JP6384097B2 - 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 for an internal combustion engine that generates electric discharge between electrodes of a spark plug and ignites an air-fuel mixture is known. In general, during the operation in the lean combustion state in the high rotation and high load region, the ignition state of the air-fuel mixture due to the discharge of the spark plug may fluctuate due to a change in the operation state or a change in environmental conditions such as temperature. . If the ignition state is poor, the ignition may not occur even when the discharge period ends, that is, misfire may occur.
Therefore, for example, the control device for an internal combustion engine disclosed in Patent Document 1 measures the discharge time by the spark plug, and switches to the stoichiometric operation when the ignition discharge time is shorter than the discharge time threshold required for the lean operation. To avoid misfire.

Japanese Patent No. 4938404

  In the prior art of Patent Document 1, it is possible to avoid the occurrence of misfires in the combustion cycles after the measured combustion cycle. However, when the ignition state is good, for example, when ignition is performed at an early stage of the combustion cycle, it is not considered that waste of energy is generated due to the discharge in the combustion cycle continuing after ignition.

  The present invention has been made in view of the above-described points, and its object is to immediately respond to the ignition state of the combustion cycle within the same cycle, eliminate waste of energy consumption, and ensure ignitability. It is to provide a possible ignition device.

The present invention is an ignition device that controls the operation of an ignition plug that ignites an air-fuel mixture in a combustion chamber of an internal combustion engine, and includes an ignition coil, an ignition switch, energy input means, input energy control means, and ignition determination means.
The ignition coil has a primary coil through which a primary current supplied from a DC power source flows, and a secondary coil that is connected to an electrode of the spark plug, generates a secondary voltage by energization and interruption of the primary current, and flows through the secondary current. .
The ignition switch is connected to a ground side that is opposite to the DC power source of the primary coil, and switches between conduction and interruption of the primary current according to the ignition signal.

The energy input means is capable of supplying energy to the ignition coil in a predetermined energy input period after the primary current is interrupted by the ignition switch and discharge of the spark plug is generated by the voltage generated by the interruption.
The ignition determination means acquires information from an ignition detector that detects ignition of the air-fuel mixture in the combustion chamber, and determines whether or not the air-fuel mixture has ignited based on the information.
Connected to the ground side of the primary coil is a rectifying element that cuts off the current flowing toward the ground and flows the current from the ground toward the ground side of the primary coil.
The energy input means includes a capacitor for storing energy, and a discharge switch provided between the capacitor and the ground side of the primary coil, and the discharge switch is in a state where the ignition switch is cut off during the energy input period. By turning on, energy stored in the capacitor can be superimposed on the ignition coil in the same polarity as the secondary current from the ground side of the primary coil. The energy input means is characterized in that when it is determined that the air-fuel mixture has ignited within the energy input period, the energy input means stops the energy input during the energy input period.

  In the present invention, it is possible to respond immediately within the same cycle according to the ignition state of the combustion cycle. Specifically, when the air-fuel mixture is ignited within the energy input period, energy input is stopped within the same period, so that waste of input energy can be eliminated.

Further, when it is determined that the air-fuel mixture has not ignited continuously within the energy input period in one combustion cycle, the ignition device of the present invention extends the energy input period or increases the energy input target value. Of these, input energy control means for performing at least one of them is further provided.
According to the present invention, when the air-fuel mixture does not ignite within the energy input period, the ignitability can be ensured because the energy input control conditions are changed within the same period.

1 is a schematic configuration diagram showing an engine system to which an ignition device according to an embodiment of the present invention is applied. It is a block diagram which shows the ignition device by one Embodiment of this invention. It is a time chart explaining the basic operation | movement of the ignition device of FIG. It is a flowchart explaining an ignition determination process. It is a time chart explaining operation | movement at the time of performing an ignition determination process.

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 of the embodiment, 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. As shown in FIG. 1, 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).
It is assumed that the engine system 10 of FIG. 1 does not have an EGR (exhaust gas recirculation) system. Alternatively, even when an EGR system is provided, the illustration is omitted because the relevance to the feature of the present embodiment is low. Further, illustration of the catalyst provided in the exhaust passage is also omitted.

  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 the crankshaft 19 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 intake valve 22 and the exhaust valve 23 are opened and closed by a valve drive mechanism 24. The valve timing of the intake valve 22 is adjusted by the variable valve mechanism 25.

  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 spark plug 7 has a pair of electrodes (see FIG. 2) facing each other with a predetermined gap in the combustion chamber 17 of the engine 13, and a high voltage sufficient to cause dielectric breakdown in the gap is between the pair of electrodes. When applied to, it generates a discharge. The electric discharge generated in the spark plug 7 becomes an electric spark and ignites the air-fuel mixture, and the air-fuel mixture burns. The ignition device 30 operates the ignition circuit unit 31 based on a command from the electronic control unit 32 and applies a high voltage from the ignition coil 40 to the ignition plug 7, thereby generating a discharge in the ignition plug 7. In the following description, “high voltage” refers to a voltage that can cause discharge between a pair of electrodes of the spark plug 7.

The electronic control unit 32 is configured by a microcomputer including a CPU, a ROM, a RAM, an input / output port, and the like, and is represented as “ECU” in the drawing. As shown in FIG. 2, for convenience of explanation, the electronic control unit 32 is functionally divided into an ignition control unit 33 and an engine control unit 34. However, this does not mean an actual physical division or arrangement.
The ignition control unit 33 corresponds to “input energy control means” described in the claims. The ignition control unit 33 in the embodiment is referred to as an “ignition control unit” because it includes not only control of input energy but also a function of generating an ignition signal IGT.

  1, the electronic control unit 32 receives detection signals from various sensors such as a crank position sensor 35, a cam position sensor 36, a water temperature sensor 37, a throttle opening sensor 38, and an intake pressure sensor 39. Entered. Based on detection signals from these various sensors, the electronic control unit 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 an ignition coil 40, an ignition circuit unit 31, and an ignition control unit 33 of an electronic control unit 32.

The ignition coil 40 includes a primary coil 41, a secondary coil 42, and a rectifying element 43, and constitutes a known step-up transformer.
One end of the primary coil 41 is 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 is grounded via an ignition switch 45. Hereinafter, the opposite side of the primary coil 41 from the battery 6 is referred to as a “ground side”.
The secondary coil 42 is magnetically coupled to the primary coil 41, one end is grounded via a pair of electrodes of the spark plug 7, and the other end is connected via a rectifier element 43 and a secondary current detection resistor 47. Is grounded.

A current flowing through the primary coil 41 is referred to as a primary current I1, and a current generated by increasing or decreasing the primary current I1 and flowing through the secondary coil 42 is referred to as a secondary current I2. As indicated by the arrows in the figure, the primary current I1 is positive in the direction from the primary coil 41 to the ignition switch 45, and the secondary current I2 is the current in the direction from the secondary coil 42 to the spark plug 7. Positive. The voltage on the spark plug 7 side of the secondary coil 42 is referred to as a secondary voltage.
The rectifying element 43 is composed of a diode and rectifies the secondary current I2.
The ignition coil 40 generates a high voltage in the secondary coil 42 by a mutual induction action of electromagnetic induction in accordance with a change in the current flowing through the primary coil 41, and applies this high voltage to the ignition plug 7. In the present embodiment, one ignition coil 40 is provided for one ignition plug 7.

  The ignition circuit unit 31 includes an ignition switch (igniter) 45, a secondary current detection resistor 47, a secondary current detection circuit 48, and an energy input unit 50. The ignition circuit unit 31 includes an ignition determination circuit 72 that is a characteristic configuration of the present invention.

The ignition switch 45 is composed of, for example, an IGBT (insulated gate bipolar transistor), and has a collector connected to the ground side of the primary coil 41 of the ignition coil 40, an emitter grounded, and a gate connected to the electronic control unit 32. Yes. The emitter is connected to the collector via the rectifying element 46.
The ignition switch 45 is turned on / off according to an ignition signal IGT input 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 in the primary coil 41 is switched between conduction and interruption by the ignition switch 45 in accordance with the ignition signal IGT.
The secondary current detection circuit 48 detects the secondary current I <b> 2 based on the voltage across the secondary current detection resistor 47.

  The energy input unit 50 as “energy input means” includes an energy storage coil 52, a charge switch 53, a charge switch driver circuit 54, and a DCDC converter 51 including a rectifier element 55, a capacitor 56, a discharge switch 57, It has a discharge switch driver circuit 58 and a rectifying element 59.

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 output the charge switch signal SWc and drive the charge 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, a 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.

  The capacitor 56 has one electrode connected to the ground side of the energy storage coil 52 via the rectifying element 55 and the other electrode grounded. Capacitor 56 stores the voltage boosted by DCDC converter 51. The voltage stored in the capacitor 56 is referred to as “capacitor voltage Vdc”.

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 coil 41, and the gate is connected to the driver circuit 58. The driver circuit 58 outputs the discharge switch signal SWd in accordance with the energy input period signal IGW and the target secondary current signal IGA input to the gate, and 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 ignition coil 40 to the capacitor 56.
Although only the configuration for one cylinder is shown in FIG. 2, in reality, the configuration after the discharge switch 57 is provided in parallel for the number of cylinders, and the current path is provided for each cylinder before the discharge switch 57. The energy stored in the capacitor 56 is distributed to each path.

The ignition determination circuit 72 as “ignition determination means” determines whether or not the air-fuel mixture has ignited based on information from the ignition detector 71 provided in the combustion chamber 17, and sends the ignition determination signal IGJ to the electronic control unit. 32. The ignition detector 71 is a means for acquiring information related to the ignition of the air-fuel mixture in the combustion chamber 17. For example, an optical sensor that detects light generated by the ignition, or when the air-fuel mixture ignites and burns. An ion probe or the like that detects an ionic current flowing between electrodes by a flame can be used. For example, when the detection value (detection value of light, ion current, etc.) by the ignition detector 71 exceeds a threshold value, the ignition determination circuit 72 determines that the air-fuel mixture is ignited.
The above is the configuration of the ignition circuit unit 31.

  Next, the ignition control unit 33 of the electronic control unit 32 generates the ignition signal IGT and the energy input period signal IGW based on the operation information of the engine 13 acquired from various sensors such as the crank position sensor 35, and the ignition circuit unit. To 31.

  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 at the H (high) level. 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 while the ignition signal IGT is at the H (high) level.

  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 at the H (high) level.

Further, the ignition control unit 33 generates a target secondary current signal IGA for instructing a target value of the secondary current I2 (hereinafter referred to as “target secondary current I2 ^* ”) and inputs the target secondary current signal IGA to the driver circuit 58. The target secondary current I2 ^* is set to a current that can favorably maintain the ignition discharge.

  Further, the ignition control unit 33 checks the ignition determination signal IGJ from the ignition determination circuit 72 during the energy input period IGW, and if the signal indicating that the air-fuel mixture has ignited has not been detected, the ignition control unit 33 sets the ignition failure count m. Count. The ignition determination signal IGJ is checked during the ignition operation of one stroke, for example, at substantially constant time intervals or at substantially constant crank angles.

[Ignition device operation]
Next, the operation of the ignition device 30 will be described with reference to the time chart of FIG.
There are the following two methods for changing the current flowing through the primary coil 41 in order to generate a high voltage in the secondary coil 42. The first is a method in which energization from the battery 6 to the primary coil 41 is interrupted by the ignition switch 40, and the second is a method in which energy is input from the ground side of the primary coil 41 by the energy input unit 50.
The operation of the ignition device 30 described below is based on a control method in which the discharge of the spark plug 7 is started by the first method and then the discharge is sustained by the second method. Was developed by the present applicant. Hereinafter, when simply referred to as “energy input control” in the present specification, this control method is meant. Here, first, an outline of operation by basic energy input control as a comparative example will be described, and features of the present embodiment will be described in detail later.

  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 charge switch signal SWc, the discharge switch signal SWd, the capacitor voltage Vdc, and the primary current I1 are shown in order from the top on the vertical axis. The time change of the secondary current I2 is shown.

  In FIG. 3, “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.

  First, 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 off. Thereby, energization of the primary current I1 in the primary coil 41 is started.

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. Then, the capacitor voltage Vdc rises stepwise during the off period after the charging switch 53 is turned on.
In this manner, the ignition coil 40 is charged and energy is accumulated in the capacitor 56 by the output of the DCDC converter 51 during the time t1 to t2 when the ignition signal IGT rises to the H level. This energy storage is completed by time t2.
At this time, the capacitor voltage Vdc, that is, the energy storage amount of the capacitor 56 can be controlled by the on-duty ratio and the number of on-off times of the charge switch signal SWc.

  Thereafter, 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 coil 41 until then is suddenly cut off. Then, an electromotive force larger than that of the battery 6 is generated in the primary coil 41, and a large secondary voltage is generated in the secondary coil 42. As a result, a high voltage is applied from the ignition coil 40 to the spark plug 7, a discharge is generated in the spark plug 7, and a secondary current I2 flows.

  Thereafter, if the energy input control is not performed, the secondary current I2 approaches 0 [A] as time passes, and the discharge ends when the discharge is attenuated to such an extent that the discharge cannot be maintained.

  On the other hand, in the energy input control, the energy input period signal IGW is raised to H level at time t3 immediately after time t2, the charge switch signal SWc is off, and the rectangular wave pulsed discharge switch signal SWd is Input to the discharge switch 57. Thereby, the discharge switch 57 is repeatedly turned on and off while the charge switch 53 is off.

Then, during the ON period of the discharge switch 57, the stored energy of the capacitor 56 is released and supplied to the ground side of the primary coil 41. At this time, the secondary coil 42 has the same polarity with respect to the secondary current I2 that has been energized so far, with the addition of the secondary current I2 that is caused by the energization of the primary current I1 caused by the input energy from the capacitor 56 having the same polarity. Superimposed. When the secondary current I2 reaches a predetermined value, the discharge switch 57 is turned off, the energization of the primary coil 41 is stopped, and the secondary current I2 decreases. When the secondary current I2 drops to a predetermined value, the discharge switch 57 is turned on again, and the current is superimposed on the secondary current I2. This superposition is repeated every time the discharge switch 57 is turned on during time t3-t4. Thereby, the secondary current I2 is maintained so as to coincide with the target secondary current I2 ^* .

Hereinafter, a period in which the energy input period signal IGW is at the H level, that is, a period in which the discharge is sustained by the energy input is referred to as an “energy input period IGW” using the same symbol. Further, in this embodiment, the intermediate value between the wavy maximum value and the minimum value of the secondary current I2 in the energy input period IGW is set as the target secondary current I2 ^* , but the maximum value or the minimum value may be set as the target value. Good.

  When the energy input period signal IGW falls to the L level at time t4, the discharge switch signal SWd remains off, and the on / off operation of the discharge switch 57 stops. Thereby, both the primary current I1 and the secondary current I2 become zero.

  In such energy input control, it is possible to maintain a ignitable state for a certain period while efficiently supplying the minimum energy by inputting energy from the low voltage side as compared with the conventional multiple discharge method or the like. .

[Ignition judgment processing]
In general, during operation in a lean combustion state in a high rotation and high load region, the ignition state of the air-fuel mixture due to the discharge of the spark plug 7 may fluctuate due to changes in the operating state and environmental conditions such as temperature. Specifically, there are cases where the ignition state is good and ignition is performed at an early stage of the energy input period IGW, or on the contrary, the ignition state is poor and ignition does not occur even when the energy input period IGW ends, resulting in misfire.

  Therefore, the ignition device 30 of the present embodiment is characterized in that it performs energy input control in accordance with the ignition state of the air-fuel mixture based on information from the ignition detector 71 that detects the ignition of the air-fuel mixture in the combustion chamber 17. Have.

  Below, the ignition determination process of this embodiment is demonstrated with reference to the flowchart of FIG. The ignition determination process of the present embodiment is executed for each combustion cycle by the ignition control unit 33. The initial value of the number of ignition failures m is zero.

In the description of the flowchart below, the symbol “S” means a step.
First, it is determined whether or not an energy input operation has been started (S1) and whether or not an energy input operation is being performed (S2). If any of them is NO, the process ends. When the energy input operation is started (S1: YES) and the energy input operation is being performed (S2: YES), the process proceeds to S3.

  In S3, the ignition determination signal IGJ from the ignition determination circuit 72 is checked, and it is determined whether or not the air-fuel mixture is ignited based on the information. If it is determined that the air-fuel mixture is not ignited, the process proceeds to S4, and if it is determined that the mixture is ignited, the process proceeds to S9.

In S4, when the air-fuel mixture is determined not to be ignited (S3: NO), the ignition failure count m is counted up.
Thereafter, in S5, it is determined whether or not the ignition failure count m is N or more. N is, for example, an arbitrary number set as a reference for determining that the ignition failure due to the spark plug 7 is not accidental but is due to apparent lack of spark energy.

When the number of ignition failures m is N or more (S5: YES), the process proceeds to S6. In S6, the target secondary current I2 ^* is increased to increase the spark energy, and / or the energy input time IGW is extended. Thereafter, in S7, the ignition failure count m is initialized.
When the number of ignition failures m is less than N (S5: NO), the process proceeds to S8 as it is.

In S8, information from the crank position sensor 35 is acquired, and it is determined whether or not the current crank position exceeds a predetermined position. The predetermined position is, for example, a position where the piston position has reached the vicinity of bottom dead center and cannot contribute to engine output even when ignited. When it is determined that the current crank position exceeds the predetermined position (S8: YES), the process proceeds to S9.
If it is determined that the current crank position does not exceed the predetermined position (S8: NO), the process returns to S3 and the ignition determination is performed again.

When it is determined that the air-fuel mixture is ignited (S3: YES), or when it is determined that the current crank position exceeds the predetermined position (S8: YES), the ignition control unit 33 lowers the energy input signal IGW to L level. As a result, the discharge switch 57 is turned off, and energy input from the capacitor 56 to the ignition coil 40 is stopped.
Thereafter, in S10, the ignition failure count m is initialized.
Thus, the ignition determination process ends.

Note that in the above-described ignition determination process, the engine 13 is selected as to which one or both of the ignition determination cycle, the target secondary current I2 ^* increase and the energy input period IGW are extended. Judgment may be made based on the operating conditions. The ignition determination cycle can be easily set by adding waiting time control using a fixed time timer while returning from S8 to S3, and is performed, for example, at approximately constant time intervals or approximately constant crank angles.

In addition, if ignition is not detected even when the energy input control conditions are corrected by increasing the target secondary current I2 ^* and extending the energy input period IGW, in addition to correcting these energy input control conditions. Alternatively, instead of the correction, a signal is output from the engine control unit 34 of the electronic control unit 32 to the actuator and the injector 16 of the throttle valve 14, and the air-fuel ratio is enriched by controlling the intake air amount and the fuel injection amount. May be. Furthermore, if the combustion state does not improve even if the air-fuel ratio is changed, a diagnosis signal may be output.
Further, the above-described processing is performed for each cylinder in principle. However, the configuration may be simplified and a plurality of cylinders may be controlled as a group. Moreover, you may reflect in learning control.

[Comparison]
Next, with reference to the time chart of FIG. 5, the case where the energy input control including the ignition determination process of the present embodiment is performed and the case where the basic energy input control as a comparative example is performed are compared. In FIG. 5, the waveform according to the present embodiment is indicated by a solid line, and the waveform according to the comparative example is indicated by a two-dot chain line.

  In the present embodiment, the ignition determination circuit 72 raises the ignition determination signal IGJ to the H level when it is determined that the air-fuel mixture has ignited between times t3 and t4 (for example, time tF). Then, the ignition control unit 33 immediately lowers the energy input signal IGW to the L level. As a result, the discharge switch signal SWd is turned off and the discharge switch 57 stops the on / off operation, so that the energy input to the ignition coil 40 is stopped. After the energy input is stopped, the secondary current I2 becomes zero. In FIG. 5, the energy input period IGW shortened by stopping the energy input is denoted as IGW ′.

In the present embodiment, the capacitor voltage Vdc gradually decreases immediately after time t3 in order to input energy to the ignition coil 40. However, after the energy input stops, the decrease stops, and the voltage value at that time Is retained.
On the other hand, in the comparative example, even when ignition occurs between times t3 and t4, the energy input period IGW does not change, and the capacitor voltage Vdc continues to decrease from time t3 to t4.
Therefore, in this embodiment, the energy obtained by adding the surplus energy ΔVdc to the comparative example can be held in the capacitor 56. By holding energy in the capacitor 56, charging of energy in the next combustion cycle can be started from the held value, and wasteful energy release can be eliminated.

(effect)
(1) The ignition device 30 of the present embodiment includes an ignition determination circuit 72 that determines whether or not the air-fuel mixture has ignited based on information detected by the ignition detector 71, and the air-fuel mixture is supplied to the energy input signal IGW. Is determined to have ignited, the energy input unit 50 immediately stops energy input in the same energy input signal IGW. Since the ignition state of the combustion cycle is immediately handled within the same cycle, the input energy is not wasted.

(2) When ignition in the energy input period IGW is not detected N times or more continuously in one combustion cycle, the ignition control unit 33 increases the target secondary current I2 ^* and the energy input period IGW. Implement one or both of the extensions. If the energy input period IGW is extended, the discharge duration of the spark plug 7 becomes longer, and if the target secondary current I2 ^* increases, the discharge current of the spark plug 7 becomes higher and ignition becomes easier. Therefore, when the air-fuel mixture does not ignite within the energy input period, the ignitability can be ensured because the energy input control conditions are changed within the same period.

(3) In the ignition device 30 of the present embodiment, the energy input unit 50 maintains the discharge by superimposing the electric energy on the ground side of the primary coil 41 during the generation of the discharge by the ignition switch 40. Adopted. Thereby, compared with the conventional methods such as multiple discharge, it is possible to maintain a state in which ignition is possible for a certain period while efficiently applying the minimum energy by inputting energy from the low voltage side.
Further, during the energy input period IGW, the secondary current I2 is always a negative value, and zero crossing is not performed as in other systems using an alternating current, so that blowout can be prevented.

(Other embodiments)
(A) The energy input unit 50 of the above embodiment employs a “method of inputting energy from the ground side of the primary coil” developed by the present applicant. In addition, as long as it is a method of providing an energy input period for continuing discharge as the “energy input means” of the present invention, the conventional multiple discharge method, “DCO method” disclosed in Japanese Patent Application Laid-Open No. 2012-167665, etc. By adopting a method, the continuation of discharge may be interrupted or extended as appropriate.

  (A) Further, in the above embodiment, the control condition in the “method of inputting energy from the ground side of the primary coil” developed by the present applicant is corrected according to the ignition state. In addition, as long as the secondary current or the energy input period can be variably controlled, the conventional multiple discharge method and the energy input control method such as “DCO method” disclosed in Japanese Patent Application Laid-Open No. 2012-167665 can be used. The present invention may be applied to correct the control value of the input energy by changing the number of discharges according to the ignition state, changing the power supply voltage of the coil, or the like.

  (C) As shown in FIG. 3, the energy input control by the ignition device 30 having the configuration shown in FIG. 2 is performed after the charge switch signal SWc is turned on and off to accumulate the capacitor voltage Vdc while the ignition signal IGT is at the H level. The method is not limited to the method in which energy is input to the ground side of the primary coil 41 during the period IGW. For example, by alternately turning on / off the charge switch signal SWc and the discharge switch signal SWd during the energy input period IGW, the energy accumulated in the energy accumulation coil 52 when the charge switch signal SWc is on is changed to the primary coil each time. 41 may be put on the ground side. In that case, the capacitor 56 may not be provided.

  (D) The control of the secondary current I2 is not limited to the form in which the secondary current detection resistor 47 and the secondary current detection circuit 48 are provided and the secondary current I2 is feedback-controlled as in the above embodiment. For example, the secondary current detection resistor 47 and the secondary current detection circuit 48 may not be provided, and the secondary current I2 may be feedforward controlled.

  (E) The ignition determination circuit 72 is not limited to the configuration included in the ignition circuit unit 31 as in the above embodiment, and may be included in the electronic control unit 32. Further, it may be configured by either hardware or software.

(F) The ignition circuit unit 31 may be housed in a housing that houses the electronic control unit 32 or may be housed in a housing that houses the ignition coil 40.
The ignition switch 45 and the energy input unit 50 may be housed in separate housings. For example, the ignition switch 45 may be housed in a housing that houses the ignition coil 40, and the energy input unit 50 may be housed in the housing that houses the electronic control unit 32.

(G) The ignition switch 45 is not limited to the IGBT, and may be composed of other switching elements 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.
(H) The DC power source 6 is not limited to a battery, and may be constituted by, for example, a DC stabilized power source in which an AC power source is stabilized by a switching regulator or the like.

  (K) In the above embodiment, the energy input unit 50 boosts the voltage of the battery 6 by the DCDC converter 51. In another embodiment, 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.

(E) The electronic control unit 32 includes a part for controlling the operating state of the entire engine 13 that is relatively unrelated to the characteristics of the above embodiment, in addition to a part for mainly controlling the ignition device 30. These may be configured as a single unit, or may be configured as separate units that communicate with each other via a signal line or the like.
The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention.

13 ... Internal combustion engine,
17 ... combustion chamber,
30 ... Ignition device,
40 ... ignition coil,
41 ... primary coil, 42 ... secondary coil,
45 ... Ignition switch,
50 ・ ・ ・ Energy input unit (energy input means),
6 ... Battery (DC power supply),
7 ... Spark plug,
71 ... Ignition detector,
72: Ignition determination circuit (ignition determination means).

Claims (2)

An ignition device (30) for controlling the operation of a spark plug (7) for igniting an air-fuel mixture in a combustion chamber (17) of an internal combustion engine (13),
A primary coil (41) through which a primary current supplied from a DC power supply (6) flows and an electrode of the spark plug are connected, and a secondary voltage is generated by energization and interruption of the primary current, and a secondary current flows. An ignition coil (40) having a secondary coil (42);
An ignition switch (45) connected to a ground side opposite to the DC power source of the primary coil and switching between conduction and interruption of the primary current according to an ignition signal (IGT);
Energy input means capable of supplying energy to the ignition coil in a predetermined energy input period (IGW) after the primary current is interrupted by the ignition switch and discharge is generated in the spark plug by the voltage generated by the interruption. 50),
Ignition determination means (72) for acquiring information from an ignition detector (71) for detecting ignition of the air-fuel mixture, and determining whether or not the air-fuel mixture has ignited based on the information;
With
Connected to the ground side of the primary coil is a rectifying element (46) that cuts off a current that is directed to the ground and flows a current that is directed from the ground toward the ground side of the primary coil.
The energy input means includes a capacitor (56) for storing energy, and a discharge switch (57) provided between the capacitor and the ground side of the primary coil, and the ignition is performed during the energy input period. When the discharge switch is turned on while the switch is cut off, the energy stored in the capacitor can be superimposed on the ignition coil in the same polarity as the secondary current from the ground side of the primary coil. Yes,
The energy input means stops the energy input during the energy input period when it is determined that the air-fuel mixture has ignited within the energy input period. When it is determined that the air-fuel mixture has not ignited continuously within the energy input period in one combustion cycle, the energy input period is extended or the energy input target value (I2 ^* ) is increased. The ignition device according to claim 1, further comprising input energy control means (33) for performing at least one of them.

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