CN114135425A - Evaporated fuel treatment device - Google Patents

Abstract

The invention provides an evaporated fuel treatment device and provides a technology capable of stabilizing the amount of evaporated fuel blown out from an adsorption tank. The evaporated fuel processing apparatus includes: a fuel tank; an adsorption canister that adsorbs evaporated fuel generated in the fuel tank; a vapor passage for transporting vaporized fuel from the fuel tank to a canister; a shutoff valve capable of shutting off the steam passage; a purge passage through which the evaporated fuel purged from the canister flows in a purge process of purging the evaporated fuel adsorbed in the canister; an opening and closing valve for opening and closing the purge passage; and a control section. The control unit controls the open state of the on-off valve based on the open state of the shut valve.

Description

Evaporated fuel treatment device

Technical Field

The technology disclosed in this specification relates to an evaporated fuel treatment apparatus.

Background

Patent document 1 discloses an evaporated fuel treatment apparatus. The evaporated fuel treatment device of patent document 1 includes: a fuel tank; an adsorption canister that adsorbs evaporated fuel generated in the fuel tank; a vapor passage (evaporated fuel delivery pipe) for transporting evaporated fuel from the fuel tank to the canister; a purge passage through which the evaporated fuel purged from the canister flows in a purge process of purging the evaporated fuel adsorbed in the canister; and an opening and closing valve (purge valve) for opening and closing the purge passage.

Documents of the prior art

Patent document

Patent document 1: japanese examined patent publication (Kokoku) No. 6-103011

Disclosure of Invention

Problems to be solved by the invention

In the evaporated fuel treatment apparatus of patent document 1, the evaporated fuel is always supplied from the fuel tank to the canister. In this configuration, in the purge process for purging the evaporated fuel adsorbed in the canister, the amount of the evaporated fuel purged from the canister may be too large. The present specification provides a technique capable of stabilizing the amount of evaporated fuel purged from an adsorption tank.

Means for solving the problems

The evaporated fuel treatment apparatus disclosed in the present specification includes: a fuel tank; an adsorption canister that adsorbs evaporated fuel generated in the fuel tank; a vapor passage that transports evaporated fuel from the fuel tank to an adsorption canister; a shutoff valve capable of shutting off the steam passage; a purge passage through which the evaporated fuel purged from the canister flows in a purge process of purging the evaporated fuel adsorbed in the canister; an opening and closing valve for opening and closing the purge passage; and a control section. The control unit controls the open state of the on-off valve based on the open state of the shut valve.

According to this structure, the amount of evaporated fuel purged from the canister can be stabilized. For example, when the shut-off valve is opened, the evaporated fuel supplied from the fuel tank to the canister increases, and therefore, by reducing the opening degree of the shut-off valve, the excessive amount of the evaporated fuel purged from the canister can be suppressed. Further, for example, when the on-off valve is closed, the opening degree of the on-off valve is increased, whereby it is possible to suppress an excessively small amount of evaporated fuel purged from the canister.

When the shut valve is closed, the control unit may make an opening degree of the on-off valve larger than that when the shut valve is opened.

With this configuration, it is possible to suppress an excessive amount of evaporated fuel purged from the canister when the evaporated fuel is not being supplied from the fuel tank to the canister.

When the shut valve is opened, the control unit may control the opening degree of the shut valve based on the opening degree of the shut valve.

According to this configuration, when the evaporated fuel is supplied from the fuel tank to the canister, for example, when the opening degree of the shut-off valve is large, the opening degree of the on-off valve is reduced, whereby the amount of the evaporated fuel purged from the canister can be suppressed from becoming excessive. Further, for example, when the opening degree of the shut-off valve is small, the opening degree of the shut-off valve is increased, whereby it is possible to suppress an excessively small amount of the evaporated fuel purged from the canister.

The evaporated fuel treatment device may further include a pressure detection means for detecting a pressure in the fuel tank. When the shut valve is opened, the control unit may control the opening degree of the shut valve based on the pressure detected by the pressure detecting unit.

According to this structure, the amount of evaporated fuel purged from the canister can be made more stable. For example, when the pressure in the fuel tank is high and the evaporated fuel easily flows from the fuel tank to the canister, the opening degree of the on-off valve is reduced to suppress the excessive amount of the evaporated fuel purged from the canister. Further, for example, when the pressure in the fuel tank is low and the evaporated fuel is hard to flow from the fuel tank to the canister, the opening degree of the on-off valve is increased, so that the amount of the evaporated fuel purged from the canister can be suppressed from being too small.

The evaporated fuel treatment device may further include a stepping motor for driving the shut valve. The control unit may control the opening degree of the shut valve based on the number of steps of the stepping motor. With this configuration, the opening degree of the shut valve can be controlled with high accuracy.

The evaporated fuel treatment device may further include: an engine that operates using fuel supplied from the fuel tank and evaporated fuel supplied from the canister; and an air-fuel ratio detection unit for detecting an air-fuel ratio of air and fuel supplied to the engine. The control unit may control the opening degree of the on-off valve based on the air-fuel ratio detected by the air-fuel ratio detection unit.

According to this structure, the amount of evaporated fuel purged from the canister can be stabilized. For example, when the ratio of the fuel supplied to the engine is large, the opening degree of the on-off valve is reduced, whereby the evaporated fuel purged from the canister can be suppressed from being excessive. Further, for example, when the ratio of the fuel supplied to the engine is small, the opening degree of the on-off valve is increased, so that the evaporated fuel purged from the canister can be suppressed from being too small.

Drawings

Fig. 1 is a schematic view of an evaporated fuel treatment apparatus according to an embodiment.

FIG. 2 is a sectional view of an adsorption tank according to an embodiment.

Fig. 3 is a graph showing the relationship between time and purge rate according to the first embodiment.

Fig. 4 is a flowchart of the valve open state control processing according to the first embodiment.

Fig. 5 is a graph showing the relationship between time and purge rate according to the second embodiment.

Fig. 6 is a flowchart (1) of the valve open state control processing according to the second embodiment.

Fig. 7 is a flowchart (2) of the valve-open state control processing according to the second embodiment.

Description of the reference numerals

1: an evaporated fuel treatment device; 10: a first adsorbent material; 12: a second adsorbent material; 20: a shut-off valve; 21: an opening and closing valve; 22: a stepping motor; 30: a fuel tank; 31: a pressure sensor; 32: a concentration sensor; 40: an adsorption tank; 44: a vapor port; 45: an atmospheric port; 46: a purge port; 71: a vapor passage; 72: an atmospheric passage; 73: a purge passage; 75: an air filter; 81: a fuel supply passage; 82: a fuel pump; 90: an intake passage; 91: an air throttle; 92: an engine; 93: an air cleaner; 94: an exhaust passage; 95: an air-fuel ratio sensor; 100: a control unit; 102: a storage section.

Detailed Description

An evaporated fuel treatment apparatus 1 according to an embodiment will be described with reference to the drawings. Fig. 1 is a schematic view of an evaporated fuel processing apparatus 1 according to an embodiment. As shown in fig. 1, the evaporated fuel treatment device 1 includes a fuel tank 30, an canister 40, and a control unit 100. The evaporated fuel treatment device 1 further includes a vapor passage 71, an atmosphere passage 72, and a purge passage 73. The evaporated fuel treatment device 1 shown in fig. 1 is mounted on a vehicle such as a gasoline automobile.

The fuel tank 30 can contain fuel f such as gasoline. The fuel f is injected into the fuel tank 30 from a not-shown injection port. A pressure sensor 31 (an example of a pressure detection means) and a concentration sensor 32 are provided in the fuel tank 30. The pressure sensor 31 is used to detect the pressure within the fuel tank 30. The concentration sensor 32 is used to detect the concentration of the evaporated fuel in the fuel tank 30. Information on the pressure detected by the pressure sensor 31 and information on the concentration detected by the concentration sensor 32 are sent to the control unit 100.

A fuel pump 82 is disposed in the fuel tank 30. The fuel pump 82 is connected to the fuel supply passage 81. The fuel pump 82 discharges the fuel f in the fuel tank 30 to the fuel supply passage 81. The fuel f injected into the fuel supply passage 81 is supplied to the engine 92 of the vehicle through the fuel supply passage 81.

The fuel f in the fuel tank 30 evaporates in the fuel tank 30. For example, the fuel f evaporates while the vehicle on which the evaporated fuel processing apparatus 1 is mounted is running. The fuel f evaporates while the vehicle mounted with the evaporated fuel processing apparatus 1 is in a stopped state. The fuel f evaporates in the fuel tank 30 to generate evaporated fuel in the fuel tank 30.

The fuel tank 30 is connected to an upstream end portion of the vapor passage 71. The gas containing the evaporated fuel generated in the fuel tank 30 flows into the vapor passage 71. The downstream end of the vapor passage 71 is connected to the canister 40. The gas flowing through the vapor passage 71 flows into the canister 40. The vapor passage 71 allows gas containing evaporated fuel generated in the fuel tank 30 to be transported from the fuel tank 30 to the canister 40.

The steam passage 71 is provided with a shut valve 20. The shutoff valve 20 is configured to be capable of shutting off the steam passage 71 and opening and closing the steam passage 71. The shut valve 20 is, for example, a shut valve, a ball valve, a gate valve, a butterfly valve, a diaphragm valve, or the like. When the shutoff valve 20 is opened, the gas in the steam passage 71 can pass through the shutoff valve 20. For example, when the shut valve 20 is opened, gas containing evaporated fuel generated from the fuel f in the fuel tank 30 passes through the shut valve 20. When the shutoff valve 20 is closed, the gas in the steam passage 71 cannot pass through the shutoff valve 20. The evaporated fuel treatment apparatus 1 is a so-called closed-box type evaporated fuel treatment apparatus 1 in which a fuel tank 30 is closed by a shut-off valve 20.

The shut valve 20 is operated by a stepping motor 22. A stepping motor 22 is mounted to the shut valve 20 for driving the shut valve 20. In a modification, the stepping motor 22 may be incorporated in the shut valve 20. The stepping motor 22 operates the shut valve 20 to the valve-opening side and the valve-closing side. For example, when the number of steps of the stepping motor 22 increases, the shut valve 20 is operated to the valve opening side. On the other hand, when the number of steps of the stepping motor 22 decreases, the shutoff valve 20 is operated to the valve closing side. The stepping motor 22 is configured to change the rotation angle by increasing or decreasing the number of steps based on the pulse signal. The rotation angle of the stepping motor 22 in 1 step is, for example, 0.72 degrees. The opening degree of the shut valve 20 is an opening degree corresponding to the number of steps of the stepping motor 22.

Next, the canister 40 will be described. Fig. 2 is a sectional view of an adsorption tank 40 according to an embodiment. As shown in fig. 2, the canister 40 includes a housing 43 and a plurality of ports (a vapor port 44, an atmospheric port 45, and a purge port 46). The housing 43 and the plurality of ports (the vapor port 44, the atmosphere port 45, and the purge port 46) are made of resin. The housing 43 is integrally formed with a plurality of ports (a vapor port 44, an atmospheric port 45, and a purge port 46).

The housing 43 includes a housing main body 50 and a partition wall 53. The housing main body 50 is integrally formed with the partition wall 53. The partition wall 53 is disposed in the case main body 50. The partition wall 53 partitions the space inside the housing main body 50. The space inside the housing main body 50 is partitioned by a partition wall 53, thereby forming a first chamber 41 and a second chamber 42 inside the housing main body 50. The first chamber 41 contains the first adsorbent 10. The second adsorbent 12 is accommodated in the second chamber 42.

The first chamber 41 is located upstream (on the fuel tank 30 side) of the second chamber 42 (see fig. 1). The first porous plate 51 and the pair of first filters 61 are disposed in the first chamber 41. The first porous plate 51 is disposed at the downstream end of the first chamber 41. The first porous plate 51 has a plurality of holes (not shown). The gas flowing through the first chamber 41 passes through a plurality of holes formed on the first porous plate 51. The pair of first filters 61 are disposed at the upstream end and the downstream end of the first chamber 41. The first adsorbent 10 is sandwiched between a pair of first filters 61. Each first filter 61 serves to remove foreign substances included in the gas flowing through the first chamber 41.

The first adsorbent 10 filled in the first chamber 41 is made of activated carbon. The activated carbon constituting the first adsorbent 10 has the ability to adsorb evaporated fuel. A part of the evaporated fuel included in the gas is adsorbed into the activated carbon during the passage of the gas containing the evaporated fuel through the first adsorbent 10. In addition, the evaporated fuel adsorbed by the activated carbon is desorbed from the activated carbon into the air during the passage of the air through the first adsorbent material 10 (i.e., the evaporated fuel is purged). Further, the first adsorbent 10 may be a porous metal complex.

The second chamber 42 is located on the downstream side (the side opposite to the fuel tank 30 (the atmospheric side)) of the first chamber 41 (see fig. 1). The second perforated plate 52 and the pair of second filters 62 are disposed in the second chamber 42. The second porous plate 52 is disposed at an upstream end portion of the second chamber 42. A plurality of holes (not shown) are formed in the second perforated plate 52. The gas flowing into the second chamber 42 passes through a plurality of holes formed in the second porous plate 52. The pair of second filters 62 is disposed at the upstream end and the downstream end of the second chamber 42. The second adsorbent 12 is sandwiched between the pair of second filters 62. Each of the second filters 62 serves to remove foreign substances included in the gas flowing through the second chamber 42.

The second adsorbent 12 filled in the second chamber 42 is made of activated carbon. The activated carbon constituting the second adsorbent 12 has the ability to adsorb the evaporated fuel. A part of the evaporated fuel included in the gas is adsorbed into the activated carbon during the passage of the gas containing the evaporated fuel through the second adsorbent material 12. In addition, the evaporated fuel adsorbed by the activated carbon is desorbed from the activated carbon into the air during the passage of the air through the second adsorbent material 12 (i.e., the evaporated fuel is purged). The second adsorbent 12 may be a porous metal complex.

An intermediate chamber 47 is formed between the first chamber 41 and the second chamber 42 of the housing 43. The space in the housing main body 50 is partitioned by the first porous plate 51 and the second porous plate 52, and an intermediate chamber 47 is formed in the housing main body 50.

The vapor port 44 of the canister 40 is provided in the housing 43 at a position adjacent to the first chamber 41 formed. The vapor port 44 communicates with the first chamber 41. Further, the vapor port 44 is connected to a downstream end portion of the vapor passage 71. The vapor passage 71 communicates with the first chamber 41 through the vapor port 44. The gas flowing through the vapor passage 71 flows into the first chamber 41 through the vapor port 44.

The atmosphere port 45 of the canister 40 is provided in the housing 43 at a position adjacent to the formed second chamber 42. The atmosphere port 45 communicates with the second chamber 42. Further, the atmosphere port 45 is connected to an upstream end portion of the atmosphere passage 72. The second chamber 42 communicates with the atmosphere passage 72 through the atmosphere port 45. The gas flowing through the second chamber 42 flows into the atmosphere passage 72 through the atmosphere port 45.

As shown in fig. 1, the downstream end of the atmosphere passage 72 is open to the atmosphere. The gas flowing through the atmospheric passage 72 is released into the atmosphere. When the purge process (desorption of evaporated fuel) described later is performed, air in the atmosphere flows into the atmosphere passage 72 from the downstream end portion of the atmosphere passage 72. The air flowing into the atmosphere passage 72 flows through the atmosphere passage 72, and flows into the second chamber 42 formed in the housing 43 through the atmosphere port 45. An air filter 75 is disposed in the atmosphere passage 72. The air filter 75 is used to remove foreign substances included in the air flowing into the atmospheric air passage 72.

The purge port 46 of the canister 40 is provided on the housing 43 at a position adjacent to the formed first chamber 41. The purge port 46 communicates with the first chamber 41. Further, the purge port 46 is connected to an upstream end portion of the purge passage 73. The first chamber 41 is communicated with the purge passage 73 through the purge port 46. The gas flowing through the first chamber 41 flows into the purge passage 73 through the purge port 46.

The purge passage 73 is provided with an on-off valve 21. The open-close valve 21 is used to open and close the purge passage 73. The opening/closing valve 21 is, for example, a shutoff valve, a ball valve, a gate valve, a butterfly valve, a diaphragm valve, or the like. When the on-off valve 21 is opened, the gas in the purge passage 73 can pass through the on-off valve 21. For example, when the on-off valve 21 is opened, the gas containing the evaporated fuel purged from the canister 40 in the purge process described later passes through the on-off valve 21. When the on-off valve 21 is closed, the gas in the purge passage 73 cannot pass through the on-off valve 21. A purge pump (not shown) may be disposed in the purge passage 73.

The opening/closing valve 21 is, for example, an electromagnetic valve. The on-off valve 21 includes, for example, an electromagnet, and the on-off valve 21 is opened and closed by switching on/off of current flowing to the electromagnet. When a current flows through the electromagnet, the on-off valve 21 is operated to the valve-opening side, and when a current does not flow through the electromagnet, the on-off valve 21 is operated to the valve-closing side. The opening and closing valve 21 is opened and closed based on, for example, a current pulse. The opening degree of the on-off valve 21 changes in accordance with the duty ratio in the current pulse. When the ratio of "on" in the current pulse increases, the opening of the opening and closing valve 21 increases, and when the ratio of "on" in the current pulse decreases, the opening of the opening and closing valve 21 decreases.

The downstream end of the purge passage 73 is connected to the intake passage 90. The gas flowing through the purge passage 73 flows into the intake passage 90. An upstream end portion of the intake passage 90 is open to the atmosphere. Air in the atmosphere flows into the intake passage 90. A downstream end portion of the intake passage 90 is connected to an engine 92 of the vehicle. The air flowing through the intake passage 90 flows into the engine 92.

An air cleaner 93 and a throttle valve 91 are provided in the intake passage 90. The air cleaner 93 removes foreign substances such as dust included in the air flowing into the intake passage 90. The throttle valve 91 changes the passage cross-sectional area of the intake passage 90. Thus, the flow rate of air flowing into the engine 92 is adjusted by adjusting the flow rate of air flowing through the intake passage 90.

The engine 92 operates by combusting a mixed gas of supplied air and fuel. The engine 92 is connected to an upstream end portion of an exhaust passage 94. The exhaust gas discharged from the engine 92 flows into the exhaust passage 94. The downstream end of the exhaust passage 94 is open to the atmosphere. The exhaust gas flowing through the exhaust passage 94 is released into the atmosphere.

An air-fuel ratio (a/F) sensor 95 (an example of air-fuel ratio detection means) is provided in the exhaust passage 94. The air-fuel ratio sensor 95 can detect the air-fuel ratio between air and fuel supplied to the engine 92 by detecting the concentration of oxygen included in the exhaust gas flowing through the exhaust passage 94 after being discharged from the engine 92. The air-fuel ratio sensor 95 can be based on, for example, O₂The oxygen concentration is detected by the resistance value of the sensor, and the air-fuel ratio is detected based on the oxygen concentration.

The Control Unit 100 of the evaporated fuel processing apparatus 1 is, for example, an ECU (Engine Control Unit) and includes a storage Unit 102. The control unit 100 includes, for example, a CPU, and executes predetermined processing and control based on a program stored in the storage unit 102.

The storage unit 102 includes, for example, a ROM and a RAM, and stores various information related to the evaporated fuel treatment device 1. The storage unit 102 stores information of a graph shown in fig. 3, for example. Fig. 3 is a graph showing the relationship between the elapsed time from the start of the purge process and the purge rate. In fig. 3, a graph a and a graph B are shown. The purge rate is represented by, for example, (purge rate ═ purge gas flow/(purge gas flow + engine intake air amount)). The purge rate determined by graph a shows a different value than the purge rate determined by graph B. If the elapsed time (t) from the start of the purge process is the same, the purge rate (At) determined by the graph a shows a value higher than the purge rate (Bt) determined by the graph B.

The control unit 100 can control the on-off valve 21 based on the duty ratio corresponding to the purge rate determined by the graphs a and B. The on-off valve 21 for opening and closing the purge passage 73 is opened and closed at a duty ratio corresponding to the purge rate determined by the graphs a and B. The purge rate determined by the graphs a and B and the duty ratio corresponding to the purge rate vary with the passage of time. In the graph shown in fig. 3, the purge rate is set low immediately after the start of the purge process. In the initial stage after the start of the purge process, the purge rate is set to substantially 0 (zero). If the elapsed time from the start of the purge process is the same, the ratio of "on" in the duty ratio corresponding to the purge rate determined by the graph a is larger than the ratio of "on" in the duty ratio corresponding to the purge rate determined by the graph B. Therefore, when the on-off valve 21 is controlled at the duty ratio corresponding to the graph a, the opening degree of the on-off valve 21 is larger than that of the on-off valve 21 when the on-off valve 21 is controlled at the duty ratio corresponding to the graph B.

Next, the operation of the evaporated fuel treatment device 1 will be described. First, the adsorption of the evaporated fuel will be described. In the evaporated fuel treatment device 1, when the shutoff valve 20 provided in the vapor passage 71 is opened, gas can pass through the vapor passage 71. In the evaporated fuel treatment device 1, the gas containing the evaporated fuel generated from the fuel f in the fuel tank 30 flows from the fuel tank 30 into the vapor passage 71. The gas containing the evaporated fuel flowing through the vapor passage 71 flows into the first chamber 41 in the housing main body 50 through the vapor port 44 of the canister 40. The gas containing the evaporated fuel that has flowed into the first chamber 41 passes through the first adsorbent 10 contained in the first chamber 41 and flows into the intermediate chamber 47. In the process in which the gas containing the evaporated fuel passes through the first adsorbent 10, the first adsorbent 10 adsorbs a part of the evaporated fuel included in the gas. The evaporated fuel that is not adsorbed by the first adsorbent 10 flows from the first chamber 41 into the intermediate chamber 47.

The gas containing evaporated fuel that has passed through the first adsorbent 10 and flowed into the intermediate chamber 47 flows into the second chamber 42 thereafter. The gas containing the evaporated fuel that has flowed into the second chamber 42 passes through the second adsorbent 12 contained in the second chamber 42, and then flows into the atmosphere passage 72 through the atmosphere port 45. In the process in which the gas containing the evaporated fuel passes through the second adsorbent 12, the second adsorbent 12 adsorbs a part of the evaporated fuel included in the gas. The evaporated fuel that is not adsorbed by the second adsorbent 12 flows from the second chamber 42 into the atmosphere passage 72.

The gas containing evaporated fuel that has passed through the second adsorbent 12 and then flowed into the atmosphere passage 72 is released into the atmosphere thereafter. The evaporated fuel that is not adsorbed by the first adsorbent 10 and the second adsorbent 12 is released into the atmosphere.

Next, the purge process (desorption of evaporated fuel) will be described. In the evaporated fuel treatment device 1, when the on-off valve 21 provided in the purge passage 73 is opened, the gas can pass through the purge passage 73. When the engine 92 of the vehicle on which the evaporated fuel processing apparatus 1 is mounted operates, air flowing through the intake passage 90 is sucked into the engine 92, and a negative pressure is generated in the intake passage 90. Then, the gas flows from the purge passage 73 into the intake passage 90. At the same time, air in the atmosphere flows into the atmosphere passage 72. The air flowing into the atmosphere passage 72 then flows into the second chamber 42 in the housing main body 50 through the atmosphere port 45 of the canister 40. The air flowing into the second chamber 42 passes through the second adsorbent 12 contained in the second chamber 42 and then flows into the intermediate chamber 47. During the passage of the air through the second adsorbent 12, the evaporated fuel adsorbed by the second adsorbent 12 is desorbed from the second adsorbent 12 into the air. That is, the evaporated fuel is purged. The air containing the purged evaporated fuel flows from the second chamber 42 into the intermediate chamber 47.

The air containing the evaporated fuel flowing into the intermediate chamber 47 flows into the first chamber 41 thereafter. The air flowing into the first chamber 41 passes through the first adsorbent 10 contained in the first chamber 41 and then flows into the purge passage 73 through the purge port 46. During the passage of the air through the first adsorbent 10, the evaporated fuel adsorbed by the first adsorbent 10 is desorbed from the first adsorbent 10 into the air. That is, the evaporated fuel is purged. The air containing the purged evaporated fuel flows from the first chamber 41 into the purge passage 73.

The air containing evaporated fuel that has flowed into the purge passage 73 flows into the intake passage 90 through the purge passage 73. The air containing the evaporated fuel flowing into the intake passage 90 is taken in by the engine 92.

Next, the valve opening state control process executed in the evaporated fuel processing apparatus 1 will be described. Fig. 4 is a flowchart of the valve open state control processing according to the first embodiment. The valve-open state control process is started when, for example, a start button of the engine 92 of the vehicle is pressed. As shown in fig. 4, when the valve-open state control process is started, the control unit 100 starts the engine 92 of the vehicle in S10 of the valve-open state control process.

In the next S12, the control unit 100 determines whether or not the purge process can be executed in the evaporated fuel processing apparatus 1. For example, the control unit 100 determines that the purge process can be executed when the fuel supplied to the engine 92 is small, and determines that the purge process cannot be executed (cannot be executed) when the fuel supplied to the engine 92 is large. Further, for example, the control unit 100 may determine that the purge process is executable when the air-fuel ratio detected by the air-fuel ratio sensor 95 is large, and the control unit 100 may determine that the purge process is not executable (non-executable) when the air-fuel ratio is small. If the purge process can be executed, the controller 100 determines yes at S12 and proceeds to S14. Otherwise, the control unit 100 determines no and stands by.

At next S14, control unit 100 determines whether or not the pressure in fuel tank 30 is equal to or higher than a predetermined reference pressure (e.g., 2 kPa). The pressure in the fuel tank 30 is detected by a pressure sensor 31 provided in the fuel tank 30. The pressure in the fuel tank 30 tends to increase when the evaporation amount of the fuel in the fuel tank 30 is large. If the pressure in fuel tank 30 is equal to or higher than the reference pressure, control unit 100 determines yes at S14 and proceeds to S20. Otherwise, the control unit 100 determines no and proceeds to S16.

In S16 after no in S14, the control unit 100 closes the shutoff valve 20 provided in the steam passage 71. When the shutoff valve 20 is closed, the vapor passage 71 is shut off, and the evaporated fuel no longer flows from the fuel tank 30 to the canister 40. In next S18, the control unit 100 selects the graph a from the information of the graphs (see fig. 3) stored in the storage unit 102.

On the other hand, in S20 after yes in S14, the control unit 100 opens the shutoff valve 20 provided in the steam passage 71. When the shutoff valve 20 is opened, the vapor passage 71 is opened, so that the evaporated fuel flows from the fuel tank 30 to the canister 40. In next S22, the control unit 100 selects the graph B from the information of the graphs (see fig. 3) stored in the storage unit 102.

In S24 following S18 and S22, the controller 100 determines the purge rate based on the graph a selected in S18 or the graph B selected in S22 (see fig. 3). The control unit 100 determines a purge rate corresponding to an elapsed time from the start of the purge process. For example, when the elapsed time is t, the purge rate At or Bt corresponding to the elapsed time is determined.

In the next S26, the control section 100 determines a duty ratio corresponding to the purge rate (for example, At or Bt) determined in S24. In S26, control unit 100 controls opening/closing valve 21 based on the determined duty ratio. When the control unit 100 controls the on-off valve 21 at the duty ratio based on the purge rate of the graph a, the ratio of "on" is increased and the opening degree of the on-off valve 21 is increased, compared to the case where the control unit 100 controls the on-off valve 21 at the duty ratio based on the purge rate of the graph B.

In S28, control unit 100 determines whether or not engine 92 has stopped. When the engine 92 is stopped, the control unit 100 determines yes in S28 and ends the valve-open state control process. Otherwise, the control unit 100 determines no and returns to S12. The control section 100 repeatedly performs the processes of S12 to S28.

The evaporated fuel treatment device 1 according to the embodiment is described above. As is apparent from the above description, the evaporated fuel treatment device 1 includes: a vapor passage 71 that transports the evaporated fuel from the fuel tank 30 to the canister 40; a shut valve 20 capable of shutting off the steam passage 71; a purge passage 73 through which the evaporated fuel purged from the canister 40 flows in a purge process of purging the evaporated fuel adsorbed in the canister 40; and an opening and closing valve 21 for opening and closing the purge passage 73. The controller 100 controls the open state of the on-off valve 21 based on the open state of the shut valve 20 (see S16-S26 in fig. 4).

With this configuration, the amount of evaporated fuel purged from the canister 40 can be stabilized. For example, when the shut-off valve 20 is opened, the evaporated fuel supplied from the fuel tank 30 to the canister 40 increases, and therefore, by reducing the opening degree of the shut-off valve 21, the amount of the evaporated fuel purged from the canister 40 can be suppressed from increasing.

When the shut valve 20 is closed, the control unit 100 makes the opening degree of the on-off valve 21 larger than the opening degree of the on-off valve 21 when the shut valve 20 is open (see S16-S22 in fig. 3 and 4). This can suppress the evaporated fuel purged from the canister 40 from being too small.

The control unit 100 controls the opening degree of the shut valve 20 based on the number of steps of the stepping motor 22. According to this configuration, the opening degree of the shut valve 20 can be controlled with high accuracy by using the stepping motor 22.

Although one embodiment has been described above, the specific mode is not limited to the above embodiment. In the following description, the same components as those in the above description are denoted by the same reference numerals, and description thereof is omitted.

(second embodiment)

In the second embodiment, the storage unit 102 of the control unit 100 stores information of the graph shown in fig. 5. In fig. 5, graphs a, B, c and d are shown. The purge rates determined by the graphs a, B, c, and d show respectively different values. When the elapsed time from the start of the purge process is the same, the purge rate determined by the graph a shows the highest value, the purge rates determined by the graphs a, B, c, and d show the values in the order from high to low, and the purge rate determined by the graph B shows the lowest value.

The control portion 100 can control the on-off valve 21 based on the duty ratio corresponding to the purge rate determined by the graphs a, B, c, and d. The open-close valve 21 for opening and closing the purge passage 73 performs opening and closing actions at a duty ratio corresponding to the purge rate determined by the graphs a, B, c, and d. The purge rate determined by the graphs a, B, c, and d and the duty ratio corresponding to the purge rate are changed with the passage of time. When the elapsed time from the start of the purge process is the same, the ratio of "on" in the duty ratio corresponding to the purge rate specified by the graph a is the largest, and the ratios of "on" in the duty ratios corresponding to the purge rates specified by the graphs a, B, c, and d are successively smaller, and the ratio of "on" in the duty ratio corresponding to the purge rate specified by the graph B is the smallest. Therefore, the opening degree of the on-off valve 21 is the largest when the on-off valve 21 is controlled at the duty ratio corresponding to the graph a, and the opening degree of the on-off valve 21 is the largest when the on-off valve 21 is controlled at the duty ratios corresponding to the graphs a, B, c, and d, and the opening degree of the on-off valve 21 is the smallest when the on-off valve 21 is controlled at the duty ratio corresponding to the graph B.

Next, the valve opening state control processing according to the second embodiment will be described. Fig. 6 is a flowchart of the valve open state control processing according to the second embodiment. As shown in fig. 6, in the valve-open state control process according to the second embodiment, in S14 after yes in S12, the control unit 100 determines whether the pressure in the fuel tank 30 is equal to or higher than a predetermined first reference pressure (for example, 2kPa), or whether the pressure in the fuel tank 30 is lower than a predetermined second reference pressure (for example, -2 kPa). The pressure in the fuel tank 30 is detected by a pressure sensor 31 provided in the fuel tank 30. The second reference pressure is a pressure smaller than the first reference pressure. If the pressure in fuel tank 30 is equal to or higher than the first reference pressure or if the pressure in fuel tank 30 is lower than the second reference pressure, control unit 100 determines yes at S14 and proceeds to S20. Otherwise, the control unit 100 determines no and proceeds to S16.

In S20 after yes in S14, the control unit 100 opens the shutoff valve 20 provided in the steam passage 71. When the shutoff valve 20 is opened, the vapor passage 71 is opened, so that the evaporated fuel flows from the fuel tank 30 to the canister 40. After the process at S20, control unit 100 proceeds to S30 (see fig. 7).

As shown in fig. 7, in S30, the control unit 100 determines whether or not the pressure in the fuel tank 30 is equal to or higher than a first reference pressure (e.g., 2 kPa). If the pressure in fuel tank 30 is equal to or higher than the first reference pressure, control unit 100 determines yes at S30 and proceeds to S34. Otherwise, the control unit 100 determines no and proceeds to S32.

The case of no at S30 is a case where the pressure inside the fuel tank 30 is less than the second reference pressure (e.g., -2 kPa). In this case, the pressure inside the fuel tank 30 becomes negative pressure. Therefore, the evaporated fuel does not flow out from the fuel tank 30 to the vapor passage 71, but the gas flows into the fuel tank 30 from the vapor passage 71. In S32 after no in S30, control unit 100 selects graph a from the information of the graphs (see fig. 5) stored in storage unit 102.

On the other hand, in S34 after yes in S30, the control unit 100 determines whether or not the opening degree of the shutoff valve 20 provided in the steam passage 71 is equal to or greater than a predetermined reference opening degree. When the opening degree of the shut valve 20 is equal to or greater than the reference opening degree, the controller 100 determines yes at S34 and proceeds to S46. Otherwise, the control unit 100 determines no and proceeds to S36.

At S36 after no at S34, control unit 100 determines whether or not the concentration of the evaporated fuel in fuel tank 30 is equal to or higher than a predetermined reference concentration. The concentration of the evaporated fuel in the fuel tank 30 is detected by a concentration sensor 32 provided in the fuel tank 30. The concentration of the evaporated fuel in the fuel tank 30 tends to increase when the evaporation amount of the fuel in the fuel tank 30 is large. If the concentration of the evaporated fuel in the fuel tank 30 is equal to or higher than the reference concentration, the control unit 100 determines yes at S36 and proceeds to S40. Otherwise, the control unit 100 determines no and proceeds to S38.

In S38 after no in S36, control unit 100 selects graph b from the information of the graphs (see fig. 5) stored in storage unit 102. In S40 after yes in S36, control unit 100 selects graph c from the information of the graphs (see fig. 5) stored in storage unit 102.

In S46 after yes in S34, control unit 100 determines whether or not the concentration of the evaporated fuel in fuel tank 30 is equal to or higher than a predetermined reference concentration. If the concentration of the evaporated fuel in the fuel tank 30 is equal to or higher than the reference concentration, the control unit 100 determines yes at S46 and proceeds to S22. Otherwise, the control unit 100 determines no and proceeds to S48.

In S48 after no in S46, control unit 100 selects graph d from the information of the graphs (see fig. 5) stored in storage unit 102. In S22 after yes in S46, control unit 100 selects graph B from the information of the graphs (see fig. 5) stored in storage unit 102. After the processing at S32, S38, S40, S48, or S22, the controller 100 proceeds to S24 (see fig. 6).

As shown in fig. 6, in S24, the controller 100 determines the purge rate based on the graph a, B, c, d, or B selected in S18, S32, S38, S40, S48, or S22 (see fig. 5). The processing from S24 onward is the same as the processing from S24 (see fig. 4) of the first embodiment described above, and therefore detailed description thereof is omitted.

The second embodiment is explained above. As is apparent from the above description, in the second embodiment, when the shut valve 20 is opened, the control unit 100 controls the opening degree of the shut valve 21 based on the opening degree of the shut valve 20 (see S34-S48, S22 of fig. 7). With this configuration, it is possible to suppress an excessive amount of evaporated fuel purged from the canister 40 when the evaporated fuel is supplied from the fuel tank 30 to the canister 40.

The evaporated fuel treatment device 1 includes a pressure sensor 31 for detecting the pressure in the fuel tank 30. The controller 100 controls the opening degree of the on-off valve 21 based on the pressure detected by the pressure sensor 31 (see S30, S32, S38, S40, S48, and S22 in fig. 7). With this configuration, the amount of evaporated fuel purged from the canister 40 can be further stabilized. For example, when the pressure in the fuel tank 30 is high, the opening degree of the on-off valve 21 is reduced, so that the excessive amount of the evaporated fuel purged from the canister 40 can be suppressed. For example, when the pressure in the fuel tank 30 is low, the opening degree of the on-off valve 21 is increased, so that the evaporated fuel purged from the canister 40 can be suppressed from being too small. The opening degree of the opening-closing valve 21 is controlled based on the duty ratio.

(modification example)

In the modification, the control unit 100 may control the opening degree of the opening/closing valve 21 provided in the purge passage 73 based on the air-fuel ratio detected by the air-fuel ratio sensor 95. When the ratio of the fuel supplied to the engine 92 is large (the air-fuel ratio is small), for example, the control unit 100 may decrease the opening degree of the on-off valve 21. This can suppress an excessive amount of evaporated fuel purged from the canister 40. Further, when the ratio of the fuel supplied to the engine 92 is small (the air-fuel ratio is large), the control unit 100 may increase the opening degree of the on-off valve 21. This can suppress the evaporated fuel purged from the canister 40 from being too small.

Specific examples of the present invention have been described in detail, but these are merely examples and are not intended to limit the claims. The techniques described in the claims include those obtained by variously changing and modifying the specific examples illustrated above. The technical elements described in the present specification and drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. The techniques illustrated in the present specification and drawings are techniques capable of achieving a plurality of objects at the same time, and achieving one of the objects is a technique having technical usefulness.

Claims (6)

1. An evaporated fuel treatment device is provided with:

a fuel tank;

an adsorption canister that adsorbs evaporated fuel generated in the fuel tank;

a vapor passage for transporting vaporized fuel from the fuel tank to the canister;

a shutoff valve capable of shutting off the steam passage;

a purge passage through which the evaporated fuel purged from the canister flows in a purge process of purging the evaporated fuel adsorbed in the canister;

an opening and closing valve for opening and closing the purge passage; and

a control part for controlling the operation of the display device,

wherein the control unit controls the open state of the on-off valve based on the open state of the shut valve.

2. The evaporated fuel treatment apparatus according to claim 1,

when the shut valve is closed, the control unit makes the opening of the on-off valve larger than that when the shut valve is opened.

3. The evaporated fuel treatment apparatus according to claim 1 or 2,

when the shut valve is opened, the control unit controls the opening of the shut valve based on the opening of the shut valve.

4. The evaporated fuel treatment apparatus according to any one of claims 1 to 3,

further comprises a pressure detection means for detecting a pressure in the fuel tank,

when the shut valve is opened, the control unit controls the opening of the shut valve based on the pressure detected by the pressure detection unit.

5. The evaporated fuel treatment apparatus according to any one of claims 1 to 4,

further comprises a stepping motor for driving the shut valve,

the control unit controls the opening degree of the shut valve based on the number of steps of the stepping motor.

6. The evaporated fuel treatment apparatus according to any one of claims 1 to 5, further comprising:

an engine that operates using fuel supplied from the fuel tank and evaporated fuel supplied from the canister; and

an air-fuel ratio detection unit for detecting an air-fuel ratio of air and fuel supplied to the engine,

wherein the control portion controls the opening degree of the opening and closing valve based on the air-fuel ratio detected by the air-fuel ratio detection unit.

Images