JP2011047765A - Encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder which can be composed of magnets of a predetermined shape, irrespective of the diameter of a magnet section. <P>SOLUTION: An encoder includes: a magnet section (4) where a magnetic pattern is formed, and which rotates around a rotating shaft (AR); and detection sections (6a, 6b) for detecting magnetic fields generated by the magnet section. The magnet section is composed of a plurality of unit magnets (4a) arranged along a circumference (C) whose center is the rotating shaft. The unit magnets are arranged so that magnetic fields in radial directions are formed between the inner peripheral side and the outer peripheral side of the circumference, and the magnetic fields are changed at least once in one round of the circumference. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an encoder.

  An encoder is known as a device that detects the number of rotations and rotation speed of a rotating body such as a rotating shaft of a motor (Patent Document 1). For example, the rotary encoder is used by being attached to a rotating shaft such as a motor. Further, as a specific configuration of the encoder, for example, a configuration for detecting the number of rotations using magnetism is known.

  The magnetic encoder having such a configuration rotates the magnet part on which the magnetic pattern is formed integrally with the rotary shaft, and reads the change in the magnetic pattern of the magnet part with a magnetic sensor, thereby rotating the rotational speed of the motor drive shaft. Etc. can be detected. As a specific configuration, for example, a configuration in which a rotating portion that rotates integrally with a drive shaft is fixed to the drive shaft and a magnet portion is held by the rotating portion is known.

  The magnet part is formed of, for example, an annular magnet. The annular magnet is provided such that the inner and outer magnetic poles are different, and the inner and outer magnetic poles are interchanged at 180 ° in the circumferential direction. As a result, when the magnet portion rotates relative to the magnetic sensor, the magnetic sensor changes in the magnetic field from the inner peripheral side to the outer peripheral side of the magnet and the change in the magnetic field from the outer peripheral side to the inner peripheral side. It is detected alternately every time.

JP-A-3-287014

  However, in the above-described conventional encoder, for example, when a hollow shaft motor is adopted, when the diameter of the drive shaft changes, the diameter of the magnet portion is changed accordingly, so the shape of the magnet may need to be changed. There was a problem. Since a magnet is manufactured by molding magnetic powder, there is a disadvantage that a mold must be manufactured each time.

  Accordingly, an aspect of the present invention provides an encoder that can use a magnet having a predetermined shape regardless of the diameter of the magnet portion.

  In order to solve the above-described problems, the aspect of the present invention adopts the following configuration corresponding to FIGS. 1 to 9 shown in the embodiment. In addition, in order to explain the present invention in an easy-to-understand manner, the description will be made in association with the reference numerals of the drawings showing an embodiment, but the present invention is not limited to the embodiment.

  An encoder (1) according to an aspect of the present invention includes a magnet unit (4) that is formed with a magnetic pattern and rotates about a rotation axis (AR), and a detection unit (2) that detects a magnetic field generated by the magnet unit. The magnet portion is composed of a plurality of unit magnets (4a) arranged along a circumference (C) centered on the rotation axis, and the unit magnets are arranged on an inner circumference side and an outer circumference side of the circumference. Are arranged so as to change the magnetic field at least once over one circumference of the circumference.

  According to the encoder of the aspect of the present invention, a magnet having a predetermined shape can be used regardless of the diameter of the magnet portion.

It is a side view showing a schematic structure of an encoder concerning a 1st embodiment of the present invention. It is a top view which shows schematic structure of the encoder which concerns on 1st Embodiment of this invention. It is a top view which shows the example of arrangement | positioning of the unit magnet which concerns on 1st Embodiment of this invention. It is a graph which shows the signal waveform of the detection part which concerns on 1st Embodiment of this invention. It is a top view which shows the magnet part of the encoder which concerns on 2nd Embodiment of this invention. It is a graph which shows the signal waveform of the detection part which concerns on 2nd Embodiment of this invention. It is a top view which shows the 1st modification of the magnet part which concerns on embodiment of this invention. It is a top view which shows the 2nd modification of the magnet part which concerns on embodiment of this invention. It is a perspective view which shows the modification of the unit magnet which concerns on embodiment of this invention. It is a top view which shows the modification of the front yoke which concerns on embodiment of this invention.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a schematic configuration of an encoder according to the present embodiment, and FIG. 2 is a plan view thereof.
As shown in FIG.1 and FIG.2, the encoder 1 is an apparatus which detects the rotation speed and rotational speed of rotating bodies, such as a motor, for example. The encoder 1 includes a detection unit 2, a rotation unit 3, and a magnet unit 4.

  The detection unit 2 is fixed to, for example, a cover (not shown) that covers the rotation unit 3 and the magnet unit 4, and is disposed in the vicinity of the rotation unit 3 and the magnet unit 4. The detection unit 2 includes a light receiving sensor 5 that reads an optical pattern, a pair of magnetic sensors 6a and 6b that detect a magnetic field, a pair of bias magnets 7a and 7b provided corresponding to the magnetic sensors 6a and 6b, and signal processing. A substrate 8 is provided. As shown in FIG. 2, the pair of magnetic sensors 6 a and 6 b are provided on the same circumference C so as to be separated by about 90 ° in the circumferential direction.

  In FIG. 2, the detection unit 2 is not shown except for the bias magnets 7a and 7b (magnetic sensors 6a and 6b). The bias magnets 7a and 7b are arranged to generate a combined magnetic field in the direction of the magnetic field that can be detected by the magnetic sensors 6a and 6b by using the magnetic field of the bias magnets 7a and 7b and the magnetic field of the magnet unit 4. The signal processing board 8 is a board for processing signals (detection signals) from the light receiving sensor 5 and signals (detection signals) from the magnetic sensors 6a and 6b. As the magnetic sensors 6a and 6b in the present embodiment, MR elements or Hall elements can be used.

  The rotating part 3 is a disk-like member fixed so as to be rotatable integrally with the drive shaft MR of the motor, and is provided so as to be rotatable about the rotation axis AR of the drive shaft MR of the motor. As shown in FIG. 2, an absolute pattern 9 composed of an M-sequence signal indicating an absolute position within one rotation and a repetitive pattern (incremental pattern) 10 are formed on the outer periphery of the rotating unit 3 over the entire periphery. Yes. The absolute pattern 9 and the repeated pattern 10 are formed at positions that can be read by the light receiving sensor shown in FIG.

  The magnet unit 4 is composed of a plurality of unit magnets 4a that are arranged in a ring shape around the rotation axis AR and form a predetermined magnetic pattern. The unit magnet 4a is fixed to the rotating unit 3 so as to be rotatable about the rotation axis AR. As shown in FIG. 2, the unit magnet 4a is provided in a rectangular shape in plan view. In the present embodiment, the shape of the unit magnet 4a is formed in a rectangular shape in plan view in which the width w1 in the direction along the circumference C around the rotation axis AR is larger than the width w2 in the radial direction of the circumference C. The long vertical bisector L1 is arranged so as to pass through the center of the circumference C (rotation axis AR). Further, the N pole and the S pole are arranged in the radial direction of the circumference C, and a radial magnetic field is formed between the inner circumference side and the outer circumference side of the circumference C.

  FIG. 3 is a plan view showing an arrangement example of the unit magnets 4a. The unit magnet 4a is arranged with the S pole facing the inner circumference over the half circumference of the circumference C, and with the N pole facing the inner circumference over the other half circumference. That is, the unit magnet 4a is different from the magnetic pole on the inner circumferential side and the magnetic pole on the outer circumferential side of the circumference C, and the magnetic pole on the inner circumferential side and the magnetic pole on the outer circumferential side are switched at 180 ° in the circumferential direction of the circumference C. Has been placed. For this reason, the direction of the magnetic field changes once over the circumference C. In addition, the unit magnets 4a in the present embodiment are arranged at equal intervals along the circumference C around the rotation axis AR, and are arranged symmetrically with respect to the boundary line L2 where the direction of the magnetic field is reversed.

  Thus, in order to reverse the direction of the magnetic field every 180 ° in the rotation direction of the magnet part 4, the number of unit magnets 4a is preferably 4 or more, or the number of unit magnets 4a is an even number of 4 or more. It is preferable. For example, when there are two unit magnets 4a, it may be necessary to use a unit magnet 4a having a curved shape along the circumference C. In this case, the shape of the unit magnet 4 may need to be changed according to the change in the diameter of the magnet unit 4.

  Further, as shown in FIG. 1, a back yoke 11 is disposed between the magnet unit 4 and the rotating unit 3. That is, the unit magnet 4 a is disposed between the back yoke 11 and the detection unit 2. The back yoke 11 is formed in an annular shape around the rotation axis AR by using a soft magnetic material such as low carbon steel or silicon steel. As shown in FIG. 2, the back yoke 11 is fixed to the rotating unit 3, and the magnet unit 4 is opposed to the magnetic sensors 6a and 6b of the detecting unit 2 at a predetermined distance (interval g1) in the direction of the rotation axis AR. Hold. Here, the gap g2 between the unit magnets 4a shown in FIG. 2 is narrower than the gap g1 between the magnetic sensors 6a, 6b and the unit magnet 4a shown in FIG.

Next, the operation of the encoder 1 of this embodiment will be described.
When the drive shaft MR of the motor rotates, the rotating unit 3 fixed to the driving shaft MR and the magnet unit 4 held by the rotating unit 3 rotate integrally. Since the detector 2 is not connected to the drive shaft MR of the motor, the detector 2 remains stationary without rotating.

  When the magnet unit 4 rotates together with the rotating unit 3, the plurality of unit magnets 4a pass under the magnetic sensors 6a and 6b, and a combined magnetic field of the magnetic field formed by the unit magnets 4a and the magnetic field formed by the bias magnets 7a and 7b is generated. For example, it is detected as a change in electric resistance by the magnetic sensors 6a and 6b. At this time, the magnetic field formed by the magnet portion 4 in the radial direction of the circumference C is alternately switched in a direction from the inner circumference side to the outer circumference side and a direction from the outer circumference side to the inner circumference side every 180 ° of rotation. . The detection unit 2 processes a change in the magnetic field detected by the magnetic sensors 6 a and 6 b by the signal processing substrate 8, thereby outputting a signal corresponding to the change in the magnetic field of the magnet unit 4.

FIG. 4 is a graph showing the signal output from the detection unit 2 with the vertical axis representing voltage and the horizontal axis representing the rotation angle of the magnet unit.
When the magnet unit 4 rotates, the H level and L level signals S1 are alternately and repeatedly detected at every 180 ° of rotation as shown in FIG. Here, when the gap between the unit magnets 4a passes below the magnetic sensors 6a and 6b, a slight drop of the signal S1 is detected. The reference for judging the H level and the L level also in the drop part SD. The signal is sufficiently separated from the potentials h and l. Therefore, it is possible to reliably recognize the switching between the H level and the L level of the signal. By obtaining such a signal S1 from the pair of magnetic sensors 6a and 6b shown in FIG. 2, it is possible to detect the rotational speed and rotational direction of the magnet unit 4.

  In addition, the absolute pattern 9 and the repetitive pattern 10 are detected by the light receiving sensor 5, and the signal output from the light receiving sensor 5 is processed by the signal processing board, thereby measuring the absolute angular position, rotational speed, etc. within one rotation. Can do.

  Here, the encoder 1 according to the present embodiment uses a plurality of unit magnets 4 a arranged along a circumference C around the rotation axis AR in order to form a magnetic pattern of the magnet unit 4. Therefore, for example, even when the diameter of the drive shaft MR of the motor is changed, the diameter of the magnet unit 4 can be adjusted by increasing or decreasing the number of unit magnets 4a. For example, when the width w1 in the direction along the circumference C of the unit magnet 4a in FIG. 3 is about 6 mm to 8 mm, the diameter φ of the drive shaft MR of the motor changes to 50 mm, 70 mm, and 90 mm. Even if it exists, it can respond to the change of the diameter of the magnet part 4 by the increase / decrease in the number of the unit magnets 4a, without changing the shape of the unit magnet 4a.

  Therefore, according to the encoder 1 of the present embodiment, the unit magnet 4a having a predetermined shape can be used regardless of the change in the diameter of the magnet unit 4. Therefore, even if the diameter of the drive shaft MR of the motor changes, the inconvenience of having to manufacture a magnet mold each time can be solved.

  Further, the magnet portion 4 is arranged such that the inner peripheral side magnetic pole and the outer peripheral side magnetic pole of the unit magnet 4a are different, and the inner peripheral side magnetic pole and the outer peripheral side magnetic pole are interchanged at 180 ° in the circumferential direction. . Therefore, the direction of the magnetic field changes only once over one rotation of the magnet unit 4. Therefore, it is possible to prevent the frequency of the signal S1 from becoming higher than when the direction of the magnetic field changes a plurality of times over one round.

Moreover, since the unit magnet 4a is arrange | positioned between the back yoke 11 and the detection part 2, the magnetic force of the unit magnet 4a in the detection part 2 side increases. Therefore, it is possible to easily detect the magnetic field in the detection unit 2, and it is possible to reduce the influence of disturbance such as noise.
Further, since the width w1 in the direction along the circumference C of the unit magnet 4a is larger than the width w2 in the radial direction, the number of unit magnets 4a arranged in the magnet portion 4 can be reduced.

The interval g2 between the unit magnets 4a is narrower than the interval between the magnetic sensors 6a and 6b and the unit magnet 4a. Therefore, compared with the case where the gap g2 between the unit magnets 4a is wider than the gap g1 between the magnetic sensors 6a, 6b and the unit magnet 4a, the drop of the signal S1 of the detection unit 2 due to the gap between the unit magnets 4a is suppressed. be able to.
Further, since the unit magnets 4a are arranged symmetrically with respect to the boundary line L2 in which the direction of the magnetic field is reversed, it is possible to stabilize the signal S1 output from the detection unit 2 by making the change of the magnetic field symmetrical.

In addition, by setting the number of unit magnets 4a to 4 or an even number of 4 or more, the unit magnets 4a can be arranged symmetrically on the boundary line L2 where the direction of the magnetic field is reversed.
Further, since the plurality of unit magnets 4a are arranged in a ring shape with the rotation axis AR as the center, the same effect as in the case of using the ring-shaped magnet can be obtained.

  Moreover, if the magnet part 4 in this embodiment is used, it will become possible to manufacture a hollow shaft type encoder easily. As a result, a hollow shaft motor having a hollow drive shaft can be readily employed. In addition, the hollow shaft motor allows wiring and piping to pass through the inside of the hollow drive shaft, improving the degree of freedom of device design for the user.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 4 to 5 with reference to FIGS. The present embodiment is different from the encoder 1 described in the first embodiment in that a front yoke 12 is disposed between the magnet unit 4 and the detection unit 2. Since other points are the same as those of the first embodiment, the same or equivalent parts are denoted by the same reference numerals and description thereof is omitted.

Fig.5 (a) is a top view which shows the magnet part of this embodiment. FIG. 5B is a cross-sectional view taken along line AA in FIG.
The magnet part 4 of this embodiment is provided with the several unit magnet 4a similarly to 1st embodiment. The magnet unit 4 is arranged between the back yoke 11 and the detection unit 2 as in the first embodiment shown in FIG. 1, and the front yoke 12 is arranged between the unit magnet 4 a and the detection unit 2. .

  The front yoke 12 is formed of, for example, the same material as that of the back yoke 11, and is continuously provided over one circumference of the circumference C centering on the rotation axis AR. Moreover, the front yoke 12 is divided | segmented into the inner peripheral side and the outer peripheral side of the unit magnet 4a arrange | positioned along the circumference C centering on the rotating shaft AR. A predetermined gap g3 is formed in the radial direction of the circumference C along the unit magnet 4a between the first front yoke 12a on the inner peripheral side and the second front yoke 12b on the outer peripheral side.

Next, the operation of the encoder of this embodiment will be described.
Similarly to the first embodiment, when the drive shaft MR of the motor rotates, the rotating portion 3 and the magnet portion 4 rotate integrally, and change every 180 ° of rotation by the magnetic sensors 6a and 6b of the detecting portion 2. The magnetic field of the magnet unit 4 is detected, and a signal S2 corresponding to a change in the magnetic field of the magnet unit 4 is output from the signal processing substrate 8.

FIG. 6 is a graph showing the signal S2 output from the detection unit 2 of the encoder of the present embodiment with the vertical axis representing voltage and the horizontal axis representing the rotation angle of the magnet unit.
As shown in FIG. 6, in the present embodiment, the sagging portion SD seen in the signal S1 of the detection unit 2 of the first embodiment is flattened. That is, in the present embodiment, in the plurality of unit magnets 4a in which different magnetic poles are arranged on the inner peripheral side and the outer peripheral side, the inner peripheral side magnetic pole is connected by the first front yoke 12a, and the outer peripheral side magnetic pole is connected to the second magnet. Are connected by the front yoke 12b. A predetermined gap g3 is provided between the first front yoke 12a and the second front yoke 12b.

As a result, a magnetic field is formed between the first front yoke 12a and the second front yoke 12b. Therefore, the magnetic field detected by the magnetic sensors 6a and 6b is prevented from decreasing in the gap between the unit magnets 4a, and the magnetic field formed in the radial direction of the circumference C around the rotation axis AR is C can be made uniform over one round.
The unit magnet 4a shown in FIGS. 5A and 5B is divided into an inner peripheral side and an outer peripheral side, and the rotation axis AR is the same as the first front yoke 12a and the second front yoke 12b. A predetermined gap may be provided in the radial direction of the circumference C around the center. Even if it does in this way, the effect similar to this embodiment can be acquired.

  Next, modifications of the magnet unit 4 described in the first embodiment and the second embodiment will be described. 7 and 8 are plan views showing modifications of the magnet unit 4. FIG. 9 is a perspective view showing a modification of the unit magnet 4a in the first embodiment.

  In the first modification shown in FIG. 7, the unit magnet 4 a is arranged along the circumference C centered on the rotation axis AR, but is formed between the inner circumference side and the outer circumference side of the magnet portion 4. In the vicinity of the boundary line L2 where the direction of the magnetic field to be reversed, the interval g4 between the unit magnets 4a is arranged to be narrow. Further, at a position far from the boundary line L2, the gaps g5 between the unit magnets 4a are arranged to be wide. By arranging the unit magnets 4a in such a manner that the intervals between the unit magnets 4a are changed, the number of the unit magnets 4a arranged on the circumference C is reduced, and the boundary where the direction of the magnetic field is switched is accurately detected. be able to.

  In the second modification shown in FIG. 8, a plurality of types of unit magnets 4a1, 4a2, and 4a3 having different widths w3, w4, and w5 in the direction along the circumference C around the rotation axis AR are arranged. Thereby, it becomes possible to respond more flexibly to changes in the diameter of the magnet portion 4. Further, the widths w3, w4, and w5 in the direction along the circumference C of the unit magnets 4a1, 4a2, and 4a3 are narrowed as approaching the boundary line L2 where the direction of the magnetic field is reversed. Thereby, the influence of the clearance gap between the unit magnets 4a1 in the vicinity of the boundary line L2 can be made smaller.

  In the third modification shown in FIG. 9, the surface of the unit magnet 4a on the side of the magnetic sensors 6a and 6b is formed in a concave shape, and the direction along the circumference C around the rotation axis AR (the direction of the arrow C1 in the figure). The thickness T1 of the end portion in the direction parallel to the rotation axis AR is thicker than the thickness T2 of the central portion in the same direction. Thereby, since the distance between the magnetic sensors 6a and 6b and the unit magnet 4a is reduced at the end, it is possible to reduce the drop of the signal due to the gap between the unit magnets 4a.

  Further, the front yoke 12 in FIG. 5 described above may be arranged as shown in FIG. 10, for example. As shown in FIG. 10, the first front yoke 12a is arranged so as to connect the same poles of the magnetic poles (N pole, S pole) among the plurality of unit magnets 4a. Among them, the magnetic poles are divided and arranged at different portions. Further, the second front yoke 12b may be arranged in the same manner as the first front yoke 12a.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the shape of the unit magnet is not limited to a rectangular shape in plan view. For example, a triangular or fan-shaped unit magnet may be used in plan view, or these may be used so as to fill a gap between rectangular unit magnets. In the present embodiment, the back yoke and the front yoke may not be provided.

1 Encoder, 2 Detector, 4 Magnet, 4a, 4a1, 4a2, 4a3 Unit magnet, 11 Back yoke, 12 Front yoke, AR rotating shaft, C circumference, g1, g2, g3, g4, g5 interval, L2 boundary Line (boundary), T1, T2 thickness, w1, w2, w3 width

Claims (14)

A magnet unit that is formed with a magnetic pattern and rotates about a rotation axis; and a detection unit that detects a magnetic field by the magnet unit;
The magnet portion is composed of a plurality of unit magnets arranged along a circumference around the rotation axis,
The unit magnet is arranged so as to form a radial magnetic field between the inner circumference side and the outer circumference side of the circumference, and to change the magnetic field at least once over the circumference of the circumference. An encoder characterized by this. The encoder according to claim 1, wherein
The magnet portion is arranged such that the inner peripheral side magnetic pole and the outer peripheral side magnetic pole of the unit magnet are different, and the inner peripheral side magnetic pole and the outer peripheral side magnetic pole are switched at 180 ° in the circumferential direction. An encoder characterized by The encoder according to claim 1 or 2,
The encoder is characterized in that the unit magnet is disposed between a back yoke and the detection unit. The encoder according to any one of claims 1 to 3,
A front yoke is disposed between the unit magnet and the detection unit. The encoder according to claim 4, wherein
The encoder is characterized in that the front yoke is provided continuously over one circumference of the circumference and is divided into an inner circumference side and an outer circumference side of the circumference. The encoder according to claim 4, wherein
The encoder is characterized in that the front yoke is arranged so as to connect the same magnetic poles of the unit magnets. The encoder according to any one of claims 1 to 3,
The encoder is characterized in that the thickness of the unit magnet in the direction parallel to the rotation axis is provided such that the end portion in the direction along the circumference is thicker than the thickness of the central portion. The encoder according to any one of claims 1 to 7,
An encoder comprising a plurality of types of unit magnets having different widths in a direction along the circumference. The encoder according to any one of claims 1 to 8,
The encoder is characterized in that the unit magnets are arranged so that the interval between the unit magnets is narrow in the vicinity of the boundary where the direction of the magnetic field between the inner peripheral side and the outer peripheral side is reversed. The encoder according to any one of claims 1 to 9,
An encoder, wherein an interval between the unit magnets is narrower than an interval between the detection unit and the unit magnet. The encoder according to any one of claims 1 to 10,
An encoder characterized in that a width of the unit magnet in a direction along the circumference is larger than a width in the radial direction. The encoder according to any one of claims 1 to 11,
The encoder is characterized in that the unit magnets are arranged symmetrically on a boundary line where the direction of the magnetic field is reversed. The encoder according to any one of claims 1 to 12,
The number of the unit magnets is an even number of 4 or more. The encoder according to any one of claims 1 to 13,
The encoder is characterized in that the plurality of unit magnets are arranged in a ring shape around the rotation axis.

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