JPH08218951A - Diagnosing device for fuel evaporation preventing device - Google Patents

Abstract

PURPOSE: To surely avoid an error diagnosis in any vehicle situation so as to properly maintain a diagnosing process concerning existence of an abnormal condition in a fuel evaporation preventing device. CONSTITUTION: In a fuel evaporation preventing device, ordinarily, fuel gas generated inside a fuel tank 12 is accumulated in a canister 16 arranged in the middle of a purge passage connecting the fuel tank 12 and an intake pipe 2 together, and the accumulated fuel gas is introduced to the intake pipe 2 while control of a flow rate is carried out according to an operation condition of an engine 1 by means of a purge control valve 23 arranged in the purge passage. An atmospheric pressure sensor 31 detecting an atmospheric pressure is arranged especially, and the detected atmospheric pressure is monitored by means of an electronic controller 40 for diagnosing whether fuel gas leaks from the fuel evaporation preventing device or not, and diagnosing process is stopped or the diagnosis result is canceled when a change in the atmospheric pressure detected in diagnosis exceeds the predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention stores a fuel gas generated in a fuel tank of an internal combustion engine in a canister, and introduces it into an intake pipe while adjusting the flow rate according to the operating state of the engine. The present invention relates to a diagnostic device for a fuel evaporation prevention device, which is for diagnosing the presence or absence of a device abnormality such as fuel gas leakage.

[0002]

2. Description of the Related Art In an internal combustion engine mounted on an automobile or the like, in order to prevent the fuel gas generated in a fuel tank from being released into the atmosphere, it is obliged to equip a fuel evaporation prevention device. There is.

As is well known in the art, a fuel evaporation preventive device stores fuel gas in a canister provided in a purge passage communicating with a fuel tank and an intake pipe of an engine, and stores the fuel gas at any time. This is a device that prevents the evaporation of fuel by opening and closing a purge control valve provided between the two in accordance with the operating state of the engine to introduce the stored fuel gas into the intake pipe.

By the way, in such a fuel transpiration prevention device, a purge passage is usually formed by connecting a rubber hose between the canister and the intake pipe and further between the fuel tank and the canister.

Therefore, for example, when the rubber hose between the canister and the intake pipe is bent and crushed, the fuel gas is not introduced into the intake pipe but continues to be stored in the canister, and the storage capacity of the canister, that is, the adsorbent in the canister. It may exceed the fuel gas adsorption capacity due to. Then, when the fuel gas that exceeds the storage capacity of the canister is generated in this way, the fuel gas that exceeds the storage capacity will be discharged into the atmosphere from the atmospheric hole provided in the canister.

Further, since the rubber hose forming the purge passage is in constant contact with the alcohol component, it may be damaged by corrosion or the like, and the atmospheric hole provided in the canister is blocked by dust or the like. In case of spillage, it is possible that it will come off due to the increase in pressure. Even in such a case, the generated fuel gas is released into the atmosphere.

Therefore, conventionally, for example, Japanese Patent Laid-Open No. 6-1771.
The diagnostic device as described in Japanese Patent No. 5 is used to diagnose the occurrence of such a situation. By the way, in the device, a valve means (canister closing valve) for opening and closing the atmosphere hole is provided in the canister, and a pressure sensor for detecting the pressure in the section from the fuel tank to the canister as a pressure difference from the atmospheric pressure, and a large An atmospheric pressure sensor for detecting atmospheric pressure is provided, and the above diagnosis is executed according to the following procedure. (1) Close the canister blocking valve. (2) After that, the purge control valve is closed after waiting for a predetermined negative pressure, and the airtightness is maintained for a predetermined time. (3) The diagnosis is performed by comparing the change in the pressure detected by the pressure sensor during that time with the determination value. (4) At that time, the pressure detected by the pressure sensor or the determination value is corrected according to the atmospheric pressure detected by the atmospheric pressure sensor.

[0008]

As described in the above publication, since a negative pressure is introduced into the fuel tank during diagnosis, a high concentration of fuel gas in the fuel tank is introduced into the intake pipe when the negative pressure is introduced. Purged and the air-fuel ratio fluctuates. For this reason, the above-mentioned diagnosis is usually performed in a driving state in which the intake air amount is large, that is, in a state in which the vehicle speed is relatively high, so that the fluctuation of the air-fuel ratio due to such purging becomes small.

In addition, for example, a slope with a 5% slope is 90 kph
When traveling at m / h, there is an altitude difference of 75 m per minute. Here, since there is a change in atmospheric pressure of 1333 Pa (Pascal) per 100 m of altitude difference, a pressure change of 998 Pa per minute occurs at the altitude difference of 75 m.

Therefore, the pressure detected by the pressure sensor is naturally affected by the change in the atmospheric pressure, and the pressure detected by the pressure sensor depends on the atmospheric pressure detected by the atmospheric pressure sensor as in the diagnostic device. Alternatively, if the judgment value is corrected, the reliability of the diagnosis result can be surely improved.

However, the time required for such a diagnosis is relatively long (usually 90 seconds or more), and when the atmospheric pressure changes frequently during the diagnosis, for example, when the vehicle runs on a sloped road in which climbing and descending are repeated. However, it becomes difficult to correct the degree of the influence accurately.

After all, even in the above-mentioned conventional diagnostic device, even in such a situation where the atmospheric pressure changes frequently, it is possible to accurately detect a minute leak in the fuel evaporation prevention device (purge passage). However, there is a possibility that the diagnosis may be wrong.

The present invention has been made in view of the above circumstances, and irrespective of the situation of the vehicle, erroneous diagnosis is surely avoided, and the diagnosis process regarding whether or not there is an abnormality in the fuel evaporation prevention apparatus is appropriately performed. An object of the present invention is to provide a diagnostic device for a fuel evaporation prevention device that can be maintained.

[0014]

In order to achieve such an object, in the invention according to claim 1, an atmospheric pressure sensor for detecting atmospheric pressure and an atmospheric pressure detected during diagnosis are used as a diagnostic device for a fuel evaporation prevention device. When the change in atmospheric pressure exceeds a predetermined amount, the diagnostic processing is stopped, or a protection means for invalidating the diagnostic result is provided.

According to a second aspect of the present invention, in the configuration of the first aspect of the present invention, the diagnostic device detects the pressure in the fuel tank or in a section from the fuel tank to the canister. A change amount of pressure detected by the pressure sensor within a predetermined time when the inside of the fuel evaporation prevention device is regulated to a predetermined first pressure and sealed, and the inside of the fuel evaporation prevention device has a predetermined second The presence / absence of a device abnormality in the fuel transpiration prevention device is diagnosed based on the amount of change in the pressure detected by the pressure sensor within the predetermined time when the pressure is adjusted to the above pressure and sealing is performed.

Further, in the invention according to claim 3, in the configuration of the invention according to claim 2, the pressure sensor is configured to have a pressure in the fuel tank or in a section from the fuel tank to the canister and an atmospheric pressure. It is configured by a differential pressure sensor that detects a differential pressure.

According to a fourth aspect of the invention, in the configuration of the invention according to the third aspect, the protection device is
After the diagnosis is started, at least the first by the pressure sensor
And when there is a change in atmospheric pressure that exceeds the limit amount at which the diagnostic accuracy by the diagnostic device can be maintained during measurement of the amount of change in each detected pressure at the second pressure, the diagnostic process is stopped or the diagnostic result is displayed. The configuration is set to disable.

[0018]

As described above, when it is attempted to diagnose the presence or absence of leakage of fuel gas from the fuel transpiration prevention device, the atmospheric pressure, which is the pressure around it, has a large effect, and, for example, the slopes where climbing and descending are repeated. If the atmospheric pressure changes frequently during diagnosis, such as when driving a vehicle, accurate diagnosis becomes extremely difficult.

Therefore, according to the invention of claim 1, an atmospheric pressure sensor for detecting the atmospheric pressure. And-protection means for stopping the diagnosis process or invalidating the diagnosis result when the change in atmospheric pressure detected during the diagnosis exceeds a predetermined amount. With this configuration, at least erroneous diagnosis caused by the change in the atmospheric pressure can be avoided, and the reliability of the diagnostic device can be improved. That is, by adopting such a configuration, the diagnosis process can always be maintained appropriately.

According to the second aspect of the invention,
A pressure sensor for detecting a pressure in the fuel tank or a section from the fuel tank to the canister is provided, and a predetermined time when the fuel evaporation prevention device is regulated to a predetermined first pressure and sealed. Based on the amount of change in the pressure detected by the pressure sensor and the amount of change in the pressure detected by the pressure sensor within the predetermined time when the fuel evaporation prevention device is pressure-controlled to a predetermined second pressure and sealed. For diagnosing whether or not there is a device abnormality in the fuel evaporation prevention device. As a result, when the diagnostic device is configured as described above, except for the case where the diagnostic process is stopped through the protection means or the diagnostic result is invalid, the purge gas from the fuel tank to the purge control valve is connected to the purge gas of the fuel gas. It becomes possible to accurately diagnose the presence or absence of leakage.

Incidentally, when there is a leak (leakage of fuel gas) in the purge passage, an outflow from the closed section to the atmosphere occurs under a positive pressure, while an inflow from the atmosphere to the closed section occurs under a negative pressure. Further, even if the same positive pressure or negative pressure is applied, if the pressures are different, the degree of outflow or inflow also changes according to the pressures. Therefore, the first and second pressures to be regulated are also set to appropriate pressures capable of determining the presence / absence of the cause of the leak based on the relationship between the cause of the leak and the pressure change.

According to the invention of claim 3,
The pressure sensor is a differential pressure sensor that detects the differential pressure between the pressure in the fuel tank or in the section from the fuel tank to the canister and the atmospheric pressure. Can be configured as. According to such a differential pressure sensor, although it is desirable to perform correction by atmospheric pressure in a mode like the above-mentioned conventional device, it is significantly larger than a sensor that measures the pressure in the above section as an absolute pressure. The cost can be reduced.

Further, particularly when the differential pressure sensor is used as the pressure sensor as described above, the protection device is provided as follows: According to the invention of claim 4, after the diagnosis is started, at least the first and the first pressure sensors are used. When there is a change in atmospheric pressure that exceeds the limit amount with which the diagnostic accuracy of the diagnostic device can be maintained during measurement of the amount of change in each detected pressure at the pressure of 2, the diagnostic process is stopped or the diagnostic result is invalidated. What to do. As described above, when there is a cause of leakage in the purge passage, (a) outflow from the closed section to the atmosphere under positive pressure, and inflow from the atmosphere to the closed section under negative pressure . (B) If the pressures are different even under the same positive pressure or negative pressure, the degree of outflow or inflow also changes according to the pressures. It is possible to improve the reliability of the pressure change amount measurement result itself under the first and second pressures that are adjusted based on the above relationship. Incidentally, when the first pressure is set to a negative pressure of, for example, about −2 kPa (kilopascal) and the second pressure is set to, for example, the atmospheric pressure, the limit amount of the change in the atmospheric pressure (claim) The “predetermined amount” of the atmospheric pressure change referred to in the invention described in 1) is set as a value of about ± 0.5 kPa.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a diagnostic device for a fuel transpiration prevention device according to the present invention.

The diagnostic device of this embodiment diagnoses whether or not there is an abnormality in the fuel transpiration prevention device mounted on a vehicle-mounted gasoline engine (internal combustion engine), that is, whether or not fuel gas leaks from its purge passage or the like. It is configured as a device.

First, with reference to FIG. 1, the structure of an engine and a fuel evaporation preventing apparatus for the engine to be diagnosed by the apparatus of this embodiment will be described. As shown in FIG. 1, an intake pipe 2 and an exhaust pipe 3 are connected to the engine 1. An air cleaner 4 for filtering air is arranged upstream of the intake pipe 2, and the air is sucked into the intake pipe 2 via the air cleaner 4. In addition, a throttle valve 6 that opens and closes in conjunction with an accelerator pedal 5 is provided in the intake pipe 2, and the intake air described above passes through the throttle valve 6 and the intake valve 7 to a combustion chamber 8
Is supplied to. Then, the exhaust gas burned in the combustion chamber 8 is discharged to the exhaust pipe 3 via the exhaust valve 9.

The exhaust pipe 3 is provided with an O2 sensor 10 for detecting the oxygen concentration of the exhaust gas. The output of the O2 sensor 10 is referred to in order to monitor the "rich / lean" state of the air-fuel ratio at each time in the air-fuel ratio feedback control described later.

A water temperature sensor 11 is provided in the water jacket of the engine 1. The water temperature sensor 11 is a sensor for detecting the cooling water temperature of the engine 1, that is, the engine temperature.

On the other hand, a fuel pump 13 is connected to the fuel tank 12 containing the liquid fuel (gasoline).
The fuel stored in the fuel tank 12 is conveyed to the fuel injection valve 14 provided in the intake pipe 2 while being pressurized by the fuel pump 13, and the fuel injection valve 14 is opened. Along with this, it is injected and supplied into the intake pipe 2. That is, the injected fuel is mixed with the intake air in the intake pipe 2, and the mixture is actually supplied to the combustion chamber 8 via the intake valve 7 and burned. .

The fuel tank 12 is also connected to a canister 16 through a communication pipe 15. Each part described below, including the fuel tank 12 and the communication pipe 15, constitutes a fuel evaporation prevention device of the engine.

That is, in the fuel transpiration prevention apparatus, an adsorbent 18 made of, for example, activated carbon for adsorbing the fuel gas generated in the fuel tank 12 is housed in the canister body 17 which is the body of the canister 16. There is. With this configuration of the device, the fuel gas generated in the fuel tank 12 is taken into the canister body 17 via the communication pipe 15 and is adsorbed by the adsorbent 18 in the canister body 17. Become.

Further, the canister body 17 is formed with an atmosphere hole 19 which is open to the atmosphere, and the canister body 17 can suck the outside air into the inside through the atmosphere hole 19. ing. In addition, this atmospheric hole 1
A canister shutoff valve 20 is arranged at 9 and can be shut off as required.
The valve structure of the canister blocking valve 20 is shown in FIG. 2 for reference.

That is, in the canister shutoff valve 20 shown in FIG. 2, when a predetermined voltage (for example, 6 V or more) is not applied to the coil 20a, the valve body 20b is used.
Is urged (sucked) by the spring 20c to open the conduit 20d communicating with the atmosphere hole 19.
On the other hand, when a predetermined voltage is applied to the coil 20a, the valve body 20b is excited by the exciting force of the spring 20c.
It moves to the right in the figure against the urging force of the
0d, so the atmosphere hole 19 is closed. Whether or not the predetermined voltage is applied to the coil 20a is controlled by the electronic control unit 40 described later.

Further, in the fuel evaporation preventing apparatus shown in FIG. 1, a hose connecting portion 21 is formed on the other surface of the canister body 17. A supply pipe 22 is attached to the hose connection portion 21, and a purge control valve 23 is connected to the other end of the supply pipe 22. The purge control valve 23 has the other end connected to the intake pipe 2 via the supply pipe 24. According to this structure of the fuel evaporation prevention device, the intake pipe 2 and the canister 16 are brought into communication by opening the purge control valve 23, and conversely, the control valve 23 is closed. The intake pipe 2 and the canister 16 are closed.
The fuel gas adsorbed by the adsorbent 18 in the canister 16 enters the intake pipe 2 based on the negative pressure generated in the intake pipe 2 in the communication state based on the opening of the purge control valve 23. Will be introduced. The valve structure of the purge control valve 23 is shown in FIG. 3 for reference.

In the purge control valve 23 shown in FIG. 3, the port 23a is a canister side port to which the supply pipe 22 is connected, and the port 23b is an intake pipe side port to which the supply pipe 24 is connected. Further, the passage 23c is a passage connecting the ports 23a and 23b, and the valve body 2
The opening degree, that is, the purge flow rate, is determined according to the position of 3d. The valve body 23d is normally in a position to block the passage 23c by the biasing force of the spring 23e as shown in the figure, and when the coil 23f is energized, it is biased by the spring 23e in accordance with the energizing amount. It moves to the left in the figure in the form of resistance. In addition,
The coil 23f is energized by a duty-controlled pulse signal, and the purge flow rate determined based on the position of the valve body 23d is also based on the duty ratio of the pulse signal, for example, as shown in FIG. Changes continuously. Such duty control of the purge flow rate is also executed through the electronic control unit 40 described later.

In the fuel evaporation prevention apparatus shown in FIG. 1, the supply pipes 22 and 24 connected to the purge control valve 23 are made of a flexible material such as a rubber hose or a nylon hose. There is. Further, the communication pipe 15 connecting the fuel tank 12 and the canister 16 is also partially formed by a rubber hose or the like.

On the other hand, the fuel tank 12 has a relief valve 12a for releasing the fuel tank 12 when the pressure in the tank 12 exceeds, for example, -40 to 150 mmHg.
Is provided. Therefore, even when the pressure fluctuation occurs in the section from the fuel tank 12 to the canister 16,
The fluctuation is always suppressed below this relief pressure range.

Further, the fuel tank 12 is further provided with a pressure sensor 25 for detecting the pressure in the fuel tank 12. The output of the pressure sensor 25 is used as a signal (measurement value) indicating the tank internal pressure in a later-described diagnostic process executed for the fuel evaporation prevention device, and also adjusts the pressure in the fuel evaporation prevention device. It is also used as a monitor signal when pressing. The pressure sensor 25 may have a structure that can withstand the above relief pressure range. Further, in the apparatus of the embodiment, as the pressure sensor 25, a differential pressure sensor that detects a differential pressure (relative pressure) between the tank internal pressure and the atmospheric pressure is used.

In addition, in the system, as also shown in FIG. 1, a throttle opening sensor 26 for detecting the opening of the throttle valve 6, an idle switch 27 for indicating whether the engine 1 is in an idle state, A vehicle speed sensor 28 for detecting the speed of the vehicle, a rotation speed sensor 29 for detecting the rotation speed of the engine 1, an intake pipe pressure sensor 30 for detecting the pressure in the intake pipe 2, and an atmospheric pressure sensor 31 for detecting the atmospheric pressure. Are provided respectively. The output of each of these sensors, including the above-mentioned O2 sensor 10, water temperature sensor 11, and pressure sensor 25, is controlled by the electronic control unit 4.
It will be taken in by 0.

The electronic control unit 40 is connected to a well-known CPU 41, a ROM 42 in which control and diagnostic programs and data are stored in advance, a RAM 43 in which control data and diagnostic data are temporarily stored, and various sensors and actuators described above. The input / output circuit 44 is the common bus 4
They are connected to each other via 5.

In the electronic control unit 40, the fuel injection valve 14 is driven based on the detection signals from the above various sensors,
In addition, the purge control valve 23 and the canister closing valve 20 are driven to comprehensively execute the fuel injection control, the canister purge control, the diagnosis process of the fuel evaporation prevention device, and the like.

FIG. 5 functionally shows the structure of the electronic control unit 40 mainly relating to the fuel injection control, the canister purge control, and the diagnostic process of the fuel transpiration prevention device. 5, the configuration of the apparatus and the function of each unit will be specifically described.

In the electronic control unit 40 shown in FIG. 5,
The basic injection amount calculation unit 401 injects the basic fuel into the engine 1 based on the output (rotation speed) NE of the rotation speed sensor 29 and the output (intake pressure) PM of the intake pipe pressure sensor 30 among the sensor signals taken in above. This is a part for calculating the quantity Tp. For this calculation, for example, a map in which the value of the same basic fuel injection amount Tp that is adapted to each operating range determined according to each value of the rotational speed NE and the intake pressure PM is registered in a memory is used. You can The value of the calculated basic fuel injection amount Tp is output to the fuel injection amount calculation unit 402.

The fuel injection amount calculation unit 402 calculates the basic fuel injection amount Tp calculated through the basic injection amount calculation unit 401.
And the air-fuel ratio correction coefficient FAF stored in the FAF memory 405 to be described later, the calculation of the following equation is executed to obtain the final fuel injection amount TAU. TAU = FAF · Tp · FALL (1) Here, FALL is another correction coefficient that does not depend on the air-fuel ratio correction coefficient FAF.

Further, the calculated fuel injection amount TAU
Is given to the drive circuit (fuel injection valve drive circuit) 403 as information indicating the operation amount (operation time) of the fuel injection valve 14. In the drive circuit 403, the fuel injection amount TAU is thus
Is given in synchronism with the intake stroke of the engine 1, the time indicated by the fuel injection amount TAU,
The fuel injection valve 14 is driven.

Further, in the electronic control unit 40, the air-fuel ratio correction coefficient calculation unit 404 sets the target air-fuel ratio based on the output THW of the water temperature sensor 11 provided that the air-fuel ratio feedback condition is satisfied. Along with
This is a part for calculating the air-fuel ratio correction coefficient FAF based on the set target air-fuel ratio and the output R (rich) / L (lean) of the O2 sensor 10.

Here, the air-fuel ratio feedback condition means that (a) the output THW of the water temperature sensor 11 indicates a water temperature of 40 ° C. or higher. (B) The output SP of the throttle opening sensor 26 indicates that the throttle opening is 70 degrees or less. Are both satisfied.

The FAF memory 405 is a memory for temporarily storing the air-fuel ratio correction coefficient FAF calculated in this way. These temporarily stored air-fuel ratio correction factors FAF
Is read by the fuel injection amount calculation unit 402 and the evaporation concentration detection unit 406 described above. The stored air-fuel ratio correction coefficient FAF may be corrected by the purge control unit 409, which will be described later, if necessary.

The evaporative emission concentration detector 406 is a portion for detecting the evaporative emission concentration CPV, that is, the fuel gas concentration in the fuel transpiration prevention device, based on the air-fuel ratio correction coefficient FAF stored in the FAF memory 405. In addition, the evaporation concentration detection unit 406 also outputs the opening degree information θ of the purge control valve 23 corresponding to the detected evaporation concentration CPV.
That is, the purge flow rate is set. The detected evaporation concentration CPV and the set opening degree information θ of the purge control valve 23 are used as the CPV memory 407 and the θ memory 40, respectively.
8 is temporarily stored.

Further, the purge control section 409 has, for example, (a) air-fuel ratio feedback control as the purge execution condition. (B) Fuel cut has not been performed. This is a part that executes canister purge control through the fuel evaporation prevention device on condition that the above conditions are satisfied. When executing this purge control, the θ memory 4
The opening degree information θ of the purge control valve 23 stored in 08 is referred to. That is, the purge control unit 409 determines the opening degree of the purge control valve 23 at each time by referring to the opening degree information θ stored in the θ memory 408 when executing the purge control. Then, the drive circuit (purge control valve drive circuit) 411 is controlled so as to match the determined opening degree. The drive circuit 411 is a circuit that duty-controls the opening degree of the purge control valve 23 in the manner shown in FIG. 4 based on the determined opening degree.

As described above, the purge control unit 409 corrects the air-fuel ratio correction coefficient FAF stored in the FAF memory 405 as needed to match the purge flow rate at each time.

On the other hand, in the electronic control unit 40, the diagnosis section 410 outputs the pressure sensor 25 (tank internal pressure).
P, the output (atmospheric pressure) PAh of the atmospheric pressure sensor 31, and the evaporation concentration C stored in the CPV memory 407.
A portion for diagnosing the presence or absence of leakage of fuel gas in the fuel evaporation prevention device while controlling the opening and closing of the purge control valve 23 and the canister closing valve 20 based on the PV and the opening degree information θ stored in the θ memory 408. Is.

Here, in the drive circuit 411, when the diagnosis unit 410 gives opening degree information (command) for the purge control valve 23, it has priority over the same information (command) from the purge control unit 409. Then, duty control based on the opening degree information (command) from the diagnosis unit 410 is performed on the purge control valve 23.

A drive circuit (canister block valve drive circuit) 412 is a circuit for driving the canister block valve 20 to open and close based on a command from the diagnosis section 410.
In addition, the timer 413 is a part that measures the time T after the reset start by the diagnosis unit 410, and the PAs memory 414 outputs the output of the atmospheric pressure sensor 31 read through the diagnosis unit 410 at the start of the diagnosis process. PAh is a memory in which atmospheric pressure initial information PAs is stored.

The first measured value memory 415 and the second measured value memory 416 are memories for temporarily storing the measured values of the tank internal pressure P by the diagnostic unit 410, and the flag (Xfail) memory 417 is The memory is a memory in which the abnormality flag Xfail is set when it is determined that the fuel vaporization prevention device has a fuel gas leak or the like as a diagnostic result based on the measured values. When the abnormality flag Xfail is set (= 1) in the flag memory 417, the driver is notified to that effect through a warning lamp (not shown) or the like, for example. (B) After that, as an error flag to be referred to at the time of diagnosis / repair by a dealer or the like, the error flag is registered in its own memory. Etc. shall be performed.

FIGS. 6 to 13 show the execution procedure of the diagnostic process mainly performed by the electronic control unit 40. Hereinafter, referring to FIGS. The diagnostic process by the apparatus of the embodiment will be described in more detail.

First, FIG. 6 shows a calculation procedure of the air-fuel ratio correction coefficient FAF executed mainly by the air-fuel ratio correction coefficient calculation section 404 of the electronic control unit 40. It should be noted that this calculation process is performed in synchronization with the rotation of the engine 1, for example, 36
It shall be executed every 0 ° CA (crank angle).

In the same calculation process, the electronic control unit 40 first determines in step 100 whether or not the above-mentioned air-fuel ratio feedback (F / B) condition is satisfied. As a result, when it is determined that the condition is not satisfied, in step 101, the air-fuel ratio correction coefficient FA
F is set to "1.0" and the processing is temporarily exited. That is, in this case, the air-fuel ratio is not corrected.

On the other hand, this air-fuel ratio feedback (F /
B) If it is determined that the conditions are met, the electronic control unit 40 further proceeds to step 102 to set the O2 sensor 10
Read the output of, and this is R (rich) / L (lean)
Which of the two is shown is determined. For this judgment,
The target air-fuel ratio is referred to as the judgment standard.

When it is determined in step 102 that the output of the O 2 sensor 10 is R (rich),
The electronic control unit 40 further compares the result of the previous determination in step 103, and further determines whether or not the result of this determination has been reversed from L (lean) to R (rich). Then, when it is determined that the L (lean) is newly changed to the R (rich) this time, in step 104, FAF ← FAF−α (α: skip amount) (2) The air-fuel ratio correction coefficient FAF is calculated. On the other hand, when it is determined that the previous time is already R (rich) and it is not newly inverted from L (lean) this time, in step 105, FAF ← FAF−β (β: integral amount , Α> β) (3) FAF is calculated as a new air-fuel ratio correction coefficient FAF.

In step 102, the O
2 When it is determined that the output of the sensor 10 is L (lean), the electronic control unit 40 compares the determination result of the previous time in step 106 with R (rich) to L in this determination.
It is further judged whether or not it has been reversed to (lean). Then, when it is determined that the R (rich) is newly inverted to the L (lean) this time, in step 107, FAF ← FAF + α (α: skip amount) (4) It is calculated as the fuel ratio correction coefficient FAF. On the other hand, if it is already L (lean) in the previous time and it is judged that it is not newly inverted from R (rich) this time, in step 108, FAF ← FAF + β (β: integral amount) ... (5) FAF is calculated as a new air-fuel ratio correction coefficient FAF.

By performing such calculation processing for the air-fuel ratio correction coefficient FAF, R (rich) and L
If there is an inversion with (lean), the same correction coefficient F
A large correction (skip) for AF is performed, and R
When the determination of (rich) or L (lean) is maintained, a comparatively gentle correction (integration) is performed with the same correction coefficient FA.
It will be done for F.

The air-fuel ratio correction coefficient FAF calculated in this way is sequentially stored in the FAF memory 405. In the apparatus of the same embodiment, the above F
In the AF memory 405, two of the air-fuel ratio correction coefficient FAFi calculated this time and the same correction coefficient FAFi-1 calculated last time are stored.
Two values shall be stored. That is, each time the air-fuel ratio correction coefficient FAF is newly calculated, the past values are sequentially updated by the calculated new value.

FIG. 7 shows the evaporation concentration CP mainly executed by the evaporation concentration detecting section 406 of the electronic control unit 40.
5 shows a procedure for detecting V and a procedure for setting a purge control valve opening degree θ set as a value corresponding to the detected evaporation concentration CPV. Note that this process is, for example, 512 m
It shall be executed by interrupting every s (millisecond).

Now, in this evaporation concentration detection processing,
First, in step 201, the electronic control unit 40 determines whether or not the purge control through the purge control unit 409 is being executed. As a result, when it is determined that the purge control is not executed, the process is temporarily exited.

On the other hand, when it is determined that the purge control is being executed, the electronic control unit 40 determines from the air-fuel ratio correction coefficients FAFi and FAFi-1 stored in the FAF memory 405 in the next step 202. The average value FAFA
Calculate V. Then, based on the calculated average value FAFAV of the air-fuel ratio correction coefficient, the size thereof is measured in steps 210 to 230, and the modes shown in steps 211 to 231 are respectively determined according to the measured sizes. Then, the corresponding evaporative concentration CPV is detected.

That is, assuming that the target value of the average value FAFAV is "1.0", the determination value KF1 is "0.95" and the determination value KF2 is "1.05". These are set respectively and these judgment values K
The magnitude of the same average value FAFAV is measured based on F1 and KF2. Then, as a result of this measurement, for example, through step 210, the size of the FAFAV is determined by the determination value KF1.
When it is determined that it is (“0.95”) or less, through the corresponding step 211, the evaporation concentration CPV is detected (increase correction) in the form of CPV = CPV + KCP (6). Here, the value KCP is a predetermined constant value for density correction. Similarly, if it is determined in step 220 that the magnitude of the FAFAV is KF1 <FAFAV <KF2, the corresponding step 2 is performed.
Through 21, the evaporative concentration CPV is detected (the current state is maintained) in the form of CPV = CPV (7). Similarly, if it is determined in step 230 that the magnitude of the FAFAV is greater than or equal to the determination value KF2 (“1.05”), then CPV = CPV is determined in step 231. The evaporation concentration CPV is detected (corrected for reduction) in the form of -KCP (8). It should be noted that all of these detected (corrected) evaporation concentration CPVs are sequentially updated and stored in the CPV memory 407.

Further, the electronic control unit 40 which has detected the evaporative concentration CPV in this way is further provided with the detected evaporative concentration CP.
Based on V, the shade is determined in steps 240 to 260, and the purge control valve 23 is determined in the manner shown in steps 241-261 in accordance with the determined shade.
The opening degree information θ of is corrected.

That is, in the steps 240 to 260, the judgment value KPV1 is the corresponding evaporation concentration C.
It is a value adapted to determine that the purge control valve 23 is too open for PV, and the determination value KPV2 is conversely, because the purge control valve 23 is too closed for the corresponding evaporation concentration CPV. It is a value adapted to determine that there is. Therefore, when the detected (corrected) evaporation concentration CPV is determined to be equal to or less than the determination value KPV1 through, for example, step 240, it is determined that the purge control valve 23 is too open, and the corresponding step. Through 241, the opening degree information θ is corrected in the closing direction in the form of θ = θ−KS1 (9).
Here, the value KS1 is a predetermined constant value for correcting the opening degree of the purge control valve 23. Similarly, as a result of the above determination, for example, through step 250, the same evaporation concentration CP
When it is determined that V is KPV1 <CPV <KPV2, it is determined that the purge control valve 23 has an appropriate opening degree, and through the corresponding step 251, the opening degree is θ = θ (10). The information θ is set (the current state is maintained). Similarly, as a result of the above determination, for example, step 2
Through 60, the same evaporative concentration CPV is the above judgment value KPV.
When it is determined that the number is 2 or more, the purge control valve 23
Is closed too much, its corresponding step 261
Through the above, the opening degree information θ is corrected in the opening direction in the form of θ = θ + KS1 (11).
The opening information θ set (corrected) is the same as the above θ.
The data is sequentially updated and stored in the memory 408.

FIGS. 8 to 13 show the procedure of the diagnosis process of the fuel transpiration prevention device, which is executed by the diagnosis unit 410 of the electronic control unit 40. It should be noted that the diagnostic process is executed by a time interrupt, for example, every 256 ms, through an appropriate flag process. However, in FIGS. 8 to 13, for convenience, the processing procedure is shown as a series of continuous processes. ing.

In the diagnosis process, the electronic control unit 40 first determines in step 301 whether or not 400 seconds have elapsed since the engine 1 was started. As a result, when it is determined that the time has not yet reached 400 seconds, it is determined that the operation state is unstable immediately after the start, and the process is temporarily exited (see FIG. 10).

On the other hand, when it is determined that 400 seconds have elapsed after the start, the electronic control unit 40 proceeds to the next step 30.
At 2, the output PAh of the atmospheric pressure sensor 31 is read and used as atmospheric pressure initial information PAs in the PAs memory 4
Store in 14.

The electronic control unit 40 that has thus stored the atmospheric pressure initial information PAs then gradually closes the purge control valve 23 fully in step 303. The purge control valve gradual closing process is shown in detail in FIG.

That is, in the purge control valve gradual closing process, the electronic control unit 40 (diagnosis unit 410) performs step 3
After reading the opening degree information θ stored in the θ memory 408 in 031, in step 3032 the CPV is read.
The evaporation concentration CPV stored in the memory 407 is read, and in the next step 3033, the gradual change amount Δθ1 corresponding to the read evaporation concentration CPV is map-calculated. As is also shown in the figure, this gradual change amount Δθ1 is
It is calculated as a value that decreases as the evaporation concentration CPV increases. In this way, the electronic control unit 40 that obtains the gradual change amount Δθ1
In steps 3034 and 3035, the calculation θ ← θ−Δθ1 (12) is repeatedly executed until the purge control valve 23 is fully closed. The calculated opening θ is sequentially given to the drive circuit 411, and the opening of the purge control valve 23 is duty-controlled through the drive circuit 411 so as to match the opening θ. As a result, the purge control valve 2
3 is the speed Δ corresponding to the evaporative emission concentration CPV at that time from the opening degree θr set according to the operating state at that time.
At θ1, the driving is gradually made to the fully closed state.

When the gradual closing process of the purge control valve 23 is completed in this way, the electronic control unit 40 then closes the canister blocking valve 20 in step 304 (FIG. 8), and then in step 305, the fully closed valve is closed. The purge control valve 23
The valve is gradually opened to a predetermined diagnosis opening θt corresponding to the tank internal pressure P. The purge control valve gradual opening process A is shown in detail in FIG.

That is, in the purge control valve gradual opening process A, the electronic control unit 40 (diagnosis unit 410) reads the output of the pressure sensor 25, that is, the tank internal pressure P in step 3051, and in the next step 3052, A map is calculated for the diagnostic opening θt corresponding to the read tank internal pressure P. As also shown in the figure, the diagnostic opening θt is calculated as a value that increases in proportion to the tank internal pressure P. The electronic control unit 40 that has obtained the diagnosis opening θt in this manner continues at step 3053.
The evaporation concentration CPV stored in 07 is read, and in the next step 3054, the read evaporation concentration CPV is read.
A map calculation is performed on the gradual change amount Δθ2 corresponding to PV. This gradual change amount Δθ2 is the same as the above-mentioned gradual change amount Δθ1 and the evaporation concentration C
The higher the PV is, the smaller the value is calculated. Then, the electronic control unit 40 proceeds to steps 3055 and 305.
At 6, the calculation θ ← θ + Δθ2 (13) is repeatedly executed until the opening of the purge control valve 23 reaches the diagnostic opening θt. As described above, the calculated opening θ is sequentially given to the drive circuit 411, and the opening of the purge control valve 23 is duty-controlled through the drive circuit 411 so as to match the opening θ. As a result, the purge control valve 23 is changed from the fully closed state to
At the speed Δθ2 corresponding to the evaporation concentration CPV at that time,
The diagnostic opening θt gradually corresponding to the tank internal pressure P at that time
Will be driven up to.

Incidentally, the above-mentioned steps 303 to 305.
In the fuel evaporation prevention apparatus, the section from the fuel tank 12 to the purge control valve 23 is once closed by the process of FIG. 8 and then the purge control valve 23 is opened up to the diagnostic opening θt. Along with the valve, negative pressure is introduced from the intake pipe 2.

Thus, the diagnostic opening θt of the purge control valve 23
The electronic control unit 40, which has completed the slow-opening process A up to, then resets and starts the timer 413 in step 306, and through steps 307 and 308, adjusts the pressure in the fuel evaporation prevention device to which the negative pressure is introduced. First diagnostic pressure K
Set to PLOW. By the way, this first diagnostic pressure K
PLOW is, for example, "-2 kPa (kilopascal)".
It is assumed that the negative pressure is about the same.

On the other hand, in step 308, the tank internal pressure P
Whether or not the pressure in the fuel transpiration prevention device, which is measured as, reaches the first diagnostic pressure KPLOW within a predetermined time is monitored based on the determination time KTLOW. As this determination time KTLOW, for example, a time of about “120 seconds” is set. Even if this judgment time KTLOW elapses, the pressure in the fuel transpiration prevention device remains the first diagnostic pressure KPLO.
If it has not reached W, it is determined that the purge passage is blocked for some reason, and the abnormality flag Xfail is set in the flag memory 417 (step 333 in FIG. 10). Then, in this case, the canister closing valve 20 is opened (step 334 in FIG. 10),
The purge control valve 23 is gradually returned to the opening degree θr according to the operating state (step 335 in FIG. 10), and then the processing relating to the diagnosis is temporarily exited.

In the pressure setting process in steps 307 to 308, when it is determined that the pressure in the fuel evaporation prevention device has reached the first diagnostic pressure KPLOW, the diagnostic process is further described below. The process of is continuously executed.

The electronic control unit 40, which has judged that the pressure setting has been completed, then proceeds to step 309 to set the purge control valve 2
3 is fully closed again, and the timer 413 is reset and started again in step 310. Then, the next step 31
Through steps 1 to 312, wait until the pressure in the sealed fuel evaporation prevention device becomes stable. That is, here, the determination time T1 is a time of about 10 seconds in which the pressure fluctuation in the fuel evaporation prevention device will be sufficiently suppressed. Also here
As in step 312, the pressure (tank internal pressure P) in the fuel evaporation prevention device is the first diagnostic pressure KPLOW.
Even if the pressure rises by a predetermined pressure KPLOW ′ (for example, 0.2 kPa), the pressure inside the fuel evaporation prevention device is considered to be stable.

The electronic control unit 40, which has thus judged that the pressure inside the fuel evaporation prevention apparatus has stabilized, then proceeds to step 31.
3 (FIG. 9), the timer 413 is reset and started, and at step 314, the tank internal pressure P at that time is started.
Is registered in the first measurement value memory 415 as the measurement value P1a. Then, after that, through steps 315 to 316, the determination time T2 (for example, 15 seconds) is awaited,
When 2 has elapsed, the tank internal pressure P at that time is registered in the first measured value memory 415 as the measured value P1b again in step 317.

Here, as in the processing of step 316, while waiting for the elapse of the time T2, a predetermined value KA is obtained.
When there is an atmospheric pressure fluctuation of H (for example, 0.5 kPa) or more, that is, the difference between the atmospheric pressure initial information PAs stored in the PAs memory 414 at the start of the previous diagnosis and the output PAh of the atmospheric pressure sensor 31 read at that time. Absolute value of | PAs
When −PAh | becomes KAH ≦ | PAs−PAh | (14), the canister blocking valve 20 is opened (see FIG. 1).
0 step 334), the purge control valve 23 is gradually returned to the opening degree θr according to the operating state (step 33 in FIG. 10).
5), temporarily exits the processing related to the diagnosis. This is a measure for preventing the erroneous diagnosis due to the atmospheric pressure fluctuation above the predetermined value because the output P of the pressure sensor 25 is easily affected by the atmospheric pressure PAh. By performing such processing, the reliability of the diagnostic apparatus of the embodiment can be greatly improved.

If the diagnosis process is not interrupted through step 316, the electronic control unit 40 further calculates in step 318 based on the measured values P1a and P1b registered in the first measured value memory 415. ΔPM1 ← P1b-P1a (15) is executed, and the obtained value ΔPM1, that is, the first value
The pressure increase amount due to the fuel gas at the diagnostic pressure KPLOW is registered in the first measured value memory 415 separately. Then, after that, in step 319, the canister closing valve 20 is opened, and in step 320, the timer 413 is reset and started to set the pressure in the fuel evaporation prevention device to the next second diagnostic pressure KPHI. The process of is started. However, here, as in the processing of the next step 321, the calculated pressure increase ΔPM1 is set to a value of, for example, about “0.5 kPa”.
If it is equal to or less than PM, the canister shutoff valve 2 is judged based on the judgment that the airtightness in the fuel evaporation prevention device is sufficiently maintained.
0 is opened (step 334 in FIG. 10: however, the valve has already been opened here), the purge control valve 23 is gradually returned to the opening degree θr according to the operating state (step 335 in FIG. 10), and the diagnosis processing is once performed. finish. That is, in this case, the measurement based on the second diagnostic pressure KPHI is unconditionally canceled.

If the condition in step 321 is not satisfied, the electronic control unit 40 further executes the second diagnostic pressure KPHI in the following procedure based on the pressure measurement based on the first diagnostic pressure KPLOW. Perform pressure measurement based on.

That is, in the electronic control unit 40, first,
Through steps 322 to 323, the pressure in the fuel evaporation prevention device released by the canister closing valve 20 is set to the second diagnostic pressure KPHI. Incidentally, the second diagnostic pressure KPHI is set to a value in the vicinity of the atmospheric pressure of, for example, "-0.2 kPa".

Further, here, for example, a time of about "90 seconds" is set as the determination time KTHI at which the pressure in the fuel evaporation prevention device will reach the second diagnostic pressure KPHI. Therefore, the pressure in the fuel evaporation prevention device measured as the tank internal pressure P is the second diagnostic pressure KPH.
If the time T measured by the timer 413 reaches the determination time KTHI even if it does not reach I, it is considered that the second diagnostic pressure has been set.

In this way, the pressure inside the fuel evaporation prevention device is the second
When the diagnostic pressure KPHI is reached, or when the time T measured above reaches the determination time KTHI, the electronic control unit 4
Next, in step 324, the canister closing valve 20 that has been opened is closed again. Then, in step 325 (FIG. 10), the timer 413 is reset and started, and in step 326, the tank internal pressure P at that time is registered in the second measured value memory 416 as the measured value P2a. And after that, steps 327 to 3
The judgment time T3 (for example, 15 seconds) is waited for through step 28, and when the time T3 has elapsed, step 329 is executed again.
Then, the tank internal pressure P at that time is registered in the second measured value memory 416 as the measured value P2b.

Here, as in the processing of step 328, while waiting for the elapse of the time T3, the above (1
Predetermined value KAH (0.5 kP
If the atmospheric pressure fluctuation is a) or above, the canister closing valve 20 is opened (step 334 in FIG. 10), and the purge control valve 23 is gradually returned to the opening degree θr according to the operating state ( Step 335 in FIG. 10), the processing relating to the diagnosis is temporarily exited. As described above, such a process is a measure for preventing an erroneous diagnosis from being performed due to an atmospheric pressure fluctuation of a predetermined value or more.

If the diagnosis process is not interrupted in step 328, the electronic control unit 40 further calculates in step 330 based on the measured values P2a and P2b registered in the second measured value memory 416, ΔPM2. ← P2b-P2a (16) is executed, and the obtained value ΔPM2, that is, the second value
The pressure increase amount due to the fuel gas at the diagnostic pressure KPHI is separately registered in the second measured value memory 416.

Thus, the first and second measurement value memory 415
In step 331, the electronic control unit 40 registers the pressure increase amount ΔPM1 at the first diagnostic pressure KPLOW and the pressure increase amount ΔPM2 at the second diagnostic pressure KPHI in 416 and 416, respectively. ΔPM1-
ΔPM2 ”is compared with a preset determination value REF. Then, as a result, if the condition of REF ≧ ΔPM1−ΔPM2 (17) is satisfied, at step 332, the abnormality flag Xfail of the flag memory 417 is cleared (Xfail ← 0), and the condition of the equation (17) is satisfied. If not established, in step 333, the flag memory 417
The error flag Xfail is set to (Xfail ←
1). That is, when fuel gas leakage or the like occurs in the fuel evaporation prevention device, the first diagnostic pressure KPL
Under a negative pressure such as OW, there is an inflow of air (ΔPM1 increases), and under a positive pressure such as the second diagnostic pressure KPHI described above, an outflow to the atmosphere occurs (ΔPM2 decreases). Therefore, when the difference “ΔPM1−ΔPM2” exceeds a predetermined value (REF) and is large, it can be diagnosed that an abnormality such as a fuel gas leakage has occurred in the fuel evaporation prevention device. it can. The abnormality flag Xf
When ail is set, the driver is notified to that effect through, for example, (a) a warning lamp or the like not shown. (B) After that, as an error flag to be referred to at the time of diagnosis / repair by a dealer or the like, the error flag is registered in its own memory. It is described above that the processing such as the above is performed.

When the diagnosis is completed in this way, the electronic control unit 4
0 is finally the canister shutoff valve 20 in step 334.
After the valve is opened, in step 335, the purge control valve 23 in the fully closed state is opened by the opening θ depending on the operating state at that time.
Open the valve gradually until r. This purge control valve gradual opening process B
13 is shown in detail in FIG.

That is, in the purge control valve gradual opening process B, the electronic control unit 40 (diagnosis unit 410) uses the opening degree information θ stored in the θ memory 408 in step 3341 to determine the opening degree according to the operating state. After being read as θr, the evaporation concentration CPV stored in the CPV memory 407 is read in step 3342, and the next step 3
At 343, the map is calculated for the gradual change amount Δθ3 corresponding to the read evaporation concentration CPV. As also shown in the figure, this gradual change amount Δθ3 is also the previous gradual change amount Δθ1 or Δ.
Similar to θ2, the higher the evaporation concentration CPV, the smaller the calculated value. The electronic control unit 40 that has obtained the gradual change amount Δθ3 in this way, in steps 3344 and 3345,
The calculation θ ← θ + Δθ3 (18) is repeatedly executed until the purge control valve 23 reaches the opening θr. The calculated opening θ is sequentially given to the drive circuit 411, and the opening of the purge control valve 23 is duty-controlled through the drive circuit 411 so as to match the opening θ.
Alternatively, it is similar to the case of 305. As a result, the purge control valve 23 is gradually driven from the fully closed state at the speed Δθ3 corresponding to the evaporative concentration CPV at that time to the opening degree θr corresponding to the operating state at that time. .
If the abnormality flag Xfail is set through the previous step 308 (FIG. 8) or if the diagnosis process is interrupted, the diagnosis opening θt and the opening θr corresponding to the operating state are set. Depending on the relationship, the gradual closing control such as θ ← θ−Δθ3 (18) ′ may be executed.

FIG. 14 shows the canister closing valve 20, the purge control valve 23, and the pressure sensor 2 which accompany the above-described diagnostic processing.
5 shows the transition of the tank internal pressure P detected through No. 5 as a whole. As shown in FIG. 14, according to the diagnostic device of this embodiment, (1) after the fuel evaporation preventing device is sealed by gradually closing the purge control valve 23 and closing the canister closing valve 20, the purge control valve is closed. The negative pressure from the intake pipe 2 is introduced into the fuel evaporation prevention device by gradually opening 23 to the diagnosis opening θt. At this time, if the tank internal pressure P does not decrease to the first diagnostic pressure KPLOW even after the predetermined time KTLOW, it is considered that there is a blocked portion in the purge passage.
The abnormality determination is performed and the diagnosis ends. (2) By the introduction of this negative pressure, the purge control valve 23 is closed when the tank internal pressure P drops to the first diagnostic pressure KPLOW, and after a stable period of time T1, a first period of time T2 is reached. The measurement is performed. In this measurement,
The pressure difference (amount of pressure increase) ΔPM1 between the tank internal pressure P1a at the start of measurement (immediately after the passage of time T1) and the tank internal pressure P1b after the passage of time T2 is obtained. FIG.
As indicated by the alternate long and short dash line in 4 (c), the tank internal pressure P
Even after the pressure has decreased to the first diagnostic pressure KPLOW by the same pressure KPLOW ', the first measurement process is started assuming that the tank internal pressure P is stable. Further, at this time, when fuel gas leaks in the fuel vaporization prevention device, since there is an inflow of the atmosphere as described above, the transition L2 indicated by a broken line from the transition L1 in the tank pressure at the normal time is shown.
A large increase in pressure will occur. That is, the value of the pressure difference ΔPM1 increases. (3) After that, the canister closing valve 20 is opened, and the atmosphere is introduced into the fuel evaporation prevention device. (4) By introducing this atmosphere, the canister closing valve 20 is closed when the tank internal pressure P rises to the second diagnostic pressure KPHI, and then the second measurement is executed over the time T3. In this measurement, the tank internal pressure P2a at the start of the measurement and the tank internal pressure P2 after the lapse of time T3
The pressure difference (pressure increase) ΔPM2 from b is obtained. At this time, when fuel gas leaks in the fuel evaporation prevention device, since there is an outflow to the atmosphere as described above, the change L in the broken line relative to the change L1 in the tank pressure during normal operation.
As shown by 2, the pressure rise is suppressed. That is, the value of the pressure difference ΔPM2 becomes small. (5) The diagnosis result is registered in the flag memory 417 based on whether or not the above expression (17) is satisfied by the values ΔPM1 and ΔPM2 obtained above. However, in the measurement in (2) or (4) above, if there is a change in atmospheric pressure equal to or higher than the predetermined value KAH, the diagnosis is interrupted and terminated. (6) With the completion of the diagnosis, the canister closing valve 20 is opened, and the purge control valve 23 is gradually opened to the opening degree θr according to the operating state at that time. The diagnosis process is executed in this manner.

Therefore, according to the apparatus of the embodiment, when the purge passage of the fuel evaporation prevention apparatus is clogged or leaks, the fact can be promptly and accurately diagnosed.

Further, according to the apparatus of the embodiment, when the purge control valve 23 is opened / closed during the pressure adjustment inside the fuel evaporation prevention apparatus, the valve position thereof gradually changes at a predetermined speed as described above. Therefore, it is possible to avoid a situation in which the fuel supply amount to the engine 1 or the intake air amount suddenly increases or decreases due to the opening and closing.

Moreover, the canister closing valve 20 is opened and closed only under the condition that the purge control valve 23 is fully closed through the above-mentioned control by the electronic control unit 40 (diagnosis section 410), so that the intake pipe is connected to the intake pipe. There is no concern that the mixture ratio (air-fuel ratio) of the supplied air-fuel mixture will change due to the opening / closing drive of the canister blocking valve 20.

Therefore, even if the above-mentioned diagnosis is executed while the vehicle is traveling, a highly accurate diagnosis of whether or not there is an abnormality in the fuel evaporation prevention device such as fuel gas leakage without causing any drivability defect. Will be done.

By the way, when the atmospheric pressure changes during the first and second measurements, the pressure increase mode of the tank internal pressure P measured, that is, the value of ΔPM1 or ΔPM2 also changes in the mode shown in FIG. 15, for example. To do.

Incidentally, in FIG. 15, the solid line L1 shows the transition of the tank internal pressure P at normal atmospheric pressure, and the one-dot chain line L3.
Indicates a transition of the tank internal pressure P in a place where the atmospheric pressure is low, such as in highlands. As described above, the tank internal pressure P tends to increase greatly as the atmospheric pressure decreases (ΔPM1 and ΔPM2 increase), and conversely, the increase is suppressed as the atmospheric pressure increases (ΔPM1 and ΔPM2 decrease). Therefore, when the atmospheric pressure changes greatly during these measurements, such as when traveling on a slope where uphill and downhill are repeated, the transition tendency of the tank internal pressure P is disturbed in the manner shown in FIG. 16, for example. It occurs and its diagnosed results are also questionable.

Therefore, as in the apparatus of the above embodiment,
Changes in atmospheric pressure detected during these measurements | PAs-PA
When h | is greater than or equal to a predetermined value KAH, if the diagnosis process is interrupted (stopped), at least an erroneous diagnosis due to the change in the atmospheric pressure can be avoided, and the reliability of the diagnosis device can be improved. It will be improved by itself. In other words, by adopting such a configuration, the diagnostic function is effectively protected, and the above-described highly accurate diagnostic process is always maintained appropriately. Incidentally, in the example of FIG. 16, as shown in FIG. 16D, the diagnosis process is interrupted at the timing tESC when the atmospheric pressure change | PAs-PAh | becomes the predetermined value KAH or more. Become.

In the apparatus of the embodiment, the diagnosis process is stopped when the atmospheric pressure change | PAs-PAh | becomes equal to or more than the predetermined value KAH in this way. , The diagnostic process itself continues to the end,
Of course, when there is such a change in atmospheric pressure that is equal to or greater than a predetermined value, the diagnosis result may be invalidated.

Further, in the apparatus of the above-mentioned embodiment, by using the above-mentioned differential pressure sensor as the pressure sensor 25, the cost can be significantly reduced as compared with the case where the sensor for measuring the tank internal pressure as an absolute pressure is used. It is possible.
However, when using such a differential pressure sensor, it is desirable to correct the pressure detected by the pressure sensor 25 or its determination value in accordance with the atmospheric pressure PAh detected by the atmospheric pressure sensor 31, for example. The pressure sensor 2
5 itself is not limited to the fuel tank 12, but the fuel tank 1
It may be arranged in any part of the section from 2 to the canister 16.

Further, in the apparatus of the above embodiment, the value of ΔPM1 obtained by the first measurement is the predetermined value KD through the processing in step 321 (FIG. 9) of the previous diagnosis processing.
If it is equal to or less than PM, the fuel transpiration prevention device is determined to be normal and the diagnosis process is directly terminated. Therefore, the useless diagnostic processing is not continued, and the limited arithmetic processing capacity of the electronic control unit 40 can be effectively utilized. The process in step 321 is the same as ΔP in step 318.
Of course, the processing structure may be executed immediately after the processing for calculating M1.

Further, in the apparatus of the above embodiment, the "close purge process" is not particularly applied to the "purge control valve closing" process in step 309 (FIG. 8) of the diagnostic process.
Practically, it is more desirable to apply the gradual closing process through the procedure shown in FIG. 11 also to the valve closing process. Incidentally, in this case, the purge control valve 23 is
The valve is gradually closed in the manner shown by the chain double-dashed line in FIG. 14B, and further improvement in drivability is expected.

Further, in the apparatus of the above-mentioned embodiment, it is possible to diagnose the presence or absence of leakage based on the difference between the negative pressure change amount ΔPM1 and the atmospheric pressure change amount ΔPM2 which are obtained through the first and second measurements. However, the values of ΔPM1 and ΔPM2 do not necessarily need to be extracted under such pressure. That is, these ΔPM
In addition, as the values of 1 and ΔPM2, both can be extracted as the pressure change amounts from the positive pressure equal to or higher than the atmospheric pressure, or conversely, both can be extracted as the pressure change amounts from the negative pressure. In the first place, if the pressure value at the start of measurement is different, the leak speed (leak) speed of the fuel gas from the damaged part will also be different, so the pressure adjustment condition (pressure adjustment condition) for starting these measurements is greater than atmospheric pressure. Whether pressure is
Or, if you pay attention to the difference in leak speed between negative pressures,
It is possible to detect the presence or absence of the cause of leakage in those closed sections.

Further, in the apparatus of the above embodiment, the evaporative concentration is detected based on the average value FAFAV of the air-fuel ratio correction coefficient FAF, but the evaporative concentration is detected by using the concentration sensor dedicated to the same. Of course you can do it. However, according to the configuration of the apparatus of the embodiment, it is possible to detect the same concentration without using any special sensor for measuring the evaporation concentration.

[0108]

As described above, according to the present invention, it is possible to surely avoid the erroneous diagnosis caused by the change in the atmospheric pressure, and appropriately maintain the diagnosis process regarding the presence or absence of the abnormality of the fuel transpiration prevention device. become able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a diagnostic device according to the present invention.

FIG. 2 is a cross-sectional view showing the valve structure of the canister blocking valve shown in FIG.

3 is a cross-sectional view showing a valve structure of the purge control valve shown in FIG.

FIG. 4 is a graph showing a duty driving mode of the purge control valve.

5 is a block diagram showing a functional configuration of the electronic control device shown in FIG.

FIG. 6 is a flowchart showing a procedure for calculating an air-fuel ratio correction coefficient by the device.

FIG. 7 is a flowchart showing a procedure for detecting the evaporation concentration by the apparatus.

FIG. 8 is a flowchart showing a processing procedure of diagnostic processing by the apparatus.

FIG. 9 is a flowchart showing a processing procedure of diagnostic processing by the apparatus.

FIG. 10 is a flowchart showing a processing procedure of diagnostic processing by the apparatus.

FIG. 11 is a flowchart showing an example of a procedure for gradually closing the purge control valve by the same device.

FIG. 12 is a flowchart showing an example of a procedure for gradually opening a purge control valve by the same device.

FIG. 13 is a flowchart showing an example of a procedure for gradually opening the purge control valve by the same device.

FIG. 14 is a time chart showing changes in the internal pressure of each valve and tank associated with the above diagnosis.

FIG. 15 is a time chart illustrating the influence of the atmospheric pressure on the tank internal pressure.

FIG. 16 is a time chart showing the relationship between the tank internal pressure and an excessive change in atmospheric pressure.

[Explanation of symbols]

1 ... Gasoline engine (internal combustion engine), 2 ... Intake pipe, 3 ...
Exhaust pipe, 4 ... Air cleaner, 5 ... Accelerator pedal, 6 ...
Throttle valve, 7 ... intake valve, 8 ... combustion chamber, 9 ...
Exhaust valve, 10 ... O2 sensor, 11 ... Water temperature sensor, 1
2 ... Fuel tank, 12a ... Relief valve, 13 ... Fuel pump, 14 ... Fuel injection valve, 15 ... Communication pipe, 16 ... Canister, 17 ... Canister body, 18 ... Adsorber, 19 ... Atmosphere hole, 20 ... Canister closing valve , 20a ... coil, 20b
... valve body, 20c ... spring, 20d ... conduit, 21 ... hose connection part, 22, 24 ... supply pipe, 23 ... purge control valve, 23a ... canister side port, 23b ... intake pipe side port, 23c ... passage, 23d ... Valve body, 23e ... Spring, 23f ... Coil, 25 ... Pressure sensor, 26 ... Throttle opening sensor, 27 ... Idle switch, 28 ... Vehicle speed sensor, 29 ... Rotation speed sensor, 30 ... Intake pipe pressure sensor, 31 ... Atmospheric pressure Sensor, 40 ... Electronic control device, 41 ...
CPU, 42 ... ROM, 43 ... RAM, 44 ... Input / output circuit, 45 ... Common bus, 401 ... Basic injection amount calculation unit, 4
02 ... Fuel injection amount calculation unit, 403 ... Drive circuit (fuel injection valve drive circuit), 404 ... Air-fuel ratio correction coefficient calculation unit, 405
... FAF memory, 406 ... Evaporation concentration detecting section, 407 ...
CPV memory, 408 ... θ memory, 409 ... Purge control unit, 410 ... Diagnostic unit, 411 ... Drive circuit (purge control valve drive circuit), 412 ... Drive circuit (canister closing valve drive circuit), 413 ... Timer, 414 ... PAs Memory, 41
5 ... 1st measurement value memory, 416 ... 2nd measurement value memory, 4
17 ... Flag memory (Xfail).

Claims (4)

[Claims] 1. A fuel gas generated in a fuel tank is stored in a canister provided in the middle of a purge passage communicating between the fuel tank and an intake pipe, and the stored fuel gas is purged in the purge passage. A diagnostic device for a fuel transpiration prevention device that detects whether there is a malfunction in the fuel transpiration prevention device that is introduced into the intake pipe while adjusting the flow rate according to the operating state of the internal combustion engine by the control valve, and detects the atmospheric pressure. An atmospheric pressure sensor, and a protection means for stopping the diagnosis process or invalidating the diagnosis result when the change in the atmospheric pressure detected during the diagnosis exceeds a predetermined amount. Diagnostic device for fuel evaporation prevention device. 2. The diagnostic device comprises a pressure sensor for detecting the pressure in the fuel tank or in the section from the fuel tank to the canister, and regulates the pressure inside the fuel evaporation prevention device to a predetermined first pressure. Change amount of the pressure detected by the pressure sensor within a predetermined time when closed and the pressure sensor within the predetermined time when the inside of the fuel transpiration prevention device is adjusted to a predetermined second pressure and sealed The diagnostic device for a fuel transpiration prevention device according to claim 1, wherein the presence or absence of a device abnormality of the fuel transpiration prevention device is diagnosed based on the amount of change in the detected pressure. 3. The fuel transpiration prevention device according to claim 2, wherein the pressure sensor is a differential pressure sensor that detects a differential pressure between a pressure in the fuel tank or a section from the fuel tank to the canister and atmospheric pressure. Diagnostic device. 4. The protection device has a limit of the diagnostic accuracy of the diagnostic device that can be maintained after the diagnosis is started and while the change amount of each detected pressure at least at the first pressure and the second pressure is measured by the pressure sensor. 4. The diagnostic device for a fuel evaporation prevention device according to claim 3, wherein when the atmospheric pressure exceeds the amount, the diagnostic process is stopped or the diagnostic result is invalidated.