JP2009121422A - Electric discharging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration of electric discharging efficiency due to increase of a dielectric loss or the lowering of a dielectric constant, when the strength of an applied electric field is changed in an electric discharging device for barrier electric discharging. <P>SOLUTION: The electric discharging device comprises a positive electrode 20 and a negative electrode 22 of which at least either one is covered by a dielectric element 21, a power source 12 applying an alternating current electric field between those electrodes 20, 22, and an dielectric element controlling means 11 controlling the dielectric constant and the dielectric loss of the dielectric element 21 according to the applied alternating current electric field. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a discharge device, and more particularly to a discharge device that can be used as an ignition or auxiliary ignition device for an internal combustion engine.

  As an ignition device for an internal combustion engine, a spark discharge spark plug is generally used. However, if the engine is to be operated with a leaner air-fuel mixture, a very high voltage must be applied between the electrodes, which increases power consumption and wears the electrode surface in a short time. There was a problem.

In order to solve this problem, in Patent Document 1, an AC electric field is applied to ions in a gas mixture generated in the ignition process of the premixed gas using a so-called barrier discharge device in which an AC electrode is covered with a dielectric. A configuration in which the air-fuel mixture is ignited efficiently as a whole is disclosed.
JP 2000-73929 A

  By the way, if the dielectric constant is low, for example, the discharge energy formed for the applied electric field is low. If the dielectric loss is large, the input power is released as thermal energy. Thus, the dielectric constant and the dielectric loss are factors that determine the conversion efficiency (discharge efficiency) of input power into discharge energy.

  However, Patent Document 1 does not describe the dielectric constant and dielectric loss of the dielectric covering the center electrode. For this reason, depending on the strength of the applied electric field, there is a possibility that the discharge efficiency may be lowered due to an increase in dielectric loss or a decrease in dielectric constant.

  Therefore, an object of the present invention is to provide a discharge device capable of discharging with high discharge efficiency regardless of the strength of an applied electric field.

  The discharge device according to the present invention includes a positive electrode and a negative electrode, at least one of which is covered with a dielectric, a power source that applies an alternating electric field between the positive and negative electrodes, and a dielectric depending on the applied alternating electric field. And a dielectric control means for controlling the dielectric constant and dielectric loss.

  According to the present invention, since the dielectric constant and the dielectric loss are controlled according to the applied AC electric field, for example, when the applied AC electric field changes, the dielectric constant does not decrease and the dielectric loss does not increase. By doing so, it is possible to discharge with high discharge efficiency regardless of the strength of the applied electric field.

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

  FIG. 1 is a diagram showing a configuration of a cylinder head portion of the internal combustion engine according to the present embodiment. 1 is a cylinder head, 2 is a combustion chamber, 3 is an intake passage, 4 is an exhaust passage, 5 is an intake valve, 6 is an exhaust valve, 7 is an intake camshaft, 8 is an exhaust camshaft, 9 is a fuel injection valve, Non-equilibrium plasma discharge device, 11 is an engine control unit (ECU), 12 is a high voltage high frequency generator, 13 is a heater, 14 is a cooling water channel, 15 is a radiator, 16 is a pump, 17 is an electromagnetic valve, 18 is a temperature sensor, Reference numeral 19 denotes a heating power source for the heater 13.

  The cylinder head 1 includes a concave combustion chamber 2 on the lower surface side. The intake passage 3 passes through the lower surface and one side surface of the cylinder head 1, and the lower surface side opens so as to face the combustion chamber 2. The opening is provided with an intake valve 5 so as to block communication between the intake passage 3 and the combustion chamber 2. Similarly, the exhaust passage 4 penetrates the lower surface and the other side surface of the cylinder head 1, and an exhaust valve 6 is provided so as to block communication with the combustion chamber 2.

  The intake camshaft 7 and the exhaust camshaft 8 rotate in synchronization with a crankshaft (not shown), and open and close the intake valve 5 and the exhaust valve 6 in synchronization with the vertical movement of a piston (not shown).

  The fuel injection valve 9 injects fuel according to an injection timing and an injection amount set by an ECU 11 described later. Normally, fuel is injected into the intake passage 3 at a predetermined time during the exhaust stroke.

  The cooling water channel 14 surrounds a portion of the dielectric 21 of the non-equilibrium plasma discharge device 10 described later outside the combustion chamber 2, and the cooling water circulates between the radiator 15 for engine cooling water. Deploy. Between the radiator 15 and the cooling water passage 14, a cooling water circulation pump 16 and a circulation / stop switching electromagnetic valve (or thermostat) 17 are interposed. The heater 13 is disposed in a portion of the dielectric 21 outside the combustion chamber 2 and is controlled by the ECU 11 to heat the dielectric 21 according to the operating state.

  The ECU 11 controls the applied voltage of the alternating high voltage generated by the high voltage high frequency generator 12, the applied wave number (frequency or application time), the application timing, and the temperature of the heater 13 at the application timing.

  Since the ECU 11 also performs integrated control of the engine, in addition to the control of the high-voltage and high-frequency generator 12 and the heater 13, based on signals input from various sensors such as an air flow meter and an accelerator opening sensor (not shown), the fuel The injection valve 9 and the like are also controlled.

  The non-equilibrium plasma discharge apparatus 10 is connected to a control unit 1 (ECU) 11 as a determination means via a high voltage high frequency generator 12. The high voltage high frequency generator 12 is controlled by the ECU 11 so as to generate a pulse at an appropriate time, and the voltage generated by the high voltage high frequency generator 12 in response to this pulse is applied to a cylinder that is the ignition timing by a distributor (not shown). The

  FIG. 2 is an enlarged view of the non-equilibrium plasma discharge apparatus 10. In the present invention, a barrier discharge mechanism is used as the nonequilibrium plasma discharge apparatus 10. Reference numeral 20 denotes a center electrode connected to the high-voltage high-frequency generator 12, 21 denotes a dielectric (insulator) covering the entire center electrode 20, and 22 is provided in the cylinder head 1 so as to open on the upper surface of the combustion chamber 2. It is a tubular electrode that defines the chamber 23.

  When a high frequency voltage is applied to the center electrode 20, the center electrode 20 starts to discharge, but the presence of the dielectric 21 limits the transition to arc discharge, so between the dielectric 21 and the tubular electrode 22, that is, In the discharge chamber 23, a plasma called a plurality of streamers in which positive ions and electrons are mixed is formed. This streamer raises the electronic temperature of the fuel and leads to ignition. Here, since a plurality of streamers are formed as shown in FIG. 2, there are a plurality of parts to be ignited, and as a result, the volume of the part where ignition occurs in the discharge chamber 23 is increased. Since the flame generated in the discharge chamber 23 is ejected to the combustion chamber 2, the combustion in the combustion chamber 2 starts from the vicinity of the opening of the discharge chamber 23, and so-called volume ignition can be realized.

  FIG. 3 is a diagram for explaining the state of discharge when a high-frequency voltage is applied. When barrier discharge (non-equilibrium plasma discharge) is performed, charges are stored on the surface of the dielectric 21. When the absolute value of the difference between the electric field V0 due to the applied voltage and the electric field Vw due to the surface charge of the dielectric 21 reaches the discharge voltage Vd, barrier discharge (non-equilibrium) occurs between the dielectric 21 and the tubular electrode 22. Plasma discharge) occurs. Accordingly, as shown in FIG. 3, eight barrier discharges (non-equilibrium plasma discharge) occur during the discharge time t.

  FIG. 4 is a diagram showing the temperature dependence of the dielectric constant and dielectric loss of the dielectric 21 used in the non-equilibrium plasma discharge apparatus 10. The dielectric 21 of the present embodiment is a ferroelectric, and as shown in FIG. 3, with a transition temperature Tc as a boundary, it is a ferroelectric phase on the low temperature side and a paraelectric phase on the high temperature side.

  The dielectric constant and dielectric loss are small in the temperature region away from the transition temperature Tc, but increase as the temperature approaches the transition temperature Tc, and take a peak value near the transition temperature Tc. In particular, the dielectric loss changes abruptly near the transition temperature Tc as compared to the dielectric constant, so that the dielectric constant is high in the vicinity of the transition temperature Tc, for example, in the region from T1 to T2, which is a paraelectric phase. However, the dielectric loss is low. The state where the dielectric constant is high and the dielectric loss is low is a state where the discharge energy formed with respect to the input energy is large, and the energy released as thermal energy is small among the input energy. That is, if the discharge efficiency is defined as in the following formula (1), the term (input power-power loss) becomes large, so it can be said that the discharge efficiency is high.

Discharge efficiency = (input power-power loss) / input power (1)
Therefore, when the discharge is performed by the non-equilibrium plasma discharge apparatus 10, the temperature of the dielectric 21 is controlled within a range where the discharge efficiency is high, for example, in a region of temperatures T1 to T2. Since there is a region where the discharge efficiency is high in the vicinity of the transition temperature Tc of the ferroelectric phase, the region may be controlled to be in that region. However, in the ferroelectric phase, when an electric field is applied once, polarization remains even when the electric field becomes zero, so-called residual polarization exists, and thus hysteresis is shown with respect to the applied voltage. Therefore, when the ferroelectric phase is set in the control range, control by the electric field strength becomes difficult. Therefore, in order to improve controllability, it is desirable to set the paraelectric phase near the transition point Tc as the control range. Specific control will be described later.

  Although FIG. 4 shows the temperature dependence, the pressure dependence is similar, and by controlling the pressure acting on the dielectric 21, a high discharge efficiency can be achieved.

  FIG. 5 is an operation region map and a discharge energy map for each operation region of the present embodiment. The vertical axis represents the engine load, and the horizontal axis represents the engine speed. As shown in FIG. 5, from the low rotation / low load region to the medium rotation / medium load region, the engine is operated by lean combustion at an air / fuel ratio that is leaner than the stoichiometric air / fuel ratio or by dilution combustion by introducing EGR gas, In the high load region, the engine is operated at the theoretical air fuel ratio (λ = 1). In the operation region where lean combustion or dilution combustion is performed, λ or the EGR rate is increased as the load decreases. In the present embodiment, since the volume ignition can be realized as described above, the lean air-fuel ratio or the EGR rate in the low load region is a leaner air-fuel ratio or a higher EGR than in the case of a general spark discharge ignition. Can be rate.

  The discharge energy is set to a constant value regardless of the engine load and engine speed in the operation region where λ = 1, and is increased as the load is reduced in the operation region where lean combustion or dilution combustion is performed. The discharge energy in the operation region where λ = 1 is set to be smaller than the minimum value of the discharge energy in the operation region where lean combustion or dilution combustion is performed.

  FIG. 6 is a flowchart of a control routine executed by the ECU 11 in order to operate with high discharge efficiency. Specifically, a control routine for setting the temperature of the dielectric 21 for operating at high discharge efficiency in addition to setting of the throttle opening and the fuel injection amount according to the operating state as in general engine control. It is.

  In step S1000, the accelerator opening and the engine speed are read from detection signals from an accelerator opening sensor and a crank angle sensor (not shown).

  In step S1010, the target engine load is determined on the basis of the accelerator opening and the engine rotational speed in the same manner as a general engine.

  In step S1020, the target discharge energy is determined from the map of FIG. 5 based on the target engine load. In the present embodiment, the magnitude of the applied voltage is constant, and the magnitude of the input energy is controlled by adjusting the frequency of the applied AC electric field. Therefore, here, the target discharge energy is determined from the map of FIG. 5, and the frequency of the alternating electric field to be applied is determined using a map (not shown). Since the relationship between the target discharge energy and the frequency of the AC electric field to be applied differs depending on the specifications of the non-equilibrium plasma discharge apparatus 10, a map is created in advance for each specification.

  In step S1030, a target dielectric constant and a target dielectric loss are set based on the target discharge energy. Here, a method for setting the target dielectric constant and the target dielectric loss will be described.

  FIG. 7 is a diagram showing the relationship between the frequency of the alternating electric field and the power loss due to dielectric loss when the applied voltage is constant.

  As shown in FIG. 7, the power loss due to the dielectric loss changes in proportion to the first power of the frequency. The higher the frequency, that is, the greater the input power, the greater the power loss. Therefore, in order to suppress an increase in power loss when the input power increases, control is performed so that the dielectric loss decreases as the frequency increases, as shown in FIG. Thereby, the inclination of the straight line of FIG. 7 becomes small. FIG. 8 sets the dielectric loss with respect to the frequency, and the dielectric loss decreases as the frequency increases. In FIG. 8, the dielectric loss is nonlinear with respect to the frequency. This is because the dielectric loss varies nonlinearly with respect to temperature (or pressure) as shown in FIG.

  Incidentally, both the dielectric constant and the dielectric loss are dependent on the temperature of the dielectric 21, and as shown in FIG. 4, both change when the temperature of the dielectric 21 is changed. Therefore, when the dielectric loss is controlled as shown in FIG. 8, the temperature of the dielectric 21 increases as the frequency increases, so that the dielectric constant decreases as the frequency increases as shown in FIG. However, the higher the dielectric constant, the greater the discharge energy formed with respect to the input power. Therefore, it is desirable that the dielectric efficiency be higher if the discharge efficiency does not deteriorate.

  Therefore, the slope of the curve in FIG. 8 (ratio of the amount of change in dielectric loss with respect to the amount of change in frequency) and the slope of the curve in FIG. 9 (dielectric with respect to the amount of change in frequency) so that the discharge efficiency does not deteriorate in any frequency region. A ratio change ratio) is set as a control map, and an optimal dielectric constant and an optimal dielectric loss are set based on these maps.

  Return to the description of the flowchart.

  In step S1040, the temperature (optimum temperature) of the dielectric 21 that is the determined optimum dielectric constant and optimum dielectric loss is obtained based on FIG. Note that by selecting an additive to be added to the member used as the dielectric 21, the transition temperature Tc is made close to the temperature of the cylinder head 1 in the vicinity of the non-equilibrium plasma discharge device 10 during engine operation. Thereby, the energy consumed for the temperature control of the dielectric 21 to be described later can be reduced.

  In step S1050, the detected value of the temperature sensor 18 is read as the cooling water temperature near the non-equilibrium plasma discharge apparatus 10.

  In step S1060, it is determined whether or not the cooling water temperature is within a preset specified range. This determination is to determine whether or not the temperature of the dielectric 21 is near the optimum temperature, and is predicted from the cooling water temperature without directly detecting the temperature of the dielectric 21. Therefore, the specified range used here is the range of the cooling water temperature when the dielectric 21 is near the optimum temperature, and is determined in advance by measurement or the like.

  If it is within the specified range, the process proceeds to step S1100. If it is out of the specified range, the process proceeds to step S1070.

  In step S1070, it is determined whether the temperature is higher than the specified range. If the temperature is higher than the specified range, the process proceeds to step S1080. If the temperature is lower than the specified range, the process proceeds to step S1090.

  In step S1080, the temperature is adjusted by the amount of water flowing through the cooling water channel 14. Specifically, the pump 16 is driven and the amount of water is adjusted by the opening degree of the electromagnetic valve (or thermostat) 17. As a result, the temperature of the non-equilibrium plasma discharge device 10 is lowered by exchanging heat with the cooling water. The cooling water whose temperature has increased due to this heat exchange is reduced in temperature by radiating heat with the radiator 15, and heat exchange is performed again with the non-equilibrium plasma discharge device 10.

  In step S <b> 1090, the heating power source 19 is activated and the non-equilibrium plasma discharge apparatus 10 is heated by the heater 13.

  The temperature adjustment in step S1080 or S1090 is repeated until the cooling water temperature falls within the specified range.

  In step S1100, the equivalence ratio corresponding to the operation state read in step S1000 is calculated based on FIG.

  In step S1110, as in the case of a general engine, the throttle opening and the fuel injection amount corresponding to the operating state are calculated.

  In step S220, the throttle opening and the fuel injection amount calculated in step S1110 are set.

  FIG. 10 is a diagram for explaining the effect when the relationship between the frequency of the alternating electric field applied, the dielectric constant, and the dielectric loss is determined as described above. The vertical axis represents the power loss due to the input power and dielectric loss, the horizontal axis represents the frequency of the applied AC electric field, the solid line represents the input power determined by the frequency (the power applied to the center electrode 20), and the broken line represents the power loss due to the dielectric loss. ing. For convenience of explanation, FIG. 10 shows a case where the frequency region is divided into three regions of low frequency, medium frequency, and high frequency, and the dielectric constant and dielectric loss are set as the representative values of the respective regions.

  As described above, the lower the frequency, the higher the dielectric constant, and the higher the frequency, the lower the dielectric constant. As a result, the lower the frequency, the larger the amount of change in input power with respect to the frequency change. In addition, the level of the dielectric constant here is a relative level in the range of temperatures T1 to T2 in FIG. In addition, since the dielectric loss decreases as the frequency increases, the power loss with respect to the amount of change in frequency decreases.

  In the low frequency region, the input power increases as the frequency increases. However, since the slope of the power loss is larger than the slope of the input power, the difference between the throwing input and the power loss decreases as the frequency increases. That is, the discharge efficiency decreases as the frequency increases.

  In the middle frequency range, the dielectric constant and dielectric loss decrease as described above, so that the slopes of input power and power loss are both smaller than in the low frequency range, and the same dielectric constant and dielectric loss as in the low frequency range remain. Compared with the case where the frequency is increased to the frequency region, the degree of decrease in discharge efficiency is suppressed. For this reason, the input power is reduced due to the decrease in the dielectric constant compared to the case of the high dielectric constant, but as a result of the suppression of the decrease in the discharge efficiency, the resulting discharge energy is larger than that in the case of the high dielectric constant. Become.

  Similarly, in the high frequency region, the degree of decrease in discharge efficiency is suppressed and the resulting discharge energy is larger than when the frequency is increased to the high frequency region while maintaining the medium frequency region.

  Thus, by controlling the temperature of the dielectric 21 so that the dielectric loss and the dielectric constant decrease as the frequency of the applied AC electric field increases, the discharge efficiency can be suppressed and the discharge can be efficiently performed. .

  Note that the flowchart of FIG. 11 may be used instead of the flowchart of FIG. FIG. 11 is the same as FIG. 6 except for step S2090.

  In step S2090, the temperature of the cooling water is raised to within a specified range by increasing the voltage applied to the center electrode 20. That is, when the applied voltage is increased, the power loss due to dielectric loss increases as shown in FIG. 14 to be described later, and this lost power is lost as heat, so the temperature of the cooling water is raised using this heat. The extent to which the applied voltage is increased is determined based on the relationship between the applied voltage and the power loss and the relationship between the amount of heat generated by the power loss and the like in advance.

  In this way, when the temperature of the cooling water is raised using the heat quantity due to dielectric loss, the heater 13 and the heating power source 19 are not necessary, and the system can be simplified.

As described above, in the present embodiment, the following effects can be obtained.
(1) The center electrode 20 and the tubular electrode 22 at least one of which is covered with the dielectric 21, the high-voltage high-frequency generator 12 that applies an alternating electric field between these electrodes, and the dielectric 21 according to the alternating electric field to be applied Since the ECU 11 that controls the dielectric constant and the dielectric loss is provided, the efficiency of discharge can be increased and the efficiency of the entire system can be improved.

  (2) Since the dielectric constant and dielectric loss of the dielectric 21 have dependence on the temperature or pressure of the dielectric 21, the dielectric constant and dielectric loss can be controlled by controlling the temperature or pressure.

  (3) Since the ECU 11 controls the dielectric constant and the dielectric loss by controlling the temperature or pressure of the dielectric 21, the dielectric constant and the dielectric loss can be controlled without using a complicated mechanism.

  (4) The dielectric constant and dielectric loss of the dielectric 21 both have a peak that is maximum near the transition temperature Tc, and the dielectric loss changes more than the dielectric constant near the transition temperature Tc. In the vicinity of the transition temperature Tc, there is a temperature range where the dielectric constant is low and the dielectric loss is low.

  (5) Since the ECU 11 controls the temperature of the dielectric 21 to a temperature range in the vicinity of the transition temperature Tc, the ECU 11 can perform discharge with a high dielectric constant and a low dielectric loss.

  (6) Since the ECU 11 controls the temperature of the dielectric 21 in the vicinity of the transition temperature Tc and in the temperature range T1 to T2 on the high temperature side, it is not affected by remanent polarization and has good controllability.

  (7) When increasing the strength of the AC electric field, the ECU 11 has a relatively low dielectric loss and a relatively low dielectric constant so as to maintain a discharge efficiency substantially equal to that before the AC field strength is increased. Since the temperature of the dielectric 21 is controlled to be higher, an increase in power loss due to dielectric loss accompanying an increase in AC electric field strength can be suppressed, and highly efficient discharge can be performed.

  (8) Since the non-equilibrium plasma discharge device 10 is used as an ignition device or an ignition auxiliary device for an internal combustion engine, it is possible to realize an increase in fuel speed due to active species generated by barrier discharge and volume ignition due to an increase in discharge volume. it can. As a result, the lean combustion operation region is expanded, and the thermal efficiency of the internal combustion engine can be increased.

  (9) As the engine load becomes lower, the ECU 11 increases the strength of the AC electric field, and the dielectric loss is lower and the dielectric constant is higher so as to maintain the discharge efficiency substantially the same as before the strength of the AC electric field is increased. Thus, since the temperature of the dielectric 21 is controlled, it is possible to suppress a decrease in discharge efficiency while improving thermal efficiency by expanding a low-load lean combustion or diluted combustion operation region.

  (10) As the engine speed becomes higher, the ECU 11 increases the AC electric field strength, and the dielectric loss is lower and the dielectric constant is higher so as to maintain the discharge efficiency substantially the same as before the AC electric field strength is increased. Since the temperature of the dielectric 21 is controlled as described above, discharge according to the rotational speed can be performed with high efficiency.

  (11) As the engine load is lower and the engine speed is higher, the ECU 11 increases the intensity of the AC electric field, and the dielectric loss decreases so as to maintain the discharge efficiency substantially the same as before the intensity of the AC electric field increases. Since the temperature of the dielectric 21 is controlled so that the dielectric constant is low and the dielectric constant is high, highly efficient discharge can be performed in a wider operating region.

  (12) Since the transition temperature of the dielectric 21 is substantially equal to the temperature during engine operation in the vicinity of the installation location of the non-equilibrium plasma discharge device 10 of the cylinder head 1, the energy input for raising the temperature is reduced. Can do.

  (13) When the temperature of the dielectric 21 is increased, the ECU 11 increases the electric field strength so that the amount of heat generated by the dielectric loss becomes the amount of heat necessary for the temperature increase. Therefore, the heating device such as the heater 13 and the heating power source 19 is installed. The dielectric 21 can be heated without being provided.

  Although a so-called port injection type engine in which fuel is injected into the intake passage 3 has been described here, the same applies to a so-called in-cylinder direct injection type engine in which fuel is directly injected into the combustion chamber 2. can do.

  A second embodiment will be described.

  In the present embodiment, the configuration of the cylinder head and the configuration of the nonequilibrium plasma discharge apparatus 10 are basically the same as those of the first embodiment, except that the spark plug 30 for spark ignition is provided, and for each operating region. The ignition method and the method for controlling the intensity of the applied AC electric field are different. In this embodiment, the intensity of the alternating electric field to be applied is controlled according to the magnitude of the applied voltage while the applied frequency is constant.

  FIG. 12 is a view of the combustion chamber 2 as viewed from the lower surface side. As shown in FIG. 12, a spark ignition spark plug 30 is provided in the vicinity of the nonequilibrium plasma discharge apparatus 10. The spark plug 30 is a general spark plug for spark ignition.

  FIG. 13 is an operation region map and a discharge energy map for each operation region. From the low rotation / low load range to the medium rotation / medium load range, the engine is operated by lean combustion at an air / fuel ratio that is leaner than the stoichiometric air / fuel ratio or dilution combustion by introducing EGR gas. Operate at a fuel ratio (λ = 1). In the operation region where lean combustion or dilution combustion is performed, λ or the EGR rate is increased as the load decreases. On the other hand, spark ignition by the spark plug 30 is performed in the region operating at λ = 1 in the high rotation region and the high load region.

  The flowchart of the control routine executed by the ECU 11 during engine operation is basically the same as that in the first embodiment. However, since the method for controlling the intensity of the applied AC electric field is different, the method for setting the optimum dielectric constant and optimum dielectric loss in step S1030 is different.

  FIG. 14 is a diagram illustrating the relationship between the applied voltage and the power loss due to dielectric loss when the applied frequency is constant.

  As shown in FIG. 14, the power loss due to dielectric loss changes in proportion to the square of the applied voltage, and the higher the applied voltage, that is, the greater the input power, the greater the power loss. Therefore, in order to suppress an increase in power loss when the input power increases, control is performed such that the dielectric loss decreases as the applied voltage increases, as shown in FIG. As a result, the slope of the curve in FIG. 14 (ratio of change in dielectric loss with respect to change in applied voltage) is reduced. FIG. 15 sets the dielectric loss with respect to the applied voltage, and the dielectric loss decreases as the applied voltage increases.

  When the dielectric loss is controlled as shown in FIG. 15, the dielectric constant decreases as the frequency increases as in the first embodiment (FIG. 16).

  The slopes of the curves in FIGS. 15 and 16 (ratio of the change in the dielectric loss and the dielectric constant with respect to the change in applied voltage) are the slopes of the curves in FIGS. 8 and 9 (the dielectric loss and the dielectric in relation to the change in frequency). Greater than the rate of change in rate). This is because the power loss due to the dielectric loss is proportional to the square of the magnitude of the applied voltage, and therefore the dielectric loss needs to be further reduced as the applied voltage increases. Because it grows.

  Therefore, the slope of the curve in FIG. 15 (ratio of the amount of change in dielectric loss with respect to the amount of change in frequency) and the slope of the curve in FIG. The ratio of the change amount of the dielectric constant is set as a control map, and the optimum dielectric constant and the optimum dielectric loss are set based on these maps.

  FIG. 17 is a diagram corresponding to FIG. 10 of the first embodiment, for explaining the effect when the relationship between the applied voltage of the alternating electric field applied, the dielectric constant, and the dielectric loss is determined as described above. FIG. The vertical axis represents power loss due to applied power and dielectric loss, the horizontal axis represents applied voltage, the solid line represents input power determined by the applied voltage (power applied to the non-equilibrium plasma discharge device 10), and the broken line represents power loss due to dielectric loss. ing. For convenience of explanation, FIG. 17 shows a case where the applied voltage region is divided into three regions of low voltage, medium pressure, and high voltage, and the dielectric constant and dielectric loss are set as representative values of the respective regions.

  As shown in FIG. 17, in this embodiment as well, as in the first embodiment, it is possible to efficiently discharge while suppressing a decrease in discharge efficiency.

  As described above, in the present embodiment, the following effects can be obtained in addition to the same effects as those of the first embodiment.

  The power loss due to dielectric loss increases in proportion to the square of the frequency, and increases in proportion to the square of the applied voltage. In the present embodiment, when the AC electric field strength is increased by increasing the applied voltage, the ECU 11 has a lower dielectric loss and a higher dielectric constant than when increasing the AC electric field strength by increasing the frequency. Thus, since the temperature of the dielectric 21 is controlled, even when the electric field strength is increased by increasing the applied voltage, the power loss due to the dielectric loss can be reduced and the discharge can be performed efficiently.

  A third embodiment will be described.

  The present embodiment relates to control at the time of engine start using the cylinder head portion and the non-equilibrium plasma discharge apparatus 10 having the same configuration as the first embodiment or the second embodiment.

  FIG. 18 is a flowchart of a control routine executed by the ECU 11 when the engine is started.

  In step S3000, the detected value of the temperature sensor 18 is read as the cooling water temperature.

  In step S3010, it is determined whether or not the coolant temperature is equal to or higher than a predetermined value set in advance for determining whether or not the cold start is performed. If it is equal to or greater than the specified value, that is, if it is not a cold start, the process proceeds to step S3030, and the throttle opening and the fuel injection amount are set in the same manner as in general start.

  On the other hand, in the case of the specified value or less, that is, in the case of cold start, the process proceeds to step S3020.

  In step S3020, a voltage is applied to the center electrode 20 so that the coolant temperature becomes equal to or higher than a specified value. This is because the temperature of the dielectric 21 is raised using heat generated by power loss due to dielectric loss, as in step S2090 of FIG.

  As described above, in the present embodiment, since the temperature of the dielectric 21 is increased by the amount of heat generated by the dielectric loss at the time of engine cold start, high efficiency can be achieved by increasing the temperature of the center electrode 20 to a high discharge efficiency in a short time. In addition, the combustion temperature can be increased with low emissions. Furthermore, it is possible to raise the exhaust purification efficiency by raising the temperature of the exhaust purification catalyst at an early stage.

  The non-equilibrium plasma discharge device 10 can be used in addition to an ignition device for an internal combustion engine. For example, the center electrode 20 and the tubular electrode 22 may be installed so as to face the exhaust passage 4 and discharge toward the exhaust passage 4. Thereby, particulates in the exhaust gas passing through the exhaust passage 4 can be burned or NOx can be decomposed, so that the exhaust performance can be improved.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a figure which shows the structure of the system of 1st Embodiment. It is a figure which shows the structure of a non-equilibrium plasma discharge apparatus. It is a figure for demonstrating the discharge time of barrier discharge. It is a figure which shows the characteristic with respect to the temperature or pressure of a dielectric constant and a dielectric loss. It is a figure which shows the magnitude | size of the discharge energy for every operation area | region (1st Embodiment). It is a flowchart showing the control routine for engine operation in the case of controlling alternating current electric field strength with a frequency. It is a figure which shows the relationship between the electric power loss by a dielectric loss, and a frequency. It is a figure which shows the control target value of dielectric loss in the case of controlling alternating current electric field strength with a frequency. It is a figure which shows the control target value of a dielectric constant in the case of controlling alternating current electric field strength with a frequency. It is a figure for demonstrating discharge efficiency in the case of controlling alternating current electric field strength with a frequency. It is a flowchart showing the control routine for engine operation in the case of controlling alternating current electric field strength with an applied voltage. It is the figure which looked at the combustion chamber from the engine lower side. It is a figure which shows the magnitude | size of the discharge energy for every operation area | region (2nd Embodiment). It is a figure which shows the relationship between the power loss by dielectric loss, and an applied voltage. It is a figure which shows the control target value of dielectric loss in the case of controlling alternating current electric field strength with an applied voltage. It is a figure which shows the control target value of a dielectric constant in the case of controlling alternating current electric field strength with an applied voltage. It is a figure for demonstrating discharge efficiency in the case of controlling alternating current electric field intensity with an applied voltage. It is a flowchart showing the control routine at the time of engine starting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Combustion chamber 3 Intake passage 4 Exhaust passage 5 Intake valve 6 Exhaust valve 7 Intake camshaft 8 Exhaust camshaft 9 Fuel injection valve 10 Non-equilibrium plasma discharge device 11 Engine control unit (ECU)
12 High Voltage High Frequency Generator 13 Heater 14 Cooling Channel 15 Radiator 16 Pump 17 Electromagnetic Valve (or Thermostat)
18 Temperature Sensor 19 Heating Power Supply 20 Center Electrode 21 Dielectric 22 Tubular Electrode 23 Discharge Chamber

Claims (20)

Positive and negative electrodes at least one of which is covered with a dielectric,
A power supply for applying an alternating electric field between the positive and negative electrodes;
Dielectric control means for controlling the dielectric constant and dielectric loss of the dielectric according to the applied AC electric field;
A discharge device comprising:   The discharge device according to claim 1, wherein the dielectric constant and dielectric loss of the dielectric have a dependency on the temperature or pressure of the dielectric.   The discharge device according to claim 2, wherein the dielectric control unit controls the dielectric constant and dielectric loss by controlling a temperature or a pressure of the dielectric.   Each of the dielectric constant and dielectric loss of the dielectric has a peak that reaches a maximum value at a predetermined temperature or pressure, and the dielectric loss changes more than the dielectric constant near the predetermined temperature or pressure. The discharge device according to claim 2, wherein:   The discharge device according to claim 1, wherein the dielectric is a ferroelectric.   6. The discharge device according to claim 3, wherein the dielectric control means controls the temperature of the dielectric to a predetermined temperature range near a transition temperature.   The discharge device according to any one of claims 3 to 6, wherein the dielectric control means controls the temperature of the dielectric within a predetermined temperature range near the transition temperature and higher than the transition temperature. Electric field control means for controlling the intensity of the alternating electric field,
The discharge device according to any one of claims 1 to 7, wherein the electric field control means controls the intensity of the AC electric field by controlling an applied voltage or an applied frequency.   When the electric field control means increases the AC electric field strength, the dielectric control means has a relatively low dielectric loss so as to maintain a discharge efficiency substantially equal to that before the AC electric field strength increases. The discharge device according to claim 8, wherein the temperature of the dielectric is controlled so as to have a relatively high dielectric constant.   When the electric field control means increases the strength of the alternating electric field by increasing the applied voltage, the dielectric control means is lower than when increasing the strength of the alternating electric field by increasing the frequency. 10. The discharge device according to claim 9, wherein the temperature of the dielectric is controlled so as to have a dielectric loss and a higher dielectric constant.   11. The discharge device according to claim 1, wherein the discharge device is used as an ignition device or an ignition auxiliary device for an internal combustion engine.   The discharge device according to claim 11, wherein the dielectric control unit controls a dielectric constant and a dielectric loss of the dielectric by controlling a temperature of the dielectric according to an engine operation state.   As the engine load becomes lower, the electric field control means increases the strength of the AC electric field, and the dielectric control means reduces the dielectric loss so as to maintain the discharge efficiency substantially the same as that before the strength of the AC electric field increases. 13. The discharge device according to claim 12, wherein the temperature of the dielectric is controlled so as to be low and the dielectric constant is high.   As the engine speed becomes higher, the electric field control means increases the intensity of the AC electric field, and the dielectric control means maintains the dielectric loss so as to maintain the discharge efficiency substantially the same as before the intensity of the AC electric field increases. 13. The discharge device according to claim 12, wherein the temperature of the dielectric is controlled so that the dielectric constant is low and the dielectric constant is high.   As the engine load is lower and the engine speed is higher, the electric field control means increases the intensity of the AC electric field, and the dielectric control means has a discharge efficiency substantially the same as that before the intensity of the AC electric field increases. 13. The discharge device according to claim 12, wherein the temperature of the dielectric is controlled so that the dielectric loss is low and the dielectric constant is high so as to maintain.   The discharge device according to any one of claims 11 to 15, wherein the discharge device operates only in a predetermined operating region of the engine.   The discharge device according to claim 16, wherein the predetermined operation region is an engine low load region.   18. The discharge device according to claim 11, wherein a transition temperature of the dielectric is substantially equal to a temperature during engine operation in the vicinity of a discharge device installation portion of the engine.   The electric field control means increases the electric field strength so that the amount of heat generated by dielectric loss becomes the amount of heat necessary for temperature rise when the dielectric control means raises the temperature of the dielectric. The discharge device according to any one of 3 to 18.   The discharge device according to claim 19, wherein the temperature rise of the dielectric by the amount of heat generated by the dielectric loss is performed at the time of engine cold start.

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