JPH071177B2 - Encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an encoder, and more specifically, it uses an optical incremental encoder to determine a moving direction, a moving amount, and a position of a machine tool or the like connected to the encoder. The present invention relates to an encoder that can calculate in an absolute format. The encoder includes a rotary type and a linear type, and the latter is particularly targeted in the present application.

[Prior art]

Encoders are widely used for precise position detection of moving work machines such as NC.

Encoders are generally classified into an incremental type and an absolute type. Taking the rotary encoder as an example, the former is a rotary plate fixed to a rotary shaft for detecting the movement of the working machine, and has a light-shielding part and a light-transmitting part at equal intervals along the circumference of the rotary plate. (Slit) is provided, and the rotary plate is illuminated from one side of the rotary plate by the light emitting element,
Further, a light receiving element is provided on the other side of the rotating plate to receive the light of the light emitting element through the light transmitting portion of the rotating plate that rotates with the rotation of the rotating shaft. Is output an incremental signal, and in the case of reverse rotation, a decremental signal is output to detect the position of the rotating shaft. On the other hand, in the latter, a plurality of rows of predetermined pattern light-transmitting channels are provided in the radial direction of the rotary plate along the circumference, the light passing through the channels is detected by a plurality of light-receiving elements, and signals of these light-receiving elements are detected. By the combination, the position of the rotary shaft can be uniquely (absolutely) detected. While the incremental encoder has the advantage that the rotating plate is simple and the detection circuit is simple, the power for the detection circuit is usually supplied from the power supply on the working machine side, and once the power is turned off, it will be restarted. There is a problem that the position of the rotation axis cannot be immediately known and the signal (incremental / decremental) from the reference position must be counted again. On the other hand, in the absolute encoder, the position of the rotary shaft can be immediately known when the power is turned on again even if the power is turned off once, but there is a problem that the structure of the rotary plate and the detection circuit become complicated.

Furthermore, both the incremental encoder and the absolute encoder described above generally detect only the rotational position within one rotation of the rotary shaft, and the encoder itself cannot detect the number of rotations of the rotary shaft. Therefore, it is necessary to integrate the number of rotations and the rotational position of the rotary shaft by using the rotational position signal within one rotation in the external circuit of the encoder, that is, to calculate the total moving distance of the working machine.

In order to solve the above-mentioned problems, "a pulse encoder for detecting the rotation of a rotating body (Japanese Patent Application No. 59-017103 and Japanese Patent Application No. 59-017104)" invented by the inventor of the present invention, and "pulse There is an encoder (filed on March 10, 1984). In each of these applications, the number of rotations and the direction of rotation of the rotating body can be detected, but all of them use an absolute encoder and the rotating code plate is rather complicated. Further, both applications of "Pulse encoder for detecting rotation of rotating body" must provide an additional transmitting element on the rotating code plate and a detecting element on the fixed portion in order to detect the number of rotations and the rotating direction of the rotating body, and the latter. The “pulse encoder” of 1 is also provided with an additional detection element, and is structurally slightly complicated. Furthermore, all of the above methods use a method of applying a power source in a sampling manner in order to reduce the power consumption of the circuit, but it has been found that the reduction in power consumption is not always sufficient.

The above-mentioned problems also apply to the conventional linear encoder.

[Object of the Invention]

An object of the present invention is to detect the moving amount and moving direction of a machine tool or the like to be detected by an encoder and the position in an absolute format with a simple structure and a simple circuit for comparison.
Moreover, it is to provide an encoder that consumes less power.

[Structure of Invention]

In order to achieve the above object of the present invention, the encoder of the present invention has been realized based on the following technical ideas. That is, the encoder main body is of the incremental type having a simple structure, and no additional light emitting element or detecting element is used. On the other hand, in order to detect the movement amount and the movement direction, the operating condition of the conventional incremental type detection element is changed by the signal processing technique according to the present invention, and the detection signal obtained by this is processed. further,
For example, one of the incremental type rotary encoder
In order to prevent the rotation position signal from being lost due to power failure, the circuit power supply uses a battery that does not turn off due to external conditions. However, the battery life depends on the encoder service period,
Alternatively, the circuit design should be such that the power consumption is minimized so that the maintenance period is sufficient.

Therefore, in the present invention, as a basic form, a code plate in which a plurality of light-transmitting regions and light-shielding regions are continuously provided at predetermined intervals, and the light-transmitting region and the light-shielding region are illuminated from one side of the code plate. And the light emitting element provided on the other side of the code plate and receiving at least the first and the second emitted light of the light emitting element that has passed through the light transmitting region of the code plate through a predetermined slit. And a second light-receiving element arranged so as to detect the movement position of the code plate with a predetermined phase difference with respect to the first light-receiving element. An oscillation circuit that generates a pulse having a shorter period than the time that the light emitted from the light-emitting element that has passed through the light-transmitting area of the plate and the predetermined slits irradiates any one of the light-emitting elements, and the first and second Signal from the light receiving element of In response to the signal, a signal processing circuit for detecting the movement position of the code plate and at least one of rising and falling of the received light signal to calculate the moving direction and the amount of movement of the code plate is provided, and the light emission is performed. Element, first
Also, an encoder is provided, characterized in that the second light receiving element and the signal processing circuit are operated in response to a pulse from the oscillation circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing a schematic cross section of an optical rotary encoder 1 in which the basic concept of the present invention is adopted as a reference for understanding the encoder of the present invention. In FIG. 1, the encoder 1 includes a rotary shaft 2 that rotates in response to movement of the work machine for detecting the position of the work machine such as NC, and a rotary plate 7 that is fixed to the rotary shaft and that rotates with the rotation of the rotary shaft 2. A light emitting element 9 mounted on a substrate 8 provided on one side of the rotary plate and irradiating the slit portion (FIG. 2) of the rotary plate 7 with light, in this embodiment, a light emitting diode. The circuit board 10 and the battery 11 described later are provided on the substrate 8. On the other hand, a base 3 having a hole through which the rotary shaft 2 penetrates is provided so as to face the substrate 8 with the rotary plate 7 interposed therebetween, and the base 3 is provided at a position facing the light emitting diode 9. Light receiving elements 4 and 5, and in this embodiment, photodiodes are provided. Rotating plate 7 and photodiode
A fixed slit 6 is provided between 4 and 5.

As shown in the plan view of FIG. 2, the rotary plate 7 is provided with light-shielding portions 71 and light-transmitting portions 72 that are alternately and continuously arranged along the circumference at regular intervals. In the present embodiment, the light shielding unit 71
And the width of the light transmitting portion 72 are the same, and 2500 pieces are provided for each round. The fixed slit 6 is shown in FIG.
The front view of is shown. Fixed slit 6 is a photodiode
It is provided between the light-transmitting portion and the light-transmitting portion of the rotary plate 7, and guides light that has passed through the light-transmitting portion of the rotary plate 7 to the photodiodes 4,5 through slits. . Here, the fixed slit 6 is arranged with a slit so that the photodiode 5 detects the transmitted light with a phase delay of 90 ° with respect to the photodiode 4.

FIG. 4 shows a circuit diagram of the electric circuit section 10 shown in FIG.
The electric circuit unit 10 uses the clock pulse CLK ₀ (Fig. 5 (a)).
, A monostable multivibrator 101 for generating a circuit driving clock pulse CLK ₁ (FIG. 5 (b)) in response to the fall of the clock pulse CLK ₀ ,
Amplifying circuits 102 and 103 each comprising a transistor and a resistor for amplifying the signals of the photodiodes 4 and 5, respectively, and a rising / falling detecting circuit 104 for detecting rising and falling of two signals SA and SB from the amplifying circuit, It is provided with OR gates 105 and 106 that take an OR when outputting the rising or falling detection signal, and an up / down (reversible) counter 107 that counts “increase” or “decrease” by the output signal of the OR gate 105 or 106. There is.

The rising / falling detection circuit 104 includes D-type flip-flops FF1 and FF2 operated by the signal SA (A-phase signal) on the photodiode 4 side, and a D-type flip-flop operated by the signal SB (B-phase signal) on the photodiode 5 side. FF3 and FF
4 and accepts the signals of these flip-flops FF1 to FF4, decodes them, and outputs a rising or falling signal 4
It consists of a line-16 line decoder DECDR. That is,
The decoder DECDR is the output SA of the flip-flops FF1 to FF4.
1, SA2, SB1, SB2 are "1", "2", "4",
It accepts as a signal of "8" and outputs it as a decimal signal of 0-15.

A battery 11 is connected to the above circuit as a power source.
The battery 11 is also used as a power source for the light emitting diode 9 and the photodiodes 4 and 5.

1 to 4 with reference to the timing chart of FIG.
The operation of the encoder of the present invention shown in the figure will be described.

The rotation speed of the rotating shaft 2 changes according to the moving speed of the work machine whose position is to be measured, but here, it is assumed that the rotating shaft 2 rotates at a maximum of 1200 rpm. As described above, the transparent portion of the rotating plate 7 is 1
Since there are 2,500 laps, the frequency becomes 50 kHz when rotating normally at the maximum speed (for example, right rotation). Therefore, if it is assumed that the light emitting diode 9 is constantly lit, the light received by the photodiode 4 or 5 through the fixed slit 6 should be a blinking light of one cycle τ = 20 μsec as shown in FIG. 5 (a). become. However, in the present invention, from the viewpoint of minimizing the power consumption of the battery 11,
As described below, the light emitting diode 9 is not always lit, but is lit only for a minimum time.

The oscillation circuit 100 generates an excitation pulse CLK ₀ for turning on the light emitting diode 9 for a minimum time. Pulse CLK
The period t of ₀ (FIG. 5 (b)) must be shorter than the period τ shown in FIG. 5 (a). In order to detect the transmitted light shown in FIG. 5 (a), at least t = τ must be satisfied, but this is because the rising and falling edges are further detected. On the other hand, when the pulse within the cycle t is divided into the on-time t ₁ and the off-time t ₂ , the on-time t ₁ is the time during which the light emitting diode 9, the photodiodes 4 and 5, and the circuit 10 can operate stably, From the viewpoint of minimizing power consumption, it is better to be as short as possible. Under the above conditions, brass is used, and in this embodiment, t = 5 μsec, t ₁ = 2 μsec, t ₃ = ₃ μse.
c, that is, the frequency of the pulse CLK ₀ is 200 kHz.
Therefore, the output clock pulse C of the multivibrator 101
Both LK ₁ (Fig. 5 (c)) is 200kHz.

When the rotating shaft 2 rotates at the maximum speed, the light emitted from the light emitting diode 9 which is turned on when the clock CLK ₀ is turned on causes the rotating plate 7 to rotate.
The photodiode 4, which receives light through the fixed slit 6 and the fixed slit 6, outputs four pulses per one pitch (one cycle) of the light transmission area according to the on-time of the clock CLK ₀ , and the pulses are amplified by the amplifier circuit 102. To obtain the A-phase output SA (Fig. 5 (d)). The photodiode 5 also outputs four pulses in the same manner, but this pulse is 90 ° out of phase with the output pulse of the photodiode 4 and is amplified by the amplifier circuit 103 to obtain the B-phase output SB (fifth phase). Figure (e)).

When the A-phase signal SA is applied to the set input of the flip-flop FF1, FF1 is set and the output SA1 is turned on (FIG. 5 (f)). The output SA1 is applied to the terminal A0 of the decoder DECDR and is also applied to the set input of the next flip-flop FF2. When the next clock CLK ₁ is applied to FF2, FF2 is set and the output SA2 is also turned on. (Fig. 5 (g)). The output SA2 is also A1 of the decoder DECDR
Applied to the terminal. Flip-flop FF1 is signal SA
Is reset at the next clock CLK ₁ with expired, FF2 is reset by the next clock CLK _1.

The flip-flop FF3 is also applied to the B-phase signal SB as described above.
And signal FF shown in FIGS. 5 (h) and (i) via FF4.
B1 and SB2 are obtained, and these signals are A of the decoder DECDR.
Applied to 2, A3 terminals.

By the signals SA1, SA2, SB1 and SB2 applied to the decoder DECDR, the decoder converts into an up-down signal SUD as shown in FIG. 5 (j) and outputs it. The output is as shown in FIG. The up / down counter 107 is appropriately connected so as to increment (add) when the rotating plate rotates in the forward direction and decrement (subtract) when the rotating plate rotates in the reverse direction. In this embodiment, the A-phase signal SA is rotating normally.
Is 90 degrees ahead of the B-phase signal SB, the up-down signals SUD are all up-pulse signals SU. The decoder DECDR is composed of gates G1 to G14 as shown in FIG. 8. When SA1 + SA2 + SB1 + SB2 are 1,7,8,14, up-pulses are output from the gates G1, G7, G8, G14. If the B-phase signal SB leads the A-phase signal SA in phase, that is, if the encoder rotates in the reverse direction, SA1 + S
When A2 + SB1 + SB2 becomes 2,4,11,13 Gate G2, G4, G11, G
Only the down pulse is output from 13.

These up or down pulse signals are counted by the up / down counter 107.

It is assumed that a voltage is constantly applied to the circuit by the battery 11. Therefore, the state of unknown position due to power-off does not occur, the rotational position of the rotary shaft is always maintained, and the up / down counter 107 can output a rotational position signal processed for forward rotation or reverse rotation as a so-called absolute signal. Alternatively, in the up / down counter 107, for example, a forward rotation pulse is generated every 2500 pulses in accordance with the number of light transmitting portions of the rotating plate. In the case of reverse rotation, a reverse rotation number pulse is generated. From this, the number of rotations and the direction of rotation can be known.

The battery 11 is, for example, a lithium battery that has a relatively long life and is stable. However, in order to always apply a voltage to the circuit, as described above, the light emitting diode 9, the photodiodes 4, 5, and the amplifiers are used. The circuits 102 and 103 have a minimum time width (Fig. 5 (b)) necessary for their operation and position detection,
The pulse of t ₁ ) is applied to minimize the power consumption, and a CMOS device, which consumes less power, is used as a circuit element.

In the above description of the operation, the case where the rotary shaft 2 rotates at the maximum speed has been described, but the rotary shaft changes depending on the moving speed of the work machine and may not rotate. For example, the rotation axis is 600 rpm
When rotated by, the one-pitch cycle τ ′ is twice that of the above example, that is, 40 μsec. (FIG. 7 (a)). On the other hand, oscillator circuit 1
If 00 has the same frequency of 50 kHz as before, the light emitting diode will blink twice in one pitch.
As in the above case, 4 pulses are sufficient to detect the rising edge or the falling edge. Therefore, as shown in FIG. 6, the output signal of the decoder DECDR, which also means the rotation speed of the rotating plate, is input through the OR gate 109, the clock pulse CLK ₁ ′ between the input pulses is counted, and the rotation axis is rotated. A circuit 108 for calculating the oscillation cycle of the oscillation circuit according to the rotation speed of the
00 'is set so that the oscillation cycle can be changed according to the command from the circuit 108. In this example, the oscillation period t'is doubled (Fig. 7 (b)). However, the time t ₁ for turning on the light emitting diode or the like is as before. By doing this,
Since the number of times the light emitting diode or the like is operated is reduced, the power consumption of the battery can be significantly reduced. By doing so, it becomes possible to extend the battery life to about the same as the service life of the encoder.

In the above example, the case of detecting both the rising edge and the falling edge is described, but it is also possible to set only one of them. Further, the rising / falling circuit 104 may be of another type as long as it has the same function as described above. Further, the up / down counter does not need to be one up / down counter as long as it performs reversible counting similar to the above, and two inexpensive counters may be combined.

In the above description, the A-phase and B-phase signals have been described, but the inverted A phase and the inverted B phase can be used together as in the conventional case.

The linear encoder of the present invention is realized by applying the basic concept of the present invention described so far to a linear encoder instead of a rotary encoder. The linear encoder itself is well known, and as shown in FIGS. 9 and 10, an LED 90 as a light emitting element and a light receiving element 40 including four phototransistors 41 to 44 are fixed slit plates.
Fixed slit plate 50 and LED 9 are provided opposite to each other.
A linear code plate 60 mechanically connected to the table 70 of the machine tool between 0 is provided. That is,
The rotary code plate 7 of the rotary encoder corresponds to the linear code plate 60. In the case of the rotary encoder, the rotary code plate 7 is rotated with the rotation of the rotary shaft connected to the table of the machine tool, and the rotation direction and the rotation amount are described above via the fixed slit 6 and the light receiving elements 4 and 5. It detects like. In the case of a linear encoder, the linear encoder 60 is an incremental encoder exactly like the above-mentioned incremental rotary encoder except that the linear code plate 60 moves linearly and moves in the forward direction or the reverse direction. It is applicable as it is.

In addition, in FIG. 10, four phototransistors 41 to
By using 44, not only the A phase and the B phase, but also these opposite phase signals can be detected.

〔The invention's effect〕

As described above, according to the present invention, by using the incremental type mechanism, it is possible to detect the substantially absolute type motion position signal, the momentum and the motion direction, and perform total position detection. A possible encoder can be realized.

Moreover, according to the present invention, the power consumption of the encoder of the present invention can be significantly reduced.

[Brief description of drawings]

1 is a sectional view of an optical rotary encoder adopting the basic concept of the present invention as a reference for understanding the present invention, FIG. 2 is a front view of a rotary plate of FIG. 1, and FIG. 1
FIG. 4 is a front view of the fixed slit shown in FIG. 4, FIG. 4 is a circuit diagram showing an embodiment of the circuit of FIG. 1, FIGS. 5 (a) to 5 (j) are timing charts of the circuit of FIG. 4, and FIG. FIG. 7 is a diagram showing another embodiment of the circuit of FIG. 1, FIGS. 7 (a) and (b) are timing diagrams of the circuit of FIG. 6, and FIG. 8 is a circuit diagram of the decoder shown in FIGS. 4 and 6. 9 and 10 are schematic configuration diagrams of an optical linear encoder as an embodiment of the present invention. (Explanation of symbols) 1 ... Rotary encoder, 2 ... Rotation axis, 3 ... Base, 4,5 ... Photodiode, 6 ... Fixed slit, 7 ... Rotating plate, 8 ... Substrate, 9 ... … Light-emitting diode, 10-electronic circuit, 11-battery, 40-light-receiving element, 50-fixed slit plate, 60-liner code plate, 90-LED.

Claims (5)

[Claims] 1. A linear code plate having a plurality of light-transmitting regions and light-shielding regions continuously provided in a long direction in a long direction on a long plate and moved in the long direction, and one side of the code plate. A light emitting element provided so as to illuminate the light transmitting area and the light shielding area, and a predetermined amount of light emitted from the light emitting element that has passed through the light transmitting area of the code plate provided on the other side of the code plate. At least the first and second light receiving elements received through the slits of the second light receiving element are arranged so as to detect the movement position of the code plate with a predetermined phase difference with respect to the first light receiving element. In the encoder provided with, a pulse having a shorter cycle than the time that the light emitted from the light emitting element through the light transmitting region of the code plate and the predetermined slit irradiates any of the light receiving elements. Generating oscillation circuit, and first and A signal for receiving the signal of the light receiving element of No. 2 and detecting the movement position of the code plate and at least one of the rising and falling of the received signal in response to the signal and calculating the moving direction and the momentum of the code plate. A processing circuit is provided to operate the light emitting element, the first and second light receiving elements, and the signal processing circuit in response to a pulse from the oscillation circuit, and a cycle of a pulse generated in the oscillation circuit is set to the above. An encoder characterized in that it is changed in response to the movement speed of the code plate. 2. The encoder according to claim 1, wherein an ON time of a pulse generated in the oscillation circuit is a minimum fixed time defined by an operation time of the light emitting element and the like. 3. A circuit in which the signal processing circuit detects at least one of rising and falling of signals of the first and second light receiving elements, and movement of the code plate in response to a signal from the detecting circuit. An encoder according to claim 2 including a counter having an up / down counting function to calculate direction and momentum. 4. The oscillation circuit and the signal processing circuit are CMOS
An encoder according to claim 3 formed with a device. 5. The encoder according to claim 4, wherein the power source of the encoder is a battery.