piece 91 protruding from the upper surface of the is bolted.

The inlet 87 of the filter case 86 is connected to a secondary air suction pipe 93. The suction pipe 93 is
For example, it is composed of a flexible pipe such as a rubber hose. The suction pipe 93 extends from the left to the right through the gap between the fuel tank 11 and the storage box 12 under the second pipe 81b. The distal end of the suction pipe 93 penetrates the right bracket 90b, and is guided rearward along the right side surface of the storage box 12. That is, as shown in FIGS. 2 and 3, the suction pipe 93 is guided rearward from the front surface of the storage box 12 along the right side surface.
It is located above the rear end of the right main pipe 4b.

A suction port 94 that is bent downward is inserted into the rear end of the suction pipe 93. The suction port 94 is covered with a damper 95 having air permeability such as a sponge. The suction port 94 covered with the damper 95 is connected to the cover 73, the right main pipe 4b, the auxiliary pipe 9
And the upper part of the rear fender 75 is pushed into the gap part, and by this pushing, the damper 95 is held on the upper surface side of the main pipe 4b.

The second pipe 81b of the secondary air introduction pipe 81
Is divided into a first half 98a and a second half 98b.
A control unit 1 for supplying secondary air to the exhaust passage 37 of the engine 17 is provided in the second pipe 81b divided portion.
00 is provided. The control unit 100 includes a box-shaped main body case 101 as shown in FIG. The main body case 101 has an inlet 102 and an outlet 103 for secondary air. These inlet 102 and outlet 1
03 is opened to the air chamber 104 in the main body case 101. The inlet 102 has a second half 9 of the second pipe 81b.
8b is connected and the outlet 103 is connected to the second
The first half 98a of the pipe 81b is connected.

A reed valve 105 is provided in the air chamber 104 of the main body case 101. The reed valve 105 is opened and closed in accordance with the pulsating pressure of the exhaust gas. When a negative pressure in the exhaust passage 37 acts on the air chamber 104 via the secondary air introduction pipe 81, the reed valve 105 is opened and the reed valve 105 is opened. 102 and the outlet 103 are communicated.

The main body case 101 includes the engine 1
7, a cut valve 108 for obtaining an appropriate amount of secondary air according to the operation state, and an actuator 109 for driving the cut valve 108 are incorporated. Cut valve 1
08 is an opening 1 of the inlet 102 to the air chamber 104.
The valve body 110 includes a valve body 110 that comes in contact with and separates from the valve body 02a, and a valve shaft 111 that supports the valve body 110. Actuator 109
Is provided with a cover 112 covered on the main body case 101, and a diaphragm 11 is provided inside the cover 112.
3 are accommodated. The diaphragm 113 is a cover 1
12 is divided into a negative pressure chamber 114 and an atmospheric pressure chamber 115. The negative pressure chamber 114 is connected to the intake pipe 45 via a negative pressure introducing hose 116.
During the operation of the engine, the intake negative pressure in the intake pipe 45 is introduced.

The valve shaft 111 of the cut valve 108 is slidably penetrated through the main body case 101 and connected to the diaphragm 113. The diaphragm 113 includes the spring 11
7, the valve body 110 is constantly pressed toward the atmospheric pressure chamber 115, and the valve
2a, the cut valve 108 is maintained in the normally open state.

The control unit 100 is supported by the crankcase 18 together with the front end of the exhaust muffler 51. Therefore, the control unit 100 is housed in the dead space 52 formed at the boundary between the exhaust muffler 51 and the crankcase 18 and the power unit 1
The control unit 100 is located above the exhaust passage 37 of the engine 17. Next, the operation of the above configuration will be described.

During operation of the engine, exhaust pulsation occurs in the exhaust passage 37, and the negative pressure in the exhaust passage 37 is applied to the reed valve 1 of the control unit 100 via the secondary air introduction pipe 81.
05, the reed valve 105 is opened.
Then, the suction port 94 located below the rear end of the seat 14
From outside air is sucked in as secondary air. This secondary air is guided to an air filter 85 through a suction pipe 93, and dust and the like are filtered while passing through the element 89. The clean secondary air filtered by the air filter 85 is
Injected into the exhaust passage 37 via the secondary air introduction pipe 81,
The exhaust gas is mixed with the exhaust gas flowing through the exhaust passage 37. Therefore, unburned components in the exhaust gas are burned in an exhaust system such as the exhaust passage 37 and the exhaust pipe 50, and the purification of the exhaust gas is promoted.

On the other hand, during a deceleration operation such as when the throttle valve of the carburetor 46 is rapidly closed, the venturi passage of the carburetor 46 is throttled, the flow speed of the intake air increases, and the amount of fuel suction increases. Then, the air-fuel mixture becomes temporarily rich, and a misfire may occur in the combustion chamber 35, so that a large amount of the unburned air-fuel mixture is discharged into the exhaust passage 37. At this time, when the secondary air is injected into the exhaust passage 37, the unburned air-fuel mixture becomes an appropriate air-fuel ratio by mixing with the secondary air and explosively burns, that is, a so-called afterburn occurs.

However, in the above configuration, since the negative pressure chamber 114 of the control unit 100 and the intake pipe 45 are communicated with each other via the negative pressure introducing hose 116, the negative pressure in the intake pipe 45 increases during the deceleration operation. Then, the diaphragm 113
Is deformed toward the negative pressure chamber 114 against the urging force of the spring 117. Due to this deformation, the valve body 110 of the cut valve 108 causes the secondary air from the air filter 85 to transfer the secondary air from the air chamber 1.
The entrance 102 leading to 04 is closed. As a result, during the deceleration operation, the supply of the secondary air to the exhaust passage 37 is stopped,
The occurrence of afterburn is prevented.

In the secondary air introduction device 80 as described above, the first pipe 81a of the secondary air introduction pipe 81 into which the high-temperature exhaust gas flows extends along the exhaust pipe 50 passing below the cylinder block 30. The exhaust pipe 50 and the first pipe 81a, which are heated during operation of the engine,
Can be collectively arranged under the cylinder block 30 inclined forward to an angle close to horizontal. Therefore, the exhaust pipe 50 and the first pipe 81a move away from peripheral components such as the intake system components and the fuel tank 11 on the power unit 16, and the thermal influence on these peripheral components is reduced.

The control unit 100 for obtaining an appropriate amount of secondary air during operation of the engine is provided by the exhaust muffler 51.
The front of the engine 17
Of the control unit 100 around the power unit 16 having a complicated structure, since it is housed in the dead space 52 obtained at the boundary with the crankcase 18. There is no need, and the arrangement of the control unit 100 can be performed without difficulty. Therefore, it is possible to obtain the secondary air introduction device 80 having a layout suitable for a scooter-type motorcycle in which the engine 17 and the exhaust muffler 51 swing with the rear wheel 23.

Further, the control unit 100 can be provided at a position higher than the exhaust passage 37 of the cylinder head 34 by tilting the cylinder 30a of the engine 17 forward to a nearly horizontal angle. Therefore, the moisture contained in the exhaust gas is reduced to the first pipe 81 of the secondary air introduction pipe 81.
a, even if dew condensation occurs in the control unit 10
0 directly into the main body case 101. Therefore, the operation of the reed valve 105 and the cut valve 108 is not impaired, and an appropriate amount of secondary air according to the engine operating condition can be supplied to the exhaust passage 37 of the engine 17.

During traveling of the motorcycle, the traveling wind from the front flows along the lower surface of the step board 10 and the cylinder block 30, so that the first pipe 81a of the secondary air introduction pipe 81 is Since the first pipe 81a into which the high-temperature exhaust gas directly flows can be efficiently cooled, the first pipe 81a into which the high-temperature exhaust gas directly flows can be efficiently disposed below the block 30.

In addition, the first pipe 81 along the exhaust pipe 50
Since a is piped through a position higher than the exhaust pipe 50, the thin and easily bendable first pipe 81a can be protected from road surface protrusions by using the exhaust pipe 50. For this reason, a special protector for the secondary air introduction pipe 81 becomes unnecessary, and the number of parts can be reduced accordingly. In the above embodiment, only the secondary air is introduced into the exhaust system of the engine, but a catalyst for purifying exhaust gas may be provided in this exhaust system.

Further, the motorcycle according to the present invention is not limited to a scooter type in which the periphery of the engine is covered with a cover, but is provided with a unit swing type power unit so that the periphery of the engine is exposed. The same can be applied to the motorcycle described above.

[0055]

According to the present invention described in detail above, the exhaust pipe and the secondary air introduction pipe, which heat up during operation of the engine, can be disposed together under the cylinder which is greatly inclined forward. The secondary air inlet tube moves away from the surrounding components on the power unit, reducing the thermal effect on these surrounding components.

A control unit for obtaining an appropriate amount of secondary air during operation of the engine is provided by moving the front end of the exhaust silencer rearward.
Boundary to crankcase by tilting
Since it is contained in the dead space obtained in the part ,
It is not necessary to secure a dedicated space for arranging the control unit around the power unit having a complicated structure, and the arrangement of the control unit can be performed without difficulty. Therefore, it is possible to obtain a secondary air introduction device having a layout suitable for a motorcycle in which the engine and the exhaust muffler swing together with the rear wheel, and it is possible to cope with stricter exhaust gas regulations without difficulty.

Further, since the control unit is located above the exhaust passage, even if moisture contained in the exhaust gas is condensed in the secondary air introduction pipe, it is difficult for the moisture to directly flow into the control unit. For this reason, the operation of the reed valve and the cut valve is not impaired, and an appropriate amount of secondary air according to the engine operating condition can be supplied to the exhaust system.

[Brief description of the drawings]

FIG. 1 shows a power unit according to an embodiment of the present invention.
The side view showing the state where the secondary air introduction device was incorporated.

FIG. 2 is a plan view showing a layout of a secondary air introduction device for a power unit, a fuel tank, and a storage box.

FIG. 3 is a plan view showing a layout of a secondary air introduction device with respect to a frame.

FIG. 4 is a view as seen from the direction of the arrow A in FIG. 3;

FIG. 5 is a sectional view showing a positional relationship of a suction end of secondary air with respect to a frame and a cover.

FIG. 6 is a sectional view schematically showing the overall configuration of a secondary air introduction device.

FIG. 7 is a cross-sectional view of the power unit around the engine.

FIG. 8 is a sectional view showing a positional relationship between a cylinder block, a fan, and a shroud.

FIG. 9 is a sectional view of a cylinder head.

FIG. 10 is a side view of the scooter type motorcycle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body (frame) 16 ... Power unit 17 ... Engine 18 ... Crank case 19 ... Transmission case 23 ... Rear wheel 30a ... Cylinder 37 ... Exhaust passage 50 ... Exhaust pipe 51 ... Exhaust silencer 52 ... Space (dead space) 81 ... Two Next air inlet pipe 100 Control unit 105 Reed valve 108 Cut valve

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI F02B 61/02 F02B 61/02 D (58) Investigated field (Int.Cl. ⁷ , DB name) F01N 3/08-3 / 38 F01N 9/00 F01N 11/00

Claims (1)

(57) [Claims] A power unit including an engine and a transmission case extending rearward from one side of a crankcase of the engine and having a rear wheel supported at a rear end thereof, wherein a front portion of the power unit is swung to a vehicle body. It is movably pivoted and is located behind the crankcase of the power unit, on the opposite side of the transmission case with the rear wheel in between.
In a motorcycle provided with an exhaust silencer that swings integrally with the power unit , the engine extends forward from the crankcase.
Connecting a cylinder, and an exhaust passage which is open downwardly at the front of the crankcase, the open end of the exhaust passage, an exhaust pipe connected to the rear of the exhaust muffler through the position lower than the cylinder extending And a secondary air introduction pipe for introducing secondary air for burning unburned components contained in the exhaust gas is connected to an exhaust system of the engine from the exhaust passage to the exhaust pipe. introduction pipe, the exhaust consumption along the exhaust pipe
In addition to guiding to the front of the sound device, exhaust air is
Reed valve that opens and closes in response to pulsation
A normally open cut valve that shuts off the introduction of secondary air to the exhaust system
And a control unit that is higher than the exhaust passage of the engine.
And the above-mentioned
Incline the front end facing the ink case upward
The front end of these exhaust silencers and the crankcase
The space that expands upward at the border of
Exhaust purifying apparatus of a motorcycle, characterized in that matches the.