Adhesive structure for thin tube for pressure sensor

Abstract

Provided is an adhesive structure for a thin tube for a pressure sensor, the adhesive structure being configured so that, regardless of the wettability of an adhesive surface, the state after application of an adhesive is made uniform, breakage caused by a decrease in the pressure resistance of a sensor element is prevented, and the characteristics are constant. The present invention comprises: a sensor element (13) of a pressure sensor; a pressure guide hole (17) formed in the sensor element (13); a pressure guide slim tube (14) inserted into the pressure guide hole (17); and an adhesive (15) which is applied to an adhesive surface (19) of the sensor element (13), said adhesive surface (19) being open to the pressure guide hole (17), so as to cover a part of the pressure guide tube (14), and which adheres the pressure guide tube (14) to the sensor element (13). A regulating part (20) for regulating the wetting and diffusion of the adhesive (15) is formed around the pressure guide hole (17).

Description

Technical Field

[0001] The present invention relates to a bonding structure of a capillary tube for a pressure sensor which is used when a capillary tube for conducting pressure is bonded to a sensor element by an adhesive. Background Art

[0002] As a conventional pressure sensor, for example, as described in Patent Document 1, a capillary tube for conducting pressure is sometimes used when the pressure of a fluid to be measured is transmitted to a sensor element. The capillary tube for conducting pressure is inserted into a pressure conducting hole formed in the sensor element and bonded to the sensor element by an adhesive. The adhesive is applied to a bonding surface of the sensor element where the pressure conducting hole is opened so as to cover a portion of the capillary tube for conducting pressure.

[0003] In order to control the coating amount and coating position, the adhesive is applied using a dispenser. The adhesive applied to the bonding surface by the dispenser wets and spreads on the bonding surface, and bulges along the capillary tube for pressure conduction. It is known that the wettability of the adhesive changes depending on the processing conditions of the sensor element surface. As processing conditions that cause changes in the wettability of the adhesive, there are conditions such as the presence or absence of organic matter adhesion, the presence or absence of cleaning of the sensor element surface or the degree of cleaning, the presence or absence of the adhesive tape pasting history, and the presence or absence of high temperature application to the sensor element. In addition, the wettability of the adhesive sometimes changes due to the time that has passed since the final processing of the sensor element in addition to the processing conditions of the sensor element. For example, the wettability changes due to the change in the organic contamination conditions of the bonding surface or the formation state of the oxide film over time.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-187046 Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] Since the wettability of the adhesive on the bonding surface varies due to various reasons, even if the adhesive is applied to multiple bonding parts using a dispenser under the same coating conditions, the size or shape of the adhesive that wets and spreads is rarely the same on the multiple bonding parts, and there is a problem of deviation in the wetting and spreading of the adhesive. Fig.11 As shown in (A), when two capillaries 2 are provided in one sensor element 1, the adhesive 3 applied to each capillaries 2 may be connected to each other. Fig.11In the two bonding portions 4 shown in (B), there are cases where the wetting and spreading of the adhesive 3 is suppressed as in the left bonding portion 4, and cases where a part of the adhesive 3 is wetted and spread more widely than other parts as in the right bonding portion 4.

[0009] In addition, when the pressure-conducting capillary 2 is bonded to the sensor element 1, the area to which the nozzle of the dispenser (not shown) can approach when applying the adhesive 3 is limited, so it is difficult to apply the adhesive 3 so as to maintain a concentric circle with respect to the capillary 2. This is one of the reasons for the deviation in the application range of the adhesive 3. For example, Fig.12 (A) Fig.12 As shown in (B), sometimes the adhesive 3 cannot wet and spread concentrically with the capillary 2, and the capillary 2 deviates from the center of the raised portion (rounded corner portion) 3a of the adhesive 3. Fig.12 (A) is a stereogram, Fig.12 (B) is a plan view.

[0010] In this way, if the application position of the adhesive 3 to the sensor element 1 or the state of wetting and spreading is not uniform, the adhesive 3 may not fully function because its shape becomes uneven after curing. For example, the sensor element 1 may be damaged due to low resistance to thermal stress generated by the difference in thermal expansion coefficients between the sensor element 1 and the capillary 2 or to tensile force generated when the sensor element 1 is under high pressure. In addition, the transmission state of the force transmitted from the capillary 2 to the sensor element 1 via the adhesive 3 differs for each bonding portion 4, resulting in deviations in the characteristics of the sensor element 1.

[0011] The object of the present invention is to provide a bonding structure for a capillary tube for a pressure sensor, in which the state of the adhesive after coating is uniform regardless of the wettability of the bonding surface, thereby preventing damage caused by reduced pressure resistance of the sensor element and maintaining constant characteristics.

[0012] [Technical means to solve the problem]

[0013] In order to achieve the above-mentioned purpose, the bonding structure of the capillary for pressure sensor of the present invention comprises: a sensor element of the pressure sensor; a pressure conducting hole formed in the sensor element; a capillary for pressure conducting, inserted into the pressure conducting hole; and an adhesive applied to the bonding surface of the pressure conducting hole opening of the sensor element in a manner covering a portion of the capillary for pressure conducting, so that the capillary for pressure conducting is bonded to the sensor element, and a limiting portion is formed around the pressure conducting hole to limit the wetting and diffusion of the adhesive.

[0014] According to the bonding structure of the capillary for the pressure sensor of the present invention, the sensor element may further include a groove surrounding the pressure conducting hole, and the limiting portion may be formed by an opening edge of the groove which is a boundary between the bonding surface forming the opening of the pressure conducting hole and the groove.

[0015] According to the bonding structure of the capillary tube for the pressure sensor of the present invention, the sensor element may further include a convex portion whose front end surface is formed by the bonding surface, and the limiting portion may be formed by a corner portion that is a boundary between the bonding surface and the side surface of the convex portion.

[0016] According to the bonding structure of the capillary tube for a pressure sensor of the present invention, the sensor element may further include a recessed portion whose inner bottom surface is formed by the bonding surface, and the limiting portion may be formed by an inner wall of the recessed portion.

[0017] [Effects of the Invention]

[0018] According to the present invention, the wetting and spreading range of the adhesive is limited by the limiting portion, and the state of the adhesive after coating is made uniform regardless of the wettability of the bonding surface of the sensor element. Therefore, a bonding structure for a capillary tube for a pressure sensor can be provided that prevents damage caused by a decrease in the pressure resistance of the sensor element and has constant characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a perspective view showing the bonding structure of the capillary tube for the pressure sensor according to the first embodiment.

[0020] Figure 2 yes Figure 3 FIG. 1 is a cross-sectional view of the sensor element taken along line II-II. FIG.

[0021] Figure 3 is a plan view of the sensor element.

[0022] Figure 4 This is a cross-sectional view of the bonding structure of a capillary tube for a pressure sensor.

[0023] Figure 5 It is a perspective view showing a bonding structure of a capillary tube for a pressure sensor according to a second embodiment.

[0024] Figure 6 yes Figure 7 sectional view of the sensor element taken along line IV-IV.

[0025] Figure 7 is a plan view of the sensor element.

[0026] Figure 8 This is a cross-sectional view of the bonding structure of a capillary tube for a pressure sensor.

[0027] Fig. 9It is a cross-sectional view of a bonding structure of a capillary tube for a pressure sensor according to a third embodiment.

[0028] Fig.10 is a cross-sectional view of the sensor element.

[0029] Fig.11 This is a plan view showing the planar shape of an adhesive applied to an adhesive surface having uneven wettability.

[0030] Fig.12 This is a diagram showing the adhesive applied in a biased manner relative to the capillary tube.

[0031] [Explanation of Symbols]

[0032] 11: Bonding structure

[0033] 12: Pressure sensor

[0034] 17: Pressure conducting hole

[0035] 14: Thin tube for pressure conduction

[0036] 15: Adhesive

[0037] 18: Slot

[0038] 18a: Open edge

[0039] 19: Bonding surface

[0040] 20: Restriction Department

[0041] 22: convex part

[0042] 22c: Corner

[0043] 31: Sensor element

[0044] 37: concave part

[0045] 37b: Inner wall DETAILED DESCRIPTION

[0046] (First Embodiment)

[0047] Below, refer to Figure 1 to Figure 4 One embodiment of the bonding structure of the capillary tube for a pressure sensor according to the present invention will be described in detail.

[0048] Figure 1 The bonding structure 11 shown is a bonding structure used when bonding the pressure guiding capillary tube 14 to the sensor element 13 constituting the pressure sensor 12 by means of an adhesive 15. The sensor element 13 is housed in a package 16, and together with the package 16, constitutes the pressure sensor 12.

[0049] Two pressure-conducting capillaries 14 are connected to the sensor element 13. The sensor element 13 measures the pressure of the fluid to be measured transmitted via a pressure transmission medium (not shown) filled in the pressure-conducting capillaries 14. The sensor element 13 includes two pressure-conducting capillaries 14, and 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.

[0050] like Figure 2 As shown, two pressure conducting holes 17 and grooves 18 surrounding the pressure conducting holes 17 are formed in the sensor element 13. The pressure conducting hole 17 is a hole for inserting the pressure conducting capillary tube 14. One end of the pressure conducting hole 17 opens at one end surface 13a of the sensor element 13, and the other end is closed by a diaphragm (not shown) provided inside the sensor element 13.

[0051] like Figure 3 As shown in the figure, the groove 18 surrounding the pressure conducting hole 17 is formed in the shape of a ring centered on the pressure conducting hole 17 on the one end surface 13a of the sensor element 13. In the embodiment, a portion of the one end surface 13a of the sensor element 13 formed between the groove 18 and the pressure conducting hole 17 serves as an adhesive surface 19, and the adhesive 15 is applied to the adhesive surface 19. In the sensor element 13 according to the embodiment, the grooves 18 of the same size and shape are respectively formed around the two pressure conducting holes 17.

[0052] The pressure conducting capillary tube 14 is a tube having a circular cross-sectional shape, and is adhered to the sensor element 13 by an adhesive 15 in a state of being inserted into the pressure conducting hole 17 .

[0053] The adhesive 15 may be, for example, an epoxy resin-based adhesive. The adhesive 15 according to the embodiment is measured with high precision by a dispenser (not shown) and applied to the bonding surface 19 where the pressure-conducting hole 17 is opened. When applying the adhesive 15, Figure 4 As shown, the pressure guiding capillary tube 14 is partially covered with the adhesive 15, and the adhesive 15 swells due to surface tension.

[0054] The adhesive 15 applied to the bonding surface 19 is restricted from wetting and spreading by the opening edge 18a of the groove 18, which is the boundary between the bonding surface 19 and the groove 18. Therefore, the adhesive 15 swells on the bonding surface 19 due to surface tension in a manner corresponding to the applied amount, and is applied in a circular mountain shape in a plan view with the pressure guiding capillary 14 located at the center. According to the embodiment, the opening edge 18a serves as a restriction portion 20 that restricts the wetting and spreading of the adhesive 15.

[0055] 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 range of the adhesive 15 wetting and spreading, the height of the raised adhesive 15, etc. are consistent in the two bonding parts, and the shape of the adhesive 15 after hardening is roughly the same. That is, regardless of the wettability of the bonding surface 19, the state of the adhesive after coating is uniform in the two bonding parts. This means that even in the case of mass production of sensor elements 13, the quality of the bonding parts in all sensor elements 13 is equal.

[0056] The adhesive 15 is evenly and sufficiently applied to all the bonding portions, so that the shape, size, etc. of the adhesive 15 do not vary in all the bonding portions. Therefore, the adhesive 15 fully functions as designed in all the bonding portions, so that the transmission of thermal stress to the sensor element 13 or the variation of the pressure resistance strength is suppressed, and the resistance to the thermal stress generated by the difference in thermal expansion coefficient between the pressure conducting capillary 14 and the sensor element 13, or the tensile force generated when the pressure in the sensor element 13 reaches a high pressure is improved. As shown in the above embodiment, in the sensor element 13 including the two pressure conducting capillary 14, the balance between the high pressure side and the low pressure side can be achieved, so that the so-called cancel-out can be achieved.

[0057] Therefore, according to the above-described embodiment, it is possible to provide a bonding structure of a capillary tube for a pressure sensor, which can prevent damage to a sensor element due to a decrease in pressure resistance and suppress variation in characteristics.

[0058] In the above embodiment, the surface tension acts on the opening edge 18a of the groove 18 to block the adhesive 15, so the outer diameter (fillet diameter) of the adhesive 15 in a circular mountain shape in plan view is the same when a small amount of the adhesive 15 is applied and when a large amount of the adhesive 15 is applied. Therefore, the degree of freedom in setting the amount of the adhesive 15 applied is high.

[0059] (Second Embodiment)

[0060] The limiting portion for limiting the wetting and spreading of the adhesive may be configured as follows: Figures 5 to 8 As shown. Figures 5 to 8 In the Figure 1 to Figure 4 The same or equivalent components as those described above are denoted by the same reference numerals, and detailed description thereof will be appropriately omitted.

[0061] Figure 5 The sensor element 21 shown in the figure has cylindrical protrusions 22 formed at two locations on one end surface 21a. Figure 6 and Figure 7As shown, a pressure conducting hole 17 is formed in the center of the convex portion 22. A pressure conducting capillary 14 is inserted into the pressure conducting hole 17, and an adhesive 15 is applied to the front end surface 22a of the convex portion 22 by a dispenser (not shown). In the embodiment, the front end surface 22a of the convex portion 22 serves as an adhesive surface 19. The adhesive 15 can be the same adhesive as that used in the first embodiment.

[0062] The adhesive 15 applied to the front end surface 22a (adhesive surface 19) wets and spreads to the corner portion 22c that is the boundary between the front end surface 22a (adhesive surface 19) and the side surface 22b (outer peripheral surface) of the convex portion 22, and bulges due to surface tension into a circular mountain shape in a plan view with the pressure conducting capillary 14 located at the center. In the above embodiment, the limiting portion 20 that limits the wet spread of the adhesive 15 around the pressure conducting hole 17 is composed of the corner portion 22c.

[0063] Therefore, in the above-described embodiment, in the plurality of bonding portions, the adhesive 15 is uniformly applied to the entire area of ​​the bonding surface 19 regardless of the wettability of the bonding surface 19 , so that in all the bonding portions, the adhesive 15 fully functions as designed.

[0064] Therefore, the transmission of thermal stress to the sensor element 21 or the deviation of the pressure resistance is suppressed, and the resistance to the thermal stress generated by the difference in thermal expansion coefficient between the pressure guiding capillary 14 and the sensor element 21 or the tensile force generated when the pressure inside the sensor element 21 reaches a high pressure is improved.

[0065] As a result, in the above-described embodiment, it is possible to provide a bonding structure of a capillary tube for a pressure sensor, which can prevent damage to a sensor element due to a decrease in pressure resistance and suppress variation in characteristics.

[0066] In the above embodiment, the surface tension acts on the corners 22c of the convex portion 22 to block the adhesive 15, so the outer diameter (corner diameter) of the adhesive 15 in a circular mountain shape in plan view is the same when a small amount of adhesive 15 is applied and when a large amount of adhesive 15 is applied. Therefore, the degree of freedom in setting the amount of adhesive 15 applied is high.

[0067] (Third Embodiment)

[0068] The limiting portion for limiting the wetting and diffusion of the adhesive may be configured as follows: Fig. 9 and Fig.10 As shown. Fig. 9 and Fig.10 In the Figures 1 to 8 The same or equivalent components as those described above are denoted by the same reference numerals, and detailed description thereof will be appropriately omitted.

[0069] Fig. 9The sensor element 31 shown in the figure has a pressure chamber 32 at the end opposite to the end of the pressure guiding capillary 14. Fig.10 As shown in FIG. 1 , the pressure chamber 32 is formed by a countersunk hole portion 33 with the pressure conducting hole 17 as an opening, a large diameter hole portion 34 connected to the countersunk hole portion 33, and a sensor diaphragm 35 that blocks the large diameter hole portion 34. The pressure conducting hole 17, the countersunk hole portion 33, and the large diameter hole portion 34 are formed in a main body portion 36 that is a part of the sensor element 31. A recessed portion 37 opening with the pressure conducting hole 17 as the center is formed at the end of the main body portion 36 from which the pressure conducting capillary tube 14 is led out.

[0070] The opening shape of the recess 37 is circular. According to the embodiment, the pressure conducting capillary tube 14 is inserted into the pressure conducting hole 17 opened in the inner bottom surface 37a of the recess 37 and the front end is inserted into the countersunk hole portion 33, and then adhered to the main body 36 by the adhesive 15. The adhesive 15 is applied in a manner such that it passes through the gap between the pressure conducting hole 17 and the pressure conducting capillary tube 14 from the recess 37 to the countersunk hole portion 33. In the embodiment, the inner bottom surface 37a of the recess 37 serves as the adhesive surface 19.

[0071] The bottom 33a of the countersunk hole 33 where the pressure conducting hole 17 opens is filled with the adhesive 15. The adhesive 15 may be the same adhesive as that used in the first embodiment.

[0072] When applying the adhesive 15 to the recess 37, the sensor element 31 is placed in a posture where the recess 37 is open at the top, and the adhesive 15 is applied by a dispenser (not shown) in a manner such that the amount of application becomes a predetermined amount. The adhesive 15 applied to the recess 37 wets and spreads from the inner bottom surface 37a of the recess 37 to the inner wall 37b of the recess 37, and bulges due to surface tension into a circular mountain shape in a plan view with the pressure conducting capillary 14 located at the center. In the above embodiment, the limiting portion 20 that limits the wet spreading of the adhesive 15 around the pressure conducting hole 17 is formed by the inner wall 37b of the recess 37.

[0073] Therefore, in the above-described embodiment, the adhesive 15 is evenly applied to the entire area of ​​the adhesive surface 19, regardless of the wettability of the adhesive surface 19, so that the adhesive 15 fully functions as designed. Therefore, the transmission of thermal stress to the sensor element 31 or the variation in the pressure resistance is suppressed, and the resistance to the thermal stress generated by the difference in thermal expansion coefficients between the pressure guiding capillary 14 and the sensor element 31, or the tensile force generated when the pressure inside the sensor element 31 becomes high, is improved.

[0074] As a result, in the above-described embodiment, it is possible to provide a bonding structure of a capillary tube for a pressure sensor, which can prevent damage to a sensor element due to a decrease in pressure resistance and suppress variation in characteristics.

[0075] In the sensor element 31 according to the embodiment, the pressure in the pressure chamber 32 is applied to the front end surface 14a of the pressure-conducting capillary 14, and the pressure acts on the pressure-conducting capillary 14 in the direction of coming out of the main body 36. When the pressure in the pressure chamber 32 becomes high pressure, a tensile force is applied to the adhesive 15 that adheres the pressure-conducting capillary 14 and the main body 36. According to the embodiment, Fig. 9 As shown by arrows A and B, the tensile force can be distributed to the portion 15a hardened in the bottom 33a of the countersunk hole portion 33 and the portion 15b hardened in a mountain shape in the recessed portion 37. Therefore, the resistance to pressure is improved, and even when the pressure chamber 32 becomes a high pressure state, the initial state in which the pressure guiding capillary 14 is bonded to the main body 36 can be reliably maintained.

Claims

1. A bonding structure for a capillary tube for a pressure sensor, It is characterized in that include: Sensor elements of pressure sensors; A pressure-conducting hole is formed in the sensor element; A thin pressure-conducting tube is inserted into the pressure-conducting hole; as well as The adhesive is applied to the bonding surface of the pressure conducting hole of the sensor element in a manner that covers a portion of the pressure conducting capillary tube, thereby bonding the pressure conducting capillary tube to the sensor element. A limiting portion is formed around the pressure conducting hole to limit the wetting and spreading of the adhesive.

2. The bonding structure of the capillary tube for pressure sensor according to claim 1, It is characterized in that The sensor element further comprises: a groove surrounding the pressure-conducting hole, The restricting portion is formed by an opening edge of the groove, and the opening edge of the groove serves as a boundary between the bonding surface where the pressure-conducting hole is opened and the groove.

3. The bonding structure of the capillary tube for pressure sensor according to claim 1, It is characterized in that The sensor element further comprises: the bonding surface serving as a convex portion of the front end surface, The restriction portion is constituted by a corner portion that serves as a boundary between the adhesive surface and a side surface of the convex portion.

4. The bonding structure of the capillary tube for pressure sensor according to claim 1, It is characterized in that The sensor element further includes: a concave portion whose inner bottom surface is formed by the bonding surface; The restricting portion is formed by an inner wall of the recessed portion.

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