JP4791424B2 - Ignition device - Google Patents

Description

  The present invention relates to an ignition device used for ignition of a spark plug that is assembled in an internal combustion engine and ignites an air-fuel mixture.

  Conventionally, in an ignition device for an internal combustion engine, a voltage is applied to both ends of a primary coil of an ignition coil and energized for a certain period of time. The mixture is ignited by applying a high voltage and causing a spark discharge. Some internal combustion engines use various fuels, and it is known that a gas engine as an example has a higher flow rate of an air-fuel mixture in a combustion chamber than a gasoline engine. In such a gas engine, if the duration of the spark discharge is long, the spark is caused to flow downstream along with the flow of the air-fuel mixture, and if it is blown out, there may be a multiple discharge that causes a spark discharge again. When multiple discharges occur, spark discharges are concentrated on the downstream side, and the electrodes near the discharges are unevenly consumed, which may shorten the life of the spark plug.

  Therefore, by re-energizing the primary coil after the start of the spark discharge, an induced electromotive force having a reverse polarity is generated on the secondary coil side, and the spark discharge is forcibly cut off by consuming energy for the spark discharge. An ignition device (ion current detection device) in which the duration of spark discharge is shortened is known (for example, see Patent Document 1). In addition, there is also known a technique in which spark discharge is interrupted by forming a closed loop circuit with a primary coil using a switching element or the like without supplying power from a battery when re-energizing the primary coil.

By the way, it is known that ions are generated as the air-fuel mixture is burned by spark discharge. In the ion current detection device described in Patent Document 1, a voltage is applied between the electrodes of the spark plug to cause an ion current to flow by utilizing the fact that the amount of generated ions varies depending on the combustion state of the air-fuel mixture. If the current is detected and the detection result is used, misfire detection, knocking detection, or the like can be performed, for example.
Japanese Patent Laid-Open No. 2002-4996

  However, it is necessary to detect the ion current in a circuit on the secondary coil side where a high voltage (for example, 30,000 V) is generated, and the ion current detection means (detection circuit) is expensive enough to withstand the high voltage. Parts must be used. Even in Patent Document 1, since the detection circuit is provided on the secondary coil side, high voltage is applied even though it does not cause spark discharge, so it is necessary to use components with high voltage resistance, and the cost is high. .

  The present invention has been made to solve the above problems, and provides a low-cost and highly reliable ignition device provided with current detection means on the primary coil side that does not require high-voltage-resistant components. With the goal.

In order to achieve the above object, an ignition device according to a first aspect of the present invention includes a primary coil and a secondary coil, and interrupts a primary current flowing through the primary coil, thereby causing the secondary coil to By applying the ignition coil for generating a voltage and the high voltage for ignition, the spark discharge is started between the spark plug for generating a spark discharge for ignition between its electrodes and the electrode of the spark plug. Then, after a lapse of a predetermined time, a spark discharge cutoff means for forcibly cutting off the spark discharge by forming a closed loop circuit with the primary coil and re-energizing the primary coil. current detecting means for detecting a current flowing through the closed loop circuit during reenergize, and the current value at the time of re-energization detected by said current detecting means, is compared with a predetermined threshold value, Serial spark plug is provided with, an abnormality judgment means for judging whether or not the abnormal state.

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the abnormality determining unit has a predetermined current value at the time of re-energization detected by the current detecting unit. If the value is equal to or less than the first threshold value, it is determined that the abnormal state of the spark plug is an electrode consumption state.

According to a third aspect of the present invention, in addition to the configuration of the second aspect of the present invention, the abnormality determining means has a predetermined current value at the time of re-energization detected by the current detecting means. When the value is equal to or smaller than the second threshold value smaller than the first threshold value, it is determined that the abnormal state of the spark plug is a failure state.

According to a fourth aspect of the present invention, in addition to the configuration of the second or third aspect of the invention, the abnormality determination unit is configured such that the current value at the time of re-energization detected by the current detection unit is It is determined, and when the value is equal to or greater than a third threshold value greater than the first threshold value, it is determined that the abnormal state of the spark plug is a smoldering state.

  In the ignition device according to the first aspect of the present invention, in order to forcibly cut off the spark discharge of the spark plug, a closed loop circuit is formed by the spark discharge cutoff means, and the current flowing through the closed loop circuit can be detected by the current detection means. The current flowing through the closed loop circuit flows due to the magnetic energy remaining in the ignition coil when the spark discharge is interrupted. The magnetic energy remaining in the ignition coil when the spark discharge is cut off corresponds to a value obtained by subtracting the energy consumed by the spark discharge from the magnetic energy stored in the ignition coil before the start of the spark discharge. That is, when the energy consumed by the spark discharge is large, the magnetic energy remaining in the ignition coil is small, and when the energy consumed by the spark discharge is small, the magnetic energy remaining in the ignition coil when the spark discharge is interrupted. There will be many. The energy consumed by the spark discharge varies depending on the dielectric breakdown voltage value between the electrodes of the spark plug during the spark discharge. Therefore, by detecting the current flowing through the closed loop circuit, it is possible to detect the dielectric breakdown voltage value between the electrodes of the spark plug during spark discharge. In other words, if the relationship between the magnitude of the current flowing through the closed loop circuit and the dielectric breakdown voltage value between the electrodes of the spark plug during spark discharge is determined in advance, the spark plug during spark discharge can be determined from the magnitude of the current flowing through the closed loop circuit. It is possible to determine the breakdown voltage value between the electrodes.

  In the invention according to claim 1, since the current detection means is provided on the primary coil side of the ignition coil, a high voltage for spark discharge applied to the spark plug during spark discharge is applied to the current detection means. There is nothing. That is, it is not necessary to use high voltage-resistant components or circuits used for the current detection means, and the circuit can be simplified and the cost can be reduced, and the durability reliability can be increased.

In addition, dielectric breakdown occurs between the electrodes at the time of spark discharge. This dielectric breakdown depends on the dielectric strength between the two electrodes, that is, changes depending on the dielectric breakdown voltage value between the two electrodes. Since the energy consumed by the spark discharge increases as the breakdown voltage value increases, the magnitude of the current flowing through the closed loop circuit corresponds to the breakdown voltage value. Therefore, if the value of the current flowing through the closed loop circuit is obtained, the change in the dielectric breakdown voltage value can be known relatively. Therefore, the magnitude of the current flowing between the electrodes during the spark discharge in the spark plug normal state, the threshold value of the magnitude of the current flowing in the abnormal state, if obtained in advance by tests and the like, the current flowing through the closed loop circuit By comparing the value with the threshold value, it can be determined whether or not the spark plug is in an abnormal state.

When the center electrode and the ground electrode of the spark plug are consumed and the dielectric breakdown voltage value between the two electrodes becomes high, the energy consumed at the time of spark discharge increases. Then, the magnetic energy remaining in the ignition coil when the spark discharge is cut off decreases, and the value of the current flowing through the closed loop circuit also decreases. Therefore, as in the invention according to claim 2 , when the electrode is in a depleted state and when it is normal, both threshold values are obtained based on possible values of the current value flowing through the closed loop circuit during re-energization. Predetermined as the first threshold value. Then, the value of the current flowing through the closed loop circuit at the time of re-energization is compared with the first threshold value, and if it is equal to or less than the first threshold value, the abnormal state of the spark plug can be regarded as the electrode consumption state.

Further, when the spark plug is in a fault state, for example, the spark discharge fails and most of the magnetic energy stored in the ignition coil before the start of the spark discharge is consumed, and the magnetism remaining in the ignition coil when the spark discharge is interrupted. There will be little energy and little current will flow through the closed-loop circuit. Therefore, as in the invention according to claim 3 , when the spark plug is in the failure state and in the exhaustion state, the threshold value of both is obtained based on the possible value of the current value flowing through the closed loop circuit at the time of re-energization. This is predetermined as the second threshold value. This second threshold value is smaller than the first threshold value. If the value of the current flowing through the closed loop circuit during re-energization is equal to or less than the second threshold value, the abnormal state of the spark plug can be regarded as a failure state.

Further, when the spark plug is smoldered, the dielectric breakdown voltage value between the center electrode and the ground electrode is lowered. Then, the energy consumed at the time of spark discharge is reduced, the magnetic energy remaining in the ignition coil when the spark discharge is interrupted is increased, and the value of the current flowing through the closed loop circuit is increased. Therefore, as in the invention according to claim 4 , when the electrode is in a smoldering state and when it is normal, both threshold values are obtained based on the possible values of the current value flowing through the closed loop circuit during re-energization. Predetermined as the third threshold value. Then, the value of the current flowing through the closed loop circuit at the time of re-energization is compared with the third threshold value, and if it is equal to or greater than the third threshold value, the abnormal state of the spark plug can be regarded as a smoldering state.

  Hereinafter, an embodiment of the present invention will be described. In the present embodiment, as an example of an internal combustion engine, a gas engine using LP gas, natural gas, or the like as a fuel is used, and an ignition device 1 that supplies electric power for spark discharge to an ignition plug attached to the gas engine is taken as an example. explain. FIG. 1 is an electric circuit diagram showing a configuration of an ignition device 1 that ignites a spark plug 9. The ignition circuit unit 2 and the spark plug 9 of the ignition device 1 are provided for each cylinder in an engine having a plurality of cylinders, but FIG. 1 shows the configuration for one cylinder.

  An ignition device 1 shown in FIG. 1 is composed of an electronic control unit (ECU) 8 for an automobile and an ignition circuit unit 2 electrically connected to the ECU 8, and a center electrode 91 of a spark plug 9 having a known configuration. And a ground electrode 92 to generate a spark discharge and determine whether or not the spark plug 9 is in an abnormal state. The ignition circuit unit 2 includes an ignition coil 5 including a primary coil 51 and a secondary coil 52, a backflow prevention diode 21 provided on the secondary coil 52 side, a transistor 22, a thyristor 23 provided on the primary coil 51 side, And a current detection unit 6.

  The ECU 8 is for controlling various devices used for driving the engine, and includes a CPU 81, a ROM 82, and a RAM 83 having a known configuration. In the present embodiment, the ECU 8 sends an instruction to the ignition circuit unit 2 to ignite the spark plug 9, and based on the detection result obtained from the current detection unit 6 according to the execution of an abnormality determination program described later, It is determined whether or not the spark plug 9 is in an abnormal state. In a predetermined storage area of the ROM 82, the smoldering state determination value D1, the failure state determination value D2, and the deterioration state determination value D3 used in the abnormality determination program are stored together with the abnormality determination program. .

  Next, the ignition circuit unit 2 generates a spark discharge by applying a high voltage to a spark discharge gap formed between the center electrode 91 of the spark plug 9 and the ground electrode 92 (grounded to the ground). The circuit for making it constitute is comprised. In the ignition circuit unit 2, one end side of the primary coil 51 and one end side of the secondary coil 52 are respectively connected to the anode side of the battery 7 that outputs a power supply voltage Vbat (for example, 12V) for supplying electric energy for spark discharge. Ignition coil 5 is provided. A cathode of a thyristor 23 described later is also connected to the anode side of the battery 7. The other end side of the secondary coil 52 of the ignition coil 5 is connected to the center electrode 91 of the spark plug 9 via the diode 21. The diode 21 has an anode connected to the center electrode 91 and is arranged in a direction in which a current flows from the center electrode 91 side to the secondary coil 52 side.

  Further, the current detection unit 6 and the collector of the transistor 22 functioning as a switching element in the ignition circuit unit 2 are connected to the other end side of the primary coil 51 of the ignition coil 5. The transistor 22 is composed of an NPN type power transistor, the emitter is grounded to the ground, and the base is connected to the ECU 8. The transistor 22 is configured such that when the collector-emitter is turned on based on the ignition instruction signal Va output from the ECU 8, the primary coil 51 of the ignition coil 5 is energized and the current Ia flows.

  Next, the current detection unit 6 is an ammeter having a known configuration that detects the magnitude of the current flowing through the resistor, for example, by measuring the voltage across the resistor provided therein, and is a current value measurement target. Arranged in series with the circuit. In the present embodiment, the thyristor 23 is connected in series between one end and the other end of the primary coil 51, and the primary coil 51, the current detection unit 6, and the thyristor 23 constitute a closed loop circuit 25. The current flowing through the closed loop circuit 25 is detected by the current detection unit 6, and a voltage value Vc obtained by current-voltage conversion of the current value is input to the ECU 8. The current detection unit 6 corresponds to “current detection means” in the present invention. A thyristor 23 that is turned on by a gate signal Vb, which will be described later, and closes the closed loop circuit 25 corresponds to the “spark discharge blocking means” in the present invention.

  The thyristor 23 has an anode connected to the current detector 6 and a cathode connected to one end of the primary coil 51. The gate is connected to the ECU 8, and when the gate signal Vb output from the ECU 8 becomes a high level, the thyristor 23 becomes conductive, and the current Ib flows through the closed loop circuit 25.

  Next, with reference to FIG. 1 and FIG. 2, the process of ignition to the spark plug 9 by the ignition device 1 will be described. FIG. 2 is a timing chart showing the relationship between the waveform of the current and signal voltage flowing at the ignition timing in the ignition circuit section 2.

  In the ignition circuit unit 2 of the ignition device 1 shown in FIG. 1 configured as described above, as shown in FIG. 2, the ignition instruction signal Va output from the ECU 8 is low level (hereinafter referred to as “L”) at the timing T1 as shown in FIG. ) To a high level (hereinafter referred to as “H”), the collector-emitter of the transistor 22 becomes conductive. Then, the current Ia starts to flow from the battery 7 to the primary coil 51 and increases with time, and magnetic energy is stored in the ignition coil 5.

  When the ignition instruction signal Va is switched from H to L at the timing T2, the conduction between the collector and the emitter of the transistor 22 is interrupted. Then, the current Ia becomes 0, and the magnetic flux density accumulated in the ignition coil 5 changes abruptly, so that an induced electromotive force is generated in the secondary coil 52 of the ignition coil 5. Due to the generation of the induced electromotive force, a negative ignition high voltage Vd lower than the ground potential is instantaneously applied between the center electrode 91 and the ground electrode 92 of the spark plug 9, and the dielectric breakdown occurs in the spark discharge gap. A spark discharge occurs. Along with this spark discharge, a discharge current flows in the spark discharge gap, and the ignition coil 5 consumes energy corresponding to the dielectric breakdown voltage value.

  After dielectric breakdown, the discharge current flows at a potential (small potential difference) higher than the potential at the time of dielectric breakdown. The remaining magnetic energy, which is accumulated in the ignition coil 5 at the timing T1 to T2 before the start of the spark discharge and subtracts the energy consumed at the time of the dielectric breakdown, continues to flow after the dielectric breakdown and a discharge current flows in the spark discharge gap. It gradually decreases as it is consumed. When the magnetic energy accumulated in the ignition coil 5 is lost, the spark discharge is naturally interrupted. However, in the present embodiment, the gate signal Vb is switched from L to H at the timing T3 when the discharge current is flowing (that is, the ignition high voltage Vd is generated). Then, the thyristor 23 becomes conductive, the closed loop circuit 25 including the primary coil 51 is closed, and the current Ib starts to flow to the primary coil 51 side by the magnetic energy remaining in the ignition coil 5. When the current Ib flows through the primary coil 51, a voltage having a polarity opposite to that of the ignition high voltage Vd is induced in the secondary coil 52. Therefore, the ignition high voltage Vd becomes 0, the spark discharge is forcibly cut off, and the discharge current does not flow. As described above, the current detection unit 6 detects the current Ib flowing through the closed loop circuit 25, and the magnitude thereof is converted into a voltage value and input to the ECU 8 as the voltage value Vc.

  After the spark discharge is cut off at the timing T3, the current Ib flows through the closed loop circuit 25 and the energy is consumed, so that the magnetic energy accumulated in the ignition coil 5 decreases. Further, at the timing T4, the gate signal Vb is switched from H to L, but since the current Ib flows, the thyristor 23 is maintained in the conductive state. When the current Ib flowing through the closed loop circuit 25 becomes 0 at the timing T5, the thyristor 23 is turned off, and a series of processes related to the spark discharge is completed.

  As described above, the current Ib flowing through the closed loop circuit 25 detected by the current detector 6 is generated when the closed loop circuit 25 is closed at the timing T3 when the spark discharge is interrupted, and the magnitude of the current Ib remains in the ignition coil 5. Responds to the magnetic energy being used. That is, the energy consumed in accordance with the dielectric breakdown voltage value of the spark discharge gap at the time of spark discharge (T2-T3 timing) is subtracted from the magnetic energy accumulated in the ignition coil 5 before the spark discharge (T1-T2 timing). It will respond to the remaining magnetic energy. Here, since the magnetic energy stored in the ignition coil 5 at the timings T1 to T2 corresponds to the length of the timings T1 to T2 (the time during which the current Ia is passed through the primary coil 51), it is substantially constant without being different at each spark discharge. It becomes. For this reason, the magnetic energy remaining in the ignition coil 5 when the primary coil 51 is re-energized when the spark discharge is interrupted (T3 timing) substantially corresponds to the dielectric breakdown voltage value of the spark discharge gap.

  By the way, when spark discharge fails, normal spark discharge may not be performed, such as when electrode consumption occurs in the center electrode 91 or the ground electrode 92, or when a side fire occurs due to contamination or the like, Such a phenomenon is caused by the difference between the size of the gap where the spark discharge is performed, that is, the dielectric breakdown voltage value between the two electrodes being normal. If a difference occurs in the dielectric breakdown resistance value at the time of spark discharge (T2 timing) due to such a phenomenon, a difference occurs in the energy consumed by the spark discharge, so that it remains in the ignition coil 5 when the spark discharge is interrupted (T3 timing). Changes in magnetic energy.

  Specifically, as shown in the graph of FIG. 3, the voltage value necessary to cause dielectric breakdown between the center electrode 91 and the ground electrode 92 during the spark discharge and the magnitude of the current Ib flowing through the closed loop circuit 25. It can be seen that there is a proportional relationship between the peak value (maximum value) and the magnitude of the current Ib as the voltage required for dielectric breakdown increases. For example, when the dielectric breakdown voltage value between the center electrode 91 and the ground electrode 92 increases due to electrode consumption or the like, the energy consumed by the spark discharge increases, and the magnetic energy remaining in the ignition coil 5 decreases, so the closed loop circuit 25. The peak value of the magnitude of the current Ib flowing through is reduced. On the other hand, for example, when a horizontal fire occurs due to smoldering or the like, and the dielectric breakdown voltage value between the center electrode 91 and the ground electrode 92 becomes small, the energy consumed by the spark discharge decreases, and the ignition coil 5 Therefore, the peak value of the magnitude of the current Ib flowing through the closed loop circuit 25 increases.

  Therefore, when the spark plug 9 is in a smoldering state by a test or the like in advance, a possible value of the peak value of the current Ib is examined, and if a threshold value for a normal state is obtained, the spark plug 9 is in a smoldering state. It is possible to determine whether or not there is. Similarly, when the spark plug 9 is in a deteriorated state due to electrode consumption or the like, the peak value of the current Ib is smaller than that in the normal state. It is also possible to determine whether 9 is in a degraded state. Further, when the spark plug 9 breaks down and no spark discharge occurs between the center electrode 91 and the ground electrode 92, almost no current flows through the closed loop circuit 25, so the threshold value for the deterioration state is also obtained. It is possible.

  As described above, the magnitude of the current Ib flowing in the closed loop circuit 25 when the primary coil 51 is energized again at the timing T3 corresponds to the magnitude of the magnetic energy remaining in the ignition coil 5 at that time. As the current Ib flows through the closed loop circuit 25 and energy is consumed, the current Ib also decreases. Therefore, in the present embodiment, focusing on the peak value (maximum value) of the current Ib flowing through the closed loop circuit 25, the relationship with the dielectric breakdown voltage value of the spark discharge gap is obtained. Such a proportional relationship with the breakdown voltage value is, for example, that the current Ib from the T3 timing to the T5 timing (that is, the timing at which the current Ib becomes 0) (or from the T3 timing to after a predetermined period has elapsed). It can also be found between the integral value and the breakdown voltage value. It can also be found between the length of the period from the T3 timing to the T5 timing and the breakdown voltage value, or between the length of the period in which the current Ib is a predetermined value or more and the breakdown voltage value.

  In the present embodiment, the threshold values of the abnormal state of the spark plug 9, that is, the smoldering state, the failure state, and the deterioration state are set as the determination values D1, D2, and D3, and are obtained in advance by a test or the like. Then, the peak value (maximum value in the present embodiment) of the current Ib flowing through the closed loop circuit 25 is detected, and whether or not the spark plug 9 is in an abnormal state is determined based on the execution of the abnormality determination program described below. Judgment is being made. Specifically, if the maximum value of the current Ib is D1 or more, it is a smoldering state, if it is D2 or less, it is in a failure state, if it is greater than D2 and less than D3, it is in a degraded state, and if it is greater than D3 and less than D1, it is in a normal state. . Hereinafter, the abnormality determination program will be described. FIG. 4 is a flowchart of the abnormality determination program.

  The abnormality determination program shown in FIG. 4 is one of the module groups of the control program for the internal combustion engine executed by the CPU 81 of the ECU 8, and is executed together with other modules when the ECU 8 is in operation. At the time of execution, first, initialization processing is performed (S11). As a variable, the acquired gate signal Vb, VbP for holding it as the previous value, and the voltage value Vc output from the current detector 6 are used. In addition, a storage area for storing VcH for holding the peak value (maximum value) and a determination result (a flag indicating the state) of the spark plug 9 is secured on the RAM 83. As an initial value, L (specifically, a flag value corresponding to a low level) is stored in Vb and VbP, and 0 is stored in Vc and VcH. Further, a flag indicating a normal state is stored as the state of the spark plug 9.

  In the abnormality determination program, the signal state of the gate signal Vb (output according to the execution of another program by the CPU 81) is monitored, and in the next S12, the gate signal Vb is acquired (S12). The gate signal Vb is at a low level (L) before ignition of the spark plug 9 or at the beginning of the ignition timing (S13: NO), and the process proceeds to S15. Furthermore, VbP is confirmed in S15, but since L is stored in the initial state (S15: NO), the process proceeds to S33, and VbP is updated by overwriting VbP with the acquired value of Vb (S33). ). Thereafter, the process returns to S12.

  In the processes of S12 to S33 after the second round, while the gate signal Vb is L, the processes of S13, S15, and S33 are repeated. When the gate signal Vb is switched to H (S13: YES), VbP storing the previous gate signal is confirmed. If it is L (S16: YES), Vb is switched from L to H. As the first round process, VcH, which is a variable for storing the maximum value of Vc, is reset (S17).

  Next, the voltage value Vc output from the current detector 6 is acquired (S19). The voltage value Vc is input to the ECU 8 via an A / D converter (not shown), and this voltage value Vc is compared with VcH (S20). VcH is reset in S17 to 0, and if the voltage value Vc is larger (S20: YES), VcH is overwritten by the voltage value Vc acquired in S19, and VcH is updated (S21). Then, the process proceeds to S33, and as described above, the update is performed by overwriting VbP with the current value of the gate signal Vb (S33), and the process returns to S12.

  Thereafter, while the gate signal Vb is H, the processes of S16 to S21 are repeated. Since Vb becomes H and VbP also becomes H after the second lap, S17 is skipped in S16 and the process proceeds to S19 (S16: NO), so that the value of VcH is not reset. Retained. Further, while the processes of S16 to S21 are repeated, Vc does not become larger than VcH (S20: NO), VcH is not updated in S21, the process proceeds to S33, and the process returns to S12.

  Thus, while the gate signal Vb is H, the maximum value VcH of the current Ib flowing through the closed loop circuit 25 detected by the current detector 6 is obtained. Then, when the gate signal Vb becomes L (S13: NO), since Vb was H last time and H is stored in VbP, the process proceeds to S23 (S15: YES).

  In S23, it is confirmed whether VcH is a value equal to or greater than D1. As described above, the maximum value of the magnitude of the current Ib generated in the closed loop circuit 25, that is, the value of VcH that is larger than the normal state indicates that the breakdown voltage value between the center electrode 91 and the ground electrode 92 is small. In this case, the energy consumed by the spark discharge is reduced, and as a result, the magnetic energy remaining in the ignition coil 5 is larger than that in the normal state. Such a state occurs, for example, when a side fire occurs due to smoldering or the like. Therefore, if VcH is equal to or greater than the determination value (threshold value) D1 (S23: YES), it is determined that a smoldering state has occurred in the spark plug 9 (S24). In accordance with this determination result, a flag indicating the smoldering state is stored as the state of the spark plug 9 in the storage area secured in the RAM 83. Then, the process proceeds to S33, returns to S12, and repeats S12, S13, S15, and S33 until the gate signal Vb is switched to H at the next ignition timing. The determination value D1 corresponds to the “third threshold value” in the present invention.

  On the other hand, when VcH is a value less than D1 in S23 (S23: NO), it is then confirmed whether VcH is a value equal to or less than D2 (S26). As described above, VcH shows a value smaller than the normal state because the dielectric breakdown voltage value between the center electrode 91 and the ground electrode 92 becomes large and the energy consumed by the spark discharge increases. This is a case where the magnetic energy remaining in the ignition coil 5 is less than that in the normal state. In particular, when the spark discharge fails and most of the magnetic energy stored in the ignition coil 5 has been consumed before the spark discharge is started, there is almost no magnetic energy remaining in the ignition coil 5 when the spark discharge is interrupted, and the closed loop circuit. No current flows through 25. Therefore, when VcH is equal to or less than the determination value D2 (S26: YES), it is determined that the spark plug 9 is in a failure state (S27). According to this determination result, a flag indicating the failure state is stored as the state of the spark plug 9 in the storage area secured in the RAM 83, and further proceeds to S33 and returns to S12, and the gate signal Vb is switched to H at the next ignition timing. S12, S13, S15, and S33 are repeated and waited until it is received. The determination value D2 corresponds to the “second threshold value” in the present invention.

  If VcH is larger than D2 in S26 (S26: NO), it is further confirmed whether VcH is equal to or smaller than D3 (S29). When the spark plug 9 is not in a failure state and VcH shows a smaller value than the normal state, as described above, the dielectric breakdown voltage value between the center electrode 91 and the ground electrode 92 has increased due to electrode wear or the like. However, it can be regarded as a state that does not lead to a failure state in which the spark discharge fails. Therefore, when VcH is greater than the determination value D2 and equal to or less than D3 (S26: NO, S29: YES), it is determined that the spark plug 9 is in a deteriorated state (S30). According to this determination result, a flag indicating the deterioration state is stored as the state of the spark plug 9 in the storage area secured in the RAM 83, and further proceeds to S33 and returns to S12, and the gate signal Vb is switched to H at the next ignition timing. S12, S13, S15, and S33 are repeated and waited until it is received. The determination value D3 corresponds to the “first threshold value” in the present invention. Further, in each process of S23, S26, and S29 described above, the CPU 81 that determines whether or not the spark plug 9 is in an abnormal state by comparing VcH with each of the determination values D1, D2, and D3, This corresponds to “abnormality determination means” in the invention.

  If VcH is greater than D3 in S29 (S29: NO), the spark plug 9 does not correspond to any of the smoldering state, the failure state, or the deterioration state, and is determined to be in a normal state ( S32). In accordance with this determination result, a flag indicating a normal state is stored as a state of the spark plug 9 in the storage area secured in the RAM 83, and further proceeds to S33 and returns to S12, and the gate signal Vb is switched to H at the next ignition timing. S12, S13, S15, and S33 are repeated and waited until it is received.

  As described above, in the ignition device 1 of the present embodiment, when the ignition to the spark plug 9 is performed, the closed loop circuit 25 including the primary coil 51 of the ignition coil 5 is formed, so that the spark discharge in the ignition plug 9 is prevented. It can be forcibly shut off. By providing the current detection unit 6 in the closed loop circuit 25, the current Ib flowing through the closed loop circuit 25 can be detected. Furthermore, based on the magnitude of the current Ib, it can be determined whether or not the spark plug 9 is in an abnormal state, that is, a smoldering state, a failure state, or a deterioration state. Note that the value of the flag indicating the state of the spark plug 9 is confirmed by another program executed together with the abnormality determination program. Based on this value, for example, notification to the user and control when the spark plug 9 is cleaned are performed. Etc. are performed.

  Further, although the ignition high voltage Vd is generated on the secondary coil 52 side of the ignition coil 5, the voltage applied to the closed loop circuit 25 side due to the interruption of the spark discharge is stored in the ignition coil 5 before the spark discharge. This corresponds to the remaining magnetic energy obtained by subtracting the energy consumed by the spark discharge from the magnetic energy, and is lower than the ignition high voltage Vd. In the ignition device 1 of the present embodiment, the current detection unit 6 is provided on the primary coil 51 side, so that a large voltage is not applied to the current detection unit 6. In other words, the ignition high voltage Vd applied during the spark discharge does not directly affect the electronic components such as the current detector 6 and the thyristor 23 that are disposed on the primary coil 51 side. Therefore, it is not necessary to use a high-voltage-resistant component for the current detection unit 6, and cost can be reduced and durability reliability can be increased.

In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, like the ignition circuit unit 102 of the ignition device 101 shown in FIG. 5, a resistor 131 is disposed in the closed loop circuit 125 instead of the current detection unit 6 (see FIG. 1), and the potential difference generated between both ends of the resistor 131 is further reduced. A differential amplifier circuit 132 for amplification may be provided to constitute the current detection means in the present invention. Since the potential difference generated at both ends of the resistor 131 is proportional to the magnitude of the current Ib flowing through the closed loop circuit 125, the differential amplifier circuit 132 corrects the potential V _Ib at one end of the resistor 131 to 0 at the time of non-ignition, and then the resistor 131. Is amplified and input to the ECU 8 as a voltage value Vc. The timing chart of FIG. 6 shows a comparison between the potential V _Ib at one end of the resistor 131 and the voltage value Vc obtained by amplifying the potential difference generated at both ends of the resistor 131 by the differential amplifier circuit 132. It can be seen that an output equivalent to the voltage value Vc as the output of the current detector 6 shown can be obtained. And if each judgment value D1-D3 is determined by a test according to this circuit structure, it can be judged whether the spark plug 9 is in an abnormal state like this Embodiment.

  Further, like the ignition circuit unit 202 of the ignition device 201 shown in FIG. 7, the cathode of the rectifying diode 233 is connected to one end side of the primary coil 51, and one end of the anode of the diode 233 is grounded. The other end of the resistor 131 is connected. Further, a switching circuit 203 is provided between the battery 7 and the ignition coil 5. By making such circuit connection, the resistor 131, the diode 233, the primary coil 51, and the transistor 22 may constitute a closed loop circuit 225 via the ground.

  In the case of the ignition device 201, in order to open and close the closed loop circuit 225, the opening and closing of the transistor 22 and the switching circuit 203 may be controlled as shown in the timing chart of FIG. Specifically, the ignition instruction signal Va that is a control signal of the transistor 22 and the power supply signal Vf that is a control signal of the switching circuit 203 are both set to H at the timing T1, so that the current Ia flows through the primary coil 51. . Then, Va and Vf are set to L at the timing T2, and the transistor 22 and the switching circuit 203 are opened to ignite the spark plug 9. Next, if only Va is set to H again at the timing T3 and the transistor 22 is closed, only the closed loop circuit 225 can be closed and the current Ib flows, so that the current Ib can be detected by the differential amplifier circuit 132. . In this way, the closed loop circuit 225 can be opened and closed without using a thyristor.

  The timing at which Va, which has been set to H again at T3 timing, may be set to L after the voltage value Vc from the differential amplifier circuit 132 becomes 0 (eg, T6 timing). In the abnormality determination program, the signal states of Va and Vf are monitored instead of the thyristor gate signal Vb. When Vf is H, VcH is updated or an abnormal state is determined regardless of the signal state of Va. You don't have to.

  Further, like the ignition circuit section 302 of the ignition device 301 shown in FIG. 9, the cathode of the diode 233 is connected to one end of the primary coil 51, and the anode is grounded to the ground. The collector of the NPN transistor 331 is connected to the other end of the primary coil 51, and the emitter is grounded via the resistor 131 having both ends connected to the differential amplifier circuit 132. By making such a circuit connection, the diode 233, the primary coil 51, the transistor 331, and the resistor 131 may constitute a closed loop circuit 325 through the ground.

  In the case of this ignition device 301, Va and Vf are set to H at the timing T1 in the timing chart of FIG. At time T2, Va and Vf are set to L, and the spark plug 9 is ignited. Next, when the control signal Ve of the transistor 331 is set to H at the timing T3, the closed loop circuit 325 is closed and the current Ib flows. Therefore, the current Ib may be detected by the differential amplifier circuit 132. Note that the timing at which Ve is set to L may be the T6 timing after the voltage value Vc from the differential amplifier circuit 132 becomes 0, as described above. In the abnormality determination program, the signal state of the control signal Ve of the transistor 331 may be monitored instead of the thyristor gate signal Vb.

  Further, like the ignition circuit unit 402 of the ignition device 401 shown in FIG. 11, the cathode of the diode 233 is connected to one end of the primary coil 51, and the anode is grounded to the ground. Further, one end of the resistor 131 whose both ends are connected to the differential amplifier circuit 132 is connected to the emitter of the transistor 22 connected to the other end of the primary coil 51, and the other end is grounded. Even if such circuit connection is made, the closed loop circuit 425 can be configured via the ground by the diode 233, the primary coil 51, the transistor 22, and the resistor 131.

  In the case of the ignition device 401, in the timing chart of FIG. 12, the control of Va and Vf for opening and closing the closed loop circuit 425 is the same as that of the ignition device 201 (see FIG. 8). In addition, since the resistor 131 connected to the differential amplifier circuit 132 is connected to the emitter side of the transistor 22, the current Ia flows through the resistor 131 also at the timing T 1 to T 2, and the voltage value Vc output from the differential amplifier circuit 132. Will result in fluctuations. In the abnormality determination program, as in the case of the ignition device 201, the signal state of Va is monitored only when Vf is L to update VcH and determine the abnormal state.

  In the present embodiment, the abnormality determination program is executed by the ECU 8. However, an ASIC having a CPU, ROM, RAM having a known configuration is separately provided, and the abnormality determination program is executed in the ASIC. The determination result may be notified from the ASIC to the ECU 8.

  In the present embodiment, the current value Ib detected by the current detection unit 6 is A / D converted from the voltage value Vc obtained by current-voltage conversion, the maximum value VcH is obtained, and VcH is determined as the determination value D1, By comparing with D2 and D3, it was determined whether or not the spark plug 9 was in an abnormal state. That is, the abnormality determination is performed by comparing the current corresponding value corresponding to the current value with the determination value, but the detected value (current value) of the current Ib may be used as it is.

  Further, a known peak hold circuit for detecting the peak value of the current Ib is provided, and it is determined whether or not the spark plug 9 is in an abnormal state based on the peak value of the current Ib output from the circuit. Good. Further, as described above, it is determined whether or not the spark plug 9 is in an abnormal state based on the integral value of the current Ib instead of the peak value of the current Ib, the time during which the current Ib is flowing at a predetermined value or more, and the like. May be.

  In the present embodiment, a gas engine is used as an example of an internal combustion engine, and an ignition device for a spark plug attached to the gas engine has been described. However, the present invention is not limited to an ignition device for a gas engine. The present invention can be suitably applied to an ignition device for an internal combustion engine using an ignition plug that ignites fuel by spark discharge, such as an ethanol engine.

2 is an electric circuit diagram showing a configuration of an ignition device 1 that performs ignition to a spark plug 9. FIG. 4 is a timing chart showing the relationship between the waveform of current and signal voltage flowing at the ignition timing in the ignition circuit section 2; To illustrate the relationship between the voltage value required to cause dielectric breakdown between the center electrode 91 and the ground electrode 92 during spark discharge and the maximum value of the magnitude of the current Ib generated in the closed loop circuit 25. It is a graph of. It is a flowchart of an abnormality determination program. It is an electric circuit diagram which shows the structure of the ignition device 101 as a modification. 3 is a timing chart showing the relationship between the current flowing at the ignition timing and the waveform of the signal voltage in the ignition circuit section 102; It is an electric circuit diagram which shows the structure of the ignition device 201 as a modification. 4 is a timing chart showing the relationship between the waveform of current and signal voltage flowing at the ignition timing in the ignition circuit section 202. It is an electric circuit diagram which shows the structure of the ignition device 301 as a modification. 4 is a timing chart showing the relationship between the waveform of current and signal voltage flowing at the ignition timing in the ignition circuit section 302. It is an electric circuit diagram which shows the structure of the ignition device 401 as a modification. 3 is a timing chart showing the relationship between the waveform of current and signal voltage flowing at the ignition timing in the ignition circuit section 402;

DESCRIPTION OF SYMBOLS 1 Ignition device 5 Ignition coil 6 Current detection part 9 Spark plug 23 Thyristor 25 Closed loop circuit 51 Primary coil 52 Secondary coil 91 Center electrode 92 Ground electrode

Claims (4)

An ignition coil that has a primary coil and a secondary coil, and generates a high voltage for ignition in the secondary coil by interrupting a primary current flowing through the primary coil;
A spark plug that generates a spark discharge for ignition between its electrodes by applying the high voltage for ignition;
The spark discharge is forcibly cut off by forming a closed loop circuit with the primary coil and re-energizing the primary coil after a predetermined time has elapsed after the spark discharge is started between the electrodes of the spark plug. In an ignition device comprising a spark discharge blocking means,
Current detecting means for detecting a current flowing through the closed loop circuit at the time of re-energization ;
An abnormality determination unit that compares the current value at the time of re-energization detected by the current detection unit with a predetermined threshold value to determine whether or not the spark plug is in an abnormal state;
An ignition device comprising: The abnormality determination unit is configured such that when the current value at the time of re-energization detected by the current detection unit is a value equal to or less than a predetermined first threshold value, the abnormal state of the spark plug is an electrode consumption state. The ignition device according to claim 1 , wherein the ignition device is determined to be present. The abnormality determination unit is configured to detect the spark plug when the current value at the time of re-energization detected by the current detection unit is a predetermined value that is less than a second threshold value that is smaller than the first threshold value. The ignition device according to claim 2 , wherein the abnormal state is determined to be a failure state. The abnormality determination unit is configured to detect the spark plug when a current value at the time of re-energization detected by the current detection unit is a predetermined value greater than or equal to a third threshold value greater than the first threshold value. ignition device according to claim 2 or 3 is in an abnormal state, characterized in that it is determined that the sooting state.

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