JP6781259B2 - Pressure sensor - Google Patents

Description

The present invention relates to a pressure sensor, and more particularly to a pressure sensor in which a pressure detection element is covered with a waterproof case or the like.

As a pressure sensor that detects the pressure of a fluid, for example, a liquid-sealed pressure sensor is conventionally known.

The liquid-sealed pressure sensor has a fluid supply unit that supplies the pressure-detected fluid to the pressure chamber, a pressure detection unit that detects the pressure of the fluid in the pressure chamber, and a pressure signal detected by the pressure detection unit to the outside. It is composed of a signal transmission unit to be transmitted, a fluid supply unit, a pressure detection unit, and an outer surface member covering the signal transmission unit.

The outer surface member is, for example, a waterproof case that has a substantially cylindrical shape and covers the circumference of the pressure detection unit and the signal transmission unit, a terminal block cap that covers the upper part of the terminal block, an inner peripheral surface of the waterproof case, and an outer peripheral surface of the housing. And a sealant that fills the space between the terminal block and the outer peripheral surface thereof is mainly provided.

Japanese Unexamined Patent Publication No. 2001-116639 Japanese Unexamined Patent Publication No. 2004-37388

In such a pressure sensor in which the pressure detection element is covered with a waterproof case or a sealing agent and the wiring is connected to the pressure detection element, moisture permeates into the product resin depending on the usage environment, and the insulation resistance of the product decreases. Sometimes. Further, if the insulation resistance is further reduced, a circuit short circuit may occur. This is because the water that has passed through the waterproof case and the halogen ions on the printed wiring board cause the transfer of metal ions, and these ions combine with the electrons and metallize again to form a new current path. Is the cause.

The PCT test (pressure cooker test) is known as a test for measuring such waterproof performance, and is used for evaluating the moisture resistance of resin-sealed electronic parts and the like. The pressure cooker test reproduces a high-density water vapor atmosphere at 100 ° C or higher, and by making the water vapor pressure in the test tank extremely higher than the partial pressure of water vapor inside the product, the infiltration of water into the product is prevented. It can be shortened in time and is used for accelerated life test of moisture resistance evaluation of electronic component materials.

As a means for improving the waterproof performance as described above, for example, a method of making the case robust is conceivable, but there are problems such as an increase in cost and an increase in manufacturing man-hours for installing parts inside. Further, Patent Document 1 describes an invention in which a sensor chip or the like is placed in a resin case of a semiconductor pressure sensor and then filled with a soft gel-like coating resin to prevent air or moisture from entering the resin case. However, it cannot cope with a harsh outdoor environment such as the PCT test described above. Further, Patent Document 2 describes an invention of a pressure sensor in which an insulating film having an electrically insulating property is coated on the surface of a sensor housing, but the waterproof performance of the coated insulating film is described. It has not been.

Therefore, an object of the present invention is to provide a pressure sensor in which a pressure detection element is covered with a waterproof case or the like and used, which can satisfy strict waterproof performance requirements such as a PCT test.

In order to solve the above problems, the pressure sensor of the present invention includes a pressure detection element for detecting the pressure of a fluid, a plurality of electric wires connected to the pressure detection element and drawn out to the outside, the pressure detection element, and the pressure sensor. In a pressure sensor including a waterproof case for accommodating the plurality of electric wires inside and a sealing agent filled in the inner peripheral portion of the waterproof case, the waterproof case and the sealing agent covering the outer peripheral surface of the pressure sensor. The coating agent further comprises a coating agent having a lower water vapor permeability than any of the above, and the above coating agent has higher water repellency than any of the above waterproof case and the above encapsulant covering the outer peripheral surface of the pressure sensor . wherein the covering all of the outer peripheral surface of the upper Kifutome agent and the waterproof case.

Further, the coating agent is preferably a fluororesin.

According to the pressure sensor of the present invention, in a pressure sensor in which a pressure detection element is covered with a waterproof case or the like and used, strict waterproof performance requirements such as a PCT test can be satisfied.

It is a vertical sectional view which shows the liquid-sealed pressure sensor as the 1st Embodiment of the pressure sensor which concerns on this invention. It is a vertical sectional view which shows the liquid-sealed pressure sensor as the 2nd Embodiment of the pressure sensor which concerns on this invention. It is a schematic diagram which shows the effect of the coating measure of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the first embodiment of the present invention will be described.

FIG. 1 is a vertical cross-sectional view showing a liquid-sealed pressure sensor 100 as a first embodiment of the pressure sensor according to the present invention.

In FIG. 1, the liquid-sealed pressure sensor 100 includes a fluid introduction unit 110 that supplies a pressure-detected fluid to a pressure chamber 112A, which will be described later, a pressure detection unit 120 that detects the pressure of the fluid in the pressure chamber 112A, and a pressure. It includes a signal transmission unit 130 that transmits a pressure signal detected by the detection unit 120 to the outside, a fluid introduction unit 110, a pressure detection unit 120, and an outer surface member 140 that covers the signal transmission unit 130.

The fluid introduction unit 110 is connected to a metal joint member 111 connected to a pipe through which a fluid whose pressure is detected is guided, and to an end portion of the joint member 111 connected to the pipe and another end portion by welding or the like. A metal base plate 112 having a bowl shape is provided.

The joint member 111 is formed with a female threaded portion 111a screwed into the male threaded portion of the above-mentioned pipe connecting portion and a port 111b for guiding the fluid introduced from the pipe to the pressure chamber 112A. The open end of the port 111b is connected to the opening provided in the center of the base plate 112 by welding or the like. Although the female thread portion 111a is provided in the joint member 111 here, a male thread may be provided, or a copper connecting pipe may be connected instead of the joint member 111. .. The base plate 112 has a bowl shape that spreads toward the side facing the joint member 111, and forms a pressure chamber 112A between the base plate 112 and the diaphragm 122 described later.

The pressure detection unit 120 includes a housing 121 having a through hole, a diaphragm 122 that isolates the pressure chamber 112A described above and a liquid sealing chamber 124A described later, and a diaphragm protective cover 123 arranged on the pressure chamber 112A side of the diaphragm 122. , Hermetic glass 124 fitted inside the through hole of the housing 121, liquid sealing chamber 124A filled with a pressure transmission medium such as silicone oil between the recess on the pressure chamber 112A side of the hermetic glass 124 and the diaphragm 122, and hermetic. A support column 125 arranged in the central through hole of the glass 124, a pressure detecting element 126 fixed to the support column 125 and arranged inside the liquid sealing chamber 124A, and a potential adjusting member 127 arranged around the liquid sealing chamber 124A. , A plurality of lead pins 128 fixed to the hermetic glass 124, and an oil filling pipe 129 fixed to the hermetic glass 124.

The housing 121 is made of a metal material such as a Fe / Ni alloy or stainless steel. Both the diaphragm 122 and the diaphragm protective cover 123 are made of a metal material, and both are welded at the outer peripheral edge of the through hole on the pressure chamber 112A side of the housing 121. The diaphragm protective cover 123 is provided inside the pressure chamber 112A to protect the diaphragm 122, and is provided with a plurality of communication holes 123a through which the fluid introduced from the fluid introduction unit 110 passes. After the pressure detection unit 120 is assembled, the housing 121 is connected by welding or the like at the outer peripheral edge of the base plate 112 of the fluid introduction unit 110.

The pressure detection element 126 is adhered and fixed to the liquid sealing chamber 124A side of the support column 125 by an adhesive layer composed of an adhesive. In the present embodiment, the support column 125 is formed of an Fe / Ni alloy, but the present invention is not limited to this, and the support column 125 may be formed of another metal material such as stainless steel. The pressure detection element 126 is an electronic type such as a semiconductor pressure sensor that detects the pressure of the fluid introduced from the fluid introduction unit 110 into the pressure chamber 112A as the pressure fluctuation of the silicone oil in the liquid sealing chamber 124A via the diaphragm 122. It is a pressure sensor.

As described in Japanese Patent No. 3987386, the potential adjusting member 127 places the pressure detecting element 126 in a no electric field (zero potential), and the chip is affected by the potential generated between the frame ground and the secondary power supply. It is provided to prevent the internal circuit and the like from being adversely affected. The potential adjusting member 127 is arranged between the pressure detecting element 126 and the diaphragm 122 in the liquid sealing chamber 124A, is formed of a conductive material such as metal, and is connected to a terminal connected to the zero potential of the pressure detecting element 126. Be connected.

A plurality of lead pins 128 and an oil filling pipe 129 are fixed to the hermetic glass 124 by a hermetic treatment in a penetrating state. In the present embodiment, a total of eight lead pins 128 are provided as the lead pins 128. That is, three lead pins 128 for external input / output (Vout), power supply (Vcc), and grounding (GND), and five lead pins 128 as terminals for adjusting the pressure detection element 126 are provided. .. In addition, in FIG. 1, four out of eight lead pins 128 are shown. The plurality of lead pins 128 are connected to the pressure detection element 126 by, for example, a metal or aluminum bonding wire 126a, and form an external input / output terminal of the pressure detection element 126.

The oil filling pipe 129 is provided to fill the inside of the liquid sealing chamber 124A with a pressure transmission medium such as silicone oil. After filling the oil, one end of the oil filling pipe 129 is crushed and closed as shown by the dotted line in FIG.

The signal transmission unit 130 is provided on the side of the pressure detection unit 120 facing the pressure chamber 112A, and is fixed to the terminal block 131 in which a plurality of lead pins 128 are arranged and the terminal block 131 with an adhesive 132a, and is fixed to the plurality of lead pins 128. A silicone system between the plurality of connection terminals 132 to be connected, the plurality of electric wires 133 electrically connected to the outer ends of the plurality of connection terminals 132 by soldering, etc., and the upper end of the housing 121 and the terminal block 131. It includes an electrostatic protection layer 134 formed of an adhesive.

The terminal block 131 has a substantially cylindrical shape, and is formed in a shape having a fixing wall for fixing the plurality of lead pins 128 described above in the vicinity of the middle stage of the cylinder, and is made of a resin material such as polybutylene terephthalate (PBT). Is formed by. The terminal block 131 is fixed to the upper part of the housing 121 of the pressure detection unit 120 with an adhesive such as epoxy resin.

The connection terminal 132 is made of a metal material and is fixed by an adhesive 132a perpendicularly to the cylindrical side wall above the above-mentioned fixing wall of the terminal block 131. In this embodiment, three connection terminals 132 for external input / output (Vout), power supply (Vcc), and grounding (GND) are provided. The inner ends of the three connection terminals 132 are electrically connected to the corresponding lead pins 128 by welding or the like, but the connection method is not limited to this, and other methods may be used for connection.

Further, in the present embodiment, three electric wires 133 are provided for connecting to the three connection terminals 132. The electric wire 133 is obtained by pre-soldering the core wire 133a, which has been stripped of the coating formed of polyvinyl chloride (PVC) or the like of the electric wire 133, and bundling the stranded wires, which is the outer end portion of the above-mentioned connection terminal 132. After penetrating through the hole provided in, it is electrically connected to the connection terminal 132 by soldering, welding, or the like, but the connection method is not limited to this, and other methods may be used for connection. Further, the three electric wires 133 are pulled out from the outer surface member 140 that covers the circumference of the pressure sensor 100, and then are covered with a protective tube 135 formed of polyvinyl chloride (PVC) or the like in a bundled state. ..

The electrostatic protection layer 134 is applied to the upper end surface of the housing 121 so as to cover the upper end surface of the hermetic glass 124, and has an annular adhesive layer having a predetermined thickness formed by a silicone-based adhesive and a plurality of lead pins 128. It is applied to the entire upper end surface of the protruding hermetic glass 124 and is composed of a coating layer made of a silicone-based adhesive. The electrostatic protection layer 134 is provided to improve the electrostatic proof stress of the pressure detection unit 120 without being affected by the presence or absence of the ESD protection circuit.

The outer surface member 140 has a substantially cylindrical shape, a waterproof case 141 that covers the periphery of the pressure detection unit 120 and the signal transmission unit 130, a terminal block cap 142 that covers the upper part of the terminal block 131, and an inner peripheral surface of the waterproof case 141. A sealant 143 that fills the space between the outer peripheral surface of the housing 121 and the outer peripheral surface of the terminal block 131 is provided.

The terminal block cap 142 is formed of, for example, a resin material. In the present embodiment, the terminal block cap 142 is formed in a shape that closes the upper portion of the above-mentioned cylindrical terminal block 131, and is covered on the upper portion of the terminal block 131 before being filled with the sealing agent 143 such as urethane resin. Will be done. However, the terminal block cap 142 is not limited to this shape, and may be formed in a shape that integrally closes the upper portion of the terminal block 131 and the upper portion of the waterproof case 141, and may be covered after being filled with the sealant 143. Alternatively, a new lid member is provided separately from the terminal block cap 142, and after the terminal block cap 142 and the sealing agent 143 are arranged, the new lid member is covered on the upper part of the waterproof case 141. Good.

The waterproof case 141 is formed of a resin material, for example, polybutylene terephthalate (PBT) into a substantially cylindrical shape, and a flange portion facing inward is provided at a lower end portion of the cylindrical shape. The outer peripheral portion of the base plate 112 of the fluid introduction portion 110 to which the signal transmission portion 130 and the pressure detection portion 120 inserted through the opening at the upper part of the waterproof case 141 are in contact with the flange portion. By filling the sealant 143 in this state, internal parts such as the pressure detection unit 120 are fixed.

In the pressure sensor 100 of the present invention shown in FIG. 1, the entire outer peripheral surface of the pressure sensor 100 including the waterproof case 141, the terminal block cap 142, and the sealing agent 143 is uniformly coated with the coating agent 144. It is not necessary to coat the joint member 111, the base plate 112, and the like, which are metal parts, with the coating agent 144. As the coating agent, it is preferable to use a coating agent having a lower water vapor permeability than either the waterproof case 141 or the sealing agent 143. Incidentally, for example, water vapor permeability of the waterproof case 141 formed with PBT is ^{1.2g · mm / m 2 · 24h} , water vapor permeability of the sealant 143 of the urethane resin is 7g · ^mm / m 2 · 24h Is. As a specific type of coating agent, a coating agent containing, for example, Fluorosurf (registered trademark) containing a fluororesin can be used, but the coating agent is not limited thereto. The fluororesin coating agent 144 is superior in performance such as resistance to adhesion, water repellency / oil repellency, heat resistance, and abrasion resistance as compared with other coating agents such as polymers.

A PCT test was conducted by uniformly coating the entire outer peripheral surface of the pressure sensor 100 with such a coating agent 144 containing a fluororesin. As a test condition, as a coating agent 144, Fluorosurf (FG-3050 series) (registered trademark) is applied at a film pressure of 120 μm and left in an environment filled with high-temperature water vapor gas at 110 ° C. and 1.4 atm. And other test conditions are conceivable.

FIG. 3 is a schematic view showing the effect of the coating measures of the present invention.
The horizontal axis shown in FIG. 3 indicates the endurance time (h), and the vertical axis indicates the dielectric strength (MΩ). As shown in FIG. 3, it can be seen that when the coating agent is present, the durability time during which the dielectric strength (here, 1000 MΩ) can be secured is longer than when the coating agent is not present.

Further, when a water-repellent coating agent such as the fluorine-based resin coating agent 144 is used as described above, the contact area with water becomes smaller in an environment where water adheres, so that the waterproof performance is further improved. ..

In the present embodiment, the liquid-sealed pressure sensor 100 has been described as an example of the pressure sensor, but the present invention is not limited to this, and the present invention is all that secure the waterproof function with a resin such as a waterproof case. It is applicable to the pressure sensor of.

As described above, according to the first embodiment of the present invention, in a pressure sensor in which a pressure detection element is covered with a waterproof case or the like, it is possible to provide a pressure sensor that can satisfy strict waterproof performance requirements such as a PCT test.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a vertical cross-sectional view showing a liquid-sealed pressure sensor 200 as a second embodiment of the pressure sensor according to the present invention.

In FIG. 2, the liquid-sealed pressure sensor 200 is different in the position where the coating agent 244 is coated as compared with the pressure sensor 100 shown in FIG. 1, and other components are the same. Similar components are designated by the same reference numerals, and description thereof will be omitted.

In FIG. 2, in the liquid-sealed pressure sensor 200, the coating agent 244 is coated only on the upper surface of the sealant 243 and the terminal block cap 242 arranged in the upper opening of the waterproof case 241. As the coating agent 244, a coating agent containing a fluororesin is used as in the first embodiment. As a result, performance equivalent to or close to that of the pressure sensor 100 of the first embodiment can be expected.

As described above, according to the second embodiment of the present invention, the effect is equivalent to that of the pressure sensor of the first embodiment, and the cost can be suppressed as compared with the pressure sensor of the first embodiment. effective.

As described above, according to the pressure sensor of the present invention, a pressure sensor in which the pressure detection element is covered with a waterproof case or the like can satisfy strict waterproof performance requirements such as a PCT test.

100, 200 Pressure sensor 110, 210 Fluid introduction part 111, 211 Joint member 111a, 211a Female thread part 111b, 211b Port 112, 212 Base plate 112A, 212A Pressure chamber 120, 220 Pressure detection part 121, 221 Housing 122, 222 Diaphragm 123, 223 Diaphragm protective cover 123a, 223a Communication hole 124, 224 Hermetic glass 124A, 224A Liquid sealing chamber 125, 225 Strut 126, 226 Pressure detection element 126a, 226a Bonding wire 127, 227 Potential adjusting member 128, 228 Lead pin 129, 229 Oil filling Pipes 130, 230 Signal transmission part 131, 231 Terminal block 132, 232 Connection terminal 132a, 232a Adhesive 133, 233 Electric wire 133a, 233a Core wire 134, 234 Electrostatic protection layer 140, 240 Outer surface member 141, 241 Waterproof case 142, 242 Terminal block cap 143, 243 Sealant 144, 244 Coating agent

Claims (2)

A pressure detection element that detects the pressure of a fluid and
A plurality of electric wires connected to the pressure detection element and pulled out to the outside,
A waterproof case for accommodating the pressure detecting element and the plurality of electric wires inside,
In a pressure sensor provided with a sealant filled in the inner peripheral portion of the waterproof case.
Further provided with a coating agent having a lower water vapor permeability than either the waterproof case or the sealant covering the outer peripheral surface of the pressure sensor.
The coating agent has higher water repellency than both the waterproof case and the sealant that cover the outer peripheral surface of the pressure sensor.
The coating agent, a pressure sensor, characterized in that covers all of the outer peripheral surface of the front Kifutome agent and the waterproof case. The pressure sensor according to claim 1, wherein the coating agent is a fluororesin.

Images