JP2676878B2 - Absolute encoder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary encoder for detecting a rotation angle of a rotating body or a linear encoder for detecting a moving amount of a linearly moving moving body, and more particularly to a linear encoder from a reference position. The present invention relates to an absolute encoder capable of detecting absolute displacement.

"Prior Art" FIG. 6 is a block diagram showing a configuration of a conventional incremental type absolute rotary encoder. In this figure, reference numeral 1 is a pitch signal track, which is provided along a predetermined circular orbit of a magnetic recording medium that rotates in conjunction with a rotating body. And this pitch signal track 1
In this, sinusoidal magnetic information having a constant wavelength λ is repeatedly recorded as a pitch signal. Reference numerals 2a and 2b denote magnetic sensors, each of which has a magnetoresistive element (MR element) formed on a glass substrate. Here, the magnetoresistive element is composed of an element material that causes a phenomenon in which the specific resistance changes according to the strength of the magnetic field when placed in a magnetic field, that is, a so-called magnetoresistive effect. Utilizing this, the sinusoidal magnetic information recorded on the pitch signal track 1 is read. Further, the magnetic sensors 2a and 2b are (k ±
1/4) λ (k is an integer) is spaced apart and is arranged to face the pitch signal track 1. And pitch signal track 1
Is movable in the direction of arrow M with respect to the magnetic sensors 2a and 2b. Further, the resistance values of the magnetoresistive element patterns of the magnetic sensors 2a and 2b are changed by the magnetic field received from the pitch signal track 1, and as a result, the magnetic sensors 2a and 2b have a level corresponding to the positional relationship with the pitch signal track 1. The signal is obtained. That is, θ = 0 to 0 for a period of one cycle of the sinusoidal magnetic information on the pitch signal track 1.
If it is 2π, sin θ from the magnetic sensor 2a, magnetic sensor 2
From b, the level signal of cos θ is obtained. Then, when the pitch signal track 1 moves with respect to the magnetic sensors 2a and 2b, the phase from the magnetic sensors 2a and 2b changes by π.
/ 2 phase-shifted detection signals sin θ (A phase) and cos θ (B
Phase) is obtained.

Next, 3 is a division circuit, which is composed of A / D (analog / digital) converters 3a and 3b and an angle calculation unit 3c.
In the A / D converter 3a, the A phase detection signal (sin θ) is A / D converted and digital data Da is output. In addition, A / D converter 3
In b, the B-phase detection signal (cos θ) is A / D converted and digital data Db is output. Then, in the angle calculation unit 3c,
From the digital data Da and Db, the angle data θ is calculated and output. Here, the angle data θ is the magnetic sensor 2a in one magnetization section of the pitch signal track 1.
Alternatively, it shows the position of 2b. The angle calculation unit 3c is composed of a digital PLL circuit or the like.
No. 1-157063.

Next, 4 is a magnetic pole counting circuit, which is a waveform shaping circuit 41, 42.
And 43, a direction discriminating circuit 44, and a counter 45. In the waveform shaping circuits 41 and 42, the A-phase and B-phase detection signals are waveform-shaped and output. in this case,
When the output signals P ₁ and P ₂ of the waveform shaping circuits 41 and 42 are rectangular waves whose phases are shifted from each other by π / 2 as shown in FIG. 7, and the rotation direction of the magnetic recording medium is the positive direction. Is a pulse
When P ₁ advances, in the negative direction, the pulse P ₂ advances. Then, in the direction determination circuit 44, for example, a pulse
When P ₁ rises, the level of pulse P ₂ is “H” or “L”
The direction is determined by whether or not. The output signal Sw of the direction determination circuit 44 is the up / down switching terminal U / of the counter 45.
Supplied to D. Then, the counter 45 counts the pulse P ₁ while switching up or down by the signal Sw. In this example, up-counting is performed when the magnetic recording medium is rotating in the positive direction, and down-counting is performed when the magnetic recording medium is rotating in the negative direction. Also, each time the origin detection sensor (not shown) passes the origin position, the origin signal Sz is detected at the origin position,
After passing through the waveform shaping circuit 43, this becomes the origin pulse Pz and is supplied to the reset terminal R of the counter 45. As a result, the counter 45 is reset every time the origin detection sensor reaches the origin position. Therefore, the counter
The count value N of 45 is a value corresponding to the number of magnetic sections (the number of magnetic poles) on the pitch signal track 1 that the magnetic sensors 2a and 2b have passed between the current position of the magnetic sensors 2a and 2b and the origin position. Become. Then, the count value N of this counter 45
And the angle data θ of the angle calculator 3c are output as absolute position data Dout.

"Problems to be Solved by the Invention" The conventional rotary encoder described above has the following problems.

A configuration for producing the origin signal Sz is required.

Since the counter 45 is not initialized until the origin signal Sz is detected at the origin position, the absolute position data Dout becomes undefined.

Direction discriminating circuit 44, counter 45 for counting the number of pitches
Etc. are required, and the configuration becomes complicated.

If the rotary encoder power supply is cut off instantaneously, the data in the counter 45 is destroyed, so it is necessary to back up the power supply.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an absolute encoder that does not need to generate an origin signal, does not need to count the number of pitches, and can obtain absolute position data. I am trying.

"Means for Solving the Problem" The present invention is a pitch signal track provided along a predetermined route on a recording medium, in which N poles and S poles are alternately recorded at a constant pitch in a sine wave shape. Moreover, the recording orbit is recorded in a sine wave shape, and the recording pitch due to the magnetization and the pitch of the undulation are recorded in a repeating number having no common prime factor between the start point and the end point. A pitch signal track, a magnetic sensor arranged to face the pitch signal track to detect a magnetization state of the pitch signal track, and a first signal based on repetition of the N pole / S pole from a detection output of the magnetic sensor. And a signal separation circuit for extracting a second signal based on the swell and a combination of the phases of the first and second signals, and the pitch signal transformer of the sensor. It is characterized by comprising detecting means for detecting the absolute position with respect to click.

[Operation] According to the above configuration, the first signal based on the change in magnetization and the second signal based on the undulation are extracted from one track. Since the change pitch of the magnetization and the pitch of the undulation are recorded as the number of repetitions having no common prime factor between the start point and the end point, the start point,
Excluding the end point, the combination of the phases of the first signal and the second signal is always different. In other words, no matter where the magnetic sensor is on the track, the combination of the phases of the first and second signals detected by the sensor is uniquely determined. Therefore, the absolute position of the sensor can be detected from the combination of the phases.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are diagrams showing the configuration of an absolute rotary encoder according to an embodiment of the present invention. FIG. 1 is a block diagram showing the electrical configuration, and FIG. 2 is a rotational angle or rotational speed detection. 1 is a perspective view of a measuring disc 11 mounted on a rotating shaft to be mounted.

A ferromagnetic material is attached to the outer peripheral surface of the measurement disk 11, and the pitch signal track Tr is formed on the outer peripheral surface by magnetization. As shown in FIG. 3 (a), the pitch signal track Tr is recorded in such a manner that the N poles and the S poles are alternately arranged at a constant pitch and the magnetization strength changes in a sinusoidal manner. The recording orbit is recorded in a sine wave pattern. In this case, the change state of the intensity of the magnetization is the wavelength λ ₁ (see FIG. 3 (a)), and it makes one round from the reference point P (start point) shown in FIG. 2 and returns to the reference point P again ( It is repeatedly recorded N ₁ times until the end point). In addition, the waviness state has a wavelength λ ₂ (see FIG. 3C), and the reference point P
It is repeatedly recorded N ₂ times from the time it takes to make one lap to return to the reference point P. Then, the number of repetitions N ₁ and N
_{The two} have a relationship that does not have common prime factors.

Next, although not shown in FIG. 2, the three magnetic sensors (MR elements) 12 facing the track Tr described above are shown.
~ 14 are placed and fixed. These magnetic sensors
Each of 12 to 14 has a detection width equal to the width of the track Tr as shown in FIG. 3B, and is attached in the positional relationship shown in FIG. That is, with reference to the mounting position 12a of the magnetic sensor 12, the magnetic sensor 13 is located at a position 13a spaced from the position 12a along the outer peripheral surface by (k ± 1/4) λ ₁ (k = 0,1,2 ...). , The magnetic sensor 14 is disposed to face the track Tr, and the magnetic sensor 14 is separated from the magnetic sensor 12a along the outer peripheral surface by (k ± 1/4) λ ₂ (k = 0,1,2 ...) At the position 14a. It is arranged opposite to. Further, the positions in the vertical direction (thickness direction of the measurement disk 11) are the same for all three, and as shown in FIG. 3B, the upper end of the magnetic sensor faces the waviness top of the track Tr. The position.

Then, when the measurement disk 11 rotates, each magnetic sensor 12 to 14 outputs a sine wave signal corresponding to the change in the magnetization of the track Tr in accordance with the rotation. Further, the magnetic sensors 12 to 14 are located at the position A1 in FIG.
When facing, the output of the magnetic sensors 12-14 becomes maximum,
Further, when the magnetic sensors 12 to 14 are located at the location A2 in FIG. 3A and the surface facing the track Tr is minimized, the output of the magnetic sensor 12 is minimized. That is, each magnetic sensor 12
The output of ~ 14 is track Tr
The sine wave signal based on the change in the magnetization of is modulated by the sine wave signal based on the waviness of the track Tr.

Next, the output signals of the above-described magnetic sensors 12 to 14 are the first
Signal separation circuit amplified by the amplifiers 15-17 shown in the figure
Supplied to 20-22. The signal separation circuits 20 to 22 are each a third
The signal having the waveform shown in FIG. 3C is separated into a sine wave signal Sm (see FIG. 5A) based on a change in magnetization and a sine wave signal Su (see FIG. 5B) based on waviness. Circuit.
Then, the signal separation circuit 20 separates the output signal of the amplifier 15 into the signal Sm1 based on the change in magnetization and the signal Su1 based on the undulation, the signal Sm1 to the A / D converter 24, and the signal Su1 to the A / D converter. Output to the converter 25 respectively. The signal separation circuit 21 separates the output signal of the amplifier 16 and converts the signal Sm2 based on the change in magnetization into an A / D converter.
Output to 26. Further, the signal separation circuit 22 separates the output signal of the amplifier 17 and outputs the swell-based signal Su3 to the A / D converter 27.

Here, the period of one cycle of the magnetization change of the track Tr is θ ₁
= 0 to 2π, the signals Sm1 and Sm2 are Sm1 = sin θ ₁ Sm2 = cos θ ₁ respectively. Similarly, when the period of one cycle of the swell of the track Tr is θ ₂ = 0 to 2π, the signals Su1 and Su3 are Su1 = sin θ ₂ Su3 = cos θ ₂ respectively.

Next, the A / D converters 24 to 26 respectively output the signals Sm1, Sm2, S described above.
u1, Su3 is converted into digital data, and angle calculation units 28,29
Output to The angle calculation units 28 and 29 are each configured by a digital PLL, and the angle calculation unit 28 uses the data sin θ ₁ and cos.
angle data theta ₁ is calculated from theta _1, the angle calculation unit 29 data
sin [theta _2, calculates the angle data theta ₂ from cos [theta] _2.

Here, the angle data θ ₁ indicates the position of the magnetic sensor 12 in one magnetization section of the track Tr, and the angle data θ ₂
Is a magnetic sensor within one cycle of the swell of the track Tr.
12 positions are shown.

By the way, as described above, the number of times N _{1 of} magnetization is repeated and the number of times N _{2 of} undulation are not related to each other. As a result, when the magnetic sensor 12 relatively makes one revolution on the outer circumference of the measurement disk 11 from the reference point P (FIG. 2) of the track Tr, the signals Sm1 and Su1 are uniformly out of phase with each other. The phase relationship at the time of departure and the phase relationship at the time of departure is restored. However, during this period, one phase relationship between the signals Sm1 and Su1 appears only once. Further details will be described. Now, the angle data θ ₁ c and θ ₂ c calculated based on the signals Sm1 and Su1 detected at the sensor position C shown in FIG. 5 will be considered. While magnetic sensor 12 rotates one round relatively track Tr, angle data theta ₁ c sensor position as obtained is N ₁ point, sensor position angle data theta ₂ c is obtained there places N _2. However, the angle data θ ₁ c
And the angle data θ ₂ c is obtained, there is only one position of the point C during one round of the track Tr. That is, if the angle data θ ₁ and the angle data θ ₂ are determined, the absolute position of the magnetic sensor 12 from the reference point P on the track Tr is uniquely determined.

Next, the absolute position data table 30 shown in FIG.
Is composed of ROM, and angle data θ ₁ , θ ₂
The absolute position data corresponding to the combination is stored. Then, the angle data θ ₁ and θ _{2 are} output from the angle calculators 28 and 29.
Is supplied, the corresponding absolute position data is read and output as data Dout.

Incidentally, in this embodiment, the angle calculation units 28 and 29
Although the angle data θ ₁ and θ ₂ output by is converted to absolute position data, the digital data output by the A / D converters 24 and 25 can be directly converted into absolute position data Dout. It is possible.

[Advantages of the Invention] As described above, according to the present invention, it is not necessary to create an origin signal, and it is not necessary to count the number of pitches.
Absolute position data can be obtained. As a result, the advantage that the configuration is simple is obtained, and the advantage that no battery backup is required is also obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an absolute encoder according to an embodiment of the present invention, FIG. 2 is a perspective view showing a measuring disk 11 used in the embodiment, and FIG. 3 is a magnetized state of a track Tr, a track Tr and a magnetic field. FIG. 4 is a diagram showing the positional relationship of the sensors and the output signals of the magnetic sensors, FIG. 4 is a diagram showing the fixed positions of the magnetic sensors 12 to 14, FIG. 5 is a waveform diagram showing the output signals of the signal separation circuit 20, and FIG. FIG. 7 is a block diagram showing a configuration of a conventional rotary encoder, and FIG. 7 is a waveform diagram showing output signals of the waveform shaping circuits 41 and 42 in FIG. 11 …… Measurement disk, 12〜14 …… Magnetic sensor, 20〜22 …… Signal separation circuit, 28,29 …… Angle calculator, 30 …… Absolute position data table, Tr …… Track.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-32117 (JP, A) JP-A-2-64407 (JP, A) JP-B 4-10975 (JP, B2)

Claims (1)

(57) [Claims] 1. A pitch signal track provided along a predetermined route on a recording medium, wherein N poles and S poles are alternately recorded at a constant pitch in a sine wave shape, and a recording track thereof. Is undulated in a sinusoidal manner, and the recording pitch by the magnetization and the pitch of the undulation are recorded from a start point to an end point in a repeating number having no common prime factor, and a pitch signal track, (B) a magnetic sensor that is arranged so as to face the pitch signal track and detects a magnetization state of the pitch signal track; and (c) a first output based on the repetition of the N pole / S pole from the detection output of the magnetic sensor. A signal separation circuit for extracting a signal and a second signal based on the undulation, respectively, and (d) a pitch signal track of the sensor based on a combination of phases of the first and second signals. An absolute encoder comprising: a detection unit that detects an absolute position with respect to.