JP2018080600A - Control method and control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the overspeed of a supercharger by reducing a turbo rotation speed even when oil enters into a combustion chamber.SOLUTION: A control method for an engine which includes a turbosupercharger 5 having a nozzle vane 5c capable of varying the flow path area of exhaust gas supplied to a turbine 5b and an intake shutter valve 7 includes a step of setting the target nozzle opening of the nozzle vane 5b and the target shutter opening of the intake shutter valve 7 according to the operating condition of an engine E, a step of controlling the opening of the nozzle vane 5b to be the target nozzle opening, a step of determining whether a TC exhaust pressure is not lower than a TC exhaust pressure first threshold value P1 or not, a step of determining whether a nozzle deviation is not smaller than a nozzle deviation threshold value Dor not, and a step of limiting the opening of the intake shutter valve 7 under the target shutter opening when the TC exhaust pressure is not lower than the TC exhaust pressure first threshold value P1 and the nozzle deviation is not smaller than the nozzle deviation threshold value D.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a control method and a control device for an engine including a variable capacity turbocharger.

In a diesel engine equipped with a supercharger, NO _X storage catalyst and to reduce emissions without NO _X using a post-processing apparatus of the urea SCR system and the like, known to be introduced into the combustion chamber a large amount of EGR gas It has been. By introducing a large amount of EGR gas, by the slow combustion with reducing the oxygen concentration in the combustion chamber, achieving a reduction of the combustion temperature, generation of the NO _X in the combustion chamber is suppressed.

  In this case, a large amount of EGR gas flows from the exhaust passage on the upstream side of the turbocharger to the intake passage on the compressor downstream side of the turbocharger, and from the exhaust passage on the downstream side of the turbine to the upstream side of the compressor. It is supplied via a low pressure EGR passage communicating with the intake passage. In such a diesel engine, EGR gas is generally introduced through a high pressure EGR passage at a low load, and EGR gas is introduced through a low pressure EGR passage at a high load.

  Since the low-pressure EGR passage has a long route to the combustion chamber, a response delay is likely to occur in the adjustment of the EGR gas flow rate through the low-pressure EGR passage. In order to compensate for this response delay, it is known to manage the oxygen concentration in the combustion chamber by supercharging pressure control by a variable capacity turbocharger (VG turbocharger).

  The VG turbo has a nozzle vane capable of expanding and reducing the flow area (nozzle area) of the exhaust gas supplied to the turbine wheel. For example, by reducing the nozzle area at low speed, the exhaust gas flow rate is increased to rotate the turbine wheel. It is possible to suppress the increase in rotation of the turbine wheel by increasing the speed and increasing the nozzle area at high speed. That is, the supercharging pressure can be adjusted with good responsiveness by opening and closing the nozzle vanes.

  The nozzle vane is opened / closed to a desired target opening degree by an actuator, but an abnormality may occur in the opening / closing operation. For example, the nozzle vane may have a response delay (also referred to as astringency) to the target opening degree in the opening / closing operation due to the influence of the exhaust pressure received from the exhaust gas. In particular, when the nozzle vane is located on the closed side, the exhaust pressure increases, and therefore a response delay of the nozzle vane is likely to occur. In addition, when a foreign matter such as a combustion product is caught in the sliding portion of the nozzle vane, the nozzle vane cannot be opened and closed and is fixed.

  As described above, when an abnormality occurs in the opening operation of the nozzle vane, the supercharging pressure cannot be adjusted with good responsiveness, and the exhaust gas performance deteriorates. In particular, when the nozzle vane is fixed, for example, if it is fixed on the open side, it is difficult to increase the supercharging pressure at low speed, and if it is fixed on the closed side, the exhaust pressure and supercharging pressure become abnormally high and the turbo is excessively increased at high speed. There is a possibility that the engine body and the supercharger may be damaged due to the rotation.

  Patent Document 1 discloses that the fuel injection amount is limited when the turbo rotational speed is equal to or higher than a predetermined value. By limiting the fuel injection amount, the exhaust gas energy supplied to the turbine wheel is reduced, and as a result, the turbo rotational speed is reduced. Japanese Patent Application Laid-Open No. 2004-228561 discloses that when the actual supercharging pressure is larger than the target supercharging pressure, it is determined whether or not the nozzle vane is in a non-fixed state.

Japanese Patent Laid-Open No. 2006-65505 JP 2011-80433 A

  Conventionally, VG turbo has been mainly used for diesel engines with medium displacement (for example, 2L class) or more, but in recent years, it has also been used for small displacement diesel engines (for example, 1.5L class). In the case of a small displacement diesel engine, particularly at a low speed, there is a case where the supercharging response is not sufficiently improved even with the VG turbo due to the small exhaust gas flow rate. For this reason, the turbocharging response is improved by reducing the inertia of the turbine shaft.

  However, by reducing the inertia of the turbine shaft, the turbo rotation speed tends to be in an overspeed state. In particular, when a response delay occurs in the nozzle vane or the nozzle vane is in a fixed state, the turbo rotational speed may be over-rotated in a short time.

  By the way, even if the fuel injection amount is limited when the turbo rotational speed is equal to or higher than a predetermined value, the turbo rotational speed may not decrease. For example, when oil enters the combustion chamber for some reason due to the entry of oil contained in the blow-by gas into the combustion chamber or the oil rising from the cylinder into the combustion chamber, the exhaust gas burned using the oil as the fuel is excessive. Supplied to the feeder. In this case, although the fuel injection amount is reduced, the exhaust gas energy is not reduced, so the turbo rotation speed is not reduced.

  Further, according to Patent Document 2, it is determined whether or not the nozzle vane is in a non-fixed state based on the supercharging pressure, and the exhaust gas energy due to the combustion of lubricating oil that has entered the combustion chamber is supplied to the supercharger. It cannot be determined that it is supplied.

  The present invention has been made in view of the above problems, and an engine control method capable of reducing the turbo rotation speed and preventing the turbocharger from over-rotating even when oil enters the combustion chamber. An object is to provide a control device.

  In order to solve the above problems, the present invention is configured as follows.

  One aspect of the present invention according to claim 1 of the present application is an engine including a variable displacement supercharger having a nozzle vane capable of changing a flow area of exhaust gas supplied to a turbine, and an intake shutter valve. A control method comprising: setting a target nozzle opening of the nozzle vane and a target shutter opening of the intake shutter valve according to an operating state of the engine; and setting the opening of the nozzle vane to the target nozzle opening A step of determining whether the exhaust pressure upstream of the supercharger is equal to or greater than a predetermined value, and a nozzle deviation that is a difference between the actual opening of the nozzle vane and the target nozzle opening is predetermined. A step of determining whether or not the exhaust pressure is greater than or equal to a value; and when the exhaust pressure is greater than or equal to the predetermined value and the nozzle deviation is greater than or equal to the predetermined value, the opening degree of the intake shutter valve is determined as the target shutter opening And a step of limiting than is characterized by.

  The invention according to claim 2 is the engine control method according to claim 1, wherein, in the limiting step, when the engine speed is equal to or higher than a predetermined value, the intake shutter valve It is characterized in that the opening degree is controlled to be substantially fully closed.

  The invention according to claim 3 is the engine control method according to claim 1 or 2, wherein, in the limiting step, when the engine speed is less than a predetermined value, the intake shutter It is characterized in that the opening of the valve is controlled to an opening that allows low speed travel.

  The invention according to claim 4 is the engine control method according to any one of claims 1 to 3, wherein after the opening degree of the intake shutter valve is limited, the turbocharger upstream It further has a step of releasing the opening restriction of the intake shutter valve when the exhaust temperature on the side falls below a predetermined value.

  The invention according to claim 5 is the engine control method according to any one of claims 1 to 4, wherein the exhaust pressure is predetermined after the opening degree of the intake shutter valve is limited. The method further includes the step of releasing the restriction on the opening degree of the intake shutter valve when the value is lower than the value.

  Still another aspect of the present invention described in claim 6 includes a variable capacity supercharger having a nozzle vane capable of changing a flow area of exhaust gas supplied to the turbine, and an intake shutter valve. A target setting unit for setting a target nozzle opening of the nozzle vane and a target shutter opening of the intake shutter valve according to an operating state of the engine, and an opening degree of the nozzle vane. A nozzle vane control unit that controls the target nozzle opening, an exhaust pressure determination unit that determines whether or not the exhaust pressure upstream of the turbocharger is greater than or equal to a predetermined value, an actual opening of the nozzle vane, and the target nozzle opening A nozzle deviation determination unit that determines whether or not a nozzle deviation that is a difference from the degree is equal to or greater than a predetermined threshold; and a case where the exhaust pressure is equal to or greater than the predetermined value and the nozzle deviation is equal to or greater than the predetermined value. Has an intake shutter valve control unit for limiting than the target shutter opening the opening of the intake shutter valve, is characterized by.

  The invention according to claim 7 is the engine control device according to claim 6, wherein the exhaust pressure is not less than the predetermined value and the nozzle deviation is not less than the predetermined value. When the engine speed is greater than or equal to a predetermined value, the intake shutter valve control unit controls the opening degree of the intake shutter valve to be substantially fully closed.

  The invention according to claim 8 is the engine control apparatus according to claim 6 or 7, wherein the exhaust pressure is not less than the predetermined value and the nozzle deviation is not less than the predetermined value. When the engine speed is less than a predetermined value, the intake shutter valve control unit controls the intake shutter valve control unit so that the intake shutter valve can be opened at a low speed. It is a feature.

  The invention according to claim 9 is the engine control device according to any one of claims 6 to 8, wherein the upstream side of the supercharger after the opening degree of the intake shutter valve is limited. When the exhaust temperature of the intake air valve is lower than a predetermined value, the intake shutter valve control unit releases the opening degree restriction of the intake shutter valve.

  The invention according to claim 10 is the engine control device according to any one of claims 6 to 9, wherein the exhaust pressure is a predetermined value after the opening degree of the intake shutter valve is limited. The intake shutter valve control unit releases the restriction on the opening degree of the intake shutter valve.

  According to the invention of each claim of the present application, the following effects can be obtained by the above configuration.

  First, according to the first aspect of the present invention, when the nozzle deviation is equal to or greater than a predetermined value and the exhaust pressure upstream of the turbocharger is equal to or greater than the predetermined value, the opening degree of the intake shutter valve is limited. The amount of intake air supplied to the engine can be limited, whereby combustion in the engine can be quickly suppressed regardless of the presence or absence of fuel present in the combustion chamber. As a result, the exhaust gas energy supplied to the supercharger is reduced, thereby reducing the exhaust pressure on the upstream side of the supercharger and reducing the nozzle deviation, thereby suppressing the overspeed of the supercharger. The

  Therefore, even if the fuel supply to the engine is limited (cut), even if fuel (for example, inflow of lubricating oil) exists in the combustion chamber, the oxygen in the combustion chamber is limited by limiting the intake air amount. By reducing the value, combustion can be quickly suppressed. As a result, the exhaust gas energy supplied to the supercharger is reduced, so that the exhaust pressure and the supercharging pressure are reduced below the threshold value, and the overspeed of the supercharger is suppressed.

  According to the second aspect of the present invention, when the engine speed is equal to or higher than a predetermined value, the intake air supplied to the combustion chamber is shut off by controlling the intake shutter valve to be substantially fully closed. As a result, the engine speed can be reduced as quickly as possible. As a result, the exhaust gas energy supplied to the supercharger is reduced, so that the exhaust pressure and the supercharging pressure are reduced, and the overspeed of the supercharger is suppressed.

  According to the third aspect of the invention, when the engine speed is less than a predetermined value, the engine can be driven at a low speed by limiting the amount of intake air supplied to the combustion chamber. Can maintain output. In addition, since the engine speed is less than a predetermined value, an increase in exhaust gas energy supplied to the supercharger is suppressed, and an increase in the exhaust pressure and supercharging pressure of the supercharger can be suppressed and Over-rotation is suppressed.

  According to the invention described in claim 4, when the exhaust gas temperature on the upstream side of the supercharger falls below a predetermined value, the exhaust gas energy supplied to the supercharger is reduced. Thus, the exhaust pressure, the supercharging pressure, and the rotational speed on the upstream side respectively decrease. Therefore, in this case, there is no need to limit the amount of intake air supplied to the engine, and the engine can be quickly returned to normal operation by releasing the opening limit of the intake shutter valve.

  According to the fifth aspect of the present invention, when the exhaust pressure on the upstream side of the supercharger falls below a predetermined value, the exhaust gas energy supplied to the supercharger is reduced. Thus, the exhaust pressure, the supercharging pressure, and the rotational speed on the upstream side respectively decrease. Therefore, in this case, there is no need to limit the amount of intake air supplied to the engine, and the engine can be quickly returned to normal operation by releasing the opening limit of the intake shutter valve.

  According to the invention described in claim 6, the effect of the invention described in claim 1 is realized in the engine control apparatus.

  According to the seventh aspect of the invention, the effect of the second aspect of the invention is realized in the engine control apparatus.

  According to the invention as set forth in claim 8, the effect of the invention as set forth in claim 3 is realized in the engine control apparatus.

  According to the ninth aspect of the invention, the effect of the fourth aspect of the invention is realized in the engine control apparatus.

  According to the invention described in claim 10, the effect of the invention described in claim 5 is realized in the engine control apparatus.

  That is, according to the control method and control apparatus for an engine according to the present invention, even when oil enters the combustion chamber, it is possible to reduce the turbo speed and prevent the turbocharger from over-rotating.

1 is a schematic configuration diagram of an engine system according to an embodiment of the present invention. It is the longitudinal cross-sectional view which expanded the turbine chamber of the turbocharger. It is explanatory drawing of the action | operation area | region of EGR. It is a flowchart which shows the basic control of an engine system. It is a block diagram which shows schematic structure of the control system of a turbocharger. It is a flowchart which shows the failure judgment control of the nozzle vane of a turbocharger. It is a flowchart which shows the subroutine which sets a guard fuel value. It is a flowchart which shows the modification of the failure determination of FIG. It is a flowchart which shows the other modification of the failure determination of FIG. It is a flowchart which shows the further modification of the failure determination of FIG.

  Hereinafter, an engine control apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

<System configuration>
First, an engine system to which an engine control apparatus according to an embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an engine system to which an engine control apparatus according to an embodiment of the present invention is applied.

  As shown in FIG. 1, the engine system 200 mainly includes an engine E as a diesel engine, an intake system IN that supplies intake air to the engine E, a fuel supply system FS that supplies fuel to the engine E, It has an exhaust system EX that exhausts exhaust gas from the engine E, sensors 99 to 122 that detect various states relating to the engine system 200, and an ECU (Electronic Control Unit) 60 that controls the engine system 200. .

First, the intake system IN has an intake passage 1 through which intake air passes, and an air cleaner 3 that purifies air introduced from the outside in order from the upstream side, and intake air that passes through the intake passage 1. The compressor 5a (compressor wheel) of the turbocharger 5 that compresses and raises the intake pressure, the intake shutter valve 7 that adjusts the flow rate of the intake air that passes through, and the water cooling that cools the intake air using the flowed cooling water Intercooler 8, electric water pump 9 that controls the flow rate of cooling water flowing through the intercooler 8, and a passage that connects the intercooler 8 and the electric water pump 9 and circulates the cooling water therebetween. And a surge tank 12 that temporarily stores intake air supplied to the engine E.
In the intake system IN, an air flow sensor 101 for detecting the intake air amount and an intake air temperature sensor 102 for detecting the intake air temperature are provided on the intake passage 1 immediately downstream of the air cleaner 3. 5 is provided with a turbo rotational speed sensor 103 for detecting the rotational speed (turbo rotational speed) of the compressor 5a, and the intake shutter valve 7 is provided with an intake shutter for detecting the opening degree of the intake shutter valve 7. A valve position sensor 105 is provided, and an intake air temperature sensor 106 for detecting the intake air temperature and an intake air pressure sensor 107 for detecting the intake air pressure are provided on the intake passage 1 immediately downstream of the intercooler 8. Is provided with an intake manifold temperature sensor 108. Each of the sensors 101 to 108 provided in the intake system IN outputs detection signals D101 to D108 corresponding to the detected parameters to the ECU 60, respectively.

Next, the engine E includes an intake valve 15 for introducing the intake air supplied from the intake passage 1 (specifically, an intake manifold) into the combustion chamber 17, a fuel injection valve 20 for injecting fuel toward the combustion chamber 17, A glow plug 21 as an auxiliary heat source for ensuring ignition at the time of starting, a piston 23 reciprocating by combustion of the air-fuel mixture in the combustion chamber 17, and a crankshaft 25 rotated by reciprocating motion of the piston 23 And an exhaust valve 27 for discharging exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber 17 to the exhaust passage 41. Further, the engine E is provided with an alternator 26 that generates electric power using the output of the engine E.
The engine E also includes a coolant temperature sensor 109 that detects the temperature of coolant that cools the engine E, the crank angle sensor 110 that detects the crank angle of the crankshaft 25, and the oil pressure and / or oil temperature. An oil pressure / oil temperature sensor 111 for detecting the oil level and an optical oil level sensor 112 for detecting the oil level are provided. Each of these sensors 109 to 112 provided in the engine E outputs detection signals D109 to D112 corresponding to the detected parameters to the ECU 60, respectively.

Next, the fuel supply system FS includes a fuel tank 30 for storing fuel, and a fuel supply passage 38 for supplying fuel from the fuel tank 30 to the fuel injection valve 20. In the fuel supply passage 38, a low-pressure fuel pump 31, a high-pressure fuel pump 33, and a common rail 35 are provided in order from the upstream side. The low pressure fuel pump 31 is provided with a fuel warmer 32, the high pressure fuel pump 33 is provided with a fuel pressure regulator 34, and the common rail 35 is provided with a common rail pressure reducing valve 36.
In the fuel supply system FS, the high-pressure fuel pump 33 is provided with a fuel temperature sensor 114 that detects the fuel temperature, and the common rail 35 is provided with a fuel pressure sensor 115 that detects the fuel pressure. These sensors 114 and 115 provided in the fuel supply system FS output detection signals D114 and D115 corresponding to the detected parameters to the ECU 60, respectively.

Next, the exhaust system EX has an exhaust passage 41 through which the exhaust gas passes. The exhaust passage 41 is rotated by the exhaust gas passing through the exhaust passage 41 in order from the upstream side. A turbine 5b (turbine wheel) of the turbocharger 5 that drives the compressor 5a, a diesel oxidation catalyst (DOC) 45 having a function of purifying exhaust gas, and a diesel particulate filter (DPF) 46 and an exhaust shutter valve 49 for adjusting the exhaust flow rate passing therethrough are provided. The DOC 45 is a catalyst that oxidizes hydrocarbon (HC), carbon monoxide (CO), and the like using oxygen in the exhaust gas to change it into water and carbon dioxide, and the DPF 46 is a particulate substance ( It is a filter that collects PM (Particulate Matter).
In the exhaust system EX, an exhaust pressure sensor 116 for detecting the exhaust pressure and an exhaust temperature sensor 117 for detecting the exhaust temperature are provided on the exhaust passage 41 on the upstream side of the turbine 5b of the turbocharger 5. Exhaust temperature sensors 118 and 119 for detecting the exhaust temperature are provided immediately upstream of the DOC 45 and between the DOC 45 and the DPF 46, respectively. The DPF 46 has the exhaust pressure of the upstream side and the downstream side of the DPF 46. A DPF differential pressure sensor 120 for detecting the difference is provided, and a linear O2 sensor 121 for detecting the oxygen concentration and an exhaust temperature sensor 122 for detecting the exhaust temperature are provided on the exhaust passage 41 immediately downstream of the DPF 46. Yes. Each of the sensors 116 to 122 provided in the exhaust system EX outputs detection signals D116 to D122 corresponding to the detected parameters to the ECU 60, respectively.

  Further, in the present embodiment, the turbocharger 5 is configured in a small size so as to be able to perform supercharging efficiently even during low-speed rotation with low exhaust energy, and a plurality of movable parts so as to surround the entire circumference of the turbine 5b. Type nozzle vanes 5c are provided, and these nozzle vanes 5c are configured as variable displacement turbochargers (VG turbo) that change the flow cross-sectional area (nozzle cross-sectional area) of exhaust gas to the turbine 5b. Has been. For example, the nozzle vane 5c is rotated by an actuator whose magnitude of the negative pressure acting on the diaphragm is adjusted by an electromagnetic valve. Moreover, the nozzle vane opening degree sensor 104 which detects the opening degree of the nozzle vane 5c by the position of such an actuator is provided. The nozzle vane opening sensor 104 outputs a detection signal D104 corresponding to the detected nozzle vane opening to the ECU 60.

Here, with reference to FIG. 2, the nozzle vane 5c of the turbocharger 5 by embodiment of this invention is demonstrated concretely. FIG. 2 schematically shows a configuration of a longitudinal section in which the turbine chamber of the turbocharger 5 is enlarged.
As shown in FIG. 2, a plurality of movable nozzle vanes 5c, 5c,... Are arranged in a turbine chamber 153a formed in the turbine casing 153 so as to surround the periphery of the turbine 5b arranged at the substantially central portion thereof. Each nozzle vane 5c is rotatably supported by a support shaft 5d penetrating one side wall of the turbine chamber 153a. When each nozzle vane 5c is rotated clockwise in FIG. 2 around the support shaft 5d and inclined so as to be close to each other, the nozzles 155, 155,... Formed between the nozzle vanes 5c are opened. The degree (nozzle cross-sectional area) is narrowed down, and high supercharging efficiency can be obtained even when the exhaust gas flow rate is small. On the other hand, if each nozzle vane 5c is rotated to the opposite side and inclined so as to be separated from each other, the nozzle cross-sectional area becomes large. Efficiency can be increased.
Further, the ring member 157 is drivingly connected to the rod 163 of the actuator via the link mechanism 158, and each nozzle vane 5c is rotated via the ring member 157 by the operation of the actuator. That is, the link mechanism 158 includes a connection pin 158a whose one end is rotatably connected to the ring member 157, and a connection plate member 158b whose one end is rotatably connected to the other end of the connection pin 158a. The columnar member 158c is coupled to the other end of the coupling plate member 158b, and one end is coupled to the columnar member 158c penetrating the outer wall of the turbine casing 153 and the protruding end of the columnar member 158c projecting out of the turbine casing 153. The other end of the connecting plate member 158d is rotatably connected to the rod 163 of the actuator by a connecting pin (not shown).

  Returning to FIG. 1, the engine system 200 according to the present embodiment further includes a high-pressure EGR device 43 and a low-pressure EGR device 48. The high pressure EGR device 43 connects the exhaust passage 41 on the upstream side of the turbine 5 b of the turbocharger 5 and the intake passage 1 on the downstream side of the compressor 5 a of the turbocharger 5 (specifically, on the downstream side of the intercooler 8). And a high pressure EGR valve 43b that adjusts the flow rate of exhaust gas that passes through the high pressure EGR passage 43a. The low pressure EGR device 48 includes an exhaust passage 41 on the downstream side of the turbine 5b of the turbocharger 5 (specifically, on the downstream side of the DPF 46 and the upstream side of the exhaust shutter valve 49) and the upstream side of the compressor 5a of the turbocharger 5. A low pressure EGR passage 48a that connects the intake passage 1 of the engine, a low pressure EGR cooler 48b that cools the exhaust gas that passes through the low pressure EGR passage 48a, and a low pressure EGR valve 48c that adjusts the flow rate of the exhaust gas that passes through the low pressure EGR passage 48a. And a low pressure EGR filter 48d.

  The amount of exhaust gas recirculated to the intake system IN by the high pressure EGR device 43 (hereinafter referred to as “high pressure EGR gas amount”) is the exhaust pressure upstream of the turbine 5 b of the turbocharger 5 and the opening of the intake shutter valve 7. It is generally determined by the intake pressure produced by the degree and the opening degree of the high pressure EGR valve 43b. Further, the amount of exhaust gas recirculated to the intake system IN by the low pressure EGR device 48 (hereinafter referred to as “low pressure EGR gas amount”) is the intake pressure on the upstream side of the compressor 5 a of the turbocharger 5 and the exhaust shutter valve 49. Is roughly determined by the exhaust pressure produced by the opening of the valve and the opening of the low pressure EGR valve 48c.

Here, referring to FIG. 3, in the embodiment of the present invention, the operating region of engine E in which high pressure EGR device 43 is operated (hereinafter referred to as “high pressure EGR region”) and low pressure EGR device 48 are operated. The operation region of the engine E (hereinafter referred to as “low pressure EGR region”) will be described. FIG. 3 shows the engine speed on the horizontal axis and the fuel injection amount (corresponding to the engine load) on the vertical axis, and schematically shows the high pressure EGR region and the low pressure EGR region.
As shown in FIG. 3, the operating region R1 (corresponding to the first operating region) of the engine E defined on the low load / low rotational speed side is a high pressure EGR region where the high pressure EGR device 43 is operated. An operation region R2 (corresponding to the second operation region) of the engine E defined on the high load / high rotation speed side from the high pressure EGR region R1 is a low pressure EGR region in which the low pressure EGR device 48 is operated. More specifically, not only the low pressure EGR device 48 but also the high pressure EGR device 43 is operated in a part of the low pressure EGR region R2 (region near the boundary with the high pressure EGR region R1), that is, the high pressure EGR device 43. And it becomes a combined use area of the low pressure EGR device 48. In addition, the operation region R3 of the engine E, which is defined on the higher load / high rotation speed side than the low pressure EGR region R2, is a region where neither the high pressure EGR device 43 nor the low pressure EGR device 48 is operated (hereinafter referred to as “non-EGR” as appropriate). Area).).

  Returning to FIG. 1, in addition to the detection signals D101 to D122 of the sensors 101 to 122 described above, the ECU 60 according to the present embodiment adds an outside air temperature sensor 98 that detects the outside air temperature, an atmospheric pressure sensor 99 that detects the atmospheric pressure, And the control with respect to the component in the engine system 200 is performed based on the detection signals D98-D100 which each of the accelerator opening degree sensor 100 which detects the opening degree (accelerator opening degree) of the accelerator pedal 95 outputs. Specifically, the ECU 60 outputs a control signal C130 to an actuator (not shown) that drives the nozzle vane 5c in order to control the opening degree of the nozzle vane 5c in the turbine 5b of the turbocharger 5. Further, the ECU 60 outputs a control signal C131 to an actuator (not shown) that drives the intake shutter valve 7 in order to control the opening degree of the intake shutter valve 7. Further, the ECU 60 outputs a control signal C132 to the electric water pump 9 in order to control the flow rate of the cooling water supplied to the intercooler 8. Further, the ECU 60 outputs a control signal C133 to the fuel injection valve 20 in order to control the fuel injection amount of the engine E and the like. The ECU 60 outputs control signals C134, C135, C136, and C137 to control the alternator 26, the fuel warmer 32, the fuel pressure regulator 34, and the common rail pressure reducing valve 36, respectively. Further, the ECU 60 outputs a control signal C138 to an actuator (not shown) that drives the high pressure EGR valve 43b in order to control the opening degree of the high pressure EGR valve 43b. Further, the ECU 60 outputs a control signal C139 to an actuator (not shown) that drives the low pressure EGR valve 48c in order to control the opening degree of the low pressure EGR valve 48c. Further, the ECU 60 outputs a control signal C140 to an actuator (not shown) that drives the exhaust shutter valve 49 in order to control the opening degree of the exhaust shutter valve 49.

<Basic control>
Next, basic control implemented in the engine system 200 according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a flowchart showing basic control according to the embodiment of the present invention. In this flow, control for realizing the target oxygen concentration and the target intake air temperature according to the required injection amount and the like is performed. This flow is repeatedly executed by the ECU 60 at a predetermined cycle.

First, in step S11, the ECU 60 acquires at least one or more of the detection signals D98 to D122 output from the sensors 98 to 122 described above.
Next, in step S12, the ECU 60 sets a target torque to be output from the engine E based on the accelerator opening detected by the accelerator opening sensor 100.
Next, in step S13, the ECU 60 sets a required injection amount (D request Q) to be injected from the fuel injection valve 20 based on the target torque set in step S12 and the engine speed.
Next, in step S14, the ECU 60 determines the fuel injection pattern, the fuel pressure, the target oxygen concentration, the target intake air temperature, and the EGR control mode (based on the required injection amount set in step S13 and the engine speed). A mode in which both or one of the high pressure EGR device 43 and the low pressure EGR device 48 is operated, or a mode in which neither the high pressure EGR device 43 nor the low pressure EGR device 48 is operated) is set.
Next, in step S15, the ECU 60 sets state quantities for realizing the target oxygen concentration and target intake air temperature set in step S14. For example, this state quantity includes the amount of exhaust gas recirculated to the intake system IN by the high pressure EGR device 43 (high pressure EGR gas amount) and the amount of exhaust gas recirculated to the intake system IN by the low pressure EGR device 48 (low pressure EGR gas amount). And a supercharging pressure by the turbocharger 5 is included.
Next, in step S16, the ECU 60 controls each actuator that drives each component of the engine system 200 based on the state quantity set in step S15. In this case, the ECU 60 sets a limit value or a limit range according to the state quantity, sets the control amount of each actuator such that the state value complies with the limit value or the limit range, and executes control.

<Turbo over-rotation prevention control and fail-safe control>
In the following, according to the embodiment of the present invention, the nozzle vane 5c is properly fixed while suppressing the temporary response delay of the nozzle vane 5c of the turbocharger 5, and the turbo rotation speed is prevented from being over-rotated. The control (turbo overspeed prevention control) for performing this will be described. In addition, control (fail-safe control) that causes the engine E and the turbo-supercharger 5 to operate in the fail-safe mode when an abnormality occurs in the turbo-supercharger 5 or the engine E will be described.

  First, an outline of control performed by the ECU 60 in the embodiment of the present invention will be described. In the present embodiment, the ECU 60 sets the target boost pressure based on the operating state of the engine E (specifically, the fuel injection amount and the engine speed), and the actual boost pressure is set to this target boost pressure. Thus, the target opening degree of the nozzle vane 5c of the turbocharger 5 is set, and the nozzle vane 5c is controlled to the target opening degree. That is, the ECU 60 uses the supercharging pressure F / B control to change the target opening of the nozzle vane 5c so as to realize the target supercharging pressure while comparing the actual supercharging pressure with the target supercharging pressure. Typically, when the actual supercharging pressure is lower than the target supercharging pressure, the ECU 60 performs control to change the target opening of the nozzle vane 5c to the close side, and the actual supercharging pressure becomes the target supercharging pressure. If the value exceeds the value, control is performed to change the target opening of the nozzle vane 5c to the open side.

  Here, in the present embodiment, the ECU 60 reduces the fuel injection amount when the nozzle deviation, which is the difference between the actual opening and the target opening of the nozzle vane 5c, is equal to or greater than a predetermined value (hereinafter referred to as “injection” as appropriate). The control is performed to limit the change of the target opening degree of the nozzle vane 5c to the closing side by the above-described supercharging pressure F / B control. Next, the ECU 60 determines that the nozzle vane is stuck or has failed due to excessive response delay, with the failure determination condition being that the state in which the nozzle deviation is equal to or greater than the predetermined value continues for a predetermined time.

  Further, when the exhaust pressure on the upstream side of the turbocharger 5 is equal to or higher than a predetermined value, the ECU 60 shifts the engine E to the fail safe mode and limits the amount of fresh air and fuel injected supplied to the engine E. To do. Thereby, the combustion in the combustion chamber 17 of the engine E is limited, and the exhaust gas energy supplied to the turbocharger 5 is reduced, thereby reducing the exhaust pressure.

  FIG. 5 is a block diagram of a control system for executing turbo overspeed prevention control and failsafe control. As shown in FIG. 5, the ECU 60 detects the nozzle vane 5 c, the fuel injection based on the detection signals from the accelerator opening sensor 100, the nozzle vane opening sensor 104, the exhaust pressure sensor 116, the exhaust temperature sensor 117, and the intake pressure sensor 107. The valve 20, the intake shutter valve 7, and the warning lamp display unit 96 are controlled.

  The ECU 60 has a nozzle vane target opening setting unit 61, a target injection amount setting unit 62, and an intake shutter valve as target setting units for setting state quantities as control targets for the nozzle vane 5 c, the fuel injection valve 20, and the intake shutter valve 7. A target opening setting unit 63 is provided.

  As described above, the nozzle vane target opening setting unit 61 obtains a target supercharging pressure necessary for realizing the target torque set based on the accelerator opening detected by the accelerator opening sensor 100. The target nozzle opening of the nozzle vane 5c is set according to the operating state of the engine E. The target injection amount setting unit 62 sets the fuel injection amount required for realizing the target torque as the target fuel injection amount (D request Q). The intake shutter valve target opening setting unit 63 sets the target opening of the intake shutter valve 7 so as to adjust the intake pressure in the intake passage 1 so as to adjust the flow rate of the EGR gas supplied via the high pressure EGR passage 43a. To do.

  Further, the ECU 60 includes a nozzle vane control unit 64, a fuel injection valve control unit 65, and an intake shutter valve control unit 66 as control units for controlling the nozzle vane 5c, the fuel injection valve 20, and the intake shutter valve 7, respectively. .

  The nozzle vane control unit 64 controls the nozzle vane 5 c to the target nozzle opening set by the nozzle vane target opening setting unit 61.

  The fuel injection valve control unit 65 controls the fuel injection amount FP injected from the fuel injection valve 20 to the D request Q. Further, as will be described later, when the nozzle deviation determining unit 67 determines that the nozzle deviation is equal to or greater than a predetermined value, the fuel injection amount FP is reduced or limited from the D requirement Q. Further, in the fail safe mode, the fuel injection amount FP is further reduced or limited.

  The intake shutter valve control unit 66 controls the opening of the intake shutter valve 7 to the target opening set by the intake shutter valve target opening setting unit 63. Further, in the fail-safe mode, the opening degree of the intake shutter valve 7 is reduced or restricted from the target opening degree, thereby reducing the amount of intake air supplied to the combustion chamber 17.

  In addition, the ECU 60 serves as an abnormality determination unit that determines abnormality of the turbocharger 5 and the engine E, a nozzle deviation determination unit 67, an exhaust pressure determination unit 68, an exhaust temperature determination unit 69, a supercharging pressure determination unit 70, and a nozzle vane. A failure determination unit 71 is provided.

Based on the actual opening of the nozzle vane 5c detected by the nozzle vane opening sensor 104, the nozzle deviation determination unit 67 calculates a nozzle deviation that is the difference between the actual opening of the nozzle vane 5c and the target nozzle opening, and the nozzle deviation Is greater than or _equal to the nozzle deviation threshold _DVGT . The nozzle deviation threshold value D _VGT is a threshold value for detecting response delay and sticking of the nozzle vane 5c with respect to the target nozzle opening, and if it is determined that the nozzle deviation is equal to or greater than the nozzle deviation threshold value D _VGT , the flag 1 is set to “ 1 ”, and the nozzle vane failure determination variable C stored in the memory of the ECU 60 is incremented by one (counted up).

The nozzle deviation threshold D _VGT is set to, for example, approximately 50% of the total opening / closing stroke amount from the fully closed position of the nozzle vane 5c to the fully opened position, and this makes it possible to accurately detect the response delay of the nozzle vane 5c. When the nozzle deviation threshold value D _VGT is set to less than 50% of the total opening / closing stroke amount, the response delay of the nozzle vane 5c will be detected excessively. Leak detection is likely to occur.

Based on the exhaust pressure detected by the exhaust pressure sensor 116, the exhaust pressure determination unit 68 determines that the TC exhaust pressure that is the exhaust pressure in the exhaust passage 41 on the upstream side of the turbocharger 5 is the TC exhaust pressure first threshold value P _EX. It is determined whether it is lower than 1. The TC exhaust pressure first threshold value P _EX 1 is a threshold value for detecting an abnormal increase in exhaust pressure due to a delay in response to the opening side of the nozzle vane 5c, an increase in the flow rate of exhaust gas discharged from the engine E, or the like. When the exhaust pressure determination unit 68 determines that the TC exhaust pressure is equal to or greater than the TC exhaust pressure first threshold value P _EX 1, the exhaust pressure determination unit 68 sets the flag 2 to “1” and shifts the engine E to the fail safe mode.

Further, after the flag 2 is set to “1”, the exhaust pressure determination unit 68 determines whether or not the TC exhaust pressure is lower than the TC exhaust pressure second threshold value P _EX 2. The TC exhaust pressure second threshold value P _EX 2 is a threshold value for detecting that the abnormal increase in the exhaust pressure has been eliminated, and is set lower than the TC exhaust pressure first threshold value P _EX 1.

After the flag 2 is set to “1”, the exhaust temperature determination unit 69 determines whether the TC exhaust temperature, which is the exhaust temperature of the exhaust passage 41 on the upstream side of the turbocharger 5, is lower than the TC exhaust temperature threshold value T _EX. Determine whether. The TC exhaust temperature T _EX is for detecting an increase in exhaust temperature due to an abnormal increase in exhaust pressure.

After flag 2 is set to “1”, it is determined that the TC exhaust pressure has dropped below the TC exhaust pressure second threshold P _EX 2 and the TC exhaust temperature has fallen below the TC exhaust temperature threshold T _EX The exhaust pressure determination unit 68 sets the flag 2 from “1” to “0”, and cancels the fail-safe mode.

The supercharging pressure determination unit 70 is based on the intake pressure detected by the intake pressure sensor 107 provided in the intake passage 1, and the intake passage 1 downstream of the compressor 5 a (more specifically, downstream of the intercooler 8). It is determined whether or not the supercharging pressure that is the intake pressure at is higher than the supercharging pressure first threshold value P _BST 1. The supercharging pressure first threshold value P _BST 1 is discharged from the compressor 5a of the turbocharger 5 due to a delay in response to the opening side of the nozzle vane 5c, an abnormal increase in the flow rate of exhaust gas discharged from the engine E, or the like. This is a threshold for detecting an abnormal increase in intake pressure.

  The nozzle vane failure determination unit 71 determines whether or not the variable C is smaller than the nozzle vane failure determination threshold CMIL, and determines that the nozzle vane 5c has failed when the variable C is equal to or greater than the nozzle vane failure determination threshold CMIL. In this case, the failure record may be stored as a service code in the memory of the ECU 60 so that it can be confirmed at the time of subsequent service. A failure indicator lamp (MIL: Malfunction Indicator Lamp) is lit on the warning lamp display unit 96, You may make it alert | report a failure of the turbocharger 5 to a driver | operator.

FIG. 6 is a flowchart showing the flow of the processing cycle of the ECU 60 in the turbo overspeed prevention control and failsafe control described above. This processing cycle is repeatedly executed by the ECU 60 at a predetermined cycle. First, in step S110, it is determined whether or not the flag 2 is “0”. As described above, the flag 2 is set to “1” when the exhaust pressure on the upstream side of the turbocharger 5 is equal to or higher than the TC exhaust pressure first threshold value P _EX 1.

When the flag 2 is “0”, that is, when the engine E is not operated in the fail-safe mode, the nozzle deviation determination unit 67 determines whether the nozzle deviation is equal to or greater than the nozzle deviation threshold _DVGT (step S120). ). If this determination is YES, it is determined whether or not the flag 1 is “1” (step S130). If the flag 1 is not “1”, the flag 1 is set to “1” (step S131). If step S130 is YES or after step S131, the variable C is incremented by one (step S140).

Next, the nozzle vane failure determination unit 71 determines whether or not the variable C is smaller than the nozzle vane failure determination threshold CMIL (step S150). Here, as described above, since this processing cycle is repeatedly executed at a predetermined cycle, when the nozzle deviation is equal to or greater than the nozzle deviation threshold _DVGT , the variable C is increased by one for each processing cycle. Become. If the variable C becomes CMIL in a certain processing cycle, that is, if the determination in step S150 is NO, the nozzle vane failure determination unit 71 determines that the nozzle vane 5c is fixed (step S151).

On the other hand, in a certain process, when the nozzle deviation is less than the nozzle deviation threshold _DVGT , that is, when step S120 is NO, it is determined whether or not the flag 1 is “1” (step S121). In the case of YES, the flag 1 is set from “1” to “0” (step S122), and then the variable C is reset to 0 (step S123).

That is, at step S150, the decision variable C is whether the nozzle vanes failure determination threshold CMIL smaller is executed when the condition nozzle deviation is nozzle deviation threshold D _VGT above is continued, the nozzle vane failure determination threshold CMIL over several processing cycles corresponding to, if the nozzle deviation is nozzle deviation threshold D _VGT above, the variable C becomes vanes failure determination threshold value CMIL above, in this case step S151, the assumed judged nozzle vanes 5c is faulty The In other words, when the state in which the nozzle deviation exceeds the nozzle deviation threshold _DVGT continues for a time corresponding to the number of processing cycles, the nozzle vane failure determination unit 71 determines that the nozzle vane 5c has failed (target opening). It is determined that there is an excessive response delay, sticking, etc.).

  The nozzle vane failure determination threshold value CMIL is set to a value corresponding to the number of processing cycles that can secure a time that prevents the turbo rotation speed from over-rotating when the nozzle vane 5c is fixed.

When step S150 is YES or after step S151, the exhaust pressure determination unit 68 determines that the TC exhaust pressure, which is the exhaust pressure in the exhaust passage 41 on the upstream side of the turbocharger 5, is equal to the TC exhaust pressure first threshold value P _EX. It is determined whether it is smaller than 1 (step S160). If this determination is YES, the fuel injection valve control unit 65 calculates a guard Q that is a fuel injection amount that is reduced or restricted from the D request Q based on the operating state (step S170).

The guard Q is calculated when the nozzle deviation is equal to or greater than the nozzle deviation threshold _DVGT . By setting the fuel injection amount FP to the guard Q, the exhaust gas energy supplied to the turbocharger 5 is reduced, whereby the response delay of the nozzle vane 5c is suppressed.

FIG. 7 is a subroutine showing a process (step S170) for calculating the guard Q. In this process, the guard Q includes a plurality of guard Qs including a guard QMAX _NT based on the turbo speed (TC speed), a guard QMAX _PEX based on the TC exhaust pressure, and a guard QMAX _PBST based on the supercharging pressure. Is calculated. In addition, the guard Q may be calculated as an upper limit fuel injection amount that can ensure a minimum required excess air ratio based on the amount of air supplied to the combustion chamber.

First, the guard QMAX _NT based on the TC rotation speed is calculated. In step S170-1, TC speed is determined whether greater than TC rotational speed threshold value _{N TC.} The TC rotation speed threshold value N _TC is a threshold value set in consideration of a margin for control with respect to a physical (in terms of strength) allowable rotation speed of the turbocharger. When the TC rotation speed is equal to or greater than the TC rotation speed threshold value N _TC , the guard QMAX _NT considers the current engine rotation speed, the TC rotation speed, and the actual opening of the nozzle vane 5c, and the TC rotation speed is the turbo rotation speed threshold value. It is set to be below the N _TC (step S170-2). Specifically, the guard QMAX _NT, the difference between the current TC speed and TC rotational speed threshold value N _TC and is calculated by the F / B control on the basis of the change rate and the change acceleration of the difference.

If the determination in step S170-1 is NO, the guard QMAX _NT is set to Q _INF that is an infinite amount (step S170-3). In this case, QMAX _NT will not be substantially limited.

Next, a guard QMAX _PEX based on the TC exhaust pressure is calculated. In step S170-4, TC exhaust pressure is determined whether TC exhaust gas pressure greater than the second threshold value _{P EX} 2. When the TC exhaust pressure is larger than the TC exhaust pressure second threshold P _EX 2, the guard QMAX _PEX takes the current engine speed, the TC exhaust pressure, and the actual opening of the nozzle vane 5c into consideration, and the TC exhaust pressure is turbo exhausted. It is set to be lower than the atmospheric pressure second threshold P _EX 2 (step S170-5). Specifically, the guard QMAX _PEX is calculated by F / B control based on the difference between the current TC exhaust pressure and the TC exhaust pressure second threshold value P _EX 2 and the change speed and change acceleration of the difference.

If the determination in step S170-4 is NO, QMAX _PEX is set to Q _INF , which is an infinite amount (step S170-6). In this case, QMAX _PEX is not substantially limited.

Next, a guard QMAX _PBST based on the supercharging pressure is calculated. In step S170-7, it is determined whether or not the supercharging pressure is greater than a supercharging pressure first threshold value P _BST 1. When the supercharging pressure is larger than the supercharging pressure first threshold value P _BST 1, the guard QMAX _PBST supercharges the supercharging pressure in consideration of the current engine speed, the supercharging pressure, and the actual opening of the nozzle vane 5c. The pressure is set to be lower than the first threshold value P _BST 1 (step S170-8). Specifically, the guard QMAX _PBST is calculated by F / B control based on the difference between the current supercharging pressure and the supercharging pressure first threshold value P _BST 1 and the change speed and change acceleration of the difference. .

If step S170-7 is _{NO, QMAX PBST} is set to _{Q INF} is infinitely amount (step S170-9). In this case, QMAX _PBST will not be substantially limited.

Next, in step S170-10, the minimum value among the guard QMAX _NT , the guard QMAX _PEX , and the guard QMAX _PBST is selected as the guard Q.

Returning to FIG. 6, in step S180, it is determined whether or not the guard Q is smaller than the D request Q based on the required torque. If this determination is YES, the fuel injection amount FP is set to the guard Q (step S190). On the other hand, if this determination is NO, the fuel injection amount FP is set to the D request Q (step S124). Further, when it is determined in step S120 that the nozzle deviation is less than the nozzle deviation threshold _DVGT , the process finally proceeds to step S124, and the fuel injection amount FP is set to the D request Q.

  In this case, when the D request Q maintains the previous state quantity or becomes equal to or more than the previous state quantity, the guard Q is smaller than the D request Q, so that the D request Q is selected as the fuel injection amount FP in step S190. Is done. On the other hand, when the D request Q falls below the guard Q due to a decrease in the accelerator opening or the like, the D request Q is selected as the fuel injection amount FP. Therefore, in any of the cases where the D request Q or the guard Q is selected in step S124 and step S190, the fuel injection amount FP is limited to the guard Q or less, so the fuel injection amount FP is Decrease.

If the TC exhaust pressure is equal to or higher than the TC exhaust pressure first threshold P _EX 1 (NO in step S160), it is determined whether or not the flag 2 is “1” (step S161), and the engine E is Transition to fail-safe mode. If the flag 2 is not “1”, the flag 2 is set to “1” (step S162). When step S161 is YES or after step S162, it is determined whether the engine speed NE is equal to or higher than the engine speed threshold value NE1 (step S163).

When the determination result is NO, that is, when the engine speed NE is less than the engine speed threshold value NE1, the intake shutter valve control unit 66 controls the opening degree of the intake shutter valve 7 to the first limit opening degree TP1 ( Step S164). Next, the fuel injection valve control unit 65 limits the fuel injection amount FP to Q _IDLE (step S165). Here, the first restriction opening TP1 is an opening for restricting the intake amount to such an extent that low-speed traveling is possible. Similarly, Q _IDLE limits the fuel injection amount to such an extent that low-speed traveling is possible. That is, when the engine speed NE is equal to or lower than the engine speed threshold value NE1, the engine E is limited to an output capable of running at a low speed.

For example, the engine speed threshold value NE1 is 1,500 rpm, and the first limit opening degree TP1 and Q _IDLE are the opening degree and fuel injection amount of the intake shutter valve 7 that enable an air amount equivalent to an idle.

If the determination in step S163 is YES, that is, if the engine speed NE is greater than or equal to the engine speed threshold value NE1, the intake shutter valve control unit 66 closes the opening degree of the intake shutter valve 7 beyond the first limit opening TP1. The second limit opening TP2 set on the side is controlled (step S166). Next, the fuel injection valve control unit 65 restricts the fuel injection amount FP to Q0 that is lower than Q _IDLE (step S167). Here, the second restriction opening TP2 is substantially fully closed, and restricts the intake amount to such an extent that the engine E does not stop. Similarly, Q0 limits the fuel injection amount to substantially zero (fuel cut).

  In other words, when the engine speed NE is equal to or higher than the engine speed threshold value NE1, the engine E is allowed to have a higher engine speed because the intake air amount and the fuel injection amount are limited so that combustion in the combustion chamber 17 is not performed. While being able to reduce as quickly as possible, the exhaust gas energy supplied to the turbocharger 5 can be reduced as much as possible. In this manner, in the fail safe mode, the engine speed NE is reduced to the engine speed threshold value NE1 or less, and the output is limited to an extent that allows low speed running.

Describing the fail-safe mode release condition, if NO determination is made in step S110, that is, if it is determined that the flag 2 is “1” and the fail-safe mode is in effect, the exhaust temperature determination unit 69 sets the TC exhaust temperature to the TC exhaust temperature threshold. It determines lower or not than T _EX (step S111). When this determination is YES, the exhaust pressure determination unit 68 determines whether or not the TC exhaust pressure is lower than the TC exhaust pressure second threshold P _EX 2 (step S112).

If this determination is YES, the exhaust pressure determination unit 68 sets the flag 2 from “1” to “0” (step S113), and the intake shutter valve control unit 66 limits the opening of the intake shutter valve 7. Is canceled (step S114). As a result, the fail safe mode is canceled, and the process proceeds to step S120. On the other hand, if either one of the TC exhaust temperature and the TC exhaust pressure is higher than the respective threshold values T _EX or P _EX 2 in step S111 or step S112, the fail safe mode is continued and the process proceeds to step S161.

That is, in this processing cycle, when the nozzle deviation is larger than the nozzle deviation threshold _DVGT , the fuel injection amount FP is limited to the guard Q, and the exhaust gas energy supplied to the turbocharger 5 decreases. Thus, the response delay that can occur in the nozzle vane 5c can be eliminated. Further, when the TC exhaust pressure is equal to or higher than the TC exhaust pressure first threshold value P _EX 1, the mode is shifted to the fail-safe mode. In this case, the fuel injection amount and the fuel injection amount and When the opening degree of the intake shutter valve 7 is limited and the engine speed NE becomes lower than the engine speed threshold value NE1, an output capable of traveling at a low speed is ensured.

  According to the processing cycle performed in the ECU 60 described above, the following effects are exhibited.

(1) When the nozzle deviation is equal to or greater than the nozzle deviation threshold D _VGT , first, the flow rate of the exhaust gas acting on the nozzle vane 5c is limited by limiting the fuel injection amount FP to the guard Q or less, thereby eliminating the nozzle deviation. Try. If the nozzle deviation does not fall below the nozzle deviation threshold _DVGT during the predetermined period even if the fuel injection amount FP is limited, it is assumed that the nozzle vane 5c is stuck or an excessive response delay occurs, and the turbocharger 5 fails. It is determined that

Therefore, when the state in which the nozzle deviation is equal to or greater than the nozzle deviation threshold _DVGT continues for a predetermined time despite the limitation of the fuel injection amount FP, it is determined that the nozzle vane 5c is stuck or excessively delayed in response. When it is determined that the feeder 5 is malfunctioning while the nozzle deviation temporarily exceeds the nozzle deviation _DVGT , that is, when there is a temporary response delay in the nozzle vane 5c, the fuel injection amount FP Since the response delay of the nozzle vane 5c can be expected to be eliminated or reduced by this limitation, erroneous determination that the turbocharger 5 has failed is suppressed in this case. That is, while eliminating the temporary response delay of the nozzle vane 5c, it is possible to appropriately detect the sticking of the nozzle vane 5c or an excessive response delay, and thus it is possible to appropriately determine the failure of the turbocharger 5.

(2) When the nozzle deviation is equal to or greater than the nozzle deviation threshold D _VGT and the TC exhaust pressure is equal to or greater than the TC exhaust pressure first threshold P _EX 1, the opening degree of the intake shutter valve 7 is limited, thereby The amount of intake air that is supplied can be limited, whereby combustion in the engine E can be suppressed as quickly as possible regardless of the presence or absence of fuel present in the combustion chamber 17. As a result, the exhaust gas energy supplied to the turbocharger 5 is reduced, whereby the TC exhaust pressure is reduced and the nozzle deviation is reduced, so that over-rotation of the turbocharger 5 is suppressed. .

  Therefore, even if fuel (for example, inflow of lubricating oil) is present in the combustion chamber 17 even though the fuel supply to the engine E is limited (cut), the intake air amount is limited in the combustion chamber. By reducing oxygen, combustion can be suppressed as quickly as possible. As a result, the exhaust gas energy supplied to the turbocharger 5 is reduced, so that the exhaust pressure and the supercharging pressure are reduced and the overspeed of the turbocharger 5 is suppressed.

(3) When the rotational speed of the engine E is equal to or higher than the engine rotational speed threshold NE1, the intake air supplied to the combustion chamber 17 is shut off by controlling the intake shutter valve 7 to be substantially fully closed. The rotational speed of the engine E can be reduced as quickly as possible. As a result, the exhaust gas energy supplied to the turbocharger 5 is reduced, so that the exhaust pressure and the supercharging pressure are reduced and the overspeed of the turbocharger 5 is suppressed.

(4) When the rotational speed of the engine E is less than the engine rotational speed threshold NE1, the engine E can be maintained at an output capable of low-speed traveling by limiting the amount of intake air supplied to the combustion chamber 17. Further, since the rotational speed of the engine E is less than the engine rotational speed threshold NE1, an increase in exhaust gas energy supplied to the turbocharger 5 is suppressed, and an increase in the exhaust pressure and the supercharging pressure of the turbocharger 5 is suppressed. As well as excessive rotation of the turbocharger 5 is suppressed.

(5) When the TC exhaust temperature falls below the exhaust temperature threshold value T _EX , the exhaust gas energy supplied to the turbocharger 5 is reduced, so that the TC exhaust pressure, the supercharging pressure, and the turbo speed are respectively Will be reduced. Therefore, in this case, it is not necessary to limit the amount of intake air supplied to the engine E, and the engine E can be quickly returned to normal operation by releasing the opening degree restriction of the intake shutter valve 7.

(6) When the TC exhaust pressure falls below the TC exhaust pressure second threshold P _EX 2, the exhaust gas energy supplied to the turbocharger 5 is reduced, so the TC exhaust pressure, the supercharging pressure, and the turbo Each rotational speed will decrease. Therefore, in this case, it is not necessary to limit the amount of intake air supplied to the engine E, and the engine E can be quickly returned to normal operation by releasing the opening degree restriction of the intake shutter valve 7.

In the above embodiment, when the nozzle deviation is larger than the nozzle deviation threshold _DVGT, it is determined that there is a response delay in the nozzle vane 5c (step S120). In addition to this, the flowchart extracted in FIG. As shown, it is determined whether or not the TC exhaust pressure is greater than the TC exhaust pressure second threshold value P _EX 2 and / or whether or not the boost pressure is greater than the boost pressure first threshold value P _BST 1. (Steps S201 and S202).

  Accordingly, it is possible to more appropriately determine whether or not the turbocharger 5 has failed by adding the TC exhaust pressure and / or the supercharging pressure to the failure determination condition.

For example, when the target opening degree of the nozzle vane 5c is controlled from the closed side to the open side immediately after acceleration, the nozzle deviation tends to become the nozzle deviation threshold _DVGT due to a temporary response delay of the nozzle vane 5c, and the nozzle vane 5c is not fixed. Even if it is a case, there exists a possibility of misjudging that the turbocharger 5 is out of order. On the other hand, since the TC exhaust pressure and the supercharging pressure do not exceed the predetermined values immediately after acceleration, the turbocharger 5 fails immediately after acceleration by making a determination based on the exhaust pressure and / or supercharging pressure. It can be prevented from being erroneously determined as being.

  Further, as shown in the flowchart extracted in FIG. 8B, instead of determining the nozzle deviation, it may be determined whether or not the TC exhaust pressure or the supercharging pressure is larger than a predetermined value. That is, when it is determined that the TC exhaust pressure or the supercharging pressure is greater than the predetermined value, it is assumed that the nozzle vane 5c is positioned closer to the target opening, so that the nozzle deviation is determined (step S120). In place of), the TC exhaust pressure and the supercharging pressure may be determined (steps S211 and S212).

Thus, when the TC exhaust pressure is equal to or higher than the TC exhaust pressure second threshold P _EX 2 or when the supercharging pressure is equal to or higher than the supercharging pressure first threshold P _BST 1, first, the fuel injection amount is limited. The flow rate of the exhaust gas acting on the nozzle vane 5c is limited, thereby attempting to reduce the TC exhaust pressure or the supercharging pressure. When the TC exhaust pressure or the supercharging pressure does not fall below the threshold value for a predetermined period even when the fuel injection amount is limited, it is determined that the turbocharger 5 has failed for the first time.

Therefore, when the state in which the TC exhaust pressure or the supercharging pressure is equal to or higher than the TC exhaust pressure second threshold value P _EX 2 continues for a predetermined time despite the limitation of the fuel injection amount, the turbocharger 5 While it can be determined that there is a failure, it can be prevented that the turbocharger 5 is erroneously determined to have failed until the TC exhaust pressure or the supercharging pressure temporarily exceeds the threshold. That is, by distinguishing between a temporary increase in the TC exhaust pressure or supercharging pressure and an increase in the TC exhaust pressure or supercharging pressure over a predetermined time, it is possible to appropriately determine whether or not the turbocharger 5 has failed. .

In the above embodiment, when the state where the nozzle deviation is larger than the nozzle deviation threshold _DVGT continues for a predetermined time, it is determined that the nozzle vane 5c is fixed, but in addition, the TC exhaust pressure, A failure determination may be made when the supercharging pressure is greater than a predetermined value. As shown in FIG. 9, first, in step S300, the exhaust pressure determination unit 68 determines whether or not the TC exhaust pressure is higher than the TC exhaust pressure first threshold value P _EX 1. When this determination is NO, the supercharging pressure determination unit 70 determines whether or not the supercharging pressure is higher than the supercharging pressure second threshold P _BST 2 (step S310). The supercharging pressure second threshold value P _BST 2 is a threshold value for detecting an abnormal increase in supercharging pressure, and is set higher than the supercharging pressure first threshold value P _BST 1.

  If YES is determined in either step S300 or step S310, it is determined that the nozzle vane 5c is fixed or an excessive response delay occurs, and the flag 3 is set to “1” (step S340). Further, the failure record may be stored as a service code in the memory of the ECU 60 (step S350) so that it can be confirmed at the time of subsequent service. The warning lamp display unit 96 is activated and the nozzle vane 5c is broken. To the passenger (step S360). In this case, when the flag 3 is “1”, the mode may be shifted to the fail-safe mode.

Explaining the return from the fail-safe mode, when the TC exhaust pressure and the supercharging pressure are respectively lower than the threshold values, that is, when NO is determined in steps S300 and S310, it is determined that the flag 3 is “1”. and (step S320) after the exhaust gas temperature determination unit 69 determines whether or not TC exhaust temperature is higher than TC exhaust temperature threshold value _{T EX} (step S330). If this determination is YES, the process proceeds to step S340 and the fail safe mode is continued. On the other hand, if this determination is NO, the process proceeds to step S370 and the flag 3 is set from “1” to “0”. Ends.

  As described above, according to the control method and the control apparatus for an engine according to the present invention, even when oil enters the combustion chamber, it is possible to reduce the turbo speed and prevent the turbocharger from over-rotating. Therefore, it may be suitably used in this kind of manufacturing technology field.

DESCRIPTION OF SYMBOLS 1 Intake passage 5 Turbocharger 5a Compressor 5b Turbine 5c Nozzle vane 7 Intake shutter valve 20 Fuel injection valve 41 Exhaust passage 60 ECU
E engine D _VGT nozzle deviation threshold P _EX 1 TC exhaust pressure first threshold P _EX 2 TC exhaust pressure second threshold T _EX TC exhaust temperature threshold P _BST 1 supercharging pressure first threshold P _BST 2 supercharging pressure second threshold

Claims (10)

An engine control method comprising a variable displacement supercharger having a nozzle vane capable of changing a flow area of exhaust gas supplied to a turbine, and an intake shutter valve,
Setting a target nozzle opening of the nozzle vane and a target shutter opening of the intake shutter valve according to the operating state of the engine;
Controlling the nozzle vane opening to the target nozzle opening;
Determining whether the exhaust pressure upstream of the supercharger is greater than or equal to a predetermined value;
Determining whether a nozzle deviation, which is a difference between the actual opening of the nozzle vane and the target nozzle opening, is a predetermined value or more;
When the exhaust pressure is greater than or equal to the predetermined value and the nozzle deviation is greater than or equal to the predetermined value, the opening of the intake shutter valve is more limited than the target shutter opening;
An engine control method comprising: In the limiting step, when the engine speed is equal to or higher than a predetermined value, the opening degree of the intake shutter valve is controlled to be substantially fully closed.
The engine control method according to claim 1. In the limiting step, when the engine speed is less than a predetermined value, the opening degree of the intake shutter valve is controlled to an opening degree at which low speed traveling is possible.
The engine control method according to claim 1 or 2. After restricting the opening degree of the intake shutter valve, further comprising the step of canceling the opening degree restriction of the intake shutter valve when the exhaust temperature upstream of the supercharger falls below a predetermined value,
The engine control method according to any one of claims 1 to 3. After restricting the opening degree of the intake shutter valve, the method further includes the step of releasing the opening degree restriction of the intake shutter valve when the exhaust pressure falls below a predetermined value.
The engine control method according to any one of claims 1 to 4. An engine control device including a variable displacement supercharger having a nozzle vane capable of changing a flow area of exhaust gas supplied to a turbine and an intake shutter valve,
A target setting unit that sets a target nozzle opening of the nozzle vane and a target shutter opening of the intake shutter valve according to the operating state of the engine;
A nozzle vane controller that controls the opening of the nozzle vane to the target nozzle opening;
An exhaust pressure determination unit for determining whether or not the exhaust pressure upstream of the supercharger is equal to or greater than a predetermined value;
A nozzle deviation determination unit that determines whether a nozzle deviation that is a difference between the actual opening of the nozzle vane and the target nozzle opening is equal to or greater than a predetermined threshold;
An intake shutter valve control unit that restricts an opening degree of the intake shutter valve from the target shutter opening degree when the exhaust pressure is equal to or larger than the predetermined value and the nozzle deviation is equal to or larger than the predetermined value;
An engine control device. When the exhaust pressure is equal to or higher than the predetermined value and the nozzle deviation is equal to or higher than the predetermined value, the intake shutter valve control unit opens the intake shutter valve when the engine speed is equal to or higher than the predetermined value. Control the degree to be almost fully closed,
The engine control device according to claim 6. When the exhaust pressure is equal to or greater than the predetermined value and the nozzle deviation is equal to or greater than the predetermined value, the intake shutter valve control unit is configured to perform the intake shutter valve control unit when the engine speed is less than the predetermined value. Controls the opening of the intake shutter valve to an opening that allows low-speed travel,
The engine control device according to claim 6 or 7. When the exhaust gas temperature on the upstream side of the supercharger falls below a predetermined value after restricting the opening degree of the intake shutter valve, the intake shutter valve control unit releases the opening degree restriction of the intake shutter valve,
The engine control device according to any one of claims 6 to 8. If the exhaust pressure falls below a predetermined value after limiting the opening of the intake shutter valve, the intake shutter valve control unit cancels the opening limit of the intake shutter valve,
The engine control device according to any one of claims 6 to 9.

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