A high-precision magnetic encoder and motor with anti-shaft jump

Abstract

The present invention discloses a high-precision magnetic encoder and motor with improved shaft runout resistance. The encoder comprises a magnet and a circuit board, with a magnetic sensor mounted on the circuit board. The encoder is characterized by: the magnet being cylindrical, with a T-shaped magnet positioned at its center. The T-shaped magnet is flanked by symmetrically arranged N-pole and S-pole magnets, respectively. The N-pole and S-pole magnets are magnetized along the magnet's axial direction, while the T-shaped magnet is magnetized toward the N-pole or S-pole magnet. This invention improves the accuracy of the magnetic encoder and addresses the low accuracy of conventional magnetic encoders caused by motor shaft eccentricity, shaft runout, and bearing seat clearance.

Description

Technical Field

[0001] The present invention relates to the field of encoders, and in particular to a high-precision magnetic encoder and a motor that are resistant to shaft jump. Background Art

[0002] A magnetic encoder can be used to detect the position of a motor's rotor magnetic field, providing accurate motor speed and position signals. The encoder then outputs these signals to the driver for analysis, comparison, and logical judgment, ultimately driving the motor. The magnetic encoder is a sensor that constantly provides accurate signals to the driver, enabling it to make precise analysis and judgments.

[0003] Taking a magnetic sensor installed on a motor as an example, a magnetic encoder primarily consists of a magnet, a circuit board, and a magnetic sensor mounted on the circuit board. The magnet is mounted on the motor shaft of the motor rotor, and the circuit board is mounted behind the motor stator via a bracket, with a gap between the circuit board and the magnet. Magnetic sensors include AMR sensors and TMR sensors.

[0004] Take the ideal installation of the motor and components, and the rotation of the motor shaft as an example, see Figure 1 As shown in the figure, the AMR sensor always faces point E of the magnet (point E is the center of the magnet, with the N pole and S pole on both sides). However, in actual application, there is gap and eccentricity in the motor shaft, such as Figure 2 As shown, the actual center point changes from the original point E to point F (point F is beside point E, not in the center of the magnet). Then, when the motor rotates, it will rotate with point F as the center. The AMR sensor will not always face point E. As the angle rotates, the AMR sensor will face point E1 (point E1 is beside point E and point F, and point E1 is not in the center of the magnet). Therefore, Figure 1 Compared with the ideal state, the magnetic field at point E and point E1 will have a significant change. Due to the change in magnetic field, the speed will have a corresponding and detailed fluctuation. Figure 3 The figure shows the parallelism of the magnetic field received by the magnetic sensor. Poor parallelism results in poor detection accuracy. Consequently, motor shaft centerline runout and bearing spacing can lead to poor magnetic encoder accuracy. Therefore, solving this technical problem is a topic for those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-precision magnetic encoder and motor with anti-shaft jump. By using this structure, the problem of poor accuracy of the magnetic encoder caused by motor shaft jump is effectively overcome, and the accuracy of the magnetic encoder is effectively improved.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a high-precision magnetic encoder with anti-shaft jump, comprising a magnet and a circuit board, a magnetic sensor being provided on the circuit board, the magnet being a cylindrical structure, a T magnet being provided at the very center of the magnet, the two sides of the T magnet being symmetrically arranged with an N-pole magnet and an S-pole magnet, the N-pole magnet and the S-pole magnet being magnetized along the axial direction of the magnet, and the T magnet being magnetized toward the N-pole magnet or the S-pole magnet.

[0007] The inner middle parts of the N-pole magnet and the S-pole magnet are respectively connected to the outer surface of the T magnet, and the inner ends of the N-pole magnet are respectively connected to the inner ends of the S-pole magnet.

[0008] In the above technical solution, the magnetization directions of the N-pole magnet and the S-pole magnet are opposite.

[0009] In the above technical solution, the magnetization direction of the T magnet is perpendicular to the magnetization direction of the N-pole magnet or the S-pole magnet.

[0010] In the above technical solution, the axial ends of the magnet are respectively a first end face and a second end face, the first end face is connected to a motor shaft via a bracket, the magnet and the motor shaft are coaxially arranged, the circuit board is arranged on one side of the second end face of the magnet, and a distance is provided between the circuit board and the second end face of the magnet; the magnetic sensor includes a group of AMR sensors and at least two groups of TMR sensors, the AMR sensor is installed at the center of the circuit board, and the AMR sensor is arranged opposite the center of the second end face of the magnet, and multiple groups of TMR sensors are arranged on the circuit board next to the AMR sensor, and the TMR sensors are arranged opposite the second end face of the magnet.

[0011] In the above technical solution, the AMR sensor is arranged facing the T magnet.

[0012] In the above technical solution, the thickness of the T magnet is equal to the thickness of the N-pole magnet and the S-pole magnet; the width of the T magnet is M, and the length of the T magnet is L;

[0013] The R+a <M<2*(R+a);

[0014] The 2*M <L<R0-2*a-R1;

[0015] Wherein, a is the maximum eccentric runout of the motor shaft;

[0016] R0 is the outer diameter of the magnet;

[0017] R is the outer diameter of the effective sensing area of the AMR sensor;

[0018] R1 is the outer diameter of the effective sensing area of the TMR sensor.

[0019] In the above technical solution, the cross-section of the T magnet is a rectangular, square, elliptical or polygonal symmetrical structure.

[0020] To achieve the above object, the present invention adopts a motor, including a motor shaft and the above-mentioned anti-shaft jump high-precision magnetic encoder, and the magnet is driven to rotate by the motor shaft.

[0021] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0022] 1. The present invention employs a laterally magnetized T-magnet positioned in the center of the magnet. Compared to conventional structures, this effectively improves the parallelism of the magnetic field. Furthermore, the magnetic field density is higher above the center of the magnet, enhancing the parallelism and intensity of the magnetic field received by the magnetic sensor. This improves the accuracy of the magnetic encoder and addresses the issues of reduced accuracy caused by shaft runout and bearing clearance, ensuring the accuracy of the encoding. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a schematic diagram of the structure of the AMR sensor facing the magnet at point E in the background technology;

[0024] Figure 2 1 is a schematic diagram of the structure of the AMR sensor facing the magnet E1 in the background technology;

[0025] Figure 3 1 is a schematic diagram of the magnetic field structure of the magnet when the AMR sensor in the background technology is facing the magnet point E1;

[0026] Figure 4 Schematic diagram of the two signals of the AMR sensor and the signal of the TMR sensor and the magnet angle in the present invention;

[0027] Figure 5 Schematic diagram of the structure of the magnet and circuit board in the magnetic encoder in the first embodiment of the present invention (the cross section of the T magnet is a square structure);

[0028] Figure 6 This is a structural diagram of the magnetization direction of the magnet in the magnetic encoder in the first embodiment of the present invention;

[0029] Figure 7 1 is a schematic diagram of the magnetic field structure when the AMR sensor in the magnetic encoder in the first embodiment of the present invention faces the magnet E1;

[0030] Figure 8 Schematic diagram of the end face structure of the magnet in the magnetic encoder in the first embodiment of the present invention (the cross section of the T magnet is a polygonal structure);

[0031] Figure 9 Schematic diagram of the end face structure of the magnet in the magnetic encoder in the first embodiment of the present invention (the cross section of the T magnet is an elliptical structure);

[0032] Figure 10 It is a structural diagram of the motor in the first embodiment of the present invention.

[0033] Among them: 1. magnet; 2. circuit board; 3. T magnet; 4. N-pole magnet; 5. S-pole magnet; 6. first end face; 7. second end face; 8. bracket; 9. motor shaft; 10. AMR sensor; 11. TMR sensor; 12. motor. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0035] In a magnetic encoder (magnets have only S-pole and N-pole magnets), the AMR sensor is mainly responsible for converting the magnet angle θ of 0° to 360° into sine and cosine information sin(2*θ) and cos(2*θ), see Figure 4 shown.

[0036] In this way, the two signals of the AMR sensor enter the MCU of the circuit board, and the digital quantities are divided:

[0037] sin(2*θ) / cos(2*θ)=tan(2*θ)=a;

[0038] Then, take the inverse tangent of the result: arctan(a) = 2*θ.

[0039] However, since the obtained value is 2*θ, it is impossible to distinguish between 0-180 degrees and 180-360 degrees. The TMR sensor is introduced. Whenever the magnet rotates, a jump edge will be generated when the TMR sensor faces the intersection of the S-pole magnet and the N-pole magnet. The signals generated by the two sets of TMR sensors are shown in Figure 2. Figure 4 As shown. Then, according to the 0 and 1 states of the TMR sensor output signal, there are 4 states: (1, 0), (1, 1), (0, 1), (0, 0); when the state is (1, 0) and (1, 1), the mechanical angle is 0° to 180°, and when the state is (0, 1) and (0, 0), the mechanical angle is 180° to 360°. Therefore, this magnet can correctly resolve the mechanical angle when combined with the AMR sensor + TMR sensor.

[0040] Example 1: See Figures 5-10As shown, a high-precision magnetic encoder with anti-shaft jump includes a magnet 1 and a circuit board 2. A magnetic sensor is provided on the circuit board. The magnet is a cylindrical structure. A T magnet 3 is provided at the center of the magnet. The two sides of the T magnet are symmetrically arranged N-pole magnets 4 and S-pole magnets 5. The N-pole magnet and S-pole magnet are magnetized along the axial direction of the magnet, and the T magnet is magnetized toward the N-pole magnet or S-pole magnet.

[0041] See also Figure 5 、 6 As shown in Figures 8 and 9, the inner middle portions of the N-pole magnet and the S-pole magnet are respectively connected to the outer surface of the T-pole magnet, and the inner ends of the N-pole magnet are respectively connected to the inner ends of the S-pole magnet. Compared with conventional cylindrical magnets, in which the N-pole magnet and the S-pole magnet are symmetrically arranged, in this embodiment, a through groove is dug in the center of the magnet, and the T-magnet is installed in this through groove, and the outer wall of the T-magnet is connected to the inner walls of the N-pole magnet and the S-pole magnet.

[0042] The magnetization directions of the N-pole magnet and the S-pole magnet are opposite.

[0043] The magnetization direction of the T magnet is perpendicular to the magnetization direction of the N-pole magnet or the S-pole magnet.

[0044] In this embodiment, the magnetization direction of the T magnet is arranged toward the N-pole magnet.

[0045] See also Figure 6 、 10 As shown, the axial ends of the magnet are respectively a first end face 6 and a second end face 7, the first end face is connected to a motor shaft 9 via a bracket 8, the magnet and the motor shaft are coaxially arranged, the circuit board is arranged on one side of the second end face of the magnet, and a distance is provided between the circuit board and the second end face of the magnet; the magnetic sensor includes a group of AMR sensors 10 and two groups of TMR sensors 11, the AMR sensor is installed at the center of the circuit board, and the AMR sensor is arranged opposite the center of the second end face of the magnet, and multiple groups of TMR sensors are arranged on the circuit board next to the AMR sensor, and the TMR sensors are arranged opposite the second end face of the magnet.

[0046] The AMR sensor is arranged opposite to the T magnet.

[0047] The above describes the principle of using magnets, AMR sensors, and TMR sensors to analyze mechanical angles. When the motor shaft is eccentric, the AMR sensor will always face the T magnet. In this way, the parallelism of the magnetic field in the direction of the magnetic field is significantly improved, and the magnetic field density between the second end face of the magnet and the circuit board is further increased, which can improve the accuracy of the magnetic encoder and ensure its accuracy.

[0048] The thickness of the T magnet is equal to the thickness of the N-pole magnet and the S-pole magnet; the width of the T magnet is M, and the length of the T magnet is L;

[0049] The R+a <M<2*(R+a);

[0050] The 2*M <L<R0-2*a-R1;

[0051] Wherein, a is the maximum eccentric runout of the motor shaft;

[0052] R0 is the outer diameter of the magnet;

[0053] R is the outer diameter of the effective sensing area of the AMR sensor;

[0054] R1 is the outer diameter of the effective sensing area of the TMR sensor.

[0055] In this embodiment, the magnetization direction of the N-pole magnet is set toward the second end face of the magnet, that is, toward the circuit board, and the magnetization direction of the S-pole magnet is set toward the first end face, that is, away from the circuit board. Since the magnetization direction of the N-pole magnet is toward the AMR sensor, the magnetization direction of the T-pole magnet will be toward the N-pole magnet, making the magnetic field density between the magnet and the circuit board higher and the magnetic field parallelism better, see Figure 7 That is to say, the magnet constitutes a parallel magnetic field generator to improve the parallelism and density of the magnetic field and thus improve the accuracy of the magnetic encoder.

[0056] By precisely designing the size of the T magnet, it is possible to ensure that the AMR sensor is facing the T magnet while also ensuring high magnetic field density and good parallelism, thereby ensuring high accuracy of the magnetic encoder.

[0057] In this embodiment, the cross-section of the T-magnet is a symmetrical rectangular, square, elliptical, or polygonal structure. A north-pole magnet and an south-pole magnet are symmetrically positioned on either side of the center of the magnet. The T-magnet is positioned between the north-pole and south-pole magnets and symmetrically positioned along the line connecting the north-pole and south-pole magnets.

[0058] To achieve the above-mentioned purpose, the present invention adopts a motor 12, which includes a motor shaft and the above-mentioned anti-shaft jump high-precision magnetic encoder, and the magnet is driven to rotate by the motor shaft.

Claims

1. A high-precision magnetic encoder with anti-shaft jump, comprising a magnet and a circuit board, wherein the circuit board is provided with a magnetic sensor, characterized in that: The magnet is a cylindrical structure, with a T-magnet located in the center of the magnet. A symmetrically arranged N-pole magnet and S-pole magnet are located on either side of the T-magnet. The N-pole magnet and S-pole magnet are magnetized along the axial direction of the magnet, and the T-magnet is magnetized toward the N-pole magnet or the S-pole magnet. The axial ends of the magnet are respectively a first end face and a second end face, the first end face is connected to a motor shaft via a bracket, the magnet and the motor shaft are coaxially arranged, the circuit board is arranged on one side of the second end face of the magnet, and a distance is provided between the circuit board and the second end face of the magnet; the magnetic sensor includes a group of AMR sensors and at least two groups of TMR sensors, the AMR sensor is installed at the center of the circuit board, and the AMR sensor is arranged opposite the center of the second end face of the magnet, and multiple groups of TMR sensors are arranged on the circuit board beside the AMR sensor, and the TMR sensors are arranged opposite the second end face of the magnet; The AMR sensor is arranged opposite to the T magnet; The thickness of the T magnet is equal to the thickness of the N-pole magnet and the S-pole magnet; the width of the T magnet is M, and the length of the T magnet is L; The R+a <M<2*(R+a); The 2*M <L<R0-2*a-R1; Wherein, a is the maximum eccentric runout of the motor shaft; R0 is the outer diameter of the magnet; R is the outer diameter of the effective sensing area of the AMR sensor; R1 is the outer diameter of the effective sensing area of the TMR sensor.

2. The anti-shaft jump high-precision magnetic encoder according to claim 1 is characterized in that: The inner middle parts of the N-pole magnet and the S-pole magnet are respectively connected to the outer surface of the T magnet, and the inner ends of the N-pole magnet are respectively connected to the inner ends of the S-pole magnet.

3. The high-precision magnetic encoder with anti-shaft jump according to claim 1 is characterized in that: The magnetization directions of the N-pole magnet and the S-pole magnet are opposite.

4. The high-precision magnetic encoder with anti-shaft jump according to claim 1 is characterized in that: The magnetization direction of the T magnet is perpendicular to the magnetization direction of the N-pole magnet or the S-pole magnet.

5. The anti-shaft jump high-precision magnetic encoder according to claim 1 is characterized in that: The cross section of the T magnet is a rectangular, square, elliptical or polygonal symmetrical structure.

6. A motor, comprising a motor shaft, characterized in that: It comprises the anti-shaft jump high-precision magnetic encoder according to any one of claims 1 to 5, wherein the magnet is driven to rotate by the motor shaft.

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