JPS6122212A - Photoencoder - Google Patents

Abstract

PURPOSE:To simplify a construction of a servo circuit, by controlling light emission quantity of a luminant element in response to two position signals emitted from a photoencoder in accordance with a moving body, and by generating and issuing a servo motor speed command reference signal. CONSTITUTION:A disk 92 provided with a slit 92a is fixed onto a rotating shaft 91, such as selection motor, space motor, etc. (not shown). A light emission diode 94 and a mask 93 are mounted onto mounting disks 97, 98 embracing a disk 92. Each four slits 93a, 93b are installed in a position deviated by angle of 90 deg. with the same distance as the slit 92a in response to the slit 92a in the mask 93. A photodiode pellet 95 is constructed with two diodes 95a, 95b in a position where a ray of light is received after it passed through the slits 93a, 93b. A position signal output of the pellet 95 is processed by an electronic circuit on a printed substrate 96 and the light emission quantity of the element 94 is controlled and a servomotor speed command reference signal is outputted. By this, accuracy of the servocontrol is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photo encoder used for servo control.

For example, in a type wheel type impact printer,
In order to perform type wheel rotation speed 2 positioning control and carriage movement speed 2 positioning control, the rotation of the selection motor that drives the type wheel and the space motor that drives the carriage is detected using a photo encoder.
Based on this detection result, the selection motor and space motor are servo controlled.

First, an example of a photo encoder used in a conventional servo control circuit will be described with reference to FIGS. 1 to 4.

As shown in Figure 1, this photo encoder is used for the rotation axis (moving body) of the selection motor and space motor.
A light-emitting diode 3, a mask 4, and a photodiode pellet 5 on which three photodiodes are formed are arranged to face each other with a disk 2 fixedly placed between them.

A slit 2a of a predetermined width is formed in the disk 2 over its entire circumference.

On the other hand, as shown in FIG.
90 for the same slit.
Two position signal generating slits 4a and 4b are formed with a phase-shifted positional relationship, and a compensation slit 4c is formed.
It is formed.

In addition, the photodiode pellet 5 has two parts of the mask 4.
Two 1d signal generating photodiodes 5a, 5b are formed corresponding to the position signal generating slits 4a, 4b, and a compensation photodiode 5c is formed corresponding to the compensation slit 4c of the mask 4. It is.

These masks 4 and photodiode pellets 5 direct the emitted light from the light emitting diode 3 to the slits 2a of the disk 2 and the slits 1-4a for generating position signals.
The photodiodes 5a and 5b receive light through the light emitting diode 4b, and the photodiodes 1<5c are arranged so that the light emitted from the light emitting diode 3 is continuously received through the compensation mask 4C.

The position signal generation/emission amount control circuit of this encoder consists of two position signal generation circuits 6 and 7 and a light emission amount control circuit 8, as shown in FIG.

The position signal generation circuit 6 generates and outputs a position signal φA from the output signal of the position signal generation photodiode 5a of the photodiode pellet 5, and outputs the position signal φA.
generates and outputs a position signal φB from the output signal of the position signal generating photodiode 5b.

Further, the light emission control circuit 8 has a volume VR.

It consists of a proportional-integral circuit consisting of an operational amplifier OP, a resistor RI, and a capacitor C1, a transistor Q1, and a resistor R2, and the base current of the transistor Q1 is controlled by the output of the proportional-integral circuit according to the output of the compensation photodiode 5C. , controls the current II- supplied to the light emitting diode B.

In this photo encoder, due to the rotation of the disk 2 in synchronization with the rotation of the rotation shaft 1 of the motor, the slits 4a and 4b of the mask 4 are in a positional relationship that is 90" out of phase with respect to the same slit of the disk 2-3. Since the position signal generation circuit 6 inputs the output signals of the position signal generation photodiodes 5a and 5b,
7, two position signals φA each have a frequency corresponding to the rotational speed of the rotary shaft 1 and a phase difference of 90", as shown in FIG.

φB is output.

In this case, it is required for the control accuracy of the speed control 9 positioning control that these two position signals φA and φB each have a constant amplitude peak level ■o.

However, the position signal generating photodiodes 5a and 5b
Output characteristics 2 The light emitting characteristics of light emitting diode B fluctuate depending on the ambient temperature and changes over time, so unless some compensation (correction) is made, the position signal φA.

The amplitude of φB also varies.

Therefore, in this encoder, a compensating photodiode 5c that directly receives the light emitted from the light emitting diode B is separately provided, and the amount of light emitted = 4-amount control circuit 8 according to fluctuations in the output signal of the compensating photodiode 5C. controls the current supplied to the light emitting diode B.

In other words, the position signal generating photodiode 5a.

Assuming that the environmental conditions of 5b and compensation photodiode 5C are the same, when the amount of light emitted from light emitting diode 2 changes due to changes in ambient temperature, etc., or when the output characteristics of position signal generation photodiodes 5a and 5b themselves change. When this occurs, the position signal generating photodiode 5a,
The fluctuation in the output of the compensation photodiode 5b is the same as the fluctuation in the output of the compensation photodiode 5C.

Therefore, the light emission amount control circuit 8 controls the current supplied to the light emitting diode B in accordance with the fluctuation in the output of the compensation photodiode 5C, thereby controlling the light emission amount.
The outputs of the position signal generating photodiodes 5a and 5b, that is, the peak levels of the amplitudes of the device signals φA and φB constituted by the position signal generating circuit 6.7 are controlled to be constant.

In this way, in a conventional photo encoder, in addition to the two position signal generation light receiving elements that receive the light emitted from the light emitting element through the slit of the disk, the emitted light from one light emitting element is directly received. A compensation light-receiving element is provided to receive light, and the amount of light emitted by the light-emitting element is controlled in accordance with output fluctuations of the compensation light-receiving element so that the peak levels of the amplitudes of the two position signals are constant.

However, in such a photo encoder, for example, the thermal conditions of the photodetector for position signal generation and the thermal conditions of the compensation photodetector may be different, or dust may enter the slit for position signal generation or compensation slit of the mask. The output fluctuation of the one-position signal generation light receiving element and the output fluctuation of the compensation light receiving element may be different due to the adhesion or the like.

Also, if the gap between the disk and the mask (light receiving element for position signal generation) changes, or if the gap between the disk and the mask (light receiving element for position signal generation) changes during one rotation due to surface runout of the disk, , the output of the compensation light-receiving element is not affected, but the output of the position signal-generating light-receiving element fluctuates.

In this way, when the output of the position signal generating light receiving element and the output of the compensation light receiving element exhibit different fluctuations, the output of the position signal generating light receiving element, that is, the position signal There is a problem in that the amplitude peak level cannot be corrected accurately and the amplitude peak level of the position signal cannot be maintained constant.

Next, a servo motor speed reference signal generation circuit in a conventional servo control circuit will be explained with reference to FIG.

This servo motor speed reference signal generation circuit inverts the device signals φA and φB made up of the above-mentioned photo encoder position signal generation circuit 6゜7 by a circuit made up of resistors R3 to R5 and an operational amplifier OP2, resulting in a total of four signals. position signals A, A, B.

The position signals A, A, B, and B are half-wave rectified by diodes I) and ~D4, and the position signals φA and φB are rectified and synthesized.

As a result, while the motor is rotating, a signal whose peak level is vp as shown by the broken line in FIG. 6, for example, is generated.

Therefore, this signal is integrated by an integrating circuit consisting of a resistor R6 and a capacitor C2, and while the motor is rotating, a product output as shown by the solid line in FIG. 6 is generated.

Then, this integrated output Va, resistor R8 and diode D
The voltage generated in step 5 is connected to resistors R8 to R1.

Addition amplification is performed using capacitor C2 and operational amplifier OP3,
Output as servo motor speed reference signal V r e f.

Furthermore, when the motor is stopped, the level of the signal input to the integrating circuit is 1/1/I'H of the peak voltage VP, as shown in Fig. 6.
Therefore, a correction circuit consisting of resistor R12, Zener diode ZDI, and diode D6 adjusts the correction voltage v
The integral output given b is held at vb to prevent the servo motor speed reference signal V r e f from falling below a certain level when the motor is stopped.

However, in such a servo motor speed reference signal generation circuit, it is not possible to completely smooth the signal.
As shown in Figure 6, a ripple ΔV = 8- occurs, and this ripple ΔV increases as the frequency of the position signal decreases, so its average value is no longer proportional to the position signal, making it difficult to perform high-precision servo control. Can not.

Furthermore, in the conventional servo control circuit as described above, the circuit for controlling the amount of light emitted from the light emitting element of the encoder and the servo motor speed reference signal generation circuit are provided completely separately and independently.

l-Sako This invention has been made in view of the above points, and an object thereof is to improve the control accuracy of servo control.

Structure-1 Hereinafter, the configuration of the present invention will be explained based on one embodiment.

FIG. 7 is an external perspective view showing an example of a type wheel type printer equipped with a photo encoder embodying the present invention.

The outer casing of this printer consists of a lower case 11 and an upper case 12 that house a mechanical section and a control section, and a cover 13 that can be opened and closed for replacing type wheels, ribbon cassettes, and the like.

FIG. 8 and FIG. S are a schematic plan view and a front view showing an example of the mechanical part of this printer.

In this mechanical section, a platen 22 is rotatably mounted between frames 21 and 21, which wraps and feeds paper to be printed.

This platen 22 is moved by a motor gear 24. An idle gear 25, a gear 26° that moves together with the idle gear 25, a timing belt 27, and a platen gear 28 are driven to automatically feed the paper.

Additionally, knobs 29 and 29 are provided at both ends of the platen 22.
is fixed, and can be manually rotated by turning the knobs 29 and 29 when loading or removing paper.

Further, in front of the platen 22, as shown in FIG. 7, a paper pail 31 equipped with a pail roller 30 is arranged so as to be biased toward the platen and swingable.

On the other hand, Rondo '53 stuck between frames 21 and 21.
．． A carriage 35 is mounted on the platen 34 so as to be movable parallel to the platen 22 in its axial direction.

The carriage 35 has a type wheel 37 on a carrier frame 36, a print hammer 38 that hits the type on the type wheel 37, a selection motor 40 that rotationally drives the type wheel 37, and a photo encoder that detects the rotation of the selection motor 40. (Selection sensor)
41 and a ribbon cassette 4 loaded with an ink ribbon 42
It is equipped with 3rd class.

A space motor 46 made of a DC motor is attached to the subframe 45, and a photo encoder (space sensor) 47 is attached to the space motor 46 to detect the rotation of its rotating shaft 46a.

Further, pinion gears 4 fixed to the rotating shaft 46a of the space motor 46 are provided on both sides of the subframe 45, 45'.
A pulley 51 integrally formed with a gear 50 that engages with the shaft 51a of the pulley 51 is rotatably mounted between the subframes 45 and 45', and a guide pulley 52 is mounted between the subframes 45 and 45'.
a is rotatably mounted on a subframe 45, 45'.

Then, a space wire 53 is stretched between these pulleys 51 and guide pulleys 52, and this space wire 53
The end of the carriage 35 is fixed to the side of the carriage 35, and the carriage 35 is moved by a space motor 46.

FIG. 10 is a block diagram showing an example of a control section of this printer.

T1061 of the control unit 60 receives print character data, space (carriage movement amount) data, line feed data for instructing line feed and pack line feed (including feed amount) from the host system side via the printer interface 62. Various data such as

Microcomputer (hereinafter referred to as "microcomputer") 6
3 consists of a CPU, ROM, RAM, T10, etc.
It controls the line feed (paper feeding) operation and the space (carriage movement) operation among the printer controls.

That is, the microcomputer 63 outputs line feed data LFD to the line feed drive circuit 64, drives and controls the line feed motor 23, controls rotation of the platen 22, and controls line feet and back line feed.

Further, the microcomputer 63 sends rotation amount data DVAC that instructs the amount of rotation of the space motor 46 corresponding to the amount of movement of the carriage 35 and a rotation direction instruction signal DIRC that specifies the direction of rotation to the space servo drive circuit 63.
is output to rotate the space motor 46 to perform a space operation in which the carriage 35 is moved by a required amount in a predetermined direction.

This space servo drive circuit 65 is a microcomputer 63
Rotation amount data DVAC, rotation direction instruction signal DTR from
, C and the position signal Pc from the space sensor 47, the space motor 46 is driven and controlled.

Note that details of this space servo drive circuit 65 will be described later. Moreover, here, the position signal Pc from the space sensor 47 includes two position signals PA (φA),
PB (φB) and motor speed command reference signal V r e
It is a general term for f.

On the other hand, the microcomputer 6 is a circuit that controls functions other than the space and line feet of the printer, such as printing and ribbon feet.

In other words, this microcomputer 66 has a hammer drive circuit 67.
Output the hammer drive pulse HD to the printing hammer 38.
Drive control of the hammer magnet 1-38A that constitutes the
The type characters on the type wheel 37 are struck by the hammer 3811.

The microcomputer 66 also outputs ribbon drive data RD to a ribbon feed drive circuit 68 to drive and control a ribbon foot motor (not shown in FIG. 8) to feed the ink ribbon 42 of the ribbon cassette 43.

Furthermore, this microcomputer 66 outputs rotation amount data DVAS that commands the rotation amount of the selection motor 40 corresponding to the rotation amount of the type wheel 37 and a rotation direction instruction signal DTR8 that specifies the rotation direction to the selection servo drive circuit 70. Then, the selection motor 40 is driven to rotate, the type wheel 37 is rotated in a predetermined direction by the required amount, and the desired type is placed in a position where it is struck by the printing hammer 38.

The selection servo drive circuit 70 controls the selection motor 40 by one drive based on the rotation amount data DVAS from the microcomputer 66, the rotation direction II indicating signal r)IR8, and the position signal Ps from the selection sensor 41.

Note that the position signal Ps from the 5 selection sensor 41 here and here refers to two position signals PA (φA).

pn (φB) and motor speed command reference signal V ref
It is a general term for.

FIG. 11 is a block diagram showing an example of the space servo drive circuit 65.

The space servo drive circuit 65 receives rotation amount data DVAC and rotation direction instruction signal DIRC from the microcomputer 63 when the carriage 35 starts moving.

The rotation direction instruction signal DIRC: is the selection circuit 7.
1, and this selection circuit 71 receives the rotation direction instruction signal D.
The output of either the adder 72 or the inverter 3 is selected according to the TRC and output to the servo amplifier 74.

Thereby, the space motor 35 starts rotating in the direction instructed by the rotation direction instruction signal DIRC.

On the other hand, the rotation amount data DVAC is set in a position error counter 75, and the contents of this position error counter 75 are sent as a position error instruction signal PE to a speed command signal generator 76. level is determined. That is, the greater the required moving distance of the carriage 35, the greater the level of the speed command signal Vc-, and the space motor 46 rotates at a higher speed.

Then, when the space motor 46 starts rotating, the space sensor 47 indicates the unit movement amount of the carriage 35 and generates two position signals by amplifying two periodic minute detection signals that are 90 degrees out of phase with each other. The signals PA and PTI are output, and the motor speed command reference signal V r e f generated from the two position signals PA and PR is output.

Position signal PA from this space sensor 47.

PR is differentiated by differentiators 78 and 79, respectively, and a differential signal d is obtained.
After being converted into A/d t and dB/d t, the aftereffects are rectified by the aftereffect rectifiers 80 and 81, and added by the aftereffect rectification adder 82. From this full-wave rectification adder 82, the space motor 46
is output as an actual speed signal Vwt.

On the other hand, the motor speed command reference signal V r e f from the space sensor 47 is input to the speed command signal generator 76 .

Furthermore, position signals PA and PI from the space sensor 47
The position pulse signal generator 84 also outputs a position pulse PP to the position error counter 75 each time the carriage 35 moves by a unit amount as the space motor 46 rotates. Ru.

As a result, the contents of the position error counter 75 are subtracted every time the position pulse PP is input, and the contents are input to the speed command signal generator 76 as the position error instruction signal PE.

Therefore, the speed command signal generator 76 determines the current position and the intended stop of the carriage 35 based on the motor speed command reference signal V r e f from the space sensor 47 and the position error command signal PE from the position error counter 75. A speed command signal Vc- of a level corresponding to the distance to the position is generated and output.

Then, the speed command signal Vc from the speed command signal generator 76 and the actual speed signal Vw from the aftereffect rectification adder 82 are added by the adder 72, and the output of the adder 72 is V c-
+ V w”, and the output of the inverter 73 that inverts the output of this adder 72, V c - + V w”,! j is selected by the selection circuit 71 according to the rotation direction instruction signal D I RC and output to the servo amplifier 74 , and the space motor 46
is driven.

As the space motor 46 rotates, the content of the position error counter 75 gradually decreases, and accordingly, the level of the speed command signal Vc- from the speed command signal generator 76 also decreases, and the rotational speed of the space motor 46 decreases. To go.

Then, when the carriage 35 reaches the target stop position and the content of the position error counter 75 becomes zero, the position error counter 75 outputs the target position arrival command signal PD to the selection circuit 71.

Thereby, the selection circuit 71 uses the position signal PA from the space sensor 47 and the differential signal dA/dt from the differentiator 78 instead of the outputs of the adder 72 and the inverter 73.
Since the output of the adder circuit 85 that adds up is selected, the difference signal between the position signal PA and the differential signal dA/dt is input to the servo amplifier 74 via the selection circuit 71, and the space motor 46 is stopped.

An example of a control time chart of the overall operation of this space servo drive circuit 65 is shown in FIG.

To explain this in the cylinder, an instruction to rotate the carriage 35, that is, the space motor 46 in the forward direction and its rotation amount is input from the microcomputer 63, and accordingly, as shown in FIG.
The speed command signal c"' shown in the figure is input to the servo amplifier 74, and the amplified voltage is applied between the terminals of the space motor 46, causing a positive motor current MT to flow as shown in FIG. .

As a result, the space motor 46 starts rotating in the forward direction, and at the same time, as shown in FIG.
PB is output, and the actual speed signal Vw shown in FIG.
4 is input.

These speed command signal vc- and actual speed signal Vw have opposite polarities and always cancel each other out, but due to the rotor inertia, load inertia, etc. of the space motor 46, the rotational speed of the space motor 46 is different from the speed command signal. It cannot respond immediately to vc and rises at a certain gradient.

At this time, Vc+VW+<O, the motor current -20=MT flows in the positive direction, and the space motor 46 continues to accelerate.

Then, when the rotation speed of the space motor 46 approaches the set speed based on the position error, V c-+ V w"=0
Therefore, the motor current MI becomes approximately zero and the motor rotates at a constant speed.

Then, as the space motor 46 rotates, the content of the position error counter 75 decreases, and when a certain position error is reached, the level of the speed command signal vc- is switched and decreases.

At this time, since the rotation of the space motor 46 cannot be determined immediately, Vc7+Vw'>0 temporarily, and the motor current M
I flows in the opposite direction.

Thereafter, the same operation is repeated, and when the carriage 35 reaches the target stop position, the content of the position error counter 75 becomes zero, and the target position arrival instruction signal PD is output to the selection circuit 81 as shown in FIG. 9(d). is output to.

At this time, the speed command signal Vc- and the actual speed signal Vw+ are cut, and instead the position signal PA and its differential signal d are applied at the target positions shown in (E) and (F) of the same figure.
A/dt is input to the servo amplifier 74, and the space motor 46 is stopped.

Note that the configuration of the selection servo drive circuit 70 is the same as that of the space drive circuit 65, so a description thereof will be omitted.

As described above, in this printer, the space sensor 47 and the space drive circuit 65 provide a servo control circuit for controlling the space motor 46, and the selection sensor 41 and the selection servo drive circuit 70 provide a servo control circuit for controlling the selection motor 40. It constitutes a circuit.

Next, details of the photo encoder embodying the present invention, which constitutes the selection sensor 24 and the space sensor 29 in this printer, will be explained with reference to FIGS. 13 and subsequent figures.

FIG. 13 is a sectional view showing the configuration of the photo encoder.

This photo encoder has a disk 9 fixed to a rotating shaft 91 of a selection motor 40, a space motor 46, etc.
2, a mask S3, and a light emitting diode 9, which is a light emitting element, facing each other with these disks 92 and mask 93 in between.
A photodiode pellet 95 having four and two photodiodes formed thereon, and this photodiode pellet 9
a printed circuit board 96 on which a position signal amplifier, etc. for amplifying and processing signals from each photodiode of 5; and a mounting plate 97 for holding these components. ! It consists of 3B.

As shown in FIG. 14, the disk S2 has a plurality of slits 92 of a predetermined width formed at equal intervals on the same circumference over the entire circumference. have.

Further, the mask 93 is attached to the disk S as shown in FIG.
The four slits 93a and 93b for position signal generation are formed in a positional relationship corresponding to the two slits 92a, at the same interval as the slits 92a, and 90 degrees out of phase with the slits 92a.

Further, the photodiode pellet 95 includes position signal generating photodiodes 95a corresponding to the four position signal generating slits 93a of the mask 9B, and four position signal generating photodiodes 95a, as shown by broken lines in FIG. 93 slits
It has a position signal generating photodiode 95b corresponding to position signal generating photodiode 95b.

FIG. 16 is a circuit diagram showing an example of a signal processing circuit of this encoder.

This signal processing circuit includes the first signal processing circuit. Second position signals φA, φB
position signal generation circuits 101 and 102 that output position signals φ from these position signal generation circuits 101 and 102
It is comprised of a light emission amount control/reference signal generation circuit 103 that controls the light emission amount of the light emitting diode 94 based on A and φB and outputs a motor speed command reference signal V r e f.

The position signal generation circuits 101 and 102 each have an operational amplifier op4. An inverting amplifier consisting of a resistor R53 and a capacitor C5, and an operational amplifier OP5. It consists of an inverting amplifier consisting of a resistor R14, an amplitude adjustment volume vR2, and an average value adjustment volume VR3.

Then, the position signal generation circuit 101 generates and outputs a position signal φ8 from the output signal of the first diode 95a for position signal generation.

Further, the position signal generating circuit 102 generates and outputs a position signal φB from the output signal of the position signal generating photodiode 95b.

The light emission amount control/reference signal generation circuit 103 receives the position signal φA from the position signal generation circuits 101 and 102.

A squaring circuit 104 that squares φB, and this squaring circuit 1
An adder circuit 105 that adds each square output from 04, and a square root (square root) that calculates the added output of this adder circuit 105.
It consists of a circuit 106 and a power supply control circuit 107 which inputs the square root output from the square root circuit 106 via a resistor R1o.

The squaring circuit 104 includes a squaring circuit M that squares the position signal φA and a squaring circuit M2 that squares the position signal φB, and outputs each square output eOI+e02 to the addition circuit 105.

The adder circuit 105 includes input resistors R, 5, R, 6, and a feedback resistor RI? , consisting of a resistor R+8 and an operational amplifier OP6,
An addition output eO3 obtained by adding each square output EIOI+eo2 from the square circuit 104 is output to the square root circuit 106.

The square root circuit 106 includes an input resistance R2o and a feedback resistance R25.
, resistor R22, square circuit M3. Operational amplifier ○P7 + capacitor c6. Diode D7 becomes active, adding circuit 105
A square root output eO4 obtained by square rooting (calculating the square root of) the addition output eo3 from eo3 is output to the power supply control circuit 107 via the resistor 23, and the square root output e04 is output as the motor speed command reference signal V r e f.

The power supply control circuit 107 has a volume VR4, an ovo amplifier OP8. It consists of a proportional-integral circuit consisting of a resistor R26++ and a capacitor c7, a transistor Q2 whose base current is controlled according to the output of this proportional-integral circuit, and a resistor R26.

Next, the principle of light emission amount control in this encoder will be explained.

First, let the peak levels of the positive and negative amplitudes of the 1-position signals φA and φB be VoZVJ, then l Vo
When l = l Vo-1 = Vo, each position signal φ
Since there is a phase difference of 90° between A and φB, φA =
V o sj, no・= (1) φ mouth = V OCo
50 ・= (2), and these (1), (
From the formula 2), the following relationship is established: =Muyuu shoulder shoulder blue=Fi... (3) where sin O+cos2B =
1, the equation (3) in -11 can be expressed as: 57 koku = 50'-1''Vo (4).

In other words, for two sine wave signals with a phase difference of 90" and equal peak amplitude levels, the square root of the sum of their squares will be a DC level (constant value) whose absolute value is equal to the peak amplitude level, It can be said that this DC level is 1:1 proportional to the peak level of the amplitudes of the two sine wave signals.

Therefore, by performing the square root of the sum of the squares of the two position signals φA and φB (taking the square root), a level signal proportional to the position signals φA and φB at a ratio of 1:1 can be obtained.

This will be explained regarding the light emission amount control/reference signal generation circuit 103 of this photo encoder.

First, each square circuit M 1 , M 2 of the square circuit 104
If the scale factor of is 1, then the square circuit M 1
, M2's square output eO1+C02 is obtained from the above equations (1) and (2) as follows: ``01''Kl'φA2=K, VO''sin'fl
-(5) C02=Kl'φB2= K 1 ・V O
' cos20 ・= (6), and the addition output eo3 of the addition circuit 105 that adds these squared outputs eO1+C02 is.

eo 3 = R++(eo 11R+s+eo 2
/R+6)...(7) Here, if R+s = R, 6, the above (
5).

From equations (6) and (7), the addition output eo3 is eo3=
(R17/RI6) ・K1 ・VO(sin
O+cosθ) = (R17/RI6) ・Kt ・Vo...
(8) becomes.

Therefore, the square root output e04 of the square root circuit 106 has a scale factor of 2 for the squaring circuit M3. this(
In formula 9), K1=2. R2゜=R2,,R15
=R,,? Then, the square root output e04 is as follows: e04=VO (10).

In other words, the square root output eO4 is composed of two sinusoidal position signals φA, φ that are at the peak amplitude level VO and have a phase difference of 90°.
B becomes a DC signal whose amplitude is proportional to the value of the peak level VO at a ratio of 1:1.

Square root output e from this square root circuit 106. 4 is resistance R23
This power supply control circuit 107 is given to the power supply control circuit 107 via C804/R23) (Vz/VR4)=O
”・The light emitting diode S is
Controls the current supplied to 4.

That is, R 231 V 7. in this formula (]1).
.

Since vR4 is constant, in order for this equation (11) to hold true, the light emitting diode 94 must be set so that e04 is constant.
The current must be controlled.

Since the control to keep e04 constant is e04''VO from the above equation (10), the peak level Vo (Vo
"lVo"1=lVo-1) is controlled to be constant.

When the peak level of the amplitude of the 1-position signals φA and φB fluctuates in this way, the light emission amount control/reference signal generation circuit 103 controls the light emitting diode 94 so that the peak level of the amplitude becomes the level before the fluctuation. The amount of light emitted is controlled by controlling the supplied current, thereby controlling the peak levels of the amplitudes of the position signals φA and φB to be constant.

The light emission amount control/position signal generation circuit 103 is
The square root output eo4 of the square root circuit 106 is outputted as the motor speed command reference signal V r e f.

As mentioned above, the square root output '1104 of the square root circuit 106 always has a DC level proportional to the position signal regardless of the frequency of the position signal, so the level does not vary depending on the frequency or ripples occur. Therefore, the ideal motor speed command reference signal V r cf is obtained, and stable and highly accurate servo control can be performed.

In this way, this photo encoder squares each of the two position signals, adds the square results, squares the sum, and supplies current to the light emitting element according to the square root result. , the square root result is output as a servo motor speed command reference signal.

This eliminates the situation in which the output of the position signal generation light receiving element and the compensation light receiving element are different and the peak level of the amplitude of the position signal cannot be accurately controlled at a constant level, unlike in the conventional F1 encoder. Therefore, it is possible to accurately control the peak level of the amplitude of the position signal to be constant at all times.

In addition, the light receiving element for compensation and the mask Surin 1
Since - is no longer necessary, it is possible to achieve miniaturization and low cost.

At the same time, since a DC level motor speed command reference signal proportional to the amplitude of the position signal is obtained, stable servo control can be performed.

In the above embodiment, an example was described in which the present invention was implemented in an encoder used for servo control of a selection motor and a space motor of a type wheel type printer, but the present invention is not limited to this, and the present invention is applicable to a type wheel type printer. Of course, the present invention can be similarly applied to line feed servo control circuits, encoders used in other dot impact printers and thermal printers, and photo encoders used in servo control circuits of various devices other than printers.

Further, in the above embodiments, an example in which the present invention is applied to a rotary encoder has been described, but the invention can also be applied to a linear encoder in the same manner.

Furthermore, as long as it is a photo encoder, any material may be used for the light emitting element-32= and the light receiving element, it may be of a reflective type as well as a transmissive type, and its configuration is the same as that of the above embodiment. Needless to say, there are no limitations.

As explained above, the photoencoder according to the present invention controls the amount of light emitted from the light emitting element based on two position signals, and also outputs the servo motor speed command reference signal, so the configuration of the servo control circuit is This simplifies the process and improves the control accuracy of the servo control.

[Brief explanation of the drawing]

Figures 1 and 2 are a schematic configuration diagram and a plan view of its structural parts showing an example of a conventional photo encoder used in a servo control circuit, and Figure 3 is a diagram showing the position signal generation/light emission amount control output circuit. A circuit diagram showing an example; Fig. 4 is a waveform diagram of device signals φA and φB similarly constructed from the position signal generation circuit; Figs. 5 and 6 are servo motor standards used in the servo controller 1-roll circuit. A circuit diagram showing an example of a signal generating circuit and a waveform diagram for explaining its operation; FIG. 7 is an external perspective view showing an example of a printer equipped with a photo encoder according to the present invention; FIGS. 8 and 9 are
Similarly, FIG. 10 is a plan view and front view showing an example of the mechanism part, and FIG. 10 is a block diagram showing the control part.
1 and 12 are block diagrams showing an example of the space servo drive circuit shown in FIG. 10, and waveform diagrams of various parts to explain its operation. FIG. 13 shows the configuration of a photo encoder embodying the present invention. 14 and 15 are plan views of the disk and mask, and FIG. 16 is a circuit diagram showing an example of the signal processing circuit. 91... Rotating shaft 92... Disk 93.
・Mask 94 ・Light emitting diode 95 ・
・F1 ・Diode pellet h 95a, 95b...Photodiode for position signal generation 101.102...Position signal generation circuit 103・Light emission amount control・Reference signal generation circuit Fig. 12 Fig. 13

Claims (1)

[Scope of Claims] 1. In a photo encoder that generates two position signals according to the movement of a moving body, the amount of light emitted from a light emitting element is controlled based on the two position signals, and a servo motor speed command reference signal is controlled. A photo encoder characterized in that it is provided with means for controlling the amount of light emitted and generating a reference signal to generate and output. 2. The light emission amount control/reference signal generation means includes squaring means for squaring each of the two position signals, addition means for adding the squared results of the squaring means, square rooting means for rooting the addition result of the addition means; 2. The photo encoder according to claim 1, further comprising power supply control means for supplying current to the light emitting element according to the square root result of the square root means, and outputting the square root result of the square root means as a servo motor speed command reference signal.