JP7601164B2 - Encoder - Google Patents

Description

This disclosure relates to an encoder.

Patent document 1 discloses a method for synchronizing a segment counter having one pulse wire (Wiegand wire) sensor with a precision position sensor.

Patent No. 5730809

Battery-less encoders may use power generating elements that generate electricity using the Barkhausen characteristic. It is desirable to increase the magnetic field change in the power generating element and thus the generated power.

The present disclosure provides an encoder that improves the efficiency of generating power.

According to one aspect of the present disclosure, an encoder is provided that includes a magnetic sensor, a first magnet that is arranged symmetrically about a rotation axis and generates a first magnetic field that is detected by the magnetic sensor, a power generating element, a plurality of second magnets that are arranged in a line in the circumferential direction of the rotation axis and generate a second magnetic field that causes the power generating element to generate electricity, and a circuit board in which the magnetic sensor is positioned opposite the first magnet and the power generating element is positioned on the outer periphery of the position opposite the second magnet.

The encoder disclosed herein can improve the efficiency of generating power.

FIG. 1 is a diagram illustrating a servo motor system using an encoder according to a first embodiment. FIG. 2 is a diagram illustrating the configuration of a servo motor using the encoder according to the first embodiment. FIG. 3 is a diagram illustrating a circuit configuration of the encoder according to the first embodiment. FIG. 4 is a diagram illustrating a circuit configuration of the encoder according to the first embodiment. FIG. 5 is a diagram illustrating a circuit configuration of the encoder according to the first embodiment. FIG. 6 is a diagram illustrating the configuration of an encoder according to the first embodiment. FIG. 7 is a diagram illustrating the configuration of an encoder according to the first embodiment. FIG. 8 is a diagram illustrating the configuration of an encoder according to the first embodiment. FIG. 9 is a diagram illustrating the configuration of an encoder according to the first embodiment. FIG. 10 is a diagram illustrating the generated power in the encoder according to the first embodiment. FIG. 11 is a diagram illustrating the configuration of an encoder according to the second embodiment. FIG. 12 is a diagram illustrating the configuration of an encoder according to the second embodiment. FIG. 13 is a diagram illustrating the configuration of an encoder according to the second embodiment. FIG. 14 is a diagram illustrating the configuration of an encoder according to the second embodiment. FIG. 15 is a diagram illustrating the configuration of an encoder according to the third embodiment. FIG. 16 is a diagram illustrating the configuration of an encoder according to the third embodiment. FIG. 17 is a diagram illustrating the configuration of an encoder according to the third embodiment.

Embodiments of the present invention will be described below with reference to the attached drawings. Note that, in the description of the specification and drawings relating to each embodiment, components having substantially the same or corresponding functional configurations may be given the same reference numerals to avoid redundant description. Also, to facilitate understanding, the scale of each part in the drawings may differ from the actual scale.

First Embodiment
The following describes an encoder according to the first embodiment. The encoder according to the first embodiment includes a first magnet that is provided symmetrically with respect to a rotation axis and generates a first magnetic field that is detected by a magnetic sensor, and a plurality of second magnets that are provided side by side in the circumferential direction of the rotation axis and generate a second magnetic field that causes a power generating element to generate power.

<Servo motor system>
First, a servo motor system using an encoder according to the present embodiment will be described below. Fig. 1 is a diagram illustrating a servo motor system 1 using an encoder 12 which is an example of the encoder according to the present embodiment.

The servo motor system 1 includes a servo motor 10 and a servo controller 20. The servo controller 20 acquires at least one of position information and rotation information of the rotating shaft 11a from the servo motor 10. The servo controller 20 controls the servo motor 10 using at least one of the acquired position information and rotation information.

The servo motor 10 includes a motor 11 and an encoder 12. The motor 11 is connected to the servo controller 20 via a line L1. The encoder 12 is connected to the servo controller 20 via a line L2.

The motor 11 rotates the rotating shaft 11a in the direction of the arrow AR based on a command from the servo controller 20. Specifically, the motor 11 rotates the rotating shaft 11a in the direction of the arrow AR based on the power supplied from the servo controller 20. The servo controller 20 controls the motor 11 by supplying controlled power from the wiring L1. The motor 11 is, for example, an AC (Alternating Current) motor, a DC (Direct Current) motor, etc.

The encoder 12 detects fluctuations in the magnetic field to detect at least one of position information and rotation information of an object such as the rotating shaft 11a of the motor 11. The encoder 12 also outputs at least one of the detected position information and rotation information to the servo controller 20 via the wiring L2. Note that the position information of the rotating shaft 11a is, for example, the angle of the rotation direction of the rotating shaft 11a. The rotation information of the rotating shaft 11a is, for example, the rotation speed of the rotating shaft 11a or the number of rotations indicating how many rotations the rotating shaft 11a has made from a given point in time.

<Servo motor 10>
Next, the configuration of the servo motor 10 using the encoder 12, which is an example of the encoder according to the present embodiment, will be described. Fig. 2 is a diagram for explaining the configuration of the servo motor 10 using the encoder 12, which is an example of the encoder according to the present embodiment. Note that lines with arrows indicate the flow of power or current supply.

[Motor 11]
The motor 11 rotates a rotating shaft 11a. The motor 11 includes well-known elements such as a bearing that supports the rotating shaft 11a, a winding that constitutes a stator for rotating the rotating shaft 11a, an iron core, and a permanent magnet that constitutes a rotor, but a description thereof will be omitted here. The motor 11 includes a disk 11d that is provided on the encoder 12 side of the rotating shaft 11a. As described later, a magnet 12m1 that is provided symmetrically on the rotating shaft 11a and a plurality of magnets 12m2 that are provided in a line in the circumferential direction of the rotating shaft 11a are attached on the disk 11d.

Disk 11d is fixed to the rotating shaft 11a. Disk 11d rotates together with the rotating shaft 11a as the rotating shaft 11a rotates in the direction of the arrow AR. A magnet 12m1 and a plurality of magnets 12m2 are fixed to the surface of disk 11d facing the encoder 12.

The magnet 12m1 and each of the multiple magnets 12m2 are permanent magnets made of neodymium or the like. When the magnet 12m1 and each of the multiple magnets 12m2 rotate together with the disk 11d, the magnetic field on the encoder 12 side changes.

The magnet 12m1 is arranged to have a north pole and a south pole parallel to the surface of the disk 11d. The magnet 12m1 generates a magnetic field that is detected by each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2.

The multiple magnets 12m2 generate a magnetic field that causes the power generating element 12g to generate power. The multiple magnets 12m2 are arranged in a Halbach array along the circumferential direction of the rotating shaft 11a. Details of the multiple magnets 12m2 will be described later.

[Encoder 12]
The encoder 12 will be described. The encoder 12 detects at least one of position information and rotation information of the rotating shaft 11a by a magnetic field that changes with the rotation of the magnet 12m1 and the multiple magnets 12m2. The encoder 12 is an absolute encoder. The encoder 12 operates at least as a multi-turn encoder. That is, the encoder 12 counts the number of rotations of the rotating shaft 11a. The encoder 12 also generates power required to operate the encoder 12 by a magnetic field that changes with the rotation of the multiple magnets 12m2.

The encoder 12 includes a power generating element 12g, a rectifier circuit 12a, a stabilized power supply circuit 12b, and a polarity detection circuit 12d. The encoder 12 also includes a drive circuit 12e1 and a drive circuit 12e2, a first magnetic sensor 12h1 and a second magnetic sensor 12h2, a signal processing circuit 12f1 and a signal processing circuit 12f2, a control circuit 12p, and a memory unit 12r. The encoder 12 also includes a magnet 12m1 and a plurality of magnets 12m2. The rectifier circuit 12a and the stabilized power supply circuit 12b are collectively referred to as a power supply circuit 12n. The polarity detection circuit 12d, the drive circuit 12e1, the drive circuit 12e2, the signal processing circuit 12f1, and the signal processing circuit 12f2 are collectively referred to as a rotation detection circuit 12k.

The encoder 12 includes a power generating element 12g that generates power by changes in magnetic flux caused by movement, and a first magnetic sensor 12h1 and a second magnetic sensor 12h2 that measure the magnetic field. The power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2 are each provided on the motor 11 side of the encoder 12 so as to be easily affected by the magnetic fields generated by the magnet 12m1 and the multiple magnets 12m2.

[Power generating element 12g]
The power generating element 12g is an element that generates power by converting magnetic energy into an electric pulse. The power generating element 12g is an element that generates power by utilizing the Barkhausen characteristic. The power generating element 12g is, for example, a Wiegand wire that is an energy harvest generator (EHG).

The power generating element 12g comprises a hard core and a soft layer wrapped around the hard core. The hard core is made of a material with a large magnetic coercive force. The soft layer is made of a material with a small magnetic coercive force. The power generating element 12g generates a power generating pulse when the direction of the external magnetic field is reversed.

For example, a Wiegand wire generates an electrical pulse near the zero point where the external magnetic field reverses, independent of the rate of change of the external magnetic flux. Therefore, a Wiegand wire generates a constant power regardless of the rotation speed of the rotating shaft 11a. A Wiegand wire generates a stable electrical pulse (voltage pulse) even with gradual changes in magnetic flux caused by slow rotation (movement). A Wiegand wire generates an electrical pulse when the magnetic field reverses.

By using an environmental power generator in the power generating element 12g, the encoder 12 does not require a battery or external power source. In other words, the encoder 12 is a battery-less encoder. Wiegand wire generates a constant amount of power regardless of the rotation speed of the rotating shaft 11a, and a stable power generation waveform can be obtained even at low rotation speeds, making it suitable for use as the power generating element 12g of the encoder 12, which is a battery-less encoder.

The power generating element 12g is not limited to Wiegand wire, but may be any power generating element that generates electricity using the Barkhausen characteristic.

The power generating element 12g generates electricity using the magnetic field generated by the magnet 12m2.

[First magnetic sensor 12h1 and second magnetic sensor 12h2]
The first magnetic sensor 12h1 and the second magnetic sensor 12h2 each detect a magnetic field. More specifically, the first magnetic sensor 12h1 and the second magnetic sensor 12h2 each detect a magnetic field generated by a magnet 12m1, which will be described later.

Each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 is, for example, a Hall element. The Hall element detects a magnetic field that crosses a semiconductor element through which a drive current flows. In the encoder 12, each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 mainly detects the magnetic field generated by the magnet 12m1. The Hall elements constituting each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 are composed of semiconductor elements such as indium antimonide (InSb) and gallium arsenide (GaAs). The Hall element outputs a voltage proportional to the drive current and the magnetic flux density that crosses the drive current.

The first magnetic sensor 12h1 outputs a magnetic field detection signal to the signal processing circuit 12f1. The first magnetic sensor 12h1 is supplied with a constant current Idr from the drive circuit 12e1. The second magnetic sensor 12h2 outputs a magnetic field detection signal to the signal processing circuit 12f2. The second magnetic sensor 12h2 is supplied with a constant current Idr from the drive circuit 12e2.

The first magnetic sensor 12h1 is supplied with a current (constant current Idr) that is the result of rectifying the power generated by the power generating element 12g in the rectifier circuit 12a and then being made constant by the drive circuit 12e1. The second magnetic sensor 12h2 is supplied with a current (constant current Idr) that is the result of rectifying the power generated by the power generating element 12g in the rectifier circuit 12a and then being made constant by the drive circuit 12e2.

Although the encoder 12 has two magnetic sensors, the number of magnetic sensors is not limited to two. The encoder 12 may have three or more magnetic sensors. In addition, the magnetic field is not limited to being measured by a Hall element as long as it is an element capable of detecting magnetism (magnetic detection element). For example, a magnetoresistance effect element or the like may be used as the magnetic sensor.

The circuit configuration of the encoder 12 will be described with reference to FIG. 3. FIG. 3 is a diagram illustrating the circuit configuration of the encoder 12, which is an example of an encoder according to this embodiment.

[Rectification circuit 12a]
The rectifier circuit 12a rectifies the power generated by the power generating element 12g to generate a positive voltage. The rectifier circuit 12a includes a full-wave rectifier circuit 12a1 and a capacitor 12a2.

The full-wave rectifier circuit 12a1 rectifies the positive and negative pulses of the voltage Vgn generated by the power generating element 12g into positive pulses. The full-wave rectifier circuit 12a1 is a so-called diode bridge circuit. For example, when the power generating element 12g is a Wiegand wire, the power generating element 12g generates positive and negative pulses. The full-wave rectifier circuit 12a1 converts the positive and negative pulses generated by the power generating element 12g into positive pulses.

Capacitor 12a2 stores the power generated by power generating element 12g. Capacitor 12a2 also smooths the positive pulse generated by full-wave rectifier circuit 12a1. Capacitor 12a2 is provided between the output terminal of full-wave rectifier circuit 12a1 and the common potential. By smoothing the positive pulse by capacitor 12a2, a smoothed voltage Vrc is output from rectifier circuit 12a.

[Stabilized power supply circuit 12b]
The stabilized power supply circuit 12b converts the voltage output from the rectifier circuit 12a into a substantially constant voltage and outputs it. The stabilized power supply circuit 12b includes a regulator 12b1. The regulator 12b1 is, for example, an LDO (Low Dropout) regulator. be.

When a voltage of a predetermined magnitude is input, the stabilized power supply circuit 12b outputs a substantially constant voltage Vdd.

[Polarity detection circuit 12d]
The polarity detection circuit 12d detects the polarity of the power generated by the power generating element 12g. Fig. 4 is a diagram illustrating the circuit configuration of the polarity detection circuit 12d in the encoder 12. The polarity detection circuit 12d includes a comparator 12d1, a filter circuit 12d2, and a diode 12d3. The diode 12d3 prevents current from flowing from the polarity detection circuit 12d to the power generating element 12g. The filter circuit 12d2 is a low-pass filter including a resistor 12d2a and a capacitor 12d2b.

The comparator 12d1 compares the voltage Vgns with a reference potential (reference potential Vref2) and outputs the comparison result to the control circuit 12p. The comparator 12d1 is a so-called comparator. The comparator 12d1 includes a differential amplifier 12d1a and resistors 12d1b, 12d1c, and 12d1d. The differential amplifier 12d1a is supplied with power of the voltage Vdd from the stabilized power supply circuit 12b. The differential amplifier 12d1a compares the voltage Vgns obtained by smoothing the voltage Vgn of the output of the power generating element 12g using the filter circuit 12d2 with the reference potential Vref2 generated by dividing the voltage Vdd using the resistors 12d1c and 12d1d. The differential amplifier 12d1a then outputs the comparison result to the control circuit 12p as a polarity signal Spl, which is a voltage signal. The resistor 12d1b is a feedback resistor.

[Drive circuit 12e1 and drive circuit 12e2]
The drive circuits 12e1 and 12e2 are so-called constant current circuits that supply a constant current Idr to the first magnetic sensor 12h1 and the second magnetic sensor 12h2, respectively. The drive circuits 12e1 and 12e2 each operate as a constant current source. The encoder 12 drives the first magnetic sensor 12h1 and the second magnetic sensor 12h2, which are Hall elements, with the constant current Idr.

The drive circuit 12e1 supplies drive power to the first magnetic sensor 12h1, which is a Hall element, so that a constant current flows as a drive current through the first magnetic sensor 12h1, which is a Hall element. The drive circuit 12e2 supplies drive power to the second magnetic sensor 12h2, which is a Hall element, so that a constant current flows as a drive current through the second magnetic sensor 12h2.

Figure 5 is a diagram illustrating the circuit configuration of the drive circuit and magnetic sensor in encoder 12, which is an example of an encoder according to this embodiment. Since drive circuit 12e1 and drive circuit 12e2 have the same circuit configuration, in Figure 5, drive circuit 12e1 and drive circuit 12e2 are each described as drive circuit 12e. Also, in Figure 5, the first magnetic sensor 12h1 and second magnetic sensor 12h2, which are Hall elements, are each equivalently shown as magnetic sensor 12h using a bridge circuit including resistors 12ha, 12hb, 12hc, and 12hd.

The drive circuit 12e includes a transistor 12ea, a current detection resistor 12eb, and a differential amplifier 12ec. The drive circuit 12e also includes a resistor 12ed, a Zener diode 12ee, and a capacitor 12ef.

The transistor 12ea is controlled so that a constant current flows through the magnetic sensor 12h. The gate terminal of the transistor 12ea is connected to the output terminal of the differential amplifier 12ec. The differential amplifier 12ec outputs a voltage based on the potential difference between the + terminal and the - terminal from the output terminal. The drive circuit 12e is controlled so that a constant current (constant current Idr) based on the voltage input to the + terminal and the resistance value of the current detection resistor 12eb flows between the drain and source of the transistor 12ea.

The magnetic sensor 12h is driven by a constant current Idr and outputs voltages Vh+ and Vh- that are proportional to the constant current Idr and the magnetic flux density crossing the magnetic sensor 12h.

The drive circuit 12e is driven by the voltage Vdd supplied from the stabilized power supply circuit 12b.

[Signal Processing Circuit 12f1 and Signal Processing Circuit 12f2]
The signal processing circuit 12f1 and the signal processing circuit 12f2 process the detection signals from the first magnetic sensor 12h1 and the second magnetic sensor 12h2, respectively, to detect the direction of the magnetic field of the magnet 12m1. Furthermore, the signal processing circuit 12f1 and the signal processing circuit 12f2 output the strength of the magnetic field of the magnet 12m1 to the control circuit 12p based on the detection signals from the first magnetic sensor 12h1 and the second magnetic sensor 12h2, respectively. The signal processing circuit 12f1 and the signal processing circuit 12f2 will be described with reference to Fig. 3. Note that the signal processing circuit 12f1 and the signal processing circuit 12f2 have the same circuit configuration, so in Fig. 3, the signal processing circuit 12f1 will be used for the description.

The signal processing circuit 12f1 includes a differential amplifier 12fa, a comparator 12fb, and a quantizer 12fc.

(Differential amplifier 12fa)
The differential amplifier 12fa amplifies the potential difference between the voltage Vh+ and the voltage Vh- output from the magnetic sensor 12h to generate a voltage Vd, and outputs the amplified voltage Vd to the comparator 12fb. The differential amplifier 12fa is supplied with power of the voltage Vdd from the stabilized power supply circuit 12b.

(Comparator 12fb)
The comparator 12fb compares the voltage Vd output from the differential amplifier 12fa with a reference potential (reference potential Vref) and outputs the comparison result to the control circuit 12p. The comparator 12fb is a so-called comparator. The comparator 12fb includes a differential amplifier 12fb1 and resistors 12fb2, 12fb3, and 12fb4. The differential amplifier 12fb1 is supplied with power of the voltage Vdd from the stabilized power supply circuit 12b. The differential amplifier 12fb1 compares the voltage Vd of the output of the differential amplifier 12fa with a reference potential Vref generated by dividing the voltage Vdd by resistors 12fb3 and 12fb4, and outputs the comparison result to the control circuit 12p as a magnetic pole signal Smg1, which is a voltage signal. The resistor 12fb2 is a feedback resistor.

(Quantizer 12fc)
The quantizer 12fc quantizes the voltage Vd output from the differential amplifier 12fa and outputs the quantized result to the control circuit 12p. The quantizer 12fc is a so-called analog/digital converter (AD converter). The quantizer 12fc quantizes the voltage Vd output from the differential amplifier 12fa, and outputs, for example, an 8-bit digital value as a magnetic field intensity signal Dmg1 to the control circuit 12p.

[Control circuit 12p]
Based on inputs from the polarity detection circuit 12d, the signal processing circuit 12f1, and the signal processing circuit 12f2, the control circuit 12p calculates at least one of position information and rotation information, such as the rotation position and the number of rotations, of the rotating shaft 11a of the motor 11. The control circuit 12p also records at least one of the detected position information and rotation information of the rotating shaft 11a of the motor 11, and transmits it to an external control system, for example, the servo controller 20.

The control circuit 12p is, for example, a microcomputer, an ASIC (application specific integrated circuit), etc. The control circuit 12p may also be, for example, an FPGA (field-programmable gate array), a PLD (programmable logic device), etc.

The control circuit 12p is connected to an externally provided memory unit 12r. Note that the control circuit 12p may be provided with a non-volatile memory such as a ferroelectric memory internally instead of the external memory unit 12r.

The control circuit 12p has at least a terminal PWR, a terminal SIG1, a terminal row SIG1d, a terminal SIG2, a terminal row SIG2d, and a terminal SIG3.

The terminal PWR of the control circuit 12p is a terminal to which a positive power supply is supplied. The terminal PWR is supplied with power of the voltage Vdd from the stabilized power supply circuit 12b. The control circuit 12p operates when power is supplied to the terminal PWR.

The terminals SIG1, SIG2, and SIG3 of the control circuit 12p are terminals to which signals are input from the outside. The terminal rows SIG1d and SIG2d of the control circuit 12p are terminal rows to which a multi-bit signal is input from the outside.

The terminal SIG1 is connected to the signal processing circuit 12f1. A magnetic pole signal Smg1, which is the detection result detected by the signal processing circuit 12f1, is input from the terminal SIG1. The magnetic pole signal Smg1 is a signal indicating the direction of the magnetic field detected by the first magnetic sensor 12h1. The terminal SIG2 is connected to the signal processing circuit 12f2. A magnetic pole signal Smg2, which is the detection result detected by the signal processing circuit 12f2, is input from the terminal SIG2. The magnetic pole signal Smg2 is a signal indicating the direction of the magnetic field detected by the second magnetic sensor 12h2.

The terminal row SIG1d is connected to the signal processing circuit 12f1. A magnetic field strength signal Dmg1, which is the detection result detected by the signal processing circuit 12f1, is input from the terminal row SIG1d. The magnetic field strength signal Dmg1 is a signal indicating the strength of the magnetic field detected by the first magnetic sensor 12h1. The terminal row SIG2d is connected to the signal processing circuit 12f2. A magnetic field strength signal Dmg2, which is the detection result detected by the signal processing circuit 12f2, is input from the terminal row SIG2d. The magnetic field strength signal Dmg2 is a signal indicating the strength of the magnetic field detected by the second magnetic sensor 12h2.

The terminal SIG3 is connected to the polarity detection circuit 12d. A polarity signal Spl, which is the detection result detected by the polarity detection circuit 12d, is input from the terminal SIG3. The polarity signal Spl is a signal that indicates the power generation polarity of the power generation element 12g.

The encoder 12 counts how many rotations the rotating shaft 11a has made. The control circuit 12p counts how many rotations the rotating shaft 11a has made using the magnetic pole signal Smg1 and the polarity signal Spl. The control circuit 12p also uses the magnetic pole signal Smg1 and the polarity signal Spl to detect which of the 90-degree regions the rotating shaft 11a is in. The control circuit 12p then stores the results of counting how many rotations the rotating shaft 11a has made and the results of detecting which region the rotating shaft is in in the memory unit 12r. The control circuit 12p also stores the most recently detected magnetic pole signal Smg1, magnetic pole signal Smg2, and polarity signal Spl in the memory unit 12r.

The control circuit 12p also uses the magnetic field strength signals Dmg1 and Dmg2 to determine the rotation angle of the rotating shaft 11a. For example, the control circuit 12p calculates the rotation angle of the rotating shaft 11a using an arctangent function from the ratio of the magnetic field strength signals Dmg1 and Dmg2.

[Memory unit 12r]
The memory unit 12r stores, for example, a rotation count and the like. The memory unit 12r is, for example, a ferroelectric memory. The control circuit 12p stores, in the memory unit 12r, at least a count value indicating how many rotations the rotating shaft 11a has made, the position of the rotating shaft, and the last detected magnetic pole signal Smg1, magnetic pole signal Smg2, and polarity signal Spl.

<Encoder configuration>
The configuration of the encoder 12 will be described. Each of Fig. 6 to Fig. 9 is a diagram for explaining the configuration of the encoder 12, which is an example of the encoder according to the first embodiment. Fig. 6 is a perspective view for explaining details of the magnet 12m1 and the plurality of magnets 12m2. Fig. 7 is a plan view for explaining details of the magnet 12m1 and the plurality of magnets 12m2. Fig. 8 is a plan view for explaining details of each of the power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2. Fig. 9 is a side view for explaining details of each of the magnet 12m1, the plurality of magnets 12m2, the power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2.

In Figure 6, the direction of magnetic flux is indicated by an arrow to show the polarity of the magnet. Also, in Figure 7, the north pole is indicated by the letter "N" and the south pole is indicated by the letter "S" to show the polarity of the magnet.

For ease of explanation, the drawings have a virtual three-dimensional coordinate system (XYZ Cartesian coordinate system) consisting of mutually orthogonal X-, Y-, and Z-axes (XYZ axes) set in them. For example, for a coordinate axis perpendicular to the plane of the drawing, a black circle in a circle on the coordinate axis indicates that the axis faces towards the viewer on the plane of the paper. A cross in a circle on the coordinate axis indicates that the axis faces away from the viewer on the plane of the paper.

However, this coordinate system is defined for the purpose of explanation and does not limit the attitude of the encoder and other components related to this embodiment.

In the following drawings, the Z-axis direction is the direction in which the rotation axis 11a extends. The X-axis direction and the Y-axis direction are both perpendicular to the Z-axis direction.

A view of an object viewed from the +Z side in the opposite direction to the Z axis along the Z axis direction is called a plan view. A view of an object viewed from the -Y side in the Y axis direction is called a side view.

The encoder 12 includes magnet 12m1 that is symmetrically arranged on the rotating shaft 11a, and magnets 12m2a to 12m2h that are arranged in a line in the circumferential direction of the rotating shaft 11a. Note that magnet 12m1 is an example of a first magnet, and magnets 12m2a to 12m2h are each an example of a second magnet. This is an example of the encoder 12 that includes eight second magnets.

(Magnet 12m1)
The magnet 12m1 has a cylindrical shape. The magnet 12m1 is a magnet magnetized in a direction parallel to the surface 11dS of the disk 11d on the side of the encoder 12. The magnet 12m1 has a height H2 that is higher than the height H1 of each of the magnets 12m2a to 12m2h. In other words, the first end face of the magnet 12m1 on the first side along the rotation axis is at a different position in the direction along the rotation axis 11a from the second end faces of the magnets 12m2a to 12m2h on the first side. The magnet 12m1 is provided so as to be close to each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2.

The magnet 12m1 does not have to be magnetized over the entire cylindrical shape. For example, the magnet 12m1 only needs to be magnetized on at least the sides of the magnet 12m1 that are close to the first magnetic sensor 12h1 and the second magnetic sensor 12h2.

(Magnet 12m2a to magnet 12m2h)
Each of the magnets 12m2a, 12m2c, 12m2e, and 12m2g has a rectangular parallelepiped shape. Each of the magnets 12m2a, 12m2c, 12m2e, and 12m2g is magnetized in a direction parallel to the surface 11dS of the disk 11d. The magnet 12m2a is magnetized in the Y-axis direction in FIG. 6. The magnet 12m2c is magnetized in the X-axis direction in FIG. 6. The magnet 12m2e is magnetized in the Y-axis direction in FIG. 6, in a direction opposite to the Y-axis. The magnet 12m2g is magnetized in the X-axis direction in FIG. 6, in a direction opposite to the X-axis.

Note that magnets 12m2a, 12m2c, 12m2e, and 12m2g are each an example of a first unit magnet having a magnetization direction in the circumferential direction.

Magnets 12m2b, 12m2d, 12m2f, and 12m2h each have a cylindrical shape. Magnets 12m2b, 12m2d, 12m2f, and 12m2h each are magnets that are magnetized in a direction perpendicular to surface 11dS of disk 11d. Magnet 12m2b is magnetized in the direction of the Z axis along the Z axis direction in FIG. 6. Magnet 12m2d is magnetized in the direction opposite to the Z axis along the Z axis direction in FIG. 6. Magnet 12m2f is magnetized in the direction of the Z axis along the Z axis direction in FIG. 6. Magnet 12m2h is magnetized in the direction opposite to the Z axis along the Z axis direction in FIG. 6.

Note that magnets 12m2b, 12m2d, 12m2f, and 12m2h are each an example of a second unit magnet having a magnetization direction along the rotation axis.

Magnets 12m2a to 12m2g are arranged in a so-called Halbach array in the circumferential direction of the rotation axis 11a (axis Ax). In other words, first unit magnets having a magnetization direction in the circumferential direction and second unit magnets having a magnetization direction along the rotation axis are arranged alternately in the circumferential direction.

(First magnetic sensor 12h1 and second magnetic sensor 12h2)
The first magnetic sensor 12h1 and the second magnetic sensor 12h2 are disposed near the center of the surface of the circuit board 12j facing the disk 11d. The first magnetic sensor 12h1 and the second magnetic sensor 12h2 are each provided near an area of the circuit board 12j facing the magnet 12m1.

As shown in FIG. 8, the first magnetic sensor 12h1 is provided at an angle of 180 degrees when the right side of the X-axis is set to an angle of 0 degrees. As shown in FIG. 8, the second magnetic sensor 12h2 is provided at an angle of 90 degrees when the right side of the X-axis is set to an angle of 0 degrees.

By arranging the first magnetic sensor 12h1 and the second magnetic sensor 12h2 at positions offset by an angle of 90 degrees, the magnetic field generated by the magnet 12m1 can be measured by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 with a phase shift. By measuring the magnetic field generated by the magnet 12m1 by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 with a phase shift, the position in the rotational direction of the rotating shaft 11a can be measured.

If the height of each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 is height h1, the height H2 of the magnet 12m1 is set so that the magnet 12m1 is close enough to each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 but does not come into contact with them.

(Power generating element 12g)
The power generating element 12g is disposed on the outer side of the surface of the circuit board 12j facing the disk 11d. The power generating element 12g is provided outside the region (position) of the circuit board 12j that faces the magnet 12m2a to the magnet 12m2g. The power generating element 12g may be provided in the region (position) that faces the magnet 12m2a to the magnet 12m2g.

As shown in FIG. 8, the power generating element 12g is positioned at an angle of 0 degrees when the right side of the X-axis is set to an angle of 0 degrees.

If the height of the generating element 12g is h2, the height H1 of each of the magnets 12m2a to 12m2g is set so that each of the magnets 12m2a to 12m2g is close enough to the generating element 12g but does not come into contact with it.

The radius R2 of the power generating element 12g from the rotation axis 11a (axis Ax) is greater than the radius R1 of each of the magnets 12m2a to 12m2g from the rotation axis 11a (axis Ax). In other words, the circuit board 12j has the power generating element 12g on the outer periphery from the positions facing each of the magnets 12m2a to 12m2g. Figure 10 is a diagram explaining the power generation in the encoder 12, which is an example of an encoder according to the first embodiment.

The horizontal axis of FIG. 10 shows the radius (R2/R1) obtained by normalizing the radius (radius R2) from the center of the rotating shaft 11a to the power generating element 12g by the radius (radius R1) from the center of the rotating shaft 11a to the magnet 12m2a, expressed as a percentage. The vertical axis of FIG. 10 shows the power generated when the power generating element 12g is positioned at the radius shown on the horizontal axis, normalized by the power generated when it is positioned opposite the magnet 12m2a, expressed as a percentage.

As shown in Figure 10, when the power generating element 12g is placed outside the magnets 12m2a to 12m2g, the generated power increases compared to placing it in a position facing each of the magnets 12m2a to 12m2g. On the other hand, when the position becomes 1.4 times or more, the magnetic field generated by each of the magnets 12m2a to 12m2g becomes smaller, and the generated power decreases.

Therefore, for example, the power generating element 12g should be 1 time (100%) or more and 1.35 times (135%) or less of the radius from the rotation axis 11a of each of the magnets 12m2a to 12m2g. Also, it is better that the power generating element 12g be 1.2 times (120%) or more and 1.35 times (135%) or less of the radius from the rotation axis 11a of each of the magnets 12m2a to 12m2g.

By arranging magnets 12m2a to 12m2g in a Halbach array, the magnetic field generated by magnets 12m2a to 12m2g can be concentrated on the power generating element 12g side. By concentrating the magnetic field generated by magnets 12m2a to 12m2g on the power generating element 12g side, the power generating efficiency of the power generating element 12g can be improved.

Second Embodiment
An encoder according to a second embodiment will now be described. The encoder according to the second embodiment differs from the encoder according to the first embodiment in the arrangement of the second magnets.

<Encoder configuration>
The configuration of the encoder according to the second embodiment will be described. Each of Figs. 11 to 14 is a diagram for explaining the configuration of the encoder according to the second embodiment. Fig. 11 is a perspective view for explaining the details of the magnet 12m1, the magnet 32m2a, the magnet 32m2c, the magnet 32m2e, and the magnet 32m2g. Fig. 12 is a plan view for explaining the details of the magnet 12m1, the magnet 32m2a, the magnet 32m2c, the magnet 32m2e, and the magnet 32m2g. Fig. 13 is a plan view for explaining the details of each of the power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2. Fig. 14 is a side view for explaining the details of each of the magnet 12m1, the magnet 32m2a, the magnet 32m2c, the magnet 32m2e, the magnet 32m2g, the power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2.

In Figure 11, the direction of magnetic flux is indicated by an arrow to show the polarity of the magnet. Also, in Figure 12, the north pole is indicated by the letter "N" and the south pole is indicated by the letter "S" to show the polarity of the magnet.

The encoder according to the second embodiment includes magnet 12m1 that is symmetrically arranged on rotating shaft 11a, and magnets 32m2a, 32m2c, 32m2e, and 32m2g that are arranged in a line in the circumferential direction on rotating shaft 11a. Note that magnet 12m1 is an example of a first magnet, and magnets 32m2a, 32m2c, 32m2e, and 32m2g are each an example of a second magnet.

Since magnet 12m1 has the same configuration as magnet 12m1 in encoder 12, which is an example of an encoder according to the first embodiment, a detailed description will be omitted and refer to the description of the first embodiment. Also, detailed descriptions of first magnetic sensor 12h1 and second magnetic sensor 12h2 will be omitted and refer to the description of the first embodiment. Since only the direction of power generating element 12g differs from that of the first embodiment, a detailed description will be omitted and refer to the description of the first embodiment.

(Magnet 32m2a, magnet 32m2c, magnet 32m2e, and magnet 32m2g)
Each of the magnets 32m2a, 32m2c, 32m2e, and 32m2g has a rectangular parallelepiped shape. Each of the magnets 32m2a, 32m2c, 32m2e, and 32m2g is a magnet that is magnetized in a direction parallel to the surface 11dS of the disk 11d. The magnet 32m2a is magnetized in the X-axis direction in FIG. 11. The magnet 32m2c is magnetized in the Y-axis direction in FIG. 11. The magnet 32m2e is magnetized in the X-axis direction in FIG. 11. The magnet 32m2g is magnetized in the Y-axis direction in FIG. 11.

Note that magnets 32m2a, 32m2c, 32m2e, and 32m2g are each an example of a third unit magnet having a magnetization direction in the radial direction relative to the rotation axis.

Third Embodiment
An encoder according to a third embodiment will now be described. The encoder according to the third embodiment differs from the encoders according to the first and second embodiments in the arrangement of the second magnets.

<Encoder configuration>
The configuration of the encoder according to the third embodiment will be described. Each of Fig. 15 to Fig. 17 is a diagram for explaining the configuration of the encoder according to the third embodiment. Fig. 15 is a perspective view for explaining the details of the magnet 12m1, the magnet 42m2a, the magnet 42m2b, the magnet 42m2c, the magnet 42m2e, the magnet 42m2f, and the magnet 42m2g. Fig. 16 is a plan view for explaining the details of the magnet 12m1, the magnet 42m2a, the magnet 42m2b, the magnet 42m2c, the magnet 42m2e, the magnet 42m2f, and the magnet 42m2g. Fig. 17 is a side view for explaining the details of the magnet 12m1, the magnet 42m2a, the magnet 42m2b, the magnet 42m2c, the magnet 42m2e, the magnet 42m2f, the magnet 42m2g, the power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2. In addition, since the power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2 have the same configuration as the encoder according to the second embodiment, please refer to FIG. 13 for details.

In Figure 15, the direction of magnetic flux is indicated by an arrow to show the polarity of the magnet. Also, in Figure 16, the north pole is indicated by the letter "N" and the south pole is indicated by the letter "S" to show the polarity of the magnet.

The encoder according to the third embodiment includes magnet 12m1 that is symmetrically arranged on rotating shaft 11a, and magnets 42m2a, 42m2b, 42m2c, 42m2e, 42m2f, and 42m2g that are arranged in a line in the circumferential direction on rotating shaft 11a. Note that magnet 12m1 is an example of a first magnet, and magnets 42m2a, 42m2b, 42m2c, 42m2e, 42m2f, and 42m2g are each an example of a second magnet.

Since magnet 12m1 has the same configuration as magnet 12m1 in encoder 12, which is an example of an encoder according to the first embodiment, a detailed description will be omitted and refer to the description of the first embodiment. Also, detailed descriptions of first magnetic sensor 12h1 and second magnetic sensor 12h2 will be omitted and refer to the description of the first embodiment. Since only the direction of power generating element 12g differs from that of the first embodiment, a detailed description will be omitted and refer to the description of the first embodiment.

(Magnet 42m2a, magnet 42m2b, magnet 42m2c, magnet 42m2e, magnet 42m2f, and magnet 42m2g)
Each of the magnets 42m2a, 42m2b, 42m2c, 42m2e, 42m2f, and 42m2g has a rectangular parallelepiped shape. Each of the magnets 42m2a, 42m2b, 42m2c, 42m2e, 42m2f, and 42m2g is magnetized in a direction parallel to the surface 11dS of the disk 11d. The magnet 42m2a is magnetized in the X-axis direction in FIG. 15. The magnet 42m2e is magnetized in the opposite direction to the X-axis direction in FIG. 15.

In FIG. 16, magnet 42m2b is magnetized at an angle of 60 degrees. The north pole of magnet 42m2b is provided on the magnet 12m1 side. In FIG. 16, magnet 42m2c is magnetized at an angle of 120 degrees. The south pole of magnet 42m2c is provided on the magnet 12m1 side. In FIG. 16, magnet 42m2f is magnetized at an angle of 240 degrees. The south pole of magnet 42m2f is provided on the magnet 12m1 side. In FIG. 16, magnet 42m2g is magnetized at an angle of 300 degrees. The north pole of magnet 42m2g is provided on the magnet 12m1 side.

Note that magnets 42m2a, 42m2b, 42m2c, 42m2e, 42m2f, and 42m2g are each an example of a third unit magnet having a magnetization direction in the radial direction relative to the rotation axis.

Each of the encoders according to the second embodiment and the encoder according to the third embodiment is an example of an encoder in which each of the multiple second magnets is a third unit magnet having a magnetization direction in the radial direction relative to the rotation axis. The second magnet is not limited to the above example, and each of the multiple second magnets may be a first unit magnet having a magnetization direction in the circumferential direction relative to the rotation axis (for example, in FIG. 6, a configuration consisting of only magnets 12m2a, 12m2c, 12m2e, and 12m2g). Also, each of the multiple second magnets may be a second unit magnet having a magnetization direction along the rotation axis (for example, in FIG. 6, a configuration consisting of only magnets 12m2b, 12m2d, 12m2f, and 12m2h). In other words, each of the multiple second magnets may be any of a first unit magnet having a magnetization direction in the circumferential direction, a second unit magnet having a magnetization direction along the rotation axis, and a third unit magnet having a magnetization direction in the radial direction relative to the rotation axis.

The combination of second magnets is not limited to the example of the encoder according to the first embodiment. The second magnet may include at least two of a first unit magnet having a magnetization direction in the circumferential direction, a second unit magnet having a magnetization direction along the rotation axis, and a third unit magnet having a magnetization direction in the radial direction relative to the rotation axis. For example, the second magnet may be arranged such that the first unit magnet having a magnetization direction in the circumferential direction and the third unit magnet having a magnetization direction in the radial direction relative to the rotation axis are alternately arranged in the circumferential direction. Furthermore, the second unit magnet having a magnetization direction in the direction along the rotation axis and the third unit magnet having a magnetization direction in the radial direction relative to the rotation axis may be arranged alternately in the circumferential direction.

Furthermore, the number of the second magnets is not limited to the above example, and may be two or more. The number of the second magnets may be an even number. Two adjacent second magnets may be magnetized in different directions.

The encoder according to this embodiment may further include a single-turn encoder. The disk 11d may have slits, for example, that form an M-sequence pattern, and the encoder according to this embodiment may include a position detection unit that has a resolution of about 20 to 24 bits in the circumferential direction by, for example, irradiating the slits with light.

The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

REFERENCE SIGNS LIST 1 Servo motor system 10 Servo motor 11 Motor 11a Rotating shaft 11d Disk 12 Encoder 12g Power generating element 12h1 First magnetic sensor 12h2 Second magnetic sensor 12j Circuit board 12m1, 12m2 Magnets 12m2a, 12m2b, 12m2c, 12m2d, 12m2e, 12m2f, 12m2g, 12m2h Magnets 32m2a, 32m2c, 32m2e, 32m2g Magnets 42m2a, 42m2b, 42m2c, 42m2e, 42m2f, 42m2g Magnet 20 Servo controller

Claims (8)

A magnetic sensor;
a first magnet that is provided symmetrically with respect to the rotation axis and generates a first magnetic field that is detected by the magnetic sensor;
A power generating element;
a plurality of second magnets arranged side by side in a circumferential direction of the rotation shaft and configured to generate a second magnetic field that causes the power generating element to generate power;
a circuit board on which the magnetic sensor is disposed at a position facing the first magnet and the power generating element is disposed on an outer periphery of a position facing the second magnet ,
the power generating element is disposed at a position greater than 1 and less than or equal to 1.35 times the radius from the rotation axis of the second magnet .
Encoder. the power generating element is disposed at a position that is 1.2 times or more and 1.35 times or less in radius from the rotation axis of the second magnet.
The encoder of claim 1 . Each of the second magnets has a magnetization direction in the circumferential direction.
An encoder according to claim 1 or 2 . Each of the second magnets has a magnetization direction in a radial direction with respect to the rotation axis.
An encoder according to claim 1 or 2 . Each of the second magnets has a magnetization direction along the rotation axis.
An encoder according to claim 1 or 2 . The second magnets include at least two of a first unit magnet having a magnetization direction in the circumferential direction, a second unit magnet having a magnetization direction in a direction along the rotation axis, and a third unit magnet having a magnetization direction in a radial direction relative to the rotation axis.
An encoder according to claim 1 or 2 . a first end surface of the first magnet on a first side along the rotation axis is located at a different position from a second end surface of the second magnet on the first side in a direction along the rotation axis;
An encoder according to claim 1 or 2 . The first end surface is closer to the circuit board than the second end surface.
The encoder of claim 7 .

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