Differential pressure sensor

Abstract

To restrain occurrence of excessive stress in an edge section of a diaphragm in a low-pressure side.SOLUTION: A differential pressure sensor 10 comprises: a diaphragm 12H that is deformed by receiving pressure HP in a high-pressure side of a measured fluid; a diaphragm 12L that is deformed by receiving pressure LP in a low-pressure side; a support member 11 that supports the diaphragms 12H and 12L while an interlocking oil O for linking the deformation of the diaphragm 12H and the deformation of the diaphragm 12L is sealed. Each of the diaphragm 12H and the diaphragm 12L is recessed to the side of the interlocking oil O when the differential pressure sensor 10 is placed at a normal temperature or under the atmosphere.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a differential pressure sensor. [Background technology]

[0002] The differential pressure sensor includes a first diaphragm that deforms when subjected to a first pressure on the high-pressure side of the fluid to be measured, a second diaphragm that deforms when subjected to a second pressure on the low-pressure side of the fluid to be measured, and a support member that supports the first and second diaphragms. The support member is filled with an interlocking fluid that interlocks the deformation of the first diaphragm with the deformation of the second diaphragm (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-89233 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional differential pressure sensors are designed so that the first and second diaphragms are flat under ambient air temperature. Therefore, when the fluid being measured is hot, the interlocking fluid is heated through the first and second diaphragms, causing the interlocking fluid to expand. This expansion causes the first and second diaphragms to expand toward the opposite side of the interlocking fluid. When a differential pressure is input to the differential pressure sensor in this state, the second diaphragm (on the low-pressure side) expands further toward the opposite side of the interlocking fluid, causing excessive stress at the edge of the second diaphragm. This excessive stress can lead to the second diaphragm breaking.

[0005] An object of the present invention is to prevent excessive stress from occurring at the edge portion of the diaphragm on the low-pressure side. [Means for solving the problem]

[0006] In order to solve the above problems, the differential pressure sensor of the present invention is a differential pressure sensor that detects the differential pressure of a fluid, and includes a first diaphragm that deforms in response to a first pressure on the high-pressure side of the fluid, a second diaphragm that deforms in response to a second pressure on the low-pressure side of the fluid, and a support member that supports the first diaphragm and the second diaphragm, and is filled with an interlocking fluid that interlocks the deformation of the first diaphragm and the deformation of the second diaphragm, and each of the first diaphragm and the second diaphragm is recessed toward the interlocking fluid when the differential pressure sensor is placed at room temperature and in the atmosphere.

[0007] Each of the first diaphragm and the second diaphragm may be configured to deform to a shape that is flat or concave toward the interlocking fluid but less concave than when at room temperature and under atmospheric pressure, when the interlocking fluid is heated and expands during use of the differential pressure sensor and the first pressure and the second pressure are the same.

[0008] The method for manufacturing a differential pressure sensor according to the present invention is a method for manufacturing the above-mentioned differential pressure sensor, and comprises a first step of sealing the interlocking fluid in the support member in a heated state, and a second step of cooling the interlocking fluid after the first step and causing the interlocking fluid to contract. [Effects of the Invention]

[0009] According to the present invention, the generation of excessive stress at the edge portion of the diaphragm on the low-pressure side is suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic plan view of a differential pressure sensor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA when the differential pressure sensor is in use. [Figure 4]FIG. 4 is a cross-sectional view of a part of the differential pressure sensor for explaining the manufacturing process of the differential pressure sensor. [Figure 5] FIG. 5 is a cross-sectional view of a part of the differential pressure sensor for explaining the manufacturing process of the differential pressure sensor. [Figure 6] FIG. 6 is a cross-sectional view of the differential pressure sensor when completed and before being cooled, for illustrating the manufacturing process of the differential pressure sensor. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention and its modifications will be described with reference to the drawings.

[0012] 1 and 2, a differential pressure sensor 10 according to one embodiment of the present invention includes a support member 11, a diaphragm layer 12, a pressure-conducting member 14, a conversion circuit 15, and a processing circuit 16. The differential pressure sensor 10 is configured to detect the differential pressure between a pressure HP (FIG. 3) on the high-pressure side of a fluid to be measured (e.g., a fluid flowing through a specified pipe) and a pressure LP (FIG. 3) on the low-pressure side.

[0013] The support member 11 supports the diaphragm layer 12. The support member 11 includes a laminate (also referred to as a support member main body) formed by stacking a first layer 11A and a second layer 11B. The first layer 11A is provided with a through-hole 11D penetrating in the vertical direction. The lower surface of the second layer 11B is provided with diaphragm chambers 11H and 11L each formed as a recess. A communication passage 11E is provided from the first layer 11A to the second layer 11B, connecting the diaphragm chambers 11H and 11L to each other. The through-hole 11D and the communication passage 11E are connected. The support member 11 also includes a seal member 11F fixed to the first layer 11A of the support member main body and sealing the through-hole 11D. The seal member 11F may have any shape. The seal member 11F may be a solder ball or the like.

[0014] The diaphragm layer 12 is fixed to the lower surface of the second layer 11B. The diaphragm layer 12 covers the diaphragm chambers 11H and 11L of the second layer 11B, sealing the diaphragm chambers 11H and 11L. The portion of the diaphragm layer 12 that covers the diaphragm chamber 11H is also referred to as the diaphragm 12H. The diaphragm 12H is supported by the support member 11 and deforms when subjected to pressure HP (Figure 3). The portion of the diaphragm layer 12 that covers the diaphragm chamber 11L is also referred to as the diaphragm 12L. The diaphragm 12L is supported by the support member 11 and deforms when subjected to pressure LP.

[0015] The space formed by through-hole 11D, communication passage 11E, and diaphragm chambers 11H and 11L is filled with interlocking oil O, which serves as an interlocking fluid that interlocks the deformations of diaphragms 12H and 12L. When through-hole 11D is filled with interlocking oil O, seal member 11F seals through-hole 11D, whereby interlocking oil O is filled and sealed in support member 11.

[0016] The pressure guide member 14 is fixed to the lower surface of the diaphragm layer 12 and has pressure guide paths 14H and 14L, which are through-holes extending in the vertical direction. As shown by the straight arrows in FIG. 3, the pressure guide path 14H guides the high-pressure side pressure HP to the diaphragm 12H. The pressure guide path 14L guides the low-pressure side pressure LP to the diaphragm 12L. The pressure guide paths 14H and 14L may have any shape. For example, the pressure guide path 14H may include a pressure guide chamber in contact with the diaphragm 12H and a connecting path that is narrower than the pressure guide chamber and connected to the lower end of the pressure guide chamber. The same applies to the pressure guide path 14L.

[0017] The inner surface of the diaphragm chamber 11H serves as a stopper surface 11HA (also called an overpressure protection mechanism) that abuts against the diaphragm 12H when the diaphragm 12H is significantly deformed convexly toward the support member 11, thereby restricting further deformation of the diaphragm 12H. Similarly, the inner surface of the diaphragm chamber 11L serves as a stopper surface 11LA that restricts excessive deformation of the diaphragm 12L. The stopper surfaces 11HA and 11LA are formed in a curved shape, for example, an aspherical shape.

[0018] Conversion circuit 15 in FIG. 1 is configured to convert the deformations (here, the amount and direction of deformation) of diaphragms 12H and 12L into electrical signals EH and EL. Conversion circuit 15 includes strain gauges S1 and S2 provided on diaphragm 12H and connected in series, strain gauges S3 and S4 provided on diaphragm 12L and connected in series, and wiring connected to strain gauges S1 to S4 to realize the circuit shown in FIG. 1. Each of strain gauges S1 to S4 is made of a piezoresistance element formed by doping p-type impurity boron into diaphragm layer 12 made of n-type single crystal silicon, for example. The wiring includes a conductive wiring pattern provided on diaphragm layer 12. A drive voltage V is applied from a DC power supply VS to both ends of the pair of strain gauges S1 and S2 and the pair of strain gauges S3 and S4.

[0019] An electrical signal EH indicating a voltage VH (a voltage with a reference potential of 0V) obtained by dividing the drive voltage V by the resistance values ​​of the strain gauges S1 and S2 is output from a node N1 connecting the two strain gauges S1 and S2. Because the resistance values ​​of the strain gauges S1 and S2 change with the deformation of the diaphragm 12H, the voltage VH changes in accordance with the deformation of the diaphragm 12H. In other words, the deformation of the diaphragm 12H is converted into the electrical signal EH and the voltage VH.

[0020] An electrical signal EL indicating a voltage VL (a voltage with a reference potential of 0 V) ​​obtained by dividing the drive voltage V by the resistance values ​​of the strain gauges S3 and S4 is output from the node N2 connecting the two strain gauges S3 and S4. Because the resistance values ​​of the strain gauges S3 and S4 change with the deformation of the diaphragm 12L, the voltage VL changes in accordance with the deformation of the diaphragm 12L. In other words, the deformation of the diaphragm 12L is converted into the electrical signal EL and the voltage VL.

[0021] The processing circuit 16 includes a processor such as a microcomputer. The processing circuit 16 detects the differential pressure that deforms the diaphragms 12H and 12L to different sides (the oil O side and the opposite side) based on the electrical signals EH and EL input from the nodes N1 and N2 via the terminals T1 and T2, respectively. The processing circuit 16 outputs the detected differential pressure to a device external to the differential pressure sensor 10 (such as a display device, a host device, or a terminal device).

[0022] In this embodiment, when the differential pressure sensor 10 is placed in an atmospheric space at room temperature, each of the diaphragms 12H and 12L is recessed in a spherical crown shape toward the oil O (upper side), as shown in FIG. 2. As a result, each of the diaphragms 12H and 12L is shaped so that the amount of displacement from a flat state gradually increases from its edge (the edge of the diaphragm chamber 11L on the underside of the support member 11 and the edge of the upper opening of the pressure guide passage 14L of the pressure guide member 14) toward the center. Room temperature is approximately 20°C. When the differential pressure sensor 10 is placed in an atmospheric space, air is introduced into the pressure guide passages 14H and 14L. At room temperature, the pressure of the oil O is lower than atmospheric pressure. In other words, due to the volume of the oil O at room temperature, both the diaphragms 12H and 12L are recessed toward the oil O.

[0023] The fluid to be measured by the differential pressure sensor 10 is often at a high temperature (e.g., a temperature of 85°C or higher). In such cases, the high-temperature fluid is heated by the interlocking oil O through the diaphragms 12H and 12L and expands. This causes each of the diaphragms 12H and 12L to deform and become nearly flat (see the solid line in Figure 3). When a differential pressure is applied to the differential pressure sensor 10 in this state, the high-pressure side pressure HP causes the diaphragm 12H to dent toward the interlocking oil O (upper side) (see the dashed-dotted line in Figure 3). This deformation of the diaphragm 12H is transmitted to the diaphragm 12L via the interlocking oil O, causing the diaphragm 12L to bulge toward the opposite side (lower side) from the interlocking oil O (see the dashed-dotted line in Figure 3). The diaphragm 12L is subjected to a low-pressure side pressure LP, and due to the relationship of pressure HP>pressure LP, the diaphragm 12L is deformed to be convex on the side opposite to the support member 11 side.

[0024] In this embodiment, before the differential pressure sensor 10 is used, that is, at room temperature and in the atmosphere, the diaphragms 12H and 12L are each recessed toward the interlocking oil O (upper side). Therefore, even when a differential pressure of a high-temperature fluid to be measured is applied during use of the differential pressure sensor 10, the degree of downward bulging (degree of deformation) of the diaphragm 12L relative to its flatness is reduced by the amount of the recess, compared to a conventional structure in which the diaphragm 12L is flat before use. In particular, in a conventional structure in which the diaphragms 12L and 12H are flat before use, the heating of the interlocking oil O by the fluid to be measured causes the diaphragms 12L and 12H to bulge downward even before a differential pressure is generated. Therefore, when the pressure HP increases and the diaphragm 12H deforms until it contacts the stopper surface 11HA, the degree of deformation increases by the amount of downward bulging before the differential pressure is generated. The degree of deformation (downward bulging) of the diaphragm 12L, which deforms in conjunction with the deformation of the diaphragm 12H, also increases accordingly. In this embodiment, the recess reduces the downward deformation of the diaphragms 12L and 12H due to the heating of the interlocking oil O, thereby reducing the maximum degree of deformation of the diaphragms 12L and 12H. As a result, the maximum stress that can occur in the diaphragm 12L during use of the differential pressure sensor 10 is reduced. In particular, excessive stress is prevented from occurring at the edge of the diaphragm 12L. This reduces the risk of rupture of the diaphragm 12L, improving the reliability of the device incorporating the differential pressure sensor 10 during operation.

[0025] Each of the diaphragms 12H and 12L is preferably configured so that when the interlocking oil O is heated and expands during use of the differential pressure sensor 10, and when the pressures HP and LP are equal, it either deforms flat or deforms into a shape that is concave toward the interlocking oil O but is less concave than when the differential pressure sensor 10 is placed at room temperature and in the atmosphere. The deformed shapes of the diaphragms 12H and 12L are adjusted, for example, by the volume of the interlocking oil O at room temperature. This structure reduces the degree of downward bulging (degree of deformation) of the diaphragm 12L relative to its flat state when a differential pressure of the fluid to be measured occurs after the interlocking oil O is pressurized, thereby suppressing excessive stress on the edge portions of the diaphragm 12L.

[0026] Next, a description will be given of a method for manufacturing the differential pressure sensor 10. First, as shown in Fig. 4, a unit is prepared by combining the support member main body (first layer 11A and second layer 11B) of the support member 11, the diaphragm layer 12, and the pressure-guiding member 14.

[0027] Next, as shown in FIG. 5, the space in the support member body (first layer 11A and second layer 11B) consisting of the through-hole 11D, the communication passage 11E, and the diaphragm chambers 11H and 11L is filled with interlocking oil O. The support member body filled with interlocking oil O is then heated, and the seal member 11F is then fixed to the first layer 11A to seal the space filled with interlocking oil O (FIG. 6). During heating, the interlocking oil O expands, causing it to overflow from the first layer 11A. By fixing the seal member 11F when the interlocking oil O overflows, air is prevented from entering the space. The interlocking oil O may be filled into the space in a heated state, and the seal member 11F may be fixed before the interlocking oil O cools down. By using any of the methods described above, the interlocking oil O is sealed in the support member 11 in a heated state. When the interlocking oil O is sealed, the diaphragms 12H and 12L are flat sheets.

[0028] The interlocking oil O is then cooled and contracted by natural cooling, air cooling, liquid cooling, etc. This results in a differential pressure sensor 10 in which the diaphragms 12H and 12L are recessed toward the interlocking oil O at room temperature and in the atmosphere, as shown in Figure 2.

[0029] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. For example, the present invention includes various modifications to the above embodiments that can be understood by a person skilled in the art within the scope of the technical concept of the present invention. Below, variations relating to such modifications are described. The configurations listed in the above embodiments and any of the configurations of the following variations can be combined as appropriate within a range that does not contradict. Also, any of the configurations may be deleted.

[0030] The diaphragms 12H and 12L may have any shape. In the above embodiment, the diaphragms 12H and 12L are flat sheets when not deformed. However, they may have a partially curved shape or unevenness to facilitate deformation. Even in such a case, the diaphragms 12H and 12L are recessed toward the interlocking oil O. "The diaphragms 12H and 12L are recessed" includes the diaphragms 12H and 12L being recessed entirely. It is preferable that both diaphragms 12H and 12L have the same shape. This reduces crosstalk (e.g., static pressure sensitivity when a non-measured fluid is flowing). Furthermore, although the interlocking oil O is used as the interlocking fluid for interlocking the deformation of the diaphragms 12H and 12L in the above embodiment, other fluids (particularly liquids) may also be used as the interlocking fluid. The configuration of the conversion circuit 15 is arbitrary. The conversion circuit 15 may be a circuit that converts the deformation of the diaphragms 12H and 12L into an electrical signal using a detection element such as a strain gauge. Processing circuitry 16 may not be an element of differential pressure sensor 10 but may be external to differential pressure sensor 10 . [Explanation of symbols]

[0031] 10...differential pressure sensor, 11...support member, 11A...first layer, 11B...second layer, 11D...through hole, 11E...communicating passage, 11F...sealing member, 11H...diaphragm chamber, 11HA...stopper surface, 11L...diaphragm chamber, 11LA...stopper surface, 12...diaphragm layer, 12H...diaphragm, 12L...diaphragm, 14...pressure guide member, 14H...pressure guide path, 14L...pressure guide path, 15...conversion circuit, 16...processing circuit, HP...high pressure side pressure, LP...low pressure side pressure, N1...node, N2...node, O...interlocking oil, S1 to S4...strain gauge, T1...terminal, T2...terminal, VS...DC power supply, V...drive voltage.

Claims

1. A differential pressure sensor for detecting a differential pressure of a fluid, a first diaphragm that deforms when subjected to a first pressure on the high-pressure side of the fluid; a second diaphragm that deforms when subjected to a second pressure on the low-pressure side of the fluid; a support member that supports the first diaphragm and the second diaphragm, the support member containing an interlocking fluid that interlocks deformation of the first diaphragm with deformation of the second diaphragm; each of the first diaphragm and the second diaphragm is recessed toward the interlocking fluid when the differential pressure sensor is placed under atmospheric pressure at room temperature; Differential pressure sensor.

2. When the interlocking fluid is heated and expanded during use of the differential pressure sensor and the first pressure and the second pressure are equal, each of the first diaphragm and the second diaphragm deforms to a shape that is flat or recessed toward the interlocking fluid but is less recessed than when the first diaphragm and the second diaphragm are at room temperature and under atmospheric pressure. The differential pressure sensor according to claim 1 .

3. 3. A method for manufacturing the differential pressure sensor according to claim 1 or 2, comprising: a first step of sealing the interlocking fluid in a heated state within the support member; a second step of cooling the interlocking fluid after the first step to cause the interlocking fluid to contract; A method for manufacturing a differential pressure sensor comprising:

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