JP2005172696A - Absolute encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturizable absolute encoder capable of simplifying its structure, reducing the weight, and calibrating automatically an absolute position detection means easily and surely. <P>SOLUTION: This absolute encoder 1 is equipped with magnetic sensors 14, 15 for detecting a magnetic field of a magnetic scale 13, a photosensor 12 for detecting reflected light from a position detection scale 11, and a data control part 70 for determining the relative position of the magnetic sensors 14, 15 to the magnetic scale 13 based on a detection result from the magnetic sensors 14, 15 and the absolute position of a position detection object based on a detection result from the photosensor 12. The absolute encoder 1 is characterized by calibrating automatically data showing the relationship between the position detection object and the absolute position in the data control part 70 based on the detection results from the photosensor 12 and the magnetic sensors 14, 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an absolute encoder.

An absolute encoder for detecting the absolute position of a moving object that rotates or linearly moves is known.
The patents related to the absolute encoder relating to the present invention are as follows.
<Magnetic absolute encoder>
For example, as shown in FIG. 10A, the drum 200 fixed to the rotating shaft 100, the magnetic recording medium 300 formed on the side surface thereof, the substrate 400, the MR element 500, and the conductor terminal 600 are provided. The detection head includes a lead wire 700 connected to the conductor terminal 600 and a drive detection circuit 800 having an output terminal to the outside. Five magnetic pattern rows n1 to n5 are written in the magnetic recording medium 300, and a magnetic field leaking from these magnetic patterns n1 to n5 acts on the corresponding MR element 500 (for example, see Patent Document 1).

<Optical absolute encoder>
In the encoder, for example, as shown in FIG. 10B, a code plate 210, a code detection member (a reference light emission light source 110 that irradiates the hologram pattern of the code plate 210), and a code image of each bit received at a predetermined position. In order to obtain a signal corresponding to the relative positional relationship between the code plate 210 and the code detection member by relatively moving the respective bits to the photoelectric conversion members 310) arranged corresponding to each other. Thus, a hologram pattern is formed on the code plate 210 such that a bright and dark code image of each bit (each layer) corresponding to the relative position is generated at a predetermined position (see, for example, Patent Document 2).
<Problems common to both types>
However, in such an encoder, a sensor is required for each pattern row, and as the number of pattern rows (layers) increases, the number of corresponding sensors increases and the pattern becomes multi-layered and complicated. There was a problem that.

JP-A-1-145520 JP-A-1-263522

  An object of the present invention is to provide an absolute encoder capable of automatically and reliably calibrating the absolute position detecting means, having a simple structure, and reducing the size and weight. It is to provide.

Such an object is achieved by the present invention described below.
The absolute encoder of the present invention includes a magnetic scale,
At least one magnetic sensor for detecting and magnetically converting a magnetic field generated from the magnetic scale;
A relative position detecting means for obtaining a relative position of the magnetic sensor with respect to the magnetic scale based on a detection result of the magnetic sensor;
A position detection scale;
A photosensor having a light emitting unit that emits light to the position detection scale, and a light receiving unit that receives light reflected from the position detection scale and photoelectrically converted from the light emitted from the light emitting unit;
An absolute encoder comprising absolute position detecting means for obtaining an absolute position of a position detection target based on a detection result of the photosensor,
The position detection scale is configured to gradually increase or decrease the amount of reflected light from the position detection scale when the irradiation position of the light to the position detection scale is moved along the position detection scale. And
The other movement with respect to one of the position detection scale and the photosensor, and the other movement with respect to one of the magnetic scale and the magnetic sensor are configured to correspond to each other.
The absolute position detecting means is automatically calibrated based on the data obtained by the relative position detecting means and the amount of the reflected light detected by the photosensor.
Thus, it is possible to provide an absolute encoder capable of automatically and surely automatically calibrating the absolute position detecting means, having a simple structure, and capable of being reduced in size and weight. Can do.

The absolute encoder of the present invention includes a magnetic scale,
At least one magnetic sensor for detecting and magnetically converting a magnetic field generated from the magnetic scale;
A relative position detecting means for obtaining a relative position of the magnetic sensor with respect to the magnetic scale based on a detection result of the magnetic sensor;
A position detection scale;
A photosensor having a light emitting unit that emits light to the position detection scale, and a light receiving unit that receives light reflected from the position detection scale and photoelectrically converted from the light emitted from the light emitting unit;
An absolute encoder comprising: a detection result of the photosensor; and an absolute position detection means for obtaining an absolute position of the position detection target based on a calibration curve indicating a relationship between the detection result and the absolute position of the position detection target. Because
The position detection scale is configured to gradually increase or decrease the amount of reflected light from the position detection scale when the irradiation position of the light to the position detection scale is moved along the position detection scale. And
The other movement with respect to one of the position detection scale and the photosensor, and the other movement with respect to one of the magnetic scale and the magnetic sensor are configured to correspond to each other.
The calibration curve is automatically calibrated based on the data obtained by the relative position detection means and the amount of the reflected light detected by the photosensor.
Accordingly, it is possible to provide an absolute encoder that can easily and reliably calibrate the calibration curve automatically, can have a simple structure, and can be reduced in size and weight. .

In the absolute encoder of the present invention, the calibration moves the other of the position detection scale and the photosensor, and detects the amount of reflected light from the position detection scale by the photosensor. , Sequentially from the first position to the second position of the position detection scale, and at this time, the magnetic sensor detects the magnetic field generated from the magnetic scale in correspondence with the detection point of the photosensor. It is preferable to carry out sequentially and based on information obtained from the photosensor and the magnetic sensor.
Thereby, highly accurate calibration can be performed.

In the absolute encoder of the present invention, it is preferable that the position detection scale and the magnetic scale are arranged so as to overlap in a plan view.
As a result, the structure can be further simplified, and the size and weight can be reduced.
In the absolute encoder of the present invention, it is preferable that the position detection scale also serves as the magnetic scale.
Thereby, the structure can be further simplified, and reduction in size and weight can be achieved.

In the absolute encoder of the present invention, it is preferable that the polarity of the magnetic scale changes at substantially equal intervals along the magnetic scale.
Thereby, highly accurate calibration can be performed.
In the absolute encoder according to the aspect of the invention, it is preferable that the position detection scale is configured so that the reflectance gradually increases or decreases along the position detection scale.
Thereby, the absolute position of the position detection target can be detected more reliably.

In the absolute encoder of the present invention, the position detection scale has a first part and a second part having different reflectances, and a ratio of the area of the first part to the area of the second part is Preferably, it gradually increases or decreases along the position detection scale.
Thereby, the absolute position of the position detection target can be detected more reliably.

In the absolute encoder of the present invention, it is preferable that a plurality of the first part and the second part are provided.
Thereby, the detection accuracy of the sensor can be increased, and the absolute position of the position detection target can be detected more reliably.
In the absolute encoder of the present invention, it is preferable that the arrangement of the first part and the second part is set by using a dither method or an error diffusion method.
Thereby, the detection accuracy of the sensor can be increased, and the absolute position of the position detection target can be detected more reliably.

In the absolute encoder of the present invention, the length of the first part in a direction substantially perpendicular to the direction of the position detection scale gradually increases along the position detection scale, and the direction of the position detection scale It is preferable that the length of the second part in a direction substantially perpendicular to the length gradually decreases along the position detection scale.
Thereby, it is possible to easily cope with noise and to detect the absolute position of the position detection target more reliably.

In the absolute encoder of the present invention, it is preferable that one each of the first part and the second part is provided.
Thereby, the absolute position of the position detection target can be detected more reliably.
In the absolute encoder according to the aspect of the invention, it is preferable that the first part is white and the second part is black or dark.
As a result, the difference in brightness between the first part and the second part can be maximized, and the absolute position of the position detection target can be detected more reliably.

Hereinafter, the absolute encoder of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a block diagram showing a first embodiment of an absolute encoder of the present invention. In the following, for convenience of explanation, the right side in FIG. 1 is referred to as “right”, the left side as “left”, the upper side as “upper”, and the lower side as “lower”.

As shown in FIG. 1, the absolute encoder 1 is a linear encoder, and includes a position detection scale (gray scale) 11, a photo sensor 12, a magnetic scale 13, magnetic sensors 14 and 15, and a data control unit 70. have. Hereinafter, each of these components will be described sequentially.
The position detection scale 11 has a band shape (substantially rectangular shape) in plan view. The position detection scale 11 is, for example, the first position, the upper side (one end side) in FIG. 1 is white, the second position, the lower side (the other end side) is black, and the upper side is the lower side. The ratio of white to black gradually decreases toward the side. That is, the light reflectance is gradually reduced along the position detection scale 11.

As a result, the light irradiation position moves (changes) along the position detection scale 11 as the position detection scale 11 moves, and the amount of light received by the light receiving unit 122 described later gradually decreases.
The photosensor 12 receives the light (reflected light) emitted from the light emitting unit 121 and reflected by the position detecting scale 11 and photoelectrically converts the light emitting unit 121 that emits light toward the position detecting scale 11. And a light receiving portion 122. Examples of the light emitting unit 121 include a light emitting diode and a laser diode, and examples of the light receiving unit 122 include a photodiode and a phototransistor.

When the light reflected by the position detection scale 11 is received by the light receiving unit 122, a current having a magnitude corresponding to the amount of received light is output by photoelectric conversion. This signal is converted into a voltage, that is, an analog signal, for example, via a resistor (not shown) provided in the photosensor 12.
The magnetic scale 13 has a belt-like shape (substantially rectangular shape), and the length in the longitudinal direction (vertical direction in FIG. 1) is substantially equal to that of the position detection scale 11. The magnetic scale 13 has a plurality of rod-shaped S pole portions in plan view and a plurality of rod-shaped N pole portions in plan view, and the longitudinal sides in the plan view in the vertical direction in FIG. It is arranged at equal intervals. That is, the polarities are alternately switched at substantially equal intervals along the vertical direction in FIG.

The magnetic sensors 14 and 15 have sensor units 141 and 151 that detect and magnetically convert a magnetic field generated from the magnetic scale 13, respectively. Examples of the magnetic sensors 14 and 15 include magnetoresistive elements.
When the magnetic field generated from the magnetic scale 13 is detected by the sensor units 141 and 151, a current having a magnitude and polarity corresponding to the magnetic field detected by the sensor units 141 and 151 is output by electromagnetic conversion. This signal is converted into a voltage, that is, an analog signal, for example, via a resistor (not shown) provided in the magnetic sensors 14 and 15.

Further, the magnetic sensor 15 is provided so as to detect a phase difference of 90 ° compared to the phase detected from the magnetic scale 13 of the magnetic sensor 14. Thereby, the magnetic sensor 15 outputs an analog signal having a phase difference of 90 ° compared to the magnetic sensor 14 to the comparators 74 and 75 described later.
Further, for example, as shown in FIG. 2, by using this resistor as a variable resistor and applying a predetermined voltage between A and B, a range of values of analog signals output from the magnetic sensors 14 and 15 is predetermined. It is also possible to adjust to the range.

The data control unit 70 includes an amplifier 71, an A / D converter 72, a CPU 73, comparators (binarization circuits) 74 and 75, and a forward / reverse determination circuit 76.
The amplifier 71 is connected to the output side of the photosensor 12. The amplifier 71 amplifies the input analog signal and outputs it. An A / D converter 72 is connected to the output side of the amplifier 71.

The A / D converter 72 converts the input analog signal into a digital signal and outputs it. A CPU 73 is connected to the output side of the A / D converter 72. The CPU 73 will be described later.
The amplifier 71, the A / D converter 72, and the CPU 73 constitute the main part of the absolute position detecting means.

  The comparator 74 is connected to the output side of the magnetic sensor 14, and the comparator 75 is connected to the output side of the magnetic sensor 15. As shown in FIG. 3, the comparators 74 and 75 output analog signals (sine waves) respectively output from the magnetic sensors 14 and 15 when the magnetic scale 13 is moved in the direction of the arrow in FIG. 3. It binarizes in comparison with the threshold value data, and outputs the binarized A-phase signal and B-phase signal, respectively. A forward / reverse determination circuit 76 is connected to the output side of the comparators 74 and 75.

As shown in FIG. 4, the forward / reverse determination circuit 76 uses, for example, a D flip-flop, and based on the binarized signals obtained from the comparators 74 and 75, the Q _A signal (positive count signal) and the Q _B signal (Reverse count signal) is output. The D flip-flop, when the phase of the B-phase signal as compared to the A-phase signal is delayed 90 ° outputs Q _A signal, the phase of the B-phase signal as compared to the A-phase signal is advanced 90 ° when outputs _{Q B} signal. The CPU 73 is connected to the output side of the forward / reverse determination circuit 76.
The CPU 73 performs a calculation based on the digital signal output from the A / D converter 72 and stores the calculation result, table data, and the like in a storage unit provided in the CPU 73.

The calculation is performed based on the digital signal output from the forward / reverse determination circuit 76. Specifically, when a pulse of Q _A signal is outputted from the forward and reverse decision circuit 76 determines that the magnetic scale 13 in the direction of the arrow in FIG is moving, the pulse of the Q _B signal, positive when output from the inverse determination circuit 76 determines that the magnetic scale 13 in the opposite direction in FIG. 3 arrow is moving, these Q _a signal and the Q _B signals, each output pulse train up-down counter And the count data (count number) is stored in the storage unit. Thereby, the relative position of the magnetic sensors 14 and 15 with respect to the magnetic scale 13 can be detected.

The CPU 73, the comparators 74 and 75, and the forward / reverse inversion circuit 76 constitute the main part of the relative position detection means.
Next, the measurement system 50 using the absolute encoder 1 will be described. FIG. 5 is a block diagram illustrating a configuration example of the measurement system 50. In the following, for convenience of explanation, the right side in FIG. 5 is referred to as “right”, the left side as “left”, the upper side as “upper”, and the lower side as “lower”.

As shown in FIG. 5, the measurement system 50 includes a linear actuator 2 and an absolute encoder 1.
The linear actuator 2 includes a plate-like base 21, a plate-like base 22, a plate-like slider 23, and a vibrating body 6. The base 21, the base 22, the slider 23, and the vibrating body 6 are installed so as to be parallel to each other (including a case where a part thereof overlaps the surface direction).

  The base 22 is installed at the center of the base 21 so as to be movable in the left-right direction in FIG. In this case, a pair of guide pins (not shown) are erected along the horizontal direction in FIG. 5 at the center of the base 21, and a pair of lengths (not shown) that are long in the horizontal direction in FIG. Holes are formed along the left-right direction in FIG. Each guide pin is inserted into a corresponding slot. Thereby, the base 22 is guided by the guide pin and can move in the left-right direction in FIG. 5 along the elongated hole.

  The base 22 is provided with a vibrating body 6 that rotationally drives a rotor (driven body) 41 described later. The vibrating body 6 has a convex portion (contact portion) 26 and a pair of arm portions 28, 28, and the arm portion 28 is arranged on each arm portion 28 with respect to the base 22 so that the convex portion 26 faces the right side in FIG. 5. It is fixed by a bolt 27 inserted into a formed hole (not shown). Thereby, the vibrating body 6 is supported by each arm part 28 so that it can vibrate. The vibrating body 6 will be described in detail later.

Further, a pair of spring retaining pins 31 are erected on the right end (corner) of the base 21 in FIG. On the other hand, the base 22 is formed with a pair of spring hooks 32 and 32. One spring hook 32 is provided on the upper side of the base 22 in FIG. 5, and the other spring hook 32 is provided on the lower side of the base 22 in FIG. 5.
Then, the corresponding spring stopper pin 31 and the spring hook portion 32 are respectively installed in a state where the coil spring (biasing means) 33 is extended (extended state). That is, each of the coil springs 33 is hung (fixed) at one end thereof on the spring hooking portion 32 of the base 22, and the other end is attached (fixed) to the spring stopper pin 31 of the base 21. ).

The base 21 is biased toward the right side in FIG. 5 by the elastic force (restoring force) of each coil spring 33, and the convex portion 26 of the vibrating body 6 abuts on and is pressed against the outer peripheral surface of the driven body described later. The
The photosensor 12 is provided on the base 21. This photosensor 12 is provided between the base 21 of the slider 23 in the vicinity of the upper coil spring 33 in FIG. 5 and the slider 23, and the position detection scale 11 is provided on the side of the slider 23 facing the base 21. It has been.

The position detection scale 11 is provided on the slider 23 so that the longitudinal direction thereof substantially coincides with the moving direction of the slider 23.
Further, various conditions such as the length of the photosensor 12 so that the light (reflected light) reflected on one end in the longitudinal direction of the position detection scale 11 when the slider 23 moves to the upper side in FIG. Is set, and various conditions such as the length of the photosensor 12 so that the light reflected from the other end in the longitudinal direction of the position detection scale 11 when the slider 23 moves to the lower side in FIG. Is set.

The magnetic scale 13 is provided on the slider 23 so that the longitudinal direction substantially coincides with the moving direction of the slider 23.
In addition, various conditions such as the length of the magnetic scale 13 so that the magnetic scale 13 detects the strength of the magnetic field at the first position of the position detecting scale 11 when the slider 23 moves to the maximum in FIG. Is set so that the magnetic scale 13 detects the strength of the magnetic field at the second position of the position detection scale 11 when the slider 23 moves to the lower side in FIG. The various conditions are set.

That is, in the linear actuator 2, as the slider 23 moves, the photosensor 12 and the magnetic sensors 14 and 15 are reflected from the position detection scale 11 provided on the slider 23 and the magnetic field of the magnetic scale 13. It is comprised so that each may be detected.
Further, a rotor 41 is rotatably installed at an end portion on the right side in FIG. 5 of the base 21 and in a central portion in the vertical direction in FIG. The rotor 41 includes a cylindrical member 42 having a substantially cylindrical shape, and a driven body 43 fixed (fixed) to the outer side (outer periphery) of the cylindrical member 42. The driven body 43 has a substantially ring shape (annular shape) and is located at a position (base end side) corresponding to the vibrating body 6.

A pinion gear 44 is formed on the outer peripheral surface of the rotor 41 on the tip side. Thereby, when the rotor 41 rotates, the driven body and the pinion gear 44 rotate integrally.
In addition, the diameter (outer diameter) of the portion (rotating body) where the pinion gear 44 of the rotor 41 is formed is set smaller than the diameter (outer diameter) of the driven body, thereby constituting a speed reduction mechanism. The

Further, two rollers 29 having grooves are rotatably installed at the left end (corner) of the base 21 in FIG.
The slider 23 is located in the groove of these rollers 29, is sandwiched between the rollers 29 and the rotor 41, and is installed so as to be movable in the vertical direction in FIG. In other words, the slider 23 is regulated by each roller 29 and the rotor 41 so that the moving direction thereof is the vertical direction in FIG. 5 and the posture is held constant.

The slider 23 has a substantially rectangular frame shape. That is, a substantially square opening is provided in the center of the slider 23.
A rack gear 231 that meshes with a pinion gear 44 provided on the rotor 41 is formed on the end face on the right side in FIG. 5 of the slider 23 along the moving direction of the slider 23. The rack gear 231 and the pinion gear 44 convert the rotational motion of the rotor 41 into linear motion of the slider 23. Therefore, the rack gear 231 and the pinion gear 44 constitute a rotation / movement conversion mechanism.

In addition, protrusions 232 are formed at both corners on the right side of the slider 23 in FIG. These protrusions 232 prevent (prevent) the slider 23 from being detached.
Next, the configuration of the vibrating body 6 and the operation (operation) of the linear actuator 2 will be described.
The vibrating body 6 has a substantially rectangular plate shape. The vibrating body 6 is configured by laminating a plate-like electrode, a plate-like piezoelectric element, a reinforcing plate, a plate-like piezoelectric element, and a plate-like electrode in this order.

  Each piezoelectric element has a rectangular shape, and expands and contracts in the longitudinal direction when a voltage is applied. The constituent material of the piezoelectric element is not particularly limited. For example, lead zirconate titanate (PZT), crystal, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zinc niobate Various types such as lead scandium niobate can be used.

  These piezoelectric elements are respectively fixed to both surfaces of the reinforcing plate. The reinforcing plate has a function of reinforcing the entire vibrating body 6 and prevents the vibrating body 6 from being damaged by over-amplitude, external force, or the like. The material of the reinforcing plate is not particularly limited as long as it is an elastic material (that can be elastically deformed). For example, various metal materials such as stainless steel, aluminum or aluminum alloy, titanium or titanium alloy, copper or copper-based alloy are used. Preferably there is.

The reinforcing plate is preferably thinner (smaller) than the piezoelectric element. Thereby, the vibrating body 6 can be vibrated with high efficiency.
The reinforcing plate also has a function as a common electrode for each piezoelectric element. That is, an AC voltage is applied to each piezoelectric element by a corresponding electrode and a reinforcing plate, that is, the vibrating body 6 is connected to a drive control circuit (not shown), and the AC voltage is applied by the drive control circuit. It is to be applied. For example, the number, shape, arrangement, etc. of the electrodes can be appropriately set according to various conditions.

Moreover, the convex part (contact part) 26 is integrally formed in the right end part in FIG. 5 of a reinforcement board.
The reinforcing plate is integrally formed with a pair (two) of arm portions 28 having elasticity (flexibility). The pair of arm portions 28 are substantially perpendicular to the longitudinal direction of the reinforcing plate in a direction substantially perpendicular to the longitudinal direction and project in opposite directions through the reinforcing plate (vibrating body 6) (see FIG. 5 in a symmetrical manner).

The piezoelectric element repeatedly expands and contracts in a predetermined direction when an AC voltage is applied. Therefore, when an AC voltage having a predetermined frequency is applied to a predetermined electrode, the vibrating body 6 is minute in a predetermined mode (resonance mode). The convex portion 26 vibrates in a predetermined pattern (for example, combined vibration of longitudinal vibration and bending vibration).
Due to the vibration of the vibrating body 6, a rotational force (driving force) in a predetermined direction is repeatedly applied (applied) to the driven body 43 from the convex portion (via the convex portion), and the rotor 41 rotates in the predetermined direction. . The rotational motion of the rotor 41 is converted into the linear motion of the slider 23 by the pinion gear 44 provided in the rotor 41 and the rack gear 231 provided in the slider 23, and the slider 23 is guided to each roller 29. And move in a predetermined direction.

  On the other hand, when the vibrating body 6 is excited so that the vibration is reversed, a rotational force in the reverse direction to the driven body 43 is repeatedly applied from the convex portion 26, and the rotor 41 rotates in the reverse direction. The rotational motion of the rotor 41 is converted into the linear motion of the slider 23 by the pinion gear 44 provided in the rotor 41 and the rack gear 231 provided in the slider 23, and the slider 23 is guided to each roller 29. And move in the opposite direction.

Hereinafter, the operation of the measurement system 50 will be described based on the flowchart shown in FIG. Electric power is supplied to the measurement system 50, and the measurement system 50 is always executed in a state where the actuator can be driven. Hereinafter, each step will be described.
First, when the measurement system 50 is activated, the measurement system 50 determines whether or not to perform a calibration operation of a calibration curve that represents the relationship between the amount of light detected by the photosensor 12 and the absolute position of the slider (position detection scale) 23. (Step S101). If calibration is performed, the process proceeds to step S102. If calibration is not performed, the process proceeds to step S103.

  When calibration is performed in step S 101, the position detection scale 11 is sampled by the A / D converter 72. Specifically, for example, the light is emitted from the light emitting portion of the photosensor 12 to the position detection scale 11, and the reflected light reflected by the position detection scale 11 is incident on the light receiving portion of the photosensor 12. The slider 23 is moved so that the position detection scale 11 passes from the one end side to the other end side on the sensor 12 (step S102). The slider 23 may be moved from the upper side to the lower side in FIG. 5 or from the lower side to the upper side.

The data control unit 70 sequentially inputs the analog signal output from the photosensor 12 in accordance with the movement to the amplifier 71, amplifies the analog signal by the amplifier 71, and inputs the amplified analog signal to the A / D converter 72. To do. The A / D converter 72 converts an analog signal into a digital signal and inputs it to the CPU 73. The CPU 73 stores the digital signal in a predetermined storage area of the storage unit (step S103).
When the slider 23 is moved in the sampling of the position detection scale 11 in step S103, the magnetic scale 13 is also sampled at the same time. Specifically, the magnetic field generated from the magnetic scale 13 is read by the magnetic sensors 14 and 15, and the values are sequentially input to the comparators 74 and 75, respectively. Thereby, the magnetic field of the magnetic scale 13 can be detected by the magnetic sensors 14 and 15 corresponding to the detection points of the position detection scale 11 by the photosensor 12.

The comparators 74 and 75 binarize the input signals, create an A phase signal and a B phase signal, respectively, and input them to the forward / reverse determination circuit 76 (step S104).
Forward and reverse decision circuit 76 based on the input A-phase and B-phase signals, to create a _{Q A} signal and _{Q B} signals are input to the CPU 73 (step S105).
The CPU 73 creates count data based on the Q _A signal and the Q _B signal, creates a calibration curve based on the relationship between the digital signal created in step S102 and the count data, and stores it in the storage unit (step S106). . The calibration curve may be a table or a mathematical expression. Hereinafter, a case where a table is typically used as the calibration curve will be described.

  If calibration is not performed in step S101, the position detection scale 11 is sampled by the A / D converter 72. Specifically, the data control unit 70 irradiates the position detection scale 11 with light from the light emitting unit 111, and the reflected light reflected by the position detection scale 11 is incident on the light receiving unit of the photosensor 12. The analog signal output from the sensor 12 is input to the amplifier 71 (step S107), amplified by the amplifier 71, and output to the A / D converter 72. The A / D converter 72 converts the analog signal into a digital signal and outputs it to the CPU 73. The CPU 73 stores the digital signal in a predetermined storage area of the storage unit (step S108).

  Thereafter, the CPU 73 extracts the table stored in the storage unit in step S106 (step S109), and calculates and obtains the absolute position of the slider 23 using this table and the stored digital signal. (Step S110). The absolute position information of the slider 23 obtained by these processes is stored in the storage unit (step S111). Thereafter, the process proceeds to step S101, and the same processing is repeated again.

As described above, according to the absolute encoder 1 of the present invention, calibration can be automatically performed with a simple configuration at the time of activation, and a highly accurate absolute encoder can be realized.
In addition, the absolute position of the slider 23 can be easily detected by sequentially detecting the amount of light received by the photosensor 12 at a predetermined position of the position detection scale 11, that is, the photoelectrically converted voltage (having a magnitude corresponding to the amount of received light). And it can detect correctly.

In this embodiment, since only one photosensor is used, the structure of the encoder can be simplified, and the entire apparatus can be easily downsized.
Further, the position detection scale of the present embodiment is configured such that the light reflectance continuously decreases gradually along the position detection scale. However, the present invention is not limited to this, and for example, the light reflectance is stepwise. You may comprise so that it may decrease gradually.

  Further, the position detection scale of the present embodiment is configured so that the light reflectance continuously decreases gradually along the position detection scale. However, the present invention is not limited to this, for example, along the position detection scale. The reflectance of light may be configured to increase continuously. In this case, the upper side of the position detection scale is black and the lower side is white, and the ratio of black to white is gradually reduced from the upper side to the lower side.

In the present embodiment, the position detection scale 11 and the magnetic scale 13 are band-shaped, but the present invention is not limited to this. For example, the position detection scale 11 and the magnetic scale 13 may be curved or bent. .
Further, the calibration operation is not limited to the activation, and can be performed in an arbitrary state such as during the operation of the absolute encoder.

Next, a second embodiment of the absolute encoder of the present invention will be described.
FIG. 4 is a plan view showing a second embodiment of the absolute encoder of the present invention.
Hereinafter, the absolute encoder 1 according to the second embodiment will be described focusing on the differences from the first embodiment described above, and description of similar matters will be omitted.
The absolute encoder 1 of the second embodiment is a rotary encoder, and is the same as that of the first embodiment described above except that the positions of the position detection scale and the magnetic scale are different.

  As shown in FIG. 7, in the absolute encoder 1 of the second embodiment, the shape of the position detection scale 11 in a plan view is a ring shape (annular shape). In the position detection scale 11, the ratio of white to black is gradually reduced counterclockwise in FIG. That is, the light reflectance is gradually decreased counterclockwise along the position detection scale 11.

  The magnetic scale 13 has a ring shape (annular shape). For example, the magnetic scale 13 is arranged so as to overlap the position detection scale 11 in a plan view, and has a plurality of rod-shaped S pole portions in a plan view and a plurality of rod-shaped N pole portions in a plan view. These longitudinal sides are arranged at equal intervals in plan view in the radial direction in FIG. That is, the polarities are alternately switched along the magnetic scale 13 at regular intervals in the clockwise direction.

According to the absolute encoder 1, the same effect as the absolute encoder 1 of the first embodiment described above can be obtained.
In this absolute encoder 1, for example, by providing this ring-shaped position detection scale on the surface of the rotating body (position detection target), the position of the rotating body can be detected easily and accurately. Moreover, you may detect an angle instead of a position.

Further, in the present embodiment, the light reflectivity is continuously decreased gradually in the clockwise direction of the position detection scale. However, the present invention is not limited to this. For example, the light reflectivity is continuously increased in the clockwise direction. You may be comprised so that it may increase gradually. In this case, the position detection scale is configured so that the ratio of black to white increases little by little in the clockwise direction.
In the present embodiment, the position detection scale 11 and the magnetic scale 13 are arranged so as to overlap with each other in plan view. However, the present invention is not limited to this, and for example, the radii may be different from each other.

Next, a third embodiment of the absolute encoder of the present invention will be described.
FIG. 8 is a plan view showing a third embodiment of the absolute encoder of the present invention.
Hereinafter, the absolute encoder 1 according to the third embodiment will be described focusing on the differences from the first embodiment described above, and description of similar matters will be omitted.
The absolute encoder 1 of the third embodiment is different in the shape of the position detection scale and the arrangement (pattern).

  As shown in FIG. 8, the position detection scale 11 of the absolute encoder 1 according to the third embodiment includes a black portion (dark color portion) 112 that is a first portion having a substantially triangular shape and a low reflectance in plan view, and a flat surface. A white portion 111 that is a second portion having a substantially triangular shape and a high reflectance is provided, and each of them is overlapped in the opposite direction to form a strip shape (substantially rectangular shape). That is, the position detection scale 11 has a band shape in plan view, and is provided with a white portion 111 and a black portion 112 via one diagonal line. With this configuration, the length of the black portion 112 in the direction substantially perpendicular to the direction from the upper side to the lower side in FIG. 8 of the position detection scale 11 gradually increases along the position detection scale. The length of the white portion 111 in a direction substantially perpendicular to the side direction gradually decreases. That is, the ratio of the area of the black portion 112 to the area of the white portion 111 of the position detection scale 11 gradually increases along the position detection scale 11.

According to the absolute encoder 1, the same effect as the absolute encoder 1 of the first embodiment described above can be obtained.
In this absolute encoder 1, since the white and black densities of the position detection scale are stable, control with higher accuracy than in the first embodiment is possible.
Further, the shapes of the first part and the second part are not limited to the present embodiment, and one of the first part and the second part gradually increases along the longitudinal direction of the position detection scale. However, it is possible to use an arbitrary shape in which the other is gradually reduced.

Next, a fourth embodiment of the absolute encoder of the present invention will be described.
FIG. 9 is a plan view showing a fourth embodiment of the absolute encoder of the present invention. Hereinafter, the absolute encoder 1 according to the fourth embodiment will be described with a focus on differences from the third embodiment described above, and descriptions of the same matters will be omitted.
The absolute encoder 1 of the fourth embodiment is the same as that of the third embodiment described above except that the position detection scale and the magnetic scale are different in shape.

  As shown in FIG. 9, the absolute encoder 1 according to the fourth embodiment is a rotary encoder, and includes a ring having a black part 112 as a first part and a white part 111 as a second part. A (annular) position detection scale 11 is provided. In the position detection scale 11, the length of the white portion 111 is gradually decreased and the length of the black portion 112 is gradually increased in a substantially vertical direction (direction toward the center of the circle) counterclockwise in FIG. 9. . That is, in the counterclockwise direction of the position detection scale 11, the ratio of the area of the black portion 112 to the area of the white portion 111 gradually increases along the position detection scale 11.

The magnetic scale 13 can be the same as that of the second embodiment.
According to the absolute encoder 1, the same effect as the absolute encoder 1 of the third embodiment described above can be obtained.
In this absolute encoder 1, for example, by providing this ring-shaped position detection scale on the surface of the rotating body (position detection target), the position of the rotating body can be detected easily and accurately.

Next, a fifth embodiment of the absolute encoder of the present invention will be described.
Hereinafter, the absolute encoder 1 according to the fifth embodiment will be described with a focus on differences from the third embodiment described above, and description of similar matters will be omitted.
The absolute encoder 1 of the fifth embodiment is the same as that of the third embodiment described above except that the arrangement of the position detection scales is different.

The absolute encoder 1 of the fifth embodiment has a position detection scale 11 expressed in area gradation. Examples of the area gradation expression include gradation expression using a dither method, an error diffusion method, or the like.
The position detecting scale 11 has a plurality of white portions and black portions, and the number of black portions is gradually increased and the number of white portions is gradually decreased. That is, the ratio of the area of the white part to the area of the black part gradually increases along the position detection scale 11.

According to the absolute encoder 1, the same effect as the absolute encoder 1 of the third embodiment described above can be obtained.
In the present embodiment, the ratio of the area of the white portion to the area of the black portion is configured to gradually increase along the position detection scale, but is not limited thereto, for example, the area of the white portion with respect to the area of the black portion The ratio may be gradually reduced along the position detection scale.

In the present embodiment, the areas and shapes of the plurality of black portions may be the same, the areas of the plurality of black portions may be different, or the shapes of the plurality of black portions are different. Also good. Further, the black portions may be in contact with each other or may be separated from each other. The same applies to the white portion.
The absolute encoder of the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. be able to. In addition, any other component may be added to the present invention.

Further, the present invention may be a combination of any two or more configurations (features) of the above embodiments.
In the embodiment, the photosensor 12 is provided on the base 21 and the position detection scale 11 is provided on the slider 23. However, the present invention is not limited to this. For example, the photosensor 12 is provided on the slider and the position detection scale is provided. 11 may be provided on the base 21.

Moreover, in the said embodiment, although the magnetic sensors 14 and 15 were each provided on the base 21, and the magnetic scale 13 was provided on the slider 23, it is not restricted to this, For example, the magnetic sensors 14 and 15 are respectively sliders. The position detection scale 11 may be provided on the base 21.
In the above embodiment, the position detection scale 11 and the magnetic scale 13 are separate from each other. However, the present invention is not limited to this. For example, it is preferable that the position detection scale 11 also serves as the magnetic scale 13.

In the above embodiment, black is used as the dark color of the position detection scale. However, the present invention is not limited to this, and other dark colors may be used.
In the embodiment, white and black are used as the position detection scale. However, the present invention is not limited to this, and for example, two colors having different brightness (reflectance) may be used.
The application of the absolute encoder of the present invention is not particularly limited, and examples thereof include an ultrasonic linear actuator and a shape memory actuator.

It is a block diagram which shows 1st Embodiment of the absolute encoder of this invention. It is a figure for demonstrating a magnetic sensor. It is a figure for demonstrating the binarization process of a comparator. It is a figure for demonstrating the process of a forward / reverse determination circuit. It is a figure which shows the structural example of the measurement system using the absolute encoder of this invention. It is a flowchart which shows the process of the measurement system using the absolute encoder of this invention. It is a block diagram which shows 2nd Embodiment of the absolute encoder of this invention. It is a block diagram which shows 3rd Embodiment of the absolute encoder of this invention. It is a block diagram which shows 4th Embodiment of the absolute encoder of this invention. It is a figure which shows the conventional absolute encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Absolute encoder, 2 ... Linear actuator, 11 ... Position detection scale, 12 ... Photosensor, 121 ... Light emission part, 122 ... Light reception part, 13 ... Magnetic scale , 14, 15 ... magnetic sensor, 141, 151 ... sensor part, 21 ... base, 22 ... base, 23 ... slider, 231 ... rack gear, 232 ... protrusion , 26 ... convex part, 27 ... bolt, 28 ... arm part, 29 ... roller, 31 ... spring retaining pin, 32 ... spring hook part, 33 ... coil spring, 41 ... Rotor, 42 ... Cylindrical member, 43 ... Driven body, 44 ... Pinion gear, 6 ... Vibrating body, 70 ... Data control unit, 71 ... Amplifier, 72 ... A / D converter, 73 ... CPU, 74, 75 ..Comparator, 76... Forward / reverse determination circuit, 50... Measurement system, 111... White part, 112... Black part, 110. ..Photoelectric conversion member, 100... Rotation axis, 200... Drum, 300 ..magnetic recording medium, 400 .. substrate, 500 .. MR element, 600. -Lead wire, 800 ... drive detection circuit, n1-n5 ... magnetization pattern sequence, S101-S107 ... step

Claims (13)

A magnetic scale,
At least one magnetic sensor for detecting and magnetically converting a magnetic field generated from the magnetic scale;
A relative position detecting means for obtaining a relative position of the magnetic sensor with respect to the magnetic scale based on a detection result of the magnetic sensor;
A position detection scale;
A photosensor having a light emitting unit that emits light to the position detection scale, and a light receiving unit that receives light reflected from the position detection scale and photoelectrically converted from the light emitted from the light emitting unit;
An absolute encoder comprising absolute position detecting means for obtaining an absolute position of a position detection target based on a detection result of the photosensor,
The position detection scale is configured to gradually increase or decrease the amount of reflected light from the position detection scale when the irradiation position of the light to the position detection scale is moved along the position detection scale. And
The other movement with respect to one of the position detection scale and the photosensor, and the other movement with respect to one of the magnetic scale and the magnetic sensor are configured to correspond to each other.
An absolute encoder that automatically calibrates the absolute position detecting means based on the data obtained by the relative position detecting means and the amount of the reflected light detected by the photosensor. A magnetic scale,
At least one magnetic sensor for detecting and magnetically converting a magnetic field generated from the magnetic scale;
A relative position detecting means for obtaining a relative position of the magnetic sensor with respect to the magnetic scale based on a detection result of the magnetic sensor;
A position detection scale;
A photosensor having a light emitting unit that emits light to the position detection scale, and a light receiving unit that receives light reflected from the position detection scale and photoelectrically converted from the light emitted from the light emitting unit;
An absolute encoder comprising: an absolute position detecting means for obtaining an absolute position of the position detection target based on a detection result of the photosensor and a calibration curve indicating a relationship between the detection result and the absolute position of the position detection target Because
The position detection scale is configured to gradually increase or decrease the amount of reflected light from the position detection scale when the irradiation position of the light to the position detection scale is moved along the position detection scale. And
The other movement with respect to one of the position detection scale and the photosensor, and the other movement with respect to one of the magnetic scale and the magnetic sensor are configured to correspond to each other.
An absolute encoder, wherein the calibration curve is automatically calibrated based on the data obtained by the relative position detection means and the amount of the reflected light detected by the photosensor.   The calibration moves the other of the position detection scale and the photosensor, and detects the amount of reflected light from the position detection scale by the photosensor. Sequentially from the first position to the second position, and in this case, the magnetic sensor sequentially detects the magnetic field generated from the magnetic scale in correspondence with the detection point of the photosensor; The absolute encoder according to claim 1, wherein the absolute encoder is performed based on information obtained from the magnetic sensor.   The absolute encoder according to any one of claims 1 to 3, wherein the position detection scale and the magnetic scale are arranged so as to overlap in a plan view.   The absolute encoder according to claim 1, wherein the position detection scale also serves as the magnetic scale.   6. The absolute encoder according to claim 1, wherein the polarity of the magnetic scale changes at substantially equal intervals along the magnetic scale.   The absolute encoder according to claim 1, wherein the position detection scale is configured such that the reflectance gradually increases or decreases along the position detection scale.   The position detection scale has a first part and a second part having different reflectances, and a ratio of the area of the first part to the area of the second part is the position detection scale. The absolute encoder according to any one of claims 1 to 6, wherein the absolute encoder gradually increases or decreases along the axis.   The absolute encoder according to claim 8, wherein a plurality of the first part and the second part are provided.   The absolute encoder according to claim 9, wherein the arrangement of the first part and the second part is set using a dither method or an error diffusion method.   The length of the first portion in a direction substantially perpendicular to the direction of the position detection scale gradually increases along the position detection scale and is a direction substantially perpendicular to the direction of the position detection scale. 9. The absolute encoder according to claim 8, wherein the length of the second part of the encoder gradually decreases along the position detection scale.   The absolute encoder according to claim 11, wherein one each of the first part and the second part is provided. The absolute encoder according to any one of claims 8 to 12, wherein the first part is white and the second part is black or dark.

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