Novel runner structure of thermal gas flow sensor

Abstract

The utility model discloses a novel flow channel structure of a thermal gas flow sensor, two ends of the flow channel are respectively provided with a gas inlet and a gas outlet, the flow channel is streamlined, and two ends of the flow channel are oppositely bent; the flow channel comprises a sensing measurement section located in the middle of the length direction, and a first flow guide section and a second flow guide section located at the two ends of the sensing measurement section respectively. A sensor sensitive element is arranged on the side wall of the sensing measurement section; the first flow guide section and the second flow guide section are in the shape that in the direction from the middle to the two ends, a first bent section bent towards one side is firstly arranged, and then a second bent section bent towards the other side in a spiral line shape is arranged. According to the scheme, the problems that gas in the flow channel flows unevenly, vortexes, backflow or dead angles are generated, and pressure loss is large during gas flowing are solved, turbulent flow and vortexes are reduced, resistance during gas flowing is reduced, friction resistance and pressure loss are reduced, and finally performance optimization of the sensor is achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of thermal gas flow sensors, and in particular relates to a new flow channel structure of a thermal gas flow sensor. Background Art

[0002] Thermal gas flow sensor, also known as thermal mass flow meter, was first proposed by Af et al. in 1974 to use MEMS technology to manufacture silicon-based flow sensor, combining MEMS technology with thermal flow meter. In the 1990s, with the gradual maturity of micro-machining and microelectronics technology, thermal flow sensor based on MEMS technology gradually became mainstream. In thermal gas flow sensor, the flow chip consists of two thermocouple stacks and a heating resistor. When the fluid is stationary, the temperature of the symmetrical positions on both sides of the heating resistor is the same; when the fluid flows through the flow channel through the chip, the temperature on both sides of the heating resistor will no longer be the same, and the temperature difference can be measured by the thermocouple stacks placed on both sides of the heating resistor. This design allows the sensor to directly measure the fluid mass flow.

[0003] At present, the development trend of thermal flow sensors is miniaturization, high precision and the ability to distinguish the direction of airflow. The relevant research around MEMS thermal sensors is mostly focused on the optimization of chip material structure, including the use of numerical simulation methods to improve and optimize the chip structure, including sensor packaging design, such as circuits, measurement pipelines and chip structure and other hardware designs. However, the design of the gas flow channel structure for the sensitive element of MEMS thermal gas sensors needs to be further deepened. A gas flow channel with an air inlet and an air outlet is provided inside the MEMS thermal gas sensor. The flow channel is directly connected to the sensitive element of the sensor. The design of the gas flow channel directly affects the accuracy and response time of the sensor in measuring flow.

[0004] The flow channel structure in the existing solution is simple, for example, it is a straight tube form, and the chip is located in the middle of the tube. Such a simple structure fails to fully consider factors such as the shape, size and surface roughness of the flow channel, which will affect the flow state of the gas in the flow channel, thereby affecting the sensor's measurement of flow. Optimizing the flow channel design can reduce adverse factors such as flow resistance, eddy currents and turbulence, and improve the accuracy of flow measurement. Reasonable flow channel design can make the gas flow quickly and evenly in the flow channel, thereby shortening the sensor's response time to flow changes. Conversely, unreasonable flow channel design may cause gas eddy currents or stagnation in the flow channel, prolonging the sensor's response time. Therefore, designing a good flow channel can improve the flow measurement performance of MEMS thermal gas sensors.

[0005] At present, it is found that the improper flow channel structure design of many gas flow sensors leads to uneven gas flow in the flow field, eddy currents, backflow or dead corners, and the flow channel structure is too narrow, resulting in large pressure loss during gas flow. Therefore, the utility model proposes a simple and effective flow channel structure design. Utility Model Content

[0006] The technical problem to be solved by the utility model is to provide a new flow channel structure of a thermal gas flow sensor, which solves the problems of poor flow channel structure, affecting measurement performance and response time in the existing technical solutions, and significantly reduces the uneven gas flow in the flow channel, the generation of eddy currents, backflow or dead corners, and large pressure loss during gas flow through the optimization of the flow channel structure. The utility model has the advantages of simple structure, good effect, and simple processing.

[0007] According to the technical scheme of the utility model, the utility model provides a new flow channel structure of a thermal gas flow sensor, wherein the two ends of the flow channel respectively have an air inlet and an air outlet, the flow channel is streamlined and the two ends are relatively bent; the flow channel includes a sensing and measuring section located in the middle of the length direction, and a first guide section and a second guide section respectively located at the two ends of the sensing and measuring section; a sensor sensitive element is provided on the side wall of the sensing and measuring section; the shape of the first guide section and the second guide section are, in the direction from the middle to the two ends, first a first curved section bent to one side, and then a second curved section bent in a spiral shape to the other side.

[0008] Furthermore, a flow channel expansion section is provided near the first bending section in the second bending section, the cross section of the flow channel expansion section is larger than the cross section of the sensing and measuring section and the remaining parts of the first guide section and the second guide section, and both ends of the flow channel expansion section are smoothly transitioned.

[0009] Furthermore, the side walls of the first curved section and the second curved section form an acute angle at the flow channel expansion section, and the outer side walls of the first curved section and the second curved section form a smooth corner at the acute angle.

[0010] Furthermore, the air inlet is connected to the first guide section through a vertical air inlet section, and the air outlet is connected to the second guide section through a vertical air outlet section; the vertical air inlet section and the vertical air outlet section are perpendicular to the plane where the flow channel is located.

[0011] Furthermore, the vertical air inlet section and the vertical air outlet section are both cylindrical in shape and match the spiral shape of the second curved section.

[0012] Furthermore, a recessed sensor sensitive element slot is provided on the side wall of the sensor measuring section, and a sensor sensitive element is provided in the sensor sensitive element slot.

[0013] Furthermore, the side surface of the sensor sensitive element facing the inside of the sensing and measuring section is flush with the side wall of the sensing and measuring section.

[0014] Furthermore, it also includes a bottom plate, an air inlet and an air outlet passing through the bottom plate, a gas flow groove is provided on one side of the bottom plate, the air inlet and the air outlet are located in the gas flow groove, and the gas flow groove forms a flow channel.

[0015] Furthermore, an air inlet chamfer is provided at the air inlet end outside the air inlet, and an air outlet chamfer is provided at the air outlet end outside the air outlet.

[0016] Furthermore, the inner surfaces of the flow channels are all polished surfaces.

[0017] Compared with the prior art, the beneficial technical effects of the utility model are as follows:

[0018] The new flow channel structure of the thermal gas flow sensor of the utility model solves the problems of uneven gas flow in the flow channel, generation of eddy currents, backflow or dead corners, large pressure loss during gas flow, etc. through the optimization of the flow channel design, thereby reducing the generation of turbulence and eddy currents, reducing the resistance during gas flow, and reducing friction resistance and pressure loss; specifically, chamfers are added to the air inlet and outlet of the sensor flow channel structure, the gas flow groove is designed to be streamlined, the cross-sectional area of ​​the gas flow groove is increased, unnecessary obstacles are avoided inside the flow channel as much as possible, the inner wall of the flow channel is polished using a chemical polishing process, and the flow channel length is appropriately shortened, thereby reducing airflow disturbance, optimizing the flow channel structure, and ultimately achieving sensor performance optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the main structure according to an embodiment of the utility model.

[0020] Figure 2 yes Figure 1 A schematic diagram of the three-dimensional structure of the embodiment shown.

[0021] Figure 3 yes Figure 1 A schematic three-dimensional structure diagram of another angle of the embodiment shown.

[0022] Figure 4 yes Figure 1 A schematic three-dimensional structural diagram of the back side of the illustrated embodiment.

[0023] Figure 5 yes Figure 1 A side perspective structural diagram of the illustrated embodiment.

[0024] Figure 6 yes Figure 1 A schematic diagram of the three-dimensional perspective structure of the illustrated embodiment.

[0025] Description of reference numerals in the accompanying drawings:

[0026] 1. Flow channel; 11. First flow guide section; 12. Second flow guide section; 13. Sensor measurement section; 101. First bending section; 102. Second bending section; 103. Flow channel expansion section; 104. Smooth corner; 2. Air inlet; 21. Vertical air inlet section; 22. Air inlet chamfer; 3. Air outlet; 31. Vertical air outlet section; 32. Air outlet chamfer; 4. Sensor sensitive element; 41. Sensor sensitive element slot; 5. Bottom plate. DETAILED DESCRIPTION

[0027] The utility model provides a new flow channel structure of a thermal gas flow sensor, specifically a design of a gas flow channel that can allow gas to flow through a sensitive element of a MEMS thermal gas sensor, solves the problems of poor flow channel structure in the prior art, affecting measurement performance and response time, and significantly reduces the uneven flow of gas in the flow channel, the generation of eddy currents, backflow or dead corners, and large pressure loss during gas flow through optimization of the flow channel structure. The utility model has the advantages of simple structure, good effect, and simple processing. The gas flow channel designed in this scheme can be used for thermal flow sensors that monitor the mass flow of dry, clean, and non-corrosive gases (except flammable and explosive gases) such as air, nitrogen, argon, carbon dioxide, and oxygen, and can be used in various industries such as environmental monitoring, industrial production, energy management, biomedicine, university scientific research, fire protection, tobacco, smart agriculture, and food.

[0028] See also Figure 1 , Figure 2 , a new structure of a flow channel of a thermal gas flow sensor based on MEMS in one embodiment of the utility model, the two ends of the flow channel 1 have an air inlet 2 and an air outlet 3 respectively, the flow channel 1 is streamlined and the two ends are bent relatively. The flow channel 1 includes a sensing and measuring section 13 located in the middle of the length direction, and a curved first guide section 11 and a second guide section 12 located at the two ends of the sensing and measuring section 13; the first guide section 11 and the second guide section 12 correspond to the air inlet 2 and the air outlet 3 respectively. The sensing and measuring section 13 is, for example, basically a straight section, and a sensor sensitive element 4, i.e., a flow chip, is provided on the side wall of the sensing and measuring section 13, and its structure, principle, etc. are not repeated. The shape of the first guide section 11 and the second guide section 12 is that, in the direction from the middle to the two ends, there is first a first curved section 101 that bends to one side, and then a second curved section 102 that bends to the other side in a spiral shape; in other words, the first guide section 11 and the second guide section 12 are both question mark-shaped; thus, a streamlined flow channel is formed. Preferably, the inner surfaces of the flow channel 1 are all polished surfaces.

[0029] More preferably, the second curved section 102 has a flow channel expansion section 103 near the first curved section 101, and the cross section of the flow channel expansion section 103 is larger than the cross section of the sensing and measuring section 13 and the rest of the first guide section 11 and the second guide section 12, and the two ends of the flow channel expansion section 103 are smoothly transitioned (gradually expanded and then gradually reduced). More specifically, the side walls of the first curved section 101 and the second curved section 102 form an acute angle (for example, about 60°) at the flow channel expansion section 103, and the outer side walls of the first curved section 101 and the second curved section 102 form a smooth corner 104 with a large radius at the acute angle, and the inner side wall is a smooth arc.

[0030] Please also see Figure 5 , Figure 6 , the air inlet 2 is connected to the first guide section 11 through the vertical air inlet section 21, and the air outlet 3 is connected to the second guide section 12 through the vertical air outlet section 31; the vertical air inlet section 21 and the vertical air outlet section 31 are perpendicular to the plane where the flow channel 1 is located. Further, the shapes of the vertical air inlet section 21 and the vertical air outlet section 31 are both cylindrical and match the spiral shape of the second curved section 102. Optionally, there is a chamfer between the vertical air inlet section 21 and the first guide section 11, and there is a chamfer between the vertical air outlet section 31 and the second guide section 12.

[0031] See also Figure 3 Preferably, a recessed sensor sensitive element slot 41 is provided on the side wall of the sensing and measuring section 13, and a sensor sensitive element 4 is embedded in the sensor sensitive element slot 41. Furthermore, the side surface of the sensor sensitive element 4 facing the inside of the sensing and measuring section 13 is flush with the side wall of the sensing and measuring section 13, and does not form an obstacle to the passing gas.

[0032] More specifically, the new flow channel structure of the thermal gas flow sensor of the utility model also includes a bottom plate 5, an air inlet 2 and an air outlet 3 passing through the bottom plate 5, a gas flow groove is provided on one side (front side) of the bottom plate 5, the air inlet 2 and the air outlet 3 are located within (the contour range of) the gas flow groove, and the gas flow groove forms a flow channel 1. Furthermore, the vertical air inlet section 21 and the vertical air outlet section 31 are part of the gas flow groove, and the vertical air inlet section 21 and the vertical air outlet section 31 are both perpendicular to the plane of the bottom plate 5. The air inlet 2 is, for example, a circular hole, which is smaller than the vertical air inlet section 21; the air outlet 3 is, for example, a circular hole, which is smaller than the vertical air outlet section 31.

[0033] Please also see Figure 4 Preferably, on the side of the bottom plate 5 facing away from the gas flow groove, an inlet chamfer 22 is provided at the inlet end outside the inlet 2, and an outlet chamfer 32 is provided at the outlet end outside the outlet 3. More preferably, for example Figure 5As shown, the air inlet chamfer 22 and the air outlet chamfer 32 are located at the front and rear sides of the bottom plate 5 and around the circular hole. The bottom plate 5 is preferably made of PBT (polybutylene terephthalate) material with excellent heat resistance, insulation and chemical stability.

[0034] The main concept and structural working principle of the utility model are as follows.

[0035] This solution optimizes the design of the flow channel in six aspects: 1. The gas flow groove is designed to be streamlined to avoid sudden changes in the cross section, thereby reducing eddy currents and flow separation. 2. A large radius smooth corner design is adopted to reduce eddy current losses in the flow. 3. Under the premise of ensuring structural strength, the cross-sectional area of ​​the gas flow groove is increased, the flow channel is expanded, and the flow velocity is reduced, thereby reducing friction resistance and pressure loss. 4. In the entire sensor flow channel, unnecessary obstacles are avoided as much as possible to reduce flow interference and eddy current generation. 5. The flow channel adopts a polished surface, and a chemical polishing process is used for the inner wall of the flow channel. Ketone solvents such as methyl ethyl ketone (MEK) or acetone are used to polish the inner wall of the flow channel. The inner wall of the flow channel is smooth, which reduces friction resistance and turbulence generation. 6. The flow channel length is appropriately shortened to reduce friction losses along the flow channel.

[0036] In addition, this solution adds chamfering treatment to the air inlet and outlet of the gas flow channel to reduce the generation of turbulence and eddy currents. Specifically, it has three functions: 1. It allows the gas to flow in smoothly, thereby reducing airflow eddy currents. 2. It avoids airflow stagnation, thereby reducing airflow resistance. 3. It avoids obstruction by edges and corners, thereby reducing local pressure loss.

[0037] In summary, when the thermal gas flow sensor is used to measure the gas flow, the gas flows through the flow meter duct where the thermal gas flow sensor is installed, and then a part of the gas flow flows in from the air inlet of the thermal gas flow sensor, flows through the sensor sensitive element slot through the gas flow groove, so that the temperature distribution of the heating resistor on the sensor sensitive element is no longer symmetrical, and finally flows out from the outlet through the gas flow groove. During this entire gas flow process, due to the optimization of the flow channel design, the problems of uneven gas flow in the flow channel, vortex, backflow or dead corner, and large pressure loss during gas flow are solved, and the generation of turbulence and vortex is reduced, the resistance during gas flow is reduced, and the friction resistance and pressure loss are reduced; specifically, by adding chamfers to the air inlet and outlet of the sensor flow channel structure, designing the gas flow groove into a streamlined shape, increasing the cross-sectional area of ​​the gas flow groove, avoiding unnecessary obstacles inside the flow channel as much as possible, polishing the inner wall of the flow channel using a chemical polishing process, and appropriately shortening the flow channel length, the air flow disturbance is reduced, the flow channel structure is optimized, and the sensor performance is finally optimized.

Claims

1. A new flow channel structure of a thermal gas flow sensor, wherein the two ends of the flow channel (1) are provided with an air inlet (2) and an air outlet (3), respectively, and the characteristics are: The flow channel (1) is streamlined and has two ends that are bent opposite to each other; the flow channel (1) comprises a sensing measurement section (13) located in the middle of the length direction, and a first guide section (11) and a second guide section (12) located at two ends of the sensing measurement section (13) respectively; a sensor sensitive element (4) is provided on the side wall of the sensing measurement section (13); the first guide section (11) and the second guide section (12) are both shaped such that, in the direction from the middle to the two ends, there is first a first curved section (101) that is bent toward one side, and then there is a second curved section (102) that is bent toward the other side in a spiral shape.

2. The new flow channel structure of the thermal gas flow sensor according to claim 1 is characterized in that: A flow channel expansion section (103) is provided at the second curved section (102) near the first curved section (101); the cross section of the flow channel expansion section (103) is larger than the cross section of the sensing and measuring section (13) and the remaining parts of the first guide section (11) and the second guide section (12); and both ends of the flow channel expansion section (103) are smoothly transitioned.

3. The new flow channel structure of the thermal gas flow sensor according to claim 2 is characterized in that: The side walls of the first curved section (101) and the second curved section (102) form an acute angle at the flow channel expansion section (103), and the outer side walls of the first curved section (101) and the second curved section (102) form a smooth corner (104) at the acute angle.

4. The new flow channel structure of the thermal gas flow sensor according to claim 1 is characterized in that: The air inlet (2) is connected to the first guide section (11) via a vertical air inlet section (21), and the air outlet (3) is connected to the second guide section (12) via a vertical air outlet section (31); the vertical air inlet section (21) and the vertical air outlet section (31) are perpendicular to the plane where the flow channel (1) is located.

5. The new flow channel structure of the thermal gas flow sensor according to claim 4 is characterized in that: The vertical air inlet section (21) and the vertical air outlet section (31) are both cylindrical in shape and match the spiral shape of the second curved section (102).

6. The new flow channel structure of the thermal gas flow sensor according to claim 1 is characterized in that: A recessed sensor sensitive element slot (41) is provided on the side wall of the sensing and measuring section (13), and the sensor sensitive element (4) is provided in the sensor sensitive element slot (41).

7. The new flow channel structure of the thermal gas flow sensor according to claim 6 is characterized in that: The side surface of the sensor sensitive element (4) facing the inside of the sensing and measuring section (13) is flush with the side wall of the sensing and measuring section (13).

8. The new flow channel structure of a thermal gas flow sensor according to any one of claims 1 to 7, characterized in that: It also includes a bottom plate (5), the air inlet (2) and the air outlet (3) passing through the bottom plate (5), one side of the bottom plate (5) having a gas circulation groove, the air inlet (2) and the air outlet (3) being located in the gas circulation groove, and the gas circulation groove forming the flow channel (1).

9. The new flow channel structure of the thermal gas flow sensor according to claim 8 is characterized in that: An air inlet chamfer (22) is provided at the air inlet end outside the air inlet (2), and an air outlet chamfer (32) is provided at the air outlet end outside the air outlet (3).

10. The new flow channel structure of a thermal gas flow sensor according to any one of claims 1 to 7, characterized in that: The inner surfaces of the flow channels (1) are all polished surfaces.

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