JP2003079189A - Driving method of dc motor, method and apparatus for feeding sheet, imaging apparatus, and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a driving method of DC motor for moving a stopping sheet and stopping it at a predetermined point in which the sheet is stopped accurately at a target sheet feed position by the digital positional signal of an encoder having a resolution equal to a positioning resolution. SOLUTION: Sheet feed is performed continuously for a plurality of digital positional signals in sections (sections A and B) where a stopping sheet is started to move and the rotational speed of a DC motor is accelerated up to a constant speed, a section (section C) where the sheet is fed continuously at the constant speed, and a section (section D) where the sheet is brought close to a target sheet feed position by decelerating the sheet feed speed significantly. Subsequently, in a section E, the sheet is brought close to a target stop position precisely and stopped while controlling the rotational speed little by little in correspondence with variation of the digital positional signal.

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 method for controlling the operation of the DC motor based on a digital position signal output from a detector for detecting the rotation amount of the DC motor. The present invention relates to an apparatus, an image forming apparatus and an image reading apparatus using the sheet feeding apparatus.

[0002]

2. Description of the Related Art In a serial printer such as an ink jet printer, printing is performed line by line by printing directly on a recording sheet while moving the recording head in the main scanning direction. Therefore, every time printing of one line is completed, before carrying out printing of the next line, a sheet conveying (line feed) operation for feeding the sheet by one line in the sub-scanning direction is performed.

In the above line feed operation, it is required to obtain an accurate carry amount so that two adjacent lines in the sub-scanning direction do not overlap or separate. For this reason, in the past, a pulse motor was generally used as the line feed motor, but in recent years, a DC motor (DC motor) may be used instead of an expensive pulse motor.

When a DC motor is used as the line feed motor, the DC motor is less expensive than the pulse motor, but it is difficult to accurately control the amount of rotation of the DC motor, that is, the sheet feeding position. Various methods have been proposed to control the.

As a method for controlling the sheet feeding position, D
There is a method of installing an optical sensor capable of detecting the rotation amount of the C motor and controlling the rotation amount of the DC motor based on the detection result of the optical sensor. Specifically, the encoder pulse (digital position signal) transmitted from the optical sensor is counted every time the DC motor rotates by a certain amount.
The sheet feed position is controlled by grasping the rotation amount of the C motor.

In the positioning control using such an encoder pulse, an encoder having a resolution equal to the positioning resolution in the line feed causes a positioning error of several pulses, which is a unique problem in digital position control. Therefore, in order to improve the accuracy of the stop position of the DC motor (that is, the stop position of the sheet that is line-fed), an encoder having a resolution several times finer than the positioning resolution is used.

On the other hand, there is also a method of performing positioning control with an encoder having a resolution equal to the positioning resolution. In this method, an encoder capable of analog output is used as the above encoder, or in addition to an encoder for counting the rotational position of the motor. There is a method such as preparing a potentiometer for obtaining an analog position signal. That is, the analog output of the encoder before waveform shaping into the encoder pulse or the analog output of the potentiometer or the like is used as the feedback signal of the positioning control.

[0008] For example, in Japanese Patent Publication No. 7-44864, a PLL (Phase-Phase-) which uses the analog output of an encoder before waveform shaping into an encoder pulse for positioning.
Looked Loop) speed control circuit is disclosed.

[0009]

However, in the above-mentioned conventional configuration, there is a problem that the equipment or control circuit used for the positioning control becomes expensive.

For example, in the positioning control using the digital pulse of the encoder, the positioning resolution is 2400DP.
In the case of I (Dot Per Inch) positioning control, assuming that the required encoder resolution is 5 times that, an encoder with a resolution of 12000 DPI is required. Therefore, the encoder becomes expensive.

Further, the positioning control using the analog output of the encoder in the above Japanese Patent Publication No. 7-44864 is very expensive because the control circuit is complicated. In particular, in a serial printer that is less expensive than other laser printers, it is inappropriate to use the control circuit as described in the above publication because it impairs the merit of low cost.

The present invention has been made to solve the above problems, and an object thereof is to accurately stop a sheet at a target stop position with a digital position signal of an encoder having a resolution equal to a positioning resolution. DC motor driving method, sheet feeding method, sheet feeding apparatus, and image forming apparatus using the sheet feeding apparatus,
An object is to provide an image reading device.

[0013]

In order to solve the above-mentioned problems, a method for driving a DC motor according to the present invention is based on a digital position signal output from a detector for detecting the rotation amount of the DC motor. In a method of driving a DC motor for controlling the operation of an electric motor, after applying a first driving force to the DC motor, a driving force increasing step of gradually increasing the driving force and a driving force increasing step in the driving force increasing step. A signal confirmation step for confirming whether or not the digital position signal of the detector changes each time it is increased by one step, and a DC position at that time when the change of the digital position signal is confirmed in the signal confirmation step. A driving force applied to the electric motor as a second driving force, and a driving force reducing step of reducing the driving force applied to the DC electric motor as compared with the second driving force. It is.

According to the above method, the rotation of the DC motor is detected by detecting the rotation of the DC motor by the change of the digital position signal while gradually increasing the driving force for the DC motor. The driving force is made smaller than the driving force (second driving force) at the time when the digital position signal changes.

That is, the second driving force is the minimum necessary driving force that can drive the DC motor by overcoming the load torque acting on the DC motor. Therefore, if the driving force is made smaller than the second driving force, the driving of the DC motor is stopped. As a result, it is possible to approach the target position without excessively speeding up the rotation of the DC motor.

Further, even if the load torque acting on the DC motor fluctuates or the driving torque of the DC motor fluctuates,
The DC motor can be driven with the minimum required drive torque that overcomes the load torque. The amount of overrun in the DC motor after detecting the change in the digital position signal is suppressed within 1 pulse of the digital position signal, and the stop position of the DC motor should greatly exceed the detection position of the digital position signal. There is no uniformization at almost the same position. As a result, it is possible to prevent the stop position from varying due to excessive overrun of the DC motor.

Further, in order to solve the above-mentioned problems, the sheet feeding method according to the present invention uses the operation of the DC motor based on the digital position signal output from the detector that detects the rotation amount of the DC motor. In the sheet feeding method for controlling the sheet feeding to be carried out, in order to stop the sheet feeding when the sheet feeding amount reaches a target sheet feeding position which is a predetermined amount, a driving method of a DC electric motor according to the present invention is provided. It is characterized by including the applied sheet feeding operation.

According to the above method, when the seat is stopped at the target position, the driving method of the DC motor according to the present invention is used. As a result, it is possible to approach the target position without excessively increasing the sheet feeding speed. Further, even if the load torque acting on the DC motor fluctuates or the driving torque of the DC motor fluctuates, the sheet feed amount after detecting the change in the digital position signal greatly exceeds the detection position of the digital position signal. Without being homogenized. As a result, it is possible to prevent the stop position from varying due to excessive overrunning of the sheet feeding, and it is possible to feed the sheet accurately.

As a result, the positioning error of several pulses, which is a particular problem in digital position control, is eliminated.
That is, as described above, the error between the target position and the actual stop position can be suppressed uniformly without significantly exceeding the detection position of the digital position signal. Therefore, it is possible to perform the sheet feeding positioning control with an encoder having the same positioning resolution. Further, the above method can be executed even in a simple and inexpensive incremental encoder as an encoder.

Further, the sheet feeding method according to the present invention is
In the above method, when the sheet feeding is stopped, the sheet feeding operation is repeated a plurality of times to reach the target sheet feeding position.

According to the above method, when the sheet feeding is stopped, the sheet is gradually fed by repeating the driving method of the DC motor according to the present invention a plurality of times, and the sheet is fed when the target position is reached. Stop. This allows
The approach to the target sheet feeding position is stabilized, and the reproducibility of the stopping operation and the sheet feeding accuracy are further improved.

Further, the sheet feeding method according to the present invention is
In the above method, after the sheet is continuously fed from the start of the sheet feeding to a position where the target sheet feeding position is not reached, the sheet feeding operation is repeated a plurality of times to reach the target sheet feeding position. Is characterized by.

According to the above method, when stopping the sheet feeding after the sheets are continuously fed, the driving method of the DC motor according to the present invention is repeated a plurality of times to gradually feed the sheet to reach the target. When the position is reached, the sheet feeding is stopped. As a result, it is possible to shorten the time for carrying out a predetermined amount of sheet feeding, and since the sheet feeding has reproducibility, it is possible to achieve accurate sheet feeding in a shorter time.

In order to solve the above-mentioned problems, the sheet feeding device according to the present invention detects a direct current electric motor which is a power source for the sheet feeding and detects the digital electric motor every time the direct current electric motor rotates by a predetermined amount, and a digital position. A sheet feed that has a detector that outputs a signal, controls the operation of the DC motor based on the digital position information obtained by counting the digital position signals output from the detector, and controls the sheet feed position. In the apparatus, the sheet feeding method according to the present invention is used to control the sheet feeding amount.

According to the above construction, when the sheet is fed,
The sheet feeding method according to the present invention is used. This makes it possible to approach the target position without excessively increasing the sheet feeding speed when the sheet is fed to the target position, such as when feeding one line of sheet each time printing of one line is completed.

Further, even if the load torque acting on the DC motor due to sliding friction of the sheet or the driving torque of the DC motor fluctuates, the sheet feed amount after detecting the change in the digital position signal is It is suppressed within one pulse of the digital position signal, and the stop position of the DC motor is made uniform at almost the same position without greatly exceeding the detection position of the digital position signal. As a result, it is possible to prevent the stop position from varying due to excessive overrunning of the sheet feeding, and it is possible to feed the sheet accurately.

As a result, the positioning error of several pulses, which is a particular problem in digital position control, is eliminated.
Therefore, it is possible to perform the sheet feeding positioning control with an encoder having the same positioning resolution. further,
As the encoder, it is not necessary to use an absolute encoder and an analog position signal, which are complicated and expensive, and a simple and inexpensive incremental encoder may be used. Therefore, a highly accurate and inexpensive sheet feeding device can be realized.

Further, the sheet feeding device according to the present invention is
In the above structure, a holding force is applied to the DC motor so that the DC motor does not move from the sheet stop position after the sheet feeding is stopped.

According to the above structure, the holding force is applied to the DC motor by the holding means such as the holding force, the brake, the worm gear, etc., so that the sheet is moved by the back tension after the sheet feeding is stopped. It can be prevented. With this, after stopping the sheet feeding,
The seat can be securely fixed to the stop position.

Further, the sheet feeding device according to the present invention is
In the above configuration, when a holding force is applied to the DC motor, a third driving force for holding the stop position of the seat is applied to the DC motor.

According to the above arrangement, when the sheet reaches the target position, the driving force applied to the DC motor is not set to 0, but the third driving force for holding the sheet stop position is applied. Give. That is, the third driving force is
The driving force applied to the DC motor is a driving force for holding the stop position against back tension, which is a load torque of the DC motor. In other words, the third driving force is a force that cancels the influence of the disturbance force that acts when holding the stop position.

As a result, after stopping the sheet feeding,
The seat can be securely fixed to the stop position. Furthermore, by using the driving force applied to the DC motor as the holding means, a brake for stopping the seat,
Since a holding mechanism such as a worm gear is not needed, the load torque acting on the DC motor is reduced.

Further, the sheet feeding device according to the present invention is
In the above structure, the disturbance torque Tf acting on the DC motor by the disturbance force acting on the sheet feeding mechanism, the driving torque Ts acting on the DC motor by the third driving force, and the sliding torque acting on the DC motor by sliding the sheet feeding mechanism. The relationship with the dynamic load torque Td is: Td> abs (Tf-Ts) where abs
(X): The third driving force is set so as to have an absolute value of X.

According to the above configuration, it is possible to properly set the third driving force with respect to the disturbance torque. Poor position accuracy due to improper driving force is applied, or the seat after stopping is stopped. Can be prevented from moving accidentally.

Further, the sheet feeding device according to the present invention is
In the above structure, the third driving force is set based on the second driving force immediately before the sheet feeding is stopped, and the third driving force is higher than the absolute value of the second driving force. It is characterized by a small absolute value of force.

According to the above arrangement, the third driving force corresponding to the stop position of the seat is applied. As a result, it is possible to set an appropriate holding force with respect to the sheet stop position even in the sheet feeding mechanism in which the fluctuation of the disturbance force is large or the sheet feeding mechanism in which the torque ripple is large. Furthermore, since the absolute value of the third driving force is smaller than the absolute value of the second driving force immediately before stopping the sheet feeding, it is possible that the third driving force becomes an inappropriate value and the stop position becomes defective. It can be prevented.

Further, the sheet feeding device according to the present invention is
In the above configuration, the third driving force is set based on the driving force applied to the DC motor when the DC motor is driven at a constant speed.

According to the above configuration, when the DC motor is driven at a constant speed, the third driving force is set based on the driving force applied to the DC motor, and after the sheet feeding is stopped, the third driving force is set. Driving force is applied.

Here, when the DC motor is driven at a constant speed, the driving force applied to the DC motor does not include the acceleration force for accelerating the rotation speed of the DC motor and the deceleration force for decelerating the rotation speed. That is, the driving force for driving the DC motor at a constant speed is the sliding load torque acting on the DC motor due to the sliding of the sheet feeding mechanism and the disturbance torque acting on the DC motor due to the disturbance force acting on the sheet feeding mechanism. It is a driving force for maintaining a constant speed with respect to the combined force.

As a result, the load state of the sheet feeding mechanism corresponding to each stop position of the sheet can be reflected in the setting of the third driving force, and the more appropriate setting of the third driving force can be performed. . As a result, it is possible to further prevent the position accuracy from being improperly applied due to the improper application of the third driving force and the incorrect movement of the stopped sheet.

Further, the sheet feeding device according to the present invention is
In the above structure, when the DC motor is driven at a constant speed, the direction of the driving force PWMc applied to the DC motor is the same as the sheet feeding direction.
And the relationship between the third driving force PWMs and the driving force PWMo applied when the DC motor is rotated at the same speed as the above-described constant speed driving without the sheet being conveyed, PWMs≈abs (PWMc− The third driving force is set so that it becomes PWMo).

According to the above construction, when the DC motor is driven at a constant speed, when the direction of the driving force PWMc applied to the DC motor is the same as the sheet feeding direction, the sliding by the constant speed rotation is performed. The dynamic load torque Td and the disturbance torque Tf can be estimated. That is,
The sliding load torque can be estimated by the driving force PWMo, and the disturbance torque Tf is the driving force PWMc and P.
It can be inferred by WMo. Since the third driving force is set based on the estimated value, the accuracy of the third driving force can be further improved.

Further, the sheet feeding device according to the present invention is
In the above configuration, when the DC motor is driven at a constant speed, the direction of the driving force PWMc applied to the DC motor is opposite to the sheet feeding direction, and the driving force PWMc
And the relationship between the driving force PWMo applied when the DC motor is rotated at the same speed as the above-mentioned constant speed driving without the sheet being conveyed and the third driving force PWMs is PWMs≈PWMc + PWMo It is characterized in that PWMs are set to.

According to the above construction, when the DC motor is driven at a constant speed, when the driving force PWMc applied to the DC motor is in the opposite direction to the sheet feeding direction, the sliding operation by the constant speed rotation is performed. The dynamic load torque Td and the disturbance torque Tf can be estimated. That is, the sliding load torque can be estimated by the driving force PWMo, and the disturbance torque Tf is the driving force PWMc and PW.
It can be inferred from Mo. Since the third driving force is set based on the estimated value, the accuracy of the third driving force can be further improved.

In order to solve the above-mentioned problems, the image forming apparatus according to the present invention prints line by line on the sheet while moving the recording head in the main scanning direction. Further, in the image forming apparatus for performing the line feed operation for feeding one sheet in the sub-scanning direction before printing the next line, in order to perform the line feed operation of the sheet, the sheet feeding apparatus according to the present invention. It is characterized by using.

According to the above construction, when the sheet is fed,
The above-described sheet feeding device according to the present invention is used. As a result, it is possible to perform the sheet feeding positioning control with an encoder having the same positioning resolution. further,
As the encoder, it is not necessary to use an absolute encoder and an analog position signal, which are complicated and expensive, and a simple and inexpensive incremental encoder may be used. Therefore, a highly accurate and inexpensive image forming apparatus can be realized.

In order to solve the above problems, the image reading apparatus according to the present invention reads the image on the read document line by line while moving the read head in the main scanning direction. Every time the reading and printing of
An image reading apparatus that performs a line feed operation for feeding a read document by one line in the sub-scanning direction before reading the next line. In order to perform the line feed operation for the read document, the sheet feeding apparatus according to the present invention. It is characterized by using.

According to the above construction, the above-mentioned sheet feeding apparatus according to the present invention is used when feeding the read original.
As a result, it is possible to perform the positioning control for feeding the read document with the encoder having the same positioning resolution. Further, as the encoder, it is not necessary to use the absolute encoder and the analog position signal, which are complicated and expensive, and a simple and inexpensive incremental encoder may be used. Therefore, a highly accurate and inexpensive image reading device can be realized.

[0049]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. First, the configuration of the control system applied to the sheet feeding method of the present embodiment will be described with reference to FIG. FIG. 2 is an MP for controlling the sheet feeding operation based on the above method.
3 is a block diagram showing a U control unit 1, a direct current motor 2 (Direct Current Motor: hereinafter referred to as a motor 2), a detector 3, and a motor drive circuit 4. FIG. It should be noted that the block diagram of FIG. 2 merely shows one configuration example of the present invention, and the present invention is not limited to this.

The motor 2 is a drive source for sending a print sheet to a printing section (line feed) in a serial printer (image reading device) (not shown) such as an inkjet printer. The motor drive circuit 4 is a drive circuit for driving the motor 2.

The detector 3 is a sensor for detecting the rotation of the motor 2, and here is a rotary encoder (Ro
tary Encorder) is used. The detector 3 emits an encoder pulse (digital position signal) Y every time the motor 2 rotates a certain amount, and the rotation amount of the motor 2 can be detected by counting the number of transmitted pulses. Is. The encoder pulse Y (hereinafter, referred to as pulse Y) is 90 for determining the rotation direction of the motor 2.
Degree-phase pulses α and β are prepared, and α is in phase advance with respect to β during forward rotation, and α is β during reverse rotation.
Is output with a phase delay. The pulse Y emitted from the detector 3 is input to the MPU control unit 1.

The MPU controller 1 discriminates the rotation direction based on the phases of α and β of the pulse Y, and counts up and down according to the rotation direction to grasp the rotation amount of the motor 2, and based on the control described later. A control signal for driving the motor 2 is transmitted to the motor drive circuit 4.

Next, a change in the rotation speed of the motor 2 (hereinafter referred to as a motor speed) while the sheet is fed once for one line will be described with reference to FIG. FIG. 1 shows the relationship between time and motor speed in one sheet feeding.

YA, YB, YC, YD and Y shown in FIG.
E and YF are the total number of the pulses Y counted by the MPU control unit 1, that is, the count value of the pulses Y input to the MPU control unit 1. The total number of pulses Y counted by the MPU control unit 1 before the sheet is fed once and stopped is YF. As shown in FIG. 1, Y = 0
The sheet feeding is started from (YA), and the control method of the motor speed is changed according to the detection of the respective count values YB, YC, YD, and YE.

Specifically, the motor drive operation until the stopped seat is moved and stopped at a predetermined point is divided into the following three sections. That is,
There are an acceleration section in which the stopped sheet starts to move and rises to a constant speed, a constant speed section in which the sheet is continuously fed at the constant speed, and a stop section in which the sheet feeding speed is reduced and the sheet is stopped at a predetermined point.

If the above three sections are made to correspond to FIG. 1, the acceleration sections are the sections A and B (count value YA-YB-
YC), the constant speed section is section C (count value YC-
YD), and the stop section corresponds to sections D and E (count value YD-YE-YF).

The acceleration section is further divided into sections A and B, and the increments of the motor speed per unit time are different in these sections. That is, if it corresponds to FIG. 1, the slope of section A and the slope of section B are different,
The slope of the section B near the section C, which is a constant speed section, is smaller (gradual) than the section A. This is to prevent the motor speed from overshooting when shifting from the acceleration section to the constant speed section.

Further, in the sheet feeding method according to the embodiment of the present invention, the stop section is also divided into section D and section E. The section D is a section in which the motor speed is greatly reduced by a constant reduction amount per unit time. On the other hand, the section E is a section in which the sheet feed is accurately brought close to the target stop position and stopped while the motor speed is controlled in small steps. Here, the count value YE of the pulse Y when shifting from the section D to the section E does not exceed the final target stop position even if some error occurs in the end position of the section D. The number of pulses is set smaller than the count value YF corresponding to the target stop position.

Details of the motor control in the section E will be described below with reference to FIG. FIG. 3 shows the waveform of the pulse Y in the section E and the change in the driving force PWM applied to the motor 2 according to the pulse Y. Detector 3 (Fig. 2
(See) repeats the state of transmitting an ON signal and the state of transmitting an OFF signal every time the motor 2 rotates a certain amount. That is, it can be said that the motor 2 is in a non-rotating state when the pulse Y continues to be in either the ON state or the OFF state.

On the other hand, the driving force PWM applied to the motor 2
Indicates that the first driving force PWML is applied at the end of the section D, that is, at the time Ea when the count value of the pulse Y reaches YE. This driving force PWML is a driving force that has not yet reached by rotating the motor 2. If the load torque acting on the motor 2 is only the sliding friction generated between the sheet and the sheet feeding mechanism such as the roller when the sheet is fed, PWML may be 0. And the driving force P
After applying WML, the driving force is increased stepwise.

As described above, by gradually increasing the driving force applied to the motor 2, the motor 2 starts to rotate at a certain point, and the pulse Y changes from the ON state to the OFF state.
Here, the fact that the pulse Y is changed from the ON state to the OFF state means that the driving torque PWML is gradually increased to overcome the load torque acting on the motor 2 and the motor 2 starts to rotate. ing.

Then, at the time point Eb when the pulse Y changes from the OFF state to the ON state, the driving force applied to the motor 2 is reduced to the driving force PWML again, and the motor 2 is stopped. At this time, the motor 2 is operating with a minimum driving force that finally overcomes the load torque acting on the motor 2. As a result, when determining the stop position of the seat, it is possible to drive with the minimum necessary torque that overcomes the load torque, and it is possible to approach the target position without speeding up.

Further, even if the sliding load torque acting on the motor 2 fluctuates or the driving torque of the motor 2 fluctuates due to the sliding of the sheet feeding mechanism, the sheet feeding amount after the change of the pulse Y is detected. Within 1 pulse of pulse Y,
Moreover, the pulse Y is made uniform at almost the same position without greatly exceeding the detected position. As a result, it is possible to prevent the stop position from changing due to excessive overrun of the sheet feeding, and it is possible to perform the sheet feeding accurately.

In the present embodiment, the section Ea shown in FIG.
The driving method indicated by −Eb is repeated until the count value of the pulse Y reaches YF, and the target sheet feeding position is reached. This stabilizes the approach to the target sheet feeding position, and further improves the reproducibility of the stop operation and the sheet feeding accuracy.

In the present embodiment, the sheets are continuously fed for the plurality of pulses Y in the section A to the section D (see FIG. 1), and then the sections Ea-Eb in FIG. 3 are shown. The driving method is repeated until the count value reaches YF to reach the target sheet feeding position. That is, with the driving method shown in the section Ea-Eb, instead of performing all the sheet feeding, at the time when the sheet comes close to the target stop position, that is, when the count value of the pulse Y becomes YE,
The above driving method is repeated. As a result, it is possible to shorten the time for carrying out a predetermined amount of sheet feeding, as compared with the case where all the sheet feeding is carried out by the driving method described above. further,
The sheet feeding has reproducibility. Therefore, accurate sheet feeding can be achieved in a shorter time.

It is desirable that the holding means holds the sheet stop position when the count value reaches YF, that is, when the sheet feed position is reached. This is because a disturbance force may act as a load torque acting on the motor 2 depending on the configuration of the sheet feeding device.

That is, the load torque acting on the motor 2 is
If there is only sliding friction between the sheet and a sheet feeding mechanism such as a roller when the sheet is fed, the driving force may be set to 0 when the count value reaches YF. That is, the driving force PWM is set to 0 by cutting off the current applied to the motor 2, the feeding mechanism is stopped, and the sheet can be kept in the stopped state.

However, depending on the structure of the sheet feeding device, a disturbance force other than the sliding friction may act on the load torque acting on the motor 2. In this case, the disturbance force causes the sheet to move from the stop position. 4 to 6 show configuration examples in which a disturbance force acts as the load torque of the motor 2.

FIG. 4 shows a sheet feeding mechanism provided in the sheet feeding device according to the embodiment of the present invention.
This is an example in which a disturbance force (back tension) acts in the opposite direction to the feeding direction of. The pickup roller 13 is for feeding one by one to the print head 10 from a plurality of sheets 16 placed on a paper feed tray (not shown) in advance. That is, first, the pair of pickup rollers 13
Sheet 16 is fed to print head 10. The sheet 16 sorted into one sheet is then fed to the sheet feeding roller 11
Then, the paper is sequentially sent by the paper discharge roller 12.

Here, when the sheet 16 is fed by the paper feed roller 11 and the paper discharge roller 12, although details are not shown, the sheet 16 is fed when the sheet 16 is fed.
The sliding frictional force between the sheet conveying path member such as a guide and a rail, the frictional force acting between the gear teeth of the drive system and the bearing, and the frictional force generated by the back tension by the sheet feeding roller 11 and the sheet discharging roller 12 are the sheet 16 The disturbance force acts in the direction opposite to the feed direction of.

On the other hand, FIG. 5 shows an example of a feeding mechanism having the same configuration as that shown in FIG. 4, in which a disturbance force acts in the feeding direction of the sheet 16. In other words, while the sheet 16 is being fed by the sheet feeding roller 11 and the sheet discharging roller 12, the gravitational force acting on the sheet 16 on the side where printing is finished exerts a disturbance force in the sheet feeding direction.

FIG. 6 shows a sheet feeding mechanism provided in a sheet feeding apparatus according to another embodiment of the present invention.
This is an example in which a disturbance force acts in the direction opposite to the feed direction of No. 6. The figure shows a state in which the sheet 16 previously wound on the roll paper 14 is sent to the print head 10 by the paper feed roller 11 and the paper discharge roller 12. The stabilizer 15 is a spring member for relieving the inertial load on the roll paper 14. Here, the force applied to the sheet 16 by the stabilizer 15 becomes a disturbance force that acts in a direction opposite to the feeding direction of the sheet 16.

The disturbance force commonly used in FIGS. 4 to 6 is the elastic force of the sheet 16 between the rollers. The elastic force becomes a disturbance force in a direction opposite to the sheet 16 feeding direction.

Therefore, in order to prevent the sheet 16 from moving due to the disturbance force as described above, the rotation of the motor 2 is surely stopped at the time when the count value reaches YF, that is, when the sheet feed position is reached. It is preferable to provide holding power. This makes it possible to more reliably fix the sheet at the stop position after the sheet feeding is stopped. A holding mechanism such as a brake or a worm gear may be used as a configuration for applying the holding force to the motor 2, but in this case, the holding mechanism increases the size of the device or increases the load torque of the motor 2. .

Therefore, in the present embodiment, the driving force PWM (holding driving force) applied to the motor 2 is used as a structure for giving the holding force to the motor 2. That is, when the count value reaches YF, the driving force PWM given to the motor 2 is not set to 0, but the driving force PWMs (third driving force) for holding the sheet feeding position is given. That is, the driving force PWMs is a driving force applied to the motor 2 and is a driving holding force for holding the stop position with respect to the back tension which is the load torque of the motor 2. In other words, the driving force PWMs is a force that cancels the influence of the disturbance force that acts when holding the stop position.

As a result, after stopping the sheet feeding,
The seat can be securely fixed to the stop position. Furthermore, by using the driving force PWM as the holding means,
A holding mechanism such as a brake and a worm gear for stopping the seat is not required, which contributes to downsizing of the device and a load torque acting on the motor 2 is reduced.

Next, details of the method for setting the driving force PWMs for maintaining the stop position will be described below.
When the disturbance force described in FIGS. 4 to 6 exists,
The stop state is maintained by applying the driving force PWMs so as to cancel the influence of the disturbance force. That is, the disturbance torque acting on the motor 2 due to the disturbance force is Tf, and the driving force PWM
The driving torque Ts acting on the motor 2 by s and the sliding load torque Td acting on the motor 2 by the sliding of the sheet feeding mechanism.
Then, so that the driving torque Ts satisfies the equation (1),
The driving force PWMs may be set.

Td> abs (Tf-Ts) (1) However, the absolute value of abs (X): X, that is, the total torque acting on the motor 2 by the force to move the seat 16 ((1 If the sliding load torque Td (the left side of the expression (1)) is larger than the right side of the expression), the seat 16 can hold the stopped state.

If the driving force PWMs is set so as to satisfy the equation (1), the driving force PWM is appropriate for the disturbance torque.
It is possible to set s, and it is possible to prevent poor position accuracy due to improper driving force applied and erroneous movement of the stopped sheet. Note that there are the following three methods for setting the driving force PWMs.

(Setting Method 1) The driving force PWMs is set based on the driving force PWM when the target position is reached. Specifically, the absolute value of the third driving force is made smaller than the absolute value of the driving force PWMb when the target position is reached. In other words, the driving force PWM just before stopping the sheet feeding is multiplied by a coefficient to maintain the stopped state.
Let s.

That is, when the driving force at the time when the count value of the pulse Y reaches YF and the waveform of the pulse Y changes from the OFF state to the ON state (see FIG. 3) is PWMb,
The value of the driving force PWMb is multiplied by, for example, a coefficient of 0.5 to output the value of PWMs. That is, multiplying PWMb by a coefficient of 0.5 means that PWMs is equal to 5 of PWMb.
The driving force is 0%.

When the coefficient is 0.5, the binary value of PWM is rotated right by 1 bit, and when it is 0.25, it is rotated right by 2 bits. May be. That is, it takes 20 to 50 clocks to execute the multiplication and division instructions, whereas 4 clocks is sufficient for the rotate shift instruction, and the processing time can be greatly shortened. The value of the coefficient set to achieve the condition of expression (1) is 1 or less. That is, the driving force PWMs for holding the stop is set to be smaller than the driving force PWMb immediately before the stop.

According to the above setting method 1, the driving force PWMs corresponding to the sheet stop position is applied.
As a result, it is possible to set an appropriate holding force with respect to the sheet stop position even in the sheet feeding mechanism in which the fluctuation of the disturbance force is large or the sheet feeding mechanism in which the torque ripple is large. Further, it is possible to reliably prevent the third driving force from having an inappropriate value and causing a defective stop position.

(Setting method 2) Basically the same as the above setting method 1, but the driving force P of each is set in advance.
The driving force PWMs is obtained by multiplying WMb by a coefficient, and this is summarized in a reference table. At the time of sheet feeding, the driving force PWMb at the time when the count value of the pulse Y reaches YF and the waveform of the pulse Y changes from the OFF state to the ON state (see FIG. 3), the driving force P for stopping and holding is held.
The WMs are referenced from the above reference table and given to the motor 2. According to the setting method 2, the calculation processing time in the setting method 1 can be shortened.

(Setting Method 3) In the setting methods 1 and 2, the driving force PWMb, which is the basis of the driving force PWMs, includes the acceleration / deceleration force. That is, the driving force PWMb is
It includes acceleration force to accelerate the motor speed or deceleration force to decelerate the motor speed. With such a driving force PWMb, the operation for holding the stop may become unstable.

When it is desired to eliminate the influence of such acceleration / deceleration force, a constant speed section immediately before sheet feeding, that is, section C
(See FIG. 1) Driving force PW applied to the motor 2
The driving force PWMs is set based on Mc. As a result, it is possible to prevent the position accuracy from being improperly applied due to the improper application of the third driving force or the sheet to be erroneously moved after being stopped.
It can be prevented further.

That is, the driving force PWMc which is the basis of the driving force PWMs does not include the acceleration force for accelerating the motor speed and the deceleration force for decelerating the motor speed. In other words, the driving force PWMc is constant with respect to the combined force of the sliding load torque acting on the motor 2 by the sliding of the sheet feeding mechanism and the disturbance torque acting on the DC motor by the disturbance force acting on the sheet feeding mechanism. Is the driving force for maintaining the speed of.

Therefore, the driving force P with respect to the combined force of the sliding load torque Td and the disturbance torque Tf in the equation (1).
The driving force PWMs is set based on WMc. As a result, the load state of the sheet feeding mechanism corresponding to each stop position of the sheet can be reflected in the setting of the driving force PWMs, and the driving force PWMs can be set more appropriately. The driving force PW is calculated based on the average of the driving force PWMc applied to the motor 2 in the constant speed section immediately before the sheet feeding.
The accuracy can be further improved by setting Ms.

Specifically, the driving force PW is set as follows.
Set Ms. First, the seat 16 is not driven in advance and the motor 2 is driven at a constant speed at a constant speed, and the driving force PWMo applied to the motor 2 at that time is stored in memory. And
When stopping the sheet 16 when the sheet 16 is properly sent,
The driving force PWMs is obtained from the driving force PWMc in the section C (see FIG. 1) in which the sheet is fed at a constant speed.

Here, the motor 2 is driven by the driving force PWMo.
When the disturbance torque acting on the motor 2 due to the disturbance torque is Tf and the constant speed driving torque Tc acting on the motor 2 due to the driving force PWMc is Tf, the disturbance speed is constant when the disturbance force is opposite to the sheet feeding direction. The drive torque Tc can be approximated as Tc≈Tf + To (2). This is because the sliding load torque Td acting on the motor 2 due to the sliding of the sheet feeding mechanism and the driving torque To can be approximated to be equal. At this time, the driving torque Ts acting on the motor 2 by the driving force PWMs is
The disturbance torque Tf is applied in the same direction as the sheet feeding direction.
If it is equal to, the stop position of the sheet can be held, and thus Ts≈Tc−To (3) can be approximated.

From the equation (3), the driving force PWMo, the driving force PWMc, and the driving force direction MD of the driving force PWMc are calculated.
If the driving force direction MD is the same as the sheet feeding direction, the driving force PWMs in the reverse rotation direction for stopping and holding is set as follows: PWMs = PWMc−PWMo (4) Good. When the disturbance force is opposite to the sheet feeding direction, the driving force direction MD is not opposite to the sheet feeding direction.

On the other hand, when the disturbance force is in the same direction with respect to the sheet feeding direction, the constant speed driving torque Tc can be approximated as Tc≅abs (Tf-To) (5). This is because the sliding load torque Td acting on the motor 2 due to the sliding of the sheet feeding mechanism and the driving torque To can be approximated to be equal. At this time, the driving torque Ts acting on the motor 2 by the driving force PWMs is
If the torque is equal to the disturbance torque Tf, the stop position of the sheet can be held. Therefore, from the equation (5), when Tf <To, the driving force direction MD of the driving force PWMc is given in the same direction as the sheet feeding direction. It is necessary, and can be approximated as Ts≈To−Tc (6).

On the contrary, when Tf> To, the driving force PWM
The driving force direction MD of c must be applied in the opposite direction to the sheet feeding direction, and can be approximated as Ts≈Tc + To (7).

From equations (6) and (7), the driving force PWMo is
, The driving force PWMc, and the driving force direction M of the driving force PWMc
If D is stored, the driving force PWMs in the reverse rotation direction for holding the stop is: PWMs = PWMo−PWMc · from the equation (6) when the driving force direction MD is the same direction as the sheet feeding direction. .. (8) should be set. When the driving force direction MD is opposite to the sheet feeding direction, it can be set from the equation (7) as follows: PWMs = PWMc + PWMo (9)

As described above, when the driving force direction MD is the same as the sheet feeding direction and when it is the reverse rotation direction,
It can be organized, and from equations (4), (8), and (9),
When the driving force direction MD is the same as the sheet feeding direction, PWMs = abs (PWMc-PWMo) (10) When the driving force direction MD is the opposite direction to the sheet feeding direction, PWMs = PWMc + PWMo. ············································································· It is possible to maintain a stable and stable stop position.

Next, the method of controlling the motor speed during line feed based on the above description will be described with reference to FIGS. 7 and 8.
A description will be given based on the flowcharts of FIGS. 8A to 8E. Note that the flowcharts of FIGS. 7 and 8A to 8E show a control method implemented in the MPU control unit 1 (see FIG. 2), in which sheet feeding is started and then stopped at a target position. It shows a line feed control method for one line up to.

FIG. 7 is a main flow chart, and FIG.
FIGS. 8A to 8E are flowcharts interrupted by the main flowchart shown in FIG. 7. YB, YC, YD, YE, and YF shown in this flowchart correspond to those shown in FIG. It should be noted that these flowcharts only show one embodiment of the present invention, and the present invention is not limited to this.

First, in S1 of FIG. 7, the MPU control unit 1
The count value y of the pulse Y input (see FIG. 2) is reset. That is, y = 0 (= YA). S2
Then, start timer 1. What is Timer 1
This is a timer for measuring the cumulative time since the start of line feed control. In S3, the motor 2 is set to the normal rotation, and in S4, at the count value y = 0 of the pulse Y,
The driving force PWM (0) is output. Where PWM (y)
Is a predetermined driving force PWM (y) at the count value y.

At S5, PWMTBL1 is selected as the speed control table for the motor 2. PWMTBL1 is
Values of PWM (y) corresponding to each count value y are in a table. The PWMTBL1 is a trapezoidal table for controlling the speed of the motor 2 so as to change the speed from YA to YE in FIG.

At S6, the interrupt of "YFB interrupt 1" is permitted. As a result, until the count value reaches YC, the control of "YFB interrupt 1" is interrupted each time the pulse Y of the detector 3 is input. "YFB interrupt 1" is to change the driving force PWM (y) according to each count value y every time the pulse Y is input. Here, "YFB
The "interrupt 1" will be described with reference to FIG.

First, in S21, the time T (n) is read by the timer 1 indicating the accumulated time. In S22, pulse Y
Is confirmed and the count value y is updated by one. That is, y = y + 1. In S23, PWM
Driving force PW according to y determined in S22 from TBL1
Read the value of M (y). Here, PWM (y) for accelerating the motor 2 is selected. In S24, S23
The PWM (y) obtained in step 3 is output to the motor drive circuit 4, and the process returns to the main flowchart of FIG.

Here, in S7 of FIG. 7, when it is confirmed that the count value y has become YC due to the rotation of the motor 2, the process proceeds to S8, and in S8, "YFB interrupt 1" is set in FIG.
Change to "YFB interrupt 2" shown in (b). As a result, "YFB interrupt 2" is interrupted each time the pulse Y of the detector 3 is input until the count value becomes YD. The "YFB interrupt 2" basically changes the driving force PWM each time the pulse Y is input, but at the same time, in order to keep the sheet feeding speed in the section C (see FIG. 1) constant, It also changes the driving force PWM. Here, "YFB interrupt 2" will be described.

First, in S31 of FIG. 8B, the time T (n) is read by the timer 1 indicating the accumulated time. S32
Then, it is confirmed that the pulse Y is input, and the count value y is updated by one. That is, y = y + 1.

In S33, the time interval between the time T (n-1) read in the previous interrupt and the time T (n) read in S31 is calculated. That is, T (n) -T (n-1)
Calculate the value of. The time T (n-1) read by the previous interruption is the time T (n (1) read in S21 of the previous "YFB interrupt 1" if it is the first time to interrupt "YFB interrupt 2". n-1), and if it is the second time or later to interrupt "YFB interrupt 2", the previous "YF interrupt"
The time T (n- read in S31 of "B interrupt 2"
1).

At S34, the speed target T which is a table of the target cumulative time Tr (y) corresponding to the count value y
The target time Tr (y) corresponding to y is searched by referring to BL. In S35, the Tr (y) retrieved in S34,
The speed error Te is calculated from T (n) -T (n-1) calculated in S33. That is, Te = Tr (y)
-(T (n) -T (n-1)).

At S36, P corresponding to the speed error Te is set.
The PWMTBL2 in which the value of WM (Te) is a table is referred to, and the PWM (Te) corresponding to Te is searched. S
At 37, the output is changed to PWM (Te) corresponding to Te, and the process returns to the main flowchart of FIG. 7. Then, each time the pulse Y is input, the speed error Te is calculated, and the driving force PWM (Te) corresponding to the speed error Te is changed.

Due to the rotation of the motor 2, the count value y becomes Y.
When it is confirmed that S has become D in S9 of FIG. 7, the process proceeds to S10, and in S10, "YFB interrupt 2" is changed to "YFB interrupt 1". As a result, until the count value becomes YE, “Y
FB interrupt 1 "is interrupted. The "YFB interrupt 1" is to change the driving force PWM (y) according to each count value y every time the pulse Y is input, and the details are shown in FIG.
This is as described above based on (a). Since the section D is a section in which the motor 2 is decelerated (see FIG. 1), S
At 23, PWM (y) for decelerating the motor 2 is selected.

The count value y becomes Y by the rotation of the motor 2.
If it is confirmed in S11 of FIG. 7 that the value has become E, the process proceeds to S12. In S12, NTM = 0 is set. NTM
Indicates the number of times the driving force PWM is increased stepwise in the interrupt processing of "timer 2 interrupt" described later.

In S13, "YFB interrupt 1" is set in FIG.
Change to “YFB interrupt 3” shown in (c). As a result, “YFB interrupt 3” is interrupted each time the pulse Y of the detector 3 is input until the count value becomes YF. “YFB interrupt 3” is to change the driving force PWM to PWML (see FIG. 3) every time the pulse Y is input. Specifically, after the processing of S41 is executed, the next step is S
By the time the process of 41 is executed, the section Ea-Eb
The driving force PWM control in (see FIG. 3) is executed once. In "YFB interrupt 3", every time the pulse Y is input, the interval timer 2 (hereinafter, referred to as timer 2) started in S14 is reset and the timer 2 is restarted.

The timer 2 manages the time until the next pulse Y is input in order to detect that the upper limit of the processing time has been exceeded due to a trouble in the drive system after changing the driving force to PWML. Is. In addition, "YFB
For the convenience of explanation, a detailed explanation of "interrupt 3" will be given after a detailed explanation of "timer 2 interruption" shown in FIG.

That is, in S41 of FIG. 8C, the driving force P
While WM is changed to PWML and output, and "YFB interrupt 3" is in a state of waiting for the input of the pulse Y, the timer 2 is started in S14 of FIG. Next, in S15, the interrupt of "timer 2 interrupt" is permitted. The "timer 2 interrupt" (driving force increasing step) basically controls the driving force PWM to be increased step by step. That is, the driving force PWM is controlled to gradually increase from PWML (see FIG. 3).

At S61, the driving force PWM is increased by one step. That is, PWM = PWM + 1. S62
Then, the NTM, which indicates the number of times the "timer 2 interrupt" interrupt processing has been performed, is updated by one. That is, NTM = N
TM + 1.

At S63, the predetermined NTM
The maximum value of NMAX is compared with NTM. NT
If M is smaller than NMAX, the process proceeds to S64. S
In 64, the driving force is changed to the PWM set in S61 and output to the motor drive circuit 4. And FIG.
Return to the main flowchart of. S61 to S
While repeating 64, the next pulse Y is input. That is, the pulse Y changes from the OFF state to the ON state.

On the other hand, since the pulse Y is input, the process of "YFB interrupt 3" waiting for the input of the pulse Y in S42 of FIG. 8C proceeds. In S42, it is confirmed that the pulse Y is input, that is, the pulse Y is changed from the OFF state to the ON state (signal confirmation step), and the count value y is updated by one.
That is, y = y + 1. In S43, the timer 2 started in S14 is reset and the timer 2 is restarted. In S44, the NTM indicating the number of times the driving force PWM is stepwise increased is reset in the "timer 2 interrupt" interrupt process. That is, NTM = 0,
The process returns to the main flowchart of FIG. "YFB
In "Interrupt 3", the output to the motor 2 is PWM in S41.
It is changed to L and the motor 2 is stopped.

At S41, the output to the motor 2 is PWML.
The input wait state is entered in S42 until the next pulse Y is input. Then, by the "timer 2 interrupt", while the steps S61 to S64 are repeated again, the OF
The next pulse Y is input by the change from the F state to the ON state, and the above S42 to S44 and S41 are executed. Then, the control of the driving force PWM in the section Ea-Eb is repeated until it is confirmed in S16 of FIG. 7 that the count value y reaches YF.

In S63 of FIG. 8E, NT
When M becomes NMAX or more, the process proceeds to S65. NT
The fact that M exceeds NMAX means that S61 to S
This means that the pulse Y is not input even if the process of 64 is performed more than NMAX times, which means that some abnormality has occurred and the rotation of the motor 2 has not been started. For example, there is a case where the device of the serial printer is caught, a large load torque is applied to the motor 2, and the motor 2 is not rotating.

In this case, in S65, the display means (not shown) of the serial printer displays that the sheet conveying operation is in a malfunction state. In S66, the driving of the motor 2 is stopped in order to prevent the motor 2 from being damaged by an overcurrent. In S67, a jump is made to malfunction control (not shown).

On the other hand, when it is confirmed in S16 that the count value y has become YF by the processing of S13 to S15 in FIG. 7, the process proceeds to S17. In S17, the interruption of the "timer 2 interrupt" is prohibited when the motor 2 reaches the stop position. In S18, the driving force PWM is set to PWMs obtained by the above-mentioned setting method.

In S19, "YFB interrupt 3" is set in FIG.
Change to “YFB interrupt 4” shown in (e). The "YFB interrupt 4" is performed when there is an abnormal operation such as the sheet being moved by the user pulling the sheet at a predetermined stop position of the sheet. That is, the value of y is monitored. The details will be described below.

"YFB interrupt 4" is a process when a pulse Y is input by some force acting on the motor 2 which does not need to operate after the line feed is completed. In this case, it is determined that the sheet has moved due to an abnormality, and the display means (not shown) of the serial printer displays in S51 that the sheet conveying operation is in the malfunction state. In S52,
In order to prevent the motor 2 from being damaged by overcurrent, the driving of the motor 2 is stopped. In S53, a jump is made to malfunction control (not shown).

With the above line feed control method, it is possible to approach the target position without excessively increasing the sheet feeding speed. Further, even if the load torque acting on the motor 2 fluctuates or the driving torque of the motor 2 fluctuates, the sheet feeding amount after detecting the change of the pulse Y does not greatly exceed the detection position of the pulse Y. , Is homogenized. As a result, it is possible to prevent the stop position from varying due to excessive overrunning of the sheet feeding, and it is possible to feed the sheet accurately.

As a result, the positioning error of several pulses, which is a particular problem in digital position control, is eliminated, and it becomes possible to perform sheet feed positioning control with an encoder having the same positioning resolution. Further, since the above line feed control method can be executed even in an incremental encoder which is simple and inexpensive as an encoder, it is possible to provide a highly accurate and inexpensive sheet feeding device and a serial printer using the sheet feeding device.

In this embodiment, the print head is moved in the main scanning direction to print on the sheet one line at a time, and every time one line is printed, the sheet is printed before the next line is printed. In the serial printer which performs the line feed operation for feeding one line in the sub-scanning direction, the case where the sheet feeding device according to the present invention is used to perform the line feed operation of the sheet is illustrated.

However, the sheet feeding device according to the present invention is not limited to the serial printer but can be applied to all the devices that perform the sheet line feed operation. For example, the print head is removed, the read head is replaced with the read head, the read head is mounted on the carriage, and the image on the read original is read line by line while moving the read head in the main scanning direction. In addition, in an image reading apparatus such as a scanner that performs a line feed operation for feeding the read document by one line in the sub-scanning direction before reading the next line, even when performing the line feed operation of the read document, The sheet feeding device according to the invention can be applied. As a result, it is possible to accurately perform the sheet feeding positioning control with an encoder having the same positioning resolution, and it is possible to realize a highly accurate and inexpensive image reading apparatus.

[0125]

The method of driving a DC motor according to the present invention is
As described above, a method of driving a DC motor, which controls the operation of the DC motor based on the digital position signal output from the detector that detects the amount of rotation of the DC motor, wherein a first driving force is applied to the DC motor. After the application, the driving force increasing step for increasing the driving force stepwise and whether or not the digital position signal of the detector changes each time the driving force is increased by one step in the driving force increasing step. When the change in the digital position signal is confirmed in the signal confirming step to confirm and the signal confirming step, the driving force applied to the DC motor at that time is used as the second driving force and is also applied to the DC motor. And a driving force reducing step of reducing the driving force to be lower than the second driving force.

Therefore, with respect to the DC motor, the rotation of the DC motor (DC motor) is detected by the change of the digital position signal while gradually increasing the driving force, and when the rotation is detected, the digital position signal is output. The driving force is made smaller than the driving force (second driving force) at the time of change. As a result, it is possible to approach the target position without excessively speeding up the rotation of the DC motor.

Further, even if the load torque acting on the DC motor fluctuates or the driving torque of the DC motor fluctuates,
The DC motor can be driven with the minimum required drive torque that overcomes the load torque. The amount of overrun in the DC motor after detecting the change in the digital position signal is suppressed within 1 pulse of the digital position signal, and the stop position of the DC motor should greatly exceed the detection position of the digital position signal. There is no uniformization at almost the same position. As a result, it is possible to prevent fluctuations in the stop position due to excessive overrun of the DC motor.

As described above, the sheet feeding method according to the present invention is performed by the operation of the DC motor based on the digital position signal output from the detector that detects the rotation amount of the DC motor. A sheet feeding method for controlling feeding, wherein a driving method of a DC motor according to the present invention is applied to stop the sheet feeding when the sheet feeding amount reaches a target sheet feeding position where a predetermined amount is reached. It is characterized by including a sheet feeding operation.

Therefore, when the seat is stopped at the target position, the driving method of the DC motor according to the present invention is used, so that the seat feeding speed can approach the target position without excessive speed over. Has the effect. Further, even if the load torque acting on the DC motor fluctuates or the driving torque of the DC motor fluctuates, the sheet feed amount after detecting the change in the digital position signal greatly exceeds the detection position of the digital position signal. Without being homogenized. As a result, it is possible to prevent fluctuations in the stop position due to excessive overrun of the sheet feeding, and it is possible to perform accurate sheet feeding.

Further, the sheet feeding method according to the present invention is
As described above, when the sheet feeding is stopped, the sheet feeding operation is repeated a plurality of times to reach the target sheet feeding position.

Therefore, when stopping the sheet feeding,
By repeating the driving method of the DC electric motor according to the present invention a plurality of times, the sheet is gradually fed, and when the target position is reached, the feeding of the sheet is stopped. As a result, the approach to the target sheet feeding position is stabilized, and the reproducibility of the stop operation and the sheet feeding accuracy are further improved.

Further, the sheet feeding method according to the present invention is
As described above, after the sheet is continuously fed from the start of the sheet feeding to the position where the target sheet feeding position is not reached, the sheet feeding operation is repeated a plurality of times to reach the target sheet feeding position. Is the way.

Therefore, when stopping the sheet feeding after continuously feeding the sheet, the driving method of the DC motor according to the present invention is repeated a plurality of times to gradually feed the sheet and reach the target position. Stop feeding the sheet at this point. As a result, it is possible to shorten the time for carrying out a predetermined amount of sheet feeding, and since the sheet feeding has reproducibility, it is possible to achieve accurate sheet feeding in a shorter time.

Further, as described above, the sheet feeding apparatus according to the present invention detects the DC electric motor which is the power source for the sheet feeding, and detects the DC electric motor each time the DC electric motor rotates by a certain amount, and outputs the digital position signal. A sheet feeding device that has a detector, controls the operation of the DC electric motor based on digital position information obtained by counting the digital position signals output from the detector, and controls the sheet feeding position. , Using the sheet feeding method according to the present invention,
The configuration is such that the sheet feed amount is controlled.

Therefore, when the sheet is fed, the sheet feeding method according to the present invention is used. Therefore, when the sheet for one line is fed every time printing of one line is finished, the sheet is fed to the target position. The effect of being able to approach the target position without excessively increasing the sheet feeding speed is obtained.

Further, even if the load torque acting on the DC motor such as the sliding friction of the sheet changes or the driving torque of the DC motor changes, the sheet feed amount after detecting the change in the digital position signal is It is suppressed within one pulse of the digital position signal, and the stop position of the DC motor is made uniform at almost the same position without greatly exceeding the detection position of the digital position signal. As a result, it is possible to prevent fluctuations in the stop position due to excessive overrunning of the sheet feeding, and it is possible to perform accurate sheet feeding.

As a result, the positioning error of several pulses, which is a particular problem in digital position control, is eliminated.
Therefore, it is possible to perform the sheet feeding positioning control with an encoder having the same positioning resolution. further,
As the encoder, it is not necessary to use an absolute encoder and an analog position signal, which are complicated and expensive, and a simple and inexpensive incremental encoder may be used. Therefore, it is possible to realize a highly accurate and inexpensive sheet feeding device.

Further, the sheet feeding device according to the present invention is
As described above, the holding force is applied to the DC electric motor so that the DC electric motor does not move from the sheet stop position after the sheet feeding is stopped.

Therefore, the holding force such as the holding driving force, the brake, and the worm gear is applied to the DC motor to prevent the sheet from moving due to back tension after the sheet feeding is stopped. Therefore, it is possible to reliably fix the sheet at the stop position after the sheet feeding is stopped.

Further, the sheet feeding device according to the present invention is
As described above, when the holding force is applied to the DC motor, the third driving force for holding the seat stop position is applied to the DC motor.

Therefore, when the sheet reaches the target position, the driving force applied to the DC motor is not set to 0, but a third driving force for holding the sheet stop position is applied. . As a result, it is possible to reliably fix the sheet at the stop position after the sheet feeding is stopped. Further, by using the driving force applied to the DC electric motor as the holding means, a holding mechanism such as a brake and a worm gear for stopping the seat is not required, and thus the load torque acting on the DC electric motor is reduced.

Further, the sheet feeding device according to the present invention is
As described above, the disturbance torque Tf acting on the DC motor by the disturbance force acting on the sheet feeding mechanism, the driving torque Ts acting on the DC motor by the third driving force, and the sliding torque acting on the DC motor by the sliding of the sheet feeding mechanism. The relationship with the dynamic load torque Td is: Td> abs (Tf-Ts) where abs
(X): The third driving force is set so as to have an absolute value of X.

Therefore, since it is possible to set the proper third driving force with respect to the above-mentioned disturbance torque, the positional accuracy becomes poor due to the improper driving force being applied, and the sheet after erroneous movement is stopped. The effect that it can prevent is done.

Further, the sheet feeding device according to the present invention is
As described above, the third driving force is set based on the second driving force immediately before the sheet feeding is stopped, and the third driving force is set to the third driving force more than the absolute value of the second driving force. The absolute value of the force is small.

Therefore, the third position depending on the stop position of the seat is set.
Since the driving force is applied to the sheet stopping position of the sheet, an appropriate holding force can be set even in the sheet feeding mechanism with large fluctuation of the disturbance force or the sheet feeding mechanism with large torque ripple. Play. Furthermore, since the absolute value of the third driving force is smaller than the absolute value of the second driving force immediately before stopping the sheet feeding,
It is possible to prevent the third driving force from having an inappropriate value and causing a stop position defect.

Further, the sheet feeding device according to the present invention is
As described above, the third driving force is set based on the driving force applied to the DC motor when the DC motor is driven at a constant speed.

Therefore, when the DC motor is driven at a constant speed, the third driving force is set based on the driving force applied to the DC motor, and after the sheet feeding is stopped, the third driving force is set. Granted. Accordingly, the load state of the sheet feeding mechanism corresponding to each stop position of the sheet can be reflected in the setting of the third driving force, and the more appropriate setting of the third driving force can be performed. As a result, it is possible to further prevent the position accuracy from being improperly applied by applying the improper third driving force and the erroneous movement of the stopped sheet.

Further, the sheet feeding device according to the present invention is
As described above, when the DC motor is driven at a constant speed, the direction of the driving force PWMc applied to the DC motor is the same as the sheet feeding direction. Driving force PWM applied when rotating the DC motor at the same speed as during constant speed driving
The third driving force is set such that the relationship between o and the third driving force PWMs is PWMs≈abs (PWMc-PWMo).

Therefore, when the direct-current motor is driven at a constant speed and the direction of the driving force PWMc applied to the direct-current motor is the same as the sheet feeding direction, the sliding load torque Td due to the constant-speed rotation is obtained. And the disturbance torque Tf can be estimated. That is, the sliding load torque can be estimated by the driving force PWMo,
The disturbance torque Tf can be estimated by the driving forces PWMc and PWMo. Since the third driving force is set based on the estimated value, it is possible to further improve the accuracy of the third driving force.

Further, the sheet feeding device according to the present invention is
As described above, when the DC motor is driven at a constant speed, the direction of the driving force PWMc applied to the DC motor is opposite to the sheet feeding direction, and the driving force PWMc and the sheet are not conveyed in the above-described manner. Driving force PWMo applied when rotating the DC motor at the same speed as during constant speed driving
And the third driving force PWMs has a relation that PWMs is set such that PWMs≈PWMc + PWMo.

Therefore, when the DC motor is driven at a constant speed and the direction of the driving force PWMc applied to the DC motor is in the opposite direction to the sheet feeding direction, the sliding load torque Td due to the constant speed rotation is obtained. And the disturbance torque Tf can be estimated. That is, the sliding load torque can be estimated by the driving force PWMo, and the disturbance torque Tf can be estimated by the driving forces PWMc and PWMo. And the third from the estimated value
Since the driving force of No. 3 is set, there is an effect that the accuracy of the third driving force can be further improved.

As described above, the image forming apparatus according to the present invention prints line by line on the sheet while moving the recording head in the main scanning direction, and after each line is printed, the next line is printed. In an image forming apparatus that performs a line feed operation for feeding a sheet in the sub-scanning direction by one line before printing, the sheet feeding apparatus according to the present invention is used to perform the line feed operation of the sheet. Is.

Therefore, when the sheet is fed, the above-mentioned sheet feeding apparatus according to the present invention is used, so that it is possible to perform the sheet feeding positioning control with the encoder having the same positioning resolution. . further,
As the encoder, it is not necessary to use an absolute encoder and an analog position signal, which are complicated and expensive, and a simple and inexpensive incremental encoder may be used. Therefore, there is an effect that a highly accurate and inexpensive image forming apparatus can be realized.

As described above, the image reading apparatus according to the present invention reads the image on the read original line by line while moving the read head in the main scanning direction.
The line feed operation of the read original is performed in the image reading apparatus that performs the line feed operation for feeding the read original by one line in the sub-scanning direction before the reading of the next line after the completion of reading and printing of one line. Therefore, the sheet feeding device according to the present invention is used.

Therefore, since the above-described sheet feeding device according to the present invention is used when feeding the read original, it is possible to perform the positioning control of the read original feeding with the encoder having the same positioning resolution. Play. Further, as the encoder, it is not necessary to use the absolute encoder and the analog position signal, which are complicated and expensive, and a simple and inexpensive incremental encoder may be used. Therefore, there is an effect that a highly accurate and inexpensive image reading device can be realized.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a change with time of a rotation speed of a direct-current motor (DC motor) while a sheet is fed once for one line in a sheet feeding method according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a control system to which the sheet feeding method is applied.

FIG. 3 is a waveform diagram showing a method of controlling a DC motor when stopping sheet feeding in the sheet feeding method.

FIG. 4 is an explanatory diagram showing an example of a disturbance force acting on a DC electric motor of the sheet feeding device according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing another example of the disturbance force acting on the DC electric motor of the sheet feeding device.

FIG. 6 is an explanatory diagram showing an example of a disturbance force acting on a DC motor of a sheet feeding device according to another embodiment of the present invention.

FIG. 7 is a main flowchart showing a procedure of the sheet feeding method according to the embodiment of the present invention.

8A and 8B are flowcharts showing the procedure of the sheet feeding method, in particular, FIG. 8A shows "YFB interrupt 1", FIG. 8B shows "YFB interrupt 2", and FIG. 8C. Is a "YFB interrupt 3", FIG. 8 (d) is a "YFB interrupt 4", and FIG. 8 (e) is a flowchart showing a "timer 2 interrupt".

[Explanation of symbols]

1 MPU controller 2 motors (DC motor) 3 detectors 4 Motor drive circuit Y encoder pulse (digital position signal) y count value Sections A and B C section Section D E section YA, YB count value YC, YD count value YE, YF count value PWM driving force

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hirotsugu Inoue             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company (72) Inventor Hiroyuki Ishikura             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F term (reference) 3F049 DA12 EA22 LA01 LB02                 5C062 AA05 AB17 AB22 AB32 AC13                       AC14 BA00                 5C072 AA05 NA06 NA08 SA01 SA04                 5H571 AA13 BB07 FF06 GG01 JJ08                       JJ28 LL33

Claims (14)

[Claims] 1. A method for driving a DC motor, which controls the operation of the DC motor based on a digital position signal output from a detector that detects the amount of rotation of the DC motor, wherein a first driving force is applied to the DC motor. After that, it is checked whether or not the digital position signal of the detector changes every time the driving force is increased by one step in the driving force increasing step of increasing the driving force stepwise. When a change in the digital position signal is confirmed in the signal confirmation step and the signal confirmation step, the driving force applied to the DC motor at that time is used as the second driving force and is applied to the DC motor. And a driving force reducing step of reducing the driving force to be lower than the second driving force. 2. A sheet feeding method for controlling sheet feeding carried out by the operation of the DC electric motor based on a digital position signal output from a detector for detecting the rotation amount of the DC electric motor. A sheet feeding method including a sheet feeding operation to which the method for driving a DC motor according to claim 1 is applied in order to stop the sheet feeding when a target sheet feeding position which is a fixed amount is reached. . 3. The sheet feeding method according to claim 2, wherein, when the sheet feeding is stopped, the sheet feeding operation is repeated a plurality of times to reach a target sheet feeding position. 4. The sheet feeding operation is repeated a plurality of times after the sheet feeding is continuously performed from the start of the sheet feeding to a position where the target sheet feeding position is not reached.
4. The sheet feeding method according to claim 3, wherein the target sheet feeding position is reached. 5. A direct current electric motor which is a power source for sheet feeding, and a detector which detects the direct current electric motor every time it rotates a predetermined amount and outputs a digital position signal, and outputs from the detector. The sheet feeding device according to claim 2, wherein the sheet feeding device controls the operation of the DC motor based on digital position information obtained by counting the digital position signal to control the sheet feeding position. A sheet feeding apparatus, characterized in that a sheet feeding amount is controlled by using a method. 6. The DC motor is prevented from moving from the sheet stop position after the sheet feeding is stopped.
The sheet feeding device according to claim 5, wherein a holding force is applied to the DC motor. 7. When applying a holding force to a DC motor,
A third means for holding the seat stop position in the DC motor
The sheet feeding device according to claim 6, wherein the driving force is applied. 8. A disturbance torque Tf acting on the DC motor by a disturbance force acting on the sheet feeding mechanism, a driving torque Ts acting on the DC motor by the third driving force, and a slider acting on the DC motor by sliding the sheet feeding mechanism. The relationship with the dynamic load torque Td is: Td> abs (Tf-Ts) However, the third driving force is set so that the absolute value of abs (X): X is set. The sheet feeding device described. 9. The third driving force is set on the basis of the second driving force immediately before the sheet feeding is stopped, and the third driving force is higher than the absolute value of the second driving force. The sheet feeding device according to claim 8, wherein the absolute value of the force is small. 10. The seat according to claim 8, wherein the third driving force is set based on the driving force applied to the DC motor when the DC motor is driven at a constant speed. Feeder. 11. The driving force PWMc applied to the DC motor when the DC motor is driven at a constant speed is in the same direction as the sheet feeding direction, and the driving force PWMc and the sheet are not conveyed when the sheet is not conveyed. Driving force PWM applied when rotating the DC motor at the same speed as during constant speed driving
The relationship between o and the third driving force PWMs is: PWMs≈abs (PWMc-PWMo) However, the third driving force is set so as to be an absolute value of abs (X): X. The sheet feeding device according to claim 10. 12. The driving force PWMc applied to the DC motor when the DC motor is driven at a constant speed is in the direction opposite to the sheet feeding direction, and the driving force PWMc and the sheet are not conveyed when the sheet is not conveyed. Driving force PWMo applied when rotating the DC motor at the same speed as during constant speed driving
11. The sheet feeding device according to claim 10, wherein the PWMs are set such that the relationship between the second driving force PWMs and the third driving force PWMs is PWMs≈PWMc + PWMo. 13. A sheet is printed one by one in the sub-scanning direction before printing the next line each time printing of one line is completed while the recording head is moved in the main scanning direction. An image forming apparatus which performs a line feed operation for feeding a line, wherein the sheet feeding apparatus according to any one of claims 5 to 12 is used to perform a line feed operation of a sheet. Forming equipment. 14. An image on a read original is read line by line while moving the read head in the main scanning direction, and each time reading and printing of one line is completed, reading is performed before reading the next line. An image reading apparatus for performing a line feed operation for feeding a document by one line in the sub-scanning direction, wherein the sheet feeding apparatus according to any one of claims 5 to 12 for performing a line feed operation for a read document. An image reading apparatus characterized by using.