JP3223674B2 - Exhaust gas recirculation system for internal combustion engine - Google Patents

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 system for an internal combustion engine that recirculates exhaust gas to an intake system of the internal combustion engine in order to reduce NOx emitted from the engine. The present invention relates to an improvement in an exhaust gas recirculation device configuration that is preferably adopted.

[0002]

2. Description of the Related Art As is well known as an exhaust gas recirculation device,
Part of the gas exhausted from an internal combustion engine, for example, a diesel engine, is taken out of the exhaust system, and the temperature, timing,
This device controls the flow rate and the like and recirculates it to the intake system of the engine. Also, by thus recirculating the exhaust gas to the intake system, the combustion temperature of the gas can be reduced,
It is also well known that the generation of harmful components of NOx (NO and NO2 of nitrogen oxides) in the combustion exhaust gas is suppressed.

In general, particularly in an exhaust gas recirculation system of a diesel engine, the amount (rate) of the exhaust gas to be controlled depends on a characteristic as shown in FIG. Will be set to.

That is, FIG. 10 shows an injection amount-exhaust gas circulation amount (rate) characteristic when the engine speed Ne is constant (const). Usually, as shown in FIG. The characteristic is that the recirculation amount (rate) of the exhaust gas is increased on the low load side with more excess air. In addition,
In FIG. 10, “QC” indicates a recirculation cut fuel injection amount (recirculation cut injection amount).

[0005]

As is apparent from the characteristics shown in FIG. 10, for example, in an acceleration state where the load suddenly increases,
The recirculation amount of the exhaust gas is controlled to be reduced or cut.

However, the above-mentioned exhaust gas recirculation system usually has a slight response delay of the control system. Particularly during such transient acceleration, the emission is controlled in spite of the fact that the fuel injection amount is increased. Gas recirculation does not decrease. Such a situation occurs. As described above, when the recirculation amount of the exhaust gas is not reduced as compared with the fuel injection amount, the combustion is performed at a low oxygen concentration with less intake air than in the steady state, and excessive smoke is generated.

This will be described in more detail with reference to FIG. That is, assuming now that the accelerator is operated to the opening degree as shown in FIG.
Accordingly, the fuel injection amount also increases in the manner shown in FIG. 11B, and shifts to the maximum injection amount. At this time, as shown in FIG. 11C, the command recirculation control amount of the exhaust gas is determined such that the above-mentioned recirculation cut injection amount QC becomes “0” as a target. , Will be controlled. However, the recirculation system has the above-mentioned response delay, and the actually controlled recirculation amount is delayed from the target recirculation amount as indicated by a broken line in FIG. 0 ". In other words, this fact is unnecessary, and the exhaust gas to be replaced with fresh air (new intake air) remains in the intake system over the period shown by hatching in FIG. Means For this reason, the excess air ratio λ during that period temporarily becomes smaller than the target value in the manner shown by the broken line in FIG. 11D, and as a result, the smoke also changes to the broken line in FIG. In the manner shown in FIG.

Conventionally, for example, Japanese Patent Application Laid-Open No. 61-6193
No. 6 or JP-A-55-78152.
In order to improve emission during acceleration, there is an apparatus for reducing the amount of recirculation of exhaust gas in accordance with a change in fuel injection amount during acceleration, as seen in the apparatus described in Japanese Patent Application Laid-Open Publication No. H11-163873. However, all of these conventional devices merely determine the reduction correction value for the exhaust gas recirculation amount in accordance with the acceleration increase of the fuel, and the recirculation caused by the response delay of the recirculation system described above. The exhaust gas remaining in the intake system cannot be fundamentally eliminated.

The present invention has been made in view of such circumstances, and it is possible to reliably reduce the recirculation exhaust gas remaining in the intake system due to a response delay of the recirculation system during acceleration. An object of the present invention is to provide an exhaust gas recirculation device for an internal combustion engine that can appropriately suppress excessive generation of smoke.

[0010]

According to the present invention, there is provided an exhaust gas recirculation system for an internal combustion engine for recirculating a part of exhaust gas of the internal combustion engine to an intake system of the internal combustion engine. A basic command value calculating means for calculating a basic command value for the recirculation amount of the exhaust gas based on the accelerator opening and the number of revolutions, and a correction value for a change amount of the calculated basic command value. Correction value calculating means, load change detecting means for detecting a load change of the internal combustion engine, and determining the recirculation amount of the exhaust gas with the basic command value until the detected load change exceeds a predetermined amount. When the detected load change exceeds a predetermined amount, the basic command value is corrected by the correction value to determine a recirculation amount of the exhaust gas.

[0011]

The basic command value for the amount of exhaust gas recirculation calculated through the basic command value calculating means means that the amount of recirculation basically has the characteristic shown in FIG. Is a command value for correcting the amount of exhaust gas recirculation to reduce the amount of oxygen consumed based on the increase in fuel injection amount during acceleration. However, as described above, it is not possible to eliminate the recirculation exhaust gas remaining in the intake system due to the response delay of the recirculation system using only the basic command value.

On the other hand, the correction value calculated through the correction value calculation means is, for example, based on the basic command value, and when the command value is corrected to decrease, the basic command value such as extremely increasing the degree of the reduction is used. It is calculated as a value corresponding to the amount of change in the value.

For this reason, when the detected load change exceeds a predetermined amount, that is, through the recirculation amount control means, the recirculation amount of the exhaust gas is determined as a value obtained by correcting the basic command value with this correction value. In some cases, even if there is a delay in the response of the recirculation system, the residual amount of the recirculated exhaust gas in the intake system due to the delay is quickly canceled.

[0014] The rapid cancellation of the residual exhaust gas in the intake system also allows the air-fuel ratio to be properly maintained, so that excessive smoke may be generated even during transient acceleration. Disappears.

The load change detecting means includes, for example, (a) an injection amount command value calculating means for calculating an injection amount command value of the internal combustion engine based on the accelerator opening and the rotational speed; And an injection amount change detecting means for detecting a change in the calculated injection amount command value. In this case, the correction value calculating means includes, for example, (c) First correction value calculating means for calculating a first correction value in proportion to the calculated basic command value for the recirculation amount of exhaust gas, and (d) the detected injection amount command value A second correction value calculating means for calculating a second correction value proportional to the difference value of the calculated injection amount command value based on the change of the first and second correction values. Maybe
And correction value setting means for setting a value corresponding to the sum of the two as the correction value. If the correction value is set as a value corresponding to the sum of the first and second correction values, the canceling action of the residual exhaust gas immediately after the basic command value has been reduced is more effectively performed. This canceling action is maintained over the entire period during which the fuel injection amount changes.

In this case, however, only one of the first correction value and the second correction value may be set as the correction value. Even in this case, the recirculation amount of the exhaust gas is determined in such a manner that the control amount is greatly reduced immediately after the start of the reduction correction of the basic command value, and the response delay of the recirculation system described above is determined. Is suitably absorbed.

When the load change detecting means has the above configuration, the correction value calculating means further includes: (f) calculating the exhaust gas recirculation cut fuel injection amount of the internal combustion engine based on the engine speed. (G) a first correction value for calculating a first correction value including a difference value between the calculated recirculation cut fuel injection amount and the calculated injection amount command value; Calculating means; (h) second correction value calculating means for calculating a second correction value proportional to a difference value of the calculated injection amount command value based on a change in the detected injection amount command value; (I) These calculated first or second correction values, or
And correction value setting means for setting a value corresponding to the sum of the two as the correction value. With such a configuration, it is possible to achieve substantially the same operation and effect as the above configuration.

In this case, the first correction value is:
Instead of the difference value between the recirculation cut fuel injection amount and the injection amount command value, a difference value between the current accelerator opening and the accelerator opening until the recirculation cut can be used.

The load change detecting means may be any as long as it can detect the presence or absence of the acceleration state based on the load change of the internal combustion engine. This may be configured as a means for detecting a change in the recirculation amount basic command value.

Further, in the these configurations, further comprising, the recirculation amount control means a correction value attenuation means for performing an operation allowed to over time attenuate the (j) before Kiho positive, -
When the detected load change is shifted from a state exceeding a predetermined amount to a state not exceeding the predetermined amount, the basic command value is corrected by a correction value attenuated through the correction value attenuating means. Determine the amount of exhaust gas recirculation. In other words, after the end of the acceleration state, the recirculation amount of the exhaust gas is gradually and smoothly shifted to the control amount determined by the basic command value. In other words, the return to the normal exhaust gas recirculation control from the so-called forced exhaust gas residual cancel operation is performed more smoothly.

[0021]

FIG. 1 shows an embodiment of an exhaust gas recirculation system for an internal combustion engine according to the present invention.

The apparatus of this embodiment is intended for a diesel engine, in which a part of the exhausted gas is taken out from an exhaust system, and the gas is recirculated to an intake system of the engine while appropriately controlling the flow rate. It is configured.

That is, in FIG. 1, an engine 1 is a diesel engine, and the engine 1 has an intake pipe 2 through which fresh air is sucked and an exhaust pipe 3 through which combustion gas is discharged.
And an exhaust gas recirculation mechanism 4 for recirculating a part of the gas discharged from the exhaust pipe 3 to the intake pipe 2. The exhaust gas recirculation mechanism 4 is also provided with a recirculation amount adjusting valve 5 for adjusting the amount of exhaust gas recirculation. The exhaust gas recirculation mechanism 4 recirculates the exhaust gas in accordance with the opening of the valve body 6. The amount is to be determined.

On the other hand, the opening degree of the valve body 6 of the recirculation amount adjusting valve 5 is adjusted in accordance with the operation of the negative pressure control valve 7. The operation amount is determined based on the recirculation amount command value EGRO output from the electronic control unit 8. That is,
The negative pressure control valve 7 to which the command value EGRO is applied from the electronic control unit 8 controls the negative pressure from the vacuum pump 9 to a predetermined value in accordance with the command value EGRO, and reduces the controlled predetermined negative pressure value. The degree of opening of the valve element 6 is determined by supplying it to the recirculation amount adjusting valve 5.

In this device, the recirculation amount command value EGRO output from the electronic control unit 8 is
The recirculation amount of the exhaust gas is determined. The engine 1 is provided with a well-known fuel supply device 10, which also controls a fuel injection amount and an injection timing for the engine 1 through a well-known injection amount control device 11 and an injection timing control device 12, respectively. It has become.
The fuel injection amount and the injection timing through the injection amount control device 11 and the injection timing control device 12 are also determined according to the injection amount command value Qi and the injection timing command value D output from the electronic control device 8, respectively. Become.

The electronic control unit 8 includes a well-known CPU, RA
It comprises a microcomputer having M, ROM, backup RAM, input / output ports and the like. In particular, in the apparatus of this embodiment, in order to determine a suitable value as the above-described recirculation amount command value EGRO from the accelerator opening signal (ACCP) and the engine speed signal (Ne), it is functionally required. , Have the configuration shown in FIG.

Next, with reference to FIG. 2, a configuration mainly related to the control of the amount of recirculated exhaust gas of the electronic control unit 8 and a specific function thereof will be described. First, the basic command value calculator 8
Reference numeral 0 denotes a portion for periodically calculating a basic command value EGRB for the exhaust gas recirculation amount from the accelerator opening signal ACCP and the engine speed signal Ne. This basic command value EGRB satisfies the characteristic shown in FIG. 10 for the same amount of exhaust gas recirculation, and is calculated as a value for performing a decrease correction in the mode shown in FIG. Is done.

Further, the injection amount command value calculating section 81 calculates the accelerator opening signal ACCP and the engine speed signal Ne from
This is a part for periodically calculating the command value Qi of the fuel injection amount to the engine 1. The arithmetic unit 81 has a memory for temporarily storing the obtained command value Qi. Each time, the newly obtained command value Qi and the previously obtained command value stored in the memory (this is the previous command value Qi) are stored. Command value Qi-1). In addition, the previous injection amount control device 11
Is the fuel injection amount command value Q
i will be given.

The injection amount change detection unit 82 detects a difference dQ between the current injection amount command value Qi output from the injection amount command value calculation unit 81 and the previous injection amount command value Qi-1. is there. Incidentally, the above-described acceleration state is determined as a state in which the difference dQ between the injection amount command values is larger than a predetermined value.

The control unit 83 compares the difference dQ between the injection amount command values detected by the injection amount change detection unit 82 with a predetermined value β to determine the presence or absence of an acceleration state. This is a part for controlling the active / inactive state of the first correction value calculator 84 and the second correction value calculator 85 to be described. When it is determined that the acceleration state has been terminated based on the above comparison, the control unit 83 adds the correction value attenuated by the correction value attenuating unit 87 for a certain period to the adding unit ADD.
Is also performed, but the details will be described later.

The first correction value calculating section 84, which is controlled to be active / inactive through the control section 83, is based on the calculated basic command value EGRB for the exhaust gas recirculation amount, and is proportional to the command value EGRB. First correction value CQEG
This is the part for calculating R. That is, it is assumed that the magnitude (absolute value) of the calculated first correction value CQEGR is proportional to the value of the basic command value EGRB as shown in FIG.

The second correction value calculation unit 85, which is similarly controlled to be active / inactive through the control unit 83, calculates a correction value of the injection amount command value (difference dQ between the injection amount command values) based on the detected change. This is a part for calculating a second correction value DQEGR proportional to the difference value of the calculated injection amount command value Qi.
The upper limit (lower limit) of the calculated second correction value DQEGR is limited to the value of the injection amount change dQ, for example, in the manner shown in FIG.

The correction value setting section 86 calculates a value corresponding to the sum of the calculated first correction value CQEGR and second correction value DQEGR as the correction value TE for the basic command value EGRB.
This is a part set as GR. The set correction value TEGR is output to the adder ADD and the correction value attenuator 87.

Here, the addition section ADD outputs a value obtained by adding the set correction value TEGR to the basic command value EGRB calculated by the basic command value calculation section 80 as the preceding final command value EGRO. It is. Therefore, when the control unit 83 determines that the vehicle is not in the acceleration state,
That is, when the first and second correction value calculation units 84 and 85 are in the inactive state, the calculated basic command value EGRB is directly provided to the preceding negative pressure control valve 7 as the final command value EGRO. Become like Conversely, the control unit 8
3, if it is determined that the vehicle is in the acceleration state, that is, if the first and second correction value calculation units 84 and 85 are in the active state, the calculated basic command value EGRB
Is given to the negative pressure control valve 7 as the final command value EGRO as corrected by the set correction value TEGR.

The correction value attenuating means 87 includes a control unit 83
After it is determined that the acceleration state has been completed, a predetermined attenuation dEGR is obtained from the correction value TEGR set by the correction value setting unit 86, and thereafter, the predetermined attenuation dEGR is obtained from the correction value TEGR over a certain period. This is a part for giving a value obtained by subtracting the attenuation dEGR to the adder ADD.
During a certain period after it is determined that the acceleration state has been completed, the control unit 83 controls the correction values sequentially attenuated by the correction value attenuating unit 87 to the adding unit ADD. As a result, after the end of the acceleration state, the recirculation amount of the exhaust gas gradually and smoothly changes to the basic command value E.
The control amount is shifted to the control amount determined by GRB.

FIG. 5 shows a control mode of the exhaust gas recirculation amount control by the apparatus of the embodiment. The operation of the apparatus of the embodiment will be further described with reference to FIG. It will be described in detail.

That is, assuming that the accelerator opening is rapidly increased and an acceleration operation is performed, the command value Q of the injection amount calculated through the injection amount command value calculation unit 81 keeps the engine speed Ne constant (constant). ), It changes, for example, in the manner shown in FIG. Where dQ
Is a change in the injection amount command value during one control cycle of the apparatus (the difference between the present command value Qi and the previous command value Qi-1). QC is the recirculation cut injection amount described above.

On the other hand, with respect to the fuel injection amount Q, the basic command value EGRB for the exhaust gas recirculation amount calculated through the basic command value calculating section 80 in this case is shown in FIG.
As shown in (b), the recirculation cut injection amount QC
, The value is determined so as to become “0”.
However, the recirculation system has the above-described response delay, and the fact that the actually controlled recirculation amount reaches “0” later than this determined value will be described with reference to FIG. As described above.

Therefore, in the apparatus of this embodiment, the control unit 83
Based on the determination that the vehicle is in the accelerating state, a correction value as shown in FIG. 5C is obtained as the first correction value CQEGR, and a correction value as shown in FIG. The correction values as shown in (d) respectively correspond to the basic command value EGRB.
And change in the injection amount command value (difference in injection amount command value dQ)
Is calculated in accordance with.

In the apparatus of this embodiment, the first correction value CQEGR and the second correction value DQE
GR is added and set as the correction value TEGR through the correction value setting unit 86, and the calculated basic command value EGRB is forcibly corrected, so to speak, by the set correction value TEGR.

As a result, the final command value EGRO applied to the negative pressure control valve 11 as the output of the electronic control unit 8 is:
As shown by the solid line in FIG. 5 (e), the control value for the exhaust gas recirculation amount becomes a value at which the control amount for the exhaust gas recirculation amount is drastically reduced at the same time as the acceleration state is detected. By the way, in this case, FIG.
FIG. 5 shows the basic command value EGRB illustrated in FIG.
By the action of the correction values shown in (c) and (d) of FIG. 5, the control amount command value for the exhaust gas recirculation amount is suppressed to the value “0” together with the detection of the acceleration state. become.

As a result, the recirculated exhaust gas remaining in the intake system due to the response delay of the recirculation system described above is promptly canceled. The cancellation also allows the air-fuel ratio to be properly maintained. And this is
This means that a situation where excessive smoke is generated can be avoided well even during the acceleration transition.

In FIG. 5D, a point PE indicates an end point of the acceleration state, and a gradually changing portion thereafter is controlled to be attenuated stepwise through the correction value attenuator 87 immediately after the end of the acceleration state. The transition of the correction value TEGR is shown.

In the example of FIG. 5, the load change in a high load region where the injection amount Q exceeds the recirculation cut injection amount QC is assumed, but the injection amount Q does not reach that level. In other words, when the load changes in a low load range, such control of the recirculation amount is performed, for example, in the manner shown in FIG.

That is, when there is a load change (acceleration) in such a low load region, the basic command value EGRB for the recirculation amount is higher than “0” as shown in FIG. , The attenuation correction amount is set.
In this case, the final command value EGRO which is forcibly corrected by the first and second correction values CQEGR and DQEGR shown in FIGS. 6B and 6C and output is also:
It is not necessarily suppressed to “0”.
The state shown by the solid line in (d) is obtained.

Thus, even in a low load range,
When a load change (acceleration) occurs, the command value for the exhaust gas recirculation amount is drastically reduced at the same time as the load change is detected. Become. For this reason, also in this case, the recirculation exhaust gas remaining in the intake system due to the response delay of the recirculation system is promptly canceled, and the air-fuel ratio in the intake system is always properly maintained. .

FIG. 7 and FIG. 8 are flowcharts showing the processing procedure of such an apparatus (mainly the electronic control unit 8) for controlling the amount of recirculated exhaust gas.
Finally, details of the processing performed by the electronic control unit 8 to implement the recirculation amount control will be sequentially described based on FIGS. 7 and 8.

First, the electronic control unit 8 executes initialization based on, for example, that the key switch of the vehicle has been turned on from the off state (step 100). The initialization includes initialization of a counter and a flag in the CPU or a RAM (data memory).

Next, at step 101, the electronic control unit 8 fetches engine parameters such as the accelerator opening signal ACCP, the engine speed signal Ne, and the water temperature sensor signal THW. A fuel injection amount command value Qi is calculated from the accelerator opening signal ACCP and the engine speed signal Ne. This command value calculation is performed through the previous injection amount command value calculation unit 81. The computing unit 81 has a memory for temporarily storing the obtained command value Qi. The command value stored in this memory is used as the "previous command value Qi-1" in the next control. Reading is performed as described above.

In step 103, the electronic control unit 8 similarly calculates an injection timing command value D from the accelerator opening signal ACCP and the engine speed signal Ne. In FIG. 2, a portion for calculating the injection timing command value D is omitted for convenience.

The electronic control unit 8 then proceeds to step 104
It is determined whether or not the exhaust gas recirculation control is possible. This determination is based on the water temperature sensor signal T
If the water temperature value THW is larger than the predetermined value α, the control is performed in step 1
If the water temperature value THW is smaller than the predetermined value α, the control is determined to be impossible and the process proceeds to step 118.

The processing of steps 105 to 125 is a part in which the processing relating to the above-described exhaust gas recirculation control by the apparatus of this embodiment is defined. That is, the electronic control unit 8
In step 105, first, a basic command value EGRB for the exhaust gas recirculation amount is calculated based on the accelerator opening signal ACCP and the engine speed signal Ne. The calculation of the basic command value is performed through the basic command value calculation unit 80 described above.

Next, the electronic control unit 8 proceeds to step 106
Then, it is determined whether or not the basic command value EGRB is in the cut state. If the basic command value EGRB is in the cut state, the process proceeds to step 126, and if not, the process proceeds to step 107. Here, a description will be given of a case where the camera is not in the cut state.

In step 107, the injection amount command value stored in the memory as the process of step 102 of the previous control is read out from the same memory as the previous command value Qi-1. The difference dQ between the command value Qi obtained by the above control and the previous command value Qi-1 is obtained. As described above, the change (difference) of the injection amount command value is extracted through the injection amount change detection unit 82.

In step 109, it is determined through the control unit 83 whether or not the difference dQ is larger than a predetermined value β.
The processing after step 110 is executed. On the other hand, this difference d
When it is determined that the value of Q is smaller than the predetermined value β,
The process proceeds to step 115 as the non-acceleration state.

If the difference dQ between the injection amount command values is larger than the predetermined value β, the first correction value CQEGR is calculated in step 110. As described above, the first correction value CQEGR is calculated based on the basic command value EGRB for the exhaust gas recirculation amount as a value proportional to the command value EGRB through the first correction value calculation unit 84. Further, as is apparent from FIG. 5C or FIG. 6B, the first correction value CQEGR is effective for promptly canceling the residual amount of the recirculated exhaust gas particularly at the start of acceleration. It becomes a correction value.

In step 111, the second correction value DQEGR is calculated in addition to the first correction value CQEGR. The second correction value DQEGR is calculated through the second correction value calculator 85 as a value proportional to the difference between the previous injection amount command values Qi based on the difference dQ between the injection amount command values calculated in step 108. Is calculated. Further, as is clear from FIG. 5D or FIG. 6C, the second correction value DQEGR is effective for compensating for the decrease in the oxygen concentration of the combustion chamber due to the change in the injection amount in the acceleration state. It becomes a correction value.

Next, at step 112, the first and second correction values CQEGR and DQEGR calculated at step 110 and step 111 are all added to set a total correction value TEGR. This total correction value TEG
The setting of R is performed through the correction value setting unit 86.

Then, the electronic control unit 8 executes step 113
The basic command value EGRB obtained above is converted to the total correction value TE.
The final command value EGRO for the exhaust gas recirculation amount is calculated by correcting with GR. This is executed in the manner of EGRO ← EGRB-TEGR through the addition unit ADD. When the first and second correction values CQEGR and DQEGR are obtained as negative values as shown in FIG. 5 or FIG. 6, the calculation is a simple addition.

Then, in step 114,
It is determined whether or not the obtained final command value EGRO is positive,
If not positive, at step 125, this command value EGR
Clear O to "0". This corresponds to the process in FIG. 5 (e) where the negative component (actually impossible) of the final command value EGRO is limited to the value “0”.

After the final command value EGRO is cleared to "0" in this way, or when it is determined in the above-mentioned step 114 that the obtained final command value EGRO is positive, the electronic control unit 8 executes the current The output process of step 126 is executed as the last process of the control.

That is, in step 126, the injection amount command value Qi calculated in step 102 is applied to the injection amount control device 11, and the injection timing instruction value D similarly calculated in step 103 is applied to the injection amount control device 11. The final command value EGRO calculated through the injection timing control device 12 and through step 113 is output to the negative pressure control valve 7.

The processing which is exceptional in the above description is executed in the following manner. First, when it is determined in step 104 that the water temperature value THW has not reached the predetermined value α, in step 118, the basic command value EGR
B is cleared to "0". In this case, step 106
Then, the recirculation cut state is determined, and the routine jumps to step 126, where the recirculation cut value, that is, the final command value EGRO = 0, is output to the negative pressure control valve 7.

When it is determined in step 109 that the difference dQ between the injection amount command values is less than the predetermined value β, the routine jumps to step 115, in which the following is performed with respect to the correction value obtained during acceleration. Is executed through the correction value attenuating section 87.

First, at step 115, it is determined whether or not the vehicle was in an acceleration state last time. As a result, if it is determined that the previous state was the acceleration state, it is determined that the state has been shifted from the acceleration state to the non-acceleration state.
At 17, the attenuation dEGR per one control is calculated.

Here, the number of times of attenuation n is obtained as a function of the number of revolutions Ne in order to synchronize with the number of revolutions of the engine Ne. In addition, the value of the number of times of attenuation n itself is arbitrary. For example, in FIG. 5D or FIG.
The number of times that the desired inclination of the gradually changing portion shown after E is satisfied is set according to the rotational speed Ne in each case.

The attenuation dEGR is obtained as dEGR ← (TEGR / n) based on the obtained number n of attenuations, and the obtained attenuation dEGR is appropriately prepared for the next and subsequent control. Is stored in the memory.

Thereafter, in step 118, based on the obtained attenuation amount dEGR, the total correction value TEGR is corrected for attenuation in the manner of TEGR ← TEGR-dEGR.

In step 119, the corrected total correction value T
It is determined whether the EGR is negative. As a result, the correction value TE
If the GR is positive, the previous step 113
And executes the above-described correction based on the correction value TEGR.

As a result of the determination in step 119,
When the attenuation-corrected correction value TEGR is negative, the routine proceeds to step 120, where a flag process (f ← 1) indicating that the attenuation control has been completed is performed to prepare for the next control. In this case, at the same time, the next step 12
In step 1, the total correction value TEGR is cleared to "0". This prevents the basic command value EGRB from being erroneously corrected thereafter.

On the other hand, if it is determined in step 115 that the vehicle is still in the non-acceleration state, it is determined in step 122 whether or not the damping control has been completed. As a result, if the attenuation is in progress (the flag is not set), the process proceeds to step 123, and if the attenuation is completed (the flag is set), the flag is cleared in preparation for the next control (step 124). .

In step 123, step 117
The attenuation amount dEGR stored in step (1) is retrieved from the memory, and the correction value TEGR is further subjected to the attenuation correction in step 118.

The correction value TEG to be corrected for attenuation in the above manner
R is always the same as in step 11 above, as long as its value is positive.
It will be reflected after 3. And step 12
After the output processing in step 6, the control returns to step 101 again, and the same control as described above is repeated. As a result, the gradual change control in the mode shown after the point PE in FIG. 5D or FIG. Will be realized.

As described above, according to the apparatus of this embodiment, the first correction value effective for promptly canceling the residual amount of the recirculated exhaust gas, especially at the start of acceleration, and the injection in the accelerated state The basic command value of the exhaust gas recirculation amount in the accelerated state is forcibly corrected by the sum of the second correction value and the second correction value effective for compensating for the decrease in the oxygen concentration in the combustion chamber due to the change in the amount.

Therefore, the recirculated exhaust gas remaining in the intake system due to the response delay of the recirculation system is promptly canceled, and the air-fuel ratio in the intake system is always properly maintained. become.

Thus, even when the acceleration is transient, a situation in which excessive smoke is generated can be satisfactorily avoided. This also makes it possible to increase the normal exhaust gas recirculation amount (rate) when the smoke level during the acceleration transition is constant, and further reduce the amount of NOx. It also means that it becomes possible.

In the apparatus of this embodiment, the basic command value is gradually corrected by the correction value gradually attenuated for a certain period immediately after the end of the acceleration state. After the end of the acceleration state, the control is very smoothly shifted to the recirculation control based on the basic command value.

In the apparatus of the above embodiment, the basic command value for the recirculation amount is used as the first correction value for canceling the residual amount of the recirculated exhaust gas. Alternatively, it is also possible to use a deviation between the injection amount before acceleration and the recirculation cut injection amount.
That is, in this case, the electronic control unit 8 includes, for example, as shown in FIG. 9, a recirculation cut injection amount calculation unit that calculates the exhaust gas recirculation cut fuel injection amount of the engine based on the engine speed Ne. A first correction value calculation unit 89 for calculating a first correction value consisting of a difference value between the calculated recirculation cut fuel injection amount and the calculated injection amount command value; It will be a configuration that includes. In FIG. 9, the same elements as those in FIG. 2 are denoted by the same reference numerals.

Further, as the first correction value, a deviation between the current accelerator opening and the accelerator opening until the recirculation cut can be used. Even in these cases,
In the mode according to FIG. 5 (c) or FIG. 6 (b), the first
It is possible to obtain a desired value as a correction value for.

Further, in the apparatus of the above embodiment, the change in the injection amount command value is used to detect the acceleration state. However, such an acceleration state may also be caused by a change in the accelerator opening or the basic command value for the recirculation amount. Can also be detected by the change in. In short, any element that changes, directly or indirectly, associated with a change in the load state of the engine can be employed as a means for detecting the acceleration state.

In the apparatus of the above-described embodiment, as a more preferable example in practical use, the first and second correction values are simultaneously used to correct the basic recirculation amount command value in the acceleration state. However, it goes without saying that the exhaust gas recirculation device according to the present invention is not limited to such a configuration. That is, even if only one of these correction values is used, the same effect as above can be obtained. Moreover, in this case, the correction value may be any value that can correspond to the amount of change with respect to the calculated basic command value.

Although the above-described attenuation control of the correction value is also a practically useful control, the presence or absence of the configuration relating to the attenuation control is arbitrary, and the exhaust gas recirculation apparatus according to the present invention has such a configuration. It is not limited to the configuration. Even if such a configuration relating to the damping control is not employed, the smoke suppression effect in the above-described manner can be obtained.

[0083]

As described above, according to the present invention, the recirculation exhaust gas remaining in the intake system due to the response delay of the recirculation system during acceleration transient can be promptly canceled. Become. Then, the air-fuel ratio is appropriately maintained by such a prompt cancellation of the exhaust gas residue in the intake system, and even if there is a transition during acceleration, excessive smoke is not generated.

[Brief description of the drawings]

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

FIG. 2 is a block diagram functionally showing the configuration of an electronic control unit of the apparatus of the embodiment.

FIG. 3 is a graph showing a relationship between a first correction value calculated by a first correction value calculation unit shown in FIG. 2 and a basic command value.

FIG. 4 is a graph showing a relationship between a second correction value calculated by a second correction value calculation unit shown in FIG. 2 and a change in injection amount.

FIG. 5 is a timing chart showing an operation example of the apparatus of the embodiment.

FIG. 6 is a timing chart showing another operation example of the apparatus of the embodiment.

FIG. 7 is a flowchart showing a control procedure by the apparatus of the embodiment.

FIG. 8 is a flowchart showing a control procedure by the apparatus of the embodiment.

FIG. 9 is a block diagram functionally showing the configuration of an electronic control unit of another embodiment of the exhaust gas recirculation device for an internal combustion engine according to the present invention.

FIG. 10 is a graph showing a relationship between a general fuel injection amount and an exhaust gas recirculation amount (rate) in a diesel engine.

FIG. 11 is a timing chart showing general characteristics of exhaust gas recirculation amount control characteristics during transient acceleration in a diesel engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Intake pipe, 3 ... Exhaust pipe, 4 ... Exhaust gas recirculation mechanism, 5 ... Recirculation amount adjustment valve, 6 ... Valve element, 7 ... Negative pressure control valve, 8 ... Electronic control device, 9 ... Vacuum pump, 1
0: fuel supply unit, 11: injection amount control unit, 12: injection timing control unit, 80: basic command value calculation unit, 81: injection amount command value calculation unit, 82: injection amount change detection unit, 83: control unit, 84: first correction value calculator, 85: second correction value calculator, 86: correction value setting unit, 87: correction value attenuator, 88 ...
Recirculation cut injection amount calculator, 89... First correction value calculator,
ADD: addition section.

Continuation of the front page (72) Inventor Shigeki Hidaka 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-60-192870 (JP, A) JP-A-5-172008 ( JP, A) JP-A-62-291458 (JP, A) JP-A-61-61936 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 25/07 530 F02M 25 / 07 550 F02M 25/07 570

Claims (4)

(57) [Claims] An exhaust gas recirculation device for an internal combustion engine for recirculating a part of exhaust gas of the internal combustion engine to an intake system of the internal combustion engine, wherein the exhaust gas recirculation is performed based on an accelerator opening and a rotation speed of the internal combustion engine. Basic command value calculating means for calculating a basic command value for the circulating amount, correction value calculating means for calculating a correction value for a change amount of the calculated basic command value , and attenuating the correction value with time Compensation value reduction
Decay means, load change detection means for detecting a load change of the internal combustion engine, and until the detected load change exceeds a predetermined amount, determines the recirculation amount of the exhaust gas with the basic command value, and performs the same detection. When the load change to be performed exceeds a predetermined amount, the recirculation amount of the exhaust gas is determined based on a value obtained by correcting the basic command value with the correction value , and the detected load change is determined.
Transition from a state where the amount exceeds the fixed amount to a state where the amount does not exceed the specified amount
The basic command value is passed through the correction value attenuating means.
The exhaust gas at a value corrected by the attenuated correction value.
An exhaust gas recirculation device for an internal combustion engine, comprising: recirculation amount control means for determining a recirculation amount of the exhaust gas. 2. An injection quantity command value calculating means for calculating an injection quantity command value of an internal combustion engine based on an accelerator opening and a rotation speed of the internal combustion engine, and the calculated injection quantity command value. And a correction value calculating means, based on a basic command value for the calculated recirculation amount of exhaust gas, the correction value calculating means comprising: A first correction value calculating means for calculating a first correction value; and a second correction value proportional to a difference value of the calculated injection amount command value based on a change in the detected injection amount command value. And a correction value setting means for setting the calculated first or second correction value or a value corresponding to the sum of the two as the correction value. The exhaust gas recirculation of the internal combustion engine according to claim 1. Apparatus. 3. A part of exhaust gas of an internal combustion engine is absorbed by the engine.
The exhaust gas recirculation system of an internal combustion engine that recirculates
The exhaust gas based on the accelerator opening and the rotational speed of the internal combustion engine.
Basic finger for calculating basic command value for gas recirculation
Command value calculating means, and compensating for a change amount of the calculated basic command value.
Correction value calculating means for calculating a positive value, load change detecting means for detecting a load change in the internal combustion engine, and the above-described base value until the detected load change exceeds a predetermined amount.
This command value determines the amount of exhaust gas recirculation and detects it
When the load change exceeds a predetermined amount, the basic command
The value of the exhaust gas is corrected using the value corrected by the correction value.
Recirculation amount control means for determining a circulation amount, wherein the load change detection means includes a recirculation amount control means for the internal combustion engine based on an accelerator opening and a rotation speed.
An injection amount command value calculating means for calculating a fuel injection amount command value, and an injection amount change value detecting a change in the calculated injection amount command value.
Is configured to include a reduction detecting means, said correction value calculation means, exhaust gas recirculation mosquito the engine based on the rotational speed of the internal combustion engine
Recirculation cut injection amount calculating means for calculating the cut fuel injection amount
And the calculated recirculation cut fuel injection amount and the calculated
Calculates a first correction value consisting of a difference value from the injection amount command value
First correction value calculating means for performing the calculation based on a change in the detected injection amount command value.
The second correction value proportional to the difference value of the injection amount command value
A second correction value calculating means for calculating, and the calculated first or second correction value, or both
Correction value setting for setting a value corresponding to the sum of
And an exhaust gas recirculation device for an internal combustion engine, comprising: 4. An exhaust gas recirculation system for an internal combustion engine according to claim 3.
In the circulating device, the correction value calculating means includes
Correction value that performs an operation to attenuate the corrected correction value over time
Means for controlling the amount of recirculation.
Transition from a state where the amount exceeds the fixed amount to a state where the amount does not exceed the specified amount
The basic command value is passed through the correction value attenuating means.
With the value corrected by the attenuated correction value, the exhaust gas
Exhaust gas for an internal combustion engine characterized by determining the amount of recirculation
Recirculation device.