JPH05231880A - Absolute encoder - Google Patents

Abstract

PURPOSE:To obtain a small size and high resolution encoder by recording separately the absolute pattern into more than two tracks parallel to a drum axis direction. CONSTITUTION:On the upper two tracks 3-1, 3-2, absolute patterns for circulation random number series are recorded supplimentary to each other and on the lower track 3-3, patterns for sine wave output are recorded. Magnetic resistor(MR) elements R11, R12, and R21, R22 are in three-terminal connection and faced to the tracks 3-1, 3-2 in the distance of 1/2 of minimum record pitch lambdato form an H bridge. By arranging n H bridges with the pitch lambda in the moving direction and rotating the magnet drum, n bits of absolute position outputs are obtained through a processing circuit. The minimum recording pitch of the track 3-2 is set and MR elements R31, R32, R41, R42 are faced with different specific pitches in three-terminal connect. Two phase sine wave obtained by inputting the outputs of each of three-terminal connection in the processing circuit is input in a CPU, the absolute value obtained before and a synthetic value is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder, and more particularly to a so-called absolute encoder in which the encoder output is coded and which can directly detect the absolute position of a rotating body.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 54-118259 and Japanese Unexamined Patent Publication No. 62-83619 disclose a magnetic drum and a magnetoresistive effect element (hereinafter referred to as M
A magnetic absolute encoder in combination with a detector utilizing an R element) is shown. Generally, in this type of absolute encoder, n tracks are required to obtain a resolution of 2 to the n-th power. In such an absolute encoder, each track 30 recording 1-bit absolute information as shown in FIG. 21 is used. A plurality of (six in the illustrated example) are arranged on the outer circumference of the magnetic drum in the axial direction, and M of the number of bits corresponding to the number of the tracks is arranged on the magnetic drum.
Magnetic sensor 2 in which R elements (R ₀₁ , R _02, ...) _Are arranged
0s are arranged to face each other, and signals obtained from the plurality of MR elements are combined to output an absolute value.

Further, Japanese Laid-Open Patent Publication No. 2-24513 discloses that an absolute signal is obtained from a code plate provided with a track having an absolute pattern. In this example, in order to obtain a resolution of 2 n, it is necessary to write 2 n pieces of information in one track.

[0004]

However, in order to increase the resolution in the conventional absolute encoder disclosed in Japanese Patent Laid-Open No. 62-83619, for example, as shown in FIG. 21, the axial direction of the magnetic drum is set. There is a drawback that the shape becomes large because it is necessary to arrange a plurality of tracks in the absolute encoder. Also, in an absolute encoder using a cyclic random number sequence code, it is necessary to write fine information in one track, and dimensional accuracy is strict and expensive. There was a drawback that it became something like.

Further, in the above-mentioned conventional absolute position detecting method, in order to increase the resolution, it is sufficient to record a plurality of absolute patterns in the circumferential direction of the magnetic drum and arrange the MR element corresponding thereto. In this case, it is advantageous to reduce the recording bit and increase the resolution when considering the shape. However, in consideration of the arrangement of the MR elements, there is a drawback that the recording pitch is limited and the shape becomes large when the number of bits is increased. The MR element signal detection method is shown in FIG.
As indicated by the arrow shown in FIG. 23, the structure is such that the leakage magnetic fields of N and S recorded on the magnetic material of the magnetic drum are sensed to obtain a signal. Therefore, when the number of bits increases, as shown in FIG. Since the magnetic sensor and the magnetic drum are in the relational position, the distance between the center and the end of the sensor differs as d and α. In the experiment, when α> d + 0.1d, the MR element cannot fully detect the leakage magnetic field and the element sensitivity. However, there was a drawback that the sensor characteristics could not be obtained due to the difference in.

An object of the present invention is to realize a small-sized high-resolution absolute encoder which solves the above-mentioned problems at a relatively low cost.

[0007]

SUMMARY OF THE INVENTION An absolute encoder of the present invention is a magnetic drum provided with a track having an absolute pattern of a cyclic random number sequence code, and a detection for reading a pattern in the longitudinal direction of the track with respect to the magnetic drum. In an absolute encoder having a container, the absolute pattern is sequentially divided and recorded on at least four tracks arranged in parallel in the axial direction of the magnetic drum.

In the absolute encoder of the present invention, an additional track for outputting a two-phase sine wave in synchronization with the track having the absolute pattern is provided on the magnetic drum, and an absolute pattern is provided by a detector for reading the pattern. It is characterized in that the absolute position values read from a plurality of tracks and the absolute position values obtained by calculating the sine wave information obtained from the additional tracks are added and output.

Further, in the absolute encoder of the present invention, the phase of the first signal from the plurality of tracks having the absolute pattern by the detector and the phase of the first signal and half the pitch of one pole of magnetic recording are phased. Second off
Of the first signal and the second signal according to the absolute position value obtained by calculating the sine wave information, and calculating the sine wave information. It is characterized in that the obtained absolute position value is added and output.

[0010]

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

FIG. 1 is a perspective view showing an absolute encoder of the present invention. Reference numeral 1 is a magnetic drum, 2 is a magnetic sensor having an MR element, and 3 is a magnetic track formed on the outer periphery of the magnetic drum 1.

In the present invention, as shown in FIG. 1, the magnetic track 3 is formed by three magnetic tracks 3-1, 3-2, 3-3 arranged along the axial direction of the magnetic drum 1.
The upper two tracks 3-1 and 3-2 are used as absolute position output tracks to record an absolute pattern based on a cyclic random number sequence, and the lower track 3-3 is provided with a sine wave signal. The magnetic poles N and S are regularly and alternately recorded.

FIG. 2 is a development view of the outer peripheral surface of the magnetic drum 1.
A portion having no recording signal is provided on the absolute position output track 3-1 and a signal is recorded on the portion of the absolute position output track 3-2 corresponding to this portion. On the contrary, no signal is recorded on the portion of the output track 3-2 corresponding to the portion of the recorded signal of the track 3-1.

FIG. 3 is a development view showing the relationship between the magnetic track of the magnetic drum 1 and the MR element in the magnetic sensor 2 according to the present invention. As is apparent from FIG. 3, in the magnetic sensor 2 of the present invention, absolute position output tracks 3-1 and 3 are provided.
-2, the MR elements R ₁₁ , R ₁₂ , R ₂₁ , and R ₂₂ for output, which are arranged so as to face each other, are coupled by three terminals, and the MR elements R ₁₁ , R ₁₂ and R ₂₁ , R _{22 are} coupled by three terminals. The respective sets are arranged so as to be separated from each other by a half pitch λ / 2 where λ is the minimum recording pitch of the magnetic tracks.

When the magnetic drum 1 is moved in the arrangement direction of magnetic recording in the arrangement shown in FIG. 3, the outputs of the MR elements coupled to each of the three terminals change as indicated by e ₁ and e ₂ in FIG. When these outputs e ₁ and e ₂ are input to the first processing circuit shown in FIG. 5, the output e _{01 of} FIG. 4 is obtained. In FIG. 5, Ri, R
f is a fixed resistor and 4a is an operational amplifier. In the developed view of FIG. 3, a 1-bit detector is composed of a set of "H bridges" formed by four MR elements R ₁₁ , R ₁₂ , R ₂₁ and R _22. If n "bridges" are arranged in the moving direction at intervals of the minimum recording pitch λ of the magnetic track, an output of absolute position of n bits can be obtained.

Two absolute position output tracks 3-
Two-phase sine wave output track 3 adjacent to 1, 3-2
The minimum recording pitch of 3 is the absolute position output track 3-
1 and 3-2 are set to λ, recording is performed at the same pitch in one round, and MR elements R ₃₁ and R ₃₂ provided facing the sine wave output track 3-3 are (n + 1/2) λ. (However, n =
0, 1, 2, ...) (n = 1 in FIG. 3) and three terminals are coupled to each other, and the MR elements R ₃₁ , R ₄₁ are nλ / n.
3 (n = 1, 2, ...) (n = 2 in FIG. 3) and the MR elements R ₄₁ and R ₄₂ are arranged at an interval of λ / 2.
Connect the terminals. When the outputs e ₃ and e ₄ obtained from the respective three-terminal couplings are input to the second processing circuit in FIG. 6, two-phase sine waves with a phase difference of π / 4, that is, sin θ, as in e02 in FIG. , Cos θ are obtained. In FIG. 6, reference numeral 4b is an operational amplifier.

The first and second three-terminal couplings are nλ as described above.
Since they are arranged at intervals of / 3 to form an "H bridge", the output after being calculated by the operational amplifier 4b shown in FIG. 6 becomes a sine wave with less distortion of the third harmonic.

FIG. 7 is a principle diagram showing the relationship between the pattern to be detected 5 and the detection section 6. In FIG. 7, a case where eight absolute positions of the rotating body are detected will be described. Detected pattern 5
Therefore, if the detection unit 6 detects a 3-bit signal, eight positions can be detected as codes 0 to 7.

That is, in FIG. 7, when 3 bits are read while shifting the detection unit 6 to the right by 1 bit, as shown in FIG.

7 6 4 0 1 2 5 3

Can be coded as Since the position of the rotating body can be read by the code of 0 to 7, the absolute value of 8 points can be read. The above 7, 6, 4, 0, 1, 2,
Regarding the absolute values of 5 and 3, if the numerical values corresponding to the code values are stored in the storage element in advance, the values 0 to 7 can be read in order.

In the above description, the case where 8 points in one rotation are read by the 3-bit detector has been described. Similarly, if the detector is composed of n bits, the absolute value of the nth power of 2 in one rotation is described. Can be read.

FIG. 9 shows an arithmetic processing unit for an absolute encoder according to the present invention. 100 is a detection unit of the absolute encoder, 101 is a code converter, 102 is a latch circuit, 103 is a sample and hold circuit, 10
4 is a CPU, 105 is an A / D converter, 106 is a ROM,
107 is a buffer.

In the output of the detecting unit 100 of the absolute encoder in the arithmetic processing unit shown in FIG. 9, the signal indicating the value of the direct absolute position obtained from the magnetic tracks 3-1 and 3-2 is the code converter 101 and Latch circuit 10
The two-phase sine wave output obtained from the magnetic track 3-3 by the CPU 104 is captured as coarse data via the A / D converter 105.
Via the CPU 104, collated with the data stored in the ROM 106, converted into dense data corresponding to the absolute position within one cycle of the sine wave, and directly combined with the absolute position value and output from the buffer 107. To be done.

Next, referring to FIG. 10, a method of obtaining the absolute position within one sine wave will be described. As shown in FIG. 10, one sinusoidal wave period is divided into eight regions (1) to (8), and sin
When the absolute values of θ and cos θ are taken, the regions (1) and (2) are 4
It is symmetrical about 5 °. Similarly, areas (3) and (4), (5) and (6), and areas (7) and (8) are also symmetrical. Therefore, if it is possible to determine which region is within 360 degrees, it is sufficient to simply calculate from 0 to 45 degrees. By using this method, the processing time of software can be shortened.

CPU 104 in the arithmetic processing unit of FIG.
The absolute position within one cycle of the sine wave calculated in step (1) is expressed as in equation 1.

[0027]

[Equation 1]

Equation 1 shows that no detection error occurs when sin θ and cos θ change synchronously.

As shown in FIG. 11, the addition section in the CPU 104 adds the signal values from the coarse signal section 7 and the fine signal section 8. That is, by adding the value of the coarse absolute position obtained from the track having the absolute pattern as the higher order and the value of the fine absolute position obtained from within one cycle of the sine wave as the lower order and outputting the result, the size is small and the resolution is small. It is possible to realize a high absolute encoder.

In the above embodiment, the magnetic recording of the magnetic tracks 3-1 and 3-2 having the absolute pattern as shown in the developed view of FIG. 3 is performed by the MR elements R ₁₁ , R ₁₂ ,
But it is intended to be detected by the R _21, R _22, relationship with the magnetic Torakkku 3-1 3-2 magnetic recording position is complementary to the developed view shown in FIG. 2, i.e., the magnetic track 3-1 side Since the magnetic recording is performed on the magnetic track 3-2 at the position where the magnetic recording disappears, the output of the MR element at the boundary position between the two is unstable. Especially, the coarse value of the absolute position immediately after the power is turned on. Is obtained by a signal directly obtained from the MR element, so that the output of the MR element is unstable, there is a possibility that the output signal is unstable immediately and causes an error.

Therefore, in another embodiment of the present invention, the magnetic tracks 3-1 and 3 are arranged as shown in FIG. 12 in order to prevent an error immediately after the power is turned on as described above.
MR element R _11, three terminal configuration and R ₃₁ of the three terminal configuration of the three-terminal structure of R ₁₂ and R _21, R ₂₂ and R _21, R ₂₂ to detect the magnetic recording -2, R ₃₂ 3 pin configuration and Four sets of three-terminal configurations of R ₄₁ and R ₄₂ are arranged at a pitch of λ / 2, and output terminals e ₁ , e ₂ , e ₃ , and e of each three-terminal configuration are arranged.
Of the _four, husband output terminal e _1, e ₂ is connected to an input terminal of the operational amplifier 4c of the third processing circuit shown in FIG. 13, similarly, the output terminal e _3, e _4, the input terminal of the operational amplifier 4d s Connect it.

FIG. 14 shows magnetic tracks 3-1 and 3-2 having an absolute pattern and a magnetic track 3-3 for obtaining a sine wave output, and correspondingly, the processing circuit O of FIG.
The waveforms of the first signal and the second signal output from the R circuit 11a, and the waveforms cos θ and si obtained from the sine wave output
nθ are shown respectively.

The first signal corresponds to the MR elements R ₁₁ and R
It is generated by processing the outputs e ₁ and e ₂ of the first three-terminal structure composed of ₁₂ and the second three-terminal structure composed of R ₂₁ and R ₂₂ by the operational amplifier 4c, and Is output by the operational amplifier 4d from the outputs e ₂ and e ₃ of the _second three-terminal structure composed of the MR elements R ₂₁ and R ₂₃ and the third three-terminal structure composed of R ₃₁ and R _32. It is generated by processing.

[0034] The first signal is the amplitude is zero at the leftmost position of the N pole of the magnetic track 3-1, maximum at the position of the increases and moves [pi / 2 to the right, while the theta ₁ constant amplitude At 3π
The amplitude decreases at the position of / 2 and changes so that the amplitude becomes zero at the position of the south pole.

On the other hand, the second signal is the magnetic track 3-1.
Is the maximum at the left end of the N pole, and moves to the right to π / 2
During this period, the maximum value continues and the amplitude decreases from π / 2 to zero at the position of π, and further to the right the amplitude increases and becomes 3π / 2.
The position becomes maximum and the maximum amplitude is maintained up to 2π.

In FIG. 13, the operational amplifier 4c is used.
Is connected to one input terminal of the AND circuit 10a and the output terminal of the operational amplifier 4d is connected to one input terminal of the AND circuit 10b. The output terminals of the AND circuit 10a and the AND circuit 10b are connected to the OR circuit 11a. To the other input terminal of the AND circuit 10a, sin θ of the obtained sine wave output is the angle π /
An ON signal is applied in the range of the value of (θ ₁ ) between 2 and 3π / 2, and the other input terminal of the AND circuit 10b has a cos θ of the angle 0 to π / 2 of the sine wave output. The ON signal is added in the range of the value between (θ ₂ ), the output of the operational amplifier 4c is selected in the range of θ ₁ , and the output of the operational amplifier 4d is selected in the range of θ ₂ to select the OR circuit 11a.
Get more absolute position signals.

As described above, the second signal is selected from the position of zero angle of the magnetic track 3-1 to π / 2 (θ ₂ ),
Select the first signal between π / 2 and 3π / 2 (θ ₁ ),
During 3π / 2 to 2π (θ ₁ ), the second signal is selected, and the absolute position signal can be detected at any position on the magnetic track.

Similar to the first embodiment, the output signal of the OR circuit 11a shown in FIG. 13 is input to the CPU 104 of the arithmetic processing unit shown in FIG. 9 and is combined with the sine wave signal.

Further, as shown in FIG. 12, (n + 1) sets of three-terminal configuration by MR elements are provided, n sets of three-terminal configuration and "H bridge" are constructed, and the output thereof is connected to the operational amplifier of FIG. Then, the n-bit absolute position signal can be obtained by selecting the first signal and the second signal via the AND circuit and the OR circuit.

In yet another embodiment of the present invention, FIG.
5, as shown in FIG. 16, when n is an even number of bits, two tracks 3 in which an absolute pattern of 1 to n / 2 bits by a cyclic random number sequence code is axially arranged on the magnetic drum 1
Recorded on -4, 3-5 and also 2 tracks 3-6
In (3-7), an absolute pattern of (n / 2) +1 to n bits is recorded at a position which is continuous with the bits of tracks 3-4 and 3-5. When n is an odd bit, 1 to (n-1) / 2 bits are recorded on tracks 3-4 and 3-5, and (n + 1) / 2 to n bits are recorded on tracks 3-6 and 3-7. To record. By doing so, the resolution can be increased without increasing the shape of the MR element, and the above-mentioned problems can be achieved without lowering the element sensitivity.

FIG. 16 is a development view of the magnetic drum 1. The upper absolute track of 1 to n / 2 bits is composed of two magnetic tracks 3-4 and 3-5. The two magnetic tracks 3-4 and 3-5 are magnetized in the opposite relationship to each other, and the part of the track (second track) 3-5 opposite to the part magnetized in the first track 3-4 is On the opposite side of the portion which is not magnetized and is not magnetized on the first track 3-4 (second track) 3-
It is magnetized in the part 5. An absolute track of (n / 2) +1 to n bits is composed of two magnetic tracks 3-6 and 3-7 of the third and fourth, and (n / 2)
The absolute pattern corresponding to +1 bit is the first
It is recorded on the third and fourth tracks 3-6 and 3-7 so as to be at the same position as the first bit of the second tracks 3-4 and 3-5.

Next, an enlarged view of FIG. 17 shows the relationship between the magnetic drum and the MR element in the above embodiment. The MR element is coupled to three terminals and arranged so as to face the absolute tracks 1st, 2nd and 3rd, 4th, respectively. or,
MR elements R _01, R ₀₂ and R ₀₃ , R ₀₄ coupled by three terminals
Are arranged λ / 2 pitch apart, where λ is the minimum recording pitch. Furthermore, absolute track Nos. 3 and 4
The upper MR elements R _17, R ₁₈ are arranged so as to be continuous with R ₁₅ , R _16, and the absolute patterns of the third and fourth tracks and the absolute patterns of the first and second tracks are arranged in the same pattern with a shift of 4 bits. ing. The magnetic drum is rotated in such a relational arrangement, and the outputs of the three-terminal couplings are input to the processing circuit of the differential amplifier to obtain an absolute output. In the developed view of FIG. 17, one set of "H bridges" represents 1-bit information, but if n "H bridges" are arranged at intervals of λ, an absolute value of n bits can be obtained.

FIG. 18 shows the difference in the gap between the MR element and the magnetic drum, but since the number of bits is divided, it is 1
There is no spread of the sensor pattern on the track, so there is almost no gap difference between the center and the end of the MR element, and d≈
Since it becomes α, the leakage magnetic field can be sufficiently sensed, so that stable output characteristics can be obtained.

Next, the absolute position detection method will be described with reference to FIG.
This will be described with reference to FIG. FIG. 19 shows the relationship between the absolute pattern arrangements of the first track 3-4 and the third track 3-6 and "1" which is bit information corresponding to each track.
It indicates “0”. The first track 3-4 obtains 4-bit information, and the third track 3-6 obtains 4-bit information. When this bit information is detected by 3 bits, 8 positions are detected as 0 to 7. it can.

As shown in FIG. 20, 3 bits are read while shifting the detection part to the right by 1 bit in the 1 to n / 2 bit part, and then (n / 2) +1 to n bit part are similarly 3 bits. When you read

4 0 1 2 5 3 7 6

It becomes In this way, since the rotating body can be read by the number of 0 to 7, it is possible to distinguish the 8 absolute positions. For the absolute position corresponding to these values 0 to 7,
If you put it in ROM beforehand, you can read the values from 0 to 7 in order.

In this embodiment, the case of reading 8 points per rotation with a 3-bit detector has been described, but if the number of recording points per rotation is 2 ⁿ and the number of detectors is n bits, 2 n in 1 rotation.
The absolute value of the multiplication point is obtained.

Although the above description of the present invention has been made with respect to a rotary magnetic encoder, the gist of the present invention can be applied to an optical encoder, and can also be applied to a linear encoder.

[0050]

Since the absolute encoder according to the present invention has the above-mentioned structure, there is an advantage that a compact encoder with high resolution can be provided at low cost.

The value of the absolute position within one sine wave can theoretically be made as fine as possible, and high resolution can be easily achieved by obtaining a sine wave with less distortion.

Furthermore, there is a merit that an accurate absolute position value can be detected immediately after the power is turned on.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an absolute encoder of the present invention.

FIG. 2 is a development view of an outer peripheral surface of a magnetic drum in an embodiment of the absolute encoder of the present invention.

FIG. 3 is a development view showing the relationship between magnetic tracks and MR elements in the absolute encoder of the present invention.

FIG. 4 is a signal waveform from a magnetic sensor and a processing circuit in the absolute encoder of the present invention.

FIG. 5 is a first processing circuit in the absolute encoder of the present invention.

FIG. 6 is a second processing circuit in the absolute encoder of the present invention.

FIG. 7 is a principle diagram showing a relationship between a detected pattern and a detection unit in the absolute encoder of the present invention.

FIG. 8 is an explanatory diagram showing a detection pattern in the absolute encoder of the present invention.

FIG. 9 is a block circuit diagram of an arithmetic processing unit of an absolute encoder of the present invention.

FIG. 10 is an explanatory diagram in which a sine wave in the absolute encoder of the present invention is divided into eight regions.

FIG. 11 is an explanatory diagram for adding a coarse signal and a fine signal in the absolute encoder of the present invention.

FIG. 12 is a development view showing the relationship between a magnetic track and an MR element in another embodiment of the absolute encoder of the present invention.

FIG. 13 is a circuit diagram of a third processing circuit in another embodiment of the absolute encoder of the present invention.

FIG. 14 is a development view showing a correlation between a magnetic track, a first signal, a second signal, and a sine wave signal in another embodiment of the absolute encoder of the present invention.

FIG. 15 is a perspective view showing still another embodiment of the absolute encoder of the present invention.

FIG. 16 is a development view of the outer peripheral surface of the magnetic drum in the above-described embodiment of the absolute encoder of the present invention.

FIG. 17 is a development view showing the relationship between the magnetic track and the MR element in the above-described embodiment of the absolute encoder of the present invention.

FIG. 18 is a diagram illustrating the relationship between the magnetic drum and the magnetic sensor gap in the above-described embodiment of the absolute encoder of the present invention.

FIG. 19 is a principle diagram showing a relationship between a detected pattern and bits in the above-described embodiment of the absolute encoder of the present invention.

FIG. 20 is an explanatory diagram showing a detection pattern in the above-described embodiment of the absolute encoder of the present invention.

FIG. 21 is a development view of a magnetic track and a magnetic sensor in a conventional absolute encoder.

FIG. 22 is a relationship between a conventional magnetic drum and a leakage magnetic field.

FIG. 23 is a diagram illustrating a relationship between a gap between a conventional magnetic drum and a magnetic sensor.

[Explanation of symbols]

1 Magnetic Drum 2 Magnetic Sensor 3 Magnetic Track 3-1 Absolute Position Output Track 3-2 Absolute Position Output Track 3-3 Track Outputting Sine Wave Signal 3-4 Absolute Position Output Track 3-5 Absolute Position output track 3-6 Absolute position output track 3-7 Absolute position output track R ₁₁ MR element R ₁₂ MR element R ₂₁ MR element R ₂₂ MR element R ₃₁ MR element R ₃₂ MR element R ₄₁ MR Element R ₄₂ MR element e ₁ output e ₂ output e ₀₁ output e ₀₂ output Ri fixed resistance Rf fixed resistance 4a operational amplifier 4b operational amplifier 4c operational amplifier 4d operational amplifier 5 detected pattern 6 detection unit 7 rough signal obtained from absolute position output track 8 Dense signal obtained from sine wave output 20 Magnetic sensor 30 Track 100 Detection unit 101 Code converter 102 Latch times Path 103 Sample and hold circuit 104 CPU 105 A / D converter 106 ROM 107 Buffer 10a AND circuit 10b AND circuit 11a OR circuit

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[Procedure amendment]

[Submission date] April 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

SUMMARY OF THE INVENTION An absolute encoder of the present invention is a magnetic drum provided with a track having an absolute pattern of a cyclic random number sequence code, and a detection for reading a pattern in the longitudinal direction of the track with respect to the magnetic drum. In an absolute encoder having a container, the absolute pattern is sequentially divided and recorded on at least two tracks arranged in parallel in the axial direction of the magnetic drum.

Claims (3)

[Claims] 1. An absolute encoder comprising a magnetic drum provided with a track having an absolute pattern based on a cyclic random number sequence code, and an absolute encoder provided with a detector for reading the pattern in the longitudinal direction of the track with respect to the magnetic drum. An absolute encoder characterized in that an absolute pattern is sequentially divided and recorded on at least four tracks arranged in parallel in the axial direction of a magnetic drum. 2. An additional track for outputting a two-phase sine wave in synchronization with the track having the absolute pattern is provided on the magnetic drum, and a detector for reading the pattern reads from the plurality of tracks having the absolute pattern. 2. The absolute encoder according to claim 1, wherein the absolute position value and the absolute position value obtained by calculating the sine wave information obtained from the additional track are added and output. .. 3. A first signal from the plurality of tracks having an absolute pattern by the detector, and a second signal which is out of phase with the first signal by half the pitch of one pole of magnetic recording. Signal, and selecting either the first signal or the second signal according to the absolute position value obtained by calculating the sine wave information, and calculating the sine wave information. 3. The absolute encoder according to claim 2, wherein the absolute encoder is added and output.