JP2002349321A - Control apparatus for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use an intake pressure sensor that forms an indispensable part together with an intake air oxygen sensor as an atmospheric pressure sensor under a specific condition in a control apparatus for an internal combustion engine provided in an intake air passageway thereof with a mechanism for purging a fuel vapor. SOLUTION: The intake air oxygen sensor 36 is disposed in the intake air passageway 20. The intake pressure sensor 40 is connected into communication with the intake air passageway 20 by way of a three-way VSV 38. The three- way VSV 38 is placed in an OFF position when the fuel vapor is purged from a canister 10 to the intake air passageway 20, thereby introducing an intake pipe pressure PM to the intake pressure sensor 40. In a condition, in which the fuel vapor is not purged, the three-way VSV 38 is placed in an ON position, thereby introducing an atmospheric pressure PA to the intake pressure sensor 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control device for an internal combustion engine, and more particularly to a control device suitable for controlling an internal combustion engine having a mechanism for purging fuel vapor in an intake passage of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 9-42074, for example, fuel vapor generated in a fuel tank is adsorbed to a canister, and the vapor is purged into an intake passage during operation of the internal combustion engine. Systems are known.
This type of system may be required to have a failure diagnosis function for promptly informing the user of the vehicle when an abnormality occurs in the system. Hereinafter, such a failure diagnosis function is referred to as “evaporation OBD (On Board Diagnosi
s) ".

[0003] The evaporation OBD checks whether a system including a fuel tank, a canister, and a purge passage connecting the canister and the intake passage, that is, a system including all of the vapor flow paths, has an improper leak. A function to diagnose is required. This function can be realized, for example, by sealing the above system, introducing a negative pressure therein, and then seeing how the pressure in the system changes. Specifically, when the pressure in the system is unduly sharply increased, it can be determined that a leak has occurred at any point in the system. On the other hand, if the change in the system pressure is sufficiently gentle, it can be determined that no leakage has occurred in the system.

[0004] When leak detection is performed by the above method, a pressure sensor for detecting the pressure in the system is required. As such a pressure sensor, a sensor that detects the pressure of the atmosphere to be measured as a relative pressure with respect to the atmospheric pressure, that is, a relative pressure sensor, has conventionally been used from the viewpoint of measurement accuracy, cost, and the like.

[0005]

However, the output of the relative pressure sensor changes not only with the change in the system pressure but also with the change of the atmospheric pressure. The atmospheric pressure surrounding the vehicle changes as the altitude of the vehicle changes. Therefore, the output of the relative pressure sensor mounted on the vehicle changes when the vehicle goes uphill or when the vehicle goes downhill. For this reason, when the relative pressure sensor is used for the evaporation OBD, there is a problem that the above-described leak detection cannot be performed accurately while the vehicle is going up or downhill.

The above problem can be solved, for example, by adding a sensor (atmospheric pressure sensor) for measuring atmospheric pressure in absolute pressure to a system for evaporation OBD. More specifically, the above-mentioned problem can be solved by correcting a variation generated in the output of the relative pressure sensor due to the variation of the atmospheric pressure based on the output of the atmospheric pressure sensor. However, if a new atmospheric pressure sensor is added, the cost of the evaporation OBD system will increase.

When the fuel vapor is purged into the intake passage, the amount of fuel supplied from the injector to the internal combustion engine, that is, the fuel injection amount needs to be corrected in accordance with the amount of the purge. Such correction is performed by, for example, providing an oxygen concentration sensor in the intake passage, detecting the vapor concentration in the intake passage from the sensor output, and further calculating the vapor purge amount and the like based on the detected value. be able to.

In general, an oxygen concentration sensor has a pressure-dependent characteristic. That is, the oxygen concentration sensor generates an output according to the number of oxygen molecules existing near the sensor element. For this reason, even if the oxygen concentration sensor has the same oxygen concentration, the pressure of the detected atmosphere is high, and a large output is generated when a large amount of oxygen molecules are present near the sensor element. When the pressure is low and only a small amount of oxygen molecules are present near the sensor element, a small output is generated.

The pressure in the intake passage fluctuates frequently and greatly according to the operating state of the internal combustion engine. For this reason, an oxygen concentration sensor (hereinafter referred to as “intake O ₂
In order to detect the oxygen concentration inside the sensor based on the output value of the "sensor"), the pressure in the intake passage is detected,
It is necessary to understand the output of the intake O ₂ sensor based on the pressure. Thus, in a system comprising the air-inlet O ₂ sensor, an intake pressure sensor for measuring the intake air pressure in absolute pressure is an essential component.

[0010] The present invention has been made in view of the above, by utilizing the intake air pressure sensor as the essential component in combination with the intake O ₂ sensor as the atmospheric pressure sensor in certain circumstances It is another object of the present invention to provide a control device for an internal combustion engine that can detect the atmospheric pressure without increasing the cost.

[0011]

According to the first aspect of the present invention,
To achieve the above object, there is provided a control device for an internal combustion engine including a purge mechanism for purging a purge gas containing fuel vapor into an intake passage, wherein the vapor generator generates an output in accordance with a fuel vapor concentration in the intake passage. A concentration sensor, an intake pressure sensor for detecting a pressure guided to the pressure inlet, and a first for guiding an intake pipe pressure in the intake passage to the pressure inlet.
And a second valve that can realize a second state of guiding atmospheric pressure to the pressure inlet, the output of the vapor concentration sensor, and the intake pipe pressure detected by the intake pressure sensor. Vapor concentration detecting means for detecting a vapor concentration in the intake passage; injection amount calculating means for calculating a fuel injection amount based on the vapor concentration; and, when the purge gas has been purged, the switching valve to the first valve. And a switching valve control means for allowing the switching valve to take the second state when the purge gas is not purged.

According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the switching valve control means includes condition determination means for determining whether a purge cut condition is satisfied. When the purge cut condition is not satisfied, the switching valve is set to the first state.

[0013] The invention according to claim 3 is the invention according to claim 1 or 2.
The control apparatus for an internal combustion engine according to claim 1, wherein the purge mechanism includes a purge control valve that controls a flow rate of the purge gas, and the switching valve control unit determines whether the purge control valve has an open abnormality. Including open abnormality determination means for determining
When the opening abnormality has occurred, the switching valve is set to the first position.
It is characterized by the following.

According to a fourth aspect of the present invention, there is provided a control device for an internal combustion engine according to any one of the first to third aspects, wherein the purge mechanism includes a canister for adsorbing fuel vapor generated in a fuel tank. A purge control valve disposed between the canister and the intake passage for controlling a flow rate of the purge gas, and sealing a system including the fuel tank, the canister, and the purge control valve, and Negative pressure introducing means for introducing a predetermined negative pressure into the system, a relative pressure sensor for detecting a relative pressure in the system, and a large pressure detected by the intake pressure sensor after the predetermined negative pressure is introduced into the system. Pressure change detecting means for detecting a pressure change occurring in the system based on the atmospheric pressure and a relative pressure in the system detected by the relative pressure sensor, and performing a failure diagnosis of the system based on the pressure change Failure diagnosis means And further comprising a.

According to a fifth aspect of the present invention, there is provided the control device for an internal combustion engine according to the fourth aspect, wherein the switching valve control means is provided only when the introduction of the predetermined negative pressure into the system is completed. The switching valve is switched from the first state to the second state.

According to a sixth aspect of the present invention, there is provided the control device for an internal combustion engine according to any one of the first to fifth aspects, wherein the intake pressure sensor is provided when the switching valve takes the first state. Switching valve failure diagnosis means for performing failure diagnosis of the switching valve based on a difference between the detected pressure and a pressure detected by the intake pressure sensor when the switching valve takes the second state. Features.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, the first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the configuration of the present embodiment includes a canister 10. A fuel tank 14 communicates with the canister 10 via a vapor passage 12. The fuel tank 14 is provided with a pressure sensor 15 that generates an output corresponding to a difference between the tank internal pressure and the atmospheric pressure, that is, a pressure sensor 15 that detects the tank internal pressure as a relative pressure. Fuel vapor generated in the fuel tank 14 is guided to the canister 10 through the vapor passage 12. The canister 10 can adsorb and hold the fuel vapor guided as described above.

The canister 10 also has a CCV (Canis
An atmosphere introduction passage 18 communicates with the air through a ter closed valve (16). The air introduction passage 18 communicates with an air cleaner 22 disposed at an end of the intake passage 20. CCV1
Reference numeral 6 denotes an on-off valve capable of setting the air introduction passage 18 in a conductive state or a cutoff state.

The canister 10 further includes an intake passage 20.
Is connected to the purge passage 24. Purge passage 2
A purge VSV (Vacuum Switching Valve) 26 that realizes an arbitrary opening degree by performing duty control is arranged in 4.

An air flow meter 28 is arranged in the intake passage 20 downstream of the air cleaner 22. The air flow meter 28 generates an output corresponding to the amount Ga of intake air flowing into the intake passage 20 through the air cleaner 22.

Downstream of the air flow meter 28, a throttle valve 30 for controlling an intake air amount Ga flowing through the intake passage 20 is arranged. The throttle valve 30 has
A throttle sensor 32 for generating an output according to the throttle opening is incorporated. The above-described purge passage 24
Communicates with the intake passage 20 downstream of the throttle valve 30.

The intake passage 20 has a surge tank 34 downstream of the throttle valve 30 and communicates with an intake port of the internal combustion engine 42 downstream of the surge tank 34. In the present embodiment, the surge tank 34 has an oxygen concentration sensor 36 (hereinafter, referred to as an “intake O ₂ sensor 3”) that generates an output corresponding to the oxygen concentration in the gas flowing therethrough.
6 "). In this embodiment, an intake pressure sensor (PM sensor) 40 is attached to the surge tank 34 via a three-way VSV 38.

The three-way VSV 38 guides the intake pipe pressure generated inside the surge tank 34 to the PM sensor 40 in a first state (off state), and guides the PM sensor 40 to the atmospheric pressure instead of the intake pipe pressure. The switching valve realizes the second state (ON state). PM sensor 40 is a three-way VSV3
An absolute pressure sensor that detects either the intake pipe pressure or the atmospheric pressure as an absolute pressure in accordance with the state 8.

As shown in FIG. 1, the configuration of this embodiment is as follows.
An ECU (Electronic Control Unit) 50 is provided.
The ECU 50, various sensor outputs described above, i.e., the pressure sensor 15, air flow meter 22, a throttle sensor 32, the intake _{O 2} sensor 36 and the PM sensor 4,
An output such as 0 is provided. The ECU 50 includes the various actuators described above, that is, the CCV1.
6. The purge VSV 26, the three-way VSV 38, and an injector (not shown) are electrically connected.

Next, the operation of the configuration shown in FIG. 1 will be described. In the configuration shown in FIG. 1, when the purge VSV 26 is opened during the operation of the internal combustion engine 42, the intake negative pressure can be guided to the canister 10 via the purge passage 24.
With the CCV 16 opened, the canister 10 is opened as described above.
When the negative pressure is introduced into the intake passage 20, the vapor adsorbed by the canister 10 is purged into the intake passage 20 together with the air sucked from the air introduction passage 18. Thus, according to the configuration of the present embodiment, the vapor adsorbed by the canister 10 can be supplied to the internal combustion engine 42 as fuel.

In the configuration of this embodiment, the canister 1
When the fuel vapor is purged from 0 to the intake passage 20, the fuel injection amount TAU injected from the injector into the internal combustion engine 42 is calculated so as to cancel the effect of the purge in order to prevent a deviation in the air-fuel ratio. There is a need to. Such a fuel injection amount TAU can be obtained, for example, by correcting a base injection amount calculated based on the intake air amount Ga based on the vapor concentration in the gas flowing in the surge tank 34.

FIG. 2 is a flowchart of a TAU calculation routine executed by the ECU 50 to determine the fuel injection amount TAU by the above method.

In the routine shown in FIG. 2, first, the intake air amount Ga is detected based on the output of the air flow meter 28 (step 100). Next, a base injection amount for obtaining a desired air-fuel ratio with respect to the intake air amount Ga is calculated (step 102). Next, in order to detect the vapor concentration in the gas flowing through the surge tank 34, the output of the intake O ₂ sensor 36 is detected (step 104).

The intake O ₂ sensor 36 is a sensor that emits an output according to the oxygen concentration in the gas, more specifically, a sensor that emits an output according to the number of oxygen molecules existing on the surface of the sensor element. While the fuel vapor is purged into the intake passage 20, a gas mixture of air and vapor is guided around the sensor element of the intake O ₂ sensor 36. In this case, a reaction between the vapor and oxygen occurs near the surface of the sensor element, and the number of oxygen molecules decreases by the amount consumed in the reaction. As a result, the intake O ₂ sensor 36, an output corresponding to the oxygen concentration in the gas flowing through the surge tank 34, i.e., the output is issued in accordance with the vapor concentration of the gas.

By the way, the number of oxygen molecules present in the periphery of the intake O ₂ sensor 36, as becomes large amount of high pressure surrounding the sensor, also a small amount as the pressure is low.
Therefore, the output of the intake O ₂ sensor 36 increases as the pressure increases and decreases as the pressure decreases, even if the oxygen concentration in the gas to be detected is the same.
Therefore, in order to accurately detect the vapor concentration in the surge tank 34 based on the output of the intake O ₂ sensor 36,
It is necessary to detect the pressure surrounding the sensor, that is, the intake pipe pressure PM generated in the surge tank 34.

Therefore, in the routine shown in FIG. 2, the output of the PM sensor 40 is detected following the processing of step 104 (step 106). 3-way VS as described below
V38 is maintained in the first state (off state) so that the intake pipe pressure PM is guided to the PM sensor 40 in an environment where the vapor is purged. Therefore, this step 10
According to the process of No. 6, the intake pipe pressure PM can be detected.

The output of the intake O ₂ sensor 36 and the intake pipe pressure P
When M is detected, the concentration of vapor in the gas flowing through the surge tank 34 is detected based on them (step 108). Then, the ECU 50 corrects the base injection amount based on the obtained vapor concentration to obtain a fuel injection amount TAU that can offset the effect of the purge (step 110).

As described above, in the present embodiment, the ECU
50 uses the intake pipe pressure PM to calculate the fuel injection amount TAU while the fuel vapor is being purged. Therefore, during the purge of the fuel vapor, the PM sensor 40
Need to function as a sensor for detecting the intake pipe pressure PM.

However, the purge of the fuel vapor is not always performed during the operation of the internal combustion engine 42. For example, during the warm-up of the internal combustion engine 42, while the fuel cut condition is being satisfied, or leak detection by the evaporation OBD (details will be described later).
During the execution of, the purge of the fuel vapor is prohibited. During these periods, that is, during the period in which the fuel vapor is not purged, the PM sensor 40 does not necessarily need to detect the intake pipe pressure PM. On the other hand, in controlling the internal combustion engine 42, detection of the atmospheric pressure may be required. Therefore, the control device of the present embodiment causes the PM sensor 40 to detect the intake pipe pressure PM during the period in which the fuel vapor is purged, and on the other hand, the PM sensor 40 detects the PM during the period in which the fuel vapor is not purged.
The detection of the atmospheric pressure by the sensor 40 is allowed.

FIG. 3 shows an example of an EC for realizing the above functions.
4 shows a flowchart of a three-way VSV control routine executed by U50. In the routine shown in FIG. 3, first, it is determined whether a predetermined purge cut condition is satisfied (step 120). The purge cut condition is a condition that is predetermined so as to be satisfied in a situation where the purge of the fuel vapor should be prohibited. Specifically, the purge cut conditions are:
For example, during a warm-up period in which the combustion state inside the internal combustion engine 42 is not stable, when a fuel cut condition for cutting off the supply of fuel to the internal combustion engine 42 is satisfied, and in a process of executing an evaporation OBD leak detection process described later. Fuel tank 14
After the introduction of the negative pressure to the system including the above is completed, it is determined that the establishment is completed.

If it is determined that the purge cut condition is not satisfied, the three-way VSV is set to the first state (off state), and the intake pipe pressure PM is guided to the PM sensor 40 (step 122). Next, the output of the PM sensor 40 is taken into the ECU 50 as the intake pipe pressure PM (step 124). Therefore, in this case, the vapor concentration in the surge tank 34 is detected based on the output of the PM sensor 40, and the appropriate fuel injection amount TAU can be calculated based on the detected value.

On the other hand, if it is determined in step 120 that the purge cut condition is satisfied, the three-way V
SV is set to the second state (ON state), and the PM sensor 40
Is introduced to the atmospheric pressure PA (step 126). Then
When the output of the PM sensor 40 is the atmospheric pressure PA, the ECU 50
(Step 128). Therefore, in this case, the atmospheric pressure PA can be detected based on the output of the PM sensor 40.

As described above, according to the routine shown in FIG. 3, the PM sensor 40 can function as an atmospheric pressure sensor under a predetermined condition. For this reason, according to the control device of the present embodiment, it is possible to realize a function of detecting the atmospheric pressure as necessary without newly providing an atmospheric pressure sensor.

FIG. 4 is a flowchart of an example of a process executed by the ECU 50 using the atmospheric pressure detected as described above. More specifically, FIG.
9 is a flowchart of an evaporation OBD leak detection routine executed with reference to the atmospheric pressure detected by the PM sensor 40.

The structure shown in FIG. 1 is provided with a mechanism for adsorbing and purging the fuel vapor, that is, a purge mechanism, in order to prevent the fuel vapor generated in the fuel tank 14 from being discharged to the outside of the vehicle. ing. The above object cannot be achieved if there is a leak in any part of the system from the fuel tank 14 to the intake passage 20, that is, the system in which the flow of the fuel vapor is allowed. For this reason, it is desirable that leaks occurring in the above system be detected promptly. The evaporative OBD leak detection routine is a routine that is executed to meet the request.

As shown in FIG. 4, in the evaporative OBD leak detection routine, first, it is determined whether or not the condition for executing the leak detection of the evaporative OBD is satisfied (step 13).
0). As a result, when it is determined that the execution condition of the leak detection is satisfied, the CCV 16 is then closed (step 132). Next, the purge VSV 26 is controlled to open (step 134). By executing these processes, the system from the fuel tank 14 to the intake passage 20 is cut off from the outside air, and the intake negative pressure starts to be introduced into the system.

When the introduction of the negative pressure into the system is started, it is determined whether or not a sufficient negative pressure has been introduced into the system based on the output of the pressure sensor 15 disposed in the fuel tank 14 (the introduction of the negative pressure is performed). Is completed) (step 136). When the completion of the introduction of the negative pressure is determined by the above processing, the purge V
The SV 26 is closed, and the system from the fuel tank 14 to the purge VSV 26 is shut off from the outside air (step 1).
38). If it is determined in step 136 that the introduction of the negative pressure has been completed, it is determined in the routine shown in FIG. 3 that the purge cut condition has been satisfied (step 120).
), The three-way VSV 38 is switched so that the PM sensor 40 detects the atmospheric pressure PA (steps 126 and 1).
28).

In the routine shown in FIG.
Subsequent to the process at step 38, a substantial change in the tank internal pressure within a predetermined period is detected (step 140). In this step 140, the substantial change in the tank internal pressure is determined by the output PT of the pressure sensor 15 arranged in the fuel tank 14.
(Relative pressure) and the atmospheric pressure PA (absolute pressure) detected by the PM sensor 40. That is, the output PT of the pressure sensor 15 is a relative pressure that represents the tank internal pressure as a pressure difference from the atmospheric pressure. Therefore, the output PT is affected by a change in the atmospheric pressure PA due to the vehicle going up or downhill. Therefore, in step 140, a substantial change in the tank internal pressure is determined by canceling the atmospheric pressure change ΔPA generated during the predetermined period from the output change ΔPT of the pressure sensor 15 generated during the predetermined period. . According to such a process, a substantial change in the tank internal pressure, that is, a substantial change in the closed system from the fuel tank 14 to the purge VSV 26 without being affected by the fluctuation of the atmospheric pressure PA. Pressure change can be detected with high accuracy.

When a substantial change in the tank internal pressure is detected, it is next determined whether or not the system from the fuel tank 14 to the purge VSV 26 is normal based on the amount of change (step 142). Purge VS from fuel tank 14
If no leak has occurred in the system up to V26, no significant pressure change occurs in the process of detecting the pressure change. Therefore, when the substantial change amount of the tank internal pressure is smaller than the predetermined threshold value, it is determined that the above system is normal. On the other hand, when the negative pressure in the system is greatly reduced in the process of detecting the pressure change and a substantially large pressure change is detected, it can be determined that a leak has occurred in the system. For this reason, when the substantial change amount of the tank internal pressure is larger than the predetermined threshold value, it is determined that the above system is abnormal.

When the normality is determined in step 142, a predetermined OK process such as recording the history of the failure diagnosis process is performed, and then the current routine is terminated (step 144). On the other hand, if an abnormality is determined in step 142, an NG such as turning on an abnormality lamp to notify the user of the abnormality of the abnormality is performed.
After the processing is executed, the current routine ends (step 146).

As described above, in the configuration of the present embodiment, when the fuel vapor is not purged, the atmospheric pressure PA is allowed to be detected by the PM sensor 40, and the atmospheric pressure PA detected in this manner is allowed. But the fuel tank 14
Is used to detect leakage of the system from the VSV 26 to the purge VSV 26. When the atmospheric pressure PA can be used, the accuracy of diagnosis can be prevented from deteriorating due to the vehicle going up or downhill, so that the situation in which a failure diagnosis can be performed more accurately than when the atmospheric pressure PA cannot be used can be expanded. . For this reason, according to the control device of the present embodiment, the restriction on the execution condition of the leak detection is reduced without adding a new atmospheric pressure sensor, and
It is possible to improve the accuracy of failure diagnosis related to leak detection.

By the way, in the first embodiment described above, although the intake O ₂ sensor 36 for detecting the fuel vapor concentration in the surge tank 34 is used, the present invention is limited to this configuration Absent. That is, the intake O
_{The two} sensors 36 are capable of detecting fuel vapor and can be replaced with various sensors (evaporation sensors or vapor sensors) that are dependent on the pressure of the detected atmosphere.

Further, in the first embodiment described above,
Although the intake O ₂ sensor 36 is provided in the surge tank 34, the arrangement position of the intake O ₂ sensor 36 is not limited to this. That is, the intake O ₂ sensor 3
6 may be arranged at any part of the intake passage 20 between the connection port communicating with the purge passage 24 and an injector (not shown).

In the first embodiment, the canister 10, the vapor passage 12, the fuel tank 14, the CC
V16, the "purging mechanism" of the purge passage 24 and the purge VSV26 said claim 1, the intake _{O 2} sensor 36
Is a three-way VS in the "oxygen concentration sensor" according to claim 1.
V corresponds to the “switching valve” of the first aspect. In the first embodiment, the ECU 50
By performing the processing of step 108, the “vapor concentration detecting means” of claim 1 performs the processing of step 110, and the “injection amount calculating means” of claim 1 executes the processing of step 110. Steps 120 to 12 above
The "switching valve control means" according to claim 1 is realized by executing the processing of FIG.

In the first embodiment described above,
The "condition determining means" according to the second aspect is realized by the ECU 50 executing the processing of step 120.

Further, in Embodiment 1 described above,
The "negative pressure introducing means" according to claim 4, wherein the ECU 50 executes the processing of steps 130 to 134.
By executing the processing of step 140, the “pressure change detecting means” of claim 4 executes the processing of step 142, and the “failure diagnosis means” of claim 4 executes the processing of step 142. Has been realized.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a flowchart of a three-way VSV control routine executed by the ECU 50 in the present embodiment. The control device according to the present embodiment differs from the system configuration according to the first embodiment in that the ECU 50
Then, it is realized by executing the routine shown in FIG. 5 instead of the routine shown in FIG. In FIG. 5, steps that are the same as the steps shown in FIG. 3 are given the same reference numerals, and descriptions thereof will be omitted or simplified.

As shown in FIG. 5, 3 in the present embodiment
In the VSV control routine, first, it is determined whether the purge VSV 26 has an open abnormality, that is, the purge VSV 26
Is determined to be unduly maintained in the open state (step 150).

When the purge VSV 26 is abnormally opened, the purge gas flows from the canister 10 toward the intake passage 20 as long as the internal combustion engine 42 continues to operate, even if the purge VSV 26 is controlled to close. Therefore, it is determined whether the purge VSV 26 has an open abnormality or not.
In a state where V26 is controlled in a closed state, the intake O ₂ sensor 36 can be determined by whether substantially vapor concentration not 0 is detected.

When the purge VSV 26 has an open abnormality, the fuel injection amount T is always corrected to offset the purge amount regardless of whether the purge cut condition is satisfied.
AU needs to be applied. Therefore, in this case, it should not be allowed to use the PM sensor 40 as an atmospheric pressure sensor. For this reason, if it is determined in step 150 that the purge VSV 26 has an open abnormality, the three-way VSV 38 is maintained in the first state (off state) (step 122), and the output of the PM sensor 40 is output. It is detected as the intake pipe pressure PM (step 124).

On the other hand, if it is determined in step 150 that the purge VSV 26 has not been abnormally opened, the three-way operation is performed based on whether the purge cut condition is satisfied, as in the first embodiment. The state of the VSV 38 can be switched. Accordingly, in this case, thereafter, as in the case of the routine shown in FIG.
To 128 are executed.

As described above, according to the routine shown in FIG. 5, when the purge VSV 26 has an open abnormality, the PM sensor 40 is used as a sensor for detecting the intake pipe pressure PM even if the purge cut condition is satisfied. You can keep it working. For this reason, according to the control device of the present embodiment, while achieving the same effect as the device of the first embodiment, furthermore, when the purge VSV 26 has an open abnormality, the internal combustion engine 4
2 can be effectively prevented from greatly deviating from the desired air-fuel ratio of the air-fuel ratio supplied to the air-fuel mixture.

In this embodiment, when the purge VSV 26 has an open abnormality, the atmospheric pressure PA cannot be detected. Therefore, under such circumstances, the atmospheric pressure PA
The leak detection of the evaporation OBD cannot be performed with high accuracy using the method. However, in this case, the abnormality of the purge VSV 26, that is, the abnormality of the purge mechanism has already been detected. The purpose of the evaporation OBD is to promptly notify the user of the vehicle when any abnormality occurs in the purge mechanism. Therefore, according to the control device of the present embodiment, even if the purge VSV 26 has an opening abnormality, even if the leak detection cannot be performed with high accuracy, the occurrence of the opening abnormality is notified to the user of the vehicle, and the evaporative OBD is performed. The goal of can be reached.

Note that, in the above-described second embodiment, E
When the CU 50 executes the process of step 150, the "open abnormality determination means" according to claim 3 is realized.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 6 shows a flowchart of a three-way VSV control routine executed by the ECU 50 in the present embodiment. The control device according to the present embodiment differs from the system configuration according to the first embodiment in that the ECU 50
Then, it is realized by executing the routine shown in FIG. 6 instead of the routine shown in FIG. In FIG. 6, steps that are the same as the steps shown in FIG. 3 are given the same reference numerals, and descriptions thereof will be omitted or simplified.

In the control device of the present embodiment, as in the case of the first and second embodiments, the three-way VSV
The surge tank 34 communicates with the surge tank 34 via a reference numeral 38. When such a configuration is adopted, it is necessary to give the three-way VSV 38 sufficient durability and reliability in accordance with the frequency of switching between the first state and the second state. Further, in order to achieve the purpose of the evaporation OBD, it is necessary to appropriately detect a failure occurring in the three-way VSV 38.

The three-way VSV control routine shown in FIG.
This is performed to realize a function of appropriately switching the M sensor 40 to an atmospheric pressure sensor and to meet the above two requirements. That is, the three-way VSV control routine shown in FIG.
It is performed to achieve the following three purposes. The PM sensor 40 is switched to the atmospheric pressure sensor within a range that does not hinder the TAU calculation. The switching frequency of the three-way VSV 38 is minimized,
Its durability and reliability are relatively increased. A failure of the three-way VSV 38 is accurately detected.

In the routine shown in FIG.
It is determined whether or not the BD leak detection execution condition is satisfied (step 160). As a result, when it is determined that the execution condition of the leak detection is not satisfied, the processing of steps 122 and 124 is executed to maintain the intake pressure sensor 40 as the intake pipe pressure detection sensor.

On the other hand, if it is determined that the conditions for performing the leak detection are satisfied, it is next determined whether the introduction of the negative pressure for the leak detection is completed (step 162). The completion of the introduction of the negative pressure in this step 162 is determined at the same time that the completion of the introduction of the negative pressure is determined in the routine after the leak detection routine of the evaporation OBD shown in FIG. 4 is started (see step 136 in FIG. 4). Is determined.

If it is determined in step 162 that the introduction of the negative pressure has not been completed, the PM sensor 4
The intake pipe pressure PM detected by 0 is recorded as the pre-switching pressure PM1 (step 164). In this case, after the processing of steps 122 and 124 is executed, the current routine is terminated.

On the other hand, if it is determined in step 162 that the introduction of the negative pressure has been completed, the purge VSV 26 is closed and the purge is cut (step 166).
38 is in the second state (ON state) (step 16).
8).

When the three-way VSV 38 is turned on,
The VSV 38 has an atmospheric pressure PA instead of the intake pipe pressure PM.
Is led. The ECU 50 records the pressure detected by the PM sensor 40 in that state as the post-switching pressure PM2 (step 170).

Next, the difference (PM) between the pressure PM1 before switching recorded in the ECU 50 and the pressure PM2 after switching is calculated.
2-PM1) is determined to be greater than or equal to a predetermined threshold value A (step 172).

If the three-way VSV 38 is functioning normally, there should be a large difference between the pre-switching pressure PM1 (intake pipe pressure PM) and the post-switching pressure (atmospheric pressure PA). Therefore, in step 172, PM
If it is determined that 2-PM1> A is not satisfied, it can be determined that the three-way VSV 38 is not functioning properly. FIG.
In this case, in the routine shown in FIG. 5, the failure of the three-way VSV 38 is determined (step 174).
After the processing of steps 2 and 124, the current routine ends.

On the other hand, in step 172, PM
If it is determined that 2-PM1> A holds, the three-way V
It can be determined that the SV 38 is functioning properly. In this case, the ECU 50 determines that the three-way VSV 38 is normal, and uses the PM sensor 40 as an atmospheric pressure sensor,
Continue the leak detection process of the evaporation OBD (step 17)
8).

In the routine shown in FIG.
Subsequent to the process at 78, it is determined whether or not the evaporation OBD has been completed (step 180). And EVAPO OBD
Until it is determined that is completed, the processing of steps 126 and 128 is executed to enable detection of the atmospheric pressure PA. On the other hand, when it is determined that the evaporation OBD has been completed, the processing of steps 122 and 124 is executed to enable detection of the intake pipe pressure PM.

As described above, the three-way VSV shown in FIG.
According to the control routine, when execution of leak detection is required, the PM sensor 40 can be switched to the atmospheric pressure sensor. Therefore, according to the control device of the present embodiment,
As in the case of the first or second embodiment, the purge VS is performed from the fuel tank 14 without adding a new atmospheric pressure sensor.
Leakage detection of the system leading to V26 can be accurately performed.

According to the routine shown in FIG. 6, when the three-way VSV 38 is switched from the first state (off state) to the second state (on state), the negative pressure is introduced during the leak detection process. Limited to completion. For this reason, according to the control device of the present embodiment, the switching frequency of the three-way VSV can be significantly reduced as compared with the case of the first or second embodiment, and its reliability and durability can be relatively reduced. Can be greatly improved.

Further, according to the routine shown in FIG. 6, the three-way VSV is determined based on whether a large difference occurs in the output of the intake pressure sensor 40 before and after the three-way VSV 38 is switched.
38 can be accurately detected as to whether it is functioning properly. Therefore, according to the control device of the present embodiment,
The objective of the evaporation OBD (early detection and display of abnormality) can be achieved also for the newly added three-way VSV 38.

Although the third embodiment does not consider whether or not the purge VSV 26 has an open abnormality, the present invention is not limited to this.
That is, in the present embodiment, similarly to the case of the above-described second embodiment, when the purge VSV 26 has an open abnormality, the three-way VSV 38 is always maintained in the first state (off state). Is also good.

In the third embodiment described above, E
The CU 50 executes steps 160 and 162 and 1
68 to implement the "switching valve control means" according to claim 5,
The "0" executes the processing of steps 164 and 170 to 176, thereby realizing the "switching valve failure diagnosing means".

[0077]

Since the present invention is configured as described above, it has the following effects. Claim 1
According to the invention described above, when the fuel vapor is purged into the intake passage, the intake pipe pressure can be detected by the intake pressure sensor. Therefore, in this case, the fuel injection amount can be appropriately corrected based on the output of the oxygen concentration sensor so that the influence of the vapor to be purged is canceled. Further, when the fuel vapor is not purged into the intake passage, that is, when it is not necessary to detect the oxygen concentration in the intake passage, a state where the atmospheric pressure can be detected by the intake pressure sensor can be provided. Therefore, according to the present invention, it is possible to detect the atmospheric pressure without newly providing an atmospheric pressure sensor.

According to the second aspect of the present invention, when the purge cut condition is not satisfied, the use of the intake pressure sensor as an atmospheric pressure sensor can be prohibited. Therefore, according to the present invention, it is possible to effectively prevent a situation in which the oxygen concentration in the intake passage cannot be detected during the purge of the fuel vapor.

According to the third aspect of the invention, it is possible to prohibit the use of the intake pressure sensor as an atmospheric pressure sensor when the purge control valve is abnormally opened. When the purge control valve has an open abnormality, the purge of the fuel vapor is continued even if the purge cut condition is satisfied. According to the present invention, in such a case, it is possible to effectively prevent a situation in which the oxygen concentration in the intake passage cannot be detected.

According to the fourth aspect of the present invention, based on the atmospheric pressure detected by the intake pressure sensor and the output of the relative pressure sensor detecting the pressure in the system including the fuel tank and the like, the system is substantially controlled. The absolute pressure inside can be detected. Therefore, according to the present invention, the fault diagnosis of the system can always be performed with high accuracy without being affected by the uphill or downhill of the vehicle.

According to the fifth aspect of the present invention, the switching valve is switched from the first state to the second state only after a negative pressure is introduced into the system following the failure diagnosis of the system. Therefore, according to the present invention, the operation frequency of the switching valve can be minimized, and the reliability and durability required for the switching valve can be suppressed low.

According to the sixth aspect of the present invention, it is possible to accurately diagnose the failure of the switching valve based on whether or not an appropriate change occurs in the output of the intake pressure sensor with the switching of the algorithmic valve. it can.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a configuration of a first embodiment of the present invention.

FIG. 2 is a flowchart of a fuel injection amount calculation routine executed by an ECU in the first embodiment.

FIG. 3 is a flowchart of a three-way VSV control routine executed by an ECU in the first embodiment.

FIG. 4 is a flowchart of an evaporative OBD leak detection routine executed by an ECU in the first embodiment.

FIG. 5 is a flowchart of a three-way VSV control routine executed by an ECU according to the second embodiment.

FIG. 6 is a flowchart of a three-way VSV control routine executed by an ECU according to a third embodiment.

[Explanation of symbols]

Reference Signs List 10 canister 12 vapor passage 14 fuel tank 15 pressure sensor 16 CCV (Canister Closed Valve) 18 atmosphere introduction passage 20 intake passage 24 purge passage 26 purge VSV (Vacuum Switching Valve) 34 surge tank 36 intake O ₂ sensor 38 three-way VSV 40 suction Pressure sensor (PM sensor) 42 Internal combustion engine 50 ECU TAU Fuel injection amount PM Intake pipe pressure PT Tank internal pressure

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 25/08 301 F02M 25/08 301H F-term (Reference) 3G044 BA22 BA23 BA40 EA19 EA53 EA55 EA57 FA00 FA02 FA05 FA10 FA22 FA29 GA01 3G084 BA13 BA27 DA00 DA27 EA11 EB22 FA00 FA07 FA11 3G301 HA14 JA00 JB09 LA03 MA11 NA08 ND41 PA00Z PA01Z PA07Z

Claims (6)

[Claims] 1. A control device for an internal combustion engine having a purge mechanism for purging purge gas containing fuel vapor into an intake passage, comprising: a vapor concentration sensor for generating an output corresponding to a fuel vapor concentration in the intake passage; An intake pressure sensor for detecting a pressure guided to a pressure inlet; a first state for guiding an intake pipe pressure in the intake passage to the pressure inlet; and a second state for guiding atmospheric pressure to the pressure inlet. A switching valve that can realize: a vapor concentration detecting unit that detects a vapor concentration in the intake passage based on an output of the vapor concentration sensor and the intake pipe pressure detected by the intake pressure sensor; An injection amount calculating means for calculating a fuel injection amount based on the concentration; and when the purge gas is purged, the switching valve is set to the first state, and the purge gas is not purged. A switching valve control means for permitting the switching valve to assume the second state. 2. The switching valve control means includes condition determination means for determining whether a purge cut condition is satisfied. If the purge cut condition is not satisfied, the switching valve is set to the first state. 2. The method according to claim 1, wherein
A control device for an internal combustion engine according to claim 1. 3. The purge mechanism includes a purge control valve for controlling a flow rate of the purge gas, and the switching valve control means determines whether or not an open abnormality has occurred in the purge control valve. 3. The control device for an internal combustion engine according to claim 1, wherein the switching valve is set to the first state when the opening abnormality occurs. 4. The purge mechanism includes a canister that adsorbs fuel vapor generated in a fuel tank, and a purge control valve that is disposed between the canister and the intake passage and controls a flow rate of the purge gas. A negative pressure introducing means for sealing a system including the fuel tank, the canister, and the purge control valve, and introducing a predetermined negative pressure into the system, a relative pressure sensor for detecting a relative pressure in the system, After the predetermined negative pressure is introduced into the system, the pressure generated in the system based on the atmospheric pressure detected by the intake pressure sensor and the relative pressure in the system detected by the relative pressure sensor The internal combustion engine according to any one of claims 1 to 3, further comprising: a pressure change detection unit that detects a change; and a failure diagnosis unit that performs a failure diagnosis of the system based on the pressure change. Control equipment . 5. The switching valve control means switches the switching valve from the first state to the second state only when the introduction of the predetermined negative pressure into the system is completed. The control device for an internal combustion engine according to claim 4, wherein 6. A pressure detected by the intake pressure sensor when the switching valve assumes the first state, and a pressure detected by the intake pressure sensor when the switching valve assumes the second state. 2. A switching valve failure diagnosis means for performing failure diagnosis of the switching valve based on a difference between the switching valve failures.
6. The control device for an internal combustion engine according to any one of claims 5 to 5.