Touch panel with force sensing function and resistive pressure sensor thereof

Abstract

The invention provides a touchpad with a force sensing function and a resistance-type pressure sensor thereof, the resistance-type pressure sensor is mainly characterized in that a Wheatstone bridge unit is arranged in a deformation area of a circuit board, and the deformation area can generate flexural deformation when pressed by external force; and the Wheatstone bridge unit comprises a first upper arm resistor and a first lower arm resistor which are connected in series, and a second upper arm resistor and a second lower arm resistor which are connected in series. Each arm resistor of the Wheatstone bridge unit is located in the deformation area, and the current directions of the first lower arm resistor and the second upper arm resistor are different from the current directions of the second lower arm resistor and the first upper arm resistor. Therefore, when the deformation area is pressed by external force, the output voltage difference of the Wheatstone bridge unit can be increased, so that the pressure induction amount is improved.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Taiwan Patent Application No. 112145416 filed on November 23, 2023, which is incorporated herein by reference for all purposes as if fully set forth herein. Technical Field

[0003] The present invention relates to a pressure sensor for a touch panel, and more particularly to a resistive pressure sensor for a touch panel. Background Art

[0004] In order to add more touch functions, the current touch panel has added force sensing function, that is, the touch panel has a touch electrode layer and a force sensing layer, and a plurality of force sensing electrodes are arranged on the force sensing layer; when an object is operated on the touch panel, the force sensing electrode will receive an excitation signal, and the excitation signal causes the force sensing electrode and the corresponding grounding circuit to generate a pair of ground-based capacitances. When the object is pressed down, the difference between the corresponding capacitance sensing values ​​generated by each force sensing electrode and the pair of ground-based capacitances can be used as the capacitance sensing change of force sensing, and the downward pressure of the object can be calculated based on this.

[0005] However, the ground-based capacitance has a certain capacitance value. When an object is pressed down, if the capacitance sensing value generated by the force applied is too different from the ground-based capacitance, it is difficult to present slight changes in the force applied. Therefore, the force sensitivity of the touch panel of the prior art is difficult to accurately present slight changes in the force applied. Therefore, it is necessary to further seek force sensing technology with other detection methods. Summary of the invention

[0006] In view of the fact that the current touch pads with force sensing function use capacitive sensing to respond to the user's downward pressure on the touch pad body, the sensing amount is still too small and the sensing is inaccurate. The main purpose of the present invention is to provide a touch pad with force sensing function and a resistive pressure sensor thereof to increase the pressure sensing amount.

[0007] The main technical means used to achieve the above purpose are that the resistive pressure sensor includes:

[0008] A circuit board having a deformation zone, when pressed by an external force, a portion of the circuit board corresponding to the deformation zone will bend and deform along a first deformation direction; and

[0009] A Wheatstone bridge unit is disposed on the circuit board and comprises:

[0010] a first series resistor unit, located in the deformation region, and comprising a first upper arm resistor and a first lower arm resistor, wherein the first upper arm resistor and the first lower arm resistor respectively have a first end and a second end, and the second end of the first upper arm resistor is connected to the first end of the first lower arm resistor; and

[0011] A second series resistor unit is located in the deformation zone and is connected in parallel with the first series resistor unit, and includes a second upper arm resistor and a second lower arm resistor connected in series with each other, the second upper arm resistor and the second lower arm resistor respectively have a first end and a second end, and the second end of the second upper arm resistor is connected to the first end of the second lower arm resistor; wherein the first end of the first upper arm resistor and the first end of the second upper arm resistor are commonly connected to the high potential end of a DC power supply, the second end of the first lower arm resistor and the second end of the second lower arm resistor are commonly connected to the low potential end of the DC power supply, and the two series nodes of the first series resistor unit and the second series resistor unit serve as two voltage output ends; wherein:

[0012] The direction of the current flowing through the first lower arm resistor and the direction of the current flowing through the second upper arm resistor are parallel to the first deformation direction; and

[0013] The direction of the current flowing through the second lower arm resistor and the direction of the current flowing through the first upper arm resistor are different from the first deformation direction.

[0014] The advantage of the present invention is that the Wheatstone bridge unit is arranged on the circuit board and the resistors of each arm are located in the deformation zone, but the current direction of the first lower arm and the second upper arm resistors is different from the current direction of the second lower arm and the first upper arm resistors; thus, when the deformation zone is pressed by external force, according to the output voltage formula of the Wheatstone bridge unit, an increased output voltage difference can be obtained, thereby increasing the pressure sensing amount and making the pressure detection response more sensitive.

[0015] The main technical means used to achieve the above purpose is to make the touch panel with force sensing function include:

[0016] A bracket having a plurality of cantilevers, each of the cantilevers having a connecting portion and a free end opposite to the connecting portion;

[0017] A plurality of resistive pressure sensors as described above, wherein the deformation zone of each resistive pressure sensor is located at a connecting portion of the corresponding cantilever; and

[0018] A touch panel body is fixed on the bracket and covers the plurality of resistive pressure sensors.

[0019] The advantage of the present invention is that a plurality of resistive pressure sensors are arranged between the touch panel body and the bracket, and the deformation zone of each resistive pressure sensor corresponds to the connecting portion of the cantilever; thus, when the touch panel body is pressed, the portion of the circuit board located on the cantilever of the bracket (i.e., the deformation zone) will deform synchronously, increasing the output voltage difference of the Wheatstone bridge unit thereon, thereby increasing the pressure sensing amount and making the pressure detection response more sensitive.

[0020] In order to further understand the technologies, means and effects adopted by the present application to achieve the intended purpose, please refer to the following detailed description and drawings of the present application. It is believed that the purpose, characteristics and features of the present application can be deeply and specifically understood thereby. However, the drawings are only provided for reference and illustration and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : A three-dimensional exploded view of the touch panel with force sensing function of the present invention;

[0022] Figure 2 : A partial cross-sectional view of a touch panel with force sensing function of the present invention;

[0023] Figure 3 : A circuit diagram of a Wheatstone bridge unit of the present invention;

[0024] Figure 4A : A top plan view of the four-arm resistors of the Wheatstone bridge unit of the present invention;

[0025] Figure 4B and Figure 4C :The resistance of one arm of the Wheatstone bridge unit of the present invention is Figure 4A Schematic diagram of the one-length stretching of the AA cut surface line;

[0026] Figure 4D and Figure 4E The other arm resistance of the Wheatstone bridge unit of the present invention is Figure 4A Schematic diagram of the one-length stretching of the middle BB cut line;

[0027] Figure 5A : A top plan view of a resistive pressure sensor of the present invention;

[0028] Figure 5B : A top plan view of another resistive pressure sensor of the present invention;

[0029] Figure 5C : A top plan view of another resistive pressure sensor of the present invention;

[0030] Fig. 6A and Figure 6B: Schematic diagram of the deformation of the touch panel with force sensing function before and after being subjected to pressure.

[0031] Wherein, the reference numerals are:

[0032] 1. Trackpad

[0033] 10: Bracket

[0034] 11: Cantilever

[0035] 111: Connecting part

[0036] 112: Free end

[0037] 12: U-shaped groove

[0038] 121:End

[0039] 13: Short side

[0040] 20: Resistive pressure sensor

[0041] 21: Circuit Board

[0042] 211: Deformation Zone

[0043] 212: Connector pad

[0044] 22: Wheatstone bridge unit

[0045] 221: first series resistance unit

[0046] 222: second series resistance unit

[0047] 30: Touch panel body

[0048] 31: Carrier board

[0049] 32: Sensing electrode

[0050] 33: Cover

[0051] 34: Controller

[0052] 40:Isolation pad

[0053] 50: Test the pressure column

[0054] D1: First deformation direction

[0055] D2: Second deformation direction

[0056] R4: The first upper arm resistor

[0057] R1: The first lower arm resistor

[0058] R4-1, R1-1: First end

[0059] R4-2, R1-2: Second end

[0060] R3: Second upper arm resistor

[0061] R2: The second lower arm resistor

[0062] R3-1, R2-1: First end

[0063] R3-2, R2-2: Second end

[0064] Vy, Vx: voltage output terminals

[0065] Vic: high potential terminal

[0066] GND: Low potential terminal

[0067] W1, W2, W3, W4, W2+: Width

[0068] L1, L2, L3, L4, L1+: length. DETAILED DESCRIPTION

[0069] The following is a combination of drawings and embodiments of the present invention to further explain the technical means adopted by the present invention to achieve the predetermined invention purpose, wherein the drawings have been simplified for illustrative purposes only, and the structure or method invention of the present invention is explained by describing the relationship between the elements and components of the present invention. Therefore, the elements shown in the drawings are not presented in actual quantity, actual shape, actual size and actual proportion, and the size or size proportion has been enlarged or simplified to provide a better description. The actual quantity, actual shape or actual size proportion has been selectively designed and configured, and the detailed element layout may be more complicated.

[0070] The present invention relates to a touch panel with force sensing function. The technical content is described in detail below with reference to embodiments and drawings.

[0071] First see Figure 1 As shown, the touch panel 1 with force sensing function of the present invention comprises a bracket 10 , a plurality of resistive pressure sensors 20 and a touch panel body 30 .

[0072] The bracket 10 includes a plurality of cantilevers 11; in the present embodiment, the bracket 10 is in the shape of a long rectangle, and the plurality of cantilevers 11 are respectively formed in four corner regions. Taking a metal plate as the bracket 10 as an example, a U-shaped through groove 12 is formed in each of the corner regions to cut the metal plate to form the cantilever 11. Each of the cantilevers 11 includes a connecting portion 111 and a free end 112, and the connecting portion 111 is located between the two ends 121 of the U-shaped through groove 12, that is, the region where the cantilever 11 is connected to the bracket 10. In one embodiment, the free ends 112 of the plurality of cantilevers 11 face one of the short sides 13 of the bracket 10 that is closest thereto, and a seismic isolation pad 40 may be further provided at the free end 112 of each of the cantilevers 11, so that the seismic isolation pad 40 is located between the bracket 10 and the touch panel body 30.

[0073] Please cooperate Figure 2 As shown, the plurality of resistive pressure sensors 20 are respectively disposed on the plurality of cantilevers 11 of the bracket 10, and each of the resistive pressure sensors 20 includes a circuit board 21 and a Wheatstone bridge unit 22 (such as Figure 3 As shown). Then combine Fig. 6A As shown, the circuit board 21 has a deformation zone 211 and a plurality of pads 212; in this embodiment, the deformation zone 211 corresponds to the connection portion 111 of the cantilever 11. When the cantilever 11 is pressed by an external force, the deformation zone 211 of the circuit board 21 is deformed accordingly with the deformation of the cantilever 11. A test pressing column 50 is pressed against one of the cantilever 11 near its free end 112 and a force is applied downward along the Z-axis direction, and the following is presented: Figure 6B At this time, the circuit board 21 placed on the cantilever 11, as shown Figure 4C As shown, in particular, the deformation amount of the deformation zone 211 of the circuit board 21 corresponding to the connection portion 111 of the cantilever 11 is the largest, wherein the deformation zone 211 has a first deformation direction D1 and a second deformation direction D2; in this embodiment, the first deformation direction D1 is parallel to the X-axis direction, and the second deformation direction D2 is different from the first deformation direction D1, preferably parallel to the Y-axis direction, that is, the second deformation direction D2 is substantially orthogonal to the first deformation direction D1. In this embodiment, the circuit board 21 is a flexible circuit board, but is not limited thereto.

[0074] Each of the Wheatstone bridge units 22 is disposed on the corresponding circuit board 21. Figure 3As shown, each of the Wheatstone bridge units 22 includes a first series resistor unit 221 and a second series resistor unit 222 connected in parallel with the first series resistor unit 221; wherein the first series resistor unit 221 includes a first upper arm resistor R4 and a first lower arm resistor R1, the first upper arm resistor R4 and the first lower arm resistor R1 respectively have a first end R4-1, R1-1 and a second end R4-2, R1-2, the second end R4-2 of the first upper arm resistor R4 is connected to the first end R1-1 of the first lower arm resistor R1, and the second series resistor unit 222 includes a second upper arm resistor R3 and a second lower arm resistor R2, the second upper arm resistor R3 and the second lower arm resistor R2 respectively have a first end R3-1, R2-1 and a second end R3-2, R2-2. The first end R4-1 of the first upper arm resistor R4 and the first end R3-1 of the second upper arm resistor R3 are connected to the high potential end Vcc of the DC power supply, the second end R1-2 of the first lower arm resistor R1 and the second end R2-2 of the second lower arm resistor R2 are connected to the low potential end GND of the DC power supply, and the two connection nodes of the first series resistor unit 221 and the second series resistor unit 222 are used as two voltage output terminals Vy and Vx respectively. In this embodiment, as Fig. 6A As shown, the multiple pads 212 of the circuit board 21 can be electrically connected to the high potential terminal Vcc and the low potential terminal GND of the DC power supply and the two voltage output terminals Vy and Vx, and are located outside the deformation zone 211; preferably, the multiple pads 212 are jointly arranged on the same side of the circuit board 21, that is, the side away from the deformation zone 211 and the free end 112 of the cantilever 11.

[0075] Please see again Figure 5A , Figure 5B and Figure 5C As shown in FIG. 1 , the first upper arm resistor R4, the first lower arm resistor R1, the second upper arm resistor R3 and the second lower arm resistor R2 of each of the Wheatstone bridge units 22 are arranged in different ways corresponding to the different size deformation zones 211 of the circuit board 21. Figure 5A For example, Figure 3 The first lower arm resistor R1 and the second upper arm resistor R3 are located at the upper and lower relative positions in the deformation zone 211, while the second lower arm resistor R2 and the first upper arm resistor R4 are located at the left and right relative positions in the deformation zone 211, and the four resistors are arranged in a cross. Figure 5B As shown, Figure 3 The first lower arm resistor R1, the first upper arm resistor R4, the second lower arm resistor R2 and the second upper arm resistor R3 are arranged in a straight line. Figure 5C For example, Figure 3The first lower arm resistor R1 and the second lower arm resistor R2 are arranged side by side at the upper side of the deformation zone 211, and the second upper arm resistor R3 and the first upper arm resistor R4 are arranged side by side at the lower side of the deformation zone 211, and the four resistors are arranged in a square shape; furthermore, the first lower arm resistor R1 and the second upper arm resistor R3 can be located at the upper and lower diagonal positions of the deformation zone 211, and the second lower arm resistor R2 and the first upper arm resistor R4 are also located at the upper and lower diagonal positions of the deformation zone 211.

[0076] Regardless of the arrangement mentioned above, the direction of the first end R1-1 of the first lower arm resistor R1 toward the second end R1-2 is the current direction, and the direction of the first end R3-1 of the second upper arm resistor R3 toward the second end R3-2 is the current direction. The current directions of the first lower arm resistor R1 and the second upper arm resistor R3 are parallel to the first deformation direction D1 (same as the X-axis direction), that is, Figure 4A and Figure 5B As shown, the distance from the first end R1-1 to the second end R1-2 of the first lower arm resistor R1 is a length L1, the distance from the first end R3-1 to the second end R3-2 of the second upper arm resistor R3 is a length L3, and the distance between the two side walls of the first lower arm resistor R1 and the second upper arm resistor R3 in a direction parallel to the second deformation direction 21 (same as the Y-axis direction) is the width W1, W3; and the direction of the first end R2-1 of the second lower arm resistor R2 toward the second end R2-2 is the current direction, and the direction of the first end R4-1 of the first upper arm resistor R4 toward the second end R4-2 is the current direction, and the current directions of the second lower arm resistor R2 and the first upper arm resistor R4 are parallel to the second deformation direction D2 (same as the Y-axis direction), that is, Figure 4A and Figure 5B As shown, the distance from the first end R2-1 to the second end R2-2 of the second lower arm resistor R2 is a length L2, the distance from the first end R4-1 to the second end R4-2 of the first upper arm resistor R4 is a length L4, and the distance between the two side walls of the second lower arm resistor R2 and the first upper arm resistor R4 in a direction parallel to the first deformation direction D1 (the same as the X-axis direction) is the width W2 and W4; in this embodiment, when the deformation zone 211 of the circuit board 21 is subjected to force and produces flexural deformation, the deformation amount in the first deformation direction D1 is greater than the deformation amount in the second deformation direction D2.

[0077] Then Figure 5B For example, since the deformation amount of the circuit board portion in the deformation zone 211 toward the first deformation direction D1 is greater than the deformation amount toward the second deformation direction D2, Figure 6B As shown in FIG. 1 , when the deformation zone 211 is deformed due to external pressure, the first lower arm resistor R1 and the second upper arm resistor R3 will be as shown in FIG. Figure 4B and Figure 4C As shown, the original length L1 of the first lower arm resistor R1 will be extended to L1+, and the same is true for the second upper arm resistor R3; Figure 4D and Figure 4E As shown, the original width W2 of the second lower arm resistor R2 is also extended to W2+, and the first upper arm resistor R4 is also the same. According to the resistance law Where ρ: resistivity, L: resistor length, W×T: cross-sectional area of ​​the first end and the second end, the resistance value of the first lower arm resistor R1 and the second upper arm resistor R3 will increase due to their length increase, while the resistance value of the second lower arm resistor R2 and the first upper arm resistor R4 will decrease due to their width increase; thus, the output voltage V of the Wheatstone bridge unit 22 is brought into O formula:

[0078]

[0079] Where V cc : DC power supply, which can increase the potential of one voltage output terminal Vy and reduce the potential of the other voltage output terminal Vx. Therefore, after subtracting the potentials of the two voltage output terminals Vy and Vx, the output voltage value V O In one embodiment, the shapes of the arm resistors can be the same or different, and can also be formed by screen printing carbon film, but not limited thereto.

[0080] The touch panel body 30 is fixed on the bracket 10, and the plurality of resistive pressure sensors 20 are distributed at the four corners between the bracket 10 and the touch panel body 30. When the touch panel body 30 is pressed downward, the four cantilevers 11 on the bracket 10 will be slightly bent downward to varying degrees according to the pressed position, and the portion of the circuit board 21 located on the cantilever 11 of the bracket 10 (i.e., the deformation zone 211) will be deformed synchronously to perform the pressure sensing as described above. In this embodiment, if Figure 1 and Figure 2 As shown, the touch panel body includes a carrier board 31, a plurality of sensing electrodes 32, a cover board 33 and a controller 34; the plurality of sensing electrodes 32 are formed on a surface of the carrier board 31, the cover board 33 covers the carrier board 31 and the plurality of sensing electrodes 32, and the controller 34 is electrically connected to the plurality of sensing electrodes 32 and the plurality of resistive pressure sensors 20.

[0081] In summary, the touch panel with force sensing function of the present invention arranges multiple resistive pressure sensors between the touch panel body and the bracket, and the deformation zone of each resistive pressure sensor corresponds to the connecting portion of the cantilever, and each arm resistor of the Wheatstone bridge unit is located in the deformation zone, but the current direction of the first lower arm and the second upper arm resistor is different from the current direction of the second lower arm and the first upper arm resistor; in this way, when the touch panel body is pressed, the part of the circuit board located on the cantilever of the bracket (i.e., the deformation zone) will be deformed synchronously, so according to the output voltage formula of the Wheatstone bridge unit, an increased output voltage difference can be obtained, thereby increasing the pressure sensing amount and making the pressure detection response more sensitive.

[0082] The above description is only an embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above by the embodiment, it is not used to limit the present invention. Any ordinary technician in the technical field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A resistive pressure sensor, characterized in that: include: A circuit board having a deformation zone, when pressed by an external force, a portion of the circuit board corresponding to the deformation zone will bend and deform along a first deformation direction; and A Wheatstone bridge unit is disposed on the circuit board and comprises: a first series resistor unit, located in the deformation region, and comprising a first upper arm resistor and a first lower arm resistor, wherein the first upper arm resistor and the first lower arm resistor respectively have a first end and a second end, and the second end of the first upper arm resistor is connected to the first end of the first lower arm resistor; and A second series resistor unit is located in the deformation zone and connected in parallel with the first series resistor unit, and includes a second upper arm resistor and a second lower arm resistor, the second upper arm resistor and the second lower arm resistor respectively have a first end and a second end, the second end of the second upper arm resistor is connected to the first end of the second lower arm resistor; wherein the first end of the first upper arm resistor and the first end of the second upper arm resistor are commonly connected to the high potential end of a DC power supply, the second end of the first lower arm resistor and the second end of the second lower arm resistor are commonly connected to the low potential end of the DC power supply, and two connection nodes between the first series resistor unit and the second series resistor unit serve as two voltage output ends; wherein: The direction of the current flowing through the first lower arm resistor and the direction of the current flowing through the second upper arm resistor are parallel to the first deformation direction; and The direction of the current flowing through the second lower arm resistor and the direction of the current flowing through the first upper arm resistor are different from the first deformation direction.

2. The resistive pressure sensor according to claim 1, wherein: The deformation zone further has a second deformation direction. When the circuit board is subjected to a force and generates a bending deformation, the deformation amount in the second deformation direction is smaller than the deformation amount in the first deformation direction. as well as The direction of the current flowing through the second lower arm resistor and the direction of the current flowing through the first upper arm resistor are parallel to the second deformation direction.

3. The resistive pressure sensor according to claim 2, wherein: The first deformation direction is substantially orthogonal to the second deformation direction.

4. The resistive pressure sensor according to any one of claims 1 to 3, characterized in that: The first lower arm resistor and the second upper arm resistor are located at diagonal positions within the deformation zone, and the second lower arm resistor and the first upper arm resistor are located at diagonal positions within the deformation zone.

5. The resistive pressure sensor according to claim 4, wherein: The first lower arm resistor, the second upper arm resistor, the second lower arm resistor and the first upper arm resistor are arranged in a cross shape or a square shape.

6. The resistive pressure sensor according to any one of claims 1 to 3, characterized in that: The first lower arm resistor, the second upper arm resistor, the second lower arm resistor and the first upper arm resistor are arranged in a straight line.

7. The resistive pressure sensor according to any one of claims 1 to 3, characterized in that: The circuit board includes a plurality of pads, which are electrically connected to the high potential end and the low potential end of the DC power supply and the two voltage output ends and are outside the deformation area.

8. A touch panel with force sensing function, characterized in that: include: A bracket having a plurality of cantilevers, each of which has a connecting portion; A plurality of resistive pressure sensors as claimed in any one of claims 1 to 7, wherein the deformation zone of each of the resistive pressure sensors is located at or adjacent to the connecting portion of the cantilever; and A touch panel body is fixed on the bracket, and the plurality of resistive pressure sensors are located between the touch panel body and the bracket. The touch panel body comprises: A carrier having a surface; A plurality of sensing electrodes are formed on the surface of the carrier; A cover plate, covering the carrier plate and the plurality of sensing electrodes; as well as A controller is electrically connected to the plurality of sensing electrodes and the plurality of resistive pressure sensors.

9. The touch panel with force sensing function as claimed in claim 8, characterized in that: Each of the cantilevers has a free end opposite to the connecting portion; and The support is a metal plate, and a plurality of U-shaped through grooves are formed on the metal plate to form the plurality of cantilevers, and the plurality of cantilevers are respectively located at the four corners of the support.

10. The touch panel with force sensing function as claimed in claim 9, characterized in that: A vibration isolation pad is arranged between the free end of each cantilever and the touch panel body.

11. The touch panel with force sensing function as claimed in claim 10, characterized in that: The free ends of the multiple cantilevers face one of the short sides of the bracket that is closest to them.

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