JPH0979929A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor which can operate singly, does not require any auxiliary mechanism when the sensor is used, and can be handled easily. SOLUTION: A pressure sensor is provided with a lower case 2 with an opened top, an upper case 3 which closes the opening of the case 2 when the case 3 is put on the case 2 and has an opening 6 on the top, a flexible lid body 7 which closes the opening 6 of the case 3, a strain sensor 4 which is housed in the case 3 and, when the lid body 7 is bent under an external pressure, directly or indirectly deformed and the electrical characteristic of which changes, and a pair of terminal members 5 and 5 which are extended through the case 2 so as to fetch the electrical characteristic of the sensor 4 to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor which detects a change in ambient pressure at an installation location and outputs the change as an electric signal.

[0002]

2. Description of the Related Art In gas equipment or pressure equipment, gas pressure or air pressure is detected in these equipment or in a pipe connecting these equipment to a gas cylinder or a pressure source, and the detection output is transmitted to a controller, A pressure sensor is installed to monitor the pressure state of the pressure sensor and the like, and to provide timings such as interruption of the electrical operation circuit and interruption of the gas cylinder or the outlet of the pressure generation source when an abnormality occurs. Such a pressure sensor is installed such that a pressure reservoir is provided in the device or a measuring section is inserted into a branch pipe branched from the middle of the pipe.

Further, a rechargeable storage battery such as a secondary battery is also provided with a pressure sensor for detecting an increase in pressure inside the storage battery. That is, even if this type of storage battery is completely charged, or if it is charged with a current larger than the specified current, an abnormality occurs in the storage battery and gas is generated in the storage battery. The pressure rises, the storage battery expands, and the electrolyte leaks due to cracks, which may adversely affect the device in which the storage battery is incorporated. Therefore, it has been practiced to provide a pressure sensor for detecting an increase in pressure in the storage battery, issue an alarm when the pressure increase is detected, and prevent a current from flowing through an electric circuit connected to the storage battery.

[0004]

However, in gas equipment and pressure equipment, when the measuring portion of the pressure sensor is attached to the pressure sump or the branch pipe, the airtightness must be sufficiently taken into consideration. There is a drawback that the sensor becomes large and the structure of the mounting portion becomes complicated. Also, when the pressure sensor is provided in the storage battery, it is desired that the pressure sensor has a simple structure and can be unitized and used (the pressure sensor can be attached at any position).

A first object of the present invention is to provide a pressure sensor which operates independently and does not require an auxiliary mechanism during use and is easy to handle.

A second object of the present invention is to provide a pressure sensor with reduced pressure loss and improved pressure sensitive characteristics.

A third object of the present invention is to provide a pressure sensor designed to prevent breakage of a member which is deformed by a pressure change.

A fourth object of the present invention is to provide a pressure sensor having a simple structure of a pressure change detecting portion and a simple electric circuit.

A fifth object of the present invention is to provide a power source through a pressure sensor when the equipment whose pressure state is to be detected is electrically driven, and to give an alarm when an abnormality occurs in the pressure. Another object of the present invention is to provide a pressure sensor that outputs a signal that can be used for display, and that can cut off the power supply when the pressure further rises and damages equipment and the like.

A sixth object of the present invention is to provide a pressure sensor which can detect a pressure change more reliably.

A seventh object of the present invention is to provide a pressure sensor which can surely be deformed by pressure.

An eighth object of the present invention is to provide a pressure sensor which is easy to assemble and whose inside can be reliably sealed.

[0013]

A first object of the present invention is to provide a housing part of which is opened, a flexible lid for closing the opening of the housing, and a housing which is housed in the housing. It has a strain sensor whose electrical characteristics are changed by being directly or indirectly deformed by the bending of the lid due to external pressure, and a pair of terminal members for taking out the electrical characteristics of this strain sensor to the outside. This is achieved by the first means in which the space between the housing and the lid and the space between the terminal members are hermetically sealed.

The second object is, in the first means,
This is achieved by the second means in which a pressing member having a convex portion that abuts the strain sensor is interposed between the lid and the strain sensor.

The third object is, in the first means,
This is achieved by a third means for forming a restriction portion that restricts the deformation amount of the strain sensor due to the pressure in the housing in the deformation direction.

The fourth object is, in the first means,
This is achieved by the fourth means in which the strain sensor is composed of a ceramic substrate and a strain resistor which is formed on at least one surface of the ceramic substrate and whose resistance value changes due to strain due to pressure.

The fifth object is, in the first means,
This is achieved by the fifth means in which the strain sensor is further provided with an electric path independent of the pressure sensitive resistor and another terminal member connected to this electric path.

The sixth object is, in the first means,
Sixth means for forming a strain sensor by a ceramic substrate and strain resistors formed on both surfaces of the ceramic substrate and having resistance values that change due to expansion and contraction, and detecting pressure based on changes in resistance values of the strain resistors on both surfaces. Achieved by

The seventh object is, in the second means,
This is achieved by the seventh means in which the convex portion of the pressing member is positioned so as to abut the substantially central portion of the strain sensor.

The eighth object is, in the first means,
The case is covered with a strain sensor inside and a lower case with an open upper part that supports the pair of terminal members so as to extend to the outside, and the opening of the lower case is covered so as to seal the upper part. This is achieved by the eighth means, which comprises an upper case having an opening for sealing the lid.

[0021]

In the first means, when the external pressure becomes higher than the predetermined value, the pressure causes the lid body to flex and the strain sensor to deform, thereby changing its electrical characteristics. This electrical characteristic is taken out by the terminal member. Since the inside of the housing is sealed, it can operate independently, no auxiliary mechanism is required during use, and it is easy to handle.
Further, the sealed place may be between the housing and the lid and between the housing and the terminal member, which can reduce the manufacturing cost.

In the second means, the lid body is deformed by a pressure change to press the pressing member in a planar manner, and the convex portion of the pressing member deforms the strain sensor.
The lid can be made of a highly flexible material, which can reduce pressure loss and enhance pressure-sensitive characteristics. On the other hand, since the pressing member receives the surface pressure of the lid, it can be efficiently transmitted to the strain sensor by being made of a hard material.

In the third means, when the strain sensor is deformed by pressure, the strain sensor is prevented from deforming until it breaks because it comes into contact with the regulating portion when the strain sensor deforms by a predetermined amount.

In the fourth means, when the ceramic substrate is deformed, the strain resistor formed on one surface of the ceramic substrate is also deformed and its resistance value changes. Therefore, the pressure change can be monitored by monitoring the resistance value between the terminal members, and a highly reliable pressure sensor can be provided although the detection circuit is simple.

In the fifth means, an alarm means or a display means for notifying a pressure change is connected to the terminal member on the pressure sensitive resistor side, and the pressure state is controlled by an electric circuit independent of the pressure sensitive resistor. If the equipment to be detected is driven electrically, the power source will be used as the power source for the pressure sensor, and if the pressure sensor is configured to be broken in the event of a pressure abnormality, the pressure sensor will be connected through the electric circuit. It is also possible to cut off the power supply to a device that has been supplied with power.

In the sixth means, since the strain resistors are provided on both sides of the ceramic substrate, when the ceramic substrate is deformed by the pressure, the resistance value of the surface extended by the deformation becomes large and the ceramic member shrinks. Since the resistance value of the surface becomes small, the change amount can be made large by taking out these two resistance values, so that the pressure change can be accurately detected.

In the seventh means, since the convex portion of the pressing member contacts the substantially central portion of the strain sensor, the strain sensor is easily deformed, and the deformation of the pressing member allows the strain sensor to operate more reliably. be able to.

In the eighth means, since the housing is composed of the lower case and the upper case, the strain sensor is housed in the lower case, and the pair of terminal members are extended to the outside. The case is assembled by covering the opening of the case with the upper case so as to seal the joint between the lower case and the upper case, between the lower case and the terminal member, and the opening of the lid and the upper case. By doing so, the inside of the housing can be reliably sealed.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to substantially the same constituents throughout the embodiments, and the duplicated description will be omitted.

First, the first embodiment shown in FIGS. 1 to 7 will be described. 1 is a plan view of a pressure sensor according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, FIG. 3 is a sectional view taken along the line BB of FIG. 1, and FIG. FIG. 5 is a diagram for explaining a state in which the strain sensor is deformed, FIG. 6 is an explanatory diagram showing a resistance change rate when the strain sensor is deformed, and FIG. 7 is a voltage division type structure using three terminals. FIG.

As shown in FIGS. 1 to 3, the pressure sensor 1 includes a lower case 2 and an upper case 3 which form a housing, a strain sensor 4 whose electrical characteristics change due to deformation, and this strain sensor. 4, the terminal member 5 attached so as to be electrically connected to both ends, the lid 7 attached to the opening 6 of the upper case 3, and the strain sensor 4 pressed by the pressing of the lid 7 to be deformed. The actuator 8 is mainly composed of a pressing member.

The lower case 2 is made of PPS and, as shown in FIGS. 2 and 3, has a recess 2a having an open upper surface,
Lateral ridges 2b projecting laterally from the outer side surface, upper ridges 2c formed on the upper portions of the side surfaces, a pair of element holding portions 2d extending in the longitudinal direction in the recesses 2a, and an element. The concave step portion 2e formed between the holding portions 2d is integrally formed. Four terminal members 5 of the strain sensor 4 penetrate through the lower case 2.

As shown in FIGS. 4 and 5, the strain sensor 4 is provided on a strip-shaped substrate 11 made of ceramic or the like having an insulating property, and on both upper and lower surfaces of the substrate 11 so as to extend in the longitudinal direction. Strain resistors 12a and 12b, and conductive portions 13a and 13b formed by applying a conductive material such as silver to the longitudinal ends of the strain resistors 12a and 12b.
And an insulating coat portion 14 formed by applying an insulating material over the entire surface of the conductive portions 13a and 13b, leaving the connection portion of the terminal member 5 therethrough. This strain sensor 4 is, for example, 0.3 m
It is formed to a thickness of m.

Although the strain sensor 4 normally extends flat, it is curved as shown in FIG. 5 when the actuator 8 is pressed by an external pressure. When the actuator 8 is released from the pressure, the original flat state is restored. A characteristic diagram of the resistance (R) change rate of the strain sensor 4 and the pressure P is shown in FIG. In this figure, AA 'indicates the rate of change that changes to the negative side between the conductive portions 13a and 13a, and BB' indicates the rate of change that changes to the positive side between the conductive portions 13b and 13b. In this case, a voltage division type structure using three terminals as shown in FIG. 7 is possible.

The terminal member 5 is attached to the strain sensor 4 by the solder 15.
It is attached to each of the connections. These terminal members 5 are made of copper wires having a diameter of 0.2 mm, for example.
Therefore, the terminal member 5 is sufficiently flexible, but the lower solder 15 is in contact with the lower case 2, and the pair of element holding portions 2d of the lower case 2 holds the strain sensor 4 in a double-supported state.

The upper case 3 is made of a material such as aluminum having a thickness of 0.3 mm, and as shown in FIGS. 1 to 3, is made up of an upper surface portion 3a and four side surface portions 3b, 3b ...
An opening 7 is bored at approximately the center of the upper surface 3a,
Further, locking piece portions 3c which are caulked inside and are locked to the lower end of the lower case 2 are provided at the lower end portions of the respective side surface portions 3b.

The lower case 2 is covered with a lid 7 so as to house and clamp the strain sensor 4 and the terminal member 5. The lid 7 is composed of an insulating packing made of an elastic material such as butyl rubber. The lid body 7 is mainly composed of a flexible portion 7a whose central portion projects upward so as to close the opening portion 7 and is elastically deformed by pressure, and a peripheral edge portion 7b extended to the peripheral edge of the flexible portion 7a. . The boundary between the flexible portion 7a and the peripheral portion 7b is formed thin. The peripheral portion of the lid 7 is brought into close contact with the lower case 2 and the upper case 3 by the elasticity of the lid 7 itself, and thus the inside surrounded by the lower case 2, the lid 7 and the upper case 3 can be reliably sealed.

The actuator 8 is made of a highly rigid material such as a phosphor bronze plate having a thickness of 0.15 mm, and is denoted by B- in FIG.
The flat portion 8a and the side plate portion 8b are formed by bending the cross section in the direction of the line B in a U shape, and the convex portion 8c protruding in the bending direction of the side plate portion 8b is provided substantially at the center of the flat portion 8a. ing. When the actuator 8 is housed in the hollow inside of the lid 7, the lower case 2 and the upper case 3, the convex portion 8 c of the actuator 8 is in contact with the center of the upper surface of the strain sensor 4.

The operation when the pressure sensor configured as described above is installed in a gas device, a pressure device, or a pipe, which is the path thereof, will be described below.

In the pressure sensor 1 under normal pressure, the flexible portion 7a of the lid 7 is slightly pressed in the direction of the actuator 8 by the pressure, but the pressure is not such that the actuator 8 is deformed. Therefore, as shown in FIG. 4, the substrate 11 of the strain sensor 4 is in a flat state, the resistance values of the strain resistors 12a and 12b are not changed, and have a preset resistance value.

When the pressure in the gas equipment, the pressure equipment, the pipe, etc. rises, the flexible portion 7 of the lid 7 is caused by the pressure.
The flexible portion 8a of the lid body 7 is bent by deforming a by bending inward.
2, the actuator 8 pushes the actuator 8 downward in FIG. 2, and the protrusion 8c of the actuator 8 pushes the strain sensor 4 downward substantially at the center thereof. Since both ends of the strain sensor 4 are placed in the recess 2a of the lower case 2 and fixed to the terminal member 5 by soldering, the movement is restricted in the long-short direction and the vertical direction. Therefore, the strain sensor 4 is deformed as shown in FIG. 5 by the pressing of the protrusion 8c, the strain resistor 12a on the upper surface is contracted and its resistance value is reduced, and the strain resistor 12b on the lower surface is expanded and its resistance value is reduced. growing. Since two changes, that is, a negative change amount and a positive change amount of the resistance value are extracted, a large change amount can be obtained. To extract such a change, the strain resistors 12a and 12b are connected in series, a voltage is applied from the strain resistor 12a to the strain resistor 12b, and the strain between the strain resistor 12a and the strain resistor 12b connected in series is generated. This can be performed by using a voltage dividing type structure with three terminals for extracting a voltage between the negative sides of the resistors 12a and 12b. In addition, the strain resistors 12a, 1
Since the insulating coat portion 14 is formed on the surface of 2b, the projection 8c of the actuator 8 made of metal does not directly contact the strain resistor 12a, so that a short circuit occurs at this contact portion and an accurate resistance value cannot be obtained. There is no such thing.

Next, a second embodiment of the present invention shown in FIG. 8 will be described. 8 is a vertical cross-sectional view showing a pressure sensor according to the second embodiment, FIG. 9 is a characteristic view of the pressure sensor according to the second embodiment, and FIG. 10 is for explaining spring characteristics of the pressure sensor according to the second embodiment. FIG. The same parts as those in the above embodiment are designated by the same reference numerals and detailed description thereof will be omitted. In the second embodiment, as shown in FIG. 9, when the pressure P is suddenly applied or an abnormally high pressure is applied, the strain sensor 4 is broken even when the strain sensor breaking pressure P2 is exceeded. Is being prevented. That is, a columnar or prismatic protrusion 21 is integrally formed at the approximate center of the concave portion 2a of the lower case 2 so as to protrude upward and serve as a regulating portion that regulates the maximum deformation amount of the strain sensor 4. This protrusion 2
1 is positioned so as to abut the substantially central portion of the strain sensor 4. Spring members 22 such as coil springs are interposed between the protrusion 21 and the terminal members 5 attached to both ends of the strain sensor 4 in the longitudinal direction. Reference numeral 5a is a strain sensor support piece in which the state of the terminal member 5 is formed by bending.
Is a curved portion in which the upper portion of the terminal member 5 is easily bent when the strain sensor 4 bends. These spring members 22 and 22 elastically support the strain sensor 4, and the spring constant thereof is fixedly supported until just before the center of the strain sensor 4 contacts the protrusion 21. However, the strain sensor 4 is set so as to descend when a force is applied so that the central portion of the strain sensor 4 comes into contact with the protrusion 21. 4 is prevented from breaking. In the second embodiment, the strain resistor 12b is provided only on the lower surface of the substrate 11, and the conductive portions 13b and 13b are provided at both longitudinal ends of the strain resistor 12b. Therefore, in this embodiment, the change in pressure is detected by the change in resistance value due to the elongation of the strain resistor 12b.

The operation of the second embodiment will be described with reference to FIGS. 9 and 10. In FIG. 10, d1 is the height of the protrusion 21, d2 is the distance between the protrusion 21 and the lower surface of the strain sensor 4, d0 is d1 + d2, dpn is the height at pressure pn, S is the opening area of the strain sensor 4, and the spring material is 22, 2
2 are both springs having the same characteristics. The strain sensor 4 receives a load of P × S against the pressure P from the outside,
When dp> d1, the load of Pn × S is almost (Pn × S
S / 2) + (Pn × S / 2), the two spring members 22, 2
You will receive it in 2. Here, dp2 <d1, dp1
The spring constant α of the spring members 22 and 22 should satisfy <d1.
By setting 1 and α2, when the pressure is higher than p1, the protrusion 21 receives the lower surface of the strain sensor 4 (dp = d1 becomes constant), the deformation of the strain sensor 4 stops, and destruction occurs. Can be prevented.

Finally, FIG. 1 shows the third embodiment of the present invention.
This will be described with reference to FIGS. 11 is a longitudinal sectional view showing a pressure sensor in the third embodiment, FIG. 12 is a perspective view showing only the strain sensor and the terminal member in the third embodiment in an exploded manner, and FIG. 13 is an equivalent strain sensor in the third embodiment. FIG. 14 is an explanatory diagram showing a circuit, and FIG. 14 is a characteristic diagram of the pressure sensor in the third embodiment. The same parts as those in the above embodiment are designated by the same reference numerals and detailed description thereof will be omitted. The third embodiment is, for example, provided in a rechargeable storage battery and has a form suitable for detecting an increase in pressure in the storage battery.
That is, the strain sensor 31 in this embodiment is similar to that shown in FIG.
As shown in FIG. 2, the lower surface of the substrate 11 is divided into two in a direction parallel to the longitudinal direction.
Conductive portions 13b and 13b are provided at both longitudinal ends of the conductive path 32, and a conductive path 32 and conductive portions 33 and 33 are provided at both longitudinal ends of the conductive path 32. Terminal members 5 and 5 are fixed to the conductive portions 13b and 13b, and changes in the resistance value of the strain resistor 12b are detected as in the first and second embodiments.
Terminal members 34, 34 are also fixed to the other conductive portions 33, 33, and these terminal members 34, 34 are connected so that a charging current from a charging power source for a storage battery (not shown) flows through the conductive path 32. I'll do it. The strain sensor 31 is set to have a strength such that the strain sensor 31 breaks when its central portion bends downward by a predetermined amount or more. An equivalent circuit of the third embodiment is shown in FIG. 13 and a characteristic diagram is shown in FIG. In these figures, A and A'indicate terminal members 34 and 34, and B and
B'indicates the terminal members 5 and 5.

With this configuration, gas is generated in the storage battery because the storage battery is further charged even if the storage battery is completely charged, the charging is performed with a current larger than the specified current, or the storage battery is abnormal. Then, when the pressure in the storage battery rises, the strain sensor 31 is deformed, and the resistance value of the strain resistor 12b first becomes larger than the initial value R0. If the change in the resistance value is taken out as a voltage and the buzzer is operated or the lamp is turned on when the voltage value set in advance is reached, the occurrence of the abnormality of the storage battery can be notified. If the pressure of the storage battery further increases, the storage battery may expand, and the electrolyte may leak out due to cracks, which may adversely affect the device in which the storage battery is incorporated. In this case, the strain sensor 31 is broken and the conductive path 32 is cut. This stops the supply of charging current to the storage battery.

[0046]

According to the invention described in claim 1, when the external pressure becomes higher than a predetermined value, the lid is bent by the pressure and the strain sensor is deformed to change its electrical characteristics. The electrical characteristics can be detected from the terminal member to the outside, and the change in pressure can be detected by monitoring the characteristics. Since the housing of the pressure sensor is hermetically sealed, it can operate as a single unit, no auxiliary mechanism is required during use, and it is easy to handle. Further, the sealed place may be between the housing and the lid and between the housing and the terminal member, which can reduce the manufacturing cost.

According to the second aspect of the present invention, the lid body is deformed by the pressure change to press the pressing member in a planar manner, and the convex portion of the pressing member deforms the strain sensor, so that the lid body is flexible. It is possible to reduce the pressure loss and improve the pressure-sensitive property. On the other hand, since the pressing member receives the surface pressure of the lid, it can be made of a hard material and efficiently transmit the pressure to the strain sensor.

According to the third aspect of the present invention, when the strain sensor is deformed by pressure, the strain sensor is prevented from deforming until it breaks because the strain sensor comes into contact with the regulating portion when the strain sensor deforms by a predetermined amount. .

According to the invention described in claim 4, when the ceramic substrate is deformed, the strain resistor formed on one surface of the ceramic substrate is also deformed and its resistance value is changed. Therefore, the pressure change can be monitored by monitoring the resistance value between the terminal members, and a highly reliable pressure sensor can be provided although the detection circuit is simple.

According to the fifth aspect of the invention, the pressure sensing resistor side is connected to the terminal member with the alarm means and the display means for notifying the pressure change, and the pressure state is provided by the electric path independent of the pressure sensing resistor. If the device to be detected is electrically driven, the pressure sensor serves as a power supply source for the power supply, and the power supply to the device can be cut off when a pressure abnormality occurs.

According to the sixth aspect of the present invention, since the strain resistors are provided on both surfaces of the ceramic substrate, when the ceramic substrate is deformed by pressure, the resistance value of the surface extended by the deformation becomes large and the ceramic substrate shrinks. Since the resistance value of the flat surface becomes small, the change amount can be made large by taking out these two resistance values, so that the pressure change can be accurately detected.

According to the invention described in claim 7, since the convex portion of the pressing member abuts the substantially central portion of the strain sensor, the strain sensor is easily deformed, and the deformation of the pressing member allows the strain sensor to operate more reliably. Can be made.

According to the eighth aspect of the invention, since the housing is composed of the lower case and the upper case, the strain sensor is housed in the lower case, and the pair of terminal members are extended to the outside. The case is assembled by covering the opening of the lower case with the upper case so as to seal the lower case and the joint between the lower case and the upper case, between the lower case and the terminal member, and the opening of the lid and the upper case. By sealing, it is possible to reliably seal the inside of the housing.

[Brief description of drawings]

FIG. 1 is a plan view showing a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a cross-sectional view showing only the strain sensor.

FIG. 5 is a diagram for explaining a deformed state of the strain sensor.

FIG. 6 is an explanatory diagram showing a resistance change rate when the strain sensor is deformed.

FIG. 7 is an explanatory diagram showing a voltage division type structure using three terminals.

FIG. 8 is a vertical sectional view showing a pressure sensor according to a second embodiment of the invention.

FIG. 9 is a characteristic diagram of a pressure sensor according to a second embodiment of the present invention.

FIG. 10 is an explanatory diagram for explaining spring characteristics in the pressure sensor according to the second embodiment of the present invention.

FIG. 11 is a vertical sectional view showing a pressure sensor according to a third embodiment of the invention.

FIG. 12 is an exploded perspective view showing only a strain sensor and a terminal member according to a third embodiment of the present invention.

FIG. 13 is an explanatory diagram showing an equivalent circuit of the strain sensor according to the third embodiment of the present invention.

FIG. 14 is a characteristic diagram of a pressure sensor according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Pressure Sensor 2 Lower Case 3 Upper Case 4,31 Strain Sensor 5,34 Terminal Member 6 Opening 7 Lid 8 Actuator 8c Convex Part 11 Substrate 12a, 12b Strain Resistor 13a, 13b, 33 Conductive Part 14 Insulation Coating Part 21 Protrusion 22 Spring material 32 Conductive path

Claims (8)

[Claims] 1. A housing partly opened, a flexible lid for closing the opening of the housing, and a housing which is housed in the housing and is directly bent by the bending of the lid due to external pressure. Or a strain sensor whose electric characteristics are changed by being indirectly deformed, and a pair of terminal members for taking out the electric characteristics of the strain sensor to the outside. A pressure sensor characterized in that the space and the terminal member are sealed. 2. The pressure sensor according to claim 1, wherein a pressing member having a convex portion that abuts on the strain sensor is interposed between the lid body and the strain sensor. 3. The pressure sensor according to claim 1, wherein the casing is formed with a restriction portion that restricts a deformation amount of the strain sensor due to pressurization in the deformation direction. 4. The strain sensor comprises a ceramic substrate,
2. The pressure sensor according to claim 1, wherein the pressure sensor is formed on at least one surface of the ceramic substrate and comprises a strain resistor whose resistance value changes due to strain due to pressure. 5. The pressure sensor according to claim 1, wherein the strain sensor further includes an electric path independent of the pressure sensitive resistor and another terminal member connected to the electric path. 6. The strain sensor comprises a ceramic substrate,
2. A strain resistor formed on both sides of the ceramic substrate and having a resistance value that changes due to expansion and contraction, and pressure is detected by a change in the resistance value of the strain resistors on both sides. Pressure sensor. 7. The pressure sensor according to claim 2, wherein the convex portion of the pressing member is positioned so as to abut a substantially central portion of the strain sensor. 8. The casing includes a lower case that accommodates the strain sensor therein and has an open upper portion that supports the pair of terminal members so as to extend to the outside, and an opening portion of the lower case. 2. The pressure sensor according to claim 1, further comprising: an upper case which is covered so as to be hermetically sealed, and which has an opening formed at an upper portion thereof for sealing the lid body.