Pressure Sensor

Abstract

To provide an inexpensive pressure sensor that reduces stress applied to a housed circuit board, and realizes simple structure for precisely ensuring liquid-tightness and can be used reliably.SOLUTION: In a pressure sensor 100 connected to a circuit board 50 in which a sensor chip 11 for detecting pressure of a measurement object is housed in a case 20, the sensor chip is installed in a pressure chamber PR so as to receive pressure of the measurement object, and the circuit board is formed liquid-tightly while a sealing material 26 is filled into the case and constitutes one portion of a space formation member for forming an installation space SR for installing a mounted component 50J of the circuit board.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure sensor that is liquid-tightly molded with resin. [Background technology]

[0002] Various sensors for detecting pressure, temperature, etc. are fixed near the object to be measured and used to send detection signals to measuring equipment, etc., and are often used either built into the measuring equipment or attached externally.

[0003] These types of sensors are incorporated into sensor units so that they can be installed in locations exposed to the same environment as the object being measured. For example, a circuit board may be installed inside the sensor unit when it is necessary to change the electrical characteristics input and output to the sensor chip (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6633597 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the pressure sensor described in Patent Document 1, as shown in Figure 5, a circuit board 1431 connected to the sensor chip 1121 in the housing 1124 is housed in a case 1135, and the case 1135 is sealed liquid-tight by filling a sealing material 1136 such as a resin material inside.

[0006] In such a structure, because there are differences in the linear expansion coefficients of the constituent materials such as the circuit board 1431, the case 1135, and the sealing material 1136, when a temperature difference occurs inside and outside the object to be measured, stress may be generated in accordance with the temperature difference. This stress may impose a load on the circuit board 1431 itself or on the components mounted on the circuit board 1431. Furthermore, there is a constant demand for cost reduction in devices such as pressure sensors.

[0007] Therefore, the present invention aims to provide an inexpensive pressure sensor that can be used with high reliability by realizing a simple structure that reduces the stress applied to the internal circuit board and ensures liquid-tightness with high precision. [Means for solving the problem]

[0008] One aspect of the invention of a pressure sensor that solves the above problem is a pressure sensor in which a sensor that detects the pressure of the object to be measured is connected to a circuit board that is installed inside a case, the sensor being installed in a pressure chamber so as to receive the pressure of the object to be measured, and the circuit board being filled with a sealing material inside the case to form a liquid-tight seal and constituting part of a space-forming member that forms an installation space in which mounted components on the circuit board are installed. [Effects of the Invention]

[0009] According to one aspect of the present invention, the components mounted on the circuit board are positioned within the installation space, preventing contact with the sealing material and preventing stress loads from being applied to the components mounted on the circuit board. Furthermore, the installation space can be formed by the circuit board, reducing the number of components and achieving a simple structure. Therefore, a reliable and inexpensive pressure sensor can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a pressure sensor according to a first embodiment of the present invention, and is a vertical cross-sectional view showing a schematic overall configuration thereof. [Figure 2] FIG. 2 is a diagram showing a pressure sensor according to a second embodiment of the present invention, and is a vertical cross-sectional view showing a schematic overall configuration thereof. [Figure 3] FIG. 3 is a diagram showing a pressure sensor according to a third embodiment of the present invention, and is a vertical cross-sectional view showing a schematic overall configuration thereof. [Figure 4] FIG. 4 is a diagram showing another aspect of the third embodiment, and is a vertical cross-sectional view showing a schematic overall configuration thereof. [Figure 5] FIG. 5 is a diagram showing the prior art of this embodiment, and is a longitudinal sectional view showing a schematic overall configuration thereof. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a diagram illustrating a pressure sensor according to a first embodiment of the present invention.

[0012] First Embodiment 1, the pressure sensor 100 is fabricated so that a pressure sensor unit 10 having a pressure sensor chip (sensor) 11 installed therein is attached to a refrigerant pipe in the unit to measure the pressure of the refrigerant in a refrigeration cycle, for example, and pressure information detected by the pressure sensor chip 11 is output to an external device A, which is a control device that controls the refrigeration cycle. The pressure sensor 100 of this embodiment is constructed so that the pressure sensor unit 10 having a metallic waterproof case 20 formed in a cylindrical shape can be connected, for example, by connecting the pressure sensor unit 10 with a metallic joint member 30 to a pipe to be measured through which a fluid such as a gas or liquid whose pressure is to be detected is conducted.

[0013] The waterproof case 20 is fixed by welding or the like over one end face of a thick-walled cylindrical metal housing 12 that houses the sensor chip 11 of the pressure sensor unit 10, and the peripheral edge of a disk-shaped metal cap 28, to which a coupling member 30 is fixed, is connected by welding or the like to the other end face of the housing 12. The coupling member 30 has an internal thread 30s formed therein so that it can be screwed to a pipe or the like whose pressure is to be measured, and a port 30a communicating with the internal thread 30s allows fluid supplied from the pipe in the direction of arrow P to be introduced into a pressure chamber PR, which is a space surrounded by the cap 28, housing 12, and a diaphragm 32 (described below). The waterproof case 20, housing 12, and cap 28 are welded from the outside at their outer peripheries by TIG welding, plasma welding, laser welding, or the like, to form a single unit with a desired joint strength.

[0014] The housing 12 is arranged so that the support 13, on which the pressure sensor chip 11 is installed at one end, is located at the center of the inner cylinder, and hermetic glass 14 is formed by filling the space between the inner surface of the housing 12 and the outer surface of the support 13 to ensure a sealed state and to fix the members that pass through the interior in a liquid-tight manner.

[0015] In this pressure sensor unit 10, a metal diaphragm 32 is bonded and fixed to the lower end surface of the housing 12. The diaphragm 32 forms an airtight pressure chamber PR on the cap 28 side, while isolating the installation space of the pressure sensor chip 11 on the support post 13 side inside the housing 12 from the pressure chamber PR.

[0016] In this pressure sensor unit 10, the installation space of the pressure sensor chip 11 formed by the hermetic glass 14 and the diaphragm 32 within the inner tube of the housing 12 is filled with, for example, a predetermined amount of silicone oil (or a fluorine-based inert liquid, etc.) as a pressure transmission medium, so as to function as a liquid-sealed chamber LR.

[0017] As a result, the pressure sensor chip 11 functions as a pressure sensor that detects the pressure of the fluid to be measured, which is introduced into the pressure chamber PR from the piping connected to the coupling member 30, as pressure fluctuations of the pressure transmission medium in the liquid-sealed chamber LR via the diaphragm 32. That is, the pressure chamber PR in this embodiment is constructed with a structure that includes a liquid-sealed chamber LR, and is fabricated with a structure that enables the pressure of the fluid to be measured introduced from the coupling member 30 to be detected by the pressure sensor chip 11. Note that the pressure chamber may not include a liquid-sealed chamber, and the pressure of the fluid to be measured may be directly applied to the sensor chip and measured. Needless to say, the object to be measured is not limited to liquid, but may also be gases such as various gases or mist-like gases containing fine fluid particles.

[0018] The pressure sensor chip 11 is configured to receive power by conductively connecting lead pins (sensor connection pin members) 40 (which are connected to a circuit board 50, described later) via bonding wires 11w from multiple lead wires (external connection members) 38 extending from an external device A, and to output a detection signal as pressure information. The liquid-sealed chamber LR between the hermetic glass 14 and the diaphragm 32 within the inner cylinder of the housing 12 is filled with a pressure transmission medium via an oil filling pipe 44. The lead pins 40 and the oil filling pipe 44 are aligned at equal intervals on the same circle around the support 13 and are supported insulated from the housing 12 by an insulator such as the hermetic glass 14. One end of the oil filling pipe 44 is closed after the pressure transmission medium is filled.

[0019] Here, the diaphragm 32 is prevented from being damaged by external forces or sudden pressures applied to the pressure chamber PR by a diaphragm protective cover 34 having a plurality of communication holes 34a bonded and fixed to the lower end surface of the housing 12. Also, a concave frame 16 is fixed to one end of the hermetic glass 14, and a lid-like shield plate 17 is attached to it. The frame 16 accommodates a pressure transmission medium that can flow freely between the pressure sensor chip 11 side and the diaphragm 32 side via communication holes 17a formed in the shield plate 17, which suppress sudden pressure fluctuations.

[0020] The lead pins 40 are arranged with two power supply terminals, one output signal terminal, and five adjustment terminals used during assembly, and are electrically connected to the pressure sensor chip 11 via bonding wires 11w. These lead pins 40 are fixedly supported by the hermetic glass 14 so as to protrude from one end face side of the housing 12.

[0021] A resin spacer 24 formed in a short, roughly bottomed cylindrical shape is fitted into and abuts against one side of the housing 12 from the bottom 24b side into the waterproof case 20, with a side wall 24s of the spacer 24 in close contact with the inner surface of the waterproof case 20. The bottom 24b of the spacer 24 is formed in a disk shape with an opening toward the center, and lead pins 40 and an oil filling pipe 44 protruding from the hermetic glass 14 of the housing 12 pass through an opening 24a in the bottom 24b, allowing connection to a circuit board 50 and filling with a pressure transmission medium. Here, in this embodiment, an example is described in which each part, including the waterproof case 20 and the spacer 24, is formed in a cylindrical shape, but this is not limited to this, and it goes without saying that a rectangular cylindrical shape is also possible, and the bottom side is not limited to a cylindrical shape with a bottom, and may be closed with a lid member.

[0022] The circuit board 50 is fixed like a lid member by fitting its outer edge into a step 24d formed at the opening end of the side wall portion 24s of the spacer 24, and the mounted components 50J on the circuit board 50 are positioned on the bottom 24b side (housing 12 side) of the spacer 24, thereby closing the opening formed by the side wall portion 24s of the spacer 24.

[0023] That is, in the sensor unit 10, the side wall 24s of the spacer 24 forms a side wall, and the bottom 24b of the spacer 24 and one side of the housing 12 (hermetic glass 14) in the opening 24a are fixed to one edge of the side wall 24s to form a closing portion, which, together with the circuit board 50, forms a space-forming member that defines the installation space SR in which the mounted component 50J is installed. The interior of the waterproof case 20 of the pressure sensor unit 10 is filled with a sealant 26 such as a urethane resin, thereby waterproofing and fixing the back side of the circuit board 50 that forms the installation space SR for the mounted component 50J. The method of fixing the circuit board 50 may be such that a portion of the outer periphery is fixed to the step 24d of the side wall 24s of the spacer 24 with an adhesive or the like, or it may be any fixing method other than adhesive, such as a snap-fit ​​structure in which a claw is provided that press-fits or elastically engages the outer periphery with the inner surface of the side wall 24s or the step 24d. Furthermore, in this embodiment, the spacer 24 and the circuit board 50 are fixed in an arbitrary manner, but the circuit board 50 may be "placed" on the open end of the spacer 24 without being fixed thereto, and the installation space SR may be formed by filling it with the sealant 26. In other words, any structure may be used as long as the sealant 26 does not leak into the installation space SR. For example, by providing the step 24d as in this embodiment, misalignment between the circuit board 50 and the spacer 24 does not occur, and leakage of the sealant 26 can also be prevented.

[0024] By positioning the mounted components 50J of the circuit board 50 in the installation space SR formed by the housing 12, spacer 24, and circuit board 50 within the waterproof case 20, a layer of air with low thermal conductivity can be formed around the mounted components 50J of the circuit board 50, preventing sudden temperature changes from around the pressure sensor on the housing 12 side or from the piping from being transmitted to the circuit board 50. Furthermore, by positioning the mounted components 50J on the circuit board 50 so that they do not come into contact with the sealant 26, mechanical stress caused by contraction and expansion of the sealant 26 due to changes in ambient temperature can be prevented from directly acting on the connecting members, the mounted components 50J, etc. Areas vulnerable to mechanical stress include the mounting area of ​​the mounted components 50J and the wiring pattern of the circuit board 50. However, by positioning at least the areas vulnerable to mechanical stress within the installation space SR so that they do not come into contact with the sealant, resistance to thermal stress loads can be improved.

[0025] Both ends of the lead pin 40 penetrate both sides of the hermetic glass 14 inside the inner tube of the housing 12, and one end on the liquid-sealed chamber LR side is electrically connected to the pressure sensor chip 11 via a bonding wire 11w, while the other end of the lead pin 40, which corresponds to the power supply terminal and the output signal terminal, penetrates through multiple through holes 50h1 in the circuit board 50 and is electrically connected by soldering or the like to a land pattern not shown.

[0026] Furthermore, the lead wire 38 that is drawn out so as to be connectable to the external device A is electrically connected by passing through the through hole 50h2 of the circuit board 50 and soldering the core wire C to a land pattern (not shown) in the direction toward the housing 12. Needless to say, the connection of the lead pin 40 and the lead wire 38 may be made not only by molten metal such as solder, but also by applying, for example, an adhesive containing a conductive material. Furthermore, as described above, in addition to the electrically connected by soldering or a conductive adhesive, the electrically connected may also be made by welding (for example, spot welding with a laser), and there is no need to limit the welding method to a particular one.

[0027] The circuit board 50 is interposed in series between the pressure sensor chip 11 and the external device A to function as part of the circuit configuration, and in this embodiment, an input / output voltage conversion adjustment circuit is mounted thereon to adjust different input / output voltages between the pressure sensor chip 11 and the external device A, for example, to convert the input voltage DC 12V or DC 3.3V of the external device A to the operating voltage DC 5V of the pressure sensor chip 11. This type of conversion adjustment circuit is not limited to this embodiment, but may be any conversion adjustment circuit that can accommodate various drive voltages and signal formats for pressure detection signals, such as a voltage output format for drive / output voltages different from this embodiment, a current output format such as a two-wire type or a three-wire type, or a digital output format.

[0028] As described above, in the pressure sensor 100 of this embodiment, the mounted components 50J of the circuit board 50, which are connected in series between the sensor chip 11 and the external device A, are accommodated in the installation space SR within the case 20, which is filled with the sealing material 26 and sealed liquid-tightly. Therefore, in the pressure sensor 100, the mounted components 50J of the circuit board 50 are positioned in the installation space SR formed on one end face side of the housing 12 by the spacer 24 and the circuit board 50, and it is possible to prevent the mechanical load caused by direct contact with the sealing material 26, which is a molten high-temperature resin, during fabrication, and the thermal stress caused by differences in the degree of expansion and contraction due to differences in the linear expansion coefficients of the constituent materials in response to temperature changes during use, from being applied as stress loads to the mounted components 50J.

[0029] As a result, the pressure sensor 100 allows the sensor unit 10 to be constructed inexpensively and to perform high-quality pressure measurements.

[0030] Second Embodiment Next, Fig. 2 is a diagram illustrating a pressure sensor according to a second embodiment of the present invention. Here, since this embodiment is configured in substantially the same manner as the above-described embodiment, the same components are assigned the same reference numerals, and detailed explanations are omitted, and only the characteristic parts are explained (the same applies to the other embodiments described below).

[0031] In Figure 2, the pressure sensor 100 is configured to connect to an external device A by soldering the core wire C of the lead wire 38 to the back side of the circuit board 50 facing the mounted component 50J without forming a through hole 50h2 in the circuit board 50, and a circuit that is conductive to the mounted component 50J, etc. is formed on the back side of the circuit board 50, and a soldering pattern (not shown) that connects the core wire C of the lead wire 38 is formed.

[0032] In this pressure sensor 100, the end of the coating 38c of the lead wire 38 is positioned outside the circuit board 50 that forms the installation space SR and is embedded (molded) in the sealing material 26 to provide a liquid-tight seal, and even if the core wire C of the lead wire 38 is a twisted wire, the space between it and the coating 38c is embedded in the sealing material 26 outside the installation space SR. Therefore, in the pressure sensor 100, even if there is moisture that has been transmitted around the core wire C of the lead wire 38, it can be prevented from infiltrating into the installation space SR.

[0033] Thus, in the pressure sensor 100 of this embodiment, the coating 38c of the lead wire 38 is stripped outside the circuit board 50 that forms the installation space SR, and the core wire C of the lead wire 38 is electrically connected without penetrating the circuit board 50.

[0034] Therefore, in addition to the effects of the above-described embodiment, the end of the coating 38c, which forms a minute gap between it and the core wire C of the lead wire 38, is embedded in the sealant 26 outside the installation space SR, so that even if moisture is present around the core wire C, it is prevented from penetrating into the installation space SR and causing short circuits or migration due to condensation, thereby enabling highly reliable use. Furthermore, in this embodiment, the conductive connection portion of the lead pin 40 and the lead wire 38 is located on the filling side of the sealant 26, which is the opposite side of the circuit board 50 from the installation space SR. Therefore, the conductive connection work between the circuit board 50, the lead pin 40, and the lead wire 38 can be performed on the same plane and simultaneously. This improves productivity compared to the first embodiment.

[0035] As a result, the pressure sensor 100 can also obtain the same effects as those of the above-described embodiment, and the insulation of the installation space SR is ensured, allowing high-quality pressure measurement.

[0036] <Third embodiment> Next, FIG. 3 is a diagram illustrating a pressure sensor according to a third embodiment of the present invention. In Figure 3, the pressure sensor 100 is coated with an insulating coating material 61, in which a resin material is applied so as to cover the entire area including the area around the through hole 50h1 of the lead pin 40 and the mounted component 50J within the installation space SR of the circuit board 50, and further coated with an insulating coating material 63, in which a resin material is applied so as to cover the entire one end face side of the penetrating and protruding portion of the lead pin 40 on the hermetic glass 14 side, including the support 13 within the housing 12.

[0037] With this structure, in this pressure sensor 100, the installation space SR side of the circuit board 50 is covered with the insulating coating material 61, thereby improving and ensuring insulation between the mounting surface of the mounted component 50J of the circuit board 50 and the lead pins 40, and the housing 12 side is also covered with the insulating coating material 63, thereby improving and ensuring insulation between the housing 12 and the lead pins 40. Furthermore, since the insulating coating material 61 reaches the outer edge of the circuit board 50, it can also seal minute gaps at the stepped portions 24d of the spacer 24, preventing the sealing material 26 from leaking into the installation space SR.

[0038] Thus, in the pressure sensor 100 of this embodiment, in addition to the effects of the above-described embodiments, the circuit board 50 side and the housing 12 side within the installation space SR are covered with insulating coating materials 61, 63, thereby improving the insulation of the connection points of the lead pins 40 as well as the mounted components 50J, thereby enabling reliable and high-quality pressure measurements to be performed.

[0039] In another aspect of the third embodiment, as shown in FIG. 4, the formation of the insulating coating material 61 may be omitted, and there is no connection point for the lead wire 38 connected from the outside to the circuit board 50 side within the installation space SR. Furthermore, the penetrating and protruding portion of the lead pin 40 on the hermetic glass 14 side is coated with the insulating coating material 63, so that insulation equivalent to that of the above embodiment can be ensured at low cost.

[0040] Furthermore, to further reduce the number of parts and achieve a simpler structure, since the waterproof case 20 and the cylindrical spacer 24 are similar in shape, the waterproof case 20 may also function as a spacer that supports the circuit board 50. Although not shown, the waterproof case 20 may be configured to have locking portions in the form of convex dimples or ribs on its inner surface at a height position that allows for the formation of an installation space SR equivalent to that of each of the above-described embodiments, and the circuit board 50 may be supported by these locking portions. Even if the spacer 24 is omitted, the locking portions of the waterproof case 20 can serve as supports for the circuit board 50, thereby forming the installation space SR between the circuit board 50 and the housing 12, and the components 50J mounted on the circuit board 50 can be arranged within this space.

[0041] As another example, the housing may also function as a spacer that supports the board. Although not shown, the housing 12 may have a cylindrical outer peripheral edge portion that extends upward, i.e., in the direction in which the lead wires 38 are pulled out, so that an installation space SR equivalent to that of each of the above-described embodiments can be formed. A step 24d that supports the circuit board 50 may be integrally formed at the end of the extension, and the step may support the circuit board 50. Even if the spacer 24 is omitted, by extending the housing 12 upward and integrally forming a support portion for the circuit board 50, an installation space SR can be formed between the circuit board 50 and the housing 12, and components 50J mounted on the circuit board can be arranged within the space.

[0042] The scope of the present invention is not limited to the exemplary embodiments shown and described, but also includes all embodiments that achieve equivalent effects to those intended by the present invention. Furthermore, the scope of the present invention is not limited to the combination of inventive features specified in each claim, but can be defined by any desired combination of each and every disclosed specific feature. [Explanation of symbols]

[0043] 10...Pressure sensor unit 11...Pressure sensor chip 12...Housing 14...hermetic glass 20...Waterproof case 24...Spacer 24b……Bottom 24d...step 24s……Side wall part 25...Cover member 26...Sealing material 30...Joint member 38...Lead wire 38c……Covering 40...Lead pin 50...Circuit board 50J...Mounted parts 50h1, 50h2...Through holes 61, 63...insulating coating material 100...Pressure sensor A……External device C...Core wire PR...Pressure chamber SR……Installation space

Claims

1. A pressure sensor in which a sensor for detecting the pressure of a measurement target is connected to a circuit board installed inside a case, A pressure sensor characterized in that the sensor is installed in a pressure chamber so as to receive the pressure to be measured, and the circuit board is formed liquid-tight by filling a sealing material inside the case, and forms part of a space-forming member that forms an installation space in which mounted components on the circuit board are installed.

2. The pressure sensor described in claim 1, characterized in that the space forming member has a side wall portion that forms the side surface of the cylindrical shape and a blocking portion located on one end edge of the side wall portion so as to block one opening of the cylindrical shape, and the circuit board is configured to block the other opening of the cylindrical shape that is on the other end edge of the side wall portion, thereby forming the installation space.

3. the circuit board is disposed between the sensor and an external device, the circuit board is electrically connected to the sensor via a sensor connection pin member that penetrates the blocking portion, and the circuit board is electrically connected to the external device via an external connection member that is drawn out to the outside, The pressure sensor according to claim 2, wherein the sensor connection pin member, which penetrates from the closing portion to the circuit board and passes through the installation space, is connected to the circuit board within the filling space of the sealing material.

4. 4. The pressure sensor according to claim 3, wherein the external connection member is connected to the circuit board within a space filled with the sealing material in the circuit board.

5. 2. The pressure sensor according to claim 1, wherein an insulating coating is applied to a mounting component mounting surface of the circuit board on the side of the installation space.

6. The pressure sensor according to claim 1, characterized in that an insulating coating is applied to at least the penetration points of a member on the forming surface of the space forming member, which is a forming surface that forms the installation space and has a penetration point of the member exposed within the installation space.

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