JP2653819B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Industrial Application Field] The present invention controls a negative pressure introduced into a diaphragm chamber,
The present invention relates to an exhaust gas recirculation control device for an internal combustion engine that recirculates an amount of exhaust gas according to the negative pressure.

[Prior Art] Conventionally, an exhaust gas recirculation control device for an internal combustion engine that recirculates an amount of exhaust gas determined according to an operation state to an intake pipe in order to reduce the amount of nitrogen oxide (NOx) emitted from the exhaust gas has been known. Have been. These devices include, for example, an exhaust gas recirculation control valve having a diaphragm chamber to recirculate an amount of exhaust gas according to the operating state, and detect a pressure introduced into the diaphragm chamber, and detect the detected pressure. Is configured to perform feedback control such that the pressure becomes an introduction negative pressure according to the operation state. As such a technique, for example, the following has been proposed. That is, (1) the target pressure value of the pressure fluid introduced into the diaphragm type exhaust gas recirculation control valve, which is determined according to any two of the engine speed, the intake air amount, and the intake pipe pressure, and the pressure sensor "Exhaust gas recirculation control device for engine" that compares the detected pressure value with the actual pressure fluid and adjusts the pressure so that the actual pressure value matches the target pressure value.
(JP-A-54-38437).

(2) When the exhaust gas is not recirculated under a light load during operation, the output of the pressure sensor corresponding to a pressure of 0 is read, and correction is performed based on this value under other exhaust recirculating conditions. "Exhaust gas recirculation control method for internal combustion engine" for correcting deviation (Japanese Patent Laid-Open No. 55-164759).

[Problems to be Solved by the Invention] By the way, in the above-mentioned prior art, the actual pressure value obtained by detecting the pressure of the pressure fluid introduced into the diaphragm type exhaust gas recirculation control valve with a pressure sensor and the operating state Feedback control has been performed so that a target pressure value determined in accordance therewith coincides. However, the feedback control as described above has a relatively large dead volume such as a fluid passage communicating the diaphragm type exhaust gas recirculation control valve and the pressure regulating valve of the pressurized fluid. As a result, the convergence of control is deteriorated, such as hunting of the actual pressure with respect to the target pressure value, and a response delay occurs. There was a problem.

Further, due to the decrease in the control accuracy of the exhaust gas recirculation control as described above, there is a problem that the exhaust gas purification performance is particularly deteriorated in a transient operation state in which the target exhaust gas recirculation amount is rapidly changed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas recirculation control device for an internal combustion engine capable of suitably improving convergence and responsiveness of pressure control of a pressure fluid introduced into a diaphragm chamber for controlling an exhaust gas recirculation amount to a target recirculation amount. And

Configuration of the Invention Means for Solving the Problems According to the present invention, which has been made to achieve the above object, as shown in FIG. 1, a recirculation pipe that recirculates exhaust gas of an internal combustion engine M1 to an intake pipe is provided. The exhaust gas recirculation means M2 changes the amount of exhaust gas recirculation according to the pressure of the pressure fluid introduced into the diaphragm chamber, and the pressure introduced into the diaphragm chamber of the exhaust gas recirculation means M2 according to a control amount commanded from the outside. Pressure adjusting means M3 for adjusting the pressure of the fluid, pressure detecting means M4 for detecting the pressure of the pressure fluid introduced into the diaphragm chamber of the exhaust gas recirculation means M2, and an operating state for detecting the operating state of the internal combustion engine M1. Detecting means M5, target pressure calculating means M6 for calculating a target pressure of the pressure fluid, which enables recirculation of an amount of exhaust determined based on the operating state detected by the operating state detecting means M5, and a pressure of the pressure fluid. An operation of performing feedback correction of the control amount so that the force matches the target pressure is performed in a plurality of different predetermined operating states, and the control amount obtained by the correction operation is stored as a learning value, and A characteristic correcting means for defining a relationship between the target pressure and the control amount in other operating states based on learning values in a plurality of predetermined operating states and sequentially updating and storing the characteristic correcting means; Control means M8, which determines a control amount corresponding to the target pressure calculated by the target pressure calculating means M6 according to the characteristic defining the relationship between the target pressure and the control amount, and instructs the pressure adjusting means M3, The gist of the present invention is an exhaust gas recirculation control device for an internal combustion engine, which is provided.

[Operation] In the exhaust gas recirculation control device for an internal combustion engine of the present invention, as exemplified in FIG. 1, the control means M8 calculates the target pressure in accordance with the relationship between the target pressure and the control amount stored in the characteristic correction means M7. Determine a control amount corresponding to the target pressure calculated by the means M6,
By instructing the control amount to the pressure adjusting means M3, the pressure of the pressure fluid introduced into the diaphragm chamber of the exhaust gas recirculation means M2 is adjusted to the target pressure, and the exhaust gas recirculation amount is set to the target exhaust gas recirculation amount according to the operation state. Control.

At this time, the relationship between the target pressure and the control amount used by the control means M8 for determining the control amount is stored in the characteristic correction means M7 as follows. That is, the operation of performing feedback correction of the control amount so that the pressure of the pressure fluid matches the target pressure is performed in a plurality of different predetermined operating states, and the control amount obtained by this correction operation is stored as a learning value. The relationship between the target pressure and the control amount in other operating states is defined and updated sequentially based on the learning values in the plurality of predetermined operating states.

Accordingly, the exhaust gas recirculation control device for an internal combustion engine according to the present invention provides a convergence and response of pressure control caused by a pressure propagation loss in a fluid passage or the like of a pressure fluid introduced into a diaphragm chamber for adjusting an exhaust gas recirculation amount. It works to suppress adverse effects such as deterioration of sex.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 shows a system configuration of a diesel engine exhaust gas recirculation control device according to a first embodiment of the present invention.

As shown in FIG. 1, an exhaust gas recirculation control device 1 for a diesel engine includes a diesel engine 2, a fuel injection pump 3 for pumping fuel to the diesel engine 2, and an electronic control device for controlling these (hereinafter simply referred to as an ECU). ) 4
It is composed of

The diesel engine 2 introduces intake air from an intake pipe 5 to an engine main body 6 and discharges exhaust gas from the engine main body 6 to an exhaust pipe 7. The exhaust pipe 7 and the intake pipe 5 are connected by an exhaust gas recirculation pipe 8.
An exhaust gas recirculation control valve (hereinafter, simply referred to as EGRV) 9 having a built-in diaphragm chamber is interposed at the connection portion of the above.
The diaphragm chamber of the EGRV 9 includes a control line 10, a negative pressure regulating valve 11,
Through a vacuum pump 12. EG above
RV9 changes its opening in accordance with a change in the negative pressure of the air supplied from the control line 10 by a negative pressure adjusting valve 11 for adjusting the negative pressure under the control of the ECU 4, and the exhaust pipe The amount of exhaust gas circulated from the intake pipe 7 to the intake pipe 5 is adjusted.

The fuel injection pump 3 supplies an amount of fuel corresponding to the rotation of an accelerator lever 14 interlocked with an accelerator pedal 13 to the engine main body 6 of the diesel engine 2 through the high-pressure injection pipes 3a, 3b, 3c, 3d for pressure feeding. The fuel injection valves 6a, 6b,
Pump to 6c, 6d.

The exhaust gas recirculation control device 1 for a diesel engine, as a detector, measures a rotation speed of a drive shaft of a fuel injection pump 3 to detect a rotation speed of the diesel engine 2, and detects a depression amount of the accelerator pedal 13. An accelerator operation amount sensor 22 for detecting, a water temperature sensor disposed in a cooling system of the diesel engine 2 and detecting a cooling water temperature
23 A pressure sensor comprising a semiconductor pressure sensor disposed in the control line 10 connecting the diaphragm chamber of the EGRV 9 and the negative pressure regulating valve 11 and detecting a negative pressure introduced into the diaphragm chamber.
It has 25.

The detection signal of each sensor is input to the ECU 4, which controls the diesel engine 2 and the fuel injection pump 3. The above ECU4 has CPU4a, ROM4b, RAM4c, backup
The RAM 4d is mainly configured as a logical operation circuit, and is connected to the input / output unit 4f via the common bus 4e to perform input / output with the outside. The detection signals of the above sensors are input / output unit 4f.
While being input to the CPU 4a, the CPU 4a outputs a control signal to the negative pressure regulating valve 11 via the input / output unit 4f.

As shown in FIG. 3, the EGRV 9 is a diaphragm-driven flow control valve, and a valve seat element 31 serving also as an orifice disposed inside the exhaust gas recirculation pipe 8.
A valve element 32 that cooperates with the valve element 32 to increase or decrease the effective passage cross-sectional area of the communicating portion between the exhaust gas recirculation pipe 8 and the intake pipe 5 from a fully open state (communication) to a fully closed state (shut off). A diaphragm 34 connected via a valve rod 33, a diaphragm casing 35 disposed on a side opposite to a connecting surface between the diaphragm 34 and the valve rod 32, a diaphragm chamber formed by the diaphragm casing 35 and the diaphragm 34. 36, a compression coil spring 37 which is built in the diaphragm chamber 36 and urges the diaphragm 34. The diaphragm chamber 36 communicates with the vacuum pump 12 via the control line 10 and the negative pressure regulating valve 11. When the negative pressure regulating valve 11, which is an electromagnetic pressure regulating valve, introduces a negative pressure (a negative pressure having a large absolute value) larger than a predetermined pressure into the diaphragm chamber 36 in response to a command signal from the ECU 4, the diaphragm 34 Resists the urging of the compression coil spring 37, deforms in the direction indicated by the arrow 0 in the figure, pulls the valve element 32 away from the valve seat element 31, and opens the valve. At this time, the valve opening amount, that is, the effective passage cross-sectional area increases with an increase in the absolute value of the negative pressure introduced into the diaphragm chamber 36, which is a negative pressure due to the pressure adjustment of the negative pressure regulating valve 11. The amount of exhaust gas recirculated from the exhaust gas recirculation pipe 8 to the intake pipe 5 also increases. On the other hand, the negative pressure regulating valve 11
When atmospheric pressure is introduced into the control line 10, the diaphragm
The arrow C in FIG.
The valve element 32 is deformed in the direction shown by the arrow and presses the valve element 32 against the valve seat element 31 to close the valve.

The ECU 4 is an operating state of the diesel engine 2, a rotation speed detected by a rotation speed sensor 21, an accelerator operation amount detected by an accelerator operation amount sensor 22, a water temperature sensor
A target introduction negative pressure that can achieve a target exhaust gas recirculation amount determined from the cooling water temperature detected by 23 and the atmospheric pressure detected by the pressure sensor 25 when the EGR execution condition is not satisfied is determined, and corresponds to the target introduction negative pressure. A command signal is output from the ECU 4 to the negative pressure regulating valve 11. The characteristic that defines the correspondence between the target introduction negative pressure and the command signal is based on the pressure sensor
Update learning is performed by feedback correction based on the deviation between the detected actual negative pressure of 25 and the target negative pressure output from the ECU 4. The feedback correction is performed, for example, by using both pressures at both ends of the negative pressure use region of the negative pressure introduced into the diaphragm chamber 36 as a learning pressure, performing feedback correction on a value of a command signal for realizing the both learning pressures, and learning. In accordance with a characteristic defining the relationship between the two learning pressures and the command signal, the command signal for the target introduction negative pressure between the two learning pressures is determined by interpolation calculation.

The control as described above is realized by the ECU 4 executing the EGR control process and the command signal feedback correction process. The EGR control process executed by the ECU 4 will be described with reference to FIG. 4, and the command signal feedback correction process will be described with reference to the flowchart shown in FIG.

The EGR control process shown in FIG.
It is executed every predetermined time. First, in step 100, a process of reading the detection results of each sensor described above is performed.
In the following step 110, it is determined whether or not the EGR execution condition is satisfied, and if a positive determination is made, the process proceeds to step 130, while
If a negative determination is made, the process proceeds to step 120. Here, the EGR execution condition is a time when the engine is in an operation state other than the high load state and other than the deceleration state after the warm-up operation is completed. In step 120 executed when a negative determination is made in step 110, the EGR
After resetting the control execution flag FEGR to 0,
This EGR control processing ends. On the other hand, in step 130 executed when an affirmative determination is made in step 110, a process of setting the EGR control execution flag FEGR to a value 1 is performed. In the following step 140, a process of calculating the basic EGR coefficient EGRB in accordance with the map shown in FIG. 5 which is stored in the ROM 4b in advance based on the engine speed Ne and the accelerator operation amount TA read in step 100 is performed. Done. Next, proceeding to step 150, a process of calculating a corrected EGR coefficient EGRC based on the coolant temperature THW and the atmospheric pressure Pat read in step 100 and according to the map shown in FIG. 6 and stored in the ROM 4b in advance. Is performed. In the following step 160, the actual EGR coefficient EGRF is
From the GRB and the corrected EGR coefficient EGRC, a process of calculating according to the following equation (1) is performed.

EGRF = f (EGRB, EGRC) (1) where f is the actual EGR coefficient EGRF and the basic EGR coefficient EGRB
And a function defining the relationship with the corrected EGR coefficient EGRC.

Next, the routine proceeds to step 170, where the target EGRV introduction negative pressure EGRT is calculated from the actual EGR coefficient EGRF calculated in step 160 as in the following equation (2).

EGRT = α × EGRF + β (2) where α and β are constants.

In the following step 180, based on the target EGRV introduction negative pressure EGRT calculated in the above step 170, it is updated at predetermined intervals and learned and stored in at least one of the RAM 4c and the backup RAM 4d as described later. Is performed according to the map shown in FIG. Next, the process proceeds to step 190, where the process of outputting the command signal DUTY calculated in step 180 to the negative pressure regulating valve 11 is performed, and then the present EGR control process is temporarily terminated. Thereafter, the present EGR control process repeatedly executes the above steps 100 to 190 at predetermined time intervals.

Next, the EG used in step 180 of the EGR control process is used.
A command signal feedback correction process for feedback-correcting a map (shown in FIG. 7) defining the relationship between the RV introduction negative pressure and the command signal DUTY will be described with reference to the flowchart shown in FIG. This command signal feedback correction process is repeatedly executed at predetermined time intervals.

First, in step 200, a process of reading data such as the detection results of the sensors described above and the calculation results of the EGR control process described above is performed. In the following step 210, it is determined whether or not the EGR control in-execution flag FEGR is set to a value 1. If the determination is affirmative, the process proceeds to step 220. If the determination is negative, the command signal feedback correction process is temporarily performed. To end. In step 220, which is executed when it is determined in step 210 that the EGR control is being executed, the target EGR
It is determined whether or not the state in which the V-introduced negative pressure EGRT is equal to the lower end pressure A [mmHg] of the negative pressure use area continues for a time a [sec] or more. When it is determined, the process proceeds to step 260. In step 230, which is executed when the target EGRV introduction negative pressure EGRT is stable at the lower end pressure A [mmHg] of the negative pressure use region, the pressure sensor 2
Absolute value of actual introduced negative pressure PIM detected in 5 and target EGRV introduced negative pressure
It is determined whether or not the absolute value of EGRT is equal.If the determination is affirmative, the process proceeds to step 250; if the determination is negative, step 2 is performed.
Go to 40 each. Still, absolute value of actual introduced negative pressure PIM and target EGR
In step 240 executed when the absolute value of the V introduction negative pressure EGRT is not equal to the absolute value of the actual introduction negative pressure PIM, the target EGRV
When it is larger than the absolute value of the introduced negative pressure EGRT, the lower end pressure A
The absolute value of the actually introduced negative pressure PIM is reduced by subtracting the integral correction term ΔDUTYI corresponding to the difference from the lower end command signal FDUTY1, which is the command signal for the EGRV, while the absolute value of the actually introduced negative pressure PIM is If the absolute value of the pressure EGRT is smaller than the absolute value of the pressure EGRT, the integral correction term ΔDUTYI is added to the lower end command signal FDUTY1, which is a command signal for the lower end pressure A, to increase the absolute value of the actually introduced negative pressure PIM. Return to 230. On the other hand, when it is determined in step 230 that the absolute value of the actual introduction negative pressure PIM is equal to the absolute value of the target EGRV introduction negative pressure EGRT, a command signal for the lower end pressure A at this time is executed in step 250. The lower end command signal FDUTY1
After performing the process of learning and storing in M4c and the backup RAM 4d, the present command signal feedback correction process is temporarily terminated.

On the other hand, when a negative determination is made in step 220, that is, when the target EGRV introduction negative pressure EGRT is not stable at the lower end pressure A [mmHg] of the negative pressure use area, the step is executed.
At 260, it is determined whether or not the state in which the target EGRV introduction negative pressure EGRT is equal to the upper end pressure B [mmHg] of the negative pressure use region continues for a time a [sec] or more.
The process proceeds to 0, and if a negative determination is made, the present command signal feedback correction process is once ended. Target EGRV introduction negative pressure
In step 270, which is executed when the EGRT is stable at the upper end pressure B [mmHg] of the negative pressure use area, the absolute value of the actual introduced negative pressure PIM detected by the pressure sensor 25 and the target EGRV introduced negative pressure EGR
It is determined whether or not the absolute value of T is equal. If the determination is affirmative, the process proceeds to step 290; if the determination is negative, the process proceeds to step 280.
Go to each. Still, absolute value of actual introduced negative pressure PIM and target EGRV
In step 280, which is executed when the absolute value of the introduced negative pressure EGRT is not equal, when the absolute value of the actual introduced negative pressure PIM is larger than the absolute value of the target EGRV introduced negative pressure EGRT, it is a command signal for the upper end pressure B. The absolute value of the actually introduced negative pressure PIM is reduced by subtracting the integral correction term ΔDUTYI according to the difference from the upper end command signal FDUTY2, while the absolute value of the actually introduced negative pressure PIM is equal to the target E
When the absolute value of the GRV introduction negative pressure EGRT is smaller than the absolute value of the actual introduction negative pressure PIM after adding the integral correction term ΔDUTYI to the upper end command signal FDUTY2 which is the command signal for the upper end pressure B, The process returns to step 270 again.
On the other hand, when it is determined in step 270 that the absolute value of the actual introduced negative pressure PIM is equal to the absolute value of the target EGRV introduced negative pressure EGRT, a command signal for the upper end pressure B at this time is executed in step 290. The upper end command signal FDUTY2 which is
After performing the process of learning and storing in the backup RAM 4d, the present command signal feedback correction process is temporarily terminated. Thereafter, the present command signal feedback correction process is repeatedly executed at predetermined time intervals by repeating steps 200 to 290 described above. By the command signal feedback correction processing, the map shown in FIG. 7 described above is successively updated and learned.

Next, the state of the above control will be described based on the timing chart shown in FIG. As shown by the broken line in FIG.
When the target EGRV introduction negative pressure changes stepwise to the increasing side at the time T1, the EGRV introduction negative pressure by the EGR control processing of the first embodiment rapidly increases from the time T1, as shown by a solid line in FIG. At time T2, it matches the target EGRV introduction negative pressure. Further, as shown by a broken line in the figure, when the target EGRV introduction negative pressure changes stepwise to the decreasing side at time T4, the EGRV introduction negative pressure by the EGR control process of the first embodiment becomes a solid line in the same figure. As shown, it decreases rapidly from time T4 and coincides with the target EGRV introduction negative pressure at time T5. Incidentally, when feedback control based on the measured value of the actual introduction negative pressure by the pressure sensor is performed as in the related art, even if the target EGRB introduction negative pressure changes stepwise to the increasing side at time T1, the EGRV introduction negative pressure As shown by a dashed line in the figure, after gradually increasing from time T1, overshooting and hunting are repeated, and finally coincides with the target EGRV introduction negative pressure at time T3. Further, as shown by a broken line in the figure, when the target EGRV introduction negative pressure changes stepwise to the decreasing side at the time T4, the EGRV introduction negative pressure by the EGR control process becomes the same as the time indicated by the one-dot chain line in FIG. After gradually decreasing from T4, underhunting was repeated and hunting was repeated, and it coincided with the target EGRV introduction negative pressure after a lapse of a predetermined delay time.

In the first embodiment, the diesel engine 2 is connected to the internal combustion engine M1, and the exhaust recirculation control valve 9 is connected to the exhaust recirculation means M2.
In addition, the negative pressure adjusting valve 11 corresponds to the pressure adjusting unit M3, the pressure sensor 25 corresponds to the pressure detecting unit M4, and the rotation speed sensor 21 and the accelerator operation amount sensor 22 correspond to the operating state detecting unit M5. Further, the ECU 4 and steps (100 to 170) of the processing executed by the ECU 4 serve as the target pressure calculating means M6, and the steps (200 to 290) serve as the characteristic correcting means M7.
To 190) function as the control means M8.

As described above, according to the first embodiment, the control conduit for communicating the diaphragm chamber 36 of the EGRV 9 with the negative pressure regulating valve 11 is provided.
Pressure propagation loss and negative pressure regulating valve due to 10 dead volumes
Hunting of EGR control caused by the open air diameter of 11 etc. can prevent control delay and reduce the target EGRV introduction negative pressure.
Convergence to EGRT is improved.

Also, in the transient operation state where the change in the exhaust gas recirculation amount is large,
Since the responsiveness and followability of the EGR control are improved, the optimal amount of exhaust gas can be recirculated to the operating state.

Furthermore, since the control accuracy of the EGR control increases, the target EGRV
Even in a transient operation state in which the introduced negative pressure EGRT changes abruptly, the emission amount of nitrogen oxides (NOx) can be suppressed, and the exhaust characteristics can be improved.

Further, an exhaust gas recirculation pipe 8, EGRV9,
Errors caused by individual differences in the control pipeline 10, the negative pressure regulating valve 11, etc., aging, and temperature characteristics can be sufficiently compensated.

Next, a second embodiment of the present invention will be described in detail with reference to the drawings. The difference between the second embodiment and the first embodiment described above is that the command signal feedback control processing is different. The rest of the device configuration and the like are the same as in the first embodiment described above, and therefore the same portions are denoted by the same reference numerals and description thereof will be omitted.

The command signal feedback correction process executed in the second embodiment will be described with reference to the flowchart shown in FIG.

The present command signal feedback correction process is executed at predetermined time intervals when the ECU 4 is started.

First, data such as the detection result of each sensor described above and the calculation result of the above-described EGR control process is read (step 30).
0), it is determined whether or not the EGR control execution flag FEGR is set to a value of 1 (step 305);
Once the present command signal feedback correction process ends, on the other hand, if a positive determination is made, the process proceeds to step 310. During the execution of the EGR control, it is determined whether or not the state in which the target EGRV introduction negative pressure EGRT is equal to the lower end pressure A [mmHg] of the negative pressure use area continues for a time a [sec] or more (step 310). If the determination is affirmative, the process proceeds to steps (315-325), and if the determination is negative, the process proceeds to step 330. Target EGRV introduction negative pressure EGRT,
When the lower end pressure A [mmHg] of the negative pressure use region is stable, it is determined whether or not the absolute value of the actually introduced negative pressure PIM detected by the pressure sensor 25 is equal to the absolute value of the target EGRV introduced negative pressure EGRT. It is determined (step 315), and if the absolute value of the actual introduction negative pressure PIM is not equal to the absolute value of the target EGRV introduction negative pressure EGRT, the absolute value of the actual introduction negative pressure PIM is not equal to the target EGRV introduction negative pressure EGRT. In order to approach the absolute value, the lower end command signal FDUTY1, which is the command signal for the lower end pressure A, is increased / decreased by the integral correction term ΔDYTYI to perform a process of increasing / decreasing the absolute value of the actually introduced negative pressure PIM (step 320). Thereafter, returning to step 315 again, when the absolute value of the actual introduced negative pressure PIM is equal to the absolute value of the target EGRV introduced negative pressure EGRT, the lower end command signal FDUTY1, which is the command signal for the lower end pressure A at this time, is stored in the RAM 4c, Backup RA
After performing the process of learning and storing in M4d (step 325), the present command signal feedback correction process is temporarily terminated.

On the other hand, when a negative determination is made in step 310, that is, when the target EGRV introduction negative pressure EGRT is not stable at the lower end pressure A [mmHg] of the negative pressure use region, the target EGRV introduction negative pressure
It is determined whether or not the state in which EGRT is equal to the upper end pressure B [mmHg] of the negative pressure use area has continued for a time a [sec] or more (step 330). If a negative determination is made, the process proceeds to step 350. Target EGRV
When the introduction negative pressure EGRT is stable at the upper end pressure B [mmHg] of the negative pressure use area, the actual introduction negative pressure detected by the pressure sensor 25 is used.
It is determined whether or not the absolute value of the PIM is equal to the absolute value of the target EGRV introduction negative pressure EGRT (step 335).
When the absolute value of IM is not equal to the absolute value of the target EGRV introduction negative pressure EGRT, a command for the upper end pressure B is set so that the absolute value of the actual introduction negative pressure PIM approaches the absolute value of the target EGRV introduction negative pressure EGRT. The upper end command signal FDUTY2, which is a signal, is increased or decreased by an integral correction term ΔDUTYI corresponding to the difference to increase or decrease the absolute value of the actually introduced negative pressure PIM (step 340).
And the absolute value of the actual introduction negative pressure PIM and the target EGRV introduction negative pressure EGR
When it is determined that the absolute value of T is equal, the upper end command signal FDUTY2 which is a command signal for the upper end pressure B at this time.
Is performed in the RAM 4c and the backup RAM 4d (step 345), and then the present command signal feedback correction processing is temporarily terminated.

On the other hand, a step executed when a negative determination is made in step 330, that is, when the target EGRV introduction negative pressure EGRT is not stable at the upper end pressure B [mmHg] of the negative pressure use region.
At 350, it is determined whether or not the state in which the target EGRV introduction negative pressure EGRT is equal to the intermediate pressure C [mmHg] in the negative pressure use region continues for a time a [sec] or more.
Proceeding to step 5, on the other hand, if a negative determination is made, the present command signal feedback correction process is once ended. Target EGRV introduction negative pressure
When the EGRT is stable at the intermediate pressure C [mmHg] in the negative pressure use area, is the absolute value of the actual introduced negative pressure PIM detected by the pressure sensor 25 equal to the absolute value of the target EGRV introduced negative pressure EGRT? It is determined whether or not the absolute value of the actual introduction negative pressure PIM is not equal to the absolute value of the target EGRV introduction negative pressure EGRT (step 350). In order to approach the absolute value of the pressure EGRT, the intermediate command signal FDUTY3, which is a command signal for the intermediate pressure C, is increased or decreased by an integral correction term ΔDUTYI corresponding to the difference to increase or decrease the absolute value of the actually introduced negative pressure PIM. After performing the process (step 360), the process returns to step 355 again, and the absolute value of the actual introduced negative pressure PIM and the target EGRV
When it is determined that the absolute value of the introduced negative pressure EGRT is equal to the absolute value of the introduced negative pressure EGRT, a process (step 370) of learning and storing the intermediate command signal FDUTY3, which is a command signal for the intermediate pressure C at this time, in the RAM 4c and the backup RAM 4d is performed. The present command signal feedback correction processing is once ended. Thereafter, the command signal feedback correction process is repeatedly executed at predetermined time intervals by repeating steps 300 to 370 described above. As a result of the present command signal feedback correction process, as shown in FIG. 11, a map defining the characteristics of the interrelation between the EGRV introduction negative pressure and the command signal DUTY is successively updated and learned.

In the second embodiment, the ECU 4 and the steps (300 to 370) of the processing executed by the ECU 4 are performed by the characteristic correcting means M7.
Function as

As described above, according to the second embodiment, when the EGRV introduction negative pressure is set between the learning pressures A and C, the command signals FDUTY1 and FDUTY3 corresponding to the learning pressures A and C are generated. The target command signal DUTY is calculated by interpolation, while the EGRV introduction negative pressure is
When set between learning pressures C and B, command signal F
Since the target command signal DUTY is calculated by interpolating DUTY3 and FDUTY2, the characteristics defining the correspondence between the EGRV introduction negative pressure and the command signal DUTY become accurate, and the control accuracy of the EGR control is further improved.

The learning pressure is not limited to three points, and learning may be performed at many points.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments at all, and it is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention. .

Effect of the Invention As described in detail above, in the exhaust gas recirculation control device for an internal combustion engine of the present invention, the control means controls the control amount corresponding to the target pressure in accordance with the relationship between the target pressure and the control amount stored in the characteristic correction means. Then, the control amount is commanded to the pressure adjusting means to adjust the pressure of the pressure fluid introduced into the diaphragm chamber to the target pressure, and the exhaust gas recirculation amount is controlled to the target exhaust gas recirculation amount according to the operation state. At this time, the relationship between the target pressure and the control amount used by the control means for determining the control amount is stored in the characteristic correction means as follows. That is, the operation of performing feedback correction of the control amount so that the pressure of the pressure fluid matches the target pressure is performed in a plurality of different predetermined operating states, and the control amount obtained by this correction operation is stored as a learning value. At the same time, the relationship between the target pressure and the control amount in other operating states is defined and sequentially updated based on the learning values in the plurality of predetermined operating states. For this reason, the pressure control loss caused by the pressure propagation loss in the fluid passage or the like of the pressure fluid introduced into the diaphragm chamber for adjusting the exhaust gas recirculation amount is not easily affected, so that the convergence of the exhaust gas recirculation control is improved, and
The responsiveness and the followability are also improved, and an excellent effect that the optimum amount of exhaust gas can be recirculated to the operating state can be obtained.

Further, since the control accuracy of the exhaust gas recirculation control is enhanced, a high level of exhaust gas purification performance can be exhibited even in a transient operation state in which the target exhaust gas recirculation amount changes rapidly.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram conceptually illustrating the contents of the present invention, FIG. 2 is a system configuration diagram of a first embodiment of the present invention, and FIG.
FIG. 4 is a schematic structural diagram showing the structure of the exhaust gas recirculation control valve, FIG. 4 is a flowchart showing the control thereof, FIG. 5, FIG. 6, and FIG. Is also a flowchart showing the control, FIG. 9 is a timing chart showing the state of the control, FIG. 10 is a flowchart showing the control of the second embodiment of the present invention, and FIG. 11 is a graph also showing the map. . M1 internal combustion engine M2 exhaust recirculation means M3 pressure adjustment means M4 pressure detection means M5 operating state detection means M6 target pressure calculation means M7 characteristic correction means M8 control means 1 ... Diesel engine exhaust gas recirculation control device 2 ... Diesel engine 4 ... Electronic control device (ECU) 4a ... CPU 8 ... Exhaust gas recirculation pipe 9 ... Exhaust gas recirculation control valve (EGRV) 10 ... Control line 11 Negative pressure adjustment valve 21 Rotation speed sensor 22 Accelerator operation amount sensor 25 Pressure sensor

Continuation of front page (72) Inventor Hiroshi Nakamura 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-54-38437 (JP, A) JP-A-55-164759 (JP, A) JP-A-1-182566 (JP, A) JP-A 64-56553 (JP, U)

Claims (1)

(57) [Claims] An exhaust gas recirculation means interposed in a recirculation pipe for recirculating exhaust gas from an internal combustion engine to an intake pipe for changing an exhaust gas recirculation amount in accordance with a pressure of a pressure fluid introduced into a diaphragm chamber; Pressure adjusting means for adjusting the pressure of the pressure fluid introduced into the diaphragm chamber of the exhaust gas recirculation means in accordance with the controlled variable; and pressure detection for detecting the pressure of the pressure fluid introduced into the diaphragm chamber of the exhaust gas recirculation means. Means, operating state detecting means for detecting an operating state of the internal combustion engine, target pressure calculating means for calculating a target pressure of the pressure fluid, which is determined based on each operating state detected by the operating state detecting means, An operation of performing feedback correction of the control amount so that the pressure of the pressure fluid matches the target pressure is performed in a plurality of mutually different predetermined operating states. Is stored as a learning value, and based on the learning values in the plurality of predetermined operating states, the relationship between the target pressure and the control amount in other operating states is defined and sequentially updated and stored. A characteristic correction unit, and a control amount corresponding to the target pressure calculated by the target pressure calculation unit is determined according to a relationship between the target pressure and the control amount stored in the characteristic correction unit. An exhaust gas recirculation control device for an internal combustion engine, comprising: control means for issuing a command.