JP3826592B2 - Control device for turbocharged engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a turbocharged engine mounted on an automobile or the like.
[0002]
[Prior art]
Conventionally, for example, as disclosed in JP-A-8-338318, an EGR passage (exhaust gas recirculation passage) that recirculates exhaust gas of a diesel engine into an intake passage, and the exhaust gas recirculation amount that is provided in the EGR passage is adjusted. In an exhaust gas recirculation device for a diesel engine having an EGR valve (exhaust gas recirculation valve), a target value of an excess air ratio (air-fuel ratio) is determined in order to suppress the generation of smoke while reducing NOx. The EGR valve is controlled so as to eliminate the deviation.
[0003]
Further, as shown in, for example, Japanese Patent Laid-Open No. 10-47070, by providing a variable blade that changes the exhaust flow area for the turbine of the turbocharger, the supercharging state can be controlled according to the operating state. Such a turbocharged engine is also known.
[0004]
[Problems to be solved by the invention]
In the turbocharged engine having variable wings as described above, as a control method for controlling the supercharging pressure, an actual intake pressure is detected by an intake pressure sensor provided in an intake passage downstream of the supercharger, A target intake pressure is set according to the operating state, a control amount for controlling the opening degree of the variable blade is determined according to a deviation between the target intake pressure and the actual intake pressure, and the control amount is driven by the variable blade. It is considered that the variable blade is feedback-controlled so that the actual intake pressure becomes the target intake pressure by outputting to the means.
[0005]
However, when the variable blade is feedback-controlled in accordance with the intake pressure as described above, the following problems remain particularly in the engine equipped with the exhaust gas recirculation device.
[0006]
That is, in a state where the actual intake pressure is controlled to become the target intake pressure, for example, during transient operation where the acceleration operation is decelerated to the deceleration operation, the target intake pressure rapidly decreases as the load decreases. Since there is a response delay in the decrease, the deviation between the actual intake pressure and the target intake pressure increases, and the variable blades are fully opened or opened close to the opening degree by supercharging pressure feedback control according to this deviation.
[0007]
On the other hand, in the exhaust gas recirculation device, the opening degree of the EGR valve is adjusted so as to increase the EGR amount as the operating state shifts to the low load side, but the variable blades are fully opened or close to the opening degree. As a result, the exhaust pressure is reduced, and the differential pressure between the exhaust pressure and the intake pressure is reduced, so that the action of deriving the exhaust gas from the exhaust system to the intake system is inhibited. Therefore, the exhaust gas recirculation amount becomes insufficient during the transient operation, and the NOx reduction effect becomes insufficient.
[0008]
Furthermore, if the variable blades are greatly opened as described above when shifting to a deceleration operation, etc., the supercharging efficiency will be reduced, so that the increase in intake pressure will be delayed at the time of reacceleration from this state, and the acceleration performance will deteriorate. There is also.
[0009]
In view of such circumstances, the present invention prevents the exhaust gas recirculation amount from becoming insufficient during transient operation in which the target intake pressure rapidly decreases in a state where the actual intake pressure is controlled to become the target intake pressure. The present invention provides a control device for an engine with a turbocharger that can maintain a good reduction effect and improve acceleration performance during reacceleration.
[0010]
[Means for Solving the Problems]
  The invention according to claim 1Diesel engineThe exhaust passage is provided with variable vanes for changing the exhaust flow area to the turbine of the turbocharger, and the upstream of the variable vanes in the exhaust passage and the intake passage are connected by an exhaust recirculation passage, and the exhaust gas is returned to the exhaust recirculation passage. With turbocharger with an exhaust recirculation valve that regulates the flow rateDieselIn the engine, an intake pressure detecting means for detecting an intake pressure state downstream of the compressor of the turbocharger, and a supercharging pressure for controlling the variable blade so that the pressure detected by the intake pressure detecting means becomes a target intake pressure. Feedback control means, and suppression means for suppressing the operation of the variable blade in the opening direction during transient operation in which the target intake pressure rapidly decreases.Furthermore, an intake throttle valve is provided upstream of the exhaust gas recirculation passage connection portion in the intake passage, and an intake pressure detection means is disposed downstream of the intake throttle valve, and the suppression means is an operating region where exhaust gas recirculation is performed, The intake throttle valve is throttled during transient operation where the target intake pressure decreases rapidlyIs.
[0011]
  According to this configurationThe target intake pressure suddenly decreases in the operating range where exhaust gas recirculation is performed.During transient operation, the change in the actual intake pressure is delayed with respect to the change in the target intake pressure, and the control by the supercharging pressure feedback control means tends to cause the variable blade to open widely. Operation in the opening direction is suppressed.In other words, the intake pressure detected by the intake pressure detecting means is reduced, and the deviation from the target intake pressure is reduced, so that the operation in the opening direction of the variable blade controlled by the supercharging pressure feedback control means is suppressed. It becomes.For this reason, it is avoided that the exhaust pressure acting on the exhaust gas recirculation passage becomes too low, and the exhaust gas exhausting action from the exhaust system to the intake system is kept good.
[0014]
  the aboveThe suppression means controls to throttle the intake throttle valve and increase the opening of the exhaust gas recirculation valve during transient operation in which the target intake pressure rapidly decreases.2In this way, the exhaust gas recirculation amount is sufficiently ensured during the transient operation.
[0015]
  If the engine is provided with an intercooler downstream of the compressor of the supercharger in the intake passage, the intake throttle valve is disposed downstream of the intercooler.3In this case, since the capacity of the intake passage downstream of the intake throttle valve is smaller than in the case where an intercooler exists downstream of the intake throttle valve, the intake throttle valve accompanying the throttle of the intake throttle valve is preferable. Lowering of the intake pressure downstream is accelerated.
[0016]
  Furthermore, if an intake throttle valve is provided downstream of the surge tank in the intake passage (claim)4), The capacity of the intake passage downstream of the intake throttle valve becomes smaller, and the lowering of the intake pressure downstream of the intake throttle valve accompanying the throttle of the intake throttle valve is further accelerated.
[0017]
  Claim5The invention according toThe exhaust passage of the diesel engine is provided with variable blades that change the exhaust flow area to the turbine of the turbocharger, and the upstream of the variable blades in the exhaust passage and the intake passage are communicated by an exhaust recirculation passage. In a diesel engine with a turbocharger having an exhaust gas recirculation valve for adjusting the exhaust gas recirculation amount, an intake pressure detection means for detecting an intake pressure state downstream from the compressor of the turbocharger, and the intake pressure detection means The supercharging pressure feedback control means that controls the variable blades so that the pressure detected by the target air pressure becomes the target intake pressure, and during transient operation where the target intake pressure decreases rapidly, And a suppression means that suppresses the opening operation of the variable blade by restricting, and the boost pressure feedback control means is an intake pressure detection unit. The variable wing is controlled by a control amount calculated based on the deviation between the pressure detected by the means and the target intake pressure, and the suppression means sets a dead band for the deviation, and the deviation is within the dead band range. Feedback control by the supercharging pressure feedback control means is stopped, and the width of the dead zone is set larger as the load is lower.Is.
[0018]
  According to this configurationIf the operating state shifts to the low load side during transient operation, the range of the dead zone is increased, and if the deviation is within the dead zone, the feedback control is stopped to suppress the operation of the variable blade. Is done.
[0019]
  In the present invention, the suppression means isfurther,At least during a transient operation where the target intake pressure decreases rapidly, a guard value is set at least for the change in the control amount in the variable blade opening direction, and the control amount is limited so as not to exceed the guard value.Preferably(Claims6). In this case, the supercharging pressure feedback control means controls the variable blade by a control amount calculated based on the deviation between the pressure detected by the intake pressure detection means and the target intake pressure, and the suppression means operates An allowable range of the control amount is set according to the state, and when the calculated value of the control amount deviates from the allowable range, the limit value of the allowable range corresponding to the guard value may be used as the control amount (claims).7).
[0020]
If it does in this way, the operation | movement of the opening direction of a variable wing | blade will be suppressed by the opening degree corresponding to the said guard value.
[0024]
  And an exhaust gas recirculation valve control means for controlling the exhaust gas recirculation valve so that the air fuel ratio becomes a target air fuel ratio in an operation region where exhaust gas recirculation is performed.8) Is preferred. In this way, the exhaust gas recirculation amount is controlled so that an air-fuel ratio suitable for reducing NOx and smoke is obtained. The operation of the variable blade in the opening direction is suppressed during transient operation, and the exhaust pressure acting on the exhaust gas recirculation passage is prevented from becoming too low, so that the exhaust gas recirculation amount can be controlled well even during transient operation. Is called.
[0025]
  The transient operation in which the target intake pressure rapidly decreases is, for example, a transition from acceleration operation to steady operation or deceleration operation (claims).9). Alternatively, it is during shifting of a transmission connected to the engine.10).
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of an engine with a turbocharger provided with a control device according to the present invention. The illustrated engine is a diesel engine, and an intake passage 2 and an exhaust passage 3 are connected to the engine body 1. The engine is also equipped with a turbocharger 5. The turbocharger 5 is provided in the exhaust passage 3 to drive the compressor 6 provided in the intake passage 2 and the compressor 6 with exhaust energy. And a variable blade 8 as will be described later. Further, the engine has an EGR device (exhaust gas recirculation device) having an EGR passage 11 communicating the exhaust gas passage 3 and the intake air passage 2 and an EGR valve (exhaust gas recirculation valve) 12 interposed in the EGR passage 11. Is provided.
[0027]
The structure of each part of the engine will be described in detail. Each cylinder 14 of the engine body 1 is provided with a multi-injection fuel injection valve 15 for injecting fuel into the combustion chamber. The fuel inlet side of these fuel injection valves 15 is connected to a common rail (common pipe) 17 through a distribution passage 16, and this common rail 17 is connected to a fuel injection pump 18 and fed from the fuel injection pump 18. The fuel is accumulated in the common rail 17 and then sent to each fuel injection valve 15. Each fuel injection valve 15 has a structure capable of controlling the fuel injection time and the injection timing in accordance with a control signal. The fuel outlet side of each fuel injection valve 15 is connected to a return passage 19.
[0028]
In the intake passage 2, an air flow sensor 21, a compressor 6 of the turbocharger 5, an intercooler 22, an intake throttle valve 23, and a surge tank 24 are disposed in that order from the upstream side, and a surge The tank 24 is provided with an intake pressure sensor (intake pressure detection means) 25.
[0029]
The intake throttle valve 23 throttles the intake passage 2 in order to promote the introduction of EGR in a specific operation region, and is driven by a negative pressure responsive actuator 23a. The actuator 23a is connected to a vacuum pump 27 via a solenoid valve 26A, and the introduction ratio of the negative pressure and the atmospheric pressure to the actuator 23a is adjusted by duty control of the solenoid valve 26A. The opening degree of the valve 23 is controlled.
[0030]
The exhaust passage 3 is provided with a turbine 7 of the turbocharger 5 and a catalytic converter 28.
[0031]
The turbocharger 5 is composed of a VGT (variable geometry turbo) having a large number of variable blades 8 forming nozzles around a turbine 7 as shown in FIG. That is, the turbocharger 5 (hereinafter referred to as VGT 5) is adjusted from the fully closed state (minimum distribution area) shown in FIG. 2A to the fully open state (circulation) shown in FIG. The opening of the variable blade 8, that is, the nozzle opening area (exhaust flow area to the turbine) is variable over the maximum area), and the turbine efficiency is thereby controlled.
[0032]
As shown in FIG. 1, the variable blade 8 is driven by a negative pressure responsive actuator 8a, which is connected to a vacuum pump 27 via an electromagnetic valve 26B. Then, the duty ratio of the electromagnetic valve 26B adjusts the introduction ratio of the negative pressure and the atmospheric pressure to the actuator 8a, thereby controlling the variable blade opening of the VGT 5.
[0033]
One end of the EGR passage 11 is connected to the upstream side of the turbine 7 in the exhaust passage 3, for example, a collecting portion of the exhaust manifold, and the other end is downstream of the intake throttle valve 23 in the intake passage 2. For example, it is connected to the surge tank 24 or upstream thereof. The EGR valve 12 provided in the EGR passage 11 is connected to a vacuum pump 27 via a duty-controllable electromagnetic valve 26C, and the electromagnetic valve 26C is duty-controlled, so that the EGR valve 12 is connected to the negative pressure chamber. The introduction ratio between the negative pressure and the atmospheric pressure is adjusted, whereby the opening degree of the EGR valve 12 is controlled.
[0034]
A control signal is output from a control unit (ECU) 30 to the fuel injection valve 15 and the electromagnetic valves 26A, 26B, and 26C. The ECU 30 receives signals from the airflow sensor 21 and the intake pressure sensor 25, and further includes an accelerator opening sensor 31 that detects the accelerator opening, a crank angle sensor 32 that detects the crank angle of the engine, and the common rail 17. A signal from a common rail pressure sensor 33 or the like for detecting the fuel pressure inside is also input.
[0035]
The control signal output from the ECU 30 to the fuel injection valve 15 controls the fuel injection amount and injection timing from the fuel injection valve 15, and the control signal (duty signal) output to the electromagnetic valves 26A, 26B, and 26C. Thus, the intake throttle valve 23, the variable vane 8 of the VGT 5 and the EGR valve 12 are controlled.
[0036]
As shown in FIG. 3, the ECU 30 includes a fuel injection amount control means 35 that controls the fuel injection amount of the fuel injection valve 15, a common rail pressure control means 36 that controls the fuel pressure in the common rail 17, and the EGR valve 12. EGR control means (exhaust recirculation valve control means) 41 for controlling, supercharging pressure feedback control means 42 for controlling the supercharging pressure by controlling the variable blade opening degree of the VGT 5, and an intake throttle for controlling the intake throttle valve 23 And valve control means 43.
[0037]
The fuel injection amount control means 35 is based on the accelerator opening degree Accel detected by the accelerator opening degree sensor 31 and the engine speed Ne detected by the engine speed detecting means 51 by measuring the cycle of the crank angle signal. The target torque Trqsol of the engine is read from the preset map 37, and is set in advance based on the target torque Trqsol, the engine speed Ne, and the actual fresh air amount FAir detected by the airflow sensor 21. The target fuel injection amount Fsol is read from the three-dimensional map 38, and the excitation time of the fuel injection valve 15 is adjusted based on the target fuel injection amount Fsol and the fuel pressure CRP in the common rail 17 detected by the common rail pressure sensor 21. By controlling the fuel injection amount It has been made.
[0038]
The common rail pressure control means 36 reads the target common rail pressure CRPsol from a preset map 39 based on the target torque Trqsol and the engine speed Ne, and based on the target common rail pressure CRPsol and the detected fuel pressure CRP. A fuel pressure adjusting means (not shown) provided in the fuel system is controlled.
[0039]
Further, the EGR control means 41 performs feedback control of the EGR valve 12 so that the air-fuel ratio becomes the target air-fuel ratio A / Fsol in the operation region where EGR is performed. That is, at the time of feedback control, the target air-fuel ratio A / Fsol is read from the preset map 44 based on the target torque Trqsol and the engine speed Ne, and the target air-fuel ratio A / Fsol and the target fuel injection amount are read. Based on Fsol, the target fresh air amount calculation unit 45 calculates the target fresh air amount FAsol of fresh air to be sucked into the combustion chamber of the engine body 1, and the calculated value of the target fresh air amount FAsol and the air flow sensor 33 detect it. The actual fresh air amount Fair is input to the EGR valve control means 41.
[0040]
Then, the EGR valve control means 41 outputs a control signal (duty signal) according to the deviation between the target fresh air amount FAsol and the actual fresh air amount FAir to the electromagnetic valve 26C for driving the EGR valve. The opening degree of the EGR valve 12 is feedback controlled so as to eliminate the above. Such control is hereinafter referred to as air flow feedback control.
[0041]
The supercharging pressure feedback control means 42 performs feedback control of the variable vane 8 of the VGT 5 so that the actual supercharging pressure (intake pressure detected by the intake pressure sensor) Bst becomes the target supercharging pressure (target intake pressure) Bstsol. . That is, the target supercharging pressure Bstsol is read from the preset map 46 based on the target torque Trqsol and the engine speed Ne, and the target supercharging pressure Bstsol and the actual supercharging detected by the intake pressure sensor 24 are read. The pressure Bst is input to the supercharging pressure feedback control means 42. Then, the supercharging pressure feedback control means 42 outputs a control signal (duty signal) according to the deviation between the actual supercharging pressure Bst and the target supercharging pressure Bstsol to the VGT driving solenoid valve 26C. The opening degree of the variable blade 8 is feedback-controlled so as to eliminate the deviation. Such control is hereinafter referred to as supercharging pressure feedback control.
[0042]
The air flow feedback control and the supercharging pressure feedback control may be performed in the entire operation region, but in the high load region near the accelerator fully open, the EGR valve 12 is kept fully closed to stop the EGR. In the high load region, the open control may be performed according to the operation state such that the variable blade 8 of the VGT 5 is closed on the low rotation side and opened on the high rotation side. Further, in the idle operation region where the excess air ratio is large, the variable blade 8 of the VGT 5 may be fully closed and the EGR valve 12 may be fully opened in order to increase the EGR amount and reduce NOx.
[0043]
The intake throttle valve control means 43 controls the intake throttle valve 23 according to the operating state. In particular, in the present embodiment, the intake throttle valve control means 43 constitutes a suppression means that suppresses the opening operation of the variable blade 8 during the transient operation in which the target supercharging pressure rapidly decreases.
[0044]
In other words, the intake throttle valve control means 43 causes the intake pressure sensor 25 to reduce the intake throttle valve 23 to a smaller opening (for example, fully closed) than during normal operation during transient operation in which the target boost pressure suddenly decreases. The decrease in the detected intake pressure is accelerated so that the target boost pressure Bstsol and the pressure Bst detected by the intake pressure sensor 25 are compared with the case where the intake throttle valve 23 is not throttled during the transient operation. Accordingly, the operation amount in the opening direction of the intake throttle valve 23 controlled in accordance with the deviation is reduced.
[0045]
An example of the control of the intake throttle valve control means 43 that functions as the suppression means will be described with reference to the flowchart of FIG.
[0046]
When the processing of this flowchart starts, first, in step S1, the engine speed Ne, the fuel injection amount, the actual intake pressure Bst detected by the intake pressure sensor 25, and the like are read. In step S2, the target intake pressure (target boost pressure) is read. Bstsol is calculated. Further, in step S3, an intake pressure deviation which is a deviation between the actual intake pressure Bst and the target intake pressure Bstsol is calculated. Subsequently, in step S4, a VGT control duty DuB is calculated in accordance with the intake pressure deviation. In this case, VGT control is performed so as to change the variable blade opening of the VGT 5 so that the actual intake pressure Bst approaches the target intake pressure Bstsol by feedback control such as PID control (proportional integral derivative control) according to the intake pressure deviation. Duty DuB is determined.
[0047]
Next, in step S5, it is determined whether or not the intake pressure deviation is larger than a predetermined threshold value set in advance. If the intake pressure deviation is smaller than the threshold value, the intake throttle valve control duty DuA is calculated in step S6 according to the operating state. In this case, as shown in FIG. 5, in the region A where the displacement is relatively small (regions ranging from low rotation and low load to low rotation and high load, medium rotation and middle load, and high rotation and low load) The intake throttle valve control duty DuA is determined according to the operating state so that the opening degree of the throttle valve 23 is small and the opening degree of the intake throttle valve 23 increases as the rotational speed and load increase. In addition, the intake valve control duty DuA is determined so that the intake throttle valve 23 is fully opened in the high rotation and high load region B where the exhaust amount is large.
[0048]
If it is determined in step S5 that the intake pressure deviation is greater than a predetermined threshold value, the intake throttle valve control duty DuA is determined in step S7 so that the intake throttle valve 23 is fully closed. .
[0049]
Subsequent to step S6 or step S7, in step S8, the VGT control duty DuB calculated in step S4 and the intake throttle valve control duty DuA obtained in step S6 or step S7 are the VGT solenoid valve 26B and the intake air. Each is output to the throttle valve electromagnetic valve 26A.
[0050]
According to the apparatus of the present embodiment as described above, the opening degree of the EGR valve 12 is controlled by airflow feedback control so that the actual fresh air amount FAir becomes the target fresh air amount FAsol during normal operation in a partial load region or the like. In addition, the variable blade opening of the VGT 5 is controlled by the supercharging pressure feedback control so that the actual intake pressure Bst becomes the target intake pressure Bstsol, and the intake throttle valve 23 corresponds to the operating state as shown in FIG. Be controlled.
[0051]
At the time of transient operation in which the target intake pressure rapidly decreases, for example, when shifting from acceleration operation to steady operation or deceleration operation, the intake pressure, VGT opening, intake throttle valve opening, and EGR amount change as shown in FIG.
[0052]
That is, the target intake pressure Bstsol suddenly decreases as indicated by a one-dot chain line at the transition time t0 from acceleration operation to deceleration operation or the like, whereas the actual intake pressure Bst is delayed because there is a delay. And the target intake pressure Bstsol becomes larger.
[0053]
In this case, just by performing the same control as in the normal state, the intake throttle valve 23 is opened to an opening according to the operating state, as shown by the broken line in the figure, and the decrease in the actual intake pressure Bst is slow. Since the state in which the deviation from the target intake pressure Bstsol is large continues for a relatively long time, the variable blade 8 of the VGT 5 is opened more than necessary by the supercharging pressure feedback control. On the other hand, the EGR valve 12 is controlled so that the air-fuel ratio becomes the target air-fuel ratio A / Fsol by the air flow feedback control, so that the EGR amount increases and the fresh air increases when shifting to the deceleration operation where the fuel injection amount decreases. Although the amount decreases, while the variable vane 8 of the VGT 5 is opened more than necessary, the exhaust pressure decreases and the differential pressure with respect to the intake pressure decreases, so the increase in the EGR amount is delayed.
[0054]
On the other hand, according to the apparatus of the present embodiment, as shown by the solid line in the figure, the intake throttle valve 23 is throttled when the intake pressure deviation becomes a predetermined value or more during the transient operation, The decrease in the intake pressure Bst downstream of the intake throttle valve is accelerated, and the state in which the intake pressure deviation increases is reduced. Accordingly, the opening direction of the variable vane 8 of the VGT 5 by supercharging pressure feedback control according to the intake pressure deviation is reduced. The movement to is suppressed. As a result, a differential pressure between the exhaust pressure acting on the EGR passage 11 and the intake pressure is secured, so that the EGR amount quickly increases to an appropriate value according to the control of the EGR valve 12 by the airflow feedback control, and the NOx reduction effect Is kept good.
[0055]
FIG. 7 is a flowchart showing another example of control that functions as a suppression unit that suppresses the operation of the variable blade 8 in the opening direction during transient operation in which the target intake pressure rapidly decreases.
[0056]
When the processing of this flowchart is started, first, in step S11, the engine speed Ne, the fuel injection amount, the actual intake fresh air amount FAir detected by the air flow sensor 21, and the like are read, and in step S12, the target fresh air amount FAsol is calculated. The
[0057]
Further, in step S13, a fresh air amount deviation which is a deviation between the actual fresh air amount FAir and the target fresh air amount FAsol is calculated. Subsequently, in step S14, the control duties DuC and DuA of the EGR and the intake throttle valve 23 are calculated. Calculated. In this case, in order to change the opening degree of the EGR valve 12 so as to bring the actual new air amount FAir closer to the target new air amount FAsol by feedback control such as PID control (proportional integral derivative control) according to the new air amount deviation. , EGR control duty DuC is obtained. Further, the intake throttle valve control duty DuA is calculated in accordance with the relationship shown in FIG. 8 in accordance with the EGR control duty DuC, that is, when the EGR control duty DuC changes in the direction in which the opening of the EGR valve 12 increases. Correspondingly, the intake throttle valve control duty DuA changes in the direction in which the opening of the intake throttle valve 23 decreases accordingly.
[0058]
After the calculation in step S14, the EGR control duty DuC is output to the EGR valve 12 (more precisely, to the EGR valve solenoid valve 26C) in step S15, and to the intake throttle valve 23 in step S16 (to be exact) In this case, the intake throttle valve control duty DuA is output).
[0059]
According to this control example, control of the variable vane 8 of the VGT 5 by supercharging pressure feedback control and control of the EGR valve 12 by air flow feedback control are performed, and the control of the intake throttle valve 23 according to the control of the EGR valve 12 Is done.
[0060]
For example, during transient operation such as shifting from acceleration operation to steady operation or deceleration operation, boost pressure feedback control is performed under the condition where the target intake pressure Bstsol rapidly decreases, and in airflow feedback control, the fuel injection amount is controlled. In order to increase the EGR amount (decrease the fresh air amount) with the decrease, the opening degree of the EGR valve 12 is controlled to be increased. In response to this, the intake throttle valve 23 is operated in the closing direction.
[0061]
Thus, during the transient operation, the intake throttle valve 23 is throttled in response to the opening of the EGR valve 12 being increased, so that the intake pressure downstream of the intake throttle valve is reduced as in the control example shown in FIG. The decrease is accelerated, the operation of the VGT 5 in the opening direction of the variable blade 8 by the supercharging pressure feedback control is suppressed, and the EGR amount quickly increases to an appropriate value according to the control of the EGR valve 12 by the airflow feedback control. Therefore, the NOx reduction effect is kept good.
[0062]
In the above embodiment, it is preferable that the capacity of the intake passage 2 downstream of the intake throttle valve 23 is small in order to increase the responsiveness of the reduction of the intake pressure in response to the throttle of the intake throttle valve 23 during the transient operation. Therefore, when an intercooler 22 having a relatively large capacity is provided in the intake passage 2 as shown in FIG. 1, an intake throttle valve 23 is provided in the intake passage 2 downstream of the intercooler 22, and the intake air downstream thereof is provided. The EGR passage 11 may be connected to the passage 2.
[0063]
Alternatively, if the intake throttle valve is provided further downstream of the surge tank 24 in the intake passage 2, the capacity of the intake passage downstream of the intake throttle valve is further reduced, and the intake air in response to the intake throttle valve being throttled. The response of the pressure drop is increased.
[0064]
In this case, as shown in FIG. 9, since the downstream side of the surge tank 24 is an independent intake passage for each cylinder, an intake throttle valve 51 is provided in each independent intake passage, and these are linked to each other. In addition, it may be driven by a common actuator 52. The downstream side of the EGR passage 11 may be branched for each cylinder and connected downstream of the intake throttle valve 51 in each independent intake passage. Further, the intake pressure sensor 53 may be provided in the independent intake passage downstream of the intake throttle valve 51. A tank 54 is preferably provided in the middle of the EGR passage 11 in order to improve EGR distribution.
[0065]
10 to 12 show still another control example. In this control example, the supercharging pressure feedback control means 42 includes a function of a suppression means that suppresses the operation in the opening direction of the variable blade 8 during a transient operation in which the target intake pressure suddenly decreases. During the transient operation, the change in the control amount of the variable blade 8 due to the supercharging pressure feedback control is limited. For example, a guard value is set for the change in the control amount in at least the variable blade opening direction. It is restricted not to exceed. Furthermore, a dead zone is set for the deviation, and if it is within the dead zone range, the boost pressure feedback control is stopped, and the dead zone is widened in an operation region that is a transition destination of the driving state during the transient operation. Yes.
[0066]
That is, as shown in FIG. 10, the supercharging pressure feedback control means 42 calculates the VGT control duty DuB by PID control according to the intake pressure deviation which is the deviation between the actual intake pressure Bst and the target intake pressure Bstsol. And a dead zone setting means 42b for setting a dead zone according to the intake pressure deviation, and a duty limit setting means 42c for setting a duty limit corresponding to the guard value of the control amount.
[0067]
The dead zone setting means 42b obtains a dead zone of the intake pressure deviation from a preset map based on the fuel injection amount Qf and the engine speed Ne.
[0068]
In this map, for example, a dead zone is set for each of the operation regions C, D, and E as shown in FIG. 11, and the dead zone is maximized in the low load region C where the fuel injection amount is small, and the fuel injection amount is increased to some extent. In the load region D, the dead zone is narrower than that in the low load region C, and in the high load region where the fuel injection amount is large, the dead zone is further narrowed.
[0069]
If the intake pressure deviation is within the dead zone set by the dead zone setting means 42b on the input side of the PID controller 42a, a process for stopping the control calculation by the PID controller 42a is performed. Yes.
[0070]
Further, the duty limit setting means 42c is configured to obtain a duty limit that is a limit of the allowable variation range of the VGT control duty from a preset map based on the fuel injection amount Qf and the engine speed Ne.
[0071]
When the duty limit map is created, a predetermined allowable range is determined around the VGT control duty DuB corresponding to the variable blade opening so that the target intake pressure Bstsol can be obtained according to the operating state. The control target of the VGT control duty DuB having the allowable range is set according to the operating state. Thus, the limit value of the allowable range set according to the operating state is stored in the memory as a duty limit map.
[0072]
In the supercharging pressure feedback control, the VGT control duty DuB is limited on the output side of the PID control unit 42a so as not to exceed the duty limit set by the duty limit setting means 42c.
[0073]
Such control will be specifically described with reference to the flowchart shown in FIG.
[0074]
When the process of this flowchart is started, first, in step S21, the engine speed Ne, the fuel injection amount Qf, the actual intake pressure Bst detected by the intake pressure sensor 25, and the like are read, and in step S22, the target intake pressure Bstsol is calculated. . In step S23, an intake pressure deviation which is a deviation between the actual intake pressure Bst and the target intake pressure Bstsol is calculated.
[0075]
Subsequently, in step S24, the intake pressure control dead zone width is calculated from the dead zone map (see FIG. 11) based on the fuel injection amount Qf and the engine speed Ne. Then, in step S25, it is determined whether or not the intake pressure deviation is within the dead band range. If it is within the dead band range, the calculation of the VGT control duty DuB by the PID control unit 42a is stopped, and the previous calculated value of the VGT control duty DuB. Is output to the VGT drive solenoid valve 26B (steps S26 and S27).
[0076]
If it is determined in step S25 that the intake pressure deviation is not within the dead zone range, in step S28, the VID control duty DuB is calculated by the PID control unit 42a according to the intake pressure deviation, and step S29. Thus, the duty limit is calculated from the limiter map (duty limit map) according to the fuel injection amount Qf and the engine speed Ne.
[0077]
Subsequently, at step S30, it is determined whether or not the calculated value of the VGT control duty DuB is within an allowable range defined by the duty limit. If it is within the allowable range, the calculated value of the VGT control duty DuB is output to the VGT drive solenoid valve 26B as it is in step S31. If it is not within the allowable range, the VGT control duty DuB is fixed to the upper limit value or the lower limit value of the allowable range in step S32, that is, if the calculated value of the VGT control duty DuB exceeds the upper limit value, When the value falls below the lower limit value, the VGT control duty DuB is fixed to the lower limit value, and the duty DuB is output to the VGT drive solenoid valve 26B.
[0078]
By such control as well, the operation in the opening direction of the variable blade 8 is suppressed during transient operation in which the target intake pressure Bstsol rapidly decreases. That is, during the transient operation, the intake pressure deviation increases due to the delay in the reduction of the actual intake pressure Bst relative to the decrease of the target intake pressure Bstsol, and the VGT control duty DuB calculated by the PID control unit 42a according to the intake pressure deviation. Greatly changes in the direction of opening the variable vane 8 of the VGT 5 and exceeds the guard value (duty limit) set by the duty limit setting means 42c. In this case, the VGT control duty DuB is fixed to the guard value and beyond The variable wing 8 is prevented from opening at the same time.
[0079]
Also, if the intake pressure deviation is within the dead zone set by the dead zone setting means 42b, the calculation of the VGT control duty DuB by the PID control unit 42a is stopped. In the case of the low load region C, the dead zone is increased. If the actual intake pressure Bst is higher than the target intake pressure Bstsol, the calculation of the VGT control duty DuB according to the intake pressure deviation is stopped. Thus, the VGT control duty DuB is maintained at the previous value. This also suppresses the movement of the variable blade 8 in the opening direction.
[0080]
Even by such control, the operation in the opening direction of the variable blade 8 during the transient operation is suppressed, so that a situation in which EGR derivation from the exhaust system to the intake system is hindered due to a decrease in exhaust pressure is prevented. The NOx reduction effect by EGR is kept good.
[0081]
In addition, the change in the intake pressure when re-acceleration is performed after the shift to the deceleration operation where the target intake pressure Bstsol rapidly decreases is the conventional apparatus that does not suppress the opening operation of the variable blade 8 during the transient operation. In contrast to the broken line shown in FIG. 13, the solid line according to the present embodiment is shown, and the acceleration performance during re-acceleration is improved.
[0082]
That is, in the conventional apparatus, when the target intake pressure Bstsol is suddenly decreased and the intake pressure deviation is increased when shifting to a deceleration operation or the like, the variable vane 8 of the VGT 5 is greatly opened, whereby the actual intake pressure Bst is set to the target intake pressure Bst. Although it is delayed with respect to the intake pressure Bstsol, it greatly decreases so as to approach the target intake pressure Bstsol. When reacceleration is performed from this state, the increase of the intake pressure is delayed. On the other hand, according to the control as in the present embodiment, even if the target intake pressure Bstsol is suddenly decreased due to the shift to the deceleration operation or the like, the actual intake pressure Bst is reduced by suppressing the opening operation of the variable blade 8. Since it becomes relatively small, when reacceleration is performed from this state, the supercharging action is quickly increased, the intake pressure is increased, and the supercharging response is improved.
[0083]
The configuration of the control means and the like in the apparatus of the present invention is not limited to the above embodiment, and can be variously changed.
[0084]
For example, in the above embodiment, as the control of the EGR valve 12, the actual fresh air amount detected by the air flow sensor 21 and the target fresh air amount obtained from the target air / fuel ratio or the like so that the air / fuel ratio becomes the target air / fuel ratio. The EGR control duty is calculated according to the deviation. The position of the EGR valve 12 is detected by a position sensor or the like, and the target opening of the EGR valve 12 is set according to the operating state. You may make it control the EGR valve 12 so that it may become a target opening degree.
[0085]
Further, as control for suppressing the operation in the opening direction of the variable blade 8 during the transient operation in which the target intake pressure rapidly decreases, the boost pressure feedback control is unconditionally stopped for a predetermined time during the transient operation, and the VGT You may make it hold | maintain a control duty to a specific fixed value (for example, the value preset according to the driving | running state).
[0086]
In the description of the above embodiment, the transition from the acceleration operation to the steady operation or the deceleration operation is cited as the transient operation in which the target intake pressure rapidly decreases, but the accelerator is also used during the shift of the transmission connected to the engine. By the operation at the time of shifting such that the stepping into the clutch is released and the clutch is turned off, a transient operation in which the target intake pressure rapidly decreases is performed as in the case of the shift from the acceleration operation to the deceleration operation. Also at this time, as in the above control examples, the control for suppressing the movement of the variable blade 8 in the opening direction is performed, so that the NOx reduction effect by EGR is kept good, and the acceleration operation (accelerator depression) is performed after the shift. The supercharging response when the operation is performed is improved.
[0087]
【The invention's effect】
As described above, the present invention provides a turbocharger engine that includes variable vanes that change the exhaust flow area to the turbine and that includes an exhaust gas recirculation passage and an exhaust gas recirculation valve, downstream of the turbocharger compressor. And a supercharging pressure feedback control means for controlling the variable blade so that the intake air pressure at the target air pressure becomes the target intake pressure, and a suppression means for suppressing the opening operation of the variable blade at the time of transient operation in which the target intake pressure rapidly decreases. Therefore, during the transient operation described above, there is a situation where the variable blades are opened too much by feedback control according to the deviation between the actual intake pressure and the target intake pressure, and the exhaust pressure acting on the exhaust gas recirculation passage becomes low. Can be prevented. Therefore, it is possible to prevent the exhaust gas recirculation amount from being insufficient during the transient operation, and to effectively exhibit the NOx reduction effect.
[0088]
Moreover, since the variable blades can be greatly opened during the transient operation, the reduction in supercharging efficiency can be suppressed, which is advantageous in improving the acceleration performance during subsequent reacceleration.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of an engine with a turbocharger equipped with a control device according to the present invention.
FIG. 2 is a schematic diagram of a structure of a variable blade arrangement portion in a VGT as an example of a supercharger.
FIG. 3 is a block diagram showing a specific configuration of an engine control unit.
FIG. 4 is a flowchart illustrating an example of a control operation.
FIG. 5 is an explanatory diagram showing control characteristics of an intake throttle valve according to an operating state.
FIG. 6 is a time chart showing temporal changes in intake pressure, VGT opening, intake throttle valve opening, and EGR amount during transient operation.
FIG. 7 is a flowchart showing another example of the control operation.
8 is a diagram showing a relationship between an EGR control duty and an intake throttle valve control duty in the flowchart of FIG.
FIG. 9 is a schematic view showing another embodiment of an engine with a turbocharger.
FIG. 10 is a block diagram showing another example of supercharging pressure feedback control means.
FIG. 11 is a diagram showing a dead zone map;
12 is a flowchart showing a control operation by the control means shown in FIG.
13 is a diagram showing a temporal change in intake pressure during transient operation when the control means of FIG. 10 is used. FIG.
[Explanation of symbols]
1 Engine body
2 Intake passage
3 Exhaust passage
5 Turbocharger
8 Variable wings
11 EGR passage
12 EGR valve
21 Air flow sensor
22 Intercooler
23 Inlet throttle valve
25 Intake pressure sensor
30 Control unit
41 EGR control means
42 Supercharging pressure feedback control means
43 Inlet throttle valve control means

Claims (10)

The exhaust passage of the diesel engine is provided with variable blades that change the exhaust flow area to the turbine of the turbocharger, and the upstream of the variable blades in the exhaust passage and the intake passage are communicated by an exhaust recirculation passage. In a diesel engine with a turbocharger that has an exhaust gas recirculation valve that adjusts the exhaust gas recirculation amount,
Intake pressure detection means for detecting the intake pressure state downstream of the turbocharger compressor;
Supercharging pressure feedback control means for controlling the variable blade so that the pressure detected by the intake pressure detection means becomes the target intake pressure;
Suppression means for suppressing the operation of the variable blade in the opening direction during transient operation in which the target intake pressure decreases rapidly ,
Furthermore, an intake throttle valve is provided upstream of the exhaust gas recirculation passage connection point in the intake passage, and an intake pressure detection means is disposed downstream of the intake throttle valve,
The control device for an engine with a turbocharger , wherein the suppression means throttles the intake throttle valve during a transient operation in which the target intake pressure rapidly decreases in an operation region where exhaust gas recirculation is performed . 2. The turbocharger-equipped engine according to claim 1, wherein the suppression unit controls the throttle valve to throttle the intake throttle valve and increase the opening of the exhaust gas recirculation valve during a transient operation in which the target intake pressure rapidly decreases . Control device. The control of the turbocharged engine according to claim 1 or 2, wherein an intercooler is provided downstream of the compressor of the supercharger in the intake passage, and an intake throttle valve is arranged downstream of the intercooler. apparatus. The control device for an engine with a turbocharger according to claim 1 or 2, wherein the intake throttle valve is provided downstream of the surge tank in the intake passage . The exhaust passage of the diesel engine is provided with variable blades that change the exhaust flow area to the turbine of the turbocharger, and the upstream of the variable blades in the exhaust passage and the intake passage are communicated by an exhaust recirculation passage. In a diesel engine with a turbocharger that has an exhaust gas recirculation valve that adjusts the exhaust gas recirculation amount,
Intake pressure detection means for detecting the intake pressure state downstream of the turbocharger compressor;
Supercharging pressure feedback control means for controlling the variable blade so that the pressure detected by the intake pressure detection means becomes the target intake pressure;
In a transient operation in which the target intake pressure suddenly decreases, the suppression means for suppressing the operation of the variable blade in the opening direction by limiting the change in the control amount of the variable blade by the supercharging pressure feedback control,
The supercharging pressure feedback control means controls the variable blade by a control amount calculated based on a deviation between the pressure detected by the intake pressure detecting means and the target intake pressure,
The suppression means sets a dead band for the deviation, and stops the feedback control by the boost pressure feedback control means if the deviation is within the dead band range, and the width of the dead band is set larger as the load is lower. A control device for an engine with a turbocharger. The suppression means sets a guard value against a change in the control amount in at least the variable blade opening direction at least during a transient operation in which the target intake pressure rapidly decreases, and restricts the control amount so as not to exceed the guard value. The control device for an engine with a turbocharger according to claim 5 . The suppression means sets an allowable range of the control amount according to the operating state, and when the calculated value of the control amount deviates from the allowable range, the limit value of the allowable range corresponding to the guard value is set as the control amount. The control device for an engine with a turbocharger according to claim 6 . In operation region where the exhaust gas recirculation is performed, the air-fuel ratio according to any one of claims 1 to 7, characterized in that it comprises an exhaust gas recirculation valve control means for controlling the exhaust gas recirculation valve so that the target air-fuel ratio Control device for turbocharged engine. Transient operation target intake pressure decreases rapidly, the turbo engine with a supercharger according to any one of claims 1 to 8, characterized in that the acceleration operation is shifting to the steady operation or deceleration operation Control device. Transient operation target intake pressure decreases rapidly, the control device of the turbocharged engine according to any one of claims 1 to 8, characterized in that the time shifting of the transmission connected to the engine .

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