JP2011012604A - Ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil utilizing a rain cover with simple shape, and releasing pressure difference without keeping pressure difference between the inside and the outside of a plug hole for a long period of time.SOLUTION: In the ignition coil, an absorbing space 115g is formed on an end side of a first air-bleeding passage, when referring to Fig.2(a). The absorbing space is approximately circular, and a section width W2 corresponding to a diameter thereof is set to be larger than a ventilation section width W1 of an annular passage 115e. As shown in Fig.2(b), in a cross-section of the first ventilation passage, the absorbing space 115g is formed of a side face, a space bottom face 115x, and a case bottom face 111c. The space bottom face 115x is provided with a bottom open end 115y corresponding to an end of the second ventilation passage 115b. In the rain cover 115, the ventilation passages function as a path connecting an open end 115f to the open end on an internal space side Fi.

Description

  The present invention relates to an ignition coil mounted on an internal combustion engine for a vehicle, and more particularly to a structure of a rain cover disposed at an upper end portion of a plug hole.

  When receiving an ignition signal or ignition power, an ignition coil mounted on an internal combustion engine for a vehicle gives an action of boosting to about several hundred volts using a battery potential of about 12V to 24V. The ignition coil applies the boosted potential thus obtained to the ignition plug, thereby burning the lean fuel in the cylinder and applying a driving force to the crankshaft via the piston of the internal combustion engine. Incidentally, in recent ignition coils, there are a wide variety of forms such as those in which ignition power is appropriately distributed by a distributor, and those in which a direct ignition method having an igniter on the head is adopted.

  FIG. 17 shows an example of a closed magnetic circuit type ignition coil. The ignition coil 10 includes a coil case 11 having a connector portion 11a and a coil housing portion 11b, an iron core 12 inserted through the coil assembly in the coil case, and a high voltage tower for transmitting a high voltage boosted by the coil assembly. 13, a plug cap 14 attached to a connection side terminal of the high-voltage tower 13, and a rain cover 15 mounted between the upper end side opening of the plug hole PH and the case bottom surface of the coil case 11 b. . In the ignition coil 10, the high-voltage tower 13 is inserted into the plug hole PH of the engine head, and the connection side terminal and the head terminal of the ignition plug are connected. The rain cover is formed from an elastic material having an insulating property, and is appropriately elastically deformed by the fixing bolt 12a, thereby preventing rainwater from entering the plug hole. Further, the rain cover is provided with a groove-like air vent passage to relieve a pressure difference generated between the internal space in the plug hole and the external space covering the engine head surface layer. Here, in the engine block that constitutes the cylinder, the temperature fluctuates significantly according to the supply / exhaust operation of the mixed gas and the ignition operation of the spark plug PG, so that such temperature change is transmitted in the plug hole and formed in the plug hole. The volume change of the internal space is periodically generated. That is, the air vent passage provided in the rain cover plays a role of releasing the pressure of the internal space that increases or decreases due to the volume change to the external space of the engine head.

  Japanese Patent No. 2576071 (Patent Document 1) introduces an ignition coil device (hereinafter referred to as an ignition coil) for the purpose of easily forming the air vent passage described above. As shown in FIG. 18A, the ignition coil includes a pressure contact portion of the coil case 11 and a seal member 15 (a rain cover in the claims). In the figure, a part of the high-pressure tower 11d is omitted for convenience. As shown in the drawing, a seal-side passage 15b is formed in the seal member 15 so as to communicate the surface in contact with the pressure contact portion and the internal space Ai of the plug hole PH. (Referred to as the case bottom surface) are formed with a coil side passage 11r having an open end on one side and an angle allowing groove 11e for communicating the seal side passage 15b and the coil side passage 11r. Here, when the ignition coil 10 is observed in the direction of the arrow of the AA cross section, as shown in FIG. 18B, the angle tolerance groove 11e has a locus with a constant radius RD centered on the axis of the plug hole PH. The opening end of the seal side passage 15b is formed at a position separated from the axis of the plug hole PH by the same radius RD. Therefore, in the ignition coil 10, when the coil case 15 is mounted, the ignition coil 10 is positioned by the internal opening surface 15a, and the opening end of the seal side passage 15b and the angle tolerance groove 11e are easily aligned. . In the diagram shown in FIG. 18B, the solid line portion indicates the outline of the rain cover 15, and the broken line portion indicates the outline of the coil side passage 11r and the angle-permissible groove 11e formed in the coil case. To do.

  FIG. 19 shows a modification of the technique according to Patent Document 1 described above. As shown in FIG. 19A, the seal member 15 includes a first seal side passage 11r having an open end on one side, an angle allowance groove 15e communicating with the seal side passage 15r, and the angle allowance groove 15e. And a second seal side passage 15b for communicating the internal space Ai. Here, when the ignition coil 10 is observed in the direction of the arrow of the AA cross section, as shown in FIG. 19B, the air vent passage composed of the angle allowance groove 15e and the communication grooves 15r, 15e is formed in the rain cover 15. Therefore, the internal space Ai and the external space Ao are communicated with each other without needing to align each other. In addition, all the solid line parts shown in FIG. 19B indicate the outline of the rain cover 15.

  In addition, Japanese Patent No. 3145880 (Patent Document 2) introduces an ignition coil that prevents intrusion of rainwater entering the plug hole through the air vent passage. As shown in FIG. 20, such an ignition coil is formed by forming a first air vent passage and a second air vent passage in an insulating cap (a rain cover in the claims), thereby providing an internal space Ai of the plug hole PH. Communicates with the external space Ao. Here, the first air vent passage includes a first communication groove 15r communicating with the external space Ao, a circumferential groove 15e formed in a substantially circumferential shape, and a groove larger than the groove width dimension of the circumferential groove 15e. An absorption space 15g having a width and having a groove bottom deeper than the depth of the circumferential groove 15e, and a level substantially equal to the groove bottom of the circumferential groove 15e and communicating with one of the absorption spaces 15g. It comprises a second air vent passage 15h. Such absorption spaces are provided at a plurality of locations along the circumferential groove 15e. On the other hand, the second air vent passage 15b has one end opened to the internal space Ai of the plug hole PH and the other end opened to the groove bottom of the second communication groove 15h. In such an ignition coil, since the groove bottom of the absorption space 15g is formed at a deeper level than the groove bottom of the first air vent passage, rainwater that has entered from the external space Ao temporarily becomes the groove bottom of the absorption space. Water is stored in the vicinity, so that inundation of the circumferential groove 15e having a shallow groove bottom is avoided, and the airway is secured.

Japanese Patent No. 2576071 Japanese Patent No. 3145880

  In recent technologies, when mass-producing rain covers, they are generally produced by an injection molding method using a mold. According to such a method, by reflecting the detailed shape of the air vent passage or the like on the mold, it is possible to realize a shape according to demand even for a rain cover having a complicated shape.

  However, according to such an injection molding method, if the shape of the details is reflected in the mold in an inseparable state, it becomes impossible to cope with a fine design change such as a hole diameter or a hole position. Since a new mold is required, production costs may increase. In addition, it is conceivable to use a mold that can be exchanged only in a part of the area as a measure to cope with the design change. It cannot be a positive measure.

  When manufacturing such a rain cover, it is possible to solve manufacturing problems associated with design changes by using both the injection molding process and the machining process. FIG. 21 shows a method of manufacturing a rain cover using an injection molding process and a machining process in combination. In the drawing, Fo is defined as the close contact surface side of the rain cover, and Fi is described as the internal space side of the rain cover. As shown in FIG. 21 (a), the rain cover cast in the injection molding process is formed with essential shapes such as the internal opening surface 15a and the flange portion. At this time, the air vent passage formed in the upper end surface may be simultaneously molded by an injection molding process as long as there is no influence by the design change. Then, as shown in the figure, when the rain cover 15 in such a state is put into the machining process, the rain cover is arranged such that the internal space side Fi is disposed below and the contact surface side Fo is disposed above. Then, the needle-like workpiece WP (the punching means in the claims) is pressed from the internal space side Fi, and punching processing at an appropriate position in the rain cover 15 is started. The needle diameter of the workpiece WP is about several millimeters and is supported by a replaceable mechanism.

  When the feeding operation of the workpiece WP proceeds, as shown in FIG. 21 (b), the needle tip of the workpiece WP reaches the contact surface side Fo. At this time, a part of the chips cut by the workpiece WP is pushed out to the internal space side Fi in accordance with the feeding operation of the workpiece WP, and the burr portion DP is formed at the end of the drilled portion.

  Thereafter, the workpiece WP is pulled back to the internal space side Fi as shown in FIG. At this time, chips adhering to the tip of the workpiece WP may accumulate on the contact surface side Fo of the air vent passage 15b, and the burr part DP may further grow. Although a difference in degree is recognized, the burr portion DP may be formed even in the internal space side Fi of the air vent passage 15b.

  FIG. 22 shows an enlarged view of the air vent passage when a rain cover using both an injection molding process and a machining process is used. In addition, in the same figure, the rain cover which concerns on patent document 1 is used, FIG. 22 (a) which observed the expanded cross section of the air vent path formed using the said rain cover, and the arrow of CC cross section FIGS. 22B and 22C observed in the line direction (plane direction) are shown. Here, referring to FIG. 22A, when the rain cover 15 comes into contact with the coil case 11, the contact surface Sfi is formed. In the close contact surface Sfi, an angle tolerance groove 11e is formed on the coil case side. Moreover, since the rain cover using both the injection molding process and the machining process is used, the burr portion DP is embedded in the ventilation space formed by the angle allowable groove 11e, and most of the space is occupied. . Such a burr portion DP fills all the ventilation cross sections of the angle allowance groove 11e like DP1 depending on the amount of accumulated chips, and in some cases, a predetermined gap is formed in the angle allowance groove 11e like DP2. There is also. Further, since the burr portion DP is formed by fine particles of chips, as shown in the figure, the defect hole portion K where the particles do not exist is formed discontinuously.

  Here, FIG. 22B shows a burr portion DP1 that completely occupies the ventilation cross section of the angle-permissible groove, and the burr portion DP1 has a defect hole only in one of the two-way air passages. It is assumed that the part K is formed. Of the paths in two directions, the path where the ventilation path is blocked by the burr portion DP1 is defined as the ventilation path Ra, and the path where the ventilation path to the internal space Ai is secured by the defect hole K is defined as the ventilation path Rb.

  Referring to the figure, when the gas flow in the angle-permissible groove 11e is observed, the gas flow is stagnated in the ventilation path Ra because the ventilation path is blocked by the burr part DP1. On the other hand, in the ventilation path Rb, even if the burr part DP1 is present, the defect hole part K is present, so that the gas flow in the direction of the plug hole PH is ensured. Further, when the internal pressure of the plug hole PH increases, the reverse path from the internal space Ai to the external space Ao is similarly secured by the ventilation path Rb.

  However, in the technique of Patent Document 1, since one of the air passages does not function, the gas flow rate in the air passage Rb increases. In such a case, since the resistance that the gas receives from the wall surface of the angle-permissible groove 11e increases in proportion to the flow velocity of the gas, the pressure difference generated between the internal space Ai and the external space Ao in the plug hole is instantaneous. There is a problem that it cannot be opened. In particular, such a problem appears remarkably under conditions where the gas flow is in a turbulent state. Here, in such an ignition coil, if the differential pressure is not released instantaneously, an unnecessary ventilation path may be formed on the contact surface between the upper opening end of the plug hole and the rain cover, and rainwater to the plug hole may be formed. There may also be a problem that the sealing function for preventing intrusion is not exhibited. Furthermore, if the negative pressure state is continued in the internal space Ai of the plug hole, there is a concern that there is a high possibility that rainwater or moisture will be sucked into the plug hole.

  Moreover, since the defect hole K has a small opening area compared to the opening cross-sectional area of the angle absorption groove, a large pressure loss is caused in the middle of the gas flow. Therefore, in such an ignition coil, the pressure gradient of the gas flowing in the opening direction from the defect hole K becomes remarkably gentle, and there is a further problem that the pressure difference generated between the two spaces cannot be effectively released.

  FIG. 22 (c) shows a burr portion DP2 that forms a slight gap in the ventilation cross section of the angle-permissible groove. Even in the burr portion DP2, the burr portion DP2 has one of the two-way air passages. Only the defect hole K is formed.

  Referring to the figure, when the gas flow in the angle-permissible groove 11e is observed, in the air passage Rb, even if the burr portion DP1 is present, the defect hole portion K is present, and therefore in the plug hole PH direction. The gas flow is ensured. On the other hand, in the ventilation path Ra, since a slight gap is formed on both sides of the burr part DP2, the gas flow merges with the ventilation path Rb.

  However, in such a case, since the ventilation cross section of the ventilation path Ra is locally reduced, the gas flow rate in the ventilation path Rb increases as described above. At this time, there arises a problem that the pressure difference generated between the internal space Ai in the plug hole and the external space Ao cannot be released instantaneously. Therefore, even in such an ignition coil, the differential pressure is not instantaneously released, so an unnecessary ventilation path is formed on the contact surface between the upper opening end of the plug hole and the rain cover, and the sealing function of the rain cover is exhibited. The problem of disappearing can occur. Furthermore, if the negative pressure state is continued in the plug hole, there is a high possibility that rainwater or moisture is sucked into the plug hole.

  Further, in such an ignition coil, since the defect hole K gives a pressure loss to the flowing gas, as described above, the pressure gradient of the gas flowing from the defect hole K in the opening direction becomes remarkably gentle, and both spaces There is also a problem that the pressure difference generated between the two cannot be effectively released.

  Next, FIG. 23 shows a rain cover according to a modified example of Patent Document 1, and FIG. 23 (a) in which an enlarged cross section of an air vent passage formed using the rain cover is observed, and C FIGS. 23 (b) and 23 (c) observed in the arrow direction (plane direction) of the −C cross section are shown. Here, referring to FIG. 23A, an angle-permissible groove 15e is formed on the rain cover side in the contact surface Sfi. Further, since the rain cover using both the injection molding process and the machining process is used, the burr portion DP is formed in the angle allowable groove 15e, and the most of the ventilation cross section is occupied by the burr portion DP. Depending on the amount of accumulated chips, the burr portion DP may fill up all the ventilation cross sections of the angle allowance groove 11e like DP1, and may form a predetermined gap in the angle allowance groove 11e like DP2. In the burr part DP, as shown in the figure, the defect hole part K where no chip particles are present is formed discontinuously.

  Here, referring to FIG. 23B, as in the technique of Patent Document 1, one of the air passages does not function, and thus the gas flow rate in the air passage Rb increases. That is, even in the modified example of Patent Document 1, there arises a problem that the pressure difference generated between the internal space Ai and the external space Ao in the plug hole cannot be released instantaneously. In such an ignition coil, since the differential pressure is not instantaneously released, an unnecessary ventilation path is formed on the contact surface with the rain cover, and the sealing function of the rain cover may not be exhibited. In addition, if the negative pressure state continues in the plug hole, there is a concern that rainwater or moisture in the engine room may be sucked. Furthermore, in such an ignition coil, the pressure gradient of the gas flowing in the opening direction is remarkably reduced due to the missing hole K, and there is a problem that the pressure difference between the inside and outside cannot be effectively released.

  Further, FIG. 23C shows a burr portion DP2 that forms a slight gap in the ventilation cross section of the angle allowable groove. The burr portion DP2 has a defect hole K formed in only one of the two-way air passages as described above. Even in such a case, since the function of one of the air passages is lowered, the same problem as that pointed out in FIG. 22C occurs.

  In addition, in the technique according to Patent Document 2, as shown in FIG. 20, since the communication path 15h is provided between the absorption space 15g and the second air vent path 15b, the second air vent is provided from the external opening end 15f. The configuration of the first air vent passage leading to the passage 15b is complicated. Here, when the rain cover 15 is injection-molded together with the first air vent passage, there arises a problem that the mold used at the time of injection molding becomes complicated with the complication of the first air vent passage. On the other hand, when the first air vent passage is machined after the injection molding of the rain cover 15, the shape of the first air vent passage is complicated, which leads to a longer machining process and higher cost. The problem also arises. Further, as described above, when the shape of the ventilation path becomes complicated, it leads to generation of unnecessary pressure loss.

  Further, as shown in FIG. 21B, the second air vent passage 15b is processed at a position separated from the communication passage 15e by a distance D1 in the radial direction. Therefore, when the rain cover is downsized, the layout of the first air vent passage and the second air vent passage becomes tight, and there is a problem that the degree of freedom in design becomes extremely narrow. When the layout around the second air vent passage becomes tight, the processing accuracy of the second air vent passage 15b is required to be high despite the processing on the elastic body.

  Furthermore, in the technique according to Patent Document 2, a burr portion having a deficient hole is formed in the communication path 15h. Such a burr portion may reach the case bottom surface 11c because the communication path 15h is at the same level as the groove bottom of the other communication path 15e. Such a deficient hole is a rare opening that connects both the air vent passages, and has a small opening area compared to the opening cross-sectional area of the communication passage 15h or the second air vent passage 15b. Therefore, a large pressure loss is given in the middle of the gas flow. That is, in such an ignition coil, the pressure gradient of the gas flowing in the opening direction from the deficient hole portion becomes remarkably gentle, and there arises a problem that the pressure difference generated between both spaces cannot be effectively released as described above. Therefore, even in the ignition coil, there may be a problem that the rain cover sealing function is deteriorated and a situation in which rainwater and moisture in the engine room are sucked into the plug hole.

  In view of the above problems, an object of the present invention is to provide an ignition coil that can use a rain cover having a simple shape and can be opened without maintaining a pressure difference between the inside and outside of a plug hole for a long time.

  In order to solve the above problems, the present invention has the following ignition coil configuration. That is, a rain that is mounted in close contact with the coil case and the case bottom surface of the coil case and the upper opening end of the plug hole, and forms an internal space of the plug hole and an external space in which the head of the coil case is disposed. An absorption having a cover, a first air vent passage formed on a close contact surface of the case bottom surface and the rain cover and communicating with the external space, and a cross-sectional width larger than a ventilation cross-sectional width of the first air vent passage. In an ignition coil comprising a space and a second air vent passage that communicates the absorption space and the internal space, the absorption space includes a side opening end that communicates directly with the first air vent passage; The space bottom surface which corresponds to the level of the bottom surface of the first air vent passage, and the bottom surface opening end formed at the space bottom surface of the end of the second air vent passage. The second air vent passage, toward the contact surface from the inner space side of the rain cover, and to be drilled using the drilling unit.

  In the present invention, the following ignition coil configuration may be used. That is, a rain that is mounted in close contact with the coil case and the case bottom surface of the coil case and the upper opening end of the plug hole, and forms an internal space of the plug hole and an external space in which the head of the coil case is disposed. An absorption having a cover, a first air vent passage formed on a close contact surface of the case bottom surface and the rain cover and communicating with the external space, and a cross-sectional width larger than a ventilation cross-sectional width of the first air vent passage. In an ignition coil comprising a space and a second air vent passage that communicates the absorption space and the internal space, the absorption space includes a side opening end that communicates directly with the first air vent passage; A space bottom surface formed at a deeper level than a bottom surface level of the first air vent passage and an end portion of the second air vent passage are formed on the space bottom surface. ; And a bottom open end, said second air vent passage, toward the contact surface from the inner space side of the rain cover, ignition coil, characterized in that the drilling using a drilling unit.

  Preferably, for each of these inventions, the absorption space is formed in the rain cover.

  More preferably, the space bottom surface includes a secondary space bottom surface formed at a deeper level than the level of the space bottom surface, and the bottom surface opening end is formed on the secondary space bottom surface.

  The first air vent passage may be configured as follows. That is, more preferably, the first air vent passage is formed by the bottom surface of the case and a cover-side passage formed on the rain cover. Furthermore, the first air vent passage is not limited to the previous configuration, and may be configured as follows. That is, the first air vent passage is formed by a case side passage formed on the bottom surface of the case and a cover side passage formed on the rain cover. In this invention, it is preferable to manufacture by the following manufacturing method. That is, the rain cover has the cover-side passage formed in the contact surface formed in the rain cover, and the absorption space is formed in the contact surface of the rain cover in a state communicating with the cover-side passage. And the step of forming the second air vent passage by using a punching means from the inner space side of the rain cover toward the contact surface side after the step.

  In addition, the first air vent passage is not limited to the previous configuration, and may be configured as follows. The ignition according to any one of claims 1 to 4, wherein the first air vent passage is formed by a case side passage formed on the bottom surface of the case and a contact surface of the rain cover. coil. In this invention, it is preferable to manufacture by the following manufacturing method. That is, the rain cover has a step of forming the absorption space on the contact surface of the rain cover in a state of communicating with the case side passage, and after the step, from the inner space side of the rain cover to the contact surface side. On the other hand, the second air vent passage is formed by using the punching means.

  According to the ignition coil of the present invention, a sufficient ventilation cross section around the communicating portion between the second air vent passage and the absorption space is secured, so that all the vent passages formed as the first air vent passage function. Thus, even when a high pressure difference occurs, the flow rate of the gas flowing through the first air vent passage is dispersed, and the pressure difference inside and outside the plug hole can be opened without maintaining for a long time. .

  In addition, by setting the bottom surface level of the absorption space lower than the bottom surface level of the first air vent passage, an opening area that communicates from the absorption space to the second air vent passage is sufficiently widened. Regardless of the presence of the formed burr part, all the ventilation paths formed as the first air vent path function. Therefore, in the ignition coil having such a configuration, even when a high pressure difference occurs, the flow rate of the gas flowing through the first air vent passage is more effectively dispersed, and the pressure difference inside and outside the plug hole is instantly released. It becomes possible to do.

  Furthermore, according to the ignition coil of the present invention, the end of the second air vent passage communicates with the space bottom surface of the absorption space, so that the first air from the external space to the second air vent passage 115b is communicated. In addition to simplifying the shape of the extraction passage, unnecessary pressure loss is prevented. In addition, the rain cover has a wide design freedom, and the design of the hole diameter or the hole position of the second air vent passage can be easily changed.

  According to the ignition coil manufacturing method of the present invention, the rain cover is machined in the second air vent passage after the injection molding step, so that the position of the bottom opening end formed in the absorption space can be freely set. It becomes possible to do. Therefore, by optimizing the positional relationship between the end portion of the first air vent passage and the bottom opening end of the absorption space, it is possible to effectively suppress the pressure loss generated around the bottom opening end. .

The figure which shows the structure of the ignition coil which concerns on this Embodiment. FIG. 3 is a diagram illustrating a structure of a rain cover according to the first embodiment. The figure which shows the air vent passage of the ignition coil which concerns on Example 1. FIG. FIG. 5 is a diagram illustrating a manufacturing process of the rain cover according to the first embodiment. FIG. 3 is an enlarged view of an air vent passage according to the first embodiment. FIG. 5 is a diagram illustrating a structure of a rain cover according to a second embodiment. The enlarged view of the air vent passage which concerns on Example 2. FIG. FIG. 6 is a diagram illustrating a structure of a rain cover according to a third embodiment. FIG. 6 is an enlarged view of an air vent passage according to the third embodiment. FIG. 6 is a diagram illustrating a structure of a rain cover according to a fourth embodiment. FIG. 10 is a diagram illustrating a layout of an absorption space according to a fifth embodiment. FIG. 10 is a diagram illustrating a layout of a second air vent space according to a sixth embodiment. The figure which shows the air bleeding passage of the ignition coil which concerns on Example 7. FIG. FIG. 10 is a diagram showing a rain cover manufacturing process according to the seventh embodiment. The figure which shows the air bleeding passage of the ignition coil which concerns on Example 8. FIG. FIG. 10 is a diagram illustrating a structure of a rain cover according to a ninth embodiment. The figure which shows the structure of the ignition coil which concerns on a prior art example. The figure which shows the structure of the rain cover which concerns on a prior art example. The figure which shows the structure of the rain cover which concerns on a prior art example. The figure which shows the structure of the rain cover which concerns on another prior art example. The figure which shows the manufacturing process of the rain cover which concerns on a prior art example. The figure which shows the air vent passage which concerns on a prior art example. The figure which shows the air vent passage which concerns on a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the ignition coil 100 includes a coil case 111, a plug cap 114, and a rain cover 115. The ignition coil 111 is connected to the ignition plug PG at the lower end portion of the plug hole PH formed in the engine head. In the present embodiment, a so-called PEN type ignition coil in which the coil portion built in the coil case 111 is accommodated in the plug hole will be described.

  The coil case 111 is made of a thermoplastic resin, and has a connector portion 111a, a head portion 111b, and a cylindrical portion 111k. The connector portion 111a is a shell-like body having an opening on one side, and a plurality of connector terminals are arranged inside. The head portion 111b is provided with an opening on one end side, and a connecting portion 111p is formed on the other end side. A case bottom surface 111c arranged in a flat shape is formed on the connecting portion 111p.

  The cylindrical part 111k has a hollow space of a predetermined length, and the coil part is accommodated in the space. Here, the coil portion is composed of a central iron core, and a primary coil and a secondary coil laminated in the outer peripheral direction of the central iron core, one end of which is wired to receive voltage application from the connector terminal, and the other end Is connected to a high voltage terminal provided on the lower end side of the cylindrical portion 111k. In the coil unit, the intermittent input voltage applied to the primary coil is boosted, and the boosted voltage obtained thereby is output. In order to relay the boosted voltage to the spark plug PG, the high voltage terminal is connected to a contact terminal with the spark plug PG at the lower end of the cylindrical portion 111k.

  The plug cap 114 is made of an insulating elastic body, and is attached to the lower end portion of the cylindrical portion 111k of the coil case. The plug cap 114 maintains the connection state with the spark plug PG so that the contact between the high-voltage terminal and the spark plug PG is not released due to vibration or impact.

  The rain cover 115 is made of an elastic body and has an annular body having an opening inside. One of the rain covers 115 is attached to the coil case 111 so that one of the rain covers 115 is in close contact with the upper opening end Uo of the plug hole PH, and the other is covered so as to be in close contact with the case bottom surface 111c of the coil case 111. Further, the rain cover 115 is disposed at the opening end Uo of the plug hole PH, thereby forming an internal space of the plug hole PH and an external space in which the head portion 111b is disposed. Note that an appropriate air vent passage is formed in the rain cover 115. The details of the air vent passage will be clarified in the embodiments showing various forms.

  In the ignition coil 100 having such a configuration, the input voltage applied via the connector terminal is supplied to the coil unit, and a boosted voltage is generated by the coil unit. Thereafter, the boosted voltage is relayed from the high voltage terminal to the spark plug PG, and the electrode portion of the spark plug PG is sparked. At this time, in the engine, the amount of heat increases or decreases according to the combustion operation, and in the internal space of the plug hole PH, the gas expands and contracts accordingly. Then, in the air vent passage of the rain cover 115, the pressure of the internal space and the pressure of the external space are adjusted to coincide with each other by allowing the gas to flow in and out.

  FIG. 2A shows a plan view of the rain cover 115. As shown in the figure, the rain cover 115 is formed with first air vent passages 115e and 115r, an absorption space 115g, and a second air vent passage 115b. 2B shows a state in which the BB cross section of the rain cover 115 is observed in the direction of the arrow.

  The first air vent passage is a passage formed with the case bottom surface 111 c of the coil case, and is formed on the close contact surface side Fo of the coil case 115. The first air vent path includes a guide path 115r having an opening end 115f and an annular path 115e formed along the inner peripheral surface 115a. In the first air vent passage, the open end 115f communicates with the annular passage 115e via the guide passage 115r. In the present embodiment, it is assumed that the width W1 of the ventilation cross section of the annular path 115e (hereinafter referred to as the ventilation cross section width W1) is substantially constant. Here, referring to FIG. 2B, the ventilation cross section of the annular path 115e is substantially rectangular, and appears on both sides of the central axis. Among these, one ventilation cross section communicates with the guide path 115r, and the other ventilation cross section communicates with the second air vent passage and the absorption space. Here, in the first air vent passage, the levels of the bottom surfaces of the guide passage 115r and the annular passage 115e are substantially the same.

  Returning to FIG. 2A, when the rain cover is observed, when the opening end 115f is set to the start point side of the first air vent passage, an absorption space 115g is provided on the end point side of the first air vent passage. The absorption space has a substantially circular shape, and the cross-sectional width W2 corresponding to the diameter of the absorption space is larger than the ventilation cross-sectional width W1 of the annular path 115e. In addition, in the absorption space 115g, as shown in the figure, two passages 115e are connected to each other, but each side of the absorption space is connected to each of the annular passages without passing through another relay passage. Side opening ends 115p and 115q that are in direct communication are formed. Further, the second air vent passage 115b appears in the inner region of the absorption space 115g. Here, referring to FIG. 2B again, a cross section of the absorption space 115g and the second air vent passage 115b appears on the end point side of the first air vent passage. The absorption space 115g is formed by a side surface, a space bottom surface 115x, and a case bottom surface 111c. The space bottom surface 115x in the present embodiment coincides with the bottom surface level 115m of the first air vent passage. A bottom opening end 115y corresponding to the end of the second air vent passage 115b is formed in the space bottom surface 115x. The rain cover 115 communicates a path from the opening end 115f to the opening end of the internal space side Fi by the first air vent passage and the second air vent passage.

  In such a rain cover 115, the space bottom surface 115x and the second air vent passage 115b are directly communicated with each other without passing through another route, so that the configuration of the rain cover is simplified. Moreover, since each annular path is directly communicated with the side surface of the absorption space without passing through another relay path, the structure of the rain cover is also simplified. Furthermore, since the configuration around the second air vent passage and the absorption space is simplified, the degree of freedom in design of the rain cover is improved, which is advantageous for downsizing. In addition, in the rain cover 115, the absorption space is formed in the rain cover. Therefore, when the second air vent passage is drilled in the machining process, the work of connecting the absorption space and the second air vent passage is performed. It becomes easy. Here, the absorption space and the first air vent passage formed on the rain cover side refer to the cover side passage in the claims.

  FIG. 3 shows a state where the rain cover 115 is attached. The rain cover 115 is disposed between the case bottom surface 111c of the coil case 111 and the opening end Uo of the plug hole. And the sealing state from rain water is ensured by the fastening force of the fixing bolt 120a. Further, the case bottom surface 111c and the rain cover are brought into close contact with each other to form the first air vent passage and the absorption space 115g. The illustrated internal space Ai and external space Ao are communicated with each other by the first air vent passage and the second air vent passage, and the pressure difference generated between the two spaces causes the gas to pass through the air vent passage. It is solved by coming and going.

  Here, the manufacturing method of the rain cover used in the present embodiment will be described. FIG. 4 sequentially shows such a manufacturing method. First, as shown in FIG. 4A, the main part of the rain cover is formed in the injection molding process. Here, the internal opening surface 115a, the guide path 115r, the annular path 115e, and the absorption space 115g are formed. In such an injection molding process, all components except for the second air vent passage are formed by injection molding using a mold.

  The rain cover which has finished the injection molding process is put into a machining process (perforation processing in claims) as shown in FIG. In this process, the needle-like workpiece WP (perforation means in claims) is set at an appropriate position, and the workpiece is fed from the inner space side Fi of the rain cover toward the contact surface side Fo.

  As the feeding process proceeds, the workpiece WP presses the material of the rain cover 115, and the workpiece penetrates from the inner space side to the contact surface side of the rain cover as shown in FIG. At this time, as shown in the drawing, a part of the chips generated by the drilling process is carried to the contact surface side, and a burr portion DP is formed in the absorption space 115g.

  Thereafter, as shown in FIG. 4D, the workpiece WP is accommodated in the internal space side Fi, and the machining process is completed. In addition, since chips are attached to the surface of the workpiece WP, the burr part DP may be grown by the accommodating operation in the same process.

  Here, a deburring process may be provided after the machining process is completed. However, in such a case, the number of processing steps is increased, leading to an increase in production cost. Further, depending on the deburring removal method, the burr part DP formed in the absorption space 115g may not be completely removed. Therefore, the rain cover 115 may be used as it is without going through the deburring process depending on the mode of the burr part DP.

  FIG. 5A shows an enlarged view of a V portion shown in FIG. In the figure, the rain cover 115 with the burr part DP left is shown. As illustrated, the absorption space 115g forms a ventilation cross section, and the burr portion DP is disposed in a predetermined range of the ventilation cross section. However, in the present embodiment, a sufficient opening area is secured on both sides of the burr portion DP in the absorption space 115g. Even in the present embodiment, since the burr part DP is formed by fine particles of chips, the defect hole part K where the particles do not exist is formed discontinuously.

  FIG. 5B shows a view in which the contact surface Sfi is observed in the internal space direction. In the drawing, one of the annular paths 115e is defined as a ventilation path Ra, and the other path is defined as a ventilation path Rb. Of the paths formed by the absorption space 115g and the burr part DP, one path is a ventilation path Rc and the other path is a ventilation path Rd. Further, in this embodiment, it is assumed that the defect hole portion K formed in the burr portion DP is formed only in the direction facing the ventilation path Rb.

  As shown in the figure, the flow of the gas flowing in from the ventilation path Rb has a deficient hole K in the shortest path from the ventilation path Rb to the second air vent path 115b, so that the gas flows through the second air vent path 115b. It is smoothly drawn into the internal space side Fi. In the case where the pressure state is reversed and the gas flow is reversed, the flow is reversed in the direction of the arrow in the figure, and in this case, the gas flow is smooth.

  On the other hand, the flow of the gas flowing in from the ventilation path Ra blocks the wall of the burr part DP on the shortest path from the ventilation path Ra to the second air vent path 115b. However, in the present embodiment, since an absorption space having an appropriate cross section is provided, a path guided from the ventilation path Ra to the defect hole portion K via the ventilation path Rc and a ventilation path from the ventilation path Ra. A path that is guided to the defect hole K via Rd is secured. Therefore, even in the flow of gas flowing in from the ventilation path Ra, the gas is smoothly drawn into the internal space side Fi through the second air vent path 115b. Even in such a path, when the pressure state is reversed and the gas flow is reversed, the flow is reversed in the direction of the arrow in the figure, and the gas flow at that time is also smooth. It is supposed to be.

  Therefore, even when the pressure difference between the internal space Ai and the external space Ao is large, the absorption space 115g sufficiently secures the size of the ventilation cross section, so that the space from the notch hole K to the ventilation path Ra is reached. The gas flow is suitably maintained until the pressure difference between the internal space Ai and the external space Ao is eliminated without receiving a significant pressure loss that reduces the flow rate.

  According to the ignition coil according to the present embodiment, a sufficient ventilation cross section around the communicating portion between the second air vent passage 115b and the absorption space 115g is secured, so that all the vents formed as the first air vent passage are provided. The paths Ra and Rb function, so that even when a high pressure difference occurs, the flow rate of the gas flowing in the first air vent passage is dispersed without maintaining the pressure difference inside and outside the plug hole for a long time. It can be opened.

  Further, since the end of the second air vent passage 115b communicates with the space bottom 115x of the absorption space 115g, the shape of the first air vent passage from the external space to the second air vent passage 115b is simple. In addition, the generation of unnecessary pressure loss is prevented. In addition, such a rain cover has a higher degree of design freedom, and it is easy to change the design of the hole diameter or hole position of the second air vent passage.

  Furthermore, according to the ignition coil manufacturing method of the present embodiment, since the rain cover is machined in the second air vent passage after the injection molding process, the position of the bottom opening end formed in the absorption space can be freely set. It becomes possible to set. Therefore, by optimizing the positional relationship between the end portion of the first air vent passage and the bottom opening end of the absorption space, it is possible to effectively suppress the pressure loss generated around the bottom opening end. .

  In the present embodiment, a modified example of the first embodiment will be described. In addition, the same code | symbol is attached | subjected to the location which has the same function mentioned above, and the description is abbreviate | omitted. FIG. 6A is a plan view of the rain cover 215 according to the second embodiment. As shown in the drawing, the rain cover 215 is formed with a first air vent passage, an absorption space 215g, and a second air vent passage 115b. That is, in this embodiment, the absorption space is modified. FIG. 6B shows a state where the BB cross section of the rain cover 115 is observed in the direction of the arrow.

  When observing FIG. 6A, when the opening end 115f is the start point side of the first air vent passage, an absorption space 215g is provided on the end point side of the first air vent passage. The absorption space 215g has a substantially circular shape, and the cross-sectional width W2 corresponding to the diameter of the absorption space 215g is larger than the ventilation cross-sectional width W1 of the annular path 115e. Here, referring to FIG. 6B, a cross section of the absorption space 215g and the second air vent passage 115b appears on the end point side of the first air vent passage. The absorption space 215g is formed by a side surface, a space bottom surface 215x, and a case bottom surface 111c. The space bottom surface 215x in the present embodiment is a level deeper than the bottom surface level 115m of the first air vent passage. A bottom opening end 215y corresponding to the end of the second air vent passage 115b is formed on the bottom surface of the space.

  FIG. 7A shows an enlarged cross-sectional view of the absorption space. In the figure, the rain cover 215 with the burr portion DP left is shown. As illustrated, the absorption space 215g forms a ventilation cross section, and the burr portion DP is disposed in a predetermined range of the ventilation cross section. In the case of the present embodiment, the absorption space 215g has a sufficient opening area on both sides with the burr portion DP interposed therebetween, and also has a sufficient space between the upper end portion of the burr portion DP and the contact surface Sfi. It is formed.

  FIG. 7B shows a view in which the contact surface Sfi is observed in the internal space direction. In the drawing, one of the annular paths 115e is defined as a ventilation path Ra, and the other path is defined as a ventilation path Rb.

  As shown in the drawing, since the gas flowing in from both the ventilation paths Ra and Rb has a sufficient space between the upper end portion of the burr portion DP and the contact surface Sfi, the second air vent passage 115b. Is smoothly drawn into the internal space side Fi. In the case where the pressure state is reversed and the gas flow is reversed, the flow is reversed in the direction of the arrow in the figure, and in this case, the gas flow is smooth.

  In the case of the present embodiment, the gas flow does not depend only on the defect hole K, but most of it flows in and out from the end face of the second air vent passage 215b. Accordingly, in the flow from the outer space Ao to the inner space Ai, the pressure loss in the vicinity of the absorption space and the end of the second air vent passage 115b is dramatically eliminated, whereby the inner space Ai and the outer space The pressure difference of Ao is eliminated instantly.

  According to the ignition coil of the present embodiment, the level 215x of the bottom surface of the absorption space 215g is set lower than the bottom surface level 115m of the first air vent passage, thereby opening the communication space from the absorption space to the second air vent passage 115b. Since the area is secured sufficiently wide, all the ventilation paths formed as the first air vent path function regardless of the presence of the burr part DP formed in the rain cover 215. Therefore, in the ignition coil having such a configuration, even when a high pressure difference occurs, the flow rate of the gas flowing through the first air vent passage is more effectively dispersed, and the pressure difference inside and outside the plug hole is instantly released. It becomes possible to do.

  In the present embodiment, a modified example of the above-described second embodiment will be described. FIG. 8A is a plan view of the rain cover 315 according to the third embodiment. As shown in the figure, the rain cover 315 has a first air vent passage, an absorption space 315g, and a second air vent passage 115b. That is, even in the present embodiment, the absorption space is modified. FIG. 8B shows a state in which the BB cross section of the rain cover 115 is observed in the direction of the arrow.

  When observing FIG. 8A, the layout of each configuration is substantially the same as the rain cover of the second embodiment. Here, referring to FIG. 8B, a cross section of the absorption space 315g and the second air vent passage 115b appears on the end point side of the first air vent passage. The absorption space 315g is formed by a side surface, a space bottom surface 315x, and a case bottom surface 111c. In this embodiment, the space bottom surface 315x is formed by a cut surface between the level 115m of the annular passage 115e and the end surface of the second air vent passage 115b, so that it is deeper than the bottom surface level of the first air vent passage. The level is realized.

  FIG. 9A shows an enlarged cross-sectional view of the absorption space. In the figure, a rain cover 315 with the burr portion DP remaining is shown. As illustrated, the absorption space 315g forms a ventilation cross section, and the burr portion DP is disposed in a predetermined range of the ventilation cross section. In the case of the present embodiment, a sufficient space is also formed between the upper end portion of the burr portion DP and the contact surface Sfi. According to such a configuration, since the burr portion DP has a space near the cut surface, when the second air vent passage is formed by a machining process, chips accumulate in the radial direction of the second air vent passage. It becomes easy to suppress the growth of the burr part DP in the vertical direction.

  FIG. 9B shows a view in which the contact surface Sfi is observed in the internal space direction. In the drawing, one of the annular paths 115e is defined as a ventilation path Ra, and the other path is defined as a ventilation path Rb.

  As shown in the drawing, since the gas flowing in from both the ventilation paths Ra and Rb has a sufficient space between the upper end portion of the burr portion DP and the contact surface Sfi, the second air vent passage 115b. Is smoothly drawn into the internal space side Fi. In the case where the pressure state is reversed and the gas flow is reversed, the flow is reversed in the direction of the arrow in the figure, and in this case, the gas flow is smooth.

  Also in the present embodiment, as in the ignition coil of the second embodiment, the pressure difference between the inner space Ai and the outer space Ao is caused by the pressure loss around the end portions of the absorption space 315g and the second air vent passage 115b. Therefore, the pressure difference is eliminated instantly.

  According to the ignition coil of the present embodiment, the opening area communicating from the absorption space 315g to the second air vent passage 115b is set by setting the level of the bottom surface of the absorption space 315g lower than the bottom surface level of the first air vent passage. Is ensured sufficiently wide, so that all the ventilation paths formed as the first air vent path function regardless of the presence of the burr portion DP formed in the rain cover 215. Therefore, in the ignition coil having such a configuration, even when a high pressure difference occurs, the flow rate of the gas flowing through the first air vent passage is more effectively dispersed, and the pressure difference inside and outside the plug hole is instantly released. It becomes possible to do.

  In the present embodiment, a modified example of the above-described second embodiment will be described. FIG. 10A1 is a cross-sectional view of the rain cover 415 according to the fourth embodiment. In the figure, in order to explain the configuration of the rain cover, the burr portion DP is omitted for convenience. As shown in the drawing, the rain cover 315 is formed with a first air vent passage, an absorption space 415g, and a second air vent passage 115b, and the absorption space 415g is further deeper than the level of the space bottom surface 415x. A secondary space bottom surface 415z is formed on the surface. Further, a bottom opening end 415y is formed in the secondary space bottom surface 415z, and thereby communicates with the second air vent passage 115b.

  FIG. 10A2 shows an actual rain cover 415 in which the burr part DP is left. As illustrated, the absorption space 415g forms a part of the ventilation cross section, and the burr portion DP is disposed in a predetermined range of the ventilation cross section. More specifically, most of the burrs DP are formed around the lower secondary space bottom surface 415z in the space forming the ventilation cross section. In such a case, a further sufficient space is formed between the upper end portion of the burr portion DP and the contact surface Sfi, so that the gas flowing through the annular passage 115e is directed to the internal space side Fi via the second air vent passage 115b. It is drawn in smoothly.

  According to the ignition coil of the present embodiment, by providing the secondary space bottom surface that is lower than the level of the bottom surface of the absorption space 415g, a wider opening area communicating from the absorption space 415g to the second air vent passage 115b is secured. All the ventilation paths formed as the first air vent passage function. Therefore, in the ignition coil having such a configuration, even when a high pressure difference occurs, the flow rate of the gas flowing through the first air vent passage is more effectively dispersed, and more effectively than the ignition coil of the second embodiment, The pressure difference inside and outside the plug hole can be released instantly.

  In the present embodiment, a modified example of the above-described fourth embodiment will be described. FIG. 10B1 is a cross-sectional view of the rain cover 515 according to the fifth embodiment. In the figure, in order to explain the configuration of the rain cover, the burr portion DP is omitted for convenience. As shown in the drawing, the rain cover 515 is formed with a first air vent passage, an absorption space 515g, and a second air vent passage 115b. The absorption space 515g has a level 2 deeper than the level of the space bottom surface 515x. A next space bottom surface 515z is formed. The secondary space bottom surface 515z is formed with a bottom surface opening end 515y, thereby communicating with the second air vent passage 115b. The cut section C is formed between the upper step portion and the lower step portion in the ventilation cross section formed thereby as shown in the figure.

  According to such a configuration, as shown in FIG. 10 (b2), in the burr part DP, a new space is formed by the cut part C. Therefore, when the second air vent passage is drilled by the machining process, This makes it easier for chips to accumulate in the radial direction of the air vent passage and to suppress the vertical growth of the burr part DP.

  According to the ignition coil of the present embodiment, since the growth of the burr part DP in the vertical direction is suppressed, the space between the upper end part of the burr part DP and the contact surface Sfi is more sufficiently ensured and more effective. In addition, the pressure difference between the inside and outside of the plug hole can be instantaneously released.

  In this embodiment, the layout of the absorption space and the bottom opening end of the second air vent passage will be described. FIG. 11 shows a layout of the absorption space and the annular path 115e. First, in FIG. 11A, as in the above-described embodiment, the center point of the absorption space 115g is arranged near the neutral line of the annular path 115e. However, the absorption space described in the claims is not limited to such a layout. For example, as shown in FIG. 11B, the absorption space 615g may be disposed on the outer peripheral side of the annular path 115e and communicated with the annular path 115e via the side surface opening end 615p. In addition, as shown in FIG. 11C, the absorption space 715g may be disposed on the inner peripheral side of the annular path 115e and communicated with the annular path 115e via the side surface opening end 715p.

  As described above, by optimizing the layout of the absorption space and the annular path, interference with other components formed in the rain cover is avoided, and the design freedom of the rain cover is improved.

  FIG. 12 shows the relationship between the absorption space and the bottom opening end of the second air vent passage. In FIG. 12A, the neutral line of the annular path 11e and the midpoint of the absorption space 115g coincide, and the midpoint of the absorption space 115g and the midpoint of the bottom opening end 115X coincide. However, the ignition coil described in the claims is not limited to such a rain cover. For example, as shown in FIG. 12B, when the neutral line of the annular path 115e substantially coincides with the midpoint of the absorption space 115g, the bottom opening end 115x is unevenly distributed in any radial direction of the annular path 115e. By perforating so, the layout of the second air vent passage can be adjusted within a certain range without providing another unnecessary route. In addition, as shown in FIG. 12 (c), if the midpoint of the absorption space 115g is displaced in the radial direction from the neutral line of the annular path 115e, the bottom opening end 115x can further change the drilling position. .

  As described above, by optimizing the layout of the absorption space, the annular path, and the bottom opening end, it is possible to avoid interference with other components formed in the rain cover and to improve the design freedom of the rain cover.

  In the embodiment described above, the first air vent passage is formed in the rain cover. However, the ignition coil according to the claims is not limited to such a mode. For example, as shown in FIG. 13, the first air vent passage may be formed by a case side passage formed on the bottom surface of the case and a contact surface of the rain cover.

  A method of manufacturing the rain cover in such a case will be described. FIG. 14 sequentially shows a method of manufacturing a rain cover according to the modified example. First, as shown in FIG. 14A, the main part of the rain cover is formed in the injection molding process. Here, only the internal opening 115a and the absorption space 115g are formed.

  The rain cover after the injection molding process is put into a machining process (perforation processing in claims) as shown in FIG. In this process, the workpiece WP is fed from the inner space side Fi of the rain cover toward the contact surface side Fo.

  As the feeding process proceeds, the workpiece WP presses the material of the rain cover 115, and the workpiece penetrates from the inner space side of the rain cover toward the contact surface side as shown in FIG. 14 (c). At this time, as shown in the drawing, a part of the chips generated by the drilling process is carried to the contact surface side, and a burr portion DP is formed in the absorption space 115g.

  Thereafter, as shown in FIG. 14 (d), the workpiece WP is accommodated in the internal space Fi, and the machining process is completed.

  That is, in this embodiment, since the first air vent passage (case side passage in the claims) is formed in the coil case 111, the shape of the rain cover is simplified.

  FIG. 15 shows an ignition coil according to a change in the first air vent passage. In the ignition coil, as shown in the figure, the first air vent passage is formed by a case side passage formed in the case bottom surface 111 c and a cover side passage formed in the rain cover 115.

  According to such an embodiment, a wide air cross section of the first air vent passage can be secured, so that a decrease in pressure loss in the first air vent passage can be expected.

  In each of the above-described embodiments, the PEN type ignition coil has been described. However, the scope of the claims is not limited to such an ignition coil. In this embodiment, the closed magnetic circuit type ignition coil described in the prior art will be described.

  As shown in FIG. 16A, the closed magnetic circuit type ignition coil (hereinafter referred to as an ignition coil in the ninth embodiment) includes a coil case 11 having a connector portion 11a and a coil housing portion 11b, An iron core 12 inserted through the coil assembly, a high voltage tower 13 for transmitting a high voltage boosted by the coil assembly, a plug cap 14 attached to a connection side terminal of the high voltage tower 13, and an upper end opening of the plug hole PH And a rain cover 15 ′ mounted between the case bottom surface of the coil case 11b. In the ignition coil 10, the high voltage tower 13 is inserted into the plug hole of the engine head, and the connection side terminal and the head terminal of the ignition plug are connected. The rain cover 15 'is formed from an elastic material having an insulating property, and is appropriately elastically deformed by the fixing bolt 12a, thereby preventing rainwater from entering the plug hole. Yes. Further, the rain cover 15 ′ is provided with a groove-like air vent passage to reduce a pressure difference generated between the internal space in the plug hole and the external space covering the engine head surface layer portion. The ignition coil according to the present embodiment has a function of applying a boosted voltage to the spark plug PG at a predetermined timing, like the PEN type ignition coil.

  FIG. 16B shows a cross-sectional view of such a rain cover 15 '. In the figure, a part of the high-pressure tower 11d is omitted for convenience. As shown in the figure, the rain cover 15 ′ forms the internal space Ai and the external space Ao as described above, and also has the annular path 15e, the guide path 15r, the absorption space 15g ′, and the second air vent. A passage 15b is formed. The annular passage 15e and the guide groove 15r form a first air vent passage and communicate from the open end facing the external space to the absorption space 15g '. In addition, the bottom surface of the absorption space 15g 'communicates directly with the second air vent passage 15b. That is, the external space and the internal space are communicated with each other by both of the air vent passages. And even when the burr part DP formed for convenience of processing remains at the bottom of the absorption space 15g ′, the absorption cross section is appropriately secured by the absorption space, so that a large pressure difference is not given to the gas flow. . Therefore, the pressure difference generated inside and outside the internal space is released at an appropriate time without maintaining the pressure difference for a long time. Such a rain cover can be applied to the above-described embodiments.

  Note that the PEN type ignition coil and the closed magnetic circuit type ignition coil described above may be of a type that is distributed by a distributor, or of a direct ignition type in which an igniter is built in the head of the case. good. Further, in the closed magnetic circuit type ignition coil, a part of the closed magnetic iron core 12 may be exposed to the outside, and all of the closed magnetic iron core 12 is accommodated in the coil case. It doesn't ask the form.

100 Ignition coil 111 Coil case 111c Case bottom PH plug hole 115 Rain cover 115e Annular path 115r Guide path 115g Absorption space 115p Side opening end 115q Side opening end 115x Hollow bottom 115y Bottom opening end

Claims (9)

A coil case, and a rain cover that is attached in close contact with the bottom surface of the coil case and the upper opening end of the plug hole and forms an internal space of the plug hole and an external space in which the head of the coil case is disposed A first air vent passage formed on a contact surface of the case bottom surface and the rain cover and communicating with the external space, and an absorption space having a cross-sectional width larger than a ventilation cross-sectional width of the first air vent passage; In the ignition coil comprising a second air vent passage for communicating the absorption space and the internal space,
The absorption space includes a side opening end that communicates directly with the first air vent passage, a space bottom surface that matches the level of the bottom surface of the first air vent passage, and the second air vent passage. An end portion having a bottom opening end formed on the bottom surface of the space;
The ignition coil according to claim 1, wherein the second air vent passage is punched using a punching means from the inner space side of the rain cover toward the contact surface side. A coil case, and a rain cover that is attached in close contact with the bottom surface of the coil case and the upper opening end of the plug hole and forms an internal space of the plug hole and an external space in which the head of the coil case is disposed A first air vent passage formed on a contact surface of the case bottom surface and the rain cover and communicating with the external space, and an absorption space having a cross-sectional width larger than a ventilation cross-sectional width of the first air vent passage; In the ignition coil comprising a second air vent passage for communicating the absorption space and the internal space,
The absorption space includes a side opening end directly communicating with the first air vent passage, a space bottom surface formed at a level deeper than the level of the bottom surface of the first air vent passage, and the second An end portion of the air vent passage has a bottom opening end formed on the bottom surface of the space,
The ignition coil according to claim 1, wherein the second air vent passage is punched using a punching means from the inner space side of the rain cover toward the contact surface side.   The ignition coil according to claim 1, wherein the absorption space is formed in the rain cover. The space bottom includes a secondary space bottom formed at a deeper level than the level of the space bottom;
The ignition coil according to claim 1, wherein the bottom opening end is formed on the bottom surface of the secondary space.   5. The ignition coil according to claim 1, wherein the first air vent passage is formed by a bottom surface of the case and a cover-side passage formed on the rain cover.   5. The first air vent passage according to claim 1, wherein the first air vent passage is formed by a case side passage formed in the bottom surface of the case and a cover side passage formed in the rain cover. Ignition coil. The rain cover is
Forming the absorption space in the contact surface of the rain cover in a state where the cover side passage is formed in the contact surface formed in the rain cover and communicating with the cover side passage;
After the step, from the inner space side of the rain cover toward the contact surface side, the step of forming the second air vent passage using a punching means,
The manufacturing method of the ignition coil according to claim 5 or 6, wherein   5. The ignition coil according to claim 1, wherein the first air vent passage is formed by a case side passage formed on the bottom surface of the case and a contact surface of the rain cover. The rain cover is
Forming the absorption space on the contact surface of the rain cover in a state communicating with the case side passage;
After the step, from the inner space side of the rain cover toward the contact surface side, the step of forming the second air vent passage using a punching means,
The method of manufacturing an ignition coil according to claim 8, wherein the ignition coil is manufactured by:

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