JPH07332163A - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] An EG equipped with an EGR control valve in the exhaust gas recirculation passage.
The R device can accurately detect clogging in the exhaust gas recirculation passage without increasing the cost. In an exhaust gas recirculation control device for an internal combustion engine having an EGR control valve in an exhaust gas recirculation passage, an operating state detecting means is caused to detect an operating state of the internal combustion engine, and an EGR is made to a target opening calculating means in accordance with the detected operating state. The target opening of the control valve is calculated, the opening detecting means detects the opening of the EGR valve, and the EGR control valve opening adjusting means controls the EGR valve control amount so that the detected opening becomes the target opening. Is adjusted and the exhaust gas flow rate characteristic according to the opening of the EGR control valve is stored in the control amount storage means of the EGR control valve in association with the control amount of the EGR control valve, and the control amount for the target opening is stored in the storage means. When the stored control amount increases by a predetermined value or more, the clogging detection means determines that clogging has occurred in the exhaust gas recirculation passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for an internal combustion engine, and more particularly to an exhaust gas recirculation control device for an internal combustion engine capable of detecting clogging of an exhaust gas recirculation passage having an EGR control valve.

[0002]

2. Description of the Related Art In order to reduce NOx in exhaust gas,
An EGR device is known in which exhaust gas flowing in an exhaust passage is recirculated into an intake passage through an exhaust gas recirculation (hereinafter referred to as EGR) passage. In such an EGR device, an EGR control valve is usually provided in the EGR passage to
The amount of EGR gas to be supplied into the intake passage is controlled by the opening of the control valve. However, EGR
If the control valve fails or the EGR passage is clogged, the exhaust gas recirculation may continue to stop, and if left undisturbed, a large amount of NOx will continue to be emitted. Further, such a decrease or stop of the exhaust gas recirculation amount cannot be recognized by the driver.

Therefore, an EGR control valve is provided with a diaphragm chamber partitioned by a diaphragm, and the opening degree of the EGR control valve is controlled by introducing a negative pressure into the diaphragm chamber. For controlling the negative pressure diaphragm chamber pressure so as to reach the target pressure, it is proposed to determine that the EGR device is abnormal when the actual negative pressure value deviates from the specified pressure value ( See JP-A-5-79405).

[0004]

However, in the proposed device, the EGR control valve is not controlled to the target opening, so the value of the control negative pressure for achieving the target opening is unknown, and E
Although the abnormality of the drive system of the GR control valve can be detected, the clogging of the exhaust gas recirculation passage cannot be detected.

Therefore, according to the present invention, the EGR is provided in the exhaust gas recirculation passage.
It is an object of the present invention to provide an exhaust gas recirculation control device for an internal combustion engine, which can accurately detect clogging in an exhaust gas recirculation passage without increasing cost in an EGR device equipped with a control valve.

[0006]

An exhaust gas recirculation control system for an internal combustion engine according to the present invention which achieves the above object, provides a flow rate of exhaust gas recirculated in an exhaust gas recirculation passage communicating an exhaust passage and an intake passage of the internal combustion engine. An exhaust gas recirculation control device for an internal combustion engine having an EGR control valve for controlling, wherein an operating state detecting means for detecting an operating state of the internal combustion engine and a target opening degree of the EGR control valve are calculated according to the detected operating state. Target opening calculation means, EGR control valve opening detection means for detecting the EGR valve opening, and EGR for adjusting the EGR valve control amount so that the detected opening becomes the target opening. A control valve opening adjustment means, an EGR control valve control amount storage means for storing the exhaust gas flow rate characteristic corresponding to the opening degree of the EGR control valve in association with a control amount of the EGR control valve, and the target opening. The control amount for the degree is When increased above the predetermined value with respect to the stored controlled variable serial storage means, it is characterized in that it comprises a clogging detecting means determines the exhaust gas recirculation passage and clogging occurs in the exhaust gas recirculation passage.

[0007]

According to the exhaust gas recirculation control device for an internal combustion engine of the present invention, the target opening degree of the EGR control valve in the exhaust gas recirculation passage is calculated according to the operating state of the internal combustion engine detected by the operating state detecting means. The EGR control valve opening adjustment means adjusts the control amount of the EGR valve so that the opening degree of the EGR valve calculated by the means and detected by the opening degree detection means of the EGR control valve becomes the target opening degree. Then, the control amount for this target opening is stored in the control amount storage means of the EGR control valve with respect to the control amount of the EGR control valve corresponding to the exhaust gas flow rate characteristic according to the opening of the EGR control valve, When it increases by a predetermined value or more, the clogging detection means of the exhaust gas recirculation passage determines that the exhaust gas recirculation passage is clogged.

[0008]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows the configuration of an internal combustion engine equipped with a failure diagnosis device for an exhaust gas recirculation system according to the present invention. In the figure, 1 is an engine body, 2 is an exhaust manifold, 3 is an intake manifold, 4 is an intake duct, 5 is a throttle valve provided in the intake duct, 6 is an intake pipe pressure sensor, and 7 is a branch pipe of the intake manifold 3. , 8 is an EGR passage communicating between the exhaust manifold 2 and the intake manifold 3, 9 is an EGR control valve provided in the EGR passage 8,
0 is a control circuit (engine control unit: E
CU), and the exhaust gas in the exhaust manifold 2 is recirculated into the intake manifold 3 via the EGR passage 8 when the EGR control valve 9 is opened.

The control circuit 10 is composed of, for example, a microcomputer, and has a ROM (Read Only Memory) 12 and a RAM interconnected by a bidirectional bus 11.
It has a (random access memory) 13, a CPU (central processing unit) 14, an input port 15 and an output port 16. The EGR control valve 9 is provided with a lift sensor 17 that detects the opening degree of the valve body, and the detection value of the lift sensor 17 is input to the input port 15 via the A / D converter 18. An intake air temperature sensor 19 is arranged in the intake duct 4, and the detected value THA of the intake air temperature sensor 19 is input to the input port 15 via the A / D converter 20. Also,
A throttle opening sensor 21 for detecting the opening of the throttle valve 5 is connected to the throttle valve 5. The detection value of the throttle opening sensor 21, that is, the accelerator opening θ is A /
It is input to the input port 15 via the D converter 22.

The intake pipe pressure sensor 6 is attached to the surge tank (intake manifold 3) downstream of the throttle valve 5, and the detected value PA of the intake pipe pressure sensor 6 is an A / D converter. Input port 15 through 29
It is connected to the. A water temperature sensor 23 that detects the engine cooling water temperature is attached to the engine body 1, and the detected value THW of the water temperature sensor 23 is input to the input port 15 via the A / D converter 24. Further, the input port 15 is connected to a rotation speed sensor 25 that generates an output signal indicating the engine rotation speed Ne. The output port 16 is connected on the one hand to the corresponding fuel injection valve 7 and the negative pressure control valve 30 via the respective drive circuits 26, 26 ', and on the other hand to the warning lamp 28 via the drive circuit 27.

FIG. 2 is an explanatory view showing, in an enlarged scale, the construction of the main part of the exhaust gas recirculation control device for an internal combustion engine constructed as described above. EGR passage 8 connecting exhaust pipe 2'and intake pipe 4
The EGR control valve 9 provided in the middle of the chamber is equipped with a diaphragm chamber 9d and an atmosphere chamber 9 which are partitioned by a diaphragm 9a.
There are two chambers e, the atmosphere chamber 9e communicates with the atmosphere, and the diaphragm chamber 9d has a spring 9c installed therein and is connected to the negative pressure control valve 30 through the negative pressure introducing pipe 31. There is. A valve body 9b that opens and closes the EGR passage 8 is provided at the tip of a rod 9f protruding from the diaphragm 9a, and the other end of the rod 9f serves to detect the opening degree of the valve body 9b. Lift sensor 17
It is connected to the. Then, the negative pressure control valve 30 is duty-controlled by the control circuit 10 so that the valve is opened according to a command value from the control circuit 10, and the vacuum pump 32 controls the negative pressure in the diaphragm chamber 9d. It is designed to adjust the pressure.

Here, the exhaust pressure of the exhaust pipe 2'is set to P ₁ , EGR
When the back pressure of the valve body 9b of the control valve is P ₂ , the intake pressure in the intake pipe 4 is P ₃ , the control negative pressure in the diaphragm chamber 9d is PC, and the urging force of the spring 9c is S, the valve body 9b is applied. Regarding the force, the control negative pressure PC and the exhaust pressure P ₁ act in the valve opening direction, the spring biasing force S and the back pressure P _{2 of the} valve body 9b act in the valve opening direction. Here, when the lift amount of the valve body 9b is constant, the forces are balanced, and therefore the following formula is established.

PC + P ₁ = S + P ₂ ... On the other hand, when carbon C adheres between the EGR passage 8 on the downstream side of the EGR control valve 9 and the intake pipe 4, a throttle portion of the flow passage is formed at that portion. Thus, the back pressure P ₂ of the valve body 9b of the EGR control valve is so increased relative intake between pressure P _3, to maintain a predetermined lift of the valve body 9b of the EGR control valve diaphragm chamber 9d by the formula The control negative pressure PC therein will increase. This increase in the control negative pressure PC is achieved by feedback controlling the lift amount of the valve body 9b.
It is done automatically.

In the present invention, the valve body 9b of this EGR control valve is used.
At a predetermined lift amount, the control negative pressure PC in the diaphragm chamber 9d that holds the valve body 9b of the EGR control valve at this lift amount is monitored, and the increase is detected to detect the EGR.
The clogging due to the adhesion of carbon C in the passage 9 is detected. Therefore, in the present invention, as shown by the straight line B in FIG. 3, when the control negative pressure PC in the diaphragm chamber 9d is changed, the valve body 9b of the EGR control valve when the EGR passage 8 is not clogged. The relationship between the lift amount (hereinafter simply referred to as the lift amount of the EGR control valve) and the EGR amount with respect to the lift amount of the EGR control valve is obtained. On the other hand, when the EGR passage 8 is clogged with carbon C, as shown by a broken line A in FIG. 3, the relationship between the lift amount of the EGR control valve and the control negative pressure PC for keeping the EGR amount constant is also shown. I ask for it. These relationships are in the form of a map and are shown in the ROM shown in FIG.
It should be stored in 12.

Next, as a first embodiment of the present invention, EG
A procedure for detecting clogging of the R passage 8 will be described with reference to FIG. The routine shown in FIG. 4 is performed by a timer interrupt process at every predetermined time when the engine recirculates exhaust gas and the EGR device is operating. In step 401, an engine operating state parameter (for example, engine speed Ne,
The accelerator opening θ, intake pressure PA, water temperature THW, etc.) are read. Then, in step 402, the target lift amount TL of the EGR control valve 9 is calculated from the operating state parameter,
The control negative pressure PC in the state where the EGR passage 8 is not clogged is calculated corresponding to the target lift amount TL. This control negative pressure PC is stored in step 403 as the negative pressure PCC1 when the EGR passage is normal. Continued Step 4
At 04, the actual lift amount AL of the EGR control valve 9 is detected by the lift sensor 17.

In subsequent steps 405 to 408, the control negative pressure PC is adjusted so that the actual lift amount AL becomes substantially equal to the target lift amount TL. That is, step 40
In 5, it is determined whether the actual lift amount AL is larger than the target lift amount TL plus a predetermined value α. And AL
When> TL + α, the routine proceeds to step 406, where the control negative pressure PC is reduced so as to reduce the opening degree of the EGR control valve 9, and conversely, when AL ≦ TL + α, the routine proceeds to step 407. In step 407, it is determined whether the actual lift amount AL is smaller than the target lift amount TL minus a predetermined value α. Then, when AL <TL-α, step 408 is performed.
The control negative pressure PC is increased so as to increase the opening degree of the EGR control valve 9, and conversely, when AL ≧ TL−α, the routine proceeds to step 409.

When the routine proceeds to step 409, the actual lift amount AL is approximately equal to the target lift amount TL TL-α.
This is when ≦ AL ≦ TL + α. Therefore, step 409
Then, the control negative pressure PC at this time is stored as the control negative pressure PC1 when the actual lift amount AL is substantially equal to the target lift amount TL. Then, in the following step 410, the actual lift amount AL stored in step 409 is compared with the target lift amount T.
The difference between the control negative pressure PC1 when it is substantially equal to L and the normal control negative pressure PCC1 corresponding to the target lift amount TL when the EGR passage 8 is not clogged is calculated, and this difference is larger than the predetermined pressure ΔP. It is determined whether or not. PC1-P
When CC1 ≦ ΔP, is the EGR passage 8 not clogged?
Alternatively, even if there is clogging, it is determined that the clogging is still slight, and the process proceeds to step 412, and the clogging occurrence lamp (warning lamp) 28 is kept off.

However, when PC1-PCC1> ΔP, the control negative pressure PC1 for making the actual lift amount AL substantially equal to the target lift amount TL is large, which is the EGR passage 8 as described above. Since the clogging has occurred, the routine proceeds to step 411, where the clogging occurrence lamp (warning lamp) 28 is turned on to inform that the clogging has occurred in the EGR passage 8.

As described above, the present invention achieves the target lift amount of the EGR control valve according to the operating state of the engine without adding any member to the structure of the exhaust gas recirculation control device for the internal combustion engine. The control negative pressure is more than the normal value by a predetermined pressure Δ
When P is larger than P, it is possible to determine that normal EGR control is not performed and give a warning. The first embodiment described above only gives a warning when it is determined that the normal EGR control is not performed.
When it is determined that normal EGR control is not performed, EGR
5 to 8 of the second embodiment in which the target value of the control valve is corrected so that the correct amount of EGR control is always performed.
Will be explained. The steps showing the same procedure as the embodiment described in FIG. 4 are assigned the same step numbers to simplify the description.

The routine shown in FIG. 5 shows the procedure in the case where the carbon C gradually adheres to the EGR passage 8 and the target lift amount TL is changed for the first time. Similar to the above-described embodiment, steps 401 and 402 are executed, and the target lift amount TL of the EGR control valve 9 and the EG
The control negative pressure PC when the R passage 8 is not clogged is calculated. In step 403 ', the control negative pressure PC is stored as the normal negative pressure PCC1 and the target lift amount TL is stored as the normal lift amount TL1.

In step 404, the actual lift amount AL of the EGR control valve 9 is detected. In the following step 501, it is determined whether or not the value TN indicating the blockage stage of the EGR passage 8 is 0. The initial value of the value TN indicating the blockage stage of the EGR passage 8 is 0, which is preset when the exhaust gas recirculation control device is manufactured. Therefore, since TN = 0 when the EGR passage 8 is not clogged, the routine proceeds to step 405, and when the EGR passage 8 is clogged and TN ≠ 0, the routine proceeds to step 601 of the routine of FIG. 6 described later. .

When it is determined in step 501 that the EGR passage 8 is not clogged, the process proceeds to step 405 and subsequent steps, and in steps 405 to 408, the actual lift amount AL is almost equal to the target lift amount TL as in the above-described embodiment. The control negative pressure PC is adjusted so as to be equal, and TL-α ≦ AL
When ≦ TL + α, the routine proceeds to step 409, where the control negative pressure PC is the actual lift amount AL and the target lift amount T.
It is stored as the control negative pressure PC1 when it is substantially equal to L.
Then, in the following step 410, the control negative pressure PC1 in which the actual lift amount AL stored in step 409 is substantially equal to the target lift amount TL, and the normal lift amount TL corresponding to the target lift amount TL in the state where the EGR passage 8 is not clogged The difference from the control negative pressure PCC1 is calculated, and it is determined whether this difference is larger than the predetermined pressure ΔP.

When PC1-PCC1≤ΔP, it is determined that the EGR passage 8 is not clogged or is slightly clogged, and the routine proceeds to step 412, where the clogging lamp (warning lamp) 28 is turned off. Leave it off.
On the other hand, when PC1−PCC1> ΔP, the control negative pressure PC1 for making the actual lift amount AL substantially equal to the target lift amount TL is large, and this is the EG as described above.
Since the R passage 8 is clogged, step 4
11 ', the clogging occurrence lamp (warning lamp) 28 is turned on to inform that clogging has occurred in the EGR passage 8, and the value TN indicating the clogging stage of the EGR passage 8 is the first stage. It is set to 1 indicating that.

Then, in the following step 502, the target lift amount TL2 corresponding to the value of the control negative pressure PC1 is RO.
Calculated from the map stored in M12,
The calculated target lift amount TL2 is stored as a new target lift amount TL. It should be noted that this map shows that, for example, under a predetermined operating condition, the control negative pressure P for securing a necessary EGR amount as the clogging of the EGR passage 8 grows.
The relationship between CC and the target lift amount TLC is investigated as a characteristic as shown in FIG. 8, and this characteristic is mapped and RO
It should be stored in M12.

When the value TN indicating the blockage stage of the EGR passage 8 is set to 1 in step 411 'to indicate that it is the first stage, the determination becomes NO the next time step 501 is reached, The process proceeds to step 601 of the routine shown in FIG. FIG. 6 shows the procedure executed when the value TN indicating the blockage stage of the EGR passage 8 is the first stage. In step 601, it is determined whether the TN value is 1 or not. To be done. When TN = 1 in step 601, the process proceeds to step 602 and subsequent steps, but TN
When ≠ 1 (TN ≧ 2), it is determined that the value TN indicating the blockage stage of the EGR passage 8 is larger than the first stage, and the routine proceeds to step 701 of the routine shown in FIG. 7, which will be described later.

In steps 602 to 606, the control negative pressure PC is adjusted so that the actual lift amount AL becomes substantially equal to the target lift amount TL (here, TL1 which is the target lift amount in the first stage). To be done. That is, step 6
In 02, the actual lift amount AL is equal to the target lift amount TL by a predetermined value β.
It is determined whether or not it is greater than the value obtained by adding AL> TL +
When β, the routine proceeds to step 603, where the control negative pressure PC is reduced and the opening degree of the EGR control valve 9 is reduced.
When ≦ TL + β, the process proceeds to step 604. Step 6
In 04, it is determined whether the actual lift amount AL is smaller than a value obtained by subtracting the predetermined value β from the target lift amount TL, and AL <TL
When -β, the routine proceeds to step 605, where the control negative pressure PC is increased and the opening degree of the EGR control valve 9 is increased. Then, after step 603 or step 605 is executed, the actual lift amount AL of the EGR control valve 9 is detected by the lift sensor 17 in step 606, and the process returns to step 602.

On the other hand, in step 604, AL ≧ TL
When it is determined to be −β, the process proceeds to step 607. When the routine proceeds to step 604, the actual lift amount AL is equal to the target lift amount TL, that is, TL−β ≦ AL ≦ TL + β, so the control negative pressure PC at this time is the stage where the EGR passage 8 is clogged. Is stored as the control negative pressure PC2 when the actual lift amount AL is substantially equal to the target lift amount TL when the value of the value TN indicating the value is in the first stage.

In the following step 608, step 607
Control negative pressure PC2 in the state of TN = 1 stored in
A difference from the control negative pressure PCC1 in a normal state in a state where the EGR passage 8 is not clogged is calculated, and this difference is a predetermined pressure ΔP +.
It is determined whether or not it is larger than P1. PC2-PCC1
When> ΔP + P1, the routine proceeds to step 609, where the control negative pressure P
The target lift amount TL3 corresponding to the value of C2 is calculated from the map stored in the ROM 12, and the calculated target lift amount TL3 is stored as a new target lift amount TL. Then, in step 610, E
The value TN indicating the stage of clogging of the GR passage 8 is set to 2 indicating the second stage, which is a state advanced from the first stage, and this routine is ended.

On the other hand, when PC2-PCC1≤ΔP + P1, the routine proceeds to step 611, where there is a difference between the control negative pressure PC2 in the state of TN = 1 and the control negative pressure PCC1 in the normal state in which the EGR passage 8 is not clogged. It is calculated and it is determined whether this difference is less than or equal to the predetermined pressure ΔP. And PC2
When −PCC1> ΔP, the value TN indicating the stage of clogging of the EGR passage 8 is larger than that in the first stage, but it is determined that the second stage, in which clogging has progressed, has not yet been reached. Exit the routine.

However, when PC2-PCC2≤ΔP, the clogging of the EGR passage 8 is cleared by some factor, and E
Since the GR passage 8 is not clogged or is slightly clogged, the routine proceeds to step 612, where the target lift amount TL is returned to the unclogging value TL1.
In step 613, the value TN indicating the stage of clogging of the EGR passage 8 is set to 0, and in the following step 614, the clogging occurrence lamp (warning lamp) 28 is turned off, and this routine is ended. In this way, after TN = 0 is set in step 613, YES is obtained in step 501 in the routine of FIG. 5, so that the routine of FIG. 5 is executed thereafter.

In step 610 of FIG. 6, if the value TN indicating the blockage stage of the EGR passage 8 is set to 2 indicating the second stage, the determination is NO when the process proceeds to step 601 next time. Therefore, the routine proceeds to step 701 of the routine shown in FIG. FIG. 7 shows a procedure executed when the value of the value TN indicating the blockage stage of the EGR passage 8 is equal to or larger than the second stage. In steps 701 to 705,
The control negative pressure PC is adjusted so that the actual lift amount AL becomes substantially equal to the target lift amount TL (= TL2). That is, in step 701, it is determined whether or not the actual lift amount AL is larger than a value obtained by adding a predetermined value γ to the target lift amount TL, and when AL> TL + γ, the routine proceeds to step 702, where the control negative pressure PC is reduced and EGR is performed. The opening degree of the control valve 9 is reduced, and conversely, when AL ≦ TL + γ, the routine proceeds to step 703. In step 703, it is determined whether or not the actual lift amount AL is smaller than a value obtained by subtracting a predetermined value γ from the target lift amount TL, and when AL <TL-γ, the routine proceeds to step 704, where the control negative pressure PC is increased and EGR is performed. The opening degree of the control valve 9 is increased. Then, step 702 or step 70
4 is executed, the actual lift amount AL of the EGR control valve 9 is detected in step 705 and step 70
Return to 1.

On the other hand, in step 703, AL ≧ TL
If −γ is determined, it means that TL−γ ≦ AL ≦ TL + γ, so the routine proceeds to step 706, where the control negative pressure P
C is the second value of TN indicating the stage of clogging of the EGR passage 8.
Is stored as the control negative pressure PC3 when the actual lift amount AL is substantially equal to the target lift amount TL.

In the following step 707, the difference between the control negative pressure PC3 in the state of TN = 2 and the control negative pressure PCC1 in the normal state in the state where the EGR passage 8 is not clogged is calculated, and this difference is calculated from the predetermined pressure ΔP + P1 + P2. It is determined whether or not it is larger. PC2-PCC1> ΔP + P1 + P2
If it is, the routine proceeds to step 708, where the control negative pressure PC3 and EG
Control negative pressure PCC1 during normal operation when R passage 8 is not clogged
Is larger than the upper limit value ΔPmax of the differential pressure. When PC2-PCC1 ≦ ΔPmax, step 7
In step 09, the target lift amount TL4 corresponding to the value of the control negative pressure PC3 is calculated from the map stored in the ROM 12, and in step 710 the calculated target lift amount TL4 is stored as a new target lift amount TL. ,
Then, in step 711, the value of the value TN indicating the blockage stage of the EGR passage 8 is set to 3 indicating that it is the third stage which is the state advanced from the second stage, and this routine is ended. .

In the third stage, in which the value TN indicating the blockage stage of the EGR passage 8 is 3, a large amount of carbon C is attached to the EGR passage 8 in this embodiment. Therefore, when the adhesion of carbon C further proceeds from this stage and PC3-PCC1> [Delta] Pmax in step 708, it can be considered that the EGR passage 8 is almost not connected. Therefore, at this time, it is considered to be meaningless to further increase the target lift amount TL. Therefore, the routine proceeds to step 712, where an alarm indicating that the EGR passage 8 is disconnected is output, and the EGR passage 8 is output.
The routine is ended by stopping the control.

On the other hand, in step 707, PC2-P
When CC1 ≦ ΔP + P1 + P2, the routine proceeds to step 713, where the control negative pressure PC3 and EGR in the state of TN = 2.
Control negative pressure PC in normal condition when passage 8 is not clogged
It is determined whether the difference from C1 is less than or equal to the predetermined pressure ΔP + P1. Then, when PC2-PCC1> ΔP + P1, E
Although the value TN indicating the clogging stage of the GR passage 8 is larger than that in the second stage, it is determined that the GR stage has not reached the third stage where clogging has progressed further, and this routine is finished as it is.

However, PC2-PCC2≤ΔP + P1
Indicates that the clogging of the EGR passage 8 has decreased due to some cause, so in step 714 the control negative pressure PC3 in the state of TN = 2 and the control negative pressure in the normal state in the state where the EGR passage 8 is not clogged. It is determined whether the difference from the PCC1 is less than or equal to the predetermined pressure ΔP. When PC3−PCC1 ≦ ΔP in step 714, the EGR passage 8 is clogged, or the EGR passage 8 is not clogged or is slightly clogged. Therefore, step 6 in FIG.
In step 12, the value ga of the target lift amount TL is returned to the value TL1 in the state where there is no jam, the value TN indicating the blockage stage of the EGR passage 8 is set to 0 in step 613, and the blockage lamp The (warning lamp) 28 is turned off, and this routine ends.

On the other hand, in step 714, PC3-P
When CC1> ΔP, it indicates that the blocked state of the EGR passage 8 has recovered from the second stage to the first stage, and therefore the routine proceeds to step 715, where the target corresponding to the value of the control negative pressure PC3 at this time. After the lift amount TL2 is calculated from the map stored in the ROM 12, the calculated target lift amount TL2 is stored as a new target lift amount TL,
Then, in step 716, the value TN indicating the stage of clogging of the EGR passage 8 is set to 1 indicating that the EGR passage 8 has returned to the first stage, and this routine is ended.

As described above, in the second embodiment,
When it is detected that the EGR passage 8 is clogged to a certain extent or more, it is divided into a first stage, a second stage, and a third stage according to the degree of clogging.
The target lift of the GR control valve 9 is increased to correct the EGR amount so that the EGR amount is not insufficient. Also,
If the clogging of the EGR passage 8 is reduced or eliminated for some reason, the EGR passage is reduced according to the reduced state.
The target lift amount of the control valve 9 is reduced so that the EGR amount is not excessive. The control described in FIGS. 5 to 7 is summarized as follows.

Control Negative Pressure Difference Target Lift Amount Clog Stage 0 to ΔP TL1 TN = 0 ΔP to ΔP + P1 TL2 TN = 1 (first stage) ΔP + P1 to ΔP + P1 + P2 TL3 TN = 2 (second stage) ΔP + P1 + P2 to ΔPmax TL = 3 (third stage) ΔPmax or more TL4 TN = 3 (EGR is not possible) As a result, in the second embodiment, when the EGR passage 8 is clogged, this is notified and the clogging state is always maintained. Appropriate EGR control can be performed. In this embodiment, the blockage of the EGR passage 8 is divided into the above-mentioned five stages, but the number of divisions is not limited.

Next, a third embodiment of the present invention will be described. FIG. 9 is an overall configuration diagram of an internal combustion engine in the third embodiment, and the same components as those of the internal combustion engine described in FIG. 1 are designated by the same reference numerals to simplify the description. Therefore, FIG.
In FIG. 1, 1 is an engine body, 2 is an exhaust manifold, 3 is an intake manifold, 4 is an intake duct, 5 is a throttle valve provided in the intake duct, 6 is an intake pipe pressure sensor, and 7 is a branch pipe of the intake manifold 3. The attached fuel injection valve 8 is an EGR that connects the exhaust manifold 2 and the intake manifold 3 with each other.
A passage, 9 is an EGR control valve provided in the EGR passage 8,
10 is a control circuit (ECU), 17 is a lift sensor, 21
Is a throttle opening sensor, 25 is a rotation speed sensor, 28 is a warning lamp, and 30 is a negative pressure control valve. Exhaust gas in the exhaust manifold 2 passes through the EGR passage 8 when the EGR control valve 9 is opened. It is recirculated into the intake manifold 3.

The control circuit 10 is also composed of a microcomputer, and has a bidirectional bus 11, a ROM 12,
It has a RAM 13, a CPU 14, an input port 15, an output port 16, A / D conversion trees 18, 20, 22, 24, 29, and drive circuits 26, 26 ', 27. The intake air temperature sensor and the water temperature sensor are not shown in this figure.

Further, as an internal structure of the internal combustion engine shown in FIG. 1, the internal combustion engine of this embodiment has a turbine 41 downstream of the exhaust manifold 2 and a compressor 42 driven by the turbine 41 in the intake duct 4. There is a turbocharger 40 equipped with. Reference numeral 43 indicates a fuel pump provided with an injection timing control valve 44. By the way, the target lift amount is determined so that the smoke in a steady state of each operating condition of the engine is a certain allowable value or less, for example, the smoke SB 1.0 or less. However, under such conditions E
When the target lift amount of the GR control valve is determined, in an engine provided with the turbocharger 40, smoke during steady operation of the engine does not become a problem because it is below an allowable value, but during transient operation, for example, During acceleration operation, the amount of air may be insufficient and the smoke may exceed the allowable level due to a delay in rising of the boost pressure of the turbocharger 40.

Therefore, in the third embodiment, in the engine provided with the turbocharger 40, the rate of change of the opening of the throttle valve 5 is calculated during the transient operation of the engine to determine the acceleration state, and the intake pipe is The actual supercharging pressure of the turbocharger 40 is detected by the pressure sensor 6, and according to the supercharging pressure difference DP from the phase constant supercharging pressure (the normal supercharging pressure under each operating condition),
The target lift amount of the EGR control valve 9 is corrected to decrease. At the same time, the injection timing control valve 44 provided in the fuel pump 43 is operated in accordance with the boost pressure difference DP to retard the injection timing.

The above operation will be described with reference to FIGS. First, when the accelerator is depressed at time t1, the throttle opening θ rapidly rises as shown in FIG. 10 (a). On the other hand, the actual supercharging pressure PA by the turbocharger 40 lags behind the characteristic indicated by the broken line corresponding to the throttle opening θ as shown by the solid line, as shown in FIG. 10 (b). FIG. 10 (c) shows the characteristic of the supercharging pressure difference DP showing the delay in the rise of the supercharging pressure.

In this embodiment, when the engine is accelerated, as shown in FIG.
The rate of change of the throttle opening shown in (a) is detected, and when the rate of change exceeds a predetermined value, the intake pipe pressure sensor 6 detects the actual boost pressure PA of the turbocharger 40. Then, the supercharging pressure difference DP between the constant supercharging pressure shown by the broken line in FIG. 10 (b) and the actual supercharging pressure PA is calculated as shown in FIG. 10 (c), and according to the calculated supercharging pressure difference DP. , The injection timing retardation amount Δφ as shown in FIG. 11 (a) is calculated. This injection timing retard amount Δ
φ is set to increase as the boost pressure difference DP increases. Then, the injection timing control valve 44 provided in the fuel pump 43 is based on the injection timing retardation amount Δφ.
Is operated to retard the injection timing.

At the same time, the correction reduction amount Δ of the target lift amount TL of the EGR control valve 9 is calculated according to the calculated boost pressure difference DP.
TL is calculated as shown in FIG. 11 (b). The correction reduction amount ΔTL of the target lift amount TL is set to increase as the supercharging pressure difference DP increases, and is set to decrease the target lift amount of the EGR control valve 9. Then, the target lift amount is reduced and corrected based on the correction reduction amount ΔTL of the target lift amount TL.

As described above, in the third embodiment, in the internal combustion engine with the turbocharger, the injection timing is retarded during the transition of the engine, and the lift amount of the EGR control valve 9 is reduced to reduce the EGR amount. . As a result, smoke during transition is prevented, and NOx is reduced by reducing the EGR amount.
Is suppressed by retarding the injection timing, and the NOx reduction characteristic is not deteriorated. Also, in general, EGR during transient operation
If the amount is large, the drivability is deteriorated, but if the EGR amount is corrected and reduced during the transition as in the control of the third embodiment, the drivability is less deteriorated.

[0048]

As described above, according to the exhaust gas recirculation control device for an internal combustion engine of the present invention, the EGR is provided in the exhaust gas recirculation passage.
In the EGR device equipped with the control valve, there is an effect that the clogging in the exhaust gas recirculation passage can be accurately detected without increasing the cost. Further, by correcting the target lift amount when the EGR passage is clogged, proper EGR control can always be performed even when the EGR passage is clogged.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of an exhaust gas recirculation control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining the configuration by enlarging the main part of the embodiment of FIG.

FIG. 3 is a graph showing a lift amount characteristic and an EGR amount of the EGR control valve with respect to a control negative pressure when the EGR passage is not clogged, and an EGR for maintaining a constant EGR amount when the EGR passage is clogged. It is a characteristic view which shows the lift characteristic of a control valve.

FIG. 4 is a flowchart showing a control procedure of the first embodiment of the present invention for detecting clogging of an EGR passage.

FIG. 5 is a flowchart showing a part of a control procedure of a second embodiment of the present invention for detecting and correcting clogging of an EGR passage.

FIG. 6 is a flowchart showing a part of a control procedure of a second embodiment of the present invention for detecting and correcting clogging of an EGR passage.

FIG. 7 is a flowchart showing a part of a control procedure of a second embodiment of the present invention for detecting and correcting clogging of an EGR passage.

FIG. 8 is a characteristic diagram showing the relationship of the target lift amount with respect to the control negative pressure of the EGR control valve when the EGR passage is clogged.

FIG. 9 is a configuration diagram showing an overall configuration of an exhaust gas recirculation control device of the present invention in an internal combustion engine provided with a turbocharger.

10 (a) is a diagram showing a throttle opening characteristic during a transient state of the engine shown in FIG. 9, (b) is a diagram showing an actual supercharging pressure characteristic with respect to a constant phase supercharging pressure at that time, and FIG. ) Is a diagram showing the difference in supercharging pressure between the phase constant supercharging pressure and the actual supercharging pressure in (b).

11A is a diagram showing the setting characteristic of the injection timing retard amount with respect to the boost pressure difference in FIG. 10C, and FIG. 11B is the target lift correction reduction amount with respect to the boost pressure difference in FIG. 10C. It is a diagram which shows a setting characteristic.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine body 2 ... Exhaust manifold 3 ... Intake manifold 5 ... Throttle valve 6 ... Intake pipe pressure sensor 8 ... EGR passage 9 ... EGR control valve 10 ... Control circuit 17 ... Lift sensor 21 ... Throttle opening sensor 28 ... Warning lamp 30 ... Negative pressure control valve 40 ... Turbocharger 43 ... Fuel pump 44 ... Injection timing control valve

Claims (1)

[Claims] 1. An exhaust gas recirculation control device for an internal combustion engine, comprising an EGR control valve for controlling a flow rate of exhaust gas that recirculates, in an exhaust gas recirculation passage communicating between an exhaust passage and an intake passage of the internal combustion engine. An operating state detecting means for detecting an operating state; a target opening calculating means for calculating a target opening of the EGR control valve according to the detected operating state; and an EGR control valve for detecting an opening of the EGR valve. An opening degree detection means, an EGR control valve opening degree adjustment means for adjusting the control amount of the EGR valve so that the detected opening degree becomes a target opening degree, and an exhaust gas flow rate according to the opening degree of the EGR control valve. Characteristics
EGR stored in association with the control amount of the EGR control valve
Exhaust gas recirculation for determining that a clogging has occurred in the exhaust gas recirculation passage when the control amount of the control valve and the control amount for the target opening degree increase by a predetermined value or more with respect to the control amount stored in the memory device. An exhaust gas recirculation control device for an internal combustion engine, comprising: passage clogging detection means.