JP2012092798A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce an NOx exhaust amount in the whole operation region of an engine in a control device of an internal combustion engine having a turbo charger with an electric motor.SOLUTION: The control device of the internal combustion engine includes: a turbo charger 20 having a turbine 22 provided in an exhaust passage 6 of the internal combustion engine 2 and a compressor 21 provided in an intake passage 5; an electric motor 24 rotating the turbine 22 and the compressor 21; an EGR device 40 having an EGR passage 41 connecting the exhaust passage 6 and the intake passage 5 and an EGR valve 43 adjusting a refluxed amount of a refluxed exhaust; an NOx concentration detecting means 50 provided in the exhaust passage 6 and detecting NOx concentration of an exhaust; and a control part 60 adjusting an opened degree of the EGR valve 43 and driving the electric motor 24 so that the refluxed amount of the exhaust is increased until a detected value is made to be an upper limit threshold or below when the detected value of the NOx concentration detecting means 50 exceeds the upper limit threshold.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine having a turbocharger with an electric motor.

  In an internal combustion engine (hereinafter referred to as an engine) such as a diesel engine, an EGR device that recirculates part of exhaust discharged from the engine to an intake system is known in order to reduce NOx in the exhaust. This EGR device attempts to reduce NOx emissions by reducing the oxygen concentration by recirculating exhaust gas containing inert gas in the cylinder of the engine.

  On the other hand, in order to ensure the output of the engine, it is necessary to ensure the absolute amount of oxygen corresponding to the fuel injection amount in the cylinder of the engine. Therefore, a turbocharger that supercharges intake air in order to ensure fresh air (hereinafter referred to as intake air) that burns fuel and recirculation exhaust (hereinafter referred to as EGR gas) that reduces NOx emissions in the cylinder of the engine. Is generally used.

  For example, Patent Document 1 discloses a system in which a diesel engine is provided with a high-pressure EGR device, a low-pressure EGR device, and a turbocharger as a system that reduces the amount of soot and NOx in exhaust gas.

JP 2010-203282 A

  By the way, in an engine having a turbocharger, it is difficult to supercharge intake air, for example, when the engine is in a low load operation with a low exhaust energy or during a transient operation in which the rotation of the turbocharger does not increase immediately. Therefore, in such an operating state, EGR gas cannot be sufficiently secured in the cylinder of the engine, and the NOx emission amount may not be sufficiently reduced.

  The present invention has been made in view of the above points, and an object of the present invention is to effectively reduce NOx emission by securing EGR gas necessary in the entire operation region of the engine.

  In order to achieve the above object, a control device for an internal combustion engine according to the present invention includes a turbine provided in an exhaust passage of the internal combustion engine, a turbocharger provided with a compressor provided in the intake passage of the internal combustion engine, the turbine, and the compressor An EGR passage that connects an electric motor that rotates the engine, an exhaust passage upstream of the turbine and an intake passage downstream of the compressor, and exhaust gas that flows through the EGR passage and recirculates to the intake system of the internal combustion engine An EGR device having an EGR valve for adjusting the amount of recirculation, a NOx concentration detection means for detecting the NOx concentration of exhaust gas provided in the exhaust passage, and a detection value when the detection value of the NOx concentration detection means exceeds an upper limit threshold In order to increase the recirculation amount of the exhaust gas until the value becomes equal to or lower than the upper threshold, the opening degree of the EGR valve is adjusted and the electric motor is Characterized in that it comprises a control unit for moving.

  The turbocharger further includes a low-pressure stage turbocharger having a low-pressure stage turbine provided in an exhaust passage downstream of the turbine and a low-pressure stage compressor provided in an intake passage upstream of the compressor. A stage turbocharger may be used.

  According to the control device for an internal combustion engine of the present invention, it is possible to effectively reduce the NOx emission amount by securing the necessary EGR gas in the entire operation region of the engine.

1 is a schematic overall configuration diagram showing a control device for an internal combustion engine according to an embodiment of the present invention. It is a typical figure showing a target NOx map of a control device of an internal-combustion engine concerning one embodiment of the present invention. It is a flow which shows the control content by the control apparatus of the internal combustion engine which concerns on one Embodiment of this invention.

  Hereinafter, based on FIGS. 1-3, the control apparatus 1 of the internal combustion engine which concerns on one Embodiment of this invention is demonstrated. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, an internal combustion engine control apparatus 1 according to an embodiment of the present invention includes an internal combustion engine (hereinafter referred to as an engine) 2 such as a diesel engine, a high-pressure turbocharger (turbocharger) 20 with an electric motor, , A low-pressure stage turbocharger 30 having a larger capacity than the high-pressure stage turbocharger 20 with an electric motor, an EGR device 40 that recirculates part of the exhaust, a NOx sensor (NOx concentration detecting means) 50, an ECU (control unit) 60, Is provided.

  As shown in FIG. 1, the engine 2 is provided with an intake manifold 3 and an exhaust manifold 4. The intake manifold 3 is connected to a high-pressure intake passage 5 for introducing high-pressure intake air sent from a high-pressure turbocharger 20 with an electric motor by opening the intake valve 2a. The exhaust manifold 4 is opened to the exhaust manifold 2b. A first exhaust passage 6 for discharging exhaust gas by a valve is connected. The high-pressure intake passage 5 is provided with an intercooler 7 that cools intake air and a throttle valve 8 that adjusts the intake air amount. The throttle valve 8 is connected to the ECU 60 via electric wiring, and is configured such that the valve opening is adjusted in accordance with a control signal output from the ECU 60.

  As shown in FIG. 1, the high-pressure turbocharger 20 with an electric motor includes a high-pressure compressor 21 provided on the upstream side of the high-pressure intake passage 5 and a high-pressure turbine 22 provided on the downstream side of the first exhaust passage 6. Have A second exhaust passage 9 is provided on the downstream side of the high-pressure turbine 22. Further, the high-pressure compressor 21 and the high-pressure turbine 22 are connected by a rotating shaft 23, and an electric motor 24 is attached to the rotating shaft 23.

  The electric motor 24 includes a rotor (not shown) provided on the rotary shaft 23 and a stator (not shown) disposed around the rotor. In addition, the electric motor 24 is connected to the ECU 60 via electric wiring, and is configured such that driving is controlled according to a control signal output from the ECU 60.

  That is, the high-pressure turbocharger 20 with an electric motor of the present embodiment also functions as a normal supercharger that performs supercharging only with exhaust energy, and can drive the electric motor 24 to perform further supercharging. It is also possible to perform regenerative power generation by rotating the electric motor 24 via the high-pressure turbine 22 with exhaust energy.

  As shown in FIG. 1, the low-pressure stage turbocharger 30 includes a low-pressure stage compressor 31 connected to the high-pressure stage compressor 21 via a low-pressure intake passage 10, and a low-pressure stage turbine 32 provided downstream of the second exhaust passage 9. Have The low-pressure compressor 31 and the low-pressure turbine 32 are connected by a rotating shaft. An air cleaner 13 is connected to the upstream side of the low-pressure stage compressor 31 via the intake passage 11, and a third exhaust passage 12 is connected to the downstream side of the low-pressure stage turbine 32. That is, the low-pressure stage turbocharger 30 drives the low-pressure stage turbine 32 with the exhaust energy of the engine 2 and compresses the intake air introduced via the air cleaner 13 by the low-pressure stage compressor 31 provided coaxially. It is configured to be sent to the compressor 21.

  As shown in FIG. 1, the EGR device 40 includes an EGR passage 41 that connects the first exhaust passage 6 and the high-pressure intake passage 5, and exhaust that flows through the EGR passage 41 and returns to the engine 2 (hereinafter referred to as EGR gas). ) And an EGR valve 43 for adjusting the amount of EGR gas. The EGR valve 43 is connected to the ECU 60 via electric wiring, and is configured such that the valve opening degree is adjusted according to a control signal output from the ECU 60.

  The NOx sensor 50 detects the NOx concentration in the exhaust, and is provided in the third exhaust passage 12 as shown in FIG. Further, the NOx sensor 50 is connected to the ECU 60 through electric wiring.

  The ECU (electronic control unit) 60 performs various controls such as a fuel injection period and a fuel injection amount according to the operating state of the engine 2, and includes a known CPU, ROM, RAM, input port, output port, and the like. Has been. In order to perform these various controls, the output signals of various sensors such as the engine rotation sensor 51, the accelerator opening sensor 52, and the NOx sensor 50 are input to the ECU 60 after A / D conversion.

  The ECU 60 includes a target NOx value setting unit 61, an EGR increase determination unit 62, and an EGR amount adjustment unit 63 as some functional elements. In the present embodiment, these functional elements are described as being included in the ECU 60, which is an integral piece of hardware. However, any one of these functional elements may be provided in separate hardware.

  The target NOx value setting unit 61 sets a target value (upper limit threshold value) of the NOx concentration contained in the exhaust discharged from the engine 2 based on the operating state of the engine 2. The target NOx value setting unit 61 stores a target NOx map (see FIG. 2) that uses the engine speed and torque (accelerator opening) created in advance by experiments and the like as parameters. Then, the target NOx value setting unit 61 sets the target based on the detection value of the engine rotation sensor 51 (hereinafter referred to as engine speed Ne) and the detection value of the accelerator opening sensor 52 (hereinafter referred to as accelerator opening Q). A NOx value corresponding to the operating state of the engine 2 is read from the NOx map and set to a target value (hereinafter referred to as a target NOx value).

  The EGR increase determination unit 62 compares a detection value (hereinafter referred to as an actual NOx value) of the NOx sensor 50 with a target NOx value and determines whether or not an increase in EGR gas is necessary. For example, when the actual NOx value is larger than the target NOx value (actual NOx value> target NOx value), it is determined that an increase in EGR gas is necessary. On the other hand, when the actual NOx value is equal to or less than the target NOx value (actual NOx value ≦ target NOx value), it is determined that an increase in EGR gas is unnecessary.

  The EGR amount adjusting unit 63 drives the electric motor 24 while adjusting the valve opening of the throttle valve 8 and the valve opening of the EGR valve 43 when the EGR increase determining unit 62 determines that the EGR gas needs to be increased. To increase EGR gas. Specifically, an actual NOx value that is a detection value of the NOx sensor 50 is constantly input to the EGR amount adjusting unit 63. Then, the EGR amount adjusting unit 63 outputs a control signal for adjusting the throttle valve 8 and the EGR valve 43 to the optimal valve opening until the actual NOx value becomes equal to or less than the target NOx value, and drives the electric motor 24. The control signal is output. For example, the control signal for restricting the slot valve 8 to the closed side and adjusting the EGR valve 43 to the open side is output, and the control signal for driving the motor 24 is output until the actual NOx value becomes equal to or less than the target NOx value. . In order to efficiently perform the control for increasing the EGR gas, the relationship between the valve opening of the throttle valve 8 and the intake air amount, the relationship between the valve opening of the EGR valve 43 and the EGR gas amount, and the rotation of the electric motor 24. It is preferable to model the relationship between the number and the compressed intake air amount.

  Since the control apparatus 1 for an internal combustion engine according to an embodiment of the present invention is configured as described above, for example, the following control is performed according to the flow shown in FIG.

  In step (hereinafter, step is simply referred to as “S”) 100, the target NOx value setting unit 61 includes a detected value of the engine rotation sensor 51 (engine speed Ne) and a detected value of the accelerator opening sensor 52 (accelerator opening Q). ) And are read.

  In S110, the target NOx value setting unit 61 calculates a target NOx value corresponding to the operating state of the engine 2 from the target NOx map (see FIG. 2) based on the engine speed Ne and the accelerator opening Q read in S100. Read.

  In S120, the EGR increase determination unit 62 compares the detected value (actual NOx value) of the NOx sensor 50 with the target NOx value, and determines whether it is necessary to increase the EGR gas. When the actual NOx value is larger than the target NOx value (actual NOx value> target NOx value), it is determined that the EGR gas needs to be increased, and the process proceeds to S130. On the other hand, when the actual NOx value is less than or equal to the target NOx value (actual NOx value ≦ target NOx value), it is determined that an increase in EGR gas is unnecessary, and this control is returned.

  In S130, the EGR amount adjusting unit 63 adjusts the throttle valve 8 and the EGR valve 43 to the optimum valve opening so that the EGR gas is increased and the actual NOx value becomes equal to or less than the target NOx value, and the electric motor 24 Is driven.

  In S140, the EGR increase determination unit 62 compares the detected value (actual NOx value) of the NOx sensor 50 with the target NOx value again. When the actual NOx value is larger than the target NOx value (actual NOx value> target NOx value), it is determined that further increase of the EGR gas is necessary, and the process returns to S130. On the other hand, when the actual NOx value becomes equal to or less than the target NOx value (actual NOx value ≦ target NOx value), it is determined that further increase of the EGR gas is unnecessary, and this control is returned.

  With the configuration as described above, the control apparatus 1 for an internal combustion engine according to one embodiment of the present invention has the following operational effects.

  When the NOx value in exhaust (actual NOx value) exceeds the target NOx value set according to the operating state of the engine 2, the throttle valve 8 and the EGR valve 43 are set so that the actual NOx value becomes equal to or less than the target NOx value. Are adjusted to an optimum valve opening, and the electric motor 24 is driven. In other words, when the electric motor 24 is driven, the high-pressure turbocharger 20 sends compressed intake air (high-pressure intake air) to the engine 2, whereby EGR gas is increased and the oxygen concentration in the cylinder of the engine 2 is decreased. Thereafter, the driving of the electric motor 24 is continued until the actual NOx value becomes equal to or less than the target NOx value.

  Therefore, EGR gas can be increased as necessary throughout the operation region of the engine 2, and the NOx emission amount can be effectively reduced throughout the operation region. Further, since the NOx emission amount is reduced, the NOx aftertreatment device can be simplified or omitted, and an increase in production cost can be effectively suppressed.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, in the above-described embodiment, the present invention has been described as being applied to a two-stage turbocharging system having the high-pressure turbocharger 20 with an electric motor and the low-pressure turbocharger 30, but only one stage of the turbocharger with an electric motor is provided. You may apply to a one-stage supercharging system. In this case, the same effects as those of the above-described embodiment can be obtained.

  Further, the NOx sensor 50 has been described as being provided in the third exhaust passage 12, but if the NOx sensor 50 has heat resistance, for example, it is provided in the first exhaust passage 6 immediately downstream of the engine 2. Also good.

2 Engine (Internal combustion engine)
5 High-pressure intake passage (intake passage)
6 First exhaust passage (exhaust passage)
20 High-pressure turbocharger with electric motor (turbocharger)
21 High-pressure compressor (compressor)
22 High-pressure turbine (turbine)
24 Electric motor 30 Low-pressure stage turbocharger 31 Low-pressure stage compressor 32 Low-pressure stage turbine 40 EGR device 41 EGR passage 43 EGR valve 50 NOx sensor (NOx concentration detection means)
60 ECU (control unit)

Claims (2)

A turbocharger having a turbine provided in an exhaust passage of the internal combustion engine and a compressor provided in an intake passage of the internal combustion engine;
An electric motor for rotating the turbine and the compressor;
An EGR passage that connects an exhaust passage upstream of the turbine and an intake passage downstream of the compressor, and an EGR that adjusts the recirculation amount of exhaust gas flowing through the EGR passage and recirculating to the intake system of the internal combustion engine An EGR device having a valve;
NOx concentration detecting means provided in the exhaust passage for detecting the NOx concentration of the exhaust;
When the detected value of the NOx concentration detecting means exceeds the upper limit threshold, the opening of the EGR valve is adjusted and the electric motor is driven to increase the exhaust gas recirculation amount until the detected value becomes equal to or lower than the upper limit threshold. A control device for an internal combustion engine. A low-pressure stage turbocharger having a low-pressure stage turbine provided in an exhaust passage downstream of the turbine and a low-pressure stage compressor provided in an intake passage upstream of the compressor;
The control apparatus for an internal combustion engine according to claim 1, wherein the turbocharger is a high-pressure stage turbocharger.

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