JPS6222803Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an optical length measuring device, and particularly to a linear encoder in which scales are added together in order to increase the length measurement range.

Optical linear encoders that require particularly high resolution use an incremental scale in which a grid-like bright and dark pattern is engraved as a scale band on a glass plate. Therefore, an example of the configuration of a conventional linear encoder will be explained with reference to FIG. In FIG. 1, a scale 1 having a scale band 1a engraved on one side of a plate glass is fixed in a case (not shown). On the other hand, in order to photoelectrically detect the graduation band 1a of the scale 1, a U-shaped detection head 2 is suspended from a moving member 3 via a piano wire 4. One end of the piano wire 4 is fixed to the movable member 3, and the other end is bent at about 90 degrees and engages with the engaging member 5.

Further, the detection head 2 is provided with a reference scale 6 for reading the scale band 1a at a position facing the scale band 1a. Furthermore, in the detection head 2,
In order to maintain a predetermined distance between the reference scale 6 and the scale band 1a, a roller 7 is rotatably supported.
a, 7b, and 7c are provided.

In such a conventional encoder, the case holding the scale 1 is attached to, for example, an object to be measured (such as a moving stage of a machine tool), and the movable member 3 is attached to a fixed body. In the assembled state attached in this manner, the piano wire 4 generates a force that urges the detection head 2 toward one side of the scale 1 and a force that urges the detection head 2 upward in the figure. Therefore, when the scale 1 and the movable member 3 move relative to each other, the rollers 7a and 7b roll on the upper surface 1b of the scale band 1a, and the roller 7c rolls on the upper surface 1b of the scale band 1a.
The reference scale 6 moves along the scale band 1a while facing each other at a predetermined interval by rolling on the lower surface 1c of the scale. Along with this movement, changes in brightness caused by the lattice pattern (slit) between the graduation band 1a and the reference scale 6 are detected by a light source and a light receiving element provided in the detection head 2.

In this way, by providing the rollers 7a, 7b, and 7c at at least three locations surrounding the reference scale 6, the surface of the reference scale 6 and the surface of the scale band 1a can be kept parallel.

By the way, in linear encoders, the longer the scale with a relatively high resolution, that is, the smaller the pitch of the lattice pattern, the more difficult it is to manufacture, and even if it can be manufactured, the scale will be curved or twisted, and This will impair the resolution of the image.

Therefore, when such a long scale is required, a shorter scale may be added. For example, as shown in FIG. 2, the end surface of another scale 101 is fixed to the end surface of the scale 1 by some method. In this way, a long scale with less curvature and twist can be easily obtained.

However, when using a scale added in this way, the detection head 2 shown in FIG. 1 cannot be used as is. That is, as shown in FIG. 2, there is always a seam G at the joint between the scale 1 and the scale 101, and when the detection head 2 passes through this seam G, the rollers 7a,
Either one of 7b and 7c falls into seam G.
This causes a change in the distance between the scale band 1a and the reference scale 6, or causes contact between the scale band 1a and the reference scale 6, and as a result, the photoelectric signal becomes extremely disturbed and a measurement error occurs. Therefore, a configuration of a detection head that is useful for such added scales is proposed, for example, in JP-A-53
-Disclosed in Publication No. 125056. This will be briefly explained with reference to FIG. Figure 3 shows
3 is a front view showing only the detection head 8 having the reference scale 6 in the center. FIG. This detection head 8
is equipped with a total of six rollers, two each of the rollers 7 shown in FIGS. 1 and 2. That is, two rollers 9 are provided at the position where roller 7a is provided.
A and 9b are supported in pairs by two rollers 10a and 10b at the position where roller 7b is provided, and two rollers 11a and 11b at the location where roller 7c is provided. Moreover, the axial distance d between the pair of rollers is set to be larger than the joint G of the scale. With such a configuration, even if any one of the six rollers 9, 10, 11 passes through the seam G, the detection head 8 comes into contact with the scale via the other five rollers. Therefore, the surface of the reference scale 6 and the scale band 1a
can pass through the seam G while maintaining a predetermined distance.

However, in the detection head 8 as shown in FIG. 3, six rollers 9a, 9b,
10a, 10b, 11a, 11b are all on the same plane (for example, the upper side 1b and the lower side 1 shown in FIG.
c) Must be adjusted during manufacture to contact above. Generally, to identify one plane, it is sufficient to determine three points, so adjusting six rollers so that they are in contact with each other on the same plane is extremely difficult and requires precise machining and assembly, making it impractical. The drawback is that it takes a lot of time and effort to convert.

SUMMARY OF THE INVENTION An object of the present invention is to solve these drawbacks and provide a length measuring device equipped with a detection head that is not affected by the joint between scales.

In order to achieve the above object, the length measuring device of the present invention includes: a main scale configured by joining a plurality of scales; a movable member movable along the length measurement direction of the main scale; and a movable member that moves together with the movable member. In the length measuring device equipped with a detection member for photoelectrically detecting the graduation band of the main scale, the main scale is in contact with one side of the main scale and on both sides of the graduation band at two and three places, respectively. five contacts arranged on the detection member such that the interval in the length measurement direction of the contact position is wider than the joint of the main scale; and a biasing member that biases the detection member against the moving member such that at least four contacts press the main scale together, and the five contacts are any one of them. In a total of 5 combinations of 4 contacts,
The areas formed by connecting the abutting positions of the respective contacts are arranged so that each combination has a common area, and the biasing member is provided so that the center of bias acts on the common area.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a front view showing the structure of the detection head in this embodiment, and FIG. 5 is a side view of FIG. 4 viewed from below. Note that in FIGS. 4 and 5, light sources, light receiving elements, etc. that are not directly related to the present invention are omitted. Also, in the following explanation, the second
The main scale is obtained by adding scale 1 and scale 101 shown in the figure. The body 20 of the detection head is conventionally provided with a reference scale 6. As shown in FIG. 4, rollers 21a and 21b serving as first and second contacts are supported on the upper side of the reference scale 6 at an interval wider than the joint between the scales. Furthermore, a roller 21c serving as a third contact is pivotally supported below the reference scale 6. The distance between the rotating shafts of these three rollers 21a, 21b, 21c is also determined to be wider than the joint, and each roller 21a, 21b, 21c is
The position is determined to be the position of each vertex of an isosceles triangle whose center of gravity is the center C of the reference scale 6. On the other hand, a roller 21d and a roller 21e are provided on both sides of the roller 21c along the moving direction of the main body 20. These rollers 21d and 21e are located at positions where they contact the main scale (positions in the surface direction where the scale bands are engraved).
It is rotatably supported by adjustment fittings 22a and 22b for adjusting. The adjustment fittings 22a, 22b are
It is rotatably attached to the main body 20 around pins 24a and 24b. Also, the fixing screw 23
a, 23b are the main body 20 and adjustment fittings 22a, 22
b. Note that these five rollers 21a, 21b, 21c, 21d, 21
The rotational axes of e are determined such that the interval along the moving direction of the main body 20 is wider than the joint between the scales.

Next, the adjustment of the main body 20 of this detection head will be explained. First, rollers 21a, 21b, 21c
is pivotally supported by the main body 20, but at this time, the surface of the reference scale 6 that faces the graduation band of the main scale is parallel to the surface containing the peripheral ends of the rollers 21a, 21b, and 21c that should come into contact with the main scales. Fix the three rollers so that Next, as shown in Figure 6, 3
With the three rollers 21a, 21b, and 21c in contact with the glass surface of the main scale, the adjustment fitting 22
A is slightly swung around the pin 24a to bring the roller 21d into contact with the glass surface. After that, the fixing screw 23a is turned to fix the adjustment fitting 22a and the main body 20 together. Thereafter, the adjustment fitting 22b is similarly swung to bring the roller 21e into contact with the glass surface, and the fixing screw 23b is tightened. Due to the above,
Five rollers 21a, 21b, 21c, 21d,
21e both abut on the glass surface.

Next, the operation of the main body 20 of this detection head will be explained using FIG. 7.

It is assumed that the main body 20 moves in the direction of the arrow in the figure on a main scale that is a combination of the scale 1 and the scale 101. At this time, as shown in FIG. 1, the main body 20 is always pressed toward the main scale by some kind of urging member. As an example, as shown in FIG. 8, three leaf springs 30a, 30b, and 30c are extended from a support 103 as a moving member to apply biasing force to the main body 20. This leaf spring 3
0a, 30b, and 30c have high rigidity against movement of the support 103 in the length measurement direction, and allow the main body 20 to move together with the support 103. On the other hand, the leaf spring 30
a, 30b, and 30c can be elastically deformed in the surface direction, that is, when moving toward the main scale side of the main body 20 (direction perpendicular to the length measurement direction).
In these three leaf springs, one end of the leaf spring 30a is fixed to the lower side of the roller 21d, and the end of the leaf spring 30b is fixed to the lower side of the roller 21d.
one end is fixed between rollers 21a and 21b,
One end of the leaf spring 30c is fixed to the lower side of the roller 21e. Further, when the biasing forces of each leaf spring are combined, it is preferable to set the biasing center so that it substantially coincides with the center C of the reference scale 6. It is sufficient to fix the leaf spring 30b to either the main body 20 or the support 103 and press the other with spring force from above to below perpendicular to the plane of the paper of FIG. The leaf spring 30b is not necessarily required.

Now, returning to FIG. 7, the explanation of the operation will be continued. In FIG. 7, when the main body 20 passes through the joint G between the scale 1 and the scale 101, any one of the five rollers passes through the joint G in sequence.

Therefore, let us consider the state of contact between these five rollers and the main scales (scale 1 and scale 101). When the roller 21e passes through the seam G, the rollers 21a, 21b, 21c, 21
d both abut on scale 1. When the roller 21b passes through the seam G, the rollers 21a, 21
c and 21d contact the scale 1, and the roller 21e contacts the scale 101. When the roller 21c passes through the seam G, the rollers 21a and 21d are on the scale 1, and the rollers 21b and 21e are on the scale 101.
comes into contact with. When the roller 21a passes through the seam G, the roller 21d is on the scale 1, and the roller 21
b, 21c, and 21e contact the scale 101. When the roller 21d passes through the seam G, the rollers 21a, 21b, 21c, and 21e all come into contact with the scale 101. However, as shown in Fig. 7, by combining any four rollers out of the five rollers, for a total of five combinations, the four rollers that come into contact with the glass surface of the main scale.
The area created by connecting the contact positions of the two rollers is 5
There is one. That is, rollers 21a, 21b, 21c,
The first area formed by connecting 21d, roller 21
The second one created by connecting a, 21b, 21c, and 21e
area, rollers 21a, 21b, 21d, 21e
The third area formed by tying the rollers 21a, 21
The fourth area formed by connecting c, 21d, and 21e,
This is the fifth area formed by connecting the rollers 21b, 21c, 21d, and 21e. A common area where these five areas overlap each other (shaded area in the figure)
The center C of the reference scale 6 is located inside. In other words, the five rollers 21 and the leaf springs 30 are positioned so that the center of bias is located in this common area.

Therefore, any one of the five rollers 21
Even when the main body 20 of the detection head passes through the seam G, the other four rollers support the main body 20 of the detection head without tilting in any way with respect to the glass surface on which the scale band is engraved.

As described above, the roller 2 as the five contacts
1a, 21b, 21c, 21d, and 21e are disposed so that two and three of them are in contact with each other on both sides of the scale band, respectively, so that when the detection head passes through the joining part, the photoelectric signal is This has the advantage that not only no disturbance occurs, but also the work of positioning each roller of the main body 20 during manufacturing is extremely simplified.

Note that the same effect cannot be obtained by using four rollers as contacts. The reason is that when one of the four rollers is arranged so as to pass through the seam, the common area created by connecting the contact positions of the remaining three rollers becomes a point instead of a surface. Unless the center of force is positioned very precisely at that point, the detection head will tilt as it passes through the seam. In practice, it is almost impossible to position the biasing center in this way.

In the above-described embodiment, the urging members include the leaf springs 30a, 30b, 30 shown in FIG.
c was used, but the same effect can be obtained by using piano wire as in the past. Furthermore, although the center C of the reference scale 6 and the biasing center are made to coincide with each other, it is not necessary to do so, and if the biasing center is in the common area (the shaded area in FIG. 7) , the reference scale 6 may be located anywhere on the main body 20. Furthermore, in the embodiment, the roller 21
c, 21d, and 21e are arranged linearly along the length measurement direction, but if the width of the lower surface 1c of the scale band is sufficient, they may be arranged not linearly but at different steps. It goes without saying that the same effect can be obtained even if the axial distance between the rollers 21b and 21b is wider than the axial distance between the rollers 21d and 21e.

As described above, according to the present invention, since the detection head as a detection member is supported by five contacts that contact at two and three places on both sides of the graduation band of the scale, three of the five contacts 1 to keep the plane of the reference scale and the plane of the scale band parallel, and the remaining 2
Only one contact needs to be adjusted, resulting in extremely easy manufacturing. Further, according to the present invention, the five contacts (rollers in the embodiment) are
In a total of five combinations of arbitrary four contacts among them, the areas formed by connecting the contact positions of each contact are arranged so that each combination has a common area, and the biasing member ( In the embodiment, the leaf springs and piano wires were provided so that the center of bias acted on the common area, so the contacts could be brought into stable contact with the main scale.
As a result, it is possible to prevent signal disturbances due to floating contactors, etc.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the configuration of a conventional linear encoder, Figure 2 is a diagram explaining adding a scale, Figure 3 is a front view of a detection head useful for the added scale, and Figure 4 is a diagram explaining the addition of a scale. A front view of the detection head showing an embodiment of the invention, FIG. 5 is a side view of FIG. 4 seen from below, and FIG. 6 shows the roller 21 with all three rollers in contact with the glass surface of the main scale
FIG. 7 is an explanatory diagram of the operation of the main body of the detection head, and FIG. 8 shows a leaf spring as an example of a biasing member that biases the main body. Description of symbols of main parts: 1, 101...scale, 21a to 21e...roller, 20...body of detection head, 30a, 30b, 30c...plate spring, 6...reference scale.

Claims (1)

[Claims for Utility Model Registration] 1. A main scale configured by joining a plurality of scales; A movable member movable along the length measurement direction of the main scale; A movable member movable along the length measurement direction of the main scale; In a length measuring device equipped with a detection member for photoelectrically detecting a scale band, two
five contacts disposed on the detection member such that they abut at two locations and three locations and the interval in the length measurement direction between each contact location is wider than the joint of the main scale; a biasing member that biases the detection member against the movable member such that at least four contacts press the main scale together with the movement of the movable member; The two contacts are arranged so that in a total of five combinations of any four contacts among them, the area formed by connecting the contact positions of each contact has a common area in each combination. ,
The length measuring device, wherein the biasing member is provided such that a biasing center acts on the common area. 2. Utility model registration characterized in that the detection member has a reference scale provided at a position facing the graduation band of the main scale, and the center of the reference scale and the biasing center of the biasing member are substantially aligned. A length measuring device according to claim 1. 3 Among the five contacts, the first and second contacts that contact one side of the scale band of the main scale, and the third contact that contacts the other side of the scale band, have respective contact positions that are isosceles. There are first, second, and third rollers arranged to correspond to each vertex of the triangle, and the other two contactors are arranged along the moving direction of the detection member.
The length measuring device according to claim 2, which is a registered utility model, characterized in that the fourth and fifth rollers are respectively arranged on both sides of the contactor. 4. The fourth and fifth rollers are rotatably supported relative to the detection member in the direction of contact with the main scale, and are fixedly supported as described in claim 3 of the utility model registration claim. length measuring device.