JPH06193542A - Electrode for preventing generation of noise radio wave - Google Patents

Abstract

PURPOSE:To suppress the generation of a noise radio wave through reduction of the generation of a capacity discharge current by sufficiently generating preliminary micro-discharge in prior to main discharge. CONSTITUTION:An electrode for preventing a noise radio wave comprises an electrode parent material 1; and a mixture film 2 with which the electrode base material 1 is covered and which consists of a resistor 21 of a metallic oxide and a dielectric 22 of a metallic oxide. At least on the surface of the mixture film 2, the dielectric 22 is formed in a needle-like state extended approximately vertically to the surface of the electrode base material 1 and uniformly dispersed. In prior to main discharge generated between the resistor 21 and a counter electrode anode, preliminary microdischarge is frequently generated between the two phases of the dielectric 22 and the resistor 21, and along therewith, a main discharge voltage can be reduced. This constitution causes effective reduction of a capacity discharge current causing the generation of a noise radio wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise electric wave preventing electrode used as a discharge electrode or the like constituting an ignition distributor of an internal combustion engine.

[0002]

2. Description of the Related Art A spark discharge generated between discharge electrodes forming an ignition distributor of an internal combustion engine of an automobile or the like, that is, between a rotor electrode and a fixed electrode emits noise radio waves. This noisy radio wave interferes with radio broadcasting, television broadcasting, various wireless communications, etc., and electronic equipment mounted in automobiles, for example, EFI.
(Electronically controlled fuel injection device), ESC (electronic skid control device), EAT (electronically controlled automatic transmission), etc. may be damaged.

Here, the spark discharge current consists of a capacitive discharge current and an induced discharge current. The capacitive discharge current is accumulated in the capacitance between the rotor electrode and the fixed electrode, the high voltage cable connecting the ignition coil and the rotor electrode and the ground, and the stray capacitance between the electrode near the discharge gap and the ground. The high-frequency current that flows during the dielectric breakdown between the gaps instantaneously (about several nanoseconds) rapidly flows. The capacitive discharge current is radiated to the outside by using the high voltage cable or the like as an antenna and causes noise radio waves.

On the other hand, the induced discharge current means a low frequency current (several tens to 100 mA) which continuously flows after the end of the capacity discharge. The ignition energy supplied to the spark plug is substantially proportional to the product of the induction discharge current and the discharge duration of the dielectric discharge current. Therefore, in order to suppress the noise radio wave without lowering the ignition energy, it is sufficient to reduce only the capacity discharge current.

Therefore, Japanese Patent Laid-Open No. 54-50735 discloses a technique for surface-treating a discharge electrode constituting an ignition distributor of an internal combustion engine to reduce the capacitive discharge current and prevent noise radio waves. ing. This surface treatment technology uses CuO
A mixed powder obtained by mixing (cupric oxide) powder and Al ₂ O ₃ (alumina) powder in a predetermined ratio is sprayed on the surface of the discharge electrode to form a mixed coating film of CuO and Al ₂ O ₃ on the discharge electrode. Is formed on the surface of.

[0006]

The reason why the capacity discharge current is reduced by forming the mixed coating film on the surface of the discharge electrode can be considered as follows. That is, as shown in FIG. 10, CuO, which is the metal oxide resistor 81 forming the mixed film, is a non-dielectric material that does not polarize when a voltage is applied, and this causes main discharge A with the counter electrode anode 82. Let Further, Al ₂ O ₃ forming the mixed film is a dielectric material 83 that is polarized when a voltage is applied, and prior to the main discharge A, a preliminary minute discharge B is formed between two phases of CuO and Al ₂ O _3.
Generate. Due to the occurrence of the preliminary minute discharge B, the voltage of the main discharge A is lowered, and the capacity discharge current is reduced.

However, even with the above-mentioned conventional surface treatment technique, the above capacity discharge current cannot be sufficiently reduced. The present invention has been made in view of the above circumstances, and by sufficiently generating a preliminary minute discharge prior to the main discharge, it is possible to reduce the capacitive discharge current and effectively suppress noise radio waves. It is intended to provide an electrode for preventing radio waves.

[0008]

A noise radio wave preventing electrode of the present invention which solves the above problems is an electrode base material, a metal oxide resistor and a metal oxide dielectric material which cover the electrode base material. And a mixed coating composed of two phases, and at least on the surface of the mixed coating, the dielectric is uniformly dispersed in the form of needles extending substantially perpendicular to the surface of the electrode base material. It is a feature.

[0009]

In the noise electric wave preventing electrode of the present invention, a mixed coating composed of two phases of a metal oxide resistor having a high electric resistance and a metal oxide dielectric is formed on the surface of the electrode base material. There is. When a voltage is applied, on the surface of this mixed film, the non-polarized resistor as a non-dielectric body becomes the main discharge part with the counter electrode anode, and the polarized dielectric body forms the dielectric body and the resistor body prior to the main discharge. A preliminary minute discharge is generated between the two phases. Due to the occurrence of this preliminary minute discharge, the main discharge voltage is lowered, and the capacitive discharge current that causes noise radio waves can be reduced.

The noise radio wave preventing electrode of the present invention is
On the surface portion of the mixed coating, the dielectric is uniformly dispersed in the form of needles extending substantially perpendicular to the surface of the electrode base material. Since the surface of the mixed coating film that covers the surface of the electrode base material has the above-described texture structure, the dielectric and the resistor are alternately present on the surface. As a result, the preliminary minute discharge is frequently generated between the two phases of the dielectric and the resistor, and the main discharge voltage is also reduced accordingly, and the capacitive discharge current that causes noise radio waves is more effective. Can be reduced to

[0011]

EXAMPLES Examples of the present invention will be specifically described below. (Embodiment 1) In this embodiment, the noise radio wave preventing electrode of the present invention is applied to a rotor electrode which serves as a cathode of a distributor. As shown in FIG. 1 and FIG. 2, the noise radio wave preventing electrode of the present embodiment is composed of an electrode base material 1 made of brass and a mixed coating 2 formed on the surface of the electrode base material 1. .

The mixed coating 2 is composed of two phases of a metal oxide resistor 21 and a metal oxide dielectric 22 having high electric resistance. The resistor 21 is CuO (second copper oxide, electrical resistivity: 10 ⁴ Ω · cm), and the dielectric 22
Is Al ₂ O ₃ (alumina, dielectric constant 8-9). Then, on the surface portion of the mixed coating film 2, the dielectric material 22 has a needle shape extending substantially perpendicular to the electrode base material 1 and is uniformly dispersed.

The thickness of the mixed coating 2 is 400 μm, and the thickness of the needle-shaped tissue layer in which the dielectric material 22 has a needle-shaped structure on the surface of the mixed coating 2 is about 50 to 300 μm. Further, the pitch (p) of the needle-like structure of the dielectric body 22, that is, the distance between the centers of two adjacent dielectric bodies 22 is 5 to 50 μm.
It is about m. In addition, the aspect ratio of the dielectric 22 in a vertical cross section (l / d, l: dimension of the dielectric 22 in a direction perpendicular to the surface of the electrode base material 1, d: dielectric 22 in a direction parallel to the surface of the electrode base material 1 The dimension) is 3 or more.

The noise radio wave preventing electrode of this example was manufactured by treating the surface of the electrode base material 1 as follows. (Spraying treatment) CuO powder (particle size 10 to 150 μm) and A
1 ₂ O ₃ powder (particle size 10 to 150 μm) by weight ratio (C
uO: Al ₂ O ₃ = 7: 3) mixed powder was sprayed onto the electrode base material 1 by the plasma spraying method, and 400 μm
Mixed coating 2 was formed.

(Laser remelting treatment) Using a YAG: Nd ³⁺ laser, as shown in FIG. 2, while moving the electrode base material 1 on which the mixed coating 2 is formed, the mixed coating 2 is formed under the following conditions. Laser irradiation was performed to remelt the surface of the mixed coating 2. Laser output: 100 W Laser pulse: 10 msec / pulse, 20 pulse / s
ec Irradiation part moving speed: about 1 cm / sec Irradiation time: 1 sec (Comparative Example 1) For comparison, Comparative Example 1 was performed in the same manner as in Example 1 except that the laser remelting treatment was not performed.
The electrode for preventing noise radio waves was obtained.

(Evaluation of Noise Electric Wave Level) The noise electric wave preventing electrode of Example 1 and Comparative Example 1 was used as a rotor electrode of a distributor and mounted on a general vehicle to evaluate the generation state of noise electric wave. The result is shown in FIG. The noise radio wave level in FIG. 3 is an evaluation obtained by measuring the magnetic field strength.

As is clear from FIG. 3, the dielectric 2 is formed on the surface of the mixed coating 2 by the laser remelting process.
The electrode of the present example in which the tissue of No. 2 has a fine and uniform needle-like structure was able to significantly reduce the noise radio wave level over the entire measurement frequency range as compared with the rotor electrode of Comparative Example 1. Further, an optical micrograph of a longitudinal section of the surface portion of the mixed coating 2 according to the above Example 1 is shown in FIG. 4, and an optical micrograph of a longitudinal section of the mixed coating 2 according to Comparative Example 1 is shown in FIG. Thereby, in the surface portion of the mixed coating film 2 according to the first embodiment,
It can be seen that the dielectric 22 has a uniform fine needle-like structure, while the dielectric 22 has a coarse granular structure on the surface portion of the mixed film according to Comparative Example 1. The interface of light and shade of color seen in the upper part of FIGS. 4 and 5 represents the surface of the mixed coating 2, and the light colored portion below this interface is the mixed coating 2. The light-colored, whitish portion of the mixed coating 2 is the resistor 21, and the other dark-colored portion of the mixed coating 2 is the dielectric 22.

As described above, by irradiating the surface of the mixed coating film 2 formed by thermal spraying with a laser, the dielectric material 22 can be made into a needle-like structure in which the dielectric material 22 is uniformly and finely dispersed. It was confirmed that the reduction could be achieved. (Relationship between the thickness of the layer showing needle-like tissue and the level of noise radio waves)
In the laser remelting process, the thickness of the remelting process is changed by changing the irradiation part moving speed of the processing conditions to 0.1 cm / sec to 10 cm / sec and the irradiation time to 0.1 sec to 10 sec. It was examined how the effect of reducing the level of noise radio waves is affected when the thickness of the layer 22 having a needle-like structure is changed. This was evaluated by setting the measurement frequency to 100 MHz and comparing it with the noise radio wave level of Comparative Example 1 above. The result is shown in FIG. The pitch between the dielectrics 22 showing the needle-like structure is 10
The vertical cross-sectional aspect ratio (l / d) of the dielectric 22 having a microstructure and a needle-like structure was 10.

As is apparent from FIG. 6, in order to effectively reduce the noise radio wave level, it is preferable that the thickness of the layer in which the dielectric 22 exhibits a needle-like structure is 100 μm or more. (Relationship between pitch of needle-like tissue and noise radio wave level) In the laser remelting process, the dielectric 22 showing needle-like tissue is obtained by changing the laser pulse of the processing condition from 0.1 msec / pulse to 50 msec / pulse. We investigated how the effect of reducing the level of noise radio waves is affected by changing the pitch. This gives a measurement frequency of 10
It was set to 0 MHz and evaluated by comparison with the noise radio wave level of Comparative Example 1 above. The result is shown in FIG. 7. The thickness of the layer in which the dielectric material 22 has a needle-shaped structure is 300 μm, and the vertical cross-sectional aspect ratio (l / d) of the dielectric material 22 having a needle-shaped structure is 1
It was set to 0.

As is apparent from FIG. 7, in order to effectively reduce the noise radio wave level, the dielectric material 22 showing the needle-like tissue is used.
It is understood that it is preferable to set the pitch of 50 μm or less. (Relationship between aspect ratio of needle tissue and noise radio wave level)
In the laser remelting process, the noise radio wave level is obtained when the longitudinal cross-sectional aspect ratio of the dielectric 22 showing the needle-like tissue is changed by changing the laser pulse of the processing condition from 5 pulses / sec to 50 pulses / sec. It was investigated what kind of influence it had on the reduction effect of. This was evaluated by setting the measurement frequency to 100 MHz and comparing it with the noise radio wave level of Comparative Example 1 above. The result is shown in FIG. The thickness of the layer in which the dielectric material 22 has a needle-like structure is 300 μm.
m, and the pitch between the dielectrics 22 having a needle-like structure was 10 μm.

As is apparent from FIG. 8, in order to effectively reduce the noise radio wave level, the dielectric material 22 having a needle-like structure is used.
It is understood that it is preferable to set the vertical cross section askt ratio to 4 or more. (Embodiment 2) In the noise electric wave prevention electrode of the present embodiment 2, the metal oxide resistor 21 having a high electric resistance constituting the mixed coating 2 is replaced by CuO instead of MnO (electrical resistivity: 10).
⁸ Ω · cm), but has the same structure as that of the above-described first embodiment.

The electrode of the second embodiment also uses Cu as the raw material powder.
MnO powder (particle size: 10 to 150 μm instead of O powder)
It was produced by the same method as in Example 1 except that m) was used. The thickness of the mixed coating 2 is 400 μm, and the thickness of the needle-shaped tissue layer in which the dielectric material 22 has a needle-shaped structure on the surface of the mixed coating 2 is about 100 μm. Further, the pitch between the dielectrics 22 having a needle-like structure is about 10 μm. In addition, the vertical cross-sectional aspect ratio of the dielectric 22 showing the needle-like structure is 10.

(Embodiment 3) In the noise electric wave preventing electrode of the third embodiment, the dielectric 22 constituting the mixed coating 2 is replaced by A
SiO ₂ instead of l ₂ O ₃ (silicon dioxide, dielectric constant:
The configuration is the same as that of the above-described first embodiment except that the above-mentioned values are set to 3.4 to 4.5). Also in the electrode of the present Example 3, SiO ₂ powder (particle size: 5 to 1) was used as the raw material powder instead of Al ₂ O ₃ powder.
It was manufactured by the same method as in Example 1 except that 50 μm) was used.

The thickness of the mixed coating 2 is 400 μm, and the thickness of the needle-shaped tissue layer in which the dielectric material 22 has a needle-shaped structure on the surface of the mixed coating 2 is about 100 μm. Further, the pitch between the dielectrics 22 having a needle-like structure is about 10 μm. In addition, the vertical cross-sectional aspect ratio of the dielectric 22 showing the needle-like structure is 10. (Comparative Example 2) In the noise radio wave preventing electrode of Comparative Example 2, a metal oxide resistor (CuO) 21 having a high electric resistance, which constitutes the mixed coating 2, is used as a metal Cu (electrical resistivity: 10 ^-6 Ω).・
cm), and has the same configuration as that of the first embodiment.

The electrode of this Comparative Example 2 is also C as a raw material powder.
Cu powder (particle size: 5 to 150 μm) instead of uO powder
Was produced by the same method as in Example 1 except that The thickness of the mixed coating 2 is 300 μm, and the thickness of the needle-shaped tissue layer in which the dielectric 22 has a needle-shaped structure on the surface of the mixed coating 2 is about 100 μm. Further, the pitch between the dielectrics 22 having a needle-like structure is about 10 μm. In addition, the vertical cross-sectional aspect ratio of the dielectric 22 showing the needle-like structure is 10.

(Evaluation of noise radio wave level) The above-mentioned second embodiment,
The noise radio wave prevention electrodes of Comparative Example 3 and Comparative Example 2 were evaluated by comparison with the noise radio wave level of Comparative Example 1 with the measurement frequency set to 100 MHz, as in Example 1. The results are shown in FIG. 9 together with the results of Example 1. As is clear from FIG. 9, the first to third embodiments in which the mixed coating 2 is a combination of the metal oxide resistor 21 and the metal oxide dielectric 22.
It can be seen that the electrodes according to No. 3 all have a great effect of reducing the level of noise radio waves. On the other hand, the mixed coating 2 is coated with metal C
In the electrode according to Comparative Example 2 in which u and a dielectric were combined, Comparative Example 1 in which the mixed coating 2 was a combination of a metal oxide resistor 21 and a metal oxide dielectric 22 and was not subjected to remelting treatment
The effect of reducing the level of noise radio waves was smaller than that of the electrode according to. This is because, when metal Cu is used for the main discharge part, when a voltage is applied, a main discharge current is generated between the metal Cu and the counter electrode anode while no preliminary minute discharge is generated between the metal Cu and the dielectric. It is thought to be because it will end up.

(Other Examples) As the metal oxide resistor 21 constituting the mixed coating 2, ZnO, BaO, CaO, in addition to CuO and MnO shown in the above examples.
A metal oxide such as CeO ₂ , CoO, Fe ₃ O ₄ , NiO, V ₂ O _{3 having} an electric resistivity of 10 ⁻² Ω · cm or more can be used. When the electric resistivity of the resistor 21 is less than 10 ^-2 Ω · cm, the main discharge occurs without the preliminary minute discharge, and the noise electric wave level reducing effect cannot be exhibited.

Further, as the metal oxide dielectric 22 constituting the mixed coating 2, the Al ₂ O shown in the above embodiment is used.
_In addition to ₃ , SiO ₂ , MgO, TiO ₂ , BeO, etc. can be adopted. A dielectric other than a metal oxide such as a resin material may be used, but it cannot be used because the heat resistance to the extreme heating during discharge is insufficient. The combination of the resistor and the dielectric is not particularly limited.

Further, in the above embodiment, during the remelting treatment,
Although a laser light source is used, other high-density energy such as an electron beam method or a plasma method can be used instead.

[0030]

As described above in detail, the noise radio wave preventing electrode of the present invention has two phases of a metal oxide resistor having a high electric resistance and a metal oxide dielectric on the surface of the electrode base material. The mixed film is formed, and on the surface portion of the mixed film, the dielectric is uniformly dispersed in the form of needles extending substantially perpendicular to the surface of the electrode base material. As a result, prior to the main discharge that occurs between the resistor and the counter electrode anode, the preliminary minute discharge frequently occurs between the two phases of the dielectric and the resistor, and the main discharge voltage is changed accordingly. Can be reduced. Therefore, the noise radio wave prevention electrode of the present invention can more effectively reduce the capacitive discharge current that causes noise radio waves.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a main part of a noise radio wave prevention electrode according to the present embodiment.

FIG. 2 is a perspective view illustrating a remelting step in one of the manufacturing steps of the noise electromagnetic wave prevention electrode according to the present embodiment.

FIG. 3 is a diagram showing a vehicle mounting evaluation of electrodes according to the present Example 1 and Comparative Example 1.

FIG. 4 is a micrograph (400 ×) showing a crystal structure of a surface portion of an electrode according to the first embodiment.

5 is a micrograph (400 ×) showing a crystal structure of a surface portion of an electrode according to Example 1. FIG.

FIG. 6 is a diagram showing the relationship between the thickness of the needle-like tissue of the mixed coating and the noise radio wave level.

FIG. 7 is a diagram showing the relationship between the pitch of the needle-like structure of the mixed film and the noise radio wave level.

FIG. 8 is a diagram showing the relationship between the aspect ratio of the acicular tissue of the mixed film and the noise radio wave level.

9 is a diagram showing noise radio wave levels of electrodes according to Examples 1 to 3 and Comparative Example 2. FIG.

FIG. 10 is a cross-sectional view schematically showing a main part of a conventional noise radio wave prevention electrode.

[Explanation of symbols]

Reference numeral 1 is an electrode base material, 2 is a mixed coating, 21 is a metal oxide resistor, and 22 is a metal oxide dielectric.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshio Asahi 1 Toyota-cho, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Akio Sato 1-cho, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. An electrode base material, and a mixed coating which covers the electrode base material and comprises two phases of a metal oxide resistor and a metal oxide dielectric, and at least the surface of the mixed coating. 2. The noise electric wave preventing electrode according to claim 1, wherein the dielectric is in the form of a needle extending substantially perpendicularly to the surface of the electrode base material and is uniformly dispersed.