Thermal flowmeter

Abstract

To provide a thermal flowmeter that is capable of keeping pressure resistance to pressure from fluid while having improved measurement accuracy.SOLUTION: A thermal flowmeter comprises: a sensor chip 10 which has one surface 10a exposed in a flow passage 51 where a fluid flows, and has a plurality of sensor elements 15a, 15b, and 15c provided on the other surface 10b located on the opposite side of the one surface 10a, the sensor chip 10 fitted to a pipe 52 forming the flow passage 51; a substrate 31 which is arranged opposite the other surface 10b, electrically connected to the sensor chip 10 on the side of the other surface 10b, and formed of a thermal conductive material having thermal conductivity; and a heat insulation member 34 which is provided between the sensor chip 10 and the pipe 52 and between the sensor chip 10 and the substrate 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a thermal flow meter. [Background technology]

[0002] Thermal flow meters have been proposed as flow meters for measuring the flow rate of fluids such as liquids. Thermal flow meters include two temperature detectors arranged along the direction of fluid flow and a heater disposed between them. Therefore, thermal flow meters measure the flow rate of a fluid by changing the heat distribution of the fluid around the heaters as the fluid moves, and detecting the accompanying temperature change with the temperature detectors. Patent Document 1 discloses such a thermal flow meter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-81263 Summary of the Invention [Problem to be solved by the invention]

[0004] In the thermal flow meter disclosed in Patent Document 1, a temperature detection unit and a heater unit are provided on one surface of a sensor chip, and the other surface of the sensor chip is exposed to a flow path and a fluid flowing through the flow path.

[0005] In the thermal flow meter disclosed in Patent Document 1, in order to obtain sufficient measurement accuracy, the temperature detection unit and the heater unit must be placed close to the fluid. In this case, the temperature detection unit and the heater unit are placed close to the fluid by thinning the thickness of the sensor chip. However, if the thickness of the sensor chip is thinned, there is a risk that the sensor chip will not be able to withstand the pressure from the fluid.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a thermal flow meter that can maintain pressure resistance against pressure from a fluid while improving measurement accuracy. [Means for solving the problem]

[0007] The thermal flow meter according to the present disclosure comprises a sensor chip having one surface exposed to a flow path through which a fluid flows and having a plurality of sensor elements provided on the other surface opposite the one surface, the sensor chip being attached to a pipe forming the flow path; a substrate arranged opposite the other surface, electrically connected to the other surface of the sensor chip, and formed of a thermally conductive material; and insulating members provided between the sensor chip and the pipe, and between the sensor chip and the substrate. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to improve measurement accuracy while maintaining pressure resistance against pressure from a fluid. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a thermal flow meter according to a first embodiment taken along a fluid flow direction. [Figure 2] 1 is a plan view of a sensor chip that is applied to a thermal flow meter according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] Embodiment 1 A thermal flow meter according to a first embodiment will be described with reference to FIGS. 1 to 4. FIG.

[0012] FIG. 1 is a cross-sectional view of a thermal flow meter according to a first embodiment in the direction of fluid flow. The thermal flow meter according to the first embodiment shown in FIG. 1 is a flow meter that measures the flow rate of a fluid such as a liquid. As will be described in detail later, the thermal flow meter according to the first embodiment measures the flow rate of the fluid by utilizing temperature changes of the fluid flowing through a flow path 51. Note that an arrow F shown in FIG. 1 indicates the flow direction of the fluid flowing through the flow path 51.

[0013] First, the configuration of the sensor chip 10 applied to the thermal flow meter according to the first embodiment will be described with reference to Figs. 1 to 4. Fig. 2 is a plan view of the sensor chip 10 applied to the thermal flow meter according to the first embodiment. Fig. 3 is a cross-sectional view taken along the line III-III in Fig. 2. Fig. 4 is a cross-sectional view taken along the line IV-IV in Fig. 2. Note that the arrow F in Figs. 2 and 4 indicates the direction of fluid flow.

[0014] As shown in Figures 2 to 4, the sensor chip 10 has a sensor substrate 11, sensor elements 15a, 15b, and 15c, a thermal insulating member 16, wiring conductors 17a, 17b, and 17c, electrodes 18a, 18b, and 18c, and a thermally conductive member 19.

[0015] As will be described in detail later, as shown in FIG. 1, the thermal flow meter according to the first embodiment can be attached to a pipe 52 that forms a flow path 51 from the outside. In this case, one surface 10a of the sensor chip 10 is an exposed surface that is exposed to the flow path 51, and the other surface 10b of the sensor chip 10 is a mounting surface on which sensor elements 15a, 15b, and 15c are mounted. The one surface 10a of the sensor chip 10 includes one surface of a sensor substrate 11 and a thermal insulating member 16, which will be described later. The other surface 10b of the sensor chip 10 includes the other surface of the sensor substrate 11 and the thermal insulating member 16, which will be described later. The one surface 10a and the other surface 10b are located on opposite sides of the thickness of the sensor chip 10.

[0016] The sensor substrate 11 is made of a material with relatively high thermal conductivity. The sensor substrate 11 is made of a thermally conductive material such as silicon. The sensor substrate 11 has a quadrangular shape in a plan view. The sensor substrate 11 also has a frame portion 12, support portions 13a, 13b, and 13c, and a through-hole 14.

[0017] The frame portion 12 is a portion that constitutes the outer frame of the sensor substrate 11. The frame portion 12 has a rectangular frame shape.

[0018] The support portions 13a, 13b, and 13c are formed so as to protrude into the inner opening of the frame portion 12 from one side of the frame portion 12 that is parallel to the flow direction F. One ends of the support portions 13a, 13b, and 13c are supported by the frame portion 12. The other ends of the support portions 13a, 13b, and 13c are not supported by the frame portion 12. In other words, the support portions 13a, 13b, and 13c are arranged inside the frame portion 12 and are cantilevered relative to the frame portion 12. The support portions 13a, 13b, and 13c extend in a direction perpendicular to the fluid flow direction F. The support portions 13a, 13b, and 13c are arranged in order at a predetermined interval from the upstream side to the downstream side of the flow direction F.

[0019] In this way, the sensor substrate 11 has through holes 14 between the inner wall of the frame portion 12 and the outer walls of the support portions 13a, 13b, and 13c, as the support portions 13a, 13b, and 13c protrude from the frame portion 12 into its inner opening.

[0020] The sensor elements 15a, 15b, and 15c are supported on one surface of the support portions 13a, 13b, and 13c, respectively. That is, the sensor elements 15a, 15b, and 15c are arranged in order at predetermined intervals from the upstream side to the downstream side in the flow direction F.

[0021] For example, sensor element 15a, which is arranged on the most upstream side, and sensor element 15c, which is arranged on the most downstream side, are temperature detection units that detect the temperature of the fluid flowing through flow path 51. Sensor element 15b, which is arranged in the middle in the flow direction between sensor elements 15a and 15c, is a heater unit that heats the fluid flowing through flow path 51. Sensor elements 15a, 15b, and 15c are supported on one surface of support parts 13a, 13b, and 13c, which have high thermal conductivity, and can detect the temperature of the fluid or heat the fluid through the other surface.

[0022] Electrodes 18a, 18b, and 18c are provided on one surface of one side of the frame 12. Electrodes 18a, 18b, and 18c correspond to sensor elements 15a, 15b, and 15c, respectively, with two electrodes provided for each sensor element 15a, 15b, and 15c. Sensor elements 15a, 15b, and 15c and electrodes 18a, 18b, and 18c are electrically connected to each other via wiring conductors 17a, 17b, and 17c. Wiring conductors 17a, 17b, and 17c are provided from one surface of support portions 13a, 13b, and 13c to one surface of one side of the frame 12.

[0023] The thermal insulating member 16 is embedded in the through hole 14. The thermal insulating member 16 is made of a thermal insulating material with low thermal conductivity. That is, the thermal insulating member 16 makes it difficult for heat to be transmitted, and the thermal conductivity of the thermal insulating member 16 is much lower than the thermal conductivity of the sensor substrate 11. The thermal insulating member 16 is made of a thermal insulating material such as glass or plastic. Therefore, the sensor elements 15a, 15b, and 15c supported by the supports 13a, 13b, and 13c are surrounded by the thermal insulating member 16, thereby mutually suppressing heat transfer.

[0024] The thermally conductive member 19 is provided on the other surface 10b of the sensor chip 10 so as to cover the peripheries of the sensor elements 15a, 15b, and 15c. That is, the thermally conductive member 19 is provided on one surface of each of the frame portion 12, support portions 13a, 13b, and 13c of the sensor substrate 11, and the thermal insulating member 16 so as to cover the sensor elements 15a, 15b, and 15c. The thermally conductive member 19 is made of a material with relatively high thermal conductivity. The thermally conductive member 19 is made of a thermally conductive material such as silicon, for example.

[0025] Next, the overall configuration of the thermal flow meter according to the first embodiment will be described with reference to FIG.

[0026] 1, the thermal flow meter according to the first embodiment can be attached to a pipe 52 that forms a flow path 51. The pipe 52 is provided with a mounting hole 53 for detachably attaching the thermal flow meter according to the first embodiment. The mounting hole 53 is a through-hole that penetrates between the inner surface (flow path 51) and the outer surface of the pipe 52. The mounting hole 53 has an inner hole portion 53a and an outer hole portion 53b.

[0027] The inner hole 53a and the outer hole 53b are in communication with each other. The inner hole 53a opens to the inner surface of the pipe 52. The inner hole 53a is located more inward of the pipe 52 than the outer hole 53b. The opening cross-section of the inner hole 53a is smaller than the opening cross-section of the outer hole 53b. The outer hole 53b opens to the outer surface of the pipe 52. The outer hole 53b is located more outward of the pipe 52 than the inner hole 53a. The opening cross-section of the outer hole 53b is larger than the opening cross-section of the inner hole 53a. Therefore, the mounting hole 53 as a whole is a through hole with a step between the inner hole 53a and the outer hole 53b.

[0028] Here, the thermal flow meter according to the first embodiment includes the sensor chip 10, a substrate 31, solder 32, lead wires 33, and a heat insulating member .

[0029] When the thermal flow meter according to embodiment 1 is attached to the attachment hole 53, the thermal flow meter is inserted from the outer hole 53b side. At this time, the sensor chip 10 is placed in the inner hole 53a with a gap between it and the inner surface of the inner hole 53a. The substrate 31 fits into the inner surface and step of the outer hole 53b.

[0030] The substrate 31 has a front surface 31a and a back surface 31b. The front surface 31a and the back surface 31b are surfaces located on opposite sides of the substrate 31 in the thickness direction. The front surface 31a faces the sensor chip 10 and is the surface on which the sensor chip 10 is mounted. The back surface 31b is exposed to the outside through the outer hole 53b of the piping 52. The substrate 31 is made of a material with high thermal conductivity. The substrate 31 is made of a thermally conductive material such as ceramics, for example.

[0031] The sensor chip 10 arranged in the inner hole 53a and the substrate 31 arranged in the outer hole 53b are electrically connected to each other via a plurality of solders 32. Specifically, the surface of the thermally conductive member 19 of the sensor chip 10 and the surface 31a of the substrate 31 are electrically connected to each other via a plurality of solders 32.

[0032] The electrodes 18a, 18b, and 18c provided on the sensor substrate 11 are electrically connected to a plurality of solders 32 in contact with the surface of the thermally conductive member 19 via conductors within the thermally conductive member 19. Furthermore, a plurality of lead wires 33 are provided inside the substrate 31. One end of the lead wires 33 is electrically connected to the solders 32. The other end of the lead wires 33 extends outward from the rear surface 31b of the substrate 31, and is thereby electrically connected to an electrical circuit (not shown) for measuring flow rate on a signal extraction board. That is, the sensor elements 15a, 15b, and 15c are electrically connected to the electrical circuit for measuring flow rate.

[0033] When sensor elements 15a and 15c function as temperature detection units and sensor element 15b functions as a heater unit, the electrical circuit for flow rate measurement changes the heat distribution of the fluid around the heater unit due to the movement of the fluid, and calculates the flow rate of the fluid by detecting the temperature change associated with this change using the two temperature detection units.

[0034] The heat insulating member 34 is provided without gaps in the space formed between the outer surface of the sensor chip 10 (the outer surface of the sensor substrate 11 and the outer surface of the thermally conductive member 19) and the inner surface of the inner hole 53a, and in the space formed between the other surface 10b of the sensor chip 10 and the surface 31a of the substrate 31. At this time, a recess 31c is formed in the surface 31a of the substrate 31. The recess 31c is provided at a position corresponding to the sensor elements 15a, 15b, and 15c. The heat insulating member 34 is also provided in the recess 31c. The heat insulating member 34 is made of a heat insulating material.

[0035] Therefore, in the thermal flow meter according to the first embodiment, by providing the heat insulating member 34 so as to surround the periphery of the sensor chip 10, the heat generated from the sensor element 15b is less likely to be transmitted to the substrate 31, and can be appropriately transmitted to the fluid flowing through the flow path 51 via the support portion 13b. Therefore, the heat generated by the sensor element 15b is appropriately distributed to the fluid. As a result, the thermal flow meter according to the first embodiment can improve the measurement accuracy of the fluid.

[0036] At this time, the heat that is about to be transferred to the substrate 31 side is transferred from the thermally conductive member 19, which has high thermal conductivity, via the solder 32 to the substrate 31, which also has high thermal conductivity, and is then released to the outside of the pipe 52. That is, the substrate 31 not only has the lead wire 33 for connecting to the electrical circuit for measuring the flow rate, but also serves as a heat dissipation path together with the thermally conductive member 19 and the solder 32.

[0037] Furthermore, in the thermal flow meter according to the first embodiment, the heat insulating member 34 is provided so as to surround the periphery of the sensor chip 10, so that the heat insulating member 34 can function as a buffer member for the sensor chip 10. Therefore, the thermal flow meter according to the first embodiment can maintain pressure resistance against pressure from the fluid even if the thickness of the sensor chip 10 is reduced. The heat insulating member 34 is preferably formed, for example, from an elastic resin material having low thermal conductivity and elasticity.

[0038] As described above, the thermal flow meter according to the first embodiment includes a sensor chip 10 having one surface 10a exposed to a flow path 51 through which a fluid flows and having a plurality of sensor elements 15a, 15b, and 15c provided on another surface 10b opposite to the one surface 10a, and attached to a pipe 52 that forms the flow path 51, a substrate 31 that is disposed opposite the other surface 10b and is electrically connected to the other surface 10b side of the sensor chip 10 and is made of a thermally conductive material, and a heat insulating member 34 that is provided between the sensor chip 10 and the pipe 52 and between the sensor chip 10 and the substrate 31. Therefore, the thermal flow meter can maintain pressure resistance against pressure from a fluid while improving measurement accuracy.

[0039] In the thermal flow meter according to the first embodiment, the substrate 31 has a recess 31c on the surface 31a facing the other surface 10b of the sensor chip 10, and the heat insulating member 34 is provided in the recess 31c. Therefore, by providing the recess 31c in the substrate 31, the thermal flow meter can expand the heat insulating area and the buffer area.

[0040] In the thermal flow meter according to the first embodiment, the sensor chip 10 has a thermally conductive member 19 provided on the other surface 10b so as to cover the periphery of the plurality of sensor elements 15a, 15b, and 15c. Therefore, the thermal flow meter can easily transfer heat that would otherwise be transferred to the substrate 31 to the substrate 31.

[0041] In the thermal flow meter according to the first embodiment, the substrate 31 and the thermally conductive member 19 are connected via solder 32. Therefore, the thermal flow meter can be provided with a heat dissipation path consisting of the thermally conductive member 19, the solder 32, and the substrate 31.

[0042] In the thermal flow meter according to the first embodiment, the heat insulating member 34 is made of an elastic resin material. Therefore, the thermal flow meter can improve the pressure resistance of the sensor chip 10 against the pressure from the fluid.

[0043] It should be noted that, within the scope of the present disclosure, any of the components of the embodiments may be modified or omitted. [Explanation of symbols]

[0044] 10 Sensor Chip 10a One side 10b The other side 11 Sensor substrate 12 Frame 13a,13b,13c Support part 14 Through holes 15a, 15b, 15c sensor elements 16 Thermal insulation materials 17a, 17b, 17c Wiring conductors 18a,18b,18c electrode 19 Thermally conductive materials 31 PCB 31a surface 31b back side 31c Recess 32 Solder 33 Lead wire 34 Heat insulating materials 51 Flow path 52 Piping 53 Mounting hole 53a Inner hole 53b Outer hole

Claims

1. a sensor chip having one surface exposed to a flow path through which a fluid flows and having a plurality of sensor elements provided on another surface opposite to the one surface, the sensor chip being attached to a pipe forming the flow path; a substrate that is disposed opposite the other surface and is electrically connected to the other surface of the sensor chip, the substrate being made of a thermally conductive material; a heat insulating member provided between the sensor chip and the piping, and between the sensor chip and the substrate; A thermal flow meter characterized by:

2. the substrate has a recess on a surface opposite to the other surface, The heat insulating member is provided in the recess.

2. The thermal flow meter according to claim 1.

3. The sensor chip comprises: a heat conductive member provided on the other surface so as to cover the periphery of the plurality of sensor elements; 3. The thermal flow meter according to claim 1 or 2.

4. The substrate and the thermally conductive member are connected via solder.

4. The thermal flow meter according to claim 3.

5. The heat insulating member is made of an elastic resin material.

2. The thermal flow meter according to claim 1.

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