JPH03260365A - Diagnostic device for evaporation fuel device - Google Patents

Abstract

PURPOSE:To easily judge the function of an evaporation fuel device by providing an atmospheric valve, which opens/closes an atmospheric passage connected to a canister, and judging the function of the evaporation fuel device normal by fluctuation of air-fuel ratio when the atmospheric valve is closed at the time of air-fuel ratio feedback control. CONSTITUTION:In an evaporation fuel device which prevents release of vaporized fuel staying in a fuel tank 14, to the atmosphere, a canister 22 for adsorptively holding the vaporized fuel is connected to an intake passage 6 on the downstream side of a throttle valve 8 and upper part space of the fuel tank 14 through a purge passage 24 and an evaporation passage 26 respectively. An atmospheric passage 28 is connected to the canister 22, and a purge valve 30, opened/closed in accordance with an engine operational condition, is interposed halfway in the purge passage 24. Here an atmospheric valve 32 is interposed in the atmospheric passage 28. In the case of air-fuel ratio fluctuated from the target air-fuel ratio by closing operation of the atmospheric valve 32 when the purge valve 30 is opened and air-fuel ratio feedback control is performed, the function of the evaporation fuel device is judged normal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a diagnostic device for a fuel vapor system, and in particular, it is capable of diagnosing the function of a fuel vapor system without requiring the addition of a large number of devices, and it is capable of diagnosing a large number of devices. The present invention relates to a diagnostic device for an evaporative fuel system that can avoid deterioration in reliability due to additional equipment and can improve the reliability of diagnosis.

[Conventional technology]

Some internal combustion engines are equipped with an evaporative fuel device in order to prevent evaporative fuel generated in a fuel tank or the like from being released into the atmosphere while the internal combustion engine is stopped. The evaporative fuel device is, for example,
It is constructed as shown in FIG. In the figure, 102 is an internal combustion engine, 104 is an air cleaner, 106 is an intake passage, 1
08 is a throttle valve, 110 is a combustion chamber, 112 is an exhaust passage, and 114 is a fuel tank.

The intake passage 106 of the internal combustion engine 102 is provided with a fuel injection valve 116 that is directed toward the combustion chamber 110 and constitutes a fuel system. The fuel injection valve 116 communicates with a fuel pump 120 in the fuel tank 114 through a fuel passage 118, and injects fuel pumped by the fuel pump 120 into the combustion chamber 110.

The evaporative fuel device that prevents the evaporative fuel generated in the fuel tank 114 from being released into the atmosphere connects a canister 122 that adsorbs and holds evaporative fuel to the intake passage 106 downstream of the throttle valve 108 of the internal combustion engine 102 and the fuel tank 114.
A purge passage 124 and an evaporation passage]2 are provided in the upper space of the
6, and this canister 12
2 is provided with an atmospheric passage 128 in communication with it. A purge valve 130 is interposed in the middle of the purge passage 124, and is opened and closed depending on the operating state of the internal combustion engine 102.

As a result, as shown in FIG. 5, in the evaporative fuel system, when the internal combustion engine 102 is stopped, the purge valve 130 is closed and the evaporative fuel generated in the fuel tank 114 is introduced into the canister 122 through the evaporative passage 126 and adsorbed. Hold. At this time, unnecessary air within the canister 122 is discharged to the atmosphere through the atmospheric passage 128. Further, the evaporative fuel device is configured to operate in a sixth mode in a predetermined operating range of the internal combustion engine
As shown in the figure, by opening the purge valve 130 and applying negative intake pressure, the vaporized fuel adsorbed and held in the canister 122 is released by fresh air introduced from the atmospheric passage 128 and is supplied to the intake passage 106. Note that in a non-predetermined operating range of the internal combustion engine 102, the purge valve 130 is closed, and the supply of the vaporized fuel adsorbed and held in the canister 122 to the intake passage 106 is stopped.

Such an evaporative fuel device is disclosed in Japanese Patent Application Laid-Open No. 56-1218.
Some of these are disclosed in Publication No. 56 and Japanese Utility Model Application Publication No. 193760/1983. The device disclosed in Japanese Unexamined Patent Publication No. 56-121856 is provided with a heating device to heat the atmospheric air introduced from an atmospheric passage communicating with the canister.

Furthermore, in the device disclosed in Japanese Utility Model Application Publication No. 63-193760, when the fuel temperature exceeds a predetermined temperature and under high load operating conditions, the atmospheric passage communicating with the key nister is closed to supply highly concentrated evaporated fuel to the intake passage. It is equipped with a solenoid valve that operates to

In addition, internal combustion engines are equipped with air-fuel ratio control devices that control the air-fuel ratio to an appropriate value in order to satisfy requirements such as low fuel consumption, low exhaust gas harmful component values, and high output under various operating conditions. There is something set up.

For example, as shown in FIG. 4, the air-fuel ratio control device includes an 02 sensor 132 that is an exhaust sensor in the exhaust passage 112 of the internal combustion engine 102, and a control section 134 that is a control means that inputs the detection signal of the 02 sensor 132. It is set up. The air-fuel ratio control device controls the 02 sensor 132 by the control unit 134.
The fuel injection valve 116 is operated in response to the detection signal, and the air-fuel ratio is feedback-controlled to the target air-fuel ratio.

Such an air-fuel ratio control device is disclosed in Japanese Patent Application Laid-Open No. 63-29
There is one disclosed in the No. 050 publication. What is disclosed in this publication is that when the feedback amount of the air-fuel ratio reaches the upper limit value, the feedback amount is temporarily reduced to a predetermined value slightly smaller than the upper limit value while the purge valve of the evaporative fuel system is closed. If the set feedback amount substantially reaches the upper limit after the setting, it is determined that the air-fuel ratio control device is malfunctioning.

[Problem that the invention seeks to solve]

By the way, when diagnosing the function of the evaporated fuel system, it is necessary to examine the canister when the purge valve, which is interposed in the middle of the purge passage that communicates the key nister that adsorbs and holds evaporated fuel with the intake passage of the internal combustion engine, is opened and closed. Detects the HC (hydrocarbon) components inside the tank and the pressure inside the purge passage,
This is done by monitoring this detected value. Therefore, diagnosing the function of the evaporative fuel system requires a component sensor that detects HC components, a pressure sensor that detects pressure, etc., and a dedicated diagnostic device that diagnoses the function from the detection signals of these sensors. shall be.

Therefore, there is an inconvenience that a large number of additional devices are required, leading to an increase in costs, and the additional installation of such devices reduces the reliability of the apparatus, thereby impairing the reliability of diagnosis.

[Purpose of the invention]

Therefore, an object of the present invention is to be able to diagnose the function of an evaporative fuel system without needing to add a large number of devices, thereby avoiding an increase in cost, and also to avoid a decrease in reliability due to the need for adding a large number of devices. An object of the present invention is to realize a diagnostic device for an evaporative fuel system that can improve the reliability of diagnosis.

[Means for solving problems]

In order to achieve this object, the present invention provides a canister that adsorbs and holds evaporated fuel and communicates with an intake passage and a fuel tank of an internal combustion engine through a purge passage and an evaporation passage, respectively, and also communicates an atmospheric passage with this canister. In the evaporative fuel system, the purge valve is provided in the middle of the purge passage and is operated to open and close depending on the operating state of the internal combustion engine. When the air-fuel ratio of the internal combustion engine is feedback-controlled to the target air-fuel ratio based on the detection signal of the exhaust sensor provided in the exhaust passage of the internal combustion engine, the air-fuel ratio of the internal combustion engine changes from the target air-fuel ratio by the closing operation of the atmospheric valve. The present invention is characterized in that a control means is provided that determines that the function of the evaporated fuel device is normal when the fuel vapor device fluctuates.

[Effect]

According to the configuration of the present invention, an atmospheric valve is provided to open and close an atmospheric passage communicating with the canister, and the control means opens the purge valve, and the internal combustion engine is emptied by the detection signal of the exhaust sensor provided in the exhaust passage of the internal combustion engine. When the fuel ratio is feedback-controlled to the target air-fuel ratio, atmospheric
If the air-fuel ratio of the internal combustion engine fluctuates from the target air-fuel ratio due to the valve closing operation, the function of the evaporative fuel system is determined to be normal, and the evaporative fuel is evaporated using the existing device in the internal combustion engine by simply adding an atmospheric valve. The function of the fuel system can be determined, and since only an atmospheric valve is additionally provided, a decrease in reliability can be avoided.

〔Example〕

Next, embodiments of the present invention will be described in detail based on the drawings.

1 to 3 show embodiments of this invention. In FIG. 1, 2 is an internal combustion engine, 4 is an air cleaner, 6 is an intake passage, 8 is a throttle valve, 10 is a combustion chamber, 12
14 is an exhaust passage, and 14 is a fuel tank.

The intake passage 6 of the internal combustion engine 2 is provided with a fuel injection valve 16 that is directed toward the combustion chamber 10 and constitutes a fuel system. This fuel injection valve 16 is connected to the fuel tank 1 by a fuel passage 18.
This fuel pump 2 is connected to the fuel pump 20 in the fuel pump 2.
0 is injected and supplied to the combustion chamber 10.

The evaporated fuel device that prevents the evaporated fuel generated in the fuel tank 14 from being released into the atmosphere connects the canister 22 that adsorbs and holds evaporated fuel to the intake passage 6 downstream of the throttle valve 8 of the internal combustion engine 2 and the fuel tank 14. A purge passage 24 and an evaporation passage 26 are provided in the upper space to communicate with each other, and an atmospheric passage 28 is provided in communication with the canister 22. In the middle of the purge passage 24, there is a purge valve 3 that is opened and closed depending on the operating state of the internal combustion engine 2.
0 is provided.

As a result, the evaporative fuel device can
When the purge valve 30 is closed, the evaporated fuel generated in the fuel tank 14 is transferred to the canister 22 through the evaporative passage 26.
and hold it by adsorption.

At this time, unnecessary air within the canister 22 is discharged to the atmosphere through the atmospheric passage 28. In addition, the evaporative fuel device
In a predetermined operating range of the internal combustion engine 2, the purge valve 30
is opened and a negative intake pressure is applied, thereby causing the vaporized fuel adsorbed and held in the canister 22 to be released by fresh air introduced from the atmospheric passage 28 and supplied to the intake passage 6. Note that in a non-predetermined operating range of the internal combustion engine 2, the purge valve 30 is closed, and the supply of the vaporized fuel adsorbed and held in the canister 22 to the intake passage 6 is stopped.

In such an evaporative fuel system, an atmospheric valve 32 is provided to open and close an atmospheric passage 28 communicating with the canister 22. This atmospheric valve 32 is connected to a control section 34, which is a control means, together with the purge valve 24. Further, an 02 sensor 36, which is an exhaust sensor provided in the exhaust passage 12 of the internal combustion engine 2, is connected to the control unit 34. When the purge valve 24 is opened and the air-fuel ratio of the internal combustion engine 2 is feedback-controlled to the target air-fuel ratio based on the detection signal of the exhaust sensor 36, the control section 34 causes the atmospheric valve 32 to close. If the air-fuel ratio changes from the target air-fuel ratio, the function of the evaporative fuel system is determined to be normal.

Note that the control unit 34 is configured to use an existing air-fuel ratio control device in the internal combustion engine 2, that is, to satisfy requirements such as a low fuel consumption rate, a small value of harmful exhaust gas components, and a high output amount under various operating conditions of the internal combustion engine 2. In order to do this, it is possible to use a control section of an air-fuel ratio control device that controls the air-fuel ratio to an appropriate value. This air-fuel ratio control device inputs the detection signal of the 0□ sensor 36, which is an exhaust sensor provided in the exhaust passage 12 of the internal combustion engine 2, to the control unit 34, and the control unit 34 uses the detection signal of the 02 sensor 32 to control the fuel injection valve. 16 to feedhack control the air-fuel ratio to the target air-fuel ratio.

The atmospheric valve 32 is connected to the control section 34 of this air-fuel ratio control device.
and the purge valve 24, and the control unit 34:
When the purge valve 24 is open and the air-fuel ratio of the internal combustion engine 2 is feedback-controlled to the target air-fuel ratio by the detection signal of the exhaust sensor 36, the air-fuel ratio of the internal combustion engine 2 is adjusted to the target air-fuel ratio by the closing operation of the atmospheric valve 32. If the value changes from , it is determined that the function of the evaporative fuel system is normal.

Next, the effect will be explained.

As shown in FIG. 2, when the control starts (200),
It is determined whether the purge valve 24 is turned on and opened and whether or not the air-fuel ratio control device is under closed-loop feedback control (202).

If this judgment (202) is NO, the process returns. If this judgment (202) is YES, the atmospheric valve 32 is turned off and closed (204), and it is judged whether the detection signal output from the 02 sensor 32 has changed to the rich side (206) I do.

Due to the closing operation of the atmospheric valve 32, the atmospheric passage 28
This means that the introduction of air from the canister 22 into the canister 22 is blocked. As a result, a large amount of evaporated fuel existing in the upper space of the fuel tank 14 is removed from the evaporative passage 26 and the purge passage 26.
4 and is directly supplied to the intake passage 6.

Therefore, if the function of the evaporative fuel system is normal, a large amount of evaporative fuel is supplied by the closing operation of the atmospheric valve 32, and the air-fuel ratio of the internal combustion engine 2 changes from the target air-fuel ratio to the rich side. Become.

Due to this fluctuation, as shown in FIG. 3, the 02 sensor 32
The detection signal output by changes to the rich side, and the feed hack control signal changes to the lean side.

Therefore, if the judgment (206) is NO,
In other words, if the detection signal output from the 02 sensor 32 does not fluctuate towards the rich side as shown in FIG.
B) is performed.

Furthermore, if the determination (206) is YES,
Process of turning on and opening the atmospheric valve 32 (210)
Then, it is determined whether the detection signal output from the 02 sensor 32 has changed to the rich side (212).

The atmospheric passage 28 is opened by the opening operation of the atmospheric valve 32.
Air will be introduced into the canister 22 from there. This prevents the evaporated fuel in the fuel tank 14 from being directly supplied to the intake passage 6, and the atmosphere introduced together with the evaporated fuel adsorbed and held in the canister 22 is supplied to the intake passage 6 via the purge passage 24. will be done.

Therefore, if the function of the evaporative fuel system is normal, the air-fuel ratio of the internal combustion engine 2 changes toward the lean side by supplying the atmosphere together with the evaporative fuel by the opening operation of the atmospheric valve 32. As a result of this fluctuation, as shown in FIG. 3, the detection signal output from the 02 sensor 32 changes to the lean side, and the feedback control signal changes to the rich side.

Therefore, if the judgment (210) is YES, that is, if the detection signal output by the 0□ sensor 32 fluctuates toward the lean side as shown in FIG. O, ni, judgment (21
4) is performed.

On the other hand, if the judgment (210) is No, that is, if the detection signal output from the 02 sensor 32 does not change to the lean side as shown in FIG. .

A determination (20B) of G is made.

Note that in the process (210), the atmospheric valve 32 was turned on and opened, but the purge valve 30 was turned off and the purge valve 30 was turned off without turning on this atmospheric valve 32 and performing the opening operation.
It can also work closed. This purge valve 30
The closing operation prevents the vaporized fuel in the fuel tank 14 from being directly supplied to the intake passage 6.

Therefore, if the function of the evaporative fuel system is normal, the air-fuel ratio of the internal combustion engine 2 changes to the lean side by blocking the supply of evaporative fuel by closing the purge valve 30. Due to this variation, as shown in Figure 3,
Since the detection signal output from the 02 sensor 32 changes to the lean side and the feedback control signal changes to the lean side,
If the judgment (210) is YES, that is, 0
If the detection signal output from the second sensor 32 fluctuates toward the lean side as shown in FIG. If the judgment (210) is NO, that is, if the detection signal output by the 02 sensor 32 does not change to the lean side as shown in FIG. , judgment (208)
will be held.

In this way, the atmospheric valve 32 that opens and closes the atmospheric passage 28 communicating with the canister 22 is provided, and the control unit 34 controls the
The purge valve 30 is opened and the purge valve 30 is opened. When the air-fuel ratio of the internal combustion engine 2 is feedback-controlled to the target air-fuel ratio by the detection signal of the sensor 36, if the air-fuel ratio of the internal combustion engine 2 fluctuates from the target air-fuel ratio due to the closing operation of the atmospheric valve 32, the evaporated fuel By determining that the function of the device is normal, it is possible to determine the function of the evaporative fuel system by using the existing device in the internal combustion engine 2, that is, the air-fuel ratio control device, by simply adding the atmospheric valve 32; Since only the atmospheric valve 32 is additionally provided, a decrease in reliability can be avoided.

Therefore, it is possible to diagnose the evaporative fuel system without needing to install a large number of additional devices, thereby avoiding an increase in cost, and also avoiding a decrease in reliability due to the additional installation of a large number of devices. The reliability of diagnosis can be increased. Further, since a large amount of evaporated fuel always exists in the upper space of the fuel tank 14, the purge valve 30
is opened and the air-fuel ratio of the internal combustion engine 2 is feedback-controlled to the target air-fuel ratio by the 02 sensor 36, by closing the atmospheric valve 32 and supplying the large amount of evaporated fuel to the intake passage 6, Since the air-fuel ratio of the internal combustion engine 2 can be varied from the target air-fuel ratio and this variation can be detected by the 02 sensor 36, the reliability of diagnosis can be increased.

Further, in the present invention, when the purge valve 30 is opened and the air-fuel ratio of the internal combustion engine 2 is feedback-controlled to the target air-fuel ratio by the detection signal of the 02 sensor 36,
If the air-fuel ratio of the internal combustion engine 2 fluctuates from the target air-fuel ratio by closing the atmospheric valve 32, it is determined that the function of the evaporative fuel system is normal. In addition to diagnosing the evaporative fuel system by utilizing the fact that the air-fuel ratio fluctuates from It is something that can be played.

〔Effect of the invention〕

As described above, according to the present invention, an atmospheric valve is provided for opening and closing the atmospheric passage communicating with the canister, and the control means opens the purge valve, and the internal combustion engine is activated by the detection signal of the exhaust sensor provided in the exhaust passage of the internal combustion engine. If the air-fuel ratio of the internal combustion engine fluctuates from the target air-fuel ratio due to the closing operation of the atmospheric valve when the air-fuel ratio of the internal combustion engine is feedback-controlled to the target air-fuel ratio, the atmospheric valve is closed by determining that the function of the evaporative fuel system is normal. By only adding an atmospheric valve, it is possible to determine the function of the evaporative fuel system using the existing device in the internal combustion engine, and by only adding an atmospheric valve, a decrease in reliability can be avoided.

Therefore, it is possible to diagnose the evaporative fuel system without needing to install a large number of additional devices, thereby avoiding an increase in cost, and it is possible to avoid a decrease in reliability due to the additional installation of a large number of devices, making it possible to diagnose Reliability can be increased. In addition, since a large amount of evaporated fuel always exists in the upper space of the fuel tank, when the purge valve is opened and the air-fuel ratio of the internal combustion engine is feedback-controlled to the target air-fuel ratio by the exhaust sensor, the atmospheric valve is closed. By supplying a large amount of evaporated fuel to the intake passage through the closing operation, the air-fuel ratio of the internal combustion engine can be varied from the target air-fuel ratio, and this variation can be detected by the exhaust sensor, making diagnosis more reliable. You can increase your sexuality.

Further, in the present invention, when the purge valve is opened and the air-fuel ratio of the internal combustion engine is feedback-controlled to the target air-fuel ratio by the detection signal of the exhaust sensor, the air-fuel ratio of the internal combustion engine is adjusted to the target air-fuel ratio by the closing operation of the atmospheric valve. If the air-fuel ratio of the internal combustion engine fluctuates from the target air-fuel ratio, the function of the evaporative fuel system is determined to be normal.
By monitoring the fluctuation state of the air-fuel ratio, the air-fuel ratio control device can also be diagnosed, and the effect of the practical engineering can be achieved.

[Brief explanation of drawings]

1 to 3 show embodiments of the present invention, and FIG.
The figure is a control flowchart, and FIG. 3 is a timing chart of the feedback control signal and the OT sensor output signal. 4 to 6 show conventional examples; FIG. 4 is a schematic diagram of an internal combustion engine equipped with an evaporative fuel device and an air-fuel ratio control device; FIG.
FIG. 6 is an explanatory diagram of a state in which vaporized fuel is separated and released by the canister. In the figure, 2 is an internal combustion engine, 6 is an intake passage, 8 is a throttle valve, 12 is an exhaust passage, 14 is a fuel tank, 16
is a fuel injection valve, 22 is a canister, 24 is a purge passage,
26 is an evaporative passage, 28 is an atmospheric passage, 30 is a purge valve, 32 is an atmospheric valve, 34 is a control unit, and 36 is an Ot sensor. Engraving of the drawing, Figure 1

Claims (1)

[Claims] 1. A canister that adsorbs and holds evaporated fuel is provided in communication with the intake passage and fuel tank of the internal combustion engine through a purge passage and an evaporative passage, respectively, and an atmospheric passage is provided in communication with this canister, and the internal combustion An evaporative fuel system including a purge valve that opens and closes depending on the operating state of the engine, wherein the atmospheric valve opens and closes the atmospheric passage, the purge valve is opened and the exhaust sensor is provided in the exhaust passage of the internal combustion engine. When the air-fuel ratio of the internal combustion engine is feedback-controlled to the target air-fuel ratio by the detection signal, if the air-fuel ratio of the internal combustion engine fluctuates from the target air-fuel ratio due to the closing operation of the atmospheric valve, the function of the evaporative fuel device is determined. 1. A diagnostic device for an evaporative fuel system, comprising a control means for determining that the fuel vapor is normal.