Pressure sensor

Abstract

To provide a pressure sensor having a resistive film pattern, which is hardly affected by strain on external bottom face and capable of detecting temperatures with high accuracy.SOLUTION: Processing is a pressure sensor comprising: a stem having a bottom wall and a side wall extending in a first direction crossing the bottom wall; a first resistive film pattern formed in an outside region of outer bottom face of the bottom wall that overlaps the side wall in a plan view from the first direction; and a second resistive film pattern formed at least partly in an inside region of the outer bottom face that does not overlap the side wall in a plan view from the first direction. The first resistive film pattern is constituted by a plurality of circumferential sections extending along the circumferential direction and differing in the distance from the center of the outer bottom face that are connected repeatedly.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pressure sensor that uses a stem. [Background technology]

[0002] A technique has been proposed for forming a resistive film pattern on the outer bottom surface of a metal stem for use as a pressure sensor or other sensor (see Patent Document 1, etc.).

[0003] As a technology for forming a resistive film pattern on the outer bottom surface of a metal stem, one has been proposed in which a resistive film for temperature detection is formed on the outer region of the outer bottom surface, and a resistive film for pressure detection is formed on the inner region of the outer bottom surface. Although the resistance value of the resistive film for pressure detection is also affected by temperature, a pressure sensor in which a resistive film for temperature detection is separately formed can determine the pressure value by excluding the effect of temperature from the output value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent Application Publication No. 2554964 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional pressure sensors, the resistive film pattern formed on the outer region of the outer bottom surface has a shape in which multiple radial patterns extending along the radial direction are folded back and connected, which means that the output of the resistive film for temperature detection is easily affected by distortion of the outer bottom surface, posing a problem in terms of temperature detection accuracy.

[0006] The present disclosure provides a pressure sensor having a resistive film pattern that is less susceptible to the effects of distortion of the outer bottom surface and is capable of highly accurate temperature detection. [Means for solving the problem]

[0007] The pressure sensor according to the present disclosure comprises: a stem having a bottom wall and a side wall extending in a first direction intersecting the bottom wall; a first resistive film pattern formed in an outer region of an outer bottom surface of the bottom wall that overlaps with the side wall in a plan view from the first direction; a second resistive film pattern formed in an inner region of the outer bottom surface that does not overlap with the side wall in a plan view from the first direction, The first resistive film pattern is configured by folding back and connecting a plurality of circumferential pattern portions that extend along the circumferential direction and are at different distances from the center of the outer bottom surface.

[0008] The pressure sensor according to the present disclosure has a first resistive film pattern formed by folding back and connecting a circumferential pattern portion extending along the circumferential direction, and the resistance value of such a first resistive film pattern is less affected by strain on the outer bottom surface, enabling highly accurate temperature detection. Regarding strain caused by pressure from a measurement object in the outer region of the outer bottom surface, radial strain tends to be larger than circumferential strain.

[0009] Furthermore, since the pressure sensor according to the present disclosure is configured by folding back and connecting multiple circumferential pattern portions, it is possible to form a first resistive film pattern that is long in the conductive direction in a limited angular region in the circumferential direction. In such a pressure sensor, it is easy to dispose electrode pads, etc., in outer regions, offset from the first resistive film pattern, which contributes to miniaturization, and it is possible to ensure the length of the first resistive film pattern even in a limited range, thereby enabling accurate temperature detection.

[0010] Furthermore, for example, the angle from one end to the other end of a first circumferential pattern portion located at the outermost periphery among the plurality of circumferential pattern portions, as viewed from the center, may be larger than the angle from one end to the other end of the other circumferential pattern portions, as viewed from the center, excluding the first circumferential pattern portion, among the plurality of circumferential pattern portions.

[0011] In this pressure sensor, the length of the first circumferential pattern portion, which is least affected by distortion of the outer bottom surface, is increased, so that the influence of distortion of the outer bottom surface on the change in resistance value of the first resistive film pattern can be more effectively suppressed. Also, since the first resistive film pattern has circumferential pattern portions other than the first circumferential pattern portion, the overall length of the first resistive film pattern can be secured, allowing for accurate temperature detection.

[0012] Furthermore, for example, the side wall may have a first side wall portion in which an inner surface of the side wall extends in the first direction, and a second side wall portion in which the inner surface of the side wall faces in a direction midway between the first side wall portion and an inner bottom surface of the bottom wall and connects the inner surface of the first side wall portion to the inner bottom surface, At least a portion of the first resistive film pattern may overlap an inner surface of the second sidewall portion in a plan view from the first direction.

[0013] In such a pressure sensor, by arranging a portion of the first resistive film pattern in the portion of the outer region adjacent to the inner region, it is possible to further miniaturize the pressure sensor while suppressing the effects of distortion of the outer bottom surface.

[0014] Furthermore, for example, the side wall may have a first side wall portion in which an inner surface of the side wall extends in the first direction, and a second side wall portion in which the inner surface of the side wall faces in a direction midway between the first side wall portion and an inner bottom surface of the bottom wall and connects the inner surface of the first side wall portion to the inner bottom surface, The first resistive film pattern may entirely overlap the first sidewall portion in a plan view from the first direction.

[0015] In such a pressure sensor, by disposing the entire first resistive film pattern in a portion of the outer region that is less susceptible to the influence of distortion of the outer bottom surface, it is possible to detect temperature with higher accuracy. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a schematic cross-sectional view of a pressure sensor according to the first embodiment. [Figure 2] FIG. 2 is a top view of the pressure sensor shown in FIG. 1 as viewed from a first direction. [Figure 3] FIG. 3 is a conceptual diagram illustrating the circumferential pattern portion of the first resistive film pattern of the pressure sensor shown in FIG. [Figure 4] FIG. 4 is a conceptual diagram showing the relationship between the sidewall and outer bottom surface area of ​​the stem in the pressure sensor shown in FIG. [Figure 5] FIG. 5 is a conceptual diagram showing the tendency of strain occurring in the pressure sensor shown in FIG. [Figure 6] FIG. 6 is a conceptual diagram illustrating the distortion tendency shown in FIG. 5 in more detail. [Figure 7] FIG. 7 is a conceptual diagram illustrating a circumferential pattern portion of the first resistive film pattern according to the first modified example. [Figure 8] FIG. 8 is a conceptual diagram illustrating a circumferential pattern portion of the first resistive film pattern according to the second modified example. [Figure 9] FIG. 9 is a conceptual diagram illustrating a circumferential pattern portion of the first resistive film pattern according to the third modified example. [Figure 10] FIG. 10 is a conceptual diagram showing the relationship between the sidewall and the outer bottom surface area of ​​the stem in the pressure sensor according to the second embodiment. [Figure 11] FIG. 11 is a conceptual diagram showing the relationship between the sidewall of the stem and the area of ​​the outer bottom surface in the pressure sensor according to the third embodiment. [Figure 12] FIG. 12 is a conceptual diagram showing the relationship between the side wall and the area of ​​the outer bottom surface of the stem in the pressure sensor according to the reference example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0018] First embodiment Fig. 1 is a schematic cross-sectional view of a pressure sensor 10 using a stem 20 according to the first embodiment. As shown in Fig. 1, the pressure sensor 10 includes a stem 20 having a bottom wall 22 and a side wall 25, and a sensor main body 18 provided on an outer bottom surface 24 of the bottom wall 22 via an insulating film 40. The sensor main body 18 includes a first resistive film pattern 50 and a second resistive film pattern 60 (see Fig. 2), which will be described later.

[0019] 1, the stem 20 has a hollow cylindrical shape and includes a bottom wall 22 and a side wall 25 extending in a first direction D1 that intersects with the bottom wall 22. The bottom wall 22 is formed at one end of the side wall 25 in the first direction D1. A part of the bottom wall 22 (an inner region 24b described below) serves as a membrane that is distorted by the pressure of the fluid whose pressure is to be measured.

[0020] Meanwhile, the other end of the side wall 25 in the first direction D1 is the open end of a hollow portion formed inside the stem 20. The hollow portion of the stem 20 is in communication with the flow path 12b of the connecting member 12. The first direction D1 in which the side wall 25 extends may be approximately perpendicular to the direction in which the outer bottom surface 24 of the bottom wall 22 extends, as shown in FIG. 1, but the side wall 25 may also be inclined so that the hollow portion widens from the bottom wall 22 side toward the opening side.

[0021] 1, in pressure sensor 10, fluid introduced into flow path 12b is guided from the hollow portion of stem 20 to inner bottom surface 23 of bottom wall 22, and fluid pressure acts on inner bottom surface 23 and bottom wall 22. Stem 20 is made of a metal such as stainless steel.

[0022] A flange portion 21 is formed on the other end of the side wall 25 of the stem 20. The flange portion 21 is formed so as to protrude radially outward from the side wall 25. The flange portion 21 is sandwiched and fixed between the connecting member 12 and the retaining member 14, thereby sealing the flow path 12b leading to the inner bottom surface 23 of the bottom wall 22.

[0023] The connecting member 12 has a thread groove 12a for connecting the pressure sensor 10 to a pipe, an external flow path, etc. The pressure sensor 10 is fixed via the thread groove 12a to a pressure chamber or the like in which a fluid whose pressure is to be measured is sealed. As a result, the flow path 12b formed inside the connecting member 12 and the hollow portion inside the stem 20 are airtightly connected to the pressure chamber in which the fluid whose pressure is to be measured resides.

[0024] A circuit board 90 serving as a signal transmission section is attached to the upper surface of the retaining member 14. The circuit board 90 has a ring-like shape that surrounds the stem 20, but the shape of the circuit board 90 is not limited to this. The circuit board 90 incorporates a circuit that transmits a detection signal from the sensor main body 18 (see FIG. 2) provided on the outer bottom surface 24 of the stem 20. The circuit board 90 is electrically connected to the electrode pads 41 to 46 (see FIG. 2) of the sensor main body 18 via connection wiring 82 formed by wire bonding or the like.

[0025] 2 is a top view of the pressure sensor 10 shown in FIG. 1 , showing the outer bottom surface 24 of the stem 20 as viewed from a first direction D1. As shown in FIG. 2, a first resistive film pattern 50 and a second resistive film pattern 60 are formed on the outer bottom surface 24. As shown in FIG. 2, the first resistive film pattern 50 is formed in an outer region 24a of the outer bottom surface 24 of the bottom wall 22, and the second resistive film pattern 60 is formed in an inner region 24b of the outer bottom surface 24 of the bottom wall 22 that is closer to the center 24c of the outer bottom surface 24 than the outer region 24a.

[0026] Fig. 4 is a conceptual diagram illustrating the outer region 24a and the inner region 24b of the outer bottom surface 24 shown in Fig. 2. In Fig. 4, a plan view of the outer bottom surface 24 of the stem 20 from the first direction D1 is shown in the upper part of the figure, and a cross-sectional view of the stem 20 taken along a cross section parallel to the first direction D1 and passing through the center 24c of the outer bottom surface 24 is shown in the lower part of the figure.

[0027] 4, the outer region 24a of the outer bottom surface 24 overlaps with the side wall 25 of the stem 20 in plan view from the first direction D1. On the other hand, the inner region 24b of the outer bottom surface 24 does not overlap with the side wall 25 of the stem 20 in plan view from the first direction D1.

[0028] 4, the side wall 25 has a first side wall portion 25a in which a first inner surface 26a of the side wall 25 extends in the first direction D1, and a second side wall portion 25b in which a second inner surface 26b of the side wall 25 faces in a direction midway between the first inner surface 26a of the first side wall portion 25a and the inner bottom surface 23 of the bottom wall 22. The second inner surface 26b of the second side wall portion 25b connects the first inner surface 26a of the first side wall portion 25a to the inner bottom surface 23.

[0029] The inner surface 26 of the side wall 25 is composed of a first inner surface 26a of the first side wall portion 25a and a second inner surface 26b of the second side wall portion 25b. The first inner surface 26a of the first side wall portion 25a has a generally cylindrical side surface shape. The second inner surface 26b of the second side wall portion 25b can be an R-shaped curved surface of revolution that is curved in cross section, or a tapered curved surface of revolution that is straight in cross section, but the detailed shape of the second inner surface 26b is not particularly limited.

[0030] 4, the outer region 24a of the outer bottom surface 24 has an outer first region 24aa that overlaps with the first sidewall portion 25a in a plan view and an outer second region 24ab that overlaps with the second inner surface 26b of the second sidewall portion 25b in a plan view. The entire first resistive film pattern 50 shown in the first embodiment overlaps with the first sidewall portion 25a in a plan view from the first direction D1 and is formed in the outer first region 24aa. By disposing the entire first resistive film pattern 50 in the outer first region 24aa, it is possible to effectively prevent the resistance value of the first resistive film pattern 50 from being affected by distortion of the bottom wall 22.

[0031] However, embodiments are also possible in which a portion of the first resistive film pattern is formed in the second outer region 24ab (see FIG. 10), or in which a portion of the first resistive film pattern is formed in the inner region 24b other than the outer region 24a. Also, embodiments are also possible in which a portion of the second resistive film pattern 60 is formed in the outer region 24a other than the inner region 24b (for example, the second outer region 24ab). The outer edge of the outer bottom surface 24 may have a chamfered portion or a curved portion as shown in FIGS. 1 and 4, or may have a flat surface continuing from the inner portion, and such an outer edge portion of the outer bottom surface 24 is also included in the outer bottom surface 24.

[0032] The second resistive film pattern 60 shown in FIG. 2 has resistors R1, R2, R3, and R4 formed at predetermined positions on the outer bottom surface 24. The resistance values ​​of the resistors R1 to R4 of the second resistive film pattern 60 change in response to the strain of the bottom wall 22 caused by the pressure of the fluid to be measured. The resistors R1 to R4 of the second resistive film pattern 60 are connected to form a Wheatstone bridge circuit. In the example shown in FIGS. 2 and 4, the resistors R1 to R4 of the second resistive film pattern 60 are formed inside the entire first resistive film pattern 50.

[0033] Changes in the resistance values ​​of the resistors R1 to R4 of the second resistive film pattern 60 are transmitted to the circuit board 90 (see FIG. 1) or the like via the electrode pads 41, 42, 43, and 44 connected to the second resistive film pattern 60. The pressure sensor 10 detects the pressure of the fluid to be measured using the output value of the second resistive film pattern 60. Note that the number of resistors R1 to R4 of the second resistive film pattern 60 and the specific circuit configuration of the second resistive film pattern 60 are not limited to those shown in FIG. 2, and any number and circuit configuration that can detect the strain of the bottom wall 22 can be used.

[0034] Fig. 3 is a plan view of the outer bottom surface 24 of the stem 20 viewed from the first direction D1, similar to Fig. 2. However, in Fig. 3, the structure of the sensor main body 18 provided on the outer bottom surface 24, other than the first resistive film pattern 50 and the electrode pads 45, 46, is omitted from the illustration.

[0035] 3, the first resistive film pattern 50 has a first circumferential pattern portion 51, a second circumferential pattern portion 52, and a third circumferential pattern portion 53, which are multiple circumferential pattern portions that extend along the circumferential direction and are at different distances from the center 24c of the outer bottom surface 24. The first resistive film pattern 50 is configured by folding back and connecting these multiple circumferential pattern portions, the first circumferential pattern portion 51, the second circumferential pattern portion 52, and the third circumferential pattern portion 53. The first resistive film pattern 50 also has a connection portion 55 that connects the first circumferential pattern portion 51 and the second circumferential pattern portion 52, and a connection portion 56 that connects the second circumferential pattern portion 52 and the third circumferential pattern portion 53.

[0036] 2, the first circumferential pattern portion 51 is located at the outermost periphery of the multiple (three in the first embodiment) circumferential pattern portions. The second circumferential pattern portion 52 is located closer to the center 24c of the outer bottom surface 24 than the first circumferential pattern portion 51, and the third circumferential pattern portion 54 is located even closer to the center 24c of the outer bottom surface 24 than the first and second circumferential pattern portions 51, 52.

[0037] 3, at least a portion of each of the first circumferential pattern portion 51, the second circumferential pattern portion 52, and the third circumferential pattern portion 54 is arranged concentrically with respect to the center 24c of the outer bottom surface 24. One end 51a of the first circumferential pattern portion 51 is connected to the electrode pad 45. The other end 51b of the first circumferential pattern portion 51 and one end 52a of the second circumferential pattern portion 52 are connected by a substantially semicircular connecting portion 55 having a larger curvature than the circumferential pattern portions 51, 52.

[0038] Furthermore, the other end 52b of the second circumferential pattern portion 52 and one end 53a of the third circumferential pattern portion 53 are connected by a substantially semicircular connecting portion 56 having a larger curvature than the circumferential pattern portions 52, 53. The other end 53b of the third circumferential pattern portion 53 is connected to the electrode pad 46. As described above, in the first resistive film pattern 50, the multiple circumferential pattern portions 51, 52 extending along the circumferential direction are connected by the connecting portion 55 so that the conductive path turns back from counterclockwise to clockwise when viewed from the one end 51a of the first circumferential pattern portion 51. Furthermore, the multiple circumferential pattern portions 52, 53 extending along the circumferential direction are connected by the connecting portion 56 so that the conductive path turns back from clockwise to counterclockwise when viewed from the one end 52a of the second circumferential pattern portion 52.

[0039] As shown in FIG. 3 , the angle θ1 from one end 51 a to the other end 51 b as viewed from the center 24 c of the first circumferential pattern portion 51 is greater than the angle θ2 from one end 52 a to the other end 52 b and the angle θ3 from one end 53 a to the other end 53 b as viewed from the centers 24 c of the second circumferential pattern portion 52 and the third circumferential pattern portion 53, which are the circumferential pattern portions other than the first circumferential pattern portion 51.

[0040] In such a pressure sensor 10, the length of the first circumferential pattern portion 51, which is least susceptible to the influence of distortion, is increased, thereby more effectively suppressing the influence of distortion of the outer bottom surface 24 on the change in resistance value of the first resistive film pattern 50. Furthermore, since the first resistive film pattern 50 has circumferential pattern portions 52 and 53 other than the first circumferential pattern portion 51, the overall length of the first resistive film pattern 50 can be secured, thereby improving the accuracy of temperature detection.

[0041] 5 shows the θ strain region 24d, which is a region where strain (tensile, positive) is large along the θ direction (circumferential direction), and the R strain region 24e, which is a region where strain (compressive, negative) is large along the R direction (radial direction), on the outer bottom surface 24 of the stem 20. The θ strain region 24d is located near the center 24c of the outer bottom surface 24 and extends into the inner region 24b. In contrast, the R strain region 24e extends near the boundary between the outer first region 24aa and the outer second region 24ab (inside the boundary between the outer first region 24aa and the outer second region 24ab).

[0042] Figure 6 is a graph showing the magnitude of strain εθ along the θ direction (circumferential direction) and the magnitude of strain εR along the R direction (radial direction) on the outer bottom surface 24 of the stem 20, corresponding to the position on the outer bottom surface 24. As can be seen from Figure 6, in the outer region 24a, the absolute values ​​of strain εθ along the θ direction and strain εR along the R direction tend to decrease from the inside to the outside. Furthermore, in the outer region 24a, the absolute value of strain εθ along the θ direction tends to be smaller than the absolute value of strain εR along the R direction overall. The resistance values ​​of the multiple circumferential pattern portions 51, 52, 53 extending along the circumferential direction are less affected by strain εR along the R direction. Therefore, in a pressure sensor configured by folding back and connecting multiple circumferential pattern portions 51, 52, and 53 extending along the circumferential direction as shown in Figure 3, the length of the resistive film can be increased while suppressing the effects of distortion on the outer bottom surface, enabling highly accurate temperature detection.

[0043] 3 are arc-shaped in plan view about the center 24c of the outer bottom surface 24, but even if the shape is slightly different from an arc, it can be determined to be a circumferential pattern portion extending along the circumferential direction as long as it is a shape that generally follows the circumferential direction. For example, for a given portion of the first resistive film pattern, if the distance from the center 24c to one end of the portion is R01, the distance from the center 24c to the other end of the portion is R02 (where R01≧R02), and the angle from the one end to the other end as viewed from the center 24c is Δθ, then if the following mathematical formula 1 is satisfied, the portion can be determined to be a circumferential pattern portion extending along the circumferential direction.

[0044] Δθ / 2π > (R01-R02) / R01 Formula 1

[0045] The change in the resistance value of the resistor formed by the first resistive film pattern 50 is transmitted to the circuit board 90 (see FIG. 1) or the like via the electrode pads 45, 46 connected to the first resistive film pattern 50. The pressure sensor 10 can perform temperature correction on the output value of the second resistive film pattern 60, for example, using the output value of the first resistive film pattern 50.

[0046] Examples of materials for the first resistive film pattern 50 and the second resistive film pattern 60 include, but are not limited to, metals such as Cr, Ni, Al, and Cu, and conductive strain-sensitive resistive films containing Cr, at least one of Ni, Al, and Cu, and at least one of N and O. The first resistive film pattern 50 and the second resistive film pattern 60 are fabricated, for example, by patterning a strain-sensitive resistive film formed by a thin-film method into a predetermined shape. The electrode pads 41 to 46 are also made of conductive thin films, similar to the strain-sensitive resistive films. Examples of materials for the electrode pads 41 to 46 include metals such as Au, Al, and Ni.

[0047] As described above, the pressure sensor 10 has the first resistive film pattern 50 configured by folding back and connecting the circumferential pattern portions 51, 52, and 53 extending along the circumferential direction, and the resistance value of such a first resistive film pattern 50 is not easily affected by distortion of the outer bottom surface, enabling highly accurate temperature detection. Furthermore, for example, the pressure sensor 10 can perform highly accurate pressure measurement over a wide temperature range by temperature-correcting the detection value of the second resistive film pattern 60 using the detection value of the first resistive film pattern 50.

[0048] Furthermore, since the pressure sensor 10 is configured by folding back and connecting multiple circumferential pattern portions 51, 52, and 53, it is possible to form the first resistive film pattern 50, which has a long length in the conductive direction, in a limited angular region in the circumferential direction. In such a pressure sensor 10, it is easy to dispose the electrode pads 41 to 46, etc., in the outer region 24a, etc., at positions offset from the first resistive film pattern 50, which contributes to miniaturization, and the length of the first resistive film pattern 50 can be secured even in a limited range, allowing for accurate temperature detection.

[0049] 2, 3, and 4, the pressure sensor 10 has a long first circumferential pattern portion 51, which is least susceptible to the effects of distortion, and therefore can more effectively suppress the effect of distortion of the outer bottom surface 24 on the change in resistance value of the first resistive film pattern 50. However, it goes without saying that the shape of the first resistive film pattern of the pressure sensor according to the present disclosure is not limited to that shown in FIG. 2, and there are various other modified examples.

[0050] Fig. 7 is a conceptual diagram showing the shape of the first resistive film pattern 150 according to the first modified example and its arrangement relative to the outer bottom surface 24. Fig. 7 shows the outer bottom surface 24 of the stem 20 as viewed from a plane in the first direction D1, but the structure of the sensor main body provided on the outer bottom surface 24 other than the first resistive film pattern 150 and the electrode pads 45, 146 is not shown.

[0051] Like the first resistive film pattern 50 shown in Figure 2, the first resistive film pattern 150 shown in Figure 7 is formed in the outer region 24a of the outer bottom surface 24 that overlaps with the side wall 25 (see Figure 4) when viewed in a plane from the first direction D1.

[0052] The first resistive film pattern 150 has a first circumferential pattern portion 151 and a second circumferential pattern portion 152 that extend along the circumferential direction and are located at different distances from the center 24c of the outer bottom surface 24. The first resistive film pattern 150 is configured by folding back and connecting these multiple circumferential pattern portions, the first circumferential pattern portion 151 and the second circumferential pattern portion 152. The first resistive film pattern 150 also has a connection portion 155 that connects the first circumferential pattern portion 151 and the second circumferential pattern portion 152.

[0053] The first circumferential pattern portion 151 is located at the outermost periphery of the multiple (two in the first modified example) circumferential pattern portions. At least a portion of each of the first circumferential pattern portion 151 and the second circumferential pattern portion 152 is concentrically arranged with the center 24c of the outer bottom surface 24 as a reference. One end 151a of the first circumferential pattern portion 151 is connected to the electrode pad 45. The other end 151b of the first circumferential pattern portion 151 and one end 152a of the second circumferential pattern portion 152 are connected to a substantially semicircular connecting portion 155 having a larger curvature than the circumferential pattern portions 151 and 152. The other end 152b of the second circumferential pattern portion 152 is connected to the electrode pad 146.

[0054] The first resistive film pattern 150 has two circumferential pattern portions 151 and 152, but the number of circumferential pattern portions that the first resistive film pattern 150 has is not particularly limited as long as it is plural. Furthermore, the first resistive film pattern 150 has one connection portion 155 that is a folded portion, but the number of folded portions that the first resistive film pattern 150 has is not limited to only one or two, and may be three or more.

[0055] As shown in FIG. 7, the angle θ1 from one end 151a to the other end 151b as viewed from the center 24c of the first circumferential pattern portion 151 is greater than the angle θ2 from one end 152a to the other end 152b as viewed from the center 24c of the second circumferential pattern portion 152, which is the circumferential pattern portion other than the first circumferential pattern portion 151.

[0056] In such a first resistive film pattern 150, the length of the first circumferential pattern portion 151, which is least susceptible to distortion, is longer, and the proportion of the first circumferential pattern portion 151 in the first resistive film pattern 150 is increased, so that the effect of distortion of the outer bottom surface 24 on changes in the resistance value of the first resistive film pattern 150 can be more effectively suppressed.

[0057] The pressure sensor according to the present disclosure can use a first resistive film pattern 150 according to a first modified example shown in Fig. 7 instead of the first resistive film pattern 50 shown in Fig. 3. The pressure sensor having the first resistive film pattern 150 shown in Fig. 7 also has similar effects to the pressure sensor 10 shown in Figs. 1 to 6 in terms of commonalities with the pressure sensor 10.

[0058] Fig. 8 is a conceptual diagram showing the shape of the first resistive film pattern 250 according to the second modified example and its arrangement on the outer bottom surface 24. Fig. 8 shows the outer bottom surface 24 of the stem 20 as viewed from above in the first direction D1, but the structure of the sensor main body provided on the outer bottom surface 24 other than the first resistive film pattern 250 and the electrode pads 45, 46 is not shown.

[0059] The first resistive film pattern 250 shown in Figure 8, like the first resistive film pattern 50 shown in Figure 2, is formed in the outer region 24a of the outer bottom surface 24 that overlaps with the side wall 25 (see Figure 4) when viewed in a plane from the first direction D1.

[0060] The first resistive film pattern 250 has a first circumferential pattern portion 251, a second circumferential pattern portion 252, and a third circumferential pattern portion 253, which are multiple circumferential pattern portions that extend along the circumferential direction and are at different distances from the center 24c of the outer bottom surface 24. The first resistive film pattern 250 is configured by folding back and connecting these multiple circumferential pattern portions, the first circumferential pattern portion 251, the second circumferential pattern portion 252, and the third circumferential pattern portion 253. The first resistive film pattern 250 also has a connection portion 255 that connects the first circumferential pattern portion 251 and the second circumferential pattern portion 252, and a connection portion 256 that connects the second circumferential pattern portion 252 and the third circumferential pattern portion 253.

[0061] The third circumferential pattern portion 253 is located at the innermost periphery of the multiple (three in the second modified example) circumferential pattern portions. At least a portion of each of the first circumferential pattern portion 251, the second circumferential pattern portion 252, and the third circumferential pattern portion 253 is concentrically arranged with respect to the center 24c of the outer bottom surface 24. One end 251a of the first circumferential pattern portion 251 is connected to the electrode pad 45. The other end 251b of the first circumferential pattern portion 251 and one end 252a of the second circumferential pattern portion 252 are connected by a substantially semicircular connecting portion 255 having a larger curvature than the circumferential pattern portions 251 and 252.

[0062] The other end 252b of the second circumferential pattern portion 252 and one end 253a of the third circumferential pattern portion 253 are connected by a substantially semicircular connecting portion 256 having a larger curvature than the circumferential pattern portions 252, 253. The other end 253b of the third circumferential pattern portion 253 is connected to the electrode pad 46.

[0063] As shown in FIG. 8, the angle θ3 from one end 253a to the other end 253b as viewed from the center 24c of the third circumferential pattern portion 253 is greater than the angle θ1 from one end 251a to the other end 251b and the angle θ2 from one end 252a to the other end 252b as viewed from the centers 24c of the first circumferential pattern portion 251 and the second circumferential pattern portion 252, which are the other circumferential pattern portions excluding the third circumferential pattern portion 253.

[0064] In such a first resistive film pattern 250, the length of the third circumferential pattern portion 253 closest to the inner region 24b where the second resistive film pattern 60 is arranged is longer, thereby reducing the error between the temperature detected by the first resistive film pattern 250 and the actual temperature of the second resistive film pattern 60.

[0065] The pressure sensor according to the present disclosure can use a first resistive film pattern 250 according to a second modified example shown in Fig. 8 instead of the first resistive film pattern 50 shown in Fig. 3. The pressure sensor having the first resistive film pattern 250 shown in Fig. 8 also has the same effects as the pressure sensor 10 shown in Figs. 1 to 6 in terms of the points in common with the pressure sensor 10.

[0066] Fig. 9 is a conceptual diagram showing the shape of the first resistive film pattern 350 according to the third modified example and its arrangement relative to the outer bottom surface 24. Fig. 9 shows the outer bottom surface 24 of the stem 20 as viewed from above in the first direction D1, but the structure of the sensor main body provided on the outer bottom surface 24 other than the first resistive film pattern 350 and electrode pads 345, 346 is not shown.

[0067] Like the first resistive film pattern 50 shown in Figure 3, the first resistive film pattern 350 shown in Figure 9 is formed in the outer region 24a of the outer bottom surface 24 that overlaps with the side wall 25 (see Figure 4) when viewed in a plane from the first direction D1.

[0068] The first resistive film pattern 350 has a first circumferential pattern portion 351 and a second circumferential pattern portion 352 that extend along the circumferential direction and are located at different distances from the center 24c of the outer bottom surface 24. The first resistive film pattern 350 is configured by folding back and connecting these multiple circumferential pattern portions, the first circumferential pattern portion 351 and the second circumferential pattern portion 352. The first resistive film pattern 350 also has a connection portion 355 that connects the first circumferential pattern portion 351 and the second circumferential pattern portion 352.

[0069] The second circumferential pattern portion 352 is located at the innermost periphery of the multiple (two in the first modified example) circumferential pattern portions. At least a portion of each of the first circumferential pattern portion 351 and the second circumferential pattern portion 352 is concentrically arranged with the center 24c of the outer bottom surface 24 as a reference. One end 351a of the first circumferential pattern portion 351 is connected to an electrode pad 345. The other end 351b of the first circumferential pattern portion 351 and one end 352a of the second circumferential pattern portion 352 are connected to an electrode pad 346 by a substantially semicircular connecting portion 355 having a larger curvature than the circumferential pattern portions 351 and 352. The other end 352b of the second circumferential pattern portion 352 is connected to an electrode pad 346.

[0070] As shown in FIG. 9, the angle θ2 from one end 352a to the other end 352b as viewed from the center 24c of the second circumferential pattern portion 352 is greater than the angle θ1 from one end 351a to the other end 351b as viewed from the center 24c of the first circumferential pattern portion 351, which is the circumferential pattern portion other than the second circumferential pattern portion 352.

[0071] In such a first resistive film pattern 350, the length of the second circumferential pattern portion 352 close to the inner region 24b where the second resistive film pattern 60 is arranged is longer, and the proportion of the first resistive film pattern 350 occupied by the second circumferential pattern portion 352 is larger, so that the error between the temperature detected by the first resistive film pattern 350 and the actual temperature of the second resistive film pattern 60 can be reduced.

[0072] The pressure sensor according to the present disclosure can use a first resistive film pattern 350 according to a third modified example shown in Fig. 9 instead of the first resistive film pattern 50 shown in Fig. 3. The pressure sensor having the first resistive film pattern 350 shown in Fig. 9 also has similar effects to the pressure sensor 10 shown in Figs. 1 to 6 in terms of commonalities with the pressure sensor 10.

[0073] Second embodiment 10 is a conceptual diagram illustrating the arrangement of an outer region 424a and an inner region 424b on the outer bottom surface 424 of a pressure sensor 410 according to the second embodiment of the present disclosure, as well as the first resistive film pattern 450 and the second resistive film pattern 60. In Fig. 10, a plan view of the outer bottom surface 424 of the stem 420 as viewed from the first direction D1 is provided in the upper part of the figure, and a cross-sectional view of the stem 420 taken along a cross section parallel to the first direction D1 and passing through the center 424c of the outer bottom surface 424 is provided in the lower part of the figure.

[0074] 10 differs from the pressure sensor 10 shown in Figure 4 etc. in that the thickness of the side wall 425 of the stem 420 is thinner than the side wall 25 shown in Figure 4 and a part of the first resistive film pattern 450 is disposed in the outer second region 424ab, but in other respects it is similar to the pressure sensor 10. The explanation of the pressure sensor 410 will focus on the differences from the pressure sensor 10, and the same reference numerals will be used to denote the commonalities with the pressure sensor 10 and explanations thereof will be omitted.

[0075] 10, the stem 420 of the pressure sensor 410 has a thinner sidewall 425 than the pressure sensor 10 shown in Fig. 4, and the area of ​​the outer region 424a of the outer bottom surface 424, particularly the area of ​​the outer first region 424aa in the outer region 424a, is narrower. As a result, part of the first resistive film pattern 450, particularly the third circumferential pattern portion 453 that is located on the innermost side of the first to third circumferential pattern portions 451, 452, 453, is formed in the outer second region 424ab of the outer region 424a.

[0076] 10 , the side wall 425 has a first side wall portion 425a in which a first inner surface 426a of the side wall 425 extends in the first direction D1, and a second side wall portion 425b in which a second inner surface 426b of the side wall 425 faces a direction midway between the first side wall portion 425a and the inner bottom surface 423 of the bottom wall 22. The second inner surface 426b of the second side wall portion 425b connects the first inner surface 426a of the first side wall portion 425a to the inner bottom surface 423.

[0077] The third circumferential pattern portion 453, which is a part of the first resistive film pattern 450, is formed in the outer second region 424ab that overlaps with the second inner side surface 426b of the second sidewall portion 425b in a plan view from the first direction D1. The shape of the first resistive film pattern 450 in a plan view from the first direction D1 is the same as that of the first resistive film pattern 50 shown in FIG.

[0078] As shown in FIG. 6, the outer second regions 424ab, 24ab partially overlap with the R strain region 24e, and tend to have large strain (compression, negative) along the R direction (radial direction), but small strain (tensile, positive) along the θ direction (circumferential direction). In the first resistive film pattern 450 shown in FIG. 10, only the third circumferential pattern portion 453 extending along the circumferential direction is formed in the outer second region 424ab. Even if at least a portion of the first resistive film pattern 450 is formed in the outer second region 424ab, if only the portion extending along the circumferential direction or the majority of the portion extending along the circumferential direction is formed, the resistance value of the first resistive film pattern 450 is unlikely to be affected by strain on the outer bottom surface.

[0079] 4, the pressure sensor 410 having the first resistive film pattern 450 shown in Fig. 10 can also be made smaller while suppressing the effects of distortion of the outer bottom surface 424. In addition, the pressure sensor 410 shown in Fig. 10 has similar effects to the pressure sensor 10 in terms of the points in common with the pressure sensor 10.

[0080] Third embodiment 11 is a conceptual diagram illustrating the arrangement of an outer region 524a and an inner region 524b on an outer bottom surface 524, and a first resistive film pattern 50 and a second resistive film pattern 560, for a pressure sensor 510 according to the third embodiment of the present disclosure. In FIG. 11, a plan view of the outer bottom surface 524 of the stem 520 as viewed from the first direction D1 is provided in the upper part of the figure, and a cross-sectional view of the stem 520 taken along a cross section parallel to the first direction D1 and passing through the center 524c of the outer bottom surface 524 is provided in the lower part of the figure.

[0081] 11 differs from the pressure sensor 10 shown in Figure 4 etc. in that the thickness of the side wall 525 of the stem 520 is thicker than the side wall 25 shown in Figure 4 and a part of the second resistive film pattern 560 is disposed in the outer second region 524ab, but in other respects it is similar to the pressure sensor 10. The explanation of the pressure sensor 510 will focus on the differences from the pressure sensor 10, and the same reference numerals will be used to denote the commonalities with the pressure sensor 10, and explanations thereof will be omitted.

[0082] 11, the stem 520 of the pressure sensor 510 has a thicker sidewall 525, and the area of ​​the outer first region 524aa on the outer bottom surface 524 is larger while the area of ​​the inner region 524b is smaller than that of the pressure sensor 10 shown in FIG. 4. As a result, part of the second resistive film pattern 560, particularly part of the resistors R3 and R4, is formed in the outer second region 524ab of the outer region 524a.

[0083] 11 , the side wall 525 has a first side wall portion 525a in which a first inner surface 526a of the side wall 525 extends in the first direction D1, and a second side wall portion 525b in which a second inner surface 526b of the side wall 525 faces a direction midway between the first side wall portion 525a and the inner bottom surface 523 of the bottom wall 22. The second inner surface 526b of the second side wall portion 525b connects the first inner surface 526a of the first side wall portion 525a to the inner bottom surface 523.

[0084] Part of the resistors R3 and R4 of the second resistive film pattern 560 is formed in an outer second region 524ab that overlaps with the second inner side surface 526b of the second sidewall portion 525b in a plan view from the first direction D1. The shape of the second resistive film pattern 560 in a plan view from the first direction D1 is the same as that of the second resistive film pattern 60 shown in FIG.

[0085] 6, the outer second regions 524ab, 24ab partially overlap with the R strain region 24e, and the strain (compression, -) along the R direction (radial direction) tends to be large. Therefore, it can be seen from FIG. 6 that even if part of the resistors R3, R4 of the second resistive film pattern 560 are formed in the outer second region 524ab, it is possible to appropriately detect the strain of the outer bottom surface 24.

[0086] In addition, the pressure sensor 410 shown in FIG. 11 has the same effects as the pressure sensor 10 in terms of the points in common with the pressure sensor 10.

[0087] The pressure sensor according to the present disclosure will be described in more detail below with reference to examples, although the pressure sensor according to the present disclosure is not limited to these examples.

[0088] A pressure sensor 10 having a first resistive film pattern 50 formed on the outer bottom surface 24 of the stem 20 as shown in Fig. 3 was prepared as an example model, while a pressure sensor having a first resistive film pattern 850 formed on the outer bottom surface 24 of the stem 20 as shown in Fig. 12 was prepared as a reference example model. The pressure sensor according to the reference example was similar to the pressure sensor 10 in all parts except for the first resistive film pattern 850.

[0089] 12 connects between the electrode pads 45 and 46, similarly to the first resistive film pattern 50 shown in Fig. 3. However, unlike the first resistive film pattern 50, the first resistive film pattern 850 has resistive film portions 850a extending along a plurality of radial directions (R directions), and is configured by folding back and connecting the plurality of resistive film portions 850a formed radially from the center 24c.

[0090] One end of the first resistive film pattern 850 is connected to the electrode pad 45, and the other end is connected to the electrode pad 46. The angle θ from one end to the other end of the first resistive film pattern 850 as viewed from the center 24c is the same as the angle from one end to the other end as viewed from the center 24c of the first resistive film pattern 50 shown in Fig. 3. The length, number, and spacing of the resistive film portions 850a constituting the first resistive film pattern 850 are determined so that the length and resistance value of the first resistive film pattern 850 shown in Fig. 12 are the same as the length and resistance value of the first resistive film pattern 50.

[0091] Furthermore, a simulation was performed to calculate the amount of change in resistance value of the first resistive film patterns 50, 850 when pressure was applied to the pressure sensor 10 of the example model having the first resistive film pattern 50 and the pressure sensor of the reference example model having the first resistive film pattern 850. As a result of the simulation, the amount of change in resistance value when pressure was applied to the pressure sensor 10 of the example model having the first resistive film pattern 50 was about half that of the pressure sensor of the reference example model having the first resistive film pattern 850.

[0092] As described above, the pressure sensor according to the present disclosure has been described using embodiments, modifications, and examples. However, the technical scope of the pressure sensor according to the present disclosure is not limited to these embodiments, modifications, and examples, and includes many other embodiments and modifications. For example, a resistive film pattern other than the first resistive film pattern and the second resistive film pattern may be formed on the outer bottom surface of the pressure sensor. Furthermore, the planar shape of the connecting portion connecting the multiple circumferential pattern portions is not limited to the arc shape shown in FIG. 3. For example, the connecting portion may be a connecting portion that linearly connects the multiple circumferential pattern portions, or the connecting portion may have a width different from that of the circumferential pattern portions. [Explanation of symbols]

[0093] 10, 410, 510...Pressure sensor 12...Connecting member 12a...Thread groove 12b...flow path 14...Retaining member 18...Sensor body 20, 420, 520...Stem 21...Flange 22...Bottom wall 23, 423, 523…Inner bottom surface 24, 424, 524...Outer bottom surface 24a, 424a, 524a...outer area 24aa, 424aa, 524aa...Outer first area 24ab, 424ab, 524ab...Outer second area 24e…R strain region 24b, 424b, 524b...inner area 24d...θ strain region 24c, 424c, 524c…center 25, 425, 525…side wall 25a, 425a, 525a...1st side wall part 26, 426, 526...Inner surface 26a, 426a, 526a...first inner surface 25b, 425b, 525b...Second side wall part 26b, 426b, 526b…Second inner surface 40...Insulating film 41, 42, 43, 44, 45, 46, 146...Electrode pads 50, 150, 250, 350, 450, 850...First resistive film pattern 51, 151, 251, 351, 451...First circumferential pattern part 52, 152, 252, 352, 452...Second circumferential pattern portion 53, 253, 453...Third circumferential pattern part 51a, 52a, 53a, 151a, 152a, 251a, 252a, 253a, 351a, 352a...One end 51b, 52b, 53b, 151b, 152b, 251b, 252b, 253b, 351b, 352b...other end θ1, θ2, θ3...Angles 55, 56, 155, 255, 256, 355...Connections 60, 560...Second resistive film pattern R1, R2, R3, R4...Resistance 90...Circuit board 82...Connection wiring 850a...Resistive film part

Claims

1. a stem having a bottom wall and a side wall extending in a first direction intersecting the bottom wall; a first resistive film pattern formed in an outer region of an outer bottom surface of the bottom wall that overlaps with the side wall in a plan view from the first direction; a second resistive film pattern at least a part of which is formed in an inner region of the outer bottom surface that does not overlap with the side wall in a plan view from the first direction, The first resistive film pattern is a pressure sensor configured by folding back and connecting a plurality of circumferential pattern portions that extend along the circumferential direction and are at different distances from the center of the outer bottom surface.

2. 2. The pressure sensor according to claim 1, wherein an angle from one end to the other end of a first circumferential pattern portion located at the outermost periphery among the plurality of circumferential pattern portions, as viewed from the center, is larger than an angle from one end to the other end of the other circumferential pattern portions, as viewed from the center, excluding the first circumferential pattern portion, among the plurality of circumferential pattern portions.

3. The side wall has a first side wall portion, an inner surface of the side wall extending in the first direction, and a second side wall portion, the inner surface of the side wall facing a direction midway between the first side wall portion and an inner bottom surface of the bottom wall, connecting the inner surface of the first side wall portion to the inner bottom surface, The pressure sensor according to claim 1 , wherein at least a portion of the first resistive film pattern overlaps with an inner surface of the second sidewall portion in a plan view from the first direction.

4. The side wall has a first side wall portion, an inner surface of the side wall extending in the first direction, and a second side wall portion, the inner surface of the side wall facing a direction midway between the first side wall portion and an inner bottom surface of the bottom wall, connecting the inner surface of the first side wall portion to the inner bottom surface, The pressure sensor according to claim 1 , wherein the first resistive film pattern entirely overlaps the first sidewall portion in a plan view from the first direction.

Images