JP2013119782A - Control device for engine with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain abnormal noise caused from pressure pulsation generated at the nozzle vane rear end in a control device for an engine with a variable nozzle vane type supercharger.SOLUTION: When the engine speed Ne is the same as or higher than a predetermined determination value, the nozzle vane opening (VN opening) is maintained in an open state from the point wherein the accelerator is turned off so that the engine speed Ne is switched from raising to lowering ([dNe/dt>0] to [dNe/dt<0]) until a predetermined set time period is passed. According to the control, since the flow rate of the exhaust gas passing through the nozzle vane is made smaller, the quasi-steady state of the gas flow rate generating Rankine vortex is avoided so that generation of the abnormal noise is restrained.

Description

  The present invention relates to a control device for an engine with a supercharger, and more particularly to an engine control device provided with a variable nozzle vane supercharger.

  2. Description of the Related Art An internal combustion engine (hereinafter also referred to as an engine) mounted on a vehicle is equipped with a supercharger (hereinafter also referred to as a turbocharger) that uses exhaust energy. In general, a turbocharger connects a turbine wheel that is rotated by exhaust gas flowing through an engine exhaust passage, a compressor impeller that forcibly feeds air in the intake passage to a combustion chamber of the engine, and the turbine wheel and the compressor impeller. Connecting shaft. In the turbocharger having such a structure, the turbine wheel disposed in the exhaust passage is rotated by the energy of the exhaust gas, and the compressor impeller disposed in the intake passage is rotated accordingly, whereby the intake air is supercharged, and the engine Supercharged air is forced into the combustion chamber of each cylinder.

  As a turbocharger mounted on a vehicle, a variable nozzle vane type turbocharger capable of adjusting a supercharging pressure with respect to exhaust energy is known.

  The variable nozzle vane turbocharger is, for example, a variable nozzle vane mechanism that is disposed in an exhaust gas flow path of a turbine housing and has a plurality of nozzle vanes (also referred to as movable vanes) that can change the flow area of the exhaust gas flow path, An actuator (for example, a motor-type actuator) that applies displacement (rotation) to the nozzle vanes is provided, and the nozzle vane opening degree (hereinafter, also referred to as VN opening degree) of the variable nozzle vane mechanism is changed so that the nozzle vanes are adjacent to each other. The flow velocity of the exhaust gas introduced toward the turbine wheel is adjusted by changing the flow passage cross-sectional area (throat cross-sectional area) (see, for example, Patent Documents 1 and 2). By adjusting the exhaust gas flow rate in this manner, the rotational speed of the turbine wheel and the compressor impeller can be adjusted, and the pressure of the air introduced into the combustion chamber of the engine can be adjusted. For example, it is possible to improve torque response that leads to acceleration, output, fuel consumption (fuel consumption rate), freedom of conformity to emissions, and the like.

JP 2009-299505 A JP 2003-129853 A JP 2009-281144 A

  By the way, in an engine equipped with a variable nozzle vane turbocharger, when switching from acceleration (engine acceleration) to deceleration, the opening degree of the nozzle vane (VN opening degree) is ensured in order to ensure re-acceleration after that (after deceleration). ) Is controlled to the closed side to prevent the turbocharger supercharging pressure from dropping. For this reason, when switching from acceleration to deceleration, the flow rate of the exhaust gas passing through the nozzle vanes (flow velocity = [flow rate] / [flow passage cross-sectional area between nozzle vanes]) may be quasi-steady. When the flow rate of the exhaust gas becomes quasi-stationary at a certain level or more, an exhaust gas vortex (Rankine vortex) is generated in the downstream of the nozzle vane.

  Here, it is known that Rankine vortices are generated at the rear end of the nozzle vane and become pressure pulsations having a frequency component proportional to the flow rate of the exhaust gas. In other words, the vortex shedding frequency f of the Rankine vortex satisfies the relationship of the theoretical formula [f = St * U / D St: Strouhal number (constant), U: flow velocity, D: wake width]. The pressure pulsation caused by the Rankine vortex has a frequency component proportional to the flow rate of the exhaust gas passing through the nozzle vane. And when the frequency of such pressure pulsations is amplified by the spatial resonance of the space in the turbine housing and the space in the exhaust pipe (turbine housing to exhaust gas passage of the catalyst), the frequency from the exhaust port through the vehicle exhaust pipe It becomes a discharge sound, and the abnormal noise becomes a problem.

  The present invention has been made in consideration of such a situation, and in a control device for an engine with a variable nozzle vane type supercharger, suppressing the generation of abnormal noise when switching from acceleration (engine acceleration) to deceleration. The purpose is to realize a control capable of.

  The present invention has a compressor impeller provided in an intake passage, a turbine wheel provided in an exhaust passage, and a plurality of nozzle vanes provided on the outer peripheral side of the turbine wheel, and changes the opening degree of the nozzle vane. And a supercharged engine control device provided with a supercharger equipped with a variable nozzle vane mechanism that adjusts the flow of exhaust gas by means of such a supercharger engine control device. When the number is equal to or greater than a predetermined determination value, the opening degree of the nozzle vane is kept open until a predetermined set time elapses after the accelerator is turned off and the engine speed is switched from increasing to decreasing. This is a technical feature.

  As a specific configuration of the present invention, when the engine speed is equal to or higher than a predetermined determination value and the change rate of the engine speed is equal to or higher than the predetermined determination value, the accelerator is turned off and the engine speed is increased. A configuration in which the opening degree of the nozzle vane is maintained in an open state until a predetermined set time elapses from the time point when switching to the lowering is performed.

  In the present invention, as a method of determining that the engine speed has switched from increasing to decreasing, for example, the engine speed changing rate (dNe / dt) is used, and the rate of change dNe / dt is [dNe / dt]. > 0] ⇒ [dNe / dt <0] can be cited as a method of determining that the engine speed has changed from increasing to decreasing.

  The operation of the present invention will be described below.

  As described above, the Rankine vortex is generated when the gas flow velocity of the exhaust gas passing through the nozzle vane becomes a quasi-stationary value of a certain value or more when switching from acceleration (engine acceleration) to deceleration. If the quasi-stationary state is avoided, the generation of abnormal noise can be suppressed. Focusing on this point, in the present invention, when the engine speed is equal to or higher than a predetermined determination value (when the engine speed is within the frequency band of spatial resonance described later), the engine speed increases. It is determined that the gas flow velocity of the exhaust gas that passes through the nozzle vane reaches a quasi-steady point when it switches to descending, and the nozzle vane is opened until a predetermined set time elapses after the engine speed is switched. Keep the degree open. By maintaining the nozzle vane opening in the open state in this way, the flow velocity of the exhaust gas passing through the nozzle vane is reduced, so that the quasi-steady state of the gas flow velocity at which Rankine vortex is generated can be avoided, and abnormal noise can be avoided. Occurrence can be suppressed.

  Here, in the variable nozzle vane turbocharger, abnormal noise does not always occur when switching from acceleration to deceleration, but abnormal noise occurs when a certain condition is satisfied. That is, as described above, Rankine vortex (pressure pulsation frequency) generated when the gas flow rate of the exhaust gas passing through the nozzle vane becomes quasi-stationary above a certain value is amplified by spatial resonance in the exhaust pipe or the like. Therefore, when the engine rotational speed (turbo rotational speed) does not enter the spatial resonance frequency band (see FIG. 11), the Rankine vortex pressure pulsation frequency is not amplified, Abnormal noise may not occur. The determination value for the engine speed is set in consideration of such points (frequency band of spatial resonance). Specifically, the engine speed (turbo speed) that falls within the above-described spatial resonance frequency band (see FIG. 11) is obtained by experiment / simulation calculation or the like, and the result (the engine that falls within the spatial resonance frequency band). The determination value is set based on the number of rotations).

  Then, by setting the condition that the engine speed is equal to or higher than a predetermined determination value in this way, the control for ensuring re-acceleration after deceleration is performed under the condition that no abnormal noise occurs (the engine speed is less than the determination value). (Control for setting the VN opening to the closing side) can be executed with priority.

  Here, in the present invention, the time for holding the nozzle vane opening in the open state (set time (time t2-t3 in FIG. 10)) is, for example, from the time when the engine speed is switched from rising to falling. The time required to pass through the loud noise region as shown in FIG. 11 is obtained by experiment / simulation calculation or the like, and set based on the result. Then, after such a set time (time for maintaining the opening degree of the nozzle vane in the open state) elapses, the opening degree of the nozzle vane is controlled to the closed side in order to ensure re-acceleration after deceleration.

  According to the present invention, when the engine speed is equal to or higher than the predetermined determination value, the opening of the nozzle vane is continued until the predetermined set time elapses after the accelerator is turned off and the engine speed is switched from rising to lowering. Since the degree is held in the open state, it is possible to suppress the generation of abnormal noise when switching from acceleration to deceleration.

It is a schematic structure figure showing an example of a diesel engine to which the present invention is applied. It is a longitudinal cross-sectional view which shows an example of the turbocharger with which an engine is equipped. It is the figure which looked at the variable nozzle vane mechanism from the outside of the turbocharger. FIG. 3 shows a state in which the nozzle vane is on the open side. It is the figure which looked at the variable nozzle vane mechanism from the inside of a turbocharger. FIG. 4 shows a state where the nozzle vane is on the open side. It is the figure which looked at the variable nozzle vane mechanism from the outside of the turbocharger. FIG. 5 shows a state in which the nozzle vane is on the closed side. It is the figure which looked at the variable nozzle vane mechanism from the inside of a turbocharger. FIG. 6 shows a state where the nozzle vane is on the closed side. It is a block diagram which shows the structure of control systems, such as ECU. It is a figure which shows typically the flow of the exhaust gas which passes a nozzle vane. It is a flowchart which shows an example of VN opening degree control which ECU performs. It is a timing chart which shows an example of VN opening degree control which ECU performs. It is a figure which shows the turbo rotation speed and the frequency band of spatial resonance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

-Engine-
A schematic configuration of an engine (internal combustion engine) to which the present invention is applied will be described with reference to FIG. FIG. 1 shows only the configuration of one cylinder of the engine.

  An engine 1 shown in FIG. 1 is an in-cylinder direct injection four-cylinder diesel engine, and a piston 1c that reciprocates in the vertical direction is provided in a cylinder block 1a constituting each cylinder. The piston 1c is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1c is converted into rotation of the crankshaft 15 by the connecting rod 16. The crankshaft 15 of the engine 1 is connected to a transmission (not shown), and can transmit power from the engine 1 to drive wheels (not shown) of the vehicle via the transmission.

  A signal rotor 17 is attached to the crankshaft 15. A plurality of protrusions (teeth) 17a... 17a are provided on the outer peripheral surface of the signal rotor 17 at equal angles. An engine speed sensor (crank position sensor) 25 is disposed near the side of the signal rotor 17. The engine speed sensor 25 is, for example, an electromagnetic pickup, and generates a pulsed signal (output pulse) corresponding to the protrusion 17a of the signal rotor 17 when the crankshaft 15 rotates.

  The cylinder block 1a of the engine 1 is provided with a water temperature sensor 21 that detects the engine cooling water temperature. A cylinder head 1b is provided at the upper end of the cylinder block 1a, and a combustion chamber 1d is formed between the cylinder head 1b and the piston 1c.

  An oil pan 18 for storing engine oil is provided below the cylinder block 1a of the engine 1. The engine oil stored in the oil pan 18 is pumped up by an oil pump through an oil strainer that removes foreign matters during operation of the engine 1 and further purified by an oil filter, and then the piston 1c, the crankshaft 15, and the connecting oil. It is supplied to the rod 16 and used for lubrication and cooling of each part.

  The cylinder head 1 b of the engine 1 is provided with an injector 2 for directly injecting fuel into the combustion chamber 1 d of the engine 1. A common rail (accumulation chamber) 3 is connected to the injector 2, and fuel in the common rail 3 is injected from the injector 2 into the combustion chamber 1 d while the injector 2 is open.

  The common rail 3 is provided with a rail pressure sensor 24 for detecting the pressure (rail pressure) of the high-pressure fuel in the common rail 3. A supply pump 4 that is a fuel pump is connected to the common rail 3.

  The supply pump 4 is driven by the rotational force of the crankshaft 15 of the engine 1. By driving the supply pump 4, fuel is supplied from the fuel tank 40 to the common rail 3, and the injector 2 is opened at a predetermined timing, whereby the fuel is injected into the combustion chamber 1 d of each cylinder of the engine 1. The injected fuel is combusted in the combustion chamber 1d and exhausted as exhaust gas. The valve opening timing (injection period) of the injector 2 is controlled by an ECU (Electronic Control Unit) 200 described later.

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 d of the engine 1. An intake valve 13 is provided between the intake passage 11 and the combustion chamber 1d. By opening and closing the intake valve 13, the intake passage 11 and the combustion chamber 1d are communicated or blocked.

  Further, an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1d. By opening and closing the exhaust valve 14, the exhaust passage 12 and the combustion chamber 1d are communicated or blocked. The opening / closing drive of the intake valve 13 and the exhaust valve 14 is performed by each rotation of the intake camshaft and the exhaust camshaft to which the rotation of the crankshaft 15 is transmitted.

  In the intake passage 11, an air cleaner (not shown), an air flow meter 22 for detecting an intake air amount (new air amount), a compressor impeller 112 of a turbocharger 100 to be described later, and the intake increased in temperature by supercharging in the turbocharger 100. An intercooler 7 for forcibly cooling air, an intake air temperature sensor 23, a throttle valve 6 and an intake manifold pressure sensor (supercharge pressure sensor) 28 for detecting the pressure (supercharge pressure) in the intake manifold 11a are arranged. ing.

  The throttle valve 6 is disposed in the intake passage 11 on the downstream side (downstream side of the intake air flow) of the intercooler 7 (compressor impeller 102 of the turbocharger 100). The throttle valve 6 is an electronically controlled valve whose opening is adjusted by a throttle motor 60. The opening of the throttle valve 6 (throttle opening) is detected by a throttle opening sensor 26. The throttle valve 6 of this example can electronically control the throttle opening independently of the driver's accelerator pedal operation.

  A front-stage S / C catalyst (start catalyst) 81 and a rear-stage U / F catalyst (underfloor catalyst) 82 are arranged in the exhaust passage 12. The S / C catalyst 81 is constituted by, for example, a three-way catalyst that can purify hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and the like. Further, the U / F catalyst 82 is constituted by, for example, a NOx catalyst (for example, NSR (NOx Storage Reduction) catalyst) having a function of storing NOx in exhaust gas and reducing the stored NOx.

-Turbocharger-
The engine 1 is equipped with a turbocharger (supercharger) 100 that supercharges intake air using exhaust pressure.

  As shown in FIGS. 1 and 2, the turbocharger 100 includes a turbine wheel 101 disposed in the exhaust passage 12, a compressor impeller 102 disposed in the intake passage 11, and the turbine wheel 101 and the compressor impeller 102 integrated with each other. The turbine wheel 101 disposed in the exhaust passage 12 is rotated by exhaust energy, and the compressor impeller 102 disposed in the intake passage 11 is rotated accordingly. Then, the intake air is supercharged by the rotation of the compressor impeller 102, and the supercharged air is forcibly sent into the combustion chamber of each cylinder of the engine 1.

  The turbine wheel 101 is accommodated in the turbine housing 111, and the compressor impeller 102 is accommodated in the compressor housing 112. The floating bearings 104 and 104 that support the connecting shaft 103 are accommodated in a center housing 113, and the turbine housing 111 and the compressor housing 112 are attached to both sides of the center housing 113.

  The turbocharger 100 of this example is a variable nozzle type turbocharger (VNT), and a variable nozzle vane mechanism 120 is provided on the turbine wheel 101 side. The opening degree of the nozzle vane 121 of the variable nozzle vane mechanism 120 (hereinafter referred to as VN). The supercharging pressure of the engine 1 can be adjusted by adjusting the opening degree. Details of the variable nozzle vane mechanism 120 will be described later.

-EGR device-
Further, the engine 1 is equipped with an EGR device 5. The EGR device 5 is a device that reduces the combustion temperature in the combustion chamber 1d and reduces the amount of NOx generated by introducing a part of the exhaust gas into the intake air.

  As shown in FIG. 1, the EGR device 5 includes an exhaust passage 12 upstream of the turbine wheel 101 of the turbocharger 100 (upstream of the exhaust gas flow) and a downstream of the intercooler 7 (compressor impeller 102 of the turbocharger 100). An EGR passage 51 communicating with the intake passage 11 on the side (downstream of the intake air flow), an EGR catalyst (for example, an oxidation catalyst) 52 provided in the EGR passage 51, an EGR cooler 53, an EGR valve 54, and the like It is configured. In the EGR device 5 having such a configuration, the EGR rate [EGR amount / (EGR amount + intake air amount (new air amount)) (%)] is changed by adjusting the opening degree of the EGR valve 54. The EGR amount (exhaust gas recirculation amount) introduced from the exhaust passage 12 to the intake passage 11 can be adjusted.

  The EGR device 5 may be provided with an EGR bypass passage that bypasses the EGR cooler 53 and an EGR bypass switching valve.

-Variable nozzle vane mechanism Next, the variable nozzle vane mechanism 120 of the turbocharger 100 will be described with reference to FIGS.

  The variable nozzle vane mechanism 120 of this example is disposed in a link chamber 114 formed between the turbine housing 111 and the center housing 113 of the turbocharger 100.

  The variable nozzle vane mechanism 120 includes a plurality (for example, twelve) of nozzle vanes 121... 121, an annular unison ring 122, and a plurality of parts that are partially engaged with the unison ring 122. Open / close arms 123, 123, drive arms 124 for driving the open / close arms 123, vane shafts 125 connected to the open / close arms 123 for driving the nozzle vanes 121, and the vane shafts 125. And a nozzle plate 126 for holding.

  The plurality of nozzle vanes 121... 121 are arranged at equal intervals on the outer peripheral side of the turbine wheel 101. Each nozzle vane 121 is disposed on a nozzle plate 126 and can be rotated by a predetermined angle about the vane shaft 125.

  The drive arm 124 is rotatable about a drive shaft 128. The drive shaft 128 is integrally attached to one end of the drive link 127. When the drive link 127 is rotated, the drive shaft 128 is rotated in accordance with this rotation, and the drive arm 124 is rotated (oscillated). )

  The outer peripheral side end of each open / close arm 123 is fitted to the inner peripheral surface of the unison ring 122, and when the unison ring 122 rotates, this rotational force is transmitted to each open / close arm 123. Specifically, the unison ring 122 is disposed so as to be slidable in the circumferential direction with respect to the nozzle plate 126. The outer peripheral side end portions of the drive arm 124 and the respective opening / closing arms 123 are fitted into a plurality of recesses 122 a provided on the inner peripheral edge of the unison ring 122, and the rotational force of the unison ring 122 is transmitted to each opening / closing arm 123. The

  Each open / close arm 123 is rotatable about a vane shaft 125. Each vane shaft 125 is rotatably supported by a nozzle plate 126, and the open / close arm 123 and the nozzle vane 121 are integrally connected by the vane shaft 125.

  The nozzle plate 126 is fixed to the turbine housing 111. A pin 126a (see FIGS. 3 and 5) is inserted into the nozzle plate 126, and a roller 126b is fitted into the pin 126a. The roller 126b guides the inner peripheral surface of the unison ring 122. Accordingly, the unison ring 122 is held by the roller 126b and can rotate in a predetermined direction.

  In the above structure, when the drive link 127 rotates, the turning force is transmitted to the unison ring 122 via the drive shaft 128 and the drive arm 124. As the unison ring 122 rotates, the open / close arms 123 rotate (swing), and the variable nozzle vanes 121 rotate.

  In the variable nozzle vane mechanism 120 of this example, a link rod 129 is rotatably connected to the other end of the drive link 127 via a connecting pin 127a. This link rod 129 is connected to the VN actuator 140. The VN actuator 140 includes an electric motor (DC motor) 141 and a conversion mechanism (for example, a gear having a worm gear and a worm wheel meshing with the worm gear) that converts the rotation of the electric motor 141 into a linear motion and transmits the linear motion to the link rod 129. Mechanism, etc. (not shown). The VN actuator 140 is driven and controlled by the ECU 200. The ECU 200 performs energization control of the electric motor 141 according to, for example, a nozzle vane opening request value required from the engine operating state. The electric motor 141 is supplied with electric power from an in-vehicle battery (not shown).

  When the link rod 129 is moved (advanced / retreated) by the VN actuator 140, the drive link 127 is rotated, and each nozzle vane 121 is rotated (displaced) accordingly.

  Specifically, as shown in FIG. 3, when the link rod 129 is pulled in the direction of the arrow X1 in the drawing (retraction of the link rod 129), the unison ring 122 rotates in the direction of the arrow Y1 in the drawing, as shown in FIG. As described above, each nozzle vane 121 rotates about the vane shaft 125 in the counterclockwise direction (Y1 direction) in the drawing, and the opening degree (VN opening degree) of the nozzle vane 121 is set large.

  On the other hand, as shown in FIG. 5, when the link rod 129 is pushed in the direction of the arrow X2 in the drawing (advance of the link rod 129), the unison ring 122 rotates in the direction of the arrow Y2 in the drawing, and as shown in FIG. Each nozzle vane 121 rotates about the vane shaft 125 in the clockwise direction (Y2 direction) in the figure, and the nozzle vane opening (VN opening) is set small.

  In the turbocharger 100 having the above structure, the turbine housing 111 containing the turbine wheel 101 is provided with a turbine housing vortex chamber 111a, and exhaust gas is supplied to the turbine housing vortex chamber 111a. The turbine wheel 101 is rotated by the gas flow. At this time, as described above, the rotational position of each nozzle vane 121 is adjusted, and the rotational angle of the nozzle vane 121 is set to adjust the flow rate and flow velocity of the exhaust from the turbine housing vortex chamber 111a to the turbine wheel 101. it can. This makes it possible to adjust the supercharging performance. For example, the rotational position (displacement) of each nozzle vane 121 so as to reduce the flow path area (throat area) between the nozzle vanes 121 when the engine 1 rotates at a low speed. Is adjusted, the flow rate of the exhaust gas increases, and a high boost pressure can be obtained from the engine low speed range.

  The ECU 200 controls the components such as the engine 1, the VN actuator 140 (electric motor 141) of the turbocharger 100, the throttle motor 60 that opens and closes the throttle valve 6, and the EGR valve 54.

-ECU-
As shown in FIG. 7, the ECU 200 includes a CPU 201, a ROM 202, a RAM 203, a backup RAM 204, and the like.

  The ROM 202 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 201 executes various arithmetic processes based on various control programs and maps stored in the ROM 202. The RAM 203 is a memory that temporarily stores calculation results of the CPU 201, data input from each sensor, and the backup RAM 204 is a nonvolatile memory that stores data to be saved when the engine 1 is stopped, for example. Memory.

  The CPU 201, the ROM 202, the RAM 203, and the backup RAM 204 are connected to each other via the bus 207, and are connected to the input interface 205 and the output interface 206.

  The input interface 205 includes a water temperature sensor 21, an air flow meter 22, an intake air temperature sensor 23, a rail pressure sensor 24, an engine speed sensor 25, a throttle opening sensor 26 that detects the opening of the throttle valve 6, and an accelerator pedal depression amount. An accelerator opening sensor 27 for detecting (accelerator opening), an intake manifold pressure sensor (supercharging pressure sensor) 28, a vehicle speed sensor 29, and the like are connected.

  The output interface 206 includes an injector 2, a throttle motor 60 for the throttle valve 6, an EGR valve 54, and a VN actuator 140 (electric motor 141) that adjusts the opening degree of the nozzle vane 121 of the variable nozzle vane mechanism 120 of the turbocharger 100. It is connected.

  The ECU 200 controls the engine 1 including the opening control of the throttle valve 6 of the engine 1, fuel injection amount / injection timing control (injector 2 opening / closing control), EGR control, and the like based on the output signals of the various sensors described above. Perform various controls. Further, the ECU 200 executes the following “VN opening degree control”.

  The control apparatus for a supercharged engine according to the present invention is realized by the program executed by the ECU 200 described above.

-VN opening control-
First, the flow rate of exhaust gas passing through the nozzle vane 121 (VN passage flow rate) will be described.

  When the variable nozzle vane mechanism 120 is provided in the turbocharger 100, the exhaust gas flows through the nozzle vane 121 toward the turbine wheel 101 as shown in FIG. As described above, when switching from acceleration (engine acceleration) to deceleration, the opening degree (VN opening degree) of the nozzle vane 121 is controlled to the closed side in order to ensure re-acceleration after that (after deceleration), and the turbo The supercharging pressure of the charger 100 is not reduced. For this reason, when switching from acceleration to deceleration, the flow rate of the exhaust gas passing through the nozzle vane 121 may become quasi-steady. When the flow rate of the exhaust gas becomes quasi-stationary above a certain level, an exhaust gas vortex (Rankine vortex) is generated downstream of the nozzle vane 121.

  As described above, Rankine vortices are generated at the rear end of the nozzle vane and have been found to be pressure pulsations having a frequency component proportional to the flow rate of the exhaust gas. In other words, the vortex shedding frequency f of the Rankine vortex satisfies the relationship of the theoretical formula [f = St * U / D St: Strouhal number (constant), U: flow velocity, D: wake width] The pressure pulsation generated by the Rankine vortex has a frequency component proportional to the flow rate of exhaust gas passing through the nozzle vane 121 (flow rate at the rear end of the nozzle vane). When the frequency of such pressure pulsation is amplified by the spatial resonance of the space in the turbine housing 111 and the space in the exhaust pipe 12a (turbine housing to catalyst exhaust gas passage: see FIG. 1), the vehicle exhaust It becomes a discharge sound from the exhaust port through the pipe, and the abnormal noise becomes a problem.

  In consideration of such points, in the present embodiment, when the engine speed Ne is equal to or higher than a predetermined determination value, the accelerator is turned off and the predetermined time is set from the time when the engine speed Ne switches from increase to decrease. Until the time elapses, the technical feature is to suppress the generation of abnormal noise by maintaining the opening degree (VN opening degree) of the nozzle vane 121 in the open state.

  An example of the specific control (VN opening degree control) will be described with reference to the flowchart of FIG. The control routine of FIG. 9 is repeatedly executed by the ECU 200 every predetermined time (for example, every 8 msec).

  When the control routine of FIG. 9 is started, first, in step ST101, it is determined whether or not it is during acceleration (when the engine 1 is being accelerated). If the determination result is negative (NO), the process returns. If the determination result in step ST101 is affirmative (YES) (when acceleration is in progress), the process proceeds to step ST102.

  The determination as to whether or not the vehicle is accelerating (when the engine 1 is accelerating) is performed, for example, when the accelerator pedal is depressed and the accelerator opening detected by the accelerator opening sensor 27 is greater than or equal to a predetermined value while the vehicle is running. (Or when the change rate (increase rate) of the accelerator opening is equal to or greater than a predetermined value), it may be determined that the vehicle is “accelerated”.

  In step ST102, it is determined whether or not the engine speed Ne calculated from the output signal of the engine speed sensor 25 is equal to or greater than a predetermined determination value Thne. If the determination result is negative (NO), the process returns. When the determination result of step ST102 is affirmative (YES) (when [Ne ≧ Thne]), the process proceeds to step ST103. The determination value Thne used for the determination process in step ST102 will be described later.

  In addition, when the determination result of this step ST102 is negative determination (NO), when switching from acceleration to deceleration, “control to keep the VN opening in an open state” described later is not executed, and the nozzle vane 121 is By controlling the opening degree (VN opening degree) to the closed side so as not to drop the supercharging pressure of the turbocharger 100, reacceleration is ensured.

  In step ST103, it is determined based on the output signal of the accelerator opening sensor 27 whether or not the accelerator is turned off. If the determination result is negative (NO), the process returns. If the determination result in step ST103 is affirmative (YES) (when the accelerator is off), the process proceeds to step ST104.

  In step ST104, it is determined whether or not the acceleration (engine acceleration) is switched to the deceleration after the accelerator is turned off. Specifically, based on the output signal of the engine speed sensor 25, the rate of change of the engine speed Ne (dNe / dt: see FIG. 10) is sequentially calculated, and the rate of change dNe / dt of the engine speed Ne is calculated. [DNe / dt> 0] => [dNe / dt <0] is determined. If the determination result in step ST104 is negative (NO), the process enters a standby state. Then, when the determination result of step ST104 is affirmative (YES) ([dNe / dt> 0] ⇒ [dNe / dt <0] (time t2 in FIG. 10), the process proceeds to step ST105.

  In step ST105, the opening degree (VN opening degree) of the nozzle vane 121 is maintained in the open state, and from [dNe / dt> 0] ⇒ [dNe / dt <0] (from time t2 in FIG. 10). Start counting elapsed time.

  Here, the control executed in step ST105 (control for keeping the VN opening in the open state) sets the VN opening to the opening side with respect to the VN opening value at the accelerator-off time (time t1 shown in FIG. 10).・ Control to hold. With respect to the VN opening set on the opening side, a VN opening that does not generate abnormal noise due to the pressure pulsation during deceleration is set to a set time (a time during which the VN opening is kept open), which will be described later. In consideration of the above, it is set in conformity with experiments and simulations. The VN opening at the time of control held in the open state may be set to the maximum opening.

  And the process of the above-mentioned step ST105 (process which maintains a VN opening degree in an open state) is from [dNe / dt> 0] ⇒ [dNe / dt <0] (time t2 in FIG. 10), This is continued until a set time to be described later elapses (until the elapsed time from time t2 reaches the set time), and when the set time elapses (time t3 in FIG. 10), that is, the determination result in step ST106 is affirmative. When (YES) is reached, the process proceeds to step ST107.

  In step ST107, the opening degree (VN opening degree) of the nozzle vane 121 is set to a value on the closing side to ensure reacceleration after deceleration.

  Next, the above-described [determination value Thne] and [set time (open state holding time)] will be described.

(Judgment value Thne)
The determination value Thne used for the determination process in step ST102 will be described. First, using CAE (Computer Aided Engineering), for the target engine 1, the space shape inside the turbine housing 111 of the turbocharger 100 and the exhaust pipe 12 a from the outlet of the turbine housing 111 to the S / C catalyst 81. A space shape of [turbine housing to catalyst] is specified by specifying a space shape (including a part of the space in the casing 81b of the S / C catalyst 81 (including the space from the inlet of the casing 81b to the catalyst main body 81a: see FIG. 1)). Resonance is evaluated to obtain a resonance frequency, and based on the result, the frequency band of spatial resonance shown in FIG. 11 (frequency band in which abnormal noise becomes large: for example, 600 Hz to 1 kHz) is specified.

  Next, using the frequency band of the spatial resonance obtained by the above processing, the rotation range of the turbocharger 100 that falls within the frequency band of the spatial resonance (range of turbo rotation speed: see FIG. 11) is obtained by experiment / simulation calculation or the like. . Then, considering the relationship between the rotational speed Ne of the engine 1 and the rotational speed of the turbocharger 100 (turbo rotational speed), etc., the engine rotational range that falls within the frequency band of the spatial resonance is determined by experiment / simulation calculation, etc. A value (for example, [lower limit value of engine rotation range] − [margin]) adapted based on the lower limit value of the engine rotation range is set as a determination value Thne used in the determination process of step ST102.

(Set time (open state holding time))
As described above, the set time used for the determination process in step ST106 in FIG. 9 is a period during which the VN opening is kept open from the time when the engine speed Ne is switched from rising to falling (time t2 in FIG. 10). (Time [t2 to t3])). This set time is the time required for the engine revolution speed Ne (turbo revolution speed) that is decreasing to pass through the frequency band of the spatial resonance shown in FIG. 11 from the time when the engine revolution speed Ne is switched from the increase to the decrease. Obtained by experiment / simulation calculation, etc., and set a suitable value based on the result. Note that the longer the set time (open state holding time of the VN opening) is preferable in terms of noise suppression, but if it is too long, the re-acceleration performance after deceleration tends to decrease. The set value (for example, about 300 msec to 500 msec) is set.

  Next, the VN opening degree control of this embodiment will be described with reference to the timing chart of FIG.

  First, at the time of acceleration (when the engine is accelerated), when the engine speed Ne is equal to or greater than a predetermined determination value Thne and the accelerator is turned off at the timing t1 shown in FIG. 10, in the conventional control (broken line in FIG. 10), The opening degree 121 (VN opening degree) is controlled to the closing side. For this reason, abnormal noise is generated for the reason described above. On the other hand, in the present embodiment, after the accelerator is turned off at the time t1, the time when the engine speed Ne is switched from the increase to the decrease ([dNe / dt> 0] ⇒ [dNe / dt <0]. At time t2, the opening degree of the nozzle vane 121 is held in the open state for a predetermined set time. By maintaining the opening degree of the nozzle vane 121 in this way, the flow rate of the exhaust gas passing through the nozzle vane 121 is reduced, so that the quasi-steady state of the gas flow rate at which Rankine vortex is generated can be avoided. Generation of sound can be suppressed. Then, the opening degree of the nozzle vane 121 is controlled to the closed side at a time t3 when a predetermined set time has elapsed from the time t2 when the engine speed Ne is switched from rising to lowering, so that re-acceleration after deceleration is ensured. Can do.

  Thus, according to the present embodiment, when the engine speed Ne is equal to or greater than the predetermined determination value Thne, the predetermined set time has elapsed since the accelerator was turned off and the engine speed Ne was switched from rising to falling. In the meantime, since the opening degree of the nozzle vane 121 is kept open, it is possible to suppress the generation of abnormal noise when switching from acceleration to deceleration.

(Modification)
Next, a modification of the above embodiment will be described. In this modification, between step ST102 and step ST103 of FIG. 9 described above, the rate of change of the engine speed Ne during acceleration (increase rate: dNe / dt: see FIG. 10) is greater than or equal to a predetermined determination value ThΔne. It is characterized in that a step for determining whether or not there is added. And when the determination result of the addition step is affirmation determination (YES), it progresses to step ST103, and when the determination result of an addition step is negative determination (NO), it returns. The reason for providing such an additional step will be described below.

  First, even in a situation where the engine speed Ne is equal to or greater than the determination value Thne, for example, when the amount of change in the accelerator depression amount by the driver during acceleration (the rate of change in the accelerator opening (the rate of increase)) is small The rate of change (increase rate) of the engine speed Ne may be reduced depending on the operating condition, such as when the transmission gear ratio during acceleration or acceleration is small. In such a case, the frequency band of the spatial resonance is reached. The case where it does not do is assumed. Considering such points, in this modified example, the determination process (dNe / dt ≧ ThΔne) of the above-described additional step ST is added, and by adding such a determination process (condition), the above-described determination process (condition) is added. The control to keep the VN opening in the open state can be performed in a more appropriate situation.

  Note that the determination value ThΔne in this case also takes into account the spatial resonance frequency band shown in FIG. 11, and is a value adapted by experiments and simulation calculations (an increase in engine speed that falls within the spatial resonance frequency band). A value adapted based on the rate dNe / dt) may be set.

-Other embodiments-
In the above example, the case where the present invention is applied to a common rail in-cylinder direct injection multi-cylinder (four-cylinder) diesel engine has been described. The present invention is not limited to this, and can be applied to a diesel engine having any other number of cylinders such as a six-cylinder diesel engine.

  Moreover, although the example of control of a diesel engine was demonstrated in the above example, this invention is not limited to this, This invention is applicable also to control of the gasoline engine provided with the variable nozzle vane type turbocharger.

  In the above example, the case where the present invention is applied to an internal combustion engine (diesel engine, gasoline engine, etc.) equipped with an EGR device (exhaust gas recirculation device) has been described. However, the present invention is not limited to this, and EGR The present invention can also be applied to control of an internal combustion engine with a supercharger (an engine with a variable nozzle vane turbocharger) that is not equipped with a device.

  In the present invention, as an actuator for driving the variable nozzle vane mechanism, for example, a negative pressure type or a hydraulic type actuator may be used in addition to a motor type actuator using an electric motor as a drive source.

  INDUSTRIAL APPLICABILITY The present invention can be used for control of an engine having a variable nozzle vane supercharger, and more specifically can be effectively used for control for suppressing abnormal noise caused by pressure pulsation generated at the rear end of the nozzle vane. .

DESCRIPTION OF SYMBOLS 1 Engine 11 Intake passage 12 Exhaust passage 25 Engine speed sensor 27 Accelerator opening sensor 100 Turbocharger (variable nozzle vane type turbocharger)
DESCRIPTION OF SYMBOLS 101 Turbine wheel 102 Compressor impeller 120 Variable nozzle vane mechanism 121 Nozzle vane 140 VN actuator 141 Electric motor 200 ECU

Claims (3)

A compressor impeller provided in the intake passage, a turbine wheel provided in the exhaust passage, and a plurality of nozzle vanes provided on the outer peripheral side of the turbine wheel, and by changing the opening of the nozzle vane, In a control device for a supercharged engine provided with a supercharger provided with a variable nozzle vane mechanism for adjusting the flow,
When the engine speed is equal to or higher than a predetermined determination value, the opening of the nozzle vane is kept open until a predetermined set time elapses after the accelerator is turned off and the engine speed is switched from rising to lowering. A control device for an engine with a supercharger, characterized in that it holds. The control device for an engine with a supercharger according to claim 1,
When the engine speed is equal to or higher than the predetermined determination value and the rate of change of the engine speed is equal to or higher than the predetermined determination value, the accelerator is turned off and the predetermined setting is made when the engine speed is switched from rising to lowering. A control device for an engine with a supercharger, wherein the opening degree of the nozzle vane is kept open until time elapses. The control device for an engine with a supercharger according to claim 1 or 2,
The supercharger-equipped engine control device, wherein the opening degree of the nozzle vane is controlled to the closed side after the set time has elapsed from the time when the engine speed is switched from rising to falling.

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