JP2016211485A - Control device for variable capacity type turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a turbine inlet pressure up to its tolerance limit, improve controllability of a turbocharger and further improve an engine performance even if the turbocharger suffers time degradation.SOLUTION: According to one embodiment of this invention, this invention relates to a control device for a variable capacity type turbocharger 14 installed at an engine 1, the device comprising a nozzle opening control part 100 for feedback controlling a nozzle opening at an inlet of a turbine 14T on the basis of a boost pressure, a guard value setting part 100 for setting a guard value of turbine inlet pressure and a stop part 100 for stopping the feedback control for the nozzle opening when a real turbine inlet pressure exceeds the guard value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for a variable displacement turbocharger provided in an engine.

  A vehicle diesel engine equipped with a variable displacement turbocharger is known. In this variable displacement turbocharger, the nozzle opening at the turbine inlet is generally feedback controlled based on the boost pressure.

JP 2014-202085 A

  The nozzle opening is controlled so that the boost pressure reaches the target value. When the boost pressure that is the target value is higher than the current value, the current value approaches the target value by reducing the nozzle opening, but a guard value is provided for the nozzle opening that exceeds the guard value. The nozzle opening is controlled so as not to decrease. This is because if the nozzle opening is smaller than the guard value, the turbine inlet pressure becomes excessively high, the pumping loss increases, the fuel consumption deteriorates, and the EGR becomes excessive, which may deteriorate the smoke.

  Thus, the guard value is adapted to a nozzle opening value as small as possible so as not to cause a problem such as an excessive increase in turbine inlet pressure. However, the guard value that was appropriate at the time of adaptation may become inappropriate due to the deterioration of the turbocharger over time, and even if the actual nozzle opening reaches the guard value, the boost pressure does not reach the target value, and the turbine The inlet pressure has not increased too much and there may still be room. In this case, it is desirable to make the nozzle opening smaller than the guard value so that a sufficient amount of the turbine inlet pressure can be effectively used for improving the engine performance such as an increase in boost pressure and consequently an improvement in output and fuel consumption.

  Therefore, the present invention was created in view of such circumstances, and its purpose is to increase the turbine inlet pressure to an allowable limit even when the turbocharger deteriorates with time, thereby improving the controllability of the turbocharger, and thus improving the engine performance. It is an object of the present invention to provide a variable capacity turbocharger control device that can be improved.

According to one aspect of the invention,
A variable capacity turbocharger control device provided in an engine,
A nozzle opening control unit that feedback-controls the nozzle opening at the turbine inlet based on the boost pressure;
A guard value setting unit for setting a guard value for the turbine inlet pressure;
When the actual turbine inlet pressure exceeds the guard value, a stop unit that stops feedback control of the nozzle opening;
A variable capacity turbocharger control device is provided.

Preferably, the nozzle opening degree control unit calculates a target value of the nozzle opening degree based on a feedforward term based on an engine operating state and a feedback term based on a difference between the target boost pressure and the actual boost pressure. ,
The guard value setting unit sets the guard value based on an engine operating state,
When the actual turbine inlet pressure exceeds the guard value, the stop unit holds the feedback term at a value immediately before the guard value is exceeded.

  According to the present invention, even when the turbocharger deteriorates with time, the turbine inlet pressure is increased to an allowable limit, the controllability of the turbocharger is improved, and the engine performance can be improved. Demonstrated.

It is the schematic which shows the structure of embodiment of this invention. It is a flowchart of the control routine in this embodiment. The calculation map of the guard value of turbine inlet pressure is shown. The calculation map of a feedforward term is shown. It is a flowchart for demonstrating the effect of this embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing a configuration of an embodiment of the present invention. The engine (internal combustion engine) 1 is a multi-cylinder compression ignition internal combustion engine mounted on a vehicle, that is, a diesel engine. Although the illustrated example shows an in-line four-cylinder engine, the cylinder arrangement type, the number of cylinders, and the like of the engine are arbitrary.

  The engine 1 includes an engine body 2, an intake passage 3 and an exhaust passage 4 connected to the engine body 2, a turbocharger 14, and a fuel injection device 5. The engine body 2 includes structural parts such as a cylinder head, a cylinder block, and a crankcase, and movable parts such as a piston, a crankshaft, and a valve housed therein.

  The fuel injection device 5 includes a common rail fuel injection device, and includes a fuel injection valve, that is, an injector 7 provided in each cylinder, and a common rail 8 connected to the injector 7. The injector 7 directly injects fuel into the cylinder 9, that is, into the combustion chamber. The common rail 8 stores the fuel injected from the injector 7 in a high pressure state.

  The intake passage 3 is mainly defined by an intake manifold 10 connected to the engine body 2 (particularly a cylinder head) and an intake pipe 11 connected to the upstream end of the intake manifold 10. The intake manifold 10 distributes and supplies the intake air sent from the intake pipe 11 to the intake ports of each cylinder. The intake pipe 11 is provided with an air cleaner 12, an air flow meter 13, a compressor 14 </ b> C of the turbocharger 14, an intercooler 15, and an electronically controlled intake throttle valve 16 in order from the upstream side. The air flow meter 13 is a sensor (intake air amount sensor) for detecting the intake air amount (intake air flow rate) per unit time of the engine 1.

  The exhaust passage 4 is mainly defined by an exhaust manifold 20 connected to the engine body 2 (particularly a cylinder head) and an exhaust pipe 21 disposed on the downstream side of the exhaust manifold 20. The exhaust manifold 20 collects exhaust gas sent from the exhaust port of each cylinder. A turbine 14 </ b> T of the turbocharger 14 is provided between the exhaust pipe 21 or between the exhaust manifold 20 and the exhaust pipe 21. In the exhaust pipe 21 downstream of the turbine 14T, an oxidation catalyst 22, a particulate filter (DPF) 23, a selective reduction type NOx catalyst (SCR) 24, and an ammonia oxidation catalyst 26 are provided in this order from the upstream side. An addition valve 25 for adding urea water as a reducing agent is provided on the upstream side of the NOx catalyst 24, particularly in the exhaust passage 4 near the inlet.

  The turbocharger 14 is a variable capacity turbocharger. A nozzle opening variable mechanism 28 that varies the nozzle opening at the turbine inlet is provided, and the nozzle opening variable mechanism 28 is operated by a nozzle actuator 29. The nozzle opening variable mechanism 28 has a plurality of movable nozzle vanes that open and close the nozzles, and the nozzle opening is increased or decreased by opening and closing the movable nozzle vanes simultaneously.

  The engine 1 also includes an EGR device 30. The EGR device 30 includes an EGR passage 31 for returning a part of exhaust gas (referred to as “EGR gas”) in the exhaust passage 4 (especially in the exhaust manifold 20) to the intake passage 3 (particularly in the intake manifold 10). The EGR cooler 32 that cools the EGR gas flowing through the EGR passage 31 and the EGR valve 33 for adjusting the flow rate of the EGR gas are provided.

  Further, in the present embodiment, an electronic control unit (hereinafter referred to as “ECU”) 100 serving as a control unit or a controller is provided. ECU 100 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like. The ECU 100 controls the injector 7, the intake throttle valve 16, the addition valve 25, the EGR valve 33, the nozzle actuator 29, and the like.

  Regarding the sensors, in addition to the air flow meter 13 described above, a rotational speed sensor 40 for detecting the rotational speed (rpm) of the engine and an accelerator opening sensor 41 for detecting the accelerator opening are provided. In addition, exhaust temperature sensors 42, 43, and 44 are provided for detecting exhaust temperatures (inlet gas temperatures) upstream or in the vicinity of the inlet of each of the oxidation catalyst 22, the DPF 23, and the NOx catalyst 24. Further, a differential pressure sensor 45 for detecting a differential pressure between the exhaust pressure upstream and downstream of the DPF 23 is provided. Output signals from these sensors are sent to the ECU 100.

  A boost pressure sensor 47 for detecting intake pressure or boost pressure and a pressure sensor 48 for detecting turbine inlet pressure are provided. Output signals from these sensors are also sent to the ECU 100. The boost pressure sensor 47 is installed in the intake pipe 11 downstream of the intake throttle valve 16 and immediately before the intake manifold 10 in this embodiment, but this installation position is arbitrary, for example, installed in the intake manifold 10. May be. In this embodiment, the pressure sensor 48 is installed in the EGR passage 31 upstream of the EGR valve 33 and the EGR cooler 32 in the EGR gas flow direction, but this installation position may be upstream of the turbine 14T (particularly the nozzle). For example, it may be installed in the exhaust manifold 20. The turbine inlet pressure may be estimated based on a predetermined model.

  Next, the control of this embodiment will be described. The ECU 100 feedback-controls the nozzle opening at the turbine inlet based on the boost pressure, sets a guard value for the turbine inlet pressure, and stops feedback control of the nozzle opening when the actual turbine inlet pressure exceeds the guard value To do. This point will be described below.

  With reference to FIG. 2, the control routine in this embodiment is demonstrated. The illustrated routine is repeatedly executed by the ECU 100 at every predetermined calculation cycle τ (for example, 10 msec).

  In step S101, the ECU 100 acquires the actual turbine inlet pressure Pe detected by the pressure sensor 48.

  In step S102, the ECU 100 sets a guard value Ge for the turbine inlet pressure based on the engine operating state. Specifically, the ECU 100 determines the guard value Ge according to a predetermined map mp1 as shown in FIG. 3 based on the detected actual engine speed NE and the fuel injection amount, particularly the target fuel injection amount Q as an instruction value. Set. The target fuel injection amount Q is calculated according to another map (not shown) based on the actual engine speed NE and the accelerator opening degree AC.

  In step S103, the ECU 100 compares the acquired actual turbine inlet pressure Pe with the guard value Ge. If the turbine inlet pressure Pe is less than or equal to the guard value Ge, the process proceeds to step S104. If the turbine inlet pressure Pe exceeds the guard value Ge, the process proceeds to step S108.

  When the turbine inlet pressure Pe is equal to or lower than the guard value Ge, the ECU 100 determines that the feed forward (F / F) term Sff used for calculating the target nozzle opening S, which is the target value of the nozzle opening, is operated in step S104. Calculate based on state. Specifically, the ECU 100 calculates the feedforward term Sff according to a predetermined map mp2 as shown in FIG. 4 based on the actual engine speed NE and the target fuel injection amount Q.

  Next, in step S105, the ECU 100 calculates a feedback (F / B) term Sfb used for calculating the target nozzle opening S in the following procedure.

  First, the ECU 100 acquires the actual boost pressure Pi detected by the boost pressure sensor 47. Next, the ECU 100 calculates a target boost pressure Pit that is a target value of the boost pressure based on the engine operating state. Specifically, ECU 100 calculates target boost pressure Pit according to a predetermined map (not shown) based on actual engine speed NE and target fuel injection amount Q. Next, the ECU 100 calculates a difference ΔPi = Pit−Pi between the target boost pressure Pit and the actual boost pressure Pi. Based on this difference ΔPi, a feedback term Sfb is calculated according to a predetermined map (not shown). When the difference ΔPi is positive, that is, when the actual boost pressure Pi is smaller than the target boost pressure Pit, the negative feedback term Sfb on the boost pressure increasing side is calculated. Conversely, when the difference ΔPi is negative, that is, when the actual boost pressure Pi is greater than the target boost pressure Pit, the positive feedback term Sfb on the boost pressure decrease side is calculated. In calculating the feedback term Sfb, the total value of the P term, the I term, and the D term corresponding to the difference ΔPi is preferably set as the feedback term Sfb in accordance with the PID control method.

  Next, in step S106, the ECU 100 adds the calculated feedforward term Sff and the feedback term Sfb to calculate a target nozzle opening S (= Sff + Sfb).

  Finally, in step S107, the ECU 100 controls the nozzle actuator 29 according to the calculated target nozzle opening S. That is, the nozzle actuator 29 is controlled so that the actual nozzle opening Sr matches the target nozzle opening S, and the nozzle opening varying mechanism 28 (movable nozzle vane) is operated. The nozzle opening variable mechanism 28 is provided with a nozzle opening sensor (not shown) for detecting the actual nozzle opening Sr, and the actual nozzle opening Sr detected by the nozzle opening sensor is the target nozzle opening. It is preferable to perform feedback control (preferably PID control) so as to match S.

  The feedforward term Sff is a value that serves as a base for the target nozzle opening S, and is a value that can generally achieve the target boost pressure in the current engine operating state. On the other hand, the target boost pressure cannot always be realized only by the feedforward term Sff because the actual engine operating state constantly changes. Therefore, the feedback term Sfb is added and the nozzle opening is precisely controlled so that the target boost pressure can be realized.

  On the other hand, in the example before reaching the idea of the present invention (referred to as “comparative example”), the guard value is determined not by the turbine inlet pressure but by the nozzle opening itself. In this case, even if the nozzle opening decreases to the guard value when the turbocharger deteriorates over time, the boost pressure does not reach the target value, the turbine inlet pressure has not increased excessively, and there is still a margin. There was something. Therefore, in this embodiment, the guard value is determined by the turbine inlet pressure, the nozzle opening is decreased from the guard value of the comparative example, the turbine inlet pressure can be increased to the allowable limit, and the actual boost pressure becomes the target value. To reach or get closer. This point will be described in detail later.

  When the turbine inlet pressure Pe exceeds the guard value Ge in step S103, the ECU 100 calculates the feedforward term Sff in step S108 as in step S104. In step S109, the ECU 100 holds the feedback term Sfb as the value calculated in the previous calculation cycle or the value immediately before the turbine inlet pressure Pe exceeds the guard value Ge. That is, the further calculation of the feedback term Sfb is stopped (= frozen). By freezing the feedback term Sfb in this way, the feedback control of the nozzle opening based on the boost pressure is substantially stopped.

  Next, in step S110, the ECU 100 calculates the target nozzle opening S by the same method as in step S106. In step S107, the ECU 100 controls the nozzle actuator 29 so that the actual nozzle opening degree Sr matches the target nozzle opening degree S.

  The feedforward term Sff in steps S104 and S108 is calculated based on the actual engine speed NE and the target fuel injection amount Q, but is corrected by the outside air temperature, intake air temperature, water temperature, atmospheric pressure, etc. The corrected value may be used.

  Next, the effect of this embodiment is demonstrated.

  FIG. 5 shows (A) nozzle opening, (B) turbine inlet pressure, (C) feedback (F / B) term Sfb calculated and stopped (freeze), (D) feed forward (F / F) term Sff It is a time chart which shows an example of a time-dependent change about the presence or absence of calculation. The nozzle opening in (A) is the target nozzle opening S or the actual nozzle opening Sr. The turbine inlet pressure in (B) is the actual turbine inlet pressure Pe. For (C), “with calculation” is set to “on” and “without calculation” is set to “freeze”. Regarding (D), “with calculation” is turned on, and “without calculation” is turned off. A solid line a indicates the case of the present embodiment, and a broken line b indicates the case of the comparative example.

  First, in the case of the present embodiment indicated by the solid line a, the nozzle opening is gradually decreased and the turbine inlet pressure is gradually increased before time t2, but the turbine inlet pressure does not exceed the guard value Ge. , F / B term and F / F term are both turned on.

  At time t2, the turbine inlet pressure exceeds the guard value Ge, and accordingly, the calculation of the F / B term is frozen, and the F / B control is substantially stopped. As a result, the nozzle opening is determined by the F / F term and the limited F / B term, and even if the actual boost pressure Pi is smaller than the target boost pressure Pit, no further feedback is provided, and the turbine inlet pressure is almost It is held at the guard value Ge, and the nozzle opening is held at a value of approximately S1.

  On the other hand, in the case of the comparative example indicated by the broken line b, at time t1 before time t2, the nozzle opening becomes smaller than the guard value Gs in the decreasing process, the calculation of the F / B term is frozen, and F / B control is performed. Is substantially stopped. The nozzle opening is limited or maintained at the guard value Gs. The guard value Gs for the nozzle opening is set according to a predetermined map based on the engine operating state (the engine speed NE and the target fuel injection amount Q), similarly to the guard value Ge for the turbine inlet pressure.

  However, at time t1, the turbine inlet pressure has not yet reached the guard value Ge. The guard value Ge of the turbine inlet pressure is the maximum value of the turbine inlet pressure that does not cause problems such as an excessive increase in the turbine inlet pressure and, consequently, fuel consumption deterioration due to an increase in pumping loss, and smoke deterioration due to excessive EGR. Pre-adapted to the limits.

  In the comparative example, the guard value Gs of the nozzle opening reaches the guard value Ge when the nozzle opening reaches the guard value Gs in the adaptation stage (or the development stage or the engine specification formulation stage). Have been adapted. However, if the performance of the turbocharger deteriorates due to deterioration of the turbocharger over time, the turbine inlet pressure does not increase to the guard value Ge even if the nozzle opening decreases to the guard value Gs (the illustrated example shows such a case), It is difficult to make full use of the performance of the turbocharger.

  Conversely, at time t1 when the nozzle opening reaches the guard value Gs, the turbine inlet pressure still has a margin up to the guard value Ge (lower than the guard value Ge), and the turbine inlet pressure can be further increased. . Therefore, the nozzle opening is made smaller than the guard value Gs of the comparative example so that the turbine inlet pressure can be increased to the allowable limit, and the turbine inlet pressure is increased to increase the boost pressure, thereby improving the output and fuel efficiency. It is desirable to be able to use it effectively.

  Therefore, in this embodiment, not the nozzle opening but the guard value Ge is set for the turbine inlet pressure so that the nozzle opening can be decreased until the turbine inlet pressure reaches the guard value Ge. The above problem is mainly caused by an excessive increase in the turbine inlet pressure, and it is more appropriate to guard the nozzle opening on the basis of the turbine inlet pressure, and it also contributes to improvement in controllability of the turbocharger. Therefore, according to this embodiment, even when the turbocharger deteriorates with time, the turbine inlet pressure can be increased to the allowable limit, and controllability can be improved. Naturally, it is possible to avoid the occurrence of the above problem due to an excessive increase in turbine inlet pressure.

  Note that it is also preferable to provide a guard value Gs ′ having a smaller nozzle opening than the comparative example, as indicated by a virtual line c in FIG. This guard value Gs 'for the nozzle opening is such that the nozzle opening does not reach the guard value Gs' even if the turbine inlet pressure reaches the guard value Ge in the turbocharger that has deteriorated over time. This nozzle opening guard value Gs' is a so-called second safety measure. That is, for example, when an abnormality occurs in which the error between the detected value of the turbine inlet pressure and the true value becomes larger than a predetermined value, the nozzle opening is excessively reduced, and the true value of the turbine inlet pressure exceeds the guard value Ge. This is to avoid that. This guard value Gs' can also be set according to a predetermined map based on the engine operating state (for example, the engine speed NE and the target fuel injection amount Q).

  As apparent from the above description, the ECU 100 constitutes a nozzle opening degree control unit, a guard value setting unit, and a stop unit according to the present invention.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

1 Engine 14 Turbocharger 14T Turbine 28 Nozzle opening variable mechanism 29 Nozzle actuator 47 Boost pressure sensor 48 Pressure sensor 100 Electronic control unit (ECU)

Claims (2)

A variable capacity turbocharger control device provided in an engine,
A nozzle opening control unit that feedback-controls the nozzle opening at the turbine inlet based on the boost pressure;
A guard value setting unit for setting a guard value for the turbine inlet pressure;
When the actual turbine inlet pressure exceeds the guard value, a stop unit that stops feedback control of the nozzle opening;
A variable capacity turbocharger control device comprising: The nozzle opening control unit calculates a target value of the nozzle opening based on a feedforward term based on the engine operating state and a feedback term based on a difference between the target boost pressure and the actual boost pressure,
The guard value setting unit sets the guard value based on an engine operating state,
2. The variable capacity according to claim 1, wherein when the actual turbine inlet pressure exceeds the guard value, the stop unit holds the feedback term as it is immediately before the guard value is exceeded. Type turbocharger control device.

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