JP4291564B2 - Displacement measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical encoder, a magnetic encoder, a capacitance encoder, an electromagnetic induction encoder, a displacement measuring device such as an encoder combining these methods, and more particularly to a displacement measuring device with reduced variation in origin position detection. .
[0002]
In a displacement measuring device for measuring the relative movement of the object to be measured, especially an incremental type encoder, an origin detection pattern for detecting the origin is formed on the main scale and the index scale opposite to the main scale. In addition, when the power is turned on or at an arbitrary time, the origin detection pattern is detected, and the origin detection signal is used as a trigger signal to perform zero setting or presetting. In addition, for example, in an analog output type scale, a displacement measuring device is also known in which the phase of the main signal can be adjusted so that the output timing of the origin detection signal falls within a specific phase area of the main signal for measurement. (Patent Document 1). That is, the one disclosed in Patent Document 1 is that a specific phase region of the main signal, for example, when the main signal is a two-phase output signal, both the A phase and the B phase advanced by 90 ° from this phase. The phase of the main signal is switched so that the origin detection signal is output in the positive phase region.
[0003]
[Patent Document 1]
JP 2002-1116060 A (paragraph 0026, FIG. 1)
[0004]
[Problems to be solved by the invention]
However, in the conventional displacement measuring apparatus described above, although the specific phase region of the main signal and the output timing of the origin detection signal are synchronized, the output timing of the origin detection signal is within the specific phase region of the main signal. May vary. The following causes can be cited as causes of such variations.
[0005]
(1) Influence of relative variation between the detector and the scale resulting from the inclusion of undesirable behavior such as moire, gap fluctuation, rolling, and pitching in addition to the movement of the scale during movement.
(2) Influence of speed variation when passing through the origin detection pattern due to delay in the signal processing system.
(3) Influence of noise included in the analog source signal for generating the detection signal of the origin detection pattern.
[0006]
When such variation in the output timing of the origin detection signal occurs, the obtained instruction value (measured value) differs every time the origin is detected. In particular, in a displacement measuring device that divides the main signal into high resolutions to make the minimum reading finer to enable fine measurement, variation in the output timing of the origin detection signal leads to variation in the indicated value for several counts. The accuracy will be greatly affected.
[0007]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a displacement measuring device that can suppress variations in the origin detection position and can always obtain accurate measurement values.
[0008]
[Means for Solving the Problems]
The displacement measuring apparatus according to the present invention includes a main scale on which a first displacement detection pattern extending in the measurement axis direction and a first origin detection pattern for detecting an origin position in the measurement axis direction are formed; The second displacement detection pattern and the second displacement detection pattern are arranged at positions corresponding to the first displacement detection pattern and the first origin detection pattern, respectively, so as to be movable relative to the main scale in the measurement axis direction. Changes in relative positions in the measurement axis direction of the index scale on which the second origin detection pattern is formed, the first displacement detection pattern of the main scale, and the second displacement detection pattern of the index scale. A main signal output circuit that outputs a main signal whose phase changes in response to the main scale, a first origin detection pattern of the main scale, and the index scale. And internal origin signal output circuit for outputting the internal origin signal in response to the opposite state between the second reference point detection pattern of the external origin signal output circuit indicates that the main signal becomes the predetermined phase An external origin signal output circuit that generates a phase signal and outputs the phase signal that rises after a predetermined margin that absorbs variations in the output timing of the internal origin signal after the internal origin signal is output as an external origin signal The external origin signal output circuit further comprises switching means for switching the phase of the output phase signal to a predetermined phase by an external operation .
[0009]
According to the present invention, the origin signal output according to the opposed state of the first origin detection pattern of the main scale and the second origin detection pattern of the index scale is used as the internal origin signal, and this internal origin signal is An external origin signal is output as an origin signal that serves as a measurement reference at a timing when the main signal has a prescribed phase after a predetermined margin that absorbs variations in the output timing of the internal origin signal after being output. Therefore, even if the output timing of the internal origin signal output by the origin detection pattern varies, the output timing of the origin signal, which is the reference for measurement, does not vary with respect to the main signal, and always provides highly accurate displacement measurement. Is possible. Also,
The external origin signal output circuit further includes switching means for switching the phase of the output phase signal by an operation from the outside, thereby taking into account variations in the output timing of the internal origin signal, The most appropriate phase can be selected.
[0010]
External origin signal output circuit has a gate output of the phase signal internal origin signal is outputted immediately after the output from the field in the portion origin signal output circuit even outputs a gate signal which becomes active only until completed a signal output circuit, the gate signal output of the phase device signals is able to configure a gate circuit to pass only during active.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an embodiment in which a displacement measuring apparatus according to the present invention is applied to an optical encoder, and is a perspective view showing a configuration of a detection system in particular.
As shown in FIG. 1, the detection system of the optical encoder includes a main scale 11 extending in the measurement axis A direction, and opposed to the main scale 11 via a minute gap. The index scale 12 is relatively movable, and the light emitting element 10 and the light receiving portions 13 and 14 are disposed to face each other with the main scale 11 and the index scale 12 interposed therebetween.
[0012]
The main scale 11 includes a first optical grating 11G extending in the measurement axis A direction for detecting a movement amount in the measurement axis A direction on the glass scale, and a first origin detection optical grating for detecting the origin position. 11Z is formed as a pattern.
The index scale 12 can form the second optical gratings 12A, 12B, 12A ′, and 12B ′ on the surface of the glass scale that faces the first optical grating 11G, and can face the first origin detection optical grating 11Z. A second origin detection optical grating 12Z is formed on the surface.
[0013]
The first optical grating 11 and the second optical gratings 12A, 12B, 12A ′, 12B ′ all have a grating pitch p. The second optical gratings 12A, 12B, 12A ′, and 12B ′ are respectively formed in a phase relationship such that the spatial phase with the first optical grating 11 is shifted by 90 ° from each other.
[0014]
The light receiving unit 13 includes four light receiving elements 13A, 13B, 13A ′, and 13B ′. These four light receiving elements 13A, 13B, 13A ′, and 13B ′ are disposed at positions facing the optical gratings 12A, 12B, 12A ′, and 12B ′, respectively. As the main scale 11 and the index scale 12 move relative to each other in the direction of the measurement axis A, the light receiving elements 13A, 13B, 13A ′, and 13B ′ receive light whose brightness changes with the same period as the grating pitch p. Is done. As a result, the light receiving elements 13A and 13B output sinusoidal detection signals A and B having a phase difference of 90 ° from each other. Similarly, the light receiving elements 13A ′ and 13B ′ output sinusoidal detection signals −A and −B having 90 ° phases different from each other. The detection signals A and -A and the detection signals B and -B are signals that are 180 degrees out of phase with each other.
[0015]
The light receiving unit 14 is for detecting an origin position defined by the origin detection optical gratings 11Z and 12Z, and is configured by a random pattern. As a result, as shown in FIG. 4, for example, an original origin signal φZ that sharply falls at a position where the main scale 11 and the index scale 12 are relatively moved and the origin detection optical gratings 11Z and 12Z completely overlap each other is obtained.
[0016]
FIG. 2 shows a signal processing circuit 20 that processes the detection signals A, -A, B, -B and the origin original signal φZ from the light receiving units 13, 14 of such a detection system. The signal processing circuit 20 includes a synthesis circuit 21, an interpolation / division circuit 22, an internal origin signal generation circuit 23, a gate signal output circuit 24, and a phase designation circuit 25.
[0017]
The synthesizing circuit 21 constitutes a main signal output circuit. In order to remove in-phase noise, the synthesizing circuit 21 synthesizes the detection signals A and -A having different phases by 180 ° to synthesize an A phase signal φA (as shown in FIG. Main signal) and detection signals B and -B having different phases by 180 ° are combined to generate a B-phase signal φB (main signal) as shown in FIG.
[0018]
The interpolation division circuit 22 outputs a square wave signal obtained by dividing a period of the A phase signal φA and the B phase signal φB by a predetermined number. Here, two-phase square wave signals D _100A and D _100B obtained by dividing the periods of the A-phase signal φA and the B-phase signal φB by 100, respectively, and a square-wave signal D _{2 obtained} by dividing the period of the A-phase signal φA by _two (FIG. 3 (c )) And a square wave signal D ₄ (see FIG. 3 (d)) obtained by dividing the period of the A-phase signal φA by four.
[0019]
Here, the 2-division and 4-division are examples, and for example, a combination of 2-division and 5-division signals is also possible. In short, a low-division signal having the same period as that of the A-phase signal φA and B-phase signal φB, and a two-phase square wave signal (D _100A , D _100B, etc.) And a division signal (medium division signal) having an intermediate division number.
The two-phase square wave signals D _100A and D _100B are output to a counter circuit (not shown), and the movement amount of the main scale 11 is output from the counter circuit.
[0020]
As shown in FIG. 4, the internal origin signal generation circuit 23 slices the original origin signal φZ at a predetermined reference level and outputs a pulsed internal origin signal Zi as shown in FIG. The internal origin signal Zi has a variation in the appearance position due to the various factors described above, as indicated by arrows and dotted lines in FIG.
[0021]
The gate signal output circuit 24 outputs a gate signal G. As shown in FIG. 3F, the gate signal output circuit 24 detects the rise of the internal origin signal Zi, raises the gate signal G, and sets the square wave signal D ₄ . The gate signal G is caused to fall with the down signal as a release signal R.
[0022]
The phase specifying circuit 25 performs a logical operation on the plurality of square wave signals D ₂ and D ₄ to generate a phase signal output at a specific phase timing of the A-phase signal φA that is the main signal, and gates this phase signal. An external origin signal output circuit that outputs an external origin signal in response to the signal G is configured. One of the square wave signal D ₂ and a signal obtained by inverting the square wave signal D ₂ by the inverter INV 1 is selected by the switch SW 1, and the selected output signal D ₂ ′ is supplied to the AND circuit 26. Similarly, one of the square wave signal D ₄ and a signal obtained by inverting the square wave signal D ₄ by the inverter INV 2 is selected by the switch SW 2, and the selected output signal D ₄ ′ is supplied to the AND circuit 26. The AND circuit 26 ANDs the output signals D ₂ ′ and D ₄ ′ and outputs the result to the gate circuit 27. This is shown in FIGS. 3C to 3E. The phase signal output from the AND circuit 26 is changed by switching the switches SW1 and SW2 and changing the combination of the 2-divided and 4-divided square wave signals D ₂ and D _{4 applied} to the AND circuit 26 and their inverted signals. The phase can be switched as appropriate. Here, the switches SW1 and SW2 constitute switching means, and the inverters INV1 and INV2, the switches SW1 and SW2 and the AND circuit 26 constitute a phase signal output circuit. The gate signal output circuit 24 and the phase specifying circuit 25 constitute an external origin signal output circuit.
[0023]
The switches SW1 and SW2 are switched appropriately by the user in consideration of the appearance position and variation of the internal origin signal Zi shown in FIG. For example by switches SW1, SW2, as shown in FIG. 5, the logical product of the inverted signal and the non-inverted signal of the square wave signal D ₄ of the square wave signal _{D 2 (-D 2 AND D 4} ) and, both square wave D ₂ , D ₄ non-inverted signals and the logical product (D ₂ AND D ₄ ) can be appropriately selected as the output (phase signal) of the AND circuit 26.
[0024]
However, when the rising edge of the internal origin signal Zi is at the position shown in FIG. 5, if the logical product signal (−D ₂ AND D ₄ ) is selected as the phase signal, the internal origin signal Zi indicated by the dotted line in the figure The external origin signal Zo appears at the position 31 in the figure or appears at the position 32 due to variations in the appearance position, so that an error corresponding to one cycle of the A-phase signal φA or the B-phase signal φB that is the main signal. Will occur. Accordingly, a logical product signal (D ₂ AND D ₄ ) that rises after a predetermined margin (for example, a distance between AB) from the rising edge of the internal origin signal Zi after absorbing a variation in the position is selected as a phase signal. It is necessary to switch the switches SW1 and SW2.
[0025]
The selection of the switches SW1 and SW2 can be performed manually at the time of shipment adjustment. However, the time between the appearance position of the internal origin signal Zi and the appearance position of each phase signal is measured during the initialization process. The phase signal that rises earliest at a predetermined margin or more may be automatically selected by a control means that is programmed to select the optimum phase signal.
[0026]
The gate circuit 27 uses the phase signal output from the AND circuit 25 after the gate signal G (see FIG. 3F) from the gate signal output circuit 24 rises as the external origin signal Zo (see FIG. 3G). While outputting to the outside, the next falling of the phase signal from the AND circuit 26 is detected, and the release signal R is output to the gate signal output circuit 24. When receiving the release signal R, the gate signal output circuit 24 stops the output of the gate signal G and releases the latch of the internal origin signal Zi. As a result, the output of the external origin signal Zo is output only once with one output of the internal origin signal Zi.
[0027]
Next, the operation of the optical encoder configured as described above will be described.
First, in order to perform zero setting or presetting, the relative position of the main scale 11 and the index scale 12 is moved in the predetermined direction after the relative position of the main scale 11 and the index scale 12 is moved to the initial position (home position). Let In this process, the positions of the first origin detection optical grating 11Z formed on the main scale 11 and the second origin detection optical grating 12Z formed on the index scale 12 coincide with each other. 14 outputs an original origin signal φZ. As a result, the internal origin signal generation circuit 23 outputs the internal origin signal Zi. Since the internal origin signal Zi is latched by the gate signal output circuit 24, the gate signal G rises.
[0028]
Now, assuming that the phase relationship between the internal origin signal Zi and the main signal is as shown in FIG. 3, after the rising of the internal origin signal Zi, the phase of the 270 ° phase of the A phase signal φA, which is the main signal, is increased. The external origin signal Zo is output at the timing. The counting circuit (not shown) is reset or preset by the external origin signal Zo, and the counting circuit counts the 100-divided outputs D _100A and D _100B from the interpolation dividing circuit 22, thereby measuring the displacement of the object to be measured. Since the output timing of the external origin signal Zo does not deviate from the main signal, accurate measurement with the same position as the origin is always possible.
[0029]
In the above-described embodiment, the present invention has been described by taking an optical encoder as an example. However, the origin detection method as in the present invention is not particularly limited to an optical encoder, and a magnetic encoder, electrostatic The present invention can be similarly applied to displacement detection devices of other detection methods such as a capacitive encoder and an electromagnetic induction encoder.
[0030]
【The invention's effect】
As described above, according to the displacement measuring apparatus of the present invention, the origin signal output according to the facing state of the first origin detection pattern of the main scale and the second origin detection pattern of the index scale. Is used as the internal origin signal, and after the internal origin signal is output, the external origin signal is measured at the timing when the main signal becomes a predetermined phase after passing through a predetermined margin that absorbs variations in the output timing of the internal origin signal. Since it is output as a reference origin signal, even if the output timing of the internal origin signal output by the origin detection pattern varies, the output timing of the origin signal as the measurement reference is Dispersion does not occur, and highly accurate displacement measurement is always possible.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of an optical encoder according to an embodiment of the present invention.
2 shows a configuration of a signal processing circuit 20 that processes detection signals from the light receiving units 13 and 14 shown in FIG.
FIG. 3 is a timing chart showing signals input to the signal processing circuit 20 or generated by the signal processing circuit 20;
4 is a conceptual diagram for explaining processing of a detection signal of a light receiving unit 14 shown in FIG.
5 is a diagram for explaining a method for selecting an output signal of an AND circuit 26 shown in FIG. 2; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Light emitting element, 11 ... Main scale, 11G ... 1st optical grating, 11Z ... 1st origin detection optical grating, 12 ... Index scale, 12A, 12B, 12A ', 12B' ... 2nd optical grating, 12Z... Second origin detecting optical grating, 13, 14... Light receiving portion, 13A, 13B, 13A ', 13B'... Light receiving element, 20 ... Signal processing circuit, 21 ... Synthesis circuit, 22 ... Interpolation division circuit, 23 ... internal origin signal generation circuit, 24 ... gate signal output circuit, 25 ... phase designation circuit, 26 ... AND circuit, 27 ... gate circuit.

Claims (4)

A main scale formed with a first displacement detection pattern extending in the measurement axis direction and a first origin detection pattern for detecting the origin position in the measurement axis direction;
The second displacement detection pattern and the second displacement detection pattern are arranged at positions corresponding to the first displacement detection pattern and the first origin detection pattern, respectively, so as to be movable relative to the main scale in the measurement axis direction. An index scale on which a second origin detection pattern is formed;
A main signal output circuit that outputs a main signal whose phase changes according to a change in the relative position in the measurement axis direction between the first displacement detection pattern of the main scale and the second displacement detection pattern of the index scale. When,
An internal origin signal output circuit that outputs an internal origin signal in accordance with the opposing state of the first origin detection pattern of the main scale and the second origin detection pattern of the index scale;
Generating a phase signal indicating that the main signal has reached the predetermined phase, and rising after passing through a predetermined margin for absorbing variations in output timing of the internal origin signal after the internal origin signal is output; An external origin signal output circuit that outputs the phase signal as an external origin signal;
With
The displacement measuring apparatus, wherein the external origin signal output circuit further comprises switching means for switching the phase of the output phase signal to a predetermined phase by an external operation . The external origin signal output circuit is
A gate signal output circuit for outputting a gate signal which becomes active only until the output of the phase signal internal origin signal is outputted immediately after from the output ends before SL internal origin signal output circuit,
The displacement measuring apparatus according to claim 1, further comprising: a gate circuit that passes the output of the phase signal only while the gate signal is active. Displacement measuring apparatus according to claim 1 or 2, characterized in, further comprising the interpolation division circuit among which outputs a divided signal for displacement measurement the main signal was further subdividing.   The interpolation division circuit is configured to output a first signal obtained by dividing the main signal by m and a second signal (m ≠ n) obtained by dividing the main signal by n. The number is smaller than the number of divisions of the divided signal for displacement
  The displacement measuring apparatus according to claim 3, wherein the phase signal is obtained by performing a logical operation on the first signal and the second signal.

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