JP5294009B2 - Absolute position detection device and motor equipped with absolute position detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve mechanical stiffness in a slit opening for detecting an absolute position, to reduce the amount of offset given to a signal for an incremental light reception section by leaked light transmitted through the slit for detecting an absolute position, and to improve absolute position detection accuracy. <P>SOLUTION: A recurring random number code having continuity is used, where bit trains detected by a slit for detecting an absolute position do not overlap mutually, and specific regions before and after the maximum slit opening in which slit openings continue in the recurring random code are thinned out. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an absolute position detection device for detecting an absolute position in a rotary or linear encoder and a motor equipped with the absolute position detection device.

  The code slit used in the absolute angle detection encoder that detects the absolute angle of the motor rotation shaft etc. mounted on the motor etc. is devised in the structure of the slit row code on the encoder plate for the purpose of preventing reading errors and obtaining arbitrary resolution. There is something that has been broken. For example, the encoder described in Document 1 is a BCD code that uses a metal encoder plate and represents an absolute angle in order to avoid reading errors associated with light refraction and scattering on the encoder plate made of glass or transparent resin. A slit row represented is provided on the rotating disk, and an oblique slit for generating an incremental signal is provided adjacent thereto. In this encoder, in order to avoid the physical separation of the opening portion of the slit row representing the absolute angle between the inner peripheral side and the outer peripheral side of the rotating disk, the slit has a pattern that does not continue more than a certain amount in the angular direction. Describes coding a code at a specific angle differently from other angle BCD codes. This prevents cords having a specific angle from continuing in the angle direction of the slit so that they are not separated on the inner and outer peripheral sides of the rotating disk.

On the other hand, a cyclic random number code is used instead of the BCD code sequence as described above, and absolute angle information is given to the circumferential slit sequence, and 2 (N-1) to 2 N (N is an integer). In order to obtain an arbitrary resolution in the range, a method of obtaining an absolute value encoder with an arbitrary resolution by thinning out a cyclic random code so that a part of the random number code becomes a continuous code without overlapping the random number code is disclosed. (For example, Document 2 and Document 3).
JP 07-074742 (Figures 1, 2 and 3) Patent No. 3184939 (paragraph 11) JP 2004-170221 (FIG. 2, paragraph 16)

  In the configuration of the conventional example described above, the separation of the slit rows can be avoided, particularly in the configuration of Reference 1, but only a small portion is connected, there is a portion with low mechanical rigidity, and light leaking from the opening is There is a problem in that the position detection accuracy as an encoder is lowered due to poor mechanical characteristics and optical characteristics as a result of signal offset being generated by reaching the incremental signal light receiving section.

For example, in a cyclic random number code of 2 (N-1) to 2 N power, there is a bit string having a maximum of N consecutive openings (when the opening is bit 0). Compared to the above, the local mechanical strength is reduced, or the leaked light that has passed through the absolute position detecting slit reaches the incremental signal light receiving unit, causing an offset of the output signal.
The present invention has been made in view of such problems, and provides an absolute position detection encoder capable of suppressing a decrease in mechanical strength and reducing an offset of an output signal, and a motor equipped with the absolute position encoder. The purpose is to do.

In order to solve the above problem, the present invention is configured as follows.
An absolute position detection device according to an aspect of the present invention is arranged so as to form one bit string with arbitrary N slits adjacent to each other while forming one bit with an opening being 0 and a non-opening being 1. In addition, a plurality of absolute positions arranged so that each bit string at an address indicating an arbitrary rotational position does not overlap with each other and the bit string of adjacent addresses is shifted by the lower one bit to indicate continuity of addresses A rotating disk that has a detection slit and is attached to a rotating shaft; a light receiving unit that includes a plurality of light receiving elements disposed to face the rotating disk; and that faces the light receiving element across the rotating disk. A plurality of absolute position detection slits, 2 N bit strings configured using 2 N cyclic random numbers. Based on, of the two from the array of bit strings of N-th power, identifying a bit string of 2 m-th power made identical to each other in a state in which thinned out predetermined bits m for thinning, 2 which are those identified Bit strings other than all bit strings arranged between one bit string and other bit strings are thinned out and deleted from the m-th bit string, and the address of the arbitrary rotation position is expressed by all the bit strings remaining after the deletion. Formed on the rotating disk.
In this absolute position detection device, the rotary disk may be provided with an incremental slit provided in parallel with the absolute position detection slit.

Also, the absolute position detection device, wherein, when the rotation disk of the metal plate is a slit is formed by punching or etching process, when the rotation disk of the glass plate is a slit is formed by etching processing, rotation When the disk is a resin, the slit may be formed by injection molding, punching, or etching.

An absolute position detection device according to another aspect of the present invention is arranged so that one bit string is formed by arbitrary N slits adjacent to each other while forming one bit with an opening being 0 and a non-opening being 1. And a plurality of absolute positions arranged such that each bit string at an address indicating an arbitrary position does not overlap with each other and bit strings of adjacent addresses are shifted by the lower 1 bit to indicate continuity of addresses A linear scale disposed on a guide having a slit for detection and movable on a straight line, arranged on a guide for restraining the movement of the slider, and N light receiving elements arranged facing the linear scale. And a plurality of slits for detecting the absolute position are N <2> to the Nth power. Based on 2 N bit strings formed using a cyclic random code, they are identical to each other in a state where a predetermined number of bits m for thinning is thinned out from the array of 2 N bit strings. 2 m bit strings are identified, and bit strings other than all bit strings arranged between one bit string and the other bit strings are thinned out and deleted after the identified 2 m bit strings The linear scale is formed so that the address of the arbitrary position is expressed by all the remaining bit strings.
In the absolute position detection device, the linear scale may be provided with an incremental slit provided in parallel with the absolute position detection slit.
Further, the absolute position detection device has a slit formed by punching or etching when the linear scale is a metal plate, and a slit formed by etching when the linear scale is a glass plate. When is a resin, the slit may be formed by injection molding, punching, or etching.
A motor according to still another aspect of the present invention is equipped with the absolute position value detection device.

According to the absolute position detecting device according to each aspect of the present invention, the light transmitted through the absolute position detecting slit generates an offset as leakage light to the incremental signal. Since the opening length can be shortened to, for example, about half or less, the offset generation amount of the output signal can be suppressed, and thereby the accuracy deterioration due to the offset can be suppressed. In addition, since the amount of offset can be suppressed, the optical gap between the code plate and the light receiving portion necessary for realizing the same level of position accuracy as in the prior art can be set larger, and the degree of freedom in design increases.
Further, it is possible to suppress a decrease in mechanical strength due to shortening of the opening, and to improve the mechanical rigidity of the entire slit row over the entire circumference of the disk. Further, the optical gap between the disk and the light receiving surface can be made smaller, and further, the leakage light is reduced, thereby reducing the offset, and finally improving the optical characteristics and accuracy.

In addition, according to this absolute position detection device , by providing an incremental slit, position measurement at high speed can be performed by an incremental method, and it can be applied to position detection in a wide range of applications.
Further, according to this absolute position detection device , the rotating disk and the linear scale can be manufactured from various materials, and the slit can be manufactured by a method suitable for the material, so that it can be manufactured with high accuracy and at low cost.
According to the motor according to each aspect of the present invention, a motor having a high accuracy and high rigidity absolute value encoder is mounted. Therefore, a motor having a wide operation range up to high-speed operation in which vibration is likely to occur can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a rotary absolute position detector 100.
In the figure, 100 is a rotary position detector, 101 is a light emitting element, 102 is a light emitting element holder, 103 is a board fixing screw, 104 is a board for position detection, 105 is a spacer, 106 is a board mounting base, 107 is a code plate, Reference numeral 108 denotes a detection element, 109 denotes a code plate holder, 110 denotes a code plate rotation center, 111a denotes an incremental slit, and 111b denotes an absolute position detection slit. The position detector substrate 104 is fixed to the substrate mounting base 106 by the substrate fixing screw 103 via the spacer 105. The code plate 107 rotates together with the code plate holder 109 around the rotation center axis 110 of the code plate. Light emitted from the light emitting element 101 fixed to the light emitting element holder 102 passes through the incremental slit 111a and the absolute position detecting slit 111b provided on the code plate 107 and is received by the detecting element 108 and processed as a position signal. Is done. The absolute position detecting slit 111b is provided with a slit serving as a cyclic random number code, and the cyclic random number code forms one bit string with N slits adjacent to each other. What is different from the prior art is a slit for detecting the absolute position of the code plate. In the cyclic random number code, the continuity (after thinning out the area in a specific area before and after the bit string corresponding to the slit having a long opening slit length) The bit strings of arbitrary adjacent addresses are in a bit shift relationship for the lower 1 bit) and the maximum continuous aperture length is reduced.

  FIGS. 2 and 3 compare and display the slits (B in the figure) of a conventional encoder and the slits (A in the figure) of the configuration of the present invention. In the configuration of the present invention (A in the figure), while maintaining the non-overlapping and the continuity of the long slit opening length so that the maximum slit opening length of the absolute position detection slit (the opening is indicated by hatching) is halved. This is an example in which a bit string in a specific area is omitted and the maximum slit opening length is halved.

FIG. 4 shows a state in which a portion having a long slit opening length is thinned out. The horizontal axis represents the address (representing the absolute position), and the vertical axis represents the slit opening length. A in the figure shows a state before thinning out (in this example, 12 slits are used as a bit string in one address). Long portions of the slit opening length (marked with * in the figure) appear at the addresses. By thinning out this portion, as shown in B in the figure, in this example, the opening length is thinned out so as to be suppressed to 7 slits or less.
As a result of FEM analysis of the rigidity of the disk when the maximum slit opening length is reduced by half according to the above, it was confirmed that the rigidity was improved by about 20% or more, and the offset was generated in the incremental signal through the absolute position detection slit. It was confirmed by actual measurement that the amount can be suppressed by about 5 to 10%.
Of course, in the above example where the slit opening length is the maximum, there is an effect of increasing the rigidity only by thinning out the portion where the 12 slits are opened.

FIG. 5 shows an example of the thinning method.
2 is an arbitrary cyclic random number code composed of N or less cyclic random number codes, and includes a slit string composed of N bit strings (N = 12 in FIG. 5) adjacent to each other and addresses of the respective bit strings. It shows the relationship. The address of the bit string directly represents the absolute position, and the bit string of each address is set so as not to overlap between different addresses.
The absolute position detecting slit creates a cyclic random number code having a small slit opening length by thinning out a portion having a long slit opening length based on a bit string composed of a cyclic random code of 2 N or less.
Since the 12th bit to the 2nd bit in the bit string of the i-th address are in a bit shift relationship of 1 bit with the i + 1-th bit string, they are equal to the 11th bit to the 1st bit of the i + 1th address. The bit string between them is continuous.
Similarly, when the 12th bit to the 2nd bit in the bit string of the i-th address and the 11th bit to the 1st bit of the j (> i) th address are equal as shown in FIG. Even if the bit string of the first address is thinned out, as described above, the i-th and j-th bits maintain the bit shift relationship of 1 bit, so that the continuity is not lost.

A second embodiment of the present invention will be described with reference to the drawings.
FIG. 6 shows an embodiment when applied to a linear position sensor.
200 is a linear position detector, 201 is a light emitting element, 202 is a light emitting element holder, 203 is a board fixing screw, 204 is a board, 205 is a spacer, 206 is a slider, 207 is a code plate, 208 is a detecting element, 209 is a guide , 210 is a code plate holder, 211a is an incremental slit, and 211b is an absolute position detecting slit.
In the position detector 200, the position detector substrate 204 is fixed to the slider 206 via the spacer 205 by the substrate fixing screw 203, and translates along the guide 209.
The code plate 207 is fixed by the code plate holder 210. The light emitted from the light emitting element 201 fixed to the light emitting element holder 202 is simultaneously transmitted through the incremental slit 211a and the absolute position detecting slit 211b provided on the code plate 207 and received by the detecting element 208 as a position signal. It is processed. The absolute position detecting slit 211b is provided with an absolute position detecting slit serving as a cyclic random number code, and the cyclic random number code forms one bit string with adjacent N slits in the first embodiment. Is the same.
The difference from the first embodiment is that it is applied to a linear type position detection apparatus. It is a slit for detecting the absolute position of the code plate, and does not lose the continuity even after thinning out the specific area having a long opening slit length from the random number sequence, and reduces the maximum opening slit length. Others are the same as those in the first embodiment, and thus the description thereof is omitted.

The rotating disk and the linear scale can be manufactured from various materials such as a metal plate, glass, and a resin molding material. In the case of manufacturing using a metal plate, the slit can be formed by punching or etching. In the case of a glass plate, it can be formed by etching. In the case of a resin mold, it can be formed by injection molding, punching or etching. Therefore, it can be formed with high accuracy and at low cost.
Further, by applying the present invention to a motor equipped with the absolute position encoder, it is possible to realize a motor that can be operated up to a high-speed region where vibration is likely to occur.

Diagram showing a rotary absolute position detector (A) Slit row enlarged schematic diagram in the first embodiment of the present invention, (B) Slit row enlarged schematic diagram in the prior art. (A) The figure which shows the code board in 1st Example of this invention, (B) The figure which shows the conventional code board (A) The figure which shows the continuous slit opening length before thinning-out execution in 1st Example of this invention, (B) The figure which shows the continuous slit opening length after thinning-out execution in 1st Example of this invention Diagram showing the relationship between random number sequence and slit address, and random number thinning Diagram showing linear absolute position detector

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Rotary type absolute position detector 101 Light emitting element 102 Light emitting element holder 103 Board fixing screw 104 Position detection board 105 Spacer 106 Board mounting base 107 Code plate 108 Detection element 109 Code plate holder 110 Code plate rotation center 111a Incremental slit 111b Absolute Position detection slit 200 Linear type absolute position detector 201 Light emitting element 202 Light emitting element holder 203 Substrate fixing screw 204 Substrate 205 Spacer 206 Slider 207 Code plate 208 Detection element 209 Guide 210 Code plate holder 211a Incremental slit 211b Absolute position detection slit

Claims (8)

Arbitrary N slits adjacent to each other are arranged so as to form one bit string while forming one bit with an opening of 0 and a non-opening of 1, and at an address indicating an arbitrary rotational position. Each bit string does not overlap with each other, and has a plurality of absolute position detection slits arranged so as to indicate the continuity of addresses in which bit strings of adjacent addresses are bit-shifted by the lower one bit, and are attached to a rotating shaft A rotating disk;
A light receiving portion comprising a plurality of light receiving elements arranged opposite to the rotating disk;
A light emitting element disposed opposite to the light receiving element across the rotating disk;
With
The plurality of absolute position detection slits are:
A state in which a predetermined number of bits m for thinning is thinned out from an array of 2 N bit strings based on 2 N bit strings formed using 2 N cyclic random codes 2m bit strings that are identical to each other are identified, and bit strings other than all bit strings arranged between one bit string and the other bit strings are thinned out of the identified 2m bit strings. An absolute position detecting device, wherein the absolute position detecting device is formed on the rotating disk so as to represent an address of the arbitrary rotating position by the all bit strings remaining after the deletion. The rotating disk includes
The absolute position detecting device according to claim 1, wherein an incremental slit provided in parallel with the absolute position detecting slit is provided. When the rotating disk is a metal plate, the slit is formed by punching or etching,
When the rotating disk is a glass plate, the slit is formed by an etching process,
The absolute position detecting device according to claim 1 or 2, wherein when the rotating disk is resin, the slit is formed by injection molding, punching, or etching.   A motor equipped with the absolute position detection device according to claim 1. Arbitrary N slits that are adjacent to each other are arranged so as to form one bit string while forming one bit with an opening of 0 and a non-opening of 1, and each address at an address indicating an arbitrary position It has a plurality of absolute position detection slits arranged so as to indicate the continuity of addresses in which bit strings do not overlap each other and bit strings of adjacent addresses are bit-shifted by the lower one bit, and can move on a straight line A linear scale disposed on a guide facing and constraining the slider;
A light receiving unit having N light receiving elements arranged to face the linear scale;
A light emitting element disposed opposite to the light receiving element across the linear scale;
With
The plurality of absolute position detection slits are:
A state in which a predetermined number of bits m for thinning is thinned out from an array of 2 N bit strings based on 2 N bit strings formed using 2 N cyclic random codes 2m bit strings that are identical to each other are identified, and bit strings other than all bit strings arranged between one bit string and the other bit strings are thinned out of the identified 2m bit strings. The absolute position detecting device is formed on the linear scale so as to represent the address of the arbitrary position by all the bit strings remaining after the deletion. The linear scale includes
The absolute position detection device according to claim 5, wherein an incremental slit provided in parallel with the absolute position detection slit is provided. When the linear scale is a metal plate, the slit is formed by punching or etching,
When the linear scale is a glass plate, the slit is formed by an etching process,
The absolute position detection device according to claim 5 or 6, wherein when the linear scale is resin, the slit is formed by injection molding, punching, or etching. A motor equipped with the absolute position value detection device according to claim 5.

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