JP2012189349A - Flow velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow velocity sensor especially in which one of a plurality of pressure-sensitive elements is not affected by change in pressure of the other pressure-sensitive element.SOLUTION: A flow velocity sensor 10 of the present invention comprises: a first diaphragm 20a for sealing a first opening of a storage space of a housing; a second diaphragm 20b for sealing a second opening of the storage space; and pressure-sensitive elements 40 that have pressure-sensitive parts and pairs of base parts, and regard directions connecting the pairs of base parts as detection axes. In the pressure-sensitive elements 40, pairs of base parts are connected to support parts of the diaphragms, the detection axes are parallel to pressure receiving surfaces of the diaphragms. The first diaphragm 20a receives pressure introduced from a dynamic pressure introduction port directed to a flow direction of fluid, and the second diaphragm 20b receives pressure introduced from a static pressure introduction port directed to a direction nearly perpendicular to the flow direction of fluid. Heat insulation parts 60 are provided on pressure receiving surface sides of the first diaphragm 20a and the second diaphragm 20b.

Description

  The present invention particularly relates to a flow rate sensor using a piezoelectric vibration element as a pressure sensitive element.

  Conventionally, a pressure sensor using a piezoelectric vibrator as a pressure-sensitive element is known for a water pressure gauge, a barometer, a differential pressure gauge, and the like. For example, the piezoelectric vibration element is formed on an electrode pattern such as an excitation electrode and an extraction electrode on a plate-like piezoelectric substrate and vibrates at a specific resonance frequency. The piezoelectric vibration element is provided at both ends of the vibration unit and is fixed to the diaphragm. The direction of the line connecting the pair of bases to each other is taken as the force detection axis. And if a to-be-measured pressure is received in the pressure receiving part of a diaphragm from the direction orthogonal to the direction of a detection axis, a pressure receiving part will bend. Accordingly, when a force is applied to the piezoelectric vibrator, a tensile stress is generated in the direction of the detection axis in the piezoelectric vibrator, so that the resonance frequency changes. The pressure value of the measured pressure can be detected from the change in the resonance frequency.

  As an example of such a pressure sensor, a pressure sensor disclosed in Patent Document 1 is known. The pressure sensor disclosed in Patent Document 1 has a first case part having openings at both ends and the openings communicating with each other, and the openings at both ends of the first case part are hermetically sealed. The first and second diaphragm portions, which form a space and have a first joint portion, a thin portion, a first holding portion, and a first central plate portion from the outside to the center portion, and the first and second diaphragm portions It is comprised from the 1st and 2nd double tuning fork vibrating piece mounted in each 1st and 2nd holding | maintenance part.

JP 2010-243276 A JP-A-6-66656 JP-A-8-86799 JP-A-8-146027

  When measuring the flow velocity of a fluid such as a river, a weir, a dam, or a water channel using such a pressure sensor, as disclosed in Patent Documents 2 to 4, the casing is exposed to the fluid. A first cap provided with a pressure sensor and a first cap provided with a dynamic pressure introduction port for introducing a dynamic pressure Pa and a static pressure introduction port for introducing a static pressure Pb on the pressure receiving surfaces of the two diaphragms, respectively. It becomes the structure which attaches 2 caps. As described above, this pressure sensor detects the dynamic pressure Pa and the static pressure Pb received by the two diaphragms, respectively.

  However, when the flow rate sensor is placed in the water to measure the flow rate of the fluid, the temperature of the atmosphere inside the container in which the pressure-sensitive element is accommodated according to the temperature change of the water temperature in the water with respect to the flow rate detection accuracy of the flow rate sensor. There is a limit to the follow-up ability that changes. For this reason, there arises a problem that a difference between the temperature of the fluid and the temperature of the atmosphere in the container occurs, and the oscillation frequency of the pressure-sensitive element associated with the pressure change cannot be measured accurately. After the flow rate sensor was placed in water, the flow rate could not be measured for a predetermined period until the temperature in the housing stabilized.

  Accordingly, the present invention focuses on the problems of the prior art described above, and an object thereof is to provide a flow rate sensor that can avoid measurement errors due to temperature changes in the measurement environment. It is another object of the present invention to provide a flow rate sensor that can maintain the temperature inside the housing at a set temperature without being affected by temperature changes in the measurement environment.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples.
[Application Example 1] A casing exposed to a fluid, a first storage space and a second storage space provided in the casing, and a dynamic pressure inlet provided in a tip portion of the casing And a static pressure introduction port provided in a side surface portion of the housing, the dynamic pressure introduction port is directed in a direction in which the fluid flows, and the static pressure introduction port is substantially orthogonal to the direction in which the fluid flows. A flow rate sensor directed in a direction, wherein a first diaphragm for sealing a first opening of the first accommodation space and a second opening for sealing a second opening of the second accommodation space are provided. Two diaphragms, a first pressure-sensitive part housed in the first housing space, and a pair of first base parts connected to both ends of the first pressure-sensitive part. A first pressure-sensitive element having a first detection axis as a direction connecting the first bases, and a second pressure-sensitive part housed in the second housing space, A second pressure-sensitive element having a pair of second bases connected to both ends of the second pressure-sensitive part and having a direction connecting the pair of second bases as a second detection axis; The first pressure-sensitive element connects the first base to a support portion of the first diaphragm, and the first detection axis is parallel to the pressure-receiving surface of the first diaphragm. The second pressure-sensitive element connects the second base to a support portion of the second diaphragm, the second detection axis is parallel to the pressure-receiving surface of the second diaphragm, The first diaphragm receives the pressure introduced from the dynamic pressure introduction port, the second diaphragm receives the pressure introduced from the static pressure introduction port, and the first and second diaphragms A flow rate sensor characterized in that a heat insulating part is provided on the pressure receiving surface side.
With the above configuration, the heat conduction is cut off from the pressure receiving surface of the diaphragm to which the pressure introduced from the dynamic pressure introduction port or the static pressure introduction port is applied, and the temperature of the atmosphere of the accommodation space is affected by the temperature change of the water temperature. It can be made difficult to receive. It is possible to accurately measure a change in oscillation frequency accompanying a pressure change without the pressure sensitive element being affected by the temperature change of the water temperature.

Application Example 2 The flow velocity sensor according to Application Example 1, wherein a heat insulating layer is provided on the side wall of the casing.
With the above configuration, the heat conduction is blocked by the heat insulating layer formed on the housing, and the influence of the temperature change of the fluid from the side surface can be avoided. Therefore, it is possible to accurately measure the change in the oscillation frequency accompanying the pressure change without being affected by the temperature change.

Application Example 3 The first pressure-sensitive element includes a first temperature detecting pressure-sensitive element integrated with at least one base of the pair of first bases, and the second The pressure sensitive element includes a second temperature detecting pressure sensitive element integrated with at least one of the pair of second base parts, and the first and second temperature detecting pressure sensitive elements. The flow velocity sensor according to Application Example 1 or Application Example 2, further comprising a temperature compensation circuit that corrects temperature characteristics of the first and second pressure-sensitive elements based on the detected value.
Thereby, the error due to the temperature change can be corrected, and the pressure detection accuracy of the pressure introduced from the dynamic pressure introduction port or the static pressure introduction port can be increased to improve the pressure sensitivity.

Application Example 4 Based on the heater resistance installed in the first and second accommodation spaces and the detection values of the first and second temperature detecting pressure sensing elements, the first and second accommodation spaces A flow rate sensor according to Application Example 3, further comprising: a temperature control circuit that controls a room temperature.
With the above configuration, the internal space of the first and / or second accommodation space can be maintained at a predetermined set temperature. Therefore, it is possible to accurately measure the change in the oscillation frequency accompanying the pressure change without being affected by the temperature change.

It is sectional drawing which shows the structure outline of the flow velocity sensor which concerns on 1st Embodiment. It is a partial exploded perspective view showing the composition outline of the flow rate sensor concerning a 1st embodiment. It is explanatory drawing of the measuring method using the flow velocity sensor of this invention. It is an example figure which installed the flow velocity sensor of a 1st embodiment in fluid. It is sectional drawing which shows the structure outline of the flow-velocity sensor which concerns on 2nd Embodiment. It is sectional drawing which shows the structure outline of the flow-velocity sensor which concerns on 3rd Embodiment. It is a partial exploded perspective view showing the composition outline of the flow rate sensor concerning a 3rd embodiment. It is sectional drawing which shows the structure outline of the flow velocity sensor which concerns on 4th Embodiment.

  Embodiments of the flow rate sensor of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a flow velocity sensor according to the first embodiment. FIG. 2 is a partial cross-sectional perspective view showing a schematic configuration of the flow velocity sensor according to the first embodiment. The flow rate sensor 10 according to the first embodiment has a housing 12, a diaphragm 20, a partition wall 13, a pressure sensitive element 40, an oscillation circuit 50, and a cap 52 as main basic configurations.

  The housing 12 is a cylindrical container, and is provided with first and second openings 17a and 17b that support peripheral edges 20e of a pair of diaphragms 20 described later on both end faces. The housing 12 serves as a housing that is exposed to the fluid. Moreover, the housing 12 forms the partition 13 parallel to an end surface in the center of the inside. Thereby, the cross section of the housing 12 is formed in a substantially H-shape as illustrated. The housing 12 is divided into two parts by a partition wall 13 to form first and second accommodation spaces 14 and 15. The housing 12 is preferably formed of a metal such as stainless steel. The partition wall 13 is preferably formed of the same metal as the housing 12, and can be formed in the housing 12 by welding or the like.

  The diaphragm 20 seals the first and second openings 17 a and 17 b of the housing 12. The diaphragm 20 has one main surface facing the outside of the housing 12 as a pressure receiving surface 22, and the pressure receiving surface 22 has a thin portion 20 c that bends and deforms under the pressure of a measured pressure environment (for example, liquid). The thin portion 20c is bent and deformed inwardly or outwardly of the housing 12 to transmit a tensile force to the pressure sensitive element 40. The diaphragm 20 is composed of first and second diaphragms 20a and 20b.

  Each of the first and second diaphragms 20a and 20b is formed in the housing 12 with a thin portion 20c that is bent and deformed by an external pressure, and is thicker than the thin portion 20c on the outer periphery of the thin portion 20c. A peripheral edge portion 20e that is joined to the inner wall of the opening and that does not bend and deform due to pressure from the outside. In addition, a pair of support portions 20d that are thicker than the thin portion 20c are formed in the thin portion 20c. The pair of support portions 20 d are formed at positions that are symmetric with respect to the center of gravity of the diaphragm 20.

  The material of the diaphragm 20 is preferably a material having excellent corrosion resistance such as a metal such as stainless steel or ceramic. For example, in the case of forming with metal, the metal base material may be formed by pressing. The diaphragm 20 may be coated on the surface exposed to the outside so as not to be corroded by liquid or gas. For example, in the case of the metal diaphragm 20, a nickel compound may be coated. Further, the peripheral edge portion 20e and the housing 12 can be connected by welding or the like.

  The pressure-sensitive element 40 has a vibrating arm 40e serving as a pressure-sensitive portion, a first base portion 40c and a second base portion 40d formed at both ends thereof, and is made of a piezoelectric material such as quartz, lithium niobate, lithium tantalate, or the like. Is formed. The pressure sensitive element 40 is composed of first and second pressure sensitive elements 40a and 40b. The first and second pressure sensitive elements 40a and 40b are connected to a pair of support portions 20d of the first and second diaphragms 20a and 20b, respectively. The pressure-sensitive element 40 is arranged so that its longitudinal direction, that is, the detection axis in which the first base portion 40 c and the second base portion 40 d are aligned is parallel to the pressure-receiving surface of the diaphragm 20. Since the pressure sensitive element 40 is fixed by the pair of support portions 20d as described above, the pressure sensitive element 40 does not bend in a direction other than the detection axis direction even if it receives a force due to the displacement of the diaphragm 20. The displacement in the axial direction acts on the pressure sensitive element as it is, and the decrease in sensitivity of the pressure sensitive element 40 in the detection axial direction can be suppressed.

  An excitation electrode (not shown) is formed on the vibrating arm 40e of the pressure sensitive element 40, and has an electrode portion (not shown) electrically connected to the excitation electrode (not shown). The pressure sensitive element 40 vibrates at an inherent resonance frequency by an AC voltage supplied from an oscillation circuit (IC) 50 described later. The pressure sensitive element 40 changes its resonance frequency by receiving a tensile stress from the longitudinal direction. In the present embodiment, a double tuning fork vibrator can be applied as the vibrating arm 40e serving as a pressure-sensitive portion. The double tuning fork vibrator has a characteristic that when a tensile stress is applied to the two vibrating beams, which are the vibrating arms 40e, the resonance frequency changes substantially in proportion to the applied stress. And the double tuning fork type piezoelectric resonator element is superior in resolution capability to detect a slight pressure difference because the resonance frequency change with respect to the tensile stress is extremely large and the variable range of the resonance frequency is large compared to the thickness shear vibrator. It is suitable for pressure sensors. When the double tuning fork type piezoelectric vibrator is subjected to a tensile stress, the amplitude width of the vibrating arm is reduced, so that the resonance frequency is increased.

  In the present embodiment, not only a pressure-sensitive part having two vibration beams but also a pressure-sensitive part composed of a single vibration beam (single beam) can be applied. If the pressure-sensitive part (vibrating arm 40e) is configured as a single beam type vibrator, the displacement is doubled when subjected to the same stress in the longitudinal direction (detection axis direction). A highly sensitive pressure sensor can be obtained. Of the above-described piezoelectric materials, quartz having excellent temperature characteristics is desirable for a piezoelectric substrate of a double tuning fork type or single beam type piezoelectric vibrator.

  The oscillation circuit 50 is a circuit that causes the pressure-sensitive element 40 to oscillate. The oscillation circuit 50 includes first and second oscillation circuits 50a and 50b, which are attached to one and the other main surfaces 13a and 13b of the partition wall 13, respectively. The first and second oscillation circuits 50a and 50b are electrically connected to the first and second pressure sensitive elements 40a and 40b via bonding wires (not shown), respectively, and oscillate the pressure sensitive element 40. Can be made.

  The cap 52 is a dish-shaped container formed so as to have substantially the same diameter as the housing 12. The cap 52 includes first and second caps 52a and 52b, and is attached to the housing 12 so as to cover the pressure receiving surfaces 22 of the first and second diaphragms 20a and 20b. In addition, the attachment method of the 1st and 2nd caps 52a and 52b can apply the structure which forms an external thread part and an internal thread part in a connection location, and is screwed together, a welding means, an adhesion | attachment means, etc.

  The first cap 52a has a dynamic pressure inlet 54 through which dynamic pressure is introduced. One dynamic pressure inlet 54 of the present embodiment is formed on the wall surface of the first diaphragm 20a facing the pressure receiving surface 22. The dynamic pressure inlet 54 may be located anywhere in the first cap 52a as long as it is directed toward the upstream side of the fluid. The second cap 52b is formed with a static pressure inlet 56 through which a static pressure is introduced. Two static pressure introduction ports 56 of the present embodiment are formed on the wall surface perpendicular to the pressure receiving surface 22 of the second diaphragm 20b. Note that the static pressure inlet 56 may be located anywhere in the second cap 52b as long as dynamic pressure is not introduced.

  In addition, silicon oil to be the heat insulating portion 60 is applied to the pressure receiving surfaces of the first and second diaphragms 20a and 20b. The heat insulation part 60 can be formed by filling from the dynamic pressure inlet 54 or the static pressure inlet 56. Alternatively, before the first and second caps 52 a and 52 b are connected to the housing 12, the heat insulating portion 60 is formed on the pressure receiving surface of the diaphragm 20, and then the first and second caps 52 a and 52 b are attached to the housing 12. You may do it.

  In addition to silicon oil, the heat insulating part 60 is not limited to this, as long as it has a low heat transfer coefficient, does not mix with water, and can cover the pressure-receiving surface of the diaphragm 20. May be applied.

  In the flow velocity sensor 10 according to the first embodiment having the above-described configuration, the opening of the housing 12 is closed by a pair of diaphragms 20 and the central portion is divided by a partition wall 13. For this reason, the first diaphragm 20a and the first pressure-sensitive element 40a are disposed in the first housing space 14, and the second diaphragm 20b and the second pressure sensor 40a are disposed in the second housing space 15. The pressure sensitive element 40b is arranged, and the first and second accommodation spaces 14, 15 become a sealed space separated from each other. The measurement accuracy of the pressure sensitive element can be improved by reducing the pressure inside the first and second accommodation spaces 14 and 15.

  The operation of the flow velocity sensor 10 of the first embodiment having the above configuration will be described below. FIG. 3 is an explanatory view of a measuring method using the flow rate sensor of the present invention. The dynamic pressure inlet 54 of the flow velocity sensor 10 of the first embodiment is installed in a stable state so as to face the direction in which water (fluid) flows in a river or the like. At this time, the static pressure introduction port 56 is installed at a position facing a direction substantially perpendicular to the direction in which the fluid flows. Water is introduced into the first cap 52a from the opening of the dynamic pressure introduction port 54 of the flow rate sensor 10, and pressure generated in the room is applied to the first diaphragm 20a. Due to this pressure, a tensile force acts on the first pressure-sensitive element 40a, and the oscillation frequency of the element changes due to the tensile stress generated inside. The pressure can be detected by detecting the amount of change.

  On the other hand, the static pressure inlet 56 of the flow rate sensor 10 has two openings formed on a straight line, and water flows into the second cap 52b from the openings. In the second cap 52b, the pressure generated in the room is applied to the second diaphragm 20b. As a result, a tensile force acts on the second pressure-sensitive element 40b, and the oscillation frequency of the element changes due to the tensile stress generated inside by the force. The pressure can be detected by detecting the amount of change.

By obtaining the difference between the obtained pressures, the dynamic pressure is obtained, and the flow velocity of the fluid can be obtained by Bernoulli's theorem shown below.
The flow rate when atmospheric pressure is added to the fluid is
Pa: Pressure introduced from the dynamic pressure inlet and received by the first diaphragm Pb: Pressure introduced from the static pressure inlet and received by the second diaphragm P0: Atmospheric pressure P1: Static pressure P2: Dynamic pressure V: Fluid velocity g: Gravitational acceleration w: Fluid unit weight

Here, if the fluid is water, the density of water is 1, so
w = 1
Than,
Therefore

Here, if the correction coefficient according to the shape of the dynamic pressure hole is k,
The flow velocity V is
It can ask for.

In addition, when the atmospheric pressure is not added to the fluid,

Here, if the fluid is water, the density of water is 1, so
w = 1
Than,
Therefore

Here, if the correction coefficient according to the shape of the dynamic pressure hole is k,
The flow velocity V is
It can ask for.

  According to the flow velocity sensor 10 of the first embodiment having the above configuration, when the sensor body is installed in the water flow and the temperature change of the water temperature occurs, the temperature change transmitted from the pressure receiving surface 22 of the diaphragm 20 that comes into direct contact with the fluid. Is blocked by the heat insulating portion 60, and heat conduction does not occur to the accommodating space 18 in the housing 12. Therefore, even when the temperature of the water temperature changes when measuring the dynamic pressure and the static pressure, the heat can be shut off via the heat insulating portion 60. Thereby, the pressure-sensitive element 40 is not affected by the temperature change of the water temperature, and the change of the oscillation frequency accompanying the pressure change can be accurately measured.

FIG. 4 is an example diagram in which the flow velocity sensor of the first embodiment is installed in a fluid.
As illustrated, the flow rate sensor 10 is provided inside the housing 110. The casing 110 has a streamlined overall shape, and is provided with a tail 112 at the rear end. A dynamic pressure introduction port 114 is provided at the front end of the housing 110 in the direction in which the fluid flows. Further, a static pressure introduction port 116 is provided on the side surface of the housing 110 in a direction substantially perpendicular to the direction in which the fluid flows. On the other hand, the first and second caps 52c, 52d of the fluid sensor have one opening on the wall surface facing the pressure receiving surface of the first or second diaphragm 20a, 20b. The dynamic pressure inlet 114 is provided with a pipe 118 connected to the first cap 52 c of the flow rate sensor 10. The static pressure introduction port 116 is provided with a pipe 119 connected to the second cap 52d of the flow rate sensor 10. When the casing 110 is exposed to a fluid, the flow velocity sensor 10 having such a configuration is arranged such that the tip portion faces the upstream side and the tail blade 112 side faces the downstream side. At this time, the dynamic pressure introduction port 114 is arranged toward the flow in the fluid, and the static pressure introduction port 116 is easily arranged in a direction substantially perpendicular to the flow of the fluid. Therefore, the pressure introduced from the dynamic pressure introduction port or the static pressure introduction port can be detected by the first or second diaphragm 20a, 20b.

FIG. 5 is a cross-sectional view showing a schematic configuration of a flow velocity sensor according to the second embodiment.
In the flow velocity sensor 100 according to the second embodiment, a heat insulating layer 70 is formed on the side wall of the housing 120. Other configurations are the same as those of the flow velocity sensor 10 according to the first embodiment, and the same reference numerals are given and detailed description thereof is omitted.

  In the flow rate sensor 100 of the second embodiment, a cylindrical sealed space serving as the heat insulating layer 70 is formed on the side surface of the housing 120, and the inside of the sealed space is held in a vacuum. For this reason, between the inner side and the outer side of the housing 120, the vacuum sealed space plays a role of a heat insulating material, and heat conduction does not occur. Therefore, a change in the oscillation frequency of the pressure sensitive element 40 does not occur due to a temperature change in the measurement environment of the flow velocity sensor 100, and an accurate pressure measurement can be performed.

  According to the flow velocity sensor 100 of the second embodiment having the above-described configuration, when the temperature change of the water temperature occurs when the sensor body is installed in the water flow, the temperature change from the pressure receiving surface 22 of the diaphragm 20 that directly contacts the fluid. Is blocked by the heat insulating portion 60, and the temperature change from the side surface of the housing 120 is blocked by the heat insulating layer 70, so that heat conduction does not occur. Therefore, when measuring the dynamic pressure and the static pressure, heat can be shut off via the heat insulating portion 60 and the heat insulating layer 70 of the housing 12 even if the temperature of the water temperature changes. As a result, the pressure sensitive element 40 is not affected by the temperature change of the measurement environment, and the change of the oscillation frequency accompanying the pressure change can be measured accurately.

  FIG. 6 is a sectional view showing a schematic configuration of a flow velocity sensor according to the third embodiment. FIG. 7 is a partially exploded perspective view showing a schematic configuration of the flow velocity sensor according to the third embodiment. The flow rate sensor 200 according to the third embodiment is provided with temperature sensors in the first and second accommodation spaces 14 and 15. Other configurations are the same as the configuration of the flow velocity sensor 100 of the second embodiment, and the same reference numerals are given and detailed description thereof is omitted.

  In the flow velocity sensor 200 according to the third embodiment, the pressure detection element 80 for temperature detection is integrated with the first and second pressure detection elements 40a and 40b for pressure detection. The first pressure-sensitive element 40a is formed integrally with at least one of the pair of base portions 40c and 40d (base portion 40d in the present embodiment), and has a resonance frequency due to a temperature change of the first housing space 14. There is provided a first temperature detecting pressure sensing element 80a that changes. The second pressure-sensitive element 40b is formed integrally with at least one of the pair of base portions 40c and 40d (the base portion 40d in the present embodiment), and has a resonance frequency due to a temperature change in the second housing space 15. Is provided with a second pressure sensing element 80b for temperature detection. The first and second temperature detecting pressure sensing elements 80a and 80b having such a configuration are configured such that stress due to the bending of the flexible portion 20d of the diaphragm 20 is not applied. Note that an oscillation circuit (not shown) for oscillating the elements is attached to each of the first and second temperature detecting pressure sensing elements 80a and 80b.

  A temperature compensation circuit 82 is attached to the first and second accommodation spaces 14 and 15. The temperature compensation circuit 82 includes first and second temperature compensation circuits 82a and 82b. The first and second temperature compensation circuits 82 a and 82 b are attached to one and the other main surfaces 13 a and 13 b of the partition wall 13. The temperature compensation circuit 82 corrects the temperature characteristics of the first and second pressure sensing elements 40a and 40b for pressure detection based on the measured values of the first and second temperature sensing elements 80a and 80b. Is going. The temperature compensation circuit 82 may be formed integrally with the oscillation circuit 50 together with an oscillation circuit for oscillating the temperature detecting pressure sensitive element 80.

  When measuring the pressure introduced from the dynamic pressure inlet or the static pressure inlet, the flow velocity sensor 200 according to the third embodiment having the above-described configuration sets the temperature in the first and second housing spaces 14 and 15 to the first and second. The detection is performed by the second temperature detecting pressure sensing elements 80a and 80b. This temperature measurement value is input to the temperature compensation circuit 82, and the first and second pressure sensing elements 40a, 40b for pressure detection are based on the difference between the set temperature or the initial temperature of the storage containers 14, 15 and the measured temperature. The frequency temperature characteristics of are corrected.

According to the flow rate sensor 200 of the third embodiment, it is possible to improve the pressure sensitivity by correcting the error due to the temperature change and increasing the pressure detection accuracy of the dynamic pressure and the static pressure. Further, the temperature sensor can be easily attached, and the entire sensor can be reduced in size.
Note that the temperature detection pressure-sensitive element 80 and the temperature compensation circuit 82 of the present embodiment may be applied to the flow velocity sensor 10 of the first embodiment.

FIG. 8 is a cross-sectional view showing a schematic configuration of a flow velocity sensor according to the fourth embodiment.
In the flow velocity sensor 300 according to the fourth embodiment, a heater resistor 90 and a temperature control circuit 92 are attached in the first and second accommodation spaces 14 and 15. Other configurations are the same as the configuration of the flow rate sensor 200 of the third embodiment, and the same reference numerals are given and detailed description is omitted.

  In the flow rate sensor 300 of the fourth embodiment, a first heater resistor 90 a and a first temperature control circuit 92 a are attached to one main surface 13 a of the partition wall 13. A second heater resistor 90b and a second temperature control circuit 92b are attached to the other main surface 13b of the partition wall 13. As the heater resistor 90, for example, a ceramic resistor element can be used. The first temperature control circuit 92a is electrically connected to the first heater resistor 90a, the first temperature detecting pressure sensitive element 80a, and the first oscillation circuit 50a. The second temperature control circuit 92b is electrically connected to the second heater resistor 90b, the second pressure sensing element 80b for temperature detection, and the second oscillation circuit 50b.

The flow velocity sensor 300 according to the fourth embodiment having the above-described configuration heats the interiors of the first and second accommodation spaces 14 and 15 by the heater resistor 90, and also uses the temperature detecting pressure sensitive element 80 to provide the first and second accommodation spaces. The temperature inside 14 and 15 is detected. The temperature control circuit 92 controls the heater heating of the heater resistor 90 so that the measured temperature falls within a predetermined set temperature range. The temperature compensation circuit 82 detects a minute temperature error in the set temperature range based on the measured value of the temperature detecting pressure sensitive element 80 and corrects the frequency temperature characteristic of the pressure sensitive element 40. .
Thereby, the inside of the 1st and 2nd accommodation space 14 and 15 thermally insulated by the heat insulation part 60 and the heat insulation layer 70 can be maintained at predetermined | prescribed temperature.

  According to the flow rate sensor 300 of the fourth embodiment, the internal spaces of the first and second accommodation spaces 14 and 15 can be maintained at a predetermined set temperature. Therefore, it is possible to accurately measure the change in the oscillation frequency accompanying the change in the dynamic pressure and the static pressure without being affected by the temperature change in the measurement environment. In addition, the housing 120 is less affected by the temperature from the outside due to the heat insulating portion 60 and the heat insulating layer 70, and can suppress diffusion of heat of the heater resistor 90. Therefore, it is possible to accurately measure the change of the oscillation frequency accompanying the pressure change without being affected by the external temperature change.

10, 100, 200, 300, 400 ......... flow velocity sensor, 12,120 ......... housing, 13 ......... partition wall, 13a ......... one main surface, 13b ......... the other main surface, 14 ... ... 1st accommodation space, 15 ......... 2nd accommodation space, 20 ......... Diaphragm, 20a ......... 1st diaphragm, 20b ...... 2nd diaphragm, 20c ......... Thin part, 20d ... ...... Supporting part, 20e ... Peripheral part, 22 ......... Pressure-receiving surface, 40 ......... Pressure-sensitive element, 40a ...... First pressure-sensitive element, 40b ......... Second pressure-sensitive element, 40c ......... first base, 40d ......... second base, 40e ......... vibrating arm, 50 ......... oscillation circuit, 52 ......... cap, 52a ......... first cap, 52b ......... Second cap 54 ... Dynamic pressure inlet 56 56 Static pressure inlet 60 Insulation , 70... Thermal insulation layer, 80... Temperature sensing pressure sensing element, 80 a... First temperature sensing pressure sensing element, 80 b. ... Temperature compensation circuit, 82a ......... First temperature compensation circuit, 82b ......... Second temperature compensation circuit, 90 ......... Heater resistance, 90a ......... First heater resistance, 90b ......... Second Heater resistance, 92... Temperature control circuit, 92 a... First temperature control circuit, 92 b.

Claims (4)

A housing exposed to the fluid;
A first accommodation space and a second accommodation space provided in the housing;
A dynamic pressure inlet provided at the tip of the housing;
A static pressure inlet provided in a side surface of the housing;
With
Directing the dynamic pressure inlet in the direction of flow of the fluid;
A flow rate sensor in which the static pressure inlet is directed in a direction substantially perpendicular to the direction in which the fluid flows,
A first diaphragm for sealing the first opening of the first accommodation space;
A second diaphragm for sealing the second opening of the second accommodation space;
The pair of first base portions, which are housed in the first housing space, have a first pressure sensing portion, and a pair of first base portions connected to both ends of the first pressure sensing portion. A first pressure sensitive element whose first detection axis is the direction connecting
A pair of second bases, which are housed in the second housing space and have a second pressure sensing part and a pair of second bases connected to both ends of the second pressure sensing part; A second pressure sensitive element whose second detection axis is a direction connecting the two,
Have
The first pressure sensitive element connects the first base to a support portion of the first diaphragm, and the first detection axis is parallel to a pressure receiving surface of the first diaphragm,
The second pressure sensitive element connects the second base to a support portion of the second diaphragm, and the second detection axis is parallel to the pressure receiving surface of the second diaphragm,
The first diaphragm receives the pressure introduced from the dynamic pressure inlet,
The second diaphragm receives pressure introduced from the static pressure inlet,
A flow rate sensor characterized in that a heat insulating portion is provided on the pressure receiving surface side of the first and second diaphragms.   The flow rate sensor according to claim 1, wherein a heat insulating layer is provided on a side wall of the casing. The first pressure sensitive element has a first temperature detecting pressure sensing element integrated with at least one of the pair of first base parts,
The second pressure-sensitive element has a second temperature-sensitive element for temperature detection integrated with at least one of the pair of second base parts,
2. A temperature compensation circuit for correcting temperature characteristics of the first and second pressure sensitive elements based on detection values of the first and second temperature detecting pressure sensitive elements. The flow rate sensor according to claim 2. Heater resistors installed in the first and second accommodation spaces;
A temperature control circuit for controlling the indoor temperature of the first and second accommodation spaces based on the detection values of the first and second temperature detecting pressure sensing elements;
The flow rate sensor according to claim 3, further comprising: