Adhesive structure of capillary tube for pressure sensor

Abstract

To provide an adhesive structure of a capillary tube for a pressure sensor that makes a state after adhesive application uniform regardless of the wettability of an adhesive surface, prevents damage due to deterioration in pressure resistance of a sensor element, and has constant characteristics.SOLUTION: An adhesive structure of a capillary tube for a pressure sensor comprises: a sensor element 13 of a pressure sensor; a pressure-conducting hole 17 formed in the sensor element 13; a pressure-conducting capillary tube 14 inserted into the pressure-conducting hole 17; and adhesive 15 applied to an adhesive surface 19 where the pressure-conducting hole 17 of the sensor element 13 opens so as to cover a part of the pressure-conducting capillary tube 14, and making the pressure-conducting capillary tube 14 adhere to the sensor element 13. A restriction part 20 is formed around the pressure-conducting hole 17 to restrict the adhesive 15 from wetting and spreading.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an adhesive structure for a thin tube for a pressure sensor, which is used when adhering a thin tube for pressure introduction to a sensor element with an adhesive. [Background technology]

[0002] As a conventional pressure sensor, for example as described in Patent Document 1, there is one that uses a pressure-conducting thin tube to transmit the pressure of the fluid to be measured to a sensor element. This pressure-conducting thin tube is inserted into a pressure-conducting hole formed in the sensor element and is bonded to the sensor element with an adhesive. The adhesive is applied to the bonding surface where the pressure-conducting hole of the sensor element opens so that a part of the pressure-conducting thin tube is covered.

[0003] The adhesive is applied using a dispenser to control the amount and position of application. The adhesive applied to the bonding surface by the dispenser spreads over the bonding surface and rises along the pressure-conducting thin tube. It is known that the wettability of the adhesive changes depending on the treatment conditions of the surface of the sensor element. Treatment conditions that can change the wettability of the adhesive include the presence or absence of organic matter adhesion, the presence or absence or degree of cleaning of the sensor element surface, the presence or absence of a history of adhesive tape attachment, and the presence or absence of high temperature application to the sensor element. In addition to the treatment conditions of the sensor element, the wettability of the adhesive can also change due to the elapsed time since the last treatment of the sensor element. For example, the wettability changes due to the organic contamination of the bonding surface or the change over time in the formation state of the oxide film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-187046 A Summary of the Invention [Problem to be solved by the invention]

[0005] Since the wettability of the adhesive on the adhesive surface varies due to various factors, even if the adhesive is applied to multiple adhesive parts using a dispenser under the same application conditions, the size and shape of the wet adhesive rarely match at multiple adhesive parts, resulting in a problem of uneven wet spread of the adhesive. For example, as shown in Figure 11(A), when two capillaries 2 are provided on one sensor element 1, the adhesive 3 applied to each capillary 2 may connect with each other. In addition, of the two adhesive parts 4 shown in Figure 11(B), there are cases where the wet spread of the adhesive 3 is suppressed as in the adhesive part 4 on the left side, and cases where a part of the adhesive 3 spreads more widely than the other parts as in the adhesive part 4 on the right side.

[0006] In addition, when adhering the pressure-conducting capillary tube 2 to the sensor element 1, the number of locations to which the nozzle of a dispenser (not shown) can be brought close when applying the adhesive 3 is limited, making it difficult to apply the adhesive 3 so as to maintain a concentric circle around the capillary tube 2. This is also one of the causes of uneven application of the adhesive 3. For example, as shown in Figures 12(A) and (B), the adhesive 3 cannot wet and spread concentrically around the capillary tube 2, and the capillary tube 2 may deviate from the center of the raised portion (fillet portion) 3a of the adhesive 3. Figure 12(A) is a perspective view, and Figure 12(B) is a plan view.

[0007] If the application position of the adhesive 3 on the sensor element 1 or the state of wet spreading is uneven in this way, the shape of the adhesive 3 after it hardens will also be uneven, and there is a risk that the adhesive 3 will not function adequately. For example, the sensor element 1 may be damaged due to a decrease in resistance to thermal stress caused by differences in the thermal expansion coefficients of the sensor element 1 and the capillary tube 2, or to tensile forces caused when high pressure is applied inside the sensor element 1. In addition, the transmission state of the force transmitted from the capillary tube 2 to the sensor element 1 via the adhesive 3 will differ for each adhesive part 4, causing variations in the characteristics of the sensor element 1.

[0008] An object of the present invention is to provide an adhesive structure for a thin tube for a pressure sensor which maintains a uniform state after adhesive application regardless of the wettability of the adhesive surface, prevents damage due to a decrease in the pressure resistance of the sensor element, and maintains consistent characteristics. [Means for solving the problem]

[0009] In order to achieve this object, the adhesive structure for a capillary tube for a pressure sensor according to the present invention comprises a sensor element of a pressure sensor, a pressure introducing hole formed in the sensor element, a pressure introducing capillary tube inserted into the pressure introducing hole, and an adhesive applied to an adhesive surface of the sensor element where the pressure introducing hole opens so as to cover a part of the pressure introducing capillary tube, and adhesive for adhering the pressure introducing capillary tube to the sensor element, and a restricting portion is formed to restrict the adhesive from spreading around the pressure introducing hole.

[0010] In the adhesive structure for a thin tube for a pressure sensor according to the present invention, the sensor element may further have a groove surrounding the pressure-conducting hole, and the regulating portion may be constituted by an opening edge of the groove which is a boundary between the adhesive surface where the pressure-conducting hole opens and the groove.

[0011] In the adhesive structure for a thin tube for a pressure sensor according to the present invention, the sensor element may further have a convex portion whose tip end surface is the adhesive surface, and the regulating portion may be constituted by a corner portion which is the boundary between the adhesive surface and a side surface of the convex portion.

[0012] In the pressure sensor capillary bonding structure of the present invention, the sensor element may further have a recess with the bonding surface serving as an inner bottom surface, and the restricting portion may be formed by an inner wall of the recess. Effect of the Invention

[0013] According to the present invention, the range over which the adhesive spreads is restricted by the restricting portion, and the state after application of the adhesive becomes uniform regardless of the wettability of the adhesive surface of the sensor element. Therefore, it is possible to provide an adhesive structure for a capillary for a pressure sensor that prevents damage due to a decrease in the pressure resistance of the sensor element and maintains constant characteristics. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an adhesive structure for a thin tube for a pressure sensor according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the sensor element taken along line II-II in FIG. [Diagram 3] FIG. 3 is a plan view of the sensor element. [Figure 4] FIG. 4 is a cross-sectional view of a bonding structure for a thin tube for a pressure sensor. [Diagram 5] FIG. 5 is a perspective view showing an adhesive structure for a thin tube for a pressure sensor according to the second embodiment. [Figure 6] FIG. 6 is a cross-sectional view of the sensor element taken along line IV-IV in FIG. [Figure 7] FIG. 7 is a plan view of the sensor element. [Figure 8] FIG. 8 is a cross-sectional view of a bonding structure for a thin tube for a pressure sensor. [Figure 9] FIG. 9 is a cross-sectional view of a bonding structure for a thin tube for a pressure sensor according to the third embodiment. [Figure 10] FIG. 10 is a cross-sectional view of the sensor element. [Figure 11] FIG. 11 is a plan view showing the planar shape of an adhesive applied to a bonding surface having non-uniform wettability. [Figure 12] FIG. 12 is a diagram showing adhesive applied unevenly to a thin tube. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (First embodiment) Hereinafter, one embodiment of an adhesive structure for a thin tube for a pressure sensor according to the present invention will be described in detail with reference to Figs. The bonding structure 11 shown in Fig. 1 is a bonding structure used when bonding a pressure-conducting thin tube 14 to a sensor element 13 constituting a pressure sensor 12 with an adhesive 15. The sensor element 13 is housed in a package 16, and constitutes the pressure sensor 12 together with the package 16.

[0016] Two pressure-conducting capillaries 14 are connected to the sensor element 13. This sensor element 13 measures the pressure of the fluid to be measured transmitted through a pressure transmission medium (not shown) filled in the pressure-conducting capillary 14. Since this sensor element 13 has two pressure-conducting capillaries 14, it can measure the differential pressure between the pressure of the fluid to be measured on the high pressure side and the pressure of the fluid to be measured on the low pressure side.

[0017] 2, the sensor element 13 is formed with two pressure introducing holes 17 and grooves 18 surrounding each of these pressure introducing holes 17. The pressure introducing holes 17 are holes into which the pressure introducing capillaries 14 are inserted. One end of the pressure introducing holes 17 opens to one end face 13a of the sensor element 13, and the other end is closed by a diaphragm (not shown) provided inside the sensor element 13. 3, the groove 18 surrounding the pressure introducing hole 17 is formed in an annular shape centered on the pressure introducing hole 17 on one end face 13a of the sensor element 13. In this embodiment, a part of the one end face 13a of the sensor element 13 formed between the groove 18 and the pressure introducing hole 17 serves as an adhesive surface 19, and the adhesive 15 is applied to this adhesive surface 19. In the sensor element 13 according to this embodiment, grooves 18 of the same size and shape are formed around each of the two pressure introducing holes 17. The pressure-conducting capillary 14 is a tube having a circular cross section, and is bonded to the sensor element 13 by adhesive 15 while being inserted into the pressure-conducting hole 17 .

[0018] The adhesive 15 may be, for example, an epoxy resin. The adhesive 15 in this embodiment is measured with high precision by a dispenser (not shown) and applied to the bonding surface 19 where the pressure introducing hole 17 opens. When applying the adhesive 15, as shown in Fig. 4, a part of the pressure introducing capillary tube 14 is covered with the adhesive 15, and the adhesive 15 is applied so that it rises due to surface tension.

[0019] The adhesive 15 applied to the bonding surface 19 is restricted from spreading by the opening edge 18a of the groove 18, which is the boundary between the bonding surface 19 and the groove 18. For this reason, the adhesive 15 rises due to surface tension to a height based on the amount of adhesive applied on the bonding surface 19, and is applied in a circular mountain shape in plan view with the pressure-conducting capillary 14 located at the center. According to this embodiment, the opening edge 18a serves as a restricting portion 20 that restricts the adhesive 15 from spreading.

[0020] The two bonding surfaces 19 of the sensor element 13 are formed to have the same area. Therefore, when the two pressure-conducting capillaries 14 are bonded to the sensor element 13, the area where the adhesive 15 spreads and the height of the adhesive 15 that rises are the same at the two bonding portions, and the shape of the adhesive 15 after hardening is approximately the same. In other words, regardless of the wettability of the bonding surface 19, the state after the adhesive is applied is uniform at the two bonding portions. This means that the quality of the bonding portions is the same in all sensor elements 13 even when the sensor elements 13 are mass-produced.

[0021] Since the adhesive 15 is applied evenly and sufficiently to all the bonding parts, there is no variation in the shape, size, etc. of the adhesive 15 in all the bonding parts. Therefore, the adhesive 15 functions sufficiently as designed in all the bonding parts, so that the transmission of thermal stress to the sensor element 13 and the variation in pressure resistance strength are suppressed, and the resistance to thermal stress caused by the difference in thermal expansion coefficient between the pressure guiding capillary 14 and the sensor element 13 and to the tensile force generated when the inside of the sensor element 13 becomes high pressure is improved. In the sensor element 13 having two pressure guiding capillaries 14 as shown in this embodiment, the high pressure side and the low pressure side are balanced, so that the so-called cancel out is possible. Therefore, according to this embodiment, it is possible to provide an adhesive structure for a thin tube for a pressure sensor, which is capable of preventing damage caused by a decrease in the pressure resistance of the sensor element and suppressing variations in characteristics.

[0022] In this embodiment, the adhesive 15 is held back by surface tension at the opening edge 18a of the groove 18, so that the outer diameter (fillet diameter) of the adhesive 15, which has a circular mountain shape in plan view, is the same whether a small amount of adhesive 15 is applied or a large amount is applied. This allows for a high degree of freedom in setting the amount of adhesive 15 to be applied.

[0023] (Second embodiment) The restricting portion that restricts the wet spreading of the adhesive can be configured as shown in Figures 5 to 8. In Figures 5 to 8, members that are the same as or equivalent to those described with reference to Figures 1 to 4 are given the same reference numerals and detailed description thereof will be omitted as appropriate. The sensor element 21 shown in Fig. 5 has cylindrical protrusions 22 formed at two locations on one end face 21a. As shown in Figs. 6 and 7, a pressure introducing hole 17 is formed in the center of the protrusion 22. A pressure introducing capillary 14 is inserted into this pressure introducing hole 17, and adhesive 15 is applied to a tip face 22a of the protrusion 22 by a dispenser (not shown). In this embodiment, the tip face 22a of the protrusion 22 becomes an adhesive face 19. The adhesive 15 may be the same as that used in the first embodiment.

[0024] The adhesive 15 applied to the tip surface 22a (adhesive surface 19) spreads up to a corner 22c which is the boundary between the tip surface 22a (adhesive surface 19) and the side surface 22b (outer circumferential surface) of the protrusion 22, and rises due to surface tension into a circular mountain shape in plan view with the pressure-guiding capillary 14 located at the center. In this embodiment, the corner 22c forms a restricting portion 20 which restricts the adhesive 15 from spreading around the pressure-guiding hole 17. For this reason, also in this embodiment, the adhesive 15 is applied evenly over the entire area of ​​the adhesive surface 19 at the multiple adhesive joints, without depending on the wettability of the adhesive surface 19, so that the adhesive 15 functions sufficiently as designed at all adhesive joints.

[0025] Therefore, the transmission of thermal stress to the sensor element 21 and variations in pressure resistance strength are suppressed, and resistance to thermal stress caused by differences in thermal expansion coefficients between the pressure-conducting capillary 14 and the sensor element 21 and to tensile forces generated when high pressure is applied inside the sensor element 21 is improved. As a result, also in this embodiment, it is possible to provide an adhesive structure for a thin tube for a pressure sensor, which is capable of preventing damage caused by a decrease in the pressure resistance of the sensor element and suppressing variations in characteristics.

[0026] In this embodiment, the adhesive 15 is blocked by surface tension at the corners 22c of the protrusions 22, so that the outer diameter (fillet diameter) of the adhesive 15 having a circular mountain shape in plan view becomes the same whether a small amount of adhesive 15 is applied or a large amount is applied. This allows for a high degree of freedom in setting the amount of adhesive 15 to be applied.

[0027] (Third embodiment) The restricting portion that restricts the wet spreading of the adhesive can be configured as shown in Figures 9 and 10. In Figures 9 and 10, members that are the same as or equivalent to those described with reference to Figures 1 to 8 are given the same reference numerals and detailed description thereof will be omitted as appropriate.

[0028] The sensor element 31 shown in Fig. 9 has a pressure chamber 32 at the end opposite to the end from which the pressure introducing capillary tube 14 is led out. As shown in Fig. 10, the pressure chamber 32 is formed by a counterbore 33 into which the pressure introducing hole 17 opens, a large diameter hole 34 connected to the counterbore 33, and a sensor diaphragm 35 that closes the large diameter hole 34. The pressure introducing hole 17, the counterbore 33, and the large diameter hole 34 are formed in a main body 36 that forms part of the sensor element 31. The end of the main body 36 from which the pressure introducing capillary tube 14 is led out is formed with a recess 37 with the pressure introducing hole 17 opening in the center.

[0029] The opening shape of the recess 37 is circular. The pressure introducing capillary tube 14 in this embodiment is inserted into the pressure introducing hole 17 that opens into the inner bottom surface 37a of the recess 37, with the tip of the pressure introducing capillary tube 14 inserted into the countersunk portion 33, and is adhered to the main body 36 with adhesive 15. The adhesive 15 is applied so as to reach the countersunk portion 33 from the recess 37 through the gap between the pressure introducing hole 17 and the pressure introducing capillary tube 14. In this embodiment, the inner bottom surface 37a of the recess 37 serves as the adhesive surface 19. A bottom 33a of the counterbore 33 where the pressure introducing hole 17 opens is filled with adhesive 15. This adhesive 15 may be the same as that used in the first embodiment.

[0030] When applying adhesive 15 to recess 37, sensor element 31 is placed in a position in which recess 37 opens upward, and a dispenser (not shown) is used to apply a predetermined amount of adhesive. Adhesive 15 applied to recess 37 spreads from the inner bottom surface 37a of recess 37 to the inner wall 37b of recess 37, and rises due to surface tension into a circular mountain shape in plan view with pressure-conducting capillary 14 located at the center. In this embodiment, restricting portion 20 that restricts adhesive 15 from spreading around pressure-conducting hole 17 is formed by inner wall 37b of recess 37.

[0031] For this reason, also in this embodiment, the adhesive 15 is applied evenly over the entire area of ​​the bonding surface 19 without depending on the wettability of the bonding surface 19, so that the adhesive 15 functions sufficiently as designed. This suppresses the transfer of thermal stress to the sensor element 31 and the variation in pressure resistance strength, and improves resistance to thermal stress caused by the difference in thermal expansion coefficient between the pressure-conducting capillary 14 and the sensor element 31, and to tensile force caused when the inside of the sensor element 31 becomes high pressure. As a result, also in this embodiment, it is possible to provide an adhesive structure for a thin tube for a pressure sensor, which is capable of preventing damage caused by a decrease in the pressure resistance of the sensor element and suppressing variations in characteristics.

[0032] In the sensor element 31 according to this embodiment, the pressure in the pressure chamber 32 is applied to the tip surface 14a of the pressure introducing capillary tube 14, so that pressure acts on the pressure introducing capillary tube 14 in the direction of exiting from the main body 36. When the pressure in the pressure chamber 32 becomes high, a tensile force is applied to the adhesive 15 bonding the pressure introducing capillary tube 14 to the main body 36. According to this embodiment, as shown by arrows A and B in FIG. 9, the tensile force can be distributed and received by the hardened portion 15a in the bottom 33a of the counterbore 33 and the hardened portion b in the mountain shape in the recess 37. This improves resistance to pressure, and the initial state in which the pressure introducing capillary tube 14 is bonded to the main body 36 can be reliably maintained even when the pressure in the pressure chamber 32 becomes high pressure. [Explanation of symbols]

[0033] 11...adhesive structure, 12...pressure sensor, 17...pressure introducing hole, 14...pressure introducing capillary, 15...adhesive, 18...groove, 18a...opening edge, 19...adhesive surface, 20...regulating portion, 22...convex portion, 22c...corner portion, 31...sensor element, 37...concave portion, 37b...inner wall.

Claims

1. A sensor element of the pressure sensor; a pressure introducing hole formed in the sensor element; a pressure introducing capillary inserted into the pressure introducing hole; an adhesive applied to an adhesive surface of the sensor element, where the pressure introducing hole is open, so as to cover a part of the pressure introducing capillary, and the adhesive is used to adhere the pressure introducing capillary to the sensor element, 4. The adhesive structure for a thin tube for a pressure sensor, comprising: a restricting portion for restricting the adhesive from spreading around the pressure introducing hole.

2. 2. The pressure sensor capillary bonding structure according to claim 1, Furthermore, the sensor element has a groove surrounding the pressure introducing hole, 2. A bonding structure for a thin tube for a pressure sensor, comprising: a groove having a groove opening and a pressure guiding hole, the groove opening being formed by a groove edge, the groove opening being a boundary between the groove and the bonding surface where the pressure guiding hole opens.

3. 2. The pressure sensor capillary bonding structure according to claim 1, Furthermore, the sensor element has a convex portion whose tip end surface is the adhesive surface, 2. The adhesive structure for a thin tube for a pressure sensor, wherein the restricting portion is formed by a corner portion that is a boundary between the adhesive surface and a side surface of the protrusion.

4. 2. The pressure sensor capillary bonding structure according to claim 1, Furthermore, the sensor element has a recess in which the adhesive surface serves as an inner bottom surface, 2. A bonding structure for a thin tube for a pressure sensor, wherein the restricting portion is formed by an inner wall of the recess.

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