JPH0821347A - Electrode for suppressing noise radio wave - Google Patents

Abstract

PURPOSE:To further prevent the generation of the noise radio wave during the discharge in an electrode such as a rotor electrode. CONSTITUTION:An electrode consists of a base body 20, and a layer 22 made of the resistant material which is covered over the surface facing the opposite electrode of the base body 20 and has the composition consisting of Al2 TiO5 and 0-90wt.% Al2O3. When the voltage is applied, the discharge is generated from the closest part to the opposite electrode of the base body 20, i.e., the base body in the vicinity of the interface between the layer 22 made of the resistant material and the base body 20. The electrons generated by this discharge are moved along the surface (the upper and lower surfaces and the tip surface) of the layer 22 made of the resistant material. When the electrons are moved along the creepage of the layer 22 made of the resistant material, the discharged energy is attenuated, and the generation of the electric and magnetic fields which are the causes of the noise can be decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise radio wave prevention electrode in which generation of noise radio waves is prevented. The noise radio wave prevention electrode of the present invention is used, for example, as a rotor electrode of an automobile distributor.

[0002]

2. Description of the Related Art In a distributor of an internal combustion engine of an automobile or the like, a rotor electrode is intermittently opposed to a side surface fixed electrode while rotating through a minute gap, and a discharge is generated between the rotor electrode and the side surface fixed electrode. It is configured to alternately supply power to a plurality of spark plugs. However, in such a power feeding method, noise electric waves (ignition noise) are generated due to the spark discharge generated between the rotor electrode and the side surface fixed electrode. Since this noise radio wave has a wide frequency band and a high level, it is mounted on televisions, radios and other wireless communication equipment, automobiles, and other electronic devices such as EFI (electronically controlled fuel injection device) and ESC (electronic skid). Control device), EAT (electronically controlled automatic transmission), etc. may be affected.

Here, the spark discharge current consists of a capacitive discharge current and an induced discharge current, as shown in FIG. The capacitive discharge current is a high-frequency current that flows at a sharp rise during the initial discharge period for about 10 μsec from the start of discharge. The induced discharge current refers to a low frequency current (several tens to 100 mA) that continuously flows for a long period of time between 500 and 1500 μsec after the end of capacitive discharge.

The ignition energy supplied to the spark plug is approximately proportional to the product of the induction discharge current and the discharge duration of the dielectric discharge current. Further, since the induced discharge current has a low absolute current level, it has almost no effect on noise radio waves. Therefore, in order to effectively suppress the noise radio wave without lowering the ignition energy, it is important to surely reduce the discharge start voltage and the capacity discharge current.

Therefore, various noise radio wave prevention measures have been taken conventionally. For example, a method in which a resistor is externally or internally provided in a plug, a method in which a resistor is inserted in a part of high-voltage wiring, a method in which a noise prevention capacitor is provided, and the like are known. However, such a method has problems that the effect is insufficient and the reliability is poor. Therefore, for example, in Japanese Patent No. 858984, it is described that a high electric resistance material is formed and added to the surface of the discharge electrode to prevent generation of noise electric waves due to the discharge gap. However, this method can only reduce noise of 5 to 6 dB at most, and it has been difficult to satisfy the recent required performance.

Further, in Japanese Patent Laid-Open No. 54-50735, surface treatment is applied to a discharge electrode constituting an ignition distributor of an internal combustion engine to reduce the discharge start voltage and the capacity discharge current to prevent noise radio waves. The technology is disclosed. In this surface treatment technique, a mixed powder obtained by mixing CuO (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 CuO and Al ₂ O ₃ The noise electric wave preventing layer made of the mixed sprayed layer of No. 1 is formed on the surface of the discharge electrode facing the counter electrode. In this noise radio wave prevention electrode, a preliminary minute discharge is generated between CuO as an oxide resistor and Al ₂ O ₃ as an oxide dielectric, so that CuO as an oxide resistor and a counter electrode are formed. The main discharge voltage generated during the period decreases, which leads to a reduction in the capacity discharge current. The effect of this preliminary micro-discharge is called the Malter effect, and a noise radio wave prevention method utilizing this Malter effect has been drawing attention in recent years.

Further, as a noise radio wave preventing electrode utilizing the Malter effect, Japanese Patent Publication No. 1-24722 includes an electrode substrate and a resistance material layer coated on the surface of the electrode substrate facing the counter electrode. Have been disclosed. The resistance material layer is made of semi-conductive alumina / ceramics material, and titania (TiO ₂ ) is added to oxide ceramics mainly composed of alumina (Al ₂ O ₃ ) and reduction treatment is performed in a reducing atmosphere containing hydrogen. Is formed on the surface of the electrode substrate. In this noise electric wave prevention electrode, the main discharge voltage generated between the counter electrode is lowered by generating a preliminary minute discharge between titania having semiconductivity, that is, resistance, and alumina as a dielectric. , Causing a decrease in capacity discharge current.

[0008]

However, even with the noise radio wave prevention method utilizing the Malter effect, the noise radio wave prevention effect is still insufficient, and it has been necessary to further prevent noise radio waves. Therefore, noise radio wave prevention H / T
Measures such as cords and bonding wires are required,
There were problems in terms of cost and assembly man-hours. Particularly, in recent vehicle engines, noise electric waves generated from the vehicle tend to increase due to increase in required ignition voltage (ignition energy), reduction in diameter of high tension cord, reduction in clearance between bonnet and distributor, and the like.

The present invention has been made in view of the above circumstances, and it is a technical subject to be solved to more effectively prevent noise electric waves only by improving electrodes.

[0010]

The noise radio wave preventing electrode according to claim 1 for solving the above-mentioned problems is a substrate and a resistance material layer made of Al ₂ TiO ₅ coated on the surface of the substrate facing the counter electrode. It consists of and.
In addition, the noise electric wave prevention electrode according to claim 2 includes a base body,
The surface of the substrate facing the counter electrode is coated with Al ₂ Ti
It is characterized by comprising a resistance material layer composed of O ₅ and 90 wt% or less of Al ₂ O ₃ .

[0011]

In the noise electric wave preventing electrode according to the first aspect of the present invention, when voltage is applied, discharge is generated from a portion of the substrate closest to the counter electrode, that is, the substrate near the boundary between the substrate and the resistance material layer. Then, the electrons due to this discharge move along the surface (upper and lower surfaces and the tip surface) of the resistance material layer. As described above, when the electrons move along the surface of the resistance material layer, the discharge energy is attenuated, so that the generation of the electric field / magnetic field that causes noise can be reduced.

Further, the noise radio wave preventing electrode according to the second aspect of the invention has the following actions in addition to the above actions. That is, since Al ₂ O ₃ is present in the resistance material layer, the creeping electric resistance is increased. Therefore, it is possible to suppress the movement of electrons during creeping discharge and more effectively attenuate the discharge energy. Note that Al ₂ O ₃ in the resistance material layer
If the ratio exceeds 90%, the impedance of the entire electrode becomes too high due to the electric resistance value, so that the discharge starting voltage increases and the noise electric wave preventing effect is extremely reduced.

[0013]

[First Embodiment]

(Embodiment 1) FIG. 1 is a sectional view of a rotor electrode 2 of this embodiment. The rotor electrode 2 is a base 2 made of brass.
0, an underlayer 21 formed on the surface of the base 20, and a resistance material layer 22 formed by coating on the surface of the underlayer 21.

The underlayer 21 is provided to secure the adhesion of the first layer 22 to the substrate 20 by thermal spraying, and Ni-5% A
It is formed with a thickness of 50 μm from the 1-alloy. The underlayer 21 was formed by using the plasma spraying method. Further, the resistance material layer 22 is formed of Al ₂ TiO ₅ -70 wt% Al ₂ O.
It was formed with a thickness of 0.4 mm from ₃ by the plasma spraying method. Al ₂ TiO ₅ is
Oxygen defects are generated and change from an insulator to a resistor.

In the rotor electrode 2 of this embodiment, the surface of the substrate 20 is coated with the underlayer 21, the surface of the underlayer 21 is coated with the resistance material layer 22, and the upper and lower surfaces of the electrode are polished.
This was completed by removing the sprayed porous layers formed on the upper and lower surfaces of the electrode. It should be noted that the sprayed porous layer on the upper and lower surfaces of the electrode is removed because discharge electrons are likely to remain in the space between the sprayed particles when the sprayed porous layer exists near the discharge generation position (upper and lower surfaces of the electrode). The reason for this is that the noise is likely to occur in the radio mounted in the car as a result of the longer period.

(Comparative Example 1) An electrode having only the substrate 20 was used as Comparative Example 1. (Comparative Example 2) Al ₂ TiO ₅ -70 wt% CuO-40 wt% instead of the resistance material layer 22 made of Al ₂ O _3.
The same as Example 1 except that the resistance material layer 22 made of Al ₂ O ₃ is formed. (Comparative Example 3) Instead of the resistance material layer 22 made of Al ₂ TiO ₅ -70 wt% Al ₂ O ₃ , TiO ₂ -70 wt%.
The same as Example 1 except that the resistance material layer 22 made of Al ₂ O ₃ is formed. (Comparative Example 4) Instead of the resistance material layer 22 made of Al ₂ TiO ₅ -70 wt% Al ₂ O ₃ , TiO ₂ -15 wt.
% Al ₂ TiO ₅ −70 wt% The same as Example 1 except that the resistance material layer 22 made of Al ₂ O ₃ is formed. (Comparative Example 5) Instead of the resistance material layer 22 made of Al ₂ TiO ₅ -70 wt% Al ₂ O ₃ , Al ₂ O ₃ (99.
(7%) except that the resistance material layer 22 of 7%) is formed.

(Evaluation) For these electrodes, the initial and 5
Noise due to noise radio waves at 180 MHz after use for 00 hours
The level was measured. The result is shown in FIG. Use
The conditions are room temperature and engine speed: 1500 rpm.
It As a result, the electrode of Example 1 was initially used for 500 hours.
It was confirmed that the noise prevention effect was excellent even after use.
Then, with respect to the electrode of Example 1,
A magnified image was taken with a speed video (0.001 sec / frame)
However, as shown in FIG.
The portion closest to the side electrode 3 among them, that is, the base body 20 and the resistance material
The base is near the boundary with the material layer 22, and the discharge path is an electrode.
Towards the side electrode (cathode) 3 along the upper and lower surfaces and the tip surface
It was observed that there was a creeping discharge. in this way,
Electrons move along the surface of the resistance material layer 22 having high electric resistance.
And the discharge energy is attenuated, which causes noise
The generation of electric and magnetic fields is reduced. In addition, in the first embodiment
In the electrode, the metal oxide in the resistance material layer 22 is a composite oxide.
Al as₂TiO_FiveIt is miscellaneous to exist in the form of
It contributes to the sound prevention effect. That is, Al₂TiO_Five
And Ti, which are the constituent elements of TiO, have low electrical resistance. ₂Form of
When it exists in the state, it does not show the above-mentioned discharge form and
Discharge is generated from the pole tip surface, that is, the tip surface of the resistance material layer 22.
Occurs, and the radio noise effect due to creeping discharge is not exhibited. This
This is plasma sprayed TiO₂Has too much electrical resistance
Since it is very low, it is closest to the side electrode 3 as the counter electrode.
Existing TiO₂This is because the discharge is generated in. This
On the other hand, the metal oxide in the resistance material layer 22 is a composite oxide.
Al as₂TiO_FiveIf it exists in the form of
₂TiO_FiveIs TiO₂Has a higher electrical resistance than
Shows the discharge path as described above, and exhibits a noise prevention effect.
It Therefore, in order to cause the creeping discharge phenomenon,
TiO in the resistance material layer 22₂It is important that
is there.

(Relationship Between Addition Amount of Al ₂ O ₃ in Resistive Material Layer 22 and Noise Prevention Effect) In Example 1 above, the addition amount of Al ₂ O ₃ in the resistive material layer 22 was changed variously, Similarly to the above, the initial performance of the radio noise level at 180 MHz was measured. FIG. 4 shows the results. As is clear from FIG. 4, the added amount of Al ₂ O ₃ in the resistance material layer 22 is 90%.
When it exceeded wt%, the radio noise level increased extremely.
It is considered that when Al ₂ O ₃ exceeds 90 wt%, the discharge start voltage increases because the impedance of the entire electrode becomes too high due to the electric resistance value.

Further, until the addition amount of the resistance material layer in 22 Al ₂ O ₃ is 80 wt%, the radio noise level taken to the addition amount is increased is decreased, the Al ₂ O ₃ This is because the increase in creeping electric resistance (suppression of electron movement). Therefore, the addition amount of Al ₂ O ₃ in the resistance material layer 22 is preferably 40 to 80 wt%.

As shown in FIG. 5, the thickness of 0.4 of Al ₂ TiO ₅ is formed on the tip surface of the substrate 20 of brass.
mm resistance material layer 22 is formed by plasma spraying, and 100 mm is formed between the upper surface of the base body 20 and the tip surface of the resistance material layer 22.
As a result of examining the DC resistance value of Al ₂ TiO ₅ when a voltage of V was applied with an ammeter 5, it was 1 × 10 ⁶ to 1 × 10 ⁷ Ω. Similarly, the direct current resistance value of TiO ₂ was 10Ω and the direct current resistance value of Al ₂ O ₃ was 1 × 10 ¹² Ω.

(Relationship Between Thickness of Resistive Material Layer 22: L and Noise Prevention Effect) In the first embodiment, the thickness of the resistive material layer 22: L is variously changed, and radio waves at 180 MHz are generated in the same manner as above. The initial performance of noise level was measured. The result is shown in FIG. As is clear from FIG. 6, when the thickness L of the resistance material layer 22 is smaller than 0.1 mm, the effect of preventing noise radio waves due to the above-mentioned creeping discharge is hardly exhibited. On the other hand, when the thickness L of the resistance material layer 22 is thicker than 1.0 mm, the impedance of the entire electrode is high and the discharge generation voltage is lower at the electrode tip, so that the discharge generation position is at the electrode tip surface, That is, it becomes the front end surface of the resistance material layer 22, and the effect of preventing noise radio waves due to creeping discharge is not exhibited. Therefore, the thickness L of the resistance material layer 22 is preferably 0.1 mm ≦ L ≦ 1.0 mm.

[0022]

As described in detail above, according to the noise electric wave preventing electrode of the present invention, noise electric waves can be prevented for a long period of time. Therefore, another noise prevention measure such as a bonding wire is not required, and the cost and man-hours can be reduced. Since the noise level is the same as that of an expensive ceramic rotor or the like, it can be used as a substitute for the ceramic rotor or the like, and a significant cost reduction can be achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a noise radio wave preventing electrode according to an embodiment of the present invention.

FIG. 2 is an overall cross-sectional view of a noise radio wave prevention electrode according to an embodiment of the present invention.

FIG. 3 is a bar graph showing the degree of radio noise level of electrodes in an example of the present invention.

FIG. 4 shows Al ₂ in a resistance material layer according to an embodiment of the present invention.
6 is a graph showing the relationship between the amount of O ₃ and the radio noise level.

FIG. 5 is a cross-sectional view illustrating how to measure an electric resistance value of a resistance material layer according to an example of the present invention.

FIG. 6 is a graph showing the relationship between the thickness of the resistive material layer and the radio noise level in the example of the present invention.

FIG. 7 is a graph showing the results of examining a current profile model at the time of a single discharge in the conventional noise radio wave prevention electrode.

[Explanation of symbols]

1: rotor 2: rotor electrode 3: side electrode (counter electrode) 20: substrate 22: resistance material layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Asahi 1 Toyota-cho, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Kimitoshi Murata 1-cho, Toyota City, Aichi Prefecture, Toyota Motor Corporation ( 72) Inventor Nobuyuki Ishihara 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. A noise electric wave preventing electrode comprising a substrate and a resistance material layer made of Al ₂ TiO ₅ coated on the surface of the substrate facing the counter electrode. 2. A substrate, and Al ₂ TiO ₅ and 90 wt% or less Al coated on the surface of the substrate facing the counter electrode.
An electrode for preventing noise electric waves, which comprises a resistance material layer made of ₂ O ₃ .