JP2007164093A - Motor control method and device, and image forming apparatus having the motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide motor control method and device for forming a high image quality image by keeping circumferential speed difference between an intermediate transfer body and a photoreceptor drum at a preset value, and to provide an image forming apparatus having the motor control apparatus. <P>SOLUTION: The prestored driving current of a motor is obtained in accordance with the speed difference desired for transfer between the circumferential speed of the photoreceptor drum and the moving speed of the intermediate transfer body. The rotational speed of the motor is controlled so as to be the obtained driving current. The speed difference desired for the transfer is obtained from the difference between the prestored circumferential speed of the photoreceptor drum and the moving speed of the intermediate transfer body, in accordance with the kind of the image to be formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor control method and apparatus, and an image forming apparatus having the motor control apparatus, and more particularly to an image forming apparatus using an electrophotographic system or an electrostatic recording system. For example, in an image forming apparatus that develops an electrostatic latent image formed on a photosensitive member with a developer using a developing unit, transfers the developed image to an intermediate transfer member, and transfers the transferred image to a recording medium to obtain an image. The present invention relates to speed difference control between the photosensitive member and the intermediate transfer member.

  In a conventional electrophotographic image forming apparatus, first, a photosensitive member is charged and then exposed to form an electrostatic latent image. The electrostatic latent image is visualized as a developer image (toner image) using a developer, temporarily transferred to a belt or the like as an intermediate transfer member, and then transferred to a recording medium to obtain a permanent recorded image.

  A rotating body such as a photosensitive member or an intermediate transfer member is driven by a DC motor or a stepping motor connected directly or via a gear train. The difference between the peripheral speeds of the photosensitive member and the intermediate transfer member (the difference between the peripheral speed of the photosensitive member surface and the moving speed of the intermediate transfer member: the peripheral speed of the surface of the drum-like intermediate transfer member = the surface speed of the belt-like intermediate transfer member) The rotational speed of the motor, the gear ratio, and the diameter of the rotating body are determined so that the (moving speed) becomes zero.

  However, if the peripheral speed difference is set to zero, the transfer efficiency is reduced, and a hollowing out phenomenon occurs in characters or fine lines. Therefore, a technique for providing a predetermined peripheral speed difference between the photosensitive member and the intermediate transfer member is generally known. It has been. On the other hand, when the peripheral speed difference is added, in the case of a color image forming apparatus, color misregistration may become prominent in the output of photographs and graphics images. For this reason, a peripheral speed difference of about 2% (to increase the moving speed of the intermediate transfer member) is provided in a monochrome image forming apparatus that is not concerned with color misregistration, and the peripheral speed difference is zero in a color image forming apparatus in which color misregistration is a concern. It was common to.

  As a method of speed control, there has conventionally been feedback control in which the rotational speed of the motor shaft is detected by an encoder and the rotational speed of the motor shaft is controlled. However, this method is a method for keeping the speed of the motor rotation shaft constant. As the rotating body wears with age, its diameter decreases, the intermediate transfer belt expands and contracts, the eccentricity of the rotating shaft and the variation of gears, etc. The rotation control method could not keep it constant.

  Therefore, with respect to the peripheral speed control of the photosensitive member, a method has been proposed in which a fine line pattern formed as a toner image on the photosensitive member is read by an optical senor and feedback controlled (for example, see Patent Document 1). However, even if the peripheral speed is kept constant by this method, it has not yet reached the idea of controlling the peripheral speed difference between the photosensitive member and the intermediate transfer member.

  On the other hand, in the control of the photosensitive member and the intermediate transfer member, a configuration has been proposed in which the rotational speeds of both the photosensitive member motor and the intermediate transfer member motor are measured and the rotational speed is made constant as shown in FIG. (For example, refer to Patent Document 2).

According to the invention of Patent Document 2, the encoders 7 and 41 generate pulses having a period corresponding to the rotational speed of the photosensitive member 5 and the moving speed of the intermediate transfer belt 6 as an intermediate transfer member, and these pulses are generated by the control circuits 8 and 42. Count. Then, the speed fluctuations of the photosensitive member 5 and the intermediate transfer member 6 are calculated based on the counted value, and the motors 40 and 44 are rotated so that the speeds of the photosensitive member 5 and the intermediate transfer belt 6 are constant. , 43 is used for motor feedback control. The encoders 7 and 41 are rotary encoders that optically detect a pattern such as a bar code row or a stamp row that is struck by a roller that rotates together with the drive motors 40 and 44 of the photosensitive member 5 and the intermediate transfer belt 6 at a predetermined interval. is there. For this reason, this method is also a method of keeping the speed of the motor rotation shaft constant, and the peripheral speed of the rotating body cannot be kept constant by the rotation control method of the motor shaft.
JP 2003-140505 A Japanese Patent Laid-Open No. 2002-132008

  However, in the conventional image forming apparatus according to Patent Document 1 and Patent Document 2, the surface of the photosensitive member and the intermediate transfer member and the pattern pattern of the roller are detected by the optical sensor, so that the pattern and the sensor are soiled due to toner scattering. There was also a false detection. Further, in Patent Document 1, since a good image cannot be transferred to a recording medium when a pattern is applied to an image forming area, it is necessary to apply a pattern to a non-image forming area, which increases the cost of the apparatus and increases the cost. It was. Furthermore, it was not possible to follow a speed difference variation smaller than the pattern interval.

  There is also a method of forming a pattern as a toner image on a photoconductor or an intermediate transfer body at non-image formation timing, and performing feedback control by reading this, but this reduces productivity because the photoconductor and intermediate transfer body need to be cleaned. There are problems such as This method also has a problem that feedback control cannot be performed at the image formation timing.

  Furthermore, in the technique such as Patent Document 1 in which pattern formation is performed using toner, since unnecessary image formation is performed, toner is consumed and the running cost is increased, resulting in a disadvantage to the user. It was.

  With the recent price reduction of color image forming apparatuses, an increasing number of users use color image forming apparatuses as substitutes for monochrome image forming apparatuses. However, the conventional color image forming apparatus is controlled so that the peripheral speed difference becomes zero, and a method for dynamically controlling the peripheral speed difference has not been proposed. For this reason, when a color image forming apparatus is used as a substitute for a monochrome image forming apparatus, there has been a concern that there will be an increase in the risk of a dropout phenomenon due to characters and fine lines.

  The present invention has been made starting from solving the above-described problems of the prior art. The object is to provide a motor control method and apparatus capable of forming a high-quality image by maintaining the peripheral speed difference between the intermediate transfer member and the photosensitive drum at a predetermined value, and image formation having the motor control device. To provide an apparatus.

  In addition, by dynamically controlling the peripheral speed difference according to the type of image, a motor capable of forming a high-quality image appropriately corresponding to both color image formation and monochrome image formation. A control method and apparatus, and an image forming apparatus having the motor control device are provided.

  Furthermore, the present invention provides a motor control method and apparatus capable of keeping a peripheral speed difference between different media in contact with each other at a predetermined value without being limited to the image forming apparatus.

  In order to achieve the above object, a motor control method of the present invention is a motor control method for controlling the rotational speed of a motor that moves a medium in contact with another medium, and the movement speed between the other medium and the medium. Corresponding to the difference, a first acquisition step of acquiring the motor drive current stored in the storage means, and a motor speed control step of controlling the rotation speed of the motor so as to obtain the acquired drive current. It is characterized by having.

  Here, the other medium is a drum-shaped photosensitive member of an image forming apparatus, and the medium is a belt-shaped or drum-shaped intermediate transfer member, and is stored in the storage unit according to the type of image to be formed. The method further includes a second acquisition step of acquiring a difference in moving speed desirable for the stored transfer. The types of images to be formed are classified into characters, character photographs, and others, and the difference in moving speed desirable for the transfer is characters, characters photographs, and the like, and the moving speed of the medium is the moving speed of the other medium. Greater than speed. Further, in the motor speed control step, the step of detecting the motor drive current is compared with the detected drive current and the acquired drive current, and if the detected drive current is smaller, the target rotational speed is set. When the detected drive current is larger, the step of decreasing the target rotational speed, the step of detecting the rotational speed of the motor, the detected rotational speed and the target rotational speed are compared, and the detection A step of increasing the drive current when the rotational speed is smaller and a step of decreasing the drive current when the detected rotational speed is larger, so that the detected drive current becomes the acquired drive current. repeat.

  The motor control device of the present invention is a motor control device that controls the rotational speed of a motor that moves a medium in contact with another medium, the difference between the movement speeds of the other medium and the medium, and the motor. Storage means for storing the correspondence relationship with the drive current for rotational driving, and motor speed control means for controlling the rotational speed of the motor so that the drive current obtained from the storage means corresponds to the difference in movement speed It is characterized by having.

  Here, the other medium is a drum-shaped photosensitive member of an image forming apparatus, the medium is a belt-shaped or drum-shaped intermediate transfer member, and the storage unit further corresponds to the type of image to be formed. Further, a difference in moving speed desirable for transfer is stored, and speed difference determining means for determining a difference in moving speed desirable for the transfer corresponding to the type of image to be formed is further provided. The types of images to be formed are classified into characters, character photographs, and others, and the difference in moving speed desirable for the transfer is characters, characters photographs, and the like, and the moving speed of the medium is the moving speed of the other medium. Greater than speed. The image forming apparatus further includes input means for inputting the type of image to be formed. Further, the motor speed control means compares the detected drive current with the acquired drive current with drive current detection means for detecting the drive current of the motor, and if the detected drive current is smaller, the target A target speed adjusting means for increasing the rotational speed and reducing the target rotational speed when the detected drive current is larger, a rotational speed detecting means for detecting the rotational speed of the motor, the detected rotational speed and the target Drive current adjusting means for comparing the rotation speed and increasing the drive current when the detected rotation speed is lower and decreasing the drive current when the detected rotation speed is higher.

  In the image forming apparatus of the present invention, the toner image formed on the photosensitive drum is transferred to a belt-like or drum-like intermediate transfer member, and then the toner image on the intermediate transfer member is transferred to a recording medium. A first motor for driving the photosensitive drum, a second motor for driving the intermediate transfer member, a peripheral speed of the photosensitive drum, and a moving speed of the intermediate transfer member. Motor control means for controlling the speed difference between the first and second motors, and the motor control means rotationally drives the difference between the peripheral speed of the photosensitive drum and the moving speed of the intermediate transfer member and the first or second motor. A motor speed for controlling the rotation speed of the motor so as to obtain a drive current obtained from the drive current storage means corresponding to a difference in a desired moving speed for transfer, and a storage means for storing a correspondence relationship with the drive current Control means And wherein the door.

  Here, the storage means further stores a difference in movement speed desirable for transfer, which differs according to the type of image to be formed, and a difference in movement speed desirable for the transfer in accordance with the type of image to be formed. It further has a speed difference determining means for determining. The image forming apparatus further includes input means for inputting the type of image to be formed. Further, the motor speed control means for controlling the rotation speed of the motor compares the detected drive current with the acquired drive current, and the detected drive current, with the drive current detection means for detecting the drive current of the motor. A target speed adjusting means for increasing a target rotational speed when the detected drive current is larger, and a target speed adjusting means for decreasing the target rotational speed when the detected drive current is larger; a rotational speed detecting means for detecting the rotational speed of the motor; The detected rotation speed is compared with the target rotation speed. When the detected rotation speed is smaller, the drive current is increased, and when the detected rotation speed is larger, the drive current adjustment is performed to decrease the drive current. Means.

  Also, the control method of the image forming apparatus of the present invention is such that after the toner image formed on the photosensitive drum is transferred to a belt-shaped or drum-shaped intermediate transfer body, the toner image of the intermediate transfer body is transferred to a recording medium. A method of controlling an image forming apparatus for forming an image, wherein the peripheral speed of the photosensitive drum and the speed of movement of the intermediate transfer member stored in a storage unit corresponding to the type of image to be formed A step of obtaining a difference; a step of obtaining a driving current of the motor stored in the storage means corresponding to the obtained speed difference; and a rotational speed of the motor so as to be the obtained driving current. And a motor speed control step for controlling the motor.

  Here, in the motor speed control step, the step of detecting the drive current of the motor is compared with the detected drive current and the acquired drive current, and if the detected drive current is smaller, the target rotational speed If the detected drive current is larger, the step of reducing the target rotational speed, the step of detecting the rotational speed of the motor, the detected rotational speed and the target rotational speed are compared, A step of increasing the drive current when the detected rotational speed is lower and a step of decreasing the drive current when the detected rotational speed is higher, so that the detected drive current becomes the acquired drive current. Repeat.

  According to the present invention, there is provided a motor control method and apparatus capable of forming a high-quality image by keeping the peripheral speed difference between the intermediate transfer member and the photosensitive drum at a predetermined current value, and the motor control device. The image forming apparatus can be provided.

  That is, a method of forming a pattern or the like with toner on the intermediate transfer belt or the photosensitive drum and detecting it with an optical sensor is not used. For this reason, it is possible to eliminate erroneous detection due to contamination of the sensor or the like due to toner scattering. Since it is not necessary to form a useless pattern, the running cost can be reduced.

  In addition, by dynamically controlling the peripheral speed difference according to the type of image, a motor capable of forming a high-quality image appropriately corresponding to both color image formation and monochrome image formation. A control method and apparatus, and an image forming apparatus having the motor control apparatus can be provided.

  Furthermore, the present invention is not limited to an image forming apparatus, and a motor control method and apparatus capable of maintaining a peripheral speed difference between different media in contact with each other at a predetermined value can be provided.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. The motor control method of the present invention is not limited to the control of the photosensitive drum motor and the intermediate transfer body motor of the image forming apparatus described below. That is, the present invention can be applied to a motor control method that generally maintains a difference in peripheral speed between different media in contact with a predetermined value, and has the same effect. The present invention includes such a motor control method.

<Features of this embodiment>
The image forming apparatus of the present invention measures and stores the difference in peripheral speed between the intermediate transfer belt and the photosensitive drum and the drive current for driving the intermediate transfer belt / photosensitive drum in association with each other. Then, the drive current for driving the intermediate transfer belt / photoreceptor drum is measured, and the rotation of the motor is controlled so that the drive current becomes the target drive current. Control is performed to keep the speed difference at a predetermined value. Therefore, there is a risk of erroneous detection due to scattering of toner as compared with the case where a pattern or barcode array is formed with toner on the surface of a conventional intermediate transfer belt or photosensitive drum and detected by an optical sensor to maintain the peripheral speed difference. Disappears. Further, since it is not necessary to form a pattern, the running cost can be reduced.

  Also, by dynamically controlling the peripheral speed difference in accordance with the type of image, a high-quality image can be formed appropriately corresponding to the formation of a color image and a monochrome image.

<Example of Configuration of Image Forming Apparatus of Present Embodiment>
(Configuration example of image forming unit: FIG. 1)
FIG. 1 is a diagram illustrating a configuration example of an image forming unit of the image forming apparatus according to the present embodiment. The image forming apparatus of the present embodiment is a laser beam printer that can form an image using an electrophotographic system, and is an example in which the image is transferred from a photosensitive drum to an intermediate transfer belt and further transferred to a recording medium.

  The image forming unit 1 includes a photosensitive drum 10a and a transfer roller 10b, a drum motor 12, an intermediate transfer belt 13, a belt motor 14, and a control unit 2 described later. The photosensitive drum 10 a and the transfer roller 10 b sandwich the intermediate transfer belt 13, and the transfer roller 10 b follows the movement of the intermediate transfer belt 2. The drum motor 12 is for applying a drive to the photosensitive drum 10a through a gear train, and is a stepping motor, for example. The belt motor 14 is used to drive the intermediate transfer belt 13 and the transfer roller 10b, and is a stepping motor, for example. The belt motor 14 performs feedback control by an encoder by a known technique.

  The control unit 2 includes drive current control units 20 to 22 based on a difference in peripheral speed, and a driver 23 that applies pulses and current corresponding to the rotation speed to the drum motor 12 and the belt motor 14. The control unit 2 is a dedicated unit for controlling the drum motor 12 and / or the belt motor 14 and may be configured to communicate with the controller of the apparatus, or a controller that controls the image forming apparatus of the present embodiment. May be configured as a part of In this example, the drum motor 12 is controlled to a constant rotational speed, and the belt motor 14 is dynamically controlled to rotate according to the peripheral speed difference. However, the reverse control is also possible.

(Configuration example of encoder: Fig. 2)
An example of the encoder of this embodiment is shown in FIG.

  The encoder 140 detects that the flag F attached to the shaft interrupts the optical path (dotted arrow) of the photo interrupter as the belt motor 14 rotates (solid arrow), and the rotation period (or rotation) of the motor rotation shaft is detected. Speed).

(Relationship between peripheral speed difference between photosensitive drum and intermediate transfer belt and drive current value: Fig. 3)
FIG. 3 shows the peripheral speeds of the photosensitive drum 10a and the intermediate transfer belt 13 of the image forming apparatus according to the present embodiment, and their peripheral speed differences (difference between the rotational speed of the photosensitive drum and the rotational speed of the intermediate transfer belt) and the belt. It is a graph which shows the relationship with the electric current value of the motor.

  The photosensitive drum 10a is rotationally controlled at a peripheral speed (constant) of 127.4 mm / s. It is assumed that the intermediate transfer belt 14 rotates at a peripheral speed of 120.0 mm / s (−6% of the photosensitive drum peripheral speed) at time 0 s. In this state, the intermediate transfer belt 14 has a driving force applied due to friction with the photosensitive drum 10a, but also slips. Therefore, a certain level of rotation holding force is required, and the driving current of the belt motor 13 is 0. About 2A. At time 2.0 s, the peripheral speed of the intermediate transfer belt 14 is gradually increased.

  At time 5.0 s, the peripheral speed difference is −2% (indicated by an arrow in the figure), and the driving current of the belt motor 13 is 0.4 A. At time 10.0 s, the peripheral speed difference is −1%, and the driving current of the belt motor 13 is 0.6 A. At time 15.0 s, the peripheral speed difference becomes 0%, and the driving current of the belt motor 13 is 0.7 A. At time 20.0 s, the peripheral speed difference becomes 1%, and the drive current of the belt motor 13 increases to 0.8A. This is because the load on the belt motor 13 increases due to the influence of friction due to the peripheral speed difference between the intermediate transfer belt 13 and the photosensitive drum 10a, and the current value increases to compensate for the load. Further, at time 25.0 s, when the peripheral speed of the intermediate transfer belt 13 is changed to 130.0 mm / s (circumferential speed difference 2%), the drive current of the bell and the motor 13 increases to 1.0 A. Thereafter, when the peripheral speed is increased, the intermediate transfer belt 14 starts to slip again, and the drive current reaches a peak at about 1.2 A.

  In the present embodiment, the peripheral speed difference is directly controlled by the driving current of the belt motor 13 by storing the relationship between the peripheral speed difference and the driving current of the belt motor 13 in association with each other.

(Configuration example of control unit 2: FIGS. 4A and 4B)
FIG. 4A is a block diagram illustrating a configuration example of the control unit 2 of the present embodiment.

  The CPU 20 as the control means provided in the control unit 2 performs basic control of the belt motor 14 in this example. As shown in FIG. 1, the control unit 2 may control the drum motor at the same time. A work RAM 21 for processing and a ROM 22 in which a control program is written are connected to the CPU 20 as storage means via an address bus or a data bus. The CPU 20 executes motor rotation control according to the contents of the control program.

  A belt motor 14 is connected to the CPU 20 via a driver 23. The driver 23 is a sub CPU for rotating the belt motor 14, and a setting register of the driver 23 is mapped to a predetermined address in the memory map of the CPU 20. From the CPU 20, a reference drive frequency, a rising curve (for example, seven representative points), a drive current, a start, and a stop are set. The CPU 20 instructs the start after setting the reference frequency, the rising curve, and the drive current in the setting register in advance. The driver 23 applies a drive current based on the set current from the current application unit 232 to the belt motor 14 and starts to rotate the belt motor 14 at a reference drive frequency based on the set speed from the pulse generator 231. Then, the belt motor 14 is started up at a frequency that linearly interpolates seven representative frequencies set in the start-up curve. The opposite is true when stopping.

  In the CPU 20, there are a speed comparison unit 200, a speed setting unit 201, a current comparison unit 202, a current setting unit 203, and a peripheral speed difference current holding unit 204. The speed setting unit 201 holds the speed (belt motor 14) set in the driver 23. The speed comparison unit 200 compares the speed of the belt motor 14 detected by the encoder 140 with the speed held in the speed setting unit 201. If the two are different, the current setting unit 203 is informed as a step-out signal that the belt motor 14 is stepping out. The current setting unit 203 holds the drive current value set in the driver 23. The peripheral speed difference current value holding unit 204 holds a current value corresponding to the peripheral speed difference. The current comparison unit 202 compares the current value held in the current setting unit 203 with the current value held in the peripheral speed difference current holding unit 204. If both are different, it is determined that there is a difference in peripheral speed, and the speed setting unit 201 is notified as a peripheral speed difference abnormality signal.

  Each unit in the CPU 20 is a functional element that is realized by the CPU 20 executing the program stored in the ROM 22 while using the RAM 21.

  FIG. 4B shows a storage configuration example of the ROM 22 and the RAM 21. In FIG. 4B, the register for transmitting information to the driver 23 is not shown. In order to avoid complexity, only the programs and data related to the characteristic operation of this embodiment are shown.

  The ROM 22 stores a system program 22a of the image forming apparatus of the present embodiment (see FIG. 8). The system program 22a includes a communication program with the central control unit in the case of distributed control, and a user interface such as a display program and an image processing program in the case of centralized control.

  Further, a peripheral speed difference control program 22b (see FIG. 5) for controlling the belt motor 14 so as to achieve the set peripheral speed difference, and a speed feedback control program 22c (for controlling the rotation of the belt motor 14 to the set rotational speed). Is stored). Further, a mode for storing a set peripheral speed difference and a drive current value corresponding to the peripheral speed difference corresponding to the type of image to be formed (in this example, characters, character photographs, etc .: mode in FIG. 4B). / Circumferential speed difference / set current value / table 22d (see FIG. 3) is stored.

  The RAM 21 stores a currently operating mode 23a, a target peripheral speed difference 23b, and a target set current value 23c. As variables under control, a detected drive current value 23d, a motor rotation setting speed 23e that changes according to the detected current, and a detected motor rotation speed 23f are stored.

<Example of Operation Procedure of Image Forming Apparatus of Present Embodiment>
Hereinafter, an example of an operation procedure of the image forming apparatus according to the present embodiment having the above configuration will be described.

(Example procedure of peripheral speed difference control: Fig. 5)
FIG. 5 is a flowchart showing a procedure example of the peripheral speed difference control according to the present embodiment. In FIG. 5, the CPU 20 executes the program while controlling each unit using the RAM 21 as a work area based on a control program stored in the ROM 22.

  First, in step S <b> 1, the current comparison unit 202 detects the current drive current value set in the current setting unit 203. Next, the process proceeds to step S2, in which the current comparison unit 202 has a target peripheral speed difference current value corresponding to the peripheral speed difference held in the peripheral speed difference current value holding unit 204, and the current value detected in step S1. Make a comparison.

  If the peripheral speed difference current value is larger than the set current value in step S2, the process proceeds to step S3 to increase the set speed of the speed setting unit 201 by 1 rpm, and then proceeds to step S4.

  On the other hand, when the peripheral speed difference current value is smaller than the detected current value, the process proceeds from step S2 to step S5, and further proceeds to step S6 to decrease the set speed by 1 rpm and then proceeds to step S4. On the other hand, if it is not determined in step S5 that the peripheral speed difference current value is smaller, the detected current and the peripheral speed difference current value coincide with each other, so that the process proceeds to step S4 without changing the set speed.

  In step S4, feedback control to the set rotation speed is performed. This feedback control will be described in detail with reference to FIG.

(Example of procedure for feedback control of rotational speed: Fig. 6)
FIG. 6 is a flowchart showing feedback control of the set rotational speed in step S4 of FIG.

  First, in step S40, when the rotation speed of the rotating shaft of the belt motor 14 is detected by the encoder 140, the process proceeds to step S41, where the speed comparison unit 200 compares the detected speed with the speed setting value held in the speed setting unit 201. Do.

  In step S41, if the set speed is greater than the detected speed, the step is being stepped out. Therefore, the process proceeds to step S42 to increase the current setting value of the current setting unit 203 by 0.1 A in order to increase the holding force. Returning to S40, the rotation control is repeated.

  On the other hand, if the set speed is smaller than the detected speed, the process proceeds from step S41 to step S43, and further to step S44, the current set value of the current setting unit 203 is reduced by 0.1 A, and then the process returns to step S40 to control the rotation. repeat.

  If it is determined in step S43 that the set speed and the detected speed are equal, the set target rotation speed is controlled, so a series of operations are terminated, and the flow returns to FIG. 5 to determine whether the peripheral speed difference is the target value. To check.

  Speed feedback control and current feedback control are performed by repeating the flow of FIGS. 5 and 6 described above. As a result, the peripheral speed difference between the photosensitive drum and the intermediate transfer belt can be controlled by controlling the driving of the belt motor (the peripheral speed difference is kept at a preset value).

  As described above, according to the example of the present embodiment, the drive current value of the belt motor 14 is monitored in order to control the peripheral speed difference. However, instead of monitoring the drive current value of the belt motor 14, the drive current value of the drum motor 12 may be monitored, and the above-described control of the present embodiment may be performed. In this case, the same effect as described above can be obtained.

(Example procedure of the image forming apparatus of this embodiment: FIG. 7)
The image forming apparatus according to the present embodiment to which the circumferential speed difference control is applied is that the user can set the image forming mode and can change the circumferential speed difference setting so as to be suitable for the set image forming mode. It is a feature. For this reason, for example, a hollowing out phenomenon may occur when the peripheral speed difference is reduced to zero with characters or fine lines, or color misregistration may occur due to the peripheral speed difference being output in the output of photographs or graphics images. Can be prevented dynamically.

  An operation touch panel 3 shown in FIG. 7 is attached to the image forming apparatus, and the user can specify various image forming modes. Hereinafter, control processing of various image forming modes set using the operation touch panel 3 will be described with reference to a control flowchart of FIG.

  First, in step S10, when the user selects an image forming mode using the operation touch panel 3, the process proceeds to step S11.

  For example, when it is received in step S10 that the user has started the image forming operation by pressing the character print mode key 30, it is confirmed in step S11 that the character print mode key 30 has been selected. Next, the process proceeds to step S12, the peripheral speed difference + 2% is designated, and then the process proceeds to step S16.

  On the other hand, when it is received in step S10 that the user has pressed the character / photo mode key 31 to start the image forming operation, the process proceeds from step S11 to step S13 to confirm that the character / photo mode key 31 has been selected. Next, the process proceeds to step S14, where the peripheral speed difference + 1% is designated and then the process proceeds to step S16.

  In step S10, when it is received that the user has started the image forming operation without selecting the image forming mode, the process proceeds to step S11, step S13, and step S15 to determine that the mode is the photo mode, and the peripheral speed difference is 0%. Is designated and then the process proceeds to step S16.

  Next, in step S16, in response to these designations, the circumferential speed difference current value is 1.0 A when the circumferential speed difference designation is 2%, and the current value is 0.8 A when the circumferential speed difference designation is 1%. When the difference is specified as 0%, the current value held in the peripheral speed difference current value holding unit 204 is changed, such as 0.7A.

  Next, in step S17, the motor start-up is started by the feedback control according to the present embodiment, and in step S18, after completion of the start-up, a series of work is finished. In the motor start-up process in step S17, the peripheral speed difference control in FIGS. 5 and 6 is realized.

  In FIG. 7, the value of the peripheral speed difference corresponding to the image type is described in the flow. However, a table for storing the peripheral speed difference in advance corresponding to the image type is provided for reference. It may be configured. The setting of the drive current corresponding to the peripheral speed difference in step S16 may be incorporated in the program or may be stored as a table.

(Example of specific peripheral speed difference control based on image type: FIG. 9)
Next, with respect to the processing described with reference to FIG. 8, the peripheral speed difference control according to the present embodiment will be described in accordance with the actual operation using the example illustrated in FIG. 9. FIG. 9 is a graph showing the relationship between the peripheral speed of the intermediate transfer belt 13 of the image forming apparatus, the current value of the belt motor 14, and the rotational speed. The photosensitive drum 10a is controlled to a peripheral speed of 127.4 mm / s by the drum motor 12 as shown in FIG.

  When the character print mode key 31 is pressed from the operation touch panel 3 at time 0, the corresponding peripheral speed difference setting is changed to + 2%. The CPU 20 changes the setting of the peripheral speed difference current value holding unit 204 from 0.7 A corresponding to the peripheral speed difference 0% to 1.0 A corresponding to the peripheral speed difference + 2%.

  When the start-up of the belt motor 14 is started, the current value held in the peripheral speed difference current value holding unit 204 and the current value held in the current setting unit 203 are compared by the current comparison unit 202, and speed control is performed. A peripheral speed difference abnormality signal is issued to the unit 201. The speed setting unit 201 increases the set speed in increments of 1 rpm. The rotational speed detected through the encoder 140 is input to the speed comparison unit 200 and compared with the speed held in the speed setting unit 201. Here, if the speed is different, a step-out signal is issued to the current setting unit 203 to change the current set value. However, if the peripheral speed difference is less than 0%, the frictional force of the photosensitive drum 10a is also added, and the motor can be started up with a current value of 0.2A.

  At time D, the peripheral speed of the intermediate transfer belt reaches 127.4 mm / s (circumferential speed difference 0%), and the drive current value becomes 0.7A. At this time, when the rotation axis radius of the belt motor 14 is 20 mm, the belt motor 14 is rotated at 382 rpm in order to rotate the intermediate transfer belt 13 at a peripheral speed of 127.4 mm / s.

  At time E, when the pressure reaches 397 rpm, the current value of the current setting unit 203 matches the current value of 1.0 A held by the circumferential speed difference current holding unit 204, so that the circumferential speed difference is maintained at + 2%. It will be.

  As described above, according to the present embodiment, the peripheral speeds of the photosensitive member and the intermediate transfer member are controlled according to the image forming mode. For this reason, there will be no hollowing out phenomenon due to zero peripheral speed difference for characters or fine lines, or color shift due to peripheral speed difference in the output of photos and graphics images. .

  In the present embodiment, an example in which the peripheral speed difference setting is changed by designating the character / character photo / photo mode has been described. However, the peripheral speed difference setting may be changed with other image forming mode settings. For example, in black and white image formation, there is no effect of color misregistration, so a peripheral speed difference is added to improve the quality of characters and fine lines, and in color image formation, there is an effect of color misregistration and the peripheral speed difference is made zero. . Further, the peripheral speed difference may be determined by automatically determining the ratio of characters and images from the original image.

  Although the present embodiment has been described using specific examples, the numerical values exemplified here are merely examples, and these numerical values can be freely changed and do not limit the present patent.

  In addition, the present invention may be applied to a system or an integrated device composed of a plurality of devices (for example, a host computer, an interface device, a printer, etc.) or an apparatus composed of a single device.

  The object of the present invention can also be achieved by using a recording medium (or storage medium) that records a program code of software that implements the functions of the above-described embodiments. In this case, this can also be achieved by supplying the recording medium to the system or apparatus, and reading and executing the program code stored in the recording medium by the computer (or CPU or MPU) of the system or apparatus. In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention.

  Further, the functions of the above-described embodiments are realized by executing the program code read by the computer. In addition, the operating system (OS) running on the computer performs part or all of the actual processing based on the instruction of the program code, and the functions of the above-described embodiments are realized. Needless to say.

  Further, the program code read from the recording medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. Thereafter, the CPU of the function expansion card or the function expansion unit performs part or all of the actual processing based on the instruction of the program code, and the function of the above-described embodiment is realized by the processing. Needless to say.

  Further, the present invention includes a mode in which program data for realizing the functions of the above-described embodiment is downloaded from the CD-ROM set in the own device or an external supply source such as the Internet to the memory of the own device. Is done.

  When the present invention is applied to the above recording medium, it is preferable that the recording medium stores program codes corresponding to the flowcharts (FIGS. 5, 6, and 8) described above.

1 is a schematic cross-sectional view of an embodiment of a photoreceptor and an intermediate transfer member of an image forming apparatus according to an embodiment. FIG. 2 is a schematic diagram illustrating a driving motor for a fixing roller provided in the photosensitive member and the intermediate transfer member in FIG. 1. FIG. 6 is a diagram illustrating an example of a relationship between a peripheral speed difference between a photosensitive member and an intermediate transfer member and a current value of an intermediate transfer belt driving motor. It is a block diagram which shows the structural example of the control unit of FIG. It is a figure which shows the memory | storage structure example in the control unit of FIG. It is a flowchart which shows the example of a procedure of the circumferential speed difference control by the belt motor of this embodiment. It is a flowchart explaining the detail of step S4 of FIG. 2 is a diagram illustrating an example of an operation panel attached to the image forming apparatus according to the present exemplary embodiment. FIG. FIG. 6 is a flowchart illustrating an example of a procedure of peripheral speed difference control in the image forming apparatus of the present embodiment. 6 is a graph showing an example of a relationship between a peripheral speed difference between a photosensitive member and an intermediate transfer member and a current value of an intermediate transfer belt drive motor. It is a figure which shows the motor control by a prior art example.

Explanation of symbols

1 Image forming unit 10a Drum roller (rotating body)
10b Transfer roller (rotating body)
12 drum motor 13 intermediate transfer belt (rotary body, intermediate transfer body)
14 Belt motor 140 Encoder

Claims (15)

A motor control method for controlling the rotational speed of a motor that moves a medium that contacts another medium,
A first acquisition step of acquiring a driving current of the motor stored in the storage unit in response to a difference in moving speed between the other medium and the medium;
And a motor speed control step of controlling a rotation speed of the motor so as to obtain the acquired drive current. The other medium is a drum-shaped photoconductor of the image forming apparatus, and the medium is a belt-shaped or drum-shaped intermediate transfer body,
2. The motor control method according to claim 1, further comprising a second acquisition step of acquiring a difference in moving speed desirable for transfer stored in the storage unit in accordance with the type of image to be formed.   The types of images to be formed are classified into characters, character photographs, and the like, and the difference in moving speed desirable for the transfer is that the moving speed of the medium is higher than the moving speed of the other medium in the order of characters, character photographs, and others. The motor control method according to claim 2, wherein the motor control method is large. In the motor speed control step,
Detecting a driving current of the motor;
The detected drive current is compared with the acquired drive current. If the detected drive current is smaller, the target rotational speed is increased, and if the detected drive current is larger, the target rotational speed is decreased. A process of
Detecting the rotational speed of the motor;
Comparing the detected rotational speed with the target rotational speed, increasing the drive current if the detected rotational speed is smaller, and decreasing the drive current if the detected rotational speed is greater; The motor control method according to claim 1, wherein the motor driving method is repeated so that the detected driving current becomes the acquired driving current. A motor control device that controls the rotational speed of a motor that moves a medium in contact with another medium,
Storage means for storing a correspondence relationship between a difference in moving speed between the other medium and the medium and a drive current for rotationally driving the motor;
A motor control device comprising: motor speed control means for controlling the rotational speed of the motor so that the drive current obtained from the storage means corresponds to a difference in movement speed. The other medium is a drum-shaped photoconductor of the image forming apparatus, and the medium is a belt-shaped or drum-shaped intermediate transfer body,
The storage means further stores a difference in moving speed desirable for transfer, which differs depending on the type of image to be formed,
6. The motor control apparatus according to claim 5, further comprising speed difference determining means for determining a difference in moving speed desired for the transfer in accordance with the type of image to be formed.   The types of images to be formed are classified into characters, character photographs, and the like, and the difference in moving speed desirable for the transfer is that the moving speed of the medium is higher than the moving speed of the other medium in the order of characters, character photographs, and the like. The motor control device according to claim 6, wherein the motor control device is large.   8. The motor control apparatus according to claim 6, further comprising input means for inputting the type of image to be formed. The motor speed control means includes
Drive current detection means for detecting the drive current of the motor;
The detected drive current is compared with the acquired drive current. If the detected drive current is smaller, the target rotational speed is increased, and if the detected drive current is larger, the target rotational speed is decreased. Target speed adjusting means to be
Rotation speed detection means for detecting the rotation speed of the motor;
The detected rotation speed is compared with the target rotation speed. When the detected rotation speed is smaller, the drive current is increased, and when the detected rotation speed is larger, the drive current is decreased. 6. The motor control device according to claim 5, further comprising an adjusting unit. An image forming apparatus for transferring a toner image formed on a photosensitive drum to a belt-shaped or drum-shaped intermediate transfer member and then transferring the toner image of the intermediate transfer member to a recording medium to form an image,
A first motor for driving the photosensitive drum;
A second motor for driving the intermediate transfer member;
Motor control means for controlling a speed difference between the peripheral speed of the photosensitive drum and the moving speed of the intermediate transfer member;
The motor control means includes
Storage means for storing a correspondence relationship between a difference between a peripheral speed of the photosensitive drum and a moving speed of the intermediate transfer member and a driving current for rotationally driving the first or second motor;
An image forming apparatus comprising: motor speed control means for controlling the rotational speed of the motor so that the drive current acquired from the drive current storage means corresponds to a difference in movement speed desired for transfer. . The storage means further stores a difference in moving speed desirable for transfer, which differs depending on the type of image to be formed,
The image forming apparatus according to claim 10, further comprising a speed difference determining unit that determines a difference in moving speed desired for the transfer in accordance with a type of the image to be formed.   The image forming apparatus according to claim 11, further comprising an input unit configured to input a type of image to be formed. Motor speed control means for controlling the rotational speed of the motor is
Drive current detection means for detecting the drive current of the motor;
The detected drive current is compared with the acquired drive current. If the detected drive current is smaller, the target rotational speed is increased, and if the detected drive current is larger, the target rotational speed is decreased. Target speed adjusting means to be
Rotation speed detection means for detecting the rotation speed of the motor;
The detected rotation speed is compared with the target rotation speed. When the detected rotation speed is smaller, the drive current is increased, and when the detected rotation speed is larger, the drive current is decreased. The image forming apparatus according to claim 10, further comprising an adjusting unit. A method for controlling an image forming apparatus in which a toner image formed on a photosensitive drum is transferred to a belt-shaped or drum-shaped intermediate transfer body, and then the toner image on the intermediate transfer body is transferred to a recording medium to form an image. There,
In accordance with the type of image to be formed, obtaining a speed difference between the peripheral speed of the photosensitive drum stored in the storage unit and the moving speed of the intermediate transfer member;
Acquiring a motor driving current stored in the storage unit in response to the acquired speed difference;
And a motor speed control step of controlling a rotation speed of the motor so as to obtain the acquired drive current. In the motor speed control step,
Detecting a driving current of the motor;
The detected drive current is compared with the acquired drive current. If the detected drive current is smaller, the target rotational speed is increased, and if the detected drive current is larger, the target rotational speed is decreased. A process of
Detecting the rotational speed of the motor;
Comparing the detected rotational speed with the target rotational speed, increasing the drive current if the detected rotational speed is smaller, and decreasing the drive current if the detected rotational speed is greater; The method of controlling an image forming apparatus according to claim 14, wherein the detected driving current is repeated so as to be the acquired driving current.

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