JP2016211421A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition device for an internal combustion engine capable of suppressing reduction in reliability of the ignition device even when current flowing in a primary coil 22 abruptly increases.SOLUTION: An EDU 10, after input of an ignition signal Si, opens/closes a switching element 50 for control to control current I2 flowing in a secondary side coil 24, on the basis of input of a discharge waveform control signal Sc. Here, an ECU 80 acquires voltage drop Vi1, and monitors inclination of current I1 flowing in a primary side coil 22. Then, when the inclination is equal to or more than a predetermined inclination, the ECU 80 opens a relay 60.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition device for an internal combustion engine including an ignition coil including a primary side coil and a secondary side coil, and an ignition plug connected to the secondary side coil and exposed to a combustion chamber of the internal combustion engine.

  For example, Patent Document 1 proposes an apparatus that determines that an abnormality has occurred in a coil when the rising of the current flowing through the primary coil when the primary coil of the ignition coil is energized becomes steep. This device aims to detect a rare short of the primary side coil or the secondary side coil or a disconnection of the secondary side coil as an abnormality of the coil (paragraph “0017”). In view of the fact that the inductance changes when a coil abnormality occurs, the presence / absence of a coil abnormality is determined based on the rise of the current flowing through the primary coil, and when it is determined that an abnormality has occurred, the igniter system is stopped.

Japanese Unexamined Patent Publication No. 2012-233483

  Incidentally, other abnormalities of the ignition coil include, for example, magnetic saturation. When the ignition coil is magnetically saturated, the current flowing through the primary coil suddenly increases, which may lead to a decrease in the reliability of the ignition device. However, in the above apparatus, when the current flowing through the primary coil suddenly rises, this cannot be dealt with immediately.

  The present invention has been made in view of such circumstances, and an object of the present invention is for an internal combustion engine that can suppress a decrease in reliability of an ignition device even when a current flowing through a primary coil suddenly increases. It is to provide an ignition device.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
An ignition device for an internal combustion engine includes an ignition coil having a primary coil and a secondary coil, an ignition plug connected to the secondary coil and exposed to a combustion chamber of the internal combustion engine, and flowing through the primary coil. A detector that detects a current gradient; and an interruption processor that interrupts energization of the primary coil when the gradient detected by the detector is equal to or greater than a predetermined gradient.

  In the above configuration, the inclination of the current flowing through the primary coil is detected by the detection unit. Here, when magnetic saturation occurs in the primary coil, the inclination detected by the detection unit is equal to or greater than the predetermined inclination. For this reason, energization to the primary side coil is interrupted by the interruption processing unit. For this reason, compared with the case where the process by an interruption process part is not made, the maximum value of the electric current which flows into a primary side coil can be reduced, and by extension, it can control that the temperature of an ignition coil becomes high too much. it can. Therefore, in the above configuration, it is possible to suppress a decrease in the reliability of the ignition device even when the current flowing through the primary coil suddenly increases.

The circuit diagram which shows the ignition device for internal combustion engines concerning one Embodiment. (A)-(g) is a time chart which shows the procedure of the ignition process concerning the embodiment. The flowchart which shows the procedure of the interruption process of the energization of the primary side coil concerning the embodiment.

Hereinafter, an embodiment of an ignition device will be described with reference to the drawings.
As shown in FIG. 1, the driver unit (EDU 10) includes an ignition coil 20 in which a primary side coil 22 and a secondary side coil 24 are magnetically coupled. In FIG. 1, black circles given to one of the pair of terminals of the primary side coil 22 and the secondary side coil 24 are open at both ends of the primary side coil 22 and the secondary side coil 24. In this state, when the magnetic flux interlinking them is changed, the terminals where the polarities of the electromotive forces generated in the primary side coil 22 and the secondary side coil 24 are equal are shown.

  The spark plug 12 is connected to one terminal of the secondary coil 24, and the other terminal is grounded via a diode 26 and a shunt resistor 28. Here, the spark plug 12 is exposed to the combustion chamber of the in-vehicle internal combustion engine. On the other hand, the diode 26 is a rectifying element that allows a current flow on the side that proceeds from the spark plug 12 to the ground via the secondary coil 24 and restricts a current flow on the reverse side. The shunt resistor 28 is a resistor for detecting the current flowing through the secondary coil 24 by the voltage drop Vi2. In other words, it is a resistor for detecting the discharge current of the spark plug 12.

  A positive electrode of an external battery 70 is connected to one terminal of the primary coil 22 of the ignition coil 20 via a terminal TRM1 of the EDU 10. The other terminal of the primary coil 22 is grounded via the ignition switching element 30. In the present embodiment, the ignition switching element 30 is an insulated gate bipolar transistor (IGBT). A diode 32 is connected in reverse parallel to the ignition switching element 30.

  The power captured from the terminal TRM1 is also captured by the booster circuit 40. In the present embodiment, the booster circuit 40 is configured by a boost chopper circuit. That is, an inductor 42 having one end connected to the terminal TRM1 side is provided, and the other end of the inductor 42 is grounded via the step-up switching element 44. In the present embodiment, the boosting switching element 44 is an IGBT. The anode side of the diode 46 is connected between the inductor 42 and the step-up switching element 44, and the cathode side of the diode 46 is grounded via a capacitor 48. The charging voltage Vc of the capacitor 48 becomes the output voltage of the booster circuit 40.

  The diode 46 and the capacitor 48 are connected between the primary coil 22 and the ignition switching element 30 via the control switching element 50 and the diode 52. In other words, the output terminal of the booster circuit 40 is connected between the primary coil 22 and the ignition switching element 30 via the control switching element 50 and the diode 52. In the present embodiment, the control switching element 50 is a MOS field effect transistor. The diode 52 is a rectifying element for preventing a current from flowing backward from the primary coil 22 and the ignition switching element 30 side to the booster circuit 40 side via the parasitic diode of the control switching element 50.

  The step-up control unit 54 is a control circuit that controls the output voltage of the step-up circuit 40 by opening and closing the step-up switching element 44 based on the ignition signal Si input to the terminal TRM2. The step-up control unit 54 monitors the output voltage of the step-up circuit 40 (the charging voltage Vc of the capacitor 48), and stops the opening / closing operation of the step-up switching element 44 when the output voltage exceeds a predetermined value.

  The discharge control unit 56 opens and closes the control switching element 50 based on the ignition signal Si input to the terminal TRM2 and the discharge waveform control signal Sc input to the terminal TRM3, so that the discharge current of the spark plug 12 is discharged. It is the control circuit which controls. In addition, the electric power of the battery 70 taken in from the terminal TRM1 via the relay 60 is input to the discharge control unit 56. The relay 60 is an opening / closing device that is opened / closed by a power command signal Sr input to the terminal TRM4. When the relay 60 is opened, the operating power supply of the discharge control unit 56 is turned off.

  The terminal TRM2 of the EDU 10 is connected to the ECU 80 via the ignition communication line Li, and the terminal TRM3 is connected to the ECU 80 via the waveform control communication line Lc. The terminal TRM4 of the EDU 10 is connected to the ECU 80 via a power supply command communication line Lr.

  A shunt resistor 90 is provided between the terminal TRM1 and the primary coil 22. The voltage drop Vi2 in the shunt resistor 90 is detected by the voltage sensor 92 and output to the outside of the EDU 10 via the terminal TRM5.

  The ECU 80 is a control device that operates various actuators such as the EDU 10 in order to control the control amount of the internal combustion engine. Next, ignition control performed by the ECU 80 using the EDU 10 will be described.

  2A shows the transition of the ignition signal Si, FIG. 2B shows the transition of the discharge waveform control signal Sc, and FIG. 2C shows the state transition of the opening / closing operation of the ignition switching element 30. FIG. 2D shows a state transition of the opening / closing operation of the step-up switching element 44. 2 (e) shows the state transition of the switching operation of the control switching element 50, FIG. 2 (f) shows the transition of the current I1 flowing through the primary coil 22, and FIG. 2 (g) The transition of the current I2 flowing through the secondary coil 24 is shown. In addition, the signs of the currents I1 and I2 define the arrow side shown in FIG. 1 as positive.

  When the ignition signal Si is input to the EDU 10 at time t1, the EDU 10 turns on (closes) the ignition switching element 30. As a result, the current I1 flowing through the primary coil 22 increases gradually. That is, when the ignition switching element 30 is closed, the first loop circuit, which is a loop circuit including the battery 70, the primary coil 22, and the ignition switching element 30, becomes a closed loop circuit, and a current flows therethrough. In addition, since the interlinkage magnetic flux of the secondary side coil 24 increases gradually when the electric current which flows into the primary side coil 22 increases gradually, in the secondary side coil 24, the electromotive force which cancels the increase of an interlinkage magnetic flux arises. However, since the electromotive force is negative on the anode side of the diode 26, no current flows through the secondary coil 24.

  As shown in FIG. 2, when the ignition signal Si is input to the EDU 10, the boost controller 54 opens and closes the boost switching element 44. Thereafter, the discharge waveform control signal Sc is input to the EDU 10 at time t2. Thereafter, when the input of the ignition signal Si is stopped at time t3, in other words, when the voltage of the ignition communication line Li is changed from a logic H voltage to a logic L voltage, the EDU 10 30 is opened. As a result, the current I <b> 1 flowing through the primary side coil 22 becomes zero, and the current flows through the secondary side coil 24 due to the counter electromotive force generated in the secondary side coil 24. As a result, the spark plug 12 starts discharging.

  That is, when the current in the primary side coil 22 is cut off and the interlinkage magnetic flux in the secondary side coil 24 attempts to decrease, the secondary coil 24 has a counter-electromotive force in the direction that cancels the decrease in the interlinkage magnetic flux. Electric power is generated, and current I2 flows through the spark plug 12, the secondary coil 24, the diode 26, and the shunt resistor 28. When the current I2 flows through the secondary coil 24, a voltage drop Vd occurs in the spark plug 12, and a voltage drop of “r · I2” corresponding to the resistance value r occurs in the shunt resistor 28. As a result, when the forward voltage drop of the diode 26 is ignored, a voltage “Vd + r · I2”, which is the sum of the voltage drop Vd at the spark plug 12 and the voltage drop at the shunt resistor 28, is applied to the secondary coil 24. . This voltage gradually reduces the interlinkage magnetic flux of the secondary coil 24. The current I2 flowing through the secondary coil 24 gradually decreases from time t3 to t4 in FIG. 2G due to the phenomenon that the voltage of “Vd + r · I2” is applied to the secondary coil 24. .

As shown in FIG. 2, after time t4, the discharge controller 56 opens and closes the control switching element 50.
In the period from time t4 to time t5 when the control switching element 50 is closed, the second loop circuit including the booster circuit 40, the control switching element 50, the diode 52, the primary side coil 22, and the battery 70 is provided. The loop circuit becomes a closed loop, and a current flows therethrough.

  On the other hand, during the period from the time t5 to the time t6 when the control switching element 50 is opened, the back electromotive force that cancels the change in magnetic flux due to the decrease in the absolute value of the current flowing through the primary side coil 22 is the primary side. It occurs in the coil 22. As a result, the third loop circuit, which is a loop circuit including the diode 32, the primary coil 22, and the battery 70, becomes a closed loop, and a current flows therethrough.

  Here, when the time ratio D of the closing operation period Ton with respect to one cycle T of the opening / closing operation of the control switching element 50 shown in FIG. 2E is operated, the current flowing through the primary coil 22 can be controlled. The discharge control unit 56 executes control to gradually increase the absolute value of the current I1 flowing through the primary coil 22 according to the duty ratio D. The sign of the current I1 during this period is opposite to that of the current I1 flowing in the primary coil 22 when the ignition switching element 30 is in the closed state. For this reason, if the magnetic flux generated by the current I1 flowing in the primary coil 22 when the ignition switching element 30 is in the closed state is positive, the current I1 generated by opening and closing the control switching element 50 is Will be reduced. Here, the gradually decreasing speed of the interlinkage magnetic flux of the secondary side coil 24 due to the current I1 flowing through the primary side coil 22 coincides with the gradually decreasing speed when the voltage of “Vd + r · I2” is applied to the secondary side coil 24. In this case, the current flowing through the secondary coil 24 does not decrease. In this case, the power loss due to the spark plug 12 and the shunt resistor 28 is compensated by the power output from the power source constituted by the booster circuit 40 and the battery 70.

  In contrast, the gradually decreasing speed of the interlinkage magnetic flux of the secondary coil 24 due to the current I1 flowing through the primary coil 22 is higher than the gradually decreasing speed when the voltage of “Vd + r · I2” is applied to the secondary coil 24. When the current is small, the current I2 flowing through the secondary coil 24 gradually decreases. With the gradual decrease of the current I2, the flux linkage gradually decreases at a gradual decrease rate when a voltage of “Vd + r · I2” is applied to the secondary coil 24. However, the gradual decrease rate of the current I2 flowing through the secondary coil 24 is smaller than when the absolute value of the current I1 flowing through the primary coil 22 is not gradually increased.

  Further, the primary reduction is such that the actual gradual decrease rate of the interlinkage magnetic flux is larger than the gradual decrease rate of the interlinkage magnetic flux of the secondary side coil 24 when the voltage of “Vd + r · I2” is applied to the secondary side coil 24. When the absolute value of the current I1 flowing through the side coil 22 is gradually increased, the voltage of the secondary side coil 24 is increased by the counter electromotive force that suppresses the decrease of the linkage flux. Then, the current I2 flowing through the secondary coil 24 increases so that “Vd + r · I2” is equal to the voltage of the secondary coil 24.

  As described above, the current I2 flowing through the secondary coil 24 can be controlled by controlling the gradually increasing rate of the absolute value of the current I1 flowing through the primary coil 22. In other words, the discharge current of the spark plug 12 can be controlled to increase or decrease.

  In the discharge control unit 56, the duty ratio D of the control switching element 50 is set in order to feedback-control the discharge current value determined from the voltage drop Vi2 of the shunt resistor 28 to the discharge current command value I2 * shown by the one-dot chain line in FIG. Manipulate.

  By the way, the voltage between both electrodes of the spark plug 12 necessary for maintaining the discharge current becomes higher as the air-fuel ratio in the combustion chamber of the internal combustion engine becomes leaner. Specifically, when the air-fuel ratio is made leaner, the voltage between both electrodes of the spark plug 12 required for controlling the discharge current to the discharge current command value I2 * increases. As a result, the current I1 flowing through the primary coil 22 is excessively increased by the feedback control, and as a result, the ignition coil 20 may be magnetically saturated. When the ignition coil 20 is magnetically saturated, the current flowing through the primary coil 22 increases abruptly, so that the amount of heat generated by the ignition coil 20 increases rapidly, which may lead to a decrease in the reliability of the EDU 10.

Therefore, in the present embodiment, such a situation is dealt with by the processing shown in FIG. The process shown in FIG. 3 is repeatedly executed by the ECU 80, for example, at a predetermined cycle.
In this series of processes, the ECU 80 first acquires the voltage drop Vi1 detected by the voltage sensor 92 as the current I1 of the primary coil 22 (S10). Then, the ECU 80 calculates the slope ΔI1 of the current I1 of the primary coil 22 based on the acquired voltage drop Vi1 (S12). Then, the ECU 80 determines whether or not the inclination ΔI1 is equal to or larger than a predetermined inclination ΔI1th (S14). This process is for determining whether magnetic saturation has occurred in the ignition coil 20. The predetermined slope ΔI1th is set to about the lower limit value of the slope that cannot be generated by the differential pressure between the charging voltage Vc of the capacitor 48 and the terminal voltage of the battery 70 when no magnetic saturation occurs in the ignition coil 20. If the ECU 80 determines that the inclination is greater than or equal to the predetermined inclination ΔI1th (S14: YES), the ECU 60 opens the relay 60 (S16). This process is a process of interrupting energization of the primary coil 22.

Note that the ECU 80 once ends the series of processes when the process of step S16 is completed or when a negative determination is made in step S14.
Here, the operation of the present embodiment will be described.

  The EDU 10 controls the current I2 flowing through the secondary coil 24 by opening and closing the control switching element 50 based on the input of the discharge waveform control signal Sc after the input of the ignition signal Si. At this time, the ECU 80 acquires the voltage drop Vi1 and monitors the slope ΔI1 of the current I1 flowing through the primary side coil 22. Then, as shown by a two-dot chain line in FIG. 2 (f), when the inclination ΔI 1 is equal to or greater than a predetermined inclination ΔI 1, the ECU 80 opens the relay 60. As a result, the discharge control unit 56 cannot close the control switching element 50, and the loop circuit including the booster circuit 40, the primary side coil 22, and the battery 70 becomes an open loop. Therefore, a current flows through the primary side coil 22 via a loop circuit including the diode 32, the primary side coil 22, and the battery 70. Decrease gradually at a fixed rate of decrease. When the current I1 flowing through the primary coil 22 becomes zero, a state in which no current flows through the primary coil 22 is maintained until the ignition switching element 30 and the like are closed.

Note that the ECU 80 opens the relay 60 and then closes the relay 60 by the timing at which the discharge waveform control signal Sc is newly output.
According to the present embodiment described above, the following effects can be obtained.

  (1) When the inclination ΔI1 is equal to or larger than the predetermined inclination ΔI1, the relay 60 is opened by the ECU 80, and energization of the primary coil 22 is interrupted. For this reason, even if it is a case where the electric current I1 which flows into the primary side coil 22 rises rapidly, the fall of the reliability of an ignition device (EDU10, ECU80) can be suppressed.

<Other embodiments>
In addition, you may change at least 1 of each matter of the said embodiment as follows.
In the above embodiment, the slope of the current flowing through the primary coil 22 is detected based on the voltage drop Vi1 of the shunt resistor 90, but the present invention is not limited to this. For example, a current transformer that detects a current flowing through an electric path between the primary coil 22 and the diode 52 is provided, and a slope of a current flowing through the primary coil 22 is detected based on a current value detected by the current transformer. May be.

  In the above embodiment, the energization of the primary coil 22 is interrupted by opening the relay 60, but this is not restrictive. For example, a relay may be provided between the battery 70 and the terminal TRM1, and this may be opened. For example, if the time required for the EDU 10 to open the control switching element 50 by stopping the output of the discharge waveform control signal Sc is sufficiently short, the output of the discharge waveform control signal Sc may be stopped. .

  It is not essential to provide a circuit for applying a voltage having a reverse polarity to that when the ignition switching element 30 is closed in the primary coil 22 in order to control the discharge current. For example, in the case of the forward type ignition coil 20 in which the spark plug 12 discharges even when the ignition switching element 30 is in the closed state, magnetic saturation occurs when the ignition switching element 30 is in the closed state. When the slope of the current flowing through the secondary coil 22 is greater than or equal to a predetermined slope, it is effective to interrupt the energization of the primary coil 22.

  DESCRIPTION OF SYMBOLS 10 ... EDU, 12 ... Spark plug, 20 ... Ignition coil, 22 ... Primary side coil, 24 ... Secondary side coil, 26 ... Diode, 28 ... Shunt resistance, 30 ... Switching element for ignition, 32 ... Diode, 40 ... Booster circuit 42... Inductor 44. Boosting switching element 46. Diode, 48. Capacitor 50. Control switching element 52. Diode 54 54 Boost controller 56 Discharge controller 60 Relay ... battery, 80 ... ECU, 90 ... shunt resistor, 92 ... voltage sensor.

Claims (1)

An ignition coil comprising a primary coil and a secondary coil;
A spark plug connected to the secondary coil and exposed to the combustion chamber of the internal combustion engine;
A detector that detects a slope of a current flowing through the primary coil;
An internal combustion engine ignition device comprising: an interruption processing unit that interrupts energization of the primary coil when the inclination detected by the detection unit is equal to or greater than a predetermined inclination.