JPH0642414A - Failure diagnostic device of evaporative purge system - Google Patents

Abstract

PURPOSE:To specify the failure part position in an evaporative system, in the failure diagnostic device of an evaporative purge system formed in such constitution that evaporation fuel in an internal combustion engine is adsorbed by adsorbent in a canister so as to discharge adsorbed fuel toward the intake air system of the internal combustion engine under prescribed operating condition. CONSTITUTION:An inner pressure control valve 29 for controlling the pressure in a tank at a constant value and a check VSV30 for making operation of the inner pressure control valve 29 valid or invalid, are provided on a passage from a fuel tank 21 to a canister 32. A micro computer 40, stores before hand the reference pressure value for each part in an evaporative system when it has any trouble, and a failure part position is judged by comparing the pressure values of a pressure sensor 31 when the inner pressure control valve 29, the check VSV30, and the purge VSV34 are opening/closing controlled respectively, with a stored reference pressure value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosing device for an evaporative purge system, and more particularly to adsorbing evaporated fuel (vapor) of an internal combustion engine to an adsorbent in a canister, and adsorbing the adsorbed fuel to an internal combustion engine under a predetermined operating condition. The present invention relates to a failure diagnostic device for an evaporative purge system that discharges (purge) to an intake system of an engine and burns it.

[0002]

2. Description of the Related Art Fuel (vapor) evaporated in a fuel tank
In order to prevent air from being released to the atmosphere, each part is hermetically sealed, and the vapor is once adsorbed by the adsorbent in the canister, and the fuel adsorbed while the vehicle is running is sucked into the intake system and burned by evaporative purging. In an internal combustion engine equipped with a system, if the vapor passage is damaged for some reason or if the pipe is disconnected, the vapor is released to the atmosphere, and if the purge passage to the intake system is blocked,
The vapor in the canister overflows and the vapor leaks from the canister to the atmosphere. Therefore, it is necessary to diagnose whether or not such a failure of the evaporative purge system has occurred.

Therefore, as the above-mentioned failure diagnosis device, the applicant of the present invention opened and closed the first control valve for opening and closing the purge passage for purging the evaporated fuel stored in the canister to the intake system of the internal combustion engine, and the atmosphere hole of the canister. A second control valve for opening the first control valve at the time of failure diagnosis, and
After closing the control valve of, the negative pressure of the intake system is introduced into the evaporative system, the first control valve is closed until a predetermined negative pressure is reached, and the airtightness is maintained for a predetermined time. We have proposed a failure diagnosis device for an evaporative purge system that diagnoses the occurrence of a failure based on the degree of change in pressure (Japanese Patent Application No. 3-
138002).

[0004]

However, in the device proposed by the applicant of the present invention, it is possible to determine whether or not there is a leakage failure in the evaporative system from the fuel tank to the first control valve. Since it is not possible to identify where the failure is, it takes time and effort to repair after the failure is discovered.

The present invention has been made in view of the above points,
An object of the present invention is to provide a failure diagnosis device for an evaporation purge system that solves the above-mentioned problems by preparing a standard pressure value for failure diagnosis for each part of the evaporation system.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention. The present invention, as shown in FIG.
Fuel vapor from the canister 1 through the vapor passage 12
3 is adsorbed by the adsorbent in the canister 13 during a predetermined operation.
The adsorbed fuel inside the intake passage 16 of the internal combustion engine 10 is opened by opening a purge control valve 15 provided in the middle of the purge passage 14.
An apparatus for diagnosing a failure of an evaporative purge system for heparging is provided with a pressure detecting means 18, a storage means 19, and a judging means 20.

The pressure detecting means 18 detects the pressure of the evaporation system 17 from the fuel tank 11 to the purge control valve 15. Further, the storage means 19 is the evaporative system 1
The standard pressure value detected at the time of a failure is stored in advance for each of the 7 parts. Further, the determining means 20 compares the pressure value detected by the pressure detecting means 18 at the time of failure diagnosis with the stored standard pressure value of the storage means 19 to determine the failed portion.

[0008]

The standard pressure value which is compared with the pressure value detected by the pressure detecting means 18 by the judging means 20 is a pressure value (including a pressure range) which is detected when there is a failure in each part of the evaporation system 17 in advance. ) Is the stored detection value stored in the storage means 19, the failure portion of the evaporation system 17 can be specified by the comparison determination of the determination means 20.

[0009]

FIG. 2 shows a system configuration diagram of an embodiment of the present invention. In the figure, the fuel tank 21 comprises a main tank 21a and a sub tank 21b. The sub tank 21b is inside the main tank 21a, communicates with the main tank 21a, and has the fuel pump 22 arranged therein.
Further, the roll-over valve 2 is provided above the fuel tank 21.
3 is provided. The rollover valve 23 is provided to prevent fuel from flowing outside when the vehicle rolls over.

The fuel pump 22 is connected to a fuel injection valve 26 via a pipe 24 and a pressure regulator 25, respectively. The pressure regulator 25 is provided to keep the fuel pressure constant, and the fuel injector 26
The surplus fuel that is not injected in is returned to the sub tank 21b through the return pipe 27.

The upper portion of the fuel tank 21 is communicated with an internal pressure control valve 29 via a vapor passage 28a, while a check VSV (vacuum switching valve) 30 is provided.
Is in communication with. Internal pressure control valve 29 and check V
The SV 30 also communicates with a canister 32 (corresponding to the canister 13) via a vapor passage 28b.
The vapor passages 28a and 28b are respectively the vapor passage 12
Equivalent to.

The internal pressure control valve 29 is a mechanical control valve consisting of a check ball 29a and a spring 29b. The spring 29b applies a biasing force to the check ball 29a in the right direction in the figure, and the spring 29b controls the internal pressure of the fuel tank 21. It is kept below a predetermined value (for example, 250 mm Aq). The check VSV 30 is an electromagnetic valve which is opened (opened) or shut off (closed) by the microcomputer 40 as described later.

The canister 32 has an activated carbon 32a as an adsorbent therein, and an atmosphere introduction hole 32 opened to the outside.
This is a known configuration in which b is formed. Fuel tank 21
A pressure sensor 31 is provided on a path (vapor path 28a) between the internal pressure control valve 29 and the check VSV 30. The pressure sensor 31 is a kind of strain gauge that detects the strain of the silicon wafer by a bridge circuit, and constitutes the pressure detecting means 18, and includes a fuel tank 21 and an internal pressure control valve 29.
Also, the difference between the pressure in the space formed by the check VSV 30 and the atmospheric pressure is measured.

The canister 32 has a purge passage 33.
(Corresponding to the purge passage 14) and a purge vacuum switching valve (VSV) 34 which is a solenoid valve.
(Corresponding to the purge control valve 15) is communicated with a position of the intake passage 37 (corresponding to the intake passage 16) downstream of the throttle valve 36. An air cleaner (AC) 35 that filters air to remove dust is provided upstream of the throttle valve 36.

The throttle valve 36 is a valve whose opening is controlled by the amount of depression of an accelerator pedal operated by the driver.
Detected by 8. The microcomputer 40 is an electronic control device that controls the evaporative purge system, has the storage means 19, realizes the determination means 20 by software operation, and turns on the warning light 41 at the time of abnormality determination, thereby causing an abnormality to the driver. Notify the occurrence.

The microcomputer 40 has a known hardware configuration as shown in FIG. 2, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 3, a microcomputer 40 includes a central processing unit (CPU) 50, a read only memory (ROM) 51 storing a processing program, and a random access memory (RAM) 5 used as a work area.
2, Backup R that retains data even after the engine is stopped
The AM 53, an input interface circuit 54 with a multiplexer, an input / output interface circuit 55, an A / D converter 56, etc. are connected to each other via a bidirectional bus 57.

In the A / D converter 56, the pressure detection signal from the pressure sensor 31, the detection signal from the throttle position sensor 38 and the like are switched by the input interface circuit 54 and sequentially input, and the signals are analog-digital converted to the bus 57. Sequentially send to. The input / output interface circuit 55 sends the signal from the throttle position sensor 38 to the bus 57, while under the control of the CPU 50, the fuel injection valve 26, the check VSV 30, and the purge VSV.
Control signals are sent to the lamp 34 and the warning lamp 41 independently of each other to control them.

Next, the normal evaporative purge operation of the system of FIG. 2 will be described. When an ignition switch (not shown) is turned on, the fuel pump 22 shown in FIG.
The fuel in the sub-tank 21b is activated by the operation of
Is discharged to the pressure regulator 25 through the pressure regulator 25 and is sent to the fuel injection valve 26 after being made to have a constant pressure.
Is injected into the intake passage 37 from. The surplus fuel is returned to the sub tank 21b via the return pipe 27.

On the other hand, the evaporated fuel (vapor) generated in the fuel tank 21 reaches the internal pressure control valve 29 and the check VSV 30 through the vapor passage 28a. Here, the check VSV 30 is a control valve that is controlled to be opened / closed by the microcomputer 40 only at the time of failure diagnosis, which will be described later, and is normally closed (shut off) during normal times other than failure diagnosis such as evaporative purge. Therefore, at the time of the above-mentioned evaporation purging, the internal pressure of the fuel tank 21 is controlled only by the internal pressure control valve 29.

Here, when the tank internal pressure is smaller than the pressure set by the internal pressure control valve 29 (for example, 250 mm Aq), the check ball 29a is in the position shown in the figure by the spring force of the spring 29b and shuts off the vapor passage 28a. Therefore, delivery of the evaporated fuel to the canister 32 is blocked.

That is, when the engine is cold-started, the tank internal pressure is close to the atmospheric pressure, and immediately after that, the fuel volume is reduced by the fuel consumption by the fuel injection valve 26, so that the tank internal pressure once decreases to a negative pressure. However, thereafter, the fuel temperature gradually rises due to the exhaust heat, the amount of evaporated fuel generated increases, the tank internal pressure rises in the positive pressure direction, and reaches the set pressure by the internal pressure control valve 29.

When vaporized fuel is further generated and the tank internal pressure exceeds the set pressure, the check ball 29a of the internal pressure control valve 29 is pushed leftward in FIG. 2 against the spring force of the spring 29b, As a result, the evaporated fuel is sent into the canister 32 through the vapor passage 28a, the internal pressure control valve 29, and the vapor passage 28b, and the activated carbon 32 in the interior is activated.
Adsorbed by a. When the evaporated fuel is delivered to the canister 32, the tank internal pressure decreases, and when the tank internal pressure becomes equal to or lower than the set pressure, the internal pressure control valve 29 is closed again as shown in the figure.

As the operation continues, the amount of evaporated fuel increases,
When the tank internal pressure becomes equal to or higher than the set pressure again, the internal pressure control valve 29 is opened again to send the evaporated fuel to the canister 32. Thereafter, in the same manner as above, the internal pressure control valve 2 is operated under normal conditions.
9 repeatedly opens and closes the valve to keep the tank internal pressure at the set pressure.

As described above, when there is no leakage in the vapor passage 28 or the fuel tank 21, the evaporated fuel is adsorbed by the activated carbon 32a in the canister 32 through the internal pressure control valve 29 as described above. Purge VSV immediately after engine start
The valve 34 is closed because the purge control condition is not satisfied.

The above-mentioned purge control conditions are operating conditions in which the adverse effect on operability and exhaust emission can be minimized even if the air-fuel ratio becomes rough due to purging. For example, the engine cooling water temperature is above a predetermined temperature and the air-fuel ratio is set to a target value. During feedback control of fuel injection, the intake air amount is equal to or more than a predetermined value, fuel cut is not performed, etc. When all of these are satisfied, the microcomputer 40 determines that the purge control conditions are satisfied.

If it is determined that the purge control condition is satisfied, the microcomputer 40 executes the purge V
SV34 is opened. Then, due to the negative pressure in the intake passage 37, the atmosphere is introduced into the canister 32 from the atmosphere introduction port 32b, the fuel adsorbed on the activated carbon 32a is desorbed, and the air is introduced through the purge passage 33 and the purge VSV 34, respectively. Evaporated fuel is sucked in. Further, the activated carbon 32a is regenerated by the above-mentioned desorption and prepared for the next adsorption of vapor.

Next, the processing operation of the failure diagnosis of the above evaporative purge system will be described. The failure diagnosis of this embodiment is performed by the microcomputer 40 at stages 0, I, I.
It is performed by sequentially executing the respective processes of I, III, IV and V (however, depending on the failure part, the stage 0
It may end at a stage other than the equal stage V, so that not all stages are necessarily executed. ).

Each of the above stages 0, I to V is executed by the failure diagnosis routine shown in FIGS. 4 to 9, and the purge VSV3 is executed.
4 and the check VSV 30 are controlled to open / close as shown in the following table.

[0029]

[Table 1]

In the above table, however, "event" indicates that the purge VSV 34 is normally opened and closed according to the evaporative purge operation described above, and "determination timing" indicates the condition of the failure site determination timing of the stage, No determination is made unless this condition is met.

Next, the operation of each of the above stages will be described in detail. The failure diagnosis routine shown in FIGS. 4 to 9 is started in the main routine or at every predetermined cycle (for example, 64 ms). First, the failure diagnosis of stage 0 is performed by the failure diagnosis routine shown in FIG.

When the failure diagnosis routine is started, it is first judged at step 101 in FIG. 4 whether or not the judgment end flag is set to "1". Since the initial value of this determination end flag is cleared to "0" by the initial routine, when this step 101 is executed for the first time, the routine proceeds to step 102, where the tank internal pressure P is detected based on the output detection signal of the pressure sensor 31. Is read.

Subsequently, it is determined whether 10 minutes have passed after the starter was started (step 103), and if 10 minutes have not passed, first a check V is performed to determine the stage 0.
The SV30 is forcibly closed (step 104), and the step
It is determined whether the tank internal pressure P read in 102 is greater than the pressure value 50 mmAq stored in the ROM 51 in advance (step 105).

When the check VSV 30 is closed, the internal pressure of the tank is controlled only by the internal pressure control valve 29. Further, when the engine is normally started, the fuel temperature rises due to exhaust heat, and the amount of vapor generated in the fuel tank 21 gradually increases. Therefore, P> 50 mmAq. Therefore, the step
Fuel tank 2 when P> 50mmAq in 105
It is judged that there is no leakage in 1 and the tank normal flag is "1"
Is set to (step 106).

On the other hand, when it is judged in step 105 that P≤50 mmAq, it is judged whether the tank internal pressure P is larger than the pressure value -50 mmAq stored in the ROM 51 in advance (step 107). When the vehicle is in a state where the fuel temperature does not rise so much or when the amount of remaining fuel in the fuel tank 21 is small, the fuel tank 2
Even if there is no leak in 1, the tank internal pressure P does not exceed 50 mmAq, and the tank internal pressure P once falls below the negative pressure of -50 mmAq together with fuel consumption. After that, the tank internal pressure P rises in the positive pressure direction as the fuel temperature rises. Therefore, when it is determined that P ≦ −50 mmAq, the fuel tank 2
It is determined that 1 is normal, and the tank normal flag is set to "1" (step 106).

On the other hand, when it is judged at step 107 that P> -50 mmAq, the tank internal pressure is close to the atmospheric pressure within 10 minutes after the start, so it is judged that the fuel tank 21 may leak, Without setting the normal flag, the pressure value stored in the ROM 51 in advance is 300 mm Aq.
And the tank internal pressure P read in step 102 are compared in magnitude (step 108).

The above pressure value of 300 mm Aq corresponds to the internal pressure control valve 29.
The pressure value is slightly larger than the set pressure of the internal pressure control valve 29.
Is normally operating, the tank internal pressure P never exceeds the set pressure of the internal pressure control valve 29. Therefore, when P> 300 mm Aq is determined in step 108, it is determined that the internal pressure control valve 29 may have a closing failure, and the internal pressure control valve temporary abnormality flag is set to "1" (step 109), Go to step 110. When it is determined that P ≦ 300 mm Aq,
The internal pressure control valve 29 is also judged to be normal, and the routine proceeds to step 110.

At step 110, it is judged if P <-300 mm Aq. In this stage 0, the purge control by the purge VSV 34 is normally performed when the purge execution condition is satisfied, so that when the purge VSV 34 opens, the negative pressure in the intake passage 37 causes the canister 32,
Although it is introduced into the fuel tank 21 via the internal pressure control valve 29 and the like, it does not become a negative pressure (absolute value of negative pressure is large) smaller than -300 mm Aq in a normal state.

Therefore, in step 110, P ≧ −300 mm Aq
If it is determined that it is normal, this routine is terminated, and if it is determined that P <−300 mm Aq, a disconnection failure of the pressure sensor 31 or the atmosphere introduction hole 3 of the canister 32 is determined.
After it is judged that the block failure of 2b has occurred, a fail code indicating that fact is stored in the backup RAM 53 (step 111), the judgment end flag is set to "1" (step 112), and this routine is ended.

After that, when this routine is started and the judgment end flag is set to "1", the routine proceeds from step 101 to step 113, and it is judged whether or not any fail code is stored in the backup RAM 53. If the fail code is not stored, the warning light 41 is turned off (step 114), and only when the fail code is stored, the warning light 41 is turned on (step 11).
5) End this routine.

In step 112, the judgment of the completion flag is not set, and the failure diagnosis of the stage 0 is started 10 times after the start.
When it is repeatedly executed until the time elapses, then step 11 in FIG. 5 is passed through steps 101, 102 and 103 in FIG.
Proceed to 6 and the stage I failure diagnosis is started.

At step 116, it is checked whether or not the stage I end flag is set to "1". Since the initial value of the stage I end flag is "0", when this step 116 is executed for the first time, the routine proceeds to step 117, where it is checked if the tank normal flag is set. The tank normal flag is a flag which is set only in step 106 of FIG. 4, and when the tank normal flag is not set, after the tank leak temporary abnormal flag is set to "1" (step
118), and proceeds to step 119. On the other hand, when the tank normal flag is set, jumps to step 118 and proceeds to step 119.

In step 119, it is determined whether the purge VSV 34 is open for 10 seconds in the normal purge control. If it has not continued for 10 seconds, this routine is once ended. When it is determined that the purge VSV 34 is continuously opened for 10 seconds, the read tank internal pressure P is compared with the pressure value -100 mm Aq stored in the ROM 51 in advance (step 120). Assuming that the internal pressure control valve 29 is opened by the above-mentioned purge control, the tank internal pressure is controlled by the purge passage 33, the canister 32, the vapor passage 28b, and the internal pressure control when the negative pressure of the intake passage 37 is opened by the purge VSV 34. By being continuously introduced into the fuel tank 21 through the valve 29 and the vapor passage 28a for 10 seconds, a negative pressure whose absolute value is larger than the pressure value -100 mm Aq is obtained.

Therefore, in step 120, P <-100 mm Aq
If it is determined that the internal pressure control valve 29 is likely to open, the internal pressure control valve open failure temporary abnormality flag is set to "1" (step 121), and the stage I end flag is set. Is set to "1" (step 122). On the other hand, if it is determined in step 120 that P ≧ −100 mm Aq, the process proceeds to step 122, and the stage I end flag is set to “1”.
Set to.

When the stage I end flag is set, the failure diagnosis of stage II in FIG. 6 is started. In addition,
Even if the failure diagnosis routine is subsequently started by setting the stage I end flag, the routine proceeds from step 116 to step 123 in FIG. 6 and the failure diagnosis of stage I is not performed.

In the stage II failure diagnosis routine of FIG. 6, it is first determined whether or not the stage II end flag is set to "1" (step 123). Since the initial value of this stage II end flag is set to "0" by the initial routine, when this step 123 is executed for the first time, it is determined that it is not set and the routine proceeds to step 124 where the purge VSV34 In the normal purge control, it is determined whether the valve closed state continues for 5 seconds.

When the valve closed state of the purge VSV 34 does not continue for 5 seconds, it is determined that it is not the determination timing and this routine is once ended. When it is determined that the purge VSV 34 is closed for 5 seconds, step 12
Go to 5 and set the read tank internal pressure P to Stage II internal pressure P
Set to 2. Subsequently, it is determined whether or not the internal pressure control valve open failure temporary abnormality flag is set to "1" (step
126).

This internal pressure control valve open failure temporary abnormality flag is a flag that is set only in step 121 of FIG. 5. When this flag is set, the routine proceeds to step 127, where the tank internal pressure P is near atmospheric pressure. If this flag is not set, step 127 is skipped and step 128 is proceeded to.

When the purge VSV 34 is continuously closed for 5 seconds, the internal pressure control valve 29 and the check VSV 3 are checked.
If 0 is opened, the fuel tank 21 and the canister 32
The tank internal pressure P becomes a value in the vicinity of the atmospheric pressure, because the atmosphere introduction hole 32b is communicated with the atmosphere introduction hole 32b via the vapor passages 28a and 28b.

Therefore, when it is judged at step 127 that P≈0, it is checked whether the internal pressure control valve 29 has an open failure VSV3.
It can be judged that the open failure is 0. Therefore, in that case, the internal pressure control valve 2
9 or the open failure fail code of the check VSV 30 is stored in the backup RAM 53 (step 129), the judgment end flag is set to "1" (step 130), and this routine is ended.

On the other hand, when it is determined in step 127 that the tank internal pressure P is not a value near the atmospheric pressure, the process proceeds to step 128 similarly to when the internal pressure control valve open failure temporary abnormality flag is not set, and stage II ends. After setting the flag to "1", the failure diagnosis of stage III in FIG. 7 is started.
When the stage II end flag is set, the stage II fault diagnosis process is not executed in step 123 even if the fault diagnosis routine is subsequently started.

In the stage III failure diagnosis routine of FIG. 7, it is first determined whether or not the stage III end flag is set to "1" (step 131). Since the initial value of this stage III end flag is set to "0" by the initial routine, this step 13
When 1 is executed, it is determined that the purge VSV 34 is not set and the routine proceeds to step 132, where the purge VSV 34 is forcibly closed and the check VSV 30 is forcibly opened.

It is judged whether or not the purge VSV 34 is closed and the check VSV 30 is opened for 10 seconds (step 133), and when it is judged that the purge VSV 34 is opened for 10 seconds, the internal pressure control valve closing temporary abnormality flag is " It is checked whether or not it is set to 1 "(step 134). This internal pressure control valve closing temporary abnormality flag is a flag which is set only in step 109 of the failure diagnosis routine of stage 0 of FIG.
If it is determined that it is set in step 134, step 13
In step 5, it is determined whether the tank internal pressure P is a value near atmospheric pressure.

Closing the purge VSV 34 and checking VS
Assuming that the valves of V30 are normally opened, the fuel tank 21 has a vapor passage 28a and a check VSV3.
0, since it is communicated with the atmosphere introduction hole 32b of the canister 32 through the vapor passage 28b and is not communicated with the intake passage 37 through the purge passage 33, the tank internal pressure P should drop to near atmospheric pressure.

Further, when the pressure sensor 31 has a short circuit failure, the detected pressure value does not change while showing a high pressure value. If it is determined in step 134 that the failure control valve closing temporary abnormality flag is set, this is the case where the tank internal pressure P at stage 0 is a positive pressure greater than 300 mm Aq. If it is determined to be 0, purge VSV
Since the closing of valve 34 and the opening of the check VSV 30 are normally performed, it is judged that it is caused by the closing failure of the internal pressure control valve 29, and the fail code to that effect is backed up R
It is stored in the AM 53 (step 136). On the other hand, step
When it is determined in 135 that the tank internal pressure P is not a value near zero (near atmospheric pressure), it is determined that the pressure sensor 31 has a short circuit failure, and a fail code to that effect is backed up R
It is stored in the AM 53 (step 137).

When it is determined in step 134 that the internal pressure control valve closing temporary abnormality flag is not set, the tank internal pressure P is compared with a predetermined negative pressure of -100 mm Aq (step).
138). As described above, when the purge VSV 34 is normally closed, the negative pressure in the intake passage 37 is equal to the negative pressure in the fuel tank 21.
However, when the purge VSV 34 has an open failure, the negative pressure is introduced into the fuel tank 21 and the tank internal pressure P becomes a negative pressure having an absolute value larger than -100 mm Aq.

Therefore, in step 138, P <-100 mm Aq
If it is determined that the purge VSV 34 has an open failure, the purge VSV open failure fail code is stored in the backup RAM 53 (step 139). When it is determined in step 138 that P ≧ −100 mm Aq, the internal pressure control valve 29 is normal, and it can be determined that the purge VSV 34 does not have at least the open failure. Therefore, the check VSV 30 is closed. P ≒ P to judge
It is determined whether or not 2 holds (step 140).

The above P2 is stored in the RAM 5 in step 125 of FIG.
2 is the tank internal pressure of stage II, which is the tank internal pressure P2 when the purge VSV34 is closed for 5 seconds in the stage II, and the purge VSV34 is closed and the check VSV30 is opened in the stage III. When the tank internal pressure P is almost the same (P≈P2), it can be determined that the check VSV 30 has a closing failure. Therefore, if it is determined in step 140 that P≈P2, check VSV
The close failure fail code is stored in the backup RAM 53 (step 141).

When the fail code is stored in the backup RAM 53 in steps 136, 137, 139 or 141,
After the judgment end flag is set to "1" (step 14
2), open the purge VSV34 and check V
The SV 30 is closed so that normal purge control is possible (step 143), and this routine is ended.

On the other hand, when it is determined in step 140 that the tank internal pressure P of the stage III is different from the tank internal pressure P2 of the stage II, the stage III end flag is set to "1" (step 144), and the air-fuel ratio correction amount is further increased. FAF to FAF
After storing in RAM52 as III (step 145),
Open permission of purge VSV34 and check VSV3
The valve 0 is closed to enable the normal purge control (step 146), and then the failure diagnosis of the next stage IV in FIG. 8 is started.

In the stage IV failure diagnosis routine of FIG. 8, it is determined whether or not the stage IV end flag is set to "1" (step 147). This Stage IV
Since the initial value of the end flag is "0", when step 147 is first executed, the process proceeds to step 148,
It is determined whether the valve opening period of the purge VSV 34 is 10 seconds or more in total.

In this stage IV, the check VSV 30 is maintained in the forcibly closed state by the last step 143 or 146 of the stage III.
The purge VSV 34 is in a normal state in which it is opened every time the purge execution condition is satisfied. Purge VS in step 148
When the V34 valve opening period has not reached 10 seconds in total, this routine is once terminated, and when it is determined that 10 seconds have passed in total, the stage IV end flag is set to "1" (step 149), It is determined whether the tank leak temporary abnormality flag is set to "1" (step 150).

This tank leak temporary abnormality flag is a flag which is set only in step 118 in the failure diagnosis routine of the stage I of FIG. 5, and when the tank internal pressure P within 10 minutes after the start is -50 mmAq <P≤50 mmAq. Is set to. When it is determined in step 150 that the tank leak temporary abnormality flag is set, the process proceeds to a failure diagnosis routine of stage V of FIG. 9 described later, but when it is determined that the tank leak temporary abnormality flag is not set. Proceeds to step 151, where it is determined whether the value of FAFIII-FAF is greater than 3%.

Here, the air-fuel ratio correction amount FAF is separately shown in FIG.
It is calculated by the routine shown in FIG. When the FAF calculation routine shown in FIG. 11 is started, for example, every 4 ms and when a predetermined air-fuel ratio feedback condition is established, the detected voltage V of the oxygen concentration detection sensor provided in the exhaust passage of the internal combustion engine is detected. Is a predetermined comparison voltage (0.45 here)
V) is compared with the size.

When the air-fuel ratio is rich (V ≧ 0.45V), it is determined whether the state is a lean state to a rich state (step 202).
If it is a reversal to rich, the previous air-fuel ratio correction amount FAF
The value obtained by subtracting the skip constant S from the value of is set as a new air-fuel ratio adjustment amount FAF (step 203). On the other hand, the previous state is also rich, and when the rich continues, the previous FAF
The integration constant K is subtracted from the value of to obtain a new FAF value (step 204), and this routine is exited.

On the other hand, when it is judged to be lean in step 201 (V ₁ <0.45), it is judged whether or not the state is a state in which it was rich until that time and a state in which it was reversed to lean (step 205). , If it is a reversal to lean, the value obtained by adding the skip constant S to the value of the previous FAF is set as the new air-fuel ratio correction amount FAF (step 206). On the other hand, when it is determined to be lean in the previous lean state as well. Is F
The integration constant K is added to the AF value to obtain a new FAF value (step 206), and this routine is ended. here,
The skip constant S is set to a value sufficiently larger than the integration constant K.

As a result, when the output voltage of the oxygen concentration detection sensor changes as shown in FIG. 11A, the air-fuel ratio correction amount FAF is reversed from lean to rich as shown in FIG. 11B. When it is done, the fuel injection time TAU is greatly attenuated by the skip constant S to change the fuel injection time TAU to a small value, and when the air-fuel ratio is reversed from rich to lean, the fuel injection time is greatly increased by the skip constant S and fuel injection is performed. Change the time TAU to a large value. Further, when the air-fuel ratio is the same, the FAF increases to a large value when lean according to the integration constant (time constant) K as shown in FIG.
When rich, it gradually changes to a smaller value.

The air-fuel ratio correction amount FAF is multiplied by the basic fuel injection time determined by the engine speed and the intake air amount (or intake pipe pressure) together with another coefficient to determine the final fuel injection time TAU. Is controlled so that the intake air-fuel mixture has the target air-fuel ratio.

Returning to FIG. 8 again, step 15 will be described.
FAF III in 1 is the air-fuel ratio correction amount during purge VSV34 valve closing stored in RAM 53 in step 145 of the failure diagnosis routine of stage III, whereas FAF in step 151 performs normal purge control in stage IV. This is the air-fuel ratio correction amount when the air-fuel ratio is corrected. If there is no leakage, the air-fuel ratio changes to the rich side compared to stage III because the adsorption vapor in the canister 32 is sucked into the intake passage 37 by the purge control. The correction amount FAF is controlled to a small value in order to correct this change in the air-fuel ratio.

Therefore, when the difference value represented by FAFIII-FAF is larger than 3%, it is judged that the purging is normally performed, the judgment end flag is set to "1", and this routine is ended. To do. That is, when all parts of the evaporative system are normal, the determination end flag is set to "1" at step 152, and the failure diagnosis ends at stage IV.

On the other hand, when it is determined in step 151 that the difference value is 3% or more, it is determined that the purge is not normally performed, and the process proceeds to step 153 in FIG.
Start fault diagnosis of.

In the failure diagnosis routine of stage V in FIG. 9, first, the purge VSV 34 is forcibly opened and the check VSV 30 is forcibly opened (step 153). Then, it is checked whether or not each valve opening period of the purge VSV 34 and the check VSV 30 has continued for 10 seconds (step 154). If not, this routine is temporarily terminated, and if 10 seconds have passed, Read tank pressure P
And the pressure value stored in advance in the ROM 51 -100 mm A
The magnitude is compared with q (step 155).

By opening the check VSV 30 described above, the tank internal pressure control of the internal pressure control valve 29 is invalidated, the fuel tank 21 and the canister 32 are communicated, and the intake passage 37 is purged by opening the purge VSV 34. The canister 32 via the VSV 34 and the purge passage 33.
Is communicated with. Therefore, there is no leakage in the purge passage 33,
If the purge VSV 34 is normally opened, the check VSV 30 has been diagnosed as faulty in the stages II and III and is determined to be normal. Therefore, the negative pressure in the intake passage 37 is introduced into the fuel tank 21. Tank pressure P is-
Negative pressure with a larger absolute value than 100 mm Aq.

Therefore, in step 155, P <-100 mm Aq
If it is determined that the condition is normal, the determination end flag is set to "1" (step 159). On the other hand, step
When it is determined that P ≧ −100 mm Aq in 155, the tank internal pressure P has not changed to a negative pressure equal to or higher than a predetermined value, so there is a leak in the evaporation system from the purge VSV 34 to the fuel tank 21 or the purge VSV 34 is closed. It is judged that there is a failure, and it is judged whether or not the tank leak temporary abnormality flag is set to "1" (step 156).

This tank leak temporary abnormality flag is a flag that is set only in step 118 in the failure diagnosis routine of stage I of FIG. 5, and this tank leak temporary abnormality flag is set to "1" in step 156. If it is determined that the tank is out of order, a failure code is stored in the backup RAM 53 (step 15).
7).

The tank leak temporary abnormality flag is set to the above-mentioned step 15
If it is determined in step 6 that the purge passage 33 is not set, it is determined that the purge passage 33 is leaking or the purge VSV 34 is closed, and a fail code to that effect is stored in the backup RAM 53.
(Step 158).

When the processing of step 157 or 158 is completed, the determination end flag is set to "1" (step
159) After permitting the purge VSV 34 to close and forcibly closing the check VSV 30 to return to the normal purge controllable state (step 160), this routine ends.

When the judgment end flag is set to "1" in any of the stages 0, II, III, IV and V (steps 112, 130, 142, 152, 159), this failure diagnosis routine is started thereafter. From step 101 in FIG.
When the process proceeds to 113, if any fail code is stored in the backup RAM 53, the warning lamp 41 is turned on (step 115) to notify the driver of the abnormality. As a result, the failing part can be immediately identified by the fail code read from the backup RAM 53 at the time of subsequent repair.

The failure judgment according to the present embodiment described above is summarized in the following table. However, in the following table, the white triangles are temporary abnormal judgments, the black triangles are failure judgments (if there is a temporary abnormal judgment,
It does not proceed to the failure judgment unless the temporary abnormality is judged).

[0080]

[Table 2]

Next, the operation of this embodiment will be described together with the change in the tank internal pressure and the opening / closing valve operation of the purge VSV 34 and the check VSV 30. FIG. 12 (C) shows changes in the tank internal pressure when all the components that make up the evaporation purge system are normal. In this normal state, stages 0, I, I
By the failure diagnosis of I, III, and IV, the purge VSV 34 and the check VSV 30 are controlled to open and close as shown in FIGS. 12A and 12B, respectively, and the determination is completed in step 152 of stage IV, and stage V is not executed.

FIG. 13C shows changes in the tank internal pressure when the internal pressure control valve 29 has a closing failure. At this time, the purge VSV3 is detected by the failure diagnosis of the stages 0, I, II and III.
4 and the check VSV 30 are controlled to open and close as shown in FIGS. 13A and 13B, respectively, and a temporary abnormality determination is made in step 109 of stage 0, and an internal pressure control valve closing failure is determined in step 136 of stage III. Therefore, in this case Stage IV
And V are not executed.

FIG. 14C shows a change in tank internal pressure when a tank leak occurs. In this case, the purge VSV 34 and the check VSV 30 are controlled to be opened / closed by the failure diagnosis up to the stage V as shown in FIGS. 14 (A) and 14 (B). In this case, the tank internal pressure is substantially constant in the vicinity of the atmospheric pressure, and the temporary abnormality determination is performed in step 118 of stage I, and the stage V
In step 157 of the above, it is determined that the tank is out of order.

FIG. 15C shows changes in the tank internal pressure when the internal pressure control valve 29 has an open failure or the check VSV 30 has an open failure, and is used to control the opening / closing of the purge VSV 34 in stages 0 and I (FIG. 15A). In response, it changes between atmospheric pressure and -200 mm Aq. In this case, a temporary abnormality determination is made in step 121 of stage I, and a failure determination is made in step 129 of stage II. Therefore, when the internal pressure control valve 29 has an open failure or the check VSV 30 has an open failure, the purge VSV is deleted.
34 and the check VSV 30 are shown in FIG.
As shown in (B), the opening / closing control of the stages 0 to II is performed, and the stage III and subsequent stages are not executed.

FIG. 16 (C) shows changes in tank internal pressure when the purge VSV 34 has an open failure, and FIG. 17 (C) shows changes in the check VSV 30 when the check VSV 30 has a closed failure. The same change in the tank pressure is shown.
In either case, the purge VSV 34 is shown in FIG.
7 (A), the check VSV30 is shown in FIG.
As shown in 7 (B), opening and closing is controlled up to stage III,
The judgment is over in Stage III.

As shown in FIG. 16C, the tank internal pressure when the purge VSV 34 has an open failure is checked V in stage III.
When the SV30 is closed, the negative pressure changes to about -200 mm Aq.
It is determined that there is a V open failure. On the other hand, check VSV3
As shown in FIG. 17 (C), the tank internal pressure at the time of the closing failure of 0 is not negative even if the instruction to open the check VSV 30 of the stage III is issued. Therefore, the tank internal pressure is checked at step 141 of the stage III. It is judged as a failure.

FIG. 18C shows the change in the tank internal pressure when the purge passage 33 leaks or when the purge VSV 34 closes. The purge VSV 34 and the check VSV 30 are shown in FIG.
As shown in (A) and (B), opening / closing is controlled up to the stage V. The tank internal pressure is as shown in FIG.
Although the change in the tank internal pressure similar to that in the normal state shown in (C) is shown, the air-fuel ratio correction amount FAF does not show a rich change above a predetermined value in step 151 of stage IV in FIG. In step 158 of stage V in FIG. 9, it can be determined that the purge passage 33 is leaking or the purge VSV 34 is closed.

As described above, according to this embodiment, the failure of each part of the evaporative purge system can be identified from the pressure change and the air-fuel ratio change of each stage, so that the failure repair can be performed in a short time. In addition, even during failure diagnosis, stage III,
Except for V, the purge control can be performed normally.

Further, according to the present embodiment, the judgment is completed at the stage IV in the normal state, and the judgment does not proceed to the stage V where only the negative pressure is introduced into the fuel tank 21.
Even if the determination is performed up to, the negative pressure is introduced into the fuel tank 21 at the stage V after the internal pressure of the tank is set to the atmospheric pressure at the stage III. The amount of vapor sucked into the intake passage 37 is small, so that the air-fuel ratio rarely becomes rich, and the deterioration of exhaust emission can be hardly caused. Further, in stage IV, the vapor accumulated in the canister 32 in stage III is purged into the intake passage 37, so that the air-fuel ratio can be prevented from becoming significantly rich.

[0090]

As described above, according to the present invention, it is possible to specify the failure part of the evaporation system based on the pressure value of the evaporation system, so that the repair after the failure is found is significantly shorter than the conventional repair. It has the advantage that it can be done in time.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a system configuration diagram of an embodiment of the present invention.

3 is a diagram showing a hardware configuration of a microcomputer shown in FIG.

FIG. 4 is a flow chart (No. 1) showing a failure diagnosis routine (stage 0) of the embodiment of the main part of the present invention.

FIG. 5 is a flowchart (part 2) showing a failure diagnosis routine (stage I) of an embodiment of the main part of the present invention.

FIG. 6 is a flowchart (No. 3) showing a failure diagnosis routine (stage II) of the embodiment of the main part of the present invention.

FIG. 7 is a flow chart (No. 4) showing a failure diagnosis routine (stage III) of the embodiment of the main part of the present invention.

FIG. 8 is a flowchart (No. 5) showing a failure diagnosis routine (stage IV) of the embodiment of the main part of the present invention.

FIG. 9 is a flowchart (No. 6) showing the failure diagnosis routine (stage V) of the embodiment of the main part of the present invention.

FIG. 10 is a flowchart showing a FAF calculation routine.

11 is a time chart showing changes in FAF and the output of the oxygen concentration detection sensor calculated by the routine of FIG.

FIG. 12 is a diagram showing the tank internal pressure and the like when normal.

FIG. 13 is a diagram showing changes in the tank internal pressure when the internal pressure control valve is closed.

FIG. 14 is a diagram showing changes in tank internal pressure and the like when a tank leakage failure occurs.

FIG. 15 is a diagram showing changes in the tank internal pressure when the check VSV opens or the internal pressure control valve opens.

FIG. 16 is a diagram showing changes in tank internal pressure and the like when the purge VSV is open.

FIG. 17 is a diagram showing changes in tank internal pressure and the like when the check VSV is closed.

FIG. 18 is a diagram showing a change in tank internal pressure and the like when a purge passage leaks or a purge VSV close failure occurs.

[Explanation of symbols]

10 Internal Combustion Engine 11, 21 Fuel Tank 12, 28a, 28b Vapor Passage 13, 32 Canister 14, 33 Purge Passage 15 Purge Control Valve 16, 37 Intake Passage 17 Evaporative System 18 Pressure Detection Means 19 Storage Means 20 Judgment Means 29 Internal Pressure Control Valve 30 Check VSV (vacuum switching valve) 31 Pressure sensor 34 Purge VSV (vacuum switching valve) 40 Microcomputer 41 Warning light

Claims (1)

[Claims] 1. An evaporated fuel from a fuel tank is adsorbed by an adsorbent in a canister through a vapor passage, and the adsorbed fuel in the canister is opened during a predetermined operation by opening a purge control valve provided in the middle of the purge passage. In a device for diagnosing a failure of an evaporation purge system for purging an intake passage of an internal combustion engine, pressure detection means for detecting a pressure of an evaporation system from the fuel tank to the purge control valve, and each part of the evaporation system. A storage unit that stores in advance a reference pressure value detected at the time of failure, a pressure value detected by the pressure detection unit at the time of failure diagnosis, and a stored standard pressure value of the storage unit are compared to determine a failed portion. A failure diagnosis apparatus for an evaporative purge system, comprising: a determination unit.