Canister device

Abstract

Provided is a canister device that is advantageous for reducing fuel vapor, which is discharged from a sub-chamber to the atmosphere.　In addition to a first purge port 32, which is provided at a place of a case 24 where a main chamber 26 is formed, a second purge port 34 is provided at a place of the case 24 where a sub-chamber 28 is formed, and a second purge passage 18 for communicating the sub-chamber 28 with an intake passage 40 is connected to the second purge port 34, thereby enabling fuel vapor adsorbed in the sub-chamber 28 to be directly guided from the second purge port 34 to the second purge passage 18 without passing through the main chamber 26. Hence, since it is advantageous for efficiently purging the sub-chamber 28, it is also advantageous for suppressing the fuel vapor which is discharged from the sub-chamber 28 to the atmosphere.

Description

Canister Device

[0001] The present invention relates to a canister device for adsorbing fuel vapors in a fuel tank of an internal combustion engine.

[0002] Vehicles equipped with internal combustion engines are provided with a canister device that absorbs fuel vapor (fuel evaporative gas) evaporating from fuel in a fuel tank and prevents the fuel vapor from evaporating into the atmosphere. The canister device includes a canister body with a case that defines a main chamber and an auxiliary chamber. The canister body includes a purge port and a charge port (vapor port) provided in the part of the case that defines the main chamber, and an atmospheric port provided in the part of the case that defines the auxiliary chamber. The canister device is configured such that the purge port is connected to a purge passage that communicates with an intake passage of the internal combustion engine, the charge port is connected to a charge passage that communicates with the fuel tank, and the atmospheric port is connected to an atmospheric passage that communicates with the atmosphere (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-40806

[0004] However, the canister device configuration disclosed in the above-mentioned patent document has a problem in that as the amount of remaining adsorbed fuel vapor in the auxiliary chamber provided with the atmospheric port increases, the adsorbed fuel vapor is more likely to be discharged from the atmospheric port through the atmospheric passage. The present invention has been devised in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a canister device that is advantageous in suppressing the amount of fuel vapor discharged into the atmosphere from the auxiliary chamber.

[0005] In order to achieve the above object, one embodiment of a canister device for adsorbing fuel vapors in a fuel tank of an internal combustion engine of the present invention comprises a canister body having a case in which a main chamber and an auxiliary chamber are provided that communicate with each other and in which a fuel vapor adsorbent is stored in the main chamber and the auxiliary chamber, a charge passage configured to be able to communicate with the fuel tank, an intake passage configured to be able to communicate with an intake pipe of the internal combustion engine, a purge passage connecting the inside of the case with the intake passage, and an atmosphere passage configured to be able to communicate the auxiliary chamber with the atmosphere, wherein the purge passage includes a first purge passage connecting the main chamber with the intake passage and a second purge passage connecting the auxiliary chamber with the intake passage. Another embodiment of the present invention is characterized in that the engine has a charge port provided in the case where the main chamber is formed and connected to the charge passage, a first purge port provided in the case where the main chamber is formed and connected to the first purge passage, an atmospheric port provided in the case where the auxiliary chamber is formed and connected to the atmospheric passage, and a second purge port provided in the case where the auxiliary chamber is formed and connected to the second purge passage. Yet another embodiment of the present invention is characterized in that the second purge port is provided in the case where the auxiliary chamber is formed and opposite the atmospheric port. Yet another embodiment of the present invention is characterized in that the axis of the second purge port and the axis of the atmospheric port are aligned. In yet another embodiment of the present invention, the first purge passage and the second purge passage are connected to the intake passage via a junction, and a three-way valve is provided at the junction, and the three-way valve is configured to be switchable between a first state in which the first purge passage communicates with the intake passage, and a second state in which the second purge passage communicates with the intake passage.Another embodiment of the present invention is characterized by comprising a first concentration sensor that detects the concentration of fuel vapor in the first purge passage and generates a signal indicating the concentration, a second concentration sensor that detects the concentration of fuel vapor in the second purge passage and generates a signal indicating the concentration, and a control unit that generates a signal to switch the three-way valve from one of the first state and the second state to the other when the concentration indicated by the signal from either the first concentration sensor or the second concentration sensor remains below a predetermined value for a predetermined period of time. Another embodiment of the present invention is characterized by comprising a concentration sensor that detects the concentration of fuel vapor in the intake passage and generates a signal indicating the concentration, and a control unit that generates a signal to switch the three-way valve from one of the first state and the second state to the other when the concentration indicated by the signal from the concentration sensor remains below a predetermined value for a predetermined period of time. Still another embodiment of the present invention is characterized by comprising a control unit that generates a signal to switch the three-way valve so that purging of fuel vapor from the auxiliary chamber is prioritized over purging of fuel vapor from the main chamber. Yet another embodiment is characterized in that it includes a control unit that measures the operating time during which a purge valve provided in the intake pipe of the internal combustion engine is open, and generates a signal to switch the three-way valve from one of the first state and the second state to the other based on the measured operating time.

[0006] According to one embodiment of the present invention, a second purge port is provided in the case defining the auxiliary chamber, and a second purge passage connecting the auxiliary chamber to the intake passage is connected to the second purge port. This allows fuel vapor adsorbed in the auxiliary chamber to be guided directly from the second purge port to the second purge passage without passing through the main chamber. This is advantageous for efficiently purging the auxiliary chamber and for reducing the amount of fuel vapor discharged from the auxiliary chamber to the atmosphere. Furthermore, if the second purge port is provided in the case defining the auxiliary chamber opposite the atmospheric port, it is more advantageous for efficiently guiding air introduced from the atmospheric passage to the auxiliary chamber via the atmospheric port from the second purge port to the second purge passage, which is more advantageous for efficiently purging the auxiliary chamber and for reducing the amount of fuel vapor discharged from the auxiliary chamber to the atmosphere. Furthermore, if the axis of the second purge port and the axis of the atmospheric port are aligned, air introduced from the atmospheric passage through the atmospheric port into the auxiliary chamber flows in a straight line within the auxiliary chamber, which is more advantageous for efficiently introducing the air introduced into the auxiliary chamber from the second purge port to the second purge passage, which is more advantageous for efficiently purging the auxiliary chamber and suppressing fuel vapor discharged from the auxiliary chamber to the atmosphere. Furthermore, if a three-way valve is provided at the junction where the first purge passage and the second purge passage connect to the intake passage, and the three-way valve is switchable between a first state that connects the first purge passage to the intake passage and a second state that connects the second purge passage to the intake passage, switching the three-way valve is advantageous for easily and reliably purging the auxiliary chamber and suppressing fuel vapor discharged from the auxiliary chamber to the atmosphere. Furthermore, if a first concentration sensor, a second concentration sensor, and a control unit that switches the three-way valve from one of the first state and the second state to the other when the concentration detected by either the first concentration sensor or the second concentration sensor remains below a predetermined value for a predetermined time period are provided, the purging operations of the auxiliary chamber and the main chamber can be reliably and stably switched and executed based on the remaining adsorption amounts in the auxiliary chamber and the main chamber, which is advantageous for efficient purging of the canister device.Furthermore, if a concentration sensor and a control unit that switches the three-way valve from one of the first and second states to the other when the concentration detected by the concentration sensor remains below a predetermined value for a predetermined time, the purging operations of the auxiliary chamber and the main chamber can be reliably and stably switched based on the remaining adsorption amounts in the auxiliary chamber and the main chamber, which is advantageous not only for efficient purging of the canister device but also for cost reduction by reducing the number of concentration sensors. Furthermore, if the control unit switches the three-way valve so that purging of the auxiliary chamber is prioritized over purging of the main chamber, this is advantageous for efficient purging of the auxiliary chamber and for reducing the amount of fuel vapor emitted into the atmosphere from the auxiliary chamber.

[0007] 1 is an explanatory diagram showing a state in which the auxiliary chamber is purged in the canister device of the first embodiment; 2 is an explanatory diagram showing a state in which the main chamber is purged in the canister device of the first embodiment; 3 is an explanatory diagram showing the configuration of a canister device of a second embodiment; 4 is a diagram showing an example of the change over time in the concentration of fuel vapor detected by a concentration sensor; 5 is an explanatory diagram showing the configuration of a canister device of a third embodiment; 6 is an explanatory diagram showing the configuration of a canister device of a fourth embodiment;

[0008] First Embodiment An embodiment of the present invention will now be described with reference to the drawings. As shown in FIGS. 1 and 2, a canister device 10A includes a canister body 12, a charge passage 14, a first purge passage 16, a second purge passage 18, an atmospheric passage 20, and a three-way valve (switching valve) 22. The canister body 12 includes a synthetic resin case 24. The case 24 includes a first wall portion 24A and a second wall portion 24B that face each other at a distance, and a peripheral wall portion 24C that connects the first wall portion 24A and the second wall portion 24B. The case 24 includes a main chamber 26 and an auxiliary chamber 28, each having a capacity smaller than that of the main chamber 26, separated by a partition wall 24D. The main chamber 26 and the auxiliary chamber 28 are connected to each other via an opening 24E provided in the partition wall 24D, and although neither is shown, they contain a fuel adsorbent (such as activated carbon) that adsorbs fuel vapor evaporating from the fuel tank.

[0009] The canister body 12 is provided with a charge port (vapor port) 30, a first purge port 32, a second purge port 34, and an atmospheric port 36. The charge port 30 is provided in a first wall portion 24A of the case 24 that defines the main chamber 26, and is connected to a charge passage (evaporative fuel introduction passage) 14 that connects the main chamber 26 to a fuel tank (not shown). The first purge port 32 is provided in the first wall portion 24A of the case 24 that defines the main chamber 26, and is connected to a first purge passage 16 that connects the main chamber 26 to an intake passage 40 that is connected to an intake pipe 41 of the internal combustion engine. The second purge port 34 is provided in a second wall portion 24B of the case 24 that defines the auxiliary chamber 28, and is connected to a second purge passage 18 that connects the auxiliary chamber 28 to the intake passage 40. In this embodiment, the second purge port 34 is provided in the second wall portion 24B, which is the portion of the case 24 that forms the auxiliary chamber 28 and faces the atmospheric port 36. The atmospheric port 36 is provided in the first wall portion 24A, which is the portion of the case 24 that forms the auxiliary chamber 28, and is the portion to which the atmospheric passage 20, which connects the auxiliary chamber 28 to the atmosphere, is connected. In addition, the axis of the second purge port 34 and the axis of the atmospheric port 36 are aligned.

[0010] The first purge passage 16 and the second purge passage 18 are connected to the intake passage 40 via a junction 38, and a three-way valve 22 is provided at the junction 38. The three-way valve 22 is configured to be switchable between a first state, which connects the first purge passage 16 to the intake passage 40 as shown in FIG. 2, and a second state, which connects the second purge passage 18 to the intake passage 40 as shown in FIG. 1. When the purge valve 42 is open during operation of the internal combustion engine, the three-way valve 22 can be configured to switch between the first and second states in response to a switching signal from a control device (not shown). In the drawing, reference numeral 42 denotes a purge valve provided in the intake passage 40 on the internal combustion engine side. The purge valve 42 is opened when purging of fuel adsorbed in the canister device 10A is being performed, and is closed when purging is not being performed. The purge valve 42 is connected at the opposite side to the three-way valve 22 to an intake pipe 41 of the internal combustion engine.

[0011] Next, the operation and effect of the canister device of this embodiment will be described. It is assumed that both the main combustion chamber 26 and the auxiliary combustion chamber 28 have sufficiently adsorbed fuel vapor, and that purging (scavenging) of the main combustion chamber 26 and the auxiliary combustion chamber 28 is required. When the internal combustion engine is operating, the intake pipe 41 becomes negative pressure. When the purge valve 42 opens in this state, the intake passage 40 also becomes negative pressure. As shown in FIG. 1 , when the three-way valve 22 is switched to its second position, air is drawn in from the atmospheric passage 20 through the atmospheric port 36, flows through the auxiliary combustion chamber 28, and is directed from the second purge port 34 to the second purge passage 18, as indicated by the dashed arrows in the figure. The air is then discharged through the three-way valve 22 into the intake passage 40, purging the fuel vapor adsorbed by the adsorbent in the auxiliary combustion chamber 28 into the intake pipe 41 of the internal combustion engine. 2, when the three-way valve 22 is switched to the first position, air is drawn in from the atmospheric passage 20 through the atmospheric port 36, and flows into the main chamber 26 via the auxiliary chamber 28, as indicated by the dashed arrows in the figure, and is then guided from the first purge port 32 to the first purge passage 16. The air is then expelled into the intake passage 40 via the three-way valve 22, and the fuel vapor adsorbed in the main chamber 26 is purged into the intake pipe 41. In this way, the auxiliary chamber 28 is purged before the main chamber 26 is purged. This series of operations is performed each time a purge operation of the canister device 10A is required.

[0012] According to this embodiment, a second purge port 34 is provided in the portion of the case 24 that defines the auxiliary combustion chamber 28, and the second purge passage 18 that connects the auxiliary combustion chamber 28 to the intake passage 40 is connected to this second purge port 34, so that fuel vapor adsorbed in the auxiliary combustion chamber 28 can be led directly from the second purge port 34 to the second purge passage 18 without passing through the main combustion chamber 26. This allows efficient purging of the auxiliary combustion chamber 28, which is advantageous in suppressing fuel vapor being discharged into the atmosphere from the auxiliary combustion chamber 28.

[0013] Furthermore, in this embodiment, the second purge port 34 is provided in a portion of the case 24 that forms the auxiliary chamber 28 and faces the atmospheric port 36, which is advantageous in efficiently guiding the air that is introduced from the atmospheric passage 20 to the auxiliary chamber 28 via the atmospheric port 36 from the second purge port 34 to the second purge passage 18. This allows the auxiliary chamber 28 to be purged more efficiently, which is advantageous in suppressing fuel vapor from being discharged into the atmosphere from the auxiliary chamber 28.

[0014] Furthermore, in this embodiment, the axis of the second purge port 34 and the axis of the atmospheric port 36 are aligned, so that the air introduced into the auxiliary chamber 28 from the atmospheric passage 20 via the atmospheric port 36 flows along a straight line within the auxiliary chamber 28, which is more advantageous in efficiently guiding the air introduced into the auxiliary chamber 28 from the second purge port 34 to the second purge passage 18. This allows for efficient purging of the auxiliary chamber 28, which is more advantageous in suppressing fuel vapor being discharged from the auxiliary chamber 28 into the atmosphere.

[0015] In this embodiment, a three-way valve 22 is provided at a junction 38 where the first purge passage 16 and the second purge passage 18 are connected to the intake passage 40, and the three-way valve 22 is configured to be switchable between a first state in which the first purge passage 16 communicates with the intake passage 40 and a second state in which the second purge passage 18 communicates with the intake passage 40. Therefore, in the first state, air introduced from the atmospheric passage 20 via the atmospheric port 36 is introduced into the first purge passage 16 via the auxiliary chamber 28 and the main chamber 26, thereby purging both the auxiliary chamber 28 and the main chamber 26. In the second state, air introduced from the atmospheric passage 20 via the atmospheric port 36 is introduced into the second purge passage 18 via the auxiliary chamber 28, thereby enabling purging of the auxiliary chamber 28 to be performed with priority over purging of the main chamber 26. Therefore, by switching the three-way valve 22, the auxiliary chamber 28 can be purged easily and reliably, which is more advantageous in suppressing fuel vapor being discharged from the auxiliary chamber 28 into the atmosphere.

[0016] Second Embodiment Next, a canister device 10B according to a second embodiment will be described with reference to FIG. 3 . In the following description, parts and components similar to those of the first embodiment are denoted by the same reference numerals, and their description will be omitted. The following description will focus on the differences. The second embodiment differs from the first embodiment in that it includes a first concentration sensor 44, a second concentration sensor 46, and a control unit 48A. The first concentration sensor 44 detects the concentration of fuel vapor in the first purge passage 16 and generates an electrical signal indicative of the detected fuel vapor concentration, which is supplied to the control unit 48A. The second concentration sensor 46 detects the concentration of fuel vapor in the second purge passage 18 and generates an electrical signal indicative of the detected fuel vapor concentration, which is supplied to the control unit 48A. In other words, the concentration detected by the first concentration sensor 44 generally indicates the remaining adsorption amount in the main chamber 26, and the concentration detected by the second concentration sensor 46 indicates the remaining adsorption amount in the auxiliary chamber 28. The control unit 48A provides the three-way valve 22 with a signal to switch from one of the first state and the second state to the other based on the concentration signals supplied from the first concentration sensor 44 and the second concentration sensor 46.

[0017] 4 shows the change over time in the concentration of fuel vapor in the canister device 10B detected by the concentration sensors. The horizontal axis represents elapsed time T, and the vertical axis represents the concentration V detected by the first and second concentration sensors 44, 46. Fuel vapor evaporating from the fuel tank is adsorbed by the adsorbent in the canister device 10B via the charge passage 14 and the charge port 30. As the amount of adsorbed fuel vapor increases, in other words, as the amount of adsorbed fuel remaining in the canister device 10B increases, the concentration V detected by the first and second concentration sensors 44, 46 increases. Then, at a certain time Ts, the purge valve 42 on the internal combustion engine side opens, initiating the purging operation of the canister device 10B, and the amount of adsorbed fuel remaining in the canister device 10B begins to decrease. Therefore, the concentration V detected by the first and second concentration sensors 44, 46 decreases over time. Here, the control unit 48A determines that the purge is complete when the concentration V falls below a predetermined threshold value V1 for a predetermined time ΔT, and generates a signal to switch the three-way valve 22 from one of the first state and the second state to the other.

[0018] The operation of the control unit 48A will be described in detail below. As in the first embodiment, it is assumed that the adsorbents in both the main combustion chamber 26 and the auxiliary combustion chamber 28 have sufficiently adsorbed fuel vapor, and that purging (scavenging) of the main combustion chamber 26 and the auxiliary combustion chamber 28 is required. When the internal combustion engine is operating, the intake pipe 41 is placed under negative pressure. Under this condition, the purge valve 42 opens, creating a negative pressure in the intake passage 40. In response to a switching signal from the control unit 48A, the three-way valve 22 is switched to the second state to initiate a purge operation, and purging of the auxiliary combustion chamber 28 is prioritized. When the signal indicating the concentration V supplied from the second concentration sensor 46 remains below the predetermined threshold value V1 for a predetermined time ΔT, the control unit 48A determines that purging of the auxiliary combustion chamber 28 is complete, and generates a signal to switch the three-way valve 22 from the second state to the first state. Therefore, when purging of the auxiliary chamber 28 is prioritized, the control unit 48A determines that purging of the auxiliary chamber 28 is complete when the signal indicating the concentration V supplied from the second concentration sensor 46 remains below the predetermined threshold value V1 for a predetermined time ΔT, and switches the three-way valve 22 from the second state to the first state. That is, purging of the main chamber 26 is then performed. Then, the control unit 48A determines that purging of the main chamber 26 is complete when the signal indicating the concentration V supplied from the first concentration sensor 44 remains below the predetermined threshold value V1 for a predetermined time ΔT, and switches the three-way valve 22 from the first state to the second state, thereby once again enabling purging of the auxiliary chamber 28 to be prioritized. This series of operations is performed each time purging of the canister device 10B becomes necessary. The control unit 48A can be configured with an electronic circuit including a memory that stores a control program for generating a signal to switch the three-way valve 22 from one of the first state and the second state to the other based on the concentration signals from the concentration sensors 44, 46, and a microprocessor that executes the program.

[0019] According to the second embodiment, there are provided a first concentration sensor 44, a second concentration sensor 46, and a control unit 48A that switches the three-way valve 22 from one of the first state and the second state to the other when a signal indicating the concentration V detected by either the first concentration sensor 44 or the second concentration sensor 46 remains at or below a predetermined value V1 for a predetermined time ΔT. Therefore, the purging operations of the auxiliary chamber 28 and the main chamber 26 can be reliably and stably switched and executed based on the concentration V detected by the first concentration sensor 44 and the second concentration sensor 46, in other words, the remaining adsorption amounts in the auxiliary chamber 28 and the main chamber 26, which is advantageous for efficient purging of the canister device 10A.

[0020] Furthermore, if the control unit 48A switches the three-way valve 22 so that purging of the auxiliary chamber 28 takes priority over purging of the main chamber 26, this is advantageous for efficiently purging the auxiliary chamber 28 and is more advantageous for suppressing fuel vapor discharged from the auxiliary chamber 28 into the atmosphere.

[0021] (Third Embodiment) Next, a canister device 10C according to a third embodiment will be described with reference to Figure 5. The third embodiment differs from the second embodiment in that a single concentration sensor 50 is provided, and a control unit 48B controls the three-way valve 22 based on the detection result of the single concentration sensor 50. The concentration sensor 50 detects the concentration V of fuel vapor in the intake passage 40 and supplies a signal indicating the detected concentration to the control unit 48B. When the signal indicating the concentration V detected by the concentration sensor 50 remains below a predetermined value for a predetermined period of time, the control unit 48B generates a signal to switch the three-way valve 22 from one of the first state and the second state to the other.

[0022] The operation of the control unit 48B will be described in detail below. As in the first and second embodiments, it is assumed that the adsorbents in both the main combustion chamber 26 and the auxiliary combustion chamber 28 have sufficiently adsorbed fuel vapor, and that purging (scavenging) of the main combustion chamber 26 and the auxiliary combustion chamber 28 is required. When the internal combustion engine is operating, the intake pipe 41 becomes negative pressure. When the purge valve 42 opens in this state, the intake passage 40 also becomes negative pressure. The control unit 48B generates a signal to switch the three-way valve 22 to the second state to initiate the purging operation. When purging of the auxiliary combustion chamber 28 is prioritized, the control unit 48B determines that purging of the auxiliary combustion chamber 28 is complete when the signal indicating the concentration V supplied from the single concentration sensor 50 remains below the predetermined threshold value V1 for a predetermined time ΔT. The control unit 48B then sends a signal to the three-way valve 22 to switch from the second state to the first state. Therefore, when purging of the auxiliary chamber 28 is prioritized, the control unit 48B determines that purging of the auxiliary chamber 28 is complete when the signal indicating the concentration V supplied from the concentration sensor 50 remains below the predetermined threshold value V1 for a predetermined time ΔT, and switches the three-way valve 22 from the second state to the first state. That is, purging of the main chamber 26 is then performed. Then, the control unit 48B determines that purging of the main chamber 26 is complete when the signal indicating the concentration V supplied from the concentration sensor 50 remains below the predetermined threshold value V1 for a predetermined time ΔT, and generates a signal to switch the three-way valve 22 from the first state to the second state, thereby once again placing the auxiliary chamber 28 in a state where purging can be prioritized. This series of operations is performed each time purging of the canister device 10C is required.

[0023] According to the third embodiment, a single concentration sensor 50 and a control unit 48B are provided that switches the three-way valve 22 from one of the first and second states to the other when the signal of the concentration V detected by the single concentration sensor 50 remains below a predetermined value V1 for a predetermined time ΔT. Therefore, as in the second embodiment, the purging operations of the auxiliary chamber 28 and the main chamber 26 can be reliably and stably switched based on the concentration V detected by the concentration sensor 50, in other words, the remaining adsorption amounts in the auxiliary chamber 28 and the main chamber 26. This is advantageous not only for efficient purging of the canister device 10C, but also for cost reduction by reducing the number of concentration sensors 50. Furthermore, compared to the second embodiment, only one concentration sensor 50 is required, which is advantageous for cost reduction of the canister device 10C.

[0024] Furthermore, the control unit 48B switches the three-way valve 22 so that purging of the auxiliary chamber 28 takes priority over purging of the main chamber 26, which is advantageous for efficient purging of the auxiliary chamber 28 and is more advantageous for suppressing fuel vapor discharged from the auxiliary chamber 28 into the atmosphere, as in the second embodiment.

[0025] Next, a canister device 10D according to a fourth embodiment will be described with reference to Fig. 6. The fourth embodiment differs from the second and third embodiments in that a concentration sensor is not provided, and a control unit 48C switches the three-way valve 22 from one of the first state and the second state to the other based on the operating time for which the purge valve 42 on the internal combustion engine side is open.

[0026] The drive time (valve opening time) of the purge valve 42 shown in FIG. 6 is measured by the control unit 48C based on a control signal of the purge valve 42 that controls the opening and closing of the purge valve 42. It is optional to provide a timer (not shown) that measures the drive time of the purge valve 42 separately from the control unit 48C, and have the control unit 48C acquire the timing results from the timer. The control signal of the purge valve 42 that controls the opening and closing of the purge valve 42 is output, for example, from an engine control unit (not shown). When the engine control unit determines that the internal combustion engine has entered an operating range in which the canister can be purged, it outputs a drive signal (valve opening signal) to the purge valve 42 according to the purge amount, thereby controlling the open time of the purge valve 42. The control unit 48C measures the drive signal indicated by the arrow in FIG. 6.

[0027] The operation of the control unit 48C will be described in detail below. As in the first to third embodiments, it is assumed that the adsorbents in both the main combustion chamber 26 and the auxiliary combustion chamber 28 have sufficiently adsorbed fuel vapor, and that purging (scavenging) of the main combustion chamber 26 and the auxiliary combustion chamber 28 is required. When the internal combustion engine is operating, the intake pipe 41 becomes negative pressure. When the purge valve 42 opens in this state, the intake passage 40 also becomes negative pressure. When the control unit 48C issues a signal to switch the three-way valve 22 to the second state to initiate a purge operation and prioritizes purging of the auxiliary combustion chamber 28, the control unit 48C determines that purging of the auxiliary combustion chamber 28 has been completed by detecting that the drive time (open time) of the purge valve 42 has exceeded the predetermined second drive time. The control unit 48C then issues a signal to switch the three-way valve 22 from the second state to the first state. Therefore, when the control unit 48C prioritizes purging of the auxiliary chamber 28, it determines that purging of the auxiliary chamber 28 is complete when the drive time of the purge valve 42 has elapsed the predetermined second drive time ΔT2, and switches the three-way valve 22 from the second state to the first state. That is, purging of the main chamber 26 is then performed. Then, the control unit 48C determines that purging of the main chamber 26 is complete when it detects that the drive time of the purge valve 42 has elapsed the predetermined first drive time ΔT1, and sends a signal to the three-way valve 22 to switch from the first state to the second state. This again enables purging of the auxiliary chamber 28 to be prioritized. The first drive time ΔT1 is set in advance as the time required to complete purging of the main chamber 26, and the second drive time ΔT2 is set in advance as the time required to complete purging of the auxiliary chamber 28. This series of operations is performed each time purging of the canister device 10D is required. This fourth embodiment not only achieves the same effects as the second and third embodiments, but also eliminates the need for a concentration sensor, which is advantageous in terms of simplifying the configuration and reducing costs, as compared to the second and third embodiments.

[0028] Furthermore, a modified canister device can be configured by removing the three-way valve 22 from the canister device 10A of the first embodiment. Removing the three-way valve 22 from the canister device 10A would result in the first purge passage 16 and the second purge passage 18 being directly connected to the intake passage 40. In this case, for example, by providing a difference in airflow resistance between the first purge passage 16 and the second purge passage 18, the ease of purge flow between the two passages can be made different, thereby increasing the flow rate through the second purge passage 18 compared to the first purge passage 16. Examples of means for providing a difference in airflow resistance include the use of an orifice inserted into the purge passage or purge passages with different inner diameters. Even with this modified canister device, the same effects as those obtained with the canister device 10A of the first embodiment described above can be obtained.

[0029] 10A, 10B, 10C, 10D Canister device 12 Canister body 14 Charge passage 16 First purge passage 18 Second purge passage 20 Atmospheric passage 22 Three-way valve (switching valve) 24 Case 24A First wall portion 24B Second wall portion 24C Peripheral wall portion 24D Partition wall 24E Opening 26 Main chamber 28 Sub-chamber 30 Charge port (vapor port) 32 First purge port 34 Second purge port 36 Atmospheric port 38 Merging point 40 Intake passage 41 Intake pipe 42 Purge valve 44 First concentration sensor 46 Second concentration sensor 48A, 48B, 48C Control unit 50 Single concentration sensor

Claims

1. A canister device for adsorbing fuel vapors in a fuel tank of an internal combustion engine, comprising: a canister body having a case in which a main chamber and an auxiliary chamber that communicate with each other are formed, and in which fuel vapor adsorbents are stored in the main chamber and the auxiliary chamber; a charge passage configured to be able to communicate with the fuel tank; an intake passage configured to be able to communicate with an intake pipe of the internal combustion engine; a purge passage connecting the inside of the case with the intake passage; and an atmosphere passage configured to connect the auxiliary chamber with the atmosphere, wherein the purge passages include a first purge passage connecting the main chamber with the intake passage, and a second purge passage connecting the auxiliary chamber with the intake passage.

2. A canister device as described in claim 1, characterized in that it has: a charge port provided in the case where the main chamber is formed and connected to the charge passage; a first purge port provided in the case where the main chamber is formed and connected to the first purge passage; an atmospheric port provided in the case where the auxiliary chamber is formed and connected to the atmospheric passage; and a second purge port provided in the case where the auxiliary chamber is formed and connected to the second purge passage.

3. The canister device according to claim 2, wherein the second purge port is provided at a location of the case where the sub-chamber is formed and which faces the atmospheric port.

4. The canister device according to claim 3, wherein the axis of said second purge port and the axis of said atmospheric port are aligned on a straight line.

5. A canister device as described in any one of claims 2 to 4, characterized in that the first purge passage and the second purge passage are connected to the intake passage via a junction, and a three-way valve is provided at the junction, and the three-way valve is configured to be switchable between a first state in which the first purge passage communicates with the intake passage, and a second state in which the second purge passage communicates with the intake passage.

6. A canister device as described in claim 5, comprising: a first concentration sensor that detects the concentration of fuel vapor in the first purge passage and generates a signal indicating the concentration; a second concentration sensor that detects the concentration of fuel vapor in the second purge passage and generates a signal indicating the concentration; and a control unit that generates a signal to switch the three-way valve from one of the first state and the second state to the other when the concentration indicated by the signal from either the first concentration sensor or the second concentration sensor remains below a predetermined value for a predetermined period of time.

7. A canister device as described in claim 5, characterized in that it comprises: a concentration sensor that detects the concentration of fuel vapor in the intake passage and generates a signal indicating the concentration; and a control unit that generates a signal to switch the three-way valve from one of the first state and the second state to the other when the concentration indicated by the signal from the concentration sensor remains below a predetermined value for a predetermined period of time.

8. The canister device according to claim 5, further comprising a control unit that generates a signal to switch the three-way valve so that purging of fuel vapor from the auxiliary chamber is given priority over purging of fuel vapor from the main chamber.

9. A canister device according to claim 5, further comprising a control unit that measures the operating time that a purge valve provided in the intake pipe of the internal combustion engine is open, and generates a signal to switch the three-way valve from one of the first state and the second state to the other based on the measured operating time.

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