JP2000055647A - Scale device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a detection never causing a discontinuation of detection signal or detection error in the joint part of a scale by providing the other detector for outputting a signal when a detector gets into the joint section of the scale. SOLUTION: A long scale B1 is formed by connecting a plurality of short scales. The output of a first detector B4 is connected to a first detecting circuit B7, and the output of a second detector B5 to a second detecting circuit B8. An output selecting circuit B10 selects the output of the first detecting circuit B7 when it is satisfactory, and selects and outputs the output form the second detecting circuit B8 when the output of the first detecting circuit B7 is deteriorated. Namely, the selecting circuit B10 synchronously operates with the output of a third detector B6 to avoid the pulse signal formed by the signal in the joint part of the scale B1, so that a pulse signal that is not the joint part of the scale B1 is regularly outputted. When the first detector B7 detects the defective section of a scale grid, the third detector B6 outputs a signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scale device used for detecting a position (relative position detection) of a linear or rotational movement in a machine tool, an industrial machine, or the like.

[0002]

2. Description of the Related Art A scale device using a long scale and a detection head is used to measure the displacement of a moving body. In this type of apparatus, a scale is attached to one of a movable body and a fixed position, and a detection head is attached to the other. When the movable body moves, a relative displacement between the movable body and the fixed position is measured.

In the above-mentioned scale apparatus, when the moving range of the moving body becomes large, it is necessary to lengthen the scale. However, manufacturing a long scale with one scale with high accuracy not only increases the manufacturing cost but also increases the manufacturing cost. It is disadvantageous in that it requires a large space for storage and transportation after production, and requires much time for installation. Therefore, it has been considered that a plurality of short scales are manufactured, arranged in a straight line, and used like a single long scale.

As an apparatus for detecting a displacement amount over a long distance using a plurality of short scales, for example, Japanese Patent No. 26481
There is a linear encoder described in JP-A-81. This encoder arranges main scales 1a and 1b along the moving direction of the table 3 as shown in FIG.
When the table 3 is moved in the longitudinal direction of the scale by the drive shaft 5, the sliders 2a and 2b
The output signal S1 obtained by reading the scales 1a and 1b by a and the output signal S2 obtained by reading the scales 1a and 1b by the slider 2b are sent to the signal processing section 40.
1 and S2 are connected and output to P _OSD .

[0005] The device (encoder) reads the read signal.
In order to switch and output the signals S1 and S2, the slider 2
Slider position data indicating where a and 2b are now
TA P _SLDAnd transmit it to the signal processor 40.
One of the signals S1 and S2 according to the slider position.
Select and output circuit, signal S1 and signal S2 are continuous
Requires a circuit to add an offset value, etc.
And operation is complicated.

[0006]

SUMMARY OF THE INVENTION The present invention provides a scale device which does not need to detect the position of a slider (detector) as in the above-described encoder. When a long scale is formed and read by a plurality of detectors, and one detector passes through the joint of the scale and its output decreases, the output of another detector that is reading a place other than the joint is used. The present invention provides a scale device in which the output is switched in order to select and output the output.

[0007] The applicant of the present application has previously filed an application for an invention of a scale device based on the above idea. (Japanese Patent Application No. 9-46
253, Japanese Patent Application No. 9-124066), in the scale devices of these applications, the output switching detects a deterioration of a read signal generated at a scale connecting portion and operates an output selection circuit based on the detected output. I'm going to let you go. For this reason, the output is switched after the output of the detector has deteriorated, which may affect the output.

[0008] The following describes how the phase modulated wave obtained when the detector detects the scale grating is described below. A phase modulated wave having no signal disturbance can be expressed by the following equation (1). Here, in the above equation, ω is an angular frequency, t is time, λ is a scale wavelength, x is a movement amount, X is a phase change, and T = ω
Let t, X = 2πx / λ.

A phase-modulated wave including signal disturbance can be expressed by the following equation (5). Where a is the first detection circuit ch
1 is the difference between the amplitude of the output of the second detection circuit ch2. Here, S and A are represented by S = {a ² [(1−cos 2X) / 2] + [(1−cos 2X) / 2]} ^1/2 ‥‥ (3) A = tan ⁻¹ (cos X / asin X) ‥‥ (4), the above equation (2) becomes as follows. f (aXT) = S · sin (T + A) ‥‥ (5)

As is apparent from the above equation (5), when two detectors are used and a signal processing circuit is provided for each of the two detectors, signal processing between the two channel signals is performed. Has an amplitude difference, the effect appears on the amplitude portion S and the phase portion A of the phase modulated wave. When there is no amplitude difference between the signals of the two channels, the phase is X as shown in equation (1). When the phase portion A of the equation (5) is subtracted from the phase X, the equation becomes as shown in the equation (6). When interpolating, it appears as an interpolation error. Δx = A−X (6) A = X + Δx

In the scale device according to the above-mentioned application, since the output is switched by the detected output after detecting a decrease in the amplitude level of the detected phase modulation wave, the phase modulation wave before switching and the phase modulation wave after switching are switched. Since an amplitude difference occurs with the wave, an interpolation error is included at the time of switching.

In general, this type of device detects a plurality of gratings as a scale device so as to increase the averaging effect in order to perform high-precision detection. When detecting while moving, the output requires a plurality of gratings to decrease, and the phase-modulated wave has two channels at different positions. When the condition that the output of the other channel does not decrease is satisfied, as can be understood from Expression (3), there are two times for each detection of one grid.

Switching between the output of the first detection circuit and the output of the second detection circuit occurs a plurality of times until the output of both channels drops. When both channels return, the same problem occurs in reverse, and a plurality of switching between the output of the first detection circuit and the output of the second detection circuit occurs. Then, an interpolation error occurs in that part, and the accumulation accuracy is deteriorated.

The present invention overcomes the above-mentioned drawbacks of the conventional scale device and forms a long scale by connecting a plurality of short scales. When the long scale is read by the detector, the detector is connected to the connecting portion of the scale. It is an object of the present invention to provide a scale device that can perform detection without causing discontinuity of a detection signal or detection error.

[0015]

In order to solve the above-mentioned problems, a scale device of the present invention connects a plurality of scales each having a scale formed at a predetermined wavelength, reads the scales, and outputs a phase-modulated wave. A scale having first and second detectors, and a detection circuit that performs signal processing on outputs of the first and second detectors based on a clock pulse and outputs a pulse signal indicating a moving direction and a moving amount of the device under test. In the apparatus, the first
A third detector that operates when the detector detects a scale joint, and a selection circuit that operates in synchronization with the clock pulse by using the output of the third detector, and a pulse generated by a signal in the scale joint. A signal is avoided so that a pulse signal which is not always a connecting portion of the scale is output.

That is, in the scale device of the present invention, a third detector is provided in parallel with the first detector, and the third detector operates when the first detector detects a section where the scale grid is missing. Then, by switching the signal of the first detector and the signal of the second detector with the operation signal, only the normal part of the detection signal is output, so that a plurality of switchings occur and the interpolation error is reduced. The above problem was solved by not using the increased signal. [Operation] Since a pulse signal including an interpolation error can be avoided in the unbalanced signal generated at the connecting portion of the scale, a high-quality pulse is processed because a normal signal is processed by a detection circuit including a selection circuit over the entire scale. A highly accurate scale device that outputs a signal can be obtained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a scale device according to the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, the present scale device connects a plurality of relatively short scales to form a long scale B1, and connects this scale B1 to a first detector B4, a second detector B5, and a third detector B6. It is configured to read using an integrally formed detector assembly.

The output of the first detector B4 is a first detection circuit B7
And the output of the second detector B5 is connected to a second detection circuit B8. The clock pulse signal supplied to the first detection circuit B7 and the second detection circuit B8 is supplied from a clock oscillator B9 provided commonly to these detection circuits.

The output of the first detection circuit B7 and the second detection circuit B
The output of 8 is connected to an output selection circuit B10. The output selection circuit B10 selects the output of the first detection circuit B7 when the output is good, and selects the second output when the output of the first detection circuit B7 is deteriorated.
This circuit selects and outputs the output from the detection circuit B8.

As shown in FIG. 1, an UP / DOWN signal output from the first detection circuit B7 and an UP / DOWN signal output from the second detection circuit B8 are input to the input of the output selection circuit B10. Signal b from one detection circuit is input. The output signal i of the third detector B6 is input to the input of the output selection circuit B10.

The signal detected by the first detector B4 is processed by the first detection circuit B7, and the signal detected by the second detector B5 is processed by the second detection circuit B8 to determine the moving direction and the moving amount, respectively. Create up / down pulse signals to represent. The first detection circuit B7 and the second detection circuit B8 have substantially the same circuit configuration, and an example is shown in FIG. FIG. 3 shows an operation waveform diagram of each part of the circuit of FIG.

FIG. 2 shows the first detection circuit B7 (see FIG. 1). The second detection circuit B8 is the same as the first detection circuit except that it has no output b. In the circuit shown in the figure, an output signal U1 of the first detector B4 is input to an input D1. This circuit converts this signal U1 into a phase modulation signal K (X) by a phase modulation signal shaper D3 and sends it to a waveform shaper D4, where it produces an S signal synchronized with the clock signal mf sent from the input D2. . Here, the phase modulation signal K (X) is represented by the following equation. f (xt) = sin {ωt + 2πx / λ} The clock signal and the S signal are as shown in FIG.

The waveform shaper D4 shapes the phase modulation signal K (X) to produce a rectangular wave S signal as shown in FIG. 3, and sends this S signal to the command signal shaper D5. The command signal shaper D5 generates the signals a, b and c shown in FIG. 3 from the clock signal mf sent from the clock oscillator B9 to the input D2 and the S signal. The signal a gives a load command to the counter D6, and the signal b gives an enable signal to the counter D6. This signal b is sent through an output D10 to an output selection circuit B10 as described above and below. When this circuit (the circuit in FIG. 2) is the second detection circuit, the signal b is not sent to the outside.

Here, as an example, it is assumed that the number to be interpolated is 10. In that case, one cycle of the basic phase modulation signal is:
If the frequency is f and the period is L, ωt = 2πft, L =
From the relation of 1 / f, the clock frequency mf when interpolating by 10 is 10 times the fundamental frequency f of the phase modulation signal.

The data of the set value set in the counter D6 is determined according to the following rules. In general, n digits 2
The number obtained by adding the base X and the two's complement of the number (X) is n + 1 digits. For example, "1" which represents 10 in a decimal number in a binary number
When "010" and its two's complement "0110" are added, 1010 + 0110 = 10000 is obtained, which is a 5-digit number, and the lower four digits are "0".

At the time when the counter D6 in FIG. 2 starts counting, the low level "L" of the enable signal represented by the signal b in FIG.
As can be seen from the start of the period, the count is advanced by three counts from the load command by the signal a. Therefore, the actual counting period of the counting period of the counter D6 is 10−3 = 7. Therefore, if the decimal number 7 is represented by a binary number, "011
1 ”, the two's complement is“ 1001 ”,
The sum of them is 0111 + 1001 = 10000, which is a 5-digit number like the above, and the lower 4 digits are 0.
Therefore, the decimal value 7 is represented by a binary number, and “1001” which is its two's complement is set as the set value.

The counter D6 shown in FIG. 2 is enabled by the signal b sent from the command signal shaper D5.
The clock pulse is measured for each cycle of the S signal having the information of the phase modulation signal shown in (1) and the data is output.

The reversible counter D7 of FIG. 2 receives the signal c shown in FIG. 3 from the command signal shaper D5, enters a load state when the signal c is at a low level "L", and the output of the counter D6 is loaded. This reversible counter D7 is composed of a 4-bit reversible binary counter, and in addition to the above load input,
It has an UP / DOWN input and an Enable input.

A reversible counter D is input to the Enable signal input.
OR output (OR) output of 4-bit data g
Is applied, and the measurement is stopped at the low level “L” of this output. Further, the negative output f bar of the most significant digit of the 4-bit data of the output of the reversible counter is applied to the UP / DOWN input of the reversible counter. If the output f-bar is low level "L", the content of the reversible counter D7 is counted up, and if the output f-bar is high level "H", the content of the reversible counter D7 is counted down.

The reversible counter D7 shown in FIG.
The signal h sent to the control circuit includes the signal g, the signal f bar, and the signal f. The NOT output of the logical product of the signal g, the signal f, and the clock shown in FIG. The NOT output of the logical product of f and the clock is the output signal DOW.
N is formed.

The UP signal and the DOWN signal depend on the phase modulation signal, and when the relative movement of the scale of the detector is stopped, the UP signal is also output to the output of the output circuit D9.
No N signal also appears. However, when the period of the phase modulation signal is modulated by the relative movement of the scale so as to be longer, a DOWN signal is output to the output of the output circuit D9, and conversely, the modulation is performed so that the period of the phase modulation signal is shorter. If
The output of the output circuit D9 outputs an UP signal. This UP
The number of signals and DOWN signals indicates the amount of movement, and indicates the direction of movement depending on whether the signal is an UP signal or a DOWN signal.

As described above, the circuit of FIG. 2 represents one of the first detection circuit B7 and the second detection circuit B8 of the circuit of FIG. In other words, the first detection circuit B7 and the second detection circuit B8 in FIG. 1 are configured as shown in FIG. Outputs of the first detection circuit and the second detection circuit are guided to an output selection circuit B10.

The output signal UP / DOWN generated by the first detection circuit B7 and the output signal UP / DOWN generated by the second detection circuit B8 are supplied to the input of the output selection circuit B10, respectively. The signal b generated by the detection circuit B7
And the signal i detected by the third detector are applied. This output selection circuit B10 switches from the output of the first detection circuit B7 to the output of the second detection circuit B8 when the third detector detects a signal drop at a connecting portion of the scale or the like, and outputs the UP signal and the D signal.
Outputs an OWN signal output.

The details of the output selection circuit B10 are shown in FIG. As shown in the figure, this circuit has flip-flop circuits FF1 to FF3 connected in three stages, and an input terminal F
1 from the third detector B6 (see FIG. 1)
Based on the output signal b from the first detection circuit B7 input to the input terminal F2 and the UP / DOWN signal from the first detection circuit B7 input to the input terminals F3 and F4, and the input terminal F5.
UP / DOWN from the second detection circuit B8 input to F6
This is a circuit that selects and outputs one of the signals.

The signal i from the third detector B6 is supplied to a preset input P of a first-stage flip-flop (FF1).
R, and the signal b from the first detection circuit B7 is
And the inverted signal thereof is applied to the reset inputs of FF2 and FF3. Here, the signal i from the third detector B6 is a signal represented by a low level “L” during operation as shown in FIG.

When the third detector B6 (see FIG. 1) operates,
When the low level signal shown in FIG. 5 is sent as the signal i, the first stage FF1 is turned on, the Q output changes to low level, and the level is maintained. When the signal b subsequently sent to the input terminal F2 changes to low level, the FF1 is turned off because a low level signal is applied to its clear terminal, and the Q output returns to high level.

At this time, the flip-flop FF2 of the second stage is turned on by the output of FF1, and outputs a low level output to the Q output as shown in FIG. FF2 is then connected to input terminal F2
Is reset when the signal b sent to the low level goes low, and its Q output goes high.

At this time, the flip-flop FF3 of the third stage is turned on by the output Q of FF2, and the Q output becomes low level as shown in FIG. This FF 3 is also reset when the signal b falls next, and the Q output becomes high.

A signal obtained by inverting the output Q of the FF1 via the inverter IV1 is applied to the D input of the FF2, and the signal b at the FF2 (where the signal b is a signal having the same period as the S signal as is clear from FIG. 3). ) Is applied to the D input of FF3, and the signal b is also applied to FF3.
An output Q that is time-shifted by one period is output.

As a result, the three cascaded flip-flops FF1 to FF3 successively change from high level "H" to low level "L", and the AND circuit A5
When the logical product of the output Q of the FF2 and the output Q of the FF3 is formed, as shown in FIG. 5, the period from when the output Q of the FF2 goes low to when the output Q of the FF3 goes high, A low level “L” is output to the output of the AND circuit A5 over two cycles of b.

The output of the AND circuit A5 is
1, and A2 are applied to one input of the AND circuit and used to control whether the UP / DOWN signal from the first detection circuit B7 sent to the other input of the AND circuit is passed or blocked. As described above, when the output of the AND circuit A5 is at a low level, the gate circuit composed of the AND circuits A1 and A2 is closed and does not pass a signal.

At this time, the output of the AND circuit A5 is inverted by the inverter IV3 to become a high level signal "H" as shown in FIG. 5, and is applied to one input of the AND circuits A3 and A4. Therefore, the gate circuit composed of the AND circuits A3 and A4 is opened, and the UP / UP signal from the second detection circuit B8 sent to the other input of the AND circuits A3 and A4 is opened.
The DOWN signal passes through the OR circuit OR1, OR2
Head for.

The output of the AND circuit A1 and the output of the AND circuit A3 are output to the output terminal F7 through the OR circuit OR1, and the output of the AND circuit A2 and the output of the AND circuit A4 are output to the output terminal F8 through the OR circuit OR2. Output, so that the first detector B4 is connected to the connecting portion B of the scale.
3, when the third detector B6 is operating, the UP / DOWN signal of the second detection circuit B8 is output, otherwise, the UP / DOWN signal of the first detection circuit B7 is output. Will be done.

Here, the operation of the third detector will be described. FIG. 6 is a perspective view of the scale and the detector assembly H6 that moves relative to the scale. In the detector assembly H6,
First detector H7, second detector H8, and third detector H9
Is incorporated.

The scale is formed by forming a scale lattice H2 on the scale main body H1 and attached to one of two relatively moving objects by an attachment screw H5. Each scale H1 is configured to be short, and as shown, a plurality of scales are connected to form one long scale. Here, as the scale, a magnetic scale, an optical scale, and various other scales can be used. Detector assembly H
As the first detector H7 and the second detector H8 mounted on 6, a magnetic sensor, an optical sensor, or the like is used according to the scale.

Here, the detector is a detector in which a sensor output of two channels is a balanced modulation wave and adds this to output a phase modulated wave, and a sensor output of two channels is a sine wave and a cosine wave of a scale signal. The modulation circuit modulates this scale signal with a modulation circuit to generate a balanced modulation wave, and adds this balanced modulation wave to output a phase modulated wave. In the above description, the output signal is described as an UP / DOWN signal, but an A / B phase pulse signal having a phase difference of 90 degrees may be output.

The third detector H mounted on the detector assembly H6
Reference numeral 9 denotes a detector provided for detecting a gap at a connecting portion of the scale, which is constituted by, for example, three metal sensors as shown in FIG. Is to be detected.

Here, the configuration and operation of the third detector will be described with reference to FIGS. As shown in FIG. 8, the lack P1 of the scale grid is larger than the non-scaled section P0. On the detector assembly J5, a first detector J2 and a second detector J3 are arranged as shown, and the distance between the first detector J2 and the second detector J3 is longer than the gap of the scale grating. It is arranged by opening. This is because when the detector assembly J5 moves relative to the scale J1, the first detector J
2 and the second detector J3 are at the same time the missing portion P1 of the scale grating.
This is to prevent them from getting inside.

In parallel with the first detector J2, the third detector J4
Is arranged. This third detector has three proximity sensors. These proximity sensors are existing metal detection proximity sensors with a built-in amplifier. The operating area of each sensor is the range indicated by P6. The distance between two adjacent proximity sensors,
That is, the pitch is an interval indicated by P2. The operation area of the first proximity sensor and the third proximity sensor is the detection range P3 of the first detector.
It is slightly more outward.

When the detector assembly J5 moves in the direction indicated by the arrow in FIG. 8, when the first detector J2 encounters a connecting portion of the scale, the proximity sensor 3 at the head detects that there is no scale. 9 goes low (logic 0) as shown at the top. The output of the proximity sensor 3 goes high again (logic 1) when it passes over the gap between the scales and reaches the next scale. Similarly, the proximity sensor 2 outputs a low-level (logic 0) output when it reaches the connecting portion of the scale, and goes to a high level (logic 1) when it passes by. Similarly, when the proximity sensor 1 passes through the connecting portion of the scale, the proximity sensor 1 temporarily goes low (logic 0) and goes high again (logic 1). The point at which the proximity sensors 3, 2, 1 become low level is determined by the pitch P2 between the sensors, and has a waveform shown in FIG. Therefore, when the output signals of these proximity sensors are input to the AND circuit shown in FIG.
A wide rectangular wave is obtained as shown in the lowermost part of the above, and this is defined as the operating range P5 of the third detector J4.

In the present embodiment, the operating section P5 of the third detector needs to be wider than the section obtained by adding the detecting section P3 of the first detector J2 and the missing section P1 of the scale grid. This is because during the period of the output switching signal sent from the third detector J4 to the output selection circuit B10, the period from when the leading end of the first detector J2 enters the scale missing portion to when the rear end escapes the scale missing portion. This is because it is necessary to set the period. To express this concisely using expressions,
Equation (7) below. P5> P1 + P3 ‥‥ (7)

Here, the scale body is composed of a scale medium and a metal (iron) base, and a scale lattice is formed on the scale medium. Therefore, since the scale grid is missing at the end of the scale medium at the connecting portion of the scale body, the missing section P1 of the scale grid is longer than the section P0 where there is no scale body, and the following equation (8) is established. P0 <P1 ‥‥ (8)

The proximity sensor detects the presence or absence of the metal base of the scale main body, and outputs a high-level output “H” when there is metal, and outputs a low-level output “L” when there is no metal at the connecting portion of the scale. . In FIG. 8, the third detector J
The pulse width P4 of the detection output that is output when one proximity sensor of No. 4 passes through the metal-free portion of the scale body is determined by the operating area P6 of the proximity sensor and the length P0 of the section without the scale.
, The following equation (9) holds. P4 = P0 + P6 ‥‥ (9)

As shown in FIG. 9, the output pulse width P4 of this proximity sensor is smaller than the operation range P5 required for the third detector J4. The operation range P5 satisfying the condition 7) cannot be obtained. Therefore, as shown in FIG. 8, three proximity sensors indicated by small circles as the third detector J4 are arranged at the pitch P2.
By using three detectors arranged in series in (3), three pulses having the waveform shown in FIG. 9 are output at partially overlapping intervals, and as shown in FIG. 7, the AND of the outputs of these three proximity sensors is obtained. Operating range P5 of the third detector J4 having the width shown in FIG.
Get.

As shown in FIG. 6, when there is a missing portion H3 of the scale grating in the scale main body H1, the portion is detected by the third detector H9 and transmitted to an output selection circuit.
The output of the scale device is switched from the output of the first detection circuit to the output of the second detection circuit and output. To detect the missing portion H3, as shown in the figure, the scale body H
A hole H4 is made in the upper part 1 so that the proximity sensor does not perform metal detection in this part. Although a detailed description is omitted, this is the same as the case where no metal is detected at the connecting portion of the scale.

In the above-described embodiment, a proximity sensor (metal detection sensor) is used to detect a connecting portion of the scale or a missing portion of the grid. However, various other methods can be considered. For example, in another embodiment of the present invention described below with reference to FIG. 10, a photo and a macro sensor (photo interrupter) are used as the third detector, and a shielding plate is used in the operation section.

In the scale device shown in FIG. 10, a scale body N1, a scale grid N2, a grid missing portion N3, a mounting screw N5, a detector assembly N6, a first detector N7, a second detector N7.
Since the detector N8 and the third detector N9 are the same as H1 to H3 and H5 to H9 in the scale device shown in FIG.
Description is omitted.

FIG. 10 differs from the scale device shown in FIG. 6 in that a shielding plate N4 is placed at the connecting portion of the scale and an optical detector is used as the third detector N9.
The configuration of the optical detector can be any configuration, but basically, it is to output a section with and without a shield plate N4.

As an example, a light-emitting element and a light-receiving element are provided to face each other, and when the third detector N9 moves relatively to the scale body N1 and passes through the scale connecting portion, the light-emitting element and the light-receiving element are shielded. It is possible to adopt a configuration in which the light from the light emitting element does not reach the light receiving element during the passage of the plate N4.

In order to position the shielding plate N4, a groove may be provided on the scale base side (scale body N1), and the shielding plate N4 may be planted in the groove. At that time, the length of the shielding plate can be adjusted to satisfy the condition of the above equation (7). If there is a missing portion N3 in the scale grid, a shield plate is erected, as in the case of the connecting portion of the scale, and when that portion passes through the first detector N7, it is detected by the third detector N9, The output is switched so that the output from the first detector N7 is not used and the output from the second detector N8 is used instead.

[0061]

The scale device of the present invention has the following effects due to the provision of the above configuration. Even if the scales are connected, only the places where the accuracy is guaranteed are detected, so that they are equivalent to one scale.・ Equipment for making a long scale is unnecessary. -Eliminates the need for complicated processing and mounting of the connecting portion. (Attach it with a random gap).・ Because the scale of the target length can be connected to the short scale, management in logistics, inventory and manufacturing becomes easy. -Accuracy can be maintained without being affected by aging and temperature changes of the scale joint.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of a scale device of the present invention.

FIG. 2 is a block diagram illustrating details of first and second detection circuits;

FIG. 3 is a waveform chart showing operation signal waveforms of the circuit of FIG. 2;

FIG. 4 is a circuit diagram showing details of an output selection circuit.

5 is an operation signal waveform diagram of the circuit of FIG.

FIG. 6 is an external perspective view of a scale device according to an embodiment of the present invention.

FIG. 7 is a circuit diagram illustrating an example of a third detector used in the scale device of FIG. 6;

FIG. 8 is an explanatory diagram used for describing the operation of the third detector.

FIG. 9 is a waveform diagram showing an output waveform of a third detector.

FIG. 10 is an external perspective view of a scale device according to another embodiment of the present invention.

FIG. 11 is a schematic view of a conventional scale device.

[Explanation of symbols]

B1 ‥‥ scale, B2 ‥‥ scale grid, B3 ‥‥
Scale connection, B4 ‥‥ first detector, B5 ‥‥ second
Detector, B6Ｂthird detector, B7 ‥‥ first detection circuit,
B8 {second detection circuit, B9} clock oscillator, B1
0 ‥‥ output selection circuit, B11, B12 ‥‥ output (terminal)

Claims (1)

[Claims] 1. A scale in which a plurality of scales each having a predetermined grating are connected, first and second detectors that read the scales and output phase-modulated waves, and output from the detectors based on clock pulses. A scale device having a detection circuit that outputs a signal indicating a moving direction and a moving amount of a device under test by performing signal processing, wherein a signal is output when the first detector enters a scale connecting section or a scale grid lacking portion. When the third detector has no signal, a signal obtained by processing the signal from the first detector is output, and when there is a signal from the third detector, the signal is output from the second detector. A scaler provided with a selection circuit that outputs a signal obtained by processing the signal of (1), wherein one of the first and second detectors secures a position that is not a joint of scales or a scale grid missing portion. .