JP4905244B2 - Ignition device for internal combustion engine - Google Patents

Description

  The present invention relates to a capacitor discharge type ignition device for an internal combustion engine.

  Conventionally, a capacitor discharge ignition device is known as an ignition device for an internal combustion engine. The capacitor discharge type ignition device includes an ignition circuit in which a primary coil of an ignition coil, an ignition capacitor, and a thyristor for charge / discharge control are connected in series, and the charge charged in the ignition capacitor is transferred to the primary coil of the ignition coil. By discharging via, a high voltage for ignition (hereinafter referred to as “ignition voltage”) is generated in the secondary coil of the ignition coil. This ignition voltage is supplied to the spark plug, and spark discharge occurs in the spark plug.

  Further, as a capacitor discharge type ignition device, an AC discharge type AC ignition device and a DC discharge type DC ignition device are known (for example, see Patent Document 1).

  In the AC ignition device, an AC discharge current flows in the primary coil of the ignition coil as the ignition capacitor is discharged, and an AC ignition voltage is generated in the secondary coil of the ignition coil. As a result, an AC spark discharge with a long duration occurs in the spark plug. By igniting the fuel with this AC spark discharge, misfire can be suppressed.

On the other hand, in the DC ignition device, a DC discharge current flows through the primary coil of the ignition coil as the ignition capacitor is discharged, and a DC ignition voltage is generated at the secondary coil of the ignition coil. As a result, a DC spark discharge is generated in the spark plug. Here, the decay time of the DC discharge current is shorter than the decay time of the AC discharge current. Therefore, even when the rotational speed of the internal combustion engine increases, it is possible to secure time for charging the ignition capacitor in the ignition cycle. Thereby, the fall of the ignition voltage accompanying the raise of the rotational speed of an internal combustion engine is suppressed.
JP-A-9-268963

  By the way, in an internal combustion engine for a vehicle, one of an AC ignition device and a DC ignition device is employed according to the specification and the like. However, the development and manufacture of both the AC ignition device and the DC ignition device respectively increase the cost of each device.

  The present invention has been made to solve the above-described problems, and has as its main object to provide an ignition device for an internal combustion engine that can selectively generate an AC ignition voltage or a DC ignition voltage. is there.

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

In the first configuration , an ignition coil, an ignition capacitor connected in series to the primary coil of the ignition coil, and a series circuit including the primary coil and the ignition capacitor are connected to both ends of the ignition circuit to open and close a discharge path of the ignition capacitor. An ignition circuit having a first switching unit; and a charging circuit for charging the ignition capacitor. In this configuration, when the ignition capacitor is discharged with the first switching unit closed, a discharge current flows through the primary coil, and an ignition voltage is generated in the secondary coil of the ignition coil.

Further, in the above configuration, the second switching unit is connected to both ends of the primary coil. According to this configuration, when the second switching unit is in the open state, an LC resonance circuit is formed by the primary coil and the ignition capacitor. Therefore, a discharge current having a predetermined resonance frequency flows through the primary coil due to the discharge of the ignition capacitor. On the other hand, when the second switching unit is in the closed state, a resonance circuit is not formed, and the discharge current is rapidly attenuated. Therefore, by switching control of the second switching unit, can flow AC discharge current to the primary coil (discharge current of alternating current) or DC discharge current (discharge current dc).

For example, when the second switching unit is configured by a thyristor as follows ( second configuration ), when the ignition capacitor is discharged with the thyristor turned off, an AC discharge current flows through the primary coil, and the thyristor is When the ignition capacitor is discharged in the on state, a DC discharge current flows through the primary coil ( third configuration ).

  That is, the anode of the thyristor as the second switching unit is connected to one end of the primary coil on the ignition capacitor side, and the cathode is connected to the other end of the primary coil. In this case, when the thyristor is turned off and the first switching unit is opened, the AC discharge current flows through the primary coil as described above. On the other hand, when the thyristor is turned on and the first switching unit is opened, a discharge current flows to the primary coil through the first switching unit as the ignition capacitor is discharged. However, the discharge current rapidly attenuates as the discharge current flowing through the primary coil flows through the thyristor. Thus, a DC discharge current flows through the primary coil.

  By controlling the second switching unit in this way, an AC discharge current or a DC spark discharge can be passed through the primary coil of the ignition coil. Thereby, AC ignition voltage or DC ignition voltage can be generated in the secondary coil of the ignition coil, and AC spark discharge or DC spark discharge can be generated in the spark plug.

In the fourth configuration , the second switching unit is controlled to open and close based on the rotational speed of the internal combustion engine. This allows AC discharge current or DC discharge current to flow through the primary coil of the ignition coil according to the rotational speed of the internal combustion engine, and generates AC ignition voltage or DC ignition voltage in the secondary coil of the ignition coil. Can be made.

  Here, the ignition cycle of the ignition device is composed of a “post-ignition rest period”, a “charging period”, and an “ignition waiting period”. The post-ignition rest period is the period from the start of the discharge of the ignition capacitor until the next start of charging of the ignition capacitor, and the charging period is the period of charging the ignition capacitor. This is a period from the end of charging of the ignition capacitor to the start of discharge of the ignition capacitor 2 next time.

  The charging of the ignition capacitor is started after the discharge current is sufficiently attenuated. That is, the length of the post-ignition rest period is a fixed time that depends on the decay time of the discharge current. The length of the charging period is a fixed time determined by the specifications of the charging circuit and ignition circuit. Therefore, when the rotation speed of the internal combustion engine increases and the ignition cycle becomes shorter, the ignition device secures a charging period in the ignition cycle by shortening the ignition waiting period. However, even when the ignition waiting period is set to 0, if a sufficient charging period cannot be ensured in the ignition cycle, the ignition voltage decreases. When the ignition voltage becomes lower than the discharge voltage (the lower limit voltage for generating spark discharge in the spark plug), no spark discharge occurs in the spark plug, resulting in misfire.

Therefore, in the fifth configuration , when the rotation speed of the internal combustion engine is equal to or higher than a predetermined speed by the opening / closing control of the second switching unit, a DC discharge current (DC discharge current) is caused to flow through the primary coil, and the rotation speed of the internal combustion engine. Is lower than a predetermined speed, an alternating discharge current (AC discharge current) is passed through the primary coil. For example, when configured with thyristors a second switching unit as in the second configuration, the rotational speed of the internal combustion engine is turned on the thyristor when the predetermined speed or higher, the rotational speed of the internal combustion engine is lower than a predetermined speed Sometimes the thyristor is turned off.

  The decay time of the DC discharge current is short compared to the AC discharge current. Therefore, even if the rotational speed of the internal combustion engine increases and the ignition cycle becomes shorter, it is possible to ensure a sufficient charging period in the ignition cycle by shortening the post-ignition pause period. Thereby, the fall of the voltage for ignition accompanying the raise of the rotational speed of an internal combustion engine can be suppressed, and the misfire resulting from the fall of the voltage for ignition can be suppressed. On the other hand, when the rotational speed of the internal combustion engine is low and the ignition cycle is long, misfiring can be suppressed by igniting the fuel with AC spark discharge having a longer duration than DC spark discharge.

In the sixth configuration , the second switching is controlled to open and close based on a parameter indicating the ignitability of the internal combustion engine. Here, the parameters indicating the ignitability of the internal combustion engine include fuel properties, compression pressure, mixture temperature, air-fuel ratio, spark plug electrode temperature, and the like.

  For example, if ignition is not possible with short-lived spark discharge due to the fuel properties, AC discharge current is caused to flow through the primary coil of the ignition coil by controlling the opening and closing of the second switching unit, and AC spark discharge is generated at the spark plug. It is good to let them. By igniting the fuel with AC spark discharge having a longer duration than DC spark discharge, misfire can be suppressed.

  The discharge voltage described above increases as the compression pressure increases, the mixture temperature decreases, the air-fuel ratio increases, and the spark plug electrode temperature decreases. In addition, the higher the discharge voltage, the higher the probability that a spark discharge will not occur in the high speed range of the internal combustion engine and a misfire will occur. That is, the ignitability deteriorates as the discharge voltage increases. In such a case, a DC discharge current having a short decay time may be supplied to the primary coil by controlling the opening and closing of the second switching unit. As a result, a decrease in the ignition voltage accompanying an increase in the rotational speed of the internal combustion engine is suppressed, so that even when the discharge voltage is high and the rotational speed of the internal combustion engine is high, spark discharge can be generated in the spark plug. it can.

In the seventh configuration , the second switching unit is opened until a predetermined time elapses from the start of discharge of the ignition capacitor, and the second switching unit is closed when the predetermined time elapses. As a result, during a period from when the ignition capacitor starts to discharge until a predetermined time elapses, a discharge current flows through the primary coil of the ignition coil, and spark discharge occurs in the spark plug. On the other hand, when the second switching unit is closed after a predetermined time has elapsed since the discharge of the ignition capacitor, the discharge current flows through the second switching unit and abruptly attenuates, so that no spark discharge occurs in the spark plug.

  According to this configuration, by controlling the opening and closing of the second switching unit, it is possible to adjust the duration of the spark discharge and adjust the decay time of the discharge current (post-ignition rest period). Specifically, the duration of the spark discharge can be increased by increasing the predetermined time. Further, by shortening the predetermined time, the decay time of the discharge current can be shortened and the post-ignition rest period can be shortened.

In the eighth configuration , the predetermined time is set based on the rotational speed of the internal combustion engine in the seventh configuration . According to this configuration, the duration of spark discharge and the ignition pause period can be adjusted according to the rotational speed of the internal combustion engine. For example, it is preferable to shorten the ignition rest period by shortening the decay time of the discharge current by shortening the predetermined time as the rotational speed of the internal combustion engine increases. Thereby, even if the rotational speed of the internal combustion engine is increased and the ignition cycle is shortened, a sufficient charging period can be secured in the ignition cycle. Thereby, the fall of the voltage for ignition accompanying the raise of the rotational speed of an internal combustion engine can be suppressed.

In the ninth configuration , the predetermined time is set based on the parameter indicating the ignitability of the internal combustion engine in the seventh configuration . According to this configuration, the duration of spark discharge and the ignition pause period can be adjusted according to the ignitability of the internal combustion engine.

In a tenth configuration , as a first switching unit, a thyristor having an anode connected to one end on the ignition capacitor side of a series circuit including a primary coil and an ignition capacitor, and a cathode connected to the other end of the series circuit; A diode connected in antiparallel to both ends of the thyristor.

  Hereinafter, a plurality of embodiments embodying the present invention will be described with reference to the drawings. In each embodiment, the component to which the same code | symbol was attached | subjected respond | corresponds with the component of the other embodiment to which the code | symbol was attached | subjected.

(First embodiment)
The first embodiment embodies the present invention as an ignition device for a vehicle engine, and its configuration will be described with reference to FIG. The present embodiment shown in FIG. 1 is a capacitor discharge type ignition device 10 that outputs an ignition voltage by discharging an electric charge charged in the ignition capacitor.

  In FIG. 1, an AC generator 11 is mounted on the vehicle. An AC-DC converter 12 is connected to the AC generator 11, and a battery 13 is connected to the AC-DC converter 12. When the AC generator 11 is driven by the engine and outputs an AC current, the AC voltage is converted into a DC current by the AC-DC converter 12, and the DC voltage is charged in the battery 13.

  A DC-DC converter 15 of the ignition device 10 is connected to the AC-DC converter 12 and the battery 13 via a diode 14. The DC-DC converter 15 includes a step-up transformer 16 connected to the diode 14, a chopper circuit 18 connected to the primary coil 16 a of the step-up transformer 16, a charge stop circuit 19 connected to the chopper circuit 18, and the like. ing.

  The chopper circuit 18 alternately repeats energization and deenergization of the primary coil 16a. The charge stop circuit 19 is connected to the control circuit 20 and permits or prohibits the energization control by the chopper circuit 18 according to the control of the control circuit 20. When the charging stop circuit 19 prohibits the energization control by the chopper circuit 18, the energization to the primary coil 16a is maintained in a stopped state.

  An ignition capacitor 24 of an ignition circuit 23 is connected to the secondary coil 16 b of the step-up transformer 16 via a diode 21. The ignition circuit 23 includes a circuit in which an ignition capacitor 24, a charge / discharge control thyristor 25, and a primary coil 26a are connected in series in this order, a diode 28 connected in parallel to the charge / discharge control thyristor 25, and a primary coil 26a. And a discharge switching thyristor 27 connected in parallel.

  Specifically, the anode of the charge / discharge control thyristor 25 is connected to the ignition capacitor 24, and the cathode thereof is connected to the primary coil 26a. On the other hand, the anode of the discharge switching thyristor 27 is connected to one end of the primary coil 26a on the ignition capacitor 24 side, and the cathode is connected to the other end of the primary coil 26a. The gates of these thyristors 25 and 27 are connected to the control circuit 20 respectively. The diode 28 is connected in the opposite direction to the charge / discharge control thyristor 25. A spark plug 29 is connected to the secondary coil 26 b of the ignition coil 26. The charge / discharge control thyristor 25 and the diode 28 correspond to a “first switching unit”. The discharge switching thyristor 27 corresponds to a “second switching unit”.

  The control circuit 20 as a control means is a circuit mainly composed of a CPU and a memory. The memory stores an ignition control program and parameters required for the control. The CPU controls each unit by executing an ignition control program stored in the memory. A crank angle sensor 30 that outputs a pulse signal for each predetermined crank angle of the engine is connected to the control circuit 20.

  Next, the ignition control of the ignition device 10 will be outlined.

  In the DC-DC converter 15, when energization control by the chopper circuit 18 is permitted by the charge stop circuit 19, the energization to the primary coil 16a of the step-up transformer 16 and the stop thereof are alternately repeated by the chopper circuit 18, and the primary coil 16a. The current flowing through changes. Then, with this current change, a pulsed high voltage (hereinafter referred to as “charging voltage”) is generated in the secondary coil 16b. At this time, if the charge / discharge control thyristor 25 is in the OFF state in the ignition circuit 23, the ignition capacitor 24 is charged by the charging voltage. When the voltage of the ignition capacitor 24 becomes higher than the predetermined voltage or the elapsed time from the time when charging is permitted becomes longer than the predetermined time, the charging stop circuit 19 prohibits the energization control by the chopper circuit 18. Thereby, the charging of the ignition capacitor 24 is completed.

  In the ignition circuit 23, when the charge / discharge control thyristor 25 is turned on, the charge charged in the ignition capacitor 24 is discharged. As a result, a discharge current flows through the primary coil 26a of the ignition coil 26, and an ignition voltage is generated at the secondary coil 26b of the ignition coil 26. As a result, spark discharge occurs in the spark plug 29. When the discharge current is sufficiently attenuated, charging of the ignition capacitor 24 is started again. Thus, in the ignition device 10, spark discharge is periodically generated.

  By the way, in the ignition circuit 23, by controlling the discharge switching thyristor 27, an AC discharge current or a DC discharge current can be selectively supplied to the primary coil 26a of the ignition coil 26.

  Hereinafter, the operation of the ignition circuit 23 will be described with reference to FIGS. 2 and 3. FIG. 2 shows the ignition circuit 23 when the discharge switching thyristor 27 is in an off state, and FIG. 3 shows the ignition circuit 23 when the discharge switching thyristor 27 is in an on state. 2A and 3A show the ignition circuit 23 in the ignition waiting period, and it is assumed that the ignition capacitor 24 is charged with the polarity shown in the figure. 2 and 3 indicate the discharge current accompanying the discharge of the ignition capacitor 24. Further, the discharge switching thyristor 27 indicated by a broken line in FIG. 2 indicates the same thyristor in an off state, and the discharge switching thyristor 27 indicated by a solid line in FIG. 3 indicates the same thyristor in an on state.

  As shown in FIG. 2A, when the discharge switching thyristor 27 is in the off state, when the charge / discharge control thyristor 25 is turned on, the ignition capacitor 24 starts discharging, and the primary coil 26a and the ignition The capacitor 24 forms an LC resonance circuit. As a result, as shown in FIG. 2B, an AC discharge current flows through the primary coil 26a as the ignition capacitor 24 is discharged.

  Specifically, when the charge / discharge control thyristor 25 is turned on, a discharge current flows through the charge / discharge control thyristor 25 and the primary coil 26a as the ignition capacitor 24 is discharged. This discharge current becomes the maximum when the ignition capacitor 24 is completely discharged (when the charge of the ignition capacitor 24 becomes 0). Even after the ignition capacitor 24 is completely discharged, the discharge current continues to flow due to the self-induced electromotive force generated in the primary coil 26a. As a result, as shown in FIG. 2 (c), the ignition capacitor 24 is charged with the opposite polarity to the previous charging. When the self-induced electromotive force of the primary coil 26a becomes 0, the ignition capacitor 24 starts discharging again as shown in FIG. 2 (d). As a result, a discharge current in the opposite direction to that of the previous discharge flows through the primary coil 26a and the diode 28, and the ignition capacitor 24 is charged with the same polarity as when initially charged (when charged by the DC-DC converter 15). (See FIG. 2 (a)). As a result of the AC discharge current flowing through the primary coil 26a in this manner, an AC ignition voltage is generated in the secondary coil 26b.

  On the other hand, when the discharge switching thyristor 27 is in the on state as shown in FIG. 3A, when the charge / discharge control thyristor 25 is in the on state, a DC discharge current flows through the primary coil 26a as follows. That is, when the charge / discharge control thyristor 25 is turned on, the discharge current becomes maximum when the ignition capacitor 24 is completely discharged, as in the case where the discharge switching thyristor 27 is turned off. However, at this time, since the self-induced electromotive force generated in the primary coil 26a is short-circuited by the discharge switching thyristor 27 (see FIG. 3B), the discharge current is rapidly attenuated. As a result of the DC discharge current flowing through the primary coil 26a in this manner, a DC ignition voltage is generated in the secondary coil 26b.

  Here, when an AC ignition voltage is generated in the secondary coil 26 b as described above, an AC spark discharge is generated in the spark plug 29. The duration of the AC spark discharge is longer than the duration of the DC spark discharge. Therefore, by generating the AC ignition voltage by the ignition circuit 23, the fuel can be reliably ignited by the AC spark discharge.

  However, since the decay time of the AC discharge current is longer than the decay time of the DC discharge current, if the engine speed is increased and the ignition cycle is shortened, a sufficient charging period cannot be ensured in the ignition cycle, and the ignition voltage may decrease. There is. In contrast, the decay time of the DC discharge current is shorter than the decay time of the AC discharge current. Therefore, even if the engine speed increases and the ignition cycle becomes shorter, a sufficient charging period can be secured in the ignition cycle by shortening the post-ignition pause period. Thereby, the fall of the voltage for ignition accompanying a raise in an engine speed can be suppressed.

  Therefore, in the ignition control of the present embodiment, the AC ignition voltage or the DC ignition voltage is switched and generated based on the engine rotation speed. Specifically, the engine rotation speed is calculated from the pulse signal output from the crank angle sensor 30. When the engine rotation speed is lower than the predetermined rotation speed, an AC ignition voltage is generated by controlling the discharge switching thyristor 27 to be turned off. When the engine rotation speed is equal to or higher than the predetermined rotation speed, A DC ignition voltage is generated by turning on the discharge switching thyristor 27.

  Next, ignition control of the ignition device 10 will be described in detail based on the time chart shown in FIG.

  In FIG. 4, a charge stop signal Xg1 indicates an input signal from the control circuit 20 to the charge stop circuit 19. The ignition signal Xg2 and the switching signal Xg3 are signals that are input from the control circuit 20 to the gates of the charge / discharge control thyristor 25 and the discharge switching thyristor 27, respectively. It is assumed that the gate current to be turned on (gate current to be turned on) flows through the corresponding thyristor. The capacitor voltage Vc indicates the voltage at the connection point between the ignition capacitor 24 and the charge / discharge control thyristor 25, and the charging voltage Vp indicates the voltage at the connection point between the secondary coil 16 b of the step-up transformer 16 and the diode 21. .

  Furthermore, in FIG. 4, it is assumed that the engine speed has increased around timing t5. Therefore, the cycle (ignition cycle) of the ignition signal Xg2 differs before and after the timing t5. As the engine speed changes, the switching signal Xg3 changes from the low level to the high level at timing t5.

  When the charge stop signal Xg1 becomes low level at the timing t1, energization control by the chopper circuit 18 is permitted, and thereafter, energization to the primary coil 16a of the step-up transformer 16 and energization stop are alternately repeated. As a result, the current flowing through the primary coil 16a changes, and a pulsed charging voltage Vp is generated in the secondary coil 16b of the step-up transformer 16. At this time, since the charge / discharge control thyristor 25 is controlled to be turned off by the low-level ignition signal Xg2, no current flows through the charge / discharge control thyristor 25 by application of the charge voltage Vp. Therefore, the ignition capacitor 24 is charged by applying the pulsed charging voltage Vp, and accordingly, the capacitor voltage Vc increases (see timings t1 to t2).

  When the charge stop signal Xg1 becomes high level at the timing t2, energization control by the chopper circuit 18 is prohibited, and energization to the primary coil 16a of the step-up transformer 16 is maintained in a stopped state. As a result, no pulsed charging voltage is generated in the secondary coil 16b of the step-up transformer 16.

  When the ignition signal Xg2 becomes high level at the timing t3, the charge / discharge control thyristor 25 is turned on. As a result, the ignition capacitor 24 is discharged. At this time, the discharge switching thyristor 27 is controlled to be turned off by the low level switching signal Xg3. Therefore, an AC discharge current flows through the primary coil 26a of the ignition coil 26, and an AC ignition voltage is generated at the secondary coil 26b. Then, after the AC discharge current is sufficiently attenuated, the charge stop signal Xg1 becomes a low level (see timing t4). As a result, charging of the ignition capacitor 24 is started again.

  When the engine rotational speed becomes equal to or higher than the predetermined speed at timing t5, the switching signal Xg3 becomes high level.

  When the ignition signal Xg2 becomes high level at the timing t6, the charge / discharge control thyristor 25 is turned on. As a result, the ignition capacitor 24 is discharged. At this time, the discharge switching thyristor 27 is controlled to be turned on by a high level switching signal Xg3. Accordingly, a DC discharge current flows through the primary coil 26a of the ignition coil 26, and a DC ignition voltage is generated at the secondary coil 26b. Then, after the DC discharge current is sufficiently attenuated, the charge stop signal Xg1 becomes low level (see timing t6). As a result, charging of the ignition capacitor 24 is started again. From timing t6 to t7, the ignition capacitor 24 is charged in the same manner as timing t1 to t2. Here, the ignition stop period when the DC discharge current is passed through the primary coil 26a (see timings t6 to t7) is from the ignition stop period when the AC discharge current is passed through the primary coil 26a (see timings t3 to t4). You can see that it is too short.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  When the engine speed is lower than the predetermined speed, an AC discharge current flows through the primary coil 26a of the ignition coil 26, and an AC ignition voltage is generated at the secondary coil 26b. As a result, an AC spark discharge is generated in the spark plug 29. Since the duration of the AC spark discharge is long, the fuel can be reliably ignited.

  On the other hand, when the engine rotation speed is equal to or higher than the predetermined speed, a DC discharge current flows through the primary coil 26a of the ignition coil 26 and a DC ignition voltage is generated at the secondary coil 26b. As described above, the decay time of the DC discharge current is shorter than the decay time of the AC discharge current. Therefore, even if the engine speed is such that a sufficient charging period cannot be secured in the ignition cycle when an AC discharge current is passed through the primary coil 26a, a DC discharge current is passed through the primary coil 26a to shorten the rest period after ignition. Thus, a sufficient charging period can be ensured in the ignition cycle. Thereby, the fall of the voltage for ignition accompanying the raise of an engine speed can be suppressed.

  In this embodiment, the AC ignition voltage or the DC ignition voltage is generated according to the engine speed. However, the ignition device 10 may function as a conventional AC ignition device, or the ignition device 10 may function as a conventional DC ignition device. Specifically, the discharge switching thyristor 27 may be always on or always off. Even in this case, the cost reduction of the ignition device can be reduced as compared with the case where both the AC ignition device and the DC ignition device are respectively developed and manufactured.

(Second Embodiment)
The circuit configuration of the second embodiment is substantially the same as that of the first embodiment. Therefore, the same code | symbol as the corresponding component of 1st Embodiment is attached, and description is abbreviate | omitted.

  In the present embodiment, the discharge switching thyristor 27 is turned off until a predetermined time (hereinafter referred to as “switching waiting time”) elapses from the start of discharge of the ignition capacitor 24, and when the switching waiting time elapses, the discharge switching thyristor 27 is turned off. Is turned on. As a result, a discharge current flows through the primary coil 26a of the ignition coil 26 and a spark discharge is generated in the spark plug 29 during the period from the start of the discharge of the ignition capacitor 24 until the switching waiting time elapses. Then, after a lapse of the switching waiting time from the start of the discharge of the ignition capacitor 24, the discharge current is rapidly attenuated by flowing through the discharge switching thyristor 27. As a result, no spark discharge occurs in the spark plug 29.

  By controlling the discharge switching thyristor 27 in this way, it is possible to adjust the duration of spark discharge and the ignition pause period. Specifically, the duration of the spark discharge can be lengthened by delaying the timing at which the discharge switching thyristor 27 is turned on. In addition, by shortening the timing for causing the discharge switching thyristor 27 to transition to the ON state, the decay time of the discharge current can be shortened and the ignition pause period can be shortened. In this embodiment, the timing at which the discharge switching thyristor 27 is shifted to the ON state is advanced as the engine speed increases. Specifically, the switching waiting time is set shorter as the engine speed increases.

  Hereinafter, the ignition control of the present embodiment will be described based on the timing chart shown in FIG. In FIG. 5, a charge stop signal Xg1, an ignition signal Xg2, and a switching signal Xg3 are signals input to the gates of the charge stop circuit 19, the charge / discharge control thyristor 25, and the discharge switching thyristor 27, respectively. The coil voltage Vl represents the voltage at the contact point between the primary coil 26a and the ignition capacitor 24.

  In FIG. 5, the ignition signal Xg2 changes from the low level to the high level at the timing t11. At the timing t12 when the switching waiting time has elapsed from the timing t11, the switching signal Xg3 transitions from the low level to the high level. Note that the waveform of Vl indicated by a broken line in FIG. 5 indicates a change in Vl when the switching signal Xg3 is not changed to the high level but maintained at the low level at the timing t12.

  When the ignition signal Xg2 becomes high level at the timing t11, the charge / discharge control thyristor 25 shifts to the ON state. As a result, the ignition capacitor 24 is discharged. During the period from the timing t11 to t12, the discharge switching thyristor 27 is controlled to be turned off by the low level switching signal Xg3, so that the AC discharge current flows through the primary coil 26a as the ignition capacitor 24 is discharged. The coil voltage Vl vibrates. As a result, an AC ignition voltage is generated in the secondary coil 26 b, and an AC spark discharge is generated in the spark plug 29.

  When the switching signal Xg3 becomes high level at the timing t12, the discharge switching thyristor 27 is turned on. Therefore, when the coil voltage Vl becomes a positive voltage after the timing t12, a discharge current flows through the discharge switching thyristor 27, and the AC discharge current and the coil voltage Vl are rapidly attenuated. When the charge stop signal Xg1 becomes low level at timing t13, charging of the ignition capacitor 24 is started.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  The discharge switching thyristor 27 was controlled to be in the OFF state during the period from the start of discharge of the ignition capacitor 24 until the switching waiting time elapses. As a result, an AC discharge current flows through the primary coil 26a of the ignition coil 26 (see timings t11 to t12 shown in FIG. 5). In addition, the discharge switching thyristor 27 was controlled to be in an ON state when the switching waiting time elapsed from the start of the discharge of the ignition capacitor 24. As a result, the AC discharge current is rapidly attenuated (see timings t12 to t13 shown in FIG. 5).

  Furthermore, the higher the engine speed, the shorter the switching waiting time, and the earlier the timing (see timing t12 shown in FIG. 5) at which the discharge switching thyristor 27 is turned on. As a result, the higher the engine speed, the shorter the decay time of the discharge current. As a result, even if the engine rotation speed increases and the ignition cycle becomes shorter, the charging period is ensured by shortening the post-ignition pause period (see timings t11 to t13 shown in FIG. 5) in the ignition cycle, and the engine rotation speed is reduced. It is possible to suppress a decrease in ignition voltage that accompanies the increase.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the first embodiment, an AC discharge current or a DC discharge current is supplied to the primary coil 26a of the ignition coil 26 in accordance with the engine speed. However, an AC discharge current or a DC discharge current may flow through the primary coil 26a according to the ignitability indicated by the engine operating conditions.

  In the second embodiment, the switching waiting time is set based on the engine speed. However, the switching waiting time may be set based on the ignitability indicated by the engine operating conditions. Further, the switching waiting time may be a fixed value set at the time of shipment. Even in this case, the cost of the ignition device can be reduced as compared with the case where a plurality of ignition devices having different durations of spark discharge are respectively developed and manufactured.

  In the first and second embodiments, the first switching unit is configured by the charge / discharge control thyristor 25 and the diode 25. However, a bidirectional switching element may be used instead of these elements. Further, although the second switching unit is configured by the discharge switching thyristor 27, in the second embodiment, a bidirectional switching element may be used instead of the discharge switching thyristor 27.

The figure which shows the ignition device of an engine. The figure which shows the action | operation of an ignition circuit. The figure which shows the action | operation of an ignition circuit. The timing chart which shows the ignition control of 1st Embodiment. The timing chart which shows the ignition control of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Ignition device, 11 ... AC generator, 12 ... AC-DC converter, 13 ... Battery, 15 ... DC-DC converter (charging circuit), 20 ... Control circuit (control means), 23 ... Ignition circuit, 24 ... Ignition Capacitor 25 ... Charge / discharge control thyristor (first switching unit) 26 ... Ignition coil 26a ... Primary coil 26b ... Secondary coil 27 ... Discharge switching thyristor (second switching unit) 28 ... Diode ( 1st switching part), 30 ... spark plug.

Claims (5)

An ignition coil, an ignition capacitor connected in series to a primary coil of the ignition coil, and a first switching that opens and closes a discharge path of the ignition capacitor connected to both ends of a series circuit including the primary coil and the ignition capacitor An ignition circuit having a portion;
A charging circuit for charging the ignition capacitor;
By discharging the ignition capacitor with the first switching unit closed, a discharge current is passed through the primary coil of the ignition coil, and an ignition voltage is generated in the secondary coil of the ignition coil. In the ignition device,
A second switching unit is provided that is connected to both ends of the primary coil, and opens or closes the connection of the both ends to flow an AC or DC discharge current to the primary coil .
An internal combustion engine comprising: a control unit that opens the second switching unit until a predetermined time elapses from the start of discharge of the ignition capacitor, and closes the second switching unit when the predetermined time elapses. Ignition system for engines.   2. The ignition for an internal combustion engine according to claim 1, wherein the second switching unit includes a thyristor having an anode connected to one end of the primary coil on the ignition capacitor side and a cathode connected to the other end of the primary coil. apparatus. The ignition device for an internal combustion engine according to claim 1 or 2, wherein the control means sets the predetermined time based on a rotation speed of the internal combustion engine. The ignition device for an internal combustion engine according to any one of claims 1 to 3, wherein the control means sets the predetermined time based on a parameter indicating ignitability of the internal combustion engine. As the first switching unit, a thyristor having an anode connected to one end of the series circuit on the ignition capacitor side and a cathode connected to the other end of the series circuit, and a diode connected in reverse parallel to both ends of the thyristor The ignition device for internal combustion engines as described in any one of Claim 1 to 4 provided with these.

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