JP2609758B2 - Exhaust gas recirculation control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device that controls a part of exhaust gas of an internal combustion engine to recirculate to an intake pipe of the internal combustion engine.

[Prior Art] Conventionally, exhaust gas recirculation as a means to reduce the NO _X in the exhaust gas of an internal combustion engine (hereinafter, EGR) exhaust gas recirculation control system for controlling (hereinafter, EGR control unit) is widely used I have. This EGR control device is BPT (Back Pressure Transd
ucer) EGR is controlled by an exhaust pressure control method using a valve.

[Problem to be Solved by the Invention] Since the above-described conventional EGR control device is configured using a BPT valve or the like, the exhaust gas recirculation amount, that is, the EGR flow rate cannot be directly detected. E due to deterioration
If the GR flow rate is increased, and lead to deterioration of the driver kink Tay, also when the EGR flow rate is decreased, there is a problem that NO _X components in the exhaust gas temperature of the engine rises to increase. Also, after the ignition key switch is turned on and the internal combustion engine is started, the actual EGR rate (first exhaust gas recirculation rate) coincides with the target EGR rate (second exhaust gas recirculation rate) for a while due to changes over time and the like. Without this, there is a problem that the exhaust gas is deteriorated during this time. Furthermore, even if the EGR control device is in an abnormal state due to deterioration of components in the EGR control device, the EGR flow rate cannot be directly detected, so that it is difficult to detect an abnormality in the device.

[Means for Solving the Problem] To solve such a problem, claim 1 of the present invention is provided.
An exhaust gas recirculation control device according to the present invention is an exhaust gas recirculation control device that performs control to recirculate a part of the exhaust gas of the internal combustion engine to the internal combustion engine again, wherein a recirculation pipe that recirculates the exhaust gas of the internal combustion engine to an intake pipe, A recirculation valve for controlling a flow rate of exhaust gas flowing through the recirculation pipe; recirculation valve passage area control means for controlling a passage area of the recirculation valve; operating state detection means for detecting an operation state of the internal combustion engine; Means for detecting a differential pressure between a pressure from the intake pipe side and a pressure from the exhaust pipe side, which is disposed at a position on the bypass passage for detecting a pressure difference between a pressure value near the outlet of the pipe and the reflux pipe; A first value based on the differential pressure and a detection value detected by the operating state detection means.
Means for calculating the exhaust gas recirculation rate, and means for calculating a second exhaust gas recirculation rate corresponding to the detection value detected by the operating state detecting means. The feedback control for increasing or decreasing the passage area of the recirculation valve so as to eliminate the deviation from the exhaust gas recirculation rate of No. 2 is performed.

An exhaust gas recirculation control device according to a second aspect of the present invention is the exhaust gas recirculation control device according to the first aspect, wherein a deviation between the first exhaust gas recirculation ratio and the second exhaust gas recirculation ratio or a difference between the first exhaust gas recirculation ratio and the second exhaust gas recirculation ratio. It is provided with storage means for storing a value corresponding to the deviation.

An exhaust gas recirculation control device according to a third aspect of the present invention is the exhaust gas recirculation control device according to the first aspect, which detects a mismatch between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate. In this case, the failure is diagnosed.

[Operation] A recirculation valve in a direction in which the deviation between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate disappears, that is, so that the first exhaust gas recirculation rate and the second exhaust gas recirculation rate match. The increase or decrease control of the passage area is performed, and as a result, accurate EGR control according to various operating conditions can be performed.

Further, a differential pressure is calculated from a difference between the detected pressure value of the intake pipe and the detected pressure value of the outlet of the recirculation valve.

Further, since a deviation between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate or a value corresponding to the deviation is stored,
Accurate EGR control can be performed even immediately after the ignition key switch is turned on.

In addition, a failure is determined by detecting a mismatch between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate.
Device failures can be detected directly and accurately.

Example Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of an exhaust gas recirculation control device according to the present invention. In the figure, 1 is an engine, 3 is an intake pipe, 4 is an intake manifold, 5 is an injector, 6 is a pressure sensor, 7 is a throttle valve, 8 is a throttle opening sensor, 11 is a recirculation valve, and 12 is a passage area control actuator. (Hereinafter, EGR solenoid), 13 is an ignition coil, 14 is an igniter, 15 is an exhaust pipe, 17 is a water temperature sensor,
18 is a differential pressure sensor, 20 is a battery, 21 is an ignition key switch, 22 is an electronic control unit, and 23 is a warning lamp.

That is, in FIG. 1, the pressure sensor 6 is
This is a semiconductor type pressure sensor that detects the intake air pressure in order to measure the amount of air taken into the engine 1 through the intake manifold 4 through the intake manifold 4. The injector 5 is arranged upstream of the throttle valve 7 and injects fuel. The throttle valve 7 is provided with a throttle opening sensor 8 for detecting the opening of the throttle valve. The water temperature sensor 17 is a thermistor-type sensor that detects the cooling water temperature of the engine 1. Further, the ignition coil 13 ignites by a signal from the igniter 14 and sends out the generated ignition signal to the electronic control unit 22.

The recirculation valve 11 is a vacuum servo type valve arranged in an exhaust gas recirculation path connecting the intake pipe 3 and the exhaust pipe 15. The EGR solenoid 12 is connected between the diaphragm chamber of the recirculation valve 11 and the intake pipe 3 and controls the above-mentioned negative pressure to the diaphragm chamber of the recirculation valve 11 according to a signal from the electronic connection unit 22. Then, the passage area of the recirculation valve 11 is changed by the negative pressure of the diaphragm chamber. Further, a bypass of the exhaust gas recirculation path is provided between the intake pipe 3 and the vicinity of the outlet of the recirculation valve 11, and a differential pressure sensor 18 is installed on the bypass, and the pressure value of the intake pipe 3 and the recirculation valve 11 The differential pressure from the pressure value near the outlet, that is, the differential pressure between two points is detected.

Next, the electronic control unit 22 controls the passage area of the EGR recirculation valve 11 by inputting signals from the pressure sensor 6, the throttle opening 8, the ignition coil 13 and the water temperature sensor 17. That is, the electronic control unit 22 determines the control amount of the EGR solenoid 12 for controlling the EGR flow rate and drives and controls the EGR solenoid 12.

FIG. 2 is a detailed block diagram of the electronic control unit 22. In FIG. 1, reference numeral 100 denotes a microcomputer, a CPU 200 for calculating a control amount of the EGR solenoid 12 according to a predetermined program, a free-running counter 201 for measuring a rotation cycle of the engine 1, and a drive applied to the EGR solenoid 12. Timer 202 that measures the duty ratio of signals, A / D converter 203 that converts analog input signals to digital signals, RAM2 that is used as work memory
05, a ROM 206 storing a program, an output port 207 for outputting a drive signal, a common bus 208, and the like. A first input interface circuit 101 shapes the waveform of the primary ignition signal of the ignition coil 13 and outputs it to the microcomputer 100 as an interrupt signal. When the interrupt signal is generated, the CPU 200 reads the value of the counter 201, calculates the cycle of the engine speed from the difference between the read value and the previous read value, and stores the cycle in the RAM 205. Reference numeral 102 denotes a second input interface circuit, which inputs each signal of the pressure sensor 6, the throttle opening sensor 8, the water temperature sensor 17, the differential pressure sensor 18, and the like and outputs the signal to the A / D converter 203. . An output interface circuit 104 amplifies the drive output from the output port 207 and outputs the amplified drive output to the EGR solenoid 12.

FIG. 3 is an explanatory diagram showing the relationship between the pressure in the intake pipe 3 and the pressure difference between two points output from the pressure sensor 18. According to this explanatory diagram, as the EGR flow rate increases, the pressure difference between two points, that is, the output value of the differential pressure sensor 18 increases.

FIG. 4 is an explanatory diagram for explaining the relationship between the output of the differential pressure sensor 18 and the EGR rate under different operating conditions, that is, different load conditions of the internal combustion engine. According to this explanatory diagram, when the load state of the internal combustion engine is A and B,
It can be seen that the relationship between the differential pressure between the two points of the differential pressure sensor 18 and the EGR rate is different. According to the present invention, the actual EGR rate is calculated in consideration of the load state of the internal combustion engine, and as a result, an appropriate EGR flow rate is controlled in accordance with the operating condition.

Hereinafter, the operation of the CPU 200 of the exhaust gas recirculation control device of the present invention will be described with reference to the flowcharts of FIGS.

FIG. 5 shows the processing of the main routine. That is, another control process is performed in step 300, and when this process ends, an EGR control process for performing exhaust gas recirculation control is performed in step 301, and the process returns to step 300 again.

 Next, the EGR control processing shown in FIG. 6 will be described.

In step 350, the engine speed Ne is detected. Subsequently, at step 351, the pressure value Pb of the intake pipe 3 is detected. Then, the EGR operation region is determined in step 352 from the detected engine speed Ne and the intake pipe pressure value Pb, and in step 353, the EGR operation region is determined.
It is determined whether or not it is in the operation area. If it is in the EGR operation region, a target EGR rate T _EGR (second exhaust gas recirculation rate) is calculated from the engine speed Ne and the intake pipe pressure value Pb in step 354, and then in step 355, the target EGR rate T to calculate a basic EGR control quantity K _bASE depending on _EGR.

Then, in step 356, the pressure difference P1 between the intake pipe 3 and the recirculation valve 11 is detected based on the signal from the differential pressure sensor 18, and the relationship between the pressure difference P1 and the actual EGR rate P _EGR is shown in FIG. As shown by, the pressure difference P1 is corrected based on the load state of the internal combustion engine in step 357, and the actual EGR rate P _EGR (first exhaust gas recirculation rate) is calculated. I do. That is, the actual EGR rate P _EGR is calculated by detecting the pressure value Pb of the intake pipe 3 and correcting the pressure difference P1 based on the detected value. Then, the actual EGR from the target EGR ratio T _EGR based on the graph shown in FIG. 7 at step 358
The control gain ΔK _EGR is calculated from the value obtained by subtracting the rate P _EGR .

7 is a graph showing characteristics of control gains [Delta] K _EGR. That is, the value obtained by subtracting the actual EGR ratio P _EGR from the target EGR ratio T _EGR on the horizontal axis respectively show the values of the control gain [Delta] K _EGR corresponding to this value on the vertical axis.

Then, to calculate the EGR control correction value K _EGR by adding EGR control correction value K _EGR before calculation in the control gain [Delta] K _EGR in step 359. Thereafter, the EGR control correction value K obtained in step 359
_{The EGR} control value K is calculated by adding the basic control amount K _BASE to the EGR (step 360), and the control duty D _EGR is calculated from the obtained EGR control value K by using the EGR control value K and the control duty D shown in FIG. Calculate based on the graph showing the relationship (step 36
1), EGR solenoid based on this control duty D _EGR
12 is driven (step 362). By such control, the deviation between the target EGR rate T _EGR and the actual EGR rate P _EGR is eliminated,
The target EGR rate T _EGR matches the actual EGR rate P _EGR .
FIG. 9 is an explanatory diagram showing the definition of the control duty D. _Assuming that the ON time is T _oN and one cycle is T, the control duty D is expressed by the following equation. That is, Also, if this device is in the idling state, for example, EG
If it is not in the R operation region and is determined to be “N” in step 353, it is determined in step 363 that the EGR flow rate is not set.
While setting the EGR control value K to “0”, step 361
, The control duty _DEGR is calculated from the EGR control value of the value “0”, and the EGR solenoid 12 is driven in step 362 by the control duty _DEGR .

Next, FIGS. 10 and 11 show the second embodiment of the EGR control device of the present invention.
6 is a flowchart showing the operation of the embodiment. First, the tenth
Description will be made from the flowchart of FIG.

In step 400, it is determined whether the power is turned on for the first time after the battery 20 is mounted. This is to detect and determine that the output voltage of the second power supply circuit 106 connected to the battery 20 has changed from a low voltage value to a high voltage value. If this is determined to be “Y”, in step 401 EGR
The control correction value K _EGR is set to “0”, and thereafter, other control processing (step 402) and EGR control processing (step 403) are sequentially performed. If it is determined in step 400 that the first power-on after the battery 20 is mounted is "N", that is, if the battery 20 is already mounted and only the ignition key switch 21 is turned on, the EGR Without setting the control correction value K _EGR to “0”, the RAM
EGR control correction value K _EGR stored in 205 as it is used in the subsequent processing step 402.

 Next, the flowchart of FIG. 11 will be described.

The processing in steps 450 to 459 of this flowchart corresponds to steps 350 to 3 in the flowchart of FIG.
Since the processing is the same as the processing in 59, detailed description thereof will be omitted. That is, in steps 450 to 459, the EGR control correction value K _EGR in the EGR operation region is calculated, and the calculated EGR control correction value K _EGR is stored in step 460, and the EGR calculated in step 459 is calculated. Control correction value
An EGR control value K is calculated by adding the basic control amount K _BASE to K _EGR (step 461), and a control duty D _EGR is calculated from the obtained EGR control value K (step 462).
_{The EGR} solenoid 12 is driven based on the EGR (Step 46
3).

In this way, when the EGR control correction value K _EGR is calculated and stored, and when this device is powered on, if this is not the first power-on after the battery 20 is mounted, Since the stored EGR control correction value _KEGR is used as the correction value before the calculation, the EGR control immediately after the ignition key switch 21 is turned on can be accurately performed.

FIGS. 12 to 14 are flowcharts showing the operation of the third embodiment of the EGR control device of the present invention. First,
Description will be made from the flowchart of FIG.

In other words, in the processing in steps 500 and 501, other control processing and EGR control processing are sequentially executed as in steps 300 and 301 in the flowchart of FIG. And
After the EGR control processing in step 501 is executed, a failure determination processing for determining a failure of the device is performed in step 502, and the process returns to step 500.

Next, details of the failure determination processing of this device will be described with reference to the flowchart of FIG.

That is, in step 550, the EGR control correction value K
It is determined whether the _EGR is smaller than a predetermined value E such that the result of the exhaust gas test is rejected. If the EGR is larger than the predetermined value E, subsequently, at step 551, the EGR control correction value K _EGR is For example, as a result of the exhaust gas test, it is determined whether or not the value is greater than a predetermined value F at which the test is failed. If the value is smaller than the predetermined value F, the EGR control device is determined to be normal at step 552, and The flag is set and the warning lamp 23 is turned off in step 553. Also, EGR
If the control correction value K _EGR is smaller than the predetermined value E and is determined to be “Y” in step 550, or the EGR control correction value K _EGR
Is larger than the predetermined value F and is determined to be “Y” in step 551, the EGR control device is determined to be abnormal in step 554, and a flag to that effect is set.
At 5, the warning lamp 23 is turned on. That is, the present invention detects a mismatch between the target EGR rate _TEGR and the actual EGR rate _PEGR ,
The EGR control device is determined to be out of order.

Next, another embodiment of the failure determination of the EGR control device will be described with reference to the flowchart of FIG.

That is, in step 600, the absolute value of the target EGR ratio T _EGR value obtained by subtracting the actual EGR ratio P _EGR and G, the absolute value G, for example, the result which the value of the exhaust gas test and failed in step 601 It is determined whether the value is larger than a predetermined value H. If the absolute value G is smaller than the predetermined value H, the EGR control device is determined to be normal in step 602, and a flag to that effect is set.
3 turns off the warning lamp 23. If the absolute value G is larger than the predetermined value H and is determined to be "Y" in step 601, the EGR control device is determined to be abnormal in step 604, and a flag to that effect is set. Turns on the warning lamp 23.

In this embodiment, the target EGR rate T _EGR and the actual EGR rate
The magnitude of the absolute value G indicating the deviation from P _EGR and the predetermined value H are compared, and as a result, the failure of the device is immediately determined. The failure of the device may be determined by confirming that the magnitude relationship between G and the predetermined value H has continued for a certain period of time.

[Effects of the Invention] As is apparent from the above description, the exhaust gas recirculation control device according to the present invention includes the first exhaust gas recirculation rate and the second exhaust gas recirculation rate.
The increase or decrease of the passage area of the recirculation valve is controlled so that the exhaust gas recirculation rate of the exhaust gas coincides with the exhaust gas recirculation rate of the exhaust gas. Also, since the deviation between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate or a value corresponding to this deviation is stored, the exhaust gas recirculation control is quickly and accurately performed when the ignition switch is turned on. Can be performed. Further, since the failure is determined by detecting a mismatch between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate, there is an effect that a failure of the device can be directly and accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an exhaust gas recirculation control device of the present invention, FIG. 2 is a block diagram of an electronic control unit for controlling the device, and FIGS. 3 and 4 are characteristics of the device. 5 and 6 are flow charts for explaining the operation of this device, FIGS. 7 and 8 are graphs showing characteristics of this device, and FIG. 9 is a diagram explaining the control duty of this device. FIGS. 10 and 11 show the second embodiment of this device.
FIGS. 12 to 14 are flowcharts for explaining the operation of the third embodiment of the apparatus. DESCRIPTION OF SYMBOLS 1 ... Engine, 3 ... Intake pipe, 4 ... Intake manifold, 5 ... Injector, 6 ... Pressure sensor, 7
…… Throttle valve, 8 …… Throttle opening sensor, 11…
... recirculation valve, 12 ... passage area control actuator (EGR solenoid), 13 ... ignition coil, 14 ... igniter, 15
…… Exhaust pipe, 17… Water temperature sensor, 18 …… Differential pressure sensor, 20
…… battery, 21 …… ignition key switch,
22 …… Electronic control unit, 23 …… Warning lamp

Claims (3)

(57) [Claims] An exhaust gas recirculation control device for performing control for recirculating a part of exhaust gas of an internal combustion engine to the internal combustion engine again,
A recirculation pipe for recirculating exhaust gas of the internal combustion engine to an intake pipe, a recirculation valve for controlling a flow rate of the exhaust gas flowing through the recirculation pipe, a recirculation valve passage area control means for controlling a passage area of the recirculation valve, Operating state detecting means for detecting an operating state of the internal combustion engine; and a pressure from an intake pipe side disposed at a position on a bypass passage for detecting a differential pressure between pressure values near the outlet of the intake pipe and the return pipe. Means for detecting a pressure difference between the pressure and the pressure from the exhaust pipe side; means for calculating a first exhaust gas recirculation rate based on the pressure difference and a detection value detected by the operation state detection means; Means for calculating a second exhaust gas recirculation rate in accordance with the detection value detected by the detection means, wherein the deviation between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate is eliminated. Increase or decrease the passage area of the recirculation valve Exhaust gas recirculation control device being characterized in that to perform the feedback control for. 2. The exhaust gas recirculation control device according to claim 1, further comprising storage means for storing a deviation between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate or a value corresponding to the deviation. An exhaust gas recirculation control device. 3. The exhaust gas recirculation control device according to claim 1, wherein a failure is diagnosed by detecting a mismatch between the first exhaust gas recirculation rate and the second exhaust gas recirculation rate. Exhaust gas recirculation control device.