Counting device

Abstract

Provided is a counting device capable of accurately counting even if there is no sufficient power generation in a power generation device. A counting apparatus includes: a power generation device that varies by a magnetic field; a magnetic sensor that detects a change in the magnetic field; a magnet generating the magnetic field change; a processing circuit that counts based on the magnetic field change; a storage circuit that records a count value counted by the processing circuit; and a determination circuit having at least two threshold values including a predetermined first threshold value and a second threshold value smaller than the first threshold value, and determining a voltage level of a generated voltage generated by the power generation device based on the at least two threshold values, the processing circuit performing processing according to the voltage level.

Description

TECHNICAL FIELD

[0001] The present application relates to a counting device. BACKGROUND

[0002] Patent Document 1 discloses an encoder including a power generation element that converts magnetic energy into an electric pulse using Barkhausen characteristic, and a polarity detection circuit that detects a polarity of a power generation pulse generated by the power generation element. Patent Document 1 also discloses that the encoder further includes an excitation circuit that, when a power supply is supplied from the outside, passes an excitation current in a direction opposite to a current polarity to excite the power generation element.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2024-014598 SUMMARY

[0004] [Problems to be Solved by the Invention]

[0005] For example, when a Vigenere wire using Barkhausen characteristic is used as a power generation device, if a magnetic field reversal is performed in a state in which a magnetic saturation of a composite alloy used for a core material is insufficient, a residual pulse in which a power generation amount is small is sometimes generated.

[0006] The present application provides a counting device that can accurately count even in a case in which a power generation device does not sufficiently generate power.

[0007] [Means for Solving the Problems]

[0008] According to one aspect of the present application, there is provided a counting device including: a power generation device that uses a magnetic field change; a magnetic sensor that detects the magnetic field change; a magnet that generates the magnetic field change; a processing circuit that counts based on the magnetic field change; a storage circuit that records a count value obtained by counting by the processing circuit; and a determination circuit that has at least two threshold values and determines a voltage level of a power generation voltage generated by the power generation device based on the at least two threshold values, the at least two threshold values including a predetermined first threshold value and a second threshold value that is smaller than the first threshold value, the processing circuit processing in accordance with the voltage level.

[0009] [Effects of the Invention]

[0010] According to the counting device of the present application, it is possible to correctly count even in a case in which a power generation device does not sufficiently generate power. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a diagram that explains a servo motor system using the encoder of the present embodiment.

[0012] Figure 2FIG. 1 is a diagram illustrating a structure of a servo motor using an encoder of the embodiment.

[0013] Figure 3 FIG. 2 is a diagram illustrating a circuit structure of the encoder of the embodiment.

[0014] Figure 4 FIG. 3 is a diagram illustrating a circuit structure of the encoder of the embodiment.

[0015] Figure 5 FIG. 4 is a diagram illustrating a circuit structure of the encoder of the embodiment.

[0016] Figure 6 FIG. 5 is a diagram illustrating a circuit structure of the encoder of the embodiment.

[0017] Figure 7 FIG. 6 is a perspective view illustrating a structure of the encoder of the embodiment.

[0018] Figure 8 FIG. 7 is a diagram illustrating a functional structure of the encoder of the embodiment.

[0019] Figure 9 FIG. 8 is a diagram illustrating an operation of the encoder of the embodiment.

[0020] Figure 10 FIG. 9 is a diagram illustrating a process of the encoder of the embodiment.

[0021] Figure 11 FIG. 10 is a diagram illustrating a process of the encoder of the embodiment.

[0022] Figure 12 FIG. 11 is a diagram illustrating a process of the encoder of the embodiment.

[0023] Figure 13 FIG. 12 is a diagram illustrating a positional relationship between a magnetic sensor and a power generating element and a magnet in the encoder of the embodiment.

[0024] Figure 14 FIG. 13 is a diagram illustrating an operation of the encoder of the embodiment.

[0025] Figure 15 FIG. 14 is a flowchart illustrating a process of the encoder of the embodiment.

[0026] Figure 16 FIG. 15 is a diagram illustrating a process of the encoder of the embodiment.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 1 servo motor system

[0029] 10 servo motor

[0030] 11 electric motor

[0031] 11a rotation axis

[0032] 11d disk

[0033] 12 encoder

[0034] 12a rectifier circuit

[0035] 12b charging circuit

[0036] 12c voltage stabilizing power supply circuit

[0037] 12d polarity detection circuit

[0038] 12e1, 12e2 drive circuit

[0039] 12f1, 12f2 signal processing circuit

[0040] 12g power generating element

[0041] 12i determination circuit

[0042] 12h1 first magnetic sensor

[0043] 12h2 second magnetic sensor

[0044] 12m1 first magnet

[0045] 12m2 second magnet

[0046] 12p processing circuit

[0047] 12r storage circuit

[0048] 12s position detection circuit

[0049] 12w magnetic sensor

[0050] 20 servo controller DETAILED DESCRIPTION

[0051] Embodiments of the present application will be described below with reference to the accompanying drawings. Furthermore, regarding the description of the specification and the drawings of each embodiment, for the constituent elements having substantially the same or corresponding functional structures, sometimes the repeated description is omitted by adding the same reference numerals. Furthermore, in order to easily understand, the scale of each part in the drawings is sometimes different from the actual one.

[0052] An encoder according to the present embodiment will be described. The encoder according to the present embodiment includes a power generation device that generates power using a change in a magnetic field, a magnetic sensor that detects the change in the magnetic field, and a magnet that generates the change in the magnetic field. Further, the encoder according to the present embodiment includes a processing circuit that counts based on the change in the magnetic field, and a storage circuit that records a count value counted by the processing circuit. Further, the encoder according to the present embodiment includes a determination circuit that has at least two threshold values, that is, a predetermined first threshold value and a second threshold value smaller than the first threshold value, and determines a voltage level of a power generation voltage generated by the power generation device based on the threshold values. Also, the processing circuit of the encoder according to the present embodiment performs processing in accordance with the voltage level. Note that the encoder according to the present embodiment is an example of a counting device.

[0053] <servo motor system>

[0054] First, a servo motor system using the encoder according to the present embodiment will be described. Figure 1 is a diagram illustrating a servo motor system 1 using an encoder 12 that is an example of the encoder according to the present embodiment.

[0055] 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 a rotation 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.

[0056] The servo motor 10 includes a motor 11 and the encoder 12. The motor 11 is connected to the servo controller 20 via a wiring L1. The encoder 12 is connected to the servo controller 20 via a wiring L2.

[0057] The motor 11 rotates the rotation shaft 11a in the direction of an arrow AR based on an instruction from the servo controller 20. Specifically, the motor 11 rotates the rotation shaft 11a in the direction of the arrow AR based on power supplied from the servo controller 20. The servo controller 20 controls the motor 11 by supplying the controlled power from the wiring L1. The motor 11 is, for example, an AC (Alternating Current) motor, a DC (Direct Current) motor, or the like.

[0058] The encoder 12 detects a variation in the magnetic field (a magnetic field pattern) and detects at least one of position information and rotation information of the rotating shaft 11a of the motor 11. Further, the encoder 12 outputs at least one of the detected position information and rotation information to the servo controller 20 through the wiring L2. Note that the position information of the rotating shaft 11a refers to, for example, an angle (an angular displacement) of the rotating shaft 11a in a rotational direction. The rotation information of the rotating shaft 11a refers to, for example, a number of rotations indicating a rotational speed of the rotating shaft 11a or a number of rotations of the rotating shaft 11a since a predetermined time point.

[0059] <servo motor 10>

[0060] Next, the structure of the servo motor 10 using the encoder 12 as an example of the encoder of the present embodiment will be described. Figure 2 is a view for explaining the structure of the servo motor 10 using the encoder 12 as an example of the encoder of the present embodiment. Note that the arrow line indicates a flow of supply of power or current.

[0061] [motor 11]

[0062] The motor 11 rotates the rotating shaft 11a. The motor 11 includes 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, and the like, but the description thereof will be omitted here. The motor 11 includes a disk 11d provided on the encoder 12 side of the rotating shaft 11a. As will be described later, a first magnet 12ml symmetrically provided on the rotating shaft 11a and a second magnet 12m2 arranged in a circumferential direction of the rotating shaft 11a in series are mounted on the disk 11d. The first magnet 12ml and the second magnet 12m2 rotate with the rotating shaft 11a as a center. As for the first magnet 12ml and the second magnet 12m2, sometimes, they are referred to as magnets 12m without distinction.

[0063] The disk 11d is fixed to the rotating shaft 11a. The disk 11d rotates with the rotating shaft 11a as the rotating shaft 11a rotates in the direction of the arrow AR. The first magnet 12ml and the second magnet 12m2 are fixed to a surface of the disk 11d on the encoder 12 side.

[0064] The first magnet 12ml and the second magnet 12m2 are permanent magnets formed of neodymium or the like. When the first magnet 12ml and the second magnet 12m2 rotate with the disk 11d, respectively, a magnetic field on the encoder 12 side changes. The first magnet 12ml and the second magnet 12m2 generate a magnetic field change, respectively.

[0065] The first magnet 12m1 is disposed so as to have an N pole and an S pole in a direction parallel to the surface of the disk 11d. The first magnet 12m1 generates a magnetic field that is detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2, respectively.

[0066] The second magnet 12m2 generates a magnetic field that causes the power generation element 12g to generate power. The second magnet 12m2 is disposed continuously in the circumferential direction of the rotation shaft 11a. The second magnet 12m2 will be described later in detail.

[0067] Further, the surface of the disk 11d on the encoder 12 side includes a plurality of slits 11s that are arranged in a prescribed optical pattern. The slits 11s are used to detect a position by a position detection circuit 12s. The slits 11s are formed on the surface of the disk 11d, for example, in such a manner that a light-dark pattern constituting an M series or a Gray code is formed in the circumferential direction.

[0068] [Encoder 12]

[0069] The encoder 12 is described. The encoder 12 detects at least one of position information and rotation information of the rotation shaft 11a using a magnetic field that varies with rotation of the first magnet 12m1 and the second magnet 12m2. Further, the encoder 12 functions as an absolute encoder. The encoder 12 functions at least as a multi-turn encoder. That is, the encoder 12 counts how many turns the rotation shaft 11a has rotated. Further, the encoder 12 generates power necessary for the at least multi-turn detection portion (a portion of the encoder 12 other than the position detection circuit 12s) of the encoder 12 to operate using a magnetic field that varies with rotation of the second magnet 12m2.

[0070] Further, the encoder 12 detects position information of the rotation shaft 11a using the position detection circuit 12s. For example, the position detection circuit 12s has a resolution of about 5 bits in the circumferential direction. The position detection circuit 12s is, for example, an angle position sensor. Further, by using the position detection circuit 12s, the encoder 12 functions as a so-called single-turn encoder. Note that the position detection circuit 12s operates when power is supplied from the servo controller 20. Further, the number of bits of the resolution of the position detection circuit 12s is not limited to the above example. For example, the number of bits of the resolution of the position detection circuit 12s can be a number of bits of 5 bits or more.

[0071] The encoder 12 includes a power generating element 12g, a rectification circuit 12a, a charging circuit 12b, a voltage stabilizing power supply circuit 12c, a polarity detection circuit 12d, and a determination circuit 12i. The encoder 12 further includes a drive circuit 12el and a drive circuit 12e2, a first magnetic sensor 12hl and a second magnetic sensor 12h2, a signal processing circuit 12fl and a signal processing circuit 12f2, a position detection circuit 12s, a processing circuit 12p, and a storage circuit 12r. The encoder 12 further includes a first magnet 12ml and a second magnet 12m2. Note that the rectification circuit 12a, the charging circuit 12b, and the voltage stabilizing power supply circuit 12c are collectively referred to as a main power supply circuit 12n. Further, the determination circuit 12i, the drive circuit 12el, the drive circuit 12e2, the signal processing circuit 12fl, and the signal processing circuit 12f2 are collectively referred to as a rotation detection circuit 12k. Further, the first magnetic sensor 12hl and the second magnetic sensor 12h2 are collectively referred to as a magnetic sensor 12w.

[0072] The encoder 12 includes a power generating element 12g that generates electricity by a change in magnetic flux, and a first magnetic sensor 12hl and a second magnetic sensor 12h2 that measure a magnetic field. Each of the power generating element 12g, the first magnetic sensor 12hl, and the second magnetic sensor 12h2 is disposed on the motor 11 side of the encoder 12 so as to be susceptible to the magnetic field generated by the first magnet 12ml and the second magnet 12m2.

[0073] [Power generating element 12g]

[0074] The power generating element 12g is an element that generates electricity by converting magnetic energy into an electric pulse. The power generating element 12g is a power generating device that utilizes a change in a magnetic field. The power generating element 12g is a power generating element that generates electricity using Barkhausen characteristic. The power generating element 12g is, for example, a Wiegand wire that is an environmental power generator (EHG: Energy Harvest Generator).

[0075] The power generating element 12g includes a hard core and a soft layer wound around the hard core. The hard core is formed of a material having a large coercive force. The soft layer is formed of a material having a small coercive force. The power generating element 12g generates a power generating pulse when the direction of an external magnetic field is reversed.

[0076] For example, the Wiegand wire generates an electric pulse near a zero point at which an external magnetic field is reversed, regardless of the speed of change in the external magnetic flux. Thus, the Wiegand wire generates constant electric power regardless of the rotation speed of the rotation shaft 11a. The Wiegand wire generates a stable electric pulse (voltage pulse) even when the magnetic flux changes slowly due to low-speed rotation (movement). The Wiegand wire generates an electric pulse at the timing at which the magnetic field is reversed.

[0077] By using the environmental generator in the power generating element 12g, the encoder 12 is able to count the rotation of the rotary shaft 11a without a battery or an external power source, for example. That is, the encoder 12 also functions as a battery-less encoder. Since the Vigenere line generates constant power regardless of the rotation speed of the rotary shaft 11a, and a stable power generation waveform can be obtained even at low speed rotation, the Vigenere line is suitable for use as the power generating element 12g when the encoder 12 is used as a battery-less encoder.

[0078] Note that the power generating element 12g is not limited to the Vigenere line, but can be any power generating element that generates power using the Barkhausen characteristic.

[0079] The power generating element 12g generates power using a magnetic field formed by the second magnet 12m2.

[0080] [First and second magnetic sensors 12h1 and 12h2 (magnetic sensor 12w)]

[0081] The magnetic sensor 12w includes a first magnetic sensor 12h1 and a second magnetic sensor 12h2. Each of the first and second magnetic sensors 12h1 and 12h2 detects a magnetic field. More specifically, each of the first and second magnetic sensors 12h1 and 12h2 detects a change in the magnetic field caused by the first magnet 12m1 described later.

[0082] Each of the first and second magnetic sensors 12h1 and 12h2 is, for example, a Hall element. The Hall element detects a magnetic field that passes through a semiconductor element through which a drive current flows. In the encoder 12, each of the first and second magnetic sensors 12h1 and 12h2 mainly detects a magnetic field generated by the first magnet 12m1. The Hall element that constitutes each of the first and second magnetic sensors 12h1 and 12h2 is constituted by a semiconductor element such as indium antimonide (InSb), gallium arsenide (GaAs), or the like, for example. The Hall element outputs a voltage that is proportional to the drive current and the magnetic flux density that crosses the drive current.

[0083] The first magnetic sensor 12h1 outputs a magnetic field detection signal to the signal processing circuit 12f1. A constant current Idr is supplied from the drive circuit 12e1 to the first magnetic sensor 12h1. Further, the second magnetic sensor 12h2 outputs a magnetic field detection signal to the signal processing circuit 12f2. A constant current Idr is supplied from the drive circuit 12e2 to the second magnetic sensor 12h2.

[0084] The electric power generated by the power generating element 12g is rectified by the rectification circuit 12a, and is constant-currentized by the drive circuit 12el, and the constant-currentized current (constant current Idr) is further supplied to the first magnetic sensor 12hl. The electric power generated by the power generating element 12g is rectified by the rectification circuit 12a, and is constant-currentized by the drive circuit 12e2, and the constant-currentized current (constant current Idr) is further supplied to the second magnetic sensor 12h2.

[0085] The second magnetic sensor 12h2 has a magnetic sensitivity direction having a 90-degree phase difference from the first magnetic sensor 12hl. The encoder 12 has magnetic sensitivity directions having a 90-degree phase difference from each other by the first magnetic sensor 12hl and the second magnetic sensor 12h2. In other words, the magnetic sensors 12w (the first magnetic sensor 12hl and the second magnetic sensor 12h2) in the encoder 12 have magnetic sensitivity directions having a 90-degree phase difference from each other.

[0086] The magnetic sensor 12w detects the change in the magnetic field of the first magnet 12ml as 2-phase electric signals having a 90-degree phase difference by including the first magnetic sensor 12hl and the second magnetic sensor 12h2 having magnetic sensitivity directions having a 90-degree phase difference from each other.

[0087] Note that although the encoder 12 includes 2 magnetic sensors, the number of magnetic sensors is not limited to 2. The encoder 12 can include 3 or more magnetic sensors. Furthermore, the measurement of the magnetic field is not limited to a Hall element, and can be any element that can detect a magnetic field (magnetic detection element). For example, a magnetoresistance effect element or the like can be used as a magnetic sensor.

[0088] A circuit structure included in the encoder 12 will be described with reference to Figure 3 A circuit structure included in the encoder 12 will be described with reference to Figure 3 is a diagram illustrating a circuit structure of the encoder 12 as an example of the encoder of the present embodiment.

[0089] [Rectification circuit 12a]

[0090] The rectification circuit 12a rectifies the electric power generated by the power generating element 12g to generate a positive voltage. The rectification circuit 12a includes a full-wave rectification circuit 12al.

[0091] The full-wave rectification circuit 12al rectifies the positive and negative pulses of the voltage Vgn generated by the power generating element 12g into positive pulses. The full-wave rectification circuit 12al is a so-called diode bridge circuit. For example, when the power generating element 12g is a Vigenere wire, the power generating element 12g generates positive and negative pulses. The full-wave rectification circuit 12al converts the positive and negative pulses generated by the power generating element 12g into positive pulses.

[0092] The rectification circuit 12a outputs the rectified voltage Vrc.

[0093] [Charging circuit 12b]

[0094] The charging circuit 12b includes a capacitor 12b1. The capacitor 12b1 stores the electric power generated by the power generating element 12g. Further, the capacitor 12b1 smoothes the positive pulse, that is, the voltage Vrc, generated by the full-wave rectifying circuit 12a1. The capacitor 12b1 is provided between the output terminal of the full-wave rectifying circuit 12a1 and the common potential. The positive pulse is smoothed by the capacitor 12b1, and the smoothed power generation voltage Vc is output from the rectifying circuit 12a.

[0095] [Regulated power supply circuit 12c]

[0096] The regulated power supply circuit 12c makes the voltage output from the rectifying circuit 12a be a substantially constant voltage and outputs it. The regulated power supply circuit 12c includes a regulator 12c1. The regulator 12c1 is, for example, an LDO (Low Dropout) regulator.

[0097] When a voltage of a prescribed magnitude is input, the regulated power supply circuit 12c outputs a substantially constant voltage Vdd.

[0098] [Polarity detection circuit 12d]

[0099] The polarity detection circuit 12d detects the polarity of the electric power generated by the power generating element 12g. Figure 4 FIG. 7 is a diagram that explains the circuit structure 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 that includes a resistor 12d2a and a capacitor 12d2b.

[0100] The comparator 12d1 compares the voltage Vgns and a potential (reference potential Vref2) that is a reference, and outputs the comparison result to the processing circuit 12p. The comparator 12d1 is a so-called comparator. The comparator 12d1 includes a differential amplifier 12d1a, a resistor 12d1b, a resistor 12d1c, and a resistor 12d1d. The differential amplifier 12d1a is supplied with the electric power of the voltage Vdd from the regulated power supply circuit 12c. The differential amplifier 12d1a compares the voltage Vgns, which is the voltage Vgn output from the power generating element 12g that is smoothed by the filter circuit 12d2, and the reference potential Vref2, which is generated by dividing the voltage Vdd using the resistor 12d1c and the resistor 12d1d. Then, the differential amplifier 12d1a outputs the comparison result as a voltage signal, that is, a polarity signal Spl, to the processing circuit 12p. The resistor 12d1b is a feedback resistor.

[0101] [Decision circuit 12i]

[0102] The decision circuit 12i detects the amplitude of the electric power generated by the power generating element 12g. In other words, the decision circuit 12i measures the power generation voltage generated by the power generating element 12g. Further, the decision circuit 12i has at least two threshold values: a predetermined first threshold value and a second threshold value smaller than the first threshold value. Also, the decision circuit 12i determines the voltage level of the power generation voltage generated by the power generating element 12g based on the at least two threshold values. Figure 5 is a diagram illustrating the circuit structure of the decision circuit 12i in the encoder 12. The decision circuit 12i includes a power supply circuit 12ii and a threshold processing circuit 12i2.

[0103] (Power supply circuit 12ii)

[0104] The power supply circuit 12ii generates a power supply voltage Vp and a reference voltage Vr based on the power generation voltage Vc.

[0105] To generate the power supply voltage Vp, the power supply circuit 12ii includes a resistor 12ia, a Zener diode 12ib, an operational amplifier 12ic, a resistor 12id, and a resistor 12ie. The resistor 12ia and the Zener diode 12ib are connected in series between the power generation voltage Vc and a common potential. The non-inverting input terminal of the operational amplifier 12ic is connected to the connection point between the resistor 12ia and the Zener diode 12ib. The resistor 12id and the resistor 12ie are connected in series between the output terminal of the operational amplifier 12ic and the common potential. The inverting input terminal of the operational amplifier 12ic is connected to the connection point between the resistor 12id and the resistor 12ie. The positive power supply terminal of the operational amplifier 12ic is connected to the power generation voltage Vc. The negative power supply terminal of the operational amplifier 12ic is connected to the common potential.

[0106] When the power generation voltage Vc is greater than or equal to the yield voltage of the Zener diode 12ib, the potential difference of the Zener diode 12ib is substantially constant. Therefore, when the power generation voltage Vc is greater than or equal to a certain predetermined voltage, a substantially constant voltage is input to the non-inverting input terminal of the operational amplifier 12ic.

[0107] The operational amplifier 12ic, the resistor 12id, and the resistor 12ie constitute an inverting amplification circuit. Therefore, by adjusting the resistance values of the resistor 12id and the resistor 12ie respectively, it is possible to generate a desired power supply voltage Vp. The power supply voltage Vp is, for example, 1.8 volts.

[0108] The power supply circuit 1211 further includes a resistor 1211f, a resistor 1211g, and an operational amplifier 1211h to reduce the power supply voltage Vp and generate a reference voltage Vr. The resistor 1211f and the resistor 1211g are connected in series between the output terminal of the operational amplifier 1211c and a common potential. The non-inverting input terminal of the operational amplifier 1211h is connected to the connection point between the resistor 1211f and the resistor 1211g. The inverting input terminal of the operational amplifier 1211h is connected to the output terminal of the operational amplifier 1211h. The operational amplifier 1211h operates as a buffer.

[0109] The reference voltage Vr is generated by dividing the power supply voltage Vp with the resistor 1211f and the resistor 1211g. The reference voltage Vr is, for example, 0.9 volts.

[0110] (Threshold processing circuit 1212)

[0111] The threshold processing circuit 1212 delays the power supply voltage Vp and outputs it as a signal Srs (reset signal).

[0112] Further, the threshold processing circuit 1212 compares the reference voltage Vr with a voltage Vcl obtained by dividing the generated voltage Vc with resistors and outputs the comparison result as a signal Sup. The threshold processing circuit 1212 compares the generated voltage Vc with a first threshold value by comparing the reference voltage Vr with the voltage Vcl obtained by dividing the generated voltage Vc with resistors.

[0113] Further, the threshold processing circuit 1212 compares the reference voltage Vr with a voltage Vc2 obtained by dividing the generated voltage Vc with resistors and outputs the comparison result as a signal Slw. The threshold processing circuit 1212 compares the generated voltage Vc with a second threshold value by comparing the reference voltage Vr with the voltage Vc2 obtained by dividing the generated voltage Vc with resistors.

[0114] The threshold processing circuit 1212 operates with the generated voltage Vc. Since the capacitor 1211 in the charging circuit 121b is charged, the generated power in the power generating element 121g is generated slightly delayed from the start of the generation of the generated voltage Vc. Therefore, the threshold processing circuit 1212 detects the generated voltage after a prescribed time elapses from the start of the generation of the power generating element 121g.

[0115] The threshold processing circuit 12i2 includes a Schmitt trigger 12i2a, a resistor 12i2b and a capacitor 12i2c, and a Schmitt trigger 12i2d (reset circuit) to generate a signal Srs. A power supply voltage Vp is connected to the power supply terminals of the Schmitt trigger 12i2a and the Schmitt trigger 12i2d respectively. A low pass filter composed of the resistor 12i2b and the capacitor 12i2c is provided between the Schmitt trigger 12i2a and the Schmitt trigger 12i2d. With the low pass filter composed of the resistor 12i2b and the capacitor 12i2c, the output of the Schmitt trigger 12i2a is delayed during being input to the Schmitt trigger 12i2d.

[0116] The threshold processing circuit 12i2 is able to output the signal Srs after the power supply voltage Vp is sufficiently stabilized by delaying the power supply voltage Vp and outputting it as the signal Srs (reset signal).

[0117] Further, the threshold processing circuit 12i2 includes a resistor 12i2e, a resistor 12i2f and a comparator 12i2g to generate a signal Sup (first comparison circuit). The resistor 12i2e and the resistor 12i2f are provided in series between the generated voltage Vc and a common potential. The positive side input terminal of the comparator 12i2g is connected to the connection point between the resistor 12i2e and the resistor 12i2f. The negative side input terminal of the comparator 12i2g is input with a reference voltage Vr. The power supply terminal of the comparator 12i2g is connected to the generated voltage Vc.

[0118] The voltage Vc1 obtained by dividing the generated voltage Vc with the resistor 12i2e and the resistor 12i2f is input to the positive side input terminal of the comparator 12i2g. The comparator 12i2g compares the reference voltage Vr and the voltage Vc1. The comparator 12i2g outputs the comparison result as the signal Sup. The comparator 12i2g compares the generated voltage Vc and the first threshold value by comparing the generated voltage Vc and the voltage Vc1. The comparator 12i2g outputs the result of comparing the generated voltage Vc and the first threshold value as the signal Sup. When the generated voltage Vc is greater than or equal to the first threshold value, the signal Sup is a high level signal. When the generated voltage Vc is less than the first threshold value, the signal Sup is a low level signal.

[0119] Further, the threshold processing circuit 12i2 includes a resistor 12i2h and a resistor 12i2i and a comparator 12i2j to generate a signal Slw (second comparison circuit). The resistor 12i2h and the resistor 12i2i are provided in series between the generated voltage Vc and a common potential. The positive side input terminal of the comparator 12i2j is connected to the connection point between the resistor 12i2h and the resistor 12i2i. The negative side input terminal of the comparator 12i2j is input with a reference voltage Vr. The power supply terminal of the comparator 12i2j is connected to the generated voltage Vc.

[0120] The voltage Vc2 obtained by dividing the generation voltage Vc by the resistance 12i2h and the resistance 12i2i is input to the positive-side input terminal of the comparator 12i2j. The comparator 12i2j compares the reference voltage Vr with the voltage Vc2. The comparator 12i2j outputs the comparison result as a signal Slw. The comparator 12i2j compares the generation voltage Vc with the second threshold value by comparing the generation voltage Vc with the voltage Vc2. The comparator 12i2j outputs the result of comparing the generation voltage Vc with the second threshold value as the signal Slw. The signal Slw is a high-level signal when the generation voltage Vc is greater than or equal to the second threshold value. The signal Slw is a low-level signal when the generation voltage Vc is less than the second threshold value. Note that the second threshold value is a value smaller than the first threshold value.

[0121] Note that the threshold processing circuit 12i2 includes the pull-up resistor 12i2k connected to the output terminal of the comparator 12i2g and the Schmitt trigger 12i2m. The power supply voltage Vp is supplied to the pull-up resistor 12i2k. The signal Srs is supplied to the power terminal of the Schmitt trigger 12i2m. The threshold processing circuit 12i2 outputs the signal Sup as the output of the comparator 12i2g after the signal Srs rises, by including the pull-up resistor 12i2k connected to the output terminal of the comparator 12i2g and the Schmitt trigger 12i2m.

[0122] Further, the threshold processing circuit 12i2 includes the pull-up resistor 12i2n connected to the output terminal of the comparator 12i2j and the Schmitt trigger 12i2p. The power supply voltage Vp is supplied to the pull-up resistor 12i2n. The signal Srs is supplied to the power terminal of the Schmitt trigger 12i2p. The threshold processing circuit 12i2 outputs the signal Slw as the output of the comparator 12i2j after the signal Srs rises, by including the pull-up resistor 12i2n connected to the output terminal of the comparator 12i2j and the Schmitt trigger 12i2p.

[0123] Note that the Schmitt trigger 12i2m and the Schmitt trigger 12i2p can be omitted. By omitting the Schmitt trigger 12i2m and the Schmitt trigger 12i2p, the signal Sup and the signal Slw as the results of comparing the generation voltage with the threshold value can be output before the signal Srs, respectively.

[0124] Note that, in the determination circuit 12i, when the generated voltage Vc is greater than or equal to the first threshold value, all of the signal Sup, the signal Slw, and the signal Srs become high-level signals. Further, in the determination circuit 12i, when the generated voltage Vc is less than the first threshold value and greater than or equal to the second threshold value, both of the signal Slw and the signal Srs become high-level signals, and the signal Sup becomes a low-level signal. Further, in the determination circuit 12i, when the generated voltage Vc is less than the second threshold value, all of the signal Sup, the signal Slw, and the signal Srs become low-level signals.

[0125] The determination circuit of the encoder according to the present embodiment can generate timing with low power consumption by a small-scale circuit.

[0126] Note that the Schmitt trigger 12i2m in the threshold processing circuit 12i2 is an example of the first buffer circuit, and the Schmitt trigger 12i2p is an example of the second buffer circuit.

[0127] [Drive circuits 12e1 and 12e2]

[0128] 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 operate as constant current sources, respectively. The encoder 12 drives the first magnetic sensor 12h1 and the second magnetic sensor 12h2 as Hall elements with the constant current Idr.

[0129] The drive circuit 12e1 supplies drive power to the first magnetic sensor 12h1 so that the constant current as a drive current flows to the first magnetic sensor 12h1 as a Hall element. The drive circuit 12e2 supplies drive power to the second magnetic sensor 12h2 so that the constant current as a drive current flows to the second magnetic sensor 12h2 as a Hall element.

[0130] Figure 6 is a diagram that illustrates a circuit structure of a drive circuit and a magnetic sensor in the encoder 12 that is an example of the encoder of the present embodiment. Note that the drive circuit 12e1 and the drive circuit 12e2 have the same circuit structure, and thus in Figure 6 , the drive circuit 12e1 and the drive circuit 12e2 are both described as the drive circuit 12e. Further, in Figure 6 , the first magnetic sensor 12h1 and the second magnetic sensor 12h2 as Hall elements are equivalently represented as the magnetic sensor 12h using a bridge circuit including the resistors 12ha, 12hb, 12hc, and 12hd.

[0131] The drive circuit 12e includes a transistor 12ea, a current detection resistor 12eb, and a differential amplifier 12ec. Further, the drive circuit 12e includes a resistor 12ed, a Zener diode 12ee, and a capacitor 12ef.

[0132] The transistor 12ea is controlled so that a constant current flows through the magnetic sensor 12h. An output terminal of the differential amplifier 12ec is connected to a gate terminal of the transistor 12ea. The differential amplifier 12ec outputs a voltage based on a potential difference between a + terminal and a - terminal from the output terminal. The drive circuit 12e is controlled so that a constant current (constant current Idr) based on a voltage input to the + terminal and a resistance value of the current detection resistor 12eb flows between a drain and a source of the transistor 12ea.

[0133] The magnetic sensor 12h is driven by the constant current Idr, and outputs a voltage Vh+ and a voltage Vh- proportional to the constant current Idr and a magnetic flux density that traverses the magnetic sensor 12h.

[0134] Note that the drive circuit 12e is driven by the voltage Vdd supplied from the voltage stabilizing power supply circuit 12c.

[0135] [Signal processing circuit 12f1 and signal processing circuit 12f2]

[0136] The signal processing circuit 12f1 and the signal processing circuit 12f2 respectively process detection signals from the first magnetic sensor 12h1 and the second magnetic sensor 12h2, and detect a magnetic field direction of the first magnet 12m1. The signal processing circuit 12f1 and the signal processing circuit 12f2 are used in common in the following Figure 3 The signal processing circuit 12f1 and the signal processing circuit 12f2 are described. Note that the signal processing circuit 12f1 and the signal processing circuit 12f2 have the same circuit structure, and thus the signal processing circuit 12f1 is described in the following Figure 3

[0137] The signal processing circuit 12f1 includes a differential amplifier 12fa and a comparator 12fb.

[0138] (Differential amplifier 12fa)

[0139] The differential amplifier 12fa outputs a voltage Vd obtained by amplifying a potential difference between the voltage Vh+ and the voltage Vh- output from the magnetic sensor 12h to the comparator 12fb. The differential amplifier 12fa is supplied with power of the voltage Vdd from the voltage stabilizing power supply circuit 12c.

[0140] (Comparator 12fb)

[0141] ​The comparator 12fb compares the voltage Vd output from the differential amplifier 12fa with a potential (reference potential Vref) as a reference, and outputs the comparison result to the processing circuit 12p. The comparator 12fb is a so-called comparator. The comparator 12fb includes a differential amplifier 12fb1, a resistor 12fb2, a resistor 12fb3, and a resistor 12fb4. The differential amplifier 12fb1 is supplied with power of the voltage Vdd from the voltage stabilizing power supply circuit 12c. The differential amplifier 12fb1 compares the voltage Vd of the output of the differential amplifier 12fa with the reference potential Vref generated by dividing the voltage Vdd with the resistor 12fb3 and the resistor 12fb4, and outputs the comparison result as a voltage signal, i.e., a magnetic pole signal Smg1, to the processing circuit 12p. The resistor 12fb2 is a feedback resistor.

[0142] [Position detection circuit 12s]

[0143] The position detection circuit 12s and the slit 11s constitute a so-called optical encoder. The position detection circuit 12s includes a light emitting portion 12s1 and a light receiving portion 12s2. The light emitting portion 12s1 irradiates a portion of the surface of the disk 11d on which the slit 11s is formed with light. The light emitting portion 12s1 includes a light emitting element such as an LED (Light Emitting Diode) or an LD (Laser Diode). The light receiving portion 12s2 receives light reflected from the slit 11s on the surface of the disk 11d. The light receiving portion 12s2 includes a light receiving element such as a PD (Photo Detector). Note that the light receiving portion 12s2 includes a plurality of light receiving elements. For example, in a case where an M series of n bits is used to receive light, the light receiving portion 12s2 includes n light receiving elements.

[0144] The position detection circuit 12s detects the intensity of light irradiated by the light emitting portion 12s1, reflected at the slit 11s, and received by the light receiving portion 12s2. Then, the position detection circuit 12s detects the position of the slit 11s of the portion of the reflected light on the disk 11d, based on the intensity of the light received by the light receiving portion 12s2. The position detection circuit 12s detects a rotational position based on the position of the slit 11s.

[0145] [Processing circuit 12p]

[0146] The processing circuit 12p calculates at least one of position information and rotation information of the rotation shaft 11a of the motor 11, such as a rotation position and a number of rotations, based on inputs from the determination circuit 12i, the signal processing circuit 12f1, and the signal processing circuit 12f2, respectively. In other words, the processing circuit 12p counts based on a change in a magnetic field. Further, the processing circuit 12p records or transmits at least one of the position information and the rotation information of the rotation shaft 11a of the motor 11 to an external control system, such as the servo controller 20.

[0147] The processing circuit 12p is, for example, a microcomputer, an ASIC (application specific integrated circuit), or the like. Further, the processing circuit 12p can be, for example, an FPGA (Field-Programmable Gate Array), a PLD (Programmable Logic Device), or the like.

[0148] The processing circuit 12p is connected to the storage circuit 12r provided outside. Note that the processing circuit 12p can also be provided with a nonvolatile memory such as a ferroelectric memory in place of the external storage circuit 12r.

[0149] The processing circuit 12p includes at least a terminal PWR, a terminal SIG1, a terminal SIG2, a terminal SIG3, a terminal SIG4, a terminal SIG5, a terminal SIG6, and a terminal string SIG7d.

[0150] The terminal PWR of the processing circuit 12p is a terminal to which a positive-side power supply is supplied. The terminal PWR is supplied with power having a voltage Vdd from the voltage stabilizing power supply circuit 12c. The processing circuit 12p operates by being supplied with power through the terminal PWR thereof. Note that the processing circuit 12p also includes a terminal connected to a common potential.

[0151] The terminal SIG1, the terminal SIG2, the terminal SIG3, the terminal SIG4, the terminal SIG5, and the terminal SIG6 of the processing circuit 12p are terminals from which signals are input from the outside, respectively. The terminal string SIG7d of the processing circuit 12p is a terminal string from which a signal of a plurality of bits is input from the outside.

[0152] The terminal SIG1 is connected to the signal processing circuit 12f1. A magnetic pole signal Smg1, which is a detection result detected by the signal processing circuit 12f1, is input from the terminal SIG1. The magnetic pole signal Smg1 is a signal indicating a direction of a 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 a detection result detected by the signal processing circuit 12f2, is input from the terminal SIG2. The magnetic pole signal Smg2 is a signal indicating a direction of a magnetic field detected by the second magnetic sensor 12h2.

[0153] The terminal SIG3 is connected to the polarity detection circuit 12d. A polarity signal Spl, which is a detection result detected by the polarity detection circuit 12d, is input from the terminal SIG3. The polarity signal Spl is a signal indicating a power generation polarity of the power generation element 12g.

[0154] The terminal string SIG7d is connected to the position detection circuit 12s. A position detection signal Ds, which is a detection result detected by the position detection circuit 12s, is input from the terminal string SIG7d. The position detection signal Ds is a signal indicating a rotational position of the rotary shaft 11a.

[0155] The terminals SIG4, SIG5, and SIG6 are connected to the determination circuit 12i, respectively. A signal Sup, which is a determination result determined by the determination circuit 12i, is input from the terminal SIG4. A signal Slw, which is a determination result determined by the determination circuit 12i, is input from the terminal SIG5. A signal Srs, which is a determination result determined by the determination circuit 12i, is input from the terminal SIG6.

[0156] The encoder 12 counts how many revolutions the rotary shaft 11a has rotated. The processing circuit 12p counts how many revolutions the rotary shaft 11a has rotated using the magnetic pole signal Smg1, the magnetic pole signal Smg2, and the polarity signal Spl. The processing circuit 12p detects in which region of regions into which one revolution is divided by every 90 degrees the rotary shaft 11a is located using the magnetic pole signal Smg1, the magnetic pole signal Smg2, and the polarity signal Spl. Then, the processing circuit 12p stores a result of counting how many revolutions the rotary shaft 11a has rotated and a result of detecting in which region the rotary shaft is located in the storage circuit 12r. The processing circuit 12p stores the last detected magnetic pole signal Smg1, magnetic pole signal Smg2, and polarity signal Spl in the storage circuit 12r.

[0157] Further, the processing circuit 12p calculates a rotational angle of the rotary shaft 11a on the basis of the position detection signal Ds.

[0158] [Storage Circuit 12r]

[0159] The storage circuit 12r stores, for example, a rotation count and the like. The storage circuit 12r is a nonvolatile memory. The storage circuit 12r is, for example, a ferroelectric memory. The processing circuit 12p stores at least a count value indicating how many times the rotation shaft 11a has rotated, a position of the rotation shaft, the last detected pole signal Smgl, the pole signal Smg2, and the polarity signal Spl in the storage circuit 12r.

[0160] <Structure of encoder>

[0161] The structure of the encoder 12 will be described in detail.

[0162] Figure 7 is a perspective view illustrating the structure of the encoder 12 as an example of the encoder of the present embodiment.

[0163] The circuit board 12j is disposed opposite the disk 11d. On the upper side of the circuit board 12j, the power generation element 12g is disposed. The power generation element 12g is disposed outward of the position opposite the second magnet 12m2. The power generation element 12g is preferably disposed within a range of 1.2 to 1.5 times the radius of the second magnet 12m2. By disposing the power generation element 12g outward of the position opposite the second magnet 12m2, the power generation efficiency of the power generation element 12g can be improved.

[0164] On the lower side of the circuit board 12j, the position detection circuit 12s and the magnetic sensor 12w are disposed. The position detection circuit 12s is disposed at a position opposite the slit 11s in the disk 11d. The magnetic sensor 12w is disposed at a position opposite the first magnet 12ml.

[0165] The disk 11d is fixed to the rotation shaft 11a. The disk 11d rotates in synchronization with the rotation of the rotation shaft 11a. Figure 7 is a view illustrating the arrangement of the magnets at a certain point in time.

[0166] The encoder 12 includes the rotationally symmetrical first magnet 12ml disposed on the disk 11d, and the rotationally symmetrical second magnet 12m2 disposed outward of the rotation shaft with respect to the first magnet 12ml. The first magnet 12ml is composed of two poles of S and N poles, and is a one-time rotationally symmetrical magnet. In the present embodiment, the second magnet 12m2 is composed of four poles, and is a two-time rotationally symmetrical magnet. In this way, by making the first magnet 12ml and the second magnet 12m2 rotationally symmetrical, the load of the motor 11 is reduced because the rotational torque (moment) is smaller compared to a non-rotationally symmetrical magnet.

[0167] Note that the encoder 12 can also have a magnetic body between the first magnet 12ml and the second magnet 12m2. By having a magnetic body between the first magnet 12ml and the second magnet 12m2, the encoder 12 can suppress weakening of the magnetic field due to mutual interference of the magnetic forces of the first magnet 12ml and the second magnet 12m2.

[0168] The encoder 12 includes, as the second magnet 12m2, a unit magnet 12m2a, a unit magnet 12m2b, a unit magnet 12m2c, and a unit magnet 12m2d having a C-shape. The second magnet 12m2 is a magnet in which the unit magnet 12m2a, the unit magnet 12m2b, the unit magnet 12m2c, and the unit magnet 12m2d having a C-shape are combined in a ring shape. The second magnet 12m2 is integrally provided in a circumferential direction. By integrally providing the second magnet 12m2 in the circumferential direction, it is possible to improve the area efficiency and the volume efficiency of the magnetic field generated by the second magnet 12m2. By improving the area efficiency and the volume efficiency of the magnetic field generated by the second magnet 12m2, it is possible to improve the power generation efficiency of the power generating element 12g.

[0169] Note that the second magnet 12m2 includes four unit magnets, but the number of unit magnets is not limited to four. The second magnet can also be a magnet in which 2 x n (n is an integer of one or more) unit magnets having a C-shape are combined.

[0170] Each of the unit magnet 12m2a, the unit magnet 12m2b, the unit magnet 12m2c, and the unit magnet 12m2d has a magnetization direction in a direction parallel to the rotation axis direction.

[0171] By combining unit magnets having a C-shape to constitute the second magnet 12m2, it is possible to easily perform assembly when assembling the magnet. For example, in the case of assembling a magnet, there are cases in which assembly work is difficult due to attraction or repulsion of the magnet. According to the encoder 12, by combining unit magnets having a C-shape and continuously providing them in the circumferential direction, it is possible to easily perform assembly. Furthermore, according to the encoder 12, by combining unit magnets having a C-shape and continuously providing them in the circumferential direction, it is possible to improve the area efficiency and the volume efficiency of the magnetic field compared to a case in which the magnet is dispersed in the circumferential direction. Furthermore, the unit magnets having a C-shape are widely available, are inexpensive, and are easy to obtain.

[0172] The first magnet 12ml has a magnetization direction in a direction in which the magnetic field of the second magnet 12m2 is zero, that is, a direction between adjacent unit magnets, and more specifically, in a direction inclined at 45 degrees from a direction between the unit magnet 12m2a and the unit magnet 12m2d.

[0173] Further, in the above example, the second magnet is a combination of unit magnets having a C-shaped form, but the second magnet can also be a ring-shaped magnet having 2xn (n is an integer of 1 or more) poles. Compared to the case of combining C-shaped unit magnets, the ring-shaped magnet is easy to manufacture and easy to assemble to the disk 11d.

[0174] Next, the functional structure of the encoder of the present embodiment will be described. Figure 8 is a diagram illustrating the functional structure of the encoder 12 as an example of the encoder of the present embodiment.

[0175] The encoder 12 includes a control section 12A, a first detection section 12B, and a second detection section 12C.

[0176] The first detection section 12B includes a first magnet 12m1, a second magnet 12m2, a power generating element 12g, a magnetic sensor 12w, and a processing circuit 12p. The processing circuit 12p performs processing of calculating how many revolutions the rotation shaft 11a has rotated based on a magnetic pattern generated by the first magnet 12m1 detected by the magnetic sensor 12w. By the processing circuit 12p performing the processing of calculating how many revolutions the rotation shaft 11a has rotated based on the magnetic pattern generated by the first magnet 12m1 detected by the magnetic sensor 12w, the first detection section 12B detects how many revolutions the rotation shaft 11a has rotated. Further, the first detection section 12B outputs a sine wave in which the change in the magnetic field of the second magnet 12m2 detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 in the magnetic sensor 12w is phase-shifted by 90 degrees.

[0177] The second detection section 12C includes a slit 11s, a position detection circuit 12s, and a processing circuit 12p. The processing circuit 12p performs processing of calculating the position (angle, angular displacement) in one revolution of the rotation shaft 11a based on an optical pattern generated by the slit 11s detected by the position detection circuit 12s. By the processing circuit 12p performing the processing of calculating the position in one revolution of the rotation shaft 11a based on the optical pattern generated by the slit 11s detected by the position detection circuit 12s, the second detection section 12C detects the position in one revolution of the rotation shaft 11a.

[0178] Next, the state of the power generating element 12g when the encoder 12 is operating will be described. Figure 9 is a diagram illustrating the operation of the encoder 12 as an example of the encoder of the present embodiment. Figure 9 is a diagram illustrating the magnetization characteristics (M-H curve) of the power generating element 12g with respect to an external magnetic field.

[0179] Figure 9 The horizontal axis of indicates the external magnetic field Hextof the power generating element 12g. Figure 9The ordinate of the graph indicates the magnetization M of the power generating element 12g. The line La indicates the magnetization state of the power generating element 12g when rotating in one direction.

[0180] Further, in Figure 9 In order to illustrate the magnetization state of the power generating element 12g, a simplified graph PS1, a simplified graph PS2, a simplified graph AS1, and a simplified graph AS2 are shown. In each of the simplified graphs PS1, PS2, AS1, and AS2, the central cylinder indicates the hard core HC, and the outer cylinder indicates the soft layer SL. Further, the arrows of the hard core HC and the soft layer SL each indicate the respective magnetization directions.

[0181] Note that the simplified graph PS1 indicates a state in which the magnetization of each of the hard core HC and the soft layer SL is oriented in the same direction as the positive external magnetic field (parallel state). The simplified graph PS2 indicates a state in which the magnetization of each of the hard core HC and the soft layer SL is oriented in the same direction as the negative external magnetic field (parallel state). The simplified graph AS1 indicates a state in which the hard core HC is oriented in the direction of the positive external magnetic field, and the soft layer SL is oriented in the direction of the negative external magnetic field, so as to be oriented in opposite directions from each other (antiparallel state). The simplified graph AS2 indicates a state in which the hard core HC is oriented in the direction of the negative external magnetic field, and the soft layer SL is oriented in the direction of the positive external magnetic field, so as to be oriented in opposite directions from each other (antiparallel state).

[0182] First, the characteristics of the power generating element 12g when rotating in one direction are described. Here, a case in which the power generating element 12g is rotated in one direction from a point A is described. Note that the point A indicates a state in which the maximum external magnetic field is applied to the power generating element 12g. At the point A, in the power generating element 12g, both the hard core HC and the soft layer SL are magnetized in the direction of the positive external magnetic field (parallel state).

[0183] When the magnet is rotated, the magnetization state of the power generating element 12g changes from the point A along the arrow B. Then, when the external magnetic field Hext changes from positive to negative, the magnetization changes sharply due to the Vignette effect, as indicated by the arrow C. The magnetization changes sharply because a large Barkhausen jump occurs when the magnetization of the soft layer SL is reversed. Due to the sharp change in the magnetization, a large power generating pulse is generated in the power generating element 12g, as indicated by the arrow C. Further, as indicated by the simplified graph AS1, the power generating element 12g is in the antiparallel state.

[0184] Then, when the magnet is further rotated, the magnetization state of the power generating element 12g changes along the arrow D. When the point E is reached, the power generating element 12g is in the parallel state, as indicated by the simplified graph PS2.

[0185] Then, similarly to the above description, the magnetization state of the power generating element 12g is changed from the point E along the arrow F. Then, when the external magnetic field Hext changes from negative to positive, as indicated by the arrow G, the magnetization changes sharply due to the Vignette effect. As indicated by the arrow G, a large power generating pulse is generated in the power generating element 12g with the sharp change in the magnetization. Also, as indicated by the simplified diagram AS2, the power generating element 12g is in the anti-parallel state. Then, the magnetization state is changed along the arrow H.

[0186] Thus, when the magnetization state of the power generating element 12g is changed by the ring (main ring) such as the line La, a large power generating pulse is generated as indicated by the arrow C and the arrow G.

[0187] Here, a case where the rotation is reversed at the point X, i.e., a case where the magnetization is reversed at the point X, after a large power generating pulse as indicated by the arrow C is generated, for example, is described.

[0188] When the magnetization is reversed at the point X, the state is changed as indicated by the line Lz. When the magnetization is reversed at the point X, the magnetization state of the power generating element 12g is changed along the arrow M. Note that, when the magnetization is reversed at the point X, the external magnetic field Hext is changed in the opposite direction before becoming the parallel state as indicated by the simplified diagram PS2. That is, the power generating element 12g is applied with the external magnetic field Hext in the opposite direction before being sufficiently magnetized. Therefore, as indicated by the arrow N, the magnetization fluctuation is small. The power generating pulse caused by the small magnetization fluctuation is called a Runt Pulse as indicated by the arrow N. Then, after the Runt Pulse is generated, the residual portion is changed as indicated by the arrow P and the arrow Q.

[0189] When the Runt Pulse is generated, since the power generation amount is small, the reversal is not counted, and a rotation error is generated.

[0190] When the main ring of the magnetization characteristics (M-H curve) with respect to the external magnetic field deviates from Figure 9 When the main ring of the magnetization characteristics (M-H curve) with respect to the external magnetic field deviates from

[0191] However, in the above principle, the case where the power generating element 12g as the Vignette line is not sufficiently magnetized and a power generation failure occurs is limited to the case where the rotation angle is reversed near 90 degrees or near 270 degrees and passes near 0 degrees. In contrast, when the boundary between the unit magnets 12m2a and 12m2d passes near 90 degrees or near 270 degrees, the above power generation failure does not occur.

[0192] Next, the operation of the determination circuit 12i will be described. Figure 10 、 Figure 11 and Figure 12 are diagrams that illustrate the processing of the encoder of the present embodiment. In Figure 10 、 Figure 11 and Figure 12 , the voltage Vth1 represents the first threshold value, and the voltage Vth2 represents the second threshold value. Further, in Figure 10 、 Figure 11 and Figure 12 , the signal Slw and the signal Sup represent signals immediately after the threshold processing. That is, the signal Slw and the signal Sup represent the outputs of the comparator 12i2j and the comparator 12i2g, respectively, in Figure 5

[0193] (Sufficiently large power generation amount in the power generating element 12g)

[0194] The case where the power generation amount in the power generating element 12g is sufficiently large will be described. Figure 10 is a diagram that helps explain the operation of the power generating element 12g when the power generation amount is sufficiently large. For example, there can be a case where the external magnetic field is reversed after reaching a state (parallel state) that is sufficiently magnetized in the power generating element 12g. Note that Figure 10 represents a state where the power generation voltage Vc is the first threshold value or more.

[0195] When the power generation amount in the power generating element 12g is sufficiently large, as shown in Figure 10 , the signal Sup, the signal Slw, and the signal Srs all become high-level signals from the middle.

[0196] When the signal Srs is a high-level signal and the signal Sup and the signal Slw are high-level signals, the processing circuit 12p reads data (reads) from the storage circuit 12r in a period indicated as R in the storage circuit in Figure 10 . Then, the processing circuit 12p performs a counting operation using the read data in a period where the processing circuit becomes a high-level signal in the processing circuit in Figure 10 . Then, the processing circuit 12p performs a counting operation using the read data in a period where the processing circuit becomes a high-level signal in the processing circuit in Figure 10 ​The processing circuit 12p writes (updates) the operation result (count value) in the storage circuit 12r during the period indicated as W. Figure 10 The processing circuit 12p corrects the count value during the period in which the signal becomes a high-level signal.

[0197] (Case in which the power generation amount in the power generation element 12g reaches a certain level)

[0198] The case in which the power generation amount in the power generation element 12g reaches a certain level is described. Figure 11 is a view for explaining the operation when the power generation amount in the power generation element 12g reaches a certain level. For example, the case in which the external magnetic field is reversed from a state in which the power generation element 12g is not sufficiently magnetized. Note that, Figure 11 indicates a state in which the power generation voltage Vc is smaller than the first threshold value and larger than or equal to the second threshold value.

[0199] When the power generation amount in the power generation element 12g reaches a certain level, as shown in Figure 11 , both the signal Slw and the signal Srs become high-level signals halfway. On the other hand, the signal Sup is a low-level signal.

[0200] In the case in which the signal Srs is a high-level signal, the signal Sup is a low-level signal, and the signal Slw is a high-level signal, the processing circuit 12p writes a flag (information indicating that there is power generation in which the power generation voltage is low) in the storage circuit 12r during the period indicated as FR. Figure 11

[0201] (Case in which the power generation amount in the power generation element 12g is insufficient)

[0202] The case in which the power generation amount in the power generation element 12g is insufficient is described. Figure 12 is a view for explaining the operation when the power generation amount in the power generation element 12g is insufficient. Note that, Figure 12 indicates a state in which the power generation voltage Vc is smaller than the second threshold value.

[0203] When the power generation amount in the power generation element 12g is insufficient, as shown in Figure 12 , all of the signal Sup, the signal Slw, and the signal Srs remain low-level signals.

[0204] The processing circuit 12p does not operate in the case in which the signal Srs is a low-level signal.

[0205] As described above, the determination circuit 12i determines which voltage level the power generation voltage generated by the power generation device is based on a predetermined first threshold value and a predetermined second threshold value. Then, the processing circuit 12p performs the write processing of the storage circuit in accordance with the voltage level determined by the determination circuit 12i.

[0206] ​The processing of the encoder 12, which is an example of the encoder of the present embodiment, will be described in detail. First, the positional relationship between the magnetic sensor and the power generating element and the magnets in the encoder of the present embodiment will be described. Figure 13 is a view illustrating the positional relationship between the magnetic sensor 12w and the power generating element 12g and the first magnet 12m1 and the second magnet 12m2 in the encoder 12, which is an example of the encoder of the present embodiment. In Figure 13 , a coordinate system (XY coordinate system) composed of an X axis and a Y axis is provided for convenience of explanation. The origin of the XY coordinate system corresponds to the rotation axis 11a.

[0207] Figure 13 is a plan view of the disk 11d when the rotation angle of the disk 11d described later is 0 degrees. Figure 13 indicates the positions of the magnetic sensor 12w and the power generating element 12g in the encoder 12 in a plan view, respectively.

[0208] In Figure 13 , the first magnet 12m1 has a magnetization direction in a direction at an angle of 45 degrees. The second magnet 12m2 has a magnetization direction in a direction at an angle of 45 degrees in the Figure 13 upper right, a unit magnet 12m2b in the upper left, a unit magnet 12m2c in the lower left, and a unit magnet 12m2d in the lower right.

[0209] The magnetic sensor 12w is provided at the origin of the XY coordinate system. Note that the first magnetic sensor 12h1 of the magnetic sensor 12w is provided on the +X side on the X axis. Further, the second magnetic sensor 12h2 of the magnetic sensor 12w is provided on the +Y side on the Y axis. The power generating element 12g is provided on the +X side on the X axis.

[0210] Next, the operation in the encoder of the present embodiment will be described. Figure 14 is a view illustrating the operation of the encoder 12, which is an example of the encoder of the present embodiment. Figure 14 is a view illustrating the operation when the disk 11d rotates at a rotation angle of 0 degrees as the position of the disk 11d is at the position shown in Figure 13 .

[0211] When the disk 11d rotates, the power generating element 12g generates power at the rotation angles of 0 degrees, 90 degrees, 180 degrees, and 270 degrees at which the direction of the magnetic field is reversed. However, in reality, since the power generating element 12g has hysteresis in the magnetization characteristics, the rotation angles deviate from 0 degrees, 90 degrees, 180 degrees, and 270 degrees depending on the rotation direction of the disk 11d.

[0212] Specifically, when disk 11d rotates counterclockwise, the power generating element 12g generates electricity at each of the following positions: rotation position POS1, rotation position POS3, rotation position POS5, and rotation position POS7. It should be noted that the polarity of the power generating element 12g varies depending on whether the magnetic field characteristics change from N to S or from S to N. Therefore, for example, when the power generating element 12g is positive (+V) at rotation position POS1, its polarity becomes negative (-V) at rotation position POS3. Similarly, when the polarity becomes positive (+V) at rotation position POS5, its polarity becomes negative (-V) at rotation position POS7.

[0213] Furthermore, when disk 11d rotates clockwise, the power generating element 12g generates electricity at each of the rotation positions POS2, POS4, POS6, and POS8. Similar to the counter-clockwise rotation, when the power generating element 12g is positive (+V) at rotation position POS2, its power generating polarity changes to negative (-V) at rotation position POS4. Likewise, when the power generating polarity changes to positive (+V) at rotation position POS6, its power generating polarity changes to negative (-V) at rotation position POS8.

[0214] Next, the results detected by the magnetic sensor 12w when the rotation angle of the generator 12g is 0 degrees, 90 degrees, 180 degrees and 270 degrees will be explained in more detail. More specifically, the results measured by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 respectively will be explained.

[0215] Near the rotation angle of 0 degrees, i.e., at rotation positions POS1 and POS8, the magnetic field detected by the first magnetic sensor 12h1 in the magnetic sensor 12w is N. Furthermore, when the rotation angle is near 0 degrees, i.e., at rotation positions POS1 and POS8, the magnetic field detected by the second magnetic sensor 12h2 in the magnetic sensor 12w is S. Figure 14 In the diagram, the magnetic field detected by the first magnetic sensor 12h1 is N and the magnetic field detected by the second magnetic sensor 12h2 is S, which is represented as "(N1, S2)".

[0216] Near a rotation angle of 90 degrees, i.e., at rotation positions POS2 and POS3, the magnetic field detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 in the magnetic sensor 12w is N. Figure 14 In the diagram, the magnetic field detected by the first magnetic sensor 12h1 is N and the magnetic field detected by the second magnetic sensor 12h2 is N, which is represented as "(N1, N2)".

[0217] In the vicinity of the rotation angle 180 degrees, that is, in the rotation position POS4 and the rotation position POS5, the magnetic field detected by the first magnetic sensor 12h1 in the magnetic sensor 12w is S. In the vicinity of the rotation angle 180 degrees, that is, in the rotation position POS4 and the rotation position POS5, the magnetic field detected by the second magnetic sensor 12h2 in the magnetic sensor 12w is N. In Figure 14 In the present embodiment, the magnetic field detected by the first magnetic sensor 12h1 is S and the magnetic field detected by the second magnetic sensor 12h2 is N, which is expressed as "(S1, N2)".

[0218] In the vicinity of the rotation angle 270 degrees, that is, in the rotation position POS6 and the rotation position POS7, the magnetic field detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 in the magnetic sensor 12w is S, respectively. In Figure 14 In the present embodiment, the magnetic field detected by the first magnetic sensor 12h1 is S and the magnetic field detected by the second magnetic sensor 12h2 is S, which is expressed as "(S1, S2)".

[0219] As Figure 14 indicated, the processing circuit 12p can determine the rotation position on the basis of the power generation characteristics of the power generation element 12g and the measurement results of the magnetic sensor 12w.

[0220] Next, the processing of the encoder of the present embodiment will be described. Figure 15 is a flowchart illustrating the processing of the encoder 12 as an example of the encoder of the present embodiment.

[0221] When the power generation element 12g generates power, the encoder 12 executes the processing illustrated in Figure 15 More specifically, when the signal Srs (reset signal) becomes a high-level signal, the processing circuit 12p of the encoder 12 executes the processing illustrated in Figure 15

[0222] (Step S10)

[0223] The processing circuit 12p determines whether the signal Slw is a high-level signal. In the case where the signal Slw is a high-level signal (YES in Step S10), the processing circuit 12p causes the processing to proceed to Step S20. In the case where the signal Slw is not a high-level signal (NO in Step S10), the processing circuit 12p ends the processing because the power required for the processing is insufficient.

[0224] (Step S20)

[0225] ​In a case where the signal Slw is a high-level signal (YES in step S10), the processing circuit 12p determines whether the signal Sup is a high-level signal. In a case where the signal Sup is a high-level signal (YES in step S20), the processing circuit 12p causes the processing to proceed to step S30. In a case where the signal Sup is not a high-level signal (NO in step S20), the processing circuit 12p causes the processing to proceed to step S100.

[0226] (Step S30)

[0227] When the signal Sup is a high-level signal (YES in step S20), the processing circuit 12p reads data from the storage circuit 12r. More specifically, the processing circuit 12p reads the previous position measurement result stored in the storage circuit 12r. More specifically, the processing circuit 12p reads the angular position at the time when the processing was performed last time from the storage circuit 12r.

[0228] (Step S40, Step S50, Step S60)

[0229] Next, the processing circuit 12p determines whether the flag is in the off state. If the flag is in the off state (YES in step S40), the processing circuit 12p proceeds to step S50 to reset the flag. If the flag is not in the off state (NO in step S40), the processing circuit 12p proceeds to step S60 to set the flag. Note that the flag is information indicating that there is power generation in which the generated voltage is low. The processing circuit 12p transmits the flag to the servo controller 20, for example. The servo controller 20 can use the transmitted flag to perform processing in a manner of trusting the result of the position detection circuit 12s, for example, when there is a discrepancy in the result from the position detection circuit 12s.

[0230] (Step S70)

[0231] Next, the processing circuit 12p determines the current position. The processing circuit 12p determines the current position, i.e., the current rotational position, based on the polarity signal Spl, the magnetic pole signal Smgl, and the magnetic pole signal Smg2.

[0232] (Step S80)

[0233] Next, the processing circuit 12p calculates the count based on the previous position measurement result and the current position measurement result. Figure 16 is a diagram illustrating the count of the encoder of the present embodiment. Note that in Figure 16In the above table, the upper line indicates the amount of change in the count number. The lower line indicates the state. "Normal" indicates that the measurement can be normally performed during continuous rotation. "Normal R" indicates that the rotation is reversed midway but the measurement can be normally performed. "R" indicates that a residual pulse is generated. Note that the number indicates the rotational position at which the residual pulse is generated. "Missing" indicates that a pulse is missing. Note that the number indicates the rotational position at which the pulse is missing. "-" indicates a combination that does not occur.

[0234] The processing circuit 12p calculates the count on the basis of the current position and the previous rotational position.

[0235] (Step S90)

[0236] The processing circuit 12p writes the calculated result into the storage circuit 12r.

[0237] (Step S100)

[0238] When the signal Sup is not a high-level signal (NO in Step S20), the processing circuit 12p sets a flag. Note that the flag is information indicating that power generation in which the generated voltage is low is present.

[0239] (Step S110)

[0240] Then, the processing circuit 12p writes the flag into the storage circuit 12r.

[0241] According to the encoder of the present embodiment, the content to be processed is changed in accordance with the amount of power generation in the power generation device, and thus the count can be correctly performed even in a case where power generation is not sufficiently performed in the power generation device.

[0242] For example, a Vigenere wire as a power generation device has an advantage that a large pulse-shaped power generation is obtained by a slight change in a magnetic field. However, if the magnetic field is reversed in a state where the magnetic saturation of a composite alloy used for a core material is not sufficient, a "residual pulse" in which the amount of power generation is reduced can be generated. The case where the "residual pulse" is generated corresponds to, for example, a case where the rotation is reversed in a device in which counting is performed by power generation (for example, an encoder of a servo motor or the like). For example, when the position at which the rotation is reversed coincides with the position at which the magnetic field is reversed, the "residual pulse" in which the power generation is reduced is generated. When the "residual pulse" is generated, the power generation cannot be counted, and a count error is generated.

[0243] For example, as a method of correcting the residual pulse, there is a method of correcting the count position that is missing in the next normal power generation. When the count position is corrected, it is difficult to distinguish whether the power generation is missing due to the residual pulse or occurs due to a hardware problem such as a broken wire or noise, and there is a case where the rotation is counted as it is in a state where the reliability is low.

[0244] According to the encoder of the present embodiment, when a "residual pulse" is generated, since there is no energy for performing a full counting process, a process capable of coping with intermediate power generation energy is performed. Then, when a "residual pulse" is generated, by recording as intermediate power generation information, counting correction can be reliably performed at the next power generation. Further, when a "residual pulse" is generated, by recording as intermediate power generation information, a failure of hardware or the like can be found early at the next power generation.

[0245] Note that the encoder 12 is an example of a counting device. Note that according to the present application, the counting device is not limited to an encoder, and the technology of the present application can be employed as long as it is a counting device that counts based on a change in a magnetic field.

[0246] Further, in the above example, the power generation voltage of the power generation device is measured by the measurement circuit, and the process is performed by the processing circuit based on the power generation voltage, but the power generation power of the power generation device can be measured by the measurement circuit, and the process can be performed by the processing circuit based on the power generation power.

[0247] It should be considered that the embodiments disclosed herein are illustrative in all aspects and are not restrictive. The above-described embodiments can be omitted, replaced, or changed in various ways without departing from the scope and spirit of the appended claims.

Claims

1. A counting device, comprising: Power generation devices that utilize changes in magnetic fields; A magnetic sensor that detects changes in the magnetic field; A magnet that generates the aforementioned magnetic field change; A processing circuit that performs counting based on the changes in the magnetic field; A storage circuit that records the count values ​​obtained by counting through the processing circuit; as well as A determination circuit has at least two thresholds and determines the voltage level of the generated voltage through the power generation device based on the at least two thresholds, wherein the at least two thresholds include a predetermined first threshold and a second threshold smaller than the first threshold. The processing circuit performs processing based on the voltage level.

2. The counting device according to claim 1, wherein, If the generated voltage is greater than or equal to the first threshold, the processing circuit updates the count value stored in the storage circuit. If the generated voltage is less than the first threshold and greater than or equal to the second threshold, the processing circuit will save the information indicating the existence of the generated voltage to the storage circuit.

3. The counting device according to claim 1 or 2, wherein, The processing circuit detects the generated voltage after a predetermined time has elapsed since the power generation element started generating electricity.

4. The counting device according to claim 1 or 2, wherein, The determination circuit has the following characteristics: A power supply circuit that generates power supply voltage; A reset circuit that delays the power supply voltage to generate a reset signal; A first comparison circuit, driven by the power supply voltage, compares the generated voltage with the first threshold. The second comparison circuit, driven by the power supply voltage, compares the generated voltage with the second threshold. The first buffer circuit is disposed at the output terminal of the first comparator circuit and is driven by the reset signal; as well as The second buffer circuit is located at the output of the second comparator circuit and is driven by the reset signal.

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