JPH05195881A - Evaporated fuel processing device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent misjudgment of abnormality diagnosis in an evaporated fuel discharge restraint system by judging whether a first control valve is abnormal or not, based on the detected pressure in a tank by a tank inner pressure detecting means, when a second control valve is in opened state. CONSTITUTION:The evaporated fuel processing device is provided with working condition detecting means 15, 16 to detect the working condition of an engine 1, and a tank inner pressure detecting means 26 to detect the inner pressure of a fuel tank 19. Further, it is provided with a pressure reducing process means 5 to control a first-a third control valves 24, 25, 33 so as to make an evaporated fuel discharge restraint system to be in a prescribed negative pressure condition, and a pressure fluctuation detecting means 5 to detect pressure fluctuation from the prescribed negative pressure condition. Furthermore, it is provided with an abnormality judging means 5 to judge whether the first control valve 24 is abnormal or not based on the inner pressure of the tank detected by the tank inner pressure detecting means 26. Thus, misjudgment of abnormality diagnosis can be avoided to the utmost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine, and more particularly to an evaporated fuel processing apparatus for an internal combustion engine which detects an abnormality of valves provided in an evaporated fuel emission restraining system.

[0002]

2. Description of the Related Art Conventionally, a fuel tank, a canister having an intake port, a first control valve interposed in a fuel vapor flow passage connecting the canister and the fuel tank, and the canister. There is widely known an evaporated fuel processing apparatus for an internal combustion engine, which is provided with an evaporated fuel emission restraining system including a second control valve interposed in a purge passage that connects an intake system of the internal combustion engine.

In this type of device, the evaporated fuel is temporarily stored in the canister, and the stored evaporated fuel is discharged (purged) to the intake system of the engine.

Further, as a method for determining an abnormality in the vaporized fuel processing apparatus, the vaporized fuel discharge inhibiting system is forcibly set to a predetermined negative pressure state, and the tank internal pressure from the time when the negative pressure state is set is elapsed. A method for determining whether or not there is an abnormality by measuring a physical change has already been proposed by the applicant of the present application (Japanese Patent Application No. 3-262857).

In this prior art, a third control valve for controlling the opening and closing of the intake port of the canister is provided near the intake port, and the third control valve is closed while the engine is operating. , The first and second control valves are opened to forcibly depressurize the fuel vapor emission restraining system to a predetermined negative pressure state, and then the second control valve is closed to place the fuel tank at an appropriate position. The pressure fluctuation of the fuel tank is measured by the tank internal pressure sensor provided in the tank, and it is judged whether the fuel vapor has leaked from the evaporated fuel discharge restraint system by the pressure fluctuation of the tank internal pressure (leak down check), The abnormality of the fuel processor is judged.

[0006]

By the way, in order to perform the abnormality diagnosis of the evaporated fuel processing device more accurately, the amount of fluctuation in the tank internal pressure from the time when the fuel tank is opened to the atmosphere is measured before depressurizing the evaporated fuel processing system. It is desirable to make an abnormality determination based on the tank internal pressure fluctuation amount and the tank internal pressure fluctuation amount at the time of the leak down check. That is, when the fuel tank is "drilled" or the like, the evaporative fuel processing system cannot be brought to a sufficiently depressurized state, and therefore an accurate abnormality diagnosis can be performed even if a leak down check is performed in such a state. I can't do it. Further, when a large amount of fuel vapor is generated in the fuel tank, the pressure fluctuation during the leak down check becomes large. That is, since a large amount of fuel vapor is generated in the fuel tank, the pressure fluctuation during the leak down check may be large, and it may be determined that the device is in an abnormal state, and accurate abnormality diagnosis cannot be performed. Therefore, as described above, it is preferable to make the abnormality determination based on the tank internal pressure fluctuation amount from the time of opening to the atmosphere and the tank internal pressure fluctuation amount at the time of leak down check.

However, in the above-described abnormality determining method, since the first control valve is closed to detect the tank internal pressure fluctuation amount, it is accurate when the first control valve is out of order. There is a problem that it is not possible to perform various abnormality diagnoses.

That is, when the first control valve is in the closed state and malfunctions, the tank internal pressure fluctuation amount of the fuel tank cannot be detected during the leak down check, so that the canister overpressures. There is a risk of becoming a state.

Further, when the first control valve is in a valve open state and malfunctions, it is not possible to detect the fluctuation amount in the tank internal pressure from the time of opening to the atmosphere, and it is not possible to perform accurate abnormality diagnosis.

The present invention has been made in view of the above problems, and detects abnormalities of valves provided in the evaporated fuel discharge restraint system promptly to prevent an overnegative pressure in the evaporated fuel discharge restraint system. At the same time, it is an object of the present invention to provide an evaporated fuel processing device for an internal combustion engine, which can avoid erroneous determination of abnormality diagnosis of the evaporated fuel emission suppression system as much as possible.

[0011]

In order to achieve the above object, the present invention provides a fuel tank, a canister having an intake port, and a fuel vapor flow passage connecting the canister and the fuel tank. Fuel processing of an internal combustion engine having an evaporative emission control system that includes a first control valve that is operated and a second control valve that is interposed in a purge passage that connects the canister and an intake system of the internal combustion engine In the device, an operating state detecting means for detecting an operating state of the engine, a third control valve for opening and closing the intake port of the canister, a tank internal pressure detecting means for detecting an internal pressure of the fuel tank, and the first To pressure reducing means for controlling the third to third control valves to bring the evaporated fuel processing system to a predetermined negative pressure state, and controlling the first to third control valves to make the evaporated fuel processing system a closed system. And the above An abnormality diagnosis processing system including a pressure fluctuation detecting means for detecting a pressure fluctuation from the negative pressure state, and the operating state detecting means detects the operating state of the engine, and the second control valve is opened. It is characterized in that it is provided with abnormality determining means for determining whether or not the first control valve is abnormal based on the tank internal pressure detected by the tank internal pressure detecting means when the state is set.

Further, according to the present invention, the abnormality determining means is configured to detect the tank internal pressure detecting means when the third control valve is set to a closed state and a valve closing signal is issued to the first control valve. When the internal pressure of the tank detected by means of a predetermined value or less is below a predetermined value, an abnormality detecting means for detecting an abnormality in the first control valve is provided, and the abnormality determining means comprises a third control means. When the tank internal pressure detected by the tank internal pressure detection means becomes equal to or higher than a predetermined value when the valve is set to the open state and the valve opening signal is issued to the first control valve, the first control is performed. It is characterized by comprising an abnormality detecting means for detecting an abnormality of the control valve.

Further, the present invention is characterized in that it has a prohibition means for prohibiting execution of the abnormality diagnosis processing by the abnormality diagnosis processing system when an abnormality of the first control valve is detected.

[0014]

According to the above construction, whether the first control valve is abnormal or not is detected based on the detected value of the tank internal pressure when the operating state of the engine is detected and the second control valve is set to the open state. To be judged.

Specifically, when the third control valve is set to the closed state and the tank internal pressure becomes equal to or lower than a predetermined value when the valve closing signal is issued to the first control valve, Alternatively, the third control valve is set in the open state and the first control valve is opened.
The abnormality of the first control valve is detected when the tank internal pressure detected by the tank internal pressure detecting means becomes equal to or higher than a predetermined value while the valve opening signal is issued to the control valve.

Further, when an abnormality of the first control valve is detected, execution of abnormality diagnosis processing by the abnormality diagnosis processing system is prohibited.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of an evaporated fuel processing apparatus for an internal combustion engine according to the present invention.

In the figure, reference numeral 1 denotes an internal combustion engine having, for example, four cylinders (hereinafter simply referred to as "engine"), a throttle body 3 is provided in the middle of an intake pipe 2 of the engine 1, and inside thereof is provided. A throttle valve 3'is provided. Further, the throttle valve 3 ′ has a throttle valve opening (θ
TH) sensor 4 is connected and outputs an electric signal according to the opening degree of the throttle valve 3 ′ and supplies it to an electronic control unit (hereinafter referred to as “ECU”) 5.

The fuel injection valve 6 is provided for each cylinder in the middle of the intake pipe 2 and slightly upstream of the intake valve (not shown) between the engine 1 and the throttle valve 3 '. Further, each fuel injection valve 6 is connected to a fuel pump 8 via a fuel supply pipe 7 and electrically connected to the ECU 5,
A signal from 5 controls the valve opening timing of fuel injection.

A negative pressure communication passage 9 and a purge pipe 10 are provided on the intake pipe 2 downstream of the throttle valve 3 ', respectively. The negative pressure communication passage 9 and the purge pipe 10 are provided with an evaporated fuel discharge inhibiting system 11 described later. It is connected to the.

Further, a branch pipe 12 is provided downstream of the purge pipe 10 of the intake pipe 2, and an absolute pressure (PBA) sensor 13 is provided at the tip of the branch pipe 12. Also,
The PBA sensor 13 is electrically connected to the ECU 5,
Absolute pressure PB in the intake pipe 2 detected by the A sensor 13
A is converted into an electric signal and supplied to the ECU 5.

An intake air temperature (TA) sensor 14 is attached to the intake pipe 2 downstream of the branch pipe 12, and the TA sensor 1
The intake air temperature TA detected by 4 is converted into an electric signal and supplied to the ECU 5.

An engine water temperature (TW) sensor 15 including a thermistor or the like is attached to the cylinder peripheral wall filled with cooling water of the cylinder block of the engine 1, and the engine cooling water temperature TW detected by the TW sensor 15 is converted into an electric signal. It is converted and supplied to the ECU 5.

An engine speed (NE) sensor 16 is provided around a cam shaft or crank shaft (not shown) of the engine 1.
Is attached.

The NE sensor 16 outputs a signal pulse (hereinafter referred to as a "TDC signal pulse") at a predetermined crank angle position every 180 degrees rotation of the crankshaft of the engine 1, and the TDC signal pulse is supplied to the ECU 5. ..

An ignition switch (IGSW) sensor 17 indicates that the engine 1 is operating.
The ON state of the SW is detected and its electric signal is supplied to the ECU 5.

However, the evaporative emission control system (hereinafter,
The "emission suppression system" 11 has a fuel tank 19 having a filler cap 18 that is opened when refueling the fuel, an activated carbon 20 as an adsorbent, and an intake port (outside air intake) 21 at the top. Provided canister 22,
A fuel vapor flow passage 23 connecting the canister 22 and the fuel tank 19, a first control valve 24 interposed in the fuel vapor flow passage 23, and a pipe of the purge pipe 10 connected to the canister 22. Purge control valve 25 installed in the passage
(Second control valve).

Further, the fuel tank 19 is connected to the fuel injection valve 6 via the fuel pump 8 and the fuel supply pipe 7, and a tank internal pressure (PT) sensor 26 is provided above the fuel injection valve 6. Further, the PT sensor 26 is electrically connected to the ECU 5, and the PT sensor 26 detects the tank internal pressure (PT) of the fuel tank 19 and supplies the electric signal to the ECU 5.

The first control valve 24 is a positive pressure valve 27.
And a negative pressure valve 28, and a first solenoid valve 30 integrally attached to the two-way valve 29. That is, the tip of the rod 30a of the first solenoid valve 30 is abutted against the diaphragm 27a of the positive pressure valve 27, and the first control valve 24 has the two-way valve 29 and the first solenoid valve 30 integrated. It will be done. The first solenoid valve 30 is electrically connected to the ECU 5, and the operating state of the first solenoid valve 30 is controlled by a signal from the ECU 5. Then, when the first solenoid valve 30 is excited (turned on), the positive pressure valve 27 of the two-way valve 29 is forcibly pushed open and the first control valve 24 is opened, while the first solenoid valve is opened. When 30 is demagnetized (off), the first control valve 24 is the two-way valve 2
The opening / closing operation is controlled by 9.

The solenoid of the purge control valve 25 is E
The purge control valve 25 is connected to the CU 5 and is controlled in response to a signal from the ECU 5 to linearly change the valve opening amount. That is, the ECU 5 outputs a desired control amount to control the valve opening amount of the purge control valve 25.

A drain shut valve 31 is provided in the negative pressure communication passage 9 connected to the intake port 21 of the canister 22, and a second solenoid valve 32 is provided downstream of the drain shut valve 31. The drain shut valve 31 and the second electromagnetic valve 32 constitute a third control valve 33.

The drain shut valve 31 is divided into an atmosphere chamber 35 and a negative pressure chamber 36 via a diaphragm 34. Further, the atmosphere chamber 35 includes a first chamber 37 having a valve element 37a therein and a second chamber 3 having an atmosphere introducing port 38a.
8 and a narrowed portion 39 connecting the second chamber 38 and the first chamber 37, and the valve body 37a is connected to the diaphragm 34 via a rod 40. In addition, the negative pressure chamber 36
Is seated with a spring 41 that is in communication with the second solenoid valve 32 and that elastically urges in the direction of arrow A.

When the solenoid of the second solenoid valve 32 is demagnetized (OFF), the atmosphere can be introduced into the negative pressure chamber 36 through the atmosphere supply port 42, and the solenoid is excited (ON). At times, it is possible to communicate with the intake pipe 2 via the negative pressure communication passage 9. Incidentally, 43 is a check valve.

Therefore, the ECU 5 shapes the input signal waveforms from the various sensors described above, corrects the voltage level to a predetermined level, and converts the analog signal value into a digital signal value. A central processing circuit (hereinafter referred to as "CPU"), storage means for storing a calculation program executed by the CPU, a calculation result, etc., the fuel injection valve 6, the first and second solenoid valves 30, 32, and a purge. And an output circuit for supplying a drive signal to the control valve 25.

Further, the ECU 5 (CPU) controls the first to third control valves 24, 25 and 33 to control the emission suppressing system 1.
The discharge suppression system 11 by controlling the decompression processing means for bringing 1 into a predetermined negative pressure state and the first to third control valves 24, 25, 33.
And a pressure fluctuation detecting means for detecting a pressure fluctuation from the predetermined negative pressure state, the pressure reducing processing means, the pressure fluctuation detecting means, the PT sensor 26, I
The GSW sensor 17, the third control valve 33, etc. constitute an abnormality diagnosis processing system.

FIG. 2 shows the respective valves when the abnormality diagnosis of the emission suppressing system 11 is made by the abnormality diagnosis processing system, that is, the first and second solenoid valves 30, 32, the drain shut valve 31, and the purge control valve 25. FIG. 6 is a diagram showing an operation pattern of No. 2 and a change state of the tank internal pressure PT at that time. This operation pattern is executed by a signal from the ECU 5 (CPU).

First, during normal operation (normal purge mode) (shown in FIG. 2), the first solenoid valve 30 is turned on, while the second solenoid valve 32 is turned off, and the IGSW is turned on. Is turned on and the operation of the engine is detected by the IGSW sensor 17, the purge control valve 25 is turned on and opened. Then, the evaporated fuel generated in the fuel tank 19 flows into the canister 22 through the fuel vapor flow passage 23, and is temporarily adsorbed and stored by the adsorbent 20 of the canister 22. As described above, during normal operation, the second electromagnetic valve 32 is off, so the drain shut valve 31 is in the open state, the outside air is supplied to the canister 22 from the atmosphere introduction port 38a, and the fuel vapor flowing into the canister 22 is supplied. Is purged into the purge pipe 10 through the second control valve 25 together with the outside air. When the fuel tank 19 is cooled due to the influence of the outside air and the negative pressure in the fuel tank 19 increases,
The negative pressure valve 28 of the two-way valve 24 opens and the canister 2
The fuel vapor stored in No. 2 is returned to the fuel tank 19.

However, when the engine 1 satisfies the predetermined abnormality diagnosis permission condition, the first and second solenoid valves 3 described above are provided.
The 0, 32 and the purge control valve 25 operate as follows to perform abnormality diagnosis of the emission suppression system 11.

First, the tank internal pressure PT is opened to the atmosphere (shown by FIG. 2). That is, the first solenoid valve 30 is maintained in the ON state to bring the fuel tank 19 and the canister 22 into communication with each other, and the second solenoid valve 32 is maintained in the OFF state to open the drain shut valve 31. Is maintained, and the purge control valve 25 is maintained in the open state (on state) to open the tank internal pressure PT to the atmosphere.

Next, the fluctuation amount of the tank internal pressure is measured (shown by FIG. 2).

That is, the second solenoid valve 32 is maintained in the off state to maintain the drain shut valve 31 in the open state and the purge control valve 25 in the open state, while the first solenoid valve 30 is maintained. Is turned off to measure the amount of fluctuation of the tank internal pressure after opening to the atmosphere and check the amount of steam generated in the fuel tank 19.

Next, the pressure of the emission control system 11 is reduced (see FIG. 2,
). That is, while switching the first solenoid valve 32 to the ON state and maintaining the purge control valve 25 in the open state,
The second electromagnetic valve 32 is turned on and the drain shut valve 31 is closed, and the suction force generated from the intake pipe 2 through the purge pipe 10 brings the discharge suppression system 11 into a predetermined negative pressure state.

Next, a leak down check is performed (shown in FIG. 2).

That is, when the discharge suppression system 11 becomes a predetermined negative pressure state, the purge control valve 25 is closed and the PT sensor 26
Check the change status of the tank pressure PT. When there is no leak from the emission suppression system 11, the change in the tank internal pressure PT hardly occurs as shown by the chain double-dashed line and the emission suppression system 1
1 is determined to be normal. On the other hand, when the fuel vapor leaks from the emission suppression system 11, the tank internal pressure approaches the atmospheric pressure as shown by the solid line. In such a case, in consideration of the fluctuation amount of the tank internal pressure measured above, it is determined whether or not the fuel vapor is leaking from the emission control system 11, that is, whether the emission control system 11 is abnormal. judge.

After the abnormality determination is completed, the process proceeds to the normal purge (shown by FIG. 2).

That is, the second solenoid valve 39 is turned off while the first solenoid valve 35 is kept on, and the purge control valve 36 is opened so that normal purging is performed.
At this time, the tank internal pressure PT is open to the atmosphere and becomes substantially equal to the atmospheric pressure.

Thus, the ECU 5 (CPU) of this embodiment
Is provided with an abnormality detecting means for detecting an abnormality in each valve such as the drain shut valve 31 (second electromagnetic valve 32), the purge control valve 25, and the first electromagnetic valve 30.

3 to 5 are flowcharts of an abnormality detection routine for detecting an abnormality in each of the valves, and this program is processed in the background.

In FIG. 3, in step S1, it is determined whether or not the PT sensor 26 is abnormal. The abnormality determination of the PT sensor 26 is determined based on the output variation amount of the previous value and the current value of the PT sensor 26, and specifically based on a PT sensor abnormality determination routine (not shown). When the answer is affirmative (YES), that is, when the PT sensor 26 is determined to be abnormal, the first solenoid valve 30 is turned off, the purge control valve 25 is closed, and the second
The solenoid valve 32 is turned off to open the drain shut valve 31 (step S2), and then the flag FMON is set to "0" to stop the abnormality diagnosis of the emission suppression system 11 (step S3). finish. That is, since the abnormality diagnosis of the emission suppression system 11 is judged based on the output value of the PT sensor 26, when the PT sensor 26 is abnormal, the abnormality diagnosis of the emission suppression system 11 is stopped.

On the other hand, when the answer to step S1 is negative (NO), it is determined whether or not the flag FMON is "1", and it is determined whether or not the abnormality of the emission suppression system 11 is being diagnosed. Here, the abnormality diagnosis includes absolute pressure in intake pipe (PBA), intake temperature (TBA).
A), engine cooling water temperature TW, various engine parameters such as engine speed NE are executed when predetermined conditions are satisfied. In other words, the flag FMON is set to "1" when the abnormality diagnosis permission routine (not shown) is executed and the various engine parameters satisfy the predetermined conditions.
An abnormality of the emission control system 11 is diagnosed. When the answer to step S4 is negative (NO), that is, when the abnormality diagnosis is not being performed, the process proceeds to step S5 and the flag FFS is set to "1".
To determine whether the valve is in the abnormality determination mode.

When the answer is negative (NO), the first solenoid valve 30 is turned on, the purge control valve 25 and the drain shut valve 31 are opened, and each valve is set to the normal purge mode. (Step S6), the flag FFS is set to "1" to set the valve abnormality determination mode, and
The timer tmDSV is reset to "0" (step S8), and this program ends.

Next, in the next loop, since the flag FFS is already set to "1" in step S7, the answer in step S5 becomes affirmative (YES), and in step S9, the tank internal pressure PT (by the PT sensor 26 is detected). It is determined whether or not (detected) is less than or equal to a predetermined value PT1. here,
The predetermined value PT1 is, for example, a value on the negative pressure side of a predetermined negative pressure state that is set to be reduced during abnormality diagnosis (for example,
-40 mmHg). When the answer is negative (NO), the program is terminated, while when the answer is affirmative (YES), it is determined whether or not the first timer tmDSV has passed a predetermined time T1 (for example, 5 sec). (Step S10). And the answer is negative (N
When the answer is affirmative (YES), it is detected that the drain shut valve 31 is in the closed state and is out of order. That is, even though the drain shut valve 31 is set to the open state in the previous loop, if the tank internal pressure PT drops to the pressure reducing side above the predetermined value in the current loop, the electrical system of the second solenoid valve 32 is set. Since the drain shut valve 31 is closed, it is determined that the drain shut valve 31 is in a closed state and malfunction occurs, and the third control valve 33
To detect abnormalities.

Thus, the drain shut valve 3
If it is determined that 1 is in the valve closed state and malfunction has occurred, the process proceeds to step S12 (FIG. 4), the flag FMON is set to "0" in order to stop the execution of the abnormality diagnosis processing in the next loop, and the purge control is performed. A valve closing signal is issued to the solenoid of the valve 25 to close the purge control valve 25. That is, when the drain shut valve 31 is in a closed state and malfunction occurs, the purge control valve 25 is closed to prevent the discharge suppression system 11 from becoming overnegative pressure.

Next, in step S14, it is determined whether or not the tank internal pressure PT has dropped to a pressure reducing side by a predetermined value (eg, 10 mmHg) or more, and if the answer is negative (NO), the second timer tmP is set to "0". To "(Step S1
5) While ending this program, if the answer in step S14 is affirmative (YES) in the subsequent loop, the process proceeds to step S16, and the second timer tmP sets the predetermined time T2.
It is determined whether (for example, 5 seconds) has elapsed. When the answer is negative (NO), the program is terminated, while when the answer is affirmative (YES), the valve of the purge control valve 25 is closed (step S13). ), The canister 22 and the intake pipe 2 of the engine 1 are not cut off, so it is determined that the exhaust control system 11 has been depressurized, the solenoid of the purge control valve 25 is short-circuited, and the purge control valve 25 operates in the open state. Detects that a defect is occurring.

On the other hand, when the answer to step S4 (FIG. 3) is affirmative (YES), the flag FFS is set to "0" to stop the abnormality determination of valves (step S18), and the leak down check is in progress ( 2) is determined (step S19). When the answer is negative (NO), the program is terminated as it is, while when the answer is affirmative (YES), the process proceeds to step S20, and the tank internal pressure PT is depressurized to a predetermined value (for example, 10 mmHg) or more. It is determined whether or not it has descended. And the answer is negative (N
If the answer is affirmative (YES), step S16 (FIG. 4) is performed while the answer is affirmative (YES).
To the second timer tmP for a predetermined time T2 (for example,
It is determined whether or not 5 seconds have elapsed, and the answer is affirmative (Y
In the case of ES), similarly to the above, it is detected that the purge control valve 25 is in the valve open state and malfunctions.

However, when the abnormality of the purge control valve 25 is detected in this way, the routine proceeds to step S21,
It is determined whether the flag FMON is "1". The answer is negative (NO), that is, S4 → S5 → S9 ... →
When an abnormality is detected in the purge control valve 25 through the flow of S14 → S16, the process proceeds to step S24, the first solenoid valve 30 is turned off, and the control of the first control valve 24 is changed to 2
The directional valve 29 is used to prevent the fuel tank 19 from becoming over negative pressure.

On the other hand, the answer in step S21 is affirmative (YE
S), that is, S4 → S18 → S19 → S20 → S16
When the abnormality of the purge control valve 25 is detected after passing through the flow of No. 3, the "ON command" signal to the purge control valve 25 is cut off, the second solenoid valve 32 is turned on, and the drain shut valve 31 is closed. After the valve is opened (step S22), the flag FM
The ON state is set to "0" to stop the abnormality diagnosis of the emission suppression system 11 (step S23), and then an OFF signal is issued to the first solenoid valve 30 to prevent the over-negative pressure of the fuel tank 19 (step S24). After that, the process proceeds to step S25,
It is determined whether or not the tank internal pressure PT has dropped to the pressure reducing side by a predetermined value (for example, 10 mmHg) or more, and the answer is negative (N
When it is O), the third timer tmWY1 is reset to "0" (step S25) and this program is terminated, while when the answer is affirmative (YES), the third timer tmWY1 is set to the predetermined time T3 (for example, 5 sec)
It is determined whether or not the time has passed (step S27). Then, when the answer is negative (NO), the program is terminated, while when the answer is affirmative (YES), it is detected that the first control valve 24 has a failure in the open state (step S28) This program ends.

That is, the answer in step S27 is affirmative (Y
ES) is the case where the tank internal pressure PT fluctuates toward the pressure reducing side despite the off signal being issued to the first solenoid valve 30. That is, when the first solenoid valve 30 is off, the control of the first control valve 24 is entrusted to the two-way valve 29. Normally, the first control valve 24 is opened. Therefore, the tank internal pressure does not fluctuate toward the pressure reducing side. Therefore, in such a case, when the tank internal pressure decreases to the pressure reducing side, the electric system of the first solenoid valve 30 is short-circuited and the first solenoid valve 30 is in the ON state, so the first control valve 24 is in the open state. And the first control valve 24
To detect abnormalities.

By executing the above abnormality detection routine in this manner, the third control valve 33 (drain shut valve 3
The abnormality detection of the first and second solenoid valves 32), the purge control valve 25, and the first control valve 24 (first solenoid valve 30) can be sequentially performed, and the discharge suppression system 11 is in the over negative pressure state. Can be avoided.

In the abnormality detection routine,
Although an example of detecting abnormalities of valves by the same software is shown, after setting the drain shut valve 31 in the closed state and the purge control valve 25 in the open state, an OFF signal is sent to the first solenoid valve 30. It is also preferable to emit the alarm to detect an abnormality of the first control valve 24. In this case, when the abnormality of the first control valve 24 is detected, the drain shut valve 31 is opened to prohibit the abnormality diagnosis processing, whereby the overnegative pressure of the canister 22 and the fuel tank 19 can be prevented. ..

FIG. 6 is a flow chart of an abnormality detection routine in the case where the first control valve 24 is in a closed state and malfunctions. This program is processed in the background. That is, the drain shut valve 31 and the purge control valve 25 are opened, an ON command is issued to the first solenoid valve (step S31), and then the tank internal pressure PT is set to a predetermined value P.
It is determined whether it is greater than 1 (step S32). Here, as the predetermined value P1, the positive pressure valve 2 of the two-way valve 29 is used.
It is set to a value lower than the set pressure of 7, for example, +5 mmHg. When the answer is negative (NO), the fourth timer tmWY2 is reset to "0" (step S
33) While ending this program, if the answer in step S32 is affirmative (YES) in the subsequent loop, it is determined whether the fourth timer has elapsed a predetermined time T4 (for example, 5 sec). Then, when the answer is affirmative (YES), it is determined that the first control valve 24 is in the closed state and malfunctions due to the disconnection of the electric system of the first solenoid valve 30, and the flag FM.
The ON state is set to "0" to prohibit the abnormality diagnosis processing of the evaporated fuel emission suppression system 11 (step S35), and the present program is terminated.

As described above, according to the present embodiment, even if the first control valve 24 fails in either the open state or the closed state, the abnormality is promptly detected to prevent damage to the emission suppression system. At the same time, it is possible to prevent erroneous determination in abnormality diagnosis.

[0064]

As described above in detail, according to the present invention, the fuel tank, the canister having the intake port, and the first fuel vapor passage connecting the canister and the fuel tank are provided. An evaporative fuel treatment apparatus for an internal combustion engine, comprising an evaporative fuel emission inhibiting system including a control valve and a second control valve interposed in a purge passage connecting the canister and an intake system of the internal combustion engine, An operating state detecting means for detecting an operating state, a third control valve for opening and closing the intake port of the canister, a tank internal pressure detecting means for detecting an internal pressure of the fuel tank, and the first to third controls. Pressure reducing means for controlling a valve to bring the evaporated fuel processing system into a predetermined negative pressure state; and controlling the first to third control valves to make the evaporated fuel processing system a closed system and the predetermined negative pressure. Pressure from pressure state An abnormality diagnosis processing system including pressure fluctuation detecting means for detecting fluctuations, and when the operating status of the engine is detected by the operating status detecting means and the second control valve is set to the open state, Since the first control valve is provided with an abnormality determining means for determining whether or not the first control valve is abnormal based on the tank internal pressure detected by the tank internal pressure detecting means, the operating state of the engine is detected and the second control valve is opened. It is determined whether the first control valve is abnormal based on the detected value of the tank internal pressure when the valve state is set.

More specifically, the abnormality determining means determines the tank internal pressure detecting means when the third control valve is set to the closed state and a valve closing signal is issued to the first control valve. The first control valve has a failure in the open state because it is provided with an abnormality detecting means for detecting an abnormality of the first control valve when the tank internal pressure detected by the above becomes less than a predetermined value. Even at this time, the abnormality of the first control valve can be detected rapidly, and the abnormality determining means sets the third control valve to the open state and opens the first control valve. When the tank signal detected by the tank internal pressure detection means has a predetermined value or more when the valve signal is issued, the first control valve is provided with an abnormality detection means for detecting an abnormality. Even when the first control valve is closed and malfunctions It can be departing quickly detect the first control valve abnormalities.

Further, when the first control valve is detected to be in an abnormal state, the first control valve has an abnormal state because it has prohibition means for prohibiting execution of the abnormality diagnosis processing by the abnormality diagnosis processing system. Even in this case, it is possible to avoid the overnegative pressure of the canister, and it is possible to prevent erroneous determination of the abnormality diagnosis of the evaporative emission control system.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an evaporated fuel processing apparatus for an internal combustion engine according to the present invention.

FIG. 2 is a diagram showing operation patterns of first and second solenoid valves, a drain shut valve, and a purge control valve.

FIG. 3 is a flowchart (1/3) showing an embodiment of the abnormality detecting means of the present invention.

FIG. 4 is a flowchart (2/3) showing an embodiment of the abnormality detecting means of the present invention.

FIG. 5 is a flowchart (3/3) showing an embodiment of the abnormality detecting means of the present invention.

FIG. 6 is a flowchart showing a second embodiment of the abnormality detecting means of the present invention.

[Explanation of symbols]

1 Internal Combustion Engine 2 Intake Pipe 5 ECU (Decompression Processing Means, Pressure Fluctuation Detection Means, Abnormality Detection Means, Inhibition Means) 10 Purge Pipe 11 Evaporative Emission Control System 19 Fuel Tank 21 Intake Port 22 Canister 23 Fuel Vapor Flow Path 24 1st Control valve 25 Purge control valve (second control valve) 26 PT sensor (tank internal pressure detection means) 33 Third control valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayoshi Yamanaka 1-4-1 Chuo, Wako, Saitama Prefecture

Claims (4)

[Claims] 1. A fuel tank, a canister having an intake port, a first control valve interposed in a fuel vapor flow passage connecting the canister and the fuel tank, the canister and an internal combustion engine. In an evaporative fuel treatment apparatus for an internal combustion engine having an evaporative fuel discharge inhibiting system including a second control valve interposed in a purge passage connecting with an intake system, an operating state detecting means for detecting an operating state of the engine; A third control valve for opening and closing the intake port of the canister,
Tank internal pressure detecting means for detecting the internal pressure of the fuel tank, decompression processing means for controlling the first to third control valves to bring the evaporated fuel processing system into a predetermined negative pressure state, and the first to third An abnormality diagnosis processing system including a pressure fluctuation detecting means for controlling a third control valve to close the evaporated fuel processing system and detecting a pressure fluctuation from the predetermined negative pressure state; Whether the first control valve is abnormal based on the tank internal pressure detected by the tank internal pressure detection means when the operating state of the engine is detected by the detection means and the second control valve is set to the open state. An evaporative fuel treatment system for an internal combustion engine, comprising: an abnormality determination means for determining whether or not. 2. The abnormality determining means is detected by the tank internal pressure detecting means when the third control valve is set to a closed state and a valve closing signal is issued to the first control valve. 2. The evaporative fuel treatment system for an internal combustion engine according to claim 1, further comprising: abnormality detection means for detecting an abnormality of the first control valve when the tank internal pressure falls below a predetermined value. 3. The abnormality determining means is detected by the tank internal pressure detecting means when the third control valve is set to an open state and a valve opening signal is issued to the first control valve. 2. The evaporated fuel processing apparatus for an internal combustion engine according to claim 1, further comprising abnormality detecting means for detecting abnormality of the first control valve when the tank internal pressure exceeds a predetermined value. 4. When the abnormality of the first control valve is detected, it has a prohibition means for prohibiting execution of the abnormality diagnosis processing by the abnormality diagnosis processing system.
An evaporated fuel processing apparatus for an internal combustion engine according to claim 3.