JP3962498B2 - Pressure sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure sensor, and more particularly to a pressure sensor that converts a fluid pressure into an electrical signal and outputs the signal to the outside.
[0002]
[Background]
For the measurement of the fluid pressure, a pressure sensor that detects a pressure difference between the detected pressure and the atmospheric pressure and converts it into an electrical signal is used.
An example of the pressure sensor is shown in FIG. In this figure, the pressure sensor is electrically connected to the metal joint 10 fixed to the installation part, the pressure detection element 20 attached to the welded part 10A of the joint 10 by beam welding, and the like. Output means 30. The fluid pressure is guided into the pressure introducing hole 11 of the joint 10 and converted into a strain of the diaphragm 21 forming the pressure detecting element 20, and this strain is detected by a strain gauge (not shown) on the diaphragm 21. An electrical signal corresponding to the resistance value is output from the output means 30.
[0003]
At this time, in consideration of the case where the pressure sensor is installed in a place where there is a lot of radio noise, the pressure sensor is provided with countermeasures against radio noise.
Conventionally, a technique that has been used as a countermeasure against radio wave noise is to weld a metal case 31 to the joint 10 so as to surround the circuit board 33 that constitutes the output means 30, and above this circuit board 33, there is a feedthrough capacitor. A metal lid member 71 having 72 is arranged to close the opening of the case 31, and an input / output line terminal 36 provided on the circuit board 33 is passed through the feedthrough capacitor 72.
According to such a measure, the radio wave noise on the input / output line is guided from the feedthrough capacitor 72 to the lid member 71 and the case 31, so that the circuit board 33 covered with the case 31 and the lid member 71 has radio wave noise. The electronic circuit component 50 on the signal amplification circuit formed on the circuit board can be prevented from malfunctioning.
[0004]
[Problems to be solved by the invention]
However, in the conventional noise countermeasure, since the terminal 36 needs to penetrate the feedthrough capacitor 72, the terminal 36 to be used must be a long one that reliably protrudes from the feedthrough capacitor 72, which hinders downsizing of the pressure sensor. It was a factor.
[0005]
Further, when the feedthrough capacitor 72 is used, it is necessary to perform soldering to the lid member 71 of the feedthrough capacitor 72 itself and the feedthrough capacitor 72 and the terminal 36, so that assembly work is troublesome. There's a problem.
[0006]
An object of the present invention is to provide a pressure sensor that can reliably obtain a radio wave shielding effect, can promote downsizing, and can easily perform an assembling operation.
[0007]
[Means for Solving the Problems]
The pressure sensor of the present invention includes a metal joint having a pressure introduction hole, a pressure detection element attached to one end side of the pressure introduction hole, and a metal joint attached to the joint so as to surround the pressure detection element. A case having an opening for taking out an output signal, the opening being covered with a circuit board, the circuit board having a conductor layer covering substantially the entire surface of the opening, and a part of the case itself. And the conductor layer is a radio wave shielding layer electrically connected to the contact portion of the case.
[0008]
According to the present invention, since the circuit board forms part of the radio wave shielding structure together with the case, the radio wave shielding effect can be obtained without attaching a conventional lid member with a feedthrough capacitor to the case. Therefore, such a lid member is not required, and the length of the terminal provided on the circuit board can be shortened regardless of the feedthrough capacitor, so that the pressure sensor can be downsized. Further, since no feedthrough capacitor is required, troublesome work such as soldering can be omitted, and assembly work can be simplified.
[0009]
In the pressure sensor of the present invention, the circuit board may be a multilayer board, and the radio wave shielding layer may be formed at least in any middle layer other than the outer surface of the circuit board.
Usually, various electronic circuit components are often mounted on the outer surface of the circuit board. For this reason, by forming a radio wave shielding layer in the middle layer where such electronic circuit components are not mounted, The pattern area can be increased, and radio wave shielding can be performed more reliably.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Members having the same functions as those described in the conventional example are denoted by the same reference numerals, and description thereof is omitted or simplified.
[0011]
[First Embodiment]
1 and 2, the circuit board 33, together with the case 31, has a radio wave shielding structure that surrounds the electronic circuit component 50 such as the pressure detection element 20 (FIG. 7) or IC housed inside and shields the radio wave from the outside. Forming. That is, the case 31 has a cylindrical shape made of metal, and the circuit board 33 closes the output signal extraction opening 32 on the upper side of the case 31 in the figure. The circuit board 33 is placed on a support portion 37 provided by cutting and raising from the case 31 and is sandwiched between the support portion 37 by bending a contact portion 38 provided in the same manner. ing. The planar positional relationship between the support portion 37 and the contact portion 38 is as shown in FIG. 1, but in FIG. 2, in order to make it easier to understand the positional relationship in the vertical direction, the planar portion of the contact portion 38 is particularly preferred. The positions are shown shifted. Further, the opening on the bottom side of the case 31 is covered with the metal joint 10 (FIG. 7) as in the conventional case.
[0012]
Such a circuit board 33 includes a radio wave shielding layer that is electrically connected to the case 31, whereby the radio wave shielding of the opening 32 of the case 31 is performed. Specifically, the circuit board 33 is a laminated board having a plurality of conductor layers, and includes an upper layer formed on the surface on the opening 32 side, an intermediate layer sandwiched between the substrate materials, and a lower layer on the surface on the pressure detection element 20 side. It has 3 layers. A plurality of terminals 36 are connected to the upper surface, and the electronic circuit component 50 is mounted on the lower surface. Although not shown here, a conductor layer for forming a necessary circuit is formed on the surface on the lower layer side, and a strain gauge formed on the diaphragm 21 (FIG. 7) of the pressure detection element 20 is formed on a part of the conductor layer. Are electrically conducted.
[0013]
The upper layer is a planar conductor layer 331 in which most regions are continuous. The contact portion 38 is in contact with the conductor layer 331, and the conductor layer 331 is grounded to the case 31. The upper layer without the conductor layer 331 is a constant width portion of the edge portion of the circuit board 33 and the inside of the terminal region 330 in the central portion.
[0014]
An island-like conductor layer 334 for connecting the lower end of the terminal 36 is left inside the terminal region 330, and each conductor layer 334 passes through the through-hole 335 to form an island-like conductor layer 336 in the lower layer. Conducted. Each terminal of the electronic circuit component 50 is connected to the conductor layer 336 so that signals from each terminal of the electronic circuit component 50 are extracted from the terminal 36. A noise filter capacitor 337 is connected between one of the upper conductor layers 334 (the negative side of the circuit) and the conductor layer 331 (earth). The installation form of the noise filter may be selected as appropriate. For example, it is best to connect the capacitor 337 to three of the positive line of the power supply, the signal output line, and the common line of the circuit. It is desirable to connect to one.
[0015]
The substantially entire surface of the middle layer is a series of conductor layers 333. The conductor layer 333 and the upper conductor layer 331 are connected by a through hole 332. The middle layer does not have the conductor layer 333 only in the constant width portion of the edge portion of the circuit board 33 and the very small portion around the through hole 335 for signal extraction.
[0016]
In such a structure, the upper conductor layer 331 of the circuit board 33 and the middle conductor layer 333 connected thereto through the through hole 332 are electrically connected to the case 31 to form a radio wave shielding layer. This radio wave shielding layer covers most of the surface of the circuit board 33. In particular, in this structure, the upper conductor layer 331 and the middle conductor layer 333 doubly shield radio waves, and the middle conductor layer 333 covers most areas except a very small area. . For this reason, the circuit board 33 can sufficiently shield the radio wave of the opening 32 on the upper surface side of the case 31.
[0017]
According to this embodiment, there are the following effects.
1) Since a radio wave shielding layer composed of an upper conductor layer 331 and a middle conductor layer 333 is formed on the circuit board 33 that closes the metal case 31, a space surrounded by the case 31 and the circuit board 33. It is possible to satisfactorily protect the pressure detection element 20 and the electronic circuit component 50 for the signal amplifier circuit from radio noise.
[0018]
2) At this time, since it is not necessary to use a conventional lid member or feedthrough capacitor, the length of the terminal 36 can be shortened, and the pressure sensor can be reduced in size.
[0019]
3) By not using a feedthrough capacitor, the soldering can be omitted, and the pressure sensor can be easily assembled.
[0020]
4) Since the radio wave shielding layer has a double structure of the upper conductor layer 331 and the middle conductor layer 333, the radio wave shielding layer can cover most of the region of the opening 32 of the case 31, and Therefore, it is possible to satisfactorily induce radio noise and improve the radio wave shielding effect.
[0021]
[Second Embodiment]
FIG. 3 shows a second embodiment of the present invention.
In the radio wave shielding structure of the first embodiment described above, the upper conductor layer 331 and the middle conductor layer 333 overlap almost entirely, but in this embodiment, they have a shape that complements each other. In other words, the upper conductor layer 331 and the middle conductor layer 333 are substantially semicircular, and each complements each other.
[0022]
In this way, the effects 1) to 4) described above can be obtained in the same manner, and there is an effect that the terminal area 330 can be made larger and another circuit configuration can be provided in the middle layer.
[0023]
[Third Embodiment]
4 and 5 show a third embodiment of the present invention.
In the present embodiment, the circuit board 33 for shielding radio waves is obtained by omitting the middle layer from the structure shown in FIGS. 1 and 2 of the first embodiment. Other elements are the same as those in the first embodiment, and are denoted by the same reference numerals.
[0024]
Even with such a structure, the same effects as in the above 1) to 3) can be obtained. However, since there is no middle layer, a double radio wave shielding layer cannot be used, so the effect is inferior, and since the portion of the terminal area 330 that is relatively wide open is not covered by the middle layer, the radio wave shielding effect is also inferior in this respect. Inevitable.
[0025]
[Fourth Embodiment]
FIG. 6 shows a fourth embodiment of the present invention.
In this embodiment, for the purpose of reducing the terminal area 330 as much as possible, the connection of the terminal 36 from the circuit board 33 is performed via the intermediate terminal 36A. Also, an auxiliary board 33A different from the circuit board 33 is installed, and a noise filter capacitor 337 is mounted here. The auxiliary board 33A is held in the case 31 by a support part 37A and a contact part 38A similar to the circuit board 33, and a conductor layer 331A contacting the contact part 38A and a conductor layer 334A separated from the conductor layer 334A are formed on the surface. The capacitor 337 is stretched over the conductor layers 331A and 334A. One end of the terminal 36 (minus side of the circuit) is connected to the conductor layer 334A.
[0026]
In such a structure, the terminal area 330 can be made small even with a normal circuit board 33, so that a good radio wave shielding effect can be obtained without providing an intermediate layer. However, the structure is complicated because the auxiliary board 33A is required. However, since the intermediate terminal 36A is provided, the size can be sufficiently reduced as compared with the conventional case, but it is necessary to consider a point that is not as much as in the first to third embodiments.
[0027]
In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.
For example, the thickness or the like of the radio wave shielding layer according to the present invention may be arbitrarily determined. When a pressure sensor is installed in a place where a larger radio wave noise is generated, the radio wave shielding layer is made thicker to provide a shielding effect. You should make sure you get it. At this time, as a method of heating the upper radio wave shielding layer in particular, it may be performed by plating with a solder leveler or the like.
[0028]
The circuit board is not limited to a double-sided board or a three-layer board, and may be a multilayer board having four or more layers. At this time, a large mounting area of the electronic circuit component on the outer surface of the circuit board may be secured by forming the electromagnetic shielding layer on one of the middle layers.
[0030]
【The invention's effect】
As described above, according to the present invention, since the circuit board forms a part of the radio wave shielding structure together with the case, the radio wave shielding effect can be obtained without attaching a conventional cover member with a feedthrough capacitor to the case. be able to. Therefore, such a lid member is unnecessary, and the length of the terminal provided on the circuit board can be shortened regardless of the feedthrough capacitor, so that the pressure sensor can be reduced in size. Further, since the feedthrough capacitor is unnecessary, troublesome work such as soldering can be omitted, and the assembling work can be simplified.
[Brief description of the drawings]
FIG. 1 is a plan view showing a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a first embodiment.
FIG. 3 is an exploded perspective view showing a second embodiment of the present invention.
FIG. 4 is a plan view showing a third embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a third embodiment.
FIG. 6 is a cross-sectional view showing a fourth embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Joint 20 Pressure detection element 31 Case 32 Opening 33 Circuit board 331,333 Conductor layer

Claims (2)

A metal joint having a pressure introduction hole, a pressure detection element attached to one end side of the pressure introduction hole, and a metal case attached to the joint so as to surround the pressure detection element,
The case has an opening for taking out an output signal,
This opening is covered with a circuit board,
Together with the circuit board to have a conductive layer covering substantially the whole surface of the opening, it is nipped by the supporting portion and the contact portion formed integrally by a part of the case itself,
The pressure sensor, wherein the conductor layer is a radio wave shielding layer that is electrically connected to a contact portion of the case. 2. The pressure sensor according to claim 1, wherein the circuit board is a multilayer board, and the radio wave shielding layer is formed on at least one middle layer other than the outer surface of the circuit board.

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