JP5909977B2 - Ignition device for internal combustion engine - Google Patents

Description

  The present invention relates to an ignition device for an internal combustion engine that discharges by applying a secondary voltage to an ignition plug.

  FIG. 19A is a diagram showing a center electrode 31 and a ground electrode 32 of a spark plug 30 provided in a general ignition type engine. Normally, a discharge generated between both electrodes 31 and 32 is as follows. As indicated by reference numeral SP1, the discharge path is formed with the shortest length. However, in recent years, there has been a tendency to increase the compression ratio for the purpose of improving fuel efficiency, and the development of technology for generating vortex flows such as tumble flow and swirl flow in the combustion chamber has progressed, particularly in lean combustion engines. In an engine that generates such a vortex, the speed of the in-cylinder airflow F is high. For this reason, the voltage at which the spark plug 30 can start discharging becomes as high as 35 kV or more, and the generated induction discharge path of several kV is stretched by the in-cylinder airflow F (see reference SP2).

  Further, when the in-cylinder airflow F is strong, the discharge blows out within a desired discharge period, and there is a concern that misfire may occur without normal ignition (Problem 1). In addition, when such a blow-off of the discharge occurs, immediately after that, a re-discharge due to the secondary voltage of the coil occurs between the shortest distances of both the electrodes 31 and 32 (path SP1). Therefore, a discharge repetition phenomenon in which discharge blow-off and re-discharge are repeated many times occurs, and consumption of the electrodes 31 and 32 (plug consumption) is promoted (Problem 2).

  The above-mentioned misfire problem 1 due to blow-off of the discharge can be solved by increasing the discharge energy by increasing the output current (secondary current I2) of the ignition coil as shown by the solid line in FIG. . However, as shown in FIG. 19B, since the secondary current I2 due to the coil gradually decreases with time, the secondary current I2 until the end time t5 of the desired discharge period Ta is blown out. In order to make it not less than a certain value (sustain current Ith), the secondary current I2 (peak current Ipeak) at the discharge start time t3 must be significantly larger than the sustain current Ith. Therefore, a new problem 3 occurs in which plug consumption at the discharge start time t3 increases. Moreover, simply increasing the secondary current I2 in this way does not solve the problem 2 because the discharge repetition phenomenon due to blow-off occurs immediately after the end of the discharge period Ta as shown in FIG. 19C.

  Therefore, in the circuit described in Patent Document 1, a DC power source that outputs the discharge sustaining current I3 is provided on the low voltage side of the secondary coil, and a current obtained by adding the discharge maintaining current I3 to the secondary current I2 is discharged by the spark plug 30. Yes. According to this, the plug current can be suppressed by reducing the peak current Ipeak from the dotted line position to the solid line position in FIG. 19D, and the secondary current I2 in the desired discharge period Ta is set to be equal to or higher than the sustain current Ith. The discharge blowout can be avoided. That is, the above-described problems 1 and 3 can be solved.

JP 58-162772 A

  However, in the DC power source described in Patent Document 1, when the output of the discharge sustaining current I3 is stopped after the end of the desired discharge period Ta, the discharge sustaining current I3 gradually decreases with time and becomes zero (see reference numeral Ip). . In the process of becoming zero, the discharge cannot be maintained and blowout occurs. When blowout occurs, the output of the coil is in a no-load state, so the secondary voltage may rise again and lead to re-discharge. For this reason, the discharge repetition phenomenon cannot be avoided during the period in which the discharge sustaining current I3 decreases in this way, and the problem 2 of plug consumption due to the phenomenon cannot be solved.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ignition device for an internal combustion engine that avoids discharge blowout and suppresses plug consumption due to repeated discharge.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

In the first invention, the ignition coil has a primary coil and a secondary coil, and outputs a secondary current flowing through the secondary coil to an ignition plug, and the secondary current output from the ignition coil is different from the ignition coil Power source means for outputting a discharge sustaining current to the spark plug, and the discharge at the spark plug is started by the output voltage of the secondary coil, and the discharge at the spark plug is ended by stopping the output of the discharge sustaining current. Discharge control means for controlling the power supply means, and the power supply means is electrically connected to the spark plug so that the discharge sustaining current is supplied to the spark plug without passing through the secondary coil.

  Here, in the invention described in Patent Document 1 described above, when the output of the discharge sustaining current I3 is stopped, a discharge repetitive phenomenon occurs due to the discharge sustaining current I3 gradually decreasing with time to zero. Is as described above. And in this conventional invention, this inventor found out that the discharge maintenance current I3 decreased gradually because the power supply means was electrically connected to the spark plug via the secondary coil. That is, in such an electrical connection, since the energy of the discharge sustaining current is stored in the secondary coil (inductance), even if the power supply means is stopped, the stored energy is discharged to the spark plug, and the discharge maintaining current is discharged. I3 will gradually decrease.

  In the above invention in view of this knowledge, since the power supply means is electrically connected to the spark plug so that the discharge sustain current is supplied to the spark plug without passing through the secondary coil, the energy of the discharge sustain current is Can be avoided. Therefore, after the discharge sustaining current from the power supply means is stopped, the discharge sustaining current does not gradually decrease under the influence of the reactor of the secondary coil. Therefore, it is possible to avoid the repeated discharge phenomenon and suppress plug consumption.

  Further, according to the above invention, since the discharge at the spark plug can be maintained by the discharge sustaining current from the power supply means, it is unnecessary to increase the secondary current from the ignition coil for the purpose of maintaining the discharge, It is possible to suppress the discharge from being blown out during a desired discharge period. In addition, even if it blows off, it is possible to avoid the discharge sustaining current from gradually decreasing as described above, so that re-discharge can be avoided. Therefore, while solving the above-described problem 3 such as plug consumption at the start of discharge, the above-described problem 2 such as misfire due to discharge blowout (problem 1) and plug consumption due to re-discharge (discharge repetition phenomenon) can also be solved.

According to a second aspect of the present invention, there is provided constant current output means for maintaining the discharge sustaining current at a constant value even when the length of the discharge path generated by the spark plug is changed.

  By the way, as exemplified by reference numeral SP2 in FIG. 19A, even when the discharge generated by the spark plug is extended to the longest possible state, the state is not blown out. In the case where a voltage that can be maintained is called a sustain voltage, the power supply means outputs a discharge sustain current within a power supply voltage range (for example, a range of 4 kV to 8 kV) that is equal to or higher than the sustain voltage and does not cause re-discharge. desirable. According to this, the certainty of avoiding discharge blow-off and avoiding re-discharge can be improved.

  However, contrary to the above invention, if the constant current output means is not provided, if the discharge sustain current is output at the maximum sustain voltage until the discharge path is not stretched, the discharge current flowing through the spark plug becomes excessive. Since it becomes large, plug consumption is promoted. On the other hand, according to the above-mentioned invention having the constant current output means, even when the length of the discharge path changes according to the state of the in-cylinder airflow, the discharge sustaining current is maintained at a constant value, and the voltage is Since it is changed within the range of the power supply voltage, it is possible to suppress plug consumption while improving the reliability of discharge blow-off and avoidance of re-discharge.

According to a third aspect of the invention, there is provided adjusting means for adjusting the magnitude of the discharge sustaining current in accordance with a change in secondary current from the ignition coil.

  Here, the secondary current from the ignition coil changes so as to gradually approach zero over time. Therefore, for example, when the secondary current gradually decreases, if the discharge sustaining current is gradually increased in accordance with the decrease, the total amount (discharge current) of the secondary current and the discharge maintaining current changes. This can be suppressed. That is, while preventing blowout, the discharge current at the start of discharge can be reduced (in the case of minus discharge) to increase the effect of suppressing plug consumption.

In a fourth aspect of the invention, the adjusting means adjusts the discharge sustain current so that a value obtained by adding the discharge sustain current to the secondary current (a value of the discharge current flowing through the spark plug) becomes a predetermined constant current value. The size is adjusted.

  According to this, the discharge current (secondary current + discharge sustaining current) flowing through the spark plug can be maintained at a substantially constant constant current value during the period from the start to the end of the discharge (see FIG. 7D). Accordingly, the discharge current at the start of discharge can be suppressed to a constant current value while avoiding blow-off, so that plug consumption at the start of discharge can be promoted while avoiding blow-off.

The figure which shows schematic structure of the ignition system in 1st Embodiment. The time chart explaining the action | operation of the ignition system in 1st Embodiment. The figure which shows the constant current circuit in 1st Embodiment. The figure which shows the on-off circuit in 1st Embodiment. The figure which shows schematic structure of the ignition system in 2nd Embodiment. The figure which shows schematic structure of the ignition system in 3rd Embodiment. The time chart explaining the action | operation of the ignition system in 3rd Embodiment. The figure which shows the correction circuit in 3rd Embodiment. The figure which shows schematic structure of the ignition system in 4th Embodiment. The time chart explaining the action | operation of the ignition system in 4th Embodiment. The figure which shows schematic structure of the ignition system in 5th Embodiment. The time chart explaining the action | operation of the ignition system in 5th Embodiment. The figure which shows the on-off circuit in 5th Embodiment. The figure which shows schematic structure of the ignition system in 6th Embodiment. The time chart explaining the action | operation of the ignition system in 6th Embodiment. The figure which shows the correction circuit in 6th Embodiment. The figure which shows schematic structure of the ignition system in 7th Embodiment. The time chart explaining the action | operation of the ignition system in 7th Embodiment. The figure explaining the conventional subject.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
The present embodiment is an ignition device intended for an ignition engine (internal combustion engine) mounted on a vehicle. In the ignition device, an ignition plug is used based on an ignition command from an electronic control unit (hereinafter referred to as ECU). It is supposed to cause ignition discharge. First, a schematic configuration of an ignition system including an ignition device will be described with reference to FIG.

  A microcomputer (microcomputer) provided in the ECU 5 (discharge control means) acquires operating state information indicating the operating state of the engine such as the engine speed and the accelerator operation amount, and optimal ignition timing based on the operating state information. Is calculated. Then, an ignition signal IGt is generated according to the ignition timing and the coil energization time, and is output to the waveform shaping circuit 10.

  The waveform shaping circuit 10 outputs a drive signal IG for turning on / off the power element 11 as the switch means based on the ignition signal IGt input from the ECU 5. Specifically, the power element 11 is turned on / off according to the ignition signal IGt, and ignition discharge is generated at the ignition timing.

  The ignition coil 20 provided for each cylinder includes a primary coil 21 and a secondary coil 22. One end of the primary coil 21 is connected to the high potential (+12 volts) side of the battery via a power supply circuit (not shown), and the other end is grounded via the power element 11. The gate of the power element 11 is connected to the waveform shaping circuit 10, and the power element 11 is on / off controlled by the drive signal IG output from the waveform shaping circuit 10.

  One end of the secondary coil 22 is connected to the spark plug 30 via the diode 12, and the other end of the secondary coil 22 is grounded. The diode 12 is connected to the center electrode 31 through the noise reducing resistor 13 built in the spark plug 30. In addition, let the current which flows through the primary coil 21 and the secondary coil 22 be the primary current I1 and the secondary current I2, respectively, and let the voltage of the primary coil 21 and the secondary coil 22 be the primary current V1 and the secondary voltage V2.

  A center electrode 31 (plus electrode) of the spark plug 30 is connected to the secondary coil 22 through the resistor 13 and the diode 12, and a ground electrode 32 (minus electrode) of the spark plug 30 is connected (grounded) to the chassis. The ignition device according to the present embodiment is a circuit that discharges (plus discharge) a current by flowing the current to the ground side by setting the secondary voltage V2 to a high potential with respect to the ground.

  The DC-DC converter 40 (power source means) functions as a power source different from the ignition coil 20, and boosts the voltage of 12V supplied from the battery to 4 kV, for example, to a constant current circuit 50 (constant current output means). ). The constant current circuit 50 outputs the 4 kV voltage input from the DC-DC converter 40 while maintaining the current value constant. The constant current at this time is set to a current that can continue the discharge after the spark, for example, 60 mA. This is called a discharge sustaining current I3, and this discharge sustaining current I3 flows into the spark plug 30 via the diode 14. . Therefore, the discharge current I4 discharged by the spark plug 30 is a value obtained by adding the discharge sustaining current I3 to the secondary current I2 (I4 = I2 + I3).

  By providing the diode 12, the discharge sustaining current I3 flows to the spark plug 30 without flowing to the secondary coil 22. In addition, by providing the diode 14, the secondary current I <b> 2 flows to the spark plug 30 without flowing to the constant current circuit 50. Further, since the DC-DC converter 40 is electrically connected to the spark plug 30 in parallel with the secondary coil 22, the discharge sustaining current I 3 is supplied to the spark plug 30 without passing through the secondary coil 22. Become.

  Here, when the discharge generated between the electrodes 31 and 32 is stretched by the in-cylinder airflow F (see symbol SP2 in FIG. 19A), the potential difference between the electrodes 31 and 32 increases. For example, the potential difference is 800 V to 1 kV at the normal time indicated by reference symbol SP1, whereas it is 2 to 3 kV when stretched as indicated by reference symbol SP2. Therefore, in the case of a power supply that does not include the constant current circuit 50, the discharge sustaining current I3 when not stretched is unnecessarily large because the discharge path is shorter than when stretched, and plug consumption increases. End up. That is, according to the present embodiment including the constant current circuit 50, the discharge sustaining current I3 can be maintained at a constant value regardless of the state of discharge, and plug consumption can be suppressed.

  The on / off circuit 60 switches on and off the constant current circuit 50 based on the ignition signal IGt input to the waveform shaping circuit 10. That is, the constant current circuit 50 switches between an output state in which the discharge sustaining current I3 is output and a stop state in which the output is stopped. When the output state is switched to the stop state, the value of the discharge sustaining current I3 becomes zero stepwise from a predetermined constant value. Similarly, when switching from the stopped state to the output state, the value of the discharge sustaining current I3 increases stepwise from zero.

  Incidentally, a circuit for gradually decreasing the discharge sustaining current I3 may be provided, or a circuit for gradually increasing the discharge sustaining current I3 may be provided. However, it is necessary not to connect the DC-DC converter 40, the spark plug 30, and the secondary coil 22 in series.

  Next, the operation of the ignition system will be described with reference to FIG. (A) to (f) in the figure are time charts showing changes in the ignition signal IGt, the secondary voltage V2, the secondary current I2, the on / off signal, the discharge sustaining current I3, and the discharge current I4, respectively.

  First, when the ignition signal IGt is switched from OFF to ON at time t1 in the figure, the power element 11 is turned ON. Thereby, energization to the primary coil 21 is started. Thereafter, when the ignition signal IGt switches from on to off at time t3, the power element 11 is turned off. Thereby, the energization to the primary coil 21 is cut off, and a high voltage is generated in the secondary coil 22 and applied to the plug electrode. When the spark voltage (for example, 35 kV) is reached between the plug electrodes, the discharge is started and the secondary current I2 starts to flow (see FIG. 2B). The magnitude of the secondary current I2 has a peak value at the time t3 'at which flow starts, but gradually decreases in the subsequent induction discharge period and becomes zero at the time t4 (see FIG. 2C).

  On the other hand, the on / off circuit 60 switches the constant current circuit 50 from the off state to the on state at time t2 immediately before the ignition signal IGt switches from on to off. As a result, the discharge sustaining current I3 can be output immediately before the time point t3 'when the spark plug 30 starts discharging (see FIG. 2D). Even after the time t2 when the discharge sustaining current I3 can be output, the spark plug 30 does not discharge until the output of the secondary current I2 is started. Then, after the discharge is generated with the high voltage from the secondary coil 22, the output of the discharge sustaining current I3 is started.

  Then, at the time t5 when the desired discharge period Ta has elapsed from the discharge start time, the on / off circuit 60 switches the constant current circuit 50 from the on state to the off state, thereby setting the discharge sustaining current I3 to zero in a stepwise manner (FIG. 2 (e)). The value of the current discharged by the spark plug 30 (discharge current I4) is a value obtained by adding the discharge sustaining current I3 to the secondary current I2 (see FIG. 2 (f)). Since the secondary current I2 has already become zero at time t5 when the discharge period Ta ends, the discharge current I4 also becomes zero in a stepped manner at time t5 when the discharge period Ta ends, similarly to the discharge sustain current I3. Become.

  Next, a specific circuit configuration of the constant current circuit 50 will be described with reference to FIG. FIG. 3A shows a configuration example employing an NPN type semiconductor switch (transistors 51 and 52). When power is supplied to the constant current circuit 50, a voltage is applied to the base of the transistor 51 by the bias resistor 53. The transistor 51 is turned on. Then, the current value flowing through the resistors 54 and 55 changes according to the current value flowing through the transistor 51, and the base voltage of the transistor 52 also changes.

  Therefore, if the current flowing through the transistor 51 is increased, the current flowing through the transistor 52 is increased by that amount, so that the base voltage of the transistor 51 is decreased. Accordingly, an increase in current flowing through the transistor 51 is limited. On the other hand, if the current flowing through the transistor 51 is to be reduced, the current flowing through the transistor 52 is reduced accordingly, and the base voltage of the transistor 51 is increased. Therefore, the current flowing through the transistor 51 is limited from being reduced.

  As described above, according to the constant current circuit 50 of FIG. 3A, the current flowing through the transistor 51 is adjusted to a constant value, and as a result, the current flowing through the resistor 54 (discharge sustaining current I3) is adjusted to a constant value. . Incidentally, when the base voltage of the transistor 52 is Vf and the resistance value of the resistor 54 is Rd, the discharge sustaining current I3 has a value of Vf / Rd.

  FIG. 3B shows a configuration example in which a PNP type semiconductor switch (transistors 51a and 52a) is adopted. Like the case of FIG. 3A, the increase and decrease of the current flowing through the transistor 51a is limited, and the resistance The current flowing through 54 (discharge sustaining current I3) is adjusted to a constant value.

  Next, a specific circuit configuration of the on / off circuit 60 will be described with reference to FIG. First, when the on / off signal input from the waveform shaping circuit 10 to the on / off circuit 60 is turned on, a voltage is applied to the base of the semiconductor switch (transistor 62) by the bias resistor 61, and the transistor 62 is turned on. Then, as the current flows through the Zener diode 63 and the resistor 64, the base voltage of the semiconductor switch (transistor 65) is lowered, and the transistor 65 is turned on. That is, the on / off circuit 60 is turned on, and the current Ia flows from the DC-DC converter 40 to the constant current circuit 50.

  On the other hand, when the ON / OFF signal is switched from ON to OFF, the transistor 62 that is ON is switched to OFF and the base voltage of the transistor 65 is raised. Therefore, the transistor 65 that has been turned on is switched to the off operation, and the current Ia is cut off. At the time of this interruption, the current Ia flowing through the transistor 65 has an inductance (secondary coil 22) connected in series between the DC-DC converter 40 and the spark plug 30 as in the invention described in Patent Document 1. Therefore, it does not gradually decrease under the influence of a reactor or the like, but is instantaneously shut off and becomes zero. Therefore, at time t5 (see FIG. 2) when the on / off signal input to the on / off circuit 60 is switched from on to off (see FIG. 2), the current Ia flowing from the DC-DC converter 40 to the constant current circuit 50 is instantaneously cut off, and the discharge maintaining current. I3 is stopped in steps.

  As described above, according to the present embodiment, since the DC-DC converter 40 is provided as a power supply source different from the ignition coil 20, the discharge at the spark plug 30 can be maintained by the discharge sustaining current I3. Therefore, it is possible to prevent the discharge from being blown out in the desired discharge period Ta while making it unnecessary to increase the secondary current I2 for the purpose of maintaining the discharge. Therefore, it is possible to avoid the occurrence of misfiring due to the discharge being blown out during the discharge period Ta while eliminating the plug consumption due to the increase in the discharge current at the start of discharge.

  Further, even when the discharge voltage increases more than expected and the discharge blows out, the voltage of the DC-DC converter 40 is set to a voltage lower than the voltage necessary for the re-discharge, so that the re-discharge is not caused. Also, plug consumption due to repeated discharge can be eliminated.

  In addition, in order to set the expected value of the discharge sustaining current so as not to blow out, it is necessary to set the voltage from the DC-DC converter 40 to a value that can be redischarged as a result, for example, about 10 kV. Even if it exists, the discharge repetition phenomenon can be avoided as follows.

  That is, since the inductance (secondary coil 22) is not connected in series between the DC-DC converter 40 and the spark plug 30, the discharge sustaining current I3 is supplied to the secondary coil 22 after the on / off circuit 60 is turned off. It does not gradually decrease under the influence of reactors. Therefore, the discharge sustaining current I3 is instantaneously interrupted and becomes zero. In addition, since the on / off circuit 60 that instantaneously cuts off the power supply from the DC-DC converter 40 to the spark plug 30 is provided, the discharge current I4 can be stopped in a stepwise manner to terminate the discharge.

  Therefore, it is possible to eliminate a period in which the discharge current I4 gradually decreases as indicated by a one-dot chain line Ip in FIG. That is, it is possible to eliminate a state in which the discharge repetitive phenomenon can occur with a small current less than the discharge sustaining current. Therefore, plug consumption due to repeated discharge can be eliminated.

  In addition, since the voltage value boosted by the DC-DC converter 40 is set to be equal to or higher than a voltage (sustain voltage) that can maintain the state without causing the discharge to blow out, and lower than a voltage at which re-discharge cannot be started. The certainty of avoiding blow-off and avoiding re-discharge can be improved. In addition, since the constant current circuit 50 that maintains the discharge sustaining current I3 supplied from the DC-DC converter 40 to the spark plug 30 at a constant value is provided, the potential difference between the electrodes 31 and 32 varies with the change in the discharge path length. Even if it changes, since the discharge sustaining current I3 is maintained at a constant value, the discharge current I4 can be prevented from becoming excessive. Therefore, it is possible to improve the certainty of avoiding discharge blow-off as described above and to suppress plug consumption.

(Second Embodiment)
In controlling the output stop timing (t5) of the discharge sustaining current I3 by the on / off circuit 60, in the first embodiment, the control is performed based on the ignition signal IGt input to the waveform shaping circuit 10. Specifically, the time when the desired discharge period Ta has elapsed from the time t3 when the ignition signal IGt falls is controlled as the output stop timing of the discharge sustaining current I3. On the other hand, in this embodiment shown in FIG. 5, the output stop timing of the discharge sustaining current I3 is controlled based on the discharge sustaining current period signal IGw described below.

  That is, in order to improve the combustion state, when changing the discharge sustaining current period according to the engine operating conditions such as the rotation speed and the load, the microcomputer of the ECU 5 calculates the discharge maintaining current period based on the operating state information. . Then, a discharge sustaining current period signal IGw that defines the discharge period is generated and output to the on / off circuit 60.

  In this way, when the discharge sustaining current period signal IGw is output from the ECU 5, in this embodiment, the falling point of the discharge sustaining current period signal IGw is controlled as the output stop timing of the discharge sustaining current I3. It should be noted that the operation of the on / off circuit 60 may be controlled based on the signal IGt input to the waveform shaping circuit 10 regardless of which of the ignition signal IGt and the discharge sustaining current period signal IGw. The operation of the on / off circuit 60 may be controlled based on the signal IGw.

(Third embodiment)
In the first embodiment, the discharge sustaining current I3 output from the constant current circuit 50 is maintained at a constant value (constant current). However, in the present embodiment shown in FIGS. 6 to 8, the secondary current I2 is maintained. Only during the period (t3 to t4) during which is outputted, the magnitude of the discharge sustaining current I3 is corrected and adjusted in accordance with the change of the secondary current I2.

  More specifically, a correction circuit 70 (adjustment means) including current detection shown in FIG. 6 is provided that detects the value of the secondary current I2 and corrects the value of the discharge sustaining current I3 according to the detected value. It correct | amends so that the value of the discharge maintenance current I3 may become small, so that the value of the next current I2 is large. In the example shown in FIG. 7, the value of the discharge sustaining current I3 is corrected so that the value obtained by adding the sustaining current I3 to the secondary current I2 becomes a predetermined constant current value Ib (FIGS. 7C and 7D). reference).

  If the above correction is not performed, the discharge current I4 at the start of discharge becomes unnecessarily high as indicated by the one-dot chain line Iq in FIG. On the other hand, according to the present embodiment in which the above correction is performed, since the discharge current I4 at the start of discharge can be reduced to the constant current value Ib, suppression of plug consumption can be promoted.

  FIG. 8 is a circuit showing an example of the correction circuit 70. The correction circuit 70 includes a plurality of semiconductor switches (transistors 71, 72, 73, 74). The four transistors 71, 72, 73, and 74 constitute two known current mirror circuits. When a current (1) flows through the transistor 71, a current (2) having the same magnitude as that of the current (1) flows through the transistor 71. In addition, a current (3) having the same magnitude as the current flowing in the transistor 73 flows in the transistor 74.

  When the spark plug 30 starts discharging, the secondary current I2 flows through the transistor 71. Then, a current (2) having the same magnitude as the secondary current I2 flows through the transistors 72 and 73, and a current (3) having the same magnitude as the current (2) flowing through the transistor 73 flows through the transistor 74. As a result, a part of the current output from the constant current circuit 50 (correction current I5) flows through the transistor 74. That is, the correction current I5 having the same magnitude as the secondary current I2 is subtracted from the current output from the constant current circuit 50. As a result, the discharge sustaining current I3 is reduced by the correction current I5. As a result, the discharge sustaining current I3 decreases as the secondary current I2 increases, and the value obtained by adding the discharge maintaining current I3 to the secondary current I2 is adjusted to a predetermined constant current value Ib.

(Fourth embodiment)
The present embodiment shown in FIG. 9 is a modification of the third embodiment shown in FIG. 6, and the capacitor 41 (power supply means) is charged by the power from the DC-DC converter 40, and the discharge maintaining current I 3 is supplied from the capacitor 41. Is output. The charge of the capacitor 41 is controlled by the operation of the field effect transistor (MOSFET 57), and the operation of the MOSFET 57 is controlled by the current control circuit 58 according to the value of the secondary current I2. Thus, similarly to the third embodiment, the value of the discharge sustaining current I3 can be corrected so that the value obtained by adding the discharge sustaining current I3 to the secondary current I2 becomes the predetermined constant current value Ib. (See FIGS. 10C and 10E).

  The DC-DC converter 40 is switched on and off based on the ignition signal IGt output from the waveform shaping circuit 10 (see FIG. 10D). Specifically, the DC-DC converter 40 is turned off during a period during which the sustaining current I3 is output (desired discharge period Ta). Until the discharge sustaining current I3 starts to be output, the DC-DC converter 40 is turned on, and the capacitor 41 is charged prior to the start of the output of the discharge sustaining current I3.

  Here, if the capacitance of the capacitor 41 is too small, there is a concern that the discharge sustaining current I3 cannot be maintained at a predetermined value during the desired discharge period Ta as indicated by a dotted line Ic in FIG. Therefore, it is necessary to select the capacitor 41 having a capacity capable of maintaining the discharge sustaining current I3 at a predetermined value during the desired discharge period Ta.

(Fifth embodiment)
In the first embodiment, the center electrode 31 of the spark plug 30 is a positive electrode, the ground electrode 32 is a negative electrode, and the discharge current I4 flows from the center electrode 31 toward the ground electrode 32 (plus discharge). ing. In contrast, in the present embodiment shown in FIG. 11, the center electrode 31 of the spark plug 30 is a negative electrode, the ground electrode 32 is a positive electrode, and a discharge current I4 flows from the ground electrode 32 toward the center electrode 31 (negative discharge). It is configured so that.

  FIG. 12 is a time chart showing changes in the secondary current I2, the discharge sustaining current I3, and the discharge current I4 when negative discharge is performed in the present embodiment, in which the respective current values shown in FIG. 2 are reversed to the negative side. It becomes.

  FIG. 13 is a diagram illustrating an example of the on / off circuit 60 according to the present embodiment. Hereinafter, the difference from FIG. 4 will be mainly described.

  First, when the on / off signal input from the waveform shaping circuit 10 to the on / off circuit 60 is turned on, the transistor 62 is turned on. Then, the transistor 67 is turned on, and the transistor 66a is turned on in conjunction with this on operation. As a result, the current Ia flows from the DC-DC converter 40 to the constant current circuit 50.

  On the other hand, when the on / off signal is switched from on to off, the transistor 62 that is on is switched to off. Then, the transistor 67 is turned off, and the transistor 66a is turned off in conjunction with the off operation. As a result, the current Ia is instantaneously interrupted from the DC-DC converter 40 to the constant current circuit 50, and the discharge sustaining current I3 is stopped stepwise.

(Sixth embodiment)
This embodiment shown in FIG. 14 is obtained by modifying the plus discharge circuit shown in FIG. 6 into a minus discharge circuit. That is, an example in which the magnitude of the discharge sustaining current I3 is corrected and adjusted in accordance with the change in the secondary current I2 is realized by a negative discharge circuit.

  FIG. 15 is a time chart showing changes in the secondary current I2, the discharge sustaining current I3, and the discharge current I4 when negative discharge is performed in the present embodiment, in which the respective current values shown in FIG. 7 are reversed to the negative side. It becomes.

  FIG. 16 is a diagram illustrating an example of the correction circuit 70A (adjustment unit) according to the present embodiment. Hereinafter, differences from FIG. 8 will be mainly described.

  The correction circuit 70A includes a plurality of semiconductor switches (transistors 74, 76, 77, 78). The four transistors 74, 76, 77, 78 constitute a known current mirror circuit. When a current (1) flows through the transistor 74, a current (2) having the same magnitude as that current is supplied from the power supply 75 to the transistor 76. Furthermore, a current (3) having the same magnitude as the current flowing through the transistor 77 flows from the power source 75 to the transistor 78.

  When the spark plug 30 starts discharging, the secondary current I2 flows through the transistor 74. Then, a current (2) having the same magnitude as the secondary current I2 flows through the transistor 76, and a current (3) having the same magnitude as the current (2) flowing through the transistor 77 flows through the transistor 78. As a result, a part of the current flowing through the constant current circuit 50 (correction current I5) flows through the transistor 78. That is, the correction current I5 having the same magnitude as the secondary current I2 is subtracted from the current flowing through the constant current circuit 50. As a result, the magnitude (absolute value) of the discharge sustaining current I3 is reduced by the correction current I5. . Thus, the absolute value of the discharge sustaining current I3 decreases as the absolute value of the secondary current I2 increases, and the value obtained by adding the discharge sustaining current I3 to the secondary current I2 is adjusted to a predetermined constant current value Ib. The Rukoto.

(Seventh embodiment)
This embodiment shown in FIG. 17 is obtained by modifying the plus discharge circuit shown in FIG. 9 into a minus discharge circuit. That is, an example in which the capacitor 41 is charged with the electric power from the DC-DC converter 40 and the discharge maintaining current I3 is output from the capacitor 41 is realized by a negative discharge circuit.

  FIG. 18 is a time chart showing changes in the secondary current I2, the discharge sustaining current I3, and the discharge current I4 when a negative discharge is performed in the present embodiment, in which each current value shown in FIG. 10 is inverted to the negative side. It becomes.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In the examples shown in FIGS. 7, 10, 15, and 18 described above, the discharge current is maintained at the secondary current I2 when the magnitude of the discharge sustain current I3 is corrected and adjusted according to the change in the secondary current I2. The value obtained by adding the current I3 (the value of the discharge current I4) is adjusted to a predetermined constant current value Ib. That is, adjustment is made so that the value of the discharge current I4 does not change at a constant value (constant current value Ib). On the other hand, the magnitude of the discharge sustaining current I3 may be corrected and adjusted according to the change of the secondary current I2 while allowing the discharge current I4 to change.

  In the example shown in FIG. 2, FIG. 12, and FIG. 18 described above, the timing (t2) for starting the discharge sustaining current I3 from the constant current circuit 50 is set earlier than the output starting timing (t3) for the secondary current I2. However, the output start timing of the discharge sustaining current I3 may be the same as the output start timing (discharge start timing) of the secondary current I2.

  DESCRIPTION OF SYMBOLS 5 ... ECU (discharge control means), 20 ... Ignition coil, 21 ... Primary coil, 22 ... Secondary coil, 30 ... Spark plug, 40 ... DC-DC converter (power supply means), 41 ... Capacitor (power supply means), 50 ... constant current circuit (constant current output means), 70, 70A ... correction circuit (adjustment means), I2 ... secondary current, I3 ... discharge sustaining current.

Claims (3)

An ignition coil having a primary coil and a secondary coil and outputting a secondary current flowing through the secondary coil to a spark plug;
Power supply means for outputting a discharge sustaining current different from the secondary current output from the ignition coil to the ignition plug;
Discharge control means for starting discharge at the spark plug by the output voltage of the secondary coil, and controlling to stop discharge at the spark plug by stopping the output of the discharge sustaining current;
A diode provided in a path connecting one end of the secondary coil and the spark plug, and provided so that the discharge sustaining current does not flow to the secondary coil ;
Adjusting means for adjusting the magnitude of the discharge sustaining current according to a change in the secondary current from the ignition coil ,
Electrically connecting the power supply means to the spark plug so that the discharge sustaining current is supplied to the spark plug without going through the secondary coil ;
The ignition device for an internal combustion engine, wherein the adjusting means adjusts the magnitude of the discharge sustaining current so that a value obtained by adding the discharge sustaining current to the secondary current becomes a predetermined constant current value . An ignition coil having a primary coil and a secondary coil and outputting a secondary current flowing through the secondary coil to a spark plug;
Power supply means for outputting a discharge sustaining current different from the secondary current output from the ignition coil to the ignition plug;
Discharge control means for starting discharge at the spark plug by the output voltage of the secondary coil, and controlling to stop discharge at the spark plug by stopping the output of the discharge sustaining current;
Adjusting means for adjusting the magnitude of the discharge sustaining current according to a change in the secondary current from the ignition coil,
Electrically connecting the power supply means to the spark plug so that the discharge sustaining current is supplied to the spark plug without going through the secondary coil;
The ignition device for an internal combustion engine, wherein the adjusting means adjusts the magnitude of the discharge sustaining current so that a value obtained by adding the discharge sustaining current to the secondary current becomes a predetermined constant current value. 3. The internal combustion engine according to claim 1, further comprising a constant current output unit configured to maintain the discharge sustaining current at a constant value even when the length of the discharge path generated by the spark plug is changed. Engine ignition device.

Images