Thermal flow sensor and flow controller

Abstract

The utility model belongs to the technical field of flow sensors, and discloses a thermal flow sensor and a flow controller. The flow channel pipe is arranged in the shell body; the at least two resistors are arranged at intervals, each resistor comprises a thermistor layer and a first insulating layer, and the thermistor layer is arranged on the first insulating layer; one surface, deviating from the thermistor layer, of the first insulating layer is arranged on the flow channel pipe so as to conduct heat of the thermistor layer to the flow channel pipe; and the bridge circuit is electrically connected with the resistor, and the bridge circuit is used for transmitting a voltage signal of the resistor. According to the thermal flow sensor provided by the embodiment of the invention, the technical problem that the thermal contact resistance between different resistors and the capillary tube is deviated in the prior art is solved.

Description

Technical Field

[0001] The present application belongs to the technical field of flow sensors, and in particular relates to a thermal flow sensor and a flow controller. Background Art

[0002] The thermal flow sensor consists of a capillary, an upstream thermistor and a downstream thermistor on the capillary, and a bridge circuit. The principle is to heat the upstream thermistor and the downstream thermistor by loading current. When gas flows in the capillary, the gas will take away the heat of the capillary, and the heat distribution on the capillary, the upstream thermistor and the downstream thermistor will change accordingly; the fluid flow rate can be calculated based on the temperature difference when a constant current flows through the upstream thermistor and the downstream thermistor, or the fluid flow rate can be calculated based on the power consumption difference when the temperature difference between the upstream thermistor and the downstream thermistor remains constant; the existing upstream thermistor and downstream thermistor are mostly thermistor wires wrapped around the outside of the capillary, and part of the arc surface of the thermistor wire is in contact with the capillary. The contact area between the thermistor wire and the capillary is difficult to control, resulting in deviations in the contact thermal resistance between different thermistor wires and the capillary, which reduces the accuracy of the fluid flow calculation. Utility Model Content

[0003] The purpose of the embodiments of the present application is to provide a thermal flow sensor and a flow controller to solve the technical problem of deviation in the contact thermal resistance between different resistors and capillaries in the prior art.

[0004] To achieve the above-mentioned purpose, in a first aspect, an embodiment of the present application provides a thermal flow sensor, comprising: a shell; a flow tube, the flow tube being arranged in the shell; at least two resistors, each of the resistors being arranged at intervals, the resistors each comprising a thermistor layer and a first insulating layer, the thermistor layer being arranged on the first insulating layer; a side of the first insulating layer facing away from the thermistor layer being arranged on the flow tube to conduct the heat of the thermistor layer to the flow tube; and a bridge circuit, the bridge circuit being electrically connected to the resistors, and the bridge circuit being used to transmit the voltage signal of the resistors.

[0005] The beneficial effect of this embodiment is that the provision of the thermistor layer and the first insulating layer can make one side of the resistor completely attached to the flow tube, thereby being able to accurately control the contact area between the resistor and the flow tube, making the thermal resistance between different positions of the same resistor and the flow tube more consistent, making the thermal resistance between different resistors and the flow tube more consistent, reducing the deviation between different thermal flow sensors, and improving the accuracy of fluid flow calculation.

[0006] In some embodiments, the first insulating layer is disposed around the flow conduit along a circumference of the flow conduit, and the thermistor layer is disposed around the first insulating layer along a circumference of the first insulating layer.

[0007] The beneficial effect of this embodiment is that the thermistor layer and the first insulating layer are arranged around the flow channel tube, so that the thermistor layer can be evenly distributed on the flow channel tube, and the fluid in the flow channel tube is heated more evenly.

[0008] In some embodiments, a side of the thermistor layer opposite to the first insulating layer is located within a side of the first insulating layer opposite to the thermistor layer.

[0009] The beneficial effect of this embodiment is that the side of the thermistor layer opposite to the first insulating layer is arranged inside the side of the first insulating layer opposite to the thermistor layer, which can reduce the situation where the edge of the thermistor layer exceeds the edge of the first insulating layer during the production process, and reduce the risk of the edge of the thermistor layer contacting the flow channel tube.

[0010] In some embodiments, each of the first insulating layers is an integral structure.

[0011] The beneficial effect of this embodiment is that each first insulating layer is arranged as an integral structure, which facilitates one-time processing and can improve production efficiency.

[0012] In some embodiments, the resistor further includes a second insulating layer, and the second insulating layer is disposed on a side of the thermistor layer facing away from the first insulating layer.

[0013] The beneficial effect of this embodiment is that the second insulating layer can be provided to isolate the thermistor layer from other components of the thermal flow sensor, thereby reducing the risk of damage to the thermistor layer and improving the working stability of the thermal flow sensor.

[0014] In some embodiments, a side of the thermistor layer opposite to the second insulating layer is located within a side of the second insulating layer opposite to the thermistor layer.

[0015] The beneficial effect of this embodiment is that the side of the thermistor layer opposite to the second insulating layer is arranged inside the side of the second insulating layer opposite to the thermistor layer, which can reduce the situation where the edge of the thermistor layer exceeds the edge of the second insulating layer during the production process, and reduce the risk of the edge of the thermistor layer contacting other components of the thermal flow sensor.

[0016] In some embodiments, each of the second insulating layers is an integral structure.

[0017] The beneficial effect of this embodiment is that each second insulating layer is arranged as an integral structure, which facilitates one-time processing and can improve production efficiency.

[0018] In some embodiments, a side of the second insulating layer facing away from the thermistor layer is coated with a thermal insulation layer;

[0019] Alternatively, the second insulating layer comprises a heat insulating material.

[0020] The beneficial effect of this embodiment is that the provision of a heat preservation layer or a heat insulating material can reduce the heat loss of the thermistor layer.

[0021] In some embodiments, a plurality of grooves are arranged at intervals on the thermistor layer to reduce the flow area of ​​the thermistor layer.

[0022] The beneficial effect of this embodiment is that by setting the groove on the thermistor layer, the length of the thermistor layer can be increased and the cross-section of the thermistor layer can be reduced on the basis of using the same amount of material, so that the resistance of the thermistor layer is larger and the heating efficiency is higher.

[0023] In the second aspect, an embodiment of the present application provides a flow controller, comprising the thermal flow sensor described in any one of the embodiments of the first aspect, and also comprising a main control circuit board and a valve, wherein the main control circuit board is connected to the bridge circuit, and the main control circuit board is used to receive an upstream voltage signal and a downstream voltage signal and convert the upstream voltage signal and the downstream voltage signal into a control voltage signal, and the control voltage signal is used to control the valve action.

[0024] The beneficial effect of this embodiment is that using the above-mentioned thermal flow sensor in a flow controller can reduce the deviation of flow measurements by different flow controllers, thereby reducing the deviation of flow control by the flow controllers, making different flow controllers more consistent, and improving the accuracy of fluid flow control. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 is a schematic diagram of an existing resistor;

[0027] Figure 2 A schematic diagram of a thermal flow sensor provided in an embodiment of the present application;

[0028] Figure 3 A schematic diagram of a resistor provided in an embodiment of the present application;

[0029] Figure 4Schematic diagram of the thermistor layer provided in the embodiment of the present application Figure 1 ;

[0030] Figure 5 Schematic diagram of the thermistor layer provided in the embodiment of the present application Figure 2 ;

[0031] Figure 6 Schematic diagram of the thermistor layer provided in the embodiment of the present application Figure 3 ;

[0032] Figure 7 Schematic diagram of the thermistor layer provided in the embodiment of the present application Figure 4 ;

[0033] Figure 8 A schematic diagram of a flow controller provided in an embodiment of the present application;

[0034] Fig. 9 A schematic diagram of the connection between the thermal flow sensor and the main control circuit board provided in an embodiment of the present application.

[0035] Among them, the reference numerals in the figure are:

[0036] 100. Flow controller;

[0037] 10. Thermal flow sensor; 11. Housing; 12. Flow channel tube; 13. Resistor; 131. First insulating layer; 132. Thermistor layer; 1321. Groove; 133. Second insulating layer; 134. Third insulating layer; 14. Conductive adhesive; 15. Bridge circuit; 151. Lead wire; 152. Upstream control circuit; 153. Downstream control circuit;

[0038] 20. Main control circuit board; 21. Sensor analog front-end circuit; 22. First converter; 23. Microcontroller; 24. Second converter; 25. Drive circuit;

[0039] 30. Valve. DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0042] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0044] First, as Figure 2 , Figure 3 , Fig. 9 As shown, the embodiment of the present application provides a thermal flow sensor 10, including a housing 11, a flow tube 12, at least two resistors 13 and a bridge circuit 15; the flow tube 12 is arranged in the housing 11; the resistors 13 are arranged at intervals, and the resistors 13 all include a thermistor layer 132 and a first insulating layer 131, and the thermistor layer 132 is arranged on the first insulating layer 131; the first insulating layer 131 is arranged on the flow tube 12 with one side away from the thermistor layer 132 to transfer the heat of the thermistor layer 132 to the flow tube 12; the bridge circuit 15 is electrically connected to the resistor 13, and the bridge circuit 15 is used to transmit the voltage signal of the resistor 13.

[0045] The housing 11 is used to isolate the resistor 13 and the flow tube 12 from the external environment, reduce the heat exchange between the external environment and the flow tube 12 and the resistor 13, and reduce the influence of the external environment on the internal components of the housing 11.

[0046] The flow tube 12 is used to be connected to a pipeline through which a fluid flows, so that part of the fluid flows into the flow tube 12, thereby facilitating the measurement of the flow rate of the fluid; optionally, the flow tube 12 is a capillary tube.

[0047] The resistor 13 is used to exchange heat with the fluid in the flow channel tube 12. According to the change of the flow rate of the fluid, the heat exchange amount of the resistor 13 changes, and the electrical signal of the resistor 13 also changes accordingly; optionally, Fig. 9As shown, when there are two resistors 13, the two resistors 13 are respectively an upstream resistor (Ru) and a downstream resistor (Rd). In the absence of fluid flow, the heating powers of the upstream resistor and the downstream resistor remain balanced. Once fluid flow occurs in the capillary, the heat exchange between the upstream resistor and the downstream resistor and the fluid will cause the heating powers of the upstream resistor and the downstream resistor to change, and this change increases with the increase of the fluid mass flow rate. By measuring the voltage on the thermistor layer 132 and converting it, the fluid flow rate can be converted into an electrical signal, thereby achieving accurate measurement of the mass flow rate.

[0048] The first insulating layer 131 is used to isolate the thermistor layer 132 from the flow channel tube 12 to prevent the thermistor layer 132 from being electrically connected to the flow channel tube 12. Optionally, the first insulating layer 131 includes a thermally conductive material to have a thermally conductive property, and the first insulating layer 131 may also include other materials to have other properties, such as an insulating material to have an insulating property; or, the first insulating layer 131 only includes a thermally conductive material; the thermally conductive material of the first insulating layer 131 includes an insulating thermally conductive material such as silicon oxide or silicon nitride.

[0049] The thermistor layer 132 is used to exchange heat with the fluid through the first insulating layer 131 and the wall of the flow channel tube 12. The thermistor layer 132 can heat up after being energized. Optionally, the thermistor layer 132 is made of materials such as platinum, nickel or copper. Optionally, the first insulating layer 131 and the thermistor layer 132 are arc structures arranged around the flow channel tube 12, and the first insulating layer 131 and the thermistor layer 132 can also be an annular structure arranged around the flow channel tube 12.

[0050] The bridge circuit 15 is used to supply power to the resistor 13 . The bridge circuit 15 can obtain and output a voltage signal of the resistor 13 , so as to facilitate calculation of the flow rate of the fluid according to the voltage signal of the resistor 13 .

[0051] like Figure 1 As shown, the existing resistor 13 is a thermistor wire wound on the flow tube 12; the thermistor wire may cause the insulation layer to be damaged when it is wound on the winding machine, thereby causing damage to the resistor 13; and the pressure between the thermistor wire and the flow tube 12 at different positions is inconsistent, resulting in different deformation amounts at the contact positions of the thermistor wire and the flow tube 12, and different contact areas and thermal resistances between different thermistor wires and the flow tube 12 are also different.

[0052] Compared with the resistor 13 made of thermistor wire, the thermistor layer 132 and the first insulating layer 131 of the present application can make one side of the resistor 13 completely attached to the flow tube 12, and then can accurately control the contact area between the resistor 13 and the flow tube 12, so that the thermal resistance between different positions of the same resistor 13 and the flow tube 12 is more consistent, and the thermal resistance between different resistors 13 and the flow tube 12 is more consistent, reducing the deviation between different thermal flow sensors 10 and improving the accuracy of fluid flow calculation; the present application can make the resistor 13 by deposition, and the manufacturing process is simpler, without the need for complex processes such as glue pre-fixing, winding, glue fixing and insulation protection. Compared with the method of setting a semiconductor substrate in a pipeline through which the fluid flows to measure the flow, the present application sets the resistor 13 outside the flow tube 12, which can avoid the erosion of the resistor 13 by the fluid.

[0053] In some embodiments, when manufacturing the resistor 13, a first insulating layer 131 is first plated on the flow channel tube 12, and then a thermistor layer 132 is plated on the first insulating layer 131. The first insulating layer 131 and the thermistor layer 132 can be manufactured by the following processes: such as atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), electrochemical deposition, spin coating or plasma enhanced chemical vapor deposition (PECVD) and the like.

[0054] Atomic layer deposition is a technology for growing ultra-thin films on a substrate surface. Materials are deposited with atomic layer precision and are very suitable for producing a first insulating layer 131 that grows uniformly and has a precisely controlled thickness.

[0055] Atomic layer deposition technology can produce a deposition layer with uniform thickness, which can make the first insulating layer 131 and the thermistor layer 132 more evenly distributed, make the resistor 13 generate heat and conduct heat more uniformly at different positions, make different resistors 13 more consistent, and reduce the measurement error between different resistors 13.

[0056] Chemical vapor deposition can be used to deposit various types of thin films, including the first insulating layer 131 and the thermistor layer 132 ; a platinum metal thin film can be chemically vapor deposited on the surface of the flow channel tube 12 using a platinum-containing precursor.

[0057] Chemical vapor deposition has a high deposition rate, and the deposited layer has good adhesion. Using chemical vapor deposition technology to manufacture the first insulating layer 131 and the thermistor layer 132 can improve production efficiency and make the connection between the first insulating layer 131 and the thermistor layer 132 more stable.

[0058] Physical vapor deposition, including sputtering or evaporation techniques, may be used to deposit the thermistor layer 132 .

[0059] The physical vapor deposition technology has a simple process, less pollution to the environment, less consumables, uniform and dense film formation, and strong bonding with the substrate; the use of physical vapor deposition technology to manufacture resistor 13 is more environmentally friendly and has lower material costs. The first insulating layer 131 and the thermistor layer 132 are firmly connected and evenly distributed, so that the resistor 13 generates heat more consistently and conducts heat more consistently at different positions, and different resistors 13 are more consistent, thereby reducing the measurement error between different resistors 13.

[0060] For platinum or other precious metals, electrochemical deposition (such as electroplating) can accurately deposit the thermistor layer 132 (metal film) of a desired thickness on the first insulating layer 131 by controlling the current and time.

[0061] The use of electrochemical deposition technology to manufacture the resistor 13 has high production efficiency and can accurately control the thickness of the first insulating layer 131 and the thermistor layer 132, so that the resistor 13 can generate heat and conduct heat more uniformly at different positions, and the thickness of different resistors 13 can be more consistent, thereby reducing the measurement error between different resistors 13.

[0062] Spin coating can make the liquid precursor evenly distributed on the surface of the substrate, and then perform heat treatment to form a hard film, so as to form the first insulating layer 131 on the flow channel tube 12.

[0063] The use of spin coating technology to manufacture resistor 13 makes it easy to obtain a coating with a higher density, and the thickness can be repeatedly controlled very accurately, so that the resistor 13 can generate heat and conduct heat more consistently at different positions, and the thickness of different resistors 13 can be more consistent, thereby reducing the measurement error between different resistors 13.

[0064] Plasma-enhanced chemical vapor deposition (PECVD) is a process that uses plasma to deposit various materials at lower temperatures, making it suitable for substrates that cannot withstand high-temperature chemical vapor deposition processes.

[0065] Plasma enhanced chemical vapor deposition technology has little effect on the structure and physical properties of the substrate, has a fast deposition rate, and can be applied to different materials; using plasma enhanced chemical vapor deposition technology to make the resistor 13 allows the materials of the first insulating layer 131 and the thermistor layer 132 to fully exert their thermal insulation, thermal conductivity, electrical conductivity and other properties, and has high production efficiency.

[0066] In some embodiments, Figure 3 As shown, the first insulating layer 131 is disposed around the flow conduit 12 along the circumference of the flow conduit 12 , and the thermistor layer 132 is disposed around the first insulating layer 131 along the circumference of the first insulating layer 131 .

[0067] The first insulating layer 131 and the thermistor layer 132 are both annular structures extending along the length direction of the flow channel tube 12 .

[0068] The beneficial effect of this embodiment is that the thermistor layer 132 and the first insulating layer 131 are arranged around the flow tube 12, so that the thermistor layer 132 can be evenly distributed on the flow tube 12, and the fluid in the flow tube 12 is heated more evenly.

[0069] In some embodiments, Figure 3 As shown, a side of the thermistor layer 132 opposite to the first insulating layer 131 is located within a side of the first insulating layer 131 opposite to the thermistor layer 132 .

[0070] In the length direction of the flow conduit 12 (the X direction in the figure is the length direction of the flow conduit 12), the two ends of the thermistor layer 132 in the same resistor 13 are arranged between the two ends of the first insulating layer 131; when the first insulating layer 131 and the thermistor layer 132 are an arc structure arranged around the flow conduit 12, in the circumferential direction of the flow conduit 12, the two ends of the thermistor layer 132 of the same resistor 13 are arranged between the two ends of the first insulating layer 131, that is, the length of the thermistor layer 132 is less than the length of the first insulating layer 131, that is, the projection of the first insulating layer 131 on the flow conduit 12 can completely cover the projection of the thermistor layer 132 on the flow conduit 12.

[0071] The beneficial effect of this embodiment is that the side of the thermistor layer 132 opposite to the first insulating layer 131 is arranged inside the side of the first insulating layer 131 opposite to the thermistor layer 132, which can reduce the situation where the edge of the thermistor layer 132 exceeds the edge of the first insulating layer 131 during the production process, thereby reducing the risk of the edge of the thermistor layer 132 contacting the flow channel tube 12.

[0072] In some embodiments, Figure 3 As shown, each first insulating layer 131 is an integral structure.

[0073] The integrated structure is that the first insulating layers 131 of the resistors 13 are connected together; when there are two resistors 13 , the two first insulating layers 131 can form an arc structure or a ring structure, and the two thermistor layers 132 are spaced apart on the first insulating layer 131 .

[0074] The beneficial effect of this embodiment is that each first insulating layer 131 is provided as an integral structure, which facilitates one-time processing and can improve production efficiency.

[0075] In some embodiments, Figure 3 As shown, the resistor 13 further includes a second insulating layer 133 , which is disposed on a side of the thermistor layer 132 facing away from the first insulating layer 131 , that is, the thermistor layer 132 is sandwiched between the first insulating layer 131 and the second insulating layer 133 .

[0076] Optionally, the second insulating layer 133 can be deposited on the thermistor layer 132 by using the following processes: such as atomic layer deposition, chemical vapor deposition, physical vapor deposition, electrochemical deposition, spin coating or plasma enhanced chemical vapor deposition.

[0077] The beneficial effect of this embodiment is that the second insulating layer 133 can be provided to isolate the thermistor layer 132 from other devices of the thermal flow sensor 10, thereby preventing the thermistor layer 132 from being electrically connected to other devices, reducing the risk of damage to the thermistor layer 132, and improving the working stability of the thermal flow sensor 10.

[0078] In some embodiments, a side of the thermistor layer 132 opposite to the second insulating layer 133 is located within a side of the second insulating layer 133 opposite to the thermistor layer 132 .

[0079] In the length direction of the flow conduit 12, the two ends of the thermistor layer 132 in the same resistor 13 are arranged between the two ends of the second insulating layer 133; when the second insulating layer 133 and the thermistor layer 132 are an arc structure arranged around the flow conduit 12, in the circumferential direction of the flow conduit 12, the two ends of the thermistor layer 132 of the same resistor 13 are arranged between the two ends of the second insulating layer 133, that is, the length of the thermistor layer 132 is less than the length of the second insulating layer 133, that is, the projection of the second insulating layer 133 on the flow conduit 12 can completely cover the projection of the thermistor layer 132 on the flow conduit 12. The area where the second insulating layer 133 exceeds the thermistor layer 132 may be parallel to the first insulating layer 131, that is, a gap is provided between the area where the second insulating layer 133 exceeds the thermistor layer 132 and the first insulating layer 131 or the flow channel tube 12, and the second insulating layer 133 does not completely cover the edge of the thermistor layer 132; or, the area where the second insulating layer 133 exceeds the thermistor layer 132 is provided on the first insulating layer 131, and the second insulating layer 133 completely covers the thermistor layer 132.

[0080] The beneficial effect of this embodiment is that the side of the thermistor layer 132 opposite to the second insulating layer 133 is arranged within the side of the second insulating layer 133 opposite to the thermistor layer 132, which can reduce the situation where the edge of the thermistor layer 132 exceeds the edge of the second insulating layer 133 during the production process, and reduce the risk of the edge of the thermistor layer 132 contacting other components of the thermal flow sensor 10.

[0081] In some embodiments, each second insulating layer 133 is an integral structure.

[0082] The integrated structure is that the second insulating layers 133 of each resistor 13 are connected together; when the number of resistors 13 is two, the two second insulating layers 133 can form an arc structure or a ring structure, and the two thermistor layers 132 are spaced apart on the second insulating layer 133 and the opposite side thereof.

[0083] The beneficial effect of this embodiment is that each second insulating layer 133 is arranged as an integral structure, which facilitates one-time processing and can improve production efficiency.

[0084] In some embodiments, a surface of the second insulating layer 133 facing away from the thermistor layer 132 is coated with a thermal insulation layer.

[0085] The insulation layer includes thermal insulation materials such as polystyrene, rock wool, and glass wool, and has good thermal insulation effect.

[0086] The beneficial effect of this embodiment is that providing the thermal insulation layer can reduce the heat loss of the thermistor layer 132 .

[0087] In some embodiments, the second insulating layer 133 includes a thermally insulating material.

[0088] Optionally, the second insulating layer 133 includes insulating and heat-preserving materials such as polyimide or acrylate.

[0089] The beneficial effects of this embodiment are: the second insulating layer 133 includes a heat-insulating material that can reduce the heat loss of the thermistor layer 132 without setting a thermal insulation layer, making the structure of the resistor 13 simpler; polyimide and acrylate both have good insulation and heat-insulating effects and are easy to obtain.

[0090] In some embodiments, Figure 3 , Fig. 9 As shown, the bridge circuit 15 includes a lead 151 , one end of which is bonded to the thermistor layer 132 via a conductive adhesive 14 ; a third insulating layer 134 is disposed on the conductive adhesive 14 , and the conductive adhesive 14 is disposed between the third insulating layer 134 and the thermistor layer 132 .

[0091] Optionally, two ends of the thermistor layer 132 along the length direction of the flow channel tube 12 are connected to the lead wires 151 .

[0092] Optionally, using insulating tape or insulating sleeve to fix lead 151 can reduce damage to lead 151 caused by vibration or pulling; for the exposed part of lead 151, heat shrink tube can be used to provide an additional protective layer, which not only ensures electrical insulation but also improves mechanical strength.

[0093] After completing the above steps, tests are required, including electrical characteristics test, insulation strength test and environmental adaptability test, to ensure the reliability and long-term stability of the system.

[0094] It can be understood that the second insulating layer 133 and the third insulating layer 134 can be an integral structure and are integrally formed during production; the second insulating layer 133 and the third insulating layer 134 can also be independently arranged and are separately formed during production.

[0095] The beneficial effects of this embodiment are: the lead 151 and the thermistor layer 132 are connected by the conductive glue 14, which is more convenient to manufacture and can ensure stable conduction between the lead 151 and the thermistor layer 132; a third insulating layer 134 is provided on the conductive glue 14 to isolate the conductive glue 14 and the thermistor layer 132 from other components of the thermal flow sensor 10, thereby reducing the risk of damage to the thermistor layer 132 and improving the working stability of the thermal flow sensor 10.

[0096] In some embodiments, Figure 5 , Figure 6 , Figure 7 As shown, a plurality of grooves 1321 are arranged at intervals on the thermistor layer 132 to reduce the flow area of ​​the thermistor layer 132 .

[0097] Optionally, multiple grooves 1321 are parallel, and one end of the groove 1321 along its length direction forms a notch at the edge of the thermistor layer 132, and the notches formed by two adjacent grooves 1321 are arranged opposite to each other, and the multiple grooves 1321 separate the thermistor layer 132 into a curved zigzag structure. After the grooves 1321 are formed, the path of the current becomes a curved zigzag, and the flow area of ​​the thermistor layer 132 is positively correlated with the distance between two adjacent grooves 1321; Figure 4 As shown, the original flow area of ​​the thermistor layer 132 is the area of ​​the cross section of the thermistor layer 132. The groove 1321 on the thermistor layer 132 can be set to different shapes:

[0098] For example, Figure 5 As shown, the groove 1321 extends along the width direction of the thermistor layer 132 (the circumferential direction of the flow channel tube 12), and the gaps formed by two adjacent grooves 1321 on the thermistor layer 132 are located at both ends of the thermistor layer 132 along the width direction of the thermistor layer 132, and the thermistor layer 132 is divided into a serpentine structure extending along its length direction.

[0099] For example, Figure 6 As shown, the groove 1321 is arranged at an angle with the length direction of the thermistor layer 132 (the length direction of the flow channel tube 12), and two adjacent grooves 1321 form notches in opposite directions on the edge of the thermistor layer 132. The thermistor layer 132 is provided with notches at both ends along its length direction and along its width direction. The thermistor layer 132 is divided into a serpentine structure extending in a direction perpendicular to the length direction of the groove 1321.

[0100] For example, Figure 7 As shown, the groove 1321 extends along the length direction of the thermistor layer 132 (the length direction of the flow channel tube 12), and the gaps formed by two adjacent grooves 1321 on the thermistor layer 132 are located at both ends of the thermistor layer 132 along the width direction of the thermistor layer 132, and the thermistor layer 132 is divided into a serpentine structure extending along its width direction.

[0101] The beneficial effect of this embodiment is that the groove 1321 is provided on the thermistor layer 132. On the basis of using the same amount of material, the length of the thermistor layer 132 can be increased, the cross section of the thermistor layer 132 can be reduced, and the resistance value of the thermistor layer 132 can be larger and the heating efficiency can be higher.

[0102] In some embodiments, Figure 2 , Figure 3 , Fig. 9As shown, the thermal flow sensor 10 includes a housing 11, a flow tube 12, two resistors 13 and a bridge circuit 15; the flow tube 12 is arranged in the housing 11; the two resistors 13 are arranged on the flow tube 12 at intervals, and the resistors 13 each include a thermistor layer 132, a first insulating layer 131 and a second insulating layer 133, the thermistor layer 132 is attached to the first insulating layer 131; the first insulating layer 131 is attached to the flow tube 11 on one side away from the thermistor layer 132; 2, so as to conduct the heat of the thermistor layer 132 to the flow channel tube 12, the two first insulating layers 131 are an integrated structure; the second insulating layer 133 is arranged on the side of the thermistor layer 132 away from the first insulating layer 131; the first insulating layer 131, the thermistor layer 132 and the second insulating layer 133 are all arranged around the flow channel tube 12 along the circumference of the flow channel tube 12; the bridge circuit 15 is electrically connected to the resistor 13, and the bridge circuit 15 is used to transmit the voltage signal of the resistor 13.

[0103] If the thermal flow sensor 10 needs to be used in a humid environment, waterproofing treatment is applied to the entire thermal flow sensor 10, such as using a waterproof packaging material or coating.

[0104] Second, as Figure 8 , Fig. 9 As shown, an embodiment of the present application provides a flow controller 100, including the thermal flow sensor 10 of any one of the first aspect embodiments, and also including a main control circuit board 20 and a valve 30. The main control circuit board 20 is connected to the bridge circuit 15. The main control circuit board 20 is used to receive upstream voltage signals and downstream voltage signals and convert the upstream voltage signals and downstream voltage signals into control voltage signals, and the control voltage signals are used to control the action of the valve 30.

[0105] Optionally, the resistor 13 includes an upstream resistor and a downstream resistor, and the bridge circuit 15 includes an upstream control circuit 152 and a downstream control circuit 153, the upstream control circuit 152 is connected to the upstream resistor and transmits an upstream voltage signal Vu, and the downstream control circuit 153 is connected to the downstream resistor and transmits a downstream voltage signal Vd.

[0106] The main control circuit board 20 calculates the flow rate of the fluid according to the upstream voltage signal Vu and the downstream voltage signal Vd, and calculates the control voltage signal of the valve 30 according to the flow rate of the fluid.

[0107] After receiving the control voltage signal from the main control circuit board 20 , the valve 30 is adjusted to a corresponding opening to control the flow rate of the fluid in the pipeline connected to the valve 30 and the flow channel pipe 12 .

[0108] The beneficial effect of this embodiment is that using the above-mentioned thermal flow sensor 10 in the flow controller 100 can reduce the deviation of flow measurement by different flow controllers 100, thereby reducing the deviation of flow control by the flow controller 100, making different flow controllers 100 more consistent, and improving the accuracy of fluid flow control.

[0109] In some embodiments, Figure 8 , Fig. 9 As shown, the main control circuit board 20 includes a sensor analog front-end circuit 21, a first converter 22, a microcontroller 23 (Microcontroller Unit, MCU), a second converter 24 and a drive circuit 25; the sensor analog front-end circuit 21 is used to receive the output signal transmitted by the bridge circuit 15, and the sensor analog front-end circuit 21 is used to pre-process the output signal and transmit it to the first converter 22; the first converter 22 is used to convert the pre-processed output signal into a digital signal and transmit the digital signal to the microcontroller 23; the microcontroller 23 is used to calculate the flow rate according to the digital signal, and the microcontroller 23 is used to generate a control signal according to the flow rate and transmit the control signal to the second converter 24; the second converter 24 is used to convert the control signal into an analog control signal; the drive circuit 25 is connected to the valve 30, and the drive circuit 25 is used to receive the analog control signal and convert the analog control signal into a control voltage signal to control the action of the valve 30; the bridge circuit 15 also includes a thermistor, which is connected to the inner wall of the shell 11 through an insulating heat conductor and is used to sense the temperature of the shell 11, and the bridge circuit 15 is used to output the voltage signal of the thermistor.

[0110] The sensor analog front-end circuit 21 receives the output signal transmitted by the thermal flow sensor 10. The output signal includes analog signals such as the upstream voltage signal Vu, the downstream voltage signal Vd and the voltage signal of the thermistor. The sensor analog front-end circuit 21 includes a preprocessing circuit. The preprocessing circuit performs preprocessing operations such as filtering, amplifying, calculating and multiplexing on the output signal.

[0111] Optionally, the first converter 22 is an analog to digital converter (ADC), and the first converter 22 converts the preprocessed output signal into a digital signal for processing by the microcontroller 23 .

[0112] The microcontroller 23 is the calculation and control center of the flow controller 100. The microcontroller 23 receives the digital signal from the first converter 22, calculates the actual flow rate and generates a corresponding digital control signal based on the values ​​of the upstream voltage signal Vu, the downstream voltage signal Vd and the temperature value of the thermistor detected in real time, and then transmits the digital control signal to the second converter 24.

[0113] The microcontroller 23 can calculate the real-time impedance of the thermistor through the voltage division value of the thermistor, and can obtain the real-time thermal boundary temperature value through the preset inherent impedance-temperature characteristic of the thermistor. The microcontroller 23 also calculates the current flow value through the upstream voltage signal Vu and the downstream voltage signal Vd and the thermal boundary temperature value. The microcontroller 23 generates a digital control signal of the valve 30 through a control algorithm according to the current flow value and the target flow value.

[0114] Optionally, the second converter 24 is a digital to analog converter (DAC), which converts the digital control signal generated by the microcontroller 23 into an analog control signal, and the analog control signal is used to adjust the input control signal of the drive circuit 25 to achieve precise control of the fluid flow.

[0115] The drive circuit 25 is connected to the second converter 24 and the valve 30. The drive circuit 25 is used to convert the analog control signal into different voltage values ​​to obtain a control voltage signal. The drive circuit 25 controls the physical movement of the valve 30 through the control voltage signal to adjust the flow rate of the fluid flowing through the valve 30 so that the measured actual flow value is the same as the target flow value.

[0116] Optionally, the driving circuit 25 is a piezoelectric driving circuit 25, the valve 30 is a piezoelectric ceramic valve 30, the piezoelectric ceramic valve 30 includes a piezoelectric actuator, the piezoelectric driving circuit 25 controls the action of the piezoelectric actuator by controlling the voltage signal, the piezoelectric actuator controls the opening of the piezoelectric ceramic valve 30, and adjusts the flow of the fluid flowing through the piezoelectric ceramic valve 30. The piezoelectric ceramic valve 30 has a fast response speed and can quickly adjust the fluid flow.

[0117] The beneficial effects of this embodiment are as follows: the analog front-end circuit, the first converter 22, the microcontroller 23, the second converter 24 and the drive circuit 25 are arranged to control the action state of the valve 30 according to the signal output by the thermal flow sensor 10, so as to control the size of the fluid flow through the pipeline and the flow tube 12, and to perform real-time automatic control of the fluid flow.

[0118] Based on the above effects, any embodiment of the present application has broad application prospects in achieving high-precision and high-stability flow control; the known and potential technical and product application fields of the embodiments of the present application and their specific application methods are exemplified as follows:

[0119] Semiconductor manufacturing: Key steps in the semiconductor manufacturing process, such as chemical vapor deposition and physical vapor deposition, require extremely high gas flow control accuracy; the embodiments of the present application can provide more accurate flow data to ensure the consistency of the semiconductor manufacturing process and the quality of the product.

[0120] Pharmaceutical industry production: In the field of biopharmaceuticals, especially in the process of culturing cells and producing drugs, precise gas control is crucial; the embodiments of the present application can improve the accuracy of gas flow control and ensure the accuracy and safety of drug synthesis.

[0121] Environmental monitoring equipment: In environmental protection fields such as air quality monitoring and water quality testing, it is necessary to continuously and accurately monitor and control the sampling flow; the embodiments of the present application can provide fast response and high-precision flow monitoring, thereby improving the reliability of environmental monitoring.

[0122] Laboratories and scientific research equipment: Scientific research experiments often require precise control and measurement of extremely small gas or liquid flow rates; the technical solution of the embodiments of the present application can provide fine flow control for various laboratories to ensure the accuracy and efficiency of scientific research work.

[0123] Chemical process control: In the field of chemical production and fine chemicals, the precise proportion of controlled fluids directly affects product quality. The technical solution of the embodiment of the present application provides key control parameters for fine chemical processes by providing stable and accurate flow measurement.

[0124] Aerospace and military equipment: In aerospace and military equipment, the accuracy and response time of flow control are critical to the performance of the entire system; the embodiments of the present application can provide the required high-precision flow control in these demanding applications.

[0125] Food and beverage industry: In the production process of food and beverage, the precise amount of gas and liquid added is very important for the taste and quality of the product; the embodiments of the present application can provide high-precision and high-stability flow control in these applications, making the gas and liquid addition more accurate.

[0126] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A thermal flow sensor, characterized in that: include: case; A flow conduit, the flow conduit being disposed in the housing; At least two resistors, each of which is arranged at intervals, each of which comprises a thermistor layer and a first insulating layer, wherein the thermistor layer is arranged on the first insulating layer; a side of the first insulating layer facing away from the thermistor layer is arranged on the flow channel tube to transfer heat from the thermistor layer to the flow channel tube; A bridge circuit is electrically connected to the resistor, and the bridge circuit is used to transmit a voltage signal of the resistor.

2. The thermal flow sensor according to claim 1, characterized in that: The first insulating layer is disposed around the flow conduit along the circumference of the flow conduit, and the thermistor layer is disposed around the first insulating layer along the circumference of the first insulating layer.

3. The thermal flow sensor according to claim 1, characterized in that: A side of the thermistor layer opposite to the first insulating layer is located within a side of the first insulating layer opposite to the thermistor layer.

4. The thermal flow sensor according to claim 1, characterized in that: Each of the first insulating layers is an integral structure.

5. The thermal flow sensor according to claim 1, characterized in that: The resistor further includes a second insulating layer, which is disposed on a side of the thermistor layer facing away from the first insulating layer.

6. The thermal flow sensor according to claim 5, characterized in that: A side of the thermistor layer opposite to the second insulating layer is located within a side of the second insulating layer opposite to the thermistor layer.

7. The thermal flow sensor according to claim 5, characterized in that: Each of the second insulating layers is an integral structure.

8. The thermal flow sensor according to claim 5, characterized in that: The second insulating layer is coated with a heat preservation layer on one side away from the thermistor layer; Alternatively, the second insulating layer comprises a heat insulating material.

9. The thermal flow sensor according to claim 1, characterized in that: A plurality of grooves are arranged at intervals on the thermistor layer to reduce the flow area of ​​the thermistor layer.

10. A flow controller, characterized in that: A thermal flow sensor comprising the thermal flow sensor described in any one of claims 1 to 9, further comprising a main control circuit board and a valve, wherein the main control circuit board is connected to a bridge circuit, and the main control circuit board is used to receive an upstream voltage signal and a downstream voltage signal and convert the upstream voltage signal and the downstream voltage signal into a control voltage signal, and the control voltage signal is used to control the valve action.

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