JP2748635B2 - Self-diagnosis device in fuel evaporative gas diffusion prevention device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a self-diagnosis device in a fuel evaporative gas diffusion prevention device.

[Prior art] Conventionally, a fuel evaporation gas diffusion prevention device has
As shown in JP-A-22066 and JP-A-58-84360, a pressure sensor or the like attached to a fuel tank (or in a passage from the fuel tank to the canister) is used.
The state of the fuel evaporative gas generated from the fuel tank is detected.

[Problems to be Solved by the Invention] However, when the sensor for detecting the state of the fuel evaporative gas fails, the fuel evaporative gas cannot be detected, and control such as purge control cannot be performed.

An object of the present invention is to provide a self-diagnosis device capable of reliably detecting an abnormality of an evaporative gas state detection sensor.

Means for Solving the Problems As shown in FIG. 1, the present invention accommodates an adsorbent for adsorbing fuel evaporative gas from a fuel tank and introducing the fuel evaporative gas into an intake passage of an internal combustion engine. A canister, an evaporative gas state detecting means for detecting a state of fuel evaporative gas in the fuel tank, a first state in which the fuel tank is in a state equal to the atmospheric pressure, and intake air from the internal combustion engine in the fuel tank. Switching means for switching to a second state in which a negative pressure is introduced from the road; and a change in the fuel evaporative gas state by the evaporative gas state detecting means when the switching is performed by the switching means. The gist of the present invention is a self-diagnosis device in a fuel evaporative gas diffusion prevention device, comprising: a determination unit for determining; and a warning unit for warning when the determination unit determines that there is an abnormality. It is intended to.

[Action]

Accordingly, the switching means switches between a first state in which the inside of the fuel tank is equal to the atmospheric pressure and a second state in which a negative pressure from the intake passage from the fuel engine is introduced into the fuel tank. Based on the change of the fuel evaporative gas state by the evaporative gas state detecting means at that time, the judging means judges whether or not the evaporative gas state detecting means is abnormal.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic configuration diagram of the fuel evaporative gas diffusion preventing device of the present embodiment. An engine 1 as an internal combustion engine is mounted on the vehicle, and an air cleaner 3 is connected to an intake pipe 2 (intake path) of the engine 1. Then, air is taken in through the air cleaner 3. A throttle valve 5 that opens and closes in conjunction with an accelerator pedal 4 is provided in the intake pipe 2. The intake pipe 2 is connected to a piston 7 through an intake valve 6.
And a combustion chamber 9 formed by the engine body 8. The combustion chamber 9 is connected to an exhaust pipe 11 via an exhaust valve 10.

On the other hand, a liquid fuel is stored in the fuel tank 12, and the fuel is pressurized by a fuel pump 13 and supplied to a fuel injection valve 14 provided in the intake pipe 2. Fuel is injected by opening and closing the fuel injection valve 14.

A canister 16 is connected to the fuel tank 12 through a communication pipe 15, and an activated carbon 18 as an adsorbent for adsorbing fuel gas is stored in a canister body 17. This activated carbon 18
The fuel evaporative gas generated in the fuel tank 12 is adsorbed through the communication pipe 15. The canister body 17 has an air opening hole 19 that is open to the atmosphere, so that air can be sucked into the inside.

In the middle of the communication pipe 15, a three-way solenoid switching valve is used as switching means
The three-way electromagnetic switching valve 20 is connected to the intake pipe 2 via a communication pipe 21. That is, the first of the three-way electromagnetic switching valve 20
The connection portion A is connected to the fuel tank 12 side communication tube 15, the second connection portion B is connected to the canister 16 side communication tube 15, and further,
The third connection portion C is connected to the intake pipe 2 side communication pipe 21.
The three-way electromagnetic switching valve 20 is connected to the fuel tank 12 and the canister.
The state can be switched between a first state in which the fuel tank 12 and the intake pipe 2 communicate with each other.

Further, the canister 16 and the intake pipe 2 are connected by a purge pipe 22, and a purge valve 23 is provided in the middle of the purge pipe 22. As the purge valve 22, an electromagnetic on-off valve is used.

The fuel tank 12 is provided with a pressure sensor 24 as evaporative gas state detecting means, and the pressure sensor 24 detects the pressure of the fuel evaporative gas in the fuel tank 12.

A control circuit 25 serving as a judging means incorporating a microcomputer includes an opening signal of the throttle valve 5 from a throttle sensor (not shown) and an engine speed from a speed sensor (not shown) for detecting the speed of the engine 1. A signal and an intake air amount signal from an intake amount sensor (not shown) for detecting an intake air amount are input. Then, the control circuit 25 detects the throttle opening, the engine speed, the intake air amount, and the like from these signals, and causes the fuel injection valve 14 to perform the fuel injection at a predetermined injection timing.

Further, the control circuit 25 receives a detection signal from the pressure sensor 24 and controls the purge valve 23 and the three-way electromagnetic switching valve 20. A warning lamp 26 is provided on the instrument panel of the vehicle as warning means, and is connected to the control circuit 25.

Next, the operation of the control circuit 25 configured as described above will be described.

First, the control circuit 25 always turns off the three-way electromagnetic switching valve 20 to the first state (a state in which the fuel tank 12 and the canister 16 communicate with each other). The fuel gas pressure is detected, and the purge valve 23 is adjusted to a predetermined opening by duty control in accordance with the gas pressure. That is, the supply amount of the fuel evaporative gas adsorbed by the activated carbon 18 in the canister 16 to the intake pipe 2 is always kept constant.

FIG. 3 shows a failure diagnosis routine of the pressure sensor 24 performed at predetermined time intervals. FIG. 4 shows the operation timing of the flag F and the counter C used in this routine. The flag F becomes "1" when the mode for failure diagnosis is set, and the counter C measures the time when the three-way electromagnetic switching valve 20 is switched for failure diagnosis.

The control circuit 25 determines in step 100 whether the determination condition has been satisfied. That is, it is determined whether or not the throttle valve 5 is fully closed. If the throttle valve 5 is not fully closed, the control circuit 25 sets the flag F to "0" in step 101 and sets the counter C to "0" in step 102.
Thereafter, the control circuit 25 executes the three-way electromagnetic switching valve 20 in step 103.
Is turned off to bring the fuel tank 12 and the canister 16 into the second state in which they communicate with each other.

If the throttle valve 5 is fully closed at step 100, the control circuit 25 determines at step 104 that the counter C has a predetermined value C0.
It is determined whether or not the flag F is "1" in step 105 because C = 0 is initially set (by the processing in step 102). Since the flag F is not initially “1” (due to the processing in step 101), the control circuit 25 records the measured pressure value of the pressure sensor 24 in the storage area m1 in step 106. Thereafter, the control circuit 25 sets the flag F to "1" in step 107, turns on the three-way electromagnetic switching valve 20 in step 108, and sets the fuel tank 12 and the intake pipe 2 to the second state (fourth state).
The timing of t1 in the figure).

In the next routine, the control circuit 25
At 105, since F = 1, the value of the counter C is incremented by "1" at step 109, and the routine goes to step 108.

When the counter C reaches the predetermined value C0 in step 104, that is, for 3 seconds, the control circuit 25
After turning on 20, at step 110, the measured pressure value of the pressure sensor 24 at that time is recorded in the storage area m2. Thereafter, the control circuit 25 sets the counter C to "0" in step 111, and determines in step 112 whether the absolute value of the difference between the measured pressure value in the storage area m1 and the measured pressure value in the storage area m2 is larger than a predetermined value α. to decide. When the absolute value of the difference between the measured pressure values is larger than the predetermined value α, the control circuit 25 operates normally and determines that the pressure sensor 24 is normal.

That is, from the state in which the canister 16 and the fuel tank 12 communicate with each other and the inside of the fuel tank 12 is at atmospheric pressure, the communication between the negative pressure intake pipe 2 and the fuel tank 12 causes the pressure sensor 24 to communicate. A change in the measured pressure due to causes the pressure sensor 24 to function normally. If the pressure sensor 24 is normal, the control circuit 25 turns off the three-way electromagnetic switching valve 20 in step 103 to turn off the fuel tank 12 and the canister 16.
Are brought into the first state (timing t1 in FIG. 4).

If the absolute value of the difference between the measured pressure values is smaller than the predetermined value α in step 112, the control circuit 25 turns on the warning lamp 26 in step 113, and then proceeds to step 103.

As described above, according to the self-diagnosis device of the present embodiment, the first connection portion A of the three-way electromagnetic switching valve 20 is connected to the fuel tank 12, the second connection portion B is connected to the canister 16, and the third connection portion C Is connected to the intake pipe 2, and the control circuit 25 (determining means) connects the three-way electromagnetic switching valve 20 to the first tank in which the fuel tank 12 communicates with the canister 16.
The state is switched to the second state in which the fuel tank 12 and the intake pipe 2 communicate with each other, and the pressure sensor 24 (evaporation gas state detection means) changes the fuel evaporative gas pressure at that time to determine whether the pressure sensor 24 is abnormal. Is determined, and when it is determined that there is an abnormality, a warning is given by the warning lamp 26 (warning means). As a result, when the pressure sensor 24 that detects the state of the fuel evaporative gas breaks down, the abnormality can be reliably detected.

The present invention is not limited to the above-described embodiment. For example, a pressure sensor
Instead of 24, a gas flow sensor 27 may be used as shown by a chain line in FIG. Note that this gas flow sensor 27
For example, a throttle provided in a gas passage and measuring a gas flow rate by a differential pressure before and after the throttle is used.

[Effects of the Invention] As described in detail above, according to the present invention, an excellent effect of reliably detecting an abnormality of the evaporative gas state detection sensor is exhibited.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims, FIG. 2 is a diagram showing a configuration around an engine of the embodiment, FIG. 3 is a flowchart for explaining the operation of the embodiment, and FIG. It is a time chart shown. M1 is a fuel tank, M2 is an intake path, M3 is a canister, A is a first connection part, B is a second connection part, C is a third connection part, M4 is a three-way valve, M5 is an evaporative gas state detecting means, M6 is Judging means, M7 is warning means.

Claims (2)

(57) [Claims] 1. A canister containing an adsorbent for adsorbing fuel vapor in a fuel tank and introducing the fuel vapor into an intake passage of an internal combustion engine, and detecting a state of the fuel vapor in the fuel tank. Evaporative gas state detecting means; and switching means for switching between a first state in which the inside of the fuel tank is equal to atmospheric pressure and a second state in which a negative pressure from an intake passage from an internal combustion engine is introduced into the fuel tank. Determining means for determining the presence or absence of an abnormality in the evaporative gas state detecting means based on a change in the fuel evaporative gas state by the evaporative gas state detecting means at the time of switching by the switching means; and determining that there is an abnormality in the determining means A self-diagnosis device in a fuel evaporative gas diffusion prevention device, comprising: 2. The evaporative gas state detecting means comprises a pressure sensor, and the judging means comprises a measuring pressure of the pressure sensor in the first state and the second state when switched by the switching means. 2. The self-diagnosis device in the fuel evaporative gas diffusion prevention device according to claim 1, wherein an abnormality is determined when the difference between the values is smaller than a predetermined value.