JP2010096112A - Plasma ignition device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of a plasma ignition device that the electric resistance of a discharge gap in an ignition plug is increased due to the influence of the wear of a central electrode or operation conditions of an engine, for example, the influence of pressure, a load, an air-fuel ratio or the like in a combustion chamber and plasma discharge omission occurs, thereby generating no desired plasma discharge and impairing stability in the ignition of the ignition plug. <P>SOLUTION: This plasma ignition device performs feedback control for increasing a plasma current value or a primary current value when a period of time Δt from the transmission of the first signal to an ECU 40 to the transmission of the second signal exceeds the predetermined period of a time due to an external cause, and prevents plasma discharge skip with respect to a first signal transmitted from a circuit 20 for spark discharge to the ECU 40 and a second signal transmitted from a circuit 30 for spark discharge to the ECU 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma ignition device for an internal combustion engine that forms plasma and ignites an air-fuel mixture.

2. Description of the Related Art Conventionally, for example, spark plugs that ignite an air-fuel mixture only by spark discharge are used in an ignition device for an internal combustion engine for automobiles. In recent years, there has been a demand for higher output and lower fuel consumption of internal combustion engines, and as a highly ignitable ignition device that can reliably ignite a lean air-fuel mixture with a higher ignition limit air-fuel ratio, a gas in a plasma state (hereinafter referred to as a gas state) , Plasma gas) is injected into the combustion chamber to ignite the air-fuel mixture (for example, see Patent Document 1).
JP 2007-287665 A

  Since a large amount of current of 100 A or more is applied to the plasma spark plug, the consumption of the center electrode or the ground electrode constituting the plasma spark plug is very large, several tens of times that of the conventional spark plug. Therefore, for example, when a constant amount of plasma current is always applied to the plasma spark plug, the center electrode or the ground electrode is consumed, and the discharge gap between the center electrode and the ground electrode is increased. As a result, the electrical resistance of the discharge gap also increases, so that it is difficult for spark discharge and plasma discharge to occur, and there is a possibility that the phenomenon of failure to ignite the air-fuel mixture, so-called plasma discharge omission occurs. Here, for example, when the center electrode is configured to be a negative electrode, the center electrode is easily consumed, and conversely, when the center electrode is configured to be a positive electrode, the ground electrode is easily consumed. Proven from experiments.

  In addition, the electrical resistance of the discharge gap increases due to not only the influence of consumption of the center electrode or ground electrode but also the operating conditions of the engine, for example, the pressure, load, air-fuel ratio, etc. in the combustion chamber, and the plasma discharge is lost. There is a risk of this happening.

  Considering such problems, in order to ignite reliably with the plasma spark plug, if excessive energy is continuously applied to the plasma spark plug from the beginning, it is possible to suppress the discharge of the plasma discharge, The consumption of the center electrode or the ground electrode is accelerated, leading to a significant decrease in the life of the plasma spark plug.

  Therefore, in view of such circumstances, the present invention provides a plasma ignition device that optimizes the life of a plasma ignition plug, suppresses the discharge of plasma discharge, and improves the ignition stability of the plasma ignition plug. Objective.

  In order to solve the above-mentioned problems, a plasma ignition device according to claim 1 is fixed to a combustion chamber side opening of a plug hole of an internal combustion engine, and is provided with a central electrode spaced apart via an insulating member Based on a trigger signal from a plasma spark plug having a discharge space between the ground electrode and an electronic control device that controls the ignition timing of the plasma spark plug based on the operating conditions of the internal combustion engine, A secondary current is passed from the secondary coil to the plasma spark plug by mutual induction with the secondary coil, and a spark discharge circuit section for generating a spark discharge in the discharge space is electrically connected to the plasma spark plug. A plasma generating capacitor that is charged by a plasma generating power source, and the plasma generating capacitor is placed in the discharge space where it falls due to the occurrence of a spark discharge. Plasma discharge circuit section that generates a plasma discharge in the discharge space by passing a plasma current from the plasma generating capacitor to the plasma ignition plug at the same time the voltage between the gap between the electrode and the ground electrode falls below the charging voltage of the plasma generating capacitor A spark discharge circuit detection unit for detecting a spark discharge occurrence time and transmitting a first signal corresponding to the detected spark discharge occurrence time to the electronic control unit; and a plasma discharge A plasma ignition device provided with a plasma discharge generation timing detection unit that is provided in the circuit unit, detects a plasma discharge generation timing, and transmits a second signal corresponding to the detected plasma discharge generation timing to the electronic control unit In the cycle in which the plasma spark plug generates plasma discharge based on one trigger signal, the first signal Second signal in the electronic control unit when it is transmitted to the electronic control unit with a delay, wherein the feedback control for boosting a power source for plasma generation is performed for.

  As a result, the plasma current value for generating plasma discharge in the plasma spark plug can be increased as appropriate, so that the transmission delay of the second signal with respect to the first signal is corrected so as to reduce the plasma discharge omission. In addition, the life of the plasma spark plug can be optimized.

  In order to solve the above problem, the plasma ignition device according to the second aspect of the present invention is fixed to the combustion chamber side opening of the plug hole of the internal combustion engine, and is provided apart via an insulating member. Based on a trigger signal from a plasma spark plug having a discharge space between the center electrode and the ground electrode, and an electronic control device that controls the ignition timing of the plasma spark plug based on the operating conditions of the internal combustion engine, the primary coil Is electrically connected to the plasma spark plug and a spark discharge circuit section for passing a secondary current from the secondary coil to the plasma spark plug by the mutual induction action between the secondary coil and the secondary coil to generate a spark discharge in the discharge space. And a plasma generating capacitor that is charged by a plasma generating power source, and the plasma generating capacitor is placed in a discharge space that falls due to the occurrence of a spark discharge. Plasma discharge that generates a plasma discharge in the discharge space by passing a plasma current from the plasma generating capacitor to the plasma ignition plug at the same time that the voltage between the gap between the center electrode and the ground electrode falls below the charging voltage of the plasma generating capacitor. A spark discharge occurrence timing detection unit that is provided in the circuit unit and the spark discharge circuit unit, detects the occurrence timing of the spark discharge, and transmits a first signal corresponding to the detected occurrence timing of the spark discharge to the electronic control unit; A plasma type comprising: a plasma discharge generation timing detection unit provided in the plasma discharge circuit unit for detecting a generation timing of the plasma discharge and transmitting a second signal corresponding to the detected generation timing of the plasma discharge to the electronic control unit In a cycle in which a plasma spark plug generates a plasma discharge based on a single trigger signal, In the electronic control unit when it is transmitted by the second signal is delayed for one signal to the electronic control unit, characterized in that the feedback control to increase the secondary current value is performed.

  That is, by executing feedback control that increases the secondary current value, the electrical resistance of the discharge space of the plasma ignition plug is reduced, thereby making it easier to energize the plasma current. Thereby, it is corrected so that the transmission delay of the second signal with respect to the first signal is reduced, so that the plasma discharge can be suppressed and the life of the plasma ignition plug can be optimized.

  According to the invention described in claim 3, the predetermined time described in claim 1 and claim 2 is one of the time from when energization to the secondary coil is started until the secondary current value exhibits a peak. / 2.

  Thereby, for example, even when the transmission of the second signal is delayed with respect to the first signal, if the plasma discharge is reliably performed without exceeding the predetermined time, the power supply for plasma generation is The feedback control for increasing the boost or the secondary current value is not executed. Therefore, the energy applied to the plasma ignition plug is not increased by the feedback control, and the center electrode or the ground electrode is suppressed from being consumed easily.

  According to the fourth aspect of the present invention, the feedback control by the electronic control device is executed after the energization of the secondary coil is started until the secondary current value converges to zero. That is, by performing feedback control until a plasma discharge is generated and the next plasma discharge is generated, it is possible to suppress the discharge of the plasma discharge and to optimize the life of the plasma spark plug.

  According to the fifth aspect of the present invention, the feedback control by the electronic control device is executed after the energization of the secondary coil is started until the secondary current value exhibits a peak. During the period from 1/2 of the time until the secondary current value takes a peak to the peak of the secondary current value, the plasma discharge is likely to be lost, and the secondary current has a peak. Later, it has been experimentally found that plasma discharge loss frequently occurs. Therefore, feedback control during this period can effectively suppress the plasma discharge loss.

  According to the invention described in claim 6, until the second signal is delayed for a predetermined time or more with respect to the first signal, the electronic control unit executes control for gradually decreasing the energy applied to the plasma ignition plug.

Specifically, in the case where the second signal is transmitted to the electronic control device without being delayed for a predetermined time or more with respect to the first signal, and no plasma discharge is lost in the plasma ignition plug, the electronic control device Then, control for reducing the voltage of the power source for generating plasma or the secondary current value is executed. As a result, reliable ignition is realized in the plasma spark plug, the amount of energy applied to the plasma spark plug is optimized, and consumption of the center electrode or the ground electrode can be suppressed.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a circuit configuration of a plasma ignition device 100 according to the present embodiment. As shown in FIG. 1, a plasma ignition device 100 includes a plasma ignition plug 10 that generates plasma discharge, and a center electrode and a ground electrode between the spark plug 10, which will be described later, in order to generate plasma discharge. A spark discharge circuit unit 20 for generating a spark discharge in the discharge gap 14 and a plasma discharge circuit for supplying a plasma current to the spark plug 10 at a predetermined timing after the spark discharge and generating a plasma discharge in the spark plug 10 And an electronic control unit (hereinafter referred to as ECU 40) that performs ignition control of the spark plug 10 and the like. Hereinafter, the spark plug 10, the spark discharge circuit unit 20, the plasma discharge circuit unit 30, and the ECU 40 that constitute the plasma ignition device will be described in detail.

  FIG. 2 is a schematic cross-sectional view of the spark plug 10. In the following, for the sake of simplicity, the upper side is the base end side and the lower side is the front end side in FIG. A spark plug 10 fixed to a combustion chamber side opening of a plug hole of an engine block (not shown) includes a center electrode 11 and a substantially cylindrical insulator 12 that is insulated and held so as to cover the center electrode 11. It is comprised with the metal ground electrode 13 formed in the substantially cyclic | annular form so that the insulator 12 might be covered. Between the front end of the center electrode 11 and the front end of the ground electrode 13, a discharge gap 14 of about 2 mm where a spark discharge is generated is formed. In addition, a space surrounded by the insulator 12 and a discharge space 15 in which plasma discharge including the discharge gap 14 is generated is formed. When a plasma current of 100 A or more is applied to the center electrode 11 of the spark plug 10, a high-temperature plasma gas is generated in the discharge space 15, and the gas in the discharge space 15 expands due to the plasma gas, resulting in a high pressure. It is injected into the combustion chamber and ignites the fuel / air mixture. Here, the plasma gas refers to a gas showing electrical neutrality in a state of being ionized into positive ions and electrons at a high temperature of several thousand degrees Celsius or higher.

  The front end side of the center electrode 11 is formed in a long axis shape with a conductive material such as iridium, iridium alloy, platinum, platinum alloy, for example. Inside the center electrode 11, there is formed a center electrode middle shaft 11a made of a metal material having good conductivity and high thermal conductivity such as nickel material, and its base end side is exposed from the insulator 12, and a spark discharge circuit which will be described later. The unit 20 and the plasma discharge circuit unit 30 are electrically connected. In the present embodiment, the center electrode 11 is configured as a negative electrode.

  The insulator 12 is made of high-purity alumina or the like excellent in heat resistance, mechanical strength, dielectric strength at high temperature, thermal conductivity, and the like, and has a substantially cylindrical shape that holds the center electrode 11.

  The ground electrode 13 constitutes a housing that holds the insulator 12 on the base end side. The spark plug 10 is fixed to the engine block so that the ground electrode 13 is exposed in the combustion chamber, and the ground electrode 13, the engine block, Is formed with a screw portion 13a for electrically grounding. A housing hexagonal portion 13b for tightening the screw portion 13a is formed on the base end side of the screw portion 13a of the ground electrode 13. The housing including the ground electrode 13 is made of a metal material such as nickel or iron.

  A spark discharge circuit unit 20 and a plasma discharge circuit unit 30, which will be described in detail below, are electrically connected to the spark plug 10 described above.

  The spark discharge circuit unit 20 includes a primary coil 21 and a primary side circuit connected to the primary coil 21, a secondary coil 22 and a secondary side circuit connected to the secondary coil 22, and is generated in the secondary coil 22. The secondary current is supplied to the spark plug 10 to generate a spark discharge in the discharge space 15.

  The primary coil 21 is formed, for example, by winding an enameled wire having a diameter of 0.3 mm to 0.8 mm for 100 to 230 turns. On the other hand, the secondary coil 22 is formed, for example, by winding 10,000 to 20000 turns of an enameled wire having a diameter of 40 μm to 50 μm. The primary coil 21 is energized with a primary current based on a trigger signal transmitted from the ECU 40 described later. A secondary current is generated in the secondary coil 22 by a mutual induction effect caused by a change in magnetic flux when the primary current is passed through the primary coil 21.

  First, as shown in FIG. 1, a primary side circuit for supplying a primary current to the primary coil 21 includes a spark discharge capacitor 23, a spark discharge power source 24, a thyristor 25, a diode 26, and the like.

  The spark discharge capacitor 23 has, for example, an electric capacity of 1 to 3 μF, and is connected to a spark discharge power source 24 composed of a DC-DC converter or the like connected to a battery (not shown). It is charged to a voltage, for example 200-400V.

  A thyristor 25, which is a switching element, is provided in the forward direction with respect to the ground between the spark discharge power source 24 and the positive electrode (left electrode in FIG. 1) of the spark discharge capacitor 23, which will be described later. It is turned on based on a trigger signal transmitted from the ECU 40. When the thyristor 25 is turned on, the spark discharge capacitor 23 in which a predetermined amount of electricity is stored is discharged through the thyristor 25, and a primary current is passed through the primary coil 21. The diode 26 connected to the negative electrode of the spark discharge capacitor 23 rectifies this primary current and generates a desired secondary voltage in the secondary coil 22 described later.

  Subsequently, as shown in FIG. 1, the secondary circuit that supplies the secondary current to the secondary coil 22 includes a diode 27, an electrical resistor 28, a current sensor 29, and the like. Due to the mutual induction action between the primary coil 21 and the secondary coil 22, the secondary current generated in the secondary coil 22 is passed through the spark plug 10 via the diode 27 and the electrical resistance 28. The diode 27 prevents a plasma current from flowing from the plasma discharge circuit unit 30 described later to the secondary coil 22 side. On the other hand, an electrical resistance 28 provided on the downstream side of the diode 27 prevents the plasma discharge circuit unit 30 described later. Removes noise originating from the flowing spark discharge current.

  The current sensor 29 is provided between the secondary coil 22 and the diode 27, detects a waveform representing a change in the secondary current value that is passed from the secondary coil 22 to the spark plug 10, and generates a spark discharge. This detected waveform corresponding to the generation time is output to the ECU 40 as a first signal. As the current sensor 29, it is preferable to use an electromagnetic pickup type sensor capable of accurately detecting a change in the secondary current.

  Next, the plasma discharge circuit unit 30 includes a plasma discharge capacitor 31, a plasma discharge power source 32, a resistor 33, two diodes 34 and 35, etc., and supplies a plasma current to the spark plug 10 to discharge space. 15 generates a plasma discharge.

  The plasma discharge capacitor 31 has, for example, an electric capacity of 0.2 to 2 μF, and is supplied with a predetermined voltage, for example, 600 to 900 V by a plasma discharge power source 32 composed of a DC-DC converter or the like connected to the battery. Is applied. The charging of the plasma discharge capacitor 31 is terminated by turning off the plasma discharge power source 32 when, for example, the primary current starts to be supplied (when the trigger signal is transmitted to the thyristor 25). Thereafter, the spark gap generated in the spark plug 10 causes the voltage between the gaps to drop and drops below the voltage of the plasma discharge capacitor 31. At the same time, a plasma current of 200 A, 100 mJ, for example, is passed from the plasma discharge capacitor 31 to the spark plug 10. The The two diodes 34 and 35 prevent the secondary voltage of the spark discharge circuit unit 20 from being applied to the plasma discharge capacitor 31 and the plasma discharge power supply 32 to be destroyed.

  A resistor 33 provided in series between the negative electrode of the plasma discharge capacitor 31 and the ground is an electric element for detecting a plasma current, and is provided between the resistor 33 and the plasma discharge capacitor 31. A second signal that is a discharge voltage waveform (plasma current waveform) of the plasma discharge capacitor 31 is output to the ECU 40 via a signal line provided in the ECU 40. The ECU 40 is mainly configured by a microcomputer including a CPU, a ROM, a RAM, and the like, and executes various control programs stored in the ROM, thereby performing ignition control and the like according to each engine operating condition. Specifically, as the ignition control, the ECU 40 calculates the ignition timing based on various detection signals that are input as needed from a crank angle sensor, an intake pipe pressure sensor, or the like attached in the vicinity of the crankshaft of the engine. Based on this, a trigger signal is output to the thyristor 25.

  In addition, the ECU 40 performs charge control of the plasma discharge capacitor 31 by driving and controlling the plasma discharge power source 32. Specifically, as the charge control, the ECU 40 starts charging the plasma discharge capacitor 31 by turning on the plasma discharge power source 32 when a predetermined standby time has elapsed from the ignition timing and the plasma discharge is completed. Charging of the plasma discharge capacitor 31 is stopped by turning off the plasma discharge power source 32 at a certain time before the next ignition timing (for example, when energization of the primary coil 21 is started). That is, the plasma discharge capacitor 31 repeatedly executes charging between ignition timings and discharging at the ignition timing. The ignition timing of the present embodiment is a timing when a trigger signal is transmitted to the thyristor 25 of the spark discharge circuit unit 20.

  Hereinafter, the characteristic operation of the first embodiment of the present invention will be described in detail.

  FIG. 3 shows the time T on the horizontal axis, (a) secondary current value on the vertical axis, (b) voltage value between gaps in the cycle in which plasma discharge is generated in the spark plug 10 based on one trigger signal, c) Changes in secondary current value and (d) plasma current value.

  When the discharge of the spark discharge capacitor 23 is started based on the trigger signal and the time when the energization of the secondary current is started is T = 0, a spark discharge occurs in the discharge gap 14 at the time T = T1, and the gap The inter-voltage value decreases rapidly. At this time, the current sensor 29 detects the first signal shown in FIG.

  FIG. 4 is a partially enlarged schematic diagram of (c) the change in the secondary current value and (d) the graph showing the plasma current value in FIG. As shown in FIG. 4, a threshold value Kth for the first signal is provided in the ECU 40 in advance, and a time t1 at which a waveform exceeding the threshold value Kth is detected by the ECU 40 is regarded as a time T1 at which a spark discharge has occurred in the discharge gap 14. .

  Also, as shown in FIG. 3, the secondary current continues to be applied after T1, and after reaching a peak at time T = T2, the secondary current value decreases and is stored in the spark discharge capacitor 23 at time T = T3. All the generated charges are discharged, and energization of the secondary current is completed. Here, although the time T1 when the spark discharge occurs and the time t1 when the detected waveform of the change in the secondary current exceeds the threshold value Kth are strictly different, the width of one peak of the first signal shown in FIG. 4 is several nsec. Since it is an order, for the sake of simplicity, the following description will be made assuming that T1≈t1.

  On the other hand, the voltage between the gaps suddenly drops at time T1, and the plasma current is supplied from the plasma discharge capacitor 31 to the spark plug 10 at the same time when the voltage between the gaps falls below the voltage of the plasma discharge capacitor 31. At this time, when the plasma current passes through the resistor 33, a second signal which is a discharge voltage waveform of the plasma discharge capacitor 31 is detected and transmitted to the ECU 40. The time at which this plasma current waveform takes a peak, in other words, the time T at which the plasma current value takes a peak is regarded as the plasma current generation time t2 in the ECU 40.

  In the ECU 40 to which the first signal and the second signal are transmitted, the following control is executed.

  The ECU 40 receives the first signal at time t1 (T1) and the second signal at time t2. Here, as shown by the solid line in (d) of FIGS. 3 and 4, the time from when the spark discharge occurs in the discharge space 15 until the plasma current value peaks, that is, t2 and t1 Δt is very short, several μsec or less. At this time, a desired plasma discharge is generated in the discharge space 15 and the air-fuel mixture is reliably ignited.

  On the other hand, the waveform indicated by the broken line in (d) in FIGS. 3 and 4 shows the plasma current value when the ignition control is repeatedly executed. In the ECU 40, the second signal corresponding to the first signal is shown. It can be seen that there is a delay in the transmission timing and Δt increases. The cause of this is that the plasma electrode is repeatedly executed, so that the center electrode 11 is mainly consumed and the distance between the gaps increases, or the engine operating conditions (in-cylinder pressure, load, air fuel consumption, etc.) are affected. Conceivable.

  Accordingly, in this embodiment, the plasma current value is controlled by the ECU 40 in order to suppress the consumption of the center electrode 11 and the loss of plasma discharge depending on the operating conditions of the engine. Specifically, for example, when Δt detected by the ECU 40 changes from several μsec to 14 μsec or more, feedback control for boosting the power supply voltage of the plasma discharge power supply 32 is executed. Thereby, after the feedback control, the amount of electricity stored in the plasma discharge capacitor 31 increases, so that the value of the plasma current supplied to the spark plug 10 also increases, and the ignition stability of the spark plug 10 is improved. In other words, by preventing Δt from being longer than 14 μsec, the plasma discharge is suppressed.

  In this embodiment, the time T2 at which the secondary current value takes a peak is about 30 μsec, and the feedback control is executed when the time becomes 14 μsec, which is shorter than this half time (15 μsec). 3 and 4, it has been experimentally proved that it is after T2 / 2 as shown by the broken line in FIGS. 3 and 4. For example, when Δt = 15 to 29 μsec, Executing the feedback control is preferable in that the ignition stability of the plasma discharge can be improved with the minimum applied energy without impairing the engine performance. Even in an engine different from the present embodiment and the engine operating conditions, the feedback control is executed immediately before the time t2 when the second signal is transmitted to the ECU 40 becomes T2 / 2 = t2, and the plasma discharge is suppressed. It is preferable from the viewpoint of both the life of the spark plug and the ignition stability.

  Further, in the present embodiment, as shown in FIG. 3, when the second signal is transmitted to the ECU 40 after time T2 (T ≧ 30 μsec), the plasma discharge is frequently lost and the engine exhibits the desired performance. It has been determined that it will not be possible. Therefore, in this case, since the air-fuel mixture is not ignited by the plasma gas, it is preferable to execute the feedback control by time T2 at the latest so as to effectively prevent the plasma discharge from being lost. Here, in the present embodiment, suppressing the plasma discharge loss means that the plasma discharge loss is not substantially generated.

  In the present embodiment, the time t2 is set as the time when the peak value of the plasma current value is detected by the resistor 33, but t2 is set in advance on the ECU 40 side where the second signal is transmitted. Therefore, the time is not limited to the peak value but may be any plasma current value. For example, the rising time of the waveform indicating the plasma current value shown in FIG. 4D may be t2, and the feedback control may be executed with an optimal Δt in the same manner as in the first embodiment.

Furthermore, the number of ECUs 40 is not necessarily one. For example, an electronic control device that outputs a trigger signal and an electronic control device that calculates Δt may be provided separately.
(Second embodiment)
Hereinafter, although the second embodiment will be described, since the basic configuration is the same as that of the first embodiment, only the differences that should be noted will be described. The same members as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment.

In the first embodiment, the difference Δt between the time t1 when the first signal is transmitted to the ECU 40 and the time t2 when the second signal is transmitted to the ECU 40 increases, and there is a possibility that the plasma discharge may be lost. In this embodiment, when the feedback control for boosting the power supply voltage of the plasma discharge power supply 32 is executed, the secondary current value is set when Δt increases and the plasma discharge may be lost. Perform incremental feedback control. That is, as shown in FIG. 5, ECU 40 and spark discharge power supply 24 are connected by a signal line, and feedback control is executed from ECU 40 to spark discharge power supply 24. Specifically, the power supply voltage of the spark discharge power supply 24 is boosted to increase the amount of electricity stored in the spark discharge capacitor 23. Thereby, the primary current value flowing through the primary coil 21 by the discharge of the spark discharge capacitor 23 increases, and as a result, the secondary current value increases. By increasing the secondary current value by feedback control in this way, the electrical resistance of the discharge gap 14 is reduced, and the plasma current is easily supplied to the discharge gap 14 and the discharge space 15. Therefore, in the plasma ignition device 200 according to the present embodiment, the ECU 40 corrects the transmission delay of the second signal with respect to the first signal so as to reduce the plasma discharge omission and stabilize the ignition of the ignition plug 10. Improves.
(Third embodiment)
In the present embodiment, when Δt increases and there is a possibility that the plasma discharge may be lost, the power supply voltages of both the plasma discharge power supply 32 and the spark discharge power supply 24 are boosted, and the plasma current value and Feedback control for increasing the next current value is executed. Thereby, in the plasma ignition device 300 according to the present embodiment, in the same manner as in the first embodiment and the second embodiment, the discharge of the plasma discharge is suppressed, and the ignition stability of the spark plug 10 is improved.
(Other examples)
In the first to third embodiments, the timing of the feedback control is determined by the difference between the input times of the first signal and the second signal input to the ECU 40. For example, a trigger signal is sent from the ECU 40 to the thyristor 25. The timing of feedback control is calculated by the ECU 40 based on the difference Δt ′ between the time t0 output to the time t2 and the time t2 when the second signal is input to the ECU 40, and the feedback control is executed at a predetermined Δt ′. Also good.

  In the above embodiment, the ground electrode 13 is made of a metal material such as nickel or iron. However, at least in the discharge portion of the ground electrode 13, like the center electrode 11, an iridium alloy having excellent wear resistance can be used. A noble metal such as a platinum alloy may be used.

  In the above embodiment, since the center electrode 11 is a negative electrode, the center electrode 11 is mainly consumed. However, conversely, the center electrode 11 may be a positive electrode and the ground electrode 13 may be mainly consumed. At this time, since the volume of the ground electrode 13 is generally larger than that of the center electrode 11, the configuration in which the ground electrode 13 is preferentially consumed in this way is preferable in terms of improving the life of the spark plug 10.

  Furthermore, in the first to third embodiments, when the transmission of the second signal is delayed by a predetermined time or more with respect to the transmission of the first signal to the ECU 40, the plasma discharge power source 32 and / or the spark discharge. Although the voltage of the power supply 24 is boosted, the ECU 40 may execute control to gradually reduce the energy applied to the spark plug 10 until the second signal is delayed for a predetermined time or more with respect to the first signal. Good.

  Specifically, when the second signal is generated with respect to the first signal without a predetermined time interval, a control signal for gradually reducing the voltage of the plasma discharge power supply 32 and / or the spark discharge power supply 24 is sent to the ECU 40. Is transmitted to the plasma discharge power source 32 and the spark discharge power source 24, respectively. By carrying out and continuing such control, it becomes a state where there is a possibility that the plasma discharge may be lost, that is, when the second signal is delayed for the predetermined time or more with respect to the first signal. Performs feedback control for boosting the plasma discharge power source 32 and / or the spark discharge power source 24 described in the first to third embodiments, and suppresses the occurrence of missing plasma discharge. As a result, it is possible to suppress the discharge of plasma discharge while suppressing the consumption of the center electrode 11 or the ground electrode 13, and the life of the spark plug 10 is improved.

1 is a block diagram showing a circuit configuration of a plasma ignition device according to a first embodiment of the present invention. It is sectional drawing of a spark plug. The horizontal axis represents time T, the vertical axis represents a) secondary current value, (b) voltage value between gaps, (c) change in secondary current value, and (d) plasma current value. FIG. 4 is a schematic diagram in which (c) a change in secondary current value and (d) a plasma current value in FIG. 3 are enlarged. It is a block diagram which shows the circuit structure of the plasma ignition device which concerns on 2nd embodiment of this invention.

Explanation of symbols

10 ... spark plug,
11 ... center electrode,
11a ... center electrode central shaft 12 ... insulator
13: Ground electrode,
13a ... Screw part,
13b ... Housing hexagon,
14 ... discharge gap,
15 ... discharge space,
20 ... Spark discharge circuit part,
21 ... Primary coil,
22 ... secondary coil,
23 ... Spark discharge capacitor,
24 ... Power source for spark discharge 25 ... Thyristor,
26, 27 ... diodes,
28 ... electric resistance,
29 ... Current sensor (spark discharge occurrence timing detection unit),
30: Circuit portion for plasma discharge,
31 ... Plasma discharge capacitor,
32 ... Power source for plasma discharge,
33. Resistor (plasma discharge generation time detection unit),
34, 35 ... diodes,
40. ECU (electronic control unit),
100: Plasma ignition device

Claims (6)

A plasma ignition plug having a discharge space between a center electrode and a ground electrode fixed to a combustion chamber side opening of a plug hole of an internal combustion engine and spaced apart via an insulating member;
Based on the trigger signal from the electronic control device that controls the ignition timing of the plasma ignition plug based on the operating condition of the internal combustion engine, the plasma type from the secondary coil by the mutual induction action of the primary coil and the secondary coil A spark discharge circuit that energizes a secondary current to the spark plug and generates a spark discharge in the discharge space;
A plasma generating capacitor that is electrically connected to the plasma spark plug and is charged by a plasma generating power source, wherein the plasma generating capacitor is lowered in the discharge space where the spark discharge occurs. At the same time that the voltage between the gap between the center electrode and the ground electrode falls below the charging voltage of the plasma generating capacitor, a plasma current is passed from the plasma generating capacitor to the plasma ignition plug to generate a plasma discharge in the discharge space. A plasma discharge circuit section to be
A spark discharge occurrence timing detection unit that is provided in the spark discharge circuit unit, detects the occurrence timing of the spark discharge, and transmits a first signal corresponding to the detected occurrence timing of the spark discharge to the electronic control unit;
A plasma discharge generation timing detection unit provided in the plasma discharge circuit unit for detecting a generation timing of the plasma discharge and transmitting a second signal corresponding to the detected generation timing of the plasma discharge to the electronic control unit; A plasma ignition device comprising:
In a cycle in which the plasma ignition plug generates plasma discharge based on the one trigger signal, the second signal is transmitted to the electronic control device after a predetermined time or more with respect to the first signal. In the electronic control device, feedback control for boosting the plasma generating power source is executed. A plasma ignition plug having a discharge space between a center electrode and a ground electrode fixed to a combustion chamber side opening of a plug hole of an internal combustion engine and spaced apart via an insulating member;
Based on the trigger signal from the electronic control device that controls the ignition timing of the plasma ignition plug based on the operating condition of the internal combustion engine, the plasma type from the secondary coil by the mutual induction action of the primary coil and the secondary coil A spark discharge circuit that energizes a secondary current to the spark plug and generates a spark discharge in the discharge space;
A plasma generating capacitor that is electrically connected to the plasma spark plug and is charged by a plasma generating power source, wherein the plasma generating capacitor is lowered in the discharge space where the spark discharge occurs. At the same time that the voltage between the gap between the center electrode and the ground electrode falls below the charging voltage of the plasma generating capacitor, a plasma current is passed from the plasma generating capacitor to the plasma ignition plug to generate a plasma discharge in the discharge space. A plasma discharge circuit section to be
A spark discharge occurrence timing detection unit that is provided in the spark discharge circuit unit, detects the occurrence timing of the spark discharge, and transmits a first signal corresponding to the detected occurrence timing of the spark discharge to the electronic control unit;
A plasma discharge generation timing detection unit provided in the plasma discharge circuit unit for detecting a generation timing of the plasma discharge and transmitting a second signal corresponding to the detected generation timing of the plasma discharge to the electronic control unit; A plasma ignition device comprising:
In a cycle in which the plasma ignition plug generates plasma discharge based on the one trigger signal, the second signal is transmitted to the electronic control device after a predetermined time or more with respect to the first signal. In the electronic control device, a feedback control for increasing the secondary current value is executed.   3. The plasma according to claim 1, wherein the predetermined time is ½ of a time from when energization to the secondary coil is started to when the secondary current value exhibits a peak. Type ignition device.   4. The plasma ignition device according to claim 3, wherein the feedback control is executed from when energization of the secondary coil is started until the secondary current value converges to 0. 5.   4. The plasma ignition device according to claim 3, wherein the feedback control is executed after energization of the secondary coil is started until the secondary current value exhibits a peak. 5.   The electronic control device executes control for gradually reducing the energy applied to the plasma ignition plug until the second signal is delayed for the predetermined time or more with respect to the first signal. The plasma ignition plug according to any one of 1 to 5.

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