JP6297899B2 - Ignition device - Google Patents

Description

  The present invention relates to an ignition device that controls the operation of a spark plug.

2. Description of the Related Art Conventionally, an ignition device that controls the operation of a spark plug that performs spark discharge on an air-fuel mixture of an internal combustion engine is known.
The ignition device described in Patent Document 1 has a first ignition coil and a second ignition coil connected in parallel. The ignition device also includes a first ignition switch that turns on and off the primary coil of the first ignition coil, and a second ignition that turns on and off the primary coil of the second ignition coil. It has a switch.
This ignition device extends the discharge time of the spark plug by turning off the second ignition switch after turning off the first ignition switch. The igniter improves the ignitability of the lean air-fuel mixture by this multiple discharge.

JP 2000-199470 A

However, the ignition device described in Patent Document 1 consumes energy larger than energy necessary for ignition of the air-fuel mixture at the initial stage of discharge by the first ignition coil and at the initial stage of discharge by the second ignition coil. In addition, at the end of the discharge by the second ignition coil, the output energy is useless because the output energy is smaller than the energy required for the discharge. Therefore, this ignition device has a large loss of energy, and there is a possibility that the fuel efficiency is deteriorated because the energy is generated. Moreover, since the energy at the initial stage of discharge of the first ignition coil and the initial stage of discharge of the second ignition coil is large, there is a concern that the life of the electrode part of the spark plug is shortened.
The present invention has been made in view of the above points, and an object of the present invention is to provide an ignition device capable of suppressing loss of energy unnecessary for discharge.

The present invention provides an ignition device including a plurality of ignition coils for supplying a secondary current to a spark plug, and a plurality of ignitions according to a maintenance target current value set in an energy input unit capable of continuing discharge of the spark plug. One of the coils is turned on or off. In particular, the present invention includes a switch that can turn on or off energization of a primary coil of another ignition coil except for one ignition coil among a plurality of ignition coils.

As a result, the peak current when the discharge of the spark plug electrode is generated by the operation of the ignition switch is adjusted by changing the number of operating ignition coils in accordance with the maintenance target current value set in the energy input means. The Therefore, the ignition device can reduce the waste of energy without making the peak current unnecessarily large with respect to the operating state of the internal combustion engine by bringing the maintenance target current value and the peak current value closer to each other. .
Further, by bringing the maintenance target current value and the peak current value close to each other, the time from when the peak current flows to the spark plug until the energy input means inputs energy is shortened. Therefore, the ignition device can shorten the time during which a secondary current larger than the maintenance target current value flows through the ignition plug.
Therefore, this ignition device can suppress wear of the electrode portion of the spark plug due to excessive energy input, and can extend the useful life of the spark plug.

Here, assuming that there is no energy input by the energy input means, the waveform of the secondary current flowing through the spark plug only by the operation of the ignition switch is referred to as a base waveform.
The ignition device includes a plurality of ignition coils having a small peak current that can be output, thereby shortening the time for the base waveform to end. Therefore, when the energy input by the energy input means is performed, the ignition device can suppress the base waveform from remaining after the energy input period ends. Therefore, this ignition device can suppress loss of energy unnecessary for discharge and improve fuel efficiency.

1 is a schematic configuration diagram of an engine system to which an ignition device according to an embodiment of the present invention is applied. It is a circuit diagram of the ignition device by one Embodiment of this invention. It is a time chart explaining basic operation of an ignition device. It is a flowchart explaining the ignition control process which an ignition device performs. (A) is a graph which shows the time change of the secondary current at the time of using three ignition coils, (B) is a graph which shows the time change of the secondary current at the time of using two ignition coils. Yes, (C) is a graph showing the time variation of the secondary current when three ignition coils are used. It is a graph which shows the time change of the secondary current in the ignition device of a comparative example.

Hereinafter, an ignition device according to an embodiment of the present invention will be described with reference to the drawings.
(One embodiment)
An ignition device according to an embodiment of the present invention is applied to an engine system mounted on a vehicle or the like. In the following description, the “internal combustion engine” described in the claims is referred to as an “engine”.

[Engine system configuration]
First, a schematic configuration of the engine system will be described with reference to FIG.
The engine system 10 includes a spark ignition engine 13. The engine 13 is a multi-cylinder engine such as, for example, four cylinders, and FIG. 1 shows only a cross section of one cylinder. The configuration described below is similarly provided to other cylinders (not shown).

The engine 13 burns an air-fuel mixture of air supplied from the intake manifold 15 through the throttle valve 14 and fuel injected from the injector 16 in the combustion chamber 17, and reciprocates the piston 18 by the explosive force at the time of combustion. . The reciprocating motion of the piston 18 is converted into a rotational motion by a crankshaft (not shown) and output. The combustion gas is released into the atmosphere through the exhaust manifold 20 and the like.
An intake valve 22 is provided at the intake port of the cylinder head 21 that is the inlet of the combustion chamber 17, and an exhaust valve 23 is provided at the exhaust port of the cylinder head 21 that is the outlet of the combustion chamber 17.

The air-fuel mixture in the combustion chamber 17 is ignited by causing a discharge between the electrodes of the spark plug 7 by the ignition device 30. The ignition device 30 operates the ignition circuit unit 31 based on a command from an electronic control unit (ECU) 32 and applies a high voltage from the ignition coils 410, 420, 430 to the ignition plug 7, thereby causing a spark discharge in the combustion chamber 17. Is generated.
The spark plug 7 has a pair of electrodes (see FIG. 2) that face each other with a predetermined gap in the combustion chamber 17 of the engine 13, and a high voltage that causes dielectric breakdown is applied between the pair of electrodes in the gap. Then, a spark discharge is generated. In the following description, “high voltage” refers to a voltage at which the spark plug 7 can generate a discharge between a pair of electrodes.

The ECU 32 is configured by a microcomputer including a CPU, a ROM, a RAM, an input / output port, and the like.
The ECU 32 receives detection signals from various sensors such as a fuel pressure sensor 34, an in-cylinder pressure sensor 35, an exhaust pressure sensor 36, a water temperature sensor 37, a NOx sensor 38, and an intake pressure sensor 39, as indicated by broken line arrows. Based on detection signals from these various sensors, the ECU 32 controls the operating state of the engine 13 by driving the throttle valve 14, the injector 16, the ignition circuit unit 31, and the like, as indicated by solid arrows.

[Configuration of ignition device]
Next, the configuration of the ignition device 30 will be described with reference to FIG.
As shown in FIG. 2, the ignition device 30 includes a first ignition coil 410, a second ignition coil 420, a third ignition coil 430, an ignition circuit unit 31, an ECU 32, and the like.

The first ignition coil 410, the second ignition coil 420, and the third ignition coil 430 have the same configuration, and are respectively primary coils 411, 421, 431, secondary coils 412, 422, 432, and rectification not shown. And a known step-up transformer.
The primary coils 411, 421, 431 have one end connected to the positive electrode of the battery 6 as a “DC power supply” capable of supplying a constant DC voltage, and the other end grounded via an ignition switch 45. The three primary coils 411, 421, 431 are connected in parallel between the battery 6 and the ignition switch 45. Hereinafter, the non-battery side of the primary coils 411, 421, 431 is referred to as “ground side”.
The secondary coils 412, 422, 432 share a magnetic circuit with the primary coils 411, 421, 431, one end is grounded via a pair of electrodes of the spark plug 7, and the other end is grounded. That is, the three secondary coils 412, 422, and 432 are connected in parallel, and one end and the other end form a closed circuit.

The current that flows through the primary coils 411, 421, and 431 is referred to as a primary current I1, and the current that is generated by the interruption following the energization of the primary current I1 and flows through the secondary coils 412, 422, and 432 is referred to as a secondary current I2. As indicated by arrows in the figure, the primary current I1 is positive in the direction from the primary coils 411, 421, 431 to the ignition switch 45, and the secondary current I2 is ignited from the secondary coils 412, 422, 432. The current in the direction toward the plug 7 is positive.
The ignition coils 410, 420, and 430 generate a high voltage in the secondary coils 412, 422, and 432 by a mutual induction action according to a change in the current flowing through the primary coils 411, 421, and 431, and this high voltage is supplied to the ignition plug 7 Apply to. In the present embodiment, three ignition coils 410, 420, and 430 are provided for one ignition plug 7.

  The ignition circuit unit 31 includes an ignition switch (igniter) 45, an energy input unit 50, a secondary current detection circuit 48, a parallel determination circuit 60, and the like.

The ignition switch 45 is composed of, for example, an IGBT (insulated gate bipolar transistor), the collector is connected to the ground side of the primary coils 411, 421, 431 of the ignition coils 410, 420, 430, the emitter is grounded, and the gate is It is connected to the ECU 32. The collector is connected to the emitter via the rectifying element 46.
The ignition switch 45 is turned on / off in response to an ignition signal IGT input from the ECU 32 to the gate. Specifically, the ignition switch 45 is turned on when the ignition signal IGT rises and turned off when the ignition signal IGT falls. The primary current I1 flowing through the primary coils 411, 421, and 431 is switched between energization and cutoff by the ignition switch 45 in accordance with the ignition signal IGT.

The energy input unit 50 as “energy input means” includes a DCDC converter 51, a capacitor 56, a discharge switch 57, a discharge switch driver circuit 58, a rectifier element 59, and a current maintenance signal determination circuit 70.
The DCDC converter 51 includes an energy storage coil 52, a charge switch 53, a charge switch driver circuit 54, and a rectifier element 55. The DCDC converter 51 boosts the voltage of the battery 6 and supplies it to the capacitor 56.
The energy storage coil 52 has one end connected to the battery 6 and the other end grounded via a charge switch 53. The charge switch 53 is configured by, for example, a MOSFET (metal oxide semiconductor field effect transistor), and has a drain connected to the energy storage coil 52, a source grounded, and a gate connected to the driver circuit 54. The driver circuit 54 can drive the charging switch 53 on and off.
The rectifying element 55 is composed of a diode, and prevents a backflow of current from the capacitor 56 to the energy storage coil 52 and the charge switch 53 side.

When the charging switch 53 is turned on, an induced current flows through the energy storage coil 52 and electric energy is stored. When the charging switch 53 is turned off, the electric energy stored in the energy storage coil 52 is superposed on the DC voltage of the battery 6 and discharged to the capacitor 56 side. By repeating the on / off operation of the charging switch 53, the energy storage coil 52 repeatedly stores and releases energy, and the battery voltage is boosted.
One electrode of the capacitor 56 is connected to the wiring between the energy storage coil 52 and the charge switch 53 via the rectifying element 55, and the other electrode is grounded. Capacitor 56 stores the voltage boosted by DCDC converter 51.

The discharge switch 57 is configured by, for example, a MOSFET, the drain is connected to the capacitor 56, the source is connected to the ground side of the primary coils 411, 421, 431, and the gate is connected to the driver circuit 58. The driver circuit 58 can drive the discharge switch 57 on and off.
The rectifying element 59 is composed of a diode, and prevents a backflow of current from the primary coils 411, 421, 431 to the capacitor 56.

The secondary current detection circuit 48 detects the sum of the secondary currents I2 flowing through the secondary coils 412 422 432. Then, the current maintenance signal determination circuit 70 determines the on-duty ratio of the discharge switch 57 by feedback control to make the secondary current I2 coincide with the target value (hereinafter referred to as “maintenance target current value I2 ^* ”). The driver circuit 58 is instructed.
The ECU 32 sets the maintenance target current value I2 ^* to a current that can satisfactorily maintain the discharge according to the operation region determined from the engine load and the rotational speed. When the ECU sets the maintenance target current value I2 ^* , it functions as “setting means” described in the claims.

The parallel determination circuit 60 determines how many of the three ignition coils 410, 420, and 430 are used to discharge the spark plug according to the maintenance target current value I2 ^* . This determination method will be described later.
A first switch 61 is provided between the primary coil 411 included in the first ignition coil 410 and the parallel determination circuit 60. A second switch 62 is provided between the primary coil 431 included in the third ignition coil 430 and the parallel determination circuit 60.
The parallel determination circuit 60 turns on both the first switch 61 and the second switch 62 when using the three ignition coils 410, 420, and 430. When using two ignition coils, the parallel determination circuit 60 turns on one of the first switch 61 and the second switch 62 and turns off the other. The parallel determination circuit 60 turns off both the first switch 61 and the second switch 62 when one ignition coil 420 is used.

The ECU 32 generates an ignition signal IGT and an energy input period signal IGW based on the operation information of the engine 13 acquired from various sensors, and outputs it to the ignition circuit unit 31. The ECU 32 generates a target secondary current signal IGA for instructing the maintenance target current value I2 ^* and outputs the target secondary current signal IGA to the driver circuit 58 via the current maintenance signal determination circuit 70.
The ignition signal IGT is input to the gate of the ignition switch 45 and the charge switch driver circuit 54. The ignition switch 45 is turned on while the ignition signal IGT is input. The driver circuit 54 repeatedly outputs a charge switch signal SWc for controlling on / off of the charge switch 53 to the gate of the charge switch 53 during the period when the ignition signal IGT is input. In the present embodiment, the charging switch signal SWc is a rectangular wave pulse signal having a constant cycle and a variable on-duty ratio.

  The energy input period signal IGW is input to the discharge switch driver circuit 58. The driver circuit 58 repeatedly outputs a discharge switch signal SWd for controlling on / off of the discharge switch 57 to the gate of the discharge switch 57 while the energy input period signal IGW is input. The driver circuit 58 changes the on-duty ratio of the discharge switch signal SWd based on the target secondary current signal IGA input from the current maintenance signal determination circuit 70. In the present embodiment, the discharge switch signal SWd is a rectangular wave pulse signal having a constant cycle and a variable on-duty ratio.

[Ignition device operation]
Next, the operation of the ignition device 30 will be described with reference to the time chart of FIG. In the time chart of FIG. 3, the horizontal axis is a common time axis, and the ignition signal IGT, the energy input period signal IGW, the capacitor voltage Vdc, the primary current I1, the secondary current I2, the input energy P, in order from the top on the vertical axis. The time change of the charge switch signal SWc and the discharge switch signal SWd is shown.
Here, “capacitor voltage Vdc” means the voltage stored in the capacitor 56. “Input energy P” means energy that is discharged from the capacitor 56 and supplied to the ignition coils 410, 420, and 430 from the low voltage side terminals of the primary coils 411, 421, and 431. The integrated value from the start of supply (the rise of the first discharge switch signal SWd) is shown.

  In FIG. 3, a case where three ignition coils 410, 420, and 430 are used will be described. In FIG. 3, “primary current I1” is the sum of the currents flowing through the three primary coils 411, 421, 431, and “secondary current I2” is the current flowing through the three secondary coils 412, 422, 432. It is sum. The “primary current I1” and “secondary current I2” have a positive current value in the direction of the arrow shown in FIG. 2 and a negative current value in the direction opposite to the arrow. In the following description, when referring to the magnitude of the negative current, the magnitude is expressed based on the “absolute current value”. That is, in the negative region, the current value increases from 0 [A] and increases as the absolute value increases, and the current increases or increases. As the absolute value approaches 0 [A] and decreases, the current decreases or decreases. That's it.

Further, the control target value of the secondary current I2 in the period from the time t3 to t4 when the energy input period signal IGW is output is defined as “maintenance target current value I2 ^* ”. The maintenance target current value I2 ^* is set to a current value at which the discharge can be satisfactorily maintained according to the operation region determined from the engine load and the rotational speed. In this embodiment, the wavy maximum value is set as the target value. However, in other embodiments, an intermediate value between the wavy maximum value and the minimum value may be set as the target value, or the minimum value may be set as the target value.

  When the ignition signal IGT rises to the H (high) level at time t1, the ignition switch 45 is turned on. At this time, since the energy input period signal IGW is at the L (low) level, the discharge switch 57 is turned off. Thereby, the primary current I1 is passed through the primary coils 411, 421, and 431.

Further, while the ignition signal IGT rises to the H level, the rectangular wave pulse-shaped charging switch signal SWc is input to the gate of the charging switch 53. As a result, the capacitor voltage Vdc rises stepwise during the off period after the charging switch 53 is turned on.
In this manner, the ignition coils 410, 420, and 430 are charged during the time t1 to t2 when the ignition signal IGT rises to the H level, and energy is stored in the capacitor 56 by the output of the DCDC converter 51. This energy storage is completed by time t2.
The capacitor voltage Vdc, that is, the amount of energy stored in the capacitor 56 can be controlled by the on-duty ratio of the charge switch signal SWc and the number of on / off times.

After that, when the ignition signal IGT falls to the L level at time t2 and the ignition switch 45 is turned off, the primary current I1 that has been energized to the primary coils 411, 421, and 431 is suddenly cut off. Then, a voltage is generated in the primary coil due to the self-dielectric action, and at the same time, a high voltage is generated in the secondary coils 412, 422, 432 sharing the magnetic circuit and the magnetic flux due to the mutual induction action, and between the electrodes of the spark plug 7. Discharge occurs at. When discharge occurs, a secondary current I2 flows.
When energy is not input after the discharge is generated at time t2, the secondary current I2 approaches 0 [A] with the passage of time as shown by the broken line, and the discharge ends when the discharge is attenuated to the extent that the discharge cannot be maintained. . Such an ignition system by discharge is called “normal ignition”.

  On the other hand, in the present embodiment, the energy input period signal IGW rises to H level at time t3 immediately after time t2, so that the discharge switch 57 is turned on while the charge switch 53 is off. As a result, the energy accumulated in the capacitor 56 is released and supplied to the ground side of the primary coils 411, 421, 431. Thereby, “primary current I1 resulting from input energy P” is energized during discharge. The input energy P increases as the capacitor voltage Vdc stored up to time t2 increases.

At this time, the secondary coils 412, 422, and 432 have an additional secondary current accompanying the energization of the primary current I 1 caused by the input energy P with respect to the secondary current I 2 that was energized between the times t 2 and t 3. I2 is superimposed with the same polarity. The superimposition of the secondary current I2 is performed every time the discharge switch 57 is turned on between time t3 and time t4.
That is, every time the discharge switch signal SWd is turned on, the primary current I1 is sequentially added by the energy accumulated in the capacitor 56, and the secondary current I2 is sequentially added correspondingly. Thereby, the secondary current I2 is maintained so as to coincide with the maintenance target current value I2 ^* .
When the energy input period signal IGW falls to L level at time t4, the on / off operation of the discharge switch signal SWd stops, and both the primary current I1 and the secondary current I2 become zero.

Thus, after the discharge at time t2, a control method in which energy is input to the ignition coils 410, 420, 430 from “the ground side of the primary coils 411, 421, 431” is referred to as “energy input control” in this specification. .
On the other hand, as in a well-known multiple discharge method, a method in which energy is input to the battery 6 side of the primary coils 411, 421, 431, or an ignition coil 410, A method of supplying energy to 420 and 430 is collectively referred to as a “conventional multiple discharge method”. Compared to the “conventional multiple discharge method”, the “energy input control” described above, by supplying energy from the low voltage side, efficiently supplies the minimum energy that can continue the discharge while maintaining the discharge arc. Can be maintained for a certain period of time.

[Features of this embodiment]
By the way, the ECU 32 can set the operation region from the load and the rotational speed of the engine 13 and change the maintenance target current value I2 ^* accordingly. Further, the ECU 32 can change the maintenance target current value I2 ^* even when the combustion state fluctuates due to a change in the operating state or a change in environmental conditions such as temperature during the lean combustion state operation. Thereby, the ignition device 30 can prevent misfire and maintain good drivability.

However, if the peak current when the discharge of the spark plug 7 is generated by the operation of the ignition switch 45 is always constant, the energy is wasted if an excessive peak current flows with respect to the operating state of the engine 13. May be. Moreover, since the wasteful consumption energy is generated, the fuel consumption is deteriorated, and there is a concern that the service life of the electrode portion of the spark plug 7 is shortened.
Therefore, in the ignition device 30 of the present embodiment, the parallel determination circuit 60 turns on or off energization of any of the three ignition coils 410, 420, and 430 according to the maintenance target current value I2 ^*. And Thereby, this ignition device 30 can suppress the loss of energy unnecessary for discharge.

Hereinafter, the ignition control process performed by the ignition device 30 of the present embodiment will be described with reference to the flowchart of FIG. In FIG. 4, the step is indicated as “S”.
This process is started when the engine 13 is driven.
First, in step 10, the ECU 32 sets an operation region by referring to a map stored in the ECU 32 from the load and the rotational speed of the engine 13.
Next, in step 11, a maintenance target current value I2 ^* suitable for the operation region set in step 10 is determined.

Subsequently, in step 12, the parallel determination circuit 60 adds a predetermined value α to the maintenance target current value I2 ^* , and calculates a peak current value necessary for starting discharge in the operation region. Here, the predetermined value α is a value obtained by subtracting the maintenance target current value I2 ^* from the target peak current value necessary for starting discharge in the operation region. The processing of the parallel determination circuit 60 corresponds to an example of “target peak current value detection means” described in the claims.

Next, the parallel determination circuit 60 compares the peak current value that can be output by one ignition coil with a value obtained by adding a predetermined value α to the maintenance target current value I2 ^* .
If the peak current value that can be output by one ignition coil is greater than or equal to the maintenance target current value I2 ^* plus a predetermined value α (step 12: YES), the process proceeds to step 13 To do.
In step 13, the parallel determination circuit 60 turns off the first switch 61 and the second switch 62 and discharges the spark plug 7 with only one ignition coil 420.
On the other hand, when the peak current value that can be output by one ignition coil is smaller than the value obtained by adding the predetermined value α to the maintenance target current value I2 ^* (step 12: NO), the process proceeds to step 14.

In step 14, the parallel determination circuit 60 compares the peak current value that can be output by the two ignition coils with a value obtained by adding a predetermined value α to the maintenance target current value I2 ^* . If the peak current value that can be output by the two ignition coils is greater than or equal to the maintenance target current value I2 ^* plus a predetermined value α (step 14: YES), the process proceeds to step 15 To do.
In step 15, the parallel determination circuit 60 turns on the first switch 61, turns off the second switch 62, and discharges the spark plug 7 with the two ignition coils 410 and 420.
On the other hand, when the peak current value that can be output by the two ignition coils is smaller than the value obtained by adding the predetermined value α to the maintenance target current value I2 ^* (step 14: NO), the process proceeds to step 16.
In step 16, the parallel determination circuit 60 turns on the first switch 61 and the second switch 62, and discharges the spark plug 7 with the three ignition coils 410, 420, and 430.

In the steps 12 and 14 described above, the process in which the parallel determination circuit 60 determines the number of ignition coils used for discharging the spark plug 7 corresponds to an example of the “ignition coil number determination means” described in the claims. .
Further, in the above-described steps 13, 15 and 16, the process of turning on or off the first switch 61 or the second switch 62 in accordance with the number of ignition coils used by the parallel determination circuit 60 for discharging the spark plug 7 Corresponds to an example of the “switch switching means” recited in the claims.

Subsequently, in step 17, the current maintenance signal determination circuit 70 compares the current value measured by the secondary current detection circuit 48 with the maintenance target current value I2 ^* . When the measured current value is larger than the maintenance target current value I2 ^* (step 17: YES), the process proceeds to step 18. In step 18, the current maintenance signal determination circuit 70 turns off the discharge switch 57 via the discharge switch driver circuit 58. Subsequently, in step 20, the current maintenance signal determination circuit 70 detects whether or not the discharge period has passed the energy input period. If the discharge period has not passed the energy input period (step 20: NO), the process returns to step 17.
In step 17, when the measured current value is smaller than the maintenance target current value I2 ^* (step 17: NOS), the process proceeds to step 19. In step 19, the current maintenance signal determination circuit 70 continuously drives the discharge switch 57 on and off via the discharge switch driver circuit 58. Subsequently, in step 20, when the discharge period has passed the energy input period, the process ends.

Next, the time change of the secondary current I2 when the number of ignition coils to be used is changed according to the maintenance target current value I2 ^* will be described with reference to FIG.
FIG. 5A shows a time change of the secondary current I2 when three ignition coils are used, and FIG. 5B shows a time change of the secondary current I2 when two ignition coils are used. FIG. 5C shows the change over time in the secondary current I2 when three ignition coils are used.

The maintenance target current value I2 ^* set by the ECU 32 in accordance with the operation region of the engine 13 is the largest in FIG. 5A and is smaller in the order of FIGS. 5B and 5C. Therefore, in FIG. 5 (A), three ignition coils are used for ignition discharge, in FIG. 5 (B), two ignition coils are used, and in FIG. 5 (C), one ignition coil is used. . Since the secondary current I2 is added according to the number of ignition coils used, the peak current at the start of discharge is the largest in FIG. 5 (A) and is smaller in the order of FIG. 5 (B) and FIG. 5 (C). Thereby, the ignition device 30 can reduce the waste of energy by flowing a peak current corresponding to the operation region of the engine 13.

In addition, when there is no energy input by the energy input unit 50, the base waveform of the current flowing through the spark plug 7 only by the operation of the ignition switch 45 is shown by a broken line. The period β during which this base waveform continues does not change depending on the number of ignition coils used. Therefore, in the ignition device 30, the energy input unit 50 starts to input energy from time t <b> 2 when the spark plug 7 starts discharging by using the plurality of ignition coils 410, 420, and 430 having a small peak current that can be output. It is possible to shorten the time until time t3. Thereby, the ignition device 30 can shorten the time during which the secondary current I2 larger than the maintenance target current value I2 ^* flows through the spark plug 7.

  Furthermore, as described above, the period β during which the base waveform continues does not change depending on the number of ignition coils 410, 420, and 430 used. Therefore, the ignition device 30 uses the plurality of ignition coils 410, 420, and 430 having a short base waveform duration β to set the base waveform duration β before the time t4 when the energy input period ends. It can be terminated.

[Comparative example]
Here, the time change of the secondary current I2 in the ignition device of the comparative example is shown in FIG. The ignition device of the comparative example includes only one ignition coil. The peak current that can be output by one ignition coil included in the comparative example corresponds to the peak current that is a combination of the three ignition coils 410, 420, and 430 of the present embodiment. In this case, the duration γ of the base waveform of the ignition coil of the comparative example is longer than the duration β of the base waveform of the ignition coil of the present embodiment.
Since the ignition device of the comparative example cannot change the peak current, energy may be wasted when the peak current required for starting discharge is small depending on the operation region of the engine 13.
In the ignition device of the comparative example, when the maintenance target current value I2 ^* is low due to the operation region of the engine 13, it takes time until the base waveform decreases to the maintenance target current value I2 ^* . Therefore, the time from the time t2 when the spark plug 7 starts discharging to the time t3 when the energy input unit 50 starts to input energy may become longer. Therefore, in the ignition device of the comparative example, the time during which the secondary current I2 larger than the maintenance target current value I2 ^* flows through the spark plug 7 becomes long, and energy may be wasted.
Further, in the ignition device of the comparative example, the base waveform remains even after time t4 when the energy input period ends, and energy may be wasted.

[Operational effects of this embodiment]
On the other hand, the ignition device 30 of this embodiment has the following effects.
(1) In the present embodiment, the parallel determination circuit 60 turns on or off energization of any of the plurality of ignition coils 410, 420, and 430 according to the maintenance target current value I2 ^* .
Thereby, the ignition device 30 can reduce the waste of energy without causing a peak current more than necessary to flow in the operating state of the engine 13 by bringing the maintenance target current value I2 ^* and the peak current value closer to each other. .
Moreover, the ignition device 30 can shorten the time from the start of discharge until the energy input unit 50 inputs energy. Therefore, the time during which a current larger than the maintenance target current value I2 ^* flows through the spark plug 7 can be shortened.
Furthermore, the ignition device 30 includes a plurality of ignition coils 410, 420, and 430 having a small peak current that can be output, thereby shortening the time when the base waveform ends. Therefore, it is suppressed that the base waveform remains after the energy input period by the energy input unit 50 ends.
Therefore, the ignition device 30 can suppress a loss of energy unnecessary for discharge and improve fuel efficiency. Furthermore, the ignition device 30 can suppress wear of the electrode portion of the spark plug 7 due to excessive energy input, and can extend the useful life of the spark plug 7.

(2) In the present embodiment, the ignition device 30 includes the first switch 61 that turns on or off the primary coil 411 included in the first ignition coil 410 based on the signal from the parallel determination circuit 60, and the third ignition coil. A second switch 62 is provided to turn on or off energization of the primary coil 431 included in 430.
Thereby, the number of switches 61 and 62 can be reduced compared with providing a switch in all the three primary coils. Further, the ignition device 30 can always be discharged by the second ignition coil 420 provided with no switch.

(3) In the present embodiment, the parallel determination circuit 60 detects the target peak current value according to the maintenance target current value I2 ^* , and allows the secondary current I2 equal to or greater than the target peak current value to flow to the spark plug 7. The number of possible ignition coils is determined, and the first switch 61 or the second switch 62 is turned on or off.
Thereby, energy loss can be reduced without supplying the secondary current I2 larger than the target peak current value required for the operating state of the engine 13 to the spark plug 7.

(4) In the present embodiment, the duration β of the base waveform of the ignition coils 410, 420, 430 is shorter than the energy input period by the energy input unit 50.
Thereby, since the base waveform is suppressed from remaining after time t4 when the energy input period ends, energy loss can be reduced.

(5) In the present embodiment, only one ignition switch 45 is provided in the wiring on the ground side of the three primary coils 411, 421, 431.
Thereby, the primary current I1 which flows into the three primary coils 411,421,431 can be interrupted | blocked simultaneously.

(Other embodiments)
(A) In the above embodiment, the secondary current I2 is maintained at the maintenance target current value I2 ^* by the energy input control by the energy input unit 50. On the other hand, in another embodiment, the secondary current I2 is changed to the maintenance target current value I2 ^* by the conventional multiple discharge method or the “DCO (Dual Coil Offset) method” disclosed in Japanese Patent Application Laid-Open No. 2012-167665. May be maintained.

  (A) In the above embodiment, the energy input control by the energy input unit 50 is performed after the charge switch signal SWc is turned on and off during the H level of the ignition signal IGT and the capacitor voltage Vdc is accumulated, as shown in FIG. Energy was input to the ground side of the primary coils 411, 421, 431 during the energy input period. On the other hand, in other embodiments, for example, the charge switch signal SWc and the discharge switch signal SWd are alternately turned on / off during the energy input period, whereby the energy storage coil 52 is stored when the charge switch signal SWc is on. The energy may be input to the ground side of the primary coils 411, 421, 431 each time. In that case, the capacitor 56 may not be provided.

(C) In the above embodiment, the current maintenance signal determination circuit 70 performs feedback control so that the secondary current I2 detected by the secondary current detection circuit 48 matches the maintenance target current value I2 ^* . On the other hand, in another embodiment, for example, the secondary current I2 may be feedforward controlled without including the current maintenance signal determination circuit 70.

(D) In other embodiments, the ignition circuit unit 31 may be housed in a case housing the ECU, or may be housed in a case housing the ignition coil.
(E) In other embodiments, the ignition switch 45 and the energy input unit 50 may be housed in separate cases. For example, the ignition switch may be accommodated in a case that accommodates the ignition coil, and the energy input unit may be accommodated in the case that accommodates the ECU.

(F) The ignition switch is not limited to the IGBT, and may be composed of another switching element having a relatively high breakdown voltage. Further, the charge switch 53 and the discharge switch 57 are not limited to MOSFETs, and may be configured by other switching elements.
(G) The DC power supply is not limited to the battery 6 and may be constituted by a DC stabilized power supply or the like in which the AC power supply is stabilized by a switching regulator or the like.

  (H) In the above embodiment, the energy input unit 50 boosts the voltage of the battery 6 by the DCDC converter 51. On the other hand, in other embodiments, when the ignition device 30 is mounted on a hybrid vehicle or an electric vehicle, the output voltage of the main battery may be used as input energy as it is or after being stepped down.

  (K) In the above embodiment, the ground side wirings of the primary coils 411, 421, 431 of the three ignition coils 410, 420, 430 are connected, and one ignition switch 45 is connected to the ground side from the connection point. Was provided. On the other hand, in another embodiment, three ignition switches may be provided for each of the ground-side wirings of the primary coils of the three ignition coils. Then, the parallel determination circuit 60 may be configured to simultaneously drive the three ignition switches on and off.

  (E) In the above embodiment, the ignition device 30 includes the three ignition coils 410, 420, and 430. On the other hand, in other embodiments, the ignition device may include two or four or more ignition coils.

(S) In the above embodiment, in step 12, the parallel determination circuit 60 adds the predetermined value α to the maintenance target current value I2 ^* , and calculates the peak current value necessary for starting discharge in the operation region. On the other hand, in other embodiments, the parallel determination circuit 60 may directly calculate the target peak current value necessary for starting discharge in the operation region from the operating state of the engine. In this case, in the description of steps 13 and 14 of the first embodiment, “the value obtained by adding the predetermined value α to the maintenance target current value I2 ^* ” is read as “the target peak current value calculated from the engine operating state”. And
Thus, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the invention.

7 ... Spark plug 30 ... Ignition device 32 ... ECU (setting means)
45 ... Ignition switch 50 ... Energy input unit (energy input means)
60 ... Parallel determination circuit 410 ... first ignition coil 420 ... second ignition coil 430 ... third ignition coil

Claims (4)

An ignition device (30) for controlling the operation of a spark plug 7 for spark discharge to an air-fuel mixture of an internal combustion engine (13),
A primary coil (411, 421, 431) through which a primary current (I1) supplied from a DC power source (6) flows, and the primary current flowing through the primary coil connected to the electrode of the spark plug are induced and cut off. A plurality of primary coils (410, 420, 430) having secondary coils (412, 422, 432) through which secondary current (I2) flows. A plurality of ignition coils that are connected in parallel and a plurality of the secondary coils are connected in parallel;
An ignition switch (45) connected to a ground-side wire that is the anti-DC power supply side of the plurality of primary coils, and switching between energization and interruption of the primary current according to an ignition signal;
The plurality of primary coils so that a secondary current that continues to discharge during a predetermined energy input period after the discharge of the spark plug electrode by the interruption of the primary current by the ignition switch flows to the spark plug electrode. Energy input means (50) capable of supplying energy to
Setting means (32) for setting a maintenance target current value (I2 ^* ) as a target value of the secondary current flowing through the electrode of the spark plug when the energy input means inputs energy in accordance with the operating state of the internal combustion engine. )When,
A parallel determination circuit (60) for turning on or off energization of any of the plurality of ignition coils in accordance with the maintenance target current value set by the setting means;
Based on the signal of the parallel determination circuit, a switch (61, 61) that can turn on or off the energization of the primary coil of the other ignition coils except for one of the plurality of ignition coils. 62)
An ignition device comprising: The parallel determination circuit includes:
A target peak current value required to start discharge of the spark plug by the operation of the ignition switch is set according to the maintenance target current value set by the setting means or based on the operating state of the internal combustion engine. Current value detection means (S12);
Ignition coil number determination means (S12, S14) for determining the number of ignition coils that can cause a secondary current greater than the target peak current value detected by the target peak current value detection means to flow to the electrode of the spark plug. When,
2. The ignition device according to claim 1 , further comprising switch switching means (S <b> 13, S <b> 15, S <b> 16) for turning on and off the switch according to the number of ignition coils determined by the ignition coil number determination means. . 3. The ignition device according to claim 1, wherein a continuation period (β) of the discharge of the ignition plug by only the operation of the ignition switch is shorter than an energy input period by the energy input unit. The ignition device according to any one of claims 1 to 3 , wherein only one ignition switch is provided on a ground-side wiring that is an anti-DC power supply side of the plurality of primary coils.

Images