JPH06117333A - Failure diagnosis device of evaporation purge system - Google Patents

Abstract

PURPOSE:To constantly carry out correct failure judgement without being influenced by flow common difference of a purge control valve, pressure loss difference of a canister, change with the elapse of time and others in a failure diagnosis device of an evaporation purge system. CONSTITUTION:A regulation means M9 regulates flow between the side of a fuel tank M1 of a vapor passage M2 and the side of a canister M3. A pressure detection means M10 separately detects pressure on the side of the fuel tank M1 and the side of the canister M3 respectively by the regulation means M9 of the vapor passage M2. A judgement value generation means 11 regulates flow of the vapor passage M2 by the regulation means M9 at the time of introducing negative pressure of a negative pressure introduction means and generates a judgement value used by a judgement means 8 in accordance with detected pressure on the side of the canister M3 of the vapor passage M2 detected by the pressure detection means M10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosing device for an evaporative purge system, and more particularly to adsorbing evaporated fuel (vapor) of an internal combustion engine to an adsorbent in a canister, and adsorbing the adsorbed fuel to an internal combustion engine under a predetermined operating condition. The present invention relates to a failure diagnostic device for an evaporative purge system that discharges (purge) to an intake system of an engine and burns it.

[0002]

2. Description of the Related Art Fuel (vapor) evaporated in a fuel tank
In order to prevent air from being released to the atmosphere, each part is hermetically sealed, and the vapor is once adsorbed by the adsorbent in the canister, and the fuel adsorbed while the vehicle is running is sucked into the intake system and burned by evaporative purging. In an internal combustion engine equipped with a system, if the vapor passage is damaged for some reason or if the pipe is disconnected, the vapor is released to the atmosphere, and if the purge passage to the intake system is blocked,
The vapor in the canister overflows, and the vapor leaks into the atmosphere through the air hole in the canister. Therefore, it is necessary to diagnose whether or not such a failure of the evaporative purge system has occurred.

Conventionally, as a failure diagnostic device for an evaporative purge system, there is one disclosed in Japanese Patent Application No. 3-323364. This device introduces the negative pressure of the intake pipe to the evaporative system up to the fuel tank, and diagnoses whether the evaporative system has a failure such as leakage based on the negative pressure value introduced within a predetermined time. .

[0004]

In the conventional apparatus, the negative pressure introduced into the fuel tank within a certain period of time due to fluctuations in the flow rate tolerance of the purge control valve for introducing the intake pipe negative pressure, pressure loss of the canister, and changes over time. The magnitude of pressure fluctuates. Therefore, for example, when the flow rate of the purge control valve is large, the introduced negative pressure becomes large and even if there is a leak, the detected negative pressure becomes large to some extent and it is erroneously judged to be normal. Even if there is no leakage, the negative pressure is small and the failure is erroneously determined, so that there is a problem that an accurate failure determination cannot be performed.

The present invention has been made in view of the above points,
By generating a judgment value for the introduced negative pressure value to the fuel tank from the introduced negative pressure value to the canister side, there is no influence of the flow control tolerance of the purge control valve, the pressure loss difference of the canister, or the change over time, and it is always accurate. It is an object of the present invention to provide a failure diagnosis device for an evaporative purge system capable of judging a failure.

[0006]

As shown in FIG. 1, a failure diagnosing device for an evaporative purge system according to the present invention causes evaporated fuel from a fuel tank M1 to be adsorbed by an adsorbent in a canister M3 through a vapor passage M2. Of the adsorbed fuel in the canister of the internal combustion engine through the purge passage M4
In the evaporative purging system for purging to No. 6, the determination means M8 makes a failure determination based on the pressure of the evaporation system detected by introducing the intake negative pressure to the evaporation system up to the fuel tank by the negative pressure introducing means M7. In the failure diagnosing device, the regulating means M9 for regulating the flow of the vapor passage M2 between the fuel tank M1 side and the canister M3 side, and the pressures on the fuel tank side and the canister side are separately detected by the vapor passage regulating means. Pressure detection means M10,
When the negative pressure is introduced by the negative pressure introducing means, the regulation means M9 regulates the circulation of the vapor passage, and the determination value generating means M11 generates a determination value based on the detected pressure on the canister side of the vapor passage detected by the pressure detecting means. Have.

[0007]

The regulating means M9 regulates the flow of the vapor passage M2 between the fuel tank M1 side and the canister M3 side.

The pressure detecting means M10 separately detects the pressures on the fuel tank side and the canister side from the vapor passage regulating means.

The judgment value generating means M11 judges on the basis of the detected pressure on the canister side of the vapor passage detected by the pressure detecting means by regulating the circulation of the vapor passage by the regulating means M9 when the negative pressure is introduced by the negative pressure introducing means. A judgment value used in the means M8 is generated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows the system configuration of the device of the present invention.
In the figure, the fuel tank 21 comprises a main tank 21a and a sub tank 21b. The sub tank 21b is inside the main tank 21a, communicates with the main tank 21a, and has the fuel pump 22 arranged therein. Also,
A rollover valve 23 is provided above the fuel tank 21. The rollover valve 23 is provided to prevent fuel from flowing outside when the vehicle rolls over.

The fuel pump 22 is connected to a fuel injection valve 26 via a pipe 24 and a pressure regulator 25, respectively. The pressure regulator 25 is provided to keep the fuel pressure constant, and the fuel injector 26
The surplus fuel that is not injected in is returned to the sub tank 21b through the return pipe 27.

The upper portion of the fuel tank 21 has a canister 30 through a vapor passage and an internal pressure control valve 29, respectively.
Is in communication with. The internal pressure control valve 29 is the check ball 2
9a and spring 29b, and spring 29b
Applies a biasing force to the check ball 29a in the right direction in the drawing, and the spring 29b keeps the internal pressure of the fuel tank 21 at a predetermined value (for example, 250 mmAq) or less.

The canister 30 has an activated carbon 30a as an adsorbent therein and has an atmosphere introduction hole 30 opened to the outside.
This is a known configuration in which b is formed.

The canister 30 has a purge passage 32.
And a purge control valve 33, which is a solenoid valve (VSV), are connected to the intake passage 36 at a position downstream of the throttle valve 35. The upstream side of the throttle valve 35 has an air cleaner (A
C) 34 is provided.

The throttle valve 35 is a valve whose opening is controlled by the amount of depression of the accelerator pedal operated by the driver.
Detected by 7. The fuel temperature sensor 40 detects the fuel temperature in the fuel tank 21, the intake air temperature sensor 41 detects the intake air temperature in the intake passage 36, and the fuel remaining amount sensor 42.
Detects the remaining amount of fuel in the fuel tank 21 and supplies respective detection signals to the microcomputer 38.

The vapor passage between the fuel tank 21 and the internal pressure control valve 29, and the internal pressure control valve 29 and the canister 30.
The vapor passage between them is communicated with a bypass control valve 45 which is a solenoid valve (VSV). When the bypass control valve 45 is opened, the internal pressure control valve 29 is bypassed and the vapor passage 28 is connected to the fuel tank 21 and the canister 30. Connect directly between the two. Further, the three-way switching valve 46 includes the fuel tank 21 and the internal pressure control valve 2
9, a vapor passage between the internal pressure control valve 29 and the canister 30, and a pressure sensor 31 are connected, and the three-way switching valve 46 is turned on by the control of the microcomputer 38. Sometimes fuel tank 2
The vapor passage on the first side is connected to the pressure sensor 31, and the vapor passage on the canister 30 side is connected to the pressure sensor 31 when it is off. The pressure sensor 31 is a kind of strain gauge that detects the strain of the silicon wafer with a bridge circuit, and measures the pressure difference between the pressure in the vapor passage connected by the three-way switching valve 46 and the atmospheric pressure.

The microcomputer 38 is an electronic control unit for controlling the evaporative purge system, and comprises the pressure change detecting means 17, the judging means 18, and the diagnostic period extending means 20.
Each is realized by software operation, and at the time of abnormality determination, the warning light 39 is turned on to notify the driver of the abnormality occurrence.

The microcomputer 38 has a known hardware configuration as shown in FIG. 2, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 3, a microcomputer 38 includes a central processing unit (CPU) 50, a read only memory (ROM) 51 storing a processing program, and a random access memory (RAM) 5 used as a work area.
2. Backup R that retains data even after the engine is stopped
The AM 53, an input interface circuit 54 with a multiplexer, an input / output interface circuit 55, an A / D converter 56, and the like are connected to each other via a bidirectional bus 57.

The A / D converter 56 sequentially fetches the pressure detection signal from the pressure sensor 31, the detection signal from the throttle position sensor 37, and the detection signals of the fuel temperature sensor and the intake air temperature sensor through the input interface circuit 54, respectively. It is converted from analog to digital and sent to the bus 57 sequentially. I / O interface circuit 5
The reference numeral 5 sends a signal from the throttle position sensor 37 to the bus 57, while the fuel injection valve 26 and the purge control valve 3 are provided.
3, control signals are selectively sent to the warning light 39, the bypass control valve 45, and the three-way switching valve 46 to control them.

Next, the operation of the normal evaporative purge of the system shown in FIG. 2 will be described. When an ignition switch (not shown) is turned on, the fuel pump 22 shown in FIG.
The fuel in the sub-tank 21b is activated by the operation of
Is discharged to the pressure regulator 25 through the pressure regulator 25 and is sent to the fuel injection valve 26 at a constant pressure there. The fuel injection time from the microcomputer 38, the fuel injection valve 26
Is injected into the intake passage 36 from. The surplus fuel is returned to the sub tank 21b via the return pipe 27.

On the other hand, the evaporated fuel (vapor) generated in the fuel tank 21 reaches the internal pressure control valve 29 through the vapor passage 28 because the bypass control valve 45 is open. Here, when the tank internal pressure is lower than the pressure set by the internal pressure control valve 29 (for example, 250 mmAq), the spring 29
The check ball 29a is located at the position shown in the figure by the spring force of b and blocks the vapor passage 28, so that the vaporized fuel is prevented from being delivered to the canister 30.

For example, when the engine is cold-started, the tank internal pressure is close to the atmospheric pressure, and immediately after that, the fuel volume is reduced by the fuel consumption by the fuel injection valve 26, so that the tank internal pressure once decreases to a negative pressure. However, thereafter, the fuel temperature gradually rises due to the exhaust heat, the amount of evaporated fuel generated increases, the tank internal pressure rises in the positive pressure direction, and reaches the set pressure by the internal pressure control valve 29.

When the evaporated fuel is further generated and the tank internal pressure becomes equal to or higher than the set pressure, the check ball 29a of the internal pressure control valve 29 is pushed leftward in FIG. 2 against the spring force of the spring 29b, As a result, the evaporated fuel is sent into the canister 30 through the vapor passage 28 and the internal pressure control valve 29, and is adsorbed by the activated carbon 30a inside. When the evaporated fuel is delivered to the canister 30, the tank internal pressure decreases, and when the tank internal pressure becomes equal to or lower than the set pressure, the internal pressure control valve 29 is closed again.

As described above, when there is no leakage in the vapor passage 28 or the fuel tank 21, the evaporated fuel is adsorbed by the activated carbon 30a in the canister 30 through the internal pressure control valve 29 as described above. Immediately after the engine is started, the purge control valve 33 is closed because the purge control condition is not satisfied.

The above-mentioned purge control conditions are operating conditions in which the adverse effect on operability and exhaust emission can be minimized even if the air-fuel ratio becomes rough due to purging. For example, the engine cooling water temperature is above a predetermined temperature and the air-fuel ratio is set to a target value. During feedback control of fuel injection, the intake air amount is not less than a predetermined value, fuel cut is not performed, etc. When all of these are satisfied, the microcomputer 38 determines that the purge control conditions are satisfied.

If it is determined that the purge control condition is satisfied, the microcomputer 38 opens the purge control valve 33. Then, due to the negative pressure in the intake passage 36, the atmosphere is introduced into the canister 30 from the atmosphere introduction port 30b, the fuel adsorbed on the activated carbon 30a is desorbed, and the air is introduced through the purge passage 32 and the purge control valve 33, respectively. The evaporated fuel is sucked into the passage 36. In addition, the activated carbon 30a is regenerated by the above desorption and prepared for the next vapor adsorption. As a result, the purge flow rate gradually increases.

Next, the failure diagnosis processing executed by the microcomputer 38 in the above system will be described. Figure 4
Shows a flow chart of an embodiment of a failure diagnosis routine. This routine is, for example, an interrupt routine every 32 msec.

In the figure, in step S10, it is determined whether or not the end flag is set to 1, and the end flag = 1.
In the case of 9, the process ends, and when the end flag ≠ 1, the process proceeds to step S12. The end flag and the later-described determination counter are reset to 0 at the time of starting.

In step S12, air-fuel ratio feedback control is executed, and it is determined whether or not a failure diagnosis execution condition such as whether the cooling water temperature is 80 ° C. or higher is satisfied, and if so, the process proceeds to step S14. If not satisfied, the process ends.

In step S14, the purge control valve 33 is opened (turned on), and in the next step S16, 1 is added to the value of the determination counter. In step S20, it is determined whether or not the value of the determination counter exceeds a predetermined value a. If the determination counter ≦ a, the bypass control valve 45 is closed (OFF) in step S22, and the three-way switching valve 46 in step S24. Is turned off and the vapor passage on the canister 30 side is connected to the pressure sensor 31.
Connect to.

Next, in step S26, it is determined whether or not the value of the determination counter has reached the predetermined value a. If the determination counter ≠ a, the process ends, and if the determination counter = a, the process proceeds to step S28. The predetermined value a is a value corresponding to the time until the engine operating state stabilizes. In step S28, the purge negative pressure P _OFF on the canister 30 side is read based on the detection signal of the pressure sensor 31. Thereafter, in step 30, the bypass control valve 45 is opened to introduce a negative pressure to the fuel tank 21, and in step S32 the three-way switching valve 46 is turned on to connect the vapor passage on the fuel tank 21 side to the pressure sensor 31. . After the execution of step S32, or if the determination counter> a in step S20, the process proceeds to step S34, it is determined whether the value of the determination counter exceeds a predetermined value b (b> a), and if the determination counter ≦ b, When the determination counter> b is completed, the process proceeds to step S36. The predetermined value b is a value for setting the time required for diagnosis (ba).

In step S36, the tank internal pressure P _ON of the fuel tank 21 is read based on the detection signal of the pressure sensor 31.

Next, in step S38, it is determined whether the tank internal pressure P _ON is less than or equal to a determination value obtained by adding a predetermined value α to the purge negative pressure P _OFF . That is, the determination value (P _OFF + α) is set according to the purge negative pressure P _OFF measured through the purge control valve 33 and the canister 30, and the influence including the flow rate tolerance of the purge control valve, the pressure loss difference of the canister, and the change over time is set. It is a value that is set occasionally.

If P _ON ≤ P _OFF + α in step S38, it is determined that there is no leakage, and the warning lamp 39 is turned off in step S40. If P _ON > P _OFF + α, there is leakage and the warning lamp is lit in step S42. . After this, set the end flag to 1
To set the process to end.

FIG. 5 shows a timing chart of the above diagnostic operation. After starting the start-up at time t _0, the value of the determination counter and execution conditions of the failure diagnosis in time t ₁ is satisfied 5
As shown in (A), the purge control valve 33 opens while increasing. After that, the bypass control valve 45 and the three-way switching valve 46 are turned off until the value of the determination counter reaches the predetermined value a, and the pressure sensor 45 is connected to the vapor passage on the canister 30 side. At time t ₂ when the value of the determination counter exceeds the predetermined value a, the bypass control valve 45 and the three-way switching valve 46 are turned on, the pressure sensor 45 is connected to the vapor passage on the fuel tank 21 side, and the value of the determination counter is the predetermined value. At time t ₃ when the value b is exceeded, failure determination is performed.

The judgment value is the purge negative pressure P._OFFTo a predetermined value
Instead of adding α, purge negative pressure P _OFFA predetermined coefficient β
It may be obtained by multiplication and is not limited to the above embodiment.

[0037]

As described above, according to the failure diagnosis device for the evaporative purge system of the present invention, the purge is performed by generating the judgment value for the introduced negative pressure value to the fuel tank from the introduced negative pressure value to the canister side. This is extremely useful in practice because it enables accurate failure determination without being affected by the flow rate tolerance of the control valve, the pressure loss difference of the canister, and the change over time.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a system configuration diagram of the present invention.

FIG. 3 is a configuration diagram of hardware of a microcomputer.

FIG. 4 is a flowchart of an embodiment of a failure diagnosis routine of the present invention.

FIG. 5 is a diagram for explaining the operation of the present invention.

[Explanation of symbols]

 M1,21 fuel tank M2,28 vapor passage M3,30 canister M4,32 purge passage M6,36 intake passage M7 negative pressure introducing means M8 determining means M9 regulating means M10 pressure detecting means M11 determination value generating means 26 fuel injection valve 29 internal pressure Control valve 31 Pressure sensor 33 Purge control valve 38 Microcomputer 39 Warning light 45 Bypass control valve 46 Three-way switching valve

Claims (1)

[Claims] 1. An evaporation purge system for adsorbing evaporated fuel from a fuel tank to an adsorbent in a canister through a vapor passage and purging the adsorbed fuel in the canister into an intake passage of an internal combustion engine through a purge passage. In the failure diagnosis device of the evaporative purge system, which performs failure judgment based on the pressure of the evaporative system detected by introducing the intake negative pressure into the evaporative system up to the tank, the fuel tank side of the vapor passage and the canister side And a pressure detecting means for separately detecting the pressures on the fuel tank side and the canister side of the vapor passage regulating means, and the regulating means when the negative pressure is introduced by the negative pressure introducing means. Judgment value that generates a judgment value based on the pressure detected on the canister side of the vapor passage detected by the pressure detection means by restricting the flow of Trouble diagnosis device for the evaporative emission control system characterized by having a forming means.