JPH0733143Y2 - Pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pressure sensor, and more particularly to a pressure sensor excellent in reliability and assembling.

[Prior art and its problems]

Generally, by applying pressure, the diaphragm is displaced, the displacement of the diaphragm is converted into the amount of change in the resistance value of the strain gauge, and the amount of change in the resistance value of the strain gauge is amplified and taken out to the outside. A pressure sensor adapted to detect pressure is constructed as shown in FIG.

That is, in the pressure sensor shown in FIG. 7, a metal diaphragm 22 for sensing pressure is arranged in a body 21 having a substantially cylindrical shape, and a strain gauge 23 is arranged on the upper surface of the metal diaphragm 22. A circuit member 24 for amplifying a signal from the strain gauge 23 and outputting the amplified signal to the outside is provided in the body 21.

A small diameter hole 25 for introducing pressure in the body 21, a medium diameter hole 26 for accommodating the metal diaphragm 22 and the strain gauge 23,
Large-diameter holes 27 for accommodating the circuit member 24 are respectively connected in series, the small-diameter holes 25 for introducing the pressure are open to the atmosphere, and a lid member 34 is caulked at the opening of the large-diameter hole 24. It is installed and the inside is blocked.

A screw portion 26a is provided on the inner peripheral surface of the medium diameter hole 26.

The metal diaphragm 22 has a disk shape, and a recess 28 that opens to one surface is provided in the central portion of the metal diaphragm 22, and the central portion of the metal diaphragm 22 is thinner than the peripheral portion by the recess 28. The pressure applied by the thin portion 22a at the center is sensed. An annular groove 36 is formed on the outer peripheral surface of the metal diaphragm 22, and an annular O-ring 30 is provided in the groove 36.

The strain gauge 23 is provided on the surface of the metal diaphragm 22 opposite to the recess 28 in the central portion, and in this case, the strain gauge 23 is formed by a film forming method such as sputtering, vapor deposition, or photolithography. Is formed in a predetermined pattern on the upper surface of.

The strain gauge 23 has a flexible circuit 29.
One end of is connected.

Then, in order to provide the metal diaphragm 22 inside the body 21, the central recess 28 is formed as a small-diameter hole 25 which is a pressure introducing hole.
And is mounted in the medium-diameter hole 26 so as to be opposed to the side, and the nut 32 is screwed from the outside (the large-diameter hole 27 side) through the fixing ring 31 to the screw portion 26a of the inner peripheral surface of the medium-diameter hole 26. By tightening with a screw, it is securely fixed in the medium diameter hole 26. In this case, by providing an annular O-ring 30 in the groove 36 on the outer peripheral surface of the metal diaphragm 22 in advance, a complete seal is provided between the metal diaphragm 22 and the inner peripheral surface of the medium diameter hole 26. Is.

The circuit member 24 is arranged in a large diameter hole 27 in the body 21, and the circuit member 24 includes the strain gauge.
A circuit for amplifying the signal from 23 and outputting it to the outside is incorporated, and the other end of the flexible circuit 29 connected to the strain gauge 23 is connected to this circuit, and this circuit member One end of a brush 33, which is a conductor, is connected to a part of the circuit of 24.
The other end of 33 contacts the inner peripheral surface of the large-diameter hole 27, that is, the body 21 (ground), and when a high voltage is applied to the circuit of the circuit member 24, the circuit of the circuit member 24 and the strain gauge are
It is designed to protect 23. Furthermore, this circuit member
One end of a flexible circuit (not shown) is also connected to the surface of the lid member 34 side of 24, and one end of a lead wire 35 penetrating the member 34 and drawn inside is connected to the other end of the flexible circuit. It is connected.

In order to detect the pressure using the pressure sensor configured as described above, the small diameter hole 25 which is the pressure introducing hole is connected to the pressure detecting portion. When pressure is applied from the pressure detecting portion through the small diameter hole 25, the pressure introduced through the small diameter hole 25 causes the thin portion 22a at the center of the metal diaphragm 22 provided in the medium diameter hole 26. Will be applied to.

Then, the thin portion 22a of the central portion of the metal diaphragm 22 that has received the pressure is displaced in the direction opposite to the direction in which the pressure is applied. The strain gauge 23 provided on the surface of the thin portion 22a on the side opposite to the pressure applying direction is also integrally deformed, and its resistance value is changed.

Then, the circuit of the circuit member 24 senses the variation of the resistance value of the strain gauge 23 via the flexible circuit 29 connected to the strain gauge 23, and the variation of the resistance value is amplified to lead wire. It is designed to output to the outside through 35 and detect the pressure applied thereby.

Further, in the above pressure detection process, when the input voltage becomes abnormally high, the high voltage is dissipated to the body 21 via the brush 33 connected to the circuit member 24, so that the strain gauge is not affected by the high voltage. The circuit of 23 and the circuit member 24 is designed to be protected.

However, in the conventional pressure sensor configured as described above, the ground between the circuit of the circuit member 24 and the body 21 relies on the contact force of the brush 33, which is a conductor, to the body 21. However, there is a problem in that the contact force (pressing force) on the body 21 varies, resulting in poor contact, which prevents stable use for a long period of time and reduces reliability. Was.

Further, since it takes time to attach the metal diaphragm 22 and the circuit member 24 and adjust the ground of the circuit member 24 to the body 21, there is a problem that assembly workability is poor.

This invention solves the above-mentioned problems of the conventional ones, and can reliably ground between the circuit of the circuit member and the body without causing contact failure, and it is stable for a long period of time. It is an object of the present invention to provide a pressure sensor that can be used as a plurality of parts and can be easily attached to a metal diaphragm or a circuit member and has excellent assembling workability.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has a tubular body, a diaphragm provided in the body and displaced by the action of pressure, and a diaphragm provided in the diaphragm, and the resistance value is changed by the displacement of the diaphragm. In a pressure sensor comprising a strain gauge to be changed and a circuit member which is provided on the body and outputs the variation of the resistance value of the strain gauge to the outside, a conductive member is printed and wired on the circuit member, and A means for bringing a member into contact with the body is adopted, and further, an urging member for urging the circuit member in the body to strengthen the contact force of the conductive member provided therein to the body. Is adopted.

[Action]

This invention adopts the above-mentioned means, whereby the circuit of the circuit member and the body are grounded by the conductor provided on the circuit member coming into direct contact with the body. By biasing the member toward the body by the biasing member, the conductor on the circuit member surely contacts the body.

〔Example〕

 An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 shows an embodiment of a pressure sensor according to the present invention. The pressure sensor shown in this embodiment is a body 1
, A metal diaphragm 2 that is a diaphragm, a strain gauge 3, and a circuit member 4.

The body 1 has a substantially cylindrical shape, and has a small diameter hole 5 as a pressure introducing hole therein, and a medium diameter which is connected to the small diameter hole 5 and accommodates the metal diaphragm 2 and the strain gauge 3. A hole 6 and a large-diameter hole 7 that is continuous with the medium-diameter hole 6 and accommodates the circuit member 4 are provided.

The metal diaphragm 2 has a disc shape, and a central portion is provided with a recess 8 opening to one surface thereof.
Due to this concave portion 8, the central portion of the metal diaphragm 2 is thinner than the peripheral portion thereof, and the pressure applied by the thin portion 2a is sensed.

As shown in FIG. 2, the strain gauge 3 is provided on the surface of the metal diaphragm 2 opposite to the recess 8 in the center thereof. In this case, the sputter, vapor deposition, and photolithography are performed in the same manner as in the conventional case. Metal diaphragm 2 by a film forming method such as
Is formed in a predetermined pattern on the upper surface of.

The strain gauge 3 has a flexible circuit 9
One end of is connected.

Then, in order to provide the metal diaphragm 2 in the medium-diameter hole 6 in the body 1, the central recess 8 is opposed to the small-diameter hole 5 side serving as the pressure introducing hole, and the bottom surface of the medium-diameter hole 6 is provided. A part of the inner peripheral surface of the body 1 from the outside (the large diameter hole 7 side) via the fixing ring 11 while being provided between the metal diaphragm 2 and the metal diaphragm 2 via the O ring 10. By caulking, it is securely fixed in the medium diameter hole 6.

Further, the circuit member 4 is provided in the large diameter hole 7,
A circuit for amplifying the signal from the strain gauge 3 and outputting the amplified signal to the outside is also incorporated in the circuit member 4 as in the conventional case, and the strain gauge 3 is further included in this circuit.
The flexible circuit 9 is connected to the other end of the flexible circuit 9 and a conductive member 12 made of copper foil or the like shown in FIG. In addition, the conductive member 12 is also connected to the circuit.

Then, in order to provide the circuit member 4 in the large diameter hole 7 of the body 1, the conductive member 12 printed and printed on the peripheral portion is brought into contact with the bottom surface of the step portion 7a of the large diameter hole 7 so that the large diameter hole 7 is formed. In addition to being provided inside, a biasing member 13 such as a spring is provided on the outside (on the side opposite to the pressure introducing direction), and a lid member 14 is caulked and attached to the opening of the large diameter hole 7 to close the inside.

In this case, by providing the annular O-ring 16 in the annular concave groove 15 provided on the outer peripheral surface of the lid member 14,
The space between the lid member 14 and the inner peripheral surface of the body 1 can be reliably sealed.

Further, a flexible circuit 17 is also connected to the surface of the circuit member 4 on the side of the lid member 14, and the other end of the flexible circuit 17 is connected to a terminal 18 provided on the lid member 14, Further, one end of a lead wire 19 is connected to the terminal 18, and the lead wire 19 penetrates the lid member 14 and is drawn out of the body 1.

When the pressure sensor according to the present invention configured as described above is used to detect pressure, the small diameter hole 5 serving as a pressure introducing hole is connected to the pressure detecting portion.

Then, when pressure is applied from the pressure detecting portion, the pressure is applied to the thin portion 2a at the center of the metal diaphragm 2 in the medium diameter hole 6 through the small diameter hole 5 which is a pressure introducing hole. The thin portion 2a at the center of the metal diaphragm 2 is displaced in the direction opposite to the pressure application direction according to the magnitude of the pressure.

Then, due to the displacement of the metal diaphragm 2, the strain gauge 3 provided in the thin portion 2a at the center of the metal diaphragm 2 is also deformed according to the displacement amount of the metal diaphragm 2 to change its resistance value. The change amount of the resistance value of the strain gauge 3 at this time is amplified by the circuit of the circuit member and taken out to the outside, and the pressure applied thereby is detected.

In this case, the conductive member 12 such as a copper foil for grounding the circuit member 4 and the body 1 is connected to the step portion 7a of the large diameter hole 7 of the body 1 by the urging force of the urging member 13 such as a spring. Since it is strongly pressed against the bottom surface, it is possible to surely prevent the contact force between the two from being lowered during use and causing poor contact.

Therefore, the circuit of the circuit member 4 is surely grounded to the body 1, whereby the circuit of the circuit member 4 and the strain gauge 3 can be reliably protected even if an abnormality occurs in the input voltage. It can be used stably for a long period of time and the reliability can be remarkably improved.

Further, the metal diaphragm 2 is to be caulked and mounted in the body 1, and after the circuit member 4 is also mounted to the body 1, the lid member 14 is caulked and mounted from the outside through the biasing member 13 such as a spring. As a result, the workability of assembling can be remarkably improved.

In the above embodiment, the circuit member 4 is biased by the spring 13 to bias the body 1. However, a leaf spring as shown in FIG. 6 is used as shown in FIGS. 4 and 5. It is good to urge to.

[Effect of device]

With this configuration, the circuit of the circuit member is surely grounded to the body, and the circuit member is always biased to the body by the biasing member such as a spring. , The contact force between the circuit of the circuit member and the body does not decrease, and a reliable ground can be obtained in the long term. Therefore, stable use can be achieved in the long term and the reliability is remarkably improved. It will be possible.

Further, since the metal diaphragm and the circuit member are attached to the body by caulking, they have an excellent effect such that the attaching workability can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a pressure sensor according to the present invention, FIG. 2 is a perspective view showing a metal diaphragm and a strain gauge shown in FIG. 1, and FIG. 3 is a conductive view showing that shown in FIG. FIG. 4 is a perspective view showing a member, FIGS. 4 and 5 are schematic sectional views showing another embodiment of the pressure sensor according to the present invention,
FIG. 6 is a perspective view showing a leaf spring used in FIGS. 4 and 5, and FIG. 7 is a schematic sectional view showing a conventional pressure sensor. 1, 21 ...... Body 2, 22 ...... Metal diaphragm 3, 23 …… Strain gauge 4, 24 …… Circuit member 5, 25 …… Small diameter hole 6, 26 …… Medium diameter hole 7, 27 …… Large diameter hole 8, 28 …… Recess 9, 17, 29 …… Flexible circuit 10, 16, 30 …… O-ring 11, 31 …… Fixing ring 12 …… Conductive member 13 …… Biasing member 14, 34 …… Lid member 15, 36 ...... Groove 18 ...... Terminal 19, 35 ...... Lead wire 20 ...... Leaf spring 32 ...... Nut 33 ...... Brush

Claims (2)

[Scope of utility model registration request] 1. A tubular body (1), a diaphragm (2) provided in the body (1) and displaced by the action of pressure, and provided on the diaphragm (2),
A strain gauge (3) that changes a resistance value by displacement of the diaphragm (2); and a strain gauge (3) provided on the body (1),
In a pressure sensor comprising a circuit member (4) for outputting the amount of change in the resistance value of the strain gauge (3) to the outside, a conductive member (12) is printed and wired on the circuit member (4), and A pressure sensor characterized in that a member (12) is brought into contact with the body (1). 2. A biasing member (1) for biasing the circuit member (4) in the body (1) so as to strengthen the contact force of the conductive member (12) provided on the circuit member (4) with the body (1). 13),
The pressure sensor according to claim 1, further comprising (20).