JPH027499A - Radio wave noise prevention device - Google Patents

Abstract

PURPOSE:To carry out high frequency wave cut of a plurality of signal paths with a sheet of radio wave noise prevention device by providing a disc dielectric, a first electrode connected to a ground of an electric part and a second electrode which is formed at various sides of the dielectric and connected to a signal terminal. CONSTITUTION:A radio wave noise prevention device 500 is mounted closely on a surface of a shield case 420 whereon a ground terminal 401 and signal terminals 402, 403 protrude, and formed by a disc dielectric 510, a first electrode 520 interposed between the shield case 420 and the dielectric 510 and two sheets of second electrodes 530 which correspond to the two signal terminals 402, 403. The dielectric 510 is provided with a grounding through hole 511 to allow the ground terminal 401 to pass through, two signal through holes 512, 513 to allow the signal terminals 402, 403 to pass through, and a through hole 514 to allow a sensing section 410 to pass through. According to this constitution, two capacitors 550, 560 are constituted in one sheet of radio wave noise prevention device 500, and electric parts are protected against electromagnetic wave interference by the shield case 420.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a radio noise prevention device for protecting electrical components such as sensors, elements, and electronic circuits housed in a shield case from electromagnetic interference.

[Prior Art] Electrical parts are often wrapped in metal cases to prevent them from malfunctioning due to radio interference caused by various radio waves emitted from broadcast stations, amateur radio, military radar, automobile ignitions, computers, etc. I am using it as a shield.

However, many electrical components are connected to other electrical components through lead wires or the like, and exchange signals with other electrical components.

In this way, when other electrical components are connected via lead wires, high-frequency noise caused by external radio waves received by the lead wires and other electrical components is transmitted to the electrical components inside the shield case via the lead wires, causing the electrical components to become damaged. There was a possibility of malfunction.

Therefore, in order to remove the high frequency noise that is transmitted to the electrical components via the lead wire, a feedthrough capacitor is installed in the shield case to eliminate unnecessary high frequency noise contained in the signal at the connection point between the internal and external electrical components. It was being cut.

[Problems to be Solved by the Invention] However, the conventional method of cutting unnecessary high frequency bands included in the signal by attaching a feed-through capacitor to the shielding case does not allow the exchange of signals between electrical components housed in the shielding case. If there are multiple signal terminals (including power supply) that perform this function, feedthrough capacitors corresponding to the number of terminals are required.

Therefore, the number of feedthrough capacitors increases, the number of assembly steps increases, and the manufacturing cost increases.

In addition, in cases where electrical components are pre-enclosed in a metal case, a shield case with a feedthrough capacitor attached to the surrounding area results in a double structure, which increases the external size and weight, as well as increases the The case had the problem of being wasted.

The present invention has been made in view of the above circumstances, and its purpose is to provide a radio noise prevention device that can protect electrical components from radio noise using a single plate capacitor, even if the electrical components are provided with a plurality of signal terminals. It is provided by.

[Means for Solving the Problems] In order to achieve the above object, the present invention is mounted on an electrical component that is housed in a conductive shield case and supported with a signal terminal protruding from the shield case. The radio noise prevention device includes: a plate-shaped dielectric body having a through hole through which the signal terminal is inserted; and a plate-shaped dielectric body formed on the dielectric body, disposed so as to be in contact with the shield case, and the electric component a first electrode that is electrically connected to the ground of the dielectric; and a second electrode that is formed on a surface of the dielectric material that is different from the surface on which the first electrode is formed and that is electrically connected to the signal terminal. The technical means is to have the following.

[Function] The present invention having the above configuration has the first electrode electrically connected to the shield case and the ground of the electrical component, and the second electrode electrically connected to the signal terminal inserted through the through hole. A capacitor is configured.

Thereby, the second electrode is formed according to the number of signal terminals,
By electrically connecting each signal terminal,
One piece of radio noise prevention device has a number of terminals depending on the number of signal terminals.
In other words, capacitors corresponding to the number of signal paths are substantially configured.

For this reason, when a signal terminal is connected to another electrical component via a connection means such as a lead wire, high-frequency noise riding on the connection means such as a lead wire can be transmitted to a single radio noise prevention device for each signal path. cut by the capacitor.

[Effects of the Invention] According to the present invention, even if an electrical component is equipped with a plurality of signal terminals, high frequency cutting of a plurality of signal paths can be performed with a single radio noise prevention device. The number of parts can be reduced compared to a structure in which a plurality of capacitors are provided depending on the number of capacitors. Therefore, assemblability becomes easy and manufacturing costs can be kept low.

In addition, if an electrical component is covered with a conductive case such as a metal case, the case of the electrical component can be used as a shielding case, so there is no need to provide an additional shielding case around the case as in the conventional case. , so if the electrical components are covered by a conductive case,
Compared to the conventional technology, the external shape can be made smaller and the weight can be reduced.

[Example] Next, a radio noise prevention device of the present invention will be described based on an example shown in the drawings.

FIG. 3 shows a cross-sectional view of the pressure sensor unit 100. This pressure sensor unit 100 is used to control an internal combustion engine of an automobile, and is a housing that is attached to an intake pipe, an exhaust pipe (not shown), etc. of the internal combustion engine. 200, consists of a connector 300 attached to this housing 200, a pressure sensor 40G supported by this connector 300, a radio noise prevention device 500 attached to this pressure sensor 400, and connected to a computer (not shown), lead wires, connecting connectors, etc. connected via.

The housing 200 is made of metal such as aluminum, iron, stainless steel, etc., and has a small diameter part 210 with a small diameter and a large diameter part with a large diameter. It has a cylindrical shape that can be roughly divided into 20 parts.

A male thread 211 is formed around this small diameter portion 210 to be screwed into an intake pipe or an exhaust pipe. In addition, the small diameter portion 2
The inner circumference of 10 is a pressure sensor 4 that measures the pressure inside the intake pipe and exhaust pipe.
It is a pressure introduction part 212 that leads to a 0G sensing part 410. A hexagonal portion 221 is formed around the large diameter portion 220 and is used when screwing the male screw 211 into an intake pipe or an exhaust pipe. Further, the inner periphery of the large diameter portion 220 is a chamber 222 that accommodates the pressure sensor 400.

The connector 30G is made of resin and is a connecting portion 3 that is connected to a connector connected to the computer via a lead wire.
1G and the pressure sensor 4GG are placed in the chamber 22 of the housing 20G.
2 and a sensor holding section 320 that is held within the sensor holding section 320.

A first recess 311 is formed in the connecting portion 310, and a second recess 321 is formed in the holding portion 320. One end of one earth bin 331 and two signal bins 332 and 333 are protruded inside the first recess 311, and a part of the pressure sensor 400 is housed inside the second recess 321. Ru.

Note that one earth bin 331 and two earth bins in the first recess 311
One end of the signal bin 332, 333 of the book is electrically connected to the computer via the connector and the lead wire when the connector is connected to the connector 310. Also,
One earth bin 331 and two signal bins 332.33
The other end of 3 is connected to the chamber 22 from the holding part 320 of the connector 300.
2, one ground terminal 4 of the pressure sensor 400
01 and two signal terminals 402 and 403. Note that the earth bin 331 and the signal bin 332 are connected to the pressure sensor 4.
It supplies power to the GG, and the earth bin 331 and signal bin 333 take out the signal from the pressure sensor 400.

The pressure sensor 400 houses electrical components (not shown) such as semiconductors in a metal shield case 420 having a cylindrical shape, and has one ground terminal 401 and two ground terminals connected to the internal electrical components. Signal terminals 402 and 403 are provided to protrude from one surface of the shield case 420. This ground terminal 401 is connected to the earth bin 331, the signal terminal 402 is connected to the signal bin 332, and the signal terminal 403 is connected to the signal bin 333. When power is supplied to the ground terminal 401 and the signal terminal 402, the pressure sensor 400 outputs a signal between the ground terminal 401 and the signal terminal 403 according to the pressure guided to the sensing section 41G.

In addition, as shown in FIG. 4, the pressure sensor 40G has an external terminal 430 on the surface from which the ground terminal 401 and the signal terminals 402 and 403 protrude to adjust the resistance value of internal electrical components.
A plurality of shield case 420 are exposed to the outside.

The radio noise prevention device gsoo is attached closely to the surface of the shield case 420 from which the ground terminal 401 and signal terminals 402 and 403 protrude. a dielectric 510 having a shape, a first electrode 52G sandwiched between the shield case 420 and the dielectric 51G,
It consists of two second electrodes 53G corresponding to two signal terminals 402 and 403.

The dielectric material 510 is made of 5rTtQs system, BaTi0. - system,
A grounding through hole 5 into which the grounding terminal 401 is inserted is a ceramic flat plate made of materials such as CaTiO3, 2nO, and SiC and having varistor properties and a dielectric constant.
11, two signal through holes 512 and 513 through which the signal terminals 402 and 403 are inserted, and a sensing portion through hole 514 through which the sensing portion 41G is inserted.

Further, on the surface of the dielectric 51G on which the shield case 420 is arranged, there are a plurality of depressions 515 that close the plurality of external terminals 430.
is provided.

The first electrode 52G is connected to the shield case 42 of the dielectric 51G.
A radio noise prevention device made of metal such as copper, nickel, aluminum, silver, or platinum formed on almost the entire surface (excluding the inside of the signal through holes 512 and 513) where 0 is arranged (lower side in Figure 2). When the pressure sensor 500 is attached to the pressure sensor 400, it is sandwiched between the shield case 42G and the dielectric 510. In addition,
In this sandwiched state, the first electrode 52G contacts the shield case 42G.

Further, since the first electrode 520 is formed on the dielectric 510, it is naturally in contact with the first electrode 520.

The first of the two second electrodes 530 is made of the same metal as the pole 520, and is connected to the signal terminal 402. A wide area is formed around the two signal through holes b12.513 into which the signals 403 are inserted. Note that since the second electrode 530 is formed on the dielectric 510, it is naturally in contact with the dielectric 510.

In addition, a grounding electrode 5 is also provided around the grounding through hole 511.
40 is formed, and this grounding electrode 540 is electrically connected to the first electrode 520 on the back surface.

As a result, one radio noise prevention bag zboo has two capacitors 55 as shown in the electrical equivalent circuit of FIG.
0.560 is configured.

The electrical components within the pressure sensor 400 of the pressure sensor unit 100 having the above configuration are protected from electromagnetic interference by the shield case 420.

Furthermore, the external terminal 430 exposed to the outside from the shield case 420 is covered by the recess 515 of the dielectric 510. The inner surface of this depression 515 is covered with a first electrode 520 that contacts the shield case 420.

Therefore, the external terminal 430 is not subjected to electromagnetic interference by the first electrode 520, and the electrical components inside the pressure sensor 400 are
Electromagnetic interference from the external terminal 430 is prevented.

Furthermore, when connecting the pressure sensor 40G and the computer, if the connection connector connected to the computer via the lead wire is connected to the connection part 310 of the connector 300, the lead wire etc. between the pressure sensor 400 and the computer is connected. , high frequency noise (radio waves generated by the igniter,
Radio waves, radar, etc.) are carried. This high frequency noise is
It is cut by two capacitors 550.56G configured in the radio noise prevention device 500. Therefore, the electrical components inside the shield case 420 have a ground terminal 401
, electromagnetic interference from the signal terminals 402 and 403 is prevented.

As a result, the electrical components inside the shield case 420 are completely shielded and work normally without malfunctioning even when used in environments subject to electromagnetic interference such as in the engine room.As a result, the pressure inside the intake pipe and exhaust pipe can be sent to the computer correctly.

Furthermore, since the dielectric 510 of this embodiment has varistor characteristics, a high voltage higher than a predetermined voltage (varistor voltage) is applied between the signal terminal 402 and the ground terminal 401 due to fluctuations in the rotational speed of the internal combustion engine. When this occurs, a current suddenly begins to flow through the second electrode 530, dielectric 510, and first electrode 520. Therefore, the electrical components inside the shield case 420 can be protected from radio noise without using a special protection circuit. protected by device 500;

As shown in the above embodiment, the high frequency cut of the two signal paths can be performed with one radio noise prevention device 50G, so compared to the conventional method in which multiple capacitors are provided depending on the number of connection terminals, You can reduce your score. Therefore, assembling is easier than in the past, and costs can be kept low.

Further, the electrical components of the pressure sensor 400 are covered in advance with a metal case, and this case can be used as the shield case 42G, so there is no need to provide an additional shield case around the case of the pressure sensor 400 as in the conventional case. For this reason, the pressure sensor 40 of this embodiment
When the electrical components are covered in advance with a conductive case, as in G, the external size can be made smaller and the weight can be reduced compared to the conventional case.

6 and 7 show other embodiments of the present invention. The radio noise prevention bag zboo of this embodiment does not have a depression 515 in the dielectric 510 but a depression 51 in the first electrode 520.
5, and the first electrode 52G is provided with a thick metal plate so that a recess 515 is formed. The first electrode 520 is bonded to the dielectric 510 using conductive paste.

Thereby, the thickness of the dielectric 510 can be easily made thinner than in the above embodiments, so that the capacitance can be increased. In other words, according to this embodiment, capacitance and varistor voltage can be easily managed.

(Modified Example) Although the example shown above has been shown in which the ground of the electrical component is used as a ground terminal and protrudes from the shield case along with the signal terminal, it is also possible to connect the ground of the electrical component to the shield case and electrically connect the shield case and the first electrode. You can let me.

Although an electrical component with two signal terminals is shown as an example, it goes without saying that the number of signal terminals may be one or three or more. In some cases, two or more radio noise prevention devices may be used in one shield case.

Although an example has been shown in which the radio noise prevention device of the present invention is used in a pressure sensor to protect the electrical components of the pressure sensor from electromagnetic interference, the present invention is not limited to this.
It can be applied to all electrical components that are affected by electromagnetic interference, such as single semiconductors such as I, and electrical circuits that combine semiconductors.

Although an example is shown in which a ceramic having varistor properties is used as the dielectric, other dielectrics such as ceramics without varistor properties, resin, glass, mica, etc. may also be used.

[Brief explanation of the drawing]

Figure 1 is a plan view of the radio noise prevention device, Figure 2 is a sectional view taken along the line A-A shown in Figure 1, Figure 3 is a sectional view of the pressure sensor unit, and Figure 4 is the external terminal of the pressure sensor. 5 is an equivalent circuit diagram of the radio noise prevention device, FIG. 6 is a plan view showing another embodiment of the radio noise prevention device, and FIG. 7 is the B shown in FIG. 6. - It is a sectional view along the B line. In the diagram 401...Earth terminal 402.403...
Signal terminal 420... Shield case 500...
Radio noise prevention device 510... Dielectric 511... Grounding through hole 512.513... Signal through hole 52
0...First electrode 53G...Second electrode Fig. 4 Foil Fig. 5

Claims (1)

[Scope of Claims] 1) A radio noise prevention device mounted on an electrical component housed in a conductive shield case and supported with a signal terminal protruding from the shield case, comprising: (a) the above-mentioned (b) a plate-shaped dielectric body having a through hole through which a signal terminal is inserted; (c) a second electrode formed on a surface of the dielectric body different from the surface on which the first electrode is formed and electrically connected to the signal terminal. Radio noise prevention device.