JP4600311B2 - Ignition control device for internal combustion engine - Google Patents

Description

  The present invention relates to an ignition control device for an internal combustion engine and an ignition coil that can be suitably used for the ignition control device.

  In a spark ignition type internal combustion engine, a high voltage is applied to the spark plug by an ignition device including an ignition coil, and a discharge spark is generated between the opposing electrodes of the spark plug. The fuel introduced into the combustion chamber is combusted by the generation of the discharge spark.

  Further, for the purpose of improving fuel efficiency, a lean burn engine that controls the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio has been developed. In the lean burn engine, a swirl flow such as swirl or tumble is generated in the air-fuel mixture in the cylinder in order to improve the combustion state. Since the airflow is generated in the cylinder, the combustion speed is increased, and the fuel consumption can be improved and the lean combustion limit can be improved. However, in the lean burn engine, the airflow generated in the cylinder becomes high speed, and there is a risk that the stability of the discharge by the spark plug may be reduced. When the discharge stability of the spark plug is lowered, the ignitability of the fuel is lowered and the combustion state is deteriorated.

  Therefore, in order to improve the combustion state, a so-called multiple discharge technique has been proposed in which a plurality of discharges are continuously repeated within a single combustion stroke. At this time, multiple discharge is performed by continuously applying a high voltage to the spark plug.

  Further, a technique has been proposed in which an auxiliary coil is provided in series with a primary coil of an ignition coil in an ignition device so that a high voltage is continuously applied to an ignition plug (see, for example, Patent Document 1). In such a technique, a high voltage applied to the spark plug is obtained by adding the secondary side voltage generated by the interruption of the current flowing through the primary side coil and the secondary side voltage generated by the current flowing through the auxiliary coil. Was increased to generate a discharge in the spark plug.

However, in each of the above technologies, a sufficient secondary current cannot be obtained although the secondary voltage is maintained at a high voltage after the secondary voltage is generated. As a result, the stability of the discharge may be reduced. In particular, in a lean burn engine, the in-cylinder flow velocity increases, so that the discharge stability is liable to be reduced, and the combustion state is deteriorated.
JP 62-48967 A

  An object of the present invention is to provide an ignition control device for an internal combustion engine capable of optimizing spark discharge generated by an ignition plug and thus maintaining an appropriate combustion state in the internal combustion engine.

  The ignition control device for an internal combustion engine according to the present invention includes an ignition coil having a power source connected to the primary coil and an ignition plug connected to the secondary coil, and the secondary coil is connected to the secondary coil at a designated ignition timing. A spark discharge is generated in the spark plug by generating the secondary high voltage. In particular, the ignition coil has a configuration in which the turn ratio (N2 / N1) between the number of turns N1 of the primary coil and the number of turns N2 of the secondary coil is variable, and the turn ratio is variably set during spark discharge. I made it.

  By variably setting the turns ratio (N2 / N1), the secondary voltage generated in the secondary coil and the magnitude of the secondary current generated in the secondary coil can be adjusted. For this reason, a desired discharge state can be realized during ignition control. As a result, it is possible to optimize the spark discharge generated by the spark plug, and thus maintain the combustion state in the internal combustion engine appropriately. For example, in a lean burn engine, the discharge can be optimized even when the in-cylinder flow velocity is relatively large, and the combustion state can be improved.

Further , at the time of spark discharge, the turn ratio (N2 / N1) of the ignition coil is increased when a discharge occurs at the ignition timing, and then the turn ratio (N2 / N1) is decreased.

  In the ignition coil, as the turn ratio (N2 / N1) increases, the secondary high voltage generated in the secondary coil increases, and as the turn ratio (N2 / N1) decreases, the secondary side generates in the secondary coil. The current increases. Therefore, by increasing the turn ratio (N2 / N1) when a discharge occurs at the ignition timing as described above, a sufficient secondary high voltage that causes dielectric breakdown can be generated. Further, by reducing the turn ratio (N2 / N1) after the occurrence of discharge, the secondary current is increased, and the discharge stability after the occurrence of discharge can be improved. Therefore, a desired discharge state can be realized.

Here, as described in claim 2 , the ignition coil is configured such that the number of turns of the primary side coil is variable, the number of turns of the primary side coil is reduced when a discharge occurs at the ignition timing, and then It is better to increase the number of turns. That is, here, the winding ratio is changed by changing the number of turns of the primary coil of the ignition coil.
According to the third and fourth aspects of the invention, in the ignition control device that performs multiple discharge, the turn ratio (N2 / N1) is increased when the first discharge occurs, and then the turn ratio (N2 / N1) is increased when the discharge continues. I try to make it smaller. In the multiple discharge, the discharge duration after the first discharge becomes long, but a good multiple discharge can be realized by changing the turns ratio as described above.

In the invention according to claim 5 , the primary coil has a plurality of coil portions, and the turns ratio (N2 / N1) is changed by switching the coil portions that are electrically connected to the power source among the plurality of coil portions. change. In this case, the change in the turns ratio can be easily realized by switching the coil portion that is electrically connected to the power source.

Meanwhile, in the invention described in claim 6, the ignition coil is provided with a primary coil and a secondary coil formed by winding a linear conductor in a cylindrical body surrounding the central core, the primary coil The number of turns is variable. In addition, a plurality of connection terminals were provided in accordance with the number of turns of the primary coil, and the plurality of connection terminals were arranged in parallel on one end side of the cylindrical body. In this case, since the plurality of connection terminals are collectively provided on one end side of the cylindrical body, switching is facilitated when each connection terminal is selectively used (connected to a power source or the like).

  In the invention according to claim 7, the primary side coil has a plurality of coil portions connected in series, and a pair of connection terminals are provided at portions that become both ends in a state where the plurality of coil portions are connected in series. In addition, another connection terminal is provided at the intermediate connection portion between the coil portions. In this case, the number of turns of the primary coil can be easily changed depending on which of the connection terminals is connected to the power supply system. Further, since the connection terminal of the intermediate connection portion is shared by the two coil portions, the configuration can be simplified.

  In the invention described in claim 8, since the plurality of coil portions are formed by winding a plurality of conductors in parallel, the irregularities on the outer side of the primary coil can be reduced, and the ignition coil can be miniaturized. In addition, since the plurality of coil portions are not manufactured in separate processes but in a single process, the primary coil can be manufactured efficiently.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the present embodiment, an ignition control system is constructed for an in-vehicle gasoline engine that is an internal combustion engine. In the control system, a spark plug is discharged based on an ignition command from an electronic control unit (hereinafter referred to as ECU). It is supposed to cause a spark.

  First, the schematic configuration of the ignition control system will be described with reference to FIG. Although FIG. 1 shows a configuration for one cylinder for the sake of convenience, a configuration for the number of cylinders of the engine is actually provided.

  In FIG. 1, as a configuration of the power supply system, an energy storage coil 12 and an IGBT 13 are connected in series to a battery 11 that is a DC power source, and energy is stored in the energy storage coil 12 when the IGBT 13 is turned on. A capacitor 15 is connected between the energy storage coil 12 and the IGBT 13 via a diode 14.

  On the other hand, the ignition coil 20 has a primary coil 21 and a secondary coil 22. In particular, the primary coil 21 is configured by connecting a plurality of coil portions in series. In the present embodiment, the first coil portion 21a and the second coil portion 21b are connected in series. The primary side coil 21 is configured. Here, the number of turns of the primary coil 21 is N1, the number of turns of the secondary coil 22 is N2, the number of turns of the first coil part 21a is N1a, the number of turns of the second coil part 21b is N1b, and the turns ratio is R = N2. / N1.

  An IGBT 25 is connected in series to the primary coil 21, and a voltage is applied from the power supply system to the primary coil 21 when the IGBT 25 is turned on. A spark plug 26 is connected in series to the secondary coil 22, and when a high voltage is generated in the secondary coil 22, a spark discharge is generated between the opposing electrodes of the spark plug 26.

  A switching circuit 27 is provided between the components of the power supply system including the battery 11 and the primary coil 21 of the ignition coil 20. The switching circuit 27 conducts either the contact a-a or the contact b-b, and the switching circuit 27 switches the conduction path of the power supply system so that the coil unit to be used is switched each time. It is done. When the contact point a-a is conducted, a voltage is applied to the first coil part 21a and the second coil part 21b when the IGBT 25 is turned on, and the contact point b-b is conducted, thereby the IGBT 25. A voltage is applied only to the second coil portion 21b when the is turned on.

  At this time, the magnitude of the secondary voltage V2 generated when the voltage of the primary coil 21 is applied is proportional to the turns ratio R, and the magnitude of the secondary current i2 is inversely proportional to the turns ratio R. Therefore, in the state in which the contact aa is conducted by the switching circuit 27, the turn ratio R is small, so the secondary current i2 can be increased. In the state in which the contact b-b is conducted, Since the turns ratio R is increased, the secondary voltage V2 can be increased.

  As is well known, the ECU 30 is mainly composed of a microcomputer including a CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, so that various types of the engine 10 can be set according to the engine operating state each time. Control is performed.

  In the engine ignition control, the ECU 30 acquires operating state information representing the operating state of the engine such as the engine speed and the accelerator operation amount, and calculates an optimal ignition timing based on the operating state information. Then, an ignition signal IGt is generated according to the ignition timing and output to the ignition control circuit 31. Further, in the present ignition control system, multiple discharge control is performed in which a plurality of discharges are continuously generated repeatedly in one combustion stroke in order to improve the combustion state. Here, the ECU 30 calculates a multiple discharge period, which is a period in which a plurality of discharges are continuously generated repeatedly. Then, a discharge period signal IGw that defines the multiple discharge period is generated and output to the ignition control circuit 31.

  The ignition control circuit 31 generates drive signals IG1, IG2 based on the ignition signal IGt and the discharge period signal IGw, and outputs the drive signals IG1, IG2 to the IGBTs 13, 25, respectively. When the IGBTs 13 and 25 are turned ON / OFF according to the drive signals IG1 and IG2, the first discharge is generated at the ignition timing. Further, the generation of discharge is continuously repeated by turning ON / OFF the IGBTs 13 and 25 repeatedly. Further, the ignition control circuit 31 controls the switching circuit 27 on the basis of the ignition signal IGt and the discharge period signal IGw, and makes either the contact a-a or the contact bb conductive. Thereby, the turn ratio of the ignition coil 20 is switched.

  By the way, in a lean burn engine or the like for the purpose of improving fuel consumption, an air flow is generated in the cylinder of the engine to increase the combustion speed. However, when the airflow in the cylinder becomes high speed, there is a risk that the discharge stability of the multiple discharge is lowered by the airflow. In this respect, in the present embodiment, at the commanded ignition timing, the secondary voltage V2 is increased by increasing the turns ratio of the ignition coil 20 when the secondary voltage V2 is generated, and then the ignition coil 20 The secondary current is increased by reducing the turns ratio. Thereby, at the time of ignition discharge by the spark plug 26, a sufficient secondary side high voltage that causes dielectric breakdown is generated, and further, discharge stability after the occurrence of discharge is improved.

  Here, the configuration of the ignition coil 20 will be described. FIG. 2 is a cross-sectional view showing the structure of the ignition coil 20, and FIG. 3 is an external view showing the structure of the primary coil 21.

  In FIG. 2, a rod-shaped central core 41 is provided at the center of the ignition coil 20. A secondary coil 22 formed by winding a linear conductor is provided on the outer periphery of the central core 41, and a primary side formed by winding a linear conductor on the outer periphery of the secondary coil 22. A coil 21 is provided. A case 42 and an outer peripheral core 43 are provided on the outer shell of the primary coil 21. The central core 41, the secondary coil 22, the primary coil 21, and the case 42 are each insulated by an insulating layer 44 made of an insulating resin, and an insulating portion 45 is provided on the upper portion of the central core 41. The insulating portion 45 is provided with a joint portion 47 for electrically connecting the connector 46 to which the control signal from the ECU 30 is input and the primary coil 21. A secondary terminal 48 is provided below the central core 41, and the secondary terminal 22 and the one end of the spring 49 are electrically connected by the secondary terminal 48. Therefore, when the ignition coil 20 is attached to the engine 10, the other end of the spring 49 is connected to an electrode portion (not shown) of the spark plug 26.

  In FIG. 3, the primary coil 21 is formed of two linear conductors. Specifically, the primary coil 21 includes a linear conductor that forms the first coil portion 21a and a linear conductor that forms the second coil portion 21b, and the two conductors are arranged in parallel. It is wound around the outer peripheral surface of a primary spool 51 as a cylindrical body. In this case, the primary side coil 21 has few outside irregularities, and the ignition coil 20 can be downsized. Further, when the ignition coil 20 is manufactured, the two coils can be manufactured not by two processes but by a single process, so that the primary coil can be manufactured efficiently.

  At one end portion (upper end portion in the figure) of the primary spool 51, two coil portion terminals 52a connected to the end portion of the first coil portion 21a and two end portions connected to the end portion of the second coil portion 21b are provided. A coil portion terminal 52b is provided. Each coil part terminal 52a, 52b is connected to three joining terminals 53a, 53b, 53c, of which the joining terminal 53b is a common terminal. Here, among the bonding terminals 53a to 53c, 53a and 53b are switching terminals for switching the number of turns of the primary coil 21, and 53c is a terminal connected to the IGBT 25.

  In this case, when the contact point aa is conducted by the switching circuit 27, the joining terminals 53a and 53c are conducted, and the number of turns N1 of the primary coil 21 is the number of turns N1a of the first coil portion 21a and the second coil. This is the sum of the number of turns N1b of the portion 21b (N1 = N1a + N1b). On the other hand, when the switching circuit 27 conducts the contact b-b, the joining terminals 53b and 53c are conducted, and the number of turns N1 of the primary coil 21 becomes the number of turns N1b of the second coil portion 21b (N1 = N1b). Therefore, the turn ratio R of the ignition coil 20 decreases when the contact point a-a conducts, and the turn ratio R increases when the contact point b-b conducts.

FIG. 4 is a time chart for explaining the discharge operation of each part. 4, (a) shows the discharge period signal IGw, (b) shows the ignition signal IGt, (c) shows the state of the IGBT 13, (d) shows the state of the IGBT 25, and (e) shows the secondary voltage V2. , (F) secondary current i2
(G) shows the conductive state between the contacts aa and b-b, respectively.

  In FIG. 4, when the ignition signal IGt is turned on at timing t1, the drive signal IG1 is turned on, and the IGBT 13 is turned on. Energy is stored in the energy storage coil 12 by turning on the IGBT 13. When the ignition signal IGt is turned off at timing t2, which is the ignition timing, the IGBT 13 is turned off and the IGBT 25 is turned on. Then, the energy stored in the energy storage coil 12 and the capacitor 15 is supplied to the primary side coil 21, and the secondary side voltage V <b> 2 is generated to generate a discharge at the spark plug 26. At this time, since bb is connected by the switching circuit 27, the turn ratio R of the ignition coil 20 is increased, and the secondary voltage V2 is increased. The maximum value of the secondary side voltage V2 at this time is 30 kV to 40 kV.

  Thereafter, during the period in which the IGBT 25 is ON, energy is supplied from the energy storage coil 12, whereby a secondary current i <b> 2 flows in the secondary coil 22 and energy is stored in the primary coil 21. . At this time, since the conduction path is switched between the contact points bb and aa by the switching circuit 27, the turn ratio R of the ignition coil 20 is reduced and the secondary current i2 is increased. The secondary current i2 at this time is 50 mA to 250 mA.

  Since the discharge period signal IGw is ON after the timing t2, the IGBTs 13 and 25 are alternately turned ON / OFF and the multiple discharge is performed after the timing t2. Specifically, after the first discharge is generated in the spark plug 26 at the timing t2, the energy is stored in the energy storage coil 12 by turning on the IGBT 13 at the timing t3, and the primary coil 21 is turned off by turning off the IGBT 25. Is stored in the spark plug 26. As a result, the spark plug 26 generates a second discharge following the first discharge.

  Thereafter, when the IGBT 13 is turned off and the IGBT 25 is turned on, the energy of the energy storage coil 12 is supplied to the primary coil. As a result, the spark plug 26 generates a third discharge following the second discharge. Then, energy is accumulated in the primary coil 21 as in the first discharge occurrence.

  Thereafter, until the discharge period signal IGw is turned OFF, ON / OFF of the IGBTs 13 and 25 is switched, and discharge is repeatedly generated. When the discharge period signal IGw is turned off at timing t4, the drive signal IG2 is turned off and the IGBT 25 is turned off. Further, the switching circuit 27 returns the conduction path between the contacts aa and bb. Thereafter, energy is stored in the capacitor 15 by the battery 11 when both the IGBTs 13 and 77 are OFF.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  At the time of ignition discharge by the spark plug 26, the turn ratio R of the ignition coil 20 is increased when the secondary side voltage V2 is generated, and then the turn ratio R is decreased. For this reason, the secondary side voltage V2 can be increased at the start of discharge by the spark plug 26, and thereafter the secondary side current i2 can be increased. Thereby, optimization of the spark discharge generated by the spark plug 26 can be achieved. Therefore, the combustion state in the internal combustion engine can be kept appropriate.

  In a lean burn engine, the in-cylinder flow velocity is particularly high and the discharge stability may be reduced. However, the discharge stability may be improved by changing the turn ratio R of the ignition coil 20 as described above. it can.

  The primary side coil 21 is configured by connecting the first coil portion 21a and the second coil portion 21b in series, and the conduction mode of each of the coil portions 21a and 21b is changed to change the primary side coil 21 of the primary side coil 21. The number of turns was changed. Thereby, the number of turns of the primary coil 21 can be easily changed.

  When performing ignition by multiple discharge, it is necessary to continue the discharge within a predetermined multiple discharge period after the first spark discharge occurs. However, as described above, the secondary current is changed by changing the turns ratio R. The desired discharge state can be maintained within the multiple discharge period by increasing the value. Therefore, the present technology is considered to be particularly useful when applied to multiple discharges.

In the above embodiment, the number of turns of the primary coil 21 is changed in two ways, but the change pattern of the number of turns may be three or more. For example, as shown in FIG. 5, the primary side coil 60 is constituted by three coil portions 60 a, 60 b, and 60 c. In this case, the switching circuit 61 has contacts a to e, and is provided between a power supply system component including the battery 11 and the primary coil 60. The switching circuit 61 conducts any one of the contacts a-c, the contacts a-d, the contacts b-d, and the contacts be-e. The switching circuit 61 switches the conduction path of the power supply system. As a result, the coil unit to be used is switched each time. When the number of turns of each of the coil portions 60a to 60c is N11a, N11b, and N11c, the number of turns N11 of the primary coil 60 is switched by the switching circuit 61 as follows.
-When conducting between the contacts a-c, the number of turns N11 = N11a + N11b + N11c.
-When conducting between the contacts a-d, the number of turns N11 = N11b + N11c.
-When conducting between the contacts b-d, the number of turns N11 = N11b + N11c.
-When conducting between the contacts be-e, the number of turns N11 = N11c.

  In such a case, when a discharge is generated by the spark plug 26, the secondary side voltage V2 can be increased by conducting the connection between the contacts be first, and thereafter, between the contacts ac or between the contacts ad. The secondary current can be increased by making either one conductive. Further, if the secondary side voltage V2 is increased by conducting between the contacts b-d when the secondary side voltage V2 is generated, then the secondary side current is increased by conducting between the contacts a-c. can do.

  In the above embodiment, the present invention is embodied in an ignition control device that performs multiple discharges. However, the present invention can also be applied to an ignition control device that performs single discharges. In such a case as well, the spark discharge generated by the spark plug can be optimized as described above, and the combustion state in the internal combustion engine can be kept appropriate.

It is a block diagram which shows the outline of the ignition control system in this Embodiment. It is a figure which shows the cross section of an ignition coil. It is a figure which shows the structure of a primary side coil. It is a time chart for demonstrating the discharge operation | movement of each part. It is a figure which shows the structure of an ignition control system in another form.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery, 20 ... Ignition coil, 21 ... Primary side coil, 21a ... 1st coil part, 21b ... 2nd coil part, 22 ... Secondary side coil, 26 ... Spark plug, 27 ... Switching circuit, 30 ... ECU 31 ... Ignition control circuit, 41 ... Central core, 51 ... Primary spool, 52a, 52b ... Coil part terminals, 53a-53c ... Joining terminals.

Claims (8)

An ignition coil having a power source connected to the primary coil and an ignition plug connected to the secondary coil;
An ignition device comprising: ignition control means for generating a spark discharge in the spark plug by generating a secondary high voltage in the secondary coil at a specified ignition timing;
The ignition coil has a configuration in which a turn ratio (N2 / N1) between the number of turns N1 of the primary coil and the number of turns N2 of the secondary coil is variable.
The ignition control device for an internal combustion engine, wherein the ignition control means increases the turn ratio of the ignition coil when a discharge occurs at the ignition timing, and then decreases the turn ratio .   The ignition coil has a configuration in which the number of turns of the primary side coil is variable, and the ignition control unit reduces the number of turns of the primary side coil when a discharge occurs at the ignition timing, and then the number of turns. The ignition control device for an internal combustion engine according to claim 1, wherein the ignition control device is increased.   The ignition control means performs a multiple discharge that continuously repeats the discharge by the spark plug in one combustion stroke, increases the turn ratio when the first discharge occurs, and then decreases the turn ratio when the discharge continues. The ignition control device for an internal combustion engine according to claim 1, wherein the ignition control device is an internal combustion engine.   An ignition coil having a power source connected to the primary coil and an ignition plug connected to the secondary coil;
  An ignition device comprising ignition control means for generating a spark discharge in the spark plug by generating a secondary high voltage in the secondary coil at a specified ignition timing;
  The ignition coil has a configuration in which a turn ratio (N2 / N1) between the number of turns N1 of the primary coil and the number of turns N2 of the secondary coil is variable.
  The ignition control means performs a multiple discharge that continuously repeats the discharge by the spark plug in one combustion stroke, increases the turn ratio when the first discharge occurs, and then decreases the turn ratio when the discharge continues. An ignition control device for an internal combustion engine.   The primary coil has a plurality of coil portions, and the ignition control means changes the turns ratio by switching a coil portion that is electrically connected to the power source among the plurality of coil portions. The ignition control device for an internal combustion engine according to any one of claims 1 to 4. Said ignition coil includes a primary coil and a secondary coil formed by winding a linear conductor in a cylindrical body surrounding the central core of the rod-like, and the number of turns of the primary coil and variable, the primary 6. The internal combustion engine according to claim 1 , wherein a plurality of connection terminals are provided in accordance with a change in the number of turns of the side coil, and the plurality of connection terminals are arranged in parallel on one end side of the cylindrical body. Ignition control device. The primary coil has a plurality of coil portions connected in series, and a pair of connection terminals are provided at both ends in a state where the plurality of coil portions are connected in series, and an intermediate between the coil portions. The ignition control device for an internal combustion engine according to claim 6, wherein another connection terminal is provided in the connection portion . The ignition control device for an internal combustion engine according to claim 6 or 7, wherein the plurality of coil portions are formed by winding a plurality of conductors in parallel .

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