JPH05180100A - Trouble diagnostic device for evaporator purge system - Google Patents

Abstract

PURPOSE:To prevent overrichness of air-fuel ratio at purge time after ending a trouble diagnosis, relating to a trouble diagnostic device for an evaporator purge system in which vaporized fuel (vapor) of an internal combustion engine is adsorbed to an adsorbent in a canister to release (purge) the adsorbed fuel, to an intake system of the internal combustion engine under a predetermined operational condition, to be burned. CONSTITUTION:When a vacuum switching valve(VSV) of a canister atmospheric hole and a purge side VSV are respectively shut off (valve closing), (step 103, 106), a change rate is calculated, from this time tank internal pressure PS and a tank internal pressure PE after alpha second, and compared with a threshold value beta, so that a trouble is diagnosed. (step 107 to 116) Thereafter, the canister atmospheric hole VSV is opened (step 117), and opening of the purge side VSV is inhibited till the tank internal pressure becomes the atmospheric pressure or positive pressure, to hold a shutoff condition (step 118, 119). In this way, vaporized fuel in a canister is purged back to a fuel tank.

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 device for diagnosing a failure of an evaporative purge system that discharges (purge) to an adsorption system of an engine and burns it.

[0002]

2. Description of the Related Art Fuel evaporated in a fuel tank (vapor)
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, the vapor supply passage is damaged for some reason,
If the pipe is disconnected, vapor is released from the canister to the atmosphere, and if the purge passage to the intake system is blocked, the vapor in the canister overflows and vapor is released from the canister atmosphere inlet to the atmosphere. It will leak. Therefore, it is necessary to diagnose whether such a failure of the evaporative purge system has occurred.

Therefore, the present applicant previously filed Japanese Patent Application No. 3-138.
No. 002 has a first control valve that opens and closes a purge passage that purges the evaporated fuel stored in the canister into the intake system of the internal combustion engine, and a second control valve that opens and closes an atmospheric hole of the canister. After closing the second control valve during failure diagnosis,
Failure diagnosis of the evaporative purge system that waits until a predetermined negative pressure is reached, closes the first control valve, maintains the airtightness for a predetermined time, and judges the occurrence of a failure based on the degree of change in pressure at that time. Proposed a device.

[0004]

In the device proposed by the applicant of the present invention, however, the second control valve is opened and the first control valve is opened when returning to the normal state after the failure determination. Or return to the opening / closing operation by normal evaporation purge control. At this time, if the second control valve is opened simultaneously with or after the opening of the first control valve, the evaporated fuel adsorbed by the canister flows into the intake system.

Here, the evaporated fuel adsorbed in the canister is generated and adsorbed more than usual because a negative pressure is applied to the fuel tank at the time of failure determination. Therefore, in the above case, the vaporized fuel including the extraly adsorbed vaporized fuel from the canister flows into the intake system all at once, resulting in overrich.

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 evaporative purge system that solves the above-mentioned problems by waiting for the opening of the second control valve and opening the first control valve.

[0007]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, the failure diagnosis apparatus of the present invention causes the evaporated fuel from the fuel tank 11 to be adsorbed by the adsorbent in the canister 13 through the vapor passage 12 and the adsorbed fuel in the canister 13 through the purge passage 14 during a predetermined operation. In the failure diagnosis device for purging the intake passage 15 of 10, the first control valve 16, the second control valve 17, the valve control means 18, the determination means 19 and the holding means 20 are provided.

The first control valve 16 connects or disconnects the purge passage 14. The second control valve 17 opens and closes the atmosphere hole of the canister 13. The valve control means 18 closes the second control valve 17 and opens the first control valve 16 to open the intake passage 1
After the pressure of 5 is introduced into the system from the purge passage 14 to the fuel tank 11, after the pressure in the system reaches a predetermined pressure value, the first
The control valve 16 is closed.

The determination means 19 is controlled by the valve control means 18
And the second control valves 16 and 17 both measure the degree of change in pressure in the system for a set time after receiving a closing command.
Whether or not the evaporative purge system has a failure is determined from the measurement result. The holding means 20 holds the closed state of the first control valve 16 at least until the second control valve 17 is opened after the determination by the determination means 19 is completed.

[0010]

In the present invention, the first and second control valves 16 and 1 are
After the determination means 19 performs the failure diagnosis of the evaporative purge system based on the rate of change of the tank internal pressure when both 7 are closed, the holding means 20 always causes the second control valve 17 to be the second. Since the first control valve 16 is opened before the first control valve 16, the atmosphere introduced from the second control valve 17 to the atmospheric hole of the canister 13 is filled with the evaporated fuel adsorbed in the canister 13 in a large amount and the system. The evaporated fuel is back purged into the fuel tank 11, and then the first control valve 16 is opened for the first time.

[0011]

FIG. 2 shows a system configuration diagram of an embodiment of the present invention. In the figure, the air from which the air cleaner 22 has removed dust, dust and the like in the atmosphere is measured by an air flow meter 23.
After the intake air amount is measured by the internal combustion engine, the flow rate is controlled by the throttle valve 25 in the intake pipe 24, and the internal combustion is passed through the surge tank 26 and the intake manifold 27 (which constitutes the intake passage 15 together with the intake pipe 24). During the period when the intake valve of the engine is open, it flows into the combustion chamber (neither is shown).

The opening of the throttle valve 25 is controlled in conjunction with an accelerator pedal (not shown), and the opening is detected by a throttle position sensor 28. Further, a fuel injection valve 29 is provided for each cylinder so that a part thereof projects into the intake manifold 27. The fuel injection valve 29 injects the fuel 31 in the fuel tank 30 into the air flow passing through the intake manifold 27 for a time designated by the microcomputer 21.

The fuel tank 30 is the fuel tank 11 described above.
The fuel 31 is accommodated and the evaporated fuel (vapor) generated inside is delivered to the canister 33 (corresponding to the canister 13) through the vapor passage 32 (corresponding to the vapor passage 12). The canister 33 is filled with an adsorbent such as activated carbon, and a part of the canister 33 has an air hole 34.
Is provided.

The atmosphere hole 34 is connected to a canister atmosphere hole vacuum switching valve (VSV) 36 through an atmosphere passage 35. Canister vent V
The SV 36 is a control valve that connects or disconnects the atmosphere introducing hole 36 a and the atmosphere passage 35 based on a control signal from the microcomputer 21, and constitutes the second control valve 17.

The canister 33 is in communication with the purge side VSV 38 via a purge passage 37. The purge-side VSV 38 is a control valve that connects or shuts off the other end of the purge passage 39, one end of which communicates with the surge tank 26, and the other end of the purge passage 37, based on a control signal from the microcomputer 21. First control valve 16
Make up.

The pressure sensor 40 is provided in the middle of the vapor passage 32, and is provided to detect the pressure in the vapor passage 32 to substantially detect the internal pressure of the fuel tank 30. The warning lamp 41 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

In such a structure, the vapor generated in the fuel tank 30 is adsorbed by the activated carbon in the canister 33 through the vapor passage 32 and prevented from being released into the atmosphere. Normally, the canister atmosphere hole VSV36 is opened, and when the evaporative purge system is operating, the purge side VS
V38 is also open. As a result, the negative pressure of the intake manifold 27 is used during operation, and the air inlet 36a
The atmosphere is introduced into the canister 33 through the canister atmosphere hole VSV 36, the atmosphere passage 35, and the atmosphere hole 34.

Then, the fuel adsorbed on the activated carbon is desorbed, and the fuel is purged by the purge passage 37 and the purge side VSV3.
8 and the purge passage 39, respectively, to be sucked into the surge tank 26. In addition, the activated carbon is regenerated by the above desorption and prepared for the next adsorption of vapor.

The microcomputer 21 is a control device for realizing the above-mentioned valve control means 18, determination means 19 and holding means 20 by software processing, and 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, the microcomputer 21 includes a central processing unit (CPU) 50, a read
Only memory (ROM) 51, random access memory (RAM) 52 used as a work area, backup RAM 5 that retains data even after the engine is stopped
3, input interface circuit 54, multiplexer-equipped A / D converter 56, and input / output interface circuit 5
5 and the like, which are connected to each other via a bus 57.

The A / D converter 56 sequentially fetches the intake air amount detection signal from the air flow meter 23, the detection signal from the throttle position sensor 28, the pressure detection signal from the pressure sensor 40, etc. through the input interface circuit 54 and fetches it. Are converted from analog to digital and are sequentially transmitted to the bus 57.

The input / output interface circuit 55 receives the detection signal from the throttle position sensor 28 and inputs it to the CPU 50 via the bus 57, while the signals input from the bus 57 are supplied to the fuel injection valve 29 and the canister. The porosity VSV 36, the purge side VSV 38, and the warning lamp 41 are selectively sent to control them.

C of the microcomputer 21 having the above structure
The PU 50 executes the processing of the flowchart described below according to the program stored in the ROM 51. FIG. 4 is a flow chart for explaining the operation of the first embodiment of the essential part of the present invention, which is interrupt-activated every 65 ms, for example. In the figure, first, it is checked whether the execution flag is set (the value is "1") (step 101). Since the execution flag has been cleared (the value is "0") by the initial routine at the time of starting the engine, it is not initially set, so the routine proceeds to the next step 102.

In step 102, it is checked whether a leak determination flag, which will be described later, is set. Since the leak determination flag is also cleared by the initial routine, it is not initially set, and the process proceeds to the next step 103 first. In step 103, the canister atmosphere hole VSV36 is shut off (closed), and in the subsequent step 104, the purge side VS is closed.
V38 is opened (valve opened).

The closing of the canister atmospheric hole VSV36 is performed at time t ₁ as shown in FIG. 5 (B), the valve opening of the purge side VSV38 is as shown in FIG. 5 (A) substantially identical time t _If it is performed at ₁ , the negative pressure to the engine combustion chamber is the purge passage 39, the purge side VSV shown in FIG.
38, purge passage 37, canister 33, vapor passage 3
2 to the fuel tank 30. As a result, the internal pressure of the fuel tank 30 (tank internal pressure) rapidly increases in the negative direction after time t ₁ (the negative pressure decreases), as shown in FIG. 5C.

Subsequently, in step 105 of FIG. 4, it is determined whether the tank internal pressure is XPa or less based on the detection signal of the pressure sensor 40. When it is XPa or less, the negative pressure is being set, and this routine is finished. The above step 101 is repeated every 65 ms until the tank internal pressure becomes larger than XPa on the negative pressure side.
~ 105 is executed repeatedly. And the tank pressure is XP
When it is determined in step 105 that the pressure has increased to the negative pressure side from a, the purge side VSV 38 is set to the time t as shown in FIG.
Block at ₂ (step 106). Step 103 above
The valve control means 18 is realized by 106.

Since the two VSVs 36 and 38 are both closed at the time t ₂ , the pressure in the system from the VSV 38 on the purge side to the fuel tank 30 is maintained if there is no failure in the system, and becomes extremely gentle. It decreases to the atmospheric pressure side.

Thereafter, it is judged whether or not the leak judgment timer is "0" (step 107). Since the leak determination timer is cleared to "0" by the initial routine described above, when the determination at step 107 is initially made, it is determined as "0" and the routine proceeds to step 108 where the current pressure is determined. The detection value of the sensor 40 is stored in the RAM 52 as the diagnosis start pressure value P _S.

Subsequently, the value of the leak determination timer is added by a predetermined value (step 109), the leak determination flag is set to "1" (step 110), and this routine is ended. The next time this routine is started again, the step
Since the leakage determination flag is set to "1" at 102, it is determined that the leakage determination is in progress, and therefore steps 103 to 10
Jump 5 and step through step 106
Reach 107.

This time, it is determined in step 107 that the leak determination timer is not "0", so it is determined whether the value of the leak determination timer is equal to the diagnostic time (leak determination time) α (step 111), and when time α has not yet come, this routine is ended via steps 109 and 110.

In this way, steps 101, 102, 10
The processing of 6, 111, 109 and 110 is repeated every 65ms,
The value of the leak determination timer becomes the value corresponding to the leak determination time α.
Then, the detection value of the pressure sensor 40 at that time is set as the diagnostic end pressure.
Force value P_EIs stored in the RAM 52 as (step 112).
 ). Then, the pressure value P read from the RAM 52_S，
P _EBased on (P_E-P_S) / Α (seconds)
The rate of change in pressure is calculated (step 114).

Subsequently, it is judged whether or not the calculated change rate is equal to or more than a predetermined threshold value β (step 115). Then, turn on the warning lamp 41 (step 11
5) After notifying the driver of the failure of the evaporative purge system, the leak failure fail code is backed up, for example.
It is stored in the AM 53 (step 116) and the process proceeds to step 117. The leakage failure fail code is read out from the backup RAM 53 at the time of subsequent repair and informs the cause of failure of the evaporative purge system.

On the other hand, when it is determined that the calculated change rate is less than β, it is determined that the leakage is normal because the leakage is less than the specified value, and steps 115 and 116 are jumped to proceed to step 117. The processing of steps 107 to 116 described above corresponds to the determination means 19.

In step 117, the canister atmospheric hole VSV
36 is opened (valve open). This canister vent
Set the valve opening time of VSV36 to t₃And the time
t₃From the atmosphere is the atmosphere inlet 36a, the canister atmosphere hole V
SV 36, atmosphere passage 35, atmosphere hole 34, canister 3
3, introduced into the fuel tank 30 through the vapor passage 32
Therefore, as shown in FIG. 5C, the tank internal pressure is at time t.₃Or
Time t after a short time from _FourReaches atmospheric pressure.

In step 118 following step 117, it is checked whether the tank internal pressure has changed to the atmospheric pressure or the positive pressure side. When the tank internal pressure is not atmospheric pressure or positive pressure, opening of the purge-side VSV 38 is prohibited (step 119).
), Exit this routine. After that, this routine is activated several times, and when it is determined in step 118 that the tank internal pressure is atmospheric pressure or positive pressure, the determination timer is cleared (step 120), the execution flag is set (step 121), And clearing the leak determination flag (step 12
After 2) is sequentially performed, this failure diagnosis process is ended. After that, even if this routine is started, step 10
Since the execution flag is judged to be "1" at 1, this routine is not executed.

As described above, according to this embodiment, the time t ₃
Even canister large pores VSV36 is opened in, until the time t ₄ the tank internal pressure reaches atmospheric pressure or positive pressure valve closing state of the purge side VSV38 is inhibited is maintained (opened by steps 118 and 119 ). That is, step 11
Reference numerals 8 and 119 realize the holding means 20.

Therefore, since the fuel tank 30 has a negative pressure during the period from time t _{3 to} t ₄ , the atmosphere introduced from the atmosphere system inlet 36a through the canister atmosphere hole VSV 36 is the atmosphere passage 35, the atmosphere hole 34, the canister. 33 to the fuel tank 30 through the vapor passage 32 and the canister 3
Although not all of the vapor adsorbed by 3 and the vapor in the system, they are back-purged in the fuel tank 30.

As a result, after the time t ₄ , when the purge side VSV 38 is opened under the control of the normal evaporative purge system, the purge amount of vapor into the surge tank 26 is smaller than that of the apparatus proposed by the applicant. Since the amount is small, the air-fuel ratio is prevented from becoming overrich.

The present invention is not limited to the above embodiment, and the evaporated fuel may be purged near the slot valve 25, for example.

[0039]

As described above, according to the present invention, the tank is closed with both the first control valve for opening and closing the purge passage and the second control valve for opening and closing the atmospheric hole of the canister. After measuring the change in internal pressure and performing failure diagnosis,
Since the first control valve is opened after the first control valve is opened, it occurs when the first and second control valves are opened simultaneously or the second control valve is opened later. It has features such as prevention of air-fuel ratio overrich.

[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.

FIG. 3 is a configuration diagram of an example of hardware of the microcomputer in FIG.

FIG. 4 is a flow chart showing an embodiment of a failure diagnosis routine of essential parts of the present invention.

5 is a time chart explaining the operation of each part of FIG. 4. FIG.

[Explanation of symbols]

11, 30 Fuel tank 12, 32 Vapor passage 13, 33 Canister 14, 37, 39 Purge passage 15 Intake passage 16 First control valve 17 Second control valve 18 Valve control means 19 Judging means 20 Holding means 21 Microcomputer 36 Canister Air vent Vacuum switching valve (VSV) 38 Vacuum switching valve on purge side (V
SV) 40 pressure sensor

Claims (1)

[Claims] 1. A failure of an evaporation purge system for adsorbing evaporated fuel from a fuel tank to an adsorbent in a canister through a vapor passage and purging the adsorbed fuel in the canister through a purge passage into an intake passage of an internal combustion engine during a predetermined operation. In the device for diagnosing, the first control valve that connects or disconnects the purge passage, the second control valve that opens and closes the atmospheric hole of the canister, and the second control valve that is closed and No. 1 control valve is opened to introduce the pressure of the intake passage into the system from the purge passage to the fuel tank, and the first control valve is closed when the pressure in the system reaches a predetermined value. Valve control means and the first and second control valves are both closed by the valve control means, and the degree of change in the pressure in the system is measured for a set time, and the evaporation rate is measured from the measurement result. Determining means for determining whether or not there is a failure in the system, and holding means for holding the closed state of the first control valve at least until the second control valve is opened after the determination by the determining means is completed. A failure diagnostic device for an evaporative purge system, comprising: