Miniature inductive absolute angular displacement sensor

Abstract

The present invention discloses a small inductive absolute angular displacement sensor, comprising a corresponding inductive circuit board and a code disk. The inductive circuit board is provided with an external excitation coil, an internal excitation coil, multiple inductive coils, and a single inductive coil. Multiple groups of multiple inductive coils and multiple elliptical inductive coils overlap and are all located between the external excitation coil and the internal excitation coil. The code disk is provided with multiple encoding plates and a single encoding plate. The multiple encoding plates are arranged in a semicircular shape on the circular surface of the code disk. The semicircular single encoding plate is arranged on the circular surface of the code disk and encloses the multiple encoding plates to form a single circular ring. The present invention significantly reduces the diameter of the inductive circuit board and the diameter of the code disk. Compared with the diameter of the inductive circuit board and code disk of a traditional inductive absolute angular displacement sensor, the diameter can be reduced by up to half while still achieving absolute angular positioning. This significantly reduces the diameter and volume of the sensor while completely unaffecting the accuracy of angular displacement detection.

Description

Technical Field

[0001] This invention relates to an angular displacement sensor, and more particularly to a small inductive absolute angular displacement sensor. Background Technology

[0002] High-reliability angular displacement sensors (or potentiometers) mainly include magnetic, RVDT, wire-wound, or conductive plastic types. Among them, magnetic angular displacement sensors are widely used in the market due to their low cost, high accuracy, long lifespan, and strong environmental adaptability. However, the accuracy of magnetic angular displacement sensors is limited by special ring-shaped coded magnets, making them unsuitable for applications requiring low cost, small size, and high accuracy. Furthermore, magnetic angular displacement sensors are generally used for incremental angular displacement detection; achieving absolute angular displacement detection would significantly increase costs. Meanwhile, other angular displacement sensors based on the aforementioned principles cannot match the high lifespan, high accuracy, and strong environmental adaptability of magnetic angular displacement sensors.

[0003] In recent years, with the increasing maturity of PCB manufacturing processes, inductive angular displacement sensors based on the principle of electromagnetic induction have gradually gained attention in the market due to their high precision, high resolution, high reliability, and relatively low cost. For example, in the prior art, the invention application with application number "200410043380.3" entitled "Inductive Rotation Angle Sensor and Automatic Synchronous Transmitter Equipped Therewith" discloses the basic principle and components of such a sensor; the invention patent with patent number "ZL200980113191.X" entitled "Inductive Rotation Angle Sensor and Method for Operating Inductive Rotation Angle Sensor" proposes a new arrangement of excitation coil and indexing element; the invention patent with patent number "201811436354.5" entitled "Position Encoder" innovates the anti-interference design of the inductive sensor based on the above-mentioned "Inductive Rotation Angle Sensor and Automatic Synchronous Transmitter Equipped Therewith" and proposes a new arrangement scheme for its stator and rotor modules.

[0004] Although the above technologies have made new designs for the excitation coil, induction coil circuit board and code disk (scale element, stator, indexing element) of inductive angular displacement sensor (or potentiometer), none of them have solved the problem of the large diameter of inductive angular displacement sensor; in addition, no solution has been proposed for dynamically calibrating the spacing between the excitation coil, induction coil circuit board and code disk, which will affect the sensing accuracy, and the optimal spacing is different for each inductive angular displacement sensor.

[0005] like Figures 1-3As shown, the structure of the sensing circuit board 1 and the code disk 8 of the latest traditional inductive angular displacement sensor is as follows: The sensing circuit board 1 is a multi-layer PCB board and is provided with multiple sets of multi-induction coils 3 and multiple sets of single induction coils 5. Each set of multi-induction coils 3 is formed by connecting multiple sinusoidal wires end to end to form a circle. Figure 1 and Figure 3 The diagram shows four sets of multi-induction coils 3, each set having a phase interval of Π / 4. A single induction coil 5 is formed by a segment of elliptical closed wire. Figure 2 and Figure 3 The image shows two single induction coils 5 that intersect each other perpendicularly. Figure 1 and Figure 3 The diagram also shows a first excitation coil 2, a second excitation coil 4, and a third excitation coil 7 arranged sequentially from the outside in, as well as a central through hole 6 on the induction circuit board 1; the code disk 8 is a PCB board, and the code disk 8 is provided with a set of multi-encoding chips 9 and a single-encoding chip 11. The multi-encoding chips 9 are composed of multiple encoding chips (generally copper sheets) arranged in a circumferential direction. Figure 2 The multi-coded chip 9 is a circle, and the single-coded chip 11 is composed of a semi-circular coded chip (copper sheet). Figure 2 The image also shows the center through-hole 10 of the code disk 8.

[0006] The aforementioned traditional inductive angular displacement sensor not only has high detection accuracy but also can detect the absolute value of angular displacement. Its principle is as follows: Figure 3 As shown, the induction circuit board 1 and the code disk 8 are parallel and correspond to each other. The multi-encoding chip 9 corresponds to four sets of multi-induction coils 3, and the single-encoding chip 11 corresponds to two single-induction coils 5. The code disk 8 rotates 360°, and the electromotive force of the two single-induction coils 5 changes in one cycle. The electromotive force change curve corresponding to each single-induction coil 5 is V-shaped, as shown in the figure. Figure 4 As shown, since the two single induction coils 5 intersect each other perpendicularly, the electromotive force change curves corresponding to the two single induction coils 5 are two "V" shapes in opposite directions. By combining the electromotive force changes corresponding to the two single induction coils 5 and the electromotive force changes of the multiple induction coils 3, the absolute angular position of the code disk 8 can be determined, that is, the absolute angular displacement value of the rotating shaft can be detected.

[0007] The shortcomings of the aforementioned traditional inductive angular displacement sensor are as follows: four sets of multi-coil induction coils 3 and two single-coil induction coils 5 are respectively located on the outer and inner rings of the induction circuit board 1, requiring a total of three excitation coils (outer, middle, and inner). The multi-encoding chip 9 and single-encoding chip 11 are respectively located on the outer and inner rings of the code disk 8. The diameters of the induction circuit board 1 and the code disk 8 are relatively large, and due to the limitations of this structure, it is difficult to reduce the size further. This results in a relatively large diameter and volume of the inductive angular displacement sensor, which cannot meet the increasing demand for smaller-volume applications. In addition, the induction circuit board 1 and the code disk 8 of the traditional inductive angular displacement sensor are fixedly installed inside the housing and on the rotating shaft, respectively. The distance between the induction circuit board 1 and the code disk 8 cannot be adjusted, which affects the sensing accuracy. Moreover, the optimal distance for each inductive angular displacement sensor is different, which reduces the detection accuracy of the inductive angular displacement sensor in specific application scenarios. Summary of the Invention

[0008] The purpose of this invention is to provide a small inductive absolute angular displacement sensor that can significantly reduce the diameter and volume in order to solve the above-mentioned problems.

[0009] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0010] A small inductive absolute angular displacement sensor includes a corresponding inductive circuit board and a code disk. The inductive circuit board is provided with an outer excitation coil, an inner excitation coil, multiple inductive coils and a single inductive coil. The inner excitation coil is located inside the outer excitation coil. The central through hole of the inductive circuit board is located inside the inner excitation coil. Multiple sets of multiple inductive coils and multiple elliptical single inductive coils overlap each other and are all located between the outer excitation coil and the inner excitation coil. The code disk is provided with multiple coding pieces and single coding pieces. The multiple coding pieces are semi-circularly arranged on the annular surface of the code disk, and the semi-circular single coding pieces are arranged on the annular surface of the code disk and together with the multiple coding pieces form the same annulus.

[0011] Preferably, to facilitate the arrangement of multiple induction coils, single induction coils, external excitation coils, internal excitation coils, shielding layers, and circuits on the induction circuit board, and to facilitate the arrangement of multiple coding chips on the code disk, the induction circuit board includes a first PCB board, a second PCB board, a third PCB board, a fourth PCB board, a fifth PCB board, and a sixth PCB board that overlap each other and are arranged sequentially from top to bottom. The four sets of multiple induction coils are respectively arranged on the first PCB board and the second PCB board. The major axes of the two single induction coils are perpendicular to each other and their centers overlap each other. The two single induction coils, the external excitation coil, and the internal excitation coil are respectively arranged on the third PCB board and the fourth PCB board. The fifth PCB board is provided with a shielding layer, and the sixth PCB board is provided with circuits. The multiple coding chips are composed of eight coding chips arranged in a semi-circle.

[0012] Preferably, to achieve rapid adjustment of the distance between the sensing circuit board and the code disk, the small inductive absolute angular displacement sensor further includes a housing, a hollow rotating shaft, a lifting adjustment cylinder, and an adjustment drive ring. The hollow rotating shaft is vertical, passing through a vertical through-hole in the housing. The hollow rotating shaft is connected to the upper and lower parts of the housing via a first bearing and a second bearing, respectively. The code disk is placed in the upper part of the housing, fitted onto the hollow rotating shaft through its central through-hole and fixedly connected. The sensing circuit board is placed in the housing below the code disk. The hollow rotating shaft passes through the central through-hole of the sensing circuit board. The diameter of the upper section of the lifting adjustment cylinder is larger than the diameter of the lower section. The upper section of the lifting adjustment cylinder is connected to the outer periphery of the sensing circuit board. The lower section of the lifting adjustment cylinder has external threads on its outer wall. The bottom of the housing has an upwardly protruding outer shell cylinder with internal threads on its inner wall. The lower section of the lifting adjustment cylinder is placed under the second bearing. The outer wall of the housing is threadedly connected to the inner wall of the outer shell cylinder. The outer bottom surface of the housing is provided with an annular housing groove. The bottom of the housing groove is provided with at least two arc-shaped housing through holes and at least two housing screw holes that are evenly distributed along the circumferential direction. The annular adjustment drive ring is placed in the housing groove. The upper part of the adjustment drive ring is provided with at least two drive protrusions that are evenly distributed along the circumferential direction and protrude upwards. The multiple drive protrusions pass through the multiple arc-shaped housing through holes corresponding to each other. The lifting adjustment cylinder is provided with vertical drive blind holes at positions corresponding to the multiple drive protrusions. The upper sections of the multiple drive protrusions are placed in the multiple drive blind holes. The adjustment drive ring is provided with at least two arc-shaped drive ring through holes that are evenly distributed along the circumferential direction. Multiple screws pass through the multiple arc-shaped drive ring through holes from bottom to top and are connected to the multiple housing screw holes corresponding to each other. The lower surface of the adjustment drive ring is provided with at least two rotation blind holes that are evenly distributed along the circumferential direction.

[0013] Preferably, for ease of assembly, the housing includes a first housing and a second housing connected to each other, with the first housing located above the second housing, and the housing cylinder and the housing recess both located on the second housing.

[0014] Preferably, in order to facilitate reliable driving and to facilitate reliable assembly of the adjusting drive ring, the housing and the lifting adjusting cylinder, there are two of each of the arc-shaped housing through hole, the driving protrusion, the driving blind hole and the rotating blind hole, and four of each of the screws, the arc-shaped drive ring through hole and the housing screw hole.

[0015] Preferably, in order to make the bottom of the sensor neat and aesthetically pleasing and easy to use, the vertical thickness of the adjustment drive ring is the same as the vertical depth of the recess in the outer casing, and the lower wall of the arc-shaped drive ring through hole is provided with a step, and the corresponding screw nut is placed in the step.

[0016] Preferably, in order to facilitate stable installation of the code disk, a protruding rotating ring is provided on the hollow rotating shaft at a position corresponding to the code disk, and the code disk is fixedly connected to the rotating ring by connecting screws.

[0017] The beneficial effects of this invention are as follows:

[0018] This invention significantly reduces the diameter of the sensing circuit board by placing multiple and single induction coils on the sensing circuit board within an overlapping annular region, while simultaneously reducing one set of excitation coils. Furthermore, by placing single and multiple encoder chips together on the same annular ring of the code disk, the diameter of the code disk is significantly reduced. Compared to the diameter of the sensing circuit board and code disk of traditional inductive absolute angular displacement sensors, the diameter can be reduced by up to half while still achieving absolute angular positioning, thus significantly reducing the sensor's diameter and volume. Simultaneously, since the induced electromotive force within the induction coils is typically on the order of a few mV, the interference between them is minimal. Moreover, the resolution of the inductive angular displacement sensor is primarily determined by the number of sinusoidal wires in the multiple induction coils, so it does not affect the angular displacement detection accuracy at all. Furthermore, by incorporating a lifting adjustment cylinder and an adjustment drive ring within the housing, and cleverly designing an arc-shaped housing through hole, a drive protrusion, a drive blind hole, an arc-shaped drive ring through hole, a screw housing screw hole, and a rotation blind hole, this invention enables the direct external adjustment of the distance between the sensing circuit board and the code disk by rotating the adjustment drive ring with a tool. This facilitates adjusting the distance between the sensing circuit board and the code disk of the inductive angular displacement sensor to the optimal distance according to the actual application scenario, thereby improving the detection accuracy of the inductive angular displacement sensor in specific application scenarios. Attached Figure Description

[0019] Figure 1 This is a top view of the sensing circuit board of a traditional inductive absolute angular displacement sensor.

[0020] Figure 2 This is a schematic diagram of the code disk structure of a traditional inductive absolute angular displacement sensor from below.

[0021] Figure 3 This is a top view of the structure of a traditional inductive absolute angular displacement sensor with multiple and single encoder chips projected onto an inductive circuit board.

[0022] Figure 4 This is a schematic diagram showing the change of the induced electromotive force of a single induction coil in a traditional inductive absolute angular displacement sensor as a function of the encoder rotation angle.

[0023] Figure 5 This is a top view of the sensing circuit board of the small inductive absolute angular displacement sensor described in this invention.

[0024] Figure 6 This is a schematic diagram of the front view layered structure of the sensing circuit board of the small inductive absolute angular displacement sensor described in this invention;

[0025] Figure 7 This is a bottom view of the encoder structure of the miniature inductive absolute angular displacement sensor described in this invention.

[0026] Figure 8 This is a top view of the multi-encoding chip and single-encoding chip of the small inductive absolute angular displacement sensor described in this invention, projected onto an inductive circuit board.

[0027] Figure 9 This is a schematic diagram of the curve of the single induction coil induced electromotive force of the small inductive absolute angular displacement sensor described in this invention changing with the rotation angle of the code disk.

[0028] Figure 10 This is a schematic diagram of the curve of the multi-coil induced electromotive force of the small inductive absolute angular displacement sensor described in this invention changing with the rotation angle of the code disk.

[0029] Figure 11 This is a schematic diagram of the front cross-sectional structure of the small inductive absolute angular displacement sensor described in this invention;

[0030] Figure 12 This is a bottom view of the adjustment drive ring of the small inductive absolute angular displacement sensor described in this invention.

[0031] Figure 13 This is a bottom view of the second housing of the small inductive absolute angular displacement sensor described in this invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings:

[0033] like Figure 5 and Figure 7As shown, the miniature inductive absolute angular displacement sensor of the present invention includes a corresponding inductive circuit board 12 and a code disk 24. The inductive circuit board 12 is provided with an outer excitation coil 13, an inner excitation coil 15, multiple inductive coils 14 and a single inductive coil 16. The inner excitation coil 15 is located inside the outer excitation coil 13. The central through hole 17 of the inductive circuit board 12 is located inside the inner excitation coil 15. Multiple sets of multiple inductive coils 14 and multiple elliptical single inductive coils 16 overlap each other and are all located between the outer excitation coil 13 and the inner excitation coil 15. The code disk 24 is provided with multiple coding pieces 25 and single coding pieces 27. The multiple coding pieces 25 are semi-circularly arranged on the annular surface of the code disk 24, and the semi-circular single coding pieces 27 are arranged on the annular surface of the code disk 24 and together with the multiple coding pieces 25 form the same annulus.

[0034] The present invention also discloses the following more optimized specific structures. According to actual needs, the above structures can be superimposed and combined with one or more of the following specific structures to form a more optimized technical solution.

[0035] like Figure 5 , Figure 6 and Figure 7 As shown, to facilitate the arrangement of multiple induction coils 14, single induction coils 16, external excitation coils 13, internal excitation coils 15, shielding layers (not shown in the figure, conventional structure), and circuits (not shown in the figure, conventional structure) on the induction circuit board 12, and to facilitate the arrangement of multiple coding chips 25 on the code disk 24, the induction circuit board 12 includes a first PCB board 18, a second PCB board 19, a third PCB board 20, a fourth PCB board 21, a fifth PCB board 22, and a sixth PCB board 23 that overlap with each other and are arranged sequentially from top to bottom. The four sets of multiple induction coils 14 are respectively arranged on the first PCB board 18 and the second PCB board 19. The major axes of the two single induction coils 16 are perpendicular to each other and their centers overlap. The two single induction coils 16, the external excitation coils 13, and the internal excitation coils 15 are respectively arranged on the third PCB board 20 and the fourth PCB board 21. The fifth PCB board 22 is provided with a shielding layer, and the sixth PCB board 23 is provided with circuits. The multiple coding chips 25 are composed of eight coding chips arranged in a semi-circle.

[0036] like Figure 11 , Figure 12 and Figure 13As shown, in order to achieve the function of quickly adjusting the distance between the sensing circuit board 12 and the code disk 24, the small inductive absolute angular displacement sensor also includes a housing, a hollow rotating shaft 32, a lifting adjustment cylinder 31, and an adjustment drive ring 38. The hollow rotating shaft 32 is vertical, passing through a vertical through hole in the housing. The hollow rotating shaft 32 is connected to the upper and lower parts of the housing via a first bearing 30 and a second bearing 34, respectively. The code disk 24 is placed in the upper part of the housing, and is fitted onto the hollow rotating shaft 32 through its central through hole 26 and fixedly connected. Next, the sensing circuit board 12 is placed below the code disk 24 and the outer casing is positioned. The hollow rotating shaft 32 passes through the central through hole 17 of the sensing circuit board 12. The diameter of the upper section of the lifting adjustment cylinder 31 (not marked in the figure) is larger than the diameter of the lower section 35. The upper section of the lifting adjustment cylinder 31 is connected to the outer peripheral edge of the sensing circuit board 12. The outer wall of the lower section 35 of the lifting adjustment cylinder 31 is provided with external threads. The bottom of the outer casing is provided with an upwardly protruding outer casing cylinder 36. The inner wall of the outer casing cylinder 36 is provided with internal threads. The lower section 35 of the lifting adjustment cylinder 31 is placed below the code disk 24. The outer wall of the second bearing 34 is threadedly connected to the inner wall of the outer shell 36. The outer bottom surface of the outer shell has an annular recess 44. The bottom of the recess 44 has at least two evenly distributed arc-shaped outer shell through holes 43 and at least two evenly distributed outer shell screw holes 45. An annular adjusting drive ring 38 is placed inside the recess 44. The upper surface of the adjusting drive ring 38 has at least two evenly distributed and upwardly protruding driving protrusions 37. These driving protrusions 37 pass through corresponding... Multiple arc-shaped outer shell through holes 43, vertical drive blind holes (not marked in the figure) are respectively provided on the lifting adjustment cylinder 31 at positions corresponding to multiple drive protrusions 37, the upper sections of multiple drive protrusions 37 are placed in multiple drive blind holes, the adjustment drive ring 38 is provided with at least two arc-shaped drive ring through holes 40 evenly distributed along the circumferential direction, multiple screws 39 pass through multiple arc-shaped drive ring through holes 40 from bottom to top and are connected to multiple corresponding outer shell screw holes 45, and the lower surface of the adjustment drive ring 38 is provided with at least two rotation blind holes 41 evenly distributed along the circumferential direction.

[0037] like Figure 11 and Figure 13 As shown, for ease of assembly, the outer shell includes a first outer shell 28 and a second outer shell 29 connected to each other. The first outer shell 28 is located above the second outer shell 29. The outer shell cylinder 36 and the outer shell groove 44 are both provided on the second outer shell 29. The hollow rotating shaft 32 passes through the central through hole of the lifting adjustment cylinder 31, the central through hole 42 of the adjustment drive ring 38, and the central through hole 46 of the second outer shell 29 from top to bottom.

[0038] like Figure 11-13As shown, in order to facilitate reliable driving and to facilitate the reliable assembly of the adjusting drive ring 38, the housing and the lifting adjusting cylinder 31 together, there are two arc-shaped housing through holes 43, two drive protrusions 37, two drive blind holes and two rotation blind holes 41, and four screws 39, four arc-shaped drive ring through holes 40 and four housing screw holes 45.

[0039] like Figure 11-13 As shown, in order to make the bottom of the sensor neat and aesthetically pleasing and easy to use, the vertical thickness of the adjustment drive ring 38 is the same as the vertical depth of the housing groove 44. The lower wall of the arc-shaped drive ring through hole 40 is provided with a step, and the nut of the corresponding screw 39 is placed in the step.

[0040] like Figure 11-13 As shown, in order to facilitate the stable installation of the code disk 24, a protruding rotating shaft ring 33 is provided on the hollow rotating shaft 32 at the position corresponding to the code disk 24, and the code disk 24 is fixedly connected to the rotating shaft ring 33 by connecting screws.

[0041] like Figures 5-13 As shown, in application, the drive shaft (not shown in the figure) of the device to be tested passes through the central through hole of the hollow rotating shaft 32, and drives the code disk 24 to rotate through the hollow rotating shaft 32. The multi-encoding chip 25 and the single-encoding chip 27 on the code disk 24 rotate synchronously. The induced electromotive force on the multi-induction coil 14 and the single-induction coil 16 on the sensing circuit board 12 changes with the rotation of the multi-encoding chip 25 and the single-encoding chip 27, respectively. After outputting the signal, the angular displacement detection function is realized.

[0042] like Figure 11-13 As shown, when adjusting the distance between the sensing circuit board 12 and the code disk 24, first loosen the screw 39 (the screw 39 can also be removed, but it is better not to remove it to prevent the adjusting drive ring 38 from detaching from the second housing 29). Then, insert a tool (which can be a structure with protrusions at both ends of a rigid rod) into the two rotating blind holes 41 and rotate it to make the adjusting drive ring 38 rotate. This drives the protrusions 37 to rotate the lifting adjusting cylinder 31. Since the lower section of the lifting adjusting cylinder 31 is threadedly connected to the outer housing 36 of the second housing 29, and the second housing 29 remains stationary, the lifting adjusting cylinder 31 will move vertically until it reaches the appropriate position so that the distance between the sensing circuit board 12 and the code disk 24 is optimal. Finally, tighten the screw 39 to complete the adjustment. During this process, the two drive protrusions 37 rotate in the two arc-shaped outer shell through holes 43 respectively, the four screws 39 remain stationary but are always located in the four arc-shaped drive ring through holes 40 respectively, and the upper ends of the two drive protrusions 37 are always located in the two drive blind holes of the lifting adjustment cylinder 3, making the operation simple and convenient.

[0043] The miniature inductive absolute angular displacement sensor described in this invention has high detection accuracy and can detect the absolute value of angular displacement. Its principle is as follows: Figure 8 As shown, the induction circuit board 12 and the code disk 24 are parallel and correspond to each other. The multi-encoding chip 25 corresponds to four sets of multi-induction coils 14, and the single-encoding chip 27 corresponds to two single-induction coils 16. The code disk 24 rotates 360°, and the electromotive force of the two single-induction coils 16 changes in one cycle. The electromotive force change curve corresponding to each single-induction coil 16 is V-shaped, as shown. Figure 9 As shown, since the two single induction coils 16 intersect each other perpendicularly, the electromotive force change curves corresponding to the two single induction coils 16 are two "V" shapes in opposite directions. At the same time, the code disk 24 rotates 360°, and the electromotive force of the multi-induction coil 14 changes for 16 cycles. By combining the electromotive force changes corresponding to the two single induction coils 5 and the electromotive force changes of the multi-induction coil 14, the absolute angular position of the code disk 24 can be determined, that is, the absolute angular displacement values ​​of the drive shaft and hollow rotating shaft 32 of the device under test can be detected.

[0044] Note: The above-mentioned induction circuit board 12, code disk 24, multiple induction coils 14, single induction coil 16, multiple coding chip 25, and single coding chip 27 correspond to the induction circuit board 1, code disk 8, multiple induction coils 3, single induction coil 5, multiple coding chip 9, and single coding chip 11 in the background art content, respectively. However, since the new structure of the present invention has changed in terms of size and arrangement, the same name is used but the marking numbers are different.

[0045] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the technical solutions of the present invention. Any technical solution that can be implemented based on the above embodiments without creative effort should be considered to fall within the scope of protection of the patent of the present invention.

Claims

1. A small inductive absolute angular displacement sensor, comprising corresponding sensing circuit boards and a code disk, characterized in that: The induction circuit board is provided with an external excitation coil, an internal excitation coil, multiple induction coils, and a single induction coil. The internal excitation coil is located inside the external excitation coil, and the central through hole of the induction circuit board is located inside the internal excitation coil. Four sets of multiple induction coils and two elliptical single induction coils overlap each other and are all located between the external excitation coils and the internal excitation coils. The code disk is provided with multiple coding pieces and single coding pieces. The multiple coding pieces are semi-circularly arranged on the annular surface of the code disk, and the semi-circular single coding pieces are arranged on the annular surface of the code disk and together with the multiple coding pieces form the same annulus. The induction circuit board includes overlapping and The PCBs are arranged from top to bottom as follows: a first PCB, a second PCB, a third PCB, a fourth PCB, a fifth PCB, and a sixth PCB. Four sets of multi-induction coils are respectively disposed on the first and second PCBs. The major axes of two single induction coils are perpendicular to each other and their centers overlap. Two single induction coils, an external excitation coil, and an internal excitation coil are respectively disposed on the third and fourth PCBs. The fifth PCB has a shielding layer, and the sixth PCB has circuitry. The multi-coded chip consists of eight coded chips arranged in a semi-circle.

2. The miniature inductive absolute angular displacement sensor according to claim 1, characterized in that: The miniature inductive absolute angular displacement sensor further includes a housing, a hollow rotating shaft, a lifting adjustment cylinder, and an adjustment drive ring. The hollow rotating shaft is vertical, passing through a vertical through-hole in the housing. The hollow rotating shaft is connected to the upper and lower parts of the housing via a first bearing and a second bearing, respectively. A code disk is placed in the upper part of the housing, fitted onto the hollow rotating shaft through its central through-hole and fixedly connected. A sensing circuit board is placed in the housing below the code disk. The hollow rotating shaft passes through the central through-hole of the sensing circuit board. The diameter of the upper section of the lifting adjustment cylinder is larger than the diameter of the lower section. The upper section of the lifting adjustment cylinder is connected to the outer periphery of the sensing circuit board. The lower section of the lifting adjustment cylinder has external threads on its outer wall. The bottom of the housing has an upwardly protruding outer shell cylinder, with internal threads on its inner wall. The lower section of the lifting adjustment cylinder is positioned between the outer wall of the second bearing and the inner wall of the outer shell cylinder. The adjusting drive ring is threadedly connected to the outer shell cylinder. The outer bottom surface of the outer shell is provided with an annular outer shell groove. The bottom of the outer shell groove is provided with at least two arc-shaped outer shell through holes and at least two outer shell screw holes that are evenly distributed along the circumferential direction. The annular adjusting drive ring is placed in the outer shell groove. The upper part of the adjusting drive ring is provided with at least two driving protrusions that are evenly distributed along the circumferential direction and protrude upwards. The multiple driving protrusions pass through the multiple arc-shaped outer shell through holes corresponding to each other. The lifting adjusting cylinder is provided with vertical driving blind holes at positions corresponding to the multiple driving protrusions. The upper sections of the multiple driving protrusions are placed in the multiple driving blind holes. The adjusting drive ring is provided with at least two arc-shaped driving ring through holes that are evenly distributed along the circumferential direction. Multiple screws pass through the multiple arc-shaped driving ring through holes from bottom to top and are connected to the multiple outer shell screw holes corresponding to each other. The lower surface of the adjusting drive ring is provided with at least two rotation blind holes that are evenly distributed along the circumferential direction.

3. The miniature inductive absolute angular displacement sensor according to claim 2, characterized in that: The outer casing includes a first outer casing and a second outer casing connected to each other. The first outer casing is located above the second outer casing, and the outer casing cylinder and the outer casing groove are both provided on the second outer casing.

4. The miniature inductive absolute angular displacement sensor according to claim 2, characterized in that: There are two of each of the arc-shaped outer shell through hole, the driving protrusion, the driving blind hole, and the rotating blind hole; and there are four of each of the screw, the arc-shaped driving ring through hole, and the outer shell screw hole.

5. The miniature inductive absolute angular displacement sensor according to claim 2, characterized in that: The vertical thickness of the adjusting drive ring is the same as the vertical depth of the outer casing groove. The lower wall of the arc-shaped drive ring through hole is provided with a step, and the corresponding screw nut is placed in the step.

6. The miniature inductive absolute angular displacement sensor according to claim 2, characterized in that: The hollow rotating shaft has an outwardly protruding rotating shaft ring at a position corresponding to the code disk, and the code disk is fixedly connected to the rotating shaft ring by connecting screws.

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