JP2580928B2 - Failure diagnosis device for evaporation purge system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis apparatus for an evaporative purge system, and more particularly to a method for adsorbing fuel vapor (vapor) of an internal combustion engine into an adsorbent in a canister and subjecting the adsorbed fuel to internal combustion under predetermined operating conditions. The present invention relates to a device for diagnosing a failure of an evaporative purge system that discharges (purges) the fuel into 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 the air from being released to the atmosphere, each part is sealed, and the vapor is temporarily adsorbed by the adsorbent in the canister, and the fuel adsorbed while the vehicle is running is sucked into the intake system and burned. In an internal combustion engine equipped with a system, the vapor supply passage may be damaged for some reason,
If the pipe is disconnected, the vapor will be released from the canister to the atmosphere, and if the purge passage to the intake system is blocked, the vapor in the canister will overflow and the vapor will be released to the atmosphere from the canister air inlet. Will leak. Therefore, it is necessary to diagnose whether a failure has occurred in such an evaporation purge system.

Therefore, the present applicant has previously filed Japanese Patent Application No. 3-138.
No. 002, a first control valve for opening and closing a purge passage for purging evaporative fuel stored in a canister to an intake system of an internal combustion engine, and a second control valve for opening and closing an atmospheric hole of the canister, At the time of failure diagnosis, after closing the second control valve,
Failure diagnosis of an evaporative purge system in which the first control valve is closed after a predetermined negative pressure is reached, and the first control valve is kept closed for a predetermined time, and whether or not a failure has occurred is determined based on a change in pressure at that time. The device was proposed.

[0004]

However, in the apparatus proposed by the present applicant, when returning to a normal state after a failure determination, the second control valve is opened and the first control valve is opened. Alternatively, the operation is returned to the opening / closing operation by the normal evaporative purge control. At this time, when 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. For this reason, in the above case, the fuel vapor including the extra fuel vapor adsorbed from the canister flows into the intake system at once, resulting in an over-rich condition.

[0006] The present invention has been made in view of the above points,
An object of the present invention is to provide a failure diagnosis apparatus for an evaporative purge system that solves the above-mentioned problem by opening the first control valve after waiting for the opening of the second control valve.

[0007]

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

The first control valve 16 conducts or shuts off the purge passage 14. The second control valve 17 opens and closes an air 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.
5 is introduced into the system from the purge passage 14 to the fuel tank 11, and after the pressure in the system reaches a predetermined pressure value, the first
Control valve 16 is closed.

The judging means 19 is controlled by the valve control means 18
A set time after both of the second control valves 16 and 17 receive the valve closing command, and a degree of a pressure change in the system is measured,
From the measurement result, it is determined whether or not a failure has occurred in the evaporative purge system. 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 judgment by the judgment means 19 is completed.

[0010]

According to the present invention, the first and second control valves 16 and 1 are provided.
After the failure diagnosis of the evaporative purge system is performed by the determination means 19 based on the rate of change of the tank internal pressure when both valves 7 are closed, the second control valve 17 is always switched to the second control valve 17 by the holding means 20. Since the first control valve 16 is opened before the first control valve 16, first, the air introduced into the air hole of the canister 13 from the second control valve 17 fills the vaporized 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, air from which dust and dust in the air have been removed by an air cleaner 22 is supplied to an air flow meter 23.
After the intake air quantity is measured by the throttle valve 25, the flow rate is controlled by a throttle valve 25 in the intake pipe 24, and further, the internal combustion engine passes through a surge tank 26 and an intake manifold 27 (which constitutes the intake passage 15 together with the intake pipe 24). During the opening of the intake valve of the engine, 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 airflow passing through the intake manifold 27 for a time specified by the microcomputer 21.

The fuel tank 30 includes the fuel tank 11 described above.
And the fuel 31 is accommodated therein, and evaporative fuel (vapor) generated inside is sent to a canister 33 (corresponding to the canister 13) through a vapor passage 32 (corresponding to the vapor passage 12). The interior of the canister 33 is filled with an adsorbent such as activated carbon, and a part of the
Is provided.

The above-mentioned air hole 34 is connected to a canister air hole vacuum switching valve (VSV) 36 through an air passage 35. Canister air hole V
The SV 36 is a control valve that communicates or shuts off between the air inlet 36 a and the air passage 35 based on a control signal from the microcomputer 21, and constitutes the second control valve 17.

The canister 33 is connected to a purge VSV 38 via a purge passage 37. The purge side VSV 38 is a control valve that communicates or shuts off one end of the purge passage 39 having one end communicating 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
Is configured.

The pressure sensor 40 is provided in the middle of the vapor passage 32, and is provided for detecting 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 configuration, the vapor generated in the fuel tank 30 is adsorbed by the activated carbon in the canister 33 through the vapor passage 32, and is prevented from being released to the atmosphere. Normally, the canister air vent VSV36 is open, and when the evaporative purge system is activated, the purge side VSV is opened.
V38 is also open. As a result, during operation, the negative pressure of the intake manifold 27 is used to release the air inlet 36a.
, The air 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 supplied to the purge passage 37, the purge side VSV3.
8 and into the surge tank 26 through the purge passage 39 respectively. The activated carbon is regenerated by the above desorption, and prepares for the next vapor adsorption.

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, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted.
In FIG. 3, a microcomputer 21 includes a central processing unit (CPU) 50 and a read / write program storing a processing program.
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, A / D converter 56 with multiplexer, and input / output interface circuit 5
5 are connected to each other via a bus 57.

The A / D converter 56 sequentially switches and takes in 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, and the like through the input interface circuit 54. Are converted from analog to digital and transmitted to the bus 57 sequentially.

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

The microcomputer C of the microcomputer 21 having the above configuration
The PU 50 executes the processing of the flowchart described below according to the program stored in the ROM 51. FIG. 4 is a flowchart for explaining the operation of the first embodiment of the main part of the present invention, which is activated by interruption 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 set at first, and the process proceeds to the next step 102.

In step 102, it is checked whether or not a leak determination flag described later is set. Since the leak determination flag is also cleared by the initial routine, the flag is not initially set, and the process proceeds to the next step 103 at first. In step 103, the canister air vent VSV 36 is closed (closed), and in step 104, the purge side VSV is closed.
V38 is opened (valve opened).

The closing of the canister atmosphere hole VSV 36 is performed at time t ₁ as shown in FIG. 5B, and the opening of the purge side VSV 38 is substantially the same time t as shown in FIG. 5A. ₁ , the negative pressure to the engine combustion chamber is reduced by the purge passage 39 and the purge side VSV shown in FIG.
38, purge passage 37, canister 33, vapor passage 3
2 to the fuel tank 30. Thus, the internal pressure of the fuel tank 30 (tank pressure), as shown in FIG. 5 (C), rapidly rises (negative pressure decreases) the time t ₁ after the negative direction.

Subsequently, at step 105 in FIG. 4, it is determined whether or not the tank internal pressure is lower than XPa based on the detection signal of the pressure sensor 40. When the pressure is lower than XPa, the negative pressure is being set, so this routine is terminated. Until the tank internal pressure becomes larger than XPa on the negative pressure side, the above step 101 is performed every 65 ms.
To 105 are repeatedly executed. And the tank pressure is XP
If it is determined in step 105 that the pressure has become larger on the negative pressure side than a, the purge side VSV 38 is set at time t as shown in FIG.
_The interruption is performed in step 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 purge side VSV 38 to the fuel tank 30 is maintained when there is no failure in the system, and is extremely gentle. It decreases to the atmospheric pressure side.

Thereafter, it is determined whether or not the leak determination timer is "0" (step 107). Since the leak determination timer has been cleared to "0" by the above-mentioned initial routine, initially when the determination in step 107 is made, it is determined to be "0" and the routine proceeds to step 108, where the current pressure stores the detected value of the sensor 40 to the RAM52 as a diagnostic starting pressure value P _S.

Subsequently, the value of the leak determination timer is added by a predetermined value (step 109), and the leak determination flag is set to "1" (step 110), and this routine is terminated. Then, when this routine is started again, the step
Since the leak determination flag is set to "1" at 102, it is determined that the leak determination is being performed.
Jump 5 and go through step 106
Up to 107.

Since it is determined in step 107 that the leak determination timer is not "0", it is determined whether the value of the leak determination timer is equal to the diagnosis time (leak determination time) α (step 107). 111) If the time has not reached α, this routine is terminated via steps 109 and 110.

In this way, steps 101, 102, 10
6, 111, 109 and 110 are repeated every 65 ms,
The value of the leak determination timer becomes a value corresponding to the leak determination time α.
Then, the detection value of the pressure sensor 40 at that time is determined as the diagnosis end pressure.
Force value P_E(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 determined whether or not the calculated rate of change is equal to or greater than a predetermined threshold value β (step 115). To turn on the warning lamp 41 (step 11).
5) After notifying the driver of the occurrence of a failure in the evaporative purge system, a leakage failure fail code is stored in, for example, a backup R
It is stored in the AM 53 (step 116), and the process proceeds to step 117. The leak failure code is read out from the backup RAM 53 at the time of subsequent repair to notify the cause of the failure of the evaporative purge system.

On the other hand, when the calculated change rate is determined to be less than β, it is determined that the leakage is normal because the leakage is equal to or less than the specified value, and the routine jumps to steps 117 and 116 and proceeds to step 117. The processing of steps 107 to 116 described above corresponds to the determination means 19.

In step 117, the canister air hole VSV
36 is opened (valve open). This canister vent
The VSV 36 valve opening time is t_ThreeIs the time
t_ThreeFrom the air inlet 36a, canister air hole V
SV36, 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._ThreeOr
T after a short time _FourTo reach atmospheric pressure.

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

As described above, according to the present 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
8, 119 realize the holding means 20.

For this reason, since the fuel tank 30 has a negative pressure during the period from the time t ₃ to the time t ₄ , the air introduced from the air system inlet 36 a through the canister air hole VSV 36 is supplied to the air passage 35, the air hole 34, and the canister. The fuel flows into the fuel tank 30 through the fuel passage 33 and the vapor passage 32, and the canister 3
Although not all of the vapor adsorbed by 3 and vapor in the system are back-purged into the fuel tank 30.

Thus, after the time t ₄ , when the purge side VSV 38 is opened based on the control of the normal evaporative purge system, the purge amount of the vapor to the surge tank 26 is smaller than that of the proposed device of the present applicant. Since it is small, the air-fuel ratio is prevented from becoming over-rich.

The present invention is not limited to the above-described embodiment. For example, the purge position of the fuel vapor may be near the slot valve 25.

[0039]

As described above, according to the present invention, the tank with both the first control valve for conducting or blocking the purge passage and the second control valve for opening and closing the air hole of the canister closed. After performing the failure diagnosis by measuring the change in the internal pressure, the second
The first control valve is opened after the first control valve is opened, so that the first and second control valves are opened simultaneously or the second control valve is opened later. It has features such as being able to prevent over-rich of the air-fuel ratio.

[Brief description of the 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 a microcomputer in FIG. 2;

FIG. 4 is a flowchart showing one embodiment of a failure diagnosis routine of a main part of the present invention.

FIG. 5 is a time chart for explaining the operation of each unit in FIG. 4;

[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 Purge side vacuum switching valve (V
SV) 40 Pressure sensor

Claims (1)

(57) [Claims] 1. A failure of an evaporative purge system for adsorbing fuel vapor from a fuel tank to an adsorbent in a canister through a vapor passage and purging the adsorbed fuel in the canister to a suction passage of an internal combustion engine through a purge passage during a predetermined operation. A first control valve that opens or closes the purge passage; a second control valve that opens and closes an air vent of the canister; and a second control valve that closes the second control valve. Opening the first control valve to introduce the pressure of the intake passage into the system from the purge passage to the fuel tank, and closing the first control valve when the pressure in the system reaches a predetermined value; A valve control unit that measures the degree of change in pressure in the system for a set time after both the first and second control valves receive a valve closing command by the valve control unit. Determining means for determining the presence or absence of a failure in the system; 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. And a failure diagnosis device for an evaporation purge system.