JP7325099B2 - pressure sensor - Google Patents

Description

The present invention relates to pressure sensors.

A liquid-sealed pressure sensor that houses a semiconductor-type pressure sensing device in a pressure-receiving chamber partitioned by a diaphragm and filled with oil is installed in freezer/refrigerators and air conditioners to detect refrigerant pressure, and is also used in industrial equipment. installed and used to detect various fluid pressures.

The semiconductor type pressure detection device is arranged in the pressure receiving chamber and has a function of converting the pressure change in the pressure receiving space into an electric signal by means of the pressure detecting element and outputting the electric signal to the outside.

A diaphragm placed in the pressure receiving space is a flexible metal plate. Therefore, if a potential difference occurs between the pressure sensing element and the diaphragm of the semiconductor type pressure sensing device and the enclosed oil is charged with static electricity, the pressure sensing element or its output signal may malfunction. A potential difference between the pressure sensing element and the diaphragm can be caused, for example, by high frequency noise transmitted from the piping system to which the pressure sensor is attached.

Therefore, by further arranging a conductive member (electrifying plate) in the pressure receiving space in which the pressure detecting element is accommodated and connecting this conductive member to the ground terminal pin using a bonding wire, the above problem can be eliminated. A pressure sensor intended to solve this problem is disclosed in Patent Document 1 below.

JP 2014-178125 A

According to the pressure sensor disclosed in Patent Document 1, providing a conductive member can provide effective noise countermeasures. There is a demand to have a pressure sensor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pressure sensor capable of suppressing the influence of noise even in an external environment where static electricity is likely to occur.

In order to achieve the above object, the pressure sensor of the present invention
a diaphragm that receives fluid pressure;
a base forming a pressure-receiving space filled with an insulating medium between itself and the diaphragm;
a pressure detection device disposed in the pressure receiving space for detecting the pressure transmitted to the insulating medium and converting it into an electrical pressure signal;
a relay board having a wiring layer electrically connected to an external electric circuit;
a plurality of terminal pins disposed through the base and electrically connected to the pressure sensing device within the pressure receiving space;
and a static elimination plate disposed in the pressure receiving space in the vicinity of the pressure detection device,
the base is formed from a conductive material,
The static elimination plate has a first insulating member provided on the base and a conductive layer formed on the surface of the first insulating member, the conductive layer being electrically conductive with respect to the base. electrically connected to a terminal pin among the plurality of terminal pins that is grounded;
The pressure detecting device includes a second insulating member provided on the base and a pressure detecting element, the second insulating member being arranged between the pressure detecting element and the base. ,
When the dielectric constant of the first insulating member is ε1, the dielectric constant of the second insulating member is ε2, and the dielectric constant of the insulating medium is ε3, the following equations (1) and ( 2) is established.
ε1>ε2 (1)
ε1>ε3 (2)

According to the present invention, it is possible to provide a pressure sensor capable of suppressing the influence of noise even in an external environment where static electricity is likely to occur.

FIG. 1 is a longitudinal sectional view of the pressure sensor according to this embodiment. FIG. 2 is a bottom view of a cross section taken along line AA of FIG. FIG. 3 is an enlarged cross-sectional view of a portion indicated by an arrow B in FIG.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a pressure sensor 1 according to this embodiment. FIG. 2 is a bottom view of a cross section taken along line AA of FIG. FIG. 3 is an enlarged cross-sectional view of a portion indicated by an arrow B in FIG.

As shown in FIG. 1, the pressure sensor 1 includes a large cylindrical portion 10a having a circular cross section, for example, and a small cylindrical portion 10b having an annular, oval, or elliptical cross section, which are coaxially arranged. , and a resin-made cover 10 having a shape in which the respective ends are formed via a stepped portion 10c. A pressure detection unit 2 is attached inside the large cylindrical portion 10 a of the cover 10 .

The pressure detection unit 2 includes a dish-shaped mounting member 30 that supports a connection nut 20 to which a fluid inflow pipe (piping) (not shown) is screwed and connected, a dish-shaped base 40 that faces the mounting member 30, and a mounting It has a metal diaphragm 50 whose outer circumference is sandwiched between the member 30 and the base 40 . The mounting member 30, the base 40, and the diaphragm 50 are made of a conductive material such as a stainless alloy, and their outer peripheral portions are integrated by a welded portion W formed by circumferential welding.

A cylindrical portion 20a is formed at the upper end of the connection nut 20 so as to protrude therefrom. On the other hand, a circular hole 30a is formed in the center of the mounting member 30. As shown in FIG. After the cylindrical portion 20a and the mounting member 30 are fitted together, they are joined by means such as brazing.

A through passage 20b is formed inside the cylindrical portion 20a, and the inside of the mounting member 30 and the inside of the connection nut 20 communicate with each other via the through passage 20b.

1 and 2, a pressure receiving space 52 defined by the base 40 and the diaphragm 50 is filled with an insulating liquid medium such as oil. After the liquid medium is filled into the pressure receiving space through the opening 40a (FIG. 2) of the base 40, a metal ball (not shown) is fixed to the base 40 by means such as welding in order to seal the space. be.

A semiconductor type pressure detection device 60 is arranged in the central portion of the base 40 on the side of the pressure receiving space 52 . The pressure detection device 60 comprises a glass base (second insulating member) 62 and a pressure detection element (semiconductor chip) 64 attached to the surface thereof. As shown in FIG. 3, the pedestal 62 is secured to the base 40 using a second insulating adhesive BD2.

In FIG. 2, the pressure sensing element 64 has eight bonding pads (electrodes) near its periphery. Three of the bonding pads are a sensor input power supply pad 64a, a ground pad 64b and a sensor output pad 64c, and the remaining five are signal conditioning pads 64d. However, the number of bonding pads is not limited to eight. In this embodiment, the sensor input power supply pad 64a is maintained at 5V, the ground pad 64b is maintained at 0V, and the voltage of the sensor output pad 64c is between 0V and 5V (preferably 0.5V) depending on the detected pressure. 4.5 V or less). Also, the arrangement of the bonding pads is not limited to the above.

A plurality of (eight in this example) terminal pins 70 and 72 are arranged around the semiconductor type pressure detection device 60 so as to pass through the base 40 . The terminal pins 70 and 72 are insulated and sealed by a hermetic seal 74 with respect to the through holes of the base 40 through which they are inserted.

One of the plurality of terminal pins is terminal pin 70 for ground. The seven terminal pins 72 other than those for grounding are connected to the terminals of the wiring layer of the relay board 90 shown in FIG. It is connected to the ground of the layer, and its lower end is joined to the conductive layer 102 (FIG. 3) of the neutralization plate 100 by means of soldering or the like.

The neutralization plate 100 has a substantially polygonal flat plate shape as shown in FIG. 2, and has a rectangular opening 100a and a through hole 100b (FIG. 1) for inserting the terminal pin 70 for ground. When attached to the base 40, the entire periphery of the pressure detection device 60 is surrounded by a rectangular opening 100a with a gap.

In FIG. 3, the neutralizing plate 100 includes an insulating plate (first insulating member) 101 made of an inorganic material such as ceramics, glass, or the like, which is highly heat-resistant, and a surface of the insulating plate 101 (a surface away from the base 40). ), and the insulating plate 101 is fixed on the base 40 via the first insulating adhesive BD1. At this time, the conductive layer 102 is insulated and not electrically connected to the base 40 . The conductive layer 102 may be composed of a thin metal plate, or may be formed into a thin film by printing or baking. The material of the conductive layer 102 is typically gold, silver, copper, aluminum, nickel, or the like, but a high-melting-point material such as tungsten or molybdenum can also be used in order to obtain high-voltage durability.

As is clear from FIG. 3, the plate thickness of the neutralizing plate 100 is thinner than the plate thickness of the pedestal 62 of the pressure detection device 60. Also, as is clear from FIG. small. Furthermore, as is clear from FIG. 2, the area of the conductive layer 102 of the neutralization plate 100 is larger than the area of the pressure detection element 64 of the pressure detection device 60. As shown in FIG.

Here, when the dielectric constant of the insulating plate 101 of the static elimination plate 100 is ε1, the dielectric constant of the pedestal 62 of the pressure detection device 60 is ε2, and the dielectric constant of the insulating medium is ε3, the following equation (1) and Equation (2) holds.
ε1>ε2 (1)
ε1>ε3 (2)
However, in this embodiment, the first insulating adhesive BD1 and the second insulating adhesive BD2 have the same composition (same composition) and the same dielectric constant εc. Therefore, the following equation (4) holds between the combined dielectric constant (ε1+εc) between the base 40 and the conductive layer 102 and the combined dielectric constant (ε2+εc) between the base 40 and the pressure sensing element 64. do.
(ε1+εc)>(ε2+εc) (4)
In addition, between the composite dielectric constant (ε1+εc) between the base 40 and the conductive layer 102 and the dielectric constant ε3 of the insulating medium between the diaphragm 50 and the pressure sensing element 64, the following equation (5) holds.
(ε1+εc)>ε3 (5)

In FIG. 1, a lead wire 94 connected to a relay board 90 via a connector 92 is connected to an electric circuit (not shown) provided in a control panel of a freezer/refrigerator, an air conditioner, or the like in which the pressure sensor 1 is installed. be done. From such an electric circuit, a power supply voltage can be applied to the pressure detection element 64 via the lead wire 94 and the terminal pins 70 and 72, and a signal for pressure detection can be output.

In FIG. 2, the semiconductor type pressure detection device 60 includes a sensor input power supply pad 64a, a sensor output pad 64c, a signal adjustment pad 64d, and a terminal pin 72 other than the ground pad 64b. 80 is connected (wired). Further, in this embodiment, the ground pad 64b is connected (wired) to the conductive layer 102 of the neutralization plate 100 via the bonding wire 82 in the pressure receiving space 52 .

When assembling the pressure sensor 1, in FIG. 1, the pressure detection unit 2 is arranged so as to abut against the stepped portion 10d formed inside the large cylindrical portion 10a of the cover 10. As shown in FIG. After that, the resin P is filled inside the cover 10 from the lower end side of the large cylindrical portion 10a and the upper end side of the small cylindrical portion 10b (the side from which the lead wire 94 is led out), and is solidified. The electrical structure of the pressure detection unit 2 is thereby fixed in the cover 10 in a hermetically sealed manner.

The pressure detection device 60 operates by receiving power from an external electric circuit via a terminal pin 72 for input power. When the fluid is introduced into the connection nut 20 and enters the fluid introduction chamber 32 inside the mounting member 30 , the pressure causes the diaphragm 50 to elastically deform and pressurize the insulating medium in the pressure receiving space 52 . The pressure detection element 64 detects this pressure variation, converts it into an electric signal, and outputs the electric signal, that is, a signal for pressure detection to the outside through the terminal pin 72 . An external electric circuit to which such a signal for pressure detection is input can accurately detect the pressure of the fluid introduced into the connection nut 20 based thereon.

According to this embodiment, since the above formula (4) is established between the pressure detection device 60 and the neutralization plate 100, for example, high-frequency noise is transmitted from the external piping to the pressure detection unit 2 via the connection nut 20. In this case, such high-frequency noise is more likely to be transmitted to the neutralization plate 100 side than to be transmitted from the pedestal 62 to the pressure detection element 64 .

Also, since the above equation (5) is established between the neutralizing plate 100 and the insulating medium, the high-frequency noise is transmitted from the diaphragm 50 to the pressure detecting element 64 via the insulating medium, and is transmitted to the neutralizing plate 100 side. easily transmitted to In this manner, the noise input to the conductive layer of the neutralization plate 100 is transmitted to the ground of the relay board 90 via the terminal pin 70 for ground.

The ground of the wiring layer of the relay board 90 is connected via a lead wire 94 (FIG. 1) to the zero potential of an electric circuit provided in the control panel of a freezer/refrigerator, air conditioner, or the like in which the pressure sensor 1 is installed. be done. As described above, the transmission of noise to the pressure detection element 64 is suppressed, and the normal operation of the pressure detection device 60 can be ensured.

Further, by providing the static elimination plate 100, the potential charged around the pressure detecting device 60 or the potential charged to the liquid medium filled in the pressure receiving space 52 is eliminated via the static elimination plate 100, thereby pressure detection. Malfunction due to charging of the device 60 is prevented.

(Modification)
In this modification, the first insulating adhesive BD1 and the second insulating adhesive BD2 are different from each other in FIG. The dielectric constant ε5 of the insulating adhesive BD2 satisfies the following equation (3)'. Other configurations are the same as those of the above-described embodiment, and redundant description will be omitted.
ε4>ε5 (3)'
However, if the first insulating adhesive BD1 and the second insulating adhesive BD2 are the same, the thickness should be changed to adjust the dielectric constant (the thickness of BD1 should be reduced to increase ε4). may Also, the first insulating adhesive BD1 and the second insulating adhesive BD2 may be the same and have the same thickness. In this case, ε4=ε5. Formula (3) holds.
ε4≧ε5 (3)

From the above equations (1) to (3), between the combined dielectric constant (ε1+ε4) between the base 40 and the conductive layer 102 and the combined dielectric constant (ε2+ε5) between the base 40 and the pressure sensing element 64, The following formula (6) holds.
(ε1+ε4)>(ε2+ε5) (6)
Further, the following equation (7) is obtained between the combined dielectric constant (ε1+ε4) between the base 40 and the conductive layer 102 and the dielectric constant ε3 of the insulating medium between the diaphragm 50 and the pressure sensing element 64. To establish.
(ε1+ε4)>ε3 (7)

According to this modification, since the above formula (6) is established between the pressure detection device 60 and the neutralization plate 100, for example, high frequency noise is transmitted from the external pipe to the pressure detection unit 2 via the connection nut 20. In this case, such high-frequency noise is more likely to be transmitted to the neutralization plate 100 side than to be transmitted from the pedestal 62 to the pressure detection element 64 .

Moreover, since the above equation (7) is established between the neutralizing plate 100 and the insulating medium, the high-frequency noise is transmitted from the diaphragm 50 to the pressure detecting element 64 via the insulating medium, and is transmitted to the neutralizing plate 100 side. easily transmitted to In this manner, the noise input to the conductive layer of the neutralization plate 100 is transmitted to the ground of the relay board 90 via the terminal pin 70 for ground. Therefore, transmission of noise to the pressure detection element 64 is further suppressed, and normal operation of the pressure detection device 60 can be ensured.

It should be noted that the present invention is not limited to the above-described embodiments. Further, within the scope of the present invention, it is possible to modify any component of the embodiment or omit any component from each embodiment.

Reference Signs List 1 pressure sensor 2 pressure detection unit 10 cover 20 connection nut 30 mounting member 32 fluid introduction chamber 40 base 50 diaphragm 52 pressure receiving space 60 pressure detection device 62 glass base 64 pressure detection element 70 ground terminal pin 72 terminal pin 74 hermetic Seal 80 Bonding Wire 82 Ground Bonding Wire 90 Relay Board 92 Connector 94 Lead Wire 100 Eliminating Plate

Claims (4)

a diaphragm that receives fluid pressure;
a base forming a pressure-receiving space filled with an insulating medium between itself and the diaphragm;
a pressure detection device disposed in the pressure receiving space for detecting the pressure transmitted to the insulating medium and converting it into an electrical pressure signal;
disposed through the base;
a plurality of terminal pins electrically connected to the pressure detection device within the pressure receiving space;
and a static elimination plate disposed in the pressure receiving space in the vicinity of the pressure detection device,
the base is formed from a conductive material,
The static elimination plate has a first insulating member provided on the base and a conductive layer formed on the surface of the first insulating member, the conductive layer being electrically conductive with respect to the base. electrically connected to a terminal pin among the plurality of terminal pins that is grounded;
The pressure detecting device includes a second insulating member provided on the base and a pressure detecting element, the second insulating member being arranged between the pressure detecting element and the base. ,
When the dielectric constant of the first insulating member is ε1, the dielectric constant of the second insulating member is ε2, and the dielectric constant of the insulating medium is ε3, the following equations (1) and ( 2) is established, The pressure sensor characterized by the above-mentioned.
ε1>ε2 (1)
ε1>ε3 (2) The base and the first insulating member are adhered via a first insulating adhesive,
The base and the second insulating member are adhered via a second insulating adhesive,
2. The pressure sensor according to claim 1, wherein said first insulating adhesive and said second insulating adhesive have the same composition. The base and the first insulating member are adhered via a first insulating adhesive,
The base and the second insulating member are adhered via a second insulating adhesive,
2. The method according to claim 1, wherein the dielectric constant .epsilon.4 of the first insulating adhesive and the dielectric constant .epsilon.5 of the second insulating adhesive satisfy the following formula (3). pressure sensor.
ε4≧ε5 (3) 4. The pressure sensor according to any one of claims 1 to 3, wherein the neutralization plate surrounds the pressure detection device.

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