JP2010101207A - High-frequency wave generator for spark-ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein, when an air-fuel mixture is ignited by reacting the plasma generated in a combustion chamber through a microwave by spark discharge with an ignition plug, since the microwave is reflected in a transmission line including a waveguide leading the microwave to the combustion chamber and the electric power of the microwave is varied by reflection of the microwave, it is difficult to correctly adjust the output of magnetron if the magnitude of the reflection is not grasped. <P>SOLUTION: This high-frequency wave generator for a spark-ignition internal combustion engine electrically connected to the high-frequency wave supply part of the spark-ignition internal combustion engine igniting the air-fuel mixture by reacting the plasma generated in the combustion chamber through a high-frequency wave by the spark discharge with the ignition plug includes: a high-frequency wave generating source outputting the high-frequency wave for generating the plasma; a resistor connected in series to the high-frequency wave supply part between the high-frequency wave generating source and the high-frequency wave supply part; and a characteristic adjusting means estimating the heating state of the resistor by measuring the voltage at either end of the resistor and adjusting the characteristic of the high-frequency wave output by the high-frequency wave generating source based on the estimated heating state of the resistor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high-frequency generator used in a spark ignition internal combustion engine that generates plasma in a combustion chamber and ignites an air-fuel mixture by plasma and spark discharge by a spark plug.

  2. Description of the Related Art Conventionally, in a spark ignition internal combustion engine mounted on a vehicle, particularly an automobile, an air-fuel mixture in a combustion chamber is ignited at each ignition timing by spark discharge between a center electrode and a ground electrode of a spark plug. In such ignition by an ignition plug, for example, in an internal combustion engine of a type in which fuel is directly injected into a cylinder, if the injected fuel is not distributed at the spark discharge position of the ignition plug, it rarely occurs.

For this reason, in such an internal combustion engine, a plasma atmosphere is generated in the discharge region of the spark plug, for example, as described in Patent Document 1, in order to compensate for the spark discharge of the spark plug, and an arc is generated in the plasma atmosphere. It is known that the discharge is performed to surely ignite the air-fuel mixture in the combustion chamber without applying a higher voltage than in the past and to obtain a stable flame.
JP 2007-32349 A

  By the way, as a method for generating plasma under atmospheric pressure, a method using a magnetron is considered. When using a magnetron, it is possible to change the energy of the plasma to be generated by adjusting the output of the magnetron. By adjusting the plasma energy in this way, it can be optimized according to the operating state of the internal combustion engine.

  However, since the adjustment of the plasma energy is to adjust the output of the magnetron, it is necessary to detect the power of the microwave output from the magnetron and radiated to the combustion chamber through a waveguide or the like. However, in the transmission line including the waveguide that guides the microwave to the combustion chamber, the reflection of the microwave occurs, and the power of the microwave changes due to the reflection. Output adjustment was difficult.

  Therefore, the present invention aims to eliminate such problems.

  That is, the high-frequency generator for a spark-ignition internal combustion engine according to the present invention is a high-frequency supply unit for a spark-ignition internal combustion engine that ignites an air-fuel mixture by reacting plasma generated in a combustion chamber by high frequency with spark discharge by an ignition plug. A spark ignition internal combustion engine high-frequency generator electrically connected to a high-frequency generator that outputs a high-frequency for generating plasma, and a high-frequency supply unit between the high-frequency generator and the high-frequency supply unit A resistor connected in series, and a characteristic adjusting means for measuring a voltage across the resistor to estimate a heat generation state of the resistor, and adjusting a high frequency characteristic output from the high frequency generation source based on the estimated heat generation state of the resistor; It is characterized by providing.

  According to such a configuration, since there is a correlation between the voltage at both ends of the resistor when a high frequency is passed through the resistor and the heat generation state of the resistor, the high frequency generation source and the high frequency supply unit are measured by measuring the voltage at both ends. The heat generation state in the line between the two can be grasped. This heat generation is caused by high-frequency reflection, and the characteristic adjusting means adjusts the characteristics of the electromagnetic wave output from the high-frequency generation source so that the target heat generation state is obtained, and thus the reflection becomes small. It is possible to suppress breakage of the line.

  In the above configuration, the high frequency characteristics include a high frequency phase and a high frequency.

  The present invention is configured as described above, and since there is a correlation between the voltage across the resistor when a high frequency is passed through the resistor and the heat generation state of the resistor, high-frequency generation is achieved by measuring the voltage across the resistor. The heat generation state in the line between the source and the spark plug can be grasped. And according to the grasped heat generation state, the characteristic adjusting means adjusts the characteristic of the electromagnetic wave output from the high-frequency generation source, so that damage to the line between the high-frequency generation source and the spark plug can be suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  A high-frequency generator HFG according to an embodiment described below is electrically connected to an antenna AT which is a high-frequency supply unit provided in a spark ignition internal combustion engine (hereinafter referred to as an engine) 100 including a spark plug 1. .

  FIG. 1 shows an engine 100, which is a spark ignition type internal combustion engine, showing an enlarged mounting portion of a spark plug 1 in one cylinder, for example, of a three-cylinder double overhead camshaft (DOHC) type. 3 and the opening 5 of the exhaust port 4 are arranged opposite to each other centering on a spark plug 1 attached to substantially the center of the ceiling portion of the combustion chamber 6 and are opened at two locations per cylinder. That is, the engine 100 is attached to the cylinder block 7, and the camshafts 9 and 10 are attached to the intake side and the exhaust side of the cylinder head 8 forming the ceiling portion of the combustion chamber 6, respectively. The intake port 2 of the cylinder head 8 is opened and closed by an intake valve 11 that reciprocates when the camshaft 9 rotates, and the exhaust port 4 is opened and closed by an exhaust valve 12 that reciprocates when the camshaft 10 rotates. Is. In addition to the spark plug 1, a microwave supply path 13 that forms part of a transmission line for supplying microwaves, which are electromagnetic waves for generating plasma, into the combustion chamber 6 is provided on the ceiling portion of the combustion chamber 6. It is provided. The antenna AT is provided at the tip of the microwave feed path 13 and is a horn type antenna having a horn portion that spreads outward. The antenna AT is filled with a dielectric 15 so that pressure does not leak from the combustion chamber 6.

  As shown in FIG. 2, the high-frequency generator HFG of this embodiment includes an antenna between a high-frequency generator 16 that outputs a high frequency for generating plasma and an antenna AT that is a high-frequency supply unit 16 and a high-frequency supply unit. A resistor 17 connected in series to the AT and a voltage at both ends of the resistor 17 are measured to estimate a heat generation state of the resistor 17, and a high frequency characteristic output from the high frequency generation source 16 based on the estimated heat generation state of the resistor 17 And a phase adjuster 18 which is characteristic adjusting means for adjusting.

  The high-frequency generation source 16 includes, for example, a magnetron that outputs a high-frequency microwave, and a control circuit that controls the operation of the magnetron. The magnetron itself may be one that is well known in the field of microwave heating or the like. The control circuit controls the output of the magnetron, the phase of the microwave, and the output timing.

  The resistor 17 has a resistance value of several ohms because the magnetron output voltage is high. The resistor 17 forms a part of the microwave transmission line 19 and also serves as a part of a current detector that detects a current value of a standing wave that appears by combining the reflected wave and the traveling wave in the transmission line 19. Function.

  The phase adjuster 18 includes, for example, a microprocessor, and measures the voltage across the input resistor 17 by software and estimates the heat generation state of the resistor 17 based on the measured voltage across the resistor 17. Since the heat generation state of the resistor 17 is substantially proportional to the standing wave current generated in the transmission line 19 to the antenna AT, the heat generation state of the transmission line 19 can be estimated from the heat generation state of the resistor 17. Then, a command (signal) for adjusting the phase of the microwave output from the magnetron is output to the high frequency generation source 16 from the estimated heat generation state. By controlling the phase, the phase of the traveling wave and the reflected wave is minimized.

  In such a configuration, when the air-fuel mixture in the combustion chamber 6 is ignited using the spark plug 1, the engine 100 reacts the spark discharge of the spark plug 1 with the plasma generated in the combustion chamber 6. The spark discharge of the spark plug 1 is made larger than the spark discharge when not reacting with plasma.

  At the time of ignition, a spark discharge is generated in the spark plug 1 by an ignition coil (not shown), and a high-frequency electric field is generated by microwaves almost simultaneously with or immediately after the spark discharge to generate plasma, whereby the combustion chamber 6 It is the structure which burns the inside air-fuel mixture rapidly.

  Specifically, the spark discharge by the spark plug 1 becomes plasma in a high-frequency electric field, and the flame becomes large.

  This is because the flow of electrons due to the spark discharge and the ions and radicals generated by the spark discharge oscillate and meander due to the influence of the high-frequency electric field, resulting in a longer path length and the number of collisions with surrounding water and nitrogen molecules. This is due to a dramatic increase. Water molecules and nitrogen molecules that have been struck by ions and radicals become OH radicals and N radicals, and the surrounding gas that has been struck by ions and radicals is ionized, in other words, a plasma state. The flame will increase dramatically.

  As a result, the air-fuel mixture is ignited by the spark discharge increased by reacting with the high-frequency electric field, so that the ignition region is expanded and the two-dimensional ignition of only the spark plug 1 is changed to the three-dimensional ignition. Therefore, the initial combustion is stabilized, and the combustion rapidly propagates into the combustion chamber 6 as the radicals increase, and the combustion expands at a high combustion rate.

  While the microwave is radiated from the antenna AT to the combustion chamber 6, a standing wave appears in the transmission line 19. This occurs when there is a mismatch between the impedance of the transmission line 19 and the microwave supply path 13 and the impedance of the antenna AT, and a reflected wave is generated. When the standing wave current increases, the voltage across the resistor 17 also increases. Accordingly, the voltage across the resistor 17 is measured to estimate the heat generation of the transmission line, and the phase adjuster 18 adjusts the phase of the microwave based on the estimated heat generation state, thereby reducing the standing wave current. Can do. Therefore, microwaves can be supplied to the combustion chamber 6 without damaging the transmission line 19.

  In addition, this invention is not limited to the above-mentioned embodiment.

  In the above-described embodiment, the characteristic adjustment unit that adjusts the phase of the microwave has been described. However, the microwave characteristic may be a microwave frequency. In this case, the frequency of the microwave is adjusted by controlling the anode current flowing through the anode of the magnetron.

  In addition to the magnetron as described above, the high frequency generation source may be a traveling wave tube or the like, and may further include a semiconductor microwave oscillation circuit.

  In addition, although the beam type antenna has been described in the above-described embodiment, a monopole type antenna may be used.

  Furthermore, the center electrode of the spark plug 1 may function as an antenna to form a high-frequency power feeding unit. In this case, if the high frequency is continuously applied to the center electrode at a constant voltage, the temperature of the center electrode rises excessively, so the high frequency voltage is set to be lower than the upper limit temperature set based on the heat resistance temperature of the center electrode. It is something to control.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, it can be used for a spark ignition type internal combustion engine that uses gasoline or liquefied natural gas as fuel and requires spark discharge by an ignition plug for ignition.

1 is an enlarged sectional view showing a main part of an engine to which an embodiment of the present invention is applied. The block diagram which shows the structure of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Spark plug 6 ... Combustion chamber 16 ... High frequency generation source 17 ... Resistance 18 ... Phase adjuster AT ... Antenna HFG ... High frequency generator

Claims (3)

A high-frequency generator for a spark-ignition internal combustion engine that is electrically connected to a high-frequency supply unit of a spark-ignition internal combustion engine that reacts plasma generated in a combustion chamber with a high frequency and spark discharge by an ignition plug to ignite an air-fuel mixture Because
A high-frequency generator that outputs a high frequency for generating plasma;
A resistor connected in series with the high-frequency supply unit between the high-frequency generation source and the high-frequency supply unit;
A high-frequency for a spark ignition internal combustion engine comprising a characteristic adjusting means for measuring a voltage across the resistor to estimate a heat generation state of the resistor and adjusting a high-frequency characteristic output from a high-frequency generation source based on the estimated heat generation state of the resistance Generator.   2. A spark ignition internal combustion engine high frequency generator according to claim 1, wherein the high frequency characteristic is a high frequency phase.   The spark-ignition internal combustion engine high-frequency generator according to claim 1, wherein the high-frequency characteristic is a high-frequency frequency.

Images