JP2007132298A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit overshoot, undershoot and hunting of supercharging pressure in an internal combustion engine provided with a plurality of kinds of supercharging pressure adjustable actuators capable of adjusting supercharging pressure of turbochargers in relation to a control device for the internal combustion engine. <P>SOLUTION: The turbocharger 14 provided with a variable nozzle mechanism 14c is installed on a diesel engine 2. A motor 15 assisting turbo revolution is installed on the turbocharger 14. ECU 70 controls the variable nozzle mechanism 14c and the motor 15 to make actual supercharging pressure detected by a supercharging pressure sensor 74 consistent with target supercharging pressure. When supercharging pressure control is performed with accompanied by assist by the motor 15, opening of the variable nozzle is fixedly controlled according to a predetermined map without reflecting feed back based on supercharging pressure difference to variable nozzle opening. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine suitable as a device for controlling an internal combustion engine with a turbocharger.

  Conventionally, an internal combustion engine with a turbocharger has been widely used. As a method of reducing the turbo lag, which is a weak point of the turbo engine, a method of providing a variable nozzle mechanism that makes the exhaust turbine inlet area variable and a method of providing an electric motor that assists in turbo rotation have been proposed. Japanese Patent Laying-Open No. 2003-239755 discloses an apparatus for controlling the supercharging pressure of a turbo engine that includes both the variable nozzle mechanism and an assisting electric motor. In this device, the supercharging pressure control by the variable nozzle is prioritized and executed over the supercharging pressure control by driving the electric motor so as to prevent instability of the control due to mutual interference between the two supercharging pressure controls. I have to

JP 2003-239755 A

  The conventional supercharging pressure control device prohibits the driving of the electric motor in the operation region other than the rapid acceleration state, and controls the supercharging pressure only by the variable nozzle. For this reason, it is possible to prevent the mutual interference of the supercharging pressure control in the operation region other than the sudden acceleration state. However, in the above-described device, the supercharging pressure is controlled by both the electric motor and the variable nozzle in a rapid acceleration state where it is necessary to increase the supercharging pressure early. For this reason, in the rapid acceleration state, there is a problem that it is difficult to prevent mutual interference between the two supercharging pressure controls.

  Further, as in the above-described apparatus, when the electric assist is executed at the time of sudden acceleration and the electric assist is not executed at the time of slow acceleration, the increase rate of the supercharging pressure greatly varies depending on the presence / absence of the electric assist. For this reason, overshoot, undershoot, hunting, etc. of the supercharging pressure are likely to occur. In these respects, the conventional technique still leaves room for improvement.

  The present invention has been made in order to solve the above-described problems. In an internal combustion engine provided with a plurality of types of supercharging pressure adjusting actuators capable of adjusting the supercharging pressure of a turbocharger, the supercharging pressure is exceeded. An object of the present invention is to provide a control device for an internal combustion engine that can suppress chute, undershoot, and hunting.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A turbocharger for supercharging the internal combustion engine;
Multiple types of supercharging pressure adjustment actuators that can adjust the supercharging pressure,
Target value determining means for determining a target value of a supercharging pressure or a target value of a supercharging pressure correlation value having a correlation with the supercharging pressure according to an operating state;
An actual value detecting means for detecting an actual value of the supercharging pressure or an actual value of a supercharging pressure correlation value having a correlation with the supercharging pressure;
Supercharging control means for controlling the state of the supercharging pressure adjusting actuator so as to make the actual value coincide with the target value;
With
The supercharging control means performs control that reflects the deviation for some of the supercharging pressure adjustment actuators, and performs fixed control that does not reflect the deviation for the remaining supercharging pressure adjustment actuators. Features.

The second invention is the first invention, wherein
Acceleration request determination means for determining the driver's acceleration request level is further provided,
The supercharging control means includes control content changing means for changing the content of the fixed control in accordance with the acceleration request level determined by the acceleration request determination means.

The third invention is the second invention, wherein
When the acceleration request level is high, the control content changing means sets the content of the fixed control to control content that emphasizes acceleration performance as compared to the basic control content, and when the acceleration request level is low, The content of the fixed control is set to control content that emphasizes fuel efficiency compared to basic control content.

According to a fourth invention, in any one of the first to third inventions,
The plurality of types of supercharging pressure adjusting actuators include one or both of a variable nozzle mechanism that makes an exhaust turbine inlet area of the turbocharger variable and an electric motor that assists turbo rotation. .

According to a fifth invention, in any one of the first to third inventions,
The plurality of types of supercharging pressure adjusting actuators include a variable nozzle mechanism that makes the exhaust turbine inlet area of the turbocharger variable and an electric motor that assists in turbo rotation,
When the electric motor is driven, the supercharging control means performs control for reflecting the deviation for the electric motor, and performs fixed control for not reflecting the deviation for the variable nozzle mechanism. .

According to a sixth invention, in any one of the first to third inventions,
The plurality of types of supercharging pressure adjusting actuators include a variable nozzle mechanism that makes the exhaust turbine inlet area of the turbocharger variable and an electric motor that assists in turbo rotation,
When the electric motor is driven, the supercharging control means performs control for reflecting the deviation for the variable nozzle mechanism, and performs fixed control for not reflecting the deviation for the electric motor. .

  According to the first invention, the supercharging control is performed so that the deviation between the target value of the supercharging pressure or the supercharging pressure correlation value and the actual value is eliminated by controlling the states of the plural types of supercharging pressure adjusting actuators. It can be carried out. During the supercharging control, some of the supercharging pressure adjustment actuators are controlled to reflect the deviation between the target value and the actual value, and the remaining supercharging pressure adjustment actuators reflect the above deviation. Do not let the fixed control. For this reason, according to the first aspect of the present invention, the influence of the control of the part of the supercharging pressure adjustment actuators on the supercharging pressure and the influence of the control of the remaining supercharging pressure adjustment actuators on the supercharging pressure are affected. Mutual interference can be prevented, and supercharging control can be stabilized. For this reason, according to 1st invention, the overshoot of a supercharging pressure, an undershoot, and hunting can be suppressed.

  According to the second aspect of the invention, the control content of the supercharging pressure adjustment actuator that is fixedly controlled can be changed according to the driver's acceleration request level. For this reason, fuel consumption, emission, etc. can be improved while satisfying the driver's acceleration request.

  According to the third aspect of the invention, when the driver's acceleration request level is high, the control content of the supercharging pressure adjustment actuator that is fixedly controlled is changed to control content that emphasizes acceleration performance compared to the basic control content. can do. Conversely, when the acceleration request level is low, the control content of the supercharging pressure adjustment actuator that is fixedly controlled can be changed to control content that emphasizes fuel efficiency compared to the basic control content. For this reason, according to the third invention, when rapid acceleration is required, it is possible to improve fuel efficiency as a whole while ensuring good acceleration performance.

  According to the fourth aspect of the invention, the above effect can be obtained in a system including a variable nozzle mechanism and a turbo rotation assist electric motor.

  According to the fifth aspect, when the supercharging pressure is controlled by the assist of the electric motor, it is possible to prevent the change in the variable nozzle opening from becoming a disturbance to the supercharging pressure control. For this reason, overshoot, undershoot, hunting, and the like of the supercharging pressure can be suppressed.

  According to the sixth aspect, when the supercharging pressure is controlled by the variable nozzle opening, it is possible to prevent the change in the assist amount by the electric motor from being a disturbance to the supercharging pressure control. For this reason, overshoot, undershoot, hunting, and the like of the supercharging pressure can be suppressed.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a diesel engine 2 having a plurality of cylinders (four cylinders in FIG. 1), a fuel supply system that supplies fuel to the diesel engine 2, an intake system that supplies air to the diesel engine 2, An exhaust system that exhausts exhaust gas from the diesel engine 2 and a control system that controls the operation of the diesel engine 2 are provided. The diesel engine 2 is mounted on a vehicle and used as a power source.

  The fuel supply system of the diesel engine 2 is provided with an in-cylinder injector 32 for directly injecting fuel into the combustion chamber. The in-cylinder injector 32 is provided for each cylinder and is connected to the common rail 34. That is, the diesel engine 2 is a common rail type diesel engine. Fuel stored in a fuel tank (not shown) is pumped up by a supply pump 36, compressed to a predetermined fuel pressure, and supplied to the common rail 34. Although not shown in the drawing, the supply pump 36 includes a low-pressure pump and a high-pressure pump.

  The exhaust system of the diesel engine 2 includes an exhaust manifold 6 and an exhaust pipe 10 connected to the exhaust manifold 6. Exhaust gas discharged from each cylinder of the diesel engine 2 is collected in the exhaust manifold 6 and discharged to the exhaust pipe 10 via the exhaust manifold 6. A catalyst container 30 is provided in the middle of the exhaust pipe 10. A catalyst such as a NOx catalyst, DPF (Diesel Particulate Filter), or DPNR (Diesel Particulate-NOx-Reduction system) is disposed in the catalyst container 30.

  The intake system of the diesel engine 2 includes an intake manifold 4 and an intake pipe 8 connected to the intake manifold 4. Air is taken into the intake pipe 8 from the atmosphere and distributed to the combustion chambers of the respective cylinders via the intake manifold 4. An air cleaner 12 is attached to the inlet of the intake pipe 8. An air flow meter 76 that outputs a signal corresponding to the flow rate of air sucked into the intake pipe 8 is provided in the vicinity of the downstream side of the air cleaner 12. An intake throttle valve 22 is provided upstream of the intake manifold 4.

  In this system, a variable nozzle type turbocharger 14 is provided. The turbocharger 14 includes a compressor 14a, an exhaust turbine 14b, and a variable nozzle mechanism 14c. The compressor 14 a is arranged in the middle of the intake pipe 8 from the air flow meter 76 to the intake throttle valve 22. The exhaust turbine 14b is provided in the middle of the exhaust pipe 10 from the exhaust manifold 6 to the catalyst container 30 in the above-described exhaust system. The rotating shafts of the compressor 14a and the exhaust turbine 14b are integrated and rotate as a unit. According to such a turbocharger 14, it is possible to perform supercharging by driving the compressor 14a with exhaust energy recovered by the exhaust turbine 14b.

  The variable nozzle mechanism 14c includes a nozzle whose opening degree can be adjusted (hereinafter referred to as “variable nozzle” or “VN”), and a drive mechanism that changes the opening degree of the variable nozzle by, for example, electricity. According to the variable nozzle mechanism 14c, the supercharging pressure can be controlled by adjusting the opening of the variable nozzle. That is, when the opening of the variable nozzle is reduced, the inlet area of the exhaust turbine 14b is reduced, and the flow rate of the exhaust gas flowing into the exhaust turbine 14b is increased. As a result, the turbo rotation speed increases and the supercharging pressure can be increased. Conversely, when the opening of the variable nozzle is increased, the inlet area of the exhaust turbine 14b is increased, and the flow rate of the exhaust gas flowing into the exhaust turbine 14b is decreased. As a result, the turbo rotation speed decreases and the supercharging pressure decreases. Hereinafter, the opening degree of the variable nozzle is referred to as “VN opening degree”.

  An electric motor 15 that assists turbo rotation is disposed between the compressor 14a and the exhaust turbine 14b. When electric power is supplied to the electric motor 15, the output of the electric motor 15 assists the turbo rotation, and the turbo rotation speed can be increased early. By providing such an electric motor 15, the turbo lag can be shortened and the response can be improved.

  The motor 15 includes a rotation speed sensor 16 that detects the rotation speed of the rotor of the motor 15, that is, the turbo rotation speed. An intercooler 17 for cooling the compressed air is provided downstream of the compressor 14a. A supercharging pressure sensor 74 that detects the supercharging pressure is disposed downstream of the intercooler 17 and downstream of the intake throttle valve 22.

  One end of a bypass pipe 50 is connected midway in the intake pipe 8 from the compressor 14 a to the intercooler 17. A bypass valve 18 capable of opening and closing the inlet is disposed at the inlet of the bypass pipe 50. The other end of the bypass pipe 50 is connected to the upstream side of the compressor 14 a in the intake pipe 8. By operating the bypass valve 18 to open the inlet of the bypass pipe 50, a part of the air compressed by the compressor 14a is returned to the inlet side of the compressor 14a again. When the turbocharger 14 is in an operating state in which a surge is likely to occur, the surge can be prevented by returning a part of the air exiting the compressor 14 a to the inlet side of the compressor 14 a through the bypass pipe 50.

  One end of the EGR pipe 24 is connected to the intake pipe 8 from the intake throttle valve 22 to the intake manifold 4. The other end of the EGR pipe 24 is connected to the exhaust manifold 6. In this system, a part of the exhaust gas can be introduced into the intake pipe 8 through the EGR pipe 24. An EGR cooler 26 for cooling the EGR gas is provided in the middle of the EGR pipe 24. An EGR valve 28 for controlling the amount of EGR gas (EGR amount) is provided downstream of the EGR cooler 26 in the EGR pipe 24. By introducing EGR gas having a large specific heat and a small amount of oxygen compared to air into the intake pipe 8, the combustion temperature in the cylinder can be lowered and the amount of NOx produced can be reduced.

  The control system of the diesel engine 2 includes an ECU (Electronic Control Unit) 70 and a motor controller 60. The motor controller 60 controls the energization state of the electric motor 15 based on a command from the ECU 70. Electric power to the electric motor 15 is supplied from the battery 62. The ECU 70 is a control device that comprehensively controls the entire system. In addition to the motor controller 60, various actuators such as the variable nozzle mechanism 14 c, the in-cylinder injector 32, the intake throttle valve 22, the EGR valve 28, and the bypass valve 18 are connected to the output side of the ECU 70. In addition to the rotational speed sensor 16, the air flow meter 76, and the supercharging pressure sensor 74, various sensors such as an accelerator opening sensor 72 and a crank angle sensor 78 are connected. The accelerator opening sensor 72 is a sensor that outputs a signal corresponding to a depression amount (accelerator opening) of an accelerator pedal (not shown), and the crank angle sensor 78 is a sensor that outputs a signal corresponding to the rotation angle of the crankshaft. is there. According to the output of the crank angle sensor 78, the engine speed NE [rpm] or the like can be detected. In addition to these devices and sensors, a plurality of devices and sensors are connected to the ECU 70, but the description thereof is omitted here. The ECU 70 drives each device according to a predetermined control program based on the output of each sensor.

[Features of Embodiment 1]
In the system of the present embodiment, the ECU 70 stores a map that defines the relationship between the operating state of the diesel engine 2 and the target boost pressure under the operating state. The ECU 70 performs feedback control of the supercharging pressure so that the actual supercharging pressure detected by the supercharging pressure sensor 74 matches the target supercharging pressure corresponding to the current operating state. That is, the ECU 70 measures the difference between the target boost pressure and the actual boost pressure (hereinafter referred to as “supercharging pressure deviation”), and performs control so that the supercharging pressure deviation becomes zero.

  In the present system, there are two types of actuators that can adjust the supercharging pressure: a variable nozzle mechanism 14 c and an electric motor 15. For this reason, there are two operation amounts for controlling the supercharging pressure: electric power supplied to the motor 15 and VN opening. Therefore, when the supercharging pressure is feedback controlled with the assistance of the electric motor 15, a method of giving feedback corresponding to the supercharging pressure deviation to both the electric power supplied to the electric motor 15 and the VN opening degree can be considered.

  However, in such a case, both the assist amount by the electric motor 15 and the VN opening degree are changed by feedback from the supercharging pressure deviation. In this case, the influence of the change in the assist amount of the motor 15 on the supercharging pressure and the influence of the change in the VN opening degree on the supercharging pressure are intertwined and interfere with each other, and the actual supercharging pressure becomes the target supercharging. It becomes difficult to converge on the pressure. That is, overshooting, undershooting, or hunting of the supercharging pressure is likely to occur.

  Therefore, in the present embodiment, when supercharging pressure control is performed with the assistance of the motor 15 in order to avoid the mutual interference, feedback based on the supercharging pressure deviation is not reflected in the VN opening. Instead, the VN opening is fixedly controlled according to a predetermined map.

[Specific Processing in Embodiment 1]
FIG. 2 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the above-described function. Note that this routine is periodically executed at predetermined time intervals.

  According to the routine shown in FIG. 2, first, predetermined processing is performed on signals input from the various sensors described above (step 100). By this input signal processing, various parameters representing the operation state of the diesel engine 2 are acquired. Specifically, the engine speed NE, accelerator opening, target throttle opening, fuel injection amount, actual boost pressure, actual turbo speed, and the like are acquired.

  Next, it is determined whether or not a condition for starting and continuing the assist by the electric motor 15 is satisfied (step 102). Specifically, these conditions are the following two points. The first point is whether or not there is a need for electric assist, for example, whether or not the diesel engine 2 is in a low rotation high load region or a transient state (acceleration state). The second point is whether there is no condition for prohibiting the electric assist, for example, whether the remaining battery level is sufficient, whether the turbo rotation speed is lower than the assist allowable value, or the like. If this electric assist start / continuation condition is not satisfied, the processing of this routine is terminated as it is.

  When the electric assist start / continuation condition is satisfied, a process for determining a target boost pressure is performed (step 104). The target boost pressure is predetermined by a map according to the engine speed NE and the engine load. By referring to the map, the target boost pressure corresponding to the current operating state is determined. In this system, the magnitude of the engine load is determined from the accelerator opening, the target throttle opening, the fuel injection amount, or the like.

  Next, the VN opening is fixed to the base VN opening according to the map (step 106). FIG. 3 is a diagram showing a map in which the base VN opening is determined. In step 106, the base VN opening according to the current operating state is determined according to the base VN opening map as shown in FIG. 3, and the actual VN opening is controlled to be the base VN opening. The

  Here, the base VN opening will be described. In general, in a variable nozzle type turbo engine, if the VN opening is reduced, the turbo rotation can be quickly increased, that is, the supercharging pressure can be rapidly increased. On the other hand, if the VN opening is reduced, the back pressure (exhaust pressure) tends to increase, and therefore the pumping loss tends to increase. For this reason, the preferable VN opening varies depending on whether the rapid rise of the supercharging pressure is important or the fuel efficiency is important. On the other hand, a preferable VN opening from the viewpoint of emission reduction is generally between the two. The base VN opening is a reference VN opening that balances the rapid rise of the supercharging pressure and fuel consumption, and is a VN opening that provides good emission performance based on experiments and the like in advance. It is the set VN opening. The base VN opening is determined according to the engine speed NE and the engine load.

  In FIG. 3, the maximum opening (fully opened) is represented as 0%, and the minimum opening is represented as 100%. The higher the rotation and load, the higher the back pressure. Therefore, it is necessary to open the variable nozzle. For this reason, the base VN opening degree map is determined so that the opening degree increases as the engine speed NE increases. Further, the base VN opening degree map moves to the opening side (lower side in FIG. 3) as the engine load is larger, and moves to the closing side (upper side in FIG. 3) as the engine load is smaller. However, in the EGR region where EGR (exhaust gas recirculation) is performed, the VN opening is determined according to the EGR amount required from the operating conditions as usual, without following such a map.

  After the VN opening is set to the base VN opening, next, power supply to the motor 15 is started and turbo rotation assist is started in order to quickly increase the actual boost pressure to the target boost pressure. (Step 108).

  FIG. 4 is a timing chart for explaining the supercharging pressure control of this embodiment. 4, (A) represents a change in supercharging pressure, (B) represents a change in electric power (motor output) supplied to the electric motor 15, and (C) represents a method for controlling the VN opening.

  As shown in FIG. 4 (A), in this system, the supercharging pressure can be quickly raised by electrically assisting the turbo rotation as compared with a normal system without the electrical assist. For this reason, turbo lag can be reduced.

  After the start of the electric assist, the output of the electric motor 15 is controlled according to the deviation (supercharging pressure deviation) between the target supercharging pressure and the actual supercharging pressure. As shown in FIG. 4B, the motor 15 is driven at full output while the supercharging pressure deviation is large.

While the electric assist is continued, the ECU 70 determines whether or not the electric assist stop condition is satisfied (step 110). When the supercharging pressure deviation is still greater than the predetermined determination value (before time t ₁ in FIG. 4) includes an electric assist stop condition is judged not satisfied. In this case, the electric assist is continued as it is. On the other hand, when the supercharging pressure deviation becomes smaller than the determination value (time t ₁ ), it is determined that the electric assist stop condition is satisfied.

When it is determined that the electric assist stop condition is satisfied, assist stop control is performed (step 112). As shown in FIG. 4B, in the assist stop control, the output of the electric motor 15 is lowered toward zero (time t _{1 to} t ₂ ).

In order to quickly and smoothly converge the actual boost pressure to the target boost pressure, the motor output drop speed during the assist stop control and the time until the assist is completely stopped (until the motor output becomes zero). (Time from time t ₁ to t ₂ ) needs to be appropriate. Therefore, in the assist stop control in step 112, the actual boost pressure is quickly and smoothly adjusted to the target boost pressure by performing feedback control on the output drop speed and the time until complete stop based on the boost pressure deviation. It is controlled to converge to.

  When the assist stop control is finished and there is no electric assist, feedback control of the VN opening is started as shown in FIG. 4C (step 114). After the start of the VN feedback control, the VN opening is controlled to be the opening obtained by adding the feedback correction term based on the boost pressure deviation to the base VN opening. The feedback correction term can be calculated by a known method such as PID control. After the electric assist is finished, the actual boost pressure is controlled to the target boost pressure by the above-described VN feedback control.

  As described above, in the present embodiment, during the execution of the electric assist, while the feedback based on the boost pressure deviation is reflected on the driving state of the electric motor 15, the VN opening is based on the boost pressure deviation. Do not reflect feedback, perform fixed control according to the map. Then, after the electric assist ends, the process shifts to VN feedback control. According to such control, it is possible to prevent the change in the VN opening amount from being a disturbance to the supercharging pressure control during the execution of the electric assist. For this reason, overshoot, undershoot, hunting, and the like of the supercharging pressure can be suppressed, and the actual supercharging pressure can be quickly and smoothly converged to the target supercharging pressure.

  In the first embodiment described above, the variable nozzle mechanism 14c and the electric motor 15 are the “supercharging pressure adjusting actuator” in the first invention, and the supercharging pressure sensor 74 is the “real value detection” in the first invention. It corresponds to “means”. Further, when the ECU 70 executes the process of step 104 above, the “target value determining means” in the first invention executes the processes of steps 106 to 112 described above. "Control means" is realized respectively.

  Moreover, although Embodiment 1 mentioned above demonstrated the case where this invention was applied to the control apparatus of the diesel engine 2, this invention is applicable also to control apparatuses of spark ignition engines, such as a gasoline engine.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 5 and FIG. 6. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Omitted or simplified. The system of the present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 6 to be described later instead of the routine shown in FIG. 2 using the hardware configuration shown in FIG.

[Features of Embodiment 2]
In the transient operation (acceleration) of the diesel engine 2, from the viewpoint of quickly raising the supercharging pressure, it is better to close the variable nozzle as much as possible as long as the back pressure and the supercharging pressure are balanced. . This is because as the variable nozzle is closed, the flow rate of the exhaust gas flowing into the exhaust turbine 14b increases, and the turbo rotation speed can be increased more quickly.

  On the other hand, from the viewpoint of improving fuel efficiency, it is preferable to maintain high turbo efficiency even during transient operation. Turbo efficiency is calculated as the product of compressor efficiency, turbine efficiency, and mechanical efficiency. If the VN opening is too small, the back pressure tends to increase, and therefore the turbo efficiency tends to decrease. For this reason, in order to maximize turbo efficiency and optimize fuel efficiency, a relatively large VN opening is required. Such a VN opening is generally larger than the base VN opening.

  Here, considering the acceleration request of the driver of the vehicle, it is preferable to raise the boost pressure as early as possible when the driver requests rapid acceleration. On the other hand, when the driver is requesting slow acceleration, there is no need to raise the supercharging pressure so quickly.

  Therefore, in the present embodiment, the VN opening degree map is switched according to the driver's acceleration request level. FIG. 5 is a diagram showing a VN opening degree map used in the second embodiment. As shown in the figure, in this embodiment, in addition to the map of the base VN opening, a map of the fuel efficiency best VN opening and a map of the acceleration best VN opening are prepared.

  As described in the first embodiment, the three VN opening maps in FIG. 5 move to the open side (lower side in FIG. 5) as the engine load increases, and as the engine load decreases. As a whole, it moves to the closing side (upper side in FIG. 5).

  The base VN opening in FIG. 5 is the same as the base VN opening in the first embodiment described above. As described above, the base VN opening is a VN opening having an intermediate characteristic that balances acceleration performance and fuel consumption performance, and is a VN opening having an optimized emission characteristic. When the acceleration request level of the driver is medium, this base VN opening degree map is selected and used.

  On the other hand, the acceleration best VN opening is a VN opening optimized to raise the supercharging pressure as early as possible and obtain the highest acceleration. The map of the acceleration best VN opening is located closer to the closing side than the base VN opening. When the acceleration request level of the driver is high, the map of the acceleration best VN opening is selected and used.

  On the other hand, the fuel efficiency best VN opening is a VN opening optimized to maximize turbo efficiency and obtain the best fuel efficiency. The map of the fuel efficiency best VN opening is located on the opening side with respect to the base VN opening. When the driver's acceleration request level is low, this map of fuel efficiency best VN opening is selected and used.

[Specific Processing in Second Embodiment]
FIG. 6 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the above function. In FIG. 6, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The routine shown in FIG. 6 is the same as the routine of the first embodiment shown in FIG. 2 except that step 106 is deleted and steps 120 to 126 are added. According to the routine shown in FIG. 6, when the assist by the electric motor 15 is executed, the level of the acceleration request from the driver is determined (step 120). In the present embodiment, the acceleration request level is determined based on the output signal of the accelerator opening sensor 72. Specifically, it is determined that the acceleration request level is higher as the detected accelerator opening degree and accelerator opening change amount are larger. Then, based on a predetermined determination value, the acceleration request level is determined in three stages of high, medium and low.

  If it is determined in step 120 that the acceleration request level is low, a map of the fuel efficiency best VN opening is selected (step 122). On the other hand, if it is determined that the acceleration request level is high, a map of the acceleration best VN opening is selected (step 124). When it is determined that the acceleration request level is medium, a map of the base VN opening is selected (step 126). While the turbo rotation assist by the electric motor 15 is continued, the VN opening is fixedly controlled according to the selected VN opening map. The processing after the electric assist stop control in step 110 is the same as that in the first embodiment.

  In the present embodiment, when the acceleration request level is low, that is, when gradual acceleration is performed, the VN opening degree can be controlled so that the fuel efficiency is more important than the rise of the supercharging pressure. For this reason, fuel consumption can be improved. On the other hand, when the acceleration request level is high, that is, when rapid acceleration is performed, it is possible to control the VN opening degree with emphasis on rising of the supercharging pressure. For this reason, the boost pressure can be raised as soon as possible, and good acceleration with less turbo lag can be performed. Further, when the acceleration request level is medium, it is possible to control the basic VN opening degree with emphasis on emission performance.

  In the second embodiment described above, the acceleration request level is determined based on the accelerator opening and the accelerator opening change amount. However, the method for determining the acceleration request level is not limited to this. For example, in a system in which the driver can select a driving mode such as a sports mode or an economy mode, the acceleration request level may be determined based on the selected driving mode.

  In the second embodiment described above, the ECU 70 executes the process of step 120, so that the “acceleration request determination means” in the second invention executes the processes of steps 122 to 126. The “control content changing means” in the second invention is realized.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 7 and FIG. 8. The difference from the above-described first embodiment will be mainly described, and the same matters will be described. Omitted or simplified. The system of the present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 8 to be described later instead of the routine shown in FIG. 2 using the hardware configuration shown in FIG.

[Features of Embodiment 3]
FIG. 7 is a timing chart for explaining the supercharging pressure control of the present embodiment. 7, (A) represents a change in supercharging pressure, (B) represents a change in electric power (motor output) supplied to the electric motor 15, and (C) represents a method for controlling the VN opening.

As shown in FIG. 7 (C), in the present embodiment, the running of the electric assist up across Assisted completed (time t ₂ later), performs VN feedback control consistently. In this VN feedback control, the VN opening is controlled to be an opening obtained by adding the feedback correction term based on the boost pressure deviation to the base VN opening. The feedback correction term can be calculated by a known method such as PID control.

FIG. 7B is a map that defines the power supplied to the motor 15 after the start of the electric assist. During the electric assist, the feedback based on the supercharging pressure deviation is not consistently reflected on the electric power supplied to the electric motor 15, and the fixed control is performed according to the map of FIG. 7B. Then, after the actual supercharging pressure converges to the target supercharging pressure by the VN feedback control (time t ₁ ), the output of the electric motor 15 is lowered and the assist is finished.

  In the present embodiment, as shown in FIG. 7B, as a map of electric power supplied to the electric motor 15, in addition to a base map, an acceleration best map and a fuel efficiency best map are prepared. The acceleration best map is a map in which the motor output is increased to full output with a steeper slope than the base map for the purpose of raising the boost pressure as soon as possible. In this embodiment, when rapid acceleration is required, the acceleration performance can be improved by adopting this acceleration best map.

  On the other hand, the map of the best fuel economy is a map in which the motor output is increased with a gentler slope than the base map in order to improve the fuel efficiency by reducing the power consumption. In this embodiment, when slow acceleration is required, the fuel efficiency can be reduced by adopting the map of the best fuel efficiency.

[Specific Processing in Embodiment 3]
FIG. 8 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the above function. In FIG. 8, the same steps as those shown in FIG. 2 or FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 8, first, various parameters representing the operation state and control state of the diesel engine 2 are acquired (step 100), and then whether the electric assist start / continuation condition for turbo rotation is satisfied. It is determined whether or not (step 102). If the electric assist start / continuation condition is satisfied, the level of the acceleration request from the driver is then determined (step 130). In this step 130, the acceleration request level is determined in three stages of high, medium, and low by the same method as in step 120 described above.

  If it is determined that the acceleration request level is low, a map of the best fuel economy is selected as a map of electric power supplied to the electric motor 15 (step 132). On the other hand, if it is determined that the acceleration request level is high, an acceleration best map is selected (step 134). If it is determined that the acceleration request level is medium, a base map is selected (step 136).

  Subsequently, the target boost pressure is determined according to the engine speed NE and the engine load (step 104). When the target boost pressure is determined, VN feedback control is started (step 138). After the start of the VN feedback control, the VN opening is controlled to be the opening obtained by adding the feedback correction term based on the deviation between the target boost pressure and the actual boost pressure to the base VN opening.

  As the VN feedback control is started, assistance for turbo rotation by the electric motor 15 is started (step 108). At this time, electric power is supplied to the motor 15 according to the map selected in step 132, 134 or 136.

  While the electric assist started as described above is continued, it is determined whether or not the electric assist stop condition is satisfied (step 140). When this stop condition is not satisfied, that is, when the supercharging pressure deviation still remains, the electric assist is continued. When the electric assist is continued, the actual supercharging pressure increases and the deviation from the target supercharging pressure decreases. Then, the actual boost pressure is converged to the target boost pressure by adjusting the VN opening by the VN feedback control.

When it is recognized that the actual boost pressure has converged to the target boost pressure, that is, that the boost pressure deviation has become sufficiently small, it is determined in step 140 that the electric assist stop condition is satisfied. (Time t ₁ ). If it is determined that the electric assist stop condition is satisfied, the electric assist is terminated (time t ₂ ). In this case, in this embodiment, as shown in FIG. 7B, the power supplied to the electric motor 15 is lowered to zero with a predetermined inclination.

  As described above, according to the present embodiment, the output of the electric motor 15 is fixedly controlled until the actual boost pressure converges to the target boost pressure by the VN feedback control. For this reason, in the VN feedback control, the output change of the electric motor 15 does not become a disturbance, and the VN feedback control can be stably performed. Therefore, overshooting, undershooting, hunting, and the like of the supercharging pressure can be suppressed, and the actual supercharging pressure can be converged quickly and smoothly to the target supercharging pressure.

  In the present embodiment, the map of the electric power supplied to the electric motor 15 is switched in three stages according to the acceleration request level of the driver. Thereby, according to the driver | operator's acceleration request level, a fuel consumption and emission can be improved, satisfying the request | requirement.

  In the third embodiment described above, the ECU 70 executes the process of step 104, so that the “target value determining means” in the first invention performs the processes of steps 130 to 134, 138 and 108. By executing this, the “supercharging control means” in the first aspect of the present invention is realized. Further, when the ECU 70 executes the process of the above step 130, the “acceleration request determining means” in the second invention executes the processes of the above steps 132 to 136, thereby performing the “control” in the second invention. "Content changing means" is realized respectively.

  In each of the embodiments described above, the system including the variable nozzle mechanism 14c and the electric motor 15 as the “supercharging pressure adjustment actuator” has been described. However, in the present invention, the supercharging pressure adjustment actuator is not limited to these. Absent. For example, the above-described intake-side bypass valve 18 or a waste gate valve (not shown) can be used as a supercharging pressure adjusting actuator in the present invention. For example, when a waste gate valve is used as a supercharging pressure adjustment actuator, the opening / closing of the waste gate valve can be electronically controlled, and the supercharging pressure control can be performed by controlling the opening timing and opening degree thereof.

  Moreover, although each embodiment mentioned above demonstrated the system using two types of supercharging pressure control actuators, this invention can also be applied to the system using three or more types of supercharging pressure adjustment actuators. .

  In each of the above-described embodiments, a system that performs supercharging control so that the actual supercharging pressure matches the target supercharging pressure has been described. Control may be performed based on the value. For example, the present invention is applied to a system that uses turbo rotation speed as a supercharging pressure correlation value and performs supercharging control so that the actual turbo rotation speed matches the target turbo rotation speed set according to the operating state. It is also possible.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the map which defined the base VN opening degree. It is a timing chart for demonstrating the supercharging pressure control of Embodiment 1 of this invention. It is a figure which shows the VN opening degree map used in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a timing chart for demonstrating the supercharging pressure control of Embodiment 3 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

2 Diesel engine 4 Intake manifold 6 Exhaust manifold 8 Intake pipe 10 Exhaust pipe 12 Air cleaner 14 Turbocharger 14a Compressor 14b Exhaust turbine 14c Variable nozzle mechanism 15 Electric motor 16 Speed sensor 17 Intercooler 18 Bypass valve 22 Intake throttle valve 24 EGR pipe 26 EGR cooler 28 EGR valve 30 Catalyst container 32 In-cylinder injector 34 Common rail 36 Supply pump 50 Bypass pipe 60 Motor controller 62 Battery 70 ECU
72 Accelerator opening sensor 74 Supercharging pressure sensor 76 Air flow meter 78 Crank angle sensor

Claims (6)

A turbocharger for supercharging the internal combustion engine;
Multiple types of supercharging pressure adjustment actuators that can adjust the supercharging pressure,
Target value determining means for determining a target value of a supercharging pressure or a target value of a supercharging pressure correlation value having a correlation with the supercharging pressure according to an operating state;
An actual value detecting means for detecting an actual value of the supercharging pressure or an actual value of a supercharging pressure correlation value having a correlation with the supercharging pressure;
Supercharging control means for controlling the state of the supercharging pressure adjusting actuator so as to make the actual value coincide with the target value;
With
The supercharging control means performs control that reflects the deviation for some of the supercharging pressure adjustment actuators, and performs fixed control that does not reflect the deviation for the remaining supercharging pressure adjustment actuators. A control device for an internal combustion engine characterized by the above. Acceleration request determination means for determining the driver's acceleration request level is further provided,
The internal combustion engine according to claim 1, wherein the supercharging control means includes control content changing means for changing the content of the fixed control in accordance with the acceleration request level determined by the acceleration request determination means. Control device.   When the acceleration request level is high, the control content changing means sets the content of the fixed control to control content that emphasizes acceleration performance as compared to the basic control content, and when the acceleration request level is low, 3. The control apparatus for an internal combustion engine according to claim 2, wherein the content of the fixed control is a control content that emphasizes fuel efficiency compared to the basic control content.   The plurality of types of supercharging pressure adjusting actuators include one or both of a variable nozzle mechanism that makes an exhaust turbine inlet area of the turbocharger variable and an electric motor that assists turbo rotation. The control device for an internal combustion engine according to any one of claims 1 to 3. The plurality of types of supercharging pressure adjusting actuators include a variable nozzle mechanism that makes the exhaust turbine inlet area of the turbocharger variable and an electric motor that assists in turbo rotation,
When the electric motor is driven, the supercharging control means performs control for reflecting the deviation for the electric motor, and performs fixed control for not reflecting the deviation for the variable nozzle mechanism. The control device for an internal combustion engine according to any one of claims 1 to 3. The plurality of types of supercharging pressure adjusting actuators include a variable nozzle mechanism that makes the exhaust turbine inlet area of the turbocharger variable and an electric motor that assists in turbo rotation,
When the electric motor is driven, the supercharging control means performs control for reflecting the deviation for the variable nozzle mechanism, and performs fixed control for not reflecting the deviation for the electric motor. The control device for an internal combustion engine according to any one of claims 1 to 3.

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