Capacitive encoder and electronic equipment
By employing a capacitive structure in the encoder, utilizing the metal sheet on the rotating shaft and the electrode plate on the flexible circuit board to form capacitive detection, the problem of balancing encoder accuracy and cost is solved, achieving high-precision, low-cost angle detection and improving rotational flexibility.
Patent Information
- Application Number
- CN202520616973.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2026-02-17
- Estimated Expiration
- 2035-04-02
AI Technical Summary
Existing encoders have shortcomings in balancing accuracy and cost. Photoelectric encoders have low accuracy and high cost, while magnetoelectric encoders are susceptible to external magnetic interference.
Design a capacitive encoder by setting a metal sheet that does not require electrical connection on the rotating shaft, which together with the transmitting and receiving plates on the flexible circuit board forms a capacitive structure. The metal sheet and the plates are concentrically arranged, and the area changes as the rotating shaft rotates, using the capacitive signal to detect the angle.
It achieves high-precision angle detection, reduces costs, and the metal sheet can rotate more than 360 degrees flexibly, improving the encoder's detection flexibility.
Smart Images
Figure CN223925764U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of encoders, and in particular to a capacitive encoder and electronic device. Background Technology
[0002] An encoder is a sensor used to measure rotational angle or linear displacement. Its main function is to convert mechanical motion into electrical or digital signals, which are then fed back to the control system to provide position, speed, or angle information, thereby enabling precise control of electronic equipment.
[0003] Currently, encoders are divided into various types, such as photoelectric encoders and magnetoelectric encoders. Low-end photoelectric encoders have low accuracy, while high-end photoelectric encoders are very expensive, making it difficult to balance cost and accuracy in photoelectric encoders. Electromagnetic encoders are susceptible to external magnetic interference, affecting their accuracy. Therefore, the industry needs an encoder structure that balances accuracy and cost. Utility Model Content
[0004] The purpose of this utility model embodiment is to provide a capacitive encoder and electronic device. Based on a high-precision, low-cost capacitive encoder, a metal sheet that does not require electrical connection is set on the rotating shaft to form a capacitive structure with the transmitting and receiving plates on the circuit board. Since the metal sheet on the rotating shaft does not require electrical connection, it can rotate more than 360 degrees flexibly without restriction, thus improving the flexibility of encoder angle detection.
[0005] To address the aforementioned technical problems, embodiments of this utility model provide a capacitive encoder, comprising: a rotating shaft, a metal sheet rotating with the rotating shaft, a flexible circuit board (FPC) surrounding the rotating shaft and spaced apart from it, and a processor; the flexible circuit board (FPC) is provided with a transmitting electrode plate and a receiving electrode plate, both of which are concentrically opposite to the metal sheet, and the projection of the metal sheet toward the flexible circuit board (FPC) overlaps with both the transmitting and receiving electrode plates; as the metal sheet rotates with the rotating shaft, the relative area between the metal sheet and the receiving electrode plate changes; the processor is used to determine the rotation angle of the rotating shaft based on the capacitance signal generated by the capacitive structure formed by the transmitting electrode plate, the receiving electrode plate, and the metal sheet.
[0006] An embodiment of this utility model also provides an electronic device, including the above-described capacitive encoder.
[0007] Compared to existing technologies, this embodiment of the invention features a metal sheet on a rotating shaft that requires no electrical connection. This metal sheet, along with a transmitting electrode and a receiving electrode on a flexible circuit board surrounding the shaft, forms a capacitor structure. Both the transmitting and receiving electrodes are concentrically positioned opposite the metal sheet. As the metal sheet rotates with the shaft, the relative area between the metal sheet and the receiving electrode changes, causing a corresponding change in the capacitance signal generated by the capacitor structure, thus enabling encoder angle detection. This angle detection structure requires only a few electrodes, ensuring detection accuracy while reducing costs. Since the metal sheet on the shaft requires no electrical connection, it can rotate freely beyond 360 degrees without restriction, improving the flexibility of encoder angle detection.
[0008] In addition, the capacitive encoder also includes: a support member disposed on the rotating shaft; the support member is provided with a groove, and the metal sheet is fixed to the groove.
[0009] In addition, the emitting electrode is a ring electrode that is attached to the flexible circuit board FPC, and there are multiple receiving electrodes arranged sequentially in the rotation direction of the rotating shaft.
[0010] Furthermore, in any state, the projection of the metal sheet toward the flexible circuit board FPC overlaps with at least two receiving plates, and the relative area between the metal sheet and at least one of the receiving plates changes as the metal sheet rotates with the shaft.
[0011] In addition, the capacitive encoder also includes a grounding unit disposed between the transmitting plate and the receiving plate.
[0012] In addition, in the direction of the shaft core, the width of the grounding unit is smaller than the width of the emitting electrode.
[0013] In addition, during the rotation of the shaft, the area of the metal sheet facing the emitting electrode remains constant, and the area of the metal sheet facing the emitting electrode is greater than a preset threshold.
[0014] In addition, the capacitive encoder also includes: a housing; the flexible circuit board (FPC) is attached to the inner surface of the housing, and the flexible circuit board (FPC) and the housing have the same degree of curvature.
[0015] In addition, the capacitive encoder also includes: a bearing disposed on the rotating shaft; the bearing is used to support the rotating shaft and constrain the displacement of the rotating shaft in the radial or axial direction. Attached Figure Description
[0016] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.
[0017] Figure 1 This is an exploded view of the capacitive encoder according to an embodiment of this solution;
[0018] Figure 2 This is a schematic diagram of the flexible circuit board in the capacitive encoder according to an embodiment of this solution;
[0019] Figure 3 This is a schematic diagram of the unfolded structure of the flexible circuit board in the capacitive encoder according to an embodiment of this solution;
[0020] Figure 4 This is a schematic diagram of the unfolded structure of the flexible circuit board in the capacitive encoder according to an embodiment of this solution;
[0021] Figure 5 This is a diagram of the capacitor structure composed of the transmitting plate, the receiving plate, and the metal sheet in the capacitive encoder according to the embodiment of this solution;
[0022] Figure 6 This is a schematic diagram of the change in the capacitance signal generated by the capacitor in the capacitive encoder according to the embodiment of this solution;
[0023] Figure 7 This is a partial structural diagram of a capacitive encoder based on an embodiment of this solution;
[0024] Figure 8 This is a cross-sectional structural diagram of a capacitive encoder according to an embodiment of this solution;
[0025] Figure 9 This is a schematic diagram of the overall structure of the capacitive encoder according to an embodiment of this solution. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the various embodiments of this utility model will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of this utility model to enable readers to better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments.
[0027] The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of this utility model. The various embodiments can be combined with or referenced by each other without contradiction.
[0028] The embodiments of this utility model relate to a capacitive encoder, such as... Figure 1 As shown, it includes: a rotating shaft 1, a metal sheet 2 that rotates with the rotating shaft 1, a flexible printed circuit board (FPC) 3 that surrounds the rotating shaft 1 and is spaced apart from the rotating shaft 1, and a processor; as Figure 2 As shown, a flexible printed circuit board (FPC) 3 is provided with an emitting electrode 41 and a receiving electrode 42. The emitting electrode 41 and the receiving electrode 42 are both concentrically opposite to the metal sheet 2, and the projection of the metal sheet 2 toward the flexible printed circuit board (FPC) 3 overlaps with the emitting electrode 41 and the receiving electrode 42. When the metal sheet 2 rotates with the rotating shaft 1, the relative area between the metal sheet 2 and the receiving electrode 42 changes. The processor is used to determine the rotation angle of the rotating shaft 1 based on the capacitance signal generated by the capacitor structure formed by the emitting electrode 41, the receiving electrode 42 and the metal sheet 2.
[0029] Compared to existing technologies, this embodiment of the invention features a metal sheet on a rotating shaft that requires no electrical connection. This metal sheet, along with a transmitting electrode and a receiving electrode on a flexible circuit board surrounding the shaft, forms a capacitor structure. Both the transmitting and receiving electrodes are concentrically positioned opposite the metal sheet. As the metal sheet rotates with the shaft, the relative area between the metal sheet and the receiving electrode changes, causing a corresponding change in the capacitance signal generated by the capacitor structure, thus enabling encoder angle detection. This angle detection structure requires only a few electrodes, ensuring detection accuracy while reducing costs. Since the metal sheet on the shaft requires no electrical connection, it can rotate freely beyond 360 degrees without restriction, improving the flexibility of encoder angle detection.
[0030] The capacitor formed by metal plate 2, emitting plate 41, and receiving plate 42 can be considered as the sum of the capacitor formed by emitting plate 41 and metal plate 2, and the capacitor formed by metal plate 2 and receiving plate 42. The capacitance of each capacitor is calculated using the physical formula for a parallel plate capacitor: C = εS / 4πkd; where ε represents the dielectric constant of the medium, determined by the medium between the plates, such as air or water; and k represents the electrostatic constant, also known as the Coulomb constant, which indicates that the force between two point charges, each with a charge of 1C, separated by a distance of 1m in a vacuum is 8.987551 × 10⁹ N, i.e., k = 8.987551 × 10⁹ N·m. 2 / C; S represents the area (projected area) of the two plates facing each other; d represents the vertical distance between the two plates. Therefore, when the area of the metal sheet 2 facing the emitting plate 41 remains constant, the capacitance signal changes according to the area of the metal sheet 2 facing the receiving plate 42. Since the change in the area of the metal sheet 2 facing the receiving plate 42 is related to the rotation angle of the shaft 1, the rotation angle of the shaft 1 can be determined from the change in the capacitance signal. The area of the metal sheet facing the emitting plate is greater than a preset threshold to ensure the strength of the capacitance signal generated by the capacitor assembly and improve the sensitivity of angle detection.
[0031] like Figure 2 As shown, the emitting electrode 41 is a circular electrode plate bonded to the flexible printed circuit board (FPC), and there are multiple receiving electrodes 42 arranged sequentially in the rotation direction of the shaft. The unfolded structure of the flexible printed circuit board (FPC) is as follows. Figure 3 As shown, there are two transmitting plates Tx, located on either side of the receiving plate 42. The transmitting plates Tx can isolate the influence of external interference signals on the receiving plates Rx. The receiving plates (Rx1, Rx2, Rx3, Rx4) are arranged sequentially along the bending direction of the flexible printed circuit board (FPC), and multiple receiving plates can be of the same size. The capacitive encoder also includes a grounding unit 43 disposed between the transmitting plate 41 and the receiving plate 42 to isolate the direct coupling between the transmitting and receiving plates. In the axial direction of the rotating shaft 1, the width of the grounding unit 43 is smaller than the width of the transmitting plate 41.
[0032] like Figure 4 As shown, in any state, the projection of the metal sheet 2 toward the flexible circuit board (FPC) overlaps with at least two receiving plates, and the relative area between the metal sheet 2 and at least one receiving plate changes as the metal sheet 2 rotates with the shaft. The rotation angle of the shaft can be determined by the change in the capacitance signal generated by each capacitor assembly formed by the metal sheet 2 and the multiple receiving plates Rx.
[0033] like Figure 5 The diagram shows a capacitor structure formed by the emitting plate 41, the receiving plate 42, and the metal sheet 2. Electric field lines are emitted from the emitting plate 41 at both ends, conducted through the metal sheet 2, and transmitted to the receiving plate 42.
[0034] Taking the setting of four receiving plates as an example, the method for detecting the rotation angle of the shaft will be explained in detail:
[0035] Assume that the capacitance formed by the transmitting plate Tx and the receiving plate Rx1 is C1, the capacitance formed by the transmitting plate Tx and the receiving plate Rx2 is C2, the capacitance formed by the transmitting plate Tx and the receiving plate Rx3 is C3, and the capacitance formed by the transmitting plate Tx and the receiving plate Rx4 is C4. When the metal plate 2 rotates counterclockwise one revolution with the shaft, the capacitance values generated by each capacitor are as follows: Figure 6 As shown, when the shaft rotates to any angle, the capacitance signals generated by at least two capacitors will change. Based on the changes in the capacitance signals of different capacitors, the rotation angle of the shaft can be determined.
[0036] Different numbers of receiving plates can be set for different types of encoders. For example, for absolute encoders, at least three receiving plates Rx are required to detect absolute position. For incremental encoders, only two receiving plates Rx are needed to determine the direction of rotation and calculate the relative displacement.
[0037] In addition, such as Figure 7 As shown, the capacitive encoder also includes: a bearing 7 mounted on the rotating shaft 1; the bearing 7 supports the rotating shaft 1 and constrains the radial or axial displacement of the rotating shaft 1. The capacitive encoder also includes: a support member 6 mounted on the rotating shaft 1; the support member 6 has a groove, and the metal sheet 2 is fixed in the groove. Alternatively, the metal sheet 2 can be directly formed on the surface of the support member 6 using laser direct forming (LDS) technology. By using the support member 6 as a carrier for the metal sheet 2, the distance between the metal sheet 2 and the receiving and transmitting electrodes can be reduced, thereby increasing the strength of the capacitive detection signal and improving the sensitivity of the detection structure. Furthermore, the machining of the metal sheet 2 can avoid affecting the rotating shaft's accuracy.
[0038] like Figure 8 The diagram shows a cross-sectional view of the capacitive encoder. The bearings 7 are symmetrically arranged relative to the shaft 1, ensuring a more balanced force distribution on the shaft. The capacitive encoder also includes a housing 5; a flexible printed circuit board (FPC) 3 is attached to the inner surface of the housing 5, with the FPC and housing exhibiting the same degree of curvature. A base 8 is located at the bottom of the entire capacitive encoder.
[0039] like Figure 9 The diagram shows the overall appearance and structure of the capacitive encoder. The outer casing 5 is a cylindrical hollow structure, containing a flexible circuit board, a rotating shaft, and other components arranged concentrically. A base 8 is located at the bottom of the outer casing 5 to prevent external dust from entering from the bottom and affecting the rotation of the rotating shaft.
[0040] Another feasible embodiment of this utility model relates to an electronic device, including the capacitive encoder as described above.
[0041] Compared with related technologies, the electronic device provided in this embodiment of the present invention is equipped with the capacitive encoder provided in the aforementioned embodiments. Therefore, it also has the technical effects provided in the aforementioned embodiments, and will not be described in detail here.
[0042] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present invention.
Claims
1. A capacitive encoder characterized in that, The capacitor encoder comprises a rotating shaft, a metal sheet rotating with the rotating shaft, a flexible printed circuit board (FPC) surrounding the rotating shaft and being spaced apart from the rotating shaft, and a processor. The FPC is provided with an emitter plate and a receiver plate, the emitter plate and the receiver plate are arranged in a concentric manner opposite to the metal sheet, and the projection of the metal sheet towards the FPC overlaps with the emitter plate and the receiver plate. When the metal sheet rotates with the rotating shaft, the relative area of the metal sheet and the receiver plate changes. The processor is configured to determine the rotation angle of the rotating shaft according to the capacitance signal generated by the capacitor structure formed by the emitter plate, the receiver plate and the metal sheet.
2. The capacitive encoder of claim 1, wherein, Further comprising: a support arranged on the rotating shaft; the support is provided with a groove, and the metal sheet is fixed in the groove.
3. The capacitive encoder of claim 1, wherein, The emitter plate is a circular ring plate attached to the FPC, and the number of receiver plates is multiple, and the multiple receiver plates are arranged in sequence in the rotation direction of the rotating shaft.
4. The capacitive encoder of claim 3, wherein, In any state, the projection of the metal sheet towards the FPC overlaps with at least two receiver plates, and when the metal sheet rotates with the rotating shaft, the relative area of the metal sheet and at least one receiver plate changes.
5. The capacitive encoder of claim 3, wherein, Further comprising: a grounding unit arranged between the emitter plate and the receiver plate.
6. The capacitive encoder of claim 5, wherein, In the axial direction of the rotating shaft, the setting width of the grounding unit is smaller than the setting width of the emitter plate.
7. The capacitive encoder of claim 1, wherein, During the rotation of the rotating shaft, the opposite area of the metal sheet and the emitter plate is always unchanged, and the opposite area of the metal sheet and the emitter plate is greater than a preset threshold.
8. The capacitive encoder of claim 1, wherein, Further comprising: a housing; the FPC is attached to the inner surface of the housing, and the FPC has the same bending degree as the housing.
9. Capacitive encoder according to any one of claims 1 to 8, characterized in that Further comprising: a bearing arranged on the rotating shaft; the bearing is used to support the rotating shaft and constrain the displacement of the rotating shaft in the radial direction or the axial direction.
10. An electronic device, comprising: The capacitor encoder comprises a rotating shaft, a metal sheet rotating with the rotating shaft, a flexible printed circuit board (FPC) surrounding the rotating shaft and being spaced apart from the rotating shaft, and a processor. The FPC is provided with an emitter plate and a receiver plate, the emitter plate and the receiver plate are arranged in a concentric manner opposite to the metal sheet, and the projection of the metal sheet towards the FPC overlaps with the emitter plate and the receiver plate. When the metal sheet rotates with the rotating shaft, the relative area of the metal sheet and the receiver plate changes. The processor is configured to determine the rotation angle of the rotating shaft according to the capacitance signal generated by the capacitor structure formed by the emitter plate, the receiver plate and the metal sheet.