JP2016094859A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform secure ignition by an ignition device which supplies AC power for an electric spark of a dielectric breakdown discharge by protecting a high-frequency AC power source even when a discharge current is discharged from a resonance capacitor of an impedance matching circuit.SOLUTION: A first AC power source which supplies an AC current to a first ignition plug is connected to a primary-side first winding of a transformer which supplies high-frequency AC power, and a first impedance matching circuit which performs impedance matching between a first discharge power source supplying a current for discharge to the first ignition plug and the first AC power source is connected to a secondary-side second winding of the transformer. A third winding is provided on the primary side of the transformer, discharge energy consumption means of consuming energy discharged from the first impedance matching circuit is connected to the third winding, and in an ignition operation by the first power source for discharge, energy discharged from a resonance capacitor of the first impedance matching circuit is consumed by the discharge energy consumption means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition device for an internal combustion engine provided with a spark plug.

  As a technique for improving the fuel consumption of an internal combustion engine, a recirculation system (EGR: Exhaust Gas Recirculation) that introduces a portion of lean fuel gas or exhaust gas to the intake side and re-intakes air, and realization of a high compression ratio are being promoted In both cases, steady ignition is an issue, and it is necessary to improve ignitability.

  As one proposal for improving ignitability in an ignition device for an internal combustion engine, there is an RF (Radio Frequency) ignition device disclosed in Patent Document 1. In a general internal combustion engine ignition device, a high voltage is generated by a discharge power source composed of an ignition coil and an igniter, and a dielectric breakdown discharge is generated between the electrodes of the ignition plug. The ignition device is an AC power supply in addition to the discharge power supply, and immediately after the dielectric breakdown discharge ignition by the discharge power supply, a high-frequency voltage is supplied between the electrodes of the spark plug to continue the high-temperature and high-pressure RF plasma. Thus, it is configured to improve the ignitability to the fuel gas.

Japanese Patent No. 5320474

  In the RF ignition device proposed in Patent Document 1, a high-voltage transmission path output from a discharge power supply and an AC current transmission path output from an AC power supply are combined into one transmission path into an ignition plug. An impedance matching circuit is provided between the transmission line and the AC power source integrated into this one, and the output impedance on the AC power source side and the input impedance on the spark plug side are configured to match, Attenuation of AC power supplied to the spark plug is prevented.

However, in the dielectric breakdown discharge at the time of ignition, a high voltage is applied between the electrodes of the spark plug, the same voltage is also applied to the resonance capacitor in the impedance matching circuit, and the discharge current from this resonance capacitor flows into the AC power supply side. It will be. On the other hand, in order to apply a high voltage between the electrodes of the spark plug during high-frequency ignition operation, a transformer for boosting and insulation is used between the impedance matching circuit and the AC power supply. The discharge current from the capacitor is multiplied by the turns ratio in the transformer, and a large current flows into the switching circuit of the AC power supply. In general, a switching circuit of an AC power supply uses a semiconductor switching element for the purpose of high-frequency driving, and does not include a rectifying element suitable for rectifying a current flowing during dielectric breakdown discharge. Therefore, there is a possibility that the semiconductor switch element is destroyed and the AC power supply fails.
In addition, in the case of a multi-cylinder configuration, it is necessary to provide two power sources, a discharge power source and an AC power source, with respect to a spark plug provided in each of the cylinders. .

  The present invention has been made to solve the above-described problems, and protects the AC power source even when discharge current is discharged from the resonant capacitor of the impedance matching circuit during dielectric breakdown discharge, thereby performing reliable ignition. An object of the present invention is to provide an ignition device for an internal combustion engine.

  An ignition device for an internal combustion engine according to the present invention is the ignition device for an internal combustion engine having a discharge power source for dielectric breakdown discharge, an AC power source, and an ignition plug, and the first ignition plug is connected to the first winding on the primary side of the transformer. A first alternating current power source for supplying an alternating current to the second winding of the transformer is connected to the first winding for supplying a discharging current to the first spark plug; A first impedance matching circuit for impedance matching with one AC power source is connected, a third winding is provided on the primary side of the transformer, and the third winding is discharged from the first impedance matching circuit. Discharge energy consuming means for consuming the generated energy is connected, and from the resonance capacitor of the first impedance matching circuit during the ignition operation by the first discharge power source It is intended to consume the electric energy by the discharge energy consumption means.

  In the internal combustion engine ignition device according to the present invention, the discharge energy consuming means connected to the third winding of the transformer is a second AC power source for supplying an AC current to the second ignition plug, The energy discharged from the first impedance matching circuit is divided and consumed by the first AC power source and the second AC power source.

In the internal combustion engine ignition device according to the present invention, the discharge energy consuming means is connected to the third winding of the transformer to discharge the energy discharged from the resonance capacitor of the impedance matching circuit during the ignition operation by the discharge power source. When consumed by the energy consuming means, it is possible to prevent an excessive current from flowing through the AC power supply and protect the semiconductor switch element of the AC power supply.
In addition, an internal combustion engine ignition device having a simple configuration can be provided by using an AC power supply for supplying an AC current to another spark plug as the discharge energy consuming means connected to the third winding.

1 is a block diagram of a configuration related to an internal combustion engine ignition device according to Embodiment 1 of the present invention. FIG. It is a figure which shows the circuit structural example which concerns on the internal combustion engine ignition device of Embodiment 1 of this invention. It is a figure which shows the example of a circuit structure based on the internal combustion engine ignition device of Embodiment 3 of this invention. It is a figure which shows the ignition timing which concerns on the internal combustion engine ignition device of Embodiment 3 of this invention. It is a block diagram of the structure which concerns on the internal combustion engine ignition device of Embodiment 4 of this invention. It is a block diagram of the structure which concerns on the internal combustion engine ignition device of Embodiment 5 of this invention.

  Hereinafter, an ignition device for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings will be denoted by the same reference numerals.

Embodiment 1 FIG.
Embodiment 1 is an internal combustion engine ignition device having an ignition plug, a dielectric breakdown discharge power source, and a high-frequency AC power source. The high-frequency AC power source is connected between the DC power source and the first winding on the temporary side of the transformer. A breakdown circuit including a switching circuit for performing DC / AC power conversion, an impedance matching circuit for resonating the AC voltage and AC current of the second winding of the transformer, and a switch for switching the connection of the third winding of the transformer. In the ignition operation by the power source for an internal combustion engine, the ignition device for the internal combustion engine is configured such that the capacitive discharge current flowing from the impedance matching circuit flows through the bypass circuit of the third winding of the transformer by turning on the switch.

  FIG. 1 is a block diagram of a configuration showing Embodiment 1 according to the present invention. The spark plug 6 is configured to be supplied with a current generated by dielectric breakdown from the power supply for dielectric breakdown discharge 7 and a high-frequency AC current from the high-frequency AC power supply 2, and impedance matching of the transmission path of these currents is taken. For this purpose, an impedance matching circuit 5 is provided. The impedance matching circuit 5 is connected to a high-frequency AC power source 2 that generates a high-frequency AC voltage via the transformer 3 and a bypass circuit 4 that switches open and short of the third winding of the transformer 3. The high frequency AC power supply 2 is connected to the DC power supply 1. The output control of the dielectric breakdown discharge power supply 7, the output control of the high-frequency AC power supply 2, and the switch control of the bypass circuit 4 are controlled by control signals from the control device 8.

FIG. 2 shows a circuit configuration example of the high-frequency AC power source 2, the transformer 3, the bypass circuit 4, and the impedance matching circuit 5.
A high frequency AC power supply 2 is connected between the DC power supply 1 and the first winding on the primary side of the transformer 3. As an example of the configuration of the switching circuit of the high-frequency AC power supply 2, a full bridge circuit is used. In the case of a vehicle engine ignition device, a lead battery is used as the DC power source 1 and a voltage of several kV is applied between the plugs. Therefore, the transformer 3 has a high turn ratio with a high step-up ratio. In order to reduce the step-up ratio of the transformer 3, there is a configuration in which a circuit having a step-up function in the high-frequency AC power source 2, that is, a step-up chopper circuit is inserted between the DC power source 1 and the full bridge circuit. An impedance matching circuit 5 is connected between the second winding on the secondary side of the transformer 3 and the spark plug 6, and a series LC resonance circuit is used as an example of the resonance circuit. It goes without saying that the same ignition operation can be performed even if another resonance circuit is applied.

In FIG. 2, the third winding on the primary side of the transformer 3 is connected to the bypass circuit 4, and as a circuit configuration, only a switch that opens or shorts the third winding is shown.
Since the switching circuit of the high-frequency AC power supply 2 requires high-frequency driving, a MOSFET is used as a semiconductor switch. However, the switch of the bypass circuit 4 is a semiconductor switching element such as an IGBT or MOSFET in order to match the ignition frequency of a low frequency. Is used.

Next, the operation of the internal combustion engine ignition device will be described. As a rough function of the ignition device for an internal combustion engine, a voltage of several tens of kV is applied between the electrodes of the spark plug 6 from the dielectric breakdown discharge power source 7 to cause a dielectric breakdown discharge of the plug. Thereafter, a voltage of several kV is applied between the electrodes of the spark plug 6 at a high frequency of several MHz from the high-frequency AC power source 2, and RF plasma is continuously generated.
Hereinafter, detailed operations including the operation of the bypass circuit 4 will be described.

  A voltage of several tens of kV is applied between the electrodes of the spark plug 6 from the power supply 7 for dielectric breakdown discharge, and a dielectric breakdown discharge is generated between the electrodes of the spark plug 6. At that time, the same voltage as the voltage between the electrodes of the spark plug 6 is applied to the resonance capacitor of the impedance matching circuit 5. The energy charged in the resonance capacitor is discharged as a voltage and a current that vibrate at the resonance frequency of the resonance reactor and the resonance capacitor. This discharge current is passed through the transformer 3 to the high-frequency AC power supply 2. In order to avoid this discharge current from flowing to the high-frequency AC power source 2, a third winding is provided on the primary side of the transformer 3, and the bypass circuit 4 is connected to the third winding.

Here, the semiconductor switch of the bypass circuit 4 is turned on before the start of the dielectric breakdown discharge, and the third winding is short-circuited. As a result, the discharge current is divided into the high-frequency AC power supply 2 and the bypass circuit 4, and a dominant current flows through the bypass circuit 4 having a small impedance.
Then, after the resonance of the discharge current is sufficiently attenuated, the semiconductor switch of the bypass circuit 4 is turned off, and the high-frequency ignition operation is started from the high-frequency AC power supply 2. Thereby, the high frequency ignition operation can be performed without being affected by the third winding on the primary side of the transformer 3. Although the semiconductor switch of the bypass circuit 4 can perform a high-frequency ignition operation even if the semiconductor switch is kept on even during the high-frequency ignition operation, a high-frequency current flows through the bypass circuit 4 and a loss occurs. Sometimes it is preferred to turn it off.
As a measure to rectify the discharge current without preparing the third winding of the transformer 3 and the bypass circuit 4, the semiconductor elements of the switching circuit of the high-frequency AC power supply 2 are connected in parallel to reduce the amount of current per semiconductor element. It is possible to do. However, the number of semiconductor elements increases and the apparatus becomes large.

  As described above, in the ignition device for an internal combustion engine of the first embodiment, the bypass circuit 4 functions as a discharge energy consuming means for consuming energy from the impedance matching circuit 5, and has the above-described configuration. As a result, the discharge current during the dielectric breakdown discharge does not flow to the high-frequency AC power supply 2, and an excessive current can be prevented from flowing to the semiconductor switch used for the high-frequency AC power supply.

Embodiment 2. FIG.
The ignition device for an internal combustion engine according to the second embodiment minimizes the turn ratio of the third winding provided on the primary side of the transformer 3 according to the first embodiment.
The effects of the internal combustion engine ignition device of the second embodiment will be described below.
The turns ratio of the primary side first winding and the secondary side second winding of the transformer 3 in the first embodiment is determined by the step-up ratio of the voltage to be applied from the high-frequency AC power supply 2 to the spark plug 6. There is no particular limitation on the turn ratio of the first winding, the second winding, and the third winding.
In the second embodiment, assuming that the number of turns of the third winding on the primary side of the transformer 3 is 1, which is the minimum, the voltage applied to the third winding at the time of insulated discharge ignition and high-frequency AC ignition can be reduced. The voltage applied to the switch of the bypass circuit 4 is equal to the voltage applied to the third winding of the transformer 3, and the required breakdown voltage of the switch can be reduced by reducing the voltage applied to the third winding. Since many low-breakdown-voltage semiconductor elements have low on-resistance, it is possible to reduce conduction loss that occurs when rectifying the discharge current during dielectric breakdown discharge.

Embodiment 3 FIG.
In the first and second embodiments, the bypass circuit 4 connected to the third winding of the transformer 3 has only a switch. However, in the bypass circuit 4 of the internal combustion engine ignition device of the second embodiment, Although a configuration is provided in which a resistor is provided in series with the switch, another embodiment will be described in which the bypass circuit 4 is configured differently and functions as discharge energy consuming means for consuming energy from the impedance matching circuit 5.
FIG. 3 shows the configuration of the internal combustion engine ignition device of the third embodiment. The difference from the first embodiment is that the configuration of the bypass circuit 4 is a serial connection configuration of a switch and a resistor. It is. The effect of inserting this resistor will be described with reference to FIG. 4 showing the operation timing of each power source.

  The ignition frequency is defined by the rotation speed [rpm], and the rotation speed [rpm] / 60 is the ignition frequency [Hz]. At the time of breakdown discharge ignition, the same high voltage is applied to the resonance capacitor of the impedance matching circuit 5 and the power supply for breakdown discharge is turned off as shown in FIG. In this way, the charging energy is discharged while oscillating at a resonance frequency determined by the capacity of the resonance reactor and the resonance capacitor. This discharge current flows into the bypass circuit 4 and the high-frequency AC power supply 2, and after the resonance of the discharge current is sufficiently attenuated, a high-frequency ignition operation is performed at a timing as shown in FIG. The high-frequency ignition operation period is operated on the order of 0.1 ms to 1.0 ms. Thereafter, neither the dielectric breakdown discharge power source 7 nor the high-frequency AC power source 2 operates during the period until the next breakdown discharge ignition, and this is repeated at the ignition frequency. Here, as in the first embodiment, the semiconductor switch of the bypass circuit 4 is turned on before the start of the dielectric breakdown discharge and the third winding is short-circuited as shown in FIG. Is divided into the high-frequency AC power supply 2 and the bypass circuit 4, and after the resonance of the discharge current is sufficiently attenuated, it is turned off and the high-frequency ignition operation is started from the high-frequency AC power supply 2. Thereby, the high frequency ignition operation can be performed without being affected by the third winding on the primary side of the transformer 3.

  However, if the period from the dielectric breakdown discharge ignition to the high frequency ignition is too long, the spark generated during the dielectric breakdown discharge ignition disappears, the spark is not amplified by the high frequency ignition operation, and a problem arises in ignitability. Therefore, it is necessary to perform a high-frequency ignition operation before the spark generated by the dielectric breakdown discharge misfires, and it is preferable that the time from the dielectric breakdown discharge ignition to the introduction of the high-frequency ignition is short. In order to shorten the time until charging, the bypass circuit 4 has a configuration in which a resistor is provided in series with the switch. By inserting a resistor, the impedance of the bypass circuit 4 increases, the shunt ratio between the high-frequency AC power supply 2 and the bypass circuit 4 changes, the amount of current flowing through the bypass circuit 4 decreases, and the discharge current decays early. , High-frequency AC ignition can be accelerated. Thereby, stable ignition operation can be performed without misfiring.

Embodiment 4 FIG.
The ignition device for an internal combustion engine of the fourth embodiment has a multi-output configuration of the second winding on the secondary side of the transformer 3 of the first embodiment, and the impedance matching circuit 5 is connected in parallel, thereby The internal combustion engine ignition device is associated with one high-frequency AC power source 2 and a transformer 3. Hereinafter, the configuration of the internal combustion engine ignition device according to the fourth embodiment will be described with reference to FIG.

A high-frequency AC power source 2 is connected between the DC power source 1 and the first winding of the transformer 3, and outputs corresponding to the number of the plurality of spark plugs 6 are prepared for the second winding of the transformer 3. Are connected to the impedance matching circuit 5 prepared according to the above. Each impedance matching circuit 5 is connected to a spark plug 6 and a dielectric discharge power source 7. The third winding on the primary side of the transformer 3 is connected to a bypass circuit 4 that switches between opening and short-circuiting the third winding of the transformer 3.
In the case of this configuration, it is possible to cope with a plurality of cylinders without changing the number of high-frequency AC power supplies 2 and transformers 3. That is, since the high-frequency AC power supply 2 and the transformer 3 can be shared, the apparatus can be miniaturized.

  Further, the ignition timing of the internal combustion engine ignition device including the plurality of ignition plugs 6 is ignited at a timing having an equal phase difference. For example, when the number of the spark plugs 6 is four, the ignition operation is sequentially performed with a phase difference of 360 degrees / 4 = 90 degrees. Therefore, the operation of the bypass circuit 4 is the same as that of the first embodiment without causing the third winding of the transformer 3 to be multi-outputted by operating every 90 degrees in accordance with the ignition operation of the four spark plugs 6. An effect can be obtained.

Embodiment 5 FIG.
In the internal combustion engine ignition device of the fifth embodiment, the multi-output winding of the transformer 3 of the fourth embodiment is also applied to the first winding, and the third winding of the transformer 3 and the bypass circuit 4 are omitted. It is what. That is, the form of the discharge energy consumption means is changed. Hereinafter, the configuration of the internal combustion engine ignition device according to the fifth embodiment will be described with reference to FIG.
A high-frequency AC power source 2 corresponding to the number of spark plugs is connected in parallel to the first winding on the primary side of the DC power source 1 and the multi-output transformer 3, and the second winding of the transformer 3 is connected to the number of spark plugs. Depending on the number of outputs, the impedance matching circuit 5 corresponding to the number of spark plugs is connected to each output. Each impedance matching circuit 5 is connected to a spark plug 6 and a dielectric breakdown discharge power source 7.

With the above configuration, since the discharge current from the impedance matching circuit 5 is shunted to each of the high-frequency AC power supplies 2 connected in parallel, the amount of discharge current flowing per unit is reduced. The bypass function constituted by the third winding of the transformer 3 and the bypass circuit 4 that has been used can be eliminated.
FIG. 6 shows an example in which the same number of high-frequency AC power supplies 2 and impedance matching circuits 5 are prepared and connected in accordance with the number of spark plugs 6. It is not an absolute condition that the number is the same as the number, and any number of units can be used.

1 DC power supply, 2 high frequency AC power supply, 3 transformer, 4 bypass circuit, 5 impedance matching circuit, 6 spark plug, 7 power supply for dielectric breakdown discharge, 8 control device

Claims (6)

  A first AC power source for supplying an AC current to the first spark plug is connected to the first winding on the primary side of the transformer, and the first spark plug is connected to the second winding on the secondary side of the transformer. A first impedance matching circuit for performing impedance matching between the first discharge power source for supplying a discharge current to the first AC power source and a first winding of the transformer is provided on the primary side of the transformer. An ignition device for an internal combustion engine, wherein discharge energy consuming means for consuming energy discharged from the first impedance matching circuit is connected to the third winding.   2. The ignition device for an internal combustion engine according to claim 1, wherein the discharge energy consuming means is a circuit including a semiconductor switch and is controlled in accordance with a timing of supplying a discharge current and supplying an alternating current. .   The internal combustion engine ignition device according to claim 2, wherein a resistor is provided in series with the semiconductor switch of the discharge energy consuming means.   The ignition device for an internal combustion engine according to any one of claims 1 to 3, wherein the number of turns of the second winding is larger than the number of turns of the third winding.   The ignition device for an internal combustion engine according to claim 1, wherein a plurality of the second windings on the secondary side of the transformer are provided in accordance with a plurality of impedance matching circuits.   The discharge energy consuming means connected to the third winding of the transformer is a second AC power source for supplying an AC current to the second spark plug, and the energy discharged from the first impedance matching circuit is used. 2. The ignition apparatus for an internal combustion engine according to claim 1, wherein the first AC power source and the second AC power source are divided and consumed.

Images