JP2013242157A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensor accuracy under a high-temperature environment in a pressure sensor of a type for welding a diaphragm to the entire periphery of a case.SOLUTION: A diaphragm 16 includes a second corrugate 24 having a bent sectional shape formed on an inner peripheral side of a welding part 18 with a housing 11 and on an outer peripheral side opposite a measuring medium chamber 14. The housing 11 includes a corrugate housing groove 25 for housing the second corrugate 24. A contraction amount difference caused by welding heat when a temperature drops after welding of the diaphragm 16 and the housing 11 is mainly absorbed by deformation of the second corrugate 24. Thus, in the decreased temperature state after the welding, a region where a first corrugate 23 disposed in a part opposite the measuring medium chamber 14 in the diaphragm 16 is easily deformable is widened.

Description

  The present invention relates to a pressure sensor that detects the pressure of a measurement medium.

  As a conventional pressure sensor of this type, a pressure detection chamber filled with oil and a measurement medium chamber into which a measurement medium flows are partitioned by a disk-shaped diaphragm, and a sensor signal corresponding to the oil pressure is output by the sensor element. The thing is proposed (for example, refer patent document 1).

  The diaphragm is formed with a corrugate that can be deformed at a portion facing the measurement medium chamber. In the region where the amount of deformation of the corrugation is small, the spring constant of the diaphragm is small, and in the region where the amount of deformation of the corrugate is greater than or equal to a predetermined amount, the corrugation gradually becomes difficult and the spring constant of the diaphragm increases rapidly.

JP 2000-329633 A

  By the way, the oil sealed in the pressure detection chamber thermally expands as the sensor temperature increases, and the internal pressure of the pressure detection chamber increases as the thermal expansion occurs. More specifically, as indicated by a broken line in FIG. 3, in a region where the sensor temperature T is low, the corrugated easily deforms and the sensor temperature T and the internal pressure P of the pressure detection chamber have a linear relationship. On the other hand, in the region where the sensor temperature T is high, the corrugate is difficult to deform and the spring constant of the diaphragm suddenly increases, so the sensor temperature T and the internal pressure P have a non-linear relationship.

  The output of the pressure sensor can be easily corrected by a circuit if the sensor temperature T and the internal pressure P are linearly related. However, since such correction is difficult in a non-linear relationship region (that is, a region where the sensor temperature T is high), the sensor accuracy decreases.

  Further, when the diaphragm is welded to the case all around, both the diaphragm and the case are thermally expanded by the welding heat. However, the expansion amount of the diaphragm is significantly larger than the thermal expansion amount of the case due to a difference in heat capacity. Therefore, when the temperature is lowered to normal temperature after welding, a tensile stress is generated on the diaphragm due to a difference in contraction amount between the diaphragm and the case, and a region where the corrugate can be easily deformed is narrowed.

  For this reason, as shown by the solid line in FIG. 3, in the pressure sensor of the type in which the diaphragm is welded to the case all around, the region where the sensor temperature T and the internal pressure P are in a linear relationship is further narrowed, and in a high temperature environment Sensor accuracy is further reduced.

  An object of the present invention is to improve the accuracy of a sensor in a high temperature environment in a pressure sensor of a type in which a diaphragm is welded to the case all around the above point.

  In order to achieve the above object, according to the first aspect of the present invention, a first case (1) forming a pressure detection chamber (2) filled with oil (19) and a measurement medium chamber (in which a measurement medium flows) 14) and a second case (11) forming the outer periphery of the second case (11) and a circle that is sandwiched between the first case and the second case, and that separates the pressure detection chamber from the measurement medium chamber. A plate-shaped diaphragm (16) and a sensor element (4) that receives a pressure of oil and outputs a sensor signal corresponding to the pressure, and the diaphragm has a cross section formed at a portion facing the measurement medium chamber. In the pressure sensor including the curved first corrugate (23), the diaphragm is formed at a position on the inner peripheral side with respect to the welded portion (18) with the second case and on the outer peripheral side with respect to the portion facing the measurement medium chamber. Curved cross section Comprising a Jo second corrugated (24), the second case is characterized in that it comprises a corrugated receiving groove (25) of the second corrugated is housed.

  According to this, when the temperature of the diaphragm drops after the diaphragm is welded to the second case, the difference in shrinkage between the diaphragm and the second case is mainly absorbed by the deformation of the second corrugate. The tensile stress at the part facing the surface becomes smaller, and the region where the corrugate can be easily deformed becomes wider. Therefore, a region where the sensor temperature and the internal pressure have a linear relationship is widened, and the accuracy of the sensor in a high temperature environment is improved.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is sectional drawing which shows the structure of the pressure sensor which concerns on one Embodiment of this invention. It is sectional drawing which expands and shows the principal part of the pressure sensor of FIG. It is a figure which shows the relationship between the sensor temperature T and the internal pressure P in the conventional pressure sensor.

  A pressure sensor according to an embodiment of the present invention will be described. The pressure sensor is mounted on, for example, an automobile and can be used as a pressure sensor that detects refrigerant pressure of an air conditioner, fluid pressure of transmission, engine oil pressure, and the like.

  As shown in FIG. 1, the pressure sensor is provided with a case plug 1 as a first case. The case plug 1 is, for example, PPS (polyphenylene sulfide) or PBT (polybutylene terephthalate) which is a heat insulating resin material. ) Or the like, and is formed in a cylindrical shape in this embodiment. A pressure detection chamber 2 is formed on one surface of one end of the case plug 1, and a connector case 3 is formed on the other end.

  The pressure detection chamber 2 is provided with a sensor element 4, which has a diaphragm (not shown) as a pressure receiving surface, converts the received pressure into an electric signal, and converts the electric signal into a sensor signal. The output is a semiconductor diaphragm type. The sensor element 4 is integrated with a pedestal 5 made of glass or the like by anodic bonding or the like, and is fixed to the case plug 1 by adhering the pedestal 5 to a wall surface forming the pressure detection chamber 2 in the case plug 1. Yes.

  In addition, the case plug 1 is provided with a plurality of metal rod-shaped terminals 8 for electrically connecting the sensor element 4 and an external circuit or the like. Only one terminal 8 is shown. The terminal 8 is made of a material obtained by performing a plating process such as Ni plating on brass, and is held in the case plug 1 by being integrally formed with the case plug 1 by insert molding.

  Specifically, each terminal 8 passes through the case plug 1, one end of each terminal 1 protrudes from the case plug 1 into the pressure detection chamber 2, and the other end from the case plug 1 to the connector case. It protrudes into the part 3. The end of each terminal 8 protruding into the pressure detection chamber 2 is electrically connected to the sensor element 4 via a bonding wire 9, and the end of each terminal 8 protruding into the connector case portion 3. Is electrically connected to an external circuit via an external wiring member such as a wire harness (not shown).

  And the sealing material 10 which consists of silicone resin is arrange | positioned in the part which the terminal 8 protrudes among the pressure detection chambers 2, for example. The sealing material 10 is for sealing a gap between the wall surface forming the pressure detection chamber 2 and the terminal 8 in the case plug 1.

  The case plug 1 is assembled with a housing 11 as a second case. In the present embodiment, the case plug 1 and the housing 11 constitute a case including the sensor element 4. Specifically, the housing 11 is provided with a housing recess 12, and one surface of the case plug 1 where the pressure detection chamber 2 is provided is inserted into the housing recess 12, and the end 13 of the housing 11 is connected to the case plug. 1, the case plug 1 and the housing 11 are integrated.

  The housing 11 is made of, for example, a metal material such as SUS or aluminum, and a measurement medium chamber 14 into which the measurement medium flows is formed inside, and a screw portion 15 for fixing the pressure sensor is formed on the outer peripheral wall surface. Has been.

  Further, on one surface of the housing 11 facing the one surface of the case plug 1 in which the pressure detection chamber 2 is formed, a disk-shaped metal diaphragm 16 made of, for example, SUS or the like, and an outer edge portion of the metal diaphragm 16 are provided. An annular ring weld 17 made of, for example, SUS or the like is provided.

  By welding the outer periphery of the metal diaphragm 16 and the ring weld 17 to the housing 11 by laser welding or the like, a welded portion 18 in which the housing 11, the metal diaphragm 16 and the ring weld 17 are melted is formed.

  The outer edge of the metal diaphragm 16 and the ring weld 17 are sandwiched between the case plug 1 and the housing 11, and the pressure detection chamber 2 and the measurement medium chamber 14 are partitioned by the inner peripheral portion of the metal diaphragm 16. In other words, the outer edge portion of the metal diaphragm 16 is a portion fixed to the case plug 1 and the housing 11 together with the ring weld 17, and the portion of the metal diaphragm 16 facing the measurement medium chamber 14 is the pressure of the measurement medium. It is a part that functions as a diaphragm part that is displaced according to the above.

  The pressure detection chamber 2 is filled with oil 19 such as fluorine oil as a pressure transmission medium. The pressure of the measurement medium in the measurement medium chamber 14 is transmitted to the diaphragm of the sensor element 4 through the metal diaphragm 16 and the oil 19 in the pressure detection chamber 2.

  An annular groove 21 is formed on one surface of the case plug 1 where the pressure detection chamber 2 is provided so as to surround the pressure detection chamber 2, and an elastic material such as silicone rubber is formed in the annular groove 21. An O-ring 22 is provided. The O-ring 22 seals the pressure detection chamber 19 by being crushed by caulking pressure caused by caulking between the case plug 1 and the housing 11.

  As shown in FIG. 2, a first corrugate 23 having a curved cross-sectional shape along the axis of the metal diaphragm 16 is provided in a portion of the metal diaphragm 16 facing the measurement medium chamber 14. More specifically, the first corrugation 23 is continuous in an annular shape, and a plurality of first corrugations 23 are provided concentrically about the axis of the metal diaphragm 16.

  Further, in the metal diaphragm 16, the cross-sectional shape along the axis of the metal diaphragm 16 is a curved shape at a position on the inner peripheral side with respect to the welded portion 18 and on the outer peripheral side with respect to the portion facing the measurement medium chamber 14. One second corrugate 24 is provided. More specifically, the second corrugate 24 is convex and continuous in an annular shape toward a corrugate housing groove to be described later. Further, the second corrugate 24 is provided concentrically with the first corrugate 23.

  An annular corrugated accommodation groove 25 in which the second corrugate 24 is accommodated is formed on one surface of the housing 11 facing the one surface of the case plug 1 in which the pressure detection chamber 2 is formed.

  Next, a method for manufacturing the pressure sensor will be described.

  First, the case plug 1 in which the terminal 8 is insert-molded is prepared. Then, the sensor element 4 that is anodically bonded to the pedestal 5 is prepared, and the pedestal 5 side is bonded to a wall surface that forms the pressure detection chamber 2 in the case plug 1 through an adhesive material such as silicone resin.

  Next, after injecting the sealing material 10 into the pressure detection chamber 2 with one surface of the case plug 1 on which the pressure detection chamber 2 is formed facing upward, the sealing material 10 is cured. At this time, it is preferable to adjust the injection amount so that the sealing material 10 does not adhere to the surface of the sensor element 4.

  Thereafter, for example, wire bonding is performed, and the sensor element 4 and the end of each terminal 8 are electrically connected via the bonding wire 9.

  Next, a predetermined amount of oil 19 is injected into the pressure detection chamber 2 by a dispenser or the like. And the thing of this state is put into a vacuum chamber, and the excess air in the pressure detection chamber 2 is removed. Thereafter, a housing 11 having a metal diaphragm 16 and a ring weld 17 welded to one surface is prepared, and the case plug 1 is fitted into the receiving recess 12 of the housing 11 while keeping the housing 11 horizontal from above in the vacuum chamber. Take it down.

  Subsequently, the case plug 1 and the ring weld 17 are pressed until they are in sufficient contact. As a result, the pressure detection chamber 2 is constituted by the pressure detection chamber 2, the metal diaphragm 16 and the ring weld 17. Then, the housing 11 and the case plug 1 are integrated by caulking the end portion 13 of the housing 11 to the case plug 1. The pressure sensor of this embodiment can be configured by such a manufacturing method.

  Next, the basic pressure detection operation of the pressure sensor of the present embodiment configured as described above will be described.

  When the pressure of the measurement medium flowing into the measurement medium chamber 14 is applied to the metal diaphragm 16, the pressure is applied to the diaphragm of the sensor element 4 through the oil 19 filled in the pressure detection chamber 2. The diaphragm of the sensor element 4 is provided with a gauge resistor formed so as to constitute a bridge circuit. When pressure is applied to the diaphragm of the sensor element 4, the resistance value of the gauge resistor changes due to the piezoresistive effect. For this reason, in the sensor element 4, the output voltage of a bridge circuit changes and the sensor signal according to the applied pressure is output. This sensor signal is transmitted from the sensor element 4 to the outside via the bonding wire 9 and the terminal 8, and based on this, the pressure of the measurement medium is detected.

  Here, in the manufacturing process of the pressure sensor, when the metal diaphragm 16 and the ring weld 17 are welded to the housing 11, the metal diaphragm 16 and the housing 11 are both thermally expanded by the welding heat. Since the expansion amount of the metal diaphragm 16 is significantly larger than the thermal expansion amount of the housing 11, a tensile stress is generated on the metal diaphragm 16 as the temperature decreases after welding.

  At this time, the difference in shrinkage between the metal diaphragm 16 and the housing 11 at the time of the temperature drop after welding is absorbed mainly by deformation of the second corrugate 24 of the first corrugate 23 and the second corrugate 24. In a state where the temperature is lowered, the tensile stress at the portion of the metal diaphragm 16 facing the measurement medium chamber 14 is reduced, and the region where the first corrugate 23 can be easily deformed is widened. Therefore, a region where the sensor temperature and the internal pressure have a linear relationship is widened, and the accuracy of the sensor in a high temperature environment is improved.

1 Case plug (first case)
2 Pressure detection chamber 4 Sensor element 11 Housing (second case)
14 Measurement medium chamber 16 Diaphragm 19 Oil 23 First corrugated 24 Second corrugated 25 Corrugated groove

Claims (2)

A first case (1) forming a pressure detection chamber (2) filled with oil (19);
A second case (11) forming a measurement medium chamber (14) into which the measurement medium flows;
A disk-shaped diaphragm (16) whose outer edge is welded all around the second case and is sandwiched between the first case and the second case, and partitions the pressure detection chamber and the measurement medium chamber; ,
A sensor element (4) that receives the pressure of the oil and outputs a sensor signal corresponding to the pressure;
In the pressure sensor, the diaphragm includes a first corrugate (23) having a curved cross section formed at a portion facing the measurement medium chamber.
The diaphragm is a second corrugate (24) having a curved cross section formed at a position on the inner peripheral side with respect to the welded portion (18) with the second case and on the outer peripheral side with respect to the portion facing the measurement medium chamber. )
The pressure sensor according to claim 2, wherein the second case includes a corrugated groove (25) in which the second corrugated is accommodated.   The pressure sensor according to claim 1, wherein one second corrugate is formed.

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