JP6035202B2 - Ignition device - Google Patents

Description

  The present invention relates to an ignition power source for igniting an internal combustion engine, and more particularly to an ignition device in which a large flame nucleus is formed at the early stage of discharge to increase a flame growth rate.

  In Patent Document 1, a DC voltage of 12 V or 24 V is boosted to 1 to 5 KVA (50 to 500 kHz) by an RF step-up transformer 20 and then a series LC resonance between a capacitance 31 provided as a high voltage circuit 20 and a dielectric element 32 is provided. The voltage is boosted to 50 to 500 KVAC (50 to 500 kHz) by the resonant action of the circuit, and a high voltage obtained as a result is applied to the electrode 40 of the spark plug, and the output terminal (point A) of the transformer 20 or the high voltage circuit 20 By controlling the secondary voltage detected from the output terminal (point B) and the energizing current of the transformer 20 to a range in which the discharge voltage-current characteristic does not shift to arc discharge, the corona discharge state is maintained and volume ignition is realized. An ignition method is disclosed.

JP 2009-8100 A

However, when the secondary voltage applied to the electrode is boosted by a high voltage circuit using LC resonance as disclosed in Patent Document 1, the resonance Q value is nearly 100 times, and therefore, in the state of corona discharge, the resonance The Q value changes greatly.
For this reason, in order to maintain the discharge voltage and obtain a stable corona discharge, pinpoint impedance matching is required.
Further, as shown in FIG. 7 and the like of Patent Document 1, various corrections are necessary to establish the control, the system becomes complicated, and there is a possibility that the manufacturing cost increases.
Further, a circuit that monitors a secondary voltage on the order of kV has a large loss, which leads to a decrease in the Q value, and there is a possibility that stable ignition cannot be realized.

  Therefore, in view of such circumstances, the present invention has a relatively small variation in the Q value in the discharge state, easy energy adjustment for ensuring ignitability according to engine conditions, and easily detecting the discharge start time, An object of the present invention is to provide an ignition device capable of correcting the start timing of a discharge start command signal, and forming a large flame nucleus in the early stage of discharge to increase the flame growth rate.

The present invention is an ignition device comprising an ignition plug (8) provided in an internal combustion engine and a high-frequency power source for applying a high-frequency alternating current high voltage to the ignition plug (8),
The spark plug (8) includes a center electrode discharge part (800), a dielectric discharge part (810) covering the center electrode discharge part (800), and a grounding provided facing each other by providing a predetermined discharge space (83). An electrode discharge part (820),
The high-frequency power source includes at least a DC power source (1), a first switching element (2), a second switching element (3), a primary winding (71), and a secondary winding (72). Including a step-up transformer (7),
A resonant capacitor (6) having a boosting function is interposed between the DC power supply (1) and the primary winding (71),
The first switching element (2) and the second switching element (3) are alternately opened and closed to apply a boosted high-frequency AC primary voltage (V1) to the primary winding (71). the by you switch the direction of the current flowing through the primary winding (71) alternately to generate a secondary voltage of the high-frequency AC high-voltage (V2) to said secondary winding (72), said ignition plug (8 ) To form an alternating current corona discharge and ignite the air-fuel mixture introduced into the combustion chamber of the internal combustion engine.

  According to the present invention, the first and second switching elements (2, 3) are alternately opened and closed to generate a high-frequency, high-voltage AC primary voltage (V1) generated in the primary winding (71). ) Is determined by the self-inductance (L1) of the primary winding (71), the self-inductance (L2) of the secondary winding (72), and the parasitic capacitance (C3) of the spark plug (8). LC resonance is generated by matching the resonance frequency (ω1), and the secondary winding (72) of the step-up transformer (7) generates a high-voltage AC high-voltage secondary voltage (V2). The spark plug (8) can generate an alternating current corona discharge, the variation of the Q value in the discharge state is relatively small, energy adjustment for ensuring ignitability according to engine conditions is easy, Release The start time easily detected, can be corrected starting time of discharge start command signal, it was found that the flame growth rate can be increased by forming a large flame core in particular discharge early.

The circuit diagram which shows the outline | summary of the ignition device in the 1st Embodiment of this invention Sectional drawing which shows the outline | summary of the ignition plug used for the ignition device in the 1st Embodiment of this invention. The characteristic view which shows the change of the primary voltage of the ignition device in the 1st Embodiment of this invention The characteristic view which shows the change of the secondary voltage of the ignition device in the 1st Embodiment of this invention The characteristic view which shows the change of the primary current of the ignition device in the 1st Embodiment of this invention The characteristic figure which shows the change of Q value in the ignition device of this invention with a comparative example The characteristic figure which shows the effect with respect to flame growth of the ignition device of this invention with a comparative example The characteristic view which shows the effect with respect to the combustion fluctuation | variation PmiCOV of the ignition device of this invention with a comparative example Timing chart showing relationship between reference clock, drive signal and output voltage The circuit diagram which shows the outline of the ignition device which provided Q value calculation means Characteristics diagram when duty is increased Characteristics diagram when duty is reduced The circuit diagram which shows the outline | summary of the ignition device in the 2nd Embodiment of this invention The circuit diagram which shows the outline | summary of the ignition device in the 3rd Embodiment of this invention

With reference to FIG. 1A and FIG. 1B, the outline | summary of the ignition device 9 in the 1st Embodiment of this invention is demonstrated.
The ignition device 9 in the present embodiment applies a high-voltage secondary voltage V2 from a high-frequency power source to a spark plug 8 provided in an internal combustion engine with a high-frequency alternating current, thereby forming an AC corona discharge on the spark plug 8. The ignition of the air-fuel mixture introduced into the combustion chamber of the internal combustion engine is performed.

The ignition device 9 includes a DC power source 1, a first switching element 2, a second switching element 3, a first capacitor 4 for dividing the voltage of the DC power source 1 into two, a second capacitor 5, a resonance A high-frequency power source including a capacitor 6 and a step-up transformer 7 and a spark plug 8 are included.
As the DC power supply 1, a DC-DC converter or the like that boosts the power supply voltage (DC12V or DC24V) to a predetermined voltage (for example, 50 to 400V) can be used.

For the first switching element 2 and the second switching element 3, it is appropriate to use, for example, a SiC-FET, a power MOSFET, an IGBT, or the like. The first switching element 2 and the second switching element 3 are connected in series.
The first switching element 2 is controlled to be opened / closed by the first drive circuit 21, and the second switching element 3 is controlled to be opened / closed by the second drive circuit 31.

The first capacitor 3 (capacitance C1, for example, 560 μF) and the second capacitor 4 (capacitance C2, for example, 560 μF) are connected in series, and the first switching element 2 and the second switching element 3 are connected to each other. Node n ₁ is connected in parallel.

The step-up transformer 7 is configured by winding a primary winding 71 (self-inductance L1, for example, 0.8 μH) and a secondary winding 72 (self-inductance L2, for example, 700 μH) around an iron core 73.
The primary winding 71 is connected to the node n ₂ between one end of the first capacitor 4 and the second capacitor, and the other end of the primary winding 71 is connected to the resonance capacitor 6 in the first switching state. It is connected to a node n ₃ between the element 2 and the second switching element 3.
One end of the secondary winding 72 of the step-up transformer 7 is grounded, and the other end is connected to the spark plug 8.

In the present invention, as shown in FIG. 1B, the spark plug 8 covers the long-axis center electrode 80 with a bottomed cylindrical dielectric 81, and surrounds the dielectric 81 with a predetermined discharge space 83 therebetween. The cylindrical ground electrode 82 formed as described above is configured to face each other.
The center electrode 80 is made of a conductive metal material such as Cu, Fe, or Ni.

The dielectric 81 is made of a dielectric material such as alumina, zirconia, or titania.
The ground electrode 82 is formed of a conductive metal material such as Fe, Ni, and stainless steel.
The ground electrode 82 also serves as the housing of the spark plug 8, and is provided with a screw portion 821 on the outer periphery, and is fixed to the engine block BRC of the internal combustion engine E / G.

In the spark plug 8, the center electrode discharge part 800 and the ground electrode discharge part 820 covered with the dielectric discharge part 810 are exposed in the discharge space 83 and the combustion chamber CMB.
A parasitic capacitance C <b> 3 is formed between the center electrode discharge part 800 on the tip side of the center electrode 80 and the ground electrode cylindrical part 820 on the tip side of the ground electrode 82.
The parasitic capacitance C <b> 3 is a combined capacitance of the capacitance of the dielectric discharge portion 830 where the dielectric 81 is exposed to the discharge space 83 and the capacitance of the discharge space 83.

The operation of the ignition device 9 in this embodiment will be described.
An ignition signal IGt is transmitted from an unillustrated engine control device according to the operating state of the internal combustion engine, and the first and second switching elements 2 and 3 are opened and closed by the first and second drive circuits 21 and 31. Start.

When the first switching element 2 is closed, the high pressure side node n ₁ of the first switching element 2 of the DC power source 1, resonance capacitor 6, the primary winding 71, current flows through a path of the DC power supply intermediate potential node n ₂ .
When the first switching element 2 is opened and the second switching element 3 is closed at the same time as the current has finished flowing, the DC power supply intermediate potential n2, the primary winding 71, the resonant capacitor 6, and the second switching A current flows through the element 3 and the ground path.

By alternately opening and closing the first switching element 2 and the second switching element 3, the electrostatic capacitance C 4 of the resonant capacitor 6, the self-inductance L 1 of the primary winding 71, and the secondary winding 73 A high-frequency alternating current having a frequency equal to the resonance frequency (ω0) determined by the self-inductance L2 and the parasitic capacitance C3 of the spark plug 8 is generated, and series LC resonance between the resonance capacitor 6 and the primary winding 71 is generated.
The primary winding 71 has a peak voltage several times (about 2 to 4 times) higher than the voltage Vin of the DC power source 1 at both ends of the primary winding 71 due to the resonance action, and the high-frequency AC primary voltage V1 is applied. Become.

The secondary winding 72 is stepped up to a secondary winding number (N2) / primary winding number (N1) turns ratio (N2 / N1≈√ (L2 / L1)), and further the self-inductance L2 of the secondary winding 72 And the parasitic capacitance C3 of the spark plug 8 are amplified several times (4 to 8 times), and a high frequency alternating current having a frequency equal to the resonance frequency (ω0) determined by the self-inductance L2 and the parasitic capacitance C3. The secondary voltage V2 is applied to the spark plug 8.
Between the center electrode discharge unit 800 covered with the dielectric discharge unit 810 and the ground electrode discharge unit 820, the surface of the dielectric discharge unit 810 and the ground electrode discharge unit 820 are charged by charges accumulated in the dielectric 81. When the electric field strength with the surface reaches a predetermined value, a corona discharge is instantaneously generated for a very short period and does not result in a continuous arc discharge.

For this reason, by alternately opening and closing the first switching element 2 and the second switching element 3, the corona discharge can be repeated in a short time.
Moreover, the discharge time can be arbitrarily adjusted by maintaining the opening and closing drive of the first switching element 2 and the second switching element 3 even after the discharge is started, and the discharge discharged into the combustion chamber CMB. You can earn energy.
For this reason, it becomes advantageous that the frequency (ω0) of the high frequency generated by opening and closing of the first switching element 2 and the second switching element 3 can be increased.

In this embodiment, the relationship between the resonance frequency ω 0, the self-inductance L 1 of the primary winding 71, the self-inductance L 2 of the secondary winding 72, the capacitance C 4 of the resonance capacitor 6, and the parasitic capacitance C 3 of the spark plug 8 is
ω0 = 1 / √ (L1 · C4) = 1 / √ (L2 · C3).

The resonance of the primary winding 71 and the resonance capacitor 6, since the power supply voltage V _IN of the DC power source 1 can be supplied with the boosted several times the primary voltage V1, blindly increasing the supply voltage V _IN of the DC power source 1 There is no need, for example, it may be about 200-300V.
Further, since the secondary voltage V2 can be further boosted and supplied to the spark plug 8 by the resonance action of the secondary windings 72 and the parasitic capacitance C3, the number of turns of the step-up transformer 7 can be reduced.
As a result, since the self-inductance L1 of the primary winding 71 can be reduced, it is possible to increase the frequency easily.
Note that the values of the resonance frequency, self-inductance, capacitance, and the like shown in the above embodiment are merely examples, and do not limit the present invention.

  In the case of the conventional spark ignition, when the discharge voltage gradually decreases to below a certain level and the discharge path is interrupted, it is impossible to maintain the discharge even if more energy is input. In the ignition device 9 of the present invention, if the primary voltage V1 is continuously supplied, the secondary voltage V2 is also continuously supplied, so that the corona discharge can be maintained for an arbitrary time.

Changes in the primary winding voltage V1, the secondary winding voltage V2, and the primary winding voltage I1 of the step-up transformer 7 of the ignition device 9 in the present embodiment will be described with reference to FIGS. 2A, 2B, and 2C.
In accordance with the ignition signal IGt, opening / closing drive with the first switching element 2 and the second switching element 3 is started, and an alternating primary voltage V1 is generated.

Due to the LC series resonance effect of the resonant capacitor 6 and the primary winding 71, the amplitude of the primary voltage V1 gradually increases as shown in FIG. 2A.
Due to the electromagnetic induction, a secondary voltage V2 having a turn ratio N2 / N1 times the primary voltage V1 is generated in the secondary winding 72.

When the secondary voltage V2 reaches a voltage capable of corona discharge, corona discharge is started between the surface of the dielectric discharge part 810 of the spark plug 8 and the surface of the ground electrode discharge part 820.
When corona discharge is started on the secondary winding 72 side, a leakage resistance component that becomes a loss for the primary-side resonance action is generated, so that the resonance Q value decreases.
As a result, the primary voltage V1 of the primary winding 71 decreases, and the secondary voltage V2 inevitably decreases as shown in FIG. 2B.

Further, as shown in FIG. 2C, the primary current I1 flowing through the primary winding 71 simultaneously decreases.
Therefore, it is possible to detect the corona discharge start timing by detecting the timing when the Q value decreases and the timing when the primary current I1 decreases.
The ignition timing control can be corrected by notifying the engine control device of this timing.
In addition, since the primary winding current I1 decreases after the start of discharge, the first and second switching elements 2 and 3 can have a margin for the allowable current for the first and second switching elements 2 and 3. By increasing / decreasing the current-carrying duty 3, the ignition energy can be optimized to improve ignitability and reduce power consumption.

Here, the effect of the present invention will be described with reference to FIGS. 3A, 3B, and 3C.
As shown in FIG. 3A, in Comparative Example 1 in which corona discharge did not occur and combustion did not occur, even if the secondary voltage V2 applied to the spark plug 8 was increased, the Q value did not change and corona discharge was not generated. In the generated first embodiment, the Q value gradually decreases in accordance with the secondary voltage V2 applied to the spark plug 8.
For this reason, it is understood that the presence or absence of discharge can be detected by determining the threshold value with reference to a predetermined threshold value Qref (for example, 3.0).
Incidentally, Q values are calculated by using an arithmetic unit 20 path to be described below the potential difference across the primary winding 71 _{(V1 = V 11 -V 10)} , divided by the power supply voltage V0 of the DC power source 1 value .

With reference to FIG. 3B, the relationship between the output voltage V2 and the magnitude of the flame after a predetermined period has elapsed since the start of driving will be described.
This figure shows a relative change in the flame core volume when a photo of the combustion chamber after a predetermined time (for example, 200 μS) has elapsed from the start of driving and the secondary voltage V2 is changed, As a comparative example, a change in flame volume due to a normal spark discharge is shown.
As shown in the figure, according to the ignition device 9 of the present invention, it has been found that the flame growth is faster than before and the ignitability can be improved.

With reference to FIG. 3C, the effect of the present invention on the ignition stability will be described.
The ignition limit of a lean mixture (high A / F mixture) by conventional spark discharge (arc discharge) is indicated by a dotted line as Comparative Example 1, and the lean mixture (high A / F) when the ignition device 9 of the present invention is used is shown. The ignition limit of the (F mixture) is shown by a solid line as Example 1 for the combustion fluctuation in the ignition device 9.

In FIG. 3C, the horizontal axis indicates air-fuel consumption A / F, and the vertical axis indicates the combustion fluctuation rate by the indicated mean effective pressure PmiCOV (%).
The smaller the fluctuation rate of combustion, the better the ignitability.
By using the ignition device 9 of the present invention to generate a high-frequency AC corona discharge, it was confirmed that there was an effect of expanding the A / F limit as compared with the conventional spark ignition.

FIG. 4 shows a timing chart showing the relationship between the reference clock, the drive signals of the first and second drive circuits 21 and 31, and the output voltage V2.
In synchronization with the rising edge of the reference clock, the driving signal for operating the first switching element 2 in the first driving circuit 21 becomes high and becomes low after a predetermined on-time TON has elapsed, and is synchronized with the falling edge of the reference clock. to drive signals for operating the second switching device 3 in the second driving circuit 31 becomes high, becomes low after a predetermined oN-time T _oN elapses.
Increase or decrease the duty _(T ON / _T%) by increasing or decreasing the length of T _ON, it is possible to increase or decrease the output voltage V2.

With reference to FIG. 5, a control method in which the Q value calculation means is provided in the ignition device 9 in the first embodiment to perform discharge determination and correction of the ignition signal IGt will be described.
In addition to the ignition device 9 shown in FIG. 1A, the power supply voltage V0 of the DC power source 1, to monitor the potential difference across the primary winding _{71 (V1 = V 11 -V 10} ), Q value calculating means for calculating a Q value (201, 202), discharge determination means 203 for determining the presence or absence of discharge from the calculation result, duty determination means 204 for determining the duty from the determination result, and feedback to the first and second drive circuits 21, 31 An arithmetic device 200 is provided which includes a timer control means 205 for performing ignition timing and an ignition timing correcting means 206 for correcting ignition timing.

Supply voltage V0 of the DC power source 1, the voltage across _{V 11, V 10} of the primary winding 71, respectively, resistors 105 and 106, resistors 101 and 102, the resistors 103 and 104 to lower the voltage by attenuation circuit connected in series Monitoring makes it easy to handle.
The voltages V ₁₁ and V ₁₀ across the primary winding 71 are respectively divided by R ₁₀₂ / (R ₁₀₁ + R ₁₀₂ ) times and R ₁₀₄ / (R ₁₀₃ + R ₁₀₄ ) times and input to the differential amplifier circuit 107. The

The output of the differential amplifier circuit 107 becomes a value obtained by dividing the potential difference (V1 = V ₁₁ −V ₁₀ ) between both ends of the primary winding 71 and is input to the peak hold circuit.
The peak hold circuit in this embodiment includes an operational amplifier 108, a diode 109, a capacitor 110, an analog switch 111, and an operational amplifier 112.
However, the peak hold circuit is not limited to the present embodiment, and a known one can be appropriately employed.

The power supply voltage V0 is divided by R ₁₀₆ / (R ₁₀₅ + R ₁₀₆ ) times by an attenuator circuit.
The output of the peak hold circuit and the voltage obtained by dividing the power supply voltage V0 are input to the A / D converter 201.

A Q value calculating means 202 is provided in the arithmetic unit 200, and the ratio (Q = V1 / V0) between the potential difference (V1 = V ₁₁ −V ₁₀ ) at both ends of the primary winding 71 and the power source voltage V0 of the DC power source 1. ) Is calculated.
As a result, the discharge determination unit 203 compares the calculated Q value with a predetermined threshold value Qref, and determines that if Q ≦ Qref, corona discharge is occurring. If Q> Qref, corona discharge is occurring. Judge that there is no.

From this determination result, the duty determining means 204 determines the duty for driving the first and second switching elements 2 and 3 in accordance with the operating condition of the engine.
Specifically, when it is determined that there is no discharge, it is determined that the discharge energy is insufficient, and an instruction to increase the duty is given. From the duty generation means 205 to the first and second drive circuits 21 and 31. The feedback signals F / B1 and F / B2 with increased duty are transmitted, and the secondary voltage V2 can be increased from 90% duty to 100% duty at any timing as shown in FIG. 6A, for example. .

When it is determined by the discharge determining means 203 that there is a discharge, and it is determined that the discharge can be maintained even when the duty is reduced, the duty determining means 204 is instructed to reduce the duty. Feedback signals F / B1 and F / B2 with reduced duty are transmitted from the generating means 205 to the first and second drive circuits 21 and 31, and the secondary voltage V2 is set to an arbitrary timing as shown in FIG. 6B. Thus, for example, the duty can be reduced from 90% duty to 80% duty.
The analog switch 111 of the peak hold circuit resets the peak value held by the peak hold circuit by being closed by the signal obtained by inverting the drive signal of the first switching element 2 by the inverter 113 and grounded. Prepare for the peak hold of the next cycle.

Further, the ignition timing correction unit 206 determines whether or not the ignition timing needs to be corrected based on the determination result of the discharge determination unit 203, and corrects the ignition signal IGt to the advance side or the retard side as necessary. It feeds back to the engine control device so as to correct it.
These determinations can be realized by preparing map data corresponding to the operating state of the internal combustion engine in the arithmetic circuit 200 in advance.

With reference to FIG. 7, the ignition device 9a in the 2nd Embodiment of this invention is demonstrated. In addition, since the same code | symbol is attached | subjected about the structure similar to the said embodiment, description is abbreviate | omitted and it demonstrates focusing on the characteristic part of this embodiment.
In the present embodiment, in addition to the ignition device 9 of FIG. 1, the presence or absence of discharge is detected by detecting the primary current I1 flowing through the primary winding 71, not the potential difference between both ends of the primary winding 71. The difference is that feedback is provided.

The primary current I1 flowing through the primary winding 71 is converted into a voltage by the current sensor 114, divided by an attenuator circuit including resistors 103a and 104a, and input to the peak hold circuit.
The peak hold circuit records a voltage corresponding to the positive peak value of the primary current I1 flowing through the primary winding 71 and inputs the voltage to the A / D converter 201 built in the arithmetic device 200a.

On the other hand, the DC power supply voltage is attenuated by the resistors 105 and 106 and input to the A / D converter 201.
The arithmetic device 200a compares the predetermined value Iref of the current calculated from the DC power supply voltage V0 with the primary current I1 detected by the current sensor 114, and determines the presence or absence of discharge.
In addition, since the change of the primary current I1 due to the presence or absence of discharge is small according to the present inventors' earnest test, it is possible in principle, but compared with the case where the discharge determination is performed using the Q value as in the above embodiment. The discharge was found to be difficult.

With reference to FIG. 8, an ignition device 9b according to a third embodiment of the present invention will be described.
In the embodiment, the resonance frequency determined by the self-inductance L1 of the primary winding 71, the capacitance C4 of the resonance capacitor 6, the self-inductance L2 of the secondary winding 72, and the capacitance C3 of the parasitic capacitor of the spark plug 8. Although an example of generating LC resonance that resonates at ω0 has been shown, the ignition device 9b of the present embodiment is different in that the resonance capacitor 6 is not used.

Even with such a configuration, the first, first and second resonance frequencies ω 1, 1 determined by the self-inductance L 1 of the primary winding 71, the self-inductance L 2 of the secondary winding 72, and the parasitic capacitance C 3 of the spark plug 8 are matched. By opening and closing the second switching elements 2 and 3, LC resonance can be generated, and a secondary voltage V2 of high frequency AC high voltage can be applied to the spark plug 8 to generate corona discharge.
In this embodiment, the relationship between the resonance frequency ω1, the self-inductance L1 of the primary winding 71, the self-inductance L2 of the secondary winding 72, the turn ratio N2 / N1, and the parasitic capacitance C3 of the spark plug 8 is
ω1 = 1 / √ [{L1 · (N2 / N1) ² + L2} · C3]

In the above embodiment, as the spark plug 8, the center electrode discharge part 800 is covered with the dielectric discharge part 810, and the ground electrode discharge part 820 is opposed with a predetermined discharge space 83 therebetween. The ignition device 9 that performs the volume ignition of the air-fuel mixture in the combustion chamber CMB by generating the above has been described. In the ignition device 9, the high-frequency alternating current obtained by opening and closing the first and second switching elements 2 and 3 is obtained. If the frequency is sufficiently high, volume ignition by corona discharge can be achieved by using a general metal electrode plug for spark discharge without using the spark plug 8 in which the center electrode discharge portion 800 is covered with the dielectric 810. Can be generated.
By increasing the frequency, the polarity of the electrode is switched in a very short period of time, so that it is possible to generate corona discharge over a long period of time without shifting to arc discharge.
Further, when the frequency is increased, it is necessary to reduce the capacitance C4 and the self-inductances L1 and L2 of the resonance capacitor 6 so as to match the resonance frequency. However, since the parasitic capacitance C3 of the spark plug differs depending on the shape of the plug, Adjust as appropriate.

9 Ignition system 1 DC power supply (DC-DC converter)
2 1st switching element 21 1st switching element drive circuit 3 2nd switching element 31 2nd switching element drive circuit 4, 5 power supply voltage dividing capacitor 6 resonance capacitor 7 step-up transformer 71 primary winding 72 iron core 73 Secondary winding 8 Spark plug 80 Center electrode 800 Center electrode discharge part 81 Dielectric 810 Dielectric discharge part 82 Ground electrode (housing)
820 Ground electrode discharge part V1 Primary voltage V11 Primary winding upstream voltage V10 Primary winding downstream voltage V2 Secondary voltage L1, L2 Self-inductance C3 Parasitic capacitance C4 Resonant capacitor

Claims (6)

An ignition device comprising an ignition plug (8) provided in an internal combustion engine and a high-frequency power source for applying a high-frequency alternating current high voltage to the ignition plug (8),
The spark plug (8) includes a center electrode discharge part (800), a dielectric discharge part (810) covering the center electrode discharge part (800), and a grounding provided facing each other by providing a predetermined discharge space (83). An electrode discharge part (820),
The high-frequency power source is
Step-up transformer (7) including at least a DC power source (1), a first switching element (2), a second switching element (3), a primary winding (71), and a secondary winding (72). ), And
A resonant capacitor (6) having a boosting function is interposed between the DC power supply (1) and the primary winding (71),
The first switching element (2) and the second switching element (3) are alternately opened and closed to apply a boosted high-frequency AC primary voltage (V1) to the primary winding (71). the by you switch the direction of the current flowing through the primary winding (71) alternately to generate a secondary voltage of the high-frequency AC high-voltage (V2) to said secondary winding (72), said ignition plug (8 ) Igniting the air-fuel mixture introduced into the combustion chamber of the internal combustion engine by forming an alternating current corona discharge in the internal combustion engine (9, 9a, 9b) The ignition device (9, 9a) according to claim 1, wherein the resonant capacitor (6) boosts the voltage of the DC power supply (1) to the primary voltage by a resonance action with the primary winding (71). The ignition device (9, 9a, 9b) according to claim 1 or 2, further comprising Q value calculating means (202) for calculating a Q value obtained by a ratio between a power supply voltage (V0) and the primary voltage (V1 ). The ignition device (9) according to claim 3, further comprising discharge determination means (203) for detecting the presence or absence of discharge by comparing the Q value with a predetermined threshold value Qref. Duty determining means (204) for determining a duty ratio for opening and closing the first switching element (2) and the second switching element (3) based on the determination result of the discharge determining means (203). Ignition device (9) according to claim 4, comprising The ignition device according to claim 4 or 5, further comprising an ignition timing correction means (206) for correcting an ignition timing based on a determination result of the discharge determination means (203).

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