JP4302475B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine configured to be able to supply nitrogen or air with an increased nitrogen concentration.

  A technique for supplying air (nitrogen-enriched air) with an increased nitrogen concentration to an engine in order to improve the exhaust characteristics of an internal combustion engine is disclosed in Patent Document 1, for example. In the apparatus shown in this document, nitrogen-enriched air is generated by a membrane-type nitrogen enricher and supplied to the combustion chamber of the engine. A membrane-type nitrogen enrichment device is a device that separates air into a gas having a high oxygen concentration and a gas having a high nitrogen concentration by a membrane.

  Patent Document 2 discloses a diesel engine in which the amount of nitrogen enrichment is increased when the fuel injection timing is maintained in the advanced state. The reason for advancing the fuel injection timing is to prevent deterioration of fuel consumption due to nitrogen enrichment.

Japanese Patent No. 2535381 Japanese Utility Model Publication No. 1-105757.

  In general, when using a low octane fuel, knocking is likely to occur if the engine output is increased. Therefore, when the occurrence of knocking is detected, a technique is used in which knocking is suppressed by retarding the ignition timing. Further, it is assumed that a low octane fuel is used in advance, and the compression ratio is reduced. However, since retarding the ignition timing or reducing the compression ratio reduces engine output, it is desirable that knocking can be effectively suppressed without reducing the retarding ignition timing or reducing the compression ratio.

  It is clear that when the nitrogen-enriched air described above is supplied to the engine, the air-fuel mixture becomes difficult to ignite. Therefore, when considering applying this technology for supplying nitrogen-enriched air to knocking suppression, there are the following problems. That is, if the nitrogen concentration of the nitrogen-enriched air is increased, ignition of the air-fuel mixture becomes difficult, and if the nitrogen concentration cannot be sufficiently increased, a sufficient knocking suppression effect cannot be obtained.

  The present invention has been made paying attention to this point, and appropriately supplies nitrogen or nitrogen-enriched air to the engine to obtain a sufficient knocking suppression effect while suppressing a decrease in engine output (deterioration in fuel consumption). An object of the present invention is to provide a control device for an internal combustion engine. In the present specification and claims, “nitrogen” includes “nitrogen-enriched air”, and “oxygen” includes “oxygen-enriched air”.

In order to achieve the above object, the invention according to claim 1 is directed to a nitrogen supply means for supplying nitrogen to an internal combustion engine, and a fuel supply timing (Fstmg) according to the rotational phase of the engine (crankshaft rotation angle, stage, etc.) , Festg) with a fuel supply means for supplying fuel to the engine, the engine includes a swirl generating mechanism for generating a swirl of intake gas in a combustion chamber, and the nitrogen supply means Nitrogen is supplied at a nitrogen supply timing (Nstmg, Nestg) according to the rotational phase of the engine , the nitrogen supply start timing (Nstmg) is set after the fuel supply start timing (Fstmg), and the supply of nitrogen is ended The timing (Nestg) is set after the fuel supply end timing (Festg) .

According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the fuel supply means is provided via a fuel injection valve (11) provided upstream of the intake valve of the engine. A fuel injection execution period setting means for supplying fuel and setting a fuel injection execution period (Tfi) by the fuel injection valve in accordance with a load (Gcyl ′) of the engine; and the fuel supply timing (Fstmg, Festg) Fuel supply timing changing means that changes according to the engine operating state (NE, PBA), the nitrogen supply means via a nitrogen injection valve (12) provided upstream of the intake valve of the engine And a nitrogen injection execution period setting means for setting a nitrogen injection execution period (Tni) by the nitrogen injection valve according to a load (Gcyl ′) of the engine, and the nitrogen supply timing (Nstmg, N has stg) operating state of the engine (NE, and a nitrogen supply timing changing means for changing in accordance with the PBA), the supply start timing of nitrogen (Nestg) or supply end timing of the fuel (Festg), the The overlap period between the fuel injection execution period (Tfi) and the nitrogen injection execution period (Tni) is made as short as possible, or the fuel injection execution period (Tfi) and the nitrogen injection execution period (Tni) are not overlapped. It is characterized by being set to.
According to a third aspect of the present invention, in the control device for an internal combustion engine according to the first or second aspect, the nitrogen supply means includes a nitrogen tank (33) and nitrogen for detecting a pressure (Pnt) in the nitrogen tank. and a tank internal pressure detection means, wherein the nitrogen injection execution period setting means, the correction to said Rukoto to reduce the nitrogen tank pressure (Pnt) higher increases the nitrogen injection execution period (Tni) .

According to a fourth aspect of the present invention, in the control apparatus for an internal combustion engine according to any one of the first to third aspects of the present invention, the control device for the internal combustion engine further includes a knocking detection unit for detecting knocking of the engine, , when knocking is detected, characterized that you corrected in the increasing direction of the nitrogen injection execution period (Tni).
According to a fifth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to fourth aspects, the nitrogen injection execution period setting means is within a predetermined time from the start completion time of the engine. It characterized that you corrected in the decreasing direction of the nitrogen injection execution period (Tni).

According to the first aspect of the present invention, the fuel is supplied at the fuel supply timing corresponding to the rotational phase of the engine, and the nitrogen is supplied at the nitrogen supply timing corresponding to the rotational phase of the engine. At this time, the nitrogen supply start timing is set after the fuel supply start timing, and the nitrogen supply end timing is set after the fuel supply end timing. In addition, since the swirl of the intake gas is generated in the combustion chamber by the swirl generation mechanism, it is possible to form a mixture layer of air and fuel in the vicinity of the spark plug in the combustion chamber and to stably form a nitrogen layer around it. It becomes. Since knocking occurs from the periphery of the combustion chamber (in the vicinity of the combustion chamber wall), the peripheral portion by the nitrogen layer can be effectively suppressed knocking. Therefore, there is no need to retard the ignition timing or lower the compression ratio, and a sufficient knocking suppression effect can be obtained while suppressing a decrease in engine output (deterioration in fuel consumption) .

According to the second aspect of the present invention, the fuel injection execution period by the fuel injection valve is set according to the engine load, the fuel supply timing is changed according to the operating state of the engine, and nitrogen according to the engine load. A nitrogen injection execution period by the injection valve is set, and the nitrogen supply timing is changed according to the operating state of the engine. By reducing the nitrogen injection execution period in an operation state in which knocking is unlikely to occur according to the engine load, it is possible to improve the combustion efficiency by improving the combustion speed. Further, at the nitrogen supply start timing or the fuel supply end timing , the overlap period between the fuel injection execution period and the nitrogen injection execution period is as short as possible, or the fuel injection execution period and the nitrogen injection execution period do not overlap. since the set as a mixture layer and the nitrogen layer in the combustion chamber are clearly separated, it is Rukoto enhance the effect of preventing knocking.
According to the third aspect of the invention, since the nitrogen injection execution period is corrected to decrease as the nitrogen tank pressure increases, accurate nitrogen injection amount control is performed even if the nitrogen tank pressure fluctuates. Can do.

According to the fourth aspect of the invention, when the knocking is detected, the nitrogen injection execution period is corrected in the increasing direction, so that it is not necessary to correct the retard of the ignition timing, and the combustion efficiency can be improved. .
According to the fifth aspect of the present invention, since the nitrogen injection execution period is corrected in a decreasing direction within a predetermined time from the completion of the start of the engine , the combustion is stabilized immediately after the start when the combustion is likely to become unstable. The amount of unburned gas (HC) emission can be reduced .

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining a configuration of a combustion chamber of the internal combustion engine shown in FIG. The 1 includes a supercharger 100 and a nitrogen supply device 200. The supercharger 100 is driven by a first compressor 7 that compresses intake air, a second compressor 36 that forms part of the nitrogen supply device 200 and compresses air that separates nitrogen, and exhaust kinetic energy. A turbine 22. The first compressor 7 and the second compressor 36 are driven by the turbine 22.

  The nitrogen supply device 200 includes an air passage 31, a nitrogen separation device 32, a nitrogen tank 33, a nitrogen supply passage 34, a nitrogen injection valve 12, an electric compressor 35, a second compressor 36, an electric flow control valve 37, a relief passage 40, and A relief valve 41 is provided. Further, an N2 supercharging pressure sensor 58 that detects a pressure (hereinafter referred to as “N2 supercharging pressure”) Pni in the air passage 31 is provided on the downstream side of the second compressor 36 in the air passage 31. An N2 tank internal pressure sensor 59 is provided for detecting the pressure in the tank (hereinafter referred to as “N2 tank internal pressure”) Pnt. The relief passage 40 is connected to the intake pipe 6 on the downstream side of the first compressor 7.

  The air flowing in through the air passage 31 is usually pressurized by the second compressor 36 and supplied to the nitrogen separation device 32. When the N2 supercharging pressure Pni exceeds the set pressure of the relief valve 41, the relief valve 41 is opened. When the pressurization by the second compressor 36 is not sufficient, pressurization by the electric compressor 35 is performed.

  The nitrogen separator 32 has, for example, an oxygen selective permeable membrane as disclosed in Patent Document 2 (for example, polyimide, polysulfone, polydimethylsiloxane, carbon or the like is used as the material), and this oxygen selectivity. Oxygen that passes through the permeable membrane is released into the atmosphere through the passage 38, and nitrogen that does not pass through the oxygen selective permeable membrane is generated. Here, oxygen is released into the atmosphere, but it can also be introduced into the intake system as necessary. In this case, it is possible to suppress a decrease in the oxygen concentration in the combustion chamber. A one-way valve 39 is provided in the passage 38 and is opened when the pressure of the separated oxygen becomes higher than the atmospheric pressure by a predetermined pressure or more. The electric flow control valve 37 is opened when the N2 tank internal pressure Pnt becomes lower than the pressure obtained by adding the pressure loss Pniloss in the nitrogen separator 32 to the N2 supercharging pressure Pni.

  The engine main body 1 is composed of four cylinders, and each cylinder is provided with a combustion chamber 2, a spark plug 3, an intake valve 4, and an exhaust valve 5. As shown in FIG. 2, the intake valve 4 and the exhaust valve 5 are arranged so that a swirl of the air-fuel mixture sucked into the combustion chamber 2 is generated. An intake pipe 6 and an exhaust pipe 21 are connected to the combustion chamber 2. A knocking sensor 55 for detecting knocking is attached to the engine body 1.

  The intake pipe 6 is provided with a first compressor 7 of the supercharger 100, an intercooler 8 that cools the pressurized air, and a throttle valve 9 in order from the upstream side, and an actuator 10 that drives the throttle valve 9. Is connected to the throttle valve 9. Further, the nitrogen injection valve 12 and the fuel injection valve 11 of the nitrogen supply device 200 are provided slightly upstream of the intake valve 4 corresponding to each cylinder. In FIG. 1, the nitrogen injection valve 12 is shown as being provided on the upstream side of the fuel injection valve 11, but this is shown in this way for the sake of explanation. As shown, both are arranged side by side in the width direction of the intake pipe 6. The fuel injection valve 11 is connected to a fuel tank (not shown), and pressurized fuel is supplied to the fuel injection valve 11.

  An airflow sensor 51 for detecting the intake air amount (flow rate) is provided between the first compressor 7 and the intercooler 8 of the intake pipe 6, and the intake air temperature TA is detected downstream of the intercooler 8. An intake air temperature sensor 52 is provided. A throttle valve opening sensor 53 for detecting the opening TH of the throttle valve 9 and an intake pipe internal pressure sensor 54 for detecting an intake pipe internal pressure (absolute pressure) PBA on the downstream side of the throttle valve are provided.

  The exhaust pipe 21 is provided with a turbine 22, a three-way catalyst 23, and a NOx adsorption catalyst 24 of the supercharger 100. A passage 25 that bypasses the turbine 22 and a waste gate valve 26 that opens and closes the passage 25 are provided. The three-way catalyst 23 purifies HC, CO, and NOx in the exhaust, and the NOx adsorption catalyst adsorbs NOx in a state where the air-fuel ratio of the air-fuel mixture supplied to the engine is set to be leaner than the stoichiometric air-fuel ratio. The adsorbed NOx is reduced in a state where the air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio.

  Between the turbine 22 of the exhaust pipe 21 and the three-way catalyst 23, a proportional air-fuel ratio sensor (hereinafter referred to as "LAF sensor") 56 for detecting the oxygen concentration (air-fuel ratio) in the exhaust gas is provided. A binary oxygen concentration sensor (hereinafter referred to as “O2 sensor”) 57 is provided between the NOx adsorption catalyst 24 and the NOx adsorption catalyst 24. The LAF sensor 56 outputs an electrical signal substantially proportional to the oxygen concentration in the exhaust gas, and the O2 sensor 57 has a characteristic that its output changes abruptly before and after the stoichiometric air-fuel ratio. High level on the rich side and low level on the lean side.

  In this embodiment, after the fuel injection by the fuel injection valve 11, the nitrogen injection by the nitrogen injection valve 12 is performed, and the fuel and air are placed in the vicinity of the spark plug 3 by the swirl in the combustion chamber 2 as shown in FIG. And a nitrogen layer is formed outside the mixture layer, in other words, at the outer edge of the combustion chamber 2 (in the vicinity of the inner wall of the cylinder). FIG. 4 is a view of the combustion chamber 2 as viewed from above. The solid line indicates the air-fuel mixture layer, and the broken line indicates the nitrogen layer. Normally, knocking occurs at the outer edge of the combustion chamber 2, so that knocking can be suppressed by forming the nitrogen layer in this way. Moreover, since the air-fuel mixture layer is formed in the vicinity of the spark plug 3, the air-fuel mixture can be reliably ignited.

  FIG. 5 is a block diagram showing the configuration of the engine control system described above. The above-described sensors 51 to 59 are connected to an electronic control unit (hereinafter referred to as “ECU”) 70, and detection signals from the sensors 51 to 59 are supplied to the ECU 70. Further, a crank angle position sensor 60, an accelerator sensor 61, a vehicle speed sensor 62, and a gear position sensor 63 are connected to the ECU 70. The crank angle position sensor 60 detects a rotation angle of a crankshaft (not shown) of the engine. The accelerator sensor 61 detects an accelerator pedal depression amount (hereinafter referred to as “accelerator pedal operation amount”) AP of a vehicle driven by the engine. The vehicle speed sensor 62 detects the traveling speed (vehicle speed) VP of the vehicle driven by the engine, and the gear position sensor 63 detects the gear position GP of the transmission of the vehicle. A signal corresponding to the rotation angle of the crankshaft (engine rotation phase), a signal indicating the accelerator pedal operation amount AP, a signal indicating the vehicle speed VP, and a signal indicating the gear position GP are supplied to the ECU 70.

  The crank angle position sensor 60 is a cylinder discrimination sensor that outputs a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine, and a predetermined top dead center (TDC) at the start of the intake stroke of each cylinder. A TDC sensor that outputs a TDC pulse at a crank angle position before the crank angle (every 180 ° crank angle in a four-cylinder engine) and one pulse (hereinafter referred to as “CRK pulse”) with a constant crank angle cycle shorter than the TDC pulse (for example, a cycle of 30 °). The CYL pulse, the TDC pulse, and the CRK pulse are supplied to the ECU 70. These signal pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE.

The ECU 70 performs drive control of the ignition plug 3, the fuel injection valve 11, the nitrogen injection valve 12, the actuator 10 of the throttle valve 9, the electric compressor 35, and the electric flow control valve 37 in accordance with the detection signal of the sensor.
The ECU 70 includes an input circuit, a central processing unit (CPU), a storage circuit, and an output circuit. The input circuit shapes the input signal waveform from the above-described sensor, corrects the voltage level to a predetermined level, and converts the analog signal value into a digital signal value. The storage circuit includes various arithmetic programs executed by the CPU, a ROM that stores various maps described later, and a RAM that stores arithmetic results. The output circuit outputs a drive signal to the fuel injection valve, the nitrogen injection valve, and the like.

  FIG. 6 is a flowchart of TDC processing that is executed by the CPU of the ECU 70 in synchronization with the generation of the TDC pulse. In step S11, the Tfi calculation process shown in FIG. 8 is executed, and the fuel injection time Tfi by the fuel injection valve 11 is calculated. In step S12, the Tni calculation process shown in FIG. 10 is executed, and the nitrogen injection time Tni by the nitrogen injection valve 12 is calculated. In step S13, the injection timing determination process shown in FIG. 12 is executed to determine the fuel injection timing and the nitrogen injection timing.

  The ECU 70 opens the fuel injection valve 11 over the fuel injection time Tfi at the fuel injection timing calculated by this processing, and opens the nitrogen injection valve 12 over the nitrogen injection time Tni at the nitrogen injection timing. As a result, an amount of fuel proportional to the fuel injection time Tfi is supplied to the combustion chamber 2 and an amount of nitrogen proportional to the nitrogen injection time Tni is supplied to the combustion chamber 2.

  FIG. 7 is a flowchart of a timer process executed by the CPU of the ECU 70 every predetermined time (for example, 10 milliseconds). In step S21, the N2 tank internal pressure control process shown in FIG. 15 is executed, the operation of the electric compressor 35 is controlled so that the N2 supercharging pressure Pni matches the target supercharging pressure Pnicmd, and the electric flow control valve 37 is opened and closed. Then, the N2 tank internal pressure Pnt is controlled to a predetermined pressure or higher. In step S22, the intake air amount control process shown in FIG. 17 is executed, and the throttle valve opening TH is controlled so that the intake air amount Gcyl of the engine matches the target intake air amount Gcylcmd.

FIG. 8 is a flowchart of the Tfi calculation process executed in step S11 of FIG.
In step S31, the intake air amount Gcyl (g / sec) calculated in the intake air amount control process of FIG. 17 is sucked into the combustion chamber 2 in one TDC period (TDC pulse generation time interval) according to the following equation (1). Is converted to Gcyl ′ (g / TDC) (hereinafter referred to as “cylinder intake air amount”). In the equation (1), the unit of the engine speed NE is rpm.
Gcyl ′ = Gcyl × 60 / 2NE (1)

  In step S32, the Tfibase table shown in FIG. 9 is searched according to the cylinder intake air amount Gcyl ', and the basic fuel injection time Tfibase is calculated. The Tfibase table is set so that the basic fuel injection time Tfibase is substantially proportional to the cylinder intake air amount Gcyl 'and the air-fuel ratio substantially coincides with the stoichiometric air-fuel ratio. Since the amount of fuel injected varies depending on the pressure of the fuel supplied to the fuel injection valve 11, the basic fuel injection time Tfibase may be corrected according to the fuel pressure. In this case, the basic fuel injection time Tfibase is corrected so as to decrease as the fuel pressure increases.

In step S33, the basic fuel injection time Tfibase is applied to the following equation (2) to calculate the fuel injection time Tfi.
Tfi = Tfibase × KCMD × KAF (2)
Here, KCMD is a target air-fuel ratio coefficient set according to the engine operating state such as the engine speed NE, the intake pipe pressure PBA, and the output of the O2 sensor 57. The target air-fuel ratio coefficient KCMD is proportional to the reciprocal of the air-fuel ratio A / F, that is, the fuel-air ratio F / A, and takes a value of 1.0 when the stoichiometric air-fuel ratio is used. KAF is an air-fuel ratio correction coefficient set according to the air-fuel ratio detected by the LAF sensor 56. Specifically, the detected equivalent ratio KACT obtained by converting the detected air-fuel ratio into the equivalent ratio is set by PID (proportional integral derivative) control or adaptive control so as to coincide with the target equivalent ratio KCMD.

FIG. 10 is a flowchart of the Tni calculation process executed in step S12 of FIG.
In step S41, a Tnibase map shown in FIG. 11A is searched according to the engine speed NE and the cylinder intake air amount Gcyl ′, and a basic nitrogen injection time Tnibase is calculated. In FIG. 11A, lines L1, L2, and L3 indicate basic nitrogen injection in which the cylinder intake air amount Gcyl ′ corresponds to the first value G1, the second value G2, and the third value G3, respectively. The time Tnibase is set, and G1 to G3 satisfy the relationship of G1>G2> G3. That is, the Tnibase map is set such that the basic nitrogen injection time Tnbase increases as the cylinder intake air amount Gcyl ′ (engine load) increases. Further, in a high load operation state in which the cylinder intake air amount Gcyl ′ is large, the basic nitrogen injection time Tnibase is set to increase in a high rotation region and a low rotation region of the engine speed NE. This is because knocking is likely to occur in a high rotation region and a low rotation region in a high load operation state.

  In step S42, the Kniaf table shown in FIG. 11B is searched according to the air-fuel ratio (specifically, the detected equivalent ratio KACT), and the N2 air-fuel ratio correction value Kniaf is calculated. The Kniaf table shows that when the air-fuel ratio is the stoichiometric air-fuel ratio, the N2 air-fuel ratio correction value Kniaf is “1.0”, and the N2 air-fuel ratio correction value Kniaf decreases as the difference between the stoichiometric air-fuel ratio and the air-fuel ratio increases. Is set to This is because knocking becomes difficult as the air-fuel ratio deviates from the stoichiometric air-fuel ratio.

  In step S43, the Knias table shown in FIG. 11C is searched according to the elapsed time TMAST after the completion of the engine start, and the N2 post-start correction value Knias is calculated. The Knias table is set such that the N2 post-start correction value Knias is “0” for the first 20 seconds and then gradually increases to “1.0” as time elapses. Immediately after the engine is started, in order to stabilize combustion, the nitrogen injection amount is set to “0” and then gradually increased to obtain a knocking suppression effect.

  In step S44, a Knipnt table shown in FIG. 11 (d) is searched according to the N2 tank internal pressure Pnt, and an N2 tank internal pressure correction value Knipnt is calculated. The Knipnt table is set so that the N2 tank internal pressure correction value Knipnt decreases as the N2 tank internal pressure Pnt increases, and the N2 tank internal pressure Pnt is equal to the pressurization request lower limit pressure Pntmin (see FIG. 15, step S61). At this time, the N2 tank internal pressure correction value Knipnt is set to “1.0”. This is because when the N2 tank internal pressure Pnt decreases, the nitrogen injection amount decreases even if the nitrogen injection time Tni is the same.

  In step S45, it is determined whether or not the knocking flag FKNOCK is “1”. The knocking flag FKNOCK is set to “1” when occurrence of knocking is detected based on the output of the knocking sensor 55 in a process (not shown). If the answer to step S45 is negative (NO), that is, if knocking has not occurred, the N2 knock correction value Knig is set to “1.0” (step S47). On the other hand, if FKNOCK = 1 and knocking occurs, the N2 knock correction value Knig is set to “1.2” (step S46).

In step S48, the nitrogen injection time Tni is calculated by applying the basic nitrogen injection time Tnibase and each correction value to the following equation (3).
Tni = Tnibase × Kniaf × Kniast
× Knipnt × Kniig (3)

  According to the process of FIG. 10, the basic nitrogen injection time Tnbase is calculated according to the engine operating state (engine speed NE and cylinder intake air amount Gcyl ′), so the nitrogen injection amount is reduced in the operating state where knocking is unlikely to occur. By reducing, the combustion efficiency can be improved by increasing the combustion speed.

  Further, by using the N2 air-fuel ratio correction value Kniaf set in accordance with the air-fuel ratio, it is possible to reduce the nitrogen injection amount and improve the combustion efficiency during the air-fuel ratio rich operation or lean operation in which knocking hardly occurs. . Further, the N2 post-start correction value Knias suppresses the nitrogen injection immediately after the completion of the engine start, so that it is possible to stabilize the combustion immediately after the start when the combustion tends to become unstable. As a result, the amount of unburned gas (HC) discharged can be reduced. Further, since the nitrogen injection time Tni is increased as the N2 tank internal pressure Pnt is reduced by the N2 tank internal pressure correction value Knipnt, accurate nitrogen injection amount control can be performed even if the N2 tank internal pressure Pnt varies. Further, when knocking occurs, the nitrogen injection amount is increased by the N2 knock correction value Knig, so that it is not necessary to correct the retard of the ignition timing, and the combustion efficiency can be improved.

FIG. 12 is a flowchart of the injection timing determination process executed in step S13 of FIG.
In step S51, the Festg map shown in FIG. 13A is searched according to the engine speed NE and the intake pipe pressure PBA, and the fuel injection end stage Festg is determined. Here, the “stage” is a period corresponding to a crank angle of 30 degrees (CRK pulse generation angle interval), and as shown in FIG. 14, the stage numbers are 0, 1, 2 in order from the start of the compression stroke of each cylinder. , 3,..., 23. The fuel injection end stage Festg is a stage that ends fuel injection. In the example shown in FIG. 14, Festg = 14. The Festg map shown in FIG. 13A is set such that the fuel injection end stage Festg advances as the engine speed NE increases and the intake pipe pressure PBA increases.

In step S52, the fuel injection start timing Fstmg is determined from the fuel injection end stage Festg and the fuel injection time Tfi. Note that the fuel injection end timing Fetmg is the start time of the fuel injection end stage Festg.
In step S53, the Nestg map shown in FIG. 13B is searched according to the engine speed NE and the intake pipe pressure PBA to determine the nitrogen injection end stage Nestg. The Nestg map is set so that the nitrogen injection end stage Nestg advances as the engine speed NE increases and the intake pipe pressure PBA increases. Further, the nitrogen injection end stage Nestg is set to be behind (retarded side) from the fuel injection end stage Festg. In the example shown in FIG. 14, Nestg = 20.

  In step S54, the nitrogen injection start timing Nstmg is determined from the nitrogen injection end stage Nestg and the nitrogen injection time Tni. The nitrogen injection end timing Netmg is the start time of the nitrogen injection end stage Nestg.

  According to the processing of FIG. 12, the nitrogen injection end stage Nestg is set after the fuel injection end stage Festg, so that nitrogen is supplied to the combustion chamber after the fuel / air mixture. Therefore, a nitrogen layer can be reliably formed on the peripheral edge of the combustion chamber. Preferably, as shown in FIG. 14, the nitrogen injection start timing Nstmg is set after the fuel injection end timing Fetmg so that the fuel injection execution period and the nitrogen injection execution period do not overlap, or It is desirable to make the overlap period as short as possible. Thereby, the air-fuel mixture layer and the nitrogen layer in the combustion chamber are clearly separated, and the effect of suppressing knocking can be enhanced.

  When the engine speed NE increases rapidly, there are cases where the nitrogen injection cannot be completed at the nitrogen injection end stage Nestg determined by the processing of FIG. 12, or the fuel injection cannot be completed at the fuel injection end stage Festg. In such a case, nitrogen injection and fuel injection are forcibly terminated at the stage of stage number 23.

FIG. 15 is a flowchart of the N2 tank internal pressure control process executed in step S21 of FIG.
In step S61, it is determined whether the N2 tank internal pressure Pnt is lower than the pressurization request lower limit pressure Pntmin. When this answer is negative (NO), the control input (hereinafter referred to as “N2 boost pressure control amount”) Unc (k) of the electric compressor 35 is set to “0” (step S65), and the process proceeds to step S66. . When the N2 tank internal pressure Pnt is higher than the pressurization request lower limit pressure Pntmin, there is no need for pressurization, so the electric compressor 35 is operated with the N2 boost pressure control amount U (k) set to “0” for power saving. Do not let it. Note that (k) indicates the discretization time discretized at the execution period (for example, 10 milliseconds) of the timer process shown in FIG.

  If Pnt <Pntmin in step S61, the Pnicmd map shown in FIG. 16 is searched according to the intake air amount Gcyl and the N2 tank internal pressure Pnt to calculate the target supercharging pressure Pnicmd (step S62). In FIG. 16, the lines L4, L5, and L6 are respectively set to the target boost pressure Pnicmd corresponding to the N2 tank internal pressure Pnt corresponding to the first value P1, the second value P2, and the third value P3. P1 to P3 satisfy the relationship of P1 <P2 <P3. That is, the Pnicmd map is set so that the target supercharging pressure Pnicmd increases as the intake air amount Gcyl increases and the N2 tank internal pressure Pnt decreases.

ここでσ(k)は下記式（５）で定義される切換関数値、Ｋｒｃｈ及びＫａｄｐは所定の値に設定されるフィードバックゲインである。
σ(k)＝Ｐｎｉ(k)−Ｐｎｉｃｍｄ(k)
＋ＰＯＬＥ×（Ｐｎｉ(k-1)−Ｐｎｉｃｍｄ(k-1)） （５） In step S63, the N2 boost pressure control amount Unc (k) is calculated by the following equation (4).

Here, σ (k) is a switching function value defined by the following equation (5), and Krch and Kadp are feedback gains set to predetermined values.
σ (k) = Pni (k) −Pnicmd (k)
+ POLE × (Pni (k−1) −Pnicmd (k−1)) (5)

  Here, POLE is a switching function setting parameter, and is set to a value between “−1” and “0”. The value of the switching function setting parameter POLE is a fixed value in the present embodiment, but may be changed as necessary. By changing the value of the switching function setting parameter POLE, the follow-up characteristic of the N2 boost pressure Pni with respect to the target boost pressure Pnicmd can be changed. Specifically, the tracking speed can be increased as the absolute value of the switching function setting parameter POLE is decreased. If the switching function value σ defined by the equation (5) is used as a parameter indicating the control deviation, the response characteristic of the control can be designated, and such control is called response designation type control. In addition, sliding mode control and backstepping control are known as response designation control. The control by the above equations (4) and (5) corresponds to the control excluding the equivalent control input in the sliding mode control.

  Feedback by response designation type control so that the N2 boost pressure Pni matches the target boost pressure Pnicmd by driving the electric compressor 35 with the N2 boost pressure control amount Unc (k) calculated by the equation (5). Control is performed. By adopting the response designation type control, it is possible to reliably prevent overshoot of the N2 boost pressure Pni with respect to the target boost pressure Pnicmd. As a result, it is possible to suppress the occurrence of unnecessary supercharging work (power consumption) for the overshoot.

  In step S64, it is determined whether or not the N2 supercharging pressure control amount Unc (k) calculated by the equation (4) is a negative value. If it is a negative value, the process proceeds to step S65. When the N2 supercharging pressure control amount Unc (k) is “0” or more, the process immediately proceeds to step S66.

  In step S66, it is determined whether or not the N2 tank internal pressure Pnt is smaller than a value obtained by adding the pressure loss Pniloss in the nitrogen separation device 32 to the N2 supercharging pressure Pni (hereinafter referred to as “set pressure”). If the answer is negative (NO) and the N2 tank internal pressure Pnt is equal to or higher than the set pressure (Pni + Pniloss), it is determined that the N2 tank internal pressure Pnt is not required and the electric flow control valve 37 is closed ( Step S68). On the other hand, when Pnt <(Pnt + Pniloss), since the N2 tank internal pressure Pnt needs to be increased, the electric flow control valve 37 is opened (step S67).

  According to the process of FIG. 15, the electric compressor 35 is driven only when the N2 tank internal pressure Pnt becomes lower than the pressurization request lower limit pressure Pntmin. That is, when a sufficient N2 tank internal pressure Pnt is obtained by pressurization by the second compressor 36 of the supercharger 100, the electric compressor 35 can be stopped to save power.

  Further, when the N2 tank internal pressure Pnt decreases, the electric compressor 35 immediately applies pressure, and the N2 tank internal pressure Pnt is maintained at a predetermined value (Pntmin) or higher, so that the nitrogen injection amount can be accurately controlled. . As a result, knocking can be reliably suppressed.

FIG. 17 is a flowchart of the intake air amount control process executed in step S22 of FIG.
In step S71, the target intake air amount Gcylcmd is determined according to the accelerator pedal operation amount AP, the vehicle speed VP, the gear position GP, and the like. Basically, the target intake air amount Gcylcmd is set so as to increase as the accelerator pedal operation amount AP increases.

In step S72, the intake air amount Gcyl is calculated by applying the air amount Gth, the intake pipe pressure PBA, and the intake air temperature TA detected by the air flow meter 51 to the following equation (6).
Gcyl = Gth (k) −Vb (PBA (k) −PBA (k−1)) / (R · TA)
(6)
Here, Vb is the volume (m ³ ) of the intake pipe 6, and R is a gas constant (g · K / (Pa · m ³ )).

ここでσ’(k)は下記式（８）で定義される切換関数値、Ｋｒｃｈ’及びＫａｄｐ’は所定の値に設定されるフィードバックゲインである。
σ’(k)＝Ｇｃｙｌ(k)−Ｇｃｙｌｃｍｄ(k)
＋ＰＯＬＥ’×（Ｇｃｙｌ(k-1)−Ｇｃｙｌｃｍｄ(k-1)） （８） In step S73, the target throttle valve opening THcmd is calculated using the following equation (7) so that the intake air amount Gcyl matches the target intake air amount Gcylcmd.

Here, σ ′ (k) is a switching function value defined by the following equation (8), and Krch ′ and Kadp ′ are feedback gains set to predetermined values.
σ ′ (k) = Gcyl (k) −Gcylcmd (k)
+ POLE '× (Gcyl (k-1) -Gcylcmd (k-1)) (8)

    Here, POLE 'is a switching function setting parameter, and is set to a value between "-1" and "0". The value of the switching function setting parameter POLE is a fixed value in the present embodiment, but may be changed as necessary. Expressions (7) and (8) have the same format as Expressions (4) and (5) described above. That is, the target throttle valve opening THcmd is calculated by response assignment control so that the intake air amount Gcyl matches the target intake air amount Gcylcmd.

  When the target throttle valve opening THcmd is calculated from the process of FIG. 17, the control amount of the actuator 10 is determined by a process (not shown) so that the throttle valve opening TH matches the target throttle valve opening THcmd. . Thereby, the intake air amount Gcyl can be matched with the target intake air amount Gcylcmd.

In the present embodiment, the crank angle position sensor 60, the ECU 70, and the nitrogen supply device 200 constitute nitrogen supply means, and the crank angle position sensor 60, the ECU 70, and the fuel injection valve 11 constitute fuel supply means. Further, the N2 tank internal pressure sensor 59 corresponds to a nitrogen tank internal pressure detecting means, the knocking sensor 55 and the ECU 70 constitute a knocking detecting means, and the ECU 70 is a fuel injection execution period setting means, a fuel supply timing changing means, a nitrogen injection execution period setting means. And nitrogen supply timing changing means. More specifically, the process of FIG. 8 and steps S51 and S52 of FIG. 12 correspond to a part of the fuel supply means, and the process of FIG. 10 and steps S53 and S54 of FIG. 12 correspond to a part of the nitrogen supply means. To do. 8 corresponds to the fuel injection execution period setting means, steps S51 and S52 in FIG. 12 correspond to the fuel supply timing changing means, and the process in FIG. 10 corresponds to the nitrogen injection execution period setting means. Steps S53 and S54 correspond to nitrogen supply timing changing means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, the Festg map and the Nestg map shown in FIG. 13 are set according to the engine speed NE and the intake pipe pressure PBA. That is, the intake pipe pressure PBA is used as a parameter indicating the engine load. However, instead of the intake pipe pressure PBA, the intake air amount Gcyl or the cylinder intake air amount Gcyl 'may be used as a parameter indicating the engine load.

In the above-described embodiment, the nitrogen supply device 200 using the nitrogen separator is shown, but a nitrogen tank filled with high-pressure nitrogen may be used instead of the nitrogen separator.
In the above-described embodiment, the structure of the intake port and the exhaust port, and the arrangement of the intake valve 4 and the exhaust valve 5 constitute a swirl generating mechanism to generate a mixture or nitrogen swirl in the combustion chamber. Alternatively, a swirl control valve may be provided in the intake port to control whether swirl is generated in the combustion chamber. Alternatively, two intake valves may be provided for each cylinder, and one of the intake valves may be stopped or set to a low lift amount according to the engine operating state to generate a swirl. It is also possible to generate a turnbull flow by combining an intake port configured at an upward angle with respect to the combustion chamber of the engine, and use the generated turnbull flow instead of the swirl flow.

  In the above-described embodiment, the internal combustion engine that injects fuel into the intake pipe is shown. However, the present invention is also applicable to a direct injection internal combustion engine that injects fuel directly into the combustion chamber. Further, the present invention can be applied to a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

It is a figure showing composition of an internal-combustion engine concerning one embodiment of the present invention. It is a schematic diagram for demonstrating a combustion chamber and the structure of the vicinity. It is a figure for demonstrating the air-fuel mixture layer and nitrogen layer in a combustion chamber. It is a figure for demonstrating that a mixed gas layer and a nitrogen layer are formed by a swirl. It is a block diagram which shows the structure of the control system of the internal combustion engine shown in FIG. It is a flowchart of the control processing performed synchronizing with the rotation phase of an internal combustion engine. It is a flowchart of the control processing performed for every predetermined time. 7 is a flowchart showing a Tfi calculation process executed in the process of FIG. 6. It is a figure which shows the table used by the process of FIG. It is a flowchart which shows the Tni calculation process performed by the process of FIG. It is a figure which shows the map and table which are used by the process of FIG. It is a flowchart which shows the injection timing determination process performed by the process of FIG. It is a figure which shows the map used by the process of FIG. It is a figure for demonstrating a fuel injection timing and a nitrogen injection timing. It is a flowchart which shows the N2 tank internal pressure control process performed by the process of FIG. It is a figure which shows the map used by the process of FIG. It is a flowchart which shows the intake air amount control process performed by the process of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Combustion chamber 3 Spark plug 4 Intake valve 5 Exhaust valve 6 Intake pipe 7 1st compressor 11 Fuel injection valve (fuel supply means)
12 Nitrogen injection valve (nitrogen supply means)
21 Exhaust pipe 22 Turbine 31 Air passage (nitrogen supply means)
32 Nitrogen separator (nitrogen supply means)
33 Nitrogen tank (nitrogen supply means)
34 Nitrogen supply passage (nitrogen supply means)
35 Electric compressor (nitrogen supply means)
36 Second compressor (nitrogen supply means)
37 Electric flow control valve (nitrogen supply means)
51 Airflow sensor 54 Intake pipe internal pressure sensor 55 Knocking sensor 58 N2 supercharging pressure sensor 59 N2 tank internal pressure sensor 60 Crank angle position sensor (nitrogen supply means, fuel supply means)
70 Electronic control unit (nitrogen supply means, fuel supply means)
100 Supercharger 200 Nitrogen supply device (nitrogen supply means, on-vehicle nitrogen generator)

Claims (5)

In a control apparatus for an internal combustion engine, comprising: a nitrogen supply means for supplying nitrogen to the internal combustion engine; and a fuel supply means for supplying fuel to the engine at a fuel supply timing according to a rotation phase of the engine.
The engine includes a swirl generating mechanism that generates a swirl of intake gas in the combustion chamber,
The nitrogen supply means supplies nitrogen at a nitrogen supply timing corresponding to the rotational phase of the engine , sets the nitrogen supply start timing after the fuel supply start timing, and sets the nitrogen supply end timing to the fuel supply end timing. A control device for an internal combustion engine, which is set after the time . The fuel supply means supplies the fuel via a fuel injection valve provided upstream of the intake valve of the engine, and sets a fuel injection execution period by the fuel injection valve according to the load of the engine Injection execution period setting means, and fuel supply timing changing means for changing the fuel supply timing according to the operating state of the engine,
The nitrogen supply means supplies the nitrogen through a nitrogen injection valve provided upstream of the intake valve of the engine, and sets a nitrogen injection execution period by the nitrogen injection valve according to the load of the engine Injection execution period setting means, and nitrogen supply timing changing means for changing the nitrogen supply timing according to the operating state of the engine,
The nitrogen supply start timing or the fuel supply end timing is set such that an overlap period between the fuel injection execution period and the nitrogen injection execution period is as short as possible, or the fuel injection execution period and the nitrogen injection execution period are 2. The control device for an internal combustion engine according to claim 1, wherein the control device is set so as not to overlap . The nitrogen supply means has a nitrogen tank and a nitrogen tank internal pressure detection means for detecting the pressure in the nitrogen tank,
The nitrogen injection execution period setting means, a control apparatus for an internal combustion engine according to claim 1 or 2, corrected to said Rukoto to reduce the nitrogen injection execution period as the nitrogen tank pressure increases. A knock detection means for detecting knocking of the engine;
The nitrogen injection execution period setting means, when the knocking is detected, the internal combustion engine according to any one of claims 1 to 3, characterized that you corrected in the increasing direction of the nitrogen injection execution period Control device. The nitrogen injection execution period setting means is within a predetermined time after start completion time of the engine, according to any one of claims 1 4, characterized that you correct the nitrogen injection execution period in the decreasing direction Control device for internal combustion engine.

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