JP2010174691A - Method for controlling ignition of plasma-type igniter and plasma-type igniter using the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a plasma-type igniter, capable of maintaining the ignition stability of a plasma-type ignition plug and a good life of the ignition plug, and an igniter using the method. <P>SOLUTION: In the method of controlling ignition of the plasma-type igniter 100 having the ignition plug 100, an ignition control circuit 20, and an electronic control device, the electronic control device 30 carries out a standard ignition control in which the ignition plug 10 is ignited after the fuel injection by an injector and a non-standard ignition control in which the ignition plug 10 is ignited only before the first fuel injection of the injector. This enables to burn out a deposit deposited in a discharge space 14 in the ignition plug 10 immediately after the engine is started. Further, since the non-standard ignition control is carried out once in a short period from starting the engine to carrying out the standard ignition control, reduction in life of the ignition plug 10 by the non-standard ignition control can be suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ignition control method for a plasma ignition device and a plasma ignition device using the method.

  Instead of a spark plug that ignites an air-fuel mixture by spark discharge, a plasma-type spark plug that generates a high-temperature gas and ignites the air-fuel mixture is known. Specifically, the plasma ignition plug includes a center electrode, an insulating member that holds the center electrode, a ground electrode, and a discharge space that is surrounded by the end surface of the center electrode and the insulating member. The discharge space is provided with an opening that opens into the combustion chamber, and high temperature of several thousand degrees Celsius or more generated by the discharge between the center electrode and the ground electrode is ejected from the opening to ignite the air-fuel mixture.

  Such a plasma type spark plug forms an initial flame nucleus having a larger volume than a spark plug, and high-temperature gas is generated in a discharge space of a substantially closed space. Flame nuclei are formed almost unaffected by the airflow. Therefore, unlike the spark plug, the flame kernel does not blow out by the air flow in the combustion chamber, and the air-fuel mixture can be stably ignited even by supercharging, for example.

  However, such a spark plug ignites the air-fuel mixture with a high-temperature gas of several thousand degrees C. or more, so that the center electrode or the ground electrode is consumed greatly. Further, since the discharge space of the spark plug has an opening that opens toward the combustion chamber, deposits (fuel, oil, etc.) are clogged in the discharge space and in the opening, and as a result, the center electrode and the ground electrode Are short-circuited or have a high insulation resistance. In such a state, the center electrode and the ground electrode are short-circuited or the breakdown voltage is higher than the generated voltage, and a desired discharge may not be generated.

  Therefore, in Patent Document 1, in addition to normal ignition that ignites the air-fuel mixture during the compression process or the expansion process after starting the internal combustion engine, in order to ensure the stability of the discharge by burning out the deposit clogged in the discharge space. Thus, it is disclosed that non-normal ignition is performed in which there is no air-fuel mixture from the normal ignition to the end of the intake process.

JP 2007-170371 A

  However, in recent years, it has been desired to further improve the wear resistance of the plasma type spark plug, and performing the above-mentioned non-regular ignition that promotes the wear of the spark plug to burn out the deposit, It cannot be said that it is a practical means because it cannot guarantee the lifetime.

  Therefore, in view of such circumstances, the present invention provides a control method for a plasma ignition device capable of ensuring ignition stability of a plasma ignition plug and a good life of the ignition plug, and an ignition device using the method. The purpose is to do.

  In order to achieve the above object, the plasma spark plug control method according to the first aspect of the present invention is attached to each cylinder of the internal combustion engine, has a discharge space between the center electrode and the ground electrode, and has a discharge space. A spark plug for igniting a mixture of air and fuel in the combustion chamber by injecting hot gas generated in the discharge space into the combustion chamber from an opening of the discharge space, and a spark plug connected to a power source An ignition control circuit that supplies ignition energy, and an electronic control device that is connected to the ignition control circuit and controls an ignition timing of an ignition plug and a fuel injection timing of an injector that injects fuel into a combustion chamber. In the ignition control method, the electronic control unit performs normal ignition control in which the ignition plug is ignited after fuel injection from the injector and only before the first fuel injection from the injector. And executes the non-normal ignition control performing an ignition plug.

  In other words, when starting the internal combustion engine, non-normal ignition control is executed prior to normal ignition control, so that deposits (fuel, oil, etc.) that may be clogged in the discharge space opening of the spark plug after the previous engine stop Is removed by the pressure of the hot gas generated in the discharge space. This facilitates the generation of high-temperature gas in the subsequent normal ignition control, and improves the ignitability of the spark plug. Since the non-regular ignition control is executed only when the internal combustion engine is started, the life of the spark plug is ensured.

  In addition, since the high temperature gas is generated in the discharge space of the spark plug by the non-normal ignition control that is executed prior to the normal ignition control, the ambient temperature in the discharge space rises. Becomes easier, and the ignitability of the spark plug is further improved.

  In the present invention, it is preferable that the non-regular ignition control is simultaneously executed in all the cylinders of the internal combustion engine. That is, in an internal combustion engine having a plurality of cylinders, the control load of the electronic control device is reduced by simultaneously executing the non-regular ignition control in all the cylinders.

  In the present invention, the ignition energy amount E1 supplied to the spark plug by the normal ignition control is different from the ignition energy amount E2 supplied to the spark plug by the non-normal ignition control. That is, if E1 is constant and the deposit is likely to clog the opening of the discharge space due to the shape of the opening of the discharge space, for example, E2 is made larger than E1, and conversely the deposit is at the opening of the discharge space. When clogging is difficult, the ignitability of the spark plug can be improved by making E2 larger than E1.

  As described above, as a preferable mode when the ignition energy amounts E1 and E2 are made different from each other, E2 may be made smaller than E1. Thereby, consumption of the center electrode and the ground electrode constituting the ignition plug by the non-regular ignition control can be suppressed.

  Further, the present invention is a plasma ignition device for executing the ignition control method described above, and the plasma ignition device can ensure the ignition stability of the plasma ignition plug and the good life of the ignition plug. It becomes possible.

The schematic diagram which shows the structure of the plasma type ignition device which concerns on embodiment of this invention. It is a mimetic diagram of a spark plug concerning an embodiment of the present invention. It is a timing chart of the signal output from the electronic controller which concerns on embodiment of this invention. It is a figure which shows the modification of FIG.

  Hereinafter, a control method for a plasma ignition device embodying the present invention and an embodiment of a plasma ignition device using the method will be described with reference to the drawings.

  FIG. 1 is a schematic view showing a plasma ignition device 100 according to the present invention. The plasma ignition device 100 is installed in each plug hole of a four-cycle vehicle engine (not shown), and generates a hot gas (not shown) as shown in FIG. An ignition control circuit 20 connected to a battery (not shown) to supply ignition energy for generating high temperature gas to the spark plug 10, and an ignition timing of the spark plug 10 and an injector (shown in FIG. And an electronic control unit 30 for controlling the fuel injection timing (not shown). Note that the engine in this embodiment has four cylinders, and a spark plug 10 is attached to each cylinder.

  As shown in FIG. 2, the spark plug 10 includes a columnar center electrode 11 made of a conductive metal material, a substantially cylindrical insulator 12 that insulates and holds the center electrode 11, and a substantially cylindrical shape that covers the insulator 12. And a ground electrode 13 made of metal.

  The front end side of the center electrode 11 is formed in a long axis shape by a conductive material such as iridium or an iridium alloy, for example, and the center electrode center shaft made of a metal material having good electrical conductivity and high thermal conductivity such as a steel material or copper inside. 111 is formed, and the base end side is exposed from the insulator 12 and is electrically connected to a spark discharge circuit unit 21 and a plasma discharge circuit unit 22 described later.

  The ground electrode 13 is formed with an opening 131 that opens toward the combustion chamber (not shown) at the lower end thereof, and a threaded portion 132 that is screwed to the engine on the outer periphery on the tip side. Yes. On the other hand, a housing part 135 for housing and holding the insulator 12 is formed on the base end side, and a hexagonal part 133 for screwing the screw part 132 is formed on the outer periphery of the housing part 135.

  The housing part 135 including the ground electrode 13 is made of a metal material such as nickel or iron.

  A discharge space 14 is formed inside the insulator 12 and discharge is possible between the center electrode 11 and the ground electrode 13.

  The discharge space 14 has a substantially cylindrical shape in which the inner peripheral wall 121 of the insulator 12 extends below the lower end surface of the center electrode 11. In addition, you may form the internal peripheral wall 121 in the substantially cone shape which expands toward the front-end | tip. In the discharge space 14, the distance between the center electrode 11 and the ground electrode 13 is referred to as a discharge gap 15.

  The insulator 12 is made of high-purity alumina or the like excellent in heat resistance, mechanical strength, high-temperature dielectric strength, thermal conductivity, etc., and the tip side ensures electrical insulation between the center electrode 11 and the ground electrode 13. The base end side ensures electrical insulation between the center electrode middle shaft 111 and the housing portion 135.

  The spark plug 10 is mounted so that a ground electrode opening 131 is opened in a combustion chamber of the internal combustion engine 40 (not shown), and the ground electrode 13 is electrically grounded to the internal combustion engine 40.

  Here, the ignition types of the spark plug and the plasma type spark plug 10 will be described. In the spark type ignition, a small current is passed over a long period of time, so that a two-dimensional linear plasma (spark discharge) is formed. On the other hand, since the plasma type ignition supplies a large amount of energy in a short time, the high temperature gas generated by the discharge between the center electrode 11 and the ground electrode 13 is not linear but elliptical and three-dimensional. The shape becomes wider. Plasma ignition is volume ignition because it is ignited by a high-temperature gas spread three-dimensionally. Plasma ignition generates hot gas in the discharge space 14 and jumps out of the discharge space 14 into the combustion chamber of the engine by explosive expansion. In this case, since it can ignite in the place where the electrodes 11 and 13 do not exist, the cooling effect | action of the electrodes 11 and 13 can be suppressed and it leads to the improvement of ignitability.

  Next, the configuration of the ignition control circuit unit that applies a high voltage to the ignition plug 10 having the above configuration will be described with reference to FIG.

  As shown in FIG. 1, the ignition control circuit unit 20 is composed of, for example, a CDI type power supply circuit, and a spark discharge circuit unit 21 for generating a spark discharge in the discharge gap 15 between the center electrode 11 and the ground electrode 13. And a plasma discharge circuit unit 22 for generating a high-temperature gas in the discharge space using the spark discharge as a trigger. In the present embodiment, the center electrode 11 is configured as a negative electrode, and the ground electrode 13 is configured as a positive electrode.

  The spark discharge circuit unit 21 is electrically connected to the center electrode middle shaft 111 of the spark plug 10 and is controlled by the electronic control device 30. Based on normal ignition control and non-normal ignition control, which will be described later, For example, it is a power supply circuit unit that generates a spark discharge by applying a high voltage of 21 kV to cause breakdown of the discharge gap 15.

  Specifically, the spark discharge circuit unit 21 includes a primary coil 211 and a primary circuit connected to the primary coil 211, and a secondary coil 212 and a secondary circuit connected to the secondary coil 212. A secondary current generated in the secondary coil 212 is supplied to the spark plug 10 to generate a spark discharge in the discharge gap 15. Here, the spark discharge in this embodiment is a creeping discharge that discharges on the inner peripheral wall 121 from the center electrode 11 toward the ground electrode 13 and an air that discharges in the air from the center electrode 11 toward the ground electrode 13. It refers to both or either of the discharges.

  The primary coil 211 is formed, for example, by winding an enameled wire having a diameter of 0.3 mm to 0.8 mm for 100 to 222 turns. On the other hand, the secondary coil 212 is formed, for example, by winding an enamel wire having a diameter of 30 μm to 50 μm for 10,000 to 21,000 turns. The primary coil 211 is energized with a primary current based on an ignition pulse signal transmitted from the electronic control unit 30 described later. A secondary current is generated in the secondary coil 212 by a mutual induction effect caused by a change in magnetic flux when the primary current is passed through the primary coil 211.

  A primary side circuit for supplying a primary current to the primary coil 211 includes a spark discharge capacitor 213, a spark discharge power source 214, a thyristor 215, a diode 216, and the like.

  The spark discharge capacitor 213 has, for example, an electric capacity of 1 to 3 μF, and is connected to a spark discharge power source 24 including a DC-DC converter connected to a battery mounted on the vehicle. It is charged to a voltage, for example 210-300V.

  A thyristor 215, which is a switching element, is provided between the spark discharge power source 214 and the positive electrode (left electrode in FIG. 1) of the spark discharge capacitor 213 in the forward direction with respect to the ground. It is turned on based on the ignition pulse signal transmitted from the electronic control unit 30. When the thyristor 215 is turned on, the spark discharge capacitor 213 in which a predetermined amount of electricity is stored is discharged through the thyristor 215, and a primary current is passed through the primary coil 211. A diode 216 connected to the negative electrode of the spark discharge capacitor 213 rectifies the primary current and generates a desired secondary voltage in the secondary coil 212 described later.

  Subsequently, a secondary side circuit for supplying a secondary current to the secondary coil 212 includes a diode 217, an electric resistance 218, and the like. The secondary current generated in the secondary coil 212 due to the mutual induction action between the primary coil 211 and the secondary coil 212 is energized to the spark plug 10 via the diode 217 and the electric resistance 218. The diode 217 prevents the plasma current from flowing from the plasma discharge circuit unit 22 described later to the secondary coil 212 side, while the electric resistance 218 provided on the downstream side of the diode 217 prevents the plasma discharge circuit unit 22 described later. Removes noise caused by the flowing current.

  Next, the plasma discharge circuit unit 22 is electrically connected to the center electrode 11 of the spark plug 10 and controlled by the electronic control device 30, and triggered by the occurrence of spark discharge in the discharge gap 15, It is a power supply circuit part for supplying energy and generating high temperature gas.

  Specifically, the plasma discharge circuit unit 22 includes a plasma discharge capacitor 221, a plasma discharge power source 222, two diodes 223, 224, and the like. Generate a discharge.

  The plasma discharge capacitor 221 has an electric capacity of 0.2 to 2 μF, for example, and is supplied with a predetermined voltage, for example, 600 to 900 V by a plasma discharge power source 222 including a DC-DC converter connected to the battery. Is applied. The charging of the plasma discharge capacitor 221 is terminated by turning off the plasma discharge power supply 222 at the start of energization of the primary current (when the ignition pulse signal is transmitted to the thyristor 215), for example. Thereafter, the voltage of the discharge gap 15 drops due to the spark discharge generated in the spark plug 10 and falls below the voltage of the plasma discharge capacitor 31. Energized. The two diodes 223 and 224 prevent the secondary voltage of the spark discharge circuit unit 21 from being applied to the plasma discharge capacitor 221 and the plasma discharge power supply 222 to be destroyed.

  Next, the electronic control unit 30 executes normal ignition control for igniting the spark plug 10 after fuel injection from the injector and non-regular ignition control for igniting the spark plug 10 only before the first fuel injection of the injector. .

  The electronic control unit 30 is mainly composed of a microcomputer composed of a CPU, ROM, RAM, etc. (not shown), and executes various control programs stored in the ROM, so that ignition control is performed according to each engine operating condition. Etc. Specifically, as the ignition control, the electronic control unit 30 determines an ignition timing (based on various detection signals input from a crank angle sensor, an intake pipe pressure sensor, and the like, which are attached near the crankshaft of an unillustrated engine, as needed. Ignition timing, fuel injection timing), an ignition pulse signal is output to the thyristor 215 based on the calculation result, and a fuel injection pulse signal is output to an injector drive circuit (not shown). Non-regular ignition control is performed.

  Further, the electronic control unit 30 charges the plasma discharge capacitor 31 by driving and controlling the plasma discharge power supply 222. Specifically, the electronic control unit 30 turns on the plasma discharge power source 222 when the predetermined standby time has elapsed from the ignition timing and plasma discharge is completed, starts charging the plasma discharge capacitor 221, and performs the next ignition. The charging of the plasma discharge capacitor 221 is stopped by turning off the plasma discharge power supply 222 at a certain time before the timing, for example, at the start of energization of the primary coil 211. In other words, the plasma discharge capacitor 221 repeatedly performs charging between ignition timings and discharging at the ignition timing.

  The present invention is an ignition control method characterized by the operation of the electronic control device 30 described above, and the characteristic operation of the embodiment of the present invention will be described below. FIG. 3 shows an ignition pulse signal and a fuel injection pulse that are input from the electronic control unit 30 to the spark discharge circuit unit 21 for each spark plug 10 disposed in each of the first to fourth cylinders of the four-cycle engine. It is a timing chart which shows the input time of a signal. As shown in FIG. 3, when the engine is started, the electronic control unit 30 executes non-normal ignition control for generating an ignition pulse signal before generating a fuel injection pulse signal for injecting fuel. Specifically, non-regular ignition control for completing ignition of the spark plug 10 is executed before the fuel injection pulse signal is input to the injector and the injector actually injects fuel. That is, the ignition plug 10 is ignited until the crankshaft of the engine starts to rotate and the fuel injection pulse signal is input from the electronic control unit 30 to the injector. Since the hot gas generated in the spark plug 10 has a high temperature of several thousand degrees Celsius, the deposit clogged in the discharge space 14 and the opening 131 of the ground electrode 13 can be burned out after the previous engine stop. Thereby, the contamination state of the discharge space 14 and the opening 131 is eliminated and reduced. Therefore, during normal ignition control in which the ignition plug 10 is ignited with subsequent fuel injection, high-temperature gas is easily injected from the discharge space 14 toward the combustion chamber, and the ignition stability of the ignition plug 10 with respect to the air-fuel mixture is improved. .

  Further, the non-regular ignition without fuel injection by the non-regular ignition control is performed only once from the start to the stop of the engine. Therefore, the consumption of the center electrode 11 or the ground electrode 13 can be suppressed as compared with the plasma ignition device 100 that always performs irregular ignition in a four-cycle engine.

  Furthermore, when the engine is started, non-normal ignition control is executed prior to normal ignition control, so that high-temperature gas is generated in the discharge space 14 of the spark plug 10 and the ambient temperature in the discharge space 14 rises. Generation of high-temperature gas during normal ignition control is facilitated, and the ignition stability of the spark plug 10 is further improved.

  In the present embodiment, the non-regular ignition control is performed on the spark plug 10 provided in each of the first to fourth cylinders of the four-cycle engine. At this time, each non-regular ignition control in each cylinder may be executed at different timings. However, in this case, the processing in the electronic control device 30 becomes complicated, and the calculation speed of the electronic control device 30 is reduced. There is a risk of lowering. Therefore, in order to reduce the load on the electronic control unit 30 by the non-normal ignition control to the maximum reduction, it is preferable to perform the non-normal ignition control simultaneously in all the cylinders as shown in FIG.

Further, it is preferable that the ignition energy amount E1 supplied to the spark plug 10 by the normal ignition control and the ignition energy amount E2 supplied to the spark plug 10 by the non-normal ignition control are different from each other. That is, when deposits clogged up in the discharge space 14 increase due to the shape of the discharge space 14, the deposit is burned out by increasing E2 larger than E1, and conversely the deposit clogged up in the discharge space 14 When there is little deposition, the deposit is burned out by making E2 smaller than E1. In order to improve the life of the spark plug 10, it is preferable to make E1 applied to burn out the deposit as small as possible. Thereby, high-temperature gas generation during normal ignition control is facilitated, and the life of the spark plug 10 can be ensured.
(Other embodiments)
In the above embodiment, the ignition pulse signal and the fuel injection pulse signal are input to each of the spark plug 10 and the injector without overlapping in time, but after the ignition pulse signal is input to the spark plug 10. The fuel injection pulse signal may be input to the injector before the spark plug 10 is actually ignited. That is, if the deposit clogged in the discharge space 14 and the opening 131 can be burned out by the heat of the high-temperature gas generated in the discharge space 14 or the deposit can be ejected from the opening 131 by the pressure of the high-temperature gas, the non-normal ignition control is performed. The ignition pulse signal at and the fuel injection pulse signal during normal ignition control may overlap in time.

  Further, in the above-described embodiment, the necessary charge accumulated in the spark discharge capacitor 213 is discharged to the primary coil 211 at once, a sudden magnetic flux change is given to the ignition coil 10, and a high voltage is generated in the secondary coil 212. However, a switching element (not shown) such as a MOS-FET is provided in the primary side circuit of the spark discharge circuit unit 21, and an induced electromotive force is generated in the secondary coil 212 by turning on and off the switching element. A full transistor system in which a high voltage is applied to the spark plug 10 may be employed.

  In the above embodiment, after the engine is started, the non-normal ignition control is executed after the crankshaft rotates. However, as shown in FIG. 4, the non-normal ignition control is executed when the engine is started, that is, when the crankshaft rotates. May be.

10 ... spark plug,
11 ... center electrode,
111 ... Center electrode middle shaft 12 ... Insulating member,
121 ... Inner wall,
13: Ground electrode,
131 ... opening,
132 ... screw part,
133 ... hexagonal part,
135 ... Housing part,
14 ... discharge space,
15 ... discharge gap,
20 ... Ignition control circuit,
21 ... Spark discharge circuit part,
211 ... primary coil,
212 ... secondary coil,
213 ... Spark discharge capacitor,
214 ... Spark discharge power source 215 ... Thyristor,
216, 217 ... diode,
218 ... electric resistance,
22: Circuit portion for plasma discharge,
221: Plasma discharge capacitor,
222: Power source for plasma discharge,
223, 224 ... diodes,
30 ... Electronic control unit,
100: Plasma ignition device

Claims (5)

It is attached to each cylinder of the internal combustion engine, has a discharge space between a center electrode and a ground electrode, and high-temperature gas generated in the discharge space is ejected into the combustion chamber from the opening of the discharge space in the discharge space A spark plug for igniting a mixture of air and fuel in the combustion chamber,
An ignition control circuit connected to a power source to supply ignition energy to the spark plug;
In an ignition control method for a plasma ignition device, comprising: an electronic control device that is connected to the ignition control circuit and controls an ignition timing of the ignition plug and a fuel injection timing of an injector that injects the fuel into the combustion chamber.
The electronic control unit executes normal ignition control for igniting the spark plug after fuel injection of the injector and non-regular ignition control for igniting the spark plug only before the first fuel injection of the injector. An ignition control method for a plasma ignition device.   2. The ignition control method for a plasma ignition device according to claim 1, wherein the electronic control unit simultaneously performs the non-regular ignition control in all the cylinders of the internal combustion engine.   The electronic control unit controls the ignition energy amount E1 supplied to the spark plug by the normal ignition control and the ignition energy amount E2 supplied to the spark plug by the non-normal ignition control to be different from each other. The ignition control method for a plasma ignition device according to claim 1 or 2.   The ignition control method for a plasma ignition device according to claim 3, wherein the ignition energy amount E2 is controlled to be smaller than the ignition energy amount E1.   A plasma ignition device that realizes the ignition control method according to any one of claims 1 to 4.

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