JPH0458057A - Diagnosing device for abnormality in evapo-purge system - Google Patents

Abstract

PURPOSE:To precisely and reliably detect an abnormal condition of an evapo- purge system by diagnosing an abnormality in the evapo-purge system when vapor is actually absorbed into a canister by a quantity greater than a predetermined value. CONSTITUTION:A diagnosing system for an abnormality in an evapo-purge system is composed of a fuel vapor absorbing means D for absorbing fuel vapor evaporating from a fuel storage section, an absorption detecting means E for detecting a vapor absorbing condition of the fuel vapor absorbing means D, and a purge performing means C for purging fuel vapor absorbed in the fuel vapor absorbing means D into an intake system of an engine E. A purge gas concentration detecting means A detects the concentration of purge gas when the purge performing means C purges fuel vapor into the intake system of the engine, and a predetermined quantity of fuel vapor absorbed into the fuel vapor absorbing means D is detected. Further, when the purge is performed, if the detected purged gas concentration does not vary by a value greater than a predetermined value, an abnormality diagnosing means B determines occurrence of an abnormality.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an abnormality diagnosis device for an evaporative purge system,
In particular, the present invention relates to an abnormality diagnosis device for an evaporative purge system, in which fuel vapor evaporated from a fuel storage section of an internal combustion engine and adsorbed in a canister is returned to a fuel supply system under predetermined conditions when the vehicle is running.

[Prior Art] Generally, in an internal combustion engine, fuel vapor (
In order to prevent HC) from being released into the atmosphere, the engine is equipped with an evaporative purge system that adsorbs fuel vapor into a canister and draws it into the intake side using negative suction pressure during engine operation.

In such an evaporative purge system, when the process (purge) of returning fuel vapor (evaporative) adsorbed in the canister to the intake side is executed, the feedback correction amount (FAF) of the air-fuel ratio changes depending on the purge gas concentration. ,
It is necessary to adjust FAF according to the amount of purge. An example of such an adjustment device is one that estimates the evaporative purge amount and adjusts the fuel injection amount by calculating the FAF control center value when the engine is idling and when the load is low (Japanese Patent Laid-Open No. 63486955). Public bulletin)
There is.

However, in such an evaporative purge system, if the evaporative purge amount cannot be accurately grasped, air-fuel ratio feedback will not be performed normally, resulting in poor fuel efficiency and emissions. Therefore, various devices have been devised to detect abnormalities in the evaporative purge system. For example, such devices can diagnose malfunctions in the evaporative purge system based on the roughness of the air-fuel ratio caused by turning the evaporative purge on and off during engine operation. There is something.

In this diagnostic device, if the evaporative purge system is operating normally and vapor is sufficiently absorbed in the canister, the intake air will be rich due to the presence of vapor in the bar share when the evaporative purge is turned on (executed). This is used to diagnose the system. That is, in this device, when the air-fuel ratio is small when the evaporative purge is turned on and off, it is determined that the evaporative purge system is malfunctioning, and the purge is stopped.

C Problems to be Solved by the Invention] However, this conventional abnormality diagnosis device for an evaporative purge system has the problem of false detection when no vapor is adsorbed in the canister or when the purge gas concentration is equal to the stoichiometric air-fuel ratio. be.

The present invention solves the problems of the conventional abnormality diagnosis device for an evaporative purge system, and detects the adsorption state of vapor in the canister, thereby detecting when no vapor is adsorbed in the canister or when the purge gas concentration is equal to the stoichiometric air-fuel ratio. An object of the present invention is to provide an abnormality diagnosis device for an evaporative purge system that does not erroneously detect that the system is abnormal even when the system is abnormal.

[Means to solve the problem]

The configuration of an abnormality diagnosis device for an evaporative purge system according to the present invention that achieves the above object is shown in FIG.

An abnormality diagnosis device for an evaporative purge system according to the present invention includes: a fuel vapor adsorption means for adsorbing fuel vapor evaporated from a fuel storage section; an adsorption state detection means for detecting a fuel vapor adsorption state of the fuel vapor adsorption means; purge execution means for purging the fuel vapor adsorbed by the vapor adsorption means into the intake system of the engine; and purge gas concentration detection means for detecting the purge gas concentration when the fuel vapor is purged into the intake system of the engine by the purge execution means. , when it is detected that a predetermined amount of fuel vapor has been adsorbed by the fuel vapor adsorption means and a purge is executed, an abnormality occurs when the detected purge gas concentration does not change by more than a predetermined value before and after the purge is executed. The present invention is characterized by comprising an abnormality determination means for determining.

[For production]

According to the abnormality diagnosis device for an evaporative purge system of the present invention, when the purge execution means executes purge, the fuel vapor adsorption state detection means detects that a certain amount of fuel vapor is adsorbed in the fuel vapor adsorption device. However, when the purge gas concentration observed by the purge gas concentration detection means does not change from before the purge is executed, the abnormality determination means determines that some abnormality has occurred in the evaporative purge system.

〔Example] Embodiments of the present invention will be described in detail below using the drawings.

FIG. 2 schematically shows an electronically controlled fuel injection type internal combustion engine equipped with an abnormality diagnosis device for an evaporative purge system according to an embodiment of the present invention. In this figure, a throttle valve 18 is provided in the intake passage 2 of an internal combustion engine 1 on the downstream side of an air flow meter (not shown) that measures the air flow rate. A throttle opening sensor 19 is provided to detect the opening. A fuel injection valve 7 is provided in the intake passage 2 on the downstream side of the throttle opening sensor 19 for each cylinder to supply pressurized fuel from the fuel supply system to the intake port.

The distributor 4 includes a crank angle sensor 5 and a crank angle sensor 5 that generate a reference position detection pulse signal every 720° CA in terms of crank angle (CA).
A crank angle sensor 6 is provided that generates a pulse signal for detecting a reference position at each time. These crank angle sensors 5,
The pulse signal No. 6 acts as an interrupt request signal for fuel injection timing, a reference timing signal for ignition timing, an interrupt request signal for fuel injection amount calculation control, and the like. These signals are supplied to the input/output interface 102 of the control circuit 10, and the output of the crank angle sensor 6 is supplied to the interrupt terminal of the CPU 103.

Further, a water temperature sensor 9 is provided in the cooling water passage 8 of the cylinder block of the internal combustion engine 1 to detect the temperature of the cooling water. The water temperature sensor 9 generates an electric signal of an analog voltage according to the temperature of the cooling water. This output is also A/
The signal is supplied to the D converter 101.

The exhaust system downstream of the exhaust manifold 11 is provided with a three-way catalytic converter 12 that simultaneously purifies three harmful components IC, Co, and NOx in the exhaust gas. Furthermore, an 0□ sensor 13, which is a type of air-fuel ratio sensor, is provided in the exhaust vibrator 14 on the downstream side of the exhaust manifold 11 and on the upstream side of the catalytic converter 12. The 0□ sensor 13 generates an electrical signal depending on the concentration of oxygen components in the exhaust gas. That is, the 0□ sensor 13 outputs different output voltages to A via the signal processing circuit 111 of the control circuit 10 depending on whether the air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio.
/D converter 101. Further, the input/output interface 102 is supplied with an on/off signal for a key switch (not shown).

Further, the internal combustion engine 1 is provided with an evaporation system that prevents vapor evaporated from the fuel tank 21 from escaping into the atmosphere. This system includes a charcoal canister 22, a water temperature sensing valve (BVSV) 24, and an electricity charge negative pressure switching valve (ν5V) 26. The charcoal canister 22 is connected to the upper bottom of the fuel tank 21 by a vapor collection pipe 25, and adsorbs vapor evaporating from the fuel tank 21. In the present invention, a flow rate switch 23, which will be described later, is provided in the middle of this vapor collection pipe 25. BVSV24 and VS
V26 is an on-off valve provided in this order in the middle of the vapor return pipe 27 that returns the vapor adsorbed in the charcoal canister 22 to the downstream side of the throttle valve 18 of the intake passage 2;
The BVSV24 is attached to the engine's cooling water reservoir 28 and opens when the water temperature exceeds a predetermined temperature.
V26 is a solenoid valve that opens and closes in response to an electric signal from the control circuit 10.

In the above-described configuration, when a key switch (not shown) is turned on, the control circuit 10 is energized and a program is started to take in the output from each sensor and control the injector 7 and other actuators.

The control circuit 10 is configured using, for example, a microcomputer, and includes the aforementioned A/D converter 101. Input/output interface 102. In addition to the CPU 103, there is also a ROM 104.
RAM 105° Backup RAM 106 that retains information even after the key switch is turned off. Clock (CLK)
107 etc. are provided, and these are connected by a bus 113.

In this control circuit 10, an injection control circuit 110 including a down counter, a flip-flop, and a drive circuit is for controlling the fuel injection valve 7. That is, when the fuel injection amount TAU is calculated by correcting the basic injection tTp calculated from the intake air amount and the engine rotational speed based on the operating state of the engine, the fuel injection amount TAU is preset in the down counter of the injection control circuit 110. At the same time, the flip-flop is also set and the drive circuit starts energizing the fuel injection valve 7.

On the other hand, when the down counter counts the clock signal (not shown) and the carrier voltage terminal finally reaches the "1" level, the flip-flop is reset and the drive circuit stops energizing the fuel injection valve 7. do. That is, the fuel injection valve 7 is energized by the above-mentioned fuel injection amount TAU, so that an amount of fuel corresponding to the fuel injection amount TAU is sent into the combustion chamber of the internal combustion engine 1.

Note that the interrupt generation of CPIJI03 is caused by the A/D converter 10.
After the A/D conversion of 1 is completed, when the input/output interface 102 receives a pulse signal from the crank angle sensor 6, when it receives an interrupt signal from the clock generation circuit 107, etc.

FIG. 3 shows an example of the configuration of the flow rate switch 23 mentioned above. In the figure, 230 is a housing, and this housing 2
30 is provided with a vapor inflow hole 231 and a vapor outflow hole 232. Inside the housing 230 is a diaphragm 233
The diaphragm 233 is partitioned into two chambers 230A and 230B by the chamber 230A, and a valve body 234 that seals the vapor flow hole 231 in a steady state is provided on the chamber 230A side of the diaphragm 233, and a contact piece 235 is provided on the chamber 230B side. is installed protrudingly. Further, a contact 236 that is turned on by movement of the piece 235 is provided in the portion M230B. One of the contacts 236 is grounded, and the other is connected to the control circuit 10.

When the engine is stopped, etc., the fuel in the fuel tank 21 evaporates and the pressure in the gas portion of the fuel tank 21 increases until it reaches a predetermined pressure. This pressure pushes the valve body 234 of the flow rate switch 23 and closes the diaphragm. 233 moves to the section 123OB side. This movement of the diaphragm 233 causes the vapor in the fuel tank 21 to flow through the vapor inlet hole 231 of the flow rate switch 23. The vapor passes through the vapor outlet hole 232 and is absorbed into the charcoal canister 22 . Diaphragm 23 at this time
3, the piece 235 contacts the contact 236 and turns it on, so that the control circuit 10 can detect the amount of vapor adsorbed to the charcoal canister 22 based on the on-time period of the flow rate switch 23.

In the above embodiment, the amount of vapor adsorbed to the charcoal canister 22 is detected using the flow rate switch 23, but the amount of vapor adsorbed to the charcoal canister 22 is detected by using a flow rate sensor, a fuel tank internal pressure sensor, etc. It is also possible to detect using

Next, an example of the operation of the control circuit 10 described above is shown in FIGS. 4 to 6.
This will be explained using the flowchart shown in the figure.

FIG. 4 shows a vapor generation detection routine, which is executed regardless of whether the engine is stopped or running. First, in step 401, it is determined whether the internal combustion engine is in a stopped state. When the engine is in a stopped state (YES), the process proceeds to step 402, and it is determined whether the vapor flow rate switch (abbreviated as SW in the figure) 23 is on. As described above, when the flow rate switch 23 is on, it indicates that fuel vapor from the fuel tank 21 is adsorbed in the charcoal canister 22, so step 403
Proceed to increment the vapor generation counter C■ (C
V+-CV+1) to end this routine.

On the other hand, when it is determined in step 401 that the engine is in operation (NO), the process proceeds to step 404, where it is determined whether the VSV 26 is on. When the VSV 26 is off (NO), the fuel vapor adsorbed in the charcoal canister 22 is not purged, so the process proceeds to step 402 as in the case when the engine is stopped, and when the VSV 26 is on (YES), the process proceeds to step 405.
Proceed to decrement the vapor generation counter C■ (
Cv←CV-1). Step 406 after this
Step 407 is to prevent the value of the vapor generation counter CV from becoming a negative value.
Step 40 only when it is determined that CV<O in 06
Proceed to step 7 and set the value of the vapor generation counter Cv to O.

FIG. 5 shows the abnormality determination routine.

The steering knob 504 from step 501 shows control when starting the engine, and first, the steering knob 501 determines whether or not the engine is started. When the engine is in the starting state (YES), in step 502, counters Fl, F2, memories FAFAVI, FAFAV2, and
and all diagnostic execution completed flags are cleared. In the following step 503, it is determined whether the value of the vapor generation counter C2 is greater than or equal to the reference value Nr. And when cV≧NrO (
If YES), the routine proceeds to step 504, where the VSV 26 is closed, and this routine ends; when CV<Nr (NO), the routine proceeds to step 505, where the VSV 26 is opened, and this routine ends.

Stelaph 506 and subsequent steps show the procedure for diagnosing an abnormality in the evaporative purge system while the engine is operating. First, in step 506, the diagnosis execution completed flag 0BDF is set to “l”.
”.This diagnosis execution completed flag 0Bf)F
becomes "l" when the abnormality diagnosis has already been completed, and becomes "0" when the abnormality diagnosis has not been completed yet. When it is determined in step 506 that 0BDF="do", the process proceeds to step 520, opens the VSV 26, and ends this routine.

On the other hand, when it is determined in step 506 that 0BDF-“0”, the process proceeds to step 507, and the vapor generation counter C
It is determined whether the value of (2) is greater than or equal to the reference value Nr.

This reference value Nr may be set, for example, as the count value of the vapor generation counter C2 when the vapor generation counter C2 adsorbs vapor for 30 minutes or more in the vapor generation detection routine described above. Then, when CV<Nr (NO), step 5
The routine proceeds to step 20 to open the VSV 26 and end this routine. However, if C≧NrO (YES), the procedure proceeds to step 508 and it is determined whether the diagnosis execution condition is met.

For example, the abnormality diagnosis execution conditions for the evaporative purge system are as follows:
The water temperature is 40°C or higher, the fuel is not being cut, the engine is not in a transient operating state, and the air-fuel ratio feedback control execution conditions are met. If this diagnosis execution condition is not satisfied (No), step 520 to step 523
Proceed to the valve closing condition counter F1 and valve opening condition counter F2.
, clears the memories FAFAv1 and FAFAV2, closes the VSV 26 in the step 524, and ends this routine.

The above is the procedure when the abnormality diagnosis of the evaporative purge system is not performed.Next, we will explain the abnormality diagnosis procedure when the abnormality diagnosis condition of the evaporative purge system is satisfied (YES). In the present invention, abnormality diagnosis of the evaporative purge system is performed in a state where vapor from the fuel tank 21 is sufficiently adsorbed in the charcoal canister 22, such as when the engine is stopped. Therefore, when an abnormality diagnosis of the evaporative purge system is performed, the answer in step 503 is YES when the engine is started, so the VSV 26 remains closed and the answer in step 503 is YES.
Proceed to 9.

When VSV26 is closed, the determination in step 509 is NO.
Then, the process proceeds to step 510 and the valve closing condition counter F1 is
Increment the value of (Fl←Fl +1).

Then, in step 511, the valve closing condition counter F1
It is determined whether the value of is greater than or equal to a predetermined value n. ■When 5V26 is closed, unless the value of the valve closing condition counter F1 is incremented a predetermined number of times in step 510, the determination in step 511 is Fl<n, and Finn
, then this routine ends without doing anything.

Note that the predetermined value n may be, for example, the value of the valve closing condition counter F1 when about 5 seconds have elapsed since step 510 was reached for the first time. On the other hand, when it is determined in step 511 that F1≧n1, step 512
The routine proceeds to step 513, where the average fuel flow rate correction value FAFAV is stored in the memory FAFAVI for storing the average fuel flow rate correction factor when not being purged, and the routine proceeds to step 513, where the VSV 26 is opened and this routine ends.

After the VSV26 is opened, the determination in step 509 is Y.
Since the result is ES, proceed to step 514 and increment the value of the valve opening condition counter F2 (F2-F2+1).
. Then, in step 515, the valve opening condition counter F
It is determined whether the value of 2 is greater than or equal to a predetermined value n2.

At this time as well, unless the value of the valve opening condition counter F2 is incremented a predetermined number of times in step 514, the determination in step 515 is that F2<nz, and if F2<nz, this routine is ended without doing anything thereafter. Here again, the predetermined value n
The value 2 may be, for example, the value of the valve opening condition counter F2 when approximately 5 seconds have elapsed since step 514 was reached for the first time.

After this, when it is determined in step 515 that F2≧n2, the process proceeds to step 516, where the average fuel flow rate correction value FAFAV is stored in the memory FAFAV2 for storing the average fuel flow rate correction factor during purging, and the process proceeds to step 517. .

In step 517, the value stored in the memory FAFAVI for storing the average fuel flow rate correction factor when not purging is changed to the memory FAF for storing the average fuel flow rate correction factor when purging is being performed.
It is determined whether the value obtained by subtracting the value stored in AV2 is greater than the determination value. When the evaporative purge system is functioning normally, the fuel vapor adsorbed in the charcoal canister 22 is transferred to the purge return pipe 2 by opening the VSV 26.
Since the fuel is drawn into the intake passage 2 through the fuel injection valve 7, the air-fuel ratio becomes rich, and the amount of fuel injected from the fuel injection valve 7 is correspondingly reduced, thereby decreasing the average fuel flow rate correction value FAFAV.

Therefore, the value stored in the memory FAFAV2 for storing the average fuel flow correction factor during purging is smaller than the value stored in the memory FAFAVI for storing the average fuel flow correction factor during non-purging, and the evaporative purge system If it is normal, FAFAVI - FAFAV2≧k (the value of k should be about 2%).

Based on the above, in step 517, FAFAVI
When FAFAν2≧(YES), the process proceeds to step 519, sets the diagnosis execution completed flag OB to 1″, and ends this routine.Meanwhile, in step 517, FAFAV
If I-FAFAV2<k (NO), step 51
Proceed to step 8 and set the abnormality flag BMGF to 1'' in step 5.
At step 19, the diagnostic execution method flag 0BOF is set to "1" and this routine ends.

When the abnormality flag EMGF is set to 'de', an alarm light inside the vehicle may be turned on or a diagnostic device may sound an alarm to notify the occupants of the abnormality.

FIG. 6 shows a calculation routine for the average fuel flow rate correction value FAFAV used in steps 512 and 516 in FIG. A control routine (referred to as B) is shown.

In step 601, first, it is determined whether or not the 02 sensor 13 is in an active state. 0□When the sensor is inactive (NO
) ends this routine without changing the value of the air-fuel ratio correction coefficient FAF. On the other hand, when it is determined in step 601 that the 0□ sensor is in the active state (YES), step 60
Proceed to step 2 to determine whether other F/B conditions are satisfied. During fuel increase operation after startup, during warm-up increase operation,
The F/B condition is not met in all cases such as power increase, and the F/B condition is met in other cases. Then, when the air-fuel ratio F/B condition is not satisfied (NO), the air-fuel ratio correction coefficient FA
If this routine is ended without changing the value of F and the F/B condition is satisfied (YES), the process proceeds to step 603 and air-fuel ratio F/B correction control is executed.

In step 603, it is determined whether the air-fuel ratio is lean. This determination of whether or not the engine is lean is made based on the output value of the 02 sensor 13. If it is lean (YES), it is determined in step 604 whether or not it is the first lean, that is, it is determined whether it is a change point from rich to lean. As a result, if it is the first lean (YES), in step 607 FAF 4-FA
A predetermined amount (skip amount) A is added as F+A, and on the other hand, if it is not the first lean (NO), a predetermined amount a is added as FAF+-FAF+a in step 606. Note that the skip amount A is set to be sufficiently larger than a.

That is, A) a.

If it is rich, which is NO in step 603, step 6
Proceed to 05. In step 605, it is determined whether or not the first rich state is reached, that is, whether it is a change point from lean to rich. As a result, if it is the first rich (YES), a predetermined amount (skip amount) B @ is subtracted as FAF + - FAF -B in step 608, and on the other hand, if it is not the first rich (NO), in step 609 FAF ← Subtract a predetermined amount as PAF-b. Here too, the skip amount B is set to be sufficiently larger than b. That is, B)b.

In other words, the control shown in steps 606 and 609 is called integral control, and the control shown in steps 607 and 608 is called integral control.
The control shown in is called skip control.

Then, in the case of integral control, this routine ends as it is, and in the case of skip control, step 607 and step 60
Using the air-fuel ratio correction coefficient FAF calculated in step 8, an average value FAFAV of the air-fuel ratio correction coefficient is calculated. This average value F
AFAν may be obtained by calculating the average value of the current and previous skip points. Therefore, step 610
, the air-fuel ratio correction coefficient F at the current skip point
AR and air-fuel ratio correction coefficient FAP at the previous skip point
The average value with O is calculated and is set as the average value FAFAV of the air-fuel ratio correction coefficient. Thereafter, in step 611, the air-fuel ratio correction coefficient PAF at the current skip point is stored as the air-fuel ratio correction coefficient FAFO at the previous skip point.

Figure 7 shows VSV26, valve closing counter F1, valve opening counter F2, and air-fuel ratio correction coefficient FAF in the above control procedure.
, and its average (ff!FAFAv) changes with time. When the diagnosis execution condition is met at time t0, the valve closing condition counter F1 starts counting time. At time t, the valve closing condition counter F1 is the predetermined value n
1, VSV26 opens and the air-fuel ratio correction coefficient F
The AF changes as shown by the solid line A, and its average value FAFAV changes as shown by the broken line. Then, the average value FAFAV at time t is stored in the memory FAFAVINI, and the valve opening condition counter F2GA starts counting the time. Time t
2, when the valve opening condition counter F2 reaches the predetermined value n2, the average value FAFAV of the air-fuel ratio correction coefficient at that time is stored in the memory FAFAV2. Therefore, depending on the value of FAFAV1-FAFAV2 at time ti,
This makes it possible to diagnose abnormalities in the evaporative purge system.

As explained above, in the device of this embodiment, since the suction state of the charcoal canister 22 is detected while the engine is stopped, the timing of abnormality diagnosis can be detected quickly and accurately. Additionally, if the adsorption state of the charcoal canister 22 reaches a predetermined value when the evaporative purge is stopped and the charcoal canister 22 is idling, the abnormality diagnosis will be performed during idling when the amount of intake air is small, and the effect of purge vapor on the air-fuel ratio will be reduced. The detection accuracy is improved compared to the conventional method.

To ensure this, the vapor generation counter Cv is incremented only when the flow rate switch 230 is turned on while the engine is stopped, and abnormality diagnosis is not performed when the vapor generation counter Cv does not reach a predetermined value while the engine is stopped. You can also do it.

Further, in this embodiment, the control circuit 10 detects the amount of vapor adsorbed to the canister 22 when the engine is stopped, but in order to prevent the battery from running out, the control circuit 10 detects the amount of vapor adsorbed by the canister 22 when the engine is stopped. It is also possible to run the . Furthermore, charges may be stored using another circuit such as a capacitor.

Although the air-fuel ratio correction coefficient FAF is used to detect the purge gas concentration in the above-mentioned embodiment, it goes without saying that it may also be detected by providing an HC sensor in the purge passage or the intake passage. Nor.

[Effects of the Invention] As explained above, according to the abnormality diagnosis device for an evaporative barge system of the present invention, an abnormality diagnosis of an evaporative barge system is performed when a predetermined amount or more of vapor is actually absorbed in the canister. This eliminates the possibility of erroneously detecting that the system is abnormal when no vapor is adsorbed in the canister or when the purge gas concentration is equal to the stoichiometric air-fuel ratio, making it possible to accurately and reliably detect abnormal conditions in the evaporative barge system. The effect is that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an abnormality diagnosis device for an evaporative barge system according to the present invention, FIG. 2 is an overall configuration diagram of an internal combustion engine equipped with an abnormality diagnostic device for an evaporative barge system according to the present invention, and FIG. 2 is a cross-sectional view showing the configuration of one embodiment of the flow rate switch, FIGS. 4 to 6 are flowcharts showing an example of an abnormality diagnosis procedure for the evaporative barge system of the control circuit shown in FIG. 2, and FIG. VSV in the control procedure of the control circuit shown in the figure,
FIG. 3 is a diagram showing changes in a valve closing counter, a valve opening counter, an air-fuel ratio correction coefficient, and an average value thereof over time. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Intake passage, 7... Fuel injection valve, 9... Water temperature sensor, 10... Control circuit, 13... 0□ sensor, 21... Fuel tank , 22... Charcoal canister, 23... Flow rate switch, 24-=Water temperature sensing valve (BVSV), 25... Vapor collection pipe, 26... Electric bill negative pressure switching valve (VSV), 27. ...Vapor reflux pipe, 28...Cooling water pool.

Claims (1)

[Scope of Claims] Fuel vapor adsorption means for adsorbing fuel vapor evaporated from a fuel storage section; adsorption state detection means for detecting a fuel vapor adsorption state of the fuel vapor adsorption means; purge execution means for purging the fuel vapor into the intake system of the engine; purge gas concentration detection means for detecting the purge gas concentration when the fuel vapor is purged into the intake system of the engine by the purge execution means; and the fuel vapor adsorption means. abnormality determination means for determining that an abnormality has occurred when it is detected that a predetermined amount of fuel vapor has been adsorbed in the fuel vapor, and when purge is executed, the detected purge gas concentration does not change by more than a predetermined value before and after the purge is executed; An abnormality diagnosis device for an evaporative purge system, characterized by comprising: and.