JP2015063931A - Ignition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent ignition device capable of improving robustness, restraining consumption of an electrode, and saving power at the same time.SOLUTION: An ignition device for inputting discharge-maintaining energy in an overlaying manner during a discharge period after high voltage V2 is applied to a spark plug 6 to generate discharge arc at least comprises: an ignition switch 30; two or more auxiliary power sources 131, 231; a discharge switch 33 for controlling discharge from the auxiliary power sources 131, 231; secondary voltage detection means 36 for detecting the secondary voltage V2 of an ignition coil 2; switch necessity determination means 37 for determining whether switching of the plural auxiliary power sources 131, 231 is required or not by comparing the detected secondary voltage V2 with a predetermined threshold Vth; and a power source changing switch SSW38 for switching connection with the discharge switch 33 to any of the plural auxiliary power sources 131, 231 according to determination results.

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 energy input power source for maintaining a discharge by flowing a current in a superimposed manner by switching after the start of discharge.

  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, various proposals have been made on a multiple discharge type ignition device that causes a spark plug to generate a plurality of discharges within a single combustion stroke.

  Patent Document 1 discloses a current detection unit that detects a secondary current flowing through a secondary coil of an ignition coil, and a current value detected by the current detection unit at the time of multiple discharge reaches a predetermined current determination value. Based on ignition control means for performing on / off switching of the first and second switch means, acquisition means for acquiring the in-cylinder flow velocity of the internal combustion engine or information correlated thereto, and flow velocity information acquired by the acquisition means There is disclosed an ignition control device for an internal combustion engine, comprising: setting means for variably setting the current determination value.

However, in the conventional ignition device, the discharge is surely cut when the first and second switch means are switched to perform the AC discharge.
For this reason, for example, when a high-velocity in-cylinder airflow is generated in the combustion chamber, when the spark discharge is extended by the in-cylinder airflow and the energy input is interrupted, the discharge path is temporarily There is a problem that a blow-off phenomenon that is interrupted occurs, and additionally input energy is consumed for re-discharge, which may lead to misfire.

For such a problem, as a control circuit 3z for controlling the opening and closing of the ignition coil 2 as shown in FIG. 3 as a comparative example, a normal ignition device including the DC power source 1, the ignition coil 2, and the ignition switch 30 is used. The auxiliary power supply 131 including the choke coil 132, the charging switch 133, the rectifying element 134, and the capacitor 135 as energy storage means, the charging driver 32z for driving the auxiliary power supply 131 to be charged, and the discharge power from the auxiliary power supply 131 are discharged. The ignition device 4z in which the discharge switch 33, the discharge driver 34 that drives the discharge switch 33, and the rectifying element 35 that rectifies the discharge current are provided and the discharge energy is input from the minus side of the primary coil 20 was studied.
The auxiliary power supply 131 and the charging driver 32z constitute a so-called DC-DC converter, and the discharge switch 33 is driven to open and close, whereby the energy stored in the capacitor 135 can be released.
In the ignition device 4z, as described in Patent Document 1, by connecting the DC-DC converter to the minus side of the primary coil 20 instead of the plus side of the primary coil, the auxiliary power supply 131 is started from a state where the secondary voltage V2 is relatively high. It was considered that the auxiliary energy can be continuously input over a long period of time without causing the secondary discharge I2 to be interrupted.

JP 2007-211631 A

However, in the configuration of the ignition device 4z shown as the comparative example, the secondary current I2 can be continuously maintained for a certain period, but it has been found that it is difficult to maintain the discharge after the middle of the discharge period.
During the discharge period, depending on the conditions of the internal combustion engine 5, when a strong in-cylinder airflow flowing in the combustion chamber is received and the discharge arc is extended and the discharge distance is relatively enlarged, the secondary voltage is increased accordingly. V2 will rise.

On the other hand, in a normal induction discharge type ignition coil, the secondary voltage V2 is determined by a winding ratio (N = N2 / N1) between the number of turns N2 of the secondary coil 21 and the number of turns N1 of the primary coil 20, A spark discharge is generated in the spark plug by obtaining a high secondary voltage V2 by using a voltage that is twice the winding ratio of the voltage V1, but the secondary voltage V2 is also generated during the discharge period. The relationship equal to the winding ratio times the primary voltage V1 is maintained.
For this reason, when the discharge arc is extended by the in-cylinder airflow and the secondary voltage V2 rises, the primary voltage V1 also increases in proportion thereto.

Further, the discharge voltage V _dc from the auxiliary power supply 131 gradually decreases every time the discharge is repeated.
At the timing when the discharge switch 33 is opened and the energy input from the auxiliary power supply 131 to the primary coil 20 of the ignition coil 2 is stopped, the discharge arc is extended by the in-cylinder airflow, and the primary voltage V1 is suddenly increased. Then, the primary voltage V1 may become higher than the discharge voltage _Vdc of the auxiliary power supply 131.

At this time, in a state in which the primary voltage V1 is higher than the discharge voltage V _dc of the auxiliary power supply 131, also is closed discharge switch 33, until the primary voltage V1 is lower than the discharge voltage V _dc from the auxiliary power 131 Input of the discharge energy to the ignition coil 2 is stopped.
When the discharge path is interrupted and the primary voltage V1 becomes lower than the discharge voltage _Vdc , the discharge from the auxiliary power supply 131 to the ignition coil 2 becomes possible. However, since the discharge path is lost, the discharge energy released from the auxiliary power supply 131 is It will be consumed to cause re-discharge.
For this reason, it has been found that the input energy from the auxiliary power supply 131 is used for the growth of flame nuclei, and there is a possibility that stable ignition cannot be realized.

  Therefore, in view of such circumstances, the present invention reliably maintains discharge over a long period of time even under difficult-ignition combustion conditions in which a strong in-cylinder airflow is generated in the combustion chamber, and exhibits stable ignitability. An object of the present invention is to provide an ignition device for an internal combustion engine.

  The ignition device (4) of the present invention is boosted by at least a DC power source (1), a primary coil (20) and a secondary coil (21) wound by a predetermined winding ratio (N = N2 / N1). An ignition coil (2) constituting a transformer, energization from the DC power source (1) to the ignition coil (2), and from the ignition coil (2) to an ignition plug (6) provided in the internal combustion engine (5) And a control circuit (3) for controlling the discharge of the spark, and applying a high secondary voltage (V2) to the spark plug (6) to generate a discharge arc, and superimposing discharge maintaining energy during the discharge period. In the ignition device to be turned on, the control circuit (3) at least discharges the ignition switch (30), two or more auxiliary power sources (131, 231), and these auxiliary power sources (131, 231). A discharge switch (33) to be controlled; The secondary voltage detection means (36) for detecting the secondary voltage (V2) of the ignition coil (2), and the plurality of auxiliary devices are compared by comparing the detected secondary voltage (V2) with a predetermined threshold value (Vth). Switching necessity determining means (37) for determining whether or not the power supply (131, 132) needs to be switched, and one of the plurality of auxiliary power supplies (131, 132) and the discharge switch (33) according to the determination result. And a power supply selector switch (SSW38) for switching the connection to the.

According to the present invention, after the spark plug (6) is discharged by the application of the high secondary voltage V2 generated in the secondary coil (21), during the induction discharge period from the secondary coil (21). In addition, discharge sustaining energy is superimposed on the ignition coil (2) from the first auxiliary power supply (131) selected from the plurality of auxiliary power supplies (131, 231) to maintain the discharge. When the secondary voltage (V2) detected by the secondary voltage detection means (36) exceeds a predetermined threshold (Vth), the power supply changeover switch (SSW38) causes the first auxiliary power supply (131) to By switching the discharge energy input to the discharge energy input from the other auxiliary power source (231), the discharge voltage (Vdc1, Vdc2) is always higher than the primary voltage (V1) of the ignition coil (2). Even if a strong in-cylinder airflow is generated in the combustion chamber, the energy is continuously supplied from the auxiliary power source (131, 231) to the ignition coil (2) without being blown out. Ignition can be realized.
In addition, since the switching from the first auxiliary power supply (131) to the second auxiliary power supply 231 is performed only when the power supply switching necessity determining means (37) determines that it is necessary, excessive energy is required. It is also possible to prevent the electrode from being consumed by the insertion.

The block diagram which shows the outline | summary of the ignition device 4 in embodiment of this invention Time chart showing the operation of the ignition device 4 of FIG. The block diagram which shows the outline | summary of the ignition device 4z shown as a comparative example Time chart showing the problems of the comparative example

With reference to FIG. 1, the outline | summary of the ignition device 4 in embodiment of this invention is demonstrated.
The ignition device 4 of the present invention includes a DC power source 1, an ignition coil 2 that constitutes a step-up transformer by a primary coil 20 and a secondary coil 21 wound by a predetermined winding ratio (N = N2 / N1), a direct current The control circuit 3 controls the energization from the power source 1 to the ignition coil 2 and the discharge from the ignition coil 2 to the ignition plug 6 provided in the internal combustion engine 5 (not shown). A high voltage V2 is applied to the ignition plug 6. An ignition device that generates a discharge arc and superimposes discharge maintenance energy during the discharge period to maintain discharge, and has the following configuration to realize stable ignition It is.
In the ignition device 4, the control circuit 3 has at least an ignition switch 30, a plurality of auxiliary power supplies 131 and 231, a discharge switch 33 that controls discharge from these auxiliary power supplies, and a secondary voltage V2 of the ignition coil 2. Secondary voltage detection means 36 to detect, switching necessity judgment means 37 for judging whether or not the auxiliary power source needs to be switched by comparing the detected secondary voltage V2 and a predetermined threshold value Vth, and a plurality of results depending on the judgment result. The power supply selector switch SSW 38 for switching between the auxiliary power supply 131 and 132 and the discharge switch 33 to be connected is provided.

Further, among the plurality of auxiliary power supplies 131 and 231, the discharge from the power supply selectively connected by the power supply switch SSW 38 to the ignition coil 2 is performed from the negative side of the primary coil 20.
In the present embodiment, an example is shown in which two auxiliary power sources, ie, the first auxiliary power source 131 and the second auxiliary power source 231 are provided, but the number of auxiliary power sources is not limited to two. Two or more is sufficient.

As the DC power source 1, a well-known DC stabilized power source or the like obtained by DC conversion of an on-vehicle battery or an AC power source using a regulator or the like is used, and a constant DC voltage + B such as 12 V or 24 V is supplied.
Further, as the DC power source 1, a power source boosted to a high voltage by a known DC-DC converter or the like may be used.

The ignition coil 2 includes at least a primary coil 20 in which the coil winding is wound N1 times, a secondary coil 21 in which the coil winding is wound N2 times, and a rectifier element 22, and a known ignition that constitutes a so-called induction discharge type step-up transformer. A coil can be used as appropriate.
The transformation ratio V2 / V1 between the primary voltage V1 and the secondary voltage V2 of the ignition coil 2 is set to a winding ratio N (= N2 / N1) between the number of turns N1 of the primary coil 20 and the number of turns N2 of the secondary coil 21. Almost equal. The present invention can be applied to both a so-called stick-type ignition coil that can be accommodated in a plug hole and a so-called plug-top type ignition coil that can be accommodated in a housing fixed to the upper part of the plug hole. is there.

In the present embodiment, the control circuit 3 includes an ignition switch 30, a first auxiliary power supply 131, a second auxiliary power supply 231, a charging driver 32, a discharging switch 33, a discharging driver 34, and a rectifying element 35. And a secondary voltage detecting means 36, a switching necessity determining means 37, and a power source changeover switch 38.
The ignition switch 30 uses a power transistor such as an IGBT or a thyristor, and is controlled to open and close in accordance with an ignition signal IGt transmitted from an engine control unit (ECU) 7 provided outside in accordance with the operating state of the internal combustion engine 5.

The first and second auxiliary power supplies 131 and 231 include first and second choke coils 132 and 231, first and second charge switches 133 and 233, and first and second rectifier elements 134, respectively. 234 and first and second capacitors 135 and 235.
For the first and second choke coils 131 and 231, coils with cores having predetermined inductances L ₁₃₁ and L ₂₃₂ (for example, 5 to 50 μH) are used.
The upstream sides of the first and second choke coils 132 and 232 are each connected to the DC power source 1, and the downstream sides are grounded via the first and second charging switches 133 and 233, respectively.

For the first and second charge switches 133 and 233, power transistors such as IGBTs and MOSFETs are used.
A charging driver 32 is connected to each gate G of the first and second charging switches 133 and 233.

The charging driver 32 generates gate voltages VG ₁₃₃ and VG ₂₃₃ that oscillate with predetermined opening / closing pulses in accordance with the ignition signal IGt transmitted from the ECU 7 and drives the first and second charging switches ₁₃₃ and ₂₃₃ to open and close. .
The charging driver 32 may generate a driving pulse by any method as long as the first and second charging switches 133 and 233 can be controlled to open and close at a predetermined cycle while the discharge period signal IGw is off. A known gate driver including a charge pump can be used as appropriate.
In the present embodiment, the example in which the first charging switch 133 and the second charging switch 233 are controlled to be opened and closed by one charging driver 132 is shown. However, the charging switches 133, An individual charging driver may be provided in 233.

Between the first and second choke coils 132 and 232 and the first and second charge switches 133 and 233, the first and second rectifier elements 134 and 234 are respectively connected to the first and second choke coils 132 and 232, respectively. Second capacitors 135 and 235 are connected in parallel.
As the first and second capacitors 135 and 235, capacitors having predetermined capacitances C1 and C2 (for example, 100 to 1000 μF) are used, respectively.
As the first and second rectifying elements 134 and 234, diodes or the like are used, and the first and second choke coils 132 and 232 from the first and second capacitors 135 and 235, or the first and second charge switches. The backflow to the 133,233 side is blocked.
By opening and closing the first and second charge switches 133 and 233, the energy stored in the first and second choke coils from the DC power supply 1 is charged in the first and second capacitors 135 and 235, respectively. .

The first and second auxiliary power supplies 131 and 231 are connected in parallel, and the outputs Vdc1 and Vdc2 are respectively connected to the first and second inputs S1 and S2 of the power supply switch SSW38.
The power supply switch SS38 switches which terminal of the first and second inputs S1 and S2 is connected in accordance with the switching signal SS of the switching necessity determination unit 37, and the first and second auxiliary power supplies 131 are switched. , 132 from which auxiliary power is to be discharged.

A discharge switch 33 is connected downstream of the changeover switch SSW38.
For the discharge switch 33, a power transistor such as an n-MOSFET or FET is used.
A discharge driver 34 is connected to the gate G of the discharge switch 33.
The drain D of the discharge switch 33 is connected to the output side of the changeover switch 38, and the source S is connected to the negative side of the primary coil 20 of the ignition coil 2.

As the discharge driver 34, a known gate driver including a charge pump or the like can be used.
The discharge driver 34 generates a gate voltage VG ₃₃ that oscillates with a predetermined open / close pulse in accordance with the discharge period signal IGw transmitted from the ECU 7, and drives the discharge switch 33 to open / close.

On the secondary side of the ignition coil 2, secondary voltage detection means 36 for detecting the secondary voltage V <b> 2 is provided.
In the present embodiment, an example is shown in which voltage dividing resistors 361 (R1) and 362 (R2) are provided as the secondary voltage detecting means 36. However, in the present invention, the secondary voltage detecting means 36 is particularly limited. Not what you want.
Any device can be used as long as the secondary voltage V2 during the discharge of the ignition coil 2 can be detected. The secondary current I2 that flows through the spark plug 6 by using a diode or a capacitor, a current sense MOSFET, A known secondary voltage detecting means such as one that detects the voltage and calculates the secondary voltage V2 can be appropriately employed.

The secondary voltage detection means 36 is connected to the secondary voltage determination means 37.
The secondary voltage determination means 37 compares the detected secondary voltage V2 with a predetermined threshold value Vth, and when the secondary voltage V2 exceeds the threshold value Vth, it is determined that the primary voltage V1 is increased by extending the discharge. Therefore, the switching signal SS is output.
The threshold value Vth is a voltage that becomes a blow-off limit at which the discharge arc is extended by the in-cylinder airflow and the discharge is blown out when energy is input only from the first auxiliary power supply 131.

The specific threshold value Vth is generated by, for example, previously providing a spark plug 6 in a pressure vessel simulating an actual engine or combustion chamber, and applying a high secondary voltage V2 using the ignition coil 2 to generate a discharge arc. After that, discharge energy is input from the first auxiliary power supply 131 to generate a strong air current acting as a discharge arc in the pressure vessel in a state of maintaining the discharge, and a secondary voltage when blowout occurs. It can be determined by measuring V2 or the like.
When the switching signal SS is output from the secondary voltage determination means 37, the switch is switched and the SSW 38 is switched from S1 to S2.

After the second auxiliary power supply 231 and the discharge switch 33 are connected by the changeover switch SSW38, energy is input from the second auxiliary power supply 231.
At this time, the discharge voltage Vdc2 of the second discharge power source 231 is much higher than the primary voltage V1, and thus discharges sufficient energy to maintain the secondary current without interruption of the discharge. be able to.
In the present embodiment, a specific example of the peak of the primary voltage V1 is about several hundred volts, but the first and second discharge voltages Vdc1, Vdc2, the primary voltage V1, two The degree to which the next voltage V2 is set is a design matter that is appropriately set depending on the winding ratio N of the ignition coil 2, the discharge gap of the spark plug 6, the combustion characteristics of the internal combustion engine to be applied, and the like. is not.

  In the ignition device 4 of the present invention, the high secondary voltage V2 generated in the secondary coil 21 of the ignition coil 2 is applied to the ignition plug 6 provided for each cylinder of the internal combustion engine 5 between the discharge electrodes of the ignition plug 6. During the induction discharge from the secondary coil 21 of the ignition coil 2, discharge sustaining energy is superimposed on the negative side of the primary coil 20 of the ignition coil 2 from the first auxiliary power supply 131. Based on maintaining the discharge, when the secondary voltage V2 detected by the secondary voltage detecting means 36 exceeds a predetermined extinction limit voltage Vth, the power supply changeover switch SSW38 causes the first auxiliary power supply 131 to By switching the discharge to the discharge from the second auxiliary power source 231, the energy is applied to the negative side of the primary coil 21 of the ignition coil 2 without causing blowout. Than it such that it is possible to maintain.

In addition, since the switching from the first auxiliary power supply 131 to the second auxiliary power supply 231 is performed only when the secondary voltage V2 is detected and determined to be necessary, electrode consumption due to excessive energy input is prevented. You can also.
The control circuit 3 can be constituted by a semiconductor integrated circuit. If necessary, a capacitor, a coil, and the like are mounted and housed in a housing (not shown) together with the ignition coil 2 for use.

With reference to FIG. 2, the basic operation and effect of the ignition device 1 according to the first embodiment of the present invention shown as Example 1 will be described.
2A shows the ignition signal IGt transmitted from the ECU 7, FIG. 2B shows the discharge period signal IGw, and FIG. 2C shows the first charge signal VG for opening and closing the first charge switch 133. the _133, (d) is a second charging signal _{VG 233} for opening and closing the second charging switch 233, (e), the opening and closing state of the ignition switch 30, (f), the opening and closing of the discharge switch 33 (G) is a change state of the power source changeover switch 38, (h) is a change of the first discharge voltage Vdc1, (i) is a change of the second discharge voltage Vdc2, (j) Is a _{graph in which} the change in the drain voltage V _DD of the discharge switch 33 and the change in the primary side generated voltage V2 / N are superimposed, (k) is the change in the primary side generated voltage V2 / N (N is the turn ratio), (L) shows the change of the secondary voltage V2, and (m) shows the change of the secondary current I2. .

Even if V1 is detected at the negative position of the primary coil 20 shown in FIG. 1, if the discharge switch 33 is on and the drain voltage V _DD is higher than the voltage generated in the primary coil 20, When the voltage generated in the primary coil 20 is equal to one of the discharge voltages Vdc1 and Vdc2 of the first and second capacitors 135 and 235 and higher than the drain voltage V _DD , the voltage is generated in the primary coil 20 Thus, a value equal to the voltage V2 / N (N is the winding ratio) is detected, and the magnitude relationship between the drain voltage V _DD and the primary voltage V1 generated in the primary coil 20 cannot be detected.
Therefore, the primary side generated voltage of (j) and (k) shows only the change of V2 / N.

As shown in FIG. 4A, an ignition signal IGt corresponding to the ignition timing of the internal combustion engine 5 is transmitted from the ECU 7.
As shown in FIG. 4B, a discharge period signal IGw set in advance according to the operating condition of the internal combustion engine 5 is transmitted from the ECU 7.

As shown in FIGS. 7C and 7D, the first and second charging drivers 32 are used to charge the first and second capacitors 135 and 235 in synchronization with the rising of the ignition signal IGt. First and second charge signals VG ₁₃₃ and VG ₂₃₃ for opening and closing the charge switches ₁₃₃ and ₂₃₃ are oscillated at a predetermined pulse cycle, and the first and second charge switches are synchronized with the fall of the ignition signal IGt. The driving of 131 and 232 is stopped.
The charging of the first and second capacitors 135 and 235 is not necessarily limited to the one that is synchronized with the ignition signal IGw as in the present embodiment, and the charging is performed so that sufficient energy can be released during the discharge period IGw. As long as the discharge period signal IGw is off, charging may be performed at any time.

  As shown in FIGS. 11 (h) and (i), the first and second capacitors 135 and 235 are charged by opening and closing the first and second charging switches 135 and 235, and the first and second capacitors 135 and 235 are charged. Discharge voltages Vdc1 and Vdc2 increase.

On the other hand, as shown in FIG. 4E, the ignition switch 30 is turned on in synchronization with the rising edge of the ignition signal IGt, and the ignition switch 30 is turned off in synchronization with the falling edge of the ignition signal IGt.
When the primary current flowing through the primary coil 20 is interrupted by opening and closing the ignition switch 30, an electromotive force V1 is generated in the primary coil 20 by self-induction as shown in FIG. ), A very high secondary voltage V2 of, for example, −20 kV to −50 kV is generated by the mutual induction action in the secondary coil 21 sharing the core.
At this time, the secondary voltage V2 is a turn ratio (N = N2 / N1) times the primary voltage V1.
When the secondary voltage V2 is applied to the spark plug 6 and exceeds the withstand voltage of the discharge space, a discharge arc is generated between the electrodes of the spark plug 6, and as shown in FIG. A current I2 flows.

When the discharge of the spark plug 6 is started, the discharge period signal IGw rises at a predetermined timing when the discharge current I2 becomes small as shown in FIG.
Then, the discharge switch 33 is driven to open and close in synchronization with the rising of the discharge period signal IGw, as shown in FIG.

At this time, as shown in FIG. 5G, the power supply selector switch SSW38 is connected to the first auxiliary power supply 131 side.
Therefore, when the discharge switch 33 is driven to open and close as shown in FIG. 5F with the first and second charge switches 133 and 233 and the ignition switch 30 turned off, the first auxiliary A first discharge voltage Vdc1 is applied from the power supply 131 to the negative side of the primary coil 21 of the ignition coil 2.

By switching on / off the discharge switch 33, the discharge from the first capacitor 135 and the stop are repeated as shown in FIG.
At this time, the discharge voltage Vdc1 of the first capacitor 135 gradually decreases.
Due to the discharge from the first capacitor 135, the primary voltage V1 changes as shown in FIG.

Due to the mutual induction action, the secondary voltage V2 that is a multiple of the turn ratio of the primary voltage V1 also changes as shown in FIG.
At this time, the secondary current I2 that flows as shown in FIG. 5 (m) is introduced as discharge energy into the spark plug 6 to maintain the discharge.

On the other hand, the secondary voltage detection means 36 monitors the secondary voltage V2 applied to the spark plug 6 and monitors whether or not a predetermined threshold value Vth is exceeded.
When the discharge arc is extended by the in-cylinder airflow flowing in the combustion chamber and the secondary voltage V2 exceeds a predetermined threshold value Vth indicating the blow-off limit as shown in FIG. Since the secondary voltage V2 is a negative value (when V2 <Vth), a switching signal SS is output from the power supply switching determination means 37, and the power supply selector switch 38, as shown in FIG. It is switched from S1 to S2.
By switching the power switch 38, the drain voltage V _DD of the discharge switch 33 is switched from the first discharge voltage Vdc1 to the second discharge voltage Vdc2, as shown in FIG.

As shown in FIGS. (K) and (l), the secondary voltage V2 increases due to the extension of the discharge arc, and the primary voltage V1 also increases in proportion to this, as shown in FIG. When the primary voltage V1 becomes higher than the first discharge voltage Vdc1, the discharge from the second auxiliary power source 231 is switched.
At this time, since the second discharge voltage Vdc2 is higher than the primary voltage V1, as shown in FIG. 6 (j), when the discharge switch 33 is opened and closed, the discharge path is not interrupted, and the second capacitor 233 Is discharged.
As a result, as shown in the figure (m), the secondary current I2 flows through the spark plug 6 over a long period of time, and the discharge is maintained, so that stable ignition can be realized.

Next, the problem of the comparative example will be described in detail again with reference to FIGS.
In the following description, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted. Differences are denoted by z as a branch number, and thus the differences are mainly described. To do.
3A shows the ignition signal IGt transmitted from the ECU 7, FIG. 3B shows the discharge period signal IGw, FIG. 3C shows the charge signal VG ₁₃₃ oscillated from the charge driver 32, and FIG. Is the open / closed state of the ignition switch 30, (e) is the open / closed state of the discharge switch 33, (f) is the change in the discharge voltage Vdc, and (g) is the change in the primary side generated voltage V2 / N. , (H) shows the change of the secondary voltage V2, and (i) shows the change of the secondary current I2.

In the comparative example, only the first auxiliary power supply 131 is used, the second auxiliary power supply 231 is not provided, and the charging driver 32z uses only the first charge switch 133 provided in the first auxiliary power supply 131. As a result, in the comparative example, according to the ignition signal IGt, the charging switch 133 is driven to open and close in accordance with the ignition signal IGt, and the first capacitor 135 is charged to the high discharge voltage Vdc. When the ignition coil 2 is opened and closed by the ignition switch 30 in synchronization with the ignition signal IGt, a high secondary voltage V2 is generated and applied to the spark plug 6, and in synchronization with the discharge period signal IGw, the discharge switch 33 When the is opened and closed, energy is input to the spark plug 6 to maintain discharge, similar to the embodiment of the present invention.

However, in the comparative example, since the second auxiliary power source 231 does not exist, a strong air flow is generated in the combustion chamber, and as shown in FIG. 4 (h), when the discharge arc is extended, the secondary voltage V2 increases. In proportion to this, as shown in FIG. 4G, the primary side generated voltage V2 / N (N is the winding ratio) also increases.
Then, as shown in FIG. 4F, the primary-side generated voltage V2 / N becomes higher than the discharge voltage Vdc1 of the first auxiliary power supply 131 while the discharge switch 33 is open.

In this state, even if the discharge switch 33 is closed, since the discharge voltage Vdc1 of the first capacitor 133 is lower than the primary side generated voltage V2 / N, a current is supplied from the first auxiliary power supply 131 to the primary coil 20. It cannot be shed.
For this reason, the secondary voltage V2 decreases due to the energy release from the secondary coil 21, and thereby the primary voltage V1 also decreases, and the discharge energy is reduced until it becomes lower than the discharge voltage Vdc1 of the first auxiliary power supply 131. The input will be stopped.

Therefore, when the discharge becomes possible again, the discharge path is interrupted and the discharge arc is blown out, and the energy input by the discharge from the first auxiliary power supply 131 is wasted for the re-discharge and the growth of the flame. Because it is not used for, there is a risk of misfire.
Further, in the period A shown in FIG. 4 (e), even if the discharge switch 33 is opened and closed, the discharge path disappears and no discharge is performed.

  The present invention has been made on the basis of the above knowledge. By detecting the secondary voltage V2 and determining the threshold value, it is generated on the primary side, which is substantially equal to the turn ratio N of the secondary voltage V1. As long as the change in voltage is predicted and the first and second auxiliary power supplies 131 and 231 are switched to maintain the discharge, the change can be appropriately made.

4 Ignition Device 1 DC Power Supply 2 Ignition Coil 20 Primary Coil 21 Secondary Coil 22 Rectifier 3 Control Circuit 30 Ignition Switch 131 First Auxiliary Power 132 First Choke Coil 133 First Charging Switch 134 First Rectifier 135 First capacitor 231 Second auxiliary power source 232 Second choke coil 233 Second charging switch 234 Second rectifier 235 Second capacitor 32 Driver for charging (DRV1)
33 Discharge switch 34 Discharge driver (DRV2)
35 Rectifier element 36 Secondary voltage detection means 37 Power supply switching necessity determination means 38 Power supply switch (SSW)
5 Internal combustion engine 6 Spark plug 7 Engine control unit (ECU)
IGt Ignition signal IGw Discharge period signal V1 Primary voltage V2 Secondary voltage SS Power supply switching signal

Claims (3)

At least an ignition coil (2) that constitutes a step-up transformer by a DC power source (1), a primary coil (20) and a secondary coil (21) wound by a predetermined winding ratio (N = N2 / N1) A control circuit (3) for controlling energization from the DC power source (1) to the ignition coil (2) and discharging from the ignition coil (2) to a spark plug (6) provided in the internal combustion engine (5). ), Applying a high secondary voltage (V2) to the spark plug (6) to generate a discharge arc, and then superimposing discharge maintenance energy during the discharge period,
The control circuit (3)
at least,
An ignition switch (30);
Two or more auxiliary power supplies (131, 231);
A discharge switch (33) for controlling discharge from these auxiliary power sources (131, 231);
Secondary voltage detection means (36) for detecting a secondary voltage (V2) of the ignition coil (2);
A switching necessity determining means (37) for determining whether or not switching of the plurality of auxiliary power sources (131, 231) is performed by comparing the detected secondary voltage (V2) with a predetermined threshold (Vth);
An ignition device comprising: a power supply selector switch (SSW38) for switching connection between any one of the plurality of auxiliary power supplies (131, 132) and the discharge switch (33) according to a result of the determination.   The discharge from the power supply selectively connected by the power supply selector switch (SSW38) among the plurality of auxiliary power supplies (131, 231) to the ignition coil 2 is performed from the negative side of the primary coil (20). Ignition device according to 1   The auxiliary power source (131, 231) includes a choke coil (132, 232), a charge switch (133, 233), a rectifier element (134, 234), and a capacitor (135, 235). The ignition device according to claim 1, wherein the ignition device is a converter.

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