Thermal conductivity flow sensor probe and sensor

Abstract

The utility model provides a kind of heat-conducting flow sensor probe and sensor, including probe tube, PCB board is installed below inside probe tube, nonmetallic rubber plug is installed below inside PCB board, still install thermistor one, thermistor two and two heating resistances between PCB board and nonmetallic rubber plug, and two heating resistances are located the upper and lower sides of thermistor one. Can greatly reduce the error of thermal flow sensor due to probe part, very good improve the precision of flow sensor;Flexible PCB is replaced ordinary FR-4's PCB, on one hand, the arrangement of heating resistance is more free, can minimize the area of heating, it is especially important for the installation of flow sensor;On one hand, design unique nonmetallic rubber plug, fill the middle position of flexible PCB, can very good insulate the temperature of two thermistors;Another aspect, thermistor can be very close to probe metal wall, can be almost pasted on it.

Description

Technical Field

[0001] This utility model belongs to the field of intelligent sensors, and in particular relates to a thermal conductivity flow sensor probe and sensor. Background Technology

[0002] The physical basis of thermal conductivity flow sensors is heat transfer. This technology addresses the problem that thermal flow sensors have large measurement errors due to the influence of various environmental variables during fluid measurement.

[0003] The working principle of a thermal flow sensor is that it encapsulates two identical temperature sensors within a sealed sensor probe; one is responsible for measuring the fluid flow rate, such as... Figure 1 Thermistor b; another, disposed together with heating resistor c, measures fluid velocity, such as... Figure 1 Thermistor A is installed with thermistor B on the water-facing side and thermistor A on the water-repellent side. Heating is achieved by a heating resistor C with a fixed power. The internal temperature of the probe must be higher than the fluid temperature. As the fluid flows, it carries away some of the heat, creating a momentary, constant temperature difference between the two thermistors. The fluid velocity is then calculated through sampling, amplification, and analysis. Currently, the installation method for the two resistors is basically as follows... Figure 1 The design involves soldering two thermistors onto two separate PCBs, with non-thermal-conductive adhesive filling the space between them for insulation. However, the inherent width of traditional FR-4 PCBs (printed circuit boards with FR-4 substrates) prevents them from being as close as possible to the metal wall of the probe, leading to temperature measurement errors on both sides. Furthermore, the inherent PCB limitations cause the distance between the two PCBs and the metal wall of the probe to vary, further increasing the error. Another challenge is that while thermally conductive adhesive should be used between each PCB and the nearest metal wall to ensure good heat exchange, non-thermal-conductive adhesive should be used between the two PCBs to insulate them from heat. The application of these two types of adhesives is inconvenient, posing a significant challenge to manufacturing. Utility Model Content

[0004] In view of this, the present invention aims to provide a thermal conductivity flow sensor probe and sensor to solve at least one of the problems existing in the prior art.

[0005] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0006] In a first aspect, this utility model provides a thermal conductivity flow sensor probe, including a probe tube, a PCB board installed inside the probe tube at the bottom, the PCB board being a flexible PCB, the PCB board having a ring structure or an arc-shaped structure, a non-metallic rubber plug installed inside the PCB board at the bottom, and a thermistor I, a thermistor II, and two heating resistors installed between the PCB board and the non-metallic rubber plug, with the two heating resistors located on the upper and lower sides of thermistor I.

[0007] Furthermore, the positions of thermistor one and thermistor two are located at both ends of the diameter line of the probe tube.

[0008] Furthermore, the non-metallic stopper is a rubber stopper.

[0009] Furthermore, the non-metallic rubber stopper has an elliptical cylindrical structure.

[0010] Furthermore, the cross-section of the non-metallic rubber plug is an elliptical structure, with the major axis diameter of the elliptical structure not less than the inner diameter of the probe tube; and the minor axis diameter of the elliptical structure being less than the inner diameter of the probe tube.

[0011] Furthermore, the first thermistor is located at one end of the major axis diameter of the elliptical structure, and the second thermistor and the two heating resistors are located at the other end of the major axis diameter of the elliptical structure.

[0012] Furthermore, the contact surfaces of the thermistor one, thermistor two, and the two heating resistors with the non-metallic rubber stopper are all interference-fitted.

[0013] Furthermore, the inner diameter of the probe tube is 7.2 mm.

[0014] Furthermore, the long axis diameter of the non-metallic rubber plug ranges from 7.2mm to 7.5mm, and the short axis diameter ranges from 4mm to 4.3mm.

[0015] Secondly, based on the same concept, this utility model also provides a thermal conductivity flow sensor, including a sensor body, on which a thermal conductivity flow sensor probe is mounted.

[0016] Compared with existing technologies, the thermal conductivity flow sensor probe and sensor of this invention have the following advantages:

[0017] The thermal conductivity flow sensor probe and sensor described in this utility model aim to greatly reduce the error caused by the probe part of the thermal flow sensor, thus significantly improving the accuracy of the flow sensor. Specifically, a flexible PCB is used instead of the ordinary FR-4 PCB. On the one hand, the arrangement of the heating resistors is more flexible, and the heating area can be minimized, which is especially important for the installation of the flow sensor. On the other hand, a unique non-metallic rubber plug is designed to fill the middle position of the flexible PCB, which can effectively isolate the temperature of the thermistors on both sides. Furthermore, the thermistors can be very close to the metal wall of the probe, almost touching it. Attached Figure Description

[0018] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0019] Figure 1 This is a schematic diagram of the structure of a thermal conductivity flow sensor probe in the prior art;

[0020] Figure 2 This is a schematic diagram of the thermal conductivity flow sensor probe structure according to an embodiment of the present invention;

[0021] Figure 3 This is a cross-sectional schematic diagram of the thermal conductivity flow sensor probe structure described in an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram showing the connection between the PCB board and each resistor according to an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram showing the connection between the PCB board, the non-metallic plug, and each resistor as described in an embodiment of this utility model.

[0024] Figure 6 This is a schematic diagram comparing the dimensions of the non-metallic rubber plug and the probe tube according to an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram showing the connection between the non-metallic rubber plug and the PCB board according to an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Probe tube; 2. PCB board; 3. Non-metallic rubber stopper; 4. Thermistor 1; 5. Thermistor 2; 6. Heating resistor. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments of the present invention can be combined with each other.

[0029] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0030] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] like Figures 2 to 7 As shown, the thermal conductivity flow sensor probe includes a probe tube 1. A PCB board 2 is installed inside the probe tube 1 at its lower part. The PCB board 2 is a flexible PCB and has a ring structure or an arc-shaped structure. A non-metallic rubber plug 3 is installed inside the PCB board 2 at its lower part. A thermistor 4, a thermistor 5, and two heating resistors 6 are also installed between the PCB board 2 and the non-metallic rubber plug 3. The two heating resistors 6 are located on the upper and lower sides of the thermistor 4. The non-metallic rubber plug 3 has an elliptical cylindrical structure.

[0033] In this embodiment, as Figure 7 As shown, the PCB board 2 is inserted into the probe tube 1 in a very small and difficult-to-process manner. The solution is to first fix the flexible PCB board 2 and the non-metallic rubber plug 3, and then use a tool such as a flat-headed cylindrical rubber rod to push the PCB board 2 and the non-metallic rubber plug 3 into the probe tube 1 together.

[0034] Since the resistor cannot directly contact the metal wall of probe tube 1, as this would cause a short circuit and damage, the solution is to ensure the resistor is as close to the tube wall as possible. This solution involves placing the surface-mount resistors on PCB board 2 with their faces inwards, so that the back of PCB board 2 directly contacts the wall of probe tube 1. This way, the distance between the resistor and the wall of probe tube 1 is only the thickness of PCB board 2. There are four resistors on PCB board 2: two thermistors (Thermistor 4 and Thermistor 5) and two heating resistors (Thermistor 6). The two thermistors (Thermistor 4 and Thermistor 5) are positioned along the diameter of probe tube 1. The two heating resistors (Thermistor 6) should be positioned around Thermistor 4 and away from Thermistor 5. Figure 3 The internal diagram of the probe is shown below;

[0035] like Figure 6 and Figure 7 As shown, due to the errors of probe tube 1 and non-metallic plug 3, how can we ensure that they can be pushed into probe tube 1 while also ensuring that PCB2 is in direct contact with the tube wall of probe tube 1? The solution is to design non-metallic plug 3 as an elliptical cylinder, with an interference fit in the direction of contact with the resistor, and a diameter in the direction perpendicular to it that is smaller than the inner diameter of the tube wall of probe tube 1. When non-metallic plug 3 is pushed inward, it is in a certain deformed state, but it is not completely in contact with the tube wall of probe tube 1. This ensures that the direction of soldering resistors reliably contacts the tube wall and that they can be pushed into the metal tube smoothly.

[0036] Installation process of thermal conductivity flow sensor probe:

[0037] Install the non-metallic rubber plug 3 of the elliptical cylinder, such as Figure 6 The length of the long side of the non-metallic rubber plug 3 must be greater than or equal to the inner diameter of the probe tube 1 to ensure that it can make a firm contact with the wall of the probe tube 1 after being pushed in. The length of the short side of the non-metallic rubber plug 3 must be less than the inner diameter of the probe tube 1 to ensure that the non-metallic rubber plug 3 cannot make full contact with the wall of the probe tube 1 after deformation, so that the non-metallic rubber plug 3 can be pushed in smoothly. The inner diameter of the probe tube 1 is 7.2 mm, the length of the long side of the non-metallic rubber plug 3 is in the range of 7.2~7.5 mm, and the length of the short side of the non-metallic rubber plug 3 is in the range of 4~4.3 mm.

[0038] PCB board 2 is fixed to non-metallic rubber plug 3 using glue. To ensure effective heat exchange between thermistors 4 and 5 and the wall of probe tube 1, the fixing points are located at the longest diameter of the non-metallic rubber plug 3 and the positions of the two thermistors 4 and 5. To avoid short circuits caused by direct contact between the resistors and the wall of probe tube 1, the resistors should face towards the rubber plug. Figure 5 ;

[0039] Use a tool to push the non-metallic rubber plug 3 and PCB board 2 into the probe tube 1 as a whole, and make sure that the non-metallic rubber plug 3 is inserted to the bottom.

[0040] The purpose of this solution is to greatly reduce the error caused by the probe part of the thermal flow sensor, thus significantly improving the accuracy of the flow sensor.

[0041] Using a flexible PCB instead of the ordinary FR-4 PCB offers several advantages. First, it allows for more flexible arrangement of heating resistors, minimizing the heating area, which is especially important for flow sensor installation. Second, a unique non-metallic plug filled in the middle of the flexible PCB effectively insulates the temperature of the thermistors on both sides. Third, the thermistors can be placed very close to the metal wall of the probe, almost touching it.

[0042] This utility model also proposes a thermal conductivity flow sensor, including a sensor body, on which a thermal conductivity flow sensor probe is mounted.

[0043] It should be noted that this utility model only improves the structure of the thermal conductivity flow sensor probe, and does not improve the control program. The control program and electrical components involved are all existing technologies.

[0044] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A thermal conductivity flow sensor probe, characterized in that: The device includes a probe tube (1), and a PCB board (2) is installed inside the probe tube (1) at the bottom. The PCB board (2) is a flexible PCB and has a ring structure or an arc structure. A non-metallic rubber plug (3) is installed inside the PCB board (2). A thermistor one (4), a thermistor two (5), and two heating resistors (6) are also installed between the PCB board (2) and the non-metallic rubber plug (3). The two heating resistors (6) are located on the upper and lower sides of the thermistor one (4).

2. The thermal conductivity flow sensor probe according to claim 1, characterized in that: The non-metallic stopper (3) is a rubber stopper.

3. The thermal conductivity flow sensor probe according to claim 2, characterized in that: The non-metallic rubber stopper (3) has an elliptical cylindrical structure.

4. The thermal conductivity flow sensor probe according to claim 3, characterized in that: The cross-section of the non-metallic rubber plug (3) is an elliptical structure, and the major axis diameter of the elliptical structure is not less than the inner diameter of the probe tube (1); the minor axis diameter of the elliptical structure is less than the inner diameter of the probe tube (1).

5. The thermal conductivity flow sensor probe according to claim 4, characterized in that: The first thermistor (4) is located at one end of the major axis diameter of the elliptical structure, and the second thermistor (5) and the two heating resistors (6) are located at the other end of the major axis diameter of the elliptical structure.

6. The thermal conductivity flow sensor probe according to claim 1, characterized in that: The contact surfaces of the thermistor one (4), thermistor two (5), and the two heating resistors (6) with the non-metallic rubber stopper (3) are all interference-fitted.

7. The thermal conductivity flow sensor probe according to claim 4, characterized in that: The inner diameter of the probe tube (1) is 7.2 mm.

8. The thermal conductivity flow sensor probe according to claim 4, characterized in that: The long axis diameter of the non-metallic rubber plug (3) ranges from 7.2 mm to 7.5 mm, and the short axis diameter ranges from 4 mm to 4.3 mm.

9. A thermal conductivity flow sensor, comprising a sensor body, characterized in that: Includes the thermal conductivity flow sensor probe according to any one of claims 1-8, wherein the thermal conductivity flow sensor probe is mounted on the sensor body.

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