Rotary shaft sensing device for sewing machine motor

Abstract

The application is a rotating shaft sensing device of sewing machine motor, which comprises a magnet rotating disc, a first IC board and a second IC board. The magnet rotating disc is magnetized with an inner ring magnetic area, an outer ring magnetic area and an upper positioning magnetic area. The first IC board senses the rotation of the magnet rotating disc to directly capture the rotation of the rotating shaft, senses the inner ring magnetic area to output R, S and T pulse signals, and senses the outer ring magnetic area to output A and B pulse signals for motor driving control. The second IC board senses the rotation of the magnet rotating disc to capture the rotation of the rotating shaft, senses the upper positioning magnetic area to output an upper positioning pulse signal for controlling the upper positioning needle stop position of the sewing machine.

Description

TECHNICAL FIELD

[0001] The present invention relates to a sensing device for a motor rotating shaft, in particular to a sensing device for a sewing machine motor rotating shaft. BACKGROUND

[0002] At present, the sewing machine encoders can be roughly divided into contact type and non-contact type according to their sensing methods. The contact type encoder has the problem of component abrasion. In order to avoid contact abrasion, the related industry has developed non-contact encoders, such as optical encoders and magnetic encoders.

[0003] Please refer to the Taiwan Utility Model Patent No. M302831 "Servo motor encoder", the encoder of this case is an optical encoder. The servo motor encoder includes a light shielding piece and a sensing device. The light shielding piece is a circular piece and is used to be combined with the rear end of the servo motor shaft. The outer or inner ring of the light shielding piece is provided with a plurality of missing slots at intervals. A plurality of light transmission holes are arranged in the concentric ring of the inner or outer ring. The sensing device is provided with a base combined with the rear end surface of the servo motor. The base is provided with a bottom plate with a through hole. A circular arc-shaped insertion body is vertically outwardly arranged at the periphery of the bottom plate and surrounds the light shielding piece. Three light interrupters for detecting the missing slots and a light encoder module for detecting each light transmission hole are combined around the insertion body. In this way, the position and action of the light shielding piece can be detected by the light interrupters and the light encoding module, and the information is encoded and output for detecting and controlling the action of the servo motor.

[0004] The aforementioned optical encoder is a rotary optical encoder commonly used in the industry for sewing machines at present. However, the mechanism of the sewing machine is to sew fabric, so many broken threads or lint will be generated during the sewing process. These broken threads or lint will adhere to the through hole of the bottom plate and the light transmission hole of the light shielding piece, which will affect the detection accuracy of the light interrupter, and thus cause the timing error of the sewing machine to be unable to normally operate.

[0005] In addition, in the non-contact encoder, the magnetic encoder also has the advantage of overcoming the component abrasion problem of the contact type encoder, which is used to convert the mechanical rotation angle of the rotating shaft into digital or analog signals to realize angle, linear displacement, rotation speed and other signal outputs. Compared with the rotary optical encoder, it does not have the problem of affecting the accuracy of sensing in harsh working environments such as oil stains or dust (or like the aforementioned broken threads or lint of the sewing machine), so if the magnetic encoder can be applied to the sewing machine, the problem encountered by the aforementioned optical encoder can be solved.

[0006] The magnetic encoder please refer to the announcement number CN203645456U "sewing machine direct drive motor and magnetic encoder synchronization device" patent, is about a kind of sewing machine direct drive motor and magnetic encoder synchronization device, its main technical means is in the output shaft sleeve of motor and is additionally equipped with a mounting seat on the shell of motor to install an additional shaft, again in shaft sleeve is equipped with a driven gear, the transmission gear and the driven gear are meshed with a transmission belt, again in shaft is disposed a magnetic element, in the path of magnetic element through corresponding sensor is provided, when motor operates, shaft is driven by the transmission relationship between the output shaft of motor, transmission gear, transmission belt, driven gear and rotates synchronously, and magnetic element can also rotate with shaft, at this time, sensor can measure the required data according to the magnetic field change of rotating magnetic element, in other words, the existing technology is mostly to hang a transmission mechanism on the output shaft, to show the rotating state on another driven shaft, then the shaft is used to drive the magnetic element to rotate for monitoring control, code generation.

[0007] However, this kind of additional transmission mechanism driven shaft technical means, it is easy to occur output unnecessary loss and transmission loss, belt wear dust, belt transmission slip, belt wear causes transmission gap, belt contact position unilateral stress is easy to cause rotating resonance and so on, further produces the problem of detection distortion, moreover, it also occupies the motor configuration space, affects heat dissipation and so on, and the magnetic element cannot be directly physically adjusted, must be positioned by the way of electronic parameter setting, and the control function is not familiar with, and it is not easy to start, and it is easy to occur setting error and affect product yield, in view of this, the rotating shaft sensing device of sewing machine motor is optimized and improved, which is the focus of the present application. SUMMARY

[0008] The main purpose of the present application is to directly sense the rotating shaft of the sewing machine motor by using double induction IC boards, so as to make the operation of the sewing machine more accurate and improve the production efficiency and yield.

[0009] In order to achieve the above purpose, the technical means of the present application includes: a magnet rotating disc, a center hole is sleeved in a ring groove of the rotating shaft, so that the magnet rotating disc rotates synchronously with the rotating shaft, the magnet rotating disc is magnetized with an inner ring magnetic area and an outer ring magnetic area; a first IC board is fixed on the rear cover, for sensing the inner ring magnetic area and the outer ring magnetic area, to output R, S, T pulse signals and output A, B pulse signals respectively; since the magnet rotating disc is directly fixed on the rotating shaft and rotates synchronously with the rotating shaft, the absolute position of the rotating shaft can be sensed, so that the signal generated is not distorted.

[0010] The sensing device further comprises a second IC board fixed on the back cover, and the magnet rotating disc is provided with an upper positioning magnetic area between the inner ring magnetic area and the outer ring magnetic area, so as to correspond to the sensing of the second IC board, output an upper positioning pulse signal, and cooperate with the pulse signal output by the first IC board to control the operation of the motor.

[0011] The sensing device is provided with a positioning mechanism on the back cover, the positioning mechanism is fixed with a second IC board, the magnet rotating disc is provided with an upper positioning magnetic area between the inner ring magnetic area and the outer ring magnetic area, so as to correspond to the sensing of the second IC board, output an upper positioning pulse signal, and cooperate with the pulse signal output by the first IC board to control the operation of the motor.

[0012] The back cover is provided with at least a first stud for fixing the first IC board, the positioning mechanism is provided with a first opening corresponding to the first stud for the first stud to pass out; the positioning mechanism has a plurality of lugs on the circumference, and an adjusting hole for locking is penetrated through each lug, so that the positioning mechanism can be rotated when loosened, the relative position of the second IC board and the upper positioning magnetic area is adjusted, and the first opening is rotated relative to the first stud; the positioning mechanism has a boss, and a groove is formed between the boss and each lug, so that a rotating disc cover is embedded in the groove.

[0013] The positioning mechanism has a plurality of lugs on the circumference, and an adjusting hole for locking is penetrated through each lug, so that the positioning mechanism can be rotated when loosened, the relative position of the second IC board and the upper positioning magnetic area is adjusted; the positioning mechanism has a boss, and a groove is formed between the boss and each lug, so that a rotating disc cover is embedded in the groove.

[0014] The sensing device further comprises a rotating disc cover, which is sleeved into the inner side of the ring groove of the rotating shaft and fixed on the back cover, so as to cover the outside of the magnet rotating disc and the first IC board.

[0015] The sensing device further comprises a rotating disc cover, which covers the outside of the magnet rotating disc and the first and second IC boards and is fixed on the back cover.

[0016] The inner ring magnetic area of the magnet rotating disc is magnetized with at least 4 poles arranged according to polarity, for the sensing of the first IC board.

[0017] The outer ring magnetic area of the magnet rotating disc is magnetized with a number of poles which is twice the number of poles arranged according to polarity, for the sensing of the first IC board; the number of poles of the outer ring magnetic area is 60 poles.

[0018] The upper positioning magnetic area of the magnet rotating disc is magnetized with 3 poles arranged according to one of NSN polarity or SNS polarity, for the sensing of the second IC board.

[0019] The magnet rotating disc is provided with a lower positioning magnetic area at a position opposite to the upper positioning magnetic area by 180 degrees, so that the second IC board can sense the lower positioning magnetic area to output a lower positioning pulse signal to control the lower positioning needle of the sewing machine to stop.

[0020] The magnet rotating disc further comprises a non-magnetic pole area, and the height of the non-magnetic pole area is less than the height of the inner ring magnetic area, the outer ring magnetic area and the upper positioning magnetic area.

[0021] The magnet rotating disc is made of plastic material and iron oxide magnet.

[0022] The sensing device further comprises a hand wheel fixed on the rotating shaft. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The combination perspective view of the preferred embodiment of the present application;

[0024] Figure 2 The exploded view of the preferred embodiment of the present application;

[0025] Figure 3 The detailed exploded view of the preferred embodiment of the present application;

[0026] Figure 4 The magnetic area view of the magnet rotating disc in the preferred embodiment of the present application;

[0027] Figure 4A Another magnetic area view of the magnet rotating disc in the preferred embodiment of the present application;

[0028] Figure 5 The cross-sectional view of the preferred embodiment of the present application;

[0029] Figure 6 The rotating front view of the positioning mechanism in the preferred embodiment of the present application;

[0030] Figure 6A The rotating rear view of the positioning mechanism in the preferred embodiment of the present application;

[0031] Figure 7 The view of the first IC board in the preferred embodiment of the present application used alone. DETAILED DESCRIPTION

[0032] Please refer to Figures 1 to 3The above is a schematic diagram of a preferred embodiment of the present invention. The sensing device of the present invention is disposed at the position corresponding to the rotation shaft 11 of the motor 10, and includes a magnetic turntable 20, a first IC board 30, a second IC board 40, a positioning mechanism 50 and a turntable cover 60.

[0033] like Figure 3 As shown, the motor 10 has a first stud 121 on the rear cover 12. The positioning mechanism 50 has a boss 51 with a smaller area than the body and a central hole 52 through it on one side. A first opening 53 is preset at the position of each first stud 121 to allow the first stud 121 to pass through. The number of first studs 121 can be increased or decreased, provided that it is sufficient to lock the first IC board 30.

[0034] The positioning mechanism 50 also has multiple lugs 54 extending outward from the periphery of its main body, forming a groove 55 between the boss 51 and the lugs 54, such as... Figure 3 As shown, each lug 54 has a long arc-shaped adjustment hole 541 passing through it. In this embodiment, the positioning mechanism 50 has three lugs 54, but the number can be increased or decreased as needed.

[0035] During assembly, the positioning mechanism 50 is fitted into the rotating shaft 11 through the center hole 52, and then through the first stud 121 through the first opening 53. Finally, the screw 56 passes through the adjustment hole 541 to fix the positioning mechanism 50 onto the back cover 12.

[0036] The first IC board 30 is fixed to the first stud 121 that protrudes from the first opening 53 with screws 31, and the second IC board 40 is locked to the second stud 57 of the positioning mechanism 50 with screws 41.

[0037] In this embodiment, the positioning mechanism 50 has a pair of second studs 57 for locking the second IC board 40. When necessary, the position of the second studs 57 can also be changed, or as... Figure 3 As shown, second studs 57 are provided at different angles for selection. The number of second studs 57 can be increased or decreased, provided that they are sufficient to secure the second IC board 40.

[0038] The magnetic turntable 20 has a disc-shaped body with a flange 21 forming on the body surrounding the central circular hole 211. In this embodiment, the magnetic turntable 20 is made of plastic material combined with iron oxide magnets, but the material is not limited to these.

[0039] During assembly, one side of the magnet turntable 20 and the gap adjustment piece 22 are inserted into the rotating shaft 11, and then the C-shaped buckle 23 is correspondingly fastened to the annular groove 111 of the rotating shaft 11, so as... Figure 5As shown, it is fixed on the rotating shaft 11, while on the other side, a flange 21 is provided for the turntable cover 60 to be fitted into, so that the magnet turntable 20 is clamped between the annular groove 111 of the rotating shaft 11 and the turntable cover 60.

[0040] After the turntable cover 60 is fitted onto the rotating shaft 11, it can hold the magnetic turntable 20, the positioning mechanism 50, the second IC board 40 on the second stud 57, and the first IC board 30 on the first stud 121 that protrudes from the positioning mechanism 50 together. Figure 5 The cover 60 is fitted into the accommodating space formed by the positioning mechanism 50, and the turntable cover 60 can be correspondingly embedded in the groove 55 between the boss 51 and the lug 54, and then locked to the back cover 12 with screws 61.

[0041] like Figure 4 As shown, the magnet turntable 20 is magnetized with an inner ring magnetic area 201, an outer ring magnetic area 202 and an upper positioning magnetic area 203. The outer ring magnetic area 202 is located on the outer ring around the body of the magnet turntable 20, the inner ring magnetic area 201 is located on the outer ring around the central circular hole 211 of the magnet turntable 20, and the upper positioning magnetic area 203 is located between the inner ring magnetic area 201 and the outer ring magnetic area 202.

[0042] The inner ring magnetic region 201 is divided into equal parts as shown in the figure and magnetized according to the NNS polarity, with at least 4 poles. In practice, the number of poles can be increased in multiples of 2 (NS) as needed, such as 6, 8, 10, 12, etc. The outer ring magnetic region 202 is divided into equal parts as shown in the figure and magnetized according to the NNS polarity, with 30 pole pairs (60 poles). In practice, the number of poles can be increased in multiples of 2 (NS) as needed. The upper positioning magnetic region 203 is magnetized according to the NNS polarity as shown in the figure, with 3 poles. In practice, depending on the sensing device, the SNS polarity arrangement can be selected.

[0043] The first IC board 30 is fixed on the first stud 121 that extends out of the positioning mechanism 50, and is positioned between the magnetic turntable 20 and the positioning mechanism 50 to correspond to the sensing of the inner ring magnetic area 201 and the outer ring magnetic area 202 of the magnetic turntable 20.

[0044] The first IC board 30, in conjunction with the inner ring magnetic area 201 of the magnet turntable 20, uses magnetic principle to sense and detect, so as to output pulse signals R, S, and T. In addition, it works with the outer ring magnetic area 202 of the magnet turntable 20 to sense and detect, so as to output pulse signals A and B.

[0045] The sensing device outputs R, S, T pulse signals and A, B pulse signals via the first IC board 30, and transmits the signals to the controller for processing (not shown in the figure) via electrical connection, so as to drive the motor. For example, it can detect the rotation direction and speed of the rotating shaft 11 to obtain the best control effect.

[0046] The second IC board 40 is fixed to the second stud 57 with screws 41 and is positioned opposite the magnetic turntable 20 and the positioning mechanism 50 to correspond to the upper positioning magnetic area 203 sensed on the magnetic turntable 20.

[0047] The second IC board 40, in conjunction with the upper positioning magnetic area 203 of the magnetic turntable 20, uses magnetic principle to detect and output an upper positioning pulse signal. The upper positioning pulse signal is then transmitted to the controller (not shown in the figure) via electrical connection to control the upper positioning needle stop position of the sewing machine.

[0048] If required for operation, a set of three-pole lower positioning magnetic areas 204 can be set at a position 180 degrees opposite to the upper positioning magnetic area 203. Figure 4A As shown, similar to the upper positioning magnetic area 203, the magnetic area is arranged according to the NSN polarity, or it can be arranged according to the SNS polarity, corresponding to the lower positioning position of the motor. The second IC board 40, in conjunction with the lower positioning magnetic area 204, uses magnetic induction to detect and output a lower positioning pulse signal, which is used to control the lower positioning needle stop position of the sewing machine.

[0049] To avoid magnetic interference during magnetization, Figure 4 The height of the non-magnetic pole region 205, excluding the inner ring magnetic region 201, outer ring magnetic region 202, and upper positioning magnetic region 203 or lower positioning magnetic region 204, is set to be lower than that of the inner ring magnetic region 201, outer ring magnetic region 202, and upper positioning magnetic region 203 or lower positioning magnetic region 204. The height reduction of the non-magnetic pole region 205 is between 0.2 and 0.6 mm, with an optimal value of 0.4 mm.

[0050] The second IC board 40 can also be loosened according to actual operational needs, such as... Figure 6 Screw 56, which is locked in the adjusting hole 541, and so on. Figure 6A By directly rotating the positioning mechanism 50, the position of the second IC board 40 on the second stud 57 can be adjusted, thereby adjusting the relative position of the second IC board 40 and the upper positioning magnetic area 203, and fine-tuning the upper positioning point, making it convenient for unfamiliar operators to make adjustments. Depending on actual needs, the second stud 57 can also be directly set at an appropriate position on the rear cover 12 to cooperate with the magnetic turntable 20 for detection, omitting the adjustment function.

[0051] During adjustment, the diameter and shape of the first opening 53 through which the first stud 121 passes and the adjustment hole 541 on the positioning mechanism 50 can be adjusted as follows: Figure 6AAs shown, the positioning mechanism 50 rotates in conjunction with the first opening 53, which allows the first stud 121 to remain protruding. This allows the positioning mechanism 50 to rotate relative to the first stud 121 through the first opening 53 without affecting its rotation. Without affecting the rotation of the positioning mechanism 50, the position of the first stud 121, the structure for fixing the first IC board 30, and the shape of the positioning mechanism 50 body can also be selectively varied accordingly.

[0052] In this embodiment, the first IC board 30 can also be used independently with the magnetic turntable 20. When using the first IC board 30 alone, such as Figure 7 As shown, the first IC board 30 can be directly locked to the first stud 121 on the back cover 12, and output pulse signals in conjunction with the corresponding magnetic zone of the magnet turntable 20. In addition, another external positioning signal device is added to control the operation of the motor 10.

[0053] The present invention may also be as follows Figure 5 As shown, a handwheel 70 can be added, which is directly fixed to the rotating shaft 11 so that the handwheel 70 can directly drive the rotating shaft 11 and the magnetic turntable 20 can also synchronously sense the rotation of the handwheel 70; or a heat insulation cover (not shown in the figure) can be added to cover the motor 10 for heat insulation.

[0054] Because the magnetic turntable 20 is directly mounted on the rotating shaft 11 and rotates synchronously with the rotating shaft 11, the generated induction signal is obtained from the absolute position, and the signal will not be distorted. Furthermore, since all values ​​are directly acquired from the rotating shaft 11, compared with general indirect acquisition methods, more accurate and undistorted signals and more absolute monitoring and control values ​​can be generated, thereby enabling the sewing machine motor to achieve the best control effect.

[0055] Furthermore, since this invention uses magnetic induction to control the motor drive and positioning, it is not affected by oil or water pollution, nor by cotton lint or dust, thus achieving the best control effect for the sewing machine motor.

[0056] The embodiments listed above are for illustrative purposes only and are not intended to limit the scope of the invention. Any simple substitutions or equivalent replacements of components or means made in accordance with the technical means of the invention should fall within the scope of the patent application of this invention.

Claims

1. A rotation shaft sensing device for a sewing machine motor, for mounting with a motor having a rotation shaft on its rear cover, characterized in that, The sensing device includes: A magnetic turntable is fitted into a ring groove fixed on the rotating shaft through a central circular hole, so that the magnetic turntable rotates synchronously with the rotating shaft. The magnetic turntable is magnetized with an inner ring magnetic area and an outer ring magnetic area. An upper positioning magnetic area is provided between the inner ring magnetic area and the outer ring magnetic area. A first IC board is fixed on the back cover to sense the inner ring magnetic area and the outer ring magnetic area, so as to output pulse signals of R, S, T and pulse signals of A, B respectively; A second IC board is fixed on the back cover to sense the upper positioning magnetic area, output the upper positioning pulse signal, and control the operation of the motor in conjunction with the pulse signal output by the first IC board. Since the magnetic turntable is directly fixed to the rotating shaft and rotates synchronously with the rotating shaft, the absolute position of the rotating shaft can be sensed, so that the signal it generates is not distorted; The inner ring magnetic region of the magnetic turntable is magnetized with at least four poles arranged according to polarity, while the outer ring magnetic region is magnetized with twice the number of poles arranged according to polarity, for sensing by the first IC board. The upper positioning magnetic area of ​​the magnetic turntable is magnetized with three poles, arranged in either NSN polarity or SNS polarity, for sensing by the second IC board.

2. A rotation shaft sensing device for a sewing machine motor, for mounting with a motor having a rotation shaft on its rear cover, characterized in that, The sensing device includes: A magnetic turntable is fitted into a ring groove fixed on the rotating shaft through a central circular hole, so that the magnetic turntable rotates synchronously with the rotating shaft. The magnetic turntable is magnetized with an inner ring magnetic area and an outer ring magnetic area. An upper positioning magnetic area is provided between the inner ring magnetic area and the outer ring magnetic area. A first IC board is fixed on the back cover to sense the inner ring magnetic area and the outer ring magnetic area, so as to output pulse signals of R, S, T and pulse signals of A, B respectively; The back cover is equipped with a positioning mechanism; A second IC board is fixed on the positioning mechanism to sense the upper positioning magnetic area, output an upper positioning pulse signal, and control the operation of the motor in conjunction with the pulse signal output by the first IC board. Since the magnetic turntable is directly fixed to the rotating shaft and rotates synchronously with the rotating shaft, the absolute position of the rotating shaft can be sensed, so that the signal it generates is not distorted; The inner ring magnetic region of the magnetic turntable is magnetized with at least four poles arranged according to polarity, while the outer ring magnetic region is magnetized with twice the number of poles arranged according to polarity, for sensing by the first IC board. The upper positioning magnetic area of ​​the magnetic turntable is magnetized with three poles, arranged in either NSN polarity or SNS polarity, for sensing by the second IC board.

3. The rotation shaft sensing device for a sewing machine motor according to claim 2, characterized in that: The back cover is provided with at least one first stud for fixing the first IC board, and the positioning mechanism is provided with a first opening corresponding to the first stud for the first stud to pass through.

4. The rotation shaft sensing device for a sewing machine motor according to claim 3, characterized in that: The positioning mechanism has multiple lugs around its periphery, and each lug has a locking adjustment hole. When released, the positioning mechanism can be rotated to adjust the relative position of the second IC board and the upper positioning magnetic area, and can be rotated relative to the first stud through the first opening.

5. The rotation shaft sensing device for a sewing machine motor according to claim 2, characterized in that: The positioning mechanism has multiple lugs around its periphery, and each lug has a locking adjustment hole. When released, the positioning mechanism can be rotated to adjust the relative position of the second IC board and the upper positioning magnetic area.

6. The rotation shaft sensing device for a sewing machine motor according to claim 4 or 5, characterized in that: The positioning mechanism has a boss and a groove formed between the boss and each of the lugs for a turntable cover to be inserted into the groove.

7. The rotation shaft sensing device for a sewing machine motor according to claim 1 or 2, characterized in that: The sensing device also includes a turntable cover, which is fitted into the inner side of the annular groove of the rotating shaft and fixed to the rear cover to cover the outside of the magnetic turntable and the first IC board.

8. The rotation shaft sensing device for a sewing machine motor according to claim 1 or 2, characterized in that: The sensing device also includes a turntable cover, which covers the outside of the magnetic turntable and the first and second IC boards and is fixed on the rear cover.

9. The rotation shaft sensing device for a sewing machine motor according to claim 1 or 2, characterized in that: The outer ring magnetic region has 60 poles.

10. The rotation shaft sensing device for a sewing machine motor according to claim 1 or 2, characterized in that: The magnetic turntable has a lower positioning magnetic area positioned 180 degrees opposite to the upper positioning magnetic area, so that the second IC board can sense the lower positioning magnetic area to output a lower positioning pulse signal and control the lower positioning needle stop position of the sewing machine.

11. The rotation shaft sensing device for a sewing machine motor according to claim 10, characterized in that: The magnet turntable also includes a non-magnetic pole region, the height of which is less than the height of the lower positioning magnetic region.

12. The rotation shaft sensing device for a sewing machine motor according to claim 11, characterized in that: The height of the non-magnetic pole region is reduced by 0.2 to 0.6 mm.

13. The rotation shaft sensing device for a sewing machine motor according to claim 12, characterized in that: The height of the non-magnetic pole region is reduced by 0.4 mm.

14. The rotation shaft sensing device for a sewing machine motor according to claim 1 or 2, characterized in that: The magnet turntable also includes a non-magnetic pole region, the height of which is less than the height of the inner ring magnetic region, the outer ring magnetic region, and the upper positioning magnetic region.

15. The rotation shaft sensing device for a sewing machine motor according to claim 14, characterized in that: The height of the non-magnetic pole region is reduced by 0.2 to 0.6 mm.

16. The rotation shaft sensing device for a sewing machine motor according to claim 15, characterized in that: The height of the non-magnetic pole region is reduced by 0.4 mm.

17. The rotation shaft sensing device for a sewing machine motor according to claim 1 or 2, characterized in that: The magnetic turntable is made of plastic and iron oxide magnets.

18. The rotation shaft sensing device for a sewing machine motor according to claim 1, characterized in that: The sensing device also includes a handwheel fixed to the rotating shaft.

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