JPH0843232A - Pressure sensor - Google Patents

Abstract

PURPOSE:To provide a pressure sensor which can be improved in shielding effect and manufacturing cost by constituting its case of a metallic case section and resin case section which is put on the metallic case section so that a feed through capacitor can be arranged. CONSTITUTION:A case 4 composed of a metallic case section 2 and resin case section 3 which is put on the section 2 and has a U-shaped cross section is provided. The opened surface of a stem 6 is matched to the opened surface of the case 4 and the engaging section 6a of the stem 6a is engaged with a projecting section 3a at the front end of the case section 3. Since a metallic enclosure is constituted of the case section 2 and stem 6 when they are brought into direct contact with each other, the shielding property of the case 4 can be improved and the occurrence of noise is reduced. In addition, the occurrence of noise is reduced by means of a feed through capacitor 8 when detecting signals are sent to lead wires 19 from a circuit board 20 through connecting terminals 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting the pressure of a fluid or the like, and more particularly to a pressure sensor for fitting a case and a stem to form a housing.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view showing a conventional pressure sensor. The pressure sensor includes a metal stem 9 in which a flange-shaped protrusion 9b is formed. The stem 9 has a hole 9a for introducing an external pressure into the pressure introducing pipe 5 of the pressure detecting element 1.
Has been drilled. Then, the pressure detecting element 1 is attached to the stem 9 by the mounting screw 12 in a state where the frame 2 for holding the insulation between the stem 9 and the pressing plate 11 holds the edge of the stem 2 and the cap 8. It is fixed. Further, a seal ring 13, an O-ring 14, and a seal ring 15 are arranged between the stem 9 and the pressure introducing pipe 5 of the pressure detecting element 1, so that the fluid or the like enters the proximal end side of the pressure introducing pipe 5. Is being prevented.

Further, the pressure sensor has a case 16 in which a metal member 16b is insert-molded on a resin member 16a, and an O is provided between the resin member 16a and the metal member 16b.
A ring 17 is arranged to prevent the ingress of moisture and the like. The tip 16c of the metal member 16b is bent in a U shape. Further, on the upper part of the case 16, a connection terminal 18 that communicates from the inside of the case 16 to the outside is arranged,
A lead wire 19 is connected to the connection terminal 18. Further, in the case 16, a circuit board 20 having a processing circuit for performing a predetermined process on the detection signal of the pressure detection element 1 is mounted.
Is fixed, and the SUB board 21 is attached to the circuit board 20.
Is installed. In addition, the circuit board 20 and the connection terminal 18
And are electrically connected via a coil spring 22.

The U-shaped tip 16 of the metal member 16b
c is fitted to the protrusion 9b of the stem 9, and the metal member 1
An O-ring 23 is arranged between 6b and the stem 9 to prevent the entry of moisture and the like. Further, the connection lead 7 of the pressure detection element 1 and the circuit board 20 are electrically connected via the relay terminal 24.

Next, the assembling of the pressure sensor will be described. A seal ring 13, an O ring 14,
The seal ring 15 is attached and the frame 10 is attached.
Then, the pressure introducing pipe 5 of the pressure detecting element 1 is fitted into the seal ring 13, the O ring 14, and the seal ring 15. Then, the pressure detection element 1 is covered with the pressing plate 11, and the stem 2 and the cap 8 are connected by the frame 10 and the pressing plate 11.
With the edge portion of the stem clamped, the pressure detecting element 1, the frame 10 and the pressing plate 11 are attached to the stem 9 by the mounting screw 12.
It is fixed integrally to.

On the other hand, the connection terminal 18 is fixed to the upper part of the case 16 by passing it from the inside to the outside of the case 16. Then, the circuit board 20 is fixed in the case 16. In addition,
A SUB board 21 is mounted on the circuit board 20.
Further, the circuit board 20 and the connection terminal 18 are electrically connected via the coil spring 22. Then, the open surface of the stem 9 and the open surface of the case 16 are aligned, and the U-shaped tip 16c of the metal member 16b of the case 16 and the projection 9 of the stem 9 are aligned.
Mate with b. At this time, an O-ring 23 is arranged between the metal member 16b and the stem 9 to prevent the entry of moisture or the like, and electrically connect the connection lead 7 of the pressure detection element 1 and the circuit board 20 via the relay terminal 24. Connect to each other. Further, the lead wire 19 is connected to the connection terminal 18.

Next, the operation will be described. The case where the pressure sensor is attached to a pipe that feeds liquid will be described. The pressure in the pipe is the pressure introducing pipe 5 of the pressure detecting element 1.
Acts on the detection chip 4 through the pressure sensor, and its pressure is converted into an electric signal by the piezoresistive effect of the detection chip 4. This detection signal is sent from the connection lead 7 to the circuit board 20 via the relay terminal 24, and the circuit board 20 and the SUB board 2 are sent.
Predetermined processing is performed by 1. Then, the processed signal is sent from the circuit board 20 to the connection terminal 18 via the coil spring 22 and further to an external device (not shown) via the lead wire 19.

[0008]

The conventional pressure sensor has the following problems.
Since it is configured as described above, the metal member 16b of the case 16 is fixed to the resin member 16a by insert molding, and it is difficult to dispose the feedthrough capacitor as a noise countermeasure, and even if the metal member 16b is used, the connection terminal is not connected. 18
Therefore, there is a problem that noise enters the inside of the sensor and causes the circuit to malfunction, resulting in noise in the detection signal. Further, since the metal member 16b is insert-molded on the resin member 16a, there is a problem that the molding cycle becomes long and the cost of parts becomes high. Furthermore, since the O-ring 17 is required to keep the airtightness in place of the resin member 16a and the metal member 16b of the case 16, there is a problem that the number of parts is increased and the cost is increased.

The present invention has been made to solve the above-mentioned problems, and the case is composed of a metal case portion and a resin case portion which is fitted onto the metal case portion.
It is an object of the present invention to provide a pressure sensor that enables placement of a feedthrough capacitor, blocks noise that enters the inside of the sensor from the connection terminal 18, enhances the shield effect, and reduces the cost.

[0010]

In a pressure sensor according to the present invention, a case is composed of a metal case portion and a resin case portion externally fitted to the metal case portion, and the case and the metal stem are fitted to each other, and the metal A pressure detection element that converts pressure into an electric signal in a space covered with the case part and the metal stem,
A processing circuit that performs a predetermined process on the detection signal of the pressure detection element is arranged, and a metal housing is formed by the metal case portion and the metal stem.

[0011]

In the pressure sensor according to the present invention, the case is composed of the metal case portion and the resin case portion fitted onto the metal case portion, the case and the metal stem are fitted to each other, and the metal case portion and the metal stem are connected to each other. A pressure detection element that converts pressure into an electric signal in a space covered with a, and a processing circuit that performs a predetermined process on the detection signal of the pressure detection element are arranged, and the metal case portion and the metal stem By forming the metal casing, the feedthrough capacitor can be arranged, the shield effect is enhanced, and the cost can be reduced.

[0012]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the pressure sensor includes a metal stem (hereinafter, abbreviated as a stem) 6 in which an engaging portion 6a having a U-shaped cross section is formed. The stem 6 detects an external pressure. A hole 6b for introducing the pressure introducing pipe 5 of the element 1 is formed. The pressure detecting element 1 includes a frame 10 and a pressing plate 11 for maintaining insulation with the stem 6.
It is fixed to the stem 6 by the mounting screw 12 in a state where the edge portion is clamped by. Further, a seal ring 1 is provided between the stem 6 and the pressure introducing pipe 5 of the pressure detecting element 1.
3, an O-ring 14, and a seal ring 15 are arranged to prevent the fluid and the like from entering the base end side of the outer circumference of the pressure introducing pipe 5.

Further, the pressure sensor has a case 4 composed of a metal case portion 2 having a U-shaped cross section and a resin case portion 3 having a U-shaped cross section which is fitted on the metal case portion 2. The metal case 2 and the resin case 3 are integrated with each other to form the case 4 by fitting the protrusion 3a formed on the resin case 3 into the hole 2a formed in the metal case 2. There is. The tip 2b of the metal case portion 2 is bent into an L shape so that it directly contacts the stem 6 to form a metallic casing. A connection terminal 18 that communicates from the inside to the outside of the case 4 is insert-molded in the resin case portion 3 at the upper part of the case 4, and the connection terminal 18 is provided with a feedthrough capacitor 8 that reduces noise. And the lead wire 19 is connected. Further, in the case 4, a circuit board 20 on which a processing circuit that performs a predetermined process on the detection signal of the pressure detection element 1 is mounted is fixed, and a SUB board 21 is mounted on the circuit board 20. . Further, the circuit board 20 and the connection terminal 18 are electrically connected via the coil spring 22.

The engaging portion 6a of the stem 6 is engaged with the projection 3a at the tip of the resin case portion 3, and an O-ring is provided between the resin case portion 3 and the engaging portion 6a of the stem 6. 25
Are placed to prevent the ingress of moisture and the like. Further, the connection lead 7 of the pressure detection element 1 and the circuit board 20 are connected to the relay terminal 24 which is insert-molded in the frame 10.
Are electrically connected via.

Next, the assembling of the pressure sensor will be described. In the stem 6, a seal ring 13, an O ring 14,
The seal ring 15 is attached and the frame 10 is attached.
Then, the pressure introducing pipe 5 of the pressure detecting element 1 is fitted into the seal ring 13, the O ring 14, and the seal ring 15. Then, the pressure detecting element 1 is covered with the pressing plate 11, and the outer peripheral portion of the pressure detecting element 1 is sandwiched between the frame 10 and the pressing plate 11, and the pressure detecting element 1, the frame 10 and the pressing plate 11 are attached by the mounting screw 12. It is fixed integrally to the stem 6.

On the other hand, by covering the metal case portion 2 with the resin case portion 3 and inserting the projection 3a formed in the resin case portion 3 into the hole 2a formed in the metal case portion 2, the metal case portion 2 and the resin A case 4 is formed integrally with the case portion 3. The circuit board 20 is fixed in the case 4.
A SUB board 21 is mounted on the circuit board 20. Further, the circuit board 20 and the connection terminal 18 are electrically connected via the coil spring 22. Then, the open surface of the stem 6 and the open surface of the case 4 are aligned, and the stem 6
The engaging portion 6a of the above is engaged with the protruding portion 3a at the tip of the resin case portion 3. At this time, the engaging portion 6 between the resin case portion 3 and the stem 6
An O-ring 25 is arranged between the a and a to prevent intrusion of water and the like. At this time, the connection lead 7 of the pressure detection element 1 and the circuit board 20 are electrically connected via the relay terminal 24, and the lead wire 19 is connected to the connection terminal 18.

Next, the operation will be described. A case where the pressure sensor is attached to a pipe that feeds liquid will be described. The pressure in the pipe acts on the detection chip 4 through the pressure introduction pipe 5 of the pressure detection element 1, and the pressure is detected by the detection chip 4
Is converted into an electric signal by the piezoresistive effect. The detection signal is sent from the connection lead 7 to the circuit board 20 via the relay terminal 24, and the circuit board 20 performs a predetermined process. At this time, the metal case portion 2 and the stem 6 are in direct contact with each other to form a metallic casing, so that the shielding property is enhanced and noise is reduced. Then, the processed signal is sent from the circuit board 20 to the connection terminal 18 via the coil spring 22 and further to an external device (not shown) via the lead wire 19. At this time, the feed-through capacitor 8 reduces noise that enters the inside of the sensor from the outside, and prevents malfunction of the circuit.

[0018]

As described above, according to the present invention, the case is composed of the metal case portion and the resin case portion which is externally fitted to the metal case portion, and the case and the metal stem are fitted to each other. A pressure detection element that converts pressure into an electric signal in a space covered by and a processing circuit that performs predetermined processing on the detection signal of the pressure detection element are arranged, and the metal case portion and the metal stem Since it is configured such that the metal casing is formed, the shield effect can be improved. In addition, feedthrough capacitors can be placed,
Noise can be reduced, and it is not necessary to insert-mold the metal case portion into the resin case portion, so that the molding cycle can be simplified and the cost can be reduced. Further, there is an effect that an O-ring is not required between the metal case portion and the resin case portion, the number of parts can be reduced, and the cost can be reduced.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing a conventional pressure sensor.

[Explanation of symbols]

 1 Pressure Detection Element 2 Metal Case Part 3 Resin Case Part 4 Case 5 Pressure Introducing Tube 6 Stem 8 Feedthrough Capacitor 29 Processing Circuit Board

Claims (1)

[Claims] 1. A case formed of a metal case section and a resin case section externally fitted to the metal case section, a metal stem fitted to the case, and a space covered with the case and the metal stem. A pressure detecting element which is arranged and converts pressure into an electric signal; and a processing circuit which is arranged in the space covered with the case and the metal stem and which performs a predetermined process on the detection signal of the pressure detecting element. A pressure sensor, comprising a metal casing formed by the metal case portion and the metal stem.