JP4661644B2 - Purge flow diagnostic device for internal combustion engine - Google Patents

Description

  The present invention relates to a purge flow diagnostic apparatus for an internal combustion engine.

  The engine includes an evaporated fuel processing device that prevents the fuel evaporated from the fuel tank from being released into the atmosphere. In the evaporative fuel processing apparatus, a canister filled with activated carbon is adsorbed and stored. The adsorbed vaporized fuel is desorbed (purged) from the canister using intake negative pressure generated by the operation of the engine, and is introduced into the combustion chamber together with fresh air from the intake passage.

  Further, the canister recovers the adsorption performance by desorbing the adsorbed evaporated fuel. However, if the evaporated fuel exceeds the capacity of the canister without being detached, the evaporated fuel may leak into the atmosphere from the canister.

  Therefore, in order to diagnose the state of the evaporated fuel processing device, it is determined whether the purge passage connected from the canister to the intake passage is normally conducted. Such a diagnosis is called a purge flow diagnosis. The purge flow diagnosis diagnoses the flow of the purge passage by measuring the pressure change inside the purge passage. The purge flow diagnosis is composed of a simple first stage diagnosis that is diagnosed during normal traveling and a second stage diagnosis with higher diagnosis accuracy.

On the other hand, in a hybrid vehicle or the like, an idle stop is temporarily performed to temporarily stop the engine in order to improve fuel efficiency when traveling with only a motor. However, if the purge flow diagnosis is executed while the engine is stopped, the pressure change inside the purge passage becomes small, and the diagnosis accuracy may deteriorate. Therefore, a technique is disclosed in which deterioration in diagnostic accuracy is suppressed by increasing the engine load or the rotational speed at the timing of performing idle stop (see Patent Document 1).
JP 2000-257498 A

  However, as in the conventional diagnostic device described above, if the engine load or the rotational speed is increased during the purge flow diagnosis, the fuel consumption is deteriorated. Further, at the time of the second stage diagnosis, if the engine load or the rotational speed is increased, the pressure difference in the purge passage before and after the opening and closing of the drain cut valve tends to decrease, and the diagnosis accuracy may deteriorate.

  The present invention has been made paying attention to such conventional problems, and an object of the present invention is to provide a purge flow diagnostic apparatus that minimizes deterioration of fuel consumption and improves diagnostic accuracy.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

In the present invention, the evaporated fuel generated in the fuel tank (10) is adsorbed by the canister (12), the fuel tank (10) and the intake passage (20) are connected, and the canister (12) is arranged. By opening and closing a purge control valve (18) provided between the canister (12) and the intake passage (20) from the purge passage (13), the evaporated fuel is sent to the combustion chamber of the internal combustion engine (30). A purge flow diagnostic device for diagnosing an abnormality in the evaporated fuel processing device leading to (31), the drain cut valve (15) provided in the canister (12 ) and opening one end of the purge passage (13) to the atmosphere And a pressure sensor (16) disposed between the purge control valve (18) and the fuel tank (10) for detecting the pressure in the purge passage (13). During the normal operation of the internal combustion engine (30), the pressure (P21) of the purge passage (13) when the purge control valve (18) is in the open state, and when the purge control valve (18) is in the closed state The first diagnosis means (step S202) which compares the pressure (P22) and determines that an abnormality occurs when the pressure difference is smaller than a predetermined first reference value, and the first diagnosis means (step S202) causes an abnormality. The purge control valve (18) is fixed at a predetermined opening, and the pressure in the purge passage (13) in a state where the drain cut valve (15) is opened, A second diagnostic means (step S207) that compares the pressure in a closed state and determines that an abnormality occurs when the pressure difference is smaller than a predetermined second reference value; and the second diagnostic means ( Step Wherein during execution of S207), characterized in that it comprises an internal combustion engine stop prohibition means for prohibiting stopping of the internal combustion engine (30) (step S401).

  According to the present invention, it is possible to improve diagnostic accuracy by prohibiting idle stop during diagnosis and ensuring a certain pressure difference in the purge passage.

  Furthermore, according to the present invention, the idle stop is prohibited only while the second diagnostic means is being executed, so that deterioration of fuel consumption can be minimized.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a configuration diagram of a purge flow diagnostic apparatus according to an embodiment of the present invention. The purge flow diagnostic device is a device for diagnosing an abnormality in the evaporated fuel processing system.

  As will be described later, the process of evaporative fuel is to mix the evaporative fuel with the intake air and lead it to the combustion chamber 31 for incineration in order to prevent the fuel evaporated from the fuel tank 10 from being discharged to the outside. . The purge flow diagnosis is a diagnosis of whether the evaporated fuel is normally guided to the combustion chamber 31.

  Hereinafter, each configuration of the purge flow diagnostic apparatus according to the embodiment of the present invention will be described.

  The fuel tank 10 stores the fuel input from the fuel filler port 19. The fuel tank 10 is connected to the fuel passage 11. The fuel passage 11 is connected to a fuel injection valve 21 disposed in the intake port 22. The fuel injection valve 21 injects fuel at a predetermined timing according to the operating state, mixes it with intake air, and sends it to the combustion chamber 31.

  The fuel tank 10 is connected to the purge passage 13. The purge passage 13 connects the fuel tank 10 and the intake passage 20. The intake passage 20 is connected to the intake port 22 of the engine 30. The intake passage 20 includes a throttle valve 23 and an air flow meter 24. The purge passage 13 is connected to the intake passage 20 downstream of the throttle valve 23.

  A canister 12 is disposed in the purge passage 13. The canister 12 is filled with activated carbon and adsorbs the fuel evaporated from the fuel tank 10. The adsorbed evaporated fuel is easily desorbed from the activated carbon by air flowing through the purge passage 13 or the like.

  The canister 12 is formed with an air hole 14 that is open to the atmosphere. A drain cut valve 15 is provided between the inside of the canister 12 and the air hole 14. When the drain cut valve 15 is opened, the canister 12 communicates with the outside. Therefore, when the drain cut valve 15 is opened during the operation of the engine 30, the outside air is taken in by the intake negative pressure. The taken-in outside air is sucked into the intake passage 20 via the canister 12 and the purge passage 13. The evaporated fuel adsorbed on the activated carbon is desorbed by the air flow generated in this way and guided to the combustion chamber 31 of the engine 30.

  On the other hand, a purge control valve 18 is provided between the canister 12 and the intake passage 20. The purge control valve 18 switches communication between the purge passage 13 and the intake passage 20.

  A pressure sensor 16 is provided between the purge control valve 18 and the intake passage 20. The pressure sensor 16 measures the pressure inside the purge passage 13.

  By the way, when the drain cut valve 15 is opened with the purge control valve 18 closed, the measured value of the pressure sensor 16 becomes atmospheric pressure. On the other hand, when the purge control valve 18 is opened with the drain cut valve 15 closed, the pressure inside the purge passage 13 is reduced by the intake negative pressure if the engine 30 is in operation.

  However, when clogging occurs between the pressure sensor 16 and the intake passage 20, even if the purge control valve 18 is opened, the pressure does not decrease because it is not affected by the negative intake pressure. Therefore, the purge flow diagnostic device of the present invention diagnoses the abnormality of the purge flow by measuring the pressure in the purge passage 13 when the purge control valve 18 and the drain cut valve 15 are opened and closed.

  The purge flow diagnostic apparatus according to the embodiment of the present invention includes an electronic control unit (hereinafter referred to as “ECU”) 40. The ECU 40 includes a CPU, a ROM, a RAM, an interface circuit, and an inverter circuit.

  The ECU 40 is connected to the pressure sensor 16 and executes a purge flow diagnosis. The ECU 40 is connected to the drain cut valve 15 and the purge control valve 18 to execute the purge control of the evaporated fuel. Note that the ECU 40 has a built-in timer that counts the time during which the pressure sensor 16 monitors the pressure inside the purge passage 13.

  Further, the ECU 40 is connected to the throttle valve 23 and the air flow meter 24, and executes control according to the operation state. The ECU 40 receives detection signals from various other sensors (not shown) via an external input circuit, and performs various controls for optimizing the driving state based on these signals.

  Subsequently, the control of the purge flow diagnostic apparatus according to the embodiment of the present invention will be described based on the flowcharts of FIGS. 2 to 4 and the time charts of FIGS. 5 and 6.

  FIG. 2 is a flowchart of purge flow diagnosis according to the embodiment of this invention. This routine is executed by the ECU 40 when a predetermined condition is satisfied. Note that once the purge flow diagnosis is executed, the operation is stopped and is not executed until the next operation is started.

  As an overview of the purge flow diagnosis, first, the first stage diagnosis is executed during normal running. When the result of the first stage diagnosis is determined to be abnormal for a predetermined number of times, the second stage diagnosis is performed. Furthermore, when it is determined that there is an abnormality in the second stage diagnosis, it is determined that the purge flow diagnosis as a whole is abnormal.

  The overall flow of the purge flow diagnosis will be shown below.

  The ECU 40 first sets the abnormality counter to “0” (step S201). The abnormality counter indicates the number of times that abnormality is continuously determined in the first stage diagnosis.

  Next, the ECU 40 executes a first stage diagnosis (step S202). The first stage diagnosis is executed during normal operation. Details of the first stage diagnosis will be described later with reference to the flowchart shown in FIG.

  When the diagnosis result of the first stage diagnosis is determined to be normal (the result of step S203 is “YES”), the purge flow is determined to be normal (step S210), and this process ends.

  On the other hand, when it is determined that the diagnosis result of the first stage diagnosis is abnormal (the result of step S203 is “NO”), the ECU 40 repeats the first stage diagnosis a predetermined number of times. When it is determined that the diagnosis result of the first stage diagnosis is abnormal, the ECU 40 adds an abnormality counter (step S204), and determines whether the abnormality counter has reached a predetermined number of times (step S205). In the embodiment of the present invention, the predetermined number of times is ten. Then, the first stage diagnosis is repeated until the abnormality counter reaches 10 times (the result of step S205 is “YES”) or until the diagnosis result is determined to be normal (the result of step S203 is “YES”).

  When the abnormality counter reaches 10 times, the ECU 40 sets the second stage diagnosis flag to ON (step S206) and executes the second stage diagnosis (step S207). The second stage diagnosis is executed by setting the purge control valve 18 to a predetermined opening and opening the drain cut valve 15. Details of the second stage diagnosis will be described later with reference to the flowchart shown in FIG.

  If the result of the second stage diagnosis is normal (the result of step S208 is “YES”), it is determined that the purge flow diagnosis is normal (step S210). If the result of the second stage diagnosis is abnormal (the result of step S208 is “NO”), the purge flow diagnosis is determined to be abnormal (step S209).

  When the ECU 40 executes the purge flow diagnosis described above and diagnoses an abnormality twice in succession, the ECU 40 notifies the driver of the abnormality by a warning lamp or the like.

  FIG. 3 is a flowchart of the first stage diagnosis of the purge flow diagnosis according to the embodiment of this invention. In the first stage diagnosis, special control for the purge control valve 18 and the drain cut valve 15 is not executed. The purge flow is diagnosed by monitoring the pressure inside the purge passage 13 during normal control during normal running. In the outline of the first stage diagnosis, an abnormality is determined by comparing the pressure in the purge passage 13 when the purge control valve 18 is open and when it is closed.

  Details of the first stage diagnosis of the purge flow diagnosis will be described below.

  First, the ECU 40 determines the opening degree of the purge control valve 18. When the opening degree of the purge control valve 18 is equal to or greater than the predetermined opening degree (A%) (the result of step S301 is “YES”), it is determined that the purge control valve 18 is open (hereinafter referred to as “open state”). To do.

  When the purge control valve 18 is in the open state, the ECU 40 executes EPRS 11 monitoring (step S302). The EPRS 11 monitor is to monitor the pressure inside the purge passage 13 when the purge control valve 18 is in an open state.

  If it is determined that the purge control valve 18 is not in the open state (the result of step S301 is “NO”) and the EPRS 11 monitor is being executed (the result of step S303 is “YES”), the EPRS 11 monitor is terminated (step S304).

  Next, when the opening degree of the purge control valve 18 is equal to or less than the predetermined opening degree (B%) (the result of step S305 is “YES”), the ECU 40 is in a state where the purge control valve 18 is closed (hereinafter “closed”). State)).

  When the purge control valve 18 is in the closed state, the ECU 40 executes EPRS 12 monitoring (step S306). The EPRS 12 monitor is to monitor the pressure inside the purge passage 13 when the purge control valve 18 is in a closed state.

  When it is determined that the purge control valve 18 is not closed (the result of step S305 is “NO”) and the EPRS 12 monitor is being executed (the result of step S307 is “YES”), the EPRS 12 monitor is terminated (step S308).

  In this way, when the EPRS 11 monitor and the EPRS 12 monitor are finished (the result of step S309 is “YES”), it is determined whether or not the diagnosis result of the purge flow diagnosis is normal (step S310).

  If the purge passage 13 is blocked, it becomes difficult to be affected by the intake negative pressure even if the purge control valve 18 is opened. Therefore, the difference between the pressure inside the purge passage 13 when the purge control valve 18 is opened and the pressure when the purge control valve 18 is closed is small.

  Therefore, in the first stage diagnosis, the result of the purge flow diagnosis is determined by comparing the pressure when the purge control valve 18 is open and the pressure when the purge control valve 18 is closed. Therefore, when the difference between the pressure detected by the EPRS 11 monitor and the pressure detected by the EPRS 12 monitor is smaller than a predetermined value (L1) (the result of step S310 is “YES”), the result of the purge flow diagnosis is displayed. It is determined as abnormal (step S311).

  On the other hand, when the difference is larger than L1 (the result of step S310 is “NO”), it is determined that the purge flow is normal (step S312).

  FIG. 4 is a flowchart of the second stage diagnosis of the purge flow diagnosis according to the embodiment of this invention.

  In the first stage diagnosis, no special opening / closing control is performed on the purge control valve 18 for the purge flow diagnosis. Therefore, it depends greatly on the operating state, and the diagnostic accuracy is not sufficient.

  Therefore, the second stage diagnosis with higher accuracy is executed. As shown in FIG. 2, the second stage diagnosis is executed only when it is determined that there is an abnormality in the first stage diagnosis.

  In the second stage diagnosis, the purge control valve 18 is fixed at a constant opening, the drain cut valve 15 provided in the canister 12 is opened, and an abnormality is determined by the pressure difference in the purge passage 13 before and after opening. By controlling in this way, it becomes difficult to be influenced by the driving state, and a highly accurate diagnosis can be executed.

  When the second stage diagnosis is started, the ECU 40 prohibits idle stop (step S401). Since the purge flow diagnosis is determined based on the pressure difference in the purge passage 13, the generation of the intake negative pressure is suppressed when the idle stop is executed. Therefore, the pressure change inside the purge passage 13 becomes small, and the diagnostic accuracy deteriorates. In the present invention, in order to improve diagnosis accuracy, idle stop is prohibited during execution of the second stage diagnosis.

  Next, the ECU 40 gradually decreases the opening of the purge control valve 18 at a constant rate (step S402). This is because if the opening degree of the purge control valve 18 is suddenly changed, a change in the pressure in the purge passage 13 increases due to the change in the opening degree, which may deteriorate the diagnostic accuracy. The ECU 40 reduces the opening degree of the purge control valve 18 until it becomes zero (step S403).

  Further, the ECU 40 gradually increases the opening degree of the purge control valve 18 at a constant rate (step S404). The reason why the opening degree of the purge control valve 18 is not changed abruptly is the same as that described in step S402. The reason why the opening of the purge control valve 18 is once increased and then increased is to stabilize the pressure in the purge passage 13 and improve the diagnostic accuracy. Then, the ECU 40 increases the opening degree of the purge control valve 18 until it reaches a predetermined opening degree θ (step S405).

  When the opening degree of the purge control valve 18 reaches the predetermined opening degree θ (the result of step S405 is “YES”), the ECU 40 fixes the opening degree to θ (step S406).

  Thereafter, the ECU 40 starts the EPRS 21 monitor (step S407). The EPRS 21 monitor is to monitor the pressure change in the purge passage 13 with the drain cut valve 15 opened. The measurement result of the EPRS 21 monitor is the maximum pressure in the purge passage 13 while monitoring is continued.

  When the ECU 40 executes the EPRS 21 monitor for a predetermined time (the result of step S408 is “YES”), the ECU 40 closes the drain cut valve 18 (step S409).

  Then, the ECU 40 starts the EPRS 22 monitor (step S410). In the EPRS 22 monitor, the pressure change in the purge passage 13 is monitored with the drain cut valve 15 closed.

  When starting the EPRS 22 monitor, the ECU 40 compares the measurement result of the EPRS 21 monitor with the pressure detected by the EPRS 22 monitor (step S411).

  When the pressure difference between the measurement result of the EPRS 21 monitor and the pressure detected by the EPRS 22 monitor is larger than a predetermined difference (L2) (the result of step S411 is “YES”), it is determined as normal ( Step S414).

  On the other hand, if the pressure difference does not become larger than L2 (the result of step S411 is “NO”), the EPRS 22 monitor is continued until the predetermined time has elapsed (the result of step S412 is “NO”).

  If the pressure difference between the measurement result of the EPRS 21 monitor and the pressure detected by the EPRS 22 monitor does not exceed L2 even after the predetermined time has elapsed (the result of step S412 is “YES”), the ECU 40 The result of the purge flow diagnosis is determined to be abnormal (step S413).

  Then, the ECU 40 sets the diagnosis end flag to ON (step S416). Further, the ECU 40 opens the drain cut valve 15 (step S416), and closes the purge control valve 18 until it gradually becomes 0% (steps S417, S418).

  Subsequently, the ECU 40 cancels the prohibition of idling stop (step S419). The conditions for canceling the idle stop prohibition are that the diagnosis end flag is set to ON and the purge control valve 18 reaches 0%.

  Thereafter, the ECU 40 gradually increases the opening degree of the purge control valve 18 at a constant rate (step S420). Then, the opening degree is increased until the opening degree of the purge control valve 18 reaches a predetermined opening degree (step S421). Thereafter, the ECU 40 shifts the control of the purge control valve 18 to normal control, and ends the second stage diagnosis.

  FIG. 5 is a time chart of the first stage diagnosis of the purge flow diagnosis according to the embodiment of the present invention. 5A shows the engine speed, FIG. 5B shows the opening degree of the purge control valve 18, FIG. 5C shows the EPRS11 monitor region, FIG. 5D shows the EPRS12 monitor region, and FIG. Indicates the pressure in the purge passage 13, and FIG. 5F shows an abnormality counter of the purge flow diagnostic apparatus.

  The first stage diagnosis is started when a predetermined condition is satisfied. Starting conditions include, for example, that the engine exceeds a predetermined rotational speed (FIG. 5A), and that the purge control valve 18 exceeds a predetermined opening degree (FIG. 5B). It is done.

  When the above-described conditions are satisfied, ECU 40 starts the first stage diagnosis (time t11 in FIG. 5C; step S202). Further, the ECU 40 clears the abnormality counter of the purge flow diagnostic device before starting the first stage diagnosis (step S201).

  Since the opening degree of the purge control valve 18 has reached A% at the time t101 (step S301), the ECU 40 starts the EPRS 11 monitor (step S302). As described above, the EPRS 11 monitor measures the pressure in the purge passage 13 when the purge control valve 18 is open. The EPRS 11 monitor requires a certain time from when the execution condition is satisfied until it is actually started (time t102 in FIG. 5E). Then, while the execution condition is satisfied (the result of step S301 is “YES”), the EPRS 11 monitor is continued (time t102 → t103).

  Subsequently, when the opening degree of the purge control valve 18 becomes B% or less (step S305; time t104 in FIG. 5B), the ECU 40 executes the EPRS monitor 12 (step S306; time in FIG. 5D). t104). Similar to the EPRS monitor 11, the EPRS monitor 12 requires a certain period of time until execution is actually started (time t105 in FIG. 5E). Note that the EPRS monitor 12 is continued until time 106 (FIG. 5D).

  In this way, the difference (h1 in FIG. 5 (E)) between the minimum value of the pressure measured by the EPRS monitor 11 and the minimum value of the pressure measured by the EPRS monitor 12 exceeds a predetermined value (L1). If not, the ECU 40 determines that the purge flow diagnosis result is abnormal (time t105 in FIG. 5E). At this time, the ECU 40 adds an abnormality counter (step S204; time t105 in FIG. 5F).

  Thereafter, the ECU 40 continues the first stage diagnosis until the abnormality counter exceeds a predetermined number of times. In the present embodiment, this predetermined number is 10 times. When the predetermined condition is satisfied, the EPRS 11 monitor is started again (time t107 in FIG. 5C, t108 in FIG. 5E). Thereafter, the EPRS 12 monitor is similarly started (time t109 in FIG. 5C, t110 in FIG. 5E). When the diagnosis result (h2 in FIG. 5E) does not exceed L1, an abnormality counter is added (time t111 in FIG. 5F).

  As described above, the first stage diagnosis is executed, and when the diagnosis result is determined to be abnormal for a predetermined number of times, the process proceeds to the second stage diagnosis (the result of step S205 is “YES”).

  FIG. 6 is a time chart of the second stage diagnosis of the purge flow diagnosis according to the embodiment of the present invention. 6A shows the opening of the purge control valve 18, FIG. 6B shows the pressure in the purge passage 13, FIG. 6C shows the open / close state of the drain cut valve 15, FIG. 6D shows the EPRS 21 monitor region, FIG. 6E shows the EPRS 22 monitor region, FIG. 6F shows the second stage execution flag, FIG. 6G shows the purge flow diagnosis end flag, and FIG. 6H shows the idle stop prohibition flag.

  After the completion of the first stage diagnosis, when the process proceeds to the second stage diagnosis, the second stage flag is set to ON (step S206; time t201 in FIG. 6F). In the second stage diagnosis, in order to improve diagnosis accuracy, idling stop is prohibited during diagnosis (step S401; time t201 in FIG. 6H). Note that the drain cut valve 15 is opened at the start of the second stage diagnosis (time t201 in FIG. 6C).

  The ECU 40 controls the opening degree of the purge control valve 18 to gradually decrease (step S402; times t201 to t202 in FIG. 6A). When the opening degree reaches 0 (the result of step S403 is “YES”; time t202 in FIG. 6A), the opening degree is controlled to gradually increase until the predetermined opening degree θ is reached (step S202). S404; times t202 to t203 in FIG. This is because the pressure inside the purge passage 13 is stabilized to make a diagnosis without depending on the operating state as much as possible.

  Then, the ECU 40 fixes the opening degree of the purge control valve 18 to a predetermined opening degree θ (step S406; times t203 to t205 in FIG. 6D), and starts the EPRS21 monitor (step S407; FIG. 6D). ) At time t203). The ECU 40 measures the pressure inside the purge passage for a predetermined time (time t203 to t204), and uses the maximum value (P21) as the measurement result of the EPRS21 monitor.

  The ECU 40 starts the EPRS 22 monitor after the end of the EPRS 21 monitor (step S410; time t204 in FIG. 6E). Further, the ECU 40 starts the EPRS 22 monitoring and closes the drain cut valve 15 (step S409; time 204 in FIG. 6C). Thereafter, the ECU 40 measures the pressure inside the purge passage for a predetermined time (time t204 to t205), and uses the minimum value (P22) as the measurement result of the EPRS22 monitor.

  The ECU 40 determines the diagnosis result based on the difference (P21−P22) between the measurement result P21 of the EPRS 21 monitor and the measurement result P22 of the EPRS 22 monitor (steps S411, S413, and S414).

  When the EPRS 22 monitor ends, the ECU 40 sets the diagnosis end flag to ON (step S415; time t205 in FIG. 6G). Then, the ECU 40 performs control so that the opening degree of the purge control valve 18 is gradually reduced (step S417; times t205 to t206 in FIG. 6A). When the opening of the purge control valve 18 reaches 0 (the result of step S418 is “YES”; time t206 in FIG. 6A), the idle stop prohibition is canceled (step S419; time t207 in FIG. 6H). ).

  Thereafter, the ECU 40 performs control so that the opening gradually increases (step S420; times t206 to t207 in FIG. 6A). When the opening degree of the purge control valve 18 reaches a predetermined opening degree (the result of step S421 is “YES”; time t207 in FIG. 6A), the ECU 40 ends the purge flow diagnosis (FIG. 6G). T207).

  According to the embodiment of the present invention, idle stop is prohibited during execution of the second stage diagnosis. Therefore, the intake negative pressure can be stably generated during the execution of the second stage diagnosis. Therefore, the pressure change in the purge passage before and after the drain cut valve 15 is opened and closed becomes large, and the diagnostic accuracy can be improved. In particular, the accuracy of purge flow diagnosis can be improved in a hybrid vehicle or the like that frequently performs idle stop.

  Further, according to the embodiment of the present invention, the period during which the idle stop is prohibited is only during the execution of the second stage diagnosis, so that deterioration of fuel consumption can be minimized.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

It is a figure which shows the structure of the purge flow diagnostic apparatus by this invention. It is a flowchart of the purge flow diagnosis which the purge flow diagnostic apparatus by this invention performs. It is a flowchart of the 1st stage diagnosis of the purge flow diagnostic apparatus by this invention. It is a flowchart of the 2nd stage diagnosis of the purge flow diagnostic apparatus by this invention. It is a time chart of the 1st stage diagnosis of the purge flow diagnostic apparatus by this invention. It is a time chart of the 2nd stage diagnosis of the purge flow diagnostic apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel tank 12 Canister 13 Purge passage 15 Drain cut valve 16 Pressure sensor 18 Purge control valve 20 Intake passage 21 Fuel injection valve 22 Intake port 30 Engine (internal combustion engine)
40 ECU

Claims (5)

Purge control provided between the canister and the intake passage from the purge passage where the fuel tank and the intake passage are connected by adsorbing the evaporated fuel generated in the fuel tank with the canister and connecting the fuel tank and the intake passage. A purge flow diagnostic apparatus for diagnosing an abnormality in an evaporative fuel processing apparatus that leads the evaporative fuel to a combustion chamber of an internal combustion engine by opening and closing a valve,
Provided in the canister motor, a drain cut valve which opens one end of the purge passage to the atmosphere,
A pressure sensor disposed between the purge control valve and the fuel tank for detecting the pressure of the purge passage;
While the internal combustion engine is operating normally, the pressure in the purge passage when the purge control valve is in the open state is compared with the pressure when the purge control valve is in the closed state, and the pressure difference is predetermined. First diagnostic means for determining an abnormality when smaller than the first reference value;
This is executed when it is determined that there is an abnormality in the first diagnosis process, and the purge control valve is fixed at a predetermined opening, and the pressure of the purge passage when the drain cut valve is open, and the valve is closed. A second diagnostic means for comparing the pressure in a state in which the pressure is in a state and determining an abnormality when the pressure difference is smaller than a predetermined second reference value;
Internal combustion engine stop prohibiting means for prohibiting the stop of the internal combustion engine during execution of the second diagnostic means;
A purge flow diagnostic apparatus for an internal combustion engine. The second diagnostic means gradually reduces the opening of the purge control valve before fixing to the predetermined opening, and then gradually increases until the predetermined opening is reached.
The purge flow diagnostic apparatus according to claim 1. The internal combustion engine stop prohibiting means is prohibited to stop the internal combustion engine simultaneously with the start of execution of the second diagnostic means.
The purge flow diagnostic apparatus according to claim 1 or 2, characterized by the above. The internal combustion engine stop prohibiting means cancels the prohibition of the stop of the internal combustion engine simultaneously with completion of execution of the second diagnostic means.
The purge flow diagnostic apparatus according to any one of claims 1 to 3, wherein the purge flow diagnostic apparatus is characterized in that: Purge control provided between the canister and the intake passage from the purge passage where the fuel tank and the intake passage are connected by adsorbing the evaporated fuel generated in the fuel tank with the canister and connecting the fuel tank and the intake passage. A purge flow diagnostic method for diagnosing an abnormality in an evaporative fuel processing apparatus that leads the evaporative fuel to a combustion chamber of an internal combustion engine by opening and closing a valve,
During normal operation of the internal combustion engine, the pressure in the purge passage between the fuel tank and the purge control valve is detected, and the pressure when the purge control valve is open and the valve closed A first diagnosis process for comparing with a pressure at a certain time and determining an abnormality when the pressure difference is smaller than a predetermined first reference value;
The purge passage, which is executed when it is determined that there is an abnormality by the first diagnosis processing, and when the drain cut valve for fixing the purge control valve at a predetermined opening and opening the purge passage to the atmosphere is open. A second diagnostic process for comparing the pressure of the valve and the pressure when the valve is closed, and determining an abnormality when the pressure difference is smaller than a predetermined second reference value;
An internal combustion engine stop prohibition process for prohibiting the stop of the internal combustion engine during the execution of the second diagnostic process;
A purge flow diagnostic method for an internal combustion engine, including:

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