JPH11210568A - Abnormality diagnosis device for evaporative gas purge system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To accurately diagnose an abnormality in an evaporative gas purge system. SOLUTION: Before performing an abnormality diagnosis of an evaporative gas purge system, a canister closing valve is fully closed, a purge control valve is opened, an intake pipe negative pressure is introduced into the evaporative gas purge system, and a fuel tank internal pressure PT is set to a predetermined value. Is reduced to the negative pressure (e.g., -5 mmHg), the evaporative gas in the fuel tank 17 is released, and the partial pressure of the evaporative gas component in the fuel tank 17 is sufficiently reduced with respect to the saturated vapor pressure. Thereafter, the canister closing valve is fully opened to return the fuel tank pressure PT to the atmospheric pressure, the evaporative gas purge system is closed, and the pressure change ΔP1 from the atmospheric pressure is detected. Thereafter, an intake pipe negative pressure is introduced into the evaporative gas purge system to reduce the fuel tank internal pressure PT to a predetermined negative pressure (for example, -15 mmHg), and a pressure change ΔP2 from the negative pressure is detected. The two pressure changes .DELTA.P1 and .DELTA.P2 are compared to determine whether there is a leak in the evaporative gas purge system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention diagnoses whether there is an abnormality in an evaporative gas purge system for purging (ejecting) evaporative gas (fuel evaporative gas) generated by evaporating fuel in a fuel tank into an intake pipe of an internal combustion engine. The present invention relates to an abnormality diagnosis device for an evaporative gas purge system.

[0002]

2. Description of the Related Art Conventionally, in an evaporative gas purge system, in order to prevent evaporative gas generated in a fuel tank from leaking into the atmosphere, the evaporative gas is adsorbed into a canister through an evaporative gas passage in the fuel tank. A purge control valve is provided in the middle of a purge passage for purging evaporative gas adsorbed to the intake pipe of the internal combustion engine, and the opening and closing of the purge control valve is controlled according to the operation state of the internal combustion engine, so that the canister can be connected to the intake pipe. The purge flow rate of the evaporative gas to be purged is controlled. It is necessary to detect the evaporative gas leakage early so as to prevent the evaporative gas purge system from leaking into the atmosphere abnormally for a long time.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 5-125997, a pressure sensor for detecting a pressure in an evaporative gas purge system from a fuel tank to a purge control valve is provided.
After detecting the pressure change amount ΔP1 from the atmospheric pressure in the evaporative gas purge system in a state where the atmospheric pressure is introduced into the evaporative gas purge system and the evaporative gas purge system is closed, the purge control valve is temporarily opened and the evaporative gas purge system is opened. With a negative pressure introduced into the gas purge system and the evaporative gas purge system sealed, a pressure change ΔP2 from the negative pressure of the evaporative gas purge system is detected, and these two pressure changes ΔP1 and ΔP2 are compared. There is an apparatus for diagnosing leakage of an evaporative gas purge system.

[0004]

Since the pressure change when the evaporative gas purge system is normal is caused by the evaporation of the fuel, the pressure change amount decreases as the amount of evaporation of the fuel (the amount of evaporative gas generated) decreases. Become smaller. Since the evaporation of the fuel occurs because the partial pressure of the evaporative gas component is lower than the saturated vapor pressure, the smaller the differential pressure between the partial pressure of the evaporative gas component and the saturated vapor pressure, the smaller the amount of fuel evaporation and the pressure. When the amount of change becomes small and the partial pressure of the evaporative gas component rises to the saturated vapor pressure, no more fuel evaporates and the pressure of the evaporative gas purge system does not change any more.

[0005] Since the partial pressure of the evaporative gas component at the start of the pressure change measurement changes under the influence of the state of the fuel system such as the fuel temperature, the measured value of the pressure change varies depending on the state of the fuel system at the start of the measurement. Resulting in. As a result, the abnormality diagnosis performed based on the pressure change amount is affected by the state of the fuel system, and this causes the accuracy of the abnormality diagnosis to decrease.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and accordingly, has as its object to provide an evaporative gas purge system capable of accurately performing an abnormality diagnosis of an evaporative gas purge system without being affected by the state of the fuel system. An object of the present invention is to provide an abnormality diagnosis device for a gas purge system.

[0007]

According to a first aspect of the present invention, there is provided an apparatus for diagnosing an abnormality in an evaporative gas purge system, comprising the steps of: Next, an operation of discharging the evaporative gas from the fuel tank to reduce the evaporative gas concentration (hereinafter referred to as “evaporative gas concentration reducing operation”) is performed. With this configuration, the differential pressure between the partial pressure of the evaporative gas component in the evaporative gas purge system and the saturated vapor pressure can be sufficiently increased before the pressure change measurement, and the evaporative pressure is not affected by the state of the fuel system. An abnormality diagnosis of the gas purge system can be accurately performed.

In this case, the measurement of the pressure change of the evaporative gas purge system includes both the measurement of the pressure change from the state where the atmospheric pressure is introduced into the evaporative gas purge system and the measurement of the pressure change from the state where the predetermined pressure is introduced. May be performed, or only one of them may be performed.However, the measurement of the pressure change from the atmospheric pressure is compared with the measurement of the pressure change from the predetermined pressure, and the partial pressure of the evaporative gas component at the start of the measurement is measured. And the saturated vapor pressure is small, so that it is easily affected by the state of the fuel system.

Therefore, when performing the evaporative gas concentration reduction operation, the pressure in the evaporative gas purge system is changed to a predetermined pressure to release the evaporative gas in the fuel tank, and then the pressure is returned to near atmospheric pressure. In this case, a change in pressure from the atmospheric pressure may be measured. With this configuration, a change in pressure from the atmospheric pressure can be accurately measured without being affected by the state of the fuel system.

When both the pressure change from the atmospheric pressure and the pressure change from the negative pressure are measured, either of them may be performed first, but the measurement of the pressure change from the negative pressure is performed first. In this case, the pressure change from the atmospheric pressure may be measured after the evaporative gas concentration reduction operation is performed after a predetermined time has elapsed since the measurement of the pressure change from the negative pressure. . In other words, when the pressure change from the negative pressure is measured and then returned to near atmospheric pressure, the evaporative gas component in the evaporative gas purge system rapidly becomes saturated, and the state in the evaporative gas purge system becomes unstable for a while. Therefore, an evaporative gas concentration reduction operation is performed after a predetermined period of time elapses until the state in the evaporative gas purge system is stabilized, so that the evaporative gas concentration in the fuel tank is reliably reduced before the pressure change measurement. Things.

When the pressure in the evaporative gas purge system is returned to near atmospheric pressure at the end of the evaporative gas concentration reduction operation,
According to the fourth aspect, the canister closing means is opened and the purge control valve is closed, or as in the fifth aspect, both the canister closing means and the purge control valve are opened. good. In any case, the atmospheric pressure can be introduced into the evaporative gas purge system by opening the canister closing means. At this time, in claim 4, by closing the purge control valve at the time of introducing the atmospheric pressure, the evaporative gas in the evaporative gas purge system is prevented from being sucked into the intake pipe. By opening the purge control valve, the evaporative gas adsorbed in the canister is prevented from returning to the fuel tank.

Incidentally, if the partial pressure of the evaporative gas component in the evaporative gas purge system is sufficiently lower than the saturated vapor pressure, it is not necessary to perform the evaporative gas concentration reduction operation before measuring the pressure change.

Therefore, it is possible to determine whether to execute or omit the evaporative gas concentration reduction operation based on at least one of the fuel temperature determined by the fuel temperature determining means and the amount of change thereof. . In other words, if the partial pressure of the evaporative gas component is estimated to be sufficiently lower than the saturated vapor pressure based on the fuel temperature and its change amount, the evaporative gas concentration reduction operation is omitted and the measurement of the pressure change is performed. Do. As a result, the time required for abnormality diagnosis of the evaporative gas purge system can be shortened.

Further, before performing the abnormality diagnosis, the pressure in the evaporative gas purge system is adjusted to a value close to the atmospheric pressure, and a preliminary measurement for measuring a pressure change is performed once or a plurality of times. It may be determined whether to execute or omit the evaporative gas concentration reduction operation based on the result. That is, if it is estimated from the preliminary measurement that the partial pressure of the evaporative gas component in the evaporative gas purge system is sufficiently lower than the saturated vapor pressure, the evaporative gas concentration reduction operation is omitted. As a result, the evaporative gas concentration reduction operation can be minimized.

[0015]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.
First, a schematic configuration of the entire system will be described with reference to FIG. An air cleaner 13 is provided on the upstream side of an intake pipe 12 of the engine 11, and air passing through the air cleaner 13 is drawn into each cylinder of the engine 11 through a throttle valve 14. The opening of the throttle valve 14 is adjusted by the amount of depression of the accelerator pedal 15. Also,
A fuel injection valve 16 is provided in the intake pipe 12 for each cylinder. Fuel (gasoline) in a fuel tank 17 is sent to each fuel injection valve 16 via a fuel pipe 19 by a fuel pump 18. The fuel tank 17 is provided with a pressure sensor 20 such as a semiconductor pressure sensor for detecting the pressure in the fuel tank 17.

Next, the structure of the evaporation gas purge system 21 will be described. A canister 23 is connected to the fuel tank 17 via a communication pipe 22. This canister 2
3, an adsorbent 24 such as activated carbon for adsorbing evaporative gas.
Is housed. At the bottom of the canister 23, an atmosphere communication pipe 25 communicating with the atmosphere is provided, and a canister closing valve 26 (canister closing means) is attached to the atmosphere communication pipe 25.

The canister closing valve 26 is constituted by an electromagnetic valve, and is kept open by a spring (not shown) in an off state, so that the atmosphere communication pipe 25 of the canister 23 is kept open to the atmosphere. Dripping. When a predetermined voltage is applied to the canister closing valve 26, the canister closing valve 26 is switched to a closed state, and the atmosphere communication pipe 25 is closed.

On the other hand, between the canister 23 and the intake pipe 12, purge passages 30a, 3 for purging (releasing) the evaporative gas adsorbed by the adsorbent 24 to the intake pipe 12.
A purge control valve 31 for adjusting the purge flow rate is provided between the purge passages 30a and 30b. This purge control valve 31 is constituted by an electromagnetic valve.

A voltage is applied to a solenoid coil (not shown) of the purge control valve 31 by a pulse signal, and the purge control is performed by adjusting the ratio (duty ratio) of the pulse width to the cycle of the pulse signal. The purge flow rate of the evaporative gas from the canister 23 to the intake pipe 12 is controlled by adjusting the ratio of the valve opening time to the opening / closing cycle of the valve 31.

A fuel cap 38 with a relief valve is attached to the fuel supply port 17a of the fuel tank 17, and the relief valve is opened when the internal pressure of the fuel tank exceeds -40 mmHg to 150 mmHg (relief pressure). And release the pressure. Therefore, the fuel tank 1
The section from 7 to the canister 23 is always kept at a pressure within this relief pressure range.

Next, the configuration of the control system will be described. The control circuit 39 is configured by mutually connecting a CPU 40, a ROM 41, a RAM 42, an input / output circuit 43, and the like via a common bus 44. The input / output circuit 43 includes a throttle sensor 45, an idle switch 46, a vehicle speed sensor 47,
Various sensors for detecting the operating state of the engine, such as an intake pipe pressure sensor 49, a cooling water temperature sensor 50, and an intake air temperature sensor 51, are connected. Signals input from these various sensors via the input / output circuit 43 and ROM 41 and RAM 42 Based on the stored programs and data, fuel injection control, ignition control, evaporative gas purge control, abnormality diagnosis of the evaporative gas purge system 21 and the like are executed, and the fuel injection valve 1
6. A drive signal is output to the ignition plug 52, the canister closing valve 26, the purge control valve 31, etc. via the input / output circuit 43, and when an abnormality of the evaporative gas purge system 21 is detected, a warning lamp 53 is lit to turn on the driver. Inform

The abnormality diagnosis program for the evaporative gas purge system 21 executed by the control circuit 39 will now be described with reference to FIG.
This will be described with reference to the flowcharts of FIGS. This abnormality diagnosis program is executed every predetermined time (for example, 256 m) when an ignition switch (not shown) is turned on.
(every second) and plays a role as abnormality diagnosis means in the claims. When the program is started, first, in steps 101 to 105 of FIG. 2, the process branches to various steps while determining whether or not the current process has progressed from the setting state of the flags F1 to F5. The flags F1 to F5 are reset to “0” by an initialization process immediately after the ignition switch is turned on.

When all the flags F1 to F5 are set to "0", that is, when the determinations in steps 101 to 105 are all "No", the process proceeds to step 106 in FIG.
It is determined whether or not to perform the evaporative gas concentration reduction operation (steps 107 to 118) based on the fuel temperature and the amount of change in the fuel temperature. In this case, the fuel temperature may be detected by attaching a fuel temperature sensor (not shown) to the fuel tank 17 or the like, but the coolant temperature, the intake air temperature (or the outside air temperature),
The fuel temperature may be estimated based on the operation time from the start, the operation state, and the like.

The execution condition of the evaporative gas concentration reduction operation determined in step 106 is that the fuel temperature is equal to or higher than a predetermined temperature α.
And the fuel temperature change amount is equal to or less than the predetermined amount β,
When the two conditions are satisfied, it is estimated that the partial pressure of the evaporative gas component in the fuel tank 17 is close to the saturated vapor pressure.
The evaporative gas concentration reduction operation is performed as follows.

First, at step 108, the canister closing valve 26 is fully closed. At step 109, the purge control valve 31 is opened, and the purge control valve 31 is removed from the fuel tank 17.
The negative pressure of the intake pipe 12 is introduced into the evaporative gas purge system up to (time T1 to T2 in FIG. 5). As a result, the evaporative gas in the evaporative gas purge system is sucked into the intake pipe 12 to reduce the concentration (partial pressure) of the evaporative gas component in the evaporative gas purge system. Increase the pressure difference.

In the next step 110, the fuel tank pressure PT detected by the pressure sensor 20 is reduced to a predetermined negative pressure (for example, −5).
mmHg) to determine whether it has decreased to -5 mm
If it has not decreased to Hg, proceed to step 111,
The first flag F1 is set to "1" which means that the negative pressure is being introduced, and the program ends. In this case, the next time this program is executed, step 1
01, “Yes” is determined, and step 1
The process is repeated in the order of 01 → step 110 →..., And the introduction of the negative pressure (opening of the purge control valve 31) is continued until the fuel tank internal pressure PT decreases to −5 mmHg or less.

As a result, at time T2 in FIG. 5, when the fuel tank internal pressure PT drops to -5 mmHg, step 1
The determination at 10 is “Yes”, the process proceeds to step 112, and the first flag F1 is reset to “0”. After this,
In step 113, the canister closing valve 26 is fully opened, and in step 114, the purge control valve 31 is fully closed,
Atmospheric pressure is introduced into the evaporative gas purge system.

In the next step 115, the fuel tank internal pressure P
It is determined whether or not T has returned to the atmospheric pressure (0 mmHg).
The second flag F2 is set to "1" which means that the atmospheric pressure is being introduced, and the program ends. In this case, the next time this program is executed, step 1
01 and “Yes” in step 102, and the processing is repeated in the order of step 101 → step 102 → step 115 →... Until the fuel tank internal pressure PT returns to the atmospheric pressure. Continue the introduction.

Thus, when the fuel tank internal pressure PT returns to the atmospheric pressure, the determination in step 115 becomes "Yes",
Proceeding to step 117, the second flag F2 is reset to "0". Thereafter, in step 118, the canister closing valve 26 is fully closed to close the evaporative gas purge system, and the amount of change in pressure .DELTA.P1 from the atmospheric pressure is measured by the processing in steps 122 to 127.

On the other hand, if it is determined in step 106 that the fuel temperature <α and the fuel temperature variation> β, the differential pressure between the partial pressure of the evaporative gas component in the fuel tank 17 and the saturated vapor pressure is satisfied. Is estimated to be relatively large, it is not necessary to perform the evaporative gas concentration reduction operation described above. Therefore,
In this case, the evaporative gas concentration reducing operation is omitted, and the routine proceeds to steps 120 and 121, where the purge control valve 31 and the canister closing valve 26 are both fully closed to close the evaporative gas purge system. By the processing, the pressure change amount ΔP1 from the atmospheric pressure is measured.

The measurement of the pressure change amount ΔP1 from the atmospheric pressure is as follows.
First, at step 122, the fuel tank internal pressure P1a at the time T3 in FIG. 5 is read, and the timer T is reset and started. Then, the routine proceeds to step 123, where it is determined whether or not the count value of the timer T becomes, for example, 15 seconds or more. . If 15 seconds have not elapsed, the routine proceeds to step 124, where the third flag F3 is set to "1" which means that the pressure change is being measured, and the program ends.

As described above, when the third flag F3 is set to "1", "No" in steps 101 and 102 and "step 10"
3 is determined to be “Yes”, and step 10
The processing is repeated in the order of 1 to 103 → step 123 →. During this time, the fuel tank internal pressure PT rises from 0 mmHg according to the amount of evaporative gas generated from the fuel in the fuel tank 17 between time T3 and time T4 in FIG.

Thereafter, when 15 seconds have elapsed since time T3 (the time point of detection of P1a), the routine proceeds to step 125 in FIG. 4, in which the fuel tank internal pressure P1b detected by the pressure sensor 20 is read. Change amount ΔP
After calculating 1 (= P1b−P1a), in step 127,
The third flag F3 is reset, and the measurement of the pressure change amount ΔP1 from the atmospheric pressure ends.

Thereafter, at step 128, the purge control valve 31 is opened, and at the same time, the timer T is reset and started. When the purge control valve 31 is opened, the intake pipe negative pressure is introduced into the evaporative gas purge system under the previous atmospheric pressure (time T4 to T5 in FIG. 5). Therefore, if there is no leak in the evaporative gas purge system, the fuel tank internal pressure PT starts to decrease.

In the next step 129, the fuel tank internal pressure PT detected by the pressure sensor 20 is reduced to a predetermined negative pressure (for example, -1).
5 mmHg) to determine whether it is still -15
If not reduced to mmHg, the routine proceeds to step 130, where it is determined whether or not a predetermined time (for example, 2 seconds) has elapsed from the start of the introduction of the negative pressure. If two seconds have not elapsed, the routine proceeds to step 133, where the fourth flag F4 is set to "1", which means that negative pressure is being introduced, and the program ends.

As described above, when the fourth flag F4 is set to "1", "No" in steps 101 to 103 and "10"
In step 4, the determination is “Yes”, and step 10
The processing is repeated in the order of 1 to 104 → step 129 →.

By such processing, if "Yes" is given in step 130 before step 129, that is, a predetermined time (for example, 2 seconds) from the start of negative pressure introduction
If the fuel tank internal pressure PT does not decrease to a predetermined negative pressure (for example, −15 mmHg) even after elapse, it means that the negative pressure cannot be introduced into the fuel tank 17. The reason why the negative pressure cannot be introduced into the fuel tank 17 may be that a clog has occurred somewhere in the evaporative gas purge system. In this case, the routine proceeds to step 131, where the clogging flag Fclose is set to "1" meaning that clogging has occurred.
The warning lamp 53 is turned on to notify the abnormality, and the program ends.

On the other hand, step 129 is the same as step 13
0, ie, within a predetermined time (for example, 2 seconds) from the start of negative pressure introduction, the fuel tank internal pressure P
If T has decreased to a predetermined negative pressure (for example, −15 mmHg), the routine proceeds to step 134, where the fourth flag F4 is reset to “0”, and in step 135, the purge control valve 31 is fully closed again. Then, the introduction of the negative pressure is terminated (time T5 in FIG. 5). Thereafter, the routine proceeds to step 136, where the fuel tank internal pressure P2a detected by the pressure sensor 20 is read and stored at a time T6 immediately after the evaporative gas purge system is brought into the negative pressure sealed state, and the timer T is reset-started. Thereafter, the fuel tank internal pressure PT increases from −15 mmHg in accordance with the amount of evaporative gas generated in the fuel tank 17 between time T6 and time T7 in FIG.

Then, in the next step 137, it is determined whether or not 15 seconds have elapsed after the reading of the fuel tank internal pressure P2a.
The fifth flag F5 is set to "1" which means that the pressure change is being detected, and the program ends. As a result, the next time the program is executed, “No” is determined in steps 101 to 104, and “Yes” is determined in step 105, and steps 101 to 105 → step 137 →
The process is repeated in the order of...

Thereafter, when 15 seconds have elapsed since the reading of the fuel tank internal pressure P2a, the routine proceeds to step 139, where the time T
7, the fuel tank internal pressure P2b detected by the pressure sensor 20
Is read and stored, and the pressure change ΔP for 15 seconds after sealing is
2 (= P2b-P2a) is calculated.

Thereafter, in step 141, it is determined whether or not there is a leak based on a leak determination condition represented by the following equation. ΔP2> α · ΔP1 + β

Here, α is a coefficient for correcting the difference in the amount of fuel evaporation due to the difference between the atmospheric pressure and the negative pressure, and β is a coefficient for correcting the detection accuracy of the pressure sensor 20, the pressure leak of the canister closing valve 26, and the like. If the above expression is satisfied, it is determined that “there is a leak”. That is, if there is a leak cause in the closed section from the fuel tank 17 to the purge control valve 31, the outflow from the closed section to the atmosphere occurs under the positive pressure, while the inflow of air from the atmosphere into the closed section under the negative pressure. Happens. Therefore,
"(Pressure change under atmospheric pressure ΔP1) = (fuel tank 17
(The amount of evaporative gas generated from air)-(the amount of outflow from the closed section to the atmosphere) rather than "(pressure change amount under negative pressure ΔP2) =
(The amount of evaporative gas generated from the fuel tank 17) + (the amount of inflow from the atmosphere into the closed section) is larger. From this relationship, the leak determination condition of the above equation is derived.

If the leak determination condition of the above equation is satisfied, that is, if it is determined in step 141 that “leakage is present”, a part causing a leak somewhere in the purge path from the fuel tank 17 to the intake pipe 12. Means that there is
Proceeding to step 142, the leak flag Fleak is set to "1", and in step 143, the warning lamp 53 is turned on to notify an abnormality and the program is terminated.

On the other hand, if "NO" is determined in the step 141, that is, if it is determined that there is no leak, the process proceeds to a step 144, where the first to fifth flags F1
F5 is reset to "0" and the program ends.

In the embodiment (1) described above, the evaporative gas in the fuel tank 17 is discharged to reduce the evaporative gas concentration before the pressure change amount ΔP1 from the atmospheric pressure is measured. Before the measurement of the amount ΔP1, the differential pressure between the partial pressure of the evaporative gas component in the fuel tank 17 and the saturated vapor pressure can be made sufficiently large, and the atmospheric pressure is not affected by the fuel system state such as the fuel temperature. Pressure change ΔP from
1 can be accurately measured, and the abnormality diagnosis of the evaporative gas purge system can be accurately performed.

Further, in the present embodiment (1), it is determined whether or not the execution condition of the evaporative gas concentration reduction operation is satisfied based on the fuel temperature and the amount of change in the fuel temperature. If the partial pressure of the evaporative gas component is estimated to be sufficiently lower than the saturated vapor pressure), the evaporative gas concentration reduction operation is omitted and the pressure change ΔP1 is measured. The time required for the abnormality diagnosis can be shortened, and a quick abnormality diagnosis can be performed.

The execution condition of the evaporative gas concentration reduction operation may be determined based on only one of the fuel temperature and the fuel temperature change amount. Further, the process of determining the execution condition of the evaporative gas concentration reduction operation may be omitted, and the evaporative gas concentration reduction operation may be performed every time. In this case, the intended object of the present invention can be sufficiently achieved.

[Embodiment (2)] In the embodiment (1), when the fuel tank internal pressure PT is returned to the atmospheric pressure at the end of the evaporative gas concentration reduction operation (T2 to T3), the canister closing valve 25 is opened and Although the purge control valve 31 is closed, in the embodiment (2) of the present invention shown in FIG. 6, when the fuel tank internal pressure PT is returned to the atmospheric pressure at the end of the evaporative gas concentration reduction operation (T2 to T3), Canister closing valve 2
5 and the purge control valve 31 are both opened. In this way, the evaporative gas adsorbed in the canister 23 can be prevented from returning to the fuel tank 17 by opening the purge control valve 31 when the atmospheric pressure is introduced, and the evaporative gas concentration in the fuel tank 17 can be reliably reduced. it can.

[Embodiment (3)] The embodiment (1),
In (2), the pressure change amount ΔP1 from the atmospheric pressure is measured, and then the pressure change amount ΔP2 from the negative pressure is measured. However, in the embodiment (3) of the present invention shown in FIG. After elapse of a predetermined time after measuring the pressure change amount ΔP2 from the pressure and returning the fuel tank internal pressure PT to the atmospheric pressure, an evaporative gas concentration reduction operation is performed, and then the pressure change amount ΔP1 from the atmospheric pressure is measured. I have. Also in this embodiment (3), the method of measuring the pressure change amounts ΔP2 and ΔP1 and the method of evaporative gas concentration reduction operation are the same as those in the above-described embodiment (1) or (2).

In this case, when the pressure change amount ΔP2 from the negative pressure is measured and then returned to the atmospheric pressure, the evaporative gas component in the fuel tank 17 rapidly becomes saturated, and for a while,
Since the state in the fuel tank 17 becomes unstable, the evaporative gas concentration reduction operation is performed after a predetermined time elapses until the state in the fuel tank 17 is stabilized, so that the pressure change amount ΔP1 is measured. Further, the concentration of the evaporative gas in the fuel tank 17 is surely reduced.

[Embodiment (4)] In the embodiment (1), it is determined whether or not to execute the evaporative gas concentration reduction operation based on the fuel temperature and the amount of change in the fuel temperature. In the illustrated embodiment (4) of the present invention, before the abnormality diagnosis of the evaporative gas purge system is performed, the fuel tank internal pressure PT
Is adjusted to the atmospheric pressure to perform a preliminary measurement for measuring the pressure change amount .DELTA.P0. The pressure change amount .DELTA.P0 is compared with a predetermined value to determine whether the evaporative gas concentration reduction operation is to be executed or omitted. That is, when the pressure change amount ΔP0 is less than the predetermined value, it is estimated that the partial pressure of the evaporative gas component in the fuel tank 17 is close to the saturated vapor pressure, and it is necessary to reduce the evaporative gas concentration in the fuel tank 17. In the same manner as in the embodiment (1), the evaporative gas in the fuel tank 17 is discharged to reduce the evaporative gas concentration. On the other hand, the pressure change ΔP0
Is greater than or equal to a predetermined value, it is estimated that the partial pressure of the evaporative gas component in the fuel tank 17 is sufficiently lower than the saturated vapor pressure, and it is not necessary to reduce the evaporative gas concentration in the fuel tank 17. The amount of pressure change ΔP1 from the atmospheric pressure is measured without performing the concentration reduction operation. The number of measurements of the pressure change amount ΔP0 may be one, but may be two or more.

[Embodiment (5)] Each of the above embodiments (1)
In (4) to (4), when returning the fuel tank internal pressure PT to the atmospheric pressure, the canister closing valve 25 is opened to introduce the atmospheric pressure into the evaporative gas purge system. In the embodiment (5), an opening valve 61 is provided in a purge path from the fuel tank 17 to the canister 23,
When returning the fuel tank pressure PT to the atmospheric pressure, the release valve 61 is opened to introduce the atmospheric pressure into the evaporative gas purge system.

Although the internal pressure of the fuel tank 17 is detected by the pressure sensor 20 in the system configuration examples shown in FIGS. 1 and 9, for example, the pressure in the communication pipe 22 for communicating the fuel tank 17 and the canister 23 is increased. May be detected. In short, the pressure at any point in the evaporative gas purge system from the fuel tank 17 to the purge control valve 31 may be detected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire system showing an embodiment (1) of the present invention.

FIG. 2 is a flowchart showing a flow of processing of an abnormality diagnosis program (part 1);

FIG. 3 is a flowchart showing the flow of processing of an abnormality diagnosis program (part 2);

FIG. 4 is a flowchart showing a flow of processing of an abnormality diagnosis program (part 3);

FIG. 5 is a time chart illustrating the relationship between the opening and closing of the purge control valve and the canister closing valve and the change in the fuel tank internal pressure at the time of abnormality diagnosis according to the embodiment (1) of the present invention.

FIG. 6 is a time chart for explaining the relationship between the opening / closing of the purge control valve and the canister closing valve and the change in the fuel tank internal pressure at the time of abnormality diagnosis in the embodiment (2) of the present invention.

FIG. 7 is a time chart for explaining the relationship between the opening and closing of the purge control valve and the canister closing valve and the change in the fuel tank internal pressure at the time of abnormality diagnosis in the embodiment (3) of the present invention.

FIG. 8 is a time chart for explaining the relationship between the opening and closing of the purge control valve and the canister closing valve and the change in the fuel tank internal pressure at the time of abnormality diagnosis in the embodiment (4) of the present invention.

FIG. 9 is a schematic configuration diagram of an entire system showing an embodiment (5) of the present invention.

[Explanation of symbols]

11 engine (internal combustion engine), 12 intake pipe, 14 throttle valve, 16 fuel injection valve, 17 fuel tank, 18 fuel pump, 20 pressure sensor, 21 evaporative gas purge system, 22 communication pipe, 23 canister, 24 adsorbent, 26 canister closing valve, 30a,
30b: purge passage, 31: purge control valve, 39: control circuit (abnormality diagnosis means), 53: warning lamp, 61: open / close valve.

Claims (7)

[Claims] 1. A canister for adsorbing evaporative gas generated by evaporating fuel in the fuel tank into a passage communicating the fuel tank with an intake pipe of an internal combustion engine, and purging the evaporative gas from the canister to the intake pipe. In the evaporative gas purge system provided with a purge control valve for controlling the pressure, the evaporative gas purge system including the fuel tank and the canister is sealed at the time of abnormality diagnosis, and the pressure change of the evaporative gas purge system is measured, and based on the measured value, Abnormality diagnostic means for diagnosing the presence or absence of an abnormality in the evaporative gas purge system, wherein the abnormal diagnostic means discharges evaporative gas in the fuel tank to reduce the evaporative gas concentration before measuring a pressure change of the evaporative gas purge system. Gas purge system characterized by performing an operation (hereinafter referred to as “evaporative gas concentration reducing operation”) Absence of abnormality diagnosis devices. 2. The apparatus according to claim 1, wherein when performing the evaporative gas concentration reducing operation, the abnormality diagnostic means changes the pressure in the evaporative gas purge system to a predetermined pressure and discharges the evaporative gas in the fuel tank. The abnormality diagnosis device for an evaporative gas purge system according to claim 1, wherein the abnormality is returned. 3. The abnormality diagnosing means measures the first pressure change after adjusting the pressure in the evaporative gas purge system to a negative pressure, and then adjusts the pressure in the evaporative gas purge system to near atmospheric pressure. Thereafter, the second pressure change is measured, and the two pressure changes are compared to diagnose the presence or absence of an abnormality in the evaporative gas purge system. The abnormality diagnosis device for an evaporative gas purge system according to claim 2, wherein the second measurement of the pressure change is performed after the evaporative gas concentration reduction operation is performed. 4. A canister closing means for opening and closing an atmosphere communication hole provided in the canister, wherein the abnormality diagnosing means returns the pressure in the evaporative gas purge system to near atmospheric pressure at the end of the evaporative gas concentration reduction operation. 4. The method according to claim 2, wherein the canister closing means is opened and the purge control valve is closed.
An abnormality diagnosis device for an evaporative gas purge system according to item 1. 5. A canister closing means for opening and closing an air communication hole provided in the canister, wherein the abnormality diagnosing means returns the pressure in the evaporative gas purge system to near atmospheric pressure at the end of the evaporative gas concentration reduction operation. 4. The abnormality diagnosis apparatus for an evaporative gas purge system according to claim 2, wherein both the canister closing means and the purge control valve are opened. 6. A fuel temperature judging means for judging a temperature of fuel in the fuel tank, wherein the abnormality diagnosing means is configured to execute the fuel temperature judging based on at least one of the fuel temperature judged by the fuel temperature judging means and a change amount thereof. 6. The abnormality diagnosis device for an evaporative gas purge system according to claim 1, wherein it is determined whether to execute or omit the evaporative gas concentration reducing operation. 7. The abnormality diagnosing means performs one or more preliminary measurements of adjusting a pressure in the evaporative gas purge system to near atmospheric pressure and measuring a pressure change before performing the abnormality diagnosis. The abnormality diagnosis device for an evaporative gas purge system according to any one of claims 1 to 6, wherein it is determined whether to execute or omit the evaporative gas concentration reducing operation based on a result.