JPH0759937B2 - Ignition distributor cap - Google Patents

Description

TECHNICAL FIELD The present invention relates to a distributor cap used in an ignition distributor of an internal combustion engine.

[Conventional technology]

Generally, the ignition distributor cap is molded using a thermoplastic synthetic resin (for example, polypropylene, polybutylene terephthalate, etc.) that can be injection-molded and has a relatively low manufacturing cost, and talc or glass is used as a filler in the resin. Inorganic powder such as fiber is blended.

FIG. 2 is a cross-sectional view showing a conventional example of this type of distributor cap, in which 1 is a distributor cap, 2 is a distribution rotor that rotates in synchronization with an internal combustion engine, 3 is a side electrode, and 4 is a center electrode. so,
The side electrode 3 is embedded in the high voltage tower portion of the cap 1 with its tip protruding to the inner circumference of the distributor cap 1, and the center electrode 4
The slider 5 is in contact with the rotor electrode 6. As is well known, the distributor cap 1 discharges the high voltage supplied to the rotor electrode 6 through the center electrode 4 and the slider 5 when the rotor electrode 6 faces the tip of each side electrode 3. The electric power is distributed to the side electrode 3 side by means of the above, but the conventional distributor cap has the following points to be improved. In addition,
A conventional example of a distribution cap molded by an injection molding method using a thermoplastic synthetic resin is, for example, Jitsuko Sho 60-14.
There are those disclosed in Japanese Patent No. 939 and U.S. Pat. No. 3,401,245.

[Problems to be solved by the invention]

That is, in the conventional distributor cap made of thermoplastic synthetic resin, the rotor 2 is turned on when it is used for a long time.
Rotor electrode 6 tip and side electrode 3 on the side of the distributor cap 1
Due to long-time power distribution to the tip portion, the resin surface in the vicinity of the side electrode 3 in the inner periphery of the cap 1 may deteriorate and become rough. If the inner surface of the ignition / distributor cap is roughened, moisture generated by the influence of the outside temperature and the like adheres to the roughened inner surface, and this moisture coronas during power distribution. When it comes into contact with nitrogen oxides generated by discharge, nitric acid is generated on the inner circumference of the cap, and a so-called wetting phenomenon occurs on the inner circumference of the cap. Such nitric acid is
It has conductivity, and as a result, when a large amount of conductive material is attached to the inner circumference of the cap in the vicinity of the side electrode 3, a high voltage leakage phenomenon (creeping leakage) distributed by spark discharge is likely to occur. In the worst case, the power distribution function may be lost.

The present invention has been made in view of the above points, and an object thereof is to effectively prevent roughening of the inner circumference of a distributor cap, which is a factor for generation of nitric acid that is a conductive substance, and distribute electricity. An object of the present invention is to provide a power distribution cap that can prevent the occurrence of a high voltage leakage phenomenon during operation and can maintain a good power distribution function for a long period of time.

[Means for solving problems]

The present invention is configured as follows to achieve the above object.

That is, the present invention relates to an ignition distributor cap in which a side electrode that cooperates with a rotor electrode to perform power distribution is provided on an inner surface of an upper wall of a cap body formed of a thermoplastic synthetic resin. The annular band molded body made of a fluororesin is limited to a portion of the wall close to the side electrode and is embedded by injection molding of the cap body so as to be a part of the inner peripheral surface of the cap body. Characterize.

[Action]

As already mentioned in the section [Problems to be solved by the invention], when a thermoplastic resin such as polypropylene or polybutylene terephthalate is used as the molding resin of the distributor cap, it operates over a long period of time. When done,
Since the deterioration of the resin progresses and the amount of nitric acid attached increases, there is a possibility of causing a high voltage leakage phenomenon.

Then, the present invention focuses on the fact that at least a portion that is easily affected by spark discharge due to distribution of electricity does not deteriorate in properties over a long period of time and that water does not easily adhere, and is most suitable for this purpose. In order to find resins, polypropylene, polybutylene terephthalate, various resins such as fluorine resin, epoxy resin, phenol resin, silicone resin, diallyl phthalate resin,
As a result of a comparative study of the wettability in the initial and long-term power distribution, polypropylene, polybutylene terephthalate, epoxy resin, etc. are easily wetted in a relatively short time, whereas only fluorine resin is used in the initial stage. It has been found that even if the above-mentioned spark discharge is affected, the property of being hard to get wet is maintained for a long period of time.

Then, an annular band molded body of fluororesin (hereinafter referred to as an annular band) is formed on one of the inner peripheral surfaces of the cap body at a position near the space where the side electrode and the electrode of the distribution rotor are discharged on the inner wall of the cap body. By arranging so as to form a portion, it is possible to prevent resin deterioration at this portion, effectively prevent the nitric acid product from adhering, and prevent occurrence of a leakage phenomenon during power distribution. In addition, as described above, the fluororesin can achieve the intended purpose by locally specifying the location on the inner wall of the cap body and locally providing it, and thus, the material cost of the distributor cap can be reduced. It can be planned. That is, since the fluorine resin is extremely expensive as compared with the conventionally used distributor cap molding resin (polypropylene, polybutylene terephthalate), it is preferable that the amount of the fluorine resin used is small as a cost reduction measure.

In addition, as a technique for incorporating the cap body with a fluororesin, there is another conceivable technique that uses a coating.However, under conditions where the temperature difference is severe as in the engine rules, the coating film may peel off due to deterioration over time. There is. In addition, the technique of partially treating the coating only near the side electrodes deep inside the cap body is complicated. On the other hand, if the annular band made of fluororesin is preformed as in the present invention and is embedded by using the resin molding (injection molding) of the cap body, the fluororesin film peels off. The above problem does not occur, and the fluororesin band is surely fixed by fusing the resins together, and the technique for integrating the cap body and the fluororesin annular band can be easily performed. Specifically, according to the present invention, no abnormality was found in the power distribution function even when a 2000 hour electrical durability test was performed.

Further, as the fluorine resin in the present invention, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, and Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers and the like are suitable, but are not particularly limited to these.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1 and Tables 1 and 2.

FIG. 1 is a cross-sectional view showing an embodiment of the present invention. In the figure, the same reference numerals as those in the conventional example shown in FIG. 2 indicate the same or common elements.

However, the difference between the present example and the conventional example is that the portion of the inner wall of the distributor cap (cap body) 1 that is prone to the influence of spark discharge during power distribution, that is, the part that is close to the side electrode 3 is made of fluororesin. Layer (annular band made of fluororesin)
8 is formed. The distributor cap 1 including the fluorine resin layer 8 is manufactured as follows. First, before cap molding, polypropylene, a thermoplastic synthetic resin for cap molding such as polybutylene terephthalate and a filler such as talc are weighed and stirred at an appropriate compounding ratio (a specific example of the compounding ratio will be described later). This thermoplastic resin composition is kneaded into pellets by using an extruder, and an annular band having a predetermined shape is manufactured by machining from a pipe-shaped material made of a fluororesin resin which has been formed in advance. Then, the distributor cap 1 is injection-molded by an injection molding machine which can be applied to a usual thermoplastic synthetic resin by using the pellet of the thermoplastic resin composition. At the time of this injection molding, the fluororesin is used. The inner surface of the cylindrical fluororesin body is made the inner surface of the resin molding by injection molding a thermoplastic synthetic resin composition after the annular band made in advance has been set at a predetermined position of the distributor mold for molding. It is embedded in a resin molded body so as to be exposed to the outside, and a partial annular fluorine resin layer 8 as shown in FIG. 1 is formed in the distributor cap 1.

The following Tables 1 and 2 show the composition ratio and the specific material of the fluororesin cylinder used as the fluororesin layer 8 in each example of the distributor cap 1 thus formed, and The result of the 2000 hour power distribution endurance test of the example is shown in comparison with the comparative example.

In Examples 1 to 5 shown in Table 1, polypropylene was used as the thermoplastic synthetic resin for molding of the distributor cap in the distributor cap 1 of FIG. 1 showing one embodiment of the present invention, and fluorine resin was used. As the layer 8, polytetrafluoroethylene, tetrafluoroethylene-hexafluprouropyrene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-peroxide, respectively. It is an example using a cylinder made of a fluoroalkyl vinyl ether copolymer. Further, Comparative Example 1 is a comparative example in which polypropylene is used as the thermoplastic synthetic resin of the distributor cap 1 and no fluorine resin is used (the configuration shown in FIG. 2). Then, when a power distribution endurance test for 2000 hours was performed on each of these Examples 1 to 5, no abnormality was found in the power distribution function even after the execution, and it was confirmed that the power distribution function was maintained even during long-term operation. Very favorable results can be expected.

On the other hand, as in Comparative Example 1, when the test results were performed on the distributor cap in which no fluorine resin was used under the same conditions, the distribution function was lost during the test.

Table 2 shows Examples 6 to 10 and Comparative Example 2,
These Examples and Comparative Examples and Examples 1 to 5 in Table 1 above.
The difference from Comparative Example 1 is that polybutylene terephthalate is used in place of polypropylene as the thermoplastic synthetic resin in the resin composition for forming the cap of the distributor.

Examples 6 to 10 are power distribution caps in which various cylinders made of fluorine resin are embedded in the same manner as in Examples 1 to 5, and a 2000-hour power distribution endurance test was performed in the same manner as in Examples 1 to 5. Even after the implementation, extremely favorable results were obtained in which no abnormalities were observed in the power distribution function.

On the other hand, when a distributor cap not using a fluorine resin was tested under the same conditions as in Comparative Example 2, the distribution function was lost during the test as in Comparative Example 1.

〔The invention's effect〕

As described above, according to the present invention, by forming a fluorine resin portion on the inner surface of the distributor cap molded using a thermoplastic synthetic resin having electrical insulation, to prevent deterioration of the inner surface of the cap, As a result, the occurrence of a high voltage leakage phenomenon can be prevented, and a good power distribution function can be maintained for a long period of time.

Furthermore, according to the present invention, even if the cap body is provided with a fluororesin that should serve as a discharge protection layer, the cost of the distributor cap can be reduced and the fluororesin layer can be easily molded and placed under a severe temperature environment. Even if the electric resin cap (thermoplastic resin) is provided with the fluorine resin layer, the peeling phenomenon does not occur, and an effect of ensuring a highly reliable power distribution effect can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a distributor cap showing an embodiment of the present invention. FIG. 2 is a sectional view of a distribution cap showing a conventional example of the distribution cap. 1 ... Cap body, 2 ... Distribution rotor, 3 ... Side electrode, 6 ... Rotor electrode, 8 ... Fluorine resin part (layer).

Claims (1)

[Claims] Claim: What is claimed is: 1. An ignition distributor cap in which a side electrode that cooperates with a rotor electrode to distribute electricity is provided on an inner surface of an upper wall of a cap body formed of a thermoplastic synthetic resin. Among them, the annular band molded body made of a fluororesin is embedded by injection molding of the cap main body so as to be a part of the inner peripheral surface of the cap main body only in a portion close to the side electrode. Ignition switch cap.