JP3976630B2 - Encoder scale manufacturing method and scale manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method and a manufacturing apparatus for a scale used in an optical encoder used in machine tools, industrial machines, and the like.
[0002]
[Prior art]
As an example of the optical encoder, FIG. 4 is a cross-sectional view showing a configuration of a linear encoder. Explaining the configuration, the linear encoder includes a scale unit 1 that includes a scale with a scale and is attached to the machine fixing member side, and a slider that is attached to the machine movable member side and moves relative to the scale unit 1. The unit 2 is constituted.
[0003]
Each unit will be described in detail. The scale unit 1 includes an optically scaled scale 1a, a base 1b for holding the scale 1a and attaching it to the machine fixing member side, and the scale 1a surrounding dust. The base 1b and the cover 1c are collectively referred to as a housing. A dust-proof lip seal 1d is attached to the lower part of the housing, and the slider unit 2 moves while scraping the lip seal 1d.
[0004]
One slider unit 2 includes a scale detector 2a that optically detects a scale carved on the scale 1a and converts it into position information, and a mount 2b that fixes the scale detector 2a to the machine movable member side. ing.
[0005]
The operation of the linear encoder configured as described above will be described. When the machine movable member moves in the longitudinal direction of the scale unit 1 with respect to the machine fixed member, the scale detection unit in the slider unit 2 moves relative to the scale 1a. The position changes, the scale of the corresponding scale 1a is read by the scale detector 2a, converted into position information, and output.
[0006]
Next, an absolute position linear encoder which is a kind of linear encoder will be described. The absolute position linear encoder is an encoder that has an absolute address on the scale and can detect the absolute position within the measurement length from the time the power is turned on, and detects the current position by counting the amount of movement from some reference point. Contrast with incremental method.
[0007]
An example of the scale used in the absolute position linear encoder is shown in FIG. In FIG. 3, a white part represents a part that transmits light. In the dense track, an optical grating in which a transmissive portion and a non-transmissive portion are repeated at a constant period is formed. In the coarse track, a code called an irregular circulation code is formed by a combination of a transmission part and a non-transmission part.
[0008]
The irregular cyclic code corresponds to binary values of 1 and 0 for the transmissive part and the non-transparent part, and pays attention to a predetermined length (number of bits) among codes formed over the scale length. Then, they are arranged so that no part of the scale length takes the same code.
[0009]
The scale configured in this way is read by a scale detector in the slider unit. Usually, since a periodic signal is obtained from the fine track, this periodic signal is electrically interpolated and divided to calculate the absolute position within one period. However, this alone cannot detect the absolute position for the entire scale length.
[0010]
Therefore, the position in the entire scale length is detected by reading the irregular circulation code of the coarse track. Then, by combining the fine position data obtained from the dense track and the coarse position data obtained from the coarse track, fine position data having a wide absolute position range is obtained.
[0011]
Next, a scale manufacturing method will be described. The scale used in the encoder as described above is usually manufactured by a photolithography technique.
[0012]
First, a master mask is manufactured in which a dense track and a coarse track are precisely patterned on a several inch square mask. For example, if the scale width is 20 to 30 mm, when a scale pattern is arranged on a 7-inch square (about 178 mm square) mask pattern, a pattern having a length of about 600 mm can be drawn (formed). it can. First, a master mask is produced.
[0013]
Next, the master mask pattern is repeatedly transferred onto a working mask substrate having a length equivalent to the actual scale. A working mask that is actually used for scale manufacture is manufactured. Next, a working mask pattern is transferred to a glass member that is actually a product.
[0014]
Here, a pattern generator or an electron beam drawing apparatus is generally used for patterning the master mask, and an optical exposure apparatus is generally used for transferring the mask pattern.
[0015]
As a specific example, a thin metal film is formed on a glass substrate of a scale, and a photosensitive agent called a resist is applied thereon. Next, the resist is exposed to light by bringing the working mask close thereto. Thereafter, an optical lattice is formed on the glass substrate through a development process, an etching process, and the like.
[0016]
[Problems to be solved by the invention]
In the case of a regular pattern such as a dense track, the master mask may be small, and a long scale can be manufactured relatively easily by transferring it to the working mask while accurately shifting the location.
[0017]
However, when using an irregular code such as a coarse track, the same pattern does not exist anywhere on the long scale. Therefore, the master mask has to be manufactured first for the length that may actually be used, and is very expensive.
[0018]
Moreover, in order to lengthen the measurement length, the glass scales may be physically joined by bonding or the like. In this case, it is necessary to perform accurate bonding so that the lattice period of the dense track is maintained even at the bonded portion. At this time, if only the dense track is used, even if the processing of the joint surface of the glass scale is not successful once, highly precise joining can be performed again by shifting by several cycles and re-working.
[0019]
However, in a scale that has already been subjected to a coarse track, the rework as described above will destroy the periodicity of the coarse track, so rework is not allowed and the scale becomes unusable after all.
[0020]
Further, as a method for detecting a long stroke, the present applicant has proposed that a plurality of scales are arranged in the longitudinal direction and detected smoothly by a plurality of sliders. In this case, in order to distinguish which scale is a plurality of scales arranged in the longitudinal direction, codes representing different positions on the scale need to be formed.
[0021]
However, in this case, since the stroke used in an actual machine is up to about 10 m, it is necessary to create a master mask that can cope with the stroke, which increases the cost.
[0022]
In particular, although there are few cases that require such a large stroke, it is useless to generate a lot of costs for that purpose.
[0023]
In addition, since the scales representing these different positions do not have any difference in appearance, mistakes are likely to occur in physical distribution from the scale production process to the actual installation.
[0024]
The present invention has been made to solve the above-described problems, and an object of the present invention is to be able to add an arbitrary coarse track to a scale in which only a dense track is formed in advance. By providing a manufacturing method and a manufacturing apparatus, it is possible to manufacture a flexible scale at a low cost.
[0025]
[Means for Solving the Problems]
The above problems can be achieved by a scale manufacturing method and a manufacturing apparatus as shown below.
[0026]
That is, the present invention is linear to detect the absolute position using both irregular circulation code track formed by closely track and irregularly arranged tracks formed at a track that is periodically arranged at regular intervals A scale manufacturing method for manufacturing a scale for use in an encoder, wherein a fine track position detecting step for detecting a position of a fine track formed in advance on the scale, and the detected fine track position are sequentially output as position data. A position data output step, an irregular cyclic code track pattern output step for sequentially outputting the track pattern of the irregular cyclic code track corresponding to the outputted position data for each outputted position data, and the output track pattern based on the opaque surface of the scale, or a non-reflective ink forward By printing, characterized in that it comprises a disordered circulation code track formation step of forming an irregular circulation code track on the scale.
[0027]
According to the scale manufacturing method including such steps, the dense track position detecting step detects the position of the dense track with respect to the scale in which only the dense track is formed in advance. Then, position data is sequentially output based on the position of the dense track detected in the position data output step.
[0028]
The irregular cyclic code track pattern output step sequentially outputs the track pattern of the irregular cyclic code track corresponding to the outputted position data for each outputted position data . Then, in the irregular circulation code track pattern irregular circulation code track formed step based, opaque to the scale of the surface based on the output track pattern, or, sequentially printing to a non-reflective ink by forming an irregular circulation code track on the scale.
[0029]
Accordingly, it is possible to provide a scale manufacturing method capable of additionally writing an arbitrary irregularly-circulated code track, and it is possible to manufacture a flexible scale at a low cost.
[0030]
Further, scale manufacturing process of the present invention comprise an irregular circulation code tracks forming means and the driving step of relatively displacing the said scale forming the irregular circulation code track on the basis of the irregular circulation code track formed step It is characterized by.
[0031]
By the driving step, the irregular circulation code track forming means and the scale are relatively displaced to a desired portion on the scale while forming the irregular circulation code track while detecting the position of the dense track. it can.
[0032]
Furthermore, in the scaled production method of the present invention, the irregular circulation code track formation step is to print an opaque ink on a transparent part on the scale is a step of forming the irregular circulation code track It is characterized by.
[0033]
According to the scale manufacturing method including such steps, an opaque substance can be depicted in a transparent part on the scale, so that the encoder detects the position of the object by the difference between the transmissive part and the non-transmissive part. The scales used can be manufactured.
[0034]
Also, in the scale production method of the present invention, the irregular circulation code track formation step is to print the non-reflective ink in the portion of high reflectivity on the scale, to form the irregular circulation code track It is a step.
[0035]
According to the scale manufacturing method including such steps, a low-reflectivity material can be depicted in a high-reflectance portion on the scale, and thus it is used for an encoder that detects the position of an object based on a difference in reflectivity. Scales can be manufactured.
[0036]
In addition, in the manufacturing method of the present invention, the irregular cyclic code track pattern output step sequentially outputs the track pattern of the irregular cyclic code track corresponding to the position data stored in advance for each output position data. It can also be a step, or it can be a step of calculating and outputting a track pattern of an irregular cyclic code track corresponding to position data.
[0037]
Furthermore, scale manufacturing apparatus of the present invention, the absolute position using both irregular circulation code track formed by closely track and irregularly arranged tracks formed at a track that is periodically arranged at regular intervals A scale manufacturing apparatus for manufacturing a scale for use in a linear encoder for detecting the position of a fine track, a fine track position detecting means for detecting the position of a fine track previously formed on the scale, and the detected position of the fine track as position data sequential position data output means for outputting, and irregular circulation code track pattern output means for a track pattern irregular circulation code track corresponding to the output position data, and sequentially outputs each output position data as being output opaque to the scale of the surface a track pattern on the basis of, or non-reflective ink By sequentially printing, characterized in that it comprises a disordered circulation code track forming means for forming an irregular circulation code track on the scale.
[0038]
According to the scale manufacturing apparatus configured as described above, the dense track position detecting unit detects the position of the dense track with respect to the scale in which only the dense track is formed in advance. Then, the position data is sequentially output based on the position of the dense track detected by the position data output means.
[0039]
The irregular cyclic code track pattern generation means sequentially outputs the track pattern of the irregular cyclic code track corresponding to the output position data for each output position data . Then, the irregular circulation code track forming means sequentially prints the opaque or non-reflective ink on the surface of the scale based on the outputted track pattern based on the irregular circulation code track pattern. by forming an irregular circulation code track on the scale.
[0040]
Accordingly, it is possible to provide a scale manufacturing apparatus capable of additionally writing an arbitrary irregularly-circulated code track, and it is possible to manufacture a flexible scale at a low cost.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention is shown in FIG. The movable table includes a position detection head, a pattern drawing head, a position detection processing device, a pattern drawing control unit, a main controller, a table drive control device, a motor, and a feed screw.
[0042]
The position detection head optically reads the optical grating of the fine track and outputs a displacement signal, similarly to the position detection unit of a normal linear encoder. The output displacement signal is input to the position detection processing device, where it becomes position data. This position data represents the position of the movable table with respect to the scale, and the position data is transmitted to the main controller.
[0043]
On the other hand, the pattern drawing head is close to the coarse track of the scale, and draws (forms) a pattern on the coarse track on the scale in accordance with a drawing command from the pattern drawing control device. The pattern drawing control device includes a function for generating a relationship between a scale position and a pattern to be drawn there. As another method, the relationship between the position of the scale and the pattern to be drawn there may be stored in advance.
[0044]
In addition, the movable table including the position detection head and the pattern drawing head can be moved precisely in the longitudinal direction of the scale. As an example, it is driven by a feed screw and a motor. The motor is connected to the table drive control device and is movable by a desired amount.
[0045]
The operation of the embodiment according to the present invention will be described below. First, the displacement signal of the fine track output from the position detection head is converted into position data by the position detection processing device, and the position data is transmitted to the main controller. With this operation, the main controller recognizes the initial position of the movable table.
[0046]
Next, the main controller transmits the position data of the movable table and the pattern drawing start command to the pattern drawing control device. The pattern drawing control device generates a pattern to be drawn on the corresponding coarse track for the position data detected in the dense track, and sends a drawing command to the pattern drawing head so that the pattern can be drawn.
[0047]
At the same time, the main controller issues a table movement command to the table drive control device. The table drive control device rotates the feed screw by rotating the motor, and moves the movable table at a desired position and speed. In this way, while detecting the position of the dense track, the pattern of the coarse track corresponding to the position is drawn. At this time, the movable table can be drawn while being repeatedly moved and stopped, or can be drawn while being moved.
[0048]
By the above method, a desired coarse track can be drawn in synchronization with the fine track. According to this method, even if there is a slight error in the lattice pattern of the fine track, the rough track drawing reference is the position obtained from the fine track, so the phase relationship between the fine track and the coarse track is Accurate drawing is possible without deviation.
[0049]
An example of a specific drawing method is shown below.
[0050]
The embodiment shown in FIG. 1 is a transmissive pattern forming method. In the scale, a periodic grating is formed in a dense track, which is composed of repeated transmission and non-transmission portions.
[0051]
As an example, the metal corresponding to the transmission portion is removed by etching from a glass-like metal film such as chromium or aluminum deposited thereon. In this case, a portion of the metal corresponding to the coarse track is also removed in advance, and is in a transparent state. A non-transmissive portion is formed in this portion using a coarse track drawing head. A non-permeable ink is transferred onto the scale surface using a thermal transfer type drawing head or the like. The forming method is not particularly limited as long as it can fix a non-permeable substance on glass.
[0052]
It is also effective to previously apply a coating on the glass surface to stabilize the fixing, or to coat a protective film after forming the non-transmissive portion.
[0053]
Next, a method for forming a reflective pattern is shown in FIG.
[0054]
A hatched portion represents a reflective portion such as a metal film, and a black portion represents a non-reflective portion. In the scale, a periodic grating is formed on a dense track, which is composed of repeated reflective and non-reflective portions.
[0055]
As an example, a non-reflective film is partially formed on a glass-like reflective metal film such as chromium or aluminum deposited thereon. In this case, a reflective metal film is formed on the portion corresponding to the coarse track, and the reflective track can be reflected. A non-reflective portion is formed in this portion using a coarse track drawing head. The non-reflective ink is transferred onto the scale surface using a thermal transfer type drawing head or the like. The forming method is not particularly limited as long as it can fix a non-reflective substance on glass.
[0056]
It is also effective to previously apply a coating on the scale to stabilize the fixing, or to coat a protective film after forming the non-reflective portion.
[0057]
If a coarse track is added later as in the present invention, the following effects are obtained.
[0058]
As mentioned above, when manufacturing a master mask of scale, for a dense track consisting of periodic optical gratings, it is also possible to manufacture a long scale by manufacturing a small master mask and repeatedly transferring it to the working mask. Although it can be done relatively inexpensively, the coarse track is not repeatable, so it is necessary to produce a master mask corresponding to the required length, which makes the initial cost very high, especially for long scale production. End up.
[0059]
On the other hand, according to the manufacturing method of the present invention, the initial master cost can be reduced by a small mask obtained by patterning only the dense track.
[0060]
In addition, when glass scales are physically joined together by bonding or the like in order to increase the measurement length, if only a dense track is joined, even if a problem occurs in the processing of the joint end face due to some reason, one cycle, or Although reworking is possible with a shift of several cycles, such reworking is impossible when there is a rough track because there is only one pattern on the rough track.
[0061]
However, according to the method of manufacturing a coarse track later as in the present invention, it is only necessary to consider maintaining the lattice period of only the dense track for joining the scales. Rework can be done when there is not, and the production yield can be increased, which contributes to the overall cost reduction.
[0062]
Furthermore, as a method for detecting a long stroke, a plurality of scales are arranged in the longitudinal direction, and in a method of detecting them by connecting them with a plurality of sliders, it is determined which scale of the plurality of scales arranged in the longitudinal direction. In order to distinguish, codes representing different positions are formed on the scale.
[0063]
Since the stroke used in an actual machine is up to about 10 m, it is necessary to create a master mask that can cope with the stroke, which increases the cost. In particular, although there are few cases that require such a large stroke, it is useless to generate a lot of costs for that purpose. In addition, since the scales representing these different positions do not have any difference in appearance, mistakes are likely to occur in physical distribution from the scale production process to the actual installation.
[0064]
By using the manufacturing apparatus of the present invention for these problems, it is possible to freely add a coarse track on any length scale, and the coarse track drawing process immediately before the process of actually attaching to the machine. By doing so, the complexity of logistics can be reduced.
[0065]
In addition, in order to increase the production efficiency, it is usually made by creating a scale that is as long as possible from the working mask, and separating the scales of various lengths. There are various upper track parts in the scaled carving.
[0066]
For example, even a scale having the same length may be a scale near zero in the upper track or a scale near 1000 mm. In this case, it is necessary to read the position data after actually attaching to the machine, and then enter a large position offset value and convert it to the position data required for the actual machine. It is possible to add a rough track after it has been cut, and it is also possible to add the same code partially on a long scale and cut it later, so that it can be obtained when the desired position data is attached to the machine .
[0067]
In the present invention, a scale using glass is described as an example, but the material of the scale is not limited, and the present invention can be applied to a scale using metal or the like. In the present invention, a so-called amplitude grating having a different transmittance or reflectance depending on the location has been described as an example.
[0068]
In addition, a method using ink has been described for pattern drawing, but pattern drawing can also be applied by a drawing method using a laser or the like. Further, as an embodiment, the example has been described in which one track is a dense track and one track is a coarse track, but the present invention can also be applied to a plurality of tracks.
[0069]
【The invention's effect】
As described above, according to the scale manufacturing method and manufacturing apparatus proposed by the present invention, it is possible to manufacture a scale having a long coarse track capable of absolute detection with an inexpensive master mask. In addition, it is possible to improve the yield of long scale manufacturing where the scales are joined together and to reduce the cost.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is a configuration diagram showing another embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a scale used in a general absolute encoder.
FIG. 4 is a configuration diagram of a conventional optical encoder.
[Explanation of symbols]
1 scale unit, 1a scale, 1b base, 1c cover, 1e bolt, 2 slider unit, 2a scale detector, 2b mount, 2c bolt.

Claims (7)

Manufactures scales for linear encoders that detect absolute positions using both dense tracks formed of regularly spaced tracks and irregularly-circulated code tracks formed of randomly arranged tracks A scale manufacturing method for
A dense track position detecting step for detecting the position of the dense track previously formed on the scale;
A position data output step for sequentially outputting the detected dense track position as position data;
An irregular cyclic code track pattern output step for sequentially outputting the track pattern of the irregular cyclic code track corresponding to the outputted position data for each outputted position data ;
Opaque to the scale of the surface based on the output track pattern, or, by sequentially printing the non-reflective ink, and irregular circulation code track formation step of forming an irregular circulation code track on the scale ,
A scale manufacturing method including: In the scale manufacturing method of Claim 1,
Scale manufacturing method characterized by comprising the driving step of relatively displacing the said scale irregular circulation code track forming means for forming an irregular circulation code track on the basis of the irregular circulation code track formed steps. In the scale manufacturing method of Claim 1 or Claim 2,
The irregular circulation code track formation step is to print an opaque ink on a transparent part on the scale, the scale manufacturing process, characterized in that the step of forming an irregular circulation code track. In the scale manufacturing method of Claim 1 or Claim 2,
The irregular circulation code tracks forming step is to print the non-reflective ink in the portion of high reflectivity on the scale, the scale manufacturing process, characterized in that the step of forming an irregular circulation code tracks . The scale manufacturing method according to claim 1, wherein:
The irregular cyclic code track pattern output step is a step of sequentially outputting a track pattern of irregular cyclic code tracks corresponding to position data, which is stored in advance , for each output position data. Method. The scale manufacturing method according to claim 1, wherein:
The irregular circulation code track pattern outputting step, scale manufacturing method characterized by by calculating the track pattern of irregular circulation code track corresponding to the position data, a step of outputting. Manufactures scales for linear encoders that detect absolute positions using both dense tracks formed of regularly spaced tracks and irregularly-circulated code tracks formed of randomly arranged tracks A scale manufacturing apparatus for
Dense track position detecting means for detecting the position of the dense track formed in advance on the scale;
Position data output means for sequentially outputting the detected dense track position as position data;
An irregular cyclic code track pattern output means for sequentially outputting a track pattern of the irregular cyclic code track corresponding to the outputted position data for each outputted position data ;
Irregular circulation code track forming means for forming irregular circulation code tracks on the scale by sequentially printing opaque or non-reflective ink on the surface of the scale based on the output track pattern; ,
Including scale manufacturing equipment.

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