JP7489583B2 - Rotation detector and motor equipped with the same - Google Patents

Description

The present disclosure relates to a rotation detector and a motor equipped with the same. In particular, the present disclosure relates to a rotation detector that detects the amount of rotation of a rotating shaft of a motor.

Conventionally, absolute encoders have been widely used to detect the rotational position and amount of rotation of the rotating shaft of a motor, etc. Absolute encoders detect the rotational position and amount of rotation based on a fixed origin position. Since absolute encoders retain data on the origin position, there is no need for position adjustments to return to the origin even if the power is cut off.

On the other hand, absolute encoders require a backup power source to retain data when the power is cut off. Typically, a battery is used as the backup power source. However, the battery needs to be replaced periodically, and battery maintenance is time-consuming. For this reason, several battery-less encoders have been proposed.

For example, Patent Document 1 discloses a rotation detector that detects the amount of rotation of a magnet and, ultimately, a rotating shaft by using first and second magnetic sensors to detect changes in the magnetic field that accompany the rotation of a magnet attached to a rotating shaft. This rotation detector further has first and second magnetic sensing parts, and uses, as drive power, pulsed electric power generated in the first and second magnetic sensing parts by changes in the magnetic field that accompany the rotation of the magnet (see Figures 15 to 18 in particular).

However, the conventional configuration disclosed in Patent Document 1 requires first and second magnetic sensing parts to supply driving power, making it difficult to miniaturize the rotation detector.

In this configuration, the amount of rotation is detected according to the timing at which pulsed power is generated. Therefore, if for some reason a pulse is not generated or its value is small, a complicated correction operation is required, reducing the robustness of the amount of rotation detection.

JP 2018-105894 A

This disclosure has been made in light of these points. The purpose of this disclosure is to provide a rotation detector that has a simple configuration and improves the robustness of rotation amount detection, and a motor equipped with the same.

In order to achieve the above object, the rotation detector according to the present disclosure is a rotation detector that detects the amount of rotation of the rotating shaft of a motor, and includes a power generating magnet that is attached to the rotating shaft and rotates integrally with it, and has four or more magnetic poles in the outer circumferential direction, at least one power generating element consisting of a magnetic sensing part and an induction coil, a first magnetic sensor, a second magnetic sensor, and a magnetic flux control member that changes position together with the power generating magnet due to the rotation of the rotating shaft, and may generate an excitation voltage in at least one of the first magnetic sensor and the second magnetic sensor, and drives the first magnetic sensor and the second magnetic sensor with the power generated by the power generating element due to the rotation of the power generating magnet.

The motor according to the present disclosure comprises at least a rotor having a rotating shaft, a stator arranged coaxially with the rotor and spaced a predetermined distance from the rotor, and a rotation detector attached to the rotating shaft.

The rotation detector of the present disclosure can realize a rotation detector with a simple configuration. The rotation detector of the present disclosure can detect the amount of rotation of a rotating shaft without a battery, improving the robustness of rotation amount detection. The motor of the present disclosure can realize a motor whose rotation state can be controlled to a desired state.

1 is a schematic cross-sectional view of a motor according to a first embodiment of the present invention. FIG. 2 is a schematic diagram of a rotary encoder as viewed from a radial direction. FIG. 2 is a schematic diagram showing a circuit board as viewed from above. FIG. 2 is a schematic diagram showing a rotating plate as viewed from above. FIG. 2 is a schematic diagram of a functional block of a signal processing circuit. 1 is a schematic plan view showing how the positions of the magnetic poles of the power-generating magnet and the magnetic shielding plate change when the rotation shaft rotates clockwise. FIG. 1 is a schematic plan view showing how the positions of the magnetic poles of the power-generating magnet and the magnetic shielding plate change when the rotation shaft rotates clockwise. FIG. 1 is a schematic plan view showing how the positions of the magnetic poles of the power-generating magnet and the magnetic shielding plate change when the rotation shaft rotates clockwise. FIG. 6A and 6B are diagrams illustrating changes in detection signals of a first magnetic sensor and a second magnetic sensor when a rotation shaft rotates clockwise. 1 is a schematic plan view showing how the positions of the magnetic poles of the power-generating magnet and the magnetic shielding plate change when the rotation shaft rotates counterclockwise. FIG. 1 is a schematic plan view showing how the positions of the magnetic poles of the power-generating magnet and the magnetic shielding plate change when the rotation shaft rotates counterclockwise. FIG. 1 is a schematic plan view showing how the positions of the magnetic poles of the power-generating magnet and the magnetic shielding plate change when the rotation shaft rotates counterclockwise. FIG. 11 is a diagram showing changes in detection signals of a first magnetic sensor and a second magnetic sensor when a rotating shaft rotates counterclockwise. FIG. 11 is a diagram showing the change in position of the magnetic poles of the power-generating magnet and the magnetic shielding plate when the rotating shaft rotates counterclockwise before and after the power is turned off. FIG. 11 is a diagram showing the change in position of the magnetic poles of the power-generating magnet and the magnetic shielding plate when the rotating shaft rotates counterclockwise before and after the power is turned off. FIG. 13 is a diagram showing the relationship between the position of the magnetic pole of the power generating magnet and area information according to the first modified example. FIG. 13 is a diagram showing changes in detection signals of the first magnetic sensor and the second magnetic sensor when the rotation shaft rotates clockwise in the second modification example. FIG. FIG. 11 is a diagram showing a planar arrangement of power generation magnets according to Modification 3. FIG. 13 is a diagram showing a planar arrangement of another power generating magnet. FIG. 2 is a diagram showing a planar arrangement of power generating elements. 13 is a schematic diagram of a rotary encoder according to a fourth modification, viewed from a radial direction; FIG. 11 is a diagram showing the planar arrangement relationship between a power generating magnet, a magnetic shielding plate, and a power generating element according to a second embodiment of the present invention. FIG. FIG. 2 is a plan view showing the layout of each component in the magnetic encoder. FIG. 11 is a schematic diagram of a rotary encoder according to a third embodiment of the present invention, as viewed from a radial direction. FIG. 2 is a schematic diagram showing a circuit board as viewed from above. FIG. 2 is a schematic diagram showing a rotating plate as viewed from above.

The following describes in detail the embodiments of the present invention with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the present invention, its applications, or its uses.

(Embodiment 1)
[Motor configuration]
Fig. 1 is a schematic cross-sectional view of a motor 300 according to a first embodiment of the present invention. Note that Fig. 1 is a schematic illustration of the structures of the motor 300 and the rotary encoder 100, and differs from the actual shapes and dimensions.

The motor 300 includes a motor case 10, a pair of brackets 21 and 22, a rotor 30, a stator 40, a pair of bearings 51 and 52, and a rotary encoder 100. In the following description, the radial direction of the motor 300, specifically the motor case 10, may be referred to as the radial direction, the inner circumferential direction of the motor 300, specifically the motor case 10, may be referred to as the circumferential direction, and the direction in which the rotating shaft 32 provided on the rotor 30 extends may be referred to as the axial direction. The radial direction of the motor case 10 is the same as the radial direction of the rotating shaft 32, the rotating plate 121 described later, and the power generating magnet 122. The inner circumferential direction of the motor case 10 is the same as the outer circumferential direction of the rotating shaft 32, the rotating plate 121, and the power generating magnet 122. In the axial direction, the side on which the rotary encoder 100 is provided may be referred to as the upper side, and the opposite side, i.e., the side on which the rotor 30 and the stator 40 are provided, may be referred to as the lower side.

The motor case 10 is a cylindrical metal member with both ends open. The rotor 30, the stator 40, and a pair of bearings 51, 52 are housed inside the motor case 10. An elastic body such as an O-ring may be provided at the contact portion between the motor case 10 and the brackets 21, 22. In this way, the inside of the motor case 10 can be kept airtight.

The pair of brackets 21, 22 are flat iron members that cover the openings at both ends of the motor case 10.

The rotor 30 is housed inside the motor case 10, and has a rotating shaft 32 at the axis of the rotor core 31. In addition, multiple magnets (not shown) are arranged along the outer periphery of the rotor core 31, and adjacent magnets have different magnetic poles. The motor 300 is a so-called IPM (Interior Permanent Magnet) motor, in which multiple magnets are embedded inside the rotor core 31.

The rotating shaft 32 is provided so as to penetrate the bracket 21 provided on the output side and protrude to the outside of the motor case 10. A load (not shown) that is rotated in response to the rotation of the rotating shaft 32 is connected to the part of the rotating shaft 32 that protrudes from the bracket 21. The rotating shaft 32 is obtained by processing a magnetic metal such as iron.

The stator 40 is housed inside the motor case 10. The stator 40 is provided radially outside the rotor 30 with a predetermined distance between them. The stator 40 is composed of a yoke 41 fixed to the inner surface of the motor case 10, a number of salient poles (not shown) provided at predetermined intervals along the circumferential direction of the yoke 41, and a number of coils 42 wound around each of the salient poles.

A pair of bearings 51, 52 are attached to the inner surfaces of a pair of brackets 21, 22, respectively, and rotatably support the rotating shaft 32.

The rotary encoder 100 is attached to a rotating shaft 32 that protrudes from the top surface of the bracket 22 to the outside. The rotary encoder 100 has an optical encoder 110 and a magnetic encoder 120. The configuration of the rotary encoder 100 will be described in detail later.

The case 160 is a cylindrical part with a bottom. The case 160 is attached and fixed to the upper surface of the bracket 22 so as to cover the rotary encoder 100. The case 160 is made of a ferromagnetic metal, for example, an iron plate, to prevent the case 160 from being affected by magnetic fields from outside the case 160. The case 160 mechanically protects the rotary encoder 100 and also serves to prevent liquids such as oil and moisture from adhering to the rotary encoder 100.

As mentioned above, the rotating shaft 32 is made of a magnetic material such as iron. For this reason, magnetic flux generated by the magnets provided in the rotor 30 or the stator 40 may pass through the rotating shaft 32 and leak into the inside of the case 160. If this occurs, the rotary encoder 100 may not be able to correctly detect the amount of rotation of the rotating shaft 32. For this reason, the axially upper portion of the rotating shaft 32 may be made of stainless steel and joined to a portion made of iron to prevent magnetic flux from leaking into the inside of the case 160.

Next, the operation and control of the motor 300 will be explained.

The multiple coils 42 provided on the stator 40 are divided into three groups in a predetermined arrangement. A three-phase current having a phase difference of 120° electrical angle flows through each group of coils 42, exciting the coils 42. This generates a rotating magnetic field in the stator 40. An interaction occurs between this rotating magnetic field and the magnetic field generated by the magnet provided on the rotor 30, generating a torque, and the rotating shaft 32 rotates while being supported by the bearings 51 and 52.

The motor control unit 60 is electrically connected to the rotary encoder 100 and each of the multiple coils 42. The rotation state of the motor 300 can be controlled to a desired state by correcting the phase and amount of current flowing through the multiple coils 42 based on the rotation position and amount of rotation of the rotating shaft 32 calculated by the rotary encoder 100. The movement amount and trajectory of the load (not shown) connected to the rotating shaft 32 can be controlled to a desired value.

Here, "amount of rotation" refers to information including the "number of rotations" indicating how many times the rotating shaft 32 has rotated, and the angular range by which the rotating shaft 32 has rotated from a predetermined origin position according to the magnetic pole arrangement of the power generation magnet 122 described later. "Rotational position" refers to the angle by which the rotating shaft 32 has rotated from a predetermined origin position, and in this embodiment, refers to the angle by which the rotating shaft 32 has rotated from the origin position within one rotation. Information on the origin position is recorded in the transmission pattern 113 of the optical encoder 110 described later. Information on the origin position can be roughly known from the detection signals of the first magnetic sensor 124 and the second magnetic sensor 125 provided in the magnetic encoder 120.

[Configuration of a rotary encoder]
Fig. 2 is a schematic diagram of the rotary encoder 100 as viewed from the radial direction. Fig. 3 is a schematic diagram of the circuit board 130 as viewed from above. Fig. 4 is a schematic diagram of the rotating plate as viewed from above. Fig. 5 is a schematic diagram of the functional blocks of the signal processing circuit.

As shown in Figures 1 and 2, the rotary encoder 100 has an optical encoder 110, a magnetic encoder 120, a circuit board 130, a sensor board 140, and a signal processing circuit 200. The rotary encoder 100 is the absolute encoder described above.

The optical encoder 110 detects the rotational position of the rotating shaft 32. The optical encoder 110 may also detect the amount of rotation of the rotating shaft 32. The magnetic encoder 120 detects the amount of rotation of the rotating shaft 32 based on changes in the magnetic field detected by the first magnetic sensor 124 and the second magnetic sensor 125. The signal processing circuit 200 determines area information (described later) based on the detection signals of the first magnetic sensor 124 and the second magnetic sensor 125. In the following description, the optical encoder 110 may be referred to as a rotational position detector, and the rotary encoder 100 may be referred to as a rotation detector.

The optical encoder 110 has a light receiving element 111, a light emitting element 112, a rotating plate 121, and a transparent pattern 113 (see Figures 1 and 4) arranged on the upper surface of the rotating plate 121. The rotating plate 121 is attached to the rotating shaft 32 so as to rotate integrally. The rotating plate 121 is shared with the magnetic encoder 120. The rotating plate 121 is made of a material that allows magnetic flux to pass through, for example, a non-magnetic metal such as aluminum or a resin. The rotating plate 121 is made of a material that allows light from the light emitting element 112 to pass through.

The light emitting element 112 is attached to the upper surface of the sensor board 140, and the light receiving element 111 is attached to the lower surface of the circuit board 130, facing each other in the axial direction. The sensor board 140 is fixedly disposed below the rotating plate 121 with a gap therebetween. The circuit board 130 is fixedly disposed above the rotating plate 121 with a gap therebetween. A terminal (not shown) of the circuit board 130 and a terminal (not shown) of the sensor board 140 are connected by a connector 150. Electricity is supplied to the light emitting element 112 via the connector 150. In addition, as shown in Figures 1 and 2, a transparent pattern 113 is disposed between the light emitting element 112 and the light receiving element 111 when viewed from the radial direction.

As shown in FIG. 4, the transmission pattern 113 is annular, with multiple slits (not shown) for transmitting light from the light-emitting element 112 and multiple mask patterns (not shown) for blocking the same light, arranged alternately at a predetermined angular pitch along the circumferential direction. Therefore, as the rotating plate 121 rotates, light is periodically incident on and blocked by the light-receiving element 111, which faces the light-emitting element 112 in the axial direction, and the light-receiving element 111 generates a time-modulated light-receiving signal. The rotational position of the rotating plate 121, and therefore the rotating shaft 32, is detected by processing this light-receiving signal by the signal processing circuit 200 attached to the circuit board 130.

The magnetic encoder 120 has a power generating magnet 122, a magnetic shielding plate 123, a first magnetic sensor 124, a second magnetic sensor 125, and a power generating element 126, and the power generating magnet 122 is attached to the upper surface of the rotating plate 121.

The power generation magnet 122 is annular in plan view, with multiple magnetic poles arranged at an equal angular pitch along the circumferential direction. Adjacent magnetic poles have different polarities. The number of magnetic poles of the power generation magnet 122 shown in FIG. 4 is eight, but is not limited to this. For example, as shown in FIGS. 6A, 6B, and 6C, it may have six poles. If there are four or more poles, the amount of rotation of the rotating shaft 32 can be detected. FIGS. 6A, 6B, and 6C are schematic plan views showing the change in position of the magnetic poles of the power generation magnet 122 and the magnetic shielding plate 123 when the rotating shaft 32 rotates clockwise.

The magnetic shielding plate 123 is a flat plate-shaped part made of a material that shields magnetism, such as iron. The magnetic shielding plate 123 is attached to the underside of the rotating plate 121. In other words, as the rotating plate 121 rotates, the power generation magnet 122 and the magnetic shielding plate 123 rotate integrally around the axis of the rotating shaft 32. As shown in FIG. 4, the magnetic shielding plate 123 has a semicircular sector shape in a plan view. However, this shape changes depending on the number of magnetic poles. For example, as shown in FIG. 6A, FIG. 6B, and FIG. 6C, when a six-pole power generation magnet 122 is used, the planar shape of the magnetic shielding plate 123 is a sector shape with a central angle of 120 degrees. The power generation magnet 122 and the magnetic shielding plate 123 are arranged concentrically.

As shown in Figs. 1 and 4, the power generating magnet 122 and the magnetic shielding plate 123 are arranged radially inward from the inner circumference of the transparent pattern 113. However, this is not limited to the above, and for example, the power generating magnet 122 and the magnetic shielding plate 123 may be arranged radially outward from the outer circumference of the transparent pattern 113.

As shown in FIG. 2, the first magnetic sensor 124 and the second magnetic sensor 125 are attached to the underside of the sensor board 140. As shown in FIG. 3, the first magnetic sensor 124 and the second magnetic sensor 125 are attached to the sensor board 140 at a predetermined interval in the circumferential direction and 90 degrees apart along the circumferential direction. The excitation voltages generated by the first magnetic sensor 124 and the second magnetic sensor 125 are transmitted as detection signals via the connector 150 to the signal processing circuit 200 attached to the circuit board 130.

As shown in Figures 2 to 4, the magnetic shielding plate 123 is provided so as to cover half of the power generation magnet 122. Therefore, when viewed from the axial direction, if the magnetic shielding plate 123 is located between the power generation magnet 122 and the first magnetic sensor 124, the first magnetic sensor 124 does not detect the magnetic field. If the magnetic shielding plate 123 is not located between the power generation magnet 122 and the first magnetic sensor 124, the first magnetic sensor 124 detects the magnetic field and generates an excitation voltage. Similarly, if the magnetic shielding plate 123 is located between the power generation magnet 122 and the second magnetic sensor 125, the second magnetic sensor 125 does not detect the magnetic field. If the magnetic shielding plate 123 is not located between the power generation magnet 122 and the second magnetic sensor 125, the second magnetic sensor 125 detects the magnetic field and generates an excitation voltage.

Therefore, when the power generating magnet 122 and the magnetic shielding plate 123 rotate together with the rotation of the rotating plate 121, periods in which an excitation voltage is generated and periods in which it is not generated are periodically repeated in each of the first magnetic sensor 124 and the second magnetic sensor 125. This is used to detect the amount of rotation of the rotating shaft 32. This will be described in detail later.

The magnetic shielding plate 123 can be said to be a member that controls the magnetic flux generated by the power generating magnet 122 from flowing into the first magnetic sensor 124 or the second magnetic sensor 125. In other words, the magnetic shielding plate 123 is a magnetic flux control member that may generate an excitation voltage in at least one of the first magnetic sensor 124 and the second magnetic sensor 125.

The first magnetic sensor 124 and the second magnetic sensor 125 are magnetic resistance sensors including magnetic resistance elements. However, they are not limited to this. For example, they may be Hall sensors including Hall elements. By using a magnetic resistance sensor, the excitation voltage is increased, and as a result, the amount of rotation can be detected with high sensitivity and reliability. In order to increase the detection sensitivity of the amount of rotation, the magnetic resistance element may be an element that exhibits a giant magnetoresistance effect. On the other hand, by using a Hall sensor, the difference in the direction of the magnetic flux detected by the sensor can be detected as a difference in the polarity of the detection signal. An element that exhibits a tunnel magnetoresistance effect may also be used.

The power generating element 126 is composed of a Wiegand wire 126a, which is a magnetically sensitive part, and an induction coil 126b arranged around it. The Wiegand wire 126a is a magnetic material with different magnetic permeability at the axis and on the outside. When a magnetic field of a predetermined value or more is applied inside the induction coil 126b along the longitudinal direction, the Wiegand wire 126a exhibits the large Barkhausen effect, and the magnetization direction is aligned to one side of the longitudinal direction. The power generating element 126 is configured such that when the direction of the magnetic flux flowing inside the induction coil 126b along the longitudinal direction changes, the magnetization direction of the Wiegand wire 126a jumps back and a voltage pulse is induced at both ends of the induction coil 126b.

As shown in Figures 1 to 3, the power generating element 126 is attached to the upper surface of the circuit board 130 so that its longitudinal direction coincides with the tangent to the circumferential direction of the power generating magnet 122. As a result, when the power generating magnet 122 rotates together with the rotating plate 121, magnetic flux flows from one end of the power generating element 126 to the other end at a certain position, and a voltage pulse is induced at both ends of the induction coil 126b. In other words, power is generated by the power generating element 126. When it rotates a further 45 degrees, the direction of the magnetic flux flowing through the power generating element 126 is reversed, and a voltage pulse of the opposite polarity to that immediately before is induced at both ends of the induction coil 126b.

The signal processing circuit 200 is attached to the upper surface of the circuit board 130 and is electrically connected to the light receiving element 111, the first magnetic sensor 124, and the second magnetic sensor 125.

As shown in FIG. 5, the signal processing circuit 200 has an optical signal processing circuit 210 that receives the light receiving signal from the light receiving element 111 and processes it, and a magnetic signal processing circuit 220 that receives the detection signals from the first magnetic sensor 124 and the second magnetic sensor 125 and processes them. Note that in this specification, the internal configuration of the optical signal processing circuit 210 will not be illustrated or described.

The signal processing circuit 200 and the first and second magnetic sensors 124 and 125 are electrically connected to a power supply 230 provided outside the rotary encoder 100. During normal operation, the driving power of each of the optical signal processing circuit 210 and the magnetic signal processing circuit 220 is supplied from the power supply 230. Similarly, the driving power of each of the first and second magnetic sensors 124 and 125 is supplied from the power supply 230.

On the other hand, if the power supply 230 stops for some reason, the driving power for the magnetic signal processing circuit 220, the first magnetic sensor 124, and the second magnetic sensor 125 is supplied from the power generating element 126. Note that during normal operation, the driving power for the magnetic signal processing circuit 220, the first magnetic sensor 124, and the second magnetic sensor 125 may be supplied from the power generating element 126.

The optical signal processing circuit 210 receives the light receiving signal from the light receiving element 111, processes it, and calculates the rotational position of the rotating shaft 32. The magnetic signal processing circuit 220 receives the detection signals from the first magnetic sensor 124 and the second magnetic sensor 125, processes them, and calculates the amount of rotation of the rotating shaft 32. It also determines the area information. Note that if the optical encoder 110 detects both the rotational position and the amount of rotation of the rotating shaft 32, a storage unit (not shown) may be provided in the optical signal processing circuit 210 to store information on the amount of rotation.

Based on the rotational position and amount of rotation of the rotating shaft 32 calculated by the signal processing circuit 200, as described above, the phase and amount of current flowing through the motor 300 are corrected, and the rotational state of the motor 300 is controlled to be in a desired state. When no power is supplied from the power source 230 to the signal processing circuit 200, that is, when the so-called power-unsupplied state is reached, the amount of rotation of the rotating shaft 32 is updated as necessary based on the area information determined by the magnetic signal processing circuit 220.

As shown in FIG. 5, the magnetic signal processing circuit 220 has a full-wave rectifier 221, a voltage regulator 224, a plurality of comparators 225a, 225b, 226a, and 226b, a logic information processing unit 227, a memory unit 228, and a communication unit 229. The magnetic signal processing circuit 220 has a disconnection diagnosis unit 223 and a backflow prevention switch 222.

The full-wave rectifier 221 is electrically connected to the power generating element 126. The voltage pulse generated by the power generating element 126 is rectified by the full-wave rectifier 221.

The voltage regulator 224 may be a so-called LDO (Low Drop Out) regulator or a so-called shunt regulator. The voltage regulator 224 outputs a constant voltage using the system ground potential (SGND) as a reference potential and the terminal voltage of the capacitor C charged with the output voltage of the full-wave rectifier 221 as an input voltage. The output voltage of the voltage regulator 224 is about 2 to 3 V, but is not particularly limited to this.

If for some reason the signal processing circuit 200 is in an unpowered state, the output voltage of the voltage regulator 224 is input to each section of the magnetic signal processing circuit 220 and used to drive these functional blocks. In the same case, the output voltage of the voltage regulator 224 is also used to drive the first magnetic sensor 124 and the second magnetic sensor 125.

The voltage regulator 224 outputs a voltage during the period when the power generating element 126 generates power and generates a voltage pulse. During this period, the magnetic signal processing circuit 220, the first magnetic sensor 124, and the second magnetic sensor 125 are driven by the output voltage of the voltage regulator 224.

The open circuit diagnosis unit 223 is connected to the input terminal of the full wave rectification unit 221 and diagnoses whether or not there is an open circuit in this part. The backflow prevention switch 222 is connected in series between the full wave rectification unit 221 and the voltage regulator 224 and prevents current from flowing back from the voltage regulator 224 to the full wave rectification unit 221.

The comparators 225a and 225b each receive the detection signal of the first magnetic sensor 124, compare it with a predetermined voltage value, and input the output voltage, which is the comparison result, to the logic information processing unit 227. The comparators 226a and 226b each receive the detection signal of the second magnetic sensor 125, compare it with a predetermined voltage value, and input the output voltage, which is the comparison result, to the logic information processing unit 227.

The logic information processing unit 227 calculates the amount of rotation of the rotating shaft 32 based on the output voltage of each comparator 225a, 225b, 226a, and 226b, and determines the area information. The memory unit 228 stores the amount of rotation and area information of the rotating shaft 32 input from the logic information processing unit 227. The memory unit 228 is composed of a non-volatile memory, for example, FRAM (registered trademark). The communication unit 229 is connected to the ASIC (application specific integrated circuit) 240 so as to be able to communicate with it by wire or wirelessly. The ASIC 240 forms part of the signal processing circuit 200, and controls communication with a motor amplifier (not shown) provided in the motor control unit 60, and generates rotational position information detected by the optical encoder 110. The ASIC 240 generates absolute position information of the rotating shaft 32 from the rotational position information and multi-rotation information S described later.

By reading out the information on the amount of rotation stored in the memory unit 228 via the communication unit 229 and combining it with the information on the rotation position calculated by the optical encoder 110, it is possible to obtain multi-rotation information S of the rotating shaft 32. For example, if the rotation position from the origin position at a certain point in time is θ and the number of rotations of the rotating shaft 32 since the motor 300 is started is n, the multi-rotation information S corresponding to the integrated rotation angle of the rotating shaft 32 can be expressed in the form shown in formula (1).

S = θ + 2πn ... (1)
The multi-rotation information S may be stored in the storage unit 228. If the motor 300 is a servo motor used in a joint axis of a robot arm, the amount of movement of the tip of the robot arm can be calculated based on the multi-rotation information S. Note that if the optical encoder 110 detects both the rotation position and amount of rotation of the rotating shaft 32, the multi-rotation information S may be calculated only from the detection result of the optical encoder 110. Also, as described above, absolute position information of the rotating shaft 32 can be found from the rotation position information detected by the optical encoder 110 and the multi-rotation information S.

The signal processing circuit 200 may have a capacitor C therein. The communication unit 229 may be provided in the optical signal processing circuit 210.

The optical signal processing circuit 210 is configured as an LSI (large scale integrated circuit). Of the magnetic signal processing circuit 220, the logic information processing unit 227, the comparators 225a, 225b, 226a, 226b, and the communication unit 229 may be provided on the same LSI as the optical signal processing circuit 210, or may be configured on different LSIs.

[Calculation and update of rotation amount and determination of area information]
Figures 6A, 6B, and 6C are schematic plan views showing the change in position of the magnetic poles of the power generation magnet and the magnetic shielding plate when the rotating shaft rotates clockwise. Figure 7 is a diagram showing the change in detection signals of the first magnetic sensor and the second magnetic sensor when the rotating shaft rotates clockwise. Figures 8A, 8B, and 8C are schematic plan views showing the change in position of the magnetic poles of the power generation magnet and the magnetic shielding plate when the rotating shaft rotates counterclockwise. Figure 9 is a diagram showing the change in detection signals of the first magnetic sensor and the second magnetic sensor when the rotating shaft rotates counterclockwise.

For ease of explanation, the power generating magnet 122 shown in Figures 6A to 9 has six poles, and the planar shape of the magnetic shielding plate 123 is a sector shape with a central angle of 120 degrees. Also, the components of the rotating plate 121, sensor board 140, circuit board 130, and optical encoder 110 are not shown.

In Figures 6A, 6B, 6C, 8A, 8B, and 8C, the positions of the power generating element 126, the first magnetic sensor 124, and the second magnetic sensor 125 are also shown when viewed from the axial direction. In Figures 6A, 6B, 6C, 8A, 8B, and 8C, among the lines that pass through the center of the power generating magnet 122 and extend in the radial direction, the solid lines indicate positions I to VI where a voltage pulse is generated in the power generating element 126 when the magnet is rotated in the clockwise direction. The dashed lines indicate positions i to vi where a voltage pulse is generated in the power generating element 126 when the magnet is rotated in the counterclockwise direction. The dashed and dotted lines indicate the outer circumference of the power generating magnet 122 and the positions of each magnetic pole at the origin position.

Here, positions I to VI and positions i to vi are the rotational positions of any one of the magnetic poles of the power generating magnet 122 with respect to the origin position. Note that each position shown in Figures 6A, 6B, 6C, 8A, 8B, and 8C is a position in the stationary coordinate system.

The direction of rotation of the rotating shaft 32, in other words, the direction of rotation of the power generating magnet 122 and the magnetic shielding plate 123, is based on the direction from bottom to top along the axial direction. In other words, it is based on the direction along the axial direction when looking at the rotary encoder 100 from the motor 300. In the following explanation, the clockwise direction may be referred to as the CW direction (CW: Clock Wise) and the counterclockwise direction as the CCW direction (CCW: Counter Clock Wise).

As shown in FIG. 6A, when viewed from the axial direction, if the magnetic shielding plate 123 is not positioned between the power generating magnet 122 and the first and second magnetic sensors 124 and 125, the first and second magnetic sensors 124 and 125 each detect magnetism and generate an excitation voltage. In the magnetic signal processing circuit 220, the signal in the state in which the excitation voltage is generated is calculated as "1". Therefore, in the state shown in FIG. 6A, a signal (11) is detected. Note that the first number in parentheses represents the detection signal of the first magnetic sensor 124, and the next number represents the detection signal of the second magnetic sensor 125.

The first magnetic sensor 124 and the second magnetic sensor 125 detect signals without distinguishing between the north and south poles of the power generating magnet 122.

When the rotating shaft 32 rotates in the CW direction, as shown in FIG. 6B, the magnetic shielding plate 123 is positioned only between the power generating magnet 122 and the second magnetic sensor 125 when viewed from the axial direction. At this time, the second magnetic sensor 125 does not detect magnetism and no excitation voltage is generated. The magnetic signal processing circuit 220 calculates the signal in a state where no excitation voltage is generated as "0". Therefore, in the state shown in FIG. 6B, a signal (10) is detected.

When the rotating shaft 32 rotates further in the CW direction, as shown in FIG. 6C, the magnetic shielding plate 123 is positioned only between the power generating magnet 122 and the first magnetic sensor 124 when viewed from the axial direction. At this time, the first magnetic sensor 124 does not detect magnetism and no excitation voltage is generated. Therefore, in the state shown in FIG. 6C, a signal (01) is detected. These signals correspond to the aforementioned area information. The area information roughly corresponds to the rotational position based on the origin position, and corresponds to three rotational positions spaced 120 degrees apart in the circumferential direction.

As shown in FIG. 7, the logical information processing unit 227 determines the angle range of the rotation shaft 32 in which the signal (11) is detected as region 1, the angle range of the rotation shaft 32 in which the signal (10) is detected as region 2, and the angle range of the rotation shaft 32 in which the signal (01) is detected as region 3.

To summarize the above, when the rotating shaft 32 rotates in the CW direction from the position shown in Figure 6A, the signals detected by the first magnetic sensor 124 and the second magnetic sensor 125 change in the order (11) → (10) → (01), and based on this change, the logical information processing unit 227 determines that the angle range of the rotating shaft 32 has transitioned in the order of area 1 → area 2 → area 3.

In addition, Figures 8A, 8B, 8C, and 9 correspond to Figures 6A, 6B, 6C, and 7, respectively, when the rotating shaft 32 rotates in the CCW direction, so only an outline will be explained.

When the rotating shaft 32 rotates in the CCW direction from the position shown in Figure 8A, the signals detected by the first magnetic sensor 124 and the second magnetic sensor 125 change in the order (11) → (01) → (10). Based on this change, the logical information processing unit 227 determines that the angular range of the rotating shaft 32 has transitioned in the order of area 1 → area 3 → area 2.

By using these facts, the amount of rotation of the rotation axis 32 can be calculated. We will explain further.

As shown in Figures 7 and 9, regions 1 to 3 each correspond to an angular range of the rotation axis 32 from the origin position. Note that because power is generated when both ends of the power generating element 126 straddle magnetic poles of opposite polarity, the position at which the power generating element 126 generates a voltage pulse does not match the position of each magnetic pole from the origin position shown in Figures 6A, 6B, 6C, 8A, 8B, and 8C. The timing at which magnetic flux flows from one end of the power generating element 126 to the other end differs during rotation in the CW direction and during rotation in the CCW direction, so the position at which the voltage pulse is generated in both cases is shifted by a certain angle in the circumferential direction.

When a voltage pulse is generated in the power generating element 126, if the region information determined when the previous voltage pulse was generated has transitioned to a predetermined region, the number of rotations can be counted up or down, allowing the number of rotations to be counted accurately. When the number of rotations is the same, the angle range of the rotation axis 32 from the origin position can be detected from the difference in the region information. The amount of rotation of the rotation axis 32 is calculated based on this information.

In the examples shown in Figures 6A, 6B, 6C, and 7, when there is a transition from region 2 to region 3, specifically, the number of rotations is counted down at position IV where a voltage pulse occurs immediately after the transition from region 2 to region 3.

In addition, for each region, there are two positions where a voltage pulse occurs. Therefore, if for some reason the voltage pulse generated at position IV is small and the region transition cannot be detected, the number of rotations is counted down at the timing when the voltage pulse occurs at position V.

Also, as shown in Figures 8A, 8B, 8C, and 9, when the rotating shaft 32 is rotating in the CCW direction, the number of rotations is counted up at position iv where a voltage pulse occurs immediately after the transition from region 3 to region 2. If for some reason the voltage pulse generated at position iv is small and the region transition cannot be detected, the number of rotations is counted up at the timing when a voltage pulse occurs at position iii.

When the area information transitions in this way, the area information stored in the memory unit 228 is rewritten at the detection timing. When the rotation speed changes, the information stored in the memory unit 228 is also rewritten and re-saved.

Next, we will explain how to update the rotation amount.

Figure 10A shows how the positions of the magnetic poles of the power generating magnet and the magnetic shielding plate change when the rotating shaft rotates counterclockwise before and after the power is turned off. Figure 10B shows how the positions of the magnetic poles of the power generating magnet and the magnetic shielding plate change when the rotating shaft rotates counterclockwise before and after the power is turned off.

When the power supply 230 stops due to a power outage or equipment shutdown, and then returns to normal, the rotating shaft 32 of the motor 300 may rotate unintentionally before or after the power supply is restored. For example, this may occur when moving equipment equipped with the motor 300.

When the power supply 230 is stopped, the optical encoder 110 is not powered, so the rotational position of the rotating shaft 32 cannot be detected. After the power supply 230 is restored, the rotational position based on the origin position is calculated, but it is not possible to determine whether the amount of rotation has changed. Even in the magnetic encoder 120, even if the rotating shaft 32 rotates within a range in which no voltage pulse is generated, the magnetic signal processing circuit 220 including the logical information processing unit 227 is not powered, so the change in the amount of rotation cannot be detected.

On the other hand, according to this embodiment, the amount of rotation of the motor 300 can be correctly updated based on the area information stored in the memory unit 228 immediately before the power supply 230 is stopped and the rotation position detected by the optical encoder 110.

For example, consider a case where the power supply 230 stops at the position shown in FIG. 10A and returns to the position shown in FIG. 10B, during which the rotating shaft 32 rotates in the CCW direction.

In the state shown in FIG. 10B where the power supply 230 has been restored, the signal processing circuit 200 including the logic information processing unit 227 is in a powered state. However, as shown in FIG. 10B, although the actual angular range of the rotation shaft 32 is in region 3, the information stored in the memory unit 228 remains in region 2 because no voltage pulse has been generated since the state shown in FIG. 10A.

On the other hand, since the rotational position is detected by the optical encoder 110, the rotational angle of the rotating shaft 32 from the origin position is calculated. Therefore, based on the rotational position detected by the optical encoder 110, the magnetic signal processing circuit 220 detects that the rotating shaft 32 has rotated before and after the power supply 230 is restored. In this case, the logical information processing unit 227 determines that there has been a transition from region 3 to region 2 based on the rotational position.

Therefore, the magnetic signal processing circuit 220 including the logical information processing unit 227 updates the amount of rotation stored in the memory unit 228 before the power supply 230 is stopped based on the rotation position detected by the optical encoder 110 after the power supply 230 is restored. Specifically, it transitions the region information from region 3 to region 2 and increments the number of rotations by +1.

In this way, the amount of rotation of the rotating shaft 32 can be detected correctly even if the power supply 230 is stopped. In addition, the rotation state of the motor 300 can be controlled to the desired state even after the power supply 230 is restored.

[Effects, etc.]
As described above, the rotary encoder (rotation detector) 100 according to this embodiment includes at least the magnetic encoder 120 , and detects at least the amount of rotation of the rotary shaft 32 of the motor 300 .

The magnetic encoder 120 is attached to the rotating shaft 32 so as to rotate as one unit, and is equipped with at least a power generating magnet 122 having multiple magnetic poles of different polarities in the circumferential direction, in this case four or more magnetic poles, at least one power generating element 126 consisting of a Wiegand wire 126a and an induction coil 126b as a magnetic sensing part, a first magnetic sensor 124, and a second magnetic sensor 125.

The magnetic encoder 120 also includes a magnetic shielding plate (magnetic flux control member) 123 whose position changes together with the power generating magnet 122 as the rotating shaft 32 rotates, and which may generate an excitation voltage in at least one of the first magnetic sensor 124 and the second magnetic sensor 125.

The magnetic encoder 120 drives the first magnetic sensor 124 and the second magnetic sensor 125 with the power generated by the power generating element 126 due to the rotation of the power generating magnet 122.

By configuring the magnetic encoder 120 in this way, a so-called battery-less rotary encoder (rotation detector) 100 can be realized with a simple configuration. In addition, the multi-rotation information S of the rotating shaft 32 can be easily detected. Furthermore, compared to the conventional configuration shown in Patent Document 1, the number of components can be reduced. Therefore, the rotary encoder 100 can be made smaller.

As mentioned above, when a magnetic field of a predetermined magnitude or greater is applied to the Wiegand wire 126a, which is the magnetically sensitive portion of the power generating element 126, the magnetization direction is reversed, and a voltage pulse is induced across the induction coil 126b. At this time, the speed at which the magnetization direction is reversed depends on the magnetic properties of the Wiegand wire 126a, and does not depend on the rotation speed of the rotating shaft 32.

Therefore, by configuring the power generating element 126 with the Wiegand wire 126a and the induction coil 126b, the magnitude of the voltage pulse generated by the power generating element 126 can be set to a predetermined value, regardless of the rotation speed of the rotating shaft 32. For example, even at a low rotation speed where electromagnetic induction alone, which depends on the rotation speed, does not generate enough power to drive the first magnetic sensor 124 or the second magnetic sensor 125, the power generating element 126 can generate a sufficient amount of power.

In addition, according to this embodiment, the first magnetic sensor 124 and the second magnetic sensor 125 are arranged at a predetermined interval along the circumferential direction, in this case 120 degrees apart, and the magnetic poles of the power generating magnet 122 are arranged in six poles along the circumferential direction, with the polarities of adjacent magnetic poles being different.

In this way, after the first magnetic sensor 124 detects a first signal, e.g., "1", and the second magnetic sensor 125 detects a second signal, e.g., "1", the power generating element 126 generates electricity twice until the first magnetic sensor 124 detects a signal "0" different from the first signal, or the second magnetic sensor 125 detects a signal "0" different from the second signal.

Therefore, even if the power generating element 126 does not supply sufficient drive power to the first magnetic sensor 124 and the second magnetic sensor 125 at the first timing when the aforementioned region transition occurs, causing a skip in the detection of the amount of rotation, the amount of rotation can be reliably detected by supplying drive power at the next timing. This improves the robustness of the detection of the amount of rotation.

In the magnetic encoder 120, when there is no magnetic shielding plate 123 between the first magnetic sensor 124 and the power generating magnet 122, an excitation voltage is generated in the first magnetic sensor 124, and when there is no magnetic shielding plate 123 between the second magnetic sensor 125 and the power generating magnet 122, an excitation voltage is generated in the second magnetic sensor 125.

In plan view, the power generating magnet 122 rotates together with the rotating shaft 32, and a portion of the power generating magnet 122 is covered by the magnetic shielding plate 123. Therefore, each of the first magnetic sensor 124 and the second magnetic sensor 125 detects the presence or absence of magnetism only when the power generating magnet 122 is not covered by the magnetic shielding plate 123 in plan view. In this way, by simplifying the detection signals of the first magnetic sensor 124 and the second magnetic sensor 125 into a set of binary values of 0 or 1, it is possible to easily calculate the amount of rotation, and in particular, the number of rotations and area information.

When viewed from above, the magnetic shielding plate 123 is fan-shaped, and it is preferable that the power generation magnet 122 and the magnetic shielding plate 123 are arranged concentrically.

By doing this, the first magnetic sensor 124 and the second magnetic sensor 125 can correctly detect the changes in the magnetic field received from the power generating magnet 122 in response to the rotation of the rotating shaft 32.

The rotary encoder 100 further includes a memory unit 228 that stores the detection information of the first magnetic sensor 124 and the second magnetic sensor 125 and the amount of rotation of the rotating shaft 32, and a logical information processing unit 227 that determines area information corresponding to the three rotation positions of the rotating shaft 32 based on the detection information of the first magnetic sensor 124 and the second magnetic sensor 125, and the area information is stored in the memory unit 228.

In this way, the amount of rotation of the rotating shaft 32 can be easily calculated. Even if the rotary encoder 100 is in an unpowered state where no power is supplied from the power source 230, the amount of rotation can be calculated based on the amount of rotation and area information stored in the storage unit 228, which is composed of a non-volatile memory.

The rotary encoder 100 further includes an optical encoder (rotational position detector) 110 that detects the rotational position of the rotating shaft 32.

When the signal processing circuit 200 goes from an unpowered state to a powered state, the logical information processing unit 227 reads the area information stored in the memory unit 228 and updates the amount of rotation of the rotating shaft 32 based on the rotation position detected by the optical encoder 110 and the area information read from the memory unit 228.

By doing this, even if the power supply 230 that supplies driving power to the rotary encoder 100 stops, the amount of rotation of the rotating shaft 32 can be correctly detected, and the rotation state of the motor 300 can be controlled to the desired state even after the power supply 230 is restored.

The motor 300 of this embodiment also includes at least a rotor 30 having a rotating shaft 32, a stator 40 that is coaxial with the rotor 30 and spaced a predetermined distance from the rotor 30, and a rotary encoder 100 that is attached to the rotating shaft 32.

By attaching the rotary encoder 100 of this embodiment to the rotating shaft 32, a motor 300 can be realized whose rotation state can be controlled to a desired state.

<Modification 1>
Fig. 11 is a diagram showing the relationship between the position of the magnetic pole of the power-generating magnet and the area information according to Modification 1. In Fig. 11, among the lines passing through the center of the power-generating magnet 122 and extending in the radial direction, the solid lines and dashed lines respectively indicate the positions where a voltage pulse is generated in the power-generating element 126 when rotating in the clockwise direction and the positions where a voltage pulse is generated in the power-generating element 126 when rotating in the counterclockwise direction, similar to those shown in Figs. 6A, 6B, 6C, 8A, 8B, and 8C.

The magnetic pole arrangement of the power generation magnet 122 shown in FIG. 11 is the same as that shown in FIG. 4. The magnetic pole arrangement of the power generation magnet 122 is eight poles arranged at an equiangular pitch along the circumferential direction. Adjacent magnetic poles have different polarities. Although not shown, the shape and arrangement of the magnetic shielding plate 123 (it is thought necessary to show it) are also the same as that shown in FIG. 4. The semicircular sector-shaped magnetic shielding plate 123 is arranged concentrically with the power generation magnet 122 in a plan view.

When the power generating magnet 122 and magnetic shielding plate 123 are arranged in this manner, there are eight positions at which voltage pulses are generated in the power generating element 126 during rotation in both the CW and CCW directions, as shown in FIG. 11. The signals detected by the first magnetic sensor 124 and the second magnetic sensor 125 are four sets of signals: (11), (10), (00), and (01), and there are four regions.

In this case, when the rotating shaft 32 moves to a predetermined region, for example, when the rotating shaft 32 rotates in the CW direction and transitions from the region corresponding to signal (01) to the region corresponding to signal (11), the number of rotations is counted down at position I. When the rotating shaft 32 rotates in the CCW direction and transitions from the region corresponding to signal (11) to the region corresponding to signal (01), the number of rotations is counted down at position viii.

By doing this, the amount of rotation of the motor 300, particularly the angle range of the rotation shaft 32 from the origin position, can be set narrower than in the case shown in embodiment 1, improving the accuracy of detecting the amount of rotation.

In the examples shown in Figures 6A to 9, one of the three regions is adjacent to the remaining two regions. For this reason, it may be difficult to determine whether the amount of rotation has been detected correctly unless the changes in region information over time are determined.

On the other hand, according to this modified example, the two adjacent regions to one of the four regions differ depending on the position of the original region. For example, the regions corresponding to signals (01) and (10) are adjacent to the region corresponding to signal (11). On the other hand, the regions corresponding to signals (11) and (00) are adjacent to the region corresponding to signal (01).

For this reason, the logical information processing unit 227 compares the immediately preceding area information stored in the memory unit 228 with the newly stored area information, and if the area information is not output from the logical information processing unit 227 in the order determined according to the rotation of the power-generating magnet 122, the logical information processing unit 227 generates and outputs an error flag as error detection information and stores the error flag in the memory unit 228. When the rotary encoder 100 goes from an unpowered state to a powered state, the signal processing circuit 200 checks the error flag stored in the memory unit 228 and warns the motor control unit 60, which is a higher-level controller, and the motor amplifier (not shown) provided therein, etc., that the current amount of rotation may be incorrect.

In the examples shown in Figures 6A to 9, when area information that should not have been output, for example, a signal (00) detected by the first magnetic sensor 124 and the second magnetic sensor 125, is output from the logical information processing unit 227, the logical information processing unit 227 similarly compares the immediately preceding area information stored in the memory unit 228 with the newly stored area information, outputs an error flag, and stores it in the memory unit 228.

In other words, if the logical information processing unit 227 does not output area information in the order determined according to the rotation of the power generation magnet 122, or if the logical information processing unit 227 outputs area information that should not have been output, it can be said that the area information determined by the logical information processing unit 227 is not a value predicted from the immediately preceding area information stored in the memory unit 228. In this case, the logical information processing unit 227 compares the immediately preceding area information stored in the memory unit 228 with the newly stored area information, outputs an error flag, and stores it in the memory unit 228.

When the rotary encoder 100 goes from an unpowered state to a powered state, the signal processing circuit 200 checks the error flag stored in the memory unit 228 and issues the above-mentioned warning.

In addition, it is possible to detect the amount of rotation of the rotating shaft 32 by using a power generating magnet 122 in which four magnetic poles are arranged at an equiangular pitch along the circumferential direction instead of the power generating magnet 122 shown in FIG. 11.

By using the magnetic pole arrangement shown in this modified example, similar to the examples shown in Figures 6A to 9, after the first magnetic sensor 124 detects a first signal and the second magnetic sensor 125 detects a second signal, power generation element 126 generates power twice before the first magnetic sensor 124 detects a signal different from the first signal or the second magnetic sensor 125 detects a signal different from the second signal.

Therefore, even if the power generating element 126 does not supply sufficient drive power to the first magnetic sensor 124 and the second magnetic sensor 125 at the first timing when the aforementioned region transition occurs, causing a skip in the detection of the amount of rotation, drive power is supplied at the next timing. This ensures that the amount of rotation is detected reliably, and the robustness of the detection of the amount of rotation can be improved.

The number of poles of the power generating magnet 122 is an integer multiple of the number of pairs of magnetic poles with mutually opposite polarities. In other words, the number of poles of the power generating magnet 122 is an even number. In this way, the amount of rotation of the motor 300 can be detected regardless of whether the rotating shaft 32 rotates in the CW direction or the CCW direction.

<Modification 2>
Fig. 12 is a diagram showing changes in the detection signals of the first magnetic sensor and the second magnetic sensor when the rotation shaft rotates clockwise in Modification 2. The arrangement of the power generation magnet 122 and the magnetic shielding plate 123 in this modification is the same as that shown in Figs. 8A, 8B, and 8C.

In the examples shown in Figures 6A to 9, as mentioned above, the polarity of the magnetic poles of the power generating magnet 122 itself is not detected, and only the changes in the magnetic fields applied to the first magnetic sensor 124 and the second magnetic sensor 125 are detected to generate signals.

In contrast, in this modified example, the first magnetic sensor 124 and the second magnetic sensor 125 are sensors that can detect the difference in the direction of the detected magnetic flux. For example, a Hall sensor can be used.

In this way, each region can be further divided into two for judgment. According to this modified example, a total of six regions can be detected: regions 1a, 1b, 2a, 2b, 3a, and 3b. Therefore, the amount of rotation of the motor 300, particularly the angle range of the rotation shaft 32 from the origin position, can be set narrower than in the case shown in embodiment 1, improving the accuracy of detecting the amount of rotation.

According to this modified example, the three regions shown in Figures 6A to 9 are subdivided into six regions. This allows the two regions adjacent to one region to differ depending on the position of the original region.

As a result, as shown in Modification Example 1, when the area information determined by the logical information processing unit 227 is not a value predicted from the immediately preceding area information stored in the memory unit 228, the logical information processing unit 227 can compare the immediately preceding area information stored in the memory unit 228 with the newly stored area information, and output an error flag. In addition, the error flag can be stored in the memory unit 228. It is also possible to warn the motor control unit 60, etc., that the current amount of rotation may be incorrect.

In this modified example, a magnetic sensor is used to detect differences in the direction of the magnetic flux generated by the power generating magnet 122. However, it may also be possible to detect differences in the polarity of the voltage pulse generated in the power generating element 126. In that case, a voltage polarity determination unit, such as a comparator, may be provided in front of the full-wave rectifier.

<Modification 3>
Fig. 13 is a diagram showing a planar arrangement of the power generation magnets 122 according to Modification 3. Fig. 14 is a diagram showing a planar arrangement of another power generation magnet 122. Fig. 15 is a diagram showing a planar arrangement of the power generation element 126.

As long as the polarities of adjacent magnetic poles in the circumferential direction are different from each other, multiple magnets each magnetized to a single pole and arranged at an equal angular pitch along the circumferential direction may be used as the power generation magnets 122. In this case, as shown in FIG. 13, the planar shape of each magnet may be circular or angular. As shown in FIG. 14, the planar shape of each magnet may be arc-shaped.

As shown in FIG. 15, multiple power generating elements 126 may be provided. In that case, it is preferable to arrange each power generating element 126 along the circumferential direction.

By doing this, the number of voltage pulses generated during one rotation of the rotating shaft 32 can be increased. This allows a stable supply of drive power to the magnetic encoder 120. It is preferable to arrange the power generating elements 126 at a predetermined interval along the circumferential direction so that they do not generate power at the same position.

In this case, the multiple power generating elements 126 are treated as one, and after the first magnetic sensor 124 detects a first signal and the second magnetic sensor 125 detects a second signal, the power generating element 126 generates power multiple times until the first magnetic sensor 124 detects a signal different from the first signal or the second magnetic sensor 125 detects a signal different from the second signal.

Therefore, even if the power generating element 126 does not supply sufficient drive power to the first magnetic sensor 124 and the second magnetic sensor 125 at the first timing when the aforementioned region transition occurs, causing a skip in the detection of the amount of rotation, sufficient drive power will be supplied at some point after the next timing. This ensures that the amount of rotation is detected reliably, and the robustness of the detection of the amount of rotation can be improved.

<Modification 4>
Fig. 16 is a schematic diagram of a rotary encoder according to Modification 4 as viewed from the radial direction. In Fig. 16, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The configuration of this modified example differs from that shown in embodiment 1 in that a reflective encoder is used as the optical encoder 110.

The optical encoder 110 has a light receiving/emitting element 114 attached to the underside of the circuit board 130 and a reflection pattern 115 attached to the upper surface of the rotating plate 121. Light from the light receiving/emitting element 114 is reflected by the reflection pattern 115 and received by the light receiving/emitting element 114, thereby detecting the rotational position of the rotating plate 121 and, ultimately, the rotating shaft 32.

This modified example can achieve the same effect as the configuration shown in embodiment 1. It is necessary to ensure that the magnetic shielding plate 123 does not block the light from the light receiving/emitting element 114. For this reason, it is preferable to attach the magnetic shielding plate 123 to the side opposite the surface on which the reflection pattern 115 is provided. In other words, it is preferable to attach it to the underside of the rotating plate 121, as in embodiment 1.

(Embodiment 2)
Fig. 17A is a diagram showing the planar arrangement relationship between the power generating magnet 122, the magnetic shielding plate, and the power generating element 126 according to the second embodiment of the present invention. Fig. 17B is a planar arrangement diagram of each component in the magnetic encoder. In Figs. 17A and 17B, the same reference numerals are used for the same parts as those in the first embodiment, and detailed description thereof will be omitted.

The configuration according to this embodiment differs from the configuration shown in embodiment 1 in the magnetic pole arrangement of the power generating magnet 122 and the arrangement of the power generating element 126 as follows.

In this embodiment, the power generating magnet 122 has multiple magnetic poles of different polarities arranged along the circumferential direction, eight poles in this case. At the same time, the power generating magnet 122 has two magnetic poles of different polarities arranged on the outer and inner sides along the radial direction, so to speak, it has a double annular shape. The power generating element 126 is arranged so that both ends are along the radial direction.

By doing this, the direction of the magnetic flux flowing between magnetic poles of opposite polarity and the longitudinal direction of the Wiegand wire 126a of the power generating element 126 can be aligned in the same radial direction. As a result, while a set of radially aligned magnetic poles passes under the power generating element, a magnetic field of the same strength is continuously applied to the Wiegand wire 126a in the longitudinal direction.

As shown in embodiment 1, when the longitudinal direction of the Wiegand wire 126a is oriented in the tangent direction to the outer circumference of the power generating magnet 122, the strength of the magnetic field applied in the longitudinal direction of the Wiegand wire 126a varies over time while a set of magnetic poles aligned in the circumferential direction passes under the power generating element 126. In other words, it gradually becomes stronger, is strongest when the magnetic flux direction coincides with the longitudinal direction of the Wiegand wire 126a, and then gradually weakens.

In such cases, depending on the rotation speed of the rotating shaft 32, the size of the magnetic poles, the length of the Wiegand wire 126a, and the magnetic field strength of the power generation magnet 122, the magnetization direction of the Wiegand wire 126a may not be sufficiently reversed, and the amount of power generation in the power generation element 126 may not be sufficient.

On the other hand, according to this embodiment, the strength and application time of the magnetic field applied to the Wiegand wire 126a in the longitudinal direction can be ensured, so that the amount of power generated by the power generating element 126 can be ensured, and the magnetic encoder 120 can be driven stably. In addition, since the power generating magnet 122 of this embodiment has multiple magnetic poles with different polarities arranged along the circumferential direction, as the rotating shaft 32 rotates, excitation voltages are periodically generated in the first magnetic sensor 124 and the second magnetic sensor 125, and are detected as signals. This can achieve the same effects as the configuration shown in embodiment 1.

Figure 17B also shows the positions of the power generating element 126, the first magnetic sensor 124, and the second magnetic sensor 125 as viewed from the axial direction. In Figure 17B, of the lines passing through the center of the power generating magnet 122 and extending in the radial direction, the solid lines indicate positions I to VIII where a voltage pulse is generated in the power generating element 126 when rotating in the clockwise direction, and the dashed lines indicate positions i to viii where a voltage pulse is generated in the power generating element 126 when rotating in the counterclockwise direction. Note that the magnetic shielding plate has a semicircular sector shape in a plan view, as shown in Figure 4.

(Embodiment 3)
Fig. 18 is a schematic diagram of a rotary encoder according to a third embodiment of the present invention as viewed from the radial direction. Fig. 19 is a schematic diagram of a circuit board as viewed from above. Fig. 20 is a schematic diagram of a rotating plate as viewed from above. In Figs. 18 to 20, the same reference numerals are used for the same parts as those in the first embodiment, and detailed descriptions thereof will be omitted.

The configuration according to this embodiment differs from the configuration shown in embodiment 1 in that a position detection magnet 170 is provided instead of the magnetic shielding plate 123. The configuration according to this embodiment differs from the configuration shown in embodiment 1 in that a reflective encoder is used as the optical encoder 110. The configuration and operation of the optical encoder 110 are the same as those shown in modified example 4.

As shown in Figures 18 and 19, in the rotary encoder 100, the first magnetic sensor 124 and the second magnetic sensor 125 are each attached to the upper surface of the circuit board 130. Since the light-emitting element 112 shown in Figure 2 is also omitted, the sensor board 140 and the connector 150 are also omitted. This allows the rotary encoder 100 to be made smaller in the axial direction. It also allows costs to be reduced.

As shown in Figures 18 and 20, the position detection magnet 170 is attached to the upper surface of the rotating plate 121. The position detection magnet 170 is attached to the inner periphery of the power generation magnet 122 with a gap therebetween. The position detection magnet 170 has a semicircular arc shape in a plan view.

The power generating magnet 122 rotates together with the rotating shaft 32, and voltage pulses are periodically generated in the power generating element 126, as in the configurations shown in the first embodiment and the first modified example. On the other hand, the position detection magnet 170, which is semicircular in plan view, rotates together with the rotating shaft 32, and excitation voltages are periodically generated in the first magnetic sensor 124 and the second magnetic sensor 125, and are detected as signals. The excitation voltage in the first magnetic sensor 124, in other words, the timing of generation of the detection signal, and the timing of generation of the detection signal in the second magnetic sensor 125 are the same as those shown in the first modified example.

Therefore, as shown in the first embodiment and the first modified example, the amount of rotation of the rotating shaft 32 can be detected based on the detection signals from the first magnetic sensor 124 and the second magnetic sensor 125.

The planar shape of the position detection magnet 170 is changed as appropriate depending on the magnetic pole arrangement of the power generation magnet 122. For example, as shown in Figures 6A to 9, when the magnetic poles of the power generation magnet 122 are arranged in six poles along the circumferential direction, the planar shape of the position detection magnet 170 is an arc with a central angle of 120 degrees. In either case, the power generation magnet 122 and the position detection magnet 170 are arranged concentrically.

The shape of the position detection magnet 170 is an arc shape. Therefore, the position detection magnet 170 generates a period in which the magnetic flux generated by itself flows into the first magnetic sensor 124 and a period in which it does not flow in conjunction with the rotation of the rotating shaft 32. Similarly, it generates a period in which the magnetic flux generated by itself flows into the second magnetic sensor 125 and a period in which it does not flow in. In other words, the position detection magnet 170 is a magnetic flux control member that may generate an excitation voltage in at least one of the first magnetic sensor 124 and the second magnetic sensor 125. In other words, the magnetic flux control member is the position detection magnet 170, and when the position detection magnet 170 approaches the first magnetic sensor 124 in accordance with the rotation of the rotating shaft 32, an excitation voltage is generated in the first magnetic sensor 124, and when the position detection magnet 170 approaches the second magnetic sensor 125, an excitation voltage is generated in the second magnetic sensor 125.

As shown in the fourth modified example, it is necessary to ensure that the position detection magnet 170 does not block the light from the light receiving/emitting element 114. For this reason, as shown in FIG. 18, it is preferable that the reflection pattern 115 is provided on the outer periphery of the power generating magnet 122 with a gap therebetween.

Other Embodiments
The components shown in the above-described embodiments and modifications can be appropriately combined to form new embodiments.

For example, the arrangement of the power generating magnet 122 and the power generating element 126 shown in embodiment 2 may be applied to the rotary encoder 100 shown in Figures 18 to 20. The power generating magnet 122 shown in Figures 13 and 14 may be modified and applied to embodiment 2. A transmission type encoder may be applied to the rotary encoder 100 shown in embodiment 3.

In the second embodiment, multiple power generating elements 126 may be arranged. In this case, the power generating elements 126 are also arranged at intervals from each other in the circumferential direction.

The motor case 10 shown in FIG. 1 may be a cylindrical shape with a bottom. In that case, for example, one of the brackets 21 and 22 is omitted. If the bracket 22 is omitted, the rotary encoder 100 is attached to the bottom wall of the motor case 10. In this case, too, it is necessary to provide magnetic shielding measures to the case 160 and the motor case 10 so that the magnetic flux from the rotor 30 and the stator 40 does not leak to the rotary encoder 100.

In FIG. 1, an IPM motor is used as an example, but it goes without saying that the rotary encoder 100 described in this specification can also be applied to other types of motors.

The rotation detector disclosed herein is useful for application to motor rotation control because it enhances the robustness of rotation amount detection.

REFERENCE SIGNS LIST 10 Motor case 21, 22 Bracket 30 Rotor 32 Rotating shaft 40 Stator 51, 52 Bearing 60 Motor control unit 100 Rotary encoder (rotation detector)
110 Optical encoder (rotational position detector)
111 Light receiving element 112 Light emitting element 113 Transmission pattern 114 Light receiving/emitting element 115 Reflection pattern 120 Magnetic encoder 121 Rotating plate 122 Power generating magnet 123 Magnetic shielding plate (magnetic flux control member)
124 First magnetic sensor 125 Second magnetic sensor 126 Power generating element 126a Wiegand wire 126b Induction coil 130 Circuit board 140 Sensor board 150 Connector 160 Case 170 Position detection magnet (magnetic flux control member)
200 Signal processing circuit 210 Optical signal processing circuit 220 Magnetic signal processing circuit 227 Logical information processing section 228 Memory section 230 Power supply 300 Motor

Claims (9)

A rotation detector that detects the amount of rotation of a rotating shaft of a motor,
a power generating magnet attached to the rotating shaft and rotating integrally with the rotating shaft, the power generating magnet having four or more magnetic poles in an outer circumferential direction;
At least one power generating element including a magnetic sensing portion and an induction coil;
A first magnetic sensor;
A second magnetic sensor;
a magnetic flux control member whose position changes together with the power-generating magnet due to rotation of the rotating shaft, and which may cause an excitation voltage to be generated in at least one of the first magnetic sensor and the second magnetic sensor;
A rotation detector that drives the first magnetic sensor and the second magnetic sensor with electric power generated by the power generating element due to rotation of the power generating magnet,
the magnetic flux control member is a magnetic shielding plate that may be positioned between at least one of the first magnetic sensor and the second magnetic sensor and the power-generating magnet in response to rotation of the rotating shaft,
A rotation detector, wherein an excitation voltage is generated in the first magnetic sensor when the magnetic shielding plate is not present between the first magnetic sensor and the power-generating magnet, and an excitation voltage is generated in the second magnetic sensor when the magnetic shielding plate is not present between the second magnetic sensor and the power-generating magnet . The rotation detector according to claim 1 , wherein the power-generating magnet and the magnetic shielding plate are arranged concentrically in a plan view. 2. The rotation detector according to claim 1, wherein, in a plan view, the power-generating magnet has magnetic poles of different polarities arranged along the outer circumferential direction and along a radial direction of the rotation shaft, and both ends of the power-generating element are arranged along the radial direction. A rotation detector that detects the amount of rotation of a rotating shaft of a motor,
a power generating magnet attached to the rotating shaft and rotating integrally with the rotating shaft, the power generating magnet having four or more magnetic poles in the outer circumferential direction;
At least one power generating element including a magnetic sensing portion and an induction coil;
A first magnetic sensor;
A second magnetic sensor;
a magnetic flux control member whose position changes together with the power-generating magnet due to rotation of the rotating shaft, and which may cause an excitation voltage to be generated in at least one of the first magnetic sensor and the second magnetic sensor;
A rotation detector that drives the first magnetic sensor and the second magnetic sensor with electric power generated by the power generating element due to rotation of the power generating magnet,
a logic information processing unit that determines at least three pieces of region information regarding a rotational position of the rotating shaft based on detection information from the first magnetic sensor and the second magnetic sensor;
a storage unit that stores detection information of the first magnetic sensor and the second magnetic sensor and an amount of rotation of the rotating shaft,
The region information is stored in the storage unit. 5. The rotation detector according to claim 4, wherein after a first signal is detected by the first magnetic sensor and a second signal is detected by the second magnetic sensor, power is generated by the power generating element a plurality of times until a signal different from the first signal is detected by the first magnetic sensor or a signal different from the second signal is detected by the second magnetic sensor . A rotational position detector for detecting a rotational position of the rotating shaft is further provided.
5. The rotation detector according to claim 4, wherein, when the logic information processing unit goes from an unpowered state to a powered state, the logic information processing unit reads out the area information and the amount of rotation stored in the memory unit, and updates the information on the amount of rotation based on the rotation position and the area information detected by the rotation position detector . 5. The rotation detector according to claim 4, wherein when the logic information processing unit goes from an unpowered state to a powered state, if the area information determined by the logic information processing unit is not a value predicted from the immediately preceding area information stored in the memory unit, the logic information processing unit outputs error detection information and stores the error detection information in the memory unit . A rotation detector that detects the amount of rotation of a rotating shaft of a motor,
a power generating magnet attached to the rotating shaft and rotating integrally with the rotating shaft, the power generating magnet having four or more magnetic poles in an outer circumferential direction;
At least one power generating element including a magnetic sensing portion and an induction coil;
A first magnetic sensor;
A second magnetic sensor;
a magnetic flux control member whose position changes together with the power-generating magnet due to rotation of the rotating shaft, and which may cause an excitation voltage to be generated in at least one of the first magnetic sensor and the second magnetic sensor;
A rotation detector that drives the first magnetic sensor and the second magnetic sensor with electric power generated by the power generating element due to rotation of the power generating magnet,
the magnetic flux control member is a position detection magnet, and when the position detection magnet approaches the first magnetic sensor in response to rotation of the rotating shaft, an excitation voltage is generated in the first magnetic sensor, and when the position detection magnet approaches the second magnetic sensor, an excitation voltage is generated in the second magnetic sensor,
A rotation detector, wherein, in a plan view, the position detection magnet is arc-shaped, and the power generation magnet and the position detection magnet are concentrically arranged. A rotor having a rotation shaft;
a stator provided coaxially with the rotor and spaced a predetermined distance from the rotor;
A rotation detector according to any one of claims 1 to 8, which is attached to the rotating shaft, and
Also equipped with a motor.

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