JP2000154759A - Failure diagnostic device for fuel steam treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out highly precise diagnosis without being influenced by a change of the atmospheric pressure concerning a device to diagnose failure of a three-way change-over valve by using pulsation of a suction air negative pressure. SOLUTION: Fuel steam trapped by a canister 12 is purged to a suction air passage 7 of an engine 4 as opening degree of a purge control valve 20 is duty-controlled. Internal pressure on the side of a fuel tank 2 and internal pressure on the side of the canister 12 are selectively detected as a three-way change-over valve 21 is changed over. An electronic control unit(ECU) 41 disgnoses failure concerning changeover of the three-way change-over valve 21 with its judgement result as a diagnostic condition by judging existence of pulsation in the tank internal pressure or the canister internal pressure selectively detected in accordance with a specified pulsation judgement value at the time when the purge control valve 20 is duty-controlled at the time of driving the engine 4. The ECU 41 is devised to compute atmospheric pressure in accordance with detection values of various sensors 32, 33, 35 and to correct the pulsation judgement value in accordance with a level of the atmospheric pressure value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel in which fuel vapor generated in a fuel tank is collected by a canister without being released to the atmosphere, and the collected fuel is purged to an intake passage of an engine. It relates to a steam treatment device. In particular, the present invention relates to a failure diagnosis device that diagnoses a failure related to the fuel vapor processing device.

[0002]

2. Description of the Related Art Conventionally, there is a fuel vapor treatment device as one of devices mounted on a vehicle. This processing device is for collecting and processing fuel vapor generated in a fuel tank for storing fuel supplied to an engine without discharging the fuel vapor to the atmosphere. In this type of processing apparatus, a canister collects fuel vapor generated in a fuel tank. The canister once adsorbs the fuel vapor to the adsorbent inside the canister, and discharges only gas containing no fuel component such as hydrocarbon (HC) to the outside through the communication passage. During operation of the engine, the fuel once collected in the canister is purged into the intake passage. Here, by appropriately controlling the opening of the purge control valve, the amount of fuel purged to the intake passage is appropriately adjusted according to the necessity of the engine.

[0003] In the case of this type of processing apparatus, if a failure relating to airtightness occurs in a fuel tank, a canister, or the like for some reason, there is a possibility that fuel vapor cannot be properly processed as intended.

[0004] Japanese Patent Laid-Open Publication No. Hei 6-108930 discloses an example of a failure diagnosis apparatus capable of diagnosing a failure relating to airtightness as described above. As shown in FIG. 19, the fuel vapor processing apparatus targeted by the failure diagnosis apparatus includes a fuel tank 81, a canister 82, a vapor line 83, a purge line 84, and the like. Purge line 8
4 connects the canister 82 to the intake passage 85 of the engine. A purge VSV (purge control valve) 86 provided in the purge line 84 is controlled by an electronic control unit (ECU) 87 during operation of the engine. A vapor control valve 88 provided in the vapor line 83 regulates the flow of fuel vapor between the fuel tank 81 and the canister 82. The vapor control valve 88 is a check valve, and has an internal pressure on the fuel tank 81 side (hereinafter, referred to as “tank internal pressure”) and an internal pressure on the canister 82 side (hereinafter, referred to as “canister internal pressure”). Open based on differential pressure. When the control valve 88 is opened, the canister 8 is moved from the fuel tank 81.
2 is allowed to flow. This failure diagnosis device has a three-way switching valve 89 and a pressure sensor 90 that can individually detect the tank internal pressure and the canister internal pressure with a vapor control valve 88 as a boundary. That is, the other two ports of the three-way switching valve 89 connected to the pressure sensor 90 are connected to the fuel tank 8 with the vapor control valve 88 as a boundary.
The vapor line 83 on the first side and the vapor line 83 on the side of the canister 82 are connected. Then, the ECU 87
However, by switching the three-way switching valve 89 as necessary, the tank internal pressure or the canister internal pressure is selectively detected by the pressure sensor 90, respectively. Then, the ECU 87
The airtightness of the fuel tank 81 and the canister 8 are determined based on the detected tank internal pressure and canister internal pressure.
The airtightness according to 2 is individually diagnosed.

[0005] By the way, in the above-mentioned fault diagnosis device,
If the three-way switching valve 89 should fail to switch for any reason, it becomes difficult to individually detect the values of the tank internal pressure and the canister internal pressure. For example, if the three-way switching valve 89 cannot be switched while the pressure sensor 90 detects the tank internal pressure, the ECU 87 sets the three-way switching valve 8
9 cannot be detected by controlling the pressure sensor 90 to detect the canister internal pressure. Conversely, if the three-way switching valve 89 cannot be switched while the pressure sensor 90 detects the canister internal pressure, even if the ECU 87 controls the three-way switching valve 89 and attempts to detect the tank internal pressure with the pressure sensor 90, Can not be done. Therefore, if the three-way switching valve 89 fails to switch, accurate values for the tank internal pressure and the canister internal pressure cannot be individually detected. As a result, a failure related to the airtightness of the fuel tank 81 and the canister 82 may not be properly diagnosed.

[0006] On the other hand, in the above failure diagnosis apparatus, if the purge control valve 86 fails out of control for some reason, it becomes difficult to accurately detect the value of the canister internal pressure. For example, when the valve body constituting the purge control valve 86 is fixed to the casing or the like in a closed state, an accurate value can be obtained for the canister internal pressure detected assuming that the valve body is open. Can not be. Conversely, if the valve body of the purge control valve 86 is fixed to the casing or the like with the valve body opened, an accurate value of the canister internal pressure detected on the assumption that the valve body is closed cannot be obtained. . Therefore, when the canister internal pressure is erroneously detected in this manner, a failure related to the airtightness of the canister 82 may not be properly diagnosed.

Here, JP-A-9-42074, JP-A-9-42075 and Toyota Technical Publication No. 7279 (issued on December 25, 1997) are used for diagnosing the above-mentioned failure. An example of each of the devices will be disclosed. The failure diagnosis device disclosed in Japanese Patent Application Laid-Open No. 9-42074 diagnoses a failure of the three-way switching valve as described above. This failure diagnosis device performs duty control with intermittent opening and closing of a purge control valve during operation of an engine, that is, is periodically turned on and off at a predetermined cycle, so that an intake negative pressure generated in an intake passage is controlled. Focuses on acting on the canister with pulsation. That is, in this failure diagnosis device, one of the diagnosis conditions is that the detection value of the pressure sensor when the three-way switching valve is switched to detect the canister internal pressure does not involve pulsation caused by the duty control of the purge control valve. As one,
It is determined that the three-way switching valve has failed while the detection destination of the pressure sensor is on the fuel tank side. On the other hand, when the detection value of the pressure sensor when the three-way switching valve is switched to detect the tank internal pressure is accompanied by pulsation due to the duty control of the purge control valve, one of the diagnostic conditions is that the pressure sensor is detected. It is determined that the three-way switching valve has failed while the tip is on the canister side. Here, the presence of the pulsation in the intake negative pressure is determined by comparing a value related to the amplitude with a predetermined determination value and evaluating the value.

The failure diagnosis device disclosed in Japanese Patent Application Laid-Open No. 9-42075 diagnoses a failure of the purge control valve as described above. This failure diagnosis apparatus is also configured by paying attention to the fact that pulsation of intake negative pressure acts on the canister by duty control of the purge control valve. That is, in this failure diagnosis device, when executing the fuel purge in which the purge control valve is to be opened by the duty control, the canister internal pressure becomes higher than a predetermined determination value, and the detection value of the pressure sensor does not involve pulsation. At some point, it is determined that a failure has occurred while the purge control valve is closed. Here, too, the presence of the pulsation in the intake negative pressure is determined by comparing and evaluating the pulsation with a predetermined determination value related to the amplitude.

[0009] On the other hand, Toyota Technical Publication No. 727
The failure diagnosis method disclosed in No. 9 diagnoses the failure of the purge control valve as described above. In this failure diagnosis method, when a purge control valve (purging VSV) is to be opened by duty control during fuel purge, the canister internal pressure (pressure in the purge passage leading to the canister) that fluctuates with pulsation is measured by a pressure sensor. Is detected.
The pulsation value of the detected canister internal pressure is subjected to averaging processing, whereby an averaging value (average value) is obtained. Further, the canister internal pressure fluctuating with pulsation is instantaneously detected in a half cycle of the control cycle of the purge control valve, that is, at a timing when the canister internal pressure becomes minimum and maximum, and the smoothed value and the instantaneous detection are detected. The difference from the value is calculated. Then, when the integrated value obtained by integrating the differences a plurality of times is smaller than a predetermined determination value, it is determined that the failure has occurred while the purge control valve is closed.

[0010]

However, in the above-described JP-A-9-42074, JP-A-9-42075, and the failure diagnosis apparatus and method of Toyota Publication No. 7279, the failure diagnosis apparatus and the failure diagnosis method described above are introduced into the intake passage. Since the pressure of the supplied air reflects the atmospheric pressure, the pulsation amplitude of the intake negative pressure acting on the canister due to the duty control of the purge control valve may be affected by the atmospheric pressure. In particular, when the fuel vapor processing device and its failure diagnosis device are mounted on a vehicle, the atmospheric pressure decreases as the altitude of the destination of the vehicle increases, so that the intake negative pressure relatively increases. As a result, the pulsation amplitude of the intake negative pressure acting on the canister tends to decrease. In the above failure diagnosis device and the like, since a predetermined determination value is used to evaluate the presence of pulsation, if the determination value is uniformly adapted to, for example, the magnitude of the atmospheric pressure in a lowland, the The determination value is poorly adapted to the magnitude of the atmospheric pressure at high altitude. Therefore, in a device that uses the pulsation of the intake negative pressure to diagnose failures of various components, that is, the three-way switching valve and the purge control valve, an error occurs in the evaluation of the presence of the pulsation, and the failure diagnosis is performed. There was a risk that the accuracy would decrease.

The present invention has been made in view of the above circumstances, and an object of the present invention is to diagnose a failure of a component using a pulsation of an intake negative pressure and to be affected by a change in atmospheric pressure. It is an object of the present invention to provide a failure diagnosis device for a fuel vapor processing device that can perform highly accurate diagnosis without any problem.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, a fuel vapor generated in a fuel tank is collected by a canister, and the fuel collected by the canister is collected by an engine. The fuel vapor processing apparatus includes a purge control valve that purges the intake passage based on a negative pressure generated in the intake passage during operation and that has an opening degree duty-controlled to adjust the amount of fuel to be purged. An internal pressure detecting means for detecting an internal pressure on the fuel tank side and an internal pressure on the canister side, wherein the internal pressure detecting means is used for diagnosing a failure relating to airtightness on the fuel tank side and the canister side. Switching means for selectively detecting the internal pressure detecting means for selectively detecting the internal pressure on the fuel tank side and the internal pressure on the canister side; When the valve is duty-controlled,
To determine the presence of pulsation in the internal pressure on the fuel tank side or the internal pressure on the canister side that is selectively detected based on a predetermined pulsation determination value, and use the determination result as a diagnostic condition to diagnose a failure related to switching of the switching means. In a failure diagnostic apparatus having diagnostic means, an atmospheric pressure detecting means for detecting the atmospheric pressure or a value corresponding to the atmospheric pressure, and a pulsation determination value according to the detected atmospheric pressure or the level of the equivalent value. It is intended that a determination value correcting means for correcting the data is provided.

According to the configuration of the invention described above, in the fuel vapor processing apparatus, the duty ratio of the purge control valve is controlled during operation of the engine, so that the fuel once collected in the canister is generated in the intake passage. The air is purged to the intake passage based on the action of the pressure. The amount of fuel to be purged is adjusted by the opening of the purge control valve determined by the duty control. Here, since the purge control valve is duty-controlled so that the control valve is periodically turned on and off with a predetermined cycle, the negative pressure generated in the intake passage acts on the canister with pulsation. As a result, the internal pressure on the canister side fluctuates with pulsation. According to the failure diagnosis device, when the purge control valve is duty-controlled during operation of the engine, the presence of pulsation in the internal pressure on the fuel tank side or the internal pressure on the canister side that is selectively detected is determined based on a predetermined pulsation determination value. The failure is determined by the diagnosis unit as a diagnosis condition, and a failure related to switching of the switching unit is diagnosed by the diagnosis unit. For example, when the internal pressure on the canister side is detected and the presence of pulsation at the internal pressure is not determined, it is diagnosed that the switching means has a failure related to switching using the determination result as a diagnostic condition. Alternatively, when the internal pressure on the fuel tank side is detected and the presence of pulsation is determined in the internal pressure, it is diagnosed that the switching means has a failure related to switching using the determination result as a diagnostic condition. By the way, since the pressure of the air introduced into the intake passage reflects the atmospheric pressure, the pulsation of the negative pressure acting on the internal pressure on the canister side due to the duty control of the purge control valve is affected by the atmospheric pressure. May change. However, according to the present invention, according to the level of the atmospheric pressure detected by the atmospheric pressure detecting means or its equivalent value,
The pulsation determination value in the diagnosis unit is corrected by the determination value correction unit. Therefore, even when the pulsation at the internal pressure on the canister side changes due to the influence of the atmospheric pressure during the failure diagnosis of the switching means, the pulsation determination value is corrected in accordance with the change in the pulsation, so that the pulsation is corrected. Misjudgment about existence is suppressed.

In order to achieve the above object, a failure diagnosis apparatus according to the present invention is characterized in that, instead of the judgment value correcting means in the failure diagnosis apparatus according to the first invention, the detected atmospheric pressure or its equivalent is detected. When the value is lower than the predetermined value, a driving frequency correction means for correcting the driving frequency related to the duty control of the purge control valve to be lower than the predetermined value is provided.

In the configuration of the present invention, the difference from the operation of the first aspect is as follows. That is, according to the present invention, when the atmospheric pressure detected by the atmospheric pressure detecting means or its equivalent value is lower than the predetermined value, the drive frequency related to the duty control of the purge control valve becomes lower than the predetermined value by the drive frequency correction means. It will be corrected lower. Therefore, at the time of failure diagnosis of the switching means, even if the pulsation in the internal pressure on the canister side becomes small due to the atmospheric pressure being lower than the predetermined value, the drive frequency related to the duty control is corrected to be lower than the predetermined value. As a result, pulsation due to the internal pressure on the canister side increases, and erroneous determination regarding the presence of the pulsation is suppressed.

According to a third aspect of the present invention, there is provided a fuel vapor processing apparatus according to the first or second aspect of the present invention, for controlling the introduction of air into the canister and the derivation of inside air. An atmosphere control valve including a check valve is further provided. A flow path for changing the flow path cross-sectional area of the air introduction passage in the air control valve in place of the determination value correction means or the drive frequency correction means in the failure diagnosis device according to the first or second aspect of the present invention. Means for varying the cross-sectional area;
When the detected atmospheric pressure or its equivalent value is lower than a predetermined value, control means for controlling the flow path cross-sectional area variable means to reduce the flow path cross-sectional area of the air introduction passage is provided. The purpose is assumed.

In the configuration of the present invention, the difference from the operation of the first or second aspect is as follows.
That is, according to the present invention, when the atmospheric pressure detected by the atmospheric pressure detecting means or its equivalent value is lower than a predetermined value, the control means controls the flow path cross-sectional area variable means, whereby the atmospheric pressure in the air control valve is controlled. The flow passage cross-sectional area of the introduction passage is reduced. Therefore, in the failure diagnosis of the switching means, even when the pulsation in the internal pressure on the canister side becomes small due to the atmospheric pressure being lower than a predetermined value, the air passage is reduced by reducing the flow path cross-sectional area of the air introduction passage. The intake resistance of the control valve increases, and the pulsation at the internal pressure on the canister side increases, and erroneous determination regarding the presence of the pulsation is suppressed.

According to a fourth aspect of the present invention, a fuel vapor generated in a fuel tank is collected by a canister, and the fuel collected by the canister is supplied to an intake passage of the engine during operation of the engine. A failure diagnosis device provided for a fuel vapor processing device including a purge control valve that purges the intake passage based on the generated negative pressure and that has a duty control of an opening to adjust the amount of fuel to be purged. An internal pressure detecting means for detecting the internal pressure of the canister, and when the purge control valve is to be opened by duty control during operation of the engine, the presence of pulsation in the detected internal pressure is determined based on a predetermined pulsation determination value. And a closed failure diagnostic means for diagnosing that the purge control valve is in a closed state and has failed with the determination result as a diagnostic condition. In the device, an atmospheric pressure detecting means for detecting the atmospheric pressure or a value corresponding to the atmospheric pressure, and a determination value correcting means for correcting the pulsation determination value according to the detected atmospheric pressure or the level of the equivalent value It is intended to have.

According to the configuration of the present invention, when the purge control valve is to be opened by the duty control during the operation of the engine, the presence of the pulsation in the internal pressure on the canister side detected by the internal pressure detecting means is determined by the predetermined pulsation determination value. Is determined by the closed-failure diagnosing means, and the result of the determination is diagnosed by the closed-failure diagnosing means as a diagnostic condition that the purge control valve is in the closed state and has failed. For example, when the presence of pulsation is not determined when the purge control valve is opened by the duty control, it is diagnosed that the purge control valve is in a closed state and malfunctions, using the determination result as a diagnostic condition. According to the present invention, the pulsation determination value in the closed failure diagnosis means is corrected by the determination value correction means in accordance with the level of the atmospheric pressure detected by the atmospheric pressure detection means or its equivalent value. Therefore, even when the pulsation at the internal pressure of the canister changes due to the atmospheric pressure during the failure diagnosis of the purge control valve, the pulsation determination value is corrected in accordance with the change of the pulsation, so that the pulsation is corrected. The erroneous determination regarding the existence of is suppressed.

According to a fifth aspect of the present invention, there is provided a failure diagnosis apparatus according to the fifth aspect of the present invention, wherein the detected atmospheric pressure or its equivalent is detected in place of the judgment value correction means in the failure diagnosis apparatus according to the fourth aspect of the invention. When the value is lower than the predetermined value, a driving frequency correction means for correcting the driving frequency related to the duty control of the purge control valve to be lower than the predetermined value is provided.

The difference between the configuration of the present invention and the operation of the fourth aspect is as follows. That is, according to the present invention, when the atmospheric pressure detected by the atmospheric pressure detecting means or its equivalent value is lower than the predetermined value, the drive frequency related to the duty control of the purge control valve becomes lower than the predetermined value by the drive frequency correction means. It will be corrected lower. Therefore, in the failure diagnosis of the purge control valve, even when the pulsation in the internal pressure of the canister becomes smaller due to the atmospheric pressure being lower than the predetermined value, the drive frequency related to the duty control is corrected to be lower than the predetermined value. By
The pulsation at the internal pressure of the canister increases, and erroneous determination on the existence of the pulsation is suppressed.

According to a sixth aspect of the present invention, there is provided a fuel vapor processing apparatus according to the fourth or fifth aspect, for controlling the introduction of the atmosphere into the canister and the derivation of the inside air. An atmosphere control valve including a check valve is further provided. A flow path for changing the flow passage cross-sectional area of the air introduction passage in the air control valve in place of the determination value correction means or the drive frequency correction means in the failure diagnosis apparatus according to the fourth or fifth aspect of the present invention. Means for varying the cross-sectional area;
When the detected atmospheric pressure or its equivalent value is lower than a predetermined value, control means for controlling the flow path cross-sectional area variable means to reduce the flow path cross-sectional area of the air introduction passage is provided. The purpose is assumed.

In the configuration of the present invention, the difference from the operation of the fourth or fifth aspect is as follows.
That is, according to the present invention, when the atmospheric pressure detected by the atmospheric pressure detecting means or its equivalent value is lower than a predetermined value, the control means controls the flow path cross-sectional area variable means, whereby the atmospheric pressure in the air control valve is controlled. The flow passage cross-sectional area of the introduction passage is reduced. Therefore, when diagnosing the failure of the purge control valve,
Even when the pulsation in the internal pressure on the canister side is reduced due to the atmospheric pressure being lower than a predetermined value, the intake air resistance of the air control valve is increased by reducing the flow path cross-sectional area of the air introduction passage, so that the canister The pulsation at the internal pressure on the side is increased, and erroneous determination regarding the presence of the pulsation is suppressed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a failure diagnosis apparatus for a fuel vapor processing apparatus according to the present invention (the invention according to claim 1) will be described with reference to the drawings. This will be described in detail with reference to FIG.

FIG. 1 shows a schematic configuration of a fuel vapor processing apparatus according to the present embodiment and a failure diagnosis apparatus therefor. A gasoline engine system mounted on an automobile 1 as a vehicle includes a fuel tank 2 for storing fuel. A fuel pump 3 is built in the fuel tank 2. The fuel discharged from the fuel pump 3 is distributed and supplied to a plurality of injectors 5 provided in the engine 4 through a fuel line 6. When each injector 5 operates, fuel is injected into the intake passage 7. Air that has been purified through an air cleaner 8 is introduced into the intake passage 7. The mixture of the air and the injected fuel is supplied to the combustion chamber of each cylinder in the engine 4. The remaining fuel without being distributed to each injector 5 is returned to the fuel tank 2 through the return line 9. Exhaust gas that has been burned in each combustion chamber of the engine 4 is discharged to the outside through an exhaust passage 10. The crankshaft 4a is rotated with the combustion of the fuel in each cylinder, and a driving force is obtained in the engine 4. This driving force is transmitted via a transmission or the like to driving wheels (both not shown).
Is transmitted to the vehicle 1 so that the vehicle 1 runs.

The fuel vapor processing apparatus according to this embodiment collects and processes the fuel vapor generated in the fuel tank 2 without releasing it to the atmosphere. This processing device
The fuel vapor generated in the fuel tank 2 is supplied to a vapor line 11.
And a canister 12 that collects through the canister. This canister 12 contains an adsorbent 13 made of activated carbon.

The canister 12 has a first atmospheric control valve 14 and a second atmospheric control valve 15. Each of the first and second atmosphere control valves 14 and 15 is a diaphragm check valve having a spring (not shown). When the internal pressure of the canister 12 is lower than the atmospheric pressure, the first atmospheric control valve 14 opens against the urging force of the spring to allow the outside air (atmospheric pressure) to be introduced into the canister 12, and the gas in the opposite direction is opened. The flow is stopped. An air pipe 16 extending from the air control valve 14 communicates with the vicinity of the air cleaner 8. The second atmospheric control valve 15 opens against the urging force of the spring when the internal pressure of the canister 12 is higher than the atmospheric pressure, and allows the derivation of gas (internal pressure) from the canister 12 to the outlet pipe 17 and the reverse direction. Block the flow of gas.

A vapor control valve 18 provided in the canister 12 controls fuel vapor flowing from the fuel tank 2 to the canister 12. This vapor control valve 18
It consists of a diaphragm type check valve and has a built-in diaphragm valve that operates under pressure. This vapor control valve 18
Is an internal pressure (hereinafter, referred to as “tank internal pressure”) PT on the side of the fuel tank 2 including the vapor line 11 and the canister 1.
Internal pressure on the side 2 (hereinafter referred to as “canister internal pressure”) PC
Open by operating the diaphragm valve element based on the pressure difference between By opening the vapor control valve 18,
Fuel vapor is allowed to flow into the canister 12. That is, the vapor control valve 18 opens when the canister internal pressure PC becomes substantially equal to the atmospheric pressure and the internal pressure PC is higher than the tank internal pressure PT to allow the fuel vapor to flow into the canister 12. In addition, the vapor control valve 18 allows the flow of gas from the canister 12 to the fuel tank 2 when the canister internal pressure PC is higher than the tank internal pressure PT.

Purge line 1 extending from canister 12
9 communicates with a surge tank 7a of the intake passage 7. The canister 12 collects only the fuel component in the fuel vapor introduced through the vapor line 11 and discharges only the gas containing no fuel component to the outside through the outlet pipe 17 when the second atmospheric control valve 15 is opened. I do. When the engine 4 is operating, the intake negative pressure generated in the intake passage 7 acts on the purge line 19, and the fuel collected by the canister 12 is purged to the intake passage 7 through the purge line 19. A purge control valve 20 provided in the purge line 19 is for adjusting a fuel purge amount passing through the purge line 19 according to the necessity of the engine 4. The purge control valve 20 is an electromagnetic valve that receives a supply of an electric signal and moves a valve body. The opening of the purge control valve 20 is duty-controlled by receiving a duty signal. Here, the duty control is control that drives the purge control valve 20 on (open) and off (close) periodically and continuously at a predetermined cycle. The duty ratio DP
It is represented as G. The opening degree of the purge control valve 20 is determined by the duty control, and the drive frequency related to the duty control is changed by changing the time required for one cycle of ON / OFF.

The failure diagnosis device for diagnosing a failure relating to the airtightness of the fuel vapor treatment device includes a pressure sensor 31 and a three-way switching valve 21. The pressure sensor 31 is configured to be able to individually detect the tank internal pressure PT and the canister internal pressure PC with the vapor control valve 18 as a boundary. That is, the three-way switching valve 21 provided in association with the pressure sensor 31 has three ports. The three-way switching valve 21 is an electromagnetic valve that receives the supply of an electric signal and switches communication between the ports. One port of the three-way switching valve 21 is connected to the pressure sensor 31, and the other two ports can communicate with the vapor line 11 on the side of the fuel tank 2 and the canister 12 with the vapor control valve 18 as a boundary. . The pressure sensor 31 is selectively connected to the vapor line 11 or the canister 12 by switching the three-way switching valve 2 as needed. In response to this switching, the pressure sensor 31 selectively detects the tank internal pressure PT and the canister internal pressure PC. In this embodiment, in order that the pressure sensor 31 preferentially detects the tank internal pressure PT, when the three-way switching valve 21 is not switched by receiving an electric signal, the pressure sensor 31 communicates with the fuel tank 2 side. 3 way switching valve 2
1 is set. In this embodiment, the pressure sensor 31 is used for diagnosing a failure related to airtightness on the side of the fuel tank 2 including the vapor line 11 and on the side of the canister 12, and detects the tank internal pressure PT and the canister internal pressure PC. Constitutes one internal pressure detecting means of the present invention. Further, the three-way switching valve 21 constitutes switching means of the present invention for switching the detection destination of the pressure sensor 31 in order to selectively detect the tank internal pressure PT and the canister internal pressure PC.

Various sensors 32, 33, 34, 35, 3
6, 37, and 38 are for detecting various parameters related to the operating state of the engine 4. That is, the intake air temperature sensor 32 provided near the air cleaner 8 detects the temperature (intake air temperature) THA of the air taken into the intake passage 7 and outputs a signal corresponding to the temperature. The intake pressure sensor 33 provided in the surge tank 7a detects a pressure (intake pressure) PM of the air taken into the intake passage 7, and outputs a signal corresponding to the pressure. The water temperature sensor 34 provided in the engine 4 detects the temperature (cooling water temperature) THW of the cooling water flowing inside the engine 4 and outputs a signal corresponding to the temperature. The rotation speed sensor 35 provided on the engine 4
The rotation speed (engine rotation speed) NE of the crankshaft 4a is detected, and a signal corresponding to the rotation speed is output. In this embodiment, the rotation speed sensor 3
Numeral 5 is for detecting a change in the rotation angle of the crankshaft 4a, that is, the "crank angle" every 30 degrees, and outputting it as a rotation pulse signal every 30 degrees. The oxygen sensor 36 provided in the exhaust passage 10 detects the oxygen concentration Ox in the exhaust gas passing through the exhaust passage 10 and outputs a signal corresponding to the concentration. Vehicle speed sensor 37 provided in the automobile 1
Detects the vehicle speed SPD and outputs a signal corresponding to the detected speed. An ignition switch (IG switch) 38 provided in the driver's seat is operated by a driver to control start / stop of the engine 4. As is well known, this IG switch 38 is, for example,
It has four-stage switching positions of off, accessory, on, and start. The IG switch 38 is switched to an accessory position to supply power to various on-vehicle accessories. The IG switch 38 is switched to an ON position in order to execute various controls by the ECU 41. The IG switch 38 is switched to a start position in order to perform cranking when the engine 4 starts.

Generally, the intake pressure PM in the intake passage 7
Is known to vary depending on the difference between the intake air temperature THA, the engine speed NE and the atmospheric pressure PA. Therefore, as for the intake pressure PM, if the values of the intake air temperature THA and the engine speed NE are known, the value of the atmospheric pressure PA can be estimated. Therefore, in this embodiment, each of the parameters THA, PM, NE, P
A is introduced into the intake passage 7 based on the intake air temperature sensor 32, the intake air pressure sensor 33, and the rotational speed sensor 35, based on the intake air temperature THW, the intake air pressure PM, and the engine rotational speed NE. The pressure of the outside air, that is, the value of the atmospheric pressure PA is calculated. Therefore, in this embodiment, the intake air temperature sensor 32, the intake pressure sensor 33, and the rotation speed sensor 35 correspond to the atmospheric pressure detecting means of the present invention for detecting a value corresponding to the atmospheric pressure PA.

The electronic control unit (ECU) 41 corresponds to the diagnosis means and the judgment value correction means of the present invention. The ECU 41 inputs signals output from the various sensors 31 to 38 and the like. The ECU 41 controls the fuel vapor processing device to execute the fuel purge control. ECU
41 outputs a duty signal required for the purge control valve 20 in order to purge an amount of fuel according to the operating state of the engine 4, that is, to control the purge control valve 20 with a required drive duty ratio DPG. I do.

The ECU 41 controls the failure diagnosis device.
The ECU 41 switches the three-way switching valve 21 as needed based on the detection signals from the various sensors 31 to 38 and the tank pressure PT selectively detected by the pressure sensor 31.
Alternatively, the user inputs the value of the canister internal pressure PC. EC
U41 diagnoses a failure related to the airtightness of the fuel tank 2 and a failure related to the airtightness of the canister 12, respectively, based on the input value of the tank internal pressure PT or the canister internal pressure PC. In addition, the ECU 41 includes the above various sensors 31 to 3
A failure relating to the functions of the purge control valve 20 and the three-way switching valve 21 is diagnosed based on the detection signal from the controller 8.

A warning lamp 22 provided in the driver's seat of the automobile 1 operates to notify the driver of a result of the diagnosis related to the above-mentioned failure. The ECU 41 turns on or blinks the warning lamp 22 when diagnosing that the various failures have occurred, and turns off the warning lamp 22 at other times.

As is well known, the ECU 41 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM, an external input circuit, an external output circuit, and the like. The ECU 41
A logical operation circuit is configured by connecting a CPU, a ROM, a RAM, a backup RAM, an external input circuit, an external output circuit, and the like by a bus. The ROM stores in advance predetermined control programs related to engine control, fuel purge control, failure diagnosis control, and the like. RAM is
This temporarily stores the calculation result of the CPU. The backup RAM stores data stored in advance. The backup RAM is for storing a diagnosis result regarding a failure as diagnosis data. CPU
Are various sensors 31 to 3 input through an input circuit.
The injector 5, the purge control valve 20, the three-way switching valve 21, the warning lamp 22, and the like are controlled in order to execute engine control, fuel purge control, failure diagnosis control, and the like based on the detection signal 8.

Next, the three-way switching valve 2 executed by the ECU 41
The processing contents relating to the first diagnosis will be described with reference to FIGS. FIGS. 2 and 3 show flowcharts relating to a “three-way switching valve diagnosis routine” for performing a failure diagnosis of the three-way switching valve 21. The ECU 41 periodically executes this routine at predetermined time intervals.

When the process proceeds to this routine, in step 100, the ECU 41 determines whether or not the start of the engine 4 has been completed. The ECU 41 determines this determination based on whether or not the engine rotation speed NE detected by the rotation speed sensor 35 exceeds a predetermined set value. The ECU 41 proceeds to step 110 after waiting for the engine 4 to be started.

In step 110, the ECU 41
It is determined whether the purge start condition is satisfied. In order to purge fuel from the canister 12 to the intake passage 7, it is necessary to apply a required intake negative pressure generated in the intake passage 7 to the canister 12. Therefore, the ECU 41
The intake pressure sensor 33 and the rotation speed sensor 35 are set when the engine 4 is idling, in which the intake pressure PM is relatively low (increases toward the negative pressure side), or when the vehicle 1 is running under light load, etc. It is determined whether the above condition is satisfied based on the detection signal from the vehicle speed sensor 37. ECU4
Step 1 waits for the purge start condition to be satisfied, and proceeds to step 1
Move to 11.

In step 111, the ECU 41
The atmospheric pressure PA is calculated based on the intake air temperature THA, the intake air pressure PM, and the engine rotational speed NE detected by the intake air temperature sensor 32, the intake pressure sensor 33, and the rotational speed sensor 35. As described above, the ECU 41 calculates the value of the atmospheric pressure PA based on the relationship among the parameters THA, PM, NE, and PA experimentally confirmed in advance.

In step 112, the ECU 41
The duty control of the purge control valve 20 is performed based on a predetermined drive duty ratio DPG. Due to the duty control of the purge control valve 20, the intake negative pressure generated in the intake passage 7 acts on the canister 12 through the purge line 19 with periodic pulsation.

Thereafter, at step 120, the ECU
41 determines whether or not the diagnosis condition of the three-way switching valve 21 is satisfied. The ECU 41 determines, based on a detection signal from the pressure sensor 31 or the like, that the above-described diagnosis condition is satisfied, based on the fact that the fuel purge is actually performed, the pressure sensor 31 has no failure such as disconnection, or the like. . Here, if the diagnosis condition is not satisfied, the ECU 41 returns the processing to step 110. If the diagnosis condition is satisfied, the ECU 41 shifts the processing to step 121.

In step 121, the ECU 41
A first counter CA for measuring a time required for reading a tank internal pressure PT described later and calculating a value related thereto is reset to “0”.

In step 122, the ECU 41 determines
By switching the three-way switching valve 21, the pressure sensor 3
1 is connected to the fuel tank 2 side. That is, the pressure sensor 3
1 enables detection of the tank internal pressure PT.

In step 130, the ECU 41
It is determined whether the value of the first counter CA has exceeded a predetermined set value ca1. Here, when the value of the first counter CA does not exceed the set value ca1, the ECU 41 executes the processing of steps 131 to 135.

That is, in step 131, the ECU 4
1 is the tank internal pressure PT detected by the pressure sensor 31
Is processed by the hard filter, and the value obtained by the processing is read as the tank internal pressure processing value PTAD. By processing the tank internal pressure PT with the hard filter in this manner, noise in the detection value of the pressure sensor 31 is removed.

In step 132, the ECU 41 determines
By smoothing the read tank pressure processing value PTAD, that is, by processing the processed value PTAD with a soft filter, the tank pressure smoothing value PTSM as an average value is calculated. The ECU 41 calculates the tank internal pressure smoothing value PTSM according to the following equation (1). By processing the tank internal pressure PT with a soft filter, the pulsation over time in the detection value of the pressure sensor 31 is removed. PTSM = PTSMo + (PTAD-PTSMo) / Ksm (1) Here, “PTSMo” means the tank internal pressure smoothing value calculated last time, and “Ksm” means a predetermined smoothing rate.

At step 133, the ECU 41
A tank pressure pulsation value DPT is calculated based on the read tank pressure processing value PTAD and the calculated tank pressure smoothing value PTSM. The ECU 41 calculates the tank pressure pulsation value DPT according to the following equation (2). DPT = | PTAD-PTSM | (2)

In step 134, the ECU 41
An integrated tank pressure pulsation value IDPT is calculated based on the calculated tank pressure pulsation value DPT. The ECU 41 calculates the tank pressure pulsation integrated value IDPT according to the following equation (3). IDPT = IDPTo + DPT (3) Here, “IDPTo” means the pulsation integrated value calculated last time.

In step 135, the ECU 41
After incrementing the first counter CA by a predetermined value, the process returns to step 130.

On the other hand, in step 130, if the value of the first counter CA exceeds the set value ca1, the ECU 4
1 shifts the processing to step 140. Step 140
The ECU 41 includes a canister internal pressure PC, which will be described later.
Is reset to "0" for measuring the time required for reading the data and calculating the value associated therewith.

In step 141, the ECU 41
By switching the three-way switching valve 21, the pressure sensor 3
1 to the canister 12 side. That is, the canister internal pressure PC can be detected by the pressure sensor 31.

At step 150, the ECU 41
It is determined whether the value of the second counter CD has exceeded a predetermined set value cd1. Here, when the value of the second counter CD does not exceed the set value cd1, the ECU 41 executes the processing of steps 151 to 155.

That is, in step 151, the ECU 4
1 processes the value of the canister internal pressure PC detected by the pressure sensor 31 with a hard filter as described above,
The value obtained by this processing is referred to as the canister internal pressure processing value P
Read as CAD. By processing the canister internal pressure PC with a hard filter, noise in the detection value of the pressure sensor 31 is removed.

In step 152, the ECU 41
The canister internal pressure smoothing value PCSM as an average value is calculated by subjecting the read canister internal pressure processing value PCAD to smoothing processing in the same manner as described above, that is, by processing the processing value PCAD with a soft filter. I do. The ECU 41 calculates the canister internal pressure averaging value PCSM according to the following equation (4). By processing the canister internal pressure PC with a soft filter, the pressure sensor 31
The pulsation over time in the detected value of is removed. PCSM = PCSMo + (PCAD−PCSMo) / Ksm (4) Here, “PCSMo” means the canister internal pressure smoothing value calculated last time, and “Ksm” means a predetermined smoothing rate.

In step 153, the ECU 41 determines
The canister internal pressure pulsation value DPC is calculated based on the read canister internal pressure processing value PCAD and the calculated canister internal pressure smoothed value PCSM. The ECU 41 calculates a canister internal pressure pulsation value DPC according to the following equation (5). DPC = | PCAD-PCSM | (5)

In step 154, the ECU 41 determines
The canister internal pressure pulsation integrated value IDPC is calculated based on the calculated canister internal pressure pulsation value DPC. ECU 41
Is the canister internal pressure pulsation integrated value ID according to the following equation (6).
Calculate PC. IDPC = IDPCo + DPC (6) Here, “IDPCo” means the pulsation integrated value calculated last time.

At step 155, the ECU 41
After incrementing the second counter CD by a predetermined value, the process returns to step 150.

That is, in the processing of steps 100 to 155, when the duty of the purge control valve 20 is controlled during the operation of the engine 4, the three-way switching valve 21 is switched to selectively change the tank internal pressure PT or the canister internal pressure PC. Is detected. And those tank pressure PT
Alternatively, the tank internal pressure pulsation integrated value IDPT or the canister internal pressure pulsation integrated value IDPC is calculated in order to confirm that the intake negative pressure pulsation generated by the duty control of the purge control valve 20 exists in the canister internal pressure PC.

On the other hand, if the value of the second counter CD exceeds the set value cd1 at step 150, the ECU 4
1 shifts the processing to step 160. Step 160
In, the ECU 41 calculates a correction coefficient Kid for each of the pulsation determination values JIC and JIT described later based on the calculated value of the atmospheric pressure PA. The ECU 41 performs this calculation by referring to the function data (map) shown in FIG. This function data has been experimentally confirmed in advance, and defines the relationship between the atmospheric pressure PA and the correction coefficient Kid. In this embodiment, the correction coefficient Kid is set so as to decrease quadratically as the atmospheric pressure PA decreases.

In step 161, the ECU 41
The pulsation determination value JIC related to the canister internal pressure PC is corrected based on the calculated value of the correction coefficient Kid. That is, the pulsation determination value JIC is corrected by calculating the pulsation determination value JIC by multiplying the reference pulsation determination value JICb by the correction coefficient Kid.

In step 162, the ECU 41
The tank internal pressure P is calculated based on the calculated value of the correction coefficient Kid.
The pulsation determination value JIT related to T is corrected. That is, the pulsation determination value JIT is corrected by calculating the pulsation determination value JIT by multiplying the reference pulsation determination value JITb by the correction coefficient Kid.

Then, at step 170, the ECU
41 is the calculated tank pressure pulsation integrated value IDPT,
It is determined whether it is smaller than the corrected pulsation determination value JIT. Here, if the tank pressure pulsation integrated value IDPT is not smaller than the pulsation determination value JIT, the ECU 41 may switch the three-way switching valve 21 to set the connection destination of the pressure sensor 31 to the fuel tank 2 side. Regardless, the detected value of the pressure sensor 31 contains a large amount of pulsation. This pulsation is obtained by detecting the pulsation of the intake negative pressure generated due to the duty control of the purge control valve 20 by the pressure sensor 31, and the three-way switching is performed while the connection destination of the pressure sensor 31 is fixed to the canister 12 side. This means that the valve 21 is out of order, that is, "canister-side fixing failure". Therefore, in step 170, if the tank pressure pulsation integrated value IDPT is not smaller than the pulsation determination value JIT, the ECU 41 proceeds to step 171 to store the failure code CMFC indicating the occurrence of the "canister-side fixed failure" in the backup RAM. Remember. Further, in step 172, the ECU 41 sets the warning lamp 22
Is turned on, and the subsequent processing is temporarily ended.

On the other hand, if the tank pressure pulsation integrated value IDPT is smaller than the pulsation determination value JIT in step 170, the connection destination of the pressure sensor 31 is normally switched to the fuel tank 2 side by the three-way switching valve 21. Then, the ECU 41 shifts the processing to step 180.

Then, at step 180, the ECU
41 is the calculated canister internal pressure pulsation integrated value IDPC
Is larger than the corrected pulsation determination value JIC. Here, the canister internal pressure pulsation integrated value IDPC
Is smaller than the pulsation determination value JIC, the ECU 41
Has tried to switch the three-way switching valve 21 to set the connection destination of the pressure sensor 31 to the canister 12 side, but the detected value of the pressure sensor 31 did not include much pulsation. The absence of such pulsation is caused by the fact that the tank internal pressure PT, which is not originally affected by the pulsation of the intake negative pressure generated due to the duty control of the purge control valve 20,
This is due to detection by the pressure sensor 31. This means that the three-way switching valve 21 has failed while the connection destination of the pressure sensor 31 is fixed to the fuel tank 2 side, that is, "tank-side fixing failure". Therefore,
In step 180, the canister internal pressure pulsation integrated value I
If DPC is not larger than the pulsation judgment value JIC, EC
U41 proceeds to step 181 to store the failure code TMFC indicating the occurrence of the "tank-side fixation failure" in the backup RAM. Further, in step 182, E
The CU 41 turns on the warning lamp 22 in order to notify the driver of the occurrence of the failure of the three-way switching valve 21 and temporarily ends the subsequent processing.

On the other hand, if the integrated pressure pulsation value IDPC in the canister is larger than the pulsation determination value JIC in step 180, the connection destination of the pressure sensor 31 is normally switched to the canister 12 by the three-way switching valve 21. The ECU 41 shifts the processing to step 183. Then, in step 183, the ECU 41
Stores a normal code NFC indicating that the three-way switching valve 21 is normal in the backup RAM. Further, in step 184, the ECU 41 turns off the warning lamp 22 to indicate that the three-way switching valve 21 is normal, and terminates the subsequent processing once.

That is, in the processes of steps 170 and 180, the tank pressure PT or the pulsation judgment value JIC is compared with the tank pressure pulsation integrated value IDPT or the canister pressure pulsation integrated value IDPC, respectively. The presence of pulsation in the canister internal pressure PC is determined, and the result of the determination is used as a diagnostic condition for a failure related to the switching of the three-way switching valve 21, that is, a “tank-side sticking failure”.
Or, a diagnosis of "canister-side fixing failure" has been made.

In the processing of steps 160 to 162, the pulsation judgment values JIT and JIC used for the above-mentioned pulsation judgment are made in accordance with the level of the atmospheric pressure PA which changes depending on the altitude of the destination of the vehicle 1. Has been corrected.

As described above, in the fuel vapor processing apparatus of this embodiment, the duty ratio of the purge control valve 20 during the operation of the engine 4 allows the fuel once collected in the canister 12 to flow through the intake passage. The air is purged to the intake passage 7 based on the action of the negative intake pressure generated in the intake passage 7. The fuel purge amount is adjusted according to the opening of the purge control valve 20 determined by the duty control.
Here, when the duty of the purge control valve 20 is controlled, the control valve 20 is periodically turned on / off at a predetermined cycle, and the valve 20 is selectively opened and closed at a predetermined cycle. Therefore, the intake negative pressure generated in the intake passage 7 acts on the canister 12 with pulsation through the purge line 19, and accordingly, the canister internal pressure PC
Fluctuates with pulsation.

In the failure diagnosis apparatus of this embodiment, when diagnosing a failure related to airtightness on the side of the fuel tank 2 including the vapor line 11 or on the side of the canister 12, the three-way switching valve 21 is controlled to be switched. . As a result, the detection destination of the pressure sensor 31 is switched, and the tank pressure PT and the canister pressure PC are selectively detected by the pressure sensor 31.

Here, when the duty of the purge control valve 20 is controlled during the operation of the engine 4, the pressure sensor 31
Of pulsation in the tank internal pressure PT or canister internal pressure PC selectively detected by
It is determined by the ECU 41 by being compared with IT and JIC. Then, the three-way switching valve 21 is used as a diagnostic condition based on the determination result, that is, the presence or absence of pulsation.
The ECU 41 diagnoses a failure related to the switching of.

For example, when the presence of pulsation in the canister internal pressure PC is not determined when the canister internal pressure PC is detected, the determination result is used as a diagnostic condition.
The ECU 41 diagnoses that the three-way switching valve 21 has a failure related to switching. That is, it is diagnosed that the three-way switching valve 21 is "tank-side fixation failure". on the other hand,
When the tank pressure PT is detected, the tank pressure PT
When it is determined that there is a pulsation, it is diagnosed that there is a failure related to switching in the three-way switching valve 21 using the determination result as a diagnostic condition. That is, it is diagnosed that the three-way switching valve 21 is "canister-side fixing failure".

Incidentally, the pressure of the air introduced into the intake passage 7 reflects the atmospheric pressure PA which can vary depending on the altitude of the destination of the vehicle 1. Therefore, the amplitude of the pulsation of the intake negative pressure acting on the canister internal pressure PC with the duty control of the purge control valve 20 may be affected by the atmospheric pressure. However, in the failure diagnosis device of this embodiment, various sensors 32, 33,
The internal pressure pulsation integrated value IDP is determined according to the level of the atmospheric pressure PA presumably calculated based on the intake air temperature THA, the intake pressure PM and the engine speed NE detected at 35.
Each pulsation judgment value JIT, JIC to be compared with T, IDPC
Are respectively corrected. Therefore, in the failure diagnosis of the three-way switching valve 21, even when the amplitude of the pulsation at the canister internal pressure PC changes due to the influence of the atmospheric pressure PA, each pulsation determination value JI corresponds to the change of the pulsation amplitude.
By correcting T and JIC, erroneous determination regarding the presence of the pulsation can be suppressed. That is, in steps 170 and 180 of the "three-way switching valve diagnosis routine" shown in FIGS. JIC calculates the calculated atmospheric pressure PA
Of the tank internal pressure PT
Alternatively, erroneous determination regarding the presence of pulsation in the canister internal pressure PC is suppressed. As a result, in the device for diagnosing the failure of the three-way switching valve 21 using the pulsation of the intake negative pressure, the three-way switching valve 21 is not affected by the change in the atmospheric pressure PA that changes depending on the altitude to which the automobile 1 moves. High-precision diagnosis of a failure can be performed.

According to the failure diagnosis apparatus of this embodiment,
When it is diagnosed that the three-way switching valve 21 has a failure, a warning lamp 22 provided in the driver's seat is turned on. For this reason,
The driver can immediately know the occurrence of the failure of the three-way switching valve 21 and can deal with the failure early. As a result, it is possible to prevent a failure related to the airtightness of the canister 12, the fuel tank 2, and the like from being erroneously diagnosed, and to improve the reliability of the fuel vapor processing device. Become.

According to the failure diagnosis apparatus of this embodiment,
When it is diagnosed that the three-way switching valve 21 has a “tank-side fixed failure” or a “canister-side fixed failure”, the respective failure codes CMFC and TMFC indicating the diagnosis are stored in the backup RAMU of the ECU 41, respectively. For this reason, when inspecting the automobile 1, the worker may use the backup RA
By reading out each of the failure codes CMFC and TMFC of M, it becomes possible to confirm the history relating to the failure. As a result, the three-way switching valve 21 can be rechecked if necessary.

[Second Embodiment] A second embodiment of the present invention (the second aspect of the present invention) will now be described with reference to the drawings. In each of the embodiments (including this embodiment) described below, the same members, the same parameters, and the same steps as those in the first embodiment are denoted by the same reference numerals. The description is omitted here.

FIGS. 5 and 6 show a flowchart relating to the "three-way switching valve diagnosis routine" in the present embodiment. 5 and 6 are flowcharts of the first embodiment shown in FIGS.
3 is based on the flowchart of FIG. The flowchart of FIG. 5 differs from the flowchart of FIG. 2 in that the process of step 200 is added between step 111 and step 112. In the flowchart of FIG. 5, the processing of steps 160, 161, and 162 is omitted between steps 150 and 170.
The contents are different from the flowchart of FIG.

That is, in the first embodiment, when diagnosing the failure of the three-way switching valve 21, the amplitude of the pulsation of the intake negative pressure acting on the canister 12 becomes small under the influence of the change in the atmospheric pressure PA. The presence / absence of the pulsation is prevented from being erroneously determined. For that purpose, FIG.
In steps 160 to 162 of the flowchart of FIG. 3, the ECU 41 determines the internal pressure pulsation integrated values IDPT, IDP
The pulsation determination values JIT and JIC to be compared with C are corrected in accordance with the level of the atmospheric pressure PA.

On the other hand, in the present embodiment, in the failure diagnosis of the three-way switching valve 21, in order to prevent the erroneous determination of the presence / absence of the pulsation as described above, the flowchart of FIG. In step 200, the ECU 41
Sets the drive frequency FDPG related to the drive duty ratio DPG for controlling the purge control valve 20 to step 111
Is corrected in accordance with the level of the atmospheric pressure PA calculated in step (1).

Specifically, the ECU 41 supplements the drive frequency FDPG by referring to the function data (map) as shown in FIG. This function data has been experimentally confirmed in advance, and the relationship between the atmospheric pressure PA and the drive frequency FDPG has been determined. In this embodiment, as the atmospheric pressure PA decreases, the drive frequency F
DPG is set to be quadratic lower. That is, the vehicle drive frequency FDPG is set relatively low as the altitude of the destination of the vehicle 1 increases.

For example, as shown in FIG. 7, when the driving frequency FDPG is set to "10 Hz" with respect to the atmospheric pressure PA of the predetermined value pa1 at low altitude, the vehicle 1 moves to the high altitude and the atmospheric pressure PA PA is a predetermined value pa2 (pa2 <pa
When changed to 1), the drive frequency FDPG is "5 Hz"
Is corrected to FIG. 8 shows that the drive duty ratio DPG of the purge control valve 20 is “about 50%” and the drive frequency FD
The pulsation amplitude of the canister internal pressure PC when PG is “10 Hz” is shown. FIG. 9 shows that only the driving frequency FDPG is changed to “5H
The pulsation amplitude of the canister internal pressure PC when z is changed to “z” is shown. As is clear from FIGS. 8 and 9, the drive frequency FDPG of the purge control valve 20 is changed from “10 Hz” to “5H”.
It can be seen that the amplitude of the pulsation of the canister internal pressure PC becomes relatively large by changing to “z”.

In this embodiment, the ECU 41 determines whether the first
The atmospheric pressure PA instead of the determination value correction means of the embodiment.
Is lower than a predetermined value (a value at low altitude), a drive for correcting the drive frequency FDPG related to the duty control of the purge control valve 20 to a predetermined value (“5 Hz”) lower than the predetermined value (“10 Hz”). It constitutes a frequency correcting means.

Therefore, even in this embodiment, even when the atmospheric pressure PA becomes lower than the value at the low altitude and the amplitude of the pulsation at the canister internal pressure PC becomes small when the three-way switching valve 21 is diagnosed as faulty, the purge control valve The drive frequency FDPG related to the drive duty ratio DPG of 20 is corrected from, for example, “10 Hz” to “5 Hz”,
The pulsation amplitude at the canister internal pressure PC increases,
The erroneous determination regarding the presence of the pulsation can be suppressed. As a result, the three-way switching valve 2 utilizes the pulsation of the intake negative pressure.
In the case of diagnosing the first failure, highly accurate diagnosis can be performed without being affected by a change in the atmospheric pressure PA. Other main functions and effects are the same as those of the failure diagnosis device of the first embodiment.

In this embodiment, the vehicle 1
The reason why the driving frequency FDPG is relatively lowered only when the atmospheric pressure PA is lowered due to the movement of the vehicle to a high altitude is as follows. One is that, when the drive frequency FDPG of the purge control valve 20 becomes relatively low, in the air-fuel ratio control of the engine 4 executed in anticipation of the amount of fuel to be purged, the change in the air-fuel ratio A / F becomes slow, and Is worse. Second, in an operating state in which the engine rotational speed NE is relatively low and the amount of intake air of the engine 4 is relatively small, the pulsation of the intake negative pressure generated in the intake passage 7 and the duty control of the purge control valve 20 are not performed. Canister internal pressure PC
This is because when the pulsation is synchronized, the air-fuel ratio A / F becomes relatively large, causing malfunction of the engine 4.
Then, in order to suppress the influence on the air-fuel ratio control of the engine 4 as described above, the vehicle 1 moves to a high altitude, the atmospheric pressure PA decreases, and the drive frequency FDP of the purge control valve 20 is reduced.
When G is changed, a guard may be set for the correction of the drive frequency FDPG. That is, the correction coefficient (FA) used to correct the air-fuel ratio A / F in the air-fuel ratio control.
When the deviation amount of F) exceeds a predetermined value, the driving frequency F
It is possible to set a guard for the DPG value or to set the engine speed N
When E falls below a predetermined value, a guard can be set to the value of the drive frequency FDPG.

[Third Embodiment] A third embodiment of the present invention (the third aspect of the present invention) will now be described with reference to the drawings.

FIG. 10 shows a schematic configuration of the fuel vapor processing apparatus according to the present embodiment and its failure diagnosis apparatus. In this embodiment, a vacuum switching valve (VSV) is provided in the middle of the air pipe 16 leading to the first atmospheric control valve 14.
23 and a stop 24 are provided in parallel. VSV23,
This is for selectively opening and closing one branch passage 16 a of the air pipe 16, and is controlled by the ECU 41. The throttle 24 reduces the cross-sectional area of the other branch passage 16b. Here, when the VSV 23 is opened, the air pipe 16 communicates with the first air control valve 14 via the VSV 23 and the throttle 24, and a flow path cross-sectional area equal to the flow cross-sectional area of the air pipe 16 itself is obtained. . On the other hand, when the VSV 23 is closed, the air pipe 16 is connected to the first air control valve 14 through the throttle 24 only.
And the flow path cross-sectional area of the air pipe 16 is reduced. In this embodiment, the first air control valve 14
Constitutes an atmosphere control valve of the present invention, and the air pipe 16 constitutes an atmosphere introducing passage of the present invention. The VSV 23 and the throttle 24 constitute a flow path cross-sectional area varying unit of the present invention for making the flow path cross-sectional area of the air pipe 16 variable.

FIGS. 11 and 12 show a part of a flowchart relating to the “three-way switching valve diagnostic routine” in the present embodiment. 11 and 12 are based on the flowcharts of FIGS. 5 and 6 of the second embodiment. In the flowchart of FIG. 11, steps 250 and 25 are performed between steps 111 and 112.
5 is different from the flowchart of FIG. 5 in that step 200 is provided. FIG.
6 differs from the flowchart of FIG. 6 in that the process of step 260 is added after steps 182 and 184.

That is, in the second embodiment, when diagnosing the failure of the three-way switching valve 21, the amplitude of the pulsation of the intake negative pressure acting on the canister 12 becomes small due to the change in the atmospheric pressure PA. The presence / absence of the pulsation is prevented from being erroneously determined. Therefore, in step 200 of the flowchart of FIG. 5, the drive frequency FDPG related to the drive duty ratio DPG for controlling the purge control valve 20 is corrected according to the level of the atmospheric pressure PA calculated in step 111. I have to.

On the other hand, in the present embodiment, in the failure diagnosis of the three-way switching valve 21, in order to prevent the erroneous determination of the presence / absence of the pulsation as described above, the flowchart of FIG. In step 250, the ECU 41
Is that the atmospheric pressure PA calculated in step 111 is equal to a predetermined value p
If it is higher than a1 (for example, the value of the atmospheric pressure in a lowland), the process directly proceeds to step 112. On the other hand, in step 250, if the atmospheric pressure PA calculated in step 111 is not higher than the predetermined value pa1, the ECU 41
Shifts the processing to step 251. Then, in step 251, the ECU 41 closes the VSV 23 and shifts the processing to step 112 in order to reduce the cross-sectional area of the air pipe 16 leading to the first atmospheric control valve 14. Further, step 26 in the flowchart of FIG.
In order to enlarge the flow path cross-sectional area of the once reduced air pipe 16 to its original size at 0, the ECU 41
V23 is opened and the subsequent processing is temporarily terminated.

In this embodiment, the ECU 41 replaces the drive frequency correction means of the second embodiment with the atmospheric pressure P.
When A is lower than the predetermined value pa1, the control means of the present invention for controlling the VSV 23 to reduce the flow path cross-sectional area of the air pipe 16 is configured.

Therefore, in this embodiment, even when the atmospheric pressure PA becomes lower than the predetermined value pa1 and the amplitude of the pulsation at the canister internal pressure PC becomes smaller when the three-way switching valve 21 is diagnosed as faulty, the first diagnosing operation is performed. The flow path cross-sectional area of the air pipe 16 communicating with the atmospheric control valve 14 is reduced. As a result, the intake resistance of the first atmospheric control valve 14 increases, and the amplitude of the pulsation at the canister internal pressure PC increases, that is, the S / N ratio of the pulsation is secured, and erroneous determination regarding the presence of the pulsation is suppressed. become. As a result, in diagnosing the failure of the three-way switching valve 21 using the pulsation of the intake negative pressure, highly accurate diagnosis can be performed without being affected by changes in the atmospheric pressure PA. Other main functions and effects are the same as those of the failure diagnosis device according to the second embodiment.

[Fourth Embodiment] A fourth embodiment of the present invention (the fourth aspect of the present invention) will now be described with reference to the drawings.

In the first to third embodiments, the failure diagnosis of the three-way switching valve 21 has been described. In the following embodiments including this embodiment, the failure diagnosis of the purge control valve 20 will be described. I do.

The schematic configuration of the fuel vapor processing apparatus and the failure diagnosis apparatus according to this embodiment is the same as that of FIG. In this embodiment, the pressure sensor 31
It constitutes the internal pressure detecting means of the present invention. Intake air temperature sensor 32,
The intake pressure sensor 33 and the rotation speed sensor 35 detect the atmospheric pressure P
It corresponds to the atmospheric pressure detecting means of the present invention for detecting a value corresponding to A. When the purge control valve 20 is to be opened by duty control during operation of the engine 4, the ECU 41 determines the presence of pulsation in the detected internal pressure based on a predetermined pulsation determination value, and purges the determination result as a diagnostic condition. The closed-failure diagnosing means of the present invention for diagnosing that the control valve 20 has failed in the closed state is configured.
Similarly, the ECU 41 constitutes a determination value correction means of the present invention for correcting the pulsation determination value according to the detected atmospheric pressure PA or the level of the corresponding value.

FIGS. 13 and 14 show flowcharts relating to the "purge control valve diagnosis routine" in the present embodiment. The ECU 41 periodically executes this routine at predetermined time intervals.

When the processing proceeds to this routine, in step 300, the ECU 41 waits for the ignition switch 38 to be turned on, and then proceeds to step 310.

[0097] In step 310, the ECU 41
The pressure sensor 31 is connected to the canister 12 by switching the three-way switching valve 21. Next, in step 311, the ECU 41 reads the canister internal pressure PC at the time of starting the engine 4, and sets RA as the starting internal pressure PCS.
Store it in M. Then, in step 312, E
The CU 41 determines whether or not the engine 4 has been started. The ECU 41 performs the determination after the start by determining whether or not the engine rotation speed NE detected by the rotation speed sensor 35 has exceeded a predetermined set value. Here, if the engine 4 has not been started, the ECU 41 repeats the processing from step 310. If the engine 4 has been started, the ECU 41 shifts the processing to step 320. That is, in steps 300 to 312, E
The CU 41 takes in the canister internal pressure PC detected from the time the ignition switch 38 is turned on until the start of the engine 4 is completed, into the RAM as the internal pressure PCS at the time of starting.

[0098] In step 320, the ECU 41
The purge control valve 20 is forcibly closed. Next, at step 321, the ECU 41 sets the purge control valve 20
Is read and the internal pressure PCE after starting is stored in the RAM. After that, in step 322, the ECU 41
It is determined whether a predetermined time has elapsed after the start of the engine 4. Here, if the predetermined time has not elapsed since the start of the engine, the ECU 41 repeats the processing from step 320. When a predetermined time has elapsed since the engine was started, E
The CU 41 shifts the processing to step 330. That is,
In steps 320 to 322, the ECU 41 sets the canister internal pressure PC detected during a period from the start of the engine until a predetermined time has elapsed as the post-start internal pressure PCE to the RAM.
It is taken in.

[0099] In step 330, the ECU 41
The forced closing of the purge control valve 20 is released. Then
In step 331, the absolute value of the differential pressure between the start internal pressure PCS and the post-start internal pressure PCE is calculated as an internal pressure deviation DPC. Then, in step 332, the ECU 41
Is that the internal pressure deviation DPC calculated this time is equal to a predetermined set value dp.
It is determined whether or not c1 or less. This set value dpc1
For example, “15 mmHg” can be applied.

FIG. 15 shows the fuel purge, the engine start, and the canister internal pressure P before and after the engine 4 is started.
The behavior of C is shown in the time chart. When the purge control valve 20 is normal, as shown in FIG. 15, when the purge control valve 20 is forcibly closed, the canister internal pressure PC before and after the engine starts gradually decreases as shown by a solid line. This is because the purge control valve 20 is closed.
This is because the negative pressure generated in the intake passage 7 after the start of the engine 4 does not act on the canister 12 at all. Therefore, the internal pressure deviation DPC between the internal pressure at start PCS detected at time t0 immediately before the start of the engine and the internal pressure PCE detected at time t2 when a predetermined time has elapsed after the start of the engine is relatively small. On the other hand, when the purge control valve 20 is open and malfunctions, that is, when the “open valve sticking failure” occurs, as shown in FIG.
The canister internal pressure PC before and after the engine starts when the valve is forcibly closed at 0 sharply decreases as shown by a broken line. This is because the negative pressure generated in the intake passage 7 after the start of the engine 4 directly acts on the canister 12 because the purge control valve 20 has the “valve-opening failure”. Therefore, the starting internal pressure PCS detected at time t0 immediately before the engine startup and the post-start internal pressure PCS detected at time t2 when a predetermined time has elapsed after the engine startup.
The internal pressure deviation DPC from E becomes relatively large. Thus, by determining the magnitude of the internal pressure deviation DPC, it is possible to determine whether or not the purge control valve 20 has a “valve-opening failure”.

In step 332, the internal pressure deviation DPC
Is not less than or equal to the set value dpc1, the ECU 41 shifts the processing to step 340 because the purge control valve 20 is in the “valve-open stuck failure”. Then, in step 340, the ECU 41 stores the valve-opening failure code MFVOC indicating the "valve-opening failure" in the backup RAM. Subsequently, in step 341, the warning lamp 22 is turned on to notify the driver or the like of the failure of the purge control valve 20, and the subsequent processing is temporarily terminated. If the internal pressure deviation DPC is equal to or less than the set value dpc1, the ECU 4 determines that the purge control valve 20 is not in the “open valve sticking failure”.
1 shifts the processing to step 350.

In step 350, the ECU 41 executes
It is determined whether the purge start condition is satisfied. This determination is based on the determination in step 110 of FIG. The ECU 41 shifts the processing to step 351 after the purge start condition is satisfied.

In step 351, the ECU 41
Intake temperature THA, intake pressure PM and engine speed N
The atmospheric pressure PA is calculated based on each value of E. This process is similar to the process of step 111 in FIG.

At step 352, the ECU 41 determines
The duty control of the purge control valve 20 is performed based on a predetermined drive duty ratio DPG. This process is similar to the process of step 112 in FIG.

In step 353, the ECU 41 determines
The counter CA for counting the elapsed time described later is reset to “0”.

In step 354, the ECU 41 determines
By switching the three-way switching valve 21, the pressure sensor 3
1 to the canister 12 side. That is, the canister internal pressure PC can be detected by the pressure sensor 31.

Thereafter, at step 360, the ECU
41 determines whether or not the value of the counter CA is equal to or more than a predetermined set value ca1. Here, if the value of the counter CA is not equal to or greater than the set value ca1, the ECU 41 executes the processing of steps 361 to 365.

That is, in step 361, the ECU 4
1 processes the value of the canister internal pressure PC detected by the pressure sensor 31 with a hard filter, and reads the value obtained by the processing as a canister internal pressure processed value PCAD. By processing the canister internal pressure PC with a hard filter, noise in the detection value of the pressure sensor 31 is removed.

At step 362, the ECU 41 determines
The canister internal pressure averaging value PCSM as an average value is calculated by averaging the read canister internal pressure processing value PCAD, that is, by processing the processed value PCAD with a soft filter. ECU 41
Is the canister internal pressure averaging value PCS according to the following equation (7).
Calculate M. By processing the canister internal pressure PC with a soft filter, the pulsation over time in the detection value of the pressure sensor 31 is removed. PCSM = PCSMo + (PCAD−PCSMo) / Ksm (7) Here, “PCSMo” means the canister internal pressure smoothing value calculated last time, and “Ksm” means a predetermined smoothing rate.

At step 363, the ECU 41 determines
The canister internal pressure pulsation value DPC is calculated based on the read canister internal pressure processing value PCAD and the calculated canister internal pressure smoothed value PCSM. The ECU 41 calculates the canister internal pressure pulsation value DPC according to the following equation (8). DPC = | PCAD-PCSM | (8)

At step 364, the ECU 41 determines
The canister internal pressure pulsation integrated value IDPC is calculated based on the calculated canister internal pressure pulsation value DPC. ECU 41
Is the canister internal pressure pulsation integrated value ID according to the following equation (9).
Calculate PC. IDPC = IDPCo + DPC (9) Here, “IDPCo” means the pulsation integrated value calculated last time.

At step 365, the ECU 41 determines
The counter CA is incremented by a predetermined value.

On the other hand, if the value of counter CA is equal to or greater than set value ca1 in step 360, ECU 41 shifts the processing to step 370. In step 370, the ECU 41 determines a correction coefficient Kid for a pulsation determination value JIC, which will be described later, based on the calculated value of the atmospheric pressure PA.
Is calculated. The ECU 41 performs this calculation, for example, by referring to the function data (map) shown in FIG. 4 described above.

In step 371, the ECU 41 determines
The pulsation determination value JIC related to the canister internal pressure PC is corrected based on the calculated value of the correction coefficient Kid. That is, the pulsation determination value JICb is corrected by multiplying the reference pulsation determination value JICb by the correction coefficient Kid to correct the reference pulsation determination value JICb.
Calculate IC.

At step 372, the ECU 41 sets
It is determined whether or not the calculated canister internal pressure smoothing value PCSM is equal to or less than a predetermined set value psm1. For example, “10 mmHg” can be applied as the set value psm1.

FIG. 16 is a time chart showing the behavior of the fuel purge and the canister internal pressure PC before and after the engine 4 is started. When the purge control valve 20 is normal, as shown in FIG. 16, the canister internal pressure PC when the purge control valve 20 is duty-controlled based on a predetermined drive duty ratio DPG in order to execute fuel purging is indicated by a solid line. Thus, it changes with pulsation. This is because, since the purge control valve 20 is duty-controlled, the intake negative pressure generated in the intake passage 7 after the start of the engine 4 acts on the canister 12 with pulsation. Therefore, the canister internal pressure PC detected after the start of the fuel purge, that is, after the time t0, changes with a relatively large negative pressure and pulsation. On the other hand, when the purge control valve 20 has failed while remaining closed, that is, when it is “valve-closed sticking failure”, FIG.
As shown in the figure, the canister internal pressure PC when the purge control valve 20 is duty-controlled hardly changes as shown by the broken line. This is because the negative pressure of the intake air does not act on the canister 12 after the start of the engine 4 because the purge control valve 20 is in the “closed valve closing failure”. Therefore, the canister internal pressure PC detected after the fuel purge starts, that is, after time t0, gradually decreases.
Thus, by determining the magnitude of the negative pressure of the canister internal pressure PC when the purge control valve 20 is duty-controlled and the presence or absence of pulsation at the internal pressure PC, the purge control valve 20 is determined to have a “closed valve sticking failure”. It can be determined whether or not there is.

In this embodiment, the purge control valve 2
The reason why the purge control valve 20 is not determined to be normal only when the canister internal pressure PC is a negative pressure when determining whether 0 is a “valve closing failure” is as follows. That is, one is that it is necessary to determine the pulsation at the canister internal pressure PC since the canister internal pressure PC becomes a negative pressure when the back purge to the fuel tank 2 occurs. Second, when the vapor control valve 18 of the canister 12 is opened, both the tank internal pressure PT and the canister internal pressure PC become negative pressures, so it is necessary to determine the pulsation at the canister internal pressure PC.

If the canister internal pressure smoothing value PCSM is equal to or smaller than the set value psm1 in step 372, the decrease in the negative pressure of the canister internal pressure PC is relatively small, so the ECU 41 shifts the processing to step 373.

In step 373, the ECU 41 determines
It is determined whether or not the calculated canister internal pressure pulsation integrated value IDPC is equal to or less than the corrected pulsation determination value JIC.
Here, if the canister internal pressure pulsation integrated value IDPC is not equal to or less than the pulsation determination value JIC, there is some pulsation in the canister internal pressure PC.
In order to make the determination of C, the ECU 41 executes the processing in step 3
Return to 50. On the other hand, the canister internal pressure pulsation integrated value IDPC
Is less than or equal to the pulsation determination value JIC, the canister internal pressure P
This means that C contained almost no pulsation. The absence of such pulsation is due to the fact that although the purge control valve 20 is about to be subjected to duty control, the control valve 20 is in a “closed valve closing failure”, so that the intake negative pressure accompanied by pulsation canister No. 12 is not effected. Therefore, if the integrated pressure pulsation value IDPC in the canister is equal to or smaller than the pulsation determination value JIC in step 373, the ECU
41 moves to step 380, where the purge control valve 20
Is a valve closing failure code indicating that is a "valve closing stuck failure"
Store FVCC in backup RAM. Further, in step 381, the ECU 41 sets the purge control valve 20
Warning lamp 2 to notify the driver of the occurrence of
2 is turned on, and the subsequent processing is temporarily terminated.

On the other hand, if the canister internal pressure smoothing value PCSM is not equal to or smaller than the set value psm1 in step 372, the decrease in the negative pressure of the canister internal pressure PC is not relatively small, so the ECU 41 shifts the processing to step 390.

Then, at step 390, the ECU
41 is the calculated canister internal pressure pulsation integrated value IDPC
Is greater than or equal to the corrected pulsation determination value JIC. If the canister internal pressure pulsation integrated value IDPC is not equal to or greater than the pulsation determination value JIC, the canister internal pressure PC
Since the pulsation does not exist to some extent, the ECU 41 returns the process to step 350 in order to determine the canister internal pressure PC again. On the other hand, when the canister internal pressure pulsation integrated value IDPC is equal to or larger than the pulsation determination value JIC, pulsation surely exists in the canister internal pressure PC. The presence of the pulsation is due to the fact that the purge control valve 20 is normal and the duty cycle of the control valve 20 causes the pulsating intake negative pressure to reliably act on the canister 12. Therefore, in step 390, if the canister internal pressure pulsation integrated value IDPC is equal to or larger than the pulsation determination value JIC, the ECU 41 proceeds to step 391 and stores a normal code NFVC indicating that the purge control valve 20 is normal in the backup RAM. Remember. Further, in step 392, the ECU 41 sets the purge control valve 2
In order to indicate to the driver that 0 is normal, the warning lamp 22 is turned off, and the subsequent processing is temporarily terminated.

As described above, according to the failure diagnosis apparatus of this embodiment, the internal pressure deviation DPC relating to the canister internal pressure PC detected before and after the purge control valve 20 is forcibly closed when the engine 4 is operating. It is possible to diagnose whether or not the purge control valve 20 has a "valve-opening failure" on the basis of the value of. On the other hand, in this embodiment, when the purge control valve 20 is to be opened intermittently by duty control during operation of the engine 4, the pressure sensor 31
Is determined based on the set value psm1, and the presence of pulsation in the canister internal pressure PC is determined based on a predetermined pulsation determination value JIC. Then, the ECU 41 diagnoses that the purge control valve 20 is a “valve-closing failure” as a diagnostic condition based on the determination results.

Incidentally, the pressure of the air introduced into the intake passage 7 reflects the atmospheric pressure PA which can vary depending on the altitude of the destination of the vehicle 1. For this reason, the pulsation of the intake negative pressure acting on the canister internal pressure PC with the duty control of the purge control valve 20 may change due to the influence of the atmospheric pressure. However, in the failure diagnosis device of this embodiment, the atmospheric pressure PA estimated and calculated based on the intake air temperature THA, the intake air pressure PM, and the engine speed NE detected by the various sensors 32, 33, and 35.
The pulsation determination value JIC in the “purge control valve diagnosis routine” is corrected in accordance with the level of the value of. Therefore, when diagnosing the "closed valve closing failure" of the purge control valve 20, the canister internal pressure P is affected by the difference in the atmospheric pressure PA.
Even when the amplitude of the pulsation in C changes, the pulsation determination value JIC is corrected in accordance with the change in the pulsation amplitude, thereby suppressing erroneous determination regarding the presence of the pulsation. That is, in steps 373 and 390 of the “purge control valve diagnosis routine” shown in FIG. 14, the pulsation determination value J to be compared with the canister internal pressure pulsation integrated value IDPC.
By correcting the IC in accordance with the calculated change in the atmospheric pressure PA, the erroneous determination regarding the presence of the pulsation in the canister internal pressure PC can be suppressed. As a result, in the apparatus for diagnosing the "closed valve closing failure" of the purge control valve 20 using the pulsation of the intake negative pressure, the apparatus is not affected by the change in the atmospheric pressure PA that changes depending on the altitude to which the automobile 1 moves. A highly accurate diagnosis of the failure of the purge control valve 20 can be performed.

According to the failure diagnosis apparatus of this embodiment,
When it is diagnosed that the purge control valve 20 has an “open valve sticking failure” or a “closed valve sticking failure”, a warning lamp 22 provided in the driver's seat is turned on. For this reason, the driver can immediately know the occurrence of the failure of the purge control valve 20, and can deal with the failure early. As a result, it is possible to prevent a failure related to the airtightness of the canister 12, the fuel tank 2, and the like from being erroneously diagnosed, and to improve the reliability of the fuel vapor processing device. Become.

According to the failure diagnosis apparatus of this embodiment,
When it is diagnosed that the purge control valve 20 has an “open valve sticking failure” or a “closed valve sticking failure”, the respective failure codes MFVOC and MFVCC indicating the diagnosis are stored in the backup RAMU of the ECU 41. For this reason, the worker can check the history regarding the failure by reading out the failure codes MFVOC and MFVCC from the backup RAM as necessary when the vehicle 1 is inspected. As a result, the purge control valve 20 can be rechecked if necessary.

[Fifth Embodiment] A fifth embodiment of the present invention (the fifth aspect of the present invention) will now be described with reference to the drawings.

FIG. 17 shows the second half of the flowchart relating to the "purge control valve diagnosis routine" in this embodiment. The flowchart of FIG. 17 is similar to the flowchart of FIG. 14 of the fourth embodiment. The first half of the flowchart of FIG. 17 is the same as the flowchart of FIG. In the flowchart of FIG.
It differs from the flowchart of FIG. 14 in that the processing of step 400 is added between 51 and step 352. Further, in the flowchart of FIG.
From between 0 and step 372, steps 370, 37
14 is different from the flowchart of FIG. 14 in that the process 1 is omitted.

That is, in the fourth embodiment, when the purge control valve 20 is diagnosed with the "valve-closing failure", the amplitude of the pulsation of the intake negative pressure acting on the canister 12 is determined by the change in the atmospheric pressure PA. In this case, the pulsation becomes smaller due to the influence of the pulsation, and the presence / absence of the pulsation is prevented from being erroneously determined. For this purpose, step 3 in the flowchart of FIG.
In 70 and 371, the ECU 41 determines the pulsation integrated value ID.
The pulsation determination value JIC to be compared with PC is determined by the atmospheric pressure PA.
Was corrected according to the height of the image.

On the other hand, in the present embodiment, when diagnosing the "valve-closing failure" related to the purge control valve 20, in order to prevent the erroneous determination of the presence / absence of pulsation in the same manner as described above, FIG. In step 400 of the flowchart of FIG. 17, the ECU 41 determines the drive frequency FDPG related to the drive duty ratio DPG for controlling the purge control valve 20 by:
The correction is made according to the level of the atmospheric pressure PA calculated in step 351.

[0130] Specifically, the ECU 41 operates as shown in FIG.
The drive frequency FDPG is supplemented by referring to the function data (map) as shown in FIG. This drive frequency FD
The effect of the correction related to the PG is the same as that shown in FIGS.

In this embodiment, when the atmospheric pressure PA is lower than the predetermined value, that is, the value at low altitude, the ECU 41 replaces the judgment value correction means of the fourth embodiment with the duty value of the purge control valve 20. A drive frequency correction means for correcting the drive frequency FDPG for control to be lower than a predetermined value, that is, “10 Hz” is configured.

Therefore, also in this embodiment, when diagnosing the "closed valve stuck failure" related to the purge control valve 20, the atmospheric pressure PA becomes lower than the value at the lowland, and the amplitude of the pulsation at the canister internal pressure PC becomes smaller. Even in such a case, the drive frequency FDPG related to the drive duty ratio DPG of the purge control valve 20 is corrected to be lower than, for example, “10 Hz”. As a result, the amplitude of the pulsation at the canister internal pressure PC increases, and erroneous determination regarding the presence of the pulsation can be suppressed. As a result, in the diagnosis of the "closed valve closing failure" of the purge control valve 20 using the pulsation of the intake negative pressure, a highly accurate diagnosis can be performed without being affected by the change in the atmospheric pressure PA. Become like Other main functions and effects are the same as those of the failure diagnosis device according to the fourth embodiment.

In this embodiment, similarly to the second embodiment, in order to suppress the influence on the air-fuel ratio control of the engine 4, the vehicle 1 moves to a high altitude and the drive frequency FDPG of the purge control valve 20 is increased. When changed, a guard may be provided for the correction of the drive frequency FDPG. That is, when the deviation amount of the correction coefficient (FAF) used to correct the air-fuel ratio A / F in the air-fuel ratio control exceeds a predetermined value, a guard is set to the value of the drive frequency FDPG, It is also possible to set a guard to the value of the drive frequency FDPG when NE falls below a predetermined value.

[Sixth Embodiment] Hereinafter, a third embodiment of the present invention (the sixth aspect of the present invention) will be described with reference to the drawings.

The schematic structure of the fuel vapor processing apparatus and the failure diagnosis apparatus according to the present embodiment is the same as that of the third embodiment described above with reference to FIG. In this embodiment, the first atmosphere control valve 14 constitutes the atmosphere control valve of the present invention, and the air pipe 16 constitutes the atmosphere introduction passage of the present invention. The VSV 23 and the throttle 24 constitute a flow path cross-sectional area varying means of the present invention for making the flow path cross-sectional area of the air pipe 16 variable.

FIG. 18 shows the second half of the flowchart relating to the "purge control valve diagnosis routine" in this embodiment. The flowchart of FIG. 18 is similar to the flowchart of FIG. 17 of the fifth embodiment. In the flowchart of FIG. 18, steps 351 and 352 are performed.
17 differs from the flowchart of FIG. 17 in that step 400 is provided in that steps 450 and 451 are added. Similarly, the flowchart of FIG. 18 differs from the flowchart of FIG. 17 in that the process of step 460 is added after steps 381 and 392.

That is, in the fifth embodiment, when diagnosing the “closed valve stuck failure” related to the purge control valve 20, the amplitude of the pulsation of the intake negative pressure acting on the canister 12 depends on the change of the atmospheric pressure PA. In this case, the pulsation becomes smaller due to the influence of the pulsation, and the presence / absence of the pulsation is prevented from being erroneously determined. Therefore, step 4 in the flowchart of FIG.
At 00, the drive frequency FDPG related to the drive duty ratio DPG for controlling the purge control valve 20 is corrected according to the level of the atmospheric pressure PA calculated in step 351.

On the other hand, in the present embodiment, in diagnosing the “valve-closing failure” of the purge control valve 20, in order to prevent the erroneous determination of the presence / absence of pulsation as described above. In step 450 of the flowchart of FIG. 18, the ECU 41 determines that the atmospheric pressure PA calculated in step 351 is a predetermined value pa1 (for example, the value of the atmospheric pressure in a lowland).
If it is higher than the above, the process directly proceeds to step 352. On the other hand, in step 450, when the atmospheric pressure PA calculated in step 351 is higher than the predetermined value pa1, to reduce the flow path cross-sectional area of the air pipe 16 leading to the first atmospheric control valve 14, the ECU 41 Step 4
At step 51, the VSV 23 is closed and the process proceeds to step 35.
Move to 2. Further, in step 460, EC is returned in order to return the flow path cross-sectional area of the air pipe 16 to the original size.
U41 opens the VSV 23 to temporarily end the subsequent processing.

In this embodiment, the ECU 41 replaces the drive frequency correction means of the fifth embodiment with the atmospheric pressure P.
When A is lower than the predetermined value pa1, the control means of the present invention for controlling the VSV 23 to reduce the flow path cross-sectional area of the air pipe 16 is configured.

Therefore, also in this embodiment, in diagnosing the "closed valve stuck failure" related to the purge control valve 20, the amplitude of the pulsation at the canister internal pressure PC is reduced because the atmospheric pressure PA becomes lower than the predetermined value pa1. Even in such a case, the flow path cross-sectional area of the air pipe 16 communicating with the first air control valve 14 is reduced, so that the first air control valve 1
4, the amplitude of the pulsation at the canister internal pressure PC increases, that is, the S / N ratio of the pulsation is secured, and erroneous determination regarding the presence of the pulsation can be suppressed. As a result, in the diagnosis of the "closed valve closing failure" of the purge control valve 20 using the pulsation of the intake negative pressure, a highly accurate diagnosis can be performed without being affected by the change in the atmospheric pressure PA. Become like Other main functions and effects are the same as those of the failure diagnosis device according to the second embodiment.

It should be noted that the present invention is not limited to the above embodiments, but may be carried out as follows, for example, without departing from the spirit of the invention.

(1) In each of the above embodiments, the intake air temperature sensor 32, the intake pressure sensor 33, and the rotational speed sensor 35 are used as atmospheric pressure detecting means for detecting a value corresponding to the atmospheric pressure PA. The atmospheric pressure PA is calculated based on the intake air temperature THA, the intake air pressure PM, and the engine speed NE. On the other hand, the atmospheric pressure PA
May be provided as atmospheric pressure detecting means.

(2) In the fourth to sixth embodiments,
In order to diagnose the failure of the purge control valve 20, the connection of one pressure sensor 31 can be switched between the tank side and the canister side by the three-way switching valve 21, and the canister internal pressure P
C or the value of the tank internal pressure PT is selectively detected. On the other hand, in order to diagnose the failure of the purge control valve 20, a dedicated pressure sensor that detects only the canister internal pressure PC may be provided.

(3) In the fourth to sixth embodiments,
In order to diagnose the "closed valve closing failure" of the purge control valve 20, the purge condition is determined based on a condition that the canister internal pressure PC is a relatively large negative pressure and that the internal pressure PC changes with pulsation. The control valve 20 is diagnosed as "closed valve failure". In contrast, the purge control valve 20
In order to diagnose the "closed valve closing failure" of the purge control valve 20, the "closed valve closing failure" of the purge control valve 20 may be diagnosed only under the condition that the canister internal pressure PC changes with pulsation.

(4) In the first and fourth embodiments, the pulsation determination values JIC and JIT are multiplied by the correction coefficient Kid calculated based on the atmospheric pressure PA to the reference pulsation determination values JICb and JITb. It was corrected. On the other hand, the pulsation determination values JIC and JIT are corrected according to the level of the atmospheric pressure PA by referring to function data determined in advance experimentally, thereby correcting the pulsation determination values JIC and JIT. You may do so.

(5) In the second and fifth embodiments, the drive frequency FDPG itself is calculated in accordance with the level of the atmospheric pressure PA by referring to function data determined experimentally in advance. The drive frequency FDPG is corrected. On the other hand, the drive drive frequency may be corrected by multiplying the reference drive frequency by a correction coefficient calculated based on the atmospheric pressure PA.

(6) In the third and sixth embodiments, the VSV 23 and the throttle 24 constitute a flow path cross-sectional area varying means, and the VSV 23 is selectively opened and closed.
The flow path cross-sectional area of the air pipe 16 was changed. On the other hand, an electromagnetic valve having a variable opening may be provided in the air pipe, and the opening may be changed to change the flow path cross-sectional area of the air pipe 16.

[0148]

According to the first aspect of the present invention,
When the purge control valve is duty-controlled, the existence of pulsation in the fuel tank side internal pressure or the canister side internal pressure selectively detected by the internal pressure detecting means by switching of the switching means is determined based on a predetermined pulsation determination value, In the failure diagnosis device that diagnoses a failure related to switching of the switching unit using the determination result as a diagnosis condition, the pulsation determination value is corrected according to the level of the atmospheric pressure detected by the atmospheric pressure detection unit or its equivalent value. Like that. Therefore, even when the pulsation of the internal pressure on the canister side changes due to the influence of the atmospheric pressure during the failure diagnosis of the switching means, the pulsation determination value is corrected in accordance with the change of the pulsation, so that the pulsation of the pulsation is corrected. Erroneous determination regarding presence is suppressed. As a result, when diagnosing the failure of the switching means using the pulsation of the intake negative pressure, an effect is provided that a highly accurate diagnosis can be performed without being affected by a change in the atmospheric pressure.

According to the second aspect of the present invention, when the duty of the purge control valve is controlled, the fuel tank side internal pressure or the canister side internal pressure selectively detected by the internal pressure detecting means by switching of the switching means. Atmospheric pressure detected by a failure diagnostic device which determines the presence of pulsation at the predetermined pulsation determination value based on a predetermined pulsation determination value, and uses the determination result as a diagnostic condition to diagnose a failure related to switching of the switching means, or an equivalent value thereof. Is lower than a predetermined value, the drive frequency related to the duty control of the purge control valve is corrected to be lower than the predetermined value. Therefore, at the time of failure diagnosis of the switching means, even if the pulsation in the internal pressure on the canister side becomes small due to the atmospheric pressure being lower than the predetermined value, the drive frequency related to the duty control is corrected to be lower than the predetermined value. As a result, pulsation due to the internal pressure on the canister side increases, and erroneous determination regarding the presence of the pulsation is suppressed. As a result, when diagnosing the failure of the switching means using the pulsation of the intake negative pressure, an effect is provided that a highly accurate diagnosis can be performed without being affected by a change in the atmospheric pressure.

According to the third aspect of the present invention, the fuel vapor processing apparatus includes an atmosphere control valve including a check valve for controlling the introduction of the atmosphere into the canister and the derivation of the inside air, and the purge control valve includes the check valve. When the duty control is performed, the existence of pulsation in the fuel tank side internal pressure or the canister side internal pressure selectively detected by the internal pressure detecting means by switching of the switching means is determined based on a predetermined pulsation determination value, and the determination result is determined. In a failure diagnosis device configured to diagnose a failure related to switching of a switching unit as a diagnosis condition, when a detected atmospheric pressure or its equivalent value is lower than a predetermined value, a flow path of an atmosphere introduction passage in an atmosphere control valve. In order to reduce the cross-sectional area, the flow path cross-sectional area variable means is controlled. Therefore, in the failure diagnosis of the switching means, even when the pulsation in the internal pressure on the canister side becomes small due to the atmospheric pressure being lower than a predetermined value, the air passage is reduced by reducing the flow path cross-sectional area of the air introduction passage. The intake resistance of the control valve increases, and the pulsation at the internal pressure on the canister side increases, and erroneous determination regarding the presence of the pulsation is suppressed. As a result, when diagnosing the failure of the switching means using the pulsation of the intake negative pressure, an effect is provided that a highly accurate diagnosis can be performed without being affected by a change in the atmospheric pressure.

According to the configuration of the present invention, when the purge control valve is to be opened by the duty control, the presence of the pulsation in the internal pressure of the canister detected by the internal pressure detecting means is set to a predetermined pulsation determination value. In the failure diagnostic apparatus, which determines that the purge control valve is in a closed state and diagnoses as a failure by using the determination result as a diagnostic condition, the atmospheric pressure detected by the atmospheric pressure detecting means or its equivalent value The pulsation determination value is corrected according to the level of the pulsation. Therefore, when diagnosing a failure while the purge control valve is closed, even if the pulsation in the internal pressure of the canister changes due to the atmospheric pressure, the pulsation determination value corresponds to the change in the pulsation. Is corrected, erroneous determination regarding the presence of the pulsation is suppressed. As a result, when diagnosing a failure of the purge control valve using the pulsation of the intake negative pressure, an effect that a highly accurate diagnosis can be performed without being affected by a change in the atmospheric pressure is exhibited.

According to the fifth aspect of the invention, when the purge control valve is to be opened by the duty control, the presence of the pulsation in the internal pressure of the canister detected by the internal pressure detecting means is set to a predetermined pulsation determination value. In the failure diagnosis device, the determination result is used as a diagnosis condition to diagnose that the purge control valve has failed while the purge control valve is closed, the detected atmospheric pressure or its equivalent value is smaller than a predetermined value. When it is low, the drive frequency related to the duty control of the purge control valve is corrected to be lower than a predetermined value. Therefore, when diagnosing the failure of the purge control valve,
Even when the pulsation at the internal pressure of the canister becomes smaller due to the atmospheric pressure becoming lower than the predetermined value, the pulsation at the internal pressure of the canister becomes larger by correcting the drive frequency related to the duty control to be lower than the predetermined value. In addition, erroneous determination regarding the presence of the pulsation can be suppressed. As a result, when diagnosing a failure of the purge control valve using the pulsation of the intake negative pressure, an effect that a highly accurate diagnosis can be performed without being affected by a change in the atmospheric pressure is exhibited.

[0153] According to the structure of the present invention, the fuel vapor treatment device is provided with an atmosphere control valve comprising a check valve for controlling the introduction of the atmosphere to the canister and the derivation of the inside air, and the purge control valve is provided. When it is to be opened by the duty control, the presence of pulsation in the internal pressure of the canister detected by the internal pressure detecting means is determined based on a predetermined pulsation determination value, and the determination result is used as a diagnostic condition to keep the purge control valve closed. In a failure diagnosis device configured to diagnose that a failure has occurred, when the detected atmospheric pressure or its equivalent value is lower than a predetermined value, the flow path cross-sectional area of the air introduction passage in the air control valve is reduced. The means for controlling the cross-sectional area of the flow path is controlled. Therefore, at the time of failure diagnosis of the purge control valve, even when the pulsation in the internal pressure on the canister side is reduced due to the atmospheric pressure being lower than a predetermined value, the flow path cross-sectional area of the air introduction passage is narrowed, The intake resistance of the air control valve increases, and the pulsation at the internal pressure on the canister side increases, thereby suppressing erroneous determination regarding the presence of the pulsation. As a result, when diagnosing a failure of the purge control valve using the pulsation of the intake negative pressure, an effect that a highly accurate diagnosis can be performed without being affected by a change in the atmospheric pressure is exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fuel vapor processing device and a failure diagnosis device thereof according to a first embodiment.

FIG. 2 is a flowchart showing a “three-way switching valve diagnostic routine”;

FIG. 3 is a flowchart showing a “three-way switching valve diagnostic routine”;

FIG. 4 is also function data (map) showing the relationship between the atmospheric pressure and the correction coefficient.

FIG. 5 is a flowchart illustrating a “three-way switching valve diagnostic routine” according to the second embodiment;

FIG. 6 is a flowchart showing a “three-way switching valve diagnostic routine”;

FIG. 7 is a function data (map) showing the relationship between the atmospheric pressure and the driving frequency.

FIG. 8 is a time chart showing behaviors of a drive duty ratio and a canister internal pressure.

FIG. 9 is a time chart showing behaviors of a drive duty ratio and a canister internal pressure.

FIG. 10 is a schematic configuration diagram showing a fuel vapor processing device and a failure diagnosis device thereof according to a third embodiment.

FIG. 11 is a flowchart showing a “three-way switching valve diagnostic routine”;

FIG. 12 is a flowchart showing a “three-way switching valve diagnostic routine”;

FIG. 13 is a flowchart illustrating a “purge control valve diagnosis routine” according to the fourth embodiment;

FIG. 14 is a flowchart showing a “purge control valve diagnosis routine”.

FIG. 15 is a time chart showing the behavior of fuel purge, engine start, and canister internal pressure.

FIG. 16 is a time chart showing the behavior of fuel purge and canister internal pressure.

FIG. 17 is a flowchart illustrating a part of a “purge control valve diagnosis routine” according to the fifth embodiment;

FIG. 18 is a flowchart illustrating a part of a “purge control valve diagnostic routine” according to the sixth embodiment.

FIG. 19 is a schematic configuration diagram showing a conventional fuel vapor processing device and its failure diagnosis device.

[Explanation of symbols]

Reference Signs List 2 fuel tank 4 engine 7 intake passage 12 canister 14 first air control valve 16 air pipe (atmosphere introduction passage) 23 VSV 24 throttle (23 and 24 constitute flow passage cross-sectional area variable means) 20 purge control valve 21 Three-way switching valve (constituting switching means) 31 Pressure sensor (constituting internal pressure detecting means) 32 Intake temperature sensor 33 Intake pressure sensor 35 Rotation speed sensor (32, 33, 35 constitutes atmospheric pressure detecting means). 41) ECU (constituting diagnosis means, closed-failure diagnosis means, determination value correction means, drive frequency correction means, control means)

Continuing from the front page (72) Inventor, Katsumi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kenichiro Kawase 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Yukihide Hashiguchi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 2G067 AA02 CC04 DD02 EE10 3G084 BA00 BA27 CA03 DA26 DA27 DA33 EA01 EA06 EA11 EB22 EB24 EB25 EC04 EC06 FA00 FA02 FA05 FA11 FA20 FA29 FA29 FA38

Claims (6)

[Claims] A fuel vapor generated in a fuel tank is collected by a canister, and the fuel collected in the canister is purged to the intake passage based on a negative pressure generated in the intake passage during operation of the engine. A failure diagnosis device provided for a fuel vapor processing device provided with a purge control valve whose opening is duty-controlled to adjust the amount of fuel to be purged, wherein the fuel tank side and the canister side Used for diagnosing a failure related to airtightness, one internal pressure detecting means for detecting the internal pressure on the fuel tank side and the internal pressure on the canister side, and the internal pressure on the fuel tank side and the internal pressure on the canister side. Switching means for switching the detection destination of the internal pressure detecting means for selectively detecting the pressure, and wherein the purge control valve performs duty control during operation of the engine. The presence or absence of a pulsation in the selectively detected internal pressure on the fuel tank side or internal pressure on the canister side is determined based on a predetermined pulsation determination value. A failure diagnosis device comprising: a diagnosis unit for diagnosing a failure according to the invention, comprising: an atmospheric pressure detection unit for detecting an atmospheric pressure or a value corresponding to the atmospheric pressure; and A failure diagnosis device for a fuel vapor processing device, comprising: a determination value correction means for correcting the pulsation determination value according to the height. 2. A fuel vapor generated in a fuel tank is collected by a canister, and the fuel collected by the canister is purged to the intake passage based on a negative pressure generated in the intake passage during operation of the engine. A failure diagnosis device provided for a fuel vapor processing device provided with a purge control valve whose opening is duty-controlled to adjust the amount of fuel to be purged, wherein the fuel tank side and the canister side Used for diagnosing a failure related to airtightness, one internal pressure detecting means for detecting the internal pressure on the fuel tank side and the internal pressure on the canister side, and the internal pressure on the fuel tank side and the internal pressure on the canister side. Switching means for switching the detection destination of the internal pressure detecting means for selectively detecting the pressure, and wherein the purge control valve performs duty control during operation of the engine. The presence or absence of a pulsation in the selectively detected internal pressure on the fuel tank side or internal pressure on the canister side is determined based on a predetermined pulsation determination value. A failure diagnosis device comprising: a diagnosis unit for diagnosing a failure according to the invention, wherein an atmospheric pressure detection unit for detecting an atmospheric pressure or a value corresponding to the atmospheric pressure; and A drive frequency correcting means for correcting a drive frequency related to duty control of the purge control valve to be lower than a predetermined value when the drive frequency is lower than a predetermined value. . 3. The fuel vapor generated in the fuel tank is collected by a canister, and the fuel collected by the canister is purged to the intake passage based on a negative pressure generated in the intake passage during operation of the engine. A purge control valve whose opening is duty-controlled to adjust the amount of fuel to be purged, and an atmosphere control valve including a check valve for controlling the introduction of air into the canister and the derivation of inside air. A failure diagnosis device provided for the fuel vapor processing device, wherein the failure diagnosis device is used for diagnosing a failure related to airtightness of the fuel tank side and the canister side, and the internal pressure of the fuel tank side and the canister side are used. One internal pressure detecting means for detecting the internal pressure; and the internal pressure detecting means for selectively detecting the internal pressure on the fuel tank side and the internal pressure on the canister side. A switching unit for switching a detection destination; and determining whether there is a pulsation in the selectively detected internal pressure on the fuel tank side or the internal pressure on the canister side when the duty of the purge control valve is controlled during operation of the engine. And a diagnostic means for diagnosing a failure related to switching of the switching means as a diagnostic condition using the determination result as a diagnostic condition. Flow path cross-sectional area variable means for making the flow path cross-sectional area variable, atmospheric pressure detecting means for detecting atmospheric pressure or a value corresponding to atmospheric pressure, and the detected atmospheric pressure or its equivalent value is Control means for controlling the flow path cross-sectional area varying means to reduce the flow path cross-sectional area of the air introduction passage when the flow rate is lower than a predetermined value. Failure diagnosis apparatus for steaming device. 4. A fuel vapor generated in a fuel tank is collected by a canister, and fuel collected in the canister is purged to the intake passage based on a negative pressure generated in the intake passage when the engine is operating. A failure diagnosis device provided for a fuel vapor processing device having a purge control valve whose opening is duty-controlled to adjust the amount of fuel to be purged, wherein the failure diagnosis device is provided for detecting an internal pressure of the canister. Internal pressure detecting means, when the purge control valve is to be opened by duty control during operation of the engine, the presence of pulsation in the detected internal pressure is determined based on a predetermined pulsation determination value, and the determination result is diagnosed. A failure diagnosis device comprising: a failure diagnosis unit configured to diagnose that the purge control valve has failed in a closed state as a condition. Atmospheric pressure detecting means for detecting a pressure or a value corresponding to the atmospheric pressure, and judgment value correcting means for correcting the pulsation judgment value according to the detected atmospheric pressure or the level of the corresponding value. A fault diagnosis device for a fuel vapor processing device. 5. A fuel vapor generated in a fuel tank is collected by a canister, and the fuel collected in the canister is purged to the intake passage based on a negative pressure generated in the intake passage during operation of the engine. A failure diagnosis device provided for a fuel vapor processing device having a purge control valve whose opening is duty-controlled to adjust the amount of fuel to be purged, wherein the failure diagnosis device is provided for detecting an internal pressure of the canister. Internal pressure detecting means, when the purge control valve is to be opened by duty control during operation of the engine, evaluates the presence of pulsation at the detected internal pressure based on a predetermined pulsation determination value, and diagnoses the evaluation result. A failure diagnosis device comprising: a failure diagnosis means for diagnosing that the purge control valve has failed in a closed state as a condition. Or an atmospheric pressure detecting means for detecting a value corresponding to the atmospheric pressure, and a drive frequency for the duty control of the purge control valve when the detected atmospheric pressure or its equivalent value is lower than a predetermined value. A failure diagnosis device for a fuel vapor processing device, comprising: a drive frequency correction means for correcting a value lower than a value. 6. A fuel vapor generated in a fuel tank is collected by a canister, and the fuel collected in the canister is purged to the intake passage based on a negative pressure generated in the intake passage during operation of the engine. A purge control valve whose opening is duty-controlled to adjust the amount of fuel to be purged, and an air control valve comprising a check valve for controlling the introduction of air into the canister and the derivation of inside air. A failure diagnosis device provided for a fuel vapor processing device provided with: an internal pressure detection unit for detecting an internal pressure of the canister; and a valve when the purge control valve is to be opened by duty control during operation of the engine. The presence of a pulsation in the detected internal pressure is evaluated based on a predetermined pulsation determination value, and the purge control valve is closed based on the evaluation result as a diagnostic condition. A failure diagnostic device comprising: a closed failure diagnostic means for diagnosing a failure in a state; and a variable flow path cross-sectional area for changing a flow path cross-sectional area of the air introduction passage in the air control valve. Means, an atmospheric pressure detecting means for detecting an atmospheric pressure or a value corresponding to the atmospheric pressure, and, if the detected atmospheric pressure or its equivalent value is lower than a predetermined value, a flow path of the air introduction passage A failure diagnosis device for a fuel vapor processing device, comprising: control means for controlling the flow path cross-sectional area variable means to reduce the cross-sectional area.