pressure sensor

Abstract

To detect differential pressure and static pressure of a fluid to be measured with a simple configuration.SOLUTION: A differential pressure sensor 10 comprises: a diaphragm 12H deformed by receiving pressure HP of a fluid to be measured on a high-pressure side; a diaphragm 12L deformed by receiving pressure LP of the fluid to be measured on a low-pressure side; and a conversion circuit 15 that converts respective deformations of the diaphragms 12H and 12L into electric signals EH and EL respectively. The differential pressure sensor 10 comprises a support member 11 that supports the diaphragms 12H and 12L and is filled with interlocking oil O interlocking with the respective deformations of the diaphragms 12H and 12L; and a processing circuit 16 that detects differential pressure at which the diaphragms 12H and 12L are deformed to be convex to different sides and static pressure of the fluid at which the diaphragms 12H and 12L are deformed to be convex to the same side on the basis of the electric signals EH and EL.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] ,

[0006] , , , ,

[0005] , , , , ,

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

Background Art

[0002] There is known a pressure sensor (differential pressure sensor) that includes a first diaphragm that is deformed by receiving a first pressure (for example, high pressure) of a fluid to be measured, which is a fluid to be measured, and a second diaphragm that is deformed by receiving a second pressure (for example, low pressure) of the fluid to be measured, and that detects a differential pressure between the first pressure and the second pressure (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above pressure sensor, there is a disadvantage that the static pressure of the fluid to be measured cannot be detected. Although it is conceivable to separately provide a diaphragm for detecting the static pressure in the above pressure sensor, in this case, the structure of the pressure sensor becomes complicated. <00000​​​​​To solve the above problems, the pressure sensor according to the present invention comprises: a first diaphragm that deforms upon receiving a first pressure of a fluid; a second diaphragm that deforms upon receiving a second pressure of the fluid; a conversion circuit that converts the deformation of the first diaphragm into a first electrical signal and the deformation of the second diaphragm into a second electrical signal; a support member that supports the first diaphragm and the second diaphragm, and is filled with a fluid that links the deformation of the first diaphragm and the deformation of the second diaphragm; and a processing circuit that detects, based on the first electrical signal and the second electrical signal, the differential pressure between the first pressure and the second pressure at which the first diaphragm and the second diaphragm deform convexly to different sides, and the static pressure of the fluid at which both the first diaphragm and the second diaphragm deform convexly to the same side.

[0007] As an example, the pressure sensor further comprises a temperature sensor for detecting the temperature of the interlocking fluid, and the processing circuit corrects the static pressure based on the temperature of the interlocking fluid detected by the temperature sensor.

[0008] As an example, the processing circuit detects a leak of the interlocking fluid from the support member when the detected static pressure exceeds a predetermined standard.

[0009] As an example, the processing circuit detects the differential pressure based on either the sum or the difference between the first value indicated by the first electrical signal and the second value indicated by the second electrical signal, and detects the static pressure based on the other of the sum and the difference between the first value and the second value.

[0010] As an example, the conversion circuit comprises two first strain gauges connected in series via a first node that convert the deformation of the first diaphragm into the first electrical signal, and two second strain gauges connected in series via a second node that convert the deformation of the second diaphragm into the second electrical signal, with the first electrical signal output from the first node and the second electrical signal output from the second node.

[0011] As an example, the conversion circuit includes a first full-bridge circuit comprising a plurality of bridge-connected strain gauges that converts the deformation of the first diaphragm into a first electrical signal, and a second full-bridge circuit comprising a plurality of bridge-connected strain gauges that converts the deformation of the second diaphragm into a second electrical signal, wherein the processing circuit detects the differential pressure based on either the sum or the difference between a first value indicated by the first electrical signal and a second value indicated by the second electrical signal, and detects the static pressure based on the other.

[0012] As an example, the second electrical signal includes a second-first electrical signal and a second-second electrical signal, and the conversion circuit comprises two third strain gauges connected in series via a third node that convert the deformation of the first diaphragm into the first electrical signal, two fourth strain gauges connected in series via a fourth node that convert the deformation of the second diaphragm into the second-first electrical signal, and two fifth strain gauges connected in series via a fifth node that convert the deformation of the second diaphragm into the second-second electrical signal, with the first electrical signal output from the third node and the second-first electrical signal output from the fourth node. The circuit outputs a signal, outputs the 2-2 electrical signal from the 5th node, and the two 4th strain gauges and the two 5th strain gauges are configured such that, due to the deformation of the 2nd diaphragm, the 2-1 value indicated by the 2-1 electrical signal and the 2-2 value indicated by the 2-2 electrical signal change by the same amount in both positive and negative directions from the value when the 2nd diaphragm is not deformed. The processing circuit detects the differential pressure based on either the sum or the difference between the 1st value indicated by the 1st electrical signal and the 2-1 value, and detects the static pressure based on either the sum or the difference between the 1st value and the 2-2 value. [Effects of the Invention]

[0013] According to the present invention, the differential pressure and static pressure of the fluid to be measured can be detected with a simple configuration. [Brief explanation of the drawing]

[0014] [Figure 1]Figure 1 is a schematic plan view of a pressure sensor according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of AA in Figure 1. [Figure 3] Figure 3 is a cross-sectional view (AA) at static pressure when the fluid being measured is not flowing. [Figure 4] Figure 4 is a cross-sectional view (AA) under static pressure and with interlocking oil leakage. [Figure 5] Figure 5 is a schematic plan view of a modified pressure sensor. [Figure 6] Figure 6 is a schematic plan view of a modified pressure sensor. [Modes for carrying out the invention]

[0015] Hereinafter, embodiments of the present invention and their modifications will be described with reference to the drawings.

[0016] (Embodiment) As shown in Figures 1 and 2, a pressure sensor 10 according to one embodiment of the present invention comprises a support member 11, a diaphragm layer 12, a sealing member 13, a pressure sensing member 14, a conversion circuit 15, and a processing circuit 16. The pressure sensor 10 is configured to detect the differential pressure between the high-pressure side pressure HP and the low-pressure side pressure LP of a fluid to be measured (for example, a fluid flowing through a predetermined pipe). Furthermore, the pressure sensor 10 is configured to also detect the static pressure of the fluid to be measured. The pressure sensor 10 is configured, for example, as a differential pressure detection unit of a differential pressure transmitter.

[0017] The support member 11 supports the diaphragm layer 12. The support member 11 has a laminated structure in which a first layer 11A and a second layer 11B are stacked. The first layer 11A is provided with a through hole 11D that penetrates in the vertical direction. The lower surface of the second layer 11B is provided with diaphragm chambers 11H and 11L, which are recesses. A connecting 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 connecting passage 11E are connected. The upper part of the through hole 11D is sealed with a sealing member 13.

[0018] The diaphragm layer 12 is fixed to the lower surface of the second layer 11B. The diaphragm layer 12 covers and seals the diaphragm chambers 11H and 11L of the second layer 11B. The portion of the diaphragm layer 12 that covers the diaphragm chamber 11H is also referred to as diaphragm 12H. The diaphragm 12H is supported by the support member 11 and is deformed by receiving the pressure HP. The portion of the diaphragm layer 12 that covers the diaphragm chamber 11L is also referred to as diaphragm 12L. The diaphragm 12L is supported by the support member 11 and is deformed by receiving the pressure LP.

[0019] The through-hole 11D, the communication passage 11E, the diaphragm chambers 11H and 11L, which are sealed by the diaphragm layer 12 and the seal member 13, are filled with an interlocking oil O as an interlocking fluid that interlocks the deformations of the diaphragms 12H and 12L.

[0020] The pressure guiding member 14 is fixed to the lower surface of the diaphragm layer 12 and has pressure guiding paths 14H and 14L that are through-holes extending in the vertical direction. The pressure guiding path 14L guides the low-pressure side pressure LP to the diaphragm 12L. The pressure guiding path 14H guides the high-pressure side pressure HP to the diaphragm 12H.

[0021] In this embodiment, due to the high-pressure side pressure HP, the diaphragm 12H is deformed convexly toward the support member 11 side (upper side) (see the dashed line in FIG. 2). This deformation of the diaphragm 12H is transmitted to the diaphragm 12L via the interlocking oil O, and the diaphragm 12L is deformed convexly toward the side opposite to the support member 11 side (lower side) (see the dashed line in FIG. 2). The low-pressure side pressure LP is applied to the diaphragm 12L, but due to the relationship of pressure HP > pressure LP, the diaphragm 12L is deformed convexly toward the side opposite to the support member 11 side. Thus, when a differential pressure, which is the difference between the pressure HP and the pressure LP, occurs, the diaphragms 12H and 12L are deformed convexly toward different sides (here, in the vertically opposite directions).

[0022] Both diaphragms 12H and 12L are also subjected to static pressure from the fluid being measured. This static pressure pushes diaphragms 12H and 12L to the same side (in this case, upward). Due to this static pressure, diaphragm 12H, which has deformed convexly toward the support member 11, deforms further toward the support member 11, and diaphragm 12L, which has deformed convexly toward the opposite side of the support member 11, is pushed back toward the support member 11, causing the interlocking oil O to contract by that amount. When the fluid being measured is not flowing, that is, when pressure HP = pressure LP and no differential pressure is generated, the static pressure from the fluid being measured pushes both diaphragms 12H and 12L to the same side, i.e., toward the support member 11. As a result, the interlocking oil O is compressed, and by that amount of compression, diaphragms 12H and 12L deform convexly toward the support member 11, as shown in Figure 3.

[0023] Returning to Figures 1 and 2, the inner surface of the diaphragm chamber 11H is a stopper surface 11HA (also called an overpressure protection mechanism) that contacts the diaphragm 12H when the diaphragm 12H deforms significantly convex toward the support member 11, thereby restricting further deformation of the diaphragm 12H. Similarly, the inner surface of the diaphragm chamber 11L is also 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.

[0024] The conversion circuit 15 is configured to convert the deformations (here, the amount of deformation and the direction of deformation) of the diaphragms 12H and 12L into electrical signals EH and EL. The processing circuit 16 includes strain gauges S1 and S2 provided on the diaphragm 12H and connected in series, and strain gauges S3 and S4 provided on the diaphragm 12L and connected in series. Each of the strain gauges S1 to S4 is a piezoresistive element constructed by introducing boron, a p-type impurity, into a diaphragm layer 12 made of n-type single-crystal silicon.

[0025] The resistance values ​​of strain gauges S1 and S2 change due to the deformation of diaphragm 12H. The resistance values ​​of strain gauges S3 and S4 change due to the deformation of diaphragm 12L. A drive voltage V from a DC power supply VS is applied to both ends of each pair of strain gauges S1 and S2, and each pair of strain gauges S3 and S4. The negative terminal of the DC power supply VS is connected to a reference potential.

[0026] Node N1, which connects the two strain gauges S1 and S2, outputs an electrical signal EH representing a voltage VH (also called a potential VH with a reference potential of 0V) obtained by dividing the drive voltage V by the respective resistance values ​​of strain gauges S1 and S2. The voltage VH changes according to the deformation of the diaphragm 12H. In other words, the deformation of the diaphragm 12H is converted into a voltage VH. This point will be explained in detail below.

[0027] Strain gauges S1 and S2 have the same shape and the same resistance value when the diaphragm 12H is undeformed (in a flat shape). Strain gauge S1 extends along the radial direction of the diaphragm 12H, and strain gauge S2 extends along the tangential direction in the circumferential direction of the diaphragm 12H. As a result, when the diaphragm 12H is deformed, strain gauges S1 and S2 deform into different shapes, and consequently, their respective resistance values ​​change to different values. Therefore, the voltage VH changes according to the amount of deformation of the diaphragm 12H.

[0028] Furthermore, strain gauges S1 and S2 are thinner than the diaphragm layer 12, i.e., the diaphragm 12H, and are unevenly distributed on either the upper or lower surface side of the diaphragm layer 12. As a result, the deformation patterns of strain gauges S1 and S2 differ depending on whether the diaphragm 12H deforms convexly toward the support member 11 or convexly toward the opposite side. Therefore, the voltage VH changes in the opposite direction of the deformation of the diaphragm 12H, relative to the voltage value when the diaphragm 12H is not deformed. Here, strain gauges S1 and S2 are configured such that when the diaphragm 12H deforms convexly toward the support member 11, the voltage VH increases and approaches the drive voltage V. When the diaphragm 12H deforms convexly toward the opposite side, the voltage VH decreases and approaches 0V, that is, the potential VH approaches the reference potential.

[0029] Node N2, which connects the two strain gauges S3 and S4, outputs an electrical signal EL that represents a voltage VL (also called a potential VL with a reference potential of 0V) obtained by dividing the drive voltage V by the respective resistance values ​​of strain gauges S3 and S4. 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 a voltage VL. The principle of the change in voltage VL is the same as the change in voltage VH. The explanation of strain gauge S3 follows the explanation of strain gauge S1, and the explanation of strain gauge S4 follows the explanation of strain gauge S2. The voltage VL, like the voltage VH, increases and approaches the drive voltage V when the diaphragm 12L deforms convexly toward the support member 11.

[0030] The electrical signals EH and EL from nodes N1 and N2 are input to the processing circuit 16 via terminals T1 and T2, which consist of bonding pads and the like. The processing circuit 16 is composed of a processor such as a microcontroller.

[0031] The processing circuit 16 detects the differential pressure that deforms the diaphragms 12H and 12L convexly to opposite sides (the support member 11 side and the opposite side), respectively, based on the electrical signals EH and EL. As described above, the direction of deformation of the diaphragm 12H when the voltage VH increases is the same as the direction of deformation of the diaphragm 12L when the voltage VL increases. Therefore, the processing circuit 16 can detect the differential pressure based on the difference between the voltage VH indicated by the electrical signal EH and the voltage VL indicated by the electrical signal EL. As an example, the processing circuit 16 detects the differential pressure by calculating the difference obtained by subtracting the voltage VL from the voltage VH. The processing circuit 16 may also detect the differential pressure by deriving the actual value of the differential pressure based on the value obtained by subtracting the voltage VL from the voltage VH and a predetermined calculation formula and / or table.

[0032] The processing circuit 16 also detects the static pressure of the fluid being measured, which deforms both diaphragms 12H and 12L convexly toward the same side (support member 11 side), based on the electrical signals EH and EL. Unlike differential pressure, the processing circuit 16 can detect static pressure based on the sum of voltage VH and voltage VL. For example, the processing circuit 16 calculates the sum of voltage VH and voltage VL and detects the sum as the static pressure. The processing circuit 16 may also detect the static pressure by deriving the actual value of the static pressure based on the value of the sum of voltage VH and voltage VL and a predetermined calculation formula and / or table.

[0033] The processing circuit 16 outputs the detected differential pressure and / or static pressure to an external device (display device, host device, terminal device, etc.) of the pressure sensor 10.

[0034] As described above, the static pressure of the fluid being measured compresses the interlocking oil O. This compression of the interlocking oil O can cause, for example, damage to the seal member 13 or detachment from the support member 11. This causes the interlocking oil O to leak to the outside of the support member 11. Due to this leak, the diaphragms 12H and 12L are significantly deformed convexly toward the support member 11 by the static pressure from the fluid being measured, and they settle on the stopper surfaces 11HA and 11LA of the support member 11, respectively (see Figure 4). In other words, the static pressure detected by the processing circuit 16 increases. Therefore, in this embodiment, the processing circuit 16 monitors the static pressure detected above, and when the monitored static pressure exceeds a predetermined standard, it detects a leak of the interlocking oil O from the support member 11. As an example, the processing circuit 16 monitors whether the sum of voltage VH and voltage VL exceeds a predetermined threshold, and determines that a leak of the interlocking oil O has occurred when it determines that it has exceeded the threshold. As another example, the processing circuit 16 monitors voltages VH and VL, and checks whether each of them exceeds the same or different preset thresholds. When it determines that the thresholds have been exceeded, it determines that a leak of the interlocking oil O has occurred. When the processing circuit 16 detects a leak of the interlocking oil O, it outputs a message to an external device.

[0035] As described above, according to this embodiment, static pressure is also detected using the diaphragms 12H and 12L that are originally used to detect differential pressure. Therefore, differential pressure and static pressure can be detected with a simple configuration without the need to provide a separate diaphragm for static pressure detection.

[0036] Furthermore, since leaks in the interlocking oil O can be detected based on the detected static pressure, the leak can be detected with a simple configuration that does not require a dedicated circuit and / or mechanism for leak detection. This also reduces the current consumption required for leak detection.

[0037] Furthermore, in this embodiment, static pressure and differential pressure detection, static pressure monitoring, and leak detection can be performed with a simple circuit configuration consisting of two strain gauges S1 and S2 connected in series via node N1 for diaphragm 12H, and two strain gauges S3 and S4 connected in series via node N2 for diaphragm 12L.

[0038] The interlocking oil O also contracts due to its temperature. This contraction can also cause deformation of the diaphragms 12H and 12L. Since this deformation is not caused by static pressure, it reduces the accuracy of static pressure detection. Therefore, as shown in Figure 1, the pressure sensor 10 may further include a temperature sensor 17. The temperature sensor 17 should be positioned so as to be able to directly or indirectly detect the temperature of the interlocking oil O. The processing circuit 16 may correct the static pressure detected above based on the temperature detected by the temperature sensor 17. The processing circuit 16 may use the corrected static pressure as the static pressure of the fluid being measured that it has detected. In other words, the static pressure detected by the processing circuit 16 includes the corrected static pressure.

[0039] As an example of correction, the processing circuit 16 uses a calculation formula or table showing the relationship between temperature and correction value to derive a correction value corresponding to the temperature detected by the temperature sensor 17, and derives the corrected static pressure by performing a calculation using the derived correction value and the static pressure detected above. As another example, the processing circuit 16 may use a calculation formula or table showing the relationship between temperature and static pressure before correction and static pressure after correction to derive the corrected static pressure corresponding to the temperature detected by the temperature sensor 17 and the static pressure detected above.

[0040] The shapes of diaphragms 12H and 12L are arbitrary, but it is preferable to make them the same shape. This reduces crosstalk (static pressure sensitivity when the non-measured fluid is flowing, and differential pressure sensitivity when the measured fluid is not flowing). Alternatively, strain gauges S1 to S4 may be used as a bridge circuit, and a circuit that acquires the difference between potentials VH and VL as the output of the bridge circuit may be provided in the processing circuit 16. In other words, in the processing circuit 16, the difference between potentials VH and VL may be derived by an analog circuit, and the derived difference may be converted from analog to digital and processed by a processor.

[0041] The conversion circuit 15 may be configured such that the direction of deformation of the diaphragm 12H when the voltage VH increases and the direction of deformation of the diaphragm 12L when the voltage VL increases are on different sides. In this case, the processing circuit 16 only needs to detect the differential pressure based on the sum of the voltages VH and VL, and detect the static pressure based on the difference between the voltages VH and VL.

[0042] (Variation 1) The pressure sensor 20 in this modified example has a full-bridge conversion circuit 25, as shown in Figure 5, instead of the conversion circuit 15. The configuration of the pressure sensor 20 will be described below, focusing on the differences from the pressure sensor 10. Any explanations not mentioned below are the same as those for the pressure sensor 10.

[0043] The conversion circuit 25 includes a full-bridge circuit B1 that converts the deformation of the diaphragm 12H into an electrical signal EH, and a full-bridge circuit B2 that converts the deformation of the diaphragm 12L into an electrical signal EL.

[0044] The full-bridge circuit B1 comprises a plurality of bridged strain gauges S11 to S14. Strain gauges S11 and S12 are connected in series, and strain gauges S13 and S14 are connected in series. The pair of strain gauges S11 and S12 and the pair of strain gauges S13 and S14 are connected in parallel. Strain gauges S11 and S14 extend along the radial direction of the diaphragm 12H, and strain gauges S12 and S13 extend along the tangential direction in the circumferential direction of the diaphragm 12H. The full-bridge circuit B1 inputs an electrical signal EH, which represents the voltage VH between node N11 connecting strain gauges S11 and S12 and node N12 connecting strain gauges S13 and S14, to the processing circuit 16 via terminals T11 and T12. The full-bridge circuit B1, i.e., strain gauges S11 to S14, is configured such that the voltage VH is 0V when the diaphragm 12H is not deformed. Furthermore, the full-bridge circuit B1 is configured such that the voltage VH increases as the diaphragm 12H deforms convexly toward the support member 11, and decreases (becomes negative) as the diaphragm 12H deforms convexly toward the opposite side of the support member 11.

[0045] The full-bridge circuit B2 comprises a plurality of bridged strain gauges S21 to S24. Strain gauges S21 and S22 are connected in series, and strain gauges S23 and S24 are connected in series. The pair of strain gauges S21 and S22 and the pair of strain gauges S23 and S24 are connected in parallel. Strain gauges S21 and S24 extend along the radial direction of the diaphragm 12L, and strain gauges S22 and S23 extend along the tangential direction in the circumferential direction of the diaphragm 12L. The full-bridge circuit B2 inputs an electrical signal EL, which represents the voltage VL between node N21 connecting strain gauges S21 and S22 and node N22 connecting strain gauges S23 and S24, to the processing circuit 16 via terminals T21 and T22. The full-bridge circuit B2, i.e., strain gauges S21 to S24, is configured such that the voltage VH is 0V when the diaphragm 12L is not deformed. Furthermore, the full-bridge circuit B2 is configured such that the voltage VL increases as the diaphragm 12L deforms convexly toward the support member 11, and decreases (becomes negative) as the diaphragm 12L deforms convexly toward the opposite side of the support member 11.

[0046] The processing circuit 16 derives differential pressure and static pressure based on electrical signals EH and EL, similar to the embodiment described above. Here, the conversion circuit 15 is configured such that the direction of deformation of the diaphragm 12H when the voltage VH increases and the direction of deformation of the diaphragm 12L when the voltage VL increases are on the same side. Therefore, the processing circuit 16 detects differential pressure based on the difference between voltage VH and voltage VL, and detects static pressure based on the sum of voltage VH and voltage VL, similar to the embodiment described above. The method for deriving differential pressure and static pressure is the same as in the embodiment described above.

[0047] Although the full-bridge circuit complicates the circuit configuration, it allows for larger absolute values ​​of voltages VH and VL compared to the above embodiment. This increases the sensor sensitivity of the pressure sensor 10.

[0048] The conversion circuit 25 may be configured such that the direction of deformation of the diaphragm 12H when the voltage VH increases and the direction of deformation of the diaphragm 12L when the voltage VL increases are on different sides, that is, one side is on the support member 11 side and the other side is on the opposite side. In this case, the processing circuit 16 detects the differential pressure based on the sum of the voltages VH and VL, and detects the static pressure based on the difference between the voltages VH and VL.

[0049] (Modification 2) The pressure sensor 30 in this modified example has a conversion circuit 35 as shown in Figure 6 instead of the conversion circuit 25. The configuration of the pressure sensor 30 will be described below, focusing on the differences from pressure sensors 10 and 20. Any explanations not mentioned below are the same as those for pressure sensors 10 and 20.

[0050] The conversion circuit 35 has a circuit configuration that is the same as the conversion circuit 25 but without the strain gauges S13 and S14. The bridge circuit B2 of the conversion circuit 35 outputs electrical signals EL from nodes N21 and N22. The electrical signals EL include an electrical signal EL+ indicating the voltage VL+ output from node N21 and an electrical signal EL- indicating the voltage VL- output from node N22. Voltages VL+ and VL- change by the same amount in opposite directions from the value when the diaphragm 12L is undeformed. When the diaphragm 12L deforms convexly toward the support member 11 side, voltage VL+ increases and voltage VL- decreases. When the diaphragm 12L deforms convexly toward the opposite side of the support member 11 side, voltage VL+ decreases and voltage VL- increases. Therefore, the direction of deformation of the diaphragm 12H when voltage VH+ increases and voltage VH- decreases is the same as the direction of deformation of the diaphragm 12L when voltage VL increases.

[0051] The processing circuit 16 derives differential pressure and static pressure based on electrical signals EH and EL, similar to the embodiment described above. Here, since the deformation direction of the diaphragm 12H when voltage VH increases and the deformation direction of the diaphragm 12L when voltage VL+ increases are on the same side, the processing circuit 16 can detect differential pressure based on the difference between voltage VH and voltage VL+. Furthermore, since voltage VL+ and voltage VL- change by the same amount in opposite directions from the value when the diaphragm 12L is not deformed, the processing circuit 16 can also detect static pressure based on the difference between voltage VH and voltage VL-. An example of a specific method for deriving differential pressure and static pressure is the same as in the embodiment described above.

[0052] With the above configuration, differential pressure and static pressure can be derived from the difference between the voltage VH indicated by the electrical signal EH and the voltages VL+ and VL- indicated by the electrical signals EL. The voltage difference can be derived with a relatively simpler circuit configuration than the sum. For example, by configuring strain gauges S11, S12, S21, and S22 as a bridge circuit, the differential pressure can be derived based on the difference between voltage VH and voltage VL+. By configuring strain gauges S11, S12, S23, and S24 as a bridge circuit, the differential pressure can be derived based on the difference between voltage VH and voltage VL-. The processing circuit 16 can detect each of the above differences using analog circuits.

[0053] The conversion circuit 35 may be configured such that the direction of deformation of the diaphragm 12H when the voltage VH increases and the direction of deformation of the diaphragm 12L when the voltage VL+ increases (and the voltage VL- decreases) are on different sides, that is, one side is on the support member 11 side and the other side is on the opposite side. In such a case, the differential pressure and static pressure can be derived from the sum of the voltage VH indicated by the electrical signal EH and the voltages VL+ and VL- indicated by the electrical signals EL. Such sums can be derived by software processing, such as a processor (the same applies to other sums).

[0054] The conversion circuit 35 may have a circuit configuration in which strain gauges S23 and S24 are omitted, instead of omitting strain gauges S13 and S14 from the conversion circuit 25. In this case, the electrical signal VH includes electrical signals VH+ and VH- indicating the voltage VH+ from node N11 and the voltage VH- from node N12, respectively, and differential pressure and static pressure may be detected based on the difference or sum of voltage VH+ and voltage VL, and the difference or sum of voltage VH- and voltage VL.

[0055] (Variation 3) The configuration of the conversion circuit is arbitrary. For example, in addition to the strain gauges described above, or in place of some of the strain gauges, a temperature-compensating strain gauge may be provided. Alternatively, some of the strain gauges may be replaced with resistors whose resistance value does not change even when the diaphragm deforms. Such resistors may be provided outside the diaphragm. Elements other than piezoresistive elements (such as load cells) may be used as strain gauges. The conversion circuit may be configured such that when the diaphragms 12H and 12L deform convexly toward the support member 11, both voltage VH and voltage VL (or VL+) decrease. In this case, when detecting a leak of the interlocking oil O, a leak may be detected when the sum of voltages VH and VL becomes smaller than a predetermined threshold, indicating that the static pressure has exceeded a predetermined standard.

[0056] (Modification 4) In the above, the differential pressure and static pressure are derived based on the voltage indicated by the electrical signal. However, the differential pressure and the sum of the pressures may also be derived based on other values ​​indicated by the electrical signal, such as the value of the current that changes due to the deformation of the diaphragm, as indicated by the electrical signal.

[0057] (Experimental variation 6) The configuration or structure of the pressure sensor 10 is arbitrary; for example, at least a part of the processing circuit 16 and the other parts 11-15 may be housed in separate enclosures and positioned far apart from each other. For example, the processor constituting the processing circuit 16 may be located outside the pressure sensor 10. The processing circuit 16 may include an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0058] (Scope of the present invention) Although the present invention has been described above with reference to embodiments and modifications, the present invention is not limited to the above embodiments and modifications. For example, the present invention includes various modifications to the above embodiments and modifications that can be understood by those skilled in the art within the scope of the technical concept of the present invention. The configurations listed in the above embodiments and modifications can be combined as appropriate to the extent that they do not contradict each other. [Explanation of symbols]

[0059] 10...Pressure sensor, 11...Support member, 11A...First layer, 11B...Second layer, 11D...Through hole, 11E...Communication passage, 11H...Diaphragm chamber, 11HA...Stopper surface, 11L...Diaphragm chamber, 11LA...Stopper surface, 12...Diaphragm layer, 12H...Diaphragm, 12L...Diaphragm, 13...Sealing member, 14...Pressure sensing member, 14H...Pressure sensing path, 14L...Pressure sensing path, 15...Conversion circuit, 16...Processing circuit, 17...Temperature sensor, 20,30 ...pressure sensor, 25, 35...conversion circuit, B1...full bridge circuit, B2...full bridge circuit, HP...pressure, LP...pressure, N1...node, N2...node, N11...node, N12...node, N21...node, N22...node, O...interlocking oil, S1~S4, S11~S14, S21~S24...strain gauge, T1...terminal, T2...terminal, T11...terminal, T12...terminal, T21...terminal, T22...terminal, VS...DC power supply, V...drive voltage.

Claims

1. A first diaphragm that deforms upon receiving a first pressure of a fluid, A second diaphragm that deforms upon receiving the second pressure of the fluid, A conversion circuit that converts the deformation of the first diaphragm into a first electrical signal and the deformation of the second diaphragm into a second electrical signal, A support member that supports the first diaphragm and the second diaphragm, the support member being filled with a fluid that links the deformation of the first diaphragm and the deformation of the second diaphragm, The system includes a processing circuit that detects, based on the first and second electrical signals, the differential pressure between the first pressure and the second pressure at which the first and second diaphragms deform convexly to different sides, and the static pressure of the fluid at which both the first and second diaphragms deform convexly to the same side. The processing circuit detects a leak of the interlocking fluid from the support member when the detected static pressure exceeds a predetermined standard. Pressure sensor.

2. A first diaphragm that deforms upon receiving a first pressure of a fluid, A second diaphragm that deforms upon receiving the second pressure of the fluid, A conversion circuit that converts the deformation of the first diaphragm into a first electrical signal and the deformation of the second diaphragm into a second electrical signal, A support member that supports the first diaphragm and the second diaphragm, the support member being filled with a fluid that links the deformation of the first diaphragm and the deformation of the second diaphragm, The system includes a processing circuit that detects, based on the first and second electrical signals, the differential pressure between the first pressure and the second pressure at which the first and second diaphragms deform convexly to different sides, and the static pressure of the fluid at which both the first and second diaphragms deform convexly to the same side. The processing circuit detects the differential pressure based on either the sum or the difference between the first value indicated by the first electrical signal and the second value indicated by the second electrical signal, and detects the static pressure based on the other of the sum and the difference between the first value and the second value. The aforementioned conversion circuit is Two first strain gauges connected in series via a first node convert the deformation of the first diaphragm into the first electrical signal, The device comprises two second strain gauges connected in series via a second node, which convert the deformation of the second diaphragm into the second electrical signal, The first node outputs the first electrical signal, The second node outputs the second electrical signal. Pressure sensor.

3. A first diaphragm that deforms upon receiving a first pressure of a fluid, A second diaphragm that deforms upon receiving the second pressure of the fluid, A conversion circuit that converts the deformation of the first diaphragm into a first electrical signal and the deformation of the second diaphragm into a second electrical signal, A support member that supports the first diaphragm and the second diaphragm, the support member being filled with a fluid that links the deformation of the first diaphragm and the deformation of the second diaphragm, The system includes a processing circuit that detects, based on the first and second electrical signals, the differential pressure between the first pressure and the second pressure at which the first and second diaphragms deform convexly to different sides, and the static pressure of the fluid at which both the first and second diaphragms deform convexly to the same side. The aforementioned conversion circuit is A first full-bridge circuit comprising multiple bridge-connected strain gauges, which converts the deformation of the first diaphragm into a first electrical signal, A second full-bridge circuit comprising multiple bridge-connected strain gauges, which converts the deformation of the second diaphragm into the second electrical signal, The processing circuit detects the differential pressure based on either the sum or the difference between the first value indicated by the first electrical signal and the second value indicated by the second electrical signal, and detects the static pressure based on the other. Pressure sensor.

4. A first diaphragm that deforms upon receiving a first pressure of fluid, A second diaphragm that deforms upon receiving the second pressure of the fluid, A conversion circuit that converts the deformation of the first diaphragm into a first electrical signal and the deformation of the second diaphragm into a second electrical signal, A support member that supports the first diaphragm and the second diaphragm, the support member being filled with a fluid that links the deformation of the first diaphragm and the deformation of the second diaphragm, The system includes a processing circuit that detects, based on the first and second electrical signals, the differential pressure between the first pressure and the second pressure at which the first and second diaphragms deform convexly to different sides, and the static pressure of the fluid at which both the first and second diaphragms deform convexly to the same side. The second electrical signal includes the second-first electrical signal and the second-second electrical signal, The aforementioned conversion circuit is Two third strain gauges connected in series via a third node convert the deformation of the first diaphragm into the first electrical signal, Two fourth strain gauges connected in series via a fourth node convert the deformation of the second diaphragm into the second-first electrical signal, The device comprises two fifth strain gauges connected in series via a fifth node, which convert the deformation of the second diaphragm into the second-second electrical signal, The third node outputs the first electrical signal, The fourth node outputs the second-first electrical signal, The fifth node outputs the second-2 electrical signal, The two fourth strain gauges and the two fifth strain gauges are configured such that, due to the deformation of the second diaphragm, the value of the second-first electrical signal and the value of the second-second electrical signal change by the same amount in opposite directions from the value of the second diaphragm when it is not deformed. The aforementioned processing circuit is The differential pressure is detected based on either the sum or the difference between the first value indicated by the first electrical signal and the value of 2-1. The static pressure is detected based on either the sum or the difference between the first value and the second-second value. Pressure sensor.

5. Further comprising a temperature sensor for detecting the temperature of the interlocking fluid, The processing circuit corrects the static pressure based on the temperature of the interlocking fluid detected by the temperature sensor. A pressure sensor according to any one of claims 1 to 4.

Images