JP7345173B2 - pressure sensor - Google Patents

Description

The present invention relates to pressure sensors.

Liquid-filled pressure sensors, which house a semiconductor pressure detection device in a pressure-receiving chamber divided by a diaphragm and filled with oil, are installed in refrigeration equipment and air conditioners to detect refrigerant pressure, and are also used in industrial equipment. It is equipped and used to detect various fluid pressures.

The semiconductor pressure detection device is disposed within the pressure receiving chamber, and has a function of converting pressure changes within the pressure receiving space into an electrical signal using a pressure detection element and outputting the electrical signal to the outside.

The diaphragm disposed within the pressure receiving space is a flexible metal plate. Therefore, if a potential difference occurs between the pressure detection element and the diaphragm of the semiconductor pressure detection device and the sealed oil is charged with static electricity, a problem may occur in the pressure detection element or its output signal. A potential difference between the pressure sensing element and the diaphragm may be caused by, for example, noise transmitted from a piping system to which the pressure sensor is attached.

On the other hand, Patent Document 1 discloses a pressure sensor in which a base on which a semiconductor-type pressure detection device is attached is formed of a ceramic material. According to the pressure sensor of Patent Document 1, an insulating effect is exhibited by attaching a semiconductor pressure detection device to a ceramic base, so that the influence of high frequency noise transmitted from the piping system can be effectively suppressed.

Japanese Patent Application Publication No. 2017-146136

According to the pressure sensor disclosed in Patent Document 1, effective noise countermeasures can be achieved by forming the base from a ceramic material, but ceramic materials generally have a high degree of processing difficulty, which leads to high costs. There's a problem.

The present invention has been made in view of such problems, and an object of the present invention is to provide a pressure sensor that can suppress the influence of noise while keeping costs low.

In order to achieve the above object, the pressure sensor of the present invention includes:
a diaphragm that receives fluid pressure;
a base forming a pressure receiving space in which an insulating medium is enclosed between the base and the diaphragm;
a pressure detection device disposed in the pressure receiving space to detect the pressure transmitted to the insulating medium and convert it into an electrical pressure signal;
a relay board including a wiring layer electrically connected to an external electric circuit;
A pressure sensor comprising a plurality of terminal pins for electrical connection between the pressure detection device and the wiring layer of the relay board,
An insulating layer having a higher dielectric constant than the insulating medium is formed on the surface of the diaphragm in the pressure receiving space only at a position facing the pressure detecting device .

According to the present invention, it is possible to provide a pressure sensor that can suppress the influence of noise while keeping costs low.

FIG. 1 is a longitudinal sectional view showing a pressure sensor according to a first embodiment. FIG. 2 is a longitudinal sectional view of the pressure detection unit according to the first embodiment. FIG. 3 is a top view of the pressure detection unit. FIG. 4 is a bottom view of a cross section taken along line AA in FIG. 2 of the pressure detection unit. FIG. 5 is a top view of a cross section taken along line BB in FIG. 2 of the pressure detection unit. FIG. 6 is a longitudinal sectional view showing a pressure sensor according to the second embodiment.

(First embodiment)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a pressure sensor 1 according to a first embodiment. FIG. 2 is a longitudinal sectional view of the pressure detection unit 2 according to the first embodiment. FIG. 3 is a top view of the pressure detection unit 2. FIG. 4 is a bottom view of a cross section taken along line AA in FIG. 2 of the pressure detection unit 2. FIG. 5 is a top view of a cross section of the pressure detection unit 2 taken along line BB in FIG.

As shown in FIG. 1, the pressure sensor 1 includes a large cylinder part 10a having a circular cross section, for example, and a small cylinder part 10b having a circular, oval, or elliptical cross section arranged coaxially. , has a resin cover 10 having a shape in which respective ends are joined via a step portion 10c. A pressure detection unit 2 is attached to the inside of the large cylindrical portion 10a 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 threadedly connected, a dish-shaped base 40 that is disposed opposite to the mounting member 30, and a mounting plate. It includes a metal diaphragm 50 whose outer periphery is held 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 steel alloy, and their outer peripheries are integrated by a weld W formed by circumferential welding. By making the base 40 metal, costs can be reduced.

Further, a cylindrical portion 20a is formed to protrude from the upper end of the connection nut 20. On the other hand, a circular hole 30a is formed in the center of the mounting member 30. After the cylindrical portion 20a and the mounting member 30 are fitted, 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 connecting nut 20 communicate with each other via the through passage 20b.

In FIGS. 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 this liquid medium is filled into the pressure receiving space through the opening 40a (FIG. 4) of the base 40, a metal ball 41 is fixed to the base 40 by means such as welding in order to seal the space.

In FIG. 5, the diaphragm 50 has a flat portion 50a at the center and an annular uneven portion 50b that is concentrically raised around the flat portion 50a or that is repeatedly raised and lowered. A circular insulating layer 51 is fixed to the surface of the flat portion 50a on the pressure receiving space 52 side. The insulating layer 51 is preferably a polyimide film, for example, and is bonded to the flat portion 50a. Insulating layer 51 has a higher dielectric constant than the insulating medium.

A semiconductor pressure detection device 60 is disposed in the center of the base 40 on the pressure receiving space 52 side, facing the insulating layer 51 . The pressure detection device 60 includes a glass pedestal 62 and a pressure detection element (semiconductor chip) 64 attached to the surface thereof. The pedestal 62 is bonded to the base 40 using an adhesive.

When the insulating layer 51 is projected onto the pressure detecting device 60 along the thickness direction of the pressure detecting device 60 (the normal direction of the surface facing the diaphragm 50), the projected insulating layer 51 is the same as that of the pressure detecting device 60. It is preferable to cover part or all of it. In particular, it is preferable to align the center of the projected insulating layer 51 with the center of the pressure detection device 60.

In FIG. 4, the pressure detection element 64 includes eight bonding pads (electrodes) near its outer 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 adjustment 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 at the sensor output pad 64c is set between 0V or more and 5V or less (preferably 0.5V) depending on the detected pressure. 4.5V or less). Furthermore, 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 penetrate 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 a ground terminal pin 70. The seven terminal pins 72 other than those for ground are connected to terminals on the wiring layer of the relay board 90 shown in FIG. The upper end of one ground terminal pin 70 is connected to the ground of the wiring layer of the relay board 90 shown in FIG. are joined by means of

The static elimination 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) through which the ground terminal pin 70 is inserted. When attached to the base 40, the entire circumference of the pressure detection device 60 is surrounded by a rectangular opening 100a with a gap.

The static eliminating plate 100 has a structure in which a conductive layer 102 is formed on the surface of an inorganic material such as ceramics or glass, or an insulating plate with high heat resistance such as polyamide, polyimide, polyethylene terephthalate (PET), or PPS. The insulating plate is fixed onto the base 40 with an adhesive. At this time, the conductive layer 102 is insulated from the base 40 and is not electrically connected. The conductive layer 102 may be made of a thin metal plate, or may be formed into a thin film by printing or baking. Furthermore, typical materials for the conductive layer 102 include gold, silver, copper, aluminum, nickel, etc., but high melting point materials such as tungsten and molybdenum can also be used in order to obtain high voltage durability.

As is clear from FIG. 2, the distance between the pressure detection device 60 and the insulating layer 51 is narrower than the distance between the static elimination plate 100 and the diaphragm 50. That is, the pressure detection device 60 protrudes toward the diaphragm 50 side rather than the static elimination plate 100.

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, air conditioner, etc. in which the pressure sensor 1 is installed. be done. From this 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, 72, and a signal for pressure detection can be output.

In FIG. 4, the sensor input power supply pad 64a, the sensor output pad 64c, the signal adjustment pad 64d, and the terminal pin 72, other than the ground pad 64b, in the semiconductor type pressure detection device 60 are connected by bonding wires 80. ) to be done. Further, in this embodiment, the ground pad 64b is connected (connected) to the conductive layer 102 of the static elimination plate 100 via the bonding wire 82.

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

The pressure detection device 60 operates by being supplied with power from an external electric circuit via a terminal pin 72 for input power. When fluid is introduced into the connection nut 20 and enters the fluid introduction chamber 32 inside the mounting member 30, the diaphragm 50 is elastically deformed by the pressure, pressurizing the insulating medium within the pressure receiving space 52. The pressure detection element 64 detects this pressure fluctuation, converts it into an electrical signal, and outputs the electrical signal, that is, the signal for pressure detection, to the outside via the terminal pin 72. Based on the input of the pressure detection signal, the external electric circuit can accurately detect the pressure of the fluid introduced into the connection nut 20.

According to this embodiment, since the insulating layer 51 having a higher dielectric constant than the insulating medium is provided on the surface of the diaphragm 50 facing the pressure detection device 60, pressure detection is more effective than in the case where the insulating layer 51 is not provided. The composite dielectric constant between device 60 and diaphragm 50 is increased. Therefore, for example, when high frequency noise is transmitted from external piping to the pressure detection unit 2 via the connection nut 20, an effect similar to that of a capacitor is exerted, and the charge due to the high frequency noise is accumulated on the insulating layer 51 side. Influence on the pressure detection element 64 is suppressed.

In particular, since the distance between the pressure detection device 60 and the insulating layer 51 is narrower than the distance between the static elimination plate 100 and the diaphragm 50, a high noise suppression effect can be achieved.

In this embodiment, the shape of the insulating layer 51 is circular to match the shape of the flat portion of the diaphragm 50, but it may be rectangular to match the shape of the pressure detection device 60. In this case, it is desirable that the size is the same as or larger than the shape of the pressure detection device 60.

Furthermore, by providing the static elimination plate 100, the electric charges that are charged around the pressure detection device 60 or the electric charges that are charged on the liquid medium filled in the pressure receiving space 52 are eliminated via the static elimination plate 100, and thereby the pressure can be detected. Malfunctions due to charging of the device 60 are prevented. However, only the insulating layer 51 may be provided without providing the static eliminating plate 100.

(Second embodiment)
FIG. 6 is a longitudinal sectional view showing a pressure sensor 1A according to the second embodiment. In this embodiment, the shape of the static elimination plate 100A of the pressure detection unit 2A is different from the embodiment described above. More specifically, the thickness of the static elimination plate 100A is thicker than in the above embodiment, and the conductive layer 102A of the static elimination plate 100A protrudes downward from the lower surface of the pressure detection device 60. That is, the distance between the pressure detection device 60 and the insulating layer 51 is wider than the distance between the static elimination plate 100A and the diaphragm 50. Since the other configurations are the same as those of the embodiment described above, the same reference numerals are given and redundant explanation will be omitted.

According to this embodiment, in addition to the noise suppression effect of the pressure detection device 60 due to the provision of the insulating layer 51, since the conductive layer 102A of the static elimination plate 100A is made to protrude downward from the lower surface of the pressure detection device 60, noise can be suppressed. During the transmission, the conductive layer 102A of the static elimination plate 100A is easily charged from the insulating medium, and the charged charge can be further transmitted to the ground via the terminal pin 70.

Note 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 embodiments or omit any component in each embodiment.

1, 1A Pressure sensor 2, 2A 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 Terminal pin for ground 72 Terminal pin 74 Hermetic seal 80 Bonding wire 82 Bonding wire for ground 90 Relay board 92 Connector 94 Lead wire 100,100A Static elimination plate

Claims (6)

a diaphragm that receives fluid pressure;
a base forming a pressure receiving space in which an insulating medium is enclosed between the base and the diaphragm;
a pressure detection device that is disposed on the base in the pressure receiving space and detects the pressure transmitted to the insulating medium and converts it into an electrical pressure signal;
A pressure sensor comprising: a plurality of terminal pins disposed through the base and electrically connected to the pressure detection device within the pressure receiving space,
A pressure sensor characterized in that an insulating layer having a higher dielectric constant than the insulating medium is formed on a surface of the diaphragm in the pressure receiving space only at a position facing the pressure detecting device . The diaphragm has a central flat portion and a concentric annular uneven portion formed around the flat portion, and the insulating layer is formed on the flat portion. 1. The pressure sensor according to 1. The pressure sensor according to claim 1 or 2, wherein the insulating layer is circular or rectangular. It has a static elimination plate disposed close to the pressure detection device in the pressure receiving space, the static elimination plate surrounds the pressure detection device, and the terminal pin connected to ground, and the static elimination plate The pressure sensor according to any one of claims 1 to 3, wherein an electrical connection is made between the conductive layer and the conductive layer. The pressure sensor according to claim 4, wherein a distance between the pressure detection device and the insulating layer is narrower than a distance between the static elimination plate and the diaphragm. 5. The pressure sensor according to claim 4, wherein a distance between the pressure detection device and the insulating layer is wider than a distance between the static elimination plate and the diaphragm.

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