Amplifier-embedded pressure sensor

An amplifier-embedded pressure sensor includes: a pressure-detecting element which detects the differential pressure between the fluid and the space where the pipe including a fluid passage of the fluid is installed, and outputs the pressure signal; an amplifier circuit board having an amplifier circuit for amplifying the pressure signal; a housing to which the pressure-detecting element is fixed; and a separation part which is fixed to the housing and separates a space inside the housing into a first space where the pressure-detecting element is disposed and a second space where the amplifier circuit board is disposed. The housing includes an inflow port for letting cooling gas for cooling the amplifier circuit board flow into the second space and a discharge port for discharging the cooling gas from the second space.

TECHNICAL FIELD

The present invention relates to an amplifier-embedded pressure sensor.

BACKGROUND ART

Conventionally, a pressure sensor is used to detect pressure of a fluid flowing through a passage. Known pressure sensors include an amplifier-embedded type which has an embedded amplifier circuit for amplifying a pressure signal detected by a pressure-detecting unit (e.g., see PTL 1), and a separate type which has no embedded amplifier circuit, but instead transmits a pressure signal to an amplifier circuit provided outside the pressure sensor.

Due to a short length of its wire for transmitting a pressure signal, which is a minute signal, to the amplifier circuit, the amplifier-embedded pressure sensor has an advantage that the pressure signal is less likely to be affected by noise, etc.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Since the amplifier circuit is disposed at a position close to the pressure-detecting unit in the amplifier-embedded pressure sensor, when a fluid to be detected is at a high temperature (e.g., temperatures of 80° C. or higher and 200° C. or lower), heat is transferred to the amplifier circuit, which may adversely affect the operation of the amplifier circuit.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an amplifier-embedded pressure sensor which, when detecting a differential pressure between a high-temperature fluid and a space where a pipe including a fluid passage of the fluid is installed, can properly detect the differential pressure between the fluid and the space where the pipe is installed, while protecting an amplifier circuit for amplifying a pressure signal from heat of the fluid.

Solution to Problem

In order to solve the above problem, the present invention has adopted the following solutions.

According to the present invention, there is provided an amplifier-embedded pressure sensor, which is connected to a pipe having a fluid passage, including: a pressure-detecting unit which has a pressure-receiving surface in contact with a fluid flowing in from the pipe, and which detects a differential pressure between the fluid in contact with the pressure-receiving surface and a space where the pipe is installed and outputs a pressure signal; an amplifier circuit board which has an amplifier circuit for amplifying the pressure signal detected by the pressure-detecting unit; a housing to which the pressure-detecting unit is fixed; and a separation part which is fixed to the housing and separates a space inside the housing into a first space where the pressure-detecting unit is disposed and a second space where the amplifier circuit board is disposed. The housing includes an inflow port for letting cooling gas for cooling the amplifier circuit board flow into the second space and a discharge port for discharging the cooling gas from the second space.

In the amplifier-embedded pressure sensor according to the present invention, the space inside the housing, to which the pressure-detecting unit is fixed, is separated by the separation part into the first space where the pressure-detecting unit is disposed and the second space where the amplifier circuit board having the amplifier circuit for amplifying the pressure signal detected by the pressure-detecting unit is disposed. The amplifier circuit board is cooled by the cooling gas flowing from the inflow port into the second space of the housing, and the cooling gas is discharged from the discharge port to the outside of the housing. Although inflow of the cooling gas causes pressure fluctuations in the second space inside the housing, no pressure fluctuation occurs in the first space, as the first space is separated from the second space by the separation part. Therefore, pressure fluctuation in the second space does not affect the detection results of the pressure-detecting unit which detects the differential pressure between the fluid to be detected and the space where the pipe is installed.

Thus, according to the present invention, it is possible to provide an amplifier-embedded pressure sensor which, when detecting the differential pressure between the high-temperature fluid and the space where the pipe including the fluid passage is installed, can properly detect the differential pressure between the fluid and the space where the pipe is installed, while protecting an amplifier circuit for pressure signals from heat of the fluid.

According to a first aspect of the amplifier-embedded pressure sensor of the present invention, the amplifier circuit board is disposed between the inflow port and the discharge port.

This allows the cooling gas to flow near both front and back surfaces of the amplifier circuit board, so that the amplifier circuit is adequately cooled.

According to a second aspect of the amplifier-embedded pressure sensor of the present invention, the separation part includes: a separation board which has an outer circumferential surface of a shape substantially matching a shape of an inner circumferential surface of the housing; and a filling material which is packed between the outer circumferential surface of the separation board and the inner circumferential surface of the housing so as not to allow the cooling gas to pass through.

According to the second aspect of the amplifier-embedded pressure sensor of the present invention, the space between the inner circumferential surface of the housing and the outer circumferential surface of the separation board, whose shape substantially matches the shape of the inner circumferential surface of the housing, is filled with the filling material, so that the cooling gas is prevented from flowing from the second space into the first space.

This allows the space inside the housing to be separated into the first space where the pressure-detecting unit is disposed and the second space where the amplifier circuit board is disposed, by a relatively simple work of packing the filling material between the outer circumferential surface of the separation board and the inner circumferential surface of the housing.

According to a third aspect of the amplifier-embedded pressure sensor of the present invention, the amplifier-embedded pressure sensor may include a coupling part to which an external wire for transmitting the pressure signal amplified by the amplifier circuit to an external device is coupled, and the first space may communicate with a space near the external device through a third space between the external wire and a cladding part cladding the external wire.

This allows gas in the space near the external device, which is disposed at a position separated from the pressure sensor by a length of the external wire, to be supplied to the first space through the third space. Thus, corrosion of the pressure-detecting unit in the first space can be prevented, as the space near the pressure sensor may corrode the pressure-detecting unit in the first space due to effects of a fluid, etc. whose pressure is to be detected.

According to a fourth aspect of the amplifier-embedded pressure sensor of the present invention, a fluid chamber is formed by the pressure-receiving surface of the pressure-detecting unit and a surface of the housing opposite to the pressure-receiving surface, and the housing includes a first passage which communicates with an external passage and a second passage which communicates the first passage and the fluid chamber, and a passage diameter of the second passage is smaller than a passage diameter of the first passage.

This allows the temperature of the fluid reaching the fluid chamber to be kept low by sufficiently cooling the high-temperature fluid flowing in from the first passage in the second passage, which has higher cooling efficiency than the first passage, before the fluid reaches the fluid chamber.

In the fourth aspect of the amplifier-embedded pressure sensor of the present invention, a passage length of the second passage may be longer than a passage length of the first passage.

This allows the cooling efficiency of the second passage to be further enhanced, so that the temperature of the fluid reaching the fluid chamber can be kept sufficiently low.

In the fourth aspect of the amplifier-embedded pressure sensor of the present invention, a diameter of an outer circumferential surface of the second passage may be smaller than a diameter of an outer circumferential surface of the first passage, and a support member may be provided which is disposed so as to surround the second passage over its passage length, and supports the second passage in a state where the space close to the outer circumferential surface of the second passage communicates with an external space.

This allows the effects of load on the second passage having a smaller passage diameter to be properly supported by the support member, so that deformation of the second passage can be adequately prevented.

According to a fifth aspect of the amplifier-embedded pressure sensor of the present invention, an opening diameter of the discharge port to the second space is larger than an opening diameter of the inflow port to the second space.

This allows the cooling gas flowing from the inflow port into the second space of the housing to be easily discharged from the discharge port, so that a failure due to high pressure in the second space can be prevented.

According to a sixth aspect of the amplifier-embedded pressure sensor of the present invention, the amplifier-embedded pressure sensor includes: a first wire for transmitting the pressure signal from the pressure-detecting unit to the separation part; a second wire for transmitting the pressure signal from the separation part to the amplifier circuit board; and a third wire for transmitting the pressure signal amplified by the amplifier circuit from the amplifier circuit board to the separation part, and the separation part includes a first terminal, to which the first wire is connected, on a first space-side surface thereof, and a second terminal, to which the second wire is connected, on a second space-side surface thereof, and the first terminal and the second terminal are electrically connected with each other.

This allows transmission of the pressure signal from the pressure-detecting unit to the amplifier circuit and transmission of the amplified pressure signal from the amplifier circuit to the separation part while separating the first space and the second space by the separation part.

Advantageous Effects of Invention

According to the present invention, it is possible to provide an amplifier-embedded pressure sensor which, when detecting a differential pressure between a high-temperature fluid and a space where a pipe including a fluid passage of the fluid is installed, can properly detect the differential pressure between the fluid and the space where the pipe is installed, while protecting an amplifier circuit for pressure signals from heat of the fluid.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, an amplifier-embedded pressure sensor of a first embodiment of the present invention will be described based on the drawings.FIG. 1is a front view of the amplifier-embedded pressure sensor of the first embodiment.FIG. 2is a cross-sectional view showing an internal structure of a pressure sensor1shown inFIG. 1along the line A-A.FIG. 3is a cross-sectional view showing the internal structure of the pressure sensor shown inFIG. 2along the line B-B.

As shown inFIGS. 1 to 3, the pressure sensor1is a sensor in which a pressure-detecting element3(pressure-detecting unit) is fixed inside a housing2which is constituted of a housing cover2aand a housing body2b.

FIG. 5is a top view of the pressure sensor shown in FIG.1. As shown inFIG. 5, the pressure sensor1can transmit a pressure signal to an external device through an external wire19which is clad with a cladding film20. The external wire19is coupled to the pressure sensor1through a connection part21to be described later.

The pressure sensor1is a sensor which is connected to a pipe (not shown) including a fluid passage, and detects a differential pressure between pressure of a fluid flowing in from the pipe and pressure of a space where the pipe is installed, and outputs a pressure signal.

The pressure sensor1includes a pressure-receiving surface3awhich contacts with the fluid and detects the differential pressure between the fluid and the space where the pipe is installed. A fluid chamber23is formed by the pressure-receiving surface3aof the pressure sensor1and a surface of the housing body2bopposite to the pressure-receiving surface3a. The fluid whose pressure is to be detected by the pressure sensor1flows in from a first passage15communicating with an external passage18, and flows into the fluid chamber23via a second passage16which couples the first passage15and the fluid chamber23. The housing body2bof the pressure sensor1and the external passage18are fastened by a cap nut17.

As shown inFIG. 2, a passage diameter D2 of the second passage16is smaller than a passage diameter D1 of the first passage15. In addition, a passage length L2 of the second passage16is longer than a passage length L1 of the first passage15. Here, the passage length L1 of the first passage15denotes a length of a portion of the housing body2bwhose passage diameter is D1 and whose inner surface is in contact with the fluid. On the other hand, the passage length L2 of the second passage16denotes a length of a portion of the housing body2bwhose passage diameter is D2 and whose inner surface is in contact with the fluid.

The pressure sensor1of the present embodiment is designed to suitably detect pressure of a fluid at a high temperature (e.g., temperatures of 80° C. or higher and 200° C. or lower). More specifically, the passage diameter D2 of the second passage16is smaller than the passage diameter D1 of the first passage15, and the passage length L2 of the second passage16is longer than the passage length L1 of the first passage15, so that the fluid flowing from the external passage18into the fluid chamber23is cooled while passing through the second passage16. The passage diameter D1 can be, e.g., 9.5 mm, while the passage diameter D2 can be, e.g., 2.5 mm.

The pressure-detecting element3is an element which detects a difference (differential pressure) between the pressure of the fluid in contact with the pressure-receiving surface3aand the pressure in the space where the pipe including the fluid passage is installed, and outputs a pressure signal. In the present embodiment, an air intake port (not shown) communicating with a first space R1 is provided in a back surface3bof the pressure-detecting element3, and the pressure in the first space R1 serves as a reference pressure. Although in the present embodiment, the pressure inside the first space R1 is assumed to be the atmospheric pressure, the present invention may have another aspect in this respect. For example, pressure in a chamber filled with gas other than air may serve as the reference pressure. In this case, various gases can be adopted as long as the gas does not affect the operation of the pressure sensor1.

The pressure-detecting element3is a columnar member having a substantially circular shape in plan view. An outer circumferential surface of the pressure-detecting element3and an outer edge of the back surface3bof the pressure-detecting element3are in contact with an inner surface of a sensor holding member9having an annular shape in cross-section. The sensor holding member9is a member which holds the pressure-detecting element3against the housing body2b. The sensor holding member9has a male screw formed on the outer circumferential surface thereof, and is fastened by the male screw being engaged with a female screw formed on the inner circumferential surface of the housing body2b.

A support base member11is disposed between screw heads of male screws12aand12b, and the sensor holding member9, and fixed to the sensor holding member9by the male screws12aand12b.

The support base member11is a member which supports a spacers10band10dfor disposing a separation member4(separation part) and an amplifier circuit board5at a distance from the pressure sensor1. As shown inFIGS. 2 and 3, the separation member4is disposed at a position away from the support base member11by spacers10band10d. Similarly, the amplifier circuit board5is disposed at a position away from the separation member4by spacers10aand10c.

A male screw13ais inserted into the amplifier circuit board5, the spacer10a, the separation member4, and the spacer10bin this order, and has a tip thereof fastened to a female screw provided in the support base member11. The male screw13bis inserted into the amplifier circuit board5, the spacer10c, the separation member4, and the spacer10din this order, and has a tip thereof fastened to a female screw provided in the support base member11. In this way, each of the separation member4and the amplifier circuit board5is disposed at the position away from the support base member11.

The separation member4is constituted of a separation board4aand a filling material4b. The separation board4ais a disk-like member of a material similar to that of a printed wiring board used for electronic circuits. The separation board4ahas an outer circumferential surface of a shape substantially matching the shape of the inner circumferential surface of the housing cover2a.

The filling material4bis provided at the outer edge of the second space-side surface of the separation board4aso as not to allow cooling gas to pass through between the outer circumferential surface of the separation board4aand the inner circumferential surface of the housing body2b. The space inside the housing2is separated into the first space R1, where the pressure-detecting element3is disposed, and the second space R2, where the amplifier circuit board5is disposed, by the separation member4fixed to the housing body2b.

The filling material4bis a resin containing a curing agent, which is applied in a state where the separation board4ais disposed on the spacer10, and cures after a certain period of time has elapsed. Among various types of resins which can be used, for example, a silicon resin or an epoxy resin can be used. As shown inFIG. 4(c), the filling material4bis packed between the outer circumferential surface of the separation board4aand the inner circumferential surface of the housing body2bover the entire circumference of the outer edge of the separation board4aso as to fill the space.

As shown inFIGS. 3 and 4(c), a terminal4c, to which a pressure signal line of a first wire24which transmits the pressure signal output from the pressure-detecting element3is connected, is provided on a surface of the separation board4aon the first space R1 side. Accordingly, the pressure signal output from the pressure-detecting element3is transmitted to the terminal4cof the separation board4athrough the first wire24. The first wire24includes the pressure signal line and a power line, and the power line is connected to a terminal4fshown inFIG. 4(c). Power from the external device is supplied to the pressure-detecting element3through the terminal4f.

The amplifier circuit board5is a board on which an amplifier circuit5ais provided, and is a disk-like member of a material similar to that of a printed wiring board used for electronic circuits.

As shown inFIGS. 3 and 4(c), a terminal4d, to which a second wire25which transmits the pressure signal from the separation board4ato the amplifier circuit board5is connected, is provided on a surface of the separation board4aon the second space R2 side. The terminal4cand the terminal4dare electrically connected with each other, and the pressure signal output from the terminal4dof the separation board4ais transmitted to the amplifier circuit board5through the pressure signal line included in the second wire25.

The second wire25includes the pressure signal line and a power line. The pressure signal line is connected to the terminal4d, while the power line is connected to a terminal4g. The terminal4gis electrically connected to the terminal4f, so that power supplied through the terminal4gis transmitted to the terminal4f.

The terminal4c, the terminal4d, the terminal4f, and the terminal4gare formed using through-holes, and the terminals and the wires are electrically connected by being soldered in a state where an end of the wire is inserted in a through-hole. Since the through-hole is filled with solder in the soldered state, gas cannot flow between the first space R1 and the second space R2 via the through-hole.

The amplifier circuit5ais a circuit which amplifies the pressure signal, which is a minute signal transmitted through the pressure signal line of the second wire25. The pressure signal amplified by the amplifier circuit5a(hereinafter referred to as an amplified signal) is transmitted to the separation board4athrough a pressure signal line of a third wire26. The amplified signal transmitted to the separation board4ais transmitted to the external wire19through a fourth wire27.

The third wire26includes the pressure signal line, a power line, and a control signal line. The pressure signal line is connected to a terminal4eof the separation board4a, the power line is connected to a terminal4h, and the control signal line is connected to a terminal4i. The terminal4eof the separation board4ais electrically connected with the pressure signal line included in the external wire19, and the amplified signal input through the terminal4eis transmitted to the external device through the external wire19.

The external wire19includes a power line, and the power line of the external wire19is electrically connected to the terminal4hof the separation board4a. Power supplied from the external device is transmitted to the amplifier circuit board5through the terminal4h.

The external wire19includes a control signal line, and the control signal line is electrically connected to the terminal4iof the separation board4a. A control signal input from the external device is transmitted to the amplifier circuit board5through the terminal4i.

A zero-point adjustment signal for executing zero-point adjustment of the pressure-detecting element3is included among various types of signals which are input from the external device as the control signal. The zero-point adjustment refers to a process of adjusting the pressure signal output by the pressure-detecting element3. When the zero-point adjustment signal is sent from the external device in a state where the pressure inside the fluid chamber23is equal to the pressure (atmospheric pressure in this embodiment) in the space where the fluid pipe is disposed, the amplifier circuit5aperforms a zero-point adjustment process. More specifically, the amplifier circuit5acorrects the pressure signal input from the pressure-detecting element3so that the pressure signal upon reception of the zero-point adjustment signal from the external device becomes a value indicating the atmospheric pressure.

A display circuit board6is constituted of a display circuit6aand a light-emitting element6b, and is electrically connected with the amplifier circuit board5through a fifth wire28. The display circuit6ais a circuit which controls the light-emitting element6b. For example, the display circuit6acontrols the light-emitting element6bsuch that it emits light when power is supplied from the external device through the external wire19. In addition, for example, the display circuit6acontrols the light-emitting element6bsuch that it flickers when the zero-point adjustment signal is sent from the external device and when the amplifier circuit5ais performing zero-point adjustment.

While inFIG. 2, the display circuit board6having one light-emitting element6bis shown, the present invention may have another aspect in this respect. For example, multiple light-emitting elements may be provided on the display circuit board6, and a numeral value indicating the pressure signal according to the amplified signal may be displayed by controlling a light-emitting state of these elements. Thus, a function of displaying the pressure detected by the pressure-detecting element3can be included in the pressure sensor1itself.

The housing cover2ais mounted to the housing body2b, and the housing cover2aand the housing body2bare fitted together to form the second space R2. The housing cover2aincludes an inflow port7for letting the cooling gas for cooling the amplifier circuit board5flow into the second space R2, and the discharge port8for discharging the cooling gas from the second space R2.

The inflow port7and the discharge port8are connected to an external cooling gas supply source (not shown), and the cooling gas is supplied from the supply source to the inflow port7, and the cooling gas is discharged from the discharge port8. Although various gases are usable as the cooling gas, air is used in the present embodiment.

As shown inFIG. 2, the outer circumferential surface of the amplifier circuit board5and the inner circumferential surface of the housing cover2aare disposed at a certain interval without contacting with each other. The amplifier circuit board5is disposed between the inflow port7and the discharge port8. Thus, the cooling gas (air) flowing in from the inflow port7cools a lower surface of the amplifier circuit board5and passes between the amplifier circuit board5and the housing cover2ato cool the upper surface of the amplifier circuit board5, and thereafter is discharged from the discharge port8.

The shapes of openings of the inflow port7and the discharge port8to the second space is circular. An opening diameter of the discharge port8to the second space R2 is larger than an opening diameter of the inflow port7to the second space R2. Thus, while the flow of the cooling gas from the inflow port7into the second space R2 is restricted, discharge of the cooling gas from the second space R2 to the discharge port8is facilitated. This prevents the pressure in the second space R2 from rising due to inflow of the cooling gas.

A coupling part22is a member which is provided in the housing body2b, and to which the external wire19for transmitting the amplified signal to the external device is coupled. A female connector is provided at an end of the coupling part22, while a male connector is provided at an end of a connecting part21of the external wire19. Connecting the female connector and the male connector brings the fourth wire27and the external wire19into an electrically connected state.

Coupling the coupling part22of the housing body2band the connection part21at an end of the external wire19connected to the external device brings an O-ring provided in the coupling part22into contact with the inner surface of the connection part21. Thus, the first space R1 of the housing2is separated from the space near the pressure sensor1.

As shown in the cross-sectional view ofFIG. 6, the external wire19is clad with the cladding film20(cladding part), and the third space R3 is provided between the external wire19and the cladding film20. InFIG. 6, the external wire19and the cladding film20are shown in a state where they are not in contact with each other over the entire circumference in the circumferential direction. However, the external wire19and the cladding film20are not in this state over the entire length of the external wire19. The external wire19and the cladding film20are in contact with each other in some portions, and not in contact in other portions.

The third space R3 between the external wire19and the cladding film20communicates with the space near the external device, and also communicates with the first space R1 inside the housing2through the coupling part22. Thus, the first space R1 communicates with the space near the external device through the third space R3, and the gas in the space near the external device is supplied to the first space R1.

While various materials are usable as the material of the cladding film20, for example, a fluorine resin such as Teflon (registered trademark) can be used. In addition, while various lengths of the external wire19are usable, the length can be, for example, about 2 m.

Next, a support member14which supports the second passage16will be described.

As shown inFIG. 3, a diameter D4 of the outer circumferential surface of the second passage16is smaller than a diameter D3 of the outer circumferential surface of the first passage15. As described above, the passage length L2 of the second passage16is longer than the passage length L1 of the first passage15. Thus, when the housing2is disposed so that the first passage15and the second passage16are positioned at a lower side in the vertical direction as shown inFIG. 3, load of an upper part of the housing2is concentrated on the second passage16, which may deform the second passage16. Furthermore, when a rotary force (torsion force) is applied to the first passage15of the housing2through the cap nut17, the second passage16may be deformed.

In order to prevent such deformation of the second passage16, the support member14is disposed so as to surround the second passage16over its passage length L2. The support member14is a member independent of the housing2, and is a member disposed in a state of being fitted to the housing body2b. As shown inFIG. 1, the support member14has an opening on one part of its outer circumferential surface, allowing the support member14to communicate with the external space.

FIG. 4(a)is a transverse cross-sectional view of the pressure sensor1shown inFIG. 2along the line C-C. As shown inFIG. 4(a), a shape of the inner circumferential surface of the support member14substantially matches a shape of the outer circumferential surface of the housing body2b, and the support member14and the housing body2bare in a fitted state. The shape of the inner circumferential surface of the support member14and the shape of the outer circumferential surface of the housing body2bare circular except for two end surfaces at upper and lower positions. When a rotary force (torsion force) centering on a central axis of the second passage16is applied to the support member14in the circumferential direction, the force applied to the support member14is transmitted to the housing body2bdue to the presence of the two end surfaces at the upper and lower positions.

FIG. 4(b)is a transverse cross-sectional view of the pressure sensor1shown inFIG. 2along the line D-D. As shown inFIG. 4(b), a part of the inner circumferential surface of the support member14and a part of the outer circumferential surface of the housing body2bare in contact with each other at four positions, and the support member14and the housing body2bare in a fitted state. When a rotary force (torsion force) centering on the central axis of the second passage16is applied to the housing body2bin the circumferential direction, the force applied to the housing body2bis transmitted to the support member14due to the contact between the inner circumferential surface of the support member14and the outer circumferential surface of the housing body2bat the four positions.

When a rotary force (torsion force) centering on a central axis of the first passage15is applied through the cap nut17to the first passage15of the housing body2bin the circumferential direction, the force applied is transmitted as follows: First, due to the structure shown inFIG. 4(b), the force applied to the housing body2bis transmitted to the support member14. Then, due to the structure shown inFIG. 4(a), the force applied to the support member14is transmitted to the housing body2b.

That is, the force applied through the cap nut17is applied not intensively on the second passage16of the housing body2balone, but is applied also to the upper part of the housing body2bthrough the support member14. Thus, the support member14can properly support the second passage16so as to prevent the second passage16from deforming.

As has been described above, in the amplifier-embedded pressure sensor1of the present embodiment, the space inside the housing2, to which the pressure-detecting element3is fixed, is separated by the separation member4into the first space R1 where the pressure-detecting element3is disposed, and the second space R2 where the amplifier circuit board5having the amplifier circuit5afor amplifying the pressure signal detected by the pressure-detecting element3is disposed.

Furthermore, the amplifier circuit board5is cooled by the cooling gas flowing from the inflow port7into the second space R2 of the housing2, and the cooling gas is discharged from the discharge port8to the outside of the housing2. Although inflow of the cooling gas causes pressure fluctuations in the second space R2 inside the housing2, no pressure fluctuation occurs in the first space R1, as the first space R1 is separated from the second space R2 by the separation member4.

Therefore, the pressure fluctuation in the second space R2 does not affect the detection results of the pressure-detecting element3which detects the differential pressure between the fluid to be detected and the space where the pipe is installed. Thus, according to the present embodiment, it is possible to provide the amplifier-embedded pressure sensor1which, when detecting the differential pressure between the high-temperature fluid and the space where the pipe is installed, can properly detect the differential pressure between the fluid and the space where the pipe is installed, while protecting the amplifier circuit5afor pressure signals from heat of the fluid.

According to the amplifier-embedded pressure sensor1of the present embodiment, the amplifier circuit board5is disposed between the inflow port7and the discharge port8. This allows the cooling gas to flow near both front and back surfaces of the amplifier circuit board5, so that the amplifier circuit5ais adequately cooled.

According to the amplifier-embedded pressure sensor1of the present embodiment, the space between the inner circumferential surface of the housing2and the outer circumferential surface of the separation board4a, whose shape substantially matches the shape of the inner circumferential surface of the housing2, is filled with the filling material4b, so that the cooling gas is prevented from flowing from the second space R2 into the first space R1.

This allows the space inside the housing2to be separated into the first space R1 where the pressure-detecting element3is disposed and the second space R2 where the amplifier circuit board5is disposed, by a relatively simple work of packing the filling material4bbetween the outer circumferential surface of the separation board4aand the inner circumferential surface of the housing2.

According to the amplifier-embedded pressure sensor1of the present embodiment, the amplifier-embedded pressure sensor may include the coupling part22to which the external wire19for transmitting the pressure signal amplified by the amplifier circuit5ato the external device is coupled, and the first space R1 may communicate with the space near the external device through the third space R3 between the external wire19and the cladding film20cladding the external wire19.

This allows the gas in the space near the external device, which is disposed at a position separated from the pressure sensor1by the length of the external wire19, to be supplied to the first space R1 through the third space R3. Thus, corrosion of the pressure-detecting element3in the first space R1 can be prevented, as the space near the pressure sensor1may corrode the pressure-detecting element3in the first space R1 due to effects of the fluid, etc. whose pressure is to be detected.

According to the amplifier-embedded pressure sensor1of the present embodiment, the fluid chamber23is formed by the pressure-receiving surface3aof the pressure-detecting element3and the surface of the housing2opposite to the pressure-receiving surface3a, and the housing2includes the first passage15which communicates with the external passage and the second passage16which communicates the first passage15and the fluid chamber23, and the passage diameter D2 of the second passage16is smaller than the passage diameter D1 of the first passage15.

This allows the temperature of the fluid reaching the fluid chamber23to be kept low by sufficiently cooling the high-temperature fluid flowing in from the first passage15in the second passage16, which has higher cooling efficiency than the first passage15, before the fluid reaches the fluid chamber23.

According to the amplifier-embedded pressure sensor1of the present embodiment, the passage length L2 of the second passage16is longer than the passage length L1 of the first passage15. This allows the cooling efficiency of the second passage16to be further enhanced, so that the temperature of the fluid reaching the fluid chamber23can be kept sufficiently low.

According to the amplifier-embedded pressure sensor1of the present embodiment, the diameter D4 of the outer circumferential surface of the second passage16may be smaller than the diameter D3 of the outer circumferential surface of the first passage15, and the support member14may be provided which is disposed so as to surround the second passage16over its passage length L2, and supports the second passage16in a state where the space close to the outer circumferential surface of the second passage16communicates with the external space.

This allows the effects of the load on the second passage16having a smaller passage diameter to be properly supported by the support member14, so that deformation of the second passage16can be adequately prevented.

According to the amplifier-embedded pressure sensor1of the present embodiment, the opening diameter of the discharge port8to the second space R2 is larger than the opening diameter of the inflow port7to the second space R2. This allows the cooling gas flowing from the inflow port7into the second space R2 of the housing2to be easily discharged from the discharge port8, so that a failure due to high pressure in the second space R2 can be prevented.

According to the amplifier-embedded pressure sensor1of the present embodiment, the amplifier-embedded pressure sensor includes: the first wire24for transmitting the pressure signal from the pressure-detecting element3to the separation member4; the second wire25for transmitting the pressure signal from the separation member4to the amplifier circuit board5; and the third wire26for transmitting the pressure signal amplified by the amplifier circuit5afrom the amplifier circuit board5to the separation member4.

The separation member4includes the first terminal4c, to which the first wire24is connected, on the first space R1 side surface, and the second terminal4d, to which the second wire25is connected, on the second space R2 side surface, and the first terminal4cand the second terminal4dare electrically connected with each other.

This allows transmission of the pressure signal from the pressure-detecting element3to the amplifier circuit5aand transmission of the amplified pressure signal from the amplifier circuit5ato the separation member4while separating the first space R1 and the second space R2 by the separation member4.

Other Embodiments

Although in the first embodiment, the first terminal4cand the second terminal4dprovided on the separation board4aare formed using through-holes, the present invention may have another aspect in this respect. As long as the first terminal4cand the second terminal4dare electrically connected with each other, for example, these terminals may be metal contacts provided on the surface of the separation board4a.

Although in the first embodiment, the display circuit board6is provided, the display circuit board6may be omitted. Alternatively, a circuit board having other functions may be provided in place of the display circuit board6. Furthermore, a circuit board having other functions may be provided in addition to the display circuit board6.

In other respects, the present invention is not limited to the above-described embodiments, but changes can be appropriately made without departing from the scope of the present invention.