JPH06108932A - Failure detecting device for evaporated fuel supply device - Google Patents

Abstract

PURPOSE:To judge the failure of an evaporated fuel supply device correctly with simple constitution even in such structure that the original read value of a pressure sensor is deviated from the true value. CONSTITUTION:The pressure in a fuel tank 13 is detected by a pressure sensor 26, and the clogging and leakage of an evaporated fuel supply passage 18 for communicating the fuel tank 13 with an intake passage 3 is judged on the basis of the detected output. On the assumption that a failure detecting device for an evaporated fuel supply device is of such constitution, the state within the specified time after the cold start of an engine 1 is caught by a sensor 27 and a control unit U, and the pressure detected by the pressure sensor 26 at that time is calibrated to atmospheric pressure by the control unit U.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detecting device for an evaporated fuel supply device.

[0002]

2. Description of the Related Art In an engine, in order to prevent evaporative fuel generated in a fuel tank from being diffused into the atmosphere, an evaporative fuel supply device is provided, and the evaporative fuel is combusted by the evaporative fuel supply device. Intake system (intake passage)
Is being introduced to. In such an evaporated fuel supply device, generally, a fuel tank and a throttle valve downstream side of an intake passage are communicated with each other via a page passage serving as an evaporated fuel supply passage, and the atmosphere passage is provided in the page passage. By providing a canister and a purge valve provided in this order from the fuel tank side toward the intake passage side, the evaporated fuel generated in the fuel tank is once adsorbed in the canister, and the purge valve is opened. By using the intake negative pressure on the downstream side of the throttle valve, the evaporated fuel in the canister is introduced into the intake passage while introducing the outside air from the atmosphere opening passage into the canister.

By the way, in the vaporized fuel supply device as described above, the clogging or leakage of the purge passage is detected, the vaporized fuel is not introduced into the intake passage, and the vaporized fuel is diffused into the atmosphere. In order to prevent the above, various failure detection devices are provided as shown in Japanese Utility Model Laid-Open No. 3-17169, etc., and among these failure detection devices, some of the failure detection devices are open to the atmosphere in the evaporated fuel supply device. There is one in which a valve for fail determination is provided in the passage and a pressure detection means is provided in the fuel tank. In this failure detection device, when detecting the clogging of the purge passage, the fail determination valve is closed and the purge valve is opened to apply an intake negative pressure in the intake passage to the fuel tank. The internal pressure of the fuel tank is to be continuously detected by the pressure detecting means. When the fuel tank internal pressure reaches the first predetermined value by the elapse of the first predetermined time from the start of the diagnosis, it is determined that the purge passage is not blocked, and the fuel tank internal pressure has passed the first predetermined time from the start of the diagnosis. However, if the internal pressure of the fuel tank is higher than the first predetermined value, it is determined that the purge passage is clogged because the intake negative pressure in the fuel tank is not sufficient. On the other hand, the leakage detection of the purge passage is to be performed when it is determined that the purge passage is not clogged. At the time of this detection, the internal pressure state of the fuel tank is set to the first predetermined value. In this state, the purge valve and the fail determination valve are closed, and the internal pressure of the fuel tank is continuously detected by the pressure detection means. If the fuel tank internal pressure is lower than the second predetermined value even after the second predetermined time has elapsed from the start of the diagnosis, it is determined that there is a leak from a slight gap in the valve, When it is determined that there is no leakage and the internal pressure of the fuel tank has reached the second predetermined value by the elapse of the second predetermined time from the start of diagnosis, it is determined that there is a leak in the purge passage.

[0004]

However, in the above-mentioned failure detection device, the read value (detected value) of the pressure detecting means is used as it is, as described above, when the failure such as clogging or leakage of the purge passage is judged. Therefore, when the reading value of the pressure detecting means is originally largely deviated from the true value (when it varies), there is a possibility that an erroneous judgment is made in the judgment of the failure detection. is there.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an accurate vaporized fuel supply device even if the original reading value of the pressure detecting means deviates from the true value. Another object of the present invention is to provide a failure detection device for an evaporated fuel supply device, which can perform the failure determination.

[0006]

In order to achieve the above object, in the present invention (first invention), a fuel tank and an intake system are communicated with each other through an evaporated fuel supply passage, and the fuel tank is connected to the fuel tank. A failure detection device for an evaporated fuel supply device, in which pressure detection means for detecting a pressure for judging a failure of the evaporated fuel supply passage is interposed between the intake system and the fuel tank side of the intake system. In the state detection means for detecting whether or not the detection area of the pressure detection means is in the atmospheric pressure equivalent state, and the detection area of the pressure detection means is determined to be the atmospheric pressure equivalent state based on the detection signal of the state detection means. And a calibration means for calibrating the pressure detected by the pressure detection means at the time of the determination to atmospheric pressure.

With the above structure, the pressure detected by the pressure detecting means is detected to be in the atmospheric pressure equivalent state, and the pressure detected by the pressure detecting means at that time is calibrated to the atmospheric pressure. The reading does not deviate significantly from the true value. Therefore, the read value of the pressure detecting means is used as it is in the failure determination of the evaporated fuel supply passage, but in the failure determination,
No erroneous determination is made.

Further, in order to achieve the above-mentioned object, in the present invention (the second invention), in claim 1, the judgment condition of the atmospheric pressure equivalent state is that the engine is in the cold state. It is configured to be within a predetermined time after the start. With the above-described configuration, in addition to the same effect as the first aspect of the invention, it is not necessary to provide a special device to obtain the atmospheric pressure equivalent state. Therefore, the structure can be simplified.

In order to achieve the above-mentioned object, according to the present invention (third invention), in claim 1, the pressure detecting means includes the fuel tank and the intake system via an atmosphere release valve. And a determination condition of being in a state corresponding to the atmospheric pressure, which is provided when the atmosphere opening valve is opened to the atmosphere. With the above configuration, the above-mentioned first
In addition to the same effect as that of the invention described above, the pressure detection means can be exposed to the atmosphere by opening the atmosphere release valve to the atmosphere. Therefore, the pressure detecting means can be calibrated immediately when desired.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an engine, and an intake passage 2 of the engine 1 is connected to an intake passage 3. In the intake passage 3, the air cleaner 4,
An air flow meter 5, a throttle valve 6, a surge tank 7, a fuel injection valve 8 and the like are provided, and its intake passage 3
Is branched into a primary passage 9 and a secondary passage 10 in a part of the downstream side of the serge tank 7, and a secondary valve 11 which is opened and closed according to the internal pressure of the serge tank 7 is arranged in the secondary passage 10. There is.

A fuel supply passage 12 is provided in the fuel injection valve 8.
The fuel tank 13 is connected via. A fuel pump 14 is connected to the upstream end of the fuel supply passage 12,
The fuel pump 14 is arranged in the fuel in the fuel tank 13. Further, the fuel injection valve 8 and the fuel tank 1
3 is also connected via a regulator passage 15, and a pressure regulator for keeping the internal pressure of the fuel injection valve 8 constant and performing stable fuel injection in the regulator passage 15. 16 are interposed.

The engine 1 is provided with an evaporated fuel supply device 17. This evaporated fuel supply device 17
Of the fuel tank 13 and the surge tank 7 on the downstream side of the throttle valve 6 serve as a fuel vapor supply passage.
Through the fuel passage 18, and the purge passage 18 is sequentially separated from the fuel tank 13 side toward the intake passage 3 side.
A canister 21 having a valve 19, an atmosphere opening passage 20, and a purge valve 22 are provided. The separator 19 has a function of separating the liquid fuel from the evaporated fuel, and in order to return the separated liquid fuel to the fuel tank 13, the separator 19 and the fuel tank 13 are returned. It is connected through a passage 23. The canister 21 temporarily adsorbs the vaporized fuel generated in the fuel tank 13 and sends the vaporized fuel to the intake passage 3.
By opening the divalve 22, the throttle valve 6
It has a function of introducing outside air into the canister 21 from the atmosphere opening passage 20 by utilizing the intake negative pressure on the downstream side, and vaporized fuel having a capacity higher than that of the canister 21 is introduced from the fuel tank 13 into the canister 21. In this case, it has a function of releasing a part of the evaporated fuel into the atmosphere via the atmosphere opening passage 20. The purge valve 22
Has a function of adjusting the action of intake negative pressure on the canister 21 by opening and closing the purge passage 18, and based on this, adjusting the supply (page) of evaporated fuel to the intake passage 3. .

The evaporative fuel supply system 17 is provided with a failure detection system 24 for early detection of clogging or leakage of the purge passage. The failure detection device 24 includes a fail determination valve 25 provided in the atmosphere open passage 20.
And a pressure sensor 26 as a pressure detecting means provided in the fuel tank 13. The fail determination valve 25 is closed only when a failure determination of the evaporated fuel supply device 17 (determination of clogging or leakage of the purge passage) described later is performed, and is opened in other states. .
The pressure sensor 26 has a function of detecting the internal pressure of the fuel tank 13.

Reference numeral U shown in FIG. 1 is a control unit composed of, for example, a microcomputer, and the control unit U is, as is known, a CPU, ROM,
It is equipped with RAM and the like. This control unit U
Various signals such as an engine cooling water temperature from a sensor 27, an ON from an ignition switch (key switch) 28, a pressure detected in the fuel tank 13 from a pressure sensor 26, and the like are input to the control unit U. From this, a control signal is output to the fail judgment valve 25, the purge valve 22 and the like.

The control contents of the control unit U will be briefly described. In the present embodiment, the conventional failure determination is performed. However, prior to the failure determination, the predetermined time after the cold start is detected, The pressure detected by the pressure sensor 26 at that time is calibrated to atmospheric pressure (0 in gauge pressure). This is because, if a predetermined time after the cold start is captured, the inside of the fuel tank 13 is in a state corresponding to the atmospheric pressure at that time, and therefore the pressure detected by the pressure sensor 26 at that time is set to the atmospheric pressure. I am trying to calibrate. In this case, it is limited to within a predetermined time after the start, but when hot fuel is returned from the fuel injection valve 8 into the fuel tank 13 through the regulator passage 15,
This is because it is considered that the evaporation of the fuel in the fuel tank 13 is promoted and the internal pressure of the fuel tank 13 rises to the atmospheric pressure or higher. Therefore, the above-mentioned predetermined time is
It is set before hot fuel is returned from the fuel injection valve 8 into the fuel tank 13 through the regulator passage 15,
Specifically, it is set to 60 seconds or less. As a result, thereafter, the reading value of the pressure sensor 26 will not largely deviate from the true value, and even if the reading value of the pressure sensor 26 is directly used as the pressure value in the failure determination of the purge passage 18, No erroneous determination is made. Moreover, in the present embodiment, the existing detection element such as the engine cooling water temperature is detected to detect that the detection area of the pressure sensor 26 is in the atmospheric pressure equivalent state, and thus the atmospheric pressure equivalent state is obtained. Therefore, it is not necessary to provide a special device, and the configuration can be simplified although the pressure sensor 26 is calibrated.

Next, the control contents of the control unit U will be described in detail with reference to the flow chart of FIG.
In addition, S shows a step. First, in response to the ON operation of the ignition switch 28, it is started, and in S1,
The various signals such as the engine cooling water temperature and the internal pressure of the fuel tank 13 are read, and it is determined in S2 whether the engine is cold. This determination is made based on, for example, the engine cooling water temperature of 80 ° C. as to whether or not the engine is in the cold state.
It is provided in order to detect the state in which the fuel inside is difficult to evaporate. If S2 is NO, the process returns to S1, while if S2 is YES, the process proceeds to S3. In S3, it is determined whether it is within a predetermined time after the start. As described above, this determination is made by the hot fuel from the fuel injection valve 8 passing through the regulator passage 15 and the fuel tank 1.
When the internal pressure of the fuel tank 13 is returned to 3, the evaporation of the fuel in the fuel tank 13 is promoted, and the internal pressure of the fuel tank 13 rises above atmospheric pressure.
Therefore, when S3 is NO, the process is returned to S1, while when S3 is YES, the process first proceeds to S4. In S4, it is assumed that both the above S2 and S3 are satisfied and the inside of the fuel tank 13 is in a state corresponding to the atmospheric pressure. Below that, the pressure detected by the pressure sensor 26 is calibrated to atmospheric pressure (0 in gauge pressure). It

Then, in the next step S5, the purge passage 1
8 failure detections are performed. This failure detection has been performed conventionally, and will be briefly described below with reference to FIG. That is, the above S2, S3
Besides, the internal pressure of the fuel tank 13 is P ₀ (e.g. gate - 0 ± 50 MMA _q di pressure) conditions the fault diagnosis conditions such as would have satisfied, Pa - fail judgment with Jibarubu 22 is opened Valve 25 is closed and intake passage 3 is closed.
The intake negative pressure of is applied to the fuel tank 13 (when T ₀ is a negative pressure start time). As a result, as shown by the solid line or the broken line in FIG. 3, the internal pressure of the fuel tank 13 gradually decreases, and by the first predetermined time T ₁ , the fuel tank 13 has the same internal pressure as the case of the solid line. The internal pressure of the first predetermined value P ₁
(E.g. -250MmA _q gate - di pressure) when lowered to the path - it is determined that clogging di passage 18 does not occur, as in the case of broken line, even if the first predetermined time T ₁ elapses, fuel When the internal pressure of the tank 13 does not drop to the first predetermined value P ₁ , it is determined that the purge passage 18 is clogged.

When it is determined that the purging passage 18 is not clogged, the leakage of the purging passage 18 is judged, and in this case, the internal pressure of the fuel tank 13 becomes the first value. In the state of 1 predetermined value P _1, the purge valve 22 is closed and the fail determination valve 25 is closed. As a result, as shown by the solid line or the broken line in FIG. 3, the internal pressure of the fuel tank 13 gradually rises, and even after the second predetermined time T ₂ has elapsed, the fuel remains as in the case of the solid line. when the internal pressure of the tank 13 does not rise up to the second predetermined value P ₂ is Pas - it is determined that the leakage to the di-passage 18 does not occur, as in the case of the broken lines, the second predetermined time T ₂
By the time the internal pressure of the fuel tank 13 reaches the second predetermined value P
When it exceeds ₂ , it is determined that the purge passage 18 is leaking. Therefore, in the failure determination, the read value of the pressure sensor 26 is used as it is, but since the pressure sensor 26 is calibrated as described above in the stage before the failure determination, the failure determination is performed. In, there will be no erroneous determination.

FIG. 4 shows another embodiment. In this embodiment, the same components as those in the previous embodiment are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the pressure sensor 26 is a three-way valve 29 as an atmosphere release valve.
It is connected to the fuel tank 13 via. Three-way valve 29
Is a first switching path that connects the fuel tank 13 and the pressure sensor 26, and a second switching path that connects the pressure sensor 26 and the atmosphere.
The first and second switching paths are configured to be switched by a changeover switch (not shown). If a changeover switch operation for selecting the second switching path is performed, the operation is grasped and the control is performed. The unit U is to calibrate the pressure sensor 26 described above.

Although the embodiments have been described above, the present invention includes the following. Providing a pressure sensor 26 for the purge passage 18. In the above embodiment, when there is no clogging in the purge passage 18 during leak detection, T ₁ is set at approximately the same time, so T ₂ is determined based on the time when the diagnostic condition is satisfied, but for the sake of accuracy. The leak detection start time point may be measured and T ₂ may be determined based on the measured time point.

[0021]

As described above, in the first to third aspects of the invention, even if the original reading value of the pressure detecting means is deviated from the true value, the accurate evaporated fuel is obtained. The failure of the supply device can be determined. Further, in the second invention, the configuration can be simplified even if the pressure detecting means is calibrated. Furthermore, in the third invention,
The pressure sensing means can be calibrated as soon as desired.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine according to an embodiment.

FIG. 2 is a flowchart showing a part of failure detection by the control unit.

FIG. 3 is an explanatory diagram illustrating a failure detection method.

FIG. 4 is an explanatory view showing another embodiment.

[Explanation of symbols]

 1 Engine 3 Intake Passage 13 Fuel Tank 17 Evaporative Fuel Supply Device 18 Purging Passage 24 Failure Detection Device 26 Pressure Sensor 27 Sensor 28 Ignition Switch 29 Three-way Valve U Control Unit

Claims (3)

[Claims] 1. A fuel tank and an intake system are communicated with each other via an evaporated fuel supply passage, and the evaporated fuel supply passage is provided between the fuel tank and the intake system on the fuel tank side of the intake system. In a failure detecting device for an evaporated fuel supply device, in which a pressure detecting means for detecting a pressure for failure determination is interposed, a state detecting means for detecting whether or not a detection area of the pressure detecting means is an atmospheric pressure equivalent state, A calibration unit that calibrates the detection pressure of the pressure detection unit at the time of the determination to the atmospheric pressure when the detection region of the pressure detection unit is determined to be the atmospheric pressure equivalent state based on the detection signal of the state detection unit, A failure detection device for an evaporated fuel supply device, comprising: 2. The failure detecting device for an evaporated fuel supply device according to claim 1, wherein the condition corresponding to the atmospheric pressure equivalent condition is that the engine is cold and within a predetermined time after starting. . 3. The pressure detecting means according to claim 1, wherein the pressure detecting means is interposed between the fuel tank and the intake system via an atmosphere opening valve, and the judgment condition of the atmospheric pressure equivalent state is the atmosphere opening. A failure detection device for an evaporated fuel supply device, characterized in that the valve is opened to the atmosphere.