TWI881501B - Airflow sensor - Google Patents

Abstract

The present invention discloses an airflow sensor comprising a substrate, a heating circuit, four sensing circuits, and a control module. The heating circuit can be powered to function as a heating resistor, thereby generating thermal energy. The four sensing circuits are formed on one side of the substrate. Each sensing circuit can be powered to act as a thermistor. The four sensing circuits are arranged around the heating circuit and are interconnected to form a Wheatstone bridge. The width of each sensing circuit progressively increases from the end closer to the heating circuit to the end farther away. The control module is positioned on the substrate and is electrically connected to both the heating circuit and the four sensing circuits. The control module can determine changes in resistance values of each sensing circuit and output a signal indicating the direction of the airflow.

Description

Air flow sensor

The present invention relates to an air flow sensor, in particular to an air flow sensor which uses a thermistor to perform air flow detection.

Please refer to FIG. 1, which shows a schematic diagram of a common air flow sensor. In the prior art, a common air flow sensor A is provided with a heating circuit A2, two sensing circuits A3 and a controller A4 on a circuit board A1, wherein the heating circuit A2 serves as a heating resistor and the two sensing circuits A3 serve as thermistors. When the heating circuit A2 is energized and generates heat energy, if the external airflow flows from the left side to the right side in the figure (i.e., the airflow flows along the direction of the arrow shown in FIG. 1), the resistance value of the thermistor located on the right side will change significantly relative to the resistance value of the thermistor located on the left side. Therefore, the controller A4 can determine the flow direction of the external airflow by obtaining the change in the resistance values of the two thermistors.

The conventional air flow sensor shown in FIG1 can only detect the air flow in a single direction in practical application. Specifically, the air flow sensor shown in FIG1 can only detect the air flow direction in the X-axis direction of the figure, and the air flow sensor cannot sense the air flow direction in the Y-axis direction of the figure.

The present invention discloses an air flow sensor, which is mainly used to improve the existing air flow sensor which can only sense the air flow in a single axial direction.

One embodiment of the present invention discloses an air flow sensor, which includes: a substrate, a heating circuit, at least four sensing circuits and a control module. The heating circuit can be powered to form a heating resistor and generate heat energy accordingly; four sensing circuits are formed on one side of the substrate, each sensing circuit can be powered to form a thermistor, the four sensing circuits are arranged around the heating circuit, and the four sensing circuits are connected to form a Wheatstone bridge; the line width of each sensing circuit gradually increases from one end close to the heating circuit to one end far from the heating circuit; the control module is arranged on the substrate, and the control module is electrically connected to the heating circuit and the four sensing circuits, and the control module can output an air flow direction signal according to the change of the resistance value of each sensing circuit.

In summary, the air flow sensor of the present invention can sense air flow in multiple directions by setting up four sensing circuits, and the air flow sensor of the present invention can greatly improve the sensing sensitivity of the air flow sensor by designing that the line width of each sensing circuit gradually increases from one end close to the heating circuit to one end far from the heating circuit.

In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, such description and drawings are only used to illustrate the present invention and do not limit the protection scope of the present invention in any way.

In the following description, if it is indicated to refer to a specific figure or as shown in a specific figure, it is only used to emphasize that most of the relevant content described in the subsequent description appears in the specific figure, but it does not limit the subsequent description to only refer to the specific figure.

Please refer to FIG. 2, which is a schematic diagram of the first embodiment of the air flow sensor of the present invention. The air flow sensor 100 comprises: a substrate 1, a heating circuit 2, four sensing circuits and a control module 4. The substrate 1 can be, for example, a hard circuit board or a flexible circuit board. In the embodiment where the substrate 1 is a flexible circuit board, the air flow sensor 100 can be used with adhesive, double-sided tape, etc. to be attached to the surface of a device, a robot arm, etc., thereby monitoring the air flow outside the device, the robot arm, etc.

The heating circuit 2 can be powered to form a heating resistor and generate heat energy accordingly. In practical applications, the heating circuit 2 can include, for example, a plurality of arc sections 31 and a plurality of bend sections 32, at least one end of each arc section 31 is connected to one of the bend sections 32, and the periphery of the heating circuit 2 can be roughly circular (or elliptical). The shape, size, wire diameter, etc. of the heating circuit 2 can be changed according to actual needs, and the figure shows only one exemplary state.

In one specific application, the heating circuit 2 can be designed to be symmetrical in the vertical direction and in the horizontal direction, and the line width at any position of the heating circuit 2 is the same, so that when the heating circuit 2 is energized to generate heat energy, the temperature at any position of the heating circuit 2 will be substantially the same. By making the line width at any position of the heating circuit 2 the same, the air flow sensor 100 can also make the resistance value changes of each sensing circuit due to the heat energy generated by the heating circuit 2 substantially the same when the external air flow is not flowing.

Four sensing lines are formed on one side of the substrate 1, and each sensing line can be powered to form a thermistor. The four sensing lines are arranged around the heating line 2, and the four sensing lines are connected to form a Wheatstone Bridge.

For the sake of explanation, the four sensing circuits located at the upper left corner, the upper right corner, the lower left corner and the lower right corner in FIG. 2 are defined as the first sensing circuit 3A, the second sensing circuit 3B, the third sensing circuit 3C and the fourth sensing circuit 3D in sequence. The first sensing circuit 3A and the second sensing circuit 3B are arranged symmetrically, the third sensing circuit 3C and the fourth sensing circuit 3D are also arranged symmetrically, the first sensing circuit 3A and the third sensing circuit 3C are arranged symmetrically, and the second sensing circuit 3B and the fourth sensing circuit 3D are arranged symmetrically.

The line width of each sensing line gradually increases from the end close to the heating line 2 to the end far from the heating line 2. In one specific application, the minimum line width D1 of each sensing line is at least 5% of the maximum line width D2 of each sensing line. Since the overall shape of the sensing line is roughly formed by extending outward from the end close to the heating line 2, when there is no airflow in the environment where the air flow sensor 100 is located, the section of the sensing line close to the heating line 2 is significantly affected by the heat energy of the heating line 2 than the section of the sensing line far from the heating line 2. Therefore, the section of the sensing line closest to the heating line 2 and the section of the sensing line farthest from the heating line 2 have a relatively large temperature difference. When there is a relatively large temperature difference between the section of the sensing circuit closest to the heating circuit 2 and the section of the sensing circuit farthest from the heating circuit 2, when the external airflow of the airflow sensor 100 flows slightly, the overall temperature of the sensing circuit will be relatively unlikely to change, and the resistance value of the airflow sensor 100 will be insensitive to changes.

In contrast, the line width of each sensing circuit of the air flow sensor 100 of the present invention gradually increases from the end close to the heating circuit 2 to the end farthest from the heating circuit 2. Therefore, when there is no airflow in the environment where the air flow sensor 100 of the present invention is located, the temperature difference between the section of each sensing circuit closest to the heating circuit 2 and the section farthest from the heating circuit 2 will not be too large. As a result, when the external airflow of the air flow sensor 100 flows slightly, the overall temperature of the sensing circuit will change relatively quickly, and the resistance value of the air flow sensor 100 will change sensitively accordingly. That is, the air flow sensor 100 of the present invention can effectively improve the sensing sensitivity of the air flow sensor 100 by changing the line width of the sensing circuit.

In practical applications, each sensing circuit may include, for example, a plurality of arc segments 31 and a plurality of bend segments 32, at least one end of each arc segment 31 is connected to one of the bend segments 32, and the overall sensing circuit is generally in the form of a plurality of S-shaped structures connected to each other.

The closer each sensing line is to the heating line 2, the shorter the length of the arc section 31 is, and the farther each sensing line is from the heating line 2, the longer the length of the arc section 31 is. In actual applications, the curvature and size of the arc section 31 of each sensing line can be changed according to actual needs, and the figure shows only one exemplary embodiment. By changing the length of the arc section 31 of each sensing circuit, when there is no airflow in the environment of the air flow sensor 100, the temperature difference between the section closest to the heating circuit 2 and the section farthest from the heating circuit 2 will not be too large. Therefore, when the airflow outside the air flow sensor 100 flows slightly, the overall temperature of the sensing circuit will change relatively quickly, and the resistance value of the air flow sensor 100 will change sensitively accordingly. In one of the preferred specific applications, the material of each sensing circuit can be gold foil, so that the resistance value of the sensing circuit can change more sensitively.

The control module 4 is electrically connected to the heating circuit 2 and the four sensing circuits, and the control module 4 can output an airflow direction signal according to the change in the resistance value of each sensing circuit. In practical applications, the control module 4 may include, for example, a microprocessor, a signal conversion circuit, a signal amplifier, a communication chip, etc., and after the microprocessor generates a corresponding airflow direction signal according to the change in the resistance value of the four sensing circuits, the microprocessor may, for example, transmit the airflow direction signal to the outside through the communication chip. Of course, in different embodiments, the microprocessor may also transmit the airflow direction signal to the outside through related flexible cables, wires, and other components connected to the substrate 1. The components included in the control module 4 and the technology of converting the resistance value change into an analog signal based on the Wheatstone bridge are all known technologies and will not be elaborated here.

The control module 4 can determine the flow direction of the airflow by measuring the change in the resistance value of the four sensing circuits. More specifically, when the external airflow of the airflow sensor 100 is not flowing, the control module 4 will measure that the four sensing circuits have approximately the same resistance value. When the external airflow of the airflow sensor 100 begins to flow, the heat energy generated by the heating circuit 2 will flow along with the airflow toward at least one of the sensing circuits, thus causing the overall temperature of the corresponding sensing circuit to rise, and the resistance value of the sensing circuit will change accordingly, thereby allowing the control module 4 to know that the airflow is flowing toward the sensing circuit.

As shown in FIG3 , in actual application, the air flow sensor 100 may further include an insulating protective layer 5. The insulating protective layer 5 is disposed on the side of the substrate 1 where the sensing circuit and the heating circuit 2 are formed, and the insulating protective layer 5 covers the sensing circuit and the heating circuit 2. The insulating protective layer 5 is used to protect the sensing circuit and the heating circuit 2, so as to greatly reduce the problem of the sensing circuit or the heating circuit 2 being peeled off from the substrate 1 due to external force, thereby further improving the service life of the air flow sensor 100. Preferably, the thickness of the insulating protective layer 5 is not greater than 0.0008 mm, thereby preventing the insulating protective layer 5 from blocking the airflow-driven heat transfer. In practical applications, the insulating protective layer 5 can be, for example, PI 9320 material. Of course, in different embodiments, the airflow sensor 100 may not include the insulating protective layer 5.

In summary, the air flow sensor of the present invention can effectively detect airflow in various directions through the design of a heating circuit, four sensing circuits and a controller, thereby effectively improving the problem that the known air flow sensor shown in FIG. 1 can only detect airflow in a single direction. In addition, the air flow sensor of the present invention can greatly improve the sensing sensitivity of the air flow sensor by gradually increasing the line width of the sensing circuit from the section close to the heating circuit to the section far from the heating circuit, and by making the length of each sensing circuit of the air flow sensor smaller as it is closer to the heating circuit and larger as it is far from the heating circuit.

Please refer to FIG. 4, which is a schematic diagram of a second embodiment of the air flow sensor of the present invention. One difference between this embodiment and the aforementioned embodiment is that each sensing line includes a plurality of straight line segments 33, and the closer the sensing line is to the heating line 2, the shorter the length of the straight line segment 33 is, and the farther the sensing line is from the heating line 2, the longer the length of the straight line segment 33 is. The closer the sensing line is to the heating line 2, the smaller the line width is, and the farther the straight line segment 33 is from the heating line 2, the larger the line width is. In one specific application, the minimum line width D3 of each sensing line is at least 5% of the maximum line width D4 of each sensing line.

Another difference between this embodiment and the aforementioned embodiment is that the heating circuit 2 includes a heating section 21 and two connecting sections 22, the two ends of the heating section 21 are connected to the two connecting sections 22, one of the connecting sections 22 is located between the first sensing circuit 3A and the third sensing circuit 3C, and the other connecting section 22 is located between the second sensing circuit 3B and the fourth sensing circuit 3D, and the line width D5 of the heating circuit 2 at any position of the heating section 21 is different from the line width D6 at any position of each connecting section 22. In one specific application, the line width D5 at any position of the heating section 21 is smaller than the line width D6 at any position of each connecting section 22.

As described above, by making the line width D5 at any position of the heating section 21 different from the line width D6 at any position of each connecting section 22, the impact of the heat energy generated by the connecting section 22 on the adjacent sensing circuit when the heating circuit 2 generates heat energy can be greatly reduced.

Furthermore, since there is no connection section 22 between the first sensing circuit 3A and the second sensing circuit 3B and between the third sensing circuit 3C and the fourth sensing circuit 3D, by making the line width of the connection section 22 larger than the line width of the heating section 21, the temperature of the connection section 22 can be greatly reduced, which affects the temperature of the surrounding sensing circuits, thereby further improving the sensing sensitivity of the sensing circuits.

In summary, the air flow sensor of the present invention has a simple overall structure and can sense airflow in multiple directions, which can effectively solve the problem that the conventional air flow sensor shown in FIG. 1 can only sense airflow in a single direction. In addition, the air flow sensor of the present invention can greatly improve the sensing sensitivity of the air flow sensor by designing the line width and length of each sensing line.

The above description is only the preferred feasible embodiment of the present invention, and does not limit the patent scope of the present invention. Therefore, all equivalent technical changes made by using the contents of the specification and drawings of the present invention are included in the protection scope of the present invention.

A: Air flow sensor A1: Circuit board A2: Heating circuit A3: Sensing circuit A4: Controller 100: Air flow sensor 1: Substrate 2: Heating circuit 21: Heating section 22: Connecting section 3A: First sensing circuit 3B: Second sensing circuit 3C: Third sensing circuit 3D: Fourth sensing circuit 31: Arc section 32: Turning section 33: Straight section 4: Control module 5: Insulation protection layer D1: Line width D2: Line width D3: Line width D4: Line width D5: Line width D6: Line width

FIG. 1 is a schematic diagram of a conventional air flow sensor.

FIG. 2 is a schematic diagram of a first embodiment of the air flow sensor of the present invention.

FIG. 3 is a schematic cross-sectional view of the air flow sensor of the present invention along the section line III-III of FIG. 2 .

FIG. 4 is a schematic diagram of a second embodiment of the air flow sensor of the present invention.

100: Air flow detector

1: Substrate

2: Heating circuit

3A: First sensing circuit

3B: Second sensing circuit

3C: The third sensing circuit

3D: Fourth sensing circuit

31: Arc section

32: Turning section

4: Control module

5: Insulation protective layer

D1: Line width

D2: Line width

Claims (9)

An airflow sensor, comprising: a substrate; a heating circuit, which can be powered to form a heating resistor and generate heat energy accordingly; at least four sensing circuits, which are formed on one side of the substrate, each of which can be powered to form a thermistor, and the four sensing circuits are arranged around the heating circuit, and the four sensing circuits are connected to form a Wheatstone bridge; the line width of each sensing circuit gradually increases from one end close to the heating circuit to one end far from the heating circuit; a control module, which is arranged on the substrate, and the control module is electrically connected to the heating circuit and the four sensing circuits, and the control module can output an airflow direction signal according to the change of the resistance value of each sensing circuit; The heating circuit includes a heating section and two connecting sections, the two ends of the heating section are connected to the two connecting sections, one of the connecting sections is located between two of the sensing circuits, and the other connecting section is located between the other two sensing circuits, and the line width of the heating circuit at any position of the heating section is different from the line width at any position of each of the connecting sections. An air flow sensor as described in claim 1, wherein the substrate is a flexible circuit board. An air flow sensor as described in claim 1, wherein the minimum line width of each of the sensing lines is at least 5 percent of the maximum line width of each of the sensing lines. An air flow sensor as described in claim 1, wherein the material of each of the sensing circuits is gold foil; two of the sensing circuits are arranged symmetrically, and the other two of the sensing circuits are arranged symmetrically. An air flow sensor as described in claim 1, wherein each of the sensing lines comprises a plurality of straight line segments, the closer each of the sensing lines is to the heating line, the shorter the length of the straight line segment is, and the farther each of the sensing lines is from the heating line, the longer the length of the straight line segment is. An air flow sensor as described in claim 1, wherein each of the sensing circuits comprises a plurality of arc segments and a plurality of turning segments, at least one end of each of the arc segments is connected to one of the turning segments; the closer each of the sensing circuits is to the heating circuit, the shorter the length of the arc segment, and the farther each of the sensing circuits is from the heating circuit, the longer the length of the arc segment. An air flow sensor as described in claim 1, wherein the heating circuit comprises a plurality of arc sections and a plurality of bend sections, at least one end of each of the arc sections is connected to one of the bend sections; and the outer periphery of the heating circuit is substantially circular. An air flow sensor as described in claim 1, wherein the line width at any position of the heating section is smaller than the line width at any position of each of the connecting sections. An air flow sensor as described in claim 1, wherein the air flow sensor further comprises an insulating protective layer, wherein the insulating protective layer is disposed on a side of the substrate where the sensing circuit and the heating circuit are formed, and the insulating protective layer covers the sensing circuit and the heating circuit, and the thickness of the insulating protective layer is not greater than 0.0008 mm.

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