pressure sensor

Abstract

A pressure sensor includes a sensor housing having an opening portion with different sizes in a long side direction and a short side direction, a sensor chip provided to the sensor housing in a manner of plugging the opening portion to form a diaphragm portion, a strain gauge portion provided to the sensor chip, and a cap member joined to the sensor chip by cap cement, wherein a joining area of a joining surface of both end portions of the diaphragm portion in the long side direction is larger than a joining area of a joining surface of both end portions of the diaphragm portion in the short side direction. Thus, in the pressure sensor, breakage of the diaphragm portion and the like can be prevented, and pressure detection sensitivity can be maintained.

Description

Technical Field

[0001] This invention relates to a pressure sensor. Background Technology

[0002] Pressure sensors that utilize piezoelectric elements are used in various fields.

[0003] For example, Patent Document 1 discloses a semiconductor differential pressure sensor installed in the fuel tank of an automobile for detecting pressure changes of gasoline vapor in the fuel tank system. Patent Document 1 discloses a method where the pressure sensing element of the semiconductor differential pressure sensor is fixed to the top of the first protrusion with an adhesive while the second protrusion is embedded in the opening, thereby achieving a strong holding force and high positional accuracy of the pressure sensing element, preventing the adhesive from flowing into the first pressure inlet and preventing blockage of the first pressure inlet.

[0004] Patent document 2 discloses a sensor chip, which is a plate-shaped component that is circular when viewed from above, and has: a diaphragm; a piezoelectric diffuser formed on the surface of the diaphragm; an electrode for extracting electrical signals; a lead diffuser that electrically connects the piezoelectric diffuser and the electrode; a silicon oxide film (protective film) formed to cover the piezoelectric diffuser and the lead diffuser; and a cover component that attaches at least a portion of the surface of the silicon oxide film to the sensor chip as a bonding surface.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-146318

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-055868 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] To improve the pressure detection sensitivity of pressure sensors using deformation sensors, thinning the diaphragm of the deformation detection unit to increase deformation relative to pressure is effective. However, as a drawback of thinning, the diaphragm's strength is reduced, raising concerns about decreased maneuverability during manufacturing and potential chip breakage.

[0011] To address this issue, it is effective to attach the cover component described in Patent Document 2 to the diaphragm for protection. However, due to the attachment of the cover component, the rigidity of the diaphragm also increases, thus leaving room for improvement in terms of reduced pressure detection sensitivity.

[0012] The purpose of this invention is to prevent damage to the diaphragm portion in a pressure sensor and to maintain pressure detection sensitivity.

[0013] Solution for solving the problem

[0014] The pressure sensor of the present invention comprises: a sensor housing having openings of different sizes in the long and short directions; a sensor chip disposed in the sensor housing to block the openings, forming a diaphragm portion; a strain gauge portion disposed in the sensor chip; and a cap member bonded to the sensor chip by a cap adhesive, wherein the bonding area of ​​the bonding surfaces of the two ends of the diaphragm portion in the long direction of the bonding surface of the cap adhesive is larger than the bonding area of ​​the bonding surfaces of the two ends of the diaphragm portion in the short direction.

[0015] Invention Effects

[0016] According to the present invention, in the pressure sensor, damage to the diaphragm portion can be prevented, and pressure detection sensitivity can be maintained. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the structure of a dispensing device that includes a pressure sensor.

[0018] Figure 2 It means Figure 1 Enlarged view of arm 16, etc.

[0019] Figure 3A This is an exploded perspective view of the pressure sensor of Embodiment 1.

[0020] Figure 3B It means Figure 3A A longitudinal sectional view of the pressure sensor.

[0021] Figure 4 It means Figure 3B An exploded 3D view of the sensor chip portion of a pressure sensor.

[0022] Figure 5A It is a longitudinal sectional view showing the deformed state (long side direction) of an existing pressure sensor in use.

[0023] Figure 5B It is observed along the shorter side. Figure 5A A longitudinal sectional view of the pressure sensor.

[0024] Figure 6A This is a longitudinal sectional view showing the deformed state (long side direction) of the pressure sensor in use according to Embodiment 1.

[0025] Figure 6B It is observed along the shorter side. Figure 6A A longitudinal sectional view of the pressure sensor.

[0026] Figure 7 This is a perspective view of the sensor chip portion of the pressure sensor in Embodiment 2.

[0027] Figure 8 This is a perspective view of the sensor chip portion of the pressure sensor in Embodiment 3.

[0028] Figure 9 This is a top view showing a modified example of the cap component of a pressure sensor.

[0029] Figure 10 This is a top view showing other variations of the cap component of the pressure sensor. Detailed Implementation

[0030] This disclosure relates to a pressure sensor, and more particularly to a pressure sensor suitable for detecting the pressure of fluids, such as in a dispensing device.

[0031] The pressure sensor disclosed herein is configured such that the cap component exerts a stronger effect on suppressing deformation of the sensor chip along the long side of the diaphragm portion and a weaker effect along the short side. In other words, the pressure sensor disclosed herein has a structure that is difficult to deform along the long side of the diaphragm portion and easy to deform along the short side.

[0032] The following describes an embodiment of applying the pressure sensor of this disclosure to a dispensing device.

[0033] Example 1

[0034] Figure 1 This is a schematic diagram showing the structure of a dispensing device that includes a pressure sensor.

[0035] As shown in the figure, the flow path system of the dispensing device 1 consists of a nozzle 2, an injection pump 4, a solenoid valve 5, a gear pump 6, and a water tank 7, all connected by piping 8. The injection pump 4 consists of a container 9, a plunger 10, a ball screw 11, and a drive motor 12. The dispensing device 1 also includes an arm 16 (dispensing arm). The drive motor 12, like the motor driving the sample dispensing mechanism 13, is controlled by the control unit 14.

[0036] A pressure sensor 15 is installed inside the arm 16. The arm 16 is capable of rotating and moving up and down to move to the position where it can suction and discharge liquid.

[0037] Figure 2 It means Figure 1 Enlarged view of arm 16, etc.

[0038] exist Figure 2The image shows the state immediately after water 21 for injection pressure transmission has been drawn into pipe 8. Pipe 8 is filled with water 21. Liquid 22 enters nozzle 2.

[0039] Segmented air 23 enters between water 21 and liquid 22. Water 21 reaches the position of pressure sensor 15.

[0040] By using an injection pump 4 ( Figure 1 Pressurizing water 21 can transmit pressure to liquid 22, and can draw and discharge liquid 22 from nozzle 2.

[0041] When liquid 22 is drawn from nozzle 2, the solenoid valve 5 ( Figure 1 With the solenoid valve 5 closed, the plunger 10 inside the injection pump 4 is pulled out. Conversely, when liquid is dispensed from the nozzle 2, with the solenoid valve 5 closed, the plunger 10 inside the injection pump 4 is pushed into the container 9.

[0042] In the case of aspirating liquid 22 such as a sample, in order to prevent the liquid 22 from mixing with the water 21 in the piping 8, the liquid 22 is aspirated after the segmented air 23 used for segmenting the nozzle 2 is aspirated.

[0043] In addition, after discharge, nozzle 2 is cleaned. During the cleaning of nozzle 2, water 21 inside the flow path is pushed out simultaneously with the water used for cleaning coming into contact with the outer wall of nozzle 2. The water 21 inside nozzle 2 during cleaning can be pushed out at a higher pressure than when pushed out by injection pump 4 by opening solenoid valve 5 and utilizing the pressure of gear pump 6.

[0044] To detect potential anomalies such as nozzle 2 blockage or cavitation during the dispensing process, a pressure sensor 15 is installed on the piping 8. The pressure sensor 15 monitors the pressure of the water 21 and detects abnormal pressure changes.

[0045] To reliably detect pressure changes within the nozzle 2, the pressure sensor 15 is preferably positioned close to the nozzle 2. Therefore, in this figure, the pressure sensor 15 is located within the arm 16. However, the location of the pressure sensor 15 is not limited to within the arm 16; for example, it could be located on the side of the sample dispensing mechanism 13.

[0046] Next, the construction of the pressure sensor disclosed herein will be described in more detail.

[0047] Figure 3A It means Figure 2 An exploded perspective view of an example of a pressure sensor.

[0048] Figure 3B It means Figure 3A A longitudinal sectional view of the pressure sensor.

[0049] like Figure 3A As shown, the pressure sensor 15 includes a sensor chip 31, a cap component 34 (cover component), a sensor housing 32, and a cover 40. A flow path 33 is formed inside the sensor housing 32. Threaded portions (not shown) are provided at both ends of the flow path 33, allowing the flow path 33 to be connected to the piping 8 of the dispensing device 1 via connectors.

[0050] Additionally, an opening 35 is provided in the sensor housing 32. The opening 35 communicates with the flow path 33. Furthermore, the opening 35 reaches the outer surface of the sensor housing 32. In other words, the opening 35 is a structure that branches off from the flow path 33 toward the outer surface of the sensor housing 32 and reaches the outer surface of the sensor housing 32.

[0051] A sensor chip 31 is disposed at the end of an opening 35 located on the outer surface of the sensor housing 32, such that the opening 35 is blocked. The sensor chip 31 is bonded to the sensor housing 32 by a sensor chip bonding agent 36. In other words, a sensor chip bonding portion consisting of the sensor chip bonding agent 36 is provided between the sensor chip 31 and the sensor housing 32. A cap member 34 is bonded to the surface of the sensor chip 31. A printed circuit board 45 is provided on the sensor housing 32 to extract the output from the sensor chip 31. The printed circuit board 45 is electrically connected to the electrode portion of the sensor chip 31 via bonding lines 46. The printed circuit board 45 is a glass epoxy board, a flexible printed circuit board, or the like.

[0052] like Figure 3B As shown, the sensor chip 31 has a diaphragm portion 31a as its deformable part. A cap member 34 (cover member) is bonded to the surface of the sensor chip 31 to protect the diaphragm portion 31a. Furthermore, a cover 40 is provided on the outer surface of the sensor housing 32 to cover the sensor chip 31. The cover 40 is fixed by adhesive, threaded fastening, snap-fit, or the like.

[0053] The diaphragm portion 31a flexes and deforms due to pressure changes in the water 21 flowing through the flow path 33. The deformation is measured using the sensor chip 31, thereby determining the pressure of the water 21 flowing within the sensor housing 32. The deformation is measured using a strain gauge mounted on the central surface of the sensor chip 31.

[0054] Figure 4 It means Figure 3B An exploded 3D view of the sensor chip portion of a pressure sensor.

[0055] In this figure, the sensor chip 31 is bonded to the terminal portion of the opening 35 via a sensor chip bonding agent 36. The portion of the sensor chip 31 opposite to the opening 35 is the diaphragm portion 31a of the pressure sensor 15. The opening 35 and the diaphragm portion 31a are oblong, with different dimensions in the long and short side directions. Furthermore, the shapes of the opening 35 and the diaphragm portion 31a are not limited to oblong; they can also be elliptical or rectangular with curvature at the corners, etc.

[0056] On the surface of the sensor chip 31, a cap member 34 is bonded to both ends in the long side direction by adhesive 37a and both ends in the short side direction by adhesive 37b. In other words, a joint portion (cap joint portion) composed of adhesive 37a and adhesive 37b in the long side direction is provided between the sensor chip 31 and the cap member 34. Here, "both ends" can also be referred to as "both ends". Therefore, adhesive 37a in the long side direction is adhesive provided at both ends in the long side direction, and adhesive 37b in the short side direction is adhesive provided at both ends in the short side direction.

[0057] The bonding surfaces of the adhesive 37a near both ends of the long side direction are the bonding surfaces 38a near both ends of the long side direction, and the bonding surfaces of the adhesive 37b near both ends of the short side direction are the bonding surfaces 38b near both ends of the short side direction. The adhesives 37a and 37b near both ends of the long side direction are thermosetting adhesives, UV addition-curing adhesives, low-melting-point glass, silver paste, etc. A strain gauge section 31b for detecting deformation is provided at the center of the surface of the sensor chip 31.

[0058] Furthermore, in this embodiment, the adhesive 37a near both ends in the long side direction and the adhesive 37b near both ends in the short side direction use adhesives with equal storage modulus.

[0059] When the diaphragm portion 31a is deformed by pressure from the water 21, the magnitude of the deformation in the diaphragm portion 31a differs between the long side direction and the short side direction of the strain gauge portion 31b.

[0060] The strain gauge unit 31b detects the deformation in both the long and short sides and outputs the difference. This is to compensate for the temperature characteristics of the strain gauge unit 31b.

[0061] In order to increase the sensitivity of the pressure sensor 15 in this manner, in addition to having a large absolute value of the deformation of the strain gauge section 31b, it is also important to have a large difference between the deformation in the long side direction and the short side direction. As a method to increase the absolute value of the deformation, it is effective to make the sensor chip 31 thin-film to make it easy to deform. However, as a drawback of thin-film, the strength of the sensor chip 31 is reduced, which raises concerns about reduced operability during manufacturing and chip breakage. In this embodiment, in order to solve this problem, the cap member 34 is joined to the sensor chip 31 to ensure strength.

[0062] However, as will be described later, when the cap component 34 is engaged, the rigidity of the diaphragm portion 31a also increases, and the absolute value of the deformation of the strain gauge portion 31b decreases, thereby reducing the sensor sensitivity.

[0063] To solve this problem, the following structure was adopted: the joint area of ​​the joint surface 38a near the two ends of the long side direction of the joint surface of the cap component 34 is larger than the joint area of ​​the joint surface 38b near the two ends of the short side direction.

[0064] Next, use Figures 5A to 6B right Figure 4 The effects of the structure are explained. Furthermore, these figures are longitudinal sections of strain gauge section 31b.

[0065] Figure 5A It is a longitudinal sectional view showing the deformed state (long side direction) of an existing pressure sensor in use.

[0066] Figure 5B It is observed along the shorter side. Figure 5A A longitudinal sectional view of the pressure sensor.

[0067] The pressure sensors shown in these figures are without cap components, so when the sensor chip 31 is subjected to water 21 ( Figure 3B When the pressure p is applied, it deforms significantly.

[0068] When the sensor chip 31 is deformed by pressure p, tensile deformation occurs in the strain gauge section 31b. The long side component of the tensile deformation is designated as εx1, and the short side component is designated as εy1, and these are marked in the respective figures.

[0069] Due to the dimensional difference between the long and short sides of the opening 35, the curvature of the strain gauge section 31b differs. Specifically, the curvature in the short side direction is greater than that in the long side direction, which, expressed in terms of the magnitude of tensile deformation, is εx1 < εy1. As the sensor output, the difference between them is output as εy1 - εx1.

[0070] Through this deformation, the portion of the sensor chip 31 bonded by the sensor chip adhesive 36 is displaced inward in both the long and short sides (in the figure, from left and right towards the center). Accompanying this displacement, the sensor chip adhesive 36 is in a state of shear deformation due to shear force from the sensor chip 31.

[0071] Figure 6A This is a longitudinal sectional view showing the deformed state (long side direction) of the pressure sensor in use according to the embodiment.

[0072] Figure 6B It is observed along the shorter side. Figure 6A A longitudinal sectional view of the pressure sensor.

[0073] The pressure sensors shown in these figures are fitted with a cap component 34, so that even if the sensor chip 31 is subjected to water 21 ( Figure 3B The pressure p, and Figure 5A as well as Figure 5B Compared to the existing examples shown, the amount of deformation is also smaller.

[0074] like Figure 6A as well as Figure 6B As shown in the respective figures, the long-side component of the tensile deformation is set as εx2, and the short-side component is set as εy2. In this case, the sensor output is εy2-εx2.

[0075] In this embodiment, tensile deformation is suppressed due to the rigidity of the cap component 34. For example... Figure 6A as well as Figure 6B As shown, the sensor chip bonding agent 36, the bonding agents 37a near both ends in the long side direction, and the bonding agents 37b near both ends in the short side direction are in a state of shear deformation due to shear force applied to the sensor chip 31. Due to the deformation suppression effect provided by the cap component 34, both εx2 and εy2 are smaller than when the cap component 34 is not installed. This is the reason for the sensitivity reduction caused by the installation of the cap component 34.

[0076] To prevent this decrease in sensitivity, in this embodiment, such as Figure 4 As shown, the bonding area of ​​the bonding surface 38a near both ends in the long side direction is larger than the bonding area of ​​the bonding surface 38b near both ends in the short side direction. Therefore, there is a difference in the ease of shear deformation between the bonding agent 37a and the bonding agent 37b near both ends in the long side direction, with the bonding agent 37b near both ends in the short side direction being more prone to shear deformation. That is, the deformation suppression effect of the cap component 34 on the sensor chip 31 is stronger along the long side direction and weaker along the short side direction. As a result, the tensile deformation εx2 of the long side direction component is significantly reduced, while the reduction in the tensile deformation εy2 of the short side direction component is smaller, thus increasing the sensor output εy2-εx2, which is the difference between the two.

[0077] Thus, according to the structure of this embodiment, the strength of the sensor chip 31 can be ensured by the cap component 34, and the sensitivity of the pressure sensor can be maintained.

[0078] Furthermore, each adhesive is positioned linearly symmetrically along both the long and short sides, but it may not be linearly symmetrical. By varying the bonding surfaces within the range where the size relationship of the bonding areas holds, the same effect can be achieved. In addition, the shape of the cap component 34 is not limited to the shape shown in the figure.

[0079] Furthermore, while the above example was explained based on the size of the joint area, a structure that achieves the same effect has the following structure: the length of the major axis of the joint surface 38a near both ends of the long side direction, i.e., the length of the joint surface 38a near both ends of the long side direction close to the opening 35, is longer than the length of the major axis of the joint surface 38b near both ends of the short side direction, i.e., the length of the joint surface 38b near both ends of the short side direction close to the opening 35. This structure is also similar to... Figure 4 The structures are consistent. In this case, such as Figure 4 As shown, it is assumed that the minor axes of the joint surfaces 38a and 38b near the two ends of the long side direction are approximately the same.

[0080] However, their minor axes can also be different. This is because, compared to the dimensions of the mating surfaces 38a and 38b near the ends of the long side direction, the dimensions of the long axis have a greater impact on the deformation suppression effect brought about by the cap component 34 than the dimensions of the minor axis.

[0081] Example 2

[0082] Figure 7 This is a perspective view showing the sensor chip portion of the pressure sensor in this embodiment.

[0083] In the pressure sensor 75 shown in this figure, the cap part 34 and the sensor chip 31 are joined by adhesive 37a near both ends of the long side and adhesive 77b near both ends of the short side, which have the same shape as in Embodiment 1.

[0084] The feature of this embodiment is that, as the bonding agent 77b near both ends in the short side direction, a bonding agent with a smaller storage modulus than the bonding agent 37a near both ends in the long side direction is selected. Therefore, compared to using a bonding agent with the same storage modulus as in Embodiment 1, the deformation suppression effect of the cap member 34 on the sensor chip 31 in the short side direction can be further reduced. Consequently, the reduction in the tensile deformation εy2 of the short side direction component can also be further reduced, increasing the sensor output εy2-εx2.

[0085] The structure of this embodiment is effective, for example, when it is desirable to maximize the contact area of ​​the cap component 34 and improve sensor sensitivity. Increasing the contact area of ​​the cap component 34 aims to ensure contact strength and prevent resonance caused by external vibrations.

[0086] Example 3

[0087] Figure 8 This is a perspective view showing the sensor chip portion of the pressure sensor in this embodiment.

[0088] In the pressure sensor 85 shown in this figure, unlike in Embodiment 1, the cap component 34 and the sensor chip 31 are joined by a bonding agent 37a near both ends in the long side direction. No bonding agent is provided near both ends in the short side direction. This is equivalent to the case in Embodiment 1 where the area (joint area) of the joint surface 38b near both ends in the short side direction is 0.

[0089] Therefore, the cap component 34 has the least effect on suppressing deformation in the short-side direction of the sensor chip 31. Consequently, the reduction in the tensile deformation εy2 of the short-side component is also minimized, increasing the sensor output εy2-εx2. Furthermore, fewer bonding areas are required, thus shortening the process of applying adhesive using a dispenser during manufacturing.

[0090] (Modified Example)

[0091] Figure 9 This is a top view showing a modified example of the cap component.

[0092] In this figure, a rib 94 is provided along the long side of the cap component 34. In other words, the cap component 34 has a rib 94 provided along the long side of the opening 35.

[0093] This structure improves the rigidity of the cap component 34 along its long side and suppresses deformation along its long side. This, in turn, helps to reduce the tensile deformation εx2 along the long side.

[0094] Figure 10 This is a top view showing other variations of the cap component.

[0095] In this figure, three ribs 94 are provided along the long side of the cap component 34.

[0096] This structure further enhances the rigidity of the cap component 34 along its long side, thereby further suppressing deformation of the cap component 34 along its long side. Consequently, it further suppresses the reduction of tensile deformation εx2 along its long side.

[0097] Furthermore, the present invention is not limited to the embodiments described above, and includes various modifications. The embodiments described above are examples detailed to facilitate understanding of the present invention, and are not limited to having all the described structures. Additionally, a portion of the structure of one embodiment can be replaced with the structure of another embodiment. Furthermore, structures of other embodiments can be added to the structure of one embodiment. Moreover, regarding a portion of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0098] Symbol Explanation

[0099] 1—Dispensing device, 2—Nozzle, 4—Injection pump, 5—Solenoid valve, 6—Gear pump, 7—Water tank, 8—Piping, 9—Container, 10—Plunger, 11—Ball screw, 12—Drive motor, 13—Sample dispensing mechanism, 14—Control unit, 15—Pressure sensor, 16—Arm, 21—Water, 22—Liquid, 23—Sectional air, 31—Sensor chip, 31a—Diaphragm part, 31b—Strain gauge part, 32—Sensor housing, 33—Flow path, 34—Cap part, 35—Opening, 36—Sensor chip bonding agent, 37a—Bond near both ends in the long side direction, 37b—Bond near both ends in the short side direction, 38a—Mating surface near both ends in the long side direction, 38b—Mating surface near both ends in the short side direction, 40—Cap, 45—Printed circuit board, 46—Bonding line.

Claims

1. A pressure sensor, characterized in that, have: The sensor housing has openings of different sizes in the long and short directions; A sensor chip is disposed in the sensor housing in such a way as to block the opening, forming a diaphragm portion; The strain gauge section is located on the sensor chip; as well as The cap component is bonded to the sensor chip by a cap adhesive. The bonding area of ​​the bonding surfaces of the two ends of the diaphragm portion in the long side direction of the bonding surface of the cap adhesive is larger than the bonding area of ​​the two ends of the diaphragm portion in the short side direction.

2. A pressure sensor, characterized in that, have: The sensor housing has openings of different sizes in the long and short directions; A sensor chip is disposed in the sensor housing in such a way as to block the opening, forming a diaphragm portion; The strain gauge section is located on the sensor chip; as well as The cap component is bonded to the sensor chip by a cap adhesive. The major axis of the joint surface of the diaphragm portion at both ends in the long side direction of the joint surface of the cap adhesive is longer than the major axis of the joint surface of the diaphragm portion at both ends in the short side direction.

3. A pressure sensor, characterized in that, have: The sensor housing has openings of different sizes in the long and short directions; A sensor chip is disposed in the sensor housing in such a way as to block the opening, forming a diaphragm portion; The strain gauge section is located on the sensor chip; as well as The cap component is bonded to the sensor chip by a cap adhesive. The cap component has ribs arranged along the long side of the opening.

4. The pressure sensor according to claim 1 or 2, characterized in that, The storage modulus of the capping adhesive at both ends of the diaphragm portion in the short side direction is smaller than that of the capping adhesive at both ends of the diaphragm portion in the long side direction.

5. The pressure sensor according to claim 1, characterized in that, The joint area of ​​the joint surfaces at both ends of the short side of the diaphragm portion is 0.

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