JPS6155616B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a power distribution device for an internal combustion engine, and more particularly to a power distribution device for an internal combustion engine that reduces generated noise radio waves. In general, internal combustion engines with electrical ignition systems generate radio noise waves in a wide known number band, which can interfere with wireless equipment such as televisions and radios, so it is required to reduce radio noise waves as much as possible. One such source of noise is a discharge in the power distribution unit of an internal combustion engine. FIG. 1 is a sectional view showing a power distributor according to the prior art. A cap 14 made of an insulator is attached to a cylindrical housing 12. A plurality of fixed electrodes 16 arranged on the same circumference are embedded in the inner surface of the head of the cap 14, one end of the fixed electrode 16 protrudes from the surface of the cap 14, and the protruding portion also extends continuously from the cap 14. covered with a formed insulator. This fixed electrode 16 is connected to spark plugs attached to a plurality of cylinders of an internal combustion engine. Also, at the center of the inner surface of the cap 14, there is a center terminal 1.
8 are buried. A contact 22 made of a carbon rod is provided on the center terminal 18 via a conductive spring 20 so as to be able to slide on the wall surface of the surrounding cap 14 . This contactor 22 is pressed into contact with a flat rotor electrode 24 made of metal by a spring 20 . The rotor electrode 24 is fixed to the surface of a disc-shaped insulating base 26, and the end of the rotor electrode 24 faces the tip side surface of the fixed electrode 16 with a small gap therebetween. Further, the insulating base 26 is fixedly placed on the end of a camshaft 28 driven by the crankshaft of the internal combustion engine. When the camshaft 28 rotates and the rotor electrode 24 to which a high voltage is applied by the central terminal 18 rotates, when the fixed electrode 16 and the rotor electrode 24 reach a position where they face each other, a discharge occurs between the two electrodes, and the rotor electrode 2
4 and the fixed electrode 16 are energized. At this moment, a high voltage is applied to the spark plug connected to the fixed electrode 16. The problem is the fixed electrode 16 and the rotor electrode 2.
Noise radio waves are generated by the discharge that occurs in the gap between 4 and 4. Conventionally, for the purpose of reducing the above-mentioned noise radio waves, a resistor was inserted into the rotor electrode 24 to provide a filter effect against high frequency noise.
Methods that set the spark to 0.25 inches have been proposed, but all of them have the disadvantage that the ignition energy is small. Therefore, a method has been proposed in which a high-resistance material is attached to the electrode surface, but this method has the disadvantage that it is difficult to obtain a device with uniform performance. In addition to this, there is a rotor electrode with an acute angle at the tip, as described in Japanese Patent Application Laid-Open No. 125943/1983.
Even in this case, there was a problem that sufficient noise reduction could not be obtained. An object of the present invention is to provide a power distribution device for an internal combustion engine that has uniform performance without reducing ignition energy and reduces radio noise. According to the present invention, the above object is achieved by maintaining at least one of the fixed electrode and the rotor electrode at a high temperature. An embodiment of a power distribution device for an internal combustion engine according to the present invention will be described below. FIG. 2 shows the main parts of a power distribution device for an internal combustion engine, which is an embodiment of the present invention. However, similar or identical components to those in FIG. 1 are indicated using the same reference numerals. A rotor electrode 30 is fixed to the surface of the insulating base 26, and an end thereof faces the fixed electrode 16. The difference between this embodiment and the prior art is that the thickness t of the rotor electrode 30 is about 1/2 to 1/5 thinner than that of the prior art. The other configurations are completely the same as the conventional example. Next, the operating principle of this embodiment will be explained. The energy lost by one discharge between the fixed electrode 16 and the rotor electrode 30 is several mm Joule. Also, the number of discharges per unit time is the rotor electrode 30.
It is expressed as the product of the rotation speed and the number of fixed electrodes. For example, when a car is running normally, the number of discharges is about 100 times/second. Therefore, thermal energy of several 100 mm joules is generated per second, and the electrode is heated. However, since conventional electrode materials used were good thermal conductors such as brass and aluminum, the average temperature of the discharge electrode surface was around 100°C. By the way, the heat source 1 generated on the rotor electrode discharge surface
flows as shown by the arrow in FIG. Therefore,
The thermal resistance of the rotor electrode is inversely proportional to the cross section S perpendicular to the direction of heat flow. Moreover, since the cross section S=width l×thickness t exists, the thermal resistance is inversely proportional to the thickness t. Therefore, since the rotor electrode used in this embodiment is thinner than the conventional rotor electrode, the thermal resistance is large, and the electrode temperature becomes high due to the above-mentioned discharge thermal energy. Recently, it has been experimentally confirmed that when at least one of the discharge electrodes reaches a high temperature, the radio noise generated by the discharge is reduced. Next, actual measurement results of the radio noise level generated by the power distributor of this embodiment will be explained. FIG. 4 shows the noise current measuring circuit used in the actual measurements. However, similar or identical components to those in FIG. 1 are indicated using the same reference numerals. The battery 32 is connected to the induction coil 34 and the primary side, and the other terminal of the induction coil 34 is connected to the capacitor 3.
It is grounded via 6. This capacitor 3
A primary contact 38 is connected in parallel to 6. The secondary side of the induction coil 34 is connected to the central terminal 18. This central terminal 18 is connected to a rotor electrode 30 via a contactor 22. Rotor electrode 30
A fixed electrode 16 is arranged around the fixed electrode 16, and each terminal of the fixed electrode 16 is grounded via a resistor 40. Both ends of this resistor 40 are connected to the noise measuring device 42.
connected to the input side of the When the primary contact 38 is turned on and off, the induction coil 3
A high voltage is generated on the secondary side of 4 and applied to the rotor electrode. The rotor electrode 30 rotates, and discharge occurs in the gap between each fixed electrode. This discharge current flows through resistor 40 to ground. At this time, the noise component generated by the discharge is input to the noise measuring device 42. The table shows industrially available rotor electrode materials and thermal conductivity.

[Table] FIG. 5 shows the relationship between electrode thickness and noise current when brass and SUS are used as the rotor electrode 30 of this embodiment. In the figure, A indicates brass and B indicates SUS. Note that the frequency component of the noise current is 100MHz. However, in the figure, the vertical axis shows the noise current (dB), and the horizontal axis shows the electrode thickness (mm). Here, the width l of the rotor electrode is normally set to 10 to 15 mm for ignition advance adjustment, but in this example,
It was set to 15mm. This result shows that the noise current decreases as the thickness of the rotor electrode becomes thinner, and a remarkable effect can be seen especially when the thickness of the SUS electrode with low thermal conductivity is 1.0 mm or less. FIG. 6 shows the relationship between thermal conductivity and noise current when the thickness of the rotor electrode is kept constant at 0.5 mm and the various materials shown in the table are used to form the rotor electrode. However, in the figure, the vertical axis shows the noise current (dB), and the horizontal axis shows the thickness (mm). This result shows that a significant noise current reduction effect is observed when the thermal conductivity is 0.5 or less, and it can be seen that the noise decreases as the thermal conductivity decreases, regardless of the type of metal material. Figure 7 shows that the rotor electrode of this example has a thickness of 0.5 mm.
This figure shows the relationship between the noise frequency and the intensity of the noise current when SUS-27 (B) is used as the rotor electrode material and when 1.5 mm thick brass (A) according to the prior art is used as the electrode material. However, in the figure, the vertical axis shows the noise current (dB), and the horizontal axis shows the noise frequency (MHz).
shows. As is clear from the figure, in a wide frequency range, using SUS-27 rotor electrodes reduces noise by approximately 20 dB compared to conventional brass rotor electrodes. Note that in this embodiment, a negative high voltage is applied to the center terminal 18. No noise reduction effect was observed when a positive high voltage was applied. Noise reduction effect does not occur unless a negative high voltage pulse is applied to the electrode held at high temperature. According to this embodiment, by reducing the thickness of the rotor electrode 30 and reducing the cross-sectional area of the electrode material in the heat flow direction to increase thermal resistance, noise generated by discharge between the stator electrode 16 and the rotor electrode 30 can be reduced. It has the effect of reducing radio waves by spreading them over a wide frequency range. Furthermore, the ignition energy for noise reduction is not reduced, and the noise reduction performance is not uneven. As is clear from the above description, according to the present invention, by maintaining at least one of the fixed electrode and the rotor electrode at a high temperature, uniform performance is achieved without reducing ignition energy, and radio noise is reduced. A reduced power distribution device for an internal combustion engine can be provided.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a power distribution device for an internal combustion engine according to the prior art, FIG. 2 is a cross-sectional view of essential parts showing an embodiment of the internal combustion engine according to the present invention, and FIG. FIG. 4 is a noise measurement circuit diagram of the power distributor according to this embodiment, FIG. 5 is a diagram showing the relationship between the thickness of the rotor electrode and noise current, and FIG.
The figure is a diagram showing the relationship between the thermal conductivity of the electrode material and the noise current, and FIG. 7 is a diagram showing the relationship between the noise frequency and the noise current. 12...Housing, 14...Cap, 16
... Fixed electrode, 18 ... Center terminal, 20 ... Conductive spring, 22 ... Contact, 24, 30 ...
Rotor electrode, 26...Insulating base, 28...Camshaft, 32...Battery, 34...Induction coil,
36...Capacitor, 38...Primary contact, 40...
...Resistance, 42...Noise measuring device.

Claims (1)

[Claims] 1. In the rotor of a power distributor that distributes high voltage pulses generated by an ignition coil to spark plugs attached to multiple cylinders of an internal combustion engine, the electrode has a thickness t (cm) in the direction perpendicular to the rotating surface.
The product of and the thermal conductivity of the electrode material (W/cm・deg) is
A power distribution device for an internal combustion engine, characterized in that it is formed of an electrode plate with a density of 2.5×10 ^-2 or less.