JPS633147Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a noise absorbing element that makes it possible to significantly reduce high frequency electrical noise generated from a micro motor or the like.

Traditionally, SiC varistors and the like have been used as spark-quenching elements in micromotors. However, in recent years, as micromotors have been increasingly used in audio equipment, noise in high frequency bands such as shortwave broadcast bands and FM broadcast bands has become a problem.
Spark-quenching elements such as SiC varistors have a drawback that they cannot absorb sufficient noise in high frequency bands because their capacitance is small, ranging from several tens of pF to several hundred pF.

On the other hand, it is known to use a capacitor to prevent motor noise. For example, the techniques described in JP-A-52-115310 and JP-A-52-126707 are known, but these techniques use a magnetic capacitor as a noise prevention capacitor. Although it is more effective in preventing noise in high frequency bands than SiC varistors,
The capacitance was not specifically regulated, and it was not possible to prevent noise to a level that would not generate noise in the high frequency band.

Therefore, in view of the above points, the present invention uses a thick film capacitor with a capacitance of approximately 3000 to 8000 pF at 1MHz to ensure sufficient noise absorption in high frequency regions such as shortwave broadcast bands and FM broadcast bands. ,
Furthermore, by forming a thick film capacitor on an electrically insulating substrate such as alumina, an inexpensive and high-performance noise absorbing element is provided.

Hereinafter, the present invention will be explained in detail based on the illustrated embodiments.

In Fig. 1, 1 is an electrically insulating substrate made of alumina or the like, 2 is a lower electrode made of silver or the like formed on the substrate 1, and 3 is a thick film capacitor formed on the dielectric porcelain sintered body. Consists of powder and glass as a binder. 4 is an upper electrode made of silver or the like.

The thick film capacitor 3 is made by adding and kneading binder glass and an organic binder to powder of dielectric porcelain sintered body to create a dielectric paste, which is applied onto the lower electrode 2 by screen printing, etc., and then baked. A capacitor film is formed using the same method. As the dielectric porcelain sintered body, it is best to choose a porcelain sintered body mainly composed of barium titanate, which has a high dielectric constant, and a grain boundary layer type dielectric porcelain sintered body mainly composed of strontium titanate. First, the dielectric porcelain sintered body is ground into powder having an average particle size of 1 to 3 μm. These powders are sufficiently melted at a temperature of 800 to 1000°C to bond the dielectric porcelain powders well, and at the same time, a glass frit that adheres well to the substrate or electrode is used with an organic binder using a mala or similar tool. Mix well to create a dielectric paste. Their dielectric constants are approximately 2000 to 3000.

As the material for the electrodes 2 and 4, a silver paste is prepared by adding an organic binder to powder having a weight ratio of 95 silver powder to 5 bismuth oxide.

Next, when manufacturing this noise absorbing element,
Silver paste was first applied onto the substrate 1 by screen printing method, dried, and then heated at a maximum temperature of 920℃ for 10 minutes.
The lower electrode 2 is formed by baking it in air through a tunnel where it is held for a minute.

Next, a dielectric paste is applied on the lower electrode 2 in the same manner, dried and baked to form the thick film capacitor 3. Subsequently, the same silver paste is applied onto the dielectric thick film capacitor 3 using the same method and baked to form the upper electrode 4.

The noise absorbing element of the present invention having the above-mentioned configuration was attached between the commutators of a DC motor as shown in the schematic diagram of the motor section in FIG. 2, and the noise electric field intensity during operation was measured. In the figure, 5, 6, 7 are commutators, 8, 9
is a brush, 10, 11, 12 are rotor coils, 1
3, 14, 15 are noise absorbing elements of the present invention, 1
7 and 18 are lead wires. Three types of motors were used for measurements: 6V, 9V, and 12V.

FIG. 3 is a diagram showing an example of measurement results. On the other hand, hearing tests have shown that no noise occurs when the noise electric field strength is -70dB or less.
From the results, the capacitance as a noise absorbing element needs to have a value of 3000 pF to 8000 pF at 1 MHz, and the noise absorption effect decreases if it is higher or lower than this range.

Further, by using dielectric paste and changing the shape of the printed pattern, various shapes can be obtained. In the case of this embodiment, three thick film capacitors are formed on a ring-shaped alumina substrate.
As described above, the manufacturing method is easier than that of conventional methods, and since it is formed on an electrically insulating substrate such as an alumina substrate, the capacitor has higher mechanical strength than a ceramic capacitor.

As described above, according to the present invention, a thick film capacitor is formed on an electrically insulating substrate, and capacitors of various shapes can be obtained using printing technology, making it easy to attach a ceramic capacitor to a motor. Compared to conventional processing, it can be obtained at a lower cost and its mechanical strength can be improved.

Moreover, since the thick film capacitor used has a capacitance of approximately 3000pF to 8000pF at 1MHz, it absorbs noise sufficiently in high frequency regions such as shortwave broadcast bands and FM broadcast bands to a level where no noise is generated. I can do that. Such noise absorbing elements can be used in a wide variety of fields, such as in micromotors in audio equipment and as noise prevention in microcomputer-applied equipment in the future, and their industrial value is extremely high. It's big.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the configuration of the noise absorbing element of the present invention, Figure 2 is a circuit diagram showing an application example of the noise absorbing element of the present invention, and Figure 3 shows the relationship between its capacitance and noise electric field strength. FIG. 1... Electrically insulating substrate, 2... Lower electrode,
3... Thick film capacitor, 4... Upper electrode.

Claims (1)

[Claims for Utility Model Registration] (1) A noise absorbing element characterized in that it is constructed by forming a thick film capacitor with a capacitance of approximately 3000 pF to 8000 pF at 1 MHz on an electrically insulating substrate. (2) Claim No. 1 for Utility Model Registration characterized in that the thick film capacitor is mainly composed of dielectric porcelain powder mainly composed of barium titanate.
Noise absorbing element described in section. (3) The noise absorbing element according to claim 1, wherein the thick film capacitor is mainly composed of grain boundary layer type dielectric ceramic powder mainly composed of strontium titanate.