JPS6111461A - Ignition distributor of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent noise as well as to reduce loss of ignition energy, by forming plural fixed electrodes or rotor electrode from a sintered body of zinc oxide powder and ferrite powder, and further by forming the outer surface layer mainly composed of ferrite on the surface of the electrode. CONSTITUTION:Fixed electrode 3 are connected to respective ignition plugs. A cam shaft 7 rotates in linkage with a crank shaft of the internal-combustion engine. A rotor electrode 10 comes in the position opposing to the fixed electrode 3 with a small space in between, in accordance with the rotation of a distributor 8. The plural fixed electrodes or rotor electrode is made of sintered body composed of zinc oside powder 80-95mol% and ferrite powder 5-20 mol%. An outermost surface layer mainly composed of ferrite is formed on the surface of the sintered body. Thus, the noise generation is sufficiently prenvented and the loss of the ignition energy is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition power distribution device that is electrically connected by an electric spark, and more specifically, a rotating electrode and a rotating The present invention relates to an ignition distributor having a noise prevention function that suppresses the generation of radio waves caused by spark discharge generated between a fixed electrode placed on the side of the ignition distributor.

[Prior Art] Noise radio waves caused by spark discharges generated in the ignition system of internal combustion engines installed in automobiles, etc. are known as decivision. Interfering with communication equipment such as radios.

The main causes of noise radio waves generated from the ignition system of an internal combustion engine are (1) spark discharge between the electrodes of the spark plug;
2) Spark discharge between rotating and fixed electrodes of power distributor, (3)
Three points can be cited: spark discharges associated with the opening and closing operations of the breaker points of power distribution equipment = 2 -.

The following methods (I) to (V) have been proposed as means for preventing noise radio waves caused by (2) among the above causes, but each has drawbacks and has not yet achieved sufficient effectiveness. has not yet been reached.

(I) Method using a rotating electrode containing a resistor In this method, a resistor is embedded in a rotating electrode. Because there is a distributed capacitance in parallel with the resistor, the noise suppression effect is small in the high frequency band of approximately 300 Mf-1z or higher, and the loss of ignition energy due to the resistor (about Ω in number) is said to be large. There are drawbacks. Note that even at frequencies below 200 MHz, where noise suppression is effective, the noise suppression effect is as small as about 5 to 6 dB.

(II) Method using a spray-coated rotating electrode In this method, a high-resistance material layer is added to the surface of the rotating electrode. This method has drawbacks such as (a) a large loss of ignition energy due to the provision of a high-resistance material layer on the electrode surface, and (b) a noise suppression effect of 5 to 6 dB, L, negligible at 200 MH2 or less.

(II) Method of increasing the discharge gap This method increases the discharge gap between the rotating electrode and the fixed electrode by 1.5 to 6.4 m.
It is expanded to about m.

This has the advantage of a noise suppression effect of 15 to 20 dB, but since the discharge gap is very large, the loss of ignition energy is very large, and the discharge voltage between the electrodes becomes high, so The disadvantage is that a gas that corrodes the rotating electrode is generated and the rotating electrode is corroded.

HV) A method of using boride, silicide, carbide, or conductive ceramics (specific resistance 10-6 to 10-2 Ωcm) for the electrode.Since these electrodes have relatively low resistance, the loss of ignition energy is small. Conversely, 300 M l-
The disadvantage is that the noise suppression effect below IZ is as small as 5 to 106 B, and since these materials have poor thermal conductivity, the electrodes are easily worn out by local discharge.

(V) Method of using conductive ferrite for electrodes This method has a good noise prevention effect of 10 to 15 dB. However, since this is a low frequency wave and has a small specific resistance, a large current flows due to the induced discharge in the discharge gap and generates heat. Furthermore, since this material has poor thermal conductivity, it has the disadvantage that the electrodes are locally worn out due to heat generation due to discharge. Conversely, when ferrite having a high specific resistance is used, the noise prevention effect and durability are good, but there is a problem that the loss of ignition energy is large.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art as described above, and provides a low-cost product which has a sufficient noise suppression effect, has little loss of ignition energy, and whose tip does not deteriorate due to wear and tear. The purpose of the present invention is to provide an ignition distributor using electrodes.

[Means and effects for solving the problems] That is, the present invention:
Fixed electrodes each connected to a plurality of spark plugs of an internal combustion engine; and a rotating electrode that rotates in conjunction with the crankshaft of the internal combustion engine and faces each fixed electrode so as to sequentially form a minute gap as the engine rotates. In the ignition distributor, the plurality of fixed electrodes or rotating electrodes are made of zinc oxide (ZnO
) A sintered body of 80 to 95 mol % powder and 5 to 20 mol % ferrite powder for an internal combustion engine, characterized in that a skin layer mainly composed of ferrite is formed on the surface of the sintered body. Regarding ignition distributors.

FIG. 1 is a sectional view showing an example of the configuration of an ignition distributor according to the present invention. The power distributor is housing 1 and housing 1
It consists of a power distributor made of an insulating material and a cap 2 attached to the holder. A fixed electrode 3 is provided circumferentially protruding from the upper bottom of the power distributor cap 2 . Each fixed electrode 3 is connected to each spark plug via a high voltage cable (not shown). Further, a center terminal 4 is attached to the center of the upper bottom of the power distributor cap 2 so as to protrude from the center. The center terminal 4 is connected to a secondary coil of an ignition coil (not shown). A conductive spring 6 is installed at the tip of the center terminal 4.
The conductive spring 6 is provided with a slider 5 in the form of a carbon rod J that is slidably supported on the power distribution cap 2 . On the other hand, a camshaft 7 is provided in an internal space formed by the housing 1 and the power distribution cap 2.

The camshaft 7 rotates in conjunction with the crankshaft of the internal combustion engine. A power distribution element 8 is provided at the upper end of the camshaft 7.

The electron distribution element 8 is composed of an insulating base 9 and a rotating electrode 10 disposed on the upper surface of the insulating base. One end of the rotating electrode 10 is brought into contact with the contact 5 by the pressing force of the conductive spring 6. Further, as the rotating electrode 10 rotates 80 times, the rotating electrode 10 is rotated so as to come to a position facing the plurality of fixed electrodes 3 one after another with a small interval therebetween. Multiple fixed electrodes 3
When the rotating electrode 10 comes to a position facing one of the ignition coils with a small interval as shown in the figure, the high voltage generated by the ignition coil is applied to the center terminal 4, and the air is The dielectric breakdown causes a spark discharge, and at the same time, a discharge is generated that spans the spark interval in the ignition plug, which is provided in series with the minute interval, resulting in the desired ignition operation. At this time, spark discharge occurs within the spark plug and discharge occurs in the minute gap between both electrodes 3 and 10 of the power distributor, causing noise generation.

In the above operation, the high voltage sent from the ignition coil does not reach its maximum value stepwise. That is,
The voltage applied across the discharge gap of the power distributor increases with a time constant determined by circuit constants of the ignition coil, high voltage cable, and the like. When the voltage value rises to a value sufficient to cause a spark discharge in the discharge gap, dielectric breakdown occurs in the air in the discharge gap and a spark discharge occurs. Because sudden dielectric breakdown occurs, the discharge current flows rapidly with a short pulse width (several tens to hundreds of amperes) and is an unstable current with a high peak value, so a large amount of harmful high frequency components are generated. , which is radiated to the outside using a high-voltage cable or the like as an antenna and becomes radio noise.

Since the sound radio waves emitted from the noise source are proportional to the noise current, it is necessary to reduce the noise current in order to suppress the noise radio waves.

By the way, the discharge current flowing between rotating and fixed electrodes is
There are two types: capacitive discharge current and inductive discharge current.

First, capacitive discharge current is the capacitance between the rotating electrode and the fixed electrode,
Charges accumulated in the stray capacitance between the high-voltage cable and the ground and between the electrode ground near the discharge gap are high-frequency currents that flow instantaneously (several n5eCPi! degrees) with a sudden rise when dielectric breakdown occurs between the gaps. This becomes the noise current mentioned above.

On the other hand, the induced discharge current is a low-frequency current (several tens to 100 mA) that continuously flows after the capacitive discharge ends, and the ignition energy supplied to the spark plug is the product of the induced discharge current and the discharge duration T. Almost proportional to IxT.

Therefore, it can be seen that in order to suppress the noise current without reducing the ignition energy, it is sufficient to reduce only the capacitive discharge current.

Therefore, as a method of suppressing the noise current, the method described above ([, (
It has been proposed to use ceramic conductors such as V>, but these have low resistance to reduce ignition energy losses. Therefore, as shown by straight line a in FIG. 2, even at low voltage, an excessive current flows through the electrodes and generates heat. In addition, since heat conduction is poor, the electrodes are worn out due to localized heat generation.

The manufacturing method of the present invention is to form a skin layer containing ferrite as a main component only on the surface by baking a material containing zinc oxide (ZnO) with one or more ferrite added in an oxygen atmosphere. Therefore, consumption of the discharge surface due to discharge can be prevented by the ferrite skin layer, and the interior is composed of a large amount of ZnO, which is a semiconductor, and its specific resistance is low, resulting in ignition energy loss as shown in Figure 4. can be made very small.

When a magnetic material such as Ni-Zn ferrite is added to ZnO, a high frequency magnetic field is generated by the noise current, and the noise current can be suppressed by the wax current product and hysteresis loss due to the high 18 wave magnetic field.

The magnetic material used here has a higher magnetic permeability at the same frequency, a larger eddy current product, and a noise current suppression factor.
The fruit is large. However, if it is too large, it is undesirable because loss due to induced discharge of low frequency current becomes large. Therefore,
There is an appropriate range. For example, a magnetic material with a relative permeability of 100 has a permeability of 50 to 500 MH within the allowable range of ignition energy loss.
It is possible to absorb and suppress noise current in two ranges.

The present invention is constructed from the above points of view.

That is, either the fixed electrode or the rotating electrode used in the ignition distributor of the present invention, or both, may be made of zinc oxide (
80 to 95 mol% of ZnO) powder and 5 to 95 mol% of ferrite powder
It is made of a sintered body containing 20 mol% of ferrite, and its surface layer has a skin layer mainly composed of ferrite. The ferrite skin is sintered in oxygen or air. In other words, the electrodes are fired in oxygen gas, or materials fired in other atmospheres are added during electrode formation.
Second, it may be finally fired in an atmosphere containing oxygen gas. As shown in Figure 3, the electrode manufactured in this way has a surface layer (with a skin layer) mainly composed of ferrite.
1911~ layer) 30, and the inside becomes a composite layer 40 made of a mixture of zinc oxide and ferrite.

Here, if the ferrite powder is 20 mol% or more, 10%
The above ignition energy loss occurs. Moreover, if it is less than 5 mol %, a sufficient ferrite layer will not be formed on the surface, and the tip will be severely worn out by long-term discharge. Therefore, the above ratio of ferrite powder is desirable.

The reason why a ferrite layer is formed on the surface when fired in an oxygen atmosphere is thought to be that in the presence of oxygen, a small amount of ferrite becomes a nucleus, making it easier for ZnO to form a solid solution in the ferrite. Furthermore, the ferrite layer formed on this surface improves the radio noise suppression effect by adding a small amount of ferrite.

Although there are many unknowns about the detailed mechanism, the higher the frequency, the more the current converges on the surface due to the skin effect, and since the surface is made of a ferrite layer, it becomes a high inductance for high frequencies. Therefore, it is considered that only high frequency components can be efficiently suppressed.

The ferrite powder that is one of the components of the sintered body used here is Ni-Zn ferrite (<Ni-Zn)Fe204]
, other ferrites such as NiFetO4 and (Ni-12-Mn)Fe204 can be used. Other ferrites include general formula, MFet04
(where M is MO.

Fe1CO1Ni, Cu, l-i, etc., or a combination of several of these), M Fe+ t O+
9 (where M is 3a, 3r, pb, etc.) iron oxide with magnetobrambite crystal structure, MF1303
(M is a rare earth element) with a perovskite type crystal structure, and M3Fe5012 (where M is a rare earth element) with a garnet type crystal structure can be used. Further, when Ni--Zn ferrite is used, it is desirable to use one having a composition ratio within the shaded area shown in the composition diagram shown in FIG. Also, zinc oxide ferrite,
(ZnFetO4) is effective in increasing magnetic permeability.

[Effects of the Invention] According to the power distributor of the present invention, zinc oxide is used as one component of the electrode. Since the fired body of zinc oxide has a low specific resistance, even if a current flows through this part, the -13-' energy loss is small. Furthermore, since a magnetic material is added thereto, high frequency components can be suppressed by utilizing eddy current loss and hysteresis loss. Further, in the present invention, since a skin layer containing ferrite as a main component is formed on the surface, the inductance of the surface portion is large, and the inductance against high frequencies can be increased, and high frequency current can be suppressed.

[Example] The present invention will be explained below with reference to Examples.

Iron oxide (FetO3) was added to 50 mol%, nickel oxide (
Zinc oxide (ZnO) 35% mol% and zinc oxide (ZnO) 15% mol% were wet mixed and pulverized in a ball mill.
Calcining was performed at ℃ for 2 hours to synthesize Ni-7n ferrite. The magnetic permeability of this ferrite was 1000.

Polyvinyl alcohol (PVA) was added as a binder to 15 mol% of the synthesized ferrite and 85 mol% of zinc oxide.
A raw material to which approximately 1% by weight of was added was dry-press-formed into the shape of a rotating electrode. The heating rate is 100°C per hour, the holding temperature is 1400°C, the holding time is 2 hours, and the cooling rate is 100°C per hour.
Sintering was performed in air at ℃. The specific resistance of the rotating electrode produced by this process was 2 at a DC of 100 V.
X105Ωcm, and the relative permeability of the skewer was approximately 30. This rotating electrode was attached to the ignition distributor, the crankshaft was rotated at a rotational speed of 1500 ppm, the ignition distributor was operated, and the frequency characteristic of the electric field strength was set to 1 μA/m = odB in the frequency band 120 Kl-12, and the measurement was performed. The results are shown in Figure 5. As can be seen from this figure, the present invention has a noise suppression effect of 10 B or more compared to a conventional power distribution device using sprayed rotor electrodes (comparative example). In addition, compared to a power distribution device composed of seven conductive lights, which is relatively effective in terms of noise suppression but has a problem with durability, the power distribution device of the present invention has high durability and is There were no problems after 10,000 km.

If the surface of the electrode according to the present invention is polished with a polisher or the like after firing, the characteristics will no longer be exhibited. This is because a layer consisting mainly of zinc oxide is exposed on the surface and the ferrite layer is removed during processing. However, if this is heat-treated in air (in an oxidizing atmosphere) at 600° C. or higher, a ferrite layer can be generated on the surface again. The thickness of this layer can be controlled by heat treatment conditions.

Figure 6 shows the results of X-ray diffraction of the electrode surface immediately after polishing, and Figure 7 shows the X-ray diffraction results of the electrode surface after heat treatment at 800°C for 10 minutes.
This is the result of line diffraction. From this, it can be seen that when heat treatment is performed, Zn
Since the o peak disappeared and only the ferrite peak was observed, it was found that a ferrite layer was again formed on the surface by firing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a specific configuration of the ignition distributor of the present invention. FIG. 2 is a current-voltage characteristic diagram of conductive Reramix used in the electrodes of a conventional ignition distributor. FIG. 3 is a schematic organizational diagram of an electrode used in the ignition distributor of the present invention. FIG. 4 is a graph showing the energy loss characteristics of electrodes prepared by varying the amount of ferrite mixed with zinc oxide. FIG. 5 is a measurement diagram showing the frequency characteristics of the noise electric field strength of the ignition distributor of the embodiment and the conventional ignition distributor (sprayed rotor). FIGS. 6 and 7 are measurement diagrams respectively showing the results of X-ray diffraction of the surface of the electrode immediately after polishing and the results of X-ray diffraction of the surface of the electrode after subsequent heat treatment. FIG. 8 is a desirable composition diagram of ferrite. 1...Distributor housing 2...Distributor gap 3...Fixed electrode 5...Carbon rod contactor 10...Rotating electrode

Claims (3)

[Claims] (1) Fixed electrodes each connected to a plurality of spark plugs of an internal combustion engine, and rotating in conjunction with the crankshaft of the internal combustion engine, facing each other so as to sequentially form minute gaps with each fixed electrode as they rotate. In the ignition distributor having rotating electrodes, the plurality of fixed electrodes or rotating electrodes are made of zinc oxide (ZnO
) Ignition of an internal combustion engine, characterized in that it is a sintered body of 80 to 95 mol% powder and 5 to 20 mol% ferrite powder, and a skin layer mainly composed of ferrite is formed on the surface thereof. power distributor. (2) The ignition distributor for an internal combustion engine according to claim 1, wherein the skin layer is formed by firing in an atmosphere containing at least oxygen gas. (3) The ignition distributor for an internal combustion engine according to claim 1, wherein the ferrite powder as a constituent material constituting the electrode is Ni-Zn ferrite or Mn-Zn ferrite.