Thermal flow sensor

Abstract

A thermal flow sensor characterized in that it comprises a ceramic substrate, a metal head and a metal rod, wherein the metal head is connected to the metal rod, and wherein the metal head is provided with an installation groove at the top of the metal head, and wherein the ceramic substrate is arranged in the installation groove, and wherein the front of the ceramic substrate faces the bottom of the installation groove, and wherein a temperature measuring unit for measuring the temperature of the gaseous medium and a heat generation unit for measuring the flow rate of the gaseous medium are arranged on the front of the ceramic substrate, and wherein an escape cavity is provided at a position on the bottom of the installation groove corresponding to the heat generation unit.

Description

TECHNICAL FIELD

[0001] The present utility model relates to the technical field of sensors, in particular a thermal flow sensor. STATE OF THE ART

[0002] The thermal flow sensor essentially comprises two measuring units, one measuring unit for measuring the temperature of the gaseous medium and the other being a heating unit for measuring the flow of the gaseous medium. The internal circuit of the sensor measures the temperature of the gaseous medium and heats the flow measuring unit. The temperature of the flow sensor is set to a constant value above the temperature of the fluid. Since the temperature of the flow sensor is higher than the temperature of the fluid, the fluid dissipates heat as it flows through the flow sensor; the higher the flow rate, the more heat is dissipated by the flow measuring unit. The lower the flow rate, the less heat is dissipated. The sensor measures the flow rate by measuring the amount of heat consumed by the heat generation unit.According to King's law of thermal effects, the heat output, temperature difference, and mass flow rate can be expressed using mathematical formulas. Based on the measured power and the known temperature difference, the mass flow rate can be calculated.

[0003] Thermal flow sensors with this type of heat transfer require good contact between the heating unit and the measured medium, and the contact can be direct or indirect. If the heat-generating unit is in direct contact with the medium, and the measured gaseous medium contains solid impurities or is corrosive, the sensor unit exposed to these conditions for a long time will be subject to wear and corrosion, leading to drift or even damage to the sensor. If the heat-generating unit is in indirect contact with the medium, the sensor's measuring unit is usually protected with insulating adhesives by potting and armoring. This requires the potting adhesive to have good thermal conductivity and high insulation, and to withstand high temperature shocks of more than 150 degrees Celsius for a long time. Few adhesives meet these requirements, and the price is high.In addition, the potting process of the adhesive is complicated. The potting compound is filled between the heat-generating unit and the armor metal shell. If the adhesive is not evenly distributed between the heat-generating unit and the metal shell, or if air bubbles remain inside, the encapsulation structure will change after the sensor is subjected to aging and high-temperature shock. This change will lead to poor insulation, poor stability, and other problems of the sensor, making it difficult to ensure the yield of the finished encapsulated products. CONTENTS OF THE PRESENT UTILITY MODEL

[0004] The present utility model aims to overcome the deficiencies of the existing technology and provide a thermal flow sensor to solve the adverse effects of the conventional thermal flow sensor caused by direct contact or indirect contact between the heat generating unit and the medium.

[0005] To achieve the above objective, the present utility model uses the following technical solution: The present utility model provides a thermal flow sensor comprising a ceramic substrate, a metal head, and a metal rod, wherein the metal head is connected to the metal rod, and wherein the metal head is provided with an installation groove provided at the tip of the metal head, and wherein the ceramic substrate is arranged in the installation groove, and wherein the front side of the ceramic substrate faces the bottom of the installation groove, and wherein a temperature measuring unit for measuring the temperature of the gaseous medium and a heat generating unit for measuring the flow rate of the gaseous medium are arranged on the front side of the ceramic substrate, and wherein an escape cavity is provided at a position of the bottom of the installation groove corresponding to the heat generating unit.

[0006] Furthermore, the ceramic substrate is connected to a wire, wherein the installation groove is provided with a wire through-hole, and wherein a free end of the wire passes through the wire through-hole.

[0007] Furthermore, the mounting gap between the ceramic substrate and the installation groove and the inside of the wire through hole are filled with a colloid.

[0008] Furthermore, the colloid is a high-temperature adhesive.

[0009] Furthermore, the metal head is provided with a sealing cavity provided at the bottom of the metal head, wherein the sealing cavity is filled with a thermosetting substance.

[0010] Furthermore, an annular insert is arranged at the tip of the metal rod, which is embedded in the sealing cavity.

[0011] Furthermore, the free end of the wire, after passing through the wire through-hole, passes through the sealing cavity and extends to the interior of the metal rod.

[0012] Furthermore, the thermosetting substance is epoxy resin.

[0013] Compared to the prior art, the present utility model has the following advantages: a thermal flow sensor comprising a ceramic substrate, a metal head and a metal rod, wherein the metal head is connected to the metal rod, and wherein the metal head is provided with an installation groove provided at the tip of the metal head, and wherein the ceramic substrate is arranged in the installation groove, and wherein the front side of the ceramic substrate faces the bottom of the installation groove, and wherein a temperature measuring unit for measuring the temperature of the gaseous medium and a heat generating unit for measuring the flow rate of the gaseous medium are arranged on the front side of the ceramic substrate, and wherein an escape cavity is provided at a position of the bottom of the installation groove corresponding to the heat generating unit.By arranging the temperature measuring unit and heat generating unit on the front side of the ceramic substrate facing the bottom of the installation groove, the heat generating unit is located inside the metal head, and the heat generating unit is not exposed on the outside of the metal head, therefore it does not come into direct contact with the measured gaseous medium, so as to avoid the problems that the heat generating unit is susceptible to wear and corrosion. Furthermore, the ceramic substrate can protect the heat generating unit and temperature measuring unit without being conducive to potting and armoring the heat generating unit and temperature measuring unit, which simplifies the production process, saves costs and guarantees the yield.

[0014] The above description is only an overview of the technical solutions of the present utility model. To facilitate a clearer understanding of the technical means of the present utility model, it can be implemented in accordance with the content of the description. To make the above-mentioned and other purposes, features, and advantages of the present utility model obvious and easy to understand, the preferred embodiments are explained in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly explain the technical solution in the embodiments of the present utility model, the accompanying drawings to be used in the explanation of the embodiments are briefly presented below. Obviously, the accompanying drawings described below show only some embodiments of the present utility model. Those of ordinary skill in the art can obtain other accompanying drawings based on the accompanying drawings without requiring any creative work. Fig. 1 shows a schematic diagram of the structure of a thermal flow sensor provided by a specific embodiment of the present utility model. Fig. 2 shows a decomposed diagram of a thermal flow sensor provided by a specific embodiment of the present invention. Fig. 3 shows a sectional view of a thermal flow sensor provided by a specific embodiment of the present invention. Fig. 4 shows a schematic diagram of the structure of a ceramic substrate of the thermal flow sensor provided by a specific embodiment of the present utility model. List of reference symbols 1 Ceramic substrate 11 Heat generation unit 12 Temperature measuring unit 2 metal heads 21 Installation groove 22 Escape cavity 23 Wire through hole 24 Sealing cavity 3 metal rods 31 Ring-shaped insert 4 wire 5 Colloid 6 Thermosetting substance DETAILED DESCRIPTION

[0016] In connection with specific embodiments of the present utility model, the technical solutions of the present utility model are explained clearly and completely below. Obviously, the explained embodiments do not represent all embodiments, but only a part of the embodiments of the present utility model. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present utility model without creative work should be considered to be covered by the scope of protection of the present utility model.

[0017] It should be understood that the terms "including" and "comprising" as used in this specification and in the claims indicate the presence of the described feature, entity, step, operation, element and / or component, but do not preclude the presence or addition of one or more other features, entities, steps, operations, elements, components and / or collections thereof.

[0018] It should also be understood that the terms used in the description of the present utility model are for the purpose of describing specific embodiments only and are not intended to limit the present utility model. As used in the description of the present utility model and the appended claims, the singular forms "a," "an," and "the" include the plural form unless the context clearly indicates otherwise.

[0019] It should be further understood that the terms "and / or" as used in the description of the present utility model and the appended claims refer to and include any combination and all possible combinations of one or more of the elements listed in conjunction.

[0020] As in Fig. 1 to 4, an embodiment of the present utility model provides a thermal flow sensor comprising a ceramic substrate 1, a metal head 2, and a metal rod 3, the metal head 2 being connected to the metal rod 3. The metal head 2 and the metal rod 3 may be made of ordinary stainless steel such as stainless steel 316L, etc. The metal head 2 is provided with an installation groove 21, the ceramic substrate 1 is disposed in the installation groove 21, and the front side of the ceramic substrate 1 faces the bottom of the installation groove 21, and the back side of the ceramic substrate 1 faces the slit opening of the installation groove 21. In the present embodiment, the installation groove 21 is provided at the tip of the metal head 2, which is conducive to the operation of the thermal flow sensor.and wherein a temperature measuring unit 12 for measuring the temperature of the gaseous medium and a heat generating unit 11 for measuring the flow rate of the gaseous medium are arranged on the front side of the ceramic substrate 1, and wherein an escape cavity 22 is provided at a position of the bottom of the installation groove 21 corresponding to the heat generating unit 11. By means of the escape cavity 22, direct contact between the heat generating unit 11 and the metal head 2 can be avoided, which ensures that the heat generating unit 11 is not affected by the heat conduction of the metal head 2, thereby improving the operational stability of the heat generating unit 11.

[0021] When the thermal flow sensor is installed in a specific working environment (e.g., a pipeline), the flow sensing surface of the thermal flow sensor (back of the ceramic substrate) is approximately parallel to the flow direction of the gas to be measured. This provides more accurate results than conventional flow sensors, where the flow sensing surface is perpendicular to the flow direction of the gas to be measured or at a greater inclination angle.

[0022] By arranging the temperature measuring unit 12 and heat generating unit 11 on the front side of the ceramic substrate 1 facing the bottom of the installation groove 21, the heat generating unit 11 is located inside the metal head 2, and the heat generating unit 11 is not exposed on the outside of the metal head 2, therefore it does not come into direct contact with the measured gaseous medium, so as to avoid the problems that the heat generating unit 11 is susceptible to wear and corrosion. Furthermore, the ceramic substrate 1 can protect the heat generating unit 11 and the temperature measuring unit 12 without being conducive to potting and armoring the heat generating unit 11 and the temperature measuring unit 12, which simplifies the production process, saves costs, and guarantees the yield of the manufactured products.

[0023] It should be noted that since the temperature measuring unit 12 and the heat generating unit 11 face the bottom of the installation groove 21 instead of being exposed on the outside of the metal head 2, they can still function properly because the ceramic substrate 1 has the thermal conductivity, and by utilizing the thermal conductivity of the ceramic substrate 1, the temperature measuring unit 12 and the heat generating unit 11 can function properly.

[0024] It should also be noted that the heat generating unit 11 and the temperature measuring unit 12 are conventional components in the field, and the present application does not specifically limit the specific models of the heat generating unit 11 and the temperature measuring unit 12. For example, the heat generating unit 11 is typically made of a material with a suitable electrical resistance, such as a platinum metal film. The temperature measuring unit 12 is made of a precise temperature-sensitive material, such as a thermistor or a platinum metal temperature sensor.

[0025] In order to further protect the heat generating unit 11 from the heat dissipation of the metal material of the thermal flow sensor, the escape cavity 22 can be filled with air or provided with other insulating materials, e.g. aluminum foil or mineral wool.

[0026] As in Fig. As shown in Figures 2 to 4, the ceramic substrate 1 is connected to a wire 4, and the installation groove 21 is provided with a wire through-hole 23, and a free end of the wire 4 passes through the wire through-hole 23. The purpose of the wire through-hole 23 is to facilitate the extension of the wire 4 into the interior of the metal rod 3, allowing the wire to be laid concealed. The function of the wire 4 is to connect the ceramic substrate 1 to the drive detection circuit of the thermal flow sensor to ensure the proper operation of the thermal flow sensor.

[0027] As in Fig. 1 and Fig. As shown in Figure 3, the mounting gap between the ceramic substrate 1 and the installation groove 21 and the interior of the wire through-hole 23 are filled with a colloid 5. The filled colloid 5 ensures the stability of the ceramic substrate 1 after assembly. The colloid 5 is preferably a high-temperature adhesive. The high-temperature adhesive can, in particular, be a silicone adhesive, an epoxy resin, etc.The advantages of using a high-temperature adhesive are that it can withstand high temperatures and will not degrade, soften, or deform due to temperature increases; at the same time, the high-temperature adhesive is chemically stable and resistant to corrosion by oils, solvents, and other chemicals, making it suitable for use in harsh industrial environments; in addition, the high-temperature adhesive maintains good mechanical properties even at high temperatures, ensuring the strength and stability of the structure.

[0028] It should be noted that the colloid 5 must not penetrate into the escape cavity 22 when filled in order to avoid affecting the operation of the heat generating unit 11.

[0029] Furthermore, as in Fig. As shown in Figure 3, the metal head 2 is provided with a sealing cavity 24 located at the bottom of the metal head 2, wherein the sealing cavity 24 is filled with a thermosetting substance 6. Preferably, the thermosetting substance 6 is epoxy resin. By providing the sealing cavity 24 filled with the thermosetting substance 6, an end of the metal rod 3 connected to the metal head 2 can be sealed.

[0030] An example is how in Fig. 3, an annular insert 31 is arranged at the tip of the metal rod 3 and embedded in the sealing cavity 24. The annular insert 31 is embedded in the sealing cavity 24, and the sealing cavity 24 serves as the peripheral boundary of the annular insert 31. After embedding, the annular insert can be further secured with adhesive or other means to ensure the strength of the connection. Of course, in other embodiments, the metal rod 3 and the metal head 2 can be connected and secured by a snap or press fit.

[0031] In the present embodiment, as shown in Fig. 3, the free end of the wire 4, after passing through the wire through-hole 23, passes through the sealing cavity 24 and extends to the inside of the metal rod 3, then it is led out from the inside of the metal rod 3.

[0032] A thermal flow sensor encapsulation method used for the above thermal flow sensor, the method comprising the steps of: S10-S50.

[0033] S10: Place the ceramic substrate in the installation groove of the metal head with the front side of the ceramic substrate facing the bottom of the installation groove.

[0034] After placing the ceramic substrate, the metal head and the ceramic substrate are fixed with a clamp or other tools for subsequent filling of colloid.

[0035] S20: Filling the mounting gap between the ceramic substrate and the installation groove and the inside of the wire through hole with a colloid.

[0036] When filling the colloid, care must be taken to prevent it from seeping into the escape cavity. Furthermore, the colloid must be filled as evenly as possible to avoid the formation of air bubbles.

[0037] S30: Place the metal head in a vertical direction after the filled colloid has hardened, with the tip of the metal head pointing downwards.

[0038] Using a tool such as a clamp, the metal head is turned upside down, which facilitates the injection of the thermosetting substance into the seal cavity.

[0039] S40: Connecting the metal rod to the metal head.

[0040] S50: Injecting the thermosetting substance through the interior of the metal rod into the sealing cavity of the metal head.

[0041] Care must be taken to avoid air bubbles as much as possible during the injection process.

[0042] In steps S10-S50, the ceramic substrate is inserted into the installation groove of the metal head during encapsulation, and the mounting gap and wire through-hole are filled with colloid 5 to provide additional mechanical stability and ensure that the substrate is not easily displaced or slipped during sensor operation. The colloid filling protects the wires and circuits from environmental influences such as moisture and dust, as well as chemical corrosion, thus extending the service life of the sensor. The thermosetting substance is injected through the interior of the metal rod into the sealing cavity of the metal head to achieve good sealing performance, preventing the external environment from damaging the sensitive components of the sensor. Overall, the encapsulation process is relatively simple, suitable for mass production, and provides stable performance to the encapsulated sensor.

[0043] In one embodiment, the method further comprises the following step S15 before step S20.

[0044] S15: Bend the wire of the ceramic substrate by ninety degrees toward the front of the ceramic substrate, and pass the free end of the wire through the wire through hole of the metal head.

[0045] Bending the wire ninety degrees reduces the space the wire occupies in the installation groove of the metal, and at the same time, bending the wire and passing the wire through the wire through hole in the metal head improves its mechanical stability and reduces movement due to vibration or other external forces.

[0046] The above content is only the detailed embodiment of the present utility model, but the scope of protection of the present utility model is not limited thereto. Modifications or substitutions that can be easily made by a person skilled in the art within the disclosed technical scope of the present utility model should be considered to be covered by the scope of protection of the present utility model. Therefore, the scope of protection of the present utility model should be defined by the claims.

Claims

[1] Thermal flow sensor, characterized by that it comprises a ceramic substrate, a metal head and a metal rod, wherein the metal head is connected to the metal rod, and wherein the metal head is provided with an installation groove provided at the tip of the metal head, and wherein the ceramic substrate is arranged in the installation groove, and wherein the front side of the ceramic substrate faces the bottom of the installation groove, and wherein a temperature measuring unit for measuring the temperature of the gaseous medium and a heat generating unit for measuring the flow rate of the gaseous medium are arranged on the front side of the ceramic substrate, and wherein an escape cavity is provided at a position of the bottom of the installation groove corresponding to the heat generating unit. [2] Thermal flow sensor according to claim 1, characterized bythat the ceramic substrate is connected to a wire, wherein the installation groove is provided with a wire through-hole, and wherein a free end of the wire passes through the wire through-hole. [3] Thermal flow sensor according to claim 2, characterized by that the mounting gap between the ceramic substrate and the installation groove and the inside of the wire through hole are filled with a colloid. [4] Thermal flow sensor according to claim 3, characterized by that the colloid is a high-temperature adhesive. [5] Thermal flow sensor according to claim 2, characterized by that the metal head is provided with a sealing cavity provided at the bottom of the metal head, wherein the sealing cavity is filled with a thermosetting substance. [6] Thermal flow sensor according to claim 5, characterized bythat an annular insert is arranged at the tip of the metal rod, which is embedded in the sealing cavity. [7] Thermal flow sensor according to claim 6, characterized by that the free end of the wire, after passing through the wire through-hole, passes through the sealing cavity and extends to the interior of the metal rod. [8] Thermal flow sensor according to claim 5, characterized by that the thermosetting substance is epoxy resin.

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