JP6040879B2 - Ignition device - Google Patents

Description

  The present invention relates to an ignition device for igniting an internal combustion engine, and more particularly, to an ignition device provided with an auxiliary power source and a soft-off circuit for maintaining a discharge by flowing a current in a superimposed manner by switching after the start of discharge. is there.

In a spark ignition type internal combustion engine, a spark is discharged to an ignition plug by an ignition device including an ignition coil, and the fuel introduced into the combustion chamber by the discharge is used for combustion.
In order to improve the combustion state of the internal combustion engine, a multiple discharge type ignition device has been proposed in which a discharge is generated in the spark plug a plurality of times within one combustion stroke.

  In Patent Document 1, in addition to a normal induction discharge type ignition device, a DC-DC converter that injects ignition energy into the secondary side of the ignition coil, an operation stop unit that stops the operation of the DC-DC converter, There is disclosed an internal combustion engine ignition device provided with an operation stop canceling means for canceling the operation stop when an operation state of the engine is detected.

Japanese Utility Model Publication 2-24066

  However, in the conventional ignition device, it is necessary to use a high breakdown voltage element for the DC-DC converter provided on the secondary side of the ignition coil in order to maintain the discharge. Therefore, there is a problem in that the size of the apparatus is increased due to the need to improve the heat dissipation and the heat dissipation, and the reliability is reduced due to heat generation of the high voltage element.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an internal combustion engine ignition device that is excellent in mountability and high in reliability without using a high withstand voltage element.

The ignition device (7, 7a, 7b) of the present invention is connected to at least a DC power source (10), a booster circuit (1) that boosts the power supply voltage of the DC power source (10), and the booster circuit (1). an ignition coil for generating a decrease by a secondary winding (41) to a high secondary voltage of the current allowed the primary winding (40) (V2) (4), the current to the previous SL primary winding (40) Combustion of the internal combustion engine by application of the secondary voltage (V2) from the secondary winding (41) connected to the ignition switching element (3) for switching between supply and shutoff and the secondary winding (41) An ignition plug (5) for generating a spark discharge in the room, and igniting the internal combustion engine, wherein the ignition plug (5) is opened and closed by opening and closing the ignition switch (3). after starting the discharge, the booster circuit (1) or these discharge and stop the superimposed performed that the Accordingly, comprising an auxiliary power supply (2) to increase the current flowing through the secondary winding (40), the auxiliary power supply (2), and stop energy charge from the auxiliary power supply (2) The auxiliary opening / closing element (20) for switching is provided , and the auxiliary opening / closing element (20) includes a soft-off circuit (22, 22a, 21b) that makes the turn-off speed slower than the turn-on speed. .

According to the ignition device of the present invention (7, 7a, 7b), since the the soft-off circuit (22, 22a, 21b), put stop of discharge energy from the auxiliary power supply (2) is carried out slowly, Since a rapid change in the secondary current (I2) is suppressed and the discharge path is maintained for a long time, the input energy is not wasted and stable ignition can be realized.

The block diagram which shows the outline | summary of the ignition device in the 1st Embodiment of this invention 1 is a time chart for explaining the operation of the ignition device of FIG. Enlarged view of the main part of FIG. 2A The time chart which shows the operation | movement of the ignition device of the structure which does not use the soft-off means which is the principal part of this invention shown as the comparative example 1 3A enlarged view of the main part of FIG. The block diagram which shows the principal part of the ignition device in the 2nd Embodiment of this invention FIG. 4A is a main part enlarged view of a time chart showing the operation of the ignition device of FIG. 4A. The block diagram which shows the outline | summary of the ignition device in the 3rd Embodiment of this invention. Time chart showing the operation of the ignition device of FIG. 5A together with the comparative example

With reference to FIG. 1, the outline | summary of the ignition device 7 in the 1st Embodiment of this invention is demonstrated.
The ignition device 7 of the present invention is provided for each cylinder of an unillustrated internal combustion engine, and generates spark discharge in the air-fuel mixture introduced into the combustion chamber to perform ignition.
The ignition device 7 includes a booster circuit 1, an auxiliary power source 2, an ignition switching element 3, an ignition coil 4, an ignition plug 5, and an electronic control device 6 (hereinafter referred to as ECU 6) provided outside. , Is composed of.

The booster circuit 1 includes an energy storage inductor 11 (hereinafter referred to as an inductor 11) connected to a power source 10, and a boost switch element 12 (hereinafter referred to as an open / close switch) that switches supply and interruption of current to the inductor 11 at a predetermined cycle. Element 12), a capacitor 15 connected in parallel, a first rectifier element 14 for rectifying current from the inductor 11 to the capacitor 15, and a primary winding 40 of the ignition coil 4. A type booster circuit is configured.
As the DC power supply 10 (hereinafter referred to as the power supply 10), a vehicle-mounted battery, a known DC stabilized power supply obtained by converting the AC power supply using a regulator or the like is used, and a constant DC voltage such as 12V or 24V is supplied. .
In the present embodiment, an example in which a so-called flyback type booster circuit is used as the booster circuit 1 is shown, but the present invention is not limited to this, and a so-called chopper type booster circuit can also be used.

As the inductor 11, a coil with a core having a predetermined inductance (L0, for example, 5 to 50 μH) is used.
A power transistor such as a thyristor or IGBT (insulated gate bipolar transistor) is used for the switching element 12.
A booster element driver (hereinafter referred to as a driver 13) is connected to the open / close element 12.
An ignition signal IGt is transmitted to the driver 13 from an engine control device 6 (hereinafter referred to as ECU 6) in accordance with the operating condition of the engine.

The driver 13 generates a drive pulse that switches between high and low at a predetermined cycle for a predetermined period at a predetermined timing in accordance with the ignition signal IGt.
A driving pulse is applied from the driver 13 to the gate G of the switching element 12, and the switching element 12 is switched on and off.

As the capacitor 15, a capacitor having a predetermined capacitance (C, for example, 100 to 1000 μF) is used.
A diode is used for the rectifying element 14 to prevent a backflow of current from the capacitor 15 to the inductor 11.
When the opening / closing element 12 is opened / closed by the driver 12 in accordance with the ignition signal IGt transmitted from the ECU 6, the electrical energy stored in the inductor 11 from the power supply 10 is superimposed and charged on the capacitor 15, and the charge / discharge voltage of the capacitor 15 is charged. Vdc is boosted to a voltage (for example, 50 V to several hundred V) higher than the power supply voltage.

The ignition coil 4 includes a primary winding 40 obtained by winding a coil wire material N1 times, a secondary winding 41 via N2 turns, a coil core 42, a diode 43, and the like.
A primary voltage V1 boosted by the booster circuit 1 is applied to the primary winding 40 of the ignition coil 4, and the current flowing through the primary winding 40 is increased or decreased to produce a secondary voltage V2 in the secondary winding 41. A high voltage (for example, −20 to −50 kV) determined by the winding ratio N2 / N1 is generated.

A power transistor PTr such as a MOS FET or an IGBT is used for the ignition switching element 3 (hereinafter referred to as the ignition element 3).
The ignition element 3 switches between supply and interruption of current to the primary winding 40 in accordance with an ignition signal IGt transmitted from the ECU 6 in accordance with the operating state of the engine.
When conduction to the primary winding 40 is interrupted by switching of the ignition element 3, the magnetic field changes rapidly, and an extremely high secondary voltage V2 is generated in the secondary winding 41 by electromagnetic induction, and the ignition plug 5 is applied.

The auxiliary power source 2 includes an auxiliary opening / closing element 20 (hereinafter referred to as an auxiliary element 20) interposed between the capacitor 15 and the primary winding 40, and an auxiliary element that drives the auxiliary element 20. The drive driver 21 (hereinafter referred to as the driver 21) includes a second rectifying element 23, a power source 10, an inductor 11, a capacitor 15, and a soft-off circuit 22 that is a main part of the present invention.
The auxiliary power source 2 performs a discharge and a stop to the connection point between the primary winding 40 of the ignition coil 4 and the ignition switching element 3 from the booster circuit 1, so as to flow into the secondary winding 41. The secondary current I2 can be increased.
Energy input from the auxiliary power supply 2 is performed from the low voltage side of the primary winding 40.

For the auxiliary element 20, a power transistor having high responsiveness such as a MOSFET is used.
A diode is used for the second rectifying element 23 and rectifies the current supplied from the capacitor 15 to the primary winding 40.

The auxiliary element 20 is connected to a driver 21 and is driven to open and close.
The driver 21 generates a drive signal V _GS for opening and closing the auxiliary element 20 according to the discharge period signal IGw transmitted from the ECU 6.
In the present embodiment, the drive signal V _GS is a rectangular pulse signal, and opens and closes the auxiliary element 20 with a predetermined duty.

The discharge period signal IGw instructs opening / closing and stopping of the auxiliary element 20.
By switching between discharging and stopping from the capacitor 15 by the auxiliary element 20, current is supplied to the primary winding 40 of the ignition coil 4 and the current / voltage generated in the secondary winding 41 is increased and blown off. Can be suppressed.
At this time, since energy is input from the primary winding 40 of the ignition coil 4, it can be input at a lower voltage than when it is input from the secondary winding 41 side.

The soft-off circuit 22 which is the main part of the present invention slowly shuts off conduction when the auxiliary element 20 is driven to open and close, and suppresses a sudden change in the secondary current I2.
In this embodiment, as a soft-off circuit, a capacitor 22 having a predetermined capacitance (C22, for example, 0.1 to 100 μF) is provided between the gate and source of an n-channel MOSFET provided as an auxiliary element 20.

With this configuration, when the auxiliary element 20 is driven to open and close by the driver 21, the turn-off speed can be made slower than the turn-on speed of the MOSFET that is used as the open / close element.
Regardless of the present invention, when the auxiliary element 20 is quickly opened and closed, the energy supply to the spark plug 6 is intermittent, but in the present embodiment, the energy is supplied from the driver 21 by the discharge from the capacitor 22. the trailing edge of the drive voltage V _GS becomes gentle, the energy supply from the auxiliary power source 2 to the ignition coil 4 is continuously and becomes to suppress an abrupt change of the secondary current, thereby preventing blow-off of the secondary current Therefore, more stable ignition can be realized.

2A and 2B, the operation of the ignition device 7 will be described as a first embodiment.
As shown in FIG. 6A, an ignition signal IGt is transmitted from the ECU 6, and on / off of the switching element 12 is started in synchronization with the rise of IGt as shown in FIG. In addition, the switching element 3 is turned on.

As the switching element 12 is turned on / off, the capacitor 15 is charged with electric energy from the inductor 11, and the discharge voltage Vdc gradually rises as shown in FIG.
In synchronization with the fall of the ignition signal IGt, the driving of the switching element 12 is stopped, and at the same time, when the switching element 3 is shut off, a high secondary voltage is applied to the secondary side of the ignition coil 4 as shown in (i). When V2 is generated and applied to the spark plug, discharge starts, and the secondary current I2 continues to flow for a certain period as shown in (j).

At this time, in the conventional spark ignition device, as indicated by a one-dot chain line in Comparative Example 1 in this figure (j), the secondary current I2 continues to flow by the amount of energy accumulated in the ignition coil 4.
However, in the present invention, the driving voltage V _GS that switches between high and low at a predetermined duty is used as an auxiliary signal as shown in (d) in synchronization with the rising of the discharge period signal IGw shown in (b). It is input between the gate and source of the element 20.

At this time, as a soft-off circuit that is the main part of the present invention, a soft-off capacitor 22 (hereinafter referred to as a capacitor 22) is provided between the gate and the source of the auxiliary element 20, so that FIG. As shown, the turn-off period becomes longer than the turn-on period of the auxiliary element 20.
For this reason, as shown in FIG. 5G, the discharge from the capacitor 15 and the stop are repeated by switching the auxiliary element 20, thereby changing the current flowing through the primary winding 40 of the ignition coil 4. As shown in FIG. (H), discharge energy is input from the secondary winding 41 to the spark plug 5.

At this time, the change of the secondary current I2 is not entrusted, but as shown in FIG. 2B, the discharge energy is slowly stopped by the soft-off of the auxiliary element 20, so that the secondary current I2 Sudden changes are suppressed.
Thus, the secondary current I2, to the fall of the discharge period signal IGw, because no less than the discharge blowout limit current I _REF, the discharge is maintained, thereby enabling energy charge.

Here, with reference to FIG. 3A and FIG. 3B, the problem when not using the soft-off circuit 22 which is the principal part of this invention shown as the comparative example 1 is demonstrated.
Comparative Example 1 is the same as the configuration of FIG. 1 shown as Example 1 except that the soft-off circuit 22 is not provided.

As shown in FIG. 3A, in Comparative Example 1, when the auxiliary element 20 is driven to open and close according to the drive pulse from the driver 13, as shown in FIGS. 3A (d) and 3A (e), the capacitor 15 Discharging and stopping are repeated, and discharging energy is input as shown in FIG. 3A (h).
However, as shown in FIGS. 3A (i) and 3B, the increase in the secondary current I2 after the stoppage of the discharge energy input is left to the end, and the discharge current is increased faster than the increase rate of the secondary current I2 due to the discharge sustain energy input. The decrease rate of the secondary current I2 due to the energy input stop is faster.

In Comparative Example 1, as shown in part A of FIG. 3A (h), the secondary current I2 is discharged as shown in FIG. 3A (j) even though the discharge from the capacitor 15 is repeated. Since it was below the blow-off limit current I _REF , it was found that discharge was blown out, and energy was not input and was wasted.
For this reason, when a strong in-cylinder airflow is generated in the combustion chamber or under conditions of low ignitability such as extremely lean combustion, sufficient discharge cannot be maintained, and ignition may become unstable.

With reference to FIG. 4A and FIG. 4B, the ignition device 7a in the 2nd Embodiment of this invention is demonstrated.
In the present embodiment, the same configuration as that of the above embodiment is basically used, and as a soft-off circuit 22a, as shown in FIG. And switching means 220 for selecting one of the capacitors 221, 222, and 223 to be used, and the driver 21 a switches not only the auxiliary element 20 but also the switching means 220. To do.

As a result, as shown in FIG. 4B, by switching the capacitors 221, 222, and 223, the capacitances C1, C2, and C3 connected in parallel between the gate and the source are changed. The turn-off time of 20 also changes, the soft-off becomes more gradual and the change in the secondary current I2 becomes gradual.
Further, in the present embodiment, when the discharge period signal IGw is on, the auxiliary capacitors 221, 222, and 223 are not opened when the soft-off capacitors 221, 222, and 223 are switched. Switching may be performed when the element 20 is turned on, or an ON / OFF circuit may be formed in each of the capacitors 221, 222, and 223 so that the capacitors 20 are sequentially turned on.

In the present embodiment, an example in which three capacitors 221, 222, and 223 are provided as a plurality of capacitors is shown, but the number of capacitors is not particularly limited, and can be appropriately changed according to the internal combustion engine. It is.
It is desirable to increase the capacitance of the capacitor interposed between the gate and source of the auxiliary element 20 as the change in the secondary current I2 increases.

With reference to FIG. 5A and FIG. 5B, the outline | summary of the ignition device 7b in the 3rd Embodiment of this invention and its effect are demonstrated.
In the above embodiment, as the soft-off circuits 22 and 22a, even if the drive signal _VGS transmitted as a rectangular pulse from the driver 21 falls by providing a capacitive component in parallel between the gate and source of the auxiliary element 20, Although the configuration has been shown in which the discharge of the secondary current I2 is not suddenly terminated by slowly turning off the auxiliary elements 20 and 20a, in the present embodiment, the drive signal V output from the driver 21b is shown. _The difference is that soft-off of the auxiliary element 20 is executed by controlling _GS .

In the above embodiment, the drive signal V _GS output from the driver 21 is generated as a rectangular pulse signal that opens and closes the auxiliary element 20 multiple times while the discharge period signal IGw rises. Although shown in the present embodiment, the drive signal V _GS is generated only once in synchronization with the rise of the discharge period signal IGw, and the drive signal V _GS is gradually generated in synchronization with the fall of the discharge period signal IGw. The driver 21b is configured to decrease.
In this embodiment, the auxiliary element 20 may be driven to open and close a plurality of times as in the above embodiment. However, in this case, the discharge period signal IGw is set to the same period as in the above embodiment.

The effect in the present embodiment will be described together with the difference from the comparative example 2. The case where the ignition device 7b is used in FIG. 5B is shown by a solid line as Example 3, and Comparative Example 2 is shown by a one-dot chain line.
In the third embodiment, the output V _{GS of the} driver 21b is controlled to fall slowly in synchronization with the fall of the discharge start signal IGw as shown by the solid line in FIG.
This control may be controlled in an analog circuit (provided with a soft-off capacitor) in the driver 21b, or may be digitally controlled by an arithmetic circuit in the driver 21b.
On the other hand, in Comparative Example 2, the soft-off circuit that is the main part of the present invention is not provided, and the output of the driver falls steeply as shown in FIG. As shown in e), the auxiliary element 20 also falls sharply in accordance with this.

As a result, as shown in this figure (i), the secondary current I2 flowing by the discharge from the auxiliary element 20 is different between Example 3 and Comparative Example 2 when the auxiliary element 20 is on. However, when the auxiliary element 20 is turned off, in Example 3, it is turned off slowly, whereas in Comparative Example 2, it is turned off steeply, so that the rising speed of the secondary current I2 is compared with the comparative example. Example 3 was slower than 2, and as a result, it was found that the discharge period could be maintained longer.
Therefore, also in this embodiment, similarly to the above-described embodiment, it is possible to eliminate waste of discharge energy, maintain discharge over a long period of time, and realize stable ignition.
In this embodiment, as in the above embodiment, a soft-off capacitor may be used together, the output of the driver 21b may be soft-off by a program, or the driver 21b may be soft-off. A capacitor may be incorporated so as to realize soft-off in an analog circuit.

7 Ignition System 1 Booster Circuit 10 DC Power Supply 11 Energy Storage Inductor 12 Booster Switch (PTr12)
13 Booster switching element driver (DRV)
14 First rectifier 15 Boosting capacitor (C)
2 Auxiliary power supply 20 Auxiliary switching element (MOS20)
21 Auxiliary switching element driver 22 Soft-off circuit (soft-off capacitor)
23 2nd rectifier 3 Opening / closing element for ignition (PTr3)
4 Ignition coil 40 Primary winding (L1)
41 Secondary winding (L2)
42 Core 43 Rectifier 5 Spark plug 6 Engine control unit (ECU)
IGt Ignition signal IGw Discharge period signal V1 Primary voltage V2 Secondary voltage I2 Secondary current

Claims (7)

At least by the increase and decrease of the current of the DC power supply (10), the booster circuit (1) that boosts the power supply voltage of the DC power supply (10), and the primary winding (40) connected to the booster circuit (1). An ignition coil (4) for generating a high secondary voltage (V2) in the secondary winding (41), an ignition switching element (3) for switching between supply and interruption of current to the primary winding (40), An ignition plug (5) connected to the secondary winding (41) and generating a spark discharge in the combustion chamber of the internal combustion engine by application of the secondary voltage (V2) from the secondary winding (41); An ignition device for igniting an internal combustion engine comprising:
By starting and discharging the spark plug (5) by opening and closing the ignition switching element (3), the discharge from the booster circuit (1) and stop are performed in a superimposed manner, thereby the secondary winding. An auxiliary power source (2) for increasing the current flowing through (41),
The auxiliary power supply (2) is provided with a auxiliary switching element (20) for switching and stopping energy charge from the auxiliary power supply (2), said auxiliary switching element (20) than the turn-on speed, the turn-off speed And an ignition device (7, 7a, 7b) characterized by comprising a soft-off circuit (22, 22a, 21b)   The auxiliary opening / closing element (20) is driven to open and close one or more times in accordance with a discharge period signal (IGw) instructing start and stop of energy input from the auxiliary power source (2). Ignition device (7, 7a, 7b) according to claim 1, comprising an element driver (21, 21a, 21b).   The soft-off circuit (22, 22a, 22b) includes one or more soft-off capacitors (22, 221, 222, 223) connected between the gate and source of the auxiliary switching element (20). Ignition device according to 1 or 2 (7, 7a, 7b) The soft-off circuit (22b) is the drive driver (21b), and slowly _drops the drive voltage (V _GS ) for driving the auxiliary switching element (20). Ignition device (7b) as described   The ignition device (7, 7a, 7b) according to any one of claims 1 to 4, wherein energy input from the auxiliary power supply (2) is performed from a low voltage side of the primary winding (40). Interrupting the booster circuit (1) comprises a DC energy storage inductor connected to a power supply (10) (11), and the supply of current to the inductor in accordance with a point fire signal (IGt) for a predetermined time period (11) A switching element (12) that switches between the inductor (11) and a capacitor (15) connected in parallel to the inductor (11), and a first rectifier that rectifies current from the inductor (11) to the capacitor (15) Ignition device (7, 7a, 7b) according to any of claims 1 to 5, comprising an element (14).   The auxiliary power source (2) is interposed between the capacitor (15) and the primary winding (40), and switches between the discharge and stop of the capacitor (15). A second rectifying element (23) for rectifying current from the capacitor (15) to the primary winding (40), the DC power supply (10), the inductor (11), and the capacitor (15) The ignition device (7, 7a, 7b) according to claim 6, comprising

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