Abstract:
The internal combustion engine has an internal combustion engine main body and a substantially columnar ignition coil. A head part at one end of the ignition coil is provided with an electromagnetic wave element for outputting electromagnetic waves irradiated into a combustion chamber of the internal combustion engine main body, and a plurality of supporting components are provided for supporting the ignition coil when an attaching part at the other end of the ignition coil is attached to a spark plug, the supporting components supporting the ignition coil either at or near a nodal point in a characteristic vibration mode of vibration occurring in the ignition coil along with vibration of the internal combustion engine main body. The ignition coil is not supported on the side toward the head part relative to the support member nearest the head part.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to an internal combustion engine that includes an ignition coil equipped with an electromagnetic wave element which outputs electromagnetic waves. 
       BACKGROUND ART 
       [0002]    Patent documents 1 discloses an ignition device provided with a microwave oscillation device as an apparatus so called an ignition coil (see  FIG. 3 ). The microwave oscillation device has an amplification element. The head part of the ignition device is provided with a mounting flange (see  FIG. 4 ). The ignition device is fixed to the internal combustion engine main body using an attachment bolt which penetrates the mounting flange. 
       PRIOR ART DOCUMENTS 
     Patent Documents 
       [0003]    Patent Document 1: JP 2010-001827A 
       THE DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0004]    in the conventional ignition coil, vibration of the internal combustion engine easily transmits to the head part because the head part is fixed to the internal combustion engine. Therefore, a strong vibration may occur in the electromagnetic wave element together with the head part when the electromagnetic wave element for outputting the electromagnetic wave and the electric circuit are provided on the head part. This can lead to a malfunction of the electromagnetic wave element because of the deformation of the electromagnetic wave element such as momentary bending deformation or the vibration of the electric circuit 
         [0005]    In view of above described circumstances, the present disclosure provides an internal combustion engine that can reduce the vibration force acting on the electromagnetic wave element on the head part of the ignition coil. 
       Means for Solving the Problems 
       [0006]    An internal combustion engine according to the present disclosure includes an internal combustion engine main body forming a plughole therein; and a pillar shaped ignition coil to be inserted in the plughole. An electromagnetic wave element is provided on a head part of the one end side of the ignition coil for outputting electromagnetic waves to be emitted to the combustion chamber of the internal combustion engine main body. The internal combustion engine comprises a plurality of supporting components that support the ignition coil at a nodal point of the characteristic vibration mode of vibration that occurs in the ignition coil accompanied by the vibration of the internal combustion engine main body when an attaching part in the other end of the ignition coil is attached to the ignition plug positioned in the combustion chamber side of the plughole. 
         [0007]    An ignition coil of the present disclosure is a pillar shaped ignition coil inserted in a plughole of an internal combustion engine. An attaching part of the one end side is attached to the spark plug positioned in the combustion chamber side of the plughole. The ignition coil comprises an electromagnetic wave element that outputs the electromagnetic waves to be emitted to the combustion chamber is provided on the head part of the other and side of the ignition coil, and a dynamic damper attached to the head part or the attaching part. 
         [0008]    An ignition coil of the present disclosure is a pillar shaped ignition coil that is inserted in a plughole of an internal combustion engine, and an attaching part in the one end side is attached to the spark plug which is positioned in the combustion chamber side of the plughole. The ignition coil comprises an electromagnetic wave element that is provided on the head part of the other end side of the ignition coil, and that outputs the electromagnetic waves to be emitted to the combustion chamber; a mounting component that mounts the electromagnetic wave element; and a dumping material made of fluid or solid material of low rigidity compared to the mounting component, wherein the dumping material is provided between the mounting component and an installation surface for installing the mounting component in the head part. 
         [0009]    An ignition coil of the present disclosure is a pillar shaped ignition coil inserted in a plughole of an internal combustion engine, where an attaching part of the one end side is attached to the spark plug positioned in the combustion chamber side of the plughole. The ignition coil comprises an electromagnetic wave element that outputs the electromagnetic waves to be emitted to the combustion chamber is provided on the head part of the other end side of the ignition coil; a mounting component that mounts the electromagnetic wave element; a holding component that holds the mounting component using a frictional force at the domain contacting with the mounting component, wherein the holding component is a component different from the mounting component. The mounting component is held using a frictional force between the holding component and the mounting component where the mounting component is not integrated with the head part. 
       Advantage of the Invention 
       [0010]    According to this disclosure, ignition coil  30  is supported at a nodal point or at its neighborhood in the internal combustion engine. Therefore, vibration force of head part  32  can be reduced compared with the conventional ignition coil fixed to cylinder head  21 , and the vibration force of amplification element  35  is thereby reduced. This reduces the malfunction of amplification element  35  due to the vibration of ignition coil  30 . The moderate gap between ignition coil  30  and a cylinder head reduces the thermal influence. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  illustrates an outline structure of an internal combustion engine according to the first embodiment. 
           [0012]      FIG. 2  ( a ) illustrates an outline structure of the head part side of the ignition coil according to the second embodiment.  FIG. 2  ( b ) illustrates an oscillation system including a dynamic damper. 
           [0013]      FIG. 3  ( a ) illustrates an outline structure of the head part side of the ignition coil according to the third embodiment.  FIG. 3  ( b ) illustrates an outline structure of the head part side of the ignition coil of the modified example according to the third embodiment. 
           [0014]      FIG. 4  ( a ) illustrates an outline structure of the head part side of the ignition coil according to the fourth embodiment.  FIG. 4  ( b ) illustrates an outline structure of the head part side of the ignition coil of the modified example according to the fourth embodiment.  FIG. 4  ( c ) illustrates an outline structure of the head part side of the ignition coil of the second modified example according to the fourth embodiment. 
           [0015]      FIG. 5  illustrates an outline structure of the head part side of the ignition coil according to the fifth embodiment. 
           [0016]      FIG. 6  illustrates an outline structure of the head part side of the ignition coil according to the other embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    In the following, a detailed description will be given by an embodiment of the present invention with reference to the accompanying drawings. It should be noted that the following embodiments are merely preferable examples, and do not limit the scope of the present invention, applied field thereof, or application thereof. 
       First Embodiment 
       [0018]    Internal combustion engine  20  equipped with ignition coil  30  (coil assy) is discussed hereafter with reference to the drawings. Internal combustion engine  20  is an example of the present invention. 
       Internal Combustion Engine 
       [0019]    Internal combustion engine  20  is a reciprocating type internal combustion engine as shown in  FIG. 1 . Internal combustion engine  20  equips the internal combustion engine main body  28  which includes cylinder head  21 , cylinder  22 , and piston  23 . Piston  23  is formed inside cylinder  22  so as to reciprocate freely. Cylinder head  21  cylinder  22  and piston  23  form combustion chamber  24 . When piston  23  reciprocates in the axial direction of cylinder  22  inside cylinder  22 , a connecting rod (not illustrated) converts the reciprocation of piston  23  to a rotational movement. 
         [0020]    Plughole  25  is formed in cylinder head  21  so as to penetrate cylinder head  21  straightly. Plughole  25  is a penetration hole having a circular section. Spark plug  26  is fixed to cylinder head  21  in the combustion chamber  24  side of plughole  25 . Ignition coil  30  of pillar shaped shape is attached to spark plug  26 . Cylinder head  21  forms therein the inlet port and exhaust port (not illustrated) that opens toward combustion chamber  24 . An intake valve is formed in the inlet port. An exhaust valve is formed in the exhaust port. Further, an injector is provided in the combustion chamber or the inlet port. Here, internal combustion engine  20  is not limited to a reciprocating type internal combustion engine. 
       Ignition Coil 
       [0021]    Ignition coil  30  is so called a “stick coil”. As shown in  FIG. 1 , ignition coil  30  equips cylindrical main body part  31 , head part  32  located in one end side of main body part  31 , and attaching part  33  located in other end side of main body part  31 . Main body part  31 , head part  32 , and attaching part  33  are integrated. Ignition coil  30  shall not be limited to the stick coil and a coil part, which will be discussed later, can be provided on head part  32 . 
         [0022]    Main body part  31  accommodates a coil part (transformer) which includes a primary coil, a secondary coil, and an iron core inside the case of body part  31 . The case of body part  31  is formed cylindrical. A High voltage terminal connected to the output side of the coil part is provided in the attaching part  33  side of body part  31 . 
         [0023]    Head part  32  equips an igniter (a switching circuit that includes a transistor) and microwave amplification element  35  (for example, an IC chip made of semiconductor device). Microwave amplification element  35  occupies a large area since this is located in addition to a transistor of the igniter. Igniter and amplification element  35  are mounted on substrate  36  (mounting component) that is fixed inside the case of head part  32 . Amplification element  35  is integrated with substrate  36 . Head part  32  is provided with a first input terminal for ignition signal, a second input terminal for battery connection, and a third input terminal for microwave. Microwave oscillation element, e.g. crystal oscillator, can be provided on head part  32  for generating microwave. Amplification element  35  and microwave oscillation element correspond to electromagnetic wave elements. 
         [0024]    Attaching part  33  is formed in an approximate cylindrical shape. Attaching part  33  is formed of an elastic component such as rubber. Spark plug  26  is inserted inside Attaching part  33 . 
         [0025]    Magnetic energy is stored in ignition coil  30  by magnetization of an iron core when the current from a battery flows into a primary coil side of the coil part via a second input terminal. The primary current is intercepted by the switching of the igniter when an ignition signal is inputted from the first input terminal in this state because the voltage occurs in the primary coil and the magnetic field around the iron core changes. As a result, a high-voltage pulse is generated in a secondary coil, and the high-voltage pulse is outputted to spark plug  26  from a high-voltage terminal. When microwaves, e.g. microwave pulses are inputted from a third input terminal, the microwaves are amplified by amplification element  35 . A mixing circuit for mixing the high-voltage pulse and microwaves is provided in main body part  31  or head part  32  of ignition coil  30 . Microwaves outputted from amplification element  35  are outputted to spark plug  26  via the mixing circuit. When the ignition signal and the microwaves are inputted into ignition coil  30  almost simultaneously, the high-voltage pulse and the microwaves are outputted to spark plug  26  from ignition coil  30  almost simultaneously. Small plasma is generated in a spark gap of spark plug  26  using spark discharge of high-voltage pulse. This plasma is enlarged by microwaves and microwave plasma is thereby generated. 
         [0026]    Ignition coil  30  is attached to spark plug  26  by inserting into plughole  25  from attaching part  33  side and by inserting an input terminal side of spark plug  26  to attaching part  33 . The high-voltage terminal is forced to the input terminal of spark plug  26  by spring component of main body part  31  in the attachment state where ignition coil  30  is attached to spark plug  26 . The entire head part  32  is located in the outside of plughole  25 . Clearances are provided between the wall surface of plughole  25  and peripheral side of main body part  31 , and between the wall surface of plughole  25  and peripheral side of attaching part  33 . When internal combustion engine  20  vibrates during an operation, the vibration of internal combustion engine  20  is transmitted to ignition coil  30  via attaching part  33 . Clearance or crevice can be provided between attaching part  33  and spark plug  26  in the attaching state. 
         [0027]    The amplitude of vibration becomes larger in the direction perpendicular to the axis of main body part  31  because ignition coil  30  is pillar shaped (beam-like shape). In case of a conventional ignition coil, the ignition coil is screwed to upper part of cylinder head  21  in the head part position together with the engine cover. The ignition coil is supported to cylinder head  21  by the head part and the attaching part. Therefore, the head part vibrates integrally with cylinder head  21  because the vibration of cylinder head  21  easily transmits to the head part, and a strong vibration acts to the amplification element. As a result, a voltage signal due to deformation of vibration may arise in the amplification element, which is a semiconductor device, and the amplification element may cause malfunction. Further, the amplification element may easily break down. 
         [0028]    On the contrary, internal combustion engine  20  of this embodiment has a support structure that reduces the vibration force of ignition coil  30  acting to amplification element  35 . The support structure comprises first support component  41  and second support component  42  that supports ignition coil  30  at nodal point  50  (node of primary basic mode) of the vibration in ignition coil  30 , where the vibration is flexural vibration in the direction perpendicular to the axis of body part  31  (this direction will be referred to “normal direction” hereafter) when ignition coil  30  vibrates accompanied by the vibration of internal combustion engine  20 . Each support components  41  and  42  supports main body part  31  of ignition coil  30  at nodal point  50  toward the wall surface of plughole  25 . The support structure does not support ignition coil  30  using first support component  41  and second support component  42  at the position that is closer to head part  32  compared with first support component  41 . 
         [0029]    Resonance frequency and vibration mode of ignition coil  30  are determined by mass and flexural rigidity of each portions. The node position (nodal point  50 ) and belly position of the vibrating ignition coil  30  is determined when the vibration mode is determined. Nodal point  50  is a position inherent to ignition coil  30 . Nodal point  50  of ignition coil  30  can be recognized using an analysis such as finite element method.  FIG. 1  illustrates, in dashed lines, first line indicating amplitude in the horizontal direction, i.e. normal direction in the vertical position of ignition coil  30 , and a second line indicating position where the amplitude becomes zero in the horizontal direction. Nodal point  50  is a position where the first and the second lines intersects in the vertical direction of ignition coil  30 , and the amplitude in the horizontal direction becomes zero in nodal point  50 . 
         [0030]    In this embodiment, each support components  41  and  42  are arranged on nodal point  50  which is acquired analytically beforehand. Each support components  41  and  42  can be fixed to the peripheral side of main body part  31  of ignition coil  30 , or can be fixed to wall surface of plughole  25 . Each support components  41  and  42  can be the protrusions that project from the peripheral surface of main body part  31  or wall surface of plughole  25 . In this embodiment, each support components  41  and  42  are located on nodal point  50 ; however, each support components  41  and  42  can be located near nodal point  50 . 
         [0031]    Each support components  41  and  42  are elastic components, e.g. rubber component. Ignition coil  30  is supported elastically by each support components  41  and  42 . Each support component  41  and  42  is formed in ring like shape. In this embodiment, support components  41  and  42  are provided one by one for each nodal point  50 ; however, multiple support components can be provided corresponding to each nodal point  50 . 
         [0032]    Non-elastic material such as steel component can be used as each support components  41  and  42 . In this case, ignition coil  30  is supported by each support components  41  and  42  when the portion contacting with each support components  41  and  42  in the casing of ignition coil  30  is an elastic material. 
       Advantage of the Present Embodiment 
       [0033]    In this embodiment, ignition coil  30  is supported, besides spark plug  26 , by support components  41  and  42  located in nodal point  50 . Therefore, vibration force of head part  32  can be reduced compared with the conventional ignition coil where head part  32  is fixed to cylinder head  21 , and can reduce the vibration occurring in amplification element  35 . Therefore, malfunction of amplification element  35  resulting from vibration of ignition coil  30  can be controlled. Further, the thermal influence can be reduced also since a moderate clearance (gap) is provided between ignition coil  30  and the cylinder head. 
       Second Embodiment 
       [0034]    In the present embodiment, vibration in the head part  32  of ignition coil  30  is reduced using dynamic damper  60 . Hereinafter the points distinct from the first embodiment will be discussed. 
         [0035]    As shown in  FIG. 2  (a), ignition coil  30  is equipped with dynamic damper  60 . Dynamic damper  60  includes small mass part  61  (weight) which functions as a secondary oscillating system, where a portion  65  (large mass part, this portion is the entirety of ignition coil  30  excluding dynamic damper  60 ), and elastic component  62  such as rubber components that connects small mass part  61  to head part  32  as shown in  FIG. 2  ( b ). The mass (modal mass) of small mass part  61  is smaller than the mass (modal mass) of large mass part  65 . The mass of small mass part  61  and spring constant k of elastic component  62  of dynamic damper  60  are determined so that the resonance frequency (natural frequency) of the system consisting small mass part  61  and elastic component  62  divides the total resonance of large mass part  65 . In  FIG. 2  ( b ), K indicates a spring constant of large mass part  65 . 
         [0036]    In the example of  FIG. 2  ( a ), small mass part  61  is made of steel materials and elastic component  62  is made of rubber material. Elastic component  62  is fixed on the upper surface of a case of head part  32 , and small mass part  61  is fixed on the upper surface of elastic component  62 . Dynamic damper  60  is formed so that the small mass part  61  vibrates in the opposite phase direction of the vibration of internal combustion engine  20  and ignition coil  30 . 
       Advantage of this Embodiment 
       [0037]    According to the present embodiment, dynamic damper  60  is attached to head part  32  and dynamic damper  60  can absorb the vibration energy. This reduces the vibration of head part  32 , which is a portion of large mass part  65 , and the vibration of amplification element  35  is thereby reduced. Therefore, malfunction of amplification element  35  resulting from the vibration of ignition coil  30  can be reduced. Dynamic damper  60  can be attached to a belly position of vibration in the characteristic vibration mode of ignition coil  30 , or can be attached to attaching part  33 . 
       Third Embodiment 
       [0038]    In this embodiment, vibration acting on amplification element  35  is reduced using a floating structure that softy supports substrate  36  so that the integrity of amplification element  35  and substrate  36  against head part  32  is reduced. Hereafter, the points distinct from the first embodiment mil be discussed. 
         [0039]    As shown in  FIG. 3  ( a ), ignition coil  30  has support component  70  as a floating structure. Support component  70  is a pliable sheet material, for example. Support component  70  has rigidity lower than substrate  36 . 
         [0040]    Support component  70  is fixed on component installation surface  32   a  inside the case of head part  32 . Substrate  36  for mounting amplification element  35  is fixed on the upper surface of support component  70 . 
         [0041]    Characteristic vibration frequency f 1  in the normal direction of resonance body consisting of substrate  36  and amplification element  35  is determined based on spring constant of support component  70  and total mass of substrate  36  and amplification element  35 . In this embodiment, the spring constant of support component  70  and the total mass of substrate  36  and amplification element  35  are determined so that characteristic vibration frequency f 1  becomes lower than frequency N, where N is frequency of fundamental degree vibration in the normal direction of internal combustion engine  20 . For example, the fundamental degree will be the second degree in case of four cylinders. 
       Advantage of the Present Embodiment  
       [0042]    According to the present embodiment, transmission of vibration from head part  32  to substrate  36  is reduced because support component  70  of floating structure is intervened between substrate  36  and component installation surface  32   a.  This reduces the vibration of amplification element  35 . Malfunction of amplification element  35  resulting from vibration of ignition coil  30  can thereby be reduced. 
         [0043]    In the present embodiment, substrate  36  hardly deforms compared to a case where a portion of substrate  36  is adhered to support component  70  because the entire back surface of substrate  36  is adhered to support component  70 . The deformation of amplification element  35  originated by vibration is thereby reduced. 
       Modification of the Present Embodiment 
       [0044]    In this modification, multiple support components  71  are formed as a floating structure as shown in  FIG. 3  ( b ). Substrate  36  is supported by multiple support components  71 . One end of each support components  71  are fixed to component installation surface  32   a,  and the other ends are fixed to substrate  36 . Multiple support components  71  support substrate  36  in the four corners of substrate  36 . Support component  71  can be a tiny rubber ball or bonding material. According to this modification, vibration of amplification element  35  can be further reduced because the flexibility between component installation surface  32   a  and substrate  36  is increased. 
       Fourth Embodiment 
       [0045]    In this embodiment, vibration force acting on dumping material  80  is reduced using dumping material  80  that can attenuate the vibration. Hereafter, the points distinct from the first embodiment will be discussed. 
         [0046]    As shown in  FIG. 4  ( a ), ignition coil  30  equips dumping material  80 . Dumping material  80  is a solid material such as a pliable sheet material having small rigidity (elastic modulus) compared to substrate  36 . Dumping material  80  is fixed to component installation surface  32   a  inside the case of head part  32 . Substrate  36  for mounting amplification element  35  is fixed to the upper surface of dumping material  80 .  
       Advantage of this Embodiment 
       [0047]    In this embodiment, substrate  36  is supported by head part  32  through dumping material  80 . The vibration of amplification element  35  on substrate  36  is thereby reduced, and malfunction of amplification element  35  resulting from vibration of ignition coil  30  is can be reduced. Further, deformation of amplification element  35  due to vibration can be reduced because the whole back surface of substrate  36  is adhered to dumping material  80  in this embodiment. 
       Modification 1 of the Present Embodiment 
       [0048]    In the modification 1, substrate  36  is supported by multiple dumping materials  81  as shown in  FIG. 4  ( b ). One ends of each dumping materials  81  are fixed to component installation surface  32   a  and the other ends are fixed to substrate  36 . For example, multiple dumping materials  81  support substrate  36  in the four corners of substrate  36 . According to modification 1, vibration of amplification element  35  can further be reduced because the pliability between component installation surface  32   a  and substrate  36  is improved. 
       Modification 2 of the Present Embodiment 
       [0049]    In modification 2, dumping material  83  is made of fluid (inactive gas, or liquids such as oil). As shown in  FIG. 4  ( c ), ignition coil  30  equips auxiliary component  85  of rectangular piped shape fixed to component installation surface  32   a.  Dumping material  83  is enclosed between substrate  36  in auxiliary component  85  and component installation surface  32   a.  A seal material can be provided in the circumference of substrate  36 . 
       Fifth Embodiment 
       [0050]    In this embodiment, vibration acting on amplification element  35  is reduced by supporting substrate  36  using frictional force only. Hereafter, the points distinct from the first embodiment will be discussed. 
         [0051]    As shown in  FIG. 5 , ignition coil  30  equips a support structure including holding component  91  that holds substrate  36  using a frictional force in the area contacting with substrate  36 . The support structure supports substrate  36  using frictional force between holding component  91  and substrate  36  without integrating substrate  36  with head part  32 . 
         [0052]    Holding component  91  is a component such as rubber, and is different from substrate  36 . Holding component  91  equips a rectangle pipe shaped main body part  91   a  and stopper  91   b  that projects inside from one end side of main body part  91 . The other end side of main body part  91   a  is fixed to component installation surface  32   a . The inner circumference of main body part  91   a  is slightly smaller than the periphery of rectangular substrate  36 . Substrate  36  is inserted in the inside of main body part  91   a . Here, main body part  91   a  presses substrate  36  inside using stability of main body part  91   a.  Substrate is held by frictional force between main body part  91   a  and contacting area of substrate  36 . Stopper  91   b  prevents substrate  36  from slipping out from main body part  91   a.  The number of holding component  91  is one in this embodiment; however, substrate  36  can be supported by multiple holding component  91  can be used. 
         [0053]    The support structure further equips support component  92 . Support component  92  is a component different from substrate  36  and is fixed to component installation surface  32   a.  The movement of substrate  36  toward the bottom side (in  FIG. 5 ) is thereby inhibited using support component  92 . The support structure does not need an additional support component  92 . The fluid can be provided between substrate  36  and component installation surface  32   a  instead of support component  92 . 
       Advantage of This Embodiment 
       [0054]    In this embodiment, substrate  36  is not integrated with head part  32  and is supported using frictional force only. The vibration transmitting to substrate  36  from head part  32  can be reduced compared to the case when substrate  36  is integrated with head part  32 . The malfunction of amplification element  35  resulting from vibration of ignition coil  30  can thereby be reduced. 
       Other Embodiment 
       [0055]    The following embodiment can be contemplated. 
         [0056]    In the above embodiment, electromagnetic wave element (amplification element  35 ) is provided inside an identical case with the igniter; however, electromagnetic wave element  35  can be provided inside a case that is different from head part  32  as shown in  FIG. 6 . Head part  32  equips first case  111  for accommodating an igniter and second case  112  for accommodating electromagnetic wave element  35 . Second case  112  is fixed to first case  111  using screw, for example. 
         [0057]    The above mentioned first embodiment can be combined with the second, third, fourth, or fifth embodiment. 
       INDUSTRIAL APPLICABILITY 
       [0058]    The present disclosure is applicable to an internal combustion engine that includes an ignition coil equipped with an electromagnetic wave element which outputs electromagnetic waves. 
       EXPLANATION OF REFERENCE NUMERALS 
       [0059]      20  Internal combustion engine 
         [0060]      25  Plughole 
         [0061]      26  Spark plug 
         [0062]      28  Internal combustion engine main body 
         [0063]      30  Ignition coil 
         [0064]      31  Main body part 
         [0065]      32  Head part 
         [0066]      33  Attaching part 
         [0067]      35  Amplification element (electromagnetic wave element) 
         [0068]      36  Substrate (mounting component) 
         [0069]      41  First support component 
         [0070]      42  Second support component 
         [0071]      50  Nodal point