JP2016048065A - Internal combustion engine ignition system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the damage of a switching element, in an ignition system which performs continuous discharge or multiple discharge by using an ignition plug.SOLUTION: An internal combustion engine ignition system comprises: a first current passage (24) which is connected to voltage supply means (11, 51) for supplying first voltages out of a plurality of voltage supply means (11, 12, 41 and 51); a second current passage (23) which is connected to the voltage supply means (12, 41 and 51) which supply second voltages higher than the first voltages out of a plurality of the voltage supply means; a third current passage (25) which is connected to a primary coil (15); passage changeover means (21) which switches a first state that the first current passage is connected to the third current passage, and a second state that the second current passage is connected to the third current passage; and primary current control means (13) which switches the passage changeover means by the first state and the second state, and performs continuous discharge or multiple discharge by using an ignition plug (20) by controlling the drive of a switching element (14).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition system used in an internal combustion engine.

  In recent years, in order to improve the fuel efficiency of an internal combustion engine for automobiles, studies are being made on technologies relating to combustion control of lean fuel (lean burn engine) or EGR for returning combustion gas to a cylinder of the internal combustion engine. In these technologies, the multiple ignition system / AC ignition system in which the ignition plug discharges continuously several times at the ignition timing of the internal combustion engine, or two ignition coils alternately for a certain time near the ignition timing. Various ignition systems for effectively burning fossil fuel contained in an air-fuel mixture, such as a DCO system that operates and discharges a spark plug continuously, have been studied.

  Since ignition systems based on these methods are required to maintain a large discharge current, the voltage applied to the primary coil (primary side of the ignition coil) is boosted by a DC-DC converter or the like (see Patent Document 1). ).

JP2012-167665A

  In the above case, the ignition signal at the start of discharge may be longer than the normal ignition signal due to a signal abnormality from the ECU. At this time, due to the high voltage, a large current is reached in a short time, and there is a possibility that an excessive current flows in a switching element such as an IGBT (insulated gate bipolar transistor) that cuts off and conducts the current flowing to the primary coil. As a result, the power consumption of the IGBT increases and may be damaged.

  The present invention has been made to solve the above-mentioned problems, and its main object is to suppress damage to switching elements in an ignition system that performs continuous discharge or multiple discharge with an ignition plug. It is.

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

  The present invention is an ignition system for an internal combustion engine, comprising an ignition plug for generating a spark discharge for igniting a combustible air-fuel mixture in a combustion chamber of the internal combustion engine, a primary coil and a secondary coil, and the secondary coil An ignition coil for applying a voltage to the ignition plug, a plurality of voltage supply means for supplying different power supply voltages to the ignition coil, a switching element for cutting off and conducting a primary current flowing to the primary coil, and the plurality of voltages Among the supply means, a first current path connected to a voltage supply means for supplying a first voltage, and a voltage supply means for supplying a second voltage higher than the first voltage among the plurality of voltage supply means. A connected second current path; a third current path connected to the primary coil; a first state where the first current path is connected to the third current path; and a second state connected to the third current path. Current A path switching means for switching between a second state and a path connected; and switching the path switching means between the first state and the second state, and controlling the driving of the switching element, thereby continuously by the spark plug Primary current control means for performing discharge or multiple discharge.

  According to the above configuration, the internal combustion engine ignition system includes a plurality of voltage supply means, and of these, the first current path connected to the voltage supply means for supplying the first voltage, A second current path connected to voltage supply means for supplying a second voltage higher than the voltage is provided. In addition, a third current path connected to the primary coil among the primary coil and the secondary coil constituting the ignition coil is provided. Here, the primary current control means controls the path switching means to connect the first current path to the third current path and disconnect the second current path, and the third current path. On the other hand, it is possible to arbitrarily switch between the second state in which the first current path is disconnected and the second current path is connected.

  The primary current flows from the first current path in the first state to the primary coil through the third current path by the voltage supply means connected to the second current path from the second state. The primary current that flows to the primary coil is turned on and off to control the cutting and conduction of the current. The primary current control means controls the switching element to control the primary current, thereby causing the spark plug to perform continuous discharge or multiple discharge. For this reason, when discharging is performed by the spark plug, for example, the voltage can be arbitrarily changed at the start of discharge of the spark plug and after the start of discharge, and as a result, damage to the switching element can be suppressed.

It is a figure which shows the circuit structure of the ignition system for internal combustion engines which concerns on this embodiment. 4 is a timing chart showing an ignition signal, a primary current, and a secondary current according to the present embodiment. It is a figure which shows the circuit structure of the ignition system for internal combustion engines (modified example). It is a figure which shows the circuit structure of the ignition system for internal combustion engines (modified example). It is a figure which shows the circuit structure of the ignition system for internal combustion engines (modified example). It is a control flowchart of the ignition system for internal combustion engines which concerns on the example of a change. It is the timing chart which showed the ignition signal which concerns on the example of a change, a primary current, and a secondary current. It is a figure which shows the circuit structure of the ignition system for internal combustion engines (modified example).

  The present embodiment will be described with reference to the drawings. An ignition system 10 for an internal combustion engine for an automobile shown in FIG. 1 includes two ignition coils 18A and 18B, two IGBTs 14A and 14B (corresponding to switching elements), a spark plug 20, and a battery 11 (corresponding to voltage supply means). ) And a DC-DC converter 12 (corresponding to voltage supply means).

  The ignition coil 18A includes a primary coil 15A, a secondary coil 16A, and an iron core 17A, and the ignition coil 18B has a similar configuration. The first ends of the primary coils 15A and 15B are connected to a power source. The second ends of the primary coils 15A and 15B are connected to the collector terminals of the IGBTs 14A and 14B, respectively, and the current detection circuit 22 (corresponding to the primary current detection means) is connected to the emitter terminals of the IGBTs 14A and 14B. The detection circuit 22 is connected to the ECU 13. The current detection circuit 22 includes a current sensor.

  The first ends of the secondary coils 16A and 16B are grounded to the ground potential. On the other hand, the second ends of the secondary coils 16A and 16B are connected to the cathode sides of the diodes 19A and 19B. The anode side of the diodes 19A and 19B is connected to the spark plug 20. That is, the diodes 19 </ b> A and 19 </ b> B are connected in the reverse direction with respect to the spark plug 20. The diodes 19A and 19B are provided to add the outputs of the two ignition coils 18A and 18B, and to prevent preignition due to energization of the ignition coils 18A and 18B. Specifically, the anode sides of these diodes 19 </ b> A and 19 </ b> B are connected and joined together, and the joined current path is connected to the input terminal of the spark plug 20. That is, each secondary coil 16A, 16B is connected to one common spark plug 20, and a negative high voltage is applied to the spark plug 20 from both spark coils 18A, 18B.

  The ECU 13 (corresponding to the primary current control means) includes a CPU, an I / O circuit, a memory circuit, a clock circuit, and the like. The ECU 13 is connected separately from each of the IGBTs 14A and 14B. The ECU 13 generates ignition signals IGT_1 and IGT_2 based on the input information, outputs them to the gate terminals of the IGBTs 14A and 14B, and controls the driving of the IGBTs 14A and 14B. Information relating to the operation state of the internal combustion engine (hereinafter referred to as operation state information) is appropriately input to the I / O circuit from various ECUs or sensors provided in each part of the automobile. The operating state information includes injector operation information, information from the crank angle sensor, and the like, and the ECU 13 recognizes information on the load state and the rotational speed of the internal combustion engine based on these information. And ECU13 sets each ignition signal IGT_1 and IGT_2 based on these information.

  Since the phases of the ignition signals IGT_1 and IGT_2 transmitted from the ECU 13 are not input to the IGBTs 14A and 14B, the IGBTs 14A and 14B are synchronized so that when one is ON, the other is OFF. Will be driven.

  Here, the battery 11 and the DC-DC converter 12 are connected in series. A current path 24 (corresponding to the first current path) that does not pass through the DC-DC converter 12 is branched between the battery 11 and the current path connected to the input side of the DC-DC converter 12. At this time, the voltage supplied from the battery 11 is about 12 (V) to 24 (V), and based on this, the DC-DC converter 12 boosts the voltage to about 40 (V) to 90 (V). Let

  Both the current path 24 not passing through the DC-DC converter 12 and the current path 23 (corresponding to the second current path) provided on the output side of the DC-DC converter 12 are interrupted on the way. A relay 21 (corresponding to route switching means) is provided to compensate for the disconnected route. The current path 25 connected to the relay 21 is connected to the first end of the primary coil 15A. A current circuit connected to the first end of the primary coil 15B branches between the primary coil 15A and the relay 21 (corresponding to a third current path). That is, the third current path is a current path that connects the primary coil 15 (15A, 15B) and the relay 21.

  The ECU 13 sends a control signal to the relay 21 so that the current path 24 is connected to the current path 25 via the relay 21 (corresponding to the first state) or the current path 23 is connected to the current path 25 via the relay 21. Whether it is connected (corresponding to the second state) is appropriately controlled. That is, the ECU 13 controls the relay 21 to connect the current path 24 to the current path 25 and disconnect the current path 23, and to disconnect the current path 24 from the current path 25. The second state in which the current path 23 is connected is arbitrarily switched.

  Next, control executed by the ECU 13 in this embodiment will be described.

  FIG. 2 is a timing chart showing the operation of the ECU 13 in the present embodiment. This figure shows the waveforms of primary currents I1_1 and I1_2 flowing through IGT_1, IGT_2, and IGBTs 14A and 14B transmitted from the ECU 13, respectively, and the waveform of the secondary current I2 generated when the primary currents I1_1 and I1_2 are cut off. ing.

  The ignition signals IGT_1 and IGT_2 transmitted by the ECU 13 are each composed of a first pulse having a long time interval and a subsequent pulse having a short time interval and occurring intermittently. The first pulse and the subsequent pulse are set so that the primary currents I1_1 and I1_2 exceed a preset set value A. The set value A is set to a target value within a range where there is no possibility of damaging the IGBTs 14A and 14B. The ECU 13 monitors the increase of the primary currents I1_1 and I1_2 by the current detection circuit 22, and turns off the IGBTs 14A and 14B when the primary currents I1_1 and I1_2 exceed the set value A, respectively.

  When the IGBTs 14A and 14B are driven by the ignition signals IGT_1 and IGT_2, primary currents I1_1 and I1_2 are intermittently generated in the primary coils 15A and 15B.

  Along with this, in each of the secondary coils 16A and 16B, a fluctuation in magnetic flux is continuously generated in synchronization with the primary currents I1_1 and I1_2, and a high voltage is continuously output. Therefore, a voltage obtained by synthesizing both high voltages is applied to the input terminal of the spark plug 20, and the secondary current I2 flows continuously.

  Further, based on the current detected by the current detection circuit 22, the ECU 13 switches the current path by the relay 21, and the voltage applied to the primary coils 15A and 15B is the voltage of the battery 11 (corresponding to the first voltage). Or the voltage boosted by the DC-DC converter 12 (corresponding to the second voltage) is appropriately controlled.

  At this time, when the discharge of the spark plug 20 starts, IGT_1 and IGT_2 transmitted to the IGBTs 14A and 14B are longer than the normal ignition signals IGT_1 and IGT_2 due to a signal abnormality from the ECU 13 in the first pulse in particular. There is. It is assumed that the voltage obtained by boosting the voltage of the battery 11 by the DC-DC converter 12 is always applied to the primary coils 15A and 15B. In this case, the primary currents I1_1 and I1_2 whose rise angles are increased by the DC-DC converter 12 flow into the IGBTs 14A and 14B for a long time, and the power consumption thereof may increase rapidly and may be damaged.

  Therefore, in the present embodiment, the current path 24 is connected to the current path 25 by the relay 21 when starting the discharge of the spark plug 20. With this configuration, the primary currents I1_1 and I1_2 flow from the battery 11 to the primary coils 15A and 15B, and the spark plug 20 is discharged by the secondary current I2 induced when the primary currents I1_1 and I1_2 are cut off. . After the discharge is started, the current path 23 is connected to the current path 25 by the relay 21. At this time, the current detection circuit 22 monitors the increase of the primary currents I1_1 and I1_2, and when both the primary currents I1_1 and I1_2 exceed the set value A once, the relay 21 is switched. With this configuration, the primary currents I1_1 and I1_2 increased by the DC-DC converter 12 flow into the primary coils 15A and 15B, and the secondary current I2 induced when the primary currents I1_1 and I1_2 are cut off causes the spark plug 20 to Is discharged.

  For example, when the discharge of the spark plug 20 starts, when the primary current I1_1 supplied from the battery 11 exceeds the set value A, the primary current I1_1 is cut off by turning off the IGBT 14A. At this time, the secondary current I2 is induced from the ground potential grounded with the spark plug 20, and the spark plug 20 is discharged by the secondary current I2.

  Then, when the primary current I1_2 exceeds the set value A, the IGBT 14A is turned on and the IGBT 14B is turned off. At the same time, the relay 21 is switched, and the power supply voltage supplied to the ignition coil 18 is changed from the voltage of the battery 11 to the voltage boosted by the DC-DC converter 12. For this reason, at the start of discharge, it is possible to suppress a rapid increase in power consumption of the IGBTs 14A and 14B.

  With the above configuration, the internal combustion engine ignition system 10 according to the present embodiment has the following effects.

  The ECU 13 controls the relay 21 when starting the discharge of the spark plug 20 so that the voltage of the battery 11 is applied to the primary coils 15A and 15B. Therefore, the primary currents I1_1 and I1_2 flowing through the primary coils 15A and 15B can be gradually increased. Then, the ECU 13 switches the relay 21 after starting the discharge of the spark plug 20, and the voltage boosted by the DC-DC converter 12 is applied to the primary coils 15A and 15B. For this reason, a high voltage is applied to the primary coils 15A and 15B after the start of discharge, and the rising angles of the primary currents I1_1 and I1_2 can be increased. For this reason, the repeated ignition interval can be shortened, and as a result, the degree of decrease in the secondary current I2 can be reduced, and can be kept substantially constant.

  By providing the current detection circuit 22, the primary currents I1_1 and I1_2 flowing through the primary coils 15A and 15B can be detected. The ECU 13 causes the current detection circuit 22 to monitor the primary currents I1_1 and I1_2, and switches the relay 21 when the primary current I1_2 exceeds a preset set value A. For this reason, it becomes possible to switch the relay 21 precisely according to the actual magnitudes of the primary currents I1_1 and I1_2, and the load on the IGBTs 14A and 14B can be reduced.

  In addition, the said embodiment can also be changed and implemented as follows.

  The first ends of the secondary coils 16A and 16B are each grounded to the ground potential. In this regard, as shown in FIG. 3, a current path connected to the first end of the secondary coil 16 may be connected to the current path 25 connected to the primary coil 15. By doing so, the ignition system can be simplified (another example 1).

  In the above-described embodiment, the primary currents I1_1 and I1_2 are monitored by the current detection circuit 22, and when the primary current I1_2 exceeds the set value A, the relay 21 is switched. In this regard, the relay 21 may be switched when a preset time has elapsed from the rise (ON start) of IGT_1 or IGT_2 without providing the current detection circuit 22. At this time, when the discharge of the spark plug 20 is started, the current path 24 is connected to the current path 25 via the relay 21 as in the above embodiment. After starting the discharge of the spark plug 20, the current path 24 is interrupted and the current path 23 is connected to the current path 25. Then, the ECU 13 controls the primary current by performing ON / OFF control of the IGBTs 14A and 14B at a preset time interval. In this control, the time for which the IGBT 14 that is performed at the start of the discharge of the spark plug 20 is kept ON is set to be longer than the time that the IGBT 14 that is performed after the start of the discharge of the spark plug 20 is kept on. By doing so, the current detection circuit 22 is not necessary, and the ignition system can be simplified (another example 2).

  In the above embodiment, the relay 21 connects the current path 23 that applies the voltage boosted by the DC-DC converter 12 to the primary coils 15A and 15B and the current path 24 that applies the voltage of the battery 11 to the primary coils 15A and 15B. It was supposed to switch the route. In this regard, a DC-DC converter may be newly provided in the current path 24 for applying the voltage of the battery 11 to the primary coils 15A and 15B (another example 3).

  In this case, the newly provided DC-DC converter boosts the voltage of the battery 11 to a voltage lower than the voltage boosted by the DC-DC converter 12. Thereby, the time until the start of discharge of the spark plug 20 can be shortened. Further, even if the ignition signals IGT_1 and IGT_2 become longer due to a signal abnormality from the ECU 13, the rising angles of the primary currents I1_1 and I1_2 are not larger than the voltage boosted by the DC-DC converter 12 provided originally. Damage to the IGBT 14 can be suppressed.

  In the above embodiment, the relay 21 connects the current path 23 that applies the voltage boosted by the DC-DC converter 12 to the primary coils 15A and 15B and the current path 24 that applies the voltage of the battery 11 to the primary coils 15A and 15B. It was supposed to switch the route. In this regard, as shown in FIG. 4, a high voltage battery 41 that supplies a voltage higher than the voltage of the battery 11 may be provided. This configuration is effective when applied to a hybrid vehicle, and can eliminate the need for the DC-DC converter 12 (another example 4).

  Further, the configuration shown in FIG. 5 can be applied to the hybrid vehicle. Also in these cases, when the discharge of the spark plug 20 is started, the ECU 13 connects the current path 24 to the current path 25 via the relay 21, and after the start of the discharge of the spark plug 20, the ECU 13 blocks the current path 24. Is connected to the current path 25. In the state where the current path 23 is connected to the current path 25, the secondary current I2 for discharging the spark plug 20 using a part of the total voltage (maximum pressure) of the high-voltage battery 51 included in the hybrid vehicle is used. You may induce (another example 5).

  In the above embodiment, the voltage of the battery 11 is applied to the ignition coils 18A and 18B when starting the discharge of the spark plug 20 in order to suppress a rapid increase in power consumption of the IGBTs 14A and 14B. After the spark plug 20 starts discharging, the voltage boosted by the DC-DC converter 12 is applied to the ignition coils 18A and 18B. In this configuration, it is assumed that the discharge of the spark plug 20 is terminated. The voltage applied to the ignition coils 18 </ b> A and 18 </ b> B after starting the discharge of the spark plug 20 is a voltage boosted by the DC-DC converter 12. For this reason, if both IGBTs 14 </ b> A and 14 </ b> B are turned off, an excessively large secondary current I <b> 2 may flow through the spark plug 20. As a result, there is a possibility that the spark plug 20 is loaded and the consumption of the electrode is accelerated.

  As a countermeasure against this, in this other example, the ECU 13 executes discharge termination control of the spark plug 20 of FIG. Thus, when the discharge of the spark plug 20 is terminated, the current path 23 is blocked by the relay 21 and the current path 24 is connected before the IGBTs 14A and 14B are cut off. Therefore, when the discharge of the spark plug 20 is finished, a voltage is applied from the battery 11 to each ignition coil 18.

  Hereinafter, the control content of the discharge end control of the spark plug 20 of FIG. 6 executed by the ECU 13 will be described. The discharge termination control of the spark plug 20 shown in FIG. 6 is repeatedly executed by the ECU 13 at a predetermined cycle while the spark plug 20 is being discharged and the ECU 13 is powered on.

  When this control is activated, it is first determined in step 100 whether or not a discharge end request has been received. The discharge end request is a signal for requesting the spark plug 20 to stop the discharge on condition that the discharge duration time required for ignition has elapsed, for example, according to the operating state (load / rotation speed) of the internal combustion engine. That is. If the discharge end request has not been received (S100: NO), the discharge is continued as it is because the discharge duration required for ignition is insufficient. If a discharge end request is received (S100: YES), the process proceeds to step 110.

  In step 110, the current path 23 is interrupted by the relay 21 and the current path 24 is connected. As a result, the voltage applied to each ignition coil 18 is switched from the voltage boosted by the DC-DC converter 12 to the voltage of the battery 11.

  In step 120, it is determined whether or not a predetermined time has elapsed since the switching of the relay 21 was completed in step 110. The predetermined time is set as a time necessary for the secondary current I2 to decrease to a predetermined value. The predetermined value is set as a value that prevents excessive secondary current I2 from flowing through the spark plug 20 when both IGBTs 14A and 14B are shut off. If the predetermined time has not elapsed since the switching of the relay 21 was completed in step 110 (S120: NO), step 120 is performed again. If the predetermined time has elapsed since the switching of the relay 21 was completed in step 110 (S120: YES), the process proceeds to step 130.

  In step 130, the control for alternately generating the secondary current I2 in each of the ignition coils 18A and 18B is stopped, and the ignition signals IGT_1 and IGT_2 are set to the corresponding IGBTs 14A and 14B so that both the IGBT 14A and IGBT 14B are turned off. Send to. And this control is complete | finished.

  FIG. 7 is a timing chart showing the operation of the ECU 13 in this another example. In this figure, “power source” is expressed as high when the voltage applied to the ignition coil 18 is a voltage boosted by the DC-DC converter 12, and is expressed as low when the voltage is from the battery 11. is there. Further, “discharge request” indicates the presence / absence of a discharge request as high / low. In addition, the waveforms of the primary currents I1_1 and I1_2 flowing through the IGT_1 and IGT_2 and the IGBTs 14A and 14B transmitted from the ECU 13 and the waveform of the secondary current I2 generated when the primary currents I1_1 and I1_2 are cut off are shown, respectively. .

  Since the primary currents I1_1 and I1_2 are intermittently generated, the secondary current I2 flows continuously through the spark plug 20 and discharge is continued (see times t1 to t2). Thereafter, when the discharge request is switched from high to low, the current path is switched by the relay 21 later, and the voltage applied to the ignition coil 18 is increased from the voltage boosted by the DC-DC converter 12 to the voltage of the battery 11. (See time t3). The switching of the current path performed at this time specifically corresponds to blocking the current path 23 by the relay 21 and connecting the current path 24.

  In this state, the ignition signals IGT_1 and IGT_2 are subsequently controlled to generate primary currents I1_1 and I1_2 intermittently. Since the voltage applied to the ignition coil 18 has changed from the voltage (40 to 90 V) boosted by the DC-DC converter 12 to the voltage (12 to 24 V) of the battery 11, the secondary current I2 starts to decrease (time t4 to t4). t5). Note that the secondary current I2 induced by cutting off the primary currents I1_1 and I1_2 has a negative value. Therefore, the positive direction is described as the decreasing direction of the secondary current I2.

  When a predetermined time elapses after switching to the voltage of the battery 11, it is determined that the secondary current I2 has exceeded a predetermined value and has become low. Even if both the IGBTs 14A and 14B are cut off, an excessive secondary current I2 is applied to the ignition coil 18. The IGBTs 14A and 14B are shut off because they do not flow (see time t5).

  If both the IGBTs 14A and 14B are turned off when the discharge of the spark plug 20 is finished, the secondary current I2 is generated in both the ignition coils 18A and 18B. At this time, if the voltage boosted by the DC-DC converter 12 is applied to the ignition coils 18 </ b> A and 18 </ b> B, the peak of the secondary current I <b> 2 flowing through the spark plug 20 becomes large, and the electrode of the spark plug 20 Consumption can be accelerated. For this reason, when the discharge of the spark plug 20 is terminated, the ECU 13 blocks the current path 23 and connects the current path 24 by the relay 21 before turning off both the IGBTs 14A and 14B. As a result, the voltage flowing through the ignition coils 18A and 18B is switched from the voltage boosted by the DC-DC converter 12 to the voltage of the battery 11, so that the secondary current I2 can be reduced. Even if both of the IGBTs 14A and 14B are turned off after this state is continued for a predetermined time, the secondary current I2 generated at that time is sufficiently small, so that the electrode consumption of the spark plug 20 can be suppressed. It becomes possible.

  This example can be applied to the configurations of Examples 1 to 5 above.

  In this other example, when the discharge of the spark plug 20 is finished, the voltage applied to the ignition coils 18A and 18B is changed from the voltage boosted by the DC-DC converter 12 to the voltage of the battery 11, and then changed to a predetermined value. The IGBTs 14A and 14B were turned off after a lapse of time. Regarding this, a secondary current sensor (corresponding to the secondary current detection means) for detecting the secondary current I2 flowing through the spark plug 20 is installed, and the secondary current I2 detected by the secondary current sensor is less than a predetermined value. The IGBTs 14A and 14B may be turned off on the condition that they have become low. In this case, since the secondary current I2 flowing through the spark plug 20 can be detected by the secondary current sensor, the peak of the secondary current I2 generated when both the IGBTs 14A and 14B are turned off can be more accurately suppressed. Is possible.

  In the above embodiment, the ignition coil 18A and the ignition coil 18B are provided. In this regard, a configuration (multiple ignition method) including only one ignition coil 18 may be used. Even in this case, when the discharge of the spark plug 20 is started, the ECU 13 connects the current path 24 to the current path 25 via the relay 21, and after the start of the discharge of the spark plug 20, the ECU 13 cuts off the current path 24. The current path 25 is connected. With this configuration, the structure can be simplified.

  The present ignition system is not limited to the DCO method and the multiple ignition method, but can be applied to an AC ignition method as shown in FIG. In the ignition system 60, a diode 67 and a capacitor 68 are connected in parallel to both ends (input end and output end) of the IGBT 66 of the igniter 65 as shown in the figure. The spark plug 20 is connected in parallel to the secondary coil 63 of the ignition coil 64 and wired so that a discharge operation is performed regardless of the polarity of the output voltage of the secondary coil 63.

  In such an ignition system 60, when the primary currents I1_1 and I1_2 exceed a specified value with the IGBT 66 in the ON state, the IGBT 66 is switched OFF, and the primary coil 61 and the capacitor 68 are repeatedly charged and discharged repeatedly. The currents I1_1 and I1_2 are oscillated. At this time, the spark plug 20 repeats discharge while alternately switching the polarity direction during the vibration period in which the primary currents I1_1 and I1_2 vibrate. As described above, also in the present ignition system 60, the discharge operation is continued for a certain period as in the DCO ignition system 10.

  In such an ignition system 60, the voltage boosted in the DC-DC converter 12 must be set so that the voltage applied to the spark plug 20 can be discharged with both positive and negative polarities. As a result, if the voltage is maintained within a certain range, the amount of charge accumulated in the capacitor 68 is also set to the designed value, so that the maximum peaks of the primary currents I1_1 and I1_2 reach the set value A.

  In this case, the current path 24 is connected to the current path 25 via the relay 21 at the start of discharge of the spark plug 20. After starting the discharge of the spark plug 20, the current path 24 is interrupted and the current path 23 is connected to the current path 25. For this reason, the continuous discharge operation with the spark plug 20 is reliably performed without excessively increasing the power consumption of the IGBT 66.

  In the present embodiment, as a path switching means for appropriately switching between the current path 24 for applying the voltage of the battery 11 to the primary coil 15 and the current path 23 for applying the voltage boosted by the DC-DC converter 12 to the primary coil 15. A relay 21 was provided. About this, you may change to a semiconductor relay, IGBT, etc.

  The path switching by the relay 21 was appropriately controlled by a signal transmitted from the ECU 13. In this regard, even if the ECU 13 does not control the relay 21, a new microcomputer or the like may be provided to control the relay 21.

DESCRIPTION OF SYMBOLS 11 ... Battery (voltage supply means), 12 ... DC-DC converter (voltage supply means), 13 ... ECU (primary current control means), 14 ... IGBT (switching element), 15 ... Primary coil, 16 ... Secondary coil, DESCRIPTION OF SYMBOLS 18 ... Ignition coil, 20 ... Spark plug, 21 ... Relay (path switching means), 23 ... Current path (second current path), 24 ... Current path (first current path), 25 ... Current path (third current path) , 41 ... high voltage battery (voltage supply means), 51 ... high voltage battery (voltage supply means), 61 ... primary coil, 63 ... secondary coil, 64 ... ignition coil, 66 ... IGBT (switching element).

Claims (8)

A spark plug (20) for generating a spark discharge for igniting a combustible mixture in a combustion chamber of an internal combustion engine;
An ignition coil (18, 64) comprising a primary coil (15, 61) and a secondary coil (16, 63), and applying a voltage to the spark plug by the secondary coil;
A plurality of voltage supply means (11, 12, 41, 51) for supplying different power supply voltages to the ignition coil;
Switching elements (14, 66) for cutting off and conducting the primary current flowing to the primary coil;
A first current path (24) connected to a voltage supply means (11, 51) for supplying a first voltage among the plurality of voltage supply means;
A second current path (23) connected to a voltage supply means (12, 41, 51) for supplying a second voltage higher than the first voltage among the plurality of voltage supply means;
A third current path (25) connected to the primary coil;
Path switching means (21) for switching between a first state in which the first current path is connected to the third current path and a second state in which the second current path is connected to the third current path;
Primary current control means (13) for switching the path switching means between the first state and the second state and controlling the driving of the switching element to cause continuous discharge or multiple discharge by the spark plug; ,
An internal combustion engine ignition system comprising:   The primary current control means causes the path switching means to switch to the first state at the start of discharge of the spark plug, and causes the path switching means to switch to the second state after the spark plug discharge starts. The ignition system for an internal combustion engine according to claim 1, wherein the ignition system is an internal combustion engine. Primary current detection means (22) for detecting the primary current flowing through the primary coil;
The primary current control means causes the path switching means to switch to the first state at the start of discharge of the spark plug, and then the primary current detected by the primary current detection means exceeds a predetermined value. The ignition system for an internal combustion engine according to claim 1 or 2, wherein the path switching means switches to the second state.   The primary current control means causes the path switching means to switch to the first state at the start of discharge of the spark plug, and causes the path switching means to switch to the second state after a predetermined time has elapsed. The ignition system for an internal combustion engine according to claim 1 or 2.   5. The ignition system for an internal combustion engine according to claim 1, wherein the primary current control unit is switched to the first state by the path switching unit when discharge of the ignition plug is finished. 6. .   The primary current control means shuts off all the switching elements when a predetermined time has elapsed after switching to the first state by the path switching means at the end of discharge of the spark plug. 6. The ignition system for an internal combustion engine according to claim 5, wherein the ignition system is an internal combustion engine. A secondary current detecting means for detecting a secondary current flowing through the spark plug;
The primary current control means is configured to switch the secondary current detected by the secondary current detection means to a value smaller than a predetermined value after switching to the first state by the path switching means at the end of discharge of the spark plug. 6. The ignition system for an internal combustion engine according to claim 5, wherein all the plurality of switching elements are shut off on condition that the condition is satisfied.   For the plurality of voltage supply means, the voltage supply means for supplying the first voltage is a battery (11), and the voltage supply means for supplying the second voltage is a DC- boosting voltage supplied from the battery. The ignition system for an internal combustion engine according to any one of claims 1 to 7, wherein the ignition system is a DC converter (12).

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