JP4635765B2 - Ignition device for internal combustion engine - Google Patents

Description

  The present invention relates to an ignition device that generates sparks at a plurality of positions in a combustion chamber of an internal combustion engine.

2. Description of the Related Art Conventionally, a multipoint ignition device that generates sparks at a plurality of positions in a combustion chamber of an internal combustion engine is known (see, for example, Patent Document 1). As shown in FIG. 7, one such conventional device includes an ignition coil 101 including a secondary coil that generates a very large voltage by mutual induction between the primary coil and the primary coil, A spark generating lead wire 103 having a plurality of spark generating portions that form a spark generating gap GP in the combustion chamber 102.
JP-A-2-123281

  In this conventional apparatus, one end of the secondary coil of the ignition coil 101 is grounded, the other end of the secondary coil is electrically connected to one end of the spark generating conductor 103, and the other end of the spark generating conductor 103 is connected. Ground the end. Thus, when the secondary coil of the ignition coil 101 generates a voltage, a spark is generated in the plurality of spark generating gaps GP of the spark generating lead 103 (discharge occurs).

  As described above, according to the conventional apparatus, sparks can be generated at a plurality of positions in the combustion chamber 102. Therefore, for example, when a mixed gas having an extremely lean air-fuel ratio is formed in the combustion chamber, the mixed gas can be ignited more reliably than when a spark is generated at one location in the combustion chamber.

  However, since a very large voltage is applied to the spark generating lead 103 in order to generate sparks at a plurality of spark generating gaps GP, the potential of the spark generating lead 103 and the potential of the wall of the combustion chamber 102 In some cases, the maximum value of the difference becomes large, and sparks may be generated between the spark generating conductor 103 and the wall surface of the combustion chamber 102. If such an abnormal spark occurs, sparks cannot be generated at a desired timing in all the spark generation gaps GP, so that the mixed gas cannot be reliably ignited at a desired timing. There was a problem.

  The present invention has been made to address the above-described problems, and one of its purposes is to spark at a plurality of positions in the combustion chamber without generating an abnormal spark with the wall surface of the combustion chamber. An ignition device for an internal combustion engine capable of generating

In order to achieve this object, an ignition device for an internal combustion engine according to the present invention includes:
An ignition coil including a secondary coil that generates a voltage by mutual induction between the primary coil and the primary coil;
An insulator disposed so that at least one surface is exposed to the combustion chamber of the internal combustion engine;
A pair of projecting portions projecting from the predetermined position at a predetermined position on the combustion chamber exposure surface, which is one surface of the insulator exposed to the combustion chamber, so as to form a spark generation gap in the combustion chamber. A plurality of spark generating portions, and a spark generating conductor having a connecting portion for connecting the plurality of spark generating portions in series to both ends of the secondary coil;
The potential at a position where the number of turns of the secondary coil from one end of the secondary coil of the ignition coil is approximately half of the total number of turns of the secondary coil is equal to the conductor portion of the wall surface of the combustion chamber. A secondary coil grounding portion for electrically connecting the secondary coil and the conductor portion of the same wall so that
And a spark is generated at each of the plurality of spark generators by a voltage generated by a secondary coil of the ignition coil.
The ignition coil is fixed so as to contact the insulator,
The insulator is a plate-like member that is configured to cover the connection portion of the spark generating conductor and is made of ceramics,
The primary coil and secondary coil of the ignition coil are embedded in an insulating resin.
The ignition coil and the insulator are fixed to the same side of the ignition coil in a state in which the ignition coil is in contact with the insulator, and the same side of the ignition coil. And the first space and the second space are formed.
The secondary coil of the ignition coil is arranged so that both end portions are exposed to each of the first space and the second space,
The connection portion of the spark generating conductor has two end portions exposed to the first space and the second space, respectively, for electrical connection to both ends of the secondary coil of the ignition coil. Arranged to
The end of the secondary coil of the ignition coil exposed in the first space and the end of the connection portion of the spark generating conductor exposed in the first space are electrically connected to each other one by one. A first member that can be stretched;
The end of the secondary coil of the ignition coil exposed in the second space and the end of the connection portion of the spark generating conductor exposed in the second space are electrically connected to each other one by one. A second member that can be stretched;
Is provided.

According to this, the maximum value of the difference between the potential of the spark generating conductor and the potential of the conductor portion of the wall of the combustion chamber is such that one end of the secondary coil is grounded and the secondary coil The other end of the spark generating conductor is electrically connected to one end of the spark generating conductor, and the other end of the spark generating conductor is approximately halved compared to a conventional apparatus in which the other end of the spark generating conductor is grounded. As a result, it is possible to prevent a spark from occurring between the spark generating part of the spark generating conductor and the conductor part of the wall surface of the combustion chamber (discharging occurs). A spark can surely be generated. As a result, the mixed gas can be reliably ignited.
Further, according to this, for example, without using other parts such as a spark plug provided with a member for maintaining the insulation of the current path, between the spark generating conductor and the conductor such as the cylinder and the cylinder block. The spark generating conductor and the secondary coil of the ignition coil can be directly connected while maintaining the insulating property of the spark by the insulator.
Moreover, since the temperature at which ceramics is fired is higher than the melting point of the resin, if an insulator in which an ignition coil containing an insulating resin (insulating resin) is incorporated is formed by firing, the insulating resin of the ignition coil Will be destroyed. On the other hand, according to the said structure, an ignition coil and an insulator can be formed separately. As a result, it is possible to prevent the insulating resin of the ignition coil from being destroyed during firing of the insulator.
Furthermore, by making the insulator a plate-shaped member having a simple shape, for example, the insulator is made of ceramics as compared with the case where the insulator is a member having a complicated shape having an internal structure for incorporating the ignition coil therein. The stress (residual stress) generated in the insulator can be reduced by cooling the insulator from a state where it has been fired to a high temperature. As a result, the strength of the insulator can be improved.
Further, ceramics shrink relatively greatly when cooled from a state of being fired and heated. Therefore, the error between the actual dimensions after firing and the design dimensions may be large. In this case, it is difficult to reliably connect the secondary coil of the ignition coil and the spark generating conductor. On the other hand, according to the above configuration, since the extendable member (expandable member) expands and contracts, the secondary coil of the ignition coil and the spark generating conductor can be reliably connected even if the error becomes relatively large. Can do.

In this case, it is preferable that the ignition coil is fixed so as to be in contact with the insulator via an elastic member.

According to this, the ignition coil and the insulator can be brought into close contact with each other via the elastic member. Thereby, since the penetration | invasion of the water | moisture content to the part which connects the secondary coil of an ignition coil and the conductor for a spark generation from the outside can be prevented, the deterioration of the part to connect can be prevented.
  Further, if the ignition coil that is a rigid body is directly fixed to the insulator that is a rigid body, stress concentration may occur in the ignition coil and the insulator. Due to such stress concentration, an insulator made of ceramics may be destroyed. On the other hand, according to the above configuration, since the stress is dispersed by the elastic member, it is possible to prevent the ignition coil and the insulator from being destroyed.

In order to achieve the above object, an ignition device for an internal combustion engine according to the present invention includes:
  An ignition coil including a secondary coil that generates a voltage by mutual induction between the primary coil and the primary coil;
  An insulator disposed so that at least one surface is exposed to the combustion chamber of the internal combustion engine;
  A pair of projecting portions projecting from the predetermined position at a predetermined position on the combustion chamber exposure surface, which is one surface of the insulator exposed to the combustion chamber, so as to form a spark generation gap in the combustion chamber. A plurality of spark generating portions, and a spark generating conductor having a connecting portion for connecting the plurality of spark generating portions in series to both ends of the secondary coil;
  The potential at a position where the number of turns of the secondary coil from one end of the secondary coil of the ignition coil is approximately half of the total number of turns of the secondary coil is equal to the conductor portion of the wall surface of the combustion chamber. A secondary coil grounding portion for electrically connecting the secondary coil and the conductor portion of the same wall so that
  And a spark is generated at each of the plurality of spark generators by a voltage generated by a secondary coil of the ignition coil.
  A back electrode is disposed inside the insulator and is electrically connected to the conductor portion so as to have the same potential as the conductor portion of the wall surface of the combustion chamber.

According to this, the maximum value of the difference between the potential of the spark generating conductor and the potential of the conductor portion of the wall of the combustion chamber is such that one end of the secondary coil is grounded and the secondary coil The other end of the spark generating conductor is electrically connected to one end of the spark generating conductor, and the other end of the spark generating conductor is approximately halved compared to a conventional apparatus in which the other end of the spark generating conductor is grounded. As a result, it is possible to prevent a spark from occurring between the spark generating part of the spark generating conductor and the conductor part of the wall surface of the combustion chamber (discharging occurs). A spark can surely be generated. As a result, the mixed gas can be reliably ignited.
  In addition, according to this, a larger electric field is formed on the surface of the insulator than when there is no back electrode. As a result, a larger amount of charge is accumulated near the surface of the insulator as compared with the case where there is no back electrode, so that a creeping discharge can be caused more reliably by applying a voltage to each spark generating portion. As a result, it is possible to reliably generate a spark at each spark generating portion.

In this case, the insulator is formed in an annular shape having an inner diameter substantially the same as the bore diameter of the cylinder, and is disposed coaxially with the bore of the cylinder so that the inner peripheral surface is exposed to the combustion chamber. ,
Furthermore, it is preferable that the ignition device includes a reinforcing member disposed on an outer periphery of the insulator so as to limit expansion of the insulator in a radial direction.

Since the insulator is pushed from the inside to the outside of the combustion chamber by the pressure generated by the combustion of the mixed gas in the combustion chamber, stress is generated in the insulator. Therefore, as in the above configuration, the insulator is formed in an annular shape and disposed so that its inner peripheral surface is exposed to the combustion chamber, thereby generating stress having the same magnitude in the circumferential direction in the insulator. Therefore, it is possible to prevent the stress from locally increasing (occurrence of stress concentration). Furthermore, since the reinforcing member is disposed on the outer periphery of the insulator, the insulator can be prevented from expanding in the radial direction. As a result, it is possible to prevent the insulator from being destroyed.

Moreover, the combustion chamber exposure surface of the insulator in any one of the ignition devices is formed to have a recess at each position where the plurality of spark generation portions are disposed,
Each of the spark generating portions is preferably configured such that the pair of projecting portions are accommodated in the concave portions.

  According to this, the flow of gas (swirl flow, tumble flow, etc.) formed in the combustion chamber prevents ions, electrons, etc. generated in the vicinity of the spark generating portion from flowing out from the vicinity of the spark generating portion. At the same time, the heat of the spark generating part and the heat of the mixed gas in the vicinity of the spark generating part are prevented from being taken away.

  Therefore, when a voltage is applied to the spark generation section, ions and electrons increase in the vicinity of the spark generation section, and the temperature of the spark generation section and the temperature of the mixed gas in the vicinity of the spark generation section increase. Can generate sparks. Furthermore, it is possible to prevent the spark from being extinguished (discharging is not maintained) during the period in which the voltage is applied. As a result, the mixed gas can be reliably ignited.

  In this case, each of the spark generators has the shortest distance among the distances from one predetermined position of the pair of protrusions to any other position of the same pair of protrusions. It is preferable to be configured so as to decrease from one base end of the projecting portion toward one distal end of the projecting portion.

  When a voltage is applied to each spark generating portion, creeping discharge occurs on the surface of the insulator. As a result, ions, electrons, and the like increase in a region near the surface of the insulator, so that after creeping discharge occurs, arc discharge occurs between a pair of protrusions in the region near the surface (spark is generated).

  By the way, if the position where the spark is generated is in the vicinity of the wall surface constituting the combustion chamber, the heat of the spark is taken away by the wall surface. Therefore, it is possible to raise the temperature of the mixed gas with high efficiency by generating a spark at a position away from the wall surface rather than generating a spark at a position close to the wall surface. .

  Therefore, as in the above configuration, when the spark generation unit is configured such that the distance between the pair of projections decreases from the base end (surface of the insulator) of the projection toward the tip of the projection, Since it occurs near the surface of the insulator and then moves to the tip of the protrusion, a spark is generated at a position that is a predetermined distance away from the wall that forms the combustion chamber (between the ends of the pair of protrusions). Can be made. As a result, the temperature of the mixed gas can be raised with high efficiency by the generated spark.

  In this case, each of the spark generating portions has a straight line between the distal ends of the same pair of projecting portions such that the distance along the combustion chamber exposure surface of the insulator between the proximal ends of the pair of projecting portions is the same. Each is preferably configured to be 3 to 10 times the distance.

  Further, in each of the spark generating parts of the ignition device, the spark has a magnitude of thermal energy transmitted between the pair of projecting parts and the gas in the combustion chamber having the same surface area of the pair of projecting parts. It is preferable that the protrusion length from the base end to the tip end of the same pair of protrusions is shorter than a predetermined length so that the area has a predetermined size that does not ignite the mixed gas before it is generated.

  If the temperature of the spark generating part is high, the mixed gas in the combustion chamber is ignited by the thermal energy transmitted from the spark generating part even if no spark is generated. In particular, when the load of the internal combustion engine is high, the temperature of the combustion gas is high, and therefore the temperature of the spark generating part is likely to rise. For this reason, the mixed gas is likely to be ignited (prematurely) before a spark is generated.

  On the other hand, according to the above configuration, it is possible to prevent the temperature of the spark generating part from becoming too high due to the thermal energy transmitted from the combustion gas to the spark generating part, and mixing in the combustion chamber from the spark generating part. It is possible to prevent the temperature of the mixed gas in the combustion chamber from becoming too high due to the thermal energy transmitted to the gas. Thereby, it is possible to prevent the mixed gas from being ignited before the spark is generated.

In this case, each of the spark generating portions is arranged so that one of the pair of protruding portions faces the other of the same pair of protruding portions via a space,
In the combustion chamber exposure surface of the insulator, the distance along the combustion chamber exposure surface between the base ends of the pair of protrusions is greater than the linear distance between the base ends of the same pair of protrusions. It is preferable to be formed as follows.

  When the distance along the surface of the insulator between the base ends of the pair of protrusions is equal to the linear distance between the base ends of the same pair of protrusions, a voltage is applied to the spark generation unit. However, only creeping discharge occurs on the surface of the insulator, and arc discharge cannot be caused between the pair of protrusions (spark can not be generated).

  On the other hand, according to the above configuration, the pair of protrusions face each other through a space, and the distance along the surface of the insulator between the base ends of the pair of protrusions is the same pair. Since it becomes larger than the linear distance between each base end of a protrusion part, the discharge path of creeping discharge becomes longer than the discharge path of arc discharge. Thereby, after creeping discharge occurs on the surface of the insulator, arc discharge can be caused between the pair of projecting portions (spark can be generated). As a result, the mixed gas can be reliably ignited.

  Hereinafter, an internal combustion engine multipoint ignition device according to each embodiment of the present invention will be described with reference to the drawings. This multipoint ignition device is applied to a multi-cylinder (four-cylinder) internal combustion engine 10 showing a partial cross section of the cylinder shown in FIG.

  The internal combustion engine 10 includes a hollow cylindrical cylinder 20 having a central axis, a substantially columnar piston 30 that reciprocates within the cylinder 20, a crankshaft (not shown), and a piston 30 and a crankshaft connected to each other. 20 includes a connecting rod 40, a cylinder head portion 50, and a multipoint ignition device 60 for converting a reciprocating motion in the shaft 20 into a rotational motion of the crankshaft. The bore wall surface of the cylinder 20 (the wall surface of the cylinder bore), the top surface of the piston 30 (piston head), and the lower surface of the cylinder head portion 50 form a combustion chamber 70. The bore wall surface of the cylinder 20 is made of metal (in this example, cast iron) and constitutes a conductor portion of the wall surface of the combustion chamber 70. The potential of the bore wall surface of the cylinder 20 is a ground potential.

  The cylinder head unit 50 includes an intake port 51 that communicates the outside of the internal combustion engine 10 with the combustion chamber 70, an intake valve 52 that opens and closes the intake port 51, an exhaust port 53 that communicates the exterior of the internal combustion engine 10 and the combustion chamber 70, An exhaust valve 54 for opening and closing the exhaust port 53 and a fuel injection valve (fuel injection means) 55 for directly injecting fuel into the combustion chamber 70 are provided.

  The fuel injection valve 55 includes a front end portion that injects fuel toward the substantially center of the combustion chamber 70, and the front end portion is exposed to the combustion chamber 70 so as to be coaxial with the central axis of the cylinder 20. It is arranged. The fuel in the fuel tank (not shown) is supplied to the fuel injection valve 55 by a fuel pressure adjusting means (not shown) and a fuel pump.

  As shown in FIG. 2, the multipoint ignition device 60 includes an ignition plate portion 61, two ignition plugs 62, an ignition coil 63, a power supply circuit 64, and an ignition control circuit 65. The ignition plate portion 61 includes an annular insulator 61a, a spark generating lead 61b held by the annular insulator 61a, and a reinforcing member 61c disposed on the outer periphery of the annular insulator 61a.

  The annular insulator 61a is an insulator made of ceramics. The annular insulator 61a has a flat plate ring shape. The inner diameter of the annular insulator 61 a is the same as the bore of the cylinder 20. The annular insulator 61 a is disposed between the cylinder 20 and the cylinder head portion 50 so as to be coaxial with the cylinder 20. In this way, the inner peripheral surface of the annular insulator 61 a constitutes a combustion chamber exposure surface exposed to the combustion chamber 70.

A plurality (eight in this example) of concave portions 61a1 are formed on the inner peripheral surface of the annular insulator 61a at regular intervals in the circumferential direction.
The opening of the recess 61a1 has a short axis parallel to the central axis of the annular insulator 61a and a long axis extending in the circumferential direction of the inner peripheral surface in a front view of the inner peripheral surface of the annular insulator 61a. It has an elliptical shape (see FIG. 1). The shape of the cross section obtained by cutting the recess 61a1 along a plane orthogonal to the central axis of the annular insulator 61a is substantially semicircular (see FIG. 2). Furthermore, recesses for accommodating the tip of the ignition coil 63 are formed at two locations on the outer peripheral portion of the annular insulator 61a.

  The spark generating lead 61b includes the same number of spark generating portions 61b1 as the concave portions 61a1 and connecting portions 61b2. The spark generating portion 61b1 includes a pair of projecting portions that form a spark generating gap GP in the combustion chamber 70 in a state where the annular insulator 61a is disposed between the cylinder 20 and the cylinder head portion 50.

  The pair of protrusions are housed in one recess 61a1. The pair of protruding portions protrude from the predetermined position toward the central axis of the annular insulator 61a with a predetermined position of a surface (recess forming surface) constituting one concave portion 61a1 as a base end of the protrusion. One of the pair of protrusions is disposed to face the other of the same pair of protrusions with a space in between.

  The pair of projecting portions is a distance between the projecting portion on the one side and the other projecting portion as it goes from the base end of the one projecting portion (predetermined position in the concave surface) to the tip of the projecting portion on the same side. Is arranged to be small. Further, in the pair of protrusions, the distance along the concave configuration surface between the base ends of the protrusions is 3 to 10 times the linear distance between the tips of the same pair of protrusions (this example). Then, each is arranged so as to be about 4 times.

  Thus, since a pair of protrusion part protrudes from the recessed part structure surface which forms a curved surface, the distance along the recessed part structure surface between each base end of a pair of protrusion part is the same pair of protrusion part. It is larger than the linear distance between the base ends.

  Furthermore, since a pair of protrusion part protrudes from a recessed part structure surface, since the several spark generation part 61b1 can be arrange | positioned in the combustion chamber 70, without greatly bending the spark generation lead 61b, the same spark generation lead By bending 61b, the stress generated in the spark generating lead 61b can be reduced. Thereby, it is possible to prevent the spark generating conductor 61b and the annular insulator 61a from being destroyed in the manufacturing process.

  The connecting portion 61b2 is a conducting wire that connects the plurality of spark generating portions 61b1 in series between the two spark plugs 62. The connecting portion 61b2 is disposed inside the annular insulator 61a.

  One end of the connecting portion 61b2 is connected to one of the two spark plugs 62, and the other end of the connecting portion 61b2 is connected to the other of the two spark plugs 62.

  A portion excluding both ends of the connection portion 61b2 is divided into a plurality of connection lines. Each connecting line includes one protruding portion (excluding the protruding portion connected to the spark plug 62) of one of the two spark generating portions 61b1 adjacent to each other in the circumferential direction of the annular insulator 61a. The other one of the two spark generating portions 61b1 (except for the protruding portion connected to the spark plug 62) is connected.

  The reinforcing member 61c is made of a metal with good ductility (in this example, copper). The reinforcing member 61c is an annular member. The inner diameter of the reinforcing member 61c is the same as the outer diameter of the annular insulator 61a. The reinforcing member 61c is disposed on the outer periphery of the annular insulator 61a so as to be coaxial with the annular insulator 61a.

  The reinforcing member 61c has two penetrations at positions corresponding to the two recesses formed on the outer peripheral portion of the annular insulator 61a in a state where the reinforcing member 61c is disposed on the outer periphery of the annular insulator 61a. It has a hole.

  The spark plug 62 includes a conductive wire and an insulating casing that insulates the conductive wire from the outside. The tip of the spark plug 62 is inserted into a through hole of the reinforcing member 61c and a recess formed in the outer peripheral portion of the annular insulator 61a.

  The ignition coil 63 includes a primary coil 63a, a secondary coil 63b having a larger number of turns than the primary coil 63a, an iron core 63c, an NPN transistor 63d, a transistor grounding conductor 63e, and a secondary coil grounding portion. And a secondary coil grounding lead wire 63f.

  One end of the primary coil 63 a is connected to the power supply circuit 64. The power supply circuit 64 constantly generates a voltage having a predetermined magnitude. The other end of the primary coil 63a is connected to the collector electrode of the transistor 63d. The base electrode of the transistor 63d is connected to the ignition control circuit 65. The emitter electrode of the transistor 63d is grounded via a transistor grounding conductor 63e.

  The ignition control circuit 65 controls the current flowing through the primary coil 63a by controlling the current supplied to the base electrode of the transistor 63d.

  The secondary coil 63b is adapted to generate a voltage by a mutual induction action with the primary coil 63a via the iron core 63c. Each of both ends of the secondary coil 63b is connected to each of the two spark plugs 62. In the secondary coil 63b, the potential at a position where the number of turns of the secondary coil 63b from one end of the secondary coil 63b is half of the total number of turns of the secondary coil 63b (coil winding number halved position) is a cylinder. Grounded (engine grounding) via a secondary coil grounding conductor 63f at a position where the number of turns of the coil is equal to that of the 20 bore wall surface (conductor portion of the wall surface of the combustion chamber 70). . That is, the position of the number of coil turns and the portion having the same potential as the bore wall surface of the cylinder 20 (for example, a cylinder block) is electrically connected.

  The operation of the system configured as described above will be described from the case where a control current having a predetermined magnitude is supplied from the ignition control circuit 65 to the transistor 63e. In this case, the transistor 63d becomes conductive, and a primary coil side current having a predetermined magnitude flows through the primary coil 63a. A magnetic field is formed in the iron core 63c by the primary coil side current.

  Thereafter, at a predetermined timing, the ignition control circuit 65 stops supplying the control current. As a result, the transistor 63d is turned off, and the primary coil side current flowing through the primary coil 63a is cut off. Thus, when the primary coil side current changes rapidly, the magnetic field in the iron core 63c changes rapidly. As a result, the secondary coil 63b generates a voltage larger than the voltage generated by the power supply circuit 64 due to the mutual induction action with the primary coil 63a via the iron core 63c.

  By the way, as shown in FIG. 7, one end of the secondary coil is grounded and the other end of the secondary coil is electrically connected to one end of the spark generating conductor. In a conventional device whose end is grounded, for example, when the secondary coil generates a voltage of 10000 V, the potential of one end of the secondary coil becomes 10000 V, and the potential of the other end of the secondary coil becomes 0 V.

  On the other hand, the secondary coil 63b of the multipoint ignition device 60 according to the present embodiment is grounded at the position where the number of coil turns is halved (electrically connected to the bore wall surface of the cylinder 20). Therefore, for example, when the secondary coil 63b generates a voltage of 10,000V, the potential at one end of the secondary coil 63b becomes −5000V, and the potential at the other end of the secondary coil 63b becomes 5000V. Therefore, the maximum value of the difference between the electric potential of the spark generating conductor 61b and the electric potential of the bore wall surface of the cylinder 20 (the conductor portion of the wall surface of the combustion chamber 70) is larger than that of the conventional device. Almost half.

  As a result, it is possible to prevent a spark from being generated (discharge occurs) between the spark generating portion 61b1 of the spark generating lead 61b and the bore wall surface of the cylinder 20, and therefore, for all the spark generating portions 61b1. Thus, the voltage can be reliably applied at a desired timing.

  In addition, since it is difficult for sparks to be generated between the spark generating lead 61b and the bore wall surface of the cylinder 20 (the conductor portion of the wall surface of the combustion chamber 70), the annular insulator 61a is compared with the conventional device. The axial thickness can also be reduced.

  When a voltage is applied to each spark generating part 61b1, creeping discharge occurs on the concave surface (the surface of the annular insulator 61a). As a result, ions, electrons, and the like increase in the vicinity of the concave surface.

In the present embodiment, each of the pair of protrusions oppose each other via a space, and the distance along the concave portion constituting surface between the base ends of each of the pair of protrusions is the same for each of the pair of protrusions Therefore, the discharge path for creeping discharge is longer than the discharge path for arc discharge. Thereby, after creeping discharge has occurred on the surface of the concave portion, it is possible to cause arc discharge (spark) between the pair of protrusions.
Furthermore, since creeping discharge occurs on the concave surface (insulator surface), the carbon deposited on the concave surface can be blown off, so this multipoint ignition device 60 can be used for a long time. Even if it exists, the stable discharge is realizable.

  In addition, according to the present embodiment, the spark generation portion 61b1 is configured such that the distance between the pair of protrusions decreases from the base end of the protrusion (the concave portion forming surface) toward the tip of the protrusion. Therefore, the spark generated in the vicinity of the concave portion construction surface then moves to the tip of the protruding portion. Thereby, a spark can be generated at a position (between the tips of the pair of protrusions) separated from the wall surface constituting the combustion chamber 70 by a predetermined distance. As a result, it is possible to prevent the heat of the generated spark from being taken away by the wall surface constituting the combustion chamber 70.

  In addition, according to the present embodiment, since the pair of projecting portions (spark generating portion 61b1) is housed in the recessed portion 61a1, the flow of gas formed in the combustion chamber 70 (swirl flow, tumble flow, etc.) This prevents ions, electrons, and the like generated in the vicinity of the spark generator 61b1 from flowing out of the vicinity of the spark generator 61b1. Further, it is possible to prevent the heat of the spark generating part 61b1 and the heat of the mixed gas in the vicinity of the spark generating part 61b1 from being taken. Thereby, when a voltage is applied to the spark generating part, it is possible to reliably generate a spark. Furthermore, it is possible to prevent the spark from being extinguished (discharging is not maintained) during the period in which the voltage is applied.

  In addition, according to the present embodiment, even if the annular insulator 61a is pushed from the inside to the outside of the combustion chamber 70 due to the combustion of the mixed gas in the combustion chamber 70, the circumference is inserted into the annular insulator 61a. Since stress having the same magnitude in the direction can be generated, it is possible to prevent the stress from locally increasing (occurrence of stress concentration). As a result, it is possible to prevent the annular insulator 61a from being destroyed.

  Furthermore, according to the present embodiment, since the reinforcing member 61c is disposed on the outer periphery of the annular insulator 61a, the mixed gas burns in the combustion chamber 70, so that the combustion chamber 70 faces from the inside to the outside. Even if the annular insulator 61a is pushed, the reinforcing member 61c prevents the annular insulator 61a from expanding in the radial direction. As a result, it is possible to prevent the annular insulator 61a from being destroyed.

  As described above, according to the first embodiment of the multipoint ignition device of the present invention, sparks can be reliably generated at predetermined timings at a plurality of positions in the combustion chamber 70.

  The pair of protrusions constituting the spark generation part 61b1 of the multipoint ignition device 60 preferably has a diameter of 1 to 2 mm and a protrusion length from the proximal end to the distal end of 1 to 2 mm. It is.

  Accordingly, the surface area of the pair of protrusions is a predetermined magnitude that does not ignite the mixed gas before the spark is generated, indicating the amount of thermal energy transmitted between the pair of protrusions and the gas in the combustion chamber 70. This is the area to be measured.

  As a result, it is possible to prevent the temperature of the spark generating portion 61b1 from becoming too high due to the thermal energy transmitted from the combustion gas to the spark generating portion 61b1, and from the spark generating portion 61b1 to the mixed gas in the combustion chamber 70. It is possible to prevent the temperature of the mixed gas in the combustion chamber 70 from becoming too high due to the transmitted thermal energy. Thereby, it is possible to prevent the mixed gas from being ignited before the spark is generated.

(Second Embodiment)
Next, a multipoint ignition device according to a second embodiment of the present invention will be described. The multipoint ignition device according to the second embodiment is applied to the internal combustion engine 10 similarly to the multipoint ignition device 60 according to the first embodiment. The multipoint ignition device according to the second embodiment is different from the multipoint ignition device 60 according to the first embodiment in that the ignition plug is not provided and a back electrode embedded in the ignition plate portion is provided. is doing. Hereinafter, this difference will be mainly described.

  As shown in FIG. 3, the multipoint ignition device 80 includes an ignition plate portion 81 and an ignition coil 82 fixed so as to be in contact with the ignition plate portion 81.

  As shown in FIG. 4 which is a sectional view of the ignition plate portion 81, the ignition plate portion 81 includes a plate-like insulator 81a, a spark generating lead 81b held by the plate-like insulator 81a, and a plate-like insulator. A back electrode 81c embedded in the body 81a.

  The plate-like insulator 81a is an insulator made of ceramics. The plate insulator 81a has a flat plate shape. The plate insulator 81a is a through hole penetrating in the thickness direction, and has a cylindrical through hole having the same diameter as the bore of the cylinder 20. The plate-like insulator 81 a is disposed between the cylinder 20 and the cylinder head portion 50 so that the through hole is coaxial with the cylinder 20.

  Further, the side wall surface of the through hole of the plate-like insulator 81a has a combustion chamber exposed surface exposed to the combustion chamber 70 in a state where the plate-like insulator 81a is disposed between the cylinder 20 and the cylinder head portion 50. It is composed. A plurality (eight in this example) of recesses 81a1 similar to the recesses 61a1 of the inner peripheral surface of the annular insulator 61a of the first embodiment are formed on the side wall surface of the through hole of the plate insulator 81a. Has been.

  The spark generating lead 81b includes a spark generating portion 81b1 and a connecting portion 81b2, similarly to the spark generating lead 61b of the first embodiment. The spark generating lead 81b is held by the plate-like insulator 81a with the same relationship as the spark generating lead 61b with respect to the annular insulator 61a in the multipoint ignition device 60 according to the first embodiment except for both ends. Yes. Details of both ends of the spark generating conductor 81b will be described later.

  The back electrode 81c is a conducting wire. Both ends of the back electrode 81c are grounded. Therefore, the back electrode 81c and the bore wall surface of the cylinder 20 are electrically connected so as to have the same potential. The back electrode 81c is disposed on the outer periphery of the connection portion 81b2 and inside the plate-like insulator 81a.

  The ignition coil 82 is a plate-like insulator as shown in FIGS. 5 and 6, which are enlarged sectional views of the ignition coil 82 taken along planes 2-2 and 3-3 in FIG. It is fixed so as to contact 81a. The ignition coil 82 includes a housing 82a, two compression springs 82b, two ignition coil side contact members 82c, a first elastic member 82d, a stress distribution plate 82e, and a second elastic member 82f.

  The housing 82a includes a base portion 82a1 and a collar portion 82a2. The base portion 82a1 is a rectangular parallelepiped member having a predetermined thickness and having a rectangular opening bottom surface formed by long sides and short sides. The collar portion 82a2 is a plate-like member that extends from the side surface on the long side of the base portion 82a1 in a direction perpendicular to the side surface at the lower end portion that constitutes the bottom surface of the base portion 82a1. The collar portion 82a2 has a plurality of (four in this example) cylindrical bolt holes penetrating in the thickness direction.

  The casing 82a is filled with an insulating resin R. The insulating resin R is an electric circuit including a primary coil, a secondary coil, an iron core, an NPN transistor, a transistor grounding conductor, and a secondary coil grounding conductor as a secondary coil grounding portion (not shown). Thus, the same electric circuit as that of the ignition coil 63 according to the first embodiment is embedded. As shown in FIG. 3, this electric circuit is connected to the power supply circuit 64 and the ignition control circuit 65, similarly to the electric circuit of the ignition coil 63 according to the first embodiment.

  In the ignition coil 82 (insulating resin R), as shown in FIG. 6, two columnar expansion / contraction member accommodation spaces SP are formed that open on the surface on the plate-like insulator 81a side (ignition coil contact surface). ing. One end of each secondary coil is exposed on the wall surface of each expansion member housing space SP.

  The compression spring 82b is made of a conductor. Each compression spring 82b is accommodated in the elastic member accommodation space SP one by one. One end of each compression spring 82b is connected to each end of the secondary coil exposed on the wall surface constituting the expansion member accommodating space SP. The other end of each compression spring 82b is connected to each ignition coil side contact member 82c.

  The ignition coil side contact member 82c is made of a columnar conductor having substantially the same diameter as the diameter of the expansion / contraction member accommodation space SP. Each ignition coil side contact member 82c is slidably accommodated in each expansion / contraction member accommodation space SP so that the compression spring 82b in each expansion / contraction member accommodation space SP is compressed.

  On the other hand, a spark generating lead 81b that is electrically connected to both ends of the secondary coil of the ignition coil 82 on the surface of the plate-like insulator 81a on the side of the ignition coil 82 (plate-like insulator contact surface). Both end portions of (connection portion 81b2) are exposed. Each of the both end portions is disposed at a position facing the opening of the elastic member accommodation space SP in a state where the ignition coil 82 is fixed to the plate-like insulator 81a. Further, the plate-like insulator 81a includes two plate-like insulator-side contact members 81a2.

  The plate-like insulator-side contact member 81a2 is made of a disk-shaped conductor having substantially the same diameter as the diameter of the elastic member accommodation space SP. Each plate-like insulator-side contact member 81a2 is disposed on the plate-like insulator 81a so as to cover a part of the plate-like insulator contact surface. The plate-like insulator-side contact member 81a2 is disposed at a position facing the opening of the expansion / contraction member accommodation space SP in a state where the ignition coil 82 is fixed to the plate-like insulator 81a, and the spark exposed on the plate-like insulator contact surface. It is connected to each of both end portions of the generating conductor 81b.

  With such a configuration, the ignition coil side contact member 82c is pushed toward the plate-like insulator-side contact member 81a2 by the compression spring 82b in a state where the ignition coil 82 is fixed so as to contact the plate-like insulator 81a. The ignition coil side contact member 82c comes into contact with the plate-like insulator side contact member 81a2.

  Thus, the compression spring 82b, the ignition coil side contact member 82c, and the plate-like insulator side contact member 81a2 are arranged at both ends of the secondary coil of the ignition coil 82 exposed to the expansion / contraction member accommodation space SP and the expansion / contraction member accommodation space SP. A stretchable member (stretchable member) that electrically connects the both ends of the spark generating conductor 81b (connecting portion 81b2) exposed to each other one by one.

  Further, the plate-like insulator 81a has four cylindrical bolt holes having through holes penetrating in the thickness direction of the plate-like insulator 81a and having the same diameter as the bolt holes formed in the collar portion 82a2. Is formed.

  The first elastic member 82d is a plate-like elastic body having substantially the same area as the ignition coil contact surface. The first elastic member 82d is formed with two cylindrical through holes that are penetrated in the thickness direction and have substantially the same diameter as the diameter of the expandable member accommodation space SP. Furthermore, the first elastic member 82d is formed with four cylindrical bolt holes having through holes penetrating in the thickness direction and having the same diameter as the bolt holes formed in the collar portion 82a2. These through holes and bolt holes are arranged with the same relative positional relationship as the opening position of the expansion / contraction member accommodating space SP and the opening position of the bolt hole on the ignition coil contact surface. The first elastic member 82d is interposed between the ignition coil contact surface and the plate-like insulator contact surface.

  The stress dispersion plate 82e is a plate-like member having substantially the same area as the first elastic member 82d, and is made of resin. Similar to the bolt holes formed in the first elastic member 82d, four bolt holes are formed in the stress distribution plate 82e.

  The second elastic member 82f is a plate-like elastic body having substantially the same area as the stress dispersion plate 82e. In the second elastic member 82f, four bolt holes are formed in the same manner as the bolt holes formed in the first elastic member 82d. The second elastic member 82f is interposed between the stress distribution plate 82e and the plate insulator 81a.

  The ignition coil 82 configured as described above is configured such that the bolt BL penetrates the bolt hole of each member from the ignition coil 82 side, and the bolt BL is fastened to the nut NT on the stress distribution plate 82e side. It is fixed so as to be in close contact with the plate insulator 81a via the first elastic member 82d and the second elastic member 82f.

  According to such a configuration, the connecting portion 81b2 of the spark generating lead 81b is covered with the plate-like insulator 81a, and the ignition coil 82 is fixed so as to be in contact with the plate-like insulator 81a. Even if other parts such as a spark plug having a member for maintaining the insulation of the spark are not used, the insulation between the spark generating conductor 81b and the conductor such as the cylinder 20 is maintained by the plate insulator 81a. However, the spark generating lead 81b and the secondary coil of the ignition coil 82 can be directly connected.

  Furthermore, according to this embodiment, since the ignition coil 82 and the plate-like insulator 81a can be formed separately, the insulating resin of the ignition coil 82 is destroyed when the plate-like insulator 81a is fired. Can be prevented.

  In addition, in this embodiment, since the plate-like insulator 81a is a simple plate-like member, the plate-like insulator 81a has a complicated shape having an internal structure for incorporating the ignition coil 82 therein. Compared with the case where the plate-like insulator 81a made of ceramics is fired and cooled from a high temperature state, the stress (residual stress) generated in the plate-like insulator 81a can be reduced. . As a result, the strength of the plate-like insulator 81a can be improved.

  In addition, according to the present embodiment, the compression spring 82b that constitutes the expansion / contraction member expands / contracts, so that the actual dimension after the ceramic is fired and cooled from a high temperature is relatively different from the design dimension. Also, the secondary coil of the ignition coil 82 and the spark generating conductor 81b can be reliably connected.

  Furthermore, according to the present embodiment, the ignition coil 82 and the plate-like insulator 81a can be brought into close contact with each other via the first elastic member 82d. Thereby, since it is possible to prevent moisture from entering the portion (extractable member accommodation space SP) that connects the secondary coil of the ignition coil 82 and the spark generating lead 81b from the outside, deterioration of the extensible member is prevented. be able to. In addition, since the stress generated when the ignition coil 82 is fixed to the plate insulator 81a can be dispersed, it is possible to prevent the ignition coil 82 and the plate insulator 81a from being destroyed in the manufacturing process. it can.

  Further, according to the present embodiment, the ground electrode (engine ground) 81c is disposed on the outer periphery of the connecting portion 81b2 of the spark generating conductor 81b and inside the plate insulator 81a. A larger electric field is formed on the side wall surface (insulator surface) of the through hole of the insulator 81a than when there is no back electrode. As a result, a larger amount of electric charge is accumulated near the surface of the insulator as compared with the case where there is no back electrode, so that a creeping discharge can be caused more reliably by applying a voltage to each spark generating portion 81b1. . As a result, it is possible to reliably generate a spark at each spark generating portion 81b1.

  Thus, according to the second embodiment of the multipoint ignition device according to the present invention, a more reliable multipoint ignition device can be provided.

  In the second embodiment, the expansion member accommodation space SP formed in the ignition coil 82 is two independent spaces, but may be a space communicating with each other.

  As described above, according to the multipoint ignition device according to each embodiment of the present invention, a spark can be reliably generated at a predetermined timing at a plurality of positions in the combustion chamber 70.

  In addition, this invention is not limited to said each embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, the present invention may be applied to an internal combustion engine that is operated by a compression self-ignition method in which a mixed gas is compressed to self-ignite and burn.

1 is a partial cross-sectional view of a multipoint ignition device and an internal combustion engine to which the multipoint ignition device according to a first embodiment of the present invention is applied. FIG. 2 is a cross-sectional view of the multipoint ignition device shown in FIG. 1 cut along a plane along line 1-1. It is a schematic top view of the multipoint ignition device which concerns on 2nd Embodiment of this invention. It is a schematic sectional drawing of the multipoint ignition device shown in FIG. It is sectional drawing which cut | disconnected the ignition coil and plate-shaped insulator which were shown in FIG. 3 by the plane along 2-2 line. It is sectional drawing which cut | disconnected the ignition coil and plate-shaped insulator which were shown in FIG. 3 by the plane along line 3-3. It is a schematic sectional drawing of the conventional multipoint ignition device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Cylinder, 30 ... Piston, 40 ... Connecting rod, 50 ... Cylinder head part, 51 ... Intake port, 52 ... Intake valve, 53 ... Exhaust port, 54 ... Exhaust valve, 55 ... Fuel injection valve, DESCRIPTION OF SYMBOLS 60 ... Multi-point type ignition device, 61 ... Ignition plate part, 61a ... Toroidal insulator, 61a1 ... Recessed part, 61b ... Conductor for spark generation, 61b1 ... Spark generation part, 61b2 ... Connection part, 61c ... Reinforcement member, 62 ... Spark plug, 63 ... ignition coil, 63a ... primary coil, 63b ... secondary coil, 63c ... iron core, 63d ... transistor, 63e ... transistor grounding conductor, 63f ... secondary coil grounding conductor, 64 ... power supply circuit, 65 ... Ignition control circuit, 70 ... combustion chamber, 80 ... multi-point igniter, 81 ... ignition plate part, 81a ... plate-like insulator, 81a1 ... concave, 81a2 ... plate-like insulation Body side contact member, 81b ... spark generating conductor, 81b1 ... spark generating part, 81b2 ... connecting part, 81c ... back electrode, 82 ... ignition coil, 82a ... housing, 82a1 ... base part, 82a2 ... rib part, 82b ... compressed Spring, 82c ... ignition coil side contact member, 82d ... first elastic member, 82e ... stress distribution plate, 82f ... second elastic member, 101 ... ignition coil, 102 ... combustion chamber, 103 ... spark generating lead, GP ... spark Gap for generation, SP: expansion member accommodating space, R: insulating resin, BL: bolt, NT: nut.

Claims (9)

An ignition coil including a secondary coil that generates a voltage by mutual induction between the primary coil and the primary coil;
An insulator disposed so that at least one surface is exposed to the combustion chamber of the internal combustion engine;
A pair of projecting portions projecting from the predetermined position at a predetermined position on the combustion chamber exposure surface, which is one surface of the insulator exposed to the combustion chamber, so as to form a spark generation gap in the combustion chamber. A plurality of spark generating portions, and a spark generating conductor having a connecting portion for connecting the plurality of spark generating portions in series to both ends of the secondary coil;
The potential at a position where the number of turns of the secondary coil from one end of the secondary coil of the ignition coil is approximately half of the total number of turns of the secondary coil is equal to the conductor portion of the wall surface of the combustion chamber. A secondary coil grounding portion for electrically connecting the secondary coil and the conductor portion of the same wall so that
A multi-point ignition device that generates a spark at each of the plurality of spark generators by a voltage generated by a secondary coil of the ignition coil ,
The ignition coil is fixed so as to contact the insulator,
The insulator is a plate-like member that is configured to cover the connection portion of the spark generating conductor and is made of ceramics,
In the multipoint ignition device in which the primary coil and secondary coil of the ignition coil are embedded in an insulating resin,
The ignition coil and the insulator are fixed in a state where the ignition coil is in contact with the insulator, the surface of the ignition coil on the insulator side, the surface of the insulator on the ignition coil side, To form a first space and a second space,
The secondary coil of the ignition coil is arranged so that both end portions are exposed to each of the first space and the second space,
The connection portion of the spark generating conductor has two end portions exposed to the first space and the second space, respectively, for electrical connection to both ends of the secondary coil of the ignition coil. Arranged to
The end of the secondary coil of the ignition coil exposed in the first space and the end of the connection portion of the spark generating conductor exposed in the first space are electrically connected to each other one by one. A first member that can be stretched;
The end of the secondary coil of the ignition coil exposed in the second space and the end of the connection portion of the spark generating conductor exposed in the second space are electrically connected to each other one by one. A second member that can be stretched;
A multipoint ignition device comprising: The multipoint ignition device according to claim 1,
  The ignition coil is a multipoint ignition device fixed so as to be in contact with the insulator through an elastic member. An ignition coil including a secondary coil that generates a voltage by mutual induction between the primary coil and the primary coil;
An insulator disposed so that at least one surface is exposed to the combustion chamber of the internal combustion engine;
A pair of projecting portions projecting from the predetermined position at a predetermined position on the combustion chamber exposure surface, which is one surface of the insulator exposed to the combustion chamber, so as to form a spark generation gap in the combustion chamber. A plurality of spark generating portions, and a spark generating conductor having a connecting portion for connecting the plurality of spark generating portions in series to both ends of the secondary coil;
The potential at a position where the number of turns of the secondary coil from one end of the secondary coil of the ignition coil is approximately half of the total number of turns of the secondary coil is equal to the conductor portion of the wall surface of the combustion chamber. A secondary coil grounding portion for electrically connecting the secondary coil and the conductor portion of the same wall so that
A multipoint ignition device that generates a spark at each of the plurality of spark generators by a voltage generated by a secondary coil of the ignition coil,
A multipoint ignition device provided with a back electrode disposed inside the insulator and electrically connected to the conductor portion so as to have the same potential as the conductor portion of the wall surface of the combustion chamber . The multipoint ignition device according to any one of claims 1 to 3,
  The insulator is formed in an annular shape having an inner diameter substantially the same as the bore diameter of the cylinder, and is disposed coaxially with the bore of the cylinder so that the inner peripheral surface is exposed to the combustion chamber.
  Furthermore, the multipoint ignition device provided with the reinforcement member arrange | positioned on the outer periphery of the insulator so that expansion | swelling to the radial direction of the said insulator may be restrict | limited. In the multipoint ignition device according to any one of claims 1 to 4,
  The combustion chamber exposure surface of the insulator is formed to have a recess at each position where the plurality of spark generation portions are arranged,
  Each of the spark generating portions is a multipoint ignition device configured such that the pair of projecting portions are accommodated in the concave portions. In the multipoint ignition device according to any one of claims 1 to 5,
  Each of the spark generating portions has the shortest distance among the distances from one predetermined position of the pair of projecting portions to any other position of the same pair of projecting portions. A multipoint ignition device configured to decrease from one base end toward one tip of the protruding portion. The multipoint ignition device according to claim 6,
  In each spark generating portion, the distance along the combustion chamber exposure surface of the insulator between the base ends of the pair of protrusions is 3 of the linear distance between the tips of the same pair of protrusions. A multi-point ignition device configured to be 10 to 10 times larger. In the multipoint ignition device according to any one of claims 1 to 7,
  Each of the spark generators does not ignite the mixed gas before the sparks are generated in the magnitude of thermal energy transmitted between the pair of protrusions having the same surface area of the pair of protrusions and the gas in the combustion chamber. A multipoint ignition device in which a protrusion length from a base end to a tip end of the same pair of protrusions is shorter than a predetermined length so as to have an area having a predetermined size. The multipoint ignition device according to any one of claims 1 to 8,
  Each of the spark generating portions is arranged such that one of the pair of protruding portions faces the other of the same pair of protruding portions via a space,
  In the combustion chamber exposure surface of the insulator, the distance along the combustion chamber exposure surface between the base ends of the pair of protrusions is greater than the linear distance between the base ends of the same pair of protrusions. A multi-point ignition device formed to be.

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