JP7491176B2 - Secondary Air Supply - Google Patents

Description

The present invention relates to a secondary air supply device.

In straddle-type vehicles such as motorcycles, a catalyst that purifies exhaust gas is placed in the exhaust passage of the engine. The catalyst is warmed up to its activation temperature by the exhaust heat of the exhaust gas in the exhaust passage, and the catalyst purifies air pollutants contained in the exhaust gas. To activate the catalyst quickly, a system is known in which secondary air is supplied from an air cleaner to the exhaust passage by an air pump (see, for example, Patent Document 1). The secondary air re-burns unburned gas in the exhaust gas in the exhaust passage, and the heat of re-burning quickly activates the catalyst, improving purification performance.

JP 2016-118205 A

However, when the air pump is running, it produces an operating noise that is unpleasant to the rider. In addition, the air pump described in Patent Document 1 is located above the engine, and the piping from the air pump to the exhaust passage is long, resulting in reduced discharge efficiency due to pressure loss within the piping. There is a frame around the air cleaner and engine, and the outside of the frame is covered by a cover, making it difficult to secure space to place the air pump.

The present invention was made in consideration of these points, and aims to provide a secondary air supply device that can reduce noise caused by the operating sound of the air pump and improve the discharge efficiency of the secondary air pump.

One embodiment of the secondary air supply device of the present invention is a secondary air supply device in which a catalyst is arranged in an exhaust passage through which engine exhaust gas passes, and which supplies secondary air to the exhaust passage from an air cleaner upstream of the catalyst, and which comprises an air pump that sends secondary air from the air cleaner toward the exhaust passage, an intake pipe that guides the secondary air taken in from the air cleaner to the air pump, and a discharge pipe that guides the secondary air discharged from the air pump to the exhaust passage, and in a front view of the vehicle, a cylinder unit is arranged in front of the crankcase of the engine, and at least a portion of the air pump overlaps the crankcase when viewed from the front of the vehicle, and at least a portion of the air pump overlaps the cylinder unit when viewed from the side of the vehicle, and the air cleaner is arranged above the air pump, and in a top view of the vehicle, at least a portion of the air pump overlaps the air cleaner, thereby solving the above problem.

According to one aspect of the secondary air supply device of the present invention, the air pump is located near the engine, so the operating sound of the air pump is less noticeable due to the engine noise. This makes it possible to suppress the noise caused by the operating sound of the air pump, which is unpleasant to the rider. In addition, because the air pump is located close to the air cleaner and the exhaust passage, the suction pipe between the air cleaner and the air pump is short, and the discharge pipe between the air pump and the exhaust passage is short. This reduces the pressure loss of the secondary air in the suction pipe and discharge pipe, improving the discharge efficiency of the air pump.

FIG. 2 is a left side view of the saddle-ride type vehicle of the present embodiment. 1 is a perspective view of an internal structure of a saddle-type vehicle according to an embodiment of the present invention; FIG. 3 is a perspective view of FIG. 2 with a body frame removed. FIG. 2 is a front view of the engine of the present embodiment. FIG. 2 is a diagram showing the arrangement of an air pump in a side view of the vehicle according to the present embodiment. FIG. 2 is a diagram showing the arrangement of air pumps in a top view of the vehicle according to the embodiment. FIG. 2 is a diagram showing the arrangement of an air pump in a front view of the vehicle according to the present embodiment.

In one embodiment of the present invention, a secondary air supply device is provided in an exhaust passage through which engine exhaust gas passes, and secondary air is supplied from an air cleaner to the exhaust passage upstream of the catalyst. Secondary air is sent from the air cleaner to the exhaust passage by an air pump, and the secondary air taken in from the air cleaner is guided to the air pump through a suction pipe, and the secondary air discharged from the air pump is guided to the exhaust passage through a discharge pipe. A cylinder unit is provided in front of the crankcase of the engine, and at least a part of the air pump overlaps with the crankcase in a front view of the vehicle, and at least a part of the air pump overlaps with the cylinder unit in a side view of the vehicle. The air pump is provided near the engine, so that the operating sound of the air pump is less noticeable due to the engine sound, and the noise caused by the operating sound of the air pump, which is harsh to the rider's ears, is suppressed. In addition, the air pump is provided close to the air cleaner and the exhaust passage, so that the suction pipe between the air cleaner and the air pump is shortened, and the discharge pipe between the air pump and the exhaust passage is shortened. The pressure loss of the secondary air in the suction and discharge pipes is reduced, improving the discharge efficiency of the air pump.

The following describes in detail a saddle-type vehicle to which the secondary air supply device of this embodiment is applied, with reference to the attached drawings. In the following description, a scooter-type motorcycle is used as an example of a saddle-type vehicle. In addition, in the following drawings, the arrow FR indicates the front of the vehicle, the arrow RE indicates the rear of the vehicle, the arrow L indicates the left side of the vehicle, and the arrow R indicates the right side of the vehicle. Figure 1 is a left side view of the saddle-type vehicle of this embodiment.

As shown in FIG. 1, a scooter-type saddle-ride vehicle 1 is configured by attaching various covers to a body frame 10 (see FIG. 2) made of steel or aluminum alloy as the exterior of the body. A front frame cover 21 is provided at the front of the vehicle, and a leg shield 22 that protects the rider's legs is provided behind the front frame cover 21. A step board 23 extends rearward from the lower end of the leg shield 22, and a rear frame cover 24 is provided behind the step board 23. A center cover 25 that connects the leg shield 22 and the rear frame cover 24 is provided on the step board 23.

A handlebar 31 is provided on the upper side of the front frame cover 21, and a front wheel 33 is rotatably supported on the lower side of the front frame cover 21 via a pair of front forks 32. A rider seat 34 and a pillion seat 35 are provided on the upper side of the rear frame cover 24, and a CVT (Continuously Variable Transmission) cover 53 is provided on the lower side of the rear frame cover 24. A rear wheel 36 is rotatably supported at the rear of the CVT cover 53. A belt-type continuously variable transmission (not shown) is housed inside the CVT cover 53, and the driving force from the engine 40 is transmitted to the rear wheel 36 via the belt.

A radiator 37, a fuel tank 38, and an engine 40 are arranged inside the center cover 25 and the rear frame cover 24 from the front to the rear of the vehicle. The engine 40 has a cylinder unit 41 tilted forward toward the front of the crankcase 42. A CVT cover 53 that is long in the front-rear direction of the vehicle is attached to the left side of the crankcase 42 in the vehicle width direction. An air cleaner 60 is arranged above the cylinder unit 41, and an intake pipe 65 (see Figure 2) extends from the air cleaner 60 to the upper part of the cylinder unit 41. An exhaust pipe 66 (see Figure 4) extends from the bottom of the cylinder unit 41 toward the rear of the vehicle, and a muffler 67 is attached downstream of the exhaust pipe 66.

A catalyst 68 (see FIG. 4) is provided in the exhaust pipe 66, and the catalyst 68 purifies air pollutants in the exhaust gas. However, the catalyst 68 cannot fully purify the exhaust gas until it reaches its activation temperature. For this reason, when the engine is cold immediately after starting, secondary air is introduced from the air cleaner 60 into the exhaust passage, causing unburned gas in the exhaust gas to be re-burned, and the catalyst 68 is quickly activated by the heat of re-burning. In addition, secondary air is introduced from the air cleaner 60 into the exhaust passage, and the air pollutants in the exhaust gas react with the oxygen in the secondary air, purifying the air pollutants.

The exhaust pulsation of the engine's combustion cycle is used to introduce secondary air. A typical engine cylinder unit is equipped with a reed valve, which opens due to the negative pressure of the exhaust pulsation, introducing secondary air from the air cleaner into the exhaust passage. However, in recent years, stronger exhaust gas regulations have led to larger catalysts, which weakens the negative pressure of the exhaust pulsation and makes it difficult for secondary air to enter the exhaust passage. For this reason, an air pump is used to suck in secondary air from the air cleaner and expel it into the exhaust passage, increasing the flow rate of secondary air from the air cleaner to the exhaust passage.

When positioning the air pump, it is necessary to take into consideration the discharge efficiency, operating noise, and heat damage of the air pump. For example, if the air pump is positioned above the cylinder unit, the air pump is brought closer to the air cleaner and the reed valve of the cylinder unit. This shortens the secondary air delivery path, reduces pressure loss, and improves the discharge efficiency of the air pump, but requires changes to the shape of the air cleaner and luggage box. In addition, the air pump is brought closer to the rider sitting on the rider's seat, and the operating noise of the air pump that reaches the rider becomes louder and more unpleasant to the ears.

When the air pump is located below the cylinder unit, the operating sound of the air pump is blocked by the cylinder unit and air cleaner, reducing the sound of the air pump reaching the rider. However, because the air pump is farther away from the air cleaner and the reed valve of the cylinder unit, the secondary air delivery path becomes longer, increasing pressure loss and reducing the discharge efficiency of the air pump. In addition, the air pump is exposed to high temperatures as it is placed close to the exhaust pipe, and ground clearance restrictions make it difficult to position the air pump. Furthermore, the presence of rear frame covers on the left and right sides of the crankcase makes it impossible to position the air pump.

As described above, there are various restrictions on locating an air pump inside a saddle-type vehicle, and it is not enough to simply locate the air pump near the engine. Therefore, in this embodiment, focusing on the fact that the dimension of the cylinder unit 41 in the vehicle width direction is smaller than that of the crankcase 42, space for locating the air pump 71 is secured to the side of the cylinder unit 41 and in front of the crankcase 42. As a result, the air pump 71 is located in an appropriate position near the engine 40, taking into consideration the discharge efficiency of the air pump 71, the operating noise of the air pump 71, the heat exhausted from the exhaust pipe 66, interference between the rear frame cover 24 and the air pump 71, etc.

The secondary air supply device will be described below with reference to Figures 2 and 4. Figure 2 is a perspective view of the internal structure of the saddle-type vehicle of this embodiment. Figure 3 is a perspective view of Figure 2 with the body frame removed. Figure 4 is a front view of the engine of this embodiment.

As shown in FIG. 2, the body frame 10 is a so-called double cradle frame, with a support frame 12 extending diagonally downward and rearward from the upper part of the head pipe 11 of the body frame 10. A pair of first front frames 13 branch off to the left and right and extend downward from the lower part of the support frame 12, and a pair of second front frames 14 branch off to the left and right and extend downward from the lower part of the head pipe 11. A pair of upper frames 15 are connected to the lower parts of the pair of first and second front frames 13, 14, and the pair of upper frames 15 extend rearward of the vehicle, passing above the fuel tank 38.

A pair of lower frames 16 are connected to the front portions of the pair of upper frames 15, and the pair of lower frames 16 extend from the front to the rear of the pair of upper frames 15 so as to surround the fuel tank 38 from below. A seat frame 17 is connected to the rear portions of the pair of lower frames 16, and the seat frame 17 is formed in an arc shape so as to connect the rear portions of the pair of lower frames 16. In addition, the middle portions of the pair of upper frames 15 are connected by a first bridge 18, and the pair of front portions of the seat frame 17 are connected by a second bridge 19. The rear portions of the pair of lower frames 16 are also connected to the second bridge 19.

The vehicle body frame 10 has a cradle portion 20 formed by a pair of upper frames 15 and a pair of lower frames 16, and a radiator 37 is attached to the front side of this cradle portion 20. A fuel tank 38 is attached to the inside of the cradle portion 20, and the fuel tank 38 is positioned rearward of the radiator 37. An engine 40 is attached to the rear side of the cradle portion 20, and a cylinder unit 41 of the engine 40 fits inside the cradle portion 20. An air cleaner 60 is attached to the top of the cradle portion 20, and the air cleaner 60 is positioned above the cylinder unit 41.

As shown in Figures 3 and 4, the engine 40 has a cylinder unit 41 disposed in front of the crankcase 42. The cylinder unit 41 has a cylinder 43 extending forward from the crankcase 42, a cylinder head 44 attached to the front end of the cylinder 43, and a cylinder head cover 45 attached to the front end of the cylinder head 44. A throttle body 46 is provided on the top of the cylinder head cover 45, and an exhaust pipe 66 extends from the bottom of the cylinder head 44. The exhaust pipe 66 extends along the right side of the engine 40 toward the muffler 67, and a catalyst 68 is disposed midway along the exhaust pipe 66.

The crankcase 42 has a left-right split structure and has a left case 51 and a right case 52. The left case 51 extends further rearward than the right case 52, and the left side of the left case 51 is open. A CVT cover 53 is attached to the left side of the left case 51 to form a space to accommodate the continuously variable transmission. The right side of the right case 52 is open, and a clutch cover 54 is attached to the right side of the right case 52 to form a space to accommodate a clutch disc (not shown). Based on the mating surface 55 between the left case 51 and the right case 52, the left side of the crankcase 42 bulges outward in the vehicle width direction more than the right side.

The air cleaner 60 has a vertically split structure and comprises an upper case 61 and a lower case 62. A filter (not shown) is provided at the boundary between the upper case 61 and the lower case 62, and the insides of the upper case 61 and the lower case 62 are divided into a dirty side and a clean side by the filter. An intake pipe 63 is provided at the front of the upper case 61, and a protrusion 64 is formed on the left side of the front of the lower case 62. The protrusion 64 extends to near the front end of the cylinder head cover 45, and the throttle body 46 is located to the right of the protrusion 64. The front end of the protrusion 64 is connected to the throttle body 46 via a U-shaped intake pipe 65.

The engine 40 is provided with a secondary air supply device 70 that supplies secondary air from the air cleaner 60 to an exhaust port 76 upstream of the catalyst 68. The secondary air supply device 70 has a cylindrical air pump 71, a suction pipe 72 that connects the air cleaner 60 and the air pump 71, and a discharge pipe 73 that connects the air pump 71 and the cylinder unit 41. The upper part of the air pump 71 has a suction port 74 to which the suction pipe 72 is connected, and the lower part of the air pump 71 has a discharge port 75 to which the discharge pipe 73 is connected. When the air pump 71 is operated, secondary air is sent from the air cleaner 60 toward the exhaust port 76.

The suction pipe 72 extends from the underside of the protruding portion 64 of the air cleaner 60 to the suction port 74 of the air pump 71, and secondary air taken into the air cleaner 60 by the suction pipe 72 is guided to the air pump 71. The discharge pipe 73 extends from the discharge port 75 of the air pump 71 to the reed valve cover 77 on the front surface of the cylinder head cover 45, and secondary air discharged from the air pump 71 by the discharge pipe 73 is guided to the exhaust port 76 through the reed valve cover 77. A reed valve (not shown) is arranged in the internal passage of the cylinder head cover 45, and the reed valve is covered by the reed valve cover 77.

In this way, secondary air is sucked from the protruding portion 64 of the air cleaner 60 through the suction pipe 72 into the suction port 74 of the air pump 71, and is discharged from the discharge port 75 of the air pump 71 through the discharge pipe 73 to the reed valve cover 77. The secondary air enters the internal passage of the cylinder head cover 45 through the reed valve inside the reed valve cover 77, and is supplied to the exhaust port 76 of the cylinder head 44 through this internal passage. Supplying secondary air to the exhaust port 76 improves the purification performance of air pollutants in the exhaust gas discharged from the exhaust port 76.

The air pump 71 is located to the left of the cylinder head 44, and is close to the engine 40 and the air cleaner 60, improving the discharge efficiency of the air pump 71. The operating sound of the air pump 71 is not noticeable due to the engine sound, and is further blocked by the air cleaner 60. The air pump 71 is located on the opposite side of the cylinder head 44 to the exhaust pipe 66, so the air pump 71 is not exposed to the exhaust heat of the exhaust pipe 66. Furthermore, the fuel tank 38 is located in front of the air pump 71, and the exhaust air from the radiator 37 is blocked by the fuel tank 38, reducing thermal damage to the air pump 71.

The arrangement of the air pump will be described with reference to Figures 4 to 7. Figure 5 is a diagram showing the arrangement of the air pump in a side view of the vehicle in this embodiment. Figure 6 is a diagram showing the arrangement of the air pump in a top view of the vehicle in this embodiment. Figure 7 is a diagram showing the arrangement of the air pump in a front view of the vehicle in this embodiment.

As shown in FIG. 4, when viewed from the front of the vehicle, a portion of the air pump 71 overlaps the crankcase 42. More specifically, the air pump 71 overlaps the mating surface 56 between the left case 51 and the CVT cover 53, and the air pump 71 is brought closer to the reed valve cover 77 in the vehicle width direction. The right half of the air pump 71 is positioned further inward in the vehicle width direction than the left side surface of the air cleaner 60, and the air pump 71 is brought closer to the air cleaner 60 in the vehicle width direction. In this case, the air pump 71 is attached to the cylinder unit 41 or the air cleaner 60 via a bracket (not shown) or the like.

The lower part of the air pump 71 is positioned above the exhaust pipe 66, and the upper part of the air pump 71 is positioned at the same height as the lower part of the reed valve cover 77. Therefore, the air pump 71 is brought closer to the reed valve cover 77 in the vertical direction. The protruding part 64 of the air cleaner 60 is positioned above the air pump 71, and the air pump 71 is brought closer to the air cleaner 60 in the vertical direction. In this way, the air pump 71 is disposed in the space to the left of the cylinder unit 41, and the air pump 71 is brought closer to the reed valve cover 77 and the air cleaner 60 in the vehicle width direction and the vertical direction.

As shown in FIG. 5, in a side view of the vehicle, a portion of the air pump 71 overlaps the cylinder head 44. More specifically, the air pump 71 is disposed inside the projection plane of the side of the cylinder head 44 and the cylinder head cover 45. The air pump 71 is tilted so that the suction port 74 at the top of the air pump 71 is brought closer to the protruding portion 64 of the air cleaner 60 in the vertical direction, and the discharge port 75 at the bottom of the air pump 71 is brought closer to the reed valve cover 77 (see FIG. 4) in the front-rear direction of the vehicle. In this embodiment, the air pump 71 is tilted so that the pump center line L1 is perpendicular to the cylinder center line L2.

In this way, the air pump 71 is disposed to the side of the cylinder head 44 and in front of the crankcase 42. Therefore, the suction pipe 72 extending from the protruding portion 64 of the air cleaner 60 to the suction port 74 of the air pump 71 is shortened, and the discharge pipe 73 extending from the discharge port 75 of the air pump 71 to the reed valve cover 77 is shortened. By shortening the suction pipe 72 and discharge pipe 73, the pressure loss occurring in the pipes is reduced, improving the discharge efficiency of the air pump 71. In addition, the suction pipe 72 and discharge pipe 73 are formed from a flexible material such as a hose.

As shown in FIG. 6, when viewed from above the vehicle, a portion of the air pump 71 overlaps the air cleaner 60. More specifically, the right half of the air pump 71 is covered by the protruding portion 64 of the air cleaner 60. As a result, the operating sound of the air pump 71 is blocked by the air cleaner 60, and the operating sound of the air pump 71 reaching the rider sitting astride the rider seat 34 (see FIG. 1) is reduced. In addition, the operating sound of the air pump 71 blends in with the engine sound and becomes less noticeable. Because the air cleaner 60 is positioned above the cylinder unit 41, a large storage space can be secured below the rider seat 34.

As shown in FIG. 7, the fuel tank 38 is disposed in front of the cylinder unit 41 (see FIG. 5), and the radiator 37 is disposed in front of the fuel tank 38. In a front view of the vehicle, a portion of the air pump 71 overlaps the fuel tank 38, and another portion of the air pump 71 exposed from the fuel tank 38 overlaps the radiator 37. More specifically, the fuel tank 38 is disposed in the center in the vehicle width direction, and the right side of the air pump 71 overlaps the fuel tank 38. The air pump 71 and the top of the fuel tank 38 are positioned at the same height, and the air pump 71 and the top of the fuel tank 38 are positioned higher than the top of the radiator 37.

The air pump 71 is positioned toward the left side (one side in the vehicle width direction), and the radiator 37 is positioned toward the right side (the other side in the vehicle width direction). In this case, the amount by which the left side of the radiator 37 protrudes from the fuel tank 38 is the same as the amount by which the left side of the air pump 71 protrudes from the fuel tank 38. Therefore, of the front portion of the air pump 71 that protrudes from the fuel tank 38 in a front view of the vehicle, only the lower left side of the air pump 71 overlaps the radiator 37. A cooling fan 39 is provided on the back of the radiator 37, and the cooling fan 39 overlaps the fuel tank 38 in a front view of the vehicle.

In this way, most of the exhaust air from the radiator 37 is blocked by the fuel tank 38, making it difficult for the exhaust air from the radiator 37 to hit the air pump 71. This reduces thermal damage to the air pump 71 caused by the exhaust air from the radiator 37, allowing the air pump 71 to operate normally even inside the vehicle where heat tends to build up. Because the cooling fan 39 overlaps the fuel tank 38 when viewed from the front of the vehicle, the exhaust air from the radiator 37 toward the air pump 71 is blocked, making it difficult for the exhaust air from the radiator 37 to hit the air pump 71.

As described above, according to this embodiment, the air pump 71 is disposed near the engine 40, so the operating sound of the air pump 71 blends in with the engine sound and becomes less noticeable. This reduces the noise caused by the operating sound of the air pump 71, which is harsh to the rider. In addition, since the air pump 71 is disposed close to the air cleaner 60 and the reed valve cover 77, the suction pipe 72 between the air cleaner 60 and the air pump 71 is shortened, and the discharge pipe 73 between the air pump 71 and the reed valve cover 77 is shortened. This reduces the pressure loss of the secondary air in the suction pipe 72 and the discharge pipe 73, improving the discharge efficiency of the air pump 71.

In this embodiment, the exhaust port formed in the cylinder head serves as the exhaust passage, and the air pump supplies secondary air to the exhaust port, but the exhaust passage is not limited to the exhaust port. The exhaust passage may be any passage through which the exhaust gas of the engine passes. For example, the exhaust pipe may serve as the exhaust passage, and the air pump may supply secondary air to the exhaust pipe.

In addition, in this embodiment, the secondary air is guided from the underside of the protruding portion of the air cleaner to the suction port of the air pump by the suction pipe, but any configuration is acceptable as long as the secondary air is guided from the air cleaner to the air pump by the suction pipe. In other words, the secondary air is guided from the clean side of the air cleaner to the suction port of the air pump by the suction pipe.

In addition, in this embodiment, the secondary air is guided from the discharge port of the air pump to the reed valve cover by the discharge pipe, but it is sufficient that the secondary air is guided from the air pump to the exhaust passage by the discharge pipe. For example, the secondary air may be guided from the discharge port of the air pump to the exhaust pipe by the discharge pipe.

In addition, in this embodiment, a portion of the air pump overlaps the cylinder head when viewed from the side of the vehicle, but it is sufficient that at least a portion of the air pump overlaps the cylinder unit. For example, the entire air pump may overlap the cylinder head, or at least a portion of the air pump may overlap the cylinder head or the cylinder.

In addition, in this embodiment, a portion of the air pump overlaps the crankcase when viewed from the front of the vehicle, but it is sufficient that at least a portion of the air pump overlaps the crankcase. For example, the entire air pump may overlap the crankcase.

In addition, in this embodiment, a portion of the air pump overlaps the air cleaner when viewed from above the vehicle, but it is sufficient that at least a portion of the air pump overlaps the air cleaner. For example, the entire air pump may overlap the air cleaner.

In addition, in this embodiment, a portion of the air pump overlaps with the fuel tank when viewed from the front of the vehicle, but it is sufficient that at least a portion of the air pump overlaps with the fuel tank. For example, the entire air pump may overlap with the fuel tank.

In addition, in this embodiment, the amount of protrusion of the left side of the radiator from the fuel tank when viewed from the front of the vehicle is configured to be the same as the amount of protrusion of the left side of the air pump from the fuel tank, but the amount of protrusion of the left side of the radiator may be less than the amount of protrusion of the left side of the air pump. Note that the amounts of protrusion being the same does not necessarily mean that the amounts of protrusion are completely the same, and may include an error that allows the amounts of protrusion to be considered to be the same.

In addition, in this embodiment, the top of the air pump is at the same height as the bottom of the reed valve cover, but the top of the air pump may be positioned higher than the bottom of the reed valve cover. Note that "same height" does not necessarily mean that the heights are exactly the same, and may include an error that allows the heights to be considered to be the same.

In addition, in this embodiment, the fuel tank is disposed in front of the air pump, and the radiator is disposed in front of the fuel tank, but it is sufficient if an obstacle that blocks the exhaust air from the radiator is disposed in front of the air pump. For example, a luggage box or an air cleaner may be disposed in front of the air pump.

In addition, in this embodiment, the air pump is configured to be located on the left side of the cylinder unit, but the air pump may also be located on the right side of the cylinder unit.

The secondary air supply device of this embodiment may be used not only in the illustrated saddle-ride vehicle, but also in other types of saddle-ride vehicles. A saddle-ride vehicle is not limited to vehicles in general on which the rider sits astride the seat, but also includes small scooter-type vehicles on which the rider does not sit astride the seat.

As described above, the secondary air supply device (70) of this embodiment is a secondary air supply device in which a catalyst (68) is arranged in the exhaust passage (exhaust port 76) through which exhaust gas from the engine (40) passes, and secondary air is supplied from the air cleaner (60) to the exhaust passage upstream of the catalyst. The secondary air supply device includes an air pump (71) that sends out secondary air from the air cleaner toward the exhaust passage, an intake pipe (72) that guides the secondary air taken in from the air cleaner to the air pump, and an exhaust pipe (73) that guides the secondary air discharged from the air pump to the exhaust passage. In the engine, a cylinder unit (41) is arranged in front of the crankcase (42), and at least a part of the air pump overlaps with the crankcase when viewed from the front of the vehicle, and at least a part of the air pump overlaps with the cylinder unit when viewed from the side of the vehicle. According to this configuration, since the air pump is arranged near the engine, the operating sound of the air pump is less noticeable due to the engine sound. Therefore, the noise caused by the operating sound of the air pump, which is unpleasant to the rider's ears, can be suppressed. In addition, because the air pump is located closer to the air cleaner and the exhaust passage, the suction pipe between the air cleaner and the air pump is shorter, and the discharge pipe between the air pump and the exhaust passage is shorter. This reduces the pressure loss of the secondary air in the suction pipe and discharge pipe, improving the discharge efficiency of the air pump.

In the secondary air supply device of this embodiment, an air cleaner is disposed above the air pump, and at least a portion of the air pump overlaps the air cleaner when viewed from above the vehicle. With this configuration, the operating sound of the air pump is blocked by the air cleaner, making it possible to reduce the operating sound of the air pump that reaches the rider. In addition, because the air pump is located closer to the air cleaner, the suction pipe between the air cleaner and the air pump is shorter, reducing the pressure loss of the secondary air in the suction pipe and improving the discharge efficiency of the air pump.

In the secondary air supply device of this embodiment, a reed valve cover (77) is placed on the front of the cylinder unit of the engine, and secondary air is guided from the air pump through the reed valve cover to the exhaust passage by a discharge pipe, with the top of the air pump positioned at the same height as the bottom of the reed valve cover. With this configuration, the air pump is brought closer to the reed valve cover, shortening the discharge pipe between the air pump and the reed valve cover, reducing the pressure loss of the secondary air in the discharge pipe and improving the discharge efficiency of the air pump.

In the secondary air supply device of this embodiment, a fuel tank (38) is disposed in front of the cylinder unit, and a radiator (37) is disposed in front of the fuel tank, with at least a portion of the air pump overlapping the fuel tank when viewed from the front of the vehicle. With this configuration, the radiator's exhaust air is blocked by the fuel tank, so heat damage to the air pump caused by the radiator's exhaust air is reduced. Therefore, the air pump can operate normally even inside the vehicle body where heat tends to build up.

In the secondary air supply device of this embodiment, the air pump is positioned toward one side in the vehicle width direction, and the radiator is positioned toward the other side in the vehicle width direction, and when viewed from the front of the vehicle, the amount by which the radiator protrudes from the fuel tank in the vehicle width direction on one side is the same as or less than the amount by which the air pump protrudes from the fuel tank in the vehicle width direction on one side. With this configuration, most of the exhaust air from the radiator is blocked by the fuel tank, making it difficult for the exhaust air from the radiator to hit the air pump.

In the secondary air supply device of this embodiment, the top of the air pump is positioned higher than the top of the radiator. This configuration makes it difficult for the exhaust air from the radiator to hit the air pump.

Although this embodiment has been described, other embodiments may be combinations of the above embodiments and variations in whole or in part.

The technology of the present invention is not limited to the above examples, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea.

1: saddle-type vehicle 37: radiator 38: fuel tank 40: engine 41: cylinder unit 42: crankcase 60: air cleaner 68: catalyst 70: secondary air supply device 71: air pump 72: suction pipe 73: discharge pipe 76: exhaust port (exhaust passage)
77: Reed valve cover

Claims (5)

A secondary air supply device comprising: a catalyst disposed in an exhaust passage through which exhaust gas from an engine passes; and an air cleaner disposed upstream of the catalyst and supplying secondary air to the exhaust passage;
an air pump that sends out secondary air from the air cleaner toward the exhaust passage;
a suction pipe for guiding the secondary air taken in from the air cleaner to the air pump;
a discharge pipe for guiding the secondary air discharged from the air pump to the exhaust passage,
In the engine, a cylinder unit is disposed in front of a crankcase,
When viewed from the front of the vehicle, at least a portion of the air pump overlaps with the crankcase,
When viewed from the side of the vehicle, at least a portion of the air pump overlaps with the cylinder unit,
The air cleaner is disposed above the air pump,
2. A secondary air supply device , comprising: a first air pump and a second air cleaner; A secondary air supply device comprising: a catalyst disposed in an exhaust passage through which exhaust gas from an engine passes; and an air cleaner disposed upstream of the catalyst and supplying secondary air to the exhaust passage;
an air pump that sends out secondary air from the air cleaner toward the exhaust passage;
a suction pipe for guiding the secondary air taken in from the air cleaner to the air pump;
a discharge pipe for guiding the secondary air discharged from the air pump to the exhaust passage,
In the engine, a cylinder unit is disposed in front of a crankcase,
When viewed from the front of the vehicle, at least a portion of the air pump overlaps with the crankcase,
When viewed from the side of the vehicle, at least a portion of the air pump overlaps with the cylinder unit,
A reed valve cover is disposed on a front surface of the cylinder unit in the engine,
The discharge pipe guides secondary air from the air pump through the reed valve cover to the exhaust passage,
A secondary air supply device characterized in that an upper portion of the air pump is positioned at the same height as a lower portion of the reed valve cover . A secondary air supply device comprising: a catalyst disposed in an exhaust passage through which exhaust gas from an engine passes; and an air cleaner disposed upstream of the catalyst and supplying secondary air to the exhaust passage;
an air pump that sends out secondary air from the air cleaner toward the exhaust passage;
a suction pipe for guiding the secondary air taken in from the air cleaner to the air pump;
a discharge pipe for guiding the secondary air discharged from the air pump to the exhaust passage,
In the engine, a cylinder unit is disposed in front of a crankcase,
When viewed from the front of the vehicle, at least a portion of the air pump overlaps with the crankcase,
When viewed from the side of the vehicle, at least a portion of the air pump overlaps with the cylinder unit,
a fuel tank is disposed in front of the cylinder unit, and a radiator is disposed in front of the fuel tank,
2. A secondary air supply device, comprising : at least a portion of the air pump overlapping with the fuel tank when viewed from the front of the vehicle. The air pump is disposed near one side in a vehicle width direction, and the radiator is disposed near the other side in the vehicle width direction,
4. The secondary air supply device according to claim 3, wherein, in a front view of the vehicle, an amount of protrusion of the radiator on one side in the vehicle width direction from the fuel tank is the same as or less than an amount of protrusion of the air pump on one side in the vehicle width direction from the fuel tank. 5. The secondary air supply device according to claim 3, wherein an upper portion of the air pump is positioned higher than an upper portion of the radiator.

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