JP2003348878A - Driving method of dc motor, paper feeding method, and paper feeding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method of a low-cost DC motor of a simple structure, together with a method and apparatus for feeding paper, capable of precisely stop at a target position with a digital position signal of an encoder having a resolution equal to a positioning resolution. <P>SOLUTION: A motor is supplied, or stopped, with first driving forces PWML5, PWML4 to PWML1 in which the driving force is sequentially reduced stepwise according to a position error from a target position YF, each time a digital position signal YFB is confirmed as the changes from a state L to a state H. Until the state L of the digital position signal YFP is confirmed to have changed to the state H after the first driving forces PWMLs are supplied, the first driving forces PWMLs are increased stepwise. The increase Dpw sequentially decreases stepwise with each driving force increment step according to a position error from the target position YF. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor driving method, a sheet feeding method, and a sheet feeding device which are controlled based on a digital position signal output from a detector for detecting a rotation amount of a DC motor. In particular, the present invention relates to a DC motor driving method, a sheet feeding method, and a sheet feeding device capable of stopping a sheet accurately with respect to a target stop position.

[0002]

2. Description of the Related Art In a serial printer such as an ink jet printer, a line feed motor for feeding one line of printing paper every time printing of one line is completed is used. Conventionally, a pulse motor has been used as the line feed motor, but in recent years, a DC motor (DC motor) has been used in some cases.

When a DC motor is used as the line feed motor instead of a pulse motor, there is a method of controlling the paper feed position by installing an optical sensor capable of detecting the rotation amount of the DC motor and controlling the rotation amount of the DC motor. . Specifically, every time the DC motor rotates by a certain amount, the encoder pulse which is a digital position signal transmitted from the optical sensor is counted, whereby the amount of rotation is grasped and the paper feeding position is controlled.

In the positioning control using such encoder pulses, a positioning error of several pulses, which is a problem peculiar to digital position control, occurs in an encoder having a resolution equal to the positioning resolution. Therefore, in order to improve the accuracy of the stop position, an encoder having a resolution several times smaller than the positioning resolution is used.

On the other hand, as a method of performing positioning control using an encoder having a resolution equal to the positioning resolution, an encoder capable of analog output is used as the encoder, or an analog position signal is obtained separately from an encoder for counting positions. There is a method of preparing a potentiometer or the like. That is, the analog output of the encoder before waveform shaping into an encoder pulse, or the analog output of a potentiometer or the like is used as a feedback signal for positioning control.

For example, in Japanese Patent Publication No. Hei 7-44864 (publication date May 15, 1995),
PLL (Phase-looked l) that uses the analog output of the encoder before positioning the waveform to the encoder pulse
oop) A speed control circuit is disclosed.

[0007]

However, in the above-described conventional driving method, sheet feeding method, and sheet feeding apparatus,
A problem arises in that equipment or a control circuit used for positioning control becomes expensive.

For example, in the positioning control using only digital pulses of the encoder, the positioning resolution is 2400.
In the case of performing DPI (Dots per inch) positioning control, an encoder having a resolution of 12000 DPI is used. Therefore, the encoder becomes expensive.

On the other hand, the positioning control using the analog output of the encoder described in the above publication is very expensive because the control circuit is complicated. In particular, it can be said that the control circuit disclosed in the above publication is inappropriate for a serial printer which is inexpensive compared to other laser printers and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a digital position signal obtained by a detector such as an encoder having a resolution equal to the positioning resolution, so that the target stop position can be accurately determined. An object of the present invention is to provide a DC motor driving method, a sheet feeding method, and a sheet feeding device which can be stopped well, have a simple structure and are inexpensive.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method of driving a DC motor according to the present invention is directed to a DC motor controlled based on a digital position signal output from a detector for detecting a rotation amount of the DC motor. In the motor driving method, a signal confirmation step of confirming that the digital position signal changes, and each time the digital position signal is confirmed to change by a predetermined amount, the DC motor has a position error from a target position. A step of applying each first driving force whose driving force is reduced step by step, or a step of decreasing the driving force to stop driving, and applying each of the first driving forces described above to obtain a digital position signal. The driving force increasing step of increasing the driving force in a stepwise manner with respect to each of the first driving forces is performed between each time until the predetermined change is confirmed.

According to the invention, in the driving force decreasing step, each time the digital position signal is confirmed to change by a predetermined amount, the DC motor is sequentially driven stepwise according to the position error from the target position. The first driving force with reduced force is applied or the driving is stopped.

Accordingly, the rotation amount of the DC motor is detected based on a predetermined change in the digital position signal, and when the current rotation amount is detected, the first driving force is reduced stepwise in accordance with a position error from the target position. Thus, the first driving force can be reduced.

After each first driving force is applied and before the digital position signal is confirmed to change by a predetermined amount, a driving force increasing step is performed for each of the first driving forces. The driving force is increased stepwise.

Therefore, by gradually increasing the driving force with respect to each of the first driving forces, the target position can be quickly approached, and in the vicinity of the target position, the load torque can be overcome with the minimum necessary torque. Can be driven.

Thus, the first driving force whose driving force is reduced step by step in accordance with the position error from the target position is applied to the target position, and the first driving force is reduced in accordance with the position error of the DC motor. In the vicinity of the target position, it can be driven with the minimum necessary torque that overcomes the load torque, absorbs variations and fluctuations in load torque, and variations and fluctuations of the DC motor, and achieves the target position without speeding up. Can be approached. As a result, the overrun of the DC motor is made uniform, and the stop position variation due to excessive overrun due to speed over is prevented.

[0017] Thus, as a detector such as an encoder, it is not necessary to use an expensive absolute encoder and an analog position signal having a complicated structure, and a simple and inexpensive incremental encoder with digital pulse output can be used.

As a result, a digital position signal from a detector such as an encoder having a resolution equal to the positioning resolution is obtained by
It is possible to provide an inexpensive method of driving a DC motor that can stop accurately at a target stop position, has a simple structure, and is inexpensive.

Further, the method for driving a DC motor according to the present invention comprises:
In order to solve the above problems, in a method of driving a DC motor controlled based on a digital position signal output from a detector that detects a rotation amount of the DC motor, a signal check for confirming that the digital position signal changes is performed. Steps and
Each time the digital position signal is confirmed to change by a predetermined amount, the first driving force whose driving force has been gradually reduced is applied to the DC motor, or the driving force is reduced to stop driving. After the step and each of the first driving forces, the driving force is applied in a stepwise manner to each of the first driving forces during a period until the digital position signal is confirmed to change by a predetermined amount. Drive power increasing step to increase, and the drive power increase in each of the drive power increase steps decreases step by step in each drive power increase step in accordance with a position error from a target position. It is characterized by having.

According to the above invention, in the driving force decreasing step, the first driving force whose driving force has been sequentially reduced is applied or the driving is stopped.

Therefore, the amount of rotation of the DC motor is detected based on a predetermined change in the digital position signal, and when the current amount of rotation is detected, the first driving force is reduced step by step so that the first driving force is reduced. Can be reduced.

In addition, after each first driving force is applied, until each time the digital position signal is confirmed to change by a predetermined amount, a driving force increasing step is performed for each of the first driving forces. The driving force is increased stepwise. further,
The amount of increase in the driving force in each driving force increase step is reduced step by step in each driving force increase step in accordance with the position error from the target position.

Therefore, by increasing the driving force stepwise according to the position error with respect to the target position for each of the first driving forces, by increasing the driving force when the position error is large, By approaching the target position promptly and increasing the resolution near the target position with high resolution, it is possible to drive with the minimum necessary torque to overcome the load torque.

In this way, the first driving force whose driving force is reduced step by step is applied to the target position, and in the vicinity of the target position, it is necessary to respond to the position error with respect to the target position in order to overcome the load torque. It can be driven with a minimum torque, and can absorb variations and fluctuations in load torque, and variations and fluctuations in the DC motor, and can approach the target position without speeding up. As a result, the overrun of the DC motor is made uniform, and the stop position variation due to excessive overrun due to speed over is prevented.

[0025] Thus, as a detector such as an encoder, it is not necessary to use an expensive absolute encoder and an analog position signal having a complicated structure, and a simple and inexpensive incremental encoder with digital pulse output can be used.

As a result, a digital position signal from a detector such as an encoder having the same resolution as the positioning resolution
It is possible to provide an inexpensive method of driving a DC motor that can stop accurately at a target stop position, has a simple structure, and is inexpensive.

Further, the method for driving a DC motor according to the present invention comprises:
In order to solve the above problems, in a method of driving a DC motor controlled based on a digital position signal output from a detector that detects a rotation amount of the DC motor, a signal check for confirming that the digital position signal changes is performed. Steps and
Each time that the digital position signal is confirmed to change by a predetermined amount, whether or not to apply each first driving force to the DC motor in which the driving force is reduced stepwise in accordance with the position error from the target position. Or between the driving force decreasing step of stopping the driving and the first driving force after the first driving force is applied, until the digital position signal is confirmed to change by a predetermined amount. Each driving force increasing step of increasing the driving force in a stepwise manner, and the driving force increasing amount of each driving force increasing step is determined for each driving force increasing step in accordance with a position error from a target position. It is characterized in that it is gradually reduced.

According to the invention described above, in the driving force decreasing step, each time the digital position signal is confirmed to change by a predetermined amount, the DC motor is sequentially driven in a stepwise manner in accordance with the position error from the target position. The first driving force with reduced force is applied or the driving is stopped.

Therefore, the rotation amount of the DC motor is detected based on a predetermined change in the digital position signal, and when the current rotation amount is detected, the first driving force is reduced stepwise in accordance with the position error from the target position. Thus, the first driving force can be reduced.

After each first driving force is applied and before the digital position signal is confirmed to change by a predetermined amount, a driving force increasing step is performed for each of the first driving forces. The driving force is increased stepwise. further,
The amount of increase in the driving force in each driving force increase step is reduced step by step in each driving force increase step in accordance with the position error from the target position.

Therefore, by increasing the driving force stepwise in accordance with the position error from the target position with respect to each of the first driving forces, when the position error is large, the amount of increase in the driving force is increased. By approaching the target position promptly and increasing the resolution near the target position with high resolution, it is possible to drive with the minimum necessary torque to overcome the load torque.

In this manner, the first driving force whose driving force is reduced step by step in accordance with the position error from the target position is applied to the target position, and the load torque is overcome in the vicinity of the target position. It can be driven with the minimum necessary torque according to the position error from the target position,
In addition, variations and fluctuations of the DC motor can be absorbed, and the target position can be approached without speeding up. As a result, the overrun of the DC motor is made uniform, and the stop position variation due to excessive overrun due to speed over is prevented.

Further, as a detector such as an encoder, it is not necessary to use an expensive absolute encoder and an analog position signal having a complicated structure, and a simple and inexpensive incremental encoder with digital pulse output can be used.

As a result, the digital position signal obtained by a detector such as an encoder having the same resolution as the positioning resolution
It is possible to provide an inexpensive method of driving a DC motor that can stop accurately at a target stop position, has a simple structure, and is inexpensive.

Further, in order to solve the above problems, the paper feeding method of the present invention is characterized in that the above-described DC motor driving method is used when paper feeding is stopped.

According to the above-described invention, when the stop position of the sheet is determined, the sheet can be driven with the minimum necessary torque to overcome the load torque, and the sheet can be stopped at the target position without overspeeding. In addition, the amount of overrun (within one pulse) after detecting the change in the digital position signal is made uniform, and the stop position fluctuation due to excessive overrun due to speed over is uniformly prevented, enabling accurate paper feeding. Become.

Therefore, it is possible to accurately stop at the target stop position with a digital position signal from a detector such as an encoder having a resolution equal to the positioning resolution, and to provide a simple and inexpensive paper feeding method. it can.

Further, according to the paper feeding method of the present invention, in the above-described paper feeding method, after stopping the paper feeding,
A stop position holding step for holding the sheet stop position is further included.

According to the above-mentioned invention, the method further includes a stop position holding step of holding the sheet stop position after stopping the sheet feeding.

Therefore, the holding means such as the holding driving force, the brake, and the worm gear can prevent the paper from moving due to the back tension acting on the paper.

Further, according to the sheet feeding method of the present invention, in the above-described sheet feeding method, after stopping the sheet feeding,
The method further includes a stop position holding step of holding the sheet feeding position by applying a second driving force smaller than the first driving force.

According to the above-mentioned invention, a stop position holding step of holding the sheet feeding position by applying a second driving force smaller than the first driving force after stopping the sheet feeding is included.

Therefore, even if there is no holding means such as a brake and a worm gear, it is possible to prevent the paper from moving due to the back tension acting on the paper. That is, the second driving force is a driving force smaller than the first driving force,
The driving torque applied to the DC motor by the second driving force is smaller than the load torque applied to the DC motor by friction of the driving mechanism or the like.

Further, since a holding mechanism such as a brake and a worm gear for stopping the sheet is not required, the load torque acting on the driving source for feeding the sheet is further reduced.

Further, a sheet feeding apparatus according to the present invention is characterized by using the above-described sheet feeding method in order to solve the above problems.

According to the above-mentioned invention, the paper feeding device uses the above-described paper feeding method. Therefore, it is possible to accurately stop at the target stop position by a digital position signal from a detector such as an encoder having the same resolution as the positioning resolution, and to provide an inexpensive sheet feeder with a simple structure.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In this embodiment, a method for driving a DC motor, a paper feeding method, and a serial printer such as an inkjet printer to which a paper feeding device is applied according to the present invention will be described.

In a serial printer such as an ink jet printer according to the present embodiment, a line feed motor is used for feeding one line of printing paper every time one line of printing is completed. A direct current motor (DC motor) is used as the line feed motor.

That is, the sheet feeder 1 of the present embodiment
0 is an MPU (Microprocessor Uniform) as shown in FIG.
t: a microprocessor) control unit 1, a DC motor (hereinafter referred to as “motor”) 2 of a peripheral device, and a detector 3
And a motor drive circuit 4 as a peripheral circuit. This configuration is merely an example of the configuration of the present invention, and the present invention is not limited to this configuration.

The motor 2 is a drive source for feeding printing paper to a printing section by line feed in a serial printer of a type in which printing of one line is performed in series one character at a time. The motor drive circuit 4 is a drive circuit for driving the motor 2.

The detector 3 is a sensor capable of detecting the rotation of the motor 2, and is, for example, an optical rotary encoder (RE) as shown in FIG. As shown in FIGS. 4A, 4B, and 4C, the detector 3 is an encoder pulse (hereinafter, simply referred to as a “pulse”) that is a digital position signal YFB every time the motor 2 rotates a predetermined amount. ). As the pulse, an A-phase pulse and a B-phase pulse having a 90-degree phase are prepared to determine the rotation direction. In the A-phase pulse and the B-phase pulse, the A-phase pulse is output with a phase advance with respect to the B-phase pulse when the rotation is normal, and the A-phase pulse is output with a phase delay with respect to the B-phase pulse when the rotation is reverse. Each pulse transmitted from the detector 3 is input to the MPU control unit 1.

The MPU control unit 1 determines the rotation direction based on the phases of the A-phase pulse and the B-phase pulse, grasps the rotation amount of the motor 2 by counting up and down according to the rotation direction, and performs control to be described later. Then, a signal is transmitted to the motor drive circuit 4 to drive the motor 2 based on the signal.

Next, a change in the rotation speed of the motor 2 until one line of paper is fed will be described with reference to FIG. It should be noted that YA, YB,
YC, YD, YE, and YF indicate the total number of pulses Y counted by the MPU control unit 1. The total number of pulses counted by the MPU control unit 1 until one sheet of paper is fed and stopped is YF.

As shown in the figure, first, a pulse Y = 0
Paper feed is started from (YA), and the motor speed is changed according to each count value YB, YC, YD, YE. Specifically, the operation of moving the stopped paper and stopping it at a predetermined point is divided into three sections. That is, a first section in which the stopped paper starts moving and rises to a certain speed, a second section in which the paper is continuously fed at the certain speed, and a second section in which the paper feeding speed is reduced and stopped at a predetermined point. This is section 3 of FIG.

If the above three sections correspond to FIG. 5,
The first section is 0 (YA) → YB → YC, the second section is YC → YD, and the third section is YD → Y
E → YF. That is, when the motor speed is increased, the interval 0
→ YB → YC, and when the motor speed is constant, the section YC → Y
D, and when the motor speed decreases, the section YD → YE →
YF.

In the first section 0 (YA) → YB → YC
Is further divided into a section YA → YB and a section YB → YC, and the slope of the section YA → YB is different from the slope of the section YB → YC. That is, as shown in the figure, the section YB → YC which is closer to the second section YC → YD has the section YA →
The inclination is small and gentle compared to YB. This is to prevent the rotation speed of the motor 2 from overshooting when shifting to a state in which paper is fed at a constant speed.

Further, in the sheet feeding method of the present embodiment, the third section YD → YE → YF is also divided into section YD → YE and section YE → YF. As shown in FIG. The motor speed is changing little by little. This section Y
E → YF indicates the motor speed when stopping the paper feed.

Here, the pulse Y in the section YE → YF and the change of the driving force applied to the motor 2 with respect to the pulse Y will be described in detail with reference to FIGS. 1 (a) and 1 (b).

First, FIG. 1B shows a change in the pulse Y of the digital position signal YFB with respect to time in the section YE → YF. That is, the digital position signal YFB
Is divided into a state where the pulse Y is "L" and a state where the pulse Y is "H" according to the rotational position of the motor 2. Further, the reason why the interval between the pulses Y of the digital position signal YFB becomes gradually longer is that the rotation speed of the motor 2 becomes gradually smaller.
The rotation speed of the slit disk shown in FIG. 4 also decreases, and the time required to pass through the fixed slit also increases. As a result, the state of each "L" and the state "H" of the digital position signal YFB also increase.

FIG. 1A shows a change in the driving force applied to the motor 2 in the section YE → YF. The horizontal axis indicates the time (count value y) in FIG. 1B. Yes, it is. Further, the waveform diagram of FIG. 1A shows an enlarged waveform diagram of the section YE → YF in FIG.

In the present embodiment, as shown in FIG. 5, when the count value y of the pulse Y becomes YE,
As shown in (a), a first driving force PWML is applied to the motor 2.
Is given. The first driving force PWML is set according to the position error ER = YF-y of the current position y with respect to the target position YF from TBL1 shown in Table 1.

That is, first, the first driving force PWML of the magnitude PWML5 is applied to the motor 2. Then
When the rotation amount of the motor 2 deviates from the position of the section YE and the digital position signal YFB reaches the initial state “H”, the position error ER of the current position y with respect to the target position YF =
Since YF-y becomes smaller than the previous value, that is, the distance, the first driving force PWML of the magnitude PWML4 decelerated from the magnitude PWML5 is applied from TBL1 shown in Table 1. In this way, every time the digital position signal YFB changes from the state “L” to the state “H”, the size PWML5 → the size PWML4 → the size PWML3 →
The first driving force PWML of a gradually smaller value such as the magnitude PWML2 → the magnitude PWML1 is applied.

[0063]

[Table 1]

On the other hand, in the present embodiment, after each first driving force PWML is applied, the driving force PWM is increased stepwise by an increment dPW as the driving force increase so as to increase the driving force. Has become. As shown in Table 2, the increase dPW of the driving force PWM is set so as to become smaller as the position error ER decreases.

[0065]

[Table 2]

As described above, the driving force PW applied to the motor 2
By incrementally increasing M, the motor 2 is driven until the digital position signal YFB changes to the next state “H”.
It is driven while the speed is gradually increased.

Then, as described above, after confirming that the digital position signal YFB has changed from the next state “L” to “H”, the driving force applied to the motor 2 is reduced again.
The speed of the motor 2 is reduced. At this time, since the driving force PWM and the increase dPW are set according to the position error ER, a large value is given when the position error ER is large,
It is possible to quickly approach the target position. on the other hand,
As the position error ER decreases, the value to be applied is reduced, and near the target position, the motor 2 moves with the minimum driving force that can finally overcome the additional torque acting on the motor 2.

Thus, when the stop position of the sheet is determined, the sheet can be driven with the minimum torque required to overcome the load torque, and the target position can be approached without speeding up. Therefore, the overrun of the DC motor is made uniform, and the stop position fluctuation due to excessive overrun due to speed over is prevented.

Further, since the driving force is increased stepwise at regular time intervals, the amount of overrun after detecting the change in the pulse Y is uniformly prevented, and accurate position control becomes possible.

Further, in this embodiment, when stopping the sheet feeding by the above-described driving method, as shown in FIG. 1A, the sheet feeding is repeated a plurality of times to reach the target sheet feeding position. As a result, the approach to the paper feed stop position is more stable, and the reproducibility of the stop operation and the paper feed accuracy are improved.

In the present embodiment, when the count value y reaches YF, that is, when the sheet feed stop position is reached, the driving force PWM applied to the motor 2 is set to 0, but the invention is not limited to this. Alternatively, the minimum driving force PWMs as the second driving force for holding the motor may be given. That is, the minimum driving force PWMs gives a driving torque smaller than a sliding load torque applied to the motor 2 due to friction of the driving mechanism in a direction opposite to the back tension or the like as a driving torque applied to the motor 2.

As a result, it is possible to prevent the paper from moving due to back tension or the like acting on the paper. Further, since a holding mechanism such as a brake and a worm gear for stopping the paper is not required, the load torque acting on the motor 2 is reduced.

A line feed control operation for one line from the start of sheet feeding to the stop at the target position in the MPU control section 1 of the sheet feeding apparatus 10 having the above configuration will be described with reference to the flowcharts of FIGS. I do. Note that the flowcharts in FIGS. 6 to 11 merely show one embodiment of the present invention, and the present invention is not limited to this. FIG. 6 is a main flowchart, and FIGS. 7 to 11 are subroutine flowcharts interrupted in FIG. Note that the pulses YB, YC, YD shown in the main flowchart
YE · YF corresponds to that shown in FIG.

First, as shown in the main flowchart of FIG. 6, the count value y of the pulse Y is reset to 0 (= YA) (S1), and a timer 1 (not shown) is started (S2). Note that the timer 1 is a timer for measuring the accumulated time.

Next, the motor 2 is set to normal rotation (S3).
Driving force PWM at count value y = 0 of pulse Y
(0) is output (S4). That is, the driving force PWM
(0) is a predetermined starting force at the count value y = 0.

Next, TBL (Table) 3 is selected (S
5). As shown in Table 3, the TBL3 is a table in which the values of the driving force PWM (y) corresponding to the respective count values y are in a table.
7 is a trapezoidal table for controlling so as to give a change in the speed of the pulse Y from YA to YE shown in FIG.

[0077]

[Table 3]

Next, an interrupt of "YFB interrupt 1" is permitted (S6). Until the count value y reaches YC (S7), every time the pulse Y of the detector 3 is input, YF
The control of B interrupt 1 is interrupted. This YFB interrupt 1
Each time the pulse Y is input, the driving force is changed to the driving force PWM (y) corresponding to each count value y.

The YFB interrupt 1 will be described with reference to the subroutine flowchart of FIG.

First, a time T (n) is read from the timer 1 (not shown) indicating the accumulated time (S21).
Is changed, and the count value y is updated by one.
That is, the count value is set to y = y + 1 (S22).

Next, the value of the driving force PWM (y) corresponding to the count value y determined in S22 is read by TBL3 (S23). Here, the driving force PWM (y) for motor acceleration is selected. Next, the driving force PWM (y) obtained in S23 is output to the motor driving circuit 4, and the process returns.

Next, as shown in the main flowchart of FIG. 6, when it is confirmed in step S7 that the count value y has become YC due to the rotation of the motor 2, "YFB interrupt 1" is changed to "YFB interrupt 2". Is performed (S8). Thus, until the count value y becomes YD (S9), the YFB interrupt 2 is interrupted every time the pulse Y of the detector 3 is input. The YFB interrupt 2 basically changes the driving force PWM every time the pulse Y changes.
The driving force PWM is also changed in order to keep the sheet feeding speed in the section YC → YD (see FIG. 5).

Here, the YFB interrupt 2 will be described with reference to a subroutine flowchart shown in FIG.

First, a timer 1 (not shown) indicating the accumulated time
Then, the time T (n) is read (S31), and it is confirmed that the pulse Y has changed, and the count value y is updated by one. That is, the count value is set to y = y + 1 (S32).

Next, the time interval between the time T (n-1) read at the previous interruption and the time T (n) read at S31 is calculated (S33). That is, the pulse interval T
Calculate the value of (n) -T (n-1). The time T (n-1) read in the previous interrupt is the time T (n-1) read in S21 of the previous YFB interrupt 1 if interrupting the YFB interrupt 2 is the first time. And
If it is the second time or later to interrupt the YFB interrupt 2, the time T read in S31 of the previous YFB interrupt 2
(N-1).

Next, the value of the target cumulative time Tr (y) corresponding to the count value y is referred to a speed target TBL (not shown) in a table to search for the target time Tr (y) corresponding to the count value y ( S34). Then, based on the target time Tr (y) retrieved in S34 and the pulse interval T (n) -T (n-1) calculated in S33, the speed error T is obtained.
e is calculated (S35). That is, the speed error Te =
Tr (y)-{T (n) -T (n-1)}.

Next, the PWM corresponding to the speed error Te
The driving force PW corresponding to the speed error Te is referred to the speed error TBL (not shown) in which the value of (Te) is stored in a table.
M (Te) is searched (S36). Then, the output is changed to the driving force PWM (Te) corresponding to the speed error Te (S37), and the process returns. In this process, the speed error Te is calculated each time the pulse Y changes, and the speed error T
The driving force is changed to PWM (Te) corresponding to e.

Next, as shown in the main flowchart of FIG. 4, in S9, when it is confirmed that the count value y has become YD due to the rotation of the motor 2, "YFB interrupt 2" is changed to "YFB interrupt 1". It is changed (S10).

Until the count value y reaches YE, every time the pulse Y of the detector 3 changes, the YFB interrupt 1
Is interrupted (S11). YFB interrupt 1 at this time
As described above (see FIG. 7), each time the pulse Y changes, the driving force is changed to the driving force PWM (y) corresponding to each count value y, and the detailed description is omitted. In the above description, the YFB interrupt 1 is a section for accelerating the motor 2 from the section YA to YC (see FIG. 1), whereas the section YD → YE is a section for decelerating the motor 2 (see FIG. 1). FIG. 1). Therefore, the YFB interrupt 1 can respond to both acceleration and deceleration of the motor 2.

Next, in S11, when it is confirmed that the count value y has become YE due to the rotation of the motor 2,
The timer 2 interrupt count NTM is set to 0 (S12). The timer 2 interrupt count NTM is a “timer 2 interrupt” described later.
Indicates the number of times the interrupt processing has been performed.

Next, "YFB interrupt 1" is changed to "YFB interrupt 3" (S13). Thereby, the count value y
Until becomes YF, the YFB interrupt 3 is interrupted every time the pulse Y of the detector 3 is input. This YFB interrupt 3
Is basically the driving force PW every time the pulse Y is input.
M is changed to the first driving force PWML (see FIG. 1A), and then the started interval timer 2 (hereinafter referred to as “timer 2”) is reset and the timer 2 is restarted. It is. Timer 2 has a driving force P
After the WM is changed to the first driving force PWML, the time until the pulse Y changes in order to detect that the upper limit of the processing time has been exceeded due to a drive system trouble or the like is managed.

The above YFB interrupt 3 will be described in detail with reference to a subroutine flowchart shown in FIG. In addition,
The YFB interrupt 3 is described as “Timer 2 interrupt” for convenience of explanation.
This is also performed after the description of FIG. 11 (see FIG. 11).

First, in order to update the current position y in response to the interruption of the detector 3, the current position y is incremented by +1 (S4
1), position error ER = Yf− with respect to final target position YF
y is calculated (S42).

For control of the section YE-YF, TBL1 shown in Table 1 and TBL2 shown in Table 2 are prepared.

Therefore, the first driving force PWML, which is the initial value of the driving force PWM corresponding to the value of the position error ER, is set to TB
Reference is made to L1 (S43, S44), and the increment dPW corresponding to the value of the position error ER when increasing stepwise is set to TBL
Reference is made in step 2 (S45, S46).

Then, the driving force PWM becomes the first driving force P
The output is changed to WML (S47). Then, timer 2
Restart processing (S48) and timer 2 interrupt count NTM
= 0 is set (S49), and the routine returns. Note that S48 and S49 make sense in the second and subsequent YFB interrupts 3.

Next, as shown in the main flowchart of FIG. 4, the timer 2 is started (S14), and the interruption of "timer 2 interrupt" is permitted (S15).

Timer 2 interrupt (step for increasing driving force)
Basically controls to increase the driving force PWM step by step. That is, as shown in FIG. 1A, control is performed to increase the first driving force from PWML to PWMT.

The above timer 2 interrupt will be described with reference to a subroutine flowchart shown in FIG.

First, the driving force PWM increases by one step (S61). That is, driving force PWM = PWM + dPW
And Next, the number of timer 2 interrupts NTM indicating the number of times the "timer 2 interrupt" interrupt processing has been performed is updated by one (S62). That is, the number of timer 2 interrupts NTM = N
Set to TM + 1.

Next, a predetermined timer N interrupt count N
Timer 2 upper limit NMAX which is the upper limit of TM and timer 2
A comparison is made with the number of interrupts NTM (S63). If the timer 2 interrupt count NTM is smaller than the timer 2 upper limit NMAX, the driving force is changed to the driving force PWM set in S61 and output to the motor driving circuit 4 (S64). Then, while repeating steps S61 to S64, the pulse Y changes. That is, the state shown in FIG.
The state changes from “L” to state “H.” In addition, the change from the state “L” to “H” causes the input of the pulse Y and the YF.
The process of B interrupt 3 is started.

In the YFB interrupt 3, as shown in FIG. 9, the output to the motor 2 is changed to the first driving force PWML in S41 to S47, and the motor 2 is stopped. Then, it is confirmed that the pulse Y has changed (signal confirmation step), and the count value y is updated by one. That is, the count value is set to y = y + 1. Thereafter, in S48, the timer 2 started in S14 of the main flowchart is reset, and the timer 2 is restarted. In step S44, the timer 2 interrupt count NTM indicating the number of times that the "timer 2 interrupt" interrupt process has been performed is reset. That is, the number of timer 2 interrupts NTM is set to 0, and the process returns to the main flowchart. Then, the timer 2 interrupt shown in the subroutine flowchart of FIG.
Step 64 is repeated again.

In S63, if the timer 2 interrupt count NTM exceeds the timer 2 upper limit NMAX,
The display means (not shown) of the serial printer indicates that the paper conveyance operation is in a malfunctioning state (S65). That is, the timer 2 interrupt count NTM is equal to the timer 2 upper limit value NM.
Exceeding AX means that the pulse Y does not change even if the processes from S61 to S64 are performed more times than the timer 2 upper limit value NMAX, and some abnormality occurs and the rotation of the motor 2 is started. Not indicate. For example, there may be a case where a paper jam or a device of a serial printer is caught, a large load torque is applied to the motor 2, and the motor 2 is not rotating.

In this case, the driving of the motor 2 is stopped to prevent the motor 2 from being damaged by an overcurrent (S66). Further, the process jumps to a malfunction process control (not shown) (S67).

On the other hand, as shown in the main flowchart of FIG. 6, the count value y is obtained by the processing from S13 to S15.
Is confirmed to be YF (S16), it is determined that the motor 2 has reached the stop position, and the interruption of the "timer 2 interrupt" is prohibited (S17). Next, in the stop position holding step, the driving force PWM is set to the minimum driving force PWMs (S18). Further, YFB interrupt 3 is changed to YFB interrupt 4 (S19).

The YFB interruption 4 is performed when an abnormal operation such as a user pulling the sheet and moving the sheet is performed at a predetermined stop position of the sheet. is there. That is, the value of the count value y is monitored.

The details will be described with reference to a subroutine flowchart shown in FIG.

That is, the YFB interrupt 4 is a process in the case where some force acts on the motor 2 which does not need to operate and the pulse Y is detected after the end of the line feed.
In this case, it is determined that it has moved from the stop position due to some abnormality, and a display means (not shown) of the serial printer indicates that the drive system operation is in a malfunctioning state (S5).
1). Further, in order to prevent the motor 2 from being damaged by the overcurrent, the driving of the motor 2 is stopped (S5).
2). Further, the process jumps to a malfunction process control (not shown) (S53).

As described above, in the driving method of the DC motor according to the present embodiment, in the driving force decreasing step, every time the MPU control unit 1 confirms that the digital position signal YFB changes from the state L to the state H, With respect to the motor 2, the target position Y
The first driving force PWML (PWML5, PWML) in which the driving force is sequentially reduced in accordance with the position error ER with respect to F
4,..., PWML1) or drive is stopped.

Therefore, the rotation amount of the motor 2 is detected by the detector 3 based on the change of the digital position signal YFB from the state L to the state H, and when the current rotation amount is detected, the target position Y is detected.
The first driving force PWML can be reduced step by step in accordance with the position error ER from F to reduce the first driving force.

Also, each first driving force PWML (PWML)
, PWML4,..., PWML1), until the digital position signal YFB changes from the state L to the state H, and as a driving force increasing step,
Each first driving force PWML (PWML5, PWML4,
.., PWML1), the driving force is increased stepwise. Furthermore, the increase dP of each driving force increase step
W gradually decreases step by step in each driving force increasing step according to the position error ER from the target position YF.

Therefore, each first driving force PWML (P
(WML5, PWML4,..., PWML1) are increased stepwise according to the position error ER from the target position YF. When the position error ER is large, the increase dPW is increased. By approaching the target position YF and increasing the resolution with high resolution near the target position YF, it is possible to drive with the minimum necessary torque to overcome the load torque.

As a result, each of the first driving forces PWML (PWML5, PML5) whose driving force is reduced stepwise with respect to the target position YF in accordance with the position error ER from the target position YF.
WML4,..., PWML1) and the target position Y
In the vicinity of F, the motor can be driven with the minimum necessary torque corresponding to the position error ER from the target position YF to overcome the load torque, and absorbs variations and fluctuations of the load torque and variations and fluctuations of the motor 2 to speed up. The target position can be approached without the need. As a result, the overrun of the motor 2 is made uniform, and the stop position fluctuation due to excessive overrun due to speed over is prevented.

Further, as a result, as the detector 3 such as an encoder, it is not necessary to use an expensive absolute encoder having a complicated structure and an analog position signal, and a simple and inexpensive incremental encoder having a digital pulse output can be used. .

As a result, a digital position signal from the detector 3 such as an encoder having the same resolution as the positioning resolution can be used to stop the target position YF with high accuracy, and a simple and inexpensive driving method for the motor 2 can be achieved. Can be provided.

Further, in the paper feeding method of the present embodiment, when the paper feeding is stopped, the above-described driving method of the motor 2 is used.

Therefore, when determining the stop position of the sheet, the sheet can be driven with the minimum necessary torque to overcome the load torque, and the sheet can be stopped at the target position YF without overspeeding. Also, the amount of overrun after detecting the change of the digital position signal YFB (within one pulse)
And the stop position fluctuation due to excessive overrun due to speed over is uniformly prevented, and accurate paper feeding is possible.

As a result, the digital position signal YF from the detector 3 such as an encoder having a resolution equal to the positioning resolution is obtained.
At B, it is possible to accurately stop at the target position YF, and to provide a simple and inexpensive sheet feeding method.

Further, in the paper feeding method of the present embodiment,
The method further includes a stop position holding step of holding the sheet stop position after stopping the sheet feeding.

Therefore, the holding means such as the holding driving force, the brake, and the worm gear can prevent the sheet from moving due to the back tension acting on the sheet.

Further, in the paper feeding method of the present embodiment,
After stopping the sheet feeding, a stop position holding step of holding the sheet feeding position by applying a minimum driving force PWMs smaller than the first driving force PWML is included.

Therefore, even if there is no holding means such as a brake and a worm gear, it is possible to prevent the paper from moving due to the back tension acting on the paper. That is, the minimum driving force PWMs is a driving force smaller than the first driving force PWML, and the driving torque applied to the motor 2 by the minimum driving force PWMs is smaller than the load torque applied to the motor 2 due to friction of the driving mechanism or the like. It is small.

Further, since a holding mechanism such as a brake and a worm gear for stopping the sheet is not required, the load torque acting on the driving source for feeding the sheet is further reduced.

The paper feeder 10 according to the present embodiment
Uses the above-described paper feeding method. Therefore, a detector 3 such as an encoder having a resolution equal to the positioning resolution is used.
Can be stopped accurately with respect to the target position YF by the digital position signal YFB, thereby providing a low-cost paper feeder 10 with a simple structure.

Note that the present invention is not limited to the above embodiment, and various changes can be made within the scope of the present invention. For example, in the above-described embodiment, the first driving force PWML is output to the motor 2 every time the MPU control unit 1 confirms that the digital position signal YFB changes from the state L to the state H. The first driving force PWM in which the driving force is sequentially reduced in accordance with the position error ER with respect to the first driving force PWM
L (PWML5, PWML4,..., PWML1) or drive is stopped. However, the present invention is not necessarily limited to this. In the driving force reduction step, the first driving force PWML in which the driving force is sequentially reduced is applied.
Alternatively, the driving can be stopped.

As a result, the rotation amount of the motor 2 is detected based on a predetermined change in the digital position signal YFB, and when the current rotation amount is detected, the first driving force PWML is sequentially reduced, and the first driving force PWML is reduced. The driving force PWML can be reduced.

In the above embodiment, each of the first driving forces PWML (PWML5, PWML4,..., PWML)
After the application of the first driving force PWML (PW), as a driving force increasing step, between each time when the digital position signal YFB is changed from the state L to the state H after the application of 1).
ML5, PWML4,..., PWML1). Further, the increment dPW of each driving force increasing step is decreased step by step in each driving force increasing step in accordance with the position error ER from the target position YF.

However, the present invention is not limited to this, and after applying each first driving force PWML, the digital position signal YFB
In each of the periods until the change of the state from the state L to the state H is confirmed, the driving force is simply increased stepwise with respect to the first driving force PWML as a driving force increasing step.

Therefore, by gradually increasing the driving force for each of the first driving forces PWML, the target position YF is quickly approached and the target position YF is increased.
In the vicinity of F, the motor can be driven with the minimum torque required to overcome the load torque.

[0130]

As described above, the method of driving a DC motor according to the present invention comprises the following steps: a signal confirmation step for confirming a change in a digital position signal; and a signal confirmation step for confirming a predetermined change in the digital position signal. To the DC motor, a driving force decreasing step of applying each first driving force whose driving force is reduced step by step according to a position error from a target position, or stopping driving, A driving force increasing step for increasing the driving force in a stepwise manner with respect to each of the first driving forces during a period from the application of the first driving force to the confirmation of a predetermined change in the digital position signal. And a method including:

Therefore, the first driving force whose driving force is reduced step by step in accordance with the position error from the target position is applied to the target position, and the first driving force is reduced in accordance with the position error of the DC motor. In the vicinity of the target position, it can be driven with the minimum torque required to overcome the load torque, absorbs variations and fluctuations in load torque, and variations and fluctuations in the DC motor, and achieves the target position without speeding up. Can be approached. As a result, the overrun of the DC motor is made uniform, and the stop position variation due to excessive overrun due to speed over is prevented.

Further, as a detector such as an encoder, a simple and inexpensive incremental encoder with digital pulse output can be used as a detector such as an encoder, which does not require an expensive absolute encoder and an analog position signal.

As a result, a digital position signal from a detector such as an encoder having a resolution equal to the positioning resolution
It is possible to provide an advantageous effect that it is possible to accurately stop at the target stop position, and to provide a simple and inexpensive DC motor driving method.

Further, the driving method of the DC motor of the present invention is as follows.
As described above, the signal confirming step for confirming that the digital position signal changes, and every time confirming that the digital position signal changes by a predetermined amount, the driving force for the DC motor is reduced step by step. A driving force decreasing step of applying each of the first driving forces or stopping the driving, and after applying each of the first driving forces, until the digital position signal is confirmed to change by a predetermined amount. And a driving force increasing step of increasing the driving force in a stepwise manner with respect to each of the first driving forces. The increasing amount of the driving force in each of the driving force increasing steps corresponds to the position with respect to the target position. This is a method in which the driving force gradually decreases in each driving force increasing step in accordance with the error.

Therefore, the first driving force whose driving force is reduced step by step is applied to the target position, and in the vicinity of the target position, it is necessary to respond to the position error with the target position in order to overcome the load torque. It can be driven with a minimum torque, and can absorb variations and fluctuations in load torque, and variations and fluctuations in the DC motor, and can approach the target position without speeding up. As a result, the overrun of the DC motor is made uniform, and the stop position variation due to excessive overrun due to speed over is prevented.

[0136] Thus, as a detector such as an encoder, it is not necessary to use an expensive absolute encoder and an analog position signal having a complicated structure, and a simple and inexpensive incremental encoder with digital pulse output can be used.

As a result, a digital position signal obtained by a detector such as an encoder having a resolution equal to the positioning resolution
It is possible to provide an advantageous effect that it is possible to accurately stop at the target stop position, and to provide a simple and inexpensive DC motor driving method.

Further, the driving method of the DC motor of the present invention is as follows.
As described above, the signal confirmation step of confirming that the digital position signal changes, and each time the digital position signal is confirmed to change by a predetermined amount, the DC motor is controlled according to the position error from the target position. A step of applying a first driving force in which the driving force is sequentially reduced or a step of reducing the driving force to stop the driving; and a step of applying the first driving force described above. And a driving force increasing step of increasing the driving force in a stepwise manner with respect to each of the first driving forces. The increment is a method in which the increment gradually decreases in each driving force increment step in accordance with the position error from the target position.

Therefore, in order to overcome the load torque in the vicinity of the target position, each first driving force whose driving force is reduced step by step in accordance with the position error from the target position is applied to the target position. Driving can be performed with a minimum required torque corresponding to a position error with respect to the target position, and variations and fluctuations in load torque, and variations and fluctuations of the DC motor can be absorbed, and the target position can be approached without speeding up. As a result, the overrun of the DC motor is made uniform, and the stop position variation due to excessive overrun due to speed over is prevented.

Further, as a detector such as an encoder, a simple and inexpensive incremental encoder having a digital pulse output can be used as a detector such as an encoder, which does not require an expensive absolute encoder and an analog position signal.

As a result, a digital position signal obtained by a detector such as an encoder having a resolution equal to the positioning resolution
It is possible to provide an advantageous effect that it is possible to accurately stop at the target stop position, and to provide a simple and inexpensive DC motor driving method.

Further, in order to solve the above-mentioned problems, the paper feeding method of the present invention uses the above-described DC motor driving method when stopping paper feeding.

Therefore, with a digital position signal from a detector such as an encoder having a resolution equal to the positioning resolution,
It is possible to accurately stop at the target stop position and to provide an inexpensive paper feeding method with a simple structure.

Further, according to the paper feeding method of the present invention, after stopping the paper feeding in the above-described paper feeding method,
This is a method further including a stop position holding step of holding the sheet stop position.

Therefore, the holding means such as the holding driving force, the brake, and the worm gear can prevent the paper from being moved by the back tension acting on the paper.

Further, according to the paper feeding method of the present invention, in the above-described paper feeding method, after the paper feeding is stopped,
This is a method including a stop position holding step of holding a sheet feeding position by applying a second driving force smaller than the first driving force.

Therefore, even if there is no holding means such as a brake and a worm gear, it is possible to prevent the paper from moving due to the back tension acting on the paper. That is, the second driving force is a driving force smaller than the first driving force, and the driving torque applied to the DC motor by the second driving force is:
It is smaller than the load torque applied to the DC motor due to friction of the drive mechanism or the like.

Further, since a holding mechanism such as a brake and a worm gear for stopping the sheet is not required, the load torque acting on the driving source for feeding the sheet is further reduced.

Further, in order to solve the above-mentioned problems, a paper feeding apparatus of the present invention uses the above-described paper feeding method.

Therefore, with a digital position signal from a detector such as an encoder having a resolution equal to the positioning resolution,
It is possible to provide an inexpensive sheet feeder that can be stopped accurately with respect to the target stop position and has a simple structure.

[Brief description of the drawings]

FIGS. 1A and 1B show an embodiment of a method for driving a DC motor according to the present invention, in which FIG. 1A is a waveform diagram showing a first driving force and a driving force at an increased amount thereof, and FIG. 7 is a waveform diagram showing a digital position signal.

FIG. 2 is a block diagram showing a sheet feeder to which the method for driving a DC motor is applied.

FIG. 3 is a perspective view showing a detection principle of a detector for detecting a rotation amount of the DC motor.

FIGS. 4A to 4C are waveform diagrams showing output signals output from the detector.

FIG. 5 is a graph showing a relationship between a motor driving time and a motor speed in one paper feed.

FIG. 6 is a main flowchart showing an operation of the driving method of the DC motor.

FIG. 7 is a flowchart showing a subroutine of a driving method of the DC motor, and is a subroutine of YFB interrupt 1;

FIG. 8 is a flowchart showing a subroutine of a driving method of the DC motor, and is a subroutine of YFB interrupt 2;

FIG. 9 is a flowchart showing a subroutine of a driving method of the DC motor, and is a subroutine of YFB interrupt 3;

FIG. 10 is a flowchart showing a subroutine of a YFB interrupt 4 showing an operation of the driving method of the DC motor.

FIG. 11 is a flowchart showing a subroutine of a timer 2 interrupt, showing an operation of the driving method of the DC motor.

[Explanation of symbols]

1 MPU control unit 2 Motor (DC motor) 3 Detector 4 Motor drive circuit 10 Paper feeder dPW increase (drive power increase) PWML first driving force PWMs Minimum driving force (second driving force) YF target position YFB digital position signal

Continuation of front page    F term (reference) 2C058 GA06 GA09 GB07 GE04 GE09                       GE10                 5H560 AA10 DA07 DB20 EB01 GG04                       RR10 XA05 XA12                 5H571 AA12 BB10 FF06 GG01 HD03                       JJ03 LL08

Claims (7)

[Claims] 1. A method for driving a DC motor controlled based on a digital position signal output from a detector for detecting a rotation amount of the DC motor, a signal confirming step for confirming that the digital position signal changes. Each time that the digital position signal is confirmed to change by a predetermined amount, whether or not to apply each first driving force to the DC motor in which the driving force is reduced stepwise in accordance with the position error from the target position. Or a driving force decreasing step of stopping the driving, and after applying each of the first driving forces, until each of the first driving forces is confirmed until the digital position signal is changed by a predetermined amount. And a driving force increasing step of increasing the driving force in a stepwise manner. 2. A method for driving a DC motor controlled based on a digital position signal output from a detector for detecting a rotation amount of the DC motor, a signal confirming step for confirming that the digital position signal changes. Each time the digital position signal is confirmed to change by a predetermined amount, the first driving force whose driving force has been gradually reduced is applied to the DC motor, or the driving force is reduced to stop driving. In the steps and after each of the first driving forces is applied, until the digital position signal is confirmed to change by a predetermined amount, the driving force is stepwise applied to each of the first driving forces. And increasing the driving force in each of the driving force increasing steps, and the driving force increment in each of the driving force increasing steps is decreased step by step in each driving force increasing step in accordance with a position error from a target position. A method for driving a DC motor, characterized in that: 3. A method of driving a DC motor controlled based on a digital position signal output from a detector for detecting a rotation amount of the DC motor, a signal confirmation step of confirming that the digital position signal changes. Each time that the digital position signal is confirmed to change by a predetermined amount, whether or not to apply each first driving force to the DC motor in which the driving force is reduced stepwise in accordance with the position error from the target position. Or a driving force decreasing step of stopping the driving, and after applying each of the first driving forces, until each of the first driving forces is confirmed until the digital position signal is changed by a predetermined amount. A driving force increasing step of increasing the driving force in a stepwise manner, and the driving force increasing step in each of the driving force increasing steps is performed in accordance with a position error with respect to the target position. A method for driving a DC motor, characterized in that it is reduced step by step in each step. 4. A method of feeding a sheet of paper, wherein the method of driving a DC motor according to claim 1 or 2 is used to stop the sheet feeding. 5. The paper feeding method according to claim 4, further comprising a stop position holding step of holding a paper stop position after stopping paper feeding. 6. A stopping position holding step for holding a sheet feeding position by applying a second driving force smaller than the first driving force after stopping the sheet feeding. The paper feed method described. 7. A sheet feeding apparatus using the sheet feeding method according to claim 4, 5 or 6.