JP2019196709A - Vaporized fuel gas discharge prevention device - Google Patents

Abstract

To provide a vaporized fuel gas discharge prevention device capable of properly determining abnormality (closing state) of an atmospheric air inlet port.SOLUTION: An ECU 1 controls a second valve to a prescribed high opening state in which pressure difference between the front and back of the second valve is a valve opening pressure difference of the second valve or more when the atmospheric air inlet port 4 is closed, and a prescribed low opening state in which the pressure difference of the second valve is less than the valve opening pressure difference when the atmospheric air inlet port 4 is closed, and determines abnormality of the atmospheric air inlet port 4 on the basis of difference in air-fuel ratios of an exhaust gas detected by an air-fuel ratio detection portion between a time when the second valve is controlled to the prescribed high opening state and a time when it is controlled to the prescribed low opening state.SELECTED DRAWING: Figure 4

Description

The present invention relates to an evaporated fuel gas emission preventing device.

  Conventionally, a technique described in Patent Document 1 is known as a technique for preventing the evaporated fuel gas generated in the fuel tank from leaking into the atmosphere. The flow diagnosis apparatus for an evaporative gas purge system described in Patent Document 1 is configured such that the pressure of a leak check module connected to a canister is opened while the purge control valve is opened and the evaporative system is sealed from the engine intake system during engine operation. A technique for determining whether or not the evaporation passage, which is a passage on the fuel tank side of the pressure sensor, is clogged based on the behavior of the pressure in the evaporation system detected by the sensor is disclosed.

JP 2009-264207 A

  However, what is described in Patent Document 1 is intended to detect abnormalities in clogging in which evaporated fuel gas circulates, and cannot detect the clogged state of the air inlet arranged in the canister. By closing the air inlet, the gas concentration of the evaporated fuel gas introduced into the intake pipe increases, and the amount of evaporated fuel gas adsorbed by the canister decreases, so that the pressure in the canister can be managed sufficiently. There is a risk of not being able to.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an evaporated fuel gas discharge prevention device that can appropriately determine the closed state of an air inlet.

  To achieve the above object, the present invention provides an evaporative fuel gas passage for purging evaporative fuel generated in a fuel tank to an intake system of an internal combustion engine, and a canister provided in the evaporative fuel gas passage for collecting evaporative fuel gas. And an evaporative fuel gas discharge prevention device provided between the fuel tank and the canister in the evaporative fuel gas passage, wherein the pressure difference between the fuel tank side and the canister side is equal to or greater than a predetermined valve opening pressure difference. A first valve that opens in the event of a failure, a second valve that is provided between the canister and the intake system in the evaporated fuel gas passage and adjusts the purge amount of the evaporated fuel gas purged from the canister to the intake system, and the canister And an air inlet for introducing the atmosphere into the canister, an air-fuel ratio detector for detecting the air-fuel ratio of the exhaust gas discharged from the internal combustion engine, and an operating state of the internal combustion engine A control unit that controls the opening degree of the second valve, and the control part has a predetermined high opening degree at which the pressure difference is equal to or greater than the valve opening pressure difference when the second valve is closed by the air inlet. And when the second valve is controlled to a predetermined high opening state when the atmospheric pressure inlet is closed and the pressure difference is less than the valve opening pressure difference. An abnormality of the air inlet is determined based on a difference between a high purge air-fuel ratio which is an air-fuel ratio and a low purge air-fuel ratio when controlled to a predetermined low opening state.

  ADVANTAGE OF THE INVENTION According to this invention, the evaporative fuel gas discharge | emission prevention apparatus which can determine appropriately the obstruction | occlusion state of an air inlet can be provided.

FIG. 1 is a schematic configuration diagram of a vehicle equipped with an evaporated fuel gas emission preventing device according to an embodiment of the present invention. FIG. 2 is a flowchart for explaining the operation of the evaporated fuel gas emission preventing apparatus according to one embodiment of the present invention. FIG. 3 is a flowchart for explaining the details of the abnormality diagnosis process for the air inlet in FIG. FIG. 4 is a timing chart for explaining the transition of the abnormality diagnosis of the air inlet by the evaporated fuel gas emission preventing device according to one embodiment of the present invention. FIG. 5 is a graph showing changes in the air-fuel ratio difference in the abnormality diagnosis of the air inlet by the evaporated fuel gas emission preventing device according to one embodiment of the present invention.

  An evaporated fuel gas emission preventing device according to an embodiment of the present invention is provided in an evaporated fuel gas passage for purging evaporated fuel generated in a fuel tank to an intake system of an internal combustion engine, and an evaporated fuel gas passage, An evaporative fuel gas emission prevention device having a canister for collecting gas, provided between a fuel tank and a canister in an evaporative fuel gas passage, wherein a pressure difference between the fuel tank side and the canister side is a predetermined valve opening A first valve that opens when the pressure difference is greater than or equal to a second valve that is provided between the canister and the intake system in the evaporated fuel gas passage and adjusts the purge amount of the evaporated fuel gas purged from the canister to the intake system. A valve, an air introduction port that is provided in the canister and introduces air into the canister, an air-fuel ratio detection unit that detects an air-fuel ratio of exhaust gas discharged from the internal combustion engine, and an internal combustion engine A control unit that controls the opening degree of the second valve according to the operating state is provided, and the control unit has a predetermined pressure difference greater than or equal to the valve opening pressure difference when the second valve is closed by the air inlet. When the high valve position is controlled to a predetermined low valve position where the pressure difference is less than the valve opening pressure difference when the air inlet is closed, and the second valve is controlled to the predetermined high valve position Characterized in that the abnormality of the air inlet is determined based on the difference between the high purge air-fuel ratio, which is the air-fuel ratio, and the low purge air-fuel ratio, which is the air-fuel ratio when the air-fuel ratio is controlled to a predetermined low opening state. To do. Thereby, the evaporated fuel gas emission preventing apparatus according to the embodiment of the present invention can provide an evaporated fuel gas emission preventing apparatus that can appropriately determine the closed state of the air inlet.

  Hereinafter, an evaporated fuel gas emission preventing device according to an embodiment of the present invention will be described with reference to the drawings. 1 to 5 are views for explaining an evaporated fuel gas emission preventing device according to an embodiment of the present invention.

  As shown in FIG. 1, the vehicle includes an internal combustion engine, a fuel tank 6, a fuel piping system, and an ECU (Electronic Control Unit) 1 as a control unit that comprehensively controls the vehicle. The

  An internal combustion engine is formed of a plurality of cylinders. In this embodiment, the internal combustion engine is configured to perform a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke for each cylinder. The internal combustion engine is provided with an intake port that communicates with the combustion chamber 14 of each cylinder and an intake pipe 13 that introduces air into the intake port. The intake pipe 13 forms a manifold (intake manifold) that branches toward each intake port at the end on the intake port side, and introduces air into each intake port.

  The internal combustion engine is provided with an exhaust port that communicates with the combustion chamber 14 of each cylinder, and an exhaust pipe 15 that exhausts exhaust discharged from the exhaust port. The exhaust pipe 15 forms a manifold (exhaust manifold) branching toward each exhaust port at the end on the exhaust port side, and discharges air for each exhaust port.

  A throttle valve 7 and an intake pressure sensor 8 are provided in the middle of the intake pipe 13. The throttle valve 7 adjusts the air taken in by the internal combustion engine by adjusting the opening of the throttle valve 7. The throttle valve 7 comprises an electronically controlled throttle valve 7 that is opened and closed by a motor (not shown). The intake pressure sensor 8 detects the pressure on the downstream side of the throttle valve 7 and detects it as the intake pressure that is the pressure in the intake pipe 13.

  In the internal combustion engine, each cylinder is provided with a fuel injection valve 9 that injects fuel into the combustion chamber 14 via an intake port, and an ignition plug (not shown) that ignites the air-fuel mixture in the combustion chamber 14. The fuel injection valve 9 and the spark plug are electrically connected to the ECU 1.

  The ECU 1 controls the fuel injection amount and fuel injection timing of the fuel injection valve 9 and the ignition timing and discharge amount of the spark plug.

  In the middle of the exhaust pipe 15, an upstream air-fuel ratio sensor 10, an exhaust purification device 11, and a downstream air-fuel ratio sensor 12 are provided. The upstream air-fuel ratio sensor 10 confirms the combustion state in the cylinder by detecting the air-fuel ratio of the exhaust exhausted from the internal combustion engine. The exhaust purification device 11 is disposed in the vicinity of the internal combustion engine and purifies the exhaust. The downstream air-fuel ratio sensor 12 detects the air-fuel ratio of the exhaust gas purified by circulating the exhaust gas exhausted from the internal combustion engine to the exhaust gas purification device 11, thereby confirming the active state of the exhaust gas purification device 11.

  The internal combustion engine is provided with a crank angle sensor 16, which detects the engine speed based on the rotational position of the crankshaft 17 and transmits a detection signal to the ECU 1.

  The fuel tank 6 is composed of a hollow container for storing gasoline as fuel for the internal combustion engine, and is fixed to a vehicle body (not shown) of the vehicle.

  The fuel pipe system is generated in the fuel tank 6, a fuel pipe that transports fuel from the fuel tank 6 to the fuel injection valve 9, a fuel pump 18 that pumps fuel from the fuel tank 6 to the fuel injection valve 9 through the fuel pipe, and the fuel tank 6. An evaporated fuel gas processing device for discharging the evaporated fuel to the intake pipe 13 is provided.

  The fuel pipe pumps fuel from the fuel tank 6 to a fuel injection valve 9 provided in each cylinder, and is fixed to a vehicle body (not shown) of the vehicle.

  The fuel pump 18 is provided in the fuel tank 6, sucks up the fuel in the fuel tank 6, and pumps it to the fuel injection valve 9 through the fuel pipe. The fuel pump 18 is an electric pump, is connected to a battery (not shown), and is driven by electric power supplied from the battery. The fuel pump 18 is electrically connected to the ECU 1 and is controlled by the ECU 1.

  The evaporated fuel gas processing apparatus is provided with an evaporated fuel gas passage (hereinafter referred to as a purge passage), a canister 3, a first valve 5, and a second valve 2. The purge passage transports the evaporated fuel gas generated in the fuel tank 6 to the intake pipe 13.

  The canister 3 is provided in the middle of the purge passage, and is filled with an adsorbent such as activated carbon in a resin container. The evaporated fuel gas discharged as pressure adjustment in the fuel tank 6 is temporarily collected by the canister 3 and prevented from being discharged outside the vehicle.

  The first valve 5 performs pressure relief that is released as pressure adjustment in the fuel tank 6 when the pressure in the fuel tank 6 and the pressure in the purge passage on the canister side exceed a predetermined pressure difference. Ensuring sealing performance.

  The second valve 2 adjusts the timing at which the evaporated fuel gas collected by the canister 3 is discharged to the intake pipe 13. The second valve 2 is electrically connected to the ECU 1 and is controlled to be opened and closed by the ECU 1.

  The canister 3 includes an inlet for introducing the evaporated fuel gas discharged from the fuel tank 6 into the canister 3, an outlet for discharging the evaporated fuel gas from the canister 3 to the intake pipe 13, and an atmosphere for adjusting the pressure in the canister 3. An introduction port 4 is provided.

  The ECU 1 is a computer unit having a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, an input port, and an output port. It is constituted by.

  The ROM of the computer unit stores various constants, various maps, and the like, and a program for causing the computer unit to function as the ECU 1. That is, when the CPU executes a program stored in the ROM using the RAM as a work area, these computer units function as the ECU 1 in this embodiment.

  Various sensors including the crank angle sensor 16, the intake pressure sensor 8, the upstream air-fuel ratio sensor 10, and the downstream air-fuel ratio sensor 12 are connected to the input port of the ECU 1.

  To the output port of the ECU 1, various control objects including a throttle valve 7, a fuel injection valve 9, a spark plug, a second valve 2 and a fuel pump 18 of the internal combustion engine are connected. The ECU 1 controls various control objects including the internal combustion engine based on information obtained from various sensors.

  That is, the internal combustion engine includes a throttle valve 7 and a fuel injection valve 9. The ECU 1 controls the operating state of the internal combustion engine by electrically controlling the opening of the throttle valve 7 (hereinafter referred to as the throttle opening), the fuel injection timing of the fuel injection valve 9, and the fuel injection amount. Further, the target output of the internal combustion engine is determined, and the internal combustion engine is controlled to generate the target output.

  Here, by controlling the operation state of the internal combustion engine, a negative pressure state closer to a vacuum state than the atmospheric pressure is generated in the intake pipe 13. In the state where the negative pressure is generated, the evaporated fuel gas adsorbed in the canister 3 is sucked by controlling the opening of the second valve 2. The sucked evaporative fuel gas is combusted in the combustion chamber 14 of the internal combustion engine, and can be prevented from being released into the atmosphere by passing through the exhaust purification device 11.

  Further, in the present embodiment, the ECU 1 determines that the pressure applied to the first valve 5 when the atmospheric introduction port 4 of the canister 3 is closed is greater than the valve opening pressure difference, and the atmospheric introduction. When the opening 4 is closed, the pressure applied to the second valve 2 is controlled to a predetermined low opening state where the pressure difference is less than the valve opening pressure difference. Further, the ECU 1 can confirm the closed state of the air inlet 4 by referring to the air-fuel ratio detected from the upstream air-fuel ratio sensor 10 that changes according to the open state of the first valve 5. Therefore, the closed state of the air inlet 4 can be confirmed regardless of the state of the evaporated fuel gas in the canister 3 by using the opened state and the closed state of the first valve 5.

  Further, the ECU 1 acquires the maximum air-fuel ratio detected by the upstream air-fuel ratio sensor 10 when the second valve 2 is driven in a predetermined high opening state as the high purge air-fuel ratio.

  Further, the ECU 1 acquires the air-fuel ratio detected by the upstream air-fuel ratio sensor 10 when a predetermined time has elapsed after changing the drive amount of the second valve 2 to a predetermined low opening state as the low purge air-fuel ratio.

  When the ECU 1 detects that the difference between the high purge air-fuel ratio and the low purge air-fuel ratio is greater than or equal to a predetermined value, the ECU 1 determines the state of the air inlet 4.

  Next, an operation executed by the ECU 1 in the evaporated fuel gas emission preventing device according to the present embodiment will be described with reference to FIG.

  In FIG. 2, the ECU 1 repeatedly determines whether or not the purge concentration initial learning condition is satisfied in order to learn the concentration of the evaporated fuel gas adsorbed by the canister 3 (step S1). Here, the ECU 1 determines, for example, whether there is a sufficient negative pressure for sucking the evaporated fuel gas in the intake pipe 13.

  When the purge concentration initial learning condition is satisfied in step 1, the ECU 1 drives the second valve 2 to open (step 2). If the purge concentration initial learning condition is not satisfied, the routine proceeds to step 4.

  When the second valve 2 is driven to open in step 2, the evaporated fuel gas collected in the canister 3 is drawn into the intake pipe 13 through the purge passage due to the negative pressure in the intake pipe 13. Here, the ECU 1 performs initial learning of the purge concentration in the canister 3 on the basis of the output value of the upstream air-fuel ratio sensor 10 that changes due to combustion of the sucked evaporated fuel gas (step 3).

  In step 3, when the initial learning of the purge concentration in the canister 3 is performed, it is determined whether or not the learned purge concentration is in an abnormal state. Here, the ECU 1 detects an abnormality based on whether the purge concentration in the canister 3 that has been initially learned or the purge concentration when the evaporated fuel gas in the canister 3 is recovered exceeds a predetermined rich-side guard threshold value. Repeat the state determination.

  If it is determined in step 4 that the evaporated fuel gas concentration is abnormal, the ECU 1 performs purge system abnormality diagnosis control (step S5), and then ends the current operation. Details of the purge system abnormality diagnosis will be described with reference to FIG.

  In FIG. 3, the ECU 1 determines whether a diagnosis condition is satisfied based on the negative pressure state of the intake pipe 13 or the air-fuel ratio state in the in-cylinder combustion (step S11).

  If the purge system abnormality diagnosis condition is satisfied in step S11 (YES in step S11), the second valve 2 is driven to open with the first control amount (step S12).

  In step S12, when the opening amount of the second valve 2 reaches a predetermined high opening state, the ECU 1 increases the maximum value of the air-fuel ratio output from the upstream air-fuel ratio sensor 10 in the predetermined high opening state. Acquired as the air-fuel ratio during purge. (Step S12).

  When the high purge air-fuel ratio is acquired in step S13, the ECU 1 changes the valve opening amount of the second valve 2 from a predetermined high opening state to a predetermined low opening state (step S14).

  In step S14, when the valve opening amount of the second valve 2 becomes a predetermined low opening state, the ECU 1 performs a predetermined time from when the valve opening amount of the second valve 2 is changed to the predetermined low opening state. The air-fuel ratio output by the upstream air-fuel ratio sensor 10 at the time when the air-fuel ratio has elapsed is acquired as the low purge air-fuel ratio.

  When the high purge amount and the low purge amount are acquired from step S12 to step S15, the ECU 1 compares the difference between the high purge amount and the low purge amount with the threshold value X (step S16).

  If step S16 is YES, the ECU 1 counts an abnormal state of the purge amount (step S17). If step S16 is NO, the ECU 1 goes to step S18 without going through step S17.

  When step S16 is NO, or when the abnormal state is counted in step S17, in step S18, the ECU 1 counts the number of executions of the abnormality diagnosis control (step S18).

  It is determined whether or not the number of executions of abnormality diagnosis control counted in step S18 has been executed for a threshold value Nth or more (step S19). When step S19 is NO, the purge system abnormality diagnosis control is executed again from S12.

  If YES in step S19, it is determined whether or not the purge amount abnormal state count that has been counted in step S17 is greater than or equal to the threshold value nth. If step S20 is YES, it is determined that the purge system is abnormal.

  Here, “the purge system is abnormal” means that the atmosphere introduction port 4 is in a closed state. If step S20 is NO, it is determined that the purge system is not abnormal. When the purge system abnormality diagnosis in step S20 and step S21 is completed, the current purge system abnormality diagnosis is terminated.

  That is, the ECU 1 can determine the abnormal state of the purge system regardless of the concentration of the evaporated fuel gas in the canister 3. Referring to FIG. 5, when the purge system abnormality diagnosis is executed in a state where the concentration in the canister 3 is low, the difference in the air-fuel ratio does not exceed the abnormality determination threshold value, so that it cannot be diagnosed as an abnormal state.

  Therefore, the ECU 1 detects the abnormal state due to the blockage of the air inlet 4 based on the difference in the air-fuel ratio when the second valve 2 is controlled to the high opening state and the low opening state in the purge system abnormality diagnosis control. Judgment is made. When the ECU 2 is driven to open the second valve 2 at a predetermined high opening, a pressure difference equal to or greater than the valve opening pressure difference of the first valve 5 is generated, so that the evaporated fuel gas in the fuel tank 6 is sucked into the intake pipe. 13 will be sucked.

  On the other hand, when the ECU 1 is driven to open the second valve 2 in a predetermined low opening state, the pressure difference acting on the first valve 5 is less than the valve opening pressure difference, so the evaporated fuel in the fuel tank 6 Is not sucked into the intake pipe 13, and the evaporated fuel gas in the canister 3 is sucked into the intake pipe 13. Accordingly, since the difference between the high purge amount and the low purge amount can be increased, it is possible to suppress the diagnosis of the purge system abnormality diagnosis. Further, the ECU 1 can perform a more suitable purge system abnormality diagnosis by determining the purge system abnormality diagnosis after diagnosing the purge system abnormality a plurality of times.

  In FIG. 4, the vertical axis represents the valve control amount of the second valve 2, the air-fuel ratio A / F output from the upstream air-fuel ratio sensor 10, or the feedback correction amount of the fuel injection amount, and the horizontal axis represents time. .

  Here, the valve control amount in the figure represents the valve opening degree of the second valve 2. The excess air ratio λ is stoichiometry (hereinafter also referred to as stoichiometry), and a value larger than the air excess ratio 1 indicates lean, and a value smaller than the air excess ratio 1 indicates rich.

  When the abnormality diagnosis control is executed, at time t1, the valve drive amount of the second valve 2 is changed to a predetermined high opening state in order to acquire a high purge amount. After the valve opening amount of the second valve 2 is changed, the negative pressure in the purge pipe increases, and the differential pressure between the fuel tank 6 side and the purge pipe in the first valve 5 increases. By doing so, the first valve 5 is opened, and the excess air ratio detected by the upstream air-fuel ratio sensor 10 changes to the rich side.

  Further, when the ECU 1 detects the excess air ratio at which the excess air ratio detected by the upstream air-fuel ratio sensor 10 is maximized, the ECU 1 acquires the high purge air-fuel ratio. Referring to FIG. 4, the ECU 1 acquires the maximum excess air ratio (t2) detected by the upstream air-fuel ratio sensor 10 in the section T1 from t1 to t3 as the high purge air-fuel ratio.

  In the present embodiment, the maximum excess air ratio in the section T1 is acquired. However, when the maximum excess air ratio is detected at the time when the excess air ratio decreases, the T1 section may be terminated. By doing in this way, it is possible to suppress the deterioration of the combustion state by the evaporated fuel gas and the exhaust gas purification performance.

  After the ECU 1 acquires the high purge air-fuel ratio, at time t3, the valve opening amount of the second valve 2 is changed to a predetermined low opening state. After the valve opening amount of the second valve 2 is changed, the time t3 after the elapse of a predetermined time in the section T3 is lowered from the time t3 when the pressure distribution in the purge pipe and the canister 3 and the concentration distribution of the evaporated fuel gas are uniformly distributed. Acquired as the air-fuel ratio during purge.

  In the present embodiment, the valve opening amount of the second valve 2 is changed again to a predetermined high opening state after a predetermined time in the section T2. By doing so, it is possible to form a state where the pressure distribution in the purge pipe and the canister 3 and the concentration distribution of the evaporated fuel gas are uniformly distributed, and the abnormality diagnosis control can be executed a plurality of times.

  After the ECU 1 acquires the low purge air-fuel ratio, at time t5, the valve opening amount of the second valve 2 is changed to a predetermined high opening state. By repeating the abnormality diagnosis control from time t1 to time t5 as described above, it is possible to execute abnormality diagnosis control for detecting an abnormal state due to the blockage of the air inlet 4 regardless of the concentration of the evaporated fuel gas in the canister 3. is there.

  As described above, in the present embodiment, the ECU 1 supplies a pressure difference equal to or greater than the valve opening pressure difference at which the first valve 5 is opened when the air introduction port 4 provided in the canister 3 is closed. The closed state of the air inlet 4 is detected based on a predetermined high opening state and an excess air ratio in a predetermined low opening state that supplies a pressure difference less than the valve opening pressure difference at which the first valve 5 is not opened.

  By doing in this way, it becomes possible to detect the obstruction | occlusion state of the air introduction port 4, and it can prevent releasing evaporated fuel gas in air | atmosphere.

  In addition to this, by supplying a pressure difference equal to or greater than the valve opening pressure difference at which the first valve 5 is opened, even if the amount of vaporized fuel gas in the canister 3 is not sufficient, the first valve 5 Is controlled to open to a predetermined high opening state, and the atmosphere introduction port 4 is closed, so that the atmosphere is not introduced from the atmosphere introduction port 4 and the evaporated fuel gas is drawn from the fuel tank 6. . For this reason, a difference in the detectable excess air ratio used for the abnormality diagnosis control is generated by the high-concentration evaporated fuel gas sucked from the gasoline tank, and the abnormality diagnosis control can be suitably executed. As a result, the abnormality (blocking state) of the air introduction port 4 can be determined appropriately.

  Further, in the present embodiment, the ECU 1 acquires the maximum air-fuel ratio detected by the air-fuel ratio detection unit when the second valve 2 is driven in a predetermined high opening state as the high purge air-fuel ratio.

  By doing so, since the first valve 5 is opened after the pressure in the canister 3 has sufficiently decreased, even if the concentration of the evaporated fuel gas in the canister 3 is low, the fuel tank 6 The evaporated fuel gas is sucked more.

  Further, in the present embodiment, the ECU 1 acquires the air-fuel ratio detected by the air-fuel ratio detection unit when a predetermined time has elapsed since the second valve 2 was changed in a predetermined low opening state as the low purge air-fuel ratio. .

  In this way, when the predetermined high opening state is changed to the predetermined low opening state, there is an influence of the high concentration evaporated fuel gas remaining in the canister 3 or the purge passage. By acquiring the detection value of the upstream air-fuel ratio sensor 10 after a predetermined time has elapsed, it is possible to form a state in which the pressure in the purge pipe and the canister 3 and the concentration of the evaporated fuel gas are uniformly distributed. is there.

  In this embodiment, when the ECU 1 detects that the difference between the high purge air-fuel ratio and the low purge air-fuel ratio is a predetermined value or more, the ECU 1 determines that the air inlet 4 provided in the canister 3 is abnormal. .

  By doing so, it is possible to form a state in which the pressure in the purge pipe and the canister 3 and the concentration of the evaporated fuel gas are uniformly distributed.

  While embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that changes may be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims.

1 ECU (control unit)
2 Second valve 3 Canister 4 Air inlet 5 First valve 6 Fuel tank 10 Upstream air-fuel ratio sensor 13 Intake pipe 15 Exhaust pipe

Claims (4)

Evaporative fuel gas discharge prevention comprising: an evaporative fuel gas passage for purging evaporative fuel generated in the fuel tank to an intake system of an internal combustion engine; and a canister provided in the evaporative fuel gas passage for collecting the evaporative fuel gas A device,
A first valve that is provided between the fuel tank and the canister in the evaporated fuel gas passage and opens when a pressure difference between the fuel tank side and the canister side exceeds a predetermined valve opening pressure difference. And a second valve that is provided between the canister and the intake system in the evaporated fuel gas passage and adjusts a purge amount of the evaporated fuel gas purged from the canister to the intake system, and is provided in the canister. An air inlet for introducing the atmosphere into the canister, an air-fuel ratio detector for detecting an air-fuel ratio of exhaust gas discharged from the internal combustion engine, and an opening of the second valve according to the operating state of the internal combustion engine And a control unit for controlling
The control unit has a predetermined high opening state where the pressure difference is equal to or greater than the valve opening pressure difference when the atmosphere introduction port is closed, and the pressure difference when the atmosphere introduction port is closed. A high purge air-fuel ratio that is the air-fuel ratio when the second valve is controlled to the predetermined low opening state where the valve opening pressure difference is less than the valve opening pressure difference and the second valve is controlled to the high opening state And the air-fuel ratio at the time of purge, which is the air-fuel ratio when the second valve is controlled to the low-opening state, to determine the abnormality of the air inlet, Gas emission prevention device.   The control unit acquires the maximum value of the air-fuel ratio detected by the air-fuel ratio detection unit when the second valve is driven in the high opening state as the high purge air-fuel ratio. The evaporative fuel gas emission preventing device according to claim 1.   The control unit acquires, as the low purge air-fuel ratio, the air-fuel ratio detected by the air-fuel ratio detection unit when a predetermined time has elapsed since the driving state of the second valve was changed in the low opening state. The evaporative fuel gas discharge prevention device according to claim 1 or 2, wherein   The control unit determines that the atmosphere introduction port is abnormal when detecting that the difference between the high purge air-fuel ratio and the low purge air-fuel ratio is a predetermined amount or more a plurality of times. The evaporative fuel gas discharge | emission prevention apparatus of any one of Claims 1-3.

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