WO2016035639A1

WO2016035639A1 - Ignition device for internal combustion engine

Info

Publication number: WO2016035639A1
Application number: PCT/JP2015/074016
Authority: WO
Inventors: 竹田　俊一; 覚中山; 金千代寺田
Original assignee: 株式会社デンソー
Priority date: 2014-09-02
Filing date: 2015-08-26
Publication date: 2016-03-10

Abstract

An ignition device for an internal combustion engine, said ignition device being provided with: a spark plug (12); a first ignition coil (15A) and a second ignition coil (15B); a battery (11); a booster circuit (31) for boosting a voltage supplied from the battery; a power transistor (13) for allowing and interrupting passage of a primary current flowing into the primary coil (17A) of the first ignition coil; a MOSFET (25) for applying and disconnecting the voltage boosted by the booster circuit to the primary coil (17B) of the second ignition coil; and an ECU (20) that controls the power transistor so as to cause the spark plug to start electric discharge and causes the MOSFET to repeat application and disconnecting of the voltage boosted by the booster circuit such that the ongoing electric discharge is maintained.

Description

Ignition device for internal combustion engine

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

As an ignition device for an internal combustion engine, in order to obtain a good ignition performance against the smoldering of the spark plug, a characteristic in which the secondary voltage rises sharply is required. On the other hand, in order to maintain the lean burn and normal combustion well In addition, long discharge characteristics are required. However, in order to raise the secondary voltage sharply, the discharge time is shortened because energy is released in a short time by reducing the number of secondary windings of the ignition coil. Thus, these requirements for both characteristics are contradictory. Therefore, by combining the individual characteristics using a plurality of ignition coils to form multiple discharges, it is possible to satisfy the two requirements simultaneously.

As a configuration satisfying the above two requirements, a cylindrical ignition coil (stick coil) is installed between the spark plug and the rocker cover, and is connected to the upper end of the stick coil to form a rectangular ignition coil on the rocker cover. (See Patent Document 1). In the thing of patent document 1, two ignition coils can be arrange | positioned compactly and the ignition device which has a multiple discharge characteristic can be reduced in size.

JP 2000-199470 A

In the device described in Patent Document 1, since a large voltage is applied to both ignition coils to such an extent that discharge of the spark plug can be started, the withstand voltage of both ignition coils must be large. In order to increase the withstand voltage of the ignition coil, it is necessary to increase the insulation distance between the primary coil and the earth body provided in the ignition coil and the secondary coil, leading to an increase in the size of the ignition coil.

The present disclosure is intended to enable continuous discharge by an ignition plug even in a case where an withstand voltage of at least one ignition coil is configured to be low in an ignition device including two ignition coils.

Hereinafter, the first aspect of the present disclosure and the effects thereof will be described.

The present disclosure is an internal combustion engine ignition device according to a first aspect, and includes an ignition plug that performs discharge for igniting a combustible air-fuel mixture in a combustion chamber of the internal combustion engine, a primary coil, and a secondary coil. A first ignition coil and a second ignition coil that apply a voltage to the spark plug by the secondary coil, and a voltage application unit that applies a predetermined voltage to the primary coil included in the first ignition coil, A voltage booster that boosts the voltage supplied by the voltage application unit; a first switching element that conducts and disconnects a primary current that flows to the primary coil of the first ignition coil; and the second ignition coil A second switching element that applies and disconnects the voltage boosted by the voltage boosting unit to the primary coil, and the spark plug by controlling the first switching element. A discharge start unit for starting the discharge, and the voltage boost unit by the second switching element boosts the discharge so that the discharge is maintained after the discharge start unit starts the discharge by the spark plug. A discharge maintaining unit that repeats application and disconnection of the applied voltage.

According to the above configuration, in the ignition device for an internal combustion engine of the present disclosure, the first ignition coil and the second ignition coil both include the primary coil and the secondary coil. A predetermined voltage is applied to the primary coil of the first ignition coil by the voltage application unit. Then, when the discharge start unit controls the first switching element, the primary current flowing to the primary coil is turned on and off, and discharge of the spark plug is started.

Further, the ignition device for an internal combustion engine of the present disclosure is further provided with a second switching element. After the spark plug starts discharging by the discharge starting unit, the second switching element is controlled by the discharge maintaining unit, and the voltage boosted by the voltage boosting unit is applied. Thereby, the discharge of the spark plug is maintained. Furthermore, application and disconnection of the boosted voltage are controlled. As a result, the discharge current can be controlled to an optimum discharge current, for example, increased or decreased, or kept constant. With this configuration, after the spark plug starts discharging, the voltage for maintaining the discharge can be as small as 10 kV or less. Therefore, the withstand voltage design of the second ignition coil can be reduced.

FIG. 1 is a circuit diagram showing an electrical configuration of an internal combustion engine ignition device (first embodiment). FIG. 2 is a cross-sectional view of the internal combustion engine ignition device. FIG. 3 is a timing chart showing a discharge signal, a primary current, and a secondary current (first embodiment). FIG. 4 is a circuit diagram showing an electrical configuration of the internal combustion engine ignition device (second embodiment). FIG. 5 is a timing chart showing a discharge signal, a primary current, and a secondary current (second embodiment). FIG. 6 is a sectional view (modified example) of the internal combustion engine ignition device.

(First embodiment)
Hereinafter, the present disclosure will be described in detail with reference to the drawings illustrating embodiments. FIG. 1 shows an embodiment of an ignition device for an internal combustion engine, and shows a configuration of an electric circuit of this embodiment. This electric circuit includes a spark plug 12, a power transistor 13 (corresponding to a first switching element), a first ignition coil 15A, a second ignition coil 15B, a booster circuit 31 (corresponding to a voltage booster), and a MOSFET 25 (second switching). Corresponding to the element),

diodes

14, 23, 27, 28, ECU 20 (corresponding to the discharge starting means and the discharge maintaining means) and the like.

Here, the ECU 20 receives signals from various sensors that detect parameters (warm-up state, engine rotation speed, engine load, presence / absence of lean combustion, degree of swirling flow, etc.) indicating the operating state and control state of the engine. The The ECU 20 includes an input circuit that processes an input signal, a CPU that performs control processing and arithmetic processing related to engine control based on the input signal, and stores data, programs, and the like necessary for engine control. And it is comprised with the output circuit etc. which output the signal required for engine control based on the various memory which hold | maintains the memory | storage, and the processing result of CPU. Then, the ECU 20 acquires engine parameters from various sensors, generates and outputs a discharge start signal IGt and a discharge continuation signal IGw according to the acquired engine parameters.

The first ignition coil 15A and the second ignition coil 15B are each provided with

primary coils

17A and 17B. The first ignition coil 15A and the second ignition coil 15B generate a secondary current I2 in the

secondary coils

16A and 16B by electromagnetic induction according to the increase and decrease of the primary currents I11 and I12 flowing through the

primary coils

17A and 17B. This is a well-known structure for causing the spark plug 12 to discharge. In each of the

primary coils

17A and 17B, a first end is connected to an output electrode of a battery (corresponding to a voltage applying means) 11 and a second end is connected to the ground via various electronic elements. With this configuration, in the internal combustion engine ignition device 10 of the present embodiment, the voltage supplied from the battery 11 can be applied to the primary coil 17A. Moreover, as for

secondary coil

16A, 16B, both 1st ends are connected to the center electrode of the spark plug 12 via the diode 14, and the 2nd end is connected to earth | ground.

The emitter terminal of the power transistor 13 is connected to the ground, and the collector terminal is connected to the second end of the primary coil 17A. The power transistor 13 conducts and disconnects the primary current I11 flowing from the battery 11 to the primary coil 17A. The conduction and disconnection are controlled by a discharge start signal IGt transmitted from the ECU 20 connected to the base terminal of the power transistor 13. That is, the discharge start signal IGt controls the on / off operation of the power transistor 13, and more specifically, is a signal that instructs a period in which magnetic energy is stored in the primary coil 17A. The power transistor 13 can be replaced with an IGBT, a MOS transistor, a thyristor, or the like.

In the internal combustion engine ignition device 10 of this embodiment, the discharge start signal IGt is given from the ECU 20, and the power transistor 13 is turned on. Thereby, the voltage of the battery 11 is applied to the primary coil 17A, the primary current I11 is energized, and magnetic energy is stored in the primary coil 17A. Thereafter, by cutting the power transistor 13, the magnetic energy stored in the primary coil 17A is converted into electric energy by electromagnetic induction. As a result, a high voltage is generated in the secondary coil 16A, and a high voltage is applied between the electrodes of the spark plug 12, causing discharge.

The booster circuit 31 boosts the voltage of the battery 11 and stores it as electric energy in the capacitor 24, and boosts and stores the voltage of the battery 11 during a period when the discharge start signal IGt is given from the ECU 20. In addition to the capacitor 24, the booster circuit 31 includes a choke coil 30, a MOSFET 22, a first control circuit 21, and a diode 23.

Here, the first end of the choke coil 30 is connected to the positive electrode of the battery 11, and the energized state of the choke coil 30 is interrupted by the MOSFET 22. The first control circuit 21 gives a control signal to the MOSFET 22 to turn the MOSFET 22 on and off. By the on / off operation of the MOSFET 22, the magnetic energy stored in the choke coil 30 is charged in the capacitor 24 as electric energy.

The first control circuit 21 is provided so as to repeatedly turn on and off the MOSFET 22 during a period when the discharge start signal IGt is given from the ECU 20.

The diode 23 prevents the electrical energy stored in the capacitor 24 from flowing back to the choke coil 30 side.

The MOSFET 25 applies and disconnects the voltage stored in the capacitor 24 to the primary coil 17B by an on / off operation. At this time, the MOSFET 25 is turned on, and the electric energy stored in the capacitor 24 is input to the primary coil 17B. As a result, in the internal combustion engine ignition device 10 of the present embodiment, a current in the same direction as the discharge current generated by turning on and off the power transistor 13 is superimposed between the electrodes of the spark plug 12, and the discharge is started following the start of the discharge. Will continue. The MOSFET 25 is turned on / off by a control signal supplied from the second control circuit 26.

The second control circuit 26 repeatedly switches the control signal between high and low during the period when the discharge continuation signal IGw is given from the ECU 20 and outputs the control signal. Here, the discharge continuation signal IGw is a signal for instructing a period for continuing the discharge. More specifically, the second control circuit 26 is a signal for instructing the duration of the voltage applied from the booster circuit 31 to the primary coil 17B by causing the MOSFET 25 to be repeatedly turned on and off.

Then, the MOSFET 25 repeatedly turns on and off while the discharge continuation signal IGw is given from the ECU 20, and sequentially supplies the electric energy of the booster circuit 31 to the primary coil 17B. Thereby, in the internal combustion engine ignition device 10 of the present embodiment, the discharge is continued. The MOSFET 25 can be replaced with a power transistor, a thyristor, or the like.

The

diodes

14A and 14B are provided between the center electrode of the spark plug 12 and the

secondary coils

16A and 16B, respectively, and the direction of the secondary current is the same when the discharge starts and when the discharge continues thereafter. More specifically, the

diodes

14A and 14B are configured so that the secondary current flowing through the secondary coil 16A when the power transistor 13 is turned on and off and the secondary current flowing through the secondary coil 16B when the MOSFET 25 is turned on and off are in the same direction. Provided.

The diode 27 is provided on the source side of the MOSFET 25, and prevents reverse current flow from the primary coil 17B to the booster circuit 31.

Furthermore, a current path branched and connected to the ground is provided between the diode 27 and the second ignition coil 15B. A diode 28 is installed in the path. The cathode side of the diode 28 is connected to the second end side of the secondary coil 16B, and the anode side of the diode 28 is connected to the ground. Therefore, the diode 28 operates as a freewheeling diode when the MOSFET 25 is switched from on to off. That is, the diode 28 circulates the current caused by the electromotive force generated in the primary coil 17B when the MOSFET 25 is turned off through the path of the primary coil 17B → the battery 11 → the ground → the diode 28 → the primary coil 17B.

At this time, in the internal combustion engine ignition device 10 of the present embodiment, a resistor is provided between the first end of the secondary coil 16B and the ground, and the current detection circuit 29 (corresponding to the secondary current detection means) is connected. Yes.

Hereinafter, the internal combustion engine ignition device 40 applied to the internal combustion engine 47 in which the ignition plug 12 is mounted in the plug hole 44 is illustrated in FIG. 2 and the configuration thereof will be described. In this configuration, the first ignition coil 15A is formed as a cylindrical ignition coil (stick coil). The second ignition coil 15B is formed as a rectangular ignition coil (rectangular coil).

The plug hole 44 is a deep hole-like portion extending from the bottom surface of the housing recess 46 provided on the outer surface of the internal combustion engine 47 (more precisely, the cylinder head or head cover) toward the combustion chamber. In the internal combustion engine ignition device 40 of the present embodiment, the first ignition coil 15A is inserted into the plug hole 44, and the second ignition coil 15B is disposed above the first ignition coil 15A. Here, the withstand voltage of the second ignition coil 15B is set to 1/3 of the withstand voltage of the first ignition coil 15A.

The first ignition coil 15A includes a center core 18, a secondary coil 16A, a primary coil 17A, and an outer iron core 19A on the outer side from the center side.

The second ignition coil 15B is mounted with a primary coil 17B, a secondary coil 16B, and an iron core 19B stacked vertically from the inside to the outside.

Here, in the first ignition coil 15A and the second ignition coil 15B, the wiring 45 extending from the secondary side of the second ignition coil 15B is in contact with the center core 18 of the first ignition coil 15A. And the lower end part of the center core 18 is connected to the electrode of the ignition plug 12 via the diode 14B for preventing premature ignition. On the other hand, the secondary coil 16A of the first ignition coil 15A is connected to the electrode of the spark plug 12 via the diode 14A.

The anode side of both diodes 14 is connected to a cap-shaped high voltage terminal 43, and the upper end of the spring terminal 42 is fitted and fixed to the lower end of the high voltage terminal 43. Both diodes 14 are connected to the lower end of the first ignition coil 15A. Furthermore, the upper end portion of the spring terminal 42 connected to the anode of the spark plug 12 is press-fitted into a cylindrical buffer member 41 disposed outside the high-voltage terminal 43 and the spring terminal 42. At this time, the upper end portion of the spring terminal 42 pushes and contracts the spring terminal 42, so that the secondary coils 16 </ b> A and 16 </ b> B of the first ignition coil 15 </ b> A and the second ignition coil 15 </ b> B can be Electrically connected. The cylindrical buffer member 41 is made of a rubber material or the like.

Next, the operation of the internal combustion engine ignition device 10 according to this embodiment will be described with reference to FIG.

In FIG. 3, “IGt” represents the input state of the discharge start signal IGt as high / low, and “IGw” represents the input state of the discharge continuation signal IGw as high / low. “On switch” represents ON / OFF of the MOSFET 25, “I11” and “I12” represent primary current values flowing through the

primary coils

17A and 17B, respectively, and “I2” represents a secondary current value.

In the internal combustion engine ignition device 10 of the present embodiment, when the discharge start signal IGt switches from low to high (see time t01), the on state of the power transistor 13 is maintained during the period when the discharge start signal IGt is high. As a result, the primary current I11 flows through the primary coil 17A, and magnetic energy is stored. Further, electric energy is stored in the booster circuit 31.

Eventually, in the internal combustion engine ignition device 10 of this embodiment, when the discharge start signal IGt switches from high to low, the power transistor 13 is turned off and the energized state of the primary coil 17A is cut (see time t02). Thereby, the magnetic energy stored in the primary coil 17A is converted into electric energy, a high voltage is generated in the secondary coil 16A, and discharge is started in the spark plug 12. The secondary current I2 induced by cutting the primary current I11 takes a negative value with respect to the current flowing from the positive electrode of the battery 11. Therefore, in the graph of the secondary current I2 in FIG. 3, the negative direction is the increasing direction of the secondary current I2.

In the internal combustion engine ignition device 10 of the present embodiment, after the discharge is started in the spark plug 12, the secondary current I2 detected by the current detection circuit 29 is attenuated into a substantially triangular wave shape. When the discharge continuation signal IGw is switched from low to high, the on / off operation of the MOSFET 25 is started (see time t03). When secondary current I2 becomes smaller than a predetermined second threshold value, discharge continuation signal IGw switches from low to high. At this time, the second threshold value is provided as a value larger than a limit current value γ determined as a current value necessary for maintaining discharge.

In the internal combustion engine ignition device 10 of the present embodiment, when the discharge continuation signal IGw switches from low to high, the second control circuit 26 alternately turns on and off the MOSFET 25 during the period when the discharge continuation signal IGw is high. Executed. For this reason, the electrical energy stored in the booster circuit 31 is sequentially input to the primary coil 17B, and the primary current I12 flows from the primary coil 17B toward the positive electrode of the battery 11. More specifically, each time the MOSFET 25 is turned on, the primary current I12 is added to the primary coil 17B in order to compensate for the decrease in the secondary current I2. As a result, the primary current I12 is repeatedly increased to the negative side compared to the previous time when the voltage was applied by the MOSFET 25 (see times t03 to t04). And in the period when the primary current I12 increases, the secondary current I2 increases. In FIG. 3, the magnitude of the secondary current I2 at the start of discharge is larger than the limit current value γ, but it may be less than that if the discharge can be started.

And in the ignition device 10 for internal combustion engines of this embodiment, the secondary current I2 is maintained within a predetermined range by increasing the primary current I12 as an overall tendency. When the secondary current I2 becomes larger than the first threshold, the MOSFET 25 is turned off by the second control circuit 26. Thereby, the increase in the primary current I12 is stopped. At this time, the first threshold is set as a value larger than the second threshold.

Thus, in the internal combustion engine ignition device 10 of the present embodiment, the second control circuit 26 controls the on / off operation of the MOSFET 25, and the discharge is continued by repeatedly performing this control.

With the above configuration, the internal combustion engine ignition device 10 according to the present embodiment has the following effects.

The internal combustion engine ignition device 10 of the present embodiment is provided with a MOSFET 25. After the spark plug 12 starts discharging, the second control circuit 26 controls the on / off operation of the MOSFET 25 so that the discharge can be maintained. As a result, a high voltage of 30 kV or more is required to start the discharge, but once the discharge is started, the discharge sustaining voltage generated between the electrodes of the spark plug 12 is reduced to 10 kV or less. Accordingly, with this configuration, the voltage required to maintain the subsequent discharge after the spark plug 12 starts discharging can be reduced, and the withstand voltage design value of the second ignition coil 15B can be lowered.

In the internal combustion engine ignition device 10 of the present embodiment, the ECU 20 controls the power transistor 13 to conduct the primary current I11 flowing through the primary coil 17A of the first ignition coil 15A. Then, after the conduction is continued, the primary current I11 is cut off, whereby the spark plug 12 starts discharging. Thereafter, the voltage boosted by the booster circuit 31 is applied by the MOSFET 25. As a result, a discharge current in the same direction as the discharge current generated by the control of the power transistor 13 can flow between the electrodes of the spark plug 12. Further, by providing a current path connected to the ground via the diode 28 between the MOSFET 25 and the second ignition coil 15B, the voltage applied from the booster circuit 31 to the second ignition coil 15B by the MOSFET 25 is disconnected. . Thereby, the second ignition coil 15B is supplied from the ground. With this configuration, it is possible to suppress an extreme decrease in the primary current I12 and, in turn, a decrease in the secondary current I2.

In the internal combustion engine ignition device 10 of the present embodiment, each time the voltage is applied by the MOSFET 25, the on time is increased or the off time is shortened compared to the previous time when the voltage was applied by the MOSFET 25. Thereby, the primary current I12 flowing through the primary coil 17B of the second ignition coil 15B is increased. For this reason, a voltage having a magnitude corresponding to the primary current I12 can be generated in the secondary coil 16B, and a decrease in the secondary current I2 can be suppressed.

In the internal combustion engine ignition device 10 of the present embodiment, the ECU 20 controls the MOSFET 25 via the second control circuit 26 after the spark plug 12 starts discharging. Thereby, application and disconnection of the voltage boosted by the booster circuit 31 are repeated, and the discharge of the spark plug 12 is maintained. With this configuration, after the spark plug 12 starts discharging, the voltage for maintaining the discharge can be small, so that the withstand voltage design of the second ignition coil 15B can be reduced.

Specifically, the withstand voltage of the first ignition coil 15A is 30 kV or more in order to start the discharge, but the withstand voltage of the second ignition coil 15B that operates after the start of the discharge only needs to satisfy 10 kV. Therefore, the withstand voltage of the second ignition coil 15B is set to 1/3 of the withstand voltage of the first ignition coil 15A. For this reason, it is possible to reduce the insulation distance between the primary coil 17B and the secondary coil 16B and the grounding body and the secondary coil 16B included in the second ignition coil 15B, and to reduce the size of the second ignition coil 15B. I can do it.

In the internal combustion engine ignition device 10 of the present embodiment, the first ignition coil 15A is inserted into the plug hole 44 formed in the internal combustion engine 47, and the second ignition coil 15B is disposed above the first ignition coil 15A. It is arranged. With this configuration, the two

ignition coils

15A and 15B can be accommodated in a compact manner.

In the internal combustion engine ignition device 10 of the present embodiment, the output side of the secondary coil 16B included in the second ignition coil 15B is connected to the center core 18 included in the first ignition coil 15A. And the lower end part of the center core 18 is connected to the spark plug 12 via the diode 14B. With this configuration, it is not necessary to extend the wiring to the spark plug 12, and the structure can be simplified.

In the internal combustion engine ignition device 10 of the present embodiment, when the secondary current I2 detected by the current detection circuit 29 is greater than the first threshold by the ECU 20, the primary current I12 is cut off by the MOSFET 25. On the other hand, when the secondary current I2 detected by the current detection circuit 29 becomes smaller than the second threshold value, the primary current I12 is conducted by the MOSFET 25. With this configuration, the secondary current I2 flowing through the secondary coil 16B of the second ignition coil 15B can be kept between the first threshold value and the second threshold value. Furthermore, even if the secondary current I2 changes unexpectedly, the secondary current I2 can be stored in a desired region by controlling the MOSFET 25.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

In the first embodiment, the current detection circuit 29 is connected by providing a resistor between the first end of the secondary coil 16B and the ground. In this embodiment, as shown in FIG. 4, a resistor is provided between the ground and the power transistor 13 to connect a current detection circuit 51 (corresponding to primary current detection means). Further, a current detection circuit 51 is connected by providing a resistor between the ground and the battery 11.

The operation of the internal combustion engine ignition device 50 according to this embodiment will be described with reference to FIG.

In the ignition device 50 for an internal combustion engine of the present embodiment, the discharge start signal IGt is switched from low to high (see time t01), and the power transistor 13 is kept on during the period when the discharge start signal IGt is high. As a result, the primary current I11 flows through the primary coil 17A, and magnetic energy is stored. Further, electric energy is stored in the booster circuit 31.

In the internal combustion engine ignition device 50 of the present embodiment, the discharge start signal IGt is switched from high to low when a first predetermined time has elapsed after the primary current I11 starts to flow through the primary coil 17A. As a result, the power transistor 13 is turned off, and the energized state of the primary coil 17A is disconnected (see time t02). Thereby, the magnetic energy stored in the primary coil 17A is converted into electric energy, a high voltage is generated in the secondary coil 16A, and discharge is started in the spark plug 12. At this time, the first predetermined time is set as a time during which the primary current I11 increases to a value that is large enough to cause the spark plug 12 to start discharging and does not damage the power transistor 13.

In the internal combustion engine ignition device 50 of the present embodiment, the discharge continuation signal IGw transmitted from the ECU 20 switches from low to high after the second predetermined time has elapsed since the discharge of the spark plug 12 started (see time t03). . Accordingly, the MOSFET 25 is turned on by the second control circuit 26 that has received the discharge continuation signal IGw, and the primary current I12 is caused to flow through the primary coil 17B. At this time, the second control circuit 26 monitors the magnitude of the primary current I12 detected by the current detection circuit 51. In the internal combustion engine ignition device 50, when the magnitude of the primary current I12 increases by the first predetermined amount after the MOSFET 25 is turned on (voltage application is started), the second control circuit 26 turns off the MOSFET 25 to turn off the voltage. To disconnect. When the primary current I12 decreases by a second predetermined amount after the MOSFET 25 is turned off (voltage cutting is started), the MOSFET 25 is turned on again and the voltage is applied again. By repeating the above-described control by the second control circuit 26, the spark plug 12 continues to be discharged (see times t03 to t04). At this time, the first predetermined amount and the second predetermined amount are values for suppressing an extreme increase or decrease in the secondary current I2, and specifically, the first predetermined amount is set larger than the second predetermined amount. Has been.

With the above configuration, the internal combustion engine ignition device 50 according to the present embodiment has the following effects.

In the internal combustion engine ignition device 50 of the present embodiment, a current detection circuit 51 is connected by providing a resistor between the ground and the power transistor 13. Further, a current detection circuit 51 is connected by providing a resistor between the ground and the battery 11. With this configuration, the primary current I11 and the primary current I12 can be monitored, and the primary currents I11 and I12 can be precisely controlled.

The internal combustion engine ignition device 50 of the present embodiment includes a current detection circuit 51 that detects a primary current I12 flowing through the primary coil 17B included in the second ignition coil 15B. The second control circuit 26 can constantly monitor the magnitude of the primary current I12 detected by the current detection circuit 51. The second control circuit 26 cuts off the primary current I12 by the MOSFET 25 when the primary current I12 detected by the current detection circuit 51 becomes larger by a first predetermined amount after starting to apply voltage to the primary coil 17B. Let Then, when the primary current I12 is reduced by a second predetermined amount after starting to cut off the voltage to the primary coil 17B, the primary current I12 is again conducted by the MOSFET 25. By repeating this control, the internal combustion engine ignition device 50 can suppress an extreme increase or decrease in the secondary current I2 flowing through the secondary coil 16B of the second ignition coil 15B.

In addition, you may implement this embodiment as follows.

As shown in FIG. 4, in this embodiment, a resistor is provided between the ground and the battery 11 to connect the current detection circuit 51. The current detection method for the primary current I12 may be other methods. For example, the current detection circuit 51 may be connected by providing a resistor between the diode 28 and the ground. Alternatively, the current detection circuit 51 may be connected by providing a resistor between the capacitor 24 and the ground.

Also, the above embodiments may be implemented with the following modifications.

In the above embodiments, the wiring 45 extending from the secondary side of the second ignition coil 15B is in contact with the center core 18 of the first ignition coil 15A. And the lower end part of the center core 18 is connected to the electrode of the ignition plug 12 via the diode 14A for preventing premature ignition. With regard to this configuration, as shown in FIG. 6, the wiring 45 extending from the secondary side of the second ignition coil 15B may be connected to the wiring 61 provided between the case 48 and the outer iron core 19A. . The wiring 61 is connected to the spark plug 12 via the diode 14B.

In the first embodiment, in order to maintain the secondary current I2 in a state larger than the limit current value γ for a certain period, the secondary current I2 is provided with two thresholds and controlled to fall within the range. In the second embodiment, the primary current I12 is monitored, and when the primary current I12 increases or decreases by a predetermined value, the MOSFET 25 is turned on / off, and the secondary current I2 is extremely increased or decreased. Suppressed feedback control was performed. About this control, you may control ON / OFF operation | movement of the power transistor 13 or MOSFET25 according to preset time (predetermined period). By controlling in this way, in each said embodiment, the electric

current detection circuits

29 and 51 are unnecessary, and simplification of an ignition device can be aimed at. At this time, when maintaining the discharge of the spark plug 12, the time for turning on the MOSFET 25 is set longer than the time for turning it off. Thus, in each of the above embodiments, the decrease in the primary current I12 that occurs when the MOSFET 25 is turned off can be increased during the period when the MOSFET 25 is turned on, and as a result, the decrease in the secondary current I2 can be suppressed. Is possible.

In the above embodiments, the first ignition coil 15A is defined as a stick coil and the second ignition coil 15B is defined as a rectangular coil, but the shape is not limited thereto. The first ignition coil 15A may be a rectangular coil, and the second ignition coil 15B may be a stick coil. In addition, two rectangular coils may be applied to the first ignition coil 15A and the second ignition coil 15B, respectively, and two stick coils may be used as the first ignition coil 15A and the second ignition coil 15B, respectively. You may apply to. Even in these cases, the withstand voltage of the ignition coil to which a voltage for maintaining the discharge is applied after the ignition plug 12 starts discharging can be designed to be small.

In the above embodiments, the withstand voltage of the second ignition coil 15B is set to 1/3 of the withstand voltage of the first ignition coil 15A, but the present invention is not limited to this. If the discharge of the spark plug 12 can be maintained, the withstand voltage of the second ignition coil 15B may be 1/3 or less of the first ignition coil 15A, or may be more than that.

DESCRIPTION OF SYMBOLS 11 ... Battery, 13 ... Power transistor, 15A ... Stick coil, 15B ... Rectangular coil, 20 ... ECU, 25 ... MOSFET, 31 ... Booster circuit, 47 ... Internal combustion engine.

Claims

A spark plug (12) for performing a discharge for igniting the combustible air-fuel mixture in the combustion chamber of the internal combustion engine (47);
A first ignition coil (15A) and a second ignition coil (15B), each having a primary coil (17A, 17B) and a secondary coil (16A, 16B), for applying a voltage to the spark plug by the secondary coil; ,
Voltage application means (11) for applying a predetermined voltage to the primary coil of the first ignition coil;
Voltage boosting means (31) for boosting the voltage supplied by the voltage applying means;
A first switching element (13) for conducting and disconnecting a primary current flowing to the primary coil of the first ignition coil;
A second switching element (25) for applying a voltage boosted by the voltage boosting means to the primary coil of the second ignition coil;
A discharge start means (20) for starting the discharge by the spark plug by controlling the first switching element;
Discharge maintaining means (20) for applying a voltage boosted by the voltage boosting means by the second switching element so that the discharge is maintained after the discharge is started by the spark plug by the discharge starting means. 26)
An internal combustion engine ignition device.
A current path connected to ground via a diode (28) between the second switching element and the second ignition coil;
The first switching element is controlled by the discharge start means, the primary current flowing through the primary coil of the first ignition coil is conducted, the primary current is disconnected after the conduction is continued, and the ignition plug The discharge is started, and then the second switching element is controlled by the discharge maintaining unit, and the voltage boosted by the voltage boosting unit is applied, so that the first plug is interposed between the electrodes of the spark plug. By causing a discharge current in the same direction as the discharge current generated by the control of the switching element to flow, and further disconnecting the voltage boosted by the voltage boosting means, the current of the second ignition coil from the ground through the current path The ignition device for an internal combustion engine according to claim 1, wherein a current is supplied to the primary coil.
Each time the voltage boosted by the voltage boosting means is applied by the second switching element, the second switching element is more than the first time the voltage boosted by the voltage boosting means is applied by the second switching element. The ignition device for an internal combustion engine according to claim 1 or 2, wherein the primary current flowing through the primary coil of a secondary ignition coil is increased.
The internal combustion engine ignition device according to any one of claims 1 to 3, wherein a withstand voltage of the second ignition coil is set to 1/3 or less of a withstand voltage of the first ignition coil.
The first ignition coil is a cylindrical ignition coil, the second ignition coil is a rectangular ignition coil,
The cylindrical ignition coil is inserted into a plug hole (44) formed in the internal combustion engine, and the rectangular ignition coil is disposed above the cylindrical ignition coil. The ignition device for internal combustion engines of any one of these.
The output side of the secondary coil (16B) of the second ignition coil is connected to the center core (18) of the first ignition coil, and the lower end of the center core is connected to the spark plug via a diode (14B). The internal combustion engine ignition device according to any one of claims 1 to 5.
Secondary current detection means (29) for detecting the magnitude of the secondary current flowing in the secondary coil of the second ignition coil;
The discharge maintaining means is boosted by the voltage boosting means by the second switching element when the magnitude of the secondary current detected by the secondary current detecting means is larger than a first threshold value. When the voltage is cut and the magnitude of the secondary current detected by the secondary current detection means is smaller than a second threshold value smaller than the first threshold value, the second switching element causes the voltage The ignition device for an internal combustion engine according to any one of claims 1 to 6, wherein a voltage boosted by a boosting means is applied.
Primary current detection means (51) for detecting the magnitude of the primary current flowing through the primary coil of the second ignition coil;
The discharge maintaining means monitors the magnitude of the primary current detected by the primary current detection means, and starts applying the voltage boosted by the voltage boosting means by the second switching element, and then the primary current Is increased by the first predetermined amount, the second switching element causes the voltage boosted by the voltage boosting means to be disconnected, and the second switching element disconnects the voltage boosted by the voltage boosting means. The voltage boosted by the voltage boosting means is applied by the second switching element when the primary current is reduced by a second predetermined amount from the start. Ignition device for internal combustion engine.