JP2849465B2 - Paper feed control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feed control device of a paper feed device using a step motor provided in a facsimile device, a scanner (document reading device), a plotter, a printer, or the like as a driving source. About.

[Conventional technology]

2. Description of the Related Art Conventionally, for example, in a facsimile apparatus, a paper feeder using a step motor as a drive source for conveying a document or recording paper has been frequently used.

As a control method of a stepping motor in such a paper feeder, for example, as shown in Japanese Utility Model Laid-Open No. 1-180900, at the time of 1-2 phase excitation, the stop line at the time of intermittent driving is stepped up by two phase excitation. If the line is advanced by one step, it is stopped. If the stop line is a line advanced by one-phase excitation, it is stopped at that stop line, so that it always starts from the two-phase excitation state. In order to eliminate variations in the rise of the pulse motor.

In a facsimile machine, unevenness in paper feed during document reading and recording deteriorates image quality,
In particular, during the intermittent driving, the feed unevenness is likely to occur.

Therefore, as described above, the step motor drive timing at the time of the intermittent operation is controlled, or the printing or reading timing is corrected, the logic of the previous line image is taken at the time of reading, and the image of the previous line is taken at the time of recording. This is achieved by recording multiple times.

[Problems to be solved by the invention]

However, these are all effective in a certain condition with respect to the sub-scanning, but it is difficult to exert the effect under all the conditions.

In particular, variations in the pulse motor and its driving circuit,
Changes due to temperature characteristics, fluctuations in power supply voltage, and the like are large, and it has been difficult to always obtain a constant image quality with any machine.

An object of the present invention is to stabilize the variation of the sub-scanning system by making the rise time of the current constant.

In addition, the variation of the pulse motor and its driving circuit varies not only between each unit but also between each phase in the same unit.

As a result, a change in the step start phase causes a change in image quality.

It is another object of the present invention to stabilize the variation between the excitation phases of a pulse motor by keeping the rise time of the current constant.

Furthermore, to reduce the heat and noise of the step motor,
In a state where reading and writing of an image are not performed, there is a method of using a lower limit current selection value.

In this case, if the selected value is set after the next read / write operation, it will be delayed.

Therefore, it is also an object of the present invention to be able to control with an appropriate limit current value from the beginning of the read / write mode.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a step motor driver for driving a step motor with a constant current, limited current switching means for switching the limited current of the driver, and motor current detecting means for detecting an actual motor drive current. ,
Time measuring means for measuring an elapsed time after the excitation phase of the stepping motor is switched, and limiting the current value detected by the motor current detecting means to a predetermined value when the value measured by the means reaches a predetermined time. And a control unit for controlling the current switching unit.

In this paper feed control device, it is preferable to provide a means for selecting the limiting current for each of the excitation phases of the step motor.

Further, means for selecting the limiting current according to the operation mode, a memory for storing a selected value of the limiting current selected for the operation mode, and a memory for storing the same when the same operation mode is entered thereafter. Means for reading the selected value and controlling the limiting current switching means.

(Operation)

The paper feed control device according to the present invention stabilizes the variation between the excitation phases of the pulse motor by keeping the rise time of the current constant, so that the variation of the motor and its driving circuit, the variation due to their temperature characteristics, and the like. Variations in the paper feed start-up characteristics caused by variations due to fluctuations in the power supply voltage can also be reduced.

Further, since the control can be performed with an appropriate limit current value from the beginning of the read / write mode, and the heat and noise of the step motor can be suppressed, the limit current can be easily reduced in a state where the image is not read or written.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a paper feed control device according to an embodiment of the present invention, in which a step motor driver (hereinafter simply referred to as "driver") 2 for driving a step motor 1 at a constant current, and a limiting current of the driver 2. Current switching unit 3 for switching the current, A / D converter 4 which is a motor current detecting means for reading a voltage value generated in current limiting resistor RL in order to detect a drive current of the motor, and suitability of a detected current value according to an operation mode. A memory 5 for storing the current value and the immediately preceding limit current value, a timer 6 for measuring the elapse of a predetermined time from the switching of the phase signal, and a control unit 7 such as a microcomputer for generally controlling these units. Is configured.

FIG. 2 shows a driving circuit of one phase by the driver 2 and the step motor 1.

When transistors Tr1 and Tr4 are turned on, step motor 1
Current flows from the terminal A to the winding L of the
Voltage is generated at L. The driver 2 turns off one of the transistors Tr1 or Tr4 when the voltage reaches a predetermined value, and turns on again when the voltage falls below the predetermined value.

FIG. 3 is an equivalent circuit when a current flows from the terminal A, where RM is the resistance of the motor winding, IL is the flowing current, and VL is the motor current detection voltage generated at both ends of the current limiting resistor RL. Reference voltage.

4 (a) to 4 (d) show the voltage of each terminal of the motor winding in the case of two-phase excitation, and FIGS. 4 (e) and 4 (f) are timing charts showing the current waveform of each phase.

The rise time of the current can be expressed by T = L / 2R = L / 2 (RM + RL). If the inductance L and the internal resistance RM of the motor winding are different, the rise time will vary. Also, the rise time changes similarly even if the power supply voltage changes.

FIG. 5 (a) shows the change in the rise time. Time t ₁
The subsequent voltage is Vp, and the reference voltage controlled by the transistor is VL.

FIG. 5B shows a change in the reference voltage VL.
The reference voltage VL varies depending on the variation of the limiting current switching unit 3 and the set value. If you want to this voltage VL constant may detect the voltage VL after the lapse of the time t _2.

FIG. 6 (a) shows the displacement amount of the rotation of the motor. If an ideal curve is a state in which the motor starts moving immediately after the phase switching and changes linearly to the stop position, there is inevitably a delay before the operation of the motor starts. The design curve is obtained by translating the ideal curve in consideration of the delay.

If there is a variation in the motor or the reference voltage VL, a paper feeding state as indicated by broken lines L and M may occur.

FIG. 6 (b) is a view showing that the feed pitch changes due to irregular paper feed, causing feed unevenness. When the feed characteristic shown by the solid line fluctuates as shown by the broken line, the feed pitch is changed. x ₁ and x ₂ vary like y ₁ and y ₂ .

FIG. 7 shows an example of a paper feed control method according to the embodiment of FIG. This will be described with reference to the flowcharts of FIGS. 8 and 9.

After time t ₁ shown in FIG. 5 (a), the timer interrupt enters,
The timer interrupt routine shown in FIG. 8 is executed.

First, the desired value VTH, to determine whether a high or low voltage Vp after time t _1. When Vp is low, the register RVL storing the level of VL is counted up so that Vp becomes one level higher. By repeating this operation, V
Vp is higher than TH.

Then, without increasing the count of the register RVL, Vp-VTH is obtained and compared with a predetermined voltage value .DELTA.V. If .DELTA.V is smaller, nothing is performed, and if .DELTA.V is larger, the register RVL is counted down. ΔV is a voltage value of about one level.

On the other hand, if Vp starts higher than VTH,
Count down until Vp−VTH becomes smaller than ΔV.

In the step interrupt routine shown in FIG. 9, the level of the register RVL set by the timer interrupt is output to the driver 2.

Next, a phase signal is output, and the time of the next timer interrupt is set. The timer value is t ₁ or t ₂ of FIG. 5.

If it is desired to control by Vp _two hours later, it is obvious that such control is possible.

FIG. 10 shows a change in Vp in each operation mode in the plotter.

(A) is a case where the next Vp is set from the last state of the previous operation mode. In this case, it takes time to reach a stable state.

(B) is a control method according to the present invention, in which the final output of the previous mode is used, so that it is possible to operate in a stable state from the time of entering the mode.

In FIG. 10, PR means recording conveyance, FD means conveyance without recording, and CUT means paper stop for cutting the recording paper.

〔The invention's effect〕

As described above, according to the paper feed control device of the present invention, the following effects can be obtained.

(1) Since the current value after a predetermined time is controlled to be constant, paper feeding can be stabilized.

(2) Since the control is performed for each phase, the paper feed can be stabilized regardless of the excitation phase of the rotation start phase.

(3) In the case where the limiting current is switched depending on the operation mode, the operation is started from the limit current value before the operation mode, so that the operation value can be corrected to an appropriate value in a short time, and the operation is started from the time of entering the operation mode Stable paper feed is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of a paper feed control device according to an embodiment of the present invention, FIG. 2 is a drive circuit diagram of one phase by a driver 2 and a step motor 1, and FIG. Fig. 4 is a timing chart showing the voltage of each end of the motor winding and the current waveform of each phase in the case of two-phase excitation, and Fig. 5 (a) shows the rise time. FIG. 6B is a diagram showing the change of the reference voltage VL, FIG. 6 is a diagram showing the displacement amount of the motor rotation and the paper feed amount, and FIG. 7 is a paper feed control according to the embodiment of FIG. FIGS. 8 and 9 are flow charts of processing by the control unit of FIG. 1, and FIG. 10 is a diagram showing a change in Vp in each operation mode of the plotter. DESCRIPTION OF SYMBOLS 1 ... Step motor 2 ... Step motor driver 3 ... Limit current switching part 4, ... A / D converter 5 ... Memory 5, Timer 6, 7 ... Control part RL ... Current limiting resistance

Claims (3)

(57) [Claims] 1. A control device for a paper feeder using a stepping motor as a driving source, comprising: a stepping motor driver for driving the stepping motor at a constant current; limiting current switching means for switching a limiting current of the driver; Motor current detecting means for detecting the motor drive current of the motor, time measuring means for measuring an elapsed time after the excitation phase of the stepping motor is switched, and motor current detecting means when the value measured by the means reaches a predetermined time. And a control means for controlling the limiting current switching means so that the current value detected at this time becomes a predetermined value. 2. The paper feed control device according to claim 1, wherein
A paper feed control device comprising means for selecting the limit current for each excitation phase of a step motor. 3. The paper feed control device according to claim 1, wherein said means for selecting said limited current according to an operation mode, and a memory for storing a selected value of said limited current selected for said operation mode. And a means for reading the selected value stored in the memory and controlling the limiting current switching means when the same operation mode is entered thereafter.