JPH03287013A - Code plate and absolute encoder using the same - Google Patents

Abstract

PURPOSE:To improve the stability and reliability without increasing the absolute number of tracks on the code plate by dividing units into two in the length direction of the tracks, and providing the same physical properties with an original code to one section and the opposite physical properties from the original code to the other. CONSTITUTION:The respective minimum read unit of length lambda of the code plate A are divided into two in the track length direction; and the original numerals are assigned to the section T2 and the reciprocal numbers are assigned to the other section T1. Plural sets of sensors S1 and S2 are arranged at a detection part B nearly at intervals 1/2lambda and differential amplifiers M are provided respectively. Each amplifier M subtracts the output of S2 from the output of S1 and outputs '0' when the result is negative or 1 when positive. Consequently, even if foreign matter sticks, the stability and reliability can be secured with one track as well as the use of two tracks.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a code plate used in an absolute encoder and a one-track absolute encoder using the code plate. The present invention relates to a pattern structure and a method for detecting the minimum reading unit from the track.

[Prior Art] Various absolute encoders are known as measuring instruments that detect angular position coordinate values associated with the rotation of a rotating body and position coordinate values associated with the movement of a linearly moving body. - Numerically speaking, an absolute encoder consists of a code plate that forms an absolute track and a detection section that is movable relative to this track, one of which is fixed to the object to be measured. The relative movement between the two along with the movement is output as a ``numeric code corresponding to the position coordinate value of the detection unit with respect to the code plate.''

Here, absolute track replaces the coordinate scale with a series of numerical codes, and each value in the series is expressed in the minimum readable unit with differences in various physical properties such as transparency, reflectance, direction of magnetization, etc. This is what I did. On the other hand, the detection section is equipped with a detector - a food sensor, a magnetic head, etc. - that detects this physical property, and the physical property detected by the detector is converted into the original numerical value, and from this numerical value the original numerical code is generated. is assembled. This numerical code corresponds to the positional coordinate values of the detection unit with respect to the code plate at this time, and determines each absolute position.

Conventionally, such an absolute encoder is a multi-track type absolute encoder that reads one binary number from each absolute track of a predetermined number of bits and assembles a "binary ordinal numerical code of a predetermined number of bits." Encoders were common. However, in recent years, one-track absolute encoders have been actively developed and reported in which the track pattern has been devised to express numerical codes using multiple minimum reading units on one track. . In this one-track type absolute encoder, the numerical code is only used to mutually determine the absolute positions of the code plate and the detection section, and does not have a regular order like the multi-track type absolute encoder. However, since only one absolute track is required, there are various advantages regarding sensor placement and code plate production.

As an example of such a one-track absolute encoder, Japanese Patent Application Laid-open No. 1-152314 discloses "n
An absolute track is formed on the code plate, representing the complete periodic series of bits in an optical light-dark pattern;
A one-track absolute encoder has been introduced in which a numerical code is assembled by simultaneously detecting n consecutive minimum reading units on this track in parallel using n sensors provided in the detection section.

The absolute track used here represents a binary number sequence called a total periodic sequence.
For example, when the minimum reading unit has 16 cycles, the sequence is: 0000110101111001 1↑1↑ ...-Transparent and opaque minimum reading units are arranged according to the movement direction. Here, after 01 at the right end, it returns to the first OO... On the other hand, the detection section is provided with four sensors that distinguish between transparent and opaque, and reads a 4-bit code from four consecutive minimum reading units on the track indicated by arrows ↑. In other words, the absolute position where this 0000 is detected is the first
As the absolute position of , when the detection part moves in one direction of the arrow,
1st absolute position: 0OOO 2nd absolute position: 0OO1 3rd absolute position: 0O10 4th absolute position: 0100 5th absolute position 1001 6th absolute position: 0O11 7th absolute position ・0111 8th Absolute position: 1111 9th absolute position: 1110 10th absolute position: 1101 11th absolute position: 1010 12th absolute position: 0I01 13th absolute position: 1011 14th absolute position: 0110 15th absolute position Absolute position: 1100 16th absolute position: 1000 1st absolute position: 0OOOO, and so on, 16 different numerical codes are read. Therefore, conversely, the absolute position of the detection unit with respect to the code plate is determined from the read numerical code.

FIG. 3 shows an example of a detection circuit employing a phytosensor as a sensor for detecting transparency or opacity in 16 minimum reading units per revolution in this one-track absolute encoder. At this time, the detection section B is provided with four sets of detection circuits for assembling a 4-bit numerical code, or only one set is shown here. Also, if the minimum reading unit is transparent, the OV is output as a value of 0, and if it is opaque, the value is ! As a result, an output of Vcc level is obtained.

In FIG. 3, a detection unit B is configured with a code plate A sandwiched therebetween. In the detection section B, a light source is arranged so as to illuminate the minimum reading unit t of the absolute track T±, and a photosensor S is arranged so as to face the light source with the code plate A in between. The emitter side of the photosensor S is grounded.
V, the collector side is connected to the power supply level VCC through the resistor R, and the voltage on the collector side is the output terminal. output level.

When the detection circuit configured as described above detects the transparent minimum reading unit t on the absolute track T as shown in FIG. It passes by and enters the foot sensor S. As a result, the foot sensor S becomes conductive, and the collector voltage, that is, the voltage at the output terminal Q becomes approximately OV.

On the other hand, when detecting the opaque minimum reading unit t, the illumination light from the light source is blocked by the code plate A and does not reach the photosensor S. As a result, the photosensor S becomes insulated, and the collector voltage, that is, the voltage at the output terminal Q increases to Vcc.

[Problems to be Solved by the Invention] By the way, in the one-track absolute encoder shown in FIG. 3, if a foreign object W is attached to one of the transparent minimum reading units of the code plate A, Part of the illumination light is blocked by the foreign object W, and the amount of light received by the photosensor S decreases, and the photosensor S enters an intermediate state between conduction and insulation, and the output from the output terminal Q becomes undefined.

Furthermore, even if there is no foreign object W, as the minimum reading unit of the absolute track becomes finer due to the miniaturization and higher resolution of single-track absolute encoders, the spacing between sensors and sensor light reception will become smaller. As the area decreases, ■ Decrease in signal-to-noise ratio due to decrease in sensor light-receiving area, ■
Mutual interference, (1) insulation problems, (2) influence of diffracted light from adjacent minimum reading units, etc. could no longer be ignored, impairing the stability and reliability of the output at the output terminal Q.

Therefore, the applicant of the present application first proposed a method for restoring and improving the stability and reliability of this output in the patent application filed in 1983-15.
No. 1199 introduces an absolute encoder using two absolute tracks.

Here, the code plate includes, for example, a first absolute track in which the minimum reading units are arranged according to the total periodic system as described above.

0000110101111001 and a second absolute track with a reverse pattern in which each minimum reading unit of the first absolute track is replaced with a minimum reading unit that has opposite physical properties: 1111001010000110 are arranged in parallel.

On the other hand, in the detection section, the first and second absolute tracks: 1st=0000110101111001...
- Two corresponding (upper and lower) minimum reading units of movement direction 2nd = 1111001010000110 are simultaneously detected to form a differential output, and a numerical code is obtained by combining a predetermined number of bits of this differential output. . In other words, in this example, if the result of subtracting the lower value from the upper value is negative, it is determined as O1. If it is positive, it is determined as 1, and the numerical code is oooo
is being read.

In this type of absolute encoder, 2
Since information from one minimum reading unit is used to determine 1.0 in each digit of the numerical code, the stability and reliability of the read numerical code is higher than that of the conventional example shown in Figure 3, and the external noise It can be said that it is also strong.

However, although this type of absolute encoder only requires two trees, it requires multiple tracks, and the minimum reading unit of each of these multiple tracks and the distance between each sensor for detecting these are Strict synchronization and positioning are essential. This is a one-track absolute
As encoders become smaller and have higher resolution, it is not easy to make the minimum reading unit of an absolute track finer.

That is, here, the problem of the conventional absolute encoder shown in FIG. 3 has not been completely solved.

SUMMARY OF THE INVENTION An object of the present invention is to provide a one-track absolute encoder that does not increase the number of absolute tracks on a code plate and provides high stability and reliability of read numerical codes.

[Means for Solving the Problems] The code plate according to claim 1 of the present invention has a predetermined pattern of 0 and 1 on a track when two minimum reading units having different physical properties are represented by 0 and 1. In a one-track absolute encoder code plate formed with It is given physical properties opposite to the sign of .

One-track absolute type according to claim 2 of the present invention.
The encoder uses a code plate (A
) and a detection unit (B
), wherein the code plate (^) is composed of the code plate according to claim N1, and each basic sensor constituting the basic sensor group has a 1/2λ
Consisting of a pair of sensors separated by a pitch, for each basic sensor, a differential amplifier (
(including an amplification factor of 1), and the absolute position is detected using the output of each differential amplifier.

One-track absolute type according to claim 3 of the present invention
The encoder includes a code plate (A+) according to claim 1, and 4 n + 2 (n is a natural number of 2 or more) sensors arranged at a 1/4λ pitch, among which 2 n odd-numbered sensors counting from the 1st This pair of sensors is made into a pair in order, and this pair is used as a basic sensor. One group consisting of a sensor and a differential amplifier is defined as a sensor group, and 2n even-numbered sensors counting from the second are formed into pairs in order, and this pair is defined as a basic sensor.For each basic sensor, A differential amplifier (including an amplification factor of 1) is provided to take the difference between the outputs of a pair of sensors, and a group consisting of n basic sensors and a differential amplifier is defined as a second sensor group. 2n odd-numbered sensors are formed into a pair in order, and this pair is used as a basic sensor, and a differential amplifier (including an amplification factor of 1) is provided for each basic sensor to take the difference between the outputs of the pair of sensors. A group consisting of n basic sensors and a differential amplifier is defined as a third sensor group. ■ 2n even-numbered sensors counting from the 4th are formed into pairs in order, and each pair is defined as a basic sensor. For basic sensors, a differential amplifier (including an amplification factor of 1) is provided to take the difference between the outputs of a pair of sensors, and a group consisting of n basic sensors and differential amplifiers is defined as a fourth sensor group. Board (
A) In an n-bit one-track absolute encoder consisting of a detecting section (B) that is movable relative to
, a control signal generating means for generating four types of control signals; 3. Selection means for selecting the fourth sensor group;

One-track absolute type according to claim 4 of the present invention.
The encoder is a one-track type absolute encoder according to claim 3, wherein the :7-ant cl- small signal generating means is provided on a code plate (A) in parallel with the absolute track and has pitches in the same phase. or λ incremental
track and the incremental track has a phase difference of 178λ
It consists of two sensors provided in the detection section (B) at a distance of 1/4λ pitch from each other.

[Claim 5 of the present invention] Track type absolute
The encoder is a one-track absolute encoder C according to claim 3, wherein the control signal generating means is provided on a code plate (A) in parallel with the absolute track, and has a phase difference of 1/8λ. An incremental track having a pitch of λ, and two sensors KS(B)&: which are in the same phase with the incremental track and are provided at a distance of 1/4λ pitch from each other.

[Function] The code plate according to claim 1 of the present invention, like the conventional code plate, has an absolute track in which a sequence of numbers such as a full period sequence is expressed in an array of minimum reading units, and has an absolute track.
This is to detect a minimum reading unit of a predetermined number of continuous bits on a track, convert it back to a numerical value, and assemble a numerical code for determining each absolute position.

However, here, unlike the conventional example shown in FIG. 3, the minimum reading unit consists of two sections divided into two in the longitudinal direction of the track, and each of the two sections has physical properties corresponding to opposite numerical values. has been granted. For example, for the total periodic sequence: 0000110101111001, if 0 is expressed as O-1 and 1 as 1-O, each numerical value 0.1 is sequentially expressed as 0-1.0-1.0-1, 0-1. ,
1-0, 1-0, 0-1, 1-010-1, l-
0, 1-0, 1-0, 1-0, 〇 -1, O-1, 1-
Therefore, on the absolute track, the number sequence = 01010101101001+00
A pattern with physical properties corresponding to 110101010010110 is formed.

Therefore, using this code plate, one minimum reading unit is
If the physical properties of the two sections are detected and converted into a single numerical value, the stability and reliability of the read numerical code will be improved, similar to the absolute encoder that uses the two-tree absolute track described above. is ensured.

In addition, for this code plate, if a sensor of a predetermined number of bits is arranged in the detection section at a pitch of the minimum reading unit length λ, the timing when the sensor passes on the minimum reading unit 2 dividing line is , all sensor outputs will be inverted at about the same time. Therefore, on the contrary, by detecting the reversal timing of all sensor outputs, a clock pulse can be obtained that captures the timing when the sensor passes on the line dividing the minimum reading unit into two. This is the absolute encoder control,
For example, it is convenient for controlling track reading timing.

One-track absolute type according to claim 2 of the present invention.
The encoder employs the code plate according to claim 1.
An example of a track type absolute encoder is shown below. Here, a pair of (two) sensors straddle a line that divides the minimum reading unit into two, and detect the physical properties of sections on both sides of this line. In addition, the determination of this minimum reading unit (O or 1) is determined by the output difference of a pair of sensors obtained by a difference!III amplifier.The combination of such a pair of sensors and a differential amplifier is By arranging a predetermined number of sets of bits in the detection unit in correspondence with the minimum reading unit of a predetermined number of consecutive bits on the absolute track,
Assembling a numerical code to determine absolute position. For example, the above sequence; 010101011010011001
For a code plate in which 10101010010110 is formed, 01010 is sent to the detection unit.
10110100110011...T↑↑1↑
↑↑1 ■■■■■■■■ ・・・-Movement direction I: 2 x 4 sets = 8 sensors are arranged, and a differential amplifier installed in each set By performing calculations and determining the answer as 0 if it is negative and 1 if it is positive, the output of a total of four differential amplifiers 01010101 ... T ↑ ↑ 1 1 1 1 1 ■ −■
■−■ ■−■ ■−■ Negative=0 Negative=0 Negative=O
Assemble the numerical code oooo from negative=O.

One-track absolute type according to claim 3 of the present invention
The encoder is also an example of a one-track absolute encoder employing the code plate according to claim 1. Again, a pair of sensors detects the physical properties of two sections within the smallest reading unit. Also, a predetermined number of bits! A pair of sensors is used to read a minimum reading unit of a predetermined number of bits on an absolute track to assemble a numerical code that determines absolute position.

By the way, in such an absolute encoder in which a pair of sensors detects the physical properties of two sections within the minimum reading unit, ■When a pair of sensors detects the physical properties of two sections within the minimum reading unit, For this purpose, it is necessary that the pair of sensors straddles the line that divides the minimum reading unit into two.

In addition, the sensor output becomes unstable near the boundary of the minimum reading unit or the line that divides the minimum reading unit into two, where physical properties differ before and after, so the output of the sensor that detects this area cannot be used. .

Therefore, in order to solve these problems and "continuously and stably read the absolute track including when the power is turned on," 4n,122 sensors arranged in the detection section are used. , a number of sensors twice the predetermined number of bits at appropriate phase positions with respect to the code plate are selected. In other words, out of 4n+2 sensors arranged at a 1/4λ pitch, the boundary of the minimum reading unit or the vicinity of the dividing line of the minimum reading unit is not detected, and the r mutual distance across the dividing line of the minimum reading unit is not detected. A pair of sensors J of 1/2λ are selected ni1, and from these sensors C, n consecutive minimum reading units are read on the absolute track.

Specifically, 4n,120 sensors are defined as a "sensor group J in which the interval between a pair of sensors is 1/2λ and the pitch between each pair is λ, and the detection position of each sensor group is absolute." - Shifted by 1/4λ on the track" Allocated to the first, second, third, and fourth sensor groups, and assigned to the first, second, third, and fourth control signals output from the control signal generation means. and the selection means select the first,
2nd, 3rd. Select the fourth sensor group.

Here, the first, second, third, and fourth control signals are:
For the first, second, third, and fourth sensor groups, respectively,
The state in which each sensor does not detect the boundary of the minimum reading unit or the vicinity of the two-part dividing line of the minimum reading unit, and moreover, straddles the two-dividing line - the relative position of the code plate and the detection unit. This is a signal indicating that the relationship is -. For example, the above number 114 0101010110100120011010101
0010110 is formed, 4n+2=4x in the detection section
When 4+2=18 sensors are placed and assigned to four sensor groups A to D, the center 14 sensors are shared by A-C and B-D, and 0*110*110*110*111* O11*1↑1
↑1↑11↑Ti ding T ding ↑↑↑ ding A, B, ^1BIA2
B2A2B2A3B3^3B3AaBaAaBaC,D
,C,D,C2D2C2D2C3D3C3D3C4D4
C, 4D4. Here, the numbers attached to A-D are
This corresponds to the number of digits of the numerical code, and for example, the first digit O of the numerical code is determined by the differential outputs of sensors ^1-8 that sandwich sensor B1. Further, the symbol 1 indicates the boundary of the minimum reading unit, and the symbol * indicates the vicinity of the line dividing the minimum reading unit into two, both of which are unobtrusive areas to be detected.

In such a phase positional relationship between the code plate and the detection section, the sensors ^l Al, ^, -^2, ^, -^8, A4
A4 is selected, and the numerical code 0 is determined by each differential output.
00o can be assembled.

Next, the phase position relationship between the code plate and the detection unit is shifted by 174λ, and 0*l lo*110*l IO*] l 1
*OI +*-111+ ↑ 1 ↑ 11 ↑
111 ↑ ↑ ↑ 11A, BIAI81A2B2A
2B2A3B3A3B'+A4BJJ<C, DIC, D
, C2D2C2ChC3D3C3D, C40, C404
Then, sensor D+ D+, It, -It2, C3
C3, C4-C4 are selected, and their respective differential outputs:
The numerical code 0001 is assembled.

Furthermore, the phase positional relationship between the code plate and the detection section is shifted by 1/4λ, resulting in 0*110*110*11o*i I 1*OI 1
*-44 tttttt 1 Ding Ding Ding T Ding T Ding ↑ ↑ Ding AIBI＾181＾2B2A2B
2^3B3A3B3A4B4A4B4CIDICIDI
C2D2C2D2C3D3C! When it comes to D3C4D4C4D4, sensors C1-C1, C2C:2, C3C3, c
, -C4 are selected, and their respective differential outputs construct the numerical value code)'0001.

Furthermore, the phase positional relationship between the code plate and the detection section shifts by 1/4λ, resulting in 0*110*110*110*111*01*→--1
111↑ 1 ↑ ↑ ↑ 1 ↑ ↑ 1 ↑ 1
↑ ↑ 1^IBIAIBl^2B2A2B2A3B3
AJ384B4A4B4CIDICIDIC2D2C2
When it comes to D2C3D3C303C404c4D4, sensor B+ L, 82-82, Bs B3, Ba-84
is selected, and its respective differential output gives the numerical code ooo
i is assembled.

Furthermore, the phase positional relationship between the code plate and the detection section shifts by 1/4λ, resulting in 0*110*110*110*111*0 1*→→-
4-1↑ ↑ ↑ ↑ ↑ ↑ 1 ↑ ↑ ↑ ↑
1 ↑ ↑ ↑ 1 ↑AIB+A+B+^2B2A2
B2A3B3^3a3La41'14B4CIDICI
DIC2D2C2D2C3D3C3D3C404C4D
4 and 1 (then sensor A, -A 82-^2, A3-A
3, A4-A4 is selected again, and the numerical code 0001 is assembled by their respective differential outputs.

In this way, the relative position of the code plate and the detection unit is 1/4λ
D-C-B-A-D-C-B
- Switch in the order of A, and for relative movement in the opposite direction,
By switching in the same order as A-B-C-D-A-..., it is possible to avoid detecting the boundary of the minimum reading unit or the vicinity of the dividing line of the minimum reading unit, and also to detect the vicinity of the dividing line of the minimum reading unit. Continuous, unbroken, absolute track readings are performed with suitable sensors.

The one-track absolute encoder according to claims 4 and 5 of the present invention are both examples of control signal generating means. Here, an incremental track with a large pitch is provided in parallel with an absolute track on the code plate, and a pair of sensors with a mutual spacing of 174λ is provided in the detection section for detecting the incremental tracks. In the control signal generating means configured in this way, the combination of outputs of the sensor is 4.
The type and the relative position of the code plate and the detection unit are obtained in order every time the relative position shifts by 1/4λ. For example, the above sequence 0101010110100110011010101
Part of the absolute track consisting of 0010110:○*11O
For *110*10*11*01*, incremental track: 0111011101110111
0111011...-The moving directions are arranged in parallel, and on the other hand, a pair of sensors are arranged in the detection section as indicated by arrow 1↑. The combination of the outputs of this pair of sensors is 1-0.0-0, o-i, 1-1.1-0,
In this way, there are four different combinations.

Therefore, the selection means is configured such that one set of sensor groups A to D is respectively assigned to one combination of outputs of a pair of sensors.

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

FIG. 1 is a schematic plan view of a one-track absolute encoder according to a first embodiment of the present invention. this is,
This is a one-track type absolute encoder that reads an absolute track T formed on a code plate A using four pairs of sensors S1 and S2 provided in a detection section B.

In Figure 1, code plate A has O for the white part and 1 for the shaded part.
As, clockwise from the landmark M, for the total periodic sequence 0000110101111001, the number sequence 0101010110100110011010101 where 0 is expressed as 0-1.1 as 1-0.
An absolute track T consisting of a pattern of 0010110 is formed. That is, each minimum reading unit of length λ is divided into two in the longitudinal direction of the track, and divided into two sections t in the clockwise backward direction.
2 is assigned the original value, and the other section t1 is assigned the opposite value.

On the other hand, in the detection part B, there are four pairs of sensors S1 and S2 with an interval of approximately 172λ. It is placed so that it can be detected by stepping over it. Each pair of sensors S1 and S2 is provided with a differential amplifier M, and the differential amplifier M subtracts the output of sensor S2 from the output of sensor S1, and when the answer is negative, O1 is positive. In this case, 1 is output to the output terminals Q1 to Q4.

In the one-track absolute encoder configured in this way, as the code plate A and the detection section B move relative to each other,
Absolute tracks are sequentially read at the timing when the pair of sensors S1 and S2 straddles a line that divides the minimum reading unit into two. As a result, output terminal Q1
- Full cycle series from Q4.

Each numerical code is output in the same order and with the same content as the numerical code obtained from 0000110101111001.

FIG. 2 is a partial side view of a one-track absolute encoder according to a first embodiment of the present invention. this is,
A state in which the pair of sensors S1 and S2 are detecting the minimum reading unit - straddling the minimum reading unit 2 dividing line - is shown,
This is for explaining a detection circuit including a differential amplifier M.

In FIG. 2, a detection unit B is configured with a code plate A sandwiched therebetween. The detection unit B is provided with light sources L], L2, or light sources L1. Photosensors S1 and S2 are arranged to face L2. The emitter sides of the photosensors S1 and S2 are connected to the ground level Ov, and the collector sides are connected to the resistor R1.
They are each connected to power supply level Vcc via R2. Further, the collector voltage of the photosensor S1 is inputted to the positive side input terminal of the differential amplifier M, and the collector voltage of the photosensor S2 is inputted to the negative side input terminal. Therefore, the differential amplifier M subtracts the collector voltage of the photosensor S2 from the collector voltage of the photosensor S1, and outputs the ground level Ov if the answer is negative, and the power supply level Vcc if the answer is positive. Output the voltage to output terminal Q.

When the detection circuit configured in this way detects the regions t1 and t2 of the minimum reading unit as shown in FIG. 2, the concave bright light from the light source L1 passes through the transparent region tl. Although the illumination light is incident on the photosensor S1, the illumination light from the light source L2 is blocked by the opaque region t2. This results in
Photo sensor S1 is in a conductive state, photosensor S2 is in an insulated state, and the collector voltage of photosensor S1 is approximately O.
V, the collector voltage of photosensor S2 increases to Vcc. Therefore, the differential amplifier M outputs the ground level Ov to the output terminal Q since the result of the subtraction is negative.

By the way, in this one-track type absolute encoder, if a foreign object W is attached to the transparent area t1 as shown in FIG. 2, the photosensor Sl
The amount of light received (S in FIG. 2) decreases. However, even in the worst case where the amount of light received decreases by 99% and the collector voltage of the photosensor S1 rises to nearly VCC, if the collector voltage of the photosensor S2 rises to Vcc, the differential amplifier M Since the result of subtraction is negative, the ground level Ov is output to the output terminal Q.

In other words, this one-track absolute encoder uses two pieces of information from a pair of sensors to determine whether each digit of the numerical code is 1 or O, similar to the aforementioned absolute encoder with two absolute tracks. Therefore, the stability and reliability of the read numerical values are higher than those of the conventional example shown in FIG.

FIG. 4 is a partial plan view of a one-track absolute linear encoder according to a second embodiment of the present invention.

This constitutes four sensor groups from sensors 3-1 to 3-10, and in order to detect absolute track 1 formed on code plate A, these four sensor groups are connected to code plate A. This is a one-track type absolute linear encoder that switches sequentially every 174 relative movements of detection section B. Further, in FIG. 4, an incremental track 2 and a pair of sensors 4a and 4b are used as a control signal generating means for controlling the timing of sequentially switching four sensor groups.
, the white part is O1, the shaded part is 1, and the number sequence: +1001, where 1 is replaced with 1-0.0 is replaced with 0-1: +1011
Absolute track 1 formed in a pattern of 0+01101110,
Incremental pattern 2 formed in the pattern of number sequence: 10110110110110 is formed in parallel.

On the other hand, in the detection unit B, the length of the minimum reading unit is λ,
Ten sensors 3-1 to 3-10 arranged at a pitch of 1/4λ for absolute track 1 detection and a pair of sensors 4a and 4b with a spacing of 174 for incremental pattern 2 detection are provided. ing. These ten sensors 3-1 to 3-10 are a first sensor group: (3-1, 3-3) (3-5, 3-7) and a second sensor group: (3-2, 3). -4) (3-6, 3-8) and the third sensor group (3-3, 3-5) (3-7, 3-9) and the fourth sensor group: (3-4, 3 -6) (3-8, 3-10).Here, one minimum reading unit is read by the two sensors enclosed in parentheses, and a total of 2 bits representing the absolute position are read. A numerical code is assembled.

FIG. 5 shows a detection circuit of a one-track absolute linear encoder according to a second embodiment of the present invention.

In FIG. 5, the signal selection circuit MS includes sensors 4a, 4
According to the combination of the outputs of the selected sensors 4a and 4b, one of the first to fourth sensor groups is selected according to the combination of the outputs of the selected sensors 4a and 4b.
At the same time as selecting a group, a 2-bit output indicating the absolute position is generated from the output of the selected sensor group.

That is, when the combination of the outputs of the selection sensors 4a and 4b is 01 as shown in FIG.
Sensor group: Select (3-1, 3-3) (3-5, 3-7) and
Calculate the output of 3-1 from the output of -3, and since the answer is negative, add O to the output Q, and calculate the output of 3-5 from the output of 3-7, and Since the answer is positive, 1 is output to output Q2. Therefore, the numerical codes Q2 and Ql assembled here are 10.

Next, if the detection part B deviates to the right by 1/8λ or more from the relative position of the code plate A and the detection part B in FIG. 4, the selection sensor 4a
, 4b is 00. At this time, the signal selection circuit MS switches the first sensor group to the second sensor group: (3-2, 3-4) (3-6, 3-8) to obtain the same minimum reading as in the case of FIG. Read units. That is, 3
Subtract the output of 3-2 from the output of -4, and since the answer is negative, O is subtracted from the output Ql, and the output of 3-5 is subtracted from the output of 3-7, and the answer is Since is positive, 1 is output to the output Q2. Therefore, the numerical codes Q2 and QI assembled here are as follows! It is 0.

In addition, if the detection part B further moves to the right and the detection part B deviates to the right by more than (1/4 + 1/8) λ from the relative position of the code plate A and the detection part B in FIG. 4, the selection is made. The combination of outputs from the sensors 4a and 4b is 01. At this time,
The signal selection circuit MS switches the second sensor group to the third sensor group: (3-3, 3-5) (3 to 7.3-9), and obtains the same minimum reading of 4L as in the case of Fig. 4. read That is,
Subtract the output of 3-3 from the output of 3-5, and since the answer is negative, O is subtracted from the output Q1, and the output of 3-7 is subtracted from the output of 3-9. Since the answer is positive, 1 is output to output Q2. Therefore, the numerical codes Q2 and Ql assembled here are also 10.

In addition, the stripping detection part B moves to the right, and the detection part B deviates to the right by more than (2/4 + 1/8) λ from the relative position of the code plate A and the detection part B in Fig. 4. The combination of the outputs of the selection sensors 4a and 4b is 11. At this time, the signal selection circuit MS switches the third sensor group to the fourth sensor group: (3-4, 3-6) (3-8, 3-10),
The same minimum reading unit as in the case of FIG. 4 is read. That is,
Subtract the output of 3-4 from the output of 3-5, and since the answer is negative, subtract 0 to the output Q1, and subtract the output of 3-8 from the output of 3-10, Since the answer is positive, 1 is output to output Q2. Therefore, the numerical codes Q2 and Ql assembled here are also 10.

Furthermore, if the detection part B further moves to the right and the detection part B deviates to the right by more than (3/4+1/8)λ from the relative position of the code plate A and the detection part B in FIG. 4, the selected sensor 4a, 4
The combination of outputs b is 01 as in the case of FIG. Therefore, the signal selection circuit MS selects the first sensor group: (3-1, 3-3) (3-5, 3-7) again. At this time, (3-1.3-3) detects the adjacent minimum reading unit that was not detected in the case of FIG. 4, and (3-5,
3-7) detects the minimum reading unit that was detected by (3-1, 3-3) in the case of FIG. That is, the signal selection circuit MS subtracts the output of 3-1 from the output of 3-3, and since the answer is negative, the signal selection circuit MS sets the output Q1 to 0.
Also, the output of 3-5 is subtracted from the output of 3-7, and since the answer is negative, O is output to the output Q2.

Therefore, here, the assembled numerical codes Q2, Ql
becomes 00.

1-track type/absolute linear/
In this way, the encoder sequentially switches the first to fourth sensor groups to read the absolute track T continuously without any break.

[Effects of the Invention] Since the code plate according to claim 1 of the present invention requires only one absolute track, it is better than a code plate with two absolute tracks that require synchronization between tracks. It is also easy to produce.

One-track absolute type according to claim 2 of the present invention.
Although the encoder does not require synchronization between the sensors that detect the two absolute tracks, as in the case of the absolute encoder that uses the two absolute tracks described above, The one-track type absolute encoder according to claim 3 of the present invention provides output stability and reliability similar to that of an absolute encoder using an absolute track.
The encoder switches the four sensor groups in order for each quarter of the relative movement between the code plate and the detection unit, ensuring a continuous and unbroken line between the boundaries of the minimum reading unit and dividing the minimum reading unit into two. Absolute track reading is performed that avoids areas where detection near lines is likely to become unstable, further increasing the stability and reliability of the output.In addition, the absolute position can be determined immediately and without error when the power is turned on. Prove.

In the one-track absolute encoder according to claims 4 and 5 of the present invention, the overall structure is not too complicated, and the code plate and An accurate control signal corresponding to a relative movement of 1/4λ of the detection section can be obtained. Furthermore, since the four sensor groups have a one-to-one correspondence with the combination of the outputs of these two sensors, they are more resistant to noise and error-free compared to, for example, sending them one by one using a latch circuit.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of a one-track absolute encoder according to a first embodiment of the present invention. FIG. 2 is a partial side view of a one-track absolute encoder according to a first embodiment of the present invention. FIG. 3 is a partial side view of a conventional one-track absolute encoder. FIG. 4 is a partial plan view of a one-track absolute linear encoder according to a second embodiment of the present invention. Figure 's5 shows a detection circuit of a one-track absolute linear encoder according to a second embodiment of the present invention. [Description of symbols of main parts] A... Code plate B... Detection section M... Differential amplifier T... Absolute tracks t1, t2... Areas Sl, S into which the minimum reading unit is divided
2... Photosensor Q1-Q4... Output terminal

Claims (5)

[Claims] (1) Two minimum reading units with different physical properties are 0 and 1
In a code plate for a one-track absolute encoder in which a predetermined pattern consisting of 0 and 1 is formed on the track, the unit is divided into two in the longitudinal direction of the track, and one section has the original code and A code board characterized in that the same physical properties are imparted to the other section, and physical properties opposite to those of the original code are imparted to the other section. (2) A code plate (A) having a one-track type absolute pattern track with a minimum reading unit length λ and a group of basic sensors of a predetermined number of bits arranged with a pitch length λ; ) which is movable relative to the detection unit (B
), wherein the code plate (A) is composed of the code plate according to claim 1, and each basic sensor constituting the basic sensor group has a 1/2λ
It consists of a pair of sensors separated by a pitch, and for each basic sensor, a differential amplifier (
(including an amplification factor of 1), and assembles a numerical code using the output of each differential amplifier to detect an absolute position. (3) The code plate (A) of claim 1 and 4n+2 (n is a natural number of 2 or more) sensors are 1/4λ
Arranged at a pitch, 2n odd-numbered sensors counting from [1] 1st are made into a pair in order, and this pair is taken as a basic sensor, and for each basic sensor, the difference in the output of that pair of sensors is calculated. A differential amplifier (including an amplification factor of 1) is provided, and one group consisting of n basic sensors and n differential amplifiers is defined as the first sensor group. 2n sensors are formed into a pair in order, and this pair is used as a basic sensor. For each basic sensor, a differential amplifier (including an amplification factor of 1) is provided to take the difference between the outputs of the pair of sensors. A group consisting of a basic sensor and n differential amplifiers is defined as a second sensor group, and [3] 2n odd-numbered sensors counting from the third are formed into a pair in order, and this pair is defined as the basic sensor. For each basic sensor, a differential amplifier (including an amplification factor of 1) that takes the difference between the outputs of that pair of sensors is provided, and a group consisting of n basic sensors and n differential amplifiers is 3 sensor groups, [4] 2n even-numbered sensors counting from the 4th are made into pairs in order, and this pair is taken as a basic sensor, and for each basic sensor, calculate the difference in the output of the pair of sensors. A differential amplifier (including an amplification factor of 1) is provided, and a fourth sensor group is a group consisting of n basic sensors and n differential amplifiers, and is movable relative to the code plate (A). detection part (B
), and in an n-bit one-track absolute encoder, each time the track is advanced by 1/4λ, the first, second, and third
, a control signal generating means for generating four types of control signals; , selection means for selecting a fourth sensor group; and an absolute encoder. (4) The control signal generating means includes an incremental signal having the same phase and a pitch of λ, which is provided on the code plate (A) in parallel with the absolute track.
track, and the phase difference is 1/8λ with respect to the incremental track.
4. The absolute encoder according to claim 3, further comprising: two sensors provided in the detection unit (B) at a distance of 1/4λ pitch from each other. (5) The control signal generating means includes an incremental track with a phase difference of 1/8λ and a pitch of λ, which is provided on the code plate (A) in parallel with the absolute track, and an incremental track with a pitch of λ. 4. The absolute encoder according to claim 3, comprising: two sensors which are in the same phase and are provided in the detection section (B) at a distance of 1/4λ pitch from each other.