JPH08177642A - Exhaust gas flux control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To feedback-correct overs and shorts of exhaust gas recirculating amount due to aged deterioration or the like, in an exhaust gas recirculation control device for a Diesel engine. CONSTITUTION: An exhaust gas recirculation control device, arranged in flow pipes 15, 17 for recirculating exhaust gas of an engine 1 partly in its intake system, is constituted by having a recirculation control valve 11 of adjusting an amount of recirculating this exhaust gas. An intake pressure sensor 46 is provided in the engine 1, to provide in the recirculation control valve 11 an opening sensor 44 for monitoring its opening. In an electronic control device 40, transition of a detected intake pressure is learned at idle time of the engine 1, also to calculate a target value of this intake pressure based on a monitored opening of the recirculation control valve 11, so as to calculate an opening correction amount of the recirculation control valve 11 capable of canceling a difference between a target value and a learned value of these intake pressures. An opening of this recirculation control valve 11, feedback-controlled to be based on a load and rotational speed of the engine 1, is corrected by this calculated correction amount.

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, which recirculates the exhaust gas to the intake system of the engine in order to reduce NOx emitted from the internal combustion engine,
In particular, the present invention relates to an improvement of a device that performs feedback control of the opening degree operation of a recirculation control valve that adjusts the recirculation amount of exhaust gas.

[0002]

2. Description of the Related Art As is well known as an exhaust gas recirculation control device, a part of gas discharged from an internal combustion engine, such as a diesel engine, is taken out from an exhaust system, and an appropriate temperature, timing,
It is a device that controls the flow rate and recirculates it to the intake system of the engine. Also, by recirculating the exhaust gas to the intake system in this way, the combustion temperature of the gas can be lowered,
It is also well known that the generation of NOx (NO and NO2 of nitrogen oxides), which are harmful components in combustion exhaust gas, is suppressed.

By the way, in such an exhaust gas recirculation control device, the opening degree of the recirculation control valve, which is the control valve, is manipulated so that the recirculation amount of the exhaust gas is precisely controlled to an ideal amount. A device adapted to perform feedback control has also been proposed and put into practical use.

In an exhaust gas recirculation control device which employs this feedback control, a target opening degree of the recirculation control valve is usually first obtained in accordance with the state of the engine, and the actual opening degree of the recirculation control valve detected by an opening sensor. The feedback control of the manipulated variable is performed so that the value follows the target opening degree.

However, as a matter of fact, the relationship between the opening degree of the recirculation control valve and the recirculation amount of the exhaust gas adjusted by the opening control valve due to changes with time in the intake system of the engine and the recirculation system of the exhaust gas. However, there is a possibility that the recirculation amount becomes larger or smaller than the target value despite the fact that the feedback control is normally performed. If the exhaust gas recirculation amount is not properly adjusted in this way, so-called smoke and NOx are excessively generated, and the emission is deteriorated.

Therefore, conventionally, for example, JP-A-57-414 has been used.
As seen in Japanese Patent Laid-Open No. 54-54: Detect the pressure downstream of the recirculation control valve in the exhaust gas recirculation passage. -Comparison between the detected actual pressure in the recirculation passage and the target pressure is detected to detect a decrease in the exhaust gas recirculation amount due to carbon adhesion. The operation opening degree of the recirculation control valve is increased and corrected according to the degree of decrease in the detected exhaust gas recirculation amount. That is, the exhaust gas recirculation amount is increased and corrected. By executing such correction control as well, the control failure caused by such a change with time is dealt with.

[0007]

According to the above-described conventional correction control, it is possible to surely appropriately cope with a change with time in the exhaust gas recirculation system such as carbon deposition in the exhaust gas recirculation passage. That is, it is possible to compensate for the decrease in the exhaust gas recirculation amount due to the carbon adhesion and the like, and to maintain the recirculation amount appropriately.

However, the above-mentioned conventional technique is merely a technique for coping with the change with time in the exhaust gas recirculation system, and for example, clogging of the air cleaner, variation of the intake throttle, etc.
It has been impossible to deal with the control failure due to the change with time in the intake system of the engine, that is, the control failure such that the exhaust gas recirculation amount increases.

Conventionally, for example, the actual Kaihei 4-89843.
As can be seen in Japanese Patent Publication: ・ Providing an air flow meter (sensor) to measure the amount of intake air into the engine and ensuring an appropriate exhaust gas recirculation amount (rate) for changes in the intake air amount. Therefore, it is possible to prevent deterioration of emission due to insufficient or excessive exhaust gas recirculation amount. Such technology is also proposed. However, in the case of the same technology, an air flow meter needs to be additionally provided, and there is an unavoidable cost disadvantage in practical use. In terms of cost, the technology for detecting the pressure downstream of the reflux control valve and dealing with carbon adhesion etc. also requires a separate pressure sensor to detect the pressure. Although correction is possible, it is still difficult to say that it is realized in a desirable manner.

The present invention has been made in view of the above circumstances, and no matter how the exhaust gas recirculation amount becomes excessive or deficient, the exhaust gas recirculation amount can be increased without adding any special device. It is an object of the present invention to provide an exhaust gas recirculation control device for an internal combustion engine, which can always perform feedback correction to an ideal amount.

[0011]

In order to achieve these objects, the invention according to claim 1 is arranged in a recirculation passage for recirculating a part of exhaust gas of an internal combustion engine to an intake system of the engine. A recirculation control valve that adjusts the recirculation amount of the exhaust gas, and an opening degree detection unit that detects the actual opening degree of the recirculation control valve,
Intake pressure detection means for detecting the intake pressure, which is the pressure in the intake pipe of the internal combustion engine, intake pressure learning means for learning the transition based on the detected intake pressure, and recirculation control valve detected by the opening degree detection means. Target intake pressure calculating means for calculating the target value of the intake pressure based on the actual opening of the recirculation control valve capable of canceling the deviation based on the difference between the target value of the intake pressure and the learned value. Correction amount calculation means for calculating the amount, target opening calculation means for calculating the target opening of the recirculation control valve based on the load and the rotational speed of the internal combustion engine, and the calculated target opening with the correction amount. An exhaust gas recirculation control device for an internal combustion engine is configured to include control means for controlling the opening of the recirculation control valve with the corrected value.

Further, in the invention according to claim 2, the learning and the target value calculation of the intake pressure are performed by the intake pressure learning means and the target intake pressure calculation means on condition that the internal combustion engine is in an idle state. The correction amount calculation means calculates the correction amount based on a difference between a target value and a learned value of the intake pressure learned and calculated when the internal combustion engine is in an idle state, and stores the correction amount in an appropriate manner. The control means is configured to update and register the target opening degree of the recirculation control valve based on the latest correction amount registered in the storage means.

According to the third aspect of the present invention, the intake pressure learning means holds the learned value as a value obtained by blunting the change in the detected intake pressure.

[0014]

In the structure according to the first aspect of the present invention, the opening degree detecting means uses the opening degree sensor or the like directly arranged in the recirculation control valve to feedback-control the exhaust gas recirculation amount. The actual opening information of is output.

However, as a matter of fact, the relationship between the opening degree of the recirculation control valve and the exhaust gas recirculation amount adjusted by it changes due to changes with time in the intake system of the engine and the exhaust gas recirculation system. As mentioned above, there is a case where a person may come. When such a change occurs, there is a problem that the exhaust gas recirculation amount becomes larger or smaller than the target value, although the feedback control is normally performed. did.

Therefore, in the invention according to claim 1, paying attention to the fact that the exhaust gas recirculation amount and the intake pressure have a linear relationship in the first place. The transition is based on the actually detected intake pressure. learn. On the other hand, based on the actual opening information of the reflux control valve,
The target value of the intake pressure is calculated. After such preprocessing, the correction amount calculation means calculates the opening correction amount of the recirculation control valve capable of canceling the deviation based on the difference between the target value and the learned value of the intake pressure.

That is, if the intake system and the exhaust gas recirculation system of the engine do not have the above-mentioned changes with time, the target value of the intake pressure and the learned value are equal, and the deviation thereof is ideally kept at "0". Maintained in a healthy state. However, if the amount of exhaust gas recirculation becomes smaller than the ideal amount due to, for example, carbon adhering to the exhaust gas recirculation passage, the relationship of target intake pressure> learning intake pressure is established, and the air cleaner is clogged. When the exhaust gas recirculation amount becomes larger than the ideal amount due to variations in the intake throttle and the intake throttle variation, the relationship of target intake pressure <learned intake pressure is conversely satisfied. Therefore, the correction amount calculation means calculates an opening correction amount of the recirculation control valve such that the difference between the target value of the intake pressure and the learned value can be set to "0", and the recirculation control valve is calculated by the calculated correction amount. If the target opening degree of is corrected, the adjusted exhaust gas recirculation amount is always maintained at an ideal amount.

The above-described structure according to the invention of claim 1 is realized by standard hardware as an exhaust gas recirculation control device for an internal combustion engine which employs feedback control. There is no need to add special hardware such as sensors.

According to the second aspect of the invention,
The intake pressure learning means and the target intake pressure calculation means, respectively, for performing the learning and the target value calculation of the intake pressure under the condition that the internal combustion engine is in the idle state. In addition to the above, the correction amount calculation means is configured to: Calculate the correction amount based on the difference between the target value and the learned value of the intake pressure that are learned and calculated when the internal combustion engine is in the idle state, and store the appropriate correction means. What is renewed and registered.
The control means corrects the target opening degree of the recirculation control valve based on the latest correction amount registered in the storage means. If so, the exhaust gas recirculation amount and the intake pressure, which have a linear relationship with each other as described above, perform the learning of the intake pressure and the calculation of the target value in a state where the relationship is the most stable, such as the idle state. Further, the opening correction amount of the recirculation control valve based on the learned value and the target value can be obtained. That is, the reliability as the same opening correction amount is greatly improved, and even when the target intake pressure and the opening correction amount are map-calculated, those maps can be easily and accurately created.

Moreover, according to the invention of claim 2,
The opening degree of the recirculation control valve is corrected based on the correction amount obtained in the immediately preceding idling state, not only in the idling state but also in other operating states. That is, even with such a configuration in which the correction amount is calculated only during idling, it is possible to reliably correct the poor control of the exhaust gas recirculation amount due to the above-described change with time.

Even in such an idle state,
The value of the intake pressure that is detected and learned changes. Therefore, as in the third aspect of the present invention, the intake pressure learning means holds, as the learned value, a value obtained by blunting a change in the detected intake pressure. Then, the reliability of the learned value is not impaired by the change of the intake pressure, and the value of the calculated opening correction amount can be made more reliable.

[0022]

FIG. 1 shows an embodiment of an exhaust gas recirculation control device for an internal combustion engine (hereinafter referred to as an EGR control device) according to the present invention.

The device of this embodiment is a device for a diesel engine, in which a part of the discharged gas is taken out from the exhaust system and is recirculated to the intake system of the engine while appropriately controlling the flow rate of the gas. Is configured as.

First, the configuration of the apparatus of the embodiment will be described with reference to FIG. That is, in FIG. 1, the engine 1 is a diesel engine, and the engine 1 includes a cylinder bore 2 and a piston 3 that slides in the cylinder bore 2.
The combustion chamber 4 is formed above the piston 3. A swirl chamber 5 communicates with the combustion chamber 4, and liquid fuel is injected and supplied from a fuel injection nozzle (not shown) through the swirl chamber 5.

The engine 1 also sucks air into the combustion chamber 4 through the intake manifold 6 and the intake port 7, and exhausts exhaust gas from the combustion chamber 4 through the exhaust port 8 to the exhaust manifold 9. To do. The intake port 7 and the exhaust port 8 are each opened and closed by a poppet valve. However, in the figure, for convenience, only the poppet valve 10 for exhaust is shown.

On the other hand, the engine 1 is provided with an exhaust gas recirculation control valve (hereinafter referred to as an EGR valve) 11. This E
The GR valve 11 has a casing 12 having an inlet port 13 and an outlet port 14. Of these, the inlet port 13 is connected to the exhaust manifold 9 by a conduit 15.
Is connected to an exhaust gas extraction port 16 formed in the intake manifold 6, and the other outlet port 14 is connected to an exhaust gas injection port 18 formed in the intake manifold 6 by a conduit 17.

The EGR valve 11 also has a valve element 19 in the casing 12. This valve element 19
When the negative pressure is not introduced into the diaphragm chamber 26 that is connected to the diaphragm device 23 by the valve rod 22 and is partitioned by the diaphragm 25 in the diaphragm device 23, the spring force of the compression coil spring 27 attached to the casing 24 is used. Is driven to the left in the figure to sit on the valve seat portion 20 and close the valve port 21. On the other hand, when a negative pressure is introduced into the diaphragm chamber 26, it is driven to the right in the figure against the spring force of the compression coil spring 27, and the valve port 21 is moved according to the magnitude of the negative pressure. To open. By opening the valve port 21 in this way, the EGR amount (rate) corresponding to the opening degree
Then, the EGR control is executed.

The diaphragm chamber 26 is connected to the negative pressure output port 30 of the negative pressure adjusting valve 29 by a conduit 28. The negative pressure adjusting valve 29 is provided from the negative pressure pump 32 to the conduit 3
Is a device that regulates the negative pressure supplied to the negative pressure input port 31 via 3 according to a command signal given from the electronic control device 40. The regulated negative pressure is controlled by the negative pressure output port 3
It is introduced into the diaphragm chamber through 0. Incidentally, the command signal output from the electronic control unit 40 to the negative pressure adjusting valve 29 is a final target EGR valve opening TE, which will be described later.
It corresponds to LF.

On the other hand, in the apparatus of the embodiment, the accelerator opening sensor 41 is a sensor for detecting the opening of an accelerator (not shown), and the rotation speed sensor 42 is a sensor for detecting the rotation speed of the engine 1. . The detected accelerator opening degree information ACCP and engine speed information Ne are output to the electronic control unit 40.

Further, in the engine 1, a water temperature sensor 43 for detecting the temperature of the cooling water, an intake air temperature sensor 45 for detecting the temperature in the intake manifold 6, and the intake manifold 6 are provided.
An intake pressure sensor 46 for detecting the internal pressure is provided. The detected water temperature information THW, intake air temperature information THA, and intake air pressure information PIM are also output to the electronic control unit 40.

Further, the EGR valve 11 is provided with an opening sensor 44 for detecting the actual opening of the valve port 21 thereof. The actual opening information AELF of the EGR valve 11, which is the output of the opening sensor 44, is
It is taken into the electronic control unit 40 as operation amount monitor information for feedback controlling the opening degree of.

In addition, the idle switch 47 is a switch for outputting information regarding whether or not the engine 1 is idle. The same information is also taken into the electronic control unit 40.

The electronic control unit 40 is a device having, for example, a microcomputer, and in particular, in the device of this embodiment, it is shown in FIG. 2 based on the output information of the above-mentioned respective sensors and the idle switch 47. In the procedure, a signal indicating the final target EGR valve opening TELF is generated.

Next, with reference to FIG. 2 as well, the EGR control procedure by the apparatus of the embodiment will be described in more detail. The processing routine shown in FIG. 2 is assumed to be activated by a time interrupt every 8 ms (milliseconds), for example.

That is, if the routine is started by such a time interruption, the electronic control unit 40 first determines in step 101 whether the engine 1 is in the idle stable state. The idle stable state means, for example, (A) that the accelerator opening ACCP is "0"%. (B) The engine speed Ne must be "850" rpm or less. (C) The "on" information is output from the idle switch 47. It means that all the conditions are met.

When it is determined that the engine is in the idle stable state, the electronic control unit 40 reads the intake pressure PIM which is the output of the intake pressure sensor 46 in step 102, and reads the intake pressure PIM in step 103. Intake pressure PIM
The intake pressure learning value GPIM is calculated based on If it is determined in step 101 that the idle stable state is not currently set, the process proceeds to step 108 described later.

When the intake pressure learning value GPIM is calculated in step 103, the electronic control unit 40 executes a blunting process represented by the following formula (1), which is commonly called "a smoothing process". GPIMi = GPIMi-1 + {(PIM-GPIMi-1) / n} (1) In this equation (1), GPIMi is the intake pressure learning value calculated in the routine started this time, and GPIMi.
Mi-1 is the intake pressure learning value calculated in the same routine that was started last time. Further, in the same expression, n is a constant set in advance to determine the rate of blunting of the intake pressure learning value GPIM, and a value such as “8” is used. By adopting such a blunting process in the calculation of the intake pressure learning value GPIM, the influence of the fluctuation of the detected intake pressure PIM on the learning value GPIM is suitably suppressed, and the reliability of the correction amount tKTELF described below is reduced. Will be greatly improved.

The electronic control unit 40, which has obtained the intake pressure learning value GPIM in this manner, then proceeds to step 104, where the actual EGR valve opening AELF, which is the output of the opening sensor 44, is output.
Also, the intake air temperature THA which is the output of the intake air temperature sensor 45 is read, and in step 105, the target intake pressure TPIM is calculated based on these values AELF and THA.

This target intake pressure TPIM is the actual opening AELF and intake air temperature THA of the EGR valve 11 at each time.
As a value corresponding to, the map is previously registered in the built-in memory of the electronic control unit 40 in the mode shown in FIG. 3, for example. In the electronic control unit 40, based on the map, the target intake pressure TPIM corresponding to those values AELF and THA is obtained.
To decide.

As shown in FIG. 4, the target intake pressure TPIM increases as the intake air temperature THA increases, and conversely decreases the intake air temperature THA, when the actual EGR valve opening AELF is constant. It tends to be reduced. When the intake air temperature THA is constant, the actual EGR is almost constant.
It increases in proportion to the valve opening AELF.

In the electronic control unit 40, when the target intake pressure TPIM is obtained in this way, further, in step 106, the deviation (TPIM-GPIM) is calculated based on the difference between the target value TPIM and the learning value GPIM for these intake pressures. An opening correction amount tKTELF of the EGR valve 11 that can be offset is calculated.

This correction amount tKTELF is also the difference (T
As a value corresponding to (PIM-GPIM), a map is previously registered in the built-in memory of the electronic control unit 40 in a mode shown in FIG. 5, for example. The electronic control unit 40 determines the correction amount tKTELF corresponding to the deviation (TPIM-GPIM) based on the map.

The correction amount tKTELF is, as shown in FIG. 6, when the difference (TPIM-GPIM) has a positive value, that is, target intake pressure TPIM> learning intake pressure GPIM (2). In this case, a positive value that is almost directly proportional to the difference value is taken, and conversely, the difference (TPIM-GPIM) becomes a negative value, that is, target intake pressure TPIM <learning intake pressure GPIM (3). In this case, it takes a negative value that is almost directly proportional to the difference value. Then, the target value TPIM of these intake pressures and the learning value G
When PIM is equal and the deviation (TPIM-GPIM) is "0", that is, when the target intake pressure TPIM = learning intake pressure GPIM (4), the correction amount tKTELF also becomes "0". .

Here, when the above equation (4) is satisfied, the above-described changes with time in the intake system and the exhaust gas recirculation system of the engine 1 have not occurred, and the ideal feedback regarding the EGR amount is performed. It means that control is maintained. Therefore, in this case, the EGR valve 1
The opening correction amount tKTELF of 1 may be “0”.

When the relation of the above equation (2) occurs, the EGR amount is smaller than the ideal amount due to, for example, carbon adhesion to the conduit 15 or 17 forming the EGR passage. It is in a state. Therefore, in this case, the opening correction amount tKTELF of the EGR valve 11 needs to be a value for increasing and correcting the valve opening according to the deviation (TPIM-GPIM).

On the other hand, when the relation of the above formula (3) occurs, the EGR amount becomes larger than the ideal amount due to, for example, clogging of the air cleaner, which is omitted in FIG. It is in a state of being. Therefore, in this case, the opening correction amount tKT of the EGR valve 11 is
The ELF needs to be a value for reducing the valve opening degree according to the deviation (TPIM-GPIM).

The electronic control unit 40, which has obtained the correction amount tKTELF in this way, determines the stored value KTELF of the built-in correction amount memory in the next step 107.
Update with KTELF.

Incidentally, the correction amount memory is a non-volatile memory whose stored value is held by battery backup or the like. In the same memory, for example, a correction amount KTELF = 0 is stored as an initial value, and the balance of the above equation (4) is lost due to a change with time thereafter, and when the relation shown in the above equation (2) or (3) is established. The value updated at any time by the value of the correction amount tKTELF calculated according to the relationship is stored as the correction amount KTELF.

After that, or in the previous step 101, the electronic control unit 40, which has determined that it is not in the idle stable state, in step 108, the rotation speed sensor 42.
Engine speed Ne which is the output of the engine, the engine speed Ne, the accelerator opening ACCP which is the output of the accelerator opening sensor 41, and the fuel which is set based on the cooling water temperature THW which is the output of the water temperature sensor 43. The injection amount command value (engine load) QFINE is read. The fuel injection amount command value QFINE is previously registered in the internal memory of the electronic control unit 40 as a value corresponding to the accelerator opening ACCP and the engine speed Ne in a map shown in FIG. 7, for example. In the electronic control unit 40, based on the map, the fuel injection amount command value Q corresponding to the values ACCP and Ne.
Determine FINE. The determined fuel injection amount command value Q
FINE is a value corresponding to the load of the engine 1 at each time.

The electronic control unit 40, which has read the engine speed Ne and the fuel injection amount command value QFINE in this way, then:
In step 109, the target EGR valve opening TELFB is calculated based on these values Ne and QFINE.

This target EGR valve opening TELFB is
A value corresponding to the optimum EGR amount (rate) according to the engine speed Ne and the load (fuel injection amount command value QFINE) of the engine 1 at each time is shown in a built-in memory of the electronic control unit 40, for example, in FIG. The map is registered in advance in a manner. In the electronic control unit 40, based on the map, those values Ne
And target EGR valve opening TEL corresponding to QFINE
Determine FB.

The target EGR valve opening TELFB
Is, for example, as shown in FIG.
When is constant, the load tends to increase as the load decreases with a large amount of excess air, and conversely decreases in an acceleration state where the load increases rapidly.

Although the optimum EGR amount (rate), the opening degree of the EGR valve 11 and the EGR valve adjusted by the opening degree of the EGR valve 11 are caused by the change with time in the intake system and the exhaust gas recirculation system of the engine 1. As described above, the relationship with the quantity will change.

Therefore, the electronic control unit 40 proceeds to step 11
At 0, the correction amount KTELF for correcting the relationship between the opening of the EGR valve 11 and the EGR amount is read from the correction amount memory, and at the next step 111, the target EGR valve opening TELFB obtained above is The final target EGR valve opening TELF is calculated by correcting the read correction amount KTELF as TELF = TELFB + KTELF (5).

The final target EGR valve opening degree TELF thus calculated is given to the negative pressure adjusting valve 29 so that the same opening degree TE is obtained.
The pressure adjustment is performed according to LF, and the adjusted negative pressure is introduced into the diaphragm chamber 26 to open the EGR valve 11 (valve port 21) according to the pressure adjustment amount. , Etc. are as described above.

FIG. 10 shows an EGR control mode of the apparatus of the embodiment based on the final target EGR valve opening degree TELF obtained through the electronic control unit 40. By executing the EGR control in this manner, even if the above-described changes with time occur in the intake system and the exhaust gas recirculation system of the engine 1, the fluctuations in the EGR amount resulting from them are preferably feedback-corrected. become.

Incidentally, referring to FIG.
Is the accelerator opening ACCP corresponding to the load state of the engine 1.
Shows the transition of. Further, FIG. 10B shows the final target EGR calculated corresponding to the accelerator opening ACCP.
FIG. 10 (c) shows the transition of the valve opening degree TELF, and the actual EGR valve opening degree AEL detected by the opening degree sensor 44.
FIG. 10D shows the transition of F, and FIG. 10D shows the transition of the actual EGR flow rate. Further, FIG. 10 (e) shows a mode of occurrence of smoke, which is a problem particularly during acceleration.
(F) shows the generation mode of NOx which becomes a problem especially during deceleration.

In the transition of each element shown in FIGS. 10 (b) to 10 (f), the solid line shows E by the apparatus of the same embodiment.
The transition when the GR amount correction is executed and the broken line indicate the transition when the EGR amount correction is not executed.

On the other hand, in FIG. 10, in each of the above elements,
The transition to the left of each line on the dashed-dotted line is based on the assumption that the EGR amount is larger than the ideal amount due to, for example, clogging of the air cleaner or variations in the intake throttle. The respective rightward transitions are based on the assumption that the EGR amount is smaller than the ideal amount due to, for example, carbon adhering to the conduit 15 or 17 that is the EGR passage.

For example, suppose that the EGR flow rate is excessive due to the change with time of the intake system (on the left side of the alternate long and short dash line), at the time of idling, the relationship of the above equation (3) occurs and the correction is performed. The quantity tKTELF is the deviation (T
PIM-GPIM) is obtained as a negative value. Therefore, in this case, the final target EGR valve opening degree TELF is reduced and corrected in the manner shown on the left side of the alternate long and short dash line in FIG.
The R valve opening AELF and EGR flow rate are also shown in FIG.
0 (c) and (d) are corrected in the weight loss direction in a manner shown on the left side of the alternate long and short dash line. FIG. 10 (e) shows EG
If such reduction of R flow rate is not corrected,
Although the smoke should be excessively generated in the form shown by the broken line with the acceleration, it is shown that the execution of the same amount reduction correction suppresses the smoke as shown by the solid line.

On the other hand, if it is assumed that the EGR flow rate is insufficient due to the change with time of the exhaust gas recirculation system (on the right side of the one-dot chain line), at the time of idling, the above (2)
As the relation of formulas arises, the correction amount tKTELF can be obtained as a positive value corresponding to the deviation (TPIM-GPIM). Therefore, in this case, the final target EGR valve opening degree TELF is increased and corrected in the manner shown on the right side of the alternate long and short dash line in FIG. 10B, and consequently the actual EGR valve opening degree AELF and the EGR flow rate are also shown in FIG. The correction is performed in the increasing direction in the manner shown to the right of the alternate long and short dash line in (c) and (d). Figure 10
(F) shows that when such increase correction of the EGR flow rate is not performed, N is changed in accordance with the deceleration in a manner indicated by a broken line.
While the Ox should be excessively generated, the execution of the same increase correction suppresses the generation of NOx as shown by the solid line.

As described above, according to the exhaust gas recirculation control device of the embodiment, the EGR caused by the change with time of the intake system and the exhaust gas recirculation system of the engine is required without any special hardware. It becomes possible to perform feedback correction for the excess and deficiency of the amount.

Therefore, in any case, a proper ideal EGR amount can always be obtained, and the generation of smoke and NOx can be suitably reduced. In the device of the embodiment, when the correction amount tKTELF is calculated, the intake pressure learning value GPIM is subjected to the blunting process (the smoothing process) based on the equation (1) to change the intake pressure fluctuating. The influence of PIM was suppressed. However, when the above-mentioned fluctuation of the intake pressure PIM is not so large at the time of the above-described idle stabilization,
Although somewhat inferior in accuracy as compared with the device of the above embodiment,
It is also possible to adopt a simpler configuration that omits the blunting process.

Further, in the apparatus of the embodiment, the correction amount tKTELF is utilized by utilizing the state in which the linear relationship between the EGR amount and the intake pressure is most stable, such as the idle stable state.
Is calculated. Therefore, the same correction amount tKT
Although it becomes possible to easily obtain a highly reliable value as the ELF, its selection is arbitrary. That is, as the calculation means of the correction amount tKTELF, based on the linear relationship between the EGR amount and the intake pressure,
The opening correction amount of the EGR valve 11 that can offset the deviation from the difference between the target value and the learned value of the intake pressure is the same correction amount tKTE.
Any means can be used as long as it can be calculated as LF, and the calculation need not necessarily be executed only in the idle stable state. Further, when the calculation of the correction amount tKTELF is executed every time the routine is started, the correction amount memory described above is not required, and the calculated correction amount tK is obtained.
It suffices to have an appropriate memory for temporarily storing the TELF. Further, even in this case, if the learning of the intake pressure is also performed with the blunting process based on the equation (1), the value of the calculated correction amount tKTELF can be made more reliable. become able to.

Further, for the sake of convenience, the processing routine illustrated in FIG. 2 adopts a control structure for reading in the engine parameters required for executing various calculations each time. For each of these engine parameters, the same routine is used. Of course, the control structure may be collectively read at the time of starting. However, according to the routine illustrated in FIG. 2, when it is determined in step 101 that the engine is not in the idle stable state, the intake pressure PIM and the actual EGR valve opening AEL are set.
The reading process of F, intake air temperature THA, etc. is omitted, and the processing load of the microcomputer constituting the electronic control unit 40 is reduced.

By the way, in the apparatus of the above embodiment,
The fuel injection amount command value Q is used as information indicating the load state of the engine 1.
Although FINE is used, in addition, for example, the accelerator opening ACCP detected by the accelerator opening sensor 41,
It can be appropriately adopted as the information indicating the same load state. This is as shown in FIG.

[0067]

As described above, according to the present invention, no special device (hardware) is required, which is caused by the change with time of the intake system and the exhaust gas recirculation system of the engine. It becomes possible to feedback-correct the excess and deficiency of the EGR amount.

Therefore, in any case, a proper ideal EGR amount can always be obtained, and the generation of smoke and NOx can be suitably reduced.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing an EGR control procedure of the embodiment.

FIG. 3 is a schematic diagram showing a map for calculating a target intake pressure.

FIG. 4 is a graph showing the characteristics of the target intake pressure set in the map.

FIG. 5 is a schematic diagram showing a map for calculating an opening correction amount.

FIG. 6 is a graph showing the characteristic of the opening correction amount set in the map.

FIG. 7 is a schematic diagram showing a map for calculating a fuel injection amount command value.

FIG. 8 is a schematic diagram showing a map for calculating a target EGR valve opening.

FIG. 9 is a graph showing the characteristics of the target EGR valve opening set in the map.

FIG. 10 is a time chart showing a mode of correcting the EGR amount according to the embodiment.

[Explanation of symbols]

1 ... Diesel engine, 2 ... Cylinder bore, 3 ... Piston, 4 ... Combustion chamber, 5 ... Vortex chamber, 6 ... Intake manifold,
7 ... Intake port, 8 ... Exhaust port, 9 ... Exhaust manifold, 10 ... Exhaust poppet valve, 11 ... EGR valve (exhaust gas recirculation control valve), 12 ... Casing, 13 ... Inlet port, 14 ... Outlet port, 15 ... Conduit , 16 ... Exhaust gas extraction port, 17 ... Conduit, 18 ... Exhaust gas injection port, 1
9 ... Valve element, 20 ... Valve seat part, 21 ... Valve port, 22 ... Valve rod, 23 ... Diaphragm device, 24 ... Casing,
25 ... Diaphragm, 26 ... Diaphragm chamber, 27 ... Compression coil spring, 28 ... Conduit, 29 ... Negative pressure control valve, 30 ...
Negative pressure output port, 31 ... Negative pressure input port, 32 ... Negative pressure pump, 33 ... Conduit, 40 ... Electronic control device, 41 ... Accelerator opening sensor, 42 ... Rotation speed sensor, 43 ... Water temperature sensor, 44 ... Opening degree Sensor, 45 ... Intake temperature sensor, 46 ... Intake pressure sensor, 47 ... Idle switch.

Claims (3)

[Claims] 1. A recirculation control valve disposed in a recirculation passage for recirculating a part of exhaust gas of an internal combustion engine to an intake system of the engine and adjusting a recirculation amount of the exhaust gas, and the recirculation control. An opening degree detection means for detecting the actual opening degree of the valve, an intake pressure detection means for detecting the intake pressure which is the intake pipe internal pressure of the internal combustion engine, and an intake pressure learning means for learning the transition based on the detected intake pressure. And a target intake pressure calculation means for calculating the target value of the intake pressure based on the actual opening of the recirculation control valve detected by the opening detection means, and based on the difference between the target value of the intake pressure and the learned value. A correction amount calculation means for calculating an opening correction amount of the recirculation control valve capable of canceling the deviation, and a target opening calculation means for calculating a target opening of the recirculation control valve based on the load and the rotation speed of the internal combustion engine. And the calculated target opening is corrected by the correction amount. An exhaust gas recirculation control device for an internal combustion engine, comprising: a control unit that controls the opening degree of the recirculation control valve based on a value. 2. The intake pressure learning means and the target intake pressure calculation means perform the learning and the target value calculation of the intake pressure on the condition that the internal combustion engine is in an idle state. The calculation means calculates the correction amount based on the difference between the target value and the learned value of the intake pressure learned and calculated when the internal combustion engine is in the idle state, and updates and registers the correction amount in an appropriate storage means, The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the control means corrects the target opening degree of the recirculation control valve based on the latest correction amount registered in the storage means. 3. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the intake pressure learning means holds a value obtained by blunting a change in the detected intake pressure as the learned value.