JPS5853286B2 - digital scale device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital scale device, and particularly to an improvement of its reference position detection device.

Digital scale devices are widely used for measuring the length of objects to be measured or as position detecting devices for machine tools, etc., and have the advantage of providing highly accurate and easy-to-read digital displays.

Digital scale devices include linear scales known as linear encoders and rotary scales known as rotary encoders, and there are photoelectric, electromagnetic, and magnetic types depending on the reading method.

The photoelectric digital scale device described above moves a main scale having a length measurement slit array and an index scale having a length measurement gate slit relative to each other, and photoelectrically detects the amount of movement between the two. A photoelectric converter detects changes in the amount of light passing through the slit.

When a digital scale device is used as a length measuring device,
The main scale or index scale moves in conjunction with the length measuring instrument's probe, and the other scale is fixed to the length measuring instrument body, detecting the amount of movement of the probe as an electrical signal, and counting the number of detected signals. The amount of movement is digitally detected.

Similarly, when a digital scale device is used as a position detection device for a machine tool, one of the scales is fixed to the feedstock of the machine tool, the other scale is fixed to the base, and the relative movement of both scales causes the feedstock to move. You can know the location of

The length measurement slit row of the main scale consists of a plurality of length measurement slits arranged in an array, and the length measurement slits are arranged at equal intervals throughout the length measurement range.

In normal cases, the slit has a width of about 10 microns,
A space of approximately 10 microns is similarly provided between each slit, and as a result, the length measurement slit pitch is set to approximately 20 microns.

The index scale is also provided with a length measurement gate slit similar to the length measurement slit, and the amount of light passing through both slits changes depending on the overlapping phase of the length measurement gate slit and length measurement slit, so that the relative movement amount of both scales can be calculated. Can be counted.

In such a digital scale device, it is preferable to determine a reference counting position in order to accurately know not only the relative movement amount of both scales but also their absolute position with respect to the movement axis.

Once the reference counting position is set, absolute length measurement or coordinates can be obtained by, for example, aligning the zero position of the length measuring device or the coordinate origin of the machine tool with the reference counting position and counting the pulses from the reference counting position. It becomes possible to determine the position as an absolute value.

In the conventional digital scale device, the reference counting position described above is set by providing a reference slit in a main scale in a row separate from the length measurement slit row.

FIG. 1 shows a conventional photoelectric digital scale device.

The main scale 10 and the index scale 12 are arranged close to each other so as to be relatively movable, and one is fixed to a fixed part and the other is fixed to a moving part of a machine tool or three-dimensional length measuring machine or other measurement probe, and the amount of relative movement is determined by an electric signal. Detected as .

The main scale 10 is provided with a length measurement slit row 14 consisting of a plurality of length measurement slits arranged in an array, and the index scale 12 is provided with two length measurement slit rows 14 corresponding to the length measurement slit row 14.
length measurement gate slits 16 and 18 are provided.

The length measurement gate slits 16 and 18 are provided with a slit arrangement offset from each other, for example, by 1/4 of the slit pitch.
As a result, the detection output from the photoelectric conversion device (not shown) is detected as a signal having a phase difference of, for example, 90 degrees with respect to each length measurement gate slit 16, 18.

In the conventional digital scale device, the main scale 10
The length measurement slit row has a length determined as an effective measurement length, and uniform length measurement slits are continuously provided between the measurement lengths.

In order to determine the reference position of such a digital scale, the main scale 10 is provided with a reference slit section 20 at a position adjacent to the length measurement slit row 14.
The index scale 12 is also provided with a reference gate slit 22 adjacent to the aforementioned length measurement gate slit.

Therefore, when the reference gate slit 22 of the index scale 12 is overlapped with the reference slit portion 20 of the main scale 10, a reference signal is detected from the reference signal generation photoelectric conversion device (not shown), and the reference signal of the digital scale device is detected. location is required.

In the conventional digital scale device described above, it is necessary to provide a reference slit section on the main scale in another row adjacent to the length measurement slit row, which has various disadvantages such as increasing the scale width and complicating processing. It had

The present invention has been developed in view of the above-mentioned conventional problems, and its object is to provide an improved digital scale device that can detect the reference position of a scale with an extremely simple structure.

In order to achieve the above object, the present invention is capable of obtaining a practically sufficient length measurement signal even if there is a slight slit missing part in a part of the length measurement slit row in a photoelectric digital scale device. The present invention is characterized by a mixed arrangement of reference position detection sections in the length measurement slit row of the main scale.

The reference position detection section in the present invention may be composed of a reference slit having a slit width larger than the length measurement slit pitch, that is, a wide slit in which an integer number of light blocking parts for the length measurement slit are missing, and may be different from the length measurement slit. The reference slit group may be composed of a plurality of slits having a slit pitch.

According to the present invention, since the reference position detection section is arranged in the length measurement slit row, the width of the main scale itself can be reduced, and the slit processing work is also extremely easy, and has various advantages. .

Preferred embodiments of the present invention will be described below based on the drawings.

2 and 3 show preferred embodiments of the digital scale device according to the present invention.

On one side surface of the main scale 30 made of glass, there is a length measurement slit row 32 consisting of a plurality of length measurement slits arranged in alignment.
is provided.

An index scale 34 is arranged adjacent to the main scale 30, and as is well known, when the index scale 34 and the main scale 30 move relative to each other, the amount of movement is photoelectrically converted.

On the side surface of the index scale 34, there are two scales with different phases.
Measurement gate slits 36 and 38 are provided.

In this embodiment, a reference position detection section 40 is formed in a part of the length measurement slit row 32, and is formed of a reference slit having a wide slit width and in which at least one light blocking section for the length measurement slit is missing. .

Note that the reference position detection section 40 is formed to have a width narrower than the width of the length measurement gate slit group.

On the other hand, the index scale 34 also has a reference gate slit 42 corresponding to the reference position detection section 40 of the main scale.
In the illustrated embodiment, the reference gate slit 42 is formed to have approximately the same slit width as the reference position detection section 40.

As is clear from FIG. 3, on the side of the main scale 30 there is a light emitter 44 corresponding to the length measurement gate slit (36.38).
．． 46 and the light emitter 4 corresponding to the reference gate slit 42
8 is provided, and on the side of the index scale 34, a light receiver 50 corresponding to the length measurement gate slit 36, 38 is provided.
．． 52 and the light receiver 5 corresponding to the reference gate slit 42
4 is provided.

These light emitters 44, 46, 48 and light receivers 50, 52
．． 54 is fixed to the same board as the index scale 34, and 44, 46, 50° 52 are the index scale 3.
48.
54 forms a reference photoelectric converter that moves relative to the index scale 34.

By doing so, in the device of this embodiment, each photoelectric converter moves integrally with the index scale 34, and for example, the light emitter 48 and light receiver provided corresponding to the reference gate slit 42 50 can accurately detect changes in the amount of light passing through the reference position detection section 40 and the reference gate slit 42, and has improved detection accuracy compared to the case where the photoelectric converter is fixed on a separate substrate from the index scale 34. can be improved.

FIG. 4 shows the relative arrangement of the slits in the embodiment of FIG. 2.

The length measurement slits 32 of the main scale 30 are separated from the length measurement slits 32b separated by light blocking portions 32a arranged at equal intervals, and the slit pitch is indicated by P.

In the illustrated embodiment, the light blocking portion 32a and the length measuring slit 32b are each set to have the same width of 10 microns, and this width is indicated by P/2.

The reference position detection unit 40 provided in the length measurement slit row is n
The slit has a wide slit width np+P/2 in which the length measuring slit light blocking portions are missing.

In the illustrated embodiment, the light blocking portions 32a are formed by a masking vapor deposition method, so that the reference position can be detected very easily by not performing vapor deposition on only n light blocking portions at desired positions of the length measurement slit array. 40 can be formed.

n is a positive integer indicating the number of missing light blocking portions, and in the illustrated embodiment n is selected to be seven.

The length measurement gate slit 36 consists of slits 36b divided by light blocking parts 36a, and the width thereof is set to P/2, that is, 10 microns, similarly to the length measurement slit row 32.

Similarly, the length measurement gate slit 38 is made up of a plurality of slits 38b separated by a light blocking section 38a, and the width thereof is also set to P/2, that is, 10 microns, similarly to the length measurement slit 32.

As is well known, both length measurement gate slits 36 and 38 are provided with their installation phases displaced, and in FIG. The length measurement gate slit 38 is provided at a position displaced by P/4, that is, 5 microns.

Due to this displacement, as described later, both length measurement gate slits)
From 36.38, two types of electrical signals with different phases can be obtained, and by combining these two signals, it is possible to obtain a length measurement accuracy finer than the slit pitch P.

Both length measurement gate slits 36 and 38 are respectively mP+P/
It has a gate width of 2, that is, it has m slits in this gate width.

In the illustrated example, m is set to 70.

As is clear from FIG. 4, the reference gate slit 42 provided in the index scale 34 is opened from a relatively wide opening having the same width as the reference position detection section 40 of the main scale 30, that is, nP+P/2. Become.

As described above, in the digital scale device according to the present invention, the slit row for length measurement and the detection section for detecting the reference position are mixedly arranged in the same row on the main scale, and the length measurement signal is obtained from such a mixed arrangement. The operation of extracting the reference position detection signal and the reference position detection signal will be explained below with reference to the waveform diagram of FIG.

A solid line 100 in FIG.
b and the light receiver 50 after passing through the length measurement gate slit 36b.
Similarly, the chain line 102 shows the signal waveform detected by the light receiver 52 after passing through the length measurement slit 32b and the length measurement gate slit 38b from the light emitter 46. .

It is understood that these signal periods are determined by the relative moving speeds of the main scale 30 and the index scale 34 and are represented by a sine curve, and that both signals 100° 102 have a phase difference of 90°.

Therefore, by supplying both of these signals 100 and 102 to a known signal dividing circuit, it is possible to obtain a length measurement accuracy finer than the slit pitch P.

As is clear from FIG. 4, the width of the light blocking part and the slit width of the length measurement slit array and the length measurement gate slit are set to be the same width, so each length measurement gate slit) 36.
38 light blocking portion 36a.

38a and the measuring slit 32b, the irradiation light from each light emitter 44.46 is completely blocked and no electrical signal is output from the light receiver 50.52.
This results in the zero port state shown in the figure.

On the other hand, each length measurement gate slit 36b.

When the length measuring slit 38b and the measuring slit 32b overlap each other, the maximum amount of light is incident on each of the light receivers 50 and 52, and a maximum signal output of 2 volts can be obtained.

A waveform 200 in FIG. 5 shows the output of the light receiver 50 when the reference position detection section 40 of the main scale 30 enters the length measurement gate slit 36, and shows the output of the light receiver 50 when the reference position detection section 40 of the main scale 30 enters the length measurement gate slit 36. Due to the intrusion, a larger amount of light is incident on the light receiver 50 than in the normal case, and as a result, the overall output level increases.

However, in the present invention, the number m of slits of the reference gate slit is equal to the number n of missing light-transmitting parts of the reference position detection section 40.
10 times the size of the light shielding part, the output voltage change due to the omission of the light blocking part is suppressed to within approximately 10%.

That is, the lowest value of the output waveform is at o and iv, and the highest value is at 1. Indicated by IV.

Therefore, such slight voltage level fluctuations can be very easily equalized during A-D conversion by a signal processing circuit, and the signal is the same as that obtained from a conventional length measurement slit array without a reference position detection section. digital detection signals can be obtained.

In the manner described above, it is possible to extract only the length measurement signal from the slit row in which the length measurement slits and the reference position detection sections coexist.

On the other hand, a waveform 300 in FIG. 5 shows a reference position detection signal detected from the light receiver 54 by the incident light from the light emitter 48 that has passed through the length measurement slit 32b and the reference gate slit 42, and the reference gate slit 42 is at the reference position. When not facing the detection unit 40, a substantially constant output level of V is maintained.

Then, the reference position detection section 40 detects the reference gate slit 42.
When the light enters the target, the light receiver 54 outputs a reference position signal indicated by a signal 300a, and its peak value becomes 2V.

That is, in a state where the reference gate slit 42 faces the normal length measurement slit row, incident light from (n+1) slits enters the light receiver 54, but the reference position detection unit 40 42, the amount of light proportional to the number of missing light blocking parts is incident on the light receiver 54, and the irradiation light corresponding to the maximum (2n+1) is incident on the light receiver 54, obtaining an output voltage that is approximately twice as large. I can do it.

Therefore, the reference voltage ■ is determined by a well-known comparator circuit.

The reference position detection signal can be detected by comparing with the reference position detection signal.

As described above, the length measurement signal can be obtained from the light receivers 50 and 52, and the reference position detection signal can be obtained from the light receiver 54.

In the embodiment, the ratio of n to m is set to 1 to 10, but any ratio can be set depending on the characteristics of the signal processing circuit.

Furthermore, the values of n and m can be set arbitrarily; for example, the value of n can be set to "1", that is, the number of missing light-transmitting parts in the reference position detection section 40 can be set to one. It is.

It is clear that as the value of n increases, the amount of light incident on the photodetector 54 increases and the detection operation becomes easier.

In addition, in the apparatus of the present invention, one of the main scale 10 and the index scale 12 may be formed as a fixed side and the other as a movable side so that they can move relative to each other. However, in this embodiment, the index scale 12 is set as a movable side. The main scale 10 is on the fixed side.

By doing so, the width of the slider can be reduced, and as a result, the sliding resistance is reduced, and the return error when the slider movement direction is reversed can be reduced.

Furthermore, by setting the index scale on the movable side and the main scale 10 on the fixed side, the position of the reference position detection section 40 formed on the main scale 10 does not fluctuate, and the positional fluctuation of the reference position detection section 40 is prevented. It is possible to prevent errors caused by such factors.

FIG. 6 shows another embodiment of the digital scale device according to the present invention, and the same members as those in the embodiment of FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, the index scale 34 has two
Individual length measurement gate slit l-36A.

36B, 38A, and 38B are provided.

Each length measurement gate slit 36A. 36B, 38A, 38B
The slit length W2 of the main scale 30 is set to approximately half the length Wl of the length measurement slit 32, and the length measurement gate slits 36A and 38B are aligned in the length direction of the slits. 38A and 36B are aligned in the length direction of the slit.

Although not shown, four length measuring gate slits l-36A
.

36B, 38A, and 38B are respectively installed with corresponding light emitting/receiving devices, and the output signals of the light receiving devices corresponding to the length measurement gate slits t-36A and 36B are subjected to difference calculation by a processing circuit (not shown). The output signals of 38A and 38B are also subjected to a difference calculation.

Therefore, fluctuations in the detection signal caused by the slit width error between the slits of the length measurement slits 32 of the main scale 30 or the width error along the slit length can be eliminated by the above-described difference calculation of the output signals.

In the embodiment shown in FIG. 6, the reference gate slit 42 has a slit length that is almost the same as the length Wl of the length measurement slit 32, and the amount of light received increases with respect to the output signal obtained from each of the length measurement gate slits described above. A relatively large output signal can be obtained, and the output voltage level of the reference position detection signal can be made comparable to that of the length measurement signal.

FIG. 7 shows still another embodiment of the digital scale device according to the present invention, in which a plurality of slits having irregular slit widths are provided at irregular intervals in the slit row 32 of the main scale. It has a reference position detection section 40.

Although not shown, the reference gate slit of the index scale also has the same slit arrangement as the reference position detection section 40, and as a result, the reference position detection signal has the waveform 300a in FIG.
As shown, when the reference slit 40 and the reference gate slit match, a sharp output waveform is shown.

In addition, in the device of the present invention, the length measurement slit, the length measurement gate slit, and the reference gate slit have the same slit pitch, and the reference position detection section is a wide light transmission slit in which the light blocking part of the length measurement slit is omitted. is also possible.

Further, by arranging the reference position detection section at the joint between two main scales, it is possible to easily manufacture a long scale.

As explained above, according to the present invention, reference slits can be mixed in the length measurement slit row of the main scale, and the manufacturing process is extremely easy compared to the conventional two-row arrangement.

In the illustrated embodiment, only one reference position detection section is provided in the length measurement slit row, but it is also possible to provide a plurality of reference position detection sections for each arbitrary length measurement interval.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a conventional digital scale device, Fig. 2 is a front view showing a preferred embodiment of the digital scale device according to the present invention, and Fig. 3 is adjacent to the main scale and index scale in Fig. 2. FIG. 4 is a plan view showing the arranged photoelectric converters, FIG. 4 is a main part layout diagram for explaining in detail the arrangement of each slit of the main scale and index scale in FIG. 2, and FIG. 5 is an example of the embodiment shown in FIG. 2. FIG. 6 is a front view showing another preferred embodiment of the digital scale device according to the present invention, and FIG. 7 is a waveform diagram showing another preferred embodiment of the digital scale device according to the present invention. FIG. 8 is a slit arrangement diagram of the main scale showing another embodiment, and FIG. 8 is a reference position detection signal waveform diagram in the embodiment of FIG. 30... Main scale, 32... Measuring slit, 34... Index scale,
36, 38... Length measurement gate slit, 40...
...Reference position detection section, 42... Reference gate slit, 44, 46° 48... Light emitter, 50
, 52, 54... Light receiver.

Claims (1)

[Scope of Claims] 1. A main scale having a length measurement slit row consisting of a plurality of length measurement slits arranged in an array, and a group of length measurement gate slits which are superimposed and compared with the length measurement slits, and which are relative to the main scale. A digital scale device including an index scale movably disposed adjacent to the main scale, and a length measurement photoelectric converter that detects a change in the amount of light passing through the length measurement slit and the length measurement gate slit of both scales. During the length measurement slit row,
A reference position detection section of a digital scale formed narrower than the width of the length measurement gate slit group is provided, and the index scale is provided with a reference gate slit corresponding to the reference position detection section of the main scale; A digital scale device 2, further comprising a reference position detection section and a reference light intensity converter for detecting a change in the amount of light passing through the reference gate slit. A digital scale device comprising a wide light transmitting slit in which a light blocking portion of the length measuring slit is missing, and a reference gate slit of an index scale having a slit width at least equal to or larger than the length measuring slit pitch. 3. In the device according to claim 1, the reference position detecting section is separated from a reference slit group including a plurality of slits having a slit pitch different from that of the length measurement slit, and the reference gate slit is a slit that is the same as the reference slit group. A digital scale device comprising a plurality of slits having a pitch. 4 In the device according to claim 1, the length measurement slit, the length measurement gate slit, and the reference gate slit have the same slit pitch, and the reference position detection section detects a wide light beam with the light blocking part of the length measurement slit missing. A digital scale device characterized by consisting of a transparent slit.