JPH02201118A - Code plate for absolute encoder - Google Patents

Abstract

PURPOSE:To reduce the influence of adjacent read units and to enhance reading accuracy by forming a signal decision part in the absolute pattern of a code plate smaller than minimum read unit. CONSTITUTION:The rising timing and the falling timing of a rectangular wave signal (e) obtained from the detection signal of a photoelectric sensor 80b corresponding to the read result of an incremental pattern are almost center of the pulse width of the minimum scale unit of the rectangular wave signals (a)-(d). The rectangular wave signal (e) is inputted in a monostable-multivibrator circuit 95 as a trigger signal and pulse output is generated at the rise and the fall of the above-mentioned trigger pulse in the circuit 95. The rectangular wave signals (a)-(d) outputted from the pulse shaping circuits 91-94 are latched and fetched to output terminals 97a-97d when the pulse outputted from the circuit 95 arrives. Thus, there is no possibility that errors occur in the output.

Description

DETAILED DESCRIPTION OF THE INVENTION [l Industrial Application Field] This invention relates to a code plate for an absolute encoder.

[Prior Art] Japanese Patent Application Laid-Open No. 54-118259 discloses a code plate having tracks with two or more rows of magnetization patterns, and a magnetoresistive element.
; hereinafter referred to as an MR element).

Generally, this type of absolute encoder requires at least N tracks as an absolute pattern to obtain 2H resolution, and if the code plate is disc-shaped, a plurality of tracks are arranged concentrically. For example, when N=4, four circular tracks are provided concentrically on the disc-shaped code plate, and an absolute pattern of a binary code according to the direction of 611 conversion is formed on these tracks. A sensor consisting of an MR element is assigned to each track, and as the code plate rotates relative to the sensor about its center, the output of each sensor obtained at any rotational position of the code plate is such that the combination of these results in a code signal that gives the absolute rotary position of the code plate.

On the other hand, Japanese Unexamined Patent Publication No. 57-175211 or Utility Model Application No. 6
0-152! ! Publication No. 16 states that two kinds of minimum reading units corresponding to the "0" signal and the "1" signal, that is, the minimum reading unit with magnetism and the minimum reading unit without magnetism, are arranged in a predetermined arrangement on one track. It consists of a code plate arranged on the top and a reading head made up of a plurality of detectors that are movable relative to the code plate and arranged in the track length direction, and convert the signal string output from each detector into a binary code. A magnetic or optical absolute encoder is shown that detects absolute position.

[Problem to be solved by the invention] In the conventional absolute encoder code plate described above,
Particularly in the case of the magnetic type, as shown in Figure 2, the two types of minimum reading units are entirely signal determining parts, so one has an adverse effect on the other, which becomes noise and ultimately reduces the reading accuracy. There was a problem with the decline.

[Means for Solving the Problems] Accordingly, the present invention provides a signal determining section for at least one of the two types of minimum reading units in such a code plate as a part of the unit rather than the entire unit.

[Operation] In the present invention, the signal determining section refers to an area (range) for determining whether the unit represents a "0" signal or a 'I J iB signal. For example, to explain the magnetic type as an example, as shown in Fig. 1 corresponding to the actual rJ has a magnetized area (hatched area) only in a part of it, whereas '
The other unit representing the 0'' signal has no magnetized portion at all.

The partial area 611 in this one unit is the signal determining section that determines that unit as an "l" signal.

On the other hand, in the conventional code plate, as shown in Figure 2, the entire area of one unit representing the "1" signal is occupied by the magnetized part, and the entire unit becomes the A3 definite part. Ta.

In addition, in the code plate of the present invention, since the signal determination part is only in a partial area of a unit, when reading that unit, it is necessary to read within the magnetized part of the partial area. Therefore, for the same type of reading unit, it is not preferable that the signal determining part be located at a different position for each unit, and it is desirable that the signal determining part be located approximately at the center of the area of the unit for any reading unit.

Furthermore, in the code plate of the present invention, since the reading unit is read by the signal determination section thereof, a separate clock signal is required for timing the reading. There is a method to obtain this clock signal using another clock, but
An incremental pattern consisting of reading units of the same unit pitch, that is, equal length, is provided along the absolute pattern on the code plate of the present invention or on another code plate installed in parallel thereto, and this is read by another detector. It is better to manually read the clock signal. In this case, the synchronization of the clock signal generally varies somewhat, so the range of this variation is calculated from the relative speed between the code plate and the reading head, and the track length of the reading position for each unit is calculated. Preferably, a variation range in the horizontal direction is determined in advance, and the minimum length range of the signal determining section is made wider than the variation range so as to include this variation range.

By attaching an incremental pattern track along the one-track absolute pattern on the same or adjacent code board, and operating the latch circuit using the clock signal generated using the incremental track as a strobe signal, each A method to obtain absolute output by simultaneously reading the output pulses of the detectors at the optimum timing (Japanese Patent Application No. 170782/1982), or a serial data format from each detector using a clock signal created from an incremental pattern using a similar code plate. A method to obtain an absolute output by inputting the absolute signal into a shift register etc. at the optimum timing and converting it into serial/parallel data (Japanese patent application No. 63-171)
922) was previously proposed. Any of these can be used as an application example of the code plate of the present invention. - As an example, an outline of the former method is shown in FIG.

In this example of FIG. 12(a), the number of scale divisions is 24=16.
(N=4) This is an example of a pulse optical method, and a disk-shaped code plate IC
Track 1 of the absolute pattern with 1 track in M
02 and incremental track 103 have been manufactured. The absolute pattern of track 102 is rooool 10101111001J. +04-1~104. -4 is track 102
This is an optical sensor (an example of a detector) for reading data, from which an absolute signal consisting of a 4-bit binary code is obtained. Incremental track 103 is read by another optical sensor 105. Note that 106 is the rotation axis of the code plate l.

'fJ12 Figure (b) shows an example of an output circuit that processes the reading results from these sensors.
Incremental signals from 5 and sensor 104-1
The absolute signals from ~104-4 are shaped into rectangular waves by pulse shaping circuits 110, 110-J ~ 110-4, respectively, and then the absolute signals are directly input to the latch circuit 114, and the incremental pulses are one-shot. A clock pulse is generated at both the rising and falling points of the circuit 112 and is used as a strobe signal for the latch circuit +14. In this case, the clock pulse is designed to rise at approximately the center of the pulse width of the unit pulse constituting the absolute signal. Each time a clock pulse arrives, the latch circuit 114 reads the high and low levels of the pulse of the absolute signal at that time (the high and low levels correspond to one and the other of the "0, 1" signals), and then inputs the next clock. The value is latched until then and continues to be output to the output terminals 116-1 to +16-4.

Although the aforementioned latching method avoided the occurrence of errors in the encoder output,
In the method of 170782, the content of No. 43, which is the minimum reading unit in the absolute pattern of the code plate, is rO, or r
As shown in Fig. 2, the signal determining section for determining whether the signal is J is formed to have the same length dimension as the minimum reading unit (dimension in the longitudinal direction of the track). The wearing part must be formed with exact length and dimensional accuracy.

In addition, in the case of an optical type, if one of the minimum reading units is represented by a hole drilled in the code plate, for example, λ, if the single 1j is continuous, the mechanical strength of the code plate will decrease, so reinforcement is not necessary. It will happen.

Furthermore, in either method, it is necessary to form a continuous unit whose longest length is N times the unit pitch λ in the absolute pattern of the code plate. It is necessary to form with high dimensional accuracy.

However, when the signal determining section is formed in a part of the reading unit area as in the present invention, these requirements are eliminated, and the assembly and adjustment of the absolute encoder becomes easier.

An absolute encoder using the code plate of the present invention is provided with a plurality of detectors that are movable relative to the code plate of the present invention in the longitudinal direction of the track, and each detector detects the high and low levels of pulses of the absolute signal. When reading the signal, only the signal determinants shorter than the length of the minimum reading unit are read at a time point within the width of the corresponding pulse in synchronization with another clock pulse signal.

In the absolute encoder using the code plate of the present invention, when the absolute pattern of the track of the code plate is read by each detector, the pulse train taken out from each detector corresponds to a digital code array according to a constant unit pitch of the absolute pattern. Therefore, the high and low levels of the unit pulses constituting the pulse train are read for each unit in synchronization with a separate clock pulse signal. As a result, each detector output is read at a stable point away from the rising and falling edges of each unit pulse of the pulse train based on the clock signal, so that errors in the encoder output can be extremely reduced. becomes possible.

In the present invention, the signal determining section that determines whether the minimum reading unit in the absolute pattern is "rO" or "1" is formed to have a smaller length, so that the distance between adjacent signal determining sections is smaller. There will be an interval between the two.

Preferably, the clock pulse is obtained from the reading result of an incremental pattern provided together with a code plate forming an absolute pattern, but it is preferable that the clock pulse is obtained from an incremental pattern of another code plate connected by an axis. In this case, the dimension of the signal determining section in the track length direction is determined taking into consideration the torsion of the shaft.

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

[Example] Figure 3 (a) (+)) shows an example of the present invention in the case of a magnetic absolute encoder using an MR element, and Figure 3 (a) shows a disc type code plate. Schematic plan of
FIG. 2B is a schematic plan view showing a sensor of an MR element that reads the absolute pattern signal written on the disc-shaped code plate.

In FIG. 3(a), the code plate 1 has a circular track 2a of Miki centered around its rotation axis 3.

2b and 2c are set concentrically.

Here, the tracks 2a and 2b are tracks having an absolute pattern, and in this embodiment, complementary double tracks are used to improve the S/N ratio of the detector reading. Of course, it is also possible to use absolute pattern tracks made of wood.

On the first circular track 2a, there are 16 marks 1 (N = 4
The absolute pattern of the hit) has magnetized scales 6a to 6d consisting of scale units (minimum reading unit) having a magnetized part (corresponding to a signal determining part) M in the magnetization direction shown by the arrow, and a magnetized part M. The non-magnetized scales 7a to 7d are formed by non-magnetized scale units (minimum readable units). The actual state of the magnetized portion M is shown in FIG. 3(e).

To explain the scale structure in order from the 12 o'clock position clockwise in the first circular track 2a in FIG. 3(a), the unmagnetized scale 7a has four consecutive "0" scales, and the magnetized scale 6a has four consecutive The two “1” scales and the unmagnetized scale 7b are
0" scale, the magnetized scale 6b is the rI scale of the car, the unmagnetized scale 7c is a single "0" scale, the magnetized scale 6c is a series of four "1" scales, and the unmagnetized scale 7d is the Two consecutive “0”
'' scale, and the magnetized scale 6d can be expressed as a single rIJ scale, so the absolute code of this pattern is rooool 10101111001J.

Also on the second circular track 2b, there are 16 divisions (N=4
The absolute pattern of the bit) is formed by the same magnetized scales 6e to 6h and the unmagnetized holes 117e to 7h as described above, but this absolute pattern is exactly the reverse pattern of the absolute pattern of the first track. Therefore, the absolute hood of this pattern is rllllooololooooloJ.

Each of the scale units constituting each of the magnetized scales 6a to 6h has a length dimension (angular range) λ of one scale, and a magnetized portion M having a dimension α×λ in the longitudinal direction of the track is provided approximately in the center thereof. They each have their own.

Here, λ is the length dimension in l scale units and the arrangement pitch in scale units, and since N=4 in Fig. 3(a), λ is the angular range on the circular track of the code plate l. This corresponds to 360/16 = 22.5 degrees (π/8 radians).

The magnetized part M is a signal determination part, and the dimension α in the track longitudinal direction is set to be less than the dimension λ of one scale unit, and as described later, the unit of the absolute signal corresponding to the dimension α of the magnetized part M is set. The dimensions are set to be sufficient to cover the relative error with the clock signal so that the clock signal as a synchronizing signal always appears in the pulse width.

The innermost third track 2C has an incremental pattern for obtaining the above-mentioned clock signal, and on this track 2C there is a length dimension (
Angle range) 16 magnetized sections N and S corresponding to λ are arranged with alternating cup characteristics, forming an incremental pattern in which the entire circumference is divided into 16.

The detector IO has N=4 for each absolute pattern track 2a, 2b of the code plate 1 as shown in FIG. 3(b).
Individual MR element sensors lla~14a and llb~+
4b, and one MR element sensor 30 for reading the incremental pattern track 2C. This detector 10 is placed opposite to the code plate 1 as shown at 98 m in FIG. At the same time as reading the absolute pattern based on the magnetization scale of the first circular track 2a, the sensors llb to 14b read the inverted absolute pattern of the second circular track 2b, and in order to obtain the synchronized clock signal at that time, the sensor 30 The incremental pattern on the circular track 2C is read.

Regarding absolute pattern reading, the arrangement interval between each MR element sensor on the same track is the unit dimension λ.
or its integer 1Q, and in FIG. 3(b), this interval is exactly λ.

However, in the case of integral multiples, the absolute pattern will be different from the above.For example, in the case of an absolute encoder with 10 scales, when the interval is λ, the absolute pattern will be as shown in Fig. 8(d),
When the interval is 2λ, an absolute pattern as shown in FIG. 9 is obtained.

Regarding the individual MR1 child sensors, the configuration of the absolute pattern reading sensors lla and +Ib is shown in FIG. 4 together with the related configuration with the incremental pattern reading sensor 30. The configurations of the other absolute pattern reading sensors 12a, 14a, b to 14a, b are the same as the configurations of the two sensors 11a, 11b and will not be described here.

As shown in FIG. 4, MR for the first track 2a
The MR element I5a constituting the element sensor lla and the MR element 15b constituting the MR element sensor Ilb for the second track 2b are connected to the track 2a in a plane parallel to the track plane of the code plate.

They are arranged in a line in the direction perpendicular to 2b. The MR element sensor 30 for the third track 2c includes two thin MR elements 15c spaced apart by λ/2 in the longitudinal direction of the track;
It consists of 15d. In this case, M of sensors Ila, llb
The R elements are aligned without any positional deviation in the track longitudinal direction, and this is because both tracks 2a and 2b are arranged side by side in the circumferential direction with zero phase difference, as shown in FIG. 3(a). , if these tracks are provided offset in the circumferential direction due to a phase difference, the sensors ]la and ll
The arrangement of the MR elements 15a and 15b in b may also be shifted by a corresponding phase difference.

the MR element 15a for reading the absolute pattern;
15b, as shown in FIG. 4, 15a and resistor 32a,
15b and resistor 32b are connected in series, and a bridge circuit is formed between the DC power terminals 17 and 20 so that the directions of current flow are opposite to each other in both series-connected buses, and the signal output terminals 18 and 19 are connected in series. The configuration is such that a detection output is generated between the two. In FIG. 4, as an example, magnetization scales 6a and 6f of both tracks are attached.

Further, the MR elements 15c and 15d of the sensor 30 for incremental pattern reading are connected in series between the DC power terminals 17 and 20 as shown in FIG. 4, and similarly connected in series between the DC power terminals. Fixed resistor 32c
, 32d constitute a bridge circuit, and the intermediate connection point of each series connection bus is connected to signal output terminals 33 and 34. When a horizontal magnetic field is applied to an MR element, its own electrical resistance value decreases in accordance with the intensity of the magnetic field, regardless of the polarity of the magnetic field. Therefore, the signals generated at the output terminals 18 and 19 of the absolute pattern reading sensor shown in FIG. 4 due to the relative movement of the detector 10 and the code plate l are as follows.

For example, when a horizontal magnetic field from the magnetization scale is applied to the MR element 15a, the resistance value of the MR element 15a decreases, so the potential at the output terminal 18 increases, and when a magnetic field is applied to the MR element 15b, the potential at the output terminal 18 decreases. do. The potential of the output terminal 19 is fixed resistor 32a.

32b, it is fixed at a predetermined potential intermediate between the DC power supply terminals 17 and 20. The patterns of both tracks are complementary, and the MR elements of both sensors do not deviate from each other in the track direction, so in both cases, the voltage generated between output terminals 18 and 19 has an amplitude waveform that is exactly up and down. They are symmetrical, and the phase shift between the two outputs corresponds to a phase difference of 90 degrees when λ is 360 degrees.

Further, the signals generated at the output terminals 33 and 34 of the sensor 30 for incremental pattern reading are as follows. That is, when a horizontal magnetic field is applied to one MR element 15c,
Since the resistance value decreases, the potential of the output terminal 33 increases, and when a horizontal magnetic field is applied to the other MR element +56, the resistance value decreases, so the potential of the output terminal 33 decreases.

On the other hand, the potential of the output terminal 34 is the fixed resistance 32C132d
is fixed at a predetermined potential intermediate between the DC power supply terminals 17 and 20.

Since the distance between the two MR elements 15c and 15d is λ/2, which is exactly half the length λ of each magnetization scale unit of the incremental pattern, one of the MR elements 15c and 15d is at the maximum resistance value. The other side has the lowest resistance value, and therefore, due to the relative movement between the code plate 1 and the detector 10, the output terminal 3
3.34, an incremental pattern of signal outputs are obtained which vary in response to the horizontal magnetic field distribution along the rack 2c.

FIG. 5 shows an example of a signal processing circuit for processing the detection output of the detector 10, and FIG. An example of the horizontal magnetic field pattern along the trunk due to each magnetized section of the incremental pattern formed in 2C and each of the eight waveforms of the signal processing circuit is shown.

In the detector 10, one output terminal 18 of the MR element sensors Ila and Ilb for absolute pattern reading is connected to the input terminal 22 of the signal processing circuit 21, and the other output terminal 19 is connected to the input terminal 23. There is. MR element sensor 12 for reading other absolute patterns
The same applies to a, t2b to 14a, and 14b, so only the set of MR element sensors lla and llb will be described here.

The magnetic field pattern based on the magnetization scale of the absolute pattern formed on the track 2a of the code plate 1 is as shown in FIG. The magnetic field pattern according to the scale is as shown in FIG. 6(b). When this is relatively scanned by the sensors 11a and jlb each consisting of an MR element, the output terminal 18 has 's6 (d) 1. : A pulsating pulse-like signal as shown appears at the other output terminal as shown in Figure 6(e).
A voltage signal of approximately constant level as shown in is generated.

When the chair numbers appearing at both output terminals 18 and 19 are input to the differential amplifier 24 of the signal processing circuit 21 and differentially amplified, the output terminal of the differential amplifier 24 has a substantially rectangular shape as shown in FIG. 6(f). A wavy signal is obtained. The pulse rise and fall of this signal are constant and steep regardless of the pulse width. Therefore, if this signal is converted into a rectangular wave at a constant comparison level by the comparator 25, the comparator 2
At the output end of 5, a rectangular wave signal as shown in FIG. 6(g) is obtained. This rectangular wave signal is input to the input end of a latch circuit 29 as part of the reading means, and similarly the sensor 1
Rectangular wave signals based on detection signals from the sets of sensors 2a and 12b, the sets of sensors 13a and j3b, and the sets of sensors 14a and 14b are also input to the corresponding input terminals C of the latch circuits, respectively.

On the other hand, the horizontal magnetic field pattern of the incremental pattern formed on the track 2C of the code plate 1 is as shown in FIG.
When relative scanning is performed by the sensor 30 consisting of the elements 15c and 15d, a pulsating pulse-like signal with a waveform corresponding to the horizontal magnetic field pattern appears between the output and output terminals 33 and 34 of the sensor 30. After the waveform is shaped into a rectangular wave by the amplifier circuit 26 and the Schmitt trigger circuit 27, the signal is input to the monomulti circuit 28. The mono multi circuit 28 is
At both the rise and fall of the rectangular wave, the clock (No. 8 strobe pulse) as shown in FIG. 6(h) is output, and this is learned by the latch circuit 29.

In this case, as shown in FIGS. 6(g) and 6(h), the strobe pulse is generated in synchronization with approximately the center of the pulse width of the minimum scale constituent unit of the rectangular wave signal that is the reading result of the absolute pattern. As a result, the timing of reading the high and low levels of the rectangular wave No. 43 from each comparator 25 is aligned with the strobe pulse time by the latch circuit 29, and the rise and rise of the rectangular wave shown in FIG. Each rectangular wave signal is simultaneously taken at 1 srA at a stable point within the pulse width apart from the falling edge to prevent reading of incorrect contents. The binary number of the read result is shown in FIG. 6(f).

In this embodiment, the selection of such reading timing is based on the combination of the tracks 2a and 2b of the absolute pattern and their detectors 11a, b to 14a, b, and the combination of the track 2C of the incremental pattern and its detectors. This is achieved by appropriately selecting the phase difference in the arrangement in combination with 30.

As described above, the latch circuit 29 latches the high and low levels of the rectangular wave signal at each input terminal each time a strobe pulse as a lock signal arrives, and outputs it to its output terminals 27a to 27d. In this way, the four output terminals 27a to 27
d for every rotation angle of π/8 radian of the code plate 1'
It is possible to obtain four-digit binary code signals with different combinations of 0.1''(7)m.

Output terminals 25a and 25b of the signal processing circuit 25 are output according to detection signals from each of the four sets of sensors.

The rectangular wave signals appearing at 25c and 25d are shown in Fig. 3(a).
(a) and (b) shown in FIG. 7 correspond to (b).
)(c)(d). Note that (8) in Figure S7 is a rectangular wave signal corresponding to the reading result of the incremental pattern output from the Schmitt trigger circuit 27, and a strobe pulse that provides the reading timing is generated at both the rise and fall of this signal. be done. In this case, it is assumed that the code plate 1 is rotating counterclockwise with respect to the fixed detector 10 as shown by the arrow in FIG. 3(b).

In this example, since N=4 as mentioned above, the absolute i-code has 2N=16 scales, and is shown in FIG.
), four sets of MR element sensors 1la-jlb, 12a-1 are arranged at intervals of λ in the circumferential direction of the code plate 1.
2b, 13a-13b, and 14a-14b so that a code signal of the same combination of ro and IJ is not generated from the output terminals 27a to 27d over one rotation of the code plate 1. A pattern arrangement (absolute code) is determined, which is rooool 10101111001J, as described above.

Therefore, output terminal 27a is 2°, 27b is 2127c is 2°
' If 27d is assigned to 23, the relative rotation angle π/
Four scale absolute signals with different contents every 8 radians are obtained, and in FIG. 7, the hexadecimal numbers corresponding to each absolute signal are added as (f). As you can see, if the rectangular wave signal in Figure 7 is digitized as it is, it will be 16 hexadecimal numbers, and this number will not be the same at every point when the code plate 1 is rotated once, so it is not an absolute value. It can be seen that the encoder is configured.

The arrangement of the absolute pattern is determined as follows.

That is, when the number of graduations is small, it may be performed sequentially by trial and error, but when the number of graduations is large, it is necessary to perform calculations using a computer.

To explain the above-mentioned case of 4 scales, for example, each scale is "0".
” always exists, so first, four consecutive “0” ro, 0. Consider O, OJ. If there are five consecutive “0”s, the same combination will occur, so “0”
I think that after four consecutive ``1''s, there will always be a ``1''. In this way, either "0" or "1" is added one after another, and when the numbers are shifted one scale at a time in groups of four, combinations with the same contents do not occur.

The results of the computer calculations are shown in FIGS. 8(a), (b), (c), and (d).

Figure 8(a) shows the absolute code for 32 scales, that is, N=5 bits, and Figure 8(b) shows the absolute code for 64 scales, that is, N
= 6 bits, absolute code, Figure 8 (C
) is the absolute code for 256 scales, ie, N=8 bits, and FIG. 8(C) is the absolute code for 1024 scales, ie, N=IO bits.

The absolute code shown in FIGS. 8(b), 8(c), and 8(d) is constructed as a series in which the scale at the end of a row is connected to the scale at the beginning of the next (lower) row.

When using these absolute codes in Fig. 8 for a rotary encoder, the last scale on the bottom line is 'fi'.
, so that it is connected to the first scale of the x row and continues endlessly.

The example in Figure 8 shows the code arrangement when MR element sensors are arranged consecutively at intervals (λ) equivalent to one scale of the absolute pattern. If the continuous arrangement in ψ1t becomes physically difficult, for example, one
The MR element sensor can be placed at a distance between two people on the scale. As such an example, FIG. 9 shows an absolute code when N=10. In this case N=10
Therefore, ten MR element sensors are arranged one scale apart, that is, at intervals of 2λ.

Of course, it is possible to appropriately define absolute codes for other intervals as well, and it is possible to create absolute codes for intervals that are an integral multiple of λ.

Since such an absolute code can realize an absolute pattern in one track, it is possible to obtain an absolute encoder whose size is almost the same as that of a so-called incremental encoder.

The above is an example of a magnetic absolute encoder.
10 and 11 show an embodiment of an optical absolute encoder.

In FIG. 10(a), the code plate 4 has a "0" scale unit formed only of opaque parts and a "1" scale unit that includes transparent parts.
A track 5a is provided with an absolute pattern similar to the above-mentioned scale unit, and a track 5b is an incremental pattern in which the -circumference is divided into 16 equal parts and each divided area is alternately repeated as an opaque part and a transparent part. is attached. Track 5 of this absolute pattern
The transparent portion T in a is a signal determining portion, and its dimension α in the track length direction is smaller than the dimension of the scale unit, as in the case of the magnetic type described above.

The code plate 4 includes light sources 81a to 84a and photoelectric sensors 81b to 84a facing each other across the code plate, as shown in FIG. 10(b).
The set 84b and the set of light source 80a and photoelectric sensor 80b are combined as a detector, and these detectors and the code plate 4 perform relative rotation about the rotation axis 9.

This detector includes four photoelectric sensors 81a arranged in the longitudinal direction of the track at intervals λ to read the track 5a;
82a, 83a, 84a, and a single photoelectric sensor 80b for reading the track 5b, and the relative arrangement thereof is the same as in the above-mentioned embodiment of the 6f1 pneumatic absolute encoder.
b are arranged along the track 5a at intervals of λ from each other,
A photoelectric sensor 80b is disposed opposite to the track 5b at a position angularly shifted by λ/2 with respect to these.

FIG. 11 shows an example of a signal processing circuit for processing the detection outputs of each of the photoelectric sensors 80b to 84b. In the signal processing circuit shown in FIG. 11, the detection outputs of these photoelectric sensors are shaped by pulse shaping circuits 90 to 94 to obtain rectangular wave signals as shown in FIG. 7, respectively, similarly to the magnetic type. In FIG. 7, (a) to (d) correspond to the outputs of the shaping circuits 91 to 94, respectively, and (e) corresponds to the output waveform of the shaping circuit 90. As shown in FIG. 7, the photoelectric sensor aob corresponds to the reading result of the incremental pattern.
The rising and falling timings of the rectangular wave signal (e) obtained from the detection signal are approximately at the center of the pulse width of the minimum scale unit of the rectangular wave signal '+(a) to (d). This rectangular wave signal (e) is input as a trigger signal to the mono multi circuit 95, and the mono multi circuit 95 generates a pulse output at both the rise and fall of the trigger pulse. Reference numeral 96 denotes a latch circuit, which receives the rectangular wave signals (a) to (d) output from the pulse shaping circuits 91 to 94 to the monomulti circuit 9.
When the pulse (strobe pulse) outputted from the output terminal 5 arrives, it is latched and taken out to the output terminals 978 to 97d. As a result, each output terminal 97a to 97d
Needless to say, a binary code signal with four scales similar to that described above can be obtained.

In the embodiments described above, a rotary encoder for reading a rotational angular position was mainly explained, but the present invention can also be applied to a linear encoder for reading a linear position, and in that case, a long plate The absolute pattern described above may be formed in a straight line on a code plate having a shape.

In addition, we have given an example of a case where an incremental pattern track is attached to the code plate to obtain a clock signal (strobe pulse), but in the case of an encoder where the code plate and detector are always moved relative to each other at a constant speed. By providing a clock pulse oscillator with a constant frequency in the signal processing circuit, the incremental pattern track and its detection system can be omitted.

[Effects of the Invention] As described above, according to the present invention, since the signal determination part in the absolute pattern of the code plate is formed smaller than the minimum reading unit, the influence of adjacent reading units is reduced. Reading accuracy improves. It also facilitates the formation of the absolute pattern of the code plate and the assembly and adjustment of the encoder. In other words, the rectangular wave signal of the reading result is
Since reading is performed based on another clock signal within a pulse width smaller than the minimum reading unit, the pulse high and low levels of the detection signal from each detector can be captured simultaneously at a stable point, resulting in errors in the output. Therefore, it is possible to obtain a high-resolution absolute encoder that is free from the risk of occurrence of problems.

[Brief explanation of the drawing]

FIG. 1 is a schematic partial plan view showing an example of the code plate of the present invention;
FIG. 2 is a schematic partial plan view of a conventional example, FIG. 3(a) is a schematic plan view of a code plate according to an uninvented embodiment for a magnetic absolute encoder, and FIG. A schematic plan view showing a detector consisting of an MR element sensor that reads an absolute pattern by a magnetized part, FIG. 4 (C) is an explanatory diagram of the magnetized part M, and FIG. , FIG. 5 is a circuit diagram showing an example of a signal processing circuit for processing the output signal of the detector, and FIG. 6(a)
~(i) is a diagram showing the horizontal magnetic field pattern based on the magnetization scale of the absolute pattern and incremental pattern formed on the track of the code plate, and the waveform of each part of the signal processing circuit, and FIGS. 7(a) to (f) are Diagrams showing the final output waveforms of the absolute encoder using the code plate of the present invention, FIGS. 8(a) to 8(d) are some of the absolute codes that determine the absolute patterns for obtaining absolute signals with different numbers of scales. FIG. 9 is an explanatory diagram showing another example of the absolute code, and FIG. 10(a) is a schematic plan view showing a code plate for an optical absolute encoder according to another embodiment of the present invention. , Fig. 11 is a circuit diagram showing an example of a signal processing circuit for embedding the output signal of the photoelectric sensor in lA in the previous figure, and Fig. 12 ( FIG. 1A is a schematic plan view of a code plate for an optical absolute encoder according to a conventional example, and FIG. 1B is a circuit diagram showing its signal processing circuit. (Explanation of symbols of main parts) 1: Code plate 2a, 2b: ) Rack (absolute) 2C Nidrak (incremental) 3: Rotation axis 68-6h: Magnetized scale 78-7h: Unmagnetized scale 10: Detector 11 a, b ~ 14a, b: MR element sensor 15a ~ d: MR element 17: + side power supply terminal 1.8.19 + output terminal (absolute) 20 knee side power supply terminal 21: signal processing circuit 246 differential amplifier 25: Comparator 28: Mono multi circuit 29: Latch circuit 30: MR element sensor

Claims (1)

[Claims] In an absolute encoder code plate in which two types of minimum reading units corresponding to "0" signals and "1" signals are arranged on one track in a predetermined arrangement, at least one of the minimum reading units is longer than the length of the unit. A code plate for an absolute encoder, characterized in that it has a short signal determination section.