JPH07174048A - Exhaust gas recirculation controller - Google Patents

Abstract

PURPOSE:To correctly carry out the exhaust gas recirculation control at all times by controlling the EGR flow rate so that the actual EGR rate based on the intake air quantity and the internal pressure in an intake pipe and the internal pressure of an EGR pipe accords with the target EGR rate based on the operation state information of an internal combustion engine. CONSTITUTION:Exhaust gas is allowed to recirculate to an intake pipe 3 through an EGR pipe 10 having an EGR valve 11. The EGR valve 11 is controlled by an electronic type control unit 22 on the basis of the operation state information of an internal combustion engine which is detected by a sensor means. In this case, as the sensor means, are arranged a sensor 12 for detecting the intake air quantity in the intake pipe 3, sensor 6 for detecting the internal pressure of the intake pipe 3, and a sensor 18 for detecting the internal pressure of the EGR pipe 10. The electronic type control unit 22 calculates the target EGR rate according to the operation state information. Further, the actual EGR rate is calculated on the basis of the detection values of the sensors 6, 12, and 18. Further, the EGR flow rate is controlled so that the actual value of the EGR rate accords with the target value, and the erroneous control due to the dispersion of the EGR valve, etc., and the variation due to the lapse of time are prevented, and the reliability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device that uses, for example, a stepper motor type EGR valve to recirculate exhaust gas from an internal combustion engine (hereinafter referred to as "EGR"), and particularly to variations in EGR valves and the like. The present invention relates to an exhaust gas recirculation control device that improves reliability by preventing erroneous control due to changes over time.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine control device for an automobile engine or the like, for example, in order to lower the combustion temperature of the internal combustion engine and suppress NOx components in the exhaust gas, a part of the exhaust gas is returned to the internal combustion engine. The technique of EGR control for recirculation is well known. FIG. 16 is a schematic diagram showing the entire system of a conventional exhaust gas recirculation control device.

In the figure, 1 is an internal combustion engine, that is, an engine, 2 is an air cleaner for purifying intake air to the engine 1, 3 is an intake pipe for supplying air through the air cleaner 2 to the engine 1, and 4 is intake air. An intake manifold (hereinafter referred to as an intake manifold) provided on the downstream side of the pipe 3, that is, on the intake side of the engine 1, 5 is an injector for injecting fuel into an intake manifold 4 of the intake pipe 3, and 7 is an intake pipe 3
A throttle valve that is provided inside to control the intake flow rate, 8 is a throttle opening sensor that detects the opening degree θ of the throttle valve 7, and 9 is an air flow rate of a passage that bypasses the upstream side and the downstream side of the throttle valve 7. It is a bypass air flow rate control means for controlling.

Reference numeral 10 is an EGR pipe for returning exhaust gas of the engine 1 to the intake pipe 3 side, and 11 is a stepper motor type EG for controlling the flow rate of exhaust gas flowing through the EGR pipe 10.
It is an R valve. The EGR valve 11 controls the EGR flow rate so that the flow rate corresponds to the operating state of the engine 1.
It constitutes a flow rate control means.

Reference numeral 12 denotes an air flow sensor for detecting the intake air amount Qa into the intake pipe 3, which is of a vane type, for example, and measures the volume flow rate as the detected air amount Qa. Therefore, inside or outside the air flow sensor 12,
Intake temperature sensor and atmospheric pressure sensor (neither shown)
Is provided, and the mass air amount actually sucked into the engine 1 is measured.

Reference numeral 13 is an ignition coil for generating a high voltage for burning each cylinder of the engine 1, and 14 is an ignition coil 1.
An igniter for shutting off the primary side current of 3, an exhaust pipe 15 for discharging exhaust gas after combustion in the engine 1,
Reference numeral 6 is a catalyst provided downstream of the exhaust pipe 15 for purifying exhaust gas.

The ignition signal Q from the ignition coil 13 driven by the igniter 14 corresponds to the rotation speed of the engine 1 and also functions as a sensor signal representing the rotation speed. Reference numeral 17 denotes a water temperature sensor that detects the temperature T of the cooling water of the engine 1, and together with the throttle opening sensor 8, the ignition coil 13 and the like, constitutes a sensor means that provides operating state information of the engine 1. Reference numeral 20 is a battery that serves as a power source for the vehicle-mounted device, 21 is a battery that is closed at the time of startup
Is an ignition key switch for supplying the electric power of the above to an in-vehicle device.

Reference numeral 22 is an electronic control unit composed of a computer system which is activated by power supply from the battery 20, and which contains operating state information from various sensor means (ie, throttle opening θ, intake air amount Qa, cooling water temperature T). , An ignition signal Q, etc.), and a combustion injection amount calculation means and an EGR flow rate calculation means for calculating the combustion injection amount and the EGR flow rate Qr according to the operating state information, and the combustion injection control signal J for the injector 5 and the EGR valve. The EGR control signal Cr for 11 is output.

FIG. 17 shows the electronic control unit 2 shown in FIG.
It is a block diagram which shows the detailed structure of 2. In the figure, 1
00 is a microcomputer, operating state information Q,
A CPU 200 that calculates a control signal J of the injector 5 and a control signal Cr of the EGR valve 11 according to a predetermined program based on Qa, θ, and T, and a free-running counter 20 for measuring the rotation cycle of the engine 1.
1 and a timer 202 for measuring time for various controls
And A / which converts an analog input signal to a digital signal
D converter 203 and RA used as a work memory
M205 and R that stores various operating programs
The OM 206, the output port 207 for outputting each control signal J and Cr, and each element 201 to 207
It is composed of a common bus 208 which is coupled to the 200.

Reference numeral 101 denotes a first input interface circuit, which waveform-shapes the ignition signal Q on the primary side of the ignition coil 13 into an interrupt signal, which is input to the microcomputer 100. When this interrupt signal is generated, the CPU 200 in the microcomputer 100 causes the counter 201 to
R value is read and the rotation cycle of the engine 1 is calculated from the difference between the present reading value and the previous reading value.
It is stored in the AM 205.

A second input interface circuit 102 includes a throttle opening sensor 8 and an air flow sensor 12.
And sensor signals θ, Qa and T from the water temperature sensor 17 and the like are fetched and input to the A / D converter 203. 1
Reference numeral 04 denotes an output interface circuit, which is an output port 2
The drive output from 07, that is, the control signals J and Cr are amplified and output to the injector 5 and the EGR valve 11.

FIG. 18 is a side sectional view showing the structure of the EGR valve 11. Reference numeral 30 is a unipolar type mounted on the upper part of the valve body of the EGR valve 11 and capable of controlling the EGR valve 11 from 48 steps to full opening. Stepper motor, 31
Is a motor shaft that is rotationally driven by the stepper motor 30,
Reference numeral 32 is a feed screw that is driven up and down by rotating in conjunction with the motor shaft 31, 33 is a valve shaft that is driven up and down by the feed screw 32 to adjust the passage area of the EGR valve 11, and 34 is a valve shaft 33. A compression coil spring that urges in the upward (open) direction, and 35 is a feed screw that is provided between the motor shaft 31 and the valve shaft 32 of the stepper motor 30 and converts the rotational motion of the motor shaft 31 into the vertical motion of the valve shaft 33. A conversion mechanism including 32.

FIG. 19 shows the flow rate of the EGR valve 11 [liter /
Is a characteristic diagram showing the relationship between the [minutes] and the number of steps of the stepper motor 30, the horizontal axis represents the number of steps of the stepper motor 30, and the vertical axis represents the EGR flow rate. In the flow rate characteristic of FIG. 19, when the step number of the stepper motor 30 is “0”, EG
The R valve 11 is fully closed, the number of steps of the stepper motor 30 is "48", and the EGR valve 11 is fully opened.

In this case, when the EGR valve 11 is fully opened (EGR
EGR valve 1 at a flow rate of 500 [liters / minute])
It shows that the pressure difference ΔP between the inlet and the outlet of No. 1 is 200 mmHg. Pressure difference ΔP before and after the EGR valve 11
Needless to say, is higher than 200 mmHg on the fully closed side.

20 and 21 are flow charts showing the operation of the CPU 200 of the conventional exhaust gas recirculation control device. FIG. 20 is a main routine process, and FIG. 21 is EGR.
A control processing routine is shown. Next, the operation of the conventional exhaust gas recirculation control device shown in FIGS. 16 to 18 will be described with reference to FIGS. 19 to 21.

First, in another control processing step S1 in the main routine, processing such as calculation of the engine speed Ne based on the ignition signal Q, reading of a sensor signal from the A / D converter 203, and fuel control are performed. Be seen. When this control processing step S1 is completed, subsequently, the EGR control processing step S2 is carried out, and the process returns to step S1. The engine 1 is controlled by the above control processing steps S1 and S2.

EGR control processing step S2 in FIG.
Is specifically executed as shown in FIG. First, in step S601, another control processing routine S has already been executed.
The engine speed Ne and the intake air amount Qa for which the processing is completed in 1 are read. Then, in step S602, the read engine speed Ne and the intake air amount Q are read.
A predetermined target stepper motor opening (number of steps) is calculated based on a.

Subsequently, in order to perform the correction according to the engine warm-up state of the engine 1, the water temperature T which has been processed by the other processing routine S1 is read in step S603. Next, in step S604, depending on the water temperature T, S6
The target stepper motor opening obtained in 02 is corrected so as to decrease as the water temperature T decreases.

Finally, in step S605, the stepper motor 30 is driven to reach the target stepper motor opening calculated and corrected in steps S602 and S604, and the process returns. The above processing steps S601-
The EGR flow rate Qr is controlled in S605.

Next, the specific operation of the stepper motor 30 will be described with reference to FIGS. 22 and 23. 22A and 22B are explanatory diagrams showing the relative relationship between the phases of the stepper motor 30 that drives the EGR valve 11 and the connection relationship between the stepper motor 30 and the electronic control unit 22. In addition, FIGS. 23A and 23B are explanatory diagrams showing a drive pattern and a rotation direction of the stepper motor 30 by the two-phase excitation method.

As shown in FIG. 22, the windings of the coil A and the coil B are bi-ferrier windings having a positive common of the battery 20, and when one is excited on the same coil, the magnetic flux directions of the other are reversed. Is configured.

The stepper motor 30 constructed as described above
Is driven by the two-phase excitation method shown in FIG. 23, the step position “0” is represented by the number in the circle in FIG. 22 (1).
Phase and (2) phase stators (hatched portions in FIG. 22A) are excited. Therefore, the stator is shown in FIG.
The distribution of magnetic poles (N, S) shown in is, and in response to this,
The S pole of the rotor is positioned at the step position "0" corresponding to the center of the N pole combined by the (1) phase and the (2) phase.

In the step position "1", the coil A is
Since the magnetic pole of is reversed and the excitation of the (1) phase is released and the (3) phase is excited, the S pole of the rotor has the (2) phase and the (2) phase as indicated by the arrow shown in FIG. 3) Move to the step position "1" corresponding to the center of the N pole synthesized by the phases.

In the step position "2", the coil B is
Since the magnetic pole of is reversed and the excitation of the (2) phase is released and the (4) phase is excited, the S pole of the rotor further moves to the step position "2". After that, the magnetic field is generated while being shifted by two phases and a similar pattern is applied to generate a rotating magnetic field, and the step movement is repeated, and the motor shaft 31 rotates counterclockwise as shown in FIG. Also, FIG.
When the pattern is changed in the opposite direction to 3 (a), the rotation direction of the motor shaft 31 becomes opposite (clockwise direction).

Using the above method, the predetermined time interval τ (100 msec, 100 PPS [pulse / pulse] in FIG.
By exciting each coil of the stepper motor 30 for (equivalent to seconds), the valve opening α of the EGR valve 11 (corresponding to the flow rate Qr) can be controlled.

Although the stepper motor type EGR valve 11 is used as the actuator for controlling the EGR amount here, a vacuum motor type EGR valve may be used. In this case, if a position sensor for detecting the EGR valve opening α is further provided, the EGR valve opening α can be controlled and the EGR flow rate Qr can be controlled as described above.

However, since the EGR valve opening α is controlled, the EGR valve 11 is controlled by E due to manufacturing variations and changes over time.
When the GR valve 11 is clogged or the like, an error ΔQr may occur in the relationship between the EGR valve opening α and the EGR flow rate Qr as shown in FIG. 24, and the exhaust gas discharge amount may increase. In FIG. 24, the solid line is the characteristic of a regular product, the broken line is the characteristic of a valve-clogging product due to aging, and the alternate long and short dash line is the upper and lower limit characteristics of manufacturing variation.

When the variation ΔQr in the EGR flow rate characteristic as shown in FIG. 24 occurs, the accurate EG is obtained only by the EGR valve opening α.
The R flow rate Qr cannot be obtained, and in particular, it becomes impossible to cope with the strengthening of the exhaust gas regulation value as seen in California in the United States in recent years. Also, due to variations in the engine 1 and other parts, EG
An error occurs in the R flow rate Qr.

Furthermore, in the case of an EGR control device equipped with a vaporized gas recovery system (not shown), the vaporized gas recovery system operates independently of the EGR control, so that the EGR
It is possible that the control and the evaporated gas recovery system operate simultaneously. In this case, the intake pipe pressure Pm changes due to the influence of the operation of the evaporated gas recovery system, and it becomes impossible to accurately calculate the EGR flow rate Qr.

[0030]

Since the conventional exhaust gas recirculation control device is constructed as described above and controls the EGR flow rate Qr by the EGR valve opening α depending on the operating condition, the EGR valve 11 E due to manufacturing variations and changes over time
When the GR valve is clogged, as shown in FIG.
There is a problem that an error occurs in the relationship between the R valve opening α and the EGR flow rate Qr, and the exhaust gas discharge amount increases.

Further, due to variations in the engine 1 and other parts, there is also a problem in that an error similarly occurs in the EGR flow rate Qr and the exhaust gas discharge amount increases.

Further, when the transpiration gas recovery system is provided and the transpiration gas recovery system operates simultaneously with the EGR control, the intake pipe pressure Pm changes due to the influence of the operation of the transpiration gas recovery system, and the accurate EGR is performed. There is a problem that the flow rate Qr cannot be calculated, an error occurs in the EGR flow rate Qr, and the exhaust gas discharge amount increases.

The first aspect of the present invention has been made to solve the above problems, and provides an exhaust gas recirculation control device capable of accurately controlling the EGR flow rate regardless of the characteristic variation of the EGR valve. The purpose is to get.

A second aspect of the present invention is to provide an exhaust gas recirculation control device according to the first aspect, which can control the EGR flow rate more accurately.

A third aspect of the present invention is to provide an exhaust gas recirculation control device according to the first or second aspect, in which the atmospheric pressure sensor can be omitted.

Further, a fourth object of the present invention is to provide an exhaust gas recirculation control device in which the reliability of EGR flow rate control is improved by omitting the intake pipe pressure sensor without increasing the cost. To do.

According to a fifth aspect of the present invention, the intake pipe pressure calculated by the fourth aspect is corrected and an error due to variations in the engine and other parts is compensated, thereby further improving the reliability of the EGR flow rate control. It is an object of the present invention to obtain an exhaust gas recirculation control device having improved exhaust gas.

A sixth object of the present invention is to provide an exhaust gas recirculation control device which omits the air flow sensor and improves the reliability of the EGR flow rate control without increasing the cost.

According to a seventh aspect of the present invention, the intake air amount obtained by the calculation in the sixth aspect is corrected to compensate for an error due to variations in the engine and other parts, thereby further improving the reliability of the EGR flow rate control. It is an object of the present invention to obtain an exhaust gas recirculation control device having improved exhaust gas.

An eighth object of the present invention is to provide an exhaust gas recirculation control device in which the atmospheric pressure sensor can be omitted.

Further, claim 9 and claim 1 of the present invention.
0 is to prevent the change of the intake pipe pressure due to the operation of the evaporated gas recovery system and eliminate the influence of the evaporated gas recovery system, thereby obtaining an exhaust gas recirculation control device with further improved reliability of EGR flow rate control. To aim.

[0042]

An exhaust gas recirculation control device according to claim 1 of the present invention controls an EGR pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, and an EGR flow rate of exhaust gas flowing in the EGR pipe. EGR valve, a sensor means for detecting the operating state of the internal combustion engine, and an EGR flow rate control means for controlling the EGR valve according to the operating state information from the sensor means. In the exhaust gas recirculation control device for recirculating to the internal combustion engine, the sensor means includes an air flow sensor that detects an intake air amount to the intake pipe, an intake pipe pressure sensor that detects a pressure in the intake pipe,
A target EGR rate calculation unit that includes an EGR pressure sensor that detects the pressure in the EGR pipe and that calculates a target EGR rate according to the operating state information, an intake air amount, an intake pipe pressure, and an E
Actual EGR for calculating the actual EGR rate based on the GR pressure
EGR flow rate calculating means including rate calculating means,
The flow rate control means changes the passage area of the EGR valve so that the EGR rate matches the target EGR rate.
It controls the flow rate.

The 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 an orifice is provided in the EGR pipe downstream of the installation position of the EGR pressure sensor.

Further, 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 or second aspect, which is based on the intake pipe pressure when the internal combustion engine is stopped or the intake pipe is fully opened. An atmospheric pressure detecting means for obtaining the atmospheric pressure is provided.

The exhaust gas recirculation control device according to claim 4 of the present invention is an EGR pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, and an EGR of exhaust gas flowing in the EGR pipe.
An EGR valve for controlling the flow rate, a sensor means for detecting the operating state of the internal combustion engine, and an EGR flow rate control means for controlling the EGR valve according to the operating state information from the sensor means are provided, In the exhaust gas recirculation control device for recirculating a part of the internal combustion engine again, the sensor means is an air flow sensor for detecting the amount of intake air to the intake pipe, and E
And an EGR pressure sensor for detecting the pressure in the GR pipe,
Intake pipe pressure calculating means for calculating the pressure in the intake pipe based on the rotational speed of the internal combustion engine and the intake air amount, target EGR rate calculating means for calculating the target EGR rate according to the operating state information, intake air amount, intake air The EGR flow rate control means includes an EGR flow rate calculation means including an actual EGR rate calculation means for calculating an actual EGR rate based on the pipe pressure and the EGR pressure.
By changing the passage area of the EGR valve, the EGR flow rate is controlled so that the EGR rate matches the target EGR rate.

Further, an exhaust gas recirculation control device according to a fifth aspect of the present invention is the exhaust gas recirculation control device according to the fourth aspect, wherein the means for determining the steady operating state of the internal combustion engine and the EGR flow rate forced when the steady operating state is determined. EGR control prohibiting means for making it to zero, EGR pressure deviation calculating means for calculating the deviation between the EGR pressure during EGR control in the steady operation state and the EGR pressure in the EGR control prohibiting state, and the intake pipe based on the EGR pressure deviation. Intake pipe pressure correction means for correcting the pressure is provided.

An exhaust gas recirculation control device according to claim 6 of the present invention is an EGR pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, and an EGR of exhaust gas flowing in the EGR pipe.
An EGR valve for controlling the flow rate, a sensor means for detecting the operating state of the internal combustion engine, and an EGR flow rate control means for controlling the EGR valve according to the operating state information from the sensor means are provided, In the exhaust gas recirculation control device for recirculating a part of the internal combustion engine again, the sensor means includes an intake pipe pressure sensor for detecting the pressure in the intake pipe and an EGR pressure sensor for detecting the pressure in the EGR pipe. Intake air amount calculating means for calculating the intake air amount to the intake pipe based on the rotation speed and the intake pipe pressure, target EGR rate calculating means for calculating the target EGR rate according to the operating state information, intake air amount, intake air The EGR flow rate control means includes an EGR flow rate calculation means including an actual EGR rate calculation means for calculating an actual EGR rate based on the pipe pressure and the EGR pressure.
By changing the passage area of the EGR valve, the EGR flow rate is controlled so that the EGR rate matches the target EGR rate.

The exhaust gas recirculation control device according to a seventh aspect of the present invention is the exhaust gas recirculation control device according to the sixth aspect, wherein the means for determining the steady operation state of the internal combustion engine and the EGR flow rate forced when the steady operation state is determined. EGR control prohibiting means for making it to zero, EGR pressure deviation calculating means for calculating the deviation between the EGR pressure during EGR control in the steady operation state and the EGR pressure in the EGR control prohibiting state, and the intake air based on the EGR pressure deviation. Intake air amount correction means for correcting the amount is provided.

Further, an exhaust gas recirculation control device according to an eighth aspect of the present invention is the exhaust gas recirculation control device according to the sixth or seventh aspect, which is based on the intake pipe pressure when the internal combustion engine is stopped or when the intake pipe is fully opened. An atmospheric pressure detecting means for obtaining the atmospheric pressure is provided.

Further, an exhaust gas recirculation control device according to a ninth aspect of the present invention is the exhaust gas recirculation control device according to any one of the first to eighth aspects, in which the vaporized gas from the fuel tank is recovered by the internal combustion engine. Means, evaporative gas introduction amount detecting means for detecting the amount of vaporized gas introduced, and EGR flow rate correction means for correcting the EGR flow rate according to the amount of vaporized gas introduced are provided.

Further, an exhaust gas recirculation control device according to a ninth aspect of the present invention is the exhaust gas recirculation control device according to any one of the first to eighth aspects, wherein vaporized gas from the fuel tank is recovered by an internal combustion engine. And means for prohibiting the operation of the vaporized gas recovery means during the execution of the EGR control.

[0052]

According to the first aspect of the present invention, the operating condition, the intake air amount, the intake pipe pressure and the EGR pressure are detected, and the target EGR ratio and the actual EGR ratio are calculated from the operating condition, the intake pipe pressure and the EGR pressure according to a predetermined calculation formula. Is estimated and calculated based on the intake air amount, the target EGR rate and the actual EGR rate.
Control the R valve opening. As a result, the EGR flow rate is accurately controlled to reduce the exhaust gas emission amount.

Further, according to the second aspect of the present invention, the orifice is used to make the pressure difference between the EGR pressure and the intake pipe pressure noticeable, and the operating state, the intake air amount, the intake pipe pressure and the EGR pressure are detected to perform the operation. The target EGR rate and the actual EGR rate are estimated and calculated from the state, the intake pipe pressure and the EGR pressure according to a predetermined calculation formula, and the EGR valve opening degree is controlled based on the intake air amount, the target EGR rate and the actual EGR rate.
As a result, the EGR flow rate is accurately controlled to reduce the exhaust gas emission amount.

Further, according to the third aspect of the present invention, the operating state, the intake air amount, the intake pipe pressure and the EGR pressure are detected, and the atmospheric pressure is estimated and detected from the intake pipe pressure at the stop operating state or when the intake pipe is fully opened. The target EG is calculated from the operating state, the intake pipe pressure and the EGR pressure according to a predetermined calculation formula.
The R rate and the actual EGR rate are estimated and calculated, and the EGR valve opening degree is controlled based on the intake air amount, the target EGR rate, and the actual EGR rate. As a result, the atmospheric pressure sensor is not required, the cost is reduced, and the EGR flow rate is accurately controlled to reduce the exhaust gas emission amount.

According to the fourth aspect of the present invention, the operating condition, the intake air amount and the EGR pressure are detected, and the intake pipe pressure, the target EGR rate, the actual EGR rate and the atmospheric pressure are estimated and calculated according to a predetermined calculation formula. The exhaust gas emission amount is reduced by controlling the EGR valve opening degree based on the intake air amount, the target EGR rate and the actual EGR rate, and accurately controlling the EGR flow rate. Further, the intake pipe pressure sensor is not required, and the cost is reduced.

Further, in the fifth aspect of the present invention, the operating condition, the intake air amount and the EGR pressure are detected, and the intake pipe pressure, the target EGR rate, the actual EGR rate and the atmospheric pressure are estimated and calculated according to a predetermined calculation formula. , The EGR valve opening degree is controlled based on the intake air amount, the target EGR rate, and the actual EGR rate, and the EGR flow rate is accurately controlled. As a result, the exhaust gas discharge amount is reduced, and the intake pipe pressure sensor is not required, and the cost is reduced. In addition, EG in a predetermined operating state
The calculated intake air amount is corrected based on the EGR passage pressure deviation with and without R to compensate for variations in parts such as the engine and the EGR valve.

According to the sixth aspect of the present invention, the operating condition, the intake pipe pressure and the EGR pressure are detected, and the intake air amount, the target EGR rate, the actual EGR rate and the atmospheric pressure are estimated and calculated according to a predetermined calculation formula. The exhaust gas emission amount is reduced by controlling the EGR valve opening degree based on the intake air amount, the target EGR rate and the actual EGR rate, and accurately controlling the EGR flow rate. Further, the cost can be reduced by eliminating the need for the air flow sensor.

According to a seventh aspect of the present invention, the operating state, the intake pipe pressure and the EGR pressure are detected, and the intake air amount, the target EGR rate, the actual EGR rate and the atmospheric pressure are estimated and calculated according to a predetermined calculation formula. , The EGR valve opening degree is controlled based on the intake air amount, the target EGR rate, and the actual EGR rate, and the EGR flow rate is accurately controlled. As a result, the exhaust gas emission amount is reduced, and the cost reduction is realized by eliminating the need for the air flow sensor. In addition, EG in a predetermined operating state
The calculated intake air amount is corrected based on the EGR passage pressure deviation with and without R to compensate for variations in parts such as the engine and the EGR valve.

According to the eighth aspect of the present invention, the operating state, the intake pipe pressure and the EGR pressure are detected, and the atmospheric pressure is estimated and detected from the stopped operating state or the intake pipe pressure at the time of full opening, and the operating state, The intake air amount, the target EGR rate, and the actual EGR rate are estimated and calculated from the intake pipe pressure and the EGR pressure according to a predetermined calculation formula, and the intake air amount, the target EGR rate are calculated.
The EGR valve opening degree is controlled based on the rate and the actual EGR rate. As a result, the EGR flow rate is accurately controlled to reduce the exhaust gas discharge amount, and the air flow sensor and the atmospheric pressure sensor are not required, and the cost is reduced.

In the ninth aspect of the present invention, the amount of vaporized gas introduced is calculated and the EGR flow rate is corrected from the amount of vaporized gas introduced to eliminate the influence of the vaporized gas recovery system.

In the tenth aspect of the present invention,
During the EGR control, the operation of the evaporated gas recovery system is prohibited to eliminate the influence of the evaporated gas recovery system.

[0062]

【Example】

Example 1. Embodiment 1 (corresponding to claims 1 to 3) of the present invention will be described below with reference to the drawings. 1 is a block diagram schematically showing the entire system of Embodiment 1 of the present invention, FIG. 2 is a block diagram showing the details of the electronic control unit 22 in FIG. 1, and FIG. 3 is an EGR pipe 10 in FIG. It is an expanded sectional view which shows a peripheral part, and in each figure, 1-5, 7-17, 20-20
22, 100 to 105 and 200 to 208 are the same as described above. In this case, the function of the EGR flow rate control means in the electronic control unit 22 is different from that described above. Also, E
The specific structure and driving method of the GR valve 11 are as shown in FIGS. 18, 19, 22, and 23. Reference numeral 6 is an intake pipe pressure sensor for detecting the intake pipe pressure Pm of the intake manifold in the intake pipe 3, and 18 is the EGR pressure Pr in the EGR pipe 10.
The intake pipe pressure Pm and the EGR pressure Pr are input to the electronic control unit 22.

Reference numeral 19 is an orifice provided in the EGR pipe 10 so that a pressure difference is easily generated between both ends of the EGR pipe 10. The orifice 19 is located downstream of the installation position of the EGR pressure sensor 18, that is, at a position closer to the intake pipe 3. It is provided. An alarm lamp 23 is turned on in response to the alarm signal F from the electronic control unit 22.

Further, in FIG. 3, Pa is the atmospheric pressure for calculating the intake air amount Qa as the mass in the intake pipe 3,
Pex is the exhaust pressure in the exhaust pipe 15. Since there is a pressure difference in the EGR pipe 10 without providing the orifice 19, the orifice 19 can be omitted.

The electronic control unit 22 calculates the target EGR flow rate Qo according to the operating state information from various sensor means including the intake pipe pressure sensor 6, the air flow sensor 12, the EGR pressure sensor 18, etc. And EGR flow rate control means for controlling the EGR valve 11 so that the EGR flow rate Qr matches the target EGR flow rate Qo, and when the internal combustion engine is stopped or the intake pipe 3 is fully open (the throttle valve 7 is fully open). Atmospheric pressure detecting means for determining the atmospheric pressure Pa based on the intake pipe pressure Pm is provided.
In the first embodiment, the target EGR flow rate calculating means is realized as means for determining the number of steps of the stepping motor.

Further, the EGR in the electronic control unit 22
The flow rate calculation means determines the target EGR rate β according to the operating state information.
target EGR rate calculating means for calculating o, and intake air amount Q
a, an actual EGR rate calculation means for calculating an actual EGR rate βr based on the intake pipe pressure Pm and the EGR pressure Pr, and the EGR flow rate control means changes the passage area of the EGR valve 11 to change the EGR rate. βr is the target EGR rate βo
The EGR flow rate Qr is controlled so as to coincide with.

The EGR rate βr is the EGR flow rate Qr with respect to the new intake air amount Qa, and is a value represented by the relational expression (Qr / Qa) described later. The target EGR rate βo is a value preset according to various operating conditions (operating state information).

Next, referring to the flow charts of FIGS. 4 and 5, the first embodiment of the present invention shown in FIGS.
The operation of will be described. When the EGR control process (step S2) is executed by the main routine of FIG. 20, the EGR control process routine of FIG. 4 is executed as follows.

First, in step S131, the engine speed Ne, the intake air amount Qa, the water temperature T, etc. are read based on various sensor input signals, and then step S1.
In 32, based on the read information, the target stepper motor opening αo and the target EGR rate β determined in advance are determined.
Read o. These steps S131 and S13
2 corresponds to steps S601 to S604 described above (FIG. 21) except that the target EGR rate βo is read.

Here, if there is no variation in the engine 1 and the EGR valve 11, the target stepper motor opening α
When the EGR valve 11 is opened at o, the target EGR rate βo is obtained. Next, in order to control the EGR rate βr, step S1
At 33, the intake pipe pressure Pm and EGR pressure Pr are read, and at step S134, the following equation (1) (Bernoulli equation) is calculated to obtain EG
The R flow rate Qr is calculated.

Qr = Kr · Ar · √ {2g · (Pr / RTr) · (Pr-Pm)} ... (1)

However, in the equation (1), Kr is the flow coefficient of the orifice 19, Ar is the passage area of the orifice 19 or the area of the EGR pipe 10 (when there is no orifice), g
Is gravity acceleration, R is a gas constant, Tr is a gas temperature upstream of the orifice 19, Pr is an EGR pressure detected by the EGR pressure sensor 18, Pm is an intake pipe pressure detected by the intake pipe pressure sensor 6, and a flow rate. The coefficient Kr, the passage area Ar, the gravitational acceleration g, and the gas constant R are constants.

In the equation (1), (Pr / RT
r) is a value related to the gas density, and is less affected by changes in the gas temperature Tr and the exhaust pressure Pex on the upstream side of the EGR pipe 10 (about 10 ppm each with respect to the change range of the gas temperature Tr and the exhaust pressure Pex). ), So can be considered almost constant. So in practice,
The equation (1) is modified and simplified as the following equation (2) to be the calculation target.

Qr≈K√ (Pr-Pm) (2)

However, in the equation (2), K = Kr · Ar
A coefficient corresponding to {square root} {2g · (Pr / RTr)}. As is clear from the equation (2), the EGR flow rate Qr is
It is obtained from the EGR pressure Pr and the intake pipe pressure Pm.

Next, in step S135, the actual EGR rate βr is calculated. At this time, the EGR rate βr is
EGR flow rate Qr and intake air amount Q equivalent to new intake mass
Using a, it can be calculated as follows.

Βr = Qr / Qa

Therefore, by substituting equation (2), EG
The R rate βr is expressed by the following equation (3).

Βr = (K / Qa) √ (Pr−Pm) (3)

Thus, steps S131 to S135
Thus, the EGR flow rate Qr can be obtained from the EGR pressure Pr and the intake pipe pressure Pm. Therefore, when the intake pipe pressure sensor 6, the air flow sensor 12 and the EGR pressure sensor 18 are provided, the intake air amount Qa,
Using the EGR pressure Pr and the intake pipe pressure Pm, the EGR
The rate βr can be accurately detected.

As described above, the target EGR rate βo and the actual E
After obtaining the GR rate βr, in step S136, a deviation Δβ between the target EGR rate βo and the actual EGR rate βr is calculated, and it is determined whether or not they match each other depending on whether or not the EGR rate deviation Δβ = 0. .

If it is determined that βo = βr (that is, YES), the actual EGR rate βr matches the target EGR rate. Therefore, in step S137, the EGR valve 11
Stop the stepper motor drive of the stepper motor opening α
Hold. On the other hand, if it is determined that the actual EGR rate βr does not match the target EGR rate (that is, NO), the process proceeds to step S138 and E calculated in step S136.
The stepper motor opening α of the EGR valve 11 is changed according to the GR rate deviation Δβ.

From the above processing, the target EGR rate βo and the actual E
The control can be performed so that the GR rate βr matches, and the EGR rate βr can be controlled according to the operating state. Further, the electronic control unit 22 detects the atmospheric pressure Pa using the intake pipe pressure Pm from the intake pipe pressure sensor 6 by the processing routine of FIG.

First, in step S141, it is determined from the engine rotation information whether the operating state is the engine stall state. If it is determined that the engine is in the stalled state (that is, YES), the intake pipe pressure Pm at this time is the atmospheric pressure Pa.
Therefore, in step S142, the intake pipe pressure Pm is taken in as the atmospheric pressure Pa, and step S14
Go to 3.

On the other hand, the engine is not in the stalled state (that is, N
If it is determined to be O), the process immediately proceeds to step S143,
Based on the information from the throttle opening sensor 8, it is determined whether or not the throttle opening θ is equal to or larger than a predetermined value indicating full opening.

If the throttle opening θ is equal to or greater than a predetermined value and the throttle valve 7 is fully open (that is, YE
If it is determined to be S) (when it is specified that the throttle opening θ is equal to or more than a predetermined value to be fully opened), the intake pipe pressure Pm at this time is determined.
Indicates a pressure reduced from the atmospheric pressure Pa by a pressure loss amount γ of the intake system, the process proceeds to step S144, the loss amount γ is added to the intake pipe pressure Pm, the atmospheric pressure Pa is taken in, and the process returns.

On the other hand, the throttle opening θ is less than the predetermined value and the throttle valve 7 is not in the fully open state (that is, N
If it is determined to be O), step S144 is skipped and the process directly returns.

The above processing (steps S141 to S14)
4), the intake pipe pressure sensor 6 provided in the intake pipe 3
Since the atmospheric pressure Pa can be detected by using, the atmospheric pressure sensor for converting the intake air amount information Qa from the air flow sensor 12 for measuring the volume flow rate into the mass flow rate is unnecessary. Therefore, without inviting cost increase
Accurate EGR control can be realized.

Further, in the device of the present invention, the EGR flow rate Q
Although the stepper motor type EGR valve 11 is used as an actuator for controlling r, if a vacuum motor type EGR valve is used as described above and a position sensor for detecting the EGR valve opening α is provided, this Similarly to the invention, the EGR valve opening α can be controlled to control the EGR flow rate Qr.

Example 2. In the first embodiment described above, it is necessary to provide the two intake pipe pressure sensors 6 and 18 to detect the intake pipe pressure Pm and the EGR pressure Pr.
Sufficient cost reduction cannot be realized. Therefore, the intake pipe pressure Pm may be calculated without using the intake pipe pressure sensor 6.

FIG. 6 is a block diagram showing the entire system of Embodiment 2 (corresponding to claim 4) of the present invention in which the intake pipe pressure sensor 6 is omitted, and FIG. 7 is a detailed configuration of the electronic control unit 22 in FIG. FIG. 1 is a block diagram showing
5, 7 to 23, 100 to 105 and 200 to 208 are the same as described above. In this case, the electronic control unit 22 includes a calculation means for calculating the intake pipe pressure Pm.

Next, the operation of the second embodiment of the present invention shown in FIGS. 6 and 7 will be described with reference to the flowchart of FIG. In FIG. 8, S131 and S132
And S134 to S138 are the same steps as described above, and S133a and S133b are the same as step S1 described above.
It corresponds to 33. When EGR control step S2 is executed in the main routine of FIG. 20, E of FIG.
The execution of the GR control routine starts.

First, in step S131, the engine speed Ne, the intake air amount Qa, and the water temperature T are read, and in step S132, the target stepper motor opening α and the target EGR rate βo are read out, based on the read information.
In order to control the EGR rate βr, in step S133a, the intake pipe pressure Pm is calculated as follows. That is, the intake pipe pressure Pm is expressed by the following equation (4) from the theoretical equation.

Pm = {(Qa + Qr) 2R · Tm} / (Vc · Ne · ηv) (4)

However, in the equation (4), Tm is the intake pipe 3
Inside temperature, Vc is the cylinder volume of the engine 1, Ne is the engine speed, and ηv is the volumetric efficiency. Here, when the actual target EGR rate βo corresponding to each operating point is determined according to the operating state, the target EGR rate βo is represented by the following equation (5) from βr = βo.

Βo = Qr / Qa (5)

By substituting the equation (5) into the equation (4), the intake pipe pressure Pm is expressed by the following equation (6).

Pm = (Qa / Ne) (1-βo) 2R · Tm / (Vc · ηv) ... (6)

Since the target EGR rate βo, the intake pipe temperature Tm, and the volumetric efficiency ηv can be set in advance based on the load (Qa / Ne) and the engine speed Ne, the intake pipe pressure Pm is equal to the load ( Qa / Ne) and the function f of the engine speed Ne can be expressed by the following equation (7).

Pm = f {(Qa / Ne), Ne} · (Qa / Ne) (7)

Next, in step S133b, the EGR
The pressure Pr is read, and the above steps S134 to
Execute S138. That is, the equation (2) is calculated in step S134 to calculate the EGR flow rate Qr, the equation (3) is calculated in step S135 to calculate the actual EGR rate βr, and the target EGR rate is calculated in step S136. It is determined whether or not βo and the actual EGR rate βr match. If they match, the stepper motor drive is stopped in step S137, and if they do not match, the stepper motor is driven according to the EGR rate deviation Δβ in step S138. Change the opening α.

From the above processing, as in the case of the first embodiment, control is performed so that the target EGR rate βo and the actual EGR rate βr match, and it is possible to control the EGR rate βr according to the operating condition. Become. Therefore, accurate EGR control can be realized without increasing costs.

Example 3. Conventionally, there is a device that performs fuel injection control using the intake pipe pressure sensor 6, but when the first embodiment of the present invention is applied, it is necessary to add the air flow sensor 12 and the EGR pressure sensor 18. Therefore, the cost is increased. Therefore, the air flow sensor 12 may be omitted and the intake air amount Qa may be calculated based on the operating state and the intake pipe pressure Pm.

FIG. 9 is a block diagram showing the entire system of Embodiment 3 (corresponding to claim 6) of the present invention in which the air flow sensor 12 is omitted, and FIG. 10 is an electronic control unit 22 in FIG.
FIG. 3 is a block diagram showing a detailed configuration of FIG.
-11, 13-23, 100-105 and 200-2
08 is the same as that described above. In this case, the electronic control unit 22 includes a calculation means for calculating the intake air amount Qa.

Next, the operation of the third embodiment of the present invention will be described with reference to the flowchart of FIG. In FIG. 11, S131 to S138 are the same steps as described above, and S200 is a step of calculating the intake air amount Qa without using the air flow sensor 12. Similar to the above, when the EGR control step S2 is executed in the main routine of FIG. 20, execution of the EGR control routine of FIG. 11 is started.

First, in step S131, the engine speed Ne, the intake pipe pressure Pm, and the water temperature T are read, and in step S132, the target stepper motor opening α and the target EGR rate βo are read based on the read information. Here, if there is no variation in the engine 1 and the EGR valve 11, the target EGR rate βo can be obtained by opening the EGR valve 11 at the target stepper motor opening αo.

Next, in step S133, E
After reading the GR pressure Pr and calculating the EGR flow rate Qr from the calculation of the above equation (2) in step S134,
In order to control the EGR rate βr, in step S200, the intake air amount Qa is calculated as follows. First, the total intake air amount Qm (= Qa + Qr) in the intake pipe 3
Is expressed by the following equation (8) from the theoretical equation.

Qm = {Vc · Ne · ηv / (2R · Tm)} × Pm (8)

However, in the equation (8), Vc is the cylinder volume, Ne is the engine speed, ηv is the volumetric efficiency, R is the gas constant, Tm is the intake pipe internal temperature, and Pm is the intake pipe pressure. Further, the volume efficiency ηv is calculated by using the function f of the intake pipe pressure Pm, the engine speed Ne and the target EGR rate βo.
It is expressed by the following equation (9).

Ηv = f (Pm, Ne, βo) (9)

In the equation (9), the actual target EG
When the R rate βo is determined by the operating state, the volumetric efficiency ηv
Is a function of the intake pipe pressure Pm and the engine speed Ne, and is expressed by the following equation (10).

Ηv = f (Pm, Ne) (10)

From the expressions (8) and (10), the total intake air amount Qm is expressed by the following expression (11).

Qm = Kp · f (Pm, Ne) · Ne · Pm (11)

However, in the equation (11), Kp is a constant and is expressed as follows.

Kp = Vc / (2R · Tm)

Therefore, the intake air amount Qa is expressed by the following equation (12).

Qa = Qm−Qr = Kp · f (Pm, Ne) · Ne · Pm−Qr (12)

Then, in step S135, the actual EGR rate βr is calculated from the above equation (3), and in step S13
In step 6, the deviation Δβ between the target EGR rate βo and the actual EGR rate βr obtained in steps S132 and S135 is calculated, and it is determined whether or not they match.

If the target EGR rate βo and the actual EGR are
If the rate βr matches, the actual EGR rate βr is the target EG.
Since the R ratio is βo, the stepper motor drive is stopped to maintain the stepper motor opening α, and if they do not match, the process proceeds to step S138, and the stepper motor is opened according to the EGR ratio deviation Δβ calculated in step S136. Change the motor opening α.

As a result, the target EGR rate βo and the actual EGR are
The control can be performed so as to match the rate βr, and the EGR rate βr can be controlled according to the operating state. With the above configuration and processing, cost increase is suppressed and accurate E
GR control can be performed.

Example 4. (Corresponding to Claim 8) In the third embodiment, since the intake pipe pressure sensor 6 is provided, the intake pipe when the engine 1 is stopped or the intake pipe is fully opened, as in the first embodiment. The atmospheric pressure sensor can be omitted by estimating and detecting the atmospheric pressure based on the pressure Pm.

Example 5. In addition, the said Example 2-Example 4
Then, in order to realize the cost reduction by omitting the sensor, the intake pipe pressure Pm and the intake air amount Qa are calculated by the predetermined arithmetic expressions, that is, the expressions (7) and (12), and the EGR control is executed. , If there are variations in the components of the engine 1, the EGR valve 11, etc., an error will occur in the intake pipe pressure Pm and the intake air amount Qa obtained from the above equation, and eventually an error will occur in the EGR control. .

Therefore, it is desirable to compensate the above EGR control error due to variations in the parts of the engine 1, the EGR valve 11 and the like. FIG. 12 shows a fifth embodiment of the present invention in which a control error due to component variation can be compensated by offset correction.
9 is a flowchart showing a compensation processing routine (corresponding to claim 5 and claim 7).

In this case, the electronic control unit 22 of the second embodiment (FIG. 6) and the third embodiment (FIG. 9) is provided with a steady operation determining means for determining the steady operation state of the internal combustion engine and a steady operation state. EGR control prohibiting means for forcibly setting the EGR flow rate Qr to 0 when determined, and a deviation ΔPr between the EGR pressure Pra during EGR control in the steady operation state and the EGR pressure Prb in the EGR control prohibiting state E
GR pressure deviation calculating means is provided.

When the fifth embodiment is applied, the EGR pressure deviation Δ is included in the electronic control unit 22 of the second embodiment.
Intake pipe pressure correction means for correcting the intake pipe pressure Pm based on Pr is provided, and the electronic control unit 22 of the third embodiment is provided.
Is based on the EGR pressure deviation ΔPr.
Intake air amount correction means for correcting the above is provided. As a result, the intake pipe pressure P calculated in step S133a
m and the intake air amount Qa calculated in step S203 are respectively compensated.

First, in step S211 in FIG. 12, it is determined whether the engine 1 is in a steady operation state. That is, after confirming that the engine 1 is in the warm-up state with the EGR control, it is determined whether the engine 1 is in the steady operation state depending on whether the variation of the engine speed Ne and the variation of the throttle opening θ are below a predetermined value. Determine whether or not.

If it is not in a steady operation state (that is, N
If it is determined to be O), the routine directly returns, and if it is determined to be in the steady operation state (that is, YES), the process proceeds to step S212, and the pressure PrA in the EGR passage 10 in the state with EGR control is detected. .

Then, in step S213, EG
After the EGR control is forcibly turned off by the R control prohibiting means, the pressure PrB in the EGR passage 10 in the state without the EGR control is detected in step S214. next,
From the detected EGR pressures PrA and PrB, EGR
The pressure deviation ΔPr is calculated. If there is no variation in the parts of the engine 1 and the like, the EGR pressure deviation ΔPr becomes a predetermined value.

On the other hand, if there are variations in the parts, E
Since the change appears in the GR pressure deviation ΔPr, step S
At 216, the correction coefficient corresponding to the EGR pressure deviation ΔPr is read by map calculation or the like. In this way, the correction coefficient for the component variation is obtained from the EGR pressure deviation ΔPr when the EGR control is switched to the presence or absence during the steady operation.

Hereinafter, using the variation correction coefficient, the intake pipe pressure Pm (see step S133a in FIG. 8) and the intake air amount Qa (FIG. 1) calculated as described above.
Multiply or add to 0) (see step S203 in 0) so as to cancel the variation error. As a result, it is possible to compensate for the EGR control error caused by the component variation.

Example 6. In addition, the said Example 1-Example 5
In the above, the EGR flow rate Qr and the atmospheric pressure Pa are detected based on the information of the intake air amount Qa, the intake pipe pressure Pm, and the EGR pressure Pr, and the EGR flow rate Qr is accurately controlled. In the case of a device having a vaporized gas recovery means), the vaporized gas is introduced into the intake manifold of the intake pipe 3 in addition to the EGR flow rate Qr, so that the intake pipe pressure Pm may change due to the introduction of the vaporized gas.

As the intake pipe pressure Pm changes,
An error occurs in the EGR flow rate Qr, which causes an error in the EGR control. Therefore, it is desirable to compensate the EGR control error due to the operation of the evaporated gas recovery system.

FIG. 13 is a block diagram showing a sixth embodiment (corresponding to claim 9) of the present invention which is capable of compensating for a control error in the case of having a vaporized gas recovery system, and FIG. 14 is an electronic control in FIG. It is a block diagram which shows the detail of the unit 22, 1-23, 100-105, and 2 in each figure.
00 to 208 are the same as those described above.

24 to 28 are constituent elements of the evaporated gas recovery system, 24 is a recovery tube for introducing evaporated gas into the intake pipe 3, and 25 is the opening and closing of the recovery pipe 24 under the control of the electronic control unit 22. And a purge solenoid 25 for selectively introducing vaporized gas into the intake pipe 3, and 26 is a purge solenoid 25.
Is a canister provided on the upstream side of the canister for adsorbing evaporated gas, 27 is a check valve provided on the upstream side of the canister 26, and 28 is a fuel tank provided on the upstream end of the recovery pipe 24 and filled with fuel. .

The vaporized gas recovery systems 24 to 28 configured as described above operate as follows. First, the fuel in the fuel tank 28 is evaporated to become vaporized gas, and when the pressure of the vaporized gas exceeds a predetermined pressure, the check valve 2
7 is opened and the vaporized gas is adsorbed by the canister 26.

On the other hand, if the predetermined condition is satisfied after the engine 1 is started, the electronic control unit 22 operates the purge solenoid 25 by the purge control signal Cp to operate the vaporized gas adsorbed by the canister 26 in the engine 1. Intake pipe 3
Introduce inside. Thereby, the evaporated gas generated from the fuel tank 28 can be recovered by the engine 1.

In this case, the evaporated gas recovery means 24 for recovering the evaporated gas from the fuel tank 28 to the engine 1 to
Since the electronic control unit 22 is provided with 27, the electronic control unit 22 estimates and detects the purge control means for generating the purge control signal Cp according to the operating state and the vaporized gas introduction amount Qp by the map calculation according to the operating state. Evaporated gas introduction amount detection means and EGR flow rate correction means for correcting the EGR flow rate Qr according to the evaporated gas introduction amount Qp are provided.

Next, the compensating operation according to the sixth embodiment of the present invention will be described with reference to the flowchart of FIG. FIG. 15 shows the EGR flow rate Q when the amount of transpiration gas is detected.
7 is a flowchart showing a processing routine for compensating for r.

First, in step S241, the amount Q of evaporated gas introduced into the engine 1 is changed according to the operating state.
Calculate p. Next, in step S242, the true EGR is calculated from the evaporated gas introduction amount Qp and the EGR flow rate Qr.
The flow rate Qr 'is calculated by the following equation (13).

Qr '= Qr-Qp (13)

As a result, the EGR flow rate Qr is corrected,
Accurate EGR control becomes possible. Needless to say, accurate EGR control is possible even when the EGR control and the evaporated gas recovery system are operated independently.

Example 7. In the sixth embodiment, the true EGR flow rate Qr 'is obtained in step S242.
The true target EGR flow rate Qo ′ is calculated to obtain the target EGR flow rate Qo.
Even if is corrected, the true EGR flow rate Qr 'can be obtained as a result. In addition, the EGR rate βr depends on the amount of transpiration gas introduction Qp.
Or even if the target EGR rate βo is corrected, the true E
The GR flow rate Qr 'is obtained and the same effect is achieved.

Example 8. In the sixth embodiment, the evaporated gas introduction amount detecting means estimates and detects the evaporated gas introduction amount Qp by the calculation based on the operating state. However, the evaporated gas introduction amount Qp is provided downstream of the purge solenoid 25. May be directly detected.

Example 9. (Corresponding to Claim 10) Further, in the sixth embodiment, the EGR flow rate Qr is corrected by subtracting the evaporated gas introduction amount Qp to obtain the true EGR flow rate Qr '. However, the electronic control unit 2
2 may be provided with a vaporized gas recovery inhibiting means to inhibit the operation of the vaporized gas recovery system during the EGR control.

That is, the evaporative gas recovery prohibiting means in the electronic control unit 22 fixes the purge control signal Cp to OFF and sets the evaporative gas introduction amount Qp to 0 when it is determined that the EGR control is being performed. As a result, the evaporated gas is not recovered, so that a control error does not occur in the EGR flow rate Qr.

[0147]

As described above, according to claim 1 of the present invention, an EGR pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, an EGR valve for controlling an EGR flow rate of exhaust gas flowing in the EGR pipe, A sensor means for detecting the operating state of the internal combustion engine and an EGR flow rate control means for controlling the EGR valve according to the operating state information from the sensor means are provided, and a part of the exhaust gas of the internal combustion engine is recirculated to the internal combustion engine. In the exhaust gas recirculation control device, the sensor means includes an air flow sensor that detects the amount of intake air to the intake pipe, an intake pipe pressure sensor that detects the pressure in the intake pipe, and an EGR pressure sensor that detects the pressure in the EGR pipe. And an actual EGR rate based on the intake air amount, the intake pipe pressure and the EGR pressure, and a target EGR rate calculating means for calculating the target EGR rate according to the operating state information. EGR including the actual EGR rate calculating means
The EGR flow rate controlling means has a flow rate calculating means, and the EGR flow rate controlling means changes the passage area of the EGR valve to change the EGR rate to the target EG.
Since the EGR flow rate is controlled so as to match the R ratio, the EG is accurately controlled regardless of the characteristic variation of the EGR valve.
There is an effect that an exhaust gas recirculation control device capable of controlling the R flow rate and reducing the exhaust gas discharge amount can be obtained.

According to a second aspect of the present invention, in the first aspect, an orifice is provided in the EGR pipe on the downstream side of the installation position of the EGR pressure sensor, and the E is formed by the orifice.
Since the pressure difference between the GR pressure and the intake pipe pressure is made remarkable, an exhaust gas recirculation control device capable of controlling the EGR flow rate more accurately can be obtained.

Further, according to claim 3 of the present invention, in claim 1 or 2, the atmospheric pressure for obtaining the atmospheric pressure based on the intake pipe pressure when the internal combustion engine is stopped or when the intake pipe is fully opened. Since the detection means is provided, there is an effect that an exhaust gas recirculation control device that can realize cost reduction by eliminating the atmospheric pressure sensor and that can accurately control the EGR flow rate regardless of the characteristic variation of the EGR valve can be obtained.

According to the fourth aspect of the present invention, the EGR pipe for recirculating the exhaust gas of the internal combustion engine to the intake pipe, and the EG
EGR for controlling the EGR flow rate of exhaust gas flowing in the R pipe
A valve, a sensor means for detecting an operating state of the internal combustion engine, and an EGR flow rate control means for controlling the EGR valve according to operating state information from the sensor means, and a part of exhaust gas of the internal combustion engine In the exhaust gas recirculation control device that recirculates into the exhaust gas, the sensor means includes an air flow sensor that detects the amount of intake air into the intake pipe and an EGR pressure sensor that detects the pressure in the EGR pipe. Intake pipe pressure calculating means for calculating the pressure in the intake pipe based on the air amount, target EGR rate calculating means for calculating the target EGR rate according to the operating state information, and based on the intake air amount, the intake pipe pressure and the EGR pressure The EGR flow rate control means includes an actual EGR rate calculation means for calculating an actual EGR rate, and the EGR flow rate control means changes the passage area of the EGR valve. Since the EGR flow rate is controlled so that the EGR rate coincides with the target EGR rate, the intake pipe pressure sensor is not required, the cost is reduced, and the exhaust gas recirculation control is improved in the reliability of the EGR flow rate control. There is an effect that the device can be obtained.

According to claim 5 of the present invention, in claim 4, the means for determining the steady operating state of the internal combustion engine and the EGR flow rate forcibly set to 0 when the steady operating state is determined. EGR control prohibition means, EGR pressure deviation calculation means for calculating the deviation between the EGR pressure during EGR control in the steady operation state and the EGR pressure in the EGR control prohibited state, and intake air for correcting the intake pipe pressure based on the EGR pressure deviation. Since the pipe pressure correcting means is provided, the intake pipe pressure sensor is not required, the cost can be reduced, the error due to the variation of the engine and other parts can be compensated, and the reliability of the EGR flow rate control is further improved. There is an effect that the exhaust gas recirculation control device can be obtained.

According to the sixth aspect of the present invention, the EGR pipe for recirculating the exhaust gas of the internal combustion engine to the intake pipe, and the EG
EGR for controlling the EGR flow rate of exhaust gas flowing in the R pipe
A valve, a sensor means for detecting an operating state of the internal combustion engine, and an EGR flow rate control means for controlling the EGR valve according to operating state information from the sensor means, and a part of exhaust gas of the internal combustion engine In the exhaust gas recirculation control device that recirculates into the exhaust gas recirculation, the sensor means includes an intake pipe pressure sensor that detects the pressure inside the intake pipe, and an EG that detects the pressure inside the EGR pipe.
An intake air amount calculation means including an R pressure sensor for calculating the intake air amount into the intake pipe based on the rotational speed of the internal combustion engine and the intake pipe pressure, and a target EGR ratio for calculating a target EGR rate according to the operating state information. The EGR flow rate control means includes an EGR flow rate calculation means including a rate calculation means and an actual EGR rate calculation means for calculating an actual EGR rate based on the intake air amount, the intake pipe pressure and the EGR pressure. By changing the passage area, the EGR flow rate is controlled so that the EGR rate matches the target EGR rate. Therefore, an air flow sensor is not required and cost reduction is realized, and the reliability of EGR flow rate control is improved. There is an effect that the exhaust gas recirculation control device can be obtained.

According to claim 7 of the present invention, in claim 6, the means for determining the steady operating state of the internal combustion engine and the EGR flow rate forcibly set to 0 when the steady operating state is determined. EGR control prohibition means, EGR pressure deviation calculation means for calculating the deviation between the EGR pressure during EGR control in the steady operation state and the EGR pressure in the EGR control prohibited state, and intake air for correcting the intake air amount based on the EGR pressure deviation Since the air amount correction means is provided, the cost can be reduced by eliminating the need for an air flow sensor, and errors due to variations in the engine and other parts can be compensated, and the reliability of EGR flow rate control is improved. There is an effect that a reflux control device can be obtained.

Further, according to claim 8 of the present invention, in claim 6 or claim 7, the atmospheric pressure for obtaining the atmospheric pressure based on the intake pipe pressure when the internal combustion engine is stopped or the intake pipe is fully opened. Since the detection means is provided, the air flow sensor and the atmospheric pressure sensor are not required, and the cost is reduced. Furthermore, an exhaust gas recirculation control device that can accurately control the EGR flow rate regardless of the characteristic variation of the EGR valve is obtained. It is effective.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the vaporized gas recovery means for recovering the vaporized gas from the fuel tank to the internal combustion engine, and the vaporized gas The amount of vaporized gas introduction detecting means for detecting the amount of vaporized gas introduced and the EGR flow rate correction means for correcting the EGR flow rate according to the amount of vaporized gas introduced are provided to prevent the intake pipe pressure from changing during the operation of the vaporized gas recovery system. Since the effect of the transpiration gas recovery system is eliminated,
There is an effect that an exhaust gas recirculation control device with improved reliability of GR flow rate control can be obtained.

According to a tenth aspect of the present invention, in any one of the first to eighth aspects, the vaporized gas recovery means for recovering the vaporized gas from the fuel tank to the internal combustion engine and the EGR control are provided. Since the evaporative gas recovery prohibition means for prohibiting the operation of the evaporative gas recovery means during the execution of
The effect of the evaporated gas recovery system on the EGR control is eliminated, and an exhaust gas recirculation control device with improved reliability of the EGR flow rate control can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing an entire system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of the electronic control unit in FIG.

FIG. 3 is an enlarged sectional view showing the periphery of an EGR pipe in FIG.

FIG. 4 is an E according to the main routine of the first embodiment of the present invention.
It is a flow chart which shows operation of GR control processing.

FIG. 5 is a flowchart showing an atmospheric pressure detection process according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram schematically showing an entire system according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a specific configuration of the electronic control unit in FIG.

FIG. 8 is a flowchart showing an operation of EGR control processing according to the second embodiment of the present invention.

FIG. 9 is a configuration diagram schematically showing an entire system of Embodiment 3 of the present invention.

10 is a block diagram showing a specific configuration of the electronic control unit in FIG.

FIG. 11 is a flowchart showing an EGR processing operation according to the third embodiment of the present invention.

FIG. 12 is a flowchart showing a compensation processing operation according to the fifth embodiment of the present invention.

FIG. 13 is a configuration diagram schematically showing an entire system of embodiment 6 of the present invention.

FIG. 14 is a block diagram showing a specific configuration of the electronic control unit in FIG.

FIG. 15 is a flowchart showing a compensation processing operation according to the amount of evaporated gas introduced according to the sixth embodiment of the present invention.

FIG. 16 is a configuration diagram showing an entire system of a conventional stepper motor type exhaust gas recirculation control device.

17 is a block diagram showing a specific configuration of the electronic control unit in FIG.

FIG. 18 is a side sectional view showing a specific configuration of the EGR valve in FIG.

FIG. 19 is a characteristic diagram showing a flow rate characteristic of a general EGR valve.

FIG. 20 is a flowchart showing a main routine of a control processing operation by a general electronic control unit.

FIG. 21 is a flowchart showing a conventional EGR control processing operation.

FIG. 22 is an explanatory diagram showing the operation principle of a general stepper motor together with a drive basic connection diagram.

FIG. 23 is an explanatory diagram showing a drive pattern and a rotation direction of a general stepper motor by a two-phase excitation method.

FIG. 24 is a characteristic diagram for explaining problems in conventional EGR control.

[Explanation of symbols]

1 engine 3 intake pipe 6 intake pipe pressure sensor 8 throttle opening sensor 10 EGR pipe 11 EGR valve 12 air flow sensor 13 ignition coil 15 exhaust pipe 17 water temperature sensor 18 EGR pressure sensor 19 orifice 22 electronic control unit 24 recovery pipe 25 purge solenoid 26 canister 27 check valve 28 fuel tank Cr EGR control signal Cp purge control signal Pa atmospheric pressure Pm intake pipe pressure Pr EGR pressure PrA EGR pressure during EGR control PrB EGR pressure when EGR control is prohibited Qa intake air amount Qr EGR flow rate T cooling Water temperature Q Ignition signal βo Target EGR rate βr Actual EGR rate θ Throttle opening S132 Step of calculating target EGR rate S133a Step of calculating intake pipe pressure S134 Step of calculating EGR flow rate S1 35 Step for calculating actual EGR rate S136 Step for comparing target EGR rate and actual EGR rate S138 Step for controlling EGR flow rate according to EGR rate deviation S141 Steps for determining stop state of internal combustion engine S142, S144 Atmospheric pressure Step S143 of estimating and detecting Step S143 Step of determining the fully open state of the intake pipe S200 Step of calculating the intake air amount S211 Step of determining the steady operation state S212 Step of detecting the EGR pressure during EGR control S213 Force the EGR flow rate to 0 Step S214 Step for detecting EGR pressure when EGR control is prohibited S215 Step for calculating EGR pressure deviation S216 Step for calculating correction coefficient based on EGR pressure deviation S241 Step for calculating and detecting introduced amount of vaporized gas S242 Steam Step of correcting the EGR rate according to the gas introduction amount

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[Procedure amendment]

[Submission date] February 10, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

FIG. 19 shows the pressure at the inlet and outlet of the EGR valve 11 .
6 is a characteristic diagram showing the relationship between the flow rate [liter / minute] of the EGR valve 11 and the number of steps of the stepper motor 30 when the force difference ΔP is 200 mmHg , the horizontal axis represents the number of steps of the stepper motor 30, and the vertical axis represents EGR. Indicates the flow rate. FIG. 19
In the flow rate characteristic, the stepper motor 30 has the number of steps "0" and the EGR valve 11 is fully closed, and the stepper motor 30 has the number of steps "48" and the EGR valve 11 is fully open.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Delete

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0129

[Correction method] Change

[Correction content]

Then, in step S213, EG
After the EGR control is forcibly turned off by the R control prohibiting means, the pressure PrB in the EGR passage 10 in the state without the EGR control is detected in step S214. As well
To forcibly introduce EGR during deceleration (without EGR)
Even if EGR is used, pressures PrA and PrB are detected.
can do. Next, the detected EGR pressure PrA
From Eq. And PrB, the EGR pressure deviation ΔPr is calculated.
If there is no variation in parts such as engine 1, EG
The R pressure deviation ΔPr has a predetermined value.

Claims (10)

[Claims] 1. An EGR pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, an EGR valve for controlling an EGR flow rate of exhaust gas flowing in the EGR pipe, and sensor means for detecting an operating state of the internal combustion engine, The EGR according to the operating state information from the sensor means.
An exhaust gas recirculation control device for recirculating a part of exhaust gas of the internal combustion engine to the internal combustion engine, the sensor means comprising: an EGR flow rate control means for controlling a valve; A target for calculating a target EGR rate in accordance with the operating state information, including an air flow sensor for detecting a pressure, an intake pipe pressure sensor for detecting a pressure in the intake pipe, and an EGR pressure sensor for detecting a pressure in the EGR pipe. An EGR rate calculating means and an actual E for calculating an actual EGR rate based on the intake air amount, the intake pipe pressure and the EGR pressure.
EGR flow rate calculation means including a GR rate calculation means is provided, and the EGR flow rate control means changes the passage area of the EGR valve so that the EGR rate matches the target EGR rate. An exhaust gas recirculation control device for controlling the exhaust gas recirculation. 2. The exhaust gas recirculation control device according to claim 1, wherein an orifice is provided in the EGR pipe downstream of the installation position of the EGR pressure sensor. 3. An atmospheric pressure detecting means for determining an atmospheric pressure based on the intake pipe pressure when the internal combustion engine is stopped or when the intake pipe is fully opened. 2. Exhaust gas recirculation control device. 4. An EGR pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, an EGR valve for controlling an EGR flow rate of exhaust gas flowing in the EGR pipe, and sensor means for detecting an operating state of the internal combustion engine, The EGR according to the operating state information from the sensor means.
An exhaust gas recirculation control device for recirculating a part of exhaust gas of the internal combustion engine to the internal combustion engine, the sensor means comprising: an EGR flow rate control means for controlling a valve; An intake air pressure sensor for detecting the pressure in the EGR pipe, and an EGR pressure sensor for detecting the pressure in the EGR pipe, and an intake pipe pressure calculating means for calculating the pressure in the intake pipe based on the rotational speed of the internal combustion engine and the intake air amount. ,
A target EGR rate calculating means for calculating a target EGR rate according to the operating state information, and an actual E for calculating an actual EGR rate based on the intake air amount, the intake pipe pressure and the EGR pressure.
EGR flow rate calculation means including a GR rate calculation means is provided, and the EGR flow rate control means changes the passage area of the EGR valve so that the EGR rate matches the target EGR rate. An exhaust gas recirculation control device for controlling the exhaust gas recirculation. 5. A means for determining a steady operating state of the internal combustion engine, an EGR control prohibiting means for forcibly reducing the EGR flow rate to 0 when the steady operating state is determined, and an EGR in the steady operating state. EGR pressure deviation calculating means for calculating a deviation between the EGR pressure during control and EGR pressure in the EGR control prohibited state, and intake pipe pressure correcting means for correcting the intake pipe pressure based on the EGR pressure deviation are provided. The exhaust gas recirculation control device according to claim 4, wherein 6. An EGR pipe that recirculates exhaust gas of an internal combustion engine to an intake pipe, an EGR valve that controls an EGR flow rate of exhaust gas that flows in the EGR pipe, and a sensor unit that detects an operating state of the internal combustion engine. The EGR according to the operating state information from the sensor means.
An exhaust gas recirculation control device that recirculates a part of the exhaust gas of the internal combustion engine to the internal combustion engine again, the sensor means detecting the pressure in the intake pipe. Intake pipe pressure sensor and EG for detecting pressure in the EGR pipe
An intake air amount calculation means for calculating the intake air amount to the intake pipe based on the rotational speed of the internal combustion engine and the intake pipe pressure; and a target EGR rate according to the operating state information. EGR flow rate calculating means including target EGR rate calculating means for performing the above, and actual EGR rate calculating means for calculating an actual EGR rate based on the intake air amount, the intake pipe pressure, and the EGR pressure. The exhaust gas recirculation control device controls the EGR flow rate so that the EGR rate matches the target EGR rate by changing the passage area of the EGR valve. 7. A means for determining a steady operating state of the internal combustion engine, an EGR control prohibiting means for forcibly reducing the EGR flow rate to 0 when the steady operating state is determined, and an EGR in the steady operating state. EGR pressure deviation calculating means for calculating a deviation between the EGR pressure during control and EGR pressure in the EGR control prohibited state, and intake air amount correcting means for correcting the intake air amount based on the EGR pressure deviation are provided. 7. The exhaust gas recirculation control device according to claim 6. 8. The atmospheric pressure detecting means for determining the atmospheric pressure based on the intake pipe pressure when the internal combustion engine is stopped or when the intake pipe is fully open. Exhaust gas recirculation control device of 7. 9. A vaporized gas recovery means for recovering vaporized gas from a fuel tank to the internal combustion engine, a vaporized gas introduction amount detecting means for detecting an introduced amount of the vaporized gas, and a vaporized gas introduction amount according to the vaporized gas introduction amount. 9. An exhaust gas recirculation control device according to claim 1, further comprising: an EGR flow rate correction means for correcting the EGR flow rate. 10. A vaporized gas recovery means for recovering vaporized gas from a fuel tank to the internal combustion engine, and vaporized gas recovery inhibiting means for inhibiting operation of the vaporized gas recovery means during execution of the EGR control. The exhaust gas recirculation control device according to claim 1, wherein the exhaust gas recirculation control device is provided.