JPH05300796A - Driver for stepping motor and image reader using the same - Google Patents

Abstract

PURPOSE:To accurately control a speed without heavy loading on a software by providing an exciting pattern storage unit for outputting a reference select signal to a reference generator for controlling conduction of a stepping motor and supplying an output for designating an exciting phase. CONSTITUTION:A programmable periodically variable rectangular wave is output from a CPU1, and input to an up/down counter 2, which counts up/down with a select signal designated by the CPU1 in a selected direction. Then, a direction of an output from an exciting pattern storage unit 3 is switched by switching the direction of the up/down counting of the counter 2. A motor exciting pattern for designating an exciting phase is output to a motor driver 5 based on an output value of the counter 2 and an exciting pattern select signal from the CPU1, and a reference signal is output to a reference generator 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor driving device capable of speed control in an image reading device, and an image reading device using the same.

[0002]

2. Description of the Related Art Conventionally, step motors have been used not only in image reading apparatuses such as facsimile machines and digital copiers, but also in writing apparatuses such as plotters. The step motor is a pulse motor that advances step by step at a constant angle by sequentially energizing the exciting coil. It has a long life because there is no mechanical sliding part like a brush, and the number of pulses and the rotation angle applied. Have the advantage that cumulative errors do not occur. 2. Description of the Related Art Conventionally, in a sub-scanning step motor such as a facsimile machine, a device for driving and controlling the speed in multiple stages selects one of the motor excitation patterns stored in advance by a microcomputer, and the microcomputer is selected. Thus, the driving data of a predetermined pattern is output in parallel at a constant cycle, and the sub-scanning speed is controlled by switching the excitation method of the sub-scanning step motor.

[0003]

As described above, in the conventional control device, since the stepper motor is rotated by outputting the parallel pattern of a constant period from the microcomputer, the next output is made by software. It was necessary to determine which parallel pattern to perform and load it to the output terminal of the microcomputer. However, the recent method requires slow-up / down control while driving the motor in the pull-out area (high-speed rotation area), so that the conventional control method imposes a heavy load on the software. -High speed rotation control has become impossible even by using speed control by switching the excitation system of the motor. In addition, the motor excitation method switching circuit becomes more complicated if the number of controllable excitation methods is increased.
As a result, the cost is increased and the circuit scale is increased. Further, in the step motor driving device, for example, when 1-2 phase excitation is performed, first, the A phase is excited and then the A,
Both phases B are excited, then phase B is excited, then A
The excitation sequence continues, such as exciting the phases. However, because the exciting force is different when only the A phase and only the B phase are excited, the high speed rotation occurs. This torque ripple sometimes causes vibration and noise, and in the worst case, step-out may occur. A first object of the present invention is to solve these conventional problems and to provide a step motor drive device capable of speed control without burdening software with a small-scale circuit. is there. A second object of the present invention is a step mode motor having a small torque ripple and capable of suppressing vibration and noise.
It is to provide a motor drive. A third object of the present invention is to provide a sub-scanning variable magnification control without imposing a load on software, and an image reading apparatus capable of high-speed reading while suppressing vibration and noise.

[0004]

In order to achieve the above object, a step motor driving device of the present invention comprises: (a) a motor driver for driving a constant current step motor and an exciting current for the motor driver. In order to output the reference selection signal to the reference generation circuit that supplies the excitation potential and the reference generation signal to the motor driver, and to supply the output that specifies the excitation phase to the motor driver, the motor excitation pattern is stored in advance. And an excitation pattern storage unit. Further, (b) the excitation patterns stored in the excitation pattern storage section are made different,
Another feature is that the stepping motor is excited by the same excitation force in all excitation directions by increasing the reference potential generated by the reference generation circuit. Further, the image reading device of the present invention is
(C) Constant current stepping motor driver, reference generation circuit for controlling the excitation current of the driver, and excitation pattern in which the motor excitation pattern is stored in advance in order to control the driver and the reference generation circuit. Motor drive pulse (square wave) output from the storage unit and CPU
It has a step motor drive circuit equipped with a counter that counts up or down according to, and outputs a rectangular wave whose cycle can be changed programmably from the CPU so that the counter counts the rectangular wave and rotates the motor. When the speed is determined and the magnification is changed in the sub-scanning direction, the method of controlling the motor speed by changing the frequency of the rectangular wave, and the excitation pattern stored in the excitation pattern storage section are used. Another feature is that the motor speed is controlled in a mixed manner by changing the excitation method.

[0005]

In the present invention, (a) several types of motor excitation patterns and motor reference select signals are stored in advance in the excitation pattern storage unit (PLD), and the reference select signals are also stored. To generate a reference to control the phase current for realizing the micro step of the motor, and the constant current motor driver rotates the motor by the excitation pattern and the reference signal. Also,
(B) In the above reference generation circuit, each reference potential is connected to the micro step generated by the ladder-shaped resistor, and by increasing these reference potentials, excitation is performed with the same excitation force in all excitation directions. To be able to. Further, in the (c) facsimile apparatus, the CPU determines the rotation direction of the motor, outputs the UP / DOWN signal, determines the excitation method of the motor, and outputs the SEL signal. Then, the motor drive pulse (rectangular wave) is output to determine the rotation speed. Also, when performing scaling in the sub-scanning direction,
If the reading density is reduced, the motor drive pulse must be made faster, and as a result, the load on the software also increases.To avoid this, the frequency of the motor drive pulse is changed to increase the motor speed. The control method and the method of controlling the motor speed by changing the excitation method are mixed and controlled. This enables a wide range of motor speed control without burdening the software.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of a sub-scanning step motor driving device showing an embodiment of the present invention. In FIG. 1, 1 is a microcomputer (hereinafter, CPU) that controls all controls, and 2 is UP / DOW that counts up / down by a motor drive pulse output from the CPU 1.
N counter section, 3 is an excitation pattern storage section in which several kinds of motor excitation patterns and motor reference select signals are stored in advance, and 4 is a motor for realizing a micro step of the motor. Reference generation circuit for phase current control,
Reference numeral 5 is a constant current motor driver for rotating the motor according to the excitation pattern of the excitation pattern storage unit 3 and the reference signal of the reference generation circuit 4, and 6 is a step mode motor for performing sub-scan movement of the optical system. It is. The step motor driving device of the present invention is composed of the above five circuits 1-5.

FIG. 4 and FIG. 5 are diagrams of the excitation pattern output output from the excitation pattern storage section of FIG. Figure 1
In, the CPU 1 can output a rectangular wave (MPCLK) whose period can be changed in a programmable manner. Square wave MPCLK is UP / DOWN counter 2
Input to the UP / DOWN counter 2 causes the UP / DOWN counter 2 to select the UP / DOWN select signal (UP / DOWN) specified by the CPU 1.
Count up or down in the direction selected by N). In the counter 2, when the UP / DOWN direction is switched, the output direction of the excitation pattern storage section 3 is also switched, so that the forward / reverse control of the motor is performed. In this case, when the UP / DOWN signal is UP, the normal rotation is performed, and when the UP / DOWN signal is DOWN, the reverse rotation is performed. Now, assuming that the counter 2 is a 5-bit counter, 2
Repeatedly counts up to ⁵ = 32, so UP / DOW
When the N signal is UP, the output of the counter 2 (CP0 to 4) repeats count-ups of 0, 1, 2, ..., 30, 31, 0, 1 ,. The excitation pattern storage unit 3 includes the output value (CP0 to 4) of the counter 2 and the CPU.
Based on the excitation pattern select signals (SEL0 to 1) from 1, the motor excitation pattern (MP0 to 3) is supplied to the motor driver 5, and the reference select signal is supplied to the reference generation circuit 4. (REFSEL0 to 2) are output respectively. In this case, since REFSEL has two kinds of states, that is, each of the three signal lines 0 to 3 is HIGH or LOW, three REFSELs can indicate eight kinds of states 0 to 7. Similarly, two SELs 0-1 can indicate four types of selection signals. Two-phase excitation when SEL is 0, 1-2 phase excitation when SEL is 1, W1- when SEL is 2
When the two-phase excitation and SEL is 3, the excitation pattern of WW1-2 phase excitation is output. In FIG. 4, the excitation pattern output at the time of 1-2 phase excitation when SEL is 1 (the outputs CP0 to CP4 of the up / down counter 2, the outputs MP0 to 3 of the excitation pattern storage unit 3, and REFSEL0 to 2) ) Is shown in FIG.
Shows the excitation pattern output (CP0 to 4, MP0 to 3, REFSEL0 to 2) at the time of WW1-2 phase excitation when SEL is 3.

FIG. 3 is a configuration diagram of the reference generation circuit in FIG. 1, and FIG. 2 is an excitation vector diagram of W1-2 phase excitation. The operation of the reference generation circuit 4 when REFSEL0 to 2 are input from the excitation pattern storage unit 3 will be described. In FIG. 3, IC1 and IC2 are 8-channel analog switches, and for the 3-bit input value of REFSEL0 to 2, REFSEL0 to BREF terminals and REFA0 to REFSEL0.
7, REFB0 to 7 are connected. For example, 2 for REFSEL
Comes, the Aref terminal and REFA2 are connected, and the Bref terminal and REFB2 are connected. REFA0-7 and REFB0-7 are
As shown in FIG. 3, it is connected to reference potentials (a to d) for microsteps generated by a ladder-shaped resistor. This reference potential is a MA in which a is equal to 1
X is the reference potential for excitation (excitation force α), b is the potential at which the equivalent excitation force is α × tan 33.75 °, c is α × tan 22.5 °, d is α × tan 11.25 It is the electric potential which becomes °. In FIG. 2, the arrow indicates the excitation vector,
The distance from the center to the circumference indicates the exciting force α. For example, when performing W1-2 phase excitation, as shown in FIG. 2, first, only the A phase is excited with the exciting force α, the A phase is the exciting force α, and the B phase is the exciting force α × tan 22.5 °. Excited, then A, B
Both phases are excited by the exciting force α, then the A phase is excited by α × tan 22.5 °, the B phase is excited by the exciting force α, and then only the B phase is excited by the exciting force α. As a result, as shown in FIG.
The steps shown in the phase excitation vector diagram are performed.

In FIG. 1, a constant current motor driver 5
, The excitation phase is determined by the input signals of MP0 to MP3.
That is, when MP3 is active, phase A is again M
When P2 is active, the B phase is excited, when MP1 is active, the -A phase is excited, and when MP0 is active, the -B phase is excited. Excitation pattern of FIG. 4 and FIG.
In the output diagram, when the value of MP0 to 4 is 0, the state is not excited, and when it is 1, the excited state (active) is shown. Further, the Aref terminal and the Bref terminal are analog voltage input sections for determining the exciting currents of the respective phases, and the higher the level of these terminals is, the more exciting current flows, so that a high exciting force can be extracted. Therefore, by controlling MP0 to 3 and the Aref terminal and Bref terminal inputs, microstepping becomes possible. In the present embodiment, it is described that the excitation system can be switched from 2-phase excitation to WW1-2-phase excitation, but the reference generation circuit 4 using CP, MP, REFSEL terminals, and ladder resistors can be added. If
Finer microstep drive is possible.

FIG. 7 is a block diagram showing another embodiment of the reference generation circuit shown in FIG. 3, and FIG. 9 is a diagram showing the excitation pattern output in FIG. As another embodiment of the present invention, a case will be described in which the configuration of the entire circuit is the same as that of FIG. 1, but only the excitation pattern and the reference generation circuit are different. In the excitation method in this case, no matter which direction the micro step is performed, the same excitation force can be applied in all the excitation directions. Reference generation circuit 4
Are connected to reference potentials (a to h) for microsteps generated by ladder-shaped resistors, as shown by REFA0 to 7 and REFB0 to 7 in FIG. The reference potential is a, where a is a reference potential for MAX excitation (excitation force is α), b is a potential at which an excitation force of 1 is α × sin 78.75 °, and c is α ×. sin6
7.5 °, d is α × sin 56.25 °, e is α × sin 45 °, f is α ×
sin 33.75 ° (= α × cos 56.25 °), g is α × sin 22.5 °, h
Is the potential that becomes α × sin 11.25 ° (= α × cos 78.75 °). For example, when performing the W1-2 phase excitation, first, only the A phase is excited with the exciting force α, then the A phase is excited by α × sin 67.5 °, and the B phase is excited by α × cos 67.5 °. Excited by force,
Next, the A phase is excited by α × sin45 °, the B phase is excited by α × cos45 °, and the A phase is excited by α × sin22.5 °.
The B phase is excited with an exciting force of α × cos 22.5 °, and then only the B phase is excited with an exciting force α. As a result, W1 = 2 shown in FIG.
The steps shown in the excitation vector diagram for phase excitation are performed.
The difference from the excitation vector diagram shown in FIG. 2 is that excitation is performed with the same excitation force in all excitation directions. Figure 9
As an example thereof, the outputs of MP0-3 and REFSEL0-2 when SEL is 3 (that is, when WW1-2 phase excitation) are shown.

FIG. 8 is a block diagram of a facsimile apparatus using the present invention. In FIG. 8, 1 is a system control unit (microcomputer) for controlling the entire system,
Reference numeral 7 denotes an image reading unit for electrically self-scanning a document illuminated by a light source in the main scanning direction by a CCD or the like, and digitizing analog image data obtained by photoelectric conversion by an AD converter. A sub-scanning control unit for moving an optical system for mechanical scanning in the scanning direction, 9 is an image signal processing unit for correcting the digital data output from the image reading unit 7 and binarizing it. Is an encoding / decoding unit that encodes and compresses the binarized data from the image signal processing unit 9 or decodes the compressed data into the original raw data, and 11 is encoded. Data is stored in the SAF memory, 12 is a transmission control unit that controls transmission and reception through the line 15, 13 is a plotter unit that records the decoded image signal, and 14 is an operation display unit for operating the facsimile apparatus. , 15 are system memories. In the facsimile apparatus shown in FIG. 8, the step motor driving apparatus of the present invention shown in FIG. 1 is installed in the sub-scanning controller 8.

In FIG. 8, first, the CPU 1 determines the rotation direction of the motor and outputs the UP / DOWN signal.
Next, the CPU 1 uses the motor excitation method (two-phase excitation or 1-phase excitation).
-2 excitation, etc.) and outputs SEL0 to 1 signals. Next, programmable rectangular wave output terminal (MPCL
The motor is rotated by outputting MPCLK of the speed (PPS) desired to be moved from K). Here, when changing the magnification in the sub-scanning direction, the frequency of this MPCLK may be changed, but as the reading density becomes smaller, it is necessary to make the MPCLK faster and the load of software increases. Therefore, the method of controlling the motor speed by changing the frequency of MPCLK and the method of changing the motor speed by changing the excitation method are mixed and controlled. This allows a fairly wide range of motor speed changes to be made without burdening the software.

[0013]

As described above, according to the present invention,
(A) Since the step motor drive circuit is equipped with a PLD or the like in which several types of motor excitation patterns are stored in advance, and a reference circuit can generate a reference capable of realizing each microstep, a small circuit Thus, the speed of the step motor can be controlled without burdening the software. In addition, the (b) reference circuit generates a reference that can be excited with the same excitation force in all directions even during microstepping, so that the torque ripple is small, and vibration and noise are suppressed. The rotation can be performed. Further, (c) the optical system sub-scanning drive unit of the facsimile machine is provided with the above (a)
Since it has the function shown in (b), it is possible to perform sub-scanning scaling control that does not burden the software and high-speed reading without vibration or noise.

[0014]

[Brief description of drawings]

FIG. 1 is a block diagram of a sub-scanning step motor driving device showing an embodiment of the present invention.

FIG. 2 is an excitation vector diagram of W1-2 phase excitation in the present invention.

FIG. 3 is a configuration diagram of a reference generation circuit in FIG.

FIG. 4 is a diagram showing an excitation pattern output of the reference generation circuit in FIG.

FIG. 5 is another excitation pattern of the reference generation circuit.
FIG.

FIG. 6 is an excitation vector diagram of W1-2 phase excitation showing another embodiment of the present invention.

7 is a configuration diagram showing another embodiment of the reference generation circuit in FIG.

FIG. 8 is a block diagram of a facsimile apparatus to which the present invention is applied.

9 is an excitation pattern of the reference generation circuit shown in FIG.
FIG.

[Explanation of symbols]

 1 Microcomputer (CPU) 2 UP / DOWN counter 3 Excitation pattern storage unit 4 Reference generation circuit 5 Motor driver 6 Motor 7 Image reading unit 8 Sub-scanning control unit 9 Image signal processing unit 10 Code decoding Part 11 SAF memory 12 Transmission control part 13 Plotter part 14 Operation display part 15 Line IC1, IC2 Analog switch Aref, Bref Output terminal to the motor driver

Claims (3)

[Claims] 1. A step motor driving device in an image reading apparatus, comprising: a motor driver for driving a constant current step motor; and a reference generation circuit for supplying an exciting potential for controlling an exciting current of the motor driver. ,
A reference pattern selection signal is output to the reference generation circuit, and an excitation pattern storage unit storing a motor excitation pattern in advance is provided for supplying an output for designating an excitation phase to the motor driver. A step motor drive device characterized by the above. 2. The step motor drive device according to claim 1, wherein the excitation patterns stored in the excitation pattern storage section are made different, and the reference potential generated by the reference generation circuit is changed. A step motor drive device characterized in that the step motor is excited by the same exciting force in all exciting directions by increasing the number of steps. 3. A constant current stepping motor driver, a reference generation circuit for controlling the excitation current of the driver, and a motor excitation pattern stored in advance for controlling the driver and the reference generation circuit. It has a step motor drive circuit equipped with an excitation pattern storage section and a counter which counts up or down by a motor drive pulse (rectangular wave) output from the CPU, and the cycle is programmable from the CPU. By outputting a rectangular wave that can be generated, the rectangular wave is counted by the counter to determine the rotation speed of the motor, and when the magnification in the sub-scanning direction is changed, the frequency of the rectangular wave is changed. -A method for controlling the motor speed and a method for controlling the motor speed by changing the excitation method of the excitation patterns stored in the excitation pattern storage section are mixed. An image reading device characterized by being controlled.