JPH0365095A - Manuscript scanning drive - Google Patents

Abstract

PURPOSE:To do proper manuscript scanning with low power by changing over the control of currents flowing in a stepping motor or application voltage during read scanning, and performing the driving control suitable for various driving conditions of the stepping motor. CONSTITUTION:The currents, which are let flow to a stepping motor 108, change by the current down signal outputted from CPU 116. When accelerating a carriage 103 in abeyance, the current down signal is made 1, and the frequency of a pulse signal CLK is raised in step. When reading a manuscript, the current down signal is made 0 to suppress vibration, and a pulse signal CLK is output at read scanning speed. When decelerating and stopping the carriage 103, the current down signal is made 1, and the frequency of a pulse signal CLK is lowered in step.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a document scanning drive device that moves a carriage or a document using a stepping motor to read the document.

[Prior Art] Conventionally, some document reading devices that use a stepping motor as a document scanning drive source switch the value of current or voltage applied to the stepping motor during document reading scanning and return scanning.

[Problems to be Solved by the Invention] However, in the conventional example described above, since the control of the current and voltage flowing through the stepping motor is constant during one scan, there are the following drawbacks.

(1) If the current is controlled to be low in order to suppress image blur caused by motor vibrations that occur during document scanning, it will not be possible to overcome the friction that occurs when the motor starts moving from a stopped state, that is, static friction. There was a drawback that it could cause loss of synchronization.

(2) When performing continuous copying with an original g4 reader that does not have page memory, a return scan is required to return the carriage to the reading start position between each document reading scan, but this is necessary to improve copy speed. Therefore, it is necessary to shorten this return scanning time.

For this reason, there are increasing cases where the return scanning speed is required to be four times or more the reading speed. However, in order to bring out the speed of this return scan, the core requires a strong current, and the power consumption is always high during the return scan.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide a document scanning drive device configured to perform appropriate document scanning with low power consumption.

[Means for Solving the Problems] A document scanning drive device according to the present invention includes a stepping motor as a document scanning drive source, a means for switching the sequence of signals for exciting each phase of the stepping motor, and a stepper motor as a source of the document scanning drive. The apparatus is equipped with means for switching control of the flowing current or the voltage applied to the motor during document scanning.

[Function 1] In the present invention, the motor can be controlled by switching the current flowing through the stepping motor or the voltage applied to the stepping motor during scanning, for example, by switching the control of at least one of the current or voltage during one scanning. This enables control that is adapted to various driving conditions.

[Example] Hereinafter, the present invention will be described in detail based on Examples.

Figure 1 shows the overall configuration of a copying apparatus according to an embodiment of the present invention. The main parts of this device include an operation unit 109 that determines copy conditions, a 5M driver 115 that outputs an excitation signal 114o to a stepping motor (hereinafter abbreviated as SM), and a control signal that outputs a control signal to the SM driver 115 according to instructions from the operation unit 109. Sending CPU (Central Processing Unit) 11
It is 6. The CPU 116 is provided with a memory 116^ in which a control program is stored. Before explaining the entire device, the 5M driver 115 will be described first. Components other than those mentioned above will be described later.

Diagram N2 shows the SM driver circuit. One SM bipolar drive 301 is required for each phase of SM 108, so if SM 108 has four phases, four are required.

The drive method of the circuit shown in FIG. 2 is called constant current chopper drive, and 302 is a constant current chopper drive unit (
chopper circuit).

FIGS. 3(A) and 3(B) show the principle of constant current chopper driving of the chopper circuit 302. FIG. 3A in FIG. 3(A) from an oscillator 304 that oscillates a triangular wave of about 20kHz.
The triangular wave shown by is used as the reference voltage, and the SM
108 is converted into a voltage, and only in the section where this voltage is lower than the reference voltage, as shown in FIG. 3(B), the SM 10B
The current is kept constant by applying a motor voltage to the motor.

Referring again to FIG. 2, 304A is a PWM (Pulse Width Modulation) comparator and 304B is an amplifier.

Due to this constant current chopper drive, the current flowing through the SM 108 becomes constant, and the current rises from OFF to ON and falls from ON to OFF becomes steep.
The responsiveness of SM 108 to high-speed rotation is improved.

Furthermore, by raising and lowering the voltage level of the triangular wave that is the reference voltage, it becomes possible to raise and lower the SM drive current level, which is kept constant. In other words, the voltage across the resistor 307 becomes an offset voltage with the output voltage of the oscillator 304 for determining the reference voltage (the voltage at point A in Figure 2), so the voltage across the resistor 307 becomes the CD (current down) voltage. ), the current flowing through the 5M108 can be changed in accordance with the row signal.

When resistors 306 and 307 are set to 1Ω and Ω, respectively, when the desk signal is +5V, diode 308 is cut off, so the offset voltage is set by resistors 306 and 30
It becomes 2.5V determined by the partial pressure ratio of 7. Then, when the ■ signal is Ov, the diode 308 becomes conductive,
The resistor 307 has a forward voltage of 0.7 of the diode 308.
v is applied.

Therefore, by changing the CD [number to Ov, Figure 3 (A
) is reduced by 1.8V, thereby driving the SM 108 with a smaller current value.

303 is a phase signal generation circuit, which generates the fourth signal in a step synchronized with the pulse signal CLH output from the CPU 116.
Phase excitation signal A to SM 108 as shown.

B, C, D, A, B, C and υ electric output T. 4 phase S
In the case of M108, the F/H signal is a signal for switching between full-step drive in which the rotation angle in one pulse is 0.9 degrees and half-step drive in which the rotation angle is 0.45 degrees.

When the F/H signal is “O”, the phase signal generation circuit 303
In order to perform half-step driving, a phase excitation sequence of 3-4 phase excitation, that is, a phase excitation sequence of the forward drive dark region shown in the direction of arrow a in FIG. 4 is output. When the F/H signal is "1", the phase excitation sequence of four-phase excitation, that is, the phase excitation sequence of the backward drive dark region shown in the direction of the arrow in Fig. 4, is executed to perform full step drive. Output.

Further, control regarding the rotational direction of the SM 108 is performed by the F/B signal. When the F/i signal is "1", the phase signal generating circuit 303 rotates the F/i clockwise, that is, in a copying machine, performs forward drive when reading an original.
When the 100 signal is "O", the SM is driven in the pulse sequence shown in Figure 4 so that counterclockwise or reverse driving is performed.
108 phase excitation signals are generated.

In FIG. 1, the rotation of SM 108 is transmitted to a pulley 107 attached coaxially with SM 108, transmitted to a pulley 105 with a diameter three times that of pulley 107 via a timing belt 117, and transmitted by a wire 118 attached to pulley 105. Carriage 103 is driven.

The carriage 103 includes a light source 101 that illuminates the original and a contact sensor 102 that receives reflected light from the original.

Since the ratio of the diameters of pulleys 105 and 107 is 3:1, when SM 108 rotates three times, pulley 105 rotates once.
Rotate. Since the diameter of the pulley 105 is 48.9 mm, the process speed in this example is 84 mm/
sec (original scanning speed at 100% copy magnification), 0.45 d per 1
When the eg is driven in a hearth step, it can be seen from the following equation that the SM 108 is driven at a pulse frequency of 1312 pps.

= 1312 (pps) In other words, the carriage 103 has 0.64 (μ
m) (84(+nm/5ec)÷1312(puls
e/5ec)) will be moved.

The actual reading scanning procedure with the above configuration will be explained based on the control sequence flowchart of the Ptl 11B shown in FIG. 5 and the timing diagram of the row signal and pulse signal CLH shown in FIG. 6.

When performing reading scanning, first, in step 5501, copying conditions such as paper size and copying magnification are set. The paper size can be determined using the paper selection key 1 located on the operation panel 109.
13, and the copy magnification is set using the copy magnification setting key 112.

Now, assume that a magnification of 100% is set for 4-size paper. The set copying conditions are sent to the CPI 1116, and based on these, the scanning distance and scanning speed are calculated in step 5502. A4 size with 100% magnification
In this case, the scanning distance is 210 mm (A4 size paper length) and the scanning speed is 1312 (+) pS) (1
312 (pps) ÷ 1).

In the next step 5503, when it is confirmed that the copy key 110 has been pressed, the process proceeds to step 5504゜550.
6, move on to the forward drive of 5508. During forward drive, the F/100x signal is set to "1" and half-step drive is performed, so F/H
Set the / number to “O”.

Also, as shown in FIG. 6, step 5504 is a step for accelerating the stopped carriage, so in order to increase the motor torque to overcome static friction, the ■ signal is set to "1".
'', and the pulse signal CL is 500 (pps),
Increase the frequency step by step to 1000 (pps).

This acceleration step is 15 (pulse) (-500 (p)
ps) X10 (msec)+1000 (pps
) x 10 (msec)), and the acceleration is ended after counting these 15 pulses (step 5505).

Step 5506 is the step of reading the original, so in order to suppress vibration, the ■signal is set to "0", and the pulse signal C is set at the reading scanning speed, that is, the frequency of 1312 (+) I)
Output LK. 32 to read an A4 size manuscript
80 (pulse) (-210 (mm) ÷ 0.06
4 (mm/pulse)) is required, and this 3280
Count the pulses and end the reading (step 5507
).

Step 5508 is a step for decelerating and stopping the carriage. In order to increase the motor torque to prevent the carriage from advancing too far when stopped, the CD signal is set to "1", and the pulse signal CLK is set to 1ooo (pps).

Lower the frequency step by step to 500 (pps).

This step 5508 is the reverse process of step 5504, and ends after counting the required number of pulses, that is, 15 pulses (
Step 5509).

FIG. 7 shows the overall configuration of a copying apparatus according to a second embodiment of the present invention. In this figure, 701 is a flag attached to the carriage 103, and when the scanner is at the reading start position, At some point, the home position sensor 702
It has the function of turning "ON". Further, the output “)IP” of the home position sensor is always input to the CPU 116. The rest of the structure is the same as that of the first embodiment shown in FIG. 1, and corresponding parts are given the same reference numerals. Further, the circuit of the 5M driver 115 is also similar to that shown in FIG.

The return scanning procedure to the reading start position in the second embodiment with the above configuration is shown in the control sequence flowchart of the CPo 116 shown in FIG. 8 and the timing diagram of the CD signal and pulse signal CLK shown in FIG. I will explain based on this.

After the reading scan is completed, driving for return scanning including acceleration, constant velocity, and deceleration is performed (Step 5P801).
, during return scanning, the CD signal is set to O" in the section where the speed is less than pth (pps), and the CD signal is set to O" in the section where the speed is more than pth (pps).
Set the signal to “1” (step 5P802.5P803
A.

5P803B).

After outputting a predetermined number of pulses (step 5P805), check the home position sensor output (
Step 5P806).

If the sensor output is "off", the carriage has not returned to the controlled position (in other words, the reading start position), so if the CD signal is set to "1" and the torque does not need to be increased, the speed threshold is reached. It can be said that the value Fth (ppS) is too high, so lower the value of Fth by a predetermined value, for example, 5oo (pps) (step 5
P807).

[Effects of the Invention] As explained above, according to the present invention, by switching the control of the current flowing to the stepping motor or the applied voltage during reading scanning, drive control is performed according to the drive conditions, and thereby an appropriate document Scanning can be performed with low power.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the overall configuration of an embodiment of the present invention, Fig. 2 is a circuit diagram of an SM driver for driving a constant current chopper in an embodiment of the invention, and Fig. 3 is a diagram showing the chopper shown in Fig. 2. A principle diagram of constant current chopper driving of the circuit, FIG. 4 is a tying diagram of an embodiment of the present invention, FIG. 5 is a flowchart of driving a stepping motor of a copying machine according to an embodiment of the present invention, and FIG. A diagram showing a CD signal and a pulse sequence to a stepping motor in one embodiment of the invention. FIG. 7 is a diagram showing the overall configuration of a second embodiment of the invention. FIG. 8 is a diagram showing a second embodiment of the invention. Fig. 9 is a stepping motor drive flowchart of a copying machine according to the second embodiment of the present invention.
FIG. 3 is a diagram showing a CD signal and a pulse sequence to a stepping motor in an embodiment of the present invention. 101...Light source, 102...Contact type sensor, 103...Carriage, 104... Document table, 105.107...Pulley, 108...Stepping motor (SM). 109...Operation unit, 110...Copy key 111...Copy magnification display section, 112...Copy magnification setting key 113...Paper selection key 115...Stepping motor motor 116...c
pu<central processing unit), 117...Timing belt, 118...Wire, 301...SM bipolar drive unit equivalent to a bow, 302...
...Constant current chopper drive section, 303...Phase signal generation circuit, 304...Triangular wave oscillation circuit, 305.306.307...Resistor, 308...Diode. Driver, time Figure 3 Figure 8

Claims (1)

[Scope of Claims] 1) A stepping motor as a document scanning drive source, means for switching the sequence of signals for exciting each phase of the stepping motor, and means for switching the sequence of signals that excite each phase of the stepping motor, and a means for changing the current flowing through the stepping motor or the voltage applied to the motor. 1. A document scanning drive device comprising means for switching control during document scanning. 2) The document scanning drive device according to claim 1, wherein control of at least one of the current flowing through the stepping motor and the voltage applied to the stepping motor is switched during one scan.