JP2010276534A - Fluid pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pressure sensor not causing a fluid that is a measuring object to stagnate, preventing contamination from arising, and allowing the diameter of a pipe to be freely chosen, with the measuring object fluid flowing within the pipe. <P>SOLUTION: This fluid pressure sensor includes the pipe allowing the fluid to flow therewithin and a pressure sensing part comprising a plate-shaped piezoelectric element, and senses a pressure of the fluid flowing within the pipe. The pipe is made of an elastically deformable material and has a recess formed on its outer surface, with the recess formed so as to reduce the thickness of the pipe. An end of the sensing part is kept in contact with the outer surface of the pipe in the vicinity of the recess so that the piezoelectric element receives the pressure of the fluid from a lateral circumferential surface of the end. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fluid pressure sensor in which the fluid to be measured does not stay, the occurrence of contamination is suppressed, and the diameter of the pipe through which the fluid to be measured flows can be freely selected. .

  Conventionally, a semiconductor diaphragm type, a capacitance type, an elastic diaphragm type, a piezoelectric type, or the like is generally used as a pressure sensor used to measure the pressure of a fluid such as gas or liquid flowing in a pipe. These conventional pressure sensors are usually provided with an introduction hole or introduction pipe for introducing a fluid to be measured, called a pressure guiding portion, into the sensor (Patent Documents 1 and 2).

  However, when the fluid to be measured is a viscous liquid, these introduction holes and the like are likely to be clogged, and the liquid stays in these introduction holes and the like, resulting in deposits derived from residues and the like. The kimono peels off and flows downstream in the pipe, and this deposit may contaminate the downstream. Further, in the case of a diaphragm type pressure sensor, stagnation may occur in the sensor due to unevenness of the diaphragm holding mechanism.

  Furthermore, the conventional pressure sensor has the common drawback that it is difficult to attach to a narrow tube. For example, when a thin tube with a tube diameter of 1/4 inch or 3/8 inch is used, it is difficult to separately install a conventional pressure sensor without using a connecting tube. It is necessary to connect the tubes together. However, when pipes having different diameters are connected to each other, a dead space is always generated, and staying also occurs in the dead space, which may cause contamination.

JP 2000-74767 A JP 2001-116638 A

  Accordingly, the present invention provides a fluid pressure sensor in which the fluid to be measured does not stay, the occurrence of contamination is suppressed, and the diameter of the pipe through which the fluid to be measured flows can be freely selected. This is what I wanted.

  That is, the fluid pressure sensor according to the present invention is a pressure sensor that includes a tube through which fluid can flow and a pressure-sensitive portion having a plate-like piezoelectric element, and senses the pressure of the fluid flowing inside the tube. The tube is made of an elastically deformable material, and has a recess formed on the outer surface thereof so that the tube thickness is reduced. The pressure-sensitive portion is formed by the piezoelectric element from the side peripheral surface of the tip. In order to receive the pressure of the fluid, a tip portion thereof is in contact with an outer surface of the tube in the vicinity of the concave portion.

  If this is the case, the pipe through which the fluid to be measured flows is made of an elastically deformable material and has a recess formed on its outer surface so that the pipe thickness is thin. The concave portion expands and contracts under the pressure of the fluid flowing inside, and its vicinity elastically deforms. Then, the pressure is transmitted to the tip of the pressure-sensitive portion in contact with the outer surface of the tube in the vicinity of the concave portion, and the piezoelectric element provided in the pressure-sensitive portion is moved from the side peripheral surface of the tip to the pressure. In response, the pressure of the fluid can be sensed. For this reason, no introduction hole or introduction pipe for introducing the fluid in the pipe 2 into the pressure-sensitive part 3 is required, and the inner surface of the pipe through which the fluid to be measured flows is flat and has no irregularities. Does not occur. Therefore, the fluid to be measured does not stay in the tube, and no contamination derived from the fluid residue or the like is generated. In addition, the inside of the tube can be easily cleaned.

  In addition, the pressure-sensitive portion receives pressure from the vibration surface of the piezoelectric element because the pressure-sensitive portion receives pressure from the side peripheral surface of the tip of the piezoelectric element when the tip portion contacts the outer surface of the tube. Compared to a conventional pressure sensor, it requires less space for mounting, and the tube may be a thin tube, and its diameter can be freely set. It can be selected appropriately.

When an unknown pressure is applied in the contour direction of the piezoelectric element, the pressure applied in the contour direction of the piezoelectric element can be derived by measuring the operating frequency fluctuation amount. In addition, when the piezoelectric element is a crystal resonator, a frequency of about 7 digits can be easily measured, and the measurement accuracy of the pressure acting on this can be 10 ⁻⁷ or more.

  Further, as compared with a conventional balance, it is possible to easily obtain higher stability and higher accuracy as well as higher resolution.

  Furthermore, in the present invention, since the vibration surface of the piezoelectric element is not used to receive pressure, the stress generated without affecting the vibration characteristics can be measured. Also, the vibration surface of the piezoelectric element is weak in mechanical strength, whereas the mechanical strength in the contour direction is very strong, so the pressure sensitivity is higher than that of the conventional pressure sensor receiving pressure from the vibration surface of the piezoelectric element. The load-bearing capacity of the part is greatly increased, and the pressure resistance is extremely excellent.

  The piezoelectric element is preferably a crystal resonator because a highly accurate oscillation frequency can be stably obtained.

  The pressure-sensitive part includes a housing in which the piezoelectric element can be stored in an airtight state in its internal space, and a head portion facing the side peripheral surface at the tip of the piezoelectric element is a thin film. Preferably used.

  When pressure is applied to the side peripheral surface of the tip of the piezoelectric element, if the piezoelectric element moves, the pressure is not sufficiently transmitted. For this reason, in order to prevent the piezoelectric element from moving, the piezoelectric element has a disk shape in which an orientation flat (hereinafter referred to as an orientation flat) is formed at the base end thereof, and the base end is held by the base end. It is preferable to be held on a table.

  As the case, for example, the piezoelectric element can be housed in an airtight state together with a thin-film-like seal member provided facing the side peripheral surface at the tip of the piezoelectric element, and the seal member. A housing body that constitutes a container, and the housing body is provided with a slit, the tip of the piezoelectric element protrudes from the slit, and the sealing member covers the slit. One that is attached. If it is such, when the pressure is applied to the side peripheral surface of the tip of the piezoelectric element via the seal member, the slit can prevent the piezoelectric element from moving together with the holding base. And it is easy to keep the internal space of the housing airtight.

  The seal member can be easily deformed, can easily transmit pressure without loss, has a strength that does not easily break even if it comes into contact with the sharp edge of the piezoelectric element, and can maintain the inside of the housing airtight. A metal thin film is preferable because it is easy.

  The pressure-sensitive part configured as described above has a piezoelectric element sealed in a housing and is not directly affected by changes in the external environment, so it can ensure reliability over a long period of time. The pressure-sensitive part may have a simpler configuration, and examples of such a pressure-sensitive part include those having a cap member fitted to the tip of the piezoelectric element.

  In order to make the pressure-sensitive part excellent in weather resistance that can withstand long-term use, a housing capable of accommodating the piezoelectric element in an airtight state is provided in its internal space, and the head of the housing The portion has a pressing portion at the tip thereof, and a tube having an inside communicating with the internal space of the housing is provided, and a rod-like body having a base end fixed to the cap member is provided in the tube. It is preferable that it is inserted.

  Thus, according to the present invention, the fluid to be measured does not stay in the pipe, and the occurrence of contamination is also suppressed. The tube may be a thin tube, and the diameter thereof can be freely set.

The front view (a) and side view (b) of the fluid pressure sensor which concern on the 1st Embodiment of this invention (a pipe | tube part is sectional drawing). The top view (a) and sectional drawing (c) of the pipe | tube in the embodiment. The front view (a), top view (b), and side view (c) of the pressure-sensitive part in the same embodiment. The block diagram of the apparatus for evaluating the performance of the fluid pressure sensor which concerns on the same embodiment. The graph which shows the relationship between a fluid pressure and an oscillation frequency. The front view (a) of the pressure sensing part in the 2nd Embodiment of this invention, and the side view (b) of a cap member. The front view (a) of the pressure-sensitive part in the 3rd Embodiment of this invention, and sectional drawing (b) of a press part vicinity. The front view (a) (a pipe part is a sectional view) and a perspective view (b) of a fluid pressure sensor concerning a 4th embodiment of the present invention. The typical top view (a) and side view (b) of the fluid pressure sensor which concern on other embodiment. The perspective view which shows the case where the sealing member in 1st Embodiment is a case-like thing (before attachment (a) and after attachment (b)).

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1, 2, and 3, the fluid pressure sensor 1 according to the present embodiment includes a tube 2 through which a fluid can flow and a pressure sensing unit 3 having a plate-like piezoelectric element 31. It is provided and senses the pressure of the fluid flowing inside the pipe 2.

  Each part will be described below. The pipe 2 has a recess 21 formed on its outer surface so that the thickness of the pipe 2 is reduced, as shown in FIG. It is. In the present embodiment, the concave portion 21 has an annular shape, and is configured such that the tip 3 a of the pressure-sensitive portion 3 is in contact with the convex portion 22 surrounded by the concave portion 21. The size of the recess 21 is, for example, when the tube 2 has an inner diameter of 4.35 mm, an outer diameter of 6.35 mm, and a tube thickness of 1 mm, and when W1 is 12 mm, W2 is 16 to 18 mm and H1 is 2 mm. In this case, H2 is 6 to 8 mm. Further, when the tube 2 has an inner diameter of 7.53 mm, an outer diameter of 9.53 mm, a tube thickness of 1 mm, and W1 is 12 mm, W2 is 16 to 20 mm, and when H1 is 4 mm, H2 is 8 to 8 mm. 12 mm. The inner surface of the tube 2 and the top of the convex portion 22 are flat and have no irregularities.

  Since the tip 3a of the pressure-sensitive portion 3 is configured to contact the convex portion 22 having a thick tube thickness, the tube 2 is damaged even when pressed by the stiff and sharp tip 31a of the piezoelectric element 31. Hateful.

  The elastically deformable material constituting the tube 2 is preferably a material having high chemical resistance, such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene. -Fluororesin such as hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-ethylene copolymer (ETFE) is preferably used.

  As shown in FIG. 3, the pressure-sensitive part 3 can accommodate the piezoelectric element 31 in a plate-like piezoelectric element 31 and its internal space in an airtight state, and is opposed to the side peripheral surface of the tip 31 a of the piezoelectric element 31. And a housing 33 having a head made of a seal member 32.

  The plate-like piezoelectric element 31 is, for example, an AT-cut 9 MHz convex crystal resonator in which a disk-shaped crystal piece 311 having an orientation flat is sandwiched between two electrode plates 312a and 312b. The end 31b is supported by being inserted into the slits 3131 of the elastic supports 313a and b with slits, and the base end thereof is fixed to the holding base 314 using an adhesive or the like. When pressure is applied to the side peripheral surface, the pressure is transmitted as it is in the vertical direction and is compressed and deformed to bend, but it is installed so as not to move in the horizontal direction or the front-rear direction.

  A thickness shear vibrator such as an AT-cut vibrator is suitable for a high frequency band, and has high oscillation frequency stability and reliability with respect to changes in the external environment in the high frequency band.

  The holding base 314 is fixed to the base 331b using an adhesive or the like. The elastic supports 313a, b with slits are made of a conductive material such as metal, and support the piezoelectric element 31 so as to be in contact with the electrode plates 312a, 3b, and also serve as lead wires.

  The housing 33 includes a seal member 32 and a housing body 331 that forms a container that can accommodate the piezoelectric element 31 in an airtight state in the internal space.

  The seal member 32 is a thin film that deforms in response to a pressure change, and is made of, for example, a metal thin film such as SUS having a thickness of about 10 to 30 μm. In the initial state, the seal member 32 and the side peripheral surface of the tip 31a of the crystal resonator 31 have a stroke of about 0.1 to 0.3 mm. A slight pressure is applied to the side peripheral surface of the tip 31a of the crystal resonator 31 in contact with the side peripheral surface of the tip 31a.

  The housing main body 331 is made of, for example, metal or the like, and has a slit 332 at the head thereof. The tip 31a of the piezoelectric element 31 protrudes from the slit 332 by about 0.1 to 0.2 mm. A seal member 32 is fixed so as to cover 332. In order to fix and seal the seal member 32 to the housing body 331, an adhesive is used or resistance welding is performed in a dry atmosphere. The housing main body 331 is divided into an upper portion provided with a slit 332 and a base 331b provided with a lead wire 333, which are similarly sealed.

The inner space of the housing 33 is filled with an inert gas such as N ₂ gas in a dry state, and is configured so that the electrode plates 312a, 3b, etc. formed by depositing gold on the base material do not corrode. ing.

  The housing 33 in the present embodiment is made of a conductive material such as metal, and includes lead wires 333a and 333b formed integrally with the housing body at the bottom. The lead wires 333a, b are in electrical communication with the slit elastic supports 313a, b, and can transmit the voltage generated in the piezoelectric element 31 to the outside as an output signal.

  In the fluid pressure sensor 1 according to this embodiment, when the pipe 2 is connected to the pipe to be connected, and the fluid to be measured flows through the pipe 2, the concave portion 21 and the convex portion 22 are elastically deformed according to the pressure, Pressure is applied to the side peripheral surface of the tip 31 a of the piezoelectric element 31 through the seal member 32. Then, when the piezoelectric element 31 is compressed and deformed and bends and stress is generated, the oscillation frequency is changed, a voltage corresponding to the oscillation frequency is generated, and the electric signals are sent to the elastic supports 313a and b with slits and the lead wire 333a. , B is transmitted to the outside as an output signal.

  And the tolerance | permissible_range of the pressure received from the side peripheral surface of the front-end | tip 31a of the crystal oscillator 31 can be defined by the optimization of the direction and dimension of the holding stand 314, orientation flat, and the elastic support bodies 313a and b with a slit.

  In order to evaluate the performance of the fluid pressure sensor 1 according to this embodiment, an apparatus having a configuration as shown in FIG. 4 is assembled, and a fluid is caused to flow through the tube 2 made of a PFA tube having an outer diameter of 8 mm × an inner diameter of 6 mm. The change in the oscillation frequency of the pressure unit 3 was measured, and the set value in the pressure calibrator was compared with the measured value in the frequency counter. The results are shown in FIG.

  As shown in FIG. 5, in the fluid pressure sensor 1, the pressure of the fluid flowing in the pipe 2 and the oscillation frequency of the pressure sensing unit 3 have a linear function relationship, and the fluid pressure is accurately sensed. confirmed.

  Therefore, according to the fluid pressure sensor 1 according to the present embodiment configured as described above, the pipe 2 in which the fluid to be measured flows is made of an elastically deformable material, and the pipe thickness is thin on the outer surface thereof. Since it has the recessed part 21 formed so that it may become, the recessed part 21 receives the pressure of the fluid which flows through an inside, and is expanded-contracted, and the recessed part 21 and the convex part 22 elastically deform. And the said pressure is transmitted to the front-end | tip part 3a of the pressure-sensitive part 3 which is in contact with the outer surface of the pipe | tube 2 in the convex part 22, and the piezoelectric element 31 with which the pressure-sensitive part 3 was equipped is the said pressure from the side peripheral surface of the front-end | tip 31a. In response, the pressure of the fluid can be sensed. For this reason, no introduction hole or introduction pipe for introducing the fluid in the pipe 2 into the pressure sensing part 3 is required, and the inner surface of the pipe 2 through which the fluid to be measured flows is flat and has no irregularities. There is no space. Therefore, the fluid does not stay in the pipe 2 and no contamination derived from a fluid residue or the like is generated. In addition, the inside of the tube 2 can be easily cleaned.

  Further, the pressure-sensitive portion 3 receives pressure from the side peripheral surface of the tip 31a of the piezoelectric element 31 by contacting the tip portion 3a with the convex portion 22 formed on the outer surface of the tube 2. Compared to a conventional pressure sensor that receives pressure from the vibration surface of the piezoelectric element 31, less space is required for mounting, the tube 2 may be a thin tube, and its diameter can be freely set. The pipe 2 having a diameter suitable for the pipe to which the pressure sensor 1 is connected can be appropriately selected.

  Moreover, since the vibration surface of the piezoelectric element is not used to receive pressure by receiving pressure from the side peripheral surface of the tip 31a of the piezoelectric element 31 through the seal member 32, the vibration characteristics are not affected. The resulting stress can be measured. Furthermore, the vibration surface of the piezoelectric element is weak in mechanical strength, whereas the mechanical strength in the contour direction is very strong, so that the pressure-sensitive part is lower than the conventional pressure sensor that receives pressure from the vibration surface of the piezoelectric element. The load-bearing capacity of No. 3 is greatly increased, and the pressure resistance is extremely excellent. If the relationship between the frequency change and the pressure is examined in advance, the pressure can be derived from the frequency change.

  Further, in the present embodiment, since a fluid introduction pipe or the like is not inserted from the pressure-sensitive portion 3 into the pipe 2, when the pipe 2 is made of a fluororesin, the chemical resistance of the fluororesin can be sufficiently exerted. .

  In addition, by using an AT-cut 9 MHz convex crystal resonator as the piezoelectric element 31, a highly accurate oscillation frequency can be stably obtained.

  Furthermore, a slit 332 is provided at the head of the housing body 331, and the tip 31 a of the piezoelectric element 31 protrudes from the slit 332, and the seal member 32 is fixed so as to cover the slit 332. When pressure is applied to the piezoelectric element 31 from the side peripheral surface of the tip 31a, the piezoelectric element 31 can be prevented from moving together with the holding base 314, and the internal space of the housing 33 can be kept airtight. Easy.

  Furthermore, by using a metal thin film made of SUS or the like as the sealing member 32, the metal thin film can be easily deformed, so that pressure is not easily lost and is easily transmitted to the side peripheral surface of the tip 31a of the piezoelectric element 31, Since the strength is high, even if it comes into contact with the sharp tip 31a of the piezoelectric element 31, it is not easily damaged, and it is easy to keep the inside of the housing 33 airtight.

  Furthermore, since the piezoelectric element 31 is sealed in the housing 44 and is not directly affected by changes in the external environment, the long-term reliability of the fluid pressure sensor 1 can be ensured.

<Second Embodiment>
Below, the 2nd Embodiment of this invention is described with reference to drawings. In the following, description will be made centering on portions that have different configurations from the first embodiment, and description of portions that have the same configurations as those of the first embodiment will be omitted.

  Although the pressure-sensitive part 3 in the first embodiment can be used for a long period of time, if it can be used for a short period of time, the crystal unit 31 is airtight in the housing 44 as shown in FIG. It does not have to be accommodated. In the present embodiment, a cap member 5 made of metal or plastic is fitted to the tip 31 a of the crystal resonator 31, and the side peripheral surface of the tip 31 a of the crystal resonator 31 is interposed via the cap member 5. The pressure is applied.

  The cap member 5 is provided with a groove 51 for fitting to the tip 31a of the crystal resonator 31, and a hole 52 is provided in the head.

<Third Embodiment>
In the pressure sensitive part 3 in the second embodiment, a cap member 5 is provided as a pressure acting part. In the third preferred embodiment, the pressure sensitive part 3 according to the second embodiment is provided. In order to withstand long-term use, as shown in FIG. 7, a housing 44 capable of accommodating the piezoelectric element 31 in an airtight state is provided in its internal space. Is provided with a tube 62 having a pressing portion 61 at its tip and communicating with the interior space of the housing 44. The tube 62 has a base end fixed to the cap member 5. The body 63 is inserted. The rod-like body 63 can slide in the tube 62.

  The tube 62 and the housing 44 are resistance-welded, and an O-ring 64 is provided between the pressing portion 61 and the tube 62, so that the internal space of the housing 44 is kept airtight.

  The cap member 5 has a hole 52 in the head, but the base end of the rod-like body 63 is screwed into the hole 52 and fixed. When pressure is applied to the pressing portion 61, the pressure is transmitted to the cap member 5 via the rod-like body 63 and further applied to the side peripheral surface of the tip 31 a of the piezoelectric element 31 via the cap member 5.

<Fourth Embodiment>
In the fourth embodiment, as shown in FIG. 8, the recess 21 is formed so as to surround the outer peripheral surface of the tube 2, and a tubular frame body 23 that fits the tube 2 is provided so as to cover the recess 21. ing. A hole 231 into which the casing 33 of the pressure-sensitive part 3 can be inserted is formed in the frame body 23, and the pressure-sensitive part 3 inserted into the hole 231 has a sealing member 32 interposed through the contact plate 24. 2 is in contact with. When the fluid to be measured flows in the tube 2, the concave portion 21 is elastically deformed according to the pressure, and the pressure is applied to the side peripheral surface of the tip 31 a of the piezoelectric element 31 via the contact plate 24 and the seal member 32. Will be added.

  The present invention is not limited to the above embodiment.

  For example, in the fluid pressure sensor according to the present invention, the pressure sensing unit 3 includes an oscillation circuit, a CPU, a memory, an A / D converter, a D / A in addition to the input unit 34 and the display 35 as shown in FIG. An arithmetic processing unit (not shown) including a converter or the like may be provided integrally.

  The piezoelectric element 31 may be any element as long as the oscillation frequency changes depending on the pressure received. The piezoelectric element 31 is not limited to a crystal resonator, and a material other than quartz such as ceramics is used as a piezoelectric body. It may be a thing.

  Further, the seal member 32 may be any member as long as it is elastically deformed in response to a change in pressure, and is not limited to a metal thin film, but may be made of another material such as carbon, a diaphragm, Bellows may be used.

  Furthermore, as shown in FIG. 10, the seal member 32 may be a case-like one having an open surface, and may be attached so as to be covered from the head of the housing body 331.

  The holding base 314 may be formed with a groove for fitting to the base end 31 b of the crystal unit 31, or may be integrally formed with the housing body 331.

  Furthermore, since the crystal unit is affected by temperature, the pressure-sensitive unit 3 may include a temperature sensor to correct the effect of temperature.

  The pressure-sensitive part 3 in the present invention has a very excellent characteristic due to the pressure-to-operating frequency variation characteristic in the contour direction of the crystal unit 31. However, as an error factor of the operation, (1) Changes due to climate, (2) influence of initial distortion of the head of the housing 44, (3) influence of frequency change due to deterioration of the crystal unit 31, and (4) sensitivity error due to different pressure acting directions. It is done.

  For (1), by grasping the crystal oscillator frequency stability due to the climate as a past frequency reference, it is possible to set the limit value of measurement error by setting the conditions in the atmosphere, and simple measurement Can be used easily.

  For (2), even if variations occur, the linearity of pressure vs. operating frequency fluctuation characteristics in the contour direction is excellent, so the sensitivity within the linearity range remains unchanged, and the frequency at the time of measurement -Only by selecting the pressure conversion program.

  With regard to (3), high stability and accuracy can be obtained by selecting a frequency band of 5 to 10 MHz, and further stability and accuracy can be improved by placing the crystal resonator 31 in an airtight state. it can. Furthermore, it is possible to further improve accuracy by calibration after use for a certain period.

  Regarding (4), when the direction in which the pressure is applied is changed, the relationship between the pressure and the amount of change in the frequency changes slightly. It can be adjusted by doing. Further, the slight pressure applied by the seal member 32 coming into contact with the side peripheral surface of the tip 31a of the crystal resonator 31 can be similarly corrected by adjusting the frequency.

  In addition, it is needless to say that some or all of the above-described embodiments and modified embodiments may be appropriately combined, and various modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 ... Fluid pressure sensor 2 ... Pipe 21 ... Recess 3 ... Pressure sensitive part 31 ... Piezoelectric element

Claims (7)

A pressure sensor that includes a tube through which a fluid can flow and a pressure-sensitive portion having a plate-like piezoelectric element, and senses the pressure of the fluid flowing through the tube;
The tube is made of an elastically deformable material, and has a recess formed on its outer surface so that the tube thickness is thin.
The fluid is characterized in that the pressure-sensitive portion has a tip that is in contact with the outer surface of the tube in the vicinity of the recess so that the piezoelectric element receives the pressure of the fluid from the side peripheral surface of the tip. Pressure sensor.   The fluid pressure sensor according to claim 1, wherein the piezoelectric element is a crystal resonator.   2. The pressure-sensitive portion includes a housing in which the piezoelectric element can be housed in an airtight state in an internal space, and a head portion facing a side peripheral surface at a tip end of the piezoelectric element is a thin film. Or the fluid pressure sensor of 2.   The fluid pressure sensor according to claim 1, wherein the pressure sensitive part includes a cap member fitted to a tip of the piezoelectric element.   5. The fluid pressure sensor according to claim 3, wherein the piezoelectric element has a disk shape in which an orientation flat is formed at a base end thereof, and the base end is held by a holding base. The housing is
A thin-film seal member provided to face the side peripheral surface of the tip of the piezoelectric element;
Along with the seal member, a housing body constituting a container capable of accommodating the piezoelectric element in an airtight state in its internal space, and
The fluid pressure sensor according to claim 3, wherein a slit is provided in the housing main body, a tip of the piezoelectric element protrudes from the slit, and the seal member is attached so as to cover the slit. A housing capable of accommodating the piezoelectric element in an airtight state in its internal space,
The head portion of the housing has a pressing portion at the distal end thereof, and a tube having an inside communicating with the internal space of the housing is provided, and a proximal end of the tube is fixed to the cap member. The fluid pressure sensor according to claim 4, wherein a rod-shaped body is inserted.