Force-sensitive touchpad and methods to improve its force sensitivity

Abstract

This invention discloses a touchpad with force sensing function, comprising a force sensing layer and a shielding layer stacked together. The force sensing layer has multiple force sensing electrodes, and the shielding layer has at least one conductive sheet corresponding to and covering the force sensing electrodes. The force sensing electrodes and the conductive sheet receive sensing signals of the same phase to reduce the basic capacitance of the force sensing electrodes to ground. When an object applies pressure to the touchpad, the capacitance sensed by the force sensing electrodes will have a significant change compared to the basic capacitance to ground, thus presenting a subtle change in force. Since the basic capacitance to ground occupies less of the internal capacitance capacity of the touchpad, the allowable capacitance sensed force is relatively large, thus also presenting a larger change in force. Therefore, this invention can improve force sensitivity for both small and large forces.

Description

Technical Field

[0001] This invention relates to a touchpad, and more particularly to a touchpad with force sensing functionality. Background Technology

[0002] As touchpads offer increasingly more functions, many touchpads have added force sensing functionality in addition to the original touch sensing function. The touchpad has a touch electrode layer and a force sensing layer. The force sensing layer has multiple force sensing electrodes. When working, an excitation signal is given to the force sensing electrodes. When an object is operated on the touchpad, the excitation signal will cause the force sensing electrodes and the corresponding ground line to generate a pair of ground base capacitances. The difference between the corresponding capacitance values ​​generated by each force sensing electrode when the object is pressed down and the pair of ground base capacitances is used as the capacitance change of the force sensing, and then the downward pressure of the object is calculated.

[0003] However, the ground capacitance has a certain capacitance value. When an object is pressed down, if the capacitance value generated by the applied force is too different from the aforementioned ground capacitance, it is difficult to present subtle changes in applied force. Therefore, the existing touch panel is less able to accurately present the force sensitivity of subtle changes in applied force.

[0004] Furthermore, touchpads have limitations on their internal capacitance, meaning there is an upper limit to the capacitance sensing value that a touchpad can generate. Although the internal capacitance can be increased by upgrading components, this would also increase manufacturing costs. In addition, the base capacitor to ground has a certain capacitance value, which limits the amount of capacitance sensing change that can be allowed. When a large amount of capacitance sensing change occurs, the upper limit may prevent the actual sensing change from being accurately represented. Therefore, existing touchpads are less likely to accurately represent the force sensitivity of large applied forces. Summary of the Invention

[0005] In view of this, the present invention addresses the shortcomings of insufficient force sensitivity in the prior art in order to improve the force sensitivity of the touchpad.

[0006] To achieve the aforementioned objective, the present invention provides a touchpad with force sensing functionality, comprising: a support; a force sensing layer disposed on the support, the force sensing layer having a plurality of force sensing electrodes; a shielding layer disposed on the force sensing layer, the shielding layer having at least one conductive sheet, the conductive sheet covering each of the force sensing electrodes, the conductive sheet being insulated from the force sensing electrodes; a touch sensing layer disposed on the shielding layer; and a protective layer disposed on the touch sensing layer; wherein the force sensing electrodes receive a first sensing signal to generate force sensing information, and the conductive sheet receives a second sensing signal, the second sensing signal being in phase with the first sensing signal.

[0007] On the other hand, the present invention also provides a method for improving the force sensitivity of a touchpad, wherein a force sensing electrode receives a first sensing signal to generate force sensing information, and a conductive sheet receives a second sensing signal, wherein the second sensing signal is in phase with the first sensing signal.

[0008] The advantage of this invention is that by covering the force-sensing electrode with a conductive sheet and providing a signal in phase with the conductive sheet and the force-sensing electrode, the potential difference between the force-sensing electrode and the conductive sheet is reduced, thereby reducing the base capacitance of the force-sensing electrode. This increases the change in force-sensing capacitance and base capacitance when an object comes into contact, thus improving the sensitivity to subtle downward pressure. At the same time, it also increases the difference between the internal capacitance carrying value and the base capacitance to ground, allowing for larger force-sensing changes. Therefore, this invention effectively improves the force sensitivity of the touchpad.

[0009] To provide a better understanding of the above and other aspects of the present invention, specific embodiments are described below in conjunction with the accompanying drawings, but these are not intended to limit the scope of the invention. Attached Figure Description

[0010] Figure 1 This is a side cross-sectional view of the touch panel of the present invention;

[0011] Figure 2 This is an exploded perspective view of the touch sensing component of the present invention;

[0012] Figure 3 This is a side cross-sectional view of the touch sensing component of the present invention;

[0013] Figure 4A This is a top view of the shielding layer of the present invention;

[0014] Figure 4B This is a top view of another embodiment of the shielding layer of the present invention;

[0015] Figure 5 The waveforms of the first and second sensing signals of the present invention are shown.

[0016] Figure 6 The waveform diagrams of the first and second sensing signals are shown in another embodiment of the present invention.

[0017] In the attached figures, the following labels are used:

[0018] 10: Bracket 11: Insulating component

[0019] 20: Touch sensing component 21: Force sensing layer

[0020] 211: Force sensing electrode; 22, 22A: Shielding layer

[0021] 220: Shielding circuit; 221, 221A: Conductive sheet

[0022] 222: Conductive wire; 223: Mesh.

[0023] 23: Touch sensing layer 231: Driving electrode layer

[0024] 232: Sensing electrode layer; 30: Protective layer

[0025] 40: Motor 50: Housing

[0026] 51: Spacing unit S 11 S 12 First sensing signal

[0027] S 21 S 22 Second sensing signal Detailed Implementation

[0028] The following description, in conjunction with the accompanying drawings and embodiments of the invention, further illustrates the technical means employed by the invention to achieve its intended purpose. The drawings are simplified for illustrative purposes only, and the structure or method of the invention is explained by describing the components and relationships between them. Therefore, the components shown in the drawings are not presented in actual quantity, shape, size, or proportion; the size or proportion has been enlarged or simplified to provide a better illustration. Actual quantity, shape, or proportion has been selectively designed and configured, and the detailed component layout may be more complex.

[0029] Please see Figure 1 As shown, the touch panel of the present invention includes a bracket 10, a touch sensing component 20, a protective layer 30 and a motor 40. The touch sensing component 20 is disposed between the bracket 10 and the protective layer 30, and the motor 40 is disposed on the bottom surface of the bracket 10.

[0030] Please see Figure 1 and Figure 2As shown, the touch sensing component 20 includes a force sensing layer 21, a shielding layer 22, and a touch sensing layer 23. The shielding layer 22 is disposed between the force sensing layer 21 and the touch sensing layer 23. The force sensing layer 21 is disposed on the bracket 10, and the protective layer 30 is disposed on the touch sensing layer 23. In one embodiment, an insulating member 11 is provided between the bracket 10 and the touch sensing component 20 to insulate the touch sensing component 20 from the bracket 10. In one embodiment, the touchpad is embedded in a housing 50. The surface of the housing 50 is provided with a plurality of spacer units 51, each of which abuts against the outer periphery of the bracket 10, thereby maintaining the relative distance between the outer periphery of the bracket 10 and the upper surface of the housing 50.

[0031] Please see Figure 2 and Figure 3 As shown, a plurality of force sensing electrodes 211 are disposed on the force sensing layer 21. In one embodiment, the force sensing electrodes 211 are respectively disposed at the four corners of the force sensing layer 21. The force sensing electrodes 211 are electrically connected to the remaining circuits disposed on the force sensing layer 21 through lines.

[0032] Please see Figures 2 to 4A As shown, the shielding layer 22 is disposed on the force-sensing layer 21, and has a plurality of conductive sheets 221 and a shielding circuit 220. Each conductive sheet 221 respectively covers one of the force-sensing electrodes 211, and the conductive sheets 221 and the force-sensing electrodes 211 are insulated from each other. In one embodiment, the number of conductive sheets 221 is equal to the number of force-sensing electrodes 211. In one embodiment, the conductive sheet 221 is a sheet covered with conductive material, such as copper sheet, silver sheet or gold foil. In one embodiment, each conductive sheet 221 is composed of several crisscrossing conductive lines 222 and a plurality of meshes 223, wherein the meshes 223 occupy less than 50% of the area of ​​the conductive sheet 221. The shielding circuit 220 is insulated from the conductive sheet 221. The shielding circuit 220 is used to ground or connect to a fixed potential and is located between the touch sensing layer 23 and the force sensing layer 21. It is insulated from both the touch sensing layer 23 and the force sensing layer 21 to avoid mutual interference between the touch sensing layer 23 and the force sensing layer 21.

[0033] Please see Figure 2 As shown, the touch sensing layer 23 is disposed on the shielding layer 22 and includes a driving electrode layer 231 and a sensing electrode layer 232. By giving a driving signal to the driving electrode layer 231 and receiving a capacitive sensing signal through the sensing electrode layer 232, the relative position of the object in contact with the protective layer 30 on the touchpad can be determined.

[0034] Please see Figure 2 , Figure 3 and Figure 5 As shown, when the touchpad of the present invention is working, a first sensing signal S is provided via a sensing circuit of the touchpad. 11 The force sensing electrode 211 is given an excitation signal, and the sensing signal coupled to the force sensing electrode 211 is received. When an object contacts the protective layer 30 and downward pressure is applied, the central part of the support 10 will sink due to the downward pressure, but the outer periphery of the support 10 will not sink due to the support of the spacer unit 51. As a result, the distance between the force sensing layer 21 and the outer periphery of the support 10 will shorten. At this time, the difference between the capacitance sensing value generated by the force sensing electrode 211 and the base capacitance can be used as the capacitance sensing change of the force, thereby calculating the downward pressure on the object. At the same time, the sensing circuit also provides a second sensing signal S. 21 The first sensing signal S is given to the conductive sheet 221. 11 With the second sensing signal S 21 Since the signals are in phase, the initial ground capacitance of the force-sensing electrode 211 is reduced. When the ground capacitance is reduced, when comparing the capacitance value generated by the force-sensing electrode 211 with the ground capacitance, if the value of the ground capacitance (the denominator) decreases, even if the change in the capacitance value generated by the force-sensing electrode 211 (the numerator) is the same, the relative ratio between the two can be significantly increased. This makes the force-sensing electrode 211 more responsive to subtle external forces, increasing force sensitivity. Furthermore, with the ground capacitance reduced, the internal capacitance of the touchpad occupied by the ground capacitance is also reduced, thus giving the touchpad more internal capacitance capacity to handle capacitance changes caused by external forces. Furthermore, when the conductive sheet 221 has mesh 223, the larger the area occupied by the mesh 223, the smaller the reduction in the basic capacitance to ground. That is, the fewer the mesh 223, the more the basic capacitance to ground is reduced. The user can determine the basic capacitance to ground by adjusting the ratio of the mesh 223 to the conductive sheet 221.

[0035] In addition to the first sensing signal S 11 With the second sensing signal S 21 In addition to being in-phase signals, the first sensing signal S can be further defined. 11 With the second sensing signal S 21 The amplitude ratio can be between 1 and 2. In one embodiment (e.g.) Figure 5 As shown), the first sensing signal S 11 With the second sensing signal S 21 The amplitudes are exactly the same; in another embodiment (such as...) Figure 6As shown), the first sensing signal S 12 With the second sensing signal S 22 The amplitude ratio is 2. In one embodiment, the first sensing signal S 11 With the second sensing signal S 21 They have the same period.

[0036] In summary, since the ground capacitance is the fundamental value used for comparison with the sensed capacitance value, a smaller ground capacitance makes it easier to discern the difference between the sensed capacitance value and the ground capacitance, thus reflecting subtle changes in force. Furthermore, a smaller ground capacitance occupies a smaller proportion of the touchpad's internal capacitance, allowing for larger capacitance changes and providing a wider force sensing range. Therefore, the touchpad of this invention significantly improves both the recognition of subtle forces and the measurement tolerance of larger applied forces.

[0037] Please see Figure 4B As shown, in another embodiment, the shielding layer 22A has a conductive sheet 221A, which is disposed over most of the area of ​​the shielding layer 22A and covers the force sensing electrode 211 and corresponds to the touch sensing layer 23. The touch sensing layer 23 and the force sensing layer 21 operate in a time-sharing manner, and the shielding layer 22A provides a shielding effect accordingly. When the touch sensing layer 23 is working to perform touch sensing, the conductive sheet 221A of the shielding layer 22A is grounded or connected to a fixed potential to avoid mutual interference between the touch sensing layer 23 and the force sensing layer 21; when the force sensing layer 21 is working to perform force sensing, the conductive sheet 221A of the shielding layer 22A receives the second sensing signal S. 21 That is, the first sensing signal S received by the force sensing electrode 211. 11 The signals are in phase, thus achieving the aforementioned effect of improving force sensitivity.

[0038] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above by way of embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the protection scope of the appended claims of the present invention.

Claims

1. A touchpad with force sensing function, characterized in that, It includes: A support frame; A force sensing layer is disposed on the support, and the force sensing layer is provided with multiple force sensing electrodes, which are respectively disposed at the four corners of the force sensing layer; A shielding layer is disposed on the force sensing layer. The shielding layer is provided with multiple conductive sheets and a shielding circuit. The number of conductive sheets corresponds to the number of force sensing electrodes. The conductive sheets are respectively aligned and cover one side of each force sensing electrode, and the conductive sheets are insulated from the force sensing electrodes. The shielding circuit is insulated from the conductive sheets. The shielding circuit is grounded or connected to a fixed potential. The shielding circuit is located between the force sensing layer and the touch sensing layer, and is insulated from both the touch sensing layer and the force sensing layer. A touch-sensing layer is disposed on the shielding layer; and A protective layer is disposed on the touch sensing layer; The force-sensing electrode receives a first sensing signal for force sensing, and the conductive sheet receives a second sensing signal, wherein the second sensing signal is in phase with the first sensing signal.

2. The touchpad with force sensing function as described in claim 1, characterized in that, The second sensing signal has the same period as the first sensing signal.

3. The touchpad with force sensing function as described in claim 1, characterized in that, Each of the conductive sheets has multiple mesh holes.

4. The touchpad with force sensing function as described in claim 3, characterized in that, The mesh area of ​​each conductive sheet is less than 50% of its area.

5. A touchpad with force sensing function as described in any one of claims 1 to 4, characterized in that, The conductive sheet is a copper sheet, a silver sheet, or a gold foil.

6. The touchpad with force sensing function as described in any one of claims 1 to 4, characterized in that, The amplitude ratio of the first sensing signal to the amplitude of the second sensing signal is 1 to 2.

7. The touchpad with force sensing function as described in any one of claims 1 to 4, characterized in that, The conductive sheet is disposed in most of the shielding layer and covers the force sensing electrode and corresponds to the touch sensing layer.

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