JP2016217269A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition device for an internal combustion engine capable of prolonging lifetime of an ignition plug while ensuring ignitability.SOLUTION: An ignition device 1 for an internal combustion engine includes an ignition plug 2 and an ignition circuit 3. The ignition circuit 3 includes a high frequency power supply part 31, a voltage booster circuit 32, and an output control part 34. The high frequency power supply part 31 alternately outputs pulse positive voltages and pulse negative voltages each having a fixed pulse width. The output control part 34 switches a state between a pulse output state in which the high frequency power supply part 31 outputs the pulse positive voltages and the pulse negative voltages, and a pulse halt state in which the high frequency power supply part 31 halts output of primary voltages. The switching between the pulse output state and the pulse halt state by the output control part 34 is performed in timing at which the pulse width of the pulse positive voltages and the pulse negative voltages immediately before and after the switching is kept equal to pulse widths of other pulse positive voltages and pulse negative voltages.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition device for an internal combustion engine.

  For example, an internal combustion engine such as an automobile gasoline engine is provided with an ignition device having an ignition plug for igniting fuel in a combustion chamber. As an ignition plug of such an ignition device, there is an ignition plug configured to generate a plasma discharge between the center electrode and a ground electrode by applying a high frequency voltage to the center electrode.

  The ignition system disclosed in Patent Document 1 includes a discharge power source that generates a spark discharge in a discharge gap in an ignition plug, and an AC power source that generates AC plasma in the discharge gap. In this ignition system, the AC plasma is generated during the duration of the spark discharge to improve the ignitability, while the AC plasma is intermittently supplied to suppress electrode consumption. In other words, by alternately providing a period during which high-frequency power is applied to the spark plug (high power period) and a period during which high-frequency power is stopped (low power period), the ignitability is suppressed while suppressing electrode consumption. Trying to secure.

JP2013-40582A

  However, Patent Document 1 does not disclose a configuration in which a booster circuit unit is provided between the high-frequency power source unit and the spark plug. In the configuration in which the primary voltage output from the high-frequency power supply unit is boosted by the boosting circuit unit and the high-voltage high-frequency secondary voltage is applied to the spark plug, the switching timing between the high power period and the low power period is not considered. Then, the secondary voltage waveform may be disturbed. If the secondary voltage waveform is disturbed, a sufficiently large secondary voltage cannot be applied to the spark plug, and the ignitability may be reduced.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an ignition device for an internal combustion engine that can achieve a long life of an ignition plug while ensuring ignitability.

One aspect of the present invention is an ignition plug configured to generate a plasma discharge between a center electrode and a ground electrode by applying a high-frequency voltage to the center electrode.
An ignition circuit for supplying high-frequency power to the spark plug;
The ignition circuit includes a high-frequency power supply unit that generates high-frequency power, a booster circuit unit that boosts a high-frequency primary voltage output from the high-frequency power supply unit and applies a secondary voltage to the ignition plug, and an output of the high-frequency power supply unit An output control unit for controlling
The high frequency power supply unit is configured to alternately output a pulse positive voltage and a pulse negative voltage having a constant pulse width as the primary voltage,
The output control unit includes a pulse output state in which the high frequency power supply unit alternately outputs the pulse positive voltage and the pulse negative voltage at a constant cycle, and a pulse pause in which the high frequency power supply unit pauses the output of the primary voltage. The state is configured to switch while the high-frequency power supply unit receives an ignition signal,
Switching between the pulse output state and the pulse pause state by the output control unit is such that the pulse width of the pulse positive voltage and the pulse negative voltage immediately before and immediately after switching is different from the other pulse positive voltage and pulse negative voltage. An ignition device for an internal combustion engine, characterized in that the ignition device is configured to perform at a timing such that the pulse width is maintained equal to the pulse width of the internal combustion engine.

  In the ignition device for an internal combustion engine, the output control unit is configured to switch between the pulse output state and the pulse pause state while the high frequency power supply unit receives an ignition signal. Therefore, even during reception of the ignition signal, a period in which no voltage is applied is provided between the center electrode of the spark plug and the ground electrode. Accordingly, it is possible to extend the life of the spark plug by suppressing the consumption of the center electrode and the ground electrode (hereinafter referred to as “electrode” as appropriate).

  The switching between the pulse output state and the pulse pause state by the output control unit is such that the pulse width of the pulse positive voltage and the pulse negative voltage immediately before and after the switching is equal to the pulse width of the other pulse positive voltage and pulse negative voltage. It is configured so as to be performed at such a timing as to be maintained. Thereby, in the pulse output state, the pulse width of the pulse positive voltage and the pulse negative voltage of the primary voltage can be prevented from being partially reduced. As a result, it is possible to prevent the voltage waveform of the secondary voltage generated by the booster circuit unit from being disturbed, to apply a sufficiently large secondary voltage to the spark plug, and to ensure ignitability.

  As described above, according to the present invention, it is possible to provide an ignition device for an internal combustion engine capable of extending the life of the spark plug while ensuring ignitability.

1 is a circuit diagram of an ignition device for an internal combustion engine in Embodiment 1. FIG. FIG. 3 is a diagram showing a pulse positive voltage, a pulse negative voltage, and a secondary voltage in the first embodiment. FIG. 3 is a diagram illustrating a high-side signal, a low-side signal, an output signal from an output control unit, a pulse positive voltage, a pulse negative voltage, and a secondary voltage in the first embodiment. FIG. 3 is a partial cross-sectional side view of the spark plug according to the first embodiment. The diagram which shows a pulse positive voltage, a pulse negative voltage, and a secondary voltage when not making an output control part function. FIG. 3 is a diagram illustrating a relationship between a frequency of a secondary voltage and a voltage gain in the first embodiment. FIG. 4 is a diagram showing a pulse positive voltage, a pulse negative voltage, and a secondary voltage when the pulse width W is less than T _0/4 . The high-side signal, low-side signal, output signal of the output controller, pulse positive voltage, pulse negative voltage, and secondary voltage when the pulse output state and pulse pause state are switched while the low-side signal is in the on state. The diagram which each shows. The circuit diagram of the ignition device for internal combustion engines in Embodiment 2. FIG. The circuit diagram of the signal generation part in Embodiment 2. FIG. FIG. 5 is a diagram illustrating a high-side signal, a low-side signal, an output signal of a control main body, and an output signal of an output control unit after correction by a synchronous sequential circuit in the second embodiment. The circuit diagram of the signal generation part in Embodiment 3. FIG. FIG. 9 is a diagram illustrating a high-side signal, a low-side signal, and an output signal of a control main body in Embodiment 3. The diagram which shows the secondary voltage in Embodiment 4. FIG. The diagram which shows the secondary voltage of the patterns 1-4 in Experimental example 1. FIG. The diagram which shows the test result in Experimental example 1. FIG. The diagram which shows the test result in Experimental example 2. FIG.

(Embodiment 1)
An embodiment of an ignition device for an internal combustion engine will be described with reference to FIGS.
As shown in FIG. 1, the ignition device for an internal combustion engine of the present embodiment includes a spark plug 2 and an ignition circuit 3 that supplies high-frequency power to the spark plug 2. The spark plug 2 is configured to generate a plasma discharge between the center electrode 21 and the ground electrode 22 by applying a high frequency voltage to the center electrode 21.

Ignition circuit 3, a high frequency power source 31 to produce a high-frequency power, a step-up circuit unit 32 to be applied to boosting the primary voltage of the high-frequency high-frequency power source 31 outputs the secondary voltage V ₂ to the ignition plug 2, the high frequency power source And an output control unit 34 that controls the output of the unit 31.

As shown in FIG. 2, the high-frequency power supply unit 31 is configured to alternately output a pulse positive voltage Vp and a pulse negative voltage Vn having a constant pulse width W as a primary voltage.
As shown in FIG. 3, the output control unit 34 includes a pulse output state A in which the high frequency power supply unit 31 alternately outputs a pulse positive voltage Vp and a pulse negative voltage Vn at a constant period, and the high frequency power supply unit 31 has a primary voltage. It is configured to switch the pulse pause state B in which the output is paused while the high frequency power supply unit 31 is receiving the ignition signal IGt. In addition, each rectangular wave in FIG. 2, FIG. 3 shows that an upper stage is ON and a lower stage is OFF, respectively. The same applies to the rectangular wave in the subsequent figures.

  The switching between the pulse output state A and the pulse pause state B by the output control unit 34 is performed in such a manner that the pulse widths of the pulse positive voltage Vp and the pulse negative voltage Vn immediately before and after the switching are the other pulse positive voltage Vp and pulse negative voltage Vn. The pulse width W is maintained at the same timing as the pulse width W.

  Specifically, the control shown in FIG. 3 described in detail later is switched from the pulse pause state B to the pulse output state A at the rising timing when the pulse positive voltage Vp is turned on from the off state. The switching from the pulse output state A to the pulse pause state B is also the timing at which the pulse positive voltage Vp is raised, that is, the rising timing of the high side signal SH described later. However, since the pulse pause state B is entered, the pulse positive voltage Vp does not actually rise at this timing. This is merely an example, and the pulse output state A and the pulse pause state B can be switched at other timings.

The switching timing between the pulse output state A and the pulse pause state B can be determined in accordance with at least one of the rotational speed of the internal combustion engine and the magnitude of the load. For example, when the rotational speed of the internal combustion engine is large or the load is large, the switching timing can be controlled so that the time ratio of the pulse output state A becomes large. Further, when the rotational speed is small or the load is small, the switching timing can be controlled so that the time ratio of the pulse output state A is small.
Further, for example, an appropriate time ratio of the pulse output state A may be mapped together with the rotational speed of the internal combustion engine and the magnitude of the load. In this case, the switching timing can be controlled by deriving the time ratio of the pulse output state A according to the rotation speed and the magnitude of the load based on the map.

For example, as shown in FIG. 4, the spark plug 2 includes a center electrode 21, an insulator 23 provided on the outer periphery side of the center electrode 21, and a ground electrode 22 provided on the outer periphery side of the insulator 23. Then, by applying a high frequency high voltage to the center electrode 21, streamer discharge is generated and propagated over the surface of the insulator 23, and discharge between the center electrode 21 and the ground electrode 22 is performed using this streamer discharge as a discharge path. An AC glow discharge or an arc discharge is generated in the part.
The ignition device 1 can be used by being mounted on a vehicle internal combustion engine such as an automobile engine.

As shown in FIG. 1, the high-frequency power supply unit 31 is configured to convert DC power supplied from the drive power supply 11 into AC high-frequency power by switching the switching elements 311 and 312 and output it. In the high frequency power supply unit 31, two resistors 315 connected in series with each other and two resistors connected in series with each other between a high potential wiring 313 connected to the driving power supply 11 and a grounded low potential wiring 314. A capacitor 316 and two switching elements 311 and 312 connected in series with each other are connected.
Between the two resistors 315 and between the two capacitors 316 is connected to the common potential 12.

  The two switching elements 311 and 312 are made of a semiconductor element such as a MOSFET (MOS field effect transistor) or an IGBT (insulated gate bipolar transistor). An output terminal 317 of the high frequency power supply unit 31 is provided between the two switching elements 311 and 312.

  With such a configuration, the high-frequency power supply unit 31 can oscillate high-frequency power evenly and output it from the output terminal 317 so that the boosting circuit unit 32 can efficiently perform boosting. Note that the resistance 315, the capacitor 316, and the switching elements 311 and 312 do not necessarily need to be two each, and the number of the resistors 315, the capacitors 316, and the switching elements 311 and 312 is particularly limited as long as they are symmetrically arranged on the high potential side and the low potential side. is not.

  The step-up circuit unit 32 includes a transformer including a primary coil 321 and a secondary coil 322 that are magnetically coupled to each other. For example, a very high voltage of 30 kVpp or more between peaks is applied to the spark plug 2, so that the boosting magnification of the booster circuit unit 32 is several tens of times. The primary coil 321 of the booster circuit unit 32 has one end connected to the output terminal 317 of the high frequency power supply unit 31 and the other end connected to the common potential 12. One end of the secondary coil 322 is connected to the center electrode 21 of the spark plug 2 and the other end is grounded.

  In addition, the high frequency power supply unit 31 includes a switching drive unit 331 that performs on / off control of the switching elements 311 and 312. That is, the switching drive unit 331 is configured to input a drive signal to the gates of the switching elements 311 and 312. The drive signal is formed as follows. The pulse signal generated in the oscillation unit 332 by inputting the ignition signal IGt is converted into the high side signal SH and the low side signal SL in the high side signal generation unit 333 and the low side signal generation unit 334, respectively. Then, a drive signal is formed by the logical product of the high-side signal SH and the low-side signal SL and the signal sent from the output control unit 34 and sent to the switching drive unit 331. The switching drive unit 331 drives the two switching elements 311 and 312 on and off based on this drive signal.

  That is, as shown in FIG. 3, when the high side signal SH is on and the output signal SA from the output control unit 34 is on, the high side switching element 311 connected to the high potential wiring 313 is on. The pulse positive voltage Vp is turned on. When the low-side signal is on and the output signal SA from the output control unit 34 is on, the low-side switching element 312 connected to the low potential wiring 314 is turned on and the pulse negative voltage Vn is turned on. .

The high-side signal SH and the low-side signal SL are alternately turned on at a constant frequency and a constant pulse width W as long as the ignition signal IGt is present. Accordingly, if the output control unit 33 is not provided, the high-side signal SH and the low-side signal SL having a constant frequency (a constant pulse width W) are alternately sent to the switching drive units 331 and 332 as shown in FIG. A positive pulse voltage Vp and a negative pulse voltage Vn having a constant frequency and a constant pulse width W are sent from the high frequency power supply unit 31 to the primary coil 321 of the booster circuit unit 32. Then, the secondary voltage V ₂ having a constant frequency is applied to the spark plug 2.

  However, the ignition device 1 includes the output control unit 34. When the output signal SA from the output control unit 34 is off, the switching drive unit 331 includes the output signal SA even if the high side signal SH or the low side signal SL is on. The on signal is not sent, and the switching elements 311 and 312 are turned off. That is, as shown in FIG. 3, during the pulse pause state B in which the output signal SA is off, even if the high side signal SH or the low side signal SL is on, both the pulse positive voltage Vp and the pulse negative voltage Vn are off. State is maintained.

  Then, the output control unit 34 performs the pulse output state A and the pulse pause state at different timings in the middle of the high-side signal SH being kept on and in the middle of the low-side signal SL being kept on. Switch to B. That is, the on / off switching timing of the output signal SA by the output control unit 34 is different between the state where the high side signal SH is kept on and the state where the low side signal SL is kept on. In the present embodiment, the switching timing is synchronized with the rising timing of the high side signal SH.

When the pulse width of the pulse positive voltage Vp and a pulse negative voltage Vn W, the resonance period of the load circuit 13 is a circuit from the output terminal 317 of the high frequency power source 31 to the ignition plug 2 and the T _0, T _0/2 ≧ W ≧ T _0/4 is satisfied. The length Ta and a length Tb of the pulse pause state B of the pulse output state A is an integral multiple of T _0/2. With T _0/2 ≧ W, the cycle of the primary voltage (i.e., the period of the pulse positive voltage Vp or pulsed negative voltage Vn), can be matched to the resonance cycle T _0. That is, since the frequency of the secondary voltage V ₂ can be matched with the frequency of the primary voltage, the frequency (period) of the primary voltage is matched with the resonance frequency f ₀ (resonance period T ₀ ) of the load circuit 13. The frequency of the secondary voltage V ₂ can be set to the resonance frequency f ₀ . As a result, as shown in FIG. 6, the gain of the secondary voltage V ₂ can be increased, and power can be efficiently supplied from the ignition circuit 3 to the spark plug 2. The horizontal axis in FIG. 6 indicates the frequency of the secondary voltage V ₂ in logarithm.

Further, with the W ≧ T _0/4, can be a sine wave of a frequency which combined waveform of the secondary voltage V ₂ to the resonance frequency f _0, to obtain a secondary voltage V ₂ of sufficiently high gain be able to. On the other hand, as shown in FIG. 7, when the pulse width W of the pulse positive voltage Vp and the pulse negative voltage Vn is less than 1/4 of the resonance frequency T ₀ , the output waveform of the secondary voltage V ₂ is made a normal sine wave. May become difficult, and the secondary voltage waveform may become a high-order abnormal waveform. As a result, it becomes difficult to sufficiently transmit the output energy of the high-frequency power supply unit 31 to the spark plug 2. The broken sine wave in FIG. 7 indicates a normal (ideal) secondary voltage waveform.

The pulse width W is within a range that does not exceed the T _0/2, it is preferable as close as possible to T _0/2. Thereby, the secondary voltage V ₂ having a high gain can be effectively generated. In consideration of the rise time tc and the fall time td of the pulse positive voltage Vp or the pulse negative voltage Vn, it is ideal that W = T ₀ / 2−tc−td.

Next, the effect of this embodiment is demonstrated.
In the ignition device 1 for the internal combustion engine, the output control unit 34 is configured to switch between the pulse output state A and the pulse pause state B while the high frequency power supply unit 31 receives the ignition signal IGt. . Therefore, even during reception of the ignition signal IGt, a period in which no voltage is applied is provided between the center electrode 21 and the ground electrode 22 of the spark plug 2. Thereby, consumption of the center electrode 21 and the ground electrode 22 can be suppressed, and the life of the spark plug 2 can be extended.

  The switching between the pulse output state A and the pulse pause state B by the output control unit 34 is performed by changing the pulse width W of the pulse positive voltage Vp and the pulse negative voltage Vn immediately before and after the switching to other pulse positive voltages Vp and pulses. The timing is such that it is maintained to be equal to the pulse width W of the negative voltage Vn. Thereby, in the pulse output state A, the pulse width W of the pulse positive voltage Vp and the pulse negative voltage Vn of the primary voltage can be prevented from being partially reduced.

That is, if the pulse width of the pulse positive voltage Vp or pulse negative voltage Vn immediately before or after switching is not maintained equal to the pulse width W of the other pulse positive voltage Vp and pulse negative voltage Vn, it is shown in FIG. As described above, the voltage waveform of the secondary voltage V ₂ is disturbed, and it becomes difficult to efficiently transmit the energy of the high-frequency power source 31 to the spark plug 2. For example, as shown in FIG. 8, when the pulse width of the pulse negative voltage Vn immediately after switching becomes shorter than other pulse widths W, the voltage waveform of the secondary voltage V ₂ induced in the secondary coil 322 is disturbed. possibility is (see V ₂₉ in the figure). Note that the state shown in FIG. 8 indicates that one of the rising timings of the output signal SA (that is, the switching timing from the pulse pause state B to the pulse output state A) is the timing during which the low-side signal SL is in the ON state. As a result, the pulse width W ₉ of the pulse negative voltage Vn is shorter than the other pulse widths W.

In contrast, in the ignition device 1 of the present embodiment, as shown in FIG. 3, the pulse widths of the pulse positive voltage Vp and the pulse negative voltage Vn immediately before and after switching are equal to other pulse widths W. I have to. That is, the switching between the pulse output state A and the pulse pause state B by the output control unit 34 is performed at a timing that does not affect the constant pulse width W of the primary voltage. As a result, the above-described disturbance is prevented from occurring in the voltage waveform of the secondary voltage V ₂ generated by the booster circuit section 32, and a sufficiently large secondary voltage V ₂ can be applied to the spark plug 2. And ignitability can be ensured.

The pulse from the pulse width W of the positive voltage Vp and pulse the negative voltage Vn and the resonance period T ₀ of the load circuit 13 satisfies _{T 0/2 ≧ W ≧ T} 0/4. Thereby, as described above, the secondary voltage V ₂ having a high gain can be obtained.
Further, the pulse width W in terms of adopting such conditions, a pulse output state A length Ta and a length Tb of the pulse pause state B, and an integral multiple of T _0/2. Thereby, the switching between the pulse output state A and the pulse pause state B by the output control unit 34 is performed so that the pulse widths of the pulse positive voltage Vp and the pulse negative voltage Vn immediately before and after the switching are changed to other pulse positive voltages Vp and pulses. It becomes easy to perform at the timing which is maintained to be equal to the pulse width W of the negative voltage Vn.

That, combined cycle of the primary voltage resonant period T _0, and when the pulse output state A of length Ta and pulse pause state B the length Tb and integral multiple of T _0/2, a pulse output state A and the pulse When there are a plurality of switching timings with the dormant state B, as shown in FIG. 3, all of them may be set at timings during which the high-side signal SH is not on or the low-side signal SL is on. It becomes easy.

  As described above, according to this embodiment, it is possible to provide an ignition device for an internal combustion engine capable of extending the life of the spark plug while ensuring ignitability.

(Embodiment 2)
As shown in FIGS. 9 to 11, the present embodiment is an embodiment of the ignition device 1 in which the output control unit 34 includes a synchronous sequential circuit 341.
In FIG. 9, the signal generation unit 30 that generates a drive signal input to the switching drive unit 331 is omitted in a dashed-dotted frame, and the configuration of the signal generation unit 30 is illustrated in FIG. 10. .

  In the present embodiment, the output control unit 34 includes a control main body 340 for switching between the pulse output state A and the pulse pause state B, and a synchronous sequential circuit 341 connected to the control main body 340. As shown in FIG. 11, the control main body 340 turns on the output signal SA0 for a predetermined period and turns it off for a predetermined period, whereby a drive signal of a logical product of the output signal SA0, the high side signal SH, and the low side signal SL is pulsed. In the rest state B, it is set to be off. However, if the on / off switching timing of the output signal SA0 of the control main body 340 is not accurately controlled, the switching timing between the pulse output state A and the pulse pause state B indicates that the high side signal SH or the low side signal SL is on. There is a risk of being on the way.

  Therefore, by providing a synchronous sequential circuit 341 in the output control unit 34, the switching timing of the output signal SA0 by the control body 340 is synchronized with the high side signal SH or the low side signal SL. That is, the output signal SA0 from the control main body 340 is corrected to the output signal SA1 by the synchronous sequential circuit 341.

For example, in the control shown in FIG. 11, the switching timing of the output signal SA1 from on to off and from off to on is synchronized with the rising timing of the high side signal SH (that is, the rising edge of the pulse signal of the oscillation unit 332). Yes. Therefore, in this case, the switching timing between the pulse output state A and the pulse pause state B is synchronized with the rising timing of the high side signal SH.
Others are the same as in the first embodiment. In addition, the same code | symbol as the code | symbol in Embodiment 1 shows the same component, etc., The previous description is referred.

  In the ignition device 1 of the present embodiment, the switching timing between the pulse output state A and the pulse pause state B is more accurately neither in the middle of the on state of the high side signal SH nor in the middle of the on state of the low side signal SL. Can be controlled to timing. As a result, the pulse widths of the pulse positive voltage Vp and the pulse negative voltage Vn immediately before and after switching can be more reliably maintained equal to the pulse width W of the other pulse positive voltage Vp and pulse negative voltage Vn. .

  In addition, as in the present embodiment, by using the synchronous sequential circuit 341, the control main body 340 can be configured by various logic circuits, or an MCU (Micro Control) that stores a control pattern set in advance for each engine condition. Unit) or the like. That is, when the control main body 340 having such a configuration is used, the switching timing between the pulse output state A and the pulse pause state B output by the control main body 340 is independent of the cycle of the pulse signal of the oscillation unit 332. It becomes. Therefore, by using the synchronous sequential circuit 341, the switching timing can be synchronized with the high-side signal SH or the low-side signal SL. As a result, the switching timing can be synchronized with the low-side signal even when the high-side signal SH is on. It is possible to make a timing that is not in the middle of the ON state of the signal SL.

In addition, the control shown in FIG. 11 synchronizes the switching timing between the pulse output state A and the pulse pause state B with the rising of the pulse positive voltage Vp (that is, the rising of the high side signal SH). It can be simplified. The switching timing is not limited to the rise of the pulse positive voltage Vp (that is, the rise of the high side signal SH), but the fall of the pulse positive voltage Vp or the rise or fall of the pulse negative voltage Vn (that is, the low side signal SL) The timing may be synchronized with the rise or fall).
In addition, the same effects as those of the first embodiment are obtained.

(Embodiment 3)
In this embodiment, as shown in FIGS. 12 and 13, the output signal SA of the output control unit 34 is regularly turned on and off repeatedly.
Specifically, the ON state and the OFF state of the output signal SA are respectively equal to two periods of the pulse signal of the oscillation unit 332 (that is, two periods of the high side signal SH or the low side signal SL). The output control unit 34 outputs.

  In the present embodiment, the output control unit 34 includes a synchronous frequency dividing circuit 342. The synchronous frequency dividing circuit 342 outputs the frequency of the pulse signal of the oscillating unit 332 with a fraction of an integer. That is, the synchronous frequency dividing circuit 342 outputs the pulse signal cycle of the oscillation unit 332 with an integral multiple. In this embodiment, the period of the pulse signal of the oscillation unit 332 is output by quadrupling. Along with this, the synchronous frequency dividing circuit 342 synchronizes the rise and fall of the output signal SA with the rise of the pulse signal of the oscillation unit 332 and the rise of the pulse positive voltage Vp.

As described above, the output control unit 34 includes the synchronous frequency dividing circuit 342, so that the pulse output state A and the pulse pause state B are alternately in two states of the pulse signal of the oscillation unit 332, respectively. Will be repeated. That is, in this embodiment, a Ta = Tb = 2T _0.

  At the start of discharge (that is, when the ignition signal IGt starts to be input), the output control unit 34 sets the timer 343 and the pause start signal generation unit 344 so that the pulse output state A continues for a predetermined time. Have. That is, the timer 343 performs control so that the first pulse pause state B appears after a predetermined time or more has elapsed from the start of the ignition signal IGt.

Note that when the above-described synchronous frequency dividing circuit 342 is used, it is preferable to provide a timer 343 and a pause start signal generation unit 344 or a circuit equivalent thereto, but without using such a circuit, A peripheral circuit 342 may be provided.
Others are the same as in the first embodiment.

In the present embodiment, the switching timing between the pulse output state A and the pulse pause state B is accurately determined with a relatively simple configuration even when the low side signal SL is in the on state even during the on state of the high side signal SH. It is possible to control at a timing that is not halfway.
Further, the ignition device 1 of the present embodiment is configured such that the first pulse pause state B appears when a predetermined time elapses from when the high-frequency power source 31 starts to receive the ignition signal IGt. ing. As a result, sufficient energy can be supplied to the spark plug 2 at the start of discharge, which requires a large amount of power.
In addition, the same effects as those of the first embodiment are obtained.

(Embodiment 4)
The present embodiment is a form of the ignition device 1 that defines the duration of the pulse output state A immediately after switching from the pulse pause state B.
In other words, the pulse output state A immediately after switching from the pulse pause state B is configured to continue at least until the secondary voltage V ₂ of the booster circuit unit 32 rises to the required voltage of the spark plug 2.

Immediately after switching from the pulse pause state B to the pulse output state A, as shown in FIG. 14, the magnitude (that is, amplitude) of the secondary voltage V ₂ may not be sufficiently large. That is, immediately after switching, the magnitude of the secondary voltage V ₂ gradually increases and may saturate after a predetermined time has elapsed to reach the maximum voltage Vmaxpp (peak-to-peak voltage). In such a case, it is preferable from the viewpoint of reliable ignition that the pulse output state A is maintained until a predetermined time t ₂ elapses from the time t ₀ when the pulse pause state B is switched to the pulse output state A. That is, it is preferable from the viewpoint of ignitability that the pulse output state A immediately after switching from the pulse pause state B is continued until the amplitude of the secondary voltage V ₂ of the booster circuit unit 32 becomes maximum.

As described above, when the magnitude of the secondary voltage V ₂ gradually increases from the time t _0, the magnitude of the secondary voltage V ₂ satisfies the required voltage Vrpp (peak-to-peak voltage) of the spark plug 2. In the absence of this, it is difficult to expect discharge. Therefore, if the pulse output state A is terminated before the secondary voltage V ₂ becomes equal to or higher than the required voltage Vrpp, the possibility that ignition of the spark plug 2 can be reduced. Therefore, the pulse output state A is continued at least until the magnitude of the secondary voltage V ₂ becomes equal to or higher than the required voltage Vrpp of the spark plug 2, that is, until at least the time t ₁ shown in FIG.

On the other hand, by setting the duration of the pulse output state A to t ₁ or more and less than t ₂ , it is possible to save energy by suppressing the output energy of the high frequency power supply unit 31. However, the time t1 varies depending on engine conditions such as engine speed and load, environment in the combustion chamber such as airflow and pressure (that is, in-cylinder environment), and the like. Therefore, in this case, it is necessary to perform precise mapping control based on these while measuring various conditions.

Thereby, in the pulse output state A, a sufficiently large secondary voltage V ₂ can be applied to the spark plug 2, and the ignitability of the spark plug 2 can be improved.
Others have the same configuration and effects as the first embodiment.

(Experimental example 1)
In this example, as shown in FIG. 15 and FIG. 16, the influence of the ignition device of Embodiment 1 on the extension of the life of the spark plug is indirectly evaluated by measuring the RMS value of the secondary current. is there.

That is, in the ignition device, how the RMS value of the secondary current is changed when the time ratio of the pulse output state A is variously changed is measured. Specifically, as shown in FIG. 15, an output pattern without the pulse pause state B (pattern 1), a pattern in which the time ratio of the pulse output state A is ½ of the whole (pattern 2), and the time of the pulse output state A The test was performed with a pattern having a ratio of 1/4 of the whole (pattern 3) and a pattern with a time ratio of the pulse output state A of 1/8 of the whole (pattern 4). Here, with respect to the patterns 2 to 4, the secondary voltage V ₂ shown in FIG. 15 is generated by applying the high-side signal SH and the low-side signal SL once every n periods of the pulse signal of the oscillation unit 332. did. That is, n = 1 in pattern 1, n = 2 in pattern 2, n = 4 in pattern 3, and n = 8 in pattern 4.

  In each test, the RMS value of the secondary current was measured. The result is shown in FIG. In FIG. 16, the horizontal axis is a value obtained by dividing the discharge time (time when the ignition signal IGt is on) by the output time (time when the voltage is applied to the spark plug 2), and the time of the pulse output state A described above. It corresponds to the reciprocal of the ratio. The vertical axis represents the ratio of the RMS value of the secondary current in each pattern to the RMS value of the secondary current in pattern 1 (hereinafter referred to as the current RMS value ratio). In FIG. 16, the plots marked with P1, P2, P3, and P4 show the measurement results in Pattern 1, Pattern 2, Pattern 3, and Pattern 4, respectively.

  As can be seen from the figure, the current RMS value ratio decreases as the discharge time / output time increases. That is, by reducing the time ratio of the pulse output state A, the energy given to the electrode can be reduced. Therefore, it can be seen that by providing the pulse pause state B, consumption of the electrodes can be suppressed.

(Experimental example 2)
In this example, as shown in FIG. 17, the ignitability of the spark plug by the ignition device of Embodiment 4 was evaluated.
First, the time Ta in the pulse output state A is set to 2T ₀ , the time Tb in the pulse pause state B is set to 6T ₀ , and an output pattern that repeats this alternately and regularly is a pattern 5. Further, the time Ta in the pulse output state A is T ₀ and the time Tb in the pulse pause state B is 3T ₀ , and an output pattern that repeats this alternately and regularly is a pattern 6. The pattern 5 and the pattern 6 are equivalent as output energy of the high frequency power supply unit 31. Note that the time Ta in the pattern 5 is sufficiently larger than the time t1 shown in the fourth embodiment, and the time Ta in the pattern 6 is smaller than the time t1.

The internal combustion engine was operated in the above two patterns. That is, when a voltage is applied to the spark plug 2 in each of the above patterns with respect to the fuel mixture introduced into the combustion chamber, it is confirmed whether there is a difference in combustion performance between the two patterns. did. The difference in combustion performance was made by measuring the lean limit A / F. That is, by gradually changing the air-fuel ratio (A / F) of the air-fuel mixture, the limit air-fuel ratio (that is, the lean limit A / F) that can be ignited is changed to the respective voltage application patterns, that is, pattern 5 and pattern 6. Compared. The result is shown in FIG. The conditions of the internal combustion engine in this test are 2000 cc displacement,
The engine speed is 1200 rpm, the indicated mean effective pressure is 300 kPa, and the compression ratio is 13.

As can be seen from FIG. 17, the lean limit A / F is 0.3 higher in the pattern 5 than in the pattern 6. That is, the output energy of the high-frequency power supply unit 31 is equivalent to the pattern 5 and the pattern 6, but it can be said that the pattern 5 is more excellent in ignitability. As described in the fourth embodiment, if the duration Ta of the pulse output state A is too short, the pulse output state A ends before the secondary voltage V ₂ becomes sufficiently large. It is considered that ignitability can be improved by sufficiently increasing the duration A of the state A.

  The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Ignition apparatus 2 Spark plug 21 Center electrode 22 Ground electrode 3 Ignition circuit 31 High frequency power supply part 32 Booster circuit part 34 Output control part

Claims (7)

A spark plug (2) configured to generate a plasma discharge between the center electrode (21) and the ground electrode (22) by applying a high-frequency voltage to the center electrode (21);
An ignition circuit (3) for supplying high-frequency power to the spark plug (2),
The ignition circuit (3) includes a high-frequency power supply unit (31) that generates high-frequency power, and a high-frequency primary voltage output from the high-frequency power supply unit (31) to boost a pulse negative voltage (V ₂ ) to the ignition plug ( 2) having a booster circuit section (32) to be applied to and an output control section (34) for controlling the output of the high frequency power supply section (31),
The high frequency power supply unit (31) is configured to alternately output a pulse positive voltage (Vp) and a pulse negative voltage (Vn) having a constant pulse width (W) as the primary voltage,
The output control unit (34) includes a pulse output state (A) in which the high-frequency power source unit (31) alternately outputs the pulse positive voltage (Vp) and the pulse negative voltage (Vn) at a constant cycle; The high frequency power supply unit (31) is configured to switch between a pulse pause state (B) in which the output of the primary voltage is stopped while the high frequency power supply unit (31) is receiving an ignition signal (IGt). And
Switching between the pulse output state (A) and the pulse pause state (B) by the output control unit (34) is performed by switching the pulse positive voltage (Vp) and the pulse negative voltage (Vn) immediately before and after the switching. An internal combustion engine configured to perform at a timing such that the pulse width is maintained equal to the pulse width (W) of the other pulse positive voltage (Vp) and the pulse negative voltage (Vn). Ignition device (1). The pulse width of the pulse positive voltage (Vp) and the pulse negative voltage (Vn) is W, and a load circuit (13) which is a circuit from the output terminal (317) of the high frequency power supply unit (31) to the spark plug (2). when the resonance period of) was _{T 0, T 0/2 ≧} W ≧ T 0/4 was filled, the length of the pulse output state (a) (Ta) and the length of the pulse pause state (B) ( Tb), the ignition apparatus for an internal combustion engine as claimed in claim 1, characterized in that an integral multiple of T _0/2, respectively (1).   The switching timing between the pulse output state (A) and the pulse pause state (B) is synchronized with the rise or fall of the pulse positive voltage (Vp) or the rise or fall of the pulse negative voltage (Vn). The ignition device (1) for an internal combustion engine according to claim 1 or 2, characterized in that it is timing. In the pulse output state (A) immediately after switching from the pulse pause state (B), at least the pulse negative voltage (V ₂ ) of the booster circuit portion (32) is the required voltage (Vrpp) of the spark plug (2). The ignition device (1) for an internal combustion engine according to any one of claims 1 to 3, wherein the ignition device (1) is continued until it rises above. The pulse output state (A) immediately after switching from the pulse pause state (B) continues at least until the amplitude of the pulse negative voltage (V ₂ ) of the booster circuit section (32) becomes maximum. An ignition device (1) for an internal combustion engine according to any one of claims 1 to 3.   The switching timing between the pulse output state (A) and the pulse pause state (B) is determined according to at least one of the rotational speed of the internal combustion engine and the magnitude of the load. Ignition device (1) for an internal combustion engine according to any one of the preceding claims.   The first high-frequency power supply unit (31) starts to receive the ignition signal (IGt), and is configured such that the first pulse pause state (B) appears when a predetermined time set in advance has elapsed. The ignition device (1) for an internal combustion engine according to any one of claims 1 to 6, characterized in that

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