JP2007085306A - Ignition device equipped with ion current detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition device equipped with an ion current detector capable of minimizing a loss of ignition energy, even when an ion detecting power supply voltage is increased. <P>SOLUTION: The ignition device is equipped with a drive power on a primary side, and a spark plug and an ion current detector on a secondary side. The ignition device minimizes the loss of ignition energy even when the detecting power supply voltage is increased, with a configuration in which a capacitor as a power source of the ion current detector is provided with a switching element for shunting the capacitor, and the switching element has a control unit for keeping an on-state at least during the first half of a discharge duration at the spark plug. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ignition device including an ion current detection device mainly used for an internal combustion engine, and detects combustion ion current generated after discharge ignition at a spark plug to control combustion such as ignition timing.

  Conventionally, several ignition devices for internal combustion engines have been proposed that perform ignition control by detecting an ionic current generated in the combustion chamber at the time of ignition (for example, JP-A-10-141197).

  However, in order to deal with recent direct-injection internal combustion engines with high-compressed lean air-fuel mixture for measures against exhaust gas and improving fuel efficiency, in addition to ordinary high-current cutoff type ignition devices, double spark ignition devices and While various high energy ignition devices such as a spark ignition device or an alternating spark ignition device have been proposed, an ion current detection device that detects the combustion state of an internal combustion engine such as misfire or knock is primarily used as a capacitor for a capacitor. The charging voltage is generally used in the range of about 70V to 300V, and the higher the voltage, the higher the S / N ratio for ion detection. This increases the degree of design freedom. Design there has been a drawback that referred to as needed.

  Furthermore, in recent exhaust gas countermeasures, there is a demand for a system that finely collects information on changes in ion current from the start of the internal combustion engine to the high speed range and controls the air-fuel ratio in combination with EGR. It has been confirmed that about 15 degrees after the top dead center is detected as an important time zone for ionic current discrimination in order to detect the combustion deterioration state and knocking at the ionic current. On the other hand, in order to deal with a direct fuel injection internal combustion engine with lean fuel, etc., a high output energy ignition device is desired as a problem before control by ion current. When used, the discharge duration is long even when the engine speed is high, so that there is a problem that sufficient time required for ion current detection cannot be obtained.

  In order to solve the above-described problems, the present invention has the following configuration. According to claim 1, in an ignition device including a drive power source on a primary side of an ignition coil constituting the ignition device and an ignition plug and an ion current detection device on a secondary side of the ignition coil, a current source of the ion current detection device A switching element that shunts the capacitor, and the switching element has a control means for turning on at least the first half of the discharge duration of the spark plug, thereby increasing the ion detection power supply voltage. Even so, an ignition device having an ion current detection device that minimizes the loss of ignition energy is obtained.

  In the ignition device provided with the ion current detection device according to claim 2 of the present invention, the ignition device is a multiple discharge ignition device, so that the ion current detection time is relatively reduced in combination with the discharge frequency control of the ignition device. Since it becomes possible to control freely, the characteristic of the control which does not impair ignition energy is exhibited to the maximum extent.

  In the ignition device including the ion current detection device according to claim 3 of the present invention, the gradient of the discharge duration of the ignition device is 0.7 ms to 1.5 ms when the internal combustion engine speed is 1000 rpm, and within 0.5 ms when the engine speed is 8000 rpm. With this configuration, detailed information on the combustion state can be obtained by detecting the ion current regardless of the engine speed.

  In the ignition device including the ion current detection device according to claim 4 of the present invention, at least 15 degrees before ATDC (after compression top dead center) in the practical engine internal rotation range, the time for the switching element to shift from the on state to the off state. By doing so, detailed information on the combustion state can be obtained by detecting the ionic current in the same manner as described above while minimizing the ignition energy loss.

  In the ignition device including the ion current detection device according to claim 5 of the present invention, the switching element is turned off while leaving the last cycle of the multiple discharge of the multiple discharge ignition device, thereby simplifying the control. Can be achieved.

  According to the present invention, a high output energy ignition device for dealing with a fuel direct injection internal combustion engine or the like with a highly compressed lean air-fuel mixture, which has been required in recent years for fuel efficiency and exhaust gas countermeasures, and from the start of the internal combustion engine For a combination of ion current detection devices that finely collect information on changes in combustion ion current up to the high engine speed range and use the air-fuel ratio in combination with EGR to control ignition timing, etc. By constructing a switching element that shunts the main circuit of the ion current detection device, and adding a control means that appropriately controls the switching time of the switching element, a loss of ignition energy can be achieved even if the ion detection power supply voltage is increased. An igniter with an ion current detector that is minimized is obtained.

  Also, in combination with a multiple discharge type ignition device with a high degree of freedom in which the multiple discharge cycle and frequency can be changed as appropriate according to the engine speed, load conditions and the power supply voltage, the combustion deterioration state and knocking with ionic current are meticulously determined. An ignition device having an ion current detection device that secures a discrimination time from about 15 degrees ATDC necessary for detection, for example, by changing the discharge duration according to the engine speed and minimizes the loss of ignition energy is obtained. It can be done.

  FIG. 1 shows an embodiment of the present invention in which a multiple discharge ignition device is used as an ignition device. FIG. 2 is a waveform diagram of each part for explaining the operation of the embodiment. FIGS. 3 and 4 are other embodiments of the present invention. In FIG. 2, the same symbols are the same or equivalent in function. .

  In FIG. 1, a DC power source 1, an ignition switch 2, an energy storage coil 3, a backflow prevention means 4, and a switching element 5 are connected in series, and the switching element 5 is a series circuit including a capacitor 6 and a primary wire 71 of the ignition coil 7. Each of the protection elements 8 of the switching element 5 made of a constant voltage diode is shunted. A spark plug 9 is connected to the high voltage side of the output of the secondary wire ring 72 of the ignition coil 7, and a terminal 10 of the ion current detector 100 is connected to the low voltage side. The control terminal of the switching element 5 is connected to the drive circuit 11, and the input terminal of the drive circuit 11 is connected to the output terminal of the ECU 12. The ion current detection device 100 constitutes a series circuit of the terminal 10, the capacitor 15, and the diode 16, and the series circuit is shunted by the constant voltage diode 17 and the second switching element 18. Further, the connection point between the capacitor 15 and the diode 16 is connected to the ion detection circuit 20 via the ion current detection register 19, and the output terminal 13 of the detection circuit 20 is connected to the input terminal of the ECU 12. The control terminal 14 of the second switching element 18 is connected to the output terminal of the ECU 12.

  The configuration comprising the backflow prevention means 4, the switching element 5, the capacitor 6, the ignition coil 7, the protection element 8, the spark plug 9, the drive circuit 11 and the ion current detection device 100 is a unit per cylinder of the internal combustion engine. Usually, it is composed of multiple cylinders that share the energy storage coil 3 and the ECU 12, but the units of other cylinders are omitted in this embodiment.

  When the ignition switch 2 is turned on, a current flows through the energy storage coil 3, the backflow prevention means 4, the capacitor 6, and the primary wire 71 of the ignition coil 7, and charges up to the DC power supply voltage are stored in the capacitor 6. Next, the drive circuit 11 and the second switching element 18 receive different signals from the ECU 12 at time t0, the switching element 5 is turned on, and the charge of the capacitor 6 is discharged to the primary wire ring 71 simultaneously. Inductive energy storage is started by the current flowing through the energy storage coil 3, while the second switching element 18 is also turned on.

  Due to the discharge of the capacitor 6 to the primary wire 71, a voltage of about 1.6 kV is induced in the secondary wire 72 via the second switching element 18. The discharge charge is a free vibration consisting of the capacitance of the capacitor 6 and the inductance of the primary ring 71, and the current direction is reversed from the energization to the switching element 5 to the energization to the protection element 8 due to the vibration period of 0.4 mS in this embodiment. Then, after a further 0.2 mS has elapsed, the switching element 5 is turned off at time t1, and the capacitor 6 is charged with an induced voltage of about 350 V stored energy in the energy storage coil 3, and at the same time the initial charge is large. When a current is applied to the primary wire 71, a voltage of about 40 kV is induced on the secondary wire 72 via the low voltage diode 17. The discharge is started in the fire hydrant 9.

  The first 0.6 mS discharge delay of the engine cranking is not a problem because the delay angle of the cranking rotational speed is about 0.5 degrees, but the time can be set short.

  Even if the switching element 5 shifts to the off state, the second switching element 18 remains on until the time tn described later, so that the capacitor 15 as the current source is not charged and the ionic current is not charged. The detection device is stationary.

  Next, after the time before the end of the discharge, for example, 0.3 mS, the switching element 5 is turned on again at time t2, so that the high charge of the capacitor 6 is applied to the primary wire 71, and the secondary wire A voltage in the direction opposite to the discharge voltage is induced in 72 via the second switching element 18, and at the same time as an inversion current flows through the spark plug 9, accumulation of induction energy starts again in the energy storage coil 3.

  Next, the switching element 5 is turned off again at time t3 after 0.3 mS, so that the capacitor 6 starts to be charged with the induced voltage of the stored energy of the energy storage coil 3 by about 300 V, and at the same time, the primary line. A voltage of about 34 kV is induced on the secondary wire 72 via the wheel 71, and the discharge current of the spark plug 9 is reversed.

  Thereafter, the switching element 5 is repeatedly turned on and off at equal intervals of 0.3 mS, so that the spark plug 9 alternately performs capacitive discharge due to discharge of the capacitor 6 and inductive discharge due to charge of the capacitor 6 by the energy storage coil 3. For example, when the switching element 5 is turned off at a time tn after 5 repetitions, the discharge of the spark plug 9 is completed, but the capacitor 6 sufficiently stores the charge charged by the induction energy of the energy storage coil 3. And wait until the next ignition timing.

  At the time tn, an off signal is applied to the second switching element 18 from the ECU 12 to shift from on to off, the switching element 5 is finally turned off, and the spark discharge at the spark plug 9 is completed. The capacitor 15 is charged to a voltage substantially limited by the low voltage diode 17 by a free oscillation voltage of several kV due to the inductance and leakage capacitance between the secondary wire 72 of the ignition coil 7 and the spark plug.

  When the charging voltage of the capacitor 15 is applied to the spark plug 9 through the secondary wire ring 72, the combustion ion current generated by the ignition by the multiple discharge spark is detected by the register 19, and the ion detection circuit 20 is detected. Then, after amplification and waveform processing, the signal is transmitted to the ECU 12 via the terminal 13.

  When the ignition timing comes again, at time t0, the switching element 5 and the second switching element 18 are turned on almost simultaneously, and the above-described sufficient charging charge is applied to the capacitor 6 to the primary wire 71, whereby the secondary line. A spark discharge is started in the spark plug 9 via the second switching element 18 by a voltage of about 40 kV induced in the ring 72, and at the same time, the accumulation of inductive energy starts in the energy storage coil 3. Subsequently, when the switching element 5 is turned off at time t1 after 0.3 mS, the induced energy becomes the charging current of the capacitor 6 and at the same time, due to the voltage induced in the secondary wire 72 via the primary wire 71, A reverse discharge current flows through the spark plug 9 via the constant voltage diode 8, and the switching element 5 is turned on again at time t2 after 0.3 mS before the discharge ends, and capacitive discharge due to the discharge of the capacitor 6 occurs. This is performed as re-inversion discharge on the spark plug 9, and thereafter, multiple discharges are repeatedly performed while the output from the drive circuit 11 based on the control signal of the ECU 12 continues. The battery is charged up to the limit voltage, whereby the combustion ion current is detected and sent to the ECU 12 via the ion detection circuit 20.

  The above-described operation is shown in FIG. 2, where S is an ignition operation range determined by the ECU 12 as appropriate determined by the engine speed, load conditions and power supply voltage, and also determines the non-operation time of the ion current detection device 100. Yes. Vs is a switching output signal to the drive circuit 11 determined by the ECU 12 as described above, Vc is a voltage across the capacitor 6, and i2 is a discharge current of the spark plug 9.

  As shown in FIG. 2, a high voltage of about 40 kV is required at the beginning of discharge of the spark plug 9, but once the discharge is performed, discharge is performed even at a low voltage of about 25 kV due to ionization in the vicinity of the spark plug 9. In order to be able to continue, the switching period of the switching element 5 is raised and the output voltage is lowered.

  The last hatched portion i0 of the output current indicated by i2 in FIG. 2 indicates the charging current applied to the capacitor 15 by the free oscillation voltage after the end of the discharge, and the substantial ion detection of the ion current detector from time ti. Start time.

  When the engine speed increases, the discharge duration S needs to be set to be inversely proportional to this, and the ON / OFF cycle of the switching element 5 is also shortened. However, depending on the load condition, it is rarely high. Since the discharge voltage may be required, it is preferable to reduce the switching frequency of the switching element 5, and the discharge duration of the ignition device is 0.7 ms to 1.5 ms when the internal combustion engine speed is 1000 rpm, and 0 when the engine speed is 8000 rpm. By adopting a configuration that changes with a gradient within 5 ms, fine information on the combustion state can be obtained by detecting the ion current regardless of the engine speed.

  By simultaneously controlling the above-described means for controlling the discharge duration in conjunction with the rotational speed and the time during which the second switching element 18 of the ion current detection device 100 shifts from the on state to the off state, at least the practical rotation of the internal combustion engine. By setting the ATDC (after compression top dead center) to 15 degrees or less in the region, ignition energy loss can be minimized, and detailed information on the combustion state can be obtained by ion current detection as described above.

  The level control of the output voltage in this embodiment is determined by the energy storage energization time to the energy storage coil 3, in other words, the on-time of the switching element 5. In particular, the first operation at the time of engine cranking when the ignition switch is turned on. Other than the above, the on-time immediately before the time tn determines the stored energy of the energy storage coil 3 and determines the charge amount of the capacitor 6. In particular, the on-time is set longer when the voltage of the DC power source 1 is low, such as during engine cranking and subsequent idle rotation.

  In the method for realizing the low cost in the above 29th paragraph, the on-time of the switching element 5 immediately before the normal time tn is fixed to be relatively long with respect to the previous on-time.

  In this case, the timing for controlling the second switching element 18 of the ion current detection device from on to off is set off while leaving the last one cycle of the multiple discharge ignition device in conjunction with the fixed setting. Control can be simplified.

  The energy storage coil 3 is normally designed not to be magnetically saturated with respect to the maximum energization time setting.

  FIG. 3 shows a second embodiment of the present invention, in which only the portion of the ion current detection device 100 of the embodiment of FIG. 1 is changed. The change from FIG. 1 is that each of the constant voltage diode 17 and the second switching element 18 that shunts the series circuit of the capacitor 15 and the diode 16 is a circuit that shunts only the capacitor 15, and further the diode 16 In addition, another diode 21 is added in the opposite direction, and the charge voltage to the capacitor 15 can be set more accurately.

  FIG. 4 shows a third embodiment of the present invention, in which only the portion of the ion current detector 100 of the embodiment of FIG. 1 is changed as in FIG. The change from FIG. 1 is that the anode of the constant voltage diode 17 that shunts the series circuit of the capacitor 15 and the diode 16 is connected to the control terminal of the second switching element 18, and another diode 21 is connected to the second diode 21. The control terminal of the switching element 18 is connected to the low voltage diode 17 in the same energizing direction, and the second switching element 18 takes over the current burden of the constant voltage diode 17 when charging the capacitor 15. In the constant voltage diode 17, only the reversal discharge current having a relatively small peak current that flows when the switching element 5 of the multiple discharge ignition device is turned off is shared with the switching element 18 via the diode 21. The capacity of the voltage diode 17 can be reduced.

  In any of the embodiments, the constant voltage diode 17 consumes a large amount of power when the multiple ignition energy is applied as it is even when a low voltage is set, but can be set to a minimum power consumption in the present invention. Therefore, the constant voltage diode 17 can be an avalanche diode as well as a normal Zener diode.

  The switching element 5 and the second switching element 18 of the multiple discharge ignition device can be appropriately selected from a normal transistor, IGBT, and FET.

  In the embodiment, a constant voltage diode is used as the protective element 8 of the switching element 5. However, a normal diode may be used, and may be omitted by adding a low resistor or a diode to the control terminal of the switching element 5. Is possible.

  Similarly, in the embodiment, the control of the signal indicated by the waveform S that determines the discharge duration and the multiple discharge period waveform indicated by Vs of the multiple discharge ignition device is performed by the control software of the ECU 12, but other ICs, etc. Can also be configured.

  Further, in the embodiment, only the multiple discharge type ignition device that alternately repeats the capacitive discharge and the inductive discharge is shown. However, even with other ignition devices, a part of the ignition energy is supplied to the current source of the ion current detection device. As long as it is an ignition device that charges a capacitor that constitutes the device, the function of the ignition device including the ion current detection device according to the present invention is not lost.

The figure which shows the 1st Example of invention. The operation | movement waveform of each part of 1st Example of invention. The figure which shows the principal part of the 2nd Example of invention. The figure which shows the principal part of the 3rd Example of invention.

Explanation of symbols

3: Energy storage coil 4: Backflow prevention means 5: Switching element 6: Capacitor 7: Ignition coil 71: Primary wire ring 72: Secondary wire ring 8: Protection element 9: Spark plug 100: Ion current detectors 10, 13, 14: Terminal of ion current detection device 11: Drive circuit 12: ECU
15: Capacitors 16, 21: Diode 17: Constant voltage diode 18: Second switching element 19: Register 20: Ion detection circuit

Claims (5)

In an ignition device including a drive power source on the primary side of an ignition coil constituting the ignition device, and an ignition plug and an ion current detection device on the secondary side of the ignition coil, a capacitor constituting a current source of the ion current detection device, An ignition device comprising an ion current detection device comprising a switching element for shunting the capacitor, the switching element having a control means for turning on at least the first half of the discharge duration of the spark plug. The ignition device comprising the ion current detection device according to claim 1, wherein the ignition device is a multiple discharge ignition device. The ion current detection according to claim 1 or 2, wherein the discharge duration at the spark plug changes with a gradient of 0.7 ms to 1.5 ms when the engine speed is 1000 rpm and within 0.5 ms when the engine speed is 8000 rpm. Ignition device comprising the device. The ignition device comprising the ion current detection device according to any one of claims 1 to 3, wherein a time for the switching element to shift from an on state to an off state is at least 15 degrees before ATDC (after compression top dead center) in a practical rotational range of the internal combustion engine. . An ignition device comprising the ion current detection device according to any one of claims 1 to 4, wherein the switching element is turned off with the last cycle of multiple discharge of the multiple discharge ignition device remaining.

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