JP2010038138A - Plasma ignition device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein plasma discharge resulting from a contact failure between a conductive spring and a plasma ignition plug is generated with momentary separation of a contact between the conductive spring and the plasma ignition plug due to vibration generated by an internal combustion engine, thus causing the melt at the base end of the plasma ignition plug to worsen the ignitability thereof. <P>SOLUTION: In a plasma ignition device, the ignition plug 11 and a high voltage terminal 42 are fit to each other, and the ignition plug 11 and an ignition circuit 10 are reliably and electrically connected to each other with a flexible conductive member 43 having both ends fixed to the high voltage terminal 42 and a high voltage terminal 41, respectively. This improves the reliability of electrically connecting the ignition circuit 10 and the ignition plug 11 to each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma ignition device for an internal combustion engine that forms plasma and ignites an air-fuel mixture.

  2. Description of the Related Art Conventionally, for example, spark plugs that ignite an air-fuel mixture by spark discharge are used in ignition devices for internal combustion engines for automobiles. In recent years, there has been a demand for higher output and lower fuel consumption of internal combustion engines, and as an ignition device with excellent ignitability that can be ignited reliably even in a lean mixture with a fast combustion spread and a higher ignition limit air-fuel ratio There has been proposed a plasma ignition device that ignites a gas mixture by injecting a gas in a plasma state (hereinafter referred to as plasma gas) into a combustion chamber (see, for example, Patent Document 1).

  The plasma ignition device is fixed to the combustion chamber side of the plug hole, and emits plasma gas toward the combustion chamber, and an ignition circuit for applying high voltage and large current to the plasma ignition plug And a plasma driver accommodated in the plug hole for electrically connecting the ignition circuit and the plasma spark plug.

The tip of the plasma driver on the combustion chamber side is composed of a rubber-made plug cap that is cylindrical, and the plug cap is fitted to the base end side (opposite to the combustion chamber) of the plasma ignition plug. Further, a conductive spring is inserted inside the plug cap, and the high voltage terminal of the ignition circuit and the base end side of the plasma spark plug are electrically connected only by the urging force of the conductive spring.
JP 2007-287665 A

  When attaching the above-described plasma ignition device to an internal combustion engine, first, a plasma ignition plug is screwed and fixed to the combustion chamber side of the plug hole, and then a high voltage terminal and a conductive spring are built in from the opening on the base end side of the plug hole. The plasma driver is housed in the plug hole and assembled so that the front end side of the conductive spring is biased toward the base end side of the plasma ignition plug.

  In the plasma ignition device attached to the internal combustion engine in this way, the electrical connection between the high voltage terminal and the plasma ignition plug is achieved simultaneously with fitting the plasma driver to the plasma ignition plug. In other words, conventionally, when the plasma driver is fitted to the plasma spark plug, the other end of the conductive spring, one end of which is held on the distal end side of the high voltage terminal, is biased toward the base end side of the plasma spark plug, The high voltage terminal and the plasma ignition plug are electrically connected via a conductive spring, and plasma gas is ejected from the plasma ignition plug to the combustion chamber side to ignite the mixture.

  However, in the case of a plasma ignition plug in which a current of 100 A or more that is much larger than that of a spark plug in which a small current such as several hundred mA is applied, vibration applied to the internal combustion engine from the outside or generated from the internal combustion engine When the contact point between the front end side of the conductive spring and the base end side of the plasma spark plug, which are electrically connected only by the urging force, is instantaneously separated by the generated vibration, it is between the conductive spring and the plasma spark plug. Will cause plasma discharge. When plasma discharge repeatedly occurs between the front end side of the conductive spring and the base end side of the plasma spark plug, the base end side of the plasma spark plug melts and the plasma spark plug body discharges the desired plasma discharge to the combustion chamber. There is a risk that it cannot be generated. That is, in a configuration in which the high voltage terminal on the ignition circuit side and the plasma spark plug are brought into contact with each other only by the urging force of a conductive spring that is not constrained at both ends, the plasma is applied with a high voltage and a large current. In the plasma ignition device having a spark plug, the reliability of the electrical connection cannot be guaranteed.

  In view of the above circumstances, an object of the present invention is to provide a plasma ignition device that improves the reliability of electrical connection between an ignition circuit and a plasma ignition plug.

  In order to solve the above problems, a plasma ignition device according to claim 1 is a center electrode fixed to a combustion chamber side opening of a plug hole of an internal combustion engine and held by an insulating member, and a center electrode And a plasma ignition plug that generates a plasma gas between the center electrode and the ground electrode, and ignition that applies a high voltage and a large current to the plasma ignition plug A circuit, a high-voltage terminal electrically connected to the ignition circuit, a high-voltage terminal that is spaced apart from the high-voltage terminal and is fitted to and electrically connected to the plasma ignition plug, and one end of the high-voltage terminal The other end is fixed to the high-voltage terminal, and the conductive member that electrically connects the high-voltage terminal and the high-voltage terminal is disposed outside the conductive member. An elastic member for energizing, high voltage terminal, high-tension terminal, encapsulating the conductive member and the elastic member, characterized in that it comprises a plasma driver housed in the plug hole.

  In this way, the plasma spark plug and the high-voltage terminal are fitted together, and the high-voltage terminal and the high-voltage terminal are electrically connected with the conductive member having both ends fixed to the high-voltage terminal and the high-voltage terminal, thereby generating plasma. The reliability of the electrical connection between the spark plug and the ignition circuit is improved.

  In addition, since the elastic member included in the plasma driver urges the high-pressure terminal toward the plasma-type spark plug when the plasma-type ignition device is assembled, the high-pressure terminal and the plasma-type spark plug can be securely fitted. it can. Therefore, the reliability of electrical connection between the ignition circuit and the plasma spark plug is improved.

  According to the second aspect of the present invention, the elastic member is a metal spring, and one end of the elastic member is fixed to the high voltage terminal and the other end is fixed to the high voltage terminal. That is, the high-voltage terminal and the high-voltage terminal are electrically connected by an elastic member that is a metal spring. At this time, since the conductive member and the elastic member are connected in parallel between the high-voltage terminal and the high-voltage terminal, the electrical resistance between the high-voltage terminal and the high-voltage terminal can be reduced between the high-voltage terminal and the high-voltage terminal only by the conductive member. It becomes smaller than the case where it connects electrically. That is, in the plasma ignition device, electric loss between the high voltage terminal and the high voltage terminal is reduced.

  According to invention of Claim 3, an elastic member, a high voltage | pressure terminal, and a high voltage terminal are fixed by welding. That is, similarly to the conductive member, both ends of the elastic member are welded to the high-voltage terminal and the high-voltage terminal, respectively, thereby improving the reliability of the electrical connection between the elastic member, the high-voltage terminal, and the high-voltage terminal.

  According to the fourth aspect of the present invention, the plurality of elastic members are disposed in parallel between the high voltage terminal and the high voltage terminal. As a result, the plurality of elastic members urge the high-voltage terminal and the high-voltage terminal, thereby increasing the force for urging both of the high-voltage terminal and the ignition circuit. In addition, the high-pressure terminal and the plasma spark plug can be more reliably brought into contact with each other. Therefore, the reliability of electrical connection between the ignition circuit and the plasma spark plug is improved.

  In order to solve the above problem, a plasma ignition device according to claim 5 is a center electrode fixed to a combustion chamber side opening of a plug hole of an internal combustion engine and held by an insulating member; A plasma ignition plug having a center electrode and a ground electrode arranged through a discharge gap, and generating plasma gas between the center electrode and the ground electrode; and a high voltage and a large current are applied to the plasma ignition plug. An ignition circuit to be applied; a high-voltage terminal electrically connected to the ignition circuit; a high-voltage terminal that is spaced apart from the high-voltage terminal and is fitted to and electrically connected to the plasma ignition plug; and one end Is connected to the high-voltage terminal and the other end is fixed to the high-voltage terminal, and includes a conductive member that electrically connects the high-voltage terminal and the high-voltage terminal, and includes the high-voltage terminal, the high-voltage terminal, and the conductive member. A plasma ignition device including a plasma driver housed therein, and between the high-pressure terminal and the high-pressure terminal on the inner surface of the plasma driver, there is a locking portion having a facing surface facing the plasma ignition plug. The high pressure terminal is in contact with the end surface of the ignition circuit side.

  In this way, the plasma ignition plug and the high-voltage terminal are fitted together, and the high-voltage terminal and the high-voltage terminal are electrically connected to each other by a conductive member having both ends fixed. The reliability of the electrical connection between the circuit and the plasma spark plug can be improved.

  Further, by locking the high pressure terminal to the base end side by the opposing surface of the locking portion, the plasma ignition plug and the high pressure terminal are integrated with vibration applied to the internal combustion engine from the outside or vibration generated from the internal combustion engine. And vibrate. Therefore, the fitting between the high-pressure terminal whose one end is fixed to the conductive member and the base end side of the plasma spark plug is reliably achieved, and the reliability of the electrical connection between the ignition circuit and the plasma spark plug is improved. .

  Furthermore, since the end face of the ignition circuit side of the high voltage terminal and the facing surface are in contact with each other, the high voltage terminal is locked to the base end side by the locking portion, so that when the plasma ignition device is assembled, The plasma spark plug can be securely fitted. Therefore, the reliability of electrical connection between the ignition circuit and the plasma spark plug is improved.

  According to the invention described in claim 6, the conductive member is fixed to the high voltage terminal and the high voltage terminal by welding. Thereby, the reliability of the electrical connection between the conductive member, the high voltage terminal, and the high voltage terminal is improved.

  According to the invention described in claim 7, the conductive member is fixed to the high-voltage terminal and the high-voltage terminal by the conductive adhesive. Thereby, the reliability of the electrical connection between the conductive member, the high voltage terminal, and the high voltage terminal is improved.

  According to the invention described in claim 8, the conductive member is formed by twisting a plurality of thin wires. Thereby, it has a big flexibility compared with the thick lead wire which consists of one conducting wire of the same diameter. Therefore, when stress is applied to the conductive member due to vibration of the internal combustion engine in which the plasma ignition device is installed or vibration applied to the plasma ignition device from the outside, the conductive member absorbs the stress by its flexibility. In addition, disconnection of the conductive member can be prevented.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  The plasma ignition device 100 according to the present embodiment generates plasma on the ignition plug 11 based on an ignition signal generated from a plasma ignition plug 11 that generates plasma discharge and an electronic control device (hereinafter referred to as ECU 60). An ignition circuit 10 to be generated and a plasma driver 40 which is attached in the plug hole 2 and electrically connects the ignition circuit 10 and the ignition plug 11 are configured.

  FIG. 1 is a schematic diagram showing circuit configurations of the ignition plug 11 and the ignition circuit 10 of the present embodiment.

  As shown in FIG. 1, a plasma-type spark plug 11 fixed to an opening of a combustion chamber 3 side of a plug hole 2 of an engine block 1 has a center electrode 12 and a substantially cylinder that is insulated and held so as to cover the center electrode 12. And a metal ground electrode 14 formed in a substantially annular shape so as to cover the insulator 13. A discharge gap 15 for generating a spark discharge, which will be described later, is formed between the front end of the center electrode 12 on the combustion chamber 3 side and the front end of the ground electrode 14 on the combustion chamber 3 side. A space surrounded by the insulator 13 is formed as a discharge space 16 in which plasma discharge, which will be described later, is generated. When a large current of 100 A or more is applied to the center electrode 12 of the spark plug 11, a high-temperature and high-pressure plasma gas is generated in the discharge space 16, and this plasma gas is injected into the combustion chamber 3.

  FIG. 2 is a schematic diagram showing attachment of the ignition circuit 10, the ignition plug 11, and the plasma driver 40 to the engine block 1. Here, for simplicity, in the axial direction of the ignition plug 11 in FIG. 2, the combustion chamber 3 side is the front end side, and the opposite side to the combustion chamber 3 is the base end side.

  The front end side of the center electrode 12 shown in FIGS. 1 and 2 is formed in a long axis shape by a conductive material such as iridium, an iridium alloy, or copper, for example. Inside the center electrode 12 is formed a center electrode center shaft 12a made of a metal material having good conductivity and high thermal conductivity such as a steel material, and its base end side is exposed from the insulator 13 and is electrically connected to the ignition circuit 10. Connected.

  The insulator 13 is made of high-purity alumina or the like excellent in heat resistance, mechanical strength, dielectric strength at high temperatures, thermal conductivity, and the like, and has a substantially cylindrical shape that holds the center electrode 12.

  The ground electrode 14 constitutes a housing that holds the insulator 13 at the base end side, and the spark plug 11 is fixed to the engine block 1 so that the ground electrode 14 is exposed in the combustion chamber 3. A screw portion 14a for electrically grounding the engine block 1 is formed. A housing hexagonal portion 14b for tightening the screw portion 14a is formed on the base end side of the screw portion 14a of the ground electrode 14. The housing including the ground electrode 14 is formed of a metal material such as nickel or iron.

  An ignition circuit 10 for applying a high voltage and a large current is electrically connected to the ignition plug 11 described above. The ignition circuit 10 is driven by power supplied from the battery 17 and generates a spark discharge along the inner surface of the insulator 13 that forms the discharge space 16, and the spark discharge circuit 16 includes a spark discharge circuit portion 20. And a plasma discharge circuit unit 30 for generating plasma discharge.

  The spark discharge circuit unit 20 includes a primary coil 21 and a secondary coil 22, and a control circuit 23 that controls energization of the primary coil 21. The primary coil 21 is connected to the control circuit 23, and the secondary coil 22 is connected to the spark plug 11 via a diode 24 and a spark discharge lead wire 25. The diode 24 prevents the plasma current from the plasma discharge circuit unit 30 from flowing to the secondary coil 22 side. In addition, the electric resistance 26 provided on the downstream side of the diode 24 is for removing noise caused by plasma current from a plasma discharge circuit section 30 described later.

  The control circuit 23 is, for example, a capacitive discharge (CDI) system including a spark discharge capacitor 23b. The control circuit 23 charges the spark discharge capacitor 23b with a spark discharge power source 23a composed of a DC-DC converter or the like, and at a desired ignition timing. By discharging the spark discharge capacitor 23b, a high voltage of 20 to 40 kV is induced in the secondary coil 22 due to a sudden change in magnetic flux of the primary coil 21. When the high voltage is applied as a discharge voltage to the spark plug 11 through the diode 24, spark discharge occurs in the discharge gap 15 of the spark plug 11.

  As shown in FIG. 3, a switching element 123b is provided in place of the spark discharge capacitor 23b, and a so-called inductive discharge (full discharge) that induces a high voltage in the secondary coil 22 by switching the switching element 123b from on to off. A transistor) type control circuit 23 may be employed.

  The plasma discharge circuit unit 30 includes a plasma discharge capacitor 32 that is charged by a plasma discharge power source 31 formed of a DC-DC converter or the like. The charge accumulated in the plasma discharge capacitor 32 is transferred to a diode 33. And is supplied to the spark plug 11 through the plasma discharge lead wire 34. Specifically, when a high voltage exceeding the dielectric breakdown voltage is applied to the discharge gap 15 of the spark plug 11 by the above-described spark discharge circuit section 20, a spark discharge is generated along the inner surface of the insulator 13 constituting the discharge space 16. Is generated, and the spark discharge reduces the voltage of the discharge gap 15. When the voltage of the discharge gap 15 falls below the voltage of the plasma discharge capacitor 32, a large current exceeding 100 A flows from the plasma discharge capacitor 32 into the discharge gap 15 of the spark plug 11, and plasma discharge is generated. A high-temperature and high-pressure plasma gas having a high density energy of, for example, 100 to 200 mJ generated by this plasma discharge expands in the discharge space 16, and the plasma gas is injected from the discharge space 16 into the combustion chamber 3. As a result, the mixture of fuel and air in the combustion chamber 3 is ignited and used for combustion. The diode 33 is provided to prevent the current from the secondary coil 22 from flowing to the plasma discharge capacitor 32 side.

  The above-described spark discharge circuit unit 20 and plasma discharge circuit unit 30 are controlled by an ECU 60 mounted on the vehicle. The ECU 60 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) composed of a CPU, a ROM, a RAM, and the like, and executes various control programs stored in the ROM, thereby injecting fuel according to each engine operating state. Various controls such as control and ignition control are performed. Specifically, as the ignition control, a microcomputer (not shown) of the ECU 60 calculates an ignition timing based on various detection signals that are input as needed from a crank angle sensor, an intake pipe pressure sensor, or the like attached to the engine, Based on the calculation result, charging and discharging signals of the spark discharge capacitor 23b are output.

  The microcomputer controls the plasma discharge power supply 31 by controlling the driving of the plasma discharge power supply 31. Specifically, as the charge control, the microcomputer starts charging the plasma discharge capacitor 32 by turning on the plasma discharge power source 31 when a predetermined standby time has elapsed from the ignition timing and the plasma discharge is completed. The charging of the plasma discharge capacitor 32 is stopped by turning off the plasma discharge power source 31 at a predetermined timing (for example, when energization of the primary coil 21 is started) before the next ignition timing. That is, in the plasma discharge capacitor 32, charging between the ignition timings and discharging at the ignition timing are repeatedly performed.

  Next, the plasma driver 40 attached in the plug hole 2 and electrically connecting the ignition circuit 10 and the ignition plug 11 will be described in detail below.

  FIG. 4 is an enlarged view of the plasma driver 40 shown in FIG. As shown in FIG. 4, the housing of the plasma driver 40 accommodated in the plug hole 2 is composed of a cylindrical member 40a, a connecting member 40b, and a plug cap 40c. The cylindrical member 40a and the connecting member 40b are made of a hard resin such as PBT, and both are fixed by fitting or bonding. Further, a rubber plug cap 40c is fitted to the distal end side of the connecting member 40b, and the distal end side of the plug cap 40c is fitted to the proximal end side of the spark plug 11.

  As shown in FIG. 5, which is an enlarged view of part A in FIG. 4, a high voltage terminal 41, a high voltage terminal 42 (42 a, 42 b), a conductive member 43, and an elastic member 44 are disposed inside the plasma driver 40. ing. Specifically, the conductive member 43 and the elastic member 44 are disposed inside the connecting member 40b and the plug gap 40c where the distal end side of the high-voltage terminal 41 and the proximal end side of the high-voltage terminal 42 face each other, and at least conductive. The member 43 electrically connects the high voltage terminal 41 and the high voltage terminal 42, whereby the ignition circuit 10 and the ignition plug 11 are electrically connected.

  Hereinafter, each component of the plasma driver 40 will be described in detail.

  6A is a perspective view of the high-voltage terminal 41, and FIG. 6B is a sectional view in the axial direction thereof. The high voltage terminal 41 made of a conductive metal such as phosphor bronze is fixed inside the base end side of the connecting member 40b. As shown in FIGS. 6A and 6B, the high-voltage terminal 41 has a bottomed cylindrical shape that opens to the base end side, and more specifically, toward the base end side at the center of the bottom surface 41 a of the high-voltage terminal 41. A protruding convex portion 41b is formed. The spark discharge lead wire 25 and the plasma discharge lead wire 34 are joined to the inner peripheral surface of the high-voltage terminal 41 by soldering or the like, and the spark discharge circuit portion 20, the plasma discharge circuit portion 30, the high-voltage terminal 41, and the like. Are electrically connected to each other. On the other hand, a conductive member 43 described later is joined to the inner surface of the convex portion 41b of the high-voltage terminal 41 by soldering or the like, and the high-voltage terminal 41 and the conductive member 43 are electrically connected. The shape of the high-voltage terminal 41 is not particularly limited as long as the spark discharge lead wire 25, the plasma discharge lead wire 34, and the conductive member 43 can be securely fixed. The shape is preferably fixable.

  A high voltage terminal 42 made of a conductive metal such as brass is provided inside the distal end side of the plug cap 40 c and on the distal end side of the high voltage terminal 41. As shown in FIGS. 7A and 7B showing a perspective view of the high-voltage terminal 42 and an axial cross-sectional view thereof, the high-voltage terminal 42 includes a small-diameter cylindrical portion 42a located on the proximal end side and a distal end side. It is comprised by the fitting part 42b which exhibits the bottomed cylindrical shape opened to the front end side with the large diameter located in this. A conductive member 43 is inserted into the cylindrical portion 42a and joined by soldering or the like at the boundary surface with the fitting portion 42b. The inner diameter of the fitting portion 42b is substantially the same as the outer diameter of the center electrode middle shaft 12a, and the fitting portion 42b and the center electrode middle shaft 12a are securely fitted.

  A conductive member 43 and an elastic member 44 are disposed between the distal end side of the high voltage terminal 41 and the proximal end side of the high voltage terminal 42.

  The conductive member 43 includes, for example, nickel, chromium, and the like, and is a single wire in which five bundles of ten stainless steel wires having a wire diameter of 0.1 mm and 60 copper wires having a wire diameter of 0.05 mm are combined. is there. As described above, one end of the conductive member 43 is joined by the convex portion 41 b of the high voltage terminal 41 and the other end is joined by the cylindrical portion 42 a of the high voltage terminal 42. The conductive member 43 has a wire diameter of about 1.5 mm and is made of a plurality of thin wires (stainless steel wire, copper wire). Therefore, the conductive member 43 is more flexible than a single wire having the same diameter. Have Therefore, when the distance between the high voltage terminal 41 and the high voltage terminal 42 is reduced by the pressure applied from the inside of the combustion chamber 3 or the vibration applied from the outside, the conductive member 43 is bent, so that both ends of the conductive member 43 are bent. Stress concentration at the joint is avoided and disconnection is difficult. Therefore, the high voltage terminal 41 and the high voltage terminal 42 are reliably electrically connected by the conductive member 43.

  The elastic member 44 is, for example, a metal spring having a diameter of 10 mm, a natural length of 35 mm, a wire diameter of 0.6 mm, and a contact length of 6.6 mm, and is configured by a piano wire type A. One end of the elastic member 44 is joined to the bottom surface 41 a of the high-voltage terminal 41, and the other end is in contact with the different-diameter boundary surface 42 c of the high-voltage terminal 42. That is, the high voltage terminal 41 and the high voltage terminal 42 are electrically connected via the elastic member 44. Accordingly, the distal end side of the high-voltage terminal 41 and the proximal end side of the high-voltage terminal 42 are electrically connected in parallel by the conductive member 43 and the elastic member 44, and the high-voltage terminal 41 and the high-voltage terminal 42 are connected to each other. The electrical resistance at is lower than when the high voltage terminal 41 and the high voltage terminal 42 are electrically connected by the conductive member 43 alone. For this reason, the electrical loss between the spark discharge circuit unit 20 and the plasma discharge circuit unit 30 and the spark plug 11 is reduced.

  In addition, it is preferable that the elastic member 44 is urged toward the distal end side and the elastic member 44 is fitted to the outer peripheral surface of the cylindrical portion 42a at the different-diameter boundary surface 42c between the cylindrical portion 42a and the fitting portion 42b. In this way, by fitting the elastic member 44 to the cylindrical portion 42a, the high-voltage terminal 42 is connected by the elastic member 44 and the high-voltage terminal 42 is centered. Fitting with the middle shaft 12a is facilitated.

  Here, a method for assembling the plasma driver 40 and the spark plug 11 of the present embodiment to the engine block 1 will be briefly described below.

  First, the screw portion 14 a is screwed into the distal end side of the plug hole 2 provided in the engine block 1 using the housing hexagonal portion 14 b, and the spark plug 11 is fixed to the engine block 1. Subsequently, the plasma driver 40 is inserted from the proximal end opening of the plug hole 2 toward the distal end side. At this time, the distal end side opening of the plug cap 40 c is fitted to the proximal end side of the spark plug 11. At the same time, the high voltage terminal 42 held by the conductive member 43 and the elastic member 44 inside the plug cap 40 c is fitted to the center electrode central shaft 12 a of the spark plug 11, and the high voltage terminal 42 is fixed by the elastic member 44. The different diameter boundary surface 42c is pressed. That is, when the plasma driver 40 and the spark plug 11 are fitted, the high voltage terminal 42 and the center electrode middle shaft 12a are securely fitted by the elastic force of the elastic member 44. Thereby, the center electrode middle shaft 12a and the high voltage terminal 42 are reliably electrically connected. Furthermore, the high-voltage terminal 42 is urged toward the base end side by the elastic force of the elastic member 44, so that even if vibration is applied from the outside, the fitting state between the high-voltage terminal 42 and the center electrode middle shaft 12a is maintained. As a result, the reliability of the electrical connection between the high voltage terminal 42 and the spark plug 11 is further improved.

  Similarly to the conductive member 43, the elastic member 44 and the high-voltage terminal 42 are soldered in order to improve the reliability of the electrical connection between the high-voltage terminal 41 and the high-voltage terminal 42 by the elastic member 44. It is preferable to join by such as. At this time, the elastic member 44 is joined at the different-diameter boundary surface 42c of the high-pressure terminal 42 or the outer peripheral surface of the cylindrical portion 42a. Thus, by soldering both ends of the elastic member 44 to the high-voltage terminal 41 and the high-voltage terminal 42, respectively, even if the conductive member 43 is disconnected, the elastic member 44 ensures that the high-voltage terminal 41 and the high-voltage terminal 42 are connected. The spark plug 11 also has a so-called fail-safe role that temporarily enables the spark plug 11 to eject plasma gas. Similarly, even when the elastic member 44 is short-circuited, the conductive member 43 can also play the role of fail-safe. The elastic member 44 is not limited to the above-described piano wire, and may be a member having elasticity and conductivity. For example, a spring stainless steel wire may be employed.

In the above embodiment, for example, the high-voltage terminal 41 and the high-voltage terminal 42 and the conductive member 43 are fixed by soldering. However, as shown in FIG. 8, for example, a conductive adhesive made of silver paste or nickel paste or the like These may be fixed using 50. Similarly, the elastic member 44 and the high voltage terminal 41 may be fixed using the conductive adhesive 50.
(Second embodiment)
Hereinafter, although the second embodiment will be described, since the basic configuration is the same as that of the first embodiment, only the differences that should be noted will be described. The same members as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment.

As shown in FIG. 9, two conductive springs 144 a and 144 b are disposed between the high voltage terminal 41 and the high voltage terminal 42. By pressing the high voltage terminal 42 toward the tip side by the two conductive springs 144a and 144b, the reliability of the fitting state between the high voltage terminal 42 and the center electrode middle shaft 12a is improved as compared with the configuration of the first embodiment. As a result, the reliability of electrical connection between the high voltage terminal 42 and the spark plug 11 can be further improved. In addition, there are three electrical paths between the high-voltage terminal 41 and the high-voltage terminal 42, including the conductive member 43 and the conductive springs 144a and 144b, and these three paths are connected in parallel. The combined resistance between the terminal 41 and the high-voltage terminal 42 is smaller than that in the first embodiment. Therefore, electrical loss between the high voltage terminal 41 and the high voltage terminal 42 is reduced.
(Third embodiment)
Hereinafter, the third embodiment will be described, but since the basic configuration is the same as that of the first embodiment, only the differences that should be noted will be described.

As shown in FIG. 10, for example, protrudes from the connecting member 40 b toward the elastic member 44 on the inner peripheral surface on the distal end side of the connecting member 40 b and faces the elastic member 44, and is inserted into the pitch of the elastic member 44. An annular ridge 140b is provided. Thereby, since the force with which the elastic member 44 on the base end side of the protrusion 140b presses the bottom surface 41a of the high-voltage terminal 41 is increased, it is not necessary to fix the high-voltage terminal 41 and the elastic member 44 by soldering or the like. Man-hours are reduced.
(Fourth embodiment)
Hereinafter, the fourth embodiment will be described, but since the basic configuration is the same as that of the above-described embodiment, only the differences that should be noted will be described.

  In order to eliminate the need for the elastic member 44 used in the above embodiment, as shown in FIG. 11, a locking portion 240 c protruding from the inner peripheral surface of the plug cap 40 c is provided on the proximal end side of the high-voltage terminal 42. The locking portion 240c is in contact with the outer peripheral surface and the base end side end surface of the cylindrical portion 42a of the high-pressure terminal 42 and the different-diameter boundary surface 42c, and the high-pressure terminal 42 and the spark plug 11 are assembled in the plasma driver 40 assembly process. A resistance force is generated against the stress applied to the base end side of the high-voltage terminal 42 during the fitting. As a result, the high voltage terminal 42 and the center electrode middle shaft 12a are securely fitted when the plasma driver 40 and the spark plug 11 are fitted. Thereby, without using the elastic member 44 of the said embodiment, the high voltage | pressure terminal 42 and the ignition plug 11 can be fitted reliably, and the reliability of electrical connection of both can be improved.

It is the schematic which shows the circuit structure of the ignition circuit which concerns on this invention. It is a schematic diagram which shows the attachment to the engine block of an ignition circuit and an ignition coil. It is a figure which shows the modification of the circuit part for spark discharge. It is sectional drawing which shows the structure of the plasma driver which concerns on 1st embodiment. It is the A section enlarged view in FIG. (A) is a perspective view of a high voltage terminal, (b) is a sectional view of the high voltage terminal. (A) is a perspective view of a high voltage terminal, (b) is a sectional view of the high voltage terminal. It is a figure which shows the modification of FIG. It is sectional drawing which shows the structure of the plasma driver which concerns on 2nd embodiment. It is sectional drawing which shows the structure of the plasma driver which concerns on 3rd embodiment. It is sectional drawing which shows the structure of the plasma driver which concerns on 4th embodiment.

Explanation of symbols

1 ... Engine block,
2 ... Plug hole,
3 ... combustion chamber,
10 ... Ignition circuit,
11 ... Spark plug,
12 ... center electrode,
12a ... Center electrode central shaft 13 ... Insulator,
14: Ground electrode,
14a ... screw part,
14b ... Housing hexagonal part,
15 ... discharge gap,
16 ... discharge space,
17 ... Battery,
20 ... Spark discharge circuit part,
21 ... Primary coil,
22 ... secondary coil,
23 ... Control circuit,
23a ... power source for spark discharge,
23b ... Spark discharge capacitor,
24 ... Diode,
25 ... Spark discharge lead wire,
26 ... electric resistance,
30: Circuit portion for plasma discharge,
31 ... Power source for plasma discharge,
32 ... Plasma discharge capacitor,
33 ... Diode,
34 ... Lead wire for plasma discharge,
40 ... Plasma driver
40a ... cylindrical member,
40b ... connecting member,
40c ... Plug cap,
41 ... high voltage terminal,
41a ... bottom surface,
41b ... convex part,
42 ... High-pressure terminal,
42a ... cylindrical portion,
42b ... fitting part,
42c ... Interface with different diameter,
43 ... conductive member,
44, 144a, 144b ... elastic members,
50 ... conductive adhesive,
60 ... ECU,
100: Plasma ignition device,
123b ... switching element,
140b ... ridges,
240c ... Locking part

Claims (8)

A center electrode fixed to a combustion chamber side opening of a plug hole of an internal combustion engine and held by an insulating member, and a ground electrode disposed via the center electrode and a discharge gap, the center electrode and the ground A plasma spark plug for generating plasma gas between the electrode and
An ignition circuit for applying a high voltage and a large current to the plasma ignition plug;
A high voltage terminal electrically connected to the ignition circuit;
A high-voltage terminal that is spaced apart from the high-voltage terminal, and is fitted and electrically connected to the plasma spark plug;
One end is fixed to the high-voltage terminal and the other end is fixed to the high-voltage terminal, and a conductive member that electrically connects the high-voltage terminal and the high-voltage terminal;
An elastic member disposed outside the conductive member and biasing the high-voltage terminal toward the plasma spark plug;
A plasma ignition device comprising: the high-voltage terminal; the high-voltage terminal; the conductive member and the elastic member; and a plasma driver accommodated in the plug hole.   The plasma ignition device according to claim 1, wherein the elastic member is a metal spring, and one end of the elastic member is fixed to the high voltage terminal, and the other end is fixed to the high voltage terminal. .   The plasma-type ignition device according to claim 1 or 2, wherein the elastic member is fixed to the high-voltage terminal and the high-voltage terminal by welding.   The plasma ignition device according to any one of claims 1 to 3, wherein a plurality of the elastic members are arranged in parallel between the high voltage terminal and the high voltage terminal. A center electrode fixed to a combustion chamber side opening of a plug hole of an internal combustion engine and held by an insulating member, and a ground electrode disposed via the center electrode and a discharge gap, the center electrode and the ground A plasma spark plug for generating plasma gas between the electrode and
An ignition circuit for applying a high voltage and a large current to the plasma ignition plug;
A high voltage terminal electrically connected to the ignition circuit;
A high-voltage terminal that is spaced apart from the high-voltage terminal, and is fitted and electrically connected to the plasma spark plug;
One end is fixed to the high-voltage terminal and the other end is fixed to the high-voltage terminal, and a conductive member that electrically connects the high-voltage terminal and the high-voltage terminal;
A plasma ignition device including the high-voltage terminal, the high-voltage terminal and the conductive member, and a plasma driver housed in the plug hole,
A locking portion having an opposing surface facing the plasma ignition plug is in contact with an end surface of the high voltage terminal on the ignition circuit side between the high voltage terminal and the high voltage terminal on the inner surface of the plasma driver. A plasma ignition device.   The plasma ignition device according to any one of claims 1 to 5, wherein the conductive member is fixed to the high-voltage terminal and the high-voltage terminal by welding.   The plasma ignition device according to any one of claims 1 to 5, wherein the conductive member is fixed to the high-voltage terminal and the high-voltage terminal with a conductive adhesive.   The plasma ignition device according to any one of claims 1 to 7, wherein the conductive member is formed by twisting a plurality of thin wires.

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