JP3139096B2 - Diagnosis device for evaporative fuel control system of vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for a fuel vapor control system for a vehicle, and more particularly, to a canister for providing a passage connecting an intake passage of an internal combustion engine and a fuel tank, and adsorbing and holding the evaporated fuel along the passage. The present invention relates to a diagnostic device for an evaporative fuel control system for a vehicle provided with the above.

[0002]

2. Description of the Related Art Evaporated fuel leaking into the atmosphere from a fuel tank, a float chamber of a vaporizer, etc. contains a large amount of hydrocarbons (HC) and is one of the causes of air pollution. Because of the connection, various techniques for preventing this are known. As a typical example, the fuel vapor in the fuel tank is temporarily adsorbed and held in a canister containing an adsorbent such as activated carbon, and the fuel vapor adsorbed and held in the canister is released (purged) during operation of the internal combustion engine.
There is an evaporation system that supplies the fuel to the internal combustion engine.

As an evaporative fuel control device for an internal combustion engine, there is one disclosed in Japanese Patent Application Laid-Open No. 2-130255. The abnormality detection device for a fuel evaporation prevention device disclosed in this publication is provided with a supply passage for guiding the fuel gas adsorbed by the adsorbent of the canister into the intake pipe by a negative pressure generated in the intake pipe. A control valve for opening and closing the supply passage is provided in accordance with the pressure, and a pressure detecting means for detecting a pressure between the canister and the control valve is provided. An abnormality detecting means for detecting an abnormality in supply of fuel gas to the intake pipe is provided.

[0004] Furthermore, there is one disclosed in Japanese Patent Application Laid-Open No. 3-26862. A self-diagnosis device for a fuel purge system in a fuel tank evaporative gas treatment device disclosed in this publication includes a fuel purge system in the fuel tank evaporative gas treatment device, a means for determining whether or not a fuel purge area is present. Means for detecting the pressure of the purge line, and means for detecting or calculating the boost pressure on the downstream side of the purge fuel introduction section of the intake passage. The detection signal output from each of these detection means provides a fuel purge area. Alternatively, a determination means is provided for determining whether the system is normal or abnormal based on the pressure of the purge line and the boost pressure when it is determined that the system is outside the region.

[0005]

The conventional diagnostic apparatus for a fuel vapor control system for a vehicle has a failure diagnosis function for detecting a so-called leak in which hydrocarbon (HC) generated in a fuel tank leaks to the atmosphere. Some do not have.

As a result, when a leak occurs in the evaporative fuel control system, it is not possible to prevent hydrocarbons (HC) from leaking into the atmosphere, which is a factor of air pollution and is disadvantageous in practical use. There is.

[0007] Further, there is one in which the pressure in the fuel tank, that is, the pressure in the tank, is regulated to a predetermined value or less. As shown in FIG. 6, the intake passage and the fuel tank 116 of the internal combustion engine (not shown)
A canister 122 is provided in the middle of a passage 120 that communicates with the fuel tank 116, and a check valve 128 is provided in the middle of the passage 120 between the canister 122 and the fuel tank 116.

At this time, even if the check valve 128 regulated below the regulation value is used, in order to minimize the generation of evaporative fuel from the fuel tank as much as possible, check as much as possible without exceeding the regulation value. I want to increase the valve setting.

However, there is a fear that the pressure in the tank cannot be maintained below the regulation value due to factors such as a manufacturing error of the check valve and a sudden increase in the pressure in the tank during operation, which is disadvantageous in practical use.

Further, if the check valve is interposed, there is a fear that the pressure inside the tank may fluctuate due to the check valve when detecting the pressure inside the tank, so that the reliability is reduced and the usability is poor.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned disadvantages, the present invention provides an evaporating system for a vehicle having a canister for adsorbing and holding evaporated fuel in a passage connecting an intake passage of an internal combustion engine and a fuel tank. In the diagnostic device of the fuel control system, a check is made to provide an atmosphere opening / closing solenoid valve in the canister, provide a purge solenoid valve between the internal combustion engine and the canister, and adjust the pressure in the tank in the middle of the passage between the fuel tank and the canister. A valve is provided, a bypass passage for bypassing the check valve is provided, a solenoid valve for opening and closing the passage is provided in the middle of the bypass passage, and a pressure sensor communicating with the passage between the fuel tank and the check valve is provided to satisfy a predetermined condition. In order to open the solenoid valve for purging and the solenoid valve for opening and closing the passage to connect the intake passage of the internal combustion engine and the pressure sensor, Then, the atmosphere opening / closing solenoid valve is closed, and when a predetermined condition is satisfied, the purge solenoid valve is closed, and a leak including the canister is determined based on a change in the tank internal pressure at this time. A control unit is provided.

[0012]

According to the invention described above, when predetermined conditions are satisfied, the control section opens the purge solenoid valve and the passage opening / closing solenoid valve to connect the intake passage of the internal combustion engine with the pressure sensor. After that, the atmosphere opening / closing solenoid valve is closed, and when the predetermined condition is satisfied, the purge solenoid valve is closed, and the change in the tank internal pressure at this time is used to determine the leak including the canister, and to evaluate the evaporator. In addition to reliably detecting system leaks, it also prevents hydrocarbons (HC) from leaking from the system to the atmosphere, and also determines solenoid valve failures.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 to FIG. 3 show a first embodiment of the present invention. In FIG. 2, 2 is an internal combustion engine, 4 is an air cleaner, 6 is a throttle valve, 8 is a surge tank, 1
0 is an intake passage, 12 is a combustion chamber, 14 is an exhaust passage, and 16 is a fuel tank. The internal combustion engine 2 has a fuel injection valve 18 provided in the intake passage 10 so as to be directed toward the combustion chamber 12. The fuel injection valve 18 is connected to the fuel tank 16 by a fuel passage (not shown).

The fuel in the fuel tank 16 is supplied to a fuel injection valve 18 via a fuel passage by a fuel pump (not shown), and is supplied to the combustion chamber 12 together with air to be burned. The exhaust gas generated by the combustion is discharged through the exhaust passage 14.

An intake passage 10 for the internal combustion engine 2, for example, a passage 20 for connecting the surge tank 8 and the fuel tank 16 downstream of the throttle valve 6 is provided, and a canister 22 for adsorbing and holding the evaporated fuel is provided in the middle of the passage 20. .

The passage 20 is formed by a first passage 24 connecting the fuel tank 16 and the canister 22 and a second passage 26 connecting the canister 22 and the intake passage 10.

A third solenoid valve 42 for opening and closing the atmosphere, which is a solenoid valve for opening and closing the atmosphere, is provided in the canister 28. A check valve 28 for adjusting the pressure in the tank is provided in the first passage 24, a bypass passage 30 for bypassing the check valve 28 is provided, and a passage opening / closing solenoid valve serving as a passage opening / closing electromagnetic valve is provided in the bypass passage 30. 1 solenoid valve 3
2, a pressure sensor 34 communicating with the first passage 24 between the fuel tank 16 and the check valve 28 is provided. When a predetermined condition is satisfied, the purge second solenoid valve 40 and the passage opening / closing first When the solenoid valve 32 is opened to control the communication between the intake passage 10 of the internal combustion engine 2 and the pressure sensor 34, the third solenoid valve 42 for opening and closing the atmosphere is closed. The second solenoid valve for purge 40 is closed, and a control unit 36 for determining a leak including the canister 28 based on a change in the tank internal pressure at this time is provided.

More specifically, a check valve 28 is provided in the first passage 24 between the fuel tank 16 and the canister 22. The check valve 28 sets the pressure in the fuel tank 16 and the pressure in the canister 22 to predetermined pressures,
6 to reduce the amount of hydrocarbons (HC) generated.

A first solenoid valve 32 is provided in parallel with the check valve 28.

The pressure sensor 34 is, as shown in FIG.
First passage 2 between check valve 28 and fuel tank 16
4, the pressure detection passage 3
8 has been contacted.

The control unit 36 includes a first solenoid valve 32 for opening and closing a passage, a pressure sensor 34, a second solenoid valve 40 for purging provided in the middle of the second passage 26, and an air opening and closing for the canister 22. The third solenoid valves 42 are connected to each other.

Then, the control unit 36 determines a predetermined condition,
That in order to reduce the influence of the exhaust gas and drivability, for example the water temperature Tw is, Tw> Tw _2, Tw _2: set water temperature vehicle speed V, V ₁ ≦ V ≦ V _2, V _1: first setting vehicle speed V ₂ : Second set vehicle speed The vehicle speed fluctuation △ ν for t seconds is △ ν <ν, ν: Set vehicle speed fluctuation The idle switch (ID SW) is in the OFF state, and the tank pressure (at gauge pressure) P is P> P
t, Pt: When all of the set tank pressures (at the gauge pressure) are satisfied, it is determined that the detection start condition has been satisfied, and the first solenoid valve 32 is opened to connect the intake passage 10 and the pressure sensor 34. Then, the presence or absence of a leak is detected.

Next, the operation will be described with reference to the control flowchart of the diagnostic device of the evaporative fuel control system shown in FIG.

During the start operation of the internal combustion engine 2, the program of the control flowchart starts (100).

Then, it is determined whether the detection start condition is satisfied (102). That is, the predetermined condition serving water temperature Tw is, Tw> Tw _2, Tw _2: set water temperature vehicle speed V, V ₁ ≦ V ≦ V _2, V _1: first setting vehicle speed V _2: vehicle speed of the second set speed t seconds Fluctuation △ ν, △ ν <ν, ν: set vehicle speed fluctuation Idle switch (ID SW) is in OFF state, tank pressure (at gauge pressure) P, P> P
t, Pt: It is determined whether or not all of the set tank pressures (at the gauge pressure) are satisfied.

When the determination (102) is NO, the determination is repeated until the determination (102) becomes YES. When the determination (102) is YES, the first solenoid valve 32 is turned on, that is, opened. (104).

At this time, the fuel tank 16 and the canister 2
2, and the pressure in the tank changes from the plus (+) side to the minus (-) side.

Whether the decrease in the tank internal pressure P is greater than the first set change amount ΔP ₁ , whether a predetermined first time Δt _{1 has} elapsed since the detection start condition was satisfied, inner pressure P for determining whether or not to satisfy any one of the determination of whether it is smaller than the first set value P ₁ (106)
I do.

If the determination (106) is NO, the process returns to the ON operation (104) of the first solenoid valve 32, and
If the determination (106) is YES, the third solenoid valve 42 is turned off, that is, closed (108).

Next, it is determined whether or not the decrease in the tank internal pressure P is larger than the second set change amount ΔP ₂ , and a predetermined second time Δt after a predetermined first time Δt ₁ has elapsed. ₂ is whether or not elapsed, tank pressure P is for determining whether or not to satisfy any one of the determination of whether it is smaller than the second set value P ₂ (110)
I do.

If the determination (110) is NO, the third solenoid valve 42 is turned off (10
Returning to 8), if the judgment (110) is YES, the second purge solenoid valve 40 is turned off, that is, closed (112).

At this time, the inside of the fuel tank is shut off from the outside, but the pressure in the tank gradually rises so as to approach the atmospheric pressure, and a leak in the evaporative fuel control system is determined from the pressure change at this time.

In other words, when the evaporative system has a leak equivalent to φα (about φ1) or more, the set value α obtained from the set change amount / time of the tank pressure in the range from the tank pressure P ₂ to P _3. Indeed third predetermined amount of change in the detected tank pressure △ P _3/3 hours △ whether a value obtained from t ₃ is less also, tank when there is a leak in the third hour △ t ₃ Judgment as to whether or not one of the judgments as to whether the set change amount ΔP _{3 of the} tank pressure is smaller than the set change amount ΔP of the internal pressure is satisfied (114).
I do.

If the determination (114) is NO, that is, if the determination is NG, a failure diagnosis lamp (not shown) is turned on (1).
16) to notify that a failure has occurred.

If the determination (114) is YES, that is, if the determination is OK, the first solenoid valve 3 for opening and closing the passage is opened.
2 is turned off, that is, closed, the third solenoid valve 42 for opening and closing the atmosphere is turned on, that is, opened, and the second solenoid valve 40 for purging is turned on, that is, opened (118).

Then, the program of the control flowchart of the diagnostic device of the evaporative fuel control system is terminated (120).
Let it.

Thus, the set value (α, ΔP) under the condition where the leak is present can be set in advance, and the presence or absence of the leak can be determined by comparing with the detected value, so that the leak of the evaporative system can be reliably detected. In addition, it is possible to prevent leakage of hydrocarbons (HC) from the system to the atmosphere, and to eliminate one factor of air pollution, which is practically advantageous.

Further, in a device for determining the presence or absence of a leak, it is possible to diagnose failures of the first to third solenoid valves 32, 40 and 42.

Further, since the configuration of the diagnostic device of the evaporative fuel control system is simple, the cost can be reduced, and
In addition to being economically advantageous, the time for failure diagnosis is shorter than that of the conventional one, and the usability can be improved.

FIGS. 4 and 5 show a second embodiment of the present invention. In the second embodiment, parts that perform the same functions as in the first embodiment will be described with the same reference numerals.

The features of the second embodiment are as follows.

That is, the passage 20 is connected to a first passage 24 which connects the fuel tank 16 to the canister 22.
Second passage 2 that connects canister 22 and intake passage 10
6 is formed. A separator 50 is provided in the middle of the first passage 24. Reference numeral 52 denotes a rollover valve provided in the fuel tank 16.

A check valve 28 is provided in the first passage 24, and a bypass passage 30 is provided to bypass the check valve 28.
A first solenoid valve 32 serving as a passage opening / closing solenoid valve in the middle
And a first valve between the fuel tank 16 and the check valve 28 is provided.
A pressure sensor for communicating with the passage; and a control unit for opening the first solenoid valve when the predetermined condition is satisfied, and controlling the communication between the intake passage of the internal combustion engine and the pressure sensor. 54 is provided.

More specifically, a check valve 28 is provided in the first passage 24 between the fuel tank 16 and the separator 28. The check valve 28 sets the pressure in the fuel tank 16 and the pressure in the canister 22 to predetermined pressures,
6 to reduce the amount of hydrocarbons (HC) generated.

A first solenoid valve 32 is provided in parallel with the check valve 28.

The pressure sensor 34 is, as shown in FIG.
First passage 2 between check valve 28 and fuel tank 16
4, the pressure detection passage 3
8 has been contacted.

The control unit 54 includes a first solenoid valve 32 for opening and closing the passage, a pressure sensor 34, a second solenoid valve 40 for purging provided in the middle of the second passage 26, and an opening and closing for the atmosphere of the canister 22. The third solenoid valves 42 are connected to each other.

The control unit 54 opens the first solenoid valve 32 when the pressure in the tank exceeds the set value, and opens the first solenoid valve 32 when the pressure in the tank is equal to or less than the set value. The closed state is maintained.

The control unit 54 opens the passage opening / closing first solenoid valve 32 and then temporarily opens the purge second solenoid valve 40 when checking the airtightness.

When the pressure in the fuel tank 16 rises to a value exceeding the set value, the control unit 54 opens the first solenoid valve 32 to connect the intake passage 10 with the fuel tank 16, When the internal pressure of the fuel tank 16 decreases to the set value or less, the control unit 54 closes the first solenoid valve 32 to control the internal tank pressure to the set value or less. Thus, the pressure control accuracy can be made high, which is practically advantageous.

Further, when checking the airtightness, FIG.
As shown in the figure, the first solenoid valve 32 is opened when the third solenoid valve 42 for opening and closing the atmosphere is closed. When the pressure sensor 34 is opened, the intake passage 10 is communicated with the pressure sensor 34 so that a negative pressure can be applied to the pressure sensor 34.

Furthermore, since the airtightness can be checked, that is, the presence or absence of a leak can be determined,
As in the case of the embodiment, the leak of the evaporation system can be reliably detected, the leak of hydrocarbon (HC) from the system to the atmosphere can be prevented, and one factor of air pollution can be eliminated, which is practically advantageous. It is.

Each of the first to third solenoid valves 3
By being able to diagnose failures of 2, 40, and 42, the usability of the apparatus can be improved.

The present invention is not limited to the above-described first and second embodiments, but can be applied to various modifications.

For example, in the first embodiment of the present invention, the opening degree of the second solenoid valve for purge is set to 50 duty between the predetermined first time Δt ₁ and the second time Δt _2.
% And the opening degree of the second solenoid valve for purge at the third time Δt ₃ was set to 0 duty%.
The opening degree of the purge second solenoid valve at the predetermined first time Δt ₁ is set to 50 duty%, and the second time Δt ₂
The opening degree of the second solenoid valve for purging at the time is set to a predetermined value Xduty%, and the opening degree of the second solenoid valve for purging at the third time Δt ₃ is set to 0 duty.
%.

[0057]

As described above in detail, according to the present invention, the canister is provided with an atmosphere opening / closing solenoid valve, the purge solenoid valve is provided between the internal combustion engine and the canister, and the tank is provided in the passage between the fuel tank and the canister. A check valve for adjusting the internal pressure is provided, a bypass passage for bypassing the check valve is provided, a passage opening / closing solenoid valve is provided in the middle of the bypass passage, and a pressure sensor communicating with a passage between the fuel tank and the check valve is provided. When the conditions are satisfied, the purge solenoid valve and the passage opening / closing solenoid valve are opened to control the communication between the intake passage of the internal combustion engine and the pressure sensor, and then the atmosphere opening / closing solenoid valve is closed. When satisfied, a purge solenoid valve was closed, and a control unit for judging a leak including the canister based on a change in the tank internal pressure at this time was provided. It is possible to determine the presence or absence of click, with can reliably detect the leakage of the evaporative system, can prevent leakage of hydrocarbons to the atmosphere (HC) from the system,
It can eliminate one factor of air pollution. In addition, the failure of the solenoid valve can be determined, and the usability can be improved.

[Brief description of the drawings]

FIG. 1 is a control flowchart of a diagnostic device of an evaporative fuel control system according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a diagnostic device of the fuel vapor control system.

FIG. 3 is a time chart of a diagnostic device of the fuel vapor control system.

FIG. 4 is a schematic diagram of a diagnostic device for an evaporative fuel control system according to a second embodiment of the present invention.

FIG. 5 is a time chart of a diagnostic device of the fuel vapor control system.

FIG. 6 is a schematic enlarged view of a fuel tank portion showing a conventional technique of the present invention.

[Explanation of symbols]

 2 internal combustion engine 10 intake passage 14 exhaust passage 16 fuel tank 20 passage 22 canister 24 first passage 26 second passage 28 check valve 30 bypass passage 32 first solenoid valve 34 pressure sensor 36 control unit 38 pressure detection passage 40 second solenoid valve 42 3rd solenoid valve

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-203039 (JP, A) JP-A-5-33732 (JP, A) JP-A-53-106357 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) F02M 25/08 301 F02M 25/08

Claims (1)

(57) [Claims] In the diagnostic apparatus according to claim 1 an internal combustion engine vehicle evaporative fuel control system having an intake passage and a fuel tank and a canister for holding adsorbing evaporative fuel during passage to contact of the air opening and closing solenoid valves provided in the canister The above
A purge electromagnetic valve is provided between the fuel engine and the canister, a check valve is provided in the passage between the fuel tank and the canister to adjust the pressure in the tank, a bypass passage is provided to bypass the check valve, and a passage is provided in the bypass passage. An opening / closing solenoid valve is provided, and a pressure sensor communicating with a passage between the fuel tank and the check valve is provided. When a predetermined condition is satisfied, the purge solenoid valve and the passage opening / closing solenoid valve are opened to open the internal combustion engine. Control to communicate the intake passage and the pressure sensor , then close the atmospheric opening / closing solenoid valve,
When the specified conditions are satisfied, the purge solenoid valve is closed.
The change in the tank internal pressure at this time causes the canister
A diagnostic device for an evaporative fuel control system for a vehicle, further comprising a control unit for determining a leak including the following .