JP3109300B2 - Method of forming a capacitor for detecting ignition voltage in a spark plug cap - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an ignition voltage detecting capacitor on a spark plug cap for detecting misfire during operation of a spark ignition type internal combustion engine such as a gasoline engine. It is.

[0002]

2. Description of the Related Art As is well known, in a spark ignition type internal combustion engine such as a gasoline engine, a high voltage generated by an ignition coil (ignition coil) is applied to a spark plug of each cylinder, and a spark between electrodes of the spark plug is generated. The discharge ignites the fuel mixture sucked into the combustion chamber of each cylinder,
Burning occurs. In the ignition / combustion process of such an internal combustion engine, a phenomenon in which combustion of the fuel mixture is not performed normally, that is, misfire may occur for some reason. The causes of such misfires are broadly classified into those caused by the fuel system and those caused by the ignition system. The misfire caused by the fuel system is caused by a lean or rich fuel mixture, and is a phenomenon in which spark discharge occurs between the electrodes of the ignition plug but is not ignited by the fuel mixture. On the other hand, the latter type of misfire caused by the ignition system is a phenomenon in which normal spark discharge does not occur due to fogging of an electrode of a spark plug or abnormality of an ignition circuit.

If a misfire occurs during the operation of the internal combustion engine, not only does the operating performance deteriorate, but also the fuel consumption deteriorates, and further, the afterburning of the unburned gas in the exhaust system adversely affects the exhaust gas purifying device and the like. And other problems occur. In addition, once misfire has occurred, it means that inconvenience such as improper adjustment or failure has occurred in the fuel system or the ignition system. Therefore, it is necessary to avoid leaving the misfire occurring. Therefore, recently, there is a strong demand for the development of a device for immediately detecting a misfire when it has occurred.

[0004] As one type of a misfire detection device proposed in the past, there is a mis-spark detection device disclosed in Japanese Patent Application Laid-Open No. 52-118135. This Miss Spark Detector
As shown in FIG. 11, a conductor 51 is wound around the outer periphery of the high voltage cord 50 of the engine ignition system to form a detection capacitor (a kind of capacitance probe) 52 using the insulating coating 50A of the high voltage cord 50 as a dielectric. A voltage dividing capacitor 53 is connected between the detecting capacitor 52 and the ground, and the detecting voltage is applied to the conductive core 50B of the high-voltage cord 50 (secondary voltage of the ignition coil). A voltage is induced between both electrodes of the detection capacitor 52 by the capacitance of the capacitor 52, and the induced voltage is electrostatically divided by the detection capacitor 52 and the voltage dividing capacitor 53, so that a voltage between both ends of the voltage dividing capacitor 53 is obtained. (Divided voltage) is sent to the electronic circuit 54 for signal processing and determination as a detection voltage, and the ignition voltage waveform becomes a normal spark. By utilizing the fact that different de the case of electrodeposition time and spark discharge does not occur (a miss spark) is to determine the occurrence of mistakes spark. Therefore, the above-described proposed device detects a misfire among the misfire phenomena particularly when no spark discharge occurs due to the ignition system.

On the other hand, the present applicant has already filed Japanese Patent Application No. 3-326.
No. 509 proposes a misfire detection device for an internal combustion engine. This misfire detection device detects the ignition voltage from the high voltage cord of the ignition system or the like based on the electrostatic partial pressure in the same manner as described above, and when the spark discharge is performed by the spark plug, the ignition voltage waveform is normal combustion and normal combustion. The misfire caused by the fuel system is determined and detected by utilizing the difference from the case where no misfire has occurred.

As described above, in the conventional misfire detecting device, as a means for detecting the ignition voltage, a strip-shaped or plate-shaped conductor is wound around the outer periphery of the high-voltage cord of the ignition system, and the conductor and the high-voltage cord are connected. In general, a so-called capacitance probe in which a detection capacitor having an insulating coating of a high-voltage cord as a dielectric is formed between the core wire and the core wire is used. However, high-pressure cords generally have flexibility and elasticity and are easily vibrated, and are susceptible to changes in surrounding humidity and water, oily dirt, dust, and the like. When the detection capacitor is formed by winding the above conductor, the capacitance is apt to change due to such misalignment due to mechanical vibration, change in humidity, wetness of water, or oil or dust. A slight change in capacitance is not a problem if it is merely to confirm the ignition voltage.However, when determining misfire, it is generally necessary to accurately detect even the voltage waveform. If a change in capacitance occurs, the detected voltage waveform deteriorates, and there is a possibility that misfire cannot be reliably determined.

Further, it is actually quite troublesome to securely mount and fix the conductor to form the detection capacitor on the insulating coating of the flexible and elastic high-voltage cord, and the maintenance thereof is difficult. However, there are also problems that require considerable effort.

On the other hand, the insulating coating of the high-voltage cord is generally made of synthetic rubber, but the rubber is liable to be deteriorated by heat, oil stains, etc. Therefore, when a conductor is wound around the outer periphery of the high-voltage cord to form a detection capacitor. In addition, not only does the capacitance change over time due to the deterioration of the insulation coating, but also the electrical insulation tends to decrease, in which case a high leakage voltage constitutes the detection capacitor. In addition to the conductor, the leak voltage may be led to the electronic circuit portion of the misfire detection device, which may cause a failure or malfunction of the electronic circuit portion. To more accurately detect the ignition voltage waveform by the detection capacitor, the conductor forming the detection capacitor should be as close as possible to the conductive core of the high-voltage cord, and the capacitance of the detection capacitor However, the insulation of the high-pressure cord made of synthetic rubber is inferior in insulation properties, and the insulation is easily deteriorated by corona discharge. Therefore, it is not sufficient to improve the detection accuracy of the ignition voltage waveform.

In order to solve the above-mentioned problems, the present inventors have already disclosed in Japanese Patent Application No. 4-56395.
It has been proposed to provide a conductor for forming a capacitor for detecting an ignition voltage in a spark plug cap inserted in a secondary circuit of an ignition system. Specifically, the above proposal is for a spark plug cap fixed to cover a terminal portion of a spark plug of an internal combustion engine, and a conductive material for high voltage conduction for guiding a high voltage for spark discharge to the terminal portion. A spark plug cap in which a high-voltage conductive conductor is surrounded by an insulator, at a position on the outer peripheral side of the high-voltage conductive conductor,
A conductor for ignition voltage detection is disposed at a predetermined distance from the surface of the high-voltage conductive conductor, and is integrated with the insulator. The gist is that a detection capacitor for detecting an ignition voltage is formed between the conductor and the conductor.

[0010] According to the above proposed structure, the detecting conductor constituting the detecting capacitor for detecting the ignition voltage for detecting the misfire in the spark ignition type internal combustion engine has a structurally stable spark plug cap. In addition to its excellent structural durability, it is detected by mechanical vibration as in the conventional case where a conductor for detection is provided on the high voltage cord of the ignition system. The detection conductor is not displaced or affected by humidity, water, oil, or dust, so that the capacitance of the detection capacitor will not change due to these. The ignition voltage can always be accurately detected up to its waveform, so that the presence or absence of a misfire can be accurately determined. Vinegar effects such as that becomes unnecessary can be obtained.

[0011]

In the structure in which the ignition voltage detecting capacitor is integrally formed in the spark plug cap as described above, various structures are required in comparison with the conventional structure in which the detecting capacitor is formed in a high-voltage cord. Although it has an excellent merit, there are the following problems when this structure is actually applied to a spark plug cap in consideration of mass productivity.

That is, the simplest method for producing a spark plug cap having the structure described above is as follows.
When an insulator (body) surrounding the outer periphery of the high-voltage conductor is molded with an insulating resin, a method of embedding the detection conductor at the same time in the resin is conceivable. However, in this case, it is necessary to float the detection conductor in the space in the mold for molding, and the molding is performed. In the actual mass production process, such molding is extremely difficult.

The present invention has been made in view of the above circumstances, and a method for easily forming a capacitor for detecting an ignition voltage without impairing mass productivity in a process of manufacturing a spark plug cap on an actual mass production scale. The purpose is to provide.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, basically, after forming an insulator body surrounding a high-voltage conductive conductor in a spark plug cap, The detection conductor is formed by fitting.

Specifically, the method according to the first aspect of the present invention comprises a high voltage conductor for guiding a high voltage from an ignition coil to a spark plug, and an insulator body surrounding the high voltage conductor. In forming a capacitor for detecting an ignition voltage on the ignition plug cap having, at a position corresponding to the high-voltage conductor on the outer periphery of the insulator body,
A concave portion that is continuous in the circumferential direction is formed in advance, and a pair of halves that form a semi-annular shape along a half circumference of the concave portion are formed by continuously forming at least an outer peripheral surface layer made of an insulating material and along a curved direction thereof. The semi-annular conductor is formed by integrally molding the same with an insulating material so as to have a configuration including a semi-annular conductor to be formed. And the ends of the half-ring conductors of one half are electrically contacted with the ends of the half-ring conductors of the other half to electrically connect both half-rings. And a detection capacitor formed between the detection conductor and the high-voltage conductor.

According to a second aspect of the present invention, there is provided a method for forming an ignition detecting capacitor in a spark plug cap according to the first aspect of the present invention, further comprising the step of: A shielding member is provided at a position outside the insulating member with an insulating material separated from the semi-annular conductor.

[0017]

According to the method of the present invention, a continuous recess in the circumferential direction is previously formed on the outer periphery of a body (insulator body) made of an insulating material surrounding the periphery of the conductor for high voltage conduction. This recess may be formed at the same time as the molding of the insulator body, or may be formed by cutting after molding.

Then, a pair of half-rings forming a semi-annular shape along a half circumference of the concave portion on the outer periphery of the insulator body are molded separately from the insulator body. Each half body has a semi-circular conductor so that at least the outer peripheral surface layer is made of an insulating material and further has a semi-circular conductor that is continuous along a curved direction (semicircular direction). It is molded with an insulating material.

Then, the pair of half bodies as described above are fitted and fixed to the concave portions on the outer periphery of the insulator body from both sides thereof. At this time, the end of the semi-annular conductor in one half is brought into contact with the end of the semi-annular conductor in the other half, and these are electrically integrated to form a detection conductor. And As described above, the detection conductor formed by electrically integrating the pair of semi-circular conductors is formed by forming a ring outside the high-voltage conductor in the spark plug cap through at least the insulating material of the insulator body. You will be surrounded by. Therefore, a detection capacitor is formed between the high-voltage conductive body and the detecting conductive body composed of a pair of semi-annular conductive bodies.

In the spark plug cap having the ignition voltage detecting capacitor formed as described above, the high voltage current for spark discharge introduced from the ignition coil causes the high voltage conductive material in the spark plug cap to be discharged. If it flows, a high voltage is induced in the detection conductor by the capacitance between the high-voltage conductor and the detection conductor. Therefore, the voltage is taken out as a detection voltage by electrostatic partial pressure or the like, subjected to signal processing as appropriate, and compared with a reference signal (usually a signal corresponding to a detection voltage waveform during normal combustion) to determine the ignition state. It can be determined whether or not there is.

Here, the insulator body surrounding the conductor for high-voltage conduction and the pair of halves can be easily and easily formed by molding without applying a special molding method. . Also, the work of fitting and fixing the pair of halves in the concave portion on the outer periphery of the insulator body from both sides thereof can be performed very easily and easily.
Therefore, the detection capacitor can be formed easily and easily.

In the method according to the second aspect of the present invention, the conductor for detection is electrically shielded from the outside. In other words, the detection capacitor consisting of the detection conductor and the high-voltage conductor in the spark plug cap is electrically shielded. Therefore, in this case, even if another conductive member is present near the spark plug cap, the capacitance of the detection capacitor changes due to a change in the distance between the conductive member and the conductive member. It is possible to effectively prevent the detection capacitor from picking up noise from the conductive member and adversely affecting the detection accuracy of the ignition voltage waveform, thus further improving the detection accuracy of the ignition voltage waveform. Can be planned.

[0023]

1 to 4 show a first embodiment of the present invention. In this embodiment, an ignition coil is provided in a one-to-one correspondence with the ignition plug of each cylinder of the engine, and the secondary voltage of the ignition coil is supplied directly to the ignition plug without passing through a distributor. An example is shown in which the present invention is applied to an ignition coil integral coupling type spark plug cap which is applied to an ignition system called (distributorless ignition type) or DI type (direct ignition type).

FIG. 1 shows an ignition plug cap 1 in a state before a detection capacitor is formed, together with an ignition coil section 2 and an ignition plug 3. In FIG. 1, an ignition coil section 2 is fixed to an upper end of a spark plug cap 1. The spark plug cap 1 is made of polybutylene terephthalate (PB) so as to form a hollow cylindrical shape as a whole.
T) and the like, and are integrally formed of a hard resin having excellent heat resistance and electrical insulation properties, and the integrally formed hard resin forms an insulator body 4 described later. The upper part of the hollow part along the axial direction of the spark plug cap 1 is an upper insertion chamber 1A into which the secondary output terminal shaft 2A of the ignition coil part 2 is inserted. A shaft-shaped high-voltage conductive conductor 6 that is electrically and mechanically in contact with the secondary output terminal shaft 2A of the ignition coil unit 2 via a conductive spring 5 is inserted into the center of the hollow portion. ing. Further, the lower part of the hollow part is a terminal part 3 on the upper part of the ignition plug 3.
A cap chamber 1B that covers and is fixed to A. The lower end of the conductor 6 for high voltage conduction is in contact with the terminal portion 3A of the ignition plug 3. Accordingly, the high-voltage conductive body 6 has a function of receiving a high voltage for spark discharge from the secondary output terminal shaft 2A of the ignition coil section 2 and guiding the same to the terminal section 3A of the ignition plug 3. The periphery of the high-voltage conductor 6 is surrounded by the insulator body 4 made of the above-described hard resin.

Further, on the outer periphery of the portion of the insulator body 4 where the high voltage conductive material 6 is located, a concave portion 8 which is continuous in the circumferential direction is formed. The recess 8 is formed such that its inner surface has a U-shaped cross section. In the insulator body 4, a signal conductor 9 made of a copper wire, a copper strip or the like having a tip 9 </ b> A exposed at the bottom of the corner of the recess 8 is embedded at a position above the recess 8. .

The ignition plug 1 shown in FIG.
The entire insulator body 4 can be integrally formed by molding, and the formation of the concave portion 8 and the embedding of the signal conductor 9 can be performed simultaneously with the molding.

FIGS. 2 and 3 show the insulator body 4 as described above.
2 shows a pair of halves 10A and 10B fitted into the concave portions 8 of the first and second halves, respectively. (Diameter) is substantially equal to the diameter of the bottom surface of the concave portion 8, and the outer diameter (curvature diameter of the convex curved surface) is approximately equal to the diameter of the outer peripheral portion of the insulator body 4. Each half body 10A, 10B is made of a half made of a good conductive material such as copper or aluminum in an insulating material 12 made of the same hard resin (for example, PBT) or another resin as the material of the insulator body 4 or rubber. The ring-shaped (semi-cylindrical) conductors 11A and 11B are integrally embedded and molded. In the illustrated example, the semi-circular conductors 11A and 11B are located at the center in the thickness direction of the half-pieces 10A and 10B. It is embedded closer to the inside than the position. Also, each semi-annular conductor 11A, 11
B have projecting portions 13A and 13B slightly projecting from the end surface position of the insulating material 12 at one end, and small recesses 1 slightly retracted from the end surface position of the insulating material 12 at the other end.
4A and 14B are formed, and the protrusions 13A and 13B on one end side are respectively formed with small recesses 14 on the other end side.
A, 14B. Note that, of the pair of half bodies 10A and 10B, one half body 10A
In the insulating material 12, a notch 15 is formed at a position corresponding to the exposed distal end 9A of the signal conductor 9, and a part of the semi-annular conductor 11A is exposed in the notch 15. .

The pair of half bodies 10A, 10B having the above-described structure and shape are formed by integrally molding the semi-annular conductors 11A, 11B with the insulating material 12.

FIG. 4 shows a state in which the above-mentioned half bodies 10A and 10B are fitted into the concave portions of the insulator body 4. As shown in FIG. 4, the half bodies 10A, 10B are fitted from both sides of the recess 8 of the insulator body 4, and the half bodies 10A, 10B are fixed to the recess 8 by pressure welding or using an adhesive. At this time, the semi-annular conductors 11 of the left and right half bodies 10A and 10B
A and 11B are respectively protruding portions 13 on one end side.
A and 13B are fitted into the small recesses 14A and 14B on the other end side, and electrical contact and mechanical joining are performed at the portions, and the pair of semi-annular conductors 11A and 11B are electrically integrated. And the detection conductor 16 having an overall annular shape.
Will be constituted. And this detection conductor 16
Is an insulating material (a part of the insulator body 4 and the insulating material 12)
), The detection capacitor 18 is formed between the detection conductor 16 and the high-voltage conductor 6. The exposed end 9A of the signal conductor 9 is fitted into the cutout 15 on the side of the half body 10A, and the front end 9A and the half body 10A are joined together.
A is in contact with the semi-annular conductor 11A, and electrical conduction therebetween is performed. Therefore, the semi-annular conductors 11A and 11B
The voltage induced in the detection conductor 16 composed of the signal conductor 9 can be guided to an external signal processing circuit or the like by the signal conductor 9.

FIGS. 5 to 8 show a second embodiment of the present invention, that is, an embodiment applied to a structure in which the outside of the semi-annular conductors 11A and 11B constituting the detection conductor 16 is electrically shielded. Examples are shown corresponding to FIGS.

In FIG. 5, a concave portion 8 is formed on the outer periphery of the insulator body 4, and the tip 9A of the signal conductor 9 embedded in the insulator body 4 is exposed in the concave portion 8. This point is the same as in FIG. In the case of this embodiment, similarly to the signal conductor 9 described above, the conductor 19 for ground potential made of a copper wire, a copper strip, or the like is placed on the side of the insulator body 4 symmetrical to the signal conductor 9. Embedded.
Also, the tip 19A of the ground potential conductor 19 is slightly exposed in the recess 8.

As shown in FIGS. 6 and 7, the half-split bodies 10A and 10B are placed in an insulating material 12 in the same manner as the semi-annular conductor 1 described above.
1A, 11B, semi-annular shield members 20A, 20A
B is embedded. Each semi-annular shield member 20A, 2
0B is a plate, foil, mesh or the like of a good conductive material such as copper, aluminum, etc.
It is formed in a semi-annular (semi-cylindrical) shape having a larger radius of curvature than 11B, and is provided outside the semi-annular conductors 11A and 11B via an insulating material 12 so as to keep a constant distance from the outer surfaces thereof. ing. Each semi-annular shield member 20A, 2
0B, like the semi-annular conductors 11A and 11B, are formed with projecting portions 21A and 21B slightly protruding from the end face position of the insulating material 12 at one end and the end face of the insulating material 12 at the other end. Small recesses 22A and 22B which are slightly retracted from the position are formed, and the protrusions 21A and 21B on one end side are formed.
Are fitted to the small recesses 22A, 22B on the other end side, respectively. Furthermore, a pair of half bodies 10
A and 10B are provided with an exposed distal end portion 9 of the signal conductor 9 in the same manner as in the embodiment of FIGS.
A notch 15 is formed at a position corresponding to A, a part of the semi-annular conductor 11A is exposed in the notch 15, and the other half body 10B is provided with a conductor 19 for ground potential. A notch 23 is formed at a position corresponding to the exposed distal end 19A, and a part of the semi-annular shield member 20B is exposed in the notch 23.

FIG. 8 shows the half body 1 shown in FIGS.
0A and 10B correspond to the concave portions 8 of the insulator body 4 shown in FIG.
Shows a state in which it has been fitted into the.

In the case shown in FIG. 8, similarly to the case shown in FIG. 4, the half bodies 10A and 10B are
And the half-split bodies 10A and 10B are fixed to the recesses 8 by pressure welding or using an adhesive. At this time,
As in the case of FIG. 4, the semi-annular conductors 11A and 11B of the left and right half bodies 10A and 10B are formed such that the protruding portions 13A and 13B on one end side are small recesses 14 on the other end side.
A and 14B are fitted into the detection conductor 16 which is formed in a ring shape as a whole.
Between the capacitor and the high-voltage conductor 6
Is formed. At this time, the left and right half bodies 10A, 1
In the semi-annular shield members 20A and 20B of 0B, the protruding portions 21A and 21B on one end side are fitted into the small recesses 22A and 22B on the other end side, respectively. Semi-annular shield members 20A, 20B
Constitutes an annular shield member 25 that surrounds the entire periphery of the detection conductor 16. Further, the exposed tip 9A of the signal conductor 9 fits into the notch 15 on one half 10A, and the ground potential conductor 19 fits into the notch 23 on the other half 10B. Of the signal conductor tip 9A and the semi-annular conductor 11A of the half-split body 10A are electrically connected to each other, and at the same time, the exposed tip part 19A of the half-segment body 10A is half-fitted with the ground potential conductor tip 19A. Body 10B
Is electrically connected to the semi-annular shield member 20B.
Therefore, the voltage induced in the detection conductor 16 composed of the semi-annular conductors 11A and 11B is guided by the signal conductor 9 to an external signal processing circuit or the like, and from the outside via the ground potential conductor 19. Semi-annular shield member 20A,
20B is maintained at the ground potential, thereby detecting conductor 1
6 and the high-voltage conductor 6 can be electrically shielded.

When the detection capacitor 18 is shielded in this way, as described above, even if another conductive member exists near the spark plug cap, the conductive It is effective that the capacitance of the detection capacitor changes due to the fluctuation of the distance to the member, or the detection capacitor picks up noise from the conductive member, which adversely affects the detection accuracy of the ignition voltage waveform. Therefore, the accuracy of detecting the ignition voltage waveform can be further improved.

FIGS. 9 and 10 show halves 10A and 10B used in the third embodiment of the present invention. In this case, at each end face portion of each half body 10A, 10B, a portion of the insulating material 12 is extended outward in the radial direction to form ribs 26A, 26B; 27A, 27B. The ribs 26A, 27A on one end side of the half bodies 10A, 10B have locking claws 28A,
28B are formed in a protruding manner, and each half 10A, 1
0B, on the other end side ribs 26B, 27B,
Engagement holes 29A, 2 with which the locking claws 28A, 28B engage
9B is formed. Other parts, that is, semi-annular conductors 11A and 11B and shield members 20A and 20
The configuration of B is the same as in FIGS. Note that rib 2
6A, 26B; 27A, 27B, locking claws 28A, 28
B, the engagement holes 29A and 29B can be formed simultaneously with the molding of the insulating material 12.

The half bodies 10A, 1 shown in FIGS.
0B is used, the halves 10A and 10B are
May be fitted into the recess 8 of the insulator body 4 of the spark plug from both sides. In this case, since the locking claws 28A, 28B are engaged with the engaging holes 29A, 29B, the left and right half bodies 10A , 10B can be increased.
Therefore, for example, the material of the insulator body 4 and the half body 10
Even in the case where the bonding properties and the adhesion to the inner peripheral surfaces of A and 10B are inferior, the half bodies 10A and 10B can be securely fixed.

9 and 10, the locking claws 28A, 8B, etc. are attached to the half bodies 10A, 10B shown in FIGS. 6 and 7, that is, the half bodies 10A, 10B having the semi-annular shield members 20A, 20B. Are formed, but in some cases, the half bodies 10A and 10B shown in FIGS.
That is, the half body 10A having no semi-annular shield member,
10B, the locking pawl 2 as in the case of FIGS.
Needless to say, 8A, 28B and the like may be additionally formed.

In each of the above embodiments, the half body 10
A and 10B have semicircular conductors 11A and 11B that are not exposed on the inner peripheral surface (concave curved surface), and semicircular conductors 11A and 11B.
The insulating material 12 also covers the inner peripheral surface (concave curved surface) of B.
The semi-annular conductors 11A and 11B may be exposed on the inner peripheral surface side of B.

Further, the present invention can of course be applied to a spark plug cap used in an ignition system having a distributor, that is, a spark plug cap in which an ignition coil is not integrally connected.

[0041]

According to the method of forming the ignition voltage detecting capacitor in the spark plug cap of the present invention, the half body corresponding to the concave portion on the outer periphery of the insulator body is separately formed separately from the insulator body of the spark plug. It is possible to form a detecting capacitor for detecting the ignition voltage simply by fitting the half body into the concave portion from both sides thereof and fixing it, so that the detecting plug can be easily and easily mounted on the spark plug cap. A capacitor can be formed, and even in the production of a spark plug cap on a mass production scale, a detection capacitor can be formed with high productivity without particularly impairing mass productivity.

According to the method of the second aspect,
A structure in which the outside of the detection capacitor is shielded can be simply and easily formed.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a spark plug cap used in a method according to a first embodiment of the present invention, together with an ignition coil portion and a spark plug.

FIG. 2 is an enlarged vertical sectional front view of a pair of halves used in the method according to the first embodiment of the present invention.

FIG. 3 is a plan view of a pair of half bodies shown in FIG. 2;

4 is a longitudinal sectional front view showing a state in which the half-split body shown in FIGS. 2 and 3 is fitted to the spark plug cap shown in FIG. 1, together with an ignition coil portion and a spark plug.

FIG. 5 is a vertical sectional front view showing a main part of a spark plug cap used in a method according to a second embodiment of the present invention.

FIG. 6 is an enlarged vertical sectional front view of a pair of halves used in the method according to the second embodiment of the present invention.

FIG. 7 is a plan view of a pair of half bodies shown in FIG. 6;

8 is a longitudinal sectional front view showing a state where the half body shown in FIGS. 6 and 7 is fitted to the spark plug cap shown in FIG. 5;

FIG. 9 is a longitudinal sectional front view of a pair of halves used in the method according to the third embodiment of the present invention.

FIG. 10 is a plan view of a pair of half bodies shown in FIG. 9;

FIG. 11 is a schematic diagram showing an example of a conventional misfire detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ignition plug cap 2 Ignition coil part 3 Ignition plug 4 Insulator body 6 High voltage conductor 8 Depression 10A, 10B Half body 11A, 11B Semi-circle conductor 12 Insulating material 20A, 20B Semi-circle shield member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02P 15/00 302 F02P 15/00 302A (72) Inventor Takashi Hisagi 1-4-1 Chuo, Wako-shi, Saitama Honda Motor Co., Ltd. Inside the laboratory (72) Inventor Shigeki Baba 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda Technical Research Institute Co., Ltd. (72) Inventor Takuji Ishioka 1-4-1 Chuo, Wako-shi, Saitama Co. (72) Inventor Jiro Takagi 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Inventor Eietsu Akiyama 1-4-1 Chuo Wako-shi, Saitama Pref. ) References JP-A-3-264776 (JP, A) JP-A-4-314969 (JP, A) JP-A-49-127645 (JP, U) JP-B-48-26688 ( P, B1) (58) investigated the field (Int.Cl. ^7, DB name) F02P 17/12 F02P 7/03 F02P 13/00 303 F02P 15/00 302

Claims (2)

(57) [Claims] 1. A spark plug cap comprising a high voltage conductor for conducting a high voltage from an ignition coil to a spark plug, and an insulator body surrounding the high voltage conductor. In forming the detection capacitor, a concave portion that is continuous in the circumferential direction is formed in advance on a position corresponding to the high-voltage conductor on the outer periphery of the insulator body, and a semi-annular shape is formed along a half circumference of the concave portion. The semi-circular conductor is formed of an insulating material such that at least the outer peripheral surface layer is formed of an insulating material and has a semi-circular conductor that is continuous along the bending direction. The two halves are formed by integrally molding with each other, and the pair of halves are fitted into and fixed to the concave portions of the insulator body from both sides thereof. other The two half-ring conductors are electrically contacted with the ends of the semi-circular conductors of the half-split body to form an electrically integrated detection conductor, and the detection conductor and the high-voltage conductor A method of forming a capacitor for detecting an ignition voltage in a spark plug cap, comprising forming a capacitor for detection with a conductor. 2. The shield member according to claim 1, wherein a shield member is provided at a position outside the semi-circular conductor in the insulating material of each half-split body, with the insulating material separated from the semi-circular conductor. Of forming an ignition voltage detecting capacitor in an ignition plug cap of the present invention.