JP2016070141A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly suppress vibration generated in a vehicle by rapidly decreasing an engine speed using exhaust pressure during engine stoppage.SOLUTION: An ECU 60 as an engine control device performs control to increase the engine speed and also performs control to fully close a flap 5c of a turbosupercharger 5 to increase the exhaust pressure that is pressure inside an exhaust passage 41 of an engine E when an engine stop request is issued.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device that executes engine stop control.

  Conventionally, it is known that when the engine speed is gradually reduced when the engine is stopped, the engine and its mount resonate and vibrations may occur in the vehicle. Specifically, the frequency range (resonance frequency range) in which such resonance occurs is in the low speed range, and vibration may occur when passing through this resonant frequency range when the engine speed decreases. is there.

  For example, Patent Document 1 proposes a technique for suppressing such vibration when the engine is stopped. Patent Document 1 proposes a technique in which when the engine stop condition is satisfied, the engine speed is first increased, the throttle valve is then operated in the closing direction, and then the engine is stopped. In this way, the amount of intake air per cycle is reduced to reduce work changes during the compression and expansion strokes of the engine, thereby suppressing engine rotation fluctuations and suppressing vibrations when the engine is stopped. ing.

Japanese Patent Laid-Open No. 2000-240483

  In the technique described in Patent Document 1 described above, a negative pressure is generated in the intake passage by operating the throttle valve in the closing direction after increasing the engine speed, and the engine speed is generated using this negative pressure. However, in this method, it takes time to generate a sufficient negative pressure, and it takes time to reduce the engine speed to zero. For this reason, it takes a long time to stay in the resonance frequency region when the engine speed decreases, and vibrations cannot be suppressed appropriately.

  The present invention has been made to solve the above-described problems of the prior art. When the engine is stopped, the engine rotation speed is quickly reduced by using the exhaust pressure, so that the vibration generated in the vehicle can be appropriately reduced. An object of the present invention is to provide an engine control device that can be suppressed to a low level.

In order to achieve the above object, the present invention provides an engine control device, an engine speed increase control means for performing control to increase the engine speed when an engine stop request is issued, and engine stop Exhaust pressure increase control means for performing control to increase the exhaust pressure that is the pressure in the exhaust passage of the engine when a request is issued.
In the present invention configured as described above, when the engine stop request is made, the control for increasing the engine speed and the control for increasing the exhaust pressure which is the pressure in the exhaust passage are performed. The exhaust pressure can be effectively increased by the engine whose exhaust capacity is increased by the increase. Therefore, this exhaust pressure increases the resistance that acts when the piston of the engine performs the ascending operation (that is, the compression stroke and the exhaust stroke), so that the engine speed can be effectively reduced. Therefore, according to the present invention, it is possible to reduce the time spent in the resonance frequency region when the engine speed is reduced, and it is possible to appropriately suppress the vibration generated in the vehicle when the engine is stopped.

In the present invention, preferably, the engine is provided with a turbocharger having a movable flap capable of adjusting a supercharging pressure, and the exhaust pressure increase control means controls the flap of the turbocharger to be fully closed. Then, the exhaust pressure is increased.
In the present invention configured as described above, when the engine is requested to stop, the flap of the turbocharger is fully closed and the exhaust gas passing through the turbine of the turbocharger is throttled to appropriately increase the exhaust pressure. be able to.

In the present invention, preferably, the exhaust pressure increase control means increases the exhaust pressure so that a predetermined exhaust pressure is secured when the engine speed increases to the target speed by the engine speed increase control means. Take control.
In the present invention configured as described above, a predetermined exhaust pressure is secured when the engine speed rises to the target speed, so that the engine speed is calculated from the target speed using this exhaust pressure. It can be effectively reduced.

In the present invention, preferably, the engine is provided with an alternator that generates electric power by the driving force of the engine, and further includes alternator control means for performing control to increase the load of the alternator when an engine stop request is issued.
In the present invention configured as described above, the load applied to the engine is increased by increasing the load of the alternator at the time of an engine stop request, so that the engine speed can be effectively reduced. Therefore, it is possible to further reduce the time spent in the resonance frequency region when the engine speed is reduced, and to effectively suppress vibration generated in the vehicle when the engine is stopped.

In the present invention, preferably, the alternator control means stops the operation of the alternator at the timing when the engine stop request is issued, and starts the operation of the alternator after a predetermined time has elapsed from the timing when the engine stop request is issued, Increase alternator load.
In the present invention configured as described above, the operation of the alternator is temporarily stopped at the timing when the engine stop request is issued, and the operation of the alternator is started after a predetermined time has elapsed from this timing. Therefore, the generated power of the alternator is supplied. It is possible to prevent the battery voltage from rising rapidly.

In this invention, Preferably, it further has an air conditioner control means for performing control to increase the load of the air conditioner when an engine stop request is issued.
In the present invention configured as described above, when the engine stop request is made, the load of the air conditioner is increased and the load applied to the engine is increased. Therefore, the engine speed can be effectively reduced, and the engine speed is reduced. It is possible to further shorten the time for staying in the resonance frequency region at the time of the decrease of.

In the present invention, the engine is preferably provided with an exhaust shutter valve for adjusting the flow rate of the exhaust gas passing through the exhaust passage, and the exhaust pressure increase control means closes the exhaust shutter valve to increase the exhaust pressure.
In the present invention configured as above, the exhaust pressure can be appropriately increased by controlling the exhaust shutter valve to be closed and shut off the exhaust gas passing through the exhaust passage when an engine stop request is made.

Preferably, the present invention further includes an intake control valve control means for performing control to fully close the intake control valve that adjusts the flow rate of intake air that passes through the intake passage of the engine when an engine stop request is issued. The engine speed increase control means performs control to increase the engine speed so that the engine speed reaches the target speed after the intake control valve is fully closed by the intake control valve control means.
In the present invention configured as described above, when the engine stop request is made, the intake control valve is controlled to be fully closed, and the engine speed reaches the target speed after the intake control valve is fully closed. In addition, since the engine speed is controlled to increase, the engine in which the suction capacity (intake capacity) is increased by the increase in the engine speed, the engine is in the intake passage from the fully closed intake control valve to the engine. By sucking the gas, the negative pressure (intake manifold negative pressure) in the intake manifold of the engine can be quickly increased. Thereby, the amplitude of the vibration generated in the resonance frequency region can be reduced. In addition, since the resistance that acts when the piston of the engine performs the lowering operation (that is, the intake stroke and the expansion stroke) increases and the engine speed decreases more rapidly, the time for staying in the resonance frequency range when the engine speed decreases. Can be further shortened. As described above, according to the present invention, it is possible to more effectively suppress vibration generated in the vehicle when the engine is stopped.

In the present invention, preferably, the intake control valve control means sets the intake control valve to a fully closed position on the control that is not completely closed, and then further closes the intake control valve from the fully closed position on the control. The intake control valve is set to a mechanical fully closed position, which is a fully closed state.
In the present invention configured as described above, after the intake control valve is temporarily set to the fully closed position for control, the intake control valve is further closed from the fully closed position for control, and the mechanical fully closed position is set. Therefore, the intake manifold negative pressure can be effectively increased by blocking the flow of gas through the intake control valve while suppressing an excessive load on the intake control valve.

In the present invention, preferably, the engine is provided with an EGR device that includes an EGR passage that recirculates the exhaust gas in the exhaust passage to the intake passage and an EGR valve that adjusts the flow rate of the exhaust gas passing through the EGR passage. And an EGR valve control means for performing control to close the EGR valve of the EGR device when an engine stop request is issued.
In the present invention configured as described above, the EGR valve is closed when the engine stop request is made, so that the gas flow between the exhaust passage and the intake passage is interrupted to give the above-described intake manifold negative pressure, exhaust pressure, or the like. An influence (specifically, a decrease in intake manifold negative pressure or a decrease in exhaust pressure) can be suppressed.

In the present invention, the engine control device is preferably applied to an engine provided with an intake control valve on an intake passage upstream of an intercooler that cools intake air.
In the present invention configured as described above, since the intake control valve is provided on the upstream side of the intercooler, the engine and the intake control are compared with the configuration in which the intake control valve is provided on the downstream side of the intercooler. Since the volume of the passage between the valve and the valve is large, it is difficult to generate the intake manifold negative pressure sufficient to suppress the vibration by simply closing the intake control valve. Since the control to raise is performed, the vibration can be appropriately suppressed by the exhaust pressure. Specifically, according to the present invention, for reasons such as layout, even when the intake control valve is provided on the upstream side of the intercooler, the engine speed is reduced by the exhaust pressure and stays in the resonance frequency range. Since the time is shortened, it is possible to appropriately suppress vibration generated in the vehicle when the engine is stopped.

In the present invention, the engine control device is preferably applied to a diesel engine.
In the present invention configured as described above, since the engine is a diesel engine, combustion in the engine can be appropriately ensured even if the fuel injection amount is increased to increase the engine speed, for example.

  According to the engine control apparatus of the present invention, when the engine is stopped, the engine rotation speed is rapidly reduced using the exhaust pressure, so that the vibration generated in the vehicle can be appropriately suppressed.

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 a time chart in the engine stop control by embodiment of this invention. It is a flowchart which shows the engine stop 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 air pressure, the intake shutter valve 7 that adjusts the intake air flow rate that passes through, and the intake water that is passed through the intake manifold, for example, that is passed through the intake manifold. A water-cooled intercooler 8 for cooling, an electric water pump 9 for controlling the flow rate of the cooling water flowing through the intercooler 8, an intercooler 8 and the electric water pump 9 are connected, and cooling water is supplied between them. A cooling water passage 10 that is a circulation passage 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 is rotated by the output of the engine E to generate electric power. The alternator 26 charges the generated electric power to a battery (not shown in FIG. 1). In addition, the engine E is provided with an air conditioner compressor (not shown in FIG. 1) that is rotated by 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 on the upstream side of the turbine 5 b of the turbocharger 5 and the intake shutter valve 7. It is generally determined by the intake pressure created by the opening and the opening 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 5a of the turbocharger 5 and the exhaust shutter valve. It is generally determined by the exhaust pressure produced by the opening of 49 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.

<Engine stop control>
Hereinafter, in the embodiment of the present invention, the control (engine stop control) performed by the ECU 60 when the engine E is stopped will be described.

  First, an overview of engine stop control according to an embodiment of the present invention will be described. In the present embodiment, the ECU 60, in other words, increases the negative pressure in the intake passage 1 (specifically, the negative pressure in the intake manifold) when a request to stop the engine E (engine stop request) is issued. In order to reduce the pressure in the intake manifold, control is performed to fully close the intake shutter valve 7, and after the intake shutter valve 7 is fully closed, the engine speed is set to a predetermined target speed (hereinafter referred to as "target target speed" as appropriate). The control is performed so as to increase the engine speed so as to reach the "number"), and then the fuel injection from the fuel injection valve 20 is stopped. Hereinafter, such control for increasing the negative pressure (intake manifold negative pressure) in the intake manifold is appropriately referred to as “intake manifold negative pressure increase control”.

Here, the reason for performing intake manifold negative pressure increase control in the present embodiment will be described. As described above, when the engine E stops, the vehicle vibrates (mount vibration) when passing through a resonance frequency range (for example, a low speed range near 300 rpm) while the engine speed gradually decreases. May occur. Since the amplitude of vibration generated in the resonance frequency range has a correlation with intake manifold negative pressure, specifically, the amplitude of vibration decreases when intake manifold negative pressure is large. Can be reduced, and vibration can be appropriately suppressed. Further, if the intake manifold negative pressure is quickly increased, the resistance that acts when the piston 23 of the engine E performs the lowering operation (that is, the intake stroke and the expansion stroke) increases, and the engine speed decreases rapidly. The time for staying in the resonance frequency region when the rotational speed is reduced is shortened, and vibration can be appropriately suppressed.
In a vehicle in which a throttle valve (corresponding to the intake shutter valve 7) is provided on the downstream side of the intercooler, the intake manifold negative pressure can be quickly generated by closing the throttle valve when the engine is requested to stop. In other words, in the configuration where the throttle valve is provided on the downstream side of the intercooler, the volume of the passage between the engine and the throttle valve is small, so by closing the throttle valve, the intake manifold negative pressure sufficient to suppress vibration is quickly generated. can do. However, in the engine system 200 according to the present embodiment, the intake shutter valve 7 is provided on the upstream side of the intercooler 8 (this is because the intercooler 8 is built in the intake manifold, and therefore the intake shutter valve 7 is provided on the downstream side of the intercooler 8. 7), because the volume of the passage between the engine E and the intake shutter valve 7 is large, simply closing the intake shutter valve 7 quickly generates intake manifold negative pressure sufficient to suppress vibration. Difficult to do.

Therefore, in the present embodiment, when the engine stop request is made, the intake shutter valve 7 is first fully closed, and then the engine speed is increased so that the intake manifold negative pressure is quickly increased. When the engine speed is increased in this way, the suction capacity (intake capacity) of the engine E is improved, so that the intake manifold negative pressure can be quickly increased. In this case, the ECU 60 increases the engine speed by increasing the fuel injection amount.
Since the engine E as a diesel engine is usually operated with excessive air, even if the intake shutter valve 7 is closed to reduce the amount of air and increase the fuel injection amount, the engine E can appropriately perform combustion. The engine speed can be increased. On the other hand, since the gasoline engine is basically operated at the stoichiometric air-fuel ratio, if the air amount is reduced and the fuel injection amount is increased in this way, the engine E cannot properly burn, The engine speed cannot be increased.

  Further, in the present embodiment, the ECU 60, in addition to the intake manifold negative pressure increase control for increasing the intake manifold negative pressure described above, in the exhaust passage 41 of the engine E in order to effectively decrease the engine speed when the engine is stopped. The control is performed to increase the exhaust pressure, which is the pressure (hereinafter referred to as “exhaust pressure increase control”). When the exhaust pressure is increased in this way, the resistance that acts when the piston 23 of the engine E performs the ascending operation (that is, the compression stroke and the exhaust stroke) increases, and the engine speed can be quickly reduced. Specifically, the ECU 60 increases the exhaust pressure by performing a control to fully close the flap 5c (see FIG. 2) of the turbocharger 5 when the engine stop request is made as the exhaust pressure increase control. In particular, when the flap 5c of the turbocharger 5 is fully closed in a state where the engine speed is increased by the intake manifold negative pressure increase control described above, the exhaust pressure is effectively increased.

  Further, the ECU 60 performs the high pressure EGR in order to cut off the gas flow between the exhaust passage 41 and the intake passage 1 when the intake manifold negative pressure increase control and the exhaust pressure increase control are executed at the time of the engine stop request. Control is performed to close the high pressure EGR valve 43b of the device 43 and the low pressure EGR valve 48c of the low pressure EGR device 48. In a situation where an engine stop request is issued, the engine E is operating in the high pressure EGR region R1 (see FIG. 3), the low pressure EGR valve 48c is already closed, and only the high pressure EGR valve 43b is open. The ECU 60 performs control to close the high pressure EGR valve 43b while maintaining the closed state of the low pressure EGR valve 48c.

  Furthermore, in this embodiment, the ECU 60 increases the load of the engine E in addition to the intake manifold negative pressure increase control and the exhaust pressure increase control described above in order to more effectively decrease the engine speed when the engine is stopped ( Hereinafter, it is referred to as “engine load increase control”). Specifically, the ECU 60 increases the load applied to the engine E by performing control to increase the load on the alternator 26 and control to increase the load on the air conditioner (air conditioning) at the time of an engine stop request. The engine speed should be reduced quickly.

  As described above, the ECU 60 corresponds to the “engine control device” in the present invention, and “engine speed increase control means”, “exhaust pressure increase control means”, “intake control valve control means” in the present invention, It functions as “alternator control means”, “air conditioner control means” and “EGR valve control means”.

  Next, a time chart in the engine stop control according to the embodiment of the present invention will be described with reference to FIG. FIG. 5 shows an example of a time chart when the engine stop control according to the embodiment of the present invention is executed.

  FIG. 5 shows time in the horizontal direction. In order from the top, the ignition signal, the pressure in the intake manifold (intake manifold pressure), the fuel injection signal supplied to the fuel injection valve 20, and the engine speed are increased. Command signal (engine speed increase command signal), engine speed, opening degree of intake shutter valve 7 (intake shutter valve opening degree), and opening degree of each of high pressure EGR valve 43b and low pressure EGR valve 48c The charging of the flap 5c of the turbocharger 5 (VGT opening), the exhaust pressure, the duty of the alternator 26, the control signal supplied to the alternator 26, and the generated power of the alternator 26 are charged. The voltage of the battery which supplies electric power to various auxiliary machines etc., the control signal of an air conditioner, and the drive signal of the compressor of an air conditioner are shown.

  First, at time t1, the ignition signal is switched from on to off (see graph G1), and an engine stop request is issued. At this time t1, the ECU 60 starts intake manifold negative pressure increase control. Specifically, the ECU 60 turns on the engine speed increase command signal (see graph G4) and gradually increases the target engine speed of the engine speed (see graph G51). In this case, the ECU 60 gradually increases the target rotational speed to a predetermined target rotational speed (for example, a rotational speed higher by about 75 to 100 rpm than the idle rotational speed). The ECU 60 increases the fuel injection signal in order to increase the fuel injection amount in accordance with the target torque increased by the feedback control based on the target rotational speed (see graph G3). As a result, the actual engine speed gradually increases (see graph G52). When some load in the vehicle decreases, the fuel injection amount may not be increased as the target rotational speed increases.

The ECU 60 also controls the intake shutter valve 7 as intake manifold negative pressure increase control. Specifically, at time t1, the ECU 60 decreases the target opening of the intake shutter valve 7 in a stepped manner so as to set the intake shutter valve 7 to a control fully closed position that is not a complete fully closed state ( (See graph G61). As a result, the actual opening of the intake shutter valve 7 is displaced to the closed side, and the intake shutter valve 7 is set to the fully closed position for control (see graph G62). Thereafter, the ECU 60 further closes the intake shutter valve 7 from the fully closed position in the control, and sets the intake shutter valve 7 to the mechanical fully closed position, which is a complete fully closed state (see graph G62). In this case, the ECU 60 controls the actuator that drives the intake shutter valve 7 so as to press the intake shutter valve 7 to the mechanically closed position for a predetermined time.
In the present embodiment, in order to effectively increase the intake manifold negative pressure, the intake shutter valve 7 is set to a mechanical fully closed position that is further closed from the normally closed position for control. In the present embodiment, if the intake shutter valve 7 in the open state is moved all at once to the mechanical fully closed position, the intake shutter valve 7 is excessively loaded. The shutter valve 7 is once set to the fully closed position for control and then set to the mechanical fully closed position. In addition, when the intake shutter valve 7 is set to the mechanical fully closed position, a load is applied to the actuator that drives the intake shutter valve 7, so that the time for setting the intake shutter valve 7 to the mechanical fully closed position is a predetermined time. It is limited to.

  As described above, when the engine speed and the intake shutter valve 7 are controlled by the intake manifold negative pressure increase control, the intake manifold pressure decreases (see graph G2), in other words, the intake manifold negative pressure increases.

Further, at time t1, the ECU 60 keeps the low pressure EGR valve 48c fully closed (see graph G72), fully closes the high pressure EGR valve 43b (see graph G71), and opens the VGT of the turbocharger 5. Exhaust pressure increase control is performed to fully close the engine (see graph G8). When the VGT opening is fully closed in this way, the exhaust pressure increases (see graph G9).
Since the high pressure EGR valve 43b and the flap 5c of the turbocharger 5 are controlled objects related to the volume, it is preferable to start the control promptly after the engine stop request is issued from the viewpoint of control responsiveness. . In particular, for the flap 5c of the turbocharger 5, a desired exhaust pressure (specifically, a pressure that can effectively reduce the engine speed) when the engine speed reaches the target rotational speed. It is desirable to execute the control so that

Further, at time t1, the ECU 60 turns on the air conditioner control signal (see graph G14) and starts driving the compressor of the air conditioner (see graph G15), thereby executing engine load increase control. Further, at time t1, the ECU 60 sets the duty of the alternator 26 to 0% (graph G10) and turns on a control signal for turning off the alternator 26 (see graph G11). In this embodiment, when the battery is fully charged, the alternator 26 is temporarily turned off when an engine stop request is issued in order to prevent the battery voltage from rapidly rising due to the generated power of the alternator 26. Thus, the battery voltage (battery capacity) is reduced by consuming the battery power (see graph G13).
As for the air conditioner, the problem that occurs when the alternator 26 is immediately turned on as described above does not occur, and since it takes time until the pressure increases after the compressor is operated, an engine stop request is issued. It is better to turn on promptly at the timing.

Thereafter, at time t2 after the elapse of the first predetermined time from time t1 when the engine stop request is issued, the ECU 60 turns off the engine speed increase command signal (see graph G4), and sets the target engine speed of the engine speed. The speed is gradually reduced to the idling speed (see graph G51). Then, immediately after time t2, specifically, at time t3 after the elapse of the second predetermined time from time t1, the ECU 60 sets the fuel injection signal to 0 and stops fuel injection (see graph G3). As a result, the actual engine speed decreases after time t3 (see graph G52).
The first predetermined time is set to a time required for the actual engine speed to reach the above-described target target speed determined by a predetermined arithmetic expression or experiment. Further, the second predetermined time is set to a time slightly longer than the first predetermined time in order to maintain the engine speed until the fuel injection is stopped (it may be set to the same time as the first predetermined time). ). For example, the second predetermined time is set to 0.5 seconds.

  Further, at time t3 after the elapse of the third predetermined time from time t1, the ECU 60 increases the duty of the alternator 26 to near 100% (graph G10) and turns on the control signal for turning on the alternator 26. By doing so (see graph G12), engine load increase control is executed. Even if the battery is in a severe state (for example, full charge) after the third predetermined time has elapsed, even if the alternator 26 is driven, the third predetermined time is such as a sudden rise in battery voltage. The time is set so that no problem occurs. In addition, the third predetermined time is set to a time before the engine speed decreases to the resonance frequency range. This is because even if the alternator 26 is turned on when the engine speed is in the vicinity of the resonance frequency range or below the resonance frequency range, the engine speed is reduced by the load applied by the alternator 26 so that the resonance frequency range is obtained. This is because the effect of shortening the staying time is reduced.

  According to the control described above (intake manifold negative pressure increase control, exhaust pressure increase control and engine load increase control), the intake manifold pressure decreases (see graph G2), in other words, the intake manifold negative pressure increases and the exhaust pressure increases (graph). As the engine load increases, the engine speed decreases rapidly (see graph G52). For this reason, the time for staying in the resonance frequency region when the engine speed decreases is shortened. In addition, the amplitude of vibration is reduced by the sufficiently secured intake manifold negative pressure. Therefore, according to the present embodiment, vibration generated in the vehicle is effectively suppressed.

  Next, the overall flow of the engine stop control according to the embodiment of the present invention will be specifically described with reference to FIG. FIG. 6 is a flowchart showing an engine stop control flow according to the embodiment of the present invention. This engine stop control flow is repeatedly executed by the ECU 60 at a predetermined cycle.

  First, in step S21, the ECU 60 reads a flag indicating an engine stop request (engine stop request flag). This engine stop request flag is set to ON at the time of key-off, ignition-off, idling stop, or the like.

  Next, in step S22, the ECU 60 determines whether an engine stop request has been issued based on the engine stop request flag read in step S21. As a result, if it is not determined that an engine stop request has been issued (step S22: No), that is, if the engine stop request flag is off, the process ends. In this case, the ECU 60 does not execute the engine stop control in the present embodiment.

On the other hand, if it is determined that an engine stop request has been issued (step S22: Yes), that is, if the engine stop request flag is on, the process proceeds to step S23. In step S23, the ECU 60 (1) fully closes the intake shutter valve 7, (2) turns on the engine speed increase command, and (3) fully closes the flap 5c of the turbocharger 5 (sets the VGT opening degree). (4) The high pressure EGR valve 43b is fully closed (the low pressure EGR valve 48c is kept fully closed), (5) the alternator 26 is turned off, and (6) the air conditioner is turned on. That is, the ECU 60 executes intake manifold negative pressure increase control, exhaust pressure increase control, and engine load increase control.
More specifically, the ECU 60 sets the intake shutter valve 7 to a fully closed position on the control that is not in the fully closed state as the control of (1), and then further takes the intake shutter from the fully closed position on the control. The valve 7 is closed, and the intake shutter valve 7 is set to a mechanical fully closed position, which is a fully closed state, for a predetermined time. In addition, as the control of (2), the ECU 60 turns on the engine speed increase command and gently reaches the engine speed to the target speed (for example, about 75 to 100 rpm higher than the idle speed). Therefore, the fuel injection amount injected from the fuel injection valve 20 is increased.

  Next, in step S24, the ECU 60 determines whether or not a first predetermined time has elapsed since the engine stop request was issued. When it is determined that the first predetermined time has elapsed (step S24: Yes), the process proceeds to step S25, where the ECU 60 switches the engine speed increase command from on to off and decreases the target engine speed of the engine speed ( For example, the target rotational speed is reduced to the idle rotational speed). On the other hand, when it is not determined that the first predetermined time has elapsed (step S24: No), the process returns to step S24. That is, the determination in step S24 is repeated until the first predetermined time has elapsed.

Next, in step S26, the ECU 60 determines whether or not a second predetermined time has elapsed since the engine stop request was issued. When it is determined that the second predetermined time has elapsed (step S26: Yes), the process proceeds to step S27, and the ECU 60 stops fuel injection from the fuel injection valve 20. On the other hand, when it is not determined that the second predetermined time has elapsed (step S26: No), the process returns to step S26. That is, the determination in step S26 is repeated until the second predetermined time has elapsed.
Note that the same time as the first predetermined time may be applied as the second predetermined time. In this case, when the first predetermined time elapses after the engine stop request is issued, the engine speed increase command is issued. The fuel injection may be stopped while turning off.

Next, in step S28, the ECU 60 determines whether or not a third predetermined time has elapsed since the engine stop request was issued. When it is determined that the third predetermined time has elapsed (step S28: Yes), the process proceeds to step S29, and the ECU 60 switches the alternator 26 from off to on to execute engine load increase control. On the other hand, when it is not determined that the third predetermined time has elapsed (step S28: No), the process returns to step S28. That is, the determination in step S28 is repeated until the third predetermined time has elapsed.
As the third predetermined time, a time shorter than the first predetermined time or a time shorter than the second predetermined time may be applied. In that case, before turning off the engine speed increase command, or The alternator 26 may be set on before stopping the fuel injection.

<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 engine stop request is made, the intake shutter negative valve 7 is fully closed and the intake manifold negative pressure increase control for increasing the engine speed is executed, so that the intake manifold negative pressure can be quickly increased. As a result, the amplitude of vibration generated in the resonance frequency range can be reduced, and the engine speed can be quickly reduced to shorten the time spent in the resonance frequency range. Therefore, it is possible to appropriately suppress vibration generated in the vehicle when the engine is stopped.
In this case, in the present embodiment, after the intake shutter valve 7 is once set to the fully closed position on the control, the intake shutter valve 7 is further closed from the fully closed position on the control to the mechanical fully closed position. Since the intake shutter valve 7 is set, it is possible to effectively increase the intake manifold negative pressure by blocking the gas flow through the intake shutter valve 7 while suppressing an excessive load on the intake shutter valve 7. .

  In addition, according to the present embodiment, when the engine stop request is made, in addition to the intake manifold negative pressure increase control described above, the exhaust pressure increase control for fully closing the flap 5c of the turbocharger 5 is executed. The engine speed can be effectively reduced by the exhaust pressure generated inside. Therefore, it is possible to further shorten the time spent in the resonance frequency region when the engine speed is reduced.

In addition, according to the present embodiment, in addition to the intake manifold negative pressure increase control and the exhaust pressure increase control described above, engine load increase control for increasing the load on the alternator 26 and increasing the load on the air conditioner when engine stop is requested. Since it performs, an engine speed can be reduced more effectively. Therefore, it is possible to greatly reduce the time spent in the resonance frequency region when the engine speed is reduced.
In this case, in the present embodiment, the alternator 26 is temporarily turned off at the timing when an engine stop request is issued, and the alternator 26 is turned on after a predetermined time has elapsed from this timing. It can be prevented from rising.

<Modification>
Next, a modification of the above-described embodiment will be described.

  In the above-described embodiment, the example in which the present invention is applied to the intake shutter valve 7 has been described. However, the present invention is also applicable to a general throttle valve. Such an intake shutter valve 7 and a throttle valve are included in the “intake control valve” in the present invention.

  In the above-described embodiment, control for fully closing the flap 5c of the turbocharger 5 is shown as exhaust pressure increase control, but the exhaust shutter valve 49 is used instead of or in addition to the control. The control for fully closing may be performed as exhaust pressure increase control. Even when the exhaust shutter valve 49 is fully closed at the time of an engine stop request, the exhaust pressure can be increased to decrease the engine speed. However, since the distance from the exhaust shutter valve 49 to the engine E is longer than the distance from the flap 5c of the turbocharger 5 to the engine E, and the exhaust gas leaks from the exhaust shutter valve 49, the exhaust shutter valve 49 The control for fully closing the exhaust gas is less effective for increasing the exhaust pressure than the control for fully closing the flap 5c of the turbocharger 5.

  In the above-described embodiment, since the generated power of the alternator 26 is supplied to the battery, the alternator 26 is not immediately turned on at the time of an engine stop request from the viewpoint of preventing a sudden increase in battery voltage. The alternator 26 is turned on after the third predetermined time has elapsed since the engine stop request). However, when the power generated by the alternator 26 is supplied to the capacitor, such a problem with the battery does not occur. The alternator 26 may be turned on immediately when a stop request is made. However, in order to obtain an effect of shortening the time spent in the resonance frequency range by reducing the engine speed by the load of the alternator 26, the alternator 26 must be operated when the engine speed is at least before the resonance frequency range. Since it is only necessary to be on, in the configuration in which the generated power of the alternator 26 is supplied to the capacitor, the alternator 26 may not be immediately turned on when the engine is requested to stop.

  Further, in the above-described embodiment, when the first predetermined time has elapsed after the engine stop request is issued, the engine speed increase command is switched from on to off, and the target engine speed is decreased. (See steps S24 and S25 in FIG. 6), the engine speed increases when the target engine speed or the actual engine speed reaches the target target engine speed without using the first predetermined time. The command may be switched from on to off to reduce the target engine speed of the engine speed. And after this or at this point, the fuel injection may be stopped,

DESCRIPTION OF SYMBOLS 1 Intake passage 5 Turbocharger 5a Compressor 5b Turbine 5c Flap 7 Intake shutter valve 8 Intercooler 20 Fuel injection valve 26 Alternator 41 Exhaust passage 43 High pressure EGR device 43b High pressure EGR valve 48 Low pressure EGR device 48c Low pressure EGR valve 49 Exhaust shutter valve 49 60 ECU
200 engine system E engine

Claims (12)

An engine control device,
An engine speed increase control means for performing control to increase the engine speed when an engine stop request is issued;
Exhaust pressure increase control means for performing control to increase the exhaust pressure that is the pressure in the exhaust passage of the engine when the engine stop request is issued;
An engine control device comprising: The engine is provided with a turbocharger having a movable flap capable of adjusting a supercharging pressure,
The engine control apparatus according to claim 1, wherein the exhaust pressure increase control means controls the flap of the turbocharger to be fully closed to increase the exhaust pressure.   The exhaust pressure increase control means performs control to increase the exhaust pressure so that a predetermined exhaust pressure is secured when the engine speed increases to a target speed by the engine speed increase control means. The engine control device according to claim 1 or 2. The engine is provided with an alternator that generates electric power by the driving force of the engine,
The engine control device according to any one of claims 1 to 3, further comprising alternator control means for performing control to increase a load of the alternator when the engine stop request is issued.   The alternator control means stops the operation of the alternator at the timing when the engine stop request is issued, and starts the alternator after a predetermined time has elapsed from the timing when the engine stop request is issued. The engine control device according to claim 4, wherein the load of the engine is increased.   The engine control device according to any one of claims 1 to 5, further comprising air conditioner control means for performing control to increase an air conditioner load when the engine stop request is issued. The engine is provided with an exhaust shutter valve for adjusting the flow rate of exhaust gas passing through the exhaust passage,
The engine control device according to any one of claims 1 to 6, wherein the exhaust pressure increase control means closes the exhaust shutter valve to increase the exhaust pressure. An intake control valve control means for performing control to fully close an intake control valve that adjusts the flow rate of intake air that passes through the intake passage of the engine when the engine stop request is issued;
The engine speed increase control means performs control to increase the engine speed so that the engine speed reaches a target speed after the intake control valve is fully closed by the intake control valve control means. The engine control device according to any one of claims 1 to 7.   The intake control valve control means sets the intake control valve to a fully closed position on the control that is not in a completely fully closed state, and further closes the intake control valve from the fully closed position on the control. The engine control device according to claim 8, wherein the intake control valve is set at a mechanical fully closed position in a fully closed state. The engine is provided with an EGR device that includes an EGR passage that recirculates exhaust gas in the exhaust passage to the intake passage, and an EGR valve that adjusts the flow rate of the exhaust gas that passes through the EGR passage.
The engine control device according to any one of claims 1 to 9, further comprising EGR valve control means for performing control to close an EGR valve of the EGR device when the engine stop request is issued.   11. The engine control device according to claim 1, wherein the engine control device is applied to an engine in which the intake control valve is provided on an intake passage upstream of an intercooler that cools intake air. Control device.   The engine control apparatus according to any one of claims 1 to 11, wherein the engine control apparatus is applied to a diesel engine.

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