JP6394038B2 - Ignition device - Google Patents

Description

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

  Conventionally, an ignition device applied to an internal combustion engine of a flexible fuel vehicle (hereinafter referred to as “FFV vehicle”) using an alcohol-containing fuel is known. For example, the engine system disclosed in Patent Document 1 adjusts ignition energy according to the alcohol concentration in the fuel. Further, the internal combustion engine ignition control device disclosed in Patent Document 2 supplies ignition energy to the ignition device based on the ratio of the different fuel components estimated by the component ratio estimation means.

JP 2009-115094 A JP 2007-187106 A

  In the device of Patent Document 2, the high voltage energy generated in the energy storage coil and stored in the capacitor for capacitor discharge is supplied to the battery side of the primary coil by the on / off operation of the transistor. In this configuration, since the primary current i1 is alternately increased and decreased, the direction of the generated secondary current i2 is alternately opposite. That is, the secondary current i2 crosses 0 [A], and the positive current and the negative current alternate. Hereinafter, the change of direction across the secondary current I2 across 0 [A] is referred to as “zero crossing”. Also, with respect to the engine system of Patent Document 1, the flow of ignition energy is considered to be the same as that of Patent Document 2.

In such an ignition device, the secondary current alternates and zero crosses, so that the spark is repeatedly strong and weak, particularly near the zero point. Therefore, when the alcohol concentration in the fuel is relatively high, ignition is difficult and there is a risk of misfire.
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 that improves ignitability when the alcohol concentration in fuel changes in an FFV vehicle.

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, and input energy setting 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 energization and interruption of the primary current according to the ignition signal.

Energy charge means blocks the primary current by the ignition switch, in a predetermined energy supply period of after generating a discharge of the spark plug by the secondary voltage (IGW), as the secondary current flows in the same direction, the primary Energy is input to the ignition coil from the ground side of the coil . The “same direction” means “the same direction as the discharge current” that flows when the spark plug is discharged.
In particular, the energy input means of the preferred embodiment of the present invention inputs energy for generating the secondary current in the same direction as the discharge current and maintaining the predetermined target value (I2 ^* ) to the ground side of the primary coil. To do.
Here, “ignition by the secondary current generated by cutting off the primary current by the ignition switch” is referred to as “normal ignition”. That is, the preferred energy input means of the present invention inputs energy to the ground side of the primary coil during the energy input period after normal ignition.
Further, “maintaining a predetermined target value” for the secondary current is not limited to strictly maintaining a constant value but includes the meaning of “within a control range based on the predetermined target value”. .

The input energy setting means sets the input energy by the energy input means.
The input energy setting means sets the input energy based on the alcohol concentration information acquired from the alcohol concentration detection means for detecting the alcohol concentration in the fuel.
Here, “detection” of the alcohol concentration includes a case of “estimating” the alcohol concentration based on, for example, the air-fuel ratio of the exhaust gas.

In the ignition device of the present invention, the energy for generating the secondary current “in the same direction as the discharge current of the normal ignition and maintaining the predetermined target value” in the predetermined energy input period is grounded to the primary coil. To the side. That is, energy is input so that the secondary current does not zero cross.
Therefore, it is possible to avoid the spark from weakening when the alternating secondary current is near zero as in the prior art ignition device. Therefore, ignitability can be improved.

Specifically, the input energy setting means sets the target value of the secondary current higher or sets the energy input period longer as the alcohol concentration in the fuel is higher.
Thereby, appropriate input energy can be set according to the atomization capability of the mixed fuel depending on the alcohol concentration. Therefore, even in a state where the alcohol concentration is high and the atomization ability is lowered, good ignitability can be ensured.

The input energy setting means sets the target value of the secondary current or the energy input period to zero while discontinuously changing the concentration threshold value when the alcohol concentration in the fuel is less than a predetermined concentration threshold value. Stop energy input by means .
In a region where the alcohol concentration is less than a predetermined concentration threshold value, sufficiently good ignition is possible by normal ignition, so that power consumption can be reduced by stopping the energy input control.

1 is a schematic configuration diagram of an engine system to which an ignition device according to each embodiment of the present invention is applied. The block diagram of the ignition device by each embodiment of this invention. The time chart explaining the action | operation of the energy injection | throwing-in control by the ignition device of FIG. The map which shows the relationship between the ethanol concentration detection value by the input energy control of 1st Embodiment, (a) target secondary current I2 ^* , and (b) energy input period IGW. The time chart explaining the action | operation of the normal ignition by the ignition device of FIG. The map which shows the relationship between the ethanol concentration detection value by the input energy control of 2nd Embodiment, (a) target secondary current I2 ^* , and (b) energy input period IGW.

Hereinafter, an ignition device according to an embodiment of the present invention will be described with reference to the drawings.
The ignition device according to each embodiment of the present invention is applied to an engine system mounted on a vehicle or the like. In the following description of the embodiments, the “internal combustion engine” described in the claims is referred to as “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 ignition device 30 operates the ignition circuit unit 31 based on a command from the electronic control unit 32 to apply a high voltage from the ignition coil 40 to the ignition plug 7, thereby generating a spark discharge in the combustion chamber 17.
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 is applied between the pair of electrodes. When generated, a discharge is generated. 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 indicated by broken line arrows, 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. . 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.

The current that flows through the primary coil 41 is referred to as a primary current I1, the current that is generated by energization and interruption of the primary current I1, and the current that flows 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 V2.
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, an energy input unit 50, a secondary current detection resistor 47, and a secondary current detection circuit 48.
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. Energization and interruption of the primary current I1 in the primary coil 41 are switched by the ignition switch 45 in accordance with the ignition signal IGT.

  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 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.
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 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 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 secondary current detection circuit 48 detects the secondary current I <b> 2 based on the voltage across the secondary current detection resistor 47 provided in the combustion chamber 17. The on-duty ratio of the discharge switch 57 is calculated and commanded to the driver circuit 58 by feedback control to make the secondary current I2 coincide with a target value (hereinafter referred to as “target secondary current I2 ^* ”).
The above is the configuration of the ignition circuit unit 31.

  Next, the electronic control unit 32 includes an ignition control unit 33 as “input energy setting means” and an alcohol concentration detection unit 34 as “alcohol concentration detection means”. The ignition control unit 33 in the present embodiment is referred to as an “ignition control unit” because it includes not only setting of input energy but also general control functions such as generation of the ignition signal IGT.

  The ignition control unit 33 of the electronic control unit 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 such as the crank position sensor 35 and outputs it to the ignition circuit unit 31. To do. In addition, the ignition control unit 33 sets the input energy based on the alcohol concentration information acquired from the alcohol concentration detection unit 34.

  Here, the alcohol concentration detector 34 detects the alcohol concentration in the fuel, and its configuration is not limited. For example, the alcohol concentration may be detected directly based on physical properties such as the conductivity or capacitance of the mixed fuel, or the air-fuel ratio of the exhaust gas may be detected using the technique disclosed in Japanese Patent Application Laid-Open No. 2009-197771. Based on the above, the alcohol concentration may be estimated. That is, it is interpreted that “detection” of the alcohol concentration detection unit 34 includes “estimation”.

  Further, it is not necessary that all components for detecting the alcohol concentration are provided in the electronic control unit 32, and if there is a portion in the electronic control unit 32 that can communicate information on the alcohol concentration to the ignition control unit 33. Good. Alternatively, at least information on the alcohol concentration detection value may be configured to be communicable from the alcohol concentration detection unit 34 to the ignition control unit 33 via a communication line or the like.

  The ignition signal IGT generated by the ignition control unit 33 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.

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.
Further, the target secondary current signal IGA for instructing the target secondary current I2 ^* is input to the driver circuit 58.

[Ignition device operation]
Next, the operation of energy input by 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. Further, “input energy P” means energy that is discharged from the capacitor 56 and supplied to the ignition coil 40 from the low-voltage side terminal side of the primary coil 41, and starts supply during one ignition timing (initial discharge) The integrated value from the rising edge of the switch signal SWd 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.

In addition, the control target value of the secondary current I2 in the period from time t3 to t4 when the energy input period signal IGW is output is defined as “target secondary current I2 ^* ”. The target secondary current I2 ^* is set to a current that can maintain the ignition discharge well. In the present embodiment, an intermediate value between the wavy maximum value and the minimum value is set as the target value. However, in other embodiments, the wavy maximum 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 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, a high voltage is generated in the secondary coil 42, and a discharge is generated between the electrodes of the spark plug 7, whereby a secondary current I2 (discharge current) flows.
If energy is not input after ignition discharge is generated at time t2, the secondary current I2 approaches 0 [A] as time elapses as shown by a broken line, and the discharge ends when the discharge is attenuated to an extent that the discharge cannot be maintained. To do. Such an ignition system by discharge is called “normal ignition”.

  On the other hand, in this embodiment, the energy input period signal IGW is raised to H level at time t3 immediately after time t2, and the discharge switch 57 is turned on while the charge switch 53 is off. Then, the stored energy of the capacitor 56 is released and is supplied to the ground side of the primary coil 41. As a result, during the ignition discharge, the “primary current I1 resulting from the input energy P” is energized. The input energy P increases as the capacitor voltage Vdc accumulated up to time t2 increases.

At this time, the secondary coil 42 is superposed with the same polarity on the secondary current I2 energized between times t2 and t3 with the same polarity as the primary current I1 caused by the input energy P. The superimposition of the primary current I1 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 stored in the capacitor 56, and the secondary current I2 is sequentially added correspondingly. When the secondary current I2 reaches a predetermined value, the discharge switch 57 is turned off and the superimposition of the primary current I1 is stopped. When I2 decreases and reaches a predetermined value, the discharge switch 57 is turned on again. Thereby, the secondary current I2 is maintained so as to coincide with the target secondary current I2 ^* .
When the energy input period signal IGW falls to the 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. Hereinafter, when the current is described as “zero”, it is not limited to strict 0 [A] but includes a very small current range substantially equivalent to 0 [A].

Thus, the control system in which energy is input to the ignition coil 40 from “the ground side of the primary coil 41” after the ignition discharge at time t2 was developed by the present applicant. Hereinafter, when simply referred to as “energy input control” in the present specification, this control method is meant.
On the other hand, in the methods used in the prior arts of Patent Documents 1 and 2, the direction of the secondary current I2 alternates with the energization and interruption of the primary current I1 flowing into the ignition coil 40 from the battery 6 side of the primary coil 41, Zero cross. For this reason, when the secondary current I2 becomes close to zero, the spark becomes weak and it is difficult to ignite.

On the other hand, in the energy input control developed by the present applicant, the secondary current I2 is "in the same direction and the predetermined target secondary current I2 ^* is maintained in the predetermined energy input period IGW after the normal ignition". "generate. Therefore, it can be avoided that the secondary current I2 becomes zero and cannot be ignited during the discharge, so that the discharge of the spark plug 7 can be stably continued for a long time. In addition, by inputting energy from the low voltage side of the ignition coil 40, the minimum energy can be input efficiently.

  By the way, in an FFV vehicle using a fuel containing alcohol such as ethanol, the evaporation temperature of alcohol is higher than the evaporation temperature of gasoline, so that the higher the alcohol concentration, the lower the volatility and the atomization ability in the combustion chamber 17. descend. Therefore, it is desirable to form a state that promotes fuel atomization in the combustion chamber 17 when the spark plug 7 is discharged, as compared with the case where gasoline fuel is used.

  Therefore, the ignition device 30 of the present embodiment continuously forms a state in which the alcohol-containing fuel is atomized and easily ignited by performing energy input control. Further, the ignition control unit 33 acquires information on the alcohol concentration from the alcohol concentration detection unit 34, so that the energy input condition is appropriately set according to the alcohol concentration.

Next, specific setting of the energy input condition by the ignition control unit 33 will be described for each embodiment.
(First embodiment)
The setting of the energy input condition according to the first embodiment of the present invention will be described with reference to FIG. In FIG. 4, ethanol concentration is illustrated as alcohol concentration.
As shown in FIG. 4A, in the first embodiment, the target secondary current I2 ^* is set higher as the ethanol concentration is higher over the range where the ethanol concentration detection value is 0% to 100%.
Alternatively, as shown in FIG. 4B, the energy input period IGW is set longer as the ethanol concentration is higher over the range where the ethanol concentration detection value is 0% to 100%.

By carrying out like this, discharge can be strengthened, or the dischargeable time can be ensured long as the ethanol concentration is high and the atomization ability is reduced. Therefore, appropriate input energy can be set according to the atomization ability of the mixed fuel depending on the alcohol concentration. In FIG. 4, the target secondary current I2 ^* or the energy input period IGW is changed linearly according to the ethanol concentration. However, the present invention is not limited to this, and it may be changed stepwise or curvedly.

Here, whether the target secondary current I2 ^* or the energy input period IGW is changed depends on, for example, the rotational speed and load conditions of the engine 13, and the higher the alcohol concentration is, the higher the alcohol concentration is. I2 ^* may be increased, and the energy input period IGW may be lengthened as the alcohol concentration increases under low rotation and low load conditions. Further, both the target secondary current I2 ^* and the energy input period IGW may be changed in consideration of weighting.

  Furthermore, since it is unlikely that the alcohol concentration frequently changes during the traveling of the vehicle, the cycle for setting the input energy in accordance with the alcohol concentration may be longer than the control cycle for general engine control. By increasing the setting cycle, the calculation load of the electronic control unit 32 can be reduced.

(effect)
(1) The ignition control unit 33 of the ignition device 30 of the present embodiment uses the target secondary current I2 ^* and the energy input period IGW as set values of input energy based on the alcohol concentration information acquired from the alcohol concentration detection unit 34. Set. Specifically, the target secondary current I2 ^* is set higher or the energy input period IGW is set longer as the alcohol concentration is higher. Thereby, appropriate input energy can be set according to the atomization capability of the mixed fuel depending on the alcohol concentration. Therefore, even in a state where the alcohol concentration is high and the atomization ability is lowered, good ignitability can be ensured.

(2) The ignition device 30 according to the present embodiment employs a method in which the input energy boosted by the DCDC converter 51 and stored in the capacitor 56 is input from the ground side of the primary coil 41 as the energy input control method. As a result, compared to an energy input method such as multiple discharge, 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.
In addition, during the energy input period IGW, the secondary current I2 is always a negative value and does not zero-cross like the prior art methods of Patent Documents 1 and 2 using an alternating current, so that it is possible to avoid weakening of the spark. it can. Therefore, ignitability can be improved.

(3) The ignition device 30 of the present embodiment includes the secondary current detection resistor 47 and the secondary current detection circuit 48, and performs feedback control of the secondary current I2. Therefore, the actual current of the secondary current I2 is compared with the feedforward control. The value can be matched with the target secondary current I2 ^* with high accuracy. Therefore, the setting of the input energy by the ignition control unit 33 can be executed accurately.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS. The symbols used in FIGS. 3 and 4 are used as the symbols in FIGS. The configuration of the ignition device of the second embodiment is the same as that of the ignition device 30 of the first embodiment shown in FIG. 2, and only the input energy setting method by the ignition control unit 33 is different.
The time chart of FIG. 5 shows the operation of the ignition device 30 when the energy input control of FIG. 3 is not executed.

The ignition control unit 33 stops the on / off operation of the charge switch 53 by the charge switch driver circuit 54 during the output period of the ignition signal IGT. Further, during the output period of the energy input period signal IGW, the on / off operation of the discharge switch 57 by the discharge switch driver circuit 58 is stopped. As a result, the capacitor voltage Vdc is not accumulated, and energy is not input to the ignition coil 40. Therefore, only “normal ignition” by the secondary current I2 generated by the interruption of the primary current I1 is performed. This state corresponds to a state where the target secondary current I2 ^* or the energy input period IGW is set to zero.

As shown in FIG. 6A, in the second embodiment, in the region I where the ethanol concentration detection value is less than the predetermined concentration threshold value α, the target secondary current I2 ^* is made constant at zero and normal ignition is performed. On the other hand, in the region II where the ethanol concentration detection value is greater than or equal to the concentration threshold value α, the target secondary current I2 ^* is set higher as the ethanol concentration is higher, as in FIG. 4A of the first embodiment.
Alternatively, as shown in FIG. 6B, in the region I where the ethanol concentration detection value is less than the predetermined concentration threshold β, the energy input period IGW is set to zero and normal ignition is performed. On the other hand, in the region II where the ethanol concentration detection value is equal to or higher than the concentration threshold β, the energy input period IGW is set longer as the ethanol concentration is higher, as in FIG. 4B of the first embodiment.
The density threshold value α in FIG. 6A and the density threshold value β in FIG. 6B may be the same or different.

In the region I where the ethanol concentration detection value is less than the concentration threshold value α or β, sufficiently good ignition is possible by normal ignition, so that the power consumption can be reduced by stopping the energy input control. On the other hand, in the region II where the ethanol concentration detection value is greater than or equal to the concentration threshold value α or β, a mixed fuel with a high ethanol concentration is used by changing the target secondary current I2 ^* or the energy input period IGW according to the ethanol concentration It is possible to ensure good ignitability.
Here, the concentration threshold values α and β may be variable using a map or the like according to parameters such as engine speed, engine load, or fuel temperature.

  Further, in the time chart of FIG. 5, since the energy input by the discharge switch 57 is stopped and the energy accumulation by the charge switch 53 is stopped, the capacitor 56 can be prevented from being overcharged. However, when the charging capacity of the capacitor 56 is sufficient, the capacitor voltage Vdc may be accumulated regardless of whether or not energy is input. Thereby, when ethanol concentration rises rapidly, the stored energy can be thrown in rapidly.

(Other embodiments)
(A) In the above-described embodiment, one ignition coil 40 and one ignition switch 45 are provided corresponding to one ignition plug 7, and the energy input unit 50 is electrically connected during discharge generated when the ignition switch 45 is turned off. Discharging is sustained by superimposing energy.
On the other hand, in another embodiment of the present invention, two ignition coils and two ignition switches are provided corresponding to one spark plug, and the energy input unit stops the discharge generated when one of the ignition switches is turned off. After that, electric energy may be supplied to the spark plug through one ignition coil to generate a discharge. The energy input unit may generate electric discharge by supplying electric energy to the spark plug through the other ignition coil after the discharge generated by turning off the other ignition switch is interrupted. The discharge may be continued by continuing the discharge.

  In another embodiment, two ignition coils and two ignition switches are provided corresponding to one ignition plug, and a discharge generated when one ignition switch is turned off and a discharge generated when the other ignition switch is turned off. The discharge may be continued by continuing the above. In such a configuration, the other ignition switch functions as an “energy input unit”.

(B) The “alcohol” whose concentration is detected by the alcohol concentration detection means is not limited to ethanol (ethyl alcohol), but is an aliphatic alcohol such as methyl alcohol or butyl alcohol, or an aromatic alcohol such as benzyl alcohol. Also good.
In addition, fatty acid methyl ester, which is a kind of biofuel, is not an alcohol in terms of chemical formula, but is interpreted as equivalent to alcohol in the light of the gist of the present invention as a heterogeneous fuel used in FFV vehicles.

  (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 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.

(E) The ignition switch is not limited to the IGBT, and may be composed of other switching elements having a relatively high breakdown voltage. Further, the charge switch and the discharge switch are not limited to MOSFETs, and may be composed of other switching elements.
(F) The direct current power source is not limited to a battery, and may be constituted by, for example, a direct current stabilized power source in which an alternating current power source is stabilized by a switching regulator or the like.

  (G) In the above embodiment, the energy input unit 50 boosts the voltage of the battery 6 by the DCDC converter 51. In addition, when the ignition device 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.

(H) The electronic control unit 32 may be configured as a unit in which the functional parts of the ignition control unit 33 and the alcohol concentration detection unit 34 are configured as one unit, or as a separate unit that communicates with each other by a signal line or the like. May be.
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,
33 ... Ignition control unit (input energy setting means),
34 ・ ・ ・ Alcohol concentration detector (alcohol concentration detector),
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.

Claims (1)

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 source (6) flows, and a secondary voltage that is connected to the electrode of the spark plug and generates a secondary voltage due to energization and interruption of the primary 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 energization and interruption of the primary current according to an ignition signal (IGT);
The primary current is interrupted by the ignition switch, and the secondary current flows in the same direction in a predetermined energy input period (IGW) after the ignition plug is discharged by the secondary voltage. Energy input means (50) for supplying energy to the ignition coil from the ground side of the primary coil;
Input energy setting means (33) for setting input energy by the energy input means;
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
Energy for generating the secondary current in the same direction and maintaining a predetermined target value (I2 ^* ) is input to the ground side of the primary coil,
The input energy setting means includes
Based on the alcohol concentration information acquired from the alcohol concentration detection means (34) for detecting the alcohol concentration in the fuel, the higher the alcohol concentration in the fuel, the higher the target value of the secondary current by the energy input means. Or set the input energy to set the energy input period longer ,
When the alcohol concentration in the fuel is below a predetermined concentration threshold,
The ignition device characterized in that the target value of the secondary current or the energy input period by the energy input means is set to zero while discontinuously changing in the concentration threshold .

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