JP2007218160A - Ignition coil for multiple discharge type ignition device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiple discharge type ignition device alternately repeating capacitive discharge and inductive discharge and having relatively high degree of freedom even if a structure is simple with one switching element in a control circuit. <P>SOLUTION: The ignition coil 4 having magnetic coupling structure in which magnetic coupling of a primary coil 41 and a secondary coil 42 is set good when spark discharge current is low and is set bad when spark discharge current is high is used for the multiple discharge type ignition device having a structure charging energy charged in an energy accumulation coil when the switching element is on and discharged when the same is off to a charge and discharge capacitor, and a structure having the primary coil of the ignition coil 4 put in a discharge path of the capacitor. Consequently, the ignition device of high degree of freedom in design is provided without being easily influenced by connection and contamination condition of a spark plug. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ignition coil of a multiple discharge ignition device mainly used for an internal combustion engine.

Conventionally, an internal combustion engine ignition device has been required to have a high energy ignition device in order to be compatible with recent high-compression lean combustion for exhaust gas countermeasures and fuel efficiency improvement, and a multiple combination of capacitive discharge and inductive discharge is required. A discharge ignition device (for example, Japanese Patent No. 2811778) is considered.
Japanese Patent No. 28117781

  However, the conventional ones such as those described above are mainly devised for a control circuit for supplying power to the ignition coil, and there is no one pursuing the optimum structure of the ignition coil for supplying power to the ignition plug. The circuit also requires two large-capacity switching elements, and its control circuit is very complicated and expensive. There is a problem. Therefore, by examining the optimum ignition coil structure for the multiple discharge ignition device in the present invention, a comparison in which capacitive discharge and inductive discharge are alternately repeated even if the switching element has a simple configuration of one control circuit. An object of the present invention is to obtain a multiple discharge ignition device having a high degree of freedom.

In order to solve the above-described problems, the present invention has the following configuration. In claim 1,
A configuration in which energy stored in the energy storage coil by the current from the DC power source when the switching element is turned on and discharged in the off state is charged in the charge / discharge capacitor, and a configuration in which at least the primary coil of the ignition coil is connected to the discharge path of the capacitor In the multiple discharge type ignition device, the magnetic coupling between the primary coil and the secondary coil of the ignition coil is set well before spark discharge at the spark plug or when the spark discharge current is small, and the spark discharge current is large. Ignition of a large output energy with a long output voltage and long discharge duration, which is less affected by the connection of the spark plug and the contamination state, by using an ignition coil of a multiple discharge ignition device characterized by a magnetic coupling structure that sometimes deteriorates A device is obtained.

  In the multiple discharge ignition device according to claim 2 of the present invention, the multiple discharge ignition device in which the primary wire and the secondary wire are arranged in a separate structure with respect to the flow direction of the magnetic flux of the magnetic circuit of the ignition coil. Ignition coil.

  In the multiple discharge ignition device according to claim 3 of the present invention, the magnetic circuit of the ignition coil is formed of a magnetic body of an outer iron type or an inner iron type closed magnetic circuit, and the vicinity where the primary wire ring and the secondary wire ring are in contact with each other. To an ignition coil of a multiple discharge ignition device in which at least one magnetic path gap is provided in the middle of the secondary wire ring.

  Similarly, in the multiple discharge ignition device according to claim 4 of the present invention, at least one of the magnetic path gaps has a polarity opposite to the polarity of the magnetic flux generated by the discharge current to the primary ring of the capacitor, By using the ignition coil of the multiple discharge ignition device provided with a magnet, the ignition coil can be reduced in size.

  In the multiple discharge ignition device according to claim 5 of the present invention, the magnetic circuit of the ignition coil is formed of a magnetic material of an outer iron type or an inner iron type closed magnetic circuit, and is interposed between the primary wire ring and the secondary wire ring. By using the ignition coil of the multiple discharge ignition device provided with the bypass magnetic circuit of the magnetic circuit, the object of the present invention can be achieved with a highly flexible design.

  Similarly, in the multiple discharge ignition device according to claim 6 of the present invention, an ignition coil of the multiple discharge ignition device in which at least one gap is provided in the bypass magnetic circuit of the magnetic circuit and the magnetic resistance is set large. Thus, the object of the present invention can be achieved with a design having a higher degree of freedom.

  In the multiple discharge ignition device according to claim 7 of the present invention, the magnetic circuit of the ignition coil is configured as an open magnetic path made of a rod-like magnetic body, and is separately provided on the outer circumference of each of the primary wire ring and the secondary wire ring. An ignition coil of a multi-discharge type ignition device provided with an auxiliary magnetic body having a slit.

  Similarly, in the multiple discharge ignition device according to claim 8 of the present invention, the magnetic circuit of the ignition coil is configured as an open magnetic path made of a rod-shaped magnetic body, and ring-shaped magnetic plates are formed at both ends of the primary wire ring. Is an ignition coil of a multiple discharge ignition device.

  Similarly, in the multiple discharge ignition device according to claim 9 of the present invention, the entire primary wire and the secondary wire wound around the rod-shaped magnetic body are arranged in a multiple with an auxiliary magnetic body having a slit on the outer periphery. By using the ignition coil of the discharge ignition device, the ignition coil can be reduced in size.

  According to the present invention, an ignition device with high output energy is desired in order to cope with a fuel direct injection internal combustion engine or the like with a highly compressed lean air-fuel mixture, which has been required in recent years for fuel efficiency and exhaust gas countermeasures. By using an ignition coil that can respond to energy of different qualities applied alternately and continuously at a relatively high frequency, high output energy can be maintained while maintaining a high output voltage that repeats capacitive discharge and inductive discharge alternately. A multiple discharge ignition device with a high degree of design freedom can be obtained at low cost.

  1 is a first embodiment of the present invention, FIG. 2 is a typical circuit diagram for operating the embodiment, FIG. 3 is a waveform diagram for explaining the operation of the circuit diagram, and FIG. 4 shows the basic characteristics of the present invention.

  FIG. 1 is a view showing the structure of the ignition coil 4. The E-type magnetic bodies 12 and 13 are abutted to each other, and a gap 15 is formed at the mating portion of the central core portion 14. A primary wire ring 41 and a secondary wire ring 42 wound around are installed in a separate structure, and constitute an outer iron type closed magnetic circuit ignition coil. Further, between the primary wire ring 41 and the secondary wire ring 42, the magnetic body 16 constituting the bypass magnetic circuit is connected to the insulating material 17 holding an appropriate gap between the magnetic circuit made of the E-type magnetic body. It is inserted integrally. Note that FIG. 1 shows the primary wire ring 41 and the secondary wire ring 42 broken below the center line.

  The ignition coil 4 having the above-described structure is extremely free of design freedom by being used in a multiple discharge ignition device that obtains a spark discharge having a large output energy with a long output voltage and a long discharge duration, which is hardly affected by the connection of the spark plug and the contamination state. Will be expensive. FIG. 2 shows an embodiment of a typical multiple discharge ignition device.

  2, the terminal 1 is connected to a DC power source (not shown), and the terminal 1 is grounded through a series circuit of an energy storage coil 2, a backflow prevention means 3, a temporary wire ring 41 of an ignition coil 4, and a switching element 5. Has been. A series circuit of the temporary wire ring 41 of the ignition coil 4 and the switching element 5 is shunted by a capacitor 6 and a diode 11, and the switching element 5 is shunted by a commutation diode 7. The spark plug 8 is connected to the output of the secondary wire ring 42 of the ignition coil 4, the control terminal of the switching element 5 is connected to the drive circuit 9, and the input terminal of the drive circuit 9 is the output terminal of the ECU 10. It is connected to the. The switching element 5, the capacitor 6, the ignition coil 4, the diodes 7 and 11, the spark plug 8, and the drive circuit 9 are the ignition units 100 per cylinder, and the ignition units 101, 102, and 103 of the other cylinders. These input terminals are connected to the output terminal of the ECU 10, and this embodiment constitutes an ignition device for a four-cylinder internal combustion engine. The diode 7 is a protection element for the switching element 5 using an avalanche diode or a constant voltage diode.

  For example, when a power supply of 42 V is turned on, a current flows through the energy storage coil 2, the backflow prevention means 3 and the capacitor 6, and charges up to the DC power supply voltage are stored in the capacitor 6. Next, when the drive circuit 9 receives an ignition signal from the ECU 10 at time t 0, the switching element 5 is turned on, and the charge of the capacitor 6 is discharged to the primary ring 41, and at the same time, the energy storage coil 2 and the ignition coil 4 are discharged. Accumulation of magnetic energy is started by the flow of current.

  The discharge of the capacitor 6 to the primary wire ring 41 induces a voltage of about 4.6 kV in the secondary wire ring 42, but the discharge charge does not reach the spark plug 8, and the discharge charge is generated from the primary wire ring 41 and the diode. 6 is discharged. Although the discharge time is substantially determined by the capacitance of the capacitor 6 and the inductance of the primary wire ring 41, the discharge time in the present embodiment is set at 0.3 mS, and from time t0 to the time before the above-mentioned approximately discharge end setting. At time t1 after 0.22 mS, the switching element 5 is turned off, and the magnetic energy stored in the ignition coil 4 is released, so that a voltage of about 30 kV is induced in the secondary wire ring 42 and a spark discharge is generated in the spark plug 8. To start. On the other hand, the capacitor 6 is charged with an induced voltage of about 300 V of magnetic energy of the energy storage coil 2.

  The discharge delay of about 0.22 mS at the beginning of the engine cranking is not a problem because the delay angle of the cranking rotational speed is about 0.18 degrees.

  Next, after the time before the end of the spark discharge, for example, 0.12 mS, the switching element 5 is turned on again at time t2, so that the high voltage charge of 300 V of the capacitor 6 is applied to the primary wire ring 41. In the secondary ring 42, a high voltage of 33 kV opposite to the discharge voltage is induced, and an inversion current flows through the spark plug 8, and at the same time, magnetic energy starts to be stored in the energy storage coil 2 again. Thus, magnetic energy is also accumulated in the ignition coil 4.

  Next, the switching element 5 is turned off again at time t3 after 0.2 mS, so that magnetic energy is induced in the ignition coil 4 in the secondary wire ring 42 and the spark discharge current of the spark plug 8 is reversed again. And last. On the other hand, the capacitor 6 is recharged by the induced voltage of the magnetic energy of the energy storage coil 2.

  Thereafter, the switching element 5 is repeatedly turned on for 0.2 mS and turned off for 0.12 mS, so that in the spark plug 8, the capacitive discharge due to the discharge of the capacitor 6 due to the charging of the energy storage coil 2 and the ignition coil 4. The inductive discharge in the direct release of the magnetic energy is alternately repeated, for example, after four repetitions, the on-time of the last switching element 5 until the time tm immediately after the discharge time end notice time tn is instructed from the ECU 10 is In order to increase the output energy induced in the secondary wire ring 42 of the first ignition coil 4 at the next ignition timing, the output energy is set to about 0.4 mS, which is longer than the above-mentioned on time, and the capacitance of the capacitor 6 and the primary After the capacitive discharge consisting of the inductance of the wire ring 41 continues, when the switching element 5 is turned off, the ignition coil 4 Product is magnetic energy, inductive discharge current of the spark plug 8 to several orders greater than that of until it becomes a high output. At the same time, the magnetic energy voltage of the energy storage coil 2 is as large as about 400 V, and the charge stored in the capacitor 6 is sufficiently stored and waits until the next ignition timing.

  When the ignition timing comes again, the switching element 5 is turned on at time t0, and the above-described sufficient charging charge is applied to the primary wire 41 to the capacitor 6 to exceed 40 kV induced in the secondary wire 42. At the same time as spark discharge is started in the spark plug 8 by the voltage, storage of magnetic energy in the energy storage coil 2 and the ignition coil 4 starts. Subsequently, when the switching element 5 is turned off at time t1 after 0.22 mS, the magnetic energy of the energy storage coil 2 becomes the charging current of the capacitor 6 and the magnetic energy of the ignition coil 4 is induced in the secondary wire ring 42. Due to the applied voltage, a reverse discharge current flows through the spark plug 8, and the switching element 5 is turned on again at time t 2 after 0.12 mS before the discharge is completed. 8 is performed as re-inversion discharge, and thereafter, as described in the previous paragraph, ON / OFF of the switching element 5 is repeated several times, and while the output from the drive circuit 9 based on the control signal of the ECU 10 continues, the multiple discharge is repeated. Is done.

  The above-described operation is shown in FIG. 3, where S is the basic operation range of the ignition unit determined by the ECU 10 by appropriate control judgment based on the engine speed, load condition, and power supply voltage, and Vs is the oscillation operation based on the control of the ECU 10. The output signal of the drive circuit 9 to be operated, Vc is the voltage across the capacitor 6, and i 2 is the discharge current of the spark plug 8.

  As shown in FIG. 3, the initial discharge voltage of the spark plug 8 when placed at the time of high compression is required to be about 25 kV high, but once the discharge is performed, about 20 kV due to ionization in the vicinity of the spark plug 8. Since discharge can be continued even at a low voltage, the switching period of the switching element 5 is increased to reduce the output voltage in consideration of the life of the spark plug 8.

  The operation diagram shown in the right half after the broken line in FIG. 3 shows a typical operation when the engine maintains a stable load condition, and the switching element 5 is set to be turned on and off three times. is there.

  Further, when the engine speed increases, it is necessary to set the discharge duration S to be inversely proportional to this, and the ON / OFF cycle of the switching element 5 is also shortened. However, depending on the load condition, it is rare. Therefore, it is preferable to reduce the switching frequency of the switching element 5 as described above, and the minimum switching frequency in this embodiment is two times.

  Further, the level control of the output voltage of the present invention is mainly determined by the energy storage energization time to the energy storage coil 2, in other words, the on-time of the switching element 5, and in particular, at the time of engine cranking when the ignition switch is turned on. Other than the occurrence, the ON time after the time tn determines the stored energy of the energy storage coil 2 and determines the charge amount of the capacitor 6. In particular, the on-time is set longer when the power supply voltage is low, such as during engine cranking and subsequent idle rotation.

  The simple configuration of the switching on / off time control circuit of the switching element 5 is to leave everything to the control of the ECU 10, but a relatively easy implementation method of the configuration is driven as in the embodiment. This can be realized by having a circuit configuration in which the switching element 5 is turned on at least once for a fixed time after the ignition command time S of the ECU 10 in the circuit 9 for a longer time than the normal on time.

  The energy storage coil 2 is normally designed not to be magnetically saturated with respect to the maximum energization time setting.

  The above mainly described the circuit operation. In order to effectively discharge the energy stored in the energy storage coil 2 to the spark plug 8 without interruption when the switching element 5 is turned on and off, The characteristics of the coil 4 are extremely important.

  That is, the secondary wire ring 42 of the ignition coil 4 generally has a floating capacity obtained by winding a magnet wire of about 0.05 times around 10,000 times and a floating capacity such as the ignition plug 8 or a connecting wire to the ignition plug 8. However, the output voltage of the ignition coil 4 must be difficult to be affected by the load state.

  Further, in order to start the spark discharge to the spark plug 8, the above-mentioned voltage of about 25 kV is required, and after starting the spark discharge, a discharge current of 30 mA or more is maintained for a predetermined time while maintaining a discharge voltage of around 1 kV. Is required. That is, an energy supply form that follows the load fluctuation of the secondary wire ring 42 is required within each time when the switching element 5 is turned on and off even at a relatively high frequency that is repeated in a short time.

  The ignition coil 4 having the structure shown in FIG. 1 has a structure designed so as to satisfy the requirements. As described above, the primary wire ring 41 and the secondary wire ring 42 are arranged in a separate structure, and further, By providing a gap and a bypass magnetic circuit in the magnetic circuit of the ignition coil 4, the influence of magnetic flux fluctuations induced on the respective winding axes of the primary and secondary wire rings can be reduced.

  That is, when the switching element 5 is turned on at time t0, the charged charge of 400 V of the capacitor 6 is discharged to the primary wire ring 41, and the magnetic flux φ1 of the magnetic circuit of the ignition coil 4 generated by the discharge current is shown in the central core portion. Is generated in the direction of the arrow, and an output voltage 90 ° behind the magnetic flux is induced in the secondary wire ring 42, and the leakage current flowing in the floating capacity of the secondary wire ring 42 and the spark plug 8 is the output voltage. Therefore, although the magnetic flux has a magnetic resistance due to the gap 15, the direction of the magnetic flux due to the leakage current is substantially in phase and generates a predetermined voltage with relatively little loss.

  Next, when the voltage applied to the spark plug 8 reaches a voltage of about 25 kV, a spark discharge current flows through the spark plug 8, and the secondary wire ring 42 has a magnetic flux in the direction of the arrow due to the current applied to the primary wire ring 41. The magnetic flux φ2 in the opposite direction flows through φ1 and becomes the magnetic flux φ2 in the direction of canceling out the magnetic flux φ1 in the direction of the arrow. However, the effect of magnetoresistance due to the interposition of the magnetic path gap 15 is further improved. When the amount of the magnetic flux φ1 at the time of no discharge is small, since the magnetic resistance is large, if both the magnetic flux φ1 and the magnetic flux φ2 are increased in the bypass magnetic circuit composed of the magnetic body 16 and the insulating material 17 having almost no magnetic flux, By forming a flow path that merges and flows from each other, the current of the primary wire ring 41 decreases when the discharge current of the spark plug 8 increases beyond the limit, and increases when the discharge current decreases. Of the spark plug 8 It is possible to continue the flowers discharge current at the optimal level.

  The output voltage V2 and current i2 generated in the secondary wire ring 42 of the ignition coil 4 exhibit the behavioral characteristics shown in FIG.

  Next, when the switching element 5 shifts from on to off at time t1, the magnetic flux φ1 generated and accumulated by the energizing current to the primary wire ring 41 and maintained at the optimum value by the magnetic path gap 15 or the like is rapidly attenuated. By doing so, the magnetic energy is discharged to the secondary wire ring 42 in the opposite direction to the polarity so far, and the current of the spark plug 8 is reversed as shown in FIG.

  Hereinafter, when the switching element 5 is turned on again at time t2, the change of the magnetic flux in the magnetic circuit of the ignition coil 4 repeats the above behavior.

  In the ignition coil 4 described in the above embodiment, the position of the gap 15 formed in the central core portion 14 with which the E-type magnetic body is abutted is two from the vicinity where the primary wire ring 41 and the secondary wire ring 42 are in contact with each other. It is preferable that the gap be set at a distance δ up to the middle of the next ring 42, and the gap is not limited to the central core portion 14, and the same characteristics can be obtained even if it is attached to both or only one of the side core portions. Can be obtained. Further, depending on the selection of the position of the gap 15 with respect to the winding width of the primary wire ring 41 and the secondary wire ring 42, the bypass magnetic circuit is unnecessary.

  The bypass magnetic circuit is for obtaining a greater degree of design freedom, and the cross-sectional area of the magnetic body 16 and the thickness of the insulator 17 are selected to be in an opposite relationship, and the cross-sectional area of the magnetic body 16 is extremely large. When the number is small, the insulator 17 can be eliminated, and when the cross-sectional area is selected to be large, the magnetic body 16 can be integrated with the E-type magnetic body forming the main magnetic circuit.

  FIG. 5 is a view showing a second embodiment of the present invention. The difference from the embodiment of FIG. 1 is that the co-type magnetic body 18 is different from the outer-type closed magnetic circuit structure of the E-type magnetic body butting structure. And an inner iron type closed magnetic circuit structure of 19 butting structures. 1 are the same or equivalent, and although not shown, a gap 15 is provided in the middle of the main magnetic circuit. Therefore, the behavior of the magnetic flux generated in the magnetic circuit is also the first implementation. As in the first embodiment, the same gap can be obtained when the gap is not limited to the central core portion 14 but is attached to both or only one of the side core portions. .

  6 (a), 6 (b) and 6 (c) show a third embodiment of the present invention, in which the magnetic circuit of the ignition coil 4 constitutes an open magnetic path made of a rod-shaped magnetic body 20, and the primary line Auxiliary magnetic bodies 21 and 22 shown in a partially broken manner with individual slits in the cross section shown in FIG. 6B are installed on the outer circumferences of the ring 41 and the secondary wire ring 42, respectively, and the primary An ignition coil 4 having an open magnetic circuit structure in which ring-shaped magnetic plates 23 and 24 shown in the plan view of FIG.

  In the third embodiment, the basic behavior of the magnetic flux generated in the magnetic circuit remains unchanged. However, although it may be separated into two in order to give a gap to the rod-shaped magnetic body 20, it is usually composed of a single rod-shaped magnetic body 20 because it is originally an open magnetic path with a large amount of leakage magnetic flux, It is also possible to omit only one or both of the ring-shaped magnetic bodies 23 and 24 and use only the auxiliary magnetic bodies 21 and 22.

  In addition, when the ring-shaped magnetic bodies 23 and 24 are used, it is possible to use the auxiliary magnetic bodies 21 and 22 having slits on the outer periphery as one body. If there is no problem in the insulation on the high voltage side, the ring-shaped magnetic body 23 can be arranged at both ends of the secondary wire 42.

  In the first to third embodiments described above, the magnetic flux φ1 generated by the current flowing through the primary wire ring 41 when the switching element 5 starting from time t0 is turned on in the gap installed in the main magnetic circuit. By inserting a magnet in a direction that impedes the flow, the cross-sectional area of the magnetic body of the main magnetic circuit can be reduced, and at the same time, the amount of change in magnetic flux when the switching element 5 is turned off at time t1 or t3. Can be increased. In addition, it is preferable that the installation location of the magnet in a 3rd Example isolate | separates the rod-shaped iron core 20 into two, or is installed in the edge part at the side of the primary wire ring 41 side.

  The circuit of FIG. 2 constituting the multiple discharge ignition device described in the above embodiment is an example of a circuit having various configurations. The capacitor 6 is provided with a shunt by the diode 11 in the capacitor 6 and the switching element 5 is turned on. The main role of the diode 11 is used to share the relatively expensive capacitor 6 in the multi-cylinder deployment of each ignition unit 100 to 103. , Is not trapped in the configuration.

  Also, in order to ensure the redundancy of component trouble, one set of main components including the energy storage coil 2, the backflow prevention means 3, the capacitor 6 and the diode 11 is set for every two cylinders when the internal combustion engine has four cylinders. In the case of six cylinders, one set may be set for every three cylinders, and in the case of eight cylinders, one set may be set for every four cylinders.

The figure which shows the 1st Example of invention. 1 is a typical circuit diagram using an embodiment of the invention. The operation waveform of each part of FIG. The characteristic view of the Example of invention. The figure which shows the 2nd Example of invention. (A), (b), (c) The figure which shows the 3rd Example of invention.

Explanation of symbols

1: power supply terminal 2: energy storage coil 3: backflow prevention means 4: ignition coil 41: primary wire ring 42: secondary wire ring 5: switching element 6: capacitor 7, 11: diode 8: spark plug 9: drive circuit 10 : ECU
12, 13: E-type magnetic body 14: Central core portion 15: Gap 16: Magnetic body 17: Insulator 18, 19: Co-type magnetic body 20: Rod-shaped magnetic bodies 21, 22: Auxiliary magnetic bodies 23, 24: Ring shape Magnetic bodies 100, 101, 102, 103: ignition unit

Claims (9)

A configuration in which energy stored in the energy storage coil by the current from the DC power source when the switching element is turned on and discharged in the off state is charged in the charge / discharge capacitor, and a configuration in which at least the primary coil of the ignition coil is connected to the discharge path of the capacitor In the multiple discharge type ignition device, the magnetic coupling between the primary coil and the secondary coil of the ignition coil is set well before spark discharge at the spark plug or when the spark discharge current is small, and the spark discharge current is large. An ignition coil of a multiple discharge ignition device characterized by a magnetic coupling structure that sometimes deteriorates. The ignition coil of the multiple discharge ignition device according to claim 1, wherein the primary wire and the secondary wire are arranged in a separate structure with respect to the flow direction of the magnetic flux of the magnetic circuit of the ignition coil. The magnetic circuit of the ignition coil is made of a magnetic material having an outer iron type or an inner iron type closed magnetic circuit, and at least 1 between the vicinity of the primary wire ring and the secondary wire ring and the vicinity of the middle of the secondary wire ring. The ignition coil of the multiple discharge ignition device according to claim 1 or 2, wherein a plurality of magnetic path gaps are provided. The ignition of the multiple discharge ignition device according to claim 3, wherein a magnet is provided in at least one of the magnetic path gaps in a direction opposite to the polarity of the magnetic flux generated by the discharge current to the primary ring of the capacitor. coil. The magnetic circuit of the said ignition coil is comprised with the magnetic body of an outer iron type or an inner iron type closed magnetic circuit, The bypass magnetic circuit of the said magnetic circuit was provided between the said primary wire ring and the secondary wire ring. 5. The ignition coil of the multiple discharge ignition device according to 4. 6. The ignition coil of a multiple discharge ignition device according to claim 5, wherein the bypass magnetic circuit of the magnetic circuit is provided with at least one gap to increase a magnetic resistance. The magnetic circuit of the said ignition coil comprises the open magnetic path which consists of a rod-shaped magnetic body, The auxiliary | assistant magnetic body which entered the separate slit in each outer periphery of the said primary wire ring and a secondary wire ring was installed. Ignition coil of multiple discharge type ignition device. The multiple discharge ignition device according to claim 2, wherein the magnetic circuit of the ignition coil comprises an open magnetic path made of a rod-shaped magnetic body, and ring-shaped magnetic plates are installed at both ends of the primary wire ring. Ignition coil. 9. The ignition coil for a multiple discharge ignition device according to claim 8, wherein an auxiliary magnetic body having a slit on the outer periphery is installed on the entire primary wire and the secondary wire wound around the rod-shaped magnetic body.

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