Vehicle

Abstract

To inhibit increase of costs and achieve purification of exhaust air by combustion of unburned gas in the exhaust air effectively even when it is difficult to change a position of an air cleaner due to limitations of an arrangement space in a vehicle including a secondary air supply structure which supplies secondary air from the air cleaner to an exhaust path, in which exhaust air of an internal combustion engine circulates, to purify the exhaust gas.SOLUTION: A vehicle includes a secondary air passage connecting a clean space of an air cleaner with an exhaust path. The secondary air passage includes: a first passage connected to the clean space of the air cleaner; and a secondary passage connected to the exhaust path. Further, the vehicle includes an intermediate chamber which has an inflow port connected to the first passage and an outflow port connected to the second passage and is disposed between the first passage and the second passage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a vehicle, and more particularly to a vehicle equipped with a secondary air supply structure in which secondary air is supplied from an air cleaner to an exhaust path through which exhaust gas from an internal combustion engine flows. [Background technology]

[0002] There is known a vehicle equipped with a secondary air supply structure that supplies secondary air to an exhaust path through which the exhaust of an internal combustion engine flows, and promotes the purification of exhaust gas by burning unburned gas in the exhaust. For example, Patent Document 1 describes that in a motorcycle, secondary air is introduced from an air cleaner to an exhaust port of the engine to promote the oxidation of unburned gas components in the exhaust gas of the engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-321657 Summary of the Invention [Problem to be solved by the invention]

[0004] When an internal combustion engine is operating, the pressure in the exhaust path pulsates. Specifically, in the exhaust path of an internal combustion engine, positive pressure occurs during the exhaust stroke, and negative pressure occurs at a specific time between the exhaust stroke and the next exhaust stroke. That is, negative pressure occurs intermittently in the exhaust path, and the duration of the negative pressure is short. Therefore, if the secondary air flow path connecting the air cleaner to the exhaust path becomes long, the negative pressure in the exhaust path cannot draw a sufficient flow rate of secondary air from the air cleaner into the exhaust path.

[0005] On the other hand, even if an air cleaner is arranged so as to shorten the secondary air flow path, it is difficult to change the position of the air cleaner if there is a space restriction. In addition, when the secondary air inlet hole of the internal combustion engine is enlarged to increase the amount of secondary air supplied to the exhaust path, not only does the cost increase, but it is also difficult to manufacture if the internal combustion engine does not have sufficient structural space. In addition, when the amount of catalyst arranged in the exhaust flow path is increased to promote purification of exhaust gas, the cost also increases.

[0006] Therefore, one aspect of the present disclosure aims to effectively achieve exhaust purification by burning unburned gas in the exhaust while suppressing cost increases in a vehicle equipped with a secondary air supply structure that purifies exhaust gas by supplying secondary air from an air cleaner to an exhaust path through which exhaust from an internal combustion engine flows, even when it is difficult to change the position of the air cleaner due to space constraints. Effect of the Invention

[0007] According to one aspect of the present disclosure, in a vehicle equipped with a secondary air supply structure that purifies exhaust gas by supplying secondary air from an air cleaner to an exhaust path through which exhaust from an internal combustion engine flows, even when it is difficult to change the position of the air cleaner due to space constraints, it is possible to effectively achieve exhaust purification by burning unburned gas in the exhaust while suppressing cost increases. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an external view of a main part of a vehicle according to a first embodiment, as viewed from the right side. [Diagram 2] FIG. 2 is a cross-sectional view of the airbox of FIG. [Diagram 3] FIG. 3 is an external view of the air box in FIG. 1 as viewed from diagonally forward right. [Figure 4] FIG. 4 is an external view of a main part of a vehicle according to the second embodiment, seen from diagonally forward right. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, each embodiment of the present disclosure will be described with reference to the drawings. Each direction shown below is based on the direction seen by a passenger in the vehicle 1. In addition, "upstream" and "downstream" shown below are based on the flow direction of secondary air in the secondary air flow passage 9 from the air cleaner 4 toward the exhaust path 8.

[0010] (First embodiment) FIG. 1 is an external view of a main part of a vehicle 1 according to a first embodiment, as viewed from the right side. The vehicle 1 is, as an example, a vehicle. The vehicle 1 of this embodiment is a straddle vehicle on which a rider straddles. The straddle vehicle is, as an example, a motorcycle. As shown in FIG. 1, the vehicle 1 includes a body frame 2, an internal combustion engine 3, a driving wheel DW, an air cleaner 4, a throttle body 5, an exhaust pipe 6, and a muffler 7. As will be described in detail later, the vehicle 1 includes a secondary air supply structure 18 in which secondary air is supplied from the air cleaner 4 to an exhaust path 8 through which exhaust gas from the internal combustion engine 3 flows. The secondary air supply structure 18 has a secondary air flow path 9. The secondary air supply structure 18 of this embodiment is of a suction type in which secondary air is sucked from the secondary air flow path 9 into the exhaust path 8 by negative pressure generated in the exhaust path 8 during operation of the internal combustion engine 3.

[0011] The vehicle frame 2 extends in the front-rear direction of the vehicle 1. The vehicle frame 2 supports an internal combustion engine 3, an air cleaner 4, and a muffler 7. The vehicle frame 2 includes a plurality of frame parts. As an example, the vehicle frame 2 includes a head pipe 2g, a pair of left and right main frame parts 2a extending rearward from the head pipe 2g, a seat frame part 2b extending rearward from the middle part of each main frame part 2a, and a lower frame part 2c including a down region extending downward from the head pipe 2g and a lower region extending rearward from the lower end of the down region and connected to each main frame part 2a. The vehicle frame 2 also includes a bracket 2d to which a mounting part 10f of an air box 10, which will be described later, is attached. The lower end of the main frame part 2a has a shaft hole Pv. A pivot shaft that rotatably supports the front end of a swing arm that supports a drive wheel DW is attached to the shaft hole Pv. The bracket 2d extends downward from the lower side surface of the main frame portion 2a.

[0012] The internal combustion engine 3 has a crankcase 30, a cylinder block 31 disposed above the crankcase 30, and a cylinder head cover 32 disposed above the cylinder block 31. The internal combustion engine 3 also has a combustion chamber 33, a piston 38, an internal intake air flow passage 34 through which intake air supplied from the outside toward the combustion chamber 33 flows, and an internal exhaust air flow passage 35 through which exhaust air from the combustion chamber 33 flows. The internal intake air flow passage 34 includes an intake port of the internal combustion engine 3. The combustion chamber 33 and the flow passages 34, 35 are disposed inside the cylinder block 31. In the vehicle 1, the internal combustion engine 3 is a driving source for traveling. As an example, the internal combustion engine 3 is a single-cylinder engine. The internal combustion engine 3 is a four-stroke engine, but may be a two-stroke engine. The driving wheels DW are driven by the rotational driving force of the internal combustion engine 3. In the vehicle 1 which is a motorcycle, the driving wheels DW are rear wheels.

[0013] The air cleaner 4 generates purified air to be supplied to the internal combustion engine 3. The air cleaner 4 has an air cleaner case 40 and a filter 41 that is housed in the air cleaner case 40 and purifies outside air supplied from the outside. The filter 41 divides the internal space of the air cleaner case 40 into a dirty space S1 and a clean space S2. Outside air flows into the dirty space S1 through an opening of the air cleaner case 40. Clean air that has passed through the filter 41 flows into the clean space S2.

[0014] The air cleaner 4 in this embodiment is disposed rearward of the internal combustion engine 3 in the front-rear direction of the vehicle 1. Specifically, the air cleaner 4 is disposed vertically below the seat frame portion 2b. More specifically, the air cleaner 4 is disposed rearward of the pivot shaft.

[0015] In the front-rear direction of the vehicle 1, the intake port of the internal combustion engine 3 is disposed on the rear side of the internal combustion engine 3. The air cleaner 4 is connected to a throttle body 5 via a pipe P1. The throttle body 5 has a main body that defines an intake passage, and an intake valve that is disposed in the intake passage and adjusts the amount of intake air supplied to the intake port of the internal combustion engine 3. The throttle body 5 is connected to the internal combustion engine 3 via a pipe P2, but may be directly connected to the internal combustion engine 3.

[0016] In the longitudinal direction of the vehicle 1, the exhaust port of the internal combustion engine 3 is disposed in front of the internal combustion engine 3. One end of the exhaust pipe 6 is connected to the internal combustion engine 3, and the other end is connected to the muffler 7. As an example, at least one catalyst C that promotes an oxidation reaction of the exhaust gas and purifies the exhaust gas is disposed inside the exhaust pipe 6. The catalyst C includes, for example, a three-way catalyst. The configuration of the catalyst C is not limited thereto. In the longitudinal direction of the vehicle 1, the exhaust pipe 6 is connected to the front of the internal combustion engine 3. In addition, in the longitudinal direction of the vehicle 1, the exhaust pipe 6 has a first portion 6a that extends from the exhaust port of the internal combustion engine 3 and is disposed in front of the internal combustion engine 3, and a second portion 6b that extends from the downstream end of the first portion 6a toward the rear along the side of the cylinder block 31 of the internal combustion engine 3. The muffler 7 reduces the exhaust sound of the internal combustion engine 3.

[0017] Here, the vehicle 1 has an exhaust path 8 through which exhaust gas from a combustion chamber 33 of the internal combustion engine 3 flows. The exhaust path 8 includes an internal exhaust flow path 35 of the internal combustion engine 3, an internal flow path 60 of the exhaust pipe 6, and an internal flow path 70 of the muffler 7. The internal exhaust flow path 35 includes an exhaust port of the internal combustion engine 3. The internal combustion engine 3 has an internal secondary air flow path 36 connected to the internal exhaust flow path 35. The internal secondary air flow path 36 opens to the outside of the internal combustion engine 3 at a front part of the internal combustion engine 3 in the front-rear direction of the vehicle 1. Since the air cleaner 4 is disposed rearward and away from the internal combustion engine 3, the distance from the air cleaner 4 to the internal secondary air flow path 36 is long in the flow direction of the secondary air.

[0018] The vehicle 1 also includes a secondary air flow path 9 that connects the clean space S2 of the air cleaner 4 to the exhaust path 8. The secondary air flow path 9 supplies clean air from the clean space S2 of the air cleaner 4 to the exhaust path 8 as secondary air. The secondary air flow path 9 includes a first flow path 90 connected to the clean space S2 of the air cleaner 4 and a second flow path 91 connected to the exhaust path 8. The secondary air flow path 9 also includes an intermediate chamber 92 disposed between the first flow path 90 and the second flow path 91. The intermediate chamber 92 has an inlet 92a connected to the first flow path 90 and an outlet 92b connected to the second flow path 91. As an example, the intermediate chamber 92 is disposed downstream of the midpoint of the secondary air flow path 9 in the flow direction.

[0019] Specifically, the vehicle 1 includes an air box 10, a first pipe 11, and a second pipe 12. The air box 10 includes an intermediate chamber 92. The first pipe 11 includes an internal flow path 11a. The second pipe 12 includes an internal flow path 12a. The flow path cross-sectional areas of the first pipe and the second pipe 12 may be the same or different. In this embodiment, the internal flow path 11a, the intermediate chamber 92, and the internal flow path 12a are arranged in series in the flow direction of the secondary air in the secondary air flow path 9. In other words, the intermediate chamber 92 is interposed between the internal flow path 11a and the internal flow path 12a.

[0020] The first pipe 11 has one end connected to the air cleaner 4 and the other end connected to the air box 10. The second pipe 12 has one end connected to the air box 10 and the other end connected to the internal combustion engine 3. The internal combustion engine 3 has a connection portion 37 that connects the other end of the second pipe 12 to the cylinder block 31. The air box 10 has a box portion 10a that defines an intermediate chamber 92. The box portion 10a of this embodiment is disposed at a position overlapping with the internal combustion engine 3 in a side view of the vehicle 1. Specifically, the box portion 10a is disposed at a position overlapping with at least one of the cylinder block 31 and the cylinder head cover 32 in a side view of the vehicle 1.

[0021] The air box 10 has a mounting portion 10f that is attached to a bracket 2d of the body frame 2. When the mounting portion 10f is attached to the bracket 2d fixed to the main frame portion 2a, the air box 10 is located between the main frame portion 2a and the lower frame portion 2c in a side view of the vehicle 1. As a result, the air box 10 is protected from the outside by the main frame portion 2a and the lower frame portion 2c. More specifically, the air box 10 is disposed vertically below the main frame portion 2a. As an example, the air box 10 is made of resin. The air box 10 is formed, for example, by blow molding. The material and the method of forming the air box 10 are not limited thereto. The air box 10 may be formed of a single part or a plurality of parts. The air box 10 may also be formed by injection molding.

[0022] The secondary air flow path 9 in this embodiment has as a part thereof an in-engine secondary air flow path 36. As an example, an opening 36a of the in-engine secondary air flow path 36 is disposed on the side of the cylinder block 31 so as to open the in-engine secondary air flow path 36 to the outside of the internal combustion engine 3. The opening 36a is positioned below the lower end of the air box 10.

[0023] The vehicle 1 also includes an air switching valve V capable of opening and closing the secondary air flow path 9, and an ECU 13 that controls the throttle body 5. The air switching valve V is disposed in a second flow path 91 of the secondary air flow path 9. The air switching valve V is, for example, an electromagnetic valve, and its opening and closing operation is controlled by the ECU 13. The air switching valve V is supported by the vehicle body frame 2. The ECU 13 is disposed near the air box 10.

[0024] As an example, the air switching valve V is disposed in the middle of the second pipe 12. Thus, the second pipe 12 includes an upstream pipe 14 disposed upstream of the air switching valve V and a downstream pipe 15 disposed downstream of the air switching valve V. In a side view of the vehicle 1, the upstream pipe 14 is disposed vertically above the cylinder head cover 32, and the downstream pipe 15 extends from above the cylinder head cover 32 toward the side of the cylinder block 31. In addition, in a side view of the vehicle 1, the air switching valve V is located forward of the air box 10 in the front-rear direction of the vehicle 1. The air box 10 is located above the lower end of the second pipe 12. In addition, the intermediate chamber 92 is disposed upstream of the air switching valve V in the secondary air flow path 9.

[0025] FIG. 2 is a cross-sectional view of the air box 10 of FIG. 1. For the sake of explanation, the binding member B shown in FIG. 3 is omitted in FIG. 2. As shown in FIG. 2, the intermediate chamber 92 of the air box 10 does not have a structure that narrows the flow of secondary air in the flow direction from the inlet 92a to the outlet 92b, nor a structure that dead-ends the flow of secondary air in the flow direction. This allows secondary air to flow throughout the entire intermediate chamber 92. As an example, with respect to a flow path cross section perpendicular to the flow path axis X of the secondary air flow path 9, the maximum flow path cross-sectional area of ​​the intermediate chamber 92 is larger than the maximum flow path cross-sectional areas of the first flow path 90 and the second flow path 91.

[0026] The air box 10 has a box portion 10a, a first protruding tubular portion 10b, and a second protruding tubular portion 10c. The box portion 10a defines an intermediate chamber 92. The first protruding tubular portion 10b and the second protruding tubular portion 10c protrude outward from the box portion 10a. The first protruding tubular portion 10b has a flow path 10d connected to the inlet 92a. The second protruding tubular portion 10c has a flow path 10e connected to the outlet 92b. The first pipe 11 is fitted into the first protruding tubular portion 10b. The second pipe 12 is fitted into the second protruding tubular portion 10c. As a result, the first flow path 90 includes the internal flow path 11a of the first pipe 11 and the flow path 10d of the first protruding tubular portion 10b, and the second flow path 91 includes the internal flow path 12a of the second pipe 12 and the flow path 10e of the second protruding tubular portion 10c.

[0027] As an example, the first protruding tubular portion 10b and the second protruding tubular portion 10c have tubular axes extending in the front-rear direction of the vehicle 1. As another example, the inlet 92a and the outlet 92b are arranged to overlap each other when viewed from the direction of the flow path axis X perpendicular to the flow path cross section of the inlet 92a. In other words, the extension of the flow path axis X of the inlet 92a passes through the outlet 92b. The tubular portions 10b, 10c and the pipes 11, 12 in this embodiment have a circular flow path cross section, but the shape of the flow path cross section is not limited.

[0028] FIG. 3 is an external view of the air box 10 in FIG. 1, seen from a diagonally forward right side. As shown in FIG. 3, in this embodiment, the size of the box portion 10a in the left-right direction of the vehicle 1 is smaller than the sizes of the box portion 10a in the front-rear direction and the up-down direction of the vehicle 1. The mounting portion 10f extends in the longitudinal direction of the main frame portion 2a below the main frame portion 2a. The mounting portion 10f has a plate shape whose thickness direction is the left-right direction of the vehicle 1. The mounting portion 10f has an insertion hole 10g opening in the thickness direction and a columnar boss 10h protruding from the plate surface to the outside. The bracket 2d of the body frame 2 has a plate shape.

[0029] The bracket 2d has two insertion holes 2e and 2f that open in the thickness direction. With the mounting portion 10f and the bracket 2d stacked in the thickness direction and the boss 10h inserted into the insertion hole 2e, a fastening member N is inserted into the insertion holes 10g and 2f. The mounting portion 10f of this embodiment is detachably attached to the bracket 2d by the fastening member N. Furthermore, the boss 10h is inserted into the insertion hole 2e, so that the air box 10 is prevented from rotating relative to the bracket 2d in the circumferential direction of the insertion hole 10g. In addition, the first pipe 11 of this embodiment is fixed to the first protruding tubular portion 10b by winding a long bundling member B in the circumferential direction. Furthermore, the second pipe 12 is fixed to the second protruding tubular portion 10c by winding a bundling member B in the circumferential direction.

[0030] Returning to FIG. 1, in the vehicle 1, when the internal combustion engine 3 is driven, the pressure in the exhaust path 8 pulsates. Specifically, in the exhaust path 8 of the internal combustion engine 3, positive pressure is generated during the exhaust stroke, and negative pressure is generated at a specific time between one exhaust stroke and the next exhaust stroke. This negative pressure acts on the secondary air flow path 9 from the exhaust path 8, causing secondary air to flow from the clean space S2 of the air cleaner 4 toward the exhaust path 8 of the internal combustion engine 3 and to be supplied to the exhaust path 8. The oxygen contained in the secondary air is used for an oxidation reaction of the exhaust gas flowing through the exhaust path 8. This promotes purification of the exhaust gas.

[0031] Here, the negative pressure occurs intermittently at the specific time. Also, the duration of the negative pressure is short. For this reason, in the past, when the secondary air flow path 9 became long, the negative pressure in the exhaust path 8 made it impossible to draw a sufficient amount of secondary air from the air cleaner 4 into the exhaust path 8.

[0032] In contrast, the secondary air flow path 9 of the vehicle 1 of this embodiment includes an intermediate chamber 92 disposed between the first flow path 90 and the second flow path 91. In addition, the distance from the exhaust path 8 to the intermediate chamber 92 in the secondary air flow direction is shorter than the distance from the exhaust path 8 to the clean space S2 of the air cleaner 4 in the secondary air flow path 9. Therefore, even if the negative pressure is not sufficiently transmitted to the clean space S2 of the air cleaner 4 at the moment when the pressure of the exhaust path 8 of the internal combustion engine 3 becomes lower than the pressure of the secondary air flow path 9 during operation of the internal combustion engine 3, the negative pressure is sufficiently transmitted to the intermediate chamber 92. Therefore, even if the secondary air flow path 9 is long, by using the intermediate chamber 92, a sufficient flow rate of secondary air can be supplied to the exhaust path 8 from the intermediate chamber 92 at a relatively low cost. As a result, even if it is difficult to change the position of the air cleaner 4 due to restrictions on the arrangement space, the purification of the exhaust gas by burning the unburned gas in the exhaust can be achieved well while suppressing an increase in cost.

[0033] This embodiment can also be applied to an existing internal combustion engine that is equipped with a secondary air flow path, for example. Therefore, the amount of secondary air supplied to the exhaust path can be increased without making any major adjustments or modifications to the internal combustion engine.

[0034] As another example, the air switching valve V of this embodiment is controlled by the ECU 13 so as to be in a closed state except when the internal combustion engine 3 is rotating at low speeds, such as during idling, at which negative pressure is more likely to occur intermittently. This allows the vehicle 1 to be adjusted so that secondary air is not supplied to the exhaust path 8 at unnecessary timing. As a result, exhaust gas can be purified stably. The opening and closing timing of the air switching valve V is not limited and can be set appropriately.

[0035] Second embodiment The second embodiment will be described below, focusing on the differences from the first embodiment. Fig. 4 is an external view of a main part of a vehicle 101 according to the second embodiment, seen from diagonally forward right. Fig. 4 also illustrates an opening 43 of an air cleaner 4 connected to a pipe P1. The vehicle 101 includes an air box 110 having an intermediate chamber 192. The size of a box portion 110a of the air box 110 in the left-right direction of the vehicle 101 is smaller than the size of the box portion 110a in the front-rear direction and the up-down direction of the vehicle 101.

[0036] The air box 110 has a first protruding tubular portion 110b and a second protruding tubular portion 110c. The air box 110 is different from the air box 10 in that the first protruding tubular portion 110b and the second protruding tubular portion 110c have their respective tubular axes extending in the vehicle width direction of the vehicle 101. The air box 110 has a mounting portion 110d that is mounted to a bracket 102d of the body frame 102 via a mounting fixture 19. The downstream pipe 15 of the second pipe 12 extends downward from the air switching valve V and is connected to the connection portion 37 of the internal combustion engine 3. In the second embodiment in which such an air box 110 is used, substantially the same effects as in the first embodiment can be obtained.

[0037] As described above, each embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. have been made as appropriate. In addition, it is also possible to combine the components described in each of the above embodiments to create a new embodiment. For example, a part of the configuration in one embodiment may be applied to another configuration, and a part of the configuration in an embodiment can be separated from the other configurations in the embodiment and arbitrarily extracted. In addition, the components described in the attached drawings and detailed description include not only components essential for solving the problem, but also components that are not essential for solving the problem in order to exemplify the technology.

[0038] When the vehicle 1, 101 is a vehicle, the vehicle is not limited to a two-wheeled vehicle. The vehicle may be a three-wheeled vehicle or a four-wheeled vehicle. The vehicle 1, 101 may have a drive source other than the internal combustion engine 3. When the vehicle 1, 101 is a vehicle, it may be a hybrid vehicle. The vehicle may be something other than a vehicle, such as a personal watercraft. The internal combustion engine 3 may have multiple cylinders. The air switching valve V is not essential and may be omitted.

[0039] The secondary air flow path 9 may also include multiple intermediate chambers. The secondary air flow path 9 may also be connected to the exhaust path 8, for example, at a midway portion of the exhaust pipe 6. In this case, the secondary air flow path 9 may be longer than when it is connected to the exhaust path 8 in the internal combustion engine 3. However, according to the present disclosure, by using the intermediate chambers 92, 192, a sufficient amount of secondary air can be supplied to the exhaust path 8 from the intermediate chambers 92, 192.

[0040] (Disclosure items) Each of the following sections is a disclosure of a preferred embodiment. [Item 1] an internal combustion engine having a combustion chamber; an exhaust path through which exhaust gas from the combustion chamber flows; An air cleaner having a filter for purifying outside air and a clean space into which the clean air that has passed through the filter flows; a secondary air flow path connecting the clean space of the air cleaner to the exhaust path, The secondary air flow path is A first flow path connected to the clean space of the air cleaner; A second flow path connected to the exhaust path; an intermediate chamber having an inlet connected to the first flow path and an outlet connected to the second flow path, the intermediate chamber being disposed between the first flow path and the second flow path.

[0041] In the above configuration, in the flow direction of the secondary air, the distance from the exhaust path to the intermediate chamber in the secondary air flow path is shorter than the distance from the exhaust path to the clean space of the air cleaner. Therefore, for example, at the moment when the pressure in the exhaust path of the internal combustion engine becomes lower than the pressure in the secondary air flow path during operation of the internal combustion engine, even if the negative pressure is not sufficiently transmitted to the clean space of the air cleaner, the negative pressure is sufficiently transmitted to the intermediate chamber. Therefore, even if the secondary air flow path is long, by using the intermediate chamber, a sufficient flow rate of secondary air can be supplied to the exhaust path from the intermediate chamber at a relatively low cost. Therefore, even if it is difficult to change the position of the air cleaner due to the constraints of the installation space, the purification of the exhaust gas by burning the unburned gas in the exhaust can be achieved well while suppressing an increase in cost.

[0042] [Item 2] 2. The vehicle of claim 1, wherein the intermediate chamber is disposed downstream of a midpoint of the secondary airflow path in a flow direction.

[0043] According to the above configuration, by locating the intermediate chamber downstream of the midpoint of the secondary airflow path in the flow direction, it is possible to easily bring the intermediate chamber closer to the exhaust path in the flow direction of the secondary airflow path. Therefore, even if the moment when the pressure in the exhaust path is lower than the pressure in the secondary airflow path becomes short during operation of the internal combustion engine, a sufficient flow rate of secondary air can be supplied from the intermediate chamber to the exhaust path.

[0044] [Item 3] an air switching valve disposed in the second flow path of the secondary air flow path and capable of opening and closing the secondary air flow path; 3. The vehicle of claim 1 or 2, wherein the intermediate chamber is disposed upstream of the air switching valve in the secondary air flow path.

[0045] According to the above configuration, when the air switching valve is closed to stop the supply of secondary air to the exhaust path, secondary air can be prevented from flowing from the intermediate chamber to the exhaust path. Therefore, by opening and closing the air switching valve, secondary air can be supplied from the intermediate chamber to the exhaust path at a desired timing.

[0046] [Item 4] 4. The vehicle according to any one of items 1 to 3, wherein the inlet and the outlet are arranged to overlap each other when viewed from a flow path axial direction perpendicular to a flow path cross section of the inlet.

[0047] According to the above configuration, the secondary air flowing from the first flow passage into the storage space through the inlet of the intermediate chamber can be efficiently circulated from the outlet of the intermediate chamber toward the second flow passage, making it easier to supply the secondary air from the intermediate chamber to the exhaust path.

[0048] [Item 5] an airbox having the intermediate chamber including the inlet and the outlet; A first pipe connected to the air box and having an internal flow path; A second pipe connected to the air box and having an internal flow path, The air box is a box portion defining the intermediate chamber; A first protruding tube portion protruding outward from the box portion and having a flow path connected to the inlet; A second protruding tube portion protruding outward from the box portion and having a flow path connected to the outlet port, The first pipe is fitted into the first protruding cylindrical portion, and the second pipe is fitted into the second protruding cylindrical portion, the first flow path includes the flow path of the first pipe and the flow path of the first protruding tube portion, 5. The vehicle according to any one of items 1 to 4, wherein the second flow path includes the flow path of the second pipe and the flow path of the second protruding tube portion.

[0049] According to the above configuration, the secondary air flow path can be easily and stably formed by fitting the first pipe to the first protruding tubular portion of the air box and fitting the second pipe to the second protruding tubular portion of the air box. Also, for example, the box portion, the first protruding tubular portion, and the second protruding tubular portion are integrally formed, which makes it easier to form the air box.

[0050] [Item 6] 6. The vehicle according to item 5, wherein a size of the box portion of the airbox in a left-right direction of the vehicle is smaller than each of the sizes of the box portion of the airbox in a front-rear direction and a top-bottom direction of the vehicle.

[0051] According to the above-mentioned configuration, it is possible to prevent the air box from increasing the size of the vehicle in the lateral direction, and it is also possible to easily arrange the air box in a limited space in the vehicle, thereby improving the degree of freedom in designing the arrangement space of the air box.

[0052] [Item 7] the air cleaner is disposed behind the internal combustion engine in a front-to-rear direction of the vehicle; The internal combustion engine has an internal exhaust flow path that is a part of the exhaust path, and an internal secondary air flow path that is a part of the secondary air flow path and is connected to the internal exhaust flow path, 7. The vehicle according to any one of items 1 to 6, wherein the in-engine secondary air flow path opens to the outside of the internal combustion engine at a front portion of the internal combustion engine in a front-to-rear direction of the vehicle.

[0053] According to the above configuration, the piping constituting a part of the secondary air flow path is connected to the internal secondary air flow path at the front of the internal combustion engine, so that the distance from the air cleaner at the rear of the internal combustion engine to the internal secondary air flow path is long, making it difficult for negative pressure to be transmitted from the exhaust path to the clean space of the air cleaner, but the presence of the intermediate chamber makes it possible to supply a sufficient flow rate of secondary air to the exhaust path including the internal exhaust flow path, thereby achieving good exhaust purification by burning unburned gas in the exhaust.

[0054] [Item 8] A vehicle body frame having a bracket; an air box having the intermediate chamber; 8. The vehicle according to any one of items 1 to 7, wherein the airbox has a mounting portion that is attached to the bracket.

[0055] According to the above-mentioned configuration, the air box can be stably supported by the body frame using the mounting portion of the air box and the bracket of the body frame, so that even if the vehicle body vibrates or an external force acts on the vehicle body, the relative position of the air box to the body frame can be maintained, and secondary air can be stably supplied from the intermediate chamber included in the air box to the exhaust path. [Explanation of symbols]

[0056] S2 Clean Space X Flow passage axis 1, 101 Vehicles 2, 102 Body frame 2d, 102d bracket 3. Internal combustion engine 4 Air cleaner 8 Exhaust route 9 Secondary Air Flow Path 10, 110 Air Box 10a Box section 10b, 110b 1st protruding cylinder part 10c, 110c 2nd protruding cylinder part 10d, 10e Flow path 10f, 110f mounting part 11 First Pipe 11a, 12a Internal flow path 12 Second piping 33 Combustion chamber 35 Engine exhaust route 36 Secondary air flow path in engine 41 Filters 90 First Channel 91 Second Stream 92, 192 Intermediate chamber 92a Inlet 92b Outlet

Claims

1. an internal combustion engine having a combustion chamber; an exhaust path through which exhaust gas from the combustion chamber flows; An air cleaner having a filter for purifying outside air and a clean space into which the clean air that has passed through the filter flows; a secondary air flow path connecting the clean space of the air cleaner to the exhaust path, The secondary air flow path is A first flow path connected to the clean space of the air cleaner; A second flow path connected to the exhaust path; an intermediate chamber disposed between the first and second flow paths, the intermediate chamber having an inlet connected to the first flow path and an outlet connected to the second flow path.

2. 2. The vehicle of claim 1, wherein the intermediate chamber is disposed downstream of a midpoint of the secondary airflow path in a flow direction.

3. an air switching valve disposed in the second flow path of the secondary air flow path and capable of opening and closing the secondary air flow path; 2. The vehicle of claim 1, wherein the intermediate chamber is disposed in the secondary air flow path upstream from the air switching valve.

4. The vehicle according to claim 1 , wherein the inlet and the outlet are arranged to overlap each other when viewed in a flow path axial direction perpendicular to the flow path cross section of the inlet.

5. an airbox having the intermediate chamber including the inlet and the outlet; a first pipe connected to the air box and having an internal flow path; A second pipe connected to the air box and having an internal flow path, The air box is a box portion defining the intermediate chamber; A first protruding tube portion protruding outward from the box portion and having a flow path connected to the inlet; a second protruding tube portion protruding outward from the box portion and having a flow path connected to the outlet port, The first pipe is fitted into the first protruding cylindrical portion, and the second pipe is fitted into the second protruding cylindrical portion, The first flow path includes the flow path of the first pipe and the flow path of the first protruding tube portion, The vehicle according to claim 1 , wherein the second flow path includes the flow path of the second pipe and the flow path of the second protruding tube portion.

6. 6. The vehicle according to claim 5, wherein a size of the box portion of the airbox in a left-right direction of the vehicle is smaller than each of sizes of the box portion of the airbox in a front-rear direction and a top-bottom direction of the vehicle.

7. the air cleaner is disposed behind the internal combustion engine in a front-to-rear direction of the vehicle; The internal combustion engine has an internal exhaust flow path that is a part of the exhaust path, and an internal secondary air flow path that is a part of the secondary air flow path and is connected to the internal exhaust flow path, 7. The vehicle according to claim 1, wherein the internal-engine secondary air flow path opens to the outside of the internal combustion engine at a front portion of the internal combustion engine in the front-rear direction of the vehicle.

8. A vehicle body frame having a bracket; an air box having the intermediate chamber; A vehicle according to any preceding claim, wherein the airbox has a mounting portion attached to the bracket.

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