JP2009168537A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor which can improve vibration-proof performance. <P>SOLUTION: The pressure sensor 1 includes: a case 2 which is tubular in shape and is provided with a small-diameter part 2a and a large-diameter part 2b; a metallic diaphragm 3 which is based tubular in shape, is housed within and fixed to the small-diameter part 2a of the case 2, and to which pressure is introduced into the inner part A; a sensor part 4 which is provided on the outer surface of a base part 3a of the metallic diaphragm 3 and has a plurality of strain gauges constituting a bridge circuit to detect the strain of the base part; a connector 6 which is fitted into the large-diameter part 2b of the case 2 and holds a processing substrate 5 which processes a signal output by the sensor part 4; and a flexible cable 7 which connects the sensor part 4 and the processing substrate 5 and is folded and housed into the case 2. The flexible cable 7 is connected to the bridge circuit of the sensor part 4 and is provided with a bent part 7a at the part of the flexible cable 7 which is housed within the large-diameter part 2b of the case 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement in a pressure sensor.

  As this type of pressure sensor, for example, a pressure sensor including a sensor unit including a plurality of strain gauges constituting a bridge circuit on the surface of a metal diaphragm is known (for example, see Patent Document 1).

  In this pressure sensor, as shown in FIG. 3, a cylindrical case 20 having a small-diameter portion 20a and a large-diameter portion 20b is accommodated and fixed in the small-diameter portion 20a of the case 20, and pressure is introduced into the inside. A bottomed cylindrical metal diaphragm 21, a sensor portion 22 provided on the outer surface of the bottom of the metal diaphragm 21 and having a plurality of strain gauges (not shown) constituting a bridge circuit, and detecting the strain of the bottom, and a case The connector 24 that holds the processing substrate 23 that is fitted in the large-diameter portion 20 b of the 20 and processes the signal output from the sensor unit 22, and the sensor unit 22 and the processing substrate 23 are connected and folded into the case 20. And a flexible cable 25 to be accommodated.

  In this pressure sensor, in particular, the case 20 is formed into a cylindrical shape, and the case 20 is not divided into one that holds the metal diaphragm 21 and one that holds the connector 24, and the single case 20 and the metal diaphragm 21. Since both of the connectors 24 are held, a seal is sufficient only for the fitting portion between the metal diaphragm 21 and the connector 24, and a structure that is advantageous in terms of the number of parts and the number of processing steps is adopted.

  The sensor unit 22 includes a bridge circuit (not shown) in which a plurality of strain gauges are connected in a loop shape, and a relay substrate 26 connected to the bridge circuit with a bonding wire, and the processing substrate 23 is connected via the relay substrate 26. Connected to the bridge circuit.

  When connecting the sensor unit 22 and the processing substrate 23, a flexible cable 25 including at least four or more conductors connected in parallel to the bridge circuit of the sensor unit and an insulating film covering the conductors is used. Yes.

The reason why such a flexible cable 25 is used is to prevent the flexible cable 25 from moving freely to some extent when vibration acts on the pressure sensor, so that an excessive load is not applied to the extremely thin bonding wire.
JP 2007-78467 A

  In such a conventional pressure sensor, in order to enjoy the various advantages described above, the case 20 has a cylindrical shape, and the sensor portion 22 provided on the metal diaphragm 21 accommodated in the small diameter portion 20a on one end side of the case 20; To assemble a pressure sensor because the flexible cable 25 is used to connect the processing substrate 23 held by the connector 24 fitted to the large-diameter portion 20b on the other end side of the case 20. First, the metal diaphragm 21 is fixed in the small diameter portion 20a of the case 20 with one end of the flexible cable 25 connected to the sensor unit 22 in advance, and then the other end of the flexible cable 25 is connected to the processing substrate 23. The connector 24 is accommodated in the large diameter portion 20b of the case 20.

  In order to enable such an assembly process, it is necessary that the other end of the flexible cable 25 can be soldered to the processing substrate 23 outside the case 20 while the metal diaphragm 21 is accommodated in the small diameter portion 20a of the case 20. Therefore, the flexible cable 25 is long enough that the other end protrudes out of the case 20 with the metal diaphragm 21 fixed to the case 20, and when the connector 24 is fitted into the large-diameter portion 20b of the case 20, the flexible cable 25 25 is folded and accommodated in the case 20.

  Then, it cannot be confirmed from the outside how the flexible cable 25 is folded in the case 20, and depending on the product, the flexible cable 25 has a boundary between the small diameter portion 20a and the large diameter portion 20b. In the case of such a pressure sensor, when vibration is repeatedly applied to the pressure sensor, the insulating film of the flexible cable 25 is not in contact with the inner edge of the step portion formed in the step portion. There is a possibility that it will be pointed out that the sensor 20 and the processing substrate 23 are electrically connected to the case 20 and the pressure sensor cannot output a signal correctly because the case 20 and the conductive wire come into contact with each other and are damaged by being rubbed against the inner edge. .

  Therefore, the present invention has been developed to improve the above-described problems, and its object is to improve the vibration resistance performance of the pressure sensor.

  In order to achieve the above object, the problem-solving means of the present invention is a cylindrical case having a small-diameter portion and a large-diameter portion, and is accommodated and fixed in the small-diameter portion of the case so that pressure is introduced therein. A bottomed cylindrical metal diaphragm, a sensor part that is provided on the outer surface of the bottom part of the metal diaphragm and has a plurality of strain gauges that form a bridge circuit, and detects the strain at the bottom part, and fits within the large diameter part of the case A pressure sensor including a connector that holds a processing substrate that processes a signal output from the sensor unit and a flexible cable that connects the sensor unit and the processing substrate and is folded and accommodated in the case. The cable has at least four conductors connected to the bridge circuit of the sensor unit and arranged in parallel, and an insulating film covering the conductors, Characterized in that a pre-bent easily bent portion in a portion which is accommodated in the large diameter portion of the case history table cable.

  According to the pressure sensor of the present invention, the flexible cable is provided with a bent portion that positively bends, and when the bent portion is pressed by the metal diaphragm, the connector, and the processing board when the pressure sensor is assembled. It bends preferentially, and a part of the periphery of the bent portion comes into contact with the inner periphery of the large-diameter portion of the case, thereby preventing contact of the flexible cable with the inner edge of the step portion in the case.

  In this way, by providing a bent portion in the flexible cable in advance, contact with the inner edge of the step portion of the flexible cable is prevented, so even if vibration is repeatedly input during use of the pressure sensor, the insulating film of the flexible cable The pressure sensor can continue to output a correct signal according to the pressure introduced into the metal diaphragm, and the vibration resistance performance of the pressure sensor is improved.

  The present invention will be described below based on the embodiments shown in the drawings. FIG. 1 is a longitudinal sectional view of a pressure sensor according to an embodiment. FIG. 2 is a longitudinal sectional view of a pressure sensor according to a modification of the embodiment.

  As shown in FIG. 1, a pressure sensor 1 according to an embodiment is basically a case 2 having a small diameter portion 2a and a large diameter portion 2b, like a conventional pressure sensor, A bottomed cylindrical metal diaphragm 3 which is housed and fixed in the small diameter portion 2a of the case 2 and pressure is introduced into the inside A, and a plurality of bridge circuits which are provided on the outer surface of the bottom portion 3a of the metal diaphragm 3 and constitute a bridge circuit (not shown). A sensor unit 4 that has a strain gauge and detects the strain of the bottom portion 3a, and a connector that holds the processing substrate 5 that is fitted in the large-diameter portion 2b of the case 2 and that processes signals output from the sensor unit 4 6 and a flexible cable 7 that connects the sensor unit 4 and the processing substrate 5 and is folded and accommodated in the case 2.

  Hereinafter, each part will be described in detail. The case 2 is provided on the outer periphery of the lower-diameter portion 2a on the lower side, the upper-diameter portion 2b on the upper side and the small-diameter portion 2a in FIG. And a O-ring 2d attached to the outer periphery of the upper end of the small-diameter portion 2a. A step 2e is formed on the inner peripheral side at the boundary between the small-diameter portion 2a and the large-diameter portion 2b. ing.

  The metal diaphragm 3 includes a bottom portion 3a and a cylindrical portion 3b, and has a bottomed cylindrical shape. The axial length is set to be shorter than the small diameter portion 2a of the case 2, and the inside of the small diameter portion 2a is internal. It is accommodated and fixed so that A faces outward. An O-ring 3c is attached to the outer periphery of the cylindrical portion 3b, and the space between the case 2 and the metal diaphragm 3 is sealed by the O-ring 3c.

  The bottom 3a is thin so as to be easily distorted by the pressure introduced into the interior A, and the sensor unit 4 is provided on the outer surface of the bottom 3a. A plate 8 having an orifice 8a is attached to the opening end of the metal diaphragm 3, and a pressure medium is introduced into the interior A of the metal diaphragm 3 through the orifice 8a. The orifice 8a serves as a low-pass filter so that the pressure change in the interior A does not become abrupt.

  Subsequently, in this embodiment, the sensor unit 4 includes a bridge circuit (not shown) in which four strain gauges are connected in a loop shape, and a relay board 4a connected to the bridge circuit with a bonding wire. Specifically, the strain gauge and the bridge circuit include a silicon dioxide film constituting an insulating layer, a silicon film constituting a strain gauge, an aluminum film constituting an electrode layer, etc. on the bottom 3a of the metal diaphragm 3. Are sequentially deposited. Instead of this, a sensor chip having a strain gauge constituting a bridge circuit may be provided in advance by bonding to the bottom 3a.

  Therefore, in this pressure sensor 1, when the bottom part 3a of the metal diaphragm 3 is distorted by the action of the pressure inside A, the sensor part 4 detects this and outputs a signal corresponding to the resistance change of the strain gauge, The pressure in the interior A can be detected.

  The relay substrate 4a is connected to the processing substrate 5 via the flexible cable 7, and the sensor portion 4 is coated and protected by the silicon gel 9 and the potting material 10 in a state where the flexible cable 7 is connected.

  Further, the connector 6 has a base 6a fitted to the large-diameter portion 2b of the case 2, a terminal provided above the base 6a, and a terminal for connecting an external power source (not shown) to the sensor unit 4 and the sensor unit 4 output. And a socket portion 6b having a terminal for taking out a signal to be output to the outside. A processing substrate 5 is suspended and fixed to the lower end of the base portion 6a.

  An O-ring 6c is attached to the outer periphery of the base portion 6a of the connector 6 so that the space between the case 2 and the large-diameter portion 2b is sealed, and the inside of the case 2 is kept watertight.

  The processing board 5 includes a processing circuit that removes noise included in the signal output from the sensor unit 4 and amplifies the signal, and is connected to the sensor unit 4 via the flexible cable 7. At the same time, it is connected to a terminal (not shown) that is inscribed in the socket portion 6 b of the connector 6, and power is supplied to the sensor portion 4 via the processing substrate 5.

  The flexible cable 7 includes five conductive wires (not shown) connected to the bridge circuit of the sensor unit 4 and arranged in parallel, and an insulating film (not shown) that covers the conductive wires.

  It should be noted that there are only four conductive wires, that is, power supply to the bridge circuit of the sensor unit 4 and grounding, and two for detecting the resistance change of the strain gauge in the bridge circuit. In this case, in order to correct a manufacturing error or the like of the resistance value of the strain gauge in the processing substrate 5, the sensor unit 4 does not completely form a bridge circuit, but partially opens the bridge via the processing substrate 5. Since the circuit is assembled, there are five conductors.

  In the case of this embodiment, the insulating film is specifically made of aramid paper, for example, and the flexible cable 7 is integrally formed by winding five conductive wires arranged in parallel so as not to contact each other with aramid paper. Formed.

  The flexible cable 7 configured in this manner is provided with a bent portion 7a that is easily bent at a portion accommodated in the large-diameter portion 2b of the case 2, and the bent portion 7a is bent once and bent. It is provided by attaching.

  Here, in order to assemble the pressure sensor 1, first, the metal diaphragm 3 is fixed in the small diameter portion 2 a of the case 2 in a state where one end of the flexible cable 7 is connected to the sensor portion 4 in advance. The end is connected to the processing substrate 5 by soldering, and finally the connector 6 is accommodated in the large diameter portion 2 b of the case 2.

  Therefore, even in the case of this embodiment, like the conventional pressure sensor, the flexible cable 7 is long, and it is compressed by the metal diaphragm 3, the connector 6 and the processing substrate 5 and folded in the case 2. Will be housed.

However, as described above, the flexible cable 7 in the present embodiment is provided with the bent portion 7a that bends positively, and this bent portion 7a is connected to the metal diaphragm 3 when the pressure sensor 1 is assembled. When it is pressed by the connector 6 and the processing substrate 5, it bends preferentially, and the bent portion 7a protrudes to the right side in the figure so that a part of the periphery of the bent portion 7a is the large diameter portion 2b of the case 2. Abuts on the inner circumference.

  And the sensor part 4 side is more than the intermediate part 7b of the flexible cable 7 by contact | abutting to the inner periphery of the large diameter part 2b of the case 2 in the intermediate part 7b which is a part of the periphery of the bending part 7a of this flexible cable 7. The inner edge of the step portion 2e of the case 2 is avoided in the shape of an arc, and contact with the inner edge of the step portion 2e of the flexible cable 7 is prevented.

  Thus, by providing the flexible cable 7 with the bent portion 7a in advance, contact with the inner edge of the step portion 2e of the flexible cable 7 is prevented, and even if vibration is repeatedly input when the pressure sensor 1 is used, the flexible cable 7 The pressure sensor 1 can continue to output a correct signal according to the pressure introduced into the inside A of the metal diaphragm 3, and the vibration resistance performance of the pressure sensor 1 is improved.

  In addition, in order to provide the bending part 7a in the flexible cable 7, you may provide a weak part to a conducting wire other than attaching the above-mentioned bending hook, but the direction by attaching a bending hook 7a It is possible to receive various advantages that the processing at the time of installation is easy and does not cost, and the strength of the conducting wire is not reduced.

  Next, a pressure sensor 11 according to a modification of the embodiment will be described. The pressure sensor 11 in this modification is different from the pressure sensor 1 of the above-described embodiment in that two flexible portions 12a and 12b are provided on the flexible bull 12 as shown in FIG.

  Except for this difference, the pressure sensor 11 in one modified example adopts the same configuration as the pressure sensor 1 in one embodiment, and these similar configurations are the same to avoid duplication of explanation. It will not be described in detail because it is only given a reference numeral.

  Hereinafter, different flexible cables 12 will be described. Similar to the flexible cable 7, the flexible cable 12 includes five conductive wires (not shown) that are connected to the bridge circuit of the sensor unit 4 and are arranged in parallel, and an insulating film (not shown) that covers the conductive wires. However, two bent portions 12a and 12b that are easy to bend in advance are provided in a portion accommodated in the large-diameter portion 2b of the case 2. The bent portions 12a and 12b are provided by bending once and attaching bending folds.

  In the case of this modification, the flexible cable 12 is provided with bent portions 12a and 12b that bend positively, so that the bent portions 12a and 12b can be used when the pressure sensor 11 is assembled. The connector 6 and the processing substrate 5 are pressed and bent preferentially, and the bent portions 12a and 12b project to the right in the figure, forming a U-shape and the portion between the bent portions 12a and 12b. 12 c contacts the inner periphery of the large diameter portion 2 b of the case 2.

  Then, the contact of the portion 12c between the bent portions 12a and 12b of the flexible cable 12 with the inner periphery of the large-diameter portion 2b of the case 2 causes the sensor from the bent portion 12a on the lower side in FIG. The part 4 side is bowed so as to avoid the inner edge of the step 2e of the case 2 and contact with the inner edge of the step 2e of the flexible cable 12 is prevented.

  Thus, by providing the flexible cable 12 with the two bent portions 12a and 12b in advance, contact with the inner edge of the step portion 2e of the flexible cable 12 is prevented, and vibration is repeatedly input when the pressure sensor 11 is used. However, the insulating film of the flexible cable 7 is not damaged, and the pressure sensor 11 can continue to output a correct signal according to the pressure introduced into the inside A of the metal diaphragm 3, and the vibration resistance performance of the pressure sensor 11 can be improved. Be improved.

  Further, in the case of this modification, by providing the flexible cable 12 with the two bent portions 12a and 12b in advance, the flexible cable 12 is prevented from being bent at a sharp angle, so that the strength of the flexible cable 12 is increased. And the U-shaped portion is formed when the flexible cable 12 is folded by the installation of the two bent portions 12a and 12b. Therefore, the portion 12c between the bent portions 12a and 12b is formed. Can sat down and abut against the inner periphery of the large-diameter portion 2b of the case 2 to maintain the state, and the interference of the flexible cable 12 to the inner edge of the step portion 2e of the case 2 can be more reliably prevented. The reliability of the pressure sensor 11 is further improved.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

It is a longitudinal cross-sectional view of the pressure sensor in one embodiment. It is a longitudinal cross-sectional view of the pressure sensor in one modification of one embodiment. It is a longitudinal cross-sectional view of the conventional pressure sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Pressure sensor 2 Case 2a Small diameter part 2b in case Large diameter part 2c in case Screw part 2d, 3c, 6c in case Oe 2e Step part in case 3 Metal diaphragm 3a Bottom part 3b in metal diaphragm Pressure receiving part 4 in metal diaphragm Sensor portion 4a Relay substrate 5 in sensor portion Processing substrate 6 Connector 6a Base portion 6b in connector Socket portion 7, 12 in flexible connector 7a, 12a, 12b Bending portion 7b in flexible cable Intermediate portion 8 of flexible cable Plate 8a Orifice in plate 9 Silicon gel 10 Potting material 12c Part A between the bent parts in the flexible cable A Inside the metal diaphragm

Claims (3)

A cylindrical case having a small-diameter portion and a large-diameter portion, a bottomed cylindrical metal diaphragm that is housed and fixed in the small-diameter portion of the case, and pressure is introduced into the inside, and a bottom outer surface of the metal diaphragm A plurality of strain gauges constituting a bridge circuit and detecting a strain at the bottom, and a processing substrate that is fitted in the large diameter portion of the case and that processes a signal output from the sensor unit In the pressure sensor including the connector to be connected, the sensor unit and the processing board, and the flexible cable folded and accommodated in the case, the flexible cable is connected to the bridge circuit of the sensor unit and arranged in parallel. At least four conductors and an insulating film covering the conductors, and accommodated in the large diameter portion of the flexible cable case. A pressure sensor, characterized in that that provided the pre-bent easily bent section to the site. The pressure sensor according to claim 1, wherein the flexible cable is provided with two bent portions, and the bent portions are in contact with the inner periphery of the large-diameter portion of the case. The pressure sensor according to claim 1 or 2, wherein the bent portion is formed by bending a flexible cable.

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