Evaporative emission system and saddle-type vehicle equipped with the evaporative emission system

Abstract

The present invention provides an evaporative emission system and a saddle-type vehicle that efficiently removes evaporated fuel from the canister, thereby maintaining the total amount of purge necessary to continue the adsorption of evaporated fuel by the canister. [Solution] The intake manifold purge pipe 6 includes a first purge pipe 6b and a second purge pipe 6c that discharge a gas G containing evaporated fuel Gf from the canister 4 to the intake passage 111a of the engine 110, a first purge control valve 7 that opens and closes the first purge pipe 6b, and a second purge control valve 8 that opens and closes the second purge pipe 6c. The first purge pipe 6b is configured as a passage with the smallest first effective cross-sectional area A1. The second purge pipe 6c is configured as a passage with a second effective cross-sectional area A2 obtained by subtracting the first effective cross-sectional area A1 from the third effective cross-sectional area A3 of the intake manifold purge pipe 6. The valve control device 11 controls the first purge control valve 7 and the second purge control valve 8.

Description

Technical Field

[0001] The present invention relates to an evaporative emission system and a saddle-type vehicle equipped with the evaporative emission system.

Background Art

[0002] A saddle-type vehicle or the like having an engine as a power source has an evaporative emission system that recovers evaporative fuel obtained by vaporization of fuel in a fuel tank. The evaporative emission system has a canister connected to the fuel tank and an intake passage of the engine by a purge pipe, respectively. The evaporative emission system adsorbs the evaporative fuel flowing from the fuel tank into the canister via the purge pipe by activated carbon in the canister. Further, the evaporative emission system discharges the evaporative fuel adsorbed by the activated carbon into the intake passage of the engine together with outside air taken in through an outside air introduction hole of the canister. That is, a gas containing the evaporative fuel is discharged into the intake passage. The evaporative fuel discharged from the evaporative emission system into the intake passage is burned in the engine.

[0003] In the evaporative emission system, the concentration of the evaporative fuel contained in the gas discharged into the intake passage increases as the amount of the evaporative fuel adsorbed by the canister increases. Further, the amount of the gas discharged from the canister into the intake passage increases as the pressure in the intake passage decreases because the engine speed of the engine or the throttle valve opening of the throttle valve of the engine decreases. On the other hand, the amount of fuel supplied to the engine decreases as the engine speed or the throttle valve opening decreases.

[0004] For example, when the engine speed is relatively low (under low load), around 2000 rpm to 3000 rpm, if evaporated fuel is discharged from the canister into the engine's intake passage, the larger the amount of evaporated fuel adsorbed on the canister, the greater the amount of evaporated fuel discharged from the canister into the intake passage. Therefore, the fluctuation in the engine's air-fuel ratio due to the discharge of evaporated fuel becomes larger.

[0005] Therefore, Patent Document 1 discloses a fuel vapor purge control device that suppresses the amount of evaporated fuel (purge amount) discharged into the intake passage at low load so as not to worsen the engine's drivability and exhaust emissions due to fluctuations in the air-fuel ratio. In the purge control device described in Patent Document 1, two inlet ports with different passage areas (effective cross-sectional areas) and an activated carbon canister are connected by a purge hose. When the engine load is low, the purge control device discharges the gas containing evaporated fuel from the small-diameter inlet port, and when the engine load is high, it discharges the gas from the large-diameter inlet port. In this way, by selectively switching between the two inlet ports based on the engine load, the amount of evaporated fuel discharged into the engine's intake passage is limited. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 61-268861 [Overview of the project] [Problems that the invention aims to solve]

[0007] The small-diameter inlet port is used in an engine speed range lower than the relatively high engine speed at which fluctuations in the engine's air-fuel ratio remain within an acceptable range when the gas is discharged into the intake passage by the large-diameter inlet port. The passage area of ​​the small-diameter inlet port is sized to suppress the amount of purge discharged into the intake passage so that fluctuations in the air-fuel ratio remain within an acceptable range. Therefore, the purge control device can keep fluctuations in the air-fuel ratio within an acceptable range by suppressing the discharge of the gas through the small-diameter inlet port in a range of relatively low engine speeds.

[0008] On the other hand, if the total amount of purge, which is the amount of evaporated fuel contained in the gas discharged into the intake passage of the engine within a predetermined time, is less than the total amount of evaporated fuel newly generated in the fuel tank within the predetermined time, the amount of evaporated fuel adsorbed by the canister increases. Therefore, when the amount of evaporated fuel adsorbed by the canister reaches its upper limit, it becomes unable to adsorb the evaporated fuel newly generated in the fuel tank. In this way, if the purge control device suppresses the discharge of the gas, it becomes impossible to secure the total amount of purge necessary to process the evaporated fuel newly generated in the fuel tank. Furthermore, in electric-powered hybrid vehicles, the fuel combustion time in the engine is shorter compared to conventional engine vehicles. For this reason, it is necessary to increase the total amount of purge.

[0009] The present invention aims to provide an evaporative emission system that controls the total amount of purge in order to continue the adsorption of the evaporated fuel by the canister, while suppressing fluctuations in the engine's air-fuel ratio within a predetermined range and efficiently detaching the evaporated fuel from the canister, and a saddle-type vehicle equipped with the evaporative emission system. [Means for solving the problem]

[0010] The inventors have investigated an evaporative emission system that controls the total amount of purge in order to continue the adsorption of the evaporated fuel by the canister, while suppressing fluctuations in the engine's air-fuel ratio within a predetermined range and efficiently detaching the evaporated fuel from the canister, and a saddle-type vehicle equipped with the evaporative emission system. As a result of diligent investigation, the inventors have come up with the following configuration.

[0011] An evaporative emission system according to one embodiment of the present invention includes: a canister for recovering evaporated fuel generated in a fuel tank that stores fuel for an engine; an outside air intake passage for introducing outside air into the canister; a fuel tank purge passage for discharging the evaporated fuel into the canister; a first purge passage and a second purge passage for discharging at least one of the recovered evaporated fuel or the introduced outside air from the canister to the engine's intake passage; a first on-off valve that switches between a closed position that blocks the first purge passage and an open position that opens it, and maintains that position; a second on-off valve that switches between a closed position that blocks the second purge passage and an open position that opens it, and maintains that position; an engine information acquisition device that acquires at least one of the engine speed or the throttle valve opening of the engine; a purge amount calculation device that determines the on-off positions of the first on-off valve and the second on-off valve; and a valve control device that controls the on-off of the first on-off valve and the second on-off valve. The first purge passage is configured as a passage having the smallest first effective cross-sectional area among a plurality of purge passages through which the gas discharged from the canister to the intake passage in the evaporative emission system passes. The second purge passage is configured as a passage having a second effective cross-sectional area obtained by subtracting the first effective cross-sectional area from a third effective cross-sectional area which is the sum of the effective cross-sectional areas of the plurality of purge passages through which the gas discharged from the canister to the intake passage in the evaporative emission system passes. The engine information acquisition device acquires at least one of the engine speed or the throttle valve opening.The purge amount calculation device selects one of the following modes based on at least one of the engine speed and throttle valve opening acquired by the engine information acquisition device: a recovery mode in which the evaporated fuel is recovered by the canister without being supplied to the engine by switching the first on / off valve to the closed position and holding that position, and switching the second on / off valve to the closed position and holding that position; a first discharge mode in which the gas that has passed through the first purge passage is supplied to the engine by switching the first on / off valve to the open position and holding that position, and switching the second on / off valve to the closed position and holding that position; a second discharge mode in which the gas that has passed through the second purge passage is supplied to the engine by switching the first on / off valve to the closed position and holding that position, and switching the second on / off valve to the open position and holding that position; and a third discharge mode in which the gas that has passed through the first purge passage and the second purge passage is supplied to the engine by switching the first on / off valve to the open position and holding that position, and switching the second on / off valve to the open position and holding that position. The valve control device controls the opening and closing of the first on / off valve and the second on / off valve so that they enter the mode selected by the purge amount calculation device.

[0012] In the above configuration, the evaporative emission system switches the amount of gas discharged to the engine in four stages by combining a switching method that changes the amount of gas discharged to the intake passage to a small or medium amount by switching either the first on-off valve or the second on-off valve to the open position and switching the other to the closed position and holding that position, and a multi-stage method that changes the amount of gas discharged to the intake passage to zero, a small amount, or a large amount by selecting one of the following: a first stage in which both the first on-off valve and the second on-off valve are switched to the closed position and held that position, a second stage in which the first on-off valve is switched to the open position and held that position, and the second on-off valve is switched to the closed position and held that position, and a third stage in which both the first on-off valve and the second on-off valve are switched to the open position and held that position. In this way, the evaporative emission system can finely adjust the amount of gas discharged to the engine by opening and closing two valves based on at least one of the engine speed or the throttle valve opening.

[0013] Furthermore, the second purge passage has the second effective cross-sectional area obtained by subtracting the first effective cross-sectional area from the third effective cross-sectional area. In other words, the evaporative emission system discharges the gas through the two purge passages within a range between the upper limit of the engine speed or throttle valve opening at which the gas can be discharged in the first emission mode, and the lower limit of the engine speed or throttle valve opening at which the gas can be discharged in the third emission mode. The cross-sectional area of ​​the second purge passage is configured to be the second effective cross-sectional area that can pass through the gas within a range where the fluctuation of the engine's air-fuel ratio remains within an acceptable range. Therefore, by selecting an emission mode based on the engine speed or throttle valve opening, the evaporative emission system separates the evaporated fuel from the canister and discharges the gas containing the evaporated fuel into the intake passage without affecting the air-fuel ratio across the entire range of changes in the engine speed or throttle valve opening. Thus, the evaporative emission system can finely adjust the amount of gas discharged based on at least one of the engine speed or the throttle valve opening, compared to supplying the gas through one of two different effective cross-sectional area purge passages. This allows for efficient removal of the evaporated fuel from the canister while keeping fluctuations in the engine's air-fuel ratio within a predetermined range, thereby maintaining the total amount of purge necessary to continue adsorbing the evaporated fuel by the canister.

[0014] From another perspective, the evaporative emission system of the present invention may have the following configuration: The first purge passage passes a gas containing evaporated fuel in a range that allows combustion of the engine to continue at at least one of the following states: the engine speed is greater than the idle speed or the throttle valve opening is greater than the opening that maintains idle speed.

[0015] In the above configuration, the evaporative emission system can, for example, maintain proper combustion of the engine by discharging the gas into the intake passage through the first purge passage when the engine is operating at idle speed. Furthermore, when the engine speed or throttle valve opening increases, the evaporative emission system switches the gas discharge mode to increase the amount of evaporated fuel discharged into the intake passage while maintaining proper combustion of the engine. Therefore, when the engine is rotating at or above idle speed, an appropriate amount of the gas can be discharged into the intake passage based on at least one of the engine speed or throttle valve opening. This allows for efficient removal of the evaporated fuel from the canister while suppressing fluctuations in the engine's air-fuel ratio within a predetermined range, thereby maintaining the total amount of purge necessary to continue adsorption of the evaporated fuel by the canister.

[0016] From another perspective, the evaporative emission system of the present invention may have the following configuration: The second effective cross-sectional area is larger than the first effective cross-sectional area.

[0017] In the above-described configuration, since the second effective cross-sectional area is larger than the first effective cross-sectional area, the amount of gas discharged into the intake passage can be increased in the order of the recovery mode, the first discharge mode, the second discharge mode, and the third discharge mode. Therefore, the amount of gas discharged into the engine can be finely adjusted based on the engine speed and the throttle valve opening. Consequently, by efficiently releasing the evaporated fuel from the canister while suppressing fluctuations in the engine's air-fuel ratio within a predetermined range, the total amount of purge necessary to continue the adsorption of the evaporated fuel by the canister can be maintained.

[0018] From another perspective, the evaporative emission system of the present invention may have the following configuration: The engine information acquisition device further acquires the crankshaft angle of the engine. The valve control device controls the opening and closing of the first on / off valve and the second on / off valve based on the crankshaft angle acquired by the engine information acquisition device.

[0019] In the above configuration, the first on-off valve and the second on-off valve are controlled, for example, to switch to the open position immediately before the intake valve of the engine opens, and to switch to the closed position immediately before the intake valve closes. Therefore, even if the engine speed fluctuates due to the load, the evaporative emission system discharges the gas into the intake passage in accordance with the intake and exhaust timings of the engine. In this way, by efficiently releasing the evaporated fuel from the canister in accordance with the intake and exhaust timings of the engine, the total amount of purge necessary to continue adsorption of the evaporated fuel by the canister can be maintained.

[0020] From another perspective, the evaporative emission system of the present invention may have the following configuration. The purge amount calculation device calculates the total purge amount, which is the total amount of evaporated fuel contained in the gas discharged into the intake passage within a predetermined time, based on at least one of the engine speed or the throttle valve opening and the first effective cross-sectional area or the second effective cross-sectional area of ​​the purge passage through which the gas passes. If the total purge amount is equal to or greater than a reference total purge amount that suppresses fluctuations in the engine's air-fuel ratio within a predetermined range, a third emission mode is selected.

[0021] In the above configuration, the estimated maximum amount of evaporated fuel adsorbed by the canister after a predetermined time has elapsed in the first or second discharge mode is the difference between the sum of the maximum amount of evaporated fuel that the canister can adsorb and the maximum amount of evaporated fuel newly generated in the fuel tank during the predetermined time, and the total amount of purge, which is the total amount of evaporated fuel contained in the gas discharged into the intake passage during the predetermined time. On the other hand, the concentration of evaporated fuel contained in the gas decreases as the amount of evaporated fuel adsorbed by the canister decreases. In other words, the concentration of evaporated fuel discharged into the intake passage is determined by the amount of evaporated fuel adsorbed by the canister. Furthermore, the maximum amount of evaporated fuel that the canister can adsorb and the maximum amount of evaporated fuel newly generated in the fuel tank during the predetermined time are both constant. Therefore, the concentration of evaporated fuel contained in the gas discharged into the intake passage is determined by the total amount of purge. The concentration of evaporated fuel contained in the gas decreases as the total amount of purge increases.

[0022] The valve control device determines that, in the first or second discharge mode, if the total purge amount increases to equal or greater than the reference total purge amount within a predetermined time, the fluctuation of the engine's air-fuel ratio will be kept within a predetermined range even if the discharge amount of the gas discharged into the intake passage is increased. At this time, the valve control device selects a third discharge pattern that discharges the maximum amount of the gas to the engine. By increasing the discharge amount of the gas, the evaporated fuel is removed from the canister more efficiently. As a result, the total purge amount necessary to continue the adsorption of the evaporated fuel by the canister can be maintained by efficiently removing the evaporated fuel from the canister while keeping the fluctuation of the engine's air-fuel ratio within a predetermined range.

[0023] A saddle-type vehicle equipped with an evaporative emission system according to an embodiment of the present invention includes an engine, a fuel tank that stores fuel for the engine, and an engine control device. The fuel tank is connected to the canister by a purge passage for the fuel tank. The intake passage is connected to the canister by the first purge passage and the second purge passage. The engine control device transmits at least one of the engine speed or the throttle valve opening of the engine to the engine information acquisition device of the evaporative emission system. Alternatively, the engine information acquisition device acquires at least one of the engine speed detected by an engine speed sensor of the engine or the throttle valve opening of the engine.

[0024] In the above configuration, the saddle-type vehicle transmits at least one of the engine speed or the throttle valve opening of the engine from the engine control device to the engine information acquisition device of the evaporative emission system. In the evaporative emission system, the gas of the purge amount calculated based on at least one of the acquired engine speed or throttle valve opening of the engine is discharged into the intake passage. Thereby, even if the engine speed frequently fluctuates based on the operating state of the saddle-type vehicle, the fluctuation of the air-fuel ratio of the engine is suppressed within a predetermined range, and the total purge amount of the evaporated fuel in the evaporative emission system can be maintained.

[0025] The technical terms used in this specification are used for the purpose of defining only specific embodiments, and are not intended to limit the invention by these technical terms.

[0026] As used in this specification, "and / or" includes all combinations of one or more of the related listed components.

[0027] As used herein, the use of "including", "comprising", "having" and their variations specify the presence of the recited features, steps, operations, elements, components, and / or their equivalents, but can include one or more of steps, actions, elements, components, and / or groups thereof.

[0028] As used herein, "attached", "connected", "coupled", and / or their equivalents are used in a broad sense and include both "direct and indirect" attachment, connection, and coupling. Further, "connected" and "coupled" are not limited to physical or mechanical connection or coupling and can include direct or indirect electrical connection or coupling.

[0029] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0030] Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and this disclosure, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0031] In the description of the present invention, it is understood that several techniques and steps are disclosed. Each of these has individual benefits and can also be used in conjunction with one or more, or in some cases all, of the other disclosed techniques.

[0032] Therefore, for clarity, the description of the present invention refrains from repeating all possible combinations of the individual steps unnecessarily. However, the present specification and claims should be read with the understanding that all such combinations are within the scope of the present invention.

[0033] This specification describes embodiments of the evaporative emission system according to the present invention and a saddle-type vehicle equipped with the evaporative emission system.

[0034] The following description includes numerous specific examples to provide a complete understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be carried out without these specific examples.

[0035] Therefore, the following disclosures should be considered illustrative examples of the present invention and are not intended to limit the present invention to any specific embodiments shown in the following drawings or description.

[0036] [Saddle-type vehicle] In this specification, a saddle-type vehicle is a vehicle in which the occupant sits on the seat while straddling it. Therefore, a saddle-type vehicle includes not only two-wheeled vehicles but also three-wheeled and four-wheeled vehicles, as long as the occupant sits on the seat while straddling it.

[0037] [Evaporative Emission System] In this specification, an evaporative emission system means a system that burns fuel vaporized in the engine's fuel tank (evaporated fuel) together with the engine's air-fuel mixture in the engine without releasing it into the atmosphere. The evaporative emission system is mounted on a vehicle powered by an engine. The evaporative emission system includes a canister for adsorbing the evaporated fuel, a first purge passage and a second purge passage connecting the canister to the engine's intake passage, a first on / off valve for opening and closing the first purge passage, a second on / off valve for opening and closing the second purge passage, an engine information acquisition device for acquiring information about the engine, a purge amount calculation device for selecting the opening and closing positions of the first on / off valve and the first on / off valve, and a valve control device for controlling the opening and closing of the first and second valves. The engine information acquisition device, the purge amount calculation device, and the valve control device may be included in the engine control device of the engine. The evaporative emission system adsorbs the evaporated fuel that flows from the fuel tank into the canister via the purge passage onto activated carbon in the canister. Furthermore, the evaporative emission system is configured to discharge the evaporated fuel adsorbed by the activated carbon into the intake passage of the engine via at least one of the first or second purge passage, together with outside air taken in through the outside air intake port of the canister.

[0038] [Valve open position] In this specification, the open position of a valve means a state in which at least a portion of the fluid passes through the valve. In other words, the open position of a valve means a state in which it is not fully closed. The open position of a valve includes not only a fully open state but also a state in which at least a portion is open. Therefore, the degree of opening of a valve in the open position is the degree of opening to which fluid can flow.

[0039] [Valve closed position] In this specification, the closed position of a valve means the state in which the movement of fluid is blocked without the fluid passing through the valve. In other words, the closed position of a valve means the state in which it is fully closed. Therefore, the opening degree of the valve in the closed position is an opening degree that prevents fluid from flowing.

[0040] [Prescribed range of air-fuel ratio] In this specification, a predetermined range of air-fuel ratio means a range of air-fuel ratios in which the emissions of carbon monoxide, hydrocarbons, and nitrogen oxides fall within the limits of exhaust gas regulations, based on the stoichiometric air-fuel ratio in which fuel and air are completely combusted without excess or deficiency in the engine. When a gas containing evaporated fuel is discharged into the exhaust passage of the engine, the air-fuel ratio is It gets smaller.

[0041] [Reference value for total purge amount] In this specification, the reference value for the total purge amount means the sum of the total amount of evaporated fuel newly generated in the fuel tank within the predetermined time and the maximum amount of evaporated fuel that the canister can adsorb. When the total purge amount, which is the total amount of evaporated fuel contained in the gas discharged into the engine's intake passage within the predetermined time, reaches the reference value for the total purge amount, it is presumed that the canister is not adsorbing any evaporated fuel. Therefore, when the total purge amount reaches the reference value, it is presumed that the gas contains only the evaporated fuel currently being generated in the fuel tank. Therefore, the gas when the total purge amount reaches the reference value has little effect on the engine's air-fuel ratio. In other words, the reference value for the total purge amount is a reference value for determining whether the gas contains an amount of evaporated fuel that does not affect the engine's air-fuel ratio.

[0042] [Evaporative fuel] In this specification, "evaporated fuel" refers to fuel such as gasoline or diesel fuel used in an engine that has vaporized due to the effects of temperature, atmospheric pressure, vibration, etc.

[0043] [Gas passage] In this specification, a gas passage means a space through which at least one of evaporated fuel or outside air passes in an evaporative emission system. The gas passage includes a space in the evaporated fuel passage upstream of the canister connecting the fuel tank and the canister, a space within the canister, a purge passage connecting the canister and the intake passage of the engine, an outside air intake passage for introducing outside air, and a space through which gas passes in an on / off valve.

[0044] [Purge passage] In this specification, a purge passage means a space through which at least one of evaporated fuel or outside air passes in an evaporative emission system, and a passage connecting the fuel tank and the canister, and a passage connecting the canister and the intake passage.

[0045] [Effective cross-sectional area] In this specification, the effective cross-sectional area means the smallest cross-sectional area of ​​the passage through which the fluid can pass, including the on / off valve, when viewed in the direction of fluid flow. The flow rate of the fluid passing through the passage is proportional to the effective cross-sectional area. [Effects of the Invention]

[0046] According to one embodiment of the present invention, an evaporative emission system and a saddle-type vehicle equipped with the evaporative emission system can be realized by efficiently detaching the evaporated fuel from the canister, thereby maintaining the total amount of purge necessary to continue adsorption of the evaporated fuel by the canister. [Brief explanation of the drawing]

[0047] [Figure 1] Figure 1 is a schematic diagram of an evaporative emission system according to Embodiment 1 of the present invention. [Figure 2] Figure 2 is a schematic diagram showing a state in which gas is not supplied to the intake pipe in the evaporative emission system according to Embodiment 1 of the present invention. [Figure 3] Figure 3 is a schematic diagram showing the state in which gas is supplied to the intake pipe through the first purge passage in an evaporative emission system according to Embodiment 1 of the present invention. [Figure 4] Figure 4 is a schematic diagram showing the state in which gas is supplied to the intake pipe through the second purge passage in the evaporative emission system according to Embodiment 1 of the present invention. [Figure 5] Figure 5 is a schematic diagram showing the state in which gas is supplied to the intake pipe through the third purge passage in the evaporative emission system according to Embodiment 1 of the present invention. [Figure 6] Figure 6 is a graph showing the relationship between engine speed and the size of the effective cross-sectional area of ​​the purge passage in the evaporative emission system according to Embodiment 1. [Figure 7] Figure 7 is a graph showing the relationship between the total amount of purge over a predetermined time and the selected emission mode in an evaporative emission system according to Embodiment 1 of the present invention. [Figure 8] Figure 8 is a schematic diagram showing the configuration of the intake purge pipe in an evaporative emission system according to a modified example 1 of Embodiment 1 of the present invention. [Figure 9] Figure 9 is a schematic diagram showing the configuration of the intake purge pipe in an evaporative emission system according to a modified example 2 of Embodiment 1 of the present invention. [Figure 10] Figure 10 is a schematic diagram showing the configuration of the intake purge pipe in an evaporative emission system according to a modified example 3 of Embodiment 1 of the present invention. [Figure 11] Figure 11 is a schematic diagram showing the configuration of a saddle-type vehicle having an evaporative emission system according to Embodiment 2 of the present invention. [Figure 12] Figure 12 is a schematic diagram of the evaporative emission system according to Embodiment 2 of the present invention and a graph showing the relationship between engine speed and the size of the effective cross-sectional area of ​​the purge passage. [Modes for carrying out the invention]

[0048] The embodiments will be described below with reference to the drawings. In each drawing, the same parts are denoted by the same reference numerals, and the description of those parts will not be repeated. Note that the dimensions of the components in each drawing do not faithfully represent the actual dimensions of the components or the dimensional ratios of each component.

[0049] [Embodiment 1] <Overall configuration of the evaporative emission system> The evaporative emission system 1 according to Embodiment 1 of the present invention will be described using Figure 1. Figure 1 is a schematic diagram of the evaporative emission system 1 according to Embodiment 1 of the present invention.

[0050] As shown in Figure 1, the evaporative emission system 1 is provided in the engine 110, which is an internal combustion engine, and the fuel tank 115, which stores the fuel F supplied to the engine 110. The engine 110 has an intake pipe 111a, which is an intake passage for drawing in outside air, an exhaust pipe 111b for exhausting combustion gases, a throttle valve 112 for adjusting the amount of outside air supplied, an engine speed sensor 113 for detecting the engine speed R of the engine 110, and a crankshaft angle sensor 114 for detecting the crankshaft angle θ of the engine 110. The engine 110 is supplied with fuel F from the fuel tank 115 by a fuel supply device (not shown).

[0051] The evaporative emission system 1 is a system that suppresses the release of evaporated fuel Gf obtained by the vaporization of fuel F in the fuel tank 115 into the atmosphere. The evaporative emission system 1 includes a shut-off valve 2, a fuel tank purge pipe 3, a canister 4, a vent pipe 5, an intake pipe purge pipe 6, a first purge pipe 6b, a second purge pipe 6c, a first purge control valve 7, a second purge control valve 8, an engine information acquisition device 9, a purge amount calculation device 10, and a valve control device 11.

[0052] The shut-off valve 2 is a switching valve in the evaporative emission system 1 that switches between a closed state, which closes the fuel tank purge passage through which a gas G containing at least one of evaporated fuel Gf and outside air Ga flows, and an open state, which opens the fuel tank purge passage, and maintains its position. The shut-off valve 2 is, for example, an electromagnetic solenoid valve. The shut-off valve 2 is connected to a fuel tank 115 that stores fuel F. In this embodiment, the shut-off valve 2 is located inside the fuel tank 115. One end of the fuel tank purge pipe 3, which is included in the fuel tank purge passage, is connected to the shut-off valve 2 from outside the fuel tank 115.

[0053] The shut-off valve 2 switches between a closed state, which closes one end of the fuel tank purge pipe 3, and an open state, which opens one end of the fuel tank purge pipe 3. When the shut-off valve 2 is in the closed state, evaporated fuel Gf in the fuel tank 115 does not flow into the fuel tank purge pipe 3. When the shut-off valve 2 is in the open state, evaporated fuel Gf in the fuel tank 115 flows through the shut-off valve 2 into the fuel tank purge pipe 3. In this way, the shut-off valve 2, through which evaporated fuel Gf flows, constitutes a part of the fuel tank purge passage. Note that the shut-off valve 2 may be located outside the fuel tank 115. Also, the shut-off valve 2 may be supported by parts other than the fuel tank 115.

[0054] The fuel tank purge pipe 3, which is a purge passage for the fuel tank, is a fuel tank purge passage that flows evaporated fuel Gf from the fuel tank 115 to the canister 4. The other end of the fuel tank purge pipe 3 is connected to the canister 4. In other words, the fuel tank purge pipe 3 connects the shut-off valve 2 and the canister 4. The fuel tank purge pipe 3 is switched by the shut-off valve 2 between a state in which evaporated fuel Gf from the fuel tank 115 flows and a state in which evaporated fuel Gf from the fuel tank 115 does not flow. In this way, the shut-off valve 2 and the fuel tank purge pipe 3, through which evaporated fuel Gf and outside air Ga flow, constitute a part of the gas passage.

[0055] Canister 4 is a fuel adsorption device for recovering evaporated fuel Gf. Canister 4 has activated carbon (not shown) as an adsorbent for adsorbing evaporated fuel Gf. The activated carbon is located in the internal space of the housing 33a.

[0056] The other end of the fuel tank purge pipe 3 is connected to the canister 4. As a result, evaporated fuel Gf from the fuel tank 115 flows into the canister 4 from the fuel tank purge pipe 3. In addition, the vent pipe 5 and the intake pipe purge pipe 6 are connected to the canister 4. Outside air Ga flows into the canister 4 from the vent pipe 5. Thus, the internal space of the canister 4 through which evaporated fuel Gf and outside air Ga flow constitutes a part of the gas passage.

[0057] The vent pipe 5 is a pipe that discharges the gas G inside the canister 4 to the atmosphere and introduces outside air Ga into the canister 4. In other words, the vent pipe 5 is configured as an outside air introduction passage that introduces outside air Ga into the canister 4. One end of the vent pipe 5 is connected to the canister 4. The other end of the vent pipe 5 is open to the atmosphere. This allows the vent pipe 5 to introduce outside air Ga into the canister 4 from the other end. The vent pipe 5 can also discharge the gas G that remains after the evaporated fuel Gf has been adsorbed by the activated carbon inside the canister 4 to the atmosphere. The vent pipe 5, through which the gas G that remains after the evaporated fuel Gf has been adsorbed flows, constitutes a part of the gas passage.

[0058] The vent valve 5a is a valve that switches between a closed state and an open state, and maintains that position, thereby closing the vent pipe 5. The vent valve 5a is, for example, an electromagnetic solenoid valve. The vent valve 5a is installed at any position on the vent pipe 5. When the vent valve 5a is in the open state, the evaporative emission system 1 discharges gas G, which does not contain evaporated fuel Gf in the canister 4, from the vent pipe 5 to the atmosphere. Also, when the vent valve 5a is in the open state, the evaporative emission system 1 introduces outside air Ga into the canister 4 from the vent pipe 5.

[0059] The intake manifold purge pipe 6 is a pipe that allows gas G, which includes evaporated fuel Gf and outside air Ga in the canister 4, to flow to the intake manifold 111a of the engine 110. The intake manifold purge pipe 6 is configured as a purge passage that discharges gas G, which includes at least one of evaporated fuel Gf or outside air Ga introduced from the vent pipe 5, from the canister 4 to the intake manifold 111a.

[0060] One end of the intake pipe purge pipe 6 is connected to the canister 4. The other end of the intake pipe purge pipe 6 is connected to the intake pipe 111a. The intake pipe purge pipe 6 has a branched section that splits into two between the one end and the other end. The intake pipe purge pipe 6 comprises an upstream purge pipe 6a that extends from the one end connected to the canister 4 to the branched section, a first purge pipe 6b and a second purge pipe 6c that constitute the branched section, and a downstream purge pipe 6d that extends from the branched section to the other end connected to the intake pipe 111a.

[0061] One end of the upstream purge pipe 6a is connected to the canister 4. The other end of the upstream purge pipe 6a is connected to one end of the first purge pipe 6b and one end of the second purge pipe 6c, respectively. The other end of the first purge pipe 6b and the other end of the second purge pipe 6c are connected to one end of the downstream purge pipe 6d. The other end of the downstream purge pipe 6d is connected to the intake pipe 111a. The first purge pipe 6b and the second purge pipe 6c are connected to the upstream purge pipe 6a and the downstream purge pipe 6d in parallel. In other words, the first purge pipe 6b and the second purge pipe 6c are located between the upstream purge pipe 6a and the downstream purge pipe 6d. In this way, the intake pipe purge pipe 6, through which the evaporated fuel Gf and outside air Ga flow, constitutes a part of the gas passage.

[0062] The first purge control valve 7, which is the first on / off valve, changes the flow rate of gas G flowing through the intake pipe purge tube 6. The first purge control valve 7 is, for example, an ON-OFF valve. The first purge control valve 7 is installed at any position in the first purge tube 6b. The first purge control valve 7 is configured to switch between a closed position Vc1 that closes the first purge tube 6b and an open position Vo1 that opens the first purge tube 6b, and to maintain that position (see Figure 2). In other words, the first purge control valve 7 switches the first purge tube 6b between a closed state and an open state. Thus, the first purge control valve 7 constitutes a part of the first purge tube 6b. Furthermore, the first purge control valve 7, through which evaporated fuel Gf and outside air Ga flow, constitutes a part of the gas passage.

[0063] The second purge control valve 8, which is a second on / off valve, changes the flow rate of gas G flowing through the intake pipe purge tube 6. The second purge control valve 8 is, for example, an ON-OFF valve. The second purge control valve 8 is installed at any position in the second purge tube 6c. The second purge control valve 8 is installed in the second purge tube 6c. The second purge control valve 8 is configured to switch between a closed position Vc2 that closes the second purge tube 6c and an open position Vo2 that opens the second purge tube 6c, and to maintain that position (see Figure 2). In this way, the second purge control valve 8 constitutes a part of the second purge tube 6c. Furthermore, the second purge control valve 8, through which evaporated fuel Gf and outside air Ga flow, constitutes a part of the gas passage.

[0064] The intake manifold purge pipe 6 comprises multiple purge passages through the opening and closing of the first purge control valve 7 and the second purge control valve 8. When the first purge control valve 7 is switched to the open position Vo1 and holds that position, and the second purge control valve 8 is switched to the open position Vo2 and holds that position, the intake manifold purge pipe 6 is configured with a third purge passage Pp3 that discharges gas G from the canister 4 through the upstream purge pipe 6a, the first purge pipe 6b, the second purge pipe 6c, and the downstream purge pipe 6d to the intake manifold 111a (see Figure 5).

[0065] When the first purge control valve 7 is switched to the open position Vo1 and maintains that position, and the second purge control valve 8 is switched to the closed position Vc2 and maintains that position, the intake pipe purge pipe 6 is configured with a first purge passage Pp1 that discharges gas G from the canister 4 through the upstream purge pipe 6a, the first purge pipe 6b, and the downstream purge pipe 6d to the intake pipe 111a (see Figure 3).

[0066] When the first purge control valve 7 is switched to the closed position Vc1 and maintains that position, and the second purge control valve 8 is switched to the open position Vo2 and maintains that position, a second purge passage Pp2 is configured in the intake pipe purge pipe 6 that discharges gas G from the canister 4 through the upstream purge pipe 6a, the second purge pipe 6c, and the downstream purge pipe 6d to the intake pipe 111a (see Figure 4).

[0067] The effective cross-sectional area of ​​each purge passage is the smallest effective cross-sectional area among the passage cross-sectional areas of the purge pipes that make up each purge passage. The effective cross-sectional area of ​​the passage of the first purge pipe 6b is the first effective cross-sectional area A1 (see Figure 3). The effective cross-sectional area of ​​the passage of the second purge pipe 6c is the second effective cross-sectional area A2 (see Figure 4). The effective cross-sectional area of ​​the passages of the upstream purge pipe 6a and the downstream purge pipe 6d, to which the first purge pipe 6b and the second purge pipe 6c are connected, is greater than or equal to the sum of the first effective cross-sectional area A1 of the passage of the first purge pipe 6b and the second effective cross-sectional area A2 of the passage of the second purge pipe 6c. Furthermore, the second effective cross-sectional area A2 of the passage of the second purge pipe 6c is greater than the first effective cross-sectional area A1 of the passage of the first purge pipe 6b.

[0068] In the third purge passage Pp3, which discharges gas G through the first purge pipe 6b and the second purge pipe c, the portion with the smallest effective cross-sectional area of ​​the passage is the portion that is bifurcated by the first purge pipe 6b and the second purge pipe 6c. Therefore, the effective cross-sectional area of ​​the third purge passage Pp3 is the third effective cross-sectional area A3, which is the sum of the effective cross-sectional area A1 of the passage of the first purge pipe 6b and the effective cross-sectional area A2 of the passage of the second purge pipe 6c (see Figure 5). The third purge passage Pp3 is configured as the purge passage with the largest effective cross-sectional area among the multiple purge passages through which gas G passes.

[0069] In the first purge passage Pp1, which discharges gas G through the first purge pipe 6b, the portion of the passage with the smallest effective cross-sectional area is the portion formed by the first purge pipe 6b. Therefore, the effective cross-sectional area of ​​the first purge passage Pp1 is the first effective cross-sectional area A1 of the passage of the first purge pipe 6b. The first purge passage Pp1 is configured as the purge passage with the smallest effective cross-sectional area among the multiple purge passages through which gas G passes.

[0070] In the second purge passage Pp2, which discharges gas G through the second purge pipe 6c, the portion of the passage with the smallest effective cross-sectional area is the portion formed by the second purge pipe 6c. The second purge pipe 6c discharges the gas G that has passed through the upstream purge pipe 6a to the downstream purge pipe 6d. Therefore, the effective cross-sectional area of ​​the second purge passage Pp2 is the second effective cross-sectional area A2 of the passage of the second purge passage 6c. The second purge passage Pp2 is configured as a purge passage with an effective cross-sectional area smaller than the third purge passage Pp3, which has the largest effective cross-sectional area among the multiple purge passages through which gas G passes, and larger than the first purge passage Pp1, which has the smallest effective cross-sectional area.

[0071] The effective cross-sectional area A1 of the first purge passage Pp1 is, for example, an area through which a gas G containing evaporated fuel Gf can pass, such that the fluctuation of the air-fuel ratio of the engine 110 remains within an acceptable range when the engine speed R is in a relatively low engine speed range (low load) of about 2000 rpm (idle speed) to 3000 rpm or at a corresponding throttle valve opening Vs of the throttle valve 112.

[0072] The third effective cross-sectional area A3, which is the effective cross-sectional area of ​​the third purge passage Pp3 formed by the entire intake manifold purge pipe 6, is the area through which gas G containing evaporated fuel Gf can pass, for example, in a relatively high engine speed range (under high load) of 5000 rpm or more, including the maximum engine speed R, or at a corresponding throttle valve opening Vs, within a range where fluctuations in the air-fuel ratio of the engine 110 remain within an acceptable range.

[0073] The second effective cross-sectional area A2 of the second purge passage Pp2 is the area obtained by subtracting the first effective cross-sectional area A1 from the third effective cross-sectional area A3. In other words, the second effective cross-sectional area A2 is the area through which gas G can pass within the range where the fluctuation of the air-fuel ratio of engine 110 remains within an acceptable range, between the upper limit of the engine speed R or the corresponding throttle valve opening Vs at which gas G that has passed through the first purge passage Pp1 can be discharged, and the lower limit of the engine speed R or the corresponding throttle valve opening Vs at which gas G that has passed through the third purge passage Pp3 can be discharged. The second effective cross-sectional area A2 is larger than the first effective cross-sectional area A1. Therefore, the third effective cross-sectional area A3 is larger than twice the first effective cross-sectional area A1.

[0074] The engine information acquisition device 9 acquires information related to the engine 110. The engine information acquisition device 9 acquires the engine speed R or the throttle valve opening Vs. The engine information acquisition device 9 is electrically connected to the throttle valve 112, the engine speed sensor 113, and the crankshaft angle sensor 114. The engine information acquisition device 9 stores various programs and data for acquiring the throttle valve opening Vs, engine speed R, and crankshaft angle θ. The engine information acquisition device 9 can acquire the throttle valve opening Vs from the throttle valve 112, the engine speed R from the engine speed sensor 113, and the crankshaft angle θ from the crankshaft angle sensor 114.

[0075] The purge amount calculation device 10 calculates the purge amount, which is the amount of gas G to be discharged into the intake manifold 111a. The purge amount calculation device 10 is electrically connected to the engine information acquisition device 9. The purge amount calculation device 10 stores various programs and data for calculating the purge amount of gas G based on at least one of the engine speed R or the throttle valve opening Vs.

[0076] The purge amount calculation device 10 calculates the amount of gas G to be purged based on at least one of the engine speed R or throttle valve opening Vs acquired by the engine information acquisition device 9. Furthermore, the purge amount calculation device 10 selects one of the following based on the calculated purge amount of gas G: recovery mode M0, in which the first purge control valve 7 is switched to the closed position Vc1 and held there, and the second purge control valve 8 is switched to the closed position Vc2 and held there; first discharge mode M1, in which the first purge control valve 7 is switched to the open position Vo1 and held there, and the second purge control valve 8 is switched to the closed position Vc2 and held there; second discharge mode M2, in which the first purge control valve 7 is switched to the closed position Vc1 and held there, and the second purge control valve 8 is switched to the open position Vo2 and held there; and third discharge mode M3, in which the first purge control valve 7 is switched to the open position Vo1 and held there, and the second purge control valve 8 is switched to the open position Vo2 and held there.

[0077] The valve control device 11 controls the opening and closing of the first purge control valve 7 and the second purge control valve 8. The valve control device 11 is electrically connected to the purge amount calculation device 10. The valve control device 11 is also electrically connected to the shut-off valve 2, the vent valve 5a, the first purge control valve 7, and the second purge control valve 8. The valve control device 11 stores various programs and data for controlling the opening and closing of the shut-off valve 2, the first purge control valve 7, and the second purge control valve 8. The valve control device 11 switches the opening degree of the first purge control valve 7 and the second purge control valve 8 to either a closed state or an open state, respectively. The valve control device 11 controls the opening and closing of the first purge control valve 7 and the second purge control valve 8, respectively, based on the mode selected by the purge amount calculation device 10.

[0078] The engine information acquisition device 9, the purge amount calculation device 10, and the valve control device 11 may be integrated as a control unit for the evaporative emission system 1.

[0079] <Purge operation of the evaporative emission system> The purging operation of the evaporative emission system 1 will be explained using Figures 1 to 6. Figure 2 is a schematic diagram showing the state in which gas G is not supplied to the intake manifold 111a in the evaporative emission system 1. Figure 3 is a schematic diagram showing the state in which gas G is supplied to the intake manifold 111a by the first purge passage Pp1 in the evaporative emission system 1. Figure 4 is a schematic diagram showing the state in which gas G is supplied to the intake manifold 111a by the second purge passage Pp2 in the evaporative emission system 1. Figure 5 is a schematic diagram showing the state in which gas G is supplied to the intake manifold 111a by the third purge passage Pp3 in the evaporative emission system 1. Figure 6 is a graph showing the relationship between the size of the effective cross-sectional area of ​​the purge passage and the engine speed R in the evaporative emission system 1.

[0080] As shown in Figures 1 to 5, the purge amount calculation device 10 selects one of the following modes for the first purge control valve 7 and the second purge control valve 8 based on at least one of the engine speed R and throttle valve opening Vs obtained from the engine information acquisition device 9: recovery mode M0, first discharge mode M1, second discharge mode M2, or third discharge mode M3. The valve control device 11 opens and closes the first purge control valve 7 and the second purge control valve 8 based on the mode selected by the purge amount calculation device 10. The valve control device 11 also controls the opening and closing of the first purge control valve 7 and the second purge control valve 8 based on the crankshaft angle θ obtained from the engine information acquisition device 9.

[0081] As shown in Figure 2, recovery mode M0 is a mode in which the gas G containing evaporated fuel Gf is recovered by the canister 4 without being discharged into the intake manifold 111a by switching the first purge control valve 7 to the closed position Vc1 and holding that position, and switching the second purge control valve 8 to the closed position Vc2 and holding that position. Recovery mode M0 is selected, for example, when the engine 110 is not running or when the engine is running at an engine speed R of less than 2000 rpm, excluding the idle speed immediately after starting the engine 110.

[0082] As shown in Figure 3, the first discharge mode M1 is a mode in which the gas G that has passed through the first purge passage Pp1 is discharged into the intake manifold 111a by switching the first purge control valve 7 to the open position Vo1 and holding that position, and switching the second purge control valve 8 to the closed position Vc2 and holding that position. In the first discharge mode M1, the upper limit of the gas G discharged into the intake manifold 111a is the smallest of the upper limits of the purge amount in the first discharge mode M1, the second discharge mode M2, and the third discharge mode M3. Therefore, the first discharge mode M1 is the mode selected when the allowable range of fluctuation in the air-fuel ratio of the engine 110 is smallest. The first discharge mode M1 is, for example, the mode selected when the engine speed R is in a relatively low engine speed range from 2000 rpm to less than 3000 rpm, including the idle speed, or when the throttle valve opening Vs is in a relatively small opening range, including the minimum opening (at low load).

[0083] As shown in Figure 5, the third exhaust mode M3 is a mode in which the gas G that has passed through the third purge passage Pp3 is discharged into the intake manifold 111a by switching the first purge control valve 7 to the open position Vo1 and holding that position, and switching the second purge control valve 8 to the open position Vo2 and holding that position. In the third exhaust mode M3, the upper limit of the purge amount of gas G discharged into the intake manifold 111a is the largest among the upper limits of the purge amount in the first exhaust mode M1, the second exhaust mode M2, and the third exhaust mode M3. Therefore, the third exhaust mode M3 is the mode selected when the allowable range of fluctuation in the air-fuel ratio of the engine 110 is the largest. The third exhaust mode M3 is selected, for example, when the engine speed R is in a relatively high engine speed range of 5000 rpm or more, including the maximum engine speed, or when the throttle valve opening Vs is in a relatively large opening range including the maximum opening (under high load).

[0084] As shown in Figure 4, the second discharge mode M2 ​​is a mode in which the gas G that has passed through the second purge passage Pp2 is supplied to the intake manifold 111a by switching the first purge control valve 7 to the closed position Vc1 and holding that position, and switching the second purge control valve 8 to the open position Vo2 and holding that position. In the second discharge mode M2, the upper limit of the purge amount of gas G discharged to the intake manifold 111a is greater than the upper limit of the purge amount in the first discharge mode M1, and less than the upper limit of the purge amount in the third discharge mode M3. Therefore, the second discharge mode M2 ​​is a mode selected, for example, when the engine speed R is in the medium-frequency range of 3000 rpm or more and less than 5000 rpm, or when the throttle valve opening Vs is in the medium opening range (under medium load).

[0085] As shown in Figures 1 to 5, when the evaporative emission system 1 burns gas G containing evaporated vapor Gf in the engine 110, the valve control device 11 switches the shut-off valve 2 and the vent valve 5a to the open state. Furthermore, the valve control device 11 controls the opening and closing of the first purge control valve 7 and the second purge control valve 8, respectively, based on at least one of the engine speed R or throttle valve opening Vs, so that the system is in one of the recovery modes M0, first discharge mode M1, second discharge mode M2, or third discharge mode M3 selected by the purge amount calculation device 10.

[0086] As shown in Figure 2, when the engine 110 is not operating, the purge amount calculation device 10 selects recovery mode M0. The valve control device 11 controls the opening and closing of the first purge control valve 7 and the second purge control valve 8, respectively, to achieve the valve opening in the selected recovery mode M0. In recovery mode M0, evaporated fuel Gf generated in the fuel tank 115 flows into the canister 4 through the fuel tank purge pipe 3. The evaporated fuel Gf that flows into the canister 4 is adsorbed by activated carbon. The gas G remaining after the adsorption of evaporated fuel Gf is discharged into the atmosphere through the vent pipe 5. Therefore, the evaporative emission system 1 does not discharge evaporated fuel Gf into the intake pipe 111a.

[0087] When the engine 110 is running, the purge amount calculation device 10 selects one of the recovery mode M0, first discharge mode M1, second discharge mode M2, and third discharge mode M3 based on at least one of the engine speed R or throttle valve opening Vs obtained by the engine information acquisition device 9. The valve control device 11 controls the opening and closing of the first purge control valve 7 and the second purge control valve 8, respectively, to the open / closed position in the mode selected by the purge amount calculation device 10. In the first discharge mode M1, second discharge mode M2, and third discharge mode M3, the pressure in one of the first purge passages Pp1, second purge passages Pp2, and third purge passages Pp3 and the canister 4 decreases as the pressure in the intake manifold 111a decreases due to the operation of the engine 110. As a result, the gas G in each purge passage and the canister 4 is discharged toward the intake manifold 111a.

[0088] As the pressure in each purge passage and within the canister 4 decreases, outside air Ga flows into the canister 4 from the vent pipe 5. The evaporated fuel Gf that was adsorbed on the activated carbon is released from the activated carbon by the incoming outside air Ga. The gas G, which is a mixture of the evaporated fuel Gf released from the activated carbon and the outside air Ga, is discharged into the intake manifold 111a from the intake manifold purge pipe 6. As a result, the evaporative emission system 1 releases the evaporated fuel Gf from the canister 4 for combustion in the engine 110 and increases the amount of evaporated fuel Gf that the canister 4 can adsorb.

[0089] As shown in Figure 2, the evaporative emission system 1 recovers the evaporated fuel Gf by the canister 4 without discharging the gas G containing the evaporated fuel Gf into the intake manifold 111a if the engine speed R or throttle valve opening Vs would cause the air-fuel ratio of the engine 110 to fluctuate outside the acceptable range. The purge amount calculation device 10 selects recovery mode M0, for example, when the engine 110 is operating at an engine speed R of less than 2000 rpm, excluding idle speed.

[0090] As shown in Figure 3, the purge amount calculation device 10 selects the first discharge mode M1 when the engine speed R of the engine 110 is operating in a relatively low engine speed range from 2000 rpm to less than 3000 rpm, including the idle speed, or when the throttle valve opening Vs is in a relatively small opening range, including the minimum opening. The valve control device 11 switches the first purge control valve 7 to the open position Vo1 and the second purge control valve 8 to the closed position Vc2 based on the crankshaft angle θ.

[0091] In this embodiment, the valve control device 11 switches the first purge control valve 7 to the open position Vo1 and the second purge control valve 8 to the closed position Vc2 at a crankshaft angle θ corresponding to the intake stroke of the engine 110 (see Figure 1). The valve control device 11 also switches the first purge control valve 7 to the closed position Vc1 and the second purge control valve 8 to the closed position Vc2 at a crankshaft angle θ corresponding to the compression stroke, combustion stroke, and exhaust stroke of the engine 110. In the evaporative emission system 1, the canister 4 and the first purge passage Pp1 become connected to the intake pipe 111a at the timing when the pressure in the intake pipe 111a decreases. In other words, the evaporative emission system 1 discharges gas G into the intake pipe 111a during the intake stroke when the pressure in the intake pipe 111a decreases, and adsorbs evaporated fuel Gf into the canister 4 during the compression stroke, the combustion stroke, and the exhaust stroke.

[0092] As a result, the evaporative emission system 1 discharges gas G through a first purge passage Pp1 that allows evaporated fuel Gf to be discharged into the intake manifold 111a in an engine 110 operating in a relatively low engine speed range R from 2000 rpm to less than 3000 rpm, or in a relatively small throttle valve opening range Vs including the minimum opening, so that fluctuations in the air-fuel ratio remain within an acceptable range.

[0093] As shown in Figure 4, the valve control device 11 selects the second discharge mode M2 ​​when, for example, the engine speed R of the engine 110 is operating in a moderate speed range of 3000 rpm to less than 5000 rpm, or when the throttle valve opening Vs is in a moderate opening range. Based on the crankshaft angle θ, the valve control device 11 switches the first purge control valve 7 to the closed position Vc1 and the second purge control valve 8 to the open position Vo2 (see Figure 1).

[0094] In this embodiment, the evaporative emission system 1 discharges gas G into the intake pipe 111a through the second purge passage Pp2 during the intake stroke when the pressure in the intake pipe 111a decreases, and adsorbs evaporated fuel Gf into the canister 4 during the compression stroke, the combustion stroke, and the exhaust stroke.

[0095] As a result, in engine 110 operating at a moderate engine speed range of 3000 rpm to less than 5000 rpm or a moderate throttle valve opening range of Vs, the evaporative emission system 1 discharges gas G, which contains evaporated fuel Gf, within a range where fluctuations in the air-fuel ratio remain within an acceptable range, through a second purge passage Pp2 that can discharge gas G into the intake manifold 111a.

[0096] As shown in Figure 5, the valve control device 11 selects the third discharge mode M3, for example, when the engine speed R of the engine 110 is operating in a relatively high speed range of 5000 rpm or more, or when the throttle valve opening Vs is in a relatively large opening range including the maximum opening. Based on the crankshaft angle θ, the valve control device 11 switches the first purge control valve 7 to the open position Vo1 and switches the second purge control valve 8 to the open position Vo2.

[0097] In this embodiment, the evaporative emission system 1 discharges gas G into the intake pipe 111a through the third purge passage Pp3 during the intake stroke when the pressure in the intake pipe 111a decreases, and adsorbs evaporated fuel Gf into the canister 4 during the compression stroke, the combustion stroke, and the exhaust stroke.

[0098] As a result, the evaporative emission system 1 discharges gas G through a third purge passage Pp3 that can discharge gas G containing evaporated fuel Gf within an acceptable range into the intake manifold 111a when the engine 110 is operating in a relatively high engine speed range of 5000 rpm or higher, or in a relatively large throttle valve opening range including the maximum opening, so that fluctuations in the air-fuel ratio remain within an acceptable range.

[0099] As shown in Figures 5 and 6, the intake manifold purge pipe 6 of the evaporative emission system 1 is configured as a passage with a third effective cross-sectional area A3 that can discharge gas G into the intake manifold 111a within a range that keeps fluctuations in the air-fuel ratio of the engine 110 within an acceptable range, for example, in a relatively high engine speed range of 5000 rpm or more, including the maximum rotational speed of the engine 110.

[0100] As shown in Figures 3 and 6, a portion of the intake manifold purge pipe 6 is configured as a first purge pipe 6b having a passage with a first effective cross-sectional area A1 that can discharge gas G into the intake manifold 111a in a range that keeps fluctuations in the air-fuel ratio of the engine 110 within an acceptable range in a relatively low engine speed range from 2000 rpm to less than 3000 rpm, which is above the idle speed of the engine 110.

[0101] As shown in Figures 4 and 6, a second purge pipe 6c is configured in parallel with the first purge pipe 6b in a portion of the intake manifold purge pipe 6. The second purge pipe 6c has a passage with a second effective cross-sectional area A2 that discharges more gas G than that which can be discharged to the intake manifold 111a by the first purge pipe 6b, and less gas G than that which can be discharged to the intake manifold 111a by the intake manifold purge pipe 6. The second purge pipe 6c discharges gas G to the intake manifold 111a such that the fluctuation of the air-fuel ratio of the engine 110 remains within an acceptable range when the engine speed R is in the rotational speed range of 3000 rpm or more and less than 5000 rpm.

[0102] The evaporative emission system 1 switches the amount of gas G purged into the intake pipe 111a in four stages by combining a switching method that selects either a first discharge mode M1, which discharges gas G that has passed through the first purge pipe 6b into the exhaust pipe 111a, or a second discharge mode M2, which discharges gas G that has passed through the second purge pipe 6c into the exhaust pipe 111a, with a multi-stage method that changes the amount of gas G purged into the intake pipe 111a to zero, a small amount, or a large amount by switching to one of three modes: recovery mode M0, which does not allow gas G to pass through the intake pipe purge pipe 6; first discharge mode M1, which discharges gas G that has passed through the first purge pipe 6b into the exhaust pipe 111a; or third discharge mode M3, which discharges gas G that has passed through the intake pipe purge pipe 6, including the first purge pipe 6b and the second purge pipe 6c, into the exhaust pipe 111a.

[0103] Thus, the evaporative emission system 1 finely adjusts the amount of gas G purged in a range from relatively low engine speeds R, including idle speed, to relatively high engine speeds R, including maximum speed (see Figure 6). This is achieved by selecting one of the following based on engine speed R or throttle valve opening Vs: a third purge passage Pp3 having a passage with the largest third effective cross-sectional area A3, a first purge passage Pp1 having a passage with the smallest first effective cross-sectional area A1, and a second purge passage Pp2 having a passage with a second effective cross-sectional area A2, which is the third effective cross-sectional area A3 minus the first effective cross-sectional area A1 (see Figure 6). This allows for efficient removal of evaporated fuel Gf from the canister 4 while suppressing fluctuations in the air-fuel ratio of the engine 110 within a predetermined range, thereby continuing the adsorption of evaporated fuel Gf by the canister 4.

[0104] Next, the relationship between the evaporated fuel Gf adsorbed by the canister 4 and the total purge amount Gft will be explained using Figures 1 and 7. Figure 7 is a graph showing the relationship between the total purge amount Gft over a predetermined time in the evaporative emission system 1 and the selected emission mode. The evaporative emission system 1 discharges the evaporated fuel Gf adsorbed by the canister 4 into the intake manifold 111a in the third emission mode M3 if it is estimated that the fluctuation in the air-fuel ratio will remain within a predetermined range even if the evaporated fuel Gf adsorbed by the canister 4 is discharged into the intake manifold 111a in the third emission mode M3.

[0105] As shown in Figures 1 and 7, the estimated maximum amount of evaporated fuel Gf adsorbed on the canister 4 after a predetermined time has elapsed since the evaporated fuel Gf was discharged is the difference between the sum of the maximum amount of evaporated fuel Gf that the canister 4 can adsorb and the maximum amount of evaporated fuel Gf newly generated in the fuel tank 115 during the predetermined time, and the total purge amount Gft, which is the total amount of evaporated fuel Gf contained in the gas G discharged into the intake pipe 111a during the predetermined time. On the other hand, the concentration of evaporated fuel Gf contained in the gas G (hereinafter simply referred to as "concentration of evaporated fuel Gf") decreases as the amount of evaporated fuel Gf adsorbed on the canister 4 decreases. Furthermore, the maximum amount of evaporated fuel Gf that the canister 4 can adsorb and the maximum amount of evaporated fuel Gf newly generated in the fuel tank 115 during the predetermined time are both constant. Therefore, the concentration of evaporated fuel Gf discharged into the intake pipe 111a is determined by the total purge amount Gft of evaporated fuel Gf discharged during the predetermined time. The concentration of evaporated fuel Gf decreases as the total purge amount Gft increases.

[0106] The purge amount calculation device 10 calculates the total purge amount Gft for a predetermined time up to the unit time, at each unit time interval. If the calculated total purge amount Gft is equal to or greater than the reference total purge amount Gfs, which is estimated to be the amount of gas G discharged with a concentration of evaporated fuel Gf that can suppress fluctuations in the air-fuel ratio of the engine 110 within a predetermined range, the purge amount calculation device 10 determines that even if the amount of gas G purged is increased, fluctuations in the air-fuel ratio of the engine 110 will be suppressed within a predetermined range. In other words, the purge amount calculation device 10 determines that the concentration of evaporated fuel Gf is such that even if the amount of gas G purged is increased, fluctuations in the air-fuel ratio of the engine 110 will remain within a predetermined range. If the total purge amount Gft is equal to or greater than the reference total purge amount Gfs, the valve control device 11 switches the first purge control valve 7 to the open position Vo1 and the second purge control valve 8 to the open position Vo2 (corresponding to the third discharge mode M3). As a result, the evaporative emission system 1 more efficiently separates the evaporated fuel Gf adsorbed on the canister 4 without affecting the air-fuel ratio of the engine 110.

[0107] As shown in Figure 7, the total purge amount Gft calculated by the purge amount calculation device 10 is greater than or equal to the reference total purge amount Gfs at time t1. Therefore, the purge amount calculation device 10 selects the third discharge mode M3 regardless of the engine speed R or throttle valve opening Vs. The valve control device 11 switches the first purge control valve 7 to the open position Vo1 and holds that position, and switches the second purge control valve 8 to the open position Vo2 and holds that position. Also, the total purge amount Gft calculated by the purge amount calculation device 10 is less than the reference total purge amount Gfs at time t2. Therefore, the purge amount calculation device 10 selects the first discharge mode M1 based on at least one of the engine speed R or throttle valve opening Vs.

[0108] Thus, when the fluctuation of the air-fuel ratio of the engine 110 is suppressed within a predetermined range, the evaporative emission system 1 switches to the third emission mode M3 to increase the emission of gas G. The evaporative emission system 1 efficiently removes evaporated fuel Gf from the canister 4 while suppressing the impact on the engine 110, thereby ensuring the total purge amount Gft necessary to continue the adsorption of evaporated fuel Gf by the canister 4.

[0109] Furthermore, as shown in Figures 1 to 5, the valve control device 11 controls the opening and closing of the first purge control valve 7 and the second purge control valve 8 to switch between open positions Vo1, Vo2 and closed positions Vc1, Vc2 at a predetermined crankshaft angle θ. For example, the valve control device 11 switches the first purge control valve 7 and the second purge control valve 8 to open positions Vo1, Vo2 just before the intake valve of the engine 110 opens, and switches the first purge control valve 7 and the second purge control valve 8 to closed positions Vc1, Vc2 just before the intake valve closes. Thus, even if the engine speed R fluctuates due to the load, the evaporative emission system 1 discharges gas G into the intake pipe 111a in accordance with the intake and exhaust timings of the engine 110. In this way, the total purge amount Gft can be maintained by efficiently releasing evaporated fuel Gf from the canister 4 in accordance with the intake and exhaust timings of the engine 110.

[0110] [Modification 1 of Embodiment 1] Using Figure 8, we will describe the evaporative emission system 1A, which is a modified example of Embodiment 1. Figure 8 is a schematic diagram showing the configuration of the intake manifold purge pipe 61 in the evaporative emission system 1A.

[0111] As shown in Figure 8, the evaporative emission system 1A has an intake manifold purge pipe 61 instead of the intake manifold purge pipe 6.

[0112] The intake manifold purge pipe 61 is a pipe that flows the gas G in the canister 4 to the intake manifold 111a of the engine 110 (see Figure 1). One end of the intake manifold purge pipe 61 is connected to the canister 4. The other end of the intake manifold purge pipe 61 is connected to the intake manifold 111a. The intake manifold purge pipe 61 has a branched section that splits into two between the one end and the other end. Therefore, the intake manifold purge pipe 61 has a first purge pipe 61a and a second purge pipe 61b that constitute the branched section at the end connected to the canister 4, and a downstream purge pipe 61c that extends from the branched section to the other end connected to the intake manifold 111a.

[0113] One end of the first purge pipe 61a and one end of the second purge pipe 61b are connected to the canister 4. The other end of the first purge pipe 61a and the other end of the second purge pipe 61b are connected to one end of the downstream purge pipe 61c. The other end of the downstream purge pipe 61c is connected to the intake pipe 111a. The first purge pipe 61a and the second purge pipe 61b are connected to the canister 4 and the downstream purge pipe 61c in parallel. In this way, the intake pipe purge pipes 61 through which evaporated fuel Gf and outside air Ga flow constitute a part of the gas passage.

[0114] The first purge control valve 7 is installed at any position in the first purge pipe 61a. The second purge control valve 8 is installed at any position in the second purge pipe 61b.

[0115] The effective cross-sectional area of ​​the first purge pipe 61a is the first effective cross-sectional area A1. The effective cross-sectional area of ​​the second purge pipe 61b is the second effective cross-sectional area A2. The effective cross-sectional area of ​​the downstream purge pipe 61c is greater than or equal to the sum of the first effective cross-sectional area A1 of the first purge pipe 61a and the second effective cross-sectional area A2 of the second purge pipe 61b. Furthermore, the second effective cross-sectional area A2 of the second purge pipe 61b is greater than the first effective cross-sectional area A1 of the first purge pipe 61a.

[0116] The effective cross-sectional area of ​​the third purge passage Pp3 is the third effective cross-sectional area A3, which is the sum of the effective cross-sectional area A1 of the first purge pipe 61a and the effective cross-sectional area A2 of the second purge pipe 61b. The effective cross-sectional area of ​​the first purge passage Pp1 is the first effective cross-sectional area A1 of the first purge pipe 61a. The effective cross-sectional area of ​​the second purge passage Pp2 is the second effective cross-sectional area A2 of the second purge passage 61b. In this way, the evaporative emission system 1A configures the first purge passage Pp1, the second purge passage Pp2, and the third purge passage Pp3, each with different effective cross-sectional areas, by switching and maintaining the open and closed positions of the first purge control valve 7 and the second purge control valve 8.

[0117] [Modification 2 of Embodiment 1] Using Figure 9, we will describe the evaporative emission system 1B, which is a modified example of Embodiment 1. Figure 9 is a schematic diagram showing the configuration of the intake manifold purge pipe 62 in the evaporative emission system 1B.

[0118] As shown in Figure 9, the evaporative emission system 1B has an intake manifold purge pipe 62 in place of the intake manifold purge pipe 6.

[0119] The intake manifold purge pipe 62 is a pipe that flows the gas G in the canister 4 to the intake manifold 111a of the engine 110 (see Figure 1). One end of the intake manifold purge pipe 62 is connected to the canister 4. The other end of the intake manifold purge pipe 62 is connected to the intake manifold 111a. The intake manifold purge pipe 62 has a branched section that splits into two between the one end and the other end. Therefore, the intake manifold purge pipe 62 has an upstream purge pipe 62a that constitutes the section from the one end connected to the canister 4 to the branched section, and a first purge pipe 62b and a second purge pipe 62c that constitute the branched section at the other end connected to the intake manifold 111a.

[0120] One end of the upstream purge pipe 62a is connected to the canister 4. The other end of the upstream purge pipe 62a is connected to one end of the first purge pipe 62b and one end of the second purge pipe 62c, respectively. The other end of the first purge pipe 62b and the other end of the second purge pipe 62c are connected to the intake pipe 111a, respectively. The first purge pipe 62b and the second purge pipe 62c are connected in parallel to the upstream purge pipe 62a and the intake pipe 111a. In this way, the intake pipe purge pipe 62, through which evaporated fuel Gf and outside air Ga flow, constitutes a part of the gas passage.

[0121] The first purge control valve 7 is installed at any position in the first purge pipe 62b. The second purge control valve 8 is installed at any position in the second purge pipe 62c.

[0122] The effective cross-sectional area of ​​the first purge pipe 62b is the first effective cross-sectional area A1. The effective cross-sectional area of ​​the second purge pipe 62c is the second effective cross-sectional area A2. The effective cross-sectional area of ​​the upstream purge pipe 62a to which the first purge pipe 62b and the second purge pipe 62c are connected is greater than or equal to the sum of the first effective cross-sectional area A1 of the first purge pipe 62b and the second effective cross-sectional area A2 of the second purge pipe 62c. Furthermore, the second effective cross-sectional area A2 of the second purge pipe 62c is greater than the first effective cross-sectional area A1 of the first purge pipe 62b.

[0123] The effective cross-sectional area of ​​the third purge passage Pp3 is the third effective cross-sectional area A3, which is the sum of the effective cross-sectional area A1 of the first purge pipe 62b and the effective cross-sectional area A2 of the second purge pipe 62c. The effective cross-sectional area of ​​the first purge passage Pp1 is the first effective cross-sectional area A1 of the first purge pipe 62b. The effective cross-sectional area of ​​the second purge passage Pp2 is the second effective cross-sectional area A2 of the second purge passage 62c. In this way, the evaporative emission system 1B configures the first purge passage Pp1, the second purge passage Pp2, and the third purge passage Pp3, each with different effective cross-sectional areas, by switching and maintaining the open and closed positions of the first purge control valve 7 and the second purge control valve 8.

[0124] [Modification 3 of Embodiment 1] Using Figure 10, we will describe the evaporative emission system 1C, which is a modification 3 of Embodiment 1. Figure 10 is a schematic diagram showing the configuration of the intake manifold purge pipe 63 in the evaporative emission system 1C.

[0125] As shown in Figure 10, the evaporative emission system 1C has an intake manifold purge pipe 63 instead of an intake manifold purge pipe 6.

[0126] The intake manifold purge pipe 63 is a pipe that flows the gas G, which includes evaporated fuel Gf and outside air Ga in the canister 4, to the intake manifold 111a of the engine 110. One end of the intake manifold purge pipe 63 is connected to the canister 4. The other end of the intake manifold purge pipe 63 is connected to the intake manifold 111a. The intake manifold purge pipe 63 consists of a first purge pipe 63a and a second purge pipe 63b. The first purge pipe 63a and the second purge pipe 63b are configured to be in parallel. Therefore, one end of the first purge pipe 63a and one end of the second purge pipe 63b are connected to the canister 4, respectively. The other end of the first purge pipe 63a and the other end of the second purge pipe 63b are connected to the intake manifold 111a, respectively. Thus, the purge pipe 63 for the intake manifold, through which the evaporated fuel Gf and outside air Ga flow, constitutes a part of the gas passage.

[0127] The first purge control valve 7 is installed at any position in the first purge pipe 63a. The second purge control valve 8 is installed at any position in the second purge pipe 63b.

[0128] The effective cross-sectional area of ​​the first purge pipe 63a is the first effective cross-sectional area A1. The effective cross-sectional area of ​​the second purge pipe 63b is the second effective cross-sectional area A2. Furthermore, the second effective cross-sectional area A2 of the second purge pipe 63b is larger than the first effective cross-sectional area A1 of the first purge pipe 63a.

[0129] The effective cross-sectional area of ​​the third purge passage Pp3 is the third effective cross-sectional area A3, which is the sum of the effective cross-sectional area A1 of the first purge pipe 63a and the effective cross-sectional area A2 of the second purge pipe 63b. The effective cross-sectional area of ​​the first purge passage Pp1 is the first effective cross-sectional area A1 of the first purge pipe 63a. The effective cross-sectional area of ​​the second purge passage Pp2 is the second effective cross-sectional area A2 of the second purge pipe 63b. In this way, the evaporative emission system 1C configures the first purge passage Pp1, the second purge passage Pp2, and the third purge passage Pp3, each with different effective cross-sectional areas, by switching and maintaining the open and closed positions of the first purge control valve 7 and the second purge control valve 8.

[0130] [Embodiment 2] Using Figure 11, we will describe the vehicle 101, which is a saddle-type vehicle according to the present invention. Figure 11 is a schematic diagram showing the configuration of a vehicle 101 having an evaporative emission system 1 according to Embodiment 2 of the present invention. The vehicle 101 is, for example, a motorcycle. The vehicle 101 comprises a body frame 102, a front wheel 104, and a rear wheel 105. The vehicle 101 turns in a tilted position. That is, the vehicle 101 tilts to the left when turning to the left and tilts to the right when turning to the right.

[0131] As shown in Figure 11, the vehicle frame 102 supports various components such as the evaporative emission system 1, handlebars 106, steering shaft 107, seat 108, transmission 109, engine 110, and fuel tank 115. The vehicle frame 102 includes a head pipe 103. The vehicle frame 102 is positioned to extend in the longitudinal direction of the vehicle 101. The vehicle frame 102 has a portion that extends rearward and upward of the vehicle 101 and a portion that extends rearward and downward of the vehicle 101.

[0132] A head pipe 103 is connected to the front of the vehicle frame 102. A fuel tank 115 for storing fuel for the engine 110 is fixed to the front upper part of the vehicle frame 102, so as to be located in the center of the vehicle 101 in the left-right direction. A seat 108 for the occupant is located in the rear and upward part of the vehicle frame 102, behind the fuel tank 115, and is also located in the center of the vehicle 101 in the left-right direction.

[0133] The lower part of the vehicle frame 102 supports the transmission 109 and the engine 110. The engine 110 is connected to an intake pipe 111a and an exhaust pipe 111b (see Figure 3), which are intake passages. The engine 110 also has an engine speed sensor 113 for detecting the engine speed R and a crankshaft angle sensor 114 for detecting the crankshaft angle θ of the engine 110.

[0134] The head pipe 103 is located at the front of the vehicle 101. The head pipe 103 is connected to the front end of the body frame 102. The steering shaft 107, which is connected to a handlebar 106 that steers the front wheels 104, is rotatably supported by the head pipe 103. Below the steering shaft 107, the front wheels 104 are rotatably supported. The rear wheels 105 are rotatably supported at the rear of the body frame 102. Power is transmitted to the rear wheels 105 from the transmission 109.

[0135] The evaporative emission system 1 is supported by the vehicle frame 102. The fuel tank 115 is connected to the canister 4 by a fuel tank purge pipe 3, which is a purge passage for the fuel tank. The canister 4 is also connected to the intake manifold 111a of the engine 110 via an intake manifold purge pipe 6, which includes a first purge pipe 6b and a second purge pipe 6c. The engine information acquisition device 9 is electrically connected to the throttle valve 112, the engine speed sensor 113, and the crankshaft angle sensor 114. The engine information acquisition device 9 is also electrically connected to the engine control device 116 of the engine 110. The engine control device 116 is configured to transmit information related to the engine 110 to the engine information acquisition device 9.

[0136] The evaporative emission system 1 acquires at least one of the engine speed R detected by the engine speed sensor 113 or the throttle valve opening Vs of the engine 110 via the engine information acquisition device 9. Based on the operation of the engine 110, the evaporative emission system 1 operates the first purge control valve 7 and the second purge control valve 8. Therefore, the evaporative emission system 1 calculates the amount of gas G, including evaporated fuel Gf, to be purged into the intake manifold 111a based on the acquired engine speed R or throttle valve opening Vs. This makes it possible to maintain the total amount of evaporated fuel Gf purged Gft in the evaporative emission system 1 while suppressing fluctuations in the air-fuel ratio of the engine 110 within a predetermined range.

[0137] [Other embodiments] In the embodiment described above, the evaporative emission system 1 has a first purge passage Pp1, a second purge passage Pp2, and a third purge passage Pp3 as a plurality of purge passages. However, the evaporative emission system may have four or more purge passages as a plurality of purge passages.

[0138] In the above-described embodiment 1, the evaporative emission system 1 has a first purge pipe 6b and a second purge pipe 6c that discharge gas G from the canister 4 to the exhaust pipe 111a. However, the evaporative emission system may have three or more purge pipes that discharge gas G from the canister to the exhaust pipe 111a.

[0139] In the above-described embodiment 1, the evaporative emission system 1 switches the first purge pipe 6b and the second purge pipe 6c between a closed state and an open state using the first purge control valve 7 and the second purge control valve 8, which are ON-OFF valves. However, the first purge control valve and the second purge control valve may be proportional control valves that can be opened and closed at any degree.

[0140] In the above-described embodiment 1, the evaporative emission system 1 has an effective cross-sectional area A1 of the first purge pipe 6b that is larger than the effective cross-sectional area A2 of the second purge pipe 6c. However, the effective cross-sectional area of ​​the second purge pipe may be smaller than the effective cross-sectional area of ​​the first purge pipe. In other words, it is sufficient that the effective cross-sectional areas of the second purge pipe and the first purge pipe are different.

[0141] In the above-described embodiment 1, the engine information acquisition device 9, the purge amount calculation device 10, and the valve control device 11 are configured as control devices for the evaporative emission system 1. However, at least one of the engine information acquisition device, the purge amount calculation device, and the valve control device may be configured integrally with the engine control device of the engine.

[0142] In the embodiments 1 and 2 described above, the engine information acquisition device 9 acquires the engine speed R from the engine speed sensor 113, the throttle valve opening Vs from the throttle valve 112, and the crankshaft angle θ from the crankshaft angle sensor 114. However, the engine information acquisition device may also be configured to acquire the engine speed R, throttle valve opening Vs, and crankshaft angle θ from the engine control device.

[0143] In the above-described embodiment 1, recovery mode M0 is selected when the engine 110 is operating at an engine speed R of less than 2000 rpm, excluding idle speed. The first emission mode M1 is selected when the engine 110 is operating at an engine speed R of between 2000 rpm and less than 3000 rpm, including idle speed. The second emission mode M2 ​​is selected when the engine 110 is operating at an engine speed R of between 3000 rpm and less than 5000 rpm. The third emission mode M3 is selected when the engine 110 is operating at an engine speed R of 5000 rpm or higher, including maximum speed. However, the engine speed or throttle valve opening to which the recovery mode, first emission mode, second emission mode, and third emission mode apply should be set to a value based on the engine performance, engine characteristics, operating environment, canister capacity, fuel tank capacity, fuel type, season, legal regulations, etc. Alternatively, the system may be configured to switch modes based on conditions other than engine speed or throttle valve opening.

[0144] Although embodiments of the present invention have been described above, the embodiments described above are merely examples for carrying out the present invention. Therefore, the invention is not limited to the embodiments described above, and it is possible to carry out the invention by appropriately modifying the embodiments described above without departing from the spirit of the invention. [Explanation of symbols]

[0145] 1, 1A, 1B, 1C: Evaporative Emission System 2. Shut-off valve 3. Purge pipe for fuel tank 4 Canister 5. Bent pipe 5a Vent valve 6, 61, 62, 63 Intake pipe purge tube 6a, 62a Upstream purge pipe 6b, 61a, 62b, 63a First purge tube 6c, 61b, 62c, 63b Second purge tube 6d, 61c Downstream purge pipe 7. First purge control valve 8. Second purge control valve 9. Engine information acquisition device 10. Purge volume calculation device 11 Valve control device 101 vehicles 102 Body frame 103 Headpipe 104 Front Wheel 105 Rear wheel 106 Handlebar 107 Steering shaft 108 seats 109 Transmission 110 engine 111a Intake pipe 111b Exhaust pipe 112 Throttle valve 113 Engine speed sensor 114 Crankshaft Angle Sensor 115 Fuel Tank 116 Engine control unit M0 Recovery Mode M1 First Emission Mode M2 Second Emission Mode M3 Third Emission Mode Pp1 First Purge Passage Pp2 Second Purge Passage Pp3 Third Purge Corridor Vo1, Vo2 open position Vc1, Vc2 closed position R Engine speed Vs Throttle valve opening θ Crank axis angle G gas F fuel Gf Evaporative Fuel Ga outside air Gft total purge amount Gfs Standard Purge Total Amount t1, t2 time

Claims

1. A canister that recovers evaporated fuel generated in the fuel tank that stores the engine's fuel, The canister includes an outside air intake passage for introducing outside air, The canister includes a purge passage for a fuel tank for discharging the evaporated fuel, A first purge passage and a second purge passage discharge a gas containing at least one of the recovered evaporated fuel or outside air introduced through the outside air intake passage from the canister into the intake passage of the engine, A first on / off valve that switches between a closed position that blocks the first purge passage and an open position that opens it, and maintains that position, A second on / off valve that switches between a closed position that blocks the second purge passage and an open position that opens it, and maintains that position, An engine information acquisition device that acquires at least one of the engine speed of the engine or the throttle valve opening degree of the engine, A purge amount calculation device that determines the open positions of the first on-off valve and the second on-off valve, A valve control device that controls the opening and closing of the first on-off valve and the second on-off valve, An evaporative emission system having, The first purge passage is, In the evaporative emission system, among the multiple purge passages through which the gas passes, it is configured as a passage having the smallest effective cross-sectional area, which is a first effective cross-sectional area. The second purge passage is, In the evaporative emission system, the passage is configured to have a second effective cross-sectional area obtained by subtracting the first effective cross-sectional area from a third effective cross-sectional area which is the sum of the effective cross-sectional areas of a plurality of purge passages through which the gas passes. The engine information acquisition device is, The engine speed or the throttle valve opening degree is obtained, The purge amount calculation device is, Based on at least one of the engine speed or throttle valve opening angle acquired by the engine information acquisition device, A recovery mode is provided in which the evaporated fuel is recovered by the canister without being supplied to the engine by switching the first on / off valve to the closed position and holding that position, and switching the second on / off valve to the closed position and holding that position, A first discharge mode is provided in which the gas that has passed through the first purge passage is supplied to the engine by switching the first on / off valve to the open position and holding that position, and switching the second on / off valve to the closed position and holding that position, A second discharge mode is provided in which the gas that has passed through the second purge passage is supplied to the engine by switching the first on / off valve to the closed position and holding that position, and switching the second on / off valve to the open position and holding that position, One of the following modes is selected: a third discharge mode in which the gas that has passed through the first purge passage and the second purge passage is supplied to the engine by switching the first on / off valve to the open position and holding that position, and switching the second on / off valve to the open position and holding that position. The valve control device is The opening and closing of the first and second on / off valves is controlled so that the purge amount calculation device enters the selected mode. Evaporative emission system.

2. In the evaporative emission system according to claim 1, The first purge passage is, In at least one of the following states, where the engine speed is greater than or equal to the idle speed, or the throttle valve opening is greater than or equal to the opening that maintains the idle speed, a gas containing evaporated fuel in a range that allows combustion of the engine to continue is passed through. Evaporative emission system.

3. In the evaporative emission system according to claim 1 or 2, The second effective cross-sectional area is, Larger than the first effective cross-sectional area, Evaporative emission system.

4. In the evaporative emission system according to any one of claims 1 to 2, The engine information acquisition device is, The crankshaft angle of the aforementioned engine is further obtained, The valve control device is The engine information acquisition device controls the opening and closing of the first on / off valve and the second on / off valve based on the crankshaft angle acquired by the engine information acquisition device. Evaporative emission system.

5. In the evaporative emission system according to claim 1 or 2, The purge amount calculation device is, Based on the rotational speed of the engine or the throttle valve opening and the first effective cross-sectional area or the second effective cross-sectional area of ​​the purge passage through which the gas passes, the total purge amount, which is the total amount of evaporated fuel contained in the gas discharged into the intake passage within a predetermined time, is calculated. If the total purge amount is equal to or greater than the reference total purge amount that suppresses fluctuations in the engine's air-fuel ratio within a predetermined range, the third emission mode is selected. Evaporative emission system.

6. A saddle-type vehicle equipped with the evaporative emission system according to claim 1 or 2, The aforementioned saddle-type vehicle is, The engine and A fuel tank for storing fuel for the aforementioned engine, Engine control device, It has, The aforementioned fuel tank is The fuel tank purge passage is connected to the canister, The aforementioned intake passage is The first purge passage and the second purge passage are connected to the canister, The aforementioned engine control device is The engine speed or at least one of the throttle valve opening degree is transmitted to the engine information acquisition device. or The engine information acquisition device is, The engine speed detected by the engine speed sensor of the engine or at least one of the throttle valve opening angle of the engine is acquired. A saddle-type vehicle.

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