JP6773004B2 - Ignition system for internal combustion engine - Google Patents

Description

The present invention relates to an ignition device for an internal combustion engine that utilizes high frequency plasma discharge.

Exhaust gas recirculation system (EGR: Exhaust Gas Recirculation) that guides a part of lean fuel gas or exhaust gas to the intake side and re-intakes it as a method to improve the fuel efficiency of internal combustion engines such as automobile engines, and high compression ratio of the combustion chamber Etc. are used. However, steady ignition is an issue for both methods, and it is necessary to improve the ignitability. As a general ignition device for an internal combustion engine, a device that generates a high voltage by a DC power source composed of an ignition coil and an igniter and generates a dielectric breakdown discharge between the electrodes of a spark plug is used.

On the other hand, a plasma ignition device has been proposed as one of the internal combustion engine ignition devices that enhances ignitability. This plasma ignition device includes a spark plug, a DC power supply, an AC power supply, a mixing unit, and an ignition control unit. Then, ignition is performed by generating AC plasma between the center electrode and the ground electrode of the spark plug, and then the AC power supplied to the spark plug is reduced to improve the life of the spark plug.
(See, for example, Patent Document 1)

Further, a high frequency plasma ignition device has been proposed as one of the circuit configuration examples of the AC power supply. This is composed of a battery, a full bridge inverter, a transformer, a resonance circuit, a spark plug, and a high voltage circuit. By sharing the arms of the inverter circuit, the number of arms is less than twice the number of spark plugs. It was. (See, for example, Patent Document 2)

JP2012-112310A (pages 3 to 13, FIGS. 1 and 2) JP 2015-86702 (pages 2 to 10, FIG. 1)

However, in the plasma ignition device proposed in Patent Document 1, the high voltage transmission line output from the DC power supply and the high frequency AC voltage transmission line output from the AC power supply are combined into one transmission line. Collectively connected to the ignition plug. The AC power supply is separated from the high voltage output by the DC power supply at the ignition timing by the condenser of the mixing section. In the plasma ignition device configured in this way, insulation destruction in the combustion chamber occurs when the voltage between the electrodes of the spark plug reaches the discharge start voltage, and the voltage between the electrodes of the spark plug is the same for the capacitor in the mixing section. A voltage is applied. There is a problem that the electric charge charged in this capacitor causes dielectric breakdown and at the same time flows into the AC power supply as a discharge current.

On the other hand, in the high-frequency plasma ignition device proposed in Patent Document 2, the discharge current is rectified by the diode of the switching element of the inverter and regenerated into the battery. However, depending on the operating conditions of the internal combustion engine, there are conditions in which the fuel gas is easily ignited, and in order to suppress the power consumption by the ignition device at this time, the AC power supply is stopped and the ignition operation is performed only by the DC power supply. .. When the ignition operation by only the DC power supply continues, the discharge current flows into the AC power supply at each ignition and is stored as regenerative power. Although the regenerative power is stored, the AC power supply does not operate, so the regenerative power cannot be consumed and the potential inside the AC power supply rises. Therefore, it is necessary to configure the AC power supply with high withstand voltage circuit elements, and there is a limit to the miniaturization of the AC power supply.

The present invention has been made to solve the above-mentioned problems, and even if the ignition operation by only the DC power supply continues and the regenerated power due to the discharge current of the capacitor is accumulated, the applied voltage inside the AC power supply rises. It is an object of the present invention to provide an ignition device for an internal combustion engine capable of preventing the above.

The ignition device for an internal combustion engine according to the present invention applies a high DC voltage between a spark plug that ignites a combustible air-fuel mixture in a combustion chamber of the internal combustion engine and an electrode of the spark plug to generate a spark discharge between the electrodes. In an ignition device for an internal combustion engine having a power supply for discharge and a high-frequency AC power supply that applies a high-frequency voltage to the discharge path of the spark discharge to generate high-frequency plasma between the electrodes.
The high-frequency AC power supply includes a DC voltage source, an input inverter, a voltage detecting means for detecting the applied voltage of the input capacitor, and a plurality of switching elements, and the DC voltage output from the DC voltage source is an AC voltage. An inverter that converts to, a transformer that has a primary winding connected to the output end of the inverter, and a transformer that is connected to the secondary winding of the transformer and has at least one capacitor and reactor, and outputs from the inverter. A resonance circuit that resonates the generated AC voltage, a current detecting means that detects a current supplied from the high-frequency AC power supply to the ignition plug, and a control unit that controls on and off operations of the switching element constituting the inverter. And with
When the detection voltage of the input capacitor is higher than a preset threshold voltage, the control unit operates the inverter so as to consume the energy stored in the input capacitor as an energy consumption operation. It is a feature.

According to the ignition device for an internal combustion engine according to the present invention, even if the ignition operation by only the discharge power supply continues and the regenerated power due to the discharge current of the resonance capacitor is accumulated in the high frequency AC power supply, the applied voltage inside the high frequency AC power supply is used. It is possible to prevent the rise.

It is a figure which shows the circuit structure example of the ignition device for an internal combustion engine which concerns on Embodiment 1 of this invention. It is a figure which shows the ignition timing of the ignition device for an internal combustion engine which concerns on Embodiment 1 of this invention. It is a figure which shows the inverter operation of the high frequency AC power source of the ignition device for an internal combustion engine which concerns on Embodiment 1 of this invention. It is a figure which shows the characteristic of the resonance load of the ignition device for an internal combustion engine which concerns on Embodiment 1 of this invention. It is a figure which shows the timing chart of the energy consumption operation of the ignition device for an internal combustion engine which concerns on Embodiment 1 of this invention. It is a figure which shows the circuit structure example of the ignition device for an internal combustion engine which concerns on Embodiment 3 of this invention. It is a figure which shows the reignition operation of the ignition device for an internal combustion engine which concerns on Embodiment 3 of this invention.

Embodiment 1.
First, the configuration of the ignition device for an internal combustion engine according to the first embodiment of the present invention will be described. FIG. 1 is a diagram showing a circuit configuration example of an ignition device for an internal combustion engine according to a first embodiment of the present invention.

The internal combustion engine ignition device 1 includes a spark plug 10, a discharge power source 11, and a high-frequency AC power source 2.

The discharge power supply 11 applies a high DC voltage in order to carry out dielectric breakdown between the electrodes of the spark plug 10. A spark discharge can be generated between the electrodes by applying a high DC voltage between the electrodes of the spark plug. The spark plug 10 ignites a combustible mixture in the combustion chamber of the internal combustion engine.

The high-frequency AC power supply 2 applies a high-frequency voltage to the spark plug 10. High-frequency plasma can be generated between the electrodes by applying a high-frequency voltage to the discharge path of the spark discharge. The high-frequency AC power supply 2 includes a DC voltage source 3, an input capacitor 4, a voltage detecting means 8, an inverter 5, a transformer 6, a resonance circuit 7, and a current detecting means 9 for detecting the current output from the high-frequency AC power supply 2 to the ignition plug 10. , And a control unit 12. The DC voltage source 3 is composed of, for example, a battery mounted on a vehicle. The voltage detecting means 8 detects the applied voltage of the input capacitor 4.

The input capacitor 4 is provided between the DC voltage source 3 and the inverter 5 in the circuit configuration, and suppresses the ripple voltage from the DC voltage source 3.

The inverter 5 has a plurality of switching elements 51, 52, 53, 54, and converts the DC voltage output from the DC voltage source 3 into an AC voltage. In the present embodiment, the DC voltage is converted into an AC voltage via the input capacitor 4.

The inverter 5 is composed of a first leg composed of a series circuit of the switching elements 51 and 52 and a second leg composed of a series circuit of the switching elements 53 and 54. The drain ends of the switching elements 51 and 53 of the inverter 5 are connected to the positive ends of the DC voltage source 3 and the input capacitor 4. Further, the source ends of the switching elements 52 and 54 of the inverter 5 are connected to the negative ends of the DC voltage source 3 and the input capacitor 4. Further, each of the switching elements 51 to 54 has an antiparallel diode (body diode).

In the present embodiment, the circuit configuration of the inverter 5 will be described by taking a full bridge circuit as an example, but other configurations such as a half bridge circuit may be used. Further, although each switching element has a MOS (Metal Oxide Semiconductor) configuration having a built-in diode, for example, it may be another semiconductor element of an IGBT (Insulated Gate Bipolar Transistor).

The transformer 6 boosts the AC voltage output from the inverter 5. The transformer 6 has a primary winding 61 and a secondary winding 62. The primary winding 61 is connected to the output end of the inverter 5, and the secondary winding 62 is connected to the resonance circuit 7.

The turns ratio between the primary winding 61 and the secondary winding 62 of the transformer 6 is 1: n. In order to boost the voltage on the secondary winding 62 side of the transformer 6 to a high voltage, n is a real number larger than 1. As a result, the voltage generated between the secondary windings 62 of the transformer 6 is converted to n times the voltage generated between the primary windings 61 of the transformer 6. Therefore, the current flowing through the secondary winding 62 of the transformer 6 is converted to 1 / n times the current flowing through the primary winding 61 of the transformer 6.

The resonance circuit 7 is connected to the secondary winding 62 of the transformer 6 and has one resonance capacitor 72 and one resonance reactor 71. The resonance circuit 7 shapes the AC voltage output from the inverter 5 into a sine wave. As an example of the resonance circuit 7, a series LC circuit is used in this embodiment. Specifically, the secondary winding 62 of the transformer 6, the resonance reactor 71, and the resonance capacitor 72 are connected in series in order. .. Needless to say, the same ignition operation can be performed by applying another resonance circuit. Further, in the present embodiment, the resonance capacitor 72 and the resonance reactor 71 are provided one by one, but the configuration may be such that at least one is provided, and a plurality of resonance capacitors 72 may be provided.

The control unit 12 controls the on and off operations of the switching elements 51, 52, 53, 54 in the inverter 5. In this control, when the applied voltage of the input capacitor 4 is higher than the preset threshold voltage, the switching elements 51 and 52 of the inverter 5 are used so as to consume the energy stored in the input capacitor 4 as an energy consumption operation. , 53, 54 are made to operate.

Next, the basic operation of the ignition device 1 for an internal combustion engine according to the present embodiment will be described. FIG. 2 is a diagram showing a timing chart of high-frequency plasma ignition according to the first embodiment of the present invention.

FIG. 2 shows the states of the ignition timing signal, the inverter drive signal, the spark plug voltage, the spark plug current, and the input capacitor applied voltage, respectively. T1 to T3 in the figure each indicate a certain time.

At time T1 in FIG. 2, the internal combustion engine ignition device 1 is spark-plugged from the discharge power supply 11 in response to a fall of an ignition timing signal output from an engine control unit (hereinafter referred to as an ECU) (not shown). Start applying a negative voltage to 10.

The time T2 in FIG. 2 is the time when the voltage applied to the spark plug 10 reaches a certain voltage. At this time T2, the dielectric breakdown between the electrodes of the spark plug 10 is generated, and a spark discharge occurs. The voltage at which the spark plug 10 reaches dielectric breakdown varies depending on the distance between the electrodes of the spark plug 10 and the state of the combustion chamber, but it is necessary to apply several kV to several tens of kV.

After the ignition plug 10 is dielectrically broken down, the operation of the high frequency AC power supply 2 is started at time T3 in FIG. 2, and the DC voltage applied to the input capacitor 4 is output as the high frequency AC voltage by the inverter 5.

The high frequency AC voltage output from the inverter 5 is boosted by the transformer 6. The AC voltage boosted by the transformer 6 is shaped into a sine wave by the resonance circuit 7, and is applied to the ignition plug 10 as a high-frequency AC voltage of several MHz having a voltage value of several 100 V to several kV. Then, high-frequency plasma ignition is performed on the mixture of fuel and air in the combustion chamber of the internal combustion engine.

Next, the operation waveform of the inverter 5 when the high-frequency AC power supply 2 is performing the high-frequency plasma ignition operation will be described with reference to FIG. Here, the inverter 5 output voltage is positive when the potential at the connection point between the switching elements 51 and 52 on the first leg is higher than the potential at the connection point between the switching elements 53 and 54 on the second leg. The direction in which the inverter 5 output current flows from the connection point between the switching elements 51 and 52 of the first leg to the connection point between the switching elements 53 and 54 of the second leg via the primary winding 61 wire of the transformer 6 is positive.

FIG. 3A shows a waveform in which the output current of the inverter 5 has a lag phase with respect to the output voltage of the inverter 5. FIG. 3B shows a waveform in which the output current of the inverter is in phase with respect to the output voltage of the inverter 5. The condition that the output current of the inverter 5 has a lag phase with respect to the output voltage of the inverter 5 is that the combined reactance composed of the resonance circuit 7 and the spark plug 10 is inductive. However, when the electrodes of the spark plug 10 are dielectrically broken down to form a discharge path, the spark plug 10 is regarded as a resistance component, so that only the synthetic reluctance of the resonance circuit 7 needs to be considered.

FIG. 3A will be described in detail. The time Ta in FIG. 3A represents the timing at which the gate signals of the switching elements 51 and 54 rise. Further, the time Tb represents the timing at which the gate signals of the switching elements 52 and 53 rise.

At the time Ta when the gate signal of the switching elements 51 and 54 rises, a negative electrode current flows through the switching elements 51 and 54. This refers to a state in which the antiparallel diodes of the switching elements 51 and 54 are conducting, and the drain-source voltage of the switching elements 51 and 54 that turn on becomes zero. Therefore, zero voltage switching is established in the switching elements 51 and 54, and the switching loss at the time of turn-on can be reduced. The same can be said for the time Tb at which the switching elements 52 and 53 whose switching polarities are inverted turn on.

FIG. 3B will be described in detail. At the time Tc when the gate signal of the switching elements 51 and 54 rises, the switching elements 51 and 54 conduct and the inverter 5 outputs a positive current.

The polarity of the inverter output current is reversed at time Td. At this time, the switching elements 51 and 54 are conducting. Therefore, a current flows from the source of the switching elements 51 and 54 toward the drain.

At time Te, the switching elements 51 and 54 turn off. As a result, a current flows through the antiparallel diodes of the switching elements 51 and 54 and is regenerated by the input capacitor 4.

Next, at time Tf, the switching elements 52 and 53 are turned on. At this time, since the switching elements 52 and 53 are conducting in a state where no current is flowing, hard switching is performed.

Further, at the same time that the switching elements 52 and 53 are conductive, the antiparallel diodes of the switching elements 51 and 54 are recovered. Since both the switching elements 51 and 52 of the first leg are in a conductive state during the recovery period, a short circuit occurs in the first leg, and a large current momentarily flows through the first leg. In the switching elements 51 and 52, a loss due to this short-circuit current occurs and heat generation of the switching element increases. Therefore, it is necessary to change to a switching element having a characteristic that can withstand the short-circuit current and to strengthen the cooling capacity.

From the above, the inverter 5 is operated in a frequency domain in which the output current of the inverter 5 has a lag phase with respect to the output voltage of the inverter 5, that is, the resonant load circuit including the resonant circuit 7 and the ignition plug 10 has an inductive reactance. And.

Next, the relationship between the resonance point and the resonance gain of the resonance reactor 71 and the resonance capacitor 72 in the resonance circuit 7 will be described. FIG. 4 is a diagram showing the relationship between the resonance point and the resonance gain of the load including the resonance reactor 71 and the resonance capacitor 72.

The vertical axis of FIG. 4 indicates the gain, and the horizontal axis indicates the frequency. In the frequency region higher than the resonance point in FIG. 4, the resonance gain becomes smaller as the frequency is increased, and the output of the high-frequency AC power supply decreases. Further, in the frequency region lower than the resonance point, the resonance gain increases as the frequency is increased, and the output of the high-frequency AC power supply increases. That is, at a frequency higher than the resonance point, the combined reactance of the resonance circuit becomes inductive for the inverter 5, and at a frequency lower than the resonance point, it becomes capacitive.

In the inverter 5 of the present embodiment, as described above, in order to perform zero voltage switching when the switching elements 51 and 54 of the inverter 5 turn on, the output current is delayed with respect to the output voltage of the inverter 5. It is working. Therefore, in the present embodiment, the inverter 5 is operated in a frequency region in which the switching frequency of the switching element is higher than the resonance point, that is, in a frequency region in which the combined reactance of the resonance circuit 7 is inductive.

By adjusting the switching frequency of the inverter 5 and changing the resonance gain, the voltage applied to the spark plug 10 can be changed and the current flowing through the spark plug 10 can be controlled. Specifically, when the detected current detected by the current detecting means 9 is lower than the current required value of the spark plug 10, the frequency is adjusted to lower the switching frequency so as to approach the resonance point. If the detected current is higher than the current required value of the spark plug, adjustment is made to increase the switching frequency. By adjusting the switching frequency in this way, it is possible to control the current flowing through the spark plug 10.

The energy consumption operation of the internal combustion engine ignition device 1 according to the present embodiment will be described with reference to FIGS. 2 and 5.

The ignition device 1 for an internal combustion engine repeats the above-mentioned ignition operation at each ignition timing. In the ignition operation, when the electrodes of the spark plug 10 are dielectrically broken down by the discharge power supply 11, a voltage equal to the voltage between the electrodes of the spark plug 10 is applied to the resonance capacitor 72 constituting the resonance circuit 7. .. The energy stored in the resonance capacitor 72 is released as a discharge current vibrating at the resonance frequency created by the resonance reactor 71 and the resonance capacitor 72 at the same time as the dielectric breakdown between the electrodes of the ignition plug 10 shown at time T2 in FIG. ..

This discharge current flows into the inverter 5 via the transformer 6. At this time, the inverter 5 is not operating, is rectified by the antiparallel diodes of the switching elements 51 to 54, and is regenerated to the input capacitor 4. The applied voltage of the input capacitor 4 rises with the regenerative power consisting of this discharge current.

After that, the high-frequency plasma ignition operation starts at time T3, and the energy of the input capacitor 4 is consumed by the operation of the inverter 5, and the applied voltage of the input capacitor 4 decreases. In this way, when the applied voltage of the input capacitor is lower than the output voltage of the DC voltage source, it is charged by the DC voltage source and has the same potential.

When performing high-frequency plasma ignition, the above-mentioned series of operations is repeated, but depending on the operating state of the internal combustion engine, ignition may be performed only by spark ignition by the discharge power source 11. When the ignition operation is repeated only by the discharge power supply 11, the input capacitor 4 of the high-frequency AC power supply 2 is repeatedly charged with the regenerated power due to the discharge current of the resonance capacitor 72. At this time, since the high-frequency plasma ignition operation by the operation of the inverter 5 is not performed, the energy of the input capacitor 4 is not consumed and the applied voltage gradually increases. In order to allow this increase in the applied voltage, a circuit element having a high withstand voltage is required, and in that case, there is a limit to the miniaturization of the AC power supply.

Therefore, in the present embodiment, when the ignition operation of only the discharge power supply 11 described above is repeated, the following operation is performed in order to avoid an increase in the applied voltage of the input capacitor 4.

FIG. 5 is a diagram showing a timing chart of the energy consumption operation. The figure shows the operating states of the ignition timing signal, the inverter drive signal, the spark plug voltage, the spark plug current, and the input capacitor applied voltage.

As an operation method for avoiding an increase in the applied voltage of the input capacitor 4, in the present embodiment, the voltage detecting means 8 monitors the applied voltage of the input capacitor 4. Then, the magnitude is compared with the preset threshold voltage. In the present embodiment, the threshold voltage is equal to or higher than the output voltage of the DC voltage source 3 and lower than the rated voltage of the circuit element constituting the high-frequency AC power supply 2.

By comparison, when the voltage detecting means 8 detects the applied voltage of the input capacitor 4 which is equal to or higher than the threshold voltage, the control unit 12 finishes the dielectric breakdown between the electrodes of the spark plug 10 by the discharge power supply 11 and returns to the insulated state. , The operation signal is output to the inverter 5. The operation of the inverter 5 at this time is the same switching operation as when normal high-frequency plasma ignition is performed, and the energy stored in the input capacitor 4 with the loss generated from the circuit elements constituting the high-frequency AC power supply 2. To consume.

When the applied voltage of the input capacitor 4 drops due to the energy consumption operation of the inverter 5 described above, and the voltage drops until the next ignition timing signal is output or the detected voltage reaches the same potential as the DC voltage source 3, the inverter 5 Stops the energy consumption operation by.

Since the output voltage of the high-frequency AC power supply 2 is less than the breakdown voltage between the electrodes of the spark plug 10, the capacitance component between the electrodes of the spark plug 10 is regarded as a load. Therefore, two series of the capacitance components of the resonance capacitor 72 and the spark plug 10 become the combined capacitance, and this combined capacitance is smaller than the capacitance of the resonance capacitor 72. Therefore, the resonance point of the load circuit in the energy consumption operation is shifted to the high frequency side as compared with the resonance point of the load circuit in the high frequency plasma ignition operation.

Make the switching frequency during high-frequency plasma ignition operation and the switching frequency during energy consumption operation the same. In this case, depending on the configuration of the resonance circuit 7, it is conceivable that the switching frequency of the inverter 5 overlaps with the frequency region or the resonance point where the capacitance becomes capacitive during the energy consumption operation. However, since the output voltage of the high-frequency AC power supply 2 is sufficiently lower than the dielectric breakdown voltage of the spark plug 10, discharge is not performed.

If it is desired to avoid overlapping the frequency region where the switching frequency of the inverter 5 becomes capacitive or the resonance point during this energy consumption operation, the resonance point of the resonance load circuit when the ignition plug 10 is dielectric breakdown and ignition The resonance point of the resonance load circuit when the plug 10 is not dielectrically broken is confirmed in advance. Then, the switching frequency of the inverter 5 in the energy consumption operation may be operated so as to be higher than the resonance point composed of the resonance circuit and the stray capacitance component of the spark plug 10.

As described above, in the ignition device 1 for an inverter of the present embodiment, when the detection voltage of the input capacitor 4 becomes higher than the preset threshold voltage, the energy stored in the input capacitor 4 as an energy consumption operation. The inverter 5 is operated so as to consume the above.

Therefore, even if the ignition operation by only the discharge power source 11 is repeated, the regenerative energy stored in the input capacitor 4 can be appropriately consumed. As a result, it is possible to prevent an increase in the applied voltage of the high-frequency AC power supply 2.

Embodiment 2.
The second embodiment is different in that the energy consumption operation of the first embodiment is carried out even during the period when the electrodes of the spark plug 10 are subjected to dielectric breakdown. In the second embodiment, the parts different from the first embodiment of the present invention will be described, and the description of the same or corresponding parts will be omitted.

The energy consumption operation in the first embodiment is limited to being performed after the dielectric breakdown between the electrodes of the spark plug 10 is completed. This is because the high-frequency AC power supply 2 outputs a voltage higher than the voltage required for high-frequency plasma discharge. At this time, if the high-frequency AC power supply 2 operates while the electrodes of the spark plug 10 are dielectrically broken, high-frequency plasma discharge is performed and an unnecessary ignition operation occurs depending on the operating state of the internal combustion engine. This ignition operation leads to energy consumption of the battery serving as the DC voltage source 3 and mechanical stress on the internal combustion engine.

Therefore, in the second embodiment, the on-pulse time ratio of the switching elements 51 to 54 of the inverter 5 is reduced when the energy consumption operation is performed. By reducing the on-time of the switching elements 51 to 54, the excitation time of the transformer 6 is reduced, and the peak values of the output voltage and output current of the high-frequency AC power supply 2 are reduced.

By making the output voltage of the high-frequency AC power supply 2 less than the discharge maintenance voltage required for high-frequency plasma ignition in this operation, energy consumption operation without high-frequency plasma discharge even if the electrodes of the ignition plug 10 have dielectric breakdown. It can be performed.

Therefore, the above-mentioned energy operation removes the limitation of the time when the energy consumption operation is performed. As a result, after the voltage detecting means 8 detects a voltage in which the applied voltage of the input capacitor 4 is equal to or higher than the threshold voltage, the energy consumption operation can be immediately performed.

Therefore, in the second embodiment, as in the first embodiment, in addition to the effect that the regenerative energy stored in the input capacitor 4 can be appropriately consumed, the consumption operation can be immediately performed. Therefore, it is possible to prevent an increase in the applied voltage of the high-frequency AC power supply 2.

Embodiment 3.
FIG. 6 is a diagram showing an ignition device for an internal combustion engine according to the third embodiment of the present invention. In FIG. 6, those having the same reference numerals as those in FIG. 1 indicate the same or corresponding configurations as those in FIG. 1, and the description thereof will be omitted. The configuration in which the diode bridge circuit 13 is connected between the inverter 5 and the transformer 6 in the high-frequency AC power supply 2 is different from the first and second embodiments of the present invention.

In the third embodiment of the present invention, the parts different from the first and second embodiments of the present invention will be described, and the same or corresponding parts will be omitted. The configuration of the high-frequency AC power supply 2 of the internal combustion engine ignition device 1 according to the third embodiment will be described with reference to FIG.

The high-frequency AC power supply 2 transmits the current output from the DC voltage source 3, the input capacitor 4, the voltage detecting means 8, the inverter 5, the transformer 6, the resonance circuit 7, and the high-frequency AC power supply 2 to the ignition plug 10. It is composed of a current detecting means 9 for detecting and a control unit 12. Further, the present embodiment has a diode bridge circuit 13 between the inverter 5 and the transformer 6.

The diode bridge circuit 13 is composed of four diodes 131, 132, 133, and 134. The cathodes of the diodes 131 and 133 are connected to the drain ends of the switching elements 51 and 53 of the inverter 5, the DC voltage source 3 and the positive end of the input capacitor 4. Further, the anodes of the diodes 132 and 134 are connected to the source ends of the switching elements 52 and 54 of the inverter 5, the DC voltage source 3 and the negative end of the input capacitor 4.

The connection point between the anode of the diode 131 and the cathode of the diode 132 is connected to one end 61a of the transformer 6 primary winding. Further, the connection point between the anode of the diode 133 of the second leg and the cathode of the diode 134 is connected to the other end 61b of the transformer 6 primary winding. That is, the series circuit of the diode 131 and the diode 132 is the first leg, and the series circuit of the diode 133 and the diode 134 is the second leg.

A misfire during ignition operation will be described. The ignition device 1 for an internal combustion engine performs an ignition operation based on an ignition timing signal from the ECU. However, the sparks formed between the electrodes of the spark plug 10 may misfire due to factors such as the state of the combustion chamber and the wear of the electrodes of the spark plug 10.

When the spark misfires, the induced energy remaining in the ignition coil of the discharge power source 11 is supplied between the electrodes of the spark plug 10, and ignition by dielectric breakdown is performed again. This ignition operation is hereinafter referred to as reignition.

The reignition is performed in synchronization with the ignition timing signal transmitted from the ECU. Therefore, even if the high frequency AC power supply 2 is in operation, reignition is performed if a misfire occurs. Further, since reignition breaks the insulation between the electrodes of the spark plug 10, a discharge current is generated by the resonance capacitor 72 as in the case of dielectric breakdown due to the ignition timing signal.

Here, a case where reignition occurs during the operation of the high-frequency AC power supply 2 not provided with the diode bridge circuit 13 and the discharge current from the resonance capacitor 72 flows into the inverter 5 will be described.

For example, when the relationship between the switching phase of the inverter 5 and the phase of the discharge current becomes the leading phase as shown in FIG. 3B described above, the antiparallel diode of each switching element is used as described in the first embodiment. Recovery occurs and it is easy to short-circuit. The length of the recovery period tends to depend on the breaking current.

Since the discharge current output from the resonance capacitor 72 is double the number of turns of the transformer 6, the breaking current is longer than the recovery period that occurs during the high-frequency plasma ignition operation. If the short-circuit period is long, the transient heat generation due to the short-circuit current becomes excessive, and the heat-resistant temperature of the constituent elements of the high-frequency AC power supply 2 is exceeded, resulting in damage. Alternatively, the threshold value of the temperature sensor (not shown) is exceeded, and the operation of the high-frequency AC power supply 2 is frequently stopped.

FIG. 7 is a diagram showing a reignition operation of the ignition device 1 for an internal combustion engine. FIG. 7 shows the operating states of the ignition timing signal, the inverter drive signal, the spark plug voltage, and the spark plug current. Further, T1 to T5 in the figure indicate a certain time.

The operation in the case of the configuration having the diode bridge circuit 13 of the third embodiment in the state of reignition will be described.

When the diode bridge circuit 13 is connected between the inverter 5 and the transformer 6, the discharge current is diverted to the inverter 5 and the diode bridge circuit 13. As a result, the discharge current can be rectified regardless of the phase of the discharge current generated from the input capacitor 4 at the time of reignition. Therefore, it is possible to suppress the recovery loss and the recovery short-circuit period that occur in the antiparallel diodes of each switching element of the inverter 5.

Further, the rectified current of the diode bridge circuit 13 can be further increased by making the forward voltage characteristic of the diode used in the diode bridge circuit 13 lower than the forward voltage characteristic of the antiparallel diode of the inverter 5. ..

Further, the connection from the transformer 6 to the diode bridge circuit 13 is configured to be the shortest. As a result, it is possible to suppress an increase in the amount of current flowing through the antiparallel diode of the switching element of the inverter 5 due to an increase in impedance due to the wiring path.

With the above configuration, reignition is performed by the discharge power supply 11 while the high frequency AC power supply 2 is operating, and even if a discharge current of any phase flows into the inverter 5 from the resonance capacitor 72, the diode bridge circuit 13 rectifies the discharge current. be able to. Further, it is possible to reduce the recovery loss of the antiparallel diode of the switching element of the inverter 5 and suppress the transient heat generation due to the recovery short circuit.
Therefore, it is possible to effectively prevent an increase in the applied voltage of the high-frequency AC power supply 2.

In the present invention, each embodiment can be freely combined, and each embodiment can be appropriately modified or omitted within the scope of the invention.

1 Ignition device for internal combustion engine, 2 High frequency AC power supply, 3 DC voltage source, 4 input capacitor, 5 inverter, 51, 52, 53, 54 switching element, 6 transformer, 61 transformer primary winding, 62 transformer secondary Side winding, 7 resonance circuit, 71 resonance reactor, 72 resonance capacitor, 8 voltage detection means, 9 current detection means, 10 ignition plug, 11 discharge power supply, 12 control unit, 13 diode bridge circuit, 131, 132, 133 134 diode

Claims (5)

A spark plug that ignites a combustible mixture in the combustion chamber of an internal combustion engine,
A discharge power source that applies a high DC voltage between the electrodes of the spark plug to generate a spark discharge between the electrodes.
A high-frequency AC power supply that applies a high-frequency voltage to the discharge path of the spark discharge to generate high-frequency plasma between the electrodes.
In the ignition device for internal combustion engines
The high frequency AC power supply
DC voltage source and
With an input capacitor
A voltage detecting means for detecting the applied voltage of the input capacitor and
An inverter that has a plurality of switching elements and converts the DC voltage output from the DC voltage source into an AC voltage.
A transformer with a primary winding connected to the output end of the inverter,
A resonant circuit connected to the secondary winding of the transformer, having at least one capacitor and reactor, and resonating the AC voltage output from the inverter.
A control unit that controls the on and off operations of the switching elements that make up the inverter,
With
The control unit
Ignition operation is performed only with the discharge power supply.
Internal organs characterized in that the inverter is operated so as to consume the energy stored in the input capacitor as an energy consumption operation when the detection voltage of the input capacitor is higher than a preset threshold voltage. Ignition system for engines. The control unit is characterized in that, when performing the energy consumption operation, the switching element of the inverter is switched at a frequency higher than the resonance point composed of the resonance circuit and the stray capacitance of the spark plug. The ignition device for an internal combustion engine according to claim 1. The control unit switches the inverter so that the AC voltage output from the secondary winding of the transformer becomes less than the discharge maintenance voltage of the high-frequency plasma discharge of the spark plug when the energy consumption operation is performed. The ignition device for an internal combustion engine according to claim 1 or 2, wherein the on-pulse time ratio of the element is reduced. The ignition device for an internal combustion engine according to any one of claims 1 to 3, wherein the high-frequency AC power supply connects a diode bridge circuit between the inverter and the transformer. The ignition device for an internal combustion engine according to claim 4, wherein the diode bridge circuit has a forward voltage smaller than that of a diode provided in the switching element of the inverter.

Images