JP6982761B2 - Engine combustion control method and combustion control device - Google Patents

Description

The techniques disclosed herein belong to the technical fields relating to engine combustion control methods and combustion control devices.

Conventionally, an engine provided with a plasma generating means for generating plasma in a combustion chamber by applying a voltage between electrodes has been known.

For example, Patent Document 1 describes an ignition plug (plasma generating means) in which a discharge is generated between the center electrode and the ground electrode, a first current meter for measuring the current flowing through the center electrode, and a current flowing through the ground electrode. When a short pulse electric field that has a second current to be measured and forms a low temperature plasma state (non-equilibrium plasma state) is generated between the electrodes, the current value measured by the first current meter and the second current meter An engine (internal engine) that measures the flow velocity of the gas flowing between the electrodes is disclosed from the current value measured in.

Japanese Unexamined Patent Publication No. 2014-141919

By the way, for example, in an operating state in which a flame nucleus that triggers combustion is difficult to form and flame propagation is difficult, such as during lean combustion of an engine, the combustion stability of the engine may decrease. On the other hand, as a result of diligent research by the present inventors, when a voltage is applied between the electrodes of the plasma generating means so that a non-equilibrium plasma is generated in the combustion chamber and discharged, the fuel burns in the combustion chamber. It has been found that promoting substances are produced and the combustion stability of the engine is improved.

Although the non-equilibrium plasma is generated in the one described in Patent Document 1, it is not disclosed at all that it is used for combustion of fuel in a combustion chamber. Therefore, there is room for improvement from the viewpoint of improving the combustion stability of the engine by utilizing the non-equilibrium plasma.

The technique disclosed herein has been made in view of these points, and the purpose thereof is to improve the combustion stability of the engine by appropriately utilizing the non-equilibrium plasma.

In order to solve the above problems, in the technique disclosed here, each process of the intake stroke, the compression stroke, the expansion stroke and the exhaust stroke is repeated in this order so as to face the engine body having a combustion chamber and the combustion chamber. A plasma generating means for generating plasma in the combustion chamber by discharging by applying a voltage between the electrodes, a fuel supply means for supplying fuel to the combustion chamber, and discharging from the combustion chamber in the exhaust stroke. A combustion control method for an engine, which is provided with an exhaust / recirculation means for recirculating the exhausted exhaust into the combustion chamber and in which an air-fuel mixture formed by the fuel supplied by the fuel supply means is burned in the combustion chamber, is targeted. At least in the compression stroke, the non-equilibrium plasma generation step of generating non-equilibrium plasma by applying a first pulse voltage between the electrodes of the plasma generation means to discharge the non-equilibrium plasma, and the end of the non-equilibrium plasma generation step. immediately after, between the electrodes of the plasma generating means, by discharging by applying a second pulse voltage, and thermal equilibrium plasma generating step of generating a thermal plasma, only contains, in the non-equilibrium plasma generating step, the The application start timing and application end timing of the first pulse voltage are the G / F which is the ratio of the gas and the fuel in the air-fuel mixture in the combustion chamber, and the amount of exhaust gas in the gas with respect to the total gas amount in the combustion chamber. It is assumed that the peak voltage of the first pulse voltage is set based on the in-cylinder pressure in the compression stroke, while it is calculated based on at least one of the EGR ratio which is the ratio .

According to this configuration, by generating non-equilibrium plasma at least in the compression stroke, a substance (hereinafter referred to as an active species) that promotes combustion of fuel is generated in the combustion chamber. This facilitates the formation of flame nuclei when a thermal equilibrium plasma is generated. Further, if the active species is diffused in the combustion chamber, the flame can easily propagate from the flame nucleus. This makes it possible to improve the combustion stability of the engine.

In one embodiment of the engine combustion control method, the first pulse voltage is a pulse voltage having a pulse width equal to or larger than the first predetermined value and smaller than the second predetermined value, which is larger than the first predetermined value and is less than the second predetermined value. The pulse voltage is a pulse voltage having a pulse width equal to or larger than the second predetermined value.

That is, in general, non-equilibrium plasma and thermal equilibrium plasma can be separately generated by controlling the pulse width of the pulse voltage applied between the electrodes of the plasma generating means. Therefore, with the above configuration, non-equilibrium plasma and thermal equilibrium plasma can be efficiently generated according to the purpose. As a result, the combustion stability of the engine can be further improved.

In the combustion control method of the engine, the non-equilibrium plasma generation step may be a step to be executed when the G / F is 16 or more in the operating state.

That is, in the operating state where the G / F is 16 or more, since it is in a lean state, the combustion stability of the engine tends to decrease. Therefore, by executing the non-equilibrium plasma generation step in an operating state where the G / F is 16 or more, the effect of improving the combustion stability of the engine can be appropriately exhibited.

The combustion control method for the engine, the upper Symbol non-equilibrium plasma generation step may be a step to be executed when a driving state where the EGR rate is 20% or more.

That is, in an operating state where the EGR rate is 20% or more, the oxygen concentration in the combustion chamber is considerably low, so that the combustion stability of the engine tends to decrease. Therefore, by executing the non-equilibrium plasma generation step and the thermal equilibrium plasma generation step in the operating state where the EGR rate is 20% or more, the effect of improving the combustion stability of the engine can be more appropriately exhibited. ..

In the combustion control method of the engine, the period for executing the non-equilibrium plasma generation step may be longer than the period for executing the thermal equilibrium plasma generation step.

According to this configuration, in the non-equilibrium plasma generation step, as many active species as possible can be generated in the combustion chamber, so that the combustion of the air-fuel mixture when the thermal equilibrium plasma generation step is executed proceeds smoothly. Therefore, the combustion stability of the engine can be further improved.

In the combustion control method of the engine, the non-equilibrium plasma generation step is at least a step executed at the latter stage of the compression stroke and after the fuel is supplied by the fuel supply means, and is a period during which the non-equilibrium plasma generation step is executed. The length may be 1/4 or more of the period during which the compression stroke is executed.

According to this configuration, a mixture of fuel and intake air becomes present around the electrode of the compression stroke plasma generation means, and the active species generated in the non-equilibrium plasma generation step causes the plasma generation means to be around the electrode. , Local low temperature oxidation reaction occurs. As a result, the temperature around the electrodes of the plasma generating means becomes high, so that flame nuclei are likely to be formed when the thermal equilibrium plasma is generated by the thermal equilibrium plasma generation step. As a result, the combustion stability of the engine is further improved.

Another aspect of the technique according to the present disclosure is the technique according to the combustion control device of the engine. Specifically, the engine body has a combustion chamber in which each step of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke is repeated in this order, the fuel supply means for supplying fuel to the combustion chamber, and the exhaust stroke. An engine combustion control device including an exhaust / recirculation means for recirculating the exhaust discharged from the combustion chamber to the combustion chamber, and burning an air-fuel mixture formed by the fuel supplied by the fuel supply means in the combustion chamber. The operation of the plasma generation means, the plasma generation means, and the fuel supply means, which are arranged so as to face the combustion chamber and generate plasma in the combustion chamber by discharging by applying a voltage between the electrodes. The control means further includes a control means for controlling, and the control means generates a non-equilibrium plasma by applying a first pulse voltage between the electrodes of the plasma generation means and discharging the gas at least in the compression stroke. A thermal equilibrium plasma that generates a thermal equilibrium plasma by executing the equilibrium plasma generation control and applying a second pulse voltage between the electrodes of the plasma generation means to discharge the non-equilibrium plasma immediately after the end of the non-equilibrium plasma generation control. It is configured to execute the generation control, and in the non-equilibrium plasma generation control, the application start timing and the application end timing of the first pulse voltage are the ratio of the gas and the fuel in the air-fuel mixture in the combustion chamber. The peak voltage of the first pulse voltage is the compression, while it is calculated based on at least one of the G / F and the EGR ratio, which is the ratio of the amount of exhaust gas in the gas to the total amount of gas in the combustion chamber. It is assumed that it is set based on the in-cylinder pressure in the stroke.

Even in this configuration, since the active species are generated in the combustion chamber, flame nuclei are likely to be formed when a thermal equilibrium plasma is generated. Further, if the active species is diffused in the combustion chamber, the flame can easily propagate from the flame nucleus. This makes it possible to improve the combustion stability of the engine.

In one embodiment of the combustion control device of the engine, the first pulse voltage is a pulse voltage having a pulse width of not less than the first predetermined value and larger than the first predetermined value and less than the second predetermined value. The pulse voltage is a pulse voltage such that the pulse width is equal to or larger than the second predetermined value.

According to this configuration, non-equilibrium plasma and thermal equilibrium plasma can be efficiently generated according to the purpose. As a result, the combustion stability of the engine can be further improved.

In the combustion control device of the engine, the control means is configured to execute the non-equilibrium plasma generation control when the operating state of the engine is an operating state in which the G / F is 16 or more. You may.

That is, since the combustion stability of the engine tends to decrease in the operating state where the G / F is 16 or more, the effect of improving the combustion stability of the engine can be appropriately exhibited according to the above configuration.

The combustion control apparatus of the engine, the control written above means, the operating state of the engine when in operation state in which the EGR rate becomes 20% or more, is configured to perform the non-equilibrium plasma generation control May be.

That is, in an operating state where the EGR rate is 20% or more, the combustion stability of the engine tends to decrease. Therefore, according to the above configuration, the effect of improving the combustion stability of the engine can be more appropriately exhibited. ..

In the combustion control device of the engine, the control means may be configured so that the period for executing the non-equilibrium plasma generation control is longer than the period for executing the thermal equilibrium plasma generation control.

According to this configuration, the non-equilibrium plasma generation control can generate as many active species as possible in the combustion chamber, so that the combustion of the air-fuel mixture when the thermal equilibrium plasma generation control is executed proceeds smoothly. Therefore, the combustion stability of the engine can be further improved.

In the combustion control device of the engine, the control means executes the non-balanced plasma generation control at least at the latter stage of the compression stroke and after the fuel is supplied by the fuel supply means, and also executes the non-balanced plasma generation control. The length of the period may be configured to be 1/4 or more of the period during which the compression stroke is executed.

According to this configuration, the active species generated by the non-equilibrium plasma generation control causes a local low temperature oxidation reaction around the electrode of the plasma generation means. As a result, the temperature around the electrodes of the plasma generation means becomes high, so that flame nuclei are likely to be formed when the thermal equilibrium plasma is generated by the thermal equilibrium plasma generation control. As a result, the combustion stability of the engine is further improved.

In the combustion control method of the engine, in the non-equilibrium plasma generation step, when the G / F is 20 or more and the EGR ratio is at least 30% or more in an operating state, the first pulse voltage is the intake air. While the application is started during the stroke and the application is terminated in the latter half of the compression stroke, the G / F does not satisfy both 20 or more and the EGR ratio is 30% or more, and the G / F is 16 or more. When the operating state satisfies at least one of less than 20 and the EGR rate of 20% or more and less than 30%, the application of the first pulse voltage is started in the first half of the compression stroke and ends in the second half of the compression stroke. It may be configured to be done.

In the combustion control device of the engine, in the non-equilibrium plasma generation control, when the G / F is 20 or more and the EGR ratio is at least 30% or more in the operating state, the first pulse voltage is the intake air. While the application is started during the stroke and the application is terminated in the latter half of the compression stroke, the G / F does not satisfy both 20 or more and the EGR ratio is 30% or more, and the G / F is 16 or more. When the operating state satisfies at least one of less than 20 and the EGR rate of 20% or more and less than 30%, the application of the first pulse voltage is started in the first half of the compression stroke and ends in the second half of the compression stroke. It may be configured to be done.

As described above, according to the technique disclosed herein, by generating non-equilibrium plasma at least in the compression stroke, it is possible to generate a substance that promotes the combustion of fuel in the combustion chamber. Then, by generating a thermal equilibrium plasma after that, a flame nucleus can be easily formed by utilizing the above-mentioned substance. As a result, the combustion stability of the engine can be improved.

It is a schematic block diagram of the engine system to which the combustion control device which concerns on an exemplary embodiment is applied. It is a schematic diagram which shows the periphery of the electrode of a discharge plug. It is a block diagram which shows the control system of an engine. It is a figure which shows typically the combustion control which does not accompany the non-equilibrium plasma generation control. It is a figure which shows typically the combustion control with the non-equilibrium plasma generation control. It is a map which shows the generation condition of the non-equilibrium plasma and the thermal equilibrium plasma. It is a graph which shows an example of the waveform of the pulse voltage at the time of generating a non-equilibrium plasma. It is a graph which shows an example of the waveform of the pulse voltage at the time of generating a thermal equilibrium plasma. It is a conceptual diagram which shows the generation start time and the generation period of a non-equilibrium plasma, and the generation start time of a thermal equilibrium plasma. It is a flowchart which shows the processing operation of PCM at the time of executing the non-equilibrium plasma generation control and the thermal equilibrium plasma generation control. It is a graph which shows the change of the heat generation rate in a combustion chamber.

Hereinafter, exemplary embodiments will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of the engine 1 to which the combustion control device according to the present embodiment is applied. The engine 1 of the present embodiment is an engine mounted on a vehicle. The engine 1 includes an engine main body 1a, an intake passage 20 for introducing combustion air into the engine main body 1a, and an exhaust passage 30 for discharging the exhaust generated by the engine main body 1a.

The engine body 1a is an in-line 4-cylinder type, and the four cylinders 2 are arranged in series in a direction orthogonal to the paper surface of FIG. The engine body 1a is used as a drive source for the vehicle.

The engine body 1a includes a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 provided on the upper surface of the cylinder block 3, and a piston fitted to the cylinder 2 so as to be able to reciprocate (here, move up and down). Has 5 and.

Cylinder 2 is a cylinder in which a combustion chamber 6 is formed. Specifically, the combustion chamber 6 is formed above the piston 5 in the cylinder 2. The combustion chamber 6 is a so-called pent-roof type, and the ceiling surface of the combustion chamber 6 composed of the lower surface of the cylinder head 4 has a triangular roof shape composed of two inclined surfaces on the intake side and the exhaust side. In the combustion chamber 6, the combustion cycle of the engine 1, that is, each of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke is repeated in this order. In the following description, the space formed between the upper surface of the piston 5 and the ceiling surface of the combustion chamber 6 in the inner space of the cylinder 2 regardless of the position of the piston 5 and the combustion state of the air-fuel mixture is referred to as a combustion chamber 6.

A water jacket 3a through which engine cooling water flows is formed around the cylinder 2 in the cylinder block 3. The water jacket 3a is formed in the cylinder block 3 so as to surround the four cylinders 2.

The piston 5 is connected to the crankshaft 7 via a connecting rod 8 in the cylinder block 3. The crankshaft 7 is rotationally driven by the reciprocating motion of the piston 5. On the upper surface of the piston 5, a cavity is formed in which a region including the central portion thereof is recessed on the opposite side (lower side) of the cylinder head 4.

The geometric compression ratio of the engine body 1a, that is, the ratio of the volume of the combustion chamber 6 when the piston 5 is at the bottom dead center and the volume of the combustion chamber 6 when the piston 5 is at the top dead center is the present implementation. In the first form, it is set to 15 to 25 (for example, about 17).

The cylinder head 4 has an intake port 9 for introducing air supplied from the intake passage 20 into the cylinder 2 (combustion chamber 6), and a mixture of fuel and air burns in the combustion chamber 6. An exhaust port 10 for leading the exhaust generated by the above to the exhaust passage 30 is formed. Two intake ports 9 and two exhaust ports 10 are formed for each cylinder 2.

The cylinder head 4 is provided with an intake valve 11 that opens and closes an opening on the combustion chamber 6 side of each intake port 9, and an exhaust valve 12 that opens and closes an opening on the combustion chamber 6 side of each exhaust port 10. ..

The cylinder head 4 is provided with an injector (fuel supply means) 14 for supplying (injecting) fuel into the combustion chamber 6. The injector 14 is attached so that the tip end portion on which the injection port is formed is located near the center of the ceiling surface of the combustion chamber 6 and faces the center of the combustion chamber 6. The injector 14 has a plurality of nozzles at its tip, and has a cone shape (specifically, a hollow cone shape) centered on the central axis of the cylinder 2 from the vicinity of the center of the ceiling surface of the combustion chamber toward the crown surface of the piston 5. It is configured to inject fuel. The taper angle (spray angle) of the cone is, for example, 90 ° to 100 °. The specific configuration of the injector 14 is not limited to this, and may be a single injector.

The injector 14 injects fuel pumped from a high-pressure pump (not shown) into the combustion chamber 6. The injection pressure of the injector 14 is increased up to about 70 MPa.

The cylinder head 4 is provided so as to face the combustion chamber 6 and is provided with a discharge plug 13 for generating plasma in the combustion chamber 6. As shown in FIG. 2, a center electrode 13a and a ground electrode 13b are formed at the tip of the discharge plug 13. The center electrode 13a has a rod shape, and the portion other than the tip is covered with the insulator 13c. The ground electrode 13b has a cylindrical shape concentric with the center electrode 13a. The center electrode 13a is connected to a power source (not shown), and when a voltage is applied from the power source, a discharge is made between the center electrode 13a and the ground electrode 13b. Then, when a discharge is made between the center electrode 13a and the ground electrode 13b, plasma is generated in the combustion chamber 6 by the energy of the discharge. From this, the discharge plug 13 corresponds to a plasma generation means for generating plasma in the combustion chamber 6 by discharging by applying a voltage between the electrodes 13a and 13b.

The intake passage 20 is provided with an air cleaner 21 and a throttle valve 22 for opening and closing the intake passage 20 in order from the upstream side. In the present embodiment, the throttle valve 22 is basically maintained at a fully open position or an opening close to the throttle valve 22 during operation of the engine 1, and is closed only under limited operating conditions such as when the engine 1 is stopped. The intake passage 20 is shut off.

The exhaust passage 30 is provided with a purification device 31 for purifying the exhaust gas. The purification device 31 has, for example, a built-in three-way catalyst.

The exhaust passage 30 is provided with an EGR device 40 for returning a part of the exhaust gas passing through the exhaust passage 30 to the intake passage 20 as EGR gas. The EGR device 40 opens and closes the EGR passage 41 and the EGR passage 41 that communicate the portion of the intake passage 20 downstream of the throttle valve 22 and the portion of the exhaust passage 30 upstream of the purification device 31. It has an EGR valve 42.

The engine 1 according to the present embodiment is not provided with a supercharger. However, the technology according to the present disclosure does not exclude application to an engine equipped with a turbocharger.

FIG. 3 shows the control system of the engine 1. The engine 1 according to the present embodiment is collectively controlled by a powertrain control module 100 (hereinafter referred to as PCM100) as a control device. The PCM 100 is composed of a CPU, a memory, a counter timer group, an interface, and a microprocessor having a path connecting these units.

The vehicle is equipped with various sensors. The PCM 100 is electrically connected to these sensors, and a detection signal from each sensor is input to the PCM 100. For example, the engine 1 has an engine temperature sensor SN1 that detects the temperature of the engine body 1a, an airflow sensor SN2 that detects the intake flow rate flowing into the intake passage 20, and the pressure of the intake air supplied to the combustion chamber 6. An intake pressure sensor SN3, a crank angle sensor SN4 that detects the rotation angle of the crankshaft 7, and an accelerator opening sensor SN5 that detects the opening (accelerator opening) of an accelerator pedal (accelerator opening) that is not shown and is operated by the driver. One is provided for each cylinder 2, and an in-cylinder pressure sensor SN6 for detecting the pressure in each cylinder 2 is provided.

The engine temperature sensor SN1 detects the temperature of the engine body 1a by detecting, for example, the temperature of the engine cooling water flowing through the water jacket 3a. The engine temperature sensor SN1 may be a sensor that detects the temperature of the engine body 1a by detecting the exhaust temperature, and detects the temperature of the engine body 1a by detecting the oil temperature of the engine oil. It may be a sensor.

The PCM100 calculates the rotation speed (engine rotation speed) of the engine body 1a from the detection result of the crank angle sensor SN4. The PCM 100 calculates the engine load from the detection result of the accelerator opening sensor SN5. The PCM 100 calculates the heat generation rate in the combustion chamber 6 from the detection result of the in-cylinder pressure sensor SN6.

The PCM 100 executes various calculations based on the input signals from the sensors SN1 to SN6 and the like to control each part of the engine 1 such as the discharge plug 13, the injector 14, the throttle valve 22, and the EGR valve 42.

<Combustion control>
Hereinafter, the combustion control in the present embodiment will be described with reference to FIGS. 4 to 9.

In the present embodiment, the PCM 100 controls the discharge plug 13 and the like so as to make the combustion mode different according to the operating state of the engine 1 and the state in the combustion chamber 6. 4 and 5 show an example of combustion control by the PCM 100, respectively. In FIGS. 4 and 5, the crank angle of the compression top dead center is set to 0 °, whereas the advance angle side (the time earlier than the compression top dead center) is represented by a minus, and the retard side (compression top dead center) is shown. (Time later than the point) is represented by a plus. The intake stroke is a period of -360 ° to −180 °, and the compression stroke is a period of −180 ° to 0 °.

FIG. 4 shows combustion control when the possibility that the combustion stability of the engine 1 is low is low, and is, for example, an example of combustion control when the engine load is a high load equal to or higher than a predetermined load. As shown in FIG. 4, for example, when the engine 1 is in the high load region, the PCM 100 injects fuel into the combustion chamber 6 by the injector 14 during the intake stroke, and then immediately before the compression top dead point in the compression stroke. Thermal equilibrium plasma generation control that generates thermal equilibrium plasma by applying a pulse voltage between the electrodes 13a and 13b of the discharge plug 13 so as to generate thermal equilibrium plasma in the combustion chamber 6 and discharging between the electrodes 13a and 13b. To execute. The thermal equilibrium plasma refers to a plasma in which the electrons in the combustion chamber 6 and the ions and molecules of the gas in the combustion chamber 6 are in a thermal equilibrium state as the gas temperature in the combustion chamber 6 rises. ..

When the engine 1 is in the high load region, the G / F, which is the mass ratio of gas and fuel in the air-fuel mixture in the combustion chamber 6, is around 14.7, which is the stoichiometric air-fuel ratio, or smaller than the stoichiometric air-fuel ratio. Fuel is injected to the extent. Also, as much fresh air as possible is introduced into the combustion chamber 6 in order to burn a large amount of fuel in the combustion chamber 6. Therefore, when the engine 1 is in the high load region, the EGR gas is not supplied so much, and the EGR ratio, which is the ratio of the amount of EGR gas (exhaust gas) in the gas to the total amount of gas in the combustion chamber 6, is small. From these facts, when the engine 1 is in the high load region, the air-fuel mixture in the combustion chamber 6 is likely to ignite. Therefore, as shown in FIG. 4, a flame nucleus can be formed around the electrodes 13a and 13b of the discharge plug 13 just by generating the thermal equilibrium plasma immediately before the compression top dead center in the compression stroke, and the combustion chamber can be formed. The air-fuel mixture in 6 can be ignited.

On the other hand, FIG. 5 is an example of combustion control when the combustion stability of the engine 1 is likely to deteriorate, for example, when the engine load is a low load less than the predetermined load. As shown in FIG. 5, for example, when the engine 1 is in the low load region, the PCM 100 injects fuel into the combustion chamber 6 by the injector 14 during the intake stroke, and then in the compression stroke, the electrode of the discharge plug 13 A pulse voltage is applied between the 13a and 13b so as to generate a non-balanced plasma in the combustion chamber 6, and the discharge is performed between the electrodes 13a and 13b to execute the non-balanced plasma generation control for generating the non-balanced plasma. Then, the PCM 100 executes the thermal equilibrium plasma generation control immediately after the end of the non-equilibrium plasma generation control. The non-equilibrium plasma refers to a plasma in which the electrons in the combustion chamber 6 and the ions and molecules of the gas in the combustion chamber 6 are not in a thermal equilibrium state without an increase in the gas temperature in the combustion chamber 6. ..

When the engine 1 is in the low load region, the amount of fuel supplied is small and a large amount of EGR gas is introduced, so that the G / F tends to be large. Further, even if the G / F itself is small to some extent, the EGR rate tends to be high. From these facts, when the engine 1 is in the low load region, the air-fuel mixture in the combustion chamber 6 is difficult to ignite only by the thermal equilibrium plasma generation control, and the combustion stability of the engine 1 may be deteriorated.

Therefore, in the present embodiment, the PCM 100 executes non-equilibrium plasma generation control in an operating state in which the combustion stability of the engine 1 is likely to deteriorate. By generating the non-equilibrium plasma, a substance (for example, ozone (O3) or OH, hereinafter referred to as an active species) that promotes the combustion of fuel is generated in the combustion chamber 6. When the active species is produced, a local low-temperature oxidation reaction occurs around the electrodes 13a and 13b of the discharge plug 13, as shown in FIG. When the low-temperature oxidation reaction occurs, the temperature around the electrodes 13a and 13b rises, and a flame nucleus is easily formed. As a result, by executing the thermal equilibrium plasma generation control immediately after the end of the non-equilibrium plasma generation control, flame nuclei are formed around the electrodes 13a and 13b as shown in FIG. Then, after the flame nucleus is formed, as shown in FIG. 5, the flame propagates and ignites the air-fuel mixture. As a result, the combustion stability of the engine 1 can be improved even in an operating state in which the combustion stability of the engine 1 is likely to decrease. The term "immediately after the end of the non-equilibrium plasma generation control" includes the period immediately after the end of the non-equilibrium plasma generation control and within 10 ° in the crank angle.

The non-equilibrium plasma and the thermal equilibrium plasma are generated according to the purpose by controlling the pulse voltage applied between the electrodes 13a and 13b of the discharge plug 13, in particular, by controlling the pulse width of the pulse voltage. Can be done. 6 to 8 show the generation conditions of the non-equilibrium plasma and the thermal equilibrium plasma. The horizontal axis of FIG. 6 is the pulse width, which is shown on a logarithmic scale. On the other hand, the vertical axis of FIG. 6 is the peak value of the applied voltage and is shown on a logarithmic scale. As shown in FIG. 6, it can be seen that when the pulse width is shortened, non-equilibrium plasma is generated, and when the pulse width is lengthened, thermal equilibrium plasma is generated. This is because ions and molecules are considerably larger than electrons, and at a pulse voltage with a short pulse width, only electrons react and ions and molecules hardly react.

In the present embodiment, the non-equilibrium plasma and the thermal equilibrium plasma are generated according to the purpose, mainly by changing the pulse width. Specifically, as shown in FIG. 7, in the non-equilibrium plasma generation control, the PCM100 has a peak voltage of 10 kV, a pulse width of the first predetermined value or more, and a second predetermined value larger than the first predetermined value. A first pulse voltage of less than is applied between the electrodes 13a and 13b of the discharge plug 13. Further, in the non-equilibrium plasma generation control, the PCM 100 repeatedly discharges the pulse voltage at a frequency of 100 kHz. As shown in FIGS. 6 and 7, the first predetermined value is, for example, 0.01 μsec, and the second predetermined value is, for example, 1 μsec. More specifically, in the non-equilibrium plasma generation control, the PCM 100 basically applies a first pulse voltage having a peak voltage of 10 kV and a pulse width of 0.1 μsec between the electrodes 13a and 13b of the discharge plug 13. I try to let you.

On the other hand, as shown in FIG. 8, in the thermal equilibrium plasma generation control, the PCM 100 discharges a second pulse voltage having a peak voltage of 10 kV and a pulse width of more than the second predetermined value and less than the third predetermined value. It is applied between the electrodes 13a and 13b of 13. Further, in the thermal equilibrium plasma generation control, the PCM 100 repeatedly discharges a pulse voltage having a pulse width of 10 μsec or less at a frequency of 100 kHz and a pulse voltage having a pulse width of more than 10 μsec at a frequency as large as possible. As shown in FIGS. 6 and 7, the third predetermined value is, for example, 5 msec. More specifically, in the thermal equilibrium plasma generation control, the PCM 100 basically applies a second pulse voltage having a peak voltage of 10 kV and a pulse width of 1 μsec between the electrodes 13a and 13b of the discharge plug 13. ing. From the viewpoint of extending the life of the discharge plug 13, it is preferable to make the pulse width of the second pulse voltage as short as possible.

The peak voltage in the first pulse voltage of the non-equilibrium plasma generation control and the second pulse voltage of the thermal equilibrium plasma generation control may be changed in the range of 1 kV or more and 30 kV or less based on the in-cylinder pressure or the like. That is, for example, when the in-cylinder pressure is high, a large amount of gas ions and molecules are present around the electrodes 13a and 13b, and as a result of limiting the movement of electrons, it is difficult to generate non-equilibrium plasma and thermal equilibrium plasma. The voltage may be higher than 10 kV.

In the present embodiment, even in an operating state in which the engine load is low, an operating state in which the combustion stability of the engine 1 tends to decrease, that is, an operation in which the G / F is large or the EGR rate is high. In the state, the above-mentioned non-equilibrium plasma generation control is executed. Specifically, the non-equilibrium plasma generation control is executed in an operating state in which the G / F is 16 or more and the EGR rate is 20% or more at least one of them. More specifically, the start time and duration of the non-equilibrium plasma generation control are changed based on the magnitudes of the G / F and the EGR ratio.

FIG. 9 shows the start time and duration of the non-equilibrium plasma generation control by the PCM 100, and the start time of the thermal equilibrium plasma generation control. In FIG. 9, similarly to FIGS. 4 and 5, the crank angle of the compression top dead center is set to 0 ° in both FIGS. 9 (a) and 9 (b), whereas the advance angle side (from the compression top dead center). (Early period) is indicated by a minus, and the retard side (the period later than the compression top dead center) is indicated by a plus. The intake stroke is a period of -360 ° to −180 °, and the compression stroke is a period of −180 ° to 0 °.

FIG. 9A shows the non-equilibrium plasma generation control in an operating state (hereinafter referred to as a first operating state) satisfying at least one of a G / F of 20 or more and an EGR rate of 30% or more. The start time and duration, and the start time of the thermal equilibrium plasma generation control are shown. In the first operating state, there is a high possibility that the combustion stability of the engine 1 will decrease. Therefore, the PCM 100 executes the non-equilibrium plasma generation control for as long as possible to generate as many active species as possible in the combustion chamber 6. Specifically, as shown in FIG. 9A, the PCM100 has the non-equilibrium plasma generation control (at the first pulse voltage by the discharge plug 13) during the intake stroke (-360 ° to −180 ° at the crank angle). Discharge) is started. The PCM 100 continues the non-equilibrium plasma generation control for a period from the start of the non-equilibrium plasma generation control to at least −45 ° in the compression stroke. Then, the PCM 100 ends the non-equilibrium plasma generation control between −45 ° and 5 °, and immediately after the end, starts the thermal equilibrium plasma generation control (discharge by the discharge plug 13 at the second pulse voltage). .. The PCM 100 continues the thermal equilibrium plasma generation control until combustion in the combustion chamber 6 is confirmed. The PCM 100 determines whether or not combustion has started in the combustion chamber 6 based on the detection result of the in-cylinder pressure sensor SN6. Specifically, when the detection result of the in-cylinder pressure sensor SN6 becomes a predetermined pressure or higher, it is determined that combustion has started in the combustion chamber 6.

In the first operating state, the non-equilibrium plasma generation control is started during the intake stroke, but the start time may be before the start of fuel injection by the injector 14, or after the start of fuel injection by the injector 14. May be. Further, the start time and end time of the non-equilibrium plasma generation control may be changed depending on the G / F value and the EGR rate. For example, the larger the G / F or the higher the EGR rate, the earlier the non-equilibrium plasma generation control is started (the timing on the advance angle side), and the later the non-equilibrium plasma generation control is started (the timing on the retard angle side). May be terminated.

On the other hand, in FIG. 9B, both the conditions of G / F of 20 or more and EGR rate of 30% or more are not satisfied, G / F is 16 or more and less than 20, and the EGR rate is. The start timing and duration of the non-equilibrium plasma generation control and the start timing of the thermal equilibrium plasma generation control in an operating state (hereinafter referred to as a second operating state) satisfying at least one of 20% or more and less than 30%. Is shown. In the second operating state, the possibility that the combustion stability of the engine 1 is lowered is lower than that in the first operating state. Therefore, the PCM 100 shortens the period for executing the non-equilibrium plasma generation control as compared with the case of the first operating state. Specifically, as shown in FIG. 9B, the PCM100 generates non-equilibrium plasma (at the first pulse voltage by the discharge plug 13) in the first half of the compression stroke (-180 ° to -90 ° at the crank angle). Discharge) is started. The PCM 100 continues the non-equilibrium plasma generation control for a period from the start of the non-equilibrium plasma generation control to at least −45 ° in the compression stroke. Then, the PCM 100 ends the generation of the non-equilibrium plasma between −45 ° and 5 °, and immediately after the end, the thermal equilibrium plasma generation control is started. The PCM 100 continues the thermal equilibrium plasma generation control until combustion in the combustion chamber 6 is confirmed. The PCM 100 determines whether or not combustion has started in the combustion chamber 6 based on the detection result of the in-cylinder pressure sensor SN6, as in the first operating state.

The start time and end time of the non-equilibrium plasma generation control in the second operating state may be changed depending on the G / F value and the EGR rate, as in the first operating state. For example, the larger the G / F or the higher the EGR rate, the earlier the non-equilibrium plasma generation control is started from an early stage (advanced angle side), and the later non-equilibrium plasma generation control is started. The control may be terminated.

As described above, in the present embodiment, the start time and duration of the non-equilibrium plasma generation control are changed based on the magnitudes of the G / F and the EGR ratio. On the other hand, as described above, in the present embodiment, the PCM 100 executes the non-equilibrium plasma generation control at least in the compression stroke in any of the first and second operating states. In particular, the PCM 100 is executed at least in the late compression stroke and after the fuel is supplied by the injector 14. That is, if the compression stroke is late and the fuel is supplied by the injector 14, a mixture of fuel and intake air will be present around the electrodes 13a and 13b of the discharge plug 13. Therefore, a local low-temperature oxidation reaction around the electrodes 13a and 13b is likely to occur due to the active species generated by the non-equilibrium plasma generation control. Therefore, the thermal equilibrium plasma generation control facilitates the generation of flame nuclei around the electrodes 13a and 13b, further improving the combustion stability of the engine 1. The latter half of the compression stroke corresponds to the latter half of the compression stroke (the period at the crank angle) evenly divided into two (the period on the retard side).

Further, in the present embodiment, the PCM 100 makes the period for executing the non-equilibrium plasma generation control longer than the period for executing the thermal equilibrium plasma generation control. In particular, the PCM 100 sets the period for executing the non-equilibrium plasma generation control to be 1/4 or more of the period during which the compression stroke is executed (that is, a length of 45 ° or more in the crank angle). Thereby, in the non-equilibrium plasma generation control, as many active species as possible can be generated in the combustion chamber 6. Further, since a part of the generated active species diffuses into the combustion chamber 6, the flame easily propagates from the flame nucleus, so that the combustion of the air-fuel mixture in the combustion chamber 6 proceeds smoothly. As a result, the combustion stability of the engine 1 can be further improved.

Next, the processing operation of the PCM 100 when the non-equilibrium plasma generation control and the thermal equilibrium plasma generation control are executed will be described with reference to the flowchart of FIG. The processing operation based on this flowchart is executed every one combustion cycle while the engine 1 is operating.

First, in step S1, the PCM 100 reads information from each sensor SN1 to SN6.

In the next step S2, the PCM 100 determines whether or not the engine load is less than a predetermined load. The PCM 100 proceeds to step S3 when the engine load is YES, which is a low load less than the predetermined load, and returns when the engine load is NO, which is a high load equal to or higher than the predetermined load.

In step S3, the PCM 100 determines whether or not the G / F is 16 or more. When YES with a G / F of 16 or more, the process proceeds to step S5, while when NO with a G / F of less than 16, the process proceeds to step S4.

In step S4, the PCM 100 determines whether or not the EGR rate is 20% or more. When the EGR rate is YES of 20% or more, the process proceeds to step S5, while when the EGR rate is NO of less than 20%, the process returns.

In step S5, the PCM 100 calculates the start time and the end time of the non-equilibrium plasma generation control in order to execute the non-equilibrium plasma generation control. In this step S5, the PCM 100 calculates the start time and the end time of the non-equilibrium plasma generation control based on the G / F and the EGR ratio. Further, in this step S5, the PCM 100 determines the peak voltage and the pulse width of the first pulse voltage based on the in-cylinder pressure and the like. Further, in this step S5, the PCM 100 determines the peak voltage and the pulse width of the second pulse voltage based on the in-cylinder pressure and the like.

In the next step S6, the PCM 100 starts the non-equilibrium plasma generation control when the start time set in the step S5 is reached. In step S6, the PCM 100 applies a first pulse voltage between the electrodes 13a and 13b of the discharge plug 13 so as to generate a non-equilibrium plasma in the combustion chamber 6.

In the following step S7, the PCM 100 determines whether or not the end time set in the above step S5 has been reached. When the end time is YES, the PCM 100 proceeds to step S8, while when the end time is NO, the non-equilibrium plasma generation control is continued until the end time is reached, and the discharge plug is used. The first pulse voltage is repeatedly applied between the electrodes 13a and 13b of 13.

In step S8, the non-equilibrium plasma generation control is terminated.

In the next step S9, the PCM100 is subjected to the above-mentioned period immediately after the end of the above-mentioned non-equilibrium plasma generation control in the above-mentioned step S8, specifically, after the end of the above-mentioned non-equilibrium plasma generation control, within a period of 10 ° in crank angle. Thermal equilibrium plasma generation control is started. In step S9, the PCM 100 applies a second pulse voltage between the electrodes 13a and 13b of the discharge plug 13 so as to generate a thermal equilibrium plasma in the combustion chamber 6.

In the next step S10, the PCM 100 determines whether or not the combustion of the air-fuel mixture in the combustion chamber 6 has started. In this step S10, the PCM 100 determines whether or not the combustion of the air-fuel mixture in the combustion chamber 6 has started based on whether or not the detection result of the in-cylinder pressure sensor SN6 is equal to or higher than the predetermined pressure. When YES, the PCM100 proceeds to step S11 when the combustion of the air-fuel mixture in the combustion chamber 6 has started, while when NO, the combustion of the air-fuel mixture in the combustion chamber 6 has not started yet, the thermal equilibrium plasma generation is generated. The control is continued, and the second pulse voltage is repeatedly applied between the electrodes 13a and 13b of the discharge plug 13.

In step S11, the PCM 100 ends the thermal equilibrium plasma generation control. After step S11, it returns.

As described above, in the operating state where the combustion stability of the engine 1 may decrease, the non-equilibrium plasma generation control is executed to generate the active species in the combustion chamber 6 and the thermal equilibrium plasma. To facilitate the formation of flame nuclei in generation control. This makes it possible to improve the combustion stability of the engine.

FIG. 11 is a graph showing the results of experimentally obtaining changes in the heat generation rate in the combustion chamber 6 when the non-equilibrium plasma generation control was executed and when it was not executed. FIG. 11A shows the change in the heat generation rate when the non-equilibrium plasma generation control is executed, while FIG. 11B shows the change in the heat generation rate when the non-equilibrium plasma generation control is not executed. Is shown. In FIGS. 11A and 11B, the vertical axis is the heat generation rate and the horizontal axis is the crank angle. In both FIGS. 11 (a) and 11 (b), the crank angle of the compression top dead center is set to 0 °, whereas the advance angle side (the time earlier than the compression top dead center) is represented by a minus, and the retard angle side (the retard angle side (). The period later than the compression top dead center) is indicated by a plus.

This experiment is the heat generation rate in the operating state where the G / F becomes 30, and the thermal equilibrium plasma generation control is performed when the crank angle is −15 ° regardless of whether or not the non-equilibrium plasma generation control is executed. Running. In this experiment, the end time of the non-equilibrium plasma generation control is before -15 ° in the crank angle.

As shown in FIG. 11B, when the non-equilibrium plasma generation control is not executed, the heat generation rate rises sharply even in the vicinity of the compression top dead center, while the heat generation rate also rises in the vicinity of the compression top dead center. It can be seen that there was a misfire with almost no increase in the heat generation rate. On the other hand, as shown in FIG. 11A, when the non-equilibrium plasma generation control is executed, the heat generation rate rises sharply in the vicinity of the compression top dead center without misfire, that is, the mixture is mixed in the combustion chamber 6. You can see that the qi is burning. As described above, it can be seen that the combustibility is improved by executing the non-equilibrium plasma generation control even in the operating state where the G / F is 30 and is considerably lean.

Further, as shown in FIG. 11A, when the non-equilibrium plasma generation control is executed, the variation in the peak value of the heat generation rate is small as compared with the case where the non-equilibrium plasma generation control is not executed. I understand. As described above, it can be seen that by executing the non-equilibrium plasma generation control, not only the ignitability is improved, but also a stable combustion state can be ensured. Therefore, the combustion stability of the engine 1 can be improved by executing the non-equilibrium plasma generation control as in the present embodiment.

Therefore, in the present embodiment, at least in the compression stroke, a first pulse voltage that causes non-equilibrium plasma to be generated in the combustion chamber 6 is applied between the electrodes 13a and 13b of the discharge plug 13 to discharge the discharge. A second pulse that executes non-equilibrium plasma generation control to generate equilibrium plasma and immediately after the end of non-equilibrium plasma generation control, generates thermal equilibrium plasma in the combustion chamber 6 between the electrodes 13a and 13b of the discharge plug 13. Thermal equilibrium plasma generation control that generates thermal equilibrium plasma is executed by applying a voltage to discharge. With this configuration, the active species can be generated in the combustion chamber 6 by generating non-equilibrium plasma at least in the compression stroke, and then the active species can be produced by executing the thermal equilibrium plasma generation control. It can be utilized to easily form a flame nucleus. As a result, the combustion stability of the engine 1 can be improved.

Further, in the present embodiment, since the period for executing the non-equilibrium plasma generation control is longer than the period for executing the thermal equilibrium plasma generation control, it is possible to generate as many active species as possible in the combustion chamber 6. can. As a result, the combustion of the air-fuel mixture when the thermal equilibrium plasma generation control is executed proceeds smoothly. As a result, the combustion stability of the engine 1 can be further improved.

Further, in the present embodiment, the non-equilibrium plasma generation control is executed at least at the late stage of the compression stroke and after the fuel is supplied by the injector 14, and the length of the period during which the non-equilibrium plasma generation control is executed is the compression stroke. Since the length is one-fourth or more of the period during which the discharge plug 13 is executed, the air-fuel mixture is present around the electrodes 13a and 13b of the discharge plug 13, and the active species generated by the non-equilibrium plasma generation control. As a result, a local low-temperature oxidation reaction occurs around the electrodes 13a and 13b of the discharge plug 13. As a result, the temperature around the electrodes 13a and 13b of the discharge plug 13 becomes high, so that a flame nucleus is likely to be formed when the thermal equilibrium plasma is generated by the thermal equilibrium plasma generation control. As a result, the combustion stability of the engine is further improved.

The technique disclosed herein is not limited to the above embodiment, and can be substituted as long as it does not deviate from the gist of the claims.

For example, in the above-described embodiment, the pulse width of the first pulse voltage is set to less than the second predetermined value (less than 1 μsec), but the present invention is not limited to this, and the pulse width of the first pulse voltage is set to a range of less than 10 μsec. It may be a second predetermined value or more. In this case, the peak voltage of the first pulse voltage may be set to less than 10 kV (for example, 8 kV).

Further, in the above-described embodiment, the supercharger is not provided, but in the case of an engine including the supercharger, the first non-equilibrium plasma generation control is performed based on the supercharging pressure of the supercharger. The peak voltage of the 1-pulse voltage and the peak voltage of the 2nd pulse voltage in the thermal equilibrium plasma generation control may be changed. More specifically, the higher the boost pressure, the higher the peak voltage of the first and second pulse voltages may be.

Further, in the above-described embodiment, the non-equilibrium plasma generation control is not executed in a high load region where the engine load is a predetermined load or more, but the present invention is not limited to this, and even if the engine load is a high load, For example, the non-equilibrium plasma generation control may be executed in an operating state where the EGR rate is 20% or more.

The above embodiments are merely examples, and the scope of the present disclosure should not be construed in a limited manner. The scope of the present disclosure is defined by the scope of claims, and all modifications and changes belonging to the equivalent scope of the scope of claims are within the scope of the present disclosure.

The technology disclosed herein comprises an engine body having a combustion chamber in which each step of an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke is repeated in this order, and a fuel supply means for supplying fuel to the combustion chamber. It is useful for engines that burn the air-fuel mixture formed by the fuel supplied by the fuel supply means in the combustion chamber.

1 Engine 1a Engine body 6 Combustion chamber 13 Discharge plug (plasma generation means)
13a Center electrode (electrode of plasma generation means)
13b Ground electrode (electrode of plasma generation means)
14 Injector (combustion supply means)
40 EGR device (exhaust gas recirculation means)
100 PCM (control means)

Claims (14)

The engine body has a combustion chamber in which each step of the intake stroke, the compression stroke, the expansion stroke and the exhaust stroke is repeated in this order, and the engine body is arranged so as to face the combustion chamber and is discharged by applying a voltage between the electrodes. A plasma generating means for generating plasma in a combustion chamber, a fuel supply means for supplying fuel to the combustion chamber, and an exhaust recirculation means for returning the exhaust discharged from the combustion chamber in the exhaust stroke to the combustion chamber. It is a combustion control method of an engine that burns an air-fuel mixture formed by the fuel supplied by the fuel supply means in the combustion chamber.
At least in the compression stroke, a non-equilibrium plasma generation step of generating non-equilibrium plasma by applying a first pulse voltage between the electrodes of the plasma generation means to discharge the plasma.
Immediately after completion of the non-equilibrium plasma generating step, between the electrodes of the plasma generating means, by discharging by applying a second pulse voltage, seen containing a thermal plasma generation step of generating a thermal plasma, a,
In the non-equilibrium plasma generation step, the application start timing and application end timing of the first pulse voltage are the G / F which is the ratio of the gas and the fuel in the air-fuel mixture in the combustion chamber, and the total gas amount in the combustion chamber. The peak voltage of the first pulse voltage is set based on the in-cylinder pressure in the compression stroke, while it is calculated based on at least one of the EGR ratios, which is the ratio of the amount of exhaust gas in the gas to the gas. Combustion control method of the engine. In the engine combustion control method according to claim 1,
The first pulse voltage is a pulse voltage having a pulse width of not less than the first predetermined value and larger than the first predetermined value and less than the second predetermined value.
The second pulse voltage is a combustion control method for an engine, wherein the pulse width is a pulse voltage equal to or larger than the second predetermined value. In the engine combustion control method according to claim 1 or 2.
The engine combustion control method is characterized in that the non-equilibrium plasma generation step is a step to be executed when the G / F is 16 or more in an operating state. In the engine combustion control method according to any one of claims 1 to 3.
Upper Symbol non-equilibrium plasma generation step, combustion control method for an engine which is a process to be executed when the EGR rate is operation state is 20% or more. In the engine combustion control method according to any one of claims 1 to 4.
A combustion control method for an engine, characterized in that the period for executing the non-equilibrium plasma generation step is longer than the period for executing the thermal equilibrium plasma generation step. In the combustion control method of the engine according to claim 5.
The non-equilibrium plasma generation step is a step executed at least in the latter stage of the compression stroke and after the fuel is supplied by the fuel supply means.
A combustion control method for an engine, characterized in that the length of the period during which the non-equilibrium plasma generation step is executed is one-fourth or more of the length of the period during which the compression stroke is executed. An engine body having a combustion chamber in which each process of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke is repeated in this order, a fuel supply means for supplying fuel to the combustion chamber, and discharge from the combustion chamber in the exhaust stroke. It is a combustion control device of an engine provided with an exhaust recirculation means for recirculating the exhausted exhaust into the combustion chamber and burning an air-fuel mixture formed by the fuel supplied by the fuel supply means in the combustion chamber.
A plasma generation means that is arranged so as to face the combustion chamber and generates plasma in the combustion chamber by electric discharge by applying a voltage between the electrodes.
Further provided with a control means for controlling the operation of the plasma generation means and the fuel supply means.
The control means executes non-equilibrium plasma generation control to generate unbalanced plasma by applying a first pulse voltage between the electrodes of the plasma generating means to discharge the plasma at least in the compression stroke. Immediately after the end of the non-equilibrium plasma generation control, the thermal equilibrium plasma generation control for generating the thermal equilibrium plasma is executed by applying a second pulse voltage between the electrodes of the plasma generation means to discharge the plasma. Has been
In the non-equilibrium plasma generation control, the application start timing and application end timing of the first pulse voltage are the G / F which is the ratio of the gas and the fuel in the air-fuel mixture in the combustion chamber, and the total gas amount in the combustion chamber. The peak voltage of the first pulse voltage is set based on the in-cylinder pressure in the compression stroke, while it is calculated based on at least one of the EGR ratios, which is the ratio of the amount of exhaust gas in the gas to the gas. The combustion control device of the engine. In the combustion control device for the engine according to claim 7.
The first pulse voltage is a pulse voltage having a pulse width of not less than the first predetermined value and larger than the first predetermined value and less than the second predetermined value.
The second pulse voltage is a combustion control device for an engine, characterized in that the pulse width is a pulse voltage equal to or higher than the second predetermined value. In the combustion control device of the engine according to claim 7 or 8.
The control means is characterized in that the non-equilibrium plasma generation control is executed when the operating state of the engine is an operating state in which the G / F is 16 or more. Combustion control device. The engine combustion control device according to any one of claims 7 to 9.
Control written above means, an engine operating condition of the engine when in operation state in which the EGR rate becomes 20% or more, characterized in that it is configured to perform the non-equilibrium plasma generation control Combustion control device. In the combustion control device for the engine according to any one of claims 7 to 10.
The control means is an engine combustion control device, characterized in that the period for executing the non-equilibrium plasma generation control is longer than the period for executing the thermal equilibrium plasma generation control. In the combustion control device for the engine according to claim 11.
The control means executes the non-equilibrium plasma generation control at least at the latter stage of the compression stroke and after the fuel is supplied by the fuel supply means, and compresses the length of the period during which the non-equilibrium plasma generation control is executed. A combustion control device for an engine, characterized in that it is configured to be at least 1/4 the length of the period in which the stroke is performed. In the engine combustion control method according to claim 1,
In the non-equilibrium plasma generation step, when the G / F is 20 or more and the EGR ratio is at least one of 30% or more, the first pulse voltage is started to be applied during the intake stroke. While the application is completed in the latter half of the compression stroke, the G / F does not satisfy both 20 or more and the EGR ratio is 30% or more, and the G / F is 16 or more and less than 20, and the EGR ratio is When the operating state satisfies at least one of 20% or more and less than 30%, the engine is characterized in that the application of the first pulse voltage is started in the first half of the compression stroke and is terminated in the second half of the compression stroke. Combustion control method. In the combustion control device for the engine according to claim 7.
In the non-equilibrium plasma generation control, when the G / F is 20 or more and the EGR ratio is at least one of 30% or more, the first pulse voltage is started to be applied during the intake stroke. While the application is completed in the latter half of the compression stroke, the G / F does not satisfy both 20 or more and the EGR ratio is 30% or more, and the G / F is 16 or more and less than 20, and the EGR ratio is When the operating state satisfies at least one of 20% or more and less than 30%, the engine is characterized in that the application of the first pulse voltage is started in the first half of the compression stroke and is terminated in the second half of the compression stroke. Combustion control device.

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