JP3130463B2 - Displacement detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long displacement detecting device which is required when a long stroke is moved on a table or the like of a large machine tool or the like, and in particular, positioning of each scale forming a long scale. The detection of the amount of displacement for performing the measurement with high accuracy.

[0002]

2. Description of the Related Art Conventionally, a long scale for connecting a plurality of scales holds one scale, and at a joint at the end of the scale, another small scale plate faces a vertical stripe scale of the scale, and the scales overlap. The moiré manuscript that is generated is visually detected, and the other scale is adjusted so that a moiré manuscript can be produced in order.

[0003]

In the above-mentioned conventional method for producing a long scale of a linear encoder, it is necessary to remove the scale cover and take out only the scale, and a mechanism for holding one of the scales is connected to the mechanism. A dedicated manufacturing apparatus having a mechanism for adjusting the other scale in the longitudinal direction is required.

[0004] In addition, the adjustment method based on the moiré draft has a problem that it depends on human perception, cannot be converted into a numerical value, and the adjustment accuracy is poor. For example, when a scale having a period of 100 μm is used, an alignment error of about 2 to 4 μm is generated. Moreover, skill was required, and a large number of man-hours were required.

The present invention has been made in view of the circumstances described above, and an object of the present invention is to adjust the scale by removing the scale cover or attaching the scale cover to a dedicated manufacturing device on the machine on which the linear encoder is mounted. It is an object of the present invention to provide a displacement detection device which can manufacture a long scale adjusted with high accuracy in a very short time without requiring such operations.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a long displacement detecting device required when a long stroke is moved on a table of a large machine tool or the like. In order to achieve the present invention, the present invention provides a displacement detecting apparatus comprising: a plurality of scales which are arranged side by side to form one long scale; and a slider means for detecting a relative position between the plurality of scales. Calculates a relative position of each scale based on a signal from each scale at a position where signals from a plurality of scales can be obtained at the same time, and detects a displacement amount to be adjusted of the plurality of scales. Means.

[0007] The scale position detecting means may determine whether or not the signal should be outputted with a predetermined phase difference based on the phase difference.
It is characterized in that the relative position of each scale is calculated.

[0008] The slider means may include at least two sliders.
And the scale position detecting means calculates a relative position of each scale based on a signal detected by each of the position detecting means.

Further, the scale position detecting means detects the amount of deviation from a reference position calculated based on a signal detected by the position detecting means from the same scale, and detects the amount of displacement from each of the different scales. The relative position of each scale is calculated based on the shift amount from the reference position calculated based on the signal.

According to the present invention, when a long scale is manufactured, no special setup or device is required for adjusting the joints of the scale, and there is no need to open the scale unit. Therefore, the productivity can be improved, and the cost can be reduced. In addition, on the main unit on which the displacement detecting device is mounted, the positioning of the scale can be realized with high accuracy.

[0011]

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a displacement detecting device according to the present invention, which comprises a main scale unit 1 and a slider 2.

The main scale unit 1 is fixed to one of two relatively displaceable devices, and a scale 3 and a scale 4, which are main scales, and an adjusting unit 5 capable of adjusting the position of one of the scales in the longitudinal direction. And In this example, the adjustment unit 5 is mounted on the scale 4 and can be removed after adjustment.

On the other hand, a slider 2 fixed to the other device which is relatively displaced has a detector 6 for obtaining detection signals from the scales 3 and 4, and the slider 2 is disposed at a joint between the scales 3 and 4. And a scale position detecting means 7 for detecting and outputting the positional relationship between the scale 3 and the scale 4 based on the detection signal at the time of the detection.

The operation of the embodiment will be described below. In the detecting section 6 in the present embodiment, an index scale 8 as shown in FIG. 2 is used.
As the detection signals, signals having phases different from each other by 90 degrees are output. For example, the a-phase signal obtained from the scale unit 8a in FIG. 2 and the b-phase signal obtained from the scale unit 8b are provided so that the phases are different by P / 4. Note that P is the interval between grid lines. If the scales 3 and 4 are arranged accurately, the a-phase and b-phase signals should be signals having a phase difference of 90 degrees. For example, if the index portions 8a and 8b face the same scale, the phase difference between the a-phase and b-phase signals will be approximately 90 degrees. The same applies to the relationship between the c-phase signal obtained from the scale unit 8c and the D-phase signal obtained from the scale unit 8d.

Therefore, in the present embodiment, the detection unit 6 is disposed at a joint between the scale 3 and the scale 4.
That is, the scale portion 8a and the scale portion 8b are arranged at positions that straddle the joint. Thereby, signals from different scales 3 and 4 can be detected simultaneously. The accuracy of scale alignment is determined based on the a-phase and b-phase signals obtained simultaneously when the detection unit 6 is placed and displaced as described above. For example, the phase difference between the a-phase and b-phase signals obtained when the slider is relatively displaced is obtained,
This value is converted to the scale positioning accuracy and output. Then, the data is transferred to an external numerical control device or display device. As an example of the phase difference, for example, when the signal period of the detection signal is
If the phase difference between the a-phase signal and the b-phase signal is 150 degrees at 100 μm, then 16.67 μm [= (150−90) / 360 * 100
], The scale 4 may be finely moved by the adjusting unit 5. Then, finally, adjustment may be made so that this value becomes a phase difference of 90 degrees. Here, the phase difference between the signals obtained from the a-phase and the b-phase should ideally be 90 degrees, but may include an error due to a scale error of the index scale 8 or the like. Then, in a state where the a phase and the b phase of the index scale 8 face the same scale, the phase difference between the a phase and the b phase of the index scale, specifically, the phase difference between the scale portions 8b and 8d is measured, and this is set to the target value. It may be.

The output value may be in the form of a phase difference or in the form of position data. Further, it may be in the form of an error or in the form of a fine movement instruction value. Further, it may be output together with the position data.

When the adjustment is completed, the adjustment unit 5
May be removed after fixing.

The phase difference between the signals may be detected by performing a Fourier transform on each signal or from the positional relationship between the zero-cross point and the peak point of the signal. Further, the phase difference of the signal can be obtained by various other methods, and the present invention is not limited to this.

As another means for judging the accuracy of the alignment of the scale, a detection signal of the phase when the index scale for the phase at the joint between the scale 3 and the scale 4 is arranged in the scale position detecting section 7 is provided. May be determined from the contrast. For example, a
Arrange the center of the index scale for the phase so that it is exactly at the joint of the scale. The scale position detection unit 7 determines the accuracy of the scale positioning based on the contrast of the a-phase signal when the slider 2 is displaced.

Here, the contrast is obtained by the following equation.

Cont = (Imax-Imin) / (Imax + Imin) = Amp / 2ofs, because Amp = Imax-Imin ofs = (Imax + Imin) / 2 cont: contrast Amp: amplitude ofs: offset Here, the value of the contrast is Adjustment unit 5 to maximize
The adjustment should be made with. This is because if the two scales 3 and 4 are precisely aligned, the intensity distribution of light incident on the a-phase index scale is uniform, but if the alignment is incorrect, for example, This method utilizes the fact that when an alignment error near P / 2 is included, the intensity distribution of incident light is not uniform and the contrast is reduced. At this time, as a guide of the maximum value of the contrast, the contrast of the signal obtained at the position where the a-phase is not a joint may be used, or the contrast of the signal of another non-seamless phase when the a-phase is at the joint may be used. Good to use. The scale position detection unit 7 may output a contrast value to the outside, or may output a difference from a target value of the contrast.

FIGS. 3 and 4 are block diagrams showing another embodiment of the present invention, in which at least two sliders 1 are provided.
0, a slider unit 9 having a slider 11. In the above embodiment, 1 is used as the slider means.
Although only one slider is provided, two sets of sliders 10 and 11 are used in the present embodiment. Slider 10
And the slider 11 are fixed at a predetermined interval. The configuration of the main scale unit 1 is the same as in the above-described embodiment. Further, each slider unit 9 has a scale position detecting section 7. The scale position detection unit 7
Each position data when both the sliders 10 and 11 face one scale as shown in FIG. 3 and the sliders 10 and 11 straddle the joint of the scale as shown in FIG. The phase relationship between the scale 3 and the scale 4 is detected based on the relationship with the position data when placed at such a position.

The position data obtained by the detector 6 can detect an absolute position within the range of the grid period P of the main scale. For example, when the lattice period P is 100 μm, the position data obtained by the slider 10 is PosA, and the position data obtained by the slider 11 is PosB. Here, both sliders 10, 11 are on one scale, for example FIG.
As shown in the figure, when it is opposed to the scale 3, the amount of deviation from a certain reference position set for each is PosA
Assume that 10 μm and PosB are 30 μm. This relationship needs to be maintained even when the slider 10 and the slider 11 are placed at positions where the sliders straddle the joints of the scales 3 and 4. In this case, precise alignment of the scale is performed. Will be. Here, PosA is 10μ when it is placed at a position that straddles the joint.
Assuming that m and PosB are 70 μm, the phase alignment error of the scale is 40 μm. The scale position detection unit 7 can detect a positioning error, that is, a displacement amount from these relationships. Then, the adjusting section 5 may finely move the scale 4 by 40 μm based on this value. In this way, adjustment is made so that the relationship between the two becomes equal. In this case, unlike the above-described embodiment, there is an advantage that the accuracy of the alignment of the scales 3 and 4 can be measured and adjusted without performing the work of finely adjusting the positions of the slider 2 and the scale 4 by relative displacement. Have.

In the embodiments described above, the positioning accuracy of the scale obtained by the scale position detecting section 7 or the instruction value of the fine movement is not directly fed back to the adjusting section 5, but is electrically operated. Feedback may be made to the adjustment unit. The adjustment unit may include a motor, or may include a fine movement mechanism using a piezoelectric element or the like.

The scale position detecting section 7 may be provided in a slider or in an external circuit or the like.

The present invention is applicable not only to an optical encoder but also to a magnetic encoder, a capacitive encoder, and an electromagnetic encoder.

As described above, according to the present embodiment, no special setup or device is required on the machine equipped with the displacement detecting device, and there is no need to open the scale unit. The performance can be improved, and the cost can be reduced.

Further, since the position error can be quantified, it is possible to perform the position adjustment of the scale without relying on human perception. Therefore, since the positioning of the scale can be realized with high accuracy, the accuracy of the long displacement detection device can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of a method for adjusting a long scale for a linear encoder according to the present invention.

FIG. 2 is a diagram of an index scale according to a first embodiment in a method for adjusting a long scale for a linear encoder according to the present invention.

FIG. 3 is a block diagram before adjustment of a second embodiment of the method for adjusting a long scale for a linear encoder according to the present invention.

FIG. 4 is a block diagram during adjustment of a second embodiment of the method for adjusting a long scale for a linear encoder according to the present invention.

[Explanation of symbols]

1 Main scale unit, 2, 10, 11 slider, 3, 4 scale, 5 adjustment unit, 6 detection unit, 7
Scale position detector, 8 index scale, 8
a, 8b, 8c, 8d Scale part, 9 slider unit.

Continuation of front page (56) References JP-A-3-18709 (JP, A) JP-A-1-162114 (JP, A) JP-A-48-42761 (JP, A) JP-A-58-70129 (JP) , A) JP-A-6-137899 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 21/00-21/32 G01B 7/00-7/34 102 G01B 11 / 00-11/30 102 G01D 5/00-5/62

Claims (4)

(57) [Claims] 1. A displacement detecting device comprising: a plurality of scales forming one long scale by juxtaposing them; and a slider means for detecting a relative position between the plurality of scales. Scale position detecting means for calculating a relative position of each scale based on a signal from each scale at a position where a signal from the scale can be obtained at the same time, and detecting a displacement to be adjusted of the plurality of scales. A displacement detection device characterized by the above-mentioned. 2. The displacement detecting device according to claim 1, wherein the scale position detecting means calculates a relative position of each scale based on a phase difference of a signal to be output with a predetermined phase difference. Displacement detector. 3. The displacement detecting device according to claim 1, wherein said slider means has at least two of said position detecting means, and said scale position detecting means is based on a signal detected by each of said position detecting means. A displacement detection device for calculating a relative position of each scale. 4. The displacement detecting device according to claim 3, wherein the scale position detecting means is configured to calculate a shift amount from a reference position calculated based on a signal detected from the same scale by each of the position detecting means; A displacement detecting apparatus, wherein a relative position of each scale is calculated based on a shift amount from a reference position calculated based on signals detected from different scales by the position detecting means.