JP2845079B2 - Evaporative fuel leak diagnostic system for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for diagnosing a leak state of fuel vapor in an internal combustion engine in a system for supplying fuel vapor stored in a fuel tank to an engine intake system.

[0002]

2. Description of the Related Art Conventionally, in order to prevent vaporized fuel vaporized in a fuel tank or the like of a vehicle from being released into the atmosphere and causing environmental destruction, the vaporized fuel adsorbed by an adsorbing means (canister) is prevented. Is provided to the intake passage by utilizing the negative pressure of the intake air of the engine, whereby the vaporized fuel is sucked into the combustion chamber together with the intake air and burned, whereby the fuel is released into the atmosphere. It has been proposed to prevent evaporation of the fuel vapor (Japanese Utility Model Laid-Open No. 1-587).
No. 60, etc.).

[0003] However, in such a device, if a leak hole is formed in the middle of the fuel vapor pipe or a defective seal is formed at the joint of the fuel vapor pipe, the fuel vapor will evaporate into the atmosphere. In some cases, the effect of the device cannot be sufficiently exhibited. So, for example, Environ
mental Protection Agency (EPA) and the California Air Resources Board (CARB)
[California Atmospheric Resources Bureau]), etc., diagnoses whether the amount of fuel vapor leak from the fuel vapor piping etc. is below an allowable value, and takes measures if the amount exceeds the allowable value. It is required to prevent transpiration into the atmosphere beforehand, and a leak diagnostic device and a diagnostic method thereof are proposed.

FIG. 5 shows such a conventional fuel vapor leak diagnosis apparatus. According to FIG. 5, one end of the fuel vapor pipe 2a is connected to the fuel tank 1, and the other end is connected to the canister 3 for adsorbing the fuel vapor. A pressure sensor 6 for detecting the pressure in the fuel vapor pipe is provided in the middle of the fuel vapor pipe 2a. The signal from the pressure sensor 6 is input to the engine control module 50, and the rate of pressure change in the fuel vapor pipe is determined based on the signal.

The engine control module
The reference value 50 stores a determination value for fuel vapor leak diagnosis. By comparing the determination value with the above-described pressure change speed, it is possible to diagnose a fuel vapor leak. One end of the fuel vapor pipe 2b is connected to the canister 3, the other end is connected to the intake passage of the engine, and a purge cut valve 4 is provided on the way. The canister 3 is provided with a drain cut valve 5 that can be opened and communicated with the atmosphere during normal engine operation and when introducing evaporated fuel into the intake passage, and can be closed and shut off from the atmosphere during a leak diagnosis. ing.

With the conventional fuel vapor leak diagnostic apparatus having the above-mentioned structure, the fuel vapor pipes 2a and 2b are communicated only with the intake system of the engine, and the change of the signal of the pressure sensor 6 in the fuel vapor supply system is monitored. A leak state of the evaporated fuel is performed based on the state. By installing a check valve 7 in the evaporative fuel pipe 2a between the fuel tank 1 and the canister 3, the check valve 7 opens at a predetermined pressure and sends the evaporative fuel to the canister 3, and the evaporative fuel is below the predetermined pressure. To prevent the fuel vapor from flowing back into the fuel tank 1 so that the fuel vapor is surely adsorbed to the canister 3. Further, in order to prevent damage to the fuel tank 1 when the inside of the fuel tank 1 becomes negative pressure due to running on a slope or the like, the evaporated fuel is returned to the fuel tank 1,
In some cases, the fuel tank 1 is protected. In this case, the check valve 7 is a two-way check valve that opens in each direction when a predetermined pressure is reached.

Therefore, in the case where the check valve 7 is interposed as described above, when performing a leak diagnosis,
When the pressure in the evaporative fuel pipe becomes a predetermined negative pressure, the check valve 7 operates so as to regulate the negative pressure. As a result, there is a possibility that an accurate change in pressure cannot be detected and an accurate leak determination cannot be made.

For this purpose, as shown in FIG. 6, a bypass passage 30 for bypassing the check valve 7 and a bypass valve 31 composed of an electromagnetic solenoid valve are added in the middle of the bypass passage 30, so that the fuel vapor is removed. In the leak diagnosis, the bypass valve 31 is opened and the check valve 7 is bypassed to eliminate the influence of the valve opening pressure of the check valve 7, thereby preventing an error from occurring in the leak diagnosis. There is also.

The bypass valve 31 is a diaphragm-type valve that is opened by introducing an intake negative pressure. When a leak is determined, the intake negative pressure is introduced to ensure communication with the bypass passage 30. Is also conceivable. In this case as well, it is necessary to select whether or not to introduce the intake negative pressure by using an electromagnetic solenoid valve.

[0010]

However, in such a conventional device for diagnosing the leak of fuel vapor, the bypass passage is not provided.
When a bypass valve 31 composed of an electromagnetic solenoid valve is added in the middle of 30,
Even when the solenoid valve 31 for selecting the introduction of the intake negative pressure is provided by using the diaphragm valve 31 as the diaphragm valve, an electromagnetic solenoid valve is required.

Providing an electromagnetic solenoid valve here leads to an increase in the weight of the entire leak diagnostic device, a complicated mechanism, and an increase in cost. In view of the above, the present invention has been made in view of such a conventional problem. In an evaporative fuel leak diagnostic device, a check valve interposed in an evaporative fuel supply system is opened without providing an electromagnetic solenoid valve. It is an object of the present invention to provide a valve for an evaporative fuel leak diagnostic device of an internal combustion engine, which can eliminate the influence of pressure and accurately perform evaporative fuel leak diagnosis.

[0012]

As shown in FIG. 1, an apparatus for diagnosing evaporative fuel leakage of an internal combustion engine according to the present invention, as shown in FIG. Pressure detecting means for detecting the pressure in the fuel supply system; and connecting the evaporative fuel supply system to only the intake system of the engine, and detecting a leak in the evaporative fuel supply system based on a subsequent pressure change in the evaporative fuel supply system. In the evaporative fuel leak diagnostic device for an internal combustion engine, the evaporative fuel leak diagnostic device includes a diaphragm for partitioning the inside of the casing into a pressure chamber and a negative pressure chamber with a diaphragm, and adsorbing the pressure chamber. Opening an open port connected to the means and an inflow port connected to the fuel tank, and opening the open port facing the diaphragm so as to be opened and closed by the diaphragm; A return spring that elastically urges the diaphragm in the contraction direction of the pressure chamber to close the communication between the open port and the inflow port, and a negative pressure introduction port connected to the atmosphere opening side of the suction means; A valve with an opening is interposed.

[0013]

In this configuration, when the fuel vapor leak diagnosis of the internal combustion engine is not performed, only when the fuel vapor pressure in the fuel tank becomes high, the diaphragm opens and opens against the elastic urging force of the return spring. The port and the inflow port are communicated with each other, and the fuel vapor is adsorbed by the adsorbing means.

When performing a fuel vapor leak diagnosis of the internal combustion engine, the fuel vapor supply system and the engine intake system are connected to each other, and the inside of the fuel vapor supply system is sucked by the engine negative pressure. The negative pressure of the engine also acts on the open side of the adsorption means to the atmosphere, but the negative side of the atmosphere is connected to the negative pressure chamber of the valve by the negative pressure introduction port. It will also act on the room.

Therefore, the open port and the inflow port, whose communication has been closed by the diaphragm, communicate with each other by the movement of the diaphragm against the elastic biasing force of the return spring due to the application of the engine negative pressure. The evaporative fuel supply system always communicates with the engine intake system. Therefore, by the evaporative fuel leak diagnosis means,
When diagnosing a leak state of the evaporative fuel supply system based on a pressure change in the evaporative fuel supply system, a check valve interposed in the evaporative fuel supply system is interposed to adjust the pressure of the check valve. Even if the check valve operates, the fuel supply system and the engine intake system always communicate with each other regardless of the operation of the check valve. Leak diagnosis can be performed with high accuracy.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the same parts as those in the conventional example shown in FIG. 5 are denoted by the same reference numerals. In FIG. 2, one end of an evaporative fuel pipe 2a is connected to an upper wall of the fuel tank 1, and the other end of the evaporative fuel pipe 2a is connected to one side 3f of a canister 3 for temporarily absorbing the evaporative fuel. Have been. A pressure sensor 6 for detecting the pressure in the fuel vapor pipe is provided in the middle of the fuel vapor pipe 2a. Here, the pressure sensor 6 constitutes a pressure detecting means.

As a configuration according to the present invention, a fuel check valve (hereinafter, referred to as FCV) 10 is interposed in the fuel vapor pipe 2a downstream of the pressure sensor 6, and the FCV 10 is first referred to FIG. The configuration will be described. The FCV 10 divides the inside of the casing 11 into two chambers by a diaphragm 13 and is divided into a pressure chamber 15 and a negative pressure chamber 17.

The pressure chamber 15 is provided between the fuel tank 1 and the inflow port 21.
And an evaporative fuel pipe 2a. The adsorbing means 3 is connected to the same side 3f to which one end of the fuel vapor pipe 2b is connected by the open port 23 and the fuel vapor pipe 2a, and the end 23a of the open port 23 is connected to the diaphragm 13 It is open to face the valve element 14 attached to.

The negative pressure chamber 17 has a return spring 25 therein.
The valve body 14 is communicated between the inflow port 21 and the open port 23 by causing the diaphragm 13 to elastically urge in a direction in which the pressure chamber 15 is reduced by making the end portion act on the diaphragm 13. Is biased in the direction of closing. Further, the negative pressure chamber 17 is connected by a negative pressure introduction port 27 and a negative pressure introduction path 29 to an atmosphere opening side 3g opposite to a side to which one end of the fuel vapor pipe 2b of the adsorption means 3 is connected. I have.

Here, the elastic biasing force of the return spring 25 is used to open the communication between the inflow port 21 and the open port 23 of the valve element 14 when a predetermined negative pressure is applied to the negative pressure chamber 17. Is set to Further, F according to the present embodiment.
The CV 10 has an umbrella valve 41 at a portion of the open port 23 protruding into the pressure chamber 15.

The umbrella valve 41 is a communication hole provided in the open port 23.
It is configured to include a shaft portion 43 that is loosely fitted to 42 and an umbrella portion 45 provided outside the open port 23. Umbrella part 45,
When the pressure in the pressure chamber 15 is slightly higher than the pressure in the open port 23, the pressure is pressed against the outer surface of the open port 23 to completely cover the communication hole 42 and close the communication in the communication hole 42. On the other hand, when the pressure in the open port 23 is slightly higher than the pressure in the pressure chamber 15, it is separated from the outer surface of the open port 23 to open the communication in the communication hole 42.

Further, the fuel vapor pipe 2 is connected to the canister 3.
One end of b is connected, the other end is connected to the intake passage of the engine, and a purge cut valve 4 is provided in the middle. The canister 3 is provided with a drain cut valve 5 as in the conventional example. In the same manner as in the related art, the engine control module 50 stores a determination value for evaporative fuel leak diagnosis, and compares the determination value with the pressure change speed detected by the pressure sensor 6 to determine The evaporative fuel leak diagnosis is performed.

Next, a fuel vapor leak diagnosis performed by the fuel vapor leak diagnostic apparatus having the above configuration will be described with reference to FIG.
This will be described with reference to the flowchart shown in FIG. In step 1 (in the figure, denoted by S1; the same applies hereinafter), the purge cut valve 4 is opened in a predetermined engine operating state, so that the evaporated fuel adsorbed on the canister 3 is reduced by the intake negative pressure of the engine. Is sucked.

In step 2, the drain cut valve 5 is closed, and by suction by the engine, first, the evaporative fuel pipe 2b, one side 3f of the canister 3, and the pipe between the open port 23 and the canister 3 in the evaporative fuel pipe 2a. The inside becomes negative pressure. Then, the negative pressure also acts on the atmosphere-opening side 3 g of the canister 3, and the negative pressure acting on the atmosphere-opening side 3 g is applied to the negative pressure introduction passage 29 and the negative pressure introduction port.
It acts on the negative pressure chamber 17 via 27. Here, the elastic urging force of the return spring 25 is set to a strength at which the communication between the inflow port 21 and the open port 23 of the valve body 14 is opened when a predetermined negative pressure acts on the negative pressure chamber 17. Has been
By the action of the intake negative pressure on the negative pressure chamber 17, the diaphragm 13 moves against the elastic biasing force of the return spring 25, and connects the inflow port 21 and the open port 23, thereby providing the fuel vapor. The pressure inside the pipe 2a is all negative.

Therefore, the fuel vapor in the fuel tank 1 is reduced to a negative pressure. In step 3, it is determined whether the pressure in the fuel vapor pipe has reached a predetermined negative pressure or whether suction has been performed for a predetermined time. In step 4, the purge cut valve 4 is closed. Thereby, an internal space for maintaining the negative pressure is formed.

In step 5, the pressure change in the internal space is monitored, and the pressure change speed (pressure rise speed) toward the atmospheric pressure is detected. In step 6, if the pressure change speed is larger than the previously stored determination value, the process proceeds to step 7, where it is diagnosed that the amount of fuel vapor leak exceeds an allowable value, and If the value is equal to or less than the determination value, the process proceeds to step 8, and it is determined that the amount of fuel vapor leak is equal to or less than the allowable value.

Thereafter, in step 9, the drain cut valve 5 is opened, and the present flow chart is terminated.
That is, the function of the evaporated fuel leak diagnosis means is performed by the engine control module 50. When the drain cut valve 5 is opened, the atmospheric pressure acts on the atmosphere opening side 3 g of the canister 3 via the drain cut valve 5, and the atmospheric pressure acting on the atmosphere opening side 3 g is reduced by the negative pressure introduction path 29 and the negative pressure introduction path. It acts on the negative pressure chamber 17 via the pressure introduction port 27. Accordingly, the action of the atmospheric pressure on the negative pressure chamber 17 causes the elastic biasing force of the return spring 25 to act, and the inflow port 21
And the communication with the open port 23 is closed.

Next, the operation of the FCV 10 as the two-way check valve according to the present embodiment will be described. When the above-described leak diagnosis of the evaporated fuel is not performed, the flow chart is in a completed state, and thus the communication between the inflow port 21 and the open port 23 is closed.

Here, when the pressure in the fuel tank 1 rises, the pressure acts on the diaphragm 13 to move the diaphragm 13 against the elastic biasing force of the return spring 25 and open the inflow port 21. The evaporative fuel is communicated with the canister 3 through the evaporative fuel pipe 2a.
Send to Further, the fuel tank 1 for evaporating fuel at a pressure lower than a predetermined pressure
Therefore, it is possible to surely adsorb the fuel vapor to the canister 3.

On the other hand, when the pressure inside the fuel tank 1 becomes negative, the pressure in the pressure chamber 15 becomes slightly lower than the pressure in the open port 23. In this case, the umbrella portion 45
The fuel tank 1 is prevented from being damaged by returning the fuel vapor to the fuel tank because the fuel tank is detached from the outer surface of the fuel tank and opens the communication in the communication hole 42. That is, in the configuration using the FCV 10 according to the present embodiment, the flow of the evaporated fuel in both directions, that is, the flow to the canister 3 and the flow to the fuel tank 1 can be regulated by the check valve function according to the FCV 10, and the intake negative pressure can be reduced. Without providing an electromagnetic solenoid valve for selecting the introduction, at the time of evaporative fuel leak diagnosis, the influence of the valve opening pressure of the FCV 10 as a check valve interposed in the evaporative fuel supply system such as the evaporative fuel pipes 2a and 2b. Therefore, there is an effect that the leak diagnosis of the evaporated fuel can be performed with high accuracy.

Thus, it is possible to accurately perform the leak diagnosis of the evaporated fuel while suppressing the increase in the weight of the entire leak diagnosis device and the cost.

[0032]

As described above, according to the present invention,
When evaporative fuel leak diagnosis means diagnoses a leak state of the evaporative fuel supply system based on a pressure change in the evaporative fuel supply system, a check valve interposed in the evaporative fuel supply system is interposed, Even when the check valve operates to regulate the pressure, regardless of the operation of the check valve,
Since the evaporative fuel supply system and the engine intake system are always in communication, the effect of opening the check valve is eliminated,
The effect that the leak diagnosis of the evaporated fuel can be performed with high accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an evaporative fuel leak diagnosis device according to the present invention.

FIG. 2 is an overall configuration diagram according to an embodiment of the present invention.

FIG. 3 is a sectional view illustrating the configuration of the fuel check valve according to the embodiment.

FIG. 4 is a flowchart according to the embodiment.

FIG. 5 is an overall configuration diagram according to a conventional example.

FIG. 6 is an overall configuration diagram according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Evaporated fuel pipe 2a Evaporated fuel pipe 2b Evaporated fuel pipe 3 Canister 4 Purge cut valve 5 Drain cut valve 6 Pressure sensor 10 Fuel check valve 13 Diaphragm 15 Pressure chamber 17 Negative pressure chamber 21 Inflow port 23 Open port 27 Negative pressure Intro port 50 Engine control module

Claims (1)

(57) [Claims] A pressure detecting means for detecting a pressure in an evaporative fuel supply system from a fuel tank to an intake system via a suction means under predetermined conditions, and the evaporative fuel supply system is communicated only with an intake system of the engine. An evaporative fuel leak diagnostic device for an internal combustion engine, the evaporative fuel leak diagnostic device comprising: an evaporative fuel leak diagnostic unit configured to diagnose a leak state of the evaporative fuel supply system based on a subsequent pressure change in the evaporative fuel supply system. In the system, the inside of the casing is partitioned into a pressure chamber and a negative pressure chamber by a diaphragm, and an open port connected to the adsorption means and an inflow port connected to the fuel tank are opened in the pressure chamber, and the open port is connected to the diaphragm by the diaphragm. The diaphragm is opened opposite to the diaphragm so as to be opened and closed, and the diaphragm is elastically urged to the negative pressure chamber in the contraction direction of the pressure chamber to communicate the opening port and the inflow port. A fuel return leak diagnostic device for an internal combustion engine, wherein a return spring for closing the valve is housed, and a valve having a negative pressure introduction port connected to the atmosphere opening side of the suction means is interposed.