Patent Publication Number: US-2021181051-A1

Title: Differential pressure measuring instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of and priority to Japanese Patent Application No. 2019-224262, filed on Dec. 12, 2019, the entire contents of which are incorporated by reference herein. 
     TECHNICAL FIELD 
     The present invention relates to a differential pressure measuring instrument. 
     BACKGROUND 
     In the related art, differential pressure measuring instruments for industrial use include a chip of the sensor element made of silicon or other materials, which is built in an enclosure made of metal such as SUS to be protected from corrosive measurement objects and the measurement environment. Such a differential pressure gauge configured as described above includes oil, or the like, enclosed as a pressure transmitting medium to transfer pressure to a chip housed in an interior thereof (see PTL 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] JP-A-H03-048128 
     SUMMARY 
     The differential pressure measuring instrument described above may be affected by heat transfer from the measurement object and measurement environment during actual measurement, and the temperature of the enclosure and the enclosed pressure transmitting medium may rise in some cases. In such cases, in the past, the temperature of the chip (sensor element) built into the enclosure rises with the rise in temperature of the enclosure and the pressure transmitting material. Since the heat resistance temperature of electronic components such as sensor elements is not very high, in the related art, a region where the temperature rise can be suppressed has been established in the interior of the enclosure, and the chips are placed in this region to alleviate the effects of heat. Alternatively, the enclosure is provided with a structure (for example, heat-dissipating fins, embedded insulation material, etc.) that suppresses heat transfer to a part where the chip is embedded. To provide the enclosure with this structure, the differential pressure measuring instruments of the related art are not easy to miniaturize while sufficiently protecting the chip from heat, for example. 
     To solve the problem described above, it is an object of the present invention to miniaturize a differential pressure measuring instrument including a chip of a sensor element built in an enclosure. 
     A differential pressure measuring instrument according to the present invention comprises: a chip constituting a pressure-sensitive sensor comprising a first diaphragm and a second diaphragm, and a first pressure introduction portion and a second pressure introduction portion that cause a pressure transmitting material to act on the first diaphragm and second diaphragm, respectively; an enclosure comprising a first barrier diaphragm provided on a first side surface, and a second barrier diaphragm provided on a second side surface, the enclosure being formed with a first pressure chamber and a second pressure chamber isolated from an exterior by the first barrier diaphragm and the second barrier diaphragm, respectively, a sensor placement chamber in which the chip is disposed, and a first communication channel and a second communication channel communicating the first pressure chamber and the second pressure chamber with the sensor placement chamber, respectively; a first pipe connected at one end thereof to the first communication channel on a side comprising the sensor placement chamber, and at the other end thereof to the first pressure introduction portion of the chip housed in the sensor placement chamber; and a second pipe connected at one end thereof to the second communication channel on a side comprising the sensor placement chamber, and at the other end thereof to the second pressure introduction portion of the chip housed in the sensor placement chamber. 
     In one configuration example of the differential pressure measuring instrument described above, a side surface of the first pipe and a side surface of the second pipe are not in contact with an inner wall of the sensor placement chamber. 
     In one configuration example of the differential pressure measuring instrument described above, the chip is supported by the first pipe and the second pipe and is separated from the inner wall of the sensor placement chamber. 
     One configuration example of the differential pressure measuring instrument described above further comprises a package disposed in the sensor placement chamber and configured to house the chip. 
     In one configuration example of the differential pressure measuring instrument described above, the chip is in contact with the inner wall in an interior of the package only in a part of a region of an outer surface of the chip, and a remaining region of the outer surface of the chip is separated from the inner wall of the package. 
     One configuration example of the differential pressure measuring instrument described above further comprises a pressure transmitting material filled in the first pressure introduction portion, the first pipe, the first communication channel, and the first pressure chamber, and a pressure transmitting material filled in the second pressure introduction portion, the second pipe, the second communication channel, and the second pressure chamber. 
     In one configuration example of the differential pressure measuring instrument described above, the chip comprises a first strain gauge provided on the first diaphragm and a second strain gauge provided on the second diaphragm. 
     As described above, according to the present invention, the first pipe connected to the first pressure introduction portion of the chip and the second pipe connected to the second pressure introduction portion of the chip for transmitting pressure from the pressure transmitting material are used to support the chip in the sensor placement chamber in the interior of the enclosure, and thus miniaturization of the differential pressure measuring instrument comprising the chip of the sensor element built in the enclosure is achieved while sufficiently protecting the chip from heat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating a configuration of a differential pressure measuring instrument according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view illustrating a partial configuration of the differential pressure measuring instrument according to the embodiment of the present invention. 
         FIG. 3  is a cross-sectional view illustrating a partial configuration of the differential pressure measuring instrument according to the embodiment of the present invention. 
         FIG. 4  is a cross-sectional view illustrating a configuration of another differential pressure measuring instrument according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , a differential pressure measuring instrument according to an embodiment of the present invention will be described. The differential pressure measuring instrument comprises a chip  101  that constitute a pressure-sensitive sensor, and an enclosure  102 . The enclosure  102  is made of, for example, metal. 
     The enclosure  102  is formed with a sensor placement chamber  103  in which the chip  101  is placed. An interior of the sensor placement chamber  103  is made airtight, and, for example, nitrogen gas is enclosed therein. The enclosure  102  also comprises a first barrier diaphragm  104  provided on a first side surface and a second barrier diaphragm  105  provided on a second side surface. 
     The enclosure  102  is formed with a first pressure chamber  106  and a second pressure chamber  107  isolated from the exterior by the first barrier diaphragm  104  and the second barrier diaphragm  105 , respectively. The enclosure  102  is formed with a first communication channel  108  and a second communication channel  109 , which communicate the first pressure chamber  106  and the second pressure chamber  107  with the sensor placement chamber  103 , respectively. 
     As illustrated in  FIG. 2 , the chip  101  comprises a base  126 , a part  123  joined to a back surface of the base  126 , a diaphragm layer  122  joined to the part  123 , and a part  121  attached to the part  123  via the diaphragm layer  122 . The base  126 , the part  123 , the diaphragm layer  122 , and the part  121  are made of Si. The base  126  is also formed with a depression  128  on a main surface thereof. The depression  128  is formed with a metal layer  129  on a front surface thereof. 
     The depression  128  is in communication with an oil storage part such as a communication channel  125  formed in the part  123 , a diaphragm chamber  124   a , and a diaphragm chamber  124   b  via a through-hole  127  penetrating through the base  126 . Oil, serving as the pressure transmitting material, is fed from the depression  128 , and oil  131  as the pressure transmitting material is filled within the oil storage part, such as the communication channel  125 , the diaphragm chamber  124   a , and the diaphragm chamber  124   b  via the through-hole  127 . After filling the oil  131  in this manner, a solder ball (ball solder) is placed on top of a metal layer  129  in the depression  128  and heated and melted. This causes the through-hole  127  to be sealed with a sealing member  130 . 
     The part  121  is also formed with a first pressure introduction portion  121   a  and a second pressure introduction portion  121   b , which are arranged at positions overlapping with the diaphragm chamber  124   a  and the diaphragm chamber  124   b  across the diaphragm layer  122 . Regions of the diaphragm layer  122 , which are interposed between the diaphragm chamber  124   a  and the first pressure introduction portion  121   a  and interposed between the diaphragm chamber  124   b  and the second pressure introduction portion  121   b , correspond to the first diaphragm  122   a  and the second diaphragm  122   b , respectively. The first pressure introduction portion  121   a  and the second pressure introduction portion  121   b  are disposed on the same side with respect to the part  121  (chip  101 ). 
     In the sensor placement chamber  103  in which the chip  101  described above is housed, the differential pressure measuring instrument comprises a first pipe  110  connecting the first communication channel  108  on the side of the sensor placement chamber  103  to the first pressure introduction portion  121   a , and a second pipe  111  connecting the second communication channel  109  on the side of the sensor placement chamber  103  to the second pressure introduction portion  121   b.    
     A side surface (pipe wall) of the first pipe  110  and a side surface (pipe wall) of the second pipe  111  are disposed out of contact with an inner wall of the sensor placement chamber  103 . The chip  101  is supported by the first pipe  110  and the second pipe  111  and is disposed out of contact with (separated from) the inner wall of the sensor placement chamber  103 . 
     In the differential pressure measuring instrument, pressure received by the first barrier diaphragm  104  is transferred to (and acts on) the first diaphragm  122   a  by a pressure transmitting material that fills the first pressure chamber  106 , the first communication channel  108 , the first pipe  110 , and the first pressure introduction portion  121   a , and deforms the first diaphragm  122   a . The pressure received by the second barrier diaphragm  105  is transmitted to (and acts on) the second diaphragm  122   b  by a pressure transmitting material that fills the second pressure chamber  107 , the second communication channel  109 , the second pipe  111 , and the second pressure introduction portion  121   b , and deforms the second diaphragm  122   b.    
     Note that an electrode, not illustrated, is formed on the diaphragm layer  122  in a region, not illustrated, extending around the part  123 . Although not illustrated, the first diaphragm  122   a  and the second diaphragm  122   b  are provided with a first strain gauge and a second strain gauge for measuring the strain of the first diaphragm  122   a  and the second diaphragm  122   b , respectively, that are deformed by the application of pressure. Each of the first strain gauge and the second strain gauge comprises, for example, a plurality of piezoresistive elements, and the plurality of piezoresistive elements constitute a bridge circuit. The bridge circuit functions, when stress is generated in the first diaphragm  122   a  and the second diaphragm  122   b  in a state in which a constant current flows therein, as a differential pressure detection part that outputs a change in resistance value of each piezoresistive element due to the generated stress as a change in voltage. Each node of the bridge circuit is connected to an electrode via a wiring pattern formed on a surface of the region, not illustrated, in the diaphragm layer  122 . 
     According to the differential pressure measuring instrument according to the embodiment described above, since the chip  101  is housed in the sensor placement chamber  103  at a position separated from the inner wall thereof, the heat of the enclosure  102  is suppressed from conducting to the chip  101 . The sensor placement chamber  103  may be configured to hermetically seal the interior in a vacuum (reduced pressure) state, and such a configuration allows the conduction of heat as described above to be further suppressed. Since heat conduction can be suppressed in this manner, there is no need to provide in an interior of the enclosure  102  with a region in which the temperature rise can be suppressed, and there is no need to embed insulation material, or the like, to suppress heat transfer to the location in which the chip  101  is built-in, so that the enclosure  102  having a smaller size can be used. As a result, according to the embodiment, miniaturization of the differential pressure measuring instrument is achieved. 
     The chip  101  may also be housed in a package  200  and disposed in the sensor placement chamber  103  as illustrated in  FIG. 3 . The package  200  comprises a package body  201  and a lid  202 . An interior of the package  200  (package body  201 ) where the chip  101  is housed is filled with, for example, nitrogen gas and is sealed by the lid  202 . 
     The chip  101  is in contact with an inner wall (chip fixing portion  203 ) of the interior of the package  200  (package body  201 ) in only part of a region of an outer surface of the chip  101  (fixing portion  101   a ), and the other regions of the outer surface of the chip  101  are separated from the inner wall of the package  200 . For example, as illustrated in  FIG. 3 , the chip  101  is fixed at the fixing portion  101   a  in a periphery of a bottom surface thereof to the chip fixing portion  203  in the interior of the package  200 , and the surface (side surface) of the chip  101  other than at the fixing portion is separated from an inner wall  204  of the package  200 . The fixation is implemented by a predetermined adhesive material. Note that the package  200  may house an electronic part for characterization (characteristic identification) of a pressure-sensitive sensor of the chip  101  along with the chip  101 . 
     As illustrated in  FIG. 4 , a chip storage structure  210  can be provided in the sensor placement chamber  103 , and the chip  101  can be placed in an interior of the chip storage structure  210 . The chip storage structure  210  has, for example, a cylindrical shape. One opening end side of the chip storage structure  210  having a cylindrical shape is fixed to an interior surface of the enclosure  102  of the sensor placement chamber  103  on a side where the first barrier diaphragm  104  and the second barrier diaphragm  105  are disposed. 
     The chip storage structure  210 , having a cylindrical shape, is provided at a closed-end portion on the other side with a first communication hole  211  and a second communication hole  212  for communicating an exterior and an interior. The first pipe  110  is connected at one end thereof to the first communication hole  211  on the interior side of the chip storage structure  210 , and the other end of the first pipe  110  is connected to the first pressure introduction portion  121   a . The second pipe  111  is connected at one end thereof to the second communication hole  212  on the interior side of the chip storage structure  210  and the other end of the second pipe  111  is connected to the second pressure introduction portion  121   b.    
     In the interior of the chip storage structure  210 , the chip  101  is supported by the first pipe  110  and the second pipe  111  and is separated from the inner wall of the chip storage structure  210 . At the closed end portion of the chip storage structure  210 , planes where interior side opening ends of the first communication hole  211  and the second communication hole  212  are disposed to face toward the side of the enclosure  102  where the first barrier diaphragm  104  and the second barrier diaphragm  105  are disposed. Accordingly, in contrast to the differential pressure measuring instrument described using  FIG. 1 , in the differential pressure measuring instrument described using  FIG. 4 , the chip  101  is arranged upside down with respect to the enclosure  102 . 
     Note that an end of the first communication channel  108  on the side of the sensor placement chamber  103  and the first communication hole  211  on an exterior side are connected with a third pipe  112 . Likewise, an end of the second communication channel  109  on the sensor placement chamber  103  side and the second communication hole  212  on the exterior side are connected with a fourth pipe  113 . 
     As described above, according to the present invention, the first pipe connected to the first pressure introduction portion of the chip and the second pipe connected to the second pressure introduction portion of the chip for transmitting pressure by the pressure transmitting material are used to support the chip in the sensor placement chamber in the interior of the enclosure, so that the chip is separated from the inner wall of the sensor placement chamber, which allows the heat of the enclosure to be suppressed from conducting to the chip. Consequently, according to the present invention, the differential pressure measuring instrument containing the chip of the sensor element built in the enclosure can be miniaturized while sufficiently protecting the chip from the heat. 
     It is apparent that the present invention is not limited to the embodiment described above and that many variations and combinations can be implemented within the technical concept of the present invention by persons having ordinary knowledge in the art. 
     DESCRIPTION OF REFERENCE NUMERALS AND SIGNS 
       101 : chip,  102 : enclosure,  103 : sensor placement chamber,  104 : first barrier diaphragm,  105 : second barrier diaphragm,  106 : first pressure chamber,  107 : second pressure chamber,  108 : first communication channel,  109 : second communication channel,  110 : first pipe,  111 : second pipe,  121   a : first pressure introduction portion,  121   b : second pressure introduction portion,  122 : diaphragm layer,  122   a : first diaphragm,  122   b : second diaphragm,  131 : oil