JP4141014B2 - Ignition device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine ignition device including an ion current detection circuit that detects an ion current that flows after spark discharge of an ignition plug.
[0002]
[Prior art]
Conventionally, in addition to misfire and knocking of the internal combustion engine, spark discharge of the ignition plug of the internal combustion engine is detected in order to detect various operating states of the internal combustion engine (air-fuel ratio, lean limit of the air-fuel ratio, limit of exhaust gas recirculation amount, etc.). A technique is known that uses an ionic current that flows later due to ions that are present in the vicinity of an electrode of a spark plug.
[0003]
That is, in the cylinder of the internal combustion engine, ions are generated during combustion (flame propagation) after spark discharge by the spark plug, and the resistance value between the electrodes of the spark plug changes according to the amount of the generated ion. The amount of ions generated varies depending on the combustion state of the internal combustion engine, and hence the operating state of the internal combustion engine. For this reason, after applying a high voltage for ignition to the spark plug (that is, after spark discharge of the spark plug), a voltage is applied to the spark plug from the outside, and the ionic current flowing thereby is detected. It is possible to detect a change in resistance value between electrodes (that is, a change in operating state).
[0004]
For example, as disclosed in Japanese Patent Laid-Open No. 4-191465, such an ion current detection circuit is configured to turn on the current flowing in the primary winding of the ignition coil by a power transistor connected in series to the primary winding. -It is applied to the so-called full transistor type ignition circuit that controls off.
[0005]
In the full-transistor type ignition circuit, as shown in FIG. 8, the power transistor is turned on at a time tp before the ignition timing ts to pass a current through the primary winding of the ignition coil, and then at the ignition timing ts. The power transistor is turned off, and a high voltage for ignition is induced in the secondary winding of the ignition coil due to a sudden change in magnetic flux generated by interrupting the current of the primary winding at the time of turn-off. A voltage is applied to the spark plug.
[0006]
In this case, in the spark discharge at the spark plug, an induction discharge (also referred to as an arc discharge) occurs following the capacitive discharge that breaks down the insulation between the electrodes, and the discharge duration τ of the spark discharge including this induction discharge is determined by the cylinder discharge. The internal combustion state and the inductance of the ignition coil are determined.
[0007]
Note that the discharge duration τ needs to be increased (about 2 to 3 ms) in order to ensure ignitability at low revolutions and light loads, such as when starting the engine and idling, and this discharge duration τ is secured. The inductance of the ignition coil is set to such a size.
[0008]
In the detection of the ion current, an estimated value Ta of the discharge duration is calculated based on the combustion state assumed from the operating state and the magnitude of the coil inductance, and this estimated value Ta has elapsed from the ignition timing ts. Although it is performed at the time point td, the calculated value is usually multiplied by a safety factor in consideration of the combustion state for each device (for example, the time from ignition timing to actual ignition), variation in inductance, etc. Estimated value Ta is set considerably longer than actual discharge duration τ.
[0009]
[Problems to be solved by the invention]
However, since the ions generated during combustion after the spark discharge exist only for a short time after ignition, when the conditions are such that the ignitability is good, such as during high revolutions and heavy loads, ignition occurs immediately after the ignition timing. Therefore, the ion existence period (see periods B and C in the figure) overlaps with the discharge duration, and the ion current cannot be detected or even if it can be detected, the detection level is extremely small and the detection accuracy deteriorates. There was a problem that.
[0010]
In order to solve the above-described problems, an object of the present invention is to provide an internal combustion engine ignition device that can detect an ionic current reliably and accurately.
[0011]
[Means for Solving the Problems]
  The invention according to claim 1, which has been made to achieve the above object, includes ignition means for applying a high voltage for ignition to a spark plug mounted on a cylinder of an internal combustion engine and causing spark discharge in the spark plug; An ignition control means for controlling the operation of the ignition means; and after the ignition control means operates the ignition means, a high voltage for detection opposite to the high voltage for ignition is applied to the spark plug, An ignition device for an internal combustion engine comprising an ion current detection means for detecting an ion current flowing between electrodes of the ignition plug, wherein the ignition means includes a capacitor connected to a power source and storing energy for discharge, a primary winding And an ignition coil connected so that the capacitor and the secondary winding form a closed loop together with the ignition plug, and a current path connecting the capacitor and the primary winding, And a switching means for repetitively intermittent in preset discharge period at a preset discharge gap in timing, the ignition control means, sets a discharge period in accordance with the operating state of the internal combustion engineThe ion current detecting means detects the ion current within a period from the end of the discharge period set by the ignition control means to the time when TDC is reached.It is characterized by doing.
[0012]
In the internal combustion engine ignition apparatus of the present invention configured as described above, the ignition control means is longer in accordance with the operating state (for example, the lower the rotation and the lighter load with poor ignitability, the longer the high with good ignitability. The discharge period is set so that the shorter the rotation and heavy load, the shorter. During this discharge period, the switching means repeatedly interrupts the current path connecting the capacitor and the primary winding during a preset discharge period at a preset discharge interval at each ignition timing. In addition, when the current path is cut off by the switching means, the energy for discharging is accumulated in the capacitor by being charged by the power supply. On the other hand, when the current path is switched to the connected state, the energy accumulated in the capacitor is accumulated. Is discharged, a large current instantaneously flows in the primary winding, and a high voltage for ignition is generated in the secondary winding.
[0013]
That is, during the discharge period set by the ignition control means, the spark plug repeats spark discharge at every discharge interval, and so-called multiple discharge is performed.
After this multiple discharge is completed, the ion current detection circuit applies a detection high voltage having a polarity opposite to that of the ignition high voltage to the spark plug, and at this time detects the ion current flowing between the electrodes of the spark plug. To do.
[0014]
As described above, in the present invention, as an ignition circuit, the capacitor connected to the primary winding of the ignition coil is charged / discharged to generate a high voltage for ignition in the secondary winding, which is multiplexed by a so-called capacitive discharge (CDI) method. In addition, a discharge is used, and the discharge period of the multiple discharge is controlled in accordance with the operating state.
[0015]
Note that the CDI method, in which current is stored in a capacitor and then discharged for a moment, is then ignited compared to the full transistor method in which current must be continuously supplied to the primary winding for a certain period. The applied voltage to the primary winding of the coil can be set high (usually several hundred volts), and the number of turns of the secondary winding is reduced accordingly, and the inductance of the secondary winding (and thus the output impedance of the ignition coil) ) Can be reduced.
[0016]
When the inductance of the secondary winding is small, the spark discharge is terminated only by the capacitive discharge without proceeding to the induction discharge, so that the discharge duration of each spark discharge that is multiple-discharged within the discharge period is short.
As a result, the ion current can be detected immediately after the end of the discharge period without waiting for the duration of induction discharge as in the case of using a full transistor type ignition circuit, and the discharge period is Since the required minimum length can be appropriately set according to the operating state, the discharge period does not overlap with the ion existence period even at high rotation and heavy load with good ignitability.
[0017]
  Therefore, according to the ignition device for an internal combustion engine of the present invention, the ionic current can be detected reliably and with high sensitivity, and various controls performed based on the detected ionic current can be performed with high accuracy.
  In the internal combustion engine ignition device of the present invention, the inductance of the secondary winding is small.SaiTherefore, not only the discharge duration in one spark discharge is short, but also the ignition high voltage induced in the secondary winding rises quickly, and thus the voltage application time between the electrodes of the spark plug is short. For this reason, the carbon adhering to the insulator surface of the spark plug is moved and aligned by the electric field generated between the electrodes when a voltage is applied, and so-called fouling that causes a decrease in the insulation resistance between the electrodes hardly occurs.
[0018]
Moreover, since the output impedance of the secondary winding can be made sufficiently small with respect to the insulation resistance of the spark plug, even if the insulation resistance between the electrodes of the spark plug is somewhat reduced due to contamination or the like, it is applied to the spark plug. The voltage is not greatly reduced, spark discharge can be performed reliably, and an ignition device that is resistant to fouling can be configured.
[0019]
  Furthermore, according to the ignition device for an internal combustion engine of the present invention, at high rotation and heavy load with good ignitability, the discharge period can be shortened and the number of discharges can be reduced, so that the electrode of the spark plug is wasted. Can prevent.
[0020]
  by the way,When a voltage that does not cause a spark discharge is applied to the spark plug after the spark discharge, as shown in FIG. 7, immediately after the spark discharge is performed until the crank top dead center (TDC) is reached, In addition to the detection of the current (first peak) P1 based on the ion divergence due to the combustion of the air-fuel mixture, the generation accompanying the increase in the combustion pressure or the increase in the gas temperature almost simultaneously with the peak of the combustion pressure thereafter. It is known that a current (second peak) P2 based on thermal ionization of an object is detected, and the second peak P2 does not appear or is very small at low rotation and low load.
[0021]
On the other hand, according to the ignition device for an internal combustion engine of the present invention, the ion current is detected within the period from the end of the discharge period to the time when the TDC is reached. It is possible to reliably detect the ionic current in the entire operation range until a heavy load.
In particular, as described in claim 2, the ion current detection means preferably detects the ion current at the first peak that occurs before TDC.
[0022]
  According to the third aspect of the present invention, the discharge period needs to be set so long that the discharge period is sufficiently ignited while the ion current can be detected.
  By the way, the multiple discharge is performed by the ignition means when the discharge duration of the spark discharge is short as in the CDI method, the flame core formed in the combustion chamber by the spark discharge is small and the flame core grows. Because it is easy to misfire without being able to do so, by repeating the spark discharge and forming many flame nuclei, the amount of heat taken away by the interaction of each flame nuclei is reduced, creating conditions that make the flame nuclei easy to grow and ignite It is improving the nature.
[0023]
That is, when the discharge interval of the spark discharge in the multiple discharge is changed, it is expected that the degree of interaction of the flame nuclei also changes and affects the ignitability.
Therefore, in order to investigate how the ignitability changes by setting various discharge intervals during multiple discharges, a test for measuring the operating limit air-fuel ratio (A / Fu) was performed. , 6 results were obtained.
[0024]
Here, the operating limit air-fuel ratio (A / Fu) is caused by misfiring by gradually increasing the air-fuel ratio (A / F) of the engine driven under a certain condition (that is, toward the lean side). It is the air-fuel ratio when the fluctuation rate of the combustion pressure exceeds 10%.
[0025]
In the test, an in-line 6-cylinder 2000 cc engine for automobiles was used, and in the first test (see FIG. 5), the duration of multiple discharge Tt (under the conditions of a rotational speed of 2000 rpm and an intake pipe negative pressure of −350 mmHg) = Tm × N) The spark discharge interval Tm and the number of discharges N are changed so that 2 ms becomes 2 ms. In the second test (see FIG. 6), the condition is that the rotation speed is 2000 rpm and the negative pressure in the intake pipe is −100 mmHg. Below, the discharge interval Tm and the number N of discharges of the spark discharge were changed so that the duration Tt of the multiple discharge was 1 ms.
[0026]
Further, the operating limit air-fuel ratio (A / Fu) in a conventional full-transistor ignition device was also measured as a reference for evaluation. In this case, the spark discharge is performed only once, and by adjusting the operating conditions of the engine, the discharge duration τ of the spark discharge is τ = 2 ms in the first test standard and τ in the second test standard. = 1 ms.
[0027]
The first test shown in FIG. 5, that is, in the case of a low load (intake pipe negative pressure−350 mmHg) that requires poor discharge and a long discharge period (here, 2 ms), is also the second test shown in FIG. Even in the case of a test, that is, a high load (i.e., negative pressure in the intake pipe—100 mmHg) that has good ignitability and a short discharge period (here, 1 ms), if the discharge interval Tm is 100 μs or shorter, It can be seen that an operation limit air-fuel ratio A / Fu comparable to that of a conventional apparatus using an ignition circuit can be obtained, and if the discharge interval Tm is 300 μs or less, A / Fu ≧ 20, which is practically sufficient. It was.
[0028]
  Therefore,Claim 4As statedThe intermittent interval of the switching means that defines the discharge interval is, 300 μs or less is desirable. Furthermore,Intermittent interval of switching means (ie discharge interval)Is more preferably set to 100 μm or less. In this case, the above-described ion current is reliably and highly sensitive without deteriorating the operation limit air-fuel ratio (A / Fu) and hence ignitability as compared with the conventional device. The effect that it can detect by can be acquired.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an ignition device for an internal combustion engine to which the present invention is applied.
As shown in FIG. 1, the ignition device for an internal combustion engine of this embodiment includes an ignition circuit 2 that causes a spark discharge of an ignition plug 10 provided for each cylinder of the internal combustion engine in accordance with an ignition signal IG, and a power source for the ignition circuit 2 A battery BT to be supplied, an ion current detection circuit 4 for detecting an ion current flowing in the vicinity of the electrode of the spark plug 10 by combustion of the air-fuel mixture according to the detection signal Sd, and an ignition signal IG to the ignition circuit 2 At the same time, an internal combustion engine control electronic control unit (hereinafter referred to as ECU) 6 that outputs a detection signal Sd and a ground signal Sg described later to the ion current detection circuit 4 and an output Vio of the ion current detection circuit 4 are AD-converted. And a detection circuit 8 serving as a signal Dio suitable for input to the ECU 6.
[0030]
Although the configuration other than the ECU 6 is provided for each cylinder of the internal combustion engine, only one cylinder is shown in FIG. 1 for easy understanding of the drawing.
The ignition circuit 2 includes an ignition coil 12 that applies a high voltage for ignition to the ignition plug 10, and a capacitor 14 is connected in series to the primary winding L1 of the ignition coil 12. The capacitor 14 and the primary winding L1 connected in series have a booster circuit 15 that boosts the voltage of the battery BT to generate a charging voltage (about 300 to 400 V in this embodiment) of the capacitor 14, and an anode Is connected to the capacitor 14 side end, and a thyristor 16 having a cathode connected to the primary winding L1 side end. Further, a timer circuit 18 that outputs a trigger signal TG for turning on the thyristor 16 in accordance with an ignition signal IG from the ECU 6 is connected to the gate of the thyristor 16.
[0031]
The secondary winding L2 of the ignition coil 12 has one end connected to the center electrode of the spark plug 10 and the other end connected to the ion current detection circuit 4, and the outer electrode of the spark plug 10 is grounded. .
In addition, the inductance of the secondary winding L2 is L [H], and the effective load capacity of the secondary circuit including the secondary winding L2 and the stray capacitance of the wiring, the load capacity of the spark plug 10, and the like is C [F]. In this case, the secondary side circuit of the ignition coil 12 is set so as to satisfy the following expression (1).
[0032]
L ・ C ≦ 250 × 10^-12[Sec²] (1)
In the ignition circuit 2 configured as described above, the capacitor 14 is charged by the charging voltage generated by the booster circuit 15 when the thyristor 16 is in the OFF state. When the thyristor 16 is turned on by the trigger signal TG from the timer circuit 18 in a state where the capacitor 14 is charged in this way, the charged charge of the capacitor 14 is discharged, and the primary winding of the capacitor 14, the thyristor 16, and the ignition coil 12 is discharged. A large current instantaneously flows in the closed loop formed by L1. As a result, a high voltage for ignition (30 to 40 kV in this embodiment) is generated in the secondary winding L2 of the ignition coil 12, and this high voltage for ignition is applied to the center electrode of the spark plug 10. Will spark discharge.
[0033]
Note that the center electrode of the spark plug 10 has a negative polarity at the time of spark discharge, and therefore, the spark discharge current Isp that flows by this spark discharge flows from the spark plug 10 toward the secondary winding L2.
Further, as shown in FIG. 2, the timer circuit 18 is configured to repeatedly output the trigger signal TG at the discharge interval Tm (100 μs in this embodiment) during the period Tt in which the ignition signal IG is at a high level. Accordingly, during this time, the spark plug 10 repeatedly performs spark discharge at the discharge interval Tm, so-called multiple discharge is performed. That is, the trigger signal TG defines the ignition timing ts for starting multiple discharge and the time Tt for continuing multiple discharge (hereinafter referred to as multiple discharge duration) Tt.
[0034]
Next, the ion current detection circuit 4 is connected in series to a resistor 20 having one end grounded, a diode 22 connected in parallel to the resistor 20 and a cathode grounded, and a side opposite to the ground side of the resistor 20 and the diode 22. The capacitor 24 is connected so that the voltage Vio across the resistor 20 is input to the detection circuit 8. In the closed loop formed by the capacitor 24, the resistor 20, and the diode 22 together with the secondary winding L2 of the ignition coil 12 and the spark plug 10, a spark is formed between the capacitor 24 and the secondary winding L2 of the ignition coil 12. A charging diode 28 whose forward direction is the direction in which the discharging current Isp flows is connected in series, and a discharging switch 30 that short-circuits both ends of the charging diode 28 according to the detection signal Sd from the ECU 6 is in parallel with the charging diode 28. It is connected to the.
[0035]
Further, the ion current detection circuit 4 has a cathode connected in parallel to the secondary winding L2 of the ignition coil 12 in parallel with the circuit comprising the capacitor 24, the resistor 20, the diode 22, the charging diode 28, and the discharging switch 30. The collector is connected to the connecting end of the Zener diode 26 having the anode connected to the ground and the secondary winding L2, the emitter is grounded, and the secondary signal is input to the base from the ECU 6 according to the ground signal Sg. A transistor 32 is provided for grounding a connection end with the winding L2.
[0036]
In the ion current detection circuit 4 configured in this way, when the discharge switch 30 is opened, it is possible to allow a current to flow only from the connection end of the ignition coil 12 to the secondary winding L2 toward the ground end. It becomes. That is, the spark discharge current Isp that flows due to the spark discharge of the spark plug 10 flows in a closed loop that passes through the charging diode 28, the capacitor 24, and the diode 22, and simultaneously flows in a direction in which the Zener diode 26 generates the Zener voltage Vz. Therefore, the capacitor 24 is charged with a voltage Vc (= Vz−2 × Vf) that is smaller than the Zener voltage Vz of the Zener diode 26 by the forward voltage Vf of the charging diode 28 and the diode 22 by the spark discharge current Isp. It will be.
[0037]
On the other hand, when the discharge switch 30 is closed and both ends of the charging diode 28 are short-circuited, the closed loop passing through the resistor 20, the capacitor 24, and the discharge switch 30 is connected to the secondary winding L2 from the ground end side. It is possible to flow current toward the end side, and the voltage Vd across the resistor 20 corresponds to the magnitude of the detection current Id flowing through this closed loop.
[0038]
At this time, the voltage Vp applied to the spark plug 10 is obtained by subtracting the voltage drop at the resistor 20 from the charging voltage Vc of the capacitor 24 (Vp = Vc−Rd × Id; where Rd is the resistance value of the resistor 20). It becomes. The applied voltage Vp needs to be set to such an extent that the spark plug 10 does not spark discharge (for example, about 1 kV), that is, the Zener voltage Vz of the Zener diode 26 needs to be set based on the applied voltage Vp. .
[0039]
Further, when the transistor 32 is turned on by the ground signal Sg and the connection end to the secondary winding L2 is grounded, the charge remaining on the electrode of the spark plug 10 is discharged.
Next, main processing executed by the ECU 6 will be described.
The ECU 6 is for comprehensively controlling the ignition timing, fuel injection amount, idle speed, etc. of the internal combustion engine. In addition to the main processing described below, the intake pipe pressure (or intake air) of the internal combustion engine is used. Amount), engine rotation speed, cooling water temperature, and other operation states are detected.
[0040]
As shown in FIG. 3, when this process is started, first, in S110, the operation state detected in the operation state detection process that is separately executed is read, and in the subsequent S120, according to the operation state read in S110, An ignition timing ts for starting multiple discharge and a multiple discharge duration Tt are set.
[0041]
The ignition timing ts and the multiple discharge duration Tt may be calculated based on a calculation formula that defines the relationship with the parameter representing the operating state, or the results obtained experimentally in advance are used as a table in a ROM or the like. In this case, the parameter may be set by reading a parameter representing the operation state from this table as a reference value. Schematically, the ignition timing ts is advanced and the multiple discharge duration time Tt is shortened as the load estimated based on the intake air amount and the like is higher and the engine speed is higher. Is done. However, the ignition timing ts and the multiple discharge duration Tt are set as values converted to crank angles.
[0042]
In subsequent S130, based on the detection result from a crank angle sensor (not shown), it is determined whether or not it is the ignition timing ts set in S120. If the determination is negative, the same step is repeatedly executed to wait. To do. When the ignition timing ts is reached and an affirmative determination is made, the process proceeds to S140 where the ignition signal IG is set to the on (High) level, thereby causing the timer circuit 18 to start outputting the trigger signal TG.
[0043]
In subsequent S150, after the ignition timing ts is reached in previous S130, it is determined whether or not the multiple discharge duration Tt set in previous S120 has elapsed. If the determination is negative, the same steps are repeated. Wait by executing. When the multiple discharge duration time Tt has elapsed and an affirmative determination is made, the process proceeds to S160, and the ignition signal IG is set to the off (Low) level, thereby stopping the timer circuit 18 from outputting the trigger signal TG. Let
[0044]
In subsequent S170, after the ignition signal IG is set to the off level, it is determined whether or not a preset standby time Tw has elapsed. If the determination is negative, the same step is repeatedly executed to wait. When the standby time Tw elapses and an affirmative determination is made, the process proceeds to S180.
[0045]
Assuming that the ignition signal IG is set to the low level and the thyristor 16 is turned on at the same time as the standby time Tw, the voltage decay oscillation generated in the secondary circuit of the ignition coil 12 after the spark discharge at the spark plug 10 occurs. The length is set so as to sufficiently converge and not exceed the crank top dead center (TDC). However, although the standby time Tw is a fixed value here, it may be variably set according to the operating state, like the ignition timing ts and the multiple discharge duration Tt.
[0046]
In S180, the discharge switch 30 is activated by short-circuiting both ends of the charging diode 28 by setting the detection signal Sd to the high level only during a predetermined detection period. This detection period is desirably set to such a length that all the electric charge of the capacitor 24 is discharged when the ion current Iio flows normally.
[0047]
In subsequent S190, the detection value Dio obtained by AD-converting the voltage Vio across the resistor 20 is read from the detection circuit 8 during the detection period (the detection signal Sd is at the high level).
When the detection period ends, in S200, the ground signal Sg is output to turn on the transistor 32, and the charge remaining in the spark plug 10 is discharged.
[0048]
That is, as shown in FIG. 4, in this embodiment, when the ignition signal IG is switched to the on level at the ignition timing ts (S130, 140) and the output of the trigger signal TG is started, the multiple discharge continues thereafter. During the time Tt, the thyristor 16 is turned on according to the trigger signal TG, so that a high voltage for ignition is applied to the center electrode of the spark plug 10 via the ignition coil 12, and the spark plug 10 sparks at every discharge interval Tm. Discharge occurs.
[0049]
The spark discharge current Isp flowing in the secondary circuit of the ignition coil 12 during this spark discharge causes the Zener diode 26 to generate a Zener voltage Vz and is supplied to the capacitor 24 via the charging diode 28 to charge the capacitor 24.
At this time, in the primary side circuit of the ignition coil 12, when the discharge current of the capacitor 14 becomes zero and the thyristor 16 is automatically turned off, the charging voltage generated by the booster circuit 15 until the next spark discharge. Thus, the capacitor 14 is quickly charged.
[0050]
Then, after the ignition timing ts, the multiple discharge duration Tt elapses and the ignition signal IG is switched to the off level (S150, S160), and the output of the trigger signal TG is stopped. Thereafter, when the standby time Tw elapses, the detection signal Sd is switched to the high level (S170, S180), and when both ends of the charging diode 28 are short-circuited by operating the discharging switch 30, the detection signal Sd During the detection period Td held at the high level, a high voltage for detection is applied between the electrodes of the spark plug 10 by the discharge of the capacitor 24, and an ion current Iio corresponding to the amount of ions between the electrodes of the spark plug 10 flows.
[0051]
During this detection period Td, the detection circuit 8 performs AD conversion on the voltage Vio across the resistor 20 caused by the ion current Iio flowing through the resistor 20, and the ECU 6 reads the conversion result as the ion current detection value Dio (S190). .
The detected ion current value Dio read into the ECU 6 is used to determine, for example, the occurrence of misfire or knocking in the internal combustion engine, or various operating states of the internal combustion engine (air-fuel ratio, lean limit of the air-fuel ratio, exhaust gas recirculation amount). This is used to determine the limit of
[0052]
Thereafter, when the detection period Td ends and the ground signal Sg is output (S200), the connection end of the ion current detection circuit 4 to the secondary winding L2 is grounded by the transistor 32, and, for example, a misfire or the like is sufficient. Since the ionic current Iio does not flow, the charge remaining on the electrode of the spark plug 10 is reliably discharged.
[0053]
As described above, in the ignition device for an internal combustion engine of the present embodiment, the ignition circuit 2 is configured to perform multiple discharge by the CDI method with a short discharge duration in one spark discharge, and the multiple The discharge duration Tt (in other words, the number of spark discharges) is longer (more) as the low rotation and light load with poor ignitability, depending on the operating state of the internal combustion engine, and conversely at high rotation and heavy load. It is set to be shorter (less).
[0054]
Therefore, according to the ignition device for an internal combustion engine of the present embodiment, the ionic current can be detected promptly after the lapse of the multiple discharge duration Tt set to the minimum necessary length according to the operating state. Therefore, unlike conventional devices with a conventional full-transistor type ignition circuit that always performs a spark discharge with a long discharge duration, the discharge period of spark discharge and the presence of ions, especially during high rotation and heavy loads with good ignitability It is possible to detect the ionic current reliably and with high sensitivity without overlapping the periods, and thus it is possible to accurately execute various controls based on the detected ionic current.
[0055]
In addition, according to the ignition device for an internal combustion engine of the present embodiment, the discharge interval Tm of the multiple discharge is set to 100 μs, so that the ignitability equivalent to that of the conventional device having a full transistor type ignition circuit is maintained. Can do.
In this embodiment, the ignition circuit 2 is the ignition means, the ion current detection circuit 4 and S170 to S200 are the ion current detection means, S110 to S160 are the ignition control means, the thyristor 16 is the switching element, and the timer circuit 18 is the switching means. Equivalent to.
[0056]
As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, It can implement in various aspects.
For example, in the above embodiment, the timer circuit 18 is configured to output the trigger signal TG only while the ignition signal IG is on level, but the number of trigger signals TG to be output instead of the ignition signal IG is determined. The timer circuit 18 may be supplied, and the timer circuit 18 may be configured to output the trigger signal TG corresponding to the number.
[0057]
In the above embodiment, the discharge interval Tm is set to 100 μs. However, the discharge interval Tm may be set to 300 μs or less and more than the time required to complete the charging by the charging voltage from the booster circuit 15. .
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating an overall configuration of an internal combustion engine ignition device according to an embodiment.
FIG. 2 is a timing chart showing the operation of the ignition circuit.
FIG. 3 is a flowchart showing the contents of processing executed by an ECU.
FIG. 4 is a timing chart showing the operation of the entire ignition device according to the embodiment.
FIG. 5 is a graph showing a result of measuring an operation limit air-fuel ratio.
FIG. 6 is a graph showing a result of measuring an operation limit air-fuel ratio.
FIG. 7 is a waveform diagram for explaining ion current detection timing.
FIG. 8 is an explanatory diagram showing problems of a conventional device.
[Explanation of symbols]
2 ... Ignition circuit 4 ... Ion current detection circuit 8 ... Detection circuit
10 ... Spark plug 12 ... Ignition coil 14 ... Capacitor
15 ... Booster circuit 16 ... Thyristor 18 ... Timer circuit
20 ... resistor 22 ... diode 24 ... capacitor
26 ... Zener diode 28 ... Charging diode
30 ... Discharge switch 32 ... Transistor
BT ... Battery L1 ... Primary winding L2 ... Secondary winding

Claims (4)

Ignition means for applying a high voltage for ignition to a spark plug mounted on a cylinder of the internal combustion engine to cause spark discharge in the spark plug;
Ignition control means for controlling the operation of the ignition means;
After the ignition control means operates the ignition means, a high voltage for detection opposite in polarity to the high voltage for ignition is applied to the spark plug to detect an ionic current flowing between the electrodes of the spark plug. In an ignition device for an internal combustion engine comprising an ionic current detection means,
The ignition means includes
A capacitor connected to a power source and storing energy for discharge;
An ignition coil having a primary winding connected to form a closed loop with the capacitor and a secondary winding together with the spark plug;
Switching means for repeatedly interrupting a current path connecting the capacitor and the primary winding during a preset discharge period at a preset discharge interval at each ignition timing;
The ignition control means sets a discharge period according to the operating state of the internal combustion engine ,
The ignition device for an internal combustion engine, wherein the ion current detection means detects the ion current within a period from the end of a discharge period set by the ignition control means to a time when TDC is reached .   2. The ignition device for an internal combustion engine according to claim 1, wherein the ion current detecting means detects the ion current at a first peak generated before TDC. 3. The internal combustion engine according to claim 1, wherein the discharge period is set to be long enough to cause ignition while being short enough to enable detection of the ion current. Ignition device. The ignition device for an internal combustion engine according to any one of claims 1 to 3, wherein an intermittent interval of the switching means that defines the discharge interval is set to 300 µs or less.

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