JPH0256169A - Constant speed control device and image reading device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a constant speed control device that controls a controlled object at a constant speed, and is used, for example, to drive control of a sub-scanning unit of an image reading device or a digital copying machine. .

2. Description of the Related Art In recent years, the image reading units of image reading devices and digital copying machines are required to have higher reading speeds and have various editing functions. High precision during control and various flexible operations are required even outside of constant speed control.

Conventional constant speed control devices generally use PLL (phase locked loop) control, making it difficult to perform flexible control other than during constant speed control.

(For example, JP-A No. 59-63876, JP-A No. 61-Sho.
45670 Publication) Problems to be Solved by the Invention In conventional constant speed control devices, it is not easy to perform controls other than constant speed control, such as stopping, reversing, and acceleration/deceleration profile control.

In view of the above problems, the present invention maintains the control performance during constant speed control equivalent to PLL control, eliminates the synchronization loss that is a drawback of PLL control, and easily performs flexible control operations other than during constant speed control. The purpose of this invention is to provide a constant speed control device that can control the speed of the vehicle.

Means for Solving the Problems A constant speed control device according to the present invention includes a controlled object to be controlled at a constant speed, a driving means for driving the controlled object, an encoder for measuring the position of the controlled object, and a device to be controlled at a constant speed. means for generating a reference clock corresponding to the speed; phase difference measuring means for measuring the phase difference between the clock and the encoder pulse corresponding to the position output by the encoder; position information of the encoder, the reference clock and the encoder pulse; The control device is composed of a position information synthesizing means for synthesizing the phase differences between the two to obtain position information of the controlled object, and a means for forming a position servo loop.

As one preferable example, the position information synthesis means uses a microprocessor.

As another preferred example, the phase difference measuring means measures the phase difference time between the reference clock and the encoder pulse corresponding to the speed to be controlled using a phase difference measuring clock having a cycle smaller than the cycle of the reference clock. Count.

An image reading device according to the present invention includes a document table on which a document is placed, a light source that illuminates the document, an image sensor, an optical system that focuses reflected light or transmitted light from the document on the image sensor, and the light source. A sub-scanning unit that scans a document on a document table, a driving means for driving the sub-scanning unit, an encoder for measuring the position of the sub-scanning unit, and a means for generating a reference clock corresponding to a sub-scanning speed. a phase difference measuring means for measuring a phase difference between the clock and an encoder pulse corresponding to a position output by the encoder; and a sub-scanning unit that synthesizes the position information of the encoder and the phase difference between the reference clock and the encoder pulse. It consists of a position information synthesizing means for generating position information, and a means for forming a position servo loop.

Operation The present invention can precisely and flexibly control a controlled object with the above-described configuration.

Embodiment A digital copying machine using a constant speed control device and an image reading device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic external view of a digital copying machine.

1 is a paper feed cassette, 2 is a document cover, 3 is an operation panel having a key display section, etc., and 4 is a paper discharge tray, which is similar to a copying machine carried on a boat. 5a.

Reference numeral 5b denotes a coordinate input tablet and pen used when performing editing operations such as trimming.

FIG. 2 is a block diagram showing the internal structure of the copying machine shown in FIG. 1 and the driving portion of the sub-scanning unit. Transparent manuscript table 14
The original 11 is placed on top of the original and the original 11 is pressed against the original table 14 by the original cover 2. The light source 15 illuminates the document surface,
The light reflected from the original is transmitted through the rod lens array 16.
It is focused onto the line image sensor 28. The image sensor 28 generates an electrical signal 30 according to the amount of light reflected from the original 11.
Output. The image signal processing unit 21 is an image sensor 28
The video data 31 is outputted to the printer section 23 after signal processing such as A/D conversion, shading correction, gamma correction, and pseudo halftone processing is performed.

Light source 15, rod lens array 16, image sensor 2
8, the sub-scanning unit 29 includes a wire 38, a Boo'J
The speed of the motor 19 which is driven in the direction of arrow S by the motor 19 via 17a and 17b to perform sub-scanning of the document;
That is, the speed and position of the sub-scanning unit 29 are obtained based on the output of the pulse encoder 20.

The white reference plate 13 is used to perform shuding correction to correct variations in sensitivity among elements of the image sensor 28 and unevenness in illuminance of the light R15.

The document position detection circuit 22 detects the position of the document on the document table from data 32 including density output from the image signal processing section 21. The position of the original is detected by pre-scanning the original.

The sub-scanning unit control unit 24 receives an output signal 36 from a pulse encoder 2o connected to a motor 19, copy mode selection data 34 from a copy mode selection key 27 on the operation panel 3, and coordinates from a coordinate input tablet 5a. Using the instruction data 35 and document position data 33 from the document position detection circuit 22, a torque command 37 given to the motor driver 25 is outputted to control the sub-scanning unit 29. The copy mode selection data 34 includes copy mode instruction data such as equal size, enlargement, reduction, movement, and continuous copying, and instruction data such as enlargement rate and reduction rate. When the power is turned on, the sub-scanning unit 29 is driven in the direction of the origin sensor 18. When the origin sensor 18 detects the sub-scanning unit 29, it outputs a detection signal 136.
is output, and a position counter (described later) included in the sub-scanning unit control unit 24 is reset.

FIG. 3 is a schematic diagram of the printer section 23. As shown in FIG.

The print paper 51 stored in the paper feed cassette 1 is guided between a pair of guides vi54 by the paper feed roller 52,
The photosensitive drum 68 is brought into contact with the pair of rollers 55 . On the other hand, the scanner motor 66 rotates the polygon mirror 65. The polygon mirror 65 reflects the laser beam from the semiconductor laser 67 and scans the photoreceptor drum 68.

The photosensitive drum 68 rotates in the direction of arrow R. Charger 57
charges the photosensitive drum 68.

Laser drive circuit 64 modulates the output laser beam of semiconductor laser 67 with video data 31. The modulated laser beam forms a latent image on photoreceptor drum 68.

A developing device 56 develops the latent image on the photosensitive drum 68 with toner. The transfer charger 59 transfers the toner on the photosensitive drum 68 onto the print paper. The stripping charger 60 strips the print paper from the photosensitive drum 68. The conveyor belt 61 conveys the print paper separated from the photoreceptor drum 68 to the fixing device 62 .

The fixing device 62 fixes the toner transferred onto the print paper onto the print paper. The print paper is discharged onto the paper discharge plate 4 by a pair of paper discharge rollers 63 .

Paper feed sensor 53 detects that print paper is fed, and outputs a paper feed detection signal 135. Such a printer unit is well known as a laser beam printer using an electrophotographic process.

Figure 4 shows the sub-scanning unit control section 2 shown in Figure 2.
4 is a block diagram of FIG. Micro processing unit (MPU)
g unit) 101 via data bus 102.
0 port 103, ROM (read only memory;
r6Bd □nly mem.

ry) -1~ROM-5, 118, 119, 120,
121 and 122 are accessed. MPUl0I is RO
Using the table data stored in M-1 to ROM-5, calculate the position where the sub-scanning unit 29 should exist (hereinafter referred to as position reference), the speed it should have (hereinafter referred to as speed reference), etc. do.

The table data stored in ROM-1 to ROM-5 will be described in detail later.

Encoder circuit 114 receives two signals from pulse encoder 20.
Direction discrimination is performed using the phase signal 36 as input, and forward rotation and reverse rotation pulses 115 and 116 of the motor 19 are generated. The position counter 117 is a reversible counter whose clock input is the stoppage and reversal pulses 115 and 116 output from the encoder circuit 114. The position counter 117 is reset by the origin detection signal 136 from the origin sensor 18. The value of the up-down counter 117 is latched by the latch 143. The clock input of the latch 143 is the clock generation circuit 11
This is the reference clock 134 output from 2. MPUl
The 0I reads the latched count output data of the position counter via the I10 port 103 and learns the current position of the sub-scanning unit 29. Furthermore, the MPUl0I receives copy mode selection data 34 from the copy mode selection key 27,
Coordinate instruction data 35 from the coordinate input tablet 5a,
The document position data 33 from the document position detection circuit 22 is
10 boat 103. A paper feed detection signal 135 from the paper feed sensor 53 is input to MPU10I as an interrupt signal.

MPUl0I, D/A converter 104, lead/lag filter 105, amplifier 106, low pass filter 1
07, motor driver 25, motor 19, pulse encoder 20, encoder circuit 114, position counter 11
7 and a phase difference detection circuit 140 constitute a position servo loop that performs position control. The phase difference detection circuit 140 will be explained in detail later. MPU 101, D/A converter 104, amplifier 109, low pass filter 11
0, motor driver 25, motor 19, pulse encoder 20, encoder circuit 114, position counter 117
Configure a speed servo loop that performs speed control. Selector 108 selects either the position servo loop or the velocity servo loop.

Next, the phase difference detection circuit 140 will be explained using FIG. 17. FIG. 17 is a block diagram of the phase difference detection circuit 140.

The two-phase signal 36 from the pulse encoder 20 is sent to the one-shot multivibrator 201.202.203.204.
Enter. Each one-shot multivibrator is triggered by a rising or falling edge and outputs a low pulse. The AND gate 205 outputs a signal in which all edges of the two-phase signal 36 output from the pulse encoder are made into low pulses.

The output of the AND gate 205 is the counter (3 bits) 20
7 is cleared and serves as the clock for D and FF 206. When there is an input to the clock of D, FF 206, the page output becomes low, the output of NOR gate 208 becomes high, and counter 207 is enabled.

The counter 207 counts the phase difference detection clock 142. When the reference clock 134 is input, the FF 206
is cleared, the counter 207 is disabled, and the count value is latched in the latch 209. This measures the time difference between all edges of the encoder pulse and the reference clock 1340 phase.

The operation will be described in the case where the sub-scanning unit 29 is controlled at a constant speed by position profile control.

The D/A converter 104 receives 8-bit data as input,
When the data is °80'H, OCV) is output.

The clock generation circuit 112 generates a reference clock 134 to generate an interrupt to the MPU10I. For example, assume that the period of the reference clock is 400 m5ec, the LSB of the output of the position counter 117 is 63.5 μm, and the period of the phase difference measurement clock 142 output from the clock generation circuit is 50 m5ec, which is 1/8 of the period of the reference clock. .

For each interrupt of the reference clock 134, MPU10I uses the position reference (16
A new position reference is calculated by adding 04H to the bit data LSB (7.9375 mm), and the calculated position reference and the value of the counter 117 are shifted to the left by 3 bits, and the 3 bits of the output data of the phase difference detection circuit are shifted to the lower order. In addition to the bit, data corresponding to the difference with the obtained position data of the sub-scanning unit 29 is written to the D/A converter 104 via the I10 port 103, and a voltage corresponding to the data is output to the D/A converter 104. do. The count value measured by the phase difference detection circuit 140 is sent to the position counter 117.
Expand the lower bits of , increasing the resolution of position information. The lead/lag filter 105 performs phase compensation on the output voltage of the D/A converter 104 to stabilize the position servo loop. Amplifier 106 amplifies the output of lead/lag filter 105 and determines the feedback gain of the position servo loop. A low-pass filter 107 removes high frequency components contained in the output of the amplifier 106. The selector 108 selects the output 137 of the low-pass filter 107 based on the position control/speed control switching signal 111 output from the MPU 101 and outputs a motor torque command 37 to the motor driver 25. Therefore, the sub-scanning unit 29 is always controlled so that the position reference calculated by the MPU 101 and the position of the sub-scanning unit 29 are equal.

The operation will be described when controlling the position of the sub-scanning unit 29. The clock generation circuit 112 uses the reference clock 1
34 to generate an interrupt to MPU10I. M
PU10I calculates a position reference every time the reference clock 134 interrupts, and corresponds to the difference between the calculated position reference and the position data of the sub-scanning unit 29 obtained by shifting the value of the position counter 117 to the left by 3 bits. The data is sent to the D/A converter 1 via the I10 port 103.
04, and outputs a voltage corresponding to the data to the D/A converter 104.

Next, the operation when controlling the speed of the sub-scanning unit 29 will be described. MPU10I is D/A converter 104
Data corresponding to the difference between the calculated speed reference and the speed of the sub-scanning unit 29 is written every time the reference clock 134 interrupts. The speed of the sub-scanning unit 29 is obtained by determining the distance that the sub-scanning unit 29 moves in a certain period of time. Amplifier 109 amplifies the output voltage of D/A converter 104 and determines the feedback gain of the speed servo loop.

Low-pass filter 110 is a noise filter.

During speed control, the position control/speed control switching signal 111 is
The selector 108 selects the output 138 of the low-pass filter 110.
is selected and controlled to output a motor torque command 37.

Figure 5 shows lead/lag filter 10 using an operational amplifier.
5 is a circuit diagram. FIG. 6 is a Bode diagram of a lead/lag filter, in which the phase of the position servo loop is compensated by advancing the phase at frequency fn.

The document position detection circuit 22 will be explained using FIGS. 7 and 8. FIG. 7 is a block diagram of the document position detection circuit 22, and FIG. 8 is an operation timing chart of the document position detection circuit 22. When detecting the document position, the color of the document side of the document table cover 2 is set to black. Both edge portions of the document in the main scanning direction are detected by performing Briscan over the entire reading area once.

The operation of the document position detection circuit 22 will be explained below. Density data 1 included in data 32 from image signal processing unit 21
51 is 8-bit data, which is "FF'H1" for black and "O'H" for white. The density data 151 is 8-bit data with respect to the clock 164 included in the data 32, and is ``FF''H for black and ``0''H for white. Concentration data 151 is clock 1 included in data 32
It is synchronized with 64. A slice level generation circuit 169 generates 8-bit data 152 (hereinafter referred to as slice level data) corresponding to an intermediate density between the background density of the original and the density on the original side of the original table. The slice level data may be output from the MPU.

Comparator 153 is concentration data (DDATA) 1
51 and slice level data 152,
Outputs a comparison signal (COMP). Inverter 162 inverts clock 164. D flip-flop 154
is the output COMP of the comparator 153 and the inverter 16
2 is latched and the signal LCOMP is output.

Line enable signal (LENB) included in data 32
L) 165 is a signal indicating the effective range of one line of DDATA 151.

Counter 161 clears LENBL 165, uses clock 164 as clock input, and outputs DDATA 151.
Outputs the coordinates of the position in the main scanning direction. A line synchronization signal (LSYNC) 166 included in the data 32 is a main scanning trigger signal.

The inverter 155 is the output L of the D flip-flop 154.
Invert COMP. The D flip-flop 156 uses the output of the inverter 155 as a clock input, and the D input is the old G
It is at H level, and LSYNC166 is used as a clear input. The latch 157 uses the output of the D flip-flop 156 as a latch clock, latches the output of the counter 161, and outputs data L1. The latch 158 uses the output LCOMP4 of the D flip-flop 154 as a latch clock, latches the output of the counter 161, and outputs data L2. Inverter 163 inverts LENBL 165. The latch 159 uses the output of the inverter 163 as a clock input, latches the output L1 of the latch 157, and stores the data L316.
Outputs 7. The latch 160 uses the output of the inverter 163 as a clock input, latches the output L2 of the latch 158, and outputs data L416B. Latch 159.16
Outputs 167 and 168 of 0 are read as data 33 by MPU10I via I10 port 103.

Next, the meaning of each signal of the document position detection circuit 22 will be explained using FIG. Concentration signal DDATA 151 is synchronized to clock 164. Line enable signal LENB
L 165 is an active high signal indicating the valid range of DDATA 151 and is synchronized to clock 164 .

When the signal LENBL 165 is non-active (LO-level), the value of DDATA 151 is "FF' H. The output COMP of the comparator 153 is clocked
The signal latched with the inverted signal of 4 is LCOMP. Signal LENBL165 is active (HIG) I level)
After that, the data latched from the output C0UNT of the counter 161 at the first rising edge of LCQMP becomes Ll.
It is. L3167 is data obtained by latching data Ll at the falling edge of LENBL. The data latched from C0UNT at the rising edge of signal LCOMP is transferred to L2.
It is.

L416B is data obtained by latching data L2 at the falling edge of LENBL. In other words, after one line scanning is completed, if there is no document in one scanned line, data L2.
L3 is 0゛. If there is a document, the coordinates of the edges of the document in the main scanning direction are data L2 and L4.

MPU10I is data L2. L4 and sub-scanning unit 2
By reading the position data No. 9 at any time during prescanning, the coordinates of the edge of the document can be known. A warning can be displayed on the operation panel 3 when the original is placed diagonally, and erroneous detection of the main scanning direction coordinates of the original edge due to dirt on the original platen 14 and the original platen cover 2 can be removed by the MPUl0I program. .

ROM-1118, ROM-2119, ROM in Figure 4
The contents of the data stored in -3120 will be explained using FIG.

ROM-1118 stores a data table of acceleration position profile data of the sub-scanning unit. Let P be the moving distance of the sub-scanning unit corresponding to one bit of the position counter 117. Interrupt pulse 134 to MPUl0I
When the interrupt frequency of is f (Hz), the nth acceleration position profile data A (n) is A(n)=INT(+A-a (1/f-n)"
1/P).

Here, INT() is an integerization function, and a is acceleration.

FIG. 9(a) shows the data arrangement of the data table of ROM-1. A (n) l in Figure 9(a) is A (n)
The lower byte of A (n) u is the upper byte. FIG. 11(a) shows a graph of data in the data table of ROM-1.

ROM-2119 stores the address of ROM-1 where position data corresponding to the position where acceleration is to be ended is stored. When performing enlargement or reduction copying in the sub-scanning direction, the enlargement ratio m
[%] can be expressed as m=Vp/Vs x 100 (%), where the speed of the sub-scanning unit 29 is Vs and the process speed of the printer is 5.

That is, the sub-scanning unit 29 has Vs-Vp/mX 1
After accelerating to a speed of 00 based on the acceleration position profile data in ROM-1, the controller shifts to constant speed position profile control. The address of ROM-1118 at which the acceleration position profile control is to be terminated is stored in ROM-2119 in accordance with the enlargement ratio in the sub-scanning direction. Data Z in the data table of ROM-2) is Z(m) = INT(2x Vp / (a - m)
・It can be expressed as 100).

If the magnification ratio actually used is in the range of 50% to 400%, then Z (e) (50≦m≦400) is valid data. FIG. 9 shows the arrangement of data in the data table of ROM-2. is the lower byte of Z (e), Z
) U is the upper byte.

The ROM-3120 stores the run-up distance from when the sub-scanning unit 29 accelerates from a stopped state until it reaches a constant speed as table data. As described above, since the document scanning speed of the sub-scanning unit 29 changes depending on the magnification ratio in the sub-scanning direction, the scanning speed of the sub-scanning unit 29 changes depending on the magnification ratio in the sub-scanning direction.
The acceleration distance changes.

The run-up distance is the sum of the acceleration distance for accelerating using the acceleration position profile data and the settling distance from the end of acceleration until settling to a constant speed. Run-up distance table data D (
m) is determined by D(m)=A ('A Zh)) +m ·b.

Here m-b is the settling distance and b is a constant. 9th
Figure (C) shows the arrangement of table data in ROM-3.

The lower byte t-D6Tl)u of D(E)2 is D) is the upper byte.

Before explaining the data contents of the ROM-4121, the direction of movement copying in the sub-scanning direction will be explained. First, the operation sequence of the sub-scanning unit 29 when copying the original 11 shown in FIG. 12(a) at the same position as shown in FIG. 12(b) will be described with reference to FIGS. 13 and 14. Arrow S in FIG. 12 indicates the direction of sub-scanning. FIG. 13 is a diagram showing the positional relationship between the sub-scanning unit 29 and the document 11.

The home position A is the position where the sub-scanning unit 29 is stopped when the copying machine is not performing a copying operation. The run-up start position point B of the sub-scanning unit is a position on the side of point A by a run-up distance X1 from the document reading start position C. Point D is the original reading end position.

FIG. 14 is an operation sequence diagram when copying without moving the original. When the copying operation is not being performed, the sub-scanning unit is stopped at the home position A point. When the copying operation is started, the MPU10I outputs a print paper feeding command 170 (FIG. 2) to the printer unit 23. On the other hand, after reading the white reference data for shading correction at point A, the sub-scanning unit 29 completes the movement to point B under speed profile control before the paper feed sensor 53 detects print paper. TOsec after the paper feed sensor 53 detects the print paper, the sub-scanning unit 29 must reach the zero point and output an image signal to the printer section 23. The time required for the sub-scanning unit 29 to accelerate is T1 se
c, the sub-scanning unit 29 is connected to the paper feed sensor 5.
3 stops at point B for To-T1 sec after detecting the print paper, and then starts accelerating according to the position profile control. The sub-scanning unit 29 scans the original 11 from point 0 to point D under position profile control, and when it reaches point D, returns to point A under speed profile control.

Next, the operation sequence of the sub-scanning unit 29 when moving and copying FIG. 12(a) as shown in FIG. 12(C) will be described with reference to FIG. 15. In this case, the standby position of the sub-scanning unit 29, that is, the acceleration start position is at point E. Point E is a position closer to point A than point F by an approach distance of 2' of the sub-scanning unit. That is, by moving the document reading start position from point B to point E, copying is performed in a direction opposite to the sub-scanning direction.

Next, the operation sequence of the sub-scanning unit 29 when performing moving copying as shown in FIGS. 12(a) and 12(d) will be described with reference to FIG. 16. In this case, the time from when the paper feed sensor 53 detects the print paper until the sub-scanning unit 29 reaches the zero point is TO+T2. When copying by moving the original by a distance in the sub-scanning direction, T t = L /
Moving copying is performed by setting Vp.

Here, the data contents of ROM-4121 will be explained. Since the run-up time T1 changes depending on the magnification ratio in the sub-scanning direction, data representing To-TI is stored in advance in the ROM-4 as table data for the magnification ratio. The data is (TO-Tl) fc, and the interrupt pulse 1 of frequency fc generated by the time measurement interrupt pulse generation circuit 113
Count the number of interrupts to the 39 MPUs. If the magnification rate in the sub-scanning direction is m%, the table data W(e) of ROM-4121 is as follows: WCm)=INT (('AZhL1/f+m-b/
Vs) fc).

However, since the interrupt count value of the frequency fc corresponding to Vs = Vp / mx 100T2 is obtained by T2・fc, MPU10I determines the interrupt count value that determines the time during which the copy is stopped at point B, depending on the moving distance of the moving copy. Values can be calculated. FIG. 10(a) shows the arrangement of table data in ROM-4.

W(m)f is W(m) is the lower byte of W(m), W(
m) u is the upper byte.

The data contents of ROM-5122 will be explained.

The data in the ROM-5 stores speed profile data used when the sub-scanning unit 29 is moved at high speed from a certain position to a target position a certain distance away.

That is, it is table data of a speed reference corresponding to the distance between the position of the sub-scanning unit 29 and the target position. At this time, the control direction of the sub-scanning unit 290 is switched to speed control. The speed ■ of the sub-scanning unit 29 is i
The sub-scanning unit 29 at time i/f (i is an integer constant)
Obtained from the distance traveled by D=jXP (j is an integer). That is, V=(jXP)/(iXi/f) The speed reference table data V(n) is r.

Here, the value 80H is 0 [■] offset data of the D/A converter 104 (FIG. 4), and a' is the acceleration. 1st
Figure 0 (b) shows the arrangement of table data in ROM-5. FIG. 11(b) shows a graph of table data of ROM-5.

Next, the driving sequence of the sub-scanning unit 29 when copying will be explained, focusing on the MPU10I program flow. When the power is turned on, MPU10I writes '70'H to the D/A converter 104.

Since the D/A converter 104 outputs a negative voltage, the torque command of the motor driver 25 becomes negative, and the sub-scanning unit 29 moves in the direction of the origin sensor 18.

When the origin sensor 18 detects the sub-scanning unit 29, the position counter 1 counts the position of the sub-scanning unit 29.
17 is cleared. After clearing the position counter 117,
Selector 108 is switched to select the speed control loop.

If the difference between the home position and the position of the sub-scanning unit 29 is dl, it is obtained by reading data V (di) from ROM-5 as a speed reference. The difference between the speed reference and the speed of the sub-scanning unit is converted to the D/A converter 104 until the sub-scanning unit is near the home position.
Output to.

In such speed profile control, the sub-scanning unit moves at high speed when the target position and the sub-scanning unit are 29 distance apart, and decelerates as the target position approaches. When the sub-scanning unit moves sufficiently close to the home position, the selector 108 is switched to select the position control loop. Until a copy request is received from the operation panel, the position reference is used as the home position, and the difference between the position reference and the position of the sub-scanning unit is output to the D/A converter 104. In the position control, the sub-scanning unit is controlled to stop at the position of the position reference.

When there is a copy request, a paper feeding command is output to the printer 23, switching to speed control, and speed profile control of the sub-scanning unit 29 is performed. The target position at this time is a position obtained by subtracting the run-up distance obtained from the table data of ROM-3 from the leading position of the original or the original reading start position input from the coordinate input tablet. This position is the standby position. Perform position control at the standby position and stop the sub-scanning unit.

To-Tl is obtained using the table data in ROM-4, and after the paper feed sensor 53 detects print paper, TO-Tl is obtained.
After Tl, acceleration of the sub-scanning unit 29 is started. At this time, the position reference is obtained by adding A (n) to the standby position using table data in ROM-1. n is incremented every time an interrupt of frequency r occurs. Position control is performed so that the position of the sub-scanning unit 29 is equal to the position reference. Acceleration is terminated using table data in ROM-2, and constant velocity position profile control is performed. The position reference at this time is obtained by adding a predetermined value to the position reference for each interrupt. By changing the interrupt frequency f, the speed at constant speed is changed according to the enlargement ratio. When the sub-scanning unit 29 reaches the document reading end position, it switches to speed control, sets the target position to the home position, performs speed profile control, and then performs position control at the home position.

When copying multiple sheets continuously, set the target position to the standby position,
After performing speed profile control, position control is performed at the standby position. When copying a plurality of sheets, the sub-scanning unit does not return to the home position each time, so the sequence operation time of the sub-scanning unit required for one sub-scanning is shortened, and the copying speed can be made faster than before.

In addition, since the position profile of the sub-scanning unit is controlled, the run-up time and run-up distance of the sub-scan unit can be accurately known, so even when copying is enlarged, reduced, or moved.
The positional accuracy of the copied image is high. Furthermore, when moving the sub-scanning unit from a certain position to a target position that is a certain distance away, speed profile control is performed, so the torque of the motor can be used to the maximum and it is possible to move at high speed.

Effects of the invention Measuring the phase difference between the encoder pulse and the reference clock,
By expanding position information using phase difference data and performing constant speed control using position profile control, control performance during constant speed control is maintained at the same level as PLL control, while eliminating synchronization, which is a drawback of PLL control. , flexible control operations other than constant speed control can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is an external view of a copying machine according to an embodiment of the present invention, FIG. 2 is a schematic block diagram showing the internal configuration of the copying machine of FIG. 1, and FIG.
The figure is a schematic block diagram showing the internal configuration of the printer section in the block diagram of FIG. 2, FIG. 4 is an internal block diagram of the sub-scanning unit control section in the block diagram of FIG. 2, and FIG. Figure 6 is a circuit diagram showing an example of the glue/lag filter in the block diagram. Figure 6 is a frequency characteristic diagram of the filter in Figure 5.
The figure is an internal block diagram of the document position detection circuit in the block diagram of Figure 2, Figure 8 is an operation timing chart of the circuit of Figure 7, and Figures 9 (a), (b), and (C) are the internal block diagram of the original position detection circuit in the block diagram of Figure 2. ROM-1, ROM-2゜ROM in the block diagram of Figure 2
10 (a) and (b) are the memory layout diagrams showing the data table of 3.
Memory layout diagrams showing the data tables of OM-4 and ROM-5, Figures 11 (a) and (b) are ROM-4 and ROM-5 data tables, respectively.
1. A graph showing the data of the data table of ROM-5. Fig. 12 is an explanatory diagram showing the positional relationship between the original and the copied image to explain moving copying. Fig. 13 is a graph showing the positional relationship between the original and the sub-scanning unit/nod. FIG. 14, FIG. 15, and FIG. 16 are sequence diagrams showing the operation sequence of the sub-scanning unit, respectively, and FIG. 17 is a sequence diagram of the phase difference detection circuit. 19...Motor, 20...Encoder, 22...Document position detection circuit, 23...
・Printer section, 29... Sub-scanning unit, 1
05...Lead-lag filter, 108...
···selector. Name of agent: Patent attorney Shigetaka Awano (1 person) Log + Hagano! Figure ROM address (α) ROM-1 ROM address RO key-2 ρn M-,? Figure (α) Figure 12 (α]

Claims (6)

[Claims] (1) A controlled object to be controlled at a constant speed, a driving means for driving the controlled object, an encoder for measuring the position of the controlled object, a means for generating a reference clock corresponding to the speed to be controlled at a constant speed, and the aforementioned a phase difference measuring means for measuring a phase difference between a clock and an encoder pulse corresponding to a position output by the encoder; and a phase difference measuring means for measuring a phase difference between a clock and an encoder pulse corresponding to a position output from the encoder; 1. A constant speed control device comprising: a position information synthesizing means for forming a position servo loop; and a means for forming a position servo loop. (2) The constant speed control device according to claim (1), wherein the position information synthesis means uses a microprocessor. (3) The phase difference measuring means counts the phase difference time between the reference clock and the encoder pulse corresponding to the speed to be controlled at constant speed using a phase difference measuring clock having a cycle smaller than the cycle of the reference clock. Characteristic claim (1)
Constant speed control device as described. (4) A document table on which a document is placed, a light source that illuminates the document, an image sensor, an optical system that focuses reflected light or transmitted light from the document on the image sensor, and a document table that includes the light source and a light source that illuminates the document. A sub-scanning unit for scanning a document, a drive means for driving the sub-scanning unit, an encoder for measuring the position of the sub-scanning unit, a means for generating a reference clock corresponding to a sub-scanning speed, and the clock. , a phase difference measuring means for measuring a phase difference between the encoder pulse corresponding to the position output by the encoder, and combining the position information of the encoder and the phase difference between the reference clock and the encoder pulse to obtain position information of the sub-scanning unit. An image reading device comprising: position information synthesis means; and means for forming a position servo loop. (5) The image reading device according to claim (4), wherein the position information synthesis means uses a microprocessor. (6) The phase difference measuring means is characterized in that the time of the phase difference between the reference clock and the encoder pulse corresponding to the sub-scanning speed is counted using a phase difference measuring clock having a cycle smaller than the cycle of the reference clock. The image reading device according to claim (4).