JP2016065504A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly prevent the overspeed of a turbocharger while continuing DPF regeneration when the overspeed of the turbocharger occurs at the DPF regeneration.SOLUTION: An engine control device has: a turbocharger 5 having a compressor 5a and a turbine 5b; a DPF 46 which collects particulate substances in an exhaust gas; and an ECU 60 which regenerates the DPF by post-injecting fuel after main injection in order to remove the particulate substances which are accumulated at the DPF 46. During the regeneration of the DPF, when a rotation number of the turbocharger 5 reaches a first prescribed value or larger, the ECU 60 decreases a fuel injection amount of the post-injection which is controlled at the DPF regeneration.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device that prevents over-rotation of a turbocharger.

  Conventionally, an engine with a turbocharger that supercharges intake air by driving a compressor by rotating a turbine with exhaust gas is known. In such a turbocharger, over-rotation (in other words, supercharging and over-exhaust pressure) may occur depending on operating conditions and the like, and if the over-rotation continues, the turbocharger may be damaged. For this reason, various techniques for preventing excessive rotation of the turbocharger have been proposed. For example, Patent Document 1 proposes a technique for reducing the fuel injection amount when the turbocharger is overrotated. Specifically, Patent Document 1 proposes a technique for reducing the fuel injection amount when the turbine speed is equal to or higher than the set value even when the boost pressure is less than the set value.

JP-A-5-280385

  By the way, conventionally, in a diesel engine, a DPF (Diesel particulate filter) that collects particulate matter in exhaust gas is provided on the exhaust passage, and the amount of particulate matter deposited on the DPF is limited. DPF regeneration is performed to remove particulate matter deposited on the DPF when the amount exceeds the fixed amount. Specifically, DPF regeneration is known in which fuel is injected by post injection after main injection to burn and remove particulate matter deposited on the DPF. According to such post-injection for DPF regeneration, the rotational speed of the turbocharger is increased in order to increase the exhaust energy (exhaust temperature). For this reason, the turbocharger may be excessively rotated. Further, if DPF regeneration is performed while the turbocharger is over-rotating, over-rotation of the turbocharger is promoted.

  In order to prevent over-rotation of the turbocharger that may occur during DPF regeneration, reducing the fuel injection amount as in the technique described in Patent Document 1 described above prevents over-rotation of the turbocharger. Even if it is possible, the post-injection fuel injection amount is greatly reduced (for example, the execution of the post injection is stopped), and the DPF regeneration may be stopped without being completed. When a request for DPF regeneration is issued, it is desirable to complete DPF regeneration promptly from the viewpoint of emission. Accordingly, it is only necessary to prevent over-rotation of the turbocharger while continuing DPF regeneration in the event that over-rotation of the turbocharger occurs during DPF regeneration.

  The present invention has been made in order to solve the above-described problems of the prior art, and in the event that turbo turbocharger over-rotation occurs during DPF regeneration, the DPF regeneration is continued while the turbocharger is maintained. An object of the present invention is to provide an engine control device that can appropriately prevent over-rotation.

In order to achieve the above-mentioned object, the present invention is an engine control device comprising a turbine provided in an exhaust passage and a compressor provided in an intake passage, and rotating the turbine by exhaust gas to thereby compress the compressor. A turbocharger that supercharges intake air by driving the engine, a DPF that is provided in the exhaust passage and collects particulate matter in the exhaust gas, and a main injection for removing particulate matter accumulated in the DPF By controlling post-injection for injecting fuel after the DPF regeneration control means for executing DPF regeneration, and while the DPF regeneration control means is executing DPF regeneration, the rotational speed of the turbocharger is first Injection amount reduction control means for reducing the post-injection fuel injection quantity controlled by the DPF regeneration control means when the value exceeds a predetermined value.
In the present invention configured as described above, when the turbocharger overspeeds during DPF regeneration, the fuel injection amount of post injection set for DPF regeneration is reduced and post injection is stopped. Therefore, the post-injection is appropriately maintained without causing excessive rotation of the turbocharger while continuing the DPF regeneration. That is, it is possible to prevent over-rotation of the turbocharger while continuing DPF regeneration while achieving both prevention of over-rotation of the turbocharger and DPF regeneration.

In the present invention, preferably, the DPF regeneration control means performs post injection by injecting fuel in multiple stages, and the injection amount reduction control means reduces the number of post injection stages in order to reduce the fuel injection quantity of post injection. .
In the present invention configured as described above, the number of post-injection stages (the number of times fuel is injected as post-injection) is reduced when the turbocharger over-rotates during DPF regeneration. Further, the fuel injection amount of the post injection can be appropriately reduced so as to reduce the turbo rotational speed.

In the present invention, the injection amount reduction control means preferably stops the post injection when the rotational speed of the turbocharger does not become less than the second predetermined value even if the fuel injection amount of the post injection is reduced. In the present invention configured as described above, even if the post-injection fuel injection amount is reduced, the overcharge of the turbocharger may not be eliminated depending on the reduction in the post-injection fuel injection amount. Since post-injection is stopped on the assumption that rotation cannot be completely prevented, the highest priority can be given to prevention of over-rotation of the turbocharger.

In the present invention, preferably, the injection amount reduction control means reduces the fuel injection amount of the main injection after stopping the post injection.
In the present invention configured as described above, since the fuel injection amount of the main injection is reduced after the post injection is stopped, it is possible to appropriately prevent the turbocharger from over-rotating even after the post injection is stopped. it can.

In the present invention, the DPF regeneration control unit preferably performs DPF regeneration by further controlling after-injection in which fuel is injected between the main injection and the post-injection in addition to the post-injection, thereby reducing the injection amount. The control means further reduces the fuel injection amount of the after injection controlled by the DPF regeneration control means in accordance with the reduction of the fuel injection amount of the main injection.
In the present invention configured as described above, the fuel injection amount of the after injection is further reduced as the fuel injection amount of the main injection is reduced, so that it is possible to effectively prevent the turbocharger from over-rotating. . In this case, since the fuel injection amount of the after injection set for the DPF regeneration is decreased, the DPF regeneration can be continued by the after injection even after the post injection is stopped as described above. .

In the present invention, it is preferable that the DPF regeneration control unit is configured such that the rotation speed of the turbocharger does not become less than the second predetermined value even if the injection amount reduction control unit reduces the fuel injection amount of the after injection to a predetermined amount. After that, the control of after injection for DPF regeneration is stopped.
In the present invention configured as described above, even if the fuel injection amount of the after injection is reduced to a predetermined amount (for example, the lower limit value of the injection amount at which the DPF regeneration can be appropriately performed), the turbocharger excessively increases. When the rotation does not disappear, the control of the after-injection for DPF regeneration is stopped and the DPF regeneration is substantially stopped. Therefore, the after-injection amount is further reduced from this, and the turbo-supercharger is Prevention can be given top priority.

In the present invention, it is preferable to perform a control for returning the main injection when the rotational speed of the turbocharger becomes less than a second predetermined value due to a reduction in the fuel injection amount by the injection amount reduction control means. There is further provided a return control means for performing control to return post injection later.
In the present invention configured as described above, when the turbocharger overspeed is resolved by reducing the fuel injection amount, the control for returning the main injection is performed, and the control for returning the post injection is performed after this control. In other words, since the main injection and the post injection are returned in the order without returning the main injection and the post injection at the same time, the torque fluctuation and the sound change accompanying the return of the fuel injection can be appropriately suppressed.

  According to the engine control apparatus of the present invention, when turbo turbocharger overrotation occurs during DPF regeneration, overrotation of the turbocharger can be appropriately prevented while continuing DPF regeneration.

1 is a schematic configuration diagram of an engine system to which an engine control device according to an embodiment of the present invention is applied. It is the longitudinal cross-sectional view which expanded the turbine chamber of the turbocharger by embodiment of this invention. It is explanatory drawing of the high voltage | pressure EGR area | region, low voltage | pressure EGR area | region, and non-EGR area | region by embodiment of this invention. It is a flowchart which shows the basic control by embodiment of this invention. It is explanatory drawing of the type of fuel injection used in embodiment of this invention. It is a time chart in the turbo excessive rotation prevention control by embodiment of this invention. It is a flowchart which shows the turbo excessive rotation prevention control flow by embodiment of this invention.

  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 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-cooled intercooler that cools the intake air using the coolant that has passed through 8 and an electric water pump 9 for controlling the flow rate of the cooling water flowing through the intercooler 8, and the intercooler 8 and the electric water pump 9 are connected to each other, and the cooling water is a passage for circulating the cooling water therebetween. A passage 10 and a surge tank 12 that temporarily stores intake air supplied to the engine E are provided.
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. These various sensors 101 to 108 provided in the intake system IN output detection signals S101 to S108 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. These various sensors 109 to 112 provided in the engine E output detection signals S109 to S112 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 various sensors 114 and 115 provided in the fuel supply system FS output detection signals S114 and S115 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 of the turbocharger 5 that drives the compressor 5a, a diesel oxidation catalyst (DOC) 45 and a diesel particulate filter (DPF) 46 having an exhaust gas purification function, and a passage And an exhaust shutter valve 49 for adjusting the exhaust flow rate. 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 O ₂ 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. ing. These various sensors 116 to 122 provided in the exhaust system EX output detection signals S116 to S122 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 flaps 5c are provided, and these flaps 5c are configured as variable geometry turbochargers (VGTs) that change the flow cross-sectional area (nozzle cross-sectional area) of the exhaust gas to the turbine 5b. . For example, the flap 5c is rotated by an actuator with the magnitude of the negative pressure acting on the diaphragm adjusted by an electromagnetic valve. Further, a VGT opening sensor 104 is provided for detecting the opening of the flap 5c (which is the flap opening, hereinafter referred to as “VGT opening” as appropriate) depending on the position of the actuator. The VGT opening sensor 104 outputs a detection signal S104 corresponding to the detected VGT opening to the ECU 60.

Here, the flap 5c of the turbocharger 5 according to the embodiment of the present invention will be specifically described with reference to FIG. 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 flaps 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 flap 5c is rotatably supported by a support shaft 131a passing through one side wall of the turbine chamber 153a. When the respective flaps 5c are rotated clockwise in FIG. 2 around the supporting shaft 5d and inclined so as to be close to each other, the nozzles 155, 155,... Formed between the respective flaps 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 flap 5c is rotated to the opposite side and inclined so as to be separated from each other, the cross-sectional area of the nozzle increases. Efficiency can be increased.
The ring member 157 is drivingly connected to the rod 163 of the actuator via the link mechanism 158, and the flaps 5c are 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 upstream of the turbine 5b of the turbocharger 5 and the intake passage 1 downstream of the compressor 5b of the turbocharger 5 (specifically, downstream 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 5b 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, the ECU 60 according to the present embodiment, in addition to the detection signals S101 to S122 of the various sensors 101 to 122 described above, 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 detection signal S98-S100 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 sends a control signal S130 to an actuator (not shown) that drives the flap 5c in order to control the opening (VGT opening) of the flap 5c in the turbine 5b of the turbocharger 5. Output. Further, the ECU 60 outputs a control signal S131 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 S132 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 S133 to the fuel injection valve 20 in order to control the fuel injection amount of the engine E and the like. Further, the ECU 60 outputs control signals S134, S135, S136, and S137 to control the alternator 26, the fuel warmer 32, the fuel pressure regulator 34, and the common rail pressure reducing valve 36, respectively. In addition, the ECU 60 outputs a control signal S138 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 S139 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 S140 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 of the detection signals S98 to S122 output from the various 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 (corresponding to the detection signal S100) detected by the accelerator opening sensor 100.
Next, in step S13, the ECU 60 sets a required injection amount 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 overspeed prevention control>
Below, the control (turbo overspeed prevention control) for preventing the overspeed of the turbocharger 5 according to the embodiment of the present invention will be described.

  First, an overview of turbo overspeed prevention control according to an embodiment of the present invention will be described. In the present embodiment, the ECU 60 executes DPF regeneration that removes particulate matter accumulated in the DPF 46 provided on the exhaust passage 41 by controlling post injection that injects fuel after main injection. The ECU 60 performs control to reduce the post-injection fuel injection amount for DPF regeneration when the turbocharger 5 is excessively rotated while the DPF regeneration is being performed. Hereinafter, the fuel injection amount applied to the post injection is referred to as “post injection amount”, and the control for reducing the post injection amount is referred to as “post injection amount reduction control”. This post injection amount reduction control is a control included in the turbo overspeed prevention control according to the embodiment of the present invention.

The reason why such post injection amount reduction control is performed is as follows. According to post-injection for regeneration of DPF, particulate matter accumulated on DPF 46 can be burned and removed, but the rotational speed of turbocharger 5 is increased to increase exhaust energy (exhaust temperature). I will let you. For this reason, the turbocharger 5 is caused to over-rotate or the turbo-supercharger 5 is encouraged to over-rotate. In particular, the turbocharger 5 configured in a small size is likely to over-rotate.
Therefore, in the present embodiment, the ECU 60 performs post-injection amount reduction control for reducing the post-injection amount for DPF regeneration when the turbocharger 5 over-rotates during DPF regeneration. In this case, the ECU 60 prevents excessive rotation of the turbocharger 5 while continuing DPF regeneration by appropriately reducing the post injection amount. In other words, the DPF regeneration is not stopped immediately in preference to preventing the turbocharger 5 from over-rotating, but the DPF regeneration is continued while preventing both the turbo-supercharger 5 from over-rotating and DPF regeneration. Meanwhile, over-rotation of the turbocharger 5 is prevented.

  As described above, the ECU 60 functions as “DPF regeneration control means” and “injection amount reduction control means” in the present invention. Although details will be described later, the ECU 60 also functions as “return control means” in the present invention.

Here, with reference to FIG. 5, the type of fuel injection used in the embodiment of the present invention will be described. As shown in FIG. 5, fuel injection is performed in the order of pre-injection, main injection (main injection), after injection, and post injection in the time axis direction defined by the crank angle.
The pre-injection is a fuel injection for generating fire types in advance in the combustion chamber 17 of the engine E in order to reduce NOx and improve combustion noise, and the main injection is a fuel injection for generating engine torque to be output. This is fuel injection for actively controlling engine torque.
Further, after injection is fuel injection (post-combustion injection) for completely burning unburned fuel (unburned fuel). The fuel injection amount of the after injection (hereinafter referred to as “after injection amount”) is correlated with the fuel injection amount of the main injection (hereinafter referred to as “main injection amount”). Specifically, the ratio between the main injection amount and the after injection amount is fixed to a predetermined value according to the operating state, and the after injection amount is increased according to the increase in the main injection amount according to this ratio. The after injection amount is reduced as the main injection amount is reduced.
Further, the post-injection is a fuel injection for increasing the exhaust gas temperature and performing post-processing (especially DPF regeneration) on the exhaust gas. As shown in FIG. 5, post injection is performed by performing multi-stage injection of fuel (for example, injection of 1 to 5 stages, and the number of stages corresponding to the total amount of fuel to be injected is applied). In the DPF regeneration, the post-injected fuel is discharged into the exhaust passage 41 without being burned in the combustion chamber 17 and is oxidized (reacts with oxygen) in the DOC 45 to generate heat. As a result, the particulate matter deposited on the DPF 46 is burned and removed. In this case, the post-injected fuel moves in the exhaust passage 41 while burning, and this energy is transmitted to the turbine 5b of the turbocharger 5 to increase the turbo rotational speed.

  Next, a time chart in the turbo overspeed prevention control according to the embodiment of the present invention will be described with reference to FIG. FIG. 6 shows an example of a time chart when the turbo overspeed prevention control according to the embodiment of the present invention is executed.

In FIG. 6, in order to compare the result of this embodiment in which the post-injection amount reduction control is executed when the turbocharger 5 is over-rotated during the DPF regeneration, and the comparison with the present embodiment, the DPF regeneration is performed. The result by the comparative example (henceforth a "1st comparative example") which did not perform post injection amount reduction | decrease control when the turbo-supercharger 5 overspeed occasionally occurs is shown.
Further, in the control according to the present embodiment shown in FIG. 6, when the turbocharger 5 over-rotates during DPF regeneration, in addition to the post-injection amount reduction control, the target excess according to the operating state of the engine E is obtained. The supercharging pressure F / B control (feedback control) for setting the actual supercharging pressure to the supply pressure is stopped. In FIG. 6, for comparison with the present embodiment, the post-injection amount reduction control is executed when the turbocharger 5 over-rotates during DPF regeneration, but the supercharging pressure F / B A result of a comparative example (hereinafter referred to as “second comparative example”) in which the supercharging pressure F / B control is continuously executed without stopping the execution of the control is also shown.
As described above, the reason for stopping the execution of the supercharging pressure F / B control in the present embodiment is as follows. If the post injection amount is reduced by the post injection amount reduction control in order to prevent overspeed of the turbocharger 5, the actual supercharging pressure is reduced (especially in the region where the engine speed is high, the actual supercharging pressure is reduced). Will be noticeable). If the supercharging pressure F / B control is executed at this time, the reduced actual supercharging pressure (specifically, the actual supercharging pressure decreased below the target supercharging pressure) is increased, that is, the target overpressure is increased. Control is performed to change the opening degree (VGT opening degree) of the flap 5c of the turbocharger 5 to the closed side so that the actual supercharging pressure deviating from the supply pressure is increased toward the target supercharging pressure. As a result, the turbo rotation speed increases. Therefore, the supercharging pressure F / B control is contrary to the post injection amount reduction control for reducing the turbo rotational speed in order to prevent the turbocharger 5 from over-rotating. That is, the supercharging pressure F / B control is a control contrary to the post injection amount reduction control as the turbo overspeed prevention control. Therefore, in this embodiment, when the turbo overspeed prevention control is executed, the execution of the supercharging pressure F / B control is stopped.

  FIG. 6 will be specifically described. FIG. 6 shows time in the horizontal direction, and shows the turbo rotation speed, the post injection amount, the VGT opening degree, and the supercharging pressure in order from the top. Specifically, the graph G11 shows the time change of the turbo rotation speed according to the present embodiment, and the graph G12 shows the time change of the turbo rotation speed according to the first comparative example. Further, the graph G21 shows the time change of the post injection amount according to the present embodiment, and the graph G22 shows the time change of the post injection amount by the first comparative example. Further, the graph G31 shows the time change of the VGT opening according to the present embodiment, and the graph G32 shows the time change of the VGT opening according to the second comparative example. The graph G41 shows the time change of the actual supercharging pressure according to this embodiment, the graph G42 shows the time change of the actual supercharging pressure according to the second comparative example, and the graph G43 shows the operating state of the engine E (engine The time change of the target supercharging pressure set based on the rotation speed, the main injection amount, etc.) is shown.

  It is assumed that the particulate matter deposited on the DPF 46 is a predetermined amount or more before time t1. At time t1, it is assumed that the opening degree of the accelerator pedal 95 (accelerator opening degree) changes in the step-down direction due to the acceleration request from the driver (not shown in FIG. 6). Therefore, from time t1, DPF regeneration execution conditions are satisfied, and DPF regeneration is started. Specifically, post injection for removing particulate matter deposited on the DPF 46 is started (see graphs G21 and G22). The post-injection amount in this case is determined by predetermined F / B control (hereinafter referred to as “post-injection F / B control”) so that the particulate matter deposited on the DPF 46 is appropriately removed. It is controlled according to the accumulation amount of the particulate matter, the exhaust temperature, the temperature of the DPF 46, and the like. Thereafter, at time t2, the turbo rotation speed becomes equal to or greater than the predetermined value Th1 (see graphs G11 and G12), that is, the turbocharger 5 is overrotated.

  According to the first comparative example, the post injection F / B control is continued after time t2, and the post injection amount by this post injection F / B control is applied (see graph G22). For this reason, the turbo rotational speed continues to increase after time t2 (see graph G12), that is, the state where the turbo rotational speed is equal to or greater than the predetermined value Th1 continues, and the overspeed of the turbocharger 5 is not eliminated. On the other hand, according to the present embodiment, post injection F / B control is stopped at time t2, and post injection amount reduction control is executed to reduce the post injection amount for DPF regeneration (see graph G21). ). Therefore, the turbo rotation speed decreases after time t2 (see graph G11). In this case, the turbo rotation speed is reduced to less than the predetermined value Th1, and the overspeed of the turbocharger 5 is eliminated.

On the other hand, according to the second comparative example, the post injection amount reduction control is executed, and the actual supercharging pressure (see graph G42) decreased by the post injection amount reduction by the post injection amount reduction control is set as the target supercharging pressure. The VGT opening degree is controlled to the closed side by the supercharging pressure F / B control so as to increase to (see graph G43) (see graph G32). In such a case, the turbo rotation speed increases (not shown in FIG. 6). On the other hand, according to the present embodiment, the supercharging pressure F / B control is stopped when the post injection amount reduction control is executed, so the VGT opening is fixed to a substantially constant opening (graph G31). Reference), that is, the change of the VGT opening to the closing side is suppressed. In this case, the actual boost pressure (see graph G41) deviates from the target boost pressure (see graph G43). According to the present embodiment, since the increase in turbo rotation speed due to the supercharging pressure F / B control is suppressed, the turbo rotation speed is effectively reduced by the post injection amount reduction control described above. (See graph G11).
Note that at time t2 when the turbo rotation speed reaches the predetermined value Th1, both the present embodiment and the second comparative example assume that the VGT opening is almost fully open (see graphs G31 and G32). .

  Next, the overall flow of the turbo overspeed prevention control according to the embodiment of the present invention will be specifically described with reference to FIG. FIG. 7 is a flowchart showing a turbo overspeed prevention control flow according to the embodiment of the present invention. This turbo overspeed prevention control flow is repeatedly executed by the ECU 60 at a predetermined cycle.

  Here, the outline of the turbo overspeed prevention control flow will be briefly described. In the turbo over-rotation prevention control flow, the ECU 60 first stops the post-injection F / B control and reduces the post-injection amount when the turbo rotation speed exceeds the first predetermined value during DPF regeneration. The injection amount reduction control is executed. Then, the ECU 60 stops the post injection amount reduction control and reduces the main injection amount when the turbo rotational speed does not become less than the second predetermined value even if the post injection amount is reduced to 0 (hereinafter referred to as “ "Main injection amount reduction control") is executed, and the supercharging pressure F / B control is stopped. When the ECU 60 reduces the main injection amount by the main injection amount reduction control as described above, the ECU 60 also reduces the after injection amount as the main injection amount is reduced. Then, the ECU 60 performs control (hereinafter referred to as “main injection return control”) to return the main injection when the turbo rotation speed becomes less than the second predetermined value by the main injection amount reduction control. Control for returning post injection (hereinafter referred to as “post injection return control”) is performed.

The turbo overspeed prevention control flow of FIG. 7 will be specifically described. First, in step S21, the ECU 60 determines whether or not a DPF regeneration flag for executing DPF regeneration is turned on. In other words, the ECU 60 determines whether or not an execution condition for DPF regeneration is satisfied. When the DPF regeneration flag is on, it is assumed that the post injection execution is permitted.
As a result of such determination, if it is not determined that the DPF regeneration flag is on (step S21: No), that is, if the DPF regeneration flag is off, the process ends. In this case, the ECU 60 does not execute the turbo overspeed prevention control according to the present embodiment.

  On the other hand, when it is determined that the DPF regeneration flag is on (step S21: Yes), the process proceeds to step S22, and the ECU 60 detects the compressor of the turbocharger 5 detected by the turbo speed sensor 103. It is determined whether the rotational speed 5a (turbo rotational speed) is equal to or greater than a first predetermined value. This first predetermined value is a threshold value for determining whether or not the post injection amount reduction control is necessary, and the rotational speed corresponding to the excessive rotation of the compressor 5a of the turbocharger 5 (for example, the compressor 5a may be damaged). Is set based on the number of revolutions). For example, the first predetermined value is set to 255000 rpm.

  As a result of the determination in step S22, if it is not determined that the turbo rotation speed is equal to or greater than the first predetermined value (step S22: No), that is, if the turbo rotation speed is less than the first predetermined value, the process proceeds to step S34. In this case, since the turbocharger 5 is not over-rotated, the ECU 60 controls the fuel injection valve 20 of the engine E to perform post-injection F / B control for DPF regeneration in step S34. Run. Specifically, the ECU 60 sets the post injection amount based on the amount of particulate matter accumulated in the DPF 46, the exhaust temperature, the temperature of the DPF 46, and the like so that the particulate matter deposited on the DPF 46 is appropriately removed. The post injection F / B control to be set is executed.

  On the other hand, when it is determined that the turbo rotation speed is equal to or higher than the first predetermined value (step S22: Yes), the process proceeds to step S23, and the ECU 60 controls the fuel injection valve 20 of the engine E to In order to reduce the rotational speed, post injection amount reduction control is executed to reduce the post injection amount for DPF regeneration. In one example, the ECU 60 reduces the post injection amount by a predetermined amount. In another example, the ECU 60 reduces the post injection amount according to the degree to which the turbo rotation speed exceeds the first predetermined value. Further, for example, the ECU 60 reduces the number of post-injection stages according to the post-injection amount to be reduced (5 stages → 4 stages, 5 stages → 3 stages, etc.).

  Next, in step S24, the ECU 60 stops the post injection F / B control. By doing so, the post injection amount reduced by the post injection amount reduction control is applied as the fuel injection amount from the fuel injection valve 20 without applying the post injection amount set by the post injection F / B control. Like that.

Next, in step S <b> 25, the ECU 60 determines that the post injection amount reduced by the post injection amount reduction control is 0, and the rotational speed of the compressor 5 a of the turbocharger 5 detected by the turbo rotational speed sensor 103. It is determined whether (turbo speed) is equal to or greater than a second predetermined value. Here, even if the post injection amount reduction control in step S23 is repeatedly performed and the post injection amount is reduced to 0, it is determined whether or not the turbocharger 5 is still over-rotating.
The second predetermined value used in step S25 is a threshold value for determining whether or not the main injection amount reduction control is necessary, and the rotation corresponding to the excessive rotation of the compressor 5a of the turbocharger 5 is the same as the first predetermined value. It is set based on the number (for example, the number of revolutions at which the compressor 5a can be damaged). For example, the second predetermined value is set to 260000 revolutions / minute, which is slightly higher than the first predetermined value. The second predetermined value is not limited to being set to a value different from the first predetermined value, and the second predetermined value may be set to the same value as the first predetermined value.

  As a result of the determination in step S25, when the post injection amount is 0 and the turbo rotation speed is not determined to be equal to or greater than the second predetermined value (step S25: No), that is, when the post injection amount is not 0 Alternatively, if the turbo rotation speed is less than the second predetermined value, the process proceeds to step S31. In this case, in step S31, the ECU 60 determines whether or not the turbo rotation speed is less than a first predetermined value. As a result, if it is not determined that the turbo rotational speed is less than the first predetermined value (step S31: No), that is, if the turbo rotational speed is greater than or equal to the first predetermined value, the process returns to step S23, and the ECU 60 The injection amount reduction control is executed again to further reduce the post injection amount. And ECU60 continues the state which stopped post injection F / B control in Step S24.

  The ECU 60 repeats such processes of steps S23, S24, S25, and S31, and gradually decreases the post injection amount while comparing the turbo rotation speed with the first predetermined value. As a result, if the turbo rotation speed does not become less than the first predetermined value while reducing the post injection amount, the post injection amount finally becomes zero. This state corresponds to a state in which post injection is substantially stopped. If the turbocharger 5 is over-rotated in this state, the determination result in step S25 is “Yes”, and the processing from step S26 described later is performed.

  On the other hand, when it is determined in step S31 that the turbo rotation speed is less than the first predetermined value (step S31: Yes), the process proceeds to step S32. In this case, since the turbocharger 5 has not been over-rotated, in step S32, the ECU 60 stops the post-injection amount reduction control and resumes the post-injection return control for regenerating the DPF regeneration. Execute. In this case, the ECU 60 returns the post-injection so that unburned components are not discharged to the outside in consideration of the combustion state and exhaust state of the engine E. Next, in step S33, the ECU 60 resumes post injection F / B control for DPF regeneration.

On the other hand, as a result of the determination in step S25, when it is determined that the post injection amount is 0 and the turbo rotation speed is equal to or greater than the second predetermined value (step S25: Yes), the process proceeds to step S26. In this case, even if the post-injection amount is reduced to 0, the turbocharger 5 is still over-rotating. Therefore, in step S26, the ECU 60 controls the fuel injection valve 20 of the engine E to In order to reduce the rotational speed, main injection amount reduction control for reducing the main injection amount is executed. In one example, the ECU 60 reduces the main injection amount by a predetermined amount. In another example, the ECU 60 reduces the main injection amount according to the degree to which the turbo rotation speed exceeds the second predetermined value.
As described above, since the ratio between the main injection amount and the after injection amount is fixed to a predetermined value according to the operating state, the ECU 60 simultaneously reduces the main injection amount by the main injection amount reduction control. The after-injection amount is also reduced according to this predetermined ratio.

  Here, in the situation where the after injection amount is reduced, the post injection is stopped. However, even if the post injection is stopped in this way, the DPF regeneration can be continued by the after injection. That is, since unburned fuel has already accumulated in the DPF 46 due to the fuel injected by the previous post injection, the DPF regeneration can be continued by the after injection even if the post injection is stopped. Therefore, in this embodiment, after post injection is stopped, DPF regeneration is performed by after injection. Specifically, the ECU 60 performs after-injection with an injection amount that can appropriately perform DPF regeneration (as described above, this after-injection amount is determined according to the ratio with the main injection amount), and so on. The amount of after-sales injection is reduced as the main injection amount is reduced.

  Next, at step 27, the ECU 60 suppresses the increase in the turbo rotational speed due to the supercharging pressure F / B control, that is, suppresses the contradiction between the supercharging pressure F / B control and the turbo overspeed prevention control. Supply pressure F / B control is stopped.

  Next, in step S28, the ECU 60 determines whether or not the rotational speed (turbo rotational speed) of the compressor 5a of the turbocharger 5 detected by the turbo rotational speed sensor 103 is less than a second predetermined value. As a result, if it is not determined that the turbo rotational speed is less than the second predetermined value (step S28: No), that is, if the turbo rotational speed is greater than or equal to the second predetermined value, the process returns to step S26, and the ECU 60 Then, the main injection amount reduction control is executed again to further reduce the main injection amount and further reduce the after injection amount. And ECU60 continues the state which stopped the supercharging pressure F / B control in step S27.

  The ECU 60 repeats the processes in steps S26, S27, and S28, and gradually decreases the main injection amount and the after injection amount while comparing the turbo rotation speed with the second predetermined value. As a result, the after injection amount falls below the lower limit value of the injection amount at which DPF regeneration can be appropriately performed, so that DPF regeneration is substantially stopped (however, the DPF regeneration flag remains on). is there). Thereafter, if the turbo rotation speed is equal to or greater than the second predetermined value, the ECU 60 further reduces the main injection amount and the after injection amount. When the main injection amount and the after injection amount are reduced in this way, the after injection amount becomes 0, but at this time, the main injection amount reduction control is substantially stopped.

  On the other hand, when it is determined in step S28 that the turbo rotation speed is less than the second predetermined value (step S28: Yes), the process proceeds to step S29. In this case, since the turbocharger 5 has not been over-rotated, in step S29, the ECU 60 stops the main injection amount reduction control and injects an amount of fuel corresponding to the accelerator opening, the engine speed, and the like. Main injection return control is executed to resume normal main injection. In this case, the ECU 60 returns the main injection after a lapse of time such that the passenger does not feel a change in torque or sound. Further, the ECU 60 also returns after injection as the main injection returns. Next, in step S30, the ECU 60 restarts the supercharging pressure F / B control for setting the actual supercharging pressure to the target supercharging pressure corresponding to the operating state of the engine E.

  Subsequently, it progresses to step S31 and the process after step S31 similar to the above is performed. Here, the process after step S31 is demonstrated easily. After the main injection return control and the supercharging pressure F / B control are resumed (steps S29 and S30), when it is determined that the turbo rotation speed is less than the first predetermined value (step S31: Yes), the ECU 60 Then, post-injection return control for resuming post-injection for DPF regeneration is executed (step S32), and thereafter post-injection F / B control for DPF regeneration is resumed (step S33).

<Effect>
Next, functions and effects of the engine control apparatus according to the embodiment of the present invention will be described.

According to the present embodiment, when the turbocharger 5 over-rotates during DPF regeneration, the post-injection amount for DPF regeneration is reduced, and post-injection is appropriately maintained without stopping post-injection. Therefore, it is possible to prevent excessive rotation of the turbocharger 5 while continuing DPF regeneration. In other words, it is possible to prevent over-rotation of the turbocharger 5 while continuing DPF regeneration while achieving both prevention of over-rotation of the turbocharger 5 and DPF regeneration.
In particular, according to the present embodiment, when the turbocharger 5 is excessively rotated during DPF regeneration, the number of post-injection stages (the number of times fuel is injected as post-injection) is reduced. The post injection amount can be appropriately reduced so as to reduce the turbo rotational speed.

Further, according to the present embodiment, when the post-injection amount is reduced and the turbocharger 5 is not over-rotated, depending on the post-injection amount reduction, the turbo-supercharger 5 can be prevented from over-rotating. Since the post-injection is stopped on the assumption that there is no such thing, the highest priority can be given to preventing the turbocharger 5 from over-rotating.
Furthermore, according to the present embodiment, the main injection amount is reduced after the post injection is stopped, so that it is possible to appropriately prevent the turbocharger 5 from over-rotating even after the post injection is stopped.
In particular, in this embodiment, since the after injection amount is further reduced as the main injection amount is reduced, it is possible to effectively prevent the turbocharger 5 from over-rotating. In this case, since the after injection amount is reduced from the injection amount at which the DPF regeneration can be appropriately performed, the DPF regeneration is continued by the after injection even after the post injection is stopped as described above. Can do.
In the present embodiment, DPF regeneration is substantially performed when excessive rotation of the turbocharger 5 is not eliminated even if the after-injection amount is reduced to the lower limit value of the injection amount that can appropriately perform DPF regeneration. Therefore, the after-injection amount can be further reduced from here, and the highest priority can be given to preventing the turbocharger 5 from over-rotating.

  Further, according to the present embodiment, when the turbo turbocharger 5 has been over-resolved due to a reduction in the fuel injection amount, the control for returning the main injection is performed, and the control for returning the post injection is performed after this control. Therefore, since the main injection and the post injection are returned in this order without returning the main injection and the post injection at the same time, it is possible to appropriately suppress the torque fluctuation and the sound change accompanying the return of the fuel injection.

1 intake passage 5 turbocharger 5a compressor 5b turbine 5c flap 20 fuel injection valve 41 exhaust passage 43 high pressure EGR device 45 DOC
46 DPF
48 Low pressure EGR device 60 ECU
200 engine system E engine

Claims (7)

An engine control device,
A turbocharger comprising a turbine provided in an exhaust passage and a compressor provided in an intake passage, and driving the compressor by rotating the turbine with exhaust gas to supercharge intake air;
A DPF that is provided in the exhaust passage and collects particulate matter in the exhaust gas;
DPF regeneration control means for performing DPF regeneration by controlling post-injection for injecting fuel after main injection to remove particulate matter deposited on the DPF;
While the DPF regeneration control means is executing the DPF regeneration, when the rotation speed of the turbocharger becomes equal to or higher than a first predetermined value, the post injection controlled by the DPF regeneration control means is performed. An injection amount reduction control means for reducing the fuel injection amount;
An engine control device comprising: The DPF regeneration control means executes the post injection by injecting fuel in multiple stages,
2. The engine control device according to claim 1, wherein the injection amount reduction control means reduces the number of stages of the post injection so as to reduce the fuel injection amount of the post injection. 3.   The said injection amount reduction | decrease control means stops the said post injection, when the rotation speed of the said turbocharger does not become less than 2nd predetermined value even if it reduces the fuel injection amount of the said post injection. Or the control apparatus of the engine of 2.   The engine control device according to claim 3, wherein the injection amount reduction control means reduces the fuel injection amount of the main injection after stopping the post injection. The DPF regeneration control means performs the DPF regeneration by further controlling after injection that injects fuel between the main injection and the post injection in addition to the post injection,
5. The engine according to claim 4, wherein the injection amount reduction control means further reduces the fuel injection quantity of the after injection controlled by the DPF regeneration control means in accordance with the reduction of the fuel injection quantity of the main injection. Control device.   The DPF regeneration control means is provided when the number of revolutions of the turbocharger does not become less than the second predetermined value even when the injection quantity reduction control means reduces the fuel injection quantity of the after injection to a predetermined quantity. The engine control device according to claim 5, wherein control of the after-injection for the DPF regeneration is stopped.   When the number of revolutions of the turbocharger becomes less than the second predetermined value due to the reduction of the fuel injection amount by the injection amount reduction control means, a control for returning the main injection is performed. The engine control apparatus according to any one of claims 4 to 6, further comprising return control means for performing control for returning injection.

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