JP3841563B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention calculates the recirculation exhaust gas ratio by detecting the total amount of intake air that is the sum of the amount of fresh air introduced into the internal combustion engine and the amount of fresh air and the amount of recirculated exhaust gas (EGR gas). The present invention relates to an exhaust gas recirculation control apparatus for an internal combustion engine that can determine a recirculation exhaust gas rate according to the operating conditions of the engine.
[0002]
[Prior art]
As a conventional exhaust gas recirculation (EGR) control device for an internal combustion engine, a recirculation exhaust gas control valve for controlling a recirculation exhaust gas amount in an exhaust gas recirculation passage (EGR passage) connecting an exhaust pipe and an intake pipe of the internal combustion engine ( EGR valve), a means for detecting the total amount of gas sucked into the engine, and a means for detecting the amount of fresh air sucked in are provided, and the difference between the detected values is determined as the recirculation value of the exhaust gas. It is known that the opening degree of the EGR valve is feedback-controlled so that this value becomes equal to the set value (see Japanese Patent Application Laid-Open No. 57-148048).
[0003]
Since the EGR valve is provided in the EGR passage through which the high-temperature exhaust gas passes, a highly reliable operation cannot be obtained by driving with an electric motor or the like. Therefore, a diaphragm type actuator is usually used for driving the EGR valve. In this case, the diaphragm chamber is connected to a negative pressure source (a negative pressure pump in the case of a diesel engine, a negative pressure port of an intake pipe in the case of a gasoline engine), and the level of the negative pressure led to the diaphragm chamber is set to a predetermined value. In order to control, a negative pressure control mechanism is provided, and it is set so that the desired EGR valve lift, that is, the EGR rate can be obtained by setting the pressure in the diaphragm chamber to a predetermined negative pressure level.
[0004]
[Problems to be solved by the invention]
In the EGR valve drive system using the negative pressure control mechanism, the diaphragm chamber is connected to a negative pressure source (negative pressure pump or intake port) via a negative pressure pipe and an electromagnetic valve for switching control of negative pressure. Therefore, if the length of the negative pressure piping system is increased, the responsiveness of the electromagnetic valve is not necessarily high. Therefore, the EGR valve is likely to be delayed due to these reasons. Such an operation delay is particularly likely to occur when the EGR rate is controlled independently for each cylinder, and the exhaust gas recirculation control device for an internal combustion engine cannot be expected to operate with high responsiveness and accuracy. It was.
[0005]
In order to solve this problem, an object of the present invention is to provide an exhaust gas recirculation control device for an internal combustion engine that always operates while maintaining high response and accuracy. The present invention is also capable of independently controlling the EGR rate of each cylinder even though the exhaust gas recirculation control device is shared by all the cylinders, thereby making the EGR rate of all the cylinders uniform. An object of the present invention is to provide an exhaust gas recirculation control device that can be aligned.
[0006]
[Means for Solving the Problems]
In the present invention, as basically shown in FIGS. 1 and 2, the crank angle position corresponding to the start timing of the intake stroke of each cylinder of the engine is detected, and the intake pipe pressure VP and the fresh air during the intake stroke are detected. The amount VN is detected, the total intake amount QA is calculated from the intake pipe pressure VP, and the exhaust gas recirculation rate target value RT is calculated. Further, an integrated value QN of the fresh air amount is calculated at the end time of the intake stroke, and an exhaust gas recirculation rate REi of the cylinder is calculated as a difference between the total intake amount QA and the integrated value QN. Further, an intake throttle valve is provided in the intake pipe, and the intake throttle valve opening is controlled independently for each cylinder to a final target opening TRFi + 1 determined so that the exhaust gas recirculation rate REi for each cylinder becomes a target value. On the other hand, the exhaust gas recirculation amount is controlled so that the inter-cylinder average value R of the exhaust gas recirculation rate becomes the target value RT.
[0007]
However, with only the control as described above, the intake throttle valve opening is controlled independently for each cylinder, but the drive timing is immediately after the final target opening TRFi + 1 of the intake throttle valve opening is calculated. The timing is not controlled independently for each cylinder. For this reason, depending on the internal combustion engine, the exhaust gas recirculation rate may not be controlled independently for each cylinder, which may affect each other among a plurality of cylinders.
[0008]
Accordingly, as a result of further research on the problem, the present inventors have conducted further research. As a result, exhaust gas recirculation of individual cylinders among a plurality of cylinders connected in parallel downstream of the intake throttle valve is provided. It has been found that there are operating timings in which the rate can be controlled independently, i.e. substantially independently of the other cylinders.
[0009]
This point will be described in more detail with reference to FIG. FIG. 3 shows that the operating condition of the four-cylinder diesel engine is that the rotational speed is 800 rpm and the output torque is 27 Nm, and the opening degree of the intake throttle valve is only 3.2 ° between 180 ° CA for each rotation of the crankshaft. The change of the EGR rate of each cylinder when operated to the valve closing side is shown. In each of the cases (a) to (d), the start timing of the closing operation of the intake throttle valve is the crank angle after the TDC of the first cylinder, (a) 500 °, (b) 545 °, (c) 590 This shows a case where the angle is delayed by 45 ° CA, such as ° and (d) 635 °. For reference, (e) shows a case where the opening of the throttle valve is fixed. “Ave” represents an average value of all cylinders.
[0010]
Compared to the EGR rate when the throttle valve is fixed as shown for reference, the EGR rates of the first cylinder and the second cylinder are greatly increased at 500 ° CA in the case of (a). When the start timing of the valve closing operation is delayed, the degree of increase in the EGR rate of the second cylinder decreases, and finally, at 635 ° CA in the case of (d), only the first cylinder is EGR. Will show an increase in rate. This fact means that if the intake throttle valve is controlled to open and close at a certain optimum timing, the EGR rate of each individual cylinder can be increased or decreased independently.
[0011]
Accordingly, the present inventors pay attention to this point, and individually control the exhaust gas recirculation rate of each cylinder by controlling the opening and closing of the intake throttle valve at an optimal timing for each cylinder, thereby exhausting the exhaust gas recirculation rate of all the cylinders. The above-mentioned problems were also solved by aligning the desired values.
[0012]
More specifically, the present invention provides an exhaust gas recirculation control device for an internal combustion engine described in each claim as a means for solving the above-mentioned problems.
[0013]
  In the technical means according to the first aspect of the present invention, the intended passage area control means (intake throttle valve) of the intake system is driven in accordance with the exhaust gas recirculation rate determined by the recirculation exhaust gas amount control valve. Control the exhaust gas recirculation rateIn addition, the exhaust gas recirculation rate of each cylinder is controlled by driving the passage area control means at the optimum time in the intake stroke of each cylinder. Therefore, the responsiveness can be improved as compared with the case where the exhaust gas recirculation rate is controlled only by the recirculated exhaust gas amount control valve driven by negative pressure. Further, the exhaust gas recirculation rate can be controlled with high responsiveness and accuracy for each cylinder, and the difference in the exhaust gas recirculation rate with other cylinders can be reliably suppressed.
[0014]
According to the technical means described in claim 2, the passage area control means is controlled independently for each cylinder. Therefore, even if there is a difference between the exhaust gas recirculation rates of the respective cylinders, it is possible to make all the exhaust gas recirculation rates uniform by individually controlling the exhaust gas recirculation rates of the respective cylinders.
[0015]
  Claim3Specifically, the exhaust gas recirculation control is performed for each cylinder using a two-dimensional map.
[0016]
  And claims4According to the technical means, the fresh air amount calculated by the first calculation means from the detection value by the first detection means, and the total intake air amount calculated by the second calculation means from the detection value by the second detection means, The exhaust gas recirculation rate is calculated by the third calculating means, and the passage area control meansControl at the optimal time independently for each cylinderThus, the same effect as that of the first aspect can be obtained.
[0017]
  Claim5According to the technical means described in the above, it is possible to accurately grasp the recirculated exhaust gas amount from the detection values of the air flow meter and the pressure detector.
  Claim6According to the technical means described in (4), fluctuation of the measured value can be prevented by integrating the detected value of the fresh air amount.
  Claim7Since the exhaust gas recirculation rate is controlled by the value of the total intake amount averaged among the cylinders, the fluctuation of the exhaust gas recirculation rate between the cylinders can be minimized. .
[0018]
  Claim8In addition to the control of the passage area control means, the exhaust gas recirculation control valve is controlled according to the average exhaust gas recirculation rate between the cylinders in addition to the control of the passage area control means. Realize faster control over
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the present invention is applied to a diesel engine with a swirl chamber equipped with a turbocharger will be described more specifically with reference to FIGS. In FIG. 4, 1 is a diesel engine body, 2 is a swirl chamber, 3 is a piston, 4 is a fuel injection valve provided in the swirl chamber 2, and 5 is an exhaust valve. The exhaust valve 5 is connected to the exhaust pipe 6. An intake valve (not shown) is connected to the intake pipe 7. Reference numeral 8 denotes a turbocharger, and the turbocharger 8 includes a turbine 9 disposed in the exhaust pipe 6 and a compressor 10 disposed in the intake pipe 7. As is well known, fuel from a fuel injection pump (only the rotating shaft 22 is shown in FIG. 1) is pumped to the fuel injection valve 4.
[0020]
The exhaust pipe 6 upstream of the turbine 9 and the intake pipe 7 downstream of the compressor 10 are connected by an exhaust gas recirculation passage (EGR passage) 11. An exhaust gas recirculation amount control valve (EGR valve) 12 is disposed on the EGR passage 11. The EGR valve 12 is connected to the valve body 13 and the valve body 13, and controls the flow rate of the recirculated exhaust gas (EGR gas) flowing through the EGR passage 11 by controlling the lift of the valve body 13 according to the negative pressure. 14. The EGR valve 12 is configured such that the larger the lift of the valve body 13, the larger the opening area and the greater the EGR gas flow rate. The magnitude of the lift of the valve body 13 is determined by the magnitude of the negative pressure in the diaphragm chamber 15 formed by the diaphragm 14. That is, the stronger the negative pressure, the larger the displacement of the diaphragm 14 in the figure and the higher the lift. The diaphragm chamber 15 is connected to the vacuum pump 16 by a negative pressure pipe 17, and the negative pressure from the vacuum pump 16 is introduced into the diaphragm chamber 15.
[0021]
In order to control the negative pressure of the diaphragm 14, a three-way solenoid valve 18 is provided on the negative pressure pipe 17. On the diaphragm chamber 15 side of the electromagnetic valve 18, the negative pressure pipe 17 is opened to the atmosphere by a pipe 18a, and an orifice 18b is provided in the atmosphere opening. Further, the electromagnetic valve 18 includes a coil 19, and the valve body 18 is driven by energization control of the coil 19, and negative pressure introduction control introduced from the vacuum pump 16 to the diaphragm chamber 15 is performed. That is, when the coil 19 of the electromagnetic valve 18 is not energized, the communication between the vacuum pump 16 and the diaphragm chamber 15 is cut off, and the EGR operation is not performed because the lift of the valve body 13 is minimized. On the other hand, when the coil 19 is energized, the negative pressure from the vacuum pump 16 is introduced into the diaphragm chamber 15 and the valve body 13 is lifted. The energization of the electromagnetic coil 19 is duty-controlled by a control circuit (microcomputer system) 50 as will be described later, and the valve body 13 of the EGR valve 12 is controlled to a desired lift, and thus the EGR amount is controlled.
[0022]
An intake throttle valve 29 as a passage area control means capable of controlling the passage area of fresh air is disposed between the confluence of the compressor 10 and the EGR passage 11 and the intake pipe 7. The valve shaft of the intake throttle valve 29 is connected to electrical rotation driving means such as a step motor 30 by connection means such as a gear (not shown). The step motor 30 is rotationally driven by receiving a drive signal from the control circuit 50, and can arbitrarily control the opening degree (ie, fresh air amount) of the intake throttle valve 29.
[0023]
An air flow meter 20 that outputs an electrical signal (analog signal) corresponding to the amount of fresh intake air is disposed upstream of the compressor 10 in the intake pipe 7. A pressure detector 21 is disposed in the intake pipe 7 downstream of the compressor 10 and outputs an electrical signal (analog signal) corresponding to the intake pipe pressure. Signals from these sensors 20 and 21 are input to the control circuit 50 as a flow rate (g / rev) per engine revolution, and the difference between the two signals is grasped as an exhaust gas recirculation amount (EGR amount). The storage device (ROM) of the control circuit 50 stores EGR amount data corresponding to the engine speed and the opening degree of the adjusting lever of the fuel injection pump, which is a factor corresponding to the engine load. If there is a difference between the detected EGR amount and the stored EGR amount, the control circuit 50 controls energization to the coil 19 in a direction to eliminate the difference.
[0024]
Although a known appropriate method can be adopted as a method for detecting the rotational speed, the rotational speed sensor of the illustrated embodiment is arranged on the rotating shaft 22 (connected to the crankshaft of the internal combustion engine) of the fuel injection pump. A rotating body having a plurality of protrusions 23 spaced apart in the direction is fixed, and an electromagnetic pickup 24 such as a Hall element is arranged to face the protrusions 23. Therefore, a pulse signal having a pulse interval corresponding to the interval between the protrusions 23 is obtained from the electromagnetic pickup 24.
[0025]
On the other hand, a rotating body having a pair of protrusions 27 is attached to the crankshaft 38 of the internal combustion engine at opposite positions on the diameter. Two electromagnetic pickups 28 are arranged. The protrusion 27 can detect a half rotation of the crankshaft, that is, a rotation of 180 °.
[0026]
Further, in order to know the position of the adjusting lever of the fuel injection pump, the potentiometer 25 in FIG. 1 is provided, and the sliding contact portion 25a of the potentiometer moves integrally with the adjusting lever of the fuel injection pump, and the position of the adjusting lever In response to this, a voltage signal can be obtained from the potentiometer 25.
[0027]
Further, a rotating body having one protrusion 40 in the circumferential direction is attached on the camshaft 26 for driving the intake and exhaust valves, and is opposed to the protrusion 40 so that the Hall element or the like is the same as described above. A third electromagnetic pickup 41 configured by is arranged. By detecting the protrusion 40, two rotations of the crankshaft, that is, a rotation of 720 ° can be detected.
[0028]
Next, the configuration of the control circuit 50 will be described with reference to FIG. The control circuit 50 includes an input terminal 501 connected to the sliding contact portion 20a of the potentiometer constituting a part of the air flow meter 20, an input terminal 502 connected to the pressure detector 21, and an adjusting lever of the fuel injection pump. An input terminal 503 connected to the sliding contact 25a of the position detecting potentiometer 25, an input terminal 504 connected to the first electromagnetic pickup 24, and an input terminal 505 connected to the second electromagnetic pickup 28; Furthermore, an input terminal 515 connected to the third electromagnetic pickup 41 is provided.
[0029]
The control circuit 50 includes an output terminal 506 connected to the electromagnetic coil 19 of the EGR valve 12. In addition, the control circuit 50 includes an analog-to-digital (A-D) converter 510, a counter 520, a central processing unit (CPU) 530, a first oscillator 540, a comparator 550, a second input terminal and an output terminal. An oscillator 560 and a drive circuit 570 are provided. The AD converter 510 is connected to input terminals 501, 502, and 503. As is well known, the AD converter 510 includes a multiplexer and an AD converter circuit, three storage circuits, a multiplexer switching circuit, and the like. And a timing pulse circuit that activates the AD converter and generates select signals of the storage circuits. The A-D converter and the three storage circuits can have a 12-bit configuration, for example.
[0030]
The counter 520 is connected to input terminals 504, 505, and 515 from the first, second, and third electromagnetic pickups 24, 28, and 41 that generate pulse signals. A counting circuit that measures the number of pulses, a storage circuit that stores the counting circuit, and a timing pulse circuit that generates a gate signal to the counting circuit, a reset signal, and a latch signal to the counting circuit. A dual code signal is output. The pulse signal from the second electromagnetic pickup 28 is used for resetting the counting circuit. The pulse signal from the third electromagnetic pickup 41 is used for cylinder discrimination.
[0031]
The CPU 530 includes a microcomputer, a three-state buffer circuit that connects the output of the A / D converter 510 and the output of the counter 520 and the microcomputer bus line, and a storage circuit that stores the output value of the microcomputer. . Since the details of the microcomputer circuit are not the main part of the present invention, the description thereof will be omitted. The microcomputer operates at an internal clock frequency of 2 MHz. When the power is turned on, initialization is performed and a program from a pre-designated ROM address is executed.
[0032]
The first oscillator 540 in the control circuit 50 generates a 20 Hz trigger pulse, which becomes a timer check signal for the CPU 530 and a reset signal for the comparator 550. The comparator 550 receives a 20 Hz clock signal from the second oscillator based on the trigger pulse from the first oscillator 540, and converts the binary code output from the CPU 530 into a pulse width. The output of the comparator 550 is input to the electromagnetic valve drive circuit 570, the input signal is amplified, and the output signal is applied to the coil 19 of the electromagnetic valve 18 from the terminal 506.
[0033]
The CPU 530 is connected to a drive circuit 580 for driving the intake throttle valve driving step motor 30, and its output signal is applied to a coil of the step motor 30 from a terminal 507. The formation of an output signal to the CPU 530 for driving the step motor 30 and the amplification method of the drive circuit 580 can employ any conventionally known method, and thus detailed description thereof is omitted.
[0034]
A constant voltage Vc is applied to both ends of the potentiometer constituting the air flow meter 20, and a voltage VN corresponding to the amount of intake air appears at the sliding contact portion 20a. The voltage VN is converted into a binary code by the AD converter 510 and stored in the memory circuit. Similarly, the voltage signal Vp corresponding to the pressure from the pressure detector 21 and the voltage signal VL corresponding to the position of the adjusting lever of the fuel injection pump are A / D converted and stored in the storage circuit. On the other hand, the counter 520 measures the number of pulses of the pulse signal from the first electromagnetic pickup 24, and the count value is stored in the internal storage circuit. The pulse signal from the second electromagnetic pickup 28 is used for clearing the counter 520. The pulse signal from the third electromagnetic pickup 41 is used to determine the start timing of the intake stroke of a specific cylinder (for example, the first cylinder).
[0035]
The operation of the CPU 530 will be described in detail below with reference to the flowcharts shown in FIGS. The processing is started when the power is turned on. In step 101, the operation is started, and all the memories, registers, and ports of the CPU 530 are initialized. In step 101-1, it is determined whether i = 0. i = 0 is a timing at which an intake stroke is started in a specific cylinder (for example, the first cylinder), and corresponds to a pulse generated at a cycle of 720 ° CA.
[0036]
In step 102, it is determined whether or not the pulse counter Cn = 0. Cn = 0 is the timing at which the intake stroke is started in one of the cylinders and the intake stroke is ended in any one of the other cylinders. That is, there is provided a counting routine that is incremented by a pulse from the first electromagnetic pickup 24 and cleared by a pulse every 180 ° from the second electromagnetic pickup 28, and the crank angle at which the second electromagnetic pickup 28 generates a pulse. At the position, one cylinder corresponds to the start of the intake stroke and another cylinder is set to correspond to the end of the intake stroke, and Cn = 0 is set at this position.
[0037]
When the counter value (Cn) is not 0, that is, when the determination at step 102 is negative, the flow goes from step 102 to step 103 to determine whether or not a signal generated every predetermined time T1 has been input. It is. When it is determined that a pulse signal generated every time T1 has elapsed, the routine proceeds to step 104. Otherwise, the routine proceeds to step 109. Steps 104 to 108 executed when it is determined that the time T1 has elapsed are routines for calculating the target value of the EGR rate. That is, in step 104, the intake pipe pressure value Vp stored in the storage circuit in the AD converter 510 is read, and in step 105, it is also stored in the storage circuit in the AD converter 510. The intake air amount value VL is read.
[0038]
Step 106 represents calculation of the engine speed N. The rotation speed N is measured by a time T180 for the crankshaft to rotate 180 °. That is, the counter 520 is cleared by a pulse signal from the second electromagnetic pickup 28 for every 180 ° rotation of the crankshaft, and the value of T180 is from the time when the number of pulses in the counter 520 becomes zero last time. This is the elapsed time to zero.
[0039]
Step 107 shows the calculation of the total gas amount QA sucked into one cylinder. The calculation of the total gas amount QA is based on the intake pipe pressure value Vp detected by the pressure detector 21 and the engine speed N. It can be carried out. That is, there is a fixed relationship between the intake pipe pressure value Vp and the engine speed N, and this relationship is stored as a two-dimensional map f in the CPU 530. Therefore, the intake pipe pressure value read at step 104 is read. The value of the total gas amount corresponding to Vp and the engine speed N calculated in step 106 is interpolated.
[0040]
Step 108 shows calculation of the target value RT of the optimum EGR rate under the engine operating conditions. That is, there is a certain relationship between the position of the adjusting lever of the fuel injection pump corresponding to the fuel injection amount (load) (the output value of the potentiometer 25) VL and the engine speed N. Since it is stored in the CPU 530 as a two-dimensional map g, in step 108, an interpolation operation of the target EGR value RT corresponding to the potentiometer output value VL and the measured value of the engine speed N is performed.
[0041]
In step 109, the optimum throttle valve opening target value TRB is calculated under the operating conditions. That is, there is a predetermined relationship between the position (potentiometer output value) VL of the adjusting lever of the fuel injection pump corresponding to the fuel injection amount (load) and the engine speed N, and this relationship is two-dimensional. The map h is stored in the CPU 530. In step 109, the interpolation operation of the target throttle valve opening TRB corresponding to the output value VL of the potentiometer 25 and the measured value of the engine speed N is executed.
[0042]
Steps 110 to 113 show the process of integrating the measurement values of the air flow meter 20. That is, step 110 is a timer check for detecting the output signal of the air flow meter, and it is determined whether or not a signal is input every predetermined time period T2. T2 is preferably shorter than the time for performing the intake stroke of one cylinder at the maximum engine speed so that the intake air amount of each cylinder can be detected even at high engine speeds. When it is determined that the T2 pulse has been input, the routine proceeds to step 111, where the measured value VN of the air flow meter 20 stored in the memory circuit in the AD converter 510 is read. In step 112, the VN value read in step 111 is integrated, that is, ΣVN is calculated. Step 113 indicates the increment of the integration counter CAD.
[0043]
When the rotation pulse counter value Cn = 0 in step 102, that is, when it is the start or end time of the intake stroke, the routine proceeds to step 201 where the cylinder mark i is incremented, and then whether or not i> 4 in step 202. Judgment is made. When i> 4, i = 1 is set at step 203. Since the processes of steps 201 to 203 are executed every 180 ° of the crank angle and the explosion order is determined, the value of i can be made to correspond to the number of the cylinder performing the intake stroke at that time. In this example, i = 1 is always determined as the first cylinder so that it does not change even when the engine is stopped and restarted.
[0044]
In step 204, the calculation of the fresh air intake air amount (gram) in the intake stroke of each cylinder in one intake stroke is as follows:
QNi = (ΣVN / CAD) × T180
Executed by. Here, T180 is the time required for the crankshaft to rotate 180 ° (that is, the crank angle of one intake stroke) as described above. In this equation, the average value of the measured values of the air flow meter is obtained by dividing the integrated value ΣVN of the measured values of the air flow meter 20 by the number of times of integration CAD, and this is the time for the crankshaft to rotate 180 °, that is, The amount of fresh air intake per intake stroke is calculated by multiplying the time required to perform one intake stroke.
[0045]
In step 205, the EGR gas amount QEi of each cylinder is calculated. That is, the EGR gas amount QE is obtained by subtracting the fresh air intake amount QNi calculated in step 204 from the total gas amount QA calculated in step 107. In step 206, the EGR rate is calculated as the ratio of the EGR gas amount QEi to the total gas amount QA. In step 207, the value of the EGR rate calculated in step 206 is stored in REi as the EGR rate of the cylinder i.
[0046]
In step 208, the EGR rates of all cylinders i = 1 to 4 are added, and the EGR rate R averaged for all the cylinders is calculated by dividing by the number of cylinders 4.
Steps 209 and 210 show the formation of a drive signal to the coil 19 of the solenoid valve 18. That is, in step 209, the control deviation ΔD is calculated by subtracting the actual measurement EGR rate RE calculated in step 208 from the target EGR rate RT calculated in step 108.
[0047]
In step 210, the ON time DP ′ of the solenoid valve 18 is
DP ′ = DP ′ + ΔD × K
Is calculated by That is, in this equation, K is a gain, and by continuing the execution of the processing of step 210, feedback is applied to the solenoid valve 18, so that the deviation is finally zero, and the average EGR rate of the four cylinders is the target EGR rate. Matches RT. That is, the opening degree of the EGR valve 12 is controlled to an average EGR rate among all cylinders.
[0048]
In step 211, a difference ΔTRi of the EGR rate REi of each cylinder with respect to the target EGR rate RT is calculated. In step 212, the intake throttle valve opening correction amount for each cylinder is determined.
TRC i = TRC i + ΔTR i × k ′
Is calculated by In this equation, k ′ is a gain. For example, when the EGR rate of a specific cylinder is smaller than the target, the correction amount of the opening is updated in the direction in which the intake throttle valve 29 is closed so as to increase the EGR rate. The
[0049]
In step 213, the final target opening degree TRFi + 1 of the intake throttle valve of the cylinder that will be the next intake stroke is calculated. TRFi + 1 is obtained by adding the target intake throttle valve opening TRB calculated in step 109 and the correction amount TRCi + 1 calculated in step 212 at the end of the previous intake stroke of the cylinder.
[0050]
On the other hand, the timing for correcting the opening of the intake throttle valve 29 is determined by the fuel injection amount (load) VL and the rotational speed N in step 213-1. As for this relationship, data obtained by conducting a test in advance is stored in the control circuit 50 as a two-dimensional map. Then, at the timing ti determined at step 213-1, the value of TRFi + 1 is reflected as an output signal of the drive circuit 580, whereby the intake throttle valve drive motor 30 is driven and a predetermined intake throttle valve is driven. The opening can be obtained. In step 214, VN and CAD are cleared for the next measurement.
[0051]
Next, the control of the electromagnetic valve 18 will be described. The ON time DP ′ of the electromagnetic valve 18 stored at a predetermined address in the RAM is transferred to the BUS line and stored in a storage circuit in the CPU 530. The comparator 550 outputs a coincidence signal when the binary code value from the CPU 530 coincides with the number of clocks from the second oscillator 560 using the trigger signal of the first oscillator 540 as a reset signal. Therefore, since the cycle of the trigger signal of the first oscillator 540 is 50 ms, the solenoid valve 18 is not changed until the number of binary codes from the CPU 530 and the number of clocks after the trigger signal is switched from the high level to the low level. The time until the trigger signal is switched from the high level to the low level after the coincidence is the OFF time of the solenoid valve 18. This is shown in FIG.
[0052]
6A shows the output signal of the first oscillator 540, and FIG. 6B shows the output signal of the comparator 550. Further, the time T is obtained by step 210 shown in FIG. 2, and coincides with DP ′ (the cycle of the second oscillator 560 0.05 msec) stored at a predetermined address in the RAM. This time T determines the ON-OFF ratio of the solenoid valve 18, that is, the EGR amount. The drive circuit 570 amplifies the signal from the comparator 550 and applies it to the coil 19 of the solenoid valve.
[0053]
In the above embodiment, the EGR valve 12 is feedback-controlled so that the inter-cylinder average value R of the EGR rate becomes the target value RT, while the intake throttle valve 29 is set so that the EGR rate REi becomes the target value for each cylinder. Have independent control. For this reason, even if there is an unavoidable deviation between cylinders, fluctuation of the EGR rate between cylinders can be prevented, and control of the EGR rate to the target value can be performed quickly. In addition, since the EGR gas intake information can be detected for each intake stroke of each cylinder, EGR control can be performed for each combustion, and desired EGR control can be performed even during a transition.
[0054]
As for the control of the EGR valve 12, feedback control is not performed as in the embodiment, and only open loop control may be performed. The simplest method may be on / off control. That is, it is possible to perform control such that the EGR valve 12 is opened during the EGR condition, and the EGR valve 12 is closed during the non-EGR condition.
[0055]
In the above embodiment, the calculation of the total gas amount is performed by the output of the pressure detector 21, but an intake thermometer is provided in the vicinity of the pressure detector 21 in order to improve the accuracy of the calculated value of the total gas amount. It is desirable to correct the calculated value of the total gas amount based on the detected pressure value based on the output. Further, although the diesel engine with a turbocharger is used as the internal combustion engine, the present invention can also be applied to an internal combustion engine in which no turbocharger is installed. In order to facilitate exhaust gas recirculation, it is particularly useful to apply the present invention to a diesel engine in which a throttle valve is installed in the intake pipe. In this case, an EGR port and a pressure detector are provided downstream of the throttle valve, and the air flow meter is positioned upstream of the throttle valve.
[0056]
In the above embodiment, the pressure detector 21 is used as a means for detecting the total amount of inhaled gas. Instead, a structure similar to the structure of the air flow meter 20 or a structure using a heat ray is used. It is also possible to adopt. However, in consideration of contamination due to the exhaust gas flowing backward, a system that detects pressure without having a mechanical moving part is desirable.
[0057]
The present invention can also be applied to a spark ignition internal combustion engine using gasoline as fuel.
[Brief description of the drawings]
FIG. 1 is a part of a flowchart for explaining the operation of a control circuit shown in FIG.
FIG. 2 is the remaining part of the flowchart of FIG.
FIG. 3 is a chart showing changes in the EGR rate of each cylinder due to the operation of the intake throttle valve.
FIG. 4 is an overall configuration diagram of an internal combustion engine as an embodiment of the present invention.
FIG. 5 is a block diagram showing a configuration of a control circuit.
FIG. 6 is a timing chart for explaining a duty ratio control operation by the control circuit.
[Explanation of symbols]
1 ... Diesel engine body
6 ... Exhaust pipe
7 ... Intake pipe
11 ... Exhaust gas recirculation passage (EGR passage)
12 ... Exhaust gas recirculation control valve (EGR valve)
15 ... Diaphragm room
18 ... Three-way solenoid valve
20 ... Air flow meter
21 ... Pressure detector
22 ... Rotary shaft of fuel injection pump
24, 28, 41 ... Electromagnetic pickup
26 ... Camshaft
29 ... Intake throttle valve
38 ... Crankshaft
50 ... Control circuit
i ... Cylinder mark
N ... Engine speed
QA ... Total intake volume
QE ... EGR gas amount
QN ... Fresh air intake
R: Average value of EGR rate between cylinders (ave)
REi ... EGR rate for each cylinder
RT: Target value of EGR rate
TRB ... Opening target value of intake throttle valve
TRCi: Intake throttle correction amount for each cylinder
TRF: Final target opening of intake throttle valve
VL ... Fuel injection amount (load)
VN ... New air volume
VP ... Intake pipe pressure

Claims (8)

The recirculation exhaust gas amount control valve for controlling the recirculation exhaust gas amount, the new air amount detection means for detecting the amount of fresh air introduced into the internal combustion engine, and the total intake amount in which the recirculation exhaust gas and the fresh air are mixed. A total intake amount detecting means for detecting; an exhaust gas recirculation rate calculating means for calculating an exhaust gas recirculation rate from the detected fresh air amount and the total intake amount; and an intake passage through which the fresh air is introduced into the internal combustion engine. Passage area control means for controlling the passage area, exhaust gas recirculation rate control means for controlling the passage area control means so as to obtain a calculated exhaust gas recirculation rate, and cylinder discrimination means for discriminating a cylinder in the intake stroke Drive timing control means for optimally controlling the timing for driving the passage area control means in the intake stroke of each cylinder, and the drive timing control means for the cylinder determined by the cylinder determination means. The passage area control means actuates the exhaust gas recirculation control system for an internal combustion engine for controlling the recirculated exhaust gas amount for each cylinder at a time of optimum by.   2. The fresh air amount and the total intake air amount are detected for each cylinder of the internal combustion engine according to claim 1, and the control of the passage area control means by the exhaust gas recirculation rate control means depends on the calculated recirculated exhaust gas quantity. An exhaust gas recirculation control device for an internal combustion engine performed for each cylinder. 2. The exhaust gas recirculation control device for an internal combustion engine according to claim 1 , wherein the drive timing control means includes a two-dimensional map for controlling a drive timing for operating the passage area control means for each cylinder. In an exhaust gas recirculation control device for an internal combustion engine having a recirculation exhaust gas amount control valve in the middle of a recirculation exhaust gas passage communicating the intake pipe and the exhaust pipe, a value corresponding to the amount of fresh air introduced into the internal combustion engine is detected. First detecting means for calculating the amount of fresh air supplied to each cylinder of the internal combustion engine based on the detection value by the first detecting means, and the sum of the fresh air amount and the recirculated exhaust gas amount Second detection means for detecting a value corresponding to the total intake amount of the internal combustion engine, and second calculation means for calculating the total intake amount for each cylinder of the internal combustion engine based on the detection value of the second detection means And third calculation means for calculating an exhaust gas recirculation rate for each cylinder from a fresh air amount for each cylinder calculated by the first calculation means and a total intake amount for each cylinder calculated by the second calculation means, The value calculated by the third calculating means is equal to the target value set for each operating condition. Ri Do and control means for controlling the operation of the passage area control means so that, together with the control of the passage area control means by said control means is performed for each intake stroke of each cylinder, wherein the controlling, cylinder discrimination means An exhaust gas recirculation control device for an internal combustion engine, which is performed by determining the cylinder in the intake stroke at that time and then driving the passage area control means at an optimal time for the cylinder by the drive timing control means . 5. The air flow meter according to claim 4 , wherein the first detection means is an air flow meter provided in the intake pipe upstream of the opening of the recirculation exhaust gas passage, and the second detection means is an opening of the recirculation exhaust gas passage. An exhaust gas recirculation control device for an internal combustion engine, which is a pressure detector for detecting the pressure of the intake pipe on the downstream side of the engine. 5. The storage unit according to claim 4 , wherein the first calculation unit accumulates information stored in the storage unit during an intake stroke period of each cylinder of the internal combustion engine. An exhaust gas recirculation control device for an internal combustion engine, wherein the integrated value is reflected in the calculation of the fresh air amount. 5. The exhaust gas recirculation control for an internal combustion engine according to claim 4 , wherein the second calculation means calculates a total intake amount averaged between the cylinders, and the calculated value is reflected in a calculated value of a difference from the fresh air amount. apparatus. 5. The fourth calculating means according to claim 4 , further comprising an average value calculating means for averaging values corresponding to the calculated exhaust gas recirculation rates of all the cylinders so that the average value becomes equal to the target value. An exhaust gas recirculation control device for an internal combustion engine that controls the operation of a recirculation exhaust gas control valve.

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