JP2007023816A - Controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To positively suppress overshoot of a boost pressure of a turbocharger in a controller of an internal combustion engine. <P>SOLUTION: A rotation number sensor is assembled into a motor for assisting rotation of the turbocharger. By the rotation number sensor, the actual turbo rotation number is detected. By determining whether the detected actual turbo rotation number exceeds a target turbo rotation number or not, the overspeed of the turbocharger is detected (step 106). When the overspeed of the turbocharger is detected, the motor is driven in reverse (step 108). When the motor is driven in reverse, the turbo rotation number is reduced by a control torque generated by the motor. As a result, overshoot of the boost pressure is suppressed. <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 equipped with a turbocharger.

  Japanese Patent Application Laid-Open No. 2004-92471 discloses an internal combustion engine system that includes a variable nozzle turbocharger and an EGR (Exhaust Gas Recirculation) device that recirculates a part of exhaust gas to an intake passage. . The variable nozzle turbocharger can adjust the supercharging pressure by opening and closing the variable nozzle. The EGR device includes an EGR passage that connects an exhaust passage and an intake passage, and an EGR valve that is installed in the EGR passage. In this case, the exhaust side end of the EGR passage is connected to the upstream side of the turbine of the turbocharger, and the intake side end of the EGR passage is connected to the downstream side of the compressor of the turbocharger.

  In the system disclosed in the above publication, the supercharging pressure is feedback controlled. That is, the variable nozzle is opened and closed based on the deviation between the target boost pressure and the actual boost pressure detected by the intake pressure sensor. Further, the EGR rate is controlled by adjusting the opening degree of the EGR valve.

JP 2004-92471 A JP 2003-239755 A JP 2004-308487 A

  In the system as described above, EGR is generally executed in the low-rotation light and medium load range, and EGR is prohibited in the high-rotation high load region. For this reason, when the vehicle is accelerated, the EGR valve may be suddenly closed to shift from the EGR execution state to the EGR prohibited state. When the EGR valve is suddenly closed, the pressure in the exhaust manifold increases rapidly, and the pressure at the turbine inlet of the turbocharger also increases rapidly. As a result, the rotational speed of the turbocharger is likely to increase rapidly. When the rotational speed of the turbocharger rises rapidly, the supercharging pressure tends to overshoot (too high). When the supercharging pressure overshoots, the variable nozzle is opened and the supercharging pressure is suppressed by the supercharging pressure feedback control described above.

  However, there is a time lag from when the rotational speed of the turbocharger suddenly increases until the actual supercharging pressure detected by the intake pressure sensor increases. For this reason, the feedback control for suppressing the overshooting supercharging pressure is easily delayed. Due to the presence of this control delay, there is a problem that the overshoot width of the supercharging pressure tends to increase.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can reliably suppress overshooting of the supercharging pressure of a turbocharger. To do.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A turbocharger,
A rotational speed detection means for detecting the rotational speed of the turbocharger;
Overspeed detection means for detecting overspeed of the turbocharger based on the actual turbo speed detected by the turbo speed detection means;
When the overspeed detection means detects an overspeed of the turbocharger, an overspeed suppression means for suppressing the number of revolutions of the turbocharger;
It is characterized by providing.

The second invention is the first invention, wherein
The over-rotation suppression means is
An electric motor that rotates with the turbocharger;
And an electric motor control means for controlling the electric motor so that the electric motor generates a braking torque when an overspeed of the turbocharger is detected.

The third invention is the first or second invention, wherein
The over-rotation suppression means is
A variable nozzle that opens and closes to make the flow rate of the exhaust gas blown to the turbine of the turbocharger variable; and
Opening degree increasing means for increasing the opening degree of the variable nozzle when over-rotation of the turbocharger is detected.

  According to the first invention, over-rotation of the turbocharger is detected based on the actual turbo rotation speed detected by the rotation speed detection means. Thereby, the overshoot of the supercharging pressure can be detected at an earlier time point compared with the case where the determination is made depending on the output of the supercharging pressure sensor. According to the present invention, when an overspeed of the turbocharger is detected, the turbo speed is suppressed and the boost pressure is reduced. Therefore, according to the present invention, it is possible to reliably avoid a significant overshoot of the supercharging pressure even in a situation where the supercharging pressure tends to overshoot. As a result, damage to the turbocharger and the intake system due to excessive supercharging pressure can be reliably prevented. Further, according to the present invention, the supercharging pressure can be accurately controlled even under a situation where the supercharging pressure is likely to overshoot.

  In the second invention, an electric motor for assisting the rotation of the turbocharger is provided. According to the second aspect of the present invention, when an overspeed of the turbocharger is detected, the electric motor can function as a brake. Thereby, the overspeed of the turbocharger can be eliminated more quickly. For this reason, the overshoot width of the supercharging pressure can be further reduced.

  According to the third aspect of the present invention, the above effect can be achieved even in the case of a hardware configuration that does not include an electric motor for assisting the rotation of the turbocharger.

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 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 the middle of the intake pipe 8 from the air flow meter 76 to the intake throttle valve 22, a compressor 14a of the variable nozzle turbocharger 14 is provided. The turbocharger 14 includes a compressor 14a, a turbine 14b, and a variable nozzle 14c. The 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 compressor 14a and the turbine 14b are integrally connected by a connecting shaft, and the compressor 14a is rotationally driven by the exhaust energy of the exhaust gas input to the turbine 14b.

  The variable nozzle 14c can be opened and closed. When the opening of the variable nozzle 14c is reduced, the inlet area of the turbine 14b is reduced, and the flow rate of the exhaust gas blown to the turbine 14b can be increased. As a result, the rotational speeds of the compressor 14a and the turbine 14b (hereinafter referred to as “turbo rotational speed”) are increased, so that the supercharging pressure can be increased.

  Conversely, when the opening of the variable nozzle 14c is increased, the inlet area of the turbine 14b is increased and the flow rate of the exhaust gas blown to the turbine 14b is decreased. As a result, the turbo rotation speed decreases, so that the supercharging pressure can be reduced.

  An electric motor 15 is disposed between the compressor 14a and the turbine 14b. A connecting shaft between the compressor 14 a and the turbine 14 b is also a rotor of the electric motor 15. That is, the compressor 14a and the turbine 14b and the rotor of the electric motor 15 rotate integrally. Therefore, the compressor 14a can be forcibly driven by operating the electric motor 15.

  The electric motor 15 incorporates a rotational speed sensor 16 that detects the rotational speed (rotational speed) of the rotor of the electric motor 15. The rotation speed sensor 16 is a sensor that reverses the Hi output and the Lo output each time the rotor of the electric motor 15 rotates by a predetermined rotation angle. According to the output of the rotation speed sensor 16, the rotation speed of the rotor of the electric motor 15 can be detected. The rotational speed of the rotor of the electric motor 15 is equal to the turbo rotational speed. Therefore, according to the output of the rotational speed sensor 16, the actual turbo rotational speed TREV [rpm] can be detected.

  An intercooler 17 for cooling the compressed air is provided downstream of the compressor 14a. A supercharging pressure sensor (intake pressure sensor) 74 that outputs a signal corresponding to the pressure of the air that has passed through the compressor 14a, that is, the supercharging pressure, is disposed downstream of the intercooler 17.

  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 switching valve 18 for switching the air flow path is disposed at the connection portion. 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 switching valve 18 to open the inlet of the bypass pipe 50, a part of the air compressed by the compressor 14a is returned again to the inlet side of the compressor 14a. 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. The exhaust gas introduced into the intake pipe 8 through the EGR pipe 24 is hereinafter referred to as “EGR gas”. 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, which has a higher specific heat than that of air and a small amount of oxygen, 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 14c, the in-cylinder injector 32, the intake throttle valve 22, the EGR valve 28, the switching valve 18 and the like 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.

The outline of the operation of the system of this embodiment will be described below.
[Supercharging pressure feedback control]
In the system of the present embodiment, supercharging pressure feedback control is performed as follows. The ECU 70 stores a map that defines the relationship between predetermined parameters such as the engine speed NE and the accelerator opening ACCP [%] and the target boost pressure PIMTRG [kPa]. With reference to this map, the target boost pressure PIMTRG corresponding to the current operating state is calculated. The opening degree of the variable nozzle 14c is controlled so that the deviation between the target boost pressure PIMTRG and the actual boost pressure PIM [kPa] detected by the boost pressure sensor 74 approaches zero.

  In the present embodiment, the electric motor 15 is operated to assist the rotation of the turbocharger 14 as necessary. Thereby, sufficient supercharging pressure can be realized even in a low rotation range where the exhaust energy is small.

[EGR control]
FIG. 2 is a map showing the relationship between the EGR ON area and the EGR OFF area in the present embodiment. In the present embodiment, as shown in this map, the light and medium load operation region in which the engine speed NE and the engine torque are within a predetermined range is an EGR ON region in which EGR is executed. On the other hand, the high load operation region is an EGR OFF region where EGR is prohibited.

  In the EGR ON region, feedback control of the ratio of EGR gas to the intake air sucked into the cylinder, that is, the EGR rate is performed as follows. The ECU 70 stores a map that defines a relationship between predetermined parameters such as the engine speed NE, the engine load, the intake air amount GA, and the target EGR rate EGRTRG [%]. With reference to this map, a target EGR rate EGRTRG corresponding to the current operating state is calculated. The actual EGR rate EGR [%] is based on the exhaust air / fuel ratio detected by an air / fuel ratio sensor (not shown) provided in the exhaust pipe 10 and the intake air amount GA detected by the air flow meter 76. Calculated. Then, the opening degree of the EGR valve 28 is adjusted so that the deviation between the target EGR rate EGRTRG and the actual EGR rate EGR approaches zero.

[Features of Operation of Embodiment 1]
In a system such as this embodiment, in a transient state such as when the vehicle is accelerating or climbing, there is a case where the EGR ON region shifts to the EGR OFF region (see the oblique arrows in FIG. 2). When shifting from the EGR ON region to the EGR OFF region, the EGR valve 28 is suddenly closed, so that the pressure in the exhaust manifold 6 is likely to increase rapidly, and the pressure at the inlet of the turbine 14b is also likely to increase rapidly. When the pressure at the inlet of the turbine 14b suddenly rises, the turbo rotational speed suddenly rises and tends to overspeed, and the supercharging pressure easily overshoots.

  When an overshoot of the supercharging pressure is detected by the supercharging pressure sensor 74, the variable nozzle 14c is opened by the supercharging pressure feedback control described above, and the supercharging pressure is suppressed.

  However, in general, an intercooler 17 or the like is installed between the outlet of the compressor 14 a and the supercharging pressure sensor 74. That is, the supercharging pressure sensor 74 is located away from the outlet of the compressor 14a. For this reason, there is a time lag from when the turbocharger 14 is overrotated until the supercharging pressure overshooting is detected by the supercharging pressure sensor 74. As a result, the opening control of the variable nozzle 14c tends to be delayed. When the opening control of the variable nozzle 14c is delayed, the supercharging pressure tends to greatly exceed the target.

  In order to solve such a problem, in the present embodiment, the overspeed of the turbocharger 14 is detected based on the actual turbo speed TREV detected by the speed sensor 16. Thereby, it is possible to detect the overshoot of the supercharging pressure at an earlier time point than in the case of only the supercharging pressure feedback control. Then, when over-rotation of the turbocharger 14 is detected, the motor 15 is reversely driven to brake the rotation of the turbocharger 14.

  The reverse drive of the electric motor 15 is to apply a drive voltage to the electric motor 15 so that the electric motor 15 exhibits a torque in the reverse rotation direction (braking torque). By reversely driving the electric motor 15, a strong braking force acts on the rotation of the turbocharger 14. As a result, the turbo rotation speed can be quickly reduced, and the supercharging pressure can be quickly reduced to an appropriate value.

[Specific Processing in Embodiment 1]
FIG. 3 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the over-rotation suppression function of the turbocharger 14 described above. Note that this routine is periodically executed at predetermined time intervals. Further, the ECU 70 performs the above-described supercharging pressure feedback control and EGR control in other routines.

  According to the routine shown in FIG. 3, first, various parameters representing the operation state and control state of the diesel engine 2 are acquired (step 100). These parameters can be acquired based on the outputs of the various sensors described above or based on calculation results in processing in other routines.

Specifically, in step 100, the engine speed NE, the accelerator opening ACCP, the fuel injection amount QFINC [mm ³ / st], the base EGR opening command value PEGBSE [%], the EGR opening feedback term PEGFB [ %], EGR opening command value PEGFIN [%] (PEGFIN = PEGBSE + PEGFB), EGR rate target value EGRTRG, actual EGR rate EGR, base VN opening command value PVNBSE [%], VN opening feedback term PVNFB [%], VN opening command value PVNFIN [%] (PVNFIN = PVNBSE + PVNFB), actual supercharging pressure PIM, target supercharging pressure PIMTRG, actual turbo speed TREV, and target turbo speed TREVTRG [rpm] are acquired. Here, “VN” refers to the variable nozzle 14c.

  In step 100 above, the target turbo speed TREVTRG is acquired as follows. The ECU 70 stores a map that defines the relationship between predetermined parameters such as the engine speed NE, the accelerator opening ACCP, and the target turbo speed TREVTRG. With reference to this map, the target turbo speed TREVTRG corresponding to the current operating state is calculated.

  Next, it is determined whether or not the operating state of the diesel engine 2 is in a transient state and whether or not the EGR ON region has shifted to the EGR OFF region (step 102). The transient state is a state in which a high output is required and the engine speed NE or the engine load is changed to the increasing side as in acceleration or climbing.

In step 102, when the actual boost pressure PIM has not yet reached the target boost pressure PIMTRG and the depression of the accelerator pedal is maintained or increased, it is determined that the engine is in a transient state. Specifically, when the following two inequalities are established, it is determined that the state is in a transient state.
PIM <PIMTRG (1)
ACCP (N) + α> ACCP (N-1) (2)
However, in the above equation (2), α is a predetermined value representing the magnitude of the accelerator opening hysteresis. N indicates the number of execution cycles of the routine shown in FIG.

In step 102, when the EGR rate target value EGRTRG becomes 0%, that is, when the following expression is established, it is determined that the EGR ON area has shifted to the EGR OFF area.
EGRTRG = 0 (3)

  If at least one of the above formulas (1) to (3) is not established in step 102, it can be determined that the supercharging pressure is not likely to overshoot. In this case, the current processing cycle is terminated. Then, normal supercharging pressure feedback control is continued.

  On the other hand, when the above equations (1) to (3) are all established, it can be determined that the supercharging pressure is likely to overshoot. In this case, first, the opening degree of the variable nozzle 14c is fixed to a value immediately before the transient state determination in step 102 (step 104). That is, the opening degree of the variable nozzle 14c is fixed to the value of the VN opening degree command value PVNFIN acquired in step 100.

  Assuming that the variable nozzle 14c is closed during the execution of EGR, the pressure in the exhaust manifold 6 increases and the amount of EGR increases, so that smoke is likely to occur. On the other hand, according to the process of step 104, since the opening of the variable nozzle 14c is prohibited, it is possible to reliably prevent the occurrence of smoke.

  While the above processing is being performed, the EGR rate target value EGRTRG is 0, so the EGR valve 28 is closed by EGR control. That is, the EGR valve 28 is fully closed in tandem with the process of step 104 described above.

  In the routine shown in FIG. 3, it is next determined whether or not the turbocharger 14 is over-rotated (step 106). Specifically, it is determined whether or not the actual turbo speed TREV detected by the speed sensor 16 exceeds the target turbo speed TREVTRG, that is, whether TREV> TREVTRG is successful.

  If it is determined in step 106 that TREV> TREVTRG is not established, it is determined that the turbocharger 14 has not over-rotated. In this case, it can be determined that there is no possibility that the supercharging pressure will overshoot. This processing cycle ends. Then, normal supercharging pressure feedback control is continued.

  On the other hand, when the establishment of TREV> TREVTRG is recognized, it is determined that the turbocharger 14 has over-rotated. In this case, it can be determined that the supercharging pressure will overshoot if the turbo rotational speed continues to increase. Therefore, reverse driving of the electric motor 15 is started to suppress the turbo rotational speed (step 108). As a result, the electric motor 15 exerts a braking torque, and a brake is applied to the rotation of the turbocharger 14. As a result, the turbo rotation speed decreases, and as a result, the supercharging pressure decreases.

In the routine shown in FIG. 3, it is next determined whether or not the overspeed of the turbocharger 14 has been eliminated, and whether or not the accelerator pedal has been returned (step 110). Specifically, the success or failure of the following two expressions is determined.
TREV = TREVTRG (4)
ACCP (N) + β> ACCP (N-1) (5)
However, in the above equation (5), β is a predetermined value representing the magnitude of the accelerator opening hysteresis.

  Until at least one of the above expressions (4) and (5) is recognized in step 110, the suppression of the turbo rotation speed, that is, the reverse drive of the electric motor 15 is continued. In other words, when the establishment of the above expression (4) is recognized in step 110, that is, when the overspeed of the turbocharger 14 is eliminated, it is determined that there is no longer a possibility that the supercharging pressure will overshoot. As a result, the reverse drive of the motor 15 is stopped (step 112). In addition, when the establishment of the above expression (5) is recognized in step 110, that is, when the accelerator pedal is returned, it can be determined that there is no risk of overshooting of the supercharging pressure. Stopped (step 112).

  According to the routine described above, it is possible to detect the overshoot of the supercharging pressure at an early time point and reduce the turbo rotation speed. For this reason, it can be avoided reliably that the supercharging pressure overshoots significantly. Therefore, it is possible to reliably prevent the turbocharger 14 and the intake system from being damaged due to excessive supercharging pressure. Furthermore, the supercharging pressure can be accurately controlled even under a situation where the supercharging pressure easily overshoots.

  Further, according to the routine described above, the rotation of the turbocharger 14 is not braked immediately after the EGR valve 28 is closed, but after the turbocharger 14 is recognized to be overrotated in step 106. A brake is applied to the rotation of the turbocharger 14. For this reason, it is possible to avoid braking the rotation of the turbocharger 14 under a situation where the depression of the accelerator pedal is slow and the supercharging pressure does not overshoot.

  By the way, in Embodiment 1 mentioned above, it is supposed that the electric motor 15 is reversely driven as a method of suppressing the excessive rotation of the turbocharger 14, but the present invention is not limited to such a method. . For example, overrotation of the turbocharger 14 may be suppressed by a method of regenerative braking by the electric motor 15, that is, a method of causing the electric motor 15 to function as a generator and charging the battery 62 with the generated electric power.

  Further, in the first embodiment described above, the turbo overload is performed only under the condition where the condition of the above step 102 is satisfied, that is, only in the transient state and when the EGR ON region is switched to the EGR OFF region. Although the overspeed suppression control of the turbocharger 14 is performed, in the present invention, the overspeed suppression control of the turbocharger 14 may be performed under a wider situation.

  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.

  In the first embodiment described above, the rotational speed sensor 16 corresponds to the “rotational speed detection means” in the first aspect of the present invention. Further, when the ECU 70 executes the process of step 106, the “over-rotation detecting means” in the first invention executes the process of step 108, and the “over-rotation suppressing means in the first invention does. Are realized.

  In the first embodiment described above, the “motor control means” according to the second aspect of the present invention is realized by causing the ECU 70 and the motor controller 60 to reversely drive the motor 15 by the processing of step 108. .

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 4. The description will focus on the differences from the first embodiment described above, and the description of similar matters will be omitted or simplified. To do. The system of the present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 4 to be described later instead of the routine shown in FIG. 3 using the hardware configuration shown in FIG.

[Features of Embodiment 2]
As described above, in the first embodiment, excessive rotation of the turbocharger 14 is suppressed by a method of reversely driving the electric motor 15. Instead of this method, in the present embodiment, a method of increasing the opening degree of the variable nozzle 14c is adopted. If the opening degree of the variable nozzle 14c is increased, the flow rate of the exhaust gas blown to the turbine 14b becomes slow, so that the turbo rotation speed can be reduced.

[Specific Processing in Second Embodiment]
FIG. 4 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the above function. Note that this routine is periodically executed at predetermined time intervals. In FIG. 4, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 4, the same control as that in the first embodiment is performed until the determination of the excessive rotation of the turbocharger 14 in step 106. If it is determined in step 106 that the actual turbo speed TREV exceeds the target turbo speed TREVTRG, a process for increasing the opening of the variable nozzle 14c is performed (step 120). That is, a process for opening the variable nozzle 14c to an opening larger than the opening fixed in Step 104 is performed. As a result of this process, the flow rate of the exhaust gas blown to the turbine 14b is slowed down, so that the turbo rotation speed is lowered and the supercharging pressure is lowered.

  In the routine shown in FIG. 4, it is next determined whether or not the overspeed of the turbocharger 14 has been eliminated, and whether or not the accelerator pedal has been returned (step 110). While the turbocharger 14 has not been over-resolved and the accelerator pedal is not returned, the open state of the variable nozzle 14c is maintained. Then, when the overspeed of the turbocharger 14 is eliminated, or when the accelerator pedal is returned, the opening degree of the variable nozzle 14c is returned to the opening degree before performing the processing of step 120 ( Step 122).

  According to the routine described above, it is possible to detect the overshoot of the supercharging pressure at an early time point and reduce the turbo rotation speed. For this reason, the effect similar to Embodiment 1 is acquired.

  By the way, the above-described second embodiment has been described on the assumption that the hardware configuration shown in FIG. 1 is used. However, this embodiment has a hardware configuration that does not include the electric motor 15, that is, a normal variable nozzle turbocharger. The present invention can also be applied to the hardware configuration used. In that case, a variable speed turbocharger may be provided with a rotational speed sensor for detecting the turbo rotational speed.

  In the second embodiment described above, the ECU 70 executes the process of step 120, whereby the “over-rotation suppressing means” in the first invention and the “opening degree increasing means” in the third invention are provided. It has been realized.

  Although the embodiment of the present invention has been described above, the method of suppressing the turbo rotation speed by the overspeed suppressing means in the present invention is limited to a method of causing the electric motor 15 to exert a braking torque and a method of opening the variable nozzle 14c. It is not something. For example, by operating the switching valve 18 to open the inlet of the bypass pipe 50 and returning a part of the air compressed by the compressor 14a to the inlet side of the compressor 14a through the bypass pipe 50, the turbo rotational speed is reduced. be able to. The overspeed suppression means may suppress the turbo rotation speed by this method.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. 3 is a map showing a relationship between an EGR ON area and an EGR OFF area in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Explanation of symbols

2 Diesel Engine 4 Intake Manifold 6 Exhaust Manifold 8 Intake Pipe 10 Exhaust Pipe 12 Air Cleaner 14 Turbo Supercharger 14a Compressor 14b Turbine 14c Variable Nozzle 15 Motor 16 Rotation Sensor 17 Intercooler 18 Switching 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 (3)

A turbocharger,
A rotational speed detection means for detecting the rotational speed of the turbocharger;
Overspeed detection means for detecting overspeed of the turbocharger based on the actual turbo speed detected by the turbo speed detection means;
When the overspeed detection means detects an overspeed of the turbocharger, an overspeed suppression means for suppressing the number of revolutions of the turbocharger;
A control device for an internal combustion engine, comprising: The over-rotation suppression means is
An electric motor that rotates with the turbocharger;
2. The internal combustion engine according to claim 1, further comprising: an electric motor control unit configured to control the electric motor so that the electric motor generates a braking torque when an overspeed of the turbocharger is detected. Engine control device. The over-rotation suppression means is
A variable nozzle that opens and closes to make the flow rate of the exhaust gas blown to the turbine of the turbocharger variable; and
2. The control apparatus for an internal combustion engine according to claim 1, further comprising an opening degree increasing means for increasing the opening degree of the variable nozzle when an overspeed of the turbocharger is detected.

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