JP2004278326A - Egr control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EGR control device for further flexibly controlling EGR quantity over a wide range by using a turbocharger. <P>SOLUTION: This EGR control device is applied to an internal combustion engine 1 having the turbocharger 10 drivable by an electric motor 10d. An ECU 17 operates the electric motor 10d so that the EGR quantity is controlled in a desired value. When the EGR quantity is insufficient for the desired value, electric power is generated by the electric motor 10d, or the electric motor 10d is operated so that the turbocharger 10 is held in a stopping state, or the electric motor 10d is driven in the inverse direction of supercharging time. When the EGR quantity is excessive to the desired value, the electric motor 10d is driven in the rotational direction at supercharging time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an EGR amount in an internal combustion engine.
[0002]
[Prior art]
In an internal combustion engine equipped with a turbocharger with a variable nozzle, when the EGR amount is insufficient even when the EGR valve is operated to the maximum opening, the variable nozzle of the turbocharger is throttled to increase the exhaust back pressure, thereby increasing the EGR amount. An EGR control device for increasing the pressure is known (for example, see Patent Document 1). In addition, there is Patent Document 2 as a related art related to the present invention.
[0003]
[Patent Document 1]
JP 2001-152879 A
[Patent Document 2]
JP 2000-500544 A
[Problems to be solved by the invention]
[0004]
However, since the variable nozzle is a device that merely restricts the exhaust gas, the control range of the back pressure is narrowly limited, and the adjustment range of the EGR amount is relatively narrow. For example, when the exhaust flow rate is absolutely low and the rotation is low, even if the nozzle is narrowed down in order to enhance the supercharging effect, the amount of change in the exhaust back pressure is small if the opening degree of the nozzle is slightly changed from that state. As described above, in the adjustment of the EGR amount by the variable nozzle, there is always a restriction according to the operating state of the internal combustion engine.
[0005]
Therefore, an object of the present invention is to provide an EGR control device capable of controlling an EGR amount more flexibly and widely using a turbocharger.
[0006]
[Means for Solving the Problems]
An EGR control device according to the present invention is an EGR control device applied to an internal combustion engine having a turbocharger drivable by the electric motor, wherein the electric motor operates the electric motor such that the EGR amount of the internal combustion engine is controlled to a target value. By providing the control means, the above-mentioned problem is solved (claim 1).
[0007]
According to the present invention, by operating the electric motor, the turbine rotor of the turbocharger can be driven in a state different from a state where the turbine rotor is freely driven to rotate by the exhaust gas. For example, electric power can be generated by a motor using the rotation of a turbine rotor, or the turbine rotor can be held in a stopped state against the flow of exhaust gas by the electric motor, or the electric motor can be rotated in the opposite direction to that during supercharging. . In these cases, the resistance of the exhaust gas when passing through the turbine rotor increases as compared with the case where the turbine rotor is freely rotated by the exhaust energy. For this reason, the exhaust back pressure increases and the EGR amount increases. On the other hand, when the electric motor is operated so as to increase the speed of the turbocharger in the rotation direction at the time of supercharging, the exhaust back pressure decreases and the EGR amount decreases. In addition, since the turbine rotor is driven by the electric motor, the rotation speed and the rotation direction of the turbine rotor can be freely changed without being restricted by the exhaust flow unlike the case where the opening degree of the nozzle is adjusted. Therefore, the EGR amount can be flexibly and widely controlled regardless of the operation state of the internal combustion engine. The operation of the motor by the motor control means according to the present invention may be any as long as it adjusts the driving state of the motor so that the EGR amount converges to the target value, and operates the motor until the EGR amount matches the target value. Is not a requirement.
[0008]
In the EGR control device of the present invention, the electric motor control means generates electric power by the electric motor when the EGR amount is insufficient with respect to the target value, or controls the electric motor so that the turbocharger is kept stopped. The electric motor may be operated, or the electric motor may be driven in a direction opposite to that at the time of supercharging (claim 2). In this case, as described above, the rotation of the turbine due to the exhaust is hindered by the operation of the electric motor, and the exhaust back pressure increases. Therefore, the shortage of the EGR amount can be compensated. On the other hand, when the EGR amount is excessive with respect to the target value, the electric motor control means may drive the electric motor in a rotation direction at the time of supercharging (claim 3). In this case, the electric motor acts so as to further increase the rotation of the turbine caused by the exhaust, and the exhaust back pressure is reduced. Therefore, the EGR amount can be reduced to contribute to eliminating the excessive state.
[0009]
In the EGR control device of the present invention, as means for controlling the EGR amount to the target value, an EGR amount adjusting means is provided separately from the electric motor control means, and the electric motor control means is controlled by the EGR amount adjusting means. The motor may be operated so as to reduce the deviation of the EGR amount from the target value that cannot be eliminated (claim 4).
[0010]
According to this aspect, it is possible to control the EGR amount which cannot be realized by the EGR amount adjusting means alone. For example, when the control of the EGR amount by the EGR amount adjusting means reaches the maximum or minimum of the adjustment range, the motor is operated so as to reduce the deviation of the remaining EGR amount from the target value (claim Item 5), the EGR amount can be increased or decreased beyond the adjustment range by the EGR amount adjusting means. Alternatively, when the electric motor is operated so as to reduce the deviation of the EGR from the target value which cannot be eliminated by the EGR amount adjusting resolution by the EGR amount adjusting means (Claim 6), the EGR amount cannot be realized by the EGR amount adjusting means. You can make fine adjustments to the volume. Further, in particular, when the EGR amount is changed by operating the turbocharger motor only when the adjustment by the EGR amount adjusting means is at a limit, the operation of the turbocharger motor for the purpose of EGR amount control is not performed. The effect on the supercharging effect can be minimized. As the EGR amount adjusting means, for example, an EGR valve whose opening degree is adjustable and which is installed in an EGR passage connecting the exhaust passage and the intake passage, and a variable valve which can control an overlapping amount of the opening timing of the intake valve and the exhaust valve. A mechanism can be used. The EGR valve and the variable valve mechanism may be combined to form EGR amount adjusting means. In addition, various devices that can adjust the EGR amount may be used as the EGR amount adjusting means.
[0011]
In the present invention, the target value of the EGR amount may be explicitly calculated based on the operating state of the internal combustion engine, or may be a potential value determined in relation to the target value of control relating to a physical quantity other than the EGR amount. May be. For example, a target value is set for the NOx emission amount, and the EGR amount is set in accordance with the deviation between the target value and the actual measurement value by the NOx sensor provided in the exhaust passage or the predicted value of the NOx emission amount predicted from the operating state of the internal combustion engine. Is controlled, the target value is not calculated for the EGR amount itself. However, there is an optimal EGR amount for controlling the actual measured value or the predicted value of the NOx emission amount to the target value, and the entity of the EGR amount control sets the EGR amount as the target value with the optimal EGR amount as the target value. It's nothing more than adjusting. The concept of the target value of the EGR amount referred to in the present invention includes such a potential target value. Therefore, the case where the EGR amount adjusting means such as the turbocharger motor or the EGR valve is operated based on the concept of the EGR rate is naturally included in the scope of the present invention in that the target value of the EGR amount can be derived from the target value of the EGR rate. It is what is done.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an embodiment of an internal combustion engine to which the EGR control device of the present invention is applied. The internal combustion engine 1 is an in-cylinder injection gasoline engine that takes in air from an intake passage 2 into a cylinder 3 and directly injects fuel from a fuel injection valve 4 into the cylinder 3 to form a fuel mixture in the cylinder 3. It is configured. The fuel mixture formed in the cylinder 3 is ignited by the ignition plug 5 and burns, and the piston 6 is reciprocated by the combustion energy. Although the internal combustion engine 1 is provided with a plurality of cylinders 3, FIG. 1 shows only a single cylinder 3 as a representative. The intake passage 2 and the exhaust passage 7 are opened and closed with respect to the cylinder 3 by an intake valve 8 and an exhaust valve 9, respectively. The internal combustion engine 1 may be a so-called port injection type gasoline engine that injects fuel from the fuel injection valve 4 into the intake passage 2 or a diesel engine using light oil as fuel.
[0013]
A turbocharger 10 is provided between the intake passage 2 and the exhaust passage 7. The turbocharger 10 includes a turbine rotor 10a housed in the exhaust passage 7, a compressor rotor 10b housed in the intake passage 2, and a spindle 10c coaxially connecting the rotors 10a and 10b. This is a well-known supercharging device that supercharges the intake air in the intake passage 2 to the cylinder 3 by integrally rotating the turbine rotor 10a, the spindle 10c, and the compressor rotor 10b using energy. However, the turbocharger 10 of the present embodiment is configured as a turbocharger with an electric motor including an electric motor 10d that drives a spindle 10c. The electric motor 10d can be configured by, for example, attaching a rotor to the spindle 10c and arranging a stator around the spindle 10c.
[0014]
The electric motor 10d can rotate the spindle 10c in both forward and reverse directions with electric power supplied from the battery 12 via the inverter 11, and can also generate electric power by being driven by the spindle 10c. The electric power generated by the electric motor 10 d is charged into the battery 12 via the inverter 11. The forward rotation of the electric motor 10d corresponds to the rotation direction when the turbine rotor 10a of the turbocharger 10 is rotated by the exhaust gas. On the turbine 10a side of the turbocharger 10, a variable nozzle may be provided in addition to the electric motor 10d as a means for adjusting the exhaust back pressure.
[0015]
An air filter 13 is arranged upstream of the compressor rotor 10b in the intake passage 2, and an intercooler 14 and a throttle valve 15 are arranged downstream of the compressor rotor 10b. An exhaust purification catalyst 16 is provided in the exhaust passage 7 downstream of the turbine rotor 10a.
[0016]
The throttle valve 15 is a so-called electronically controlled throttle valve whose opening is controlled by operating a throttle motor 18 by an engine control unit (ECU) 17. The ECU 17 is configured as a computer having a CPU, a RAM, a ROM, and an input / output interface as peripheral devices necessary for the operation of the internal combustion engine 1 and various programs attached to the internal combustion engine 1 according to various programs recorded in the ROM. Control the operation of the device. To control the opening of the throttle valve 15, information on the operation amount of the accelerator pedal 20 detected by the pedal position sensor 19 and information on the opening of the throttle valve 15 detected by the throttle opening sensor 21 are input to the ECU 17. You.
[0017]
In addition to the opening of the throttle valve 15, the ECU 17 also controls the fuel injection timing of the fuel injection valve 4, the ignition timing of the ignition plug 5, and the EGR valve 23 installed in the EGR passage 22 connecting the exhaust passage 7 and the intake passage 2. , An opening / closing operation of a bypass valve 25 provided in a bypass passage 24 bypassing the turbocharger 10, an operation of a variable valve mechanism 26 for changing the opening / closing timing of the intake valve 8, and the like. The EGR valve 23 is an electronically controlled flow control valve whose opening is adjusted according to an instruction from the ECU 17.
[0018]
In order to appropriately control the operations of the various devices described above in accordance with the operating state of the internal combustion engine 1, the ECU 17 transmits the intake pressure in addition to the information detected by the pedal position sensor 19 and the throttle opening sensor 21 described above. Information corresponding to the pressure of the intake passage 2 (intake pipe pressure) detected by the sensor 27 and information corresponding to the crank angle detected by the crank angle sensor 28 are input. In addition, the temperature of the cooling water of the internal combustion engine 1, the air-fuel ratio in the exhaust passage 7, and the like are detected by sensors and input to the ECU 17, but these are not shown. The procedure of control of the fuel injection valve 4, the ignition plug 5, the EGR valve 23, and the bypass valve 25 by the ECU 17 may be the same as that for a known internal combustion engine, and is not the gist of the present invention, so that the description is omitted here.
[0019]
The ECU 17 controls the EGR amount toward a predetermined target value by adjusting the opening degree of the EGR valve 23 or the amount of overlap between the opening timings of the intake valve 8 and the exhaust valve 9 by the variable valve mechanism 26. Is done. The target value of the EGR amount here is a value necessary for optimally controlling the combustion state in the cylinder 3 in view of the operation state of the internal combustion engine 1. The target value of the EGR amount may be calculated by the ECU 17 based on detection signals from various sensors, or may be a potential value specified by a target value of a physical quantity other than the EGR amount representing the operating state of the internal combustion engine 1. May be. The EGR amount can be adjusted by operating the bypass valve 25 to adjust the supercharging pressure, or by adjusting the opening of the variable nozzle of the turbocharger 10. However, in the present embodiment, the EGR valve is particularly controlled. It is assumed that 23 and / or the variable valve mechanism 26 correspond to the EGR amount adjusting means.
[0020]
The electric motor 10d of the turbocharger 10 is operated by the ECU 17 via the inverter 11. For example, when a sufficient supercharging effect cannot be obtained only by the rotation of the turbine rotor 10a due to the exhaust energy, the electric motor is supplied from the battery 12 through the inverter 11 so that the supercharging effect according to the supercharging instruction from the ECU 17 is obtained. Electric power is supplied to 10d, and the electric motor 10d is driven forward. When the turbine rotor 10a is rotating in spite of not requiring a supercharging effect as in the case of deceleration of the internal combustion engine 1, that is, when the turbine rotor 10a has excess rotational energy, a power generation instruction from the ECU 17 is issued. , The operation state of the inverter 11 is switched, and electric power is generated by the electric motor 10 d, and the obtained power is charged into the battery 12 via the inverter 11. The operation of the electric motor 10d of the turbocharger 10 for the purpose of controlling the supercharging pressure may be performed in the same manner as the control of other turbochargers with electric motors.
[0021]
The ECU 17 also functions as a motor operation unit that operates the electric motor 10d to control the EGR amount to a target value. In the ROM of the ECU 17, conditions for executing the adjustment of the EGR amount using the electric motor 10d are stored in advance in association with the operating state of the internal combustion engine 1, and when the operating state of the internal combustion engine 1 satisfies the conditions, the ECU 17 Executes the EGR amount control routine of FIG. 2 for controlling the EGR amount and operates the electric motor 10d. Note that the routine of FIG. 2 is repeatedly executed at predetermined intervals while the internal combustion engine 1 is operating.
[0022]
In the EGR amount control routine of FIG. 2, the ECU 17 first determines in step S1 whether the operation of the turbocharger with a motor (MAT, Motor Assist Turbo) 10 is required for controlling the EGR amount based on the above-described conditions. Judge in light of the light. The case where the condition is satisfied and the electric motor 10d is driven for adjusting the EGR amount will be described later.
[0023]
If no operation is requested in step S1, the current routine ends. On the other hand, if the operation is requested, the process proceeds to step S2, and it is determined whether or not an increase in the exhaust back pressure is required, in other words, whether or not the increase in the EGR amount is required. If an increase in the exhaust back pressure is required, the process proceeds to step S3, in which an instruction is given to the inverter 11 to charge the electric motor 10d, that is, to generate electric power using the rotation of the spindle 10c. As a result, the exhaust back pressure rises and the pressure difference between the exhaust passage 7 and the intake passage 2 increases, so that the flow rate of the exhaust gas returned to the intake passage 2 via the EGR passage 22 increases, and the exhaust gas remains in the cylinder 3. The amount of combustion gas (internal EGR gas) to be increased also increases. These actions increase the EGR amount.
[0024]
In the following step S4, the ignition timing map stored in the ROM is read so as to be referred to during the charge driving, and the ignition timing of the ignition plug 5 suitable for the charge driving of the electric motor 10d is obtained. Further, in step S5, the throttle opening map stored in the ROM is read so as to be referred to during the charge driving, and the opening of the throttle valve 15 suitable for the charge driving of the electric motor 10d is acquired. That is, when the electric motor 10d is charged and driven, the supercharging effect actually obtained is smaller than the supercharging effect required for the turbocharger 10. Therefore, the effect is determined by the ignition timing of the spark plug 5 and the throttle valve. In step S4 and step S5, an appropriate ignition timing and throttle opening are obtained so as to be suppressed by the correction of the opening of step 15. In this case, the shortage of the supercharging effect is compensated by increasing the ignition timing and increasing the throttle opening.
[0025]
On the other hand, if it is determined in step S2 that an increase in the exhaust back pressure is not required, the process proceeds to step S6, in which the electric motor 10d is assist-driven, that is, the electric motor 10d is driven in the forward direction so that the rotation speed of the turbine rotor 10a is only the exhaust gas. An instruction is given to the inverter 11 so that the rotation speed becomes higher than the rotation speed when the motor is rotated. In the following step S7, the ignition timing map stored in the ROM is read so as to be referred to during the assist driving, and the ignition timing of the ignition plug 5 suitable for the assist driving of the electric motor 10d is obtained. Further, in step S8, the throttle opening map stored in the ROM is read so as to be referred to at the time of assist driving, and the opening of the throttle valve 15 suitable for assist driving of the electric motor 10d is acquired. That is, when the electric motor 10d is assist-driven, the supercharging effect actually obtained is larger than the supercharging effect required for the turbocharger 10. Therefore, the effect is determined by the ignition timing of the spark plug 5 and the throttle valve. In step S7 and step S8, an appropriate ignition timing and throttle opening are obtained so as to be suppressed by the correction of the opening of step 15. In this case, the surplus of the supercharging effect is suppressed by delaying the ignition timing and decreasing the throttle opening.
[0026]
After the ignition timing and the throttle opening are obtained in step S4, S5 or S7, S8, the process proceeds to step S9 so that the obtained ignition timing and throttle opening are reflected in the actual operation of the internal combustion engine 1. Is set to the operating condition of the internal combustion engine 1. Thus, the current EGR amount control routine ends.
[0027]
Next, a specific example in which the EGR amount is controlled by the EGR amount control routine of FIG. 2 will be described with reference to FIGS.
[0028]
FIG. 3 shows the relationship between the rotational speed (rotational speed) of the internal combustion engine 1, the MAT operation flag, and the exhaust back pressure when the EGR amount is controlled by the electric motor 10 d on condition that the internal combustion engine 1 is in a cold start. Is shown. In this example, immediately after the start of the internal combustion engine 1, a measured value or a predicted value of a physical quantity such as a cooling water temperature or a combustion chamber temperature, which can be used for determining whether or not the engine is in a cold start, is referred to. Is determined, the MAT operation flag requesting the operation of the turbocharger 10 is changed from "0" to "1". In step S1 of FIG. 2, when this MAT operation flag is set to "1", it is determined that there is a MAT operation request, and a step following the case where the drive of the electric motor 10d corresponding to the cold start is requested. A positive determination is made in S2, and the electric motor 10d is driven to be charged. As a result, as shown in FIG. 3, during a certain period A immediately after the start, the exhaust back pressure increases in response to the charge driving of the electric motor 10d.
[0029]
When the electric motor 10d is charged and driven during the cold start of the internal combustion engine 1 as described above, the amount of the so-called internal EGR gas remaining in the cylinder 3 increases due to an increase in the exhaust back pressure. As a result, the pressure in the cylinder 3 increases, and the atomization of the fuel injected from the fuel injection valve 4 is promoted, whereby a favorable combustion state is realized, and as a result, the amount of HC emission decreases. Even in the case of a port injection type gasoline engine, the amount of air blown back from the cylinder 3 to the intake passage 2 while the intake valve 8 is open increases with the increase of the exhaust back pressure, thereby promoting the atomization of fuel. Thus, the same combustion improving effect can be obtained. When the internal combustion engine 1 is a diesel engine, the amount of smoke and particulate matter (PM) emitted is reduced. Further, when secondary air is supplied to the exhaust passage 7 for the purpose of promoting warm-up of the catalyst 16 and fuel is injected in the expansion stroke or the exhaust stroke, the distance between the fuel particles is reduced as the exhaust back pressure increases. In addition, the secondary combustion in the catalyst 16 is promoted, and the catalyst 16 exhibits its purification performance early.
[0030]
The advantages associated with the charging operation of the electric motor 10d as described above can also be obtained by increasing the EGR amount by opening the EGR valve 23 as an EGR amount adjusting means or operating the variable valve mechanism 26. However, in particular, the state where the increase of the EGR amount by the EGR amount adjusting means such as the EGR valve 23 has reached the limit (for example, when the EGR valve 23 is adjusted to the maximum opening degree or when the intake valve 8 and the exhaust valve 9 are opened) If the EGR amount is insufficient to its target value and the electric motor 10d is charge-driven, the EGR amount adjustment is performed. The combustion can be improved by increasing the EGR amount to a target value exceeding the limit by the means. FIG. 4 shows an example of such control. In FIG. 4, the EGR valve 23 is set to the maximum opening degree in the period B. When the MAT operation flag is switched from “0” to “1” in accordance with the period B and the electric motor 10 d is charged and driven, the increase control of the EGR amount by the electric motor 10 d is not performed (in FIG. 4, an imaginary line). The EGR rate increases as compared with the above.
[0031]
It should be noted that the EGR amount control by the electric motor 10d may also be executed when the EGR amount control by the EGR amount adjusting means reaches the minimum of the adjustment range and the EGR amount is to be further reduced. For example, in a state in which the EGR valve 23 is closed to stop the EGR through the EGR passage 22 and the amount of overlap between the opening periods of the intake valve 8 and the exhaust valve 9 is set to the minimum by the variable valve mechanism 26, the internal EGR is performed. To further reduce the amount, if the electric motor 10d is assist-driven, the exhaust back pressure can be reduced and the internal EGR amount can be reduced.
[0032]
FIG. 5 shows an example in which when the EGR valve 23 is controlled near the minimum opening and the deviation of the EGR amount from the target value is less than the resolution of the EGR valve 23, the motor 10d is driven to reduce the deviation. I have. In this example, when the opening degree of the EGR valve 23 is driven by the resolution △ a (for example, when the EGR valve 23 is driven by a stepping motor, the amount corresponding to one step), the EGR amount changes by △ b. However, in the periods C and D, the MAT operation flag is switched to “1” and the electric motor 10d is charged and driven, so that the EGR amount changes by Δc and Δd smaller than Δb. Thereby, the EGR amount can be adjusted with higher accuracy. Such control can be realized by setting as a condition for making an affirmative determination in step S1 of FIG. 2 that the deviation of the EGR amount from the target value is smaller than the minimum resolution Δa of the EGR amount by the EGR valve 23. When the EGR amount needs to be adjusted with a resolution that cannot be realized by the operation control of the variable valve mechanism 26, the EGR amount may be adjusted by the electric motor 10d as in the example of FIG.
[0033]
FIG. 6 shows a case where the assist operation is performed by the electric motor 10d to reduce the EGR amount. In this example, a region where the rotation speed of the internal combustion engine 1 is low and the load is high is set as an execution region of the EGR amount adjustment by the assist drive of the electric motor 10d (the shaded portion in the drawing). Therefore, in the EGR amount control routine of FIG. 2, in step S1, the rotational speed and the load of the internal combustion engine 1 are read to determine whether or not the output of the internal combustion engine 1 is included in the execution range in the figure. It is determined that there is a request for the assist operation by the electric motor 10d while the operation is being performed, and the process proceeds from step S2 to step S6.
[0034]
In this manner, the setting of the low-speed high-load operation as the execution range is more advantageous in that the combustion speed is reduced as an inert gas during the high-load operation in which the temperature in the cylinder 3 increases, rather than the preferable effect of the EGR of lowering the combustion temperature. This is because an undesired effect of the EGR of lowering the pressure becomes relatively large, and particularly when the engine speed is low, the possibility of occurrence of knocking or abnormal combustion increases. In the low-speed and high-load operation range, by assisting the electric motor 10d to reduce the amount of EGR, the occurrence of knocking and abnormal combustion is suppressed, thereby increasing the fuel consumption rate of the internal combustion engine 1 and preventing the internal combustion engine 1 from being damaged. can do.
[0035]
In the example of FIG. 6, whether the assist operation by the electric motor 10 d is performed is determined based on whether the operation state specified from the rotation speed and the load of the internal combustion engine 1 is in the execution range. The high temperature may be added as a condition for executing the assist operation by the electric motor 10d. The presence or absence of heavy knocking after ignition or self-ignition (preignition) before ignition is monitored by a knocking sensor or an in-cylinder pressure sensor, and the assist operation by the electric motor 10d may be executed on condition that these phenomena occur. .
[0036]
The present invention is not limited to the above embodiments, and may be implemented in various forms. For example, in the EGR amount control routine shown in FIG. 2, the electric motor 10d is driven to be charged when an increase in the exhaust back pressure is required. However, the turbine rotor 10a is stopped by the electric motor 10d against the flow of exhaust gas. , Or by rotating the electric motor 10d in the opposite direction to that at the time of supercharging to increase the exhaust back pressure. Charge driving, stop holding, or reverse rotation driving of the electric motor 10d may be selectively used according to the required adjustment amount of the exhaust back pressure.
[0037]
The operation of the electric motor of the turbocharger according to the present invention is not limited to the examples shown in FIGS. 3 to 6 and may be performed in various states in which the adjustment of the EGR amount by the electric motor of the turbocharger is considered appropriate.
[0038]
【The invention's effect】
As described above, according to the present invention, by operating the motor, the exhaust gas back pressure is increased or decreased by appropriately changing the rotational speed or the rotational direction of the turbine regardless of the operation state of the internal combustion engine, Thus, the EGR amount can be controlled flexibly and over a wide range.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an internal combustion engine to which an EGR control device according to an embodiment of the present invention is applied and an accessory device thereof.
FIG. 2 is a flowchart showing an EGR amount control routine executed by an ECU of FIG. 1;
FIG. 3 is a diagram showing the relationship among the rotation speed, the MAT operation flag, and the exhaust back pressure of the internal combustion engine when the EGR amount is increased using a turbocharger with an electric motor when the internal combustion engine is started.
FIG. 4 is a diagram showing the relationship among the EGR valve opening, the MAT operation flag, and the EGR rate when the EGR amount is further increased by using a turbocharger with a motor in a state where the opening of the EGR valve is fully opened.
FIG. 5 is a diagram showing the relationship between the EGR valve opening, the MAT operation flag, and the EGR amount when the EGR amount is adjusted with a resolution finer than the adjustment resolution by the EGR valve using a turbocharger with a motor.
FIG. 6 is a diagram showing an execution range of an operation of reducing an EGR amount by reducing an exhaust back pressure by using a turbocharger with a motor in relation to a rotation speed and a load of the internal combustion engine.
[Explanation of symbols]
1 Internal combustion engine
2 Intake passage
3 cylinder
4 Fuel injection valve
10 Turbocharger
10a Turbine rotor
10b Compressor rotor
10c spindle
10d electric motor
11 Inverter
15 Throttle valve
17 Engine control unit (motor control means)
22 EGR passage
23 EGR valve (EGR amount adjusting means)
26 Variable valve mechanism (EGR amount adjusting means)

Claims (6)

In an EGR control device applied to an internal combustion engine having a turbocharger drivable by an electric motor,
An EGR control device for an internal combustion engine, comprising: electric motor control means for operating the electric motor so that the EGR amount of the internal combustion engine is controlled to a target value. The electric motor control means generates electric power by the electric motor when the EGR amount is insufficient with respect to the target value, or operates the electric motor such that the turbocharger is kept stopped, or the electric motor The EGR control device according to claim 1, wherein the EGR control device is driven in a direction opposite to a direction at the time of supercharging. 2. The EGR control device according to claim 1, wherein the motor control unit drives the motor in a rotation direction at the time of supercharging when an EGR amount is excessive with respect to the target value. 3. As means for controlling the EGR amount to the target value, an EGR amount adjusting means is provided separately from the electric motor control means, and the electric motor control means is configured to adjust the target value of the EGR amount which cannot be eliminated by the EGR amount adjusting means. The EGR control device according to claim 1, wherein the motor is operated so as to reduce a deviation from the EGR. The electric motor control means operates the electric motor so as to reduce a deviation of the remaining EGR amount from the target value in a state where the control of the EGR amount by the EGR amount adjustment means reaches a maximum or a minimum of the adjustment range. The EGR control device according to claim 4, wherein: 5. The EGR according to claim 4, wherein the motor control unit operates the motor so as to reduce a deviation of the EGR from the target value, which cannot be resolved by the resolution of the EGR amount adjustment by the EGR amount adjustment unit. Control device.

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